- Device and design features of anchor fasteners
- Effort calculation methodology
- Selection of anchors depending on the base material
- Mechanical anchoring rules
- Use of chemical anchors
The choice of a method for attaching critical structures to the bases is not always obvious, and yet there are quite universal options that can be used in different conditions. In the article we will talk about the types of anchoring systems: chemical and mechanical.
Device and design features of anchor fasteners
In a broad sense, an anchor is a two-piece rod, one part of which deforms the other in order to expand and anchor in the hole tightly enough so that the entire structure can withstand a load comparable to its deformation threshold.
Frame anchors can be considered as an example, they are the most popular. The design of the fastener includes a tube with a metal rod inside, at one end of which there is a thread, and at the other – a head for a hex or Phillips screwdriver. The tube has longitudinal slots; a wedge-shaped element with an internal thread and external slots is installed in them, which prevents rotation when tightening. As the rod rotates, the wedge nut shifts axially and crushes the tube, expanding it in the hole.
Bolt anchors have the same principle of operation, but a different design: the wedge-shaped expansion is located on the rod, and the nut is located at its threaded end in the visible part of the fastener. Such anchors are used in cases where the dimensions of the protruding part of the fastening are not critical, because the anchor rod can be pulled out when fastened by 3–6 cm. A subspecies of anchor bolts are collet fasteners in which the spacer part is compressed by two wedges on both sides.
There are also anchors in which the nut is firmly fixed in a mandrel at the end of a tube that has 4 stamped slots along its entire length. Such anchors are called Molly bolts and are used for fastening to sheet materials and hollow walls. When tensioned with a pin, the tube folds into an X-shaped structure and, thus, the mount reliably crimps even a thin rear sight.
Other structural features relate to the shape of the head; it may have an earring or a hook at the end. The anchors have a diameter of 6 to 24 mm and a length of 72 to 300 mm. Elongation occurs mainly due to the non-expansion part of the fastener: the degree of deepening does not matter, so long anchors are used to fasten thicker parts.
Effort calculation methodology
There are two types of load on anchor fasteners – traction and transverse. Although anchors are generally not designed to resist pull-out, they are sometimes used in these conditions, increasing the number of points to obtain distributed fasteners..
For anchors of different types and manufacturers, the permissible loads vary greatly, but in any case they are directly proportional to the static tensile strength of the metal core. When calculating the traction load, the degree of crumbling of the base material also plays an important role, due to which the breakdown of the fastener without destroying it or loosening of the anchor and its partial deformation is possible..
The spacing of the axes of the multi-point attachment should also be taken into account: the distance between the anchors should not be less than 15 diameters of the hole for them. The same rule applies to the distance from the edge of the array at which the anchors are fixed..
Since in most cases anchors are selected with a large margin of safety, the following permissible loads will be a guaranteed guideline in the calculation:
|Nominal diameter, mm||Permissible lateral load, N / kg||Permissible pulling load, N / kg||Recommended tightening torque|
The permissible loads are given for anchors with a soft steel core anchored in B30 concrete, in which minor structural defects are allowed: cracks or overstresses. Ideally, anchors are able to withstand much higher loads (up to 5 times higher than those given), so their reliability directly depends on the characteristics of the base.
Selection of anchors depending on the base material
The main requirement for the base for anchoring is the absence of elasticity, fragility and high hardness of the material. Masonry and concrete are ideal for anchoring. Less reliable, but still acceptable is anchoring in hollow structures – GWP and cinder block. A prerequisite is that the length of the anchor must be sufficient for fastening to the second partition (behind the void). In other cases, Molly bolts should be used, first of all, this applies to false walls and partitions assembled using “dry” technologies.
Bolted anchoring to walls made of aerated concrete, shell rock and similar porous materials is categorically unacceptable. In such cases, either distributed fasteners with steel screws or chemical anchors should be used. The principle of their operation is simple: the hole is injected with two-component glue, and then a steel pin is inserted. When solidified, the substance increases in volume and hardens, providing high resistance to pulling out and locally strengthening the structure of the material due to impregnation.
Chemical anchors for any wall material increase the fixing strength of the steel core by 40%, that is, the effect of crumbling concrete is almost completely absent.
Mechanical anchoring rules
The key moment when fastening with anchor bolts is strict regulation of the tightening torque. Excessive force is no better than insufficient force, very often due to exceeding the deformation threshold of the base material, its pronounced crumbling is observed. Recommended torque values are set by the manufacturer, but if the official specification is not available, the following guidelines can be used:
|Diameter||Recommended torque for frame / bolt anchors, Nm|
There are also subtleties of the installation process: the holes must be cleaned, or better – rinsed from the drill crumbs. If there are several anchoring points for one node, you should first pre-fix the anchors in the holes, and only then final tighten them. In the latter, order is important: the anchors are tightened in pairs from diametrically opposite attachment points.
Use of chemical anchors
The technique of fastening with chemical anchors is generally simpler, but the exact composition of installation operations differs from almost every manufacturer. Correct preparation of the hole is important here as nowhere else: it is first blown out with a hand pump, and then cleaned with a steel brush and dust is blown out again.
For household installation, anchors are used, in which the components of the glue are placed in a sealed capsule, which is destroyed when the stud is screwed in. This is the simplest type of installation, but it is not suitable for the assembly of critical structures due to insufficient mixing of the components.
For a more durable fastening, anchor chemistry compositions are used, supplied in special two-component syringes. In the prepared hole, the composition is injected at half the depth, after which a hairpin or a mortgage rod is inserted into the mass in one motion. This method is distinguished not only by its high strength, but also by a very economical consumption of glue..


text:
Have you ever applied Dermabond to a simple laceration in your ED, and had the patient react like this:
“Really? You are just using super glue? I could have bought that at a hardware store and done that myself.”
Think for a moment. How would you respond to a comment like that?
I had an interaction like this not too long ago. Though the patient was ultimately amicable and appreciative for my services, I came to realize that I didn’t really have a great answer for my patient as to why this particular product in my hands was better than Krazy glue from Ace Hardware applied by himself in front of his bathroom mirror. This got me thinking about the topic, and about my limited knowledge of tissue adhesives as a medical provider. It also got me reading about the specific merits of 2-octyl cyanoacrylate (Dermabond) and other commercially available tissue adhesive glues for medical use.
In my search, I found some of the answers I was looking for, as well as some recently published interesting case reports regarding tissue adhesive glue use that help to illustrate the point. The goal of this brief post is to give you a little food for thought regarding tissue adhesives that may help arm you better for this discussion with your patient. Without further ado, I present three things you didn’t know about skin glue:
#1: Gluing skin is not totally harmless. You can get burned!
This image is the leg of a 2-year-old boy who sustained a full thickness burn when he applied an over-the- counter cyanoacrylate glue (akin to Krazy Glue) to his leg while wearing cotton pajamas. The burn depth and area was significant enough as to require a skin graft! A link to the details of this interesting case report is found here.
This is an uncommon outcome of applying cyanoacrylate glue to your skin, but it does illustrate an important point. When cyanoacrylate glues are placed in contact with cotton or other fabrics, it can lead to a rapid exothermic reaction which can cause burns. This is is felt to be less of a problem with medically produced tissue adhesive glues such as 2-octyl-cyanoacrylate. These glues have longer alkyl chains than over the counter glue for non-medical use (remember the figure at the top of this post that you didn’t quite understand why I included? That’s why.). Thus, they polymerize more slowly and release less heat.
#2: It is safer to eat dermabond than crazy glue.
Probably the most interesting recent novel use of Dermabond was published last year in the Journal of Emergency Medicine as a case report.
The case describes a 7-year-old-boy who had a laceration of his tongue. The parent of the child refused other methods of closure, leaving tissue adhesive glue as the only option for primary repair.
Appropriately, the physician caring for the patient wanted to make sure there was no chemical hazard related to swallowing 2-octyl cyanoacrylate before trying it. As it turns out, the earliest generations of medical tissue adhesives, introduced in the 1950s, actually did have some cell toxicity (in the lab setting). But newer generations of tissue adhesives like 2-octyl cyanoacrylate have longer alkyl chains (I know, I know…again with the long alkyl chains), which effectively means they degrade slowly and this limits exposure of the patient to by-products. So…safe if swallowed.*
(*There is a theoretical risk of bowel injury if the glue hardens in such a way as to form a sharp point when swallowed, but this has never actually been reported.)
Generally, we think of tissue adhesives as not being the best choice for “wet areas,” like intraoral lacerations. If you read the package insert for Dermabond by the manufacturers, it is specifically stated that it is not approved for use on mucosal surfaces. So, repairing a tongue would be considered an off-label use. But, there are other reports in the literature of the use of tissue adhesive glue for cleft palate repair and dental indications, thus there is a precedent.
So in this case, the physicians repaired the tongue using dermabond. I’ll let you refer to the actual case report for details of the technique, but take a look at the final outcome:
#3: It is not “just” superglue. It is antimicrobial.
An interesting property that is common to all cyanoacrylate glues is a bacteriostatic (and possibly bactericidal) effect. Many very smart biochemists have done excellent work trying to figure out what the exact mechanism(s) of action is/are, but it is still not totally clear.
What we do know is that the antimicrobial effect is stronger against gram-positive than gram-negative organisms; that the anti-microbial effect seems to be at least in part be due to the physical barrier that the polymerized glue creates; and that if the glue is compromised or cracked, the anti-microbial effect is diminished.
Over the counter cyanoacrylate glues tend to be more brittle and apt to crack compared with medically produced ones, which are made intentionally more flexible to accommodate the dynamic movements of the skin. (Once again, this has something to do with those long alkyl chains.) Thus, further argument for the use of medically-approved tissue adhesive glue compared with hardware store Krazy Glue: while all the cyanoacrylates are antimicrobial, medical glue is perhaps more antimicrobial?
A source for this blog post and an excellent, comprehensive review of cyanoacrylate glues was published last year in Wilderness and Environmental Medicine. The authors compare and contrast medical and non-medical cyanoacrylate glues in incredible detail. Their intent was to determine if non-medical glues have justification for use in austere settings (can you guess what their conclusion was?). I encourage you to read their review. Their discussion is much more detailed than the simple points made in this blog post.
Thanks for reading. I hope that when you are using Dermabond for your next patient with a simple traumatic laceration, you will do so knowing just a little bit more about why you are doing it. If you remember nothing else, remember to tell the patient with confidence: “this specially formulated skin glue has a long alkyl chain.” Trust me, the patient will be impressed.
For a review of the technique of application of tissue adhesive glue, click here.

domain: medical


text:
WILMINGTON — A suspect in an alleged assault with a machete is claiming self-defense.
Rob Baker, defense attorney for Lee DeBord, made a new claim of self-defense at a hearing in Clinton County Common Pleas Court on Wednesday.
DeBord faces two charges of felonious assault and one charge of tampering with evidence for allegedly assaulting his roommate, Roger Tucker, with a machete at their residence in the community of Cuba, south of Wilmington, in late July.
Baker also made a motion to have an expert in wounds and blood splatter as a witness.
Baker told Judge John W. “Tim” Rudduck he has spoken with two experts in wounds and blood spatter that could potentially testify and prove the self-defense claim.
“An expert can in many cases taking a look at the wounds, the angle in which the wound was caused, the depth of the wound, the location on the body to determine it was an offensive move or a defensive move,” said Baker.
Rudduck asked if Baker had an estimated cost or timeline as to when this could take place. Baker said he did not, but he advised he was also waiting to hear back from a third possible expert.
Rudduck decided to continue the hearing on Nov. 8 so Baker could provide an estimated cost and timeline.
Authorities have said they believe this wasn’t a “random act of violence.”
DeBord fled the scene and evaded authorities for about a week until he was apprehended in Clermont County, police said.
Reach John Hamilton at 937-382-2574

domain: law


text:
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We tend not to think about France as a world capital of contemporary theater. The most popular French playwright of the past few years is Yasmina Reza, author of Broadway and regional hits such as "Art" and "God of Carnage." More often we're used to seeing French plays of an older vintage, by Molière, Sartre or Ionesco.
"Des Voix ... Found in Translation" is a theater project that wants to change how we think about modern French theater. Subtitled "A Festival of Contemporary French Playwrights in Translation," this new event, happening Friday through next Sunday, is a trans-Atlantic collaboration between organizations in San Francisco and Paris.

domain: artistic


text:
Jennett I have been looking for information on the Hairs of NC for a long time and just came across your post. There must not be too much research from NC Hairs on their families as I too am receiving no response to my posts.
I have been looking for info on Jesse Hair who married Dicey Lockerman in 1836 in Cumberland County, NC. I think I can help you some if you have not found your answers. I recently found the website for the Cumberland County Register of Deeds and their database of land records go back to 1754. A search will reveal a division of the estate of your Jesse Hair by the Court of Pleas and Quarters. This document names the wife of Jesse and some of his children. The rest of his children can be found from deeds where they sold their shares of the estate to siblings.
Jesse's wife was Nancy and they had 12 children.
Catherine b. abt. 1798 d. abt 1842 m. Duncan Bedsole 1825 Margaret b. abt 1800 m. Matthew Hale 1817 Nancy b. abt 1804 m. William Hollingsworth 1825 Mary b. abt 1804 m. Jonathan Averitt 1829 John b. 1809 d. 1887 m. Eliza Ann McGill 1837 Roger b. 1810 m. Ann Jane Sterling 1835 Jesse b. 1811 d. bet. 1884-1888 m. Dicey Lockerman 1836 Duncan b. abt 1814 m. Martha Jane Anderson 1843 William m. Margaret Everitt 1846 Stephen m. Nancy Averitt 1843 Reuben m. Nancy Anderson 1844 Jennett b. abt 1803 m. James Hall 1826
All of the marriages occurred in Cumberland County. I believe most of them stayed in NC. John, Roger and Jesse moved to Georgia after they married.
Jesse may have had a brother named Stephen and their father may have been Simon Pharis Hair of Bladen County. I have only pieced this together in the last couple of months so I am not 100% sure it is correct but it appears promising. Maybe it will give you a boost if you still need it.

domain: history


ŠTV 1 Live Streaming and TV Listings
Competitions available on ŠTV 1
Germany - Bundesliga (2021-2024)
Germany - Bundesliga 2 (2021-2024)
Netherlands - Eredivisie (2021-2024)
What satellites is ŠTV 1 available on?
|DVB-S2, QPSK, MPEG-4
ŠTV 1 History, Coverage, Features
Sport TV 1 is a Slovenian television channel owned and operated by Sport TV ASPN. This channel became the first public sports network in the country when it was launched on October 14, 2006. The network has included two more channels, Sport TV 2 and Sport TV 3 to add depth to the network’s sports coverage in the country.
Over the years, Sport TV 1 has been known for covering a wide variety of sports, which have included football, ice hockey, basketball, handball, rugby, triathlon, sailing, cycling, and motorsports. While the network has focused on international tournaments, there have been some domestic competitions aired on its channels as time has gone by.
Speaking of football, Sport TV 1 has aired leagues such as the German Bundesliga, the Australian A-League, the Eredivisie, and the Czech First League. Other high-profile tournaments that have been aired on this channel have included the Copa del Rey and the International Champions Cup. On top of that, national team football has also been available on Sport TV 1, with competitions such as the Copa América, the AFC Asian Cup, or the Toulon Tournament being covered on this channel.
Sport TV 1 was conceived as a Standard Definition channel, but satellite TV users might be able to watch an upscaled version of the channel.
The published listings of live, re-aired, and on-demand match and program events published on this website are broadcast by the official rights holders. They are available on various platforms such as terrestrial TV, radio, cable, satellite, IPTV, mobile and desktop apps. Where possible, we will provide links to the streaming events available on the platforms provided by the official broadcasters. Please note that in many cases, a digital subscription or user authentication with a TV or internet provider will be required. We endeavor to provide as accurate and detailed broadcast information as possible. However, broadcast schedules are subject to change at any time. If you find incorrect or missing information, please let us know


text:
MADISON, Wis. – In a recent interview with the Cap Times, Republican candidate for governor Rebecca Kleefisch failed to outline a comprehensive plan to improve public safety or defend her disastrous record on slashing funds that have helped hire first responders.
Kleefisch’s proposals for public safety have already been panned by her primary opponent, Kevin Nicholson, as “not a serious” plan. Nicholson also hasn’t presented a public safety plan that amounts to more than talking points … but we agree with him: Kleefisch isn’t serious about public safety.
Lieutenant Governor Kleefisch’s administration slashed shared revenue to localities, which is a crucial funding stream for various programs, including police departments, by $76 million in 2011 alone. Then she made the situation worse by cutting off the lifelines from localities that might have allowed them to make up the difference.
The Cap Times reports: “Wisconsin has seen a 15% decrease in the number of law enforcement officers working in the state, the Badger Project reported last May. During mostly the same period — from 2014 to 2021 — shared revenue from the state to local municipalities has barely grown.”
These policy decisions made it harder for localities across the state to be able to fully fund their community’s commitment to public safety.
According to the Cap Times, Kleefisch now wants to add additional restraints on how communities spend shared revenue, but didn’t say whether she supports increasing those funds to local governments. She also failed to offer specifics on how the state would assume responsibility for hiring local officers, a responsibility that falls on local departments and municipalities.
Kleefisch’s refusal to prioritize public safety doesn’t come as a surprise. In fact, cutting shared revenue is not the only move that defunded public safety in Wisconsin under the Walker-Kleefisch administration, they also:
On the other hand, Governor Evers has made funding public safety a priority. While attempts to restore funding to shared revenue have been rejected on multiple attempts by the Republican legislature, Gov. Evers has provided funding to law enforcement through funding of body-worn cameras, equipment, training, community-oriented police houses, increases to the Department of Corrections and Department of Justice, and mental health crisis intervention. Gov. Evers also recently invested $45 million in public safety efforts across the state, including $8 million to the Milwaukee Office of Violence Prevention.
“Their lack of a comprehensive plan to address public safety and invest in violence prevention makes it clear: Rebecca Kleefisch and Kevin Nicholson would make Wisconsin less safe,” said Democratic Party of Wisconsin Rapid Response Director Hannah Menchhoff. “Kleefisch says she wants to put more police on the streets when, in fact, she was responsible for undercutting localities’ ability to hire more law enforcement in the first place. Republicans are part of the problem, not part of the solution.”

domain: sociology


im using SONY-DVD-RW(DMW47A2)blank media-for burning video-files
the dvd states that it can hold 4.7GB/120mins of data
i have just burned a folder containing 4.1gbs= 22 individual wmp video clips all ranging from 10-15mins in length…onto the dvd
doesnt that exceed the so called 120mins?
i burned the dvd as a data dvd in nero…all went smooth
and i can play each clip fine on the pc.
but if you add all these video clips length together it exceeds well more that 120mins???
why does the dvd state it can only hold 120mins of video…when ive managed to burn over 4hrs worth


text:
|Born||1 September 1861|
|Died||13 February 1931 (aged 69)
Lieutenant-General Louis Bernheim (1 September 1861 – 13 February 1931) was a Belgian career soldier and general, best known for his service during World War I. He is also notable as one of Belgium's highest ranking soldiers of Jewish origin.
Louis Bernheim was born into a Jewish family in Saint-Josse-ten-Noode, Brussels in Belgium on 1 September 1861.  His parents had emigrated to Belgium from Nancy, France in 1858.  Entering the École Militaire in 1878, he joined the Regiment of Grenadiers as a second lieutenant at the age of 19.  He later taught at the Royal Military Academy in Brussels and rose through the ranks rapidly. By the time of the German invasion of Belgium in August 1914, Bernheim was serving as a lieutenant-colonel in the 7th Regiment of the Line.
Bernheim was promoted to command the 3rd Brigade during the Siege of Antwerp in September 1914 and commanded his unit during the fighting around the Nete.  He was promoted to major-general in November and, in 1915, was given command of the 1st Army Division in the Steenstrate section of the Yser Front.  During an inspection of his troops at the front in September 1915, he was severely wounded by an enemy artillery shell but returned to service after just two months' convalescence.  In March 1916, he was promoted to the rank of lieutenant-general. His command of the 1st Army Division coincided with the emergence of the Frontbeweging in 1917, a Flemish Movement group which began to agitate against perceived discrimination in the Belgian Army. Bernheim was criticized personally by Flamingant soldiers for his attempts to suppress it.
In September 1918, he was placed in command of a group of three army divisions on the Yser during the Belgian advance in the Hundred Days' Offensive.  Berheim's units were notably involved in the capture of the important forest at Houthulst.  After the end of the war, he was promoted to Inspector General of the Infantry and he officially retired from the army in 1926.  Among the awards received by Bernheim during his career was the Légion d'honneur and the Order of the Bath.
Bernheim died in 1931 while visiting his daughter in Paris, France. As a freethinker, he had demanded to be cremated at his death and, because Belgian law did not permit it at the time, was cremated in France.  His funeral was attended by King Albert I  and the former prime minister, Charles de Broqueville. Bernheim is memorialised by an avenue in Etterbeek and by a public statue by Edmond de Valériola on the Square Marie-Louise, both in Brussels.


text:
As I already mentioned on the Quotes of the Week post, I have decided that this will be my last Recipes of the Week post. I'm not sure what I'm going to do, but ideas would be appreciated. What is your favorite thing to eat in the world?
What is your favorite type of cuisine (Chinese, Italian, Mexican, et cetera)?
Do you have a favorite recipe to follow?

domain: food


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|Weight:||100 KG||Power:||220V 50Hz Single Phase|
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Covered with air bubble film before put the machine into the wooden case, which not only has good shock absorption, impact resistance, heat sealing and also has the advantages of nontoxic, odorless, moisture corrosion, good transparency etc.
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Hot Air Cycling Drying Temperature Humidity Test Chamber Economical Customized


text:
Polarization-sensitive optical coherence tomography (PS-OCT) enables noninvasive, high-resolution imaging of tissue polarization properties. In the anterior segments of human eyes, PS-OCT allows the visualization of birefringent and depolarizing structures. We present the use of PS-OCT for imaging the murine anterior eye. Using a spectral domain PS-OCT setup operating in the 840-nm regime, we performed in vivo volumetric imaging in anesthetized C57BL/6 mice. The polarization properties of murine anterior eye structures largely replicated those known from human PS-OCT imagery, suggesting that the mouse eye may also serve as a model system under polarization contrast. However, dissimilarities were found in the depolarizing structure of the iris which, as we confirmed in postmortem histological sections, were caused by anatomical differences between both species. In addition to the imaging of tissues in the anterior chamber and the iridocorneal angle, we demonstrate longitudinal PS-OCT imaging of the murine anterior segment during mydriasis as well as birefringence imaging of corneal pathology in an aged mouse.
We implemented a wide field-of-view visible-light optical coherence microscope (OCM) for investigating ex-vivo brain tissue of patients diagnosed with Alzheimer’s disease (AD) and of a mouse model of AD. A submicrometer axial resolution in tissue was achieved using a broad visible light spectrum. The use of various objective lenses enabled reaching micrometer transversal resolution and the acquisition of images of microscopic brain features, such as cell structures, vessels, and white matter tracts. Amyloid-beta plaques in the range of 10 to 70 μm were visualized. Large field-of-view images of young and old mouse brain sections were imaged using an automated x − y − z stage. The plaque load was characterized, revealing an age-related increase. Human brain tissue affected by cerebral amyloid angiopathy was investigated and hyperscattering structures resembling amyloid beta accumulations in the vessel walls were identified. All results were in good agreement with histology. A comparison of plaque features in both human and mouse brain tissue was performed, revealing an increase in plaque load and a decrease in reflectivity for mouse as compared with human brain tissue. Based on the promising outcome of our experiments, visible light OCM might be a powerful tool for investigating microscopic features in ex-vivo brain tissue.
Polarization-sensitive optical coherence tomography (PS-OCT) provides intrinsic contrast related to tissue microstructure. In the past, PS-OCT has been successfully used for imaging the anterior eye of humans in a variety of pathologic conditions. Here, we present PS-OCT imaging of the anterior eye in mice. Spectral domain PS-OCT centered at a wavelength of 840 nm was performed in anaesthetized laboratory mice. Three dimensional data sets were acquired at a 70 kHz A-line rate. PS-OCT images displaying phase retardation, birefringent axis orientation and degree of polarization uniformity (DOPU) were computed. Similar to human anterior segments, depolarization was observed in the corneal stroma and in structures containing melanin pigments such as the iris and the ciliary body. Birefringence was detected in the sclera close to the limbus. Aside from depolarizing foci observed within structures affected by cataract, the lens appeared mostly polarization preserving. Increased birefringence was observed in a scarred cornea. Given the similarity of the polarization characteristics in the murine eye and the human eye, PS-OCT lends itself as an ideal candidate for non-invasive imaging in preclinical studies in mouse models of anterior segment pathology.
A few-mode fiber based detection for OCT systems is presented. The capability of few-mode fibers for delivering light through different fiber paths enables the application of these fibers for angular scattering tissue character- ization. Since the optical path lengths traveled in the fiber change between the fiber modes, the OCT image information will be reconstructed at different depth positions, separating the directly backscattered light from the light scattered at other angles. Using the proposed method, the relation between the angle of reflection from the sample and the respective modal intensity distribution was investigated. The system was demonstrated for imaging ex-vivo brain tissue samples of patients with Alzheimer’s disease.
A visible light spectral domain optical coherence microscopy system operating in the wavelength range of 450-680 nm was developed. The resulting large wavelength range of 230 nm enabled an ultrahigh axial resolution of 0.88μm in tissue. The setup consisted of a Michelson interferometer combined with a homemade spectrometer with a spectral resolution of 0.03 nm. Scanning of 1 x 1 mm2 and 0.5 x 0.5 mm2 areas was performed by an integrated microelectromechanical mirror. After scanning the light beam is focused onto the tissue by a commercial objective with a 10 x magnification, resulting in a transverse resolution of 2 μm . Specification measurements showed that a -89 dB sensitivity with a 24 dB/mm roll-off could be achieved with the system. First of all the capabilities of the system were tested by investigating millimeter paper, tape and the USAF (US Air Force) 1951 resolution test target. Finally cerebral tissues from non-pathological and Alzheimer's disease affected brains were investigated. The results showed that structures, such as white and gray matter, could be distinguished. Furthermore a first effort was made to differentiate Alzheimer's disease from healthy brain tissue.

domain: biology


text:
Joburg’s most loved art event returns to Sandton this September with a celebration guaranteed to excite and delight.
For a decade, the hotly anticipated FNB JoburgArtFair has been an undisputed highlight in South Africa’s art calendar. For one weekend, the Sandton Convention Centre’s main exhibition hall becomes the heart of art and a visual celebration of the work of over 600 of the greatest contemporary African artists alive. A weekend of education, appreciation and celebration, it’s guaranteed to make you feel proud of the immense artistic talent coming out of Africa.
Since the fair’s inception in 2008, the organising team have worked hard to go beyond just exhibiting the works of contemporary African artists: instead, each of their events is also rooted in growing a sustainable industry for the arts, with a solid base of both local and international buyers. The fair reaches record sales and visitor numbers each year, with 2017 set to be more impressive than ever before. And with such a varied schedule of immense talent, that’s no surprise: From a programme of lectures, discussion and interviews, to an artisanal choice of food and wine for visitors to enjoy between galleries, and, of course, the artworks themselves, the fair is guaranteed to thrill and intrigue.
At the FNB JoburgArtFair’s first edition, Cape Town-born artist Robin Rhode was chosen to be the fair’s inaugural Featured Artist, and will this year he will be filling this role once again. Now living and working in Berlin, and having had major shows across the world, Rhode’s return to the fair is a beautiful symbolic celebration of how the event has grown so much in ten years – just as the artist has himself.
An unmissable feast for the eyes, it’s clear that celebration will be a key focus of the fair this year. “This year is about celebrating our galleries who have grown with the Fair, our artists who drive the discourse, our patrons who have unwaveringly supported us and our audience whose curiosity continues to inspire our delivery,” says FNB JoburgArtFair director, Mandla Sibeko. “Over the years, FNB JoburgArtFair has become a benchmark platform for contemporary African art and we look forward to continuing that tradition in our 10th edition this September.”
The fair runs from 8 to 10 September, and tickets are available from www.tixsa.co.za.
Taste for yourself:
- FNB JoburgArtFair | 011 447 3868 | fnbjoburgartfair.co.za
This article originally appeared in Neighbourhood, Sunday Times.


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June 6, 2012
Each year young adults from all over Suffolk County put their "book smarts" to the test as they compete in The Battle of the Books. This year's booklist has been announced!
Happy summer reading,
Battle of the Books 2012posted Jun 5, 2012, 6:00 PM by Christine Brower-Cohen [ updated Jun 5, 2012, 6:00 PM by Ryan Case ]

domain: literature


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“Jack Reacher,” with Tom Cruise starring as the title character, is an action film about an Army cop investigating a seemingly senseless shooting and the alleged perpetrator. “Reacher” reached deep into my soul and touched me deeply. Cruise cruises through his performance as the charismatic, loner, rule breaker, who just kicks donkey and takes names through out the movie.Reacher is a retired Army investigator who is personally requested by the alleged shooter. Of course the shooter is being framed and it’s up to Reacher to figure this out. No SPOILER ALERT: because the movie opens up with the shooting and the audience can clearly see that the shooter is the not the man arrested.
Cruise comes cruising in, via the public bus, the minute the DA and lead investigator are exasperated from a fruitless search for Reacher. Side not, the DA’s daughter just so happens to be representing the accused gunman.
Reacher is the consummate “bad donkey” there’s just not other way to describe him. Numerous people come from a confrontation with him in much worse shape than before the encounter, yet nobody seems to learn his lesson. I call them “Wyatt Earp Moments,” similar to but not synonymous with “(Foolish) Moments” made famous by “Granddad,” “Riley” and “Huey” Freeman on “The Boondocks.”
Allow me to explain, “Wyatt Earp Moments.” For most American men between the ages of 30-45 “Tombstone” starring Kurt Russell as Wyatt Earp and Val Kilmer as Georgia’s own, Doc Holiday, is THE western cult classic. It just is, if you’ve seen it you know, if you haven’t seen it, why do you hate America?
When my dad saw “Tombstone” for the first time, we came to the “Easy Kid” scene. For those who don’t know, a young man bumps into to Earp, and the following exchange takes place:
“I aint easy, and I aint your kid. I’ll fight you right now.”
The young man then promptly pulls his vest back to reveal his side arm. Earp responds by grabbing the young man’s side arm and knocking him out with his own weapon. At this my dad asked a most significant question.
“Don’t they know he’s Wyatt Earp?”
Hence the “Wyatt Earp Moment” was born, in short, it’s when one is watching a movie/TV show and someone challenges the character that is known for being a “bad donkey.” Why would you do that? It’s obvious this guy is not one that takes kindly to be harassed, yet people constantly harass him and they always end up hurt or dead.
That’s Reacher in a nutshell. The entire movie I’m just watching and shaking my head, thinking, “didn’t you just see the last guy get his (donkey) whooped? Now here you go.”
SPOILER ALERT: Now I have to admit “Reacher” “had me at hello,” so to speak. On a previous nerd night we saw a trailer for “Reacher” that showed Cruise in a high speed chase with the police, which ends with Cruise calmly stepping out of the car and onto the bus stop while the car continues to roll by. The people at the bus stop promptly step in front of Cruise and one guy hands him a hat. HIGHLARIOUS, I knew at that moment I had to see “Jack Reacher.”
While watching it in the theater, it was interesting to see/hear the audience’s reaction, because that scene was not in any of the TV commercials so most people had no idea that was about to happen. The audience seemed to enjoy it as much as I did the first time around.
Speaking of the audience I must say that while I normally don’t encourage loud outbursts in the theater; however, one gentleman’s boisterous description as a character “got Pacquiaoed” may have been the most apropos outburst ever.
I’m strongly considering replacing Smokey’s most famous description of Red getting knocked out by Debo with “You got Pacquiaoed” as the go to for those worldstar situations where someone gets dropped like Tears Tebow on the depth chart.
In short, reach for “Jack Reacher,” it definitely does not overreach with too much plot and story; just enough to keep the movie going in between fight scenes. Robert Duvall has a small part as a retired sharp shooting Marine that is just icing on the cake, and the chemistry between Reacher and the defense lawyer is palatable.
SPOLER ALERT: Reacher’s reaching for the keys, (you’ll know when you see it) is one of the funniest, most awkward, don’t be so stuck on yourself moments I’ve ever seen. Also Rene from “True Blood’s” last meal is truly finger food.


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HASBROUCK HEIGHTS, NJ - The 2020 Hasbrouck Heights Municipal Budget was passed along party lines Wednesday night at the meeting of the Hasbrouck Heights Mayor and Council. The meeting was conducted online via Zoom. Mayor Jack DeLorenzo announced that the July meeting will be held in Council Chambers.
Democratic Councilmen Christopher Hillmann and Steven Reyngoudt voted against the budget as well as an ordinance establishing a cap bank. A “cap bank” allows the governing body to “bank” the permission it was given to spend a certain amount of money in one year, but which was not actually spent, for use in subsequent years.
Republican Councilmen Justin DiPisa, Ron Kistner, Russell Lipari and Councilwoman Josephine Ciocia voted to approve both measures.
The budget, which can be found on the Hasbrouck Heights website, would raise taxes, for the municipal portion approximately $114 according Hasbrouck Heights Borough Administrator Michael Kronyak. He noted that does not include the County and School Budgets, which he is not responsible for, but gets passed through local tax bills.
Councilman DiPisa was appointed the Hasbrouck Heights Municipal Representative to the Bergen County Community Development Regional Committee, with Councilman Kistner as the Alternate Representative. Hasbrouck Heights Recreation Director Rob Brady was appointed as Hasbrouck Heights’ representative to the Open Space Trust Municipal Program Regional Committee.
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domain: news


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Simply stated, Materion makes advanced materials that improve the world. We are a global leader in creating innovative, high performance engineered material solutions and services for a wide range of growth industries: high-tech consumer electronics , telecommunications , commercial aerospace , defense , medical , automotive , and many more.
Our products, services and expertise help enable our customers' technologies. We supply sophisticated thin film coatings for hard disk drives, specialty inorganic chemicals for solar energy panels, bio-compatible materials for implantable medical devices, specialty alloys for miniature consumer electronics components, optical filters for thermal imaging, critical components for infrared sensing technology, special materials for LEDs and much more. As the world's only integrated "mine-to-mill" supplier of beryllium-based products, we also offer beryllium, specialty engineered beryllium alloys and beryllium composites.
In 2016, we generated approx. $1B in revenue. As a team of 2,500 associates, we partner with customers in more than 50 countries. In early 2017, Materion closed on an exciting new acquisition that expands our footprint in the U.S., Europe and Asia.
For more information, please visit our website at http://materion.com/About and check out our video " Materion Is " along with other videos of our employees sharing what it means for them to work at Materion.
Click on any of the icons below to connect with Materion on social media.
JOB PURPOSE AND REPORTING STRUCTURE
* Under the direction of the Associate Supervisor, the Chemical Operator is responsible for the proper refining of precious metals.
ESSENTIAL DUTIES & RESPONSIBILITIES
* Responsible for the chemical refining of precious scrap in accordance with all standard operating procedures as directed.
* Responsible for the proper care and use of refinery equipment and safe chemical handling.
* Must be able to safely receive and store chemicals from chemical deliveries and replenish emptied chemical containers.
* Helps to monitor pollution control equipment to assure compliance with air and water discharges.
* The above statement reflects the general details necessary to describe the principle functions of the position described and shall not be construed as a detailed description of all the work requirements that may be inherent in the role.
EDUCATION and/or EXPERIENCE
Background in chemical processing preferred. High school graduate or equivalent. Background in chemistry preferred. Knowledge of safe chemical handling and storage preferred. Must complete company training program.
** Starting salary approximately $40,000+ based on experience **
Monday-Friday - 2nd shift - 2:30pm-11pm
Training occurs during the day for ~6months

domain: chemistry


Two goals from Scott Barbour, and a contribution from Roy Noble, was enough for Fraserburgh to secure a comfortable 3-0 win against Junior side Broughty Athletic for the Lyall Murdoch trophy.
The Lyall Murdoch Trophy is an annual competition in which the trophy is switched between Dundee and the Broch. This year’s victory is only the second time Fraserburgh have held the trophy since the tournament’s beginnings four years ago.
Broughty looked to dictate the tempo of the game at Bellslea with their attacking flourish, with a number of chances wasted from the Broch.
Graham Johnston made the most of his chance, but his miss, in the first-half, on Saturday saw his powerful free-kick safely taken care of by the travelling Alan Cormack in goal.
Scott Barbour, who would later confirm the win for the Broch also saw a shot go wide of the post, his attempt rolling safely by the far post.
Just before half-time, and, arguably, the best chance for a goal came when Johnston smashed another free-kick from the byline into the danger area. Bryan Hay was present to direct the ball goalwards with a header, seeing it rebound from the crossbar before Steven Davidson tried smashing it in from short range, Broughty’s Cormack getting in the way to ensure that the sides would go into the second-half all square.
Whether something was said at half-time or not, Fraserburgh looked to have found their composure in front of goal, with Scott Barbour - a regular contributor to last season’s Highland League efforts - sending the Broch in front early into the second-half.
From a corner, Barbour smashed a volley towards the goal from several yards out, leaving the Broughty ‘keeper helpless to prevent his side going behind.
Barbour continued to lead the Broch’s attack throughout the second-half, coming close to making Broughty pay for a poor back-pass, being fed the ball by Zander Davidson, his attempt, while finding away past the Broughty keeper, was unlucky to find the post in defiant mood.
It was Roy Noble who found the second goal that all but sealed Broughty’s defeat last weekend, his day made easy with a goal coming shortly after his substitution and via a short-range tap-in following a Mark Cowie cross.
Scott Barbour, however, made sure that his name was not forgotten by the travelling Dundee side when he showed up not long after Noble’s goal to fire a shot into the back of the net despite heavy marking from Broughty.
Fraserburgh, with trophy in hand and victory against a Dundee side will not look to continue to build upon their form with their next pre-season game at Longside, tonight.
On Tuesday, however, the Broch suffered defeat to old rivals Peterhead when they missed out on adding the Buchan Shield to their trophy cabinet.
A goal from the Blue Toon’s Robbie Winters, beating John Calder in goal for the Broch, was enough to ensure that the Broch, who held their own in the tightly contested fixture against the Third Division side, would be leaving Balmoor empty handed.
The fixture was part of Peterhead’s Scottish Week celebrations.
The Fraserburgh Supporters Club are running a bus to Fraserburgh’s game at Huntly on Saturday, August 4 from the Harbour Office.
The bus leaves at 12:45pm.


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District says it reported a complaint to the Arizona Interscholastic Association
YUMA, Ariz. (KYMA, KECY) - A Yuma High School varsity basketball player claims she was inappropriately touched by a referee at a game in Phoenix.
The alleged incident happened on January 19, during the Lady Criminals' game at Shadow Mountain High School.
The victim's mother reached out to us saying the game continued to be played after the alleged incident. The mother claims her daughter had just made a play and put her hands on her knees and bent over to catch a breath. She claims at that time, the referee came behind her and grabbed her rear with an open hand.
She says that her daughter and a teammate immediately reacted to the referee’s actions and that the two were suspended for two games by the school.
Both games Thursday and Friday were cancelled.
The Yuma High School principal provided us with this response:
"Regarding the allegation of “inappropriate touching” by an official in the Shadow Mountain game on Jan. 19: Yuma High School administrators were made aware of the incident on the night of the game. We have worked with the student-athlete’s parents to support them, including sharing our concerns with the Arizona Interscholastic Association (AIA), speaking with the Paradise Valley School District athletic director, and speaking with administrators at Shadow Mountain. AIA has assured us that the incident was reviewed and they are taking appropriate measures."
We have reached out to the Arizona Interscholastic Association for comment, and are waiting to hear back.
To note, the team has had issues with having enough players on the roster. We asked YHS about the matter, to which the school responded, "As for your second question about the team in general, the number of varsity student-athletes has fluctuated throughout the season, unfortunately. This has been related to a number of factors, including academic commitments for some of the girls."
The district also said two games were recently canceled due to a limited number of available student-athletes. The district said, "Assistant Coaches Jasmine Barraza and Isabel Ponce have been leading the team recently. We are unable to provide any additional details regarding personnel matters at this time."


Inertial sensors have been used for several decades in aerospace system for attitude control and navigation. Drastic advances in microelectromechanic systems (MEMS) have lead to the development of miniaturized strapdown inertial measurement units (IMUs), which entered a multitude of new application domains from autonomous drones to ambulatory human motion tracking.
In strapdown IMUs, the angular rate and acceleration – and sometimes also the magnetic field vector – are measured in a sensor-intrinsic three-dimensional coordinate system, which moves along with the sensor. Estimating the orientation, velocity or position of the sensor with respect to some inertial frame requires strapdown integration of the angular rates and sensor fusion of the aforementioned raw measurement signals (cf. Figure1).
To estimate the orientation of an IMU from its raw measurement signals in real time is a fundamental standard problem of inertial sensor fusion. A large variety of filter algorithms have been proposed previously, some of which are implemented in motion processing units of modern miniature IMUs. It is well known that the attitude of the sensor can be determined by 6D sensor fusion, i.e. fusing 3D gyroscope and 3D accelerometer readings, while estimating the full orientation (attitude and heading) requires 9-axis sensor fusion, i.e. using 3D magnetometer readings in addition to the 6D signals.
Existing solutions to inertial attitude estimation are typically model-based and heuristically parameterized. They use mathematical models of measurement errors and three-dimensional rotations and transformations of the gravitational acceleration. They require a reasonable choice of covariance matrices, fusion weights or parameters that define how weights are adjusted. While considerably high accuracies have been achieved with such solution approaches in many application domains, it is also well-known that different parameterizations perform differently well for different types of motions and disturbances. In fact, to the best of our knowledge, there is to date no filter algorithm that yields consistently small errors across all types of motion that a MEMS-based IMU might perform.
Abundant research has demonstrated the capabilities of artificial neural networks in providing data-based solutions to problems that have conventionally been addressed by model-based approaches. If sufficiently large amounts of data and computation capability are available, generally usable solutions may be found for most problems. While ample work has shown that a number of problems can also be solved using neural networks, the practically more relevant question whether neural networks can outperform conventional solutions often remains unanswered.
In the present work, we investigate whether a neural network can solve the real-time attitude estimation task with similar or even better performance than a state-of-the-art inertial orientation estimation filter. Moreover, we analyze at which cost this can be achieved, in terms of required number of data sets, required complexity and application-specific structure of the neural network.
Ii Related Work
We first briefly review the state-of-the-art in real-time attitude estimation from inertial sensor signals and then describe previous work on the use of artificial neural networks for inertial motion analysis.
Ii-a Inertial Attitude Estimation
As mentioned above, the attitude of an IMU can be determined by sensor fusion of the accelerometer and gyroscope readings. Accelerometers yield accurate attitude information in static conditions, i.e. when the sensor moves with constant velocity. Under dynamic conditions, however, their readings are only useful under certain assumption, for example that the average change of velocity is zero on sufficiently large time scales. Gyroscopes yield highly accurate information on the change of attitude. However, pure strapdown integration of the angular rates is prone to drift resulting from measurement bias, noise, clipping and undersampling. Accurate attitude estimation under non-static conditions requires sensor fusion of both 3D signals.
. Most filters use either an extended Kalman filter scheme or a complementary filter scheme, and unit quaternions are a common choice for mathematical representation of the three-dimensional orientation. The balance between gyroscope-based strapdown integration and accelerometer-based drift correction is typically adjusted to the specific application by manual tuning of covariance matrices or other fusion weights. Methods have been proposed that analyze the accelerometer norm to distinguish static and dynamic motion phases and adjust the fusion weights in real time.
A rather recently developed quaternion-based orientation estimation filter is described in . It uses geodetic accelerometer-based correction steps and optional magnetometer-based correction steps for heading estimation. The correction steps are parametrized by intuitively interpretable time constants, which are adjusted automatically if the accelerometer norm is far from the static value or has been close to that value for several consecutive time steps. The performance of this filter and five other state-of-the-art filters has recently been evaluated across a wide range of motions. For all filters, errors between two and five degrees were found for different speeds of motion . To the best of our knowledge, a significantly more accurate solution for attitude estimation in MEMS-based IMUs does not exist.
Ii-B Neural Networks for Attitude Estimation
In inertial motion tracking, neural networks have mostly been applied to augment existing conventional filter solutions. In  a Recurrent Neural Network (RNN) is used for movement detection in order to decide which Kalman filter should be applied to the current system state. In
a feed forward neural network is used as for smoothing the output of a Kalman filter, while a RNN is used for data pre-processing of Kalman filter inputs in. A similar approach is used in , where a convolutional neural network is used for error correction of the gyroscope signal as part of a strapdown integration.
In  and  RNNs are used as blackboxes for the orientation integration over time. While the former uses a combination of gyroscope and visual data, the latter only relies on the gyroscope achieving similar results. In a few more recent works, neural networks have been applied directly as blackboxes for angle estimation problems. In  a RNN is used for human limb assignment and orientation estimation of IMUs that are attached to human limbs. It achieved a high accuracy at the assignment problem but was only partially successful at the orientation estimation problem. In  a bidirectional RNN is used for velocity and heading estimation on a two-dimensional plane in polar coordinates.
To conclude, an end-to-end neural network model for IMU-based attitude estimation has not been developed yet. All of the presented neural networks are either an addition to classical filters for attitude estimation or they address different problems.
Iii Problem Statement
Consider an inertial sensor with an intrinsic right-handed coordinate system . Neglect the rotation of the Earth and define an inertial frame of reference with vertical z-axis. The orientation of the sensor with respect to the reference frame is then described by the rotation between both coordinate systems, which can be expressed as a unit quaternion, a rotation matrix, a set of three Euler angles or a single angle and a corresponding rotation axis. Both frames are said to have the same attitude if the axis of that rotation is vertical.
If the true orientation of the sensor is given by the unit quaternion and an attitude estimation algorithm yields an estimate , then is the estimation error quaternion expressed in reference frame axes. The attitude estimation is said to be perfect if the estimated orientation is correct up to a rotation around the vertical axis. This is the case if the rotation axis of is vertical. If that axis is not vertical, then can be decomposed into a rotation around the vertical axis and a rotation around a horizontal axis. For any given with real part and third imaginary part , the smallest possible rotation angle of is . This corresponds to the smallest rotation by which one would need to correct the estimate to make its attitude error zero in the aforementioned sense.
These definitions allow us to formulate the following attitude estimation problem: Given a sampled sequence of three-dimensional accelerometer and gyroscope readings of a MEMS-based IMU moving freely in three dimensional space, estimate the attitude of that IMU with respect to the reference frame at each sampling instant only based on current and previous samples. Denote the sensor readings by and , respectively, with being the discrete time and the number of samples. The desired algorithm should then yield a sampled sequence of estimates with a possibly small cumulative attitude estimation error defined by
where is the true orientation of the sensor at time . In the following sections, we aim to develop an artificial neural network that solves the given problem and compare it to an established attitude estimation filter.
Iv Neural Network Model
In this work a neural network model with state-of-the-art best practices for time series will be implemented. Building upon that, further optimizations are introduced that utilize domain-specific knowledge.
Iv-a Neural Network Structure with general best practices
The performance of a neural network model depends on the model architecture and the training process. First we identify potential model architectures for attitude estimation. After that we develop an optimized training process for these architectures.
The model architecture consists of multiple layers that may be connected in multiple ways leading to different characteristics. First a method for modelling the dynamic system states has to be chosen. A common practice is to connect the model output to the model input creating an autoregressive model that stores the system state information in the single autoregressive connection. For longer sequences, the autoregressive model’s inherent sequential nature prevents parallelization and therefore an efficient use of hardware acceleration, which slows down the training. Using neural network layers that are able to model system states avoids the need of autoregression for dynamic systems. The most commonly used ones are Recurrent Neural Networks (RNNs) and Temporal Convolutional Networks (TCNs).
RNNs have recurrent connections between samples in their hidden activations for modelling the state of a dynamic system. There are different variants of RNNs with Long Short-Term Memories (LSTMs) being the most prevalent. LSTMs add three gates to the classical RNN, which regulate the information flow of its hidden activations. This stabilizes the stored state, enabling the application to systems with long-term dependencies, like integrating movements over a long amount of time. Because LSTMs are prone to overfitting, several regularization methods for sequential neural networks have been developed . Increasing the amount of regularization together with the model size is the main approach for improving a neural network without domain-specific knowledge. In the present work, we use a two-layer LSTM Model with a hidden size of 200 for each layer and a final linear layer that reduces the hidden activation count to four. These four activations represent the elements of the estimated attitude quaternion. In order to always generate a unit quaternion, the elements are divided by their Euclidean norm. The structure of the RNN model used in this work is visualized in Figure 2.
An alternative approach to RNNs for sequential data are TCNs. TCNs are causal one-dimensional dilated convolutional neural networks with receptive fields big enough to model the system dynamics. The main advantage of TCNs compared to RNNs is their pure feed-forward nature. Having no sequential dependencies leads to parallelizability and therefore fast training on hardware accelerators . The TCN’s receptive field describes the amount of samples taken into account for predicting a sample. Because TCNs are stateless, the receptive field needs to be large enough to implicitly estimate the system state from the input signals. Because of the dilated convolutional layers, the receptive field grows exponentially with the depth of the neural network allowing for large windows using a manageable amount of layers. In the present work, we use a 10-layer TCN with a receptive field of samples and a hidden size of 200 for each layer. The structure of that TCN model is visualized in Figure 3.
For linear and convolutional layers, batchnorm
is used. Batchnorm standardizes the layer activations, enabling larger learning rates and better generalization. Instead of the commonly used sigmoid or rectified linear unit activation functions, we use Mish, which achieved state-of-the-art results in multiple domains
. Mish combines the advantages of both activation functions. On the one hand, it is unbounded in positive direction and thus avoids saturation like rectified linear units. On the other hand, it is smooth like sigmoid functions, which improves gradient-based optimization.
For training, long overlapping sequences get extracted from the measured sequences, so the Neural Networks initializes with different states. Because RNNs can only be reasonably trained with a limited amount of time steps for every minibatch, truncated backpropagation through time is used
. That means that the long sequence gets split in shorter windows that are used for training, transferring the hidden state of the RNN between every minibatch. The measured sequences are standardized with the same mean and standard deviation values to improve training stability.
. For the training process we used the Fastai 2 API, that is built upon Pytorch
. One of the most important hyperparameters for training a neural network is the learning rate of the optimizer. We choose the maximum learning rate with the learning rate finder heuristic and use cosine annealing for faster convergence
. The learning rate finder heuristic determines the maximum learning rate by exponentially increasing the learning rate in a dummy training and finding the point at which the loss has the steepest gradient. Cosine annealing starts with the maximum learning rate, keeps it constant for a given amount of epochs and then exponentially decreases it over time.
The other hyperparameters of the neural network model, such as activation dropout and weight dropout, form a vast optimization space. To find a well performing configuration, we use population-based training . It is an evolutionary hyperparameter optimization algorithm that is parallelizable and computationally efficient. It creates a population of neural networks with different hyperparameters and trains them for some epochs. Then the hyperparameters and weights of the best performing models are overriding the worst ones, and minor hyperparameter variations are introduced. Repeating this process quickly yields a well performing solution.
Iv-B Loss Function
The output of the model is a quaternion that describes the attitude of the sensor. The loss function describes the accumulated error between the estimated and the ground truth values. In most cases, the mean-squared-error between the estimated and reference values are taken. In the present case, an elementwise mean-squared-error of the quaternion is not a reasonable choice, since the orientation cannot be estimated unambiguously with only accelerometer and gyroscope signals –a magnetometer would be necessary. An obvious solution would be to choose the loss function equal to the attitude error functionwith
However, experiments show that using this error definition leads to unstable training resulting from an exploding-gradient problem. This is caused by thefunction, whose derivative function explodes for arguments approaching 1, which is the target of the optimization problem:
Truncating close to 1 leads to a solution that is numerically stable with rare exceptions. Replacing the function with a linear term avoids the exploding gradient completely while keeping the monotonicity and correlation with the attitude:
Figure 4 visualizes the differences between both functions and their gradients.
Iv-C Data Augmentation
Data augmentation is a method for increasing the size of a given dataset by introducing domain-knowledge. This is a regularization method that improves the generalizability of a model and has already been applied successfully in computer vision and audio modelling . In case of the present attitude estimation task, we virtually rotate the IMU by transforming the measured accelerometer, gyroscope and reference attitude data by a randomly generated unit quaternion. Thereby, orientation invariance for sensor measurements will be introduced to the model.
Iv-D Grouped Input Channels
The default way of processing a multivariate time series is to put all the input signals into the same layer. An alternative way is to create groups of signals that interact with each other and disconnect them from those they don’t need to interact with. The idea is to alleviate the neural network’s effort in finding interactions between signals. This method has been applied previously to other tasks but without analysis of its impact on the performance . In the present application, the accelerometer and gyroscope are grouped separately, with the accelerometer providing attitude information at large time scales and the gyroscope providing accurate information on the change of orientation, as visualized in Figure 6.
The performance of the proposed neural network is compared to the performance of an established attitude estimation filter in experiments with a ground truth based on marker-based optical motion tracking. A MEMS-based IMU (aktos-t, Myon AG, Switzerland) is rigidly attached to a 3D-printed X-shaped structure with three reflective markers whose position is tracked at millimeter accuracy by a multi-camera system (OptiTrack, Natural Point Inc., USA). For each moment in time, the three-dimensional marker positions are used to determine a ground-truth sensor orientation with sub-degree accuracy.
To analyze the algorithm performance across different types of motions and different levels of static or dynamic activity, we consider a large number of data sets from different experiments with the following characteristics:
rotation: The IMU is rotating freely in three-dimensional space while remaining close to the same point in space.
translation: The IMU is translating freely in three-dimensional space while remaining in almost the same orientation.
arbitrary: The IMU is rotating and translating freely in three-dimensional space.
slow versus medium versus fast: The speed of the motion is varied between three different levels.
paused versus nonstop: The motion is paused every thirty seconds and continued after a ten-seconds break or it is performed non-stop for the entire duration of the five-minutes recordings.
Different combinations of these characteristics lead to a diverse data set of 15 recordings each of which contains more than 50,000 samples of accelerometer and gyroscope readings and ground-truth orientation at a sampling rate of 286 Hz. Figure 5 shows the Euclidean norms of the three axis of acceleration (acc) and angular rate signal (gyr) over time for three experiments with different combinations of the described characteristics.
The experimental data is used to validate and compare the following two attitude estimation algorithms:
Baseline: a quaternion-based attitude estimation filter with accelerometer-based correction steps and automatic fusion weight adaptation . The filter time constant and weight adaptation gain are numerically optimized to yield the best performance across all data sets.
Neural Network (NN): The proposed neural network is trained on a subset of the available (augmented) data sets and validated on the complementary set of data.
The characteristics of applying neural networks to the attitude estimation problem are analyzed in three experiments. The first one compares the performance of the optimised neural network with the filter. The second one is an ablation study that quantifies the effect of every optimization and compares the performance of the RNN and TCN model. The last experiment analyzes the effect of scaling the size of the neural network.
V-a Performance Analysis
In order to compare the performance of the proposed neural network model with the filter, the 15 recordings will be used for a leave-one-out cross-validation. That means that the model will be trained with 15 recordings and validated on the one that was left out. This leads to an increase in computation time because for every recording a new independent model has to be trained, but it provides a better view on generalizability of the model architecture. The neural network used is the RNN with all the proposed optimizations applied.
The boxplot in Figure 7 compares the error distribution of the 15 recordings between the neural network and the baseline filter. It visualizes that (1) the neural network has a better average performance and (2) that it performs more consistently in difficult cases, exhibiting clearly smaller maximum errors. The performance comparison for each individual recording is visualized in Figure 8. It shows that, in the slow cases, both methods perform similarly, while the baseline filter sometimes diverges in the fast- and arbitrary-motion cases. The diverging behaviour may be observed in Figure 5 in the fast arbitrary-motion case. Between the movements, when the IMU is resting, the algorithms use the gravitational acceleration to quickly converge towards the true attitude. Overall, the neural network outperforms the baseline filter significantly, which is even more remarkable in light of the fact that the baseline filter has been optimized on the whole dataset, while the neural network has never seen any of the validation data.
V-B Ablation Study
In the ablation study, the effect of every domain-specific optimization on the performance of the neural network is analyzed. Furthermore, the performance of the RNN and TCN architectures on the attitude estimation problem are compared. In this study, the 15 recordings are split in 12 training recordings and 3 validation recordings. In order to be representative, the validation recordings are the ones that yielded the maximum, minimum and median error in the performance analysis. To both the RNN and TCN architecture with current best practices for time series as basemodels, the three domain-specific optimizations are added iteratively. First the elementwise mean-squared-error loss is replaced by the optimized attitude error with smooth-l1-loss. In the second step, the data augmentation, which simulates a rotated IMU, is added. In the last step, the input layers are grouped in acceleration and gyroscope signals.
The results of the study are visualized in Figure 9. Without the optimizations, the RNN and TCN model perform at a similar level. However, after adding the optimizations, the RNN has a much smaller error. This is plausible with the TCN being limited to its receptive field, while the RNN can track the IMU movement for an indefinite time with its hidden states. Even extending the TCN’s receptive field to samples, which is a time window of more than seconds, the results stay the same. When the IMU moves for a longer duration than the time window, the estimation diverges. For this application, especially with real time applications in mind, the RNN is the better approach.
The second result is that all the optimizations improve both the RNN and the TCN. Grouping the input leads consistently to minor improvements, while the loss optimization and data augmentation have a significant impact on the performance. When the data augmentation is added to the model, the other general regularization methods need to be reduced or deactivated in order to avoid over-regularization. Training and validation loss drop with same pace, which shows that it is very effective at regularizing the model. The same effect probably could be achieved by increasing the size of the dataset by several orders of magnitude, which would require more costly recordings.
The final result is that both the loss optimization and the data augmentation are necessary to outperform the baseline filter. Without these domain-specific optimizations, even the highly optimized general purpose neural networks do not generalize well enough. If all aforementioned optimizations are applied, the neural network performs significantly better than the baseline filter.
V-C Model Size Analysis
In order to analyze the effect of the model size to the attitude error, the RNN model of the first experiment is applied to the 12 training and 3 validation recordings of the second experiment. The amount of neurons of each layer of the RNN is scaled from 10 to 200, and the attitude error is compared.
The results of the study are visualized in Figure 10. As expected, the error decreases with increasing hidden size, with the gradient decreasing at bigger neuron counts. In this example, 20 neurons per layer are already enough to achieve the same mean attitude error as the baseline filter. Decreasing the hidden size of RNNs helps to reduce the memory footprint and overall computation time, which is important for embedded systems. But it only marginally reduces the training and prediction time on hardware accelerators with high parallelization capabilities, because of its sequential nature.
This work has shown that neural networks are a potent tool for IMU-based real-time attitude estimation. If domain-specific optimizations are in place, then large recurrent neural networks can outperform state-of-the-art nonlinear attitude estimation filters. These optimizations require knowledge about the process that the neural network identifies. However, it does not require the specific knowledge (equations, signal characteristics, parameters) that is needed for implementing a well-performing filter. Another requirement for the neural-networks-based solution is a sufficiently rich set of data with ground truth attitude. However, data augmentation was proven to reduce this demand significantly.
Leave-one-out cross validation was used to show that the trained network performs well on new data from motions that were used for training. Future research will focus on generalizing applying the trained network to data from different IMUs with different sampling rates and different error characteristics. This will answer the question whether a sufficiently trained neural network can be used as a competitive solution in new sensor and environment settings without the need for collecting and using new training data.
This work was partly funded by the German Federal Ministry of Education and Research (BMBF, Funding number: 16EMO0262).
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Smart fluid controlled with light
Members of the Complex Fluids and Nanomaterials Group, at the University of Maryland have discovered a new class of "smart fluids" capable of switching from gel to liquid upon exposure to ultraviolet light.
A paper detailing the group's findings, titled "A simple class of photorheological fluids: Surfactant solutions with viscosity tunable by light," was recently published in the Journal of the American Chemical Society ("A Simple Class of Photorheological Fluids: Surfactant Solutions with Viscosity Tunable by Light"). The paper was authored by graduate students Aimee M. Ketner and Rakesh Kumar, alumnus Tanner S. Davies, undergraduate Patrick W. Elder, and professor Raghavan. It is already generating interest in the scientific community, most recently being discussed by Nature magazine's website, Chemical Processing magazine, Materials Today, and ScienceDaily.
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