Holman, B W B; Alvarenga, T I R C; van de Ven, R J; Hopkins, D L
2015-07-01
The Warner-Bratzler shear force (WBSF) of 335 lamb m. longissimus lumborum (LL) caudal and cranial ends was measured to examine and simulate the effect of replicate number (r: 1-8) on the precision of mean WBSF estimates and to compare LL caudal and cranial end WBSF means. All LL were sourced from two experimental flocks as part of the Information Nucleus slaughter programme (CRC for Sheep Industry Innovation) and analysed using a Lloyd Texture analyser with a Warner-Bratzler blade attachment. WBSF data were natural logarithm (ln) transformed before statistical analysis. Mean ln(WBSF) precision improved as r increased; however the practical implications support an r equal to 6, as precision improves only marginally with additional replicates. Increasing LL sample replication results in better ln(WBSF) precision compared with increasing r, provided that sample replicates are removed from the same LL end. Cranial end mean WBSF was 11.2 ± 1.3% higher than the caudal end. PMID:25828163
H. Zhuang; E.M. Savage; Smith, D P; Berrang, M E
2008-01-01
Advantages of air chilling (AC) methods over immersion chilling (IC) methods in quality retention and improvement of deboned chicken breast meat depend on experimental conditions, such as deboning time. The objective of this study was to evaluate the effect of a dry-AC method on shear force and water-holding capacity (WHC) of broiler breast meat deboned 4h postmortem compared to hot-boned (no chill) or immersion-chilled meat. Ready-to-cook broiler carcasses were hot-boned, chilled by ice wate...
Scientific Electronic Library Online (English)
C., Gomes; L.B., Karam; R.E.F., Macedo.
2013-04-01
Full Text Available Avaliaram-se as características sensoriais e determinou-se a força de cisalhamento de cortes de carne de paca (Agouti paca). As análises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por cocção até a temperatura interna de 70ºC. A avaliação de aspecto, co [...] r, sabor, odor e maciez foi realizada pela aplicação de teste afetivo a 146 provadores, utilizando-se escala hedônica, e a força de cisalhamento foi determinada pela técnica Warner Bratzler. Na avaliação sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferença significativa (p0,05) entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante à carne suína e com boa aceitação pelos consumidores. O estudo evidenciou o potencial da paca como uma espécie silvestre para a produção comercial de carne para o mercado de carnes vermelhas ou exóticas. Abstract in english Sensory characteristics and shear force of paca meat (Agouti paca) were assessed in this study. Analyses were performed in the bonelessshoulder,loin andhamobtained from nine paca carcassesprepared by cookinguntil reaching the internal temperatureof 70°C. The evaluation of flavor, aroma, color, appea [...] rance and tenderness was carried out by the application of an affective test using the hedonic scaleand a 146 consumer panel. Shear force was determined by the Warner-Bratzler technique. Shoulder, loin and ham had significant differences (p 0.05) among the cuts, which were similarly tender. Paca meat was found to resemble pork meat in sensory evaluation and had good acceptance by consumers. This study showed the potential of paca (Agouti paca) asa wild species for meat production in the red or exotic meat market.
2004-01-01
It is with great sadness that we learned that our friend and former colleague, David Warner, passed away on Christmas Eve. The funeral was held the following Monday. David was a "linac man". His career centred around linacs, but with a multitude of different subjects. He began at CERN by building the 3 MeV linac in the extension of the South Hall. He did pioneering work on this machine, which paved the way towards the design of the Alvarez cavities for the CERN Linac 2, for which he was responsible. After this challenge was successfully finished, David was the first member of the small but growing team, that was in charge of building the LEP Injector Linacs (LIL). After having been recognised as a proton linac expert, he quickly converted to electron linacs where he soon became the respected key expert for the design, parameters and ultimate performance of LIL. His predilection for precise and detailed documentation, and his vision that the know-how acquired with LIL should be preserved a...
DEFF Research Database (Denmark)
Christensen, L.; Andersen, L.
2011-01-01
Long term heat treatment at low temperature (LTLT) is known to decrease toughness of meat. However, the contribution from the connective tissue to the toughness of LTLT treated meat is not clear. The aim of the present study was to investigate the effect of LTLT treatments on shear force and cooking loss in semitendinosus from cows (4-6 years) and young bulls (12-14 months), representing 2 categories of beef with varying thermal strength of connective tissue. Vacuum packed muscle samples were heat treated at 53°C, 55°C, 58°C and 63°C in water baths for 2½, 7½ and 19½ h. Cooking loss and Warner-Bratzler shear force were measured after heat treatment and subsequent cooling. Shear force of semitendinosus from young bulls heated at 53°C for 2½ h was significantly higher compared with all other heat treatments. A decrease of app. 40 N was observed when increasing the heating temperature from 53°C to 55°C, or when increasing heating time from 2½ to 7½ h at 53°C. In semitendinosus from cows shear force decreased significantly with increasing temperature, and with increasing heating time from 2½ to 19½ h at 55°C and 63°C. Cooking loss increased with increasing heating temperature in both beef categories. The results show that prolonged heating at low temperatures reduce toughness in beef semitendinosus, and that a reduction in toughness require higher temperatures and longer heating times in semitendinosus from cows compared with young bulls.
Arp, T S; Howard, S T; Woerner, D R; Scanga, J A; McKenna, D R; Kolath, W H; Chapman, P L; Tatum, J D; Belk, K E
2013-12-01
Effect of ractopamine hydrochloride (RH) and zilpaterol hydrochloride (ZH) on LM shear force and sensory attributes was determined using pens (n = 40) British × Continental crossbred steers randomly allocated to one of the following treatments: control; RH fed at 200 (RH 200) or 300 mg • steer(-1) • d(-1) (RH 300), or 400 mg • steer(-1) • d(-1) (RH 400) top-dressed for the final 30 d of feeding; or ZH fed at 7.5 mg/kg, beginning 23 d before slaughter with a 3-d withdrawal. Two replicates (pens) per treatment were represented in four blocks. Eighteen carcasses per pen were randomly selected and one 5-cm LM sample was removed from both carcass sides to be used for shear force and sensory evaluation. Samples were aged for 14 d, frozen at -28.8 °C, and cut into 2.5-cm steaks. All steaks were cooked to an internal temperature of 71.1 °C before being evaluated for Warner-Bratzler shear force (WBSF), slice shear force (SSF), or being fed to trained sensory panelists. Increasing dose and potency of ?-agonist increased WBSF by 4 to 17% and SSF by 5 to 24% (P 0.05). Probability of steaks failing to meet shear force standards to be certified tender (WBSF 0.05). Steaks from steers fed RH 300 and RH 400 were comparable for all sensory attributes; however, both RH 300 and RH 400 were rated lower for overall tenderness than controls (P 0.05). Results from this study indicated ?-agonists negatively affected beef tenderness and these effects may be more noticeable in steers supplemented with ZH and higher doses of RH. PMID:24166996
Corbin, C H; O'Quinn, T G; Garmyn, A J; Legako, J F; Hunt, M R; Dinh, T T N; Rathmann, R J; Brooks, J C; Miller, M F
2015-02-01
The palatability of tender [Warner-Bratzler shear force values umami (r=0.59) flavors. Fat level was the primary driver of beef flavor acceptability in all samples when no undesirable off-flavors were present. PMID:25299587
2013-10-31
...131 0152] Actavis, Inc. a corporation, and Warner Chilott PLC; Analysis of Agreement Containing Consent Orders To Aid Public...from Actavis, Inc. (``Actavis'') and Warner Chilcott plc (``Warner Chilcott'') that is designed to remedy the...
Morfología de Neochetina eichhorniae (Warner (Coleoptera: Curculionidae
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Oscar Martínez-Morales
2014-01-01
Full Text Available En este trabajo se describen e ilustran características morfológicas de Neochetina eichhorniae (Warner, 1970. Esta especie se ha utilizado para el control biológico del lirio acuático (Eichhornia crassipes (Mart. Solms-Laubach, 1883. En el huevo, el aspecto cambiante del corion es dado por el desarrollo embrionario. En la larva se realizó una descripción de la quetotaxia de la cápsula cefálica y se identificaron tres ínstares larvales con la medición de su anchura; también se revisó la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en tórax y abdomen, también se observaron dos tipos de espiráculos; el más característico es el espiráculo abdominal por su posición dorsal, que además de ser esclerosado, posee órganos sensoriales en su ápice. La morfología externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Además se proporciona una descripción de las alas, proventrículo y genitalia, estructuras importantes en la taxonomía. Las características morfológicas de N. eichhorniae encontradas en éste trabajo pueden ser útiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926, la cual ha sido liberada en muchos países. Es el primer trabajo de morfología N. eichhorniae en México.
MORFOLOGÍA DE NEOCHETINA EICHHORNIAE (WARNER (COLEOPTERA: CURCULIONIDAE
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Oscar MART\\u00CDNEZ-MORALES
2014-01-01
Full Text Available En este trabajo se describen e ilustran características morfológicas de Neochetina eichhor- niae (Warner, 1970. Esta especie se ha utilizado para el control biológico del lirio acuático ( Eichhornia crassipes (Mart. Solms-Laubach, 1883. En el huevo, el aspecto cambiante del corion es dado por el desarrollo embrionario. En la larva se realizó una descripción de la quetotaxia de la cápsula cefálica y se identificaron tres ínstares larvales con la medición de su anchura; también se revisó la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en tórax y abdomen, también se observaron dos tipos de espiráculos; el más característico es el espiráculo abdominal por su posición dorsal, que además de ser esclerosado, posee órganos sensoriales en su ápice. La morfología externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Además se proporciona una descripción de las alas, proventrículo y genitalia, estructuras importantes en la taxonomía. Las características morfológicas de N. eichhorniae encontradas en éste trabajo pueden ser útiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926, la cual ha sido liberada en muchos países. Es el primer trabajo de morfología N. eichhorniae en México.
Scientific Electronic Library Online (English)
Oscar, Martínez-Morales; Edith G., Estrada-Venegas; Armando, Equihua-Martínez; Jorge, Valdez-Carrasco.
Full Text Available En este trabajo se describen e ilustran características morfológicas de Neochetina eichhorniae (Warner, 1970). Esta especie se ha utilizado para el control biológico del lirio acuático (Eichhornia crassipes (Mart.) Solms-Laubach, 1883). En el huevo, el aspecto cambiante del corion es dado por el des [...] arrollo embrionario. En la larva se realizó una descripción de la quetotaxia de la cápsula cefálica y se identificaron tres ínstares larvales con la medición de su anchura; también se revisó la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en tórax y abdomen, también se observaron dos tipos de espiráculos; el más característico es el espiráculo abdominal por su posición dorsal, que además de ser esclerosado, posee órganos sensoriales en su ápice. La morfología externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Además se proporciona una descripción de las alas, proventrículo y genitalia, estructuras importantes en la taxonomía. Las características morfológicas de N. eichhorniae encontradas en éste trabajo pueden ser útiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926), la cual ha sido liberada en muchos países. Es el primer trabajo de morfología N. eichhorniae en México. Abstract in english In this study morphological characteristics of Neochetina eichhorniae (Warner, 1970) are described and illustrated. This species has been used for the Biological Control of waterhyacinth (Eichhornia crassipes (Mart.) Solms-Laubach, 1883). In the egg, the changing appearance of the chorion is given b [...] y the embryonic development. Description of larval head capsule chaetotaxy was done. Three larval instars were identified by measuring the head capsule width; microsculpture of the body larva was studied, microspines were evident with different arrangements in thorax and abdomen, two types of spiracles were found; the more distinctive was the dorsal spiracle in the abdomen, which is sclerotized, with sensory organs at its apex. The external morphology of N. eichorniae adult is very similar in both sexes, the main difference among them is the rostrum. Description of the wings, proventriculus and genitalia, important structures in the taxonomy, is provided. The morphological characteristics of N. eichhorniae found in this study can be use to separate from N. bruchi (Hustache) which has been released in many countries. This is the first morphological study of N. eichhorniae in Mexico.
ESTIMATED GENETIC PARAMETERS FOR PALATABILITY TRAITS OF STEAKS FROM BRAHMAN CATTLE
Heritabilities and genetic and phenotypic correlations were estimated from carcass and beef palatability data collected from Brahman calves (n = 504) born in central Florida from 1996 to 2000. Traits evaluated included Warner-Bratzler shear force (after 7, 14, and 21 d of aging), panel tenderness sc...
The Warner Map Collection at the W.S. Hoole Special Collections Library
Based at the University of Alabama Libraries, the Warner Map Collection was a gift from the estate of Mildred Westervelt Warner, who passed away in 1974. Warner was an inveterate collector of antiquarian maps, and her collection ranges from 16th-century maps of the "New World" to an 1831 map of Alabama and Georgia. On the website, users can learn more about the Warner collection, and then peruse the fifteen different sections here. The sections include geographic regions ("The Caribbean") and cartographers, such as "Maps by Blaeu". There are only two maps in the collection by Blaeu, but they are both worth a look, as they are both interesting renderings of America in the 17th century. It's worth nothing that all of the maps also have high-resolution versions available, which makes it quite easy to examine each item in scrupulous detail.
Martin, George M
2005-01-01
On behalf of American Aging Association and his many biogerontological colleagues, the author thanks Huber R. Warner for his 21 years of exemplary service at the National Institute on Aging (NIA). In so honoring Dr. Warner, we also honor his many associates at that “user friendly” branch of the National Institutes of Health. Some highlights of Dr. Warner's scientific training, academic career and special contributions while serving in a leadership position at the NIA are reviewed. We wish him...
Histomorphology and Physical Characteristics of Buffalo Meat at Different Sex and Age
Mahmudah, *; H. Nuraini; A. Winarto; C. Sumantri
2013-01-01
The aim of this experiment was to evaluate histology and physical variables of buffalo meat at different sex and ages. Thirty head of buffaloes were used in this experiment. Muscle fiber diameter, fasciculus diameter, thickness of connective tissue, pH, water holding capacity, Warner-Bratzler shear force and cooking loss were measured in this experiment. Analysis of variance of randomized factorial design was used to analyse the data. The differences were analysed by Tukey test. The result sh...
Shelf-life and Microbiological Profiler of Chicken Wing Products Following Sous vide Treatment
Wang, S H; M. H. Chang; Chen, T.C.
2004-01-01
Chicken wings were vacuum-packaged and cooked (sous vide) at 75 and 90°C until the internal temperature reached 73.8°C was reached. The cooked samples were stored at 2 and 7°C, separately. The TBA values, aerobic plate count, aerobic and anaerobic plate counts and Warner-Bratzler (WB) shear force of the samples were evaluated weekly for 7 wk. The sous vide treatment chicken wings had lower TBA values, aerobic and anaerobic plate counts throughout the 7 wk of storage when compared with the con...
Use of near infrared spectroscopy for assessment of beef quality traits
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L. Gallo
2010-04-01
Full Text Available Chemical and physical traits and fatty acid composition of meat samples from 148 Piemontese beef samples were predicted by near infrared spectroscopy. Coefficients of determination in calibration (R2 ranged between 0.44 and 0.99 for chemical composition and between 0.02 and 0.98 for fatty acid (FA profile, being in general more accurate for the major FA. The calibration results gave inaccurate prediction for cholesterol and collagen content and for most physical traits, such as Warner-Bratzler shear force, cooking loss, drip loss, colour (L, a, b and pH.
Akta?, Nesimi; AKSU, Muhammet ?rfan; Kaya, Mükerrem
2003-01-01
Longissimus dorsi muscle obtained from beef carcasses was used in this study. Meat cores 2.54 cm in diameter were marinated in 0.34, 0.68 and 1.02 M sodium chloride (NaCl) and 0.05, 0.1 and 0.15 M calcium chloride (CaCl2) solutions at 5 °C for 72 h. Warner Bratzler Shear (WBS) values were significantly different between samples. The samples marinated with CaCl2 held less water than those marinated in NaCl. Cooking losses were lower in the control samples than in the marinated samples. Differe...
Bainy, Eduarda Molardi; Bertan, Larissa Canhadas; Corazza, Marcos Lucio; Lenzi, Marcelo Kaminski
2015-08-01
The influence of two common cooking methods, grilling and baking, on chemical composition, water retention, fat retention, cooking yield, diameter reduction, expressible water, color and mechanical texture of tilapia (Oreochromis niloticus) fish burgers was investigated. Texture analyses were performed using a Warner-Bratzler test. The fish burger had a softer texture with a lower shear force than other meat products reported in the literature. There were no significant differences in proximate composition, diameter reduction, fat retention and expressible water between the grilled and oven-baked fish burgers. Cooking methods did not affect the cooking times and cooking rates. Warner-Bratzler parameters and color were significantly influenced by the cooking method. Grilling contributed to a shear force and work of shearing increase due to the lower cooking yield and water retention. Raw burgers had the highest L* (69.13?±?0.96) and lowest b* (17.50?±?0.75) values. Results indicated that baking yielded a product with better cooking characteristics, such as a desired softer texture with lower shear values (4.01?±?0.54) and increased water retention (95.82?±?0.77). Additionally, the baked fish burgers were lighter (higher L*) and less red (lower a*) than the grilled ones. PMID:26243932
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M. Ern
2006-06-01
Full Text Available In order to incorporate the effect of gravity waves (GWs on the atmospheric circulation most global circulation models (GCMs employ gravity wave parameterization schemes. To date, GW parameterization schemes in GCMs are used without experimental validation of the set of global parameters assumed for the GW launch spectrum. This paper focuses on the Warner and McIntyre GW parameterization scheme. Ranges of parameters compatible with absolute values of gravity wave momentum flux (GW-MF derived from CRISTA-1 and CRISTA-2 satellite measurements are deduced for several of the parameters and the limitations of both model and measurements are discussed. The findings presented in this paper show that the initial guess of spectral parameters provided by Warner and McIntyre (2001 are some kind of compromise with respect to agreement of absolute values and agreement of the horizontal structures found in both measurements and model results. Better agreement can be achieved by using a vertical wavenumber launch spectrum with a wider saturated spectral range and reduced spectral power in the unsaturated part. Still, even global features of the measurements remain unmatched, and it is inevitable to provide a globally varying source distribution in future.
Directory of Open Access Journals (Sweden)
M. Ern
2006-01-01
Full Text Available In order to incorporate the effect of gravity waves (GWs on the atmospheric circulation most global circulation models (GCMs employ gravity wave parameterization schemes. To date, GW parameterization schemes in GCMs are used without experimental validation of the set of global parameters assumed for the GW launch spectrum. This paper focuses on the Warner and McIntyre GW parameterization scheme. Ranges of parameters compatible with absolute values of gravity wave momentum flux (GW-MF derived from CRISTA-1 and CRISTA-2 satellite measurements are deduced for several of the parameters and the limitations of both model and measurements are discussed. The findings presented in this paper show that the initial guess of spectral parameters provided by by Warner and McIntyre (2001 are some kind of compromise with respect to agreement of absolute values and agreement of the horizontal structures found in both measurements and model results. Better agreement can be achieved by using a vertical wavenumber launch spectrum with a wider saturated spectral range and reduced spectral power in the unsaturated part. However, even with this optimized set of global launch parameters not all features of the measurements are matched. This indicates that for further improvement spatial and seasonal variations of the launch parameters should be included in GW parameterization schemes.
Magnetohydrodynamic Shearing Waves
Johnson, Bryan M.
2006-01-01
I consider the nonaxisymmetric linear theory of a rotating, isothermal magnetohydrodynamic (MHD) shear flow. The analysis is performed in the shearing box, a local model of a thin disk, using a decomposition in terms of shearing waves, i.e., plane waves in a frame comoving with the shear. These waves do not have a definite frequency as in a normal mode decomposition, and numerical integration of a coupled set of amplitude equations is required to characterize their time depe...
Scientific Electronic Library Online (English)
Lindon W, Mamani-Linares; Carmen, Gallo.
2011-12-01
Full Text Available Se comparó la composición química y calidad instrumental de carne de bovino, llama, y caballo finalizados bajo pastoreo. Los bovinos (n=31), llamas (n=21) y caballos (n=27) fueron faenados bajo procedimientos estándares de Chile. Las canales fueron refrigeradas durante 24 horas a 4 ºC. En el músculo [...] Longissimus lumborum (LL) se determinó la composición proximal, contenido de colesterol y colágeno, pH, color (L*, a*, b*, H*, C*), capacidad de retención de agua (WHC), pérdida de cocción, pérdida del descongelado y fuerza de corte Warner-Bratzler (WBSF). La carne de llama presentó mayores niveles de proteína y colágenos totales (p Abstract in english This study compared the chemical composition and instrumental meat quality of bovine, llama and horse from animals finished under grazing systems. The bovines (n=31), llamas (n=21) and horses (n=27) were slaughtered using Chilean standard procedures. Carcasses were stored for 24 h in a cold room (4 [...] ºC). The Longissimus lumborum muscle (LL) was collected for determining the chemical composition, cholesterol, collagen content, pH, colour (L*, a*, b*, H*, C*), water holding capacity (WHC) and Warner-Bratzler shear-force (WBSF). Llama meat had higher levels of protein and total collagen (p
Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.
2009-01-01
We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.
Ruda, Mitchell C. (Tucson, AZ); Greynolds, Alan W. (Tucson, AZ); Stuhlinger, Tilman W. (Tucson, AZ)
2009-07-14
One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.
A “coherent and sustained program” of improved radar detection of weather, pilot training, and better communication between pilots and air controllers can greatly reduce the risk of wind shear to airplanes landing or taking off, according to a National Research Council (NRC) committee.Wind shear, characterized by winds rapidly changing direction and speed, has caused several serious accidents in recent years; among the most notable is the July 8, 1982, crash of a Pan American World Airlines jetliner at the New Orleans International Airport, which killed 153 persons. Following the accident, Congress directed the Federal Aviation Administration (FAA) to contract with the NRC to study wind shear.
Scientific Electronic Library Online (English)
María C., Miquel; Edgardo, Villarreal; Carlos, Mezzadra; Lilia, Melucci; Liliana, Soria; Pablo, Corva; Alejandro, Schor.
Full Text Available The objective of this paper was to determine the association of a SNP in the µ-calpain gene at position 316 with growth and quality of meat traits of steers grown on pasture. Fifty-nine Brangus and 20 Angus steers were genotyped for CAPN1 316. Warner Bratzler shear force was measured in l. lumborum [...] samples after a 7-day aging period. A multivariate analysis of variance was performed, including shear force (WBSF), final weight (FW), average daily gain (ADG), backfat thickness (BFT), average monthly fat thickness gain (AMFTG), rib-eye area (REA), and beef rib-eye depth (RED) as dependent variables. The CAPN1 316 genotype was statistically significant. Univariate analyses were done with these variables. The marker genotype was statistically significant (p
Piórkowska, K; Nowak, J; Po?towicz, K
2015-08-01
The aim of this study was to assess mRNA abundance of calpain 1 (CAPN1) and calpain 3 (CAPN3) in breast muscle of 80 fast-growing (FG) and slow-growing broilers (SG) and relate gene expression in relation to growth and Warner Bratzler (WB) shear force of breast muscle. The expression of CAPN1 and CAPN3 genes was higher in the FG compared to the SG line, but significant results were obtained only for CAPN1. The CAPN1 mRNA level was strongly dependent on line and gender interaction. Lower values of shear force were observed in the FG line, where a higher level of calpain expression was shown. A new panel of housekeeping genes (RPL4 and SDHA) for normalisation of gene expression in muscle tissues could be used in other studies of gene expression in chicken. PMID:26042540
Direct Shear Tests with Evaluation of Variable Shearing Area
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Šar?nas Skuodis
2014-12-01
Full Text Available Investigations of soil shear strength properties for Baltic Sea shore sand along Klaip?da city are presented. Investigated sand angle of internal friction (? and cohesion (c is determined via two different direct shear tests procedures. First procedure is standard and ordinary in geotechnical practice, when direct shear test is provided using constant shearing area A0. Second test procedure is different because shearing area according to horizontal displacement each test second is recalculated. This recalculated shearing area author’s call corrected shearing area A. Obtained normal and tangential stresses’ difference via two different testing procedures was 10%.
Bi, Dapeng; Zhang, Jie; Chakraborty, Bulbul; Behringer, R P
2011-12-15
A broad class of disordered materials including foams, glassy molecular systems, colloids and granular materials can form jammed states. A jammed system can resist small stresses without deforming irreversibly, whereas unjammed systems flow under any applied stresses. The broad applicability of the Liu-Nagel jamming concept has attracted intensive theoretical and modelling interest but has prompted less experimental effort. In the Liu-Nagel framework, jammed states of athermal systems exist only above a certain critical density. Although numerical simulations for particles that do not experience friction broadly support this idea, the nature of the jamming transition for frictional grains is less clear. Here we show that jamming of frictional, disk-shaped grains can be induced by the application of shear stress at densities lower than the critical value, at which isotropic (shear-free) jamming occurs. These jammed states have a much richer phenomenology than the isotropic jammed states: for small applied shear stresses, the states are fragile, with a strong force network that percolates only in one direction. A minimum shear stress is needed to create robust, shear-jammed states with a strong force network percolating in all directions. The transitions from unjammed to fragile states and from fragile to shear-jammed states are controlled by the fraction of force-bearing grains. The fractions at which these transitions occur are statistically independent of the density. Jammed states with densities lower than the critical value have an anisotropic fabric (contact network). The minimum anisotropy of shear-jammed states vanishes as the density approaches the critical value from below, in a manner reminiscent of an order-disorder transition. PMID:22170683
Development of conjugate shear bands during bulk simple shearing
Harris, L. B.; Cobbold, P. R.
In rocks possessing a strong planar fabric, shear bands of constant shear sense and oriented at an oblique angle to the foliation are considered by many authors to be characteristic of a non-coaxial bulk deformation history, whereas conjugate shear bands are considered to indicate coaxial shortening. However, in two areas where bulk deformation history appears to be non-coaxial (Cap Corse, Corsica and Ile de Groix, Brittany), conjugate shear bands are observed. In order to investigate this problem, experiments were performed by bulk simple shearing using Plasticine as a rock analogue. When slip between layers of the model is permitted, shear bands of normal-fault geometry form with both the same and opposite shear sense as the bulk simple shearing at approximately the same angle with the layering (40°) irrespective of layer orientation in the undeformed state (for initial orientations of 50, 30 and 15°). Shear bands are initially formed within individual layers and may propagate across layer interfaces when further movement along these is inhibited. The existence of conjugate shear bands in Corsica and Ile de Groix is therefore not incompatible with a model of bulk simple shearing for these two regions. In field studies, one should perhaps exercise care in using shear bands to determine the kind of motion or the sense of bulk shearing.
Hillary Clinton / Judith Warner
Warner, Judith
1994-01-01
Kõige mõjuvõimsam naine maailmas - algus EA 22. veebruar 1994. May/4,11,18,25 lk. 22;22;22;21; Jun/1,8,15,22,29 lk. 21; Jul/6,13,20,27 21; Aug/3,10,17,24,31 lk. 21; Sep/7,14,21,28 lk. 21; Oct/5,12,19 lk. 21
Shearing behavior of polydisperse media
Wackenhut, M; Herrmann, H; Wackenhut, Martin; Namara, Sean Mc; Herrmann, Hans
2004-01-01
We study the shearing of polydisperse and bidisperse media with a size ratio of 10. Simulations are performed with a the two dimensional shear cell using contact dynamics. With a truncated power law for the polydisperse media we find that they show a stronger dilatancy and greater resistance to shearing than bidisperse mixtures. Motivated by the practical problem of reducing the energy needed to shear granular media, we introduce "point-like particles" representing charged particles in the distribution. Even though changing the kinematic behavior very little, they reduce the force necessary to maintain a fixed shearing velocity.
Effect of Breed of Sire on Carcass Traits and Meat Quality of Katahdin Lambs
Directory of Open Access Journals (Sweden)
José A. Partida
2012-09-01
Full Text Available Crossbred lambs (n = 40 of 137 ± 3 days of age from Katahdin ewes with either Charollais (KCh, Dorper (KD, Suffolk (KS and Texel (KT sires were used in this study. The effect of sire breeds on carcass traits, chemical composition of muscle, meat quality and consumer acceptability was determined. Regarding carcass traits, KCh animals had the highest fat thickness. KT lambs had the smallest M. Longissimusdorsi (MLD area compared tothat of KCh, KD and KS (17.0, 15.9, 15.5 and 13.9 cm2; respectively. Breed of sire had no effect (P>0.05 on the chemical composition, pH or Warner-Bratzler shear force (WBSF of lamb; however, it did affect meat color. KS lambs had lower L*, a*, b* and Ch* values compared to the other crossbreeds (P<0.05. Consumer acceptability of lamb was similar (P>0.05 across genotypes.
The Hypertrophic Marchigiana: physical and biochemical parameters for meat quality evaluation
Directory of Open Access Journals (Sweden)
F. M. Sarti
2010-04-01
Full Text Available The aim of this study was to evaluate the meat quality of double muscled Marchigiana young bulls characterized by different genotypes for the hypertrophy: normal and mutated (heterozygous. Calpain and calpastatin activities were determined to verify the state of aging meat on a sample of Longissimus thoracis muscle (XIII thoracic rib taken at slaughtering (0h and after 24 hours (24h. After 14 days of aging, another sample of muscle was taken to evaluate physical and chemical parameters of meat quality. The results showed a better meat quality of mutated animals respect normal animals. Another interesting result was the correlation between the biochemical parameters and some physical parameters, such as WBS (Warner Bratzler Shear Force, CL (Cooking loss. These results showed the relationship between the proteolytic activity of calpain system and meat tenderness.
Comparison of textural atributes of selected meat sausages using instrumental analysis
Directory of Open Access Journals (Sweden)
Vladimír Vietoris
2013-03-01
Full Text Available Normal 0 21 false false false SK X-NONE X-NONE The aim of the study was to compare textural atributes of selected meat sausages using instrumental analysis. For this purpose, seven different meat sausage samples were treated by instrumental analysis, by the use of Warner-Bratzler probe, to find differences for two selected textural parameter firmness and work of shear. As expected, various values of mentioned atributes were obtained for different samples tested in fresh stage and after storage under controlled conditions (48 hrs., 30 °C temp., and 60 % R.H. before and after cooking. For statistical evaluation of results, paired T test was used, statistically significant differences were taken at pdoi:10.5219/273
Duan, Q; Tait, R G; Schneider, M J; Beitz, D C; Wheeler, T L; Shackelford, S D; Cundiff, L V; Reecy, J M
2015-08-01
The objective of this study was to evaluate sire breed effect on mineral concentration in beef longissimus thoracis (LT) and investigate the correlations between beef mineral concentrations and carcass and palatability traits. Steer progeny (N=246) from the Germplasm Evaluation project-Cycle VIII were used in this study. In addition to carcass traits, LT was evaluated for mineral concentrations, Warner-Bratzler shear force, and palatability traits. A mixed linear model estimated breed effects on mineral concentrations. No significant sire breed (P?0.43) or dam breed (P?0.20) effects were identified for mineral concentrations. Pearson correlation coefficients were calculated among mineral concentrations, carcass, and sensory traits. Zinc concentration was positively correlated (P?0.05) with total iron (r=0.14), heme iron (r=0.13), and magnesium (r=0.19). Significant (Ppalatability traits. PMID:25866932
Orange peel flour effect on physicochemical, textural and sensory properties of cooked sausages
Directory of Open Access Journals (Sweden)
Sonia Hernandez Garcia
2010-06-01
Full Text Available Orange peel flours as a source of fiber, protein, and flavonoids as antioxidants was added to meat batters in order to improve nutritional quality and physicochemical, textural and sensory properties. Orange peel flour in meat batters improved yield and reduced expressible moisture. Hardness in orange peel flour samples was higher, but less resilient and cohesive. Warner-Bratzler shear force was not different between control (no orange peel flour and samples with this functional ingredient. A no trained panel determinate that there was no difference between control and orange peel flour added sausages at a 5% (w/w level. In this view, orange peel flour can be employed to improve yield and texture of cooked meat products.
International Nuclear Information System (INIS)
An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions ? is discussed. Provided that ? approx-lt 0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t ? ?) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with ?>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included
Reyssat, E.; Tallinen, T.; Le Merrer, M.; Mahadevan, L.
2012-12-01
A soft solid is more easily sliced using a combination of normal and shearing deformations rather than diced by squeezing down on it normally with the same knife. To explain why this is so, we experimentally probe the slicing and dicing of a soft agar gel with a wire, and complement this with theory and numerical simulations of cutting of a highly deformable solid. We find that purely normal deformations lead to global deformations of the soft solid, so that the blade has to penetrate deeply into the sample, well beyond the linear regime, to reach the relatively large critical stress to nucleate fracture. In contrast, a slicing motion leads to fracture nucleation with minimal deformation of the bulk and thus a much lower barrier. This transition between global and local deformations in soft solids as a function of the angle of shear explains the mechanics of the paper cut and design of guillotine blades.
Energy Technology Data Exchange (ETDEWEB)
Butler, B.D.; Hanley, H.J.M.; Straty, G.C. [National Institute of Standards and Technology, Boulder, CO (United States); Muzny, C.D. [Univ. of Colorado, Boulder, CO (United States)
1995-12-31
An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.
Plasticity Approach to Shear Design
DEFF Research Database (Denmark)
Hoang, Cao Linh; Nielsen, Mogens Peter
1998-01-01
The paper presents some plastic models for shear design of reinforced concrete beams. Distinction is made between two shear failure modes, namely web crushing and crack sliding. The first mentioned mode is met in beams with large shear reinforcement degrees. The mode of crack sliding is met in non-shear reinforced beams as well as in lightly shear reinforced beams. For such beams the shear strength is determined by the recently developed crack sliding model. This model is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed in uncracked concrete. Good agree between theory and tests has been found.Keywords: dsign, plasticity, reinforced concrete, reinforcement, shear, web crushing.
Scientific Electronic Library Online (English)
Márcia Arocha, Gularte; Rosa de Oliveira, Treptow; Juvêncio Luís Fernandes, Pouey; José Carlos, Osório.
2000-06-01
Full Text Available A maciez da carne geralmente é o atributo mais importante para o consumidor. Vários são os fatores que influem sobre esSe aspecto no animal, como por exemplo: genótipo, idade, sexo, entre outros. Neste estudo, verificou-se a influência da idade e do sexo na maciez do músculo Longissimus dorsi de ovi [...] nos da raça Corriedale, através de métodos sensoriais e instrumentais. Após o abate, realizou-se a avaliação visual da textura do músculo pela granulação da superfície do mesmo. As amostras foram congeladas por 5 meses. Após a cocção, foi analisada a maciez da carne pelo equipamento Warner-Bratzler shear medindo a força de cisalhamento, e por avaliação sensorial realizada por uma equipe treinada de julgadores. Resultados obtidos pela avaliação sensorial e instrumental indicaram que o músculo Longissimus dorsi de fêmeas e de animais de menor idade foram mais macios. Abstract in english The meat tenderness is the most important atribute to the consumer. Several factors have influence in this aspect, for exemple: genotype, age, sex and others. The objective of this work was to study the influence of age and sex on Longissimus dorsi muscle tenderness of Corriedale lineage lamb, throu [...] gh sensory and instrumental methods. After slaughter Longissimus dorsi, texture was evaluated by granite’s surface method. The samples were frozen for five months. After thawing and cooking, meat tenderness was evaluated by Warner-Bratzler shear and sensory evaluation by a group of trained judges. The results indicated that female and younger animals produced more tender meat.
Tempo de cozimento e textura de raízes de mandioca / Cooking time and texture of cassava roots
Scientific Electronic Library Online (English)
Simone Vilela, Talma; Selma Bergara, Almeida; Rozana Moreira Pereira, Lima; Henrique Duarte, Vieira; Pedro Amorim, Bebert.
2013-06-01
Full Text Available O objetivo deste trabalho foi avaliar a adequação de medidas instrumentais de textura como índice de qualidade de raízes da mandioca de mesa e sua correlação com o tempo de cozimento. Quinze raízes de mandioca foram colhidas no 11.º mês de cultivo na região noroeste fluminense. Pedaços de raízes for [...] am cozidos em água, sendo o tempo de cozimento determinado, em triplicata, quando se observou pouca resistência à penetração do garfo. A resistência ao corte foi realizada nas polpas cruas e cozidas, em cinco a nove repetições, operando o texturômetro TA. XT Plus Texture Analyser com probe Warner-Bratzler Blade HDP/BSW, velocidades de pré-teste de 0,2 cm/s, de pós-teste e de teste de 0,5 cm/s, e distância de 5 cm. Os dados foram analisados por ANOVA e teste de média Tukey (tempo de cozimento); GLM, LSMEANS e PDIFF (resistência ao corte) e análise de correlação de Pearson (p Abstract in english The objective of this work was to evaluate the adequacy of instrumental texture analyses as a quality index for cassava roots for direct consumption, and the correlation with cooking time. Fifteen cassava roots were harvested in the eleventh month of growth in the northwest of the State of Rio de Ja [...] neiro. Pieces of roots were boiled in water and the cooking time determined in triplicate, to the point where there was little resistance to penetration by a fork. The shear strength was determined in the raw and cooked pulps with five to nine replicates, using the texturometer TA-XT Plus Texture Analyser with the Warner-Bratzler Blade HDP / BSW probe, a pre-test speed of 0.2 cm/s, post-test and test speed of 0.5 cm/s and distance of 5 cm. The data were analyzed by ANOVA and Tukey (cooking time), GLM, LSMEANS and PDIFF (shear resistance) and Pearson's correlation analysis (p
Dislocation kinetics behind shear shocks
International Nuclear Information System (INIS)
High velocity oblique impact experiments result in both compression and shear shock waves. Behind the shear shock wave the particle velocity is transverse to the shock front. At large transverse particle velocities, dislocation kinetics can contribute a portion of the velocity. Based on a kinematic and thermodynamic model of dislocation kinetics, an analysis is made of the transverse strain and velocity behind a shear shock. Kinematics of dislocations in transverse motion behind the shock is formulated. A solution is given for an ideal case where the dislocation density function propagates as a pulse behind the shear shock. 9 refs
Dislocation kinetics behind shear shocks
Energy Technology Data Exchange (ETDEWEB)
Stout, R.B.; Anderson, G.D.
1985-06-01
High velocity oblique impact experiments result in both compression and shear shock waves. Behind the shear shock wave the particle velocity is transverse to the shock front. At large transverse particle velocities, dislocation kinetics can contribute a portion of the velocity. Based on a kinematic and thermodynamic model of dislocation kinetics, an analysis is made of the transverse strain and velocity behind a shear shock. Kinematics of dislocations in transverse motion behind the shock is formulated. A solution is given for an ideal case where the dislocation density function propagates as a pulse behind the shear shock. 9 refs.
Jiang, Weifeng; Xuan, Shouhu; Gong, Xinglong
2015-04-01
Dense non-Brownian suspension has rich rheology and is hard to understand, especially for distinguishing continuous shear thickening (CST) from discontinuous shear thickening (DST). By studying the shear stress dependent rheology of a well-known DST suspension of cornstarch in water, we find that the transition from CST to DST could occur not only by increasing the volume fraction ? but also by increasing the shear stress ?. For the recovery process of jammed suspension, we observe that the shear activates the time-dependent nature of particle rearrangement. DST can then be interpreted as the consequence of shear-induced jamming. Based on the test data, we plot the schematic phase diagram in the ?-? plane and find out that ? and ? perform almost the same effect on flow-state transition.
Bayesian Lensing Shear Measurement
Bernstein, Gary M
2013-01-01
We derive an estimator of weak gravitational lensing shear from background galaxy images that avoids noise-induced biases through a rigorous Bayesian treatment of the measurement. The Bayesian formalism requires a prior describing the (noiseless) distribution of the target galaxy population over some parameter space; this prior can be constructed from low-noise images of a subsample of the target population, attainable from long integrations of a fraction of the survey field. We find two ways to combine this exact treatment of noise with rigorous treatment of the effects of the instrumental point-spread function and sampling. The Bayesian model fitting (BMF) method assigns a likelihood of the pixel data to galaxy models (e.g. Sersic ellipses), and requires the unlensed distribution of galaxies over the model parameters as a prior. The Bayesian Fourier domain (BFD) method compresses galaxies to a small set of weighted moments calculated after PSF correction in Fourier space. It requires the unlensed distributi...
Scientific Electronic Library Online (English)
Lindon W., Mamani-Linares; Faustina, Cayo; Carmen, Gallo.
2013-04-01
Full Text Available Se compararon las características tecnológicas de doce músculos de llamas que fueron criadas al pastoreo. Las llamas (n=10) fueron faenadas bajo procedimientos estándares de Bolivia. Las canales fueron refrigeradas durante 24 horas a 4 ºC. Los músculos fueron removidos de cada canal después del desp [...] oste. Cinco bifes de 2.54 cm de espesor fueron cortados de cada músculo. En cada músculo se determinó el pH24, color (L*, a*, b*), capacidad de retención de agua y fuerza de corte Warner-Bratzler (WBSF). No se observaron diferencias estadísticas en el pH entre los músculos. Los valores de L* (luminosidad) y b* (tenor de amarrillo) de los músculos L. thoracis, L. lumborum y Semimembranosus fueron mayores que en Triceps brachii y Psoas major (p Abstract in english This study compared the technological quality of twelve muscles of llama that were raised in a grazing system. The llamas (n=10) were slaughtered using Bolivian standard procedures. Carcasses were stored for 24 h in a cold room (4 ºC). Muscles were removed from the left side of each carcass in the s [...] laughter house. Five steaks (2.54 cm thick) were cut from each muscle. In each muscle was determined pH, colour (L*, a*, b*), water holding capacity (WHC) and Warner-Bratzler shear-force (WBSF). No statistical difference was found in pH between muscles. Values of L* (lightness) and b* (tenor of yellow) in L. thoracis, L. lumborum and Semimembranosus were higher than those in Triceps brachii and Psoas major (p
Shear angle of magnetic fields.
Yanping, Lü; Wang, Jingxiu; Wang, Huaning
1993-11-01
The authors introduce a new parameter, the shear angle of vector magnetic fields, ??, to describe the non-potentiality of magnetic fields in active regions, which is defined as the angle between the observed vector magnetic field and its corresponding current-free field. In the case of highly inclined field configurations, this angle is approximately equal to the "angular shear", ??, defined by Hagyard et al. (1984). ?? can be considered as the projection of the shear angle, ??, on the photosphere. For the active region studied, the shear angle, ??, seems to have a better and neater correspondence with flare activity than does ??. It gives a clearer explanation of the non-potentiality of magnetic fields. It is a better measure of the deviation of the observed magnetic field from a potential field, and is directly related to the magnetic free energy stored in non-potential fields.
Fatigue strength of shear connectors
Xie, En; Valente, Isabel
2011-01-01
Nowadays steel and concrete composite beams are widely applied in structures mainly subjected to dynamic loads, such as railway and road bridges exposed to traffic loads and industrial crane runways exposed to folk-lift truck loads, the fatigue resistance of these structures must be generally and carefully verified. And normally the shear forces between concrete flange and steel beams are all transferred by different kinds of shear connectors, fatigue failure of composite beam may happen on s...
Palotti, Matthew Lee
The outflows from young, massive protostars are observed to contain, in many instances, more mass than the protostar producing them. Entrainment, spurred on by hydrodynamical or magnetohydrodynamical instabilities, is one possible mechanism of gathering the extra mass. The instability found at a shear flow boundary layer is known as the Kelvin-Helmholtz instability (KHI). This thesis lays the groundwork to start answering the outflow question by examining the KHI in more detail through the use of 2D simulations. I investigate the role of resistivity on the saturation and non-linear evolution of the KHI under the influence of a weak magnetic field. The models run cover magnetic Reynolds numbers ranging from Rm = 1000 toRm = 50000 which, admittedly, is much lower than the Reynolds numbers found in the ISM (Rm ˜ 10 15). Wherever possible, I have tried to postulate the effects of going to even higher Reynolds numbers. Additionally, I have also examined the mixing properties of the KHI by utilizing passive Lagrangian particles initially distributed evenly within the boundary layer. The particles are then tracked as they are advected through the velocity field. Finally, I examine the KHI in a weakly ionized medium. In reality, the molecular interstellar medium is partially ionized, with an ionization fraction Xe ˜ 10-8--10-7. In the absence of collisions, the ions will evolve as the MHD instability does and the neutrals will evolve as the HD instability. However, collisions between the ions and neutrals will affect that evolution. I found that the role of resistivity has a large effect on the non-linear evolution, causing the kinetic and magnetic energy to decay on a much longer timescale. The transport of momentum is greater in the MHD model, with an increasing effect with magnetic Reynolds number, than in the HD model. However, the particle transport remains the same for both the HD and MHD models. The effect is attributed to a large effect on the momentum transport from the Maxwell Stress. Collisions tend to damp out the energy in the instability for a strong magnetic field case.
Isogeometric analysis of shear bands
Berger-Vergiat, Luc; McAuliffe, Colin; Waisman, Haim
2014-08-01
Numerical modeling of shear bands present several challenges, primarily due to strain softening, strong nonlinear multiphysics coupling, and steep solution gradients with fine solution features. In general it is not known a priori where a shear band will form or propagate, thus adaptive refinement is sometimes necessary to increase the resolution near the band. In this work we explore the use of isogeometric analysis for shear band problems by constructing and testing several combinations of NURBS elements for a mixed finite element shear band formulation. Owing to the higher order continuity of the NURBS basis, fine solution features such as shear bands can be resolved accurately and efficiently without adaptive refinement. The results are compared to a mixed element formulation with linear functions for displacement and temperature and Pian-Sumihara shape functions for stress. We find that an element based on high order NURBS functions for displacement, temperature and stress, combined with gauss point sampling of the plastic strain leads to attractive results in terms of rate of convergence, accuracy and cpu time. This element is implemented with a -bar strain projection method and is shown to be nearly locking free.
Scientific Electronic Library Online (English)
Wesley Oliveira de, Sousa; Germano Henrique, Rosado-Neto; Marinêz Isaac, Marques.
2012-09-01
Full Text Available A teoria plastrão foi testada em adultos de Neochetina eichhorniae Warner, 1970, por meio da análise da estrutura que reveste o tegumento destes insetos e em experimentos laboratoriais de submersão. Os processos tegumentares foram reconhecidos em três tipos: escamas aglutinadas e com perfurações lar [...] gas; escamas plumosas de tamanhos e formas variadas; e pêlos. Os experimentos realizados com 264 indivíduos adultos os quais permaneciam submersos por diferentes intervalos de tempo (n = 11) e em dois tratamentos, água natural não aerada e água previamente fervida, com quatro repetições para cada tratamento, revelaram uma mortalidade máxima após 24 horas de mergulho no tratamento água previamente fervida. A sobrevivência dos adultos foi negativa e significativamente correlacionada com os tratamentos empregados e entre os diferentes intervalos de tempo. Os valores de oxigênio dissolvido (mg/l) na água diferiram significativamente entre os tratamentos aplicados, sendo positivamente correlacionado com a sobrevivência dos adultos nos dois tratamentos, embora mais acentuadamente no tratamento com água previamente fervida. A mortalidade dos adultos após 24 horas de mergulho no tratamento com água previamente fervida pode estar associada às condições físico-químicas da água não testadas neste estudo, como, por exemplo, baixa tensão superficial e concentração de solutos. Estes resultados sugerem uma funcionalidade do plastrão nos adultos desta espécie. Abstract in english The plastron theory was tested in adults of Neochetina eichhorniae Warner, 1970, through the analysis of the structure that coats these insects' integument and also through submersion laboratorial experiments. The tegument processes were recognized in three types: agglutinated scales with large perf [...] orations, plumose scales of varied sizes and shapes, and hairs. The experiments were carried out on 264 adult individuals which were kept submerged at different time intervals (n = 11) and in two types of treatment, natural non-aerated water and previously boiled water, with four repetitions for each treatment. The tests showed a maximum mortality after 24 hours of immersion in the previously boiled water treatment. The survival of the adults was negative and significantly correlated with the types of treatment employed and within the different time intervals. The values of oxygen dissolved in water (mg/l) differed significantly within the types of treatment employed. They were positively correlated with the survival of the adults in the two types of treatment, although more markedly in the treatment with previously boiled water. The mortality of adults after 24 hours of submersion in the treatment with previously boiled water may be associated with the physical-chemical conditions of the non-tested water in this study, such as low surface tension and concentration of solutes. These results suggest plastron functionality in the adults of this species.
Liu, J. T. C.; Kaptanoglu, H. T.
1987-01-01
The fundamental aspects of controlled multiple coherent mode presence in turbulent shear flows is first discussed, including the supplementary averaging procedures in addition to the Reynolds average and the nonlinear energy transfer mechanisms coupling the coherent modes, mean flow and fine-grained turbulence. Then the problem of a fundamental mode and its subharmonic in a developing mixing layer, the prototype problem of subharmonic cascade, is examined. An integral method is presented which allows the determination of the coherent wave envelope or amplitude simultaneously with the mean flow growth rate and turbulence energy. This is then generalized to the presence of multiple subharmonics using a binary-frequency interaction argument. Free shear layer control is discussed in terms of initial coherent mode amplitudes, dimensionless initial frequencies, phase angle between the modes and fine-grained turbulence levels, in particular, how these parameters could enhance or suppress the shear layer spreading rate and the levels of fine-grained turbulence.
Shear loading of costal cartilage
Subit, Damien
2014-01-01
A series of tests were performed on a single post-mortem human subject at various length scales. First, tabletop tests were performed. Next, the ribs and intercostal muscles were tested with the view to characterize the load transfer between the ribs. Finally, the costal cartilage was tested under shear loading, as it plays an important in the transfer of the load between the ribs and the sternum. This paper reports the results of dynamic shear loading tests performed on three samples of costal cartilage harvested from a single post-mortem human subject, as well as the quantification of the effective Young's modulus estimated from the amount of cartilage calcification.
Shear transfer across cracks in reinforced concrete
International Nuclear Information System (INIS)
An experimental and analytical investigation was conducted to assess the transfer of cyclic shear forces in cracked reinforced concrete by means of the interface shear transfer and dowel action mechanisms. Two test series evaluated the transfer of shear forces by the combination of the interface shear transfer and dowel action mechanisms, and the dowel action mechanism alone. The initial crack width and the reinforcement ratios provided at the shear plane, the number of loading cycles, and the cyclic shear stress intensity were the main variables studied using a test specimen modeled after an idealized section of the cracked structure. The average shear displacement, crack width, and reinforcement strains were measured in each specimen for all load increments. Simplified equations were developed to describe the first loading cycle stiffness exhibited by both the interface shear transfer and dowel action mechanism. A bilinear idealization was proposed for the experimental hysteresis curve of each mechanism together with the corresponding stiffness coefficients. Equations were derived from a nonlinear regression analysis for the splitting failure force for axial or dowel forces, and for their interaction. An equation was also proposed for the ultimate shear stress that can be transferred across a precracked shear plane. The research concluded that shear forces can be efficiently transferred across cracked surfaces by the combined action of the interface shear transfer and dowel action mechanisms. The investigation was motivated by the desire to assess the behavior of the shear transfer mechanism in cracked secondary nuclear containment vessels
Effects of shear on proteins in solution
THOMAS, C. R.; Geer, D.
2010-01-01
Abstract The effects of “shear” on proteins in solution are described and discussed. Research on this topic covers many decades, beginning with investigations of possible denaturation of enzymes during processing, whilst more recent concerns are how the quality of therapeutic proteins might be affected by shear or shear related effects. The paradigm that emerges from most studies is that shear in the fluid mechanical sense is unlikely by itself to damage most proteins and that inte...
Refraction of shear zones in granular materials
Unger, Tamas
2006-01-01
We study strain localization in slow shear flow focusing on layered granular materials. A heretofore unknown effect is presented here. We show that shear zones are refracted at material interfaces in analogy with refraction of light beams in optics. This phenomenon can be obtained as a consequence of a recent variational model of shear zones. The predictions of the model are tested and confirmed by 3D discrete element simulations. We found that shear zones follow Snell's law...
Gap opening in graphene by shear strain
Cocco, Giulio; Cadelano, Emiliano; Colombo, Luciano
2010-01-01
We exploit the concept of strain-induced band structure engineering in graphene through the calculation of its electronic properties under uniaxial, shear, and combined uniaxial-shear deformations. We show that by combining shear deformations to uniaxial strains it is possible modulate the graphene energy gap value from zero up to $0.9$ eV. Interestingly enough, the use of a shear component allows for a gap opening at moderate absolute deformation, safely smaller than the gr...
Kinematics and shear heat pattern of ductile simple shear zones with `slip boundary condition'
Mulchrone, Kieran F.; Mukherjee, Soumyajit
2015-06-01
Extrusion by Poiseuille flow and simple shear of hot lower crust has been deciphered from large hot orogens, and partial-slip boundary condition has been encountered in analogue models. Shear heat and velocity profiles are deduced from a simplified form of Navier-Stokes equation for simple shear together with extrusive Poiseuille flow and slip boundary condition for Newtonian viscous rheology. A higher velocity at the upper boundary of the shear zone promotes higher slip velocity at the lower boundary. The other parameters that affect the slip are viscosity and thickness of the shear zone and the resultant pressure gradient that drives extrusion. In the partial-slip case, depending on flow parameters (resultant pressure gradient, density and viscosity) and thickness of the shear zone, the velocity profiles can curve and indicate opposite shear senses. The corresponding shear heat profiles can indicate temperature maximum inside shear zones near either boundaries of the shear zone, or equidistant from them.
Pure shear axes and elastic strain energy
Norris, Andrew N.
2006-01-01
It is well known that a state of pure shear has distinct sets of basis vectors or coordinate systems: the principal axes, in which the stress is diagonal, and pure shear bases, in which diag(stress)=0. The latter is commonly taken as the definition of pure shear, although a state of pure shear is more generally defined by tr(stress)=0. New results are presented that characterize all possible pure shear bases. A pair of vector functions are derived which generate a set of pur...
International Nuclear Information System (INIS)
Subpicosecond lifetimes of states in shears band 1 in 197Pb were measured by means of the recoil distance method employing Gammasphere and the New Yale Plunger Device. The extracted reduced matrix elements, B(M1) , show a clear sensitivity to the crossing of different shears configurations reflecting the closing and reopening of the shears blades. The energies and B(M1) values in the band crossing region are successfully described in the framework of the semiclassical model of the shears bands. The relevance of core rotation contributions are shown. The results point to the existence of shears states with an angular momentum coupling angle larger than 90o
Magnetic shear. II - Hale region 17244
International Nuclear Information System (INIS)
A B-gamma(delta) sunspot group with growing delta-spots of trailing polarity shows evidence in H-alpha filament structure of a transition from a state of weak magnetic shear to a state of strong shear. The shear develops in the chromosphere and transition region to the corona overlying the photospheric magnetic neutral line separating the delta-spots from the leading polarity at a time when the delta-spots are undergoing rapid growth. Several major flares occur along the sheared portion of the neutral line following the shear development. Other segments of the neutral line far removed from the delta-spots show similar evidence of shear in the H-alpha filament structure and in C IV velocity patterns as well. These quiescent regions of shear are relatively steady or decaying with time and show very little related activity. 11 references
Phase Dynamic of Shear Melting
Directory of Open Access Journals (Sweden)
Manko N.N.
2014-08-01
Full Text Available The melting of an ultrathin lubricating film clamped between two atomically smooth solid surfaces that are in relative motion is analyzed. The influence of additive stresses fluctuations, strain and temperature on the process of lubricant melting is investigated taking into account the shear modulus deformation defect. The influence of the system parameters on the phase diagram, where the temperature noise intensity and the temperature of friction surfaces define the areas of dry, liquid and stick-slip friction, is analyzed.
Shear Stabilization in the Levitron
International Nuclear Information System (INIS)
The levitron is a toroidal hard-core tube of 30-cm minor diameter, with a ring core left unsupported for 20 msec. A 5-kG toroidal field, and a comparable poloidal field based on a ring-core current, are pulsed on with 60-to 16,000-?sec rise times. The magnetic shear is always large, insuring infinite-conductivity hydromagnetic stability. Finite-resistivity and non-hydromagnetic instabilities are expected, however; and their study is the object of the experiment. Levitron experiments in the high-current regime (for example, ?50-kA induced current, lasting 1 to 2 msec, at ?3 x 1013 -cm-3 plasma density and electron temperatures in the 100-eV range) show a small-scale ''magnetic flutter'' (?5 G, ?100 kc/sec) of flutelike structure. The stability analysis for the hard-core geometry, however, proves categorically that the observed mode cannot be of the finite-resistivity ''tearing'' type. To what extent shear stabilization is valid even in the absence of directed current, is theoretically still disputed. In this context we are studying electron-cyclotron heating at 10 Gc/sec. Hot-electron plasmas with the usual dilute high-energy (10 to 1000 keV) and dense (?1012 cm-3) low-energy components have been contained for 1 to 10 msec times after ?-wave cut off. When the initially generated high-energy component is left by itself, it proves highly unstable to cross-field transport, with or without shear, due partly to the mirror localization associated with the hard-core field in toroidal geometry. In the absence of shear (pure poloidal field), the flute instability limits the electron temperature of the dense-plasma component to ? 5 eV. With an additional toroidal field ?150 G, electron temperatures of 50 eV are attained, but they are still limited by a (presumably resistive) flute instability that is insensitive to a further 10-fold increase in shear. (author)
Influence of shearing displacement error study on two dimensional lateral shearing interferometry
Wang, Hongjun; Zhang, Cong; Tian, Ailing; Liu, Bingcai
2015-02-01
Lateral shearing interference detection is a economically efficient method which is used to the online testing process of aspheric surface. Whereas, when shear plate is used in lateral shearing interference to detect large aperture aspherical surface, the real moving shear plate can produce shearing error, which brings error into the two-dimensional wavefront reconstruction of aspheric surface. So, for shearing error, Zernike polynomial fitting method is used to study shearing displacement error on the influence of two-dimensional wavefront information reconstruction by computer simulation. For the same measured non-spherical surface, different shearing displacement error influences on the precision of wavefront reconstruction are compared by computer simulation - and finally build the corresponding relations between wave information integrity and shearing displacement error
Shear strength properties of wet granular materials
Richefeu, V; Radja"i, F; Richefeu, Vincent; Youssoufi, Moulay Sa\\"{i}d El; Radja\\"{i}, Farhang
2006-01-01
We investigate shear strength properties of wet granular materials in the pendular state (i.e. the state where the liquid phase is discontinuous) as a function of water content. Sand and glass beads were wetted and tested in a direct shear cell and under various confining pressures. In parallel, we carried out three-dimensional molecular dynamics simulations by using an explicit equation expressing capillary force as a function of interparticle distance, water bridge volume and surface tension. We show that, due to the peculiar features of capillary interactions, the major influence of water content over the shear strength stems from the distribution of liquid bonds. This property results in shear strength saturation as a function of water content. We arrive at the same conclusion by a microscopic analysis of the shear strength. We propose a model that accounts for the capillary force, the granular texture and particle size polydispersity. We find fairly good agreement of the theoretical estimate of the shear...
Hierarchical Cosmic Shear Power Spectrum Inference
Alsing, Justin; Jaffe, Andrew H; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till
2015-01-01
We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models \\emph{a posteriori} without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear $E$-...
Mixing in shear thinning fluids
Scientific Electronic Library Online (English)
H., Ameur; M., Bouzit.
2012-06-01
Full Text Available In the present study, a CFD characterization of the flow generated by curved-blade impellers in a cylindrical unbaffled vessel was carried out. The tank diameter was 300 mm, with a flat bottom. The liquid height was equal to the vessel diameter. The fluids simulated have a shear thinning behavior. A [...] nalyses concern the effect of the impeller speed, the fluid rheology and the number of impeller blades on the induced flow patterns and the power consumption. The predictions were compared with literature data and a satisfactory agreement was found.
Collision statistics in sheared inelastic hard spheres
Bannerman, Marcus N.; Green, Thomas E.; Grassia, Paul; Lue, Leo
2009-01-01
The dynamics of sheared inelastic-hard-sphere systems are studied using non-equilibrium molecular dynamics simulations and direct simulation Monte Carlo. In the molecular dynamics simulations Lees-Edwards boundary conditions are used to impose the shear. The dimensions of the simulation box are chosen to ensure that the systems are homogeneous and that the shear is applied uniformly. Various system properties are monitored, including the one-particle velocity distribution, g...
Fluid shear stress threshold regulates angiogenic sprouting
Galie, Peter A.; Nguyen, Duc-Huy T.; Choi, Colin K; Cohen, Daniel M.; Janmey, Paul A; Chen, Christopher S
2014-01-01
A great deal of research has investigated the biochemical factors that regulate angiogenic sprouting, but less is known about the role of fluid shear stress. Some studies have suggested distinct regulation by luminal flow within the vessel vs. transmural flow through its walls. In this paper, we demonstrate the existence of a shear stress threshold that when surpassed, induces angiogenic sprouting regardless of whether the shear is applied by primarily luminal or transmural flow. In addition ...
Residual Shear Deformations in the Coronary Artery
Wang, Ruoya; Gleason, Rudolph L.
2014-01-01
Quantifying arterial residual deformations is critical for understanding the stresses and strains within the arterial wall during physiological and pathophysiological conditions. This study presents novel findings on residual shear deformations in the left anterior descending coronary artery. Residual shear deformations are most evident when thin, long axial strips are cut from the artery. These strips deform into helical configurations when placed in isotonic solution. A residual shear angle...
Massive shear wall testing for nuclear industry
International Nuclear Information System (INIS)
Consequences of earthquakes have proven the need to study the shear mechanism of low-rise reinforced concrete shear walls thoroughly. Because of the complexity of reinforced concrete behavior generalized problem solutions are not readily available. Experimental testing remains essential for investigating concrete elements. The contribution deals with cyclic shear testing of thick low-rise reinforced concrete walls. Analysis of the data obtained resulted in the determination of hysteresis characteristics, nonlinear effects for shear, ultimate capacity and damping of the tested specimens. Various strength assessments and comparison to test results is given. The experimental investigation provides valuable results applicable in monitoring and design of structures. (author)
Confined Cubic Blue Phases under Shear
Henrich, O; Marenduzzo, D; Coveney, P V; Cates, M E
2011-01-01
We study the behaviour of confined cubic blue phases under shear flow via lattice Boltzmann simulations. We focus on the two experimentally observed phases, blue phase I and blue phase II. The disinclination network of blue phase II continuously b reaks and reforms under shear, leading to an oscillatory stress response in time. The oscillations are only regular for very th in samples. For thicker samples, the shear leads to a "stick-slip" motion of part of the network along the vorticity direction. Blue phase I responds very differently: its defect network undergoes seemingly chaotic rearrangements under shear, irrespective of system size.
Shear banding phenomena in a Laponite suspension
Ianni, F; Gentilini, S; Ruocco, G
2007-01-01
Shear localization in an aqueous clay suspension of Laponite is investigated through dynamic light scattering, which provides access both to the dynamics of the system (homodyne mode) and to the local velocity profile (heterodyne mode). When the shear bands form, a relaxation of the dynamics typical of a gel phase is observed in the unsheared band soon after flow stop, suggesting that an arrested dynamics is present during the shear localization regime. Periodic oscillations of the flow behavior, typical of a stick-slip phenomenon, are also observed when shear localization occurs. Both results are discussed in the light of various theoretical models for soft glassy materials.
Shear localization in a model glass
Varnik, F; Barrat, J L; Berthier, L
2002-01-01
Using molecular dynamics simulations, we show that a simple model of a glassy material exhibits the shear localization phenomenon observed in many complex fluids. At low shear rates, the system separates into a fluidized shear-band and an unsheared part. The two bands are characterized by a very different dynamics probed by a local intermediate scattering function. Furthermore, a stick-slip motion is observed at very small shear rates. Our results, which open the possibility of exploring complex rheological behavior using simulations, are compared to recent experiments on various soft glasses.
Novel shear mechanism in nanolayered composites
Energy Technology Data Exchange (ETDEWEB)
Mara, Nathan [Los Alamos National Laboratory; Bhattacharyya, Dhriti [Los Alamos National Laboratory; Hirth, John P [Los Alamos National Laboratory; Dickerson, Patricia O [Los Alamos National Laboratory; Misra, Amit [Los Alamos National Laboratory
2009-01-01
Recent studies have shown that two-phase nanocomposite materials with semicoherent interfaces exhibit enhanced strength, deformability, and radiation damage resistance. The remarkable behavior exhibited by these materials has been attributed to the atomistic structure of the bi-metal interface that results in interfaces with low shear strength and hence, strong barriers for slip transmission due to dislocation core spreading along the weak interfaces. In this work, the low interfacial shear strength of Cu/Nb nanoscale multilayers dictates a new mechanism for shear banding and strain softening during micropillar compression. Previous work investigating shear band formation in nanocrystalline materials has shown a connection between insufficient strain hardening and the onset of shear banding in Fe and Fe-10% Cu, but has also shown that hardening does not necessarily offset shear banding in Pd nanomaterials. Therefore, the mechanisms behind shear localization in nanocrystalline materials are not completely understood. Our findings, supported by molecular dynamics simulations, provide insight on the design of nanocomposites with tailored interface structures and geometry to obtain a combination of high strength and deformability. High strength is derived from the ability of the interfaces to trap dislocations through relative ease of interfacial shear, while deformability can be maximized by controlling the effects of loading geometry on shear band formation.
Shear strength in one- and two-way slabs according to the critical shear crack theory
Muttoni, Aurelio; Fernández Ruiz, Miguel
2008-01-01
Currently, there is no generally-accepted theory giving a physical explanation of the shear strength in one- and two-way slabs. Furthermore, for members without transverse reinforcement, shear strength is estimated in most codes of practice following empirical or semi-empirical approaches. In this paper, the fundamentals of the Critical Shear Crack Theory (CSCT) are introduced. This theory, based on a mechanical model, is shown to provide a unified approach for one- and two-way shear in...
Shear wall ultimate drift limits
International Nuclear Information System (INIS)
Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated
Shear wall ultimate drift limits
Energy Technology Data Exchange (ETDEWEB)
Duffey, T.A. [Duffy, (T.A.) Tijeras, NM (United States); Goldman, A. [Goldman, (A.), Sandia, Los Alamos, NM (United States); Farrar, C.R. [Los Alamos National Lab., NM (United States)
1994-04-01
Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated.
Rearrangements and Dilatancy for Sheared Dense Materials
Lemaître, Anaël
2001-01-01
Constitutive equations are proposed for dense materials, based on the identification of two types of free-volume activated rearrangements associated to shear and compaction. Two situations are studied: the case of an amorphous solid in a stress-strain test, and the case of a lubricant in tribology test. Varying parameters, strain softening, shear thinning, and stick-slip motion can be observed.
On the shear instability of fluid interfaces
Alexakis, A.; Young, Y; Rosner, R.
2001-01-01
We examine the linear stability of fluid interfaces subjected to a shear flow. Our main object is to generalize previous work to arbitrary Atwood number, and to allow for surface tension and weak compressibility. The motivation derives from instances in astrophysical systems where mixing across material interfaces driven by shear flows may significantly affect the dynamical evolution of these systems.
Finite element modelling of fabric shear
Lin, Hua; Clifford, Mike J.; Long, Andrew C.; Sherburn, Martin
2009-01-01
In this study, a finite element model to predict shear force versus shear angle for woven fabrics is developed. The model is based on the TexGen geometric modelling schema, developed at the University of Nottingham and orthotropic constitutive models for yarn behaviour, coupled with a unified displacement-difference periodic boundary condition. A major distinction from prior modelling of fabric shear is that the details of picture frame kinematics are included in the model, which allows the mechanisms of fabric shear to be represented more accurately. Meso- and micro-mechanisms of deformation are modelled to determine their contributions to energy dissipation during shear. The model is evaluated using results obtained for a glass fibre plain woven fabric, and the importance of boundary conditions in the analysis of deformation mechanisms is highlighted. The simulation results show that the simple rotation boundary condition is adequate for predicting shear force at large deformations, with most of the energy being dissipated at higher shear angles due to yarn compaction. For small deformations, a detailed kinematic analysis is needed, enabling the yarn shear and rotation deformation mechanisms to be modelled accurately.
Finite element modelling of fabric shear
International Nuclear Information System (INIS)
In this study, a finite element model to predict shear force versus shear angle for woven fabrics is developed. The model is based on the TexGen geometric modelling schema, developed at University of Nottingham and orthotropic constitutive models for yarn behaviour, coupled with a unified displacement-difference periodic boundary condition. A major distinction from prior modelling of fabric shear is that the details of picture frame kinematics are included in the model, which allows the mechanisms of fabric shear to be represented more accurately. Meso- and micro-mechanisms of deformation are modelled to determine their contributions to energy dissipation during shear. The model is evaluated using results obtained for a glass fibre plain woven fabric, and the importance of boundary conditions in the analysis of deformation mechanisms is highlighted. The simulation results show that the simple rotation boundary condition is adequate for predicting shear force at large deformations, with most of the energy being dissipated at higher shear angles due to yarn compaction. For small deformations, a detailed kinematic analysis is needed, enabling the yarn shear and rotation deformation mechanisms to be modelled accurately
Nonlinear shear viscosity and long time tails
Zwanzig, R.
1981-01-01
A theoretical connection between nonlinear shear viscosity and the long time tail of the equilibrium stress-stress correlation function is pointed out. The connection is a consequence of the Goddard-Miller rheological equation of state which takes into account the angular rotation of a fluid in steady uniform shear.
Plastic deformation: Shearing mountains atom by atom
Energy Technology Data Exchange (ETDEWEB)
Müllner, Peter, E-mail: petermullner@boisestate.edu [Department of Materials Science and Engineering, Boise State University, Boise, ID 83725 (United States)
2013-11-15
Highlights: ? Rocks, wood, ceramics, semiconductors, and metals all deform in the same way, namely by heterogeneous shear banding via hierarchical orthogonal shear modes. ? While the governing principles of deformation are the same for rocks, wood, ceramics, semiconductors, and metals, these materialsdiffer in their microscopic deformation mechanisms and in the width of the shear band, which covers twelve orders of magnitude from angstroms to hundreds of meters. ? Microscopic deformation mechanisms couple to macroscopic deformation mechanisms, i.e. shear banding, through the collective properties of defect groups on the mesoscale. -- Abstract: Conventional wisdom established atomistic defects, dislocations, as agents of plastic deformation. On macroscopic scale, rock, wood, steel, tough ceramics, fiber reinforced composites, and silicon all deform in the same way and produce the same pattern; shear bands. The argumentation presented here, starts on the largest length scale of the problem at hand and leads through a number of hierarchical levels down to the atomistic mechanism. Shear bands develop discontinuously by the motion of a process zone. Locally, i.e. in the process zone, deformation proceeds perpendicularly to the macroscopic shear, in combination with a rotation. The microscopic shear itself may occur again in a discontinuous manner and again orthogonally to the intermediate level and so on at ever smaller scale. Material properties come into play at the highest hierarchical level, i.e. at the smallest length scale where they control the well-known micromechanisms.
Solvable groups and a shear construction
DEFF Research Database (Denmark)
Freibert, Marco; Swann, Andrew Francis
2015-01-01
The twist construction is a geometric model of T-duality that includes constructions of nilmanifolds from tori. This paper shows how one-dimensional foliations on manifolds may be used in a shear construction, which in algebraic form builds certain solvable Lie groups from Abelian ones. We discuss other examples of geometric structures that may be obtained from the shear construction.
Quadruple Lap Shear Processing Evaluation
Thornton, Tony N.; McCool, A. (Technical Monitor)
2000-01-01
The Thiokol, Science and Engineering Huntsville Operations (SEHO) Laboratory has previously experienced significant levels of variation in testing Quadruple Lap Shear (QLS) specimens. The QLS test is used at Thiokol / Utah for the qualification of Reusable Solid Rocket Motor (RSRM) nozzle flex bearing materials. A test was conducted to verify that process changes instituted by SEHO personnel effectively reduced variability, even with normal processing variables introduced. A test matrix was designed to progress in a series of steps; the first establishing a baseline, then introducing additional solvents or other variables. Variables included normal test plan delay times, pre-bond solvent hand-wipes and contaminants. Each condition tested utilized standard QLS hardware bonded with natural rubber, two separate technicians and three replicates. This paper will report the results and conclusions of this investigation.
Vorticity Waves in Shear Flows
Directory of Open Access Journals (Sweden)
Horia DUMITRESCU
2015-03-01
Full Text Available The main purpose of this paper is to bring about the vorticity-creation process at the boundary surfaces on one hand and to understand the interaction of concentrated vorticity structures on the shear flow on the other hand. The paper address the simulation of flow visualization of the vortical structures accounting for both the circulation and the degree of concentration of vorticity via the exact nonlinear solution of Stuart for an inviscid unsteady mixing layer. At a fixed volume of circulation an increased concentration of vorticity is provoked by decreasing the area containing most of the vorticity, and then it spreads over an increased area of the flow. A concentration parameter characterizing vorticity is defined and flow patterns, representing waves travelling in the flow direction are found for different combinations of vorticity concentration and circulation.
Compressibility effects in turbulent shear layers
Bogdanoff, D. W.
1983-06-01
For a number of reasons, it would be desirable to have a better understanding of the behavior of compressible turbulent shear layers. Such shear layers are important in the production of jet and rocket engine noise. They are present in supersonic combustion jet engine designs. Compressible shear layers are also important in many high power laser systems. In the present investigation, it is proposed to employ a Mach number M+ which may be of value in correlating compressibility effects. Experimental results showing the decrease of shear layer width with increasing Mach number are compared with the corresponding variations of theoretical instability growth rates calculated by Blumen et al. (1975). The agreement between theoretical and experimental results suggests that an important factor contributing to the decrease in the shear layer growth rate with increasing M+ is the decrease in the maximum growth rates of the large-scale Kelvin-Helmholtz instabilities.
Dynamics and control of turbulent shear flows
1989-05-01
Topics of study during this time period include: Bounded Shear Flow - Experimental Approaches, Control of Laminar Separated Shear Layer on Airfoils; Control of Large Scale Features in Turbulent Mixing Layers; Direct Numerical Simulations of Flow Control; Control of Entrainment in Confined Shear Layers; Theoretical Underpinnings: Amplitude and Phase Descriptions of Coherent Structures; Phase Control of Vortex Structures in Shear Flows; Mathematical Analysis of Navier Stokes Equations; and Effects of Longitudinal Roughness Elements upon Turbulent Boundary Layer. Other areas of concern are: Some ideas on the Control of Near Wall Eddies; A technique for Acoustic Excitation of Separated Shear Flow; Heat Transfer in Rayleigh-Benard Convection; Energy Transfer and Non local Interactions in Homogeneous Isotopic Turbulence. Invarient Manifold Theory for Hydrodynamic transition; The theory of nonstationary viscous flow Past Plane Domains with Noncompact Boundaries; and Stability Properties of Subsonic Mixing Layers.
Squirming through shear-thinning fluids
Datt, Charu; Elfring, Gwynn J; Pak, On Shun
2015-01-01
Many microorganisms find themselves immersed in fluids displaying non-Newtonian rheological properties such as viscoelasticity and shear-thinning viscosity. The effects of viscoelasticity on swimming at low Reynolds numbers have already received considerable attention, but much less is known about swimming in shear-thinning fluids. A general understanding of the fundamental question of how shear-thinning rheology influences swimming still remains elusive. To probe this question further, we study a spherical squirmer in a shear-thinning fluid using a combination of asymptotic analysis and numerical simulations. Shear-thinning rheology is found to affect a squirming swimmer in nontrivial and surprising ways; we predict and show instances of both faster and slower swimming depending on the surface actuation of the squirmer. We also illustrate that while a drag and thrust decomposition can provide insights into swimming in Newtonian fluids, extending this intuition to problems in complex media can prove problemat...
Experimental study on the adiabatic shear bands
International Nuclear Information System (INIS)
Four martensitic steels (Z50CDV5 steel, 28CND8 steel, 35NCDV16 steel and 4340 steel) with different hardness between 190 and 600 Hsub(B) (Brinell hardness), have been studied by means of dynamic compressive tests on split Hopkinson pressure bar. Microscopic observations show that the fracture are associated to the development of adiabatic shear bands (except 4340 steel with 190 Hsub(B) hardness). By means of tests for which the deformation is stopped at predetermined levels, the measurement of shear and hardness inside the band and the matrix indicates the chronology of this phenomenon: first the localization of shear, followed by the formation of adiabatic shear band and ultimatly crack initiation and propagation. These results correlated with few simulations by finite elements have permitted to suggest two mecanisms of deformation leading to the formation of adiabatic shear bands in this specific test
Predictive modelling of JET optimised shear discharges
International Nuclear Information System (INIS)
Transport analysis of high performance JET plasmas with optimised magnetic shear (OMS) has revealed many interesting features which can not be explained by the existing JET empirical transport model. TRANSP analysis shows that transport coefficients in OMS plasmas are often reduced in the plasma core to the level of ion neoclassical transport. TRANSP analysis and predictive modelling with JETTO show that this region of improved confinement appears near the plasma centre and then expands outwards in a way which does not follow either the evolution of the region with the negative magnetic shear or the propagation of the region with a large shear in plasma rotation. The best agreement with experiment has been achieved by using a transport model which combines the effect of a long wavelength decoupling due to small magnetic shear with its suppression by strong rotational shear. Predictive modelling of some of the characteristic JET OMS plasmas gives quite good agreement between such a model and the experimental data. (author)
Miyamoto, Naokazu; Hirata, Kosuke; Kanehisa, Hiroaki; Yoshitake, Yasuhide
2015-01-01
Ultrasound shear wave elastography is becoming a valuable tool for measuring mechanical properties of individual muscles. Since ultrasound shear wave elastography measures shear modulus along the principal axis of the probe (i.e., along the transverse axis of the imaging plane), the measured shear modulus most accurately represents the mechanical property of the muscle along the fascicle direction when the probe’s principal axis is parallel to the fascicle direction in the plane of the ultrasound image. However, it is unclear how the measured shear modulus is affected by the probe angle relative to the fascicle direction in the same plane. The purpose of the present study was therefore to examine whether the angle between the principal axis of the probe and the fascicle direction in the same plane affects the measured shear modulus. Shear modulus in seven specially-designed tissue-mimicking phantoms, and in eleven human in-vivo biceps brachii and medial gastrocnemius were determined by using ultrasound shear wave elastography. The probe was positioned parallel or 20° obliquely to the fascicle across the B-mode images. The reproducibility of shear modulus measurements was high for both parallel and oblique conditions. Although there was a significant effect of the probe angle relative to the fascicle on the shear modulus in human experiment, the magnitude was negligibly small. These findings indicate that the ultrasound shear wave elastography is a valid tool for evaluating the mechanical property of pennate muscles along the fascicle direction. PMID:25853777
Shear stress distribution due to shear and Rayleigh wave propagation at deep soil sites
International Nuclear Information System (INIS)
Earthquake strong motion at ground surface may be described as the combined result of body (compression and shear) waves and surface waves. In the course of earthquake engineering site response analyses, it is usually assumed that surface motions are a result of vertically propagating body waves. In studies of liquefaction potential, it is assumed that soil shear strains are a result of vertically propagating shear waves. However, shear strains are also caused by surface Rayleigh waves and solutions to strains from each source are derived and compared in the paper, and the results for shear strain in terms of surface acceleration and wave length are presented in non-dimensional form. The results of this investigation show that the distribution of soil shear strain as a function of depth below the ground surface is different depending upon whether shear waves or Rayleigh waves are assumed to be the source of horizontal motions at the ground surface. (Auth.)
Transient dynamics in dense colloidal suspensions under shear: shear rate dependence
International Nuclear Information System (INIS)
A combination of confocal microscopy and rheology experiments, Brownian dynamics (BD) and molecular dynamics (MD) simulations and mode coupling theory (MCT) have been applied in order to investigate the effect of shear rate on the transient dynamics and stress-strain relations in supercooled and glassy systems under shear. Immediately after shear is switched on, the microscopic dynamics display super-diffusion and the macroscopic rheology a stress overshoot, which become more pronounced with increasing shear rate. MCT relates both to negative sections of the generalized shear modulus, which grow with increasing shear rate. When the inverse shear rate becomes much smaller than the structural relaxation time of the quiescent system, relaxation through Brownian motion becomes less important. In this regime, larger stresses are accumulated before the system yields and the transition from localization to flow occurs earlier and more abruptly.
Sheared Ising models in three dimensions
Hucht, Alfred; Angst, Sebastian
2013-03-01
The nonequilibrium phase transition in sheared three-dimensional Ising models is investigated using Monte Carlo simulations in two different geometries corresponding to different shear normals [A. Hucht and S. Angst, EPL 100, 20003 (2012)]. We demonstrate that in the high shear limit both systems undergo a strongly anisotropic phase transition at exactly known critical temperatures Tc which depend on the direction of the shear normal. Using dimensional analysis, we determine the anisotropy exponent ? = 2 as well as the correlation length exponents ?? = 1 and ?? = 1 / 2 . These results are verified by simulations, though considerable corrections to scaling are found. The correlation functions perpendicular to the shear direction can be calculated exactly and show Ornstein-Zernike behavior. The nonequilibrium phase transition in sheared three-dimensional Ising models is investigated using Monte Carlo simulations in two different geometries corresponding to different shear normals [A. Hucht and S. Angst, EPL 100, 20003 (2012)]. We demonstrate that in the high shear limit both systems undergo a strongly anisotropic phase transition at exactly known critical temperatures Tc which depend on the direction of the shear normal. Using dimensional analysis, we determine the anisotropy exponent ? = 2 as well as the correlation length exponents ?? = 1 and ?? = 1 / 2 . These results are verified by simulations, though considerable corrections to scaling are found. The correlation functions perpendicular to the shear direction can be calculated exactly and show Ornstein-Zernike behavior. Supported by CAPES-DAAD through PROBRAL as well as by the German Research Society (DFG) through SFB 616 ``Energy Dissipation at Surfaces.''
Scientific Electronic Library Online (English)
Tereza C.A., ALMEIDA; Marília I.S., FOLEGATTI; Maria Teresa A., FREIRE; Márcia S., MADEIRA; Fernando T., SILVA; Maria Aparecida A.P. da, SILVA.
1999-05-01
Full Text Available Onze provadores selecionados e treinados avaliaram a aparência, aroma, sabor e textura de seis diferentes marcas de figo em calda, comercializadas no mercado brasileiro, utilizando o método de Análise Descritiva Quantitativa (ADQ) adaptado. As amostras foram testadas utilizando-se blocos incompletos [...] balanceados e os resultados estatisticamente analisados por Análise de Variância (ANOVA) e Análise de Componente Principal (ACP). Figos em calda provenientes de indústrias distintas mostraram uma grande diferença quanto ao perfil sensorial. Dos quinze descriptores desenvolvidos pela equipe sensorial, suculência e aroma doce foram os mais importantes para discriminar as amostras entre si. As medidas de cor obtidas através do colorímetro de Hunter mostraram boa relação com as medidas sensoriais, entretanto, as medidas de textura realizadas pelo aparelho Warner-Bratzler não refletiram as variações de textura encontradas nas amostras pela equipe sensorial. A metodologia desenvolvida no presente estudo demonstrou ser bastante eficiente na caracterização e discriminação de amostras, em função de seus perfis sensoriais. Assim, a presente metodologia pode ser muito útil a laboratórios de Controle de Qualidade e Desenvolvimento de Novos Produtos nas indústrias de alimentos. Abstract in english Eleven selected and trained panelists evaluated the appearance, aroma, flavor and texture of six different brands of Brazilian canned figs by adapted Quantitative Descriptive Analysis. A descriptive ballot and reference material illustrating sensory characteristics of the figs were developed. Sample [...] s were tested using a incomplete block design and the results analyzed by Analysis of Variance (ANOVA) and Principal Component Analysis (PCA). The samples sensory profiles showed large differences. From the fifteen descriptors developed by the panel, juiciness and sweet aroma were the most important for discriminating among samples. Instrumental measurements of color, obtained with a Hunter colorimeter, showed good relation with sensory measurements; but the shear force, obtained with a Warner-Bratzler shear instrument, did not related well with sensory measurements of texture. The methodology developed in this study was very efficient for characterizing and discriminating among the samples as a function of their sensory profiles; furthermore, it can be very useful to the Quality Control and Product Development laboratories of food industries.
Directory of Open Access Journals (Sweden)
Tereza C.A. ALMEIDA
1999-05-01
Full Text Available Onze provadores selecionados e treinados avaliaram a aparência, aroma, sabor e textura de seis diferentes marcas de figo em calda, comercializadas no mercado brasileiro, utilizando o método de Análise Descritiva Quantitativa (ADQ adaptado. As amostras foram testadas utilizando-se blocos incompletos balanceados e os resultados estatisticamente analisados por Análise de Variância (ANOVA e Análise de Componente Principal (ACP. Figos em calda provenientes de indústrias distintas mostraram uma grande diferença quanto ao perfil sensorial. Dos quinze descriptores desenvolvidos pela equipe sensorial, suculência e aroma doce foram os mais importantes para discriminar as amostras entre si. As medidas de cor obtidas através do colorímetro de Hunter mostraram boa relação com as medidas sensoriais, entretanto, as medidas de textura realizadas pelo aparelho Warner-Bratzler não refletiram as variações de textura encontradas nas amostras pela equipe sensorial. A metodologia desenvolvida no presente estudo demonstrou ser bastante eficiente na caracterização e discriminação de amostras, em função de seus perfis sensoriais. Assim, a presente metodologia pode ser muito útil a laboratórios de Controle de Qualidade e Desenvolvimento de Novos Produtos nas indústrias de alimentos.Eleven selected and trained panelists evaluated the appearance, aroma, flavor and texture of six different brands of Brazilian canned figs by adapted Quantitative Descriptive Analysis. A descriptive ballot and reference material illustrating sensory characteristics of the figs were developed. Samples were tested using a incomplete block design and the results analyzed by Analysis of Variance (ANOVA and Principal Component Analysis (PCA. The samples sensory profiles showed large differences. From the fifteen descriptors developed by the panel, juiciness and sweet aroma were the most important for discriminating among samples. Instrumental measurements of color, obtained with a Hunter colorimeter, showed good relation with sensory measurements; but the shear force, obtained with a Warner-Bratzler shear instrument, did not related well with sensory measurements of texture. The methodology developed in this study was very efficient for characterizing and discriminating among the samples as a function of their sensory profiles; furthermore, it can be very useful to the Quality Control and Product Development laboratories of food industries.
An, J Y; Zheng, J X; Li, J Y; Zeng, D; Qu, L J; Xu, G Y; Yang, N
2010-08-01
The objective of the present study was to evaluate the role of myofiber characteristics and the thickness of 2 major muscle membranes, perimysium and endomysium, in determining the breast meat tenderness of chickens. Birds from 2 breeds (White Leghorn and a line of broiler) were chosen. Chicks were sexed and wing-banded at hatch and were grown in separate cages in a single house. Sixty broilers and 60 White Leghorns were harvested at 6 wk of age, respectively, whereas another 60 White Leghorns were slaughtered at 18 wk of age. An equal number of males and females was maintained for each group. Body weight, breast muscle weight, pH, drip loss, cooking loss, Warner-Bratzler shear force value (SFV), total energy of shear force, fiber diameter, sarcomere length, myofiber density, and the thickness of endomysium and perimysium of the breast were determined for each bird. At 6 wk of age, histological examination indicated that the size of myofiber and thickness of endomysium and perimysium of broilers were larger than that those of White Leghorns (P cooking loss of broilers were smaller (P cooking loss of broilers were smaller than those of White Leghorns at similar BW (P < 0.01). Meat tenderness was negatively correlated with myofiber density (-0.27) and the thickness of endomysium (-0.29) and positively correlated with the thickness of perimysium (0.20). It is suggested that muscle membrane should be considered in evaluating meat tenderness of the chicken. PMID:20634533
Directory of Open Access Journals (Sweden)
R.E. Dyer
2005-01-01
Full Text Available The effects of Zeranol and castration on organoleptic and mechanically assessed tenderness were studied using the 193 young beef cattle described in the companion paper (Impact of castration and zeranol implants on bullocks: I. Behavior, growth and carcass traits. Sensory panel evaluations showed that steaks from control and implanted steer carcasses had higher mean scores for tenderness, juiciness, flavor and overall palatability than those from control and implanted bulls. Implanting did not influence juiciness or flavor within the bull or steer groups, but control bulls and steers were significantly (P<.005 more tender and more palatable overall than were implanted bulls and steers. When comparing the mechanical measurements there was considerable variation among the instruments. The Armour tenderometer ranked meat from the implanted steers significantly tougher than either the control or implanted bulls. The Warner-Bratzler shear, Krammer shear and Instron Press ranked steaks from steers significantly more tender than those from bulls. Implanted and control groups of animals were similar in tenderness when judged by the mechanical measurements. Behavior and palatability characteristics of implanted and control bulls and steers were also studied. Implantation made bulls and steers more docile. The libido measurements were also lower for the implanted bulls and steers. Within group of implanted bulls and steers those that were least aggressive tended to be more tender than their more aggressive counterparts.
Keyser, Daniel; Anthes, Richard A.
1982-08-01
A series of numerical experiments with the Hoskins-Bretherton horizontal shear model of frontogenesis in an, amplifying, two-dimensional baroclinic wave is performed. The analytic solutions from the Boussinesq, semi-geostrophic model provide initial conditions for numerical integrations with a two-dimensional, dry version of the fully compressible, hydrostatic primitive equation (PE) model of Anthes and Warner with 40 km horizontal resolution. The PE model is integrated 1) without planetary boundary layer (PBL) physics; 2) with a one-layer bulk-drag scheme; and 3) with a high-vertical-resolution PBL model. The lower boundary is thermally insulated in order to isolate the effect of the internal mixing of heat in the PBL.The simulation with the high-resolution PBL physics resolves several realistic features including 1) a narrow updraft at the top of the PBL above the sea-level pressure trough at the warm edge of the frontal zone; 2) a stable layer capping the PBL to the rear of the frontal zone; and 3) slightly unstable or neutral lapse rates in the PBL behind the front and stable lapse rates in the PBL ahead of the front. A diagnostic analysis of the frontogenesis indicates that the fine structure resulting from adding PBL physics can be attributed to the frictionally driven, ageostrophic inflow in the PBL toward the surface pressure trough in which the frontal zone is located. A finding of particular interest is that the stability patterns in the PBL on either side of the front evolve independently of sensible heating at the surface.
Development of Short Stroke Shearing Technology For FBR Fuel Pin
Higuchi, Hidetoshi; Koizumi, Kenji; Hirano, Hiroyasu; Tasaka, Masayuki; Washiya, Tadahiro; Kobayashi, Tsuguyuki
The short stroke shearing tests with simulated fuel pin bundle were carried out in engineering scale. The shearing device was designed to handle the simulated Monju (FBR prototype reactor) type fuel pin bundle. Monju type and Commercial reactor type simulated fuel pins were used for the test. The sheared pin length and the opening ratio of sheared section were measured under several shearing conditions such as the pressure to hold pin bundle, the shearing speed and the filling-ratio of pins in the pin magazine. Both types of fuel pin were able to be sheared accurately at the length of about 10mm, and the opening ratio of sheared section was not significantly reduced. As the results, fundamental data of the short stroke shearing characteristics were obtained and that shearing method was confirmed to be promising with the reliable shearing device.
Shear viscosity of liquid mixtures: Mass dependence
International Nuclear Information System (INIS)
Expressions for zeroth, second, and fourth sum rules of transverse stress autocorrelation function of two component fluid have been derived. These sum rules and Mori's memory function formalism have been used to study shear viscosity of Ar-Kr and isotopic mixtures. It has been found that theoretical result is in good agreement with the computer simulation result for the Ar-Kr mixture. The mass dependence of shear viscosity for different mole fraction shows that deviation from ideal linear model comes even from mass difference in two species of fluid mixture. At higher mass ratio shear viscosity of mixture is not explained by any of the emperical model. (author)
Shear instability in magnetized, collisional dusty plasmas
Energy Technology Data Exchange (ETDEWEB)
Pandey, B. P. [Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales 2109 (Australia); Vladimirov, S. V.; Samarian, A. A. [School of Physics, University of Sydney, New South Wales 2006 (Australia)
2012-06-15
The shear instability of magnetized, collisional dusty plasma is investigated in the present work. It is demonstrated that the relative drift between the charged dust and magnetised electrons and ions which give rise to the Hall effect is crucial to this instability. Although the nature of present shear instability is similar to the Kelvin-Helmholtz instability, the role of magnetic field in the present case is important in destabilising waves. The maximum growth rate of the instability is proportional only to the shear gradient and is independent of the ambient magnetic field strength. Most unstable wavenumber is a function of ambient dust parameters.
Particle dynamics in sheared granular matter
Losert, W; Lubenskii, T C; Gollub, J P
2000-01-01
The particle dynamics and shear forces of granular matter in a Couette geometry are determined experimentally. The normalized tangential velocity $V(y)$ declines strongly with distance $y$ from the moving wall, independent of the shear rate and of the shear dynamics. Local RMS velocity fluctuations $\\delta V(y)$ scale with the local velocity gradient to the power $0.4 \\pm 0.05$. These results agree with a locally Newtonian, continuum model, where the granular medium is assumed to behave as a liquid with a local temperature $\\delta V(y)^2$ and density dependent viscosity.
A magnetorheological elastomer compressive and shear sensor
Ghafoorianfar, Nima; Gordaninejad, Faramarz
2015-04-01
A magnetorheological elastomer (MRE)-based wireless sensor is designed, developed and tested, which is capable of sensing compression and shear forces. The MRE wireless sensor system consists of a disk-shape MRE sample with two thin steel electrodes attached to both sides and two wires connected to electrodes. Electrical resistance of MRE sensor samples changes due to piezoresistance behavior of MRE as various axial and shear stresses are applied. Electrical resistance decreases as the applied compressive axial forces increases, on the other hand, the electrical resistance increases as the applied shear force increases. Different MRE sensor configurations are evaluated for design optimization.
Wittmer, J. P.; Xu, H; Benzerara, O.; Baschnagel, J
2015-01-01
The shear stress relaxation modulus $G(t)$ may be determined from the shear stress $\\tau(t)$ after switching on a tiny step strain $\\gamma$ or by inverse Fourier transformation of the storage modulus $G^{\\prime}(\\omega)$ or the loss modulus $G^{\\prime\\prime}(\\omega)$ obtained in a standard oscillatory shear experiment at angular frequency $\\omega$. It is widely assumed that $G(t)$ is equivalent in general to the equilibrium stress autocorrelation function $C(t) = \\beta V \\la...
Effect of shear on aircraft landing
Luers, J. K.; Reeves, J. B.
1973-01-01
A simulation study was conducted to determine the effect of wind shear on aircraft landings. The landing of various type of commercial and military aircraft was digitally simulated starting from an initial altitude of 300 feet. Assuming no pilot feedback during descent, the deviation in touchdown point due to vertical profiles of wind shear was determined. The vertical profiles of wind shear are defined in terms of surface roughness, Z sub 0, and stability, L, parameters. The effects on touchdown due to Z sub 0 and L have been calculated for the different type aircraft. Comparisons were made between the following types of aircraft: (1) C-130E, (2) C-135A, (3) C-141, (4) DC-8, (5) Boeing 747, and (6) an augmentor-wing STOL. In addition, the wind shear effect on touchdown resulting from different locations of the center of gravity and gross weights was also analyzed.
Mesoscale Elucidation of Biofilm Shear Behavior
Barai, Pallab; Mukherjee, Partha P
2015-01-01
Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regions: a) initial increase in stiffness due to strain stiffe...
Shear thickening, frictionless and frictional rheologies
Mari, Romain; Morris, Jeffrey F; Denn, Morton M
2014-01-01
Particles suspended in a Newtonian fluid raise the viscosity and also generally give rise to a shear-rate dependent rheology. In particular, pronounced shear thickening is observed at large solid volume fractions. In a recent article (R. Seto, R. Mari, J. F. Morris, and M. M. Denn., Phys. Rev. Lett., 111:218301, 2013) we have considered the minimum set of components to reproduce the experimentally observed shear thickening behavior, including Discontinuous Shear Thickening (DST). We have found frictional contact forces to be essential, and were able to reproduce the experimental behavior by a simulation including this physical ingredient. In the present article, we thoroughly investigate the effect of friction and express it in the framework of the jamming transition. The viscosity divergence at the jamming transition has been a well known phenomenon in suspension rheology, as reflected in many empirical laws for the viscosity. Friction can affect this divergence, and in particular the jamming packing fractio...
Recent progress in shear punch testing
International Nuclear Information System (INIS)
The shear punch test was developed in response to the needs of the materials development community for small-scale mechanical properties tests. Such tests will be of great importance when a fusion neutron simulation device is built, since such a device is expected to have a limited irradiation volume. The shear punch test blanks a circular disk from a fixed sheet metal specimen, specifically a TEM disk. Load-displacement data generated during the test can be related to uniaxial tensile properties such as yield and ultimate strength. Shear punch and tensile tests were performed at room temperature on a number of unirradiated aluminum, copper, vanadium, and stainless steel alloys and on several irradiated aluminum alloys. Recent results discussed here suggest that the relationship between shear punch strength and tensile strength varies with alloy class, although the relationship determined for the unirradiated condition remains valid for the irradiated aluminum alloys
Granular Shear Flow in Varying Gravitational Environments
Murdoch, N; Green, S F; de Lophem, T-L; Michel, P; Losert, W
2013-01-01
Despite their very low surface gravities, asteroids exhibit a number of different geological processes involving granular matter. Understanding the response of this granular material subject to external forces in microgravity conditions is vital to the design of a successful asteroid sub-surface sampling mechanism, and in the interpretation of the fascinating geology on an asteroid. We have designed and flown a Taylor-Couette shear cell to investigate granular flow due to rotational shear forces under the conditions of parabolic flight microgravity. The experiments occur under weak compression. First, we present the technical details of the experimental design with particular emphasis on how the equipment has been specifically designed for the parabolic flight environment. Then, we investigate how a steady state granular flow induced by rotational shear forces differs in varying gravitational environments. We find that the effect of constant shearing on the granular material, in a direction perpendicular to t...
Torsion and shear stresses in ships
Shama, Mohamed
2010-01-01
This book covers an area of ship structure analysis and design that has not been exhaustively examined by other references. It presents the basic concepts of the methods and procedures required to calculate torsion and shear stresses in ship structures.
Heterogeneous shear in hard sphere glasses
Mandal, Suvendu; Raabe, Dierk; Varnik, Fathollah
2012-01-01
There is growing evidence that the flow of driven amorphous solids is not homogeneous, even if the macroscopic stress is constant across the system. Via event driven molecular dynamics simulations of a hard sphere glass, we provide the first direct evidence for a correlation between the fluctuations of the local volume-fraction and the fluctuations of the local shear rate. Higher shear rates do preferentially occur at regions of lower density and vice versa. The temporal behavior of fluctuations is governed by a characteristic time scale, which, when measured in units of strain, is independent of shear rate in the investigated range. Interestingly, the correlation volume is also roughly constant for the same range of shear rates. A possible connection between these two observations is discussed.
Shear viscosity in antikaon condensed matter
Nandi, Rana; Banik, Sarmistha; Bandyopadhyay, Debades
2009-01-01
We investigate the shear viscosity of neutron star matter in the presence of an antikaon condensate. The electron and muon number densities are reduced due to the appearance of a $K^-$ condensate in neutron star matter, whereas the proton number density increases. Consequently the shear viscosity due to scatterings of electrons and muons with themselves and protons is lowered compared to the case without the condensate. On the other hand, the contribution of proton-proton co...
4-D ultrafast shear-wave imaging.
Gennisson, Jean-Luc; Provost, Jean; Deffieux, Thomas; Papadacci, Clément; Imbault, Marion; Pernot, Mathieu; Tanter, Mickael
2015-06-01
Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE. PMID:26067040
Shear stress and the endothelial transport barrier
Tarbell, John M.
2010-01-01
The shear stress of flowing blood on the surfaces of endothelial cells that provide the barrier to transport of solutes and water between blood and the underlying tissue modulates the permeability to solutes and the hydraulic conductivity. This review begins with a discussion of transport pathways across the endothelium and then considers the experimental evidence from both in vivo and in vitro studies that shows an influence of shear stress on endothelial transport properties after both acut...
Assessment of Shear Strength in Silty Soils
Directory of Open Access Journals (Sweden)
Stefaniak Katarzyna
2015-06-01
Full Text Available The article presents a comparison of shear strength values in silty soils from the area of Pozna?, determined based on selected Nkt values recommended in literature, with values of shear strength established on the basis of Nkt values recommended by the author. Analysed silty soils are characterized by the carbonate cementation zone, which made it possible to compare selected empirical coefficients both in normally consolidated and overconsolidated soils
Transport Far From Equilibrium --- Uniform Shear Flow
Lee, Mirim; Dufty, James W.
1997-01-01
The BGK model kinetic equation is applied to spatially inhomogeneous states near steady uniform shear flow. The shear rate of the reference steady state can be large so the states considered include those very far from equilibrium. The single particle distribution function is calculated exactly to first order in the deviations of the hydrodynamic field gradients from their values in the reference state. The corresponding non-linear hydrodynamic equaitons are obtained and the...
Sheared-flow Modes in Toroidal Geometry
International Nuclear Information System (INIS)
Using a Fourier-Bessel representation for the fluctuating (turbulent) electrostatic potential, an equation governing the sheared-flow modes in toroidal geometry is derived from the gyrokinetic Poisson equation, where both the adiabatic and non-adiabatic responses of the electrons are taken into account. It is shown that the principal geometrical effect on sheared-flow modes of the electrostatic potential is due to the flux-surface average of 1/B, where B is the magnetic field strength
Liquid migration in sheared unsaturated granular media
Mani, Roman; Herrmann, Hans J
2012-01-01
We show how liquid migrates in sheared unsaturated granular media using a grain scale model for capillary bridges. Liquid is redistributed to neighboring contacts after rupture of individual capillary bridges leading to redistribution of liquid on large scales. The liquid profile evolution coincides with a recently developed continuum description for liquid migration in shear bands. The velocity profiles which are linked to the migration of liquid as well as the density profiles of wet and dry granular media are studied.
ITER TF coils: casing versus shear plates
International Nuclear Information System (INIS)
The design of ITER EDA is featured by many new concepts. As far as the magnetic system is concerned the layer winding of the TF coils with incorporated steel shear plates is among the most remarkable. Mechanical calculations of the TF coils have been performed and manufacturing processes have been analysed to compare the design of ITER EDA with shear plates inserted in the winding and a more classical design using a steel casing with circular keys concept: ITER Compact Design. (orig.)
Cosmic Shear with Keck: Systematic Effects
Massey, Richard; Bacon, David; Refregier, Alexandre; Ellis, Richard
2001-01-01
Cosmic shear probes the distribution of dark matter via gravitational lensing of distant, background galaxies. We describe our cosmic shear survey consisting of deep blank fields observed with the Keck II telescope. We have found biases in the standard weak lensing analysis, which are enhanced by the elongated geometry of the Keck fields. We show how these biases can be diagnosed and corrected by masking edges and chip defects.
Influence of Shear on Rotation Capacity of Reinforced Concrete Members Without Shear Reinforcement
Vaz Rodrigues, Rui; Muttoni, Aurelio; Fernández Ruiz, Miguel
2010-01-01
The influence of shear on the rotation capacity of one-way slabs without shear reinforcement is investigated in this paper by means of an experimental study. The experimental program consisted of 11 slab strips 8400 mm (331 in.) long and 450 mm (17.7 in.) thick with a flexural reinforcement ratio of 0.79%. The rotation capacity was investigated for various values of the shear span and for two types of flexural reinforcement (hot-rolled and cold-worked bars). The specimens developed shear fail...
Punching shear capacity of reinforced concrete slabs with headed shear studs
DEFF Research Database (Denmark)
Hoang, Linh Cao; Pop, Anamaria
2015-01-01
Punching shear in slabs is analogous to shear in beams. Despite this similarity, current design codes provide distinctly different methods for the design of shear reinforcement in the two situations. For example, the Eurocode method for beam shear design is founded on the theory of rigid plasticity. To design shear reinforcement in slabs, on the other hand, the engineer must settle for an empirical equation. The aim of the study reported is to demonstrate that it is possible in a simple manner to design shear reinforcement in slabs based on the same rigid-plasticity foundation as for beam shear design. For this purpose, an extension of the upper-bound crack sliding model is proposed. This involves analysis of sliding mechanisms in yield lines developed both within and outside the zone with shear reinforcement. Various types of headed shear studs were considered. The results obtained using the model were compared with a large number of published test results, and satisfactory agreements were found.
Fan-structure shear rupture mechanism as a source of shear rupture rockbursts
Scientific Electronic Library Online (English)
B.G., Tarasov.
2014-10-01
Full Text Available This paper proposes the further development of a recently identified shear rupture mechanism (fan mechanism) that elucidates a paradoxical feature of hard rocks - the possibility of shear rupture propagation through a highly confined intact rock mass at shear stresses that can be significantly less [...] than frictional strength. In the fan mechanism, failure is associated with consecutive creation of small slabs (known as 'domino blocks') from the intact rock in the rupture tip, driven by a fan-shaped domino structure representing the rupture head. The fan head combines such unique features as extremely low shear resistance, self-sustaining stress intensification, and self-unbalancing conditions. Consequently, the failure process caused by the mechanism is inevitably spontaneous and violent. Physical and mathematical models explain unique and paradoxical features of the mechanism, which can be generated in primary ruptures and segmented faults. The fan mechanism provides a novel point of view for understanding the nature of spontaneous failure processes, including shear rupture rockbursts. The process explains, in particular, features of shear rupture rockbursts such as activation at great depths, generation of new shear ruptures in intact rock mass, nucleation of hypocentres at significant distances from the excavation, shear rupture development at low shear stresses, and abnormal rupture violence.
Cosmology with cosmic shear observations: a review.
Kilbinger, Martin
2015-07-01
Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations. PMID:26181770
Vesicle dynamics in shear and capillary flows
International Nuclear Information System (INIS)
The deformation of vesicles in flow is studied by a mesoscopic simulation technique, which combines multi-particle collision dynamics for the solvent with a dynamically triangulated surface model for the membrane. Shape transitions are investigated both in simple shear flows and in cylindrical capillary flows. We focus on reduced volumes, where the discocyte shape of fluid vesicles is stable, and the prolate shape is metastable. In simple shear flow at low membrane viscosity, the shear induces a transformation from discocyte to prolate with increasing shear rate, while at high membrane viscosity, the shear induces a transformation from prolate to discocyte, or tumbling motion accompanied by oscillations between these two morphologies. In capillary flow, at small flow velocities the symmetry axis of the discocyte is found not to be oriented perpendicular to the cylinder axis. With increasing flow velocity, a transition to a prolate shape occurs for fluid vesicles, while vesicles with shear-elastic membranes (like red blood cells) transform into a coaxial parachute-like shape
Cosmology with cosmic shear observations: a review
Kilbinger, Martin
2015-07-01
Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations.
Analysis of shear banding in twelve materials
Batra, R. C.; Kim, C. H.
The problem of the initiation and growth of shear bands in 12 different materials, namely, OFHC copper, Cartridge brass, Nickel 200, Armco IF (interstitial free) iron, Carpenter electric iron, 1006 steel, 2024-T351 aluminum, 7039 aluminum, low alloy steel, S-7 tool steel, Tungsten alloy, and Depleted Uranium (DU -0.75 Ti) is studied with the objectives of finding out when a shear band initiates, and upon what parameters does the band width depend. The nonlinear coupled partial differential equations governing the overall simple shearing deformations of a thermally softening viscoplastic block are analyzed. It is assumed that the thermomechanical response of these materials can be adequately represented by the Johnson-Cook law, and the only inhomogeneity present in the block is the variation in its thickness. The effect of the defect size on the initiation and subsequent growth of the band is also studied. It is found that, for each one of these 12 materials, the deformation has become nonhomogeneous by the time the maximum shear stress occurs. Also the band width, computed when the shear stress has dropped to 85 percent of its peak value, does not correlate well with the thermal conductivity of the material. The band begins to grow rapidly when the shear stress has dropped to 90 percent of its maximum value.
Resolution of axial shear strain elastography
International Nuclear Information System (INIS)
The technique of mapping the local axial component of the shear strain due to quasi-static axial compression is defined as axial shear strain elastography. In this paper, the spatial resolution of axial shear strain elastography is investigated through simulations, using an elastically stiff cylindrical lesion embedded in a homogeneously softer background. Resolution was defined as the smallest size of the inclusion for which the strain value at the inclusion/background interface was greater than the average of the axial shear strain values at the interface and inside the inclusion. The resolution was measured from the axial shear strain profile oriented at 450 to the axis of beam propagation, due to the absence of axial shear strain along the normal directions. The effects of the ultrasound system parameters such as bandwidth, beamwidth and transducer element pitch along with signal processing parameters such as correlation window length (W) and axial shift (?W) on the estimated resolution were investigated. The results show that the resolution (at 450 orientation) is determined by the bandwidth and the beamwidth. However, the upper bound on the resolution is limited by the larger of the beamwidth and the window length, which is scaled inversely to the bandwidth. The results also show that the resolution is proportional to the pitch and not significantly affected by the axial window shift
Resolution of axial shear strain elastography
Energy Technology Data Exchange (ETDEWEB)
Thitaikumar, Arun [Ultrasonics Laboratory, Department of Diagnostic and Interventional Imaging, University of Texas Medical School, Houston, TX (United States); Righetti, Raffaella [Ultrasonics Laboratory, Department of Diagnostic and Interventional Imaging, University of Texas Medical School, Houston, TX (United States); Krouskop, Thomas A [Ultrasonics Laboratory, Department of Diagnostic and Interventional Imaging, University of Texas Medical School, Houston, TX (United States); Ophir, Jonathan [Ultrasonics Laboratory, Department of Diagnostic and Interventional Imaging, University of Texas Medical School, Houston, TX (United States)
2006-10-21
The technique of mapping the local axial component of the shear strain due to quasi-static axial compression is defined as axial shear strain elastography. In this paper, the spatial resolution of axial shear strain elastography is investigated through simulations, using an elastically stiff cylindrical lesion embedded in a homogeneously softer background. Resolution was defined as the smallest size of the inclusion for which the strain value at the inclusion/background interface was greater than the average of the axial shear strain values at the interface and inside the inclusion. The resolution was measured from the axial shear strain profile oriented at 45{sup 0} to the axis of beam propagation, due to the absence of axial shear strain along the normal directions. The effects of the ultrasound system parameters such as bandwidth, beamwidth and transducer element pitch along with signal processing parameters such as correlation window length (W) and axial shift ({delta}W) on the estimated resolution were investigated. The results show that the resolution (at 45{sup 0} orientation) is determined by the bandwidth and the beamwidth. However, the upper bound on the resolution is limited by the larger of the beamwidth and the window length, which is scaled inversely to the bandwidth. The results also show that the resolution is proportional to the pitch and not significantly affected by the axial window shift.
Accurate shear measurement with faint sources
International Nuclear Information System (INIS)
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys
Accurate shear measurement with faint sources
Energy Technology Data Exchange (ETDEWEB)
Zhang, Jun; Foucaud, Sebastien [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, 955 Jianchuan road, Shanghai, 200240 (China); Luo, Wentao, E-mail: betajzhang@sjtu.edu.cn, E-mail: walt@shao.ac.cn, E-mail: foucaud@sjtu.edu.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai, 200030 (China)
2015-01-01
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.
Study of shear thickening behavior in colloidal suspensions
Directory of Open Access Journals (Sweden)
N Maleki Jirsaraee
2015-01-01
Full Text Available We studied the shear thickening behavior of the nano silica suspension (silica nanoparticles 12 nm in size suspended in ethylene glycol under steady shear. The critical shear rate for transition into shear thickening phase was determined at different concentrations and temperatures. The effect of temperature and concentration was studied on the shear thickening behavior. In silica suspension, it was observed that all the samples had a transition into shear thickening phase and also by increasing the temperature, critical shear rate increased and viscosity decreased. Our observations showed that movement in silica suspension was Brownian and temperature could cause a delay in transition into shear thickening phase. Yet, we observed that increasing the concentration would decrease critical shear rate and increase viscosity. Increasing temperature increased Brownian forces and increasing concentration increased hydrodynamic forces, confirming the contrast between these two forces for transition into shear thickening phase for the suspensions containing nano particles
Energy Technology Data Exchange (ETDEWEB)
Showalter, S.; Wood, F.; Vimmerstedt, L.
2010-06-01
The U.S. federal government is considering actions to reduce greenhouse gas emissions. Renewable energy and energy efficiency technologies could help reduce greenhouse gas emissions, so the cost of these technologies could significantly influence the overall cost of meeting greenhouse gas limits. This paper examines the potential benefit of reduced technology cost by analyzing the case of the Lieberman-Warner Climate Security Act of 2007 (S.2191). This act had a goal of reducing national carbon emissions in 2050 to levels 72 percent below 2006 emission levels. In April 2008, the U.S. Department of Energy, Energy Information Administration (EIA) published an analysis of the effects of S.2191 on the U.S. energy sector. This report presents a similar analysis: both analyses examined the impacts of S.2191, and both used versions of the National Energy Modeling System. The analysis reported here used modified technology assumptions to reflect U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE) program goals. The results show that achieving EERE program goals could reduce the cost of meeting greenhouse gas limits, reduce the cost of renewable electricity generation and biofuels, and reduce energy intensity.
Shear-enhanced compaction in viscoplastic rocks
Yarushina, V. M.; Podladchikov, Y. Y.
2012-04-01
The phenomenon of mutual influence of compaction and shear deformation was repeatedly reported in the literature over the past years. Dilatancy and shear-enhanced compaction of porous rocks were experimentally observed during both rate-independent and rate-dependent inelastic deformation. Plastic pore collapse was preceding the onset of dilatancy and shear-enhanced compaction. Effective bulk viscosity is commonly used to describe compaction driven fluid flow in porous rocks. Experimental data suggest that bulk viscosity of a fluid saturated rock might be a function of both the effective pressure and the shear stress. Dilatancy and shear-enhanced compaction can alter the transport properties of rocks through their influence on permeability and compaction length scale. Recent investigations show that shear stresses in deep mantle rocks can be responsible for spontaneous development of localized melt-rich bands and segregation of small amounts of melt from the solid rock matrix through shear channeling instability. Usually it is assumed that effective viscosity is a function of porosity only. Thus coupling between compaction and shear deformation is ignored. Spherical model which considers a hollow sphere subjected to homogeneous tractions on the outer boundary as a representative elementary volume succeeded in predicting the volumetric compaction behavior of porous rocks and metals to a hydrostatic pressure in a wide range of porosities. Following the success of this simple model we propose a cylindrical model of void compaction and decompaction due to the non-hydrostatic load. The infinite viscoplastic layer with a cylindrical hole is considered as a representative volume element. The remote boundary of the volume is subjected to a homogeneous non-hydrostatic load such that plane strain conditions are fulfilled through the volume. At some critical values of remote stresses plastic zone develops around the hole. The dependence of the effective bulk viscosity on the properties of individual components as well as on the stress state is examined. We show that bulk viscosity is a function of porosity, effective pressure and shear stress. Decreasing porosity tends to increase bulk viscosity whereas increasing shear stress and increasing effective pressure reduce it.
Microscopic Mechanism of Shear Bands in Amorphous Solids
Ratul Dasgupta; Hentschel, H. George E.; Itamar Procaccia
2012-01-01
The fundamental instability responsible for the shear localization which results in shear bands in amorphous solids remains unknown despite enormous amount of research, both experimental and theoretical. As this is the main mechanism for the failure of metallic glasses, understanding the instability is invaluable in finding how to stabilize such materials against the tendency to shear localize. In this Letter we explain the mechanism for shear localization under shear, which...
Shear Localization and Comminution of Granular and Fragmented Silicon Carbide
Shih, C; Nesterenko, V.; Meyers, M.
1997-01-01
Granular and pre-fractured bulk silicon carbide were subjected to high strain, high-strain-rate deformation by radial symmetric collapse of a thick-wall cylinder. Profuse shear-band formation was observed, indicating the deformation had inhomogeneous characteristics. The granular silicon carbide had lower shear-band displacement, spacing between shear bands and thickness of shear bands than the pre-factured silicon carbide. Bimodal particle size distribution was seen inside the shear bands fo...
Boundary Shear Stress Along Vegetated Streambanks
Clark, L. A.; Wynn, T.
2007-12-01
Sediment, a leading cause of water quality impairment, damages aquatic ecosystems and interferes with recreational uses and water treatment processes. Streambank retreat can contribute as much as 85% of watershed sediment yield. Vegetation is an important component of stream restoration designs used to control streambank retreat, but vegetation effects on streambank boundary shear stress (SBSS) need to be quantified. The overall goal of this experiment is to predict boundary shear stress along vegetated streambanks. This goal will be met by determining a method for measuring boundary shear stress in the field along hydraulically rough streambanks, evaluating the effects of streambank vegetation on boundary shear stress in the field, and developing predictive methods based on measurable vegetative properties. First, three streambank vegetation types (herbaceous, shrubbery, and woody) will be modeled in a flume study to examine both boundary shear stress measurement theory and instruments for field use. An appropriate method (law of the wall, Reynold's stresses, TKE, or average wall shear stress) and field instrument (ADV, propeller, or Pitot tube) will be selected, resulting in a field technique to measure SBSS. Predictive methods for estimating SBSS, based on common vegetation measurements, will be developed in the flume study and validated with field data. This research is intended to improve our understanding of the role of riparian vegetation in stream morphology by evaluating the effects of vegetation on boundary shear stress, providing insight to the type and density of vegetation required for streambank stability. The results will also aide in quantifying sediment inputs from streambanks, providing quantitative information for stream restoration projects and watershed management planning.
Scientific Electronic Library Online (English)
Gaspar Manuel, Parra-Bracamonte; Ana María, Sifuentes-Rincón; Williams, Arellano-Vera; Juan Gabriel, Magaña-Monforte; José Alberto, Ramírez-De León; Gonzalo, Velázquez.
2014-04-01
Full Text Available La suavidad de la carne bovina es un rasgo importante para la satisfacción del consumidor y es la principal característica asociada a su palatabilidad, por lo que es importante evaluar su variabilidad en diferentes razas bovinas. Un experimento fue diseñado para evaluar la Fuerza de Corte de Warner- [...] Bratzler (FCWB) de carne del ojo de la costilla de bovinos Brangus rojos y su aceptabilidad. La suavidad de la carne fue evaluada mediante la FCWB; además, se realizó una evaluación de preferencia de consumo para estimar cuantitativamente la suavidad, jugosidad, sabor, término y aceptación general de los cortes evaluados. La media de la FCWB fue 5.03 kg ± 0.93 kg, lo que teóricamente representa una carne dura. En la distribución de las muestras se registraron 21 % y 11 % de cortes, respectivamente, de carne moderadamente suave y suave. La condición de los animales (toros o novillos) no fue significativa para la FCWB (p > 0.5). Todas las características evaluadas en la evaluación hedónica tuvieron alrededor de 6 puntos de un total de 8 (8 era mejor). La suavidad, jugosidad y sabor mostraron una correlación alta y significativa (p Abstract in english Beef tenderness is an important trait in consumer satisfaction and has been considered as the main trait for palatability, for which reason it is important to evaluate its variability in different cattle breeds. An experiment was designed to evaluate the Warner Bratzler Shear Force (WBSF) of Red Bra [...] ngus cattle rib eye steaks and consumer acceptance. The tenderness of beef rib eye steaks was evaluated by the WBSF. A consumer preference evaluation test was carried out to quantitatively estimate tenderness, juiciness, flavor, doneness and general acceptance of the evaluated steaks. Mean WBSF was 5.03 kg ± 0.93 kg, theoretically indicating a tough beef. The distribution of the samples showed 21 % and 11 % of moderately tender and tender beef cuts, respectively. Cattle condition (bulls and steers) was not significant for the WBSF (p > 0.5). All the traits evaluated in the hedonic evaluation had approximately 6 points of a total of 8 (8 was best). Tenderness, juiciness and flavor presented a high and significant correlation (p
Shear flexoelectric coefficient ?1211 in polyvinylidene fluoride
Zhang, Shuwen; Xu, Minglong; Liang, Xu; Shen, Shengping
2015-05-01
Defined as a strain gradient-induced electric polarization, flexoelectricity exists in all dielectric materials. The coefficient that exists between the strain gradient and the electric polarization defines the flexoelectric coefficient tensor. The tensor components along the longitudinal and transverse directions have been studied widely. However, little progress has been reported on flexoelectric properties in the shear direction to date. In this work, a novel method for measurement of the shear flexoelectric coefficient ?1211 of polyvinylidene fluoride is presented. An experiment is conducted on a tubular unpolarized specimen, where shear strain gradient is generated along the radial direction by applying torque to the ends of the tube-shaped specimen. Dynamic torque is exerted on specimens with a static bias value and at different frequencies. The generated shear strain gradient is calculated via finite element analysis and the corresponding induced electrical polarization is measured using a charge amplifier. The shear flexoelectric coefficient ?1211 is found to have an average value of 7.318 × 10-10 C/m at room temperature. The experimental results show good agreement with the theoretical predictions and indicate the potential value of this material property for electromechanical device fabrication.
Shear alignment of a disordered lamellar mesophase
Kumaran, V.; Raman, D. S. S.
2011-03-01
The shear alignment of an initially disordered lamellar phase is examined using lattice Boltzmann simulations of a mesoscopic model based on a free-energy functional for the concentration modulation. For a small shear cell of width 8?, the qualitative features of the alignment process are strongly dependent on the Schmidt number Sc=?/D (ratio of kinematic viscosity and mass diffusion coefficient). Here, ? is the wavelength of the concentration modulation. At low Schmidt number, it is found that there is a significant initial increase in the viscosity, coinciding with the alignment of layers along the extensional axis, followed by a decrease at long times due to the alignment along the flow direction. At high Schmidt number, alignment takes place due to the breakage and reformation of layers because diffusion is slow compared to shear deformation; this results in faster alignment. The system size has a strong effect on the alignment process; perfect alignment takes place for a small systems of width 8? and 16?, while a larger system of width 32? does not align completely even at long times. In the larger system, there appears to be a dynamical steady state in which the layers are not perfectly aligned—where there is a balance between the annealing of defects due to shear and the creation due to an instability of the aligned lamellar phase under shear. We observe two types of defect creation mechanisms: the buckling instability under dilation, which was reported earlier, as well as a second mechanism due to layer compression.
Viscoelasticity and shear thinning of nanoconfined water
Kapoor, Karan; Amandeep, Patil, Shivprasad
2014-01-01
Understanding flow properties and phase behavior of water confined to nanometer-sized pores and slits is central to a wide range of problems in science, such as percolation in geology, lubrication of future nano-machines, self-assembly and interactions of biomolecules, and transport through porous media in filtration processes. Experiments with different techniques in the past have reported that viscosity of nanoconfined water increases, decreases, or remains close to bulk water. Here we show that water confined to less than 20-nm-thick films exhibits both viscoelasticity and shear thinning. Typically viscoelasticity and shear thinning appear due to shearing of complex non-Newtonian mixtures possessing a slowly relaxing microstructure. The shear response of nanoconfined water in a range of shear frequencies (5 to 25 KHz) reveals that relaxation time diverges with reducing film thickness. It suggests that slow relaxation under confinement possibly arises due to existence of a critical point with respect to slit width. This criticality is similar to the capillary condensation in porous media.
Nonmonotonic flow curves of shear thickening suspensions
Mari, Romain; Seto, Ryohei; Morris, Jeffrey F.; Denn, Morton M.
2015-05-01
The discontinuous shear thickening (DST) of dense suspensions is a remarkable phenomenon in which the viscosity can increase by several orders of magnitude at a critical shear rate. It has the appearance of a first-order phase transition between two hypothetical "states" that we have recently identified as Stokes flows with lubricated or frictional contacts, respectively. Here we extend the analogy further by means of stress-controlled simulations and show the existence of a nonmonotonic steady-state flow curve analogous to a nonmonotonic equation of state. While we associate DST with an S -shaped flow curve, at volume fractions above the shear jamming transition the frictional state loses flowability and the flow curve reduces to an arch, permitting the system to flow only at small stresses. Whereas a thermodynamic transition leads to phase separation in the coexistence region, we observe a uniform shear flow all along the thickening transition. A stability analysis suggests that uniform shear may be mechanically stable for the small Reynolds numbers and system sizes in a rheometer.
Pressure-shear experiments on granular materials.
Energy Technology Data Exchange (ETDEWEB)
Reinhart, William Dodd (Sandia National Laboratories, Albuquerque, NM); Thornhill, Tom Finley, III (, Sandia National Laboratories, Albuquerque, NM); Vogler, Tracy John; Alexander, C. Scott (Sandia National Laboratories, Albuquerque, NM)
2011-10-01
Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.
Review article: Cosmology with cosmic shear observations
Kilbinger, Martin
2014-01-01
Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as ...
Predictive modelling of JET optimized shear discharges
International Nuclear Information System (INIS)
Transport analysis of high performance JET plasmas with optimized magnetic shear (OMS) has revealed many interesting features which cannot be explained by the existing JET empirical transport model (Erba, M., et al., Plasma Phys. Control. Fusion 39 (1997) 261). TRANSP analysis shows that transport coefficients in OMS plasmas are often reduced in the plasma core (Cottrell, G.A., et al., in Controlled Fusion and Plasma Physics (Proc. 24th Eur. Conf. Berchtesgaden, 1997), Vol. 21A, Part I, European Physical Society, Geneva (1997) 81) to the level of ion neoclassical transport. TRANSP analysis and predictive modelling with JETTO show that this region of improved confinement appears near the plasma centre and then expands outwards in a way which does not follow either the evolution of the region with the negative magnetic shear or the propagation of the region with a large shear in plasma rotation. The best agreement with experiment has been achieved by using a transport model which combines the effect of a long wavelength decoupling due to small magnetic shear with its suppression by strong rotational shear. Predictive modelling of some of the characteristic JET OMS plasmas gives quite good agreement between such a model and the experimental data. (author)
Piezoelectric energy harvesting through shear mode operation
Malakooti, Mohammad H.; Sodano, Henry A.
2015-05-01
Piezoelectric materials are excellent candidates for use in energy harvesting applications due to their high electromechanical coupling properties that enable them to convert input mechanical energy into useful electric power. The electromechanical coupling coefficient of the piezoelectric material is one of the most significant parameters affecting energy conversion and is dependent on the piezoelectric mode of operation. In most piezoceramics, the d15 piezoelectric shear coefficient is the highest coefficient compared to the commonly used axial and transverse modes that utilize the d33 and the d31 piezoelectric strain coefficients. However, complicated electroding methods and challenges in evaluating the performance of energy harvesting devices operating in the shear mode have slowed research in this area. The shear deformation of a piezoelectric layer can be induced in a vibrating sandwich beam with a piezoelectric core. Here, a model based on Timoshenko beam theory is developed to predict the electric power output from a cantilever piezoelectric sandwich beam under base excitations. It is shown that the energy harvester operating in the shear mode is able to generate ?50% more power compared to the transverse mode for a numerical case study. Reduced models of both shear and transverse energy harvesters are obtained to determine the optimal load resistance in the system and perform an efficiency comparison between two models with fixed and adaptive resistances.
Relation between ordering and shear thinning in colloidal suspensions.
Xu, Xinliang; Rice, Stuart A; Dinner, Aaron R
2013-03-01
Colloidal suspensions exhibit shear thinning and shear thickening. The most common interpretation of these phenomena identifies layering of the fluid perpendicular to the shear gradient as the driver for the observed behavior. However, studies of the particle configurations associated with shear thinning and thickening cast doubt on that conclusion and leave unsettled whether these nonequilibrium phenomena are caused primarily by correlated particle motions or by changes in particle packing structure. We report the results of stokesian dynamics simulations of suspensions of hard spheres that illuminate the relation among the suspension viscosity, shear rate, and particle configuration. Using a recently introduced sampling technique for nonequilibrium systems, we show that shear thinning can be decoupled from layering, thereby eliminating layering as the driver for shear thinning. In contrast, we find that there is a strong correlation between shear thinning and a two-particle measure of the shear stress. Our results are consistent with a recent experimental study. PMID:23431185
High-shear-rate capillary viscometer for inkjet inks
International Nuclear Information System (INIS)
A capillary viscometer developed to measure the apparent shear viscosity of inkjet inks at high apparent shear rates encountered during inkjet printing is described. By using the Weissenberg-Rabinowitsch equation, true shear viscosity versus true shear rate is obtained. The device is comprised of a constant-flow generator, a static pressure monitoring device, a high precision submillimeter capillary die, and a high stiffness flow path. The system, which is calibrated using standard Newtonian low-viscosity silicone oil, can be easily operated and maintained. Results for measurement of the shear-rate-dependent viscosity of carbon-black pigmented water-based inkjet inks at shear rates up to 2x105 s-1 are discussed. The Cross model was found to closely fit the experimental data. Inkjet ink samples with similar low-shear-rate viscosities exhibited significantly different shear viscosities at high shear rates depending on particle loading.
Experimental and 3D Numerical Simulation of Reinforced Shear Joints
Jalalifar, Hossein; Aziz, N.
2010-02-01
The load transfer capacity and failure mechanism of a fully grouted bolt installed across a joint in shear is investigated, both experimentally and numerically, in five types of bolt. The double-shearing testing of bolts were studied in concrete blocks of 20, 40 and 100 MPa strengths, subjected to different pretension loads of 0, 5, 10, 20, 50 and 80 KN, respectively. The parameters examined include: shear resistance, shear displacement, induced strains and stresses during the bolt-bending process, and its ultimate failure across the sheared joint planes. The conclusions drawn from the study were that the strength of the concrete, bolt profile configuration and bolt pretension load played a significant influence on the shear resistance, shear displacement and failure mechanism of the reinforced medium. Experimental and numerical simulations showed that the failure occurs as a result of the induced axial and shear stresses acting between the hinge point distances in the vicinity of the shear joint plane.
Undulatory Swimming in Shear-thinning Fluids
Shen, Xiaoning; Gagnon, David; Arratia, Paulo
2012-11-01
Many fluids in which microorganisms move, feed, and reproduce possess shear-rate dependent viscosity behavior (e.g. shear-thinning). Such fluids include wet soil, clay suspension, mucus, and gels. In this talk, we experimentally investigate the effects of shear-rate dependent viscosity on the swimming behavior of the nematode Caenorhabditis elegans using velocimetry and tracking methods. Here, aqueous solutions of xanthan gum, which is a rod-like stiff polymer, are used with concentrations varying from the semi-dilute to the concentrated regime. The data is compared to swimming in simple, Newtonian fluids. We find that the nematode swims at an approximately constant speed in the semi-dilute regime. Surprisingly, the nematode exhibits 40% increases in swimming speed once immersed in a concentrated solution. The enhancement in swimming speed seems to be related to the dynamics of rod-like polymer networks formed in concentrated solutions. This work was supported by NSF-CAREER (CBET)-0954084.
Shear viscosity of a hot pion gas
Energy Technology Data Exchange (ETDEWEB)
Lang, R.; Kaiser, N.; Weise, W. [Technische Universitaet Muenchen, Physik Department, Garching (Germany)
2012-08-15
The shear viscosity of an interacting pion gas is studied using the Kubo formalism as a microscopic description of thermal systems close to global equilibrium. We implement the skeleton expansion in order to approximate the retarded correlator of the viscous part of the energy-momentum tensor. After exploring this in g{phi}{sup 4} theory we show how the skeleton expansion can be consistently applied to pions in chiral perturbation theory. The shear viscosity {eta} is determined by the spectral width, or equivalently, the mean free path of pions in the heat bath. We derive a new analytical result for the mean free path which is well conditioned for numerical evaluation and discuss the temperature and pion-mass dependence of the mean free path and the shear viscosity. The ratio {eta}/s of the interacting pion gas exceeds the lower bound 1/4{pi} from AdS/CFT correspondence. (orig.)
Bounds on Surface Stress Driven Shear Flow
Hagstrom, George I
2013-01-01
The background method is adapted to derive rigorous limits on surface speeds and bulk energy dissipation for shear stress driven flow in two and three dimensional channels. By-products of the analysis are nonlinear energy stability results for plane Couette flow with a shear stress boundary condition: when the applied stress is gauged by a dimensionless Grashoff number $Gr$, the critical $Gr$ for energy stability is 139.5 in two dimensions, and 51.73 in three dimensions. We derive upper bounds on the friction (a.k.a. dissipation) coefficient $C_f = \\tau/\\bar{u}^2$, where $\\tau$ is the applied shear stress and $\\bar{u}$ is the mean velocity of the fluid at the surface, for flows at higher $Gr$ including developed turbulence: $C_f le 1/32$ in two dimensions and $C_f \\le 1/8$ in three dimensions. This analysis rigorously justifies previously computed numerical estimates.
Miocene dextral shearing between Himalaya and Tibet
Pécher, Arnaud; Bouchez, Jean-Luc; Le Fort, Patrick
1991-07-01
The Main Central thrust zone is the major structural feature of the Himalayas. It was active during Miocene time and accommodated at least 100 km, and possibly as much as 300 km, of convergence between India and Tibet. We present evidence that late in the tectonic history, another large shear zone, located north of the High Himalayas (the North Himalayan shear zone), underwent a phase of dextral strike-slip motion. The most plausible explanation for this phase of motion is that it reflects the onset of extension in Tibet. It is usually thought that extension began about 2.5 Ma. The phase of dextral shear we report occurred between 25 and 15 Ma. If our explanation for this movement is correct, it places the onset of extension at least 12 m.y. earlier than previously thought.
Spiral morphology and galactic shear rate
Grand, Robert J J; Cropper, Mark
2012-01-01
Spiral galaxies are observed to exhibit a range of morphologies, in particular in the shape of spiral arms. A key diagnostic parameter is the pitch angle, which describes how tightly wound the spiral arms are. Observationally and analytically, a correlation between pitch angle and galactic shear rate has been detected. For the first time, we perform a suite of N-body simulations to calculate and compare the pitch angles of both individual density waves and overall spiral structure by use of two independent techniques. We find that higher galactic shear rates produce more tightly wound spiral arms, both in individual mode patterns (density waves) and in the overall density enhancement. Although the mode pattern pitch angles by construction remain constant with time, the overall logarithmic spiral arm winds over time, which is consistent with both the observational scatter in pitch angle versus shear seen from observations, and the recent idea that multiple mode patterns may interfere with each other to create ...
Magnetic shear. III - Hale region 17255
International Nuclear Information System (INIS)
Hale active region 17255, which in many respects was the most vigorous active region observed during the first operational period of SMM, appears to lie between two large areas of flow (observed in C IV) converging toward the major axis of the region. In the 6-day period from November 6-12, 1980, the major axis of the region rotates by about 25 deg. Several segments of the magnetic neutral line show C IV flow velocities of opposite sign on either side of the neutral line. Those segments whose orientation is favorable for measuring velocity components parallel to the neutral line show evidence that such flow is present, which is interpreted as evidence for magnetic shear. This, together with other evidence, suggests that magnetic shear is widespread in this region, as in the two previous regions studied. It is concluded that magnetic shear is often associated with flaring activity but is not a sufficient condition for flaring to occur. 8 references
Transversely Compressed- and Restrained Shear Joints
DEFF Research Database (Denmark)
Schmidt, Jacob Wittrup; Hansen, Christian Skodborg
2013-01-01
Anchorage of FRP strengthening systems where the deformation perpendicular to the FRP material is restrained or a compressive force is applied on the strengthening, seems to provide ductility, increased utilization of the FRP and failure modes which can be controlled through the anchorage method. This paper presents theoretical model which can predict the response of transversely compressed and restrained single- and double lap shear joints. The interface material model is based on a cohesive law in the shear-slip plane with a descending branch and a uniform frictional stress added due to the friction in the crack, emanating from the transverse pressure or restraint. The theoretical model is compared with experimental results from transversely compressed single- and double shear joints. Also theoretical predictions of a mechanical integrated sleeve-wedge anchorage load capacity are carried out and compared with tests. It is seen that the theory correlates well with the experimental results.
Shear viscosity of a hot pion gas
International Nuclear Information System (INIS)
The shear viscosity of an interacting pion gas is studied using the Kubo formalism as a microscopic description of thermal systems close to global equilibrium. We implement the skeleton expansion in order to approximate the retarded correlator of the viscous part of the energy-momentum tensor. After exploring this in g?4 theory we show how the skeleton expansion can be consistently applied to pions in chiral perturbation theory. The shear viscosity ? is determined by the spectral width, or equivalently, the mean free path of pions in the heat bath. We derive a new analytical result for the mean free path which is well conditioned for numerical evaluation and discuss the temperature and pion-mass dependence of the mean free path and the shear viscosity. The ratio ?/s of the interacting pion gas exceeds the lower bound 1/4? from AdS/CFT correspondence. (orig.)
Progress of simulations for reacting shear layers
Yu, Sheng-Tao
1991-10-01
An attempt was made to develop a high speed, chemically reactive shear layer test rig. The purpose of the experiment was to study the mixing of oxidizer and fuel streams in reacting shear layers for various density, velocity, and Mach number. The primary goal was to understand the effects of the compressibility upon mixing and combustion in a fundamental way. Therefore, a two-dimensional shear layer is highly desirable for its simplicity to quantify the compressibility effects. The RPLUS 2D code is used to calculate the flow fields of different sections of the test rig. The emphasis was on the supersonic nozzle design, the vitiation process for the hot air stream and the overall thermodynamic conditions of the test matrix. The k-epsilon turbulence model with wall function was successfully implemented in the RPLUS code. The k and epsilon equations are solved simultaneously and the LU scheme is used to make it compatible with the flow solver.
Mitigating shear lag in tall buildings
Gaur, Himanshu; Goliya, Ravindra K.
2015-09-01
As the height of building increases, effect of shear lag also becomes considerable in the design of high-rise buildings. In this paper, shear lag effect in tall buildings of heights, i.e., 120, 96, 72, 48 and 36 stories of which aspect ratio ranges from 3 to 10 is studied. Tube-in-tube structural system with façade bracing is used for designing the building of height 120 story. It is found that bracing system considerably reduces the shear lag effect and hence increases the building stiffness to withstand lateral loads. Different geometric patterns of bracing system are considered. The best effective geometric configuration of bracing system is concluded in this study. Lateral force, as wind load is applied on the buildings as it is the most dominating lateral force for such heights. Wind load is set as per Indian standard code of practice IS 875 Part-3. For analysis purpose SAP 2000 software program is used.
Shear banding in soft glassy materials.
Fielding, S M
2014-10-01
Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic 'glassy' features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike. PMID:25303030
Hydrodynamic and contact contributions to shear thickening in colloidal suspensions
Lin, Neil Y C; Hermes, Michiel; Ness, Chris; Sun, Jin; Poon, Wilson C K; Cohen, Itai
2015-01-01
Shear thickening is a widespread phenomenon in suspension flow that, despite sustained study, is still the subject of much debate. The longstanding view that shear thickening is due to hydrodynamic clusters has been challenged by recent theory and simulations suggesting that contact forces dominate, not only in discontinuous, but also in continuous shear thickening. Here, we settle this dispute using shear reversal experiments on micron-sized silica and latex colloidal particles to measure directly the hydrodynamic and contact force contributions to shear thickening. We find that contact forces dominate even continuous shear thickening. Computer simulations show that these forces most likely arise from frictional interactions.
Compressibility and shock wave interaction effects on free shear layers
Samimy, M.; Erwin, D. E.; Elliott, G. S.
1989-01-01
Two compressible free shear layers with convective Mach numbers of .51 and .86 were studied as baseline configurations to investigate the effects of compressibility on the turbulence characteristics. These shear layers were then disturbed by the placement of an obstruction in the shear layer in an attempt to enhance the shear layer growth rate. These models produced a curved shock in the supersonic side of the shear layer. The results indicate a significant reduction in turbulence levels with increased compressibility. However, there are not any significant changes due to the bow shock interaction with the shear layer.
Integration of the TDWR and LLWAS wind shear detection system
Cornman, Larry
1991-01-01
Operational demonstrations of a prototype TDWR/LLWAS (Terminal Doppler Weather Radar/Low Level Wind shear Alarm System) integrated wind shear detection system were conducted. The integration of wind shear detection systems is needed to provide end-users with a single, consensus source of information. A properly implemented integrated system provides wind shear warnings of a higher quality than stand-alone LLWAS or TDWR systems. The algorithmic concept used to generate the TDWR/LLWAS integrated products and several case studies are discussed, indicating the viability and potential of integrated wind shear detection systems. Implications for integrating ground and airborne wind shear detection systems are briefly examined.
Shear-induced conformation change in ?-crystalline nylon6
International Nuclear Information System (INIS)
A study of shear deformation of ?-crystalline nylon6 is undertaken, using dispersion-corrected density functional theory. The shear stress-strain relationship and shear strength for interlayer shear deformation are computed. A conformation change induced by shear is identified along twinning deformation, whereby the conformation of chains, specifically the location of non-H-bonded hydrogen atoms, changes continuously. This paves a way for the modulation of properties of this group of materials by small shear deformation, if the non-H-bonded hydrogens are chemically substituted to form non-equivalent conformations when deformed
Yamakoshi, Yoshiki; Yamamoto, Atsushi; Kasahara, Toshihiro; Iijima, Tomohiro; Yuminaka, Yasushi
2015-07-01
We have proposed a quantitative shear wave imaging technique for continuous shear wave excitation. Shear wave wavefront is observed directly by color flow imaging using a general-purpose ultrasonic imaging system. In this study, the proposed method is applied to experiments in vivo, and shear wave maps, namely, the shear wave phase map, which shows the shear wave propagation inside the medium, and the shear wave velocity map, are observed for the skeletal muscle in the shoulder. To excite the shear wave inside the skeletal muscle of the shoulder, a hybrid ultrasonic wave transducer, which combines a small vibrator with an ultrasonic wave probe, is adopted. The shear wave velocity of supraspinatus muscle, which is measured by the proposed method, is 4.11 ± 0.06 m/s (N = 4). This value is consistent with those obtained by the acoustic radiation force impulse method.
Shear viscosity coefficient of liquid lanthanides
Patel, H. P.; Sonvane, Y. A.; Thakor, P. B.; Prajapati, A. V.
2015-05-01
Present paper deals with the computation of shear viscosity coefficient (?) of liquid lanthanides. The effective pair potential v(r) is calculated through our newly constructed model potential. The Pair distribution function g(r) is calculated from PYHS reference system. To see the influence of local field correction function, Hartree (H), Tailor (T) and Sarkar et al (S) local field correction function are used. Present results are compared with available experimental as well as theoretical data. Lastly, we found that our newly constructed model potential successfully explains the shear viscosity coefficient (?) of liquid lanthanides.
Compressibility effects in free shear layers
Samimy, M.; Elliott, G. S.
1990-01-01
High-Reynolds-number compressible free shear layers were studied experimentally to explore the effects of compressibility on the turbulence field. A reduction in both the level and the lateral extent of turbulence fluctuations with increasing convective Mach number (Mc) (reported earlier for Mc of 0.51 and 0.64) is much higher at Mc of 0.86. The higher-order moments of turbulence fluctuations such as skewness and flatness show that the intermittency due to the excursion of large-scale structures into the free streams at the edge of shear layers was significantly reduced (both in the level and the extent) due to increased Mc.
Harmonic Shears of Slit and Polygonal Mappings
Ponnusamy, Saminathan; Rasila, Antti
2012-01-01
In this paper, we study harmonic mappings by using the shear construction, introduced by Clunie and Sheil-Small in 1984. We consider two classes of conformal mappings, each of which maps the unit disk D univalently onto a domain which is convex in the horizontal direction, and shear these mappings with suitable dilatations \\omega. Mappings of the first class map the unit disk D onto four-slit domains and mappings of the second class take D onto regular n-gons. In addition, we discuss the minimal surfaces associated with such harmonic mappings. Furthermore, illustrations of mappings and associated minimal surfaces are given by using Mathematica.
Harmonic Shears of Slit and Polygonal Mappings
Ponnusamy, Saminathan; Quach, Tri; Rasila, Antti
2012-01-01
In this paper, we study harmonic mappings by using the shear construction, introduced by Clunie and Sheil-Small in 1984. We consider two classes of conformal mappings, each of which maps the unit disk D univalently onto a domain which is convex in the horizontal direction, and shear these mappings with suitable dilatations \\omega. Mappings of the first class map the unit disk D onto four-slit domains and mappings of the second class take D onto regular n-gons. In addition, w...
Halo abundances and shear in void models
DEFF Research Database (Denmark)
Alonso, David; García-Bellido, Juan
2012-01-01
We study the non-linear gravitational collapse of dark matter into halos through numerical N-body simulations of Lemaitre-Tolman-Bondi void models. We extend the halo mass function formalism to these models in a consistent way. This extension not only compares well with the simulated data at all times and radii, but it also gives interesting clues about the impact of the background shear on the growth of perturbations. Our results give hints about the possibility of constraining the background shear via cluster number counts, which could then give rise to strong constraints on general inhomogeneous models, of any scale.
Fuhrmann, Alexander; Engler, Adam J.
2015-02-01
Several methods have been developed to quantify population level changes in cell attachment strength given its large heterogeneity. One such method is the rotating disk chamber or ‘spinning disk’ in which a range of shear forces are applied to attached cells to quantify detachment force, i.e. attachment strength, which can be heterogeneous within cell populations. However, computing the exact force vectors that act upon cells is complicated by complex flow fields and variable cell morphologies. Recent observations suggest that cells may remodel their morphology and align during acute shear exposure, but contrary to intuition, shear is not orthogonal to the radial direction. Here we theoretically derive the magnitude and direction of applied shear and demonstrate that cells, under certain physiological conditions, align in this direction within minutes. Shear force magnitude is also experimentally verified which validates that for spread cells shear forces and not torque or drag dominate in this assay, and demonstrates that the applied force per cell area is largely independent of initial morphology. These findings suggest that direct quantified comparison of the effects of shear on a wide array of cell types and conditions can be made with confidence using this assay without the need for computational or numerical modeling.
Scientific Electronic Library Online (English)
J.J.E., Cloete; L.C., Hoffman; S.W.P., Cloete.
2008-04-01
Full Text Available This study details the slaughter traits of lambs born from a terminal crossbreeding experiment that involved five Merino type dam lines crossed with Dormer and Suffolk sires. Dam lines included dual purpose types; South African Mutton Merino (SAMM), Dohne Merino, SAMM rams crossed to commercial Meri [...] no ewes (SAMM cross) and specialist Merino lines selected either for clean fleece weight (FW+) or for an increased fertility (Rep+). Data include between 228 and 483 individual records, depending on the trait. The unadjusted fat depth 25 mm from the midline at the 13th rib of lambs from dual-purpose ewes was between 22 and 32% greater than that of lambs from FW+ Merino ewes. Progeny from Rep+ Merino ewes showed a closer resemblance to the progeny of dual-purpose breeds than to those of FW+ Merino ewes in this instance. Adjustment for slaughter weight eliminated these differences. The initial pH of meat from progeny of FW+ Merino ewes was lower than that from progeny of dual-purpose ewes, and Rep+ Merino ewes. No differences in Warner-Bratzler shear values of the meat were found between the different crosses. Crossbred progeny of the Merino lines performed satisfactorily for all the traits considered, and will not be discriminated against in the market. No conclusive differences in favour of either sire breed were found.
Scientific Electronic Library Online (English)
Isabella Dias Barbosa, Silveira; Vivian, Fischer; Luis Henrique Ebling, Farinatti; João, Restle; Dari Celestino, Alves Filho; Luís Fernando Glasenapp de, Menezes.
2012-06-01
Full Text Available The relation between temperament with performance and meat quality was determined in 79 Charolais × Nellore steers kept in feedlot. Temperament was evaluated according to exit velocity, scale composite score and flight distance four times in the finishing phase, along with body weight, intake and fe [...] ed conversion measures. Cattle were classified as calm, intermediate and excited according to exit velocity measures at the beginning of the trial. Excited cattle presented larger values for composite score and flight distance. Irrespective of genotype, excited cattle presented lower average daily gain, dry matter intake and worse feed conversion. Temperament categories did not affect most of beef quality traits, except for calm Bos indicus steers, which presented greater pH measured 1 hour post mortem compared with more reactive steers. However, moderate but negative correlations were detected between exit velocity, flight distance and composite score and beef quality as well as Warner-Bratzler shear value, luminosity, pH measured 24 hours post mortem, although they were not consistent between genotypes raised under the same conditions.
Meat quality of lambs produced in the Mesopotamia region of Argentina finished on different diets.
Perlo, F; Bonato, P; Teira, G; Tisocco, O; Vicentin, J; Pueyo, J; Mansilla, A
2008-07-01
The meat quality of Corriedale lambs (40kg live weight) produced in the Mesopotamia region (Argentina) was assessed. These lambs had different finishing diets: only native grass pasture, ground alfalfa and alfalfa-linseed pellet (70/30). Carcass yield, longissimus dorsi area, backfat thickness, marbling, pH, meat and subcutaneous fat color, cooking loss, Warner-Bratzler shear force, fat, protein and moisture content were determined. Lambs finished on alfalfa-linseed pellet had the highest carcasses yield and backfat thickness and their meat had a lighter color (higher L(?) value), higher marbling and tenderness than meat from lambs reared on native grass pasture. Grass-based finishing can lead to the production of leaner meat, with a more reddish color (higher a(?) value). The ground alfalfa finishing diet seems to be intermediate between native grass pasture and alfalfa-linseed pellet with respect to carcass yield, backfat and meat color. In addition, the animals fed on ground alfalfa showed the highest muscle area. PMID:22062919
Enhancement technology improves palatability of normal and callipyge lambs.
Everts, A K R; Wulf, D M; Wheeler, T L; Everts, A J; Weaver, A D; Daniel, J A
2010-12-01
The objective of this research was to determine if BPI Processing Technology (BPT) improved palatability of normal (NN) and callipyge (CN) lamb meat and to determine the mechanism by which palatability was improved. Ten ewe and 10 wether lambs of each phenotype were slaughtered, and carcass traits were assessed by a trained evaluator. The LM was removed at 2 d postmortem. Alternating sides served as controls (CON) or were treated with BPT. Muscles designated BPT were injected to a target 120% by weight with a patented solution containing water, ammonium hydroxide, carbon monoxide, and salt. Muscle pH, cooking loss, Warner-Bratzler shear force (WBS), sarcomere length, cooked moisture retention, and desmin degradation were measured. A trained sensory panel and a take-home consumer panel evaluated LM chops. Callipyge had a heavier BW and HCW, less adjusted fat thickness, reduced yield grades, and greater conformation scores than NN (P size, like of color, like of leanness, overall like of appearance) and greater consumer ratings for eating characteristics (like of juiciness, like of flavor) than CN (P cooked moisture retention, smaller WBS values, greater juiciness ratings, less off-flavors, and greater consumer ratings for raw characteristics (like of portion size, like of color, overall like of appearance) and eating characteristics (like of juiciness, like of flavor) than CON (P effect on sarcomere length and desmin degradation, but improved palatability of NN and CN lamb by increasing cooked moisture retention, improving consumer acceptability of CN to near-normal levels. PMID:20675603
Picard, Brigitte; Gagaoua, Mohammed; Micol, Didier; Cassar-Malek, Isabelle; Hocquette, Jean-François; Terlouw, Claudia E M
2014-10-01
Previous proteomic analyses established a list of proteins biomarkers of beef tenderness. The present study quantified the relative abundance of 21 of these proteins by dot-blot technique in the Longissimus thoracis and Semitendinosus muscles of 71 young bulls from three breeds: Aberdeen Angus (AA), Limousin (LI), and Blond d'Aquitaine (BA). For both muscles overall tenderness was estimated by sensory analysis; shear force was measured with a Warner-Bratzler instrument, and an index combining sensory and mechanical measurements was calculated. Multiple regressions based on relative abundances of these proteins were used to propose equations of prediction of the three evaluations of tenderness. Hsp70-1B appeared to be a good biomarker of low tenderness in the three breeds and in the two muscles. Proteins such as lactate dehydrogenase-B, myosin heavy chain IIx, and small heat shock proteins (Hsp27, Hsp20, and ?B-crystallin) were related to tenderness but inversely according to the muscle and breed. The results demonstrate that prediction of tenderness must take into account muscle characteristics and animal type. PMID:25175407
Directory of Open Access Journals (Sweden)
ALINA NARCISA POSTOLACHE
2014-11-01
Full Text Available This research is subscribed of an extensive project that has as main objective the production of crossbred specialized beef hybrids from reformed Romanian Black Spotted cattle's with bulls from breeds specialized for meat production (Blue Blanch Belgique, Aberdeen-Angus and Limousin. Averaged biochemical indicators analyzed showed a normal state of animal's health. The obtained half-breeds products (bulls were raised under semi-intensively conditions and slaughtered at 12 months of age. Live weight, back-fat thickness and carcass traits were significantly influenced by breed, all fat parameters being lower at this age than at standard minimum age of slaughter for meat production (18 months. Drip loss and chemical composition were similar for the breeds. The meat was lighter and pH24 values of longissimus muscle were between 5.57 and 5.64. Sensory panel tenderness and Warner-Bratzler shear force values indicated tougher meat at RBSxAA than at RBSxL1 or RBSxBBB. Differences in meat quality were probably due to the combined effects of brute chemical composition and pH dynamic during ripening. It is concluded that slaughtering steers at younger ages may require supplementary feeding, being recommended a slaughter age between 18 and 25 months old.
Duckett, S K; Fernandez Rosso, C; Volpi Lagreca, G; Miller, M C; Neel, J P S; Lewis, R M; Swecker, W S; Fontenot, J P
2014-10-01
Angus-cross steers (n = 96; BW = 309 ± 34 kg; 13.5 mo of age) were used to determine the effects of frame size (medium or small) and time-on-pasture (TOP) on meat composition and palatability in a 2-yr study. Finishing steers grazed mixed pastures (bluegrass/white clover; April start) and were slaughtered after 89-, 146-, and 201-d TOP. At 24 h postmortem, carcass traits were collected and a rib from each carcass was obtained for proximate and fatty acid composition, Warner-Bratzler shear force (WBSF), and postmortem proteolysis. In yr 1, postmortem aging treatments included 14 and 28 d, whereas in yr 2, postmortem aging treatments included 2, 4, 7, 14, and 28 d. Increasing frame size of the finishing steers produced greater (P 0.05) due to frame size or 2-way interaction with TOP. Increasing TOP resulted in quadratic increases (P 0.05) compared to the 14-d postmortem aging WBSF values. However, in steaks from 201-d TOP, additional postmortem aging to 28 d reduced (P < 0.001) WBSF. In pasture-based beef finishing systems, increasing TOP increases animal age, HCW, fat thickness, and marbling score; however, tenderness of ribeye steaks decreased with advanced TOP such that longer postmortem aging times were required to achieve similar tenderness levels. PMID:25267999
Wheeler, T L; Cundiff, L V; Shackelford, S D; Koohmaraie, M
2010-09-01
The objective of this experiment was to evaluate alternative sources of tropically adapted cattle germplasm and compare them with Angus- (AN) and Hereford- (HE) sired steers. Carcass, yield, and longissimus thoracis palatability traits from F(1) steers (n = 621) obtained from mating AN and MARC III cows to HE, AN, Brangus (BR), Beefmaster (BM), Bonsmara (BO), or Romosinuano (RO) sires were compared. Data were adjusted to constant age (426 d), carcass weight (340 kg), fat thickness (1.0 cm), fat trim percentage (25%), and marbling (Small(00)) endpoints. For Warner-Bratzler and slice shear force and trained and untrained sensory panel traits, data were obtained on LM from ribeye steaks stored at 2 degrees C for 14 or 15 d postmortem. The following comparisons were from the age-constant endpoint. Carcasses from BM-, AN-, and BR-sired steers (358, 355, and 351 kg, respectively) were heavier (P American composite breeds BM and BR were heavier, fatter, lesser yielding, with similar marbling scores but less tender LM than BO and RO. Angus carcasses were similar in size, fatter, lesser yielding, with more marbling and more tender LM compared with BM and BR. Bonsmara and RO provide tropically adapted germplasm and produce carcasses that are lighter, leaner, greater yielding, with similar marbling and LM that tend to be more tender than carcasses from BM and BR. PMID:20453085
Scientific Electronic Library Online (English)
Lauren L. Hulsman, Hanna; Dorian J., Garrick; Clare A., Gill; Andy D., Herring; James O., Sanders; David G., Riley.
2014-12-01
Full Text Available The objectives of this study were to 1) compare four models for breeding value prediction using genomic or pedigree information and 2) evaluate the impact of fixed effects that account for family structure. Comparisons were made in a Nellore-Angus population comprising F2, F3 and half-siblings to em [...] bryo transfer F2 calves with records for overall temperament at weaning (TEMP; n = 769) and Warner-Bratzler shear force (WBSF; n = 387). After quality control, there were 34,913 whole genome SNP markers remaining. Bayesian methods employed were BayesB ( ? = 0.995 or 0.997 for WBSF or TEMP, respectively) and BayesC (? = 0 and ?), where ? is the ideal proportion of markers not included. Direct genomic values (DGV) from single trait Bayesian analyses were compared to conventional pedigree-based animal model breeding values. Numerically, BayesC procedures (using ?) had the highest accuracy of all models for WBSF and TEMP ( ?gg = 0.843 and 0.923, respectively), but BayesB had the least bias (regression of performance on prediction closest to 1, ?y,x = 2.886 and 1.755, respectively). Accounting for family structure decreased accuracy and increased bias in prediction of DGV indicating a detrimental impact when used in these prediction methods that simultaneously fit many markers.
Scientific Electronic Library Online (English)
S., Y& #252; ksel; M., Yanar; L., Turgut; A., & #214; zl& #252; t& #252; rk; S., Kopuzlu; E., Sezgin.
Full Text Available Fifteen young Holstein Friesian bulls (18 mo of age) were divided into three groups of five. All groups were fed a diet consisting of 60% concentrate and 40% roughage. The control (C) group received a mixture of dry meadow hay, dry lucerne and wheat straw as roughage. The second and third treatment [...] groups were fed a similar mixture of roughage partially substituting wheat straw with wet sugar beet pulp (SBP) at levels of 4% and 8% on a dry matter (DM) basis, respectively. Dry matter intake and feed efficiency ratio (kg DM intake/kg weight gain) of the C group were significantly higher than those of the 4% SBP and 8% SBP groups. Slaughter and carcass traits indicated that there were no significant differences between dietary treatments. The inclusion of 8% SBP significantly improved panel ratings for tenderness, juiciness, beef flavour intensity and general acceptance, as well as number of chews before swallowing and the Warner Bratzler Shear value. Proximate analysis of the meat did not demonstrate differences between meat from the bulls fed C and the SBP diets. It was concluded that wheat straw could be replaced by 8% SBP in the finishing diet for young Holstein Friesian bulls in order to improve feed efficiency and sensory quality characteristics of their meat.
Commercial application of high-dose irradiation to produce shelf-stable meat products. Part 3 - Effect of polyphosphates on the tenderness and sensory properties of beef silverside sterilised at 45 kGy
International Nuclear Information System (INIS)
The effect of five mixtures of sodium chloride, sodium tripolyphosphate and tetrasodiumpyrophosphate on the texture and sensory properties of irradiated beef M. biceps femoris and M. semitendinosus muscles sterilised at 45 kGy were evaluated using pH after injection, drip loss measurement, Instron texture measurement and descriptive sensory analysis. The effect of cattle race was also investigated. Three breeds of cattle namely Afrikaner (Bos indicus), Hereford (Bos taurus) and Simmentaler (Bos taurus) were used. Steers were fed and raised in a controlled environment until 18 months of age, followed by slaughtering using the same procedure for each carcass. It was found that cattle breed had a significant influence on irradiated meat tenderness and juiciness. Afrikaner breed meat was the most tender and the most juicy. The Energy to break point measured using a Warner Bratzler Shear cell correlated with the ease of fragmentation (using fingers) as well as Initial Juiciness and Sustained Juiciness. Using polyphosphate levels of 13.2 mmol/kg produced undesirable flavours in the meat. The same tenderness was obtained using levels of 8.2 mmol/kg in the meat without undesirable taste. No differences were found between sodium tripolyphosphate and tetrasodium pyrophosphate treatments. Warmed Over Flavour was a significant factor influencing the quality of the products. (author)
Effect of bleeding method and low voltage electrical stimulation on meat quality of ostriches
Scientific Electronic Library Online (English)
L.C., Hoffman; S.W.P., Cloete; S.J., van Schalkwyk; S.St.C., Botha.
Full Text Available The effect on ostrich muscle quality of an additional thoracic stick (TS) to the normal ventral throat slit to bleed ostriches after electrical stunning was evaluated. The additional TS had no negative or positive effect on the drip loss, cooking loss, colour or pH and temperature readings of the fi [...] llet (Muscularis iliofibularis), big drum (M. gastrocnemius, pars interna) and inside loin (M. iliotibialis cranialis). None the less, personal observations would recommend the use of TS due to ethical considerations. An early post mortem low voltage electrical stimulation (ES) of the carcasses also had no influence on the cooking loss, drip loss and colour of these muscles. Electrical stimulation did result in a lower pH45 in both the fillet and big drum muscles. However, after 24 h the pH of the muscles did not differ. Electrical stimulation also caused elevated initial muscle temperatures, although this effect was only temporary due to the efficient cooling mechanism used in the abattoir. Electrical stimulation also had no effect on the Warner Bratzler shear force values in the fillet. It can be concluded that low voltage ES has no advantage pertaining to physical quality characteristics of importance in an ostrich abattoir.
Rapid detection of frozen pork quality without thawing by Vis-NIR hyperspectral imaging technique.
Xie, Anguo; Sun, Da-Wen; Xu, Zhongyue; Zhu, Zhiwei
2015-07-01
Quality determination of frozen food is a time-consuming and laborious work as it normally takes a long time to thaw the frozen samples before measurements can be carried out. In this research, a rapid and non-destructive determination technique for frozen pork quality was tested with a hyperspectral imaging (HSI) system. In this study, 120 pieces of pork meat were frozen by four kinds of methods with various freezing temperatures from -20 to -120°C. The hyperspectral images of the samples were acquired at the frozen state. Quality indicators including drip loss, pH value, color, cooking loss and Warner-Bratzler shear force (WBSF) of the samples were measured after thawing. The spectral characteristics of the frozen meat samples were studied and it was revealed that the reflectance at 1100nm had a close relationship with the freezing temperature (R=-0.832, pcooking loss, b*, drip loss and a* were 0.907, 0.845, 0.814, 0.762, and 0.716, respectively. However there were low correlations (Rp(2)) for pH and WBSF measurements. The current study indicated that HSI had the potential for non-destructive determination of frozen meat quality without thawing. PMID:25882428
Kamruzzaman, Mohammed; Elmasry, Gamal; Sun, Da-Wen; Allen, Paul
2013-11-01
The purpose of this study was to develop and test a hyperspectral imaging system (900-1700 nm) to predict instrumental and sensory tenderness of lamb meat. Warner-Bratzler shear force (WBSF) values and sensory scores by trained panellists were collected as the indicator of instrumental and sensory tenderness, respectively. Partial least squares regression models were developed for predicting instrumental and sensory tenderness with reasonable accuracy (Rcv=0.84 for WBSF and 0.69 for sensory tenderness). Overall, the results confirmed that the spectral data could become an interesting screening tool to quickly categorise lamb steaks in good (i.e. tender) and bad (i.e. tough) based on WBSF values and sensory scores with overall accuracy of about 94.51% and 91%, respectively. Successive projections algorithm (SPA) was used to select the most important wavelengths for WBSF prediction. Additionally, textural features from Gray Level Co-occurrence Matrix (GLCM) were extracted to determine the correlation between textural features and WBSF values. PMID:23768372
Evolution of anomalous transport in shear flow of toroidal devices
International Nuclear Information System (INIS)
The experimentally determined velocity shear in Uragan-3M (U-3M) torsatron in (L-H) - like transition is up to ten times greater than the drift wave frequency. The temporal evolution of the drift and Alfven turbulence and the resulted anomalous transport are considered under the conditions of modest (flow shear parameter v0' is of the order of the instabilities growth rate) and strong flow shear (flow shear parameter v0' is greater than the drift frequency) on the grounds of the non-modal approach. The studies of the dynamics of packets of nonmodal drift waves, eta-i modes, Alfven waves have shown that the wave packets are stagnated or reflected by the shear flow. The components of the group velocity along the flow shear rapidly vanish with time. The calculated anomalous ion transport displays rapid decreasing with time. The comparative analysis of the linear non-modal effects and nonlinear turbulent effects, such as the effect of the enhanced by flow shear nonlinear decorrelation, on the instabilities evolution and saturation is performed. The renormalized kinetic theory of drift and drift-cyclotron instabilities of a plasma with a transverse inhomogeneous shear flow, which accounts for the turbulent scattering of ions across the shear flow and the enhanced scattering of ions along the shear flow, is developed. The saturation level of the shear-flow-modified drift turbulence and the reduced by the shear flow anomalous fluxe reduced by the shear flow anomalous fluxes of ions and electrons are determined. (author)
Towards shear tactile displays with DEAs
Knoop, Lars E.; Rossiter, Jonathan
2014-03-01
Much research has been done on the development of tactile displays using Dielectric Elastomer Actuators (DEAs). It has been argued that they offer the potential to create low-cost full-page tactile displays — not achievable with conventional actuator technologies. All research to date has considered tactile elements moving perpendicular to the skin and thus applying a normal force distribution. In contrast to previous work, we have investigated the use of laterally moving tactile elements that apply shear forces to the skin. This allows for the areal expansion of the DEA to be exploited directly, and a tactile display could be made with no elements moving out of the plane. There is evidence that humans are very sensitive to shear force distributions, and that in some cases a shear stimulus is indistinguishable from a normal stimulus. We present a prototype shear tactile display actuated by a DEA, and demonstrate that the DEA can generate the necessary forces and displacements. We also present and discuss different display topologies.
International Nuclear Information System (INIS)
The experimental data from RHIC, especially the measured elliptic flow indicate that the matter produced in Au+Au collisions exhibit properties which are more like a strongly interacting liquid than a weakly interacting gas. The shear viscosity ? or the internal friction of the fluid symbolizes the ability to transfer momentum over a distance of ? mean free path. Therefore, in a system where the constituents interact strongly the transfer of momentum is performed easily - resulting in lower values of ?. Consequently such a system may be characterized by a small value of ?/s. The importance of viscosity also lies in the fact that it damps out the variation in the velocity and make the fluid flow laminar. A very small viscosity (large Reynold number) may make the flow turbulent. Although a large amount of work has been done on shear viscosity in QGP phase, the shear viscosity in hadronic matter has received much less attention so far. In the present work shear viscosity has been evaluated in a kinetic theory approach by solving Boltzmann transport equation using the relaxation time approximation
Excitation of vortex meandering in shear flow
Schröttle, Josef; Dörnbrack, Andreas; Schumann, Ulrich
2015-06-01
This paper investigates the evolution of a streamwise aligned columnar vortex with vorticity {\\boldsymbol{ ? }} in an axial background shear of magnitude ? by means of linear stability analysis and numerical simulations. A long wave mode of vorticity normal to the plane spanned by the background shear vector {\\boldsymbol{ ? }} and the vorticity of the vortex are excited by an instability. The stationary wave modes of the vertical and lateral vorticity are amplified. In order to form a helical vortex, the lateral and vertical vorticity can be phase shifted by half a wavelength. The linear and nonlinear evolutions of the vortex in the shear flow are studied numerically. Linearized simulations confirm the results of the stability analysis. The nonlinear simulations reveal further evolution of the helix in the shear flow. The linearly excited mode persists in co-existence with evolving smaller scale instabilities until the flow becomes fully turbulent at the time of O(100 {{? }-1}). Turbulent mixing dampens the amplifying mode. The described phenomenon of vortex meandering may serve as an alternative explanation for the excitation of wind turbine wake meandering in the atmospheric boundary layer.
Modeling of Turbulent Free Shear Flows
Yoder, Dennis A.; DeBonis, James R.; Georgiadis, Nicolas J.
2013-01-01
The modeling of turbulent free shear flows is crucial to the simulation of many aerospace applications, yet often receives less attention than the modeling of wall boundary layers. Thus, while turbulence model development in general has proceeded very slowly in the past twenty years, progress for free shear flows has been even more so. This paper highlights some of the fundamental issues in modeling free shear flows for propulsion applications, presents a review of past modeling efforts, and identifies areas where further research is needed. Among the topics discussed are differences between planar and axisymmetric flows, development versus self-similar regions, the effect of compressibility and the evolution of compressibility corrections, the effect of temperature on jets, and the significance of turbulent Prandtl and Schmidt numbers for reacting shear flows. Large eddy simulation greatly reduces the amount of empiricism in the physical modeling, but is sensitive to a number of numerical issues. This paper includes an overview of the importance of numerical scheme, mesh resolution, boundary treatment, sub-grid modeling, and filtering in conducting a successful simulation.
Vortex-shear interaction and vortex identification.
Czech Academy of Sciences Publication Activity Database
Kolá?, Václav
Jalan : Institution of Engineers, 2006, s. 1015-1020. ISBN 983-42965-0-9. [Asian Congress of Fluid Mechanics /11./. Kuala Lumpur (MY), 22.05.2006-25.05.2006] R&D Projects: GA AV ?R IAA2060302 Institutional research plan: CEZ:AV0Z20600510 Keywords : vortex identification * vortex -shear interaction Subject RIV: BK - Fluid Dynamics
Crossing of shears bands in 196Pb
International Nuclear Information System (INIS)
High-spin states in 196Pb have been populated using the reaction 170Er(30Si, 4n). The previously observed shear bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin. (orig.)
Wall Shear Stress Measurements in Microfluidic Systems.
Czech Academy of Sciences Publication Activity Database
Tihon, Jaroslav; P?nkavová, V?ra; Stanovský, Petr; Vejražka, Ji?í
- : -, 2014, s. 607. ISBN N. [European Fluid Mechanics Conference EFMC10 /10./. Copenhagen (DK), 15.09.2014-18.09.2014] R&D Projects: GA ?R(CZ) GAP101/12/0585 Institutional support: RVO:67985858 Keywords : microfluidics * electrodiffusion method * wall shear stress Subject RIV: CI - Industrial Chemistry, Chemical Engineering http://www.efmc10.org/
Granular dynamics under shear with deformable boundaries
Geller, Drew; Backhaus, Scott; Ecke, Robert
2015-03-01
Granular materials under shear develop complex patterns of stress as the result of granular positional rearrangements under an applied load. We consider the simple planar shear of a quasi two-dimensional granular material consisting of bi-dispersed nylon cylinders confined between deformable boundaries. The aspect ratio of the gap width to total system length is 50, and the ratio of particle diameter to gap width is about 10. This system, designed to model a long earthquake fault with long range elastic coupling through the plates, is an interesting model system for understanding effective granular friction because it essentially self tunes to the jamming condition owing to the hardness of the grains relative to that of the boundary material, a ratio of more than 1000 in elastic moduli. We measure the differential strain displacements of the plates, the inhomogeneous stress distribution in the plates, the positions and angular orientations of the individual grains, and the shear force, all as functions of the applied normal stress. There is significant stick-slip motion in this system that we quantify through our quantitative measurements of both the boundary and the grain motion, resulting in a good characterization of this sheared 2D hard sphere system.
Shear bands as bottlenecks in force transmission
Tordesillas, Antoinette; Pucilowski, Sebastian; Tobin, Steven; Kuhn, Matthew R.; Andò, Edward; Viggiani, Gioacchino; Druckrey, Andrew; Alshibli, Khalid
2015-06-01
The formation of shear bands is a key attribute of degradation and failure in soil, rocks, and many other forms of amorphous and crystalline materials. Previous studies of dense sand under triaxial compression and two-dimensional analogues from simulations have shown that the ultimate shear band pattern may be detected in the nascent stages of loading, well before the band's known nucleation point (i.e., around peak stress ratio), as reported in the published literature. Here we construct a network flow model of force transmission to identify the bottlenecks in the contact networks of dense granular media: triaxial compression of Caicos ooid and Ottawa sand and a discrete element simulation of simple shear. The bottlenecks localise in the nascent stages of loading —in the location where the persistent shear band ultimately forms. This corroborates recent findings on vortices that suggest localised failure is a progressive process of degradation, initiating early in the loading history at sites spanning the full extent, yet confined to a subregion, of the sample. Bottlenecks are governed by the local and global properties of the sample fabric and the grain kinematics. Grains with large rotations and/or contacts having minimal load-bearing capacities per se do not identify the bottlenecks early in the loading history.
Shear crack formation and propagation in reinforced Engineered Cementitious Composites
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2011-01-01
This paper describes an experimental investigation of the shear behaviour of beams consisting of steel reinforced Engineered Cementitious Composites (R/ECC). Based on the strain hardening and multiple cracking behaviour of ECC, this study investigates the extent to which ECC influences the shear capacity of beams loaded primarily in shear. The experimental program consists of ECC with short randomly distributed polyvinyl alcohol (PVA) fiber beams with different stirrup arrangements and conventional reinforced concrete (R/C) counterparts for comparison. The shear crack formation mechanism of ECC is investigated in detail and can be characterized by an opening and sliding of the crack. Photogrammetry was utilized to monitor the shear deformations of the specimens. Multiple shear cracking and strain hardening of ECC was observed under shear loading and based upon photogrammetric results fundamental descriptions of shear crack opening, sliding and subsequent failure are presented.
Predicting km-scale shear zone formation
Gerbi, Christopher; Culshaw, Nicholas; Shulman, Deborah; Foley, Maura; Marsh, Jeffrey
2015-04-01
Because km-scale shear zones play a first-order role in lithospheric kinematics, accurate conceptual and numerical models of orogenic development require predicting when and where they form. Although a strain-based algorithm in the upper crust for weakening due to faulting appears to succeed (e.g., Koons et al., 2010, doi:10.1029/2009TC002463), a comparable general rule for the viscous crust remains unestablished. Here we consider two aspects of the geological argument for a similar algorithm in the viscous regime, namely (1) whether predicting km-scale shear zone development based on a single parameter (such as strain or shear heating) is reasonable; and (2) whether lithologic variability inherent in most orogenic systems precludes a simple predictive rule. A review of tectonically significant shear zones worldwide and more detailed investigations in the Central Gneiss belt of the Ontario segment of the Grenville Province reveals that most km-scale shear zones occur at lithological boundaries and involve mass transfer, but have fairly little else in common. As examples, the relatively flat-lying Twelve Mile Bay shear zone in the western Central Gneiss belt bounds the Parry Sound domain and is likely the product of both localized anatexis and later retrograde hydration with attendant metamorphism. Moderately dipping shear zones in granitoids of the Grenville Front Tectonic Zone apparently resulted from cooperation among several complementary microstructural processes, such as grain size reduction, enhanced diffusion, and a small degree of metamorphic reaction. Localization into shear zones requires the operation of some spatially restricted processes such as stress concentration, metamorphism/fluid access, textural evolution, and thermal perturbation. All of these could be due in part to strain, but not necessarily linearly related to strain. Stress concentrations, such as those that form at rheological boundaries, may be sufficient to nucleate high strain gradients but are insufficient to maintain them because the stress perturbations will dissipate with deformation. Metamorphism can unquestionably cause sufficient rheological change, but only in certain rock types: for example, granitoids have much less capacity for metamorphically induced rheologic change than do mafic rocks. The magnitude of phase geometry variation observed in natural systems suggests that morphological change (e.g., interconnection of weak phases) likely has little direct affect on strength changes, although other textural factors related to diffusion paths and crystallographic orientation could play a significant role. Thermal perturbation, mainly in the form of shear heating, remains potentially powerful but inconclusive. Taken together, these observations indicate that a simple algorithm predicting shear zone formation will not succeed in many geologically relevant instances. One significant reason may be that the inherent lithologic variation at the km scale, such as observed in the Central Gneiss belt, prevents the development of self-organized strain patterns that would form in more rheologically uniform systems.
Liu, Guoxi; Zhang, Chunli; Dong, Shuxiang
2014-08-01
This paper investigates the magnetoelectric (ME) effect of magnetostrictive/piezoelectric laminated composite operating in a shear-shear (S-S) mode, i.e., the magnetostrictive and piezoelectric phases of the laminated composite both operate in thickness shear modes. Theoretical analysis shows that the S-S mode laminated ME composite exhibits stronger ME coupling coefficients, i.e., the ME electric field, voltage, and charge coefficients, than those of a typical L-T mode laminated ME composite (longitudinally magnetized and transversely polarized) because of the higher piezomagnetic and piezoelectric coefficients in thickness shear modes of the magnetostrictive and piezoelectric phases, respectively. Our theoretical analysis provides the optimum design method for practical applications of the S-S mode laminated ME composite.
High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates
Becnel, Andrew C.
This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter crew seat. Characterization tests were carried out on the LMEAS using a 40 vol% MRF used in the previous magnetorheometer tests. These were analyzed using both flow curves and apparent viscosity vs. Mason number diagrams. The nondimensionalized Mason number analysis resulted in data for all conditions of temperature, fluid composition, and shear rate, to collapse onto a single characteristic or master curve. Significantly, the temperature corrected Mason number results from both the bench top magnetorheometer and full scale rotary vane MREA collapse to the same master curve. This enhances the ability of designers of MRFs and MREAs to safely and effectively apply characterization data collected in low shear rate, controlled temperature environments to operational environments that may be completely different. Finally, the Searle cell magnetorheometer was modified with an enforced eccentricity to work in both squeeze and shear modes simultaneously to achieve so called squeeze strengthening of the working MRF, thereby increasing the apparent yield stress and the specific energy absorption. By squeezing the active MR fluid, particles undergo compression-assisted aggregation into stronger, more robust columns which resist shear better than single chains. A hybrid model describing the squeeze strengthening behavior is developed, and recommendations are made for using squeeze strengthening to improve practical MREA devices.
Shearing of fibrillar adhesive microstructure: friction and shear-related changes in pull-off force.
Varenberg, M; Gorb, S
2007-08-22
To characterize the effect of shearing on function of fibrillar adhesive microstructure, friction and shear-related changes in pull-off force of a biomimetic polyvinylsiloxane mushroom-shaped fibrillar adhesive microstructure were studied. In contrast to a control flat surface, which exhibited pronounced stick-slip motion accompanied with high friction, the fibrillar microstructure demonstrated a stable and smooth sliding with a friction coefficient approximately four times lower. The structured contact also manifested zero pull-off force in a sheared state, while the flat surface exhibited highly scattered and unreliable pull-off force when affected by contact shearing. It appears that the fibrillar microstructure can be used in applications where a total attachment force should be generated in a binary on/off state and, most surprisingly, is suitable to stabilize and minimize elastomer friction. PMID:17327201
Gap size and shear history dependencies in shear thickening of a suspension ordered at rest
International Nuclear Information System (INIS)
An investigation is made of the flow properties of a suspension of uniform 197 nm diameter spheres at a volume fraction of 0.50 dialyzed to equilibrium against 10-3 M KCl which displayed long-range orientational order at rest. In wide gap rheometers (i.e., tool gaps ?0.5 mm), microstructures and flow properties are similar to those seen in many suspensions which are ordered at rest. Low shear rate response is found to be independent of rheometer tool gap down to 4.5 ?m. However, the shear rate marking the onset of thickening is a decreasing function of rheometer tool gap for gaps smaller than 15 ?m. These results are consistent with abrupt shear thickening seen in dense suspensions containing uniform particles arising from the formation of percolating clusters produced during shear melting
Spurious Shear in Weak Lensing with LSST
Energy Technology Data Exchange (ETDEWEB)
Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.
2012-09-19
The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.
Management of distal humeral coronal shear fractures
Yari, Shahram S; Bowers, Nathan L; Craig, Miguel A; Reichel, Lee M
2015-01-01
Coronal shear fractures of the distal humerus are rare, complex fractures that can be technically challenging to manage. They usually result from a low-energy fall and direct compression of the distal humerus by the radial head in a hyper-extended or semi-flexed elbow or from spontaneous reduction of a posterolateral subluxation or dislocation. Due to the small number of soft tissue attachments at this site, almost all of these fractures are displaced. The incidence of distal humeral coronal shear fractures is higher among women because of the higher rate of osteoporosis in women and the difference in carrying angle between men and women. Distal humeral coronal shear fractures may occur in isolation, may be part of a complex elbow injury, or may be associated with injuries proximal or distal to the elbow. An associated lateral collateral ligament injury is seen in up to 40% and an associated radial head fracture is seen in up to 30% of these fractures. Given the complex nature of distal humeral coronal shear fractures, there is preference for operative management. Operative fixation leads to stable anatomic reduction, restores articular congruity, and allows initiation of early range-of-motion movements in the majority of cases. Several surgical exposure and fixation techniques are available to reconstruct the articular surface following distal humeral coronal shear fractures. The lateral extensile approach and fixation with countersunk headless compression screws placed in an anterior-to-posterior fashion are commonly used. We have found a two-incision approach (direct anterior and lateral) that results in less soft tissue dissection and better outcomes than the lateral extensile approach in our experience. Stiffness, pain, articular incongruity, arthritis, and ulnohumeral instability may result if reduction is non-anatomic or if fixation fails. PMID:25984515
Edge Sheared Flows and Blob Dynamics
Myra, J. R.
2012-10-01
The dynamics of blob-filaments [S. I. Krasheninnikov, et al. J. Plasma Phys. 74, 679 (2008); D. A. D'Ippolito, et al., Phys. Plasmas 18, 060501 (2011)] in the strongly radially inhomogeneous edge and scrape-off-layer (SOL) region of a tokamak plasma is considered, with emphasis on sheared flow generation and interaction. The work is motivated by the potential importance of edge sheared flows for turbulence regulation, (e.g. the L-H transition), and the influence of flows on the character of emitted blob-filament structures which ultimately contact plasma-facing components. To study the dynamics of blobs and sheared flows, we employ both numerical simulations and experimental data analysis. The simulations use the fluid-based 2D curvature-interchange model embedded in the SOLT (SOL turbulence) code [D. A. Russell, et al, Phys. Plasmas 16, 122304 (2009)]. A blob-tracking algorithm has also been developed and applied to NSTX and Alcator C-Mod data. The algorithm is based on 2D time-resolved images from the gas puff imaging (GPI) diagnostic [S. J. Zweben, et al. Phys. Plasmas 9, 1981 (2002)]. The algorithm is able to track the blob motion and changes in blob structure, such as elliptical deformations, that can be affected by sheared flows. Results of seeded blob simulations are compared with the experimental data to determine the role of plasma parameters on the blob tracks and to evaluate the exchange of momentum between the blobs and flows. Seeded blob simulations are shown to reproduce many qualitative and quantitative features of the data including size, scale and direction of perpendicular (approximately poloidal) flows and the inferred Reynolds forces, poloidal reversal of blob tracks, and blob trapping and/or ejection. Simulation and experimental data comparisons permit the inference of dynamical mechanisms associated with blob motion and sheared flow generation in these shots, and their relation to previous theoretical work.
Ductility correlations between shear punch and uniaxial tensile test data
Toloczko, M. B.; Hamilton, M. L.; Lucas, G. E.
2000-12-01
The shear punch test was developed to address the need of the fusion reactor structural materials community for small scale mechanical properties tests. It has been demonstrated that effective shear strength data obtained from the shear punch test can be linearly related to uniaxial tensile strength for a wide variety of alloys. The current work explores the existence of a similar relationship between shear punch test data and both the tensile strain hardening exponent and the uniform elongation.
Ductility correlations between shear punch and uniaxial tensile test data
International Nuclear Information System (INIS)
The shear punch test was developed to address the need of the fusion reactor structural materials community for small scale mechanical properties tests. It has been demonstrated that effective shear strength data obtained from the shear punch test can be linearly related to uniaxial tensile strength for a wide variety of alloys. The current work explores the existence of a similar relationship between shear punch test data and both the tensile strain hardening exponent and the uniform elongation
Shear thickening in electrically stabilized non-aqueous colloidal suspensions
Kaldasch, J (Joachim); B. Senge; Lavèn, J (Jozua=Jos)
2012-01-01
The authors previously introduced an activation model for the onset of shear thickening in electrically stabilized colloidal suspensions. It predicts that shear thickening occurs, when particles arranged along the compression axis in a sheared suspension do overcome the electrostatic repulsion at a critical shear stress, and are captured in the primary minimum of the DLVO interaction potential. A comparison with an experimental investigation on non-aqueous silica suspensions...
Relation between ordering and shear thinning in colloidal suspensions
Xu, Xinliang; Rice, Stuart A; Dinner, Aaron R.
2013-01-01
Colloidal suspensions exhibit shear thinning and shear thickening. The most common interpretation of these phenomena identifies layering of the fluid perpendicular to the shear gradient as the driver for the observed behavior. However, studies of the particle configurations associated with shear thinning and thickening cast doubt on that conclusion and leave unsettled whether these nonequilibrium phenomena are caused primarily by correlated particle motions or by changes in particle packing s...
Turbulent transport across shear layers in magnetically confined plasmas
Energy Technology Data Exchange (ETDEWEB)
Nold, B.; Ramisch, M. [Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Universität Stuttgart, D-70569 Stuttgart (Germany); Manz, P.; Birkenmeier, G. [Physik-Department E28, Technische Universität München, James-Franck-Str.1, D-85748 Garching (Germany); Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Ribeiro, T. T.; Müller, H. W.; Scott, B. D. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Fuchert, G. [IJL, Université de Lorraine, CNRS (UMR 7198), BP 40239 Vandoeuvre-lès-Nancy (France); Stroth, U. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Physik-Department E28, Technische Universität München, James-Franck-Str.1, D-85748 Garching (Germany)
2014-10-15
Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatial-temporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.
Turbulent transport across shear layers in magnetically confined plasmas
International Nuclear Information System (INIS)
Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatial-temporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process
Shearing of fibrillar adhesive microstructure: friction and shear-related changes in pull-off force
Varenberg, M; Gorb, S
2007-01-01
To characterize the effect of shearing on function of fibrillar adhesive microstructure, friction and shear-related changes in pull-off force of a biomimetic polyvinylsiloxane mushroom-shaped fibrillar adhesive microstructure were studied. In contrast to a control flat surface, which exhibited pronounced stick–slip motion accompanied with high friction, the fibrillar microstructure demonstrated a stable and smooth sliding with a friction coefficient approximately four times lower. The structu...
The effect of shearing rate and slope angle on the simple shear response of marine clays
Biscontin, G.; Rutherford, C.
2010-12-01
The response of submarine slopes to seismic or storm loading has become an important element in the risk assessment for offshore structures and local tsunami hazard. Evaluation of submarine slope stability requires characterization of soil behavior and relies on the selection of appropriate parameter values. Although the traditional simple shear device has been used to investigate cyclic loading effects on marine clay, it does not allow for complex loading conditions which often contribute to the failure on submarine slopes. Understanding the interaction between the initial shear stress, the slope angle, and the multi-directional shaking due to earthquakes or storm loading is an important aspect to understanding the failure mechanisms of submarine slope failures. The initial static driving force on the slope is combined with the dynamic loading by storms and earthquakes to create complex loading paths. Therefore, the ability to apply complex stress or strain paths is important to fully study the shear response of marine clays on submarine slopes. A new multi-directional simple shear device developed at Texas A&M University allows loading along three independent axes, two perpendicular horizontal directions to allow any stress or strain paths in the horizontal plane, and a third in the vertical direction. This device is used to investigate the response of Gulf of Mexico marine deposits to different loading conditions. To study the effect of slope angle on the shear response of the soil, samples are subjected to a shear stress during consolidation, K? consolidation. One-dimensional monotonic and cyclic shearing of Ko consolidated specimens is used to simulate level ground conditions, whereas sloping surfaces were simulated using K? consolidation for both monotonic and cyclic tests. The effects of shearing rate on the soil response are investigated using strain controlled tests at varying frequencies.
López-Barrón, Carlos R.; Gurnon, A. Kate; Eberle, Aaron P. R.; Porcar, Lionel; Wagner, Norman J.
2014-04-01
We present direct measurements of the evolution of the segmental-level microstructure of a stable shear-banding polymerlike micelle solution during flow startup and cessation in the plane of flow. These measurements provide a definitive, quantitative microstructural understanding of the stages observed during flow startup: an initial elastic response with limited alignment that yields with a large stress overshoot to a homogeneous flow with associated micellar alignment that persists for approximately three relaxation times. This transient is followed by a shear (kink) band formation with a flow-aligned low-viscosity band that exhibits shear-induced concentration fluctuations and coexists with a nearly isotropic band of homogenous, highly viscoelastic micellar solution. Stable, steady banding flow is achieved only after approximately two reptation times. Flow cessation from this shear-banded state is also found to be nontrivial, exhibiting an initial fast relaxation with only minor structural relaxation, followed by a slower relaxation of the aligned micellar fluid with the equilibrium fluid's characteristic relaxation time. These measurements resolve a controversy in the literature surrounding the mechanism of shear banding in entangled wormlike micelles and, by means of comparison to existing literature, provide further insights into the mechanisms driving shear-banding instabilities in related systems. The methods and instrumentation described should find broad use in exploring complex fluid rheology and testing microstructure-based constitutive equations.
Estimation of seabed shear-wave velocity profiles using shear-wave source data.
Dong, Hefeng; Nguyen, Thanh-Duong; Duffaut, Kenneth
2013-07-01
This paper estimates seabed shear-wave velocity profiles and their uncertainties using interface-wave dispersion curves extracted from data generated by a shear-wave source. The shear-wave source generated a seismic signature over a frequency range between 2 and 60 Hz and was polarized in both in-line and cross-line orientations. Low-frequency Scholte- and Love-waves were recorded. Dispersion curves of the Scholte- and Love-waves for the fundamental mode and higher-order modes are extracted by three time-frequency analysis methods. Both the vertically and horizontally polarized shear-wave velocity profiles in the sediment are estimated by the Scholte- and Love-wave dispersion curves, respectively. A Bayesian approach is utilized for the inversion. Differential evolution, a global search algorithm is applied to estimate the most-probable shear-velocity models. Marginal posterior probability profiles are computed by Metropolis-Hastings sampling. The estimated vertically and horizontally polarized shear-wave velocity profiles fit well with the core and in situ measurements. PMID:23862796
Wittmer, J. P.; Kriuchevskyi, I.; Baschnagel, J; Xu, H
2015-01-01
Shear-strain and shear-stress correlations in isotropic elastic bodies are investigated both theoretically and numerically at either imposed mean shear-stress $\\tau$ ($\\lambda=0$) or shear-strain $\\gamma$ ($\\lambda=1$) and for more general values of a dimensionless parameter $\\lambda$ characterizing the generalized Gaussian ensemble. It allows to tune the strain fluctuations $\\mu_{\\gamma\\gamma} \\equiv \\beta V \\la \\delta \\gamma^2 \\ra = (1-\\lambda)/G_{eq}$ with $\\beta$ being t...
Reda, Daniel C.; Wilder, Michael C.; Nixon, David (Technical Monitor)
1998-01-01
The shear-sensitive liquid crystal coating (SSLCC) method is an image-based technique for both visualizing dynamic surface-flow phenomena, such as transition and separation, and for measuring the continuous shear-stress vector distribution acting on an aerodynamic surface. Under proper lighting and viewing conditions (discussed below), the coating changes color in response to an applied aerodynamic shear. This color-change response is continuous and reversible, with a response time of milliseconds, and is a function of both the shear magnitude and the shear vector orientation relative to the observer. The liquid crystal phase of matter is a weakly-ordered, viscous, non-Newtonian fluid state that exists between the nonuniform liquid phase and the ordered solid phase of certain organic compounds. Cholesteric liquid crystal compounds possess a helical molecular arrangement that selectively scatters white light, incident along the helical axis, as a three-dimensional spectrum. This property is linked to the helical pitch length, which is within the range of wavelengths in the visible spectrum. The pitch length, and hence the wavelength of the scattered light, is influenced by shear stress normal to the helical axis. This unique optical property produces a measurable color change in response to an applied shearing force. The full-surface shear stress vector measurement method, developed at NASA-Ames, is schematically illustrated. As with the visualization method, the coated test surface is illuminated from the normal direction with white light and the camera is positioned at an above-plane view angle of approximately 30 deg. Experiments have been initiated at NASA Ames to begin the process of quantifying surface-inclination (surface-curvature) effects on shear vector measurement accuracy. In preliminary experiments, surface-inclination angles theta(sub x), theta(sub y) of 0, +/-5, +/-10, and +/-15 deg were employed. In this arrangement, white-light illumination was positioned normal to the untilted test surface, and the camera above-plane view angle was set at 30 deg relative to the untilted test surface. As can be seen, vector-aligned lambda(sub d) values showed no dependence on theta(sub x) or theta(sub y) for absolute values of these tilt angles is less than or equal to 15 deg. Acquisition and analyses of full-surface color images are presently underway to definitively document the insensitivity limits of the shear vector measurement methodology to surface-slope variations.
Shear zones in granular media: 3D Contact Dynamics simulation
Ries, Alexander; Unger, Tamas; Wolf, Dietrich E
2007-01-01
Shear zone formation is investigated in slow 3D shear flows. We simulate the linear version of the split-bottom shear cell. It is shown that the same type of wide shear zones is achieved in the presence as well as in the absence of gravity. We investigate the relaxation of the material towards a stationary flow and analyze the stress and the velocity fields. We provide the functional form of the widening of the shear zone inside the bulk. We discuss the growth of the region ...
Velocity profiles in shear-banding wormlike micelles
Salmon, J B; Manneville, S; Molino, F; Salmon, Jean-Baptiste; Colin, Annie; Manneville, Sebastien; Molino, Francois
2003-01-01
Using Dynamic Light Scattering in heterodyne mode, we measure velocity profiles in a much studied system of wormlike micelles (CPCl/NaSal) known to exhibit both shear-banding and stress plateau behavior. Our data provide evidence for the simplest shear-banding scenario, according to which the effective viscosity drop in the system is due to the nucleation and growth of a highly sheared band in the gap, whose thickness linearly increases with the imposed shear rate. We discuss various details of the velocity profiles in all the regions of the flow curve and emphasize on the complex, non-Newtonian nature of the flow in the highly sheared band.
Swinging of red blood cells under shear flow
Abkarian, M; Viallat, A; Abkarian, Manouk; Faivre, Magalie; Viallat, Annie
2007-01-01
We reveal that under moderate shear stress (of the order of 0.1 Pa) red blood cells present an oscillation of their inclination (swinging) superimposed to the long-observed steady tanktreading (TT) motion. A model based on a fluid ellipsoid surrounded by a visco-elastic membrane initially unstrained (shape memory) predicts all observed features of the motion: an increase of both swinging amplitude and period (1/2 the TT period) upon decreasing the shear stress, a shear stress-triggered transition towards a narrow shear stress-range intermittent regime of successive swinging and tumbling, and a pure tumbling motion at lower shear stress-values.
Ring shear apparatus and its utilization to soil mechanics
Hong, Yong
2011-10-01
In this paper, a geotechnical ring shear apparatus and its utilization in the geotechnical tests of studying soil properties were introduced. The testing methods and technology of studying the static and dynamic mechanical properties of soils under large shear displacement were elaborated. It was found that, under the testing conditions of fast shear rate and dynamic loadings, the soil samples present very different features in contrast with the normal shear tests. The discrepancy can be attributed to the marked variations of pore pressure and geomorphology of shear band in the tests.
Search for shears mechanism in 142Sm
International Nuclear Information System (INIS)
Generation of angular momentum in weakly deformed nuclei by shears mechanism is a well known phenomenon in nuclear structure physics. During the last two decades, rotational-like bands consisting of dipole transitions have been observed systematically near the spherical region and interpreted as Magnetic Rotor. In this mechanism the total angular momentum along the band is generated by the gradual alignment of the two angular momentum blades and the shears arrangement of the high j orbital give rise to a large transverse magnetic dipole moment. In the present INGA experiments at TIFR, the level structure of 141,142Sm is studied in order to look for the possible observation of magnetic and anti magnetic rotational bands by measuring the life time of the excited states using DSAM technique
Shear instabilities in shallow-water magnetohydrodynamics
Mak, Julian; Hughes, D W
2015-01-01
Within the framework of shallow-water magnetohydrodynamics, we investigate the linear instability of horizontal shear flows, influenced by an aligned magnetic field and stratification. Various classical instability results, such as H{\\o}iland's growth rate bound and Howard's semi-circle theorem, are extended to this shallow-water system for quite general profiles. Two specific piecewise-constant velocity profiles, the vortex sheet and the rectangular jet, are studied analytically and asymptotically; it is found that the magnetic field and stratification (as measured by the Froude number) are generally both stabilising, but weak instabilities can be found at arbitrarily large Froude number. Numerical solutions are computed for corresponding smooth velocity profiles, the hyperbolic-tangent shear layer and the Bickley jet, for a uniform background field. A generalisation of the long-wave asymptotic analysis of Drazin & Howard (1962) is employed in order to understand the instability characteristics for both ...
Hierarchical probabilistic inference of cosmic shear
Schneider, Michael D; Marshall, Philip J; Dawson, William A; Meyers, Joshua; Bard, Deborah J; Lang, Dustin
2014-01-01
Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the glo...
Shear Viscosity in a CFL Quark Star
Manuel, C; Llanes-Estrada, F J; Manuel, Cristina; Dobado, Antonio; Llanes-Estrada, Felipe J.
2005-01-01
We compute the shear viscosity in the color-flavor locked (CFL) phase of dense quark matter at low temperature T. Then the contributions of mesons, quarks and gluons to the transport coefficients are Boltzmann suppressed. CFL quark matter displays superfluid properties, and transport phenomena in such cold regime are dominated by phonon-phonon scattering. We study phonons within thermal field theory and compute the mean free path associated to their most relevant collision processes. While the mean free path relevant for shear viscosity usually concerns large-angle collisions, small-angle processes turn out to be more efficient for transport phenomena in the CFL matter. We find the same T-dependence for the phonon damping rate and mean free path as for that of superfluid He4. Our results are relevant for the study of rotational properties of compact stars, and correct wrong estimates existing in the literature.
Impurity in a sheared inelastic Maxwell gas.
Garzó, Vicente; Trizac, Emmanuel
2012-01-01
The Boltzmann equation for inelastic Maxwell models is considered in order to investigate the dynamics of an impurity (or intruder) immersed in a granular gas driven by a uniform shear flow. The analysis is based on an exact solution of the Boltzmann equation for a granular binary mixture. It applies for conditions arbitrarily far from equilibrium (arbitrary values of the shear rate a) and for arbitrary values of the parameters of the mixture (particle masses m(i), mole fractions x(i), and coefficients of restitution ?(ij)). In the tracer limit where the mole fraction of the intruder species vanishes, a nonequilibrium phase transition takes place. We thereby identify ordered phases where the intruder bears a finite contribution to the properties of the mixture, in a region of parameter space that is worked out in detail. These findings extend previous results obtained for ordinary Maxwell gases, and further show that dissipation leads to new ordered phases. PMID:22400560
Brownian forces in sheared granular matter
Baldassarri, A; Petri, A; Zapperi, S; Pontuale, G; Pietronero, L; Baldassarri, Andrea; Dalton, Fergal; Petri, Alberto; Zapperi, Stefano; Pontuale, Giorgio; Pietronero, Luciano
2005-01-01
The response of granular matter to a slow applied shear is erratic and intermittent, the so called "stick-slip" motion. In this state, observable quantities can display power law statistics in common with many other phenomena ranging from solid-on-solid friction to earthquakes, suggesting analogies between such different phenomena. Here we present results from a series of experiments on a granular medium sheared in a Couette geometry and show that their statistical properties can be computed in a quantitative way from the assumption that the resultant from the set of forces acting in the system performs a Brownian motion. The same assumption has been utilised, with success, to describe other phenomena, such as the Barkhausen effect in ferromagnets, and so the scheme suggests itself as a more general description of a wider class of driven instabilities.
Direct measurement of shear properties of microfibers
Energy Technology Data Exchange (ETDEWEB)
Behlow, H.; Saini, D.; Durham, L.; Simpson, J.; Skove, M. J.; Rao, A. M. [Department of Physics and Astronomy, and Clemson Nanomaterials Center, Clemson University, Clemson, South Carolina 29634 (United States); Oliveira, L. [School of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634 (United States); Serkiz, S. M. [Department of Physics and Astronomy, and Clemson Nanomaterials Center, Clemson University, Clemson, South Carolina 29634 (United States); Savannah River National Laboratory, Aiken, South Carolina 29808 (United States)
2014-09-15
As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar{sup ®} 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively.
Undulatory swimming in shear-thinning fluids
Gagnon, David A; Arratia, Paulo E
2014-01-01
The swimming behaviour of microorganisms can be strongly influenced by the rheology of their fluid environment. In this manuscript, we experimentally investigate the effects of shear-thinning viscosity on the swimming behaviour of an undulatory swimmer, the nematode Caenorhabditis elegans. Tracking methods are used to measure the swimmer's kinematic data (including propulsion speed) and velocity fields. We find that shear-thinning viscosity modifies the velocity fields produced by the swimming nematode but does not modify the nematode's speed and beating kinematics. Velocimetry data show significant enhancement in local vorticity and circulation, and an increase in fluid velocity near the nematode's tail, compared to Newtonian fluids of similar effective viscosity. These findings are in good agreement with recent theoretical and numerical results.
Direct measurement of shear properties of microfibers
Behlow, H.; Saini, D.; Oliveira, L.; Durham, L.; Simpson, J.; Serkiz, S. M.; Skove, M. J.; Rao, A. M.
2014-09-01
As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar® 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively.
Fiber optic plantar pressure/shear sensor
Soetanto, William; Nguyen, Ngoc T.; Wang, Wei-Chih
2011-04-01
A full-scale foot pressure/shear sensor that has been developed to help diagnose the cause of ulcer formation in diabetic patients is presented. The design involves a tactile sensor array using intersecting optical fibers embedded in soft elastomer. The basic configuration incorporates a mesh that is comprised of two sets of parallel optical fiber plane; the planes are configured so the parallel rows of fiber of the top and bottom planes are perpendicular to each other. Threedimensional information is determined by measuring the loss of light from each of the waveguide to map the overall pressure distribution and the shifting of the layers relative to each other. In this paper we will present the latest development on the fiber optic plantar pressure/shear sensor which can measure normal force up from 19.09 kPa to 1000 kPa.
Pulsatile Fluid Shear in Bone Remodeling
Frangos, John A.
1997-01-01
The objective of this investigation was to elucidate the sensitivity to transients in fluid shear stress in bone remodeling. Bone remodeling is clearly a function of the local mechanical environment which includes interstitial fluid flow. Traditionally, load-induced remodeling has been associated with low frequency (1-2 Hz) signals attributed to normal locomotion. McLeod and Rubin, however, demonstrated in vivo remodeling events associated with high frequency (15-30 Hz) loading. Likewise, other in vivo studies demonstrated that slowly applied strains did not trigger remodeling events. We therefore hypothesized that the mechanosensitive pathways which control bone maintenance and remodeling are differentially sensitive to varying rates of applied fluid shear stress.
Shear unzipping of double stranded DNA
Prakash, Shikha
2011-01-01
We propose a simple nonlinear scaler displacement model to calculate the distribution of effect created by a shear stress on a double stranded DNA (dsDNA) molecule and the value of shear force $F_c$ which is required to separate the two strands of a molecule. It is shown that as long as the force pulls entire strand in the direction of its application the value of $F_c$ depends linearly on the length; the deviation from linear behaviour takes place when part of a strand moves in opposite direction under the influence of force acting on the other strand. The calculated values of $F_c$ as a function of length of dsDNA molecules are in very good agreement with the experimental values of Hatch et al (Phys. Rev. E $\\bf 78$, 011920 (2008)).
Drop impact of shear thickening liquids
Boyer, Francois; Dijksman, J Frits; Lohse, Detlef
2013-01-01
The impact of drops of concentrated non-Brownian suspensions (cornstarch and polystyrene spheres) onto a solid surface is investigated experimentally. The spreading dynamics and maxi- mal deformation of the droplet of such shear thickening liquids are found to be markedly different from the impact of Newtonian drops. A particularly striking observation is that the maximal de- formation is independent of the drop velocity and that the deformation suddenly stops during the impact phase. Both observations are due to the shear-thickening rheology of the suspensions, as is theoretically explained from a balance between the kinetic energy and the viscously-dissipated en- ergy, from which we establish a scaling relation between drop maximal deformation and rheological parameters of concentrated suspensions.
Shear and rotation in Chaplygin cosmology
Del Popolo, A; Maydanyuk, S P; Lima, J A S; Jesus, J F; 10.1103/PhysRevD.87.043527
2013-01-01
We study the effect of shear and rotation on results previously obtained dealing with the application of the spherical collapse model (SCM) to generalized Chaplygin gas (gCg) dominated universes. The system is composed of baryons and gCg and the collapse is studied for different values of the parameter $\\alpha$ of the gCg. We show that the joint effect of shear and rotation is that of slowing down the collapse with respect to the simple SCM. This result is of utmost importance for the so-called unified dark matter models, since the described slow down in the growth of density perturbation can solve one of the main problems of the quoted models, namely the instability described in previous papers [e.g., H. B. Sandvik {\\it et al.}, Phys. Rev. D {\\bf 69}, 123524 (2004)] at the linear perturbation level.
Turbulent Shear Layers in Supersonic Flow
Smits, Alexander J
2006-01-01
A good understanding of turbulent compressible flows is essential to the design and operation of high-speed vehicles. Such flows occur, for example, in the external flow over the surfaces of supersonic aircraft, and in the internal flow through the engines. Our ability to predict the aerodynamic lift, drag, propulsion and maneuverability of high-speed vehicles is crucially dependent on our knowledge of turbulent shear layers, and our understanding of their behavior in the presence of shock waves and regions of changing pressure. Turbulent Shear Layers in Supersonic Flow provides a comprehensive introduction to the field, and helps provide a basis for future work in this area. Wherever possible we use the available experimental work, and the results from numerical simulations to illustrate and develop a physical understanding of turbulent compressible flows.
A bilateral shear layer between two parallel Couette flows
Narasimhamurthy, Vagesh D; Andersson, Helge I
2012-01-01
We consider a shear layer of a kind not previously studied to our knowledge. Contrary to the classical free shear layer, the width of the shear zone does not vary in the streamwise direction but rather exhibits a lateral variation. Based on some simplifying assumptions, an analytic solution has been derived for the new shear layer. These assumptions have been justified by a comparison with numerical solutions of the full Navier-Stokes equations, which accord with the analytical solution to better than $1\\%$ in the entire domain. An explicit formula is found for the width of the shear zone as a function of wall-normal coordinate. This width is independent of wall velocities in the laminar regime. Preliminary results for a co-current laminar-turbulent shear layer in the same geometry are also presented. Shear-layer instabilities were then developed and resulted in an unsteady mixing zone at the interface between the two co-current streams.
Influence of Reinforced Concrete Shear Wall on Multistorey Buildings
Directory of Open Access Journals (Sweden)
Venkata Sairam Kumar.N
2013-08-01
Full Text Available This work presents the behavior and change in length of shear wall in buildings varied by increasing equal heights from 3.5m to 28m i.e, ground storey (G to G+7 keeping thickness of shear wall as constant of 250mm and observing the dimension of shear wall in length only. The study was carried by considering both wind and seismic forces for all the zones and soil types as per IS: 1893(part I:2002 and wind loads as per IS: 875(part III:1987. A total of 96 buildings were analyzed for this work using RESIST software. Buildings with symmetrical dimensions (20mx20m, varying wall length and keeping wall thickness as constant (250mm the effect of shear wall length, wind drift, wind shear, wind moment, seismic drift, seismic shear, and seismic moment, base moment, base shear are studied and results are presented in graphs with height.
Dynamics of a trapped Brownian particle in shear flows
Holzer, Lukas; Rzehak, Roland; Zimmermann, Walter
2009-01-01
The Brownian motion of a particle in a harmonic potential, which is simultaneously exposed either to a linear shear flow or to a plane Poiseuille flow is investigated. In the shear plane of both flows the probability distribution of the particle becomes anisotropic and the dynamics is changed in a characteristic manner compared to a trapped particle in a quiescent fluid. The particle distribution takes either an elliptical or a parachute shape or a superposition of both depending on the mean particle position in the shear plane. Simultaneously, shear-induced cross-correlations between particle fluctuations along orthogonal directions in the shear plane are found. They are asymmetric in time. In Poiseuille flow thermal particle fluctuations perpendicular to the flow direction in the shear plane induce a shift of the particle's mean position away from the potential minimum. Two complementary methods are suggested to measure shear-induced cross-correlations between particle fluctuations along orthogonal directio...
Magnetic shear. IV - Hale regions 16740, 16815, and 16850
International Nuclear Information System (INIS)
Dopplergrams made in C IV 1548 A are studied for evidence of velocity shear near H-alpha dark filaments and for large-scale flow convergent on active regions. The three regions studied support earlier conclusions that shear is a common property of active regions and that active regions may be the foci of converging plasma flow. Flow patterns near filaments show divergence or convergence as well as shear. Also the sense of the shear can be either cyclonic or anticyclonic. No preference is noted for convergence or divergence or for a particular sense of shear, and there appears to be no correlation between the sense of the shear and the sign of the velocity gradient normal to the filament. The close association of H-alpha dark filaments with shear lines leads to the suggestion that the filaments may arise from a cooling instability induced by the Bernoulli effect. 12 references
Shear sensing based on a microstrip patch antenna
International Nuclear Information System (INIS)
A microstrip patch antenna sensor was studied for shear sensing with a targeted application of measuring plantar shear distribution on a diabetic foot. The antenna shear sensor consists of three components, namely an antenna patch, a soft foam substrate and a slotted ground plane. The resonant frequency of the antenna sensor is sensitive to the overlapping length between the slot in the ground plane and the antenna patch. A shear force applied along the direction of the slot deforms the foam substrate and causes a change in the overlapping length, which can be detected from the antenna frequency shift. The antenna shear sensor was designed based on simulated antenna frequency response and validated by experiments. Experimental results indicated that the antenna sensor exhibits high sensitivity to shear deformation and responds to the applied shear loads with excellent linearity and repeatability. (paper)
Lubricant limiting shear stress effect on EHD film thickness
Gecim, B.; Winer, W. O.
1979-01-01
A Grubin-like EHD inlet analysis utilizing a non-linear viscous fluid model with a limiting shear stress is reported. The shear rheological equation requirs only a low shear stress viscosity and the limiting shear stress both functions of pressure. Values employed for these properties are taken from measurements on typical lubricants. Reductions of EHD film thickness are found to be up to 40 percent compared with the standard Grubin prediction for typical operating conditions. Slide-roll ratio, limiting shear stress dependence on pressure, and atmospheric pressure value of limiting shear stress are new variables required to determine film thickness with the first two being more important than the last. The EHD film thickness is reduced by increasing slide-roll ratio and/or decreasing the pressure dependence of the limiting shear stress.
Quasi phase transition model of shear bands in metallic glasses
International Nuclear Information System (INIS)
A quasi phase transition model of shear bands in metallic glasses (MGs) is presented from the thermodynamic viewpoint. Energy changes during shear banding in a sample-machine system are analyzed following fundamental energy theorems. Three characteristic parameters, i.e. the critical initiation energy ?Gc, the shear band stability index k0, and the critical shear band length lc, are derived to elucidate the initiation and propagation of shear bands. The criteria for good plasticity in MGs with predominant thermodynamic arrest of shear bands are proposed as low ?Gc, large k0, and small lc. The model, combined with experimental results, is used to analyze some controversial phenomena of deformation behavior in MGs, such as the size effect, the effect of testing machine stiffness and the relationship between elastic modulus and plasticity. This study has important implications for a fundamental understanding of shear banding as well as deformation mechanisms in MGs and provides a theoretical basis for improving the ductility of MGs.
Shear-accelerated crystallization in a supercooled atomic liquid
Shao, Zhen; Singer, Jonathan P.; Liu, Yanhui; Liu, Ze; Li, Huiping; Gopinadhan, Manesh; O'Hern, Corey S.; Schroers, Jan; Osuji, Chinedum O.
2015-02-01
A bulk metallic glass forming alloy is subjected to shear flow in its supercooled state by compression of a short rod to produce a flat disk. The resulting material exhibits enhanced crystallization kinetics during isothermal annealing as reflected in the decrease of the crystallization time relative to the nondeformed case. The transition from quiescent to shear-accelerated crystallization is linked to strain accumulated during shear flow above a critical shear rate ??c?0.3 s-1 which corresponds to Péclet number, Pe˜O (1 ) . The observation of shear-accelerated crystallization in an atomic system at modest shear rates is uncommon. It is made possible here by the substantial viscosity of the supercooled liquid which increases strongly with temperature in the approach to the glass transition. We may therefore anticipate the encounter of nontrivial shear-related effects during thermoplastic deformation of similar systems.
Vertical shear in the Jovian equatorial zone.
Layton, R. G.
1971-01-01
Jupiter photographs taken in two different wavelength regions (blue and red) are studied for clues to differing Jovian atmosphere motions. The relative motions of features visible on these photographs may be interpreted as a vertical shear at visible cloud level. The value obtained implies that the north equatorial zone must be about 0.35 deg K warmer than the adjacent equatorial zone. Deeper in the atmosphere the reverse must hold.
Optimisation and control of shear flows
Monokrousos, Antonios
2011-01-01
Transition to turbulence and flow control are studied by means of numerical simulations for different simple shear flows. Linear and non-linear optimisation methods using the Lagrange multiplier technique are employed. In the linear framework as objective function the standard disturbance kinetic energy is chosen and the constraints involve the linearised Navier–Stokes equations. We consider both the optimal initial condition leading to the largest disturbance energy growth at finite times an...
Atomization of Shear Coaxial Liquid Jets
Essam A. Ibrahim; R. Jeremy Kenny; Nathan B. Walker
2010-01-01
The instability and subsequent atomization of a viscous liquid jet emanated into a high-pressure gaseoussurrounding is studied both computationally and experimentally. Liquid water issued into nitrogen gas atelevated pressures is used to simulate the flow conditions in a coaxial shear injector element relevant to liquidpropellant rocket engines. The theoretical analysis is based on a simplified mathematical formulation of thecontinuity and momentum equations in their conservative form. Numeri...
Harmonic Shears and Numerical Conformal Mappings
Quach, Tri
2014-01-01
In this article we introduce a numerical algorithm for finding harmonic mappings by using the shear construction introduced by Clunie and Sheil-Small in 1984. The MATLAB implementation of the algorithm is based on the numerical conformal mapping package, the Schwarz-Christoffel toolbox, by T. Driscoll. Several numerical examples are given. In addition, we discuss briefly the minimal surfaces associated with harmonic mappings and give a numerical example of minimal surfaces.
Shear adhesion strength of aligned electrospun nanofibers.
Najem, Johnny F; Wong, Shing-Chung; Ji, Guang
2014-09-01
Inspiration from nature such as insects' foot hairs motivates scientists to fabricate nanoscale cylindrical solids that allow tens of millions of contact points per unit area with material substrates. In this paper, we present a simple yet robust method for fabricating directionally sensitive shear adhesive laminates. By using aligned electrospun nylon-6, we create dry adhesives, as a succession of our previous work on measuring adhesion energies between two single free-standing electrospun polymer fibers in cross-cylinder geometry, randomly oriented membranes and substrate, and peel forces between aligned fibers and substrate. The synthetic aligned cylindrical solids in this study are electrically insulating and show a maximal Mode II shear adhesion strength of 27 N/cm(2) on a glass slide. This measured value, for the purpose of comparison, is 270% of that reported from gecko feet. The Mode II shear adhesion strength, based on a commonly known "dead-weight" test, is 97-fold greater than the Mode I (normal) adhesion strength of the same. The data indicate a strong shear binding on and easy normal lifting off. Anisotropic adhesion (Mode II/Mode I) is pronounced. The size and surface boundary effects, crystallinity, and bending stiffness of fibers are used to understand these electrospun nanofibers, which vastly differ from otherwise known adhesive technologies. The anisotropic strength distribution is attributed to a decreasing fiber diameter and an optimized laminate thickness, which, in turn, influences the bending stiffness and solid-state "wettability" of points of contact between nanofibers and surface asperities. PMID:25105533
A wall-shear stress predictive model
Energy Technology Data Exchange (ETDEWEB)
Marusic, Ivan; Mathis, Romain; Hutchins, Nicholas, E-mail: imarusic@unimelb.edu.au [Department of Mechanical Engineering, University of Melbourne, Victoria 3010 (Australia)
2011-12-22
Following the approach of Marusic et al. (2010b), here we develop a predictive model for the fluctuating wall-shear stress, where the only required input is large-scale information of the streamwise velocity at a location in the outer, logarithmic region of the flow. The model consists of two components, incorporating a superposition and modulation effect of outer region motions that interact with the flow field in the viscous sublayer. The model is seen to capture Reynolds number trends reliably.
Buoyancy Driven Shear Flows of Bubble Suspensions
Hill, R. J.; Zenit, R.; Chellppannair, T.; Koch, D. L.; Spelt, P. D. M.; Sangani, A.
1998-11-01
In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We > 1 , so that the bubbles are relatively undeformed and the flow is inviscid and approximately irrotational. Nitrogen is introduced through an array of capillaries at the base of a .2x.02x2 m channel filled with an aqueous electrolyte solution (0.06 molL-1 MgSO_4). The rising bubbles generate a unidirectional shear flow, where the denser suspension at the lower surface of the channel falls, while the less dense suspension at the upper surface rises. Hot-film anemometry is used to measure the resulting gas volume fraction and fluid velocity profiles. The bubble collision rate with the sensor is related to the gas volume fraction and the mean and variance of the bubble velocity using an experimentally measured collision surface area for the sensor. Bubble collisions with the sensor are identified by the characteristic slope of the hot-film anemometer signal when bubbles collide with the sensor. It is observed that the steady shear flow develops a bubble phase pressure gradient across the channel gap as the bubbles interchange momentum through direct collisions. The discrete phase presssure gradient balances the buoyancy force driving bubbles toward the upper surface resulting in a steady void fraction profile across the gap width. The strength of the shear flow is controlled by the extent of bubble segregation and by the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion (Kang et al. 1997; Spelt and Sangani, 1998), for a range of gas volume fractions and channel inclination angles.
Structures and shear response of lipid monolayers
International Nuclear Information System (INIS)
This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases
Shear rheological characterization of motor oils
Bair, Scott; Winer, Ward O.
1988-01-01
Measurements of high pressure viscosity, traction coefficient, and EHD film thickness were performed on twelve commercial automotive engine oils, a reference oil, two unformulated base oils and two unformated base oil and polymer blends. An effective high shear rate inlet viscosity was calculated from film thickness and pressure viscosity coefficient. The difference between measured and effective viscosity is a function of the polymer type and concentration. Traction measurements did not discriminate mileage formulated oils from those not so designated.
Nonequilibrium fluctuations of an interface under shear
Thiébaud, Marine; Bickel, Thomas
2009-01-01
The steady state properties of an interface in a stationary Couette flow are addressed within the framework of fluctuating hydrodynamics. Our study reveals that thermal fluctuations are driven out of equilibrium by an effective shear rate that differs from the applied one. In agreement with experiments, we find that the mean square displacement of the interface is strongly reduced by the flow. We also show that nonequilibrium fluctuations present a certain degree of universa...
Shear Stress Sensing using Elastomer Micropillar Arrays
Wohl, Christopher J.; Palmieri, Frank L.; Lin, Yi; Jackson, Allen M.; Cissoto, Alexxandra; Sheplak, Mark; Connell, John W.
2013-01-01
The measurement of shear stress developed as a fluid moves around a solid body is difficult to measure. Stresses at the fluid-solid interface are very small and the nature of the fluid flow is easily disturbed by introducing sensor components to the interface. To address these challenges, an array of direct and indirect techniques have been investigated with various advantages and challenges. Hot wire sensors and other indirect sensors all protrude significantly into the fluid flow. Microelectromechanical systems (MEMS) devices, although facilitating very accurate measurements, are not durable, are prone to contamination, and are difficult to implement into existing model geometries. One promising approach is the use of engineered surfaces that interact with fluid flow in a detectable manner. To this end, standard lithographic techniques have been utilized to generate elastomeric micropillar arrays of various lengths and diameters. Micropillars of controlled length and width were generated in polydimethylsiloxane (PDMS) elastomer using a soft-lithography technique. The 3D mold for micropillar replication was fabricated using laser ablative micromachining and contact lithography. Micropillar dimensions and mechanical properties were characterized and compared to shear sensing requirements. The results of this characterization as well as shear stress detection techniques will be discussed.
Singular eigenfunctions for shearing fluids I
International Nuclear Information System (INIS)
The authors construct singular eigenfunctions corresponding to the continuous spectrum of eigenvalues for shear flow in a channel. These modes are irregular as a result of a singularity in the eigenvalue problem at the critical layer of each mode. They consider flows with monotonic shear, so there is only a single critical layer for each mode. They then solve the initial-value problem to establish that these continuum modes, together with any discrete, growing/decaying pairs of modes, comprise a complete basis. They also view the problem within the framework of Hamiltonian theory. In that context, the singular solutions can be viewed as the kernel of an integral, canonical transformation that allows us to write the fluid system, an infinite-dimensional Hamiltonian system, in action-angle form. This yields an expression for the energy in terms of the continuum modes and provides a means for attaching a characteristic signature (sign) to the energy associate with each eigenfunction. They follow on to consider shear-flow stability within the Hamiltonian framework. Next, the authors show the equivalence of integral superpositions of the singular eigenfunctions with the solution derived with Laplace transform techniques. In the long-time limit, such superpositions have decaying integral averages across the channel, revealing phase mixing or continuum damping. Under some conditions, this decay is exponential and is then the fluid analogue of Landau damping. Finally, the authors discuss the energetics of continuum damping
Turbulent shear control with oscillatory bubble injection
International Nuclear Information System (INIS)
It is known that injecting bubbles into shear flow can reduce the frictional drag. This method has advantages in comparison to others in simplicity of installation and also in environment. The amount of drag reduction by bubbles depends on the void fraction provided in the boundary layer. It means, however, that certain power must be consumed to generate bubbles in water, worsening the total power-saving performance. We propose oscillatory bubble injection technique to improve the performance in this study. In order to prove this idea of new type of drag reduction, velocity vector field and shear stress profile in a horizontal channel flow are measured by ultrasonic velocity profiler (UVP) and shear stress transducer, respectively. We measure the gas-liquid interface from the UVP signal, as well. This compound measurement with different principles leads to deeper understanding of bubble-originated drag reduction phenomena, in particular for unsteady process of boundary layer alternation. At these experiments, the results have demonstrated that the intermittency promotes the drag reduction more than normal continuous injection for the same void fraction supplied.
Behaviour of voids in a shear field
DEFF Research Database (Denmark)
Tvergaard, Viggo
2009-01-01
When voids are present in a ductile material subject to a shear dominated stress state under low stress triaxiality the voids collapse to micro-cracks, which subsequently rotate and elongate in the shear field. In the present plane strain analyses for cylindrical voids a surface load normal to a plane connecting the ends of the micro-crack is used as an approximate representation of contact stresses during frictionless sliding. In a previous study of the same problem the author applied hydrostatic pressure inside the nearly closed micro-crack to approximate contact conditions. The transverse surface loads used in the present analyses avoid the tendency to unrealistically elongate the voids. It is found that even though the model applied here gives significantly later occurrence of a maximum overall shear stress than that found by using hydrostatic pressure, the present model does predict a maximum in all the cases analyzed and thus illustrates the micro-mechanism leading to failure of the material by localization of plastic flow.
Spurious Shear in Weak Lensing with LSST
Chang, C; Jernigan, J G; Peterson, J R; AlSayyad, Y; Ahmad, Z; Bankert, J; Bard, D; Connolly, A; Gibson, R R; Gilmore, K; Grace, E; Hannel, M; Hodge, M A; Jee, M J; Jones, L; Krughoff, S; Lorenz, S; Marshall, P J; Marshall, S; Meert, A; Nagarajan, S; Peng, E; Rasmussen, A P; Shmakova, M; Sylvestre, N; Todd, N; Young, M
2012-01-01
The Large Synoptic Survey Telescope (LSST) is one of the most powerful ground-based weak lensing survey telescopes in the upcoming decade. The complete 10-year survey will image $\\sim$ 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to $r\\sim27.5$, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of \\textit{additive} systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing ana...
Density-shear instability in electron MHD
Wood, Toby S; Lyutikov, Maxim
2014-01-01
We discuss a novel instability in inertia-less electron magneto-hydrodynamics (EMHD), which arises from a combination of electron velocity shear and electron density gradients. The unstable modes have a lengthscale longer than the transverse density scale, and a growth-rate of the order of the inverse Hall timescale. We suggest that this density-shear instability may be of importance in magnetic reconnection regions on scales smaller than the ion skin depth, and in neutron star crusts. We demonstrate that the so-called Hall drift instability, previously argued to be relevant in neutron star crusts, is a resistive tearing instability rather than an instability of the Hall term itself. We argue that the density-shear instability is of greater significance in neutron stars than the tearing instability, because it generally has a faster growth-rate and is less sensitive to geometry and boundary conditions. We prove that, for uniform electron density, EMHD is "at least as stable" as regular, incompressible MHD, in...
Vesicles in a shear and Poiseuille flows
Misbah, Chaouqi
2010-11-01
Vesicles, capsules and Red Blood Cells (RBCs) under flow are subject to considerable attention from theoretical, numerical and experimental point of views. Understanding their motions and dynamics is essential both at the fundamental level as a branch of biocomplex fluids, and at the technological level, such as the lab-on-chip technologies, targeted drug delivery, and blood flow diseases. First, we describe the dynamics of individual biomimetic (vesicles and capsules) and biological entities (RBCs) under a simple shear flow, and overview the current state of the knowledge. Comparison with available experiments will be provided. We then discuss the non-trivial rheology of dilute vesicle suspensions and results from experiments involving oscillatory shear with non-zero mean shear rate. Finally, we address a longstanding puzzle in the blood microcirculatory research: why do red blood cells adopt a non-symmetrical shape (called slipper shape) even in a symmetric flow? Our work shows that the symmetric shape is unstable in flow conditions encountered in microvasculature. Moreover, by adopting a slipper shape, the RBC acquires higher flow efficiency than the symmetric (parachute) shape. The extension of this study to a collection of cells will be outlined.
Electrical conductivity anisotropy in partially molten peridotite under shear deformation
Zhang, Baohua; Yoshino, Takashi; Yamazaki, Daisuke; Manthilake, Geeth; Katsura, Tomoo
2014-11-01
The electrical conductivity of partially molten peridotite was measured during deformation in simple shear at 1 GPa in a DIA type apparatus with a uniaxial deformation facility. To detect development of electrical anisotropy during deformation of partially molten system, the electrical conductivity was measured simultaneously in two directions of three principal axes: parallel and normal to the shear direction on the shear plane, and perpendicular to the shear plane. Impedance spectroscopy measurement was performed at temperatures of 1523 K for Fe-bearing and 1723 K for Fe-free samples, respectively, in a frequency range from 0.1 Hz to 1 MHz. The electrical conductivity of partially molten peridotite parallel to shear direction increased to more than one order of magnitude higher than those normal to shear direction on the shear plane. This conductivity difference is consistent with the magnitude of the conductivity anisotropy observed in the oceanic asthenosphere near the Eastern Pacific Rise. On the other hand, conductivity perpendicular to the shear plane decreased gradually after the initiation of shear and finally achieved a value close to that of olivine. The magnitude and development style of conductivity anisotropy was almost the same for both Fe-bearing and Fe-free melt-bearing systems, and also independent of shear strain. However, such conductivity anisotropy was not developed in melt-free samples during shear deformation, suggesting that the conductivity anisotropy requires a presence of partial melting under shear stress. Microstructural observations of deformed partially molten peridotite samples demonstrated that conductivity anisotropy was attributed to the elongation of melt pockets parallel to the shear direction. Horizontal electrical conductivity anisotropy revealed by magnetotelluric surveys in the oceanic asthenosphere can be well explained by the realignment of partial melt induced by shear stress.
Shear strength of non-shear reinforced concrete elements : Part 3. Prestressed hollow-core slabs
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
The paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions.In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding model developed by Jin-Ping Zhang. The model takes into account the resistance against formation of cracks due to prestressing as well as the variation of the prestressing force in the transfer zone.Due to the fact that the anchorage of the reinforcement takes place by bond, a rotation failure, which is induced by a crack formed at the support with subsequent slip of the reinforcement, is also considered. This failure mode is likely to occur in cases with a high prestressing force combined with a short shear span.The theoretical calculations are compared with test results from the literature. A good agreement has been found.
Modeling combined tension-shear failure of ductile materials
International Nuclear Information System (INIS)
Failure of ductile materials is usually expressed in terms of effective plastic strain. Ductile materials can fail by two different failure modes, shear failure and tensile failure. Under dynamic loading shear failure has to do with shear localization and formation of adiabatic shear bands. In these bands plastic strain rate is very high, dissipative heating is extensive, and shear strength is lost. Shear localization starts at a certain value of effective plastic strain, when thermal softening overcomes strain hardening. Shear failure is therefore represented in terms of effective plastic strain. On the other hand, tensile failure comes about by void growth under tension. For voids in a tension field there is a threshold state of the remote field for which voids grow spontaneously (cavitation), and the material there fails. Cavitation depends on the remote field stress components and on the flow stress. In this way failure in tension is related to shear strength and to failure in shear. Here we first evaluate the cavitation threshold for different remote field situations, using 2D numerical simulations with a hydro code. We then use the results to compute examples of rate dependent tension-shear failure of a ductile material.
Evolution of thermal ion transport barriers in reversed shear/optimised shear plasmas
International Nuclear Information System (INIS)
The effects of the magnetic and ExB rotation shears on the thermal ion transport in advanced tokamak scenarios are analyzed through the predictive modelling of the evolution of internal transport barriers. Such a modelling is performed with an experimentally validated L-mode thermal diffusivity completed with a semi-empirical shear correction which is based on simple theoretical arguments from turbulence studies. A multi-machine test of the model on relevant discharges from the ITER Data Base (TFTR, DIII-D and JET) is presented. (author)
Shear Wave Seismic Interferometry for Lithospheric Imaging
Frank, J.; Ruigrok, E. N.; Wapenaar, C. A.
2013-05-01
Green's function retrieval by seismic interferometry (SI) exists in a variety of forms. A common theme uniting many of the approaches of SI centers on the ability to create new seismic traces by cross correlating a received signal recorded at two separate locations. The sum of this operation for multiple sources results in the creation of a new signal such that one of the recording locations acts as a virtual source to the other. This presentation focuses on the use of teleseismic earthquake events to create a virtual shear wave source for imaging lithospheric features. Events are selected at long offsets for primarily two reasons: namely, (a) at large offsets the incoming wavefront approximates a plane wave due to spread of the wavefront in relation to the comparatively finite seismic array, and (b) the large distances act as a natural temporal filter to separate the incident P and S arrivals. Furthermore, using shear wave energy as an imaging source benefits from a variety of properties including a lower propagation velocity and the possibility for separate treatment of the shear vertical and shear horizontal fields. Prior to selecting a field dataset, a series of 1D earth forward modeling experiments with 2D elastic propagation were conducted. Initial modeling results indicate that SP converted energy maps primarily to the vertical component with little presence on the radial component. This suggests that decomposition techniques may be unnecessary as preprocessing for field data, but remains an option should field data dictate its use. Sufficient illumination by unique ray parameter sampling is essential for clearly resolving subsurface features through SI; however, initial decimation studies indicate that while clarity is reduced proportional to reduction of available ray parameters, it is still possible to identify strong reflectors even with relatively poor sampling. A challenge encountered by using earthquake events as an imaging source is the complexity of the source time function (STF). The heterogeneous subsurface near the source locations gives rise to complications of the incident field that need to be mitigated for successful SI application. The frequency and phase spectrum of such events is influenced by the event depth, ghost reflections, near surface complexity, earth's intrinsic attenuation of high frequency content, and travel distance. Numerical experiments indicate that correcting the received signal via whitening, or deconvolution, and bandpass filtering will be required to limit the impact of the STF on data quality. Finally, a field dataset is selected from southern Mexico with over 100 earthquake events that meet our criteria for magnitude and location. By azimuthally limiting a window around the relatively linear orientation of the seismometer array, earthquakes that vary in offset correspond to sampling of unique ray parameters. In earthquakes with sufficient shear energy, the S, SS, ScS, and SKS phases can be treated as separate events with individual ray parameters. Both of these techniques help to improve the overall illumination of the subsurface with better sampling. By using shear wave SI as a preprocessing technique, we hope to produce an image of the unique subduction setting beneath the seismometer array that offers new interpretable value to the region.
Transport Bifurcation Induced by Sheared Toroidal Flow in Tokamak Plasmas
Highcock, E G; Parra, F I; Schekochihin, A A; Roach, C M; Cowley, S C
2011-01-01
First-principles numerical simulations are used to describe a transport bifurcation in a differentially rotating tokamak plasma. Such a bifurcation is more probable in a region of zero magnetic shear, where the component of the sheared toroidal flow that is perpendicular to the magnetic field has the strongest suppressing effect on the turbulence, than one of finite magnetic shear. Where the magnetic shear is zero, there are no growing linear eigenmodes at any finite value of flow shear. However, subcritical turbulence can be sustained, owing to the transient growth of modes driven by the ion temperature gradient (ITG) and the parallel velocity gradient (PVG). Nonetheless, in a parameter space containing a wide range of temperature gradients and velocity shears, there is a sizeable window where all turbulence is suppressed. Combined with the relatively low transport of momentum by collisional (neoclassical) mechanisms, this produces the conditions for a bifurcation from low to high temperature and velocity gr...
Shear Strengthening of Reinforced Concrete Beams Using GFRP Wraps
Directory of Open Access Journals (Sweden)
M. A. A. Saafan
2006-01-01
Full Text Available The objective of the experimental work described in this paper was to investigate the efficiency of GFRP composites in strengthening simply supported reinforced concrete beams designed with insufficient shear capacity. Using the hand lay-up technique, successive layers of a woven fiberglass fabric were bonded along the shear span to increase the shear capacity and to avoid catastrophic premature failure modes. The strengthened beams were fabricated with no web reinforcement to explore the efficiency of the proposed strengthening technique using the results of control beams with closed stirrups as a web reinforcement. The test results of 18 beams are reported, addressing the influence of different shear strengthening schemes and variable longitudinal reinforcement ratios on the structural behavior. The results indicated that significant increases in the shear strength and improvements in the overall structural behavior of beams with insufficient shear capacity could be achieved by proper application of GFRP wraps.
Predictions of turbulent mixing in axisymmetric compressible shear layers
Viswanathan, K.; Morris, P. J.
1992-06-01
Models are described for the turbulent mixing of compressible, axisymmetric shear layers. The models assume that the mixing process is dominated by large-scale coherent structures. These large-scale structures are described locally as linear instability waves. Calculations are made for the development of the axisymmetric shear layer as a function of free stream Mach numbers and velocity and density ratios. The predictions for the axisymmetric shear layer are compared with both experimental measurements and predictions for a plane shear layer. The effects of the initial thickness of the shear layer and the initial amplitudes of the large-scale structures on the growth of the shear layer are examined. The effect of the description of the mean velocity profile is considered.
Assessment of susceptibility of rape stems to shearing
Directory of Open Access Journals (Sweden)
Vielikanov L.
2000-12-01
Full Text Available In the present study, the authors used a dynamic shearing and densitometric method for the asses- sment of susceptibility of stems of winter rape, vars Mar, Bolko, Leo, Ceres and Libravo to shearing. They determi- ned dynamic shearing energy per a unit of the stem cross section area, in the natural state as well as after the removed of parenchyma, density and DOD parameter, indicating the amount of X-ray energy absorbed by the stems. It was found that susceptibility of rape stems to shearing depends on their structure. A strict correlation was shown to exist between the dynamic shearing energy and the amount of X-ray radiation energy absorbed by the stem. Moreover, in study showed that the application of the X-ray method greatly enhanced the possibility to determine of the suscep- tibility of rape stems to shearing.
dc-Magnetic-field generation in unmagnetized shear flows.
Grismayer, T; Alves, E P; Fonseca, R A; Silva, L O
2013-07-01
The generation of dc magnetic fields in unmagnetized electron-ion shear flows is shown to be associated to either initial thermal effects or the onset of electron-scale shear instabilities, in particular the cold Kelvin-Helmholtz instability. This mechanism, intrinsic to shear gradients on the electron scale, is described through a kinetic model that predicts the growth and the saturation of the dc field in both scenarios. The theoretical results are confirmed by multidimensional particle-in-cell simulations, demonstrating the formation of long-lived magnetic fields (t~100's ?(pi)(-1)) along the full longitudinal extent of the shear layer, with a typical transverse width of ?[?(0)]c/?(pe), reaching magnitudes eB(dc)/m(e)c?(pe)~?(0)?[?(0)] for an initial sharp shear. The case of an initial smooth shear is also discussed. PMID:23863009
Discontinuous shear thickening of frictional hard-sphere suspensions
Seto, Ryohei; Morris, Jeffrey F; Denn, Morton M
2013-01-01
Discontinuous Shear Thickening (DST) observed in many dense athermal suspensions has proven difficult to understand and to reproduce numerically. By introducing a numerical scheme including both relevant hydrodynamic interactions and granular-like contacts, we show that contact friction is essential for having DST. Above a critical volume fraction, we observe the existence of two states: a low viscosity, contactless (hence frictionless) state, and a high viscosity frictional shear jammed state. These two states are separated by a critical shear stress, associated with a critical shear rate where DST occurs. The shear jammed state is reminiscent of the jamming phase of granular matter. Continuous Shear Thickening is seen as a lower volume fraction vestige of the jamming transition.
Shear-induced displacement of isotropic-nematic spinodals
Lenstra, T. A. J.; Dogic, Z.; Dhont, J. K. G.
2001-06-01
The shear dependent location of the isotropic-nematic spinodals in suspensions of bacteriophage fd is studied by means of time resolved birefringence experiments. The hysteresis in the birefringence on increasing and subsequently decreasing the shear-rate allows the determination of the location of points in the shear-rate vs concentration phase diagram between the isotropic-to-nematic and the nematic-to-isotropic spinodals. Experimental hysteresis curves are interpreted on the basis of an equation of motion for the orientational order parameter tensor, as derived from the N-particle Smoluchowski equation. The spinodals are found to shift to lower concentrations on increasing the shear-rate. Above a critical shear-rate, where shear forces dominate over thermodynamic forces, no spinodal instability could be detected.
Investigation into ferrofluid magnetoviscous effects under an oscillating shear flow
Energy Technology Data Exchange (ETDEWEB)
Pinho, M., E-mail: marcos.pinho.etu@univ-lemans.fr [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France); Brouard, B.; Genevaux, J.M. [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France); Dauchez, N. [LISMMA - Institut Superieur de Mecanique de Paris (SUPMECA), 93407 Saint Ouen (France); Volkova, O. [Centre de micro et nanorheometrie, Universite de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice-cedex2 (France); Meziere, H.; Collas, P. [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France)
2011-10-15
The use of ferrofluid seals in mechanical systems can lead to viscous damping that affects their dynamic behavior. This paper describes an investigation into local viscous properties in the case of an axial harmonic force. The influence of magnetic field level, shear stress amplitude and frequency are studied. Even for ferrofluid particles in a highly saturated magnetic field, it is shown that viscosity increases with magnetic intensity, decreases with the frequency of harmonic excitation and is not sensitive to shear rate amplitude. Viscosity is lower for oscillatory flows than for steady flows. - Highlights: > Extension of the magnetoviscous effect of ferrofluids to the oscillatory shear flow. > Influence of magnetic field level, shear stress amplitude and frequency is studied. > Ferrofluid viscosity is lower for oscillatory than for steady flow shearing. > Ferrofluid viscosity is not sensitive to shear rate amplitude. > Negative-viscosity effect occurs even for a null magnetic field.
Hysteresis and Lubrication in Shear Thickening of Cornstarch Suspensions
Chu, Clarence E; Sieber, Hannah L; Miller, James G; Okamoto, Ruth J; Katz, Jonathan I
2014-01-01
Aqueous and brine suspensions of corn starch show striking discontinuous shear thickening. We have found that a suspension shear-thickened throughout may remain in the jammed thickened state as the strain rate is reduced, but an unjamming front may propagate from any unjammed regions. Transient shear thickening is observed at strain rates below the thickening threshold, and above it the stress fluctuates. The jammed shear-thickened state may persist to low strain rates, with stresses resembling sliding friction and effective viscosity inversely proportional to the strain rate. At the thickening threshold fluid pressure depins the suspension's contact lines on solid boundaries so that it slides, shears, dilates and jams. In oil suspensions lubrication and complete wetting of confining surfaces eliminate contact line forces and prevent jamming and shear thickening, as does addition of immiscible liquid surfactant to brine suspensions. Starch suspensions in glycerin-water solutions, viscous but incompletely wett...
Flexure of thick orthotropic plates by exponential shear deformation theory
Scientific Electronic Library Online (English)
A. S., Sayyad.
2013-05-01
Full Text Available In the present paper, a variationally consistent exponential shear deformation theory taking into account transverse shear deformation effect is presented for the flexural analysis of thick orthotropic plates. The inplane displacement field uses exponential function in terms of thickness coordinate [...] to include the shear deformation effect. The transverse shear stress can be obtained directly from the constitutive relations satisfying the shear stress free surface conditions on the top and bottom surfaces of the plate, hence the theory does not require shear correction factor. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. Results obtained for static flexure of simply supported orthotropic plates are compared with those of other refined theories and elasticity solution wherever applicable. The results obtained by present theory are in excellent agreement with those of exact results and other higher order theories. Thus the efficacy of the present refined theory is established.
Propagation of waves in shear flows
Fabrikant, A L
1998-01-01
The state of the art in a theory of oscillatory and wave phenomena in hydrodynamical flows is presented in this book. A unified approach is used for waves of different physical origins. A characteristic feature of this approach is that hydrodynamical phenomena are considered in terms of physics; that is, the complement of the conventionally employed formal mathematical approach. Some physical concepts such as wave energy and momentum in a moving fluid are analysed, taking into account induced mean flow. The physical mechanisms responsible for hydrodynamic instability of shear flows are conside
A Simple Model for Sheared Granular Layers
Furukawa, A; Furukawa, Akira; Hayakawa, Hisao
2004-01-01
We phenomenologically investigate stick-slip motion of sheared granular layers. Our phenomenology is constructed in the context of nucleation-and-growth of the fluidized area which is triggered by collapsing of stress chains. Based on this picture, we give a simple friction model by introducing the degree of the fluidization. It is found that the present model can successfully reproduce major features of the experimental results reported by Nasuno {\\it et al.} (Phys. Rev. E {\\bf 58}, 2161 (1998)) with quantitatively good agreement.
The rheology of chain molecules under shear
Moore, Jonathan David
The rheology of chain molecules is a subject that comprises a wide variety of complex physical phenomena, challenging scientific questions, and fundamentally important practical applications. In this work, nonequilibrium molecular dynamics (NEMD) is employed to study linear and branched alkane chains in the melt state under transient and steady-state shearing conditions. This study focuses on three isomers of C30H62 (n- triacontane, squalane, and 9-n- octyldocosane) as well as a linear short-chain polyethylene (C100H202). A transferable united atom potential is used to model these alkane chains, and the simulations of planar Couette flow are performed using the SLLOD algorithm and a multi- timestep, simulation technique. The strain rates studied in this work (108-10 12 s-1) are extremely difficult to study experimentally yet typical of the severe conditions commonly found in engines and other machinery. NEMD and the united atom model underpredict the kinematic viscosities of n-triacontane and 9- n-octyldocosane but accurately predict the values for squalane (within 15%) at temperatures of 311 and 372 K. The predicted kinematic viscosity index values for both 9- n-octyldocosane and squalane are in quantitative agreement with experiment and represent the first such predictions by molecular simulation. Thus, this same general potential model and computational approach can be used to predict this important lubricant property for potential lubricants prior to their synthesis, offering the possibility of simulation-guided lubricant design. Simulations of C100H202 under steady-state shearing conditions reveal a pronounced minimum in the hydrostatic pressure at an intermediate strain rate that is associated with a minimum in the intermolecular potential energy as well as transitions in the strain-rate-dependent behavior of several other viscous and structural properties of the system. Upon onset of shear, the stress overshoot curves calculated for C100 are in good quantitative agreement with Doi-Edwards theory if the terminal relaxation time is assumed to have the same strain-rate dependence as the calculated self-diffusion coefficient in the flow direction. This shear-enhanced diffusion offers a possible mechanism for strain-rate-dependent relaxation times in the fast flows of polymers.
Nonequilibrium fluctuations of an interface under shear
Thiébaud, Marine; Bickel, Thomas
2010-03-01
The steady-state properties of an interface in a stationary Couette flow are addressed within the framework of fluctuating hydrodynamics. Our study reveals that thermal fluctuations are driven out of equilibrium by an effective shear rate that differs from the applied one. In agreement with experiments, we find that the mean-square displacement of the interface is reduced by the flow. We also show that nonequilibrium fluctuations present a certain degree of universality in the sense that all features of the fluids can be factorized into a single control parameter. Finally, the results are discussed in the light of recent experimental and numerical studies.
Waves in Turbulent Stably Stratified Shear Flow
Jacobitz, F. G.; Rogers, M. M.; Ferziger, J. H.; Parks, John W. (Technical Monitor)
2002-01-01
Two approaches for the identification of internal gravity waves in sheared and unsheared homogeneous stratified turbulence are investigated. First, the phase angle between the vertical velocity and density fluctuations is considered. It was found, however, that a continuous distribution of the phase angle is present in weakly and strongly stratified flow. Second, a projection onto the solution of the linearized inviscid equations of motion of unsheared stratified flow is investigated. It was found that a solution of the fully nonlinear viscous Navier-Stokes equations can be represented by the linearized inviscid solution. The projection yields a decomposition into vertical wave modes and horizontal vortical modes.
Powder fed sheared dispersal particle generator
Morrisette, E. L.; Bushnell, D. M. (inventors)
1984-01-01
A particle generating system is described which is capable of breaking up agglomerations of particles and producing a cloud of uniform, submicron-sized particles at high pressure and high flow rates. This is achieved by utilizing a tubular structure which has injection microslits on is periphery to accept and disperse the desired particle feed. By suppling a carrying fluid at a pressure, of approximately twice the ambient pressure of the velocimeter's settling chamber, the microslits operate at choked flow conditions. The shearing action of this choked flow is sufficient to overcome interparticle bonding forces, thereby breaking up the agglomerates of the particles feed into individual particles.
A shear localization mechanism for lubricity of amorphous carbon materials
Tian-Bao Ma; Lin-Feng Wang; Yuan-Zhong Hu; Xin Li; Hui (Wendy) Wang
2014-01-01
Amorphous carbon is one of the most lubricious materials known, but the mechanism is not well understood. It is counterintuitive that such a strong covalent solid could exhibit exceptional lubricity. A prevailing view is that lubricity of amorphous carbon results from chemical passivation of dangling bonds on surfaces. Here we show instead that lubricity arises from shear induced strain localization, which, instead of homogeneous deformation, dominates the shearing process. Shear localization...
Rheological properties for inelastic Maxwell mixtures under shear flow
Garzo, Vicente; Trizac, Emmanuel
2009-01-01
The Boltzmann equation for inelastic Maxwell models is considered to determine the rheological properties in a granular binary mixture in the simple shear flow state. The transport coefficients (shear viscosity and viscometric functions) are {\\em exactly} evaluated in terms of the coefficients of restitution, the (reduced) shear rate and the parameters of the mixture (particle masses, diameters and concentration). The results show that in general, for a given value of the co...
A Virtual Reality Simulation System for Flying Shears
Fuwen Hu; Jiajun Li
2013-01-01
Flying shears in rolling lines are used to cut rolled products into predefined lengths. A virtual reality simulation system was developed for two typical flying shears: rotary-crank type and rotary-drum type. Its main function modules consist of motion simulation, parameters calculation and a 3D visual knowledge base for the design and utilization of flying shears. Firstly, the development process of the virtual reality simulation system was put forward. Then the implementations of core funct...
Tension, compression and shear fatigue of a closed cell foam
Zenkert, Dan; Burman, Magnus
2007-01-01
A closed cell foam of Polymetacrylimide (Rohacell) with three different densities is studied. The foam is tested quasistatically in tension, compression and shear. The tensile properties scale very well with the relative density of the foam, but the compression and shear properties do not. It is believed to be due to cell edge and cell wall buckling being the dominated deformation mechanism in compression and shear for lower densities that does not occur for higher densities. Fatigue testing ...
Field-induced Energy Gaps in Bilayer Graphene under Shear
Choi, Seon-Myeong; Son, Young-Woo
2013-03-01
Using the first-principles calculations method, we study the effects of shear on field-induced insulating states of bilayer graphene (BLG). It is shown that the low energy bands near the charge neutral point of BLG change significantly upon application of shear. We also find that the energy gap of BLG under transverse electric field sensitively depend on both direction and amount of shear. Generally, the field-induced energy gap decreases as the sliding increases under shear. For BLG with the specific direction of shear, the shear can quench the energy gap to zero completely even in the presence of electric field thus realizing insulator-to-metal transition just by sliding. We discuss origins of these interesting phenomena and suggest some experimental methods to detect the transition. Using the first-principles calculations method, we study the effects of shear on field-induced insulating states of bilayer graphene (BLG). It is shown that the low energy bands near the charge neutral point of BLG change significantly upon application of shear. We also find that the energy gap of BLG under transverse electric field sensitively depend on both direction and amount of shear. Generally, the field-induced energy gap decreases as the sliding increases under shear. For BLG with the specific direction of shear, the shear can quench the energy gap to zero completely even in the presence of electric field thus realizing insulator-to-metal transition just by sliding. We discuss origins of these interesting phenomena and suggest some experimental methods to detect the transition. Computational resources have been provided by KISTI Supercomputing Center (Project No. KSC-2011-C1-21) and the CAS of KIAS.
The DES Science Verification Weak Lensing Shear Catalogs
Jarvis, M.(Imperial College, London, UK); Sheldon, E.; Zuntz, J; Kacprzak, T.; Bridle, S. L.; Amara, A; Armstrong, R.; Becker, M. R.; Bernstein, G M; Bonnett, C.; Chang, C; Das, R.; Dietrich, J. P.; Drlica-Wagner, A.; Eifler, T. F.
2015-01-01
We present weak lensing shear catalogs for 139 square degrees of data taken during the Science Verification (SV) time for the new Dark Energy Camera (DECam) being used for the Dark Energy Survey (DES). We describe our object selection, point spread function estimation and shear measurement procedures using two independent shear pipelines, IM3SHAPE and NGMIX, which produce catalogs of 2.12 million and 3.44 million galaxies respectively. We detail a set of null tests for the s...
Bulk and shear viscosities of hot and dense hadron gas
Kadam, Guru Prakash; Mishra, Hiranmaya
2014-01-01
We estimate bulk and shear viscosity at finite temperature and baryon densities of hadronic matter within hadron resonance gas model. For bulk viscosity we use low energy theorems of QCD for the energy momentum tensor correlators. For shear viscosity coefficient, we estimate the same using molecular kinetic theory to relate the shear viscosity coefficient to average momentum of the hadrons in the hot and dense hadron gas. The bulk viscosity to entropy ratio increases with ch...
Shear crack formation and propagation in reinforced Engineered Cementitious Composites
Paegle, Ieva; Fischer, Gregor
2012-01-01
This paper describes an experimental investigation of the shear behaviour of beams consisting of steel reinforced Engineered Cementitious Composites (R/ECC). Based on the strain hardening and multiple cracking behaviour of ECC, this study investigates the extent to which ECC influences the shear capacity of beams loaded primarily in shear. The experimental program consists of ECC with short randomly distributed polyvinyl alcohol (PVA) fiber beams with different stirrup arrangements and conven...
Low-n shear Alfven spectra in axisymmetric toroidal plasmas
International Nuclear Information System (INIS)
In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfven continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed. 17 refs., 4 figs
Shear Rate Moderates Community Diversity in Freshwater Biofilms
Rickard, Alexander H.; McBain, Andrew J.; Stead, Amy T.; Gilbert, Peter
2004-01-01
The development of freshwater multispecies biofilms at solid-liquid interfaces occurs both in quiescent waters and under conditions of high shear rates. However, the influence of hydrodynamic shear rates on bacterial biofilm diversity is poorly understood. We hypothesized that different shear rates would significantly influence biofilm diversity and alter the relative proportions of coaggregating and autoaggregating community isolates. In order to study this hypothesis, freshwater biofilms we...
Shear band dynamics from a mesoscopic modeling of plasticity
Jagla, E. A.
2010-01-01
The ubiquitous appearance of regions of localized deformation (shear bands) in different kinds of disordered materials under shear is studied in the context of a mesoscopic model of plasticity. The model may or may not include relaxational (aging) effects. In the absence of relaxational effects the model displays a monotonously increasing dependence of stress on strain-rate, and stationary shear bands do not occur. However, in start up experiments transient (although long li...
Shear strength measurements of lubricants at high pressure
Bair, S.; Winer, W. O.
1979-01-01
Measurements of lubricant shear rheological behavior in the amorphous solid region and near the liquid-solid transition are reported on three lubricants under pressure. Elastic, plastic and viscous behavior was observed. The maximum yield shear stress (limiting shear stress) is a function of temperature and pressure and is believed to be the property which determines the maximum traction in elastohydrodynamic contacts such as traction drives.
Structure formation of surfactant membranes under shear flow
Shiba, Hayato; Noguchi, Hiroshi; Gompper, Gerhard
2013-01-01
Shear-flow-induced structure formation in surfactant-water mixtures is investigated numerically using a meshless-membrane model in combination with a particle-based hydrodynamics simulation approach for the solvent. At low shear rates, uni-lamellar vesicles and planar lamellae structures are formed at small and large membrane volume fractions, respectively. At high shear rates, lamellar states exhibit an undulation instability, leading to rolled or cylindrical membrane shape...
Shear zones between rock units with no relative movement
DEFF Research Database (Denmark)
Koyi, Hemin; Schmeling, Harro
2013-01-01
Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two "blocks" that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other. Such deformation zones, which we call wakes, form due to the movement of exotic blocks within a viscous medium (denser blocks sinking within a salt structure, (the paths) between separated boudins), melt in partially molten surroundings (melt movement during migmatisation), or solid blocks sinking through a partially molten magma body (stoping). From the fluid dynamics perspective these shear zones can be regarded as low Reynolds number deformation zones within the wake of a body moving through a viscous medium. While compact moving bodies (aspect ratio 1:1:1) generate axial symmetric (cone like) shear zones or wakes, elongated bodies (vertical plates or horizontal rod-like bodies) produce tabular shear zones or wakes. Unlike conventional shear zones across which shear indicators usually display consistent symmetries, shear indicators on either side of the shear zone or wake reported here show reverse kinematics. Thus profiles exhibit shear zones with opposed senses of movement across their center-lines or -planes.We have used field observations and results from analytical and numerical models to suggest that examples of wakes are the transit paths that develop where denser blocks sink within salt structures, bodies of melt rise through migmatites, between boudins separated by progressive extension and (perhaps) where slabs of subducted oceanic lithosphere delaminate from the continental crust and sink into the asthenosphere. We also argue that such shear zones may be more common than they have been given credit for and may be responsible for some reverse kinematics reported in shear zones.
Polarized Shear Waves for Crack Detection and Characterization
Turner, S. J.; Maxfield, B. W.
2010-02-01
This paper describes a new approach to the detection and sizing of cracks in metals. It uses a newly developed technique based on interrogating materials with shear waves having varying polarization direction generated by a specially designed EMAT where the polarization direction is established by a combination of coil design and system software and hardware parameters. The reflected/scattered shear wave resulting from each incident shear wave is received and detected with respect to the excitation pulse parameters.
Rheology of concentrated suspensions and shear-induced migration
Dbouk, Talib
2011-01-01
This thesis deals with an experimental and numerical investigation of the phenomenon of shear-induced particle migration in inhomogeneous shear flows of mono-dispersed non-colloidal suspensions at neglected inertia. Variety of diffusion flux models that predict the shear-induced migration were presented. However, in this work, the Suspension Balance Model (SBM) is adopted. The latter describes the migration flux of particles as the divergence of the particle Stress tensor. According to the ne...
Anisotropy of force distributions in sheared soft particle systems
Boberski, Jens; Shaebani, M. Reza; Wolf, Dietrich E.
2014-01-01
In this numerical study, measurements of the contact forces inside a periodic two-dimensional sheared system of soft frictional particles are reported. The distribution of normalized normal forces exhibits a gradual broadening with increasing the pure shear deformation, leading to a slower decay for large forces. The process however slows down and the distribution approaches an invariant shape at high shear deformations. By introducing the joint probability distribution in s...
Shear-induced assembly of lambda-phage DNA.
Haber, C.; Wirtz, D
2000-01-01
Recombinant DNA technology, which is based on the assembly of DNA fragments, forms the backbone of biological and biomedical research. Here we demonstrate that a uniform shear flow can induce and control the assembly of lambda-phage DNA molecules: increasing shear rates form integral DNA multimers of increasing molecular weight. Spontaneous assembly and grouping of end-blunted lambda-phage DNA molecules are negligible. It is suggested that shear-induced DNA assembly is caused by increasing th...
Scientific Electronic Library Online (English)
Rodrigo, Cruz; Elizabeth, Barthel; Jaime, Espinoza.
2013-06-01
Full Text Available Curvularia inaequalis (Shear) Boedijn es un hongo dematiáceo, saprófito y fitopatógeno, presente principalmente en áreas tropicales y subtropicales, asociado a distintos sustratos orgánicos. Se ha identificado escasamente en infecciones sistémicas, cutáneas y sólo existe una comunicación de un caso [...] de rinosinusitis alérgica descrito anteriormente. Presentamos el caso clínico de un paciente con una rinosinusitis alérgica fúngica por Curvularia inaequalis (Shear) Boedijn en cuyo diagnóstico se consideró los síntomas y signos clínicos, la TAC de senos paranasales y el cultivo de la mucina. El paciente fue tratado con un aseo quirúrgico por vía endoscópica, además del uso de corticoesteroides inhalatorios e itra-conazol sistémico. Presentó una buena respuesta clínica, encontrándose asintomático a un año del tratamiento. Abstract in english Curvularia inaequalis (Shear) Boedijn is a fungus dematiaceo, saprophyte and plant pathogen found mainly in tropical and subtropical areas, associated with various organic substrates. Rarely been identified in systemic infections, skin and there is only one report of allergic rhinosinusitis describe [...] d above. A case of allergic fungal rhinosinusitis by Curvularia inaequalis (Shear) Boedijn in which diagnosis was considered the signs and symptoms, sinus CT and cultivation of mucin.The patient was treated with endoscopic surgical toilet, plus use of inhaled steroids and itraconazole systemic. With good clinical response, is asymptomatic at one year.
Turbulent bands in a planar shear flow without walls
Chantry, Matthew; Barkley, Dwight
2015-01-01
Turbulent bands are a ubiquitous feature of transition in wall-bounded shear flows. We show that these are also a robust feature of Waleffe flow -- a shear flow driven by a sinusoidal body force between stress-free boundaries -- thus demonstrating that rigid walls are not a prerequisite for band formation. Exploiting the Fourier dependence of Waleffe forcing, we construct a model flow that uses only four wavenumbers in the shear direction and yet captures uniform turbulence, turbulent bands, and spot expansion. The model is simultaneously a reduction of the full Navier-Stokes equations and an extension of minimal models of the self-sustaining process of shear turbulence.
Interface shear and pressure characteristics of wheelchair seat cushions
Directory of Open Access Journals (Sweden)
Jonathan S. Akins
2011-03-01
Full Text Available Pressure ulcer incidence rates have remained constant despite advances in support surface technology. Interface shear stress is recognized as a risk factor for pressure ulcer development and is the focus of many shear reduction technologies incorporated into wheelchair cushions; however, shear reduction has not been quantified in the literature. We evaluated 21 commercial wheelchair seat cushions using a new methodology developed to quantify interface shear stress, interface pressure, and horizontal stiffness. Interface shear stress increased significantly with applied horizontal indenter displacement, while no significant difference was found for interface pressure. Material of construction resulted in significant differences in interface shear stress, interface pressure, and horizontal stiffness. This study shows that the existing International Organization for Standardization (ISO 16840-2 horizontal stiffness measure provides similar information to the new horizontal stiffness measure. The lack of a relationship between interface shear stress and the overall horizontal stiffness measure, however, suggests that a pressure and shear force sensor should be used with the ISO 16840-2 horizontal stiffness measure to fully quantify a cushion's ability to reduce interface shear stress at the patient's bony prominences.
Compressive and shear properties of commercially available polyurethane foams.
Thompson, MS; McCarthy, ID; Lidgren, L.; Ryd, L
2003-01-01
BACKGROUND: The shear properties of rigid polyurethane (PU-R) foams, routinely used to simulate cancellous bone, are not well characterized. METHOD OF APPROACH: The present assessment of the shear and compressive properties of four grades of Sawbones "Rigid cellular" PU-R foam tested 20 mm gauge diameter dumb-bell specimens in torsion and under axial loading. RESULTS: Shear moduli ranged from 13.3 to 99.7 MPa, shear strengths from 0.7 MPa to 4.2 MPa. Compressive yield strains varied little wi...
Seeking shear waves in liquids with picosecond ultrasonics
International Nuclear Information System (INIS)
Picosecond shear acoustic pulses can be generated in solids using ultrashort optical pulses. Here we use this technique to seek high frequency shear waves in water, ethylene glycol and glycerol while simultaneously measuring high frequency longitudinal wave velocity and attenuation. We use a silica thin film on (114) GaAs to generate shear and longitudinal acoustic pulses at frequencies up to ?50 GHz by ultrashort pulsed optical excitation. The acoustic pulses are transmitted into adjacent liquids, and are detected through variations in the optical reflectivity. Although we could not detect shear waves in these liquids, we did detect gigahertz longitudinal elastic stiffening
Pair distribution function of a sheared colloidal suspension
Szamel, Grzegorz
2000-03-01
We propose a simple theory for the pair distribution function of a sheared colloidal suspension. The starting point is an exact equation for the stationary state pair distribution. We assume that in a shear flow the higher order distributions can be expressed through the pair distribution in the same way as in a non-uniform equilibrium state. Finally, to get explicit results we use a simple decoupling approximation for the higher order equilibrium correlations. For low shear rates predictions of our theory agree with those of more complicated approaches. Its simplicity makes it a promising starting point for an investigation of high shear rate effects.
Shear-induced structures in concentrated surfactant micellar phases
International Nuclear Information System (INIS)
Constant and oscillatory Couette shear flow have been used in combination with small-angle neutron scattering to observe the shear-induced ordering in concentrated surfactant micellar phases. For the lamellar phase of hexaethylene glycol monohexadecyl ether, C16E6, two distinct lamellae orientations have been identified. At low shear gradients the lamellae are ordered parallel to the flow-vorticity plane, whereas at higher shear gradients the lamellae order parallel to the flow-shear gradient plane, corresponding to a rotation through 90 of the axis of orientation. At intermediate values of constant shear and for oscillatory shear, both lamellae orientations are simultaneously observed for the first time in a surfactant lamellar phase. For the lamellar phase, a dispersion of the binary surfactant mixtures of dioleyl cationic and 2-ethyl hexaglycerol monoether surfactants, a high degree of alignment, in the direction parallel to the flow-vorticity plane, is observed at zero and low shear. With time, during the application of a shear gradient of 25 s-1, the lamellar phase transforms to a highly ordered solution of monodisperse multi-lamellar vesicles. (orig.)
Re-entrant phenomena in a lamellar phase under shear
International Nuclear Information System (INIS)
The influence of shear on an defective lamellar phase of the ternary mixture sodium dodecyl sulphate/decanol/D2O was studied using small-angle neutron scattering at D11. Shear-flow leads to an alignment of lamellae along the flow direction but we found, in addition, a re-orientation of the layer normal at increasing shear-rates from perpendicular to the velocity gradient direction to parallel to it. This behaviour could be interesting for industrial engineering of layered systems because shear deformation is involved in the processing of such materials. (authors)
Nonlinear Brownian dynamics of interfacial fluctuations in a shear flow
Thiébaud, Marine; Amarouchene, Yacine; Bickel, Thomas
2014-12-01
Using Brownian dynamics simulations, we investigate the effect of an external flow on the fluctuations of a liquid–liquid interface for a wide range of shear rates. Although the statistics is Gaussian at low shear, we observe a transition to a nonlinear phenomenology above a critical shear rate. In particular, we show that statistical properties at high forcing share striking similarities with Burgers turbulence. An energy criterion allows us to predict the onset of non-Gaussian statistics. It also provides a simple explanation for the development of shock singularities through the exchange of kinetic energy from regions with positive to negative gradients in the shear direction.
Nonlinear Brownian dynamics of interfacial fluctuations in a shear flow
International Nuclear Information System (INIS)
Using Brownian dynamics simulations, we investigate the effect of an external flow on the fluctuations of a liquid–liquid interface for a wide range of shear rates. Although the statistics is Gaussian at low shear, we observe a transition to a nonlinear phenomenology above a critical shear rate. In particular, we show that statistical properties at high forcing share striking similarities with Burgers turbulence. An energy criterion allows us to predict the onset of non-Gaussian statistics. It also provides a simple explanation for the development of shock singularities through the exchange of kinetic energy from regions with positive to negative gradients in the shear direction. (paper)
Aerosol penetration through a seismically loaded shear wall
International Nuclear Information System (INIS)
An experimental study was performed to measure the aerosol penetration through a reinforced concrete shear wall after simulated seismic damage. Static load-cycle testing, to stress levels sufficient to induce visible shear cracking, was used to simulate the earthquake loading. Air permeability tests were performed both before and after the simulated seismic loading damaged the structure. Aerosol penetration measurements were conducted on the cracked shear wall structure using 0.10 ?m monodisperse particles. The measured aerosol number penetration through the cracked shear wall was 0.5%. 7 refs
Aerospace Threaded Fastener Strength in Combined Shear and Tension Loading
Steeve, B. E.; Wingate, R. J.
2012-01-01
A test program was initiated by Marshall Space Flight Center and sponsored by the NASA Engineering and Safety Center to characterize the failure behavior of a typical high-strength aerospace threaded fastener under a range of shear to tension loading ratios for both a nut and an insert configuration where the shear plane passes through the body and threads, respectively. The testing was performed with a customized test fixture designed to test a bolt with a single shear plane at a discrete range of loading angles. The results provide data to compare against existing combined loading failure criteria and to quantify the bolt strength when the shear plane passes through the threads.
Strong near-inertial shear in the Gulf Stream front
Whitt, D. B.; Thomas, L. N.; Lee, C. M.; Klymak, J. M.; Ordonez, C.; Shearman, R. K.; D'Asaro, E. A.
2012-12-01
Coherent bands of strong ageostrophic shear, characteristic of amplified near-inertial waves, were observed below the surface boundary layer in the highly baroclinic north wall of the Gulf Stream. These were observed under strong and variable wind forcing during the February-March 2012 LATeral MIXing (LATMIX) experiment. Lines of constant ageostrophic shear, nearly parallel to slanted isopycnals, propagate upwards with time and show a pronounced peak in energy at near-inertial frequencies. Vertical profiles of the shear show enhanced clockwise over counter-clockwise polarization with depth suggesting predominantly downward energy propagation. The gradient Richardson number, Ri, is also coherently banded and regions of low Ri coincide with maxima in ageostrophic shear. Within these bands there are areas about 1 km wide and 10 m deep where Ri waves propagating in submesoscale, geostrophic currents, that the strong ageostrophic shear is likely associated with the modification of the waves by both the baroclinicity and relative vorticity of the Gulf Stream front. This interaction preconditions the flow for shear instability. The amplified wave shear is superimposed on an already strong geostrophic shear and may enhance diapycnal mixing as well as isopycnal mixing—the latter through shear dispersion. To investigate this claim, we analyze the LATMIX data set, which includes high spatial and temporal resolution observations of velocity, hydrography, and microstructure made with a variety of shipboard, towed, and glider-mounted instruments collected in a nearly Lagrangian frame of reference.
Morphologies of three-dimensional shear bands in granular media
Fazekas, S; Kertész, J; Wolf, D E
2005-01-01
Using three-dimensional Distinct Element Method with spherical particles we simulated shear band formation of granular materials in axisymmetric triaxial shear test. The calculated three-dimensinoal shear band morphologies are in good agreement with those found experimentally. We observed spontaneous symmetry braking strain localization provided it was allowed by the boundaries. If the symmetry was enforced, we found strain hardening. We discuss the formation mechanism of shear bands in the light of our observations and compare our results with high resolution NMR experiments.
Shear-induced metastable states of end-grafted polystyrene
International Nuclear Information System (INIS)
The in situ molecular scale response of end-grafted polystyrene to shear against a deuterated polystyrene melt was investigated with neutron reflectometry. The derived grafted polystyrene density profiles showed that the grafted polystyrene was retained on the quartz wafer during the measurements. The profiles suggested that the end-grafted polystyrene response to shear results in a series of metastable states, rather than equilibrium states assumed in the current theory. Except for some possible extension and/or contraction of the grafted polystyrene with shear, there was no obvious correlation between the grafted polymer structure and the shear thinning behavior observed in these samples.
Viscoelastic Properties of Dynamically Asymmetric Binary Fluids Under Shear Flow
Dwivedi, V; Lookman, T; Saxena, A; Dwivedi, Vinay; Ahluwalia, Rajeev; Lookman, Turab; Saxena, Avadh
2003-01-01
We study theoretically the viscoelastic properties of sheared binary fluids that have strong dynamical asymmetry between the two components. The dynamical asymmetry arises due to asymmetry between the viscoelastic stresses, particularly the bulk stress. Our calculations are based on the two-fluid model that incorporates the asymmetric stress distribution. We simulate the phase separation process under an externally imposed shear and compare the asymmetric case with the usual phase separation under a shear flow without viscoelastic effects. We also simulate the behavior of phase separated stable morphologies under applied shear and compute the stress relaxation.
Viscous shear heating instabilities in a 1-D viscoelastic shear zone
Homburg, J. M.; Coon, E. T.; Spiegelman, M.; Kelemen, P. B.; Hirth, G.
2010-12-01
Viscous shear instabilities may provide a possible mechanism for some intermediate depth earthquakes where high confining pressure makes it difficult to achieve frictional failure. While many studies have explored the feedback between temperature-dependent strain rate and strain-rate dependent shear heating (e.g. Braeck and Podladchikov, 2007), most have used thermal anomalies to initiate a shear instability or have imposed a low viscosity region in their model domain (John et al., 2009). By contrast, Kelemen and Hirth (2007) relied on an initial grain size contrast between a predetermined fine-grained shear zone and coarse grained host rock to initiate an instability. This choice is supported by observations of numerous fine grained ductile shear zones in shallow mantle massifs as well as the possibility that annealed fine grained fault gouge, formed at oceanic transforms, subduction related thrusts and ‘outer rise’ faults, could be carried below the brittle/ductile transition by subduction. Improving upon the work of Kelemen and Hirth (2007), we have developed a 1-D numerical model that describes the behavior of a Maxwell viscoelastic body with the rheology of dry olivine being driven at a constant velocity at its boundary. We include diffusion and dislocation creep, dislocation accommodated grain boundary sliding, and low-temperature plasticity (Peierls mechanism). Initial results suggest that including low-temperature plasticity inhibits the ability of the system to undergo an instability, similar to the results of Kameyama et al. (1999). This is due to increased deformation in the background allowing more shear heating to take place, and thus softening the system prior to reaching the peak stress. However if the applied strain rate is high enough (e.g. greater than 0.5 x 10-11 s-1 for a domain size of 2 km, an 8 m wide shear zone, a background grain size of 1 mm, a shear zone grain size of 150 ?m, and an initial temperature of 650°C) dramatic instabilities can occur. The instability is enhanced by the development of a self-localizing thermal perturbation in the fine grained zone that is narrower than the original width of the fine-grained zone. To examine the effect of melting, we include a parameterization of partially molten rock viscosity as a function of temperature assuming a simple relationship between melt fraction and temperature. At T > ~1400°C, all other deformation mechanisms are deactivated but shear heating continues, allowing for continued temperature evolution. In addition a strain rate cap proportional to the shear wave velocity in olivine has been imposed, reflecting the maximum rate that changes in stress can be communicated through the system. While Kelemen and Hirth (2007) allowed for grain size evolution, this has not yet been implemented in our model. Adding grain size evolution as an additional strain softening mechanism would probably allow instabilities to develop at more geologically reasonable applied strain rates. In addition to discussing the stability of the olivine only system, we will explore grain size evolution during system evolution and evaluate the consequences that the grain size evolution and lithology have on the stability of the system.
Plasticity Approach to HSC Shear Wall Design
DEFF Research Database (Denmark)
Liu, Lunying; Nielsen, Mogens Peter
1998-01-01
The paper describes a simple theory for determining the ultimate strength of shear walls. It is based on application of the theory of perfectly plastic materials. When applied to concrete the theoretical solutions must be modified by inserting into the solutions a reduced compressive strength of concrete. The reduced strength is named the effective strength. The paper describes simple lower bound solutions. They consist of pure strut action or strut action combined with diagonal compression fields outside the struts. Near moment maximum and near supports the stress fields are modified to save longitudinal reinforcement. Upper bound solutions are summarized briefly. The lower bound method has been compared with around 200 tests taken from the literature. With very simple formulas for the effectiveness factor, excellent agreement has been obtained. The testscover concrete compressive strengths up to 140 MPa and reinforcement yield strengths up to 1420 MPa. The work was carried out as a Ph.D. study by the first author, the second author supervising the study.Keywords: shear wall, plasticity, strut and tie, load-carrying capacity, concrete, reinforcement.
Shear-induced rigidity in athermal materials
Chakraborty, Bulbul; Sarkar, Sumantra
2014-03-01
In this talk, we present a minimal model of rigidity and plastic failure in solids whose rigidity emerges directly as a result of applied stresses. Examples include shear-jamming (SJ) in dry grains and discontinuous shear thickening (DST) of dense non-Brownian suspensions. Both SJ and DST states are examples of non-equilibrium, self-assembled structures that have evolved to support the load that created them. These are strongly-interacting systems where the interactions arise primarily from the strict constraints of force and torque balance at the local and global scales. Our model is based on a reciprocal-space picture that strictly enforces the local and global constraints, and is, therefore, best suited to capturing the strong correlations in these non-equilibrium systems. The reciprocal space is a tiling whose edges represent contact forces, and whose faces represent grains. A separation of scale between force fluctuations and displacements of grains is used to represent the positional disorder as quenched randomness on variables in the reciprocal space. Comparing theoretical results to experiments, we will argue that the packing fraction controls the strength of the quenched disorder. Sumantra Sarkar et al, Phys. Rev. Lett. 111, 068301 (2013)
Testing Modified Gravity with Cosmic Shear
Harnois-Déraps, Joachim; Valageas, Patrick; van Waerbeke, Ludovic; Brax, Philippe; Coles, Peter; Rizzo, Luca
2015-01-01
We use the cosmic shear data from the Canada-France-Hawaii Telescope Lensing Survey to place constraints on $f(R)$ and {\\it Generalized Dilaton} models of modified gravity. This is highly complimentary to other probes since the constraints mainly come from the non-linear scales: maximal deviations with respects to the General-Relativity + $\\Lambda$CDM scenario occurs at $k\\sim1 h \\mbox{Mpc}^{-1}$. At these scales, it becomes necessary to account for known degeneracies with baryon feedback and massive neutrinos, hence we place constraints jointly on these three physical effects. To achieve this, we formulate these modified gravity theories within a common tomographic parameterization, we compute their impact on the clustering properties relative to a GR universe, and propagate the observed modifications into the weak lensing $\\xi_{\\pm}$ quantity. Confronted against the cosmic shear data, we reject the $f(R)$ $\\{ |f_{R_0}|=10^{-4}, n=1\\}$ model with more than 99.9% confidence interval (CI) when assuming a $\\Lam...
Shear viscosity in a CFL quark star
International Nuclear Information System (INIS)
We compute the mean free path and shear viscosity in the color-flavor locked (CFL) phase of dense quark matter at low temperature T, when the contributions of mesons, quarks and gluons to the transport coefficients are Boltzmann suppressed. CFL quark matter displays superfluid properties, and transport phenomena in such cold regime are dominated by phonon-phonon scattering. We study superfluid phonons within thermal field theory and compute the mean free path associated to their most relevant collision processes. Small-angle processes turn out to be more efficient in slowing transport phenomena in the CFL matter, while the mean free path relevant for the shear viscosity is less sensitive to collinear scattering due to the presence of zero modes in the Boltzmann equation. In analogy with superfluid He4, we find the same T power law for the superfluid phonon damping rate and mean free path. Our results are relevant for the study of rotational properties of compact stars, and correct wrong estimates existing in the literature
Developing accurate quantified speckle shearing data
Wan Abdullah, W. S.; Petzing, Jon N.; Tyrer, John R.
1999-08-01
Electronic Speckle Pattern Shearing Interferometry (ESPSI) is becoming a common tool for the qualitative analysis of material defects in the aerospace and marine industries. Current trends in the development of this optical metrology nondestructive testing (NDT) technique is the introduction of quantitative analysis, which attempts to detail the defects examined and identified by the ESPSI systems. Commercial systems use divergent laser illumination, this being a design feature imposed by the typically large sizes of objects being examined, which negates the use of collimated optics. Furthermore, commercial systems are being applied to complex surfaces which distort the understanding of the instrumentation results. The growing commercial demand for quantitative out-of-lane and in-plane ESPSI for NDT is determining the quality of optical and analysis instrument. However very little attention is currently being paid to understanding, quantifying and compensating for the numerous error sources which are a function of ESPSI interferometers. This paper presents work which has been carried out on the measurement accuracy due to the divergence of the illumination wavefront and associated with the magnitude of lateral shearing function. The error is measured by comparing measurements using divergent (curvature) illumination with respect to collimated illumination. Results show that the error is increased by approximately a power factor as the distance from the illumination source to the object surface decreases.
Coupling effects in multiphase free shear flows
International Nuclear Information System (INIS)
The primary goal of this research program is to examine the effects of two-way multiphase coupling on the development of organized vortex structures in free shear flows and the resultant multiphase dispersion. Previous research studies have determined that one-way coupled particle dispersion in free shear flows is strongly dependent on the vortex structures present in these flows and their interactions as well as the ratio of the particle aerodynamic response time to the time scale of the dominant vortex structures. Current research efforts are directed towards exploring the effects that two-way momentum, mass and energy coupling have on the multiphase dispersion processes previously uncovered. These efforts involve analytical, numerical and experimental investigations. Recent analytical and numerical results indicate that momentum coupling effects can significantly alter the global stability and potentially the large scale features of the multiphase flow field. These multiphase coupling effects may have significant importance with regard to predicting the performance of many energy conversion systems
An expert system for wind shear avoidance
Stengel, Robert F.; Stratton, D. Alexander
1990-01-01
The principal objectives are to develop methods for assessing the likelihood of wind shear encounter (based on real-time information in the cockpit), for deciding what flight path to pursue (e.g., takeoff abort, landing go-around, or normal climbout or glide slope), and for using the aircraft's full potential for combating wind shear. This study requires the definition of both deterministic and statistical techniques for fusing internal and external information, for making go/no-go decisions, and for generating commands to the aircraft's autopilot and flight directors for both automatic and manually controlled flight. The expert system for pilot aiding is based on the results of the FAA Windshear Training Aids Program, a two-volume manual that presents an overview, pilot guide, training program, and substantiating data that provides guidelines for this initial development. The Windshear Safety Advisor expert system currently contains over 140 rules and is coded in the LISP programming language for implementation on a Symbolics 3670 LISP Machine.
Bierwage, Andreas; Yu, Qingquan; Günter, Sibylle
2007-01-01
The effect of a narrow sub-Alfvenic shear flow layer near the minimum q_min of the tokamak safety factor profile in a configuration with reversed central shear is analyzed. Sufficiently strong velocity shear gives rise to a broad spectrum of fast growing Kelvin-Helmholtz (KH)-like ideal magnetohydrodynamic (MHD) modes with dominant mode numbers m,n ~ 10. Nonlinear simulations with finite resistivity show magnetic reconnection near ripples caused by KH-like vortices, the form...
Zhu, Jiang; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K Kirk; Zhou, Qifa; Chen, Zhongping
2015-05-01
We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan. PMID:25927794
Rheometry-PIV of shear-thickening wormlike micelles.
Marín-Santibañez, Benjamín M; Pérez-Gonzalez, José; de Vargas, Lourdes; Rodríguez-Gonzalez, Francisco; Huelsz, Guadalupe
2006-04-25
The shear-thickening behavior of an equimolar semidilute aqueous solution of 40 mM/L cetylpyridinium chloride and sodium salicylate was studied in this work by using a combined method of rheometry and particle image velocimetry (PIV). Experiments were conducted at 27.5 degrees C with Couette, vane-bob, and capillary rheometers in order to explore a wide shear stress range as well as the effect of boundary conditions and time of flow on the creation and destruction of shear-induced structures (SIS). The use of the combined method of capillary rheometry with PIV allowed the detection of fast spatial and temporal variations in the flow kinematics, which are related to the shear-thickening behavior and the dynamics of the SIS but are not distinguished by pure rheometrical measurements. A rich-in-details flow curve was found for this solution, which includes five different regimes. Namely, at very low shear rates a Newtonian behavior was found, followed by a shear thinning one in the second regime. In the third, shear banding was observed, which served as a precursor of the SIS and shear-thickening. The fourth and fifth regimes in the flow curve were separated by a spurtlike behavior, and they clearly evidenced the existence of shear-thickening accompanied by stick-slip oscillations at the wall of the rheometer, which subsequently produced variations in the shear rate under shear stress controlled flow. Such a stick-slip phenomenon prevailed up to the highest shear stresses used in this work and was reflected in asymmetric velocity profiles with spatial and temporal variations linked to the dynamics of creation and breakage of the SIS. The presence of apparent slip at the wall of the rheometer provides an energy release mechanism which leads to breakage of the SIS, followed by their further reformation during the stick part of the cycles. In addition, PIV measurements allowed the detection of apparent slip at the wall, as well as mechanical failures in the bulk of the fluid, which suggests an extra contribution of the shear stress field to the SIS dynamics. Increasing the residence time of the fluid in the flow system enhanced the shear-thickening behavior. Finally, the flow kinematics is described in detail and the true flow curve is obtained, which only partially fits into the scheme of existing theoretical models for shear-thickening solutions. PMID:16618140
Structure and rheology of model-ferrofluids under shear flow
International Nuclear Information System (INIS)
Nonequilibrium simulations of ferromagnetic colloids in the presence of a magnetic field and plane shear flow are performed. Results for the nonequilibrium magnetization and the nonequilibrium structure factor are presented. We observe that the nonequilibrium magnetization and the magnetoviscosity are enhanced due to dipolar interactions. Structure formation due to magnetic field and shear flow are observed in qualitative agreement with experimental results
Micromechanics of sea ice gouge in shear zones
Sammonds, Peter; Scourfield, Sally; Lishman, Ben
2015-04-01
The deformation of sea ice is a key control on the Arctic Ocean dynamics. Shear displacement on all scales is an important deformation process in the sea cover. Shear deformation is a dominant mechanism from the scale of basin-scale shear lineaments, through floe-floe interaction and block sliding in ice ridges through to the micro-scale mechanics. Shear deformation will not only depend on the speed of movement of ice surfaces but also the degree that the surfaces have bonded during thermal consolidation and compaction. Recent observations made during fieldwork in the Barents Sea show that shear produces a gouge similar to a fault gouge in a shear zone in the crust. A range of sizes of gouge are exhibited. The consolidation of these fragments has a profound influence on the shear strength and the rate of the processes involved. We review experimental results in sea ice mechanics from mid-scale experiments, conducted in the Hamburg model ship ice tank, simulating sea ice floe motion and interaction and compare these with laboratory experiments on ice friction done in direct shear, and upscale to field measurement of sea ice friction and gouge deformation made during experiments off Svalbard. We find that consolidation, fragmentation and bridging play important roles in the overall dynamics and fit the model of Sammis and Ben-Zion, developed for understanding the micro-mechanics of rock fault gouge, to the sea ice problem.
Cold versus hot shear banding in bulk metallic glass
Cheng, Y. Q.; Han, Z.; Li, Y.; Ma, E.
2009-10-01
We present an analysis of the shear-banding dynamics in a bulk metallic glass (BMG), including the temperature rise in the band, the sliding speed of the band, and the time elapsed as well as the step size of the shear offset growth in a stop-and-go cycle. This model analysis quantitatively demonstrates that the major shear band can remain cold and slide in a stick-slip manner. We predict that the shear step (distance covered by a stop-and-go cycle) scales with the sample size and machine stiffness. We also illustrate the conditions when such serrated shear is unsustainable and a hot shear band directly develops in a runaway instability (catastrophe). These findings provide physical insight into the shear-instability processes and offer useful information for improving the plasticity of BMGs. The calculation results are used to explain several intriguing recent experimental observations, including the stick slip of the dominant shear-band and the sample-size effects on the plastic-flow behavior of BMGs.
Distribution of Magnetic Shear Angle in an Emerging Flux Region
Gosain, Sanjay
2010-01-01
We study the distribution of magnetic shear in an emerging flux region using the high-resolution Hinode/SOT SP observations. The distribution of mean magnetic shear angle across the active region shows large values near region of flux emergence i.e., in the middle of existing bipolar region and decreases while approaching the periphery of the active region.
Sheared and unsheared rotation of driven dust clusters
Energy Technology Data Exchange (ETDEWEB)
Schablinski, Jan; Block, Dietmar; Carstensen, Jan; Greiner, Franko; Piel, Alexander [Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universitaet Kiel, Leibnizstraße 19-Kiel, SH 24098 (Germany)
2014-07-15
Finite size plasma crystals confined in an anisotropic potential well were studied under a rotating and radially unsheared drive in experiment and simulation at moderate rotational frequencies. A radially sheared rotation of these strongly coupled systems is observed for most cluster configurations with a low symmetry. The results show that a differential rotation can be effected by a non-sheared driving force.
Constant rate shearing on two-dimensional cohesive discs
International Nuclear Information System (INIS)
We performed two-dimensional molecular dynamics simulations of cohesive discs under shear. The cohesion between the discs is added by the action of springs between very next neighbouring discs, modelling capillary forces. The geometry of the cell allows disc-disc shearing and not disc-cell wall shearing as is commonly found in the literature. Does a stick-slip phenomenon happen though the upper cover moves at a constant velocity, i.e. with an infinite shearing force? We measured the forces with which the discs acted on the upper cover for different shearing rates, as well as the disc velocities as a function of the distance to the bottom of the cell. It appears that the forces measured versus time present a periodic behaviour, very close to a stick-slip phenomenon, for shearing rates larger than a given threshold. The discs' collective displacements in the shearing cell (back and ahead) are the counterpart of the constant velocity of the upper cover, leading to a periodic behaviour of the shear stress
Constant rate shearing on two dimensional cohesive disks
Olivi-Tran, N; Fraysse, N
2005-01-01
We performed two-dimensional Molecular Dynamics simulations of cohesive disks under shear. The cohesion between the disks is added by the action of springs between very next neighbouring disks, modelling capillary forces. The geometry of the cell allows disk-disk shearing and not disk-cell wall shearing as it is commonly found in literature. Does a stick-slip phenomenon happen though the upper cover moves at a constant velocity, i.e. with an infinite shearing force? We measured the forces acted by the disks on the upper cover for different shearing rates, as well as the disk velocities as a function of the distance to the bottom of the cell. It appears that the forces measured versus time present a periodic behavior,very close to a stick slip phenomenon, for shearing rates larger than a given threshold. The disks' collective displacements in the shearing cell (back and ahead) is the counterpart of the constant velocity of the upper cover leading to a periodic behavior of the shear stress.
Innovative isogeometric formulations for shear deformable beams and plates
Kiendl, Josef; Auricchio, Ferdinando; Beirao da Veiga, Lourenco; Lovadina, Carlo; Reali, Alessandro
2013-01-01
We present different innovative formulations for shear deformable beams and plates exploiting the high inter-element continuity provided by NURBS basis functions. We develop isogeometric collocation methods in standard and mixed formulations as well as Galerkin methods using an alternative set of discrete variables. All methods are free of shear locking, which is con?rmed by numerical tests.
A refined shear deformation theory for flexure of thick beams
Scientific Electronic Library Online (English)
Yuwaraj M., Ghugal; Rajneesh, Sharma.
2011-06-01
Full Text Available A Hyperbolic Shear Deformation Theory (HPSDT) taking into account transverse shear deformation effects, is used for the static flexure analysis of thick isotropic beams. The displacement field of the theory contains two variables. The hyperbolic sine function is used in the displacement field in ter [...] ms of thickness coordinate to represent shear deformation. The transverse shear stress can be obtained directly from the use of constitutive relations, satisfying the shear stress-free boundary conditions at top and bottom of the beam. Hence, the theory obviates the need of shear correction factor. Governing differential equations and boundary conditions of the theory are obtained using the principle of virtual work. General solutions of thick isotropic simply supported, cantilever and fixed beams subjected to uniformly distributed and concentrated loads are obtained. Expressions for transverse displacement of beams are obtained and contribution due to shear deformation to the maximum transverse displacement is investigated. The results of the present theory are compared with those of other refined shear deformation theories of beam to verify the accuracy of the theory.
Shear band formation in sub-microcrystalline Ni
Energy Technology Data Exchange (ETDEWEB)
Beausir, Benoit; Hollang, Lutz; Skrotzki, Werner [Institut fuer Strukturphysik, Technische Universitaet Dresden, 01062 Dresden (Germany); Dey, Suhash Ranjan [Department of Materials Science and Engineering, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram-502205, Andhra Pradesh (India); Hieckmann, Ellen [Institut fuer Angewandte Physik, Technische Universitaet Dresden, 01062 Dresden (Germany)
2011-07-01
The stability of sub-microcrystalline nickel produced by pulsed electrodeposition without any additives was investigated during cyclic deformation at very high plastic strain amplitude of 1% at room temperature. The initial microstructure having an average grain size of 160 nm in the growth plane and a weak <110> fibre texture along the growth direction undergoes considerable grain growth during cyclic loading without significant changes in texture. After a certain number of loading cycles the specimen suddenly developed a single macro shear band. The shear band appeared in the tensile half cycle under 45 to the loading axis and acts as crack starter. Investigations in the scanning electron microscope using electron backscatter diffraction revealed that the main macro shear band consists of relaxed grains elongated along the shear plane displaying a texture induced by shear. The texture in the shear band was reproduced with the viscoplastic self-consistent polycrystal model using {l_brace}111{r_brace}<110> slip systems. Detailed investigations of the surrounding of the macro shear band reveal the existence of a large number of regularly spaced micro shear bands.
Surface Shear Transformation Zones in Amorphous Solids
Cao, Penghui; Park, Harold S
2014-01-01
We perform a systematic study of the characteristics of shear transformation zones (STZs) that nucleate at free surfaces of two-dimensional amorphous solids subject to tensile loading using two different atomistic simulation methods, the standard athermal, quasistatic (AQ) approach and our recently developed self-learning metabasin escape (SLME) method to account for the finite temperature and strain-rate effects. In the AQ, or strain-driven limit, the nonaffine displacement fields of surface STZs decay exponentially away from their centers at similar decay rates as their bulk counterparts, though the direction of maximum nonaffine displacement is tilted away from the tensile axis due to surface effects. Using the SLME method at room temperature and at the high strain rates that are seen in classical molecular dynamics simulations, the characteristics for both bulk and surface STZs are found to be identical to those seen in the AQ simulations. However, using the SLME method at room temperature and experimenta...
Lattice shear distortions in fluorite structure oxides
International Nuclear Information System (INIS)
Crystallographic shear distortions have been observed in fluorite structure, single crystals of UO2 and Zr(Ca)O2/sub-x/ by neutron-diffraction techniques. These distortions localize on the oxygen sublattice and do not require the presence of an external strain. The internal rearrangement mode in UO2 is a transverse, zone boundary q vector = 2?/a (0.5, 0.0) deformation with amplitude 0.014 A. In Zr(Ca)O/sub 2-x/, the mode is a longitudinal, q vector = 2-/a (0,0,0.5) deformation with amplitude 0.23 A. Cation-anion elastic interactions dominate in selecting the nature of the internal distortion
Spatially localized solutions of shear flows
Gibson, J F
2013-01-01
We present several new spatially localized equilibrium and traveling-wave solutions of plane Couette and channel flows. The solutions exhibit strikingly concentrated regions of vorticity that are flanked on either side by high-speed streaks. For several traveling-wave solutions of channel flow, the concentrated vortex structures are confined to the near-wall region and form particularly isolated and elemental coherent structures in the near-wall region of shear flows. The solutions are constructed by a variety of methods: application of windowing functions to previously known spatially periodic solutions, continuation from plane Couette to channel flow conditions, and from initial guesses obtained from turbulent simulation data. We show how the symmetries of localized solutions derive from the symmetries of their periodic counterparts, analyze the exponential decay of their tails, examine the scale separation and scaling of their streamwise Fourier modes, and show that they develop critical layers for large R...
Fluidization of Wet Granulates under Hydrodynamic Shear
Battiato, I
2012-01-01
We investigate the fluidization threshold of three-dimensional cohesive granulates under hydrodynamic shear forces exerted by a creeping ow. A continuum model of flow through porous media provides an analytical expression for the average drag force on a single grain. The balance equation for the forces and a force propagation model are then used to investigate the effects of porosity and packing structure on the stability of the pile. We obtain a closed-form expression for the fluidization threshold of a regular packing of mono-disperse frictionless cohesive spherical grains in a planar fracture. The compound effect of structural (packing orientation and porosity) and dynamical properties of the system on its stability is quantified.
Cockpit display of hazardous wind shear information
Wanke, Craig; Hansman, R. John, Jr.
1990-01-01
Information on cockpit display of wind shear information is given in viewgraph form. Based on the current status of windshear sensors and candidate data dissemination systems, the near-term capabilities for windshear avoidance will most likely include: (1) Ground-based detection: TDWR (Terminal Doppler Weather Radar), LLWAS (Low-Level Windshear Alert System), Automated PIREPS; (2) Ground-Air datalinks: Air traffic control voice channels, Mode-S digital datalink, ACARS alphanumeric datalink. The possible datapaths for integration of these systems are illustrated in a diagram. In the future, airborne windshear detection systems such as lidars, passive IR detectors, or airborne Doppler radars may also become available. Possible future datalinks include satellite downlink and specialized en route weather channels.
Friction welding; Magnesium; Finite element; Shear test.
Directory of Open Access Journals (Sweden)
Leonardo Contri Campanelli
2013-06-01
Full Text Available Friction spot welding (FSpW is one of the most recently developed solid state joining technologies. In this work, based on former publications, a computer aided draft and engineering resource is used to model a FSpW joint on AZ31 magnesium alloy sheets and subsequently submit the assembly to a typical shear test loading, using a linear elastic model, in order to conceive mechanical tests results. Finite element analysis shows that the plastic flow is concentrated on the welded zone periphery where yield strength is reached. It is supposed that “through the weld” and “circumferential pull-out” variants should be the main failure behaviors, although mechanical testing may provide other types of fracture due to metallurgical features.
The SDSS Coadd: Cosmic Shear Measurement
Energy Technology Data Exchange (ETDEWEB)
Lin, Huan; /Fermilab; Dodelson, Scott; /Fermilab /Chicago U., EFI /Chicago U., KICP; Seo, Hee-Jong; /UC, Berkeley; Soares-Santos, Marcelle; /Fermilab; Annis, James; /Fermilab; Hao, Jiangang; /Fermilab; Johnston, David; /Fermilab; Kubo, Jeffrey M.; /Fermilab; Reis, Ribamar R.R.; /Fermilab /Rio de Janeiro Federal U.; Simet, Melanie; /Chicago U., EFI /Chicago U., KICP
2011-11-01
Stripe 82 in the Sloan Digital Sky Survey was observed multiple times, allowing deeper images to be constructed by coadding the data. Here we analyze the ellipticities of background galaxies in this 275 square degree region, searching for evidence of distortions due to cosmic shear. The E-mode is detected in both real and Fourier space with > 5-{sigma} significance on degree scales, while the B-mode is consistent with zero as expected. The amplitude of the signal constrains the combination of the matter density {Omega}{sub m} and fluctuation amplitude {sigma}{sub 8} to be {Omega}{sub m}{sup 0.7} {sigma}{sub 8} = 0.276{sub -0.050}{sup +0.036}.
Quasilinear transport modelling at low magnetic shear
Energy Technology Data Exchange (ETDEWEB)
Citrin, J.; Hogeweij, G. M. D. [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Nieuwegein (Netherlands); Bourdelle, C.; Cottier, P. [CEA, IRFM, F-13108 Saint Paul Lez Durance (France); Escande, D. F. [UMR 6633 CNRS-Universite de Provence, Marseille (France); Guercan, Oe. D. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex (France); Hatch, D. R.; Jenko, F.; Pueschel, M. J. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany)
2012-06-15
Accurate and computationally inexpensive transport models are vital for routine and robust predictions of tokamak turbulent transport. To this end, the QuaLiKiz [Bourdelle et al., Phys. Plasmas 14, 112501 (2007)] quasilinear gyrokinetic transport model has been recently developed. QuaLiKiz flux predictions have been validated by non-linear simulations over a wide range in parameter space. However, a discrepancy is found at low magnetic shear, where the quasilinear fluxes are significantly larger than the non-linear predictions. This discrepancy is found to stem from two distinct sources: the turbulence correlation length in the mixing length rule and an increase in the ratio between the quasilinear and non-linear transport weights, correlated with increased non-linear frequency broadening. Significantly closer agreement between the quasilinear and non-linear predictions is achieved through the development of an improved mixing length rule, whose assumptions are validated by non-linear simulations.
Effect of shear on failure waves in soda lime glass
International Nuclear Information System (INIS)
By means of in-material stress gauges, failure waves in shock-compressed soda lime glass have been shown to be distinguished by a marked reduction in shear stress. To explore further the relation between failure waves and shearing resistance, a series of pressure-shear impact experiments have been performed involving the impact of a glass plate by a steel flyer plate and vice versa. The latter configuration is designed to allow direct measurements of the shearing resistance of the failed material. In both configurations, the normal and transverse motion of the free surface of the target is monitored using laser interferometry. The transverse velocity-time profiles show a pronounced loss in shearing resistance of the glass at impact velocities above the threshold for failure waves to occur
Smoothing and roughening of slip surfaces in direct shear experiments
Sagy, Amir; Badt, Nir; Hatzor, Yossef H.
2015-04-01
Faults in the upper crust contain discrete slip surfaces which have absorbed a significant part of the shear displacement along them. Field measurements demonstrate that these surfaces are rough at all measurable scales and indicate that surfaces of relatively large-slip faults are statistically smoother than those of small-slip faults. However, post faulting and surface erosion process that might affect the geometry of outcrops cannot be discounted in such measurements. Here we present experimental results for the evolution of shear surface topography as function of slip distance and normal stress in direct shear experiments. A single prismatic fine grain limestone block is first fractured in tension mode using the four-point bending test methodology and then the fracture surface topography is scanned using a laser profilometer. We then shear the obtained tensile fracture surfaces in direct shear, ensuring the original fracture surfaces are in a perfectly matching configuration at the beginning of the shear test. First, shearing is conducted to distances varying from 5 to 15 mm under constant normal stress of 2MPa and a constant displacement rate of 0.05 mm/s using two closed-loop servo controlled hydraulic pistons, supplying normal and shear forces (Davidesko et al., 2014). In the tested configuration peak shear stress is typically attained after a shear displacement of about 2-3 mm, beyond which lower shear stress is required to continue shearing at the preset displacement rate of 0.05 mm/s as is typical for initially rough joints. Following some initial compression the interface begins to dilate and continues to do so until the end of the test. The sheared tensile fracture surface is then scanned again and the geometrical evolution, in term of RMS roughness and power spectral density (PSD) is analyzed. We show that shearing smooth the surface along all our measurements scales. The roughness ratio, measured by initial PSD / final PSD for each wavelength, increases as a function of slip amount. The roughness measured after slip can be fitted by a power-law similar to that of the initial tensile surface. In the next series of experiments a similar procedure is applied when the roughness evolution is measured as a function of increasing normal stress for a fixed displacement amount of 10 mm. While samples sheared under a constant normal stress of 5 MPa generated surface smoothing, shearing under normal stress of 7.5 MPa to 15 MPa exhibited surface roughening at the measured range of scales. We find that roughening is correlated with the attained peak shear stress values, stress drop (peak shear stress minus residual shear stress) and with wear accumulation, a novel measurement procedure of which is developed here. Analysis of the sheared samples shows that roughening is generated by sets of dense fractures that significantly damaged the sample in the immediate proximity to large asperities. This roughening is related to penetrative damage during transient wear in rough surfaces.
Scale by scale budget and similarity laws for shear turbulence
Casciola, C M; Benzi, R; Piva, R
2002-01-01
Turbulent shear flows, such as those occurring in the wall region of turbulent boundary layers, manifest a substantial increase of intermittency with respect to isotropic conditions. This suggests a close link between anisotropy and intermittency. However, a rigorous statistical description of anisotropic flows is, in most cases, hampered by the inhomogeneity of the field. This difficulty is absent for the homogeneous shear flow. For this flow the scale by scale budget is discussed here by using the appropriate form of the Karman-Howarth equation, to determine the range of scales where the shear is dominant. The issuing generalization of the four-fifths law is then used as the guideline to extend to shear dominated flows the Kolmogorov-Obhukhov theory of intermittency. The procedure leads naturally to the formulation of generalized structure functions and the description of intermittency thus obtained reduces to the K62 theory for vanishing shear. Also here the intermittency corrections to the scaling exponen...
Shear induced phase transitions induced in edible fats
Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.
2003-03-01
The food industry crystallizes fats under different conditions of temperature and shear to obtain products with desired crystalline phases. Milk fat, palm oil, cocoa butter and chocolate were crystallized from the melt in a temperature controlled Couette cell. Synchrotron x-ray diffraction studies were conducted to examine the role of shear on the phase transitions seen in edible fats. The shear forces on the crystals induced acceleration of the alpha to beta-prime phase transition with increasing shear rate in milk fat and palm oil. The increase was slow at low shear rates and became very strong above 360 s-1. In cocoa butter the acceleration between beta-prime-III and beta-V phase transition increased until a maximum of at 360 s-1, and then decreased, showing competition between enhanced heat transfer and viscous heat generation.
Sources of low-level wind shear around airports
Fichtl, G. H.; Camp, D. W.; Frost, W.
1977-01-01
Some potential sources of low-level wind shear in and around airports and their likely effects are probed and analyzed. Wind shear over flat terrain with near-homogeneous surface properties (roughness, specific heat), the turning layer, shear flows over inhomogeneous terrain (airport + urban areas), thunderstorms, turbulent flowfields over bluff bodies (individual buildings), and recirculating wake flow downstream of three-dimensional block bodies are among the topics covered. Overshoot or undershoot of runways, and induced moments (pitch, roll, yaw) in takeoff and landing, and other potential hazards traceable to wind shear patterns at low heights are discussed, with emphasis on mean flow or steady-state wind shear (time-averaged, say 2-min averaged, wind fields). Wind tunnel studies and V/STOL operations are included in the study.
The DES Science Verification Weak Lensing Shear Catalogs
Jarvis, M; Zuntz, J; Kacprzak, T; Bridle, S L; Amara, A; Armstrong, R; Becker, M R; Bernstein, G M; Bonnett, C; Chang, C; Das, R; Dietrich, J P; Drlica-Wagner, A; Eifler, T F; Gangkofner, C; Gruen, D; Hirsch, M; Huff, E M; Jain, B; Kent, S; MacCrann, N; Melchior, P; Plazas, A A; Refregier, A; Rowe, B; Rykoff, E S; Samuroff, S; Sánchez, C; Suchyta, E; Troxel, M A; Vikram, V; Abbott, T; Abdalla, F B; Allam, S; Annis, J; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, F J; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Doel, P; Neto, A Fausti; Flaugher, B; Fosalba, P; Frieman, J; Gaztanaga, E; Gerdes, D W; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Li, T S; Lima, M; March, M; Martini, P; Miquel, R; Mohr, J J; Neilsen, E; Nord, B; Ogando, R; Reil, K; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Walker, A R; Wechsler, R H
2015-01-01
We present weak lensing shear catalogs for 139 square degrees of data taken during the Science Verification (SV) time for the new Dark Energy Camera (DECam) being used for the Dark Energy Survey (DES). We describe our object selection, point spread function estimation and shear measurement procedures using two independent shear pipelines, IM3SHAPE and NGMIX, which produce catalogs of 2.12 million and 3.44 million galaxies respectively. We detail a set of null tests for the shear measurements and find that they pass the requirements for systematic errors at the level necessary for weak lensing science applications using the SV data. We also discuss some of the planned algorithmic improvements that will be necessary to produce sufficiently accurate shear catalogs for the full 5-year DES, which is expected to cover 5000 square degrees.
Velocity shear and low-frequency plasma instabilities
International Nuclear Information System (INIS)
The effects of transverse velocity shear on the low-frequency stability of a plasma are examined theoretically for a low-? resistive plasma in a uniform magnetic field. Cylindrical geometry is used and the velocity shear is introduced by a nonuniform E X B rotation. Both numerical and analytic methods are used. The principal analytic result is a dispersion relation for instabilities caused by a thin velocity shear layer. This dispersion relation describes the Q machine edge oscillation, which is identified either as a Kelvin-Helmholtz instability or as a velocity-shear analogue of the resistive drift wave, depending on the parallel wave-length. The numerical results show that properties of instabilities observed in several experiments agree reasonably well with theory. The effect of velocity shear on the drift instability is to make it into either a local or nonlocal type of normal mode. 24 refs., 9 figs
Shear thickening of dense suspensions: from frictionless to frictional flow
Mari, Romain; Seto, Ryohei; Morris, Jeffrey F.; Denn, Morton M.
2014-03-01
Discontinuous shear thickening (DST) observed in many dense athermal suspensions has proven difficult to understand and to reproduce by numerical simulation. By introducing a numerical scheme including both relevant hydrodynamic interactions and granularlike contacts, we show that contact friction is essential for having DST. Above a critical volume fraction, we observe the existence of two states: a low viscosity, contactless (hence, frictionless) state, and a high viscosity frictional shear jammed state. These two states are separated by a critical shear stress, associated with a critical shear rate where DST occurs. The existence of a transition between two separate states in the case of DST, as opposed to a continuous shear thickening where the change is gradual, is discussed in the framework of a kinetic mechanism.
MEMS-based shear characterization of soft hydrated samples
Higgs, Gadryn C.; Simmons, Chelsey S.; Gao, Yingning; Fried, Andrew T.; Park, Sung-Jin; Chung, Cindy; Pruitt, Beth L.
2013-08-01
We have designed, fabricated, calibrated and tested actuators for shear characterization to assess microscale shear properties of soft substrates. Here, we demonstrate characterization of dry silicone and hydrated polyethylene glycol. Microscale tools, including atomic force microscopes and nanoindenters, often have limited functionality in hydrated environments. While electrostatic comb-drive actuators are particularly susceptible to moisture damage, through chemical vapor deposition of hexamethyldisiloxane, we increase the hydrophobicity of our electrostatic devices to a water contact angle 90 ± 3°. With this technique, we determine the effective shear stiffness of both dry and hydrated samples for a range of soft substrates. Using computational and analytical models, we compare our empirically determined effective shear stiffness with existing characterization methods, rheology, and nanoindentation, for samples with shear moduli ranging from 5-320 kPa. This work introduces a new approach for microscale assessment of synthetic materials that can be used on biological materials for basic and applied biomaterials research.
Wave-equation shear wave splitting tomography
Long, Maureen D.; de Hoop, Maarten V.; van der Hilst, Robert D.
2008-01-01
The main focus of this paper is the development of a theoretical framework for the tomographic inversion of (broad-band) shear wave splitting measurements in terms of anisotropic structure in the upper mantle. We show that the partial differential equations (PDEs) that govern wave equation shear wave splitting tomography are, upon linearization with the Born approximation, similar in structure to the equations that describe wave equation transmission and reflection tomography. For full broad-band analysis these PDEs can be evaluated numerically, but we show here the leading order asymptotic (i.e. `ray born') behaviour of the associated finite-frequency sensitivity kernels. For simplicity we assume that the anisotropic model is invariant in one horizontal direction. This 2.5-D geometry is well suited for studying upper-mantle anisotropy associated with subduction of lithospheric plates if the trench-slab system is approximately 2-D. With the so-called splitting intensity as the metric for data fit, and under the assumption of weak anisotropy, we derive expressions for the sensitivity kernels. We focus on two anisotropic parameters that describe tilted transverse isotropy: the dip ?0 of the symmetry axis with respect to the horizontal plane and the anellipticity parameter ?A, which represents the strength of the anisotropy. We illustrate the finite-frequency effects both for homogeneous and heterogeneous (anisotropic) background models. The sensitivity kernels in heterogeneous media are calculated for initial models obtained from numerical modelling of flow and finite strain beneath the Ryukyu arc. Kernels calculated in heterogeneous media differ substantially from those in a homogeneous background. This demonstrates the importance of iterative model (and kernel) assessment for reaching the full (resolution) potential of finite frequency tomography.
Elasto-plastic impact response analysis of shear-failure-type RC beams with shear rebars
International Nuclear Information System (INIS)
In this paper, to establish a simple elasto-plastic impact analysis method for shear-failure-type reinforced concrete (RC) beams, falling-weight impact tests and three-dimensional finite element (FE) analyses were conducted. Here, twelve simply supported rectangular RC beams were used, each with dimensions of (width x depth x length) 200 x 400 x 2,400 mm. Shear rebar ratio and impact velocity were taken as variables. Impact load was applied at the mid-span of RC beam by dropping a 400 kg steel weight from pre-determined position. LS-DYNA nonlinear transient finite element analysis code was used for this research. From this study, it is seen that the time histories of impact force, reaction force and mid-span displacement, and crack patterns on the side-surface of RC beam can be predicted accurately by using the proposed FE analysis method
Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2010-01-01
This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear capacity of beams loaded primarily in shear and if ECC can partially or fully replace the conventional transverse steel reinforcement in beams. However, there is a lack of understanding of how the fibers affect the shear carrying capacity and deformation behavior of structural members if used either in combination with conventional transverse reinforcement or exclusively to provide shear resistance. The experimental investigation focuses on the influence of fibers on the shear caring capacity and the crack development in ECC beams subjected to shear. The experimental program consists of ECC with short randomly distributed PVA (polyvinyl alcohol) fiber beams with different stirrup spacing and reinforced concrete (RC) beams for comparison. Displacement and strain measurements taken using the ARAMIS photogrammetric data acquisition system by means of processing at high frame rate captured images of applied a high contrast speckle pattern to the beams surface. The multiple micro cracking resulting from the strain-hardening response of ECC in tension develop in a di-agonal between the load and support point. The formation of multiple micro cracks is highly dependent on the tensile stress-strain behavior of the ECC. The shear crack formation mechanism of ECC is investigated and found to be characterized by an opening of the cracks prior to sliding. Several analytical models on shear de-sign of ECC and concrete beams are evaluated and compared to the experimentally obtained results. The pro-visions of the Eurocode and ACI Code are found to be over-conservative but can be modified by utilizing the tensile strength of ECC. An expression for the load carrying capacity is proposed by expressing the ECC shear strength in terms of the crack angle.
Strengthening of flat slabs against punching shear using post-installed shear reinforcement
Fernández Ruiz, Miguel; Muttoni, Aurelio; Kunz
2010-01-01
A significant number of existing flat slabs currently require strengthening against punching shear for safety reasons (the increase of applied loads and deficiencies during design or construction) or to comply with more stringent code requirements. Available strengthening methods are, however, not completely satisfactory, or they cannot be applied in many cases (depending on the possibilities to enlarge column sizes or to intervene on the upper face of slabs). In this paper, an innovative sys...
Asadi, M. S.; Rasouli, V.; Barla, G.
2013-07-01
Different failure modes during fracture shearing have been introduced including dilation, sliding, asperity cut-off and degradation. Several laboratory studies have reported the complexity of these failure modes during shear tests performed under either constant normal load (CNL) or constant normal stiffness (CNS) conditions. This paper is concerned with the mechanical behaviour of synthetic fractures during direct shear tests using a modified shear cell and related numerical simulation studies. The modifications made to an existing true triaxial stress cell (TTSC) in order to use it for performing shear tests under CNL conditions are presented. The large loading capacity and the use of accurate hydraulic pumps capable of applying a constant shear velocity are the main elements of this cell. Synthetic mortar specimens with different fracture surface geometries are tested to study the failure modes, including fracture sliding, asperity degradation, and to understand failure during shearing. A bonded particle model of the direct shear test with the PFC2D particle flow code is used to mimic the tests performed. The results of a number of tests are presented and compared with PFC2D simulations. The satisfactory results obtained both qualitatively and quantitatively are discussed.
Derks, Didi; Wisman, Hans; van Blaaderen, Alfons; Imhof, Arnout
2004-09-01
We report on novel possibilities for studying colloidal suspensions in a steady shear field in real space. Fluorescence confocal microscopy is combined with the use of a counter-rotating cone-plate shear cell. This allows imaging of individual particles in the bulk of a sheared suspension in a stationary plane. Moreover, this plane of zero velocity can be moved in the velocity gradient direction while keeping the shear rate constant. The colloidal system under study consists of rhodamine labelled PMMA spheres in a nearly density and refractive index matched mixture of cyclohexylbromide and cis-decalin. We show measured flow profiles in both the fluid and the crystalline phase and find indications for shear banding in the case of a sheared crystal. Furthermore, we show that, thanks to the counter-rotating principle of the cone-plate shear cell, a layer of particles in the bulk of a sheared crystalline suspension can be imaged for a prolonged time, with the result that their positions can be tracked.
International Nuclear Information System (INIS)
We report on novel possibilities for studying colloidal suspensions in a steady shear field in real space. Fluorescence confocal microscopy is combined with the use of a counter-rotating cone-plate shear cell. This allows imaging of individual particles in the bulk of a sheared suspension in a stationary plane. Moreover, this plane of zero velocity can be moved in the velocity gradient direction while keeping the shear rate constant. The colloidal system under study consists of rhodamine labelled PMMA spheres in a nearly density and refractive index matched mixture of cyclohexylbromide and cis-decalin. We show measured flow profiles in both the fluid and the crystalline phase and find indications for shear banding in the case of a sheared crystal. Furthermore, we show that, thanks to the counter-rotating principle of the cone-plate shear cell, a layer of particles in the bulk of a sheared crystalline suspension can be imaged for a prolonged time, with the result that their positions can be tracked
Directory of Open Access Journals (Sweden)
Ammar N. HANOON
2014-12-01
Full Text Available Self-compacting concrete (SCC is a new generation of high-performance concrete, known for its excellent deformability and high resistance to segregation and bleeding. Nonetheless, SCC may be incapable of resisting shear because the shear resistance mechanisms of this concrete are uncertain, especially the aggregate interlock mechanism. This uncertainty is attributed to the fact that SCC contains a smaller amount of coarse aggregates than normal concrete (NC does. This study focuses on the shear strength of self-compacting reinforced concrete (RC beams with and without shear reinforcement. A total of 16 RC beam specimens was manufactured and tested in terms of shear span-to-depth ratio and flexural and shear reinforcement ratio. The test results were compared with those of the shear design equations developed by ACI, BS, CAN and NZ codes. Results show that an increase in web reinforcement enhanced cracking strength and ultimate load. Shear-tension failure was the control failure in all tested beams.
Microscopic Order Parameter for Shear Anisotropy for Systems near Shear Jamming
Behringer, Robert; Wang, Dong; Ren, Jie; Dijksman, Joshua
2014-03-01
Sheared granular systems at packing fractions between ?S jammed states, both having high stress and fabric anisotropy. The onset of shear jammed states resembles an order-disorder transition. In recent work, we showed that the order appears in a force space (Bi et al. PRL 2013). Here, we identify an order parameter associated with individual particles, making it possible to construct spatial correlations. We identify local (particle-scale) order with ?, the deviatoric part of the force-moment tensor. This is a real symmetric, traceless matrix characterized by two coefficients, a and b, such that ? = aU1 + bU2 , and where U1 is diagonal with elements +/- 1 , and U2 has 0's on the diagonal, and 1 for the off-diagonal elements. The Ui's are orthogonal under an appropriate scalar product. Then, (a , b) provides a vector particle-scale order parameter. ? is additive over all particles, and is analogous to the magnetization in a spin system. Also, particles with orthogonal shear stresses now correspond to anti-parallel vectors. We use this representation to investi This work has been supported by: NSF-DMR, NSF-DMS, NASA, ARO, DTRA.
Numerical simulations of pattern evolution of shear bands during pure shear of geomaterials
Chen, Tielin; Liu, Jingjing; Jie, Yuxin; Zhang, Dingli
2015-07-01
Numerical simulations with finite element method were carried out and five types of patterns of shear bands and their process of self-organization were obtained. The elasto-plastic theory of constitutive relationship with the non-associated flow rule, vertex-like yielding surfaces and strain softening of strength were adopted to describe the mechanical behavior of geomaterials of rock or soil. The non-symmetrical matrix due to the adoption of the non-associated flow rule was solved with the algorithm of dynamical relaxation of finite element method. The discrete or banded patterns of shear strain in the form of superlattice, parallel strips, super lattice turned parallel strips, rhomboid net and concentric rhomboid loops, were gradually formed as the loading increased. The mechanism of the structural pattern generation and the process of pattern self-organization in geomaterials of rock and soil were a process of mechanical equilibrium of stresses and the allocation of material deformation between the elastic sites and plastic sites. The approach provided a way for researching mechanical origin of shear band pattern.
Improved Shear Performance of Bent-Up Bars in Reinforced Concrete Beams .
Abdul Qader S. Najmi; Moayyad M. Al-Nasra; Naiem M. Asha
2013-01-01
Shear failure of reinforced concrete beams is often sudden and catastrophic. This sudden failure, due to shear, made it necessary to explore more effective ways to design reinforced concrete beam for shear. The reinforced concrete beams show different behavior at the failure stage in shear compare to the bending, which is considered to be unsafe mode of failure. The shear cracks progressive rapidly without sufficient advanced warning, and the diagonal cracks that develop due to excess shear f...
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Ivona ?urkin
2009-12-01
Full Text Available The present study was performed in order to investigate a relationship between polymorphisms on the calpastatin gene (CAST and pig meat quality traits. The investigation was carried out on 29 gilts and barrows, crosses of Large White x German Landrace randomly selected at slaughter line. Pigs were slaughtered at 130-150 kg of live weight and blood samples were taken for genomic DNA analysis. The following indicators of meat quality and meat chemical composition were evaluated: pH and electric conductivity measured 45 minutes post mortem in m. Longissimus dorsi (LD muscle and in M. Semimembranosus (SM muscle; electric conductivity measured at the same locations after 24h of cooling; drip loss (determined by “bag method”; colour (measured with Minolta chromameter and expressed as Hunter L, a, b values; instrumental tenderness assessed as Warner-Bratzler (WB shear force and moisture, fat, protein and collagen content (% determined on cooked LD muscle after 24h of thawing. The amplification products of the CAST gene were digested with HinfI restriction endonuclease and three genotypes (AA, BB and AB were revealed. Statistical analysis showed that meat originated from pigs of AB genotype had the lowest WB shear force and the highest protein content of cooked LD muscle. As for the indicators of technological meat quality, statistically significant differences (p<0.05 were found between genotype AA and both BB and AB genotype for electric conductivity measured in LD muscle after 24h of cooling, as well as between BB and both AA and AB genotypes for drip loss.
The extent of proteolysis is independent of sarcomere length in lamb longissimus and psoas major.
Wheeler, T L; Koohmaraie, M
1999-09-01
The objective of this experiment was to determine the effect of sarcomere length on postmortem proteolysis and meat tenderness. Eighteen Dorset market-weight sheep were slaughtered conventionally. The longissimus thoracis et lumborum and psoas major from each carcass were either left intact on the carcass (control), which was chilled at 0 degrees C, or excised from the carcass and chilled in an ice slurry (0 degrees C). At 24 h, control muscles were excised, and all muscles were cut into sections and assigned to 1 or 10 d of postmortem storage at 2 degrees C. Sarcomere length was shorter (P .05) by aging time. Western blot analysis of troponin-T and desmin indicated no effect (P > .05) of the shortened treatment compared to the control on the extent of proteolysis. Regardless of aging time or treatment, troponin-T was more degraded (P < .01) in longissimus than in psoas major (38.1 vs 23.5%) and desmin tended to be more degraded (P = .08) in longissimus than in psoas major (50.4 vs 35.1%). Regardless of muscle or treatment, aging 10 d compared to 1 d increased degradation of troponin-T (46.3 vs 15.3%) and desmin (69.3 vs 16.1%). Warner-Bratzler shear force was greater (P < .01) in the shortened treatment than in control (6.9 vs 3.8 kg), greater (P < .01) in longissimus than in the psoas major (6.5 vs 4.2 kg), and greater (P < .01) with 1 d than with 10 d of aging time (6.1 vs 4.6 kg). A muscle x aging time interaction (P < .05) indicated shear force declined more in longissimus than in psoas major during aging. We conclude that sarcomere length did not affect the extent of proteolysis. However, sarcomere length may have an indirect effect on tenderization during aging due to its effect on initial tenderness. PMID:10492451
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Marielen de Lima Silva
2007-09-01
Full Text Available O presente experimento foi realizado para determinar a efetividade do tratamento térmico em água e vapor a 80 °C tendo como objetivo a inativação do Clostridium botulinum tipo E, utilizando-se amostras de Semintendinosus. Foram realizadas ainda a avaliação da maciez objetiva, utilizando-se a análise de força de cisalhamento, e a avaliação sensorial dos atributos de suculência, maciez subjetiva, "flavor" e presença de colágeno. O tratamento a 80 °C foi efetivo na eliminação do microrganismo, contudo não houve diferença significativa no atributo maciez objetiva (força de cisalhamento avaliado nos dois tratamentos utilizados. A avaliação sensorial apresentou correlação positiva entre os atributos maciez e suculência, enquanto o colágeno apresentou correlação negativa com a maciez. O "flavor" não apresentou correlação com os atributos maciez, suculência e presença de colágeno.The purpose of the experiment reported here was to determine the effectiveness of heat treatments in water and in steam at 80 °C to inactivate the bacterium Clostridium botulinum type E in samples of beef Semitendinosus muscle. The product’s tenderness was evaluated based on a Warner-Bratzler Shear Force (WBSF analysis and its attributes of juiciness, subjective tenderness, flavor and connective tissue were evaluated sensorially. The treatment at 80 °C effectively killed the bacterium, but no significant difference was found in the attribute of objective tenderness (shear force evaluated after the two treatments. The sensorial analysis indicated a positive correlation between the attributes of juiciness and tenderness, while the connective tissue showed a negative correlation to tenderness. Flavor proved uncorrelated with tenderness, juiciness and connective tissue.
Scientific Electronic Library Online (English)
Marielen de Lima, Silva; Carmen Josefina, Contreras-Castillo; Edwin Moisés Marcos, Ortega.
2007-09-01
Full Text Available O presente experimento foi realizado para determinar a efetividade do tratamento térmico em água e vapor a 80 °C tendo como objetivo a inativação do Clostridium botulinum tipo E, utilizando-se amostras de Semintendinosus. Foram realizadas ainda a avaliação da maciez objetiva, utilizando-se a análise [...] de força de cisalhamento, e a avaliação sensorial dos atributos de suculência, maciez subjetiva, "flavor" e presença de colágeno. O tratamento a 80 °C foi efetivo na eliminação do microrganismo, contudo não houve diferença significativa no atributo maciez objetiva (força de cisalhamento) avaliado nos dois tratamentos utilizados. A avaliação sensorial apresentou correlação positiva entre os atributos maciez e suculência, enquanto o colágeno apresentou correlação negativa com a maciez. O "flavor" não apresentou correlação com os atributos maciez, suculência e presença de colágeno. Abstract in english The purpose of the experiment reported here was to determine the effectiveness of heat treatments in water and in steam at 80 °C to inactivate the bacterium Clostridium botulinum type E in samples of beef Semitendinosus muscle. The product’s tenderness was evaluated based on a Warner-Bratzler Shear [...] Force (WBSF) analysis and its attributes of juiciness, subjective tenderness, flavor and connective tissue were evaluated sensorially. The treatment at 80 °C effectively killed the bacterium, but no significant difference was found in the attribute of objective tenderness (shear force) evaluated after the two treatments. The sensorial analysis indicated a positive correlation between the attributes of juiciness and tenderness, while the connective tissue showed a negative correlation to tenderness. Flavor proved uncorrelated with tenderness, juiciness and connective tissue.
Friction and degradation of rock joint surfaces under shear loads
Homand, F.; Belem, T.; Souley, M.
2001-08-01
The morpho-mechanical behaviour of one artificial granite joint with hammered surfaces, one artificial regularly undulated joint and one natural schist joint was studied. The hammered granite joints underwent 5 cycles of direct shear under 3 normal stress levels ranging between 0.3 and 4 MPa. The regularly undulated joint underwent 10 cycles of shear under 6 normal stress levels ranging between 0.5 and 5 MPa and the natural schist replicas underwent a monotonics shear under 5 normal stress levels ranging between 0.4 and 2.4 MPa. These direct shear tests were performed using a new computer-controlled 3D-shear apparatus. To characterize the morphology evolution of the sheared joints, a laser sensor profilometer was used to perform surface data measurements prior to and after each shear test. Based on a new characterization of joint surface roughness viewed as a combination of primary and secondary roughness and termed by the joint surface roughness, SRs, one parameter termed joint surface degradation, Dw, has been defined to quantify the degradation of the sheared joints. Examinations of SRs and Dw prior to and after shearing indicate that the hammered surfaces are more damaged than the two other surfaces. The peak strength of hammered joint with zero-dilatancy, therefore, significantly differs from the classical formulation of dilatant joint strength. An attempt has been made to model the peak strength of hammered joint surfaces and dilatant joints with regard to their surface degradation in the course of shearing and two peak strength criteria are proposed. Input parameters are initial morphology and initial surface roughness. For the hammered surfaces, the degradation mechanism is dominant over the phenomenon of dilatancy, whereas for a dilatant joint both mechanisms are present. A comparison between the proposed models and the experimental results indicates a relatively good agreement. In particular, compared to the well-known shear strength criteria of Ladanyi and Archambault or Saeb, these classical criteria significantly underestimate and overestimate the observed peak strength, respectively, under low and high normal stress levels. In addition and based on our experimental investigations, we put forward a model to predict the evolution of joint morphology and the degree of degradation during the course of shearing.Degradations of the artificial undulated joint and the natural schist joint enable us to verify the proposed model with a relatively good agreement. Finally, the model of Ladanyi and Archambault dealing with the proportion of total joint area sheared through asperities, as, once again, tends to underestimate the observed degradation.
2010-07-01
...brakes. (iv) All hammering machines, such as drop hammers and power hammers. (v) All shearing machines, such as guillotine or squaring shears; alligator shears; and rotary shears. (2) The occupations of setting up, adjusting,...
Shear band propagation from a crack tip subjected to shear wave loading
Zhang, Zhizhou
Pressure-shear plate impact experiments have been used to study the response of semi-infinite cracks in 4340 VAR steel subjected to either pure Mode II or pure Mode III loading. The material is heat-treated to achieve a fully-martensitic microstructure, which is confirmed through hardness tests and optical microscope observations of etched samples. Half-through, mid-plane cracks are grown in the target plates by means of fatigue loading. In order to obtain pure shear wave loading, flyer and target plate geometries are designed to ensure that the compressive wave passes through the crack plane before the shear wave arrives. The rear surface motion of the target is monitored by a combined normal displacement interferometer (NDI) and transverse displacement interferometer (TDI). For the case of Mode II loading, an improved TDI using a combined lens-beamsplitter unit is introduced to obtain high quality records in the presence of substantial rotation of the rear surface of the target. Both normal velocity-time profiles and transverse velocity-time profiles are obtained through post-processing from interferometric data. Numerical simulations based on both elastic and elastic viscoplastic response indicate that the deformation is essentially elastic except near the crack tip. Simulated velocity-time profiles for the case of a stationary crack agree quite well with those obtained in the experiments. Numerical simulations based on elastic response are also used to probe the effects of various parameters, e.g. friction coefficients, surface roughness, surface flatness, tilt, and etc., on the velocity-time profiles. Microscopic examinations of the recovered samples show long shear bands emanating from the tip of the fatigue crack. Numerical simulations using a power law viscoplasticity model are performed on a supercomputer to gain insight into the shear band formation process. Mesh size effects of the FEM calculations are noted and extrapolation is used to obtain temperature distributions for a mesh with zero size. The length of the band and the level of the temperature rise fall far short of what are suggested by microscopical observations. Further simulations following adjustments of power law model parameters to enhance localization fail to produce the shear band features observed in the experiments. Several closely related investigations are reported in appendices. An analytic approach employing a Green's function is used to estimate a shear band speed and a displacement jump across the band for the case of a mode III crack problem. Further improvement of this approach by including a band of failed material is also considered. Weiner-Hopf methodology is used for the Mode II case to obtain an analytical solution for assessing the accuracy of the FEM simulations. Finally, an attempt to remove the reflected tensile wave by introducing a transparent window is also described.
Je?ábek, Petr; Bukovská, Zita
2015-04-01
The South Armorican Shear Zone in France represents a major right-lateral strike slip shear zone formed in the late stages of Variscan orogeny. The active deformation in this shear zone is associated with the development of S-C fabrics in granitoids where thin shear bands (C) overprint an earlier higher grade metamorphic foliation (S). In the studied samples covering low to high intensity of shear band overprint, we identified three stages of shear band evolution associated with distinct microstructures and deformation mechanisms. The initiation of shear bands stage I is associated with the formation of microcracks crosscutting the S fabric and detected namely in the recrystallized quartz aggregates. The microcracks of suitable orientation are filled by microcline, albite, muscovite and chlorite which is a typical assemblage also for the well developed shear bands. Phase equilibrium modeling in PERPLEX indicates that this assemblage formed at pressure-temperature range of 0.1-0.4 GPa and 300-340 °C. Stage II of shear band evolution is characterized by dynamic recrystallization and grain size reduction of quartz aggregates along the microcracks and replacement of quartz by microcline along grain boundaries. This process leads to disintegration of quartz aggregate fabric and phase mixing in the shear bands. The inferred deformation mechanism for this stage is solution-precipitation creep although recrystallization of quartz is still active at the contact between quartz aggregates and shear bands. The coarse grained microstructure of quartz aggregates with ca ~250 microns average grain size reduces to ~10 microns grain size when recrystallized along extremely thin shear bands/microcracks and to ~20 microns grain size when recrystallized along the thicker shear bands. By using the flow law of Patterson and Luan (1990) for dislocation creep in quartz and the quartz piezometer of Stipp and Tullis (2003) corrected after Holyoke and Kronenberg (2010), the quartz recrystallization along thin shear bands records strain rates of ~10^-14 whereas the recrystallization along thick shear bands records strain rates of ~10^-15. The contemporaneous operation of solution-precipitation creep in shear bands and dislocation creep in quartz along the shear band boundary suggests low viscosity contrast between the mixed phase shear band matrix and pure quartz aggregate implying that the solution-precipitation creep reflect similar stress and strain rate conditions as the dislocation creep in quartz. Stage III of shear band evolution is characterized by interconnection of dispersed muscovite grains and the deformation becomes accommodated by dislocation creep in thin muscovite bands separating the inactive domains of stage II microstructure. References: Holyoke III, C. W., & Kronenberg, A. K. (2010). Accurate differential stress measurement using the molten salt cell and solid salt assemblies in the Griggs apparatus with applications to strength, piezometers and rheology. Tectonophysics, 494(1-2), 17-31. Paterson, M. S., & Luan, F. C. (1990). Quartzite rheology under geological conditions. In R. J. Knipe & E. H. Rutter (Eds.), Deformation Mechanisms, Rheology and Tectonics (pp. 299-307). London: Geological Society Special Publications. Stipp, M., & Tullis, J. (2003). The recrystallized grain size piezometer for quartz. Geophysical Research Letters, 30(21), 1-5.
Velocity shear generated Alfven waves in electron-positron plasmas
International Nuclear Information System (INIS)
Linear MHD modes in cold, nonrelativistic electron-positron plasma shear flow are considered. The general set of differential equations, describing the evolution of perturbations in the framework of the nonmodal approach is derived. It is found, that under certain circumstances, the compressional and shear Alfven perturbations may exhibit large transient growth fuelled by the mean kinetic energy of the shear flow. The velocity shear also induces mode coupling allowing the exchange of energy as well as the possibility of a strong mutual transformation of these modes into each other. The compressional Alfven mode may extract the energy of the mean flow and transfer it to the shear Alfven mode via this coupling. The relevance of these new physical effects to provide a better understanding of the laboratory e+ e- plasma is emphasized. It is speculated that the shear-induced effects in the electron-positron plasmas could also help solve some astrophysical puzzles (e.g., the generation of pulsar radio emission). Since most astrophysical plasma are relativistic, it is shown that the major results of the study remain valid for weakly sheared relativistic plasmas. (author). 21 refs, 4 figs
Fibrillar morphology formation in a sheared polypropylene melt
Pantani, R.; Nappo, V.; De Santis, F.; Titomanlio, G.
2014-05-01
In common polymer processing operations such as injection molding, film blowing, and fiber spinning, the molten polymer is subjected to shear and/or elongational flow fields that are often so intense to induce the formation of highly oriented crystalline structures, namely a fibrillar morphology. This peculiar morphology highly affects the resulting mechanical and functional properties of semicrystalline polymers and thus the study of the conditions under which it forms are of high scientific and industrial interest. In this work, crystallization during step shear experiments at 140°C were carried out in a plate-plate geometry by means of a Linkam shearing cell. The evolution of crystalline structures was observed during the tests at a fixed radial position. After the shear step the samples were allowed to fully crystallize at the test temperature and then were cooled down to room temperature. The samples were then analyzed by optical microscopy and the radial position at which a transition between spherulitic and fibrillar morphology took place was measured. Since in a plate-plate geometry, each radial position means a different shear rate, the analysis of the samples allowed to detect the critical shear rate at which, after a given shearing time, the fibrillar morphology replaces the spherulitic structure.
Structure parameter of electrorheological fluids in shear flow.
Jiang, Jile; Tian, Yu; Meng, Yonggang
2011-05-17
A structure parameter, Sn = ?(c)?/?(E), is proposed to represent the increase of effective viscosity due to the introduction of particles into a viscous liquid and to analyze the shear behavior of electrorheological (ER) fluids. Sn can divide the shear curves of ER fluids, ?/E(2) versus Sn, into three regimes, with two critical values Sn(c) of about 10(-4) and 10(-2), respectively. The two critical Sn(c) are applicable to ER fluids with different particle volume fractions ? in a wide range of shear rate ? and electric field E. When Sn 10(-2). The electric current of ER fluids under E varied with shear stress in the same or the opposite trend in different shear rate ranges. Sn(c) also separates the conductivity variation of ER fluids into three regimes, corresponding to different structure evolutions. The change of Sn with particle volume fraction and E has also been discussed. The shear thickening in ER fluids can be characterized by Sn(c)(L) and Sn(c)(H) with a critical value about 10(-6). As an analogy to friction, the correspondence between ?/E(2) and friction coefficient, Sn and bearing numbers, as well as the similarity between the shear curve of ER fluids and the Stribeck curve of friction, indicate a possible friction origin in ER effect. PMID:21488694
Numerical experiments on dynamo action in sheared and rotating turbulence
Yousef, T A; Rincon, F; Schekochihin, A A; Kleeorin, N; Rogachevskii, I; Cowley, S C; McWilliams, J C
2008-01-01
Numerical simulations of forced turbulence in elongated shearing boxes are carried out to demonstrate that a nonhelical turbulence in conjunction with a linear shear can give rise to a mean-field dynamo. Exponential growth of magnetic field at scales larger than the outer (forcing) scale of the turbulence is found. Over a range of values of the shearing rate S spanning approximately two orders of magnitude, the growth rate of the magnetic field is proportional to the imposed shear, gamma ~ S, while the characteristic spatial scale of the field is l_b ~ S^(-1/2). The effect is quite general: earlier results for the nonrotating case by Yousef et al. 2008 (PRL 100, 184501) are extended to shearing boxes with Keplerian rotation; it is also shown that the shear dynamo mechanism operates both below and above the threshold for the fluctuation dynamo. The apparently generic nature of the shear dynamo effect makes it an attractive object of study for the purpose of understanding thegeneration of magnetic fields in ast...
Shear strength of palm oil clinker concrete beams
International Nuclear Information System (INIS)
Highlights: ? Palm oil clinker can be used as lightweight aggregate for the production of structural concrete. ? The palm oil clinker concrete can be classified as lightweight concrete. ? Full scale reinforced palm oil clinker concrete beams without shear reinforcement were tested. ? The CSA based design equation can be used for the prediction of shear capacity with a limit. - Abstract: This paper presents experimental results on the shear behavior of reinforced concrete beams made of palm oil clinker concrete (POCC). Palm oil clinker (POC) is a by-product of palm oil industry and its utilization in concrete production not only solves the problem of disposing this solid waste but also helps to conserve natural resources. Seven reinforced POCC beams without shear reinforcement were fabricated and their shear behavior was tested. POCC has been classified as a lightweight structural concrete with air dry density less than 1850 kg/m3 and a 28-day compressive strength more than 20 MPa. The experimental variables which have been considered in this study were the POCC compressive strength, shear span–depth ratio (a/d) and the ratio of tensile reinforcement (?). The results show that the failure mode of the reinforced POCC beam is similar to that of conventional reinforced concrete beam. In addition, the shear equation of the Canadian Standard Association (CSA) can be used in designing reinforced POCC beam with ? ? 1. However, a 0.5 safety factor should be included in the formula for ? < 1
Shear band dynamics from a mesoscopic modeling of plasticity
International Nuclear Information System (INIS)
The ubiquitous appearance of regions of localized deformation (shear bands) in different kinds of disordered materials under shear is studied in the context of a mesoscopic model of plasticity. The model allows us to include relaxational (ageing) effects. In the absence of relaxational effects the model displays a monotonically increasing dependence of stress on strain rate, and stationary shear bands do not occur. However in start-up experiments transient (although long lived) shear bands occur, that widen without bound in time. I investigate this transient effect in detail, reproducing and explaining a t1/2 law for the thickness increase of the shear band that has been obtained in atomistic numerical simulations. Relaxation produces a negatively sloped region in the stress versus strain-rate curve that stabilizes the formation of shear bands of a well-defined width, which is a function of strain rate. Simulations at very low strain rates reveal a non-trivial stick–slip dynamics of very thin shear bands that has relevance in the study of seismic phenomena. In addition, other non-stationary processes, such as stop-and-go, or strain-rate inversion situations display a phenomenology that matches very well the results of recent experimental studies
High-Frequency Shear Viscosity of Low-Viscosity Liquids
Kaatze, U.; Behrends, R.
2014-11-01
A thickness shear quartz resonator technique is described to measure the shear viscosity of low-viscosity liquids in the frequency range from 6 MHz to 130 MHz. Examples of shear-viscosity spectra in that frequency range are presented to show that various molecular processes are accompanied by shear-viscosity relaxation. Among these processes are conformational variations of alkyl chains, with relaxation times of about 0.3 ns for -pentadecane and -hexadecane at 25 C. These variations can be well represented in terms of a torsional oscillator model. Also featured briefly are shear-viscosity relaxations associated with fluctuations of hydrogen-bonded clusters in alcohols, for which values between 0.3 ns (-hexanol) and 1.5 ns (-dodecanol) have been found at 25 C. In addition, the special suitability of high-frequency shear-viscosity spectroscopy to the study of critically demixing mixtures is demonstrated by some illustrative examples. Due to slowing, critical fluctuations do not contribute to the shear viscosity at sufficiently high frequencies of measurements so that the non-critical background viscosity of critical systems can be directly determined from high-frequency shear-viscosity spectroscopy. Relaxations in appear also in the shear-viscosity spectra with, for example, 2 ns for the critical triethylamine-water binary mixture at temperatures between 10 C and 18 C. Such relaxations noticeably influence the relaxation rate of order parameter fluctuations. They may be also the reason for the need of a special mesoscopic viscosity when mutual diffusion coefficients of critical polymer solutions are discussed in terms of mode-coupling theory.
Study of magnetorheological fluids at high shear rates
Energy Technology Data Exchange (ETDEWEB)
Wang, Xiaojie; Gordaninejad, Faramarz [University of Nevada, Department of Mechanical Engineering, Reno, NV (United States)
2006-08-15
The tunable rheological properties of magnetorheological (MR) materials at high shear rates are studied using a piston-driven flow-mode-type rheometer. The proposed method provides measurement of the apparent viscosity and yield stress of MR fluids for a shear rate range of 50 to 40,000 s{sup -1}. The rheological properties of a commercial MR fluid, as well as a newly developed MR polymeric gel, and a ferrofluid-based MR fluid are investigated. The results for apparent viscosity and dynamic and static shear stresses under different applied magnetic fields are reported. (orig.)
Testing of Undrained Shear Strength in a Hollow Cylinder Apparatus
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Wrzesi?ski Grzegorz
2015-06-01
Full Text Available The paper presents the results of tests performed in a Torsional Shear Hollow Cylinder Apparatus on undisturbed cohesive soils. The tests were performed on lightly overconsolidated clay (Cl and sandy silty clay (sasiCl. The main objective of the tests was to determine the undrained shear strength at different angles of rotation of the principal stress directions. The results of laboratory tests allow assessing the influence of rotation of the principal stress directions on the value of undrained shear strength that should be used during designing structure foundations
Role of shear in the isotropic-to-lamellar transition
Cates, M. E.; Milner, S. T.
1989-04-01
In the isotropic-to-lamellar transition, nonlinear fluctuation terms lower the transition temperature ?c and drive the transition first order. Here we show that steady shear, by suppressing the fluctuations, raises ?c in a certain temperature range the lamellar phase can be induced by applying shear. A study ofo the effective potential indicates that the transition remains first order, though becoming very weak at high shear rate. We argue heuristically that the lamellar ordering first occurs with wave vector normal to both the velocity and the velocity gradient.
A Virtual Reality Simulation System for Flying Shears
Directory of Open Access Journals (Sweden)
Fuwen Hu
2013-01-01
Full Text Available Flying shears in rolling lines are used to cut rolled products into predefined lengths. A virtual reality simulation system was developed for two typical flying shears: rotary-crank type and rotary-drum type. Its main function modules consist of motion simulation, parameters calculation and a 3D visual knowledge base for the design and utilization of flying shears. Firstly, the development process of the virtual reality simulation system was put forward. Then the implementations of core function modules were discussed in detail based on the Virtools’ behavior technologies. Finally, the last section concludes the presented work and describes the future work.
Influence of Reinforced Concrete Shear Wall on Multistorey Buildings
Venkata Sairam Kumar.N; Krishna Sai.M.L.N; Satyanarayana S
2013-01-01
This work presents the behavior and change in length of shear wall in buildings varied by increasing equal heights from 3.5m to 28m i.e, ground storey (G) to G+7 keeping thickness of shear wall as constant of 250mm and observing the dimension of shear wall in length only. The study was carried by considering both wind and seismic forces for all the zones and soil types as per IS: 1893(part I):2002 and wind loads as per IS: 875(part III):1987. A total of 96 buildings were analyzed for this wor...
Impact of a shear flow on double tearing nonlinear dynamics
International Nuclear Information System (INIS)
The dynamics of global reconnection in the presence of a poloidal shear flow located in between magnetic islands is investigated. Different linear and nonlinear regimes are identified depending on the resistivity, the equilibrium velocity amplitude, and the distance between the low-order resonant surfaces. It is found that nonlinearly, the shear flow can significantly delay DTM generation and global reconnection. It is shown that this delay is linked to a symmetry breaking imposed by the shear flow and the generation of mean poloidal flows in the resistive layers. It is also found that turbulence can be generated by Kelvin-Helmholtz instability in between the resonance layers and enhance magnetic reconnection processes.
Impact of a shear flow on double tearing nonlinear dynamics
Voslion, T.; Agullo, O.; Beyer, P.; Yagi, M.; Benkadda, S.; Garbet, X.; Itoh, K.; Itoh, S.-I.
2011-06-01
The dynamics of global reconnection in the presence of a poloidal shear flow located in between magnetic islands is investigated. Different linear and nonlinear regimes are identified depending on the resistivity, the equilibrium velocity amplitude, and the distance between the low-order resonant surfaces. It is found that nonlinearly, the shear flow can significantly delay DTM generation and global reconnection. It is shown that this delay is linked to a symmetry breaking imposed by the shear flow and the generation of mean poloidal flows in the resistive layers. It is also found that turbulence can be generated by Kelvin-Helmholtz instability in between the resonance layers and enhance magnetic reconnection processes.
Stimulated bioluminescence by fluid shear stress associated with pipe flow
International Nuclear Information System (INIS)
Dinoflagellate can be stimulated bioluminescence by hydrodynamic agitation. Two typical dinoflagellate (Lingulodinium polyedrum and Pyrocystis noctiluca) was choosed to research stimulated bioluminescence. The bioluminescence intensity and shear stress intensity were measured using fully developed pipe flow. There is shear stress threshold to agitate organism bioluminescence. From these experiment, the response thresholds of the stimulated bioluminscence always occurred in laminar flows at a shear stress level of 0.6-3 dyn/cm2. At the same time, the spectral characteristc of dinoflagellate was recorded, the wavelength of them is about 470nm, and the full width at half maximum is approximate 30nm.
Stimulated bioluminescence by fluid shear stress associated with pipe flow
Energy Technology Data Exchange (ETDEWEB)
Cao Jing; Wang Jiangan; Wu Ronghua, E-mail: caojing981@126.com [Col. of Electronic Eng., Naval University of Engineering, Wuhan 430033 (China)
2011-01-01
Dinoflagellate can be stimulated bioluminescence by hydrodynamic agitation. Two typical dinoflagellate (Lingulodinium polyedrum and Pyrocystis noctiluca) was choosed to research stimulated bioluminescence. The bioluminescence intensity and shear stress intensity were measured using fully developed pipe flow. There is shear stress threshold to agitate organism bioluminescence. From these experiment, the response thresholds of the stimulated bioluminscence always occurred in laminar flows at a shear stress level of 0.6-3 dyn/cm{sup 2}. At the same time, the spectral characteristc of dinoflagellate was recorded, the wavelength of them is about 470nm, and the full width at half maximum is approximate 30nm.
Profile control studies for JET optimised shear regime
International Nuclear Information System (INIS)
This report summarises the profile control studies, i.e. preparation and analysis of JET Optimised Shear plasmas, carried out during the year 1999 within the framework of the Task-Agreement (RF/CEA/02) between JET and the Association Euratom-CEA/Cadarache. We report on our participation in the preparation of the JET Optimised Shear experiments together with their comprehensive analyses and the modelling. Emphasis is put on the various aspects of pressure profile control (core and edge pressure) together with detailed studies of current profile control by non-inductive means, in the prospects of achieving steady, high performance, Optimised Shear plasmas. (authors)
Shear viscosity of liquid argon and liquid rubidium
International Nuclear Information System (INIS)
A direct evaluation of the shear viscosity coefficient for models of liquid rubidium and liquid argon is presented by neglecting the cross-terms in the autocorrelation function of the transverse component of the momentum stress tensor. The time dependence of the shear viscosity for liquid argon is found to display a long decaying tail in qualitative agreement with a computer calculation of Levesque et al. However, the numerical values of the shear viscosity coefficients are smaller than the experimentally determined values of about 45% for liquid rubidium and 35% for liquid argon
Shear flow effects on double tearing mode global magnetic reconnection
Voslion, Thibaut; Beyer, Peter; Yagi, Masatoshi; Benkadda, Sadruddin; Garbet, Xavier; Itoh, Kimitaka; Itoh, Sanae-I
2009-01-01
The dynamics of a global reconnection in the presence of a poloidal shear flow which is located in between magnetic islands is investigated. Different linear regimes are identified according to the value of the resistivity and the distance between the low-order resonant surfaces. It is found that the presence of a small shear flow affects and significantly delays the global reconnection processes. It is shown that this delay is linked to a breaking of symmetry imposed by the existence of the shear flow and the generation of a mean poloidal flow in the resistive layers.
Relaxation and flow in linearly sheared two-dimensional foams
Möbius, M. E.; Katgert, G.; van Hecke, M.
2010-05-01
We probe the relation between rheology and shear-induced relaxation in experiments on two-dimensional foams at steady shear. The characteristic relaxation time tr, which we extract from the non-affine part of the bubble displacements, scales non-linearly with the local strain rate \\dot{\\gamma} . In particular, the relative strength of the non-affine part grows when \\dot{\\gamma} \\rightarrow 0 —hence the foam flow is not quasistatic down to the lowest experimentally accessible shear rate. Furthermore, we establish a direct connection between the relaxation time scaling and the macroscopic rheology.
Profile control studies for JET optimised shear regime
Energy Technology Data Exchange (ETDEWEB)
Litaudon, X.; Becoulet, A.; Eriksson, L.G.; Fuchs, V.; Huysmans, G.; How, J.; Moreau, D.; Rochard, F.; Tresset, G.; Zwingmann, W. [Association Euratom-CEA, CEA/Cadarache, Dept. de Recherches sur la Fusion Controlee, DRFC, 13 - Saint-Paul-lez-Durance (France); Bayetti, P.; Joffrin, E.; Maget, P.; Mayorat, M.L.; Mazon, D.; Sarazin, Y. [JET Abingdon, Oxfordshire (United Kingdom); Voitsekhovitch, I. [Universite de Provence, LPIIM, Aix-Marseille 1, 13 (France)
2000-03-01
This report summarises the profile control studies, i.e. preparation and analysis of JET Optimised Shear plasmas, carried out during the year 1999 within the framework of the Task-Agreement (RF/CEA/02) between JET and the Association Euratom-CEA/Cadarache. We report on our participation in the preparation of the JET Optimised Shear experiments together with their comprehensive analyses and the modelling. Emphasis is put on the various aspects of pressure profile control (core and edge pressure) together with detailed studies of current profile control by non-inductive means, in the prospects of achieving steady, high performance, Optimised Shear plasmas. (authors)
Influence of microfluidic shear on keratin networks in living cells
International Nuclear Information System (INIS)
Intermediate filaments play a key role in cell mechanics, providing cells with compliance to small deformations and reinforcing them when large forces are applied. Here, we present a study of networks of keratin intermediate filaments in living cells under the influence of external forces. We expose the cells to controlled shear forces applied by microflow and investigate the response of the keratin network in situ. Our results show that bundle dynamics are reduced upon the application of shear flow. It is likely that cytoskeletal cross-talk is involved in this shear stress response via actin–keratin coupling. (paper)
Influence of microfluidic shear on keratin networks in living cells
Nolting, Jens-Friedrich; Köster, Sarah
2013-04-01
Intermediate filaments play a key role in cell mechanics, providing cells with compliance to small deformations and reinforcing them when large forces are applied. Here, we present a study of networks of keratin intermediate filaments in living cells under the influence of external forces. We expose the cells to controlled shear forces applied by microflow and investigate the response of the keratin network in situ. Our results show that bundle dynamics are reduced upon the application of shear flow. It is likely that cytoskeletal cross-talk is involved in this shear stress response via actin-keratin coupling.
Performance testing of a Savonius windmill rotor in shear flows
Mojola, O. O.; Onasanya, O. E.
The effects of flow shear and/or unsteady behavior on the power generation capability of a Savonius wind turbine rotor are assessed in view of measurements conducted, both in two statistically steady shear flows and in the wind, of rotor tip speed and torque at a number of streamwise stations for each of four values of the rotor bucket overlap ratio. It is found that, even in the absence of shear, the power coefficient of a Savonius wind turbine rotor is most strongly dependent on tip speed ratio.
Coherent structures in compressible free-shear-layer flows
Energy Technology Data Exchange (ETDEWEB)
Aeschliman, D.P.; Baty, R.S. [Sandia National Labs., Albuquerque, NM (United States). Engineering Sciences Center; Kennedy, C.A.; Chen, J.H. [Sandia National Labs., Livermore, CA (United States). Combustion and Physical Sciences Center
1997-08-01
Large scale coherent structures are intrinsic fluid mechanical characteristics of all free-shear flows, from incompressible to compressible, and laminar to fully turbulent. These quasi-periodic fluid structures, eddies of size comparable to the thickness of the shear layer, dominate the mixing process at the free-shear interface. As a result, large scale coherent structures greatly influence the operation and efficiency of many important commercial and defense technologies. Large scale coherent structures have been studied here in a research program that combines a synergistic blend of experiment, direct numerical simulation, and analysis. This report summarizes the work completed for this Sandia Laboratory-Directed Research and Development (LDRD) project.
Digital speckle pattern shearing interferometry: Limitations and prospects
DEFF Research Database (Denmark)
Owner-Petersen, Mette
1996-01-01
Since shearing interferometry, also called shearography, does not depict fringes caused by object tilt, it is a tool well suited for either nondestructive testing of objects under load or for quantitative evaluation of flexural strains. In traditional shearing interferometry, observation of fringes requires optical processing of double exposed interferograms. Hence the technique is not in real time. This paper explores the possibilities and limitations for real time shearing fringe observation using the electronic speckle pattern interferometry technique. Prospects for quantitative determination of local tilt and flexural strain using the the phase shifting technique are commented on, and some preliminary results are shown.
Piezoelectric shear wave resonator and method of making same
Wang, Jin S. (Harbor City, CA); Lakin, Kenneth M. (Ames, IA); Landin, Allen R. (Ames, IA)
1988-01-01
An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppm/.degree.C.
Song, Shaozhen; Joy, Joyce; Wang, Ruikang K.; Huang, Zhihong
2015-03-01
A quantitative measurement of the mechanical properties of biological tissue is a useful assessment of its physiologic conditions, which may aid medical diagnosis and treatment of, e.g., scleroderma and skin cancer. Traditional elastography techniques such as magnetic resonance elastography and ultrasound elastography have limited scope of application on skin due to insufficient spatial resolution. Recently, dynamic / transient elastography are attracting more applications with the advantage of non-destructive measurements, and revealing the absolute moduli values of tissue mechanical properties. Shear wave optical coherence elastography (SW-OCE) is a novel transient elastography method, which lays emphasis on the propagation of dynamic mechanical waves. In this study, high speed shear wave imaging technique was applied to a range of soft-embalmed mouse skin, where 3 kHz shear waves were launched with a piezoelectric actuator as an external excitation. The shear wave velocity was estimated from the shear wave images, and used to recover a shear modulus map in the same OCT imaging range. Results revealed significant difference in shear modulus and structure in compliance with gender, and images on fresh mouse skin are also compared. Thiel embalming technique is also proven to present the ability to furthest preserve the mechanical property of biological tissue. The experiment results suggest that SW-OCE is an effective technique for quantitative estimation of skin tissue biomechanical status.
The Lamella High Shear Rate REFLUX™ Classifier
Scientific Electronic Library Online (English)
T, Orupold; D, Starr; T, Kenefick.
2014-07-01
Full Text Available This paper covers the commercial development of gravity separation of fine particles using a Lamella High Shear Rate REFLUX™ Classifier (REFLUX™ Classifier), focusing primarily on coal applications. The REFLUX™ Classifier is a fluidized bed device that incorporates a system of closely spaced paralle [...] l inclined channels located above the fluidized bed. These channels make it possible to achieve a significant suppression of the effects of particle size, resulting in a highly effective separation on the basis of density. The improved gravity separation performance is shown to be remarkably high, with a significant reduction in the variation of separation density with particle size, and a significant reduction in the change in Ecart probable error (Ep) with size. The first full commercial-sized units of the REFLUX™ Classifier were field-tested in late 2009 in coal applications. More recently, the technology has been applied in fine particle separation in minerals applications and there are a number of full-sized units operating in chrome applications in South Africa. Initially, pilot-scaled units (typically the RC™300) were trialled in iron ore, mineral sands, and manganese plants amongst other minerals, typically after other technologies failed to achieve the desired results. Currently a number of laboratories globally are carrying out more testing in minerals applications. More than 50 RC™ units are now operating in coal and minerals applications. This paper introduces the REFLUX™ Classifier technology, identifies commercial applications, and gives some commercial results.
Limb positioning and shear flows in tetrapods
Boryskina, O. P.; Al-Kilani, A.; Fleury, V.
2011-08-01
There is increasing evidence that animal morphogenesis consists of a large scale tissue flow, which defines the gross characteristics of the animal body at a very early developmental stage. We have studied the vertebrate embryo cell trajectories between a moment when it is flat and formless, to a moment when the body plan is recognizable (chicken embryo days 2-3 of development). We find that a large vortex flow patterns the vertebrate bauplan, and especially the limb territories, both hindlimbs and forelimbs. In vivo velocity measurements show that the vortices are dragged by a localized shear oriented along the median axis. A simple hydrodynamic model accounts for the lenticular shape of the limb plates. On the hindlimb plate, the flow propagates in the form of a solid-body vortex on the limb plate, dragged by a Poiseuille flow along the backbone. In vivo tonometry measurements show that there exist stress gradients in the embryonic tissue, and that the flow pattern is congruent with the direction of decrease of stress magnitude.
Hydrodynamics of shear coaxial liquid rocket injectors
Tsohas, John
Hydrodynamic instabilities within injector passages can couple to chamber acoustic modes and lead to unacceptable levels of combustion instabilities inside liquid rocket engines. The instability of vena-contracta regions and mixing between fuel and oxidizer can serve as a fundamental source of unsteadiness produced by the injector, even in the absence of upstream or downstream pressure perturbations. This natural or "unforced" response can provide valuable information regarding frequencies where the element could conceivably couple to chamber modes. In particular, during throttled conditions the changes in the injector response may lead to an alignment of the injector and chamber modes. For these reasons, the basic unforced response of the injector element is of particular interest when developing a new engine. The Loci/Chem code was used to perform single-element, 2-D unsteady CFD computations on the Hydrogen/Oxygen Multi-Element Experiment (HOMEE) injector which was hot-fire tested at Purdue University. The Loci/Chem code was used to evaluate the effects of O/F ratio, LOX post thickness, recess length and LOX tube length on the hydrodynamics of shear co-axial rocket injectors.
A New Annular Shear Piezoelectric Accelerometer
DEFF Research Database (Denmark)
Liu, Bin; Kriegbaum, B.
2000-01-01
This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass is made of tungsten. All processes and materials comply with MIL-STD-11268. The mounted resonance frequency exceeds 40kHz. The sensitivity is 10mV/g ±5%. During the design process, the new design is evaluated and sufficiently optimized by using the Finite Element (FE) simulation before making actual prototype. Reasonable agreement between the experimental results of the physical prototype and the simulation results is achieved. The design becomes more efficient. In addition, Type 4511 has a built in DeltaTronâ charge amplifier with ID and complies with IEEE-P1451.4 standard, which is a smart transducer interface for sensors including mixed-mode communication protocols and transducer electronic data sheet (TEDS).
Palberg, Thomas; Biehi, Ralf
2003-01-01
We constructed an optical plate-plate shear cell suitable for the study of aqueous suspensions of charged colloidal spheres under low electrolyte concentrations (10(-6) M). The variable gap height was adjusted to 30 microm corresponding to 15-30 interparticle distances. The concentration of 300 microm diameter polystyrene spheres was chosen around 1 microm(-1) where previous studies had revealed the equilibrium structure to be fluid or body centred cubic. Under shear, layer structures of hexagonal symmetry form, often coexistent with a fluid phase. We used an adapted high resolution video microscope to perform a detailed study of the structure. The central ray of light was prevented from entering the objective and the images are constructed from higher order scattered light. The cover glass correction was adjusted in such a way that several layers of particles were visible simultaneously. The effective depth of sharpness was thus increased to several microm. From the 2D video frames we constructed time averaged 2D particle correlation diagrams (PCD) which correspond to the distribution functions for the projections of particle positions into the x y-plane. They allow us to discriminate different layers and to analyse their structure and their relative position. Layer structures showed approximately hexagonal symmetry bat with an elongation in the flow direction. They were always observed to be wall based. Melting in the z-direction occurred before in-plane melting and with a different mechanism. The resulting salt concentration-shear rate phase diagram is discussed in comparison with results from computer simulation. PMID:12638859
International Nuclear Information System (INIS)
This paper describes the ultimate load capacities of typical post-installed anchor bolts under static tension, shear and combined tension and shear (combination) loads. The static loading test applying tension, shear, and combination loads was carried out on post-installed anchor bolts, such as resin-anchor bolt, and two types of mechanical anchor bolt: undercut type and sleeve-expansion type. Based on the test results, the equations currently used to calculate the ultimate allowable loading capacity of post-installed anchor bolts were investigated to establish the confidence level. Particular attention was paid to the ultimate load carrying capacities for combination loads
Stability of nanofluids in quiescent and shear flow fields
Directory of Open Access Journals (Sweden)
Chen Haisheng
2011-01-01
Full Text Available Abstract An experimental study was conducted to investigate the structural stability of ethylene glycol-based titanium dioxide nanoparticle suspensions (nanofluids prepared by two-step method. The effects of particle concentration, fluid temperature, shear rate and shear duration were examined. Particle size and thermal conductivity measurements in quiescent state indicated the existence of aggregates and that they were stable in temperatures up to 60°C. Shear stability tests suggested that the structure of nanoparticle aggregates was stable in a shear interval of 500-3000 s-1 measured over a temperature range of 20-60°C. These findings show directions to resolve controversies surrounding the underlying mechanisms of thermal conduction and convective heat transfer of nanofluids.
On the variation of the experimental shear modulus of elastomers
Rahim, M. I. Seth A.; Kamarudin, A. M.
2010-05-01
Shear modulus is a fundamental property independent of test piece geometry. It is therefore one of the very important properties influencing the design of rubber engineering components such as seismic rubber bearings, bushes and vibration isolators. Unfortunately it has been observed that the measured sheared modulus shows a variation even for a similar rubber compound. This paper discusses factors such as Mullin's effect, shape factor, compressive load, temperature increment and the compliance of the testing jig and machine that could influence the final measured shear modulus. The results of both the scaled down test pieces and real size components will be discussed. In addition the shear modulus results obtained from the finite element analysis study are also presented.
Simple shear behaviour of palm biodiesel contaminated soil
Directory of Open Access Journals (Sweden)
Chew S. J.
2010-12-01
Full Text Available Palm biodiesel contaminations may bring adverse effect on basic geotechnical properties of foundation soils. This paper presents the results of an experimental study on shear behaviour of palm biodiesel contaminated sandy soil. A comprehensive set of laboratory experiments have been undertaken in a direct simple shear device on samples of palm biodiesel contaminated sandy soil. In the experiments the soil samples were prepared by mixing the sandy soil with B20 palm biodiesel ranging from 0% to 20% by weight. Stress-strain and shear strength response for the samples were monitored continuously during the experiments. The effect of the palm biodiesel content, relative density and normal stress on the shear behaviour of the sandy soil is investigated and discussed.
A study on the mechanics of shear spinning of cones
International Nuclear Information System (INIS)
The shear spinning process, where the plastic deformation zone is localized in a very small portion of the work piece, shows a promise for increasingly broader application to the production of axially symmetric parts. In this paper, the three components of working force are calculated by the newly proposed deformation model in which the spinning process is understood as shearing deformation after uniaxial yielding by bending, and shear stress, ?rz becomes ?, yield limit in pure shear, in the deformation zone. The tangential forces are first calculated and the feed forces and the normal forces are obtained by the assumption of uniform distribution of roller pressure on the contact surface. The optimum contact area is obtained by minimizing the bending energy required to get the assumed deformation of the blank. The calculated forces are compared with experimental results. A comparison shows that theoretical prediction is reasonably in good agreement with experimental results
Bulk and shear viscosities of hot and dense hadron gas
Kadam, Guru Prakash
2014-01-01
We estimate bulk and shear viscosity at finite temperature and baryon densities of hadronic matter within hadron resonance gas model. For bulk viscosity we use low energy theorems of QCD for the energy momentum tensor correlators. For shear viscosity coefficient, we estimate the same using molecular kinetic theory to relate the shear viscosity coefficient to average momentum of the hadrons in the hot and dense hadron gas. The bulk viscosity to entropy ratio increases with chemical potential and is related to the reduction of velocity of sound at nonzero chemical potential. The shear viscosity to entropy ratio on the other hand, shows a nontrivial behavior with the ratio decreasing with chemical potential for small temperatures but increasing with chemical potential at high temperatures and is related to decrease of entropy density with chemical potential at high temperature due to finite volume of the hadrons.
Influence of Grain Size Coarse Soil on Shear Strength
Directory of Open Access Journals (Sweden)
Moulay smaîne Ghembaza
2014-04-01
Full Text Available The geo- mechanical behavior of coarse soils is difficult to grasp by geotechnical methods , mainly due to the presence of large elements that disrupt or prevent the tests . Our work presents a study of the mechanical behavior of two coarse soils of different types namely Tuff MEKKEDRA and crushed gravel SIDI ALI- Benyoub west of Algeria by observing the effect of the size of diameters of the grains on the shear strength. Two aspects are considered. The first relates to a state of the art parameters which have a direct influence on the shear strength of coarse material . The second part concerns a presentation and analysis of the results of direct shear tests of materials prepared for Optimum Proctor. It is noted that the grain size affects in a significant way the properties of the shear strength. The bigger the diameter, the greater the angle of friction is important. However, the cohesion decreases with increasing grain size.
Shear-wave dynamic behavior using two different orientations
International Nuclear Information System (INIS)
For laterally complex media, it may be more suitable to take a different orientation of the displacement vector of Shear-waves. This may change the sign of several imaginary reflections and conversion coefficients to be used in reservoir characterization and Amplitude Versus Offset analysis or modeling. In this new convention the positive direction of the displacement vector of reflected Shear-waves is chosen to the left of ray tangent (in the direction of wave propagation). Therefore, the definition of the displacement vector of shear-waves can be used properly even for very complicated media. Finally the shear-wave dynamic behavior of a reservoir zone can be illustrated for laterally varying structures in terms of the amplitude variation and phase behavior using this new orientation
Transverse electron-scale instability in relativistic shear flows
Alves, E. P.; Grismayer, T.; Fonseca, R. A.; Silva, L. O.
2015-08-01
Electron-scale surface waves are shown to be unstable in the transverse plane of a sheared flow in an initially unmagnetized collisionless plasma, not captured by (magneto)hydrodynamics. It is found that these unstable modes have a higher growth rate than the closely related electron-scale Kelvin-Helmholtz instability in relativistic shears. Multidimensional particle-in-cell simulations verify the analytic results and further reveal the emergence of mushroomlike electron density structures in the nonlinear phase of the instability, similar to those observed in the Rayleigh Taylor instability despite the great disparity in scales and different underlying physics. This transverse electron-scale instability may play an important role in relativistic and supersonic sheared flow scenarios, which are stable at the (magneto)hydrodynamic level. Macroscopic (?c /?p e ) fields are shown to be generated by this microscopic shear instability, which are relevant for particle acceleration, radiation emission, and to seed magnetohydrodynamic processes at long time scales.
Vibrational stability of graphene under combined shear and axial strains
Cocco, Giulio; Fiorentini, Vincenzo
2015-07-01
We study the vibrational properties of graphene under combined shear and uniaxial tensile strain using density-functional perturbation theory. Shear strain always causes rippling instabilities with strain-dependent direction and wavelength; armchair strain contrasts this instability, enabling graphene stability in a large range of combined strains. A complementary description based on membrane elasticity theory nicely clarifies the competition of shear-induced instability and uniaxial tension. We also report the large strain-induced shifts of the split components of the G optical phonon line, which may serve as a shear diagnostic. As to the electronic properties, we find that conical intersections move away from the Brillouin zone border under strain, and they tend to coalesce at large strains, making the opening of gaps difficult to assess. By a detailed search, we find that even at large strains, only small gaps in the tens-of-meV range open at the former Dirac points.
Stratified shear flow instabilities in the non-Boussinesq regime
Heifetz, Eyal
2015-01-01
Effects of the baroclinic torque on wave propagation normally neglected under the Boussinesq approximation is investigated here, with a special focus on the associated consequences for the mechanistic interpretation of shear instability arising from the interaction between a pair of vorticity-propagating waves. To illustrate and elucidate the physical effects that modify wave propagation, we consider three examples of increasing complexity: wave propagation supported by a uniform background flow; wave propagation supported on a piecewise-linear basic state possessing one jump; and an instability problem of a piecewise-linear basic state possessing two jumps, which supports the possibility of shear instability. We find that the non-Boussinesq effects introduces a preference for the direction of wave propagation that depends on the sign of the shear in the region where waves are supported. This in turn affects phase-locking of waves that is crucial for the mechanistic interpretation for shear instability, and i...
On the shear dependent flow properties of Victorian brown coal
Energy Technology Data Exchange (ETDEWEB)
Kealy, T.J.; Tiu, C. [Monash University, Melbourne, Vic. (Australia). Co-Operative Research Centre for Clean Power from Lignite
2000-07-01
This work outlines a new technique for lignite rheology assessment, based on torque measurement at the shaft of a laboratory scale, instrumented kneading mixer, for a typical brown coal, mined in the Latrobe Valley, Victoria, Australia. It is demonstrated that this technique yields reliable and reproducible data, allowing prediction of the sheared coal product flow properties even at low shear rates where previous attempts at characterisation have been unsuccessful or unreliable. Typical samples of run-of-mine lignite have been subjected to shearing forces in the apparatus and the effects of processing parameters such as particle size and the duration and intensity of shearing have been analysed in terms of their effect on the behaviour of lignite.
Dense colloidal suspensions under time-dependent shear
Brader, J M; Cates, M E; Fuchs, M
2006-01-01
We consider the nonlinear rheology of dense colloidal suspensions under a time-dependent simple shear flow. Starting from the Smoluchowski equation for interacting Brownian particles advected by shearing (ignoring fluctuations in fluid velocity) we develop a formalism which enables the calculation of time-dependent, far-from-equilibrium averages. Taking shear-stress as an example we derive exactly a generalized Green-Kubo relation, and an equation of motion for the transient density correlator, involving a three-time memory function. Mode coupling approximations give a closed constitutive equation yielding the time-dependent stress for arbitrary shear rate history. We solve this equation numerically for the special case of a hard sphere glass subject to step-strain.
Order-disorder transitions in a sheared many body system
Pfeifer, Jens C; Ehlers, Georg; Eckhardt, Bruno
2015-01-01
Motivated by experiments on sheared suspensions that show a transition between ordered and disordered phases, we here study the long-time behavior of a sheared and overdamped 2-d system of particles interacting by repulsive forces. As a function of interaction strength and shear rate we find transitions between phases with vanishing and large single-particle diffusion. In the phases with vanishing single-particle diffusion, the system evolves towards regular lattices, usually on very slow time scales. Different lattices can be approached, depending on interaction strength and forcing amplitude. The disordered state appears in parameter regions where the regular lattices are unstable. Correlation functions between the particles reveal the formation of shear bands. In contrast to single particle densities, the spatially resolved two-particle correlation functions vary with time and allow to determine the phase within a period. As in the case of the suspensions, motion in the state with low diffusivity is essent...
Shear Zone Development and Rheology in the Deep Orogenic Crust
Marsh, J. H.; Johnson, S. E.; Gerbi, C. C.; Culshaw, N. G.
2008-12-01
Within the Central Gneiss Belt (CGB) of the southwestern Grenville Province, Ontario, Canada, a number of allocthonous lithotectonic domains are juxtaposed along crustal-scale shear zones. Extensive exposure of variably reworked granulites of the interior Parry Sound domain (iPSD) has enabled investigation of the structural and petrologic character of domain-bounding shear zones within the deep orogenic crust. Recent detailed mapping and structural data collected along the southwestern margin of the iPSD is consistent with the suggestion of Culshaw et al. (in prep) that spaced outcrop-scale shear zones have coalesced and progressively reworked layered granulites into a transposed amphibolite-facies tectonite. The tectonites comprise the Twelve Mile Bay Shear Zone (TMBSZ), which separates the iPSD from para-autocthonous rocks to the south. This study investigates the grain- and outcrop-scale mechanisms involved in shear zone development and attempts to quantify the associated changes in rock rheology. Northwest of TMBSZ, samples collected across individual outcrop-scale shear zones (i.e., across large strain gradients) have distinct differences in mineralogy and microstructure. In mafic layers the original granulite texture and cpx + opx + pl + hbl +/- grt assemblage is commonly retained away from the shear zones within unsheared "panels". With proximity to the shear zones pyroxenes and garnet are progressively consumed in hydration reactions producing hornblende and biotite, which define a new planar foliation within the highly attenuated and deflected layering. Felsic layers generally have only minor mineralogical changes across the zones, but develop an increasingly intense and recrystallized structural fabric into the sheared margin. The shear zones are commonly cored by variably deformed pegmatite dikes that were emplaced prior to, or during the early stages of shearing. Evidence for incipient shear zone formation along mineralized fracture sets that cut unsheared granulites, often with clear centimeter-decimeter wide alteration halos, is preserved in adjacent rocks closer to the domain interior. Approaching the TMBSZ, the proportion of undeformed panel is decreased considerably and a finer-grained tectonite fabric becomes dominant. Panels in this area are more podiform, and relict layering is often at a much lower angle to the transposed fabric that wraps it. Large feldspar porphyroclasts, often with extensive tails parallel to layering, are commonly observed in the tectonite suggesting that these rocks represent widened and strongly attenuated pegmatite-cored shear zones. Thus, a six-stage conceptual model is proposed in which iPSD granulites are reworked into amphibolite facies tectonites (of the TMBSZ) through growth of spaced shear zones that initiated on fluid-filled fractures, and progressive consumption and rotation of relict granulite panels. Previous experimental studies have shown that changes in rock mineralogy and microstructure can have a substantial effect on bulk rheology and the partitioning of strain. For reactions where relatively rigid phases such as garnet and pyroxene are replaced by well-aligned biotite and amphibole, orders of magnitude strength drops may be possible. Structural data and observations are used here to constrain grain- and outcrop-scale numerical modeling exercises that evaluate the 1) strength contrasts between the shear zones and the granulite protolith, 2) bulk strength of crustal blocks with variable proportions of shear zones, and 3) sensitivity to various physical parameters.
Stress and deformation of wheat in direct shear test
Directory of Open Access Journals (Sweden)
Ross J.
1998-06-01
Full Text Available A method was developed and a device constructed to measure the force of internal friction of granular materials. The angle of internal friction of wheat grain was determined for two displacement speeds (0.5 and 5 mm/min in the normal pressure range from 2.8 to 48 kPa. The angle of internal friction was found to decrease with an increase in normal pressure. Slip-stick behaviour was observed when the shearing speed equaled 0.5 mm/min. With an increase in displacement the deformation is localised in a shear zone. The thickness of the shear zone stabilised soon after the shear stress reached maximum value.
Shear strength measurements at high temperatures and pressures
International Nuclear Information System (INIS)
A method for measuring the shear strength of materials at high pressures and temperatures up to 500degC is described. Two different experimental techniques are evaluated. The method is subsequently applied to pyrophyllite, boron nitride, and aluminium. (author)
Stiffness of low-aspect-ratio, reinforced concrete shear walls
International Nuclear Information System (INIS)
This report summarizes the information relating to stiffness of low-aspect-ratio, reinforced concrete shear walls that has been obtained from static and dynamic tests of scale-model Seismic Category 1 structures (exclusive of containment) and structural elements. Although numerous static and dynamic tests of shear wall elements are reported in the technical literature, most of these were ultimate strength tests. When these tests are examined to determine stiffness values, there is a considerable range in the results obtained. The types of structures and structural elements tested, the test procedures, the methods used to measure stiffness (both directly and indirectly), and a summary of the results are discussed. This report concludes by showing the changes in stiffness of shear walls as a function of the peak nominal base shear stress that the structure experiences during a seismic event
Critical transition model of edge shear flow formation
International Nuclear Information System (INIS)
Recently, the experimental results for the emergence of the plasma shear flow layer in TJ-II have been explained as a second-order phase transition like process by using a simple model of envelope equations for the fluctuation level, the averaged poloidal velocity shear, and the pressure gradient. Here, we extend this model by incorporating radial coupling. The model is applied to the study of the turbulence-shear flow interaction when the energy flux is low. Transition dynamics and their concomitant thresholds are examined within the context of this model. The effect of an external torque has also been considered. In particular, we analyze the damping rate of the shear flow once the external torque has been removed. (author)
Stability of two-layer shear-thinning film flows
Millet, S.; Botton, V.; Ben Hadid, H.; Henry, D.; Rousset, F.
2013-10-01
The stability of a two-layer film flow of non-Newtonian fluids is studied with a linear temporal approach. Shear-thinning fluids are considered, which follow the four-parameter inelastic Carreau model. A modified Orr-Sommerfeld equation system is obtained, which is solved by using a spectral Tau collocation method based on Chebyshev polynomials. The effects of density and viscosity stratification are considered, as well as the influence of the shear-thinning properties of the fluid. It is found that, when the viscosity is stronger in the upper layer, the base flow and the stability properties are almost not influenced by the change of the shear-thinning properties in this upper layer. In the other situations, the shear-thinning properties have an influence on the different instabilities, the long-wave surface instability and the short- and long-wave interface instabilities.
Pressure and shear sensing based on microstrip antennas
Mohammad, I.; Huang, H.
2012-04-01
A foot ulcer is the initiating factor in 85% of all diabetic amputations. Ulcer formation is believed to be contributed by both pressure and shear forces. There are commercially available instruments that can measure plantar pressure. However, instruments for plantar shear measurement are limited. In this paper, we investigate the application of antenna sensors for shear and pressure measurement. The principle of operation of both antenna sensors will be discussed first, followed by detailed descriptions on the antenna designs, sensor fabrication, experimental setup, procedure and results. Because the antenna sensors are small in size, can be wirelessly interrogated, and are frequency multiplexable, we plan to embed them in shoes for simultaneous mapping of plantar shear and pressure distributions in the future.
Density gradient effects on transverse shear driven lower hybrid waves
Energy Technology Data Exchange (ETDEWEB)
DuBois, Ami M.; Thomas, Edward [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States); Amatucci, William E.; Ganguli, Gurudas [Plasma Physics Division, Naval Research Laboratory, Washington D.C. 20375 (United States)
2014-06-15
Shear driven instabilities are commonly observed in the near-Earth space, particularly in boundary layer plasmas. When the shear scale length (L{sub E}) is much less than the ion gyro-radius (?{sub i}) but greater than the electron gyro-radius (?{sub e}), the electrons are magnetized in the shear layer, but the ions are effectively un-magnetized. The resulting shear driven instability, the electron-ion hybrid (EIH) instability, is investigated in a new interpenetrating plasma configuration in the Auburn Linear EXperiment for Instability Studies. In order to understand the dynamics of magnetospheric boundary layers, the EIH instability is studied in the presence of a density gradient located at the boundary layer between two plasmas. This paper reports on a recent experiment in which electrostatic lower hybrid waves are identified as the EIH instability, and the effect of a density gradient on the instability properties are investigated.
Three-dimensional imaging of colloidal glasses under steady shear
Besseling, R; Schofield, A B; Poon, W C K; Weeks, Eric R.
2006-01-01
Using fast confocal microscopy we image the three-dimensional dynamics of particles in a colloidal glass under continuous, steady shear. The quiescent glass, with particles permanently caged by neighbors, shear-melts into an ergodic state in which successive plastic cage rearrangements lead to nearly isotropic diffusion at long times. For small shear rate $\\dot{\\gamma}$ the inverse structural relaxation time $\\tau_\\alpha^{-1}(\\dot{\\gamma})$ and diffusivity increase linearly with $\\dot{\\gamma}$ (`ideal' shear thinning), but for larger $\\dot{\\gamma}$ they increase only {\\it sub-linearly}, as predicted theoretically and seen in simulations of model glasses. Microscopically, the plastic rearrangements are heterogeneous for $t \\lesssim \\tau_{\\alpha}$ and appear cooperative in nature.
Production of functional proteins: balance of shear stress and gravity
Goodwin, Thomas John (Inventor); Hammond, Timothy Grant (Inventor); Kaysen, James Howard (Inventor)
2011-01-01
A method for the production of functional proteins including hormones by renal cells in a three dimensional culturing process responsive to shear stress uses a rotating wall vessel. Natural mixture of renal cells expresses the enzyme 1-.alpha.-hydroxylase which can be used to generate the active form of vitamin D: 1,25-diOH vitamin D.sub.3. The fibroblast cultures and co-culture of renal cortical cells express the gene for erythropoietin and secrete erythropoietin into the culture supernatant. Other shear stress response genes are also modulated by shear stress, such as toxin receptors megalin and cubulin (gp280). Also provided is a method of treating an in-need individual with the functional proteins produced in a three dimensional co-culture process responsive to shear stress using a rotating wall vessel.
Comment on "Accelerating cosmological expansion from shear and bulk viscosity"
Giovannini, Massimo
2015-01-01
In a recent Letter [Phys. Rev. Lett. 114 091301 (2105)] the cause of the acceleration of the present Universe has been identified with the shear viscosity of an imperfect relativistic fluid even in the absence of any bulk viscous contribution. The gist of this comment is that the shear viscosity, if anything, can only lead to an accelerated expansion over sufficiently small scales well inside the Hubble radius.
Waves in geomaterials with negative Cosserat shear modulus
Dyskin, Arcady; Pasternak, Elena
2015-04-01
Materials with negative moduli cannot exist on its own as they break the positive definiteness of the elastic energy making such materials unstable. They can however be statically stable as a part of an encompassing system that is stiff enough to stabilise the negative stiffness material. There indeed exist mechanisms that produce reversible descending branch giving rise to negative elastic stiffness (modulus). One such mechanism is rotation of non-spherical grains under shear stress in the presence of high compressive load. This mechanism creates an effect of negative Cosserat shear modulus that relates the non-symmetric part of the shear stress with the rotation. While the negative shear modulus makes the potential energy non-positive, there still exists a range of values of this negative modulus at which the wave propagation is possible. All four types of travelling waves known in isotropic Cosserat continuum (p-wave, two shear waves and a twist wave) exist. Furthermore, while in the conventional isotropic Cosserat continuum the twist wave and one of the shear waves exist only at high frequencies, higher than a certain threshold frequency, the presence of formally negative Cosserat shear modulus removes this threshold and makes all four waves exist in all frequencies. In general, negative values of the Cosserat shear modulus break isotropy making the corresponding Cosserat continuum orthotropic. This means that the properties of the travelling waves depend on the direction of travel. We investigate this dependence analyse the method to used the directional observations (measurements) of these waves can provide a method of detecting the presence of the negative modulus.
Variable-amplitude oscillatory shear response of amorphous materials
Perchikov, Nathan; Bouchbinder, Eran
2014-01-01
Variable-amplitude oscillatory shear tests are emerging as powerful tools to investigate and quantify the nonlinear rheology of amorphous solids, complex fluids and biological materials. Quite a few recent experimental and atomistic simulation studies demonstrated that at low shear amplitudes, an amorphous solid settles into an amplitude- and initial conditions-dependent dissipative limit cycle, in which back-and-forth localized particle rearrangements periodically bring the...
Schematic models for dynamic yielding of sheared colloidal glasses
Fuchs, Matthias; Cates, Michael E.
2003-01-01
The nonlinear rheological properties of dense suspensions are discussed within simplified models, suggested by a recent first principles approach to the model of Brownian particles in a constant-velocity-gradient solvent flow. Shear thinning of colloidal fluids and dynamical yielding of colloidal glasses arise from a competition between a slowing down of structural relaxation, because of particle interactions, and enhanced decorrelation of fluctuations, caused by the shear a...
Minimal dissipation theory and shear bands in biaxial tests
Stegmann, Thomas; Török, Janos; Brendel, Lothar; Wolf, Dietrich E.
2011-01-01
True biaxial tests of granular materials are investigated by applying the principle of minimal dissipation and comparing to two dimensional contact dynamics simulations. It is shown that the macroscopic steady state manifested by constant stress ratio and constant volume is the result of the ever changing microscopic structure which minimizes the dissipation rate. The shear band angle in the varying shear band structures is found to be constant. We also show that introducing...
Simple shear behaviour of palm biodiesel contaminated soil
Chew S. J.; Lee, C.Y.
2010-01-01
Palm biodiesel contaminations may bring adverse effect on basic geotechnical properties of foundation soils. This paper presents the results of an experimental study on shear behaviour of palm biodiesel contaminated sandy soil. A comprehensive set of laboratory experiments have been undertaken in a direct simple shear device on samples of palm biodiesel contaminated sandy soil. In the experiments the soil samples were prepared by mixing the sandy soil with B20 palm biodiesel ranging from 0% t...
Cosmic Shear Measurements with DES Science Verification Data
Becker, M. R.; Troxel, M. A.; MacCrann, N.; Eifler, T. F.; Friedrich, O.; Nicola, A.; Refregier, A.; Amara, A; Bacon, D.; Bernstein, G M; Bonnett, C.; Bridle, S. L.; Busha, M. T.; Chang, C; Dodelson, S.
2015-01-01
We present measurements of weak gravitational lensing cosmic shear two-point statistics using Dark Energy Survey Science Verification data. We demonstrate that our results are robust to the choice of shear measurement pipeline, either ngmix or im3shape, and robust to the choice of two-point statistic, including both real and Fourier-space statistics. Our results pass a suite of null tests including tests for B-mode contamination and direct tests for any dependence of the two...
Shear zone refraction and deflection in layered granular materials
Borzsonyi, Tamas; Unger, Tamas; Szabo, Balazs
2009-01-01
Refraction and deflection of shear zones in layered granular materials was studied experimentally and numerically. We show, that (i) according to a recent theoretical prediction [T. Unger, Phys. Rev. Lett. 98, 018301 (2007)] shear zones refract in layered systems in analogy with light refraction, (ii) zone refraction obeys Snell's law known from geometric optics and (iii) under natural pressure conditions (i.e. in the presence of gravity) the zone can also be deflected by th...
Shear instabilities in a fully compressible polytropic atmosphere
Witzke, V.; Silvers, L. J.; Favier, B.
2015-01-01
Shear flows have an important impact on the dynamics in an assortment of different astrophysical objects including accreditation discs and stellar interiors. Investigating shear flow instabilities in a polytropic atmosphere provides a fundamental understanding of the motion in stellar interiors where turbulent motions, mixing processes, as well as magnetic field generation takes place. Here, a linear stability analysis for a fully compressible fluid in a two-dimensional Cart...
Feedback Control of Turbulent Shear Flows by Genetic Programming
Duriez, Thomas; Parezanovi?, Vladimir; von Krbek, Kai; Bonnet, Jean-Paul; Cordier, Laurent; Noack, Bernd R.; Segond, Marc; Abel, Markus; Gautier, Nicolas; Aider, Jean-Luc; Raibaudo, Cedric; Cuvier, Christophe; Stanislas, Michel; Debien, Antoine; Mazellier, Nicolas
2015-01-01
Turbulent shear flows have triggered fundamental research in nonlinear dynamics, like transition scenarios, pattern formation and dynamical modeling. In particular, the control of nonlinear dynamics is subject of research since decades. In this publication, actuated turbulent shear flows serve as test-bed for a nonlinear feedback control strategy which can optimize an arbitrary cost function in an automatic self-learning manner. This is facilitated by genetic programming pro...
The performance of soil reinforcement in bending and shear
Pedley, Martin John; Milligan, G. W. E.
1990-01-01
Previous experimental studies of soil-reinforcement interaction have generally concentrated on the effect of reinforcement working in axial tension; this study looks at reinforcement working in bending and shear. The experimental programme was carried out in a large scale direct shear apparatus able to contain a cubic soil sample of side 1m. A previous study showed that the apparatus required improvements to its boundaries. Modifications to the apparatus resulted in a significant improvem...
Halo asphericity and the shear 3-pt function
Ho, S; Ho, Shirley; White, Martin
2003-01-01
We demonstrate through the use of a simple toy model that asphericity in dark matter halos has a measurable effect on the configuration dependence of the weak lensing shear 3-point function at small scales. This sensitivity provides a way, in principle, to measure the shapes of dark matter halos. The distribution of halo ellipticities should be included in models aiming at a high fidelity prediction of n-point shear correlation statistics.
Multiple block plane shear slope failure: Part II. Computer progam
Energy Technology Data Exchange (ETDEWEB)
Barron, K.; Stimpson, B.; Kozar, K.
1985-03-01
Multiple block plane shear failures have been occurring in some coal strip mines in Alberta. These failures cause a rapid deterioration of the bench from which the dragline operates, resulting in reduced productivity and increased safety hazards. This second, of a three part report, contains a computer program developed to perform an analysis of multiple block plane shear failure for pit walls comprising two slopes with an intervening bench, with a horizontal water table. The programming language is FORTRAN IV.
Multiple block plane shear slope failure: Part I. Theoretical analysis
Energy Technology Data Exchange (ETDEWEB)
Barron, K.; Stimpson, B.; Kozar, K.
1985-03-01
Multiple block plane shear failures have been occurring in some coal strip mines in Alberta. These failures cause a rapid deterioration of the bench from which the dragline operates, resulting in reduced productivity and increased safety hazards. The first of a three part report, this volume develops a theoretical analysis of multiple block shear failure for the case of two slopes with an intervening bench and a horizontal water table. 1 ref.
Formation of shear-bands in drying colloidal dispersions
Kiatkirakajorn, Pree-Cha; Goehring, Lucas
2015-01-01
In directionally-dried colloidal dispersions regular bands can appear behind the drying front, inclined at $\\pm45^\\circ$ to the drying line. These have been described as shear bands, based on similarities to such features in metals. Through microscopy of silica and polystyrene dispersions, dried in Hele-Shaw cells, we confirm that the bands are associated with local shear strains. We further show how the bands form, that they scale with the thickness of the drying layer, and...
An analytical analysis of vesicle tumbling under a shear flow
Rioual, F.; Biben, T.; Misbah, C (Chaouqi)
2004-01-01
Vesicles under a shear flow exhibit a tank-treading motion of their membrane, while their long axis points with an angle < 45 degrees with respect to the shear stress if the viscosity contrast between the interior and the exterior is not large enough. Above a certain viscosity contrast, the vesicle undergoes a tumbling bifurcation, a bifurcation which is known for red blood cells. We have recently presented the full numerical analysis of this transition. In this paper, we in...
An experimental investigation for external RC shear wall applications
Directory of Open Access Journals (Sweden)
M. Y. Kaltakci
2010-09-01
Full Text Available The strength and rigidity of most reinforced concrete (RC buildings in Turkey, which are frequently hit by destructive earthquakes, is not at a sufficient level. Therefore, the result of earthquakes is a significant loss of life and property. The strengthening method most commonly preferred for these type of RC buildings is the application of RC infilled walls (shear walls in the frame openings of the building. However, since the whole building has to be emptied and additional heavy costs arise during this type of strengthening, users prefer not to strengthen their buildings despite the heavy risk they are exposed to. Therefore, it is necessary to develop easier-to-apply and more effective methods for the rapid strengthening of housing and the heavily-used public buildings which cannot be emptied during the strengthening process (such as hospitals and schools. This study empirically analyses the different methods of a new system which can meet this need. In this new system, named "external shear wall application", RC shear walls are applied on the external surface of the building, along the frame plane rather than in the building. To this end, 7 test samples in 1/2 and 1/3 geometrical scale were designed to analyse the efficiency of the strengthening technique where the shear wall leans on the frame from outside of the building (external shear wall application and of the strengthening technique where a specific space is left between the frame and the external shear wall by using a coupling beam to connect elements (application of external shear wall with coupling beam. Test results showed that the maximum lateral load capacity, initial rigidity and energy dissipation behaviours of the samples strengthened with external shear wall were much better than those of the bare frames.
Study of the behavior of GFRP – RC beams under shear
Directory of Open Access Journals (Sweden)
Mettu Bhaskara Rao 1 , P.J. Rao2 , M.V.S. Rao3 , K.J. Rao
2013-07-01
Full Text Available The present paper reviews the study of Glass Fiber Reinforced Polymer (GFRP flats under shear in reinforced concrete beams. Many failures in concrete structures in particular bridges are due to corrosion of reinforcement, particularly in aggressive environments. This has prompted researcher’s world over to look for an alternative non corrosive and non metallic reinforcement for strengthening the reinforced concrete structures both in flexure and shear.
Measurement of Cosmic Shear with the Space Telescope Imaging Spectrograph
Rhodes, Jason; Refregier, Alexandre; Collins, Nicholas R.; Gardner, Jonathan. P.; Groth, Edward J.; Hill, Robert S.
2003-01-01
Weak lensing by large-scale structure allows a direct measure of the dark matter distribution. We have used parallel images taken with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope to measure weak lensing, or cosmic shear. We measure the shapes of 26036 galaxies in 1292 STIS fields and measure the shear variance at a scale of 0.51 arcminutes. The charge transfer efficiency (CTE) of STIS has degraded over time and introduces a spurious elliptic...
Shear-induced overaging in a polymer glass
Wallace, Matthew L.; Joos, Bela
2005-01-01
A phenomenon recently coined as ``overaging'' implies a slowdown in the collective (slow) relaxation modes of a glass when a transient shear strain is imposed. We are able to reproduce this behavior in simulations of a supercooled polymer melt by imposing instantaneous shear deformations. The increases in relaxation times $\\Delta \\tau_{1/2}$ rise rapidly with deformation, becoming exponential in the plastic regime. This ``overaging'' is distinct from standard aging. We find ...
Relating microstructure to shear strength of thin calcium phosphate coatings
King, ONF; Czernuszka, JT
2004-01-01
The changes in shear strength and crystallinity along with microscopy of the thin calcium phosphate coating surface and sample fracture surfaces were analyzed. Samples of stainless steel were made the cathode in the reaction while platinum was made the anode. Coated samples and fractured surfaces from lapshear tests were carbon coated and viewed in a Jeol 840F FEG SEM at accelerating shear strength. It was found that increase in maturation time led to an increase in coating thickness and a re...
Experimental investigation of reinforced concrete slabs with punching shear reinforcement
Lips, Stefan; Muttoni, Aurelio
2010-01-01
Over the past century, the use of flat slabs in buildings and especially in parking garages has been growing as it is an economic and efficient solution. Flat slabs are easy to build and have, through their smaller depth, an economical and architectural advantage compared to slabs on girders. Because of their limited depth, flat slabs are especially sensitive to deflections and to punching shear, which are their main design criteria. Furthermore, flat slabs without punching shear reinforcemen...
The rheology and processing of “edge sheared” colloidal polymer opals
Energy Technology Data Exchange (ETDEWEB)
Wong, Hon Sum; Mackley, Malcolm, E-mail: mrm5@cam.ac.uk; Butler, Simon [Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA (United Kingdom); Baumberg, Jeremy; Snoswell, David; Finlayson, Chris; Zhao, Qibin [Cavendish Laboratory, NanoPhotonics Centre, University of Cambridge, Cambridge CB3 OHE (United Kingdom)
2014-03-15
This paper is concerned with the rheology and processing of solvent-free core shell “polymer opals” that consist of a soft outer shell grafted to hard colloidal polymer core particles. Strong iridescent colors can be produced by shearing the material in a certain way that causes the initially disordered spheres to rearrange into ordered crystalline structures and produce colors by diffraction and interference of multiple light scattering, similar to gemstone opals. The basic linear viscoelastic rheology of a polymer opal sample was determined as a function of temperature, and the material was found to be highly viscoelastic at all tested temperatures. A Cambridge multipass rheometer was specifically modified in order to make controlled mechanical measurements of initially disordered polymer opal tapes that were sandwiched between protective polyethylene terephthalate sheets. Axial extension, simple shear, and a novel “edge shearing” geometry were all evaluated, and multiple successive experiments of the edge shearing test were carried out at different temperatures. The optical development of colloidal ordering, measured as optical opalescence, was quantified by spectroscopy using visible backscattered light. The development of opalescence was found to be sensitive to the geometry of deformation and a number of process variables suggesting a complex interaction of parameters that caused the opalescence. In order to identify aspects of the deformation mechanism of the edge shearing experiment, a separate series of in situ optical experiments were carried out and this helped indicate the extent of simple shear generated with each edge shear deformation. The results show that strong ordering can be induced by successive edge shearing deformation. The results are relevant to polymer opal rheology, processing, and mechanisms relating to ordering within complex viscoelastic fluids.
Interfacial shear stress measurement using high spatial resolution multiphase PIV
André, Matthieu A.; Bardet, Philippe M.
2015-06-01
In multiphase flows, form drag and viscous shear stress transfer momentum between phases. For numerous environmental and man-made flows, it is of primary importance to predict this transfer at a liquid-gas interface. In its general expression, interfacial shear stress involves local velocity gradients as well as surface velocity, curvature, and surface tension gradients. It is therefore a challenging quantity to measure experimentally or compute numerically. In fact, no experimental work to date has been able to directly resolve all the terms contributing to the shear stress in the case of curved and moving surfaces. In an attempt to fully resolve the interface shear stress when surface tension gradients are negligible, high-resolution particle image velocimetry (PIV) data are acquired simultaneously on both sides of a water-air interface. The flow consists of a well-conditioned uniform and homogeneous water jet discharging in quiescent air, which exhibits two-dimensional surface waves as a result of a shear layer instability below the surface. PIV provides velocity fields in both phases, while planar laser-induced fluorescence is used to track the interface and obtain its curvature. To compute the interfacial shear stress from the data, several processing schemes are proposed and compared, using liquid and/or gas phase data. Vorticity at the surface, which relates to the shear stress through the dynamic boundary condition at the surface, is also computed and provides additional strategies for estimating the shear. The various schemes are in agreement within the experimental uncertainties, validating the methodology for experimentally resolving this demanding quantity.
High shear stress behavior of some representative lubricants
Jakobsen, J.; Winer, W. O.
1974-01-01
Shear stress independent behavior observed for representative, synthetic, nonblended lubricants is found to be of the same magnitude as the shear stress in sliding elastohydrodynamic contacts. It is shown that dissipation heating is the only mechanism of importance in the generation of deviations from constant viscosity as measured with capillary tube viscometric methods. Newtonian end corrections for capillary tubes are found to be constant for nonblended liquid lubricants.
Resonant alignment of microswimmer trajectories in oscillatory shear flows
Hope, Alexander; Croze, Ottavio A.; Poon, Wilson C. K.; Bees, Martin A.; Haw, Mark D.
2015-01-01
Oscillatory flows are common in the environment, industrial applications and rheological investigations. We experimentally characterise the response of the alga {\\it Dunaliella salina} to oscillatory shear and squeeze flows, and report the surprising discovery that algal swimming trajectories orient perpendicular to the flow-shear plane. The ordering has the characteristics of a resonance in the driving parameter space, which is qualitatively reproduced by a model accounting...
Probability of second law violations in shearing steady states
International Nuclear Information System (INIS)
We propose a new definition of natural invariant measure for trajectory segments of finite duration for a many-particle system. On this basis we give an expression for the probability of fluctuations in the shear stress of a fluid in a nonequilibrium steady state far from equilibrium. In particular we obtain a formula for the ratio that, for a finite time, the shear stress reverse sign, violating the second law of thermodynamics. Computer simulations support this formula
Coupling of sound and internal waves in shear flows
International Nuclear Information System (INIS)
Gravity waves in the parallel shear flow of a continuously stratified compressible fluid are considered. It is demonstrated that the shear induces a coupling between the sound waves and the internal gravity waves. The conditions for the effectiveness of the coupling are defined and a corresponding linear mechanism of wave transformation and energy transfer between the modes is described. It is also shown that, under suitable conditions, beat waves can be generated. (author). 28 refs, 5 figs
Probing dark energy with the shear-ratio geometric test
Taylor, A.N.; Kitching, T. D.; Bacon, D. J.; Heavens, A. F.
2006-01-01
We adapt the Jain--Taylor (2003) shear-ratio geometric lensing method to measure the dark energy equation of state, and its time derivative from dark matter haloes in cosmologies with arbitrary spatial curvature. The full shear-ratio covariance matrix is calculated for lensed sources, including the intervening large-scale structure and photometric redshift errors as additional sources of noise, and a maximum likelihood method for applying the test is presented. Combining wit...
Behaviour of fasteners under monotonic or cyclic shear displacements
Vintzéleou, Elizabeth; Eligehausen, Rolf
1991-01-01
An experimental program was carried out to investigate the behaviour of metallic fasteners (undercut, torque controlled expansion and chemical anchors) embedded in cracked concrete and subjected to shear displacements, under shear displacements is similar. Fasteners situated close to an edge and loaded towards the edge exhibit brittle concrete failure. Cyclic loadings are possible only for displacements which are much lower than the values corresponding to the monotonic peak load. Fastenings ...
Shear stress in spiral-pancake solenoid magnet coils
International Nuclear Information System (INIS)
Mechanical stresses in solenoid magnet coils are generally calculated using equations based on an axi-symmetric coil model. This model lacks sufficient detail to allow computation of shear stresses which must exist in any coil wound with helical turns. An analysis is presented which yields the differential equations describing the state of stress in a pancake coil. Simple approximate solutions are presented which allow the calculation of shear stresses in various regions of a coil
Separation of microscale chiral objects by shear flow
Marcos; Fu, Henry C.; Powers, Thomas R.; Stocker, Roman
2010-01-01
We show that plane parabolic flow in a microfluidic channel causes nonmotile, helically shaped bacteria to drift perpendicular to the shear plane. Net drift results from the preferential alignment of helices with streamlines, with a direction that depends on the chirality of the helix and the sign of the shear rate. The drift is in good agreement with a model based on resistive force theory, and separation is efficient (>80%) and fast (
Shearing Strength and Reliability of Recycled Concrete Beams
Bin Lei; Yusong Yan; Hui Wu
2013-01-01
The shearing behaviour of recycled concrete beams is studied here, by putting forward the formula for calculating shearing strength of recycled concrete beams and then assessing their reliability therefore. Based on the comparison between the experimental data by domestic and overseas researchers and the calculated results by formula from the code for design of concrete structures (GB 50010-2010) (CDCS), the applicability of the CDCS for the recycled concrete beams is validated statistically....
Shear layer characteristics of supersonic free and impinging jets
Davis, T. B.; Kumar, R.
2015-09-01
The initial shear layer characteristics of a jet play an important role in the initiation and development of instabilities and hence radiated noise. Particle image velocimetry has been utilized to study the initial shear layer development of supersonic free and impinging jets. Microjet control employed to reduce flow unsteadiness and jet noise appears to affect the development of the shear layer, particularly near the nozzle exit. Velocity field measurements near the nozzle exit show that the initially thin, uncontrolled shear layer develops at a constant rate while microjet control is characterized by a rapid nonlinear thickening that asymptotes downstream. The shear layer linear growth rate with microjet control, in both the free and the impinging jet, is diminished. In addition, the thickened shear layer with control leads to a reduction in azimuthal vorticity for both free and impinging jets. Linear stability theory is used to compute unstable growth rates and convection velocities of the resultant velocity profiles. The results show that while the convection velocity is largely unaffected, the unstable growth rates are significantly reduced over all frequencies with microjet injection. For the case of the impinging jet, microjet control leads to near elimination of the impingement tones and an appreciable reduction in broadband levels. Similarly, for the free jet, significant reduction in overall sound pressure levels in the peak radiation direction is observed.
Spherulitic nucleation and growth rates in a sheared polypropylene melt
De Santis, F.; Scermino, R.; Pantani, R.; Titomanlio, G.
2014-05-01
In common polymer processing operations such as injection molding, film blowing, and fiber spinning, the molten polymer is subjected to intense shear and/or elongational flow fields and crystallizes during or after the application of flow. The semicrystalline morphology that develops in the final product is typically very different from what is observed during quiescent crystallization of the same polymer, and the properties change accordingly. The possibility of controlling the final morphology and the resulting mechanical and functional properties of semicrystalline polymers based on the study of polymer melt crystallization stimulated by flow is highly intriguing. This work starts from the experimental evidence that there exists qualitatively three regimes of crystallization under shear: (a) very low shear rates, in which there is no effect on kinetics; (b) higher shear rates, in which orientational effects enhance just the nucleation and growth rates, and spherulitic crystallization is observed; and (c) high shear rates, in which molecular stretching occurs giving rise to a fibrillar morphology development under very fast kinetics. The first two regimes are explored and analyzed by means of experimental protocols developed on purpose. In particular: - spherulitic nucleation and growth rates under continuous shear rates were carefully measured and related to molecular strain - the condition below which crystallization turns out to be essentially quiescent was evidenced.
Mechanical characterization of hyperelastic polydimethylsiloxane by simple shear test
International Nuclear Information System (INIS)
Graphical abstract: Display Omitted Research highlights: ? Mechanical characterization of Polydimethylsiloxane under large shear deformations ? Non-linear shear stress-strain relationship is achieved in simple shear tests ? Constitutive modeling of large shear deformations in rubber-like materials is proposed. - Abstract: Polydimethylsiloxane (PDMS) is a commercially silicone rubber widely used in mechanical sensors, electronic products and medical devices. This paper describes and analyzes the mechanical behavior of polymer PDMS under large shear deformations. The goal of this work is to estimate experimentally the angular distortions associated with different applied forces, considering a simple shear test based on single lap joints. The experimental procedure to obtain the displacement field is carried out using the digital image correlation (DIC) method, which is an optical-numerical experimental approach developed for full-field and non-contact measurements. The material parameters, associated with classical Mooney-Rivlin model, are estimated from experimental data by means of Levenberg-Marquardt method. Furthermore, due to nonlinear stress-strain behavior observed in experimental data, it is proposed a new nonlinear model and two new parameters are determined in the same way.
Power Spectra of Force Fluctuations in Granular Materials Under Shear
Corwin, Eric; Jaeger, Heinrich; Nagel, Sidney
2006-03-01
We measure the time-varying forces at the bottom surface of a granular system sheared at the top. The shear is applied by rotating a roughened piston while maintaining a constant, uniaxial compressive force. We report on the force autocorrelation and the corresponding power spectrum S of the variation of force on individual grains at the bottom surface. These forces are obtained from video tracking of imprints in a pressure-sensitive birefringent layer across the bottom surface. Averaging over concentric annuli we find power-law behavior S ˜1/f^? over several orders of magnitude in each annulus. The power law exponents ? appear to be correlated with the in-plane shear strain rate. In our system friction with the stationary side walls introduces a radial gradient in the shear rate, which is maximum at the outer edge and zero at the center. The corresponding power law exponents suggest strict 1/f noise (?= 1) at the outer, shearing edge and an increasing index as one approaches the center and the shear rate vanishes.
Investigation of sheared liquids by neutron backscattering and reflectivity
Wolff, M; Hock, R; Frick, B; Zabel, H
2002-01-01
We have investigated by neutron scattering structural and dynamical properties of water solutions of the triblock copolymer P85 under shear. To this end a shear cell that suits the requirements for neutron backscattering and another for reflectivity experiments have been built. In reflectivity measurements we find the polymer concentration (nominal concentration of 33% by weight) to vary right at the surface between 12% and 52% for hydrophilic or hydrophobic coated silicon wavers, for temperatures between 18 C and 73 C and for shear rates up to 2500 s sup - sup 1. Additional structural changes deeper in the bulk are also observed. On the backscattering instrument (IN10 at ILL) we find that the liquid appears to stick to the plates of the shear cell, implying an unusual macroscopic velocity distribution that differs from that found earlier for lubrication oils. We report further on changes of the quasielastic line width in the direction of the shear gradient for different temperatures and shear rates. (orig.)
Shear deformable finite beam elements for composite box beams
Kim, Nam-Il; Choi, Dong-Ho
2014-04-01
The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. Seven governing equations are derived for the coupled axial-flexural-torsional-shearing buckling based on the principle of minimum total potential energy. Based on the present analytical model, three different types of finite composite beam elements, namely, linear, quadratic and cubic elements are developed to analyze the flexural, torsional, and buckling problems. In order to demonstrate the accuracy and superiority of the beam theory and the finite beam elements developed by this study, numerical solutions are presented and compared with the results obtained by other researchers and the detailed three-dimensional analysis results using the shell elements of ABAQUS. Especially, the influences of the modulus ratio and the simplified assumptions in stress-strain relations on the deflection, twisting angle, and critical buckling loads of composite box beams are investigated. [Figure not available: see fulltext.
Critical wall shear stress for the EHEDG test method
DEFF Research Database (Denmark)
Jensen, Bo Boye Busk; Friis, Alan
2004-01-01
In order to simulate the results of practical cleaning tests on closed processing equipment, based on wall shear stress predicted by computational fluid dynamics, a critical wall shear stress is required for that particular cleaning method. This work presents investigations that provide a critical wall shear stress of 3 Pa for the standardised EHEDG cleaning test method. The cleaning tests were performed on a test disc placed in a radial flowcell assay. Turbulent flow conditions were generated and the corresponding wall shear stresses were predicted from CFD simulations. Combining wall shear stress predictions from a simulation using the low Re k-epsilon and one using the two-layer model of Norris and Reynolds were found to produce reliable predictions compared to empirical solutions for the ideal flow case. The comparison of wall shear stress curves predicted for the real RFC with the empirical solution showed that the empirical solution gives a good prediction even in the real RFC from a radius of 15 mm andoutwards.
A shear-shear torsional beam model for nonlinear aeroelastic analysis of tower buildings
Piccardo, G.; Tubino, F.; Luongo, A.
2015-08-01
In this paper, an equivalent one-dimensional beam model immersed in a three-dimensional space is proposed to study the aeroelastic behavior of tower buildings: linear and nonlinear dynamics are analyzed through a simple but realistic physical modeling of the structure and of the load. The beam is internally constrained, so that it is capable to experience shear strains and torsion only. The elasto-geometric and inertial characteristics of the beam are identified from a discrete model of three-dimensional frame, via a homogenization process. The model accounts for the torsional effect induced by the rotation of the floors around the tower axis; the macroscopic shear strain is produced by bending of the columns, accompanied by negligible rotation of the floors. Nonlinear aerodynamic forces are evaluated through the quasi-steady theory. The first aim is to investigate the effect of mechanical and aerodynamic coupling on the critical galloping conditions. Furthermore, the role of aerodynamic nonlinearities on the galloping post-critical behavior is analyzed through a perturbation solution which permits to obtain a reduced one-dimensional dynamical system, capable of capturing the essential dynamics of the problem.
Bierwage, Andreas; Yu, Qingquan; Günter, Sibylle
2007-01-01
The effect of a narrow sub-Alfvénic shear flow layer near the minimum qmin of the tokamak safety factor profile in a configuration with reversed central shear is analyzed. Sufficiently strong velocity shear gives rise to a broad spectrum of fast growing Kelvin-Helmholtz (KH)-like ideal magnetohydrodynamic modes with dominant mode numbers m ,n˜10. Nonlinear simulations with finite resistivity show magnetic reconnection near ripples caused by KH-like vortices, the formation of turbulent structures, and a flattening of the flow profile. The KH modes are compared to double tearing modes that dominate at lower shearing rates. The possible application of these results in tokamaks with internal transport barrier is discussed.
International Nuclear Information System (INIS)
The effect of a narrow sub-Alfvenic shear flow layer near the minimum qmin of the tokamak safety factor profile in a configuration with reversed central shear is analyzed. Sufficiently strong velocity shear gives rise to a broad spectrum of fast growing Kelvin-Helmholtz (KH)-like ideal magnetohydrodynamic modes with dominant mode numbers m,n?10. Nonlinear simulations with finite resistivity show magnetic reconnection near ripples caused by KH-like vortices, the formation of turbulent structures, and a flattening of the flow profile. The KH modes are compared to double tearing modes that dominate at lower shearing rates. The possible application of these results in tokamaks with internal transport barrier is discussed
International Nuclear Information System (INIS)
The microstructure-rheology relationship for a model, thermoreversible nanoparticle gel is investigated using a new technique of time-resolved neutron scattering under steady and time-resolved large amplitude oscillatory shear (LAOS) flows. A 21 vol. % gel is tested with varying strength of interparticle attraction. Shear-induced structural anisotropy is observed as butterfly scattering patterns and quantified through an alignment factor. Measurements in the plane of flow show significant, local anisotropy develops with alignment along the compressional axis of flow, providing new insights into how gels flow. The microstructure-rheology relationship is analyzed through a new type of structure-Lissajous plot that shows how the anisotropic microstructure is responsible for the observed LAOS response, which is beyond a response expected for a purely viscous gel with constant structure. The LAOS shear viscosities are observed to follow the “Delaware-Rutgers” rule. Rheological and microstructural data are successfully compared across a broad range of conditions by scaling the shear rate by the strength of attraction, providing a method to compare behavior between steady shear and LAOS experiments. However, important differences remain between the microstructures measured at comparatively high frequency in LAOS experiments and comparable steady shear experiments that illustrate the importance of measuring the microstructure to properly interpret the nonlinear, dynamic rheological response
Energy Technology Data Exchange (ETDEWEB)
Min Kim, Jung; Kate Gurnon, A.; Wagner, Norman J., E-mail: wagnernj@udel.edu [Department of Chemical and Biomolecular Engineering and Center for Neutron Science, University of Delaware, Newark, Delaware 19716 (United States); Eberle, Aaron P. R. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Porcar, Lionel [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9 (France)
2014-09-01
The microstructure-rheology relationship for a model, thermoreversible nanoparticle gel is investigated using a new technique of time-resolved neutron scattering under steady and time-resolved large amplitude oscillatory shear (LAOS) flows. A 21 vol. % gel is tested with varying strength of interparticle attraction. Shear-induced structural anisotropy is observed as butterfly scattering patterns and quantified through an alignment factor. Measurements in the plane of flow show significant, local anisotropy develops with alignment along the compressional axis of flow, providing new insights into how gels flow. The microstructure-rheology relationship is analyzed through a new type of structure-Lissajous plot that shows how the anisotropic microstructure is responsible for the observed LAOS response, which is beyond a response expected for a purely viscous gel with constant structure. The LAOS shear viscosities are observed to follow the “Delaware-Rutgers” rule. Rheological and microstructural data are successfully compared across a broad range of conditions by scaling the shear rate by the strength of attraction, providing a method to compare behavior between steady shear and LAOS experiments. However, important differences remain between the microstructures measured at comparatively high frequency in LAOS experiments and comparable steady shear experiments that illustrate the importance of measuring the microstructure to properly interpret the nonlinear, dynamic rheological response.
EFFECT OF DIFFERENT POSITION OF SHEAR WALL ON DEFLECTION IN HIGH RISE BUILDING
Rajesh Jayarambhai Prajapati; Vinubhai. R. Patel
2013-01-01
This paper discusses importance of the lateral stiffness of a building on its wind and seismic design. To reduce damage in the event of wind and an earthquake, it is desirable to have large lateral stiffness. Shear walls contribute significant lateral stiffness, strength, and overall ductility and energy dissipation capacity. Therefore we have introduced shear walls at different location on plan of building like side centre shear wall, corner shear wall, shear wall at near to centre of buildi...
Shear crack formation and propagation in fiber reinforced cementitious composites (FRCC)
Paegle, Ieva; Fischer, Gregor
2012-01-01
Knowledge of the mechanisms controlling crack formation, propagation and failure of FRCC under shear loading is currently limited. This paper presents a study that utilized photogrammetry to monitor the shear deformations of two FRCC materials and ordinary concrete (OC). Multiple shear cracks and strain hardening of both FRCC materials was observed under shear loading. The influence of fibers, fiber type, including polyvinyl alcohol (PVA) and polypropylene (PP) fibers, and shear crack angl...
Empirical paths of poles to planes (eppps) constrain the kinematics of geological shear zones
Talbot, Christopher J.
2014-09-01
Ductile shear zones are tabular bodies of deformed rocks bound by less deformed wall rocks. This work introduces a simple empirical approach to analysing the 3D kinematics of shear zones. The orientations of pre-shear planar markers distorted across natural shear zones by local strains are systematically measured and plotted as poles on lower hemisphere equal area projections that constrain smooth empiricalpaths ofpoles toplanes (eppps). Such eppps recording local strain gradients are used to fix a reference frame to the plane of greatest shear in any homogeneous bulk strain. Assuming that space can be taken as a proxy for time, the curvatures of pre-shear planar markers across shear zones are interpreted as the records of the 3D bulk strain histories of shear zones. The sig- or zig-moidal symmetries of sheared markers record different amounts of the same general strain within the same overall movement pattern (i.e. in a constant flow field) whatever its geometry or history. In effect eppps represent the strain memories of shear zones with successively inward readings recording successively younger shearing. In planes other than the bulk XY, great circle eppps indicate simple shear while hyperbolic eppps indicate pure shear. Eppps for suites of shear zones in Proterozoic gneisses in Sweden exhibit the parabolic shapes indicative of pure rather than simple shear.
Insulation interlaminar shear strength testing with compression and irradiation
International Nuclear Information System (INIS)
The Compact Ignition Tokamak (CIT) project identified the need for research and development for the insulation to be used in the toroidal field coils. The requirements included tolerance to a combination of high compression and shear and a high radiation dose. Samples of laminate-type sheet material were obtained from commercial vendors. The materials included various combinations of epoxy, polyimide, E-glass, S-glass, and T-glass. The T-glass was in the form of a three-dimensional weave. The first tests were with 50 x 25 x 1 mm samples. These materials were loaded in compression and then to failure in shear. At 345-MPa compression, the interlaminar shear strength was generally in the range of 110 to 140 MPa for the different materials. A smaller sample configuration was developed for irradiation testing. The data before irradiation were similar to those for the larger samples but approximately 10% lower. Limited fatigue testing was also performed by cycling the shear load. No reduction in shear strength was found after 50,000 cycles at 90% of the failure stress. Because of space limitations, only three materials were chosen for irradiation: two polyimide systems and one epoxy system. All used boron-free glass. The small shear/compression samples and some flexure specimens were irradiated to 4 x 109 and 2 x 1010 rad in the Advanced Technology Reactor at Idaho National Engineering Laboratory. A lead shield was used to ensure that the majority of the dose was from neutrons. The shear strength with compression before and after irradiation at the lower dose was determined. Flexure strength and the results from irradiation at the higher dose level will be available in the near future. 7 refs., 7 figs., 2 tabs
NUMERICAL SIMULATION OF AN AGRICULTURAL SOIL SHEAR STRESS TEST
Directory of Open Access Journals (Sweden)
Salvatore Faugno
2007-03-01
Full Text Available In this work a numerical simulation of agricultural soil shear stress tests was performed through soil shear strength data detected by a soil shearometer. We used a soil shearometer available on the market to measure soil shear stress and constructed special equipment that enabled automated detection of soil shear stress. It was connected to an acquisition data system that displayed and recorded soil shear stress during the full field tests. A soil shearometer unit was used to the in situ measurements of soil shear stress in full field conditions for different types of soils located on the right side of the Sele river, at a distance of about 1 km from each other, along the perpendicular to the Sele river in the direction of the sea. Full field tests using the shearometer unit were performed alongside considered soil characteristic parameter data collection. These parameter values derived from hydrostatic compression and triaxial tests performed on considered soil samples and repeated 4 times and we noticed that the difference between the maximum and minimum values detected for every set of performed tests never exceeded 4%. Full field shear tests were simulated by the Abaqus program code considering three different material models of soils normally used in the literature, the Mohr-Coulomb, Drucker-Prager and Cam-Clay models. We then compared all data outcomes obtained by numerical simulations with those from the experimental tests. We also discussed any further simulation data results obtained with different material models and selected the best material model for each considered soil to be used in tyre/soil contact simulation or in soil compaction studies.
Scientific Electronic Library Online (English)
Jessé Siqueira, Ortiz; Ciniro, Costa; Cledson Augusto, Garcia; Liciana Vaz de Arruda, Silveira.
2005-12-01
Full Text Available Objetivou-se avaliar o efeito de três níveis de proteína (15, 20 e 25% PB) na ração sobre as medidas objetivas das carcaças e do músculo Longissimus dorsi, os pesos e rendimentos dos cortes, além da composição química e maciez da carne de cordeiros Suffolk alimentados e terminados em creep feeding. [...] Foram utilizados 15 cordeiros inteiros, originados de partos simples, abatidos ao atingirem peso vivo final de 28 kg. As carcaças foram mantidas em câmara de refrigeração a 5ºC, durante 24 horas, para registro das medidas objetivas, realizado após separação dos cortes comerciais, na meia-carcaça esquerda. A área do músculo Longissimus dorsi foi mensurada para determinação da área de olho de lombo (AOL cm²). No lombo esquerdo congelado, realizou-se a análise de composição química e, no direito, também congelado, o teste de maciez peloWarner Bratzler Shear Force. Os níveis de proteína bruta não influenciaram as medidas objetivas de carcaça nem as do músculo Longissimus dorsi. Houve efeito significativo para peso e rendimento da paleta, com superioridade para o tratamento contendo 25% de proteína bruta. Nas análises químicas do músculo Longissimus dorsi, observou-se efeito significativo para extrato etéreo, cinzas e maciez. No sistema de alimentação e terminação de cordeiros Suffolk em creep feeding, a ração formulada com farelo de soja como fonte protéica deve ser balanceada com 25% de proteína bruta por diminuir o teor de gordura e melhorar a maciez da carne e o peso e rendimento da paleta, sem afetar as medidas objetivas da carcaça, os demais pesos e os rendimentos dos cortes. Abstract in english The objective of this trial was to evaluate the effects of three concentrate protein levels (15, 20 or 25% CP) on measurements of carcass and Longissimus dorsi muscle, weights and yields of cuts, and chemical composition and tenderness of meat of Suffolk lambs in creep feeding. Fifteen single birth [...] lambs were used in this study. Lambs were slaughtered when they reached a final body weight of 28 kg. After slaughter, carcasses were maintained in a refrigerator at 5ºC for 24 hours followed by measurements on the left half carcass done after separation of the commercial cuts. The Longissimus dorsi area was measured to obtain the loin eye area (LEA, cm2). Both left and right loins were frozen; the left was used for determination of chemical composition while the right for a tenderness test ("Warner Bratzler Shear Force"). Different concentrate crude protein levels did not affect carcass measurements as well as measurements on the Longissimus dorsi. However, significant differences among treatments were observed for weight and yield of shoulder clod with the highest values found on the 25% crude protein concentrate. Chemical analyses of Longissimus dorsi showed significant differences across treatments for ether extract, ash, and tenderness. It can be concluded that the diet containing soybean meal must be formulated to yield 25% of crude protein because it reduced the fat content and improved the tenderness of the meat. In addition, it also increased both weight and yield of shoulder clod with no changes on carcass measurements and weight and yields of the remaining cuts.
Directory of Open Access Journals (Sweden)
Jessé Siqueira Ortiz
2005-12-01
Full Text Available Objetivou-se avaliar o efeito de três níveis de proteína (15, 20 e 25% PB na ração sobre as medidas objetivas das carcaças e do músculo Longissimus dorsi, os pesos e rendimentos dos cortes, além da composição química e maciez da carne de cordeiros Suffolk alimentados e terminados em creep feeding. Foram utilizados 15 cordeiros inteiros, originados de partos simples, abatidos ao atingirem peso vivo final de 28 kg. As carcaças foram mantidas em câmara de refrigeração a 5ºC, durante 24 horas, para registro das medidas objetivas, realizado após separação dos cortes comerciais, na meia-carcaça esquerda. A área do músculo Longissimus dorsi foi mensurada para determinação da área de olho de lombo (AOL cm². No lombo esquerdo congelado, realizou-se a análise de composição química e, no direito, também congelado, o teste de maciez peloWarner Bratzler Shear Force. Os níveis de proteína bruta não influenciaram as medidas objetivas de carcaça nem as do músculo Longissimus dorsi. Houve efeito significativo para peso e rendimento da paleta, com superioridade para o tratamento contendo 25% de proteína bruta. Nas análises químicas do músculo Longissimus dorsi, observou-se efeito significativo para extrato etéreo, cinzas e maciez. No sistema de alimentação e terminação de cordeiros Suffolk em creep feeding, a ração formulada com farelo de soja como fonte protéica deve ser balanceada com 25% de proteína bruta por diminuir o teor de gordura e melhorar a maciez da carne e o peso e rendimento da paleta, sem afetar as medidas objetivas da carcaça, os demais pesos e os rendimentos dos cortes.The objective of this trial was to evaluate the effects of three concentrate protein levels (15, 20 or 25% CP on measurements of carcass and Longissimus dorsi muscle, weights and yields of cuts, and chemical composition and tenderness of meat of Suffolk lambs in creep feeding. Fifteen single birth lambs were used in this study. Lambs were slaughtered when they reached a final body weight of 28 kg. After slaughter, carcasses were maintained in a refrigerator at 5ºC for 24 hours followed by measurements on the left half carcass done after separation of the commercial cuts. The Longissimus dorsi area was measured to obtain the loin eye area (LEA, cm2. Both left and right loins were frozen; the left was used for determination of chemical composition while the right for a tenderness test ("Warner Bratzler Shear Force". Different concentrate crude protein levels did not affect carcass measurements as well as measurements on the Longissimus dorsi. However, significant differences among treatments were observed for weight and yield of shoulder clod with the highest values found on the 25% crude protein concentrate. Chemical analyses of Longissimus dorsi showed significant differences across treatments for ether extract, ash, and tenderness. It can be concluded that the diet containing soybean meal must be formulated to yield 25% of crude protein because it reduced the fat content and improved the tenderness of the meat. In addition, it also increased both weight and yield of shoulder clod with no changes on carcass measurements and weight and yields of the remaining cuts.
Directory of Open Access Journals (Sweden)
Jane M. RUBENSAM
1998-10-01
Full Text Available Amostras de contrafilé (músculo L. dorsi provenientes de 26 bovinos, sendo 14 Polled Hereford (HH, sete 3/4Hereford 1/4Nelore (3/4H1/4N e cinco 5/8Hereford 3/8Nelore (5/8H3/8N, machos castrados, abatidos aos dois anos de idade, foram coletadas 24 h após o abate e analisadas quanto à atividade de calpastatina e textura, tanto no 1o dia post mortem quanto após um período de maturação de 10 dias a 2o C. A atividade de calpastatina foi determinada pelo ensaio de inibição da m-calpaína e a textura através da força de cisalhamento (Warner-Bratzler. A carne de novilhos 5/8H3/8N apresentou, no 1o dia, maiores (p0,05 entre os grupos HH e 3/4H1/4N para as mesmas características. Após 10 dias, houve uma diferença na atividade de calpastatina, porém não significativa (p>0,05, entre o grupo 5/8H3/8N (1,57U/g e os demais (HH=1,23U/g; 3/4H1/4N=1,35U/g, e diferença significativa entre os grupos HH e 5/8H3/8N para força de cisalhamento (3,67 e 5,00kg, respectivamente. Conclui-se que a atividade de calpastatina determinada 24 h post mortem pode ser útil para a previsão da textura da carne, maturada ou não, em programas de melhoramento genético, e que a participação crescente do genótipo Bos indicus nos rebanhos da Região Sul, a par das conhecidas vantagens zootécnicas, poderá resultar em carne de pior textura.Boneless rib steaks (L. dorsi muscle from 26 two years old steers, 14 Polled Hereford, seven 3/4Hereford 1/4Nelore (3/4H1/4N and five 5/8Hereford 3/8Nelore (5/8H3/8N, were collected 24 hs after slaughter and analysed for calpastatin activity and texture at the 1st day post mortem and at the 10th day of aging at 2o C. Calpastatin activity was determined by m-calpain inhibition assay and texture by shear force (Warner-Bratzler. Beef from 5/8H3/8N steers showed higher (p0.05 were detected in the same traits between groups HH and 3/4H1/4N. After 10 days of aging, there was a difference in calpastatin activity, although non-significant (p>0.05, amongst group 5/8H3/8N (1.57U/g and the others (HH=1.23U/g; 3/4H1/4N=1.35U/g, and a significant difference in shear force between groups HH and 5/8H3/8N (3.67 and 5.00kg, respectively. It was concluded that the calpastatin activity determined 24 hs post mortem can be useful to predict the texture of beef, aged or not, in genetic improvement programs. Also, the increasing participation of Bos indicus genotype in the South Region herds of cattle, besides the productivity advantages, may result in beef of lower texture quality.
Directory of Open Access Journals (Sweden)
Cristian Faturi
2002-09-01
Full Text Available Foram estudadas as características quantitativas e qualitativas da carcaça e da carne de novilhos pertencentes a quatro grupos genéticos, Charolês (C, Nelore (N, mestiços com predominância de sangue C (3/4 C 1/4 N e 5/8 C 3/8 N - CRC e mestiços com predominância de sangue N (3/4 N 1/4 C e 5/8 N 3/8 C - CRN, submetidos a quatro tratamentos alimentares durante a fase de terminação em confinamento, os quais corresponderam aos seguintes níveis de substituição do grão de sorgo (Sorghum bicolor L. Moench por grão de aveia preta (Avena strigosa no concentrado: 0, 33, 66 e 100%. O volumoso utilizado nos primeiros 35 dias do confinamento foi a silagem de sorgo forrageiro (Sorghum bicolor L. Moench e nos 32 dias restantes, silagem de milho (Zea mays. A relação volumoso:concentrado durante todo o período de confinamento foi de 60:40. Não foi observado efeito de tratamento para nenhuma das características avaliadas. No entanto, avaliando grupo genético, verificou-se que os animais N apresentaram menores peso de abate e peso de carcaça fria que os demais, apresentando, também, menor porcentagem do corte comercial costilhar e maior do corte dianteiro, não diferindo, no entanto, quanto à porcentagem do corte traseiro. Os animais C e CRC apresentaram maior porcentagem de músculo e área do músculo Longissimus dorsi em relação aos N e CRN, porém apresentaram menor porcentagem de gordura na carcaça. Os animais N apresentaram, ainda, carne com textura mais grosseira, carne menos macia, quando avaliada pelo aparelho Warner-Bratzler Shear, e maior perda durante o descongelamento. Não foram verificadas diferenças, entre grupos genéticos, para as características espessura de gordura de cobertura, cor, marmoreio, maciez avaliada pelo painel, palatabilidade, suculência e quebra durante a cocção.The objective of the experiment was to study the quantitative and qualitative characteristics of carcass and meat of steers of four genetic groups, Charolais (C, Nellore (N, crossbreds with predominance of C (3/4 C 1/4 N and 5/8 C 3/8 N - CRC and crossbreds with predominance of N (3/4 N 1/4 C and 5/8 N 3/8 C - CRN, submitted to four feed treatments during the feedlot finishing phase, which were the following levels of substitution of sorghum grain (Sorghum bicolor L. Moench by oat grain (Avena strigosa in the concentrate: 0%; 33%; 66% and 100%. The roughage used in the first 35 days of feedlot was sorghum silage (Sorghum bicolor L. Moench, and in the last 32 days the corn silage (Zea mays was used. The roughage:concentrate ratio during the whole feedlot was 60:40. No significant effect of substitution level was observed for carcass and meat characteristics. However, analysing the genetic group effect, it was observed that N animals showed lower slaughter and cold carcass weight than the other genetic groups, lower sidecut percentage and higher percentage of forequarter, not differing in the sawcut percentage. The C and CRC animals showed higher muscle percentage in the carcass and higher Longissimus dorsi muscle area in relation to N and CRN, but showed lower fat percentage in the carcass. The N showed meat with coarser texture, lower tenderness, when evaluated by Warner-Bratzler Shear, and higher thawing losses. No differences were observed among genetic groups for subcutaneous fat thickness, meat color, marbling, tenderness evaluated by the test panel, palatability, juiciness and cooking losses.
Scientific Electronic Library Online (English)
Cristian, Faturi; João, Restle; Ivan Luiz, Brondani; José Henrique Souza da, Silva; Miguelangelo Ziegler, Arboitte; Charles de Oliveira, Carrilho; Luiz Antero de Oliveira, Peixoto.
2002-09-01
Full Text Available Foram estudadas as características quantitativas e qualitativas da carcaça e da carne de novilhos pertencentes a quatro grupos genéticos, Charolês (C), Nelore (N), mestiços com predominância de sangue C (3/4 C 1/4 N e 5/8 C 3/8 N - CRC) e mestiços com predominância de sangue N (3/4 N 1/4 C e 5/8 N 3 [...] /8 C - CRN), submetidos a quatro tratamentos alimentares durante a fase de terminação em confinamento, os quais corresponderam aos seguintes níveis de substituição do grão de sorgo (Sorghum bicolor L. Moench) por grão de aveia preta (Avena strigosa) no concentrado: 0, 33, 66 e 100%. O volumoso utilizado nos primeiros 35 dias do confinamento foi a silagem de sorgo forrageiro (Sorghum bicolor L. Moench) e nos 32 dias restantes, silagem de milho (Zea mays). A relação volumoso:concentrado durante todo o período de confinamento foi de 60:40. Não foi observado efeito de tratamento para nenhuma das características avaliadas. No entanto, avaliando grupo genético, verificou-se que os animais N apresentaram menores peso de abate e peso de carcaça fria que os demais, apresentando, também, menor porcentagem do corte comercial costilhar e maior do corte dianteiro, não diferindo, no entanto, quanto à porcentagem do corte traseiro. Os animais C e CRC apresentaram maior porcentagem de músculo e área do músculo Longissimus dorsi em relação aos N e CRN, porém apresentaram menor porcentagem de gordura na carcaça. Os animais N apresentaram, ainda, carne com textura mais grosseira, carne menos macia, quando avaliada pelo aparelho Warner-Bratzler Shear, e maior perda durante o descongelamento. Não foram verificadas diferenças, entre grupos genéticos, para as características espessura de gordura de cobertura, cor, marmoreio, maciez avaliada pelo painel, palatabilidade, suculência e quebra durante a cocção. Abstract in english The objective of the experiment was to study the quantitative and qualitative characteristics of carcass and meat of steers of four genetic groups, Charolais (C), Nellore (N), crossbreds with predominance of C (3/4 C 1/4 N and 5/8 C 3/8 N - CRC) and crossbreds with predominance of N (3/4 N 1/4 C and [...] 5/8 N 3/8 C - CRN), submitted to four feed treatments during the feedlot finishing phase, which were the following levels of substitution of sorghum grain (Sorghum bicolor L. Moench) by oat grain (Avena strigosa) in the concentrate: 0%; 33%; 66% and 100%. The roughage used in the first 35 days of feedlot was sorghum silage (Sorghum bicolor L. Moench), and in the last 32 days the corn silage (Zea mays) was used. The roughage:concentrate ratio during the whole feedlot was 60:40. No significant effect of substitution level was observed for carcass and meat characteristics. However, analysing the genetic group effect, it was observed that N animals showed lower slaughter and cold carcass weight than the other genetic groups, lower sidecut percentage and higher percentage of forequarter, not differing in the sawcut percentage. The C and CRC animals showed higher muscle percentage in the carcass and higher Longissimus dorsi muscle area in relation to N and CRN, but showed lower fat percentage in the carcass. The N showed meat with coarser texture, lower tenderness, when evaluated by Warner-Bratzler Shear, and higher thawing losses. No differences were observed among genetic groups for subcutaneous fat thickness, meat color, marbling, tenderness evaluated by the test panel, palatability, juiciness and cooking losses.
Examining the Displacement of Energy during Formation of Shear Bands
Hernandez, M.; Hilley, G. E.
2011-12-01
M.X. Hernandez, G. Hilley Department of Geological and Environmental Sciences, Stanford University, Stanford, CA This study has originated from an experimental (sandbox) setting that we have previously used to document the link between the kinematics and dynamics of deforming sand in the verge of frictional failure. Our initial experimental setting included a load control system that allowed us to track the changes in load, that when applied to the sand, deform and generate individual shear bands or localized faults. Over the course of earlier experiments, three cameras located at different positions outside the sandbox monitored the movement throughout the run. This current stage of analysis includes using computer programs such as QuickTime to create image sequences of the shear band formation, and Microsoft Excel to visually graph and plot each data sequence. This allows us to investigate the correlation between changes in work measured within our experiments, the construction of topography, slip along shear bands, and the creation of new shear bands. We observed that the measured load generally increased during the experiment to maintain a constant displacement rate as the sand wedge thickened and modeled topography increased. Superposed on this trend were periodic drops in load that appeared temporally coincident with the formation of shear bands in the sand. Using the time series of the loads applied during the experiment, changes in the position of the backstop over time, and the loads measured before, during, and after the time of each shear band formation, we are examining the fraction of the apples work that is absorbed by friction and shear band formation, and what fraction of the apples work is expended in increasing the potential energy of the thickening sand wedge. Our results indicate that before the formation of a continuous shear band, the rate of work done on the sand by the experimental apparatus decreases. This may suggest that once formed, work done against friction in the sand is significantly less than that expended in forming shear bands and thickening the sand wedge.
Shear strength of vibrated granular/granular-fluid mixtures
Utter, Brian; Herman, Ralph; Foltz, Ben
2011-03-01
The behavior of dense granular materials can be characterized by the continuous forming and breaking of a strong force network resisting flow. This jamming/unjamming behavior is typical of a variety of systems and is influenced by factors such as grain packing fraction, applied shear stress, and the random kinetic energy of the particles. We present experiments on shear strength of granular and granular-water mixtures under the influence of external vibrations, one parameter that leads to unjamming. We use low vibration (< 1g) and slow shear and measure avalanching statistics in a rotating drum and the torque required to move a stirrer through a sand/water mixture. We find that external vibration (i) increases granular strength at small vibrations in the dry system, (ii) removes history dependence (memory), and (iii) decreases shear strength at all accessible saturation levels in the sand-fluid system. Additionally, shear strength is found to be smallest for both dry and completely saturated mixtures. Additional ongoing experiments probe beyond a dimensionless acceleration of 1 and explore jamming and surface chemistry effects in the avalanching flow of granular/fluid mixtures.
Copper-Filled Electrically Conductive Adhesives with Enhanced Shear Strength
Ho, Li-Ngee; Nishikawa, Hiroshi
2014-09-01
In this study, the effects of diethyl carbitol (diluent) and tertiary amines on the electrical, mechanical, and rheological properties of the Cu-filled polyurethane-based electrically conductive adhesives (ECAs) were investigated. Significant difference could be observed in the electrical resistivity and shear strength of ECA prepared with different amount of diethyl carbitol. Reduced electrical resistivity was found in ECAs prepared with addition of tertiary amines, but no obvious change was observed in the shear strength of the ECA joint. Rheological property of the ECA paste was investigated in order to understand the correlation of the viscosity of ECA paste and electrical resistivity and shear strength of ECA joint. Results revealed that decrease in viscosity of the ECA paste reduced electrical resistivity and enhanced shear strength of ECA joint. A Cu-filled polyurethane-based ECA with considerably low electrical resistivity at the magnitude order range of 10-3 ? cm, and significantly high shear strength (above 17 MPa) could be achieved.
Estimation of shear stress in counter-current annular flow
International Nuclear Information System (INIS)
The accuracy to which the friction factor is correlated is important in counter-current flow (CCF) analysis using a two-fluid model. Current two-fluid model codes use correlations of friction factors developed for co-current flow, or correlations developed on the assumption of zero wall shear stress. An assessment of two-fluid model codes with these existing correlations shows that the downward flow rate of water is overestimated. An analytical model is developed to calculate the shear stress profile in a liquid film of the CCF in order to obtain information on the shear stress between the interface and the wall. Both this analysis and Bharathan's CCF data show that the wall shear stress acting on the falling water film is approximately of same order as the interfacial shear stress, and the correlation for co-current flow cannot be applied to CCF. Tentative correlations of interfacial and wall friction factors are developed based on the results of the present study. (author)
Rocking shear wall foundations in regions of moderate seismicity
Scientific Electronic Library Online (English)
J E, van der Merwe; J A, Wium.
Full Text Available This paper presents a study which investigates the feasibility of a concept to reduce the size of shear wall foundations for earthquake forces in regions of moderate seismicity. The approach is to allow rocking of the shear wall foundation and to include the contribution of a shear wall and reinforc [...] ed concrete frame to assist as a lateral force-resisting system. A simplified multi degree-of-freedom model with non-linear material properties was used to investigate this lateral-force-resisting system subjected to base accelerations from recorded ground motions. An example building was studied with the shear wall foundation designed to resist 0%, 20%, 40%, 60%, 80% and 100% of the design overturning moment from the seismic event. Non-linear time-history analyses were performed with input from seven scaled ground-motion records. It is shown that the concept warrants more detailed studies and that a significantly reduced shear wall foundation size is possible without failure of the lateral force-resisting system.
The shear diffusion coefficient for generalized theories of gravity
International Nuclear Information System (INIS)
Near the horizon of a black brane in Anti-de Sitter (AdS) space and near the AdS boundary, the long-wavelength fluctuations of the metric exhibit hydrodynamic behaviour. The gauge-gravity duality then relates the boundary hydrodynamics for generalized gravity to that of gauge theories with large finite values of 't Hooft coupling. We discuss, for this framework, the hydrodynamics of the shear mode in generalized theories of gravity in d+1 dimensions. It is shown that the shear diffusion coefficients of the near-horizon and boundary hydrodynamics are equal and can be expressed in a form that is purely local to the horizon. We find that the Einstein-theory relation between the shear diffusion coefficient and the shear viscosity to entropy ratio is modified for generalized gravity theories: Both can be explicitly written as the ratio of a pair of polarization-specific gravitational couplings but implicate differently polarized gravitons. Our analysis is restricted to the shear-mode fluctuations for simplicity and clarity; however, our methods can be applied to the hydrodynamics of all gravitational and matter fluctuation modes
Shear-Rate-Independent Diffusion in Granular Flows.
Fan, Yi; Umbanhowar, Paul B; Ottino, Julio M; Lueptow, Richard M
2015-08-21
We computationally study the behavior of the diffusion coefficient D in granular flows of monodisperse and bidisperse particles spanning regions of relatively high and low shear rate in open and closed laterally confined heaps. Measurements of D at various flow rates, streamwise positions, and depths collapse onto a single curve when plotted as a function of ?[over ?]d[over ¯]^{2}, where d[over ¯] is the local mean particle diameter and ?[over ?] is the local shear rate. When ?[over ?] is large, D is proportional to ?[over ?]d[over ¯]^{2}, as in previous studies. However, for ?[over ?]d[over ¯]^{2} below a critical value, D is independent of ?[over ?]d[over ¯]^{2}. The acceleration due to gravity g and particle stiffness (or, equivalently, the binary collision time t_{c}) together determine the transition in D between regimes. This suggests that while shear rate and particle size determine diffusion at relatively high shear rates in surface-driven flows, diffusion at low shear rates is an elastic phenomenon with time and length scales dependent on gravity (sqrt[d[over ¯]/g]) and particle stiffness (t_{c}sqrt[d[over ¯]g]), respectively. PMID:26340210
Ordering fluctuations in a shear-banding wormlike micellar system
DEFF Research Database (Denmark)
Angelico, R.; Rossi, C. Oliviero
2010-01-01
We present a first investigation about the non-linear flow properties and transient orientational-order fluctuations observed in the shear-thinning lecithin–water–cyclohexane wormlike micellar system at a concentration near to the zero-shear isotropic–nematic phase transition. From rheological measurements the stress plateau was found shifted to very low values of the applied shear rate , compared to most of the concentrated living polymer systems reported in the literature. Rheo-small angle neutron scattering (Rheo-SANS) experiments performed in the flow-vorticity plane revealed periodical fluctuations of both the order parameter P2 and the angular deviation from the vorticity axis as determined from the scattering peaks. The periods of the oscillations were not found to depend on imposed . A theoretical model was also developed to explain the oscillatory dynamics of the shear-induced nematic order parameter in terms of the presence of standing waves of the director orientation profile along the circumference of the Couette cell. The experimental results of the periodic order parameter fluctuations together with their theoretical modelling shed significant new insights on the shear banding phenomenon, particularly its microscopic mechanism.
Instabilities and vortex dynamics in shear flow of magnetized plasmas
International Nuclear Information System (INIS)
Gradient-driven instabilities and the subsequent nonlinear evolution of generated vortices in sheared E x B flows are investigated for magnetized plasmas with and without gravity (magnetic curvature) and magnetic shear by using theory and implicit particle simulations. In the linear eigenmode analysis, the instabilities considered are the Kelvin-Helmholtz (K-H) instability and the resistive interchange instability. The presence of the shear flow can stabilize these instabilities. The dynamics of the K-H instability and the vortex dynamics can be uniformly described by the initial flow pattern with a vorticity localization parameter ?. The observed growth of the K-H modes is exponential in time for linearly unstable modes, secular for marginal mode, and absent until driven nonlinearly for linearly stable modes. The distance between two vortex centers experiences rapid merging while the angle ? between the axis of vortices and the external shear flow increases. These vortices proceed toward their overall coalescence, while shedding small-scale vortices and waves. The main features of vortex dynamics of the nonlinear coalescence and the tilt or the rotational instabilities of vortices are shown to be given by using a low dimension Hamiltonian representation for interacting vortex cores in the shear flow. 24 refs., 19 figs., 1 tab
Wall Orientation and Shear Stress in the Lattice Boltzmann Model
Matyka, Maciej; Miros?aw, ?ukasz
2013-01-01
The wall shear stress is a quantity of profound importance for clinical diagnosis of artery diseases. The lattice Boltzmann is an easily parallelizable numerical method of solving the flow problems, but it suffers from errors of the velocity field near the boundaries which leads to errors in the wall shear stress and normal vectors computed from the velocity. In this work we present a simple formula to calculate the wall shear stress in the lattice Boltzmann model and propose to compute wall normals, which are necessary to compute the wall shear stress, by taking the weighted mean over boundary facets lying in a vicinity of a wall element. We carry out several tests and observe an increase of accuracy of computed normal vectors over other methods in two and three dimensions. Using the scheme we compute the wall shear stress in an inclined and bent channel fluid flow and show a minor influence of the normal on the numerical error, implying that that the main error arises due to a corrupted velocity field near ...