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1

A database consisting of 331 beef animals (Brahman-crossbred) was used to determine the multivariate relationships between carcass and beef palatability traits of Venezuelan cattle and to develop prediction equations for Warner-Bratzler shear force (WBSF). The first three principal components (PC) explained 77.53% of the standardized variance. Equations were obtained for each sex class and the total variability observed in WBSF could be explained by its orthogonal regression with carcass weight (CW), fat cover (FC), fat thickness (FT), and skeletal maturity (SM). Prediction equations were: WBSF(steers)=3.566+0.003(CW)-0.033(FC)-0.015(FT)+0.0004(SM); WBSF(heifers)=4.824+0.002(CW)-0.229(FC)+0.096(FT)-0.064(SM); WBSF(bulls)=3.516+0.009(CW)+0.154(FC)-0.129(FT)-0.006(SM). A higher proportion of the variation was explained by the PC when variables of greater weight were selected to define each PC. The equation set presented herein could become an important tool to improve the Venezuelan carcass grading system. PMID:23261538

Jerez-Timaure, N; Huerta-Leidenz, N; Ortega, J; Rodas-González, A

2013-03-01

2

We performed a genome-wide association study for Warner-Bratzler shear force (WBSF), a measure of meat tenderness, by genotyping 3360 animals from five breeds with 54 790 BovineSNP50 and 96 putative single-nucleotide polymorphisms (SNPs) within ?-calpain [HUGO nomenclature calpain 1, (mu/I) large subunit; CAPN1] and calpastatin (CAST). Within- and across-breed analyses estimated SNP allele substitution effects (ASEs) by genomic best linear unbiased prediction (GBLUP) and variance components by restricted maximum likelihood under an animal model incorporating a genomic relationship matrix. GBLUP estimates of ASEs from the across-breed analysis were moderately correlated (0.31-0.66) with those from the individual within-breed analyses, indicating that prediction equations for molecular estimates of breeding value developed from across-breed analyses should be effective for genomic selection within breeds. We identified 79 genomic regions associated with WBSF in at least three breeds, but only eight were detected in all five breeds, suggesting that the within-breed analyses were underpowered, that different quantitative trait loci (QTL) underlie variation between breeds or that the BovineSNP50 SNP density is insufficient to detect common QTL among breeds. In the across-breed analysis, CAPN1 was followed by CAST as the most strongly associated WBSF QTL genome-wide, and associations with both were detected in all five breeds. We show that none of the four commercialized CAST and CAPN1 SNP diagnostics are causal for associations with WBSF, and we putatively fine-map the CAPN1 causal mutation to a 4581-bp region. We estimate that variation in CAST and CAPN1 explains 1.02 and 1.85% of the phenotypic variation in WBSF respectively. PMID:22497286

McClure, M C; Ramey, H R; Rolf, M M; McKay, S D; Decker, J E; Chapple, R H; Kim, J W; Taxis, T M; Weaber, R L; Schnabel, R D; Taylor, J F

2012-12-01

3

The objective of this study was to assess the effects of treating chicken breast forequarters with sodium tripolyphosphate (STPP) after various postchill storage times on meat quality. Sixty-four commercially reared broilers (two replicates of 32 birds each) were slaughtered and chilled, and then the forequarters (split breasts with spine and ribs) were harvested and aged for 0, 120, 180, or 240 min postchill. After each aging period, one forequarter from each of 16 birds was marinated with a NaCl solution and the opposite forequarter was marinated with the same NaCl solution containing STPP. The quarters were then cooked and the following traits measured: marinade absorption, cooking loss, objective color values, and Warner-Bratzler shear values. As aging time prior to marination increased, cooking loss and redness of the cooked meat decreased, but marinade absorption and the color values were unaffected. The STPP treatment increased marinade absorption, decreased cooking losses, and decreased cooked meat redness (P STPP-treated breast meat. When the STPP treatment was applied immediately after carcass chilling, the STPP-treated meat exhibited shear values more than 60% greater than those of the controls (9.14 and 5.69 kg, respectively). Results indicate that time postchill at which further processed products are treated with STPP can have a significant effect on quality, especially cooked product texture. PMID:9355155

Young, L L; Lyon, C E

1997-11-01

4

Directory of Open Access Journals (Sweden)

Full Text Available 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 water immersion (0.3 °C, 50 min or chilled by cross-flow cold, dry air (0.7 °C, 150 min. Pectoralis (p. major and p. minor were removed from the bone at 4 h postmortem. Shear force was measured using a Warner-Bratzler (WB method and WHC was estimated using cooking yield, drip loss, amount of bound water (filter paper method and water uptake (swell/centrifugation method. Regardless of muscle type, the WB shear force value of AC samples was significantly lower than that of hot-boned samples; however, there was no difference in the shear force between AC and IC. Regardless of measurement methods, there were no differences (P > 0.05 in WHC between the three treatments. These results demonstrate that when compared to no chill, AC followed by 4 h postmortem deboning can lead to a difference in WB shear values while WHC properties can be retained. For broiler breast meat deboned 4 h postmortem, AC does not result in any significant differences in shear force and WHC when compared to IC.

H. Zhuang

2008-01-01

5

Directory of Open Access Journals (Sweden)

Full Text Available Sun-dried beef is a frequently consumed and valued product in Brazil, however, there have been no scientific studies on its texture. To assess the tenderness of sun-dried beef, an instrumental analysis (Warner-Bratzler Shear Force; WBSF, a sensory analysis (Quantitative Descriptive Analysis; QDA and the sarcomere length (SL were used as indicators. Significant differences were observed among the sun-dried beef samples. Sample 3 (composed of sun-dried meat purchased at three fairs from Region 3 in the city of João Pessoa-PB was considered the most tender by the assessors, with a score of 6.7, and its WBSF analysis revealed a maximum value of 2.70 kgf. Additionally, this sample exhibited the highest SL value (1.89 µm. Samples 1 and 2 (composed of sun-dried meat purchased at three fairs from Regions 1 and 2, respectively, in the city of João Pessoa exhibited very similar tenderness values (WBSF and QDA but differed in their SL values, which suggested that sample 2 was the least tender. In conclusion, these results demonstrate that the studied parameters are complementary and can be used as tenderness indicators for sun-dried beef. However, although the difference was beyond the detection limit of the assessors and the texturometer, the SL analysis appears to have been the most effective.

Marta Madruga

2013-08-01

6

The tenderness and palatability of retail and food service beef steaks from across the United States (12 cities for retail, 5 cities for food service) were evaluated using Warner-Bratzler shear (WBS) and consumer sensory panels. Subprimal postfabrication storage or aging times at retail establishments averaged 20.5 d with a range of 1 to 358 d, whereas postfabrication times at the food service level revealed an average time of 28.1 d with a range of 9 to 67 d. Approximately 64% of retail steaks were labeled with a packer/processor or store brand. For retail, top blade had among the lowest (P 0.05) in WBS values between moist-heat and dry-heat cookery methods for the top round and bottom round steaks or between enhanced (contained salt or phosphate solution) or nonenhanced steaks. Food service top loin and rib eye steaks had the lowest (P < 0.05) WBS values compared with top sirloin steaks. Retail top blade steaks and food service top loin steaks received among the greatest (P < 0.05) consumer sensory panel ratings compared with the other steaks evaluated. Prime food service rib eye steaks received the greatest ratings (P < 0.05) for overall like, like tenderness, tenderness level, like juiciness, and juiciness level, whereas ungraded rib eye steaks received the lowest ratings (P < 0.05) for like tenderness and tenderness level. The WBS values for food service steaks were greater (P < 0.05) for the Select and ungraded groups compared with the Prime, Top Choice, and Low Choice groups. The WBS values and sensory ratings were comparable to the last survey, signifying that no recent or substantive changes in tenderness have occurred. PMID:23230117

Guelker, M R; Haneklaus, A N; Brooks, J C; Carr, C C; Delmore, R J; Griffin, D B; Hale, D S; Harris, K B; Mafi, G G; Johnson, D D; Lorenzen, C L; Maddock, R J; Martin, J N; Miller, R K; Raines, C R; VanOverbeke, D L; Vedral, L L; Wasser, B E; Savell, J W

2013-02-01

7

To determine the effects of zilpaterol hydrochloride (ZH; 6.8 g/t on 90% DM basis) feeding duration (0, 20, 30, and 40 d) on Warner-Bratzler shear force (WBSF) of longissimus lumborum (LL), triceps brachii (TB), and gluteus medius (GM) muscles, beef from feeding trials was collected and shipped to participating universities. Animals were slaughtered at commercial processing facilities across the United States. Strip loin, shoulder clod, and top sirloin butt subprimals (IMPS 180, 114, and 184, respectively) were obtained from a portion of USDA Choice and Select grade carcasses for WBSF using standardized procedures and equipment. Feeding ZH increased (P < 0.001) LL WBSF values of USDA Choice and Select steaks. A significant linear contrast existed for both quality grades, indicating increased WBSF values were associated with longer feeding durations. Increased postmortem aging decreased LL WBSF of control and treated steaks. Postmortem aging from 7 to 21 d decreased LL WBSF values by 17.6 and 16.4% for USDA Choice and Select steaks, respectively. The percentage of LL steaks from ZH-supplemented cattle with a WBSF value <4.5 kg was significantly less than control steaks for both quality grades. Postmortem aging from 7 to 21 d postmortem increased (P < 0.001) the percentage of LL Choice and Select steaks with WBSF <4.5 kg for all ZH feeding durations. Feeding ZH for 20, 30, or 40 d increased (P < 0.01) WBSF of USDA Choice TB and GM steaks compared with 0-d controls. Feeding ZH for 0, 20, and 40 d had a similar effect on WBSF of USDA Select GM steaks, and produced lesser values than steaks from cattle fed ZH for 30 d. Feeding ZH for 20, 30, and 40 d had no effect on WBSF values of USDA Select TB steaks. However, the 20-, 30-, and 40-d duration produced WBSF values greater (P < 0.05) than control (0 d) TB steaks. Postmortem aging decreased (P < 0.05) WBSF of USDA Choice and Select TB and GM steaks, but the percentage improvement in WBSF attributed to aging was less than observed for LL steaks. The results of this study indicate feeding ZH increased (P < 0.001) WBSF of LL, TB, and GM. The ZH feeding also decreased (P < 0.01) the percentage of steaks with WBSF <4.5 kg regardless of US quality grade, whereas postmortem aging increased (P < 0.01) the percentage of US Choice and Select steaks with WBSF <4.5 kg. Finally, postmortem aging reduced (P < 0.05) WBSF of steaks from ZH-supplemented beef cattle. PMID:19648496

Brooks, J C; Claus, H C; Dikeman, M E; Shook, J; Hilton, G G; Lawrence, T E; Mehaffey, J M; Johnson, B J; Allen, D M; Streeter, M N; Nichols, W T; Hutcheson, J P; Yates, D A; Miller, M F

2009-11-01

8

Longissimus lumborum (LL) muscles from 117 steers plus LL, gluteus medius (GM), and triceps brachii (TB) muscles from 132 heifers were evaluated for effects of feeding duration of zilpaterol hydrochloride (Zilmax(R); ZH; 7.56g/907kg on a dry matter basis) and aging time on tenderness. Both genders were blocked by initial weight into six blocks of four pens. Pens were assigned to treatments of control (C), or 20, 30 or 40days on ZH, with a 3day withdrawal. Steaks from each subprimal were vacuum aged individually for 7, 14 or 21days, frozen, thawed, and cooked to 71 degrees C for Warner-Bratzler shear force (WBSF). All muscles from steers and heifers from ZH30 and ZH40 treatments had higher (P0.05) for WBSF of GM steaks from heifers. Percentage of intramuscular fat had little effect on tenderness. Percentages of steer LL and heifer TB steaks with WBSF values below thresholds of either 5.0 or 4.6kg from the ZH20 treatment were quite high, whereas percentages of heifer LL and GM muscles below 5.0kg (67%) and 4.6kg (57%) were low. Feeding ZH20days generally increased WBSF values, but mean WBSF values for steer LL and heifer TB were below 4.6kg. Feeding ZH 20days resulted in>40% of GM steaks with WBSF values above 4.6kg. PMID:20374910

Claus, H L; Dikeman, M E; Murray, L; Brooks, J C; Shook, J; Hilton, G G; Lawrence, T E; Mehaffey, J M; Johnson, B J; Allen, D M; Streeter, M N; Nichols, W T; Hutcheson, J P; Yates, D A; Miller, M F; Hunt, M C; Killefer, J

2010-06-01

9

Our objectives were to determine the effects of zilpaterol hydrochloride (ZH) and the release rate of trenbolone acetate and estradiol-17? on the Warner-Bratzler shear force (WBSF) and slice shear force (SSF) of longissimus lumborum (LL) and the WBSF of gluteus medius (GM) and psoas major (PM) in response to various aging periods. British × Continental steers (n = 168) were assigned to treatments in a 3 × 2 factorial. The main effects of treatment were implant (no implant, Revalor-S, Revalor-XS, Intervet/Schering Plough Animal Health, De Soto, KS) and ZH (0 or 8.3 mg/kg of DM for 20 d). Slaughter group was included as a random effect to account for the variation in days on feed (153 or 174 d). Loins (n = 96) were fabricated to obtain strip loin, top sirloin butt, and tenderloin subprimals. Five 2.54-cm steaks were cut from each subprimal and assigned to 1 of 5 aging periods (7, 14, 21, 28, or 35 d postmortem). Feeding ZH increased (P ? 0.01) LL WBSF and SSF values at each aging period compared with controls. Implanting increased (P 0.05). Only Revalor-S increased (P ? 0.05) WBSF values at 28 and 35 d compared with no implant or Revalor-XS. The percentage of LL steaks with a WBSF value below 4.6 kg did not differ (P > 0.05) between ZH supplementation or implant strategy at any aging period, and by d 28, more than 99% of LL steaks registered WBSF values below 4.6 kg. Feeding ZH increased (P 0.05) on GM WBSF values. The percentage of GM steaks with a WBSF value below 4.6 kg did not differ (P > 0.05) between ZH supplementation or implant strategy at any aging period. Neither ZH nor implant strategy affected PM WBSF values (P > 0.05). All PM WBSF values were below 4.6 kg on d 7. The results of this study indicated that feeding ZH increased WBSF and SSF of LL steaks, regardless of the aging period; however, the percentage of steaks with WBSF below 4.6 kg did not differ because of ZH or implant. Implanting increased LL WBSF values, but not SSF values. These results showed that although differences existed between implanting, as well as ZH supplementation of British × Continental steers, 99% of LL steaks were classified as tender based on WBSF values by extending aging to 28 d postmortem. It should be noted that 21.2% of 7-d, 13.8% of 14-d, and 17.3% of 21-d ZH steaks had WBSF values greater than 4.6 kg, but 0% of nonsupplemented steaks were greater than 4.6 kg at these aging periods. However, because ZH and implants can increase retail yield of valuable subprimals, such as the tenderloin, considerable value could be captured through ZH supplementation with anabolic implants because shear force was not affected in PM steaks. PMID:21680791

Garmyn, A J; Knobel, S M; Spivey, K S; Hightower, L F; Brooks, J C; Johnson, B J; Parr, S L; Rathmann, R J; Starkey, J D; Yates, D A; Hodgen, J M; Hutcheson, J P; Miller, M F

2011-11-01

10

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A padronização da textura é um dos principais problemas relacionados à qualidade da carne bovina. Por isso, a avaliação objetiva da maciez, por métodos mecânicos, vem sendo estudada há muitos anos. Para que a avaliação instrumental da textura seja uma ferramenta efetiva nos estudos envolvendo a maci [...] ez da carne, é necessário minimizar as causas de variação envolvidas na análise. Atualmente, a força de cisalhamento Warner-Bratzler é o método mais amplamente empregado para essa finalidade. O protocolo padrão dessa técnica analítica preconiza a utilização de uma lâmina de cisalhamento de 1,016mm de espessura. Neste trabalho, foram comparados dados de textura de carne bovina obtidos com a lâmina de cisalhamento padrão Warner-Bratzler, de 1,016mm de espessura, e uma lâmina mais grossa, de 3,05mm de espessura. Após o abate, amostras de músculo Longissimus dorsi, semelhantes em relação aos teores de umidade, lipídeos e proteínas, foram submetidas a duas diferentes temperaturas de resfriamento, atingindo diferentes velocidades de queda de temperatura e, consequentemente, diferentes graus de contração do tecido muscular, o que foi confirmado pela determinação do comprimento dos sarcômeros. Os resultados demonstraram uma maior sensibilidade da lâmina padrão Warner-Bratzler na detecção de variações da textura da carne, em função da velocidade de resfriamento. Abstract in english Standardization of texture is one of the main problems related to beef quality. Because of that, objective evaluation of tenderness performed by mechanic methodologies has been studied for years. In order to count on instrumental texture evaluation as a valuable tool in meat tenderness studies, it i [...] s necessary to minimize the causes of variation that might be involved in the trial. Nowadays, Warner-Bratzler shear force is widely used for meat tenderness determination. The standard protocol of this methodology establishes the utilization of shear blade 1.016mm tick. The aim of this study was to compare beef texture data provided by Warner-Bratzler standard shear blade, 1.016mm thick, with those provided by a thicker one, 3.05mm thick. After slaughtering, Longissimus dorsi muscle samples with similar contents of moisture, lipids and proteins were subjected to two different cooling temperatures,reaching different rates of temperature drop and hence different muscle contraction extents, which were confirmed by the determination of sarcomere length. Results indicated the superior sensibility of the Warner-Bratzler standard shear blade to detect variations in meat texture due to cooling velocity.

Marcos Franke, Pinto; Elisa Helena Giglio, Ponsano; Ana Paula da Silva, Almeida.

11

In-home consumer and shear force evaluation of steaks from the M. serratus ventralis thoracis.

The M. serratus ventralis thoracis was obtained from US Select arm chucks (n=87) to investigate if this underutilized muscle can be used as a steak alternative. Muscles were assigned randomly into three treatment groups: (1) control; (2) blade tenderization; and (3) injection, containing salt, phosphate, and papain. Steaks were cut from each muscle for in-home consumer evaluation (n=136) and Warner-Bratzler shear (WBS) force determination. The WBS values for injected steaks (13.1N) were lower (Pmerchandising steaks from this muscle may be a viable option in the marketplace, especially if blade tenderization or injection processes are used for further enhancement. PMID:20374872

Bagley, J L; Nicholson, K L; Pfeiffer, K D; Savell, J W

2010-05-01

12

Warner Brothers Online is a nicely-done entertainment site for both kids and adults. It includes episodes of the original Superman Radio show (via RealAudio), a singalong with Looney Toons Karaoke, clips of Madonna songs, and the Kids WB, with downloadable games, a history of Warner Brothers animation, and the "Sylvester and Tweety mysteries". However, the most interesting feature of the entire site is "Send a WeB card to a friend", which allows you to send a personalized e-mail "postcard" to a friend. The friend receives a message, with a URL and a "secret key" allowing them to retrieve their postcard. Time and bandwidth spent having fun. http://www.warnerbros.com/

13

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...

2004-01-01

14

“Decipher its noises for us”: Understanding Sycorax’s Island in Marina Warner’s Indigo

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Marina Warner’s novel Indigo, or Mapping the Waters (1992) explores the effects of colonialism on the islanders of Liamuiga and the Everard family through a complex retelling of Shakespeare’s The Tempest that spans over three hundred years. Much like the appropriative novels of Gloria Naylor, in which past and present blend and meld, Indigo also suggests that time is not linear in its development. The subtitle, or Mapping the Waters, positions a sense of place at the crux of Warner’...

Presley, Erin M.

2012-01-01

15

...Function Under Subsection 1225(a) of the John Warner National Defense Authorization Act...Function Under Subsection 1225(a) of the John Warner National Defense Authorization Act...President under subsection 1225(a) of the John Warner National Defense Authorization...

2009-01-01

16

High-angular Resolution Laser Threat Warner

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the design and development aspects of a high-angular resolution laser-threat Warner developed at the Laser Science & Technology Centre (LASTEC, Delhi are presented. It describes a high-angular resolution laser-threat warner capable of giving warning with a resolution of i 3" when it is exposed to laser radiation from visible and near-IR pulsed solid-state laser source. It has a field of view of 90' in the azimuth direction, whereas the elevation coverage is between -5" and + 25". It is capable of handling multiple types of laser threats covering wavelength from 400 nm to 1100 nm and has an operational range of 4 km for a Q-switched laser source energy (10 ns of 10 mJ/pulse and output beam divergence of 1 mrad. The paper also describes its simulated evaluation process and field-testing which it has undergone. The result of field-testing confirms that it meets all its performance specifications mentioned above.

Sushil Kumar

2007-07-01

17

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

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

18

DEFF Research Database (Denmark)

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 53Â°C, 55Â°C, 58Â°C and 63Â°C in water baths for 2Â½, 7Â½ and 19Â½ 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 53Â°C for 2Â½ h was significantly higher compared with all other heat treatments. A decrease of app. 40 N was observed when increasing the heating temperature from 53Â°C to 55Â°C, or when increasing heating time from 2Â½ to 7Â½ h at 53Â°C. In semitendinosus from cows shear force decreased significantly with increasing temperature, and with increasing heating time from 2Â½ to 19Â½ h at 55Â°C and 63Â°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.

Christensen, L.; Andersen, L.

2011-01-01

19

Propaganda in Warner Brothers World War II Cartoons.

To examine the role of the animated cartoon in propaganda associated with World War II, 194 of 262 cartoons produced for theatrical release by Warner Brothers, Inc., from 1939 to 1946 were analyzed. Propaganda content was determined by the number and nature of symbols used and the cartoon's "attitudes" toward these symbols. An analysis grid was…

Machowski, James Stanley; Brown, James William

20

Directory of Open Access Journals (Sweden)

Full Text Available Throughout the history, translation has played an important role in conveying thoughts and knowledge from one nation to other nations. Apart from this importance, the act of translating is not simply changing a message from the source language into the target one; translation is an act of problem–solving. Sometimes it is difficult to solve problems existing in translation, and so the notion of untranslatability emerges. Regarding the text–types, this problem is more prominent in the translation of literary texts like poems. This study attempts to investigate untranslatable elements in a poem, and for this purpose it concentrates on the story of Rustam & Sohrab selected from Shahnameh by Firdowsi and its equivalent translation by Warner & Warner. Then it focuses on the relation of untranslatablility in the story of Rustam & Sohrab with the semantic translation of Warner & Warner and the style of Firdowsi. Further research is required in this direction to answer questions concerning the notion of untranslatability and other related matters like the purpose of translation and untranslatability.

Habibollah Mashhady

2012-07-01

21

Semiclassical quantization of Rotating Strings in Pilch-Warner geometry

Some of the recent important developments in understanding string/ gauge dualities are based on the idea of highly symmetric motion of ``string solitons'' in $AdS_5\\times S^5$ geometry originally suggested by Gubser, Klebanov and Polyakov. In this paper we study symmetric motion of certain string configurations in so called Pilch-Warner geometry. The two-form field $A_2$ breaks down the supersymmetry to $\\mathcal{N}=1$ but for the string configurations considered in this paper the classical values of the energy and the spin are the same as for string in $AdS\\times S^5$. Although trivial at classical level, the presence of NS-NS antisymmetric field couples the fluctuation modes that indicates changes in the quantum corrections to the energy spectrum. We compare our results with those obtained in the case of pp-wave limit in hep-th/0206045.

Dimov, H; Rashkov, R C; Viswanathan, K S

2003-01-01

22

Ecological investigation of a hazardous waste site, Warner Robins, Georgia

Energy Technology Data Exchange (ETDEWEB)

Landfill No. 4 and the sludge lagoon at Robins Air Force Base, Warner Robins, Georgia, were added to the United States Environmental Protection Agency (EPA) National Priorities List in 1987 because of highpotential for contaminant migration. Warner Robins is located approximately 90 miles southeast of Atlanta. In 1990 CH2M HILL conducted a Remedial Investigation at the base that recommended that further ecological assessment investigations be conducted (CH2M HILL 1990). The subject paper is the result of this recommendation. The ecological study was carried out by the Hazardous Waste Remedial Actions Program (HAZWRAP)Division of Martin Marietta Energy Systems, Inc., working jointly with its subcontractor CDM (CDM 1992a). The primary area of investigation (Zone 1) included the sludge lagoon, Landfill No. 4, the wetland area east of the landfill and west of Hannah Road (including two sewage treatment ponds), and the area between Hannah Road and Horse Creek (Fig. 1). The bottomland forest wetlands of Zone 1 extend from the landfill east to Horse Creek. Surface water and groundwater flow across Zone 1 is generally in an easterly direction toward Horse Creek. Horse Creek is a south-flowing tributary of the Ocmulgee River Floodplain. The objective of the study was to perform a quantitative analysis of ecological risk associated with the ecosystems present in Zone 1. This investigation was unique because the assessment was to be based upon many measurement endpoints resulting in both location-specific data and data that would assess the condition of the overall ecosystem. The study was segregated into five distinct field investigations: hydrology, surface water and sediment, aquatic biology, wetlands ecology, and wildlife biology.

Wade, M. [Oak Ridge National Lab., TN (United States); Billig, P. [Camp Dresser and McKee, Inc., Denver, CO (United States)

1993-05-01

23

Walter Warner (ca.1557-1643) and his notes on Animal Organisms

Digital Repository Infrastructure Vision for European Research (DRIVER)

As opposed to most of his contemporaries, Thomas Hobbes (1588-1679) assumed that all phenomena could be explained in terms of matter in motion. All the more intriguing is his suggestion that what he wrote came out of his own head. Yet, already during his lifetime he was accused of having taken his natural philosophy from the mathematician and natural philosopher Walter Warner (ca. 1557-1643). Warner’s posthumous notes were said to suggest that he worked on the development of ...

Prins, Johannes Lambertus Maria

1992-01-01

24

Introduction of the Waterhyacinth Weevil ('Neochetina eichhorniae' Warner) into Puerto Rico.

The waterhyacinth weevil 'Neochetina eichhorniae Warner' was introduced into quarantine in Puerto Rico in anticipation of future release of the insect to aid in the control of its host aquatic plant 'Eichhornia crassipes (Mart.) Solms'. The insect is bein...

L. Bonnefil M. A. Rodriguez E. Lebron E. de Aragon

1979-01-01

25

Geothermal hydrology of Warner Valley, Oregon: a reconnaissance study

Energy Technology Data Exchange (ETDEWEB)

Warner Valley and its southern extension, Coleman Valley, are two of several high-desert valleys in the Basin and Range province of south-central Oregon that contain thermal waters. At least 20 thermal springs, defined as having temperatures of 20/sup 0/C or more, issue from Tertiary basaltic flows and tuffs in and near the valleys. Many shallow wells also produce thermal waters. The highest measured temperature is 127/sup 0/C, reported from a well known as Crump geyser, at a depth of 200 meters. The hottest spring, located near Crump geyser, has a surface temperature of 78/sup 0/C. The occurrence of these thermal waters is closely related to faults and fault intersections in the graben and horst structure of the valleys. Chemical analyses show that the thermal waters are of two types: sodium chloride and sodium bicarbonate waters. The warmer waters are likely to have higher concentrations of sodium and chloride, as well as sulfate, silica, and dissolved solids, than the cooler waters. Chemical indicators show that the geothermal system is a hot-water rather than a vapor-dominated system. Conductive heat flow in areas of the valley unaffected by hydrothermal convection is probably about 75 milliwatts per square meter. The normal thermal gradient in valley-fill deposits in these areas may be about 40/sup 0/C per kilometer. Extensive areas underlain by thermal ground water occur near Crump geyser and Fisher Hot Spring.

Sammel, E.A.; Craig, R.W.

1981-01-01

26

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

2005-01-01

27

The Intensities and High Sensitivity of a Gifted Creative Genius: Sylvia Ashton-Warner

This article explores the inner world of Sylvia Ashton-Warner, a gifted woman whose writing and teaching pedagogy earned her national and international acclaim. However, the acknowledged genius of her work is not explored herein. Rather, the inner world of a creatively gifted adult is examined, with particular reference to Dabrowski's…

White, Sonia

2014-01-01

28

Two trials investigated zilpaterol hydrochloride (ZH) feeding duration, enhancement, blade tenderization, and postmortem aging effect on Warner-Bratzler shear force (WBSF; trial 1) and consumer sensory ratings (trial 2). For trial 1, USDA Select beef strip loins were obtained from carcasses of beef steers fed ZH (6.8 g/t on 90% DM) the last 0, 20, 30, or 40 d of the feeding period. One-half of each strip loin was enhanced (110%) with a brine solution, whereas the remaining portion was not enhanced. Both pieces were portioned into steaks, which were aged 7, 14, or 21 d for WBSF analysis. For trial 2, paired USDA Select beef strip loins were obtained from carcasses of beef steers fed ZH the last 0 or 20 d of feeding. Paired strip loins were fabricated into 4 pieces and assigned to control, moisture enhanced, blade tenderized, and blade tenderized + moisture enhanced treatments. Strip loin pieces were then portioned into steaks that were aged 14 or 21 d postmortem. Consumers panelists (n = 458) indicated their like or dislike of tenderness, juiciness, flavor, and overall like of each sample using 8-point, verbally anchored scales, as well as tenderness and overall acceptability. With exception of 20 d ZH-treated steaks, results from trial 1 indicate WBSF values decreased (P < 0.05) with enhancement. Among enhanced steaks, steaks from cattle fed ZH for 20, 30, and 40 d had greater (P < 0.05) WBSF values than controls. Among nonenhanced steaks, 20 d ZH-treated steaks had WBSF values similar to 0, 30, and 40 d ZH-treated steaks, whereas 30 and 40 d ZH-treated steaks had greater (P < 0.05) WBSF values than controls. Postmortem aging for 21 d improved (P < 0.05) WBSF values for all ZH durations when compared with 7-d aging treatments. Results from trial 2 indicate ZH feeding for 20 d had no effect on flavor scores, decreased tenderness scores (P < 0.05), and tended (P < 0.10) to decrease juiciness and overall like scores when compared with controls for steaks aged 14 d. After 21 d aging, steaks from 20 d ZH-fed cattle had reduced (P < 0.05) tenderness, juiciness, and overall like scores and tended (P < 0.10) to have decreased flavor scores when compared with controls. These results indicate enhancement improved WBSF, but was not sufficient to overcome the detrimental effect of ZH feeding duration on WBSF until steaks were aged for 21 d postmortem. Consumer scores indicate 20 d ZH feeding had no effect on overall acceptability, but decreased tenderness and tenderness acceptability scores when compared with controls. PMID:20081069

Brooks, J C; Mehaffey, J M; Collins, J A; Rogers, H R; Legako, J; Johnson, B J; Lawrence, T; Allen, D M; Streeter, M N; Nichols, W T; Hutcheson, J P; Yates, D A; Miller, M F

2010-05-01

29

Directory of Open Access Journals (Sweden)

Full Text Available Durante os últimos quarenta anos, investigou-se e discutiu-se o aspecto pós-colonial da peça A tempestade, de Shakespeare. O romance Indigo, de Marina Warner, publicado em 1992, é a reescrita da peça, na qual os papéis femininos são realçados e analisados numa narrativa múltipla que compreende a invasão de uma ilha caribenha no século XVII e a fortuna dos descendentes desses invasores no século XX. Enquanto a ideologia dos colonizadores ingleses se baseava na construção de império, as duas personagens femininas, Sícorax e Serafine, se esforçam na construção de comunidades. Nessa versão feminina de A tempestade, Warner apresenta uma alternativa para suplantar o patriarcalismo e fundar princípios básicos para uma sociedade mais douradora e mais igualitáriaDuring the last four decades the postcoloniality in Shakespeare’s The Tempest has been investigated and discussed. Marina Warner’s novel Indigo, published in 1992, is a reworking of the play in which feminine roles are enhanced and analysed in a multiple narrative comprehending the 17th century invasion of a Caribbean island and the fortune of the invaders’ descendents in the 20th century. In contrast to the English colonizers stance of empire building, the two female characters of the novel, Sycorax and Serafine, endeavour to build communities. In this feminine version of The Tempest, Warner shows an alternative way to replace patriarchy and establish the basic tenets of a more-enduring and equalitarian society

Thomas Bonnici

2003-06-01

30

International Nuclear Information System (INIS)

A shear machine for irradiated nuclear fuel elements has a replaceable shear assembly comprising a fuel element support block, a shear blade support and a clamp assembly which hold the fuel element to be sheared in contact with the support block. A first clamp member contacts the fuel element remote from the shear blade and a second clamp member contacts the fuel element adjacent the shear blade and is advanced towards the support block during shearing to compensate for any compression of the fuel element caused by the shear blade (U.K.)

1980-01-01

31

Energy Technology Data Exchange (ETDEWEB)

Due to possible worker exposure to 1,3-butadiene, a walk-through industrial-hygiene survey was conducted at Borg Warner Chemicals Woodmar Facility, Washington, West Virginia. The primary products of the facility are ABS plastics, polybutadiene latex and styrene butadiene rubber latex. In September 1981, a butadiene recovery system was added to the process vent streams. Of the total work force, 54 employees have potential for exposure to 1,3-butadiene. The mean 8-hour time-weighted average (TWA) of 23 personal samples collected during several periods in 1983 and 1985 was 4.5 parts per million (ppm). Analysis of a bulk sample showed traces of 1,3-butadiene, in the 0.04 to 0.2 nanograms/milligram range. The exposures to 1,3-butadiene were greater than 10ppm for two job classifications, control room and high heat operators. The company has accurate records on terminated and current employees. The author concludes that the facility is a candidate for inclusion in an in-depth industrial hygiene survey regarding 1,3-butadiene. Recommendations were given.

Roberts, D.

1986-08-01

32

In the mid-1970s, Women Against Violence Against Women (WAVAW), the first national feminist organization to protest mediated sexual violence against women, pressured the music industry to cease using images of violence against women in its advertising. This article presents a case study of WAVAW's national boycott of Warner Communications, Inc. and documents the activists' successful consumer campaign. The study reveals that media violence was central to feminist organizing efforts, and that WAVAW and related organizations helped establish a climate of concern about violence that motivated scientific research on the relationship between exposure to media violence and subsequent aggression. PMID:18359878

Bronstein, Carolyn

2008-04-01

33

Dr. John Atkinson, of the University of the West of England, developed a site for undergraduate students wanting to learn more about soil classification. His site addresses issues such as: shear strength, peak strength, and residual strength testing. Filled with charts, diagrams, statistics, the information is pertinent and easily understood by almost any audience.

Atkinson, John

2008-10-07

34

Use of near infrared spectroscopy for assessment of beef quality traits

Directory of Open Access Journals (Sweden)

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.

L. Gallo

2010-04-01

35

Hillary Clinton / Judith Warner

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

Warner, Judith

1994-01-01

36

Correlation and Categories of Meat Tenderness Based on Equipment and Panelist Test

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study was to determine the correlation between Warner-Bratzler shear force (WBSF and cooking loss with sensory local trained panelists rating on beef tenderness, also to determine WBSF range at each tenderness categories (extremely tender, tender, rather tender, rather tough, tough, and extremely tough. Meat from knuckles of Australian Beef Cross (ABX steer were broiled until internal temperature 70, 80 and 90oC to get some WBSF values. Cooking loss was counted as percentages of meat weight losses during cooking. Each WBSF values and cooking loss data were correlated with panelists test scores used linier regression equation. Then, based on that linier regression were estimated WBSF range at each tenderness level. The result indicated that WBSF was positive correlated with panelists test that was indicated with determination coefficient 0.7668 (r2 = 0.7668. Cooking loss was strongly positive correlated with panelists rating tenderness (r2 = 0.8114. The result of meat tenderness range categories: extremely tender 0–3.30 kg/cm2, tender >3.30–5.00 kg/cm2, rather tender >5.00–6.71 kg/cm2, rather tough >6.71–8.42 kg/cm2, tough >8.42-10.12 kg/cm2, extremely tough >10.12 kg/cm2. (Animal Production 10(3: 188-193 (2008 Key Words: Meat tenderness, tenderness categories, panelist test, Warner-Bratzler shear, force, cooking loss

T Suryati

2008-09-01

37

Directory of Open Access Journals (Sweden)

Full Text Available A study was conducted to determine the effect of probiotics and thyme essential oil (TEO as feed additives on the sensory attributes, cooking loss and the texture of broiler chicken meat. Day-old broilers Ross 308 (n = 400 were randomly divided into four groups based on the feed supplement as follows: control, probiotics 0.05%, TEO 0.05% and combination of probiotics and TEO, while the fattening period was 42 days. Warner Bratzler shear force, cooking loss and the following sensory attributes (colour, odour, taste, texture, meat decomposing and overall acceptability were tested. The obtained results of the Warner Bratzler shear force show that there was significant different (P < 0.05 between control and TEO group and for the cooking loss there was no significant difference between groups. The descriptive sensory analysis results show that the probiotics group results were somewhat similar to that obtained by control while the TEO group and the combination group results were similar. Regarding the sensory analysis we can state that the combination of the probiotics and TEO have a positive effect on the chicken meat sensory characteristics.

Ebrahim Alfaig

2014-05-01

38

Rotatable shear plate interferometer

Energy Technology Data Exchange (ETDEWEB)

A rotatable shear plate interferometer comprises a transparent shear plate mounted obliquely in a tubular supporting member at 45.degree. with respect to its horizontal center axis. This tubular supporting member is supported rotatably around its center axis and a collimated laser beam is made incident on the shear plate along this center axis such that defocus in different directions can be easily measured.

Duffus, Richard C. (Livermore, CA)

1988-01-01

39

Energy Technology Data Exchange (ETDEWEB)

There is disclosed a ram type blowout preventer having a pair of shear rams adapted to shear pipes suspended in the bore of the preventer and subsequently seal off the bore. The rams utilize a transverse packing for sealing between the shear blades when they are closed. One shear ram has a ramp adapted to engage a shoulder on the opposing ram so as to urge the shearing blades closer together as they are closing and thereby reduce the vertical gap which the transverse seal must bridge.

Jones, M.R.

1982-09-07

40

We investigate the distortions due to this shear in the microlensing light curves and in the astrometric microlensing centroid shift trajectories. As expected, the light curve deviation increases as the shear increases and the impact parameter decreases. Although the light curve in the presence of a small shear is similar to the simple Paczynski curve with a slightly smaller impact parameter, the detailed difference between the light curve with and without shear reflects the direction and the magnitude of the shear. The centroid shift trajectory also deviates from a simple ellipse in the presence of shear. The distortion of the centroid shift trajectory increases as the impact parameter decreases, and the shape of the trajectory becomes complicated when the impact parameter becomes small enough. The magnitude of the maximum distortion depends on the magnitude and the direction of the shear. For a source trajectory in a given direction, the time of the maximum distortion depends mostly on the impact parameter ...

Ryu, Yoon-Hyun

2007-01-01

41

Scientific Electronic Library Online (English)

Full Text Available SciELO Peru | Language: Spanish Abstract in spanish 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

Mamani-Linares, Lindon W; Gallo, Carmen.

42

Energy Technology Data Exchange (ETDEWEB)

The 46.5-acre USAF Robins Air Force Base site is a logistics management and repair center for aircraft, missiles, and support systems in Warner Robins, Houston County, Georgia. The Zone 1 area, which includes a 45-acre inactive landfill and a 1.5-acre sludge lagoon is part of the 8,855-acre Robins Air Force Base. Types of wastes generated at the facility included electroplating wastes, organic solvents from cleaning operations, and pesticides, all of which were disposed of in the lagoon and landfill areas. The Record of Decision (ROD), which focuses on OU1, addresses the remediation of Landfill No. 4 and the sludge lagoon. The selected remedial action for the site includes treating 15,000 cubic yards of soil in the sludge lagoon using in-situ soil vapor extraction; removing volatile contaminants from the air using condensation, distillation, and carbon adsorption; controlling and treating landfill leachate; renovating the landfill cover; and treating the sludge lagoon to remove VOCs.

1991-06-25

43

Energy Technology Data Exchange (ETDEWEB)

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.

Ruda, Mitchell C. (Tucson, AZ); Greynolds, Alan W. (Tucson, AZ); Stuhlinger, Tilman W. (Tucson, AZ)

2009-07-14

44

Magnetohydrodynamic Shearing Waves

I consider the nonaxisymmetric linear theory of an isothermal magnetohydrodynamic (MHD) shear flow. The analysis is performed in the shearing box, a local model appropriate for a thin disk geometry. Linear perturbations in this model can be decomposed in terms of shearing waves (shwaves), which appear spatially as plane waves in a frame comoving with the shear. The time dependence of these waves cannot in general be expressed in terms of a frequency eigenvalue as in a normal mode decomposition, and numerical integration of a set of first-order amplitude equations is required for a complete characterization of their behavior. Their generic time dependence, however, is oscillatory with slowly-varying frequency and amplitude, and one can construct accurate analytic solutions by applying the Wentzel-Kramers-Brillouin method to the full set of amplitude equations. For the bulk of wavenumber space, therefore, the shwaves are well-approximated as modes with time-dependent frequencies and amplitudes. The incompressiv...

Johnson, B M

2006-01-01

45

Characterization of beef semimembranosus and adductor muscles from US and Mexican origin.

The purpose of this study was to compare the chemical composition and sensory characteristics of two beef muscles (semimembranosus, SM and adductor, AD) from the inside round of Mexican and US origins. Inside rounds were obtained from 20 Mexican bull carcasses, representing beef of Mexican origin. Forty-vacuum packaged USDA Choice and Select inside rounds were purchased from a local trader, representing US beef. Muscles were analyzed for chemical composition, Warner-Bratzler shear force (WBSF), cooking loss percentage, instrumental color, textural profile, and consumer acceptability. Muscles imported from the US contained more intramuscular fat, had higher cooking loss percentages, lower shear force values, and higher consumer ratings for overall desirability than Mexican counterparts (P0.05). Consumers found differences in juiciness and tenderness ratings between the two muscles, with the SM being tougher and less juicy than the AD (P<0.05). PMID:22060985

Rubio L, M S; Méndez M, R D; Huerta-Leidenz, N

2007-07-01

46

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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

María C., Miquel; Edgardo, Villarreal; Carlos, Mezzadra; Lilia, Melucci; Liliana, Soria; Pablo, Corva; Alejandro, Schor.

47

Digital Repository Infrastructure Vision for European Research (DRIVER)

We discuss crack propagation along the interface between two dissimilar materials. The crack edge separates two states of the interface, ``stick'' and ``slip''. In the slip region we assume that the shear stress is proportional to the sliding velocity, i.e. the linear viscous friction law. In this picture the static friction appears as the Griffith threshold for crack propagation. We calculate the crack velocity as a function of the applied shear stress and find that the mai...

Brener, Efim A.; Marchenko, V. I.

2002-01-01

48

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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.

Wesley Oliveira de, Sousa; Germano Henrique, Rosado-Neto; Marinêz Isaac, Marques.

49

Bayesian lensing shear measurement

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 derived shear estimator disposes with the assignment of ellipticities to individual galaxies that is typical of previous approaches to galaxy lensing. Shear estimates from the mean of the Bayesian posterior are unbiased in the limit of large number of background galaxies, regardless of the noise level on individual galaxies. 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 (PSF) and sampling. The Bayesian model-fitting (BMF) method assigns a likelihood of the pixel data to galaxy models (e.g. Sérsic ellipses), and requires the unlensed distribution of galaxies over the model parameters as a prior. The Bayesian Fourier domain (BFD) method compresses the pixel data to a small set of weighted moments calculated after PSF correction in Fourier space. It requires the unlensed distribution of galaxy moments as a prior, plus derivatives of this prior under applied shear. A numerical test using a simplified model of a biased galaxy measurement process demonstrates that the Bayesian formalism recovers applied shears to drawback that shear biases will occur since galaxies do not fit any finite-parameter model, but has the advantage of being robust to missing data or non-stationary noise. Both BMF and BFD methods are readily extended to use data from multiple exposures and to inference of lensing magnification.

Bernstein, Gary M.; Armstrong, Robert

2014-02-01

50

Mixing through shear instabilities

In this paper we present the results of numerical simulations of the Kelvin-Helmholtz instability in a stratified shear layer. This shear instability is believed to be responsible for extra mixing in differentially rotating stellar interiors and is the prime candidate to explain the abundance anomalies observed in many rotating stars. All mixing prescriptions currently in use are based on phenomenological and heuristic estimates whose validity is often unclear. Using three-dimensional numerical simulations, we study the mixing efficiency as a function of the Richardson number and compare our results with some semi-analytical formalisms of mixing.

Brüggen, M

2000-01-01

51

Using deformed critters to determine angular shear and shear strain

This activity provides a step by step example to help students figure out how to determine the angular shear and shear strain, using fossils with bilateral symmetry. Students first complete the work on an idealized critter, and then on a sheared trilobite using simple graphical techniques and basic trigonometry.

Moore, Angela

52

Propagation of Adiabatic Shear Bands

Digital Repository Infrastructure Vision for European Research (DRIVER)

The dynamic propagation of a shear band is assessed in mode II. A layer of finite thickness is subjected to siinple shearing. The band propagates in the shear direction under steady state conditions. A variational approach is developed to calculate the shear band velocity and the length of the process zone. We analyse the roles of inertia, of loading conditions and of material properties such as yield stress, strain (or thermal) softening, strain hardening, strain rate sensitivity. The effect...

Mercier, S.; Molinari, A.

1997-01-01

53

Cosmic shear offers a remarkbly clean way to measure the equation of state of the Universe and its evolution. Resolution over a wide field is paramount, and Antarctica offers unique possibilities in this respect. There is an order of magnitude gain in speed over temperate sites, or a factor three in surface density. This means that PILOT outperforms much larger telescopes elsewhere, and can compete with the proposed DUNE space mission. Keywords: Antarctic astronomy, Surveys, Adaptive optics, Weak lensing

Saunders, W

2008-01-01

54

We present a time-dependent Ginzburg-Landau model of nonlinear elasticity in solid materials. We assume that the elastic energy density is a periodic function of the shear and tetragonal strains owing to the underlying lattice structure. With this new ingredient, solving the equations yields formation of dislocation dipoles or slips. In plastic flow high-density dislocations emerge at large strains to accumulate and grow into shear bands where the strains are localized. In addition to the elastic displacement, we also introduce the local free volume {\\it m}. For very small $m$ the defect structures are metastable and long-lived where the dislocations are pinned by the Peierls potential barrier. However, if the shear modulus decreases with increasing {\\it m}, accumulation of {\\it m} around dislocation cores eventually breaks the Peierls potential leading to slow relaxations in the stress and the free energy (aging). As another application of our scheme, we also study dislocation formation in two-phase alloys (...

Onuki, A; Minam, A; Onuki, Akira; Furukawa, Akira; Minam, Akihiko

2004-01-01

55

Llama Meat Nutritional Properties

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to determine the chemical composition of the muscle Longissimus thoracis taken from 20 llama males, reared in the Andean region, slaughtered at an age of 25 months and at a mean final body weight of 74kg. Llama meat showed a low fat (3.51% and cholesterol content (58.16mg/100g, a good protein content (22.42% and an ash content of 3.06%. The Warner-Bratzler shear force values determined in llama meat was 6.56 kg/cm2. This study confirmed that llama meat is healthy and nutritious, and represents a good source of proteins for Andean population.

G. Lebboroni

2010-04-01

56

Beta agonists used as growth enhancers are known to affect the aging potential of beef muscle negatively. On the other hand, procedures like electrical stimulation could accelerate rigor and the aging process. In this study, 20 out of 40 young steers received no beta agonist (C), the remaining twenty steers received a beta agonist (zilpaterol hydrochloride) (Z) for the 30 days prior to slaughter followed by 4 days withdrawal. After slaughter carcasses were split, the left side electrically stimulated (ES) and the right side not stimulated (NES). Samples were aged for 3 or 14 days post mortem. Parameters included Warner Bratzler shear force (WBSF), myofibril filament length (MFL), sarcomere length and calpastatin and calpain enzyme activity. Zilpaterol resulted in increased (Pzilpaterol supplemented steers, although steers without zilpaterol will still have an advantage in final tenderness. PMID:20619545

Hope-Jones, M; Strydom, P E; Frylinck, L; Webb, E C

2010-11-01

57

Angus-cross steers (n = 60) were used to assess the effect of forage species [alfalfa (AL; Medicago sativa L.), bermudagrass (BG; Cynodon dactylon), chicory (CH; Cichorium intybus L.), cowpea (CO; Vigna unguiculata L.), and pearl millet (PM; Pennisetum glaucum (L. R Br.)] in replicated 2-ha paddocks for finishing on cattle performance, carcass quality, and meat quality in a 2-yr study. Steers were blocked by BW and assigned randomly to finishing-forage treatments before the start of the experiment. Steers grazing AL and CH had greater (P 1 kg/d). Finishing on legumes (AL and CO) increased dressing percentage, reduced Warner-Bratzler shear force values, and increased consumers preference, whereas finishing on grasses (BG and PM) enhanced anticarcinogenic fatty acid concentrations. PMID:23825343

Schmidt, J R; Miller, M C; Andrae, J G; Ellis, S E; Duckett, S K

2013-09-01

58

Post-slaughter muscle energy metabolism meat colour of South African production systems were compared; steers (n=182) of Nguni, Simmental Brahman crossbreds were reared on pasture until A-, AB-, or B-age, in feedlot until A-AB-age. After exsanguination carcasses were electrically stimulated (400 V for 15 s). M. longissimus dorsi muscle energy samples were taken at 1, 2, 4 and 20 h. Post-mortem samples for meat quality studies were taken at 1, 7 and 14 days post-mortem. Production systems affected muscle glycogen, glucose, glucose-6-P, lactic acid, ATP, creatine-P glycolytic potential (P0.5) water holding capacity, drip loss, and Warner Bratzler shear force. Muscle energy only affected muscle contraction of the A-age-pasture system (shortest sarcomere length of 1.66 ?m vs 1.75 ?m highest WBS of 6 kg vs 5 kg 7 days post-mortem). PMID:23305833

Frylinck, L; Strydom, P E; Webb, E C; du Toit, E

2013-04-01

59

Effect of Breed of Sire on Carcass Traits and Meat Quality of Katahdin Lambs

Directory of Open Access Journals (Sweden)

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.

José A. Partida

2012-09-01

60

Directory of Open Access Journals (Sweden)

Full Text Available The experiment was performed with thirty-two Altamurana and Trimeticcio lambs slaughtered at 42 and at 70 days of age. Meat organoleptic characteristics were determined on samples of M. Longissimus lumborum and Longissimus thoracis. Colour parameters were not affected by genotype, while L* value and index of yellow decreased (P<0.01 and P<0.05, respectively as age of slaughtering increased. Meat from Altamurana lambs showed lower juiciness (P<0.01 and fatness (P<0.05 than Trimeticcio lambs. No genotype and age of slaughtering effects were found for Warner-Bratzler shear force (WBSF values. Meat from younger lambs was more tender and chewable (P<0.01 but less juicy (P<0.001 and fatty (P<0.05 than meat from lambs slaughterd at 70 days.

A. Girolami

2010-04-01

61

Effect of probiotics and thyme essential oil on the texture of cooked chicken breast meat

Directory of Open Access Journals (Sweden)

Full Text Available Background. Texture is probably the single most critical quality factor associated with the consumers’ ultimate satisfaction with a poultry meat product and can be affected by several factors including the type of feed used for chickens fattening. The use of probiotics for meat and carcass quality improvement has been questioned, while the possibility of deposition of essential oils in various muscle tissues can alter the sensory attributes of the chicken’s meat. Material and methods. Probiotics and thyme essential oil in the percentage of 0.05% were used as feed supplements for Ross 308 broiler chickens, as the broilers were reared in four separated groups based on the feed supplement as follows: control, probiotics, thyme essential oil and combination of probiotics and thyme essential oil group, while the fattening period was 42 days. TA.XT Plus-Texture analyser apparatus was used for determination of the texture profile and Warner Bratzler shear force for the cooked breast meat. Results. Warner Bratzler shear test results showed that the tested feed additives were not affecting the texture of the chicken breast meat, while probiotic appears to have moderately effect on the hardness, cohesiveness, springiness and chewiness attributes of the cooked breast meat compared with the other groups, this effect of probiotics considered as negligible, as the results showed that all the tested groups meat were very tender according to the tenderness scale. Conclusions. According to the obtained results it can be concluded the combination of probiotics and thyme group resulted in the lowest score for the hardness, cohesiveness, springiness and chewiness attributes, while probiotics group scored the highest compared with the control.

Ebrahim Alfaig

2013-12-01

62

Shear viscosity of nuclear matter

In this talk I report my recent study on the shear viscosity of neutron-rich nuclear matter from a relaxation time approach. An isospin- and momentum-dependent interaction is used in the study. Effects of density, temperature, and isospin asymmetry of nuclear matter on its shear viscosity have been discussed. Similar to the symmetry energy, the symmetry shear viscosity is defined and its density and temperature dependence are studied.

Xu, Jun

2013-01-01

63

Direct Measurement of Turbulent Shear

A photon correlation method is introduced for measuring components of the shear rate tensor in a turbulent soap film. This new scheme, which is also applicable to three-dimensional flows, is shown to give the same results as Laser Doppler velocimetry, but with less statistical noise. The technique yields the mean shear rate s, its standard deviation, and a simple mathematical transform of the probability density function P(s) of the shear rate itself.

Stefanus, Stefanus; Goldburg, Walter

2010-01-01

64

Shear-banding and microstructure of colloids in shear flow.

We shall discuss the following phenomena found in various colloidal systems in shear flow. We recently observed shear-banding in suspensions of fd-virus in a cylindrical shear cell. Small angle light scattering experiments revealed that the shear-banding transition is preceded by a relatively fast process (minutes) of nematic-to-paranematic phase separation during which inhomogeneities on the micrometer length scale are formed. After the formation of these inhomogeneities, a slow (hours) appearence of shear-bands is observed, which have a height of a few mm. In the stationary state it is found, by means of polarization microscopy, that inhomogeneities exist within the bands. Small angle, time resolved light scattering experiments on near-critical microstructural order in a mixture of colloidal spheres and free polymer under stationary shear flow are discussed. The unexpected distortion of microstructure in directions perpendicular to the flow direction is quantitatively explained by extending an already existing theory, to include shear-induced short-ranged microstructural distortion. In colloidal systems consisting of "hairy colloids", where a spherical core is decorated with relatively long polymers, shear-induced polymer brush deformation might be important for its structural and rheological behavior. Preliminary neutron scattering and rheology experiments are performed to study polymer brush deformation in (semi-) dilute suspensions. PMID:12638861

Dhont, Jan K G; Lettinga, M Pavlik; Dogic, Zvonimir; Lenstra, Tjerk A J; Wang, Hao; Rathgeber, Silke; Carletto, Philippe; Willner, Lutz; Frielinghaus, Henrich; Lindner, Peter

2003-01-01

65

Bayesian Lensing Shear Measurement

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...

Bernstein, Gary M

2013-01-01

66

Scaling of Entropic Shear Rigidity

The scaling of the shear modulus near the gelation/vulcanization transition is explored heuristically and analytically. It is found that in a dense melt the effective chains of the infinite cluster have sizes that scale sub-linearly with their contour length. Consequently, each contributes k_B T to the rigidity, which leads to a shear modulus exponent d\

Xing, X; Goldbart, P M

2004-01-01

67

Scientific Electronic Library Online (English)

Full Text Available SciELO Peru | Language: Spanish Abstract in spanish 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

Mamani-Linares, Lindon W.; Cayo, Faustina; Gallo, Carmen.

68

Two hundred sixty-eight strip loins were collected from heifers fed at Oklahoma State University in Stillwater, OK. In Exp. 1, heifers (n = 127) were assigned to 1 of 3 health management treatment groups: antimicrobial administrations were given based on standard feedlot protocol (SFP) or ruminal temperature (RT) or given a metaphylactic treatment of tulathromycin (MT) followed by visual assessment (VA). In Exp. 2, heifers (n = 155) were assigned to the same treatment groups as above and were supplemented zilpaterol hydrochloride (ZH) or control (CON). Three steaks were collected from each strip loin, 1 each for retail display, sensory evaluation, and Warner-Bratzler shear force (WBSF). Color was evaluated from the retail display steak using a trained color panel and objectively using a HunterLab Miniscan XE. An Instron Universal Testing Machine with a Warner-Bratzler head was used for evaluation of instrumental tenderness, and a trained sensory panel was used to assess palatability traits. Heifers treated by VA had the least number of antimicrobial administrations and lowest yield grade and also had the lightest HCW (P 0.05) across all health management systems or antimicrobial administrations. There were no differences in carcass and performance traits for any antimicrobial administrations treatment groups (P > 0.05). Heifers who had 0 or 1 antimicrobial administrations had lower (P Zilpaterol hydrochloride supplementation caused a decrease (P < 0.05) in internal fat and yield grade, but no interactions were observed between the number of antimicrobial administrations and ZH supplementation. With the supplementation of ZH, WBSF significantly increased (P < 0.05). At the end of retail display, the control group had a greater (P < 0.05) surface discoloration when compared with the ZH group. Treatment and detection of bovine respiratory diseases (BRD) is critical to the industry economically and results from this study show that different methods can be used to detect BRD without dramatically impacting carcass, sensory, and retail case life characteristics. PMID:23658348

Bloomberg, B D; Mafi, G G; Pye, B J; Wahrmund, J L; Richards, C J; Morgan, J B; Vanoverbeke, D L

2013-07-01

69

Subcritical dynamos in shear flows

Identifying generic physical mechanisms responsible for the generation of magnetic fields and turbulence in differentially rotating flows is fundamental to understand the dynamics of astrophysical objects such as accretion disks and stars. In this paper, we discuss the concept of subcritical dynamo action and its hydrodynamic analogue exemplified by the process of nonlinear transition to turbulence in non-rotating wall-bounded shear flows. To illustrate this idea, we describe some recent results on nonlinear hydrodynamic transition to turbulence and nonlinear dynamo action in rotating shear flows pertaining to the problem of turbulent angular momentum transport in accretion disks. We argue that this concept is very generic and should be applicable to many astrophysical problems involving a shear flow and non-axisymmetric instabilities of shear-induced axisymmetric toroidal velocity or magnetic fields, such as Kelvin-Helmholtz, magnetorotational, Tayler or global magnetoshear instabilities. In the light of sev...

Rincon, F; Proctor, M R E; Cossu, C

2008-01-01

70

Shear behaviour of ferrocement plates

Directory of Open Access Journals (Sweden)

Full Text Available Ferrocement members can be used in the form of plates Such as for walling unit, marine structures etc. Such plates are subjected to shear buckling hence shear resistance capacity of plate need to be verified. Various authors have studied shear behaviour on different specimens such as box beams, panels, and plates. The ansys software used for finite element analysis (FEM of plates. In the present study an attempt is made to observe behaviour of ferrocement plate with various mesh patterns. The results gives that Increasing the volume fraction (VF of the wire mesh layer subsequently increases the shear carrying capacity of the plate To attain this advantage, supports and loading points should be design and strengthened to prevent local failure, Shear behaviour of ferrocement plates (SBFP.The stress intensity is determined using FEM (Ansys and compared with the available results. it is observed that stress intensity as well as cracking shear strength of plate depends upon volume fraction. the available equations from literature can be used for analysis of mesh plate.

MADHURI N.SAVALE

2013-03-01

71

Shear shocks in fragile networks.

A minimal model for studying the mechanical properties of amorphous solids is a disordered network of point masses connected by unbreakable springs. At a critical value of its mean connectivity, such a network becomes fragile: it undergoes a rigidity transition signaled by a vanishing shear modulus and transverse sound speed. We investigate analytically and numerically the linear and nonlinear visco-elastic response of these fragile solids by probing how shear fronts propagate through them. Our approach, which we tentatively label shear front rheology, provides an alternative route to standard oscillatory rheology. In the linear regime, we observe at late times a diffusive broadening of the fronts controlled by an effective shear viscosity that diverges at the critical point. No matter how small the microscopic coefficient of dissipation, strongly disordered networks behave as if they were overdamped because energy is irreversibly leaked into diverging nonaffine fluctuations. Close to the transition, the regime of linear response becomes vanishingly small: the tiniest shear strains generate strongly nonlinear shear shock waves qualitatively different from their compressional counterparts in granular media. The inherent nonlinearities trigger an energy cascade from low to high frequency components that keep the network away from attaining the quasi-static limit. This mechanism, reminiscent of acoustic turbulence, causes a superdiffusive broadening of the shock width. PMID:24309379

Ulrich, Stephan; Upadhyaya, Nitin; van Opheusden, Bas; Vitelli, Vincenzo

2013-12-24

72

The limited growth of vegetated shear layers

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In contrast to free shear layers, which grow continuously downstream, shear layers generated by submerged vegetation grow only to a finite thickness. Because these shear layers are characterized by coherent vortex structures and rapid vertical mixing, their thickness controls exchange between the vegetation and the overlying water. Experiments conducted in a laboratory flume show that the growth of these obstructed shear layers is arrested once the production of shear-layer-scale turbulent ki...

Ghisalberti, M.; Nepf, Heidi

2003-01-01

73

Bicontinuous Microemulsions under Steady Shear Flow

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dynamic response of microemulsions to shear deformation on the basis of two-order-parameter time dependent Ginzburg-Landau model is investigated by means of cell dynamical system approach. Time evolution of anisotropic factor and excess shear stress under steady shear flow is studied by changing shear rate and total amount of surfactant. As the surfactant concentration is increased, overshoot peak height of the anisotropic factor increases whereas that of the excess shear stress is almost unc...

1997-01-01

74

Yield shear stress and disaggregating shear stress of human blood

This review presents two distinct rheological parameters of blood that have the potential to indicate blood circulation adequacy: yield shear stress (YSS) and disaggregating shear stress (DSS). YSS and DSS reflect the strength of red blood cell (RBC) aggregation in suspension under static and dynamic conditions, respectively. YSS, defined as the critical stress to disperse RBC aggregates under static conditions, was found to be dependent upon hematocrit, fibrinogen, and red cell deformability, but not temperature. DSS, defined as the minimum shear stress to disperse RBC aggregates under dynamic conditions, is dependent upon fibrinogen, red cell deformability, and temperature but not hematocrit. Owing to recent advances in measurement technology, these two parameters can be easily measured, and thus, their clinical significance in blood circulation can be verified.

Jung, Jinmu; Lee, Byoung-Kwon; Shin, Sehyun

2014-05-01

75

Energy Technology Data Exchange (ETDEWEB)

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.

Showalter, S.; Wood, F.; Vimmerstedt, L.

2010-06-01

76

Superstrings in Sheared Polymer Blends

We report the discovery of a droplet-string-ribbon transition in concentrated polymer blends which occurs when the droplet size of the dispersed component becomes comparable to the gap between the boundary plates. Above a critical shear rate (or gap width), dispersed droplets continuously coalescence and breakup; the upper limit on their size is set by the Taylor length. Below this critical shear rate, droplets coalesce into strings and then ribbons in a four stage kinetic process. The mass ratio of string / droplet can be as large as 10^4. The transition is sharp, occurring over a shear interval of 2droplet-string transition is a manifestation of the weakening of the Rayleigh-Tomatika instability which occurs when the system becomes quasi two-dimensional. Possible applications of this technology are ultra-thin materials of high one-dimensional strength, polymer blend wires, and novel polymeric scaffolds.

Migler, Kalman

2000-03-01

77

Terapixel Surveys for Cosmic Shear

The recent detections of cosmic shear signal announced by several groups have demonstrated the feasibility of this challenging program and convinced astro- nomers of its potential for cosmology. Cosmic shear analysis demands to handle Gigabytes of data in order to probe several square degrees in subarcsecond deep imaging mode. The success of these surveys is sensitive to the designs of the observation strategy, the organization of the data reduction pipelines and the links of the data base with surveys like X-ray or spectroscopic follow up. We describe the cosmic shear surveys we have carried out at the VLT and at CFHT and the way we handle this huge data set in a more general context including the VIRMOS and the XMM-LSS surveys, and the future CMB surveys.

Mellier, Y; Radovich, M; Bertin, E; Dantel-Fort, M; Cuillandre, J C; McCracken, H J; Lefèvre, O; Didelon, P; Morin, B; Maoli, R; Erben, T; Bernardeau, F; Schneider, P; Fort, B; Jain, B K

2000-01-01

78

Shear loading of costal cartilage

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.

Subit, Damien

2014-01-01

79

Shearing of frictional sphere packings

Digital Repository Infrastructure Vision for European Research (DRIVER)

We measure shear response in packings of glass beads by pulling a thin, rough, metal plate vertically through a bed of volume fraction phi, which is set, before the plate is pulled, in the range 0.575 to 0.628. The yield stress is velocity independent over 4 decades and increases exponentially with phi, with a transition at phi approximately 0.595. An analysis of the measured force fluctuations indicates that the shear modulus is significantly smaller than the bulk modulus.

Me?tayer, Jean-franc?ois; Suntrup Iii, Donald J.; Radin, Charles; Swinney, Harry L.; Schro?ter, Matthias

2010-01-01

80

Shear thickening oscillation in a dilatant fluid

We report experimental observations of the shear thickening oscillation; spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluids. Using a phenomenological fluid dynamics model for dilatant fluids, we have been predicted theoretically that a dilatant fluid under constant shear stress oscillates due to the shear thickening property coupled with the fluid dynamics. However, such a macroscopic oscillation has never been reported in the literature. In this presentation, we report that strong vibrations of the frequency around 20 Hz is observed using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width. The oscillation behavior is consistent with the theoretical prediction.

Nagahiro, Shin-Ichiro; Nakanishi, Hiizu; Mitarai, Namiko

2013-03-01

81

Measuring shear viscosity using correlations

Digital Repository Infrastructure Vision for European Research (DRIVER)

Measurements of transverse momentum fluctuations can be used to determine the shear viscosity [1]. We use current data to estimate the viscosity-to-entropy ratio in the range from 0.08 to 0.3, and discuss how future measurements can reduce this uncertainty.

Gavin, Sean; Abdel-aziz, Mohamed

2007-01-01

82

Geoboards are viewed as excellent vehicles for developing intuitive understandings of various topics in transformational geometry. The activities described are designed to show pupils that when a triangle or parallelogram is subjected to a transformation called a shear, its area is not changed. Ways for finding areas are detailed. (MP)

Spitler, Gail

1982-01-01

83

Measuring shear viscosity using correlations

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Measurements of transverse momentum fluctuations can be used to determine the shear viscosity [1]. We use current data to estimate the viscosity-to-entropy ratio in the range from 0.08 to 0.3, and discuss how future measurements can reduce this uncertainty. [...

Gavin, Sean; Abdel-Aziz, Mohamed.

84

The mechanism for shear thickening in suspensions

Densely packed suspensions can shear thicken, in which the viscosity increases with shear rate. Video microscopy along with rheology measurements show the shear thickening regime is a transition from negligible particle motion at low stresses to fully developed shear flow at higher stresses. The onset of shear thickening occurs when the shear stress is sufficient to pull particles apart; for example against gravity for large particles, and can be tuned by inducing electric or magnetic dipoles. Dilation can be observed as particles penetrate the fluid surface in the high stress regime. The maximum stress of the shear thickening regime is shown to match, for a wide range of suspensions, the ratio of surface tension divided by a radius of curvature comparable to the particle size. This suggests the large stress associated with shear thickening comes from capillary forces as a consequence of dilation.

Brown, Eric; Jaeger, Heinrich

2009-11-01

85

Fabric of Kaolinite in Direct Shear Tests.

Fabric data on kaolinite samples sheared in drained direct shear are obtained from carbowax impregnated samples that were examined by light microscopy and x-ray diffraction. Previous research in this laboratory has repeatedly demonstrated that when proper...

R. T. Martin

1972-01-01

86

Residual shear deformations in the coronary artery.

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 is introduced as a parameter to quantify the residual shear deformations. Furthermore, a stress analysis is performed to study the effects of residual shear deformations on the intramural shear stress distribution of an artery subjected to pressure, axial stretch, and torsion using numerical simulation. The results from the stress analyses suggest that residual shear deformations can significantly modulate the intramural shear stress across the arterial wall. PMID:24686990

Wang, Ruoya; Gleason, Rudolph L

2014-06-01

87

Role of shear in the cosmological distance.

The effect of shear along light rays on the distance-redshift relation in an inhomogeneous universe is investigated on the basis of relativistic optical equations. With some reasonable assumptions, an analytic formula for the shear in a simplified cosmolo...

K. Watanabe M. Sasaki

1990-01-01

88

Shear Strength of RC Bridge Deck Cantilevers

Digital Repository Infrastructure Vision for European Research (DRIVER)

An experimental and theoretical investigation of the shear strength of reinforced concrete slabs without shear reinforcement is under way at the Ecole Polytechnique Fédérale de Lausanne. The first part of the program consists of 6 tests on two large scale bridge deck cantilevers. The specimens are tested under different configurations of concentrated forces simulating traffic loads. The observed failure mode is shear. The second part of the experimental program consists of shear tests on 12...

Vaz Rodrigues, Rui

2006-01-01

89

Shear deformation laminate theory used for sandwiches

Directory of Open Access Journals (Sweden)

Full Text Available The shear deformation laminate theory is very useful for the calculation of the sandwich composites. Sandwich can be defined as a special laminate with three layers and therefore can be modeled using shear deformation laminate theory by neglecting of membrane and bending deformations in the core and the shear deformation in the facings.

E. Kormaníková

2011-07-01

90

Shear deformation laminate theory used for sandwiches

Digital Repository Infrastructure Vision for European Research (DRIVER)

The shear deformation laminate theory is very useful for the calculation of the sandwich composites. Sandwich can be defined as a special laminate with three layers and therefore can be modeled using shear deformation laminate theory by neglecting of membrane and bending deformations in the core and the shear deformation in the facings.

2011-01-01

91

Armchair graphene nanoribbons under shear strain

The symmetry and electronic properties of armchair graphene nanoribbons (AGNRs) have been investigated using density functional theory calculations. For the shear strained AGNRs, the D6h (6/mmm) symmetry of the hexagonal lattice further turns into 2/m. The stability improves with increasing ribbon width under the same shear strain. Besides, the modification of the energy gap under shear strain is weak.

Qu, Li-Hua; Zhang, Jian-Min; Xu, Ke-Wei; Ji, Vincent

2014-06-01

92

Controlled shear/tension fixture

Energy Technology Data Exchange (ETDEWEB)

A test fixture for simultaneously testing two material test samples is provided. The fixture provides substantially equal shear and tensile stresses in each test specimens. By gradually applying a load force to the fixture only one of the two specimens fractures. Upon fracture of the one specimen, the fixture and the load train lose contact and the second specimen is preserved in a state of upset just prior to fracture. Particular advantages of the fixture are (1) to control the tensile to shear load on the specimen for understanding the effect of these stresses on the deformation behavior of advanced materials, (2) to control the location of fracture for accessing localized material properties including the variation of the mechanical properties and residual stresses across the thickness of advanced materials, (3) to yield a fractured specimen for strength measurement and an unfractured specimen for examining the microstructure just prior to fracture.

Hsueh, Chun-Hway (Knoxville, TN); Liu, Chain-tsuan (Knoxville, TN); George, Easo P. (Knoxville, TN)

2012-07-24

93

Scaling of entropic shear rigidity.

The scaling of shear modulus near the gelation-vulcanization transition is explored heuristically and analytically. It is found that in a dense melt the effective chains of the infinite cluster have sizes that scale sublinearly with their contour length. Consequently, each chain contributes k(B)T to the rigidity, which leads to a shear-modulus exponent dnu. In contrast, in phantom elastic networks the scaling is linear in the contour length, yielding an exponent identical to that of the random resistor network conductivity, as predicted by de Gennes. For nondense systems, the exponent should cross over to dnu when the percolation correlation length is much larger than the density-fluctuation length. PMID:15601099

Xing, Xiangjun; Mukhopadhyay, Swagatam; Goldbart, Paul M

2004-11-26

94

Shear instability in skin tissue

We propose two toy-models to describe, predict, and interpret the wrinkles appearing on the surface of skin when it is sheared. With the first model, we account for the lines of greatest tension present in human skin by subjecting a layer of soft tissue to a pre-stretch, and for the epidermis by endowing one of the layer's faces with a surface tension. For the second model, we consider an anisotropic model for the skin, to reflect the presence of stiff collagen fibres in a softer elastic matrix. In both cases, we find an explicit bifurcation criterion, linking geometrical and material parameters to a critical shear deformation accompanied by small static wrinkles, with decaying amplitudes normal to the free surface of skin.

Ciarletta, Pasquale; Gower, Artur L

2013-01-01

95

Mixing in shear thinning fluids

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. Analyses 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 lit...

Ameur, H.; Bouzit, M.

2012-01-01

96

Cosmological Parameters from Cosmic Shear

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present simulations of a cosmic shear survey and show how the survey geometry influences the accuracy of determination of cosmological parameters. We numerically calculate the full covariance matrices of the two-point statistics \\xi_+, \\xi_- and and use maximum likelihood and Fisher matrix analyses in order to derive expected constraints on the cosmological parameters \\Omega_m, \\sigma_8, \\Gamma, n_s and \\Omega_\\Lambda.

Kilbinger, Martin

2003-01-01

97

Experimental observation of shear thickening oscillation

We report experimental observations of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed that well-marked vibrations of frequency around 20 Hz appear via a Hopf bifurcation upon increasing externally applied shear stress. The parameter range and the frequency of the vibration are consistent with those expected by a simple phenomenological model of the dilatant fluid.

Nagahiro, Shin-ichiro; Nakanishi, Hiizu; Mitarai, Namiko

2013-10-01

98

Ideal stability limits of reverse shear equilibria

International Nuclear Information System (INIS)

The dependence on various plasma parameters of the ideal stability limit of reverse shear current profiles in TFTR and other tokamaks has been thoroughly explored. Profiles with reverse shear allow core access to the second ballooning stability region. In addition, for sufficient shear reversal, modes with n = 2 and greater are also stabilized. The n = 1 stability threshold is only slightly affected by reverse shear and becomes the limiting instability. The mode is predominately an infernal mode with a significant external contribution. Particular emphasis will be on analysis of recent experimental results of enhanced reverse shear (ERS) profiles in TFTR and a study of those profile characteristics which optimize TFTR performance

1996-03-18

99

Magnetic shear. II - Hale region 17244

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.

Athay, R. G.; Jones, H. P.; Zirin, H.

1985-01-01

100

Stability Criteria of 3D Inviscid Shears

The classical plane Couette flow, plane Poiseuille flow, and pipe Poiseuille flow share some universal 3D steady coherent structure in the form of "streak-roll-critical layer". As the Reynolds number approaches infinity, the steady coherent structure approaches a 3D limiting shear of the form ($U(y,z), 0, 0$) in velocity variables. All such 3D shears are steady states of the 3D Euler equations. This raises the importance of investigating the stability of such inviscid 3D shears in contrast to the classical Rayleigh theory of inviscid 2D shears. Several general criteria of stability for such inviscid 3D shears are derived. In the Appendix, an argument is given to show that a 2D limiting shear can only be the classical laminar shear.

Li, Y Charles

2009-01-01

101

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)

1966-04-01

102

Biomechanics of single chondrocytes under direct shear.

Articular chondrocytes experience a variety of mechanical stimuli during daily activity. One such stimulus, direct shear, is known to affect chondrocyte homeostasis and induce catabolic or anabolic pathways. Understanding how single chondrocytes respond biomechanically and morphologically to various levels of applied shear is an important first step toward elucidating tissue level responses and disease etiology. To this end, a novel videocapture method was developed in this study to examine the effect of direct shear on single chondrocytes, applied via the controlled lateral displacement of a shearing probe. Through this approach, precise force and deformation measurements could be obtained during the shear event, as well as clear pictures of the initial cell-to-probe contact configuration. To further study the non-uniform shear characteristics of single chondrocytes, the probe was positioned in three different placement ranges along the cell height. It was observed that the apparent shear modulus of single chondrocytes decreased as the probe transitioned from being close to the cell base (4.1 +/- 1.3 kPa), to the middle of the cell (2.6 +/- 1.1 kPa), and then near its top (1.7 +/- 0.8 kPa). In addition, cells experienced the greatest peak forward displacement (approximately 30% of their initial diameter) when the probe was placed low, near the base. Forward cell movement during shear, regardless of its magnitude, continued until it reached a plateau at ~35% shear strain for all probe positions, suggesting that focal adhesions become activated at this shear level to firmly adhere the cell to its substrate. Based on intracellular staining, the observed height-specific variation in cell shear stiffness and plateau in forward cell movement appeared to be due to a rearrangement of focal adhesions and actin at higher shear strains. Understanding the fundamental mechanisms at play during shear of single cells will help elucidate potential treatments for chondrocyte pathology and loading regimens related to cartilage health and disease. PMID:19644718

Ofek, Gidon; Dowling, Enda P; Raphael, Robert M; McGarry, J Patrick; Athanasiou, Kyriacos A

2010-04-01

103

Rheology of discontinuously shear thickening suspensions beyond simple shear

The behavior of discontinuously shear thickening suspensions in flows other than simple shear is not well understood, in part due to unresolved experimental challenges. For example, such suspensions thicken most easily close to rigid boundaries due to the no-slip condition. This makes experiments highly dependent on the shape and size of the container used. We show that by placing a lubricating layer of oil between the suspension and the container we can generate flows where thickening is nearly independent of rigid boundaries. This method is particularly useful in creating quasi one- and two-dimensional flows, which can be easily visualized. We use this method to conduct capillary breakup experiments with thickening suspensions of silica and cornstarch particles, in which we observe the formation of beads-on-a-string morphologies with multiple satellite and sub-satellite bead generations, similar to the morphologies observed in breakup of viscoelastic fluids. Using a one-dimensional continuum model, we show how nonlinear rheology of thickening suspensions results in the creation of these complex morphologies.

Zimoch, Pawel; McKinley, Gareth; Hosoi, Anette

2012-02-01

104

Mixing in shear thinning fluids

Directory of Open Access Journals (Sweden)

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. Analyses 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.

H. Ameur

2012-06-01

105

Simulation of sheared, caking powder

We introduce a visco-elastic contact model for DEM simulations, which takes caking into account and investigate the impacts of this time dependent inter particle cohesion force on the bulk behavior under biaxial deformation. Starting from the assumption that the cohesion force between two particles develops on a characteristic timescale tc, we show, that two regimes can be identified. If tc is small compared to the shear rate ??, full cohesion is reached within the typical contact duration. The cohesion strength remains homogeneous throughout the sample. However, if tc >> ?? crystallization bridges at fluctuating contacts never fully recover. Heterogeneous cohesion forces and granules are the consequence.

Weuster, A.; Brendel, L.; Wolf, D. E.

2013-06-01

106

Directory of Open Access Journals (Sweden)

Full Text Available Effect of low voltage electrical stimulation (LVES; 45 volt, 3 amps for approx 100 sec and calcium chloride (CaCl2 injection on physical properties of meat were evaluated. Six mutton were devided into 3 groups. One carcass of each group was subjected to within 30 min postmortem (PM. After LVES, longissimi thoracis et lumbarum muscles were removed and treated: without CaCl2 injection, CaCl2 injection (200 mM, 5% w/w at about 2 h and 24 h PM. Samples were stored in vacuum pack at 1 ± 1o C. Physical properties evaluated were Warner–Bratzler (WB shear force, cooking loss and sarcomere length. The LVES had no significant effect on WB shear force, cooking loss and sarcomere length. There wasn’t interaction effect between LVES and CaCl2 injection on WB shear force, cooking loss and sarcomere length. CaCl2 injection decreased sarcomere length (P<0.01, therefore resulted in tougher meat with higher cooking loss.

T. Suryati

2004-12-01

107

Influence of post-mortem aging in tenderness of chicken breast fillets

Directory of Open Access Journals (Sweden)

Full Text Available In this work, analysis of chicken breast fillets was performed for shear values and sensory evaluation after different times of aging. Aging process was carried out by holding carcasses in covered plastic boxes, in a cold room, at 3 +/- 1masculineC; groups of 5 carcasses were stored and classified according to the period of storage in cold room as 0 (control, 2, 4, 8, 12 and 24 hours. The variation in pH of chicken carcasses during rigor decreased from 6.4 to 5.9. However, during the process of aging, the pH values increased up to 6.2 in the first 12h, probably as the result of proteolysis. The Warner-Bratzler shear values decreased as aging time increases, resulting in a first order kinetic. The carcasses presented a more accentuated decline in shear values in the first two hours of aging. After this period, the curve had a similar performance, achieving values of less than 1 kgf in 4 hours or more, with complete aging being accomplished at 8 hours. The samples with higher period of aging (8, 12 and 24 hours were preferred in sensorial analysis, without significant differences among them.

Santos Helena Caminha

2004-01-01

108

DEFF Research Database (Denmark)

BACKGROUND: Marination of beef muscles with brine solutions containing proteolytic enzymes from fruit extracts has been shown to tenderize meat. However, the effect of marination with actinidin on tenderness of pork muscles has not been investigated. Tenderness and eating quality of porcine M. biceps femoris was investigated by Warner-Bratzler (WB) shear test and sensory evaluation after injection of brine containing up to 11 g L-1 actinidin-containing kiwi fruit powder and 2, 5 or 9 days of storage. RESULTS: actinidin decreased WB shear force, increased tenderness and did not affect flavour and juiciness. Injection of 2.8g L-1 actinidin powder and storage for 2 days resulted in WB shear force values similar to control samples stored for 5 or 9 days. In samples injected with 10 g L-1 actinidin powder, degradation of desmin and percentage of heat-soluble collagen (P <0.05) increased compared to control samples. Myofibrillar particle size tended to decrease (P <0.1) with increasing actinidin concentration. No major changes were observed by proteome analysis. Atomic force microscopy showed actinidin-induced damage of endomysium surrounding isolated single muscle fibres. CONCLUSION: Our results indicate that actinidin tenderizes pork M. biceps femoris by affecting both the myofibrils and connective tissue.

Rozlosnik, Noemi

2009-01-01

109

Perspectives on the application of zilpaterol hydrochloride in the United States beef industry.

Zilpaterol hydrochloride (ZH) is a beta-adrenergic agonist approved to be fed at a rate of 8.3 mg/kg (100% DM basis) during the final 20 to 40 d of the finishing period in beef cattle followed by a minimum 3-d withdrawal period antemortem. The Federal Drug Administration (FDA) approved label claims of increased rate of BW gain, improved feed efficiency, and increased carcass leanness. Before the release of ZH for commercial use in 2007, approximately 10 independent research trials at various universities and commercial feedlots were initiated. Articles in recent issues of the Journal of Animal Science are a result of the large comprehensive body of research designed to increase the understanding of the effect of ZH on beef cattle growth, carcass traits, and beef quality. The feeding of ZH for 20 to 40 d with a 3-d withdrawal resulted in significantly increased ADG. The increases equate to an average of 9 kg heavier BW in ZH-fed steers. Hot carcass weight has been shown to increase to a larger degree compared with BW, with an average improvement of 15 kg. Dressing percent is increased by 1.5 to 2.0% with the feeding of ZH. Increases in carcass leanness were reported for cattle fed ZH mainly through a reduction in yield grades. The LM area was increased, along with yield of subprimal cuts from the round, flank, and loin. Warner-Bratzler shear force studies have shown LM steaks from ZH-treated cattle to have increased shear force values of 1.1 to 1.7 kg for 7-d-aged steaks, 0.4 to 1.3 kg for 14-d-aged steaks, and 0.27 to 1.4 kg for 21-d-aged steaks compared with controls. Recent research has suggested that the aging response is normal in ZH steaks. Consumers were able to identify tenderness differences in 14-d-aged Choice steaks from cattle fed ZH for 20 d compared with 14-d-aged steaks from control cattle; this difference was mitigated with 21 d of postmortem aging. Zilpaterol hydrochloride has been shown to increase cattle growth and efficiency as well as lean tissue deposition in the carcass, with some impact on carcass traits such as Warner-Bratzler shear force. PMID:20382871

Delmore, R J; Hodgen, J M; Johnson, B J

2010-08-01

110

Redox Going with Vascular Shear Stress

Digital Repository Infrastructure Vision for European Research (DRIVER)

Shear stress plays a critical role in the regulation of vascular biology and diseases, such as atherosclerosis, via modulation of signal transduction and redox balance. Atherosclerosis preferentially occurs in a site-specific manner linked to disturbed flow. In this Forum on Vascular Shear Stress, emerging role of redox-dependent molecular mechanisms by which shear stress regulates pro- and antiatherogenic responses in endothelial cells both in vitro and in vivo are reviewed in depth by exper...

Noguchi, Noriko; Jo, Hanjoong

2011-01-01

111

Elastic Turbulence in Shear Banding Wormlike Micelles

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the dynamics of the Taylor-Couette flow of shear banding wormlike micelles. We focus on the high shear rate branch of the flow curve and show that for sufficiently high Weissenberg numbers, this branch becomes unstable. This instability is strongly subcritical and is associated with a shear stress jump. We find that this increase of the flow resistance is related to the nucleation of turbulence. The flow pattern shows similarities with the elastic turbulence, so far only observed for...

Fardin, Marc-antoine; Lopez, D.; Croso, J.; Gregoire, G.; Cardoso, O.; Mckinley, Gareth H.; Lerouge, S.

2010-01-01

112

Viscoelastic shear properties of the corneal stroma.

The cornea is a highly specialized transparent tissue which covers the front of the eye. It is a tough tissue responsible for refracting the light and protecting the sensitive internal contents of the eye. The biomechanical properties of the cornea are primarily derived from its extracellular matrix, the stroma. The majority of previous studies have used strip tensile and pressure inflation testing methods to determine material parameters of the corneal stroma. Since these techniques do not allow measurements of the shear properties, there is little information available on transverse shear modulus of the cornea. The primary objectives of the present study were to determine the viscoelastic behavior of the corneal stroma in shear and to investigate the effects of the compressive strain. A thorough knowledge of the shear properties is required for developing better material models for corneal biomechanics. In the present study, torsional shear experiments were conducted at different levels of compressive strain (0-30%) on porcine corneal buttons. First, the range of linear viscoelasticity was determined from strain sweep experiments. Then, frequency sweep experiments with a shear strain amplitude of 0.2% (which was within the region of linear viscoelasticity) were performed. The corneal stroma exhibited viscoelastic properties in shear. The shear storage modulus, G', and shear loss modulus, G?, were reported as a function of tissue compression. It was found that although both of these parameters were dependent on frequency, shear strain amplitude, and compressive strain, the average shear storage and loss moduli varied from 2 to 8kPa, and 0.3 to 1.2kPa, respectively. Therefore, it can be concluded that the transverse shear modulus is of the same order of magnitude as the out-of-plane Young's modulus and is about three orders of magnitude lower than the in-plane Young's modulus. PMID:24368145

Hatami-Marbini, Hamed

2014-02-01

113

Shear wall experiments and design in Japan

International Nuclear Information System (INIS)

This paper summarizes the results of recent survey studies on the available experimental data bases and design codes/standards for reinforced concrete (RC) shear wall structures in Japan. Information related to the seismic design of RC reactor buildings and containment structures was emphasized in the survey. The seismic requirements for concrete structures, particularly those related to shear strength design, are outlined. Detailed descriptions are presented on the development of Japanese shear wall equations, design requirements for containment structures, and ductility requirements

1994-12-14

114

Dynamo quenching due to shear flow

Digital Repository Infrastructure Vision for European Research (DRIVER)

We provide a theory of dynamo (? effect) and momentum transport in three-dimensional magnetohydrodynamics. For the first time, we show that the ? effect is reduced by the shear even in the absence of magnetic field. The ? effect is further suppressed by magnetic fields well below equipartition (with the large-scale flow) with different scalings depending on the relative strength of shear and magnetic field. The turbulent viscosity is also found to be significantly reduced by shear and magn...

2008-01-01

115

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

1994-01-01

116

Shear instability of a gyroid diblock copolymer

DEFF Research Database (Denmark)

The stability of the gyroid phase of diblock copolymers has been studied using combined oscillatory shear and small-angle neutron scattering (SANS) techniques. It is shown that the gyroid phase of polystyrene-polyisoprene (PS-PI) is unstable when exposed to combined large-amplitude and high-frequency shear deformations. The bicontinuous cubic gyroid structure (G) transforms to the hexagonally cylinder phase (HEX). The transition is perfectly reversible, but with a significant difference in time constants. Upon application of shear the G --> HEX transition is instantaneous within experimental resolution, while the HEX --> G relaxation after cessation of shear takes hours. The texture of the shear-induced cylinder phase is shown to be a near ideal monodomain, while the relaxed gyroid phase constitutes a two-dimensional powder with the characteristic 10-spot scattering pattern. The shear-induced destabilization is discussed in relation to analogous observations on shear-induced order-to-order and disorder-to-order transitions observed in related block copolymer systems and in microemulsions. It is discussed whether these phenomena originate in shear-reduced fluctuations or shear-induced dislocations.

Eskimergen, RÃ¼ya; Mortensen, Kell

2005-01-01

117

Measurement of temperature using speckle shearing interferometry.

A laser speckle shearing interferometric technique is used for measuring the temperature profile inside a gaseous flame. The experimental results are compared with the values obtained by a thermocouple and also by speckle photography. Good agreement is seen among the temperatures measured by speckle shearing interferometry, speckle photography, and the thermocouple. Speckle shearing interferometry is easier to implement than speckle photography. This is because in speckle shearing interferometry the accurate positions of the fringes can be known without point-by-point analysis and correction for the halo effect. PMID:20885553

Shakher, C; Nirala, A K

1994-04-10

118

Novel shear mechanism in nanolayered composites

Energy Technology Data Exchange (ETDEWEB)

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.

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

119

Dynamic shear deformation in high purity Fe

Energy Technology Data Exchange (ETDEWEB)

The forced shear test specimen, first developed by Meyer et al. [Meyer L. et al., Critical Adiabatic Shear Strength of Low Alloyed Steel Under Compressive Loading, Metallurgical Applications of Shock Wave and High Strain Rate Phenomena (Marcel Decker, 1986), 657; Hartmann K. et al., Metallurgical Effects on Impact Loaded Materials, Shock Waves and High Strain rate Phenomena in Metals (Plenum, 1981), 325-337.], has been utilized in a number of studies. While the geometry of this specimen does not allow for the microstructure to exactly define the location of shear band formation and the overall mechanical response of a specimen is highly sensitive to the geometry utilized, the forced shear specimen is useful for characterizing the influence of parameters such as strain rate, temperature, strain, and load on the microstructural evolution within a shear band. Additionally, many studies have utilized this geometry to advance the understanding of shear band development. In this study, by varying the geometry, specifically the ratio of the inner hole to the outer hat diameter, the dynamic shear localization response of high purity Fe was examined. Post mortem characterization was performed to quantify the width of the localizations and examine the microstructural and textural evolution of shear deformation in a bcc metal. Increased instability in mechanical response is strongly linked with development of enhanced intergranular misorientations, high angle boundaries, and classical shear textures characterized through orientation distribution functions.

Cerreta, Ellen K [Los Alamos National Laboratory; Bingert, John F [Los Alamos National Laboratory; Trujillo, Carl P [Los Alamos National Laboratory; Lopez, Mike F [Los Alamos National Laboratory; Gray, George T [Los Alamos National Laboratory

2009-01-01

120

Shear-stress dependence of dinoflagellate bioluminescence.

Fluid flow stimulates bioluminescence in dinoflagellates. However, many aspects of the cellular mechanotransduction are incompletely known. The objective of our study was to formally test the hypothesis that flow-stimulated dinoflagellate bioluminescence is dependent on shear stress, signifying that organisms are responding to the applied fluid force. The dinoflagellate Lingulodinium polyedrum was exposed to steady shear using simple Couette flow in which fluid viscosity was manipulated to alter shear stress. At a constant shear rate, a higher shear stress due to increased viscosity increased both bioluminescence intensity and decay rate, supporting our hypothesis that bioluminescence is shear-stress dependent. Although the flow response of non-marine attached cells is known to be mediated through shear stress, our results indicate that suspended cells such as dinoflagellates also sense and respond to shear stress. Shear-stress dependence of flow-stimulated bioluminescence in dinoflagellates is consistent with mechanical stimulation due to direct predator handling in the context of predator-prey interactions. PMID:17565113

Maldonado, Elisa M; Latz, Michael I

2007-06-01

121

Shear localization in a model glass

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.

Varnik, F; Barrat, J L; Berthier, L

2002-01-01

122

Piping shear lug stress analysis

International Nuclear Information System (INIS)

Due to space limitations present in many of the current nuclear power plants, it is frequently necessary to apply restraints skewed to a piping system's axis in order to restrain the piping against hydraulic transient and seismic loads. In order to assure that the restraints function as required, shear lugs are often used to eliminate relative motion between the pipe and the restraint. Detailed stress analyses of the pipe-lug system are presented and expressions for the needed indices are deduced. The analyses are accomplished through use of three-dimensional finite-element modeling employing the computer program SAP IV. Eight node brick elements are used to represent both the pipe and the lug. The resulting mesh consists of 316 elements and 558 nodes and incorporates the symmetry aspects of the physical system. The mesh is a graded one with small elements employed in the area of the lug. A check on the expected accuracy is obtained through a comparison with both an approximate elasticity solution and a proprietary computer program ISOPAR-SHL. The latter allows local stress concentration regions to be modeled by using higher order three-dimensional elements (36 nodes) while the remaining structure is represented by curved shell elements, with transition elements connecting the two. Numerical results are carried out for typical pipe diameters and loadings are then interpreted and recast in terms of the Code design criteria. They are furthermore compared with the results obtained by employing the procedure given in WRC Bulletin 198. This comparison illustrates the conservativeness of the WRC approach, especially for small lugs and lugs whose long dimension is in the circumferential direction. In particular, for a circumferential lug on a 12 in. diameter pipe subjected to loading representative of the up set condition, use of the WRC procedure yields results which are larger by a factor of four for the shear term and by 1.5 for the bending term

1977-08-19

123

Dynamic wetting of shear thinning fluids

The impact of non-Newtonian behavior on dynamic wetting is critical since many fluids exhibit such behavior somewhere in the high-shear environment inherent in the wedge flow near a moving contact line. This impact will be different for two broad categories of non-Newtonian behavior, shear thinning, and elasticity. In this paper, we discuss the steady-state wetting of a fluid, aqueous solutions of xanthan gum, dominated by shear thinning but with negligible elasticity. In the shear thinning fluid, viscous bending near the contact line is greatly reduced compared to a Newtonian fluid having the same zero-shear viscosity. Concomitant with this reduction in viscous bending, the effective dynamic contact angle has a much weaker dependence on capillary number, Ca, than is observed in, or predicted for, Newtonian fluids. A simple lubrication model using a constitutive relation with power-law shear thinning at high shear rates and a Newtonian plateau at low shear rates mimics the trends seen in our data and elucidates the origins of the reduced viscous bending.

Seevaratnam, G. K.; Suo, Y.; Ramé, E.; Walker, L. M.; Garoff, S.

2007-01-01

124

Study of shear-stiffened elastomers

Shear thickening fluids, which are usually concentrated colloidal suspensions composed of non-aggregating solid particles suspended in fluids, exhibit a marked increase in viscosity beyond a critical shear rate. This increased viscosity is seen as being both 'field-activated', due to the dependence on shearing rate, as well as reversible. Shear thickening fluids have found good applications as protection materials, such as in liquid body armor, vibration absorber or dampers. This research aims to expand the protection material family by developing a novel solid status shear thickening material, called shear-stiffened elastomers. These new shear-stiffened elastomers were fabricated with the mixture of silicone rubber and silicone oil. A total of four SSE samples were fabricated in this study. Their mechanical and rheological properties under both steady-state and dynamic loading conditions were tested with a parallel-plate. The effects of silicone oil composition and angular frequency were summarized. When raising the angular frequency in dynamic shear test, the storage modulus of conventional silicone rubber shows a small increasing trend with the frequency. However, if silicone oil is selected to be mixed with silicone rubber, the storage modulus increases dramatically when the frequency and strain are both beyond the critical values.

Tian, Tongfei; Li, Weihua; Ding, Jie; Alici, Gursel; Du, Haiping

2013-06-01

125

Direct measurement of piezoelectric shear coefficient

Piezoelectric materials exhibit electromechanical coupling which has led to their widespread application for sensors, actuators, and energy harvesters. These materials possess anisotropic behavior with the shear coefficient, and have the largest electromechanical coupling coefficient. However, the shear mode is difficult to measure with existing techniques and thus has not been fully capitalized upon in recent devices. Better understanding of the full shear response with respect to the driving electric field would significantly help the design of optimized piezoelectric shear devices. Here, a simple and low cost direct measurement method based on digital image correlation is developed to characterize the shear response of piezoelectric materials and its nonlinear behavior as a function of external field. The piezoelectric shear coefficient (d15) of a commercial shear plate actuator is investigated in both bipolar and unipolar electric fields. Two different nonlinearities and hysteresis behaviors of the actuators were observed, and the relation between the driving field amplitude and the corresponding d15 coefficient is determined. Moreover, the measured transverse displacement of the plate actuator in simple shear condition is validated through a laser interferometry technique.

Malakooti, Mohammad H.; Sodano, Henry A.

2013-06-01

126

Plastic deformation: Shearing mountains atom by atom

Energy Technology Data Exchange (ETDEWEB)

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.

Müllner, Peter, E-mail: petermullner@boisestate.edu [Department of Materials Science and Engineering, Boise State University, Boise, ID 83725 (United States)

2013-11-15

127

Plastic deformation: Shearing mountains atom by atom

International Nuclear Information System (INIS)

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

2013-11-15

128

Shear induced phase transitions in simple fluids

International Nuclear Information System (INIS)

Computer simulation indicates that the pressure of a fluid under shear is a function of the strain rate. The phase diagram will be dependent on the shear and, in particular the critical point will be shifted. The effect is shown quantitatively for a Lennard-Jones fluid. (orig.)

1980-01-01

129

Shear free solutions of Maxwell's equations

International Nuclear Information System (INIS)

A twisting shear free solution of Maxwell's equations is obtained by transforming to a complex coordinate system in which the corresponding solution is complex but twist free. The equations in this system are easily solved, and, by transforming back to the original coordinates, a twisting shear free solution of Maxwell's equations is obtained. (author)

1975-01-01

130

Shear Flows and Shear Viscosity in a Two-Dimensional Yukawa System (Dusty Plasma)

The shear viscosity of a two-dimensional liquid-state dusty plasma was measured experimentally. A monolayer of highly charged polymer microspheres, with a Yukawa interaction, was suspended in a plasma sheath. Two counter-propagating Ar laser beams pushed the particles, causing shear-induced melting of the monolayer and a shear flow in a planar Couette configuration. By fitting the particle velocity profiles in the shear flow to a Navier-Stokes model, the kinematic viscosity was calculated; it was of order 1 mm^2/s, depending on the monolayer's parameters and shear stress applied.

Nosenko, V

2004-01-01

131

Magnetic Field Generation by Relativistic Shear Flows

We report PIC simulation results of magnetic field generation by relativistic shear flows. We find that the shear flow boundary layer in initially non-magnetic shear flows is unstable to the growth of oblique 2-stream and Weibel instabilities near the boundary layer. Such instabilities generate current sheets and loops which eventually form nonlinear ordered structures resembling magnetic flux tubes with alternating polarity, orthogonal to the shear flow direction. Peak magnetic fields can reach almost equipartition values. The size and amplitude of such magnetic structures reach a steady state when the free energy input of the shear flow is balanced by turbulence dissipation. Nonthermal particles are efficiently accelerated, likely by the drift-kink instability, into a power-law energy distribution. These results have important implications for many astrophysical settings, including multi-component blazar jets and gamma-ray bursts. This work was supported by NSF AST0909167 and NASA Fermi grants.

Liang, Edison; Boettcher, Markus; Smith, Ian

2011-11-01

132

Weak Lensing Mass Reconstruction: Flexion vs Shear

Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the Universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of a shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone not be used to do convergence map reconstruction, even on small scales...

Pires, S

2010-01-01

133

Numerical analysis of cross shear plate rolling

DEFF Research Database (Denmark)

The rolling process is widely applied for industrial production of metal plates. In conventional plate rolling the two work rolls are rotating at the same peripheral speed. By introducing a specific difference in the speed of the two work rolls, cross shear rolling is introduced forming a central shear zone between the forward and backward slip zones in the deformation zone thus lowering the rolling load. A numerical analysis of the cross shear rolling process is carried out based on the slab method adopting Wanheim and Bay's general friction model. The pressure distribution along the contact are in the roll gap, the position and the size of the shear zone and the rolling load are calculated. Experimental results are presented verifying the calculations. The numerical analysis facilitates a better understanding of the mechanics in cross shear plate rolling.

Zhang, Wenqi; Bay, Niels

1997-01-01

134

Ceramics: 1. Shear and dilatation effects

International Nuclear Information System (INIS)

Transformation plasticity in ZrO2-containing ceramics generally exhibits shear and dilation effects of comparable magnitude. The coupling between external stresses and crystallographic strains assists the tetragonal-monoclinic transformation, which, via shear localization, gives rise to macroscopic shear and dilatant deformation. Application of a yield criterion based on both shear and dilatation effects correctly correlates deformation data from tension, compression, bending, and indentation, and further delineates a crack-tip process zone comparable to the one observed experimentally. Similar shear and dilatation effects in microcracking due to transformation plasticity are explored. These findings suggest that the strength of the ultimate transformation-toughened structural ceramics should be yield limited and sensitive to the stress state. Strategies for fracture control are recommended

1986-01-01

135

Role of velocity shears in turbulent dissipation

The discussion about what processes are important in solar wind plasma heating usually concentrates on wave particle interactions or on energization by low frequency structures like current sheets and reconnection sites. Less attention has been paid to the role of local velocity shears in plasma heating. We study this problem using Hall-FLR MHD and hybrid codes. We see that the velocity shear sites are related to hot spots and most of the dissipated energy comes from velocity shears. The ultimate energy deposition mechanism is electromagnetic interactions but these interactions are enhanced at the velocity shear sites making them an attractive candidate for sites of dissipation along with magnetic shear sites like the current sheets and reconnection sites.

Parashar, T. N.; Ghosh, S.

2013-12-01

136

Boundary Shear Stress around Bridge Piers

Directory of Open Access Journals (Sweden)

Full Text Available This research presents the measurement of boundary shear stress around the base of some elliptical shaped bridge piers using Preston tube technique. The uniform flow was established and a series of measurements having different discharges and channel bed slopes were undertaken. General results are established and then the effects of flow separation on the hydraulic theory are assessed. The Analysis of results shows that behind the bridge piers (horseshoe area; the amount of boundary shear stress reduces dramatically. The figure for the rate of boundary shear stress of nose to end is about ?r = ?n/?e = 3.6. It has a remarkable reduction even in steep slopes. The bed shear stress was found to intensify near the nose of the piers. The distribution of boundary shear stress in both mild and steep channel bed slopes along spanwise direction is presented that may give a valuable perspective of the flow action around piers.

Mirali Mohammadi

2008-01-01

137

Shear accommodation in dirty grain boundaries

The effect of solutes (dirt) on the mechanics of crystalline interfaces remains unexplored. Here, we perform atomic-scale simulations to study the effect of carbon segregation on the shear accommodation at select grain boundaries in the classical ?-Fe/C system. For shear velocities larger than the solute diffusion rate, we observe a transition from coupled motion to sliding. Below a critical solute excess, the boundaries break away from the solute cloud and exhibit in a coupled motion. At smaller shear velocities, the extrinsic coupled motion is jerky, occurs at relatively small shear stresses, and is aided by fast convective solute diffusion along the boundary. Our studies underscore the combined effect of energetics and kinetics of solutes in modifying the bicrystallography, temperature and rate dependence of shear accommodation at grain boundaries.

Wang, C.; Upmanyu, M.

2014-04-01

138

Determining Shear Stress Distribution in a Laminate

A "simplified shear solution" method approximates the through-thickness shear stress distribution within a composite laminate based on an extension of laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather, it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply-level stresses can be efficiently determined from global load resultants at a given location in a structure and used to evaluate the margin of safety on a ply-by-ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. The method has been incorporated within the HyperSizer commercial structural sizing software to improve its predictive capability for designing composite structures. The HyperSizer structural sizing software is used extensively by NASA to design composite structures. In the case of through-thickness shear loading on panels, HyperSizer previously included a basic, industry-standard, method for approximating the resulting shear stress distribution in sandwich panels. However, no such method was employed for solid laminate panels. The purpose of the innovation is to provide an approximation of the through-thickness shear stresses in a solid laminate given the through-thickness shear loads (Qx and Qy) on the panel. The method was needed for implementation within the HyperSizer structural sizing software so that the approximated ply-level shear stresses could be utilized in a failure theory to assess the adequacy of a panel design. The simplified shear solution method was developed based on extending and generalizing bi-material beam theory to plate-like structures. It is assumed that the through-thickness shear stresses arise due to local bending of the laminate induced by the through-thickness shear load, and by imposing equilibrium both vertically and horizontally, the through-thickness shear stress distribution can be calculated. The resulting shear stresses integrate to the applied shear load, are continuous at the ply interfaces, and are zero at the laminate-free surfaces. If both Qx and Qy shear loads are present, it is assumed that they act independently and that their effects can be superposed. The calculated shear stresses can be rotated within each ply to the principal material coordinates for use in a ply-level failure criterion. The novelty of the simplified shear solution method is its simplicity and the fact that it does not require solution of a particular boundary value problem. The advantages of the innovation are that an approximation of the though-thickness shear stress distribution can be quickly determined for any solid laminate or solid laminate region within a stiffened panel.

Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.

2010-01-01

139

Three dimensional fabric evolution of sheared sand

Energy Technology Data Exchange (ETDEWEB)

Granular particles undergo translation and rolling when they are sheared. This paper presents a three-dimensional (3D) experimental assessment of fabric evolution of sheared sand at the particle level. F-75 Ottawa sand specimen was tested under an axisymmetric triaxial loading condition. It measured 9.5 mm in diameter and 20 mm in height. The quantitative evaluation was conducted by analyzing 3D high-resolution x-ray synchrotron micro-tomography images of the specimen at eight axial strain levels. The analyses included visualization of particle translation and rotation, and quantification of fabric orientation as shearing continued. Representative individual particles were successfully tracked and visualized to assess the mode of interaction between them. This paper discusses fabric evolution and compares the evolution of particles within and outside the shear band as shearing continues. Changes in particle orientation distributions are presented using fabric histograms and fabric tensor.

Hasan, Alsidqi; Alshibli, Khalid (UWA)

2012-10-24

140

The properties of both untangled and entangled linear polymer melts under shear flow are studied by nonequilibrium molecular dynamics simulations. The results reveal that the dependence of shear viscosity ? on shear rate dot{? }, expressed by ? ˜ dot{? }^{-n}, exhibits three distinct regimes. The first is the well-known Newtonian regime, namely, ? independent of shear rate at small shear rates dot{? }polymer relaxation time at equilibrium). In the non-Newtonian regime (dot{? }>?0^{-1}), the shear dependence of viscosity exhibits a crossover at a critical shear rate dot{? }c dividing this regime into two different regimes, shear thinning regime I (ST-I) and II (ST-II), respectively. In the ST-I regime (?^{-1}_0dot{? }c) a universal power law ? ˜ dot{? }^{-0.37} is found for considered chain lengths. Furthermore, the longer the polymer chain is, the smaller the shear viscosity for a given shear rate in the ST-II regime. The simulation also shows that a characteristic chain length, below which dot{? }c will be equal to ?0^{-1}, lies in the interval 30 nature of shear thinning in flexible linear polymer melts.

Xu, Xiaolei; Chen, Jizhong; An, Lijia

2014-05-01

141

Establishment of the Deep-sea Soft Sediments Shearing Strength-Shearing Displacement Model

Directory of Open Access Journals (Sweden)

Full Text Available The shearing strength-shearing displacement model of deep-sea soft sediments is very important to predict the traction and slip ratio of nodule collector, and optimize the running mechanism of nodule collector. According to the physical mechanics characters of the deep-sea soft sediments, the 400 sodium molybdate swell soils are selected as the preparation materials of the deep-sea soft sediments, and the demixion preparation method is adopted to simulate the deep-sea soft sediments in the lab, and the shearing test of the rectangle board of 20×50 cm under different grounding pressures is completed in the soil slot. The test result shows that the simulated deep-sea soft sediments have the representative shearing strength-shearing displacement character of brittle soils. Three shearing strength-shearing displacement models of brittle soils are analyzed in the article, and the shearing strength-shearing displacement model being the same with the deep-sea soft sediments based on maximum shearing strength, residual shearing strength, and elastic modules is established, which can offer theoretical support for the structure optimization of running track and the enhancement of the running performance.

Hongyun Wu

2009-12-01

142

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.

2012-11-21

143

Reversible shear thickening at low shear rates of electrorheological fluids under electric fields.

By shearing electrorheological (ER) fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (100 V/mm), which can be characterized by a critical apparent viscosity. Shear thickening and electrostatic particle interaction-induced interparticle friction forces are considered to play an important role in the origin of lateral shear resistance of ER fluids, while the applied electric field controls the extent of shear thickening. The electric-field-controlled reversible shear thickening has implications for high-performance electrorheological-magnetorheological fluid design, clutch fluids with high friction forces triggered by applying a local electric field, other field-responsive materials, and intelligent systems. PMID:21405692

Tian, Yu; Zhang, Minliang; Jiang, Jile; Pesika, Noshir; Zeng, Hongbo; Israelachvili, Jacob; Meng, Yonggang; Wen, Shizhu

2011-01-01

144

Modified Shear Box Test Apparatus for Measuring Shear Strength of Unsaturated Residual Soil

Directory of Open Access Journals (Sweden)

Full Text Available Residual soils occur in most countries of the world but the greater areas and depths are normally found in tropical humid areas. Most of these soils exhibit high suctions for most of the year. The shear strength parameters, c’ and Î¦’, of soil can be obtained using conventional shear strength tests. However the conventional shear strength test equipments would not be able to measure Î¦b value (change of shear strength to change in suction without certain modification to them. This study describes the modifications that have been made to a standard shear box test apparatus to enable it to test soil samples in unsaturated conditions. The modifications include fabrication of an air pressure chamber, modifications of the shear box assembly inside the air pressure chamber, modification to the normal loading system, as well as additions of data acquisition devices to enhance the performance and simplify the usage of the modified shear box test apparatus.

Bujang B.K. Huat

2005-01-01

145

Tempo de cozimento e textura de raízes de mandioca / Cooking time and texture of cassava roots

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese 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

Talma, Simone Vilela; Almeida, Selma Bergara; Lima, Rozana Moreira Pereira; Vieira, Henrique Duarte; Bebert, Pedro Amorim.

146

The objective of this study was to examine the effects of supplemental feeding of full-fat extruded cottonseed pellets (FFECS) compared with tallow on carcass characteristics, sensory traits, retail display color, and fatty acid profiles, especially CLA isomers in finishing heifers. Twenty-one Angus heifers (450 ± 5 kg) were assigned randomly to 1 of 3 experimental diets: 1) 100% supplemental fat from tallow at 4.1% of ration DM (TAL), 2) a 50:50 ratio of supplemental fat from a combination of tallow at 2.1% and FFECS at 12.8% of ration DM (TAL/ECS), and 3) 100% supplemental fat from FFECS at 25.6% ration DM (ECS). All rations were formulated to contain 7.5% fat on a DM basis. Heifers were individually fed, ad libitum, for 82 d, and BW, G:F, DMI, ADG, and body composition via ultrasound were collected at 3 to 4 wk intervals. After 82 d on feed heifers were slaughtered under federal inspection, and carcass characteristics were measured (at 24 h). The LM was removed for retail display color (1, 3, 6, 10 d), Warner-Bratzler shear force (1, 3, 7, 14, 21 d postmortem aging), sensory analysis (1, 7, 14, 21 d postmortem aging), and fatty acid profile analysis. Subcutaneous fat, including all layers, was removed from the LM for fatty acid profile analysis, and ground beef patties (80:20) were produced with lean from the brisket and fat from the plate for retail color analysis (1, 2, 4, 7 d). Supplemental fat source did not influence feedlot performance for any of the traits measured (P > 0.12) or any carcass traits related to yield, quality, or LM color at the 12th- to 13th-rib interface (P > 0.15). Supplemental fat source did not affect Warner-Bratzler shear force or any sensory traits (P > 0.20), but LM steaks became more tender as postmortem aging time increased up to 14 d (P beef patties, the only difference was LM steaks from ECS were darker (lower L* value) than TAL or TAL/ECS steaks (P beef patty objective and subjective color deteriorated (P 0.90). Full-fat extruded cottonseed pellets are interchangeable with tallow in heifer finishing diets without impacting feeding performance, meat quality, shelf life color, or CLA content of adipose sites. PMID:23893987

Stelzleni, A M; Froetschel, M A; Pringle, T D

2013-09-01

147

Dietary zilpaterol hydrochloride. II. Carcass composition and meat palatability of beef cattle.

Experiments were conducted at 3 US locations (California, Idaho, and Texas) to determine the effects of dietary zilpaterol hydrochloride and duration of zilpaterol feeding on carcass composition and beef palatability. At each site, 160 steers and 160 heifers were stratified within sex by initial BW (study d -1) and assigned randomly within BW strata to 1 of 4 treatments in a randomized complete block design (4 blocks/treatment for each sex). The 4 treatments were arranged in a 2 (no zilpaterol vs. zilpaterol) x 2 (20- or 40-d duration of zilpaterol feeding) factorial. When included in the diet, zilpaterol was supplemented at 8.3 mg/kg (DM basis). Each pen consisted of 10 animals. After slaughter 2 carcasses per pen (n=64 per trial site) were selected. The entire right side of the selected carcasses was collected for dissection and chemical analysis of the soft tissue. Additionally, the left strip loin was collected for Warner-Bratzler shear force determinations and aged to 28 d postmortem. Sensory analysis was conducted on the Idaho trial site samples only. All data were pooled for analyses. Feeding zilpaterol hydrochloride increased carcass muscle deposition (P0.11) by the zilpaterol treatment. In heifer carcasses, carcass moisture percentage was increased (P=0.04) and bone percentage was decreased (P=0.02), whereas in steer carcasses, carcass moisture and bone percentage were not affected (P>0.10). In heifer carcasses, carcass ash percentage was not affected (P=0.61) by zilpaterol, whereas in steer carcasses, carcass ash percentage tended (P=0.07) to be increased. The protein-to-bone ratio was increased (Pzilpaterol hydrochloride treatment in both steers and heifers, whereas the protein-to-fat ratio was not affected (P=0.10). Cooking loss of the LM was not affected (P=0.41) by zilpaterol treatment of steers or heifers. However, LM Warner-Bratzler shear force was increased (P=0.003) on average (3.3 vs. 4.0 kg) due to zilpaterol hydrochloride treatment of both steers and heifers. In both steers and heifers, LM sensory panel scores of overall juiciness (6.2 vs. 6.0), tenderness (6.2 vs. 6.0), and flavor intensity (6.2 vs. 6.0) tended (P=0.06) to be decreased in cattle supplemented with zilpaterol. Zilpaterol hydrochloride is a repartitioning agent that seems to affect carcass composition primarily through protein deposition. However, zilpaterol treatment can adversely affect tenderness and other palatability traits. PMID:18849379

Leheska, J M; Montgomery, J L; Krehbiel, C R; Yates, D A; Hutcheson, J P; Nichols, W T; Streeter, M; Blanton, J R; Miller, M F

2009-04-01

148

Our objective was to compare the effects of feeding steam-flaked, high-oil corn with normal steam-flaked corn to which yellow grease was added to equalize dietary fat on performance and carcass characteristics of finishing beef steers, and palatability, retail case life, and fatty acid composition of strip loins. Angus steers (n = 120; initial BW = 288 kg) were allotted to dietary treatments consisting of 1) normal mill-run, steam-flaked corn plus added fat (NMR) or 2) high-oil, steam-flaked corn (HOC) and assigned randomly to pens (12 pens/treatment with 5 steers/pen). Performance (ADG, DMI, and G:F) was measured over time, and cattle were shipped to a commercial abattoir for collection of carcass data after 165 d on feed. Carcass data were collected at 48 h postmortem on all carcasses, and 2 carcasses from each pen were selected randomly for collection of strip loins (IMPS #180A). At 14 d postmortem, 4 steaks (2.54 cm thick) were removed for retail display, trained sensory panel analysis, Warner-Bratzler shear force determination, and fatty acid analysis. Daily BW gain was greater (P = 0.03) and G:F was increased 8.4% (P = 0.01) for steers fed NMR compared with HOC, but DMI was not affected (P > 0.10) by treatment. No treatment differences were observed (P > 0.10) for HCW, 12th-rib fat, KPH, and yield grade. Marbling scores were greater (P = 0.01) for NMR than for HOC, and LM area tended (P = 0.07) to be greater in NMR than in HOC carcasses. The proportion of carcasses grading USDA Choice did not differ (P = 0.77) between treatments, but a greater (P = 0.04) proportion of carcasses graded in the upper two-thirds of Choice for NMR vs. HOC. Trained sensory panel traits and Warner-Bratzler shear force values did not differ between treatments (P > 0.10), and no differences (P > 0.10) were detected for purge loss or fatty acid composition. Overall, ADG and G:F were less and marbling score was decreased, but there were no differences between treatments in beef palatability, retail case life, or concentrations of fatty acids in strip loins. PMID:21097687

Price, B D; Garmyn, A J; Derington, H M; Galyean, M L; Jackson, S P; Smith, S B; Miller, M F

2011-03-01

149

The present experiment was carried out to evaluate the effects of electrical stimulation (ES) immediately prescalding (PS), ES immediately postdefeathering (PD), or PS combined with PD (PSPD) on the quality of early deboned (2 h) broiler breast muscles, pectoralis major (fillets), and pectoralis minor (tenders). No stimulation, early-deboned (2 h), and 24-h deboned (24 h) fillets were used for the comparison. The 42-d-old broiler carcasses were electrically stimulated with pulsed current at 200 V for 30 s over a 90-s time interval (total of 1 min over 180 s for PSPD), and breast meat was deboned 2 h postmortem. Quality indicators evaluated were CIE L*, a*, and b* color and pH of the raw fillets and cook yields and Warner-Bratzler (WB) shear force of the fillets and tenders. There were no differences in raw fillet color, pH, and cook yields of both the fillets and tenders between the 3 ES treatments. Effects of different ES treatments on meat WB shear force values varied with breast muscles. For the fillets, the average WB shear force values of both the PS and PSPD samples, which were not different from each other, were significantly lower than those of the PD samples. For the tenders, there were no differences in the average shear force values between the 3 ES treatments. Regardless of ES treatment and breast muscle, early deboned broiler breast meat from ES carcasses required significantly less force to shear than the 2-h control. These results indicate that ES can tenderize early deboned poultry breast muscles; however, the effectiveness of ES tenderization varies with ES treatments for the fillets. The PS treatment is more effective in reducing fillet shear values than PD, and there is no further reduction in shear values with PSPD compared with the PS treatment. PMID:20634531

Zhuang, H; Savage, E M; Lawrence, K

2010-08-01

150

On liquid migration in sheared granular matter

Mixing liquids with powders is of great importance, e.g. in process engineering and for pharmaceutical applications. Generally, one might expect that homogeneously shearing or stirring wet granular matter would lead to a homogeneous liquid distribution, however, it is not clear what happens when shear is applied non-homogeneously, e.g. in shear bands. It is commonly accepted that at large liquid contents, liquid flows inside dilating zones as percolating liquid networks prevent air from entering the dilating pores, but it is unknown what happens at low liquid contents. We present experimental measurements showing a decreased liquid concentration inside a shear band where glass beads are sheared in a split bottom shear cell. Furthermore, a microscopic model for liquid transport at low liquid contents is presented, where fluid dynamics between individual liquid structures driven by Laplace pressure differences is taken into account. Our model shows liquid depletion patterns in quantitative agreement with experiments. On the other hand, our model is also applicable to the situation where shear is applied homogeneously, showing diffusive spreading of liquid.

Mani, R.; Kadau, D.; Or, D.; Herrmann, H. J.

2013-06-01

151

Tenderization of beef with bacterial collagenase.

The feasibility of using a purified collagenase produced by Clostridium histolyticum as a meat tenderizer was studied. Experiments were conducted with enzymes in model systems to compare collagenase with the currently used plant proteinases, papain, bromelain and ficin. Collagenase was shown to have a greater activity in hydrolyzing insoluble collagen than salt-soluble-protein (SSP) and highest activity between 40° and 60°C, with little to no activity above 60°C. Collagenase was added to raw steaks and steaks were placed in bags and cooked in a water bath to 6.5°C. Tenderness was evaluated by analyzing components of Warner-Bratzler shear-deformation curves. The results suggested that addition of NaCl or a combination of CaCl(2), NaCl and collagenase would cause equivalent tenderization. The lack of a significant tenderization due to collagenase could be related to a lack of sensitivity in the shear evaluation or an effect on the enzyme activity due to the meat environment. PMID:22055648

Allen Foegeding, E; Larick, D K

1986-01-01

152

Directory of Open Access Journals (Sweden)

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.

R.E. Dyer

2005-01-01

153

The effect of breed of sire and age at feeding on muscle tenderness in the beef chuck.

Steers (n = 59) produced from the mating of Braford, Simbrah, Senepol, and Simmental bulls to Brahman- and Romana Red-sired cows and Brahman bulls to Angus cows were used in this study. Effects of sire breed and age at feeding on muscle tenderness in the major muscles of the chuck when steers were fed to 1.0 cm 12th rib fat were determined. There were no muscle tenderness effects due to sire breed group, with the exception of the serratus ventralis muscle, which was more tender in Brahman- and Braford-sired steers than in Simmental-sired steers. Additionally, the supraspinatus muscle from the yearlings was lower in shear value than that from the calves. The Brahman-sired steers had serratus ventralis muscles with higher percentages (P less than .05) of intramuscular fat than those of Braford-, Simbrah-, and Simmental-sired steers. Fat deposited within the muscle or between muscles in the chuck was not related to muscle tenderness as measured by Warner-Bratzler shear values. Also, percentages of intramuscular fat of the triceps brachii, serratus ventralis, or supraspinatus muscles were not influenced (P greater than .05) by age at feeding. PMID:1938650

Christensen, K L; Johnson, D D; West, R L; Marshall, T T; Hargrove, D D

1991-09-01

154

Fluid shear stress threshold regulates angiogenic sprouting.

The density and architecture of capillary beds that form within a tissue depend on many factors, including local metabolic demand and blood flow. Here, using microfluidic control of local fluid mechanics, we show the existence of a previously unappreciated flow-induced shear stress threshold that triggers angiogenic sprouting. Both intraluminal shear stress over the endothelium and transmural flow through the endothelium above 10 dyn/cm(2) triggered endothelial cells to sprout and invade into the underlying matrix, and this threshold is not impacted by the maturation of cell-cell junctions or pressure gradient across the monolayer. Antagonizing VE-cadherin widened cell-cell junctions and reduced the applied shear stress for a given transmural flow rate, but did not affect the shear threshold for sprouting. Furthermore, both transmural and luminal flow induced expression of matrix metalloproteinase 1, and this up-regulation was required for the flow-induced sprouting. Once sprouting was initiated, continuous flow was needed to both sustain sprouting and prevent retraction. To explore the potential ramifications of a shear threshold on the spatial patterning of new sprouts, we used finite-element modeling to predict fluid shear in a variety of geometric settings and then experimentally demonstrated that transmural flow guided preferential sprouting toward paths of draining interstitial fluid flow as might occur to connect capillary beds to venules or lymphatics. In addition, we show that luminal shear increases in local narrowings of vessels to trigger sprouting, perhaps ultimately to normalize shear stress across the vasculature. Together, these studies highlight the role of shear stress in controlling angiogenic sprouting and offer a potential homeostatic mechanism for regulating vascular density. PMID:24843171

Galie, Peter A; Nguyen, Duc-Huy T; Choi, Colin K; Cohen, Daniel M; Janmey, Paul A; Chen, Christopher S

2014-06-01

155

Principal component analysis of shear strain effects.

Shear stresses are always present during quasi-static strain imaging, since tissue slippage occurs along the lateral and elevational directions during an axial deformation. Shear stress components along the axial deformation axes add to the axial deformation while perpendicular components introduce both lateral and elevational rigid motion and deformation artifacts into the estimated axial and lateral strain tensor images. A clear understanding of these artifacts introduced into the normal and shear strain tensor images with shear deformations is essential. In addition, signal processing techniques for improved depiction of the strain distribution is required. In this paper, we evaluate the impact of artifacts introduced due to lateral shear deformations on the normal strain tensors estimated by varying the lateral shear angle during an axial deformation. Shear strains are quantified using the lateral shear angle during the applied deformation. Simulation and experimental validation using uniformly elastic and single inclusion phantoms were performed. Variations in the elastographic signal-to-noise and contrast-to-noise ratios for axial deformations ranging from 0% to 5%, and for lateral deformations ranging from 0 to 5 degrees were evaluated. Our results demonstrate that the first and second principal component strain images provide higher signal-to-noise ratios of 20 dB with simulations and 10 dB under experimental conditions and contrast-to-noise ratio levels that are at least 20 dB higher when compared to the axial and lateral strain tensor images, when only lateral shear deformations are applied. For small axial deformations, the lateral shear deformations significantly reduces strain image quality, however the first principal component provides about a 1-2dB improvement over the axial strain tensor image. Lateral shear deformations also significantly increase the noise level in the axial and lateral strain tensor images with larger axial deformations. Improved elastographic signal and contrast-to-noise ratios in the first principal component strain image are always obtained for both simulation and experimental data when compared to the corresponding axial strain tensor images in the presence of both axial and lateral shear deformations. PMID:19201435

Chen, Hao; Varghese, Tomy

2009-05-01

156

Stress pulse attenuation in shear thickening fluid

The stress pulse attenuation of the 62 vol/vol. % dense silica particle-ethylene glycol suspension was investigated by using a modified spilt Hopkinson pressure bar. In comparison to the neat ethylene glycol solution, the transmission pulse of the shear thickening is much weaker under the same impact condition. No energy loss is progressed for the neat ethylene glycol solution, thus it can be concluded that the energy dissipation behavior was happened in the silica particle based shear thickening fluid. In this work, the energy dissipation of the shear thickening fluid was reversible.

Jiang, Weifeng; Gong, Xinglong; Xuan, Shouhu; Jiang, Wanquan; Ye, Fang; Li, Xiaofeng; Liu, Taixiang

2013-03-01

157

Bubbles in sheared two-dimensional foams

Oscillatory shear on two-dimensional monodisperse liquid foams was performed. We show that the effect of the oscillatory shear is to cause the migration of bubbles which size is greater than that of a typical bubble of the foam. These so-called flaws move towards the periphery of the foam in a non random motion, thus realizing size segregation in a system which is by construction gravity insensitive. We also show that elongated cavities in the foam could be relaxed towards a more isotropic form with oscillatory shear, and we discuss the pertinent parameters of this relaxation.

Quilliet, C; Dollet, B; Berthier, L; Yekini, A

2005-01-01

158

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)

2002-01-01

159

Shear resistance for concrete dams : Laboratory tests

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Mohr-Coulomb shear strength failure criterion is used nowadays by most of the countries in their guidelines to estimate the shear capacity between the dam and the foundation. However, the Mohr-Coulomb model does not take into consideration the roughness of the concrete-to-rock interface. The fact the roughness the influence of the roughness is ignored by the guidelines leads to an overestimation of the shear capacity between the dam and the rock. Therefore, there is a need to increase the...

Colio Gutie?rrez, Manuel

2013-01-01

160

Surface instability of sheared soft tissues

Digital Repository Infrastructure Vision for European Research (DRIVER)

When a block made of an elastomer is subjected to large shear, its surface remains flat. When a block of biological soft tissue is subjected to large shear, it is likely that its surface in the plane of shear will buckle (apparition of wrinkles). One factor that distinguishes soft tissues from rubber-like solids is the presence -- sometimes visible to the naked eye -- of oriented collagen fibre bundles, which are stiffer than the elastin matrix into which they are embedded but are nonetheless...

2008-01-01

161

The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate based on laminated beam theory. The method does not consider the solution of a particular boundary value problem, rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.

Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.

2007-01-01

162

The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate or panel based on laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.

Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.; Collier, Craig S.

2008-01-01

163

Development of Short Stroke Shearing Technology For FBR Fuel Pin

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.

Higuchi, Hidetoshi; Koizumi, Kenji; Hirano, Hiroyasu; Tasaka, Masayuki; Washiya, Tadahiro; Kobayashi, Tsuguyuki

164

Lateral shearing interferometer with variable shearing for measurement of a small beam.

A lateral shearing interferometer with variable shearing for measurement of a small beam is proposed. The interferometer is composed of a polarization beam splitter, a thick birefringent plate, a quarter-wave plate, a mirror, and an image sensor. The shearing amount can be tiny by using the thick birefringent plate as the shear generator. The shearing amount of the interferometer can be continuously adjusted by rotating the thick birefringent plate, and 2D interferograms can be obtained by rotating the thick birefringent plate along the mutually perpendicular directions. The optical path difference is compensated with a double lateral shearing by using a quarter-wave plate and a mirror. The interferometer is verified by simulation and experiment; the experiment result is well coincident with the simulation result. The usefulness of the interferometer is verified. PMID:24686657

Liu, Lei; Zeng, Aijun; Zhu, Linglin; Huang, Huijie

2014-04-01

165

Pulsed laser Doppler measurements of wind shear

There is a need for a sensor at the airport that can remotely detect, identify, and track wind shears near the airport in order to assure aircraft safety. To determine the viability of a laser wind-shear system, the NASA pulsed coherent Doppler CO2 lidar (Jelalian et al., 1972) was installed in a semitrailer van with a rooftop-mounted hemispherical scanner and was used to monitor thunderstorm gust fronts. Wind shears associated with the gust fronts at the Kennedy Space Center (KSC) between 5 July and 4 August 1978 were measured and tracked. The most significant data collected at KSC are discussed. The wind shears were clearly visible in both real-time velocity vs. azimuth plots and in postprocessing displays of velocities vs. position. The results indicate that a lidar system cannot be used effectively when moderate precipitation exists between the sensor and the region of interest.

Dimarzio, C.; Harris, C.; Bilbro, J. W.; Weaver, E. A.; Burnham, D. C.; Hallock, J. N.

1979-01-01

166

Shear wave instability for electrified falling films.

The effect of an electric field on the shear wave instability pertaining to a gravity driven conducting liquid film is studied based on the Chebyshev-Tau method. The shear wave appears at very large values of the Reynolds number when the inclination angle is sufficiently small. The presence of an electric field shows peculiar behavior on the critical Reynolds number corresponding to the shear mode. It suppresses shear wave instability through the amplification of the critical Reynolds number and leads to a nontrivial stabilizing effect when inclination angle B?3'. On the other hand, the reduction of the critical Reynolds number is found if the inclination angle is further lowered in magnitude. PMID:24329346

Samanta, Arghya

2013-11-01

167

Motifs of Networks from Shear Fractures

Rupture's sequence of shear fractures using a transformation form of aperture patterns to complex networks was studied, and then sub-graphs abundance within the corresponding networks was analyzed. Furthermore, to distinguish the role of contact zones and flow of energy in ruptures tips, the contact strings were constructed. The contacts 'strings were connected by using constrained geometrical distance and amount of net-contact area per string, yields directed networks. For shear rupture, we observed approximately similar trend in sub-graphs distribution which were the results of parallel and transversal aperture profiles (a super-family phenomena). We confirmed the same inherent dynamic of sheared fracture yields the nearly same family of sub-graphs. For directed networks, our results confirmed the role of the feed-forward sub-graphs in flow of energy through the development of shear rupture.

Ghaffari, H O

2011-01-01

168

Shear thickening, frictionless and frictional rheologies

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...

Mari, Romain; Morris, Jeffrey F; Denn, Morton M

2014-01-01

169

Semi-classical shears and effective forces

International Nuclear Information System (INIS)

We present a semi-classical analysis of the B(M1) and B(E2) transition probabilities in the shears bands in 193-199Pb as a function of the shears angle. This provides a semi-empirical confirmation of the shears mechanism proposed by S. Frauendorf using the Tilted-Axis-Cranking model. We interpret this as a consequence of a residual interaction between the proton and neutron blades, and it is shown that the main ingredient of this effective force can be described by a P2(?) term with a strength of 400-600 keV. Such an interaction can be mediated through the core by particle-vibration coupling. The competition between the shears and the rotation of the core is investigated within the framework of a classical solution of two particles-plus-rotor model. (c) 1999 American Institute of Physics

1999-09-02

170

Heterogeneous shear in hard sphere glasses

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.

Mandal, Suvendu; Raabe, Dierk; Varnik, Fathollah

2012-01-01

171

Shear-flow-enhanced barrier crossing

We consider a single Brownian particle confined in a double well potential (DWP) and investigate its response to a linear shear flow by means of the probability density and current determined via numerical solution of the Fokker-Planck equation. Besides a shear-dependent distortion of the probability distribution, we find that the associated current crossing the potential barrier exhibits a convex dependency on the shear rate when the DWP's minima are far apart. With decreasing distance this functional dependency changes from a convex to concave characteristics accompanied with an increase of the probability current crossing the DWP's barrier. Through the difference map of the particle density distribution it is possible to extract the shear-flow-induced contribution to the particle density driving the barrier-crossing current. This may open the possibility to design specific flow profiles to optimize flow-induced activated transport of nanoparticles.

Kienle, Diego; Bammert, Jochen; Zimmermann, Walter

2011-10-01

172

Recent progress in shear punch testing

Energy Technology Data Exchange (ETDEWEB)

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.

Hamilton, M.L. [Pacific Northwest Lab., Richland, WA (United States); Toloczko, M.B.; Lucas, G.E. [Univ. of California, Santa Barbara, CA (United States)

1994-09-01

173

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

1994-09-22

174

Effect of shear rate on the microstructure and rheological properties of sheared wheat doughs

Digital Repository Infrastructure Vision for European Research (DRIVER)

Structure formation in dough systems is the result of an interplay between processing conditions and subsequent interactions in the protein phase. These interactions can be both of a covalent (disulfide bonds) and physical nature and occur at all length scales. The aim of this work was to investigate the effect of simple shear deformation at various shear rates on wheat dough rheological properties, microstructure and GMP fraction. Shear processing was compared with a z-blade mixing. The cont...

Peressini, D.; Peighambardoust, S. H.; Hamer, R. J.; Sensidoni, A.; Goot, A. J.

2008-01-01

175

Current-diffusive ballooning mode in low shear and negative shear regions of tokamaks

International Nuclear Information System (INIS)

The stability of the current-diffusive ballooning mode in tokamaks with high toroidal mode number is analyzed in the region of second stability against the ideal magnetohydrodynamic mode. It is found that the growth rate of the current-diffusive ballooning mode is decreased upon the reduction of the geodesic curvature driving force. The reduction of thermal conductivity in the limit of very weak shear or negative shear in comparison with standard shear is also shown. (author)

1994-01-01

176

IMAGE ANALYSIS FOR MODELLING SHEAR BEHAVIOUR

Digital Repository Infrastructure Vision for European Research (DRIVER)

Through laboratory research performed over the past ten years, many of the critical links between fracture characteristics and hydromechanical and mechanical behaviour have been made for individual fractures. One of the remaining challenges at the laboratory scale is to directly link fracture morphology of shear behaviour with changes in stress and shear direction. A series of laboratory experiments were performed on cement mortar replicas of a granite sample with a natural fracture perpendic...

2000-01-01

177

Shear dispersion in dense granular flows

We formulate and solve a model problem of dispersion of dense granular materials in rapid shear flow down an incline. The effective dispersivity of the depth-averaged concentration of the dispersing powder is shown to vary as the P\\'eclet number squared, as in classical Taylor--Aris dispersion of molecular solutes. An extensions to generic shear profiles is presented, and possible applications to industrial and geological granular flows are noted.

Christov, Ivan C

2014-01-01

178

The Rotation and Shear of a String

Digital Repository Infrastructure Vision for European Research (DRIVER)

Whether a string has rotation and shear can be investigated by an anology with the point particle. Rotation and shear involve first covariant spacetime derivatives of a vector field and, because the metric stress tensor for both the point particle and the string have no such derivatives, the best vector fields can be identified by requiring the conservation of the metric stress. It is found that the best vector field is a non-unit accelerating field in x, rather than a unit ...

Roberts, Mark D.

2002-01-01

179

Sheared-flow Modes in Toroidal Geometry

Energy Technology Data Exchange (ETDEWEB)

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.

J.L.V. Lewandowski; T.S. Hahm; W.W. Lee; Z. Lin

1999-10-01

180

Mean magnetic field generation in sheared rotators

Digital Repository Infrastructure Vision for European Research (DRIVER)

A generalized mean magnetic field induction equation for differential rotators is derived, including a compressibility, and the anisotropy induced on the turbulent quantities from the mean magnetic field itself and a mean velocity shear. Derivations of the mean field equations often do not emphasize that there must be anisotropy and inhomogeneity in the turbulence for mean field growth. The anisotropy from shear is the source of a term involving the product of the mean veloc...

Blackman, Eric G.

1999-01-01

181

Shear Viscosity of a Hot Pion Gas

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 $g\\phi^4$ theory we show how the skeleton expansion can be consistently applied to pions in chiral perturbation theory. The shear viscosity $\\eta$ is determined...

Lang, Robert; Kaiser, Norbert; Weise, Wolfram

2012-01-01

182

Buckling of sheared and compressed microfibrils

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we study the stability of an initially straight elastic fibril clamped at one end, while the other end is subjected to a constant normal compressive force and a prescribed shear displacement. We found the buckling load of a sheared fibril to be always less than the Euler buckling load. Furthermore, if the end of the fibril loses adhesion, then the buckling load can be considerably less. Our result suggests that the static friction of microfibre arrays can decrease with increasi...

Nadermann, Nichole; Kumar, Ajeet; Goyal, Sachin; Hui, Chung-yuen

2010-01-01

183

Structure and shear in a cohesive powder:

Digital Repository Infrastructure Vision for European Research (DRIVER)

Handling of powders and granular materials is of great importance to industry. However, the knowledge of many powder related processes in industry is poor. In this work, the flow behaviour of powder has been investigated with an advanced tester: the Flexible Wall Biaxial Tester. Flow of powder occurs via the formation of shear planes. For non-cohesive materials one assumes a width of such a shear plane of 10 particle diameters. In this work the Neutron Depolarization technique has been used t...

2001-01-01

184

Permeability anisotropy induced by a shear displacement

Digital Repository Infrastructure Vision for European Research (DRIVER)

The permeability anisotropy that results from a shear displacement 'u' between the complementary self-affine walls of a rough fracture is investigated. Experiments in which a dyed fluid displaces a transparent one as it is radially injected into a transparent fracture exhibit a clear anisotropy in the presence of shear displacements, and allow us to estimate the ratio of the permeabilities for flows parallel and perpendicular to 'u'. A simple model which accounts for the dev...

Auradou, H.; Drazer, G.; Hulin, J. P.; Koplik, J.

2004-01-01

185

Avalanches in anisotropic sheared granular media

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the influence of particle shape anisotropy on the occurrence of avalanches in sheared granular media. We use molecular dynamic simulations to calculate the relative movement of two tectonic plates. % with transform boundaries. Our model considers irregular polygonal particles constituting the material within the shear zone. We find that the magnitude of the avalanches is approximately independent on particle shape and in good agreement with the Gutenberg-Richter law...

Pen?a, Andre?s A.; Mcnamara, Sean; Lind, Pedro G.; Herrmann, Hans J.

2008-01-01

186

Adiabatic shearing study by dynamic compression

International Nuclear Information System (INIS)

The adiabatic shearing study was carried out by dynamic compression tests made on a Hopkinson's rod. The deformation rate is around 2x10"3 s"-"1; the materials studied are in martensitic steel and a titanium alloy, at ambient temperature and up to 500"0C. Microscopic observations show how the break appears, associated with the development of adiabatic shearing bands. The mechanical results are discussed and compared against the theoretical approaches

1982-07-05

187

Shear state of freely evolving granular gases

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hydrodynamic equations are used to identify the final state reached by a freely evolving granular gas above but close to its shear instability. The theory predicts the formation of a two bands shear state with a steady density profile. There is a modulation between temperature and density profiles as a consequence of the energy balance, the density fluctuations remaining small, without producing clustering. Moreover, the time dependence of the velocity field can be scaled ou...

Brey, J. Javier; Ruiz-montero, M. J.; Dominguez, A.

2008-01-01

188

Measurement of shear impedances of viscoelastic fluids

Energy Technology Data Exchange (ETDEWEB)

Shear-wave reflection coefficients from a solid/fluid interface are derived for non-Newtonian fluids that can be described by Maxwell, Voigt, and power-law fluid models. Based on model calculations, we have identified the measurable effects on the reflection coefficients due to fluid non-Newtonian behavior. The models are used to interpret the viscosity data obtained by a technique based on shear impedance measurement.

Sheen, Shuh-Haw; Chien, Hual-Te; Raptis, A.C.

1996-12-31

189

Shear Driven Aggregation in Latex Colloids

Reynolds number is small in colloidal flow and therefore, colloidal volume fraction and Peclet number are important. AS the volume fraction and attractive coupling between particles increase, relaxation time and Weisenberg number become significant. Shear-induced aggregation of latex colloids is due to the interplay between the shear-induced formation and breakage of latex .particles. While particle size is limited by breakage, their number density increases with the shearing-time. Upon cessation of shear, the particles interconnect into an assembly held by grainy bonds. It results in increase in yield stress and dynamic modulus. A contact model enables aggregates maintaining their structures under low stress while being restructured under high stress. Modeling involves solution of Navier- Stokes equation with moving particles as boundary condition for the flow like using the Lattice Boltzmann approach or by using (accelerated) Stokesian Dynamics. Alternate approach is to model the fluid phase by soft repulsive particles with pair-wise noise and friction, known as dissipative particle dynamics (DPD). This method by construction produces full inertial hydrodynamics, but applying the correct fluid-particle boundary condition is non-trivial. Both particle to particle and particle to wall collisions can be considered using Johnson-Kendall- Roberts (JKR) analysis of collision dynamics of dissipative forces using a soft-sphere modeling technique. Our experimental work used emulsion polymerized latex that was subjected to steady and dynamic shear. Yield stress, dynamic modulus and relaxation time increased on shearing in conjunction with changes in aggregate size.

Ahuja, Suresh

2013-03-01

190

Analysis of shear banding in twelve materials

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.

Batra, R. C.; Kim, C. H.

191

Shear induced structures in crystallizing cocoa butter

Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

2004-03-01

192

Surface instability of sheared soft tissues

When a block made of an elastomer is subjected to large shear, its surface remains flat. When a block of biological soft tissue is subjected to large shear, it is likely that its surface in the plane of shear will buckle (apparition of wrinkles). One factor that distinguishes soft tissues from rubber-like solids is the presence -- sometimes visible to the naked eye -- of oriented collagen fibre bundles, which are stiffer than the elastin matrix into which they are embedded but are nonetheless flexible and extensible. Here we show that the simplest model of isotropic nonlinear elasticity, namely the incompressible neo-Hookean model, suffers surface instability in shear only at tremendous amounts of shear, i.e., above 3.09, which corresponds to a 72 degrees angle of shear. Next we incorporate a family of parallel fibres in the model and show that the resulting solid can be either reinforced or strongly weakened with respect to surface instability, depending on the angle between the fibres and the direction of s...

Destrade, M; Prikazchikov, D A; Saccomandi, G

2008-01-01

193

Wind-shearing in gaseous protoplanetary disks

One of the first stages of planet formation is the growth of small planetesimals and their accumulation into large planetesimals and planetary embryos. This early stage occurs much before the dispersal of most of the gas from the protoplanetary disk. Due to their different aerodynamic properties, planetesimals of different sizes/shapes experience different drag forces from the gas at these stage. Such differential forces produce a wind-shearing effect between close by, different size planetesimals. For any two planetesimals, a wind-shearing radius can be considered, at which the differential acceleration due to the wind becomes greater than the mutual gravitational pull between the planetesimals. We find that the wind-shearing radius could be much smaller than the gravitational shearing radius by the Sun (the Hill radius), i.e. during the gas-phase of the disk wind-shearing could play a more important role than tidal perturbations by the Sun. Here we study the wind-shearing radii for planetesimal pairs of dif...

Perets, Hagai B

2010-01-01

194

The brittle-viscous-plastic evolution of shear bands in the South Armorican Shear Zone

Shear bands are microscale shear zones that obliquely crosscut an existing anisotropy such as a foliation. The resulting S-C fabrics are characterized by angles lower than 45° and the C plane parallel to shear zone boundaries. The S-C fabrics typically occur in granitoids deformed at greenschist facies conditions in the vicinity of major shear zones. Despite their long recognition, mechanical reasons for localization of deformation into shear bands and their evolution is still poorly understood. In this work we focus on microscale characterization of the shear bands in the South Armorican Shear Zone, where the S-C fabrics were first recognized by Berthé et al. (1979). The initiation of shear bands in the right-lateral South Armorican Shear Zone is associated with the occurrence of microcracks crosscutting the recrystallized quartz aggregates that define the S fabric. In more advanced stages of shear band evolution, newly formed dominant K-feldspar, together with plagioclase, muscovite and chlorite occur in the microcracks, and the shear bands start to widen. K-feldspar replaces quartz by progressively bulging into the grain boundaries of recrystallized quartz grains, leading to disintegration of quartz aggregates and formation of fine-grained multiphase matrix mixture. The late stages of shear band development are marked by interconnection of fine-grained white mica into a band that crosscuts the original shear band matrix. In its extremity, the shear band widening may lead to the formation of ultramylonites. With the increasing proportion of shear band matrix from ~1% to ~12%, the angular relationship between S and C fabrics increases from ~30° to ~40°. The matrix phases within shear bands show differences in chemical composition related to distinct evolutionary stages of shear band formation. The chemical evolution is well documented in K-feldspar, where the albite component is highest in porphyroclasts within S fabric, lower in the newly formed grains within microcracks and nearly absent in matrix grains in the well developed C bands. The chemical variation between primary and secondary new-formed micas was clearly identified by the Mg-Ti-Na content. The microstructural analysis documents a progressive decrease in quartz grain size and increasing interconnectivity of K-feldspar and white mica towards more mature shear bands. The contact-frequency analysis demonstrates that the phase distribution in shear bands tends to evolve from quartz aggregate distribution via randomization to K-feldspar aggregate distribution. The boundary preferred orientation is absent in quartz-quartz contacts either inside of outside the C bands, while it changes from random to parallel to the C band for the K-feldspar and and K-feldspar-quartz boundaries. The lack of crystallographic preferred orientation of the individual phases in the mixed matrix of the C planes suggests a dominant diffusion-assisted grain boundary sliding deformation mechanism. In the later stages of shear band development, the deformation is accommodated by crystal plasticity of white mica in micaceous bands. The crystallographic and microstructural data thus indicate two important switches in deformation mechanisms, from (i) brittle to Newtonian viscous behavior in the initial stages of shear band evolution and from (ii) Newtonian viscous to power law in the later evolutionary stages. The evolution of shear bands in the South Armorican Shear Zone thus document the interplay between deformation mechanisms and chemical reactions in deformed granitoids.

Bukovská, Zita; Je?ábek, Petr; Morales, Luiz F. G.; Lexa, Ondrej; Milke, Ralf

2014-05-01

195

A generalized rheological model for shear thinning fluids

Energy Technology Data Exchange (ETDEWEB)

A generalized rheological model for shear thinning fluids has been developed. The new model relates shear stress to shear rate for this type of fluids and predicts the behaviour of hyperbolic, parabolic, elliptic, and Newtonian fluids with or without yield stress at one or both extremes of the shear rate. It correlates the shear stress to the shear rate for a variety of drilling fluids better than both the power-law and Hershel-Bulkley model. It can also predict the viscosity of these fluids. The shear stress and viscosity are required for pressure drop calculations of flow in pipes, annuli, and packed beds

Al-Zahrani, Saeed M. [King Saud University, Chemical Engineering Department, Riyadh (Saudi Arabia)

1997-05-01

196

Shear Localization and Comminution of Granular and Fragmented Silicon Carbide

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Shih, C.; Nesterenko, V.; Meyers, M.

1997-01-01

197

NUMERICAL SIMULATION OF AN AGRICULTURAL SOIL SHEAR STRESS TEST

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 mea...

Andrea Formato; Salvatore Faugno

2007-01-01

198

Turbulent transport in reversed magnetic shear plasma

International Nuclear Information System (INIS)

The turbulent transport of particles and ion heat in reversed magnetic shear plasma are investigated. A dispersion relation for the electrostatic drift wave driven by ion temperature gradient, electron temperature gradient, magnetic field gradient, and trapped electrons is derived within the framework of two-fluid theory and in sheared coordinate system. Correspondingly the turbulent particle and ion thermal diffusivities in quasi-linear approximation are obtained. The present model self-consistently includes five factors: the magnetic shear and the sheared velocity, and the three ways of coupling between them. It is found that the five factors presented in the turbulent transport coefficients as well as the dispersion relation can produce turbulent particle- and heat-pinch, i.e., turbulent diffusivity of particles and that of ion heat in the negative magnetic shear region are smaller than zero. Hence the particle and ion heat diffusivities reduce significantly in that region. The numerical results for the particle and ion heat diffusivity are in good agreement with the experimental results

2001-08-01

199

Pressure-shear experiments on granular materials.

Energy Technology Data Exchange (ETDEWEB)

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.

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

200

Galaxy shear estimation from stacked images

Statistics of the weak lensing of galaxies can be used to constrain cosmology if the galaxy shear can be estimated accurately. In general this requires accurate modelling of unlensed galaxy shapes and the point spread function (PSF). I discuss suboptimal but potentially robust methods for estimating galaxy shear by stacking images such that the stacked image distribution is closely Gaussian by the central limit theorem. The shear can then be determined by radial fitting, requiring only an accurate model of the PSF rather than also needing to model each galaxy accurately. When noise is significant asymmetric errors in the centroid must be corrected, but the method may ultimately be able to give accurate un-biased results when there is a high galaxy density with constant shear. It provides a useful baseline for more optimal methods, and a test-case for estimating biases. I test stacking methods on the simple toy simulations with constant PSF and shear provided by the GREAT08 project, on which most other existin...

Lewis, Antony

2009-01-01

201

Ballooning mode stabilization by moderate sheared rotation

International Nuclear Information System (INIS)

Sheared toroidal plasma rotation has been known for some time to have a stabilizing effect on the ballooning modes. A recent calculation showed that a large flow shear, with d?/dq of the order of the Alfven toroidal frequency, can stabilize the ballooning modes. This latest result is, in fact, not so optimistic. For observed flows with Mach number of order unity one gets d?/dq smaller by a factor O(??) from the required level (if the flow shear length is of the same order as the magnetic shear length). Moreover, the calculation does not take into account a possibly large transient growth of the mode amplitude due to its Floquet structures We show here that, in fact, there is a general tendency of the ballooning mode to stabilize as soon as the flow shear d?/dq exceeds the (O?? smaller) open-quotes slowclose quotes magnetosonic wave frequency. Our analysis is perturbative, where the small parameter is related to the small coupling between the slow and Alfven waves-as is the case in a high aspect-ratio tokamak. (In the perturbation it is important to take the Hamiltonian nature of the governing equations into account.) Moreover, our results apply to the relevant transient growth of the mode amplitude

1996-03-18

202

Accurate Shear Measurement with Faint Sources

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. 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 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 accuracy even for images of signa...

Zhang, Jun; Foucaud, Sebastien

2013-01-01

203

Stochastic parametric resonance in shear flows

Directory of Open Access Journals (Sweden)

Full Text Available Time-periodic shear flows can give rise to Parametric Instability (PI, as in the case of the Mathieu equation (Stoker, 1950; Nayfeh and Mook, 1995. This mechanism results from a resonance between the oscillatory basic state and waves that are superimposed on it. Farrell and Ioannou (1996a, b explain that PI occurs because the snap-shots of the velocity profile are subject to transient growth. If the flows were purely steady the transient growth would subside and not have any long lasting effect. However, the coupling between transient growth and the time variation of the basic state create PI. Mathematically, transient growth, and therefore PI, are due to the nonorthogonal eigenspace in the linearized system. Poulin et al. (2003 studied a time-periodic barotropic shear flow that exhibited PI, and thereby produced mixing at the interface between Potential Vorticity (PV fronts. The instability led to the formation of vortices that were stretched. A later study of an oscillatory current in the Cape Cod Bay illustrated that PI can occur in realistic shear flows (Poulin and Flierl, 2005. These studies assumed that the basic state was periodic with a constant frequency and amplitude. In this work we study a shear flow similar to that found in Poulin et al. (2003, but now where the magnitude of vorticity is a stochastic variable. We determine that in the case of stochastic shear flows the transient growth of perturbations of the snapshots of the basic state still generate PI.

F. J. Poulin

2005-01-01

204

Sheath fold morphology in simple shear

Sheath folds are highly non-cylindrical structures often associated with shear zones. We investigate the formation of sheath folds around a weak inclusion acting as a slip surface in simple shear by means of an analytical model. We present results for different slip surface orientations and shapes. Cross-sections perpendicular to the shear direction through the sheath fold display closed contours, so called eye-structures. The aspect ratio of the outermost closed contour is strongly dependent on the initial slip surface configuration. The center of the eye-structure is subject to change in height with respect to the upper edge of the outermost closed contour for different cross-sections perpendicular to the shear direction. This results in a large variability in layer thickness across the sheath fold length, questioning the usefulness of eye-structures as shear sense indicators. The location of the center of the eye structure is largely invariant to the initial configurations of the slip surface as well as to strain. The values of the aspect ratios of the closed contours within the eye-pattern are dependent on the strain and the cross-section location. The ratio (R') of the aspect ratios of the outermost closed contour (Ryz) and the innermost closed contour (Ry'z') shows values above and below 1. R' shows dependence on the slip surface shape and orientation but not on the number of involved contours. Using R' measurements to deduce the bulk strain type may be erroneous.

Reber, Jacqueline E.; Dabrowski, Marcin; Galland, Olivier; Schmid, Daniel W.

2013-08-01

205

Shear flow aerodynamics - Lifting surface theory

A lifting surface theory based on a parallel shear flow model is presented for steady, incompressible flows. The theory is intended to account approximately for the presence of a boundary layer. The method of Fourier transforms is used to calculate the pressure on a surface of infinite extent and arbitrary contour. Immediately above the surface is a region of sheared flow (the boundary layer), outside of which the flow velocity is constant. The Fourier transform of the pressure on this surface is used to derive the shear flow equivalent to the kernel function of classical potential flow lifting surface theory. The kernel function provides an integral relation between the upwash at a given point on the surface and the pressure everywhere on the surface. This relation is treated as an integral equation for the pressure, and is solved numerically. Computations are presented for the lift and pitching moment on a flat plate in two-dimensional flow, and for flat, rectangular wings of aspect ratio 1, 2, and 5. As expected, the shear layer decreases the lift curve slope; however, the shear layer (whose thickness is constant along the wing chord) has little effect on the center of pressure.

Ventres, C. S.

1975-01-01

206

COMPUTATIONAL APPROACH TO PREDICT SOIL SHEAR STRENGTH

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents an artificial neural network technique to predict the shear strength parameters of medium compressibility soil, which influenced by basic properties of soil in unconsolidated undrained conditions. Obviously obtained the undisturbed samples of soil to determination of shear strength parameters is a tedious work. Commercial software’s MATLAB-7 was used for this study. Triaxial shear tests were conducted to obtain these parameters at different water contents and densities. The results were used to predict the strength parameters. A set of 198 experimental results were used to construct the ANN model out of which 120 for training , 39 for validation and 39 for testing or prediction of shear strength parameters ( Cohesion & Angle of internal friction were used. The correlation between the basic properties and shear strength parameters were obtained from the trained neural network. For trained the feed forward ANN models: multilayer perceptrons and radial basis function neural network, followings parameters were considered as input data – the compaction energy, degree of saturation, dry density and C & ? were output parameter. The regression coefficient and MSEwere 0.94, 0.76 and 0.0642, 0.253 respectively. In addition, the experimental results were compared to MLPN and RBF networks predicted results. It was concluded that the performance of the multilayer perceptron feed forward neural network model with three hidden layers is better than radial basis function neural network model.

Rajeev Jain,

2010-08-01

207

Transversely Compressed- and Restrained Shear Joints

DEFF Research Database (Denmark)

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.

Schmidt, Jacob Wittrup; Hansen, Christian Skodborg

2013-01-01

208

On shear rheology of gel propellants

Energy Technology Data Exchange (ETDEWEB)

Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel-Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine-based fuels, gelled with polysaccharides, were characterized as shear-thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red-fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers-Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

Rahimi, Shai; Peretz, Arie [RAFAEL, MANOR Propulsion and Explosive Systems Division, Haifa (Israel); Natan, Benveniste [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)

2007-04-15

209

Shear Viscosity of a Hot Pion Gas

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 $\\phi^4$ 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.

Lang, Robert; Weise, Wolfram

2012-01-01

210

Shear flow over a porous particle

International Nuclear Information System (INIS)

Linear axisymmetric Stokes flow over a porous spherical particle is investigated. An exact analytical solution for the fluid velocity components and the pressure inside and outside the porous particle is obtained. The solution is generalized to include the cases of arbitrary three-dimensional linear shear flaw as well as translational-shear Stokes flow. As the permeability of the particle tends to zero, the solutions obtained go over into the corresponding solutions for an impermeable particle. The problem of translational Stokes flow around a spherical drop (in the limit a gas bubble or an impermeable sphere) was considered. A solution of the problem of translational Stokes flow over a porous spherical particle was given. Linear shear-strain Stokes flow over a porous spherical drop was investigated

1995-11-01

211

Dynamic Modes of Red Blood Cells in Oscillatory Shear Flow

The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle $\\theta$, and phase angle $\\phi$ of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. i) tank-treading (TT): $\\phi$ rotates while the shape and $\\theta$ oscillate. ii) tumbling (TB): $\\theta$ rotates while the shape and $\\phi$ oscillate. iii) intermediate motion: both $\\phi$ and $\\theta$ rotate synchronously or intermittently. In oscillatory shear flow, RBCs show various dynamics based on these three motions. For a low shear frequency with zero mean shear rate, a limit-cycle oscillation occurs, based on the TT or TB rotation at a high or low shear amplitude, respectively. This TT-based oscillation well explains recent experiments. In the middle shear amplitude, RBCs show an intermittent or synchronized oscillation. As shear frequency increases, the vesicle oscillation beco...

Noguchi, Hiroshi

2010-01-01

212

Dynamic modes of red blood cells in oscillatory shear flow

The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle ? , and phase angle ? of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. (i) tank-treading (TT): ? rotates while the shape and ? oscillate. (ii) tumbling (TB): ? rotates while the shape and ? oscillate. (iii) intermediate motion: both ? and ? rotate synchronously or intermittently. In oscillatory shear flow, RBCs show various dynamics based on these three motions. For a low shear frequency with zero mean shear rate, a limit-cycle oscillation occurs, based on the TT or TB rotation at a high or low shear amplitude, respectively. This TT-based oscillation well explains recent experiments. In the middle shear amplitude, RBCs show an intermittent or synchronized oscillation. As shear frequency increases, the vesicle oscillation becomes delayed with respect to the shear oscillation. At a high frequency, multiple limit-cycle oscillations coexist. The thermal fluctuations can induce transitions between two orbits at very low shear amplitudes. For a high mean shear rate with small shear oscillation, the shape and ? oscillate in the TT motion but only one attractor exists even at high shear frequencies. The measurement of these oscillatory modes is a promising tool for quantifying the viscoelasticity of RBCs, synthetic capsules, and lipid vesicles.

Noguchi, Hiroshi

2010-06-01

213

Shear strain localization in elastodynamic rupture simulations

We study strain localization as an enhanced velocity weakening mechanism on earthquake faults. Fault friction is modeled using Shear Transformation Zone (STZ) Theory, a microscopic physical model for non-affine rearrangements in granular fault gouge. STZ Theory is implemented in spring slider and dynamic rupture models of faults. We compare dynamic shear localization to deformation that is uniform throughout the gouge layer, and find that localized slip enhances the velocity weakening of the gouge. Localized elastodynamic ruptures have larger stress drops and higher peak slip rates than ruptures with homogeneous strain.

Daub, Eric G; Carlson, Jean M

2008-01-01

214

Buckling of sheared and compressed microfibrils.

In this paper, we study the stability of an initially straight elastic fibril clamped at one end, while the other end is subjected to a constant normal compressive force and a prescribed shear displacement. We found the buckling load of a sheared fibril to be always less than the Euler buckling load. Furthermore, if the end of the fibril loses adhesion, then the buckling load can be considerably less. Our result suggests that the static friction of microfibre arrays can decrease with increasing normal compressive load and, in some cases, friction force can actually become negative. PMID:20444710

Nadermann, Nichole; Kumar, Ajeet; Goyal, Sachin; Hui, Chung-Yuen

2010-11-01

215

Encoding of Memory in Sheared Amorphous Solids

We show that memory can be encoded in a model amorphous solid subjected to athermal oscillatory shear deformations, and in an analogous spin model with disordered interactions, sharing the feature of a deformable energy landscape. When these systems are subjected to oscillatory shear deformation, they retain memory of the deformation amplitude imposed in the training phase, when the amplitude is below a "localization" threshold. Remarkably, multiple persistent memories can be stored using such an athermal, noise-free, protocol. The possibility of such memory is shown to be linked to the presence of plastic deformations and associated limit cycles traversed by the system, which exhibit avalanche statistics also seen in related contexts.

Fiocco, Davide; Foffi, Giuseppe; Sastry, Srikanth

2014-01-01

216

Halo abundances and shear in void models

DEFF Research Database (Denmark)

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.

Alonso, David; GarcÃa-Bellido, Juan

2012-01-01

217

Stability Criteria of 3D Inviscid Shears

Digital Repository Infrastructure Vision for European Research (DRIVER)

The classical plane Couette flow, plane Poiseuille flow, and pipe Poiseuille flow share some universal 3D steady coherent structure in the form of "streak-roll-critical layer". As the Reynolds number approaches infinity, the steady coherent structure approaches a 3D limiting shear of the form ($U(y,z), 0, 0$) in velocity variables. All such 3D shears are steady states of the 3D Euler equations. This raises the importance of investigating the stability of such inviscid 3D she...

Li, Y. Charles

2009-01-01

218

Universal Anisotropy in Force Networks under Shear

Scaling properties of patterns formed by large contact forces are studied as a function of the applied shear stress, in two-dimensional static packings generated from the force network ensemble. An anisotropic finite-size-scaling analysis shows that the applied shear does not affect the universal scaling properties of these patterns, but simply induces different length scales in the principal directions of the macroscopic stress tensor. The ratio of these length scales quantifies the anisotropy of the force networks, and is found not to depend on the details of the underlying contact network, in contrast with other properties such as the yield stress.

Ostojic, S; Nienhuis, B; Ostojic, Srdjan; Vlugt, Thijs J. H.; Nienhuis, Bernard

2006-01-01

219

Comment on "Phase-shifting shearing interferometer".

The role of the liquid-crystal layer in the phase-shifting shearing interferometer that was proposed by Griffin [Opt. Lett. 26, 140 (2001)] is analyzed. An extra voltage-dependent phase difference is produced when the phase retarder is oriented at an angle from the optical axis of the laser beam such that the interferogram will not repeat itself after a 2pi phase change of the liquid-crystal retarder in either the common Mach-Zehnder interferometer or the phase-shifting shearing interferometer. PMID:18007847

Chang, Kuo-Hui; Hsu, A-Chuan; Chern, Jyh-Long

2002-04-01

220

Effective-Temperature Induced Shear Banding in the Shear-Transformation-Zone Theory of Plasticity

This paper examines the stability of a previously proposed version of the shear-transformation-zone (STZ) theory of plasticity where the total STZ population is determined by an effective temperature and compares it to experimental results for a metallic glass. In particular, the addition of effective temperature dynamics to the shear transformation zone theory leads to the existence of a range of strain rates for which the strain localizes into shear bands. Yet while the steady-state results qualitatively agree, the instability of the dynamics of the system while loading begins better describes the experimental observations.

Foglia, A

2006-01-01

221

Numerical Simulation of Tripolar Vortex in Dusty Plasma with Sheared Flow and Sheared Magnetic Field

This article presents a study we have made of one class of coherent structures of the tripolar vortex. Considering the sheared flow and sheared magnetic field which are common in the thermonuclear plasma and space plasma, we have simulated the dynamics of the tripolar vortex. The results show that the tripolar vortex is largely stable in most cases, but a strongly sheared magnetic field will make the structure less stable, and lead it to decays into single vortices with the large space scale. These results are consistent with findings from former research about the dipolar vortex.

Wang, Ge; Chen, Yinhua; Tan, Liwei

2005-08-01

222

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

Kamruzzaman, Mohammed; Elmasry, Gamal; Sun, Da-Wen; Allen, Paul

2013-11-01

223

Beef biceps femoris muscles (n=45) were used to evaluate the effect of enhancement with solutions comprising 2.0% sodium chloride and either sodium hexametaphosphate (SHMP), sodium tripolyphosphate (STPP), or tetrasodium pyrophosphate (TSPP) at either 0.2% or 0.4% of product weight. All solutions were injected into muscle samples at either 112% (12% pump) or 118% (18% pump) of raw product weight. Muscles treated with all three phosphate types had decreased (PSTPP- and SHMP-treated muscles did not differ (P>0.05) from CNT. Disregarding phosphate type, steaks with 0.4% phosphate inclusion bound more (PSTPP or TSPP had decreased (P0.05) from CNT. Steaks injected at 18% pump had greater (P0.05) in free water, water binding, or cooking losses from steaks injected at 12% pump. Although there were no differences (P>0.05) in Warner-Bratzler shear force in this study, steaks with SHMP, STPP, and TSPP all were rated more tender, and juicier (PSTPP or TSPP can improve water retention, yield, and palatability characteristics. Additionally, enhancement with a phosphate/salt solution at an 18% pump rate, compared to a 12% pump rate, can allow for improved sensory tenderness perceptions without decreasing product yields. PMID:22063476

Baublits, R T; Pohlman, F W; Brown, A H; Johnson, Z B

2005-06-01

224

Directory of Open Access Journals (Sweden)

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 feed 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.

Isabella Dias Barbosa Silveira

2012-06-01

225

Scanning electron microscopy (SEM) was utilized to evaluate microstructural changes in intramuscular connective tissue of beef semimembranosus muscle subjected to hydrodynamic pressure processing (HDP). Samples were HDP treated in a plastic container (HDP-PC) or a steel commercial unit (HDP-CU). Control and HDP samples were obtained immediately post-treatment and after 14days of aging for SEM and Warner-Bratzler shear force (WBSF) analysis. Immediately post-treatment, HDP treated samples exhibited lower (P<0.01) WBSF than did controls. After aging, HDP-PC samples had lower (P<0.01) WBSF than that of aged controls. SEM analysis indicated that HDP-PC treatment disrupted the integrity of the collagen fibril network of the endomysium in both the non-aged and aged samples. Aging effects on the intramuscular connective tissue were observed in the HDP-PC and control samples. Both WBSF and connective tissue changes were greater in the HDP-PC than in the HDP-CU treated samples. Data suggest that shockwave alterations to connective tissue contribute to the meat tenderization of HDP. PMID:23803280

Zuckerman, H; Bowker, B C; Eastridge, J S; Solomon, M B

2013-11-01

226

In this study, 20 young steers received no beta-agonist (C), 100 animals all received zilpaterol hydrochloride (Z), with 1 group only receiving Z while the other 4 groups received zilpaterol and vitamin D3 at the following levels (IU/animal/day) and durations before slaughter: 7 million for 3 days (3D7M); 7 million for 6 days (6D7M); 7 million for 6 days with 7 days no supplementation (6D7M7N) and 1 million for 9 days (9D1M). Left carcass sides were electrically stimulated (ES) and the right side not stimulated (NES). Samples were aged for 3 or 14 days post mortem. Parameters included Warner-Bratzler shear force (WBSF), myofibril filament length, sarcomere length and calpastatin and calpain enzyme activity. Both ES and prolonged aging reduced WBSF (P<0.001). 6D7M, 6D7M7N and Z remained significantly tougher than C (P<0.001), while 3D7M and 9D1M improved WBSF under NES conditions. ES is more effective to alleviate beta-agonist induced toughness than high vitamin D3 supplements. PMID:21658849

Strydom, P E; Hope-Jones, M; Frylinck, L; Webb, E C

2011-12-01

227

In this study, 10 young steers received no beta agonist (C), 50 animals all received zilpaterol hydrochloride (Z), with 1 group receiving Z while the other 4 groups received Z and vitamin D(3) at the following levels (IU/animal /day) and durations before slaughter: 7 million for 3 days (3D7M) or 6 days (6D7M), 7 million for 6 days with 7 days no supplementation (6D7M7N) and 1 million for 9 days (9D1M). LD samples were vacuum-aged 14 days post mortem, and repacked in high-oxygen modified atmosphere (70% O(2)/30% CO(2)) for a further 7 days. Parameters included Warner Bratzler shear force (WBSF), myofibril fragment length, thiobarbituric acid reactive substances, free thiol levels, muscle fat, and instrumental colour parameters. When allowing for a conversion period of vitamin D(3) to its active metabolites, supplementing the zilpaterol treated steers with a high dosage of vitamin D(3) (6D7M7N) resulted in improved colour stability, higher stability towards protein oxidation and lower stability towards lipid oxidation. PMID:21723673

Hansen, Stine; Frylinck, Lorinda; Strydom, Phillip E

2012-01-01

228

Several studies have shown that feeding of an energy-dense diet over short periods to cull cows could be profitable in terms of increased saleable yield and improved carcass conditions. Although the application of growth promoters, such as anabolic implants and beta agonists, in finishing of cull cows have been recorded, there is no conclusive evidence as to the timing and duration of beta agonists in cull cow production. In this study, 288 cull cows with four or more permanent incisors and varying weights and body conditions were divided into four treatment groups so that variation in age, weight and body condition were equally distributed among groups. One group received concentrate feed without any beta agonist (C), whereas the other three groups also received concentrate feed with zilpaterol hydrochloride (6 p.p.m.) for 20 (Z20), 30 (Z30) or 40 (Z40) days, respectively, followed by a 2-day withdrawal. Animals were adapted for 10 days on a grain-based diet and fed an additional 40 days before slaughter. Growth rate and efficiency (live and carcass), trimmed meat yield and meat tenderness (Warner Bratzler shear force and sensory) of the aged (10 days) m. longissimus thoracis (LT) and m. semitendinosus (ST) were recorded. In general, Z cows had higher carcass gains and efficiency of gain than C cows (P zilpaterol for 30 days showed better growth performance and higher trimmed meat yield than 20 and 40 days supplementation. PMID:22444052

Strydom, P E; Smith, M F

2010-04-01

229

Histomorphology and Physical Characteristics of Buffalo Meat at Different Sex and Age

Directory of Open Access Journals (Sweden)

Full Text Available 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 showed that muscle fiber diameter was influenced by ages. The difference muscle fiber diameter among ages indicated that 8-12 mo and 1.5 yr old have smaller diameter compared to three year old (P<0.05, but there was no differences between two, three and four years old. The fasciculus diameter, thickness of connective tissue, tenderness, pH value, water holding capacity, and cooking lost indicated no significant found in all stage of age and sex of samples. Meat qualities of buffaloes were not affected by age (2-4 yr and sex.

Mahmudah

2013-04-01

230

Effect of slaughter weight and aging time on the quality of meat from Awassi ram lambs.

Thirty Awassi ram lambs were used to investigate the effects of live weight at slaughter (SW) and aging time (AT) on meat quality attributes of Mm. Semitendinosus, Semimembranosus, Biceps femoris and Longissimus. Lambs were slaughtered at 20, 30 or 40kg live weight, and muscles of each lamb carcass were aged for either 24h or 7days. Warner-Bratzler shear force values increased (P<0.01) with increasing live weight and decreased (P<0.01) by increasing AT in both M. Semimembranosus and Biceps femoris. Lightness (L*) of the four muscles decreased (P<0.001) with increasing weight but was not affected by AT. Aging time increased (P<0.05) redness (a*) in Mm.Semitendinosus and Longissimus. Cooking loss was reduced (P<0.001) by increased AT in M. Longissimus and by increasing (P<0.001) live weight in M.Semitendinosus. Aging time had no effect on expressed juice of all muscles but it was improved (P<0.001) with increasing live weight in M. Semimembranosus. pH values were significantly influenced for Mm. Semimembranosus and Biceps femoris and values were higher for lighter weight and decreased with increasing weight. Aging time did not influenced pH. In conclusion, meat quality for lambs slaughtered up to 30kg was better than for lambs slaughtered at 40kg with quality being improved by increasing aging time. PMID:20416727

Abdullah, Abdullah Y; Qudsieh, Rasha I

2009-07-01

231

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)

2003-01-01

232

Effect of bleeding method and low voltage electrical stimulation on meat quality of ostriches

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english 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.

L.C., Hoffman; S.W.P., Cloete; S.J., van Schalkwyk; S.St.C., Botha.

233

Red blood cell in simple shear flow

The dynamics of red blood cells (RBC) in blood flow is critical for oxygen transport, and it also influences inflammation (white blood cells), thrombosis (platelets), and circulatory tumor migration. The physical properties of a RBC can be captured by modeling RBC as lipid membrane linked to a cytoskeletal spectrin network that encapsulates cytoplasm rich in hemoglobin, with bi-concave equilibrium shape. Depending on the shear force, RBC elasticity, membrane viscosity, and cytoplasm viscosity, RBC can undergo tumbling, tank-treading, or oscillatory motion. We investigate the dynamic state diagram of RBC in shear and pressure-driven flow using a combined immersed boundary-lattice Boltzmann method with a multi-scale RBC model that accurately captures the experimentally established RBC force-deformation relation. It is found that the tumbling (TU) to tank-treading (TT) transition occurs as shear rate increases for cytoplasm/outer fluid viscosity ratio smaller than 0.67. The TU frequency is found to be half of the TT frequency, in agreement with experiment observations. Larger viscosity ratios lead to the disappearance of stable TT phase and unstable complex dynamics, including the oscillation of the symmetry axis of the bi-concave shape perpendicular to the flow direction. The dependence on RBC bending rigidity, shear modulus, the order of membrane spectrin network and fluid field in the unstable region will also be discussed.

Chien, Wei; Hew, Yayu; Chen, Yeng-Long

2013-03-01

234

Kinetic ballooning mode with negative shear

International Nuclear Information System (INIS)

Kinetic analysis on the ballooning mode in tokamaks has indicated the existence of a residual ballooning mode in the negative shear region (si), and is characterized by a broad eigenfunction ?(?) extending to ??50 in the ballooning space. copyright 1996 The American Physical Society

1996-01-01

235

Shear stress in magnetorheological finishing for glasses.

We report in situ, simultaneous measurements of both drag and normal forces in magnetorheological finishing (MRF) for what is believed to be the first time, using a spot taking machine (STM) as a test bed to take MRF spots on stationary parts. The measurements are carried out over the entire area where material is being removed, i.e., the projected area of the MRF removal function/spot on the part surface, using a dual force sensor. This approach experimentally addresses the mechanisms governing material removal in MRF for optical glasses in terms of the hydrodynamic pressure and shear stress, applied by the hydrodynamic flow of magnetorheological fluid at the gap between the part surface and the STM wheel. This work demonstrates that the volumetric removal rate shows a positive linear dependence on shear stress. Shear stress exhibits a positive linear dependence on a material figure of merit that depends upon Young's modulus, fracture toughness, and hardness. A modified Preston's equation is proposed that better estimates MRF material removal rate for optical glasses by incorporating mechanical properties, shear stress, and velocity. PMID:19412219

Miao, Chunlin; Shafrir, Shai N; Lambropoulos, John C; Mici, Joni; Jacobs, Stephen D

2009-05-01

236

SUPERSONIC SHEAR INSTABILITIES IN ASTROPHYSICAL BOUNDARY LAYERS

Energy Technology Data Exchange (ETDEWEB)

Disk accretion onto weakly magnetized astrophysical objects often proceeds via a boundary layer (BL) that forms near the object's surface, in which the rotation speed of the accreted gas changes rapidly. Here, we study the initial stages of formation for such a BL around a white dwarf or a young star by examining the hydrodynamical shear instabilities that may initiate mixing and momentum transport between the two fluids of different densities moving supersonically with respect to each other. We find that an initially laminar BL is unstable to two different kinds of instabilities. One is an instability of a supersonic vortex sheet (implying a discontinuous initial profile of the angular speed of the gas) in the presence of gravity, which we find to have a growth rate of order (but less than) the orbital frequency. The other is a sonic instability of a finite width, supersonic shear layer, which is similar to the Papaloizou-Pringle instability. It has a growth rate proportional to the shear inside the transition layer, which is of order the orbital frequency times the ratio of stellar radius to the BL thickness. For a BL that is thin compared to the radius of the star, the shear rate is much larger than the orbital frequency. Thus, we conclude that sonic instabilities play a dominant role in the initial stages of nonmagnetic BL formation and give rise to very fast mixing between disk gas and stellar fluid in the supersonic regime.

Belyaev, Mikhail A.; Rafikov, Roman R., E-mail: rrr@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States)

2012-06-20

237

Dilatancy and shear thickening of particle suspensions

Shear thickening is a fascinating subject, as 99.9% of complex fluids are thinning; thickening systems thus are the ``exception to the rule'' that needs to be understood. Moreover, such tunable systems show very promising applications, e.g. to block large underground pores in oil recovery to maintain a constant oil flow by plugging water filled pores (an approach used in oil recovery by e.g. Shell), or to manufacture bulletproof vests that are comfortable to wear, but stop bullets nonetheless. We study the rheology of non-Brownian particle suspensions (notably, cornstarch) that exhibit shear thickening. Using magnetic resonance imaging (MRI), the local properties of the flow are obtained by the determination of local velocity profiles and concentrations in a Couette cell. We also perform macroscopic rheology experiments in different geometries. The results suggest that the shear thickening is a consequence of dilatancy: the system under flow attempts to dilate but instead undergoes a jamming transition, because it is confined. This proposition is confirmed by an independent measurement of the dilation of the suspension as a function of the shear rate.

Bonn, Daniel

2013-03-01

238

Infrared low-level wind shear work

Results of field experiments for the detection of clear air disturbance and low level wind shear utilizing an infrared airborne system are given in vugraph form. The hits, misses and nuisance alarms scores are given. Information is given on the infrared spatial resolution technique. The popular index of aircraft hazard (F= WX over g - VN over AS) is developed for a remote temperature sensor.

Adamson, Pat

1988-01-01

239

Hydrodynamic Modeling and the QGP Shear Viscosity

In this article, we will briefly review the recent progress on hydrodynamic modeling and the extraction of the quark-gluon plasma (QGP) specific shear viscosity with an emphasis on results obtained from the hybrid model VISHNU that couples viscous hydrodynamics for the macroscopic expansion of the QGP to the hadron cascade model for the microscopic evolution of the late hadronic stage.

Song, Huichao

2012-01-01

240

Structure and texture of micelles under shear

The diffraction patterns of a 20 wt% (weight per cent) solution of Pluronic F127 in water near the origin of the reciprocal space measured in GISANS geometry show 2D and 3D powder crystalline structures for hydrophobic and hydrophilic terminated container walls. Under shear a pronounced texture develops for both surface coatings.

Walz, Marco; Magerl, Andreas; Wolff, Max; Zabel, Hartmut

2007-02-01

241

History of wind shear turbulence models

The Office of Flight Operations, Flight Technical Programs Div., at the FAA Headquarters, interfaces with industry, R&D communities and air carriers during the introduction of new types of equipment into operational services. A brief highlight of the need which FAA operations sees for new wind shear and turbulence data sets from the viewpoint of equipment certification and simulation is presented.

Cusimano, Lou

1987-01-01

242

Shear deformation in thick auxetic plates

International Nuclear Information System (INIS)

This paper aims to understand the effect of auxeticity on shear deformation in thick plates. Three models for the shear correction factor of plates as a function of Poisson’s ratio were proposed: an analytical model, a cubic fit model and a modified model. Of these three, the cubic fit model exhibits the best accuracy over the entire range of Poisson’s ratio from ?1 to 0.5. The extent of shear deformation is herein investigated using the example of uniformly loaded circular plates. It was found that the maximum deformation of such plates based on Mindlin theory approximates to those according to Kirchhoff theory when the Poisson’s ratio of the plate material is highly negative. When the Poisson’s ratio of the plate material is ?1 and the edge of the plate is simply supported, the calculation of the maximum deflection by Mindlin theory simplifies into that by Kirchhoff theory. These results suggest that auxeticity reduces shear deformation in thick plates, permitting the use of classical plate theory for thick plates only if the plate material is highly auxetic. (paper)

2013-08-01

243

Velocity shear generation of solar wind turbulence

Energy Technology Data Exchange (ETDEWEB)

The authors use a two-dimensional, incompressible MHD spectral code to establish that shear-driven turbulence is a possible means for producing many observed properties of the evolution of the magnetic and velocity fluctuations in the solar wind and, in particular, the evolution of the cross helicity ({open_quotes}Alfvenicity{close_quotes}) at small scales. They find that large-scale shear can nonlinearly produce a cascade to smaller scale fluctuations even when the linear Kelvin-Helmholtz mode is stable and that a roughly power law inertial range is established by this process. While the fluctuations thus produced are not Alfvenic, they are nearly equipartitioned between magnetic and kinetic energy. The authors report simulations with Alfvenic fluctuations at high wave numbers, both with and without shear layers and find that it is the low cross helicity at low wave numbers that is critical to the cross helicity evolution, rather than the geometry of the flow or the dominance of kinetic energy at large scales. The fluctuations produced by shear effects are shown to evolve similarly but more slowly in the presence of a larger mean field and to be anisotropic with a preferred direction of spectral transfer perpendicular to the mean field. The evolution found is similar to that seen in some other simulations of HMD turbulence, and thus seems in many respects to be an instance of a more generic turbulent evolution rather than due to specific conditions in the solar wind. 75 refs., 18 figs.

Roberts, D.A.; Goldstein, M.L.; Ghosh, S. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Matthaeus, W.H. [Univ. of Delaware, Newark, DE (United States)

1992-11-01

244

Self-assemblying systems in shear flow

The Ginzburg-Landau free-energy approach [1] used to describe the equilibrium phase diagram of self-assemblying systems and ternary mixtures can be extended to take into account the presence of imposed flows [2,3]. Our results mainly concern the effects of a shear flow on transient and stationary properties of microemulsions. Equal time and two-time correlations have been calculated in the framework of a self-consistent approximation. The structure factor is anisotropic and at high shear rates is dominated by two peaks at kx = 0 corresponding to interfaces aligned with the flow. The stress as a function of the shear rate has been calculated: shear thinning is observed to occurr at two characteristic shear rates, the first corresponding to the inverse of the structural relaxation time. When the flow is applied starting from a quiescent condition, the transient behaviour shows a maximum of the stress followed by a relaxation to the stationary value. This can be interpreted as an accumulation of stress in the original microemulsion structure followed by a topology change with breakdowns in the interface connectivity. We have also done a similar study for micellar solutions comparing our results with the experimental data of [4]. [1] G. Gompper and M. Schick, Phys. Rev. Lett. 65, 1116 (1990). [2] G. Pätzold and K. Dawson, Phys. Rev. E 54, 1669 (1996); G. Pätzold and K. Dawson, J. Chem. Phys. 104, 5932 (1996). [3] F. Corberi, G. Gonnella, and D. Suppa, cond-mat/0004282, Phys. Rev. E - Rapid Comm. 63, 040501(R) (2001). [4] P. Boltenhagen, Yuntao Hu, E.F. Matthys and D.J. Pine, Europhys. Lett. 38, 389 (1997). R. Bandyopadhyay, G. Basappa and A. K. Sood, Phys. Rev. Lett.

Gonnella, Giuseppe; Ruggieri, Marco; Corberi, Federico

2002-03-01

245

Spurious Shear in Weak Lensing with LSST

Energy Technology Data Exchange (ETDEWEB)

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.

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

246

Digital Repository Infrastructure Vision for European Research (DRIVER)

A phenomenological model of a rigid, work hardening, plastic material, with rate hardening and thermal softening, is analysed to determine susceptibility to the formation of adiabatic shear bands. Emphasis is placed on the influence of finite thermal conductivity.

Wright, T.

1991-01-01

247

Shear Test on RC Elements with Circular Cross Section

DEFF Research Database (Denmark)

Reinforced concrete members with circular cross section are widely used in bridge engineering, either as piers or as piles to support pile caps. In codes, guidelines for shear design of circular concrete members are almost none-existing. Some codes specify rules based on shear models for rectangular members. The shear behaviour of members with circular cross section is, however, quite different from that of rectangular members. The published experimental research on the shear behaviour of circular members contains only test results with very low shear reinforcement percentages. In this paper shear tests on a series of heavily confined concrete members are reported. The specimens have shear reinforcement percentages (hoops) up to more than three times the maximum percentage found in existing tests. The test results are compared with a recently developed shear design model for circular members Good agreement has been found.

Jensen, U.G.; Hoang, L.C.

2009-01-01

248

Shear crack formation and propagation in reinforced Engineered Cementitious Composites

DEFF Research Database (Denmark)

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.

Paegle, Ieva; Fischer, Gregor

2011-01-01

249

Variational bounds for the shear viscosity of gelling melts

We study shear stress relaxation for a gelling melt of randomly crosslinked, interacting monomers. We derive a lower bound for the static shear viscosity $\\eta$, which implies that it diverges algebraically with a critical exponent $k\\ge 2\

K"ohler, C H; Müller, P; Zippelius, A; K\\"ohler, Claas H.; L\\"owe, Henning; M\\"uller, Peter; Zippelius, Annette

2007-01-01

250

Transient and steady state behaviors of rapid granular shear flows

Energy Technology Data Exchange (ETDEWEB)

Rapid granular shear flow is a classical example in granular materials which exhibits fluid-like behavior solely or fluid-like and solid-like behaviors simultaneously. We have performed experiments on annular granular shear flows using monodisperse steel spheres with 2-mm and 3-mm diameters. We discuss some transient (static failure of material due to shear) and steady-state (completely sheared and partially sheared flows) features of rapid granular flows. Our results map out the boundary between overall compaction and dilation that characterizes multiphase behavior of the system. Dimensionless stresses rise as more material is loaded into the system. On the other hand, increasing the compressive force or shear rate is equal to easing the process of shearing by decreasing the ratio of shear to normal stress. (orig.)

Jalali, P.; Ritvanen, J.; Sarkomaa, P. [Lappeenranta University of Technology, Department of Energy and Environmental Technology, Lappeenranta (Finland)

2005-09-01

251

Naesliden Project: direct shear tests of filled and unfilled joints

Energy Technology Data Exchange (ETDEWEB)

Joints from the Naesliden mine have been tested in a small field shear box and in a large shear rig. The large shear rig is described in detail, and its ability to test joints with an area of 600 mc/sup 2/ at a maximum normal stress of up to 20 MPa is emphasized. The stiffness and shear strength of the discontinuities in the Naesliden mine is presented. The values estimated at direct shear tests are compared with results from in situ measurements and tests on drillcores. The results show that the in situ measurements give lower values for the shear resistance than the direct shear tests. Estimation of the normal stiffness for joints in drill cores gave much higher stiffness than the estimations in the shear rig.

Ludvig, B.

1980-05-01

252

Digital Repository Infrastructure Vision for European Research (DRIVER)

Assessing the strength of existing structures has become a major issue for structural engineers. Such analyses are often performed after changes of use of the structure or due to new design codes requirements. This is particularly relevant with respect to the shear strength of post-tensioned concrete bridges. Such structures were often designed in the past with fairly low amounts of shear reinforcement and do not comply with current code requirements in terms of amount of transverse reinforce...

Rupf, Michael; Ferna?ndez Ruiz, Miguel; Muttoni, Aurelio

2013-01-01

253

New provisions for punching shear in Model Code 2010 based on the Critical Shear Crack Theory

Digital Repository Infrastructure Vision for European Research (DRIVER)

The provisions for punching shear around concentrated loads in the new Model Code 2010 (MC2010) have been updated, covering a large number of design cases such as slabs with and without transverse reinforcement, different column/slab geometries and prestressed slabs amongst others. The theoretical framework used was based on the mechanical model of the Critical Shear Crack Theory (CSCT). This approach, in contrast to empirical formulas, provides the designer with a physical understanding of t...

Sagaseta, Juan; Tassinari, Luca; Muttoni, Aurelio; Ferna?ndez Ruiz, Miguel

2011-01-01

254

Dynamic modes of microcapsules in steady shear flow: effects of bending and shear elasticities.

The dynamics of microcapsules in steady shear flow were studied using a theoretical approach based on three variables: the Taylor deformation parameter ?D , the inclination angle ? , and the phase angle ? of the membrane rotation. It is found that the dynamic phase diagram shows a remarkable change with an increase in the ratio of the membrane shear and bending elasticities. A fluid vesicle (no shear elasticity) exhibits three dynamic modes: (i) tank treading at low viscosity ?in of internal fluid (?D and ? relaxes to constant values), (ii) tumbling (TB) at high ?in (? rotates), and (iii) swinging (SW) at middle ?in and high shear rates ? (? oscillates). All of three modes are accompanied by a membrane (?) rotation. For microcapsules with low shear elasticity, the TB phase with no ? rotation and the coexistence phase of SW and TB motions are induced by the energy barrier of ? rotation. Synchronization of ? rotation with TB rotation or SW oscillation occurs with integer ratios of rotational frequencies. At high shear elasticity, where a saddle point in the energy potential disappears, intermediate phases vanish and either ? or ? rotation occurs. This phase behavior agrees with recent simulation results of microcapsules with low bending elasticity. PMID:20866334

Noguchi, Hiroshi

2010-05-01

255

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.

López-Barrón, Carlos R.; Gurnon, A. Kate; Eberle, Aaron P. R.; Porcar, Lionel; Wagner, Norman J.

2014-04-01

256

Band crossing in Shears band of $^{108}$Cd

The level lifetimes have been measured for a Shears band of $^{108}$Cd which exhibits bandcrossing. The observed level energies and B(M1) rates have been successfully described by a semi-classical geometric model based on shear mechanism. In this geometric model, the bandcrossing in Shears band has been described as the reopening of the angle between the blades of a shear.

Roy, Santosh; Pal, S; Chattopadhyay, S; Bhattacharya, S; Goswami, A; Jain, H C; Joshi, P K; Bhowmik, R K; Kumar, R; Muralithar, S; Singh, R P; Madhavan, N; Rao, P V Madhusudhana

2010-01-01

257

Band formation in HPC subjected to steady and oscillatory shear

The formation of a regular banded structure perpendicular to the direction of applied shear, in the lyotropic liquid crystal hydroxypropylcellulose (HPC) as observed by optical microscopy is presented. This is a phenomenon that has been the subject of much attention in the literature. Use of a specialised optical shear cell allowed in-situ observation of the HPC whilst subjected to steady or oscillatory shear stress in a parallel plate geometry. Using the shear cell, textural observations of the formation of band structure during and after cessation of shear stress were obtained. Band formation was found to be dependent on the magnitude of reduction in steady shear rate. A reduction of the shear rate by more than 10 1/s was required for effective band formation. A larger reduction in shear rate led to more rapid and extensive band formation. When subjected to oscillatory shear, larger transverse bands were observed during oscillation at sufficiently high frequency and amplitude;formation of the smaller bands was also apparent on cessation. Higher oscillation frequencies yielded more extensive band formation. Application of steady shear rate greater than 10 reciprocal seconds to HPC showed the gradual build up of wavy herring-bone texture. On relaxation of the shear stress the sample was seen to decelerate slowly with residual flow in the shear direction. The bands formed as a result of this crumpling motion inducing a sinusoidal ripple in the sample. The bands were also visible without crossed-polars indicating a periodic density distribution in addition to the orientational distribution. The texture observed was found to be dependent on shear rate; at applied shear rates of less than 10 1/s, the stable texture was vertically-striated whilst at shear rates greater than 10 1/s a herring-bone texture was observed. No transverse bands were seen on cessation of a shear rate of less than 10 1/s in the absence of the herring-bone texture.

Fischer, C. L. Bower; H.

258

Short-span compressive strength and interlaminar shear resistance

Energy Technology Data Exchange (ETDEWEB)

A relatively simple relation between short-span compressive strength and ultimate interlaminar shear strain is derived and shown to fit data for machine-made boards from different sources. Interlaminar shear resistance seems to be the pertinent bond test for edgewise compression strength studies. Experimental results illustrate how (shear) bond strength can be monitored by measuring in-plane modulus and short-span compression strength. Practical aspects of the interlaminar shear resistance test are also discussed.

Amini, J.; Robillard, N. [Domtar Inc., Senneville, Quebec (Canada); Bardeau, C.E. [3M Canada Inc., London, Ontario (Canada)

1995-12-31

259

Fluid Effects on Shear Waves in FInely Layered Porous Media

Energy Technology Data Exchange (ETDEWEB)

Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored by this modulus by a term that ranges from the smallest to the largest shear moduli of the VTI system. But, since there are five shear moduli in play, the increase in shear energy overall is reduced by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of shear modulus, being about 20% of the permitted range, when gas is fully replaced by liquid. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% partially offsets the effect of this shear modulus increase. Thus, an increase of shear wave speed on the order of 5 to 10% is shown to be possible when circumstances are favorable - i.e., when the shear modulus fluctuations are large (resulting in strong anisotropy), and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity.

Berryman, J G

2004-05-21

260

Standard test method for shear fatigue of sandwich core materials

Energy Technology Data Exchange (ETDEWEB)

This method covers determination of the effect of repeated shear loads on sandwich core materials. If the facings of a sandwich construction are designed so that they are elastically stable, the most critical stress to which the core is subjected is shear. The effect of repeated shear stresses on the core material is therefore important.

1980-01-01

261

Directory of Open Access Journals (Sweden)

Full Text Available Square-plate twist (SPT tests were conducted to measure the shear modulus and shear strength using the method, which was a modification of the International Organization for Standardization (ISO 15310 standardized method. In the SPT test, the length/thickness ratio varied. In addition, asymmetric four-point bending (AFPB tests were conducted, and the shear modulus and shear strength obtained were compared with those obtained by the SPT tests. The shear modulus was obtained effectively by the SPT test when the specimen was thin enough. Although the shear strength was evaluated as higher than that obtained by the AFPB tests, it might be regarded as an apparent value of shear strength when the range of length/thickness is limited. To obtain the actual shear strength by the SPT test, some modification of the equation is required.

Hiroshi Yoshihara

2012-03-01

262

This report is intended to provide internal documentation for the U.S. Geological Survey laboratory's automatic data acquisition system. The operating procedures for each type of test are designed to independently lead a first-time user through the various stages of using the computer to control the test. Continuing advances in computer technology and the availability of desktop microcomputers with a wide variety of peripheral equipment at a reasonable cost can create an efficient automated geotechnical testing environment. A geotechnical testing environment is shown in figure 1. Using an automatic data acquisition system, laboratory test data from a variety of sensors can be collected, and manually or automatically recorded on a magnetic device at the same apparent time. The responses of a test can be displayed graphically on a CRT in a matter of seconds, giving the investigator an opportunity to evaluate the test data, and to make timely, informed decisions on such matters as whether to continue testing, abandon a test, or modify procedures. Data can be retrieved and results reported in tabular form, or graphic plots, suitable for publication. Thermistors, thermocouples, load cells, pressure transducers, and linear variable differential transformers are typical sensors which are incorporated in automated systems. The geotechnical tests which are most practical to automate are the long-term tests which often require readings to be recorded outside normal work hours and on weekends. Automation applications include incremental load consolidation tests, constant-rate-of-strain consolidation tests, direct shear tests, ring shear tests, and triaxial shear tests.

Powers, Philip S.

1983-01-01

263

Holographic Chiral Shear Waves from Anomaly

International Nuclear Information System (INIS)

We study dispersion relations of hydrodynamic waves of hot N=4 SYM plasma at strong coupling with a finite U(1) R-charge chemical potential via holography. We first provide complete equations of motion of linearized fluctuations out of a charged AdS blackhole background according to their helicity, and observe that helicity ±1 transverse shear modes receive a new parity-odd contribution from the 5D Chern-Simons term, which is dual to 4D U(1)3 anomaly. We present a systematic solution of the helicity ±1 wave equations in long wave-length expansion, and obtain the corresponding dispersion relations. The results depen d on the sign of helicity, which may be called chiral shear waves. (author)

2009-01-01

264

Polarization phase shifting lateral shearing interferometer

A polarization phase shifting lateral shearing interferometer based on a polarization beam splitting plate(PBSP) is proposed. The front surface of the PBSP is coated with polarization beam splitting film and its back surface is coated with total reflection film. The beam to be tested is split by the PBSP with an incidence angle of 45° and divided into two mutually perpendicular linearly polarization beams. Phase shifting can be introduced to the interferometer when the PBSP is combined with a polarzation temporal or spatial phase shifter. A polarizaiton temporal phase shifting lateral shearing interferometer system is built up both with the ASAP software and the experiments. The usefulness of the interferometer is verified.

Liu, Lei; Zeng, Aijun; Zhu, Linglin; Song, Qiang; Huang, Huijie

2013-08-01

265

Turbulent Shear Layers in Supersonic Flow

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.

Smits, Alexander J

2006-01-01

266

Shear and rotation in Chaplygin cosmology

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.

Del Popolo, A; Maydanyuk, S P; Lima, J A S; Jesus, J F; 10.1103/PhysRevD.87.043527

2013-01-01

267

Shear viscosity, cavitation and hydrodynamics at LHC

Energy Technology Data Exchange (ETDEWEB)

We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.

Bhatt, Jitesh R., E-mail: jeet@prl.res.in [Theoretical Physics Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 (India); Mishra, Hiranmaya, E-mail: hm@prl.res.in [Theoretical Physics Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 (India); Sreekanth, V., E-mail: skv@prl.res.in [Theoretical Physics Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 (India)

2011-10-25

268

Shear viscosity, cavitation and hydrodynamics at LHC

We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid become invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early during the evolution of the hydrodynamics in time $\\lesssim 2 $fm/c. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal term used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.

Bhatt, Jitesh R; Sreekanth, V

2011-01-01

269

Brownian forces in sheared granular matter

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.

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

270

Magnetic reconnection in sheared solar magnetic arcades

Energy Technology Data Exchange (ETDEWEB)

The evolution of solar magnetic arcades is investigated with the use of MHD simulations imposing resistivity on sheared magnetic fields. It is found that there is a critical amount of shear, over which magnetic reconnection can take place in an arcade-like field geometry to create a magnetic island. The process leading to reconnection cannot be solely attributed to a tearing instability, but rather to a reactive evolution of the magnetic arcade under resistivity. The natures of the arcade reconnection are governed by the spatial pattern of resistivity. A fast reconnection with a small shock angle can only be achieved when the diffusion region is localized. In this case, a highly collimated reconnection outflow can tear the plasmoid into a pair, and most of principal features in solar eruptive processes are reproduced.

Choe, G.S.

1996-12-31

271

Shear-induced polymerization of benzene

Energy Technology Data Exchange (ETDEWEB)

Both slow and fast chemical reactions can be induced by strains; with or without the assistance of temperature. Shear strains are especially effective. Defects, particularly dislocations, are also important as strain amplifiers. In covalent solids metallization has been associated with the bending (shearing) of chemical bonds. In ionic solids isotropic compression is also important. Metals may be influenced by distortions of the spd-hybrid bonds. A prototype is the polymerization of benzene. Normally, benzene rings are flat. It is proposed that compression buckles the rings into the chair'' configuration. This will close the HOMO-LUMO energy gap, thereby delocalizing the bonding electrons which then rearrange to link two or more molecules. The criteria for this, and the implications, are discussed. [copyright] 1994 American Institute of Physics

Gilman, J.J. (Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)); Armstrong, R.W. (University of Maryland, College Park, Maryland 20742 (United States))

1994-07-10

272

Implications of Orientation in Sheared Cocoa Butter

We will present x-ray and mechanical studies of oriented phases of cocoa butter. The structural elements of foods play an important role in determining such things as quality and shelf stability. The specific structure and properties of cocoa butter, however, are complicated due to the ability of the cocoa butter to form crystals in six polymorphic forms. Recent work has shown that the application of shear not only accelerates the transitions to more stable polymorphs, but also causes orientation of the crystallites[1]. The implications of orientation on the structures formed under conditions of shear and cooling will be described using x-ray diffraction and mechanical measurements. 1 G. Mazzanti, S. E. Guthrie, E. B. Sirota et al., Crystal Growth & Design 3 (5), 721 (2003).

Guthrie, Sarah E.; Mazzanti, Gianfranco; Marangoni, Alejandro; Idziak, Stefan H. J.

2004-03-01

273

Shear-bulk coupling in nonconformal hydrodynamics

We compute the temporal evolution of the pressure anisotropy and bulk pressure of a massive gas using second-order viscous hydrodynamics and anisotropic hydrodynamics. We then compare our results with an exact solution of the Boltzmann equation for a massive gas in the relaxation time approximation. We demonstrate that, within second-order viscous hydrodynamics, the inclusion of the full set of kinetic coefficients, particularly the shear-bulk couplings, is necessary to properly describe the time evolution of the bulk pressure. We also compare the results of second-order hydrodynamics with those obtained using the anisotropic hydrodynamics approach. We find that anisotropic hydrodynamics and second-order viscous hydrodynamics including the shear-bulk couplings are both able to reproduce the exact evolution with comparable accuracy.

Denicol, Gabriel S; Ryblewski, Radoslaw; Strickland, Michael

2014-01-01

274

The shear mode of multilayer graphene

The quest for materials capable of realizing the next generation of electronic and photonic devices continues to fuel research on the electronic, optical and vibrational properties of graphene. Few-layer graphene (FLG) flakes with less than ten layers each show a distinctive band structure. Thus, there is an increasing interest in the physics and applications of FLGs. Raman spectroscopy is one of the most useful and versatile tools to probe graphene samples. Here, we uncover the interlayer shear mode of FLGs, ranging from bilayer graphene (BLG) to bulk graphite, and suggest that the corresponding Raman peak measures the interlayer coupling. This peak scales from ~43?cm-1 in bulk graphite to ~31?cm-1 in BLG. Its low energy makes it sensitive to near-Dirac point quasiparticles. Similar shear modes are expected in all layered materials, providing a direct probe of interlayer interactions.

Tan, P. H.; Han, W. P.; Zhao, W. J.; Wu, Z. H.; Chang, K.; Wang, H.; Wang, Y. F.; Bonini, N.; Marzari, N.; Pugno, N.; Savini, G.; Lombardo, A.; Ferrari, A. C.

2012-04-01

275

Ideal Shear Strength of a Quantum Crystal

Using path-integral Monte Carlo simulations, we compute the ideal shear strength (ISS) on the basal plane of hcp He4. The failure mode upon reaching the ISS limit is characterized by the homogeneous nucleation of a stacking fault and it is found to be anisotropic, consistent with Schmid's law of resolved shear stress. Comparing the ISS of hcp He4 to a large set of classical crystals shows that it closely fits the approximately universal modified Frenkel model of ideal strength. In addition to giving quantitative stress levels for the homogeneous nucleation of extended defects in hcp He4, our findings lend support to assumptions in the literature that inherently classical models remain useful for the description of mechanical behavior in quantum crystals.

Borda, Edgar Josué Landinez; Cai, Wei; de Koning, Maurice

2014-04-01

276

Undulatory swimming in shear-thinning fluids

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.

Gagnon, David A; Arratia, Paulo E

2014-01-01

277

Shear Viscosity Coefficient from Microscopic Models

The transport coefficient of shear viscosity is studied for a hadron matter through microscopic transport model, the Ultra--relativistic Quantum Molecular Dynamics (UrQMD), using the Green--Kubo formulas. Molecular--dynamical simulations are performed for a system of light mesons in a box with periodic boundary conditions. Starting from an initial state composed of $\\pi, \\eta ,\\omega ,\\rho ,\\phi$ with a uniform phase--space distribution, the evolution takes place through elastic collisions, production and annihilation. The system approaches a stationary state of mesons and their resonances, which is characterized by common temperature. After equilibration, thermodynamic quantities such as the energy density, particle density, and pressure are calculated. From such an equilibrated state the shear viscosity coefficient is calculated from the fluctuations of stress tensor around equilibrium using Green--Kubo relations. We do our simulations here at zero net baryon density so that the equilibration times depend o...

Muronga, A

2004-01-01

278

Motional Effect on Wall Shear Stresses

DEFF Research Database (Denmark)

Atherosclerosis is the leading cause of death and severe disability. Wall Shear Stress (WSS), the stress exerted on vessel walls by the flowing blood is a key factor in the development of atherosclerosis. Computational Fluid Dynamics (CFD) is widely used for WSS estimations. Most CFD simulations are based on static models to ease computational burden leading to inaccurate estimations. The aim of this work was to estimate the effect of vessel wall deformations (expansion and bending) on WSS levels.

Kock, Samuel Alberg; Torben FrÃ¼nd, Ernst

279

Brownian forces in sheared granular matter

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 descrip...

Baldassarri, Andrea; Dalton, Fergal; Petri, Alberto; Zapperi, Stefano; Pontuale, Giorgio; Pietronero, Luciano

2005-01-01

280

Stochastic dynamics of a sheared granular medium

Digital Repository Infrastructure Vision for European Research (DRIVER)

We experimentally investigate the response of a sheared granular medium in a Couette geometry. The apparatus exhibits the expected stick-slip motion and we probe it in the very intermittent regime resulting from low driving. Statistical analysis of the dynamic fluctuations reveals notable regularities. We observe a possible stability property for the torque distribution, reminiscent of the stability of Gaussian independent variables. In this case, however, the variables are ...

Petri, Alberto; Baldassarri, Andrea; Dalton, Fergal; Pontuale, Giorgio; Pietronero, Luciano; Zapperi, Stefano

2008-01-01

281

Shear rheological characterization of motor oils

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.

Bair, Scott; Winer, Ward O.

1988-01-01

282

Stochastically driven instability in rotating shear flows

International Nuclear Information System (INIS)

The origin of hydrodynamic turbulence in rotating shear flows is investigated, with particular emphasis on the flows whose angular velocity decreases but whose specific angular momentum increases with the increasing radial coordinate. Such flows are Rayleigh stable, but must be turbulent in order to explain the observed data. Such a mismatch between the linear theory and the observations/experiments is more severe when any hydromagnetic/magnetohydrodynamic instability and then the corresponding turbulence therein is ruled out. This work explores the effect of stochastic noise on such hydrodynamic flows. We essentially concentrate on a small section of such a flow, which is nothing but a plane shear flow supplemented by the Coriolis effect. This also mimics a small section of an astrophysical accretion disc. It is found that such stochastically driven flows exhibit large temporal and spatial correlations of perturbation velocities and hence large energy dissipations of perturbation, which presumably generate the instability. A range of angular velocity (?) profiles of the background flow, starting from that of a constant specific angular momentum (? = ?r2; r being the radial coordinate) to a constant circular velocity (v? = ?r), is explored. However, all the background angular velocities exhibit identical growth and roughness exponents of their perturbations, revealing a unique universality class for the stochastically forced hydrodynamics of rotating shear flows. This work, to the best of our knowledge, is the first attempt to understand the origin of instability and turbulence in three-dimensional Rayleigh stable rotating shear flows by introducing additive noise to the underlying linearized governing equations. This has important implications to resolve the turbulence problem in astrophysical hydrodynamic flows such as accretion discs. (paper)

2013-01-25

283

Kinetic ballooning mode with negative shear

Energy Technology Data Exchange (ETDEWEB)

Kinetic analysis on the ballooning mode in tokamaks has indicated the existence of a residual ballooning mode in the negative shear region ({ital s}{lt}0). The instability has a small threshold in {alpha} (the ballooning parameter), requires a finite ion temperature gradient ({eta}{sub {ital i}}), and is characterized by a broad eigenfunction {phi}({theta}) extending to {theta}{approx_equal}50 in the ballooning space. {copyright} {ital 1996 The American Physical Society.}

Hirose, A.; Elia, M. [Plasma Physics Laboratory, University of Saskatchewan, 116 Science Place, Saskatoon, S7N 5E2 (CANADA)

1996-01-01

284

Shear modulus of neutron star crust

Digital Repository Infrastructure Vision for European Research (DRIVER)

Shear modulus of solid neutron star crust is calculated by thermodynamic perturbation theory taking into account ion motion. At given density the crust is modelled as a body-centered cubic Coulomb crystal of fully ionized atomic nuclei of one type with the uniform charge-compensating electron background. Classic and quantum regimes of ion motion are considered. The calculations in the classic temperature range agree well with previous Monte Carlo simulations. At these temper...

Baiko, D. A.

2011-01-01

285

Thin front propagation in random shear flows

Digital Repository Infrastructure Vision for European Research (DRIVER)

Front propagation in time dependent laminar flows is investigated in the limit of very fast reaction and very thin fronts, i.e. the so-called geometrical optics limit. In particular, we consider fronts evolving in time correlated random shear flows, modeled in terms of Ornstein-Uhlembeck processes. We show that the ratio between the time correlation of the flow and an intrinsic time scale of the reaction dynamics (the wrinkling time $t_w$) is crucial in determining both the ...

Chinappi, M.; Cencini, M.; Vulpiani, A.

2005-01-01

286

Nonequilibrium shear viscosity computations with Langevin dynamics

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the mathematical properties of a nonequilibrium Langevin dynamics which can be used to estimate the shear viscosity of a system. More precisely, we prove a linear response result which allows to relate averages over the nonequilibrium stationary state of the system to equilibrium canonical expectations. We then write a local conservation law for the average longitudinal velocity of the fluid, and show how, under some closure approximation, the viscosity can be extra...

Joubaud, Remi; Stoltz, Gabriel

2011-01-01

287

Surface shear rheology of saponin adsorption layers.

Saponins are a wide class of natural surfactants, with molecules containing a rigid hydrophobic group (triterpenoid or steroid), connected via glycoside bonds to hydrophilic oligosaccharide chains. These surfactants are very good foam stabiliziers and emulsifiers, and show a range of nontrivial biological activities. The molecular mechanisms behind these unusual properties are unknown, and, therefore, the saponins have attracted significant research interest in recent years. In our previous study (Stanimirova et al. Langmuir 2011, 27, 12486-12498), we showed that the triterpenoid saponins extracted from Quillaja saponaria plant (Quillaja saponins) formed adsorption layers with unusually high surface dilatational elasticity, 280 ± 30 mN/m. In this Article, we study the shear rheological properties of the adsorption layers of Quillaja saponins. In addition, we study the surface shear rheological properties of Yucca saponins, which are of steroid type. The experimental results show that the adsorption layers of Yucca saponins exhibit purely viscous rheological response, even at the lowest shear stress applied, whereas the adsorption layers of Quillaja saponins behave like a viscoelastic two-dimensional body. For Quillaja saponins, a single master curve describes the data for the viscoelastic creep compliance versus deformation time, up to a certain critical value of the applied shear stress. Above this value, the layer compliance increases, and the adsorption layers eventually transform into viscous ones. The experimental creep-recovery curves for the viscoelastic layers are fitted very well by compound Voigt rheological model. The obtained results are discussed from the viewpoint of the layer structure and the possible molecular mechanisms, governing the rheological response of the saponin adsorption layers. PMID:22830458

Golemanov, Konstantin; Tcholakova, Slavka; Denkov, Nikolai; Pelan, Edward; Stoyanov, Simeon D

2012-08-21

288

Study of Shear Viscosity of Amorphous Materials

Digital Repository Infrastructure Vision for European Research (DRIVER)

Viscoelastic properties of amorphous solids deformed under uniform shear stress were studied using a kind of sandwich method with utilizing a sensitive optical technique. Time-dependent deformation data were analyzed on the basis of a mechanical model of anelasticity plus viscosity. Experiments were performed to determine the temperature dependence of viscosity for several kinds of inorganic glasses and an amorphous polymer below their glass transition temperatures. Activation energies contro...

1996-01-01

289

Multiphase gas transport in a shear zone

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the post-operational phase of a Low/Intermediate-Low radioactive waste repository, gas will be generated in the caverns due to anaerobic corrosion of metals, and also chemical and microbial degradation of organic substances. Previous investigations on gas migration have indicated that discrete water conducting features (e.g. shear zones) are mainly responsible for gas transport from the caverns through the geosphere. Two phase flow processes occur in these water conducting features; the c...

Jo?dar Bermu?dez, Jorge

2007-01-01

290

Multiphase gas transport in a shear zone

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the post-operational phase of a Low/Intermediate-Low radioactive waste repository, gas will be generated in the caverns due to anaerobic corrosion of metals, and also chemical and microbial degradation of organic substances. Previous investigations on gas migration have indicated that discrete water conducting features (e.g. shear zones) are mainly responsible for gas transport from the caverns through the geosphere. Two phase flow processes occur in these water conducting features; the co...

Jo?dar, Jorge

2007-01-01

291

Shear friction capacity of recycled concretes

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this research was to determine the behavior of recycled concrete in response to the phenomenon of shear transfer. To perform it, a conventional control concrete and a concrete with 50% recycled coarse aggregate were designed. An additional goal was to shed light on how this behavior is modified with a pozzolanic addition, silica fume. Therefore, two types of concrete were designed, a conventional and a recycled concrete, both made with 8% of silica fume. In conclusion, a...

Gonza?lez Fonteboa, B.; Marti?nez, F.; Carro, D.; Eiras, J.

2010-01-01

292

Timescales in shear banding of wormlike micelles

We show the existence of three well defined time scales in the dynamics of wormlike micelles after a step between two shear rates on the stress plateau. These time scales are compatible with the presence of a structured interface between bands of different viscosities and correspond to the isotropic band destabilization during the stress overshoot, reconstruction of the interface after the overshoot and travel of a fully formed interface. The last stage can be used to estimate a stress diffusion coefficient.

Radulescu, O; Decruppe, J P; Lerouge, S; Berret, J F; Porte, G

2002-01-01

293

Optimisation and control of shear flows

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Monokrousos, Antonios

2011-01-01

294

Shear viscosity of hadronic gas mixtures

We investigate the effects of baryon chemical potential \\mu on the shear viscosity coefficient \\eta and the viscosity to entropy density ratio \\eta/s of a pion-nucleon gas mixture. We find that \\eta is an increasing function of T and \\mu, while the ratio \\eta/s turns to a decreasing function in a wide region of T-\\mu plane. In the kinematical region we studied, the smallest value of \\eta/s is about 0.3.

Itakura, K; Otomo, H

2008-01-01

295

Atomization of Shear Coaxial Liquid Jets

Digital Repository Infrastructure Vision for European Research (DRIVER)

The instability and subsequent atomization of a viscous liquid jet emanated into a high-pressure gaseous

surrounding is studied both computationally and experimentally. Liquid water issued into nitrogen gas at

elevated pressures is used to simulate the flow conditions in a coaxial shear injector element relevant to liquid

propellant rocket engines. The theoretical analysis is based on a simplified mathematical formulation of the

continuity ...

2010-01-01

296

Turbulent shear flows subject to system rotation

Digital Repository Infrastructure Vision for European Research (DRIVER)

Turbulent flows in rotating frame-of-reference are of considerable interest in a variety of industrial, geophysical and astrophysical applications. In these flows, the system rotation induces additional body forces, i.e. centrifugal and Coriolis forces, acting on the turbulent flow, so that the momentum mechanism becomes more complicated. The present doctoral thesis concerns the system rotation influence on turbulent shear flows. To this end, direct numerical simulations (DNSs) have bee...

Barri, Mustafa

2009-01-01

297

Effect of Aging on Deformability of Erythrocytes in Shear Flow

Directory of Open Access Journals (Sweden)

Full Text Available To study the effect of aging on deformability of an erythrocyte, rheological measurement has been performed after exposure to a shear field in vitro. Deformability was evaluated with shear stress responsiveness and with critical elongation calculated from an exponential curve between an elongation index and shear stress. Human erythrocytes were classified according to their density by a centrifugal method. Deformability decreases in erythrocytes of high density after shearing. Even after exposure to the shear field of 640 1/s for one hour, erythrocytes deform from biconcave to ellipsoidal and their deformability is maintained.

Shigehiro HASHIMOTO

2005-02-01

298

Swinging of red blood cells under shear flow

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.

Abkarian, M; Viallat, A; Abkarian, Manouk; Faivre, Magalie; Viallat, Annie

2007-01-01

299

Investigation of polymer brushes and adsorbed layers under shear

International Nuclear Information System (INIS)

Neutron reflectometry was used to investigate the density profiles of polymer brushes and an adsorbed polymer layer under shear. The brushes consisted of end-functionalized deuterated polystyrene. The adsorbed polymer was a random copolymer of deuterated styrene and 4-vinylpyridine. The brush and the adsorbed layer were sheared by the flowing of solvents over the polymer, with a maximum shear rate of 104s-1. Density profiles of the brush and the layer were determined before, during and after shear. The shear had no observable effect on the polymer profiles in any of the experiments. We discuss these results in the context of other experiments and a recent theory. (orig.)

1997-10-01

300

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

1995-01-01

301

Spurious Shear in Weak Lensing with LSST

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...

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

302

Natural instability of free shear layers

Under controlled small-amplitude excitation, an initially laminar free shear layer experiences maximum growth rate at a Strouhal number St(theta) of 0.017 (consistent with theory) and maximum growth at St(theta) = 0.011, while the natural instability frequency St(theta-n) (of an unexcited shear layer) is found to have an intermediate value. Investigations in both axisymmetric and plane shear layers in a number of independent facilities reveal that the St(theta-n) value falls in the range 0.0125-0.0155, depending on the exit boundary-layer fluctuation level and the spanwise radius of curvature. The St(theta-n) value decreases with increasing jet diameter or exit boundary-layer fluctuation level, but is not a direct function of the exit momentum thickness Reynolds number. For a given facility, the instability details are found to be independent of whether the entrainment at the lip is parallel to the stream or orthogonal (due to the addition of an end plate). The steamwise evolutions of the amplitudes at the fundamental frequency and its harmonics and subharmonics are unique functions of the downstream distance nondimensionalized by the exit momentum thickness, but their details remain functions of the flow geometry (i.e., axisymmetric or plane).

Husain, Z. D.; Hussain, A. K. M. F.

1983-01-01

303

Vesicles in a shear and Poiseuille flows

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.

Misbah, Chaouqi

2010-11-01

304

Density-shear instability in electron MHD

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...

Wood, Toby S; Lyutikov, Maxim

2014-01-01

305

Supersonic Shear Instabilities in Astrophysical Boundary Layers

Disk accretion onto weakly magnetized astrophysical objects often proceeds via a boundary layer that forms near the object's surface, in which the rotation speed of the accreted gas changes rapidly. Here we study the initial stages of formation for such a boundary layer around a white dwarf or a young star by examining the hydrodynamical shear instabilities that may initiate mixing and momentum transport between the two fluids of different densities moving supersonically with respect to each other. We find that an initially laminar boundary layer is unstable to two different kinds of instabilities. One is an instability of a supersonic vortex sheet (implying a discontinuous initial profile of the angular speed of the gas) in the presence of gravity, which we find to have a growth rate of order (but less than) the orbital frequency. The other is a sonic instability of a finite width, supersonic shear layer, which is similar to the Papaloizou-Pringle instability. It has a growth rate proportional to the shear i...

Belyaev, Mikhail

2011-01-01

306

Shear thinning in soft particle suspensions

Suspensions of soft deformable particles are encountered in a wide range of food and biological materials. Examples are biological cells, micelles, vesicles or microgel particles. While the behavior of suspenions of hard spheres - the classical model system of colloid science - is reasonably well understood, a full understanding of these soft particle suspensions remains elusive. The relation between single particle properties and macroscopic mechanical behavior still remains poorly understood in these materials. Here we examine the surprising shear thinning behavior that is observed in soft particle suspensions as a function of particle softness. We use poly-N-isopropylacrylamide (p-NIPAM) microgel particles as a model system to study this effect in detail. These soft spheres show significant shear thinning even at very large Peclet numbers, where this would not be observed for hard particles. The degree of shear thinning is directly related to the single particle elastic properties, which we characterize by the recently developed Capillary Micromechanics technique. We present a simple model that qualitatively accounts for the observed behavior.

Voudouris, Panayiotis; van der Zanden, Berco; Florea, Daniel; Fahimi, Zahra; Wyss, Hans

2012-02-01

307

Shear strength of oil palm shell foamed concrete beams

International Nuclear Information System (INIS)

Four reinforced oil palm shell foamed concrete (OPSFC) beams were fabricated, and their shear behaviour was tested. The OPSFC has a target density of approximately 1600 kg/m3 and a 28-day compressive strength of about 20 MPa. Two beams were cast with shear reinforcements while the other two were cast without such reinforcements. For comparison, four reinforced normal weight concrete (NWC) beams were also cast. The beams that contained shear links failed in flexure mode, while those without links failed in shear mode. The experimental results indicated that the shear capacities of OPSFC beams without shear links are higher than those of the NWC beams and exhibit more flexural and shear cracks.

2009-06-01

308

Shear sensing based on a microstrip patch antenna

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.

Mohammad, I.; Huang, H.

2012-10-01

309

Dynamics of a trapped Brownian particle in shear flows

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...

Holzer, Lukas; Rzehak, Roland; Zimmermann, Walter

2009-01-01

310

Atomic structure of amorphous shear bands in boron carbide

Amorphous shear bands are the main deformation and failure mode of super-hard boron carbide subjected to shock loading and high pressures at room temperature. Nevertheless, the formation mechanisms of the amorphous shear bands remain a long-standing scientific curiosity mainly because of the lack of experimental structure information of the disordered shear bands, comprising light elements of carbon and boron only. Here we report the atomic structure of the amorphous shear bands in boron carbide characterized by state-of-the-art aberration-corrected transmission electron microscopy. Distorted icosahedra, displaced from the crystalline matrix, were observed in nano-sized amorphous bands that produce dislocation-like local shear strains. These experimental results provide direct experimental evidence that the formation of amorphous shear bands in boron carbide results from the disassembly of the icosahedra, driven by shear stresses.

Reddy, K. Madhav; Liu, P.; Hirata, A.; Fujita, T.; Chen, M. W.

2013-09-01

311

Shear behavior of cable bolt supports in horizontal bedded deposits

Energy Technology Data Exchange (ETDEWEB)

Testing of cable bolts for resisting high shear forces in longwall mining is described. Pairs of concrete bolts with joint surfaces ranging from rough to smooth were subjected to shear tests. The tests were conducted in blocks with and without reinforcement with 15.2 mm diameter steel cables. The loads and displacements along the normal and shear axes and the loads on the cable were monitored. The test results show that a cable bolt placed across a joint more than doubles shear resistance of shear blocks with smooth or rough joint surfaces. The shear resistance increased much more rapidly at shorter displacements for shear blocks in which the cables were grouted than for blocks where the cables were not grouted. 5 refs., 8 figs.

Goris, J.M.; Martin, L.A.; Curtin, R.P. [U.S. Bureau of Mines, Spokane, WA (United States). Spokane Research Center

1995-05-01

312

Shear flow effect on ion temperature gradient vortices in plasmas with sheared magnetic field

DEFF Research Database (Denmark)

The effect of velocity shear on ion temperature gradient (ITG) driven vortices in a nonuniform plasma in a curved, sheared magnetic field is investigated. In absence of parallel ion dynamics, vortex solutions for the ITG mode are studied analytically. It is shown that under certain conditions the coupled equations for potential and pressure exhibit special tripolar vortex-like structures. For the general case, however, parallel ion dynamics is included and the equation describing the stationary ITG vortex has the structure of a nonlinear Poisson-type equation. Analytical as well as numerical solutions of this equation are presented for various possible cases. It is shown that, for a critical value of the velocity shear asymmetric dipolar vortices can arise which are strongly modified as a localized vortex chain at resonance. For strong velocity shear these structures are destroyed and ultimately lead to a dominating monopolar form. The effects of magnetic shear indicate it may destroy these structures. (C) 1999 American Institute of Physics.

Juul Rasmussen, J.

1999-01-01

313

Dynamic Modes of Microcapsules in Steady Shear Flow: Effects of Bending and Shear Elasticities

The dynamics of microcapsules in steady shear flow was studied using a theoretical approach based on three variables: The Taylor deformation parameter $\\alpha_{\\rm D}$, the inclination angle $\\theta$, and the phase angle $\\phi$ of the membrane rotation. It is found that the dynamic phase diagram shows a remarkable change with an increase in the ratio of the membrane shear and bending elasticities. A fluid vesicle (no shear elasticity) exhibits three dynamic modes: (i) Tank-treading (TT) at low viscosity $\\eta_{\\rm {in}}$ of internal fluid ($\\alpha_{\\rm D}$ and $\\theta$ relaxes to constant values), (ii) Tumbling (TB) at high $\\eta_{\\rm {in}}$ ($\\theta$ rotates), and (iii) Swinging (SW) at middle $\\eta_{\\rm {in}}$ and high shear rate $\\dot\\gamma$ ($\\theta$ oscillates). All of three modes are accompanied by a membrane ($\\phi$) rotation. For microcapsules with low shear elasticity, the TB phase with no $\\phi$ rotation and the coexistence phase of SW and TB motions are induced by the energy barrier of $\\phi$ rotat...

Noguchi, Hiroshi

2010-01-01

314

Energy Technology Data Exchange (ETDEWEB)

A 3D lattice Boltzmann model for two-phase flow with amphiphilic surfactant was used to investigate the evolution of emulsion morphology and shear stress in starting shear flow. The interfacial contributions were analyzed for low and high volume fractions and varying surfactant activity. A transient viscoelastic contribution to the emulsion rheology under constant strain rate conditions was attributed to the interfacial stress. For droplet volume fractions below 0.3 and an average capillary number of about 0.25, highly elliptical droplets formed. Consistent with affine deformation models, gradual elongation of the droplets increased the shear stress at early times and reduced it at later times. Lower interfacial tension with increased surfactant activity counterbalanced the effect of increased interfacial area, and the net shear stress did not change significantly. For higher volume fractions, co-continuous phases with a complex topology were formed. The surfactant decreased the interfacial shear stress due mainly to advection of surfactant to higher curvature areas. Our results are in qualitative agreement with experimental data for polymer blends in terms of transient interfacial stresses and limited enhancement of the emulsion viscosity at larger volume fractions where the phases are co-continuous.

Roar Skartlien; Espen Sollum; Andreas Akselsen; Paul Meakin

2012-07-01

315

Shear bliss : tiny mud shear unit pre-treats drilling fluid

Energy Technology Data Exchange (ETDEWEB)

The Mud Demon is a mud shear unit designed for shearing drilling mud directly at a wellsite. Designed by Demon Oilfield, the tool-box size device applies the same forces of stress and shear to drilling muds that are encountered downhole. The device is bolted to the metal grill covering the mud tank. A high-volume hose feeds directly into the unit, through which unsheared mud is pumped at high volumes exiting from the bottom of the toolbox into the tank. Use of the device allows operators to pre-shear mud as well as limiting waste. The Mud Demon will also minimize the environmental impacts of drilling activities. Although the Mud Demon has been used successfully for both horizontal and vertical wells, the speed at which the Mud Demon shears drilling fluid depends on several variables, including the mud volume the rig is using, and the power and capacity of the rig's mud pumps. While a single circulation cycle can prevent overflow from shale-shakers, 2 full cycles are needed to achieve good results. It was concluded that the Mud Demon provides increased well stability, and helps to ensure that drillbits do not become stuck. 2 figs.

Mahony, J.

2007-01-15

316

Fluid migration in ductile shear zones

Fluid migration in metamorphic environments depends on a dynamically evolving permeable pore space, which was rarely characterised in detail. The data-base behind our understanding of the 4-dimensional transport properties of metamorphic rocks is therefore fragmentary at best, which leaves conceptual models poorly supported. Generally, it seems established that deformation is a major driver of permeability generation during regional metamorphism, and evidence for metamorphic fluids being channelled in large scale shear zones has been found in all depth segments of the continental crust. When strain localizes in ductile shear zones, the microfabric is modified until a steady state mylonite is formed that supports large deformations. A dynamic porosity that evolves during mylonitisation controls the distinct transport pathways along which fluid interacts with the rock. This dynamic porosity is controlled by a limited number of mechanisms, which are intrinsically linked to the metamorphic evolution of the rock during its deformational overprint. Many mid- and lower-crustal mylonites comprise polyphase mixtures of micron-sized grains that show evidence for deformation by dissolution/precipitation-assisted viscous grain boundary sliding. The establishment of these mineral mixtures is a critical process, where monomineralic layers are dispersed and grain growth is inhibited by the heterogeneous nucleation of secondary mineral phases at triple junctions. Here we show evidence from three different mid- and lower-crustal shear zones indicating that heterogeneous nucleation occurs in creep cavities. Micro- and nanotomographic observations show that creep cavities provide the dominant form of porosity in these ultramylonites. They control a "granular fluid pump" that directs fluid migration and hence mass transport. The granular fluid pump operates on the grain scale driven by viscous grain boundary sliding, and requires only small amounts of fluid. The spatial arrangement of creep cavities suggests that the synkinematic permeability is highly anisotropic and responds to mechanical boundary conditions. In summary, we present observations indicating that the evolution of porosity in ductile shear zones is directly coupled to the tectonometamorphic processes controlling strain localisation and rock deformation on the grain scale. The location and spatiotemporal extent of these processes determine fluid transport pathways and hence sites of fluid-rock interaction in steady state shear zones.

Fusseis, Florian; Menegon, Luca

2014-05-01

317

Introduction: In this study we examine the repeatability of measuring muscle shear modulus using ultrasound shear-wave elastography between trials and between days, and the association between shear modulus and contraction intensity over a wide range of intensities. Methods: Shear modulus of the biceps brachii was determined using ultrasound shear-wave elastography during static elbow flexion (up to 60% of maximal contraction) in healthy young adults. Results: The correspondence of shear modulus was confirmed in phantoms between the manufacturer-calibrated values and the shear-wave elastography values. The intraclass correlation coefficient of muscle shear modulus was high: 0.978 between trials and 0.948 between days. Shear modulus increased linearly with elbow flexion torque across contraction intensity, and its slope was associated negatively with muscle strength. Conclusions: Muscle shear modulus measured with ultrasound shear-wave elastography may be useful for inferring muscle stiffness across a wide range of contraction intensity. In addition, it has high repeatability between trials and between days. Muscle Nerve 50: 103-113, 2014. PMID:24155045

Yoshitake, Yasuhide; Takai, Yohei; Kanehisa, Hiroaki; Shinohara, Minoru

2014-07-01

318

Shear viscosity of dense-phase slurries at varying shear-rates

International Nuclear Information System (INIS)

A method is presented for predicting the viscosity of highly concentrated suspensions at varying shear-rates and for specified particle size distributions. Data for several different suspensions are shown to confirm the crucial significance of the maximum packing concentration phi/sub m/ and the intrinsic viscosity [eta]. It is demonstrated that d/sub m/ can be calculated analytically for well-dispersed systems with spherical particles of nonuniform size distribution, and can be corrected for the other suspensions using a very strong correlation that was obtained between the calculated and measured phi/sub m/ values. Also shown is that both phi/sub m/ and [eta] represent the particle surface conditions of each suspension to be evaluated at high shear-rates, and that the viscosity variations with the shear-rate can be uniquely represented by a single particle interaction parameter, eta

1986-01-01

319

A minimal model for chaotic shear-banding in shear-thickening fluids

We present a minimal model for spatiotemporal oscillation and rheochaos in shear-thickening complex fluids at zero Reynolds number. In the model, a tendency towards inhomogeneous flows in the form of shear bands combines with a slow structural dynamics, modelled by delayed stress relaxation. Using Fourier-space numerics, we study the nonequilibrium `phase diagram' of the fluid as a function of a steady mean (spatially averaged) stress, and of the relaxation time for structural relaxation. We find several distinct regions of periodic behavior (oscillating bands, travelling bands, and more complex oscillations) and also regions of spatiotemporal rheochaos. A low-dimensional truncation of the model retains the important physical features of the full model (including rheochaos) despite the suppression of sharply defined interfaces between shear bands. Our model maps onto the FitzHugh-Nagumo model for neural network dynamics, with an unusual form of long-range coupling.

Aradian, A

2005-01-01

320

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)

1999-12-01

321

Strain localization in experimentally sheared gouge layers

Laboratory studies designed to understand fault and earthquake processes often use rotary-shear apparatus to investigate the frictional properties of rocks. Rotary-shear apparatus can apply a wide range of slip velocities and impose high displacements on cohesive and non-cohesive rocks and are thus ideal to study deformation processes taking place throughout the seismic cycle. However, in experiments performed on gouges, the mechanical results and the developing microstructures are often hard to interpret, because little is known about the distribution of strain (i.e., the ratio of displacement to the thickness of the deforming zones) within the gouge layer. A better understanding of the strain distribution may help to interpret microstructures associated with varying degrees of strain localization and infer the underlying physical-chemical processes. We report preliminary results from a series of experiments carried out with strain markers using the rotary-shear apparatus SHIVA at INGV in Rome. Within an annular steel sample holder (with outer and inner radii of 55 and 35 mm, respectively), a 3 mm thick calcite gouge layer (starting grain size <250 ?m) was prepared with a 2 mm wide dolomite gouge strain marker cutting vertically through the calcite layer. The marker was orientated perpendicular to the imposed shear direction. Dolomite was selected for the strain marker because it has similar mechanical properties to calcite. The strain marker experiments were conducted at varying slip rates (10-3 m/s and 1 m/s), displacements (8 cm to 1.5 m), normal stresses (3 to 20 MPa) and ambient conditions (room-humid and wet) to test the dependence of the strain distribution. Mechanical data (shear stress, shortening and dilation, etc.) were recorded during the experiments. Afterwards, the preserved samples were cut vertically through the dolomite strain markers (approximately parallel to the slip direction) and microstructural analysis was conducted with the scanning electron microscope. Preliminary results show that at a slip velocity of 0.1 m/s and normal stress of 3 MPa, localization to a relatively high-strain slipping zone occurs rapidly. Progressive strain localization at the onset of shearing is associated with gouge layer dilation and strain hardening. The onset of dynamic weakening (i.e. at the end of the strain hardening phase) broadly correlates with the establishment of a discrete slip surface that develops within the high strain slipping zone. Interestingly, the value of strain (? ~2) in the low-strain zone does not change significantly with increasing displacement, suggesting that, once formed, the high strain slipping zone and slip surface accommodate most of the ongoing displacement. More quantitative information on the dependence of strain distribution on displacement, slip rate, and normal stress will be gained from further microstructural analysis.

Di Toro, G.; Rempe, M.; Smith, S. A.; Mitchell, T. M.

2013-12-01

322

Shear dominated, intersonic decohesion of interfaces

Energy Technology Data Exchange (ETDEWEB)

In this work we describe a series of impact experiments performed on PMMA/4340 steel edge cracked bimaterial plates. Specimens were impacted at 20 m s{sup -1} in a one point bend configuration using a high speed gas gun. Dynamic interfacial crack propagation was observed using the optical method of Coherent Gradient Sensing and high speed photography. Very high crack tip accelerations (108 in s-2) and very high cracks tip speeds (up to 1.5C{sub R}{sup PMMA}) were measured and are reported. Quantitative measurements show that in experiments in which the crack tip speed entered the intersonic range for PMMA, the stress field surrounding the crack tip was shear dominated. The observation of high shear around the crack tip can also be explained using wave propagation arguments. It is found that the reason for attainment of intersonic (with respect to PMMA) crack tip speeds is directly related to the large amounts of energy necessary to initiate the crack tip under shear dominated conditions. A comparison with the theoretical results is also made. There seems to be an unfavorable region of stable crack propagation velocities in the intersonic regime. This region is C{sub S}{sup PMMA} < v < (2C{sub S}{sup PMMA}){sup 1/2}. In all experiments performed, the propagating crack accelerated quickly out of this region. In the few interferograms that do actually correspond to crack propagation in this unfavorable velocity range, crack face contact was observed. This observation is also in agreement with the theoretical findings.

Rosakis, A.J.; Lambros, J. [California Institute of Technology, Pasadena, CA (United States)

1995-12-31

323

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to determine the effects of age on chemical composition and tenderness of donkey meat. These characteristics were determined on Longissimus thoracis samples taken from 40 entire donkey males of Martina Franca breed slaughtered at 12 (Group 1, n = 20 and at 18 months (Group 2, n = 20 of age. Tenderness was evalu-ated at two and seven days post slaughter using a Warner-Bratzler shear force device. The chemical composition showed a significant increase in protein content (P < 0.05 in the meat of donkeys slaughtered at 18 months of age (22.3 g/100 g compared to the meat of younger animals (21.4 g/100 g. Intramuscular fat content was significantly lower (P < 0.05 in Group 1 (2.41 g/100 g compared to Group 2 (3.71 g/100 g. Shear force values at seven days post slaughter were significantly (P < 0.01 lower (5.15 ± 0.31 kg/cm2 in Group 1 compared with the results obtained at two days post slaughter (6.25 ± 0.53 kg/cm2. In Group 2 shear force values obtained seven days post mortem were higher (5.88 ± 0.23 kg/cm2 compared with Group 1 after the same ageing period but significantly (P < 0.05 lower if compared with those (6.53 ± 0.23 kg/cm2 determined in the same animals two days post slaugher.

S. Vincenzetti

2011-05-01

324

Directory of Open Access Journals (Sweden)

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 < 0.05 for WBSF (kg: CC: 4.41 ± 0.57; CG: 5.58 ± 0.20; GG: 6.29 ± 0.18, FW (kg: CC: 360.23 ± 14.71; CG: 381.34 ± 5.26; GG: 399.23 ± 4.68, and ADG (kg/d: CC: 0.675 ± 0.046; CG: 0.705 ± 0.016; GG: 0.765 ± 0.014 Shear force, final weight and average daily gain were significantly different according to the CAPN1 316 marker genotypes. The marker genotype was statistically significant in the multivariate analysis (p = 0.001. The first characteristic root explained 89% of the differences among genotypes. WBSF, FW and ADG were the most important traits in the first vector, indicating that animals with the marker genotype for lowest WBSF also have the lowest FW and ADG.

María C. Miquel

2009-01-01

325

Propagation of waves in shear flows

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

Fabrikant, A L

1998-01-01

326

Brownian forces in sheared granular matter.

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 utilized, 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. PMID:16605874

Baldassarri, A; Dalton, F; Petri, A; Zapperi, S; Pontuale, G; Pietronero, L

2006-03-24

327

Shear-Alfven Waves in Gyrokinetic Plasmas

International Nuclear Information System (INIS)

It is found that the thermal fluctuation level of the shear-Alfven waves in a gyrokinetic plasma decreases with plasma b(* cs2/uA2), where cs is the ion acoustic speed and uA is the Alfven velocity. This unique thermodynamic property based on the fluctuation-dissipation theorem is verified in this paper using a new gyrokinetic particle simulation scheme, which splits the particle distribution function into the equilibrium part as well as the adiabatic and nonadiabatic parts

2000-01-01

328

Shear-free axially symmetric dissipative fluids

We study the general properties of axially symmetric dissipative configurations under the shear-free condition. The link between the magnetic part of the Weyl tensor and the vorticity, as well as the role of the dissipative fluxes, are clearly exhibited. As a particular case we examine the geodesic fluid. In this latter case, the magnetic part of the Weyl tensor always vanishes, suggesting that no gravitational radiation is produced during the evolution. Also (for the geodesic case), in the absence of dissipation, the system evolves towards a FRW spacetime if the expansion scalar is positive.

Herrera, L; Ospino, J

2014-01-01

329

Nonhelical turbulent dynamos: shocks and shear

Small scale turbulent dynamo action in compressible transonic turbulence is discussed. It is shown that the critical value of the magnetic Reynolds number displays a bimodal behavior and changes from a typical value of 35 for small Mach numbers to about 80 for larger Mach numbers. The transition between the two regimes is relatively sharp. The direct simulations are then compared with simulations where shocks are captured using a shock viscosity that becomes large at locations where there are shocks. In the presence of shear it is shown that large scale dynamo action is possible.

Brandenburg, A; Mee, A J

2005-01-01

330

Self-organization in circular shear layers

DEFF Research Database (Denmark)

Experiments on forced circular shear layers performed in both magnetized plasmas and in rotating fluids reveal qualitatively similar self-organization processes leading to the formation of patterns of coherent vortical structures with varying complexity. In this paper results are presented from both weakly nonlinear analysis and full numerical simulations that closely reproduce the experimental observations. Varying the Reynolds number leads to bifurcation sequences accompanied by topological changes in the distribution of the coherent structures as well as clear transitions in the total energy and enstrophy of the system. Various oscillating and quasiperiodic states have been found, and regimes have been investigated that so far have been experimentally inaccessible.

Bergeron, K.; Coutsias, E.A.

1996-01-01

331

A Simple Model for Sheared Granular Layers

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.

Furukawa, A; Furukawa, Akira; Hayakawa, Hisao

2004-01-01

332

The SDSS Coadd: Cosmic Shear Measurement

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 $\\Omega_m$ and fluctuation amplitude $\\sigma_8$ to be $\\Omega_m^{0.7}\\sigma_8 = 0.276^{+0.036}_{-0.050}$.

Lin, Huan; Seo, Hee-Jong; Soares-Santos, Marcelle; Annis, James; Hao, Jiangang; Johnston, David; Kubo, Jeffrey M; Reis, Ribamar R R; Simet, Melanie

2011-01-01

333

Explosion Shear Wave Generation and Scattering

We use observations of explosion-generated Lg together with three separate types of numerical models to determine how underground nuclear explosions generate shear wave phases. This question is fundamental to how Lg phases are interpreted for use in explosion yield estimation and earthquake/explosion discrimination. A simple point explosion in a uniform medium generates no shear waves, so the Lg phase is generated entirely by non-spherical components of the source and conversions through reflections and scattering. Our results indicate that the most important sources of high frequency explosion shear waves are P to S conversions at the free surface and S waves generated directly by a realistic distributed explosion source including nonlinear effects due to the free surface and gravity. In addition, Rg scattering may contribute to lower frequency Lg. Near source S is observed on both radial and tangential component records from a diverse set of explosion data. The data sets include 1) Degelen Mountain explosions recorded at distances less than 100 km and corresponding recordings at Borovoye (BOR) at 650 km; 2) recordings from Russian deep seismic sounding experiments; 3) Nevada Test Site (NTS) explosion sources including the Nonproliferation Experiment (NPE) and nuclear tests covering a range of source depths and media properties. We model the overburied NPE, and underburied and overburied Degelen explosions, using point sources and two-dimensional nonlinear finite difference calculations to quantify the source effects. We use energy conservation to determine an upper bound on Rg to Lg scattering. Results indicate that Rg to Lg scattering may be important at frequencies less than 1 Hz, and in Lg coda, but is less than Lg generated directly by the explosion at higher frequencies. We use 2D and 3D finite difference calculations, using the known topography and velocity structure at Degelen Mt. and lateral heterogeneities within the crust, to estimate the effect of surface and crustal scattering on Lg. Results indicate that topographic scattering can significantly disrupt the surface pS scattered phase, so more shear wave energy is trapped in the crust. The topography also appears to be the most significant scatterer of Rg, and has a profound effect on its dispersion.

Baker, G. E.; Stevens, J. L.; Xu, H.

2004-12-01

334

Shear viscosity in the postquasistatic approximation

International Nuclear Information System (INIS)

We apply the postquasistatic approximation, an iterative method for the evolution of self-gravitating spheres of matter, to study the evolution of anisotropic nonadiabatic radiating and dissipative distributions in general relativity. Dissipation is described by viscosity and free-streaming radiation, assuming an equation of state to model anisotropy induced by the shear viscosity. We match the interior solution, in noncomoving coordinates, with the Vaidya exterior solution. Two simple models are presented, based on the Schwarzschild and Tolman VI solutions, in the nonadiabatic and adiabatic limit. In both cases, the eventual collapse or expansion of the distribution is mainly controlled by the anisotropy induced by the viscosity.

2010-05-15

335

Hysteresis and Lubrication in Shear Thickening of Cornstarch Suspensions

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...

Chu, Clarence E; Sieber, Hannah L; Miller, James G; Okamoto, Ruth J; Katz, Jonathan I

2014-01-01

336

Resonant Low Frequency Interlayer Shear Modes in Folded Graphene Layers

Naturally or artificially stacking extra layers on single layer graphene (SLG) forms few-layer graphene (FLG), which has attracted tremendous attention owing to its exceptional properties inherited from SLG and new features generated by introducing extra freedom. In FLG, shear modes play a critical role in understanding its distinctive properties. Unfortunately, energies of shear modes are so close to excitation lasers to be fully blocked by a Rayleigh rejecter. This greatly hinders investigations of shear modes in FLG. Here, we demonstrate dramatically enhanced shear modes in properly folded FLG. Benefiting from the extremely strong signals, for the first time, enhancement mechanism, vibrational symmetry, anharmonicity and electron-phonon coupling (EPC) of shear modes are uncovered through studies of two-dimensional (2D) Raman mapping, polarization- and temperature-dependent Raman spectroscopy. This work complements Raman studies of graphene layers, and paves an efficient way to exploit low frequency shear m...

Cong, Chunxiao

2013-01-01

337

Shear Thickening of Cornstarch Suspensions as a Reentrant Jamming Transition

We study the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits shear thickening. From magnetic resonance imaging velocimetry and classical rheology it follows that as a function of the applied stress the suspension is first solid (yield stress), then liquid, and then solid again when it shear thickens. For the onset of thickening we find that the smaller the gap of the shear cell, the lower the shear rate at which thickening occurs. Shear thickening can then be interpreted as the consequence of dilatancy: the system under flow wants to dilate but instead undergoes a jamming transition because it is confined, as confirmed by measurement of the dilation of the suspension as a function of the shear rate.

Fall, Abdoulaye; Huang, N.; Bertrand, F.; Ovarlez, G.; Bonn, Daniel

2008-01-01

338

Discontinuous Shear Thickening of Frictional Hard-Sphere Suspensions

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 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.

Seto, Ryohei; Mari, Romain; Morris, Jeffrey F.; Denn, Morton M.

2013-11-01

339

Discontinuous shear thickening of frictional hard-sphere suspensions

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.

Seto, Ryohei; Morris, Jeffrey F; Denn, Morton M

2013-01-01

340

Shear Strengthening of Reinforced Concrete Beams Using GFRP Wraps

Directory of Open Access Journals (Sweden)

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.

M. A. A. Saafan

2006-01-01

341

Shear dispersion and turbulence decorrelation by differential rotation

DEFF Research Database (Denmark)

The shear enhanced dispersion of a passive scalar field subject to differential rotation is investigated analytically and interpretations are given in terms of turbulence shear decorrelation. Using the method of advected coordinates, the enhanced dispersion caused by steady and oscillatory flows with uniform shear is derived and the well-known turbulence shear decorrelation theory is recovered. The additional role of kinetic energy transfer due to differential advection of vorticity is also pointed out. Finally, the shear enhanced dispersion due to flows with periodic variations in space as well as time is given. It is found that radially alternating flows may significantly reduce the turbulence decorrelation time provided the root mean square flow shear is larger than the flow oscillation frequency. In the opposite limit of fast flow oscillations there is no turbulence decorrelation. (C) 2005 American Institute of Physics.

Garcia, O.E.; Bian, N.H.

2005-01-01

342

Transport Bifurcation Induced by Sheared Toroidal Flow in Tokamak Plasmas

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...

Highcock, E G; Parra, F I; Schekochihin, A A; Roach, C M; Cowley, S C

2011-01-01

343

Shear-induced diffusion in dilute curved fiber suspensions in simple shear flow

Shear-induced self-diffusion of fibers suspended in an incompressible Newtonian fluid in simple shear flow at low Reynolds number is studied by simulation. Two models are employed: a linked rigid rod model and a bead chain model. Hydrodynamic interactions are neglected in both models. The shear-induced diffusivity of suspensions of fibers increases with increasing concentration and increasing static friction between contacts. The diffusivities in both the gradient and vorticity directions are larger for suspensions of curved fibers than for suspensions of straight fibers. For suspensions of curved fibers, significant enhancements in the diffusivity in the gradient direction are observed. The enhanced diffusivities are attributed to fiber drift observed in prior work for isolated curved fibers [J. Wang, E. J. Tozzi, M. D. Graham, and D. J. Klingenberg, "Flipping, scooping, and spinning: Drift of rigid curved nonchiral fibers in simple shear flow," Phys. Fluids 24, 123304 (2012)]. Here, for some initial orientations, curved fibers will drift in the positive or negative gradient direction with nearly constant speed. In dilute suspensions, this drift occurs for a fraction of the fibers, which increases the mean-squared displacement in the gradient direction, and thus increases the diffusivity in the gradient direction.

Wang, Jianghui; Graham, Michael D.; Klingenberg, Daniel J.

2014-03-01

344

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish 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.

Rodrigo, Cruz; Elizabeth, Barthel; Jaime, Espinoza.

345

From supersonic shear wave imaging to full-field optical coherence shear wave elastography

Elasticity maps of tissue have proved to be particularly useful in providing complementary contrast to ultrasonic imaging, e.g., for cancer diagnosis at the millimeter scale. Optical coherence tomography (OCT) offers an endogenous contrast based on singly backscattered optical waves. Adding complementary contrast to OCT images by recording elasticity maps could also be valuable in improving OCT-based diagnosis at the microscopic scale. Static elastography has been successfully coupled with full-field OCT (FF-OCT) in order to realize both micrometer-scale sectioning and elasticity maps. Nevertheless, static elastography presents a number of drawbacks, mainly when stiffness quantification is required. Here, we describe the combination of two methods: transient elastography, based on speed measurements of shear waves induced by ultrasonic radiation forces, and FF-OCT, an en face OCT approach using an incoherent light source. The use of an ultrafast ultrasonic scanner and an ultrafast camera working at 10,000 to 30,000 images/s made it possible to follow shear wave propagation with both modalities. As expected, FF-OCT is found to be much more sensitive than ultrafast ultrasound to tiny shear vibrations (a few nanometers and micrometers, respectively). Stiffness assessed in gel phantoms and an ex vivo rat brain by FF-OCT is found to be in good agreement with ultrasound shear wave elastography.

Nahas, Amir; Tanter, Mickaël; Nguyen, Thu-Mai; Chassot, Jean-Marie; Fink, Mathias; Claude Boccara, A.

2013-12-01

346

Analysis of two-point statistics of cosmic shear: III. Covariances of shear measures made easy

In recent years cosmic shear, the weak gravitational lensing effect by the large-scale structure of the Universe, has proven to be one of the observational pillars on which the cosmological concordance model is founded. Several cosmic shear statistics have been developed in order to analyze data from surveys. For the covariances of the prevalent second-order measures we present simple and handy formulae, valid under the assumptions of Gaussian density fluctuations and a simple survey geometry. We also formulate these results in the context of shear tomography, i.e. the inclusion of redshift information, and generalize them to arbitrary data field geometries. We define estimators for the E- and B-mode projected power spectra and show them to be unbiased in the case of Gaussianity and a simple survey geometry. From the covariance of these estimators we demonstrate how to derive covariances of arbitrary combinations of second-order cosmic shear measures. We then recalculate the power spectrum covariance for gene...

Joachimi, B; Eifler, T

2007-01-01

347

The rheology of dense, polydisperse granular fluids under shear

Digital Repository Infrastructure Vision for European Research (DRIVER)

The solution of the Enskog equation for the one-body velocity distribution of a moderately dense, arbitrary mixture of inelastic hard spheres undergoing planar shear flow is described. A generalization of the Grad moment method, implemented by means of a novel generating function technique, is used so as to avoid any assumptions concerning the size of the shear rate. The result is illustrated by using it to calculate the pressure, normal stresses and shear viscosity of a mod...

Lutsko, James F.

2004-01-01

348

Shear-induced disordering of an intermetallic compound

Energy Technology Data Exchange (ETDEWEB)

Numerical simulations have been employed to study the shear-induced amorphization of the NiZr{sub 2} intermetallic compound. The application of a shear stress generates an increasing distortion of atomic coordination shells and the consequent formation of defectively coordinated atoms. Structural and chemical disordering take place concurrently, determining the appearance of an amorphous layer. It grows at a rate dependent on the shearing rate and according to a mechanism involving ballistic atomic displacement rather then conventional thermal diffusion.

Delogu, F. [Dipartimento di Ingegneria Chimica e Materiali, Universita degli Studi di Cagliari, piazza d' Armi, I-09123 Cagliari (Italy)]. E-mail: delogu@dicm.unica.it

2006-06-25

349

Shear-induced disordering of an intermetallic compound

International Nuclear Information System (INIS)

Numerical simulations have been employed to study the shear-induced amorphization of the NiZr2 intermetallic compound. The application of a shear stress generates an increasing distortion of atomic coordination shells and the consequent formation of defectively coordinated atoms. Structural and chemical disordering take place concurrently, determining the appearance of an amorphous layer. It grows at a rate dependent on the shearing rate and according to a mechanism involving ballistic atomic displacement rather then conventional thermal diffusion

2006-06-25

350

Shear Rate Moderates Community Diversity in Freshwater Biofilms

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Rickard, Alexander H.; Mcbain, Andrew J.; Stead, Amy T.; Gilbert, Peter

2004-01-01

351

Shear stress fluctuations in the granular liquid and solid phases

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report on experimentally observed shear stress fluctuations in both granular solid and fluid states, showing that they are non-Gaussian at low shear rates, reflecting the predominance of correlated structures (force chains) in the solidlike phase, which also exhibit finite rigidity to shear. Peaks in the rigidity and the stress distribution's skewness indicate that a change to the force-bearing mechanism occurs at the transition to fluid behaviour, which, it is shown, can...

Dalton, Fergal; Farrelly, Francis; Petri, Alberto; Pietronero, Luciano; Pitolli, Luca; Pontuale, Giorgio

2005-01-01

352

Shear zones between rock units with no relative movement

DEFF Research Database (Denmark)

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.

Koyi, Hemin; Schmeling, Harro

2013-01-01

353

Shear Strengthening of Reinforced Concrete Beams Using GFRP Wraps

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 eff...

2006-01-01

354

Inherent Shear-Dilatation Coexistence in Metallic Glass

International Nuclear Information System (INIS)

Shear deformation can induce normal stress or hydrostatic stress in metallic glasses [Nature Mater. 2 (2003) 449, Intermetallics 14 (2006) 1033]. We perform the bulk deformation of three-dimensional Cu46Zr54 metallic glass (MG) and Cu single crystal model systems using molecular dynamics simulation. The results indicate that hydrostatic stress can incur shear stress in MG, but not in crystal. The resultant pronounced asymmetry between tension and compression originates from this inherent shear-dilatation coexistence in MG

2009-01-01

355

A transport bifurcation model for enhanced confinement with negative shear

International Nuclear Information System (INIS)

A magnetic shear driven transport bifurcation model for transition to enhanced confinement regime with negative shear and neutral beams is proposed. Strong fueling by high power beams leads to peaking of pressure profile and generation of large bootstrap current. The resulting negative shear reduces the growth of fluctuations. The transition to enhanced confinement regime occurs when fluctuations are completely quenched. Relevance of this to recent results from TFTR is briefly discussed. (author)

1997-09-01

356

Investigation of the physical mechanisms of shear-force imaging

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is shown that shear-force imaging, as is commonly used for distance regulation in scanning near-field optical microscopy, is not a reliable technique for accurate topographic measurements. This is because different materials experience different shear-force damping. Results of the shear-force damping characteristics are presented for a number of different materials, and some consequences of the different dampings for different materials are demonstrated. It is also shown that there are at ...

Shvets, Igor

1996-01-01

357

Plastic shearing at high and very high strain rates

Digital Repository Infrastructure Vision for European Research (DRIVER)

Shear straining at different velocities, including high and very high strain rates, is discussed. Some experimental techniques which allows for experiments at high and very high strain rates are briefly reviewed. A new experimental technique based on direct impact on Modified Double Shear a specimen (MDS) is also reviewed. A one-dimensional model for simple shear is applied together with a constitutive relation which takes into account rate and temperature sensitivity a generalised condition ...

Klepaczko, J.

1994-01-01

358

Enhanced safety with post-installed shear reinforcement

Digital Repository Infrastructure Vision for European Research (DRIVER)

The safety of existing concrete slabs against shear may be insufficient for several reasons such as design and construction errors, structural modifications or increased loads. Moreover, the knowledge about shear design has significantly increased over the last few decades and therefore, even structures correctly built according to older codes may not comply with newer codes based on the latest state of the art. This paper presents a method to enhance the one way shear strength of RC slabs or...

Kunz; Ferna?ndez Ruiz, Miguel; Muttoni, Aurelio

2013-01-01

359

Shear strength measurements of lubricants at high pressure

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.

Bair, S.; Winer, W. O.

1979-01-01

360

Nonlinear effects of particle shape angularity in sheared granular media

Digital Repository Infrastructure Vision for European Research (DRIVER)

We analyze the effects of particle shape angularity on the macroscopic shear behavior and texture of granular packings simulated by means of the contact dynamics method. The particles are regular polygons with an increasing number of sides ranging from 3 (triangles) to 60. The packings are analyzed in the steady shear state in terms of their shear strength, packing fraction, connectivity, and fabric and force anisotropies, as functions of the angularity. An interesting finding is that the she...

2012-01-01

361

Shear crack formation and propagation in reinforced Engineered Cementitious Composites

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Paegle, Ieva; Fischer, Gregor

2012-01-01

362

The role of shear in the cosmological distance

International Nuclear Information System (INIS)

The effect of shear along light rays on the distance-redshift relation in an inhomogeneous universe is investigated on the basis of relativistic optical equations. With some reasonable assumptions, an analytic formula for the shear in a simplified cosmological model is derived. We compare the derived formula with numerical calculations and discuss the validity and limitation of our formula. Then the role of shear in the distance-redshift relation is discussed in detail. (author)

1990-01-01

363

Experimental study of rebar lap splices at shear stress zone

International Nuclear Information System (INIS)

Lap splice is considered the best method of jointing reinforcing deformed steel bars (rebars) in reinforced concrete members. Large shear walls are used in nuclear power plants. The purpose is to seize the influencing parameters on the structural characteristics of lap splice in shear wall. Authors have developed a test method by which lap spliced specimens at shear stress zones are subjected to tensile force at both ends. 19 specimens were tested and arranged for testing 7 parameters. (orig./HP)

1987-01-01

364

Multi-functional direct joint shear test machine

Energy Technology Data Exchange (ETDEWEB)

A shear testing machine to carry out precise and comprehensive studies of the frictional properties of rock interfaces has been designed. The shear box testing machine has been used to investigate the frictional properties of the discontinuities in Coal Measures rocks associated with opencast coal mining in the UK; the parameters that affect the frictional behaviour that is the surface roughness; and the direct shear strength of weaker rock types within the strata, that is, mudstone, cleatearth, etc.

Hassani, F.P.

1980-01-01

365

Patterns and dynamics in transitional shear flows

One of the greatest mysteries in fluid dynamics is surely transition to turbulence. The classic shear flows -- channel, plane Couette and pipe flow -- while linearly stable, undergo sudden transition to 3D turbulence. In recent years, transition has been attacked with an arsenal of weapons from dynamical systems theory, such as low-dimensional chaos, unstable periodic orbits, heteroclinic connections, fractal basin boundaries. At the same time, 3D physical mechanisms such as streamwise vorticity and streaks have supplanted the 2D picture of linear instability long promoted by Squire's theorem. A striking recent discovery by experimentalists at CEA-Saclay is that large-aspect-ratio plane Couette flow near transition actually takes the form of a steady pattern of wide turbulent and laminar bands, with a fixed angle and wavelength. We have been able to reproduce these remarkable flows in numerical simulations of the Navier-Stokes equations. Simulations display a rich variety of variants of these patterns, including spatio-temporal intermittency, branching and travelling states, and localized states analogous to spots. Because similar patterns have since also been observed in Taylor-Couette, channel and pipe flow, it appears that they are inevitable intermediate states on the route from turbulent to laminar flow in large aspect-ratio shear flows. In addition to their intrinsic interest, these patterns provide clues to the transition to turbulence.

Tuckerman, Laurette

2009-11-01

366

Yielding and flow of sheared colloidal glasses

International Nuclear Information System (INIS)

We have studied some of the rheological properties of suspensions of hard-sphere colloids with particular reference to behaviour near the concentration of the glass transition. First we monitored the strain on the samples during and after a transient step stress. We find that, at all values of applied step stress, colloidal glasses show a rapid, apparently elastic, recovery of strain after the stress is removed. This recovery is found even in samples which have flowed significantly during stressing. We attribute this behaviour to 'cage elasticity', the recovery of the stress-induced distorted environment of any particle to a more isotropic state when the stress is removed. Second, we monitored the stress as the strain rate dot ? of flowing samples was slowly decreased. Suspensions which are glassy at rest show a stress which becomes independent of dot ? as dot ? ?0. This limiting stress can be interpreted as the yield stress of the glass and agrees well both with the yield stress deduced from the step stress and recovery measurements and that predicted by a recent mode coupling theory of sheared suspensions. Thus, the behaviours under steady shearing and transient step stress both support the idea that colloidal glasses have a finite yield stress. We note however that the samples do exhibit a slow accumulation of strain due to creep at stresses below the yield stress

2004-09-29

367

Criterion for thermo-plastic shear instability

Energy Technology Data Exchange (ETDEWEB)

Dynamic torsional Kolsky (split-Hopkinson) bar experiments on thin-walled tubes of 1018 cold-rolled and 1020 hot-rolled steel are modeled using a deformation plasticity theory which incorporates a specific constitutive model for the shear stress in terms of strain, strain-rate, and temperature into a system of differential equations. The exact time-dependent homogeneous flow solution of the equations is found and used to derive a special case of a generally accepted instability criterion. For given material parameters, this criterion predicts a critical strain at which a homogeneous deformation can bifuricate into a localized deformation, i.e., a shear band, at constant strain-rate. Stability diagrams of strain-rate vs. strain can be constructed for the two types of steel using the criterion. The Kolsky bar data is shown to be consistent with this analysis, and an explanation for the instability criterion is given which assumes that small perturbations on the non-steady homogeneous flow are isentropic to first order.

Burns, T.J.; Grady, D.E.; Costin, L.S.

1981-01-01

368

Reynolds stress and shear flow generation

DEFF Research Database (Denmark)

The so-called Reynolds stress may give a measure of the self-consistent flow generation in turbulent fluids and plasmas by the small-scale turbulent fluctuations. A measurement of the Reynolds stress can thus help to predict flows, e.g. shear flows in plasmas. This may assist the understanding of improved confinement scenarios such as H-mode confinement regimes. However, the determination of the Reynolds stress requires measurements of the plasma potential, a task that is difficult in general and nearly impossible in hot plasmas in large devices. In this work we investigate an alternative method, based on density measurements, to estimate the Reynolds stress, and demonstrate the validity range of this quantity, which we term the pseudo-Reynolds stress. The advantage of such a quantity is that accurate measurements of density fluctuations are much easier to obtain experimentally. Prior to the treatment of the pseudo-Reynolds stress, we present analytical and numerical results which demonstrate that the Reynolds stress in a plasma, indeed, generates a poloidal shear flow. The numerical simulations are performed both in a drift wave turbulence regime and a resistive interchange turbulence regime. Finally, the implications of misaligned probe arrays on the determination of Reynolds stresses are investigated, and alignment is found to be important but not severe.

Korsholm, SÃ¸ren Bang; Michelsen, Poul

2001-01-01

369

Tooth design to avoid shearing stresses

Energy Technology Data Exchange (ETDEWEB)

Teeth disposed on the bit face of a rotating bit are, angularly oriented on the sloping surface of the bit face such that a vertical loading force which is applied to each tooth vectorially sums with a wedging force exerted by the rock formation on each tooth to create a resultant force applied to the diamond cutting element included within the tooth. The angular orientation of the tooth is chosen such that the resultant force is applied to the diamond cutting element in a direction which minimizes shear stress on the element. For example, in the case where the diamond cutting element is an equilateral triangular prismatic element tangentially set on the bit face with one apical edge defined by two adjacent triangular sides outermost on the tooth, the orientation or inclination of the tooth with respect to the vertical loading force and wedge force is such that the resulting force lies near or on the disector of the dihedral angle formed by the apical edge. Similarly, the diamond cutting element is rearwardly raked in the longitudinal direction, generally parallel to the tangential motion during normal drilling as defined by the rotation of the bit, such that the vectorial sum of the vertical loading force in a reactive cutting force applies a resultant force on the diamond cutting element in a direction which minimizes shear stress, namely, in the example in a direction approximately perpendicular to one of the end faces of the triangular prismatic diamond cutting element.

Mengel, H. E.; Munzel, H.

1985-05-07

370

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

1993-05-03

371

Amorphous Systems in Athermal, Quasistatic Shear

We present results on a series of 2D atomistic computer simulations of amorphous systems subjected to simple shear in the athermal, quasistatic limit. The athermal quasistatic trajectories are shown to separate into smooth, reversible elastic branches which are intermittently broken by discrete catastrophic plastic events. The onset of a typical plastic event is studied with precision, and it is shown that the mode of the system which is responsible for the loss of stability has structure in real space which is consistent with a quadrupolar source acting on an elastic matrix. The plastic events themselves are shown to be composed of localized shear transformations which organize into lines of slip which span the length of the simulation cell, and a mechanism for the organization is discussed. Although within a single event there are strong spatial correlations in the deformation, we find little correlation from one event to the next, and these transient lines of slip are not to be confounded with the persiste...

Maloney, C E; Maloney, Craig E.; Lema\\^{\\i}tre, Ana\\"el

2005-01-01

372

Simulations of Granular Media Under Shear

Simulations of dry granular material under shear are presented. Our simulations use a micromechanical model which includes realistic material models for each deformable grain, and a Coulomb friction model for interactions between grains. We measure the probability density function governing the volume distribution of stress for mono- and poly-disperse samples, circular and polygonal grains, and various values of microscopic friction coefficients, yield stresses, and packing fractions. Remarkably, PDF's are similar in form for all cases simulated, and similar to those observed in experiments with granular materials under both compression and shear. Namely, the simulations yield an exponential probability of large stresses above the mean. The relationship between distributions of boundary tractions and volume distributions of stress is discussed. The ratio of normal and tangential components of traction on the boundary defines a bulk frictional response, which is shown to increase with the inter-granular friction coefficient. However, the bulk friction is always larger than the inter-granular friction for densely packed samples. Bulk friction is also strongly dependent on grain size distribution and shape. New observations of force-chain banding during recrystallization, of slip systems in monodisperse samples, and of the effects of plastic yield, are also presented.

Sulsky, Deborah; Bardenhagen, Scott; Brackbill, Jeremiah

2000-11-01

373

Shear waves in acoustic anisotropic media

Energy Technology Data Exchange (ETDEWEB)

Acoustic transversely isotropic (TI) media are defined by artificially setting the shear-wave velocity in the direction of symmetry axis, VS0, to zero. Contrary to conventional wisdom that equating VS0 = 0 eliminates shear waves, we demonstrate their presence and examine their properties. Specifically, we show that SV-waves generally have finite nonzero phase and group velocities in acoustic TI media. In fact, these waves have been observed in full waveform modeling, but apparently they were not understood and labeled as numerical artifacts. Acoustic TI media are characterized by extreme, in some sense infinite strength of anisotropy. It makes the following unusual wave phenomena possible: (1) there are propagation directions, where the SV-ray is orthogonal to the corresponding wavefront normal, (2) the SV-wave whose ray propagates along the symmetry axis is polarized parallel to the P-wave propagating in the same direction, (3) P-wave singularities, that is, directions where P- and SV -wave phase velocities coincide might exist in acoustic TI media. We also briefly discuss some aspects of wave propagation in low-symmetry acoustic anisotropic models. Extreme anisotropy in those media creates bizarre phase- and group-velocity surfaces that might bring intellectual delight to an anisotropic guru.

Grechka, Vladimir; Zhang, Linbin; Rector, James W.

2003-01-02

374

Atomization of Shear Coaxial Liquid Jets

Directory of Open Access Journals (Sweden)

Full Text Available 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. Numerical solutions of the governing equationssubject to appropriate initial and boundary conditions are obtained via a robust finite difference scheme. Thecomputations yield real-time evolution and subsequent breakup characteristics of the liquid jet. The experimentalinvestigation utilizes a digital imaging technique to measure resultant drop sizes. Data were collected for liquidReynolds number between 2,500 and 25,000, aerodynamic Weber number range of 50-500 and ambient gaspressures from 150 to 1200 psia. Comparison of the model predictions and experimental data for drop sizes atgas pressures of 150 and 300 psia reveal satisfactory agreement particularly for lower values of investigatedWeber number. The present model is intended as a component of a practical tool to facilitate design andoptimization of coaxial shear atomizers.

Essam A Ibrahim

2010-04-01

375

Shear viscosity coefficient from microscopic models

International Nuclear Information System (INIS)

The transport coefficient of shear viscosity is studied for a hadron matter through microscopic transport model, the ultrarelativistic quantum molecular dynamics (UrQMD), using the Green-Kubo formulas. Molecular-dynamical simulations are performed for a system of light mesons in a box with periodic boundary conditions. Starting from an initial state composed of ?,?,?,?,? with a uniform phase-space distribution, the evolution takes place through elastic collisions, production, and annihilation. The system approaches a stationary state of mesons and their resonances, which is characterized by common temperature. After equilibration, thermodynamic quantities such as the energy density, particle density, and pressure are calculated. From such an equilibrated state the shear viscosity coefficient is calculated from the fluctuations of stress tensor around equilibrium using Green-Kubo relations. We do our simulations here at zero net baryon density so that the equilibration times depend on the energy density. We do not include hadron strings as degrees of freedom so as to maintain detailed balance. Hence we do not get the saturation of temperature but this leads to longer equilibration times

2004-04-01

376

Error in Estimates of Tissue Material Properties from Shear Wave Dispersion Ultrasound Vibrometry

Digital Repository Infrastructure Vision for European Research (DRIVER)

Shear wave velocity measurements are used in elasticity imaging to find the shear elasticity and viscosity of tissue. A technique called shear wave dispersion ultrasound vibrometry (SDUV) has been introduced to use the dispersive nature of shear wave velocity to locally estimate the material properties of tissue. Shear waves are created using a multifrequency ultrasound radiation force, and the propagating shear waves are measured a few millimeters away from the excitation point. The shear wa...

Urban, Matthew W.; Chen, Shigao; Greenleaf, James F.

2009-01-01

377

The dynamics of internal transport barrier formation in reverse shear and weak shear discharges

International Nuclear Information System (INIS)

The experimental regime with reversed central magnetic shear and a coincident enhanced confinement region has opened an operating window which provides the confinement benefits of VH-mode discharges without the difficulties of coupling to the edge physics. A theoretical challenge is to model the dynamics of the transition to the enhanced confinement regime. This requires incorporating the linear effects of the reversed shear profiles in a nonlinear model to capture the bifurcation dynamics. A simple first principles model incorporating the nonlinear coupling between the turbulent fluctuations and the sheared radial electric field is used to investigate the dynamics of the transition to an enhanced confinement mode in the reversed shear/weak shear discharges. From this simple version of the model it is found that by incorporating both growth rate profiles and particle/power deposition profiles a rich variety of transition dynamics exist. The power threshold for the transition is found to depend on the local growth rate and the local gradient in the deposition profile. The size of the enhanced confinement region is predicted to depend on the growth rate profile and the total deposition inside the reversal region. The transition itself can take the form of a propagating front like transition. After the transition the transport in the enhanced regime is neoclassical with the performance limits determined by MHD stability which is not included in the model presented. The simple model can predict the evolution of the transition, scaling of the threshold levels and the optimal deposition profiles. In order to allow an increasingly reasonable investigation of power thresholds and hysteresis effects a more complete transport model is needed. This transport model is coupled to the simple dynamical model allowing the transition dynamics to be self-consistently evolved

1996-03-18

378

Landward propagation of retro shear zones following subduction initiation

Deforming regions at convergent plate margins are bounded by a retro-shear zone on the subducting plate and a pro-shear zone on the overriding plate. In the popular 2-sided wedge model of Willet et al (Geology 1993), the position of the pro shear zone propagates onto the subducting plate as the orogen grows while the position of the retro shear zone remains fixed. We suggest that the fixed position of the retro shear zone is a result of unrealistic model geometry and present an alternative model for orogen growth following subduction initiation in which the retro shear zone propagates landward onto the overriding plate. The entire lithosphere must fail along some plane for subduction to begin and this failure plane must dip in the direction of subduction. Thus the initial geometry of the overriding plate is better approximated as a tapered wedge than as a layer of uniform thickness. Material accreted to the tapered end of the overriding plate drives deformation and causes a rearward propagating retro shear zone. The retro shear zone is ultimately arrested either by reaching the s-point or by encountering strong material in the overriding plate. We demonstrate this model, including the migration of the retro shear zone, using a sandbox-type analog model of a subduction zone. We measure the velocity field within the model mountain belt using particle image velocimetry (PIV) and compute instantaneous strain rates and total displacements.

DeWolf, W.; Ma, K. F.; Brandon, M. T.

2011-12-01

379

Compression Enhanced Shear Yield Stress of Electrorheological Fluid

International Nuclear Information System (INIS)

Shear tests of an electrorheological fluid with pre-applied electric field and compression along the field direction are carried out. The results show that pre-compressions can increase the shear yield stress up to ten times. Under the same external electric field strength, a higher compressive strain corresponds to a larger shear yield stress enhancement but with slight current density decrease, which shows that the particle interaction potentials are not increased by compressions but the compression-induced chain aggregation dominates the shear yield stress improvement. This pre-compression technique might be useful for developing high performance flexible ER or magnetorheological couplings

2009-04-01

380

Aerospace Threaded Fastener Strength in Combined Shear and Tension Loading

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.

Steeve, B. E.; Wingate, R. J.

2012-01-01

381

Critical behavior from geometric confinement in shear thickening suspensions

We performed rheometry measurements on shear thickening suspensions. The viscosity is measured as a shear stress over shear rate in the shear thickening region to have divergent scalings of both the magnitude and slope at a critical packing fraction ?c. The yield stress also has a divergent scaling at ?c. This is qualitatively different form jamming models in which the yield stress grows gradually from an onset packing fraction. The value of ?c depends only on particle shape and equals 0.56 for hard spheres, corresponding to random loose packing and the onset of dilation.

Brown, Eric; Jaeger, Heinrich

2009-03-01

382

Interface shear and pressure characteristics of wheelchair seat cushions

Directory of Open Access Journals (Sweden)

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.

Jonathan S. Akins

2011-03-01

383

Analysis of shear banding in metallic glasses under bending

International Nuclear Information System (INIS)

An analytical model is proposed for studying the formation of shear bands in metallic glasses over a wide range of size scales when subjected to plane strain bending. The model is based on elasto-plastic beam bending and the evolution of shear offset in shear bands. The spacing of shear bands is assumed to be governed by a scaling law depending on a non-dimensional material parameter which is determined from experiments. The macroscopic inelastic deformation due to bending is thought to be accommodated by slip along shear bands. The model is based on comparison of the energy dissipated along shear bands with the macroscopic dissipation obtained from the elasto-plastic theory of beam bending. The model is able to capture the following experimentally-observed scaling laws: (i) for a given thickness, the shear band spacing varies linearly with curvature; (ii) for a given curvature, the shear band offset varies as the square of the thickness; (iii) the shear band spacing varies linearly with the thickness; and (iv) failure strain (bend ductility) decreases with increasing thickness

2005-09-01

384

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

1992-08-24

385

Punching and radial shear problems in reinforced concrete containments

International Nuclear Information System (INIS)

Current design approaches for punching (peripheral) shear are discussed in light of recent experimental results which show little decrease in punching strength with increasing biaxial tension up to about 0.9f/sub y/. It appears that considerable increase in design capacity is warranted, leading to much less congestion of steel. The problem of radial shear in pressurized containments is discussed, especially the complex state of stresses deformations, and cracking near the base. Research required to finalize improved design and licensing methods for punching shear and radial shear is described, together with potential benefits in terms of material savings, safety, qualification of existing facilities for higher loads, and quality control

1982-10-01

386

Shear Localization in Quartz Aggregates Deformed in Torsion

Torsion tests were performed on natural quartz aggregates (Dover flint) in a gas-medium apparatus (Paterson rig) in the semibrittle field. Tests were carried out at constant twist rate (corresponding to maximum shear strain rate of 10-4 s-1) at 1300 K under drained conditions. The samples were first heat-treated for six hours. After heat-treatment, the connected porosity was around 4.5%. At low shear strain (? deformation and a decrease in porosity. The hardening stages were associated with a porosity increase. During hardening, synthetic Riedel shears at a low angle (15-20° ) to the shear zone boundary developed. In the TEM, these Riedel shears showed a higher porosity than the surrounding material. These high porosity shears were more developed in samples with a high hardening rate and a higher shear strain. Two samples were unloaded at a shear strain of ? = 1.3 and 2.5, respectively, and reloaded after 0.5 h annealing at the deformation temperature and pressure. Both of them flowed at a lower level of shear stress than before unloading. Subsequent deformation occurred by sliding along the pre-existing Riedel shears with an associated small decrease in shear stress. The microstructure showed the evolution of the Riedel shears into proper faults with a clearly visible displacement and grain-size reduction. At these high shear strains, the Riedel shears were not planar surfaces but had a wavy geometry. R1, R2 and Y shear surfaces were present. Texture measurements (EBSD, synchrotron, x-ray goniometer) indicated a weak lattice preferred orientation in the matrix with an oblique c-axis girdle opposite to the sense of shear. These weak but clearly developed textures in high strain samples are attributed to a minor component of intracrystalline plasticity in the bulk rock, but may also be affected by fluid-enhanced oriented growth. TEM analysis indicated that no recovery or recrystallization occurred in the deformed samples. Locally, high dislocation densities occurred at grain boundaries. No crushing of grains or displacement at microfractures was observed. These observations, in conjunction with the high porosity, suggest that the dominant deformation mechanism was granular flow.

Schmocker, M.; Bystricky, M.; Stuenitz, H.; Burlini, L.; Kunze, K.

2001-12-01

387

The role of shear in dissipative gravitational collapse

In this paper we investigate the physics of a radiating star undergoing dissipative collapse in the form of a radial heat flux. Our treatment clearly demonstrates how the presence of shear affects the collapse process; we are in a position to contrast the physical features of the collapsing sphere in the presence of shear with the shear-free case. By employing a causal heat transport equation of the Maxwell-Cattaneo form we show that the shear leads to an enhancement of the core temperature thus emphasizing that relaxational effects cannot be ignored when the star leaves hydrostatic equilibrium.

Govender, M; Maharaj, S D

2013-01-01

388

Rheo-NMR studies of liquid crystals in shear flow

International Nuclear Information System (INIS)

Nuclear magnetic resonance spectroscopy has proven a useful tool for the investigation of shear-induced phenomena in liquid crystals. Due to the anisotropy of the interactions of nuclear spins, information about shear-induced orientations can be obtained. In deuterium NMR, the quadrupolar interaction is used to probe the orientation of the liquid crystalline director. In situ observations of director orientations under shear can reveal the microscopic origin of macroscopic rheological phenomena. Recent examples for deuterium NMR investigations of shear phenomena in different types of liquid crystals, such as nematic, lamellar and hexagonal phases will be presented

2008-02-25

389

Rheo-NMR studies of liquid crystals in shear flow

Energy Technology Data Exchange (ETDEWEB)

Nuclear magnetic resonance spectroscopy has proven a useful tool for the investigation of shear-induced phenomena in liquid crystals. Due to the anisotropy of the interactions of nuclear spins, information about shear-induced orientations can be obtained. In deuterium NMR, the quadrupolar interaction is used to probe the orientation of the liquid crystalline director. In situ observations of director orientations under shear can reveal the microscopic origin of macroscopic rheological phenomena. Recent examples for deuterium NMR investigations of shear phenomena in different types of liquid crystals, such as nematic, lamellar and hexagonal phases will be presented.

Ar, Goenuel; Shafaei, Shahram; Schmidt, Claudia [Department Chemie, Universitaet Paderborn (Germany)

2008-07-01

390

Analysis of shear banding in metallic glasses under bending

Energy Technology Data Exchange (ETDEWEB)

An analytical model is proposed for studying the formation of shear bands in metallic glasses over a wide range of size scales when subjected to plane strain bending. The model is based on elasto-plastic beam bending and the evolution of shear offset in shear bands. The spacing of shear bands is assumed to be governed by a scaling law depending on a non-dimensional material parameter which is determined from experiments. The macroscopic inelastic deformation due to bending is thought to be accommodated by slip along shear bands. The model is based on comparison of the energy dissipated along shear bands with the macroscopic dissipation obtained from the elasto-plastic theory of beam bending. The model is able to capture the following experimentally-observed scaling laws: (i) for a given thickness, the shear band spacing varies linearly with curvature; (ii) for a given curvature, the shear band offset varies as the square of the thickness; (iii) the shear band spacing varies linearly with the thickness; and (iv) failure strain (bend ductility) decreases with increasing thickness.

Ravichandran, Guruswami [Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, CA 91125 (United States)]. E-mail: ravi@caltech.edu; Molinari, Alain [Laboratoire de Physique et Mecanique des Materiaux, Universite Paul Verlaine, Ile du Saulcy, 57045 Metz Cedex 01 (France)

2005-09-15

391

Dynamics of a tethered polymer in shear flow.

The dynamics of a single polymer tethered to a solid surface in a shear flow was observed using fluorescently labeled DNA chains. Dramatic shear enhanced temporal fluctuations in the chain extension were observed. The rate of these fluctuations initially decreased for increasing shear rate gamma; and increased above a critical gamma;. Simulations revealed that these anomalous dynamics arise from a continual recirculating motion of the chain or cyclic dynamics. These dynamics arise from a coupling of the chain velocity in the flow direction to thermally driven fluctuations of the chain in the shear gradient direction. PMID:10990792

Doyle, P S; Ladoux, B; Viovy, J L

2000-05-15

392

Nanocrystallization in a shear band: An in situ investigation

International Nuclear Information System (INIS)

Preferential nanocrystal formation in shear bands that occurred upon applying a tensile strain on an Al-rich metallic glass has been analyzed in situ in a transmission electron microscope as a function of time after the shear band initiation and as a function of local heating. The results indicate the presence of a transient period before nanocrystal formation sets in, as well as the necessity of thermal activation and further show that nanocrystals developed only within the shear bands. These results support models that explain nanocrystal formation in shear bands based on an increased local mobility.

2011-06-20

393

The Higher Himalayan Shear Zone (HHSZ) in the Sutlej section reveals (1) top-to-SW ductile shearing, (2) top-to-NE ductile shearing in the upper- and the lower strands of the South Tibetan Detachment System (STDSU, STDSL), and (3) top-to-SW brittle shearing corroborated by trapezoid-shaped minerals in micro-scale. In the proposed extrusion model of the HHSZ, the E1-phase during 25-19 Ma is marked by simple shearing of the upper sub-channel defined by the upper strand of the Main Central Thrust (MCTU) and the top of STDSU as the lower- and the upper boundaries, respectively. Subsequently, the E2a-pulse during 15-14 Ma was characterized by simple shear, pure shear, and channel flow of the entire HHSZ. Finally, the E2b-pulse during 14-12 Ma observed simple shearing and channel flow of the lower sub-channel defined by the lower strand of the Main Central Thrust (MCTL) and the top of the STDSL as the lower- and the upper boundaries, respectively. The model explains the constraints of thicknesses of the STDSU and the STDSL along with spatially variable extrusion rate and the inverted metamorphism of the HHSZ. The model predicts (1) shear strain after ductile extrusion to be maximum at the boundaries of the HHSZ, which crudely matches with the existing data. The other speculations that cannot be checked are (2) uniform shear strain from the MCTU to the top of the HHSZ in the E1-phase; (3) fastest rates of extrusion of the lower boundaries of the STDSU and the STDSL during the E2a- and E2b-pulses, respectively; and (4) variable thickness of the STDSL and rare absence of the STDSU. Non-parabolic shear fabrics of the HHSZ possibly indicate heterogeneous strain. The top-to-SW brittle shearing around 12 Ma augmented the ductile extruded rocks to arrive a shallower depth. The brittle-ductile extension leading to boudinage possibly did not enhance the extrusion.

Mukherjee, Soumyajit; Koyi, Hemin A.

2010-09-01

394

Structure formation in thermoresponsive microgel suspensions under shear flow

International Nuclear Information System (INIS)

Shear-induced structures of concentrated temperature-sensitive poly(N-isopropylacrylamide) (PNiPAM) microgel suspensions have been studied employing small angle neutron scattering (rheo-SANS). The interaction potential of swollen PNiPAM microgels could be varied from repulsive at temperatures below the lower critical solution temperature to attractive at temperatures above the lower critical solution temperature. In contrast to the case for suspensions of rigid spheres, the effective volume fraction could be changed by means of temperature while the mass concentration and particle number density were kept constant. Thus, aqueous PNiPAM microgels are interesting model systems with unique colloidal properties. Complementary information about shear-induced changes of both the internal particle structure and the overall microstructural phenomena were obtained from rheo-SANS experiments with PNiPAM microgels with different particle sizes. The shear-induced particle arrangements strongly depended on the particle-particle interaction potential. When the interaction potential was repulsive at temperatures below the lower critical solution temperature, no significant deformation of the swollen PNiPAM particles was observed even at high shear rates. Shear-induced ordering was found at high shear rates resulting in the formation of two-dimensional hexagonal close packed layers that aligned along the flow direction giving rise to shear thinning. The formation of sliding hexagonal close packed layers under shear flow is therefore proposed to be a general property of colloidal dispersion independent of the internal structure of the particle. At temperatures near the lower critical solution temperature, when the particle interaction potential is not yet strongly attractive, shear flow induces the collapse of an individual particle in concentrated suspension at high shear rates. A so-called butterfly scattering pattern indicates the shear-induced enhancement of concentration fluctuations along the flow direction leading to solvent being squeezed out of the particles until phase separation occurs finally

2004-09-29

395

Tensile & shear strength of porous dust agglomerates

Context.Within the sequential accretion scenario of planet formation, planets are build up through a sequence sticking collisions. The outcome of collisions between porous dust aggregates is very important for the growth from very small dust particles to planetesimals. In this work we determine the necessary material properties of dust aggregates as a function the porosity. Aims: Continuum models such as SPH that are capable of simulating collisions of macroscopic dust aggregates require a set of material parameters. Some of them such as the tensile and shear strength are ?difficult to obtain from laboratory experiments. The aim of this work is to determine these parameters from ab-initio molecular dynamics simulations. Methods: We simulate the behavior of porous dust aggregates using a detailed micro-physical model of the interaction of spherical grains that includes adhesion forces, rolling, twisting, and sliding. Using different methods of preparing the samples we study the strength behavior of our samples...

Seizinger, Alexander; Kley, Wilhelm

2013-01-01

396

Capillary breakup of discontinuously shear thickening suspensions

Extensional rheology of discontinuously shear thickening suspensions is not well understood, in part due to unresolved experimental challenges. Such suspensions tend to sag, drain or fracture when tested using traditional tools such as filament-stretching or capillary breakup extensional rheometers. We present an alternative method of conducting capillary breakup experiments with thickening suspensions by placing them between two layers of immiscible oil. In experiments conducted with silica and cornstarch particles we observe the formation of bead-on-a-string morphologies with multiple satellite and sub-satellite bead generations, similar to the morphologies observed in breakup of viscoelastic fluids. Using a one dimensional numerical model, we show that formation of beads is a consequence of the discontinuous nature of thickening in the suspensions. Finally, we delineate the parameter regimes where formation of beads occurs, and where it is suppressed.

Zimoch, Pawel; McKinley, Gareth; Hosoi, Anette

2011-11-01

397

Studies of Glassy Colloidal Systems Under Shear

In analogy with the glass transition of polymer (and other molecular) liquids, colloidal suspensions can undergo dynamic arrest to form a glassy solid, when the system is concentrated beyond a critical volume fraction. However, in contrast to their molecular counterparts, studies of the glass transition in colloidal systems are facilitated by their natural length- and time-scales, which make it possible to directly visualize the behaviour of the individual constituent particles. Using confocal microscopy, we follow the dynamics of colloidal suspensions near the glass transition, and in particular, their reaction to an imposed deformation. We investigate the evolution from a quiescent solid to a shear melted liquid, to elucidate the nature of the structural rearrangements that govern the properties of glassy materials.

Massa, Michael; Kim, Chanjoong; Weitz, David

2008-03-01

398

Lattice shear distortions in fluorite structure oxides

International Nuclear Information System (INIS)

Crystallographic shear distortions have been observed in fluorite structure, single crystals of UO_2 and Zr(Ca)O_2/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 UO_2 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

1979-03-25

399

Shear viscosity of a crosslinked polymer melt

Starting from a microscopic Rouse model, we calculate exactly the critical behavior of the mean static shear viscosity $\\left$ for a randomly crosslinked polymer melt, as the vulcanization transition is approached. Technically, this is achieved by methods from graph theory which relate the viscosity of a random polymer cluster to the Wiener index of a random graph. Using in addition the known cluster statistics from a mean-field-like theory of random graphs, we find that $\\left$ diverges logarithmically with the distance to the critical point. Replicas provide an alternative to the graph-theoretical methods and yield identical results. The method presented does also allow to compute exactly the behavior of the averaged viscosity for randomly branched polymers when the number of monomers $n$ of the polymer tends to infinity. In this case it turns out that $\\left_n\\sim n^{1/2}$.

Broderix, K; Müller, P; Zippelius, A; Broderix, Kurt; Löwe, Henning; Müller, Peter; Zippelius, Annette

1999-01-01

400

Entanglements in Quiescent and Sheared Polymer Melts

We visualize entanglements in polymer melts using molecular dynamics simulation. A bead at an entanglement interacts persistently for long times with the non-bonded beads (those excluding the adjacent ones in the same chain). The interaction energy of each bead with the non-bonded beads is averaged over a time interval $\\tau$ much longer than microscopic times but shorter than the onset time of tube constraints $\\tau_{\\rm e}$. Entanglements can then be detected as hot spots consisting of several beads with relatively large values of the time-averaged interaction energy. We next apply a shear flow with rate much faster than the entangle motion. With increasing strain the chains take zigzag shapes and a half of the hot spots become bent. The chains are first stretched as a network but, as the bends approach the chain ends, disentanglements subsequently occur, leading to stress overshoot observed experimentally.

Yamamoto, R; Yamamoto, Ryoichi; Onuki, Akira

2004-01-01

401

Shear Resistance between Concrete-Concrete Surfaces

The application of precast beams and cast-in-situ structural members cast at different times has been typical of bridges and buildings for many years. A load-bearing frame consists of a set of prestressed precast beams supported by columns and diaphragms joined with an additionally cast slab deck. This article is focused on the theoretical and experimental analyses of the shear resistance at an interface. The first part of the paper deals with the state-of-art knowledge of the composite behaviour of concrete-concrete structures and a comparison of the numerical methods introduced in the relevant standards. In the experimental part, a set of specimens with different interface treatments was tested until failure in order to predict the composite behaviour of coupled beams. The experimental part was compared to the numerical analysis performed by means of FEM basis nonlinear software.

Kova?ovic, Marek

2013-12-01

402

Lattice shear distortions in fluorite structure oxides

Energy Technology Data Exchange (ETDEWEB)

Crystallographic shear distortions have been observed in fluorite structure, single crystals of UO/sub 2/ and Zr(Ca)O/sub 2//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 UO/sub 2/ is a transverse, zone boundary q vector = 2..pi../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.

Faber, J. Jr.; Mueller, M.H.; Hitterman, R.L.

1979-01-01

403

The SDSS Coadd: Cosmic Shear Measurement

Energy Technology Data Exchange (ETDEWEB)

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}.

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

404

Adjustable shear stress erosion and transport flume

Energy Technology Data Exchange (ETDEWEB)

A method and apparatus for measuring the total erosion rate and downstream transport of suspended and bedload sediments using an adjustable shear stress erosion and transport (ASSET) flume with a variable-depth sediment core sample. Water is forced past a variable-depth sediment core sample in a closed channel, eroding sediments, and introducing suspended and bedload sediments into the flow stream. The core sample is continuously pushed into the flow stream, while keeping the surface level with the bottom of the channel. Eroded bedload sediments are transported downstream and then gravitationally separated from the flow stream into one or more quiescent traps. The captured bedload sediments (particles and aggregates) are weighed and compared to the total mass of sediment eroded, and also to the concentration of sediments suspended in the flow stream.

Roberts, Jesse D. (Carlsbad, NM); Jepsen, Richard A. (Carlsbad, NM)

2002-01-01

405

Fluidization of Wet Granulates under Hydrodynamic Shear

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.

Battiato, I

2012-01-01

406

Shear friction capacity of recycled concretes

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this research was to determine the behavior of recycled concrete in response to the phenomenon of shear transfer. To perform it, a conventional control concrete and a concrete with 50% recycled coarse aggregate were designed. An additional goal was to shed light on how this behavior is modified with a pozzolanic addition, silica fume. Therefore, two types of concrete were designed, a conventional and a recycled concrete, both made with 8% of silica fume.
In conclusion, a reduction of shear friction capacity was observed in recycled concretes, considerably higher in the case of the specimen without reinforcement. The addition of silica fume improved the behavior of recycled concretes.
The results obtained were compared with the formulations of the different authors. In all cases, these were found to be conservative. However, the safety margins offered by recycled concretes are lower than those obtained with conventional concretes.

En esta investigación se estudió el comportamiento de los hormigones reciclados frente al fenómeno de transmisión de cortante. Para ello se diseñó un hormigón convencional de control y un hormigón con el 50% del árido grueso reciclado. Adicionalmente, para determinar cómo este comportamiento se ve modificado con la incorporación de una adición puzolánica (humo de sílice, se procedió al diseño de un hormigón convencional y su correspondiente reciclado con un 8% de humo de sílice.
Los resultados indicaron una disminución de la capacidad frente a este fenómeno en los hormigones reciclados, más acusada en ausencia de armadura pasante. La adición de humo de sílice mejora el comportamiento de este material.
Los resultados experimentales obtenidos se compararon con formulaciones teóricas de diversos autores, concluyéndose que éstas son, en todos los casos, conservadoras, aunque reducen el margen de seguridad en los hormigones reciclados.

Eiras, J.

2010-09-01

407

Interlaminar shear strength evaluation of curved composite samples

To assess the bonding quality between the different layers of composite rings fabricated by filament winding it is necessary to choose a useful shear test. A method for measuring the shear strength of thin curved samples is proposed herein. Stress distribution within the probe is calculated and evaluated by finite element method.

Lauke, B.; Beckert, W.; Schneider, K.

1994-07-01

408

Research Concerning the Shearing Strength of Black Locust Wood

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents the experimental resultsobtained for the shearing strength of black locustwood (Robinia pseudacacia L. harvested from twogeographical areas (North and South of Romania.Wood is subjected to shearing stress when usedwithin different fields, and especially inconstructions. Tangential stresses are produced inthe shearing sections and they are influenced by thestructure of wood through the position of theshearing plane and of the force direction towards thegrain. Accordingly, several shearing types arepossible. The shearing strengths for the three mainshearing types, both on radial and tangentialdirection were determined within the present study.The evaluation of data was achieved by using theANOVA analysis, in order to test the level ofsignificance depending on the shearing planeorientation and the harvesting area. The obtainedresults were compared to the values mentionedwithin reference literature for this wood species andtwo other hardwood species with similar density. It isworth to be mentioned that the shearing strengths ofblack locust wood from Romania (both from Northand South are generally higher than those indicatedby reference literature for oak and beech. Thisrecommends black locust wood as constructionwood and for other applications where wood issubjected to shearing stress.

Mihaela POROJAN

2011-06-01

409

The Behavior of Granular Materials under Cyclic Shear

The design and development of a parallel plate shear cell for the study of large scale shear flows in granular materials is presented. The parallel plate geometry allows for shear studies without the effects of curvature found in the more common Couette experiments. A system of independently movable slats creates a well with side walls that deform in response to the motions of grains within the pack. This allows for true parallel plate shear with minimal interference from the containing geometry. The motions of the side walls also allow for a direct measurement of the velocity profile across the granular pack. Results are presented for applying this system to the study of transients in granular shear and for shear-induced crystallization. Initial shear profiles are found to vary from packing to packing, ranging from a linear profile across the entire system to an exponential decay with a width of approximately 6 bead diameters. As the system is sheared, the velocity profile becomes much sharper, resembling an...

Mueggenburg, N W

2004-01-01

410

Stationary spectra in a sheared plasma (linear limit)

International Nuclear Information System (INIS)

The short-wave low-frequency stationary spectra of correlated electromagnetic fluctuations in a sheared current-currying plasma, are obtained in a linear approximation. Even being weak, the shear may considerably alter the spectral characteristics of plasma perturbations. 3 refs. (author)

1992-01-01

411

Alfven wave current drive in tokamak reversed shear plasmas

International Nuclear Information System (INIS)

The current drive due to Alfven wave in tokamak reversed shear plasmas is studied. In cylindrical geometry, an expression for driving current density J_z is given by means of the single-fluid magnetohydrodynamic (MHD) model taking plasma rotation and magnetic shear into account. The current drive due to the compressional Alfven wave and the shear Alfven wave is considered, respectively. It is found that the efficiency of the Alfven wave current drive without the magnetic shear is independent of rotating plasma density. Moreover, it is shown that a higher efficiency can be obtained in the presence of rotation. For the shear Alfven wave, the magnetic shear has a more distinct effect on the current drive than one for the compressional Alfven wave. The effect of the negative magnetic shear on the Alfven wave current drive is opposite to the effect of the positive, and the negative shear enhances the driven current density J_z. These results show that the Alfven waves may be an excellent current drive candidate for tokamak fusion reactors

2001-08-01

412

The shear viscosity of gauge theory plasma with chemical potentials

We consider strongly coupled gauge theory plasma with conserved global charges that allow for a dual gravitational description. We study the shear viscosity of the gauge theory plasma in the presence of chemical potentials for these charges. Using gauge theory/string theory correspondence we prove that at large 't Hooft coupling the ratio of the shear viscosity to the entropy density is universal.

Benincasa, P; Naryshkin, R; Benincasa, Paolo; Buchel, Alex; Naryshkin, Roman

2007-01-01

413

Dynamic Shear Moduli and Damping Ratios for Dry Sands.

Using the Torsional Simple Shear Device, the authors investigated the equivalent dynamic shear moduli G sub eq and the damping ratio lambda for Ottawa sand, Del Monte sand, Golden Gardens and Seward Park sands. Based on their experimental findings the aut...

M. A. Serif I. Ishibashi

1976-01-01

414

Solve membrane fouling problems with high-shear filtration

Energy Technology Data Exchange (ETDEWEB)

High-shear advancements are allowing membrane separation systems to displace some conventional separation methods such as centrifuging, evaporation, and clarifying. Applications range from wastewater treatment to biological separations. This paper describes fouling problems, tangential flow, high-shear filtration systems, vibration antifouling technology, spinning disc, spinning cylinder, system differences, limitations, costs, and selecting a solids/liquids separator.

Culkin, B.; Plotkin, A.; Monroe, M. [New Logic International, Inc., Emeryville, CA (United States)

1998-01-01

415

E x B shearing rate in quasi-symmetric plasmas

Energy Technology Data Exchange (ETDEWEB)

The suppression of turbulence by the E x B shear is studied in systems with quasi-symmetry using the nonlinear analysis of eddy decorrelation previously utilized in finite aspect ratio tokamak plasmas. The analytically derived E x B shearing rate which contains the relevant geometric dependence can be used for quantitative assessment of the fluctuation suppression in stellarators with quasi-symmetry.

Hahm, T.S.

1997-06-20

416

Constant rate shearing on two dimensional cohesive disks

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.

Olivi-Tran, N; Fraysse, N

2005-01-01

417

Safety shear apparatus and method for production wells

Energy Technology Data Exchange (ETDEWEB)

An apparatus and method for shutting in a well in the event all other control equipment on the well fails to close and hold. The apparatus includes a lower and upper tubing head in which the tubing extends from the well upwardly through the lower head and into the upper head and sealingly engages both heads. A sealing and shear ram is positioned between the heads for shearing and sealing the tubing. The shear tubing is moved away from the shear rams after shearing to allow the rams to seal. The tubing is preferably supported from only one of the tubing heads. In one embodiment the tubing is supported initially from the upper head and after shearing the lower tubing portion moves downwardly to seat on the lower tubing head for allowing the rams to seal. In another embodiment the tubing is supported from the lower head and after shearing the upper portion of the tubing is raised to allow the shear rams to seal.

Hansen, A.

1985-07-30

418

Distribution of Magnetic Shear Angle in an Emerging Flux Region

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.

Gosain, Sanjay

2010-01-01

419

Single-fluid stability of stationary plasma equilibria with velocity shear and magnetic shear

International Nuclear Information System (INIS)

By using incompressible single-fluid equations with a generalized Ohm's law neglecting the electron inertia, a linear eigenmode equation for a magnetic field perturbation is derived for stationary equilibria in a slab geometry with velocity and magnetic shears. The general eigenmode equation contains a fourth-order derivative of the perturbation in the highest order and contains Alfven and whistler mode components for a homogeneous plasma. The ratio of the characteristic ion inertia length to the characteristic inhomogeneity scale length is chosen as a small parameter for expansion. Neglecting whistler mode in the lowest order, the eigenmode equation becomes a second-order differential equation similar to the ideal magnetohydrodynamic eigenmode equation except for the fact that the unperturbed perpendicular velocity contains both electric and ion diamagnetic drifts. A sufficient condition for stability against the Kelvin-Helmholtz instability driven by shear in the ion diamagnetic drift velocity is derived and then applied to tokamaks.

2009-10-01

420

Standard Test Method for Shear Strength and Shear Modulus of Aerospace Glazing Interlayer Materials

1.1 This test method covers the determination of the shear strength and shear modulus of interlayer materials that are restrained by relatively high modulus plies in laminated transparencies. This test method can be used with single or multiple plies of the same interlayer materials. 1.2 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health