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1

Beef customer satisfaction: trained sensory panel ratings and Warner-Bratzler shear force values.

Trained sensory panel ratings and Warner-Bratzler shear force (WBS) values from the Beef Customer Satisfaction study are reported. Carcasses were chosen to fit into USDA quality grades of Top Choice (upper two-thirds of USDA Choice), Low Choice, High Select, and Low Select. A trained, descriptive attribute panel evaluated top loin, top sirloin, and top round steaks for muscle fiber tenderness, connective tissue amount, overall tenderness, juiciness, flavor intensity, cooked beef flavor intensity, and cooked beef fat flavor intensity. Four steaks from each of the three cuts from each carcass were assigned randomly to one of four cooking endpoint temperature treatments (60, 65, 70, or 75 degrees C) for WBS determination. For all trained panel measures of tenderness and WBS, regardless of USDA quality grade, top loin steaks were rated higher than top sirloin steaks, which were rated higher than top round steaks (P tenderness, connective tissue amount, overall tenderness, juiciness, flavor intensity, and cooked beef fat flavor were significant (P predict from objective data how consumers will rate meat at home. PMID:12597384

Lorenzen, C L; Miller, R K; Taylors, J F; Neely, T R; Tatum, J D; Wise, J W; Buyek, M J; Reagan, J O; Savell, J W

2003-01-01

2

Beef ribeye rolls (n=40) from Select, low Choice, top (upper 2/3) Choice, and Prime quality grade carcasses were used to determine the relationship of visible and near-infrared spectroscopy (VNIR) reflectance, Warner-Bratzler shear force (WBSF), and Meullenet-Owens razor shear (MORS) with consumer responses for tenderness and overall impression. Steaks (2.54 cm) were cut and assigned to either 14 or 28d aging (n=4/aging period). Reflectance in the VNIR spectrum was measured 1d from the box-date no less than 30 min after cutting, and prior to aging. The steak used for VNIR measurement was designated for WBSF and MORS measurement, whereas three adjacent steaks were cooked for evaluation by a consumer panel (n=240 members). Steaks from the Select-grade ribeye rolls had the greatest (P=0.06) WBSF values and lower (PConsumer panelists evaluated steaks aged 28 d as more tender (Pconsumer panel responses for tenderness than with overall impression, and those relationships were stronger for the Select grade than for quality grades with higher degrees of marbling. The 2nd derivatives of VNIR measurements were more successful at predicting consumer panel responses of tenderness and overall impression than WBSF and MORS; thus, VNIR methodology was less invasive and more predictive than other, more traditional tenderness measurements. PMID:20416819

Yancey, J W S; Apple, J K; Meullenet, J-F; Sawyer, J T

2010-07-01

3

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

4

To estimate the heritability (h2) of postrigor calpastatin activity (CA), 555 steers were reared and processed conventionally. Breed-types included purebreds (Angus [A], Braunvieh [B], Charolais [C], Gelbvieh [G], Hereford [H], Limousin [L], Pinzgauer [P], Red Poll [RP], and Simmental [S]), composite populations (MARC I [1/4 C, 1/4 B, 1/4 L, 1/8 H, 1/8 A], MARC II [1/4 S, 1/4 G, 1/4 H, 1/4 A], and MARC III [1/4 RP, 1/4 H, 1/4 P, 1/4 A]), and F1 crosses (H, A, C, G, P, Shorthorn, Galloway, Longhorn, Nellore, Piedmontese, or Salers x H or A). Steers were serially slaughtered on an age-constant (across breed groups) basis. Heritability estimates for CA, i.m. fat content (IMF), Warner-Bratzler shear (WBS) force, retail product yield (RPY), and ADG were .65 +/- .19, .93 +/- .02, .53 +/- .15, .45 +/- .18, and .32 +/- .26, respectively. The genetic correlations (rg) of CA with WBS, RPY, and ADG were .50 +/- .22, .44 +/- .25, and -.52 +/- .37, respectively. The rg of IMF with WBS, RPY, and ADG were -.57 +/- .16, -.63 +/- .15, and -.04 +/- .11, respectively. These h2 and rg estimates indicate that it should be possible to select for improvements in CA, IMF, and WBS. However, selection against CA may be a more suitable approach for improving meat tenderness than selection for increased IMF because the level of genetic antagonism between CA and RPY was not as great as that between IMF and RPY. PMID:8014150

Shackelford, S D; Koohmaraie, M; Cundiff, L V; Gregory, K E; Rohrer, G A; Savell, J W

1994-04-01

5

Two experiments were conducted to investigate mechanical measures of tenderness on uncooked USDA Select longissimus muscle as a means to predict Warner-Bratzler shear force (WBSF) and trained sensory panel tenderness (SPT) of cooked steaks. In Exp. 1, strip loins (n = 24) were aged 14 d postmortem and fabricated into steaks (2.54 cm). Medial, center, and lateral locations within uncooked steaks were evaluated by a plumb bob device and correlated with WBSF and SPT of cooked steaks. In Exp. 2, 24 strip loins were used to evaluate how well plumb bob and needle probe devices used on uncooked steaks predicted WBSF and SPT of cooked steaks. At 2 d postmortem, two steaks were fabricated from the anterior end. One uncooked steak (2.54 cm) was assigned to the plumb bob treatment and the other uncooked steak (5.08 cm) was assigned to needle probe treatment. At 14 d postmortem, one uncooked steak (5.08 cm) was assigned to needle probe treatment, a second uncooked steak (2.54 cm) was assigned to plumb bob treatment, whereas the remaining steaks (2.54 cm) were cooked and evaluated by a trained sensory panel and WBSF device. In Exp. 1, average plumb bob values were negatively correlated (P 0.05). In Exp. 2, regression models to predict SPT from needle probe and plumb bob measurements individually taken at 2 d postmortem had R2 of 0.54 and 0.51, respectively. Combining needle probe and plumb bob measurements resulted in an R2 of 0.76; when quadratic terms for both variables were in the model, the R2 was 0.80. Regressing needle probe and plumb bob measurements at 2 d postmortem with WBSF produced R2 values of 0.51 and 0.45, respectively. If linear terms of both probes were combined to predict WBSF, the R2 increased to 0.77. An equation to predict WBSF, including both the linear and quadratic terms of needle probe and plumb bob measurements, resulted in an R2 of 0.84. Using plumb bob and needle probe devices on uncooked longissimus muscle at 2 d postmortem can predict cooked WBSF and SPT of USDA Select Grade steaks at 14 d postmortem. PMID:12854808

Timm, R R; Unruh, J A; Dikeman, M E; Hunt, M C; Lawrence, T E; Boyer, J E; Marsden, J L

2003-07-01

6

Directory of Open Access Journals (Sweden)

Full Text Available 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 maciez 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.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 is 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

2010-06-01

7

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.

1405-14-01

8

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.

9

...TA-W-71,775] Warner Brothers Entertainment, Inc., Warner Brothers Theatrical...Distributing, Inc., Warner Brothers Home Entertainment, Inc., Warner Brothers Studio Enterprises...Studio Facilities, and Warner Brothers Entertainment Company, Burbank, CA; Amended...

2010-11-23

10

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/

11

In the December 16, 1999 issue of Nature, researchers from Australia and California used chemical tests to show that coral reef fish often spend their life cycle close to home, rather than drifting in the open ocean. These findings have important implications for global fisheries management. This site provides further information on Robert Warner, one of the lead researchers on the UC Santa Barbara paper, and an established professor of Marine Biology.

12

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 (Ptenderized (18.4N) and control (19.9N) steaks. Tenderness ratings for the injected steaks were higher (Ptenderized and injected steaks resulted in increased palatability ratings, whereas increased doneness for control steaks generally resulted in lowered palatability ratings. Consumer ratings and WBS values for the M. serratus ventralis thoracis indicate that merchandising 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

13

The Myth of "Pop Warner": Carlisle Revisited.

The myth of Pop Warner's sterling character hides the distasteful story behind the closure of Warner's Carlisle School for Indians on the grounds of moral corruption and misuse of athletic funds. (LH)

Howell, Reet A; Howell, Maxwell L.

1978-01-01

14

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Avaliaram-se as características sensoriais e determinou-se a força de cisalhamento de cortes de carne de paca (Agouti paca). As análises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por cocção até a temperatura interna de 70ºC. A avaliação de aspecto, co [...] r, sabor, odor e maciez foi realizada pela aplicação de teste afetivo a 146 provadores, utilizando-se escala hedônica, e a força de cisalhamento foi determinada pela técnica Warner Bratzler. Na avaliação sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferença significativa (p0,05) entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante à carne suína e com boa aceitação pelos consumidores. O estudo evidenciou o potencial da paca como uma espécie silvestre para a produção comercial de carne para o mercado de carnes vermelhas ou exóticas. Abstract in english Sensory characteristics and shear force of paca meat (Agouti paca) were assessed in this study. Analyses were performed in the bonelessshoulder,loin andhamobtained from nine paca carcassesprepared by cookinguntil reaching the internal temperatureof 70°C. The evaluation of flavor, aroma, color, appea [...] rance and tenderness was carried out by the application of an affective test using the hedonic scaleand a 146 consumer panel. Shear force was determined by the Warner-Bratzler technique. Shoulder, loin and ham had significant differences (p 0.05) among the cuts, which were similarly tender. Paca meat was found to resemble pork meat in sensory evaluation and had good acceptance by consumers. This study showed the potential of paca (Agouti paca) asa wild species for meat production in the red or exotic meat market.

C., Gomes; L.B., Karam; R.E.F., Macedo.

15

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Avaliaram-se as características sensoriais e determinou-se a força de cisalhamento de cortes de carne de paca (Agouti paca). As análises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por cocção até a temperatura interna de 70ºC. A avaliação de aspecto, co [...] r, sabor, odor e maciez foi realizada pela aplicação de teste afetivo a 146 provadores, utilizando-se escala hedônica, e a força de cisalhamento foi determinada pela técnica Warner Bratzler. Na avaliação sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferença significativa (p0,05) entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante à carne suína e com boa aceitação pelos consumidores. O estudo evidenciou o potencial da paca como uma espécie silvestre para a produção comercial de carne para o mercado de carnes vermelhas ou exóticas. Abstract in english Sensory characteristics and shear force of paca meat (Agouti paca) were assessed in this study. Analyses were performed in the bonelessshoulder,loin andhamobtained from nine paca carcassesprepared by cookinguntil reaching the internal temperatureof 70°C. The evaluation of flavor, aroma, color, appea [...] rance and tenderness was carried out by the application of an affective test using the hedonic scaleand a 146 consumer panel. Shear force was determined by the Warner-Bratzler technique. Shoulder, loin and ham had significant differences (p 0.05) among the cuts, which were similarly tender. Paca meat was found to resemble pork meat in sensory evaluation and had good acceptance by consumers. This study showed the potential of paca (Agouti paca) asa wild species for meat production in the red or exotic meat market.

C., Gomes; L.B., Karam; R.E.F., Macedo.

2013-04-01

16

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 53°C, 55°C, 58°C and 63°C in water baths for 2½, 7½ and 19½ h. Cooking loss and Warner-Bratzler shear force were measured after heat treatment and subsequent cooling. Shear force of semitendinosus from young bulls heated at 53°C for 2½ h was significantly higher compared with all other heat treatments. A decrease of app. 40 N was observed when increasing the heating temperature from 53°C to 55°C, or when increasing heating time from 2½ to 7½ h at 53°C. In semitendinosus from cows shear force decreased significantly with increasing temperature, and with increasing heating time from 2½ to 19½ h at 55°C and 63°C. Cooking loss increased with increasing heating temperature in both beef categories. The results show that prolonged heating at low temperatures reduce toughness in beef semitendinosus, and that a reduction in toughness require higher temperatures and longer heating times in semitendinosus from cows compared with young bulls.

Christensen, L.; Andersen, L.

2011-01-01

17

The present experiments were conducted to determine whether improved beef longissimus shear force methodology could be used to assess pork longissimus tenderness. Specifically, three experiments were conducted to: 1) determine the effect of belt grill (BG) cookery on repeatability of pork longissimus Warner-Bratzler shear force (WBSF), 2) compare the correlation of WBSF and slice shear force (SSF) with trained sensory panel tenderness ratings, and 3) estimate the repeatability of pork longissimus SSF for chops cooked with a BG. In Exp. 1 and 2, the longissimus was removed from the left side of each carcass (Exp. 1, n = 25; Exp. 2, n = 23) at 1 d postmortem and immediately frozen to maximize variation in tenderness. In Exp. 1, chops were cooked with either open-hearth electric broilers (OH) or BG, and WBSF was measured. Percentage of cooking loss was lower (P tenderness ratings was slightly stronger than the correlation of WBSF (r = -0.66; P tenderness ratings, indicating that the two methods had a similar ability to predict tenderness ratings. In Exp. 3, duplicate samples from 372 carcasses at 2 and 10 d postmortem were obtained, cooked with BG, and SSF was determined. The repeatability of SSF was 0.90, which is comparable to repeatability estimates for beef and lamb. Use of BG cookery and SSF could facilitate the collection of accurate pork longissimus tenderness data. Time and labor savings associated with BG cookery and the SSF technique should help to decrease research costs. PMID:14753367

Shackelford, S D; Wheeler, T L; Koohmaraie, M

2004-01-01

18

...131 0152] Actavis, Inc. a corporation, and Warner Chilott PLC; Analysis of Agreement Containing Consent Orders To Aid Public...from Actavis, Inc. (``Actavis'') and Warner Chilcott plc (``Warner Chilcott'') that is designed to remedy the...

2013-10-31

19

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

20

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 maciez 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 ess...

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

2010-01-01

21

Evaluation of slice shear force as an objective method of assessing beef longissimus tenderness.

Experiments were conducted to develop an optimal protocol for measurement of slice shear force (SSF) and to evaluate SSF as an objective method of assessing beef longissimus tenderness. Whereas six cylindrical, 1.27-cm-diameter cores are typically removed from each steak for Warner-Bratzler shear force (WBSF) determination, a single 1-cm-thick, 5-cm-long slice is removed from the lateral end of each longissimus steak for SSF. For either technique, samples are removed parallel to the muscle fiber orientation and sheared across the fibers. Whereas WBSF uses a V-shaped blade, SSF uses a flat blade with the same thickness (1.016 mm) and degree of bevel (half-round) on the shearing edge. In Exp. 1, longissimus steaks were acquired from 60 beef carcasses to determine the effects of belt grill cooking rate (very rapid vs. rapid) and conditions of SSF measurement (hot vs cold) on the relationship of SSF with trained sensory panel (TSP) tenderness rating. Slice shear force was more strongly correlated with TSP tenderness rating when SSF measurement was conducted immediately after cooking (r = -.74 to -.76) than when steaks were chilled (24 h, 4 degrees C) before SSF measurement (r = -.57 to -.72). When SSF measurement was conducted immediately after cooking, the relationship of SSF with TSP tenderness rating did not differ among the belt grill cooking protocols used to cook the SSF steak. In Exp. 2, longissimus steaks were acquired from 479 beef carcasses to compare the ability of SSF and WBSF of 1.27-cm-diameter cores to predict TSP tenderness ratings. Slice shear force was more strongly correlated with sensory panel tenderness rating than was WBSF (r = -.82 vs -.77). In Exp. 3, longissimus steaks were acquired from 110 beef carcasses to evaluate the repeatability (.91) of SSF over a broad range of tenderness. Slice shear force is a more rapid, more accurate, and technically less difficult technique than WBSF. Use of the SSF technique could facilitate the collection of more accurate data and should allow the detection of treatment differences with reduced numbers of observations and reduced time requirements, thereby reducing research costs. PMID:10521029

Shackelford, S D; Wheeler, T L; Koohmaraie, M

1999-10-01

22

...TA-W-74,489] Warner Chilcott Pharmaceuticals, Inc. Including On-Site Leased...applicable to workers of Warner Chilcott Pharmaceuticals, Inc., Norwich, New York. The...employment related to the supply of pharmaceutical research and development...

2010-10-15

23

Sylvia Ashton-Warner: Reclaiming Personal Meaning in Literacy Teaching.

Discusses the work of New Zealand educator and writer Sylvia Ashton-Warner. Describes her organic philosophy and how it is the basis for whole-language teaching; describes her Key Vocabulary method. Discusses adapting organic learning and whole language to upper-level literacy teaching. Discusses group inquiry learning and personalized teaching.…

Thompson, Nancy S.

2000-01-01

24

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish En este trabajo se describen e ilustran características morfológicas de Neochetina eichhorniae (Warner, 1970). Esta especie se ha utilizado para el control biológico del lirio acuático (Eichhornia crassipes (Mart.) Solms-Laubach, 1883). En el huevo, el aspecto cambiante del corion es dado por el des [...] arrollo embrionario. En la larva se realizó una descripción de la quetotaxia de la cápsula cefálica y se identificaron tres ínstares larvales con la medición de su anchura; también se revisó la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en tórax y abdomen, también se observaron dos tipos de espiráculos; el más característico es el espiráculo abdominal por su posición dorsal, que además de ser esclerosado, posee órganos sensoriales en su ápice. La morfología externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Además se proporciona una descripción de las alas, proventrículo y genitalia, estructuras importantes en la taxonomía. Las características morfológicas de N. eichhorniae encontradas en éste trabajo pueden ser útiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926), la cual ha sido liberada en muchos países. Es el primer trabajo de morfología N. eichhorniae en México. Abstract in english In this study morphological characteristics of Neochetina eichhorniae (Warner, 1970) are described and illustrated. This species has been used for the Biological Control of waterhyacinth (Eichhornia crassipes (Mart.) Solms-Laubach, 1883). In the egg, the changing appearance of the chorion is given b [...] y the embryonic development. Description of larval head capsule chaetotaxy was done. Three larval instars were identified by measuring the head capsule width; microsculpture of the body larva was studied, microspines were evident with different arrangements in thorax and abdomen, two types of spiracles were found; the more distinctive was the dorsal spiracle in the abdomen, which is sclerotized, with sensory organs at its apex. The external morphology of N. eichorniae adult is very similar in both sexes, the main difference among them is the rostrum. Description of the wings, proventriculus and genitalia, important structures in the taxonomy, is provided. The morphological characteristics of N. eichhorniae found in this study can be use to separate from N. bruchi (Hustache) which has been released in many countries. This is the first morphological study of N. eichhorniae in Mexico.

Oscar, Martínez-Morales; Edith G., Estrada-Venegas; Armando, Equihua-Martínez; Jorge, Valdez-Carrasco.

25

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

26

Near-infrared reflectance analysis for predicting beef longissimus tenderness.

Near-infrared reflectance spectra (1,100 to 2,498 nm) were collected on beef longissimus thoracis steaks for the purpose of establishing the feasibility of predicting meat tenderness by spectroscopy. Partial least squares (PLS) analysis (up to 20 factors) and multiple linear regression (MLR) were used to predict cooked longissimus Warner-Bratzler shear (WBS) force values from spectra of steaks from 119 beef carcasses. Modeling used the combination of log(1/R) and its second derivative. Overall, absorption was higher for extremely tough steaks than for tender steaks. This was particularly true at wavelengths between 1,100 and 1,350 nm. For PLS regression, optimal model conditions (R2 = .67; SEC = 1.2 kg) occurred with six PLS factors. When the PLS model was tested against the validation subset, similar performance was obtained (R2 = .63; SEP = 1.3 kg) and bias was small (predicted within 1.0, 2.0, and 3.0 kg, respectively, of the observed Warner-Bratzler shear force value. The optimal PLS model was able to predict whether a steak would have a Warner-Bratzler shear force value 6 kg) for Warner-Bratzler shear force. These data indicate that NIR is capable of predicting Warner-Bratzler shear force values of longissimus steaks. Refinement of this technique may allow nondestructive measurement of beef longissimus at the processing plant level. PMID:9734861

Park, B; Chen, Y R; Hruschka, W R; Shackelford, S D; Koohmaraie, M

1998-08-01

27

Semiclassical quantization of rotating strings in Pilch-Warner geometry

International Nuclear Information System (INIS)

Some of the recent important developments in understanding string/gauge dualities are based on the idea of the highly symmetric motion of 'string solitons' in the AdS5xS5 geometry originally suggested by Gubser, Klebanov, and Polyakov. In this paper we study the symmetric motion of certain string configurations in the so-called Pilch-Warner geometry. The two-form field A2 breaks down the supersymmetry to 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 AdSxS5. Although trivial at the classical level, the presence of the 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 the pp-wave limit

28

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

29

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

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[Federal Register Volume 77, Number...TA-W-80,275] Pfizer Therapeutic Research, Formerly Known as Warner Lambert Company, Pfizer Worldwide Research & Development Division, Antibacterials Research Unit, Pharmacokinetics,...

2012-06-12

31

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. 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 dpeosits in these areas may be about 40/sup 0/C per kilometer. Geothermometers and mixing models indicate that temperatures of equilibration are at least 170/sup 0/C for the thermal components of the hotter waters. The size and location of geothermal reservoirs are unknown.

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

1981-01-01

32

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

33

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

34

Universal principles for Kazdan-Warner and Pohozaev-Schoen type identities

The classical Pohozaev identity constrains potential solutions of certain semilinear PDE boundary value problems. The Kazdan-Warner identity is a similar necessary condition important for the Nirenberg problem of conformally prescribing scalar curvature on the sphere. For dimensions $n\\geq 3$ both identities are captured and extended by a single identity, due to Schoen in 1988. In each of the three cases the identity requires and involves an infinitesimal conformal symmetry. For structures with such a conformal vector field, we develop a very wide, and essentially complete, extension of this picture. Any conformally variational natural scalar invariant is shown to satisfy a Kazdan-Warner type identity, and a similar result holds for scalars that are the trace of a locally conserved 2-tensor. Scalars of the latter type are also seen to satisfy a Pohozaev-Schoen type identity on manifolds with boundary, and there are further extensions. These phenomena are explained and unified through the study of total and co...

Gover, A Rod

2010-01-01

35

Relationship between pre-slaughter stress responsiveness and beef quality in three cattle breeds.

The relationship between stress responsiveness and beef quality of 40 Nguni, 30 Bonsmara and 30 Angus steers was determined. The L(?) values, pHu, cooking loss (CL) and Warner-Bratzler shear force (WBSF) were determined. Catecholamine levels were determined from urine samples collected at slaughter. Bonsmara steers had the highest (PBonsmara, dopamine was correlated (Pbeef quality traits may not be similar in different breeds. PMID:20416575

Muchenje, V; Dzama, K; Chimonyo, M; Strydom, P E; Raats, J G

2009-04-01

36

Orange peel flour effect on physicochemical, textural and sensory properties of cooked sausages

Digital Repository Infrastructure Vision for European Research (DRIVER)

Orange peel flours as a source of fiber, protein, and flavonoids as antioxidants was added to meat batters in order to improve nutritional quality and physicochemical, textural and sensory properties. Orange peel flour in meat batters improved yield and reduced expressible moisture. Hardness in orange peel flour samples was higher, but less resilient and cohesive. Warner-Bratzler shear force was not different between control (no orange peel flour) and samples with this functional ingredient. ...

Sonia Hernandez Garcia; Norma Güemes Vera

2010-01-01

37

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

38

Directory of Open Access Journals (Sweden)

Full Text Available In order to incorporate the effect of gravity waves (GWs on the atmospheric circulation most global circulation models (GCMs employ gravity wave parameterization schemes. To date, GW parameterization schemes in GCMs are used without experimental validation of the set of global parameters assumed for the GW launch spectrum. This paper focuses on the Warner and McIntyre GW parameterization scheme. Ranges of parameters compatible with absolute values of gravity wave momentum flux (GW-MF derived from CRISTA-1 and CRISTA-2 satellite measurements are deduced for several of the parameters and the limitations of both model and measurements are discussed. The findings presented in this paper show that the initial guess of spectral parameters provided by Warner and McIntyre (2001 are some kind of compromise with respect to agreement of absolute values and agreement of the horizontal structures found in both measurements and model results. Better agreement can be achieved by using a vertical wavenumber launch spectrum with a wider saturated spectral range and reduced spectral power in the unsaturated part. Still, even global features of the measurements remain unmatched, and it is inevitable to provide a globally varying source distribution in future.

M. Ern

2006-06-01

39

Directory of Open Access Journals (Sweden)

Full Text Available In order to incorporate the effect of gravity waves (GWs on the atmospheric circulation most global circulation models (GCMs employ gravity wave parameterization schemes. To date, GW parameterization schemes in GCMs are used without experimental validation of the set of global parameters assumed for the GW launch spectrum. This paper focuses on the Warner and McIntyre GW parameterization scheme. Ranges of parameters compatible with absolute values of gravity wave momentum flux (GW-MF derived from CRISTA-1 and CRISTA-2 satellite measurements are deduced for several of the parameters and the limitations of both model and measurements are discussed. The findings presented in this paper show that the initial guess of spectral parameters provided by by Warner and McIntyre (2001 are some kind of compromise with respect to agreement of absolute values and agreement of the horizontal structures found in both measurements and model results. Better agreement can be achieved by using a vertical wavenumber launch spectrum with a wider saturated spectral range and reduced spectral power in the unsaturated part. However, even with this optimized set of global launch parameters not all features of the measurements are matched. This indicates that for further improvement spatial and seasonal variations of the launch parameters should be included in GW parameterization schemes.

M. Ern

2006-01-01

40

Application of exogenous enzymes to beef muscle of high and low-connective tissue.

Exogenous enzymes tenderize meat through proteolysis. Triceps brachii and Supraspinatus were randomly assigned to the seven enzyme treatments, papain, ficin, bromelain, homogenized fresh ginger, Bacillus subtilis protease, and two Aspergillus oryzae proteases or control to determine the extent of tenderization (Warner-Bratzler shear and sensory evaluation) and mode of action (myofibrillar or collagen degradation). Sensory evaluation showed improvement (Ptenderness and connective tissue component and all except ginger had a lower shear force than the control (Ppapain increased soluble collagen (Ptenderness via myofibrillar and collagenous protein degradation with no difference among high and low-connective tissue muscles. PMID:20416788

Sullivan, G A; Calkins, C R

2010-08-01

41

The objective of this study was to evaluate the effects of barley- or corn-based diets containing 0, 10, or 20% potato by-product (DM basis) on Warner-Bratzler shear force and palatability of beef. One hundred forty-four crossbred beef steers (333+/-.44 kg) were allotted within weight block (3) to a randomized complete block design with a 2 x 3 factorial arrangement of dietary treatments. Main effects were grain (barley or corn) and level of potato by-product (0, 10, or 20% of diet DM). There were a total of 18 pens with eight steers per pen and three pens per treatment. Steers were fed diets containing 83% concentrate (grain plus potato by-product), 10% supplement, and 7% alfalfa (DM basis) for an average of 130 d. Longissimus muscle cuts were used for Warner-Bratzler shear force determination (four steers per pen) and evaluation (two steers per pen) by a 10-member trained laboratory panel, a professional flavor/texture profile panel, and by consumer panels. Diet did not affect (P > .10) Warner-Bratzler shear force or trained laboratory panel tenderness, juiciness, and flavor intensity scores. Flavor/texture profile panel scores indicated feeding a corn-based diet as opposed to barley-based diet produced a more appropriate well-balanced and well-blended beef flavor and texture. However, the magnitudes of the differences were relatively small, and flavor and texture amplitude ratings for both barley- and corn-fed beef were well above average. Beef from steers fed 10 or 20% potato by-product had lower (P .05) by level of potato. Moreover, consumer panel overall acceptability scores were not affected by diet. Thus, feedlot diets containing corn or barley with or without potato by-product should result in palatable beef products. PMID:10907825

Busboom, J R; Nelson, M L; Jeremiah, L E; Duckett, S K; Cronrath, J D; Falen, L; Kuber, P S

2000-07-01

42

The present study demonstrates the effects of different muscle types and chiller ageing periods on the chemical composition, meat quality parameters, sensory characteristics and volatile compounds of Karean native cattle beed. Longissimus dorsi (LD) and Semitendinosus (ST) muscles aged for 7 days and 28 days were used. Moisture, cooking loss, total collagen and Warner-Bratzler shear force (WBSF) values for the ST were higher than the LD muscle regardless of ageing period (P?important volatile compounds were decreased. These results clearly demonstrate that muscle type and ageing have a potential effect on meat quality, sensory characteristics and volatile profile. PMID:23911040

Ba, Hoa Van; Park, KyoungMi; Dashmaa, Dashdorj; Hwang, Inho

2014-02-01

43

From May 2006 to August 2007, the U.S. Geological Survey (USGS) collected 793 gravity stations, about 102 line-kilometers of truck-towed and ground magnetometer data, and about 325 physical-property measurements in northeastern California, northwestern Nevada, and southern Oregon. Gravity, magnetic, and physical-property data were collected to study regional crustal structures and geology as an aid to understanding the geologic framework of the Surprise Valley geothermal area and, in general, geothermal systems throughout the Great Basin. The Warner Mountains and Surprise Valley mark the transition from the extended Basin and Range province to the unextended Modoc Plateau. This transition zone, in the northwestern corner of the Basin and Range, is relatively diffuse compared to other, more distinct boundaries, such as the Wasatch front in Utah and the eastern Sierran range front. In addition, this transition zone is the site of a geothermal system with potential for development, and previous studies have revealed a complex structural setting consisting of several obliquely oriented fault sets. As a result, this region has been the subject of several recent geological and geophysical investigations. The gravity and magnetic data presented here support and supplement those studies, and although the study area is composed predominantly of Tertiary volcanic rocks of the Modoc Plateau rocks, the physical properties of these and others rocks create a distinguishable pattern of gravity and magnetic anomalies that can be used to infer subsurface geologic structure.

Ponce, David A.; Glen, Jonathan M.G.; Egger, Anne E.; Bouligand, Claire; Watt, Janet T.; Morin, Robert L.

2009-01-01

44

Energy Technology Data Exchange (ETDEWEB)

Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.

Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr. /Northwestern U.; Shapiro, Charles; /Chicago U. /KICP, Chicago; White, Martin J.; /UC, Berkeley, Astron.

2005-08-01

45

International Nuclear Information System (INIS)

The Fe II oscillator strengths of Warner have previously been shown to contain a systematic error, the size of which depends upon the energy of the upper level of the transition. The present paper shows that this error should affect all of the oscillator strengths of Warner for the second spectra of the iron group. A correction formula for the results of Warner is developed and the corrected f-values are compared with other measured data for Ti II, V II and Fe II. The comparisons show that the correction improves the usefulness of Warner's results and that the corrected f-values contain no large systematic dependence on wavelength, upper or lower level energy, or line strength. Solar abundances calculated using the original and the corrected Warner f-values are compared with currently recommended abundances for the iron group elements. The corrected f-values provide more consistent results. The semi-empirical oscillator strength data of Kurucz and Peytremann for Fe I, Ti II and V II are also compared with measured data in order to assess the accuracy of these calculations. The absolute scale of the calculated f-values is roughly correct but a small fraction of the data are subject to errors of a factor of 10 or more. (author)

46

We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.

Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.

2009-01-01

47

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

48

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

49

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

50

It has already been shown that the Fe II absolute oscillator strengths (f-values) measured by Warner (1967) contain a systematic error, the magnitude of which depends on the energy of the transition's upper level. The present paper demonstrates that this error affects all of Warner's oscillator strengths for the second spectra of the iron group and develops a correction formula for Warner's results. A comparison of the corrected f-values with other measured f-values for Ti II, V II, and Fe II indicates that the correction improves the usefulness of Warner's data and that the corrected f-values have no large systematic dependence on wavelength, level energy, or line strength. Solar abundances for iron-group elements computed using the original and corrected f-values are compared with recently suggested abundances, and it is found that the corrected f-values yield more consistent results. Semiempirical oscillator strengths calculated by Kurucz and Peytremann (1975) for Fe I, Ti II, and V II are also compared with measured data to evaluate the accuracy of the calculations. It is found that the absolute scales of these results are roughly correct, but some of them are subject to very large errors.

Smith, P. L.

1976-01-01

51

The results of both an experimental test program and a finite element analysis of selected graphite/polyimide rail shear test specimens are discussed. The two dimensional finite element analysis includes both mechanical and thermal loading (differential expansion) of the specimens and their elastic rails. Parameters in this analysis of unidirectional and symmetric, balanced angle-ply laminates include ply layup angles, the effect of flexible rails, the method of load introduction to the specimen and the effect of uniform heating of the specimen and rails. Two types of tensile rail shear fixtures were investigated experimentally: a uniform thickness, bolted-rail shear fixture loaded diagonally across the specimen test section; and a tapered thickness, bonded-rail shear fixture loaded axially along the center-line of the specimen test section. Test results include room-temperature and 589K strain data taken from the center of the specimen test section during loading.

Garcia, R.; Mcwithey, R. R.

1979-01-01

52

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

53

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

Lindon W, Mamani-Linares; Carmen, Gallo.

54

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

Lindon W, Mamani-Linares; Carmen, Gallo.

2011-12-01

55

Shear Stress and Atherosclerosis

Hemodynamic shear stress, the frictional force acting on vascular endothelial cells, is crucial for endothelial homeostasis under normal physiological conditions. When discussing blood flow effects on various forms of endothelial (dys)function, one considers two flow patterns: steady laminar flow and disturbed flow because endothelial cells respond differently to these flow types both in vivo and in vitro. Laminar flow which exerts steady laminar shear stress is atheroprotective while disturbed flow creates an atheroprone environment. Emerging evidence has provided new insights into the cellular mechanisms of flow-dependent regulation of vascular function that leads to cardiovascular events such as atherosclerosis, atherothrombosis, and myocardial infarction. In order to study effects of shear stress and different types of flow, various models have been used. In this review, we will summarize our current views on how disturbed flow-mediated signaling pathways are involved in the development of atherosclerosis. PMID:24781409

Heo, Kyung-Sun; Fujiwara, Keigi; Abe, Jun-ichi

2014-01-01

56

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 <1 part in 103 accuracy as well as providing accurate uncertainty estimates. BFD is the first shear measurement algorithm that is model free and requires no approximations or ad hoc assumptions in correcting for the effects of PSF, noise, or sampling on the galaxy images. These algorithms are good candidates for attaining the part-per-thousand shear inference required for hemisphere-scale weak gravitational lensing surveys. BMF has the 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

57

Shear consolidation of powders

The manufacture of bulk parts from metastable powder materials requires new approaches to cold consolidation. One potential technique is equal-channel angular extrusion (ECAE), a simple shear process. This thesis describes an investigation into the effects of confining pressure (back-pressure) on single-pass, right-angled ECAE consolidation of copper and aluminum 6061 powders below 250°C, using an extrusion machine designed and constructed for this purpose. Empirical relationships for punch pressure requirements as a function of back-pressure and billet length are determined experimentally and compared with published theory. Powder particle boundaries are examined in extruded billets, revealing pores and regions of localized shear formed under low back-pressure conditions. This shear localization is considered with a visualization experiment involving wax spheres in a transparent die, and a linear stability analysis of simple shear of a thin strip of material described by a generalized powder yield function and flow rule. The back-pressures required to obtain homogeneous, pore-free microstructures are determined, and related to the response of the powders during the initial compaction stage of ECAE. Interparticle bond formation in cold powder processing is briefly discussed in the context of multi-pass extrusions.

Hanna, James A.

58

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.

59

Shelf-life and Microbiological Profiler of Chicken Wing Products Following Sous vide Treatment

Directory of Open Access Journals (Sweden)

Full Text Available Chicken wings were vacuum-packaged and cooked (sous vide at 75 and 90°C until the internal temperature reached 73.8°C was reached. The cooked samples were stored at 2 and 7°C, separately. The TBA values, aerobic plate count, aerobic and anaerobic plate counts and Warner-Bratzler (WB shear force of the samples were evaluated weekly for 7 wk. The sous vide treatment chicken wings had lower TBA values, aerobic and anaerobic plate counts throughout the 7 wk of storage when compared with the control. The sous vide treatment did not affect the WB shear force of chicken wings. At 2°C, the sous vide cooked chicken wings had a shelf life of at least 7 wk. Results demonstrate that sous vide treatment was an effective method to prevent lipid oxidation during storage and enhance shelf life of chicken wing products.

S.H. Wang

2004-01-01

60

Energy Technology Data Exchange (ETDEWEB)

An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.

Butler, B.D.; Hanley, H.J.M.; Straty, G.C. [National Institute of Standards and Technology, Boulder, CO (United States); Muzny, C.D. [Univ. of Colorado, Boulder, CO (United States)

1995-12-31

61

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

62

The objective of this study was to identify quantitative trait loci for economically important traits in two families segregating an inactive copy of the myostatin gene. Two half-sib families were developed from a Belgian Blue x MARC III (n = 246) and a Piedmontese x Angus (n = 209) sire. Traits analyzed were birth, weaning, and yearling weight (kg); preweaning average daily gain (kg/d); postweaning average daily gain (kg/d); hot carcass weight (kg); fat depth (cm); marbling score; longissimus muscle area (cm2); estimated kidney, pelvic, and heart fat (%); USDA yield grade; retail product yield (%); fat yield (%); and wholesale rib-fat yield (%). Meat tenderness was measured as Warner-Bratzler shear force at 3 and 14 d postmortem. The effect of the myostatin gene was removed using phase information from six microsatellite markers flanking the locus. Interactions of the myostatin gene with other loci throughout the genome were also evaluated: The objective was to use markers in each family, scanning the genome approximately every 25 to 30 centimorgans (cM) on 18 autosomal chromosomes, excluding 11 autosomal chromosomes previously analyzed. A total of 89 markers, informative in both families, were used to identify genomic regions potentially associated with each trait. In the family of Belgian Blue inheritance, a significant QTL (expected number of false-positives = 0.025) was identified for marbling score on chromosome 3. Suggestive QTL for the same family (expected number of false-positives = 0.5) were identified for retail product yield on chromosome 3, for hot carcass weight and postweaning average daily gain on chromosome 4, for fat depth and marbling score on chromosome 8, for 14-d Warner-Bratzler shear force on chromosome 9, and for marbling score on chromosome 10. Evidence suggesting the presence of an interaction for 3-d Warner-Bratzler shear force between the myostatin gene and a QTL on chromosome 4 was detected. In the family of Piedmontese and Angus inheritance, evidence indicates the presence of an interaction for fat depth between the myostatin gene and chromosome 8, in a similar position where the evidence suggests the presence of a QTL for fat depth in the family with Belgian Blue inheritance. Regions identified underlying QTL need to be assessed in other populations. Although the myostatin gene has a considerable effect, other loci with more subtle effects are involved in the expression of the phenotype. PMID:11325189

Casas, E; Stone, R T; Keele, J W; Shackelford, S D; Kappes, S M; Koohmaraie, M

2001-04-01

63

The effects of the bovine myostatin gene on chromosome 2 on birth and carcass traits have been previously assessed. The objective of this study was to identify additional quantitative trait loci (QTL) for economically important traits in two families segregating an inactive copy of myostatin. Two half-sib families were developed from Belgian Blue x MARC III (n = 246) and Piedmontese x Angus (n = 209) sires. Traits analyzed were birth (kg) and yearling weight (kg); hot carcass weight (kg); fat depth (cm); marbling score; longissimus muscle area (cm2); estimated kidney, pelvic, and heart fat (%); USDA yield grade; retail product yield (%); fat yield (%); and wholesale rib-fat yield (%). Meat tenderness was measured as Warner-Bratzler shear force at 3 and 14 d postmortem. The effect of myostatin on these traits was removed by using phase information obtained from the previous study with six microsatellite markers flanking the locus. Selective genotyping was done on 92 animals from both families to identify genomic regions potentially associated with retail product yield and fat depth, using a total of 150 informative markers in each family. Regions in which selective genotyping indicated the presence of QTL were evaluated further by genotyping the entire population and additional markers. For the family with Belgian Blue inheritance (n = 246), a significant QTL for birth and yearling weight was identified on chromosome 6. Suggestive QTL were identified for longissimus muscle area and hot carcass weight on chromosome 6 and for marbling on chromosomes 17 and 27. For the family with Piedmontese inheritance (n = 209), suggestive QTL on chromosome 5 were identified for fat depth, retail product yield, and USDA yield grade and on chromosome 29 for Warner-Bratzler shear force at 3 and 14 d postmortem. Interactions suggesting the presence of QTL were observed between myostatin and chromosome 5 for Warner-Bratzler shear force at 14 d postmortem and between myostatin and chromosome 14 for fat depth. Thus, in families segregating an inactive copy of myostatin in cattle, other loci influencing quantitative traits can be detected. These results are the initial effort to identify and characterize QTL affecting carcass and growth traits in families segregating myostatin. PMID:10764062

Casas, E; Shackelford, S D; Keele, J W; Stone, R T; Kappes, S M; Koohmaraie, M

2000-03-01

64

Shear Profiles and Velocity Distribution in Dense Shear Granular Flow

International Nuclear Information System (INIS)

We perform DEM simulations to investigate the influence of the packing fraction ? on the shape of mean tangential velocity profile in a 2D annular dense shear granular flow. There is a critical packing fraction ?c. For ? c, the mean tangential velocity profile shows a roughly exponential decay from the shearing boundary and is almost invariant to the imposed shear rate. However, for ? > ?c, the tangential velocity profile exhibits a rate-dependence feature and changes from linear to nonlinear gradually with the increasing shear rate. Furthermore, the distributions of normalized tangential velocities at different positions along radial direction exhibit the Gaussian or the composite Gaussian distributing features

65

ADIABATIC SHEAR IN POROUS MEDIA

Digital Repository Infrastructure Vision for European Research (DRIVER)

An advanced model of shear deformation occuring in high strain rate deformation of ductile porous solids is proposed under simple planar shear loading superposed by hydrostatic pressure. To describe porous - rigid thermoplastic material the Gurson theory of dilatant plasticity is applied and appearance of an adiabatic shear is interpreted in terms of mathematical instabilities in the underlying differential equations. The substantial influence of porosity on strain hardening and thermal softe...

Kotoul, M.; Bi?lek, Z.

1988-01-01

66

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 sbar , its standard deviation ?, and a simple mathematical transform of the probability density function P(s) of the shear rate itself.

Stefanus, S.; Steers, S.; Goldburg, W. I.

2011-11-01

67

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

68

Shear behaviour of ferrocement plates

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. Th...

Savale, Madhuri N.; Alandkar, Prof P. M.

2013-01-01

69

Magnetorheological dampers in shear mode

In this study, three types of shear mode damper using magnetorheological (MR) fluids are theoretically analyzed: linear, rotary drum, and rotary disk dampers. The damping performance of these shear mode MR dampers is characterized in terms of the damping coefficient, which is the ratio of the equivalent viscous damping at field-on status to the damping at field-off status. For these three types of shear mode MR damper, the damping coefficient or dynamic range is derived using three different constitutive models: the Bingham-plastic, biviscous, and Herschel-Bulkley models. The impact of constitutive behavior on shear mode MR dampers is theoretically presented and compared.

Wereley, N. M.; Cho, J. U.; Choi, Y. T.; Choi, S. B.

2008-02-01

70

Magnetorheological dampers in shear mode

International Nuclear Information System (INIS)

In this study, three types of shear mode damper using magnetorheological (MR) fluids are theoretically analyzed: linear, rotary drum, and rotary disk dampers. The damping performance of these shear mode MR dampers is characterized in terms of the damping coefficient, which is the ratio of the equivalent viscous damping at field-on status to the damping at field-off status. For these three types of shear mode MR damper, the damping coefficient or dynamic range is derived using three different constitutive models: the Bingham–plastic, biviscous, and Herschel–Bulkley models. The impact of constitutive behavior on shear mode MR dampers is theoretically presented and compared

71

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

72

Scaling of Entropic Shear Rigidity

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2004-01-01

73

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.

2012-09-01

74

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.

75

Textural properties of chicken breast treated by different means

Directory of Open Access Journals (Sweden)

Full Text Available Normal 0 false false false CS JA X-NONE The aim of the study was to compare textural atributes of cooked chicken breast samples subjected to different storage or preparation conditions (raw meat after cooking, raw meat after freezing/subsequent thawing, after storage under modified – controlled conditions using instrumental analysis. For this purpose, samples were subjected to texture testing by the use of Warner-Bratzler probe, to find changes in muscle hardness by determination of firmness and work of shear. As expected, various values of mentioned atributes were obtained for tested samples treated by three different ways. For statistical evaluation of the results, macro function of Exponent software and paired T test were used, statistically significant differences were taken at p <0.05. In conclussion, different forces were needed for cutting of tested samples, subjected to selected storage conditions, prior to cooking. Normal 0 false false false CS JA X-NONE

Jozef ?urlej

2013-07-01

76

Hydrodynamic pressure processing (HDP) or shockwave treatment improved tenderness (18% reduction in Warner-Bratzler shear force (WBSF) of beef loin steaks. Endogenous muscle proteolyic activities (cathepsins and peptidases) and protein fragmentation of sarcoplasmic and myofibrillar proteins detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were not influenced by HDP. However, microstructure changes were clearly detected using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Specifically a disruption of the structure at the muscle fiber bundles and an increased endomysium space were observed. The present paper supports the evidence of physical disruption of the muscle fibers as a cause behind the tenderness improvement. The paper discusses the possible mechanisms responsible for the meat tenderisation induced by HDP treatment. PMID:25117876

Bolumar, Tomas; Bindrich, Utte; Toepfl, Stefan; Toldrá, Fidel; Heinz, Volker

2014-12-01

77

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

78

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

79

The influence of dietary lecithin at doses of 0, 4, 20 or 80 g/kg fed to finisher gilts for six weeks prior to slaughter on growth performance, carcass quality and pork quality was investigated. M. longissimus lumborum (loin) was removed from 36 pig carcasses at 24h post-mortem for Warner-Bratzler shear force, compression, collagen content and colour analyses. Dietary lecithin increased dressing percentage (P=0.009). Pork chewiness and collagen content were decreased by dietary lecithin (Pcohesiveness or hardness (P>0.05, respectively). Dietary lecithin reduced loin muscle L* values and increased a* values (P<0.05, respectively) but no changes on b* values (P=0.56). The data showed that dietary lecithin improved dressing percentage and resulted in less chewy and less pale pork. PMID:24334033

Akit, H; Collins, C L; Fahri, F T; Hung, A T; D'Souza, D N; Leury, B J; Dunshea, F R

2014-03-01

80

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

81

Shear band regularization with peridynamics

An extreme form of strain localization, known as shear-banding, is an important phenomenon in many engineering applications and processes especially in high strain-rate settings such as those encountered in ballistic impact. Concrete knowledge and robust computational tools for simulation of shear localization will help to predict these failure modes and optimize designs. It is well known that classical finite-element simulations of shear-banding can produce extremely mesh dependent results. Peridynamics, a non-local theory, is applied in this research to resolve this problem. Peridynamic simulations are compared to finite-element simulation results and show a regularization effect on the strain-localization.

Khan, Md. Imran Hossain

82

Localized states in sheared electroconvection

Electroconvection in a thin, sheared fluid film displays a rich sequence of bifurcations between different flow states as the driving voltage is increased. We present a numerical study of an annular film in which a radial potential difference acts on induced surface charges to drive convection. The film is also sheared by independently rotating the inner edge of the annulus. This simulation models laboratory experiments on electroconvection in sheared smectic liquid crystal films. The applied shear competes with the electrical forces, resulting in oscillatory and strongly subcritical bifurcations between localized vortex states close to onset. At higher forcing, the flow becomes chaotic via a Ruelle-Takens-Newhouse scenario. The simulation allows flow visualization not available in the physical experiments, and sheds light on previously observed transitions in the current-voltage characteristics of electroconvecting smectic films.

Tsai, Peichun; Daya, Zahir A

2008-01-01

83

A QTL affecting leg muscle and fat traits has been identified within the New Zealand Texel population. The QTL maps to a region on OAR 2 with a two-marker haplotype test established at markers BULGE20 and BM81124. These markers encompass the likely position of Growth Differentiation Factor 8 (GDF8). The pleiotropic effects of this QTL on meat quality traits are tested. Objective measures of meat quality including pH, color (L*, a*, and b*), and tenderness (as assessed by Warner-Bratzler shear force measurements) were assessed on longissimus and semi-membranosus muscles of 540 progeny from six Texel sires. Four of these sires were subsequently identified as segregating for leg muscle and fat traits. For these segregating sires, comparison of progeny that had inherited the favorable haplotype from their sire with those that had received the alternate haplotype revealed no significant differences in the meat quality traits assessed. This finding suggests that the muscling QTL does not have pleiotropic effects on meat quality. A general scan for meat quality QTL was carried out using genotype data for eight markers from FCB128 to RM356 flanking 122cM of OAR 2 using Haley-Knott regression. This analysis revealed two QTL for a single sire. A QTL detected in the region of Marker INRA40 for color L* mapped to a site close to the muscling QTL, but there was evidence to suggest it is at a distinct locus. The QTL in the region of Marker RM356 might map distal to Marker RM356, as no peak was observed. This QTL, which seems to affect pH, color a*, color b*, and Warner-Bratzler shear measurements, requires further characterization. PMID:16282610

Johnson, P L; McEwan, J C; Dodds, K G; Purchas, R W; Blair, H T

2005-12-01

84

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

85

Equilibrium Flow Shear and Magnetic Shear Effect on Zonal Flow

International Nuclear Information System (INIS)

Full text: A global transport simulation on ion temperature gradient driven drift wave (ITG) turbulence is performed by using electrostatic gyro-fluid code. The collapse mechanism of internal transport barrier (ITB) is investigated systematically focused on the de-correlation effect of the toroidal mode coupling in qmin region by flow shear which is induced by toroidal momentum source and radial electric field source, and zonal flow (ZF). A heat source is introduced into the model and temporal evolutions of the temperature profile and the ITG turbulence is studied simultaneously in a reversed magnetic shear configuration. In the first case, the off-resonant modes below the qmin region are not taken into account in the simulation, where a internal transport barrier like structure is formed around qmin position. It is found that steady ZF is generated at the edge of rational surfaces of the toroidally coupled ITG modes. The dependence of safety factor profile on the ZF is also studied. Reversed magnetic shear profiles with the same qmin value but different magnetic shear in the core region are examined. For relatively weak magnetic shear cases, the increase of the ZF around qmin region is observed intermittently. Especially, the ZF for the case with the weakest magnetic shear exhibits periodic oscillation. For rather strong magnetic shear case, such intermittent growth of ZF is not observed, in other words, the geod is not observed, in other words, the geodesic acoustic mode (GAM) oscillation is weak. However, the ZF is not so strong to quench the transport completely and the strong barrier formation is not observed for both cases. In the next, the toroidal momentum source and the radial electric field source are introduced into the model independently. The effects of flow shear by these sources on the evolution of the energy propagation in spatial and wave number spaces are examined. It is found that the toroidal flow shear is not so effective for both suppression of ITG mode and toroidal coupling in the radial direction. On the other hand, it is found that E x B flow shear induced by the electric field source locates around qmin region suppresses a meso-scale structure around qmin and contributes to the sustainment of ITB. The effect of off-resonance modes on turbulence suppression will be also discussed, which is now undergoing. (author)

86

Shear strength of granular materials

Digital Repository Infrastructure Vision for European Research (DRIVER)

The shear strength properties of granular materials re?ect their inherent force and fabric anisotropy. We analyze the role of fabric and force anisotropies with respect to the critical-state shear strength. Then, a model of accessible geometrical states in terms of particle connectivity and contact anisotropy is presented. This model incorporates in a simple way the fact that, due to steric exclusions, the highest levels of connectivity and anisotropy cannot be reached simultaneously, a pro...

Radjai, Farhang; Aze?ma, Emilien

2009-01-01

87

Fatigue strength of shear connectors

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nowadays steel and concrete composite beams are widely applied in structures mainly subjected to dynamic loads, such as railway and road bridges exposed to traffic loads and industrial crane runways exposed to folk-lift truck loads, the fatigue resistance of these structures must be generally and carefully verified. And normally the shear forces between concrete flange and steel beams are all transferred by different kinds of shear connectors, fatigue failure of composite beam may happen on s...

Xie, En; Valente, Isabel

2011-01-01

88

Shear behaviour of ferrocement plates

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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

89

Shear behaviour of reinforced phyllite concrete beams

International Nuclear Information System (INIS)

Highlights: ? Phyllite concrete beams often exhibited shear with anchorage bond failure. ? Different shear design provisions for reinforced phyllite beams are compared. ? Predicted shear capacity of phyllite beams must be modified by a reduction factor. -- Abstract: The shear behaviour of concrete beams made from phyllite aggregates subjected to monotonic and cyclic loading is reported. First diagonal shear crack load of beams with and without shear reinforcement was between 42–58% and 42–92% of the failure loads respectively. The phyllite concrete beams without shear links had lower post-diagonal cracking shear resistance compared to corresponding phyllite beams with shear links. As a result of hysteretic energy dissipation, limited cyclic loading affected the stiffness, strength and deformation of the phyllite beams with shear reinforcement. Generally, beams with and without shear reinforcement showed anchorage bond failure in addition to the shear failure due to high stress concentration near the supports. The ACI, BS and EC codes are conservative for the prediction of phyllite concrete beams without shear reinforcement but they all overestimate the shear strength of phyllite concrete beams with shear reinforcement. It is recommended that the predicted shear capacity of phyllite beams reinforced with steel stirrups be modified by a reduction factor of 0.7 in order to specify a high enough safety factor on their ultimate strength. It is also recommended that susceptibility of phyllite concrete beams to undergo anchorage bond failure is averted in design by the provision of greater anchorage lengths than usually permitted.

90

Biological aerosol warner and analyser

The development of an integrated sensor device BiSAM (Biological Sampling and Analysing Module) is presented which is designed for rapid detection of aerosol or dust particles potentially loaded with biological warfare agents. All functional steps from aerosol collection via immuno analysis to display of results are fully automated. The core component of the sensor device is an ultra sensitive rapid analyser PBA (Portable Benchtop Analyser) based on a 3 dimensional immuno filtration column of large internal area, Poly HRP marker technology and kinetic optical detection. High sensitivity despite of the short measuring time, high chemical stability of the micro column and robustness against interferents make the PBA an ideal tool for fielded sensor devices. It is especially favourable to combine the PBA with a bio collector because virtually no sample preparation is necessary. Overall, the BiSAM device is capable to detect and identify living micro organisms (bacteria, spores, viruses) as well as toxins in a measuring cycle of typically half an hour duration. In each batch up to 12 different tests can be run in parallel together with positive and negative controls to keep the false alarm rate low.

Schlemmer, Harry; Kürbitz, Gunther; Miethe, Peter; Spieweck, Michael

2006-05-01

91

GPU-based shear-shear correlation calculation

Light rays are deflected when travelling through a gravitational potential: this phenomenon is known as gravitational lensing. It causes the observed shapes of distant galaxies to be very slightly distorted by the intervening matter in the Universe, as their light travels towards us. This distortion is called cosmic shear. By measuring this component it is possible to derive the properties of the mass distribution causing the distortion. This in turn can lead to the measurement of the accelerated expansion of the Universe, as matter clumps together differently depending on its dynamics at each cosmological epoch. The measurement of the cosmic shear requires the statistical analysis of the ellipticities of millions of galaxies using very large astronomical surveys. In the past, due to the computational cost of the problem, this kind of analysis was performed by introducing simplifications in the estimation of such statistics. With the advent of scientific computing using graphics processing units, analysis of the shear can be addressed without approximations, even for very large surveys, while maintaining an affordable execution time. In this work, we present the creation and optimization of such a graphics processing unit code to compute the so-called shear-shear correlation function.

Cárdenas-Montes, Miguel; Vega-Rodríguez, Miguel A.; Bonnett, Christopher; Sevilla-Noarbe, Ignacio; Ponce, Rafael; Sánchez Alvaro, Eusebio; Rodríguez-Vázquez, Juan José

2014-01-01

92

Shear history independence in colloidal aggregation.

Stimulated by experiments, we have carried out detailed simulations of aggregation in the presence of shear in a model colloidal system with a short-range attractive potential. For weak shear rates, we find that the shear enhanced the aggregation and that the long-time state of the system is independent of the shear history. For strong shear rates, precipitous fragmentation occurred after the shear was turned on and, after an induction period, the aggregation quickly rebounded in a stochastic manner similar to classical nucleation phenomena. However, the long-time state of the system is, once again, independent of the shear history. Thus, for both weak and strong shear cases, the shear rate acts as a state variable of the aggregating system. Shear rates employed in the simulations can be attained in laboratory experiments, as confirmed by computing the dimensionless Péclet numbers. PMID:22794190

Heinson, William R; Sorensen, Christopher M; Chakrabarti, Amitabha

2012-08-01

93

Nonlinear water waves with shear

Various aspects of nonlinear inviscid gravity waves in the presence of shear in the air and water are investigated. The shear, which appears due to the presence of wind in the air and current in the water, is modeled by a piecewise linear velocity profile. The interaction of short and long gravity waves is studied numerically, using spectral methods, and analytically, using perturbation methods. Special attention is paid to the verification of observations and experimental results. It is confirmed that finite amplitude waves propagating in the same direction as the wind or current are more stable with respect to superharmonic infinitesimal perturbations than the waves moving against the wind or current. Infinitesimal perturbations in the form of side bands are also investigated both numerically and analytically. The nonlinear cubic Schrodinger equation for the wave envelope of a slowly varying wave train is derived. It is shown that depending on the direction of propagation (along or against the shear) of the finite amplitude waves, the effect of the shear on the stability is substantially different. In most cases, however, the shear strength increase first enhances the instability, but later suppresses it. Three-wave interactions of gravity waves with shear in the water are considered. The interaction equations are derived with the help of two different perturbation approaches. The question of stability is addressed for both resonant and near-resonant interactions. The regions of explosive and 'pump-wave' instability are identified for various types of three-wave interactions. A new type of steady two-dimensional gravity waves with water shear is computed numerically. These waves appear at relatively low amplitudes and lack symmetry with respect to any crest or trough. A boundary integral formulation is used to obtain a one-parameter family of non-symmetric solutions through a symmetry-breaking bifurcation.

Baumstein, Anatoly I.

94

Isogeometric analysis of shear bands

Numerical modeling of shear bands present several challenges, primarily due to strain softening, strong nonlinear multiphysics coupling, and steep solution gradients with fine solution features. In general it is not known a priori where a shear band will form or propagate, thus adaptive refinement is sometimes necessary to increase the resolution near the band. In this work we explore the use of isogeometric analysis for shear band problems by constructing and testing several combinations of NURBS elements for a mixed finite element shear band formulation. Owing to the higher order continuity of the NURBS basis, fine solution features such as shear bands can be resolved accurately and efficiently without adaptive refinement. The results are compared to a mixed element formulation with linear functions for displacement and temperature and Pian-Sumihara shape functions for stress. We find that an element based on high order NURBS functions for displacement, temperature and stress, combined with gauss point sampling of the plastic strain leads to attractive results in terms of rate of convergence, accuracy and cpu time. This element is implemented with a -bar strain projection method and is shown to be nearly locking free.

Berger-Vergiat, Luc; McAuliffe, Colin; Waisman, Haim

2014-08-01

95

Colloidal glasses under shear strain

We have studied the effects of oscillatory shear strain on the structure of a colloidal hard-sphere glass. By light scattering, we measure the kinetic development of ordered structures induced by shearing between parallel plates. Diffusing wave spectroscopy ``echo'' experiments show that for peak to peak oscillatory strain below around 30% the colloidal glass strains approximately reversibly. At higher strains a partly ordered structure develops, the kinetics of the ordering being strongly dependent on strain. Kinetic measurements demonstrate an ``induction'' time for crystallization with a divergentlike behavior as strain decreases toward ~25-30 %. We compare the behavior of glassy samples with that of samples at lower volume fraction, where in equilibrium without shear the sample is fully (poly)crystalline. At the lower volume fraction, irreversible yielding is observed at lower strains. There appears some tendency for very high volume fraction glass samples to ``fracture.'' Similar evidence of fracture is not observed at the lower volume fractions.

Haw, M. D.; Poon, W. C. K.; Pusey, P. N.; Hebraud, P.; Lequeux, F.

1998-10-01

96

FEM Simulation of Incremental Shear

International Nuclear Information System (INIS)

A popular way of producing ultrafine grained metals on a laboratory scale is severe plastic deformation. This paper introduces a new severe plastic deformation process of incremental shear. A finite element method simulation is carried out for various tool geometries and process kinematics. It has been established that for the successful realisation of the process the inner radius of the channel as well as the feeding increment should be approximately 30% of the billet thickness. The angle at which the reciprocating die works the material can be 30 deg. . When compared to equal channel angular pressing, incremental shear shows basic similarities in the mode of material flow and a few technological advantages which make it an attractive alternative to the known severe plastic deformation processes. The most promising characteristic of incremental shear is the possibility of processing very long billets in a continuous way which makes the process more industrially relevant

97

High shear rate characterization of magnetorheological fluids

Shear mode or rotary drum-type magnetorheological energy absorbers (MREAS) are an attractive option for use in occupant or payload protection systems that operate at shear rates well over 25,000 s-1. However, their design is still performed using material properties measured using low-shear rate (<1,000 s-1) characterization techniques. This paper details a method for characterizing MR fluids at high shear rates, and presents characterization results for three commercially available MR fluids. It is proposed to utilize the perspective of apparent viscosity (the ratio of shear stress over shear rate) vs. shear rate to describe the behavior of the fluid at these shear rates. Good agreement between the measured data and predictions of MR fluid behavior are achieved using this framework. By expanding the knowledge of MR fluid behavior to these high shear strain rates, the design of MREAs is enabled for occupant protection systems for crash and mine blast events.

Becnel, Andrew C.; Hu, Wei; Wereley, Norman M.

2012-04-01

98

Fluid depletion in shear bands

How does pore liquid reconfigure within shear bands in wet granular media? Conventional wisdom predicts that liquid is drawn into dilating granular media. We, however, find a depletion of liquid in shear bands despite increased porosity due to dilatancy. This apparent paradox is resolved by a microscale model for liquid transport at low liquid contents induced by rupture and reconfiguration of individual liquid bridges. Measured liquid content profiles show macroscopic depletion bands similar to results of numerical simulations. We derive a modified diffusion description for rupture-induced liquid migration.

Mani, Roman; Or, Dani; Herrmann, Hans J

2012-01-01

99

Noise Correlations in Shear Flows

We consider the effects of a shear on velocity fluctuations in a flow. The shear gives rise to a transient amplification that not only influences the amplitude of perturbations but also their time correlations. We show that, in the presence of white noise, time correlations of transversal velocity components are exponential and that correlations of the longitudinal components are exponential with an algebraic prefactor. Cross correlations between transversal and downstream components are strongly asymmetric and provide a clear indication of non-normal amplification. We suggest experimental tests of our predictions.

Eckhardt, B; Eckhardt, Bruno; Pandit, Rahul

2003-01-01

100

There are contradictory published data on the behavior of fluid slip at high shear rates. Using three methodologies (molecular dynamics simulations, an analytical theory of slip, and a Navier-Stokes-based calculation) covering a range of fluids (bead-spring liquids, polymer solutions, and ideal gas flows) we show that as shear rate increases, the amount of slip, as measured by the slip length, asymptotes to a constant value. The results clarify the molecular mechanics of how slip occurs. Furthermore, they indicate that in this limit, molecular dynamics simulations must accurately account for heat transfer to the solid.

Martini, Ashlie; Hsu, Hua-Yi; Patankar, Neelesh A.; Lichter, Seth

2008-05-01

101

Unexpected shear strength change in magnetorheological fluids

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Full Text Available Smart materials of magnetorheological (MR fluids could be turned from a liquid state into a solid state, which solidification extent or shear strength often increases monotonically with the applied magnetic field. In this study, the shear stress of a dilute MR fluid decreased with increasing applied magnetic field at a constant shear rate. The dynamic shear stress was significantly higher than the stable counterpart at medium magnetic fields. They are ascribed to the slow particle structure transformation. A higher shear rate and particle volume fraction could reduce the transient time and the shear strength difference.

Yu Tian

2014-09-01

102

Experimental observation of shear thickening oscillation

We report experimental observation of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. The shear thickening oscillation is caused by the interplay between the fluid dynamics and the shear thickening, and has been predicted theoretically by the present authors using a phenomenological fluid dynamics model for the dilatant fluid, but never been reported experimentally. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed strong vibrations of the frequency around 20 Hz, which is consistent with our theoretical prediction.

Nagahiro, Shin-ichiro; Mitarai, Namiko

2012-01-01

103

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. [...

Sean, Gavin; Mohamed, Abdel-Aziz.

104

The Influence of Shearing Velocity on Shear Behavior of Artificial Joints

In this paper, the effects of shear velocity on the shearing behavior of artificial joints have been studied at different normal stress levels. Here, artificial joints with planar and rough surfaces were prepared with the plaster (simulating soft rock joints) and concrete (medium-hard rock joints) materials. The rough joints had triangular shaped asperities with 10° and 20° inclination angles. Direct shear tests were performed on these joints under various shear velocities in the range of 0.3-30 mm/min. The planar plaster-plaster and planer concrete-concrete joints were sheared at three levels of normal stress under constant normal load boundary condition. Also, the rough plaster-plaster and concrete-concrete joints were sheared at one level of normal stress under constant normal stiffness boundary condition. The results of the shear tests show that the shearing parameters of joints, such as shear strength, shear stiffness and friction angle, are related to the shear velocity. Shear strength of planar and rough plaster-plaster joints were decreased when the shear velocity was increased. Shear strength of concrete joints, except for rough joints with 10° inclination, increased with increasing shear velocity. Regardless of the normal stress level, shear stiffness of both planar plaster-plaster and concrete-concrete joints were decreased when the shear velocity was increased.

Atapour, Hadi; Moosavi, Mahdi

2014-09-01

105

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

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

2013-04-01

106

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

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

107

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

108

Granular Couette Flow at High Shear Rates

We present an experimental study of couette flow of granular material at very high shear rates. Wall velocities up to 9.4 m/s and shear rates up to 2400 s-1 (based on a shear band that is 4 particle diameters thick) are achieved. We find a surprising non-monotonic dependence of the torque on the shear rate. This effect shows large variability even when the obvious variables such as temperature, humidity and preparation history are controlled. We interpret the variability as arising from particle wear that changes the frictional interactions that dominate the torque at lower shear rates. At very high shear rates, the torque increases monotonically with shear rate and is quite reproducible. We interpret this behavior as reflecting collisional dynamics at high shear rates. Non-dimensional parameters that control the change from friction dominated to collision dominated interactions will be discussed. (Work supported by NSF Division of Materials Research)

Voth, Greg; Sundquist, Jamie; Gollub, Jerry

2002-11-01

109

External Shear in Quadruply Imaged Lens Systems

We use publicly available N-body simulations and semi-analytic models of galaxy formation to estimate the levels of external shear due to structure near the lens in gravitational lens systems. We also describe two selection effects, specific to four-image systems, that enhance the probability of observing systems to have higher external shear. Ignoring additional contributions from "cosmic shear" and assuming that lens galaxies are not significantly flattened, we find that the mean shear at the position of a quadruple lens galaxy is 0.11, the rms shear is roughly 0.15, and there is roughly a 45% likelihood of external shear greater than 0.1. This is much larger than previous estimates and in good agreement with typical measured external shear. The higher shear primarily stems from the tendency of early-type galaxies, which are the majority of lenses, to reside in overdense regions.

Holder, G P; Holder, Gilbert P.; Schechter, Paul L.

2003-01-01

110

Identification of Shear Band using Elastic Shear Wave Propagation

Directory of Open Access Journals (Sweden)

Full Text Available Localization in soil under high stress level is usually investigated using some indirect measures, e.g., X-ray diffraction method. In the present study, the propagation velocity of shear wave was used to detect localization in sandy soil. Firstly, the general expression to exhibit the stress and density dependencies characteristics under consolidation and triaxial testing conditions of the tested soil was proposed. Adopted the proposed correlation as a reference together with the observed geometry, the shear wave velocity of the localized zone may be assumed. It was found that the density in the localized zone could be much looser than those ever reported in the literature. The void ratio of the localized zone is even larger than the maximum void ratio.

T. Nachiengtai

2008-01-01

111

Rapid Shear Zones - Unspecific Microstructures

The record of episodic deformation at 500-550°C and 0.7+/-0.2 GPa was identified in eclogite- amphibolites on Rugsundoya island in the Western Gneiss Region of Norway, in the footwall of the low angle Nordfjord Sogn Detachment Zone (Birtel and Stöckhert 2008). An event of fracture formation was followed by inhomogeneous ductile deformation, during which the fractures developed into open cavities sealed by quartz. The structural relations indicate contemporaneous formation of veins and shear zones, also demonstrated by the fact that the quartz veins do nowhere transect the shear zones and the shear zones do nowhere transect the quartz veins. The deformation is ascribed to brittle failure driven by stress redistribution during a large earthquake, followed by an episode of inhomogeneous ductile deformation during postseismic stress relaxation. The peculiar record is thus interpreted to represent a single seismic cycle and to obey the respective time scales, with quasi-instantaneous loading and subsequent stress relaxation over time spans on the order of 102 to 103 years. If this is true, the shear zones linking the open cavities (now quartz veins) must have formed by markedly non-steady state deformation starting at high stress and very high strain rate. Here we examine the microfabrics of the shear zones. The amphibolite facies shear zones are made up of a fine-grained amphibole and plagioclase matrix, with a typical grain size of 0.1 mm for both phases. Millimetre-sized porphyroclasts of amphibole are widespread. The matrix microstructure is characterized by smooth grain and interphase boundaries. The amphiboles reveal a marked shape preferred orientation (SPO) combined with a crystallographic preferred orientation (CPO). In contrast to amphibole, plagioclase shows no CPO. The chemical composition of amphibole and plagioclase within the shear zones corresponds to that in the undeformed host rock, with only slight inhomogeneity and rather unsystematic zoning patterns in both porphyroclasts and matrix amphiboles. The microfabrics of the shear zones are found to be unspecific in terms of deformation mechanisms. The combined CPO and SPO is very common for amphiboles. It does not necessarily indicate deformation by dislocation creep, but can be the product of various processes from anisotropic growth to cataclastic flow (e.g. Brodie and Rutter 1985, Nyman et al. 1992). The unsystematic chemical zoning pattern and the tendency towards a low-energy grain shape indicates that the synkinematic microstructures became erased during annealing at amphibolite facies conditions. The term "blastomylonite" is therefore probably appropriate to characterize the fine-grained amphibolite within the shear zones. We conclude that rapid non-steady state ductile deformation, presumably by a variety of deformation mechanisms sequentially activated at decaying stress, leaves no specific record at the given temperatures of 500-550°C. The synkinematic microfabrics, including those developed at an early stage at exceptionally high strain rate, become obliterated by annealing at such temperatures. References Birtel, S. and Stöckhert, B (2008) Tectonophysics 457: 53-63. Brodie, K. H. and Rutter, E.H. (1985) in Kinetics, Textures, and Deformation. A. B. Thompson and D. C. Rubie. (eds) New York, Springer. 4: 138-179. Nyman, M. W., Law, R. D. and Smelik, E.A. (1992) Geology 20: 455-458.

Birtel, S.; Stoeckhert, B.

2008-12-01

112

High shear rheology of shear banding fluids in microchannels

We characterize heterogeneous flows of a wormlike micelles solution in microchannels. Combining a pressure resistant microfabrication technology and a performant particle image velocimetry setup, we succeed in determining the nonlinear rheology of this fluid over 4 decades in shear rate and in particular more than 1 decade beyond the end of the stress plateau. We performed an independent measurement of the slip length with 1 ?m resolution.

Nghe, Philippe; Degré, Guillaume; Tabeling, Patrick; Ajdari, Armand

2008-11-01

113

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

114

Non Steady State Granular Shear Flows

We experimentally investigate the shear flow of granular matter in a cylindrical Couette cell. Since granular flows dissipate energy, they must be continuously driven to remain in a flowing state. Previous experiments on steady state shear flows have found that velocity gradients are confined to a thin shear band, and that the shear force is roughly independent of shear rate if the material is allowed to dilate. Our experiments in a Couette geometry focus on two related questions about non-steady state flows: 1) How does a granular shear flow start? 2) How does a granular system respond to oscillatory shear? In particular, we investigate the role of boundary conditions, which we expect to be of particular importance, since granular flows must be continuously driven (in general from a boundary) in order to be sustained. In our Couette cell a shear flow is generated by moving either the inner cylinder or the outer cylinder or both cylinders. The motion of grains on the top surface is measured directly with fast imaging and particle tracking techniques. Previous studies have indicated that the velocity profile on the top surface is very similar to the velocity profile within the bulk. Measurements of the corresponding shear forces are in progress. Initial experiments determined the steady state flow profiles under different driving conditions, with either inner, outer or both cylinders moving. In steady state, velocity gradients are confined to a roughly exponential shearband several particle diameters wide. The shear band is always located at the inner cylinder. A probable reason for this observation is the slightly smaller surface area of the inner cylinder compared to the outer cylinder. Since shear forces are transmitted from one cylinder to the other, the smaller surface area of the inner cylinder leads to larger shear stresses. Shear flow confined to regions of high stress can be reproduced in continuum mechanics models which include plastic flow, non-Newtonian fluid models, or locally Newtonian hydrodynamic models that include a strong density dependence of viscosity. Most of these models are isotropic with respect to the shear direction. However, anisotropies manifest themselves in two distinct flow transients, when rotation of one of the cylinders is started. When the cylinder had been rotated in the same direction before, the thin shear band immediately forms. When the previous motion of the cylinder had been in the opposite direction, particles far from the moving cylinder are initially more mobile. After an extra displacement of up to six particle diameters, a thin shearband forms again in steady state. The extra displacement of particles far from the shear surface does not strongly depend on the shear rate prior or after the stop, solely on the direction of prior shear. This indicates that the static configuration of grains after a shear flow exhibits anisotropies. The flow transient, at least, can then no longer be modeled with the isotropic form of the models described above. Finally, we investigate oscillatory shear flow. During small amplitude oscillations the shear flow is confined to a thin shear band. In addition, a gradual compaction and strengthening of the granular material is observed. For sufficiently large oscillation amplitudes, the flow resembles a sequence of shear reversals. In oscillatory flows driven by the outer cylinder, coexistence of shearbands at the outer and inner cylinder can be found. In summary, we have elucidated important properties of granular shear flows from non-steady state flow measurements: First, shear bands form preferentially near the inner cylinder, even when the outer cylinder is sheared. Transiently a shear band can also form near the outer cylinder during oscillatory driving. These observations should help refine models of granular shear flow. One challenge in improving models of granular shear flow is the observation that the initial flow transient contains 'memory' of the direction of previously applied shear. In order to incorporate this observation into flow model

Losert, Wolfgang; Kwon, Gene

2002-11-01

115

Controlled shear/tension fixture

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

116

Shear instability in nanoporous si.

Elastic properties of nanoporous Si (np-Si), which is composed of bulk Si containing ordered, nanometer-sized cylindrical pores, are investigated based on first-principles density functional theory calculations. By separately varying the pore size and spacing, it is demonstrated that the elastic stiffness of np-Si under the shear strain perpendicular to the pore axis turns negative when the volume fraction of pores becomes greater than a critical value. The total energy calculations reveal that the negative values in the stiffness originate from the enhanced strain energy, which leads to significant rotation in bonds near the pore surface. Moreover, the high sensitivity of the elastic stiffness to shear induces a structural transformation in np-Si from tetragonal (D2d) to orthorhombic (C2v) phase, which makes it necessary to properly take the effect of external strain due to substrates or electrical leads into account in np-Si-based applications. PMID:25153784

Lee, Joo-Hyoung

2014-09-10

117

Phase Dynamic of Shear Melting

Directory of Open Access Journals (Sweden)

Full Text Available The melting of an ultrathin lubricating film clamped between two atomically smooth solid surfaces that are in relative motion is analyzed. The influence of additive stresses fluctuations, strain and temperature on the process of lubricant melting is investigated taking into account the shear modulus deformation defect. The influence of the system parameters on the phase diagram, where the temperature noise intensity and the temperature of friction surfaces define the areas of dry, liquid and stick-slip friction, is analyzed.

Manko N.N.

2014-08-01

118

Apparatus for shearing spent nuclear fuel assemblies

International Nuclear Information System (INIS)

A method and apparatus are described for shearing spent nuclear fuel assemblies of the type comprising an array of fuel pins disposed within an outer metal shell or shroud. A spent fuel assembly is first compacted in a known manner and then incrementally sheared using fixed and movable shear blades having matched laterally projecting teeth which slidably intermesh to provide the desired shearing action. Incremental advancement of the fuel assembly after each shear cycle is limited to a distance corresponding to the lateral projection of the teeth to ensure fuel assembly breakup into small uniform segments which are amenable to remote chemical processing

119

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

120

Experimental observation of shear thickening oscillation

DEFF Research Database (Denmark)

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

2013-01-01

121

Layered Systems Under Shear Flow

We discuss and review a generalization of the usual hydrodynamic description of smectic A liquid crystals motivated by the experimentally observed shear-induced destabilization and reorientation of smectic A like systems. We include both the smectic layering (via the layer displacement u and the layer normal hat{p}) and the director hat{n} of the underlying nematic order in our macroscopic hydrodynamic description and allow both directions to differ in non equilibrium situations. In a homeotropically aligned sample the nematic director couples to an applied simple shear, whereas the smectic layering stays unchanged. This difference leads to a finite (but usually small) angle between hat{n} and hat{p}, which we find to be equivalent to an effective dilatation of the layers. This effective dilatation leads, above a certain threshold, to an undulation instability of the layers with a wave vector parallel to the vorticity direction of the shear flow. We include the couplings of the velocity field with the order parameters for orientational and positional order and show how the order parameters interact with the undulation instability. We explore the influence of the magnitude of various material parameters on the instability. Comparing our results to available experimental results and molecular dynamic simulations, we find good qualitative agreement for the first instability. In addition, we discuss pathways to higher instabilities leading to the formation of onions (multilamellar vesicles) via cylindrical structures and/or the break-up of layers via large amplitude undulations.

Svenšek, Daniel; Brand, Helmut R.

122

Turbulence in homogeneous shear flows

Homogeneous shear flows with an imposed mean velocity U=Syx? are studied in a period box of size Lx×Ly×Lz, in the statistically stationary turbulent state. In contrast with unbounded shear flows, the finite size of the system constrains the large-scale dynamics. The Reynolds number, defined by Re?SL2y/? varies in the range 2600?Re?11300. The total kinetic energy and enstrophy in the volume of numerical integration have large peaks, resulting in fluctuations of kinetic energy of order 30%-50%. The mechanism leading to these fluctuations is very reminiscent of the ``streaks'' responsible for the violent bursts observed in turbulent boundary layers. The large scale anisotropy of the flow, characterized by the two-point correlation tensor depends on the aspect ratio of the system. The probability distribution functions (PDF) of the components of the velocity are found to be close to Gaussian. The physics of the Reynolds stress tensor, uv, is very similar to what is found experimentally in wall bounded shear flows. The study of the two-point correlation tensor of the vorticity suggests that the small scales become isotropic when the Reynolds number increases, as observed in high Reynolds number turbulent boundary layers. However, the skewness of the z component of vorticity is independent of the Reynolds number in this range, suggesting that some small scale anisotropy remains even at very high Reynolds numbers. An analogy is drawn with the problem of turbulent mixing, where a similar anisotropy is observed.

Pumir, Alain

1996-11-01

123

Shear Alfven waves in tokamaks

International Nuclear Information System (INIS)

Shear Alfven waves in an axisymmetric tokamak are examined within the framework of the linearized ideal MHD equations. Properties of the shear Alfven continuous spectrum are studied both analytically and numerically. Implications of these results in regards to low frequency rf heating of toroidally confined plasmas are discussed. The structure of the spatial singularities associated with these waves is determined. A reduced set of ideal MHD equations is derived to describe these waves in a very low ? plasma. Analytic expressions for the continuum are obtained by solving a set of coupled differential equations on each flux surface in an expansion scheme in powers of the small inverse aspect ratio, epsilon = a/R0, where a and R0 are the minor and major radii, respectively, of the toroid. To lowest order in epsilon, the continuum is given by an appropriate generalization of its counterpart in an infinitely long, axially periodic, cylindrically symmetric screw pinch. First order corrections due to toroidicity induce a coupling of particular poloidal harmonics about rational q surfaces, where q is the safety factor. The coupling leads to the formation of gaps in the continuum. Depending on the structure of the continuum near the gaps, it may not be possible to heat the plasma with certain oscillator frequencies and helicities. Numerical solutions for the shear Alfven continuum of the Tokapole II device at the University of Wisconsin, Madison, are in qualitative agreement with the predictions of the analytic model

124

Microstructure in Concentrated Sheared Dispersions

This work describes a theory for predicting microstructure of concentrated colloidal hard spheres as a function of P'eclet number Pe = 6??? a^3/kT and particle volume fraction, ?; ? is the shear rate, a is the particle radius, ? is fluid viscosity and kT is the thermal energy. We study the pair distribution using the pair Smoluchowski equation. Many-body effects in the conservation equation were then formulated self-consistently through probabilistic third-particle integrals, with emphasis on capturing the interaction of flow and excluded volume effects. The resulting integro-differential equation was solved iteratively. Comparison between theory predictions and simulation results show that the theory is able to predict known near-equilibrium (Pe1) and dilute-suspension large-Pe results. The approach accurately predicts the major features of microstructure at concentrated ? under strong shear, which differentiates it from previous theoretical work. Rheological quantities of shear stress, normal stress differences, and particle pressure are computed from the structure.

Morris, Jeff; Nazockdast, Ehssan

2010-11-01

125

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

126

Shear Dynamics in Higher Dimensional FLRW Cosmology

We study the shear dynamics of higher dimensional Friedmann-Lema\\^{i}tre-Robertson-Walker (FLRW) cosmology by considering a non-perfect fluid which exerts different pressure in the normal and extra dimensions. We generalise the definition of shear tensor for higher dimensional space-time and prove it to be consistent with the evolution equation for shear tensor obtained from the Ricci identities. The evolution of shear tensor is investigated numerically. The role of extra dimensions and other parameters involved in shear dynamics is discussed in detail. We find that with increase in anisotropy parameter, time of decay of shear increases while with increase in number of extra dimensions, shear tends to decay early.

Pahwa, Isha; Goswami, Umananda Dev

2014-01-01

127

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)

128

Evolution of twist-shear and dip-shear in Faring active region NOAA 10930

We study the evolution of magnetic shear angle in a flare productive active region NOAA 10930. The magnetic shear angle is defined as the deviation in the orientation of the observed magnetic field vector with respect to the potential field vector. The shear angle is measured in horizontal as well as vertical plane. The former is computed by taking the difference between the azimuth angles of the observed and potential field and is called the twist-shear, while the latter is computed by taking the difference between the inclination angles of the observed and potential field and is called the dip-shear. The evolution of the two shear angles is then tracked over a small region located over the sheared penumbra of the delta sunspot in NOAA 10930. We find that, while the twist-shear shows an increasing trend after the flare the dip-shear shows a significant drop after the flare.

Gosain, Sanjay

2010-01-01

129

Mixing in shear thinning fluids

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english In the present study, a CFD characterization of the flow generated by curved-blade impellers in a cylindrical unbaffled vessel was carried out. The tank diameter was 300 mm, with a flat bottom. The liquid height was equal to the vessel diameter. The fluids simulated have a shear thinning behavior. A [...] nalyses concern the effect of the impeller speed, the fluid rheology and the number of impeller blades on the induced flow patterns and the power consumption. The predictions were compared with literature data and a satisfactory agreement was found.

H., Ameur; M., Bouzit.

2012-06-01

130

Development of the FFTF rotary shear

International Nuclear Information System (INIS)

In support of the Process Facility Modifications (PFM) Project, development testing has been conducted by Rockwell Hanford Operations (Rockwell) on various methods of mechanically segmenting Fast Flux Test Facility (FFTF) fuel. Initial tests, using alluminum oxide-filled stainless steel tubing, were performed at Oak Ridge National Laboratory (ORNL) to evaluate the performance of a reciprocating blade bundle shear. Feasibility tests completed in 1984 demonstrated that slow-speed rotary shearing offered improvements to PFM over the reciprocating blade bundle shear. Development testing, completed in 1986 at Rockwell using a prototype rotary shear, established specific equipment configurations and identified pertinent operating parameters for incorporating slow-speed rotary shearing into PFM. This document discusses the final test results of the FFTF fuel shear development test

131

Joint roughness characteristics in shear strength

International Nuclear Information System (INIS)

For the numerical analysis of the roughness of a joint surface, six statistical parameters and fractal dimension are calculated from the 10 standard roughness profiles suggested by Barton and Choubey (1977). These parameters are compared with the joint roughness coefficient (JRC) values given by them. The result of the analysis shows that fractal dimension (D) has the strongest correlation with the JRC values. To take the scale effect into account, the Barton's empirical equation was modified by replacing JRC value for the value of fractal dimension. The shear box test is performed on the 22 selected core samples of gneiss to validate the application of the modified empirical equation. The empirical relationship between shear strength (Te) estimated by the modified empirical equation and the shear strength (Tr) determined by the universal shear box test is established. The estimated shear strength correlates strongly to the measured shear strength with a correlation coefficient of 0.76

132

Shear strength properties of wet granular materials

We investigate shear strength properties of wet granular materials in the pendular state (i.e. the state where the liquid phase is discontinuous) as a function of water content. Sand and glass beads were wetted and tested in a direct shear cell and under various confining pressures. In parallel, we carried out three-dimensional molecular dynamics simulations by using an explicit equation expressing capillary force as a function of interparticle distance, water bridge volume and surface tension. We show that, due to the peculiar features of capillary interactions, the major influence of water content over the shear strength stems from the distribution of liquid bonds. This property results in shear strength saturation as a function of water content. We arrive at the same conclusion by a microscopic analysis of the shear strength. We propose a model that accounts for the capillary force, the granular texture and particle size polydispersity. We find fairly good agreement of the theoretical estimate of the shear...

Richefeu, V; Radja"i, F; Richefeu, Vincent; Youssoufi, Moulay Sa\\"{i}d El; Radja\\"{i}, Farhang

2006-01-01

133

Local Gravitational Instability of Magnetized Shear Flows

The effect of magnetic shear and shear flow on local gravitationally induced instabilities is investigated. A simple model is constructed allowing for an arbitrary entropy gradient and a shear plasma flow in the Boussinesq approximation. A transformation to shearing magnetic coordinates achieves a model with plasma flow along the magnetic field lines where the coordinate lines are coincident with the field lines. The solution for the normal modes of the system depends on two parameters: the Alfven Mach number of the plasma flow and the entropy gradient. The behavior of the unstable normal modes of this system is summarized by a stability diagram. Important characteristics of this stability diagram are the following: magnetic shear is stabilizing and the entropy gradient must exceed a threshold value for unstable mode growth to occur; flow acts to suppress mode growth in a substantially unstable regime as expected, yet near marginal stability it can lessen the stabilizing effect of magnetic shear and enhance t...

Howes, G G; McWilliams, J C; Howes, Gregory G.; Cowley, Steven C.; Williams, James C. Mc

2001-01-01

134

Kinetic equilibria of plasma shear layers

The analysis of plasma beam and shear problems in magnetic fields is usually based on a hydromagnetic fluid model. In a low-density collisionless plasma, however, the kinetic effects of the plasma, such as finite Larmor radius effects, are not yet clearly understood. In this paper, the kinetic equilibria of plasma shears in a uniform and fixed magnetic field, with full ion motion, are discussed by solving the Vlasov equation with a given electric field and drift velocity. In this model, the ion density profile through the plasma shear layer is quite different from the one predicted by a hydromagnetic model. As a result of a complicated ion gyromotion through the shear layer, single- and double-humped ion density profiles are obtained. The dependence on the temperature and the strength of the shear will be discussed. The results show a significant difference between positive and negative shears.

Cai, D.; Storey, L. R. O.; Neubert, T.

1990-01-01

135

Laser nephelometry of erythrocytes in shear flows

Laser backscattering nephelometry has been used to study dynamic properties of aggregating and nonaggregating suspensions of erythrocytes and of the whole blood in shear flows. The exponential dependences of total amplitude of aggregation on the hematocrit and on the shear rate have been found and the characteristic rapid and slow aggregation times have been estimated. A possibility to evaluate the shear diffusion coefficient for a suspension of nonaggregating erythrocytes has been demonstrated. 1.

Firsov, Nikolai N.; Priezzhev, Alexander V.; Stepanian, A. S.

1991-05-01

136

Simple shear flow in inelastic Maxwell models

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Boltzmann equation for inelastic Maxwell models is considered to determine the velocity moments through fourth degree in the simple shear flow state. First, the rheological properties (which are related to the second-degree velocity moments) are {\\em exactly} evaluated in terms of the coefficient of restitution $\\alpha$ and the (reduced) shear rate $a^*$. For a given value of $\\alpha$, the above transport properties decrease with increasing shear rate. Moreover, as expec...

Santos, Andres; Garzo, Vicente

2007-01-01

137

Shear Effects in Non-Homogeneous Turbulence

Motivated by recent experimental and numerical results, a simple unifying picture of intermittency in turbulent shear flows is suggested. Integral Structure Functions (ISF), taking into account explicitly the shear intensity, are introduced on phenomenological grounds. ISF can exhibit a universal scaling behavior, independent of the shear intensity. This picture is in satisfactory agreement with both experimental and numerical data. Possible extension to convective turbulence and implication on closure conditions for Large-Eddy Simulation of non-homogeneous flows are briefly discussed.

Toschi, F; Ruiz-Chavarria, G

2000-01-01

138

Crystal Nucleation of Colloidal Suspensions under Shear

We use Brownian Dynamics simulations in combination with the umbrella sampling technique to study the effect of shear flow on homogeneous crystal nucleation. We find that a homogeneous shear rate leads to a significant suppression of the crystal nucleation rate and to an increase of the size of the critical nucleus. A simple, phenomenological extension of classical nucleation theory accounts for these observations. The orientation of the crystal nucleus is tilted with respect to the shear direction.

Blaak, R; Frenkel, D; Löwen, H; Blaak, Ronald; Auer, Stefan; Frenkel, Daan; Lowen, Hartmut

2004-01-01

139

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

140

A technique for measuring optical beam shear is based on collecting light from the four quadrants of the beam and comparing the optical power collected from each quadrant with that from the other three quadrants. As used here, "shear" signifies lateral displacement of a beam of light from a nominal optical axis. A sensor for implementing this technique consists of a modified focusing lens and a quad-cell photodetector, both centered on the nominal optical axis. The modification of the lens consists in cutting the lens into four sectors (corresponding to the four quadrants) by sawing along two orthogonal diameters, then reassembling the lens following either of two approaches described next. In one approach, the lens is reassembled by gluing the sectors back together. In the simplest variant of this approach, the kerf of the saw matches the spacing of the photodetector cells, so that the focus of each sector crosses the axis of symmetry to fall on the opposite photodetector cell (see figure). In another variant of this approach, the lens sectors are spaced apart to make their individual foci to fall on separate photodetector cells, without crossing the optical axis. In the case of a sufficiently wide beam, the modified lens could be replaced with four independent lenses placed in a square array, each focusing onto an independent photodetector

Martin, Stefan; Szwaykowski, Piotr

2007-01-01

141

Shear wall ultimate drift limits

Energy Technology Data Exchange (ETDEWEB)

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.

Duffey, T.A. [Duffy, (T.A.) Tijeras, NM (United States); Goldman, A. [Goldman, (A.), Sandia, Los Alamos, NM (United States); Farrar, C.R. [Los Alamos National Lab., NM (United States)

1994-04-01

142

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

143

Confined cubic blue phases under shear.

We study the behaviour of confined cubic blue phases under shear flow via lattice Boltzmann simulations. We focus on the two experimentally observed phases, blue phase I and blue phase II. The disclination network of blue phase II continuously breaks and reforms under shear, leading to an oscillatory stress response in time. The oscillations are only regular for very thin samples. For thicker samples, the shear leads to a 'stick-slip' motion of part of the network along the vorticity direction. Blue phase I responds very differently: its defect network undergoes seemingly chaotic rearrangements under shear, irrespective of system size. PMID:22738991

Henrich, O; Stratford, K; Marenduzzo, D; Coveney, P V; Cates, M E

2012-07-18

144

Confined Cubic Blue Phases under Shear

We study the behaviour of confined cubic blue phases under shear flow via lattice Boltzmann simulations. We focus on the two experimentally observed phases, blue phase I and blue phase II. The disinclination network of blue phase II continuously b reaks and reforms under shear, leading to an oscillatory stress response in time. The oscillations are only regular for very th in samples. For thicker samples, the shear leads to a "stick-slip" motion of part of the network along the vorticity direction. Blue phase I responds very differently: its defect network undergoes seemingly chaotic rearrangements under shear, irrespective of system size.

Henrich, O; Marenduzzo, D; Coveney, P V; Cates, M E

2011-01-01

145

Shear banding phenomena in a Laponite suspension

Shear localization in an aqueous clay suspension of Laponite is investigated through dynamic light scattering, which provides access both to the dynamics of the system (homodyne mode) and to the local velocity profile (heterodyne mode). When the shear bands form, a relaxation of the dynamics typical of a gel phase is observed in the unsheared band soon after flow stop, suggesting that an arrested dynamics is present during the shear localization regime. Periodic oscillations of the flow behavior, typical of a stick-slip phenomenon, are also observed when shear localization occurs. Both results are discussed in the light of various theoretical models for soft glassy materials.

Ianni, F; Gentilini, S; Ruocco, G

2007-01-01

146

Cyclic shearing deformation behavior of saturated clays

The apparatus for static and dynamic universal triaxial and torsional shear soil testing is employed to perform stress-controlled cyclic single-direction torsional shear tests and two-direction coupled shear tests under unconsolidated-undrained conditions. Through a series of tests on saturated clay, the effects of initial shear stress and stress reversal on the clay’s strain-stress behavior are examined, and the behavior of pore water pressure is studied. The experimental results indicate that the patterns of stress-strain relations are distinctly influenced by the initial shear stress in the cyclic single-direction shear tests. When the initial shear stress is large and no stress reversal occurs, the predominant deformation behavior is characterized by an accumulative effect. When the initial shear stress is zero and symmetrical cyclic stress occurs, the predominant deformation behavior is characterized by a cyclic effect. The pore water pressure fluctuates around the confining pressure with the increase of cycle number. It seems that the fluctuating amplitude increases with the increase of the cyclic stress. But a buildup of pore water pressure does not occur. The deformations of clay samples under the complex initial and the cyclic coupled stress conditions include the normal deviatoric deformation and horizontal shear deformation, the average deformation and cyclic deformation. A general strain failure criterion taking into account these deformations is recommended and is proved more stable and suitable compared to the strain failure criteria currently used.

Qi, Jianfeng; Luan, Maotian; Feng, Xiuli; Ma, Tailei; Nie, Ying

2007-10-01

147

Massive shear wall testing for nuclear industry

International Nuclear Information System (INIS)

Consequences of earthquakes have proven the need to study the shear mechanism of low-rise reinforced concrete shear walls thoroughly. Because of the complexity of reinforced concrete behavior generalized problem solutions are not readily available. Experimental testing remains essential for investigating concrete elements. The contribution deals with cyclic shear testing of thick low-rise reinforced concrete walls. Analysis of the data obtained resulted in the determination of hysteresis characteristics, nonlinear effects for shear, ultimate capacity and damping of the tested specimens. Various strength assessments and comparison to test results is given. The experimental investigation provides valuable results applicable in monitoring and design of structures. (author)

148

Hydrodynamical fluctuations in smooth shear flows

International Nuclear Information System (INIS)

velocity appears in the correlation function of pressure; the fluctuation background of the acoustic waves is completely different at low and moderate shear rates (at low shear rates it is reduced in Dk in comparison to the uniform (non-shear) flow; at moderate shear rates it it comparable to the background of the vortex fluctuations). The fluctuation background of both the vortex and the acoustic wave modes is anisotropic. The possible significance of the fluctuation background of vortices for the subcritical transition to turbulence and Brownian motion of small macroscopic particles is also discussed. (author)

149

Shear flow generation due to electromagnetic instabilities

International Nuclear Information System (INIS)

Shear flow is the most important ingredient governing nonlinear behavior of many types of plasma instability. Electromagnetic effects on shear flow generation have been studied for an electro- magnetic drift wave called resistive drift-Alfven mode (RDAM) and a global MHD mode called resistive wall mode (RWM). For RDAM it is found that the generated shear flow stabilizes the dominant modes; however, other modes are destabilized. For RWM Maxwell stress due to magnetic fluctuations has a tendency to suppress the poloidal flow near the plasma surface, which gives almost same saturation level, since the shear flow stabilization disappears. (author)

150

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, Rüya; Vigild, Martin Etchells

2005-01-01

151

Continuous shear - a method for studying material elements passing a stationary shear plane

DEFF Research Database (Denmark)

Traditionally, material response to shear deformation has been studied with methods where the shear is gradually increasing from zero to the final value over a certain fixed deformation zone, e.g. in the well-known torsion test of a tube with a defined shear zone established by a machined circumferential groove. Normally shear in metal forming processes is of another nature, namely where the material elements move through a stationary shear zone, often of small width. In this paper a method enabling the simulation of this situation is presented. A tool for continuous shear has beeen manufactured and tested with AlMgSil and copper. The sheared material has thereafter been tested n plane strain compression with different orientation concerning the angle between the shear plane and the compression direction.

Lindegren, Maria; Wanheim, Tarras

2003-01-01

152

Samples of M. longissimus dorsi from 16-20 month Friesian bulls or steers (80/group) were assessed for a range of meat quality characteristics after being held at ambient temperature for 24h (to avoid cold-shortening) and then at 0-2°C for 6 days. Mean ultimate pH was significantly higher for samples from the bulls (6·35 versus 5·89), and as a consequence, reflectance values were lower, sarcomere lengths were shorter, and expressed juice and cooking losses were lower. Mean Warner-Bratzler shear values did not differ between the groups, apparently because the bull values were mainly above the peak of the pH/shear force curve, while the steer values were mainly below it. There was no evidence that the relationship between shear force and pH differed for samples from the bulls and steers. Results suggested that the increased shear force with increased pH up to 6·2 was at least partly due to a decreased sarcomere length. It is suggested that some of the differences in tenderness between beef from bulls and steers, that have been reported elsewhere, may have been largely due to differences in ultimate pH values. PMID:22055226

Purchas, R W

1990-01-01

153

Shear Behavior Of Reinforced High-Strength Concrete Beams Without Shear Reinforcement

Digital Repository Infrastructure Vision for European Research (DRIVER)

Eighteen rectangular singly reinforced high-strength concrete beams without web reinforcement were tested in combined shear and flexure. The main variables were the longitudinal steel reinforcement ratio and the shear-span to effective depth ratio. The uniaxial compressive strength of concrete was about 93 MPa (13,500 psi). The experimental shear capacities were compared with the shear capacities predicted by different empirical equations presented in literatures. Two empirical equations have...

Wafa, Faisal F.

1994-01-01

154

Turbulence suppression by E x B shear in JET optimized shear pulses

International Nuclear Information System (INIS)

The authors calculate microinstability growth rates in JET optimized shear plasmas with a comprehensive gyrofluid model, including sheared E x B flows, trapped electrons, and all dominant ion species in realistic magnetic geometry. They find good correlation between E x B shear suppression of microinstabilities and both the formation and collapse of the internal transport barrier

155

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

156

Shear deformation in granular materials

Energy Technology Data Exchange (ETDEWEB)

An investigation into the properties of granular materials is undertaken via numerical simulation. These simulations highlight that frictional contact, a defining characteristic of dry granular materials, and interfacial debonding, an expected deformation mode in plastic bonded explosives, must be properly modeled. Frictional contact and debonding algorithms have been implemented into FLIP, a particle in cell code, and are described. Frictionless and frictional contact are simulated, with attention paid to energy and momentum conservation. Debonding is simulated, with attention paid to the interfacial debonding speed. A first step toward calculations of shear deformation in plastic bonded explosives is made. Simulations are performed on the scale of the grains where experimental data is difficult to obtain. Two characteristics of deformation are found, namely the intermittent binding of grains when rotation and translation are insufficient to accommodate deformation, and the role of the binder as a lubricant in force chains.

Bardenhagen, S.G.; Brackbill, J.U. [Los Alamos National Lab., NM (United States); Sulsky, D.L. [Univ. of New Mexico, Albuquerque, NM (United States)

1998-12-31

157

Cosmic shear without shape noise

We describe a new method for reducing the shape noise in weak lensing measurements by an order of magnitude. Our method relies on spectroscopic measurements of disk galaxy rotation and makes use of the Tully-Fisher (TF) relation in order to control for the intrinsic orientations of galaxy disks. For this new proposed experiment, the shape noise ceases to be an important source of statistical error. Using CosmoLike, a new cosmological analysis software package, we simulate likelihood analyses for two spectroscopic weak lensing survey concepts (roughly similar in scale to Dark Energy Survey Task Force Stage III and Stage IV missions) and compare their constraining power to a cosmic shear survey from the Large Synoptic Survey Telescope (LSST). Our forecasts in seven-dimensional cosmological parameter space include statistical uncertainties resulting from shape noise, cosmic variance, halo sample variance, and higher-order moments of the density field. We marginalize over systematic uncertainties arising from pho...

Huff, Eric M; Eifler, Tim; George, Matthew R; Schlegel, David

2013-01-01

158

Magnetoconvection in sheared magnetic fields

International Nuclear Information System (INIS)

The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B0 is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resistive interchange instability, reveals that the latter is characterized by the existence of viscoresistive boundary layers of vertical width which scales as Q-1/6, where Q is the Chandrasekhar number. The situation is analogous to the one encountered in magnetically confined laboratory plasmas, where convective flows are constrained by the magnetic shear to develop in boundary layers located around resonant magnetic surfaces in order to fulfill the ''interchange condition''k·B0=0, where k is the wave vector of the magnetic perturbation. It follows that when the effect of thermal diffusion is taken into account in the process, convection can only occur above a certain critical value of the Rayleigh number which scales as Q2/3 for large Q. At the onset, the convection pattern is a superposition of identically thin convective rolls everywhere aligned with the local magnetic field lines and which therefore adopt the magnetic field geometry, a situation also reminiscent of the penumbra of sunspots. Using this degeneracy, equations describing the weakly nonlinear state are obtained and discussed. A reduced magnetohydrodynamic description of magnetoconvection is introduced. Since it is valid for arbitrary magnetic field configurations, it allows a simple extension to the case where there exists an inclination between the direction of gravity and the plane spanned by the equilibrium magnetic field. These reduced magnetohydrodynamic equations are proposed as a powerful tool for further investigations of magnetoconvection in more complex field line geometries.

159

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 resulty 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

160

Rearrangements and Dilatancy for Sheared Dense Materials

Constitutive equations are proposed for dense materials, based on the identification of two types of free-volume activated rearrangements associated to shear and compaction. Two situations are studied: the case of an amorphous solid in a stress-strain test, and the case of a lubricant in tribology test. Varying parameters, strain softening, shear thinning, and stick-slip motion can be observed.

Lemaître, A

2001-01-01

161

Directory of Open Access Journals (Sweden)

Full Text Available The algebraic proof of the fundamental theorem concerning pure shear, by making use only of the notion of orthogonal projector, is presented. It has been shown that the state of pure shear is the same for all singular symmetric traceless tensors in E3, up to the rotation.

Jari? Jovo P.

2010-01-01

162

This article briefly describes the in-situ shear vane test, including images and typical results. This procedure tests the undrained shear strength of soil. Procedures of the test are not outlined, but a general overview is given. The site contains photos, charts, diagrams and instructional test to help guide the user.

2008-09-24

163

Crosswind Shear Gradient Affect on Wake Vortices

Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.

Proctor, Fred H.; Ahmad, Nashat N.

2011-01-01

164

Spatial phase-shifting lateral shearing interferometer

The phase-shifting lateral shearing interferometer is widely adopted for wavefront measurement with high accuracy. For real-time wavefront measurement, a spatial phase-shifting lateral shearing interferometer is proposed. The interferometer includes a polarization lateral shearing module, a spatial phase-shifting module and an imaging module. The polarization lateral shearing module consists of a Savart polariscope. The spatial phase-shifting module is component of a non-polarization beam splitter, a polarization beam splitter, two rectangular prisms and a half wave-plate. The imaging module includes an imaging system and a CCD. The measured wavefront is sheared by the polarization lateral shearing module. The polarization directions of the two shearing beams are perpendicular to each other. The two shearing beams are split into four groups of beams by the spatial phase-shifting module to form four interferograms in a 2x2 matrix. The phase step of the four interferograms is 90 degrees. The four interferograms are captured in a single frame image by the imaging module. In experiments, a spherical wavefront with large radius of curvature was measured. Four spatial phase-shifting interferograms of the wavefront was obtained simultaneously. The usefulness of the interferometer is verified.

Guo, Xiaoxian; Zeng, Aijun; Huang, Huijie

2008-12-01

165

Asymmetric time correlations in turbulent shear flows

Cross correlations between normal and downstream velocity fluctuations in a turbulent shear flow are shown to carry information about the non-normal amplification process. The creation of spanwise modulated streaks by downstream vortices implies an asymmetry in temporal correlation functions. We verify this in numerical simulations in shear flows with $Re_lambdaapprox 100$.

Eckhardt, B; Schumacher, J; Eckhardt, Bruno; Jachens, Arne

2003-01-01

166

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

167

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

168

Borehole Shear Device Feasibility and Preliminary Studies.

The present studies try to overcome the difficulties inherent to the determination of in-situ shear modulus of soils over the complete range of strains. A new apparatus is proposed: the BSD (Borehole Shear Device). It essentially consists of a self-boring...

R. Sidey, J. Marti, L. Rodriguez, D. White

1980-01-01

169

Steel shear walls, behavior, modeling and design

International Nuclear Information System (INIS)

In recent years steel shear walls have become one of the more efficient lateral load resisting systems in tall buildings. The basic steel shear wall system consists of a steel plate welded to boundary steel columns and boundary steel beams. In some cases the boundary columns have been concrete-filled steel tubes. Seismic behavior of steel shear wall systems during actual earthquakes and based on laboratory cyclic tests indicates that the systems are quite ductile and can be designed in an economical way to have sufficient stiffness, strength, ductility and energy dissipation capacity to resist seismic effects of strong earthquakes. This paper, after summarizing the past research, presents the results of two tests of an innovative steel shear wall system where the boundary elements are concrete-filled tubes. Then, a review of currently available analytical models of steel shear walls is provided with a discussion of capabilities and limitations of each model. We have observed that the tension only 'strip model', forming the basis of the current AISC seismic design provisions for steel shear walls, is not capable of predicting the behavior of steel shear walls with length-to-thickness ratio less than about 600 which is the range most common in buildings. The main reasons for such shortcomings of the AISC seismic design provisions for steel shear walls is that it ignores the compression field in the shear walls, which can be significant in typical shear walls. The AISC method also is not capable of incorporating stresses in the shear wall due to overturning moments. A more rational seismic design procedure for design of shear walls proposed in 2000 by the author is summarized in the paper. The design method, based on procedures used for design of steel plate girders, takes into account both tension and compression stress fields and is applicable to all values of length-to-thickness ratios of steel shear walls. The method is also capable of including the effect of overturning moments and any normal forces that might act on the steel shear wall

170

Interface Roughness Parameters and Shear Strength

Directory of Open Access Journals (Sweden)

Full Text Available The interlayer bond strength between binder and wearing course and several possible treatments of enhancing the contact surface roughness and the interlocking are investigated. For this purpose, conventional methods, such as shear tests, but also laser image acquisition of the binder upper surface have been used. The mechanical outcomes of a shear test device and the binder surface roughness parameters, have been compared looking for a relation between the shear performance and the surface characteristics. The comparison between the roughness average and the root mean square of the profile heights with the maximum shear stress shows the achievement of the same strength level for treatments with similar roughness parameters, as proved by the statistical analysis. Furthermore, the comparison between the roughness parameter kurtosis and the maximum height of the profile with the slope of the response curve before the peak and residual shear stress, demonstrates a better locking for more high peaks.

Antonio D'Andrea

2013-09-01

171

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

172

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

173

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

174

Visualization of shear banding in colloidal glasses

Shear banding, i.e. the localization of shear flow, occurs in a manifold of systems ranging from hard materials such as metallic glasses to soft materials such as clays, shaving cream or mayonnaise. We investigate this phenomenon in a dense colloidal system using confocal microscopy that enables to track individual particles in 3D space and time. The particle motions reveal a transition from homogeneous flow to shear localization above a critical shear rate. We elucidate this transition using spatial correlations in the displacement of the particles. The diffusive motion of the particles is correlated over large length, and shows intermittent, scale-free behavior, reminiscent of crystal plasticity. Further, we associate an order parameter with the mobility of particles and demonstrate that shear banding is phase coexistence of regions differing in mobilities.

Chikkadi, Vijayakumar; Schofield, Andrew; Nienhuis, Bernard; Schall, Peter

2010-03-01

175

Turbulence structure at high shear rate

The structure of homogeneous turbulence in the presence of a high shear rate is studied using results obtained from three-dimensional time-dependent numerical simulations of the Navier-Stokes equations on a grid of 512 x 128 x 128 node points. It is shown that high shear rate enhances the streamwise fluctuating motion to such an extent that a highly anisotropic turbulence state with a one-dimensional velocity field and two-dimensional small-scale turbulence develops asymptotically as total shear increases. Instantaneous velocity fields show that high shear rate in homogeneous turbulent shear flow produces structures which are similar to the streaks present in the viscous sublayer of turbulent boundary layers.

Lee, Moon Joo; Kim, John; Moin, Parviz

1987-01-01

176

Structure of turbulence at high shear rate

The structure of homogeneous turbulence subject to high shear rate has been investigated by using three-dimensional, time-dependent numerical simulations of the Navier-Stokes equations. This study indicates that high shear rate alone is sufficient for generation of the streaky structures, and that the presence of a solid boundary is not necessary. Evolution of the statistical correlations is examined to determine the effect of high shear rate on the development of anisotropy in turbulence. It is shown that the streamwise fluctuating motions are enhanced so profoundly that a highly anisotropic turbulence state with a 'one-component' velocity field and 'two-component' vorticity field develops asymptotically as total shear increases. Because of high-shear rate, rapid distortion theory predicts remarkably well the anisotropic behavior of the structural quantities.

Lee, Moon Joo; Kim, John; Moin, Parviz

1990-01-01

177

Instabilities in Diamond under High Shear Stress

We investigate, through first-principles calculations, lattice instabilities induced in diamond by the application of high shear stresses. For shear stresses as low as 95 GPa a lattice instability will occur, leading to graphitelike layered structures. This effect is highly anisotropic. The reversal of the direction of the applied shear forces may cause a change of 80 GPa in the shear stress value at which the instability develops. The same reversal also causes different bonds to be broken, resulting in a drastic change in the orientation of the resulting graphitelike structures. We also find that an additional compressive stress of 50 GPa along the (111) direction does not eliminate the shear-induced instability.

Chacham, H.; Kleinman, Leonard

2000-12-01

178

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

179

Shear stress distribution due to shear and Rayleigh wave propagation at deep soil sites

International Nuclear Information System (INIS)

Earthquake strong motion at ground surface may be described as the combined result of body (compression and shear) waves and surface waves. In the course of earthquake engineering site response analyses, it is usually assumed that surface motions are a result of vertically propagating body waves. In studies of liquefaction potential, it is assumed that soil shear strains are a result of vertically propagating shear waves. However, shear strains are also caused by surface Rayleigh waves and solutions to strains from each source are derived and compared in the paper, and the results for shear strain in terms of surface acceleration and wave length are presented in non-dimensional form. The results of this investigation show that the distribution of soil shear strain as a function of depth below the ground surface is different depending upon whether shear waves or Rayleigh waves are assumed to be the source of horizontal motions at the ground surface. (Auth.)

180

A series of numerical experiments with the Hoskins-Bretherton horizontal shear model of frontogenesis in an, amplifying, two-dimensional baroclinic wave is performed. The analytic solutions from the Boussinesq, semi-geostrophic model provide initial conditions for numerical integrations with a two-dimensional, dry version of the fully compressible, hydrostatic primitive equation (PE) model of Anthes and Warner with 40 km horizontal resolution. The PE model is integrated 1) without planetary boundary layer (PBL) physics; 2) with a one-layer bulk-drag scheme; and 3) with a high-vertical-resolution PBL model. The lower boundary is thermally insulated in order to isolate the effect of the internal mixing of heat in the PBL.The simulation with the high-resolution PBL physics resolves several realistic features including 1) a narrow updraft at the top of the PBL above the sea-level pressure trough at the warm edge of the frontal zone; 2) a stable layer capping the PBL to the rear of the frontal zone; and 3) slightly unstable or neutral lapse rates in the PBL behind the front and stable lapse rates in the PBL ahead of the front. A diagnostic analysis of the frontogenesis indicates that the fine structure resulting from adding PBL physics can be attributed to the frictionally driven, ageostrophic inflow in the PBL toward the surface pressure trough in which the frontal zone is located. A finding of particular interest is that the stability patterns in the PBL on either side of the front evolve independently of sensible heating at the surface.

Keyser, Daniel; Anthes, Richard A.

1982-08-01

181

IMAGE ANALYSIS FOR MODELLING SHEAR BEHAVIOUR

Directory of Open Access Journals (Sweden)

Full Text Available 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 perpendicular to the axis of the core. Results show that there is a strong relationship between the fracture's geometry and its mechanical behaviour under shear stress and the resulting damage. Image analysis, geostatistical, stereological and directional data techniques are applied in combination to experimental data. The results highlight the role of geometric characteristics of the fracture surfaces (surface roughness, size, shape, locations and orientations of asperities to be damaged in shear behaviour. A notable improvement in shear understanding is that shear behaviour is controlled by the apparent dip in the shear direction of elementary facets forming the fracture.

Philippe Lopez

2011-05-01

182

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

183

Shear modulus of elasticity of the esophagus

DEFF Research Database (Denmark)

Experimental and diagnostic procedures like distension of a balloon catheter, bougie, and esophagogastroduodenoscopy can induce shear deformation in the esophageal wall. However, the shear modulus of the esophagus is yet unknown. The aim of this study was to determine the esophageal shear modulus and its dependence on the circumferential and longitudinal stresses and strains in the rat. The constitutive equation including the shear deformation based on a pseudo-strain-energy function was generated. Results were obtained using a new triaxial instrument to perform simultaneous torsion, inflation, and longitudinal stretching tests. The shear modulus varied with the inflation pressure and the longitudinal stretch ratio. The shear modulus at the longitudinal stretch ratio of 1.5 and between inflation pressures of 0 and 2.0 kPa ranged from 5.43 to 185.01 kPa. The mechanical constant of the esophagus showed that the esophageal wall was anisotropic with different stiffness in the circumferential, longitudinal, and the shear directions. The stiffness in the longitudinal direction was higher than in the circumferential direction (P < 0.001). This test can be extended for further mechanical remodeling experiments and for other tubular organs such as the small intestine or blood vessels.

Yang, Jian; Liao, Donghua

2004-01-01

184

Generalized shear of a soft rectangular block

The problem of the simple shear of a block has been treated in terms of a shear displacement, applied uniformly in a lateral direction and assumed to be a linear function of the height above the base. In this paper, simple shear is generalized: the shear displacement is neither uniform in the lateral direction nor necessarily a linear function of the height. Using second-order isotropic elasticity, the analytical solutions show that the shear displacements are characterized by the product of sine and hyperbolic sine functions of the height and depth variables, respectively. The height dependence of the shear displacement is predicted to be a combination of linear and sinusoidal functions, and is verified against the test data of agar-gelatin cuboidal blocks. If the gravity effect is incorporated, a quadratic dependence on height is additionally predicted. The calculation of stresses reveals the presence of not only negative normal stresses but also sinusoidally varying shear stresses on the lateral planes tending to distort the block about the height direction. These results can be of great importance in tissue/cell mechanics.

Wang, Dong; Wu, M. S.

2014-10-01

185

Shear Reinforcements in the Reinforced Concrete Beams

Directory of Open Access Journals (Sweden)

Full Text Available - This study focuses on the use of different types of shear reinforcement in the reinforced concrete beams. Four different types of shear reinforcement are investigated; traditional stirrups, welded swimmer bars, bolted swimmer bars, and u-link bolted swimmer bars. Beam shear strength as well as beam deflection are the main two factors considered in this study. Shear failure in reinforced concrete beams is one of the most undesirable modes of failure due to its rapid progression. This sudden type of failure made it necessary to explore more effective ways to design these beams for shear. The reinforced concrete beams show different behavior at the failure stage in shear compare to the bending, which is considered to be unsafe mode of failure. The diagonal cracks that develop due to excess shear forces are considerably wider than the flexural cracks. The cost and safety of shear reinforcement in reinforced concrete beams led to the study of other alternatives. Swimmer bar system is a new type of shear reinforcement. It is a small inclined bars, with its both ends bent horizontally for a short distance and welded or bolted to both top and bottom flexural steel reinforcement. Regardless of the number of swimmer bars used in each inclined plane, the swimmer bars form plane-crack interceptor system instead of bar-crack interceptor system when stirrups are used. Several reinforced concrete beams were carefully prepared and tested in the lab. The results of these tests will be presented and discussed. The deflection of each beam is also measured at incrementally increased applied load.

Moayyad M. Al-Nasra

2013-10-01

186

Shear coaxial injector instability mechanisms

There is no definitive knowledge of which of several concurrent processes ultimately results in unstable combustion within liquid rocket chambers employing shear coaxial injectors. Possible explanations are a detrimental change in the atomization characteristics due to a decrease in the gas-to-liquid velocity ratio, a change in the gas side injector pressure drop allowing acoustic coupling to the propellant feed system or the disappearance of a stabilizing recirculation region at the base of the LOX post. The aim of this research effort is to investigate these proposed mechanisms under conditions comparable to actual engine operation. Spray characterization was accomplished with flash photography and planar laser imaging to examine the overall spray morphology and liquid jet breakup processes and with a PDPA to quantify the spatial distribution of droplet size and mean axial velocity. A simplified stability model based on the Rayleigh criterion was constructed for the flow dynamics occurring within the chamber and injector to evaluate the potential coupling between the chamber and injector acoustic modes and was supported by high frequency measurements of chamber and injector pressure oscillations. To examine recirculation within the LOX post recess, velocity measurements were performed in the recess region by means of LDV. Present experiments were performed under noncombusting conditions using LOX/GH2 stimulants at pressures up to 4 MPa.

Puissant, C.; Kaltz, T.; Glogowski, M.; Micci, M.

1994-01-01

187

Shear viscosity from effective couplings of gravitons

International Nuclear Information System (INIS)

We calculate the shear viscosity of field theories with gravity duals using Kubo formula by calculating the Green function of dual transverse gravitons and confirm that the value of the shear viscosity is fully determined by the effective coupling of transverse gravitons on the horizon. We calculate the effective coupling of transverse gravitons for Einstein and Gauss-Bonnet gravities coupled with matter fields, respectively. Then we apply the resulting formula to the case of AdS Gauss-Bonnet gravity with F4 term corrections of Maxwell field and discuss the effect of F4 terms on the ratio of the shear viscosity to entropy density.

188

Measuring cosmic shear with the ring statistics

Digital Repository Infrastructure Vision for European Research (DRIVER)

Commonly used methods to decompose E- and B-modes in cosmic shear, namely the aperture mass dispersion and the E/B-mode shear correlation function, suffer from incomplete knowledge of the two-point correlation function (2PCF) on very small and/or very large scales. The ring statistics, the most recently developed cosmic shear measure, improves on this issue and is able to decompose E- and B-modes using a 2PCF measured on a finite interval. First, we improve on the ring stati...

Eifler, Tim; Schneider, Peter; Krause, Elisabeth

2009-01-01

189

Topological defects in gravitational lensing shear fields

International Nuclear Information System (INIS)

Shear fields due to weak gravitational lensing have characteristic coherent patterns. We describe the topological defects in shear fields in terms of the curvature of the surface described by the lensing potential. A simple interpretation of the characteristic defects is given in terms of the the umbilical points of the potential surface produced by ellipsoidal halos. We show simulated lensing shear maps and point out the typical defect configurations. Finally, we show how statistical properties such as the abundance of defects can be expressed in terms of the correlation function of the lensing potential

190

German bundle shear - cold test results

International Nuclear Information System (INIS)

In the planned Federal Republic of Germany (FRG) reprocessing plant, the mechanical decladding of the fuel elements will be done with a bundle shear. This shear was designed and built with Thyssen Henschel by adapting the experiences of the Wiederaufarbeitungsanlage Karlsruhe (WAK), the FRG reprocessing pilot plant. The tests included boiling water reactor (BWR) and pressurized water reactor (PWR) dummy elements filled with porcelain as well as steel fuel rod simulators. During the test period with prototype bundle shear, some technical improvements have been found that refer both to operating conditions and to remote handling. In 1987 the acceptance tests will be run

191

Topological Defects in Gravitational Lensing Shear Fields

Shear fields due to weak gravitational lensing have characteristic coherent patterns. We describe the topological defects in shear fields in terms of the curvature of the surface described by the lensing potential. A simple interpretation of the characteristic defects is given in terms of the the umbilical points of the potential surface produced by ellipsoidal halos. We show simulated lensing shear maps and point out the typical defect configurations. Finally, we show how statistical properties such as the abundance of defects can be expressed in terms of the correlation function of the lensing potential.

Vitelli, Vincenzo; Kamien, Randall D

2009-01-01

192

The shear viscosity of holographic superfluids

International Nuclear Information System (INIS)

We study the ratio of the shear viscosity to the entropy density for various holographic superfluids. For the s-wave case, the ratio has the universal value 1/(4?) as in various holographic models. For the p-wave case, there are two shear viscosity coefficients because of the anisotropic boundary spacetime, and one coefficient has the universal value. For the (p+ip)-wave case, the existing technique is not applicable since there is no tensor mode of metric perturbations which decouples from Yang-Mills perturbations. Our results indicate that the shear viscosity does not show a singular behavior at the critical point for holographic superfluids. (author)

193

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

194

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)

195

Shear instability in magnetized, collisional dusty plasmas

Energy Technology Data Exchange (ETDEWEB)

The shear instability of magnetized, collisional dusty plasma is investigated in the present work. It is demonstrated that the relative drift between the charged dust and magnetised electrons and ions which give rise to the Hall effect is crucial to this instability. Although the nature of present shear instability is similar to the Kelvin-Helmholtz instability, the role of magnetic field in the present case is important in destabilising waves. The maximum growth rate of the instability is proportional only to the shear gradient and is independent of the ambient magnetic field strength. Most unstable wavenumber is a function of ambient dust parameters.

Pandey, B. P. [Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales 2109 (Australia); Vladimirov, S. V.; Samarian, A. A. [School of Physics, University of Sydney, New South Wales 2006 (Australia)

2012-06-15

196

Shear instability in magnetized, collisional dusty plasmas

International Nuclear Information System (INIS)

The shear instability of magnetized, collisional dusty plasma is investigated in the present work. It is demonstrated that the relative drift between the charged dust and magnetised electrons and ions which give rise to the Hall effect is crucial to this instability. Although the nature of present shear instability is similar to the Kelvin-Helmholtz instability, the role of magnetic field in the present case is important in destabilising waves. The maximum growth rate of the instability is proportional only to the shear gradient and is independent of the ambient magnetic field strength. Most unstable wavenumber is a function of ambient dust parameters.

197

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

198

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

199

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

200

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

201

Shear strength measurements of ductile polymer films with controlled normal to shear plane angles

International Nuclear Information System (INIS)

to fracture and could be used for the investigation of shear bands by scanning electron microscopy (SEM). As the normal to shear plane angle was increased from 30 to 60o, the shear bands were more concentrated on the center region owing to the higher normal compressive stress. For the fractured specimen, the fracture surface investigated by SEM showed the striations which can be related to the shear bands. As the normal to shear plane angle was increased from 30 to 45o, the concentrated shear bands caused less striations perpendicular to the fracture direction. Interestingly, it also leaded to the appearance of the striations parallel to the fracture direction. As the angle was further increased to 60o, small islands formed by the cross-over of parallel and perpendicular striations appeared in the fracture surface. A possible mechanism for the formation of this unique fracture surface was proposed.

202

Nucleation and initial propagation of shear cracks

Directory of Open Access Journals (Sweden)

Full Text Available SUMMARY. - By means of the dislocation theory, an explanation is found

for the antientropic process of microcracking-macrocracking transition in the

shear fracture initial propagation.

F. MULARGIA

1977-06-01

203

Turbulent diffusion with memories and intrinsic shear

The first part of the present theory is devoted to the derivation of a Fokker-Planck equation. The eddies smaller than the hydrodynamic scale of the diffusion cloud form a diffusivity, while the inhomogeneous, bigger eddies give rise to a nonuniform migratory drift. This introduces an eddy-induced shear which reflects on the large-scale diffusion. The eddy-induced shear does not require the presence of a permanent wind shear and is intrinsic to the diffusion. Secondly, a transport theory of diffusivity is developed by the method of repeated-cascade and is based upon a relaxation of a chain of memories with decreasing information. The full range of diffusion consists of inertia, composite, and shear subranges, for which variance and eddy diffusivities are predicted. The coefficients are evaluated. Comparison with experiments in the upper atmosphere and oceans is made.

Tchen, C. M.

1974-01-01

204

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

205

Acoustic waves in unbounded shear flows

International Nuclear Information System (INIS)

The linear evolution of acoustic waves in fluid flow with constant density and uniform shear of velocity is investigated. The process of the mean flow energy extraction by the three-dimensional acoustic waves which is due to the non-normality of linear dynamics in shear flows is analyzed. The thorough examination of the dynamics of different physical quantities, specifying the wave evolution, is outlined. The revealing of the behaviour becomes possible owing to the nonmodal approach that has been extensively used in the study of the perturbations evolution in shear flows since the beginning of the nineties. In addition, a detailed analyses of the physics of shear energy gain by vortex and acoustic perturbations is presented. (author). 28 refs, 7 figs

206

Turbulence evolution in plasma shear flows

International Nuclear Information System (INIS)

The renormalized nonlinear analysis of the temporal evolution of drift-type modes in plasma shear flows is developed. The theory accounts for the effect of the turbulent motions of plasma on the saturation of the resistive drift instability. The nonlinear balance equation, which determines the saturation level of the resistive drift instability in shear flow is obtained. It was prowed that the “nonlinear effect of the enhanced decorrelation by shear flow” has nothing in common with process of the saturation. The same conclusion is applicable to all fluid models of plasma, obtained in drift approximation, in which all nonlinearities, other than E×B are ignored. The linear non-modal kinetic theory to the Vlasov-Poisson system is developed. This theory reveals the velocity shear in a non-modal time-dependent effect of the finite Larmor radius. (author)

207

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

208

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

209

Granular Shear Flow in Varying Gravitational Environments

Despite their very low surface gravities, asteroids exhibit a number of different geological processes involving granular matter. Understanding the response of this granular material subject to external forces in microgravity conditions is vital to the design of a successful asteroid sub-surface sampling mechanism, and in the interpretation of the fascinating geology on an asteroid. We have designed and flown a Taylor-Couette shear cell to investigate granular flow due to rotational shear forces under the conditions of parabolic flight microgravity. The experiments occur under weak compression. First, we present the technical details of the experimental design with particular emphasis on how the equipment has been specifically designed for the parabolic flight environment. Then, we investigate how a steady state granular flow induced by rotational shear forces differs in varying gravitational environments. We find that the effect of constant shearing on the granular material, in a direction perpendicular to t...

Murdoch, N; Green, S F; de Lophem, T-L; Michel, P; Losert, W

2013-01-01

210

Wall Shear Rates in Taylor Vortex Flow

Directory of Open Access Journals (Sweden)

Full Text Available Wall shear rate and its axial and azimuthal components were evaluated in stable Taylor vortices. The measurements were carried out in a broad interval of Taylor numbers (52-725 and several gap width (R1/R2 = 0.5 – 0.8 by two three-segment electrodiffusion probes and three single probes flush mounted in the wall of the outer fixed cylinder. The axial distribution of wall shear rate components was obtained by sweeping the vortices along the probes using a slow axial flow. The experimental results were verified by CFD simulations. The knowledge of local wall shear rates and its fluctuations is of primordial interest for industrial applications like tangential filtration, membrane reactors and bioreactors containing shear sensitive cells.

V. Sobolik

2011-01-01

211

Evolution of circular shear layers

International Nuclear Information System (INIS)

The Kelvin-Helmholtz instability is a generic pathway for the formation of coherent vortical structures in quasi-neutral and non-neutral plasmas, as well as in ordinary fluids. Both plasma and fluid experiments have demonstrated rich bifurcation sequences accompanied by topological changes in the distribution of the coherent structures, in addition to various oscillating, quasiperiodic or chaotic states. The authors have performed both analytical and numerical studies which demonstrate that such transitions can be accurately described by reducing the system of slightly viscous, forced Navier-Stokes equations to a system of ordinary differential equations of few degrees of freedom. The simplest case studied so far in detail leads to an equation of the Landau type describing the saturation of the Kelvin-Helmholtz instability in terms of the amplitude A(?) of the most unstable mode, with ? a slow time scale. In this case the dynamical equation assumes the form ?A?= ?A + ?A2A*. The complex coefficients of this reduced equation are computed by numerical solution of appropriate eigenvalue problems. In conjunction with these analytical calculations, a highly accurate spectral code has been used to directly simulate the forced, circular shear flows. Both the analytical and the numerical results are in excellent agreement with fluid experiments and show the same qualitative behavior as the plasma experiments where a detailed quantitative comparison a detailed quantitative comparison is difficult due to limitations in the experimental information. The two approaches supplement each other in predicting the transition to states of ever increasing complexity, even beyond regimes that have so far been experimentally accessible

212

Digital Repository Infrastructure Vision for European Research (DRIVER)

An optical set-up for electronic speckle pattern shearing interferometry (ESPSI) using a photopolymer diffractive optical element as a shearing element, is presented. A laser beam illuminates the object at an angle to the normal to the object surface. The holographic diffraction grating is placed in front of the object. The zero and the first order of diffraction form the image and the sheared image of the object. The images are imaged onto the CCD camera, whose optical axis coincides w...

Mihaylova, Emilia; Naydenova, Izabela; Martin, Suzanne; Toal, Vincent

2005-01-01

213

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 ?, expressed by n ~ ?(-n), exhibits three distinct regimes. The first is the well-known Newtonian regime, namely, ? independent of shear rate at small shear rates ? ?0(-1)) the shear dependence of viscosity exhibits a crossover at a critical shear rate ?c dividing this regime into two different regimes, shear thinning regime I (ST-I) and II (ST-II), respectively. In the ST-I regime (?0(-1) ?c) a universal power law n ~ ?(-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 ?c will be equal to ?0(-1), lies in the interval 30 differences N1 and N2 follow power laws of N1 ~ ?(2/3) and N2 ~ ?(0.82), respectively; the orientation resistance parameter mG follows the relation mG ~ ?(0.75) and the tumbling frequency ftb follows ftb ~ ?(0.75). These results imply that the effects of entanglement on the shear dependences of these properties may be negligible in the ST-II regime. These findings may shed some light on the nature of shear thinning in flexible linear polymer melts. PMID:24811663

Xu, Xiaolei; Chen, Jizhong; An, Lijia

2014-05-01

214

Transformation between ion sound waves and shear vortices in plasma with strong shear flow

International Nuclear Information System (INIS)

Temporal evolution of the low frequency electrostatic perturbations in an unmagnetized plasma with strong shear flow is investigated. From fluid equations, the differential equations governing the low frequency electrostatic perturbations are deduced. Using the Non-modal approach, the temporal evolution equations with Spatial Fourier Harmonics for the disturbed quantities are obtained, and have been studied numerically. Numerical calculations show that the shear vortices can be transformed into the ion sound waves under the condition of high shear parameter

215

Shear History Effect on a Phase Transition under Shear of a Salt Free CTAB Solution

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the results of rheological measurements showing the evolution of shifting Nematic/Isotropic temperature transition under shear. Nematic phase is induced from shear and disappears when temperature rises (always under shear). Successive temperature sweeps on the same solution have a significative effect on the transition temperature showing thus a kind of memory effect. The micellar system studied here is cationic (CTAB) without salt added at concentration of 0.6 M/l which is near b...

Cappelaere, E.; Cressely, R.

1995-01-01

216

Shear stress distribution due to shear and Rayleigh wave propagation at deep soil sites

International Nuclear Information System (INIS)

Earthquake strong motion at ground surface may be described as the combined result of body (compression and shear) waves and surface waves. In the course of earthquake engineering site response analyses, it is usually assumed that surface motions are a result of vertically propagating body waves. In studies of liquefaction potential, it is assumed that soil shear strains are a result of vertically propagating shear waves. However, shear strains are also caused by surface Rayleigh waves and solutions to strains from each source are derived and compared in the paper, and the results for shear strain in terms of surface acceleration and wave length are presented in non-dimensional form. The results of this investigation show that the distribution of soil shear strain as a function of depth below the gound surface is different depending upon whether shear waves or Rayleigh waves are assumed to be the source of horizontal motions at the ground surface. It is shown that the shear strains derived from Rayleigh waves are greater near the surface but decrease faster with depth than the shear strains derived from vertically propagating shear waves. It is noted that the more rapid attenuation of shear strains with depth as predicted by Rayleigh wave theory is more consistent with observed cases of soil liquefaction which are usually limited to shallow depths, generally not in excess of 10 to 20 meters. On the contrary, vertical shear propagation theory predicts liquefaction occupagation theory predicts liquefaction occurring at loose sand sites at much greater depths. The differences are significant enough to influence the decision regarding liquefaction potential of a soil site

217

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 2x103 s-1; the materials studied are in martensitic steel and a titanium alloy, at ambient temperature and up to 5000C. 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

218

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

219

Liquid migration in sheared unsaturated granular media

We show how liquid migrates in sheared unsaturated granular media using a grain scale model for capillary bridges. Liquid is redistributed to neighboring contacts after rupture of individual capillary bridges leading to redistribution of liquid on large scales. The liquid profile evolution coincides with a recently developed continuum description for liquid migration in shear bands. The velocity profiles which are linked to the migration of liquid as well as the density profiles of wet and dry granular media are studied.

Mani, Roman; Herrmann, Hans J

2012-01-01

220

Supertransient magnetohydrodynamic turbulence in Keplerian shear flows

A subcritical transition to turbulence in magnetized Keplerian shear flows is investigated using a statistical approach. Three-dimensional numerical simulations of the shearing box equations with zero net magnetic flux are employed to determine the transition from decaying to sustained turbulence as a function of the magnetic Reynolds number Rm. The results reveal no clear transition to sustained turbulence as the average lifetime of the transients grows as an exponential function of Rm, in accordance with a type-II supertransient law.

Rempel, Erico L; Proctor, Michael R E

2010-01-01

221

Rheology of Dense Sheared Granular Liquids

Digital Repository Infrastructure Vision for European Research (DRIVER)

The rheology of dense sheared granular liquids is investigated based on the mode-coupling theory (MCT). This extended MCT includes correlations for the density-current mode as well as the density-density correlation mode, and a self-consistent coupling equation for the energy balance condition. The extended MCT exhibits disappearance of the two-step relaxation of the density-density correlation function, and also successfully reproduces the density dependence of the shear vi...

Suzuki, Koshiro; Hayakawa, Hisao

2013-01-01

222

Shear strength properties of wet granular materials

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate shear strength properties of wet granular materials in the pendular state (i.e. the state where the liquid phase is discontinuous) as a function of water content. Sand and glass beads were wetted and tested in a direct shear cell and under various confining pressures. In parallel, we carried out three-dimensional molecular dynamics simulations by using an explicit equation expressing capillary force as a function of interparticle distance, water bridge volume ...

Richefeu, Vincent; El Youssoufi, Moulay Sai?d; Radjai, Farhang

2006-01-01

223

Resistive interchange instability in reversed shear tokamaks

Energy Technology Data Exchange (ETDEWEB)

Resistive interchange modes become unstable due to the magnetic shear reversal in tokamaks. In the present paper, the parameter dependences, such as q (safety factor) profile and the magnetic surface shape are clarified for improving the stability, using the local stability criterion. It is shown that a significant reduction of the beta limit is obtained for the JT-60U reversed shear configuration with internal transport barrier, since the local pressure gradient increases. (author)

Furukawa, Masaru; Nakamura, Yuji; Wakatani, Masahiro [Graduate School of Energy Science, Kyoto University, Uji, Kyoto (Japan)

1999-04-01

224

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

225

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

226

Electroviscous effects of simple electrolytes under shear

On the basis of a hydrodynamical model analogous to that in critical fluids, we investigate the influences of shear flow upon the electrostatic contribution to the viscosity of binary electrolyte solutions in the Debye-H\\"{u}ckel approximation. Within the linear-response theory, we reproduce the classical limiting law that the excess viscosity is proportional to the square root of the concentration of the electrolyte. We also extend this result for finite shear. An analytic expression of the anisotropic structure factor of the charge density under shear is obtained, and its deformation at large shear rates is discussed. A non-Newtonian effect caused by deformations of the ionic atmosphere is also elucidated for $\\tau_D\\dot{\\gamma}>1$. This finding concludes that the maximum shear stress that the ionic atmosphere can support is proportional to $\\lambda_D^{-3}$, where $\\dot{\\gamma}$, $\\lambda_D$ and $\\tau_D=\\lambda_D^2/D$ are, respectively, the shear rate, the Debye screening length and the Debye relaxation tim...

Wada, H

2005-01-01

227

Edge Sheared Flows and Blob Dynamics

International Nuclear Information System (INIS)

Full text: A study of sheared flows in the edge and scrape-off layer (SOL) and their interaction with blob-filaments is presented. Edge sheared flows are believed to be important for the L-H, and H-L transitions. Blob generation and dynamics impacts both the (near-separatrix) scrape-off-layer (SOL) width critical for power handling in the divertor, and the interaction of plasma in the far SOL with plasma-facing components. These topics are critical for ITER and future devices. A fluid-based 2D curvature-interchange model embedded in the SOLT code is employed to study these issues. Sheared binormal flows both regulate the power flux crossing the separatrix and control the character of emitted turbulence structures such as blob-filaments. At a critical power level (depending on parameters) the laminar flows containing intermittent, but bound, structures give way to full-blown blob emissions signifying a transition from quasi-diffusive to convective transport. In order to diagnose sheared flows in experiments and assess their interaction with blobs, a blob-tracking algorithm has been developed and applied to both NSTX and Alcator C-Mod data. Blob motion and ellipticity can be affected by sheared flows, and are diagnosed and compared with seeded blob simulations. A picture of the interaction of blobs and sheared flows is emerging from advances in the theory and simulation of edge turbulence, combined with ever-improving capabilities for edge diagnostics and their analysis. (author)

228

Two-state shear diagrams for complex fluids in shear flow

The possible ``phase diagrams'' for shear-induced phase transitions between two phases are collected. We consider shear-thickening and shear-thinning fluids, under conditions of both common strain rate and common stress in the two phases, and present the four fundamental shear stress vs. strain-rate curves and discuss their concentration dependence. We outline how to construct more complicated phase diagrams, discuss in which class various experimental systems fall, and sketch how to reconstruct the phase diagrams from rheological measurements.

Olmsted, P D

1999-01-01

229

Two orogens One shear belt: 1 Ga of repeated deformation along the Central Tanzanian Shear Belt

The Central Tanzanian Shear Belt (CTSB) constitutes a 300-km long W-E trending dextral shear belt that was active during Paleoproterozoic and Neoproterozoic orogenies. It formed along the southern margin of the Archean Tanzania Craton that acted as rigid indenter during both orogenies. Based on structural and microtextural methods several deformational stages have been identified. Paleoproterozoic shear is recorded in the 1.8-2.0 Ga old magmatic Usagaran Belt. This shear was accompanied by vast melt intrusions in a hot and soft crust leading to low strain and coaxial flow. It ceased in an exhumation phase with localized non-coaxial shear followed by the deposition of nonconform sediments dated around 1.9 Ga. In the Neoproterozoic, the CTSB is found as reactivated shear zones in the Usagaran Orogen and as megascale shear zone in the metamorphic Mozambique Belt. It is a release (or counterflow) structure that evolved in the course of crustal thickening in a strong crust around 0.6 Ga. Along the strike of the Neoproterozoic CTSB syntectonic conditions change from localized brittle shear along the Tanzania Craton to distributed high temperature coaxial shear in the eastern section of the orogen's root. This goes along with a significant change in microstructures and LPO patterns.

Tenczer, Veronika; Fritz, Harald; Bauernhofer, Andreas; Hauzenberger, Christoph

2007-10-01

230

Shear strength of non-shear reinforced concrete elements : Part 2. T- beams

DEFF Research Database (Denmark)

The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange. The position of the crack in which sliding takes place is determined by the crack sliding model developed by Jin-Ping Zhang. The theoretical calculations are compared with test results reported in the literature. A good agreement has been found.A simplified method to calculate the shear capacity of T-beams is presented.

Hoang, Cao linh

1997-01-01

231

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

232

Shear Deformation of 3D Carbon Woven Fabrics

International Nuclear Information System (INIS)

This study was to analyze the mechanism of shear deformation and yarn slippage in the 3D (Three Dimensional) carbon woven fabric. For this study three weaves orthogonal, layer to layer and angle interlock were tested in Kawabata shearing instrument and all the results were analyzed. The relationship between the shear load and shear angle was measured in both warp and weft directions. It is shown that the fabric having highly compact structure exhibits high shear rigidity and it can withstand high shearing load. The orthogonal weave has shown much higher shear rigidity as compared to other weave structures. (author)

233

How to create mylonitic shear zones in the presence of shear heating

Lithospheric-scale shear zones are commonly defined as regions inhomogeneous and localized deformation. Strain softening has been demonstrated to be necessary for localization in those shear zones, but there is still debate about the physical cause of this softening. Here, we investigate the interplay between two mechanisms that have been suggested to have a significant impact on lithospheric localization: shear heating and grain size reduction. Shear heating has been suggested to play an important role in i) creating deep focus as well as intermediate-depth earthquakes (Ogawa (1987), Kelemen and Hirth (2007)) and ii) creating lithospheric-scale shear zones, thus creating a weak decoupling interface that enables subsequent subduction initiation (Kaus and Podlatchikov (2006), Crameri and Kaus (2010)). As natural shear zones typically have a significantly reduced grain size, it has been put forward that grain size reduction provides the necessary strain softening to localize deformation. As grain size reduces, the dominant deformation mechanism switches from dislocation to diffusion creep, thus requiring less stress to deform the rock. Usually, the equilibrium grain size is thought to follow a piezometric relationship, thus indicating the stress under which a shear zone deformed. Recent work (Austin and Evans (2007), Rozel et al. (2011)) suggests that the equilibrium grain size is not dependent on stress, but rather on the deformational work. In our study, we employ the grain size evolution law of Rozel et al. and use 1D viscoelastic numerical models of simple shear deformation to investigate the influence of both weakening mechanisms and their interaction for a variety of boundary conditions. We find that grain size reduction in pure olivine does not localize very efficiently, as grain size very rapidly reaches a steady state. Even when a fraction of the deformational work is used by grain size reduction processes, shear heating is found to localize very efficiently (Kaus & Podlatchikov (2005), Braeck et al. (2009)) and the significant temperature increase induced by shear heating severely affects the grain size in the shear zone. Generally, we find that the elevated temperature inside the shear zone results in a larger grain size inside the shear zone compared to the surrounding rock matrix. This finding is not compatible with field observations, where shear zones are usually characterized by small grain sizes. This indicates that further mechanisms are needed to keep either the grain size small (e.g. pinning by secondary phases (Herwegh et. al (2011), Bercovici and Ricard (2012) ) or to limit the temperature increase inside the shear zone.

Thielmann, Marcel; Rozel, Antoine; Kaus, Boris; Ricard, Yanick

2013-04-01

234

A New Shear Estimator for Weak Lensing Observations

We present a new shear estimator for weak lensing observations which properly accounts for the effects of a realistic point spread function (PSF). Images of faint galaxies are subject to gravitational shearing followed by smearing with the instrumental and/or atmospheric PSF. We construct a `finite resolution shear operator' which when applied to an observed image has the same effect as a gravitational shear applied prior to smearing. This operator allows one to calibrate essentially any shear estimator. We then specialize to the case of weighted second moment shear estimators. We compute the shear polarizability which gives the response of an individual galaxy's polarization to a gravitational shear. We then compute the response of the population of galaxies, and thereby construct an optimal weighting scheme for combining shear estimates from galaxies of various shapes, luminosities and sizes. We define a figure of merit --- an inverse shear variance per unit solid angle --- which characterizes the quality o...

Kaiser, N

1999-01-01

235

Precursors to the shear failure of rock discontinuities

geophysical monitoring of potential failure along mechanical discontinuities in rock requires identification of precursory signatures to failure in geophysical signals. Active ultrasonic monitoring of shear failure along frictional discontinuities was performed to determine the signatures of potential failure. An instrumented direct shear apparatus was used to apply a constant shearing rate to a discontinuity that was held under a constant normal stress. Transmitted and reflected compressional and shear waves were recorded during the shearing process. Ultrasonic precursors were identified as distinct maxima in the amplitude of transmitted shear waves as well as minima in the amplitude of reflected shear waves that occurred well before the peak shear strength of a frictional discontinuity. The precursors are linked to changes in the local shear specific stiffness along the discontinuity, while the discontinuity's macroscopic shear strength continues to increase prior to failure.

Hedayat, Ahmadreza; Pyrak-Nolte, Laura J.; Bobet, Antonio

2014-08-01

236

High shear stress rheology of liquid lubricants

Energy Technology Data Exchange (ETDEWEB)

It is well known that non-Newtonian behavior may manifest when the liquid under study is a high molecular weight polymer, a mixture of a polymer and low viscosity liquid, or a suspension. However, it is shown that at sufficiently high shear stress even traditionally Newtonian liquids become highly nonlinear and that they display a yield stress analogous to that of solids and of roughly the same magnitude. This phenomena has implications for any engineering application for which a very large shear stress must be sustained by a liquid such as metalworking, bearing lubrication, liquid jet machining, and ballistic impacts. Included are measurements of the variation of viscosity with pressure and temperature and the determination of the glass transition temperature and dielectric relaxation time at elevated pressure. These studies motivated the search for solid-like response of liquid lubricants at high pressure and subsequently, measurements of elastic modulus and yield strength. The observed variation of yield strength of these liquids with shear rate led to the conclusion that a rate independent limiting shear stress model is appropriate. Measurements on liquids above the glass transition temperature showed that the limiting stress concept governs the high shear stress rheology in the liquid state as well as for amorphous solids. A constitutive law is presented which includes viscous, elastic and plastic behavior, and appears to be consistent with all observed behavior in uniaxial shear. Many rheometers were developed. Shear stresses were generated in liquids essentially free of thermal effects to levels about one hundred times greater than were achieved before. Viscosities as high as 10{sup 12} Pa were measured and PVT data were generated on liquids at pressures to 1.7 GPa (250,000 psi).

Bair, S.

1990-01-01

237

Boundary Shear Stress Along Vegetated Streambanks

Sediment, a leading cause of water quality impairment, damages aquatic ecosystems and interferes with recreational uses and water treatment processes. Streambank retreat can contribute as much as 85% of watershed sediment yield. Vegetation is an important component of stream restoration designs used to control streambank retreat, but vegetation effects on streambank boundary shear stress (SBSS) need to be quantified. The overall goal of this experiment is to predict boundary shear stress along vegetated streambanks. This goal will be met by determining a method for measuring boundary shear stress in the field along hydraulically rough streambanks, evaluating the effects of streambank vegetation on boundary shear stress in the field, and developing predictive methods based on measurable vegetative properties. First, three streambank vegetation types (herbaceous, shrubbery, and woody) will be modeled in a flume study to examine both boundary shear stress measurement theory and instruments for field use. An appropriate method (law of the wall, Reynold's stresses, TKE, or average wall shear stress) and field instrument (ADV, propeller, or Pitot tube) will be selected, resulting in a field technique to measure SBSS. Predictive methods for estimating SBSS, based on common vegetation measurements, will be developed in the flume study and validated with field data. This research is intended to improve our understanding of the role of riparian vegetation in stream morphology by evaluating the effects of vegetation on boundary shear stress, providing insight to the type and density of vegetation required for streambank stability. The results will also aide in quantifying sediment inputs from streambanks, providing quantitative information for stream restoration projects and watershed management planning.

Clark, L. A.; Wynn, T.

2007-12-01

238

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...

Salvatore Faugno; Andrea Formato

2007-01-01

239

Logarithmic Wind Profile: A Stability Wind Shear Term

Digital Repository Infrastructure Vision for European Research (DRIVER)

A stability wind shear term of logarithmic wind profile based on the terms of turbulent kinetic energy equation is proposed. The fraction influenced by thermal stratification is considered in the shear production term. This thermally affected shear is compared with buoyant term resulting in a stability wind shear term. It is also considered Reynolds stress as a sum of two components associated with wind shear from mechanical and thermal stratification process. The stability ...

Sakagami, Yoshiaki; Santos, Pedro A. A.; Haas, Reinaldo; Passos, Julio C.; Taves, Frederico F.

2014-01-01

240

Shear-Thickening Response of Fumed Silica Suspensions under Steady and Oscillatory Shear

Suspensions of fumed silica in polypropylene glycol exhibit shear-thickening under steady shear and "strain-thickening" under oscillatory shear. Strain-thickening refers to a sharp increase in the complex viscosity eta* observed at critical combinations of strain-amplitude and frequency. Two regimes of strain-thickening behavior have been found: The first occurs at high critical strains and low frequencies, whereas the second occurs at high critical frequencies and a constant lower strain. Strain-thickening in the first regime can be explicitly correlated with steady shear-thickening, using a modified version of the Cox-Merz rule. Accordingly, strain-thickening data for the complex viscosity eta* as a function of the maximum dynamic shear-rate gamma0omega can be superposed against shear-thickening data for the steady viscosity as a function of the steady shear rate. Such a correlation between the two kinds of thickening phenomena has not been reported previously. The combination of shear- and strain-thickening behavior can be qualitatively explained using a clustering mechanism, which attributes the various phenomena to the formation of temporary, flow-induced clusters. The two regimes of strain-thickening are a result of differences in the relative ease of cluster formation. PMID:9056301

Raghavan; Khan

1997-01-01

241

Dilute rigid dumbbell suspensions in large-amplitude oscillatory shear flow: Shear stress response

We examine the simplest relevant molecular model for large-amplitude shear (LAOS) flow of a polymeric liquid: the suspension of rigid dumbbells in a Newtonian solvent. We find explicit analytical expressions for the shear rate amplitude and frequency dependences of the first and third harmonics of the alternating shear stress response. We include a detailed comparison of these predictions with the corresponding results for the simplest relevant continuum model: the corotational Maxwell model. We find that the responses of both models are qualitatively similar. The rigid dumbbell model relies entirely on the dumbbell orientation to explain the viscoelastic response of the polymeric liquid, including the higher harmonics in large-amplitude oscillatory shear flow. Our analysis employs the general method of Bird and Armstrong ["Time-dependent flows of dilute solutions of rodlike macromolecules," J. Chem. Phys. 56, 3680 (1972)] for analyzing the behavior of the rigid dumbbell model in any unsteady shear flow. We derive the first three terms of the deviation of the orientational distribution function from the equilibrium state. Then, after getting the "paren functions," we use these for evaluating the shear stress for LAOS flow. We find the shapes of the shear stress versus shear rate loops predicted to be reasonable.

Bird, R. B.; Giacomin, A. J.; Schmalzer, A. M.; Aumnate, C.

2014-02-01

242

Shear-current effect in a turbulent convection with a large-scale shear.

The shear-current effect in a nonrotating homogeneous turbulent convection with a large-scale constant shear is studied. The large-scale velocity shear causes anisotropy of turbulent convection, which produces the mean electromotive force epsilon (W) proportional to W x J and the mean electric current along the original mean magnetic field, where W is the background mean vorticity due to the shear and J is the mean electric current. This results in a large-scale dynamo even in a nonrotating and nonhelical homogeneous sheared turbulent convection, whereby the alpha effect vanishes. It is found that turbulent convection promotes the shear-current dynamo instability, i.e., the heat flux causes positive contribution to the shear-current effect. However, there is no dynamo action due to the shear-current effect for small hydrodynamic and magnetic Reynolds numbers even in a turbulent convection, if the spatial scaling for the turbulent correlation time is tau(k) proportionalto to k-2, where k is the small-scale wave number. PMID:17500991

Rogachevskii, Igor; Kleeorin, Nathan

2007-04-01

243

Shear-current effect in a turbulent convection with a large-scale shear

The shear-current effect in a nonrotating homogeneous turbulent convection with a large-scale constant shear is studied. The large-scale velocity shear causes anisotropy of turbulent convection, which produces the mean electromotive force $\\bec{\\cal E}^{(W)} \\propto {\\bf W} {\\bf \\times} {\\bf J}$ and the mean electric current along the original mean magnetic field, where ${\\bf W}$ is the background mean vorticity due to the shear and ${\\bf J}$ is the mean electric current. This results in a large-scale dynamo even in a nonrotating and nonhelical homogeneous sheared turbulent convection, whereby the $\\alpha$ effect vanishes. It is found that turbulent convection promotes the shear-current dynamo instability, i.e., the heat flux causes positive contribution to the shear-current effect. However, there is no dynamo action due to the shear-current effect for small hydrodynamic and magnetic Reynolds numbers even in a turbulent convection, if the spatial scaling for the turbulent correlation time is $\\tau(k) \\propto ...

Rogachevskii, I

2007-01-01

244

Microstructural Evolution in Adiabatic Shear Localization

Shear bands were generated under prescribed and controlled conditions in stainless steel( Fe-18Hat-shaped specimens, deformed in a Hopkinson bar were used, yielding strain rates of approximately 104s-1 and shear strains that could be varied between 1 and 100.Specimens recovered from the collapse of thick-walled cylinders were also investigated. Microstructural characterization was performed by electron backscattered diffraction (EBSD) with orientation imaging microscopy(OIM), and transmission electron microscopy (TEM). The shear-band thickness was approximately 8 µm. This low-stacking fault energy alloy deforms, at the imposed strain rates (outside of the shear band), by planar dislocations and stacking fault packets, twinning, and occasional martensitic phase transformations at twin-twin intersections. EBSD reveals gradual lattice rotations of the grains approaching the core of the band. A [110] fiber texture (with the [110] direction perpendicular to both shear direction and shear plane normal) develops both within the shear band and in the adjacent grains. The formation of this texture, under an imposed global simple shear, suggests that rotations take place concurrently with the shearing deformation. This can be explained by compatibility requirements between neighboring deforming regions.EBSD could not reveal the deformation features at large strains because their scale was beklow thwe resolution of this technique.Transmission electron microscopy reveals a number of features that are interpreted in terms of the mechanisms of deformation and recovery/recrystallization postulated. They include the observation of grains with sizes in the nanocrystalline domain. The microstructural changes are described by an evolutionary model, leading from the initial grain size of 15 µm to the final submicronic (sub)grain size. Calculations are performed on the rotations of grain boundaries by grain-boundary diffusion, which is 3 orders of magnitude higher than bulk diffusion at the deformation temperatures. They indicate that the microstructural reorganization can take place within the deformation times of a few milliseconds. Research supported by US Army Research Office MURI Program under Contract DAAH04-96-1-0376 and the Department of Energy Grant DEFG0300SF2202.

Meyers, M. A.; Perez-Prado, M. T.; McNelley, T. R.; Xue, Q.; Xu, Y.

2001-06-01

245

Extreme model reduction of shear layers

The aim of this research is to develop nonlinear low-dimensional models (LDMs) to describe vortex dynamics in shear layers. A modified Proper Orthogonal Decomposition (POD)/Galerkin projection method is developed to obtain models at extremely low dimension for shear layers. The idea is to dynamically scale the shear layer along y direction to factor out the shear layer growth and capture the dynamics by only a couple of modes. The models are developed for two flows, incompressible spatially developing and weakly compressible temporally developing shear layers, respectively. To capture basic dynamics, the low-dimensional models require only two POD modes for each wavenumber/frequency. Thus, a two-mode model is capable of representing single-wavenumber/frequency dynamics such as vortex roll-up, and a four-mode model is capable of representing the nonlinear dynamics involving a fundamental wavenumber/frequency and its subharmonic, such as vortex pairing/merging. Most of the energy is captured by the first mode of each wavenumber/frequency, the second POD mode, however, plays a critical role and needs to be included. In the thesis, we first apply the approach on temporally developing weakly compressible shear layers. In compressible flows, the thermodynamic variables are dynamically important, and must be considered. We choose isentropic Navier-Stokes equations for simplicity, and choose a proper inner product to present both kinetic energy and thermal energy. Two cases of convective Mach numbers are studied for low compressibility and moderate compressibility. Moreover, we study the sensitivity of the compressible four-mode model to several flow parameters: Mach number, the strength of initial perturbations of the fundamental and its subharmonic, and Reynolds number. Secondly we apply the approach on spatially developing incompressible shear layers with periodicity in time. We consider a streamwise parabolic form of the Navier-Stokes equations. When we add arbitrary excitation at different harmonics to the model, we observe the promoting or delaying/eliminating of vortex merging events as a result of mode competition. To study coherent structures in shear layers, we solve the Direct Lyapunov Exponents (DLEs) to identify the Lagrangian coherent structures (LCS). The negative-time LCS provide structures similar to the ones shown by flow visualization in experiments. The positive-time LCS are also important in describing the dynamics. Both negative and positive LCS are plotted together to give a complete picture of dynamics in shear layers.

Qawasmeh, Bashar Rafee

246

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

247

Review article: Cosmology with cosmic shear observations

Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as ...

Kilbinger, Martin

2014-01-01

248

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

249

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

250

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

251

Strength of Footing with Punching Shear Preventers

The punching shear failure often governs the strength of the footing-to-column connection. The punching shear failure is an undesirable failure mode, since it results in a brittle failure of the footing. In this study, a new method to increase the strength and ductility of the footing was proposed by inserting the punching shear preventers (PSPs) into the footing. The validation and effectiveness of PSP were verified through a series of experimental studies. The nonlinear finite element analysis was then performed to demonstrate the failure mechanism of the footing with PSPs in depth and to investigate the key parameters that affect the behavior of the footing with PSPs. Finally, the design recommendations for the footing with PSPs were suggested.

Lee, Sang-Sup; Moon, Jiho; Park, Keum-Sung; Bae, Kyu-Woong

2014-01-01

252

Vorticity production through rotation, shear and baroclinicity

In the absence of rotation and shear, and under the assumption of constant temperature or specific entropy, purely potential forcing by localized expansion waves is known to produce irrotational flows that have no vorticity. Here we study the production of vorticity under idealized conditions when there is rotation, shear, or baroclinicity, to address the problem of vorticity generation in the interstellar medium in a systematic fashion. We use three-dimensional periodic box numerical simulations to investigate the various effects in isolation. We find that for slow rotation, vorticity production in an isothermal gas is small in the sense that the ratio of the root-mean-square values of vorticity and velocity is small compared with the wavenumber of the energy carrying motions. For Coriolis numbers above a certain level, vorticity production saturates at a value where the aforementioned ratio becomes comparable with the wavenumber of the energy carrying motions. Shear also raises the vorticity production, but...

Del Sordo, Fabio

2010-01-01

253

Long nonlinear waves in stratified shear flows

The propagation of finite-amplitude internal waves in a shear flow is considered for wavelengths that are long compared to the shear-layer thickness. Both singular and regular modes are investigated, and the equation governing the amplitude evolution is derived. The theory is generalized to allow for a radiation condition when the region outside the stratified shear layer is unbounded and weakly stratified. In this case, the evolution equation contains a damping term describing energy loss by radiation which can be used to estimate the persistence of solitary waves or nonlinear wave packets in realistic environments. A continuous three-layer model is studied in detail and closed-form expressions are obtained for the phase speed and the coefficients of the nonlinear and dispersive terms in the amplitude equation as a function of Richardson number.

Maslowe, S. A.; Redekopp, L. G.

1980-01-01

254

Streamline curvature in supersonic shear layers

Results of an experimental investigation in which a curved shear layer was generated between supersonic flow from a rectangular converging/diverging nozzle and the freestream in a series of open channels with varying radii of curvature are reported. The shear layers exhibit unsteady large-scale activity at supersonic pressure ratios, indicating increased mixing efficiency. This effect contrasts with supersonic flow in a straight channel, for which no large-scale vortical structure development occurs. Curvature must exceed a minimum level before it begins to affect the dynamics of the supersonic shear layer appreciably. The curved channel flows are compared with reference flows consisting of a free jet, a straight channel, and wall jets without sidewalls on a flat and a curved plate.

Kibens, V.

1992-01-01

255

Scaling effects in direct shear tests

Laboratory experiments of the direct shear test were performed on spherical particles of different materials and diameters. Results of the bulk friction vs. non-dimensional shear displacement are presented as a function of the non-dimensional particle diameter. Simulations of the direct shear test were performed using the Discrete Element Method (DEM). The simulation results show Considerable differences with the physical experiments. Particle level material properties, such as the coefficients of static friction, restitution and rolling friction need to be known a priori in order to guarantee that the simulation results are an accurate representation of the physical phenomenon. Furthermore, laboratory results show a clear size dependency on the results, with smaller particles having a higher bulk friction than larger ones. ?? 2009 American Institute of Physics.

Orlando, A. D.; Hanes, D. M.; Shen, H. H.

2009-01-01

256

Bounds on Surface Stress Driven Shear Flow

The background method is adapted to derive rigorous limits on surface speeds and bulk energy dissipation for shear stress driven flow in two and three dimensional channels. By-products of the analysis are nonlinear energy stability results for plane Couette flow with a shear stress boundary condition: when the applied stress is gauged by a dimensionless Grashoff number $Gr$, the critical $Gr$ for energy stability is 139.5 in two dimensions, and 51.73 in three dimensions. We derive upper bounds on the friction (a.k.a. dissipation) coefficient $C_f = \\tau/\\bar{u}^2$, where $\\tau$ is the applied shear stress and $\\bar{u}$ is the mean velocity of the fluid at the surface, for flows at higher $Gr$ including developed turbulence: $C_f le 1/32$ in two dimensions and $C_f \\le 1/8$ in three dimensions. This analysis rigorously justifies previously computed numerical estimates.

Hagstrom, George I

2013-01-01

257

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

258

Crystallization in a sheared colloidal suspension

We study numerically the crystallization process in a supersaturated suspension of repulsive colloidal particles driven by simple shear flow. The effect of the shear flow on crystallization is two-fold: while it suppresses the initial nucleation, once a large enough critical nucleus has formed its growth is enhanced by the shear flow. Combining both effects implies an optimal strain rate at which the overall crystallization rate has a maximum. To gain insight into the underlying mechanisms, we employ a discrete state model describing the transitions between the local structural configurations around single particles. We observe a time-scale separation between these transitions and the overall progress of the crystallization allowing for an effective Markovian description. By using this model, we demonstrate that the suppression of nucleation is due to the inhibition of a pre-structured liquid.

Lander, Boris; Seifert, Udo; Speck, Thomas

2013-06-01

259

Speckle-motion artifact under tissue shearing.

Research has shown that, for a rotating phantom, the speckle pattern may not replicate the phantom motion, rather it may show a large lateral translation component in addition to rotation. This translation effect was labeled speckle-motion artifact. An image formation model has been shown to explain the phenomenon, pointing to the curvature of the imaging system point spread function (PSF) at the origin of this effect. The present paper extends this analysis and proposes a model, which predicts that a lateral motion artifact also would occur with shear motion. In the model, the artifact is found to be proportional to the shear angle and dependent of shear orientation, being maximal for shear that runs parallel to the axial direction; as for rotation, the artifact increases with frequency and beamwidth. This would mean that, when viewing a parabolic flow in the far field or with a highly curved PSF, an apparent contraction/expansion pattern in the direction of the vessel wall would be superimposed to the real velocity profile. In elastography, when viewing an inclusion subjected to an axial strain, four motion artifact regions are expected near the inclusion. The model is developed using the Fourier domain representation of the speckles for tissue-motion compensated signals, also called Lagrangian speckle. It can explain the artifact in terms of a simple spectral translation of a parabolic phase profile; given this, it is shown the artifact would be proportional to the lateral derivative of the axial displacement field. The spectral representation of Lagrangian speckle, for shear, also provides a simple geometrical interpretation for speckle decorrelation in terms of the shear strength and orientation, and in terms of the beam characteristics, i.e., the axial and lateral bandwidth. PMID:18238459

Maurice, R L; Bertrand, M

1999-01-01

260

Shear banding in soft glassy materials

Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic ‘glassy’ features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

Fielding, S. M.

2014-10-01

261

Shear banding in soft glassy materials.

Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic 'glassy' features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike. PMID:25303030

Fielding, S M

2014-10-01

262

Combined shearing interferometer and hartmann wavefront sensor

International Nuclear Information System (INIS)

A sensitive wavefront sensor combining attributes of both a Hartmann type of wavefront sensor and an AC shearing interferometer type of wavefront sensor. An incident wavefront, the slope of which is to be detected, is focussed to first and second focal points at which first and second diffraction gratings are positioned to shear and modulate the wavefront, which then diverges therefrom. The diffraction patterns of the first and second gratings are positioned substantially orthogonal to each other to shear the wavefront in two directions to produce two dimensional wavefront slope data for the AC shearing interferometer portion of the wavefront sensor. First and second dividing optical systems are positioned in the two diverging wavefronts to divide the sheared wavefront into an array of subapertures and also to focus the wavefront in each subaperture to a focal point. A quadrant detector is provided for each subaperture to detect the position of the focal point therein, which provides a first indication, in the manner of a Hartmann wavefront sensor, of the local wavefront slope in each subaperture. The total radiation in each subaperture, as modulated by the diffraction grating, is also detected by the quadrant detector which produces a modulated output signal representative thereof, the phase of which relative to modulation by the diffraction grating provides a second indication of the local wavefront slope in each subaperture, in the manner of an AC shearing interferometer wavefront sensor. The data from both types of sensors is then combined by long term averaging thereof to provide an extremely sensitive wavefront sensor

263

Carcass (n = 854) and longissimus thoracis palatability (n = 802) traits from F1 steers obtained from mating Hereford, Angus, and MARC III cows to Hereford or Angus (HA), Tuli (Tu), Boran (Bo), Brahman (Br), Piedmontese (Pm), or Belgian Blue (BB) sires were compared. Data were adjusted to constant age (444 d), carcass weight (333 kg), fat thickness (1.0 cm), fat trim percentage (21%), and marbling (Small00) end points. Results presented in this abstract are for age-constant data. Carcasses from BB- and HA-sired steers were heaviest (P < 0.05) and carcasses from Bo- and Tu-sired steers were lightest (P < 0.05). Adjusted fat thickness was greatest (P < 0.05) on carcasses from HA-sired steers and least (P < 0.05) on carcasses from BB- and Pm-sired steers. Numerical USDA yield grades were lowest (P < 0.05) for carcasses from Pm- and BB-sired steers and highest (P < 0.05) for carcasses from HA- and Br-sired steers. Marbling scores were highest (P < 0.05) for carcasses from HA- and Tu-sired steers and lowest (P < 0.05) for carcasses from Br-, BB-, and Pm-sired steers. Longissimus thoracis from carcasses of HA-, Pm-, and Tu-sired steers had the lowest (P < 0.05) 14-d postmortem Warner-Bratzler shear force values. Carcasses from HA-sired steers had longissimus thoracis with the highest (P < 0.05) tenderness ratings at 7 d postmortem. Longissimus thoracis from carcasses of Br- and Bo-sired steers had the highest (P < 0.05) Warner-Bratzler shear forces and the lowest (P < 0.05) tenderness ratings at 7 d postmortem. Adjustment of traits to various slaughter end points resulted in some changes in sire breed differences for carcass traits but had little effect on palatability traits. Carcasses from BB- and Pm-sired steers provided the most desirable combination of yield grade and longissimus palatability, but carcasses from HA-cross steers provided the most desirable combination of quality grade and longissimus palatability. Tuli, a breed shown to be heat-tolerant, had longissimus tenderness similar to that of the non-heat-tolerant breeds and more tender longissimus than the heat-tolerant breeds in this study. PMID:11374541

Wheeler, T L; Cundiff, L V; Shackelford, S D; Koohmaraie, M

2001-05-01

264

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

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

2013-06-01

265

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

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

266

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

267

High-shear-rate capillary viscometer for inkjet inks

Energy Technology Data Exchange (ETDEWEB)

A capillary viscometer developed to measure the apparent shear viscosity of inkjet inks at high apparent shear rates encountered during inkjet printing is described. By using the Weissenberg-Rabinowitsch equation, true shear viscosity versus true shear rate is obtained. The device is comprised of a constant-flow generator, a static pressure monitoring device, a high precision submillimeter capillary die, and a high stiffness flow path. The system, which is calibrated using standard Newtonian low-viscosity silicone oil, can be easily operated and maintained. Results for measurement of the shear-rate-dependent viscosity of carbon-black pigmented water-based inkjet inks at shear rates up to 2x10{sup 5} s{sup -1} are discussed. The Cross model was found to closely fit the experimental data. Inkjet ink samples with similar low-shear-rate viscosities exhibited significantly different shear viscosities at high shear rates depending on particle loading.

Wang Xi [FUJIFILM Dimatix, Inc., Lebanon, New Hampshire 03766 (United States); Carr, Wallace W.; Bucknall, David G. [School of Polymer, Textile, and Fiber Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Morris, Jeffrey F. [Department of Chemical Engineering and Benjamin Levich Institute for Physico-Chemical Hydrodynamics, City College of New York, New York, New York 10031 (United States)

2010-06-15

268

International Nuclear Information System (INIS)

The non-potentiality of solar magnetic fields is traditionally measured in terms of a magnetic shear angle, i.e., the angle between the observed and potential field azimuths. Here, we introduce another measure of the shear that has not been previously studied in solar active regions, i.e., the one that is associated with the inclination angle of the magnetic field. This form of the shear, which we call 'dip shear', can be calculated by taking the difference between the observed and the potential field inclination. In this Letter, we study the evolution of the dip shear as well as the conventional twist shear in a ?-sunspot using high-resolution vector magnetograms from the Hinode space mission. We monitor these shears in a penumbral region located close to a flaring site during 2006 December 12 and 13. It is found that (1) the penumbral area close to the flaring site shows a high value of the twist shear and dip shear as compared with other parts of the penumbra, (2) after the flare, the value of the dip shear drops in this region while the twist shear tends to increase, (3) the dip shear and twist shear are correlated such that pixels with a large twist shear also tend to exhibit a large dip shear, and (4) the correlation between the twist shear and dip shear is tighter after the flare. The present study suggests that monitoring the twist shear alone during the flare is not sufficient, but we need to monitor it together with the dip shear.

269

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

270

Continuum stress characteristics inside shear bands

A defining aspect of the large strain, fully developed plastic flow regime, or ``critical state'', for granular materials undergoing localized failure is the continual growth of new force chains amidst collapse by buckling of old force chains in the persistent shear band. This paper explores the constitutive response inside shear bands, in particular, the birth-death evolution of force chains for a Cosserat medium, whereby closure relationships for stresses and couple stresses satisfy the isostatic condition, albeit in a spatiotemporal average sense only. The continuum stress-equilibrium relations comprise a hyperbolic system of partial differential equations giving rise to characteristic lines referred to in the literature as stress chains.

Tordesillas, Antoinette; Peters, John F.; Shi, Jingyu

2013-06-01

271

MICROSTRUCTURE OF SHEAR ZONES IN FONTAINEBLEAU SANDSTONE

Digital Repository Infrastructure Vision for European Research (DRIVER)

On the basis of image analysis, porosity and grain-size changes have been studied inside the shear bands formed in triaxial testing on a Fontainebleau sandstone. For this rock the shear band is characterized by a white coloration visible to the naked eye. It is obtained that for specimens tested under relatively low confining pressure (7 MPa), the porosity reaches a maximal value of about 30% inside the band and decreases rapidly towards the initial value of 21% outside the band. This is inte...

El Bied, Amine; Sulem, Jean; Martineau, Franc?ois

2002-01-01

272

Bubbles in sheared two-dimensional foams

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Quilliet, C.; Idiart, M. A. P.; Dollet, B.; Berthier, L.; Yekini, A.

2005-01-01

273

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

274

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, Srdjan; Vlugt, Thijs J. H.; Nienhuis, Bernard

2007-03-01

275

Enhancing Rotational Diffusion Using Oscillatory Shear

Taylor dispersion—shear-induced enhancement of translational diffusion—is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle’s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids.

Leahy, Brian D.; Cheng, Xiang; Ong, Desmond C.; Liddell-Watson, Chekesha; Cohen, Itai

2013-05-01

276

Energy Technology Data Exchange (ETDEWEB)

Studies have also shown that physico-chemical forces of repulsion and attraction exist in swelling or active clay-water systems. However, common direct shear testing practices typically ignore pore fluid effects. This study investigated the effect of pore fluid chemistry on direct shear testing. Samples were tested from 2 overburden dumps and a tailings facility located in the Mildred Lake Settling Basin in Alberta. Back analyses of case records were conducted using a limit equilibrium methodology. The chemistry and mineralogy of the area was tested. Pore fluid chemistry was simulated and 2 direct shear tests were conducted on samples consolidated with a slurry. The analyses considered mobilized strength at deformation levels. The 3 case histories were used to demonstrate that proper fill height considerations and depths below the Pleistocene, field shear strength of clay Clearwater soil units is in alignment with strengths of approximately 8 degrees. The study demonstrated that tests conducted with distilled water in laboratory conditions can often produce unrealistically low test results. Direct shear laboratory tests should focus on matching pore water chemistry by using shear box reversals to create residual shear planes. Pore water chemistry must match the zone and location of potential slip planes. It was concluded that future designs must use appropriate pore water pressure ratios that correspond to the height of the fill. 21 refs., 5 tabs., 7 figs.

McRoberts, E.C. [AMEC Earth and Environmental Ltd., Edmonton, AB (Canada); Cameron, R.; Mimura, W. [Syncrude Canada Ltd., Fort McMurray, AB (Canada)

2008-07-01

277

Rate-dependent shear bands in a shear-transformation-zone model of amorphous solids

We use shear transformation zone (STZ) theory to develop a deformation map for amorphous solids as a function of the imposed shear rate and initial material preparation. The STZ formulation incorporates recent simulation results [T. K. Haxton and A. J. Liu, Phys. Rev. Lett. 99, 195701 (2007)] showing that the steady state effective temperature is rate dependent. The resulting model predicts a wide range of deformation behavior as a function of the initial conditions, including homogeneous deformation, broad shear bands, extremely thin shear bands, and the onset of material failure. In particular, the STZ model predicts homogeneous deformation for shorter quench times and lower strain rates, and inhomogeneous deformation for longer quench times and higher strain rates. The location of the transition between homogeneous and inhomogeneous flow on the deformation map is determined in part by the steady state effective temperature, which is likely material dependent. This model also suggests that material failure occurs due to a runaway feedback between shear heating and the local disorder, and provides an explanation for the thickness of shear bands near the onset of material failure. We find that this model, which resolves dynamics within a sheared material interface, predicts that the stress weakens with strain much more rapidly than a similar model which uses a single state variable to specify internal dynamics on the interface.

Manning, M. L.; Daub, E. G.; Langer, J. S.; Carlson, J. M.

2009-01-01

278

Rate-dependent shear bands in a shear-transformation-zone model of amorphous solids.

We use shear transformation zone (STZ) theory to develop a deformation map for amorphous solids as a function of the imposed shear rate and initial material preparation. The STZ formulation incorporates recent simulation results [T. K. Haxton and A. J. Liu, Phys. Rev. Lett. 99, 195701 (2007)] showing that the steady state effective temperature is rate dependent. The resulting model predicts a wide range of deformation behavior as a function of the initial conditions, including homogeneous deformation, broad shear bands, extremely thin shear bands, and the onset of material failure. In particular, the STZ model predicts homogeneous deformation for shorter quench times and lower strain rates, and inhomogeneous deformation for longer quench times and higher strain rates. The location of the transition between homogeneous and inhomogeneous flow on the deformation map is determined in part by the steady state effective temperature, which is likely material dependent. This model also suggests that material failure occurs due to a runaway feedback between shear heating and the local disorder, and provides an explanation for the thickness of shear bands near the onset of material failure. We find that this model, which resolves dynamics within a sheared material interface, predicts that the stress weakens with strain much more rapidly than a similar model which uses a single state variable to specify internal dynamics on the interface. PMID:19257110

Manning, M L; Daub, E G; Langer, J S; Carlson, J M

2009-01-01

279

Genome scan for meat quality traits in Nelore beef cattle.

Meat quality traits are economically important because they affect consumers' acceptance, which, in turn, influences the demand for beef. However, selection to improve meat quality is limited by the small numbers of animals on which meat tenderness can be evaluated due to the cost of performing shear force analysis and the resultant damage to the carcass. Genome wide-association studies for Warner-Bratzler shear force measured at different times of meat aging, backfat thickness, ribeye muscle area, scanning parameters [lightness, redness (a*), and yellowness] to ascertain color characteristics of meat and fat, water-holding capacity, cooking loss (CL), and muscle pH were conducted using genotype data from the Illumina BovineHD BeadChip array to identify quantitative trait loci (QTL) in all phenotyped Nelore cattle. Phenotype count for these animals ranged from 430 to 536 across traits. Meat quality traits in Nelore are controlled by numerous QTL of small effect, except for a small number of large-effect QTL identified for a*fat, CL, and pH. Genomic regions harboring these QTL and the pathways in which the genes from these regions act appear to differ from those identified in taurine cattle for meat quality traits. These results will guide future QTL mapping studies and the development of models for the prediction of genetic merit to implement genomic selection for meat quality in Nelore cattle. PMID:24022219

Tizioto, P C; Decker, J E; Taylor, J F; Schnabel, R D; Mudadu, M A; Silva, F L; Mourão, G B; Coutinho, L L; Tholon, P; Sonstegard, T S; Rosa, A N; Alencar, M M; Tullio, R R; Medeiros, S R; Nassu, R T; Feijó, G L D; Silva, L O C; Torres, R A; Siqueira, F; Higa, R H; Regitano, L C A

2013-11-01

280

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

281

Using reflectance spectroscopy to predict beef tenderness.

A study was conducted to determine if reflectance measurements made in the near-infrared region of the spectrum were additive to reflectance measurements made in the visible region of the spectrum for predicting Warner-Bratzler shear force (WBSF) values. Eighty seven strip loins were collected following fabrication over 3d at a commercial beef processing facility from heifer carcasses with Slight or Traces marbling scores. Spectroscopic measurements were made at approximately 50h postmortem using a Hunter-Lab UltraScan. Subsequently, all strip loins were aged for 14d, cooked to an internal temperature of 70°C, and sheared to obtain WBSF values. Reflectance measurements obtained in the near-infrared region of the spectrum were correlated with WBSF values, however, these measurements were not additive to the predictive ability of reflectance measurements (R(2) values did not differ) made in the visible portion of the spectrum when the use of broad-band wavelength filters were simulated. It was therefore determined, that both the visible and near-infrared spectra measure reflectance and that both methods are acceptable methods of tenderness prediction. PMID:20416616

Bowling, M B; Vote, D J; Belk, K E; Scanga, J A; Tatum, J D; Smith, G C

2009-05-01

282

Thermomechanical properties of beef muscle.

Differential scanning calorimetry (DSC) was used to follow the three major endothermic transitions (T(1), T(2) and T(3)) of beef muscle during heating. Borchardt and Daniels reaction kinetics were used to predict the three time and temperature treatments required to sequentially eliminate each transition. Longissimus dorsi and semimembranosus muscles were removed from beef carcasses suspended by Achilles tendon or pelvis. Samples prepared by heating for 5 min at 57°C (I), 70°C (II) and 81°C (III) were assessed by sensory panel for tenderness, juiciness and residual connective tissue. Weight loss, Warner-Bratzler (W-B) shear and microstructure using transmission electron microscopy (TEM) were also determined. The I treatment showed a significant difference in tenderness and residual connective tissue between muscles, but not between contraction states. The II treatment produced collagen shrinkage and a significant drop in W-B shear and residual connective tissue, coupled with increased tenderness in semimembranosus muscle. An increased W-B value, decreased juiciness, increased weight loss and a reduction in sarcomere and A-band length accompanied the III transition. Muscles from carcasses that had been suspended by the pelvis were found to be significantly more tender than the same muscles from Achilles hung carcasses. It is concluded that DSC is capable of determining amount of protein denaturation and, hence, degree of cooking. PMID:22054744

Findlay, C J; Stanley, D W; Gullett, E A

1986-01-01

283

Differences in quality characteristics of normal, PSE and DFD pork.

Differences in water-holding capacity, colour and tenderness/toughness were studied in 21 pork loins belonging to three quality categories, i.e. dark firm dry (DFD), normal and pale soft exudative (PSE). The division into the three groups was based upon the ultimate pH-values of the loins (pH 5·5, pH 5·5-6·0, pH > 6·4). The PSE loins were characterized by a poor waterholding capacity, higher cooking loss and paler colour in contrast to the DFD category. The normal loins took an intermediate position. Neither sarcomere length, determined on fresh muscle tissue, nor Armour tenderometer values showed significant differences between the various quality categories. This was in contrast to the Warner-Bratzler (W-B) shear force values, determined on cooked loins, which had the lowest values in the DFD category. A strong relationship between the W-B values and the cooking losses was found. It was concluded that neither sarcomere length nor Armour tenderometer measurements were able to predict the shear force values of cooked pork loins. PMID:22055811

van der Wal, P G; Bolink, A H; Merkus, G S

1988-01-01

284

The effect of post mortem temperature treatment on suckling lamb carcass and meat quality was study. Conventional (2 °C for 24 h), ultra-rapid (-20 °C for 3.5 h, 2 °C until 24 h) and slow chillings (12 °C for 7 h, 2 °C until 24 h) were compared. Total viable counts (TVC), weight losses, and pH and temperature falls were recorded on carcasses. Meat colour, water holding capacity (WHC), Warner-Bratzler shear force, sarcomere length and sensory analysis were evaluated in M. longissimus. Ultra-rapid treatment reduced TVC and weight losses. The pH decline was faster in slow chilled carcasses than in faster chilled carcasses. No significant differences were found for colour and WHC. Slow treatment carcasses showed significantly lower shear force and higher sarcomere length. In the sensory analysis, tasters also rated the early post mortem slow-treated meat as more tender, less fibrous and chewy. Therefore, delay chilling in suckling lamb carcasses made it possible to obtain meat with better organoleptic characteristics, without affecting weight loss or hygienic quality. PMID:22726698

Fernández, A M; Vieira, C

2012-12-01

285

Analysis of shear test method for composite laminates

An elastic plane stress finite element analysis of the stress distributions in four flat test specimens for in-plane shear response of composite materials subjected to mechanical or thermal loads is presented. The shear test specimens investigated include: slotted coupon, cross beam, losipescu, and rail shear. Results are presented in the form of normalized shear contour plots for all three in-plane stess components. It is shown that the cross beam, losipescu, and rail shear specimens have stress distributions which are more than adequate for determining linear shear behavior of composite materials. Laminate properties, core effects, and fixture configurations are among the factors which were found to influence the stress distributions.

Bergner, H. W., Jr.; Davis, J. G., Jr.; Herakovich, C. T.

1977-01-01

286

We carried out pointwise local velocity measurements on 40 mM cetylpyridinium chloride-sodium salicylate (CPyCl-NaSal) wormlike micellar solution using high-frequency ultrasound velocimetry in a Couette shear cell. The studied wormlike solution exhibits Newtonian, shear-thinning and shear-thickening rheological behavior in a stress-controlled environment. Previous rheology, flow visualization and small-angle light/neutron scattering experiments in the shear-thickening regime of this system showed the presence of stress-driven alternating transparent and turbid rings or vorticity bands along the axis of the Couette geometry. Through local velocity measurements we observe a homogeneous flow inside the 1mm gap of the Couette cell in the shear-thinning (stress-plateau) region. Only when the solution is sheared beyond the critical shear stress (shear-thickening regime) in a stress-controlled experiment, we observe inhomogeneous flow characterized by radial or velocity gradient shear bands with a highly sheared band near the rotor and a weakly sheared band near the stator of the Couette geometry. Furthermore, fast measurements performed in the shear-thickening regime to capture the temporal evolution of local velocities indicate coexistence of both radial and vorticity shear bands. However the same measurements carried out in shear rate controlled mode of the rheometer do not show such rheological complexity. PMID:18415043

Herle, V; Manneville, S; Fischer, P

2008-01-01

287

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

288

Directory of Open Access Journals (Sweden)

Full Text Available Maximum shear stress intensity for nearly circular cracks subjected to equal and opposite shear stresses are considered. A hypersingular integral equation containing the crack opening displacement is formulated. Conformal mapping technique is employed to transform the obtained hypersingular equation into a similar equation over a circular crack. A suitable collocation points are chosen to reduce the hypersingular integral equation into a system of linear equations. Numerical solution of the linear equations and the corresponding maximum shear intensity is obtained and presented graphically. Our results seem to agree with the existing asymptotic solution.

Koo Lee Feng

2013-02-01

289

The global wall shear stress measurement technique using shear-sensitive liquid crystal (SSLC) is extended to wind tunnel measurements. Simple and common everyday equipment is used in the measurement; in particular a tungsten-halogen light bulb provides illumination and a saturation of SSLC coating color change with time is found. Spatial wall shear stress distributions of several typical flows are obtained using this technique, including wall-jet flow, vortex flow generated by a delta wing and junction flow behind a thin cylinder, although the magnitudes are not fully calibrated. The results demonstrate that SSLC technique can be extended to wind tunnel measurements with no complicated facilities used.

Zhao, Ji-Song; Scholz, Peter; Gu, Liang-Xian

2012-10-01

290

Dynamic effective shear strength of saturated sand

The dynamic effective shear strength of saturated sand under cyclic loading is discussed in this paper. The discussion includes the transient time dependency behaviors based on the analysis of the results obtained in conventional cyclic triaxial tests and cyclic torsional shear triaxial tests. It has been found that the dynamic effective shear strength is composed of effective frictional resistance and viscous resistance, which are characterized by the strain rate dependent feature of strength magnitude, the coupling of consolidation stress with cyclic stress and the dependency of time needed to make the soil strength sufficiently mobilized, and can also be expressed by the extended Mohr-Coulomb's law. The two strength parameters of the dynamic effective internal frictional angle ?d and the dynamic viscosity coefficient ? are determined. The former is unvaried for different number of cyclic loading, dynamic stress form and consolidation stress ratio. And the later is unvaried for the different dynamic shear strain ratedot ? _t developed during the sand liquefaction, but increases with the increase of initial density of sand. The generalization of dynamic effective stress strength criterion in the 3-dimensional effective stress space is studied in detail for the purpose of its practical use.

Shengjun, Shao; Dingyi, Xie

2002-08-01

291

Crossing of shears bands in 196Pb

International Nuclear Information System (INIS)

High-spin states in 196Pb have been populated using the reaction 170Er(30Si, 4n). The previously observed shear bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin. (orig.)

292

Towards shear tactile displays with DEAs

Much research has been done on the development of tactile displays using Dielectric Elastomer Actuators (DEAs). It has been argued that they offer the potential to create low-cost full-page tactile displays — not achievable with conventional actuator technologies. All research to date has considered tactile elements moving perpendicular to the skin and thus applying a normal force distribution. In contrast to previous work, we have investigated the use of laterally moving tactile elements that apply shear forces to the skin. This allows for the areal expansion of the DEA to be exploited directly, and a tactile display could be made with no elements moving out of the plane. There is evidence that humans are very sensitive to shear force distributions, and that in some cases a shear stimulus is indistinguishable from a normal stimulus. We present a prototype shear tactile display actuated by a DEA, and demonstrate that the DEA can generate the necessary forces and displacements. We also present and discuss different display topologies.

Knoop, Lars E.; Rossiter, Jonathan

2014-03-01

293

Shear deformation in thick auxetic plates

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.

Lim, Teik-Cheng

2013-08-01

294

Shear induced diffusion in dense granular flows

The dynamics of dense granular flows subjected to gravity induced shear are investigated experimentally using the refractive index matching technique. The system consists of grains flowing inside a bin with a rectangular cross-section and sheared by a rough boundary on one side and smooth boundaries on the remaining sides. The particles flow within a viscous interstitial liquid having the same refractive index as particles and are imaged in the bulk using laser fluorescence. The particle positions are identified very accurately and tracked over long durations to obtain the mean and fluctuating properties. The shear is observed to be non-linear and localized in a region of 3 to 4 particles near the boundary. The boundary imposes a packing order, and the grains are observed to flow in layers, parallel to the shearing boundary, which get progressively more disordered with distance from the walls. We have also carried out soft particle simulations in a equivalent system incorporating the Cundall-Strack contact model between the particles and ignoring the hydrodynamic effects of the interstitial liquid to understand the effect of particle friction coefficient, elasticity, contact model and polydispersity on the mean and fluctuating flow properties. We find the mean velocity and the number density of the particles as a function of flow cross-section and the particle fluctuation properties observed in the experiments and the simulations to in very good agreement after appropriate scaling.

Orpe, Ashish V.; Rycroft, Chris H.; Kudrolli, Arshad A.

2010-05-01

295

An implementation of Bayesian lensing shear measurement

The Bayesian gravitational shear estimation algorithm developed by Bernstein & Armstrong can potentially be used to overcome multiplicative noise bias and recover shear using very low signal-to-noise ratio (S/N) galaxy images. In that work, the authors confirmed that the method is nearly unbiased in a simplified demonstration, but no test was performed on images with realistic pixel noise. Here, I present a full implementation for fitting models to galaxy images, including the effects of a point spread function (PSF) and pixelization. I tested the implementation using simulated galaxy images modelled as Sérsic profiles with n = 1 (exponential) and n = 4 (De Vaucouleurs'), convolved with a PSF and a flat pixel response function. I used a round Gaussian model for the PSF to avoid potential PSF-fitting errors. I simulated galaxies with mean observed, post-PSF full width at half-maximum equal to approximately 1.2 times that of the PSF, with lognormal scatter. I also drew fluxes from a lognormal distribution. I produced independent simulations, each with pixel noise tuned to produce different mean S/N ranging from 10-1000. I applied a constant shear to all images. I fitted the simulated images to a model with the true Sérsic index to avoid modelling biases. I recovered the input shear with fractional error ?g/g requirements for planned surveys.

Sheldon, Erin S.

2014-10-01

296

Shear behavior of bovine scleral tissue.

Ocular tissue properties have been widely studied in tension and compression for humans and a variety of animals. However, direct shear testing of the tissues of the sclera appear to be absent from the literature even though modeling, analyses, and anatomical studies have indicated that shear may play a role in the etiology of primary open angle glaucoma (POAG). In this work, the mechanical behavior of bovine scleral tissue in shear has been studied in both out-of-plane and in-plane modes of deformation. Stress-strain and relaxation tests were conducted on tissue specimens at controlled temperature and hydration focusing on trends related to specimen location and orientation. There was generally found to be no significant effect of specimen orientation and angular location in the globe on shear stiffness in both modes. The in-plane response, which is the primary load carrying mode, was found to be substantially stiffer than the out-of-plane mode. Also, within the in-plane studies, tissue further from the optic nerve was stiffer than the near tissue. The viscosity coefficient of the tissue varied insignificantly with distance from the optic nerve, but overall was much higher in-plane than out-of-plane. PMID:24805965

Argento, Alan; Kim, Wonsuk; Rozsa, Frank W; DeBolt, Kori L; Zikanova, Sophia; Richards, Julia R

2014-07-01

297

Evaporating shear-driven liquid film

The study of an evaporating shear-driven liquid film with a localized heating is motivated by potential application in cooling of microelectronics on earth and in space. The work is also a part of the preparation of the ESA SAFIR experiment onboard the ISS. The modeling of evaporating thin liquid film driven by body force or shear stress is important both from a practical point of view and as task in investigation of film local dry-out resulting in formation of apparent contact lines. Two types of models for shear-driven liquid film with phase transitions have been developed. One of them is a two-sided model that is capable to evaluate the evaporation effect on heat transfer enhancement. Some quantitative and qualitative comparisons with experimental results are presented. The one-sided mathematical model is developed in the framework of the lubrication approximation describing the behavior of contact line. Evaporation, slip, disjoining pressure, capillarity and shear stresses effects are included in the model. The effect of the slip condition at the solid-liquid surface has been examined.

Gatapova, Elizaveta; Kabov, Oleg

2008-11-01

298

'Slings' enable neutrophil rolling at high shear.

Most leukocytes can roll along the walls of venules at low shear stress (1?dyn?cm?2), but neutrophils have the ability to roll at tenfold higher shear stress in microvessels in vivo. The mechanisms involved in this shear-resistant rolling are known to involve cell flattening and pulling of long membrane tethers at the rear. Here we show that these long tethers do not retract as postulated, but instead persist and appear as 'slings' at the front of rolling cells. We demonstrate slings in a model of acute inflammation in vivo and on P-selectin in vitro, where P-selectin-glycoprotein-ligand-1 (PSGL-1) is found in discrete sticky patches whereas LFA-1 is expressed over the entire length on slings. As neutrophils roll forward, slings wrap around the rolling cells and undergo a step-wise peeling from the P-selectin substrate enabled by the failure of PSGL-1 patches under hydrodynamic forces. The 'step-wise peeling of slings' is distinct from the 'pulling of tethers' reported previously. Each sling effectively lays out a cell-autonomous adhesive substrate in front of neutrophils rolling at high shear stress during inflammation. PMID:22763437

Sundd, Prithu; Gutierrez, Edgar; Koltsova, Ekaterina K; Kuwano, Yoshihiro; Fukuda, Satoru; Pospieszalska, Maria K; Groisman, Alex; Ley, Klaus

2012-08-16

299

Effects of high shear on ideal ballooning

Energy Technology Data Exchange (ETDEWEB)

Ideal ballooning modes are investigated for the case of plane magnetized slab geometry. Toroidal effects are simulated by a gravitational acceleration periodically varying along magnetic field lines. High shear is shown to be very effective in stabilizing these modes even when field line curvature is most unfavorable to their stability.

Dagazian, R.Y. (Los Alamos National Lab., NM (USA)); Paris, R.B. (CEA Centre d' Etudes Nucleaires de Fontenay-aux-Roses, 92 (France))

1982-06-01

300

Slings enable neutrophil rolling at high shear

Most leukocytes can roll along the walls of venules at low shear stress (1 dyn/cm2), but neutrophils have the ability to roll at 10-fold higher shear stress in microvessels in vivo1,2. The mechanisms involved in this shear-resistant rolling are known to involve cell flattening3 and pulling of long membrane tethers at the rear4–6. Here, we show that these long tethers do not retract as postulated6,7, but instead persist and appear as ‘slings’ at the front of rolling cells. We demonstrate slings in a model of acute inflammation in vivo and on P-selectin in vitro, where P-selectin-glycoprotein-ligand-1 (PSGL-1) is presented as discrete sticky patches while LFA-1 is expressed over the entire length on slings. As neutrophils roll forward, slings wrap around the rolling cells and undergo a step-wise peeling from the P-selectin substrate enabled by the failure of PSGL-1 patches under hydrodynamic forces. The ‘step-wise peeling of slings’ is distinct from the ‘pulling of tethers’ reported previously4–6,8. Each sling effectively lays out a cell-autonomous adhesive substrate in front of neutrophils rolling at high shear stress during inflammation. PMID:22763437

Sundd, Prithu; Gutierrez, Edgar; Koltsova, Ekaterina K.; Kuwano, Yoshihiro; Fukuda, Satoru; Pospieszalska, Maria K.; Groisman, Alexander; Ley, Klaus

2012-01-01

301

A cutter mounting tool for shears

International Nuclear Information System (INIS)

The tool is aimed for cutters with a block shape and sharp edges, to be mounted on a blade holder through pressure or locking screws, at the bottom of specific recessions, ensuring a good alignment of the cutting edges. The tool has been especially designed for maintenance robot manipulation of nuclear fuel pin sawing shears. 3 refs., 7 figs

302

Dynamics of microcapsules in oscillating shear flow

We present a three-dimensional numerical study on the dynamics of deformable capsules in sinusoidally oscillating shear flow. We consider capsules of spherical and oblate spheroid resting shapes. For spherical resting shapes, we find an identical deformation response during positive and negative vorticities. However, the deformation response becomes unequal and shows complex behavior for nonspherical resting shapes. The average elongation is higher in the retarding phase of the shear flow than in the accelerating phase. Primarily two types of dynamics are observed for nonspherical shapes: a clockwise/counter-clockwise swinging motion in response to the altering flow direction that occurs at both high and low values of shear rate amplitudes, and a continuous/unidirectional tumbling motion that occurs at intermediate values. The unidirectional tumbling motion occurs despite the fact that the time-average vorticity is zero. Such a tumbling motion is accompanied by a continuous tank-treading motion of the membrane in the opposite direction. We obtain phase diagram that shows existence of two critical shear rates and two oscillation frequencies. The unidirectional tumbling motion occurs in the intermediate range, and the clockwise/counter-clockwise swinging motion occurs otherwise. We also find that the dynamics is highly sensitive to the initial condition. A swinging is generally observed when the capsule is released aligned with the extensional or compressional axis of the shear flow, and a tumbling is observed otherwise. These results suggest the possibility of chaotic behavior of cells in time-dependent flows. We provide explanations of such complex dynamics by analyzing the coupling between the shape and angular oscillation and the imposed flow oscillation.

Zhao, Mengye; Bagchi, Prosenjit

2011-11-01

303

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

304

High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter crew seat. Characterization tests were carried out on the LMEAS using a 40 vol% MRF used in the previous magnetorheometer tests. These were analyzed using both flow curves and apparent viscosity vs. Mason number diagrams. The nondimensionalized Mason number analysis resulted in data for all conditions of temperature, fluid composition, and shear rate, to collapse onto a single characteristic or master curve. Significantly, the temperature corrected Mason number results from both the bench top magnetorheometer and full scale rotary vane MREA collapse to the same master curve. This enhances the ability of designers of MRFs and MREAs to safely and effectively apply characterization data collected in low shear rate, controlled temperature environments to operational environments that may be completely different. Finally, the Searle cell magnetorheometer was modified with an enforced eccentricity to work in both squeeze and shear modes simultaneously to achieve so called squeeze strengthening of the working MRF, thereby increasing the apparent yield stress and the specific energy absorption. By squeezing the active MR fluid, particles undergo compression-assisted aggregation into stronger, more robust columns which resist shear better than single chains. A hybrid model describing the squeeze strengthening behavior is developed, and recommendations are made for using squeeze strengthening to improve practical MREA devices.

Becnel, Andrew C.

305

Three processing methods were compared to develop a low dose (0.1%) immediate release tablet. Similar formulations were used to evaluate low shear, high shear, and fluid bed granulation methods. For each granulation process, the drug was dissolved or suspended in the granulating fluid and sprayed into the granulator. Both water and methanol were evaluated as granulating fluids. The low shear granulation was performed in a Patterson-Kelley V-Blender with I-bar. The high shear granulation was performed in a GRAL (top entry impeller) and a Diosna (bottom mounted impeller). Fluid bed granulation was also performed using top-spray. Acceptable content uniformity was obtained using each technology. The type of granulator and granulating solvent affected the granulation particle size distributions and bulk/tap densities. However, the addition of extragranular microcrystalline cellulose minimized the effect of variable granulation properties and allowed similar tablets to be produced from each granulation process. PMID:15109025

Hausman, Debra S

2004-03-01

306

Influence of High Axial Tension on the Shear Strength of non-shear RC Beams

DEFF Research Database (Denmark)

This paper deals with the influence of high axial tension on the shear strength of beams without shear reinforcement. An experimental program with shear-tension tests was carried out. The experimental results have been used to evaluate the applicability of the Eurocode 2 (EC2) design formula in cases with large normal forces. In addition, the experiments have been used to evaluate an extension of the plasticity based Crack Sliding Model (CSM) to cover cases with large normal forces. The test results show, that even in the present of very high axial tensile stresses and strains, the member is still able to carry significant shear stresses. The analysis reveals that the EC2 formula is over conservative in this regard.

JØrgensen, H.B.; Hoang, Linh Cao

2013-01-01

307

Chaotic dynamics in shear-thickening surfactant solutions

We report the observation of dynamical behaviour in dilute, aqueous solutions of a surfactant CTAT (cetyl trimethylammonium p-toluenesulphonate), below the overlap concentration c$^{\\star}$. At these concentrations, CTAT forms cylindrical micelles and shows a pronounced shear thickening transition above a concentration-dependent critical shear rate $\\dot\\gamma_{c}$. An analysis of the time-series of the stress relaxations at controlled shear rates in the shear-thickening regime shows the existence of correlation dimensions greater than two and positive Lyapunov exponents. This indicates the existence of deterministic chaos in the dynamics of stress relaxation at these concentrations and shear rates. The observed chaotic behaviour may be attributed to the stick-slip between the shear - induced structure (SIS) formed in the sheared surfactant solution and the coexisting dilute phase. At still higher shear rates, when the SIS spans the Couette, there is a transition to higher-dimensional dynamics arising out of ...

Bandyopadhyay, R M

2000-01-01

308

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

309

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

310

Conjugate-shear folding: A model for the relationships between foliations, folds and shear zones

Microstructural mapping of whole thin sections cut from two samples of micaschist containing cm-scale folds plus garnet porphyroblasts has provided new insight in the relationships between folding, shearing and foliation development. The garnets exhibit coherent inclusion-trail patterns that place important constraints on the kinematic development of both samples, which are shown to be representative of coaxial versus non-coaxial deformation in rocks containing a pre-existing schistosity. A comparison of crenulations-cleavages geometries in both samples and a review of the geometry of natural and experimental multilayer folds leads to the conclusion that folding involves conjugate shearing at different scales. At microscopic scales, crenulation cleavages nucleate as conjugate-kink or shear instabilities and develop further as a function of the macroscopic partitioning of deformation. In fold-hinge domains, bulk-coaxial deformation results in equal development of conjugate crenulations that progressively coalescence into symmetrical crenulation patterns so that, macroscopically, parallelism is achieved between foliation, fold-axial planes and long axes of strain ellipses. Fold-limb domains represent a system of conjugate-shear zones where single sets of crenulation instabilities with synthetic shearing component preferentially develop producing oblique relationships between the aforementioned elements. Cleavage fanning is inferred as a direct consequence of this conjugate-shear origin of folds. The model implies that crenulation cleavages and S-C fabrics in shear zones form by analogous processes, in both cases involving a component of shearing along foliation planes. The development of conjugate sets of foliation planes surrounding porphyroblasts during early, relatively coaxial stages of deformation explains continued "gyrostatic" behaviour during more advanced non-coaxial stages, as indicated by consistently oriented inclusion trails in the studied samples.

Aerden, Domingo G. A. M.; Sayab, Mohammad; Bouybaouene, Mohamed L.

2010-08-01

311

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. PMID:24827245

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

2014-04-01

312

Adiabatic shearing behavior of different steels under extreme high shear loading

International Nuclear Information System (INIS)

The adiabatic shearing behavior of S15C low carbon steel, S50C medium carbon steel, and SKS 93 tool steel with a high carbon and low alloy content (abbreviated to high carbon steel hereafter) is examined using a compressive-type split-Hopkinson pressure bar (SHPB) at strain rates ranging from (5-20) x 104 s-1. Metallographic observations of the sheared specimens suggest that the shear flow stress and the hardness and width of the shear band depend strongly on the carbon content and strain rate. The formation of the deformed and martensitic transformed shear bands is a function of the carbon content and the shear load. The fracture surface of the low carbon steel exhibits a dimple-like structure. However, the fracture surfaces of the medium and high carbon steels exhibit both a dimple-like structure and knobby features. The formation of the knobby features is attributed to an increased carbon content and a higher strain rate

313

Adiabatic shearing behavior of different steels under extreme high shear loading

Energy Technology Data Exchange (ETDEWEB)

The adiabatic shearing behavior of S15C low carbon steel, S50C medium carbon steel, and SKS 93 tool steel with a high carbon and low alloy content (abbreviated to high carbon steel hereafter) is examined using a compressive-type split-Hopkinson pressure bar (SHPB) at strain rates ranging from (5-20) x 10{sup 4} s{sup -1}. Metallographic observations of the sheared specimens suggest that the shear flow stress and the hardness and width of the shear band depend strongly on the carbon content and strain rate. The formation of the deformed and martensitic transformed shear bands is a function of the carbon content and the shear load. The fracture surface of the low carbon steel exhibits a dimple-like structure. However, the fracture surfaces of the medium and high carbon steels exhibit both a dimple-like structure and knobby features. The formation of the knobby features is attributed to an increased carbon content and a higher strain rate.

Lee, W.-S. [Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)], E-mail: wslee@mail.ncku.edu.tw; Liu, C.-Y.; Chen, T.-H. [Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

2008-02-29

314

Adiabatic shearing behavior of different steels under extreme high shear loading

The adiabatic shearing behavior of S15C low carbon steel, S50C medium carbon steel, and SKS 93 tool steel with a high carbon and low alloy content (abbreviated to high carbon steel hereafter) is examined using a compressive-type split-Hopkinson pressure bar (SHPB) at strain rates ranging from (5-20) × 10 4 s -1. Metallographic observations of the sheared specimens suggest that the shear flow stress and the hardness and width of the shear band depend strongly on the carbon content and strain rate. The formation of the deformed and martensitic transformed shear bands is a function of the carbon content and the shear load. The fracture surface of the low carbon steel exhibits a dimple-like structure. However, the fracture surfaces of the medium and high carbon steels exhibit both a dimple-like structure and knobby features. The formation of the knobby features is attributed to an increased carbon content and a higher strain rate.

Lee, Woei-Shyan; Liu, Chen-Yang; Chen, Tao-Hsing

2008-02-01

315

Shear banding fluids in microchannels: high shear rheology, slippage and Poiseuille flow instability

We characterize by Particle Image Velocimetry the Poiseuille flow a semi-dilute solution of wormlike micelles (a CTAB and sodium nitrate aqueous solution) in pressure resistant microchannels. At low shear rates, we observe a parabolic profile. Increasing the pressure driving the flow, the fluid separates into two phases above a critical shear rate at the wall. This is the so called shear-banding regime. Deducing the non-linear rheology from the velocity profiles by a local calculation, we are able to measure the stress versus shear rate curve at least one order of magnitude above the dynamical range attainable in Couette geometries, independently from the slippage, revealing a strongly shear-thinning structure. In addition, by extrapolation of the velocity profiles to the wall position, we measure an absence of slippage at the wall. Looking into more details to the increase in velocity fluctuations in the downstream direction, we characterize a supercritical instability in this shear-banded Poiseuille flow, localized at the interface between the two phases with a wavelength comparable to the confining dimension.

Nghe, Philippe; Degre, Guillaume; Tabeling, Patrick; Ajdari, Armand

2009-03-01

316

Nonlinear shear-current dynamo and magnetic helicity transport in sheared turbulence

The nonlinear mean-field dynamo due to a shear-current effect in a nonhelical homogeneous turbulence with a mean velocity shear is discussed. The transport of magnetic helicity as a dynamical nonlinearity is taken into account. The shear-current effect is associated with the ${\\bf W} {\\bf \\times} {\\bf J}$ term in the mean electromotive force, where ${\\bf W}$ is the mean vorticity due to the large-scale shear motions and ${\\bf J}$ is the mean electric current. This effect causes the generation of large-scale magnetic field in a turbulence with large hydrodynamic and magnetic Reynolds numbers. The dynamo action due to the shear-current effect depends on the spatial scaling of the correlation time $\\tau(k)$ of the background turbulence, where $k$ is the wave number. For Kolmogorov scaling, $\\tau(k) \\propto k^{-2/3}$, the dynamo instability occurs, while when $\\tau(k) \\propto k^{-2}$ (small hydrodynamic and magnetic Reynolds numbers) there is no the dynamo action in a sheared nonhelical turbulence. The magnetic h...

Rogachevskii, I; Liverts, E

2006-01-01

317

Turbulent transport across shear layers in magnetically confined plasmas

Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatial-temporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.

Nold, B.; Manz, P.; Ribeiro, T. T.; Fuchert, G.; Birkenmeier, G.; Müller, H. W.; Ramisch, M.; Scott, B. D.; Stroth, U.

2014-10-01

318

Nongeometrically converted shear waves in marine streamer data :

Digital Repository Infrastructure Vision for European Research (DRIVER)

Under certain circumstances, marine streamer data contain nongeometrical shear body wave arrivals that can be used for imaging. These shear waves are generated via an evanescent compressional wave in the water and convert to propagating shear waves at the water bottom. They are called “nongeometrical” because the evanescent part in the water does not satisfy Snell’s law for real angles, but only for complex angles. The propagating shear waves then undergo reflection and refraction in th...

Drijkoningen, G. G.; El Allouche, N.; Thorbecke, J. W.; Bada, G.

2012-01-01

319

Quantifying Hepatic Shear Modulus In Vivo Using Acoustic Radiation Force

Digital Repository Infrastructure Vision for European Research (DRIVER)

The speed at which shear waves propagate in tissue can be used to quantify the shear modulus of the tissue. As many groups have shown, shear waves can be generated within tissues using focused, impulsive, acoustic radiation force excitations, and the resulting displacement response can be ultrasonically tracked through time. The goals of the work herein are two-fold: first, to develop and validate an algorithm to quantify shear wave speed from radiation force-induced, ultrasonically-detected ...

Wang, Michael H.; Dahl, Jeremy J.; Frinkley, Kristin D.; Nightingale, Kathryn R.

2008-01-01

320

Relaxation of jammed colloidal suspensions after shear cessation

The dynamics of heterogeneities in a shear thickening, concentrated colloidal suspension is investigated through speckle visibility spectroscopy, a dynamic light scattering technique recently introduced [P. K. Dixon and D. J. Durian, Phys. Rev. Lett. 90, 184302 (2003)]. Formation of shear-induced heterogeneities is observed in the jamming regime, and their relaxation after shear cessation is monitored as a function of the applied shear stress. The relaxation time of these heterogeneities increases when a higher stress is applied.

Ianni, Francesca; Lasne, David; Sarcia, Régis; Hébraud, Pascal

2006-07-01

321

The effect of friction on wide shear bands

Digital Repository Infrastructure Vision for European Research (DRIVER)

Frictional and frictionless granular materials in a split-bottom ring shear cell geometry show wide shear bands under slow, quasi-static deformation. Here, the differences between frictional and frictionless materials are elaborated using discrete element simulations (DEM). Several continuum fields like the density, the velocity field, the deformation gradient, and the stress are used here for comparison. Interestingly, the shear stress intensity, i.e., the shear stress divided by the pre...

Luding, S.

2008-01-01

322

Testing the Shear Strength of Gummy Bear Mountain

Students do background reading from the text on physical weathering and the components of shear strength. Students write hypotheses about the shear strength of different sizes and shapes of gummy candy. The students then uses simple experiments to demonstrate and test the shear strength of the candy types.

Keen-Zebert, Amanda

323

49 CFR 178.338-12 - Shear section.

...2010-10-01 2010-10-01 false Shear section. 178.338-12 Section 178...Vehicle Transportation § 178.338-12 Shear section. Unless the valve is located...of liquid or vapor, must incorporate a shear section or breakage groove adjacent...

2010-10-01

324

Fluid Effects on Shear Waves in Finely Layered Porous Media

International Nuclear Information System (INIS)

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

325

International Nuclear Information System (INIS)

The shear strength of NSC (Normal Strength Concrete) has been extensively researched. However, very little data is available on the shear strength of HSC beams for fc > 6000 psi (40MPa). In this research, 35 beams with five values of longitudinal steel and seven values of shear span to depth (aid) ratio have been tested to study the effect of longitudinal steel and shear span to depth ratio. The results have been compared with the provisions of ACI 318-06 as well. The results have shown that shear failure is anticipated when the longitudinal steel ratio for p > 1 %. The shear strength of HSC normally increases with the increase of longitudinal steel and decreases with the increase in shear span to depth ratio, as exhibited in normal strength, but the failure is more sudden and brittle. The ACI 318 provisions for shear strength of beams are normally good predictors but for a/d >5. (author)

326

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

327

Shear capacity of high-strength concrete beams with their point of inflection within the shear span

Digital Repository Infrastructure Vision for European Research (DRIVER)

The shear strength of concrete does not increase in proportion with the concrete grade. Thus, when high-strength concrete is used in place of normal-strength concrete, the shear capacity of the structure could become critical. In the study presented, the effect of concrete strength on the shear capacity of concrete beams was investigated. As previous research on normal-strength concrete beams has shown that the presence of an inflection point within the shear span can significantly influence ...

Islam, Ms; Pam, Hj; Kwan, Akh

1998-01-01

328

A comparison between magnetic shear and flare shear in a well-observed M-class flare

International Nuclear Information System (INIS)

We give an extensive multi-wavelength analysis of an eruptive M1.0/1N class solar flare, which occurred in the active region NOAA 10044 on 2002 July 26. Our emphasis is on the relationship between magnetic shear and flare shear. Flare shear is defined as the angle formed between the line connecting the centroids of the two ribbons of the flare and the line perpendicular to the magnetic neutral line. The magnetic shear is computed from vector magnetograms observed at Big Bear Solar Observatory (BBSO), while the flare shear is computed from Transition Region and Coronal Explorer (TRACE) 1700 A images. By a detailed comparison, we find that: 1) The magnetic shear and the flare shear of this event are basically consistent, as judged from the directions of the transverse magnetic field and the line connecting the two ribbons' centroids. 2) During the period of the enhancement of magnetic shear, flare shear had a fast increase followed by a fluctuated decrease. 3) When the magnetic shear stopped its enhancement, the fluctuated decreasing behavior of the flare shear became very smooth. 4) Hard X-ray (HXR) spikes are well correlated with the unshearing peaks on the time profile of the rate of change of the flare shear. We give a discussion of the above phenomena. (invited reviews)

329

Influence of particle elasticity in shear testers

Two dimensional simulations of non-cohesive granular matter in a biaxial shear tester are discussed. The effect of particle elasticity on the mechanical behavior is investigated using two complementary distinct element methods (DEM): Soft particle molecular dynamics simulations (Particle Flow Code, PFC) for elastic particles and contact dynamics simulations (CD) for the limit of perfectly rigid particles. As soon as the system dilates to form shear bands, it relaxes the elastic strains so that one finds the same stresses for rigid respectively elastic particles in steady state ow. The principal stresses in steady state ow are determined. They are proportional to each other, giving rise to an effective macroscopic friction coefficient which is about 10 % smaller than the microscopic friction coefficient between the grains.

Kadau, D; Theuerkauf, J; Wolf, D E; Kadau, Dirk; Schwesig, Dominik; Theuerkauf, Joerg; Wolf, Dietrich E.

2005-01-01

330

Microstructure and velocity fluctuations in sheared suspensions

The velocity fluctuations present in macroscopically homogeneous suspensions of neutrally buoyant, non-Brownian spheres undergoing simple shear flow, and their dependence on the microstructure developed by the suspensions, are investigated in the limit of vanishingly small Reynolds numbers using Stokesian dynamics simulations. We show that, in the dilute limit, the standard deviation of the velocity fluctuations is proportional to the volume fraction, in both the transverse and the flow directions, and that a theoretical prediction, which considers only for the hydrodynamic interactions between isolated pairs of spheres, is in good agreement with the numerical results at low concentrations. We also simulate the velocity fluctuations that would result from a random hard-sphere distribution of spheres in simple shear flow, and thereby investigate the effects of the microstructure on the velocity fluctuations. Analogous results are discussed for the fluctuations in the angular velocity of the suspended spheres. ...

Drazer, G; Khusid, B; Acrivos, A

2003-01-01

331

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

332

Bulk and Shear Viscosity in Hagedorn Fluid

Assuming that the Hagedorn fluid composed of known particles and resonances with masses $m<2\\,$GeV obeys the {\\it first-order} theory (Eckart) of relativistic fluid, we discuss the transport properties of QCD confined phase. Based on the relativistic kinetic theory formulated under the relaxation time approximation, expressions for bulk and shear viscosity in thermal medium are derived. The relaxation time in the Hagedorn dynamical fluid exclusively takes into account the decay and eventually van der Waals processes. We comment on the {\\it in-medium} thermal effects on bulk and shear viscosities and averaged relaxation time with and without the excluded-volume approach. As an application of these results, we suggest the dynamics of heavy-ion collisions, non-equlibrium thermodynamics and the cosmological models, which require thermo and hydrodynamics equations of state.

Tawfik, A

2010-01-01

333

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

334

Direct measurement of shear properties of microfibers.

As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar(®) 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively. PMID:25273783

Behlow, H; Saini, D; Oliveira, L; Durham, L; Simpson, J; Serkiz, S M; Skove, M J; Rao, A M

2014-09-01

335

Search for shears mechanism in 142Sm

International Nuclear Information System (INIS)

Generation of angular momentum in weakly deformed nuclei by shears mechanism is a well known phenomenon in nuclear structure physics. During the last two decades, rotational-like bands consisting of dipole transitions have been observed systematically near the spherical region and interpreted as Magnetic Rotor. In this mechanism the total angular momentum along the band is generated by the gradual alignment of the two angular momentum blades and the shears arrangement of the high j orbital give rise to a large transverse magnetic dipole moment. In the present INGA experiments at TIFR, the level structure of 141,142Sm is studied in order to look for the possible observation of magnetic and anti magnetic rotational bands by measuring the life time of the excited states using DSAM technique

336

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

337

Shear induced instabilities in layered liquids

Motivated by the experimentally observed shear-induced destabilization and reorientation of smectic A like systems, we consider an extended formulation of smectic A hydrodynamics. We include both, the smectic layering (via the layer displacement u and the layer normal p) and the director n of the underlying nematic order in our macroscopic hydrodynamic description and allow both directions to differ in non equilibrium situations. In an homeotropically aligned sample the nematic director does couple to an applied simple shear, whereas the smectic layering stays unchanged. This difference leads to a finite (but usually small) angle between n and p, which we find to be equivalent to an effective dilatation of the layers. This effective dilatation leads, above a certain threshold, to an undulation instability of the layers. We generalize our earlier approach [Rheol. Acta, vol.39(3), 15] and include the cross couplings with the velocity field and the order parameters for orientational and positional order and show...

Auernhammer, G K; Pleiner, H; Auernhammer, Guenter K.; Brand, Helmut R.; Pleiner, Harald

2002-01-01

338

Hierarchical probabilistic inference of cosmic shear

Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the glo...

Schneider, Michael D; Marshall, Philip J; Dawson, William A; Meyers, Joshua; Bard, Deborah J; Lang, Dustin

2014-01-01

339

Bac clones generated from sheared dna

Energy Technology Data Exchange (ETDEWEB)

BAC libraries generated from restriction-digested genomic DNA display representational bias and lack some sequences. To facilitate completion of genome projects, procedures have been developed to create BACs from DNA physically sheared to create fragments extending up to 200kb. The DNA fragments were repaired to create blunt ends and ligated to a new BAC vector. This approach has been tested by generating BAC libraries from Drosophila DNA, with insert lengths of 50 kb to 150 kb. The libraries lack chimeric clone problems as determined by mapping paired BAC-end sequences of one library to the D. melanogaster genome sequence. The utility of ''sheared'' libraries was demonstrated by closure of a previous clone gap and by isolation of clones from telomeric regions, which were notably absent from previous Drosophila BAC libraries.

Osoegawa, Kazutoyo; Vessere, Gery M.; Shu, Chung Li; Hoskins,Roger A.; Abad, Jose P.; de Pablos, Beatriz; Villasante, Alfredo; deJong, Pieter J.

2006-08-09

340

Inertial particles in homogeneous shear turbulence

International Nuclear Information System (INIS)

The characteristics of inertial particles distribution in a uniformly sheared turbulent flow are investigated, with the aim of quantifying the effects associated with the large-scale anisotropy induced by the mean velocity gradient. The focus of the analysis is on clustering aspects, and in particular on the dependence of the radial distribution function on both the directionality and the magnitude of the observation scale. We discuss experimental data measured in a homogeneous shear flow seeded with particles of size comparable with the Kolmogorov length scale and Stokes number St ? 0.3, and discuss their distribution properties in comparison with results provided by related one-way coupled direct numerical simulations which make use of the point-force approximation.

341

Inertial particles in homogeneous shear turbulence

Energy Technology Data Exchange (ETDEWEB)

The characteristics of inertial particles distribution in a uniformly sheared turbulent flow are investigated, with the aim of quantifying the effects associated with the large-scale anisotropy induced by the mean velocity gradient. The focus of the analysis is on clustering aspects, and in particular on the dependence of the radial distribution function on both the directionality and the magnitude of the observation scale. We discuss experimental data measured in a homogeneous shear flow seeded with particles of size comparable with the Kolmogorov length scale and Stokes number St Almost-Equal-To 0.3, and discuss their distribution properties in comparison with results provided by related one-way coupled direct numerical simulations which make use of the point-force approximation.

Nicolai, Claudia; Jacob, Boris [CNR-INSEAN, via di Vallerano 139, 00128 Rome (Italy); Gualtieri, Paolo; Piva, Renzo, E-mail: claudia.nicolai@uniroma1.it [DMA, Sapienza Universita di Roma, Via Eudossiana 18, 00184 Rome (Italy)

2011-12-22

342

Effective temperature of a sheared foam

We perform computer simulations of a model for an overdamped, sheared foam in two dimensions at zero temperature. We measure an effective temperature with the use of an embedded oscillator, in manner analogous to experiments done by Abate and Durian on a different system [arXiv:0806.0765v2]. Our oscillator is one of the bubbles in the foam, which, in addition to its interaction with other bubbles, is also subject to a harmonic potential. We define an effective temperature based on the fluctuations in the position of the oscillator. We compare our results to the effective temperatures computed with the use of measurements of the fluctuations of the shear stress and fluctuations of the energy, respectively.

Valdez-Balderas, Daniel; Olsson, Peter; Teitel, Stephen

2009-03-01

343

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

344

Direct measurement of shear properties of microfibers

As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar® 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively.

Behlow, H.; Saini, D.; Oliveira, L.; Durham, L.; Simpson, J.; Serkiz, S. M.; Skove, M. J.; Rao, A. M.

2014-09-01

345

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 (4)He. 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 (4)He 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 (4)He, our findings lend support to assumptions in the literature that inherently classical models remain useful for the description of mechanical behavior in quantum crystals. PMID:24785047

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

2014-04-18

346

Static inelastic analysis of RC shear walls

A macro-model of a reinforced concrete (RC) shear wall is developed for static inelastic analysis. The model is composed of RC column elements and RC membrane elements. The column elements are used to model the boundary zone and the membrane elements are used to model the wall panel. Various types of constitutive relationships of concrete could be adopted for the two kinds of elements. To perform analysis, the wall is divided into layers along its height. Two adjacent layers are connected with a rigid beam. There are only three unknown displacement components for each layer. A method called single degree of freedom compensation is adopted to solve the peak value of the capacity curve. The post-peak stage analysis is performed using a forced iteration approach. The macro-model developed in the study and the complete process analysis methodology are verified by the experimental and static inelastic analytical results of four RC shear wall specimens.

Chen, Qin; Qian, Jiaru

2002-06-01

347

Linear Inviscid Damping for Monotone Shear Flows

In this article we prove linear stability, inviscid damping and scattering of the 2D Euler equations around regular, strictly monotone shear flows $(U(y),0)$ in a periodic channel under Sobolev perturbations. We treat the settings of an infinite channel, $\\mathbb{T} \\times \\mathbb{R}$, as well as a finite channel, $\\mathbb{T} \\times [0,1]$, with impermeable boundary. We first prove inviscid damping with optimal algebraic rates for strictly monotone shear flows under the assumption of controlling the regularity of the scattered vorticity. Subsequently, we establish linear stability of the scattering equation in Sobolev spaces under perturbations which are of not too large wave-length with respect to $x$, depending on $U''$.

Zillinger, Christian

2014-01-01

348

Power spectrum from weak-shear data

We demonstrate that the aperture mass as a measure for cosmic shear closely approximates (to better than ~5%) the scaled and shifted power spectrum of the projected mass density. This cosmological weak-lensing information can thus be used to directly infer the projected matter power spectrum with high accuracy. As an application, we show that aperture-mass observations can be used to constrain the cosmic density parameter and the power-spectrum amplitude. We show that, for a particular example, it should be possible to constrain Omega_0 to within ~ +/- 27%, and sigma_8 to within ~ +/- 8% using weak-shear data on a square-shaped field of 8 degrees side length.

Bartelmann, M; Bartelmann, Matthias; Schneider, Peter

1999-01-01

349

Shear adhesion strength of aligned electrospun nanofibers.

Inspiration from nature such as insects' foot hairs motivates scientists to fabricate nanoscale cylindrical solids that allow tens of millions of contact points per unit area with material substrates. In this paper, we present a simple yet robust method for fabricating directionally sensitive shear adhesive laminates. By using aligned electrospun nylon-6, we create dry adhesives, as a succession of our previous work on measuring adhesion energies between two single free-standing electrospun polymer fibers in cross-cylinder geometry, randomly oriented membranes and substrate, and peel forces between aligned fibers and substrate. The synthetic aligned cylindrical solids in this study are electrically insulating and show a maximal Mode II shear adhesion strength of 27 N/cm(2) on a glass slide. This measured value, for the purpose of comparison, is 270% of that reported from gecko feet. The Mode II shear adhesion strength, based on a commonly known "dead-weight" test, is 97-fold greater than the Mode I (normal) adhesion strength of the same. The data indicate a strong shear binding on and easy normal lifting off. Anisotropic adhesion (Mode II/Mode I) is pronounced. The size and surface boundary effects, crystallinity, and bending stiffness of fibers are used to understand these electrospun nanofibers, which vastly differ from otherwise known adhesive technologies. The anisotropic strength distribution is attributed to a decreasing fiber diameter and an optimized laminate thickness, which, in turn, influences the bending stiffness and solid-state "wettability" of points of contact between nanofibers and surface asperities. PMID:25105533

Najem, Johnny F; Wong, Shing-Chung; Ji, Guang

2014-09-01

350

Wave-equation shear wave splitting tomography

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main focus of this paper is the development of a theoretical framework for the tomographic inversion of (broad-band) shear wave splitting measurements in terms of anisotropic structure in the upper mantle. We show that the partial differential equations (PDEs) that govern wave equation shearwave splitting tomography are, upon linearization with the Born approximation, similar in structure to the equations that describe wave equation transmission and reflection tomography. F...

Long, M. L.; Hoop, M. V.; Hilst, R. D.

2008-01-01

351

Viscoelastic Phase Separation in Shear Flow

Digital Repository Infrastructure Vision for European Research (DRIVER)

We numerically investigate viscoelastic phase separation in polymer solutions under shear using a time-dependent Ginzburg-Landau model. The gross variables in our model are the polymer volume fraction and a conformation tensor. The latter represents chain deformations and relaxes slowly on the rheological time giving rise to a large viscoelastic stress. The polymer and the solvent obey two-fluid dynamics in which the viscoelastic stress acts asymmetrically on the polymer and...

Imaeda, Tatsuhiro; Furukawa, Akira; Onuki, Akira

2003-01-01

352

The Electrorheological Fluids with High Shear Stress

A series of high performance ER fluids newly manufactured in our laboratory are presented. The yield stress of those ER fluids can reach several tens of kPa, 100 kPa and even 200 kPa, respectively. For understanding the high shear stress effect a model is proposed base on the electric field induced molecular bounding effect. The main effective factors in fabricating the high performance ER are discussed.

Lu, Kunquan; Shen, Rong; Wang, Xuezhao; Sun, Gang; Wen, Weijia

353

Shear viscosity of a crosslinked polymer melt

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate the static shear viscosity on the sol side of the vulcanization transition within a minimal mesoscopic model for the Rouse-dynamics of a randomly crosslinked melt of phantom polymers. We derive an exact relation between the viscosity and the resistances measured in a corresponding random resistor network. This enables us to calculate the viscosity exactly for an ensemble of crosslinks without correlations. The viscosity diverges logarithmically as the critical...

Broderix, Kurt; Loewe, Henning; Mueller, Peter; Zippelius, Annette

1998-01-01

354

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

355

Structures and shear response of lipid monolayers

International Nuclear Information System (INIS)

This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases

356

Shear alignment and instability of smectic phases

We consider the shear flow of well-aligned one-component smectic phases, such as thermotropic smectics and lamellar diblock copolymers, below the critical region. We show that, as a result of thermal fluctuations of the layers, parallel (c) alignment is generically unstable and perpendicular (a) alignment is stable against long-wavelength undulations. We also find, surprisingly, that both a and c are stable for a narrow window of values for the anisotropic viscosity.

Goulian, M; Goulian, Mark; Milner, Scott T

1995-01-01

357

Accelerating cosmological expansion from shear viscosity

The dissipation of energy from local velocity perturbations in the cosmological fluid affects the time evolution of spatially averaged fluid dynamic fields and the cosmological solution of Einstein's field equations. We show how this backreaction effect depends on shear viscosity and other material properties of the dark sector, as well as the spectrum of perturbations. If sufficiently large, this effect could account for the acceleration of the cosmological expansion.

Floerchinger, Stefan; Wiedemann, Urs Achim

2014-01-01

358

Shear flow pumping in open microfluidic systems

We propose to drive open microfluidic systems by shear in a covering fluid layer, e.g., oil covering water-filled chemical channels. The advantages as compared to other means of pumping are simpler forcing and prevention of evaporation of volatile components. We calculate the expected throughput for straight channels and show that devices can be built with off-the-shelf technology. Molecular dynamics simulations suggest that this concept is scalable down to the nanoscale.

Rauscher, M; Koplik, J; Rauscher, Markus; Koplik, Joel

2006-01-01

359

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

360

Velocity profiles in shear-banding wormlike micelles

Using Dynamic Light Scattering in heterodyne mode, we measure velocity profiles in a much studied system of wormlike micelles (CPCl/NaSal) known to exhibit both shear-banding and stress plateau behavior. Our data provide evidence for the simplest shear-banding scenario, according to which the effective viscosity drop in the system is due to the nucleation and growth of a highly sheared band in the gap, whose thickness linearly increases with the imposed shear rate. We discuss various details of the velocity profiles in all the regions of the flow curve and emphasize on the complex, non-Newtonian nature of the flow in the highly sheared band.

Salmon, J B; Manneville, S; Molino, F; Salmon, Jean-Baptiste; Colin, Annie; Manneville, Sebastien; Molino, Francois

2003-01-01

361

Avalanche contribution to shear modulus of granular materials

Shear modulus of frictionless granular materials near the jamming transition under oscillatory shear is numerically investigated. It is found that the shear modulus G satisfies a scaling law to interpolate between G ˜(?-?J)1/2 and G ˜?0-1/2(?-?J) for a linear spring model of the elastic interaction between contacting grains, where ?, ?J, and ?0 are, respectively, the volume fraction of grains, the fraction at the jamming point, and the amplitude of the oscillatory shear. The linear relation between the shear modulus and ? -?J can be understood by slip avalanches.

Otsuki, Michio; Hayakawa, Hisao

2014-10-01

362

Chemical reactions in controlled high-strain-rate shear bands

International Nuclear Information System (INIS)

Controlled high-strain-rate shear bands were generated in porous mixtures (Nb+Si, Ti+Si) using axially symmetric experimental configurations (open-quotes Thick-Walled Cylinderclose quotes) method. Shear strains up to 100 and strain rates of approximately 107sec-1 were generated inside shear bands. Particle fracture, melting, and regions of partial reaction were observed inside shear bands for the Nb+Si system. Under the same conditions of deformation, for the Ti-Si system the reaction initiated inside shear bands and propagated through the entire sample. copyright 1996 American Institute of Physics

363

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

364

Three-Dimensional Imaging of Colloidal Glasses under Steady Shear

Using fast confocal microscopy we image the three-dimensional dynamics of particles in a yielded hard-sphere colloidal glass under steady shear. The structural relaxation, observed in regions with uniform shear, is nearly isotropic but is distinctly different from that of quiescent metastable colloidal fluids. The inverse relaxation time ??-1 and diffusion constant D, as functions of the local shear rate ??, show marked shear thinning with ??-1?D???0.8 over more than two decades in ??. In contrast, the global rheology of the system displays Herschel-Bulkley behavior. We discuss the possible role of large scale shear localization and other mechanisms in generating this difference.

Besseling, R.; Weeks, Eric R.; Schofield, A. B.; Poon, W. C. K.

2007-07-01

365

Supercooled liquids under shear: A mode-coupling theory approach

We generalize the mode-coupling theory of supercooled fluids to systems under stationary shear flow. Our starting point is the generalized fluctuating hydrodynamic equations with a convection term. The method is applied to a two dimensional colloidal suspension. The shear rate dependence of the intermediate scattering function and shear viscosity is analyzed. The results show a drastic reduction of the structural relaxation time due to shear and strong shear thinning behavior of the viscosity which are in qualitative agreement with recent simulations. The microscopic theory with minimal assumptions can explain the behavior far beyond the linear response regime.

Miyazaki, K; Reichman, D R; Miyazaki, Kunimasa; Yamamoto, Ryoichi; Reichman, David R.

2003-01-01

366

Shear induced orientation of edible fat and chocolate crystals

Shear-induced orientation of fat crystallites was observed during crystallization of cocoa butter, milk fat, stripped milk fat and palm oil. This universal effect was observed in systems crystallized under high shear. The minor polar components naturally present in milk fat were found to decrease the shear-induced orientation effect in this system. The competition between Brownian and shear forces, described by the Peclet number, determines the crystallite orientation. The critical radius size, from the Gibbs-Thomson equation, provides a tool to understand the effect of shear at the onset stages of crystallization.

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

2003-03-01

367

Parallel-field electrorheological clutch: Enhanced high shear rate performance

We present an electrorheological (ER) fluid cylindrical clutch which achieves stable shear stress at high shear rate, and demonstrates superior performance compared with the traditional ER clutches. The design is realized by employing alternate-stripe electrodes on the inner cylinder, with either dielectric or metallic outer rotor. The alternate stripe electrodes generate electric fields with a component parallel to the shearing direction, so that ER particles can form chain structures parallel to shear and thereby bring significant enhanced device performance at a high shear rate. Differences due to the use of dielectric or metallic outer rotor are shown to be compatible with expectations based on simulated electric-field patterns.

Liu, Liyu; Huang, Xixiang; Shen, Cai; Liu, Zhengyou; Shi, Jing; Wen, Weijia; Sheng, Ping

2005-09-01

368

Inherent Rheology of a Granular Fluid in Uniform Shear Flow

In contrast to normal fluids, a granular fluid under shear supports a steady state with uniform temperature and density since the collisional cooling can compensate locally for viscous heating. It is shown that the hydrodynamic description of this steady state is inherently non-Newtonian. Differing degrees of inelasticity sample the complete nonlinear dependence of the shear viscosity on the shear rate. As a consequence, the Newtonian shear viscosity cannot be determined from experiments or simulation of uniform shear flow. The relationship to the Chapman-Enskog method to derive hydrodynamics is clarified using an exactly solvable kinetic model.

Santos, A; Dufty, J W

2004-01-01

369

Shear bands in metallic glasses are not necessarily hot

We have used the fusible tin coating method to detect shear band heating in amorphous Zr57Ti5Cu20Ni8Al10 loaded under quasi-static uniaxial compression. High-rate load data allowed a precise determination of the duration of shearing events and final fracture. When loading was halted prior to fracture we saw no evidence of melted tin despite the presence of shear offsets up to 6 ?m on some shear bands. Samples loaded to fracture showed evidence of tin melting near the fracture surface. We attribute the difference to the duration of the events, which is much longer for shear banding (milliseconds) than for fracture (microseconds).

Slaughter, Stephanie K.; Kertis, Felicitee; Deda, Erin; Gu, Xiaojun; Wright, Wendelin J.; Hufnagel, T. C.

2014-09-01

370

This paper deals with flow-induced shape changes of elastic capsules. The state of the art concerning both theory and experiments is briefly reviewed starting with dynamically induced small deformation of initially spherical capsules and the formation of wrinkles on polymerized membranes. Initially non-spherical capsules show tumbling and tank-treading motion in shear flow. Theoretical descriptions of the transition between these two types of motion assuming a fixed shape are at odds with the full capsule dynamics obtained numerically. To resolve the discrepancy, we expand the exact equations of motion for small deformations and find that shape changes play a dominant role. We classify the dynamical phase transitions and obtain numerical and analytical results for the phase boundaries as a function of viscosity contrast, shear and elongational flow rate. We conclude with perspectives on time-dependent flow, on shear-induced unbinding from surfaces, on the role of thermal fluctuations and on applying the concepts of stochastic thermodynamics to these systems.

Finken, R.; Kessler, S.; Seifert, U.

2011-05-01

371

Shear strength of metals behind shock fronts

Results are presented from a numerical modeling of experiments, conducted by J. Lipkin, R. Asay, L. Chabildas, and J. Wise, in which shock-compressed aluminum and polycrystalline beryllium were loaded again by shock waves. Reproduction of the experimental structures of the impulses in the calculations made it possible to determine the stresses acting in the materials during the primary and secondary shock loading, as well as to study the dynamics of the secondary shock load. It is shown that resistance to plastic strain is maintained in aluminum and beryllium behind the front of weak shock waves with intensities up to 10 GPa. The shear strength of the material behind the front does not correspond to the shear stresses at the Hugoniot elastic limit. For aluminum alloy 6061-T6 and beryllium, shear strength behind the fronts of shock waves with amplitudes up to 10 GPa is lower than in the elastic precursor but is greater than the static yield point of the material in the initial state.

Skripnyak, V. A.; Potekaev, A. I.

1995-10-01

372

Shear viscosity and out of equilibrium dynamics

Using Grad’s method, we calculate the entropy production and derive a formula for the second-order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance, the shear tensor and the shear viscosity to entropy density ratio ?/s are numerically calculated by an iterative and self-consistent prescription within the second-order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with ?/s obtained using the Navier-Stokes approximation, the present result is about 20% larger at a QCD coupling ?s ? 0.3 (with ?/s ? 0.18) and is a factor of 2–3 larger at a small coupling ?s ? 0.01. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on ?/s, except when employing a small ?s . On the other hand, we demonstrate that for such small ?s , the gluon syst...

El, Andrej; Xu, Zhe; Greiner, Carsten

2009-01-01

373

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

374

Behaviour of voids in a shear field

DEFF Research Database (Denmark)

When voids are present in a ductile material subject to a shear dominated stress state under low stress triaxiality the voids collapse to micro-cracks, which subsequently rotate and elongate in the shear field. In the present plane strain analyses for cylindrical voids a surface load normal to a plane connecting the ends of the micro-crack is used as an approximate representation of contact stresses during frictionless sliding. In a previous study of the same problem the author applied hydrostatic pressure inside the nearly closed micro-crack to approximate contact conditions. The transverse surface loads used in the present analyses avoid the tendency to unrealistically elongate the voids. It is found that even though the model applied here gives significantly later occurrence of a maximum overall shear stress than that found by using hydrostatic pressure, the present model does predict a maximum in all the cases analyzed and thus illustrates the micro-mechanism leading to failure of the material by localization of plastic flow.

Tvergaard, Viggo

2009-01-01

375

Platelet function under high shear conditions.

Blood platelets are the first line of defense against bleeding and as such involved in the haemostatic repair of damaged vasculature. Their true prowess seems to be displayed under high shear conditions where platelets interact with a variety of plasma proteins, all of which are tightly regulated to close the leak but at the same time prevent lumen occlusion and thromboembolism. The first task is to arrest fast flowing platelets on exposed collagen of the damaged subendothelial surface. Although platelets are endowed with several collagen receptors, most notably integrin alpha2bbeta1 and the immunoglobulin superfamily member GPVI, they can not arrest platelets at high shear rates. The latter requires binding of the platelet receptor GPIbalpha to the A1-binding domain of von Willebrand factor (VWF), which first has to be immobilized from the flowing blood onto the site of injury. Under high shear conditions further accrual of newly arriving platelets again requires VWF, which has to bridge platelets not only to the exposed collagen but also to each other by being sandwiched between the multiple platelet layers of the haemostatic plug. PMID:19151841

Reininger, A J

2009-01-01

376

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

377

Singular eigenfunctions for shearing fluids I

Energy Technology Data Exchange (ETDEWEB)

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.

Balmforth, N.J.; Morrison, P.J.

1995-02-01

378

Permeability anisotropy in clay-rich shear zones

International Nuclear Information System (INIS)

A series of permeability measurements are presented on a consolidated and sheared smectite-rich clay from the Barbados accretionary complex using custom-designed oedometric and ring shear permeameters. The clay, when sheared under fully drained conditions, developed permeability anisotropy with progressive consolidation and shear displacement, increasing from around 15 at 100 kPa effective stress to over 35 at effective stresses of up to 20 MPa. The consolidated clay had a similar level of absolute permeability to that of the sheared clay in the direction parallel to the shear zone. These results suggest that high levels of anisotropic permeability in shear zones cannot by caused by clay fabric alignment alone. Other mechanism is required to explain enhanced fluid flow observed along the decollement of the Barbados accretionary complex. (R.P.)

379

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. PMID:24052052

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

2013-01-01

380

Influence of Reinforced Concrete Shear Wall on Multistorey Buildings

Directory of Open Access Journals (Sweden)

Full Text Available This work presents the behavior and change in length of shear wall in buildings varied by increasing equal heights from 3.5m to 28m i.e, ground storey (G to G+7 keeping thickness of shear wall as constant of 250mm and observing the dimension of shear wall in length only. The study was carried by considering both wind and seismic forces for all the zones and soil types as per IS: 1893(part I:2002 and wind loads as per IS: 875(part III:1987. A total of 96 buildings were analyzed for this work using RESIST software. Buildings with symmetrical dimensions (20mx20m, varying wall length and keeping wall thickness as constant (250mm the effect of shear wall length, wind drift, wind shear, wind moment, seismic drift, seismic shear, and seismic moment, base moment, base shear are studied and results are presented in graphs with height.

Venkata Sairam Kumar.N

2013-08-01

381

Hydrodynamic lubrication in nanoscale bearings under high shear velocity

The setting up process in a nanoscale bearing has been modeled by molecular dynamics simulation. Contrary to the prediction from the classical Reynolds' theory, simulation results show that the load capacity of the nanoscale bearing does not increase monotonically with the operation speed. This is attributed to the change of the local shear rate, which will decrease with the shear velocity of the bearing as the shear velocity exceeds a critical value, i.e., the local shear rate has an upper limit. A simple nonlinear dynamic model indicates that the momentum exchange between the liquid and the solid wall is reduced with the shear velocity when the shear velocity is above a critical value. The weak momentum exchange results in a decrease of the local shear rate, which in turn causes a sharp increase of the slip length.

Chen, Yunfei; Li, Deyu; Jiang, Kai; Yang, Juekuan; Wang, Xiaohui; Wang, Yujuan

2006-08-01

382

A bilateral shear layer between two parallel Couette flows

We consider a shear layer of a kind not previously studied to our knowledge. Contrary to the classical free shear layer, the width of the shear zone does not vary in the streamwise direction but rather exhibits a lateral variation. Based on some simplifying assumptions, an analytic solution has been derived for the new shear layer. These assumptions have been justified by a comparison with numerical solutions of the full Navier-Stokes equations, which accord with the analytical solution to better than $1\\%$ in the entire domain. An explicit formula is found for the width of the shear zone as a function of wall-normal coordinate. This width is independent of wall velocities in the laminar regime. Preliminary results for a co-current laminar-turbulent shear layer in the same geometry are also presented. Shear-layer instabilities were then developed and resulted in an unsteady mixing zone at the interface between the two co-current streams.

Narasimhamurthy, Vagesh D; Andersson, Helge I

2012-01-01

383

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.

384

Finite element analysis for the shear strength appearing in in situ rock shear tests

International Nuclear Information System (INIS)

The mechanisms of the strength which appeared in in situ rock shear tests were examined with a finite element analysis in this paper. A set of plaster model laboratory tests simulating the in situ rock shear tests was analyzed. The plaster models were expressed initially with constant strain triangles (CSTs). Then, the displacement was imposed gradually, and each CST was replaced with a triangular element containing an embedded interface at the point when the stress in each CST reached the failure criterion of the material. The cracking patterns and the deformation obtained from the computation resembled those in the laboratory tests. The cracking pattern under each normal stress deviated from that under different conditions; and therefore, the stress path and the shear strength appeared differently under the various normal stress conditions. The relationship between the apparent shear strength and the failure criterion of the material also changed depending on the normal stress. The shear strength measured in the model tests appeared to be lower than the material strength in the lower and in the higher normal stress ranges. Such differences were thought to occur due to the influence of the stress distributions, which were not assumed, but were caused by several different cracking patterns.

385

Distribution functions of a simple fluid under shear. II. High shear rates

Energy Technology Data Exchange (ETDEWEB)

The distortion of structure of a simple, inverse 12 soft-sphere fluid undergoing plane Couette flow is studied by nonequilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) with a high-shear-rate version of the nonequilibrium (NE) potential obtained recently from the NE distribution function theory of Gan and Eu [Phys. Rev. A 45, 3670; 46, 6344 (1992)]. The theory suggests a NE potential under which the equilibrium structure of the fluid is that of a NE fluid, and also suggests a corresponding Ornstein-Zernike equation with its closure relations. As in the low-shear-rate case [Yu. V. Kalyuzhnyi, S. T. Cui, P. T. Cummings, and H. D. Cochran, Phys. Rev. E 60, 1716 (1999)] the agreement between EMD and the modified hypernetted chain version of the theory is good. Although the high-shear-rate version of the NE potential improves the agreement between NEMD and EMD results (in comparison with the low-shear-rate version), its predictions are still unsatisfactory. With the high-shear-rate NE potential, EMD gives qualitatively correct predictions only for the shift of the position of the first maximum of the NE distribution function. The corresponding changes in the magnitude of the first maximum predicted by EMD have an opposite direction in comparison with those predicted by NEMD. It is concluded that the NE potential used is not very successful, and more accurate models for the potential are needed.

Kalyuzhnyi, Yu. V.; Cui, S. T.; Cochran, H. D.

2001-01-01

386

Distribution functions of a simple fluid under shear. II. High shear rates

International Nuclear Information System (INIS)

The distortion of structure of a simple, inverse 12 soft-sphere fluid undergoing plane Couette flow is studied by nonequilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) with a high-shear-rate version of the nonequilibrium (NE) potential obtained recently from the NE distribution function theory of Gan and Eu [Phys. Rev. A 45, 3670; 46, 6344 (1992)]. The theory suggests a NE potential under which the equilibrium structure of the fluid is that of a NE fluid, and also suggests a corresponding Ornstein-Zernike equation with its closure relations. As in the low-shear-rate case [Yu. V. Kalyuzhnyi, S. T. Cui, P. T. Cummings, and H. D. Cochran, Phys. Rev. E 60, 1716 (1999)] the agreement between EMD and the modified hypernetted chain version of the theory is good. Although the high-shear-rate version of the NE potential improves the agreement between NEMD and EMD results (in comparison with the low-shear-rate version), its predictions are still unsatisfactory. With the high-shear-rate NE potential, EMD gives qualitatively correct predictions only for the shift of the position of the first maximum of the NE distribution function. The corresponding changes in the magnitude of the first maximum predicted by EMD have an opposite direction in comparison with those predicted by NEMD. It is concluded that the NE potential used is not very successful, and more accurate models for the potential are needed

387

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

388

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

389

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

390

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

391

Electrical conductivity anisotropy in partially molten peridotite under shear deformation

The electrical conductivity of partially molten peridotite was measured during deformation in simple shear at 1 GPa in a DIA type apparatus with a uniaxial deformation facility. To detect development of electrical anisotropy during deformation of partially molten system, the electrical conductivity was measured simultaneously in two directions of three principal axes: parallel and normal to the shear direction on the shear plane, and perpendicular to the shear plane. Impedance spectroscopy measurement was performed at temperatures of 1523 K for Fe-bearing and 1723 K for Fe-free samples, respectively, in a frequency range from 0.1 Hz to 1 MHz. The electrical conductivity of partially molten peridotite parallel to shear direction increased to more than one order of magnitude higher than those normal to shear direction on the shear plane. This conductivity difference is consistent with the magnitude of the conductivity anisotropy observed in the oceanic asthenosphere near the Eastern Pacific Rise. On the other hand, conductivity perpendicular to the shear plane decreased gradually after the initiation of shear and finally achieved a value close to that of olivine. The magnitude and development style of conductivity anisotropy was almost the same for both Fe-bearing and Fe-free melt-bearing systems, and also independent of shear strain. However, such conductivity anisotropy was not developed in melt-free samples during shear deformation, suggesting that the conductivity anisotropy requires a presence of partial melting under shear stress. Microstructural observations of deformed partially molten peridotite samples demonstrated that conductivity anisotropy was attributed to the elongation of melt pockets parallel to the shear direction. Horizontal electrical conductivity anisotropy revealed by magnetotelluric surveys in the oceanic asthenosphere can be well explained by the realignment of partial melt induced by shear stress.

Zhang, Baohua; Yoshino, Takashi; Yamazaki, Daisuke; Manthilake, Geeth; Katsura, Tomoo

2014-11-01

392

Energy Technology Data Exchange (ETDEWEB)

The rheological behavior of cement slurries may be described in terms of a few elementary behaviors: - the rapid formation of a gel, at rest; - the collapse of this gel under a critical stress directly related to the strength of the interparticle forces; - the progressive destruction of the gel fragments under moderate shear rate, with an increasingly shear-thinning behavior as the elementary particles gets smaller; - the reconstruction, at high shear rate, of shear-resistant structures, probably cis chains cf grains at contact; - complete jamming possibly. We analyze the transition mechanisms from one step to the next one. We show how the addition of a dispersing agent favors shear-thickening at the expense of shear-thinning and how the control of the particle surface state and of interparticle friction restricts shear-thickening and the risk of jamming. (authors)

Lootens, D.; Lecolier, E. [Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France); Hebraud, P.; Van Damme, H. [l' Ecole Superieure de Physique et de Chimie Industrielles (ESPCI), Physico-Chimie des Polymeres et des Milieux Disperses (UMR CNRS 7615), 75 - Paris (France)

2004-07-01

393

Edge fracture occurs frequently in non-Newtonian fluids. A similar instability has often been reported at the free surface of fluids undergoing shear banding, and leads to expulsion of the sample. In this paper the distortion of the free surface of such a shear banding fluid is calculated by balancing the surface tension against the second normal stresses induced in the two shear bands, and simultaneously requiring a continuous and smooth meniscus. We show that wormlike micelles typically retain meniscus integrity when shear banding, but in some cases can lose integrity for a range of average applied shear rates during which one expects shear banding. This meniscus fracture would lead to ejection of the sample as the shear banding region is swept through. We further show that entangled polymer solutions are expected to display a propensity for fracture, because of their much larger second normal stresses. These calculations are consistent with available data in the literature. We also estimate the meniscus di...

Skorski, Stanislav

2011-01-01

394

International Nuclear Information System (INIS)

Analytical solution of transverse shear strain vibration of a tube caused by internal gaseous detonation near the second critical speed (shear group velocity) is not reported in the literature. It is performed based on a steady state model and first order shear deformation theories (model I and II) in this paper, and the results are verified through comparison with the finite element results reported in the literature. There are no known experimental ways of directly measuring dynamic transverse shear strain and only theoretical results and numerical data are available. The finite element method is very time consuming compared with the analytical solution. It is shown in this paper that the resonance phenomenon of the transverse shear strain vibration near the second critical speed can be predicted by steady state model and first order shear deformation theories. The first order shear deformation theory (model II) has a good agreement with finite element results in prediction of dynamic amplification factors and critical speeds.

395

Shear strength of irradiated insulation under combined shear/compression loading

International Nuclear Information System (INIS)

The shear strengths of irradiated insulation systems were measured at 4 K under combined shear and compression loads. Sandwich-type (316LN/bonded insulation/316LN) specimens were irradiated at 4 K and tested at 4 K after storage at room temperature. Some specimens were stored at room temperature; others, at 77 K. Insulation systems included diglycidylether of bisphenol-A and tetraglycidyl diaminodiphenyl methane epoxies and polyimide resins reinforced with S-2 glass. Some contained polyimide film or mica electrical barriers. All specimens were irradiated to a fast neutron fluence of 1.8 X 1022 n/m2. Insulation systems are compared on the basis of their irradiated and unirradiated shear strengths

396

Turbulence reduction and poloidal shear steepening in reversed shear plasmas on Tore Supra

International Nuclear Information System (INIS)

Infra-red light scattering is used to characterize turbulence during reversed shear scenario obtained by a fast current ramp-up on Tore Supra. The preformed hollow profile is frozen using ion cyclotron resonance frequency minority heating (ICRH). Turbulence intensity is recorded to dramatically decrease during the ramp-up and to recover smoothly as the discharge is ended. The core reduction, deduced from the light scattering measurements, is confirmed by the effective heat diffusivity behaviour. Turbulence reduction is shown to occur simultaneously with the steepening of the radial electric field shear, deduced from the frequency spectra, as well as with the negative or flat magnetic shear. In consequence, a confinement improvement of about 40% is achieved for about two seconds. (authors)

397

Property of Alfven eigenmode in JT-60U reversed shear and weak shear discharges

International Nuclear Information System (INIS)

This paper reports activity of Alfven eigenmode (AE) in the JT-60U reversed shear (RS) and weak shear (WS) plasmas. The AEs with a rapid frequency sweeping and then saturation of frequency as qmin decreases has been observed in low-?h RS discharges with Negative-ion-based NBI (NNBI) or ICRH. We introduce the new type of AE which we call reversed-shear-induced Alfven Eigenmode (RSAE) near qmin. This puzzling frequency change can be explained by considering the properties of RSAE and their transition to toroidal Alfven Eigenmodes (TAEs). We verify the existence of RSAEs and their transition to TAEs from magnetic fluctuations and measured q-profile in JT-60U plasmas. The AE amplitude is maximum during this transition, e.g., ?2.4 min min transition range of n = 1 AE to avoid substantial fast ion loss by large amplitude AEs in RS plasmas. (author)

398

Property of Alfven eigenmode in JT-60U reversed shear and weak shear discharges

International Nuclear Information System (INIS)

This paper reports activity of Alfven Eigenmode (AE) in the JT-60U reversed shear (RS) and weak shear (WS) plasmas. The AEs with a rapid frequency sweeping and then saturation of frequency as qmin decreases has been observed in low- ?h RS discharges with Negative-ion-based NBI (NNBI) or ICRH. We introduce the new type of AE which we call reversed-shear-induced Alfven Eigenmode (RSAE) near qmin. This puzzling frequency change can be explained by considering the properties of RSAE and their transition to toroidal Alfven Eigenmodes (TAEs). We verify the existence of RSAEs and their transition to TAEs from magnetic fluctuations and measured q-profile in JT-60U plasmas. The AE amplitude is maximum during this transition, e.g., ?2.4 min min transition range of n = 1 AE to avoid substantial fast ion loss by large amplitude AEs in RS plasmas. (author)

399

Shear Stress Measurements of Non-Spherical Particles in High Shear Rate Flows

The behavior of liquid-solid flows varies greatly depending on fluid viscosity; particle and liquid inertia; and collisions and near-collisions between particles. Shear stress measurements were made in a coaxial rheometer with a height to gap ratio (b/r0) of 11.7 and gap to outer radius ratio (h/b) of 0.166 that was specially designed to minimize the effects of secondary flows. Experiments were performed for a range of Reynolds numbers, solid fractions and ratio of particle to fluid densities. With neutrally buoyant particles, the dimensional shear stress exhibits a linear dependence on Reynolds number: the slope is monotonic but a non-linear function of the solid fraction. Though non-neutrally buoyant particles exhibit a similar linear dependence at higher Reynolds numbers, at lower values the shear stress exhibits a non-linear behavior in which the stress increases with decreasing Reynolds number due to particle settling.

Koos, Erin; Hunt, Melany L.; Brennen, Christopher E.

2008-07-01

400

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

401

New method of measuring multigrade oil-shear elasticity and viscosity at high shear rates

Energy Technology Data Exchange (ETDEWEB)

Recent journal-bearing oil-film thickness data (1) strongly suggest that, in order to develop minimum-viscosity multigrade oils for maximizing fuel economy, it is not enough to examine viscosity n alone, it is essential also to examine a certain kind of shear elasticity, of which one measure is the first normal stress difference N1 in shear flow. Within a group of isoviscous multigrade oils, N1 values can differ significantly; for 10W-40 and 15W-40 oils, an average of 75% of the minimum oil-film thickness can be attributed to N1.

Lodge, A.S.

1987-01-01

402

A new method of measuring multigrade oil shear elasticity and viscosity at high shear rates

Recent journal bearing oil film thickness data strongly suggest that, in order to develop minimum-viscosity multigrade oils for maximizing fuel economy, it is not enough to examine viscosity eta alone, it is essential also to examine a certain kind of shear elasticity, of which one measure is the first normal stress difference N1 in shear flow. Within a group of isoviscous multigrade oils, N1 values can differ significantly; for 10W-40 and 15W-40 oils, an average of 75 percent of the minimum oil film thickness can be attributed to N1.