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排序方式: 共有61条查询结果,搜索用时 15 毫秒
1.
Vince J. van Joolen Beny Neta Dan Givoli 《International journal for numerical methods in engineering》2005,63(7):1041-1068
Recently developed non‐reflecting boundary conditions are applied for exterior time‐dependent wave problems in unbounded domains. The linear time‐dependent wave equation, with or without a dispersive term, is considered in an infinite domain. The infinite domain is truncated via an artificial boundary ??, and a high‐order non‐reflecting boundary condition (NRBC) is imposed on ??. Then the problem is solved numerically in the finite domain bounded by ??. The new boundary scheme is based on a reformulation of the sequence of NRBCs proposed by Higdon. We consider here two reformulations: one that involves high‐order derivatives with a special discretization scheme, and another that does not involve any high derivatives beyond second order. The latter formulation is made possible by introducing special auxiliary variables on ??. In both formulations the new NRBCs can easily be used up to any desired order. They can be incorporated in a finite element or a finite difference scheme; in the present paper the latter is used. In contrast to previous papers using similar formulations, here the method is applied to a fully exterior two‐dimensional problem, with a rectangular boundary. Numerical examples in infinite domains are used to demonstrate the performance and advantages of the new method. In the auxiliary‐variable formulation long‐time corner instability is observed, that requires special treatment of the corners (not addressed in this paper). No such difficulties arise in the high‐derivative formulation. Published in 2005 by John Wiley & Sons, Ltd. 相似文献
2.
Corrugator supercilii muscle activity is considered an objective measure of valence because it increases in response to negatively valenced facial expressions (angry) and decreases to positive expressions (happy). The authors sought to determine if corrugator activity could be used as an objective measure of positivity-negativity bias. The authors recorded corrugator responses as participants rated angry, happy, and surprised faces as “positive” or “negative.” The critical measure of bias was the percentage of positive versus negative ratings assigned to surprised faces by each participant. Reaction times for surprise expressions were longer than for happy and angry expressions, consistent with their ambiguous valence. Participants who tended to rate surprised faces as negative showed increased corrugator activity to surprised faces, whereas those who tended to rate surprise as positive showed decreased activity. Critically, corrugator responses reflected the participants’ bias (i.e., their tendency to rate surprise as positive or negative). These data show that surprised faces constitute a useful tool for assessing individual differences in positivity-negativity bias, and that corrugator activity can objectively reflect this bias. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
This paper analyzes the stability and accuracy of various finite element approximations to the linearized two-dimensional advection equation. Four triangular elements with linear basis functions are included along with a rectangular element with bilinear basis functions. In addition, second-and fourth-order finite difference schemes are examined for comparison. Time is discretized with the leapfrog method. The criss-cross triangle formulation is found to be unstable. The best schemes are the isosceles triangles with linear functions and the rectangles with bilinear basis functions. 相似文献
4.
Nair do Amaral Sampaio Neta José Cleiton Sousa dos Santos Soraya de Oliveira Sancho Sueli Rodrigues Luciana Rocha Barros Gonçalves Ligia R. Rodrigues José A. Teixeira 《Food Hydrocolloids》2012
Sugar esters are compounds with surfactant properties (biosurfactants), i.e., capable of reducing the surface tension and promote the emulsification of immiscible liquids. On the other hand, as with all emulsions, coconut milk is not physically stable and is prone to phase separation. Therefore, the aim of this work was to evaluate the synthesis of fructose, sucrose and lactose esters from the corresponding sugars using Candida antarctica type B lipase immobilized in two different supports, namely acrylic resin and chitosan, and evaluate its application in the stabilization of coconut milk emulsions. The enzyme immobilized on chitosan showed the highest yield of lactose ester production (84.1%). Additionally, the production of fructose ester was found to be higher for the enzyme immobilized on the acrylic resin support (74.3%) as compared with the one immobilized on chitosan (70.1%). The same trend was observed for the sucrose ester, although with lower percentage yields. Sugar esters were then added to samples of fresh coconut milk and characterized according to their surface tension, emulsification index and particle size distribution. Although the microscopic analysis showed similar results for all sugar esters, results indicated lactose ester as the best biosurfactant, with a surface tension of 38.0 N/m and an emulsification index of 54.1%, when used in a ratio of 1:10 (biosurfactant:coconut milk, v/v) for 48 h experiments. 相似文献
5.
Poster DL Chaychian M Neta P Huie RE Silverman J Al-Sheikhly M 《Environmental science & technology》2003,37(17):3808-3815
Radiolytic (electron beam) and photolytic (ultraviolet, UV) dechlorination of polychlorinated biphenyls (PCBs) in a marine sediment are described. Samples of a PCB-laden marine sediment, Standard Reference Material (SRM) 1944, NewYork/New Jersey Waterway Sediment, have been mixed with aqueous alcohol solutions and irradiated with an electron beam or photolyzed. Additives, such as alcohol, enhance the radiolytic yield and PCB dechlorination. In the electron beam irradiated samples, the concentrations of 29 PCB congeners decrease with irradiation dose. At the highest dose (500 kGy), the total concentration of PCBs is decreased by 83%. Photolysis leads to little dechlorination, but photolysis with added triethylamine leads to dechlorination (about 60%). It is likely that photolysis under optimal conditions (other additives, exposure time) may be as effective as electron beam radiolysis for the dechlorination of PCBs in sediment. 相似文献
6.
Yael Abarbanel-Vinov Neta Aizenbud-Reshef Ilan Beer Cindy Eisner Daniel Geist Tamir Heyman Iris Reuveni Eran Rippel Irit Shitsevalov Yaron Wolfsthal Tali Yatzkar-Haham 《Formal Methods in System Design》2001,19(1):35-44
We examine IBM's exploitation of formal verification using RuleBase—a formal verification tool developed by the IBM Haifa Research Laboratory. The goal of the paper is methodological. We identify an integrated methodology for the deployment of formal verification which involves three complementary modes: architectural verification, block-level verification, and design exploration. 相似文献
7.
Dechlorination of polychlorinated biphenyls in industrial transformer oil by radiolytic and photolytic methods 总被引:3,自引:0,他引:3
Jones CG Silverman J Al-Sheikhly M Neta P Poster DL 《Environmental science & technology》2003,37(24):5773-5777
Used electrical transformer oils containing low or high concentrations of polychlorinated biphenyls (PCBs) were treated using electron, gamma, and ultraviolet radiation, and the conditions for complete dechlorination were developed. Dechlorination was determined by analysis of the inorganic chloride formed and the concentrations of remaining PCBs. Transformer oil containing approximately 95 microg g(-1) PCB (approximately 3.5 mmol L(-1) Cl) is completely dechlorinated by irradiation with 600 kGy after the addition of 10% triethylamine (TEA). Transformer oil containing >800,000 microg g(-1) PCB (17.7 mol L(-1) Cl) requires an additional solvent to prevent solidification. When this oil is diluted with 2-propanol (2-PrOH) and TEA (v/v/v, 1/79/20), complete dechlorination is achieved with a dose of 2500 kGy. Ultraviolet photolysis of the same oil/2-PrOH/TEA solutions led to 90% dechlorination after exposure for 120 h in our experimental setup. Such yields were obtained by radiolysis with a dose of 2000 kGy (300 h in our Gammacell). Replacing TEA with KOH in 2-PrOH solutions greatly increases the yield of dechlorination in both the radiolytic and the photolytic experiments, demonstrating that a chain reaction plays a role in both of these treatment methods and suggesting that both methods deserve further consideration for large-scale application. 相似文献
8.
The chemistry and physiology of sour taste--a review 总被引:1,自引:0,他引:1
Ramos Da Conceicao Neta ER Johanningsmeier SD McFeeters RF 《Journal of food science》2007,72(2):R33-R38
ABSTRACT: Sour taste is the key element in the flavor profile of food acidulants. Understanding the chemistry and physiology of sour taste is critical for efficient control of flavor in the formulation of acid and acidified foods. After a brief introduction to the main applications of food acidulants, several chemical parameters associated with sour taste are discussed. Special emphasis is given to hydrogen ions, protonated (undissociated) acid species, titratable acidity, anions, molar concentration, and physical and chemical properties of organic acids. This article also presents an overview of the physiology of sour taste and proposed theories for the transduction mechanisms for sour taste. The physiology of sour taste perception remains controversial and significant diversity exists among species with regard to cellular schemes used for detection of stimuli. The variety of mechanisms proposed, even within individual species, highlights the complexity of elucidating sour taste transduction. However, recent evidence suggests that at least one specific sour taste receptor protein has been identified. 相似文献
9.
Mikulincer Mario; Gillath Omri; Halevy Vered; Avihou Neta; Avidan Shelly; Eshkoli Nitzan 《Canadian Metallurgical Quarterly》2001,81(6):1205
Five studies examined the effects of chronic and contextual activation of attachment security on reactions to others' needs. The sense of attachment security was contextually primed by asking participants to recollect personal memories, read a story, or look at a picture of supportive others or by subliminally exposing them to proximity-related words. This condition was compared against the priming of neutral themes, positive affect, or attachment-insecurity schemas. Then reports of empathy and personal distress or the accessibility of empathy and personal-distress memories were assessed. Attachment-security priming strengthened empathic reactions and inhibited personal distress. Self-reports of attachment anxiety and avoidance were inversely related to empathy, and attachment anxiety was positively related to personal distress. The discussion emphasizes the relevance of attachment theory for explaining reactions to others' needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
In this note, we obtain a method of order at least four to solve a singular system of nonlinear algebraic equations. This is achieved by enlarging the system to a higher dimensional one whose solution is isolated. For the larger system we use a method developed by B. Neta. 相似文献