Electric-Field Induced Morphological Transitions in Elastic Contact Instability of Soft Solid Films

A soft elastic film, when placed in adhesive proximity with a contactor in a crack-like geometry, spontaneously undergoes a surface instability to form finger patterns with a characteristic wavelength of approximately 4h, where h is the film thickness. We study the morphological evolution and control of this elastic contact instability under the influence of an external electric field. The distinct electric field induced morphological changes, leading to the formation of two-dimensional hexagonally arranged pillars, large-amplitude fingers, and straightening of contact edge, which are studied comprehensively. The conditions for the evolution of morphologically distinct patterns are governed by the film parameters, such as its shear modulus and thickness. A theoretical model and its stability analysis provide an approximate estimate of the critical voltage required for the onset of changes and its scaling with the film parameters (thickness and shear modulus). Further, three-dimensional simulations based on energy minimization are presented to provide important clues regarding the physics of pattern evolution on soft elastic interfaces.     

Optimized Mn and Bi co-doping in SnTe based thermoelectric material:A case of band engineering and density of states tuning

Tin telluride(SnTe)overwhelmingly continues to be studied owing to its promising thermoelectric prop-erties,tunable electronic structure,and its potential as an alternate to toxic lead telluride(PbTe)based materials.In this research,we engineer the electronic properties of SnTe by co-doping Mn and Bi below their individual solubility limit.The First principles density functional theory studies reveal that both Bi and Mn introduce resonance states,thereby increasing the density of states near the Fermi level leading to enhanced Seebeck coefficient.This unique combination of using two resonant dopants to introduce flatter bands is effective in achieving higher performance at lower temperatures manifesting into a large Seebeck value of～91 μV/K at room temperature in the present case.Both elements optimally co-doped results in a very high power factor value of～24.3 μW/cmK2 at 773 K when compared to other high performance SnTe based materials.A zT of～0.93 at 773 K is achieved by tuning the proportion of the co-dopants Mn and Bi in SnTe.The hardness value of pristine SnTe was also seen to increase after dop-ing.As a result,synergistic optimized doping proves to be a suitable means for obtaining thermoelectric materials of superior characteristics without the need for heavy doping.     

A quasi-conforming triangular laminated composite shell element based on a refined first-order theory

A quasi-conforming triangular laminated shell element based on a refined first-order shear deformation theory is presented. The Hu-Washizu variational principle, involving strain and displacement fields as variables, with stresses being considered as Lagrange multipliers, is used to develop the laminate composite shell element. Both strains and displacements are discretized in the element, while displacements alone are discretized at the boundary. The inter-element C ¹ continuity is satisfied a posteriori in a weak form. Due to the importance of rotations and shear deformation in the geometrically non-linear analyses of shells, 7 degrees of freedom per node are chosen, viz. three displacements, two first-derivatives in the in-plane directions of the out-of-plane displacement, and two transverse shear strains at each node. To consider the effect of transverse shear deformation on the global behavior of the laminated composite shell, the Reissner-Mindlin first-order theory, with shear correction factors of Chow and Whitney, is adopted. The transverse shear stresses are obtained through the integration of the 3-D equilibrium equations; and the warping induced by transverse shear is considered in the calculation of the in-plane stresses to improve their accuracy. Numerical examples show that the element has good convergence properties and leads to highly accurate stresses.     

Guest Editors' Introduction: Dynamic Information Dissemination

Dissemination and delivery of rapidly changing information to large user communities remains a challenge on the Web. Consequently, we need techniques to disseminate such data as efficiently as possible. To this end, researchers are focusing on new approaches to building efficient, resilient, and scalable content-distribution networks.     

Sharc: managing CPU and network bandwidth in shared clusters

We argue the need for effective resource management mechanisms for sharing resources in commodity clusters. To address this issue, we present the design of Sharc-a system that enables resource sharing among applications in such clusters. Sharc depends on single node resource management mechanisms such as reservations or shares, and extends the benefits of such mechanisms to clustered environments. We present techniques for managing two important resources-CPU and network interface bandwidth-on a cluster-wide basis. Our techniques allow Sharc to 1) support reservation of CPU and network interface bandwidth for distributed applications, 2) dynamically allocate resources based on past usage, and 3) provide performance isolation to applications. Our experimental evaluation has shown that Sharc can scale to 256 node clusters running 100,000 applications. These results demonstrate that Sharc can be an effective approach for sharing resources among competing applications in moderate size clusters.     

Method to determine the optical properties of turbid media

A novel method to determine the optical properties, namely, absorption coefficient, scattering coefficient, and anisotropy factor of turbid solutions, single constituent or multiconstituent, is presented. Turbid solutions of milk, ink, and a mixture of both were illuminated by a laser beam and measurements were carried out in scattered light. Experimental results were matched to the corresponding results of Monte Carlo simulation to obtain the optical properties of the turbid media.     

Categorizing facial expressions: a comparison of computational models

Recognizing expressions is a key part of human social interaction, and processing of facial expression information is largely automatic for humans, but it is a non-trivial task for a computational system. The purpose of this work is to develop computational models capable of differentiating between a range of human facial expressions. Raw face images are examples of high-dimensional data, so here we use two dimensionality reduction techniques: principal component analysis and curvilinear component analysis. We also preprocess the images with a bank of Gabor filters, so that important features in the face images may be identified. Subsequently, the faces are classified using a support vector machine. We show that it is possible to differentiate faces with a prototypical expression from the neutral expression. Moreover, we can achieve this with data that has been massively reduced in size: in the best case the original images are reduced to just 5 components. We also investigate the effect size on face images, a concept which has not been reported previously on faces. This enables us to identify those areas of the face that are involved in the production of a facial expression.     

Numerical investigation of influence of number of stent cells and type of link on expansion and haemodynamic behaviour of balloon-expandable coronary stent

Coronary stents are tubular, mesh-like structures used to force open clogged artery. Mounted on an inflatable balloon, stent compresses calcified plaque inside atherosclerotic artery with an inflating device, which transfers the load through the compliant balloon, thus maintaining the patency of lumen. One of the contributors for success of angioplasty is type of stents, which mainly differs in its geometrical design. A clinician recommends a stent based on comparative advantages. An ideal stent should be flexible to manoeuver through tortuous artery, easy to expand, provide good scaffolding to the vessel, have less radial recoil and foreshortening, possess uniformity in expansion and induce minimum alteration in physiological blood flow dynamics. In a stent these parameters are in competition with each other and are optimized by trade-offs. The present work tries to sequentially investigate the effect of number of stent cells and type of links on the expansion and haemodynamics behaviour through computational analysis based on finite element and finite volume techniques. The study compares performance within same classes of designs rather than comparing the designs that are completely different form each other. Results show that more number of stent cells in longitudinal direction considerably decrease the radial recoil, but increase the foreshortening effect. Restenosis-prone zones are localized around the stent struts and are predominant during end of systolic phase of cardiac cycle. Shorter links are preferred for better recoil and favourable distribution of wall shear stress while longer links are preferred for favourable foreshortening.     

Cataclysm: Scalable overload policing for internet applications

In this paper we present the Cataclysm server platform for handling extreme overloads in hosted Internet applications. The primary contribution of our work is to develop a low overhead, highly scalable admission control technique for Internet applications. Cataclysm provides several desirable features, such as guarantees on response time by conducting accurate size-based admission control, revenue maximization at multiple time-scales via preferential admission of important requests and dynamic capacity provisioning, and the ability to be operational even under extreme overloads. Cataclysm can transparently trade-off the accuracy of its decision making with the intensity of the workload allowing it to handle incoming rates of several tens of thousands of requests/second. We implement a prototype Cataclysm hosting platform on a Linux cluster and demonstrate the benefits of our integrated approach using a variety of workloads.