Use of Material Interfaces in DEM to Simulate Soil Fracture Propagation in Mode I Cracking

Mode I fracture is common in geomechanics in desiccation cracking, hydraulic fracture, and pressuremeter testing. The cohesive crack model has been used extensively and successfully in numerical modeling of such fracture in concrete and steel but has not been applied in modeling of soil fracture to the same extent. It is argued that the cohesive crack model may be more appropriate than linear elastic fracture mechanics (LEFM) for soils because it takes into account finite tensile strength and any likely plasticity during fracture. With special reference to the Universal Distinct Element Code (UDEC) computer program, a methodology of using interfaces in the distinct element method (DEM) of analysis to model fracture has been validated herein, and this approach is considered to be useful in geomechanical modeling applications. The methodology is based on the cohesive crack approach and shows how softening laws could be back-calculated from load-displacement curves of test specimens. It has been validated using three geometries: a tension test with a rectangular cross section, a notched three-point bend beam, and a compact tension test. Approximate softening laws for St. Albans clay from Canada are proposed.     

An unsteady MHD flow of a second-grade fluid passing through a porous medium in the presence of radiation absorption exhibits Hall and ion slip effects

In the presence of radiation absorption, we analyzed the effects of Hall and ion slip effects on an unsteady laminar magnetohydrodynamics convective rotating flow of heat-producing or absorbing second-grade fluid across an inclined moving permeable surface in the presence of chemical reaction and radiation absorption. Using the perturbation method, the nondimensional equations for the governing flow are solved to the most excellent conceivable investigative answer. The effects of various factors on velocity, temperature, and concentration are visually and explored in depth. Shear stresses, Nusselt number, and Sherwood number are calculated analytically, rendered computationally in a tabular style, and discussed concerning the essential characteristics for engineering inquiry. It is inferred that an increase in radiation absorption, Hall, and ion slip parameters across the fluid area leads to a rise in the resulting velocity. The thermal and solutal buoyancy forces contribute to the resultant velocity, constantly growing to a very high level. The rotation parameter is used to reduce skin friction, while the Hall and ion slip effects enhance it. The rate of mass transfer increases when the chemical reaction parameter is raised.     

Thermoplastic vulcanizate nanocomposites based on thermoplastic polyurethane and millable polyurethane blends reinforced with organoclay prepared by melt intercalation technique: Optimization of processing parameters via statistical methods

Statistical approaches including Taguchi design of experiments (DOE), analysis of variance (ANOVA), and multiple linear regression analysis were employed to determine optimum processing conditions for successful preparation of a thermoplastic vulcanizate nanocomposite (TPVNC) based on thermoplastic polyurethane (TPU)/millable polyurethane (MPU) blend reinforced with an organoclay (TPU/MPU/organoclay = 50/50/3 wt/wt/wt) using an internal mixer. Total numbers of mixing layouts were designed by the application of Taguchi's orthogonal array (OA) methodology based on three parameters and three levels in the L₉ selector matrix model. Mechanical properties of all runs were measured and fitted into the statistical software to determine signal to noise (S/N) ratio. Ranks of the parameters were determined based on the delta statistics of the larger is better case of the S/N ratio. The ANOVA parameters were analyzed and percentage contribution of each factor, along with the correlation coefficient of each variable, was measured. The multiple linear regression models for each property were correlated with the parameters through mathematical equations. Fourier transform infrared (FTIR) analysis was performed to examine any interfacial interactions between polyurethane matrix and organoclay. X‐ray diffraction (XRD) analysis and field emission transmission electron microscope (FETEM) were employed to analyze the dispersion of organoclays in the polymer matrix. Field emission scanning electron microscope (FESEM) was employed to observe cryo‐fractured morphology. Dynamic mechanical analysis (DMA) and dynamic shear rheometer (DSR) were used to investigate dynamic mechanical properties and rheological properties of the trials, respectively. Based on all of these characterizations, an optimum processing condition was determined. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The Marine Polyketide Myriaporone 3/4 Stalls Translation by Targeting the Elongation Phase

Myriaporone 3/4, a cytotoxic polyketide, has been reported as an inhibitor of eukaryotic protein synthesis. However, the mechanism by which it inhibits translation was unknown. Here we show that myriaporone 3/4 stalls protein synthesis in the elongation phase by inducing phosphorylation of eukaryotic elongation factor 2. The phosphorylation results from direct binding of myriaporone 3/4 to eukaryotic elongation factor 2 kinase. Our study also shows that myriaporone 3/4 in the nanomolar range inhibits in vitro tube formation by endothelial cells without being cytotoxic. In general, myriaporone 3/4 was at least 300 times less toxic to primary cells than to tumor cells.     

Organization of copper nanoclusters in Langmuir-Blodgett films

Stable nanoclusters of Cu were synthesized using Langmuir-Blodgett films of octadecylsuccinic acid (ODSA) as template. The Langmuir-Blodgett films of ODSA formed from subphase containing copper ions were first subjected to sulphidation (S) using sodium sulphide and then hydrogenated (H) using hydrogen gas. Diffuse reflectance UV-visible spectroscopy (DIR-UV-vis), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) used to characterize these films indicated the formation of Cu(0) metallic clusters ranging in size from 3 ∼ 10 nm.     

Managing QoS in Multimedia Services

We present a case study of multimedia servicedelivery in the World Wide Web environment. Our systemis founded on the notion of end-to-endQuality-of-Service (QoS) management. We outline our viewof an integrated management frame and explain how ourQoS management architecture fits into this framework. Wethen describe our object-oriented multimedia deliverysystem based on CORBA and Java. We discuss some issues of stream delivery and managementwith reference to our own experiences.     

Aluminum Coatings for Steel

Aluminum coated steel possesses excellent oxidation and corrosion resistance in sulfur and marine: environments and can substitute for expensive alloy of steels. Hot dip aluminizing (HAD) and pack cementation calorizing (CAL) are dealt with in detail. IN HDA coats, some alloying action takes place, when the substrate is dipped in molten Al at 973 K for 1-2 minutes. The coat consists of an outer pure Al layer, followed by a hard intermetallic layer consisting of FeAl₃ and Fe₂Al₅, forming a serrated interface with the base. Isothermal holding of such samples at 773-933 K for 10 minutes leads to further diffusion and phase changes. This improves resistance to thermal shock and bending. In CAL coats, the process parameters (1173-1223 K/2-4 h and pack composition), were optimized, resulting in appreciable alloying. The surface layer consists of Fe3Al and FeAl, which is comparable to the inner alloy layer of HDA coats. The structures/ property correlation is carried out for both coatings and the results compared.     

Differential transform method for solving the linear and nonlinear Klein-Gordon equation

In this paper, we implemented relatively new, exact series method of solution known as the differential transform method for solving linear and nonlinear Klein-Gordon equation. Several illustrative examples are given to demonstrate the effectiveness of the present method.     

Multicasting with selective delivery: a SafetyNet for vertical handoffs

In the future, mobility support will require handling roaming in heterogeneous access networks. In order to enable seamless roaming it is necessary to minimize the impact of the vertical handoffs. Localized mobility management schemes such as Fast Handovers for Mobile IPv6 (FMIPv6) and Hierarchical Mobile IPv6 do not provide sufficient handoff performance, since they have been designed for horizontal handoffs. In this paper, we propose the SafetyNet protocol, which allows a Mobile Node to perform seamless vertical handoffs. Further, we propose the SafetyNet handoff timing algorithm, to enable a Mobile Node to delay or even completely avoid upward vertical handoffs. We implement the SafetyNet protocol and compare its performance with the FMIPv6 protocol in our wireless test bed and analyze the results. The experimental results indicate that the proposed SafetyNet protocol can provide an improvement of up to 95% for TCP performance in vertical handoffs, when compared with FMIPv6 and an improvement of 64% over FMIPv6 with bicasting. We use numerical analysis of the protocol to show that its over the air signaling and data transmission overhead is comparable to FMIPv6 and significantly smaller than that of FMIPv6 with bicasting.