Inverse Identification of Thermal Properties of Charring Ablators

The modified Levenberg-Marquardt method is used for simultaneous estimation of decomposition kinetic coefficients and temperature-dependent thermophysical properties of charring ablators with a moving boundary over a wide temperature range. No prior information is used for the functional forms of the unknown thermal conductivity and specific heat. The procedure used differs from the traditional one in that it does not require prescribed time-dependent surface heat flux, recession rate, and pyrolysis gas mass flow rate. These time-dependent quantities may recover during an iterative procedure. The measured temperatures are simulated numerically by the Charring material ablation code, which accounts for unsteady ablation. The method can determine unknown parameters in an efficient manner with reasonable accuracy, without exact advance knowledge about the net surface heat flux, surface recession, and gas flux through the material.     

Surface and Subsurface Deformation of Wear-Resistant Steels Exposed to Impact Wear

The impact wear resistance of four different wear-resistant steel grades was investigated using different impact bodies. Post-test evaluation of the impact tested samples was performed by different techniques including 3D surface profilometry, microhardness indentation, optical and scanning electron microscopy, and energy dispersive x-ray spectroscopy. The tribological response of the steel plates during the impact is strongly dependent on the properties of the impacting body. The subsurface deformation was found to increase with increasing impact energy and/or impact velocity and decreasing steel hardness. On a microscopic scale, a number of interesting mechanisms were revealed within the deformed impact sites. Besides an overall plastic deformation, localized deformation resulting in narrow adiabatic shear bands with an ultra-fine microstructure was observed. Within these shear bands, showing intense shearing strain, nucleation of microvoids was frequently observed. Growth and linkage of these voids lead in crack formation along the shear bands and eventually flake-like wear fragments are detached when these cracks reach the surface.     

Facile synthesis of extremely biocompatible double‐network hydrogels based on chitosan and poly(vinyl alcohol) with enhanced mechanical properties

An easy and ecofriendly method for designing double‐network (DN) hydrogels based on chitosan and poly(vinyl alcohol) (PVA) with high mechanical performance is described. When covalent bonds in the networks are used as crosslinking agents in the achievement of a higher mechanical strength, the irreversible deformation of these hydrogels after a large force is applied is still one of the most important obstacles. To overcome this problem, we used physical crosslinking for both networks. The mechanical strength, surface morphology, and cytotoxicity of the films were studied by tensile testing, scanning electron microscopy analysis, and an MTT assay. The synthesized chitosan–PVA DN hydrogels showed a large improvement in the tensile strength to 11.52 MPa with an elongation of 265.6%. The surface morphologies of the films demonstrated the effective interactions between the two networks and a suitable porosity. Also, because of the use of a natural polymer and honey as a plasticizer, the cell culture indicated that the synthesized DN hydrogels had good biocompatibility (with 327.49 ± 11.22% viability) and could be used as capable biomaterials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45752.     

Detection and resolution of feature interactions in IP multimedia subsystem

The IP Multimedia Subsystem (IMS) enables the delivery of multimedia services through different access networks. 3GPP adopted the Session Initiation Protocol (SIP) as the IMS signalling protocol. However, IMS interaction with these services faces the ‘feature interaction’ problem encountered in traditional telephony networks. This problem occurs as features invoked during a session behave correctly when processed separately from each other, but not when running together. Although much research work has explored managing feature interactions, applying these solutions in IMS remains challenging and further investigation is needed. This paper aims to analyze the feature interaction issue in IMS and to propose a new solution. We defined a SIP‐based algorithm and the associated mechanisms to enhance IMS service invocation. This algorithm is the core of the Service Broker, a new functional entity in charge of managing feature interaction. We validated our proposal through a performance evaluation and prototyped the Service Broker on an open source IMS platform. Copyright © 2008 John Wiley & Sons, Ltd.     

Green synthesis of stable silver nanoparticles by the main reduction component of green tea (Camellia sinensis L.)

Recently the use of medicinal plants potential in the production of nanoparticles has received serious attention. Here, the main component of Camellia sinensis L. (green tea) extract was detected by spectroscopy and the optimal conditions were determined for their performance in green synthesis of silver nanoparticles at room temperature. Epigallocatechin gallate was identified as the dominant component in the extract as determined by spectroscopy, and it was established that its oxidation was a function of the solution pH. Transmission electron microscopy, dynamic light scattering, and visible absorption spectroscopy (UV‐Vis) confirmed the reduction in silver ions to silver nanoparticles (Ag NPs). Controlling over Ag NPs shape and narrow size distribution was achieved with 10 ml green tea leaf extract solution and in different reaction pH. Spherical colloidal Ag NPs with well‐defined hydrodynamic diameters (with average hydrodynamic size of 27.9–50.2 nm) were produced. Silver nitrate concentrations used in this study were lower than that of reported in similar works, and synthesis efficiency was also higher. Nanoparticles were perfectly spherical and their uniformity, compared to similar studies, was much higher. These NPs showed higher degree of stability and were aqueously stable for >10 months in dark glasses at 4°C.Inspec keywords: hydrodynamics, nanoparticles, particle size, pH, visible spectra, ultraviolet spectra, reduction (chemical), transmission electron microscopy, silver, microorganisms, nanofabrication, colloids, biomedical materials, nanomedicine, drug delivery systemsOther keywords: transmission electron microscopy, dynamic light scattering, visible absorption spectroscopy, silver ions, narrow size distribution, silver nitrate concentrations, green synthesis, medicinal plants, solution pH, green tea leaf, hydrodynamic size, silver nanoparticles, Camellia sinensis L, drug delivery, reduction component, epigallocatechin gallate, UV‐visible spectra, hydrodynamic diameters, spherical colloidal Ag NPs, temperature 4.0 degC, Ag     

Iron chelation by digests of insoluble chicken muscle protein: the role of histidine residues

The role of histidine residues in the chelation of iron at neutral pH by peptides from chicken muscle was investigated to see if it could contribute to the effect of muscle tissue on iron absorption. When ferric iron was chelated by L ‐histidine at pH 6, the ratio of iron chelated to loss of reactive histidine was 1:1. Chelation of iron by soluble peptides in a digest of insoluble chicken muscle protein was accompanied by a small loss of reactive histidine (4–7%) in the peptides. When peptides were modified with diethylpyrocarbonate, increasing loss of histidine led to a progressive decrease in iron chelation. However, even 89% loss of histidine only reduced iron chelation by 30%. It was concluded that histidyl residues do contribute to iron chelation and therefore could by involved in the promotion of iron absorption by muscle tissue. However, other amino acid residues are likely to be involved. © 2000 Society of Chemical Industry     

The dirty dozen: Twelve failures of the Hurricane Katrina response and how psychology can help.

This comprehensive analysis addresses the United States' alarming lack of preparedness to respond effectively to a massive disaster as evidenced by Hurricane Katrina. First, a timeline of problematic response events during and after Hurricane Katrina orients readers to some of the specific problems encountered at different levels of government. Second, a list of the "Dirty Dozen"--12 major failures that have occurred in prior disasters, which also contributed to inadequate response during and after Hurricane Katrina--is presented. Third, this article encourages expanding psychology's role beyond the treatment of trauma to encompass disaster planning and mitigation efforts from a broader public health perspective. Finally, areas for important interdisciplinary research in human behavior that will influence our nation's overall preparedness for future catastrophes are identified, and ways psychologists can become personally involved beyond treating casualties are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)