Effect of artificial perspiration and cleaning chemicals on the mechanical and chemical properties of ballistic materials

During routine field use of soft body armor, the ballistic panels become saturated with perspiration. This condition motivates the user to clean and/or deodorize the armor, and anecdotal evidence is given for various methods used to accomplish this. Although the cleaning/deodorization is usually performed on the armor liners and coverings, there is concern that the chemicals could seep into the ballistic panels and damage the fibers. The purpose of this study was to assess the effect of artificial perspiration and cleaning chemicals on the mechanical and chemical properties of aramid, poly(p‐phenylene benzobisoxazole), and ultrahigh‐molecular‐weight polyethylene yarns after controlled cycles of exposure to artificial perspiration and dilute solutions of common cleaning chemicals. It was observed that the effect of the artificial perspiration on the properties of all of the materials tested was the same as that of water alone. Of all of the cleaning chemicals used, only chlorine bleach had a detrimental effect on the yarn properties. All other cleaning chemicals had the same effect as water alone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sintering of glass-added BaZn1/3Nb2/3O3 ceramics

The complex perovskite oxide Ba(Zn_1/3Nb_2/3)O₃ (BZN) has been studied for its attractive dielectric properties which place this material interesting for applications as multilayer ceramics capacitors or hyperfrequency resonators. This material is sinterable at low temperature with combined glass phase–lithium salt additions, and exhibits, at 1 MHz very low dielectric losses combined with relatively high dielectric constant and a good stability of this later versus temperature. The 2 wt.% of ZnO–SiO₂–B₂O₃ glass phase and 1 wt.% of LiF-added BZN sample sintered at 900 °C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant ?_r of 39, low dielectrics losses (tan(δ) < 10⁻³) and a temperature coefficient of permittivity τ_? of 45 ppm/°C⁻¹. The 2 wt.% ZnO–SiO₂–B₂O₃ glass phase and 1 wt.% of B₂O₃-added BZN sintered at 930 °C exhibits also attractive dielectric properties (?_r = 38, tan(δ) < 10⁻³) and it is more interesting in terms of temperature coefficient of the permittivity (τ_? = −5 ppm/°C). Their good dielectric properties and their compatibility with Ag electrodes, make these ceramics suitable for L.T.C.C applications.     

Characterizing the shape of anatomical structures with Poisson's equation

Poisson's equation, a fundamental partial differential equation in classical physics, has a number of properties that are interesting for shape analysis. In particular, the equipotential sets of the solution graph become smoother as the potential increases. We use the displacement map, the length of the streamlines formed by the gradient field of the solution, to measure the "complexity" (or smoothness) of the equipotential sets, and study its behavior as the potential increases. We believe that this function complexity = f(potential), which we call the shape characteristic, is a very natural way to express shape. Robust algorithms are presented to compute the solution to Poisson's equation, the displacement map, and the shape characteristic. We first illustrate our technique on two-dimensional synthetic examples and natural silhouettes. We then perform two shape analysis studies on three-dimensional neuroanatomical data extracted from magnetic resonance (MR) images of the brain. In the first study, we investigate changes in the caudate nucleus in Schizotypal Personality Disorder (SPD) and confirm previously published results on this structure. In the second study, we present a data set of caudate nuclei of premature infants with asymmetric white matter injury. Our method shows structural shape differences that volumetric measurements were unable to detect.     

99Tc- and 239Pu-Doped Glass Leaching Experiments: Residual Alteration Rate and Radionuclide Behavior

The long-term behavior of high-level nuclear glass subjected to alpha/beta radiation by long-life radionuclides must be investigated with respect to geological disposal. This study focuses on the effects of alpha and beta radiations on the chemical reactivity of R7T7 glass with pure water, mainly on the residual alteration rate regime. Glass specimens doped with 0.85 wt% ²³⁹PuO₂ (α emitter) and 0.24 wt% ⁹⁹TcO₂ (β emitter) that simulate alpha and beta dose rate corresponding to long-term disposal conditions are leached under static conditions in argon atmosphere at 90°C, in initially pure water and at a high surface-area-to-volume ratio (S/V = 20/cm). The alteration rate is monitored by the release of glass alteration tracer elements (B, Na, and Li). Radiation effects on the leached glass and its gel network are characterized by SEM and TEM analyses. Plutonium and technetium releases are also measured by radiometry, and their chemical oxidation state is assessed by measuring the pH and reduction–oxidation potential of the leachates. The results do not highlight any significant effect of alpha/beta radiation on the residual alteration of these doped glasses. These observations are consistent with solid characterizations, which show that a protective layer can be formed under such irradiation fields. Under our experimental conditions (Eh~380 mV/SHE, pH_90°C = 8–8.6), very low concentrations of soluble plutonium are measured in the leachate, indicating strong plutonium retention, whereas technetium performs as a soluble element and is not retained in the altered layer.     

黄原胶用于大体积空腔容器静态泡沫去污初探

黄原胶作为一种用途很广的生物增稠剂和发泡剂,具有抗剪切性和耐酸、耐碱和抗氧化等特点,这些特点恰好满足静态泡沫去污对增稠剂的要求。本文测量并分析了碱性体系中(Na2CO3体系)影响发泡液粘度的几种因素(搅拌速度、黄原胶浓度、碳酸钠浓度及温度);以及酸性体系中(HNO3+H3PO4体系)黄原胶浓度和发泡液放置时间对泡沫稳定性的影响;比较分析了铝片在酸性发泡液及其生成泡沫中的失重情况。试验结果表明黄原胶无论是在碱性溶液还是在酸性溶液中均具有一定的稳定性,能够满足泡沫去污的要求;其稳定性随时间推移而降低的特性有利于泡沫去污产生的二次废液的处理。黄原胶酸性发泡液能够产生稳定的泡沫,对铝片具有良好的腐蚀效果。在本实验中,当铝片处于距底端4cm高度位置时,腐蚀速率达到1.0 mg/(cm2.h)。因此,黄原胶有望作为放射性污染大体积空腔容器静态泡沫去污的增稠剂。     

Complex permittivity characterization of benzocyclobutene for terahertz applications

High-quality polymers such as the benzocyclobutene polymer (BCB) provide interesting dielectric feature for terahertz applications. Already used in silicon integrated circuit technologies, this material could become one of the most promising candidates for the realization of future THz waveguides and interconnections on a silicon substrate but also after active devices process on the top of any other technology (GaAs, InP, GaN…). A frequency-dependent complex permittivity of spin-coated thick layers of this low-k dielectric is obtained from transmittance spectra measured with Fourier transform spectroscopy in the frequency range of 0.5-5.4 THz. The dielectric constant and the loss tangent are discussed according to curing conditions of the photosensitive resin used. A low loss tangent value of 7 − 9 × 10^-3 at 1 THz is obtained with polymerisation in oxygen-free atmosphere. An incomplete curing and a high dose UV exposure have a weak impact on losses. These results associated with the high compatibility of this polymer with silicon and metals make BCB layers well suited for the design of microelectronic THz devices and circuits.     

Charge compensation mechanisms in Li-substituted high-entropy oxides and influence on Li superionic conductivity

The charge compensation mechanisms that occur when Li⁺ substitutes a 2+ element in superionic conductor (MgCoNiCuZn)O high-entropy oxide have been studied using a combination of thermogravimetric analysis and X-ray photoemission spectroscopy. Depending on the concentration of Li⁺ in the compound, the charge compensation involves first partial oxidation of Co²⁺ into Co³⁺ for low fraction of Li⁺, and then a combination of both the oxidation of cobalt and the formation of oxygen vacancies for large fraction of Li⁺.     

Airflow inside an open ventilated system: Influence of operator’s arms or moving conveyor

This study deals with the influence of static and dynamic objects on the airflow (generated by a unidirectional air supply) inside an “open” ventilated system used in an agro-food production line. Firstly, the presence of operator’s arms, considered here as objects, leads to the appearance of recirculating zones under each arm. The influence of different positions of the static arms protected by gloves on the airflow organization has been studied. Secondly, modifications induced by the motion of a conveyor system or of moving arms on the airflow have been explored.In an experimental approach, airflow organization has been studied by visualization and by Particle Image Velocimetry for static cases and moving conveyor case.Numerical simulations were carried out using Computational Fluids Dynamics codes. Results obtained for moving gloves cases highlight the contribution of dynamic meshes tools, implemented in the CFD codes to make simulations of moving objects.     

Effect of juice processing on cranberry antibacterial properties

The effects of the industrial juice process on the ability of neutralized cranberry samples and extracts (polar, apolar and anthocyanins) to inhibit the growth of Enterococcus faecium resistant to vancomycin (ERV), Escherichia coli O157:H7 EDL 933, E. coli ATCC 25922, Listeria monocytogenes HPB 2812, Pseudomonas aeruginosa ATCC 15442, Salmonella Typhimurium SL1344 and Staphylococcus aureus ATCC 29213 were investigated. The juice process appeared to have a general enhancing effect on the antibacterial properties of cranberry polar and anthocyanin extracts. The lowest minimum inhibitory concentrations (MICs) (1.80–7.0 μg phenol/well) were obtained when S. aureus, S. Typhimurium, and ERV were exposed to the juice concentrate. The growth of P. aeruginosa, L. monocytogenes, E. coli ATCC, and E. coli O157:H7 was not inhibited by the juice concentrate, but did show sensitivity (maximal tolerated concentrations of 0.007–0.4 μg phenol/well). The lowest MICs (22.6–90.5 μg phenol/well) for P. aeruginosa, S. aureus, S. Typhimurium, and ERV were observed when they were exposed to the cranberry anthocyanin extract obtained from cranberry pomace. The results also showed a negative effect of the juice process on the antibacterial properties of the cranberry apolar extracts: the one obtained from frozen cranberries was most efficient against P. aeruginosa, S. aureus, L. monocytogenes and S. Typhimirium (MIC of 45.50 μg phenol/well). The tested bacteria showed the greatest resistance toward the cranberry extracts obtained from the mash and the macerated and depectinized mash.     

Linear regression-based multifidelity surrogate for disturbance amplification in multiphase explosion

Structural and Multidisciplinary Optimization - When simulations are very expensive and many are required, as for optimization or uncertainty quantification, a way to reduce cost is using...