Effects of Temperature and Humidity on the Characterization of C-4 Explosive Threats

Both the quantity and the amount of time that an explosive is present on the surface of a material is dependent upon the amount of explosive originally deposited on the surface, the adhesive forces, temperature and humidity, as well as other environmental factors. This laboratory study focused on evaluating RDX crystal morphology changes resulting from variations in temperature and humidity conditions of the sample. The temperature and humidity conditions were controlled using a Tenney THRJ environmental chamber and a Tenney T11RC-1.5 environmental chamber. These chambers allow the temperature and humidity to be held within ±3?°C and ±5?% RH. The temperature and humidity conditions used for this test series were: 4?°C/40?%RH, 21?°C/20?%RH (samples left on benchtop), 21?°C/70?%RH, 21?°C/95?%RH, 35?°C/40?%RH, 35?°C/70?%RH, and 35?°C/95?%RH. These temperature and humidity set points were chosen to represent a wide range of conditions that may be found in real world scenarios. C-4 (RDX crystals and binder material) was deposited on the surface of one of six substrates by placing a fingerprint from the explosive block onto the matrix surface. The substrates were chosen to provide a range of items that are commonly used. Six substrate types were used during these tests: 50?% cotton/50?% polyester as found in T-shirts, 100?% cotton with a smooth surface such as that found in a cotton dress shirt, 100?% cotton on a rough surface such as that found on canvas or denim, suede leather such as might be found on jackets, purses, or shoes, painted metal obtained from a car hood, and a computer diskette. The samples were not pre-cleaned prior to testing and contained sizing agents, and in the case of the metal: oil, dirt, scratches, and rust spots. The substrates were photographed at various stages of testing, using a Zeiss Discover V12 stereoscope with Axiocam ICc1 3 megapixel digital camera, to determine any changes in the crystalline morphology. Some of the samples were examined using scanning electron microscopy and atomic force microscopy in an attempt to determine how the explosive was bound to the substrate. This is the second article in a series on the effects of temperature and relative humidity on trace explosive threats.     

机械图样两种画法的异同及其转化

目前世界各国的工程机械图样有两种画法,即第一角画法和第三角画法。通过对第一角画法和第三角画法的对比研究,分析了它们的异同,提出了两种画法图样的相互转化方法,为快速阅读国外的机械图纸提供了参考。     

电视节目非线性编辑网拓扑结构异同与安全性辩析

电视节目非线性编辑与传统线性编辑相比有许多无法比拟的优势.非线性编辑网在我国各级电视台的应用越来越广泛,网络安全问题日益突出,本文介绍了几种常用的非线性编网络拓扑结构,并分析了在网络拓扑结构在安全性方面的特点.     

Modeling Clutter from Bosnian and Puerto Rican Rough Ground Surfaces for GPR Subsurface Sensing Applications Using the SDFMM

The Steepest Descent Fast Multipole Method (SDFMM) is used to analyze the distorting effect of random rough ground surfaces on scattered and transmitted electromagnetic waves. Two well-measured loamy soils: Bosnian and Puerto Rican clay loam are investigated, each with a variety of surface roughness. This study is important in understanding the effects of different soil properties and is meant to be an a priori phase of investigating scattering from buried targets under the rough ground. In this work, we investigated the scattering from rough soil ground without buried objects. The SDFMM is an integral equation-based fast algorithm that is well suited for two-dimensional penetrable rough surfaces (3-D scattering) in the frequency domain. The scattered and transmitted near electric field of an incident Gaussian beam are calculated at different locations above and below the mean plane of the dielectric rough interface. The receiver locations above are chosen to simulate GPR measurement protocols. The obtained numerical results show that the scattered field undergoes more distortion than the transmitted field from both soil types. Moreover, the transmitted fields into the higher dielectric constant Puerto Rican soil experience more distortion than those transmitted into Bosnian soil.     

Lessons from the Lollipop: Biotribology,Tribocorrosion, and Irregular Surfaces

Biotribology and tribocorrosion are often not included in numerical or computational modeling efforts to predict wear because of the apparent complexity in the geometry, the variability in removal rates, and the challenge associated with mixing time-dependent removal processes such as corrosion with cyclic material removal from wear. The lollipop is an accessible bio-tribocorrosion problem that is well known but underexplored scientifically as a tribocorrosion process. Stress-assisted dissolution was found to be the dominant tribocorrosion process driving material removal in this system. A model of material removal was described and approached by lumping the intrinsically time-dependent process with a mechanically driven process into a single cyclic volumetric material removal rate. This required the collection of self-reported wear data from 58 participants that were used in conjunction with statistical analysis of actual lollipop cross-sectional information. Thousands of repeated numerical simulations of material removal and shape evolution were conducted using a simple Monte Carlo process that varied the input parameters and geometries to match the measured variability. The resulting computations were analyzed to calculate both the average number of licks required to reach the Tootsie Roll^® center of a Tootsie Roll^® pop, as well as the expected variation thereof.     

Estimating Gastric Rhythm Differences Using a Wavelet Method from the Electrogastrograms of Normal and Diabetic Subjects

Abstract

Electrogastrogram (EGG) is the cutaneous recording of gastric electrical activity. Some patients with nausea, vomiting, early satiety, and patients with long term insulin‐dependent diabetes exhibit gastric electrical rhythm disturbances. We are interested in investigating the EGG to determine if abnormalities of the EGG occur in association with those gastric complaints. The aim of this document is to investigate long term diabetics with a history of such gastric dysrhythmia complaints in an effort to further characterize the frequency of abnormalities of the EGG in real clinical diabetic gastroparesis patients. For feature extraction purposes, we have performed Wavelet‐Packet analysis of EGG signals and have obtained power spectral density of wavelet‐packet details and approximation coefficients in diabetic patients suffering from gastric dysrhythmia (tachygastria, bradygastria) and healthy volunteers. Wavelet‐Packet analysis provides details of changes in frequency components at any time point, and enhanced interpretation of cutaneous EGG recordings. In conclusion, this paper has shown that the Wavelet‐Packet analysis method is very useful in the analysis of cutaneous EGG recordings, especially in detecting dysrhythmic events.     

Techniques in the study of impact and sliding wear of Zircaloy-4

A wear test apparatus has been designed to conduct detailed measurements of the contact forces and motion during impact and sliding (and combinations of the two). After carrying out pure impact and sliding tests on Zircaloy-4 couples in air at room temperature, it appears that the test apparatus has acceptable dynamic characteristics for wear studies.In pure impact, the wear rate of Zircaloy-4 was primarily influenced by the initial impact force which was measured dynamically. Secondary vibrations had a minimal effect on the wear rate.The wear rate in pure sliding was dependent upon the characteristics of the apparatus, such as its compliance, and the test conditions. Consequently the sliding amplitude should be monitored continuously throughout the test. In general, sliding wear was more severe than impact wear and good correlation between the average sliding amplitude and weight loss was observed. An indication of the relative motion between the wear specimens was given by the magnitude and form of the coefficient of friction which tended to increase with weight loss.     

从控制污染谈油箱设计与制造问题

系统污染是产生故障的重要原因,从油箱设计制造的角度阐述控制污染。     

从控制污染谈油箱设计和制造的几个问题

液压系统的污染是液压系统产生故障的重要原因。本文从油箱设计和制造的角度论述了如何控制油箱的污染。     

液压污染控制技术第5讲液压系统的主动维护策略及实施

设备的维护修理是机械装置正常工作的前提和保证．它主要是通过大家所熟悉的“擦拭、清扫、润滑、调整、修理”等环节来进行。一般性的维护只能消除设备表面上的异常现象，而对设备内部的隐患性故障及根源就无能为力了。要想达到治标又治本，则需采用主动维护技术．即对引起设备故障的根源性参数进行识别，     

Existence of Good Bonding between Coated B4C Reinforcement and Al Matrix via Semisolid Techniques: Enhancement of Wear Resistance and Mechanical Properties

An Al 6061 alloy matrix reinforced with the coated B₄C particles was used for the present study. The cohesion of the reinforcing ceramic particles is poor at temperatures near the melting point of aluminum and leads to inferior mechanical and tribological properties of developed aluminum matrix composites with nonuniform distribution of the reinforcement. The main reason for coating the particles is to improve the bond between the reinforcement and molten alloy and thus to eliminate interfacial reactions. The great enhancement in strength values of the composites in this study can be ascribed to the effective load-bearing capacity of disintegrated B₄C particles that are adherently bonded to the matrix alloy. Homogeneity and reduction in the particle size of B₄C during the extrusion process is evidenced in the microstructural studies.     

Identification of Explosives from Porous Materials: Applications Using Reverse Phase High Performance Liquid Chromatography and Gas Chromatography

High performance liquid chromatography and gas chromatography techniques are well documented and widely used for the detection of trace explosives from organic solvents. These techniques were modified to identify and quantify explosives extracted from various materials taken from people who had recently handled explosives. Documented techniques were modified to specifically detect and quantify trace levels of the military explosives, RDX, TNT, and PETN from denim, colored flannel, vinyl, and canvas extracted in methanol and filtered using no additional sample cleanup of the sample extract prior to analysis. The filtered methanol extracts were injected directly into several different column types and analyzed by high performance liquid chromatography using ultraviolet detection and/or gas chromatography using electron capture detection. This paper describes general screening methods that were used to determine the presence of explosives (RDX, TNT, and PETN) in unknown samples of denim, colored flannel, vinyl and canvas in addition to techniques that have been optimized for quantification of each explosive from the substrate extracts.     

Initiation of Galling in Metal Forming: Differences Between Aluminium and Austenitic Stainless Steel Studied In Situ in the SEM

High friction and transfer of work material to tool surfaces constitute important industrial problems in forming of many metals and alloys. However, it is very hard to gain a deeper understanding of these phenomena by studying real forming operations. In this paper, we have tried to gain fundamental understanding by avoiding as much as possible of the complexity of real forming. This has been realised by studying the friction and material transfer between well-defined tool material surfaces; uncoated and DLC-coated tool steel, and a needle shaped austenitic stainless steel tip, in situ in the SEM. The tool materials were tested in two conditions; well polished and well polished with local intentional scratches. It was found that work material was immediately transferred to the tool steel surface. When passing an intentional scratch, the local transfer was on a much larger scale, and the friction was higher, but the effect was mostly local. For the polished DLC-coated surface, almost no work material was transferred and the friction was low. An intentional scratch in the polished DLC surface barely influenced the galling behaviour. The present results are discussed in the light of previously published results from an analogous study with aluminium as work material.     

Differences in microstructure and properties between selective laser melting and traditional manufacturing for fabrication of metal parts: A review

Selective laser melting (SLM), as one of the additive manufacturing technologies, is widely investigated to fabricate metal parts. In SLM, parts are manufactured directly from powders in a layer-by-layer fashion; SLM also provides several advantages, such as production of complex parts with high three-dimensional accuracy, compared with other additive manufacturing technologies. Therefore, SLM can be applied in aeronautics, astronautics, medicine, and die and mould industry. However, this technique differs from traditional methods, such as casting and forging; for instance, the former greatly differs in terms of microstructure and properties of products. This paper summarizes relevant studies on metal material fabrication through SLM. Based on a work completed in Huazhong Univ. Sci Tech., Rapid Manuf. Center (HUST-RMC) and compared with characteristics described in other reported studies, microstructure, properties, dimensional accuracy, and application of SLM are presented.     

Raman Spectroscopy Techniques for the Detection of Biological Samples in Suspensions and as Aerosol Particles: A Review

This article reviews current scientific literature focusing on Raman spectroscopy modalities that have been successfully applied to the detection of biological samples in aqueous suspensions and in aerosols. Normal Raman, surface enhanced Raman scattering, coherent anti-stokes Raman scattering, resonance Raman and UV-Raman spectropies, allow the detection of biological samples in situ in the near field and as well as in the far field at standoff distances. Applications span from fundamental studies to applied research in areas of defense and security and in monitoring of environmental pollution. A primary focus has been placed on biological samples including bacteria, pollen, virus, and biological contents in these specimens, in suspensions, and in aerosols. Several Raman spectroscopy studies have been reviewed to show how various modalities can achieve detection in these biosystems. Current data generated by our group is also included. Necessary parameters used to accomplish the detection and data analysis, which could also be used to interpret the results and to render the methodologies robust and reliable, are discussed.     

Differences between nanoscale structural and electrical properties of AZO:N and AZO used in polymer light‐emitting diodes

Conducting atomic force microscopy and scanning surface potential microscopy were adopted to investigate the nanoscale surface electrical properties of N‐doped aluminum zinc oxide (AZO:N) films that were prepared by pulsed laser deposition (PLD) at various substrate temperatures. Experimental results demonstrated that when the substrate temperature is 150°C and the N₂O background pressure is 150 mTorr, the N‐dopant concentration on the surface is optimal. In addition, the root‐mean‐square roughness value of the film surface, the low contact current (<400 nA) conducting region as a percentage of the total area, and the mean work function value are 1.43 nm, 96.9%, and 4.88 eV, respectively, all of which are better than those of the optimal AZO film made by PLD. This result indicates that N‐doped AZO films are better for use as window materials in polymer light‐emitting diodes. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc.     

Using data from multiplex networks on vehicles in road tests,in intelligent transportation systems,and in self-driving cars

The possibility of using data from multiplex networks on vehicles in road tests, in the development of intelligent transportation systems, and in control systems for autonomous (self-driving) vehicles is considered.