纤维爆炸索水下爆炸声信号特征的小波分析

为了研究纤维爆炸索爆炸水声信号特征,在获得水下爆炸压力测试结果的基础上,对其进行了声压级分析,并采用小波变换对水下爆炸信号进行了时频特性分析,讨论了水下爆炸声信号在各频段的能量分布状况。研究结果表明,纤维爆炸索水下爆炸具有很强的声功率,纤维爆炸索水下爆炸声信号能量主要集中在40KHz以内,尤以5KHz以下频带能量最高,如果作为水声干扰源,完全可以覆盖各类水声器材的各工作频段,或许能在水声对抗中发挥重要作用。采用小波分析可以对纤维爆炸索爆炸水声信号特性进行合理研究,达到准确分析信号特征的目的。     

基于HHT变换的小水池水下爆炸振动分析

为了探讨水下毫秒延时起爆对爆炸振动信号的影响,在小型圆筒形爆炸水池(直径5.5m、高3.62m)中进行单药包和双药包两种形式爆炸实验。使用UBOX-5016测振仪采集爆炸振动信号,并对采集到的水下爆炸振动信号进行HHT分析。结果表明,随着测试距离的增加,振动速度减小而主振频率增大,装药量增加,振速增大;通过Hilbert能量谱、边际谱分析可知,水下爆炸振动能量的频率基本分布在100Hz以下的低频区,且主要分布于50Hz内;主振频带在3¹0Hz范围内;分别通过对能量谱、边际谱的分析,进一步验证了延时起爆能够降低水下爆炸振动能量,减小振动效应。实验结果与分析对水工建筑结构抗震设计及水下军事对抗防护等方面具有一定参考意义。     

基于HHT变换的小水池水下爆炸振动分析

为了探讨水下毫秒延时起爆对爆炸振动信号的影响,在小型圆筒形爆炸水池(直径5.5m、高3.62m)中进行单药包和双药包两种形式爆炸实验。使用UBOX-5016测振仪采集爆炸振动信号,并对采集到的水下爆炸振动信号进行HHT分析。结果表明,随着测试距离的增加,振动速度减小而主振频率增大,装药量增加,振速增大;通过Hilbert能量谱、边际谱分析可知,水下爆炸振动能量的频率基本分布在100Hz以下的低频区,且主要分布于50Hz内;主振频带在3~10Hz范围内;分别通过对能量谱、边际谱的分析,进一步验证了延时起爆能够降低水下爆炸振动能量,减小振动效应。实验结果与分析对水工建筑结构抗震设计及水下军事对抗防护等方面具有一定参考意义。     

水下爆炸船舱冲击响应时频特征的小波包分析

设计了带设备双层隔振系统的双层底船舱抗爆结构,进行了水下爆炸冲击试验。应用小波包分析方法,研究了水下爆炸压力和船舱冲击响应的时频分布规律,得到了船舱冲击响应时频特征与冲击环境之间的关系。研究结果表明:水下爆炸压力出现冲击波、滞后流和二次压力波过程,含有丰富的频率成分;冲击波主要作用在1kHz以上的高频段,易造成舰船局部结构的破损;滞后流主要作用在10Hz―1kHz的中频段,是舰船设备隔离系统产生冲击振动的主要来源;二次压力波主要作用在100Hz以下的低频段,会加速设备隔离系统的冲击响应;带设备双层隔振系统的双层底船舱抗爆结构,能有效提高船舶的抗爆性能。     

两装药水下爆炸毁伤目标振动信号时频分析

针对某水下目标抗水下爆炸试验数据,研究两装药水爆炸下冲击波的相互作用及气泡脉动的相互作用现象,分析非平稳结构响应信号时频特征,分别提取前爆冲击波、后爆冲击波及前爆气泡脉动三个不同时段信号进行能量与频率分析,并由此确定不同时段对目标毁伤的影响。结果表明,后爆冲击波能量最大,前爆冲击波与后爆冲击波均处于较宽频率范围,主要作用在780 Hz以上,前爆气泡脉动能量主要作用在100～400 Hz内。与结构自振频率频段重合,因此前爆气泡脉动作用不可忽视。     

基于HHT的爆炸冲击波信号分布特性测试分析

爆炸冲击波的信号分析是研究其毁伤特性的关键,以某次空中爆炸试验获得的冲击波压力信号为研究对象,采用方法对信号进行时-频分析.方法可以有效获得非平稳信号的瞬时频率,表征信号的时频分布特征;利用该方法得到被测信号的分量、瞬时能量和能量谱,表征了时间、频率和压力的三维关系,确定冲击波载荷能量的分布及传播特征.对实测信号的分析结果表明,该时频分析方法能够提取空中爆炸载荷信号不同时段内的频率成分,准确确定冲击波信号在时间、频率和压力之间的关系,对综合评估爆炸冲击波的毁伤性能有重要意义.     

基于能量谱的爆炸冲击波毁伤特性研究

能量谱是评价爆炸冲击波的重要特征参量,大量实验发现爆炸冲击波在某频段内的能量谱值越高,对自振频率在相同频段内目标的毁伤效果越好。为研究爆炸冲击波的能量谱特性,设计了2组对比实验,分别测得同种炸药在不同爆心距及不同炸药在同种爆心距的爆炸冲击波压力信号。为准确提取爆炸冲击波信号中的能量谱,提出了一种基于小波包的改进HHTT(希尔伯特一黄变换)能量谱提取方法。针对噪声对能量谱特征的影响,采用小波包对原始信号进行滤波,结合IMF(固有模态函数)分量与滤波后信号的相关系数,筛选出有效IMF分量,结果表明改进HHT方法提高了能量谱计算精度和速度。通过分析不同工况下爆炸冲击波能量谱发现,爆炸冲击波低频段能量随距离的增加衰减慢,毁伤范围大;高频段能量随距离的增加衰减快,毁伤效果较弱;同时,不同类型炸药的爆炸冲击波具有不同的能量分布,高频能量与低频能量可有明显差异,以上规律可为战斗部毁伤效能评估提供新的思路。     

球形炸药设计及其水下爆炸冲击波特性

雷管等爆炸元件的爆炸能量分布通常并不均匀,在离心机中研究爆炸问题对爆源的尺寸和爆炸能量分布要求较高,爆炸能量不均匀对试验结果存在影响,不符合爆炸力学中的点源假定。采用黑索金炸药制作球形炸药,探讨了细径导爆索及无起爆药雷管作为起爆方式的适用性。最终确定微型导爆雷管中心起爆球形炸药的方式,并研究了其水下爆炸冲击波特性,峰值压力与比例距离近似成线性关系,冲击波压力波形可以较好地采用冲击波压力公式拟合。     

混凝土中瞬时爆炸波测试技术及分离的实验研究

为稳定测量混凝土中炮孔周围的爆炸波,对应变片和超动态应变测试系统的频响及最优匹配开展了系统研究,得到了应变片相对误差δ与其允许最高频率fmax之间的关系,测试系统的阶跃信号响应上升时间为0.3μs。基于一维应力波原理,提出了用SHPB技术中透射杆上的应力动态标定试件上输出电压的新方法,得到了爆炸冲击波作用下测试系统的频响和时频分布。针对爆炸波微信号传输中的易受干扰问题,采用了电磁屏蔽等抗干扰技术。用该系统对混凝土模型开展了不耦合装药爆炸波测试,成功测得了23μs内在爆炸近中区激起的爆炸波。通过Rihaczek分布,将爆炸波分离为[(2.3～4.5μs),(0～829 kHz)]的爆炸冲击波区、[(4.5～7.2μs),(0～743 kHz)]的应力波区及[(7.2～24.7μs),(0～514 kHz)]的爆生气体膨胀作用区,并就分离各区作用过程做了分析。     

一种改进的水下爆炸冲击波信号修正方法

爆炸载荷是舰船抗冲击设计和分析的基础,爆炸冲击波是表征炸药威力的一个关键物理量。在水下爆炸试验中,由于PCB138A50型电气石水下传感器在高频段存在失真,使得水下爆炸自由场压力信号存在上升沿、峰值失真的情况。当爆源与测点的水平距离远大于测点深度时,测点接收的信号需考虑反射波影响,一般会出现水面截断,形成驼峰现象。这都会使压力信号的冲击波能量计算产生误差,进而影响舰船的抗冲击分析。文章用Jensen提出的方法修正峰值,使用Cole函数对冲击波进行拟合修正。经对比,Cole函数拟合法比传统的指数拟合法修正后的冲击波能量更接近于试验炸药冲击波能量的理论值。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.