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。     

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。     

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。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.