超高射频串联发射弹组有限元分析

弹丸结构设计及其强度分析是超高射频串联发射核心技术之一。在分析超高射频串联发射整体结构的基础上,设计了弹丸结构,利用ABQUS软件建立了两发串联弹组的有限元分析模型。通过仿真得出了发射过程中两发串联弹组在最大膛压作用下的轴向形变及等效应力分布情况,分析了弹丸前端锥度和圆台大小对支撑部分受力的影响。该有限元分析的结论可为减小弹前阻力、优化弹丸结构及选取弹丸材料提供理论依据。

一种不下箱状态的弹上惯组一体化标定方法

为缩短标定时间、简化标定流程,将导弹、发射箱随弹上惯组共同参与标定,从而在不下箱状态下完成对弹上惯组的标定。然而由于导弹体积、质量较大,使得转台转动受限。基于此,提出了一种不下箱状态的弹上惯组一体化标定方法。根据转台转动的限制条件,并考虑加速度计、光纤陀螺标定方法的特点,设计了一种包含6个静止位置的转动路径。通过转台连续转动,实现对加速度计、光纤陀螺的一起标定。考虑到转台转动时间较短,光纤陀螺常值漂移累积的误差量较小,难以进行估计。因此,采用双位置测漂法对光纤陀螺常值漂移进行标定。仿真结果表明,本文的标定方法能够取得与传统标定方法相近的标定效果,具有较高的标定精度;利用标定结果对常值漂移进行补偿后,重新对光纤陀螺进行标定,标定精度得到提升。

弹载惯组的杆臂效应补偿

在舰载系统和机载系统,当子母惯导之间存在杆臂长度时,在传递对准中通常先消除杆臂效应误差再进行对准,以提高对准精度。在弹载环境中人们往往忽视杆臂效应,受制于弹体空间的限制,弹载惯组中的加速度计通常根据系统体积最小的原则寻找剩余空间布置,此时三个加速度计测量的是弹体三个不同点的加速度,不但存在外杆臂还存在内杆臂,导致惯组总体的杆臂误差。通过深入分析内外杆臂的形成机理,提出对弹载惯组也应进行杆臂效应误差补偿,对补偿算法进行了仿真和实验研究。系统半物理仿真表明补偿后在某些弹道条件下可以显著提高弹体攻击精度,其攻击目标误差由120m缩小为26 m。

当代民族管弦乐配器中的共性追求与个性表达--以弹拨组为例

以“当代”为时间跨度,以“民族管弦乐配器”为研究对象,以“弹拨组”为限定范畴,以小见大、以点带面地阐明作曲家在创作中的共性追求及包容在共性中的个性化表达。探究民族管弦乐配器中的方式、方法及规律,探究当代作曲家在民族管弦乐创作中的思维模式、语言方式及音乐理念,进而总结其成功经验,以此为创作者、研究者提供有参考价值的现实依据。

超高射频串联发射系统设计

基于弹药串联装填发射原理,给出了超高射频串联发射系统设计,就整体结构、弹丸设计和控制系统进行了详细讨论,设计了多发串联弹组,精确控制了内弹道药室初容积和弹丸启动压力2个重要初始参数。针对超高射频的特点设计了系统试验方案,通过调整串联弹组中尾翼连接长度,按照不同的射频进行了多发弹丸连续射击,测试了点火脉冲及其频率、弹丸膛口速度、实际射频以及膛内压力变化曲线,并对试验结果进行了分析讨论。试验实现稳定高初速射频10000r/min5连发射击,验证了超高射频串联发射系统设计的合理可行。

Influence of Zr content on microstructure and mechanical properties of implant Ti-35Nb-4Sn-6Mo-xZr alloys

The influence of Zr content on the microstructure and mechanical properties of implant Ti-35Nb-4Sn-6Mo-xZr （x=0, 3, 6, 9, 12, 15; mass fraction） alloys was investigated. It is shown that Ti-35Nb-4Sn-6Mo-xZr alloys appear to have equiaxed single β microstructure after solution treatment at 1023 K. It is found that the grains are refined first and then coarsened with the increase of Zr content. It is also found that Zr element added to titanium alloys has both the solution strengthening and fine-grain strengthening effect, and affects the lattice parameters. With increasing the Zr content of the alloys, the strength increases, the elongation decreases, whereas the elastic modulus firstly increases and then decreases. The mechanical properties of Ti-35Nb-4Sn-6Mo-9Zr alloy are as follows： σb=785 MPa, δ=11%, E=68 GPa, which is more suitable for acting as human implant materials compared to the traditional implant Ti-6Al-4V alloy.

Effects of T9I6 thermo-mechanical process on microstructure, mechanical properties and ballistic resistance of 2519A aluminum alloy

The effects of T916 thermo-mechanical process on microstructures, mechanical properties and ballistic resistance of 2519A aluminum alloy were investigated by optical microscopy （OM）, transmission electron microscopy （TEM）, tensile tests and ballistic resistance test. After T916 treatment, the yield strength, tensile strength and elongation rate of 2519A aluminum alloy reach 501 MPa, 540 MPa and 14%, respectively. And the ballistic limit velocity of 2519A-T916 alloy （30 mm in thickness） is 715 rn/s. The microstructure varies near the sidewalls of crater. The interrupted ageing contributes to these excellent properties of the alloy. During T916 process, the precipitation of Guinier Preston （GP） zone is finer and denser during the interrupted ageing, thus resulting in well precipitated strengthening phase.

Relationship between Vascular Elasticity and Spontaneous Rupture of Hepatocellular Carcinoma

Objective Spontaneous rupture of hepatocellular carcinoma (HCC) is common in Asia and Africa with unclear mechanism. In our previous study, we found that the deposition of immune complex on vascular wall and vascular injury were related to the HCC rupture. In this study, the structure of elastin around the small artery was deeply investigated to confirm our previous study. Methods Immunohistochemical technique and transmission electron microscopy were used to study 23 specimens from ruptured HCC and 30 cases of nonruptured HCC. Results The layer of elastin around the vascular wall was significant thicker in patients with ruptured HCC than that in nonruptured HCC. The proliferation of elastin, abnormal distribution of neutrophil elastase and degradation of collagen fibril were predominantly present in the specimens from ruptured HCC. The phenomenon of electron—dense deposit in the elastic lamina that represented the deposition of immune complex, and the signs of infiltrated neutrophils from bloodstream into the vascular wall that caused the vascular injury, also can be found in ruptured HCC. Since the damaged vessels could become stiff and weak, which would more prone to be splitting and results in hemorrhage and the rupture of HCC, we postulated that the preexisting of immune complex deposition and vascular injury may be relate to the ruptured HCC. Conclusion The vascular injury caused by immune complex deposition might relate to ruptured HCC. Key words hepatocellular carcinoma - rupture - elastin - elastase

Computation of elastic properties of 3D digital cores from the Longmaxi shale

The dependence of elastic moduli of shales on the mineralogy and microstructure of shales is important for the prediction of sweet spots and shale gas production. Based on 3D digital images of the microstructure of Longmaxi black shale samples using X-ray CT, we built detailed 3D digital images of cores with porosity properties and mineral contents. Next, we used finite-element （FE） methods to derive the elastic properties of the samples. The FE method can accurately model the shale mineralogy. Particular attention is paid to the derived elastic properties and their dependence on porosity and kerogen. The elastic moduli generally decrease with increasing porosity and kerogen, and there is a critical porosity （0.75） and kerogen content （ca. ≤3%） over which the elastic moduli decrease rapidly and slowly, respectively. The derived elastic moduli of gas- and oil-saturated digital cores differ little probably because of the low porosity （4.5%） of the Longmaxi black shale. Clearly, the numerical experiments demonstrated the feasibility of combining microstructure images of shale samples with elastic moduli calculations to predict shale properties.

Optimization of elastolysis conditions and elastolytic kinetic analysis with elastase from Bacillus licheniformis ZJUEL31410

The solubilization of elastin by Bacillus licheniformis elastase cannot be analyzed by conventional kinetic methods because the biologically relevant substrate is insoluble and the concentration of enzyme-substrate complex has no physical meaning. In this paper we report the optimization of elastolysis conditions and analysis of elastolytic kinetics. Our results indicated that the hydrolyzing temperature and time are very important factors affecting elastolysis rate. The optimized conditions using central composite design were as follows： elastolysis temperature 50 ℃, elastase concentration 1 × 10^4 U/ml, elastin 80 mg, elastolytic time 4 h. Investigation of the effects of substrate content, elastase concentration and pH was also revealed that low or high elastin content inhibits the elastolysis process. Increasingelastase improves elastin degradation, but high elastase may change the kinetics characterization. Alkaline environment can decrease elastin degradation rate and pH may affect elastolysis by changing elastase reaction pH. To further elucidate the elastolysis process, the logistic model was used to elastolysis kinetics study showing clearly that the logistic model can reasonably explain the elastolysis process, especially under lower elastase concentration. However, there is still need for more investigations with the aid of other methods, such as biochemical and molecular methods.

Viscoelastic Analysis of a Surface Acoustic Wave Gas Sensor Coated by a New Deposition Technique

An analysis of the response of surface acoustic wave sensors coated with polymer film based on new coating deposition （self-assemble and molecularly imprinted technology） is described and the response formulas are hence deduced. Using the real part of shear modulus, the polymer can be classified into three types： glassy film, glassy-rubbery film and rubbery film, Experimental results show that the attenuation response is in better consistence with the simulation than in Martin＇s theory, but the velocity response does not accord with the calculation exactly. Maybe it is influenced by the experimental methods and environment. In addition, simulations of gas sorption for polymer films are performed. As for glassy film, the SAW sensor response increases with increasing fihn thickness, and the relationship between the sensor response and the concentration of gas is pretty linear, while as for glassy-rubbery flint and rubbery film, the relationship between the sensor sensitivity anti concentration of gas is very complicated. The ultimately calculated results indicate that the relationship between the sensor response and frequency is not always linear due to the viscoelastic prooerties of the polymer.

Simulation of Morphologies and Mechanical Properties of A/B Polymer Blend Film

The effects of blend composition and micro-phase structure on the mechanical behavior of A/B polymer blend film are studied by coupling the Monte Carlo(MC) simulation of morphology with the lattice spring model(LSM) of micro mechanics of materials.The MC method with bond length fluctuation and cavity diffusion algorithm on cubic lattice is adopted to simulate the micro-phase structure of A/B polymer blend.The information of morphology and structure is then inputted to the LSM composed of a three-dimensional network of springs to obtain the mechanical properties of polymer blend film.Simulated results show that the mechanical response is mainly affected by the density and the composition of polymer blend film through the morphology transition.When a force is applied on the outer boundary of polymer blend film,the vicinity of the inner cavities experiences higher stresses and strains responsible for the onset of crack propagation and the premature failure of the entire system.

Calculation of Random Response Spectral Moments of Elastic-viscoelastic Combined Systems

In random vibration analysis, the importance of spectral moments of the response stems from their relevance to system performance prediction. Usually,spectral moments are obtained by the frequency domain method. In present paper, the random response spectral moments of elastic-viscoelastic combined systems are calculated by complex modal analysis in the time domain. The analytical form results are obtained for random response spectral moments of an elastic-viscoelastic combined system to a stationary white noise excitation. The method presented is simple and easy to apply. It is hoped that this study would pave a way for the analysis of reliability of elastic-viscoelastic combined systems subjected to random excitations.

Microstructure evolution of depleted uranium impacted by steel projectile at velocity of 50m/s

The deformed microstructure evolution of depleted uranium impacted by steel projectile at a velocity of50m/s was investigated by means of confocal laser scanning microscope,electron backscatter diffraction,transmission electron microscope and indenter technique.The experimental results showed that the spherical cap crater was formed in depleted uranium target impacted by steel projectile,and the diameter and depth of the impacted crater were5.45and1.01mm,respectively.From crater rim to deep matrix,four deformed zones were classified,including twin fragmentation zone,high density deformation twin zone,low density deformation twin zone and matrix zone.Twinning was considered as the dominant plastic deformation mechanism of depleted uranium subjected to impact loadings.Besides twinning,the dislocation slipping also played an important role to accommodate the plastic deformation.Finally,the deformed microstructure evolution of depleted uranium under high velocity impact was proposed.

Mechanical and ballistic properties of powder metal 7039 aluminium alloy joined by friction stir welding

7039 Al alloy plates which were used as armor materials were produced by powder metallurgy method. The prepared mixed powders were pressed and plated by extrusion process. These plates, after being subjected to T6 heat treatment, were joined double-sided by friction stir welding method. Microstructure and microhardness of the welded plate were investigated. It was determined that the finest grain structure and the lowest hardness value occurred in the stir zone as 2-6 mm and HV 80.9, respectively. In order to determine the ballistic properties of welded plates, 7.62 mm armor piercing projectiles were shot to the base metal（BM）, heat affected zone（HAZ）, and thermomechanically affected zone＋stir zone（TMAZ＋SZ）. Ballistic limits（v_（50）） of these zones were determined. The ballistic limits of the BM, TMAZ＋SZ, and HAZ of the plate were approximately 14.7%, 15.3%, and 17.9% lower than that of the standard plate at the same thickness, respectively. It was determined that the armor piercing projectiles created petaling and ductile hole enlargement failure types at the armor plate. Ballistic and mechanical results can be enhanced by hot-cold rolling mills after extrusion and particle reinforcement.

Diagnostic accuracy of real-time tissue elastography for breast cancer:a meta-analysis

Objective The present study aimed to determine the accuracy of real-time tissue elastography （RTE） for the diagnosis of breast cancer. Methods The search was conducted in the PubMed, Web of Science, Cochrane Library, and China Biology Medicine databases from inception through December 31, 2014, without language restrictions. The meta-analysis was conducted using STATA version 12.0 and Meta-Disc version 1.4. We calculated the summary statistics for sensitivity （Sen）, specificity （Spe）, positive and negative likelihood ratio （LR＋/LR–）, diagnostic odds ratio （DOR）, and summary receiver operating characteristic （SROC） curve. Results Ten studies that met al inclusion criteria were included in the meta-analysis. A total of 608 ma-lignant breast lesions and 1292 benign breast tumors were assessed. Al breast lesions were histological y confirmed after RTE. The pooled Sen was 0.83 （95% CI = 0.79–0.86）; the pooled Spe was 0.86 （95% CI = 0.84–0.88）. The pooled LR＋ was 9.87 （95% CI = 2.66–36.71）; the pooled LR– was 0.20 （95% CI = 0.17–0.23）. The pooled DOR of RTE for the diagnosis of breast cancer was 62.21 （95% CI = 33.88–114.24）. The area under the SROC curve was 0.9334 （standard error = 0.00125）. We found no evidence of publica-tion bias （t = –0.57, P = 0.582）. Conclusion RTE may have high diagnostic accuracy for the dif erential diagnosis of benign and malig-nant breast tumors. RTE may be a good tool for breast cancer diagnosis.

The Feminist Movement in the Moroccan Spring： Roles, Specificity, and Gains

The Moroccan Spring in 2011 has been a golden opportunity for Moroccan women to put their country on the democratization track. Their decision to take an integral part in all aspects of the uprisings stems from their belief that their participation and contribution are necessary for any potential democratic changes that would undoubtedly secure and bring them more rights. However, the appointment of only one female minister in the first Islamist-led government and the reluctance to implement the provisions of the new constitution, namely the issue of gender parity, are but two of the new alarming examples that have disappointed Moroccan women. Based on interviews with women＇s movement organizations＇ leaders and 20 February Movement （20-FMVT） female activists and through following the development of the Arab Spring in Morocco in particular and in the Middle Eastern ＆ Northern Africa region in general, this paper considers the different roles, specificity, and gains of Moroccan women during and after the so-called Moroccan Spring. The paper argues that despite their limited gains in the aftermath of this momentum, Moroccan women managed once again to prove their agency and ability to change laws and instigate reforms.

Mechanical Analysis and Numerical Simulation for New Type of Dynamic Control Devices

The conventional dynamic control devices,such as fluid viscous damper(VFD)and isolating bearings,are unsuitable for the double-deck cable-stayed bridge due to a lack of sustainability,so it is necessary to introduce some high-tech dynamic control devices to reduce dynamic response for double-deck cable-stayed bridges under earthquakes.A(90+128)m-span double-deck cable-stayed bridge with a steel truss beam is taken as the prototype bridge.A 3D finite element model is built to conduct the nonlinear time-history analysis of different site categories in fortification intensityⅨ(0.40 g)degree area.Two new types of dynamic control devices-cable sliding friction aseismic bearings(CSFABs)and elasticity fluid viscous dampers composite devices(EVFDs)are introduced to reduce the dynamic responses of double-deck cable-stayed bridges with steel truss beam.The parametric optimization design for the damping coefficient C and the elastic stiffness of spring K of EVFDs is conducted.The following conclusions are drawn:(1)The hybrid support system by EVFDs and CSFABs play a good function under both seismic and regular work,especially in eliminating the expansion joints damage;(2)The hybrid support system can reduce the beam-end displacement by 75%and the tower-bottom bending moment by 60%under the longitudinal seismic excitation.In addition,it can reduce the pier-bottom bending moment by at least 45%under transverse seismic and control the relative displacement between the pier and beam within 0.3 m.(3)Assuming the velocity indexα=0.3,the parametric optimization suggests the damping coefficient C as 2000 kN·s·m-1in siteⅠ0,4000kN·s·m-1in siteⅡ,6000 kN·s·m-1in siteⅣ,and the elastic stiffness of spring K as 10000 kN/m in siteⅠ0,50000 kN/m in siteⅡ,and 100000 kN/m in siteⅣ.

浅谈鼓形侧墙的组焊回弹

从我公司生产实际出发，针对车体生产中出现的问题一鼓形侧墙组焊回弹，分析其致使车体宽度（车体最宽处的宽度）缩小的原因，并提出相应地解决方案。

Virtual brain surgery simulation system based on haptic interaction

To improve the accuracy and interactivity of soft tissue delormatlon simulation, a new plate spring model based on physics is proposed. The model is parameterized and thus can be adapted to simulate different organs. Different soft tissues are modeled by changing the width, number of pieces, thickness, and length of a single plate spring. In this paper, the structural design, calcula- tion of soft tissue deformation and real-time feedback operations of our system are also introduced. To evaluate the feasibility of the system and validate the model, an experimental system of haptic in- teraction, in which users can use virtual hands to pull virtual brain tissues, is built using PHANTOM OMNI devices. Experimental results show that the proposed system is stable, accurate and promising for modeling instantaneous soft tissue deformation.