机枪系统虚拟样机建模及仿真分析

以某大口径机枪系统为物理样机模型，对联合CAD建模软件Pro／E和动力学仿真软件ADAMS对其进行动力学仿真时的模型传递方法进行了研究，并以此在仿真环境中建立了机枪系统的虚拟样机模型。然后对机枪的自动机动力学和供输弹机构的运动进行了仿真分析，将仿真结果与试验数据进行了比较，并对工作弹簧进行了参数化设计。这证实了将虚拟样机技术引入自动武器研制领域的可行性，并为进一步的仿真工作奠定了基础。     

伪脐子流形的两个Pinching定理

设Mn+p+q2是n+p+q维拟常曲率的黎曼流形,Mn+p1(c1)为Mn+p+q2中的n+p维常曲率为c1的子流形,Mn为Mn+p1(c1)中具有平行平均曲率向量的紧致伪脐子流形,给出了Mn是Mn+p1(c1)的全脐子流形的几个充分条件.     

Development of the CAS-IBB single-particle microbeam for localized irradiation of living cells

A single-particle microbeam facility has been constructed at the Key Laboratory of Ion Beam Bioengineering (LIBB), Chinese Academy of Sciences (CAS). The system was designed to deliver a defined numbers of hydrogen ions, produced by a van de Graaff accelerator, in an energy range of 2.0-3.0 MeV, into an area smaller than that of the nucleus of an individual living cell. The beam is collimated by a borosilicate glass capillary that forms the beam-line exit. An integrated computer program recognizes the cells and locates them one by one over the microbeam exit for irradiation. We present technical details of the CAS-LIBB microbeam facility, particularly on the collimator, hardware, control program, as well as cell irradiation protocols available. Various factors contributing to the targeting and positioning precision are discussed along with accuracy measurement results.     

The Application of Similarity Theory in Designing Large Deflection Buckling Spring-Piece

Large Deflection Buckling Spring-Piece (LDBSP) refers to the deformation of an end-fixed flat spring-piece under normal loadings. Plastic deformation usually appears in LDBSP.The static characteristic curve is very particular, because within its linear deflection region, the spring constant can be designed to be any value from minus to plus. With its obvious advantages of large liner deflection range, low spring constant, etc., the LDBSP has now been extensively applied to the exciting device, low-frequency shock absorbers and so on. The static characteristic curve of LDBSP belongs to the nonlinear problem of an arch with varying section. Therefore, it is difficult to obtain it theoretically. The formulae for designing LDBSP have not been set up yet. In this study,the authors apply similarity theory to analyze the liner deflection range A and the spring constant K, and derive the relationship of similarity criterion, finally obtain a set of formulae for designing LDBSP by model test and the least square method, which can be applied in engineering design.Through the research, it is proved that it is unnecessary to keep geometrical similarity of spring-piece shape. This fact extends the application scope of the formulae. The proposed formulae for designing LDBSP thereby can be applied for any dimensions within the range allowed.     

年轻火山岩激光40Ar/39Ar定年中的n值与MSWD值

激光熔蚀⁴⁰Ar/³⁹Ar等时线法是第四纪年轻火山岩样品精细定年的新方法, 该方法处于逐步完善过程中。针对怎样判定获得的年龄结果是否可靠的问题, 通过对数据处理过程中所用参数的分析, 认为样品属性是决定年轻火山岩精细定年结果质量和可靠性的关键因素, 与样品测试数n值相关的加权均方差MSWD(mean square weighted deviation)是判断同一样品各测试点的数据是否符合正态分布, 能否用来客观地评价测试结果, 进而评估样品是否适合进行相关测试, 结果是否可靠的重要指标。其次, 属于同一真实年龄值样品的MSWD在99.7%置信区间的取值范围可通过计算加以确认, 并提出对于表面年龄和等时线年龄数据, 必须定量地考察相应的MSWD值, 判定在具有足够样品测试数(足够大的n值)的情况下, 是否符合概率统计的正态分布, 确定样品是否对应同一年龄真实值。在MSWD值达不到理想值1.0的情况下, 可以利用表面年龄概率密度曲线, 区分测试样品内部包含的非同源或非等时或封闭不好体系的数据, 再结合MSWD与n值关系, 适量地去除部分偏离正态分布的测试数据, 识别出可能归属多个年龄真实值的测试数据组, 并以此计算不同数据组的反等时线年龄, 获得年轻火山岩喷发的准确年龄。     

3D建模与快速成型技术在个体化膝关节假体术中的应用

目的探讨3D建模与快速成型技术在个体化膝关节肿瘤假体手术治疗中的新方法,评价3D建模与快速成型技术的应用价值.方法选取3例膝关节骨肿瘤患者,术前均对膝关节周围病损区行CT扫描,获得原始数据后,导入Mimics19.0软件,在软件中模拟手术规划,并且设计与切除后剩余的骨组织相契合的钛合金"植物.随访期间应用国际骨与软组织肿瘤保肢(Musculoskeletal Tumor Society,MSTS)功能评分系统对患者的术后功能情况进行评价.结果 3例患者均获随访,随访时间5~26个月,平均16个月.末次随访MSTS得分为18~29分,平均24.3分,其中优2例,良1例,优良率达100%.结论通过3D建模与快速成型技术在膝关节肿瘤手术中的应用,可精确指导截骨界限,设计个体化膝关节假体,韧带附丽点接近生理结构,为膝关节骨肿瘤治疗提供新方法.     

相干测风激光雷达带通采样方法的仿真研究

根据相干测风雷达回波信号载频高、带宽窄的特点,尤其星载相干测风雷达回波信号数千兆赫兹,采用传统采样方式对采集卡的采样率要求很高.鉴于采集卡的采样率和分辨力互相制约,提出将带通采样引入到相干测风雷达系统.本文以1.5 μm全光纤相干测风激光雷达的实测数据作为仿真输入,经Simulink滤波、带通采样,结果表明,在对探测距离影响不大的情况下,与低通采样方式相比径向风速反演结果最大相差0.5 μm/s;数据处理的时间复杂度降低,其下降值是带通采样频率与低通采样频率的比值;但信噪比会恶化,其下降值介于1~3 dB.      

混响室条件下临界辐射干扰场强测试的影响因素分析

为了对前期提出的混响室条件下临界辐射干扰场强测试方法进行规范和完善,分析了影响测试结果准确性的因素,得到了不同条件下测试误差的变化情况.发现被测设备的电尺寸是影响该方法适用范围的主要因素,通过试验研究了电尺寸减小对测试结果的影响.结果表明,当被测设备电尺寸较大时,通过合理选择测试参数,可以将测试误差控制在3 dB以内;当被测设备电尺寸较小时,该方法的不确定度会增加,误差可能会大于3 dB.因此,该方法更加适用于电大尺寸设备的临界辐射干扰场强测试.      

Surface modification of Ti-45Al-8.5 Nb alloys by microarc oxidation to improve high-temperature oxidation resistance

Microarc oxidation(MAO)electrolysis plasma deposition was used to prepare Al_2O_3coatings on Ti-45Al-8.5 Nb alloys to improve high temperature oxidation resistance.The surface and cross-section morphologies before and after high-temperature oxidation,the chemical composition,and the phase identification of the coatings were investigated by scanning electron microscopy(SEM),electron probe microanalyses(EPMA),and X-ray diffraction(XRD).The results show that Al_2O_3coatings with a thickness of approximately 8μm can be obtained on the Ti-45Al-8.5 Nb alloys by MAO for 600 s.The samples with the Al_2O_3coatings exhibited better high-temperature oxidation resistance.A minimal weight gain of only 0.396 g/m~2after 100 h oxidation at 900°C was observed for the coatings formed with a deposition voltage of 400 V and using a duty cycle of 3%.The deposition mechanism of the Al_2O_3coatings and the effect of the MAO parameters are also described.     

力学性能对矿柱体系破坏影响的三维数值分析

在深部高应力等复杂地质条件下开采时,由多个矿柱构成的矿柱体系的稳定性对矿山安全生产至关重要.利用RFPA^3D-Parallel程序,研究了单轴抗压强度对串行和并行矿柱体系破裂过程的影响.结果表明,串行矿柱中强度较弱部分的失稳决定整个体系的稳定,对该段加固和监测有助于体系的稳定性控制;对并行布设的矿柱体系,其压力传递与柱的抗压强度密切相关,较弱柱先破坏,应力依次向强度较高的柱转移,直到矿柱系统失稳;可将声发射数的多峰现象或声发射累积增长阶梯型弧段作为矿柱体系中弱柱失稳破裂、应力向相邻强柱转移的依据.