主动雷达抗拖曳式诱饵干扰的角度提取方法

通过对拖曳式有源雷达诱饵干扰的分析,得到了平衡状态下对导引头测角值进行数据积累并且取均值后,导引头将指向大功率辐射源的结论。在诱饵信号从功率上压制栽机回波信号的前提下,对导引头处于平衡状态时的测量角公式进行数学推导。结果表明：可由导引头处理时间内任意两次测角值及其对应的和支路振幅比求得载机、诱饵和导弹三者形成的夹角的角平分线方向,从而间接求得小功率辐射源（载机）的角度。最后,结合比例导引规律,通过飞行弹道仿真验证了雷达型空空导弹应用上述方法可以获得准确的目标角度,进而导引导弹准确命中目标。     

不同围压下共面双裂隙脆性砂岩裂纹演化特性颗粒流模拟研究

岩体中含有大量节理、裂隙、断层等各类结构面,结构面在应力作用下的扩展与贯通是导致岩体破坏的重要原因。数值流形方法(NMM)可以有效模拟连续和非连续问题,然而,其在多裂纹动态扩展的模拟方面仍处于探索阶段。该文以线弹性断裂力学原理为基础,提出了一种基于高阶数值流形方法的多裂纹扩展模拟算法。通过在基函数中增加关键项来考虑裂纹尖端位移场的奇异性;裂纹尖端的应力强度因子则采用了J积分来计算;Ⅰ型-Ⅱ型混合裂纹的开裂和扩展方向依据最大周向拉应力准则来判断;采用假设-修正的多裂纹扩展算法解决了多裂纹的扩展问题。根据强化后的基函数,对于不符合单纯形积分形式的被积函数,采用了泰勒级数展开式计算近似解。通过多个静态裂纹扩展的经典问题的数值模拟对计算方法的合理性和计算精度及进行了验证。     

等离子体处理对氧化铟锡(ITO)润湿性及性能参数的影响

在预处理室中对ITO薄膜进行等离子体处理,研究分别在氧气、氮气、氩气及空气四种工作气体下,等离子体处理压强和处理时间对薄膜的润湿性及性能参数的影响。接触角测试仪表征表明,等离子体处理时间越长、处理压强越大,静态H₂O接触角越小,其润湿性越高。分光光度计测试结果表明,经等离子体处理,ITO薄膜透过率较未处理均有所下降。四种工作气体下,等离子体处理压强越大对透过率的影响越小,但随着处理时间的增长影响会增大;相较其他工作气体,氧气等离子体处理整体变化最小。四点探针表征表明,处理后的ITO薄膜方块电阻无明显变化,这是由于等离子体处理只对ITO薄膜表面进行改性,没有改变内部性质。利用霍尔效应测量载流子浓度,没有发现明显变化,与方块电阻不变结论一致。     

地面井抽采卸压瓦斯技术在新疆大倾角多煤组矿区的应用

针对新疆艾维尔沟矿区大倾角多煤组地表岩层移动与覆岩破坏特征,分析了大倾角多煤组地面井失稳机制,合理选择了地面井位置,优化了钻固井工艺及井身结构,并进行了适用性试验考察。试验工作面推过后井身结构稳定,套管基本未发生异常变形破坏,地面井抽采瓦斯持续稳定,可为新疆矿区大倾角多煤组地面井高效抽采瓦斯提供技术支撑及示范作用。     

不规则钢筋砼板的塑性理论计算

不规则钢筋砼板的计算,目前尚无明确的方法和统一的计算结果。本探讨不规则的钢筋砼板在极限状态下承载能力的计算方法。用屈服线分析法求板的承载能力的数值解,对角部效应的影响提出了补偿内力功的概念,采用局部配置板顶钢盘的方法。     

永磁同步电机的无速度传感器直接转矩控制

在高性能的永磁同步电机控制系统中,机械传感器的存在会使系统的成本增加,可靠性降低,容易受到外部环境的影响.在叙述永磁同步电机直接转矩控制原理的基础上,采用了一种基于转子磁链的转速估计方法,该方法根据定子磁链角和负载角确定出转子磁链角,进而估计出电机的转速.仿真和实验结果验证了该方法能够在电机全速范围内准确地估计出转速,具有优良的动静态性能,适合于永磁同步电机的直接转矩控制.     

汽车车轮锁圈槽开裂原因及对策

分析钢制汽车车轮在CO2气体自动保护焊接过程中开裂的原因及防止措施,通过金属材料成份和焊接工艺规范的分析及汽车车轮弯曲疲劳试验,分析引起汽车车轮锁圈槽开裂的各种因素。为防止汽车车轮锁圈槽开裂,降低不良率提供参考。     

New Linkage with Linear Actuator for Tracking PV Systems with Large Angular Stroke

This paper focuses on the development of an optimized photovoltaic tracking system involving low-cost, relative simple mechanisms, with linear actuators able to insure strokes comparable with those resulted when using gear rotary actuators. Starting with a rhombus linkage, with a linear actuator on the diagonal used for the elevation motion till 90°, a new performance solution is generated. This new linkage allows large angular strokes by using an asymmetric rhombus and an eccentrically positioned linear ac...     

Advanced neutron imaging methods with a potential to benefit from pulsed sources

During the last decade neutron imaging has seen significant improvements in instrumentation, detection and spatial resolution. Additionally, a variety of new applications and methods have been explored. As a consequence of an outstanding development nowadays various techniques of neutron imaging go far beyond a two- and three-dimensional mapping of the attenuation coefficients for a broad range of samples. Neutron imaging has become sensitive to neutron scattering in the small angle scattering range as well as with respect to Bragg scattering. Corresponding methods potentially provide spatially resolved and volumetric data revealing microstructural inhomogeneities, texture variations, crystalline phase distributions and even strains in bulk samples. Other techniques allow for the detection of refractive index distribution through phase sensitive measurements and the utilization of polarized neutrons enables radiographic and tomographic investigations of magnetic fields and properties as well as electrical currents within massive samples. All these advanced methods utilize or depend on wavelength dependent signals, and are hence suited to profit significantly from pulsed neutron sources as will be discussed.     

Quantitative measurement of cementite dissociation in drawn pearlitic steel

Fractional dissociation of cementite was quantified as a function of strain by measuring the volume change of cementite in the pearlitic steel. The amount of carbon dissolved into the ferrite was estimated from the decrease of cementite volume, to correlate with the hardness in different strain level. The hardness showed linear relationship with the carbon dissolved into the ferrite matrix, which is believed to contribute in strengthening the drawn wire. Defects introduced from the deformation were believed to lower the energy barrier of cementite break-ups and to enhance the dissolution of carbon into ferrite.