电桥法测定电缆三相绝缘故障的新方法

在电缆三相同时发生绝缘故障时,用电桥法定位将产生较大误差。本文通过理论分析导得一校正公式：ｌｃｘ＝（ｋ＋１／ｋ－１）ｌｍｘ－２ｌ／（ｋ－１）,其中ｋ为近似完好相与故障相绝缘电阻比,ｌ为电缆的全长,ｌｍｘ为故障位置的测量值,ｌｃｘ为ｌｍｘ的校正值。实验表明,如ｋ＞２,经校正的定位误差将小于±１％,其准确度能完全满足工程测量的要求。     

企业生产过程中边角余料的会计处理方法

在企业的实际会计工作中,对产品生产过程中产生的边角余料如何进行会计处理,一直是广大会计工作者难以解决的问题.从理论上就其会计处理进行了阐述,以供企业的会计工作者借鉴.     

渤南洼陷坡折断层控砂动态分析

渤南洼陷沙三段沉积了一套大型浊积岩体，其中沙三段中、上亚段可划分为9个砂层组，通过对1-9砂层组中主力砂体平面展布特征与主要同沉积断裂活动性的配套分析，系统研究了坡折断层控砂的动态过程。综合研究表明，平面上几何形态相同的坡折断层构成样式，在演化过程中表现出不同的控砂特征，原因在于断层活动性在时间上的变化，引起古构造面貌和主要物源方向的演变，进而影响了不同时期砂体的发育和展布。     

干式高压环境对TIG焊接电弧温度的影响

干式高压焊接时,环境压力对焊接电弧的影响不容忽视.电弧温度是焊接电弧物理特性的重要参数之一,测定高压环境下的电弧温度对于深入理解焊接电弧在高压环境下的物理特性,从而寻求改善水下干式高压焊接质量的新途径有重要意义.介绍了电弧等离子体光谱诊断方法,对高压环境下的TiG电弧光谱进行分析,建立了一套切实可行的高压环境电弧温度测量方法.对高压环境焊接电弧温度变化规律进行了分析,建立了环境压力与电弧温度的函数关系式,并对试验结果进行了讨论.研究结果对于高压环境焊接电弧物理特性的研究具有参考价值.     

Al含量对高钨铸造高温合金显微组织和高温拉伸性能的影响

对Al含量分别为4.5%、5.5%、6.5%和7% (质量分数,%)4炉高W铸造镍基高温模具合金的显微组织和1100 ℃的高温抗拉强度进行了对比研究,结果表明：4.5%和7%的合金由于主要强化相次生γ′ 含量不足50%(体积分数),且高Al量合金的共晶γ′ 和析出的α(W,Mo)相是1100 ℃下高温强度不高的主要原因。5.5%和6.5%的合金次生γ′ 含量为56%~57%,共晶γ′ 含量为6%~12%,其1100 ℃高温拉伸强度达到同类合金最高水平,为488~518 MPa。目前该合金已用于制造1050~1080 ℃工作的大型等温锻造模具,其Al含量的成分范围为5.5%~6.5%(质量分数)。     

股票期权驱动下的企业财务欺诈的研究

股票期权的推广运用,在美国20世纪90年代经济的持续高速发展中功不可没。在多数情况下,这种激励机制通过让高管人员分享剩余收益,能够有机地协调经营者与所有者之间的利益关系,激励高管人员创造优异的业绩。然而,在承认股票期权激励先进性的同时,也必须正视股票期权潜在的负面影响,即股票期权可以因所有者缺位、经营者篡位而成为企业管理者进行财务欺诈的工具。笔者尝试性地探讨了股票期权与财务欺诈之间的关系,在此基础上提出了完善我国股票期权制度,以防范财务欺诈的具体建议。     

Preparation and characterization of poly (styrene-acrylonitrile) (SAN)/clay nanocomposites by melt intercalation

Poly (styrene-acrylonitrile) (SAN)/clay nanocomposites have been prepared by melt intercalation method from pristine montmorillonite (MMT), using hexadecyl trimethyl ammonium bromide (C16) and hexadecyl triphenyl phosphonium bromide (P16) as the reactive compatibilizers between polymer and clay. The influence of the reactive compatibilizers proportion relative to the clay on the structure and properties of the SAN/clay nanocomposites is investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The effects of the two different clays (MMT and organic modified MMT) on the nanocomposites formation, morphology and property are also studied. The results indicate that the SAN cannot intercalate into the interlayers of the MMT and results in microcomposites. In the presence of the reactive compatibilizers, the dispersion of clay in SAN is rather facile and the SAN/clay nanocomposites reveal an intermediate morphology, an intercalated structure with some exfoliation and the presence of small tactoids. The appropriate proportion with 3 wt% reactive compatibilizers to 5 wt% MMT induces well-dispersed morphology and properties in the SAN matrix. The TGA analyses show that the thermal stability properties of the SAN/clay nanocomposites have been improved compared with those of the pristine SAN. The DMA results show that the storage modulus and glass transition temperature (Tg) of the SAN/clay nanocomposites have remarkably enhancements compared with the pristine SAN. At last the intercalation mechanism of the technology is discussed.     

Characteristic verification and parameter optimization of airbags cushion system for airborne vehicle

Abstract： The major methods to investigate the airbags cushion system are experimental method, thermodynamic method and finite element method （FEM）. Airbags cushion systems are very complicated and very difficult to be investigated thoroughly by such methods For experimental method, it is nearly impossible to completely analyze and optimize the cushion characteristics of airbags of airborne vehicle because of charge issue, safety concern and time constraint. Thermodynamic method fails to take the non-linear effects of large airbag deformation and varied contact conditions into consideration. For finite element method, the FE model is usually complicated and the calculation takes tens of hours of CPU time. As a result, the optimization of the design based on a nonlinear model is very difficult by traditional iterative approach method. In this paper, a model based on FEM and control volume method is proposed to simulate landing cushion process of airborne vehicle with airbags cushion system in order to analyze and optimize the parameters in airbags cushion system. At first, the performance of airbags cushion system model is verified experimentally. In airdrop test, accelerometers are fixed in 4 test points distributed over engine mount, top, bottom and side armor plate of hull to obtain acceleration curves with time. The simulation results are obtained under the same conditions of the airdrop test and the simulation results agree very well with the experimental results, which indicate the established model is valid for further optimization. To optimize the parameters of airbags, equivalent response model based on Latin Hypercube DOE and radial basis function is employed instead of the complex finite element model. Then the optimal results based on equivalent response model are obtained using simulated annealing algorithm. After optimization, the maximal acceleration of airborne vehicle landing reduces 19.83%, while the energy absorption by airbags increases 7.85%. The performance of the airbags cushion system thus is largely improved through optimization, which indicates the proposed method has the capability of solving the parameter optimization problem of airbags cushion system for airborne vehicle.     

Single-Crystal Nanowire Cesium Tin Triiodide Perovskite Solar Cell

This work reports for the first time a highly efficient single-crystal cesium tin triiodide (CsSnI₃) perovskite nanowire solar cell. With a perfect lattice structure, low carrier trap density (≈5 × 10¹⁰ cm⁻³), long carrier lifetime (46.7 ns), and excellent carrier mobility (>600 cm² V⁻¹ s⁻¹), single-crystal CsSnI₃ perovskite nanowires enable a very attractive feature for flexible perovskite photovoltaics to power active micro-scale electronic devices. Using CsSnI₃ single-crystal nanowire in conjunction with highly conductive wide bandgap semiconductors as front-surface-field layers, an unprecedented efficiency of 11.7% under AM 1.5G illumination is achieved. This work demonstrates the feasibility of all-inorganic tin-based perovskite solar cells via crystallinity and device-structure improvement for the high-performance, and thus paves the way for the energy supply to flexible wearable devices in the future.