隧道尾排水型快艇性能试验研究

采用隧道尾而增大螺肇桨直径是提高排水型快艇快速性能的一条重要途径。文章介绍了１艘隧道尾排水型快艇的模型阻力,自航试验结果,并分析了过渡阶段快艇的自航要素特点,可供此类艇的设计参考。     

REGULATION OF PRODUCTION OF PARATHYROID HORMONE－RELATED PEPTIDE （PTHrP） AND EXPRESSION OF ITS mRNA IN A HUMANLIVER－DERIVED CE

ＲＥＧＵＬＡＴＩＯＮＯＦＰＲＯＤＵＣＴＩＯＮＯＦＰＡＲＡＴＨＹＲＯＩＤＨＯＲＭＯＮＥ－ＲＥＬＡＴＥＤＰＥＰＴＩＤＥ（ＰＴＨｒＰ）ＡＮＤＥＸＰＲＥＳＳＩＯＮＯＦＩＴＳｍＲＮＡＩＮＡＨＵＭＡＮＬＩＶＥＲ－ＤＥＲＩＶＥＤＣＥＬＬＬＩＮＥＬｉＨｕｓｏｎｇ；Ｐ...     

Stress intensity factor measurement of cracks using piezoelectric element

A stress intensity factor (SIF) measurement method for cracks using a piezoelectric element and an electrostatic voltmeter is presented. In this method, an isotropic piezoelectric element is first attached near the tip of the crack. Then surface electrodes are attached to three different positions on the piezoelectric element. The electric potentials of the surface electrodes, which are proportional to the sum of the stress ( _x + _y ) on the structural member, are measured by an electrostatic voltmeter during load cycling. The mode I and mode II SIFs of the crack are estimated using the relationship between the SIF and ( _x + _y ). The applicability of the proposed method is examined through experiments and numerical analysis.     

Public transit subsidies, output effect and total factor productivity

This paper extends previous works on total factor productivity decomposition when firms receive both operating and capital subsidies. It shows that previous works considered either the lump-sum or substitution effects of these subsidies but not together. Using constrained cost minimization as the framework it offers formal proofs to show that cost increases are inevitable if the total effects of the subsidies are considered, and that total factor productivity growth results from increasing amounts of subsidies under economies of scale and in the absence of technical change. Applications of the decomposition equations derived to a sample of transit systems finds near constant returns to scale and negative contributions of these subsidies to total factor productivity growth. Technical change reverses this decline and results in total factor productivity growth. Further, it finds that the lump-sum effects of the subsidies reduce total factor productivity more than does the substitution effect.     

静载锚固性能试验影响因素分析

结合铁路工程钢绞线一锚具组装件的静载锚固性能试验检测，对影响试验结果的各种因素进行了分析，并指出相应的解决措施。提出试验过程的有效控制是试验科学性和数据结果可靠性的有力保证。     

并联混合动力汽车ECMS的时变等效因子提取算法的研究

为解决当前等效燃油消耗最小控制策略(ECMS)未能根据实际工况选取最优等效因子的问题,利用动态规划算法(DP)和ECMS各自的优点,构建并联混合动力汽车能量算法模型,即采用动态规划算法的等效燃油消耗最小控制策略(ECMSwDP),将等效因子作为全局最优算法的控制变量,通过对等效因子的离散全局优化,获得基于工况的最佳时变等效因子。在标准工况下对时变等效因子实时控制策略与全局最优控制策略DP的各项性能参数进行了数值仿真,验证了时变等效因子提取算法的有效性和等效因子初始值选取方法的可行性。     

基于多目标规划的公交车调度方法研究

公交调度要考虑公司和乘客的多方利益。目标规划法是运筹学中解决多目标问题的有效方法,而优先因子的采用可以区分调度中的各方利益的主次。同一优先因子下加入了权重,可根据实际情况做出灵活有效的调度方案。     

旧路改造期间运营安全评价

旧路改造期间不断交施工,交通量较大,应对其运营安全预先分析评价。通过对沿线设施预先危险性分析可知,危险因素等级均为Ⅱ级,并提出防范措施。通过对改建期运营预先危险性分析可知,危险因素中车辆伤害、起重伤害等级为Ⅲ级,对可能造成人员重大伤亡及设施严重破坏的灾难性事故,应立即采取防范对策。     

永磁同步发电机PWM整流系统初步研究

针对传统发电机整流系统谐波含量大，功率因数低的特点，为永磁同步发电机设计了一套PWM整流系统，通过电流前馈解耦控制，实现有功无功解耦，实现发电机侧单位功率因数运行。实验结果验证了该控制方案的可行性，可有效减少发电机电流谐波含量，并能在发电频率较大范围变动时仍能保持系统稳定运行。     

西安市小学生行为问题及其影响因素调查分析

为了解儿童心理发育状况及其影响因素 ,应用 Achenbach′s儿童行为量表 ,测查了西安市 86 2名小学生。结果显示小学生行为问题检出率为 14.7%。多因素分析表明 ,影响小学生行为发育的因素主要有父母婚姻状况不佳、父亲健康状况差、不良的教育方式及不适当的期望等。提示小学生中存在的行为问题较为严重 ,在儿保及学校卫生工作中应重视加强精神卫生保健。