查询词典 alternating current

Conversion of alternating to unidirectional current.

直流电和交流电同步转换的机器。

To solve the problem of interference between main arc and pilot arc and improve the stability of main arc, all possible ways such as adopting noncontinuous or alternating pilot arc or making main arc and pilot arc have different current passages and detailed measures are proposed.

论述了等离子弧焊中维弧的存在形式及其对主弧的稳定机理，提出了解决主、维弧相互干涉的各种可能途径如采用断续维弧、交流维弧或使主、维弧具有不同通道及从维弧形态等方面提高主弧稳定性的具体措施。

At first, this paper gives the brief introduction of the history and present status of accelerometer and its testing technology, the working principium and math model of the liquid floated pendu-lous accelerometer, and then, decides the binary width pulse force retrim loop as the design proposal of testing system, researches the transfer function of every part in the system emphasizly, analyses the stability of the whole accelerometer testing system from the angle of control theoretics by the open loop transfer function of system, and designed the correcting net, analyses the basal problems such as resolution, sampling restraint, precision and so on, designs the hardware testing circuits such as preamplification, band-pass filter, alternating amplifier, phase sensitive demodulatorn, pulse-width modulation, frequency scale circuit, moment current generator. Finally, using the graphics program language LabV-IEW which is designed for testing field especially by NI accomplishes the solfware design of testing system,realized the testing functions.

首先对加速度计及其测试技术的发展历史和现状，液浮摆式加速度计的工作原理和数学模型等作了简要的介绍，然后确定了以二元调宽脉冲再平衡测试回路为设计方案，并从控制理论的角度进行了分析，着重研究了系统中各部分的传递函数，利用系统开环传递函数分析了系统的稳定性，同时设计了系统的校正网络；分析了二元调宽脉冲再平衡测试回路的分辨率、采样约束以及测试精度等基本问题，并按照系统分析的结果设计了包括前置放大、带通滤波、交流放大、相敏解调、脉宽调制、频标电路以及力矩电流发生器等测试系统各部分硬件电路，验证了电路的正确性，最后按照测试系统的要求，采用了美国NI公司专为测试领域所开发的虚拟仪器工具——LabVIEW作为测试软件开发工具，利用该图形化编程语言完成了测试系统软件部分的设计，实现了测试功能。

The current densityin a wire carrying alternating currentis not uniformover the cross sectionof the wire but is greater near the surface, a phenomenon known as skin effect

集肤效应。载有交流电的导线中的电流密度，在导线的横截面上并不是均匀分布的，而是在表面附近比较大，这一现象成为集肤效应。

Electricity of a current flowing in one direction only; not alternating .

只沿着一个方向的电流；没有交替。

Simultaneously, the exports of ionization rate and nonionzed concentration are set up as a powerful tool for studying thoroughly the freeze-out effect. dN〓/dp and dN〓/dn are neglected in the linearized equation system of the iteration methods of Newton and Gummel, due to having lower 15 orders or more than dN〓/dn and dN〓/dp, thus the computing effort is cut down with no effect on precision. A new cut-off technique is adopted to accelerate the convergence speed, about twice reduced for Newton iteration method and six times or so for Gummel iteration method. The approximate formulae of Fermi-Dirac statistics are also put forward with simpler form and higher precision. 3. A term dependent on time is added to the electron and hole current succession equations respectively. It is only this model that conservation of charge in transient analysis and alternating small-signal analysis at low temperature can be kept by. 4. The performance of SE-PISCES is explained by the simulation example of PISCES-2B, diode.

研究了低温半导体器件模拟的数值方法：对载流子浓度进行了新的归一化；编制了不考虑掺杂所引进的内建电场时的电离率计算程序；由于低温杂质电离率随偏压状态而变化，为此编制了每次求解迭代时的电离浓度计算程序，并将其插入到求解迭代程序中；同时，设置了杂质电离率和未电离杂质浓度的出口点，为更深入地研究冻析效应提供了有力工具；在Newton迭代法和Gummel迭代法的线性化方程组中忽略了dN〓/dp、dN〓/dn，是因为它们比dN〓/dn、dN〓/dp低15个数量级以上，这样减小了计算量又不影响模拟精度；对Newton迭代法和Gummel迭代法采取了新的截断技术，提高了收敛速度，Newton法迭代法和两次左右，Gummel法减少六次左右；给出了表达式更简单而精度更高的Fermi-Dirac积分近似计算公式。

Also, we select the signal collecting circuit of three output polars, the coupling circuit using capacitance and resistance, the alternating amplify processing circuit, the positive feedback retardation comparsion, the driving circuit of output current and the stabilization voltage supply circuit.

选择了InSb磁阻三端输出型信号采集电路，阻容耦合型交流放大电路，正反馈迟滞型电压比较器和大电流推挽驱动电路及稳压电源电路。

The specimen is placed in a space with nulled field (such as produced with Helmholz coils) and then subjected to an alternating magnetic field which is then reduced gradually to zero by decreasing the current of the field coil or by pulling the specimen from the coil.

样品放置在一个零磁场(如亥姆霍兹线圈产生的场)作用空间内，然后作用以交变磁场，该交变磁场通过减少激励线圈或将样品从线圈中逐渐抽出使得场强逐渐减小至零。

It is considered that fatigue crack is early produced on drill pipes, because the vibration load of drilling tools in air drilling is more severe than that in mud drilling. Fatigue cracks easily occur under alternating vibration. Because the current wellhead detecting instruments can not be used to reflect the change of pump pressure produced after drill pipe piercement timely and accurately, effective measures can not be taken in time to prevent the expansion of fatigue cracks. As a result, drill pipe fracture accidents occur.

失效分析表明，钻杆属于早期疲劳断裂，断裂主要原因是在空气钻井过程中钻具受到的震动载荷远大于钻井液钻井过程中的震动载荷，在交变的震动载荷作用下，钻具容易产生疲劳裂纹；由于现有的井口检测仪表不能精确及时反映钻杆刺穿之后产生的泵压变化，无法及时采取预防措施，疲劳裂纹不断扩展，最终导致了钻杆断裂失效。

It is considered that fatigue crack is early produced on drill pipes, because the vibration load of drilling tools in air drilling is more severe than in mud drilling. Fatigue cracks easily occur under alternating vibration. Because the current wellhead detecting instruments can not be used to reflect the change of pump pressure produced after drill pipe piercement timely and accurately, effective measures can not be taken in time to prevent the expansion of fatigue cracks. As a result, drill pipe fracture accidents occur.

失效分析表明，钻杆属于早期疲劳断裂，断裂主要原因是在空气钻井过程中钻具受到的震动载荷远大于钻井液钻井过程中的震动载荷，在交变的震动载荷作用下，钻具容易产生疲劳裂纹；由于现有的井口检测仪表不能精确及时反映钻杆刺穿之后产生的泵压变化，无法及时采取预防措施，疲劳裂纹不断扩展，最终导致了钻杆断裂失效。

On the other hand, the more important thing is because the urban housing is a kind of heterogeneity products.

另一方面，更重要的是由于城市住房是一种异质性产品。

Climate histogram is the fall that collects place measure calm value, cent serves as cross axle for a few equal interval, the area that the frequency that the value appears according to place is accumulated and becomes will be determined inside each interval, discharge the graph that rise with post, also be called histogram.

气候直方图是将所收集的降水量测定值，分为几个相等的区间作为横轴，并将各区间内所测定值依所出现的次数累积而成的面积，用柱子排起来的图形，也叫做柱状图。