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It concluded DC-DC convector and grid-connected inverter.

该系统主要包括DC-DC变换及并网逆变电路。。

Firstly, chaotic kinetic characteristic of Kent mapping is analyzed, using it to encrypt watermark image; Secondly, an algorithm of only modifying the decimal part of DC components is given, bringing the least error, effectively solving the problem which embedding watermark in DC components is easy to the image's block effect; Watermark is extracted without original image utilizing two-bits algorithm.

深入分析了帐篷映射的混沌动力学特性，并将其应用于水印图像的预处理；在分析了 DCT域嵌入对策的基础上提出了一种只修改 DC 分量小数部分的嵌入算法，引入的误差小，有效的解决了以往人们在 DC 分量嵌入水印容易引起图像块效应的问题；检测过程中利用二值离散算法使得水印提取时无需原始图像。

There are two main disadvantages in the present differential algebra equation model used in AC/DC system: one is that 'dimensional calamity' can occur with the increment of DC transmission lines

目前普遍使用的AC/DC系统的微分代数模型主要存在2大缺陷：①随着直流线路的增加可能出现"维数灾难"问题

The circuit topology of the differential Forward DC-DC converter mode inverter with high frequency link was proposed. Circuit topology, transient voltage control strategy, steady principle characteristic and design criteria for the key circuit parameters were deeply investigated.

提出差动正激直流变换器型高频环节逆变器电路拓扑，并对该变换器的电路拓扑、瞬时电压控制策略、稳态原理特性、关键电路参数设计准则等进行了深入地分析研究。

According to the demand of high magnetic field power supply, reference is increased with a set ramp rate and stops at a set stable value, so reference system is composed of digital setting and digit to analog converting circuit. But the stability of reference is mostly guaranteed by the performance of D/A circuit, so D/A circuit is particularly studied in reference system. The scheme of D/A circuit, the selection of DAC and its voltage reference, hardware anti-jamming design and PCB design are discussed in detail, and software of remote control and PLC are discussed in brief. Zero-flux DC current transformer well satisfies the demands of the high stability of Load current detection unit, so the principle of zero-flux DC current transformer is analyzed; in the mean time a project which detects the long term stability is designed. During 8 hours, analog signal which is detected with high precision digit multimeter is recorded in computer at 1HZ frequency by GPIB communication. The drift error source and related parameters are explained in the compare-amplify part. Detailed subtraction circuit is designed; also amplifier chip and periphery components are selected and verified according to the theory of error analysis.

根据强磁场电源的需求，参考源应按照软件设定的斜率逐渐上升到设定稳态值，则参考源系统应由数字给定和数模转换电路两大部分组成，而参考源的稳定度主要依靠完成数模转换功能的模拟电路的性能来保证，因此本文对参考源系统的研究以数模转换电路为重点，分别从电路方案的确定、数模转换芯片及其基准电压源的选取和验证、电路板硬件抗干扰和PCB设计几方面进行了论述，然后对数字给定部分的远控组态和PLC程序设计作了简要介绍；采用零磁通原理的直流电流转换器很好地满足了对负载电流检测单元高稳定度的需求，本文详细分析了零磁通检测的原理，并在选定此种类型电流转换器的基础上设计了一套检测长期稳定度的方案，8小时内以1秒为采样周期，通过计算机Labview程序和高精度数字电压表的GPIB通讯，将被高精度数字电压表数字化后的模拟信号采样值连续记录至计算机中；比较放大环节简要阐述了漂移产生的原因和相关参数指标，确定了具体的减法电路形式，并根据误差分析理论对运算放大器和外围元器件进行了选取和验证。

A DC motor driver with constant frequency PWM is developed based on PIC, and the running performance of the DC motor is improved greatly.

另外使用PIC器件完成了单芯片集成式运行电路的设计，实现了直流电机的正常驱动，简化了控制逻辑系统。

Duality principle ; DC DC converter ; directed topological graph

对偶原理；直流；直流变换器；有向拓扑图。

The Non-perfect Elastic Collision DC model in half space is presented, considering the influence of participating soil mass and the interaction of tamper and ground during DC. Series solutions of displacement, velocity, acceleration and impact stress are obtained.

通过与边界元法、Laplace—Hankel联合反变换法的计算结果，以及山西某湿陷性黄土地基和南京某填土地基工程中的实测数据的验证和对比表明，该模型是符合实际的，它可用于分析强夯规律，计算冲击应力，解释强夯加固机理和工程中的现象，便于工程应用，而且比其他方法简单易行。

It is extensively used for different occasions that require DC power supply, including electrolytic chemistry, transmission, traction, electrostatic precipitation, electroplating and DC transmission etc.

整流变压器是指把电力网的三相正弦交流电压变换为所需要的交流整流电源的电压和相数的电源变压器，它广泛应用于点解化学、传动、牵引、静电除尘、电镀、直流输电等需要提供直流电源的场合。

This paper discusses a method, which can be used to approximately calculate the equivalent resistance and to approximately calculate the efficiency of different topologies. It could benefit a lot in designing DC-DC converters.

本文提出了一种近似计算等效电阻的方法，其原理是将变换器中各元件的损耗之和等效为输出电阻的损耗，可以简便计算变换器的效率，有助于选择合适的电路。

For I will re-establish my covenant with you, that you may know that I am the LORD

我要与你重订盟约，你要承认我是上主

Results The artery frequency spectrum of high speed and low resistance were found in malignant trophoblastic tumors. The ulterine muscular layer in malignant trophoblastic tumor was hypervascular and the resistive index was less than 0.4. After chemotherapy, the hypervascularity decreased, RI increased higher, and β-HCG returned normal.

结果 恶性滋养细胞肿瘤子宫动脉RI值较低，为高速低阻力性动脉频谱；恶性滋养细胞肿瘤宫壁血流异常丰富，子宫肌层病灶内血管阻力指数RI.4；恶性滋养细胞肿瘤患者全身化疗取得疗效后子宫肌层血流丰富区逐渐缩小，RI呈逐渐升高趋势，血β-HCG逐渐恢复正常。