差频

The first disadvantage of MMI device is wavelength sensitive, which leads to restricted applications. To reduce the wavelength insensitivity in optical network applications, the demand of light source with a specific wavelength is needed, especially for power splitters. For this reason, a wideband criterion for MMI splitter is proposed. The basic principle is based on reducing the interference length difference and making it shorter than the spot size for constructive mode interference. Simulation results show the spectra of proposed MMI splitter is wide enough (1.26-1.61um) to cover the fiber communication band and the size of the splitter is more compact than that of the conventional MMI or Y-branch splitter.

多模干涉元件的第一个缺点为波长敏感，此缺点会限制其在实际上的用途；因元件在网路上的应用时，通常都需要降低波长敏感性，以减低对光源波长准确性的要求；有鉴於此，本论文提出多模干涉分光器的宽频标准；基本原理是建立在缩短其多模干涉区的长度差，并使之小於建设性干涉的光点大小；透过模拟后发现，操作频宽可涵盖光纤通信全波段(1.26-1.61um)，且长度小於Y形分支结构的分光器。

The variance of Gaussian distribution is the sum of the variance of the spread spectrum signal and the variance of the noise, so if it; is estimated, it can be used as the threshold in designing the interference suppression filter.

由于高斯分布的方差即为直扩信号和高斯白噪声方差之和，因此估计出变换域数据的方差，将为频域抑制滤波器的门限设置提供参考。

To improve the simulation accuracy and to make the increment of computation amount the smallest, the quantitative comparison was used to compare the effect of incident direction and difference accuracy on numerical dispersion with the changing of the ratio of horizontal and vertical gird. The results show that the rectangular grid is better than square mesh in suppressing dispersion and can avoid the low computational efficiency caused by high-order difference.

为提高模拟精度，同时又尽可能减少计算量，采用定量分析的方法，对比分析了横纵网格比变化时入射方向和差分精度等因素对数值频散的影响，分析结果表明，矩形网格较之正方形网格能更好地压制频散，同时可以避免高阶差分导致的低计算效率。

This system uses the deuterium lamp as its blazed lamp-house, and makes mechanical turnplate in use of modulating light signal with two frequencies, which is drived by in-phase electromotor with constant velocity. A potomultiplier tube is used to conversion optical signal to electric signal. Using Lock-In Amplifiers to realize magnifying the metrical signal using difference method with two different frequencies. We also analyze its principle of each part of the apparatus and design the realization circuits of each part. The data analysis and the in-phase electromotor control circuits are fulfilled by SCM; the single chip control systems hardware interface and software design are given.

该系统的光路部分使用氘灯作为激发光源，用同步电机恒速驱动的机械盘调制出双频光信号，利用一个光电倍增管进行光电信号转换；信号处理部分采用锁相放大器实现信号双频差分处理，分析了其各组成部分的原理，设计了各部分的具体实现电路；使用单片机进行数据差分处理和电机控制，给出了单片机控制处理系统的硬件接口电路和软件设计。

Corona discharge or midfrequency frenguency high-voltage, high-voltage discharge for processing to the plastic surface to surface activation, polyporous, hnproving plastic film on ink adhesion, improve film business card printing and membership card making suitable to their needs.

电晕充电拔取矮频矮压或洋频矮压充电，差塑料暗不天举行办理，使其暗不天活冻，呈多孔性，以调矮塑料薄膜暗不天差油不朱的黏附辛，恶冻薄膜的制卡和会员卡制作适性。

Through Hilbert transform, a signal's plane trace can be get. There are two frequencies in the tested signal, so the signal's plane trace may be looked as the track of the out pole's end when two poles rotate around parallel axles. Using the knowledge of motion synthesis in theory mechanics, a formula to describing the change of plane trace's step length and angle for two-frequency be get. So we may prolongate the tested signal's plane trace from the echo's initial arriving moment, and get a certain length of the signal's prolongation.

通过Hilbert变换可得到测试信号的平面迹线，测试信号中只含有两个频率成分，视为双频信号，双频信号的平面迹线相当于两连杆绕平行轴转动时外杆杆端迹线，利用理论力学中运动合成和瞬心知识，推导出双频信号平面迹线步长平方满足余弦线性复合函数，而迹线转角可视为线性变化，据此可对回波到来之前的测试信号平面迹线作延长，得到一定长度的信号延展段，信号延展段与实测段作差可得到一次、二次回波的第一个波峰值。

Building Products: fan coil digital LCD temperature controller, mechanical temperature control panel, electronic temperature control switch, three-speed switch, fan-coil electric two-way valve (three-way valve) and matching drives, proportional-integral regulation of electric valves, electric actuators, pressure side of the control-way valve, temperature and humidity sensors, electrical valve drive, pressure controllers, pressure sensors, pressure switches, gas flow switches, liquid flow switches, network control unit and related software, direct digital controller, communication modules, expansion modules, such as air-conditioning control products, inverter device control products; with Honeywell,×é, Siemens AG, Johnson, etc. from multiple vendors and agents set up a good relationship of cooperation; Security Equipment: Card, canteen consumption machine, access control systems, attendance punch card machines, parking, smart key counters, video intercom doorbell, hotel lock, the types of RF cards, shaped cards, business card printing produced; network equipment: routers, switches, group telephone, wire and cable materials such as sales; with CISCO, Huawei-3COM,, INTEL, D-LINK, Paul, NEC, SAMSUNG multiple vendors, such as set up a good relationship of cooperation, to become special agents; company by selling products ranging from consulting, purchasing, installation, after-sale tracking security services; company to "innovative, pragmatic, enterprising" as the forward power enterprises; always adhering to the "to perfection ---- Switch TO Perfection" design philosophy, the "customer first" as our business purpose.

楼宇设备产品：风机盘管液晶数显温控器、机械式温控面板、电子温控开关、三速开关、风机盘管电动二通阀及配套驱动器、比例积分调节电动阀、电动执行器、压差旁控制通阀、温湿度传感器、电动风阀驱动器、压力控制器、压差传感器、压差开关、气体流量开关、液体流量开关、网络控制单元及相关软件、直接数字控制器、通讯模块、扩展模块等空调控制产品、变频器设备控制产品；与霍尼韦尔、卓灵、西门子、江森等多家厂商及代理商建立了良好的合作关系；安防设备：一卡通、食堂消费机、门禁系统、打卡考勤机、停车场、智能钥匙柜、可视对讲门铃、酒店锁、各种射频卡、异型卡、证卡制作印刷业务；网络设备：路由器、交换机、集团电话、电线电缆等材料的销售；与CISCO、华为3COM、、INTEL、D-LINK、国威、NEC、SAMSUNG等多家厂商建立了良好的合作关系，成为特约代理商；公司对所销售产品提供从咨询、选购、安装、售后的全程跟踪保障服务；公司以&创新、求实、进取&作为企业的前进动力；始终秉承&至臻完美----Switch TO Perfection&的设计理念，把&用户至上&作为我们的经营宗旨。

To investigate the detecting capability of GPR in the dispersive medium, we propose a Finite Difference Time Domain method to solve Maxwells equations. We give an iterative method for calculation of the electrical displacement and magnetic fields in the Debye medium, and a method to compute the electric field from electrical displacement.

为了研究地质雷达在频散介质中的探测能力，提出了频散介质中时间域有限差分法计算麦克斯韦方程的方法，给出了满足Debye关系的频散介质中的电位移和磁场的迭代算法，以及由电位移计算电场的算法。

In terms of code and phase observables and their observational equations, code multipath observation is derived and discussed.

其中伪距观测值中的多路径效应的分析又分为单频接收机和双频接收机两种情况进行了讨论；而相位观测值中的多路径效应的相关分析是利用相对定位的平差残差进行的。

Based on the research of the Zeeman effect of 633 nm He-Ne laser, we have observed and measured the beat frequency tuning curve of 543nm He-Ne laser under different magnetic field orientations and intensities.

参照633nmHe－Ne激光器的塞曼效应，对543nm He－Ne激光器在不同方向和强度磁场下的拍频调谐特性进行了观测，发现在横向磁场作用下激光器的频差过低而且调谐曲线不规则，而纵向磁场下的调谐曲线较好，所以决定采用纵向塞曼激光器进行稳频。

I am sure after a few weeks of adaptation and familiarization I will have no difficulty in functioning on a daily basis in an English speaking society or in participating fully in graduate studies.

在大学的三年的学习生活不仅给予我自身的充实，更重要的是磨练和培养了我较强的自觉能力和严谨，踏实的作风以及不怕困难的精神，对未来充满了信心！

As the first volcanoes erupted, one of the gases that bellowed out was steam.

在第一批火山喷发时，喷出的气体之一就是水蒸汽。