缘成语-黄龙汤

arget back to the radar and enters the receiver via the same antenna as used for transmitting. 一个用于探测 100 或 200 英里以外的常规飞机的典型雷达可能采用 1～10 兆瓦的峰值功率, 数十微秒的脉宽,每秒几百周的脉冲重复频率.由发射机产生的(被)调制射频脉冲沿传输 线送到天线,在那里被辐射到空中.通常发射和接收使用同一天线.在发射时一个被称为收 发开关的快速开关将接收机断开.如果不把接收机断开,或者发射机功率过大,接收机就可 能被损坏.当发射信号通过后,收发开关重新将接收机与天线接通.随后辐射功率的一部分 被目标反射回到雷达,通过发射时用的同一天线进入接收机. 2. Bear in mind that the design is aimed at a signal with a prescribed time domain amplitude envelope to meet the maximum power delivery requirement, and a prescribed frequency domain spectral magnitude to achieve a desirable time resolution and sidelobe levels at the receiver. However, the time domain and frequency domain requirements cannot be satisfied simultaneously. A signal formed in the time domain with |s(t)| = B[f(t)] perfectly conforms with the maximum input voltage constraints, but has ripples in its spectrum, violating the frequency domain requirement. This is similar, but not analogous, to the spectral ripples in the Fourier transform of a truncated time domain function. 记住, (我们的)目标是设计这样一个信号,它既具有指定的时域幅度包络以满足最大输出功 率的要求,又有指定的频谱幅度函数以在接受端达到所要求的时间分辨率.然而时域和频域 的要求不可能同时满足.在时域中按|s(t)| = B[f(t)]形成的信号能严格满足最大输入电压的约束 条件,但其频谱中却存在纹波,因而不满足频域的要求.这和一段截断的时域函数 Fourier 变 换中的纹波相似,但二者并不能类比. 3. Communication may be broadly defined as the transfer of information from one point to another. When the information is to be conveyed over any distance a communication system is usually required. Within a communication system the information transfer is frequently achieved by superimposing or modulating the information on to an electromagnetic wave which acts as a carrier for the information signal. This modulated carrier is then transmitted to the required destination where it is received and the original information signal is obtained by demodulation. Sophisticated techniques have been developed for this process by using electromagnetic carrier waves operating at radio frequencies as well as microwave and millimeter wave frequencies. However, communication may also be achieved by using an electromagnetic carrier that is selected from the optical range of frequencies. 通信可以广义地定义为从一处到另一处的信息传递.当要将信息传输到任何距离以外时就需 要有一个通信系统.在通信系
统内部,信息的传输经常通过将信息叠加或调制到作为信号载 体的电磁波上来实现.经调制的载波然后被传送到要求的目的地,在那里被接收,原始信号
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《信息与通信工程专业科技英语》
通过解调被恢复出来.为了实现这一过程,已经利用工作在射频,微波以及毫米波频率上的 电磁载波开发了复杂的技术.不过通信也可以用光波频段上的电磁载波来实现. 4. During an experiment in December 1947, two closely spaced gold-wire probes were pressed into the surface of a germanium crystal. It was found that the voltage output at the collector probe with respect to the base was greater than the input to the emitter probe. It was immediately recognized that this was the effect to be looked for; and the solid-state amplifier was born. These first transistors, however, were very noisy and unreliable due to the metallic point contacts. The junction transistor based on diffusion instead of current conduction was then proposed. 在 1947 年 12 月的一次实验中,两个十分接近的金丝探针被压入一片锗晶体表面.人们发现 在集电极探针上相对于基片的输出电压大于加在发射极上的输入电压,立刻意识到这正是要 寻求的效应.固体放大器就此诞生了.但由于金属接点的关系,第一批的这些晶体管噪声很 大,也不可靠.随后就提出了基于扩散而不是导电的结型晶体管. 5. Digital image processing encompasses a wide variety of techniques and mathematical tools. They have all been developed for use in one or the other of the two basic activities that constitute digital image processing, image enhancement, and image analysis. Image enhancement accepts a digital image as input and produces an enhanced image as output; in this context enhanced means better in some respect. This includes increasing or decreasing the contrast, removing or introducing geometric distortion, edge sharpening or smoothing, or altering the image in some respect that facilitates the interpretation of its information content. Image analysis, on the other hand, accepts digital images as input but as output produces a report of some type. It may be a simple count of the number of triangles in the format or a complex report that assigns each pixel to a land cover category and a tabular list of the aggregate acreage of each land cover category in each census tract in the image. 数字图象处理包括了多种多样的技术和数学工具,这些工具都是为构成数字图象处理的图象 增强和图象分析这两个基本领域之一而发展起来的.图象增强接受一幅数字图象作为输入, 并产生一个增强了的图象作为输出.就此而论,增强意味着在某些方面更好.这包括增加或 降低对比度,去处或引入几何变形,锐化或平滑边缘,或在某些方面改变图象以便于对其信 息内容的解释.另一方面,图象分析则将数字图象
作为输入而产生某种类型的报告作为输出. 这可以是对具有三角形形式的(对象的)简单计数,也可以是将各像素赋予某一地面覆盖种 类的复杂报告,以及图象中各调查区地面覆盖种类累计面积的列表.
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瞠目结舌读音-青衿

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这的成语-折戟读音

上谓侍臣曰-大难不死

锋面雨-赤岭

弹指一挥间下一句-允文允武

爬山虎的特点-音韵的意思

皐月-叹息的意思