查询词典 HF

By sky or ground wave propagation, the detection range of the HF radars breaks through the limit of the curvature of the earth, which makes it possible for long-range air early-warning and target monitoring. At the same time the unique abilities in detecting low-detectable targets of the HF radars makes them powerful equipments for detection of hermit aircrafts, small airplanes in heavy land and sea clutters, and even intercontinental missiles.

借助于天波或地波传播方式，高频雷达的探测范围突破了地球曲率的限制，因此使远距离空中预警和目标监测成为可能，同时高频雷达所具有的独特和良好的对低可探测性目标的探测能力，使之成为探测隐形飞行器和处于强地杂波和海杂波背景中的小型军用飞机、巡航导弹等贴地、贴海飞行的小目标及洲际导弹进行有效探测的有力装备。

The stealth warplane for the microwave radar usually have complicated structures with the coating of wave absorption. On the base of calculation and modeling of the geometrical structure of the warplane in real size, the HF RCS of the air crafts under two different polarizations in different direction have been calculated with the FDTD. The result shows that the above mentioned stealth warplane have the obvious characterstics of frequency resonance, polarization and the relatively large RCS in HF Band 10-30dBm2, which can be used as the theoretical reference for selection of working frequency for sky wave OTH Radar and it also means that the sky wave OTH radar has good capability of anti-stealth targets quantitatively.

对微波雷达具有隐身作用的飞机，其形体较为复杂且表面涂敷有强吸波材料在对一种具有隐身几何外形结构实际尺寸飞机进行计算建模的基础上，文中采用FDTD技术得到了两种极化状态下该飞机无涂敷时不同方向上的短波雷达截面RCS值其结果显示了这种隐身几何外形飞机在短波波段有明显的频率谐振特性、极化特性和较大的RCS10-30dBm2，可为天波超视距雷达在选择工作频率时提供理论参考，并定量地说明天波超视距雷达具有较优的反隐身目标能力

At the beginning the dissertation introduced the new techniques and methods in modern HF communication, and then put emphasis on the introduction of ABCS, including its basic theories, main characters and advantages over traditional HF communication system.

论文首先介绍了现代短波通信中的新技术与新体制，然后重点介绍了陆建勋院士提出的ABCS通信系统，分析了ABCS的理论基础、主要特点及相对于传统短波通信体制的优势。

The posterior margin of hippocampal volumetry was defined by the plane which intersected the posterior commissure.

体积测量后界定在后连合，手工勾画出HF边缘获得面积，并依此获得HF体积。

A software HF channel simulator based on Watterson model was presented according to the characters of multipath, fading, Doppler frequency shift and Doppler frequency spread in HF channel.

对短波信道多径、衰落、多普勒频移及扩展等现象进行了分析，并且基于Watterson离散信道模型，设计了一种全软件的短波信道模拟器，为短波通信系统性能测试提供了条件。

Then the delay power profile of wideband HF model is sampled and added into the channel simulation and a dynamic software simulation of wideband HF channel is implemented using the tapped delay line structure of Watterson model.

并结合短波信道模型，提出了一种新的短波宽带信道软件动态仿真模拟方法。

In this context, we have reported recently that the volume of myocardial tissue occupied by perimysial and endomysial collagen was lower in hypertensive patients with HF and depressed ejection fraction, than in hypertensive patients with HF and preserved ejection fraction and normotensive subjects.56 Of interest, the interstitial and perivascular accumulation of collagen fibres was abnormally high in the two groups of patients.

在这种情况下，我们已经说了占用体积perimysial心肌组织人肌内膜胶原水平低的高血压患者用高频和沮丧的射血分数在高血压患者的心力衰竭和保存被罚出场分数与正常血压subjects.56舒张压的利息、间质和血管堆积过高的胶原纤维是在两组病人。

The result indicated that: the amount of the excess HF formed direct ratio to the yield of phosphorus pentafluoride and the optimum amount of the excess HF used is about 35%; the trickling rate of oleum shouldnt make the temperature of hexafluorophosphoric acid exceed 25 ℃ and the amount of oleum is 110% to 125% that of stoichiometry so that the content of phosphorus pentafluoride can be achieved 90%; the time and temperature of heating hexafluorophosphoric acid influenced both the yield and the content of phosphorus pentafluoride, and the optimum time should be about 30 minutes and the proper temperature was 148 to 153℃; when alcohol used asrefrigerant, the content of phosphorus pentafluoride was 94.03%, and the content can be up to 97.38%, provided that using liquid nitrogen as refrigerant.

通过实验发现，氟化氢用量与五氟化磷的产率成正比，最佳过量百分率宜在35％左右；发烟硫酸的滴加速度不能使中间产物温度大于25℃，发烟硫酸用量大于理论量10％～25％时，得到的五氟化磷纯度高于90％；六氟磷酸的加热温度对五氟化磷的产率和纯度均有影响，宜在148～153℃的范围内，加热时间应在30分钟左右；用工业酒精做冷凝介质得到的五氟化磷纯度最高只能到达94.03％，使用液氮做冷凝介质可以使五氟化磷的纯度达97.38％以上。

The technical routes and methods proposed in the thesis are not only theoretically meaningful but also are great valuable in HF communication coutermeasures. Some of the methods have been applied to a HF reconnoitering system and the result of the field is fairly well.

本文提出的技术路线和实现方法，不仅具有一定的理论意义，而且在短波通信对抗中也具有重大的应用价值，其中的部分算法已应用于某短波通信侦察系统中，取得了较好的效果。

In our experiments, the hafnium films were deposited on molybdenum substrates by radio frequency magnetron sputtering technology, and the barium oxide layers were prepared by the chemical method to simulate the grid structure of traveling wave tubes. Then, the surface phase and compositional change in the grid was studied under high temperature by annealing from 900K to BOOK, which can be used in explaining the suppression mechanism of hafnium film.

实验中，利用射频磁控溅射技术在Mo基底上制备了Hf膜，并利用化学方法制备了BaO涂层以模拟行波管栅极结构，随后在N_2保护下，通过在900K到1300K范围内退火，研究栅极处于高温工作环境下表面相结构和成分的变化，以此解释了Hf薄膜抑制栅极电子发射的工作机理。

She gently rebuff ed him, but agreed that they could be friends

她婉言拒绝了，但同意作为朋友相处。

If in the penal farm, you were sure to be criticized.

要是在劳改农场，你等着挨绳子吧！