微波炉怎么加热食物

<正>要知道微波炉怎么加热食物,我们得先弄明白微波是什么。微波是一类波长1毫米～1米、频率300吉赫～300兆赫的电磁波,与无线电波、红外线、可见光、紫外线等都是电磁波"家族"的"成员"。微波具有直线传播、方向性强、频率高等特性。目前,它被广泛地应用于导航、卫星通信等诸多方面。     

微波技术在丝绸工业上的应用

七十年代初,微波技术在我国有了很大的发展,不论在军事,还是在工业、农业和医疗卫生等方面,都取得了显著的效果。微波技术在丝绸工业上也大有用武之地。微波,是波长在1毫米至30厘米之间的电磁波。其频率在300兆赫到300千兆赫范围内。它除了具有一般电磁波的共性之外,还有其独有的特性:遇到金属则反射,而遇到介质能穿透。由于介质分子极性本身的特     

利用物质的介质损耗系数进行微波检测

当微波照射在物质上,会呈现出穿透、反射和吸收三个特性.物质对微波的吸收程度主要由物质的介质损耗系数决定,物质吸收电磁波后会产生诸如发热等物理特性的变化,相应的电磁波能量就会衰减.通过检测这些物理变化,可以检测物质的存在以及含量,利用电磁波具有穿透特性可以实现无损检测.     

双基推进剂火箭排气羽流的微波衰减

本文从电磁波在火箭发动机排气羽流等离子体中的传输特性,分析了电磁波频率、羽流等离子体振荡频率和磁撞频率对电磁波衰减的影响。概略地论述了自由电子密度和碰撞频率的有关理论,分析了一些实验规律,指出了固体推进剂设计与降低电磁波衰减的关系,对研究微波衰减小的固体推进剂设计有一定参考意义。     

微波通信线路--科技进步的"催化剂"

收音机收到的声音，电视机屏幕上的图像，都是由电台、电视台通过电磁波送来的。电磁波有长波短波，而波长在1米至0.1毫米之间的电磁波，称为微波。使用微波进行的通信被称为微波通信。     

微波在无机材料热处理中的应用

微波是波长介于可见光与通讯波之间的电磁波。微波照射可以引起物质的发热而升温。其原理是电磁波耦合内部的极化因子并使之高频反转。文中归纳影响材料微波加热效应的材料相关因素有介电常数、损耗正切、耦合温度、材料密度等因素,列举了目前微波加热处理的关注领域,主要有微波合成、微波焊接、微波烧结等。其中,微波将在原子扩散、结晶相变和复合材料设计中发挥特殊的优势。     

波在周期磁化等离子体中的传播特性

电磁波与等离子体之间的相互作用是等离子体电子学和高功率微波器件研究的重点,加载等离子体可以大幅度提高微波器件的输出功率和效率。文章提出了一种新型介质周期结构即正弦周期磁化等离子体介质结构,通过采用广义反射理论和介质边界条件严格推导出电磁波在其中传播时的左旋圆极化波和右旋圆极化波的色散方程并进行了数值计算和分析,从而研究了电磁波在该介质结构中的传播特性。     

微波炉:炊用炉具的革命(1947)

1946年,斯潘瑟还是美国雷声公司的研究员。一个偶然的机会,他发现微波溶化了糖果。事实证明,微波辐射能引起食物内部的分子振动,从而产生热量。于是,雷声公司决定开发生产斯潘瑟设计的微波炉。顾名思义,微波炉就是用微波来煮饭烧菜的。微波是一种电磁波,这种电磁波的能量不仅比通常的无线电波大得多,而且还很有“个性”:微波一碰到金属就发生反射,所以金属根本没有办法吸收或传导它;微波可以穿过玻璃、陶瓷、塑料等绝缘材料,但不会消耗能量;而含有水分的食物,微波不但不能透过,其能量反而会被吸收掉。微波炉正是利用微波的这些特性制作的。…     

波在密度周期变化等离子体圆波导中的传播特性

电磁波与等离子体之间的相互作用是等离子体电子学和高功率微波器件研究的重点,加载等离子体可以大幅度提高微波器件的输出功率和效率.该文提出了一种加载密度周期变化等离子体圆波导的周期慢波结构,即加载密度轴向正弦变化等离子体圆波导的介质周期慢波结构,并研究了电磁波在该介质结构中的传播特性,根据严格的理论推导,得出电磁波在其中传播的色散方程并进行了数值计算和分析.     

休斯型耦合腔电磁色散特性研究

微波电子器件中填充等离子体是提高其输出功率和效率增加工作带宽的有效途径之一.利用电磁场分析理论模型,研究了行波管耦合腔高频慢波结构的色散特性,建立了填充等离子体耦合腔高频慢波结构的色散分析模型.研究表明,填充等离子体后高频慢波结构的色散行为发生了重大变化.首先是当电磁波频率高于等离子体频率时,色散频谱有一个微小的上移;其次是当电磁波频率低于等离子体频率时,发现了一种新的电磁波模式——混合模.工作在混合模的行波管具有更宽的带宽,可达到未填充等离子体时的带宽的一倍以上.混合模是体积模,电场在电子通道的对称轴附近最强,更有利于电子与微波之间能量的有效交换,易于实现大功率微波电子器件.     

地物温度波及其应用

根据热传导方程和热传导的付里叶定律,推导出地物温度波和热流密度波的表达式,提出一些修正因素,并讨论温度波在热红外遥感,气象学和建筑学中的应用。     

基于柱Kadomtsev-Petviashvili模型的海洋内孤立波非线性相互作用传播特征仿真模拟研究

在考虑到海洋内波的二维效应时,含有横向微扰的二维模型可以较好地模拟海洋内波的传播,因此为更好地描述海洋内波这一复杂非线性现象的传播特性,利用二维柱Kadomtsev-Petviashvili模型研究了海洋内波非线性相互作用的传播特征。首先,利用解析法获得该二维模型的双抛物线型孤子解,同时模拟研究了南海东沙群岛的海洋内波的弹性碰撞及随时间变化的传播特性;其次,基于不同的海域背景参数分析研究了上升型和下降型抛物线海洋内波弹性碰撞引起的海洋表层流速的变化。经比较分析,本文模拟结果与已有的遥感卫星图像较一致,因此可为进一步深入研究海洋内波的传播特性、动力学机制解及内波参数反演等提供一定的借鉴。     

Nonlinear dynamics, granular media and dynamic earthquake triggering

The 1992 magnitude 7.3 Landers earthquake triggered an exceptional number of additional earthquakes within California and as far north as Yellowstone and Montana. Since this observation, other large earthquakes have been shown to induce dynamic triggering at remote distances--for example, after the 1999 magnitude 7.1 Hector Mine and the 2002 magnitude 7.9 Denali earthquakes--and in the near-field as aftershocks. The physical origin of dynamic triggering, however, remains one of the least understood aspects of earthquake nucleation. The dynamic strain amplitudes from a large earthquake are exceedingly small once the waves have propagated more than several fault radii. For example, a strain wave amplitude of 10(-6) and wavelength 1 m corresponds to a displacement amplitude of about 10(-7) m. Here we show that the dynamic, elastic-nonlinear behaviour of fault gouge perturbed by a seismic wave may trigger earthquakes, even with such small strains. We base our hypothesis on recent laboratory dynamic experiments conducted in granular media, a fault gouge surrogate. From these we infer that, if the fault is weak, seismic waves cause the fault core modulus to decrease abruptly and weaken further. If the fault is already near failure, this process could therefore induce fault slip.     

Linear surface capillary-gravity short-crested waves on a current

One of the forward situations in the study of water waves is the basic three-dimensional surface wave motion of short-crested waves. Capillary waves result in rich effects concerned closely with remote sensing in the open ocean. Ocean currents experience a complete process in surface wave motion. Based on the above ideas, a linear dynamical system of surface capillary-gravity short-crested waves is developed by considering the current effects, thus leading to the following analytical expressions of the kinematic and dynamic variables： the wave height, the wave steepness, the phase velocity, the wave-particle velocities, accelerations and trajectories and the wave pressure. A number of the classical, typical and latest special wave cases can arise from these expressions.     

动物呼吸规律的遥测系统

本文报告一种动物呼吸规律遥测系统的研制和初步应用,该遥测系统包括具有电容传感器的发送装置,接收装置,数字显示和绘图仪,可测量多种动物的呼吸,并能用数字和波形的方式记录下来,借以观察和研究其规律,通过测定鱼类和蛇类呼吸规律的实验,表明该系统性能良好,结果令人满意。     

Triggering of earthquake aftershocks by dynamic stresses

It is thought that small 'static' stress changes due to permanent fault displacement can alter the likelihood of, or trigger, earthquakes on nearby faults. Many studies of triggering in the near-field, particularly of aftershocks, rely on these static changes as the triggering agent and consider them only in terms of equivalent changes in the applied load on the fault. Here we report a comparison of the aftershock pattern of the moment magnitude Mw = 7.3 Landers earthquake, not only with static stress changes but also with transient, oscillatory stress changes transmitted as seismic waves (that is, 'dynamic' stresses). Dynamic stresses do not permanently change the applied load and thus can trigger earthquakes only by altering the mechanical state or properties of the fault zone. These dynamically weakened faults may fail after the seismic waves have passed by, and might even cause earthquakes that would not otherwise have occurred. We find similar asymmetries in the aftershock and dynamic stress patterns, the latter being due to rupture propagation, whereas the static stress changes lack this asymmetry. Previous studies have shown that dynamic stresses can promote failure at remote distances, but here we show that they can also do so nearby.     

流体饱和度对Rayleigh波传播影响研究

基于三相孔隙弹性介质理论,本文推导出两种不相混的、黏性的、可压缩的流体饱和孔隙介质Rayleigh波控制方程解析解.该Rayleigh波沿着孔隙介质自由的、可渗透的表面传播.Rayleigh波频散方程解析表达式为三次多项式方程.求解频散方程的结果表明,该种介质存在三种类型的Rayleigh波（分别标记为R1,R2和R3）.在一定的频率范围内（1Hz-1 MHz）,本文数值研究了含水饱和度对三种Rayleigh波传播特性的影响.数值结果显示,孔隙介质的含水饱和程度对三种面波的传播速度和衰减有明显影响.三种面波在传播方向（x方向）和垂直于传播方向（z方向）上均存在振幅衰减.R1波传播速度最快,R3波居中,R2波最慢.R1波传播中衰减最小,R2和R3波次之,且R2和R3波随含水饱和度和频率的变化趋势基本相同.     

水面无人艇远程控制系统设计与实验

针对海上复杂环境对水面无人艇操纵性能的影响,在风、浪等环境因素干扰下研究基于模糊PID （proportional integral differential）的无人艇航向偏差控制,开发以DSP (digital signal processing) 结合ARM为核心控制器的艇载运动控制系统,采用阿里云服务器、Web服务器、Apache服务器及MySQL数据库,研发无人艇远程控制系统,并集成研发了样船。实验表明,所研发的无人艇远程控制系统具有远程通信、运动控制、状态监测、数据存储和数据共享的功能,能够满足远程通信实时性、运动控制灵活性精确性的设计要求,进一步提高对无人艇航迹控制精度,为近海小型智能船舶的研发奠定基础。     

卫星微波遥感中云层的影响

本文在微波频率1—300GHz(波长1mm一30cm)范围内,卫星微波遥感以陆地和海洋为背景,分析8种典型的云层情况,衡量各因子的作用,进行分析讨论。为卫星微波遥感中消除云层污染及微波遥感云层特性提供了数据。     

Remote triggering of deep earthquakes in the 2002 Tonga sequences

It is well established that an earthquake in the Earth's crust can trigger subsequent earthquakes, but such triggering has not been documented for deeper earthquakes. Models for shallow fault interactions suggest that static (permanent) stress changes can trigger nearby earthquakes, within a few fault lengths from the causative earthquake, whereas dynamic (transient) stresses carried by seismic waves may trigger earthquakes both nearby and at remote distances. Here we present a detailed analysis of the 19 August 2002 Tonga deep earthquake sequences and show evidence for both static and dynamic triggering. Seven minutes after a magnitude 7.6 earthquake occurred at a depth of 598 km, a magnitude 7.7 earthquake (664 km depth) occurred 300 km away, in a previously aseismic region. We found that nearby aftershocks of the first mainshock are preferentially located in regions where static stresses are predicted to have been enhanced by the mainshock. But the second mainshock and other triggered events are located at larger distances where static stress increases should be negligible, thus suggesting dynamic triggering. The origin times of the triggered events do not correspond to arrival times of the main seismic waves from the mainshocks and the dynamically triggered earthquakes frequently occur in aseismic regions below or adjacent to the seismic zone. We propose that these events are triggered by transient effects in regions near criticality, but where earthquakes have difficulty nucleating without external influences.