Structural design and experimental research of microwave radiation heater for asphalt pavements

In order to improve the efficiency of heating and the uniformity of temperature distribution in recycling asphalt mixtures, a pyramidal radiation heater is designed. The principles of designing horn surface size and antenna length are established according to the law of energy conservation and microwave antenna radiation theory. Modeling and simulation are carried out using IE3D software. The simulation results demonstrate that, with a fixed horn surface size, the shortened electric antenna length is the main factor leading to the improved heating uniformity. On the other hand, with a fixed antenna length and diminished surface size, the standing wave ratio decreases with the improved radiation efficiency. Furthermore, the efficiency of radiation drops with increased distance between the horn surface and the asphalt pavement. Microwave heating experiments are carried out using this type of heater. The temperature distribution of asphalt samples is obtained by the grid temperature measurement method, and Matlab simulation is performed. The experimental results are in good agreement with the simulation.

The Origin of Cosmic Microwave Background Radiation

This paper explains the Olbers paradox and the origin of cosmic microwave background radiation (CMBR) from the viewpoint of the quantum redshift effect. The derived formula dispels the Olbers paradox, confirming that the CMBR originates from the superposition of light radiated by stars in the whole universe, not the relic of the Big Bang. The dark-night sky and CMBR are all caused by Hubble redshift—the physical mechanism is the quantum redshift of the photon rather than cosmic expansion. So this theory supports the infinite and steady cosmology.

Establishment of injury models in studies of biological effects induced by microwave radiation

Microwave radiation has been widely used in various fields,such as communication,industry,medical treatment,and military applications.Microwave radiation may cause injuries to both the structures and functions of various organs,such as the brain,heart,reproductive organs,and endocrine organs,which endanger human health.Therefore,it is both theoretically and clinically important to conduct studies on the biological effects induced by microwave radiation.The successful establishment of injury models is of great importance to the reliability and reproducibility of these studies.In this article,we review the microwave exposure conditions,subjects used to establish injury models,the methods used for the assessment of the injuries,and the indicators implemented to evaluate the success of injury model establishment in studies on biological effects induced by microwave radiation.

A low-cost invasive microwave ablation antenna with a directional heating pattern

Microwave ablation(MWA) is a cancer treatment method. The tumor tissue absorbs electromagnetic energy, which heats and kills it. A microwave ablation antenna plays a critical role in this process. Its radiation field must completely cover the tumor but not the healthy tissue. At present, the radiation pattern of most invasive ablation antennas is spherical.However, in the clinic, the shape of some tumors may be asymmetrical or the antenna cannot be inserted into the center of the tumor for some other reason. In order to solve these problems, a directional heating antenna for microwave ablation is proposed in this paper. The proposed antenna, operating at 2.45 GHz, consists of a monopole and a reflector. The feed is given by a substrate integrated coaxial line(SICL) and coplanar waveguide(CPW). The omnidirectional radiation field of the monopole is reflected by a reflector that is extended from the outer conductors of the SICL to form a directional radiation field. The impedance matching network is designed on SICL to match the antenna to 50 Ω. The antenna is fabricated using a mature printed circuit board(PCB). The reflection coefficient of the antenna in porcine liver tissue measured by a vector network analyzer shows good agreement with the simulations. Then, an ablation experiment in porcine liver is conducted with power of 10 W for 10 min, and the experimental results confirm the validity of the design.

Heat transfer model for microwave hot in-place recycling of asphalt pavements

In order to solve for temperature fields in microwave heating for recycling asphalt mixtures, a two-dimensional heat transfer model for the asphalt mixtures within the heating range is built based on the theory of unsteady heat conduction. Four onedimensional heat transfer models are established for the asphalt mixtures outside the heating range, which are simplified into four half-infinite solids. The intensity of the radiation electric field is calculated through experiment by using heating water loads. It is suggested that the mathematical model of boundary conditions can be established in two ways, which are theoretical deduction and experimental reverse. The actual temperature field is achieved by fitting temperatures of different positions collected in the heating experiment. The simulant temperature field, which is solved with the Matlab PDE toolbox, is in good agreement with the actual temperature field. The results indicate that the proposed models have high precision and can be directly used to calculate the temperature distribution of asphalt pavements.

Microwave sintering effects on the microstructure and mechanical properties of Ti–51at%Ni shape memory alloys

Ti–51at%Ni shape memory alloys(SMAs) were successfully produced via a powder metallurgy and microwave sintering technique.The influence of sintering parameters on porosity reduction,microstructure,phase transformation temperatures,and mechanical properties were investigated by optical microscopy,field-emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),compression tests,and microhardness tests.Varying the microwave temperature and holding time was found to strongly affect the density of porosity,presence of precipitates,transformation temperatures,and mechanical properties.The lowest density and smallest pore size were observed in the Ti–51at%Ni samples sintered at 900°C for 5 min or at 900°C for 30 min.The predominant martensite phases of β2 and β19′ were observed in the microstructure of Ti–51at%Ni,and their existence varied in accordance with the sintering temperature and the holding time.In the DSC thermograms,multi-transformation peaks were observed during heating,whereas a single peak was observed during cooling;these peaks correspond to the presence of the β2,R,and β19′ phases.The maximum strength and strain among the Ti–51at%Ni SMAs were 1376 MPa and 29%,respectively,for the sample sintered at 900°C for 30 min because of this sample's minimal porosity.

Preparation of CaS:Eu^(2+) Phosphor by Microwave Heating Method and its Luminescence

This is the first report of using the microwave heating technique to synthesize calcium sulphide activated by europium whose structure is determined as the face-centered cubic by conventional X-ray powder diffraction method. The phosphor has maximum excitation peaks located at 280 urn and 560 urn and the maximum emission of the phosphor is 630 nm. When the concentration of Eu^(2+) in CaS increases from I .0 × 10^(-5) to l.0 × 10^(-2) mole per mole host, the body colour of the calcium sulphide activated with europium changes from white, through light-red to pink to deep-red. The phosphor obtains the longest afterglow at the concentration of 0.1% Eu^(2+)doped and is a kind of good material excited by sunlight.

Mechanism of Microwave Effects on Conductivity of Solution

The relation between microwave conductivity and normal conductivity of solution is compared in this thesis. By building mathematical model and theoretical analyses, it indicates that the relationship of in situ conductivity of solution in microwave field and temperature is similar to that in non-microwave field. It can be expressed by quadratic equation but the values of both conductivities are different. Microwave field has effect on the mean path δ or hot vibrational frequency ν of ions in solution. In microwave field, the mean energy barrier, which ions must surmount as they transit, is the function relation to temperature.

Incorporating metal nanoparticles in porous materials via selective heating effect using microwave

Metal nanoparticle@porous material composites have attracted increasing attention due to their excellent synergistic catalytic performance.However,it is a challenge to introduce metal nanoparticles into cavities of porous materials without agglomeration on the exterior.Despite the progress achieved,a universal approach that can integrate different kinds of metal nanoparticles and porous materials is still highly desirable.Here we report a facile and general approach to fabricating metal nanoparticle@porous materials by microwave-triggered selective heating.The microwave can pass through the non-polar solvent and act on the polar solvent in the porous materials,causing the polar solvent to be heated,vaporized,and away from the pores of porous materials.The local void produced by the escape of polar solvent facilitates non-polar solvent containing metallic precursor to be dragged into the narrow pores,followed by further reduction,resulting in the complete encapsulation of nanoparticles.A series of metal nanoparticles@porous materials,ranging from metal-organic frameworks(MOFs)to zeolites,are successfully prepared by this method and show excellent size selectivity in catalytic reactions.

Quinacrine pretreatment reduces microwave-induced neuronal damage by stabilizing the cell membrane

Quinacrine, widely used to treat parasitic diseases, binds to cell membranes. We previously found that quinacrine pretreatment reduced microwave radiation damage in rat hippocampal neurons, but the molecular mechanism remains poorly understood. Considering the thermal effects of microwave radiation and the protective effects of quinacrine on heat damage in cells, we hypothesized that quinacrine would prevent microwave radiation damage to cells in a mechanism associated with cell membrane stability. To test this, we used retinoic acid to induce PC12 cells to differentiate into neuron-like cells. We then pretreated the neurons with quinacrine （20 and 40 mM） and irradiated them with 50 mW/cm^2 microwaves for 3 or 6 hours. Flow cytometry, atomic force microscopy and western blot assays revealed that irradiated cells pretreated with quinacrine showed markedly less apoptosis, necrosis, and membrane damage, and greater expression of heat shock protein 70, than cells exposed to microwave irradiation alone. These results suggest that quinacrine stabilizes the neuronal membrane structure by upregulating the expression of heat shock protein 70, thus reducing neuronal injury caused by microwave radiation.

Analysis and FDTD Modeling of the Influences of Microwave Electromagnetic Waves on Human Biological Systems

The interactions of electromagnetic waves with the human body are complex and depend on several factors related to the characteristics of the incident wave, including its frequency, its intensity, the polarization of the tissue encountered, the geometry of the tissue and its electromagnetic properties. That’s to say, the dielectric permittivity, the conductivity and the type of coupling between the field and the exposed body. A biological system irradiated by an electromagnetic wave is traversed by induced currents of non-negligible density;the water molecules present in the biological tissues exposed to the electromagnetic field will begin to oscillate at the frequency of the incident wave, thus creating internal friction responsible for the heating of the irradiated tissues. This heating will be all the more important as the tissues are rich in water. This article presents the establishment from a mathematical and numerical analysis explaining the phenomena of interaction and consequences between electromagnetic waves and health. Since the total electric field in the biological system is unknown, that is why it can be determined by the Finite Difference Time Domain FDTD method to assess the electromagnetic power distribution in the biological system under study. For this purpose, the detailed on the mechanisms of interaction of microwave electromagnetic waves with the human body have been presented. Mathematical analysis using Maxwell’s equations as well as bio-heat equations is the basis of this study for a consistent result. Therefore, a thermal model of biological tissues based on an electrical analogy has been developed. By the principle of duality, an electrical model in the dielectric form of a multilayered human tissue was used in order to obtain a corresponding thermal model. This thermal model made it possible to evaluate the temperature profile of biological tissues during exposure to electromagnetic waves. The simulation results obtained from computer tools show that the temperature in the biological tissue is a linear function of the duration of exposure to microwave electromagnetic waves.

Modeling and Simulation of High Frequency Electromagnetics Wave Propagation on Vivaldi Antenna Using Finite Element Method

The simulation of the electromagnetic wave propagation plays an important role in predicting the performance of wireless transmission and communication systems. This research paper performs a numerical simulation using the finite element method (FEM) to study electromagnetic propagation through both conductive and dielectric media. The simulations are made using the COMSOL Multiphysics software which notably implements the finite element method. The microwave is produced by a Vivaldi antenna at the respective frequencies of 2.6 and 5 GHz and the propagation equation is formulated from Maxwell’s equations. The results obtained show that in the air, strong electric fields are observed in the slot and the micro-strip line for the two frequencies, they are even greater when the wave propagates in the glass and very weak for the copper. The 3D evolutions of the wave in air and glass present comparable values at equal frequencies, the curves being more regular in air (dielectric). The radiation patterns produced for air and glass are directional, with a large main lobe, which is narrower at 5 GHz. For copper, the wave propagation is quite uniform in space, and the radiation patterns show two main lobes with a much larger size at 2.6 GHz than at 5 GHz. The propagation medium would therefore influence the range of values of the gain of the antenna.

铁元素含量及含水状态对砂岩微波辐射升温损伤的影响

为研究砂岩的铁元素含量与含水状态对微波辐射升温损伤的影响规律,开展了砂岩试件微波辐射对比试验,试验分为12组,包含3种铁元素含量和4种含水状态(干燥、自然、浸水24 h与饱和)。试验采用X射线荧光光谱测量(XRF)技术检测试件表面铁元素含量,通过实时红外热成像监测表面升温过程,运用对比方法分析辐射前后P波波速与抗拉强度的关联特征。试验结果表明:(1)干燥状态下,砂岩试件升温过程均呈前期缓慢、中期活跃、后期稳定的趋势;铁元素含量越高,升温速率峰值就越高(2.66,2.40,1.66℃/s)、也就越早达峰(70,100,110 s);(2)干燥、自然、浸水24 h状态下,升温速率峰值平均值分别为:2.26,3.34,3.24℃/s,达峰时间分别为:90,70,20 s;饱和状态下,升温速率峰值为1.3℃/s,达峰时间为80 s;(3)含水状态对砂岩结构损伤的影响最为显著,饱和状态砂岩辐射180 s的损伤大于其他含水状态辐射300 s的损伤;铁元素含量直接影响岩石表面温度分布的均匀程度,铁元素含量越高,岩石表面温差越大;(4)相较于干燥和自然含水状态,浸水24 h和饱和状态下砂岩辐射后巴西劈裂初始压密阶段占比增加,起裂模式由端部起裂向中心起裂转变。研究成果可为类似原生和再生状态下微波辅助破岩效果的研究提供借鉴与参考。

微波辐射深井砂岩升温损伤特征与钻进效果对比研究

为了研究微波辐射深井砂岩升温损伤特征与钻进效果,采用恒源煤业标高-940 m回风辅助石门取芯的深井砂岩为研究对象,分析其深井砂岩在相同输入能量微波辐射后温度、质量、纵波波速及钻进实验后的机械钻平均转速、扭矩随不同路径处理下的变化规律。研究结果表明:在模拟试件单面辐射时,高功率短时间(1.4 kW,214 s)比低功率长时间(1.0 kW,300 s)微波辐射后质量变化、试件前侧后表面最高温度变化更大,且波速差值和损伤因子随试件表面温度升高而增大;微波辐射前后测量试件对应5个标记点位置处的纵波波速,发现波速差值和损伤因子较大的地方主要集中在试件表面升温最高的地方;在对比有无受限变形条件下钻进实验效果分析开展了A组微波未辐射、有受限变形(路径1),B组微波功率为1.0 kW、微波辐射时间为300 s、有受限变形(路径2),C组微波功率为1.0 kW、微波辐射时间为300 s、无受限变形(路径3),D组微波功率为1.4 kW、微波辐射时间为214 s、有受限变形(路径4)4种路径的处理方式,得到钻进效果从优到差的路径依次为:路径3>路径4>路径2>路径1;分析得到在相同输入能量有受限变形条件制约下,功率在1.4 kW微波辐射下钻进效率是功率在1.0 kW微波辐射下的1.3倍左右,而有受限变形条件制约下,微波辅助钻进法的效率是无微波辐射常规法的8.5倍左右,即有受限变形条件制约下机械钻进较为困难。研究成果为较弱吸波能力深井砂岩的损伤路径优化及低能耗高效率破岩提供了借鉴与参考。

天然气水合物储层微波加热能量补充装置设计

针对天然气水合物降压开采后期储层温度下降、产气速率下降、开采效率逐渐降低的问题,设计了储层微波加热能量补充装置,该装置能够对储层进行能量补充,提供水合物分解所需的温度和热量。通过建立储层微波能量补充仿真模型,研究了不同微波天线的结构参数对储层内平均电场强度的影响,优化了微波天线的结构参数;并针对优化后的结构参数,分析了不同微波参数下微波加热10 h后储层的升温效果。模拟结果表明:微波天线的最优结构参数为槽口形状为椭圆形槽口,槽口周期长度为187 mm,长轴为50 mm,短轴为11 mm,槽口角度为19°;微波频率为1.5 GHz、微波输入功率为3 kW时,微波加热10 h后水合物储层半径1 m范围内的平均温度为10.43℃,升高约5℃。所设计的微波加热能量补充装置能为水合物的分解提供驱动力。研究结果可使微波加热技术应用在水合物开采中,为天然气水合物的高效开发提供了一种新的方案。

混合小型化波导热疗天线设计

热疗天线由于体积较大,辐射的微波能量范围也较大,天线设计使用较为复杂,不适用于治疗体积较小的肿瘤。针对这一问题设计了一种小型化波导热疗天线来治疗小体积肿瘤,考虑到透热深度与天线体积的兼顾,选用了915 MHz的中心频率,使用混合小型化技术将天线小型化,即通过对天线加脊的同时加入短路探针将天线半径缩小到了19 mm,其高为36 mm。比吸收率仿真时馈入1 W的能量最高点能够达到45 W/kg,温度场仿真时馈入20 W能量加热30分钟后最热的区域温度可达45℃,体模实验结果与仿真实验相吻合,这些实验结果均表明其能够达到治疗乳房内部肿瘤的效果。

论回旋电子与涡旋电磁波量子:涡旋电磁波量子辐射

回旋电子辐射涡旋电磁波量子的理论模型是量子态涡旋电磁波技术的关键.本文为“论回旋电子与涡旋电磁波量子”的第二部分,建立“涡旋电磁波量子辐射”相关理论模型.电子通过能级跃迁能够辐射单个携带内禀OAM(Orbital Angular Momentum)的电磁波量子.为了给出这一辐射机理,推导了非相对论和相对论效应中电子在朗道能级的跃迁概率.由于非相对论效应中朗道能级与内禀OAM模态值的线性关系,电子无论以何种初始状态跃迁都只能辐射平面波量子.相对论效应情况正好相反,可以得到丰富内禀OAM模态值的电磁波量子.在实际工程上,可用特定回旋装置作为产生单个涡旋电磁波量子的辐射源;模态选择上,根据不同内禀OAM模态间具有频率差的特性,利用虹膜嵌入式波导滤波器进行频率筛选,同时选择出特定内禀OAM模态的电磁波量子.最后分析强调了量子态和统计态涡旋电磁波的差异,以及二者在无线传输应用时的优缺点.

高功率微波天线电磁仿真方法研究进展

高功率微波(high-power microwave,HPM)天线作为HPM系统与外界交互能量的通道,其对HPM系统的性能具有重要的影响。设计HPM天线时,受制于有限的测量手段和高昂的实验成本,难以通过实验方法对HPM天线性能进行分析。相较于实验方法,高效精确的电磁仿真方法是分析HPM天线性能最有效、最经济的研究手段。目前,HPM天线主流电磁仿真方法包括:全波仿真方法、高频渐近方法以及混合方法。本文对近年来HPM天线电磁仿真方法的新进展进行了介绍,总结了各种电磁仿真方法的优缺点,可为HPM天线性能仿真方法的选取提供思路。

X波段接收机强电磁脉冲的毁伤效应

为解决低轨道侦察卫星的侦察行动使战场丧失隐蔽性的问题,采用电磁脉冲攻击卫星接收机的毁伤方法,利用电磁仿真软件CST、电路仿真软件ADS对电子目标进行建模,进行电磁脉冲辐照模拟试验。结果表明,高功率微波发射源以30 GW的发射功率、70 dB的发射增益,在距离目标400 km处,可造成接收机设备部分器件损毁;若以30 GW的发射功率、90 dB的发射增益、在距离目标400 km处,可造成接收机设备完全损毁。结果验证了电磁脉冲武器攻击低轨道微小卫星接收机方案的可行性。

双级PIN限幅器的微波脉冲响应机理及规律

基于双级限幅器中两个PIN二极管的多物理场仿真模型与限幅器中其他电路元器件的SPICE模型,搭建了Si基双级PIN限幅器的场路协同仿真模型,利用这一模型对微波脉冲作用下限幅器中两级PIN二极管的温度响应特性进行了仿真.在此基础上对限幅器在不同频率、幅值微波脉冲信号作用下内部发生熔化现象所需的时间与能量进行了仿真,并对这一过程进行了机理分析与响应特性规律总结.仿真结果表明,当限幅器中第一级PIN二极管内部最高温度已达到材料熔点时,第二级PIN二极管的温度变化幅度较小.限幅器内部发生熔化现象所消耗的时间与能量随信号幅值、频率的变化呈现出规律性关系,发生熔化现象所需的时间随信号幅值或频率的提升而减小;发生熔化现象所需的能量随频率的提升而降低,随幅值的变化存在极大值点;限幅器的响应特性对信号参数表现出了不同的敏感性.