Improved Algorithm for Efficient Extraction of Relaxation Parameter Values from Wideband Permittivity of Baijiu

The complex permittivity of baijiu varies with frequency,and dielectric spectroscopy has been used to evaluate the quality.To simplify the analysis and reduce the number of the parameters,a dielectric relaxation model is often used to fit the permittivity data.However,existing fitting methods such as the least squares and particle swarm optimization methods are often computationally complex and require preset initial values.Therefore,a simpler calculation method of the relaxation parameters considering the geometric characteristics of the permittivity spectrum is proposed.It is based on the relationship between the Cole-Cole relaxation parameters and the Cole-Cole diagram,which is fitted by a geometric method.First,the concepts of the Cole-Cole parameters and the diagram are introduced,and then the process of obtaining the parameters from the complex permittivity measurement data is explained.Taking baijiu with 56%alcohol by volume(ABV)as an example,the fitting is better than the least squares method and similar to the particle swarm optimization.This method is then used for the parameter fitting of baijiu with ABV of 42-52%,and the average error is less than 1%,demonstrating its wider applicability.Finally,a prediction model is used for baijiu with 53%ABV,and the error is only 1.51%.Hence,the method can be applied to the measurement of ABV of baijiu.

Relative Dielectric Permittivity Variations during Compaction as a Mean of Compaction Quality Control: Case Study on Laterite Samples from Senegal

This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.

平板介质的微波分裂腔法介电常数测试技术

为实现微波频段平板类介质材料的介电常数的无损测试,研究了分裂式圆柱形谐振腔测试方法。介绍了分裂式圆柱形谐振腔的电磁场分析理论,采用模式匹配技术实现了介质加载条件下腔内电磁场分布的精确求解,得到了腔体谐振频率与材料介电常数之间的准确关系。在理论分析的基础上,制作了空腔谐振频率为10 GHz的分裂式谐振腔,并与前期研制的闭式谐振腔进行对比测试,介电常数实部测量结果相对误差小于1%。与国外同类产品进行对比测试,介电常数实部结果基本一致,损耗角正切测量结果更接近于文献参考值。因此,微波分裂腔法能够实现平板介质板材的无损测量,具有准确度高,使用方便等突出优势,可在微波频段内实现介电常数为1~20,损耗角正切为1×10-3~1×10-5,板材厚度为0.1~2.0 mm的各类平板介质材料介电常数的准确测试。

利用探地雷达测定东北黑土层厚度在坡面的空间变化

准确掌握黑土层厚度分布信息对于黑土资源评价和保护具有重要意义。然而,传统土层厚度测定方法包括土壤剖面法、插钎法和钻孔法等对于大范围的土壤厚度测定效率较低且连续性较差。本研究利用探地雷达探测了东北黑土区直型、凸型和凹型3种坡型坡面的黑土层厚度。室内模拟试验对黑土及黄土母质土壤分别设置不同的容重和含水量,探究土壤含水量和容重对土壤介电常数的影响以及探地雷达测定黑土厚度的可行性。野外试验通过开挖剖面和预埋标识物,验证了探地雷达测量黑土厚度的准确性。结果表明:土壤介电常数随容重的增大而增大,随土壤含水量的增加而减小;黑土和黄土母质层土壤含水量、容重和介电常数之间的关系可以用两个对数方程来描述,其精确度为95.26%~99.66%。探地雷达测量黑土厚度与剖面实测厚度相比,精确度为87.05%~95.58%。3个坡面的黑土厚度空间分布不同,且坡脚发生沉积处的黑土厚度较大,坡肩和坡背土壤侵蚀较严重处的黑土厚度较薄。本研究可为进一步探明和保护黑土资源提供一种高效、准确的土壤厚度调查方法。

基于基片集成波导加载开口环的介电测量传感器

基于微扰理论,提出了一种在基片集成波导(SIW)结构上加载椭圆形开口环的小型化介电常数测量传感器。在传感器表面刻蚀椭圆开口环,增加电流路径的同时,降低工作频率,实现器件的小型化。在中心区域挖有通孔,当放入具有不同介电常数的待测物体时,传感器的S参数会发生改变。通过仿真软件对传感器进行分析,介电常数实部从1至10变化,频率的相对偏移达到32.4%。测量结果表明:传感器对介电常数的测量误差小于3%,具有很好的测量效果。

HFO_(2)铁电体薄膜移相器设计

移相器作为阵列天线的关键部件,用来调整阵列天线中各个天线单元之间的相位差,从而实现波束的扫描。基于传输线周期性加载可变电容理论,设计了一款工作于K波段的HFO_(2)铁电薄膜移相器。为了实现低插损和紧凑型,该移相器采用HFO_(2)铁电体薄膜材料,相比传统的BST材料,其有着更大的调谐率、厚度更薄且损耗角正切更低,容易集成,同时结合共面波导叉指电容结构设计,该移相器有非常紧凑的尺寸。通过改变HFO_(2)铁电材料的介电常数从而实现电容的变化,进而实现相位的调控。仿真结果表明,通过加入直流偏置电压改变铁电体薄膜的介电常数,该移相器在22 GHz频点的移相量为80°,最大插损为-2.5 dB,回波损耗优于-10 dB。

低含水油水两相流等效介电常数模型

电容法测油水两相流含水率在油田的地面油水计量及井中的产出剖面分层测试中都得到广泛应用。持水率(水相体积分数)的测量需要建立油水两相流持水率与传感器电容的关系,为此需要建立混相等效介电常数与持水率的理论模型或经验模型。由于油井采出的地层水以及地面实验室标定所用的自来水在低频和中频时均具有良好导电性,因此,单纯考虑介电性而不考虑导电性会对持水率测量的准确性产生显著影响。基于电介质极化的有效电场理论,在低含水且油水状态为精细泡状流条件下,将水视为良导体,建立了油水两相流等效介电常数模型。按此模型,油水两相流的等效介电常数只取决于持水率和油相介电常数,与水相介电常数以及水相电导率无关,初步实验验证了模型正确。该研究对于油为连续相时油水两相流的含水率传感器的设计和现场应用具有重要意义。

用于测量材料介电常数的高精度微波传感器

提出了一种用于测量材料介电常数的微波传感器,其特点是成本低、测量精度高。在传统的互补裂环结构上进行优化设计,实现了更大范围的测量区域;并加载了金属通孔结构,将电场限制在测量区域内,达到了更好的测量效果。结果显示传感器的测量灵敏度为2.89%。传感器在空载时谐振频率为2GHz;当样品加载到测量区域时,测量区域的电场将发生变化,从而导致频移。选取了介电常数值为1~10的样品进行了模拟加载试验,得到了介电常数与谐振频率的拟合经验关系式,同时采用5种常见的高频板材对拟合公式进行了验证。结果表明:传感器具有很高的测量精度,整体测量误差为0.8%,证实了利用该传感器测量材料介电常数的可行性。

Solid-state impedance spectroscopy studies of dielectric properties and relaxation processes in Na_(2)O–V_(2)O_(5)–Nb_(2)O_(5)–P_(2)O_(5) glass

Solid-state impedance spectroscopy(SS-IS)was used to investigate the influence of structural modifications resulting from the addition of Nb2O5 on the dielectric properties and relaxation processes in the quaternary mixed glass former(MGF)system 35Na_(2)O–10V_(2)O_(5)–(55-x)P_(2)O_(5)–xNb_(2)O_(5)(x=0–40,mol%).The dielectric parameters,including the dielectric strength and dielectric loss,are determined from the frequency and temperature-dependent complex permittivity data,revealing a significant dependence on the Nb2O5 content.The transition from a predominantly phosphate glass network(x<10,region I)to a mixed niobate–phosphate glass net-work(10≤x≤20,region II)leads to an increase in the dielectric parameters,which correlates with the observed trend in the direct-cur-rent(DC)conductivity.In the predominantly niobate network(x≥25,region III),the highly polarizable nature of Nb5+ions leads to a fur-ther increase in the dielectric permittivity and dielectric strength.This is particularly evident in Nb-40 glass-ceramic,which contains Na_(13)Nb_(35)O_(94) crystalline phase with a tungsten bronze structure and exhibits the highest dielectric permittivity of 61.81 and the lowest loss factor of 0.032 at 303 K and 10 kHz.The relaxation studies,analyzed through modulus formalism and complex impedance data,show that DC conductivity and relaxation processes are governed by the same mechanism,attributed to ionic conductivity.In contrast to glasses with a single peak in frequency dependence of imaginary part of electrical modulus,M″(ω),Nb-40 glass-ceramic exhibits two distinct contributions with similar relaxation times.The high-frequency peak indicates bulk ionic conductivity,while the additional low-fre-quency peak is associated with the grain boundary effect,confirmed by the electrical equivalent circuit(EEC)modelling.The scaling characteristics of permittivity and conductivity spectra,along with the electrical modulus,validate time-temperature superposition and demonstrate a strong correlation with composition and modification of the glass structure upon Nb_(2)O_(5) incorporation.

基于多区域面积分方程的电大非均匀等离子体电磁特性高效计算方法

针对临近空间等离子体包覆目标的电磁特性快速准确评估这一迫切需求,本文运用基于多区域面积分方程(multi-region surface integral equation, MR-SIE)的全波数值计算方法,展现电大尺度、非均匀、高负介电常数等离子体的电磁散射与辐射问题的仿真能力。首先,推导了非均匀等离子体的MR-SIE,使用间断伽辽金(discontinuous Galerkin, DG)方法提高对多区域复杂等离子体目标的建模与计算效率,研究了不同方程的数值性能;随后针对电子密度较大的高负介电常数区等离子体,运用一种简洁高效的截断策略,进一步提升了多层快速多极子算法的鲁棒性,避免了SIE计算高损耗介质内问题面临的数值不稳定性。数值实验表明,该方法在计算多种分割方式的多区域等离子体鞘套模型时具有良好的精度和效率,可用于大尺度复杂等离子体目标电磁辐射与散射特性的快速精确评估。

无纺土工织物垂直渗透特性试验研究

采用单位面积质量为200,300,400g/m^(2)的无纺土工织物开展了一系列垂直渗透试验,分析了各组试验结果的差异,并探讨了试样单位面积质量和层数对试验结果的影响。结果表明:流速与水头差成线性关系,并随着试样层数的增加而减小;透水率随着单位面积质量和试样层数的增加逐渐下降;各组试样的垂直渗透系数值在同一数量级,相同单位面积质量的试样垂直渗透系数随层数的变化无明显规律;相同层数试样的垂直渗透系数随着单位面积质量的增加而减小。

Sm/Gd-Nd协同置换对高介电常数石榴石微波铁氧体性能的影响

采用固相法陶瓷制备工艺,利用Bi^(3+)与稀土离子Gd^(3+)-Nd^(3+)、Sm^(3+)-Nd^(3+)协同置换对石榴石铁氧体进行高介电常数和高功率性能的复合,开发了新型高介电常数高功率石榴石铁氧体,研究不同烧结温度下制备的铁氧体的电磁性能。利用X射线衍射仪、扫描电子显微镜对铁氧体的物相组成和微观形貌进行了表征,确认均为单一的石榴石相结构。该铁氧体良好地复合了高介电常数与高功率特性,且具有tan δ<2×10^(-4),T_(c)>260℃等良好性能。两种高介电常数高功率铁氧体具有不同的烧结特性,在1 090℃、1 100℃烧结的Sm-Nd协同置换的铁氧体出现过烧,电磁性能恶化;而Gd-Nd协同置换的铁氧体则在整个烧结温度内均有较稳定的性能。

锂电池聚合物基固态电解质的研究现状与进展

本文介绍了目前锂离子电池在电解质方面的发展现状与面临的挑战,指出固态电解质成为提高锂电池安全性与能量密度的研究关键。本文对各类聚合物电解质进行了分析,对可行的改进策略进行了讨论,分析表明聚合物基固态电解质与电极界面接触良好、易于加工,在实现高比能固态锂电池的发展上具有明显优势,有望大规模产业化应用。本文最后对未来聚合物基固态电解质的研究方向和前景进行了展望,采用交联、共聚、接枝、添加塑化剂等改性途径,以及有机与无机复合制备固态电解质的方法,是发展聚合物基固态电解质的关键策略。

Effective permittivity and permeability of one-dimensional dielectric photonic crystal within a band gap

We take a finite dielectric photonic crystal as a homogeneous slab and have extracted the effective parameters. Our systematic study shows that the effective permittivity or permeability of dielectric photonic crystal is negative within a band gap region. This means that the band gap might act as ε-negative materials （ENMs） with ε 〈 0 and μ 〉 0, or μ-negative materials （MNMs） with ε 〉 0 and μ 〈 0. Moreover the effective parameters sensitively rely on size, surface termination, symmetry, etc. The effective parameters can be used to design full transmission tunnelling modes and amplify evanescent wave. Several cases are studied and the results show that dielectric photonic band gap can indeed mimic a single negative material （ENM or MNM） under some restrictions.

Annealing effects on the microwave permittivity and permeability properties of Fe_(79)Si_(16)B_5 microwires and their microwave absorption performances

This paper reports that amorphous magnetic microwires （Fe79Si16Bs） have been fabricated by a melt-extraction technique and have been annealed at 600℃ and 750℃ respectively. Differential scanning calorimeter measurements show that nanocrystalline magnetic phase （α-Fe） has been formed in the amorphous matrix when it was annealed at 600℃. Hard magnetic phase （Fe2B） was formed in the microwires annealed at 750℃, which increases the magnetic coercivity. Microwave permittivity and permeability are found to be dependent on the microstruetures. The permittivity fitting results show that multi Lorentzian dispersion processes exist. For microwires annealed at 750℃, their resonance peaks due to the domain wall movements and natural resonance are found higher than those of microwires annealed at 600℃. The microwave absorption performance of microwires annealed at 600℃ is found better than microwires annealed at 750℃.

The determination of the relative permittivity of periodic stratified media based on the iterative time-reversal method

In this paper, we present a new method to determine the relative permittivity of periodic stratified media using the iterative time-reversal method. Based on transmission line theory, the focal peak value of iterative time-reversal electro- magnetic waves, which contain information about the periodic stratified medium, is computed in pulse-echo mode. Using the relationship between the focal peak value and the relative permittivity of the periodic stratified medium, the relative permittivity can be obtained by measuring the focal peak value. Numerical simulations are conducted, and the results demonstrate the feasibility of the proposed approach to the measurement of the relative permittivity of a periodic stratified medium.

Design of Broadband Metamaterial Absorbers for Permittivity Sensitivity and Solar Cell Application

A broadband and ultra-thin absorber for solar cell application is designed. The absorber consists of three layers, and the difference is that the four split ring resonators made of metal gold are encrusted in the gallium arsenide （GaAs） plane in the top layer. The simulated results show that a perfect absorption in the region from 481.2 to 684.0THz can be obtained for either transverse electric or magnetic polarization wave due to the coupling effect between the material of GaAs and gold. The metamaterial is ultra-thin, having the total thickness of 56nm, which is less than one-tenth resonance wavelength, and the absorption coefficients at the three resonance wavelengths are above 90%. Moreover, the effective medium theory, electric field and surface current distributions are adopted to explain the physical mechanism of the absorption, and the permittivity sensing applications are also discussed. As a result, the proposed structure can be used in many areas, such as solar cell, sensors, and integrated photodetectors.

Large Scale Analysis of Complex Permittivity of Breast Cancer in Microwave Band

To obtain some prior knowledge of breast cancer detection by microwave imaging, we have measured and analyzed the complex permittivity of tissues extracted from over 140 breast cancer surgeries. The relative permittivity and conductivity of tumor at 1.6 GHz were 17.5% and 16.2% higher than those of mammary gland tissue, respectively. In invasive ductal carcinoma of scirrhous type, 8 out of 64 had higher relative permittivity and conductivity of mammary gland than those of tumor. However, when evaluated by the Debye parameter considering the frequency dependence of the tissue, it is rare that ε∞ and Δε of cancer are simultaneously lower than those of mammary gland. The relative permittivity and conductivity of fibroadenoma are almost the same as those of mammary glands. The relative permittivity and conductivity of each tissue showed strong linearity. Microwave imaging requires accurate reconstruction of ε∞ and Δε to distinguish cancer from normal tissue.

Dielectric Permittivity of Various Cement-Based Materials during the First 24 Hours Hydration

The dielectric permittivity of cementitious materials during 24 hours hydration period at a frequency of 2.45 GHz using a network analyzer with open-ended probe technique was measured. Influences of water-to-cementitious ratios, cement types, pozzolans and aggregate types are taken into consideration. The results show that dielectric permittivity is strongly affected by initial water-to-cementitious ratio and the rate of hydration reaction which can be changed by fineness of cement (Types 1 and 3), pozzolan materials and aggregates (river sand with/without crushed limestone rock). Dielectric permittivity is relatively high and remains constant during the dormant period, after that it decreases rapidly when the hydration reaction resumes and continues to decrease during the acceleratory period.

Enhanced dielectric permittivity of graphite oxide/polyimide composite films

Graphite oxide(GO) was prepared by the pressurized oxidation method and incorporated into polyimide(PI) matrix to fabricate high-k composite films by in-situ polymerization and subsequent thermal treatment. The results show that the as-prepared GO had good dispersion and compatibility in PI matrix due to the introduction of abundant oxygen-containing functional groups during the oxidation. The residual graphitic domains and the thermal treatment induced reduction of GO further enhanced the dielectric permittivity of the resulting GO–PI composites. The dielectric permittivity of the GO–PI composites exhibited a typical percolation behavior with a percolation threshold of 0.0347 of volume ratio and a critical exponent of 0.837. Near the percolation threshold, the dielectric permittivity of the GO–PI composite increased to 108 at 10~2 Hz and was 26 times that of the pure PI.