测量介质材料复介电常数的准光腔法

针对介质材料,介绍了在毫米波段和亚毫米波段能够准确测量其复介电常数的准光学谐振腔法。准光学谐振腔具有高Q值、使用简便、样品放置容易等许多优点,能够有效地完成介质材料电介质参数精密测量的任务。这种谐振腔为半球型并由一个平面镜和一个凹面铜镜组成,采用固定腔长法或固定频率法进行测量。另外,还介绍了准光学谐振腔的测试系统和最新的研究成果及改进方法,例如测量多层薄膜及在更高频段的测量方法。     

薄膜材料的微波复介电常数测量

为了精确测量厚度在以1 μm以下薄膜材料的微波复介电常数,提出一种基于金属谐振腔微扰理论的测量方法和装置,对该方法进行了理论分析和实验验证,实验样品采用0.81μm厚度的MC-91(BaO-(SmNdLa)2O3-Bi2O3-TiO2)介质陶瓷薄膜,测试频率在2.4 GHz左右,对测量结果进行了误差分析,其相对误差＜7%,其中3%的误差是由薄膜厚度的测量误差引起的.     

介质材料复介电常数测试的同轴线谐振腔法研究

利用同轴线谐振腔对介质材料复介电常数进行测试得到其谐振频率f0,品质因数Q0通过联立两个独立方程,求解出tanδ(即ε’’/ε’),同轴线谐振腔传输的为TEM波,由谐振频率f0根据相关公式求解出ε’,从而掌握该材料的特性参数。     

传输/反射法测量固体复介质材料介电常数

介绍/传输反射法测量固体介质材料复介电常数等关键技术难点,通过建立固体介质材料的介电谱和磁谱测量装置,开展复介电常数、复磁导率、复损耗角正切测量技术研究,在30 MHz～18 GHz采用空气线同轴传输的方法、在18～50 GHz采用三段波导传输的方法,实现了30 MHz～50 GHz全频段固体介质材料电磁参数的测试能力,提出了复介电常数、复磁导率、复损耗角正切测量的数学模型,编制了材料测试软件,实现了同轴和波导的全频段测量。     

分体圆柱谐振腔法用于金刚石膜微波介电性能测试的研究

针对金刚石膜微波介电损耗低、厚度薄带来的微波介电性能测试难点, 研制了一台分体圆柱谐振腔式微波介电性能测试装置。利用不同直径的蓝宝石单晶样品, 用上述装置对低损耗薄膜类样品微波介电性能的测试能力及样品直径对测试结果的影响进行了实验研究。在此基础上, 使用分体圆柱谐振腔式微波介电性能测试装置对微波等离子体化学气相沉积法和直流电弧等离子体喷射法制备的高品质金刚石膜在Ka波段的微波介电性能进行了测试比较。测试结果表明, 由Raman光谱、紫外-可见光谱等分析证明品质较优的微波等离子体化学气相沉积法制备的金刚石膜具有更高的微波介电性能, 其相对介电常数和微波介电损耗值均低于直流电弧等离子体喷射法制备的金刚石膜。     

一种用于水声材料设计的动态参数测试方法

针对提高水声材料设计中动态参数输入精度的问题，提出了一种复杨氏模量及泊松比准确测试方法。对于复杨氏模量测试，通过将Williams-Landel-Ferry(WLF)方程引入到Havriliak-Negami(H-N)模型中，采用信赖域反射算法对未知参数进行拟合得到材料参数宽频域主曲线。对于泊松比测试，根据同一材料不同形状因子表观杨氏模量之比与泊松比存在唯一量化关系的特性，仅通过两种不同形状因子试样的准静态有限元模拟，获得表观杨氏模量比值与泊松比量化曲线。因此，根据橡胶样品表观杨氏模量测试结果，可以直接利用局部加权回归获得其泊松比。最后，将前述材料制成直径为55 mm、厚度为50 mm的声管样品，放置在水声管中进行吸声系数测试。同时，把橡胶的复杨氏模量和泊松比的测量结果输入到水-橡胶-水分层介质模型中进行吸声系数计算。结果表明两者吻合，验证了上述测试方法的正确性和有效性。     

多铁性材料Bi1-xBaxFeO3的微波吸收性能

用溶胶-凝胶法制备了Bi1-xBaxFeO3(x=0.0,0.15,0.25,0.35,0.4),用X射线衍射(XRD)和扫描电镜(SEM)表征了样品的晶体结构、微观形貌,用综合物性测试系统(PPMS)测试了样品的室温磁滞回线,用微波矢量网络分析仪测试了样品在2~18GHz微波频率范围的复介电常数、复磁导率并计算了电磁损耗因子和微波反射率,分析了材料的微波吸收性能和电磁损耗机制。结果表明:Bi1-xBaxFeO3粉晶呈球状,晶体结构为钙钛矿型,呈较弱的铁磁性;当x=0.35、厚度d=2.7mm时,在频率f=10.64GHz位置的吸收峰值为30.43dB,10dB带宽为2.4GHz,微波吸收以介电损耗为主兼具一定的磁损耗。     

自由空间法测量复合材料复电磁参数

自由空间法可以方便地改变入射电磁波的角度和极化方向, 适用于测量复合材料的电磁参数。对自由空间法测量复合材料电磁参数进行了初步研究, 探讨了测量结果在计算过程中产生的多值问题, 并通过理论分析给出了一些有效的解决方案。用自由空间法测量了4种聚合物复合材料样品在X波段(8.2~12.4GHz)的复电磁参数, 并用波导测量法进行了验证。研究结果表明自由空间法测量复合材料电磁参数具有较高的精确度。      

生物介质复介电常数的微扰法测量

由谐振腔微扰理论出发，得到复介电常数计算式，测量了不同浓度的NaCl溶液及小鼠血液、肿瘤细胞悬液等样品的复介电常数；所得结果较为精确，证明了本测量系统的可靠性；对测量的系统、方法、仪器所引入的误差做了一定分析。     

基于共面波导传输线的宽频带介电常数提取方法

提出了一种基于共面波导传输线的宽频带低损耗材料介电常数提取方法。设计5根共面波导传输线作为标准覆盖待测样品介电常数频率范围,采用在片矢量网络分析仪测得各传输线未经修正的S参数,经过多线TRL校准算法提取传播常数;采用quasi-TEM模型计算传输线的单位长度电阻R和单位长度电感L;最终求得0.1~50GHz GaAs材料的介电常数。相比于传统的腔体法只能点频测试,且需设计待测样品腔体结构,该测试方法支持宽频带介电常数的连续测试,且测试效率更高;测试结果与谐振腔法偏差±2.5%,满足工程实践需要。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。