科氏质量流量传感器性能优化技术与发展

基于科氏质量流量传感器敏感结构设计原理,将具有不确定度分布的科氏质量流量传感器结构参数、被测流体的密度以及测量管的密度作为输入参数,科氏质量流量传感器的固有频率以及检测灵敏度作为输出参数.通过量化各输入参数的离散程度,采用随机收敛分析决定输入参数组合的数量,最终建立了基于样本的随机模型.在考虑加工尺寸误差的同时,详细评估了科氏质量流量传感器各结构参数对其检测灵敏度以及固有频率的相对影响程度,从而获得了其影响的关键因素,为相应传感器敏感结构设计与优化提供一定的理论依据.     

太阳电池翼的高精度质量特性测试方法研究

航天器的质量特性(包括质量和质心等)是影响航天器在轨运行的重要参数。为了解决太阳电池翼传统质量特性测试方法中存在的测量精度低、测量效率低、测量手段落后的问题,设计了一种高精度、高效、自动化的太阳电池翼质量特性测试方法。通过姿态调整装置对太阳电池翼进行倾斜姿态调整,并采用多次测量值取算数平均的方法,测得太阳电池翼的质量和质心。姿态调整装置可匹配太阳电池翼多种接口形式,实现多平台太阳电池翼俯仰姿态（0°~60°）的调整,并结合所提方法的集成软件算法,实现太阳电池翼质量、质心的自动求解。最后通过实验验证了所提方法的可行性。结果表明所提方法的质量测量精度高于0.01%G（满量程）+0.1kg,质心测量精度高于0.5 mm,测量时间从原先的8 h缩短至40 min,在满足测量精度的基础上,提高了太阳电池翼质量特性的测试效率,大大节省了人力成本,为后续航天器太阳电池翼生产线量产奠定了基础。     

Efficient homogeneously weighted dispersion control charts with an application to distillation process

Monitoring disturbances in process dispersion using control chart is mostly based on the assumption that the quality characteristic follows normal distribution, which is not the case in many real-life situations. This paper proposes a set of new dispersion charts based on the homogeneously weighted moving average (HWMA) scheme, for efficient detection of shifts in process standard deviation (σ). These charts are based on a variety of σ estimators and are investigated for normal as well as heavy tailed symmetric and skewed distributions. The shift detection ability of the charts is evaluated using different run length characteristics, such as average run length (ARL), extra quadratic loss (EQL), and relative ARL measures. The performance of the proposed HWMA control charts is also compared with the existing EWMA dispersion charts, using different design parameters. Furthermore, an illustrative example is presented to monitor the vapor pressure in a distillation process.     

Calculating Centroids in Constrained Mixture Experiments

In constrained mixture experiments the centroid of a constraint region has traditionally been defined as the average of all extreme vertices of the region. This differs from the classical physics definition of a centroid as the center of mass (or volume) of a region. An algorithm for calculating a centroid based on the center of mass definition is discussed and illustrated with an example. This centroid calculation technique can be used to calculate centroids of various dimensional faces and edges of the constraint region as well as of the overall centroid. Results of the center-of-mass and averaged-extreme-vertices centroid computation techniques are compared using examples from the literature.     

斜拉桥动力分析的三维有限单元模型

建立了一种三维斜拉桥的有限单元模型，并将其用于ＫａｐＳｈｕｉＭｕｎ斜拉桥动态特性分析。同时考虑了各种结构参数（结构质量的分布和偏心，结构刚度，索单元划分，索自重垂度，边界条件等）对斜拉桥自振特性的影响。数值计算结果与脉动试验结果较吻合，说明了该有限单元模型几乎能够分析出斜拉桥所有重要的动力特性     

Differential scheme for the effective elastic properties of nano-particle composites with interface effect

The differential scheme is developed to evaluate the effective elastic properties of nano-composites with interface effect through the solution of an infinitely dilute dispersion of nano-particles in a matrix. The differential equations presented in this paper for overall modulus of composites extend the application of classic differential scheme to the nano-scale, and they are valid for both mono-sized and poly-sized nano-particle composites. Particle size distribution functions are introduced. Continuous and discrete size distributions are taken into consideration for poly-sized filled nano-particles. The numerical examples exhibit that the effective properties of mono-sized nano-particle composite are size dependent, which agrees well with previous studies. As for poly-sized particle composite, the results show that the elastic properties are dependent on particle size distributions. Some distribution parameters, such as the mean size and the standard deviation, may significantly affect the effective mechanical properties. The proposed differential equations can be reduced to the classic ones, and are supposed to be in wider application.     

Some fields of applications of automatic image analysis in civil engineering

This paper illustrates the use of automatic image analysis technique to investigate the morphology of cement, concrete and fibre-reinforced concrete. First the methods to be used for powders and secondly for mortar and concrete are introduced. The dispersed phases are characterized by classical morphological parameters: these also enable to accede to the hydration process. The covariances give quantitative information on the homogeneity and dispersion of the different components: gravel, air-voids and cement paste. Air-voids are characterized by granulometric distributions and their mean free paths. Rose of directions gives information on feature orientation: fibres, microcracks for fibre-reinforced concrete, etc. Finally probabilistic models can be used to simulate the microstructure of such materials.     

Axial power flow distributions of ultrasonic guided waves in viscous liquid-filled pipes

The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-thickness product (fd) for the test of pipes filled with viscous liquid are chosen according to APF and attenuation distributions. The results show that the APF magnitude distribution is an important parameter in choosing the modes and parameters. A particular mode has weak dispersion in ranges of fd values with large group velocity, while other modes with smaller group velocity in the same fd ranges have stronger dispersion. It has been observed that, within these ranges, the chosen mode has a larger APF on the pipe's wall. Therefore, in the region of fd values where a particular mode has a large group velocity, this mode will be effective to be used in testing elastic pipes filled with viscous liquid. The results obtained from both the APF analysis and attenuation distribution are consistent.     

Assessment of the molecular weight distribution of tannin fractions through MALDI-TOF MS analysis of protein-tannin complexes

An innovative mass spectrometry method was developed for determining mass distributions of tannin fractions that cannot be approached through direct MALDI-TOF analysis. It was applied to three procyanidin fractions with average degrees of polymerizations = 3, 9, and 28, respectively, and one gallotannin fraction (Tara tannin). The proposed approach consists of MALDI-TOF analysis of the soluble complexes formed between these tannin fractions and bovine serum albumin (BSA). Complexes were detected as an unresolved "hump" following the BSA signal, and spectra were mathematically processed to determine the parameters relative to the protein-tannin complexes, which are the number-average molecular weight (Mn), the weight-average molecular weight (Mw), and the polydispersity index (PI) for each tannin fraction. Regarding condensed tannins, results are consistent with those of the standard method (thiolysis followed by HPLC separation) for all tested fractions. The method was successfully applied to a hydrolyzable tannin fraction but no standard method is available for comparison.     

The stability of swirling flows with a heat source

The absolute instability of a Rankine vortex with an axial flow and paraxial heat source is investigated. The dispersion relation for vortex modes is derived analytically. The dependence of dispersion properties of the media on control parameters such as swirl parameter S, velocity a, and heat source power (density parameter Q) is studied. The frequency of helical waves increases and the increment decreases with increasing heat source power, accompanied by a decrease in the width of the neutral stability region. Numerical analysis also suggests that one of the dispersion curve branches could include an instability region of a parametric nature.     

Quantitative assessment of collagen fibre orientations from two-dimensional images of soft biological tissues

In this work, we outline an automated method for the extraction and quantification of material parameters characterizing collagen fibre orientations from two-dimensional images. Morphological collagen data among different length scales were obtained by combining the established methods of Fourier power spectrum analysis, wedge filtering and progressive regions of interest splitting. Our proposed method yields data from which we can determine parameters for computational modelling of soft biological tissues using fibre-reinforced constitutive models and gauge the length scales most appropriate for obtaining a physically meaningful measure of fibre orientations, which is representative of the true tissue morphology of the two-dimensional image. Specifically, we focus on three parameters quantifying different aspects of the collagen morphology: first, using maximum-likelihood estimation, we extract location parameters that accurately determine the angle of the principal directions of the fibre reinforcement (i.e. the preferred fibre directions); second, using a dispersion model, we obtain dispersion parameters quantifying the collagen fibre dispersion about these principal directions; third, we calculate the weighted error entropy as a measure of changes in the entire fibre distributions at different length scales, as opposed to their average behaviour. With fully automated imaging techniques (such as multiphoton microscopy) becoming increasingly popular (which often yield large numbers of images to analyse), our method provides an ideal tool for quickly extracting mechanically relevant tissue parameters which have implications for computational modelling (e.g. on the mesh density) and can also be used for the inhomogeneous modelling of tissues.     

Shifts in peptide and protein charge state distributions with varying spray tip orifice diameter in nanoelectrospray Fourier transform ion cyclotron resonance mass spectrometry

The influence of the diameter of the spray tip employed for nano-electrospray mass spectrometry (nano-ES-MS) upon mass spectral charge state distributions was investigated using angiotensin I (M(r) = 1296), insulin (M(r) = 5774), and ubiquitin (M(r) = 8560) as test analytes. Under a variety of experimental conditions, the charge state distributions of the test peptides and protein consistently shifted toward higher values as the tip orifice diameter decreased. This finding indicates that the use of narrow diameter capillaries can promote the formation of higher charge state ions that are more reactive precursors in tandem mass spectrometry experiments. A detailed comparison of charge state distributions obtained for nanospray capillaries of varying diameters was undertaken while systematically varying experimental parameters such as sample flow rate, analyte concentration, solvent composition, and electrospray current. The general tendency to obtain higher charge states from narrow diameter capillaries was conserved throughout, but tips with smaller orifices were more sensitive to sample flow rate (the average charge state was lowered significantly as flow was raised), whereas tips with bigger orifices were more sensitive to analyte concentration and pH of the solution (as each was lowered, the average charge state increased).     

Elastic,electronic, and vibrational properties of RhN compound

The structural, electronic, mechanical, and vibrational properties of 4d transition metal mononitride, RhN, are investigated using the norm-conserving pseudopotentials within the local density approximation (LDA) in the frame of density functional theory. The calculated lattice parameters and the bulk modulus almost agree with the previous theoretical values. The second-order elastic constants have been calculated and the other related quantities such as Young’s modulus, shear modulus, anisotropy factor, sound velocities, and Debye temperature also estimated. Charge distributions and density of states are reported to understand the bonding character in the stable phases. We have also obtained the phonon dispersion curves without LO/TO splitting.     

平缝机刺布挑线机构的动力学优化

工业平缝机是缝制行业应用最为广泛的装备之一,其刺布挑线机构对整机的振动与冲击影响较大,对该机构进行优化有助于整机的减振降噪。建立了平缝机刺布挑线机构的虚拟样机模型,对其进行动力学分析。基于部分平衡理论,以针杆曲柄处最大惯性力最小为优化目标,建立优化数学模型,通过改变构件的质心坐标位置及质量等参数来实现机构惯性力的最佳平衡。试验表明该优化方法具有一定的可信度,部分平衡法应用于解决如高速平缝机等复杂机械系统的振动和噪声有一定的参考价值。     

The role of flaw size and fiber distribution on tensile ductility of PVA-ECC

Polyvinyl Alcohol-Engineered Cementitious Composites (PVA-ECC) designed based on micromechanics exhibit high tensile ductility (above 1%) and limited crack widths (below 100 μm). The tensile performance of ECC is dependent on the fiber and flaw size distributions. These parameters are known to be influenced by the matrix flowability and mix processing; however, a comprehensive quantitative analysis framework linking fiber and flaw size distributions to the tensile performance of PVA-ECC is needed to supplement theoretical understanding of the relationship between micromechanical parameters and composite macro-properties. In the present work, fiber distribution (dispersion and orientation) of two different ECCs in terms of matrix flowability was investigated using fluorescence microscopy and advanced digital image analysis. The maximum flaw size distribution along the specimens was also analyzed by cross-sectional image analysis. The influences of fiber and flaw size distributions on the composite behavior of PVA-ECCs were experimentally established.     

基于SOPC的太阳敏感器信息处理系统

基于内嵌处理器软核MicroBlaze的FPGA,设计了一种太阳敏感器信息处理系统。采用MicroBlaze软核实现光斑质心提取和姿态换算,并通过其它逻辑资源实现图像传感器驱动、图像存储和接口通信等模块的时序控制,同时根据MicroBlaze软核的特点,提出了一种基于扫描方式的质心提取算法。结果表明,具有单精度浮点运算能力的MicroBlaze软核能够保证太阳敏感器质心提取和姿态计算的精度;基于扫描方式的质心提取算法流程简单,占用资源少;采用SOPC的太阳敏感器无需DSP或ARM等协处理器,减小了硬件设计复杂性,提高了系统的集成度和性能。     

Effect of experimental parameters on the ESI FT-ICR mass spectrum of fulvic acid

Fulvic acid (FA) is a heterogeneous mixture of organic macromolecules found in the waters, soils, and sediments of the earth's surface. The ability of electrospray ionization (ESI) to effectively transfer large ions from the solution phase to the gas phase and the coupling of ESI to the high-mass-resolution capabilities of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provide a potential method for the mass spectrometric analysis of FA. Positive- and negative-ion ESI FT-ICR MS analyses of four reference International Humic Substances Society FAs were performed. The spray solution composition was found to have a dramatic effect on the ion distributions, with high-mass aggregates (m/z approximately 2000-4000) being formed in less polar spray solutions. Positive-ion spectra for each FA obtained under optimum conditions resulted in number-average molecular weights ranging from 1700 to 1900. The mass spectra were extremely complex, with ion distributions on the order of m/z approximately 500-3000. The presence of more than one ion at each nominal mass was routinely observed. Negative-ion ESI analysis of the FA samples resulted in the observation of multiply charged ions whose distributions could be affected by the acidification of the spray solution. Solution parameters which have been reported to affect molecular weight distributions of FA such as pH, ionic strength, and concentration of multivalent cations were found to have little or no effect on the observed m/z distributions.     

On the Performance of Phase‐I Bivariate Dispersion Charts to Non‐Normality

A phase‐I study is generally used when population parameters are unknown. The performance of any phase‐II chart depends on the preciseness of the control limits obtained from the phase‐I analysis. The performance of phase‐I bivariate dispersion charts has mainly been investigated for bivariate normal distribution. However, this assumption is seldom fulfilled in reality. The current work develops and studies the performance of phase‐I |S| and |G| charts for monitoring the process dispersion of bivariate non‐normal distributions. The necessary control charting constants are determined for the bivariate non‐normal distributions at nominal false alarm probability (FAP₀). The performance of these charts is evaluated and compared in a situation when samples are generated by bivariate logistic, bivariate Laplace, bivariate exponential, or bivariate t₅ distribution. The analysis shows that the proper consideration to underlying bivariate distribution in the construction of phase‐I bivariate dispersion charts is very important to give a real picture of in or out of control process status. Copyright © 2016 John Wiley & Sons, Ltd.     

Quantitative optical analysis of filler dispersion degree in MWCNT–epoxy nanocomposite

Recently developed methodology of quantitative analysis based on optical analysis of filler particles’ area distributions is applied now to estimate the dispersion efficiency of multiwall carbon nanotubes in nanocomposite prepared by solution intercalation method. Experimental parameters of dispersing (temperature, duration and power level of ultrasonication) were optimized and the most effective experimental procedure was determined. The methodology of determination of dispersion parameter is proved by indirect method of light transmittance experiments. The nanocomposite specimens having lower dispersion parameter represented the highest transmittance over the nanocomposite specimens.     

A survey of modeling techniques for consequence analysis of accidental chemical releases to the atmosphere

This paper surveys techniques for estimating the consequences of accidental chemical releases to the atmosphere. The first section is devoted to a discussion of the characterization of gas, liquid and two-phase releases. In addition to the mass release rate, parameters such as phase composition, density and velocity are shown to be of critical importance in the subsequent dispersion of the release. Emissions due to boiling and evaporation from liquid spill pools are also treated. The second part of the paper describes the techniques for calculating the spatial and temporal variation of chemical concentrations due to jet and heavy gas dispersion. Methods are also presented for estimating the damage resulting from the ignition of a flammable plume or liquid spill pool. Finally, the paper deals with model prediction uncertainty and its impact upon the process of emergency response planning.