膨胀波透过大孔隙率结构化球阵时气流场的数值模拟

针对膨胀波透过大孔隙率结构化球阵时的气体流动问题,采用三维雷诺时均Navier-Stokes方程和可实现k-epsilon湍流模型,对不同球阵(或固相)体积分数、破膜压比和球阵排列条件下的气流场进行了数值模拟,分析了上述因素对膨胀波的传播特性和球体阻力系数的影响规律。结果表明:入射膨胀波在传播透过球阵时,会被球面不断地反射,这导致大量反射膨胀波的出现。当破膜压比较小时,反射膨胀波具有较强的聚集叠加效应,容易长时间稳定存在,并汇集形成规则的阵面,此时球体阻力系数增大。在确定工况条件下,对于一个给定的球阵排列,存在一个临界体积分数,当实际体积分数大于它时,能够形成反射膨胀波阵面,反之则不能形成。在大孔隙率限制条件下,体积分数的增大,有利于增强反射膨胀波的干涉,从而增大球体阻力系数。对比晶体立方(Crystal cubic,CC)、双面心立方(Bis-face-centered cubic,BFCC)和交错立方(Staggered cubic,SC)三种排列方式,阻力系数的排序为SC排列、BFCC排列、CC排列,这主要由邻近球间距的差异导致。

激波诱导模型球阵非稳态阻力的数值模拟研究

采用CFD软件,对激波诱导单排四球模型球阵绕流场进行三维数值模拟,在计算模型和方法准确性验 证基础上,分析模型球非稳态阻力的形成机理,并揭示激波马赫数Ms和无量纲间距H对非稳态阻力和激波结构的影响.结果表明：模型球阻力系数Cd曲线存在一个尖锐的最大值波峰和一个波谷的结构,且最终趋于某一稳态正值; Ms越小,Cd峰值越大,谷值越小, Cd曲线波动幅度越大;激波反射、衍射、聚焦和干涉行为共同影响非稳态阻力系数;无量纲间距H越小,相邻球的激波干涉越显著,Cd峰值越大.

高功率半导体激光器列阵光纤耦合模块

根据大功率半导体激光二极管列阵与光纤列阵耦合方式,分别从理论和实验两方面讨论、分析了大功率半导体激光二极管列阵与微球透镜光纤列阵耦合。将19根芯径均为200μm的光纤的端面分别熔融拉锥成具有相同直径的微球透镜,利用V形槽精密排列,排列周期等于激光二极管列阵各发光单元的周期。将微球透镜光纤列阵直接对准半导体激光二极管列阵的19个发光单元,精密调节两者之间的距离,使耦合输出功率达到最大。半导体激光二极管列阵与微球透镜光纤列阵直接耦合后,不仅从各个方向同时压缩了激光束的发散角,有效地实现了对激光束的整形、压缩,而且实现30 W的高输出功率,最大耦合效率大于80%,光纤的数值孔径为0.16。

Void defect detection in BGA solder joints using mathematical morphology

Voids are one of the major defects in ball grid array （BGA） solder joints due to a large amount of outgassing flux that gets entrapped during reflow. X-ray nondestructive machines are used to make voids visible as lighter areas inside the solder joints in X-ray images for detection However, it has always been difficult to analyze this problem automatically because of some challenges such as noise, inconsistent lighting and void-like artifacts. This study realized accurate extraction and automatic a-nalysis of void defects in solder joints by adopting a technical proposal, in which Otsu algorithm was used to segment solder balls and void defects were extracted through opening and closing operations and top-hat transformation in mathematical mor-phology. Experimental results show that the technical proposal mentioned here has good robustness and can be applied in the detection of voids in BGA solder joints.

Matrix dimensionality reduction for mining typical user profiles

Recently clustering techniques have been used to automatically discover typical user profiles. In general, it is a challenging problem to design effective similarity measure between the session vectors which are usually high-dimensional and sparse. Two approaches for mining typical user profiles, based on matrix dimensionality reduction, are presented. In these approaches, non-negative matrix factorization is applied to reduce dimensionality of the session-URL matrix, and the projecting vectors of the user-session vectors are clustered into typical user-session profiles using the spherical k -means algorithm. The results show that two algorithms are successful in mining many typical user profiles in the user sessions.

谈CSP封装器件的返修工艺流程

球栅列阵封装技术,简称BGA封装,早在80年代已用于尖端军备、 导弹和航天科技中,它对于电子设备的微型化和多功能化起到决 定性作用。随着半导体工艺技术的发展,近年来在各行各业中都亦 广泛地使用到BGA封装IC元件,领导这一发展趋势的芯片级封装 (CSP)在今天已开始得到广泛应用,随之而来对于CSP封装器件的 返修更显重要。

Some Suggestions Improving Apollo Lunar Laser Retroreflector Arrays

According to our engineering research on satellite-borne laser retroreflector array, some suggestions are proposed on how to manufacture a new Apollo LLRA that can make us measure one illuminating point and unilluminating area on the moon's surface. These suggestions are: to control the dihedral angle offset within ± 0.1″; to use the larger aperture of the transparent face of cube corner prisms; to investigate how to separate out Apollo's reflected laser from mixed beam hitting on the LLR system.

采用安捷伦5DX系统优化测试策略和取得显著成效

为了让安捷伦科技提出建议来进一步优化华为现有的测试策略,华为聘请安捷伦科技研究华为现有的测试策略和生产流程。安捷伦5DX系统为其进行测试,其优越性在于:改进后的测试策略将带来重大的经济效益。因为早期发现了缺陷,所以下游测试处理量可以提高,维修费用将降低。同时它还减少对手动视觉检测的需要,减少在线测试和FT的再次测试,与现在没有5DX系统的测试策略相比,总的检测范围显著扩大。从这次研究的结果可以看出,华为能够在它自己的生产环境中决定最为有效和最合适的测试策略来测试复杂的电路板。研究结果也表明5DX系统是最为有效的测试工具,在检测缺陷时,检测效果高达91%。华为现在已经配备了完整的测试设备,防止生产出有BGA开路这种缺陷的电路板。这次的实验研究加深了他们对结构测试的认识,现在华为继续在他们的常规测试策略中采用5DX测试系统。

A Machine Vision System for Ball Grid Array Package Inspection

An optical inspection method of the Ball Grid Array package(BGA) was proposed by using a machine vision system. The developed machine vision system could get main critical factors for BGA quality evaluation, such as the height of solder ball, diameter, pitch and coplanarity. The experiment has proved that this system is available for BGA failure detection.

LOW FREQUENCY VARIABILITY OF INTERANNUAL CHANGE PATTERNS FOR GLOBAL MEAN TEMPERATURE DURING THE RECENT 100 YEARS

The TEEOF method that expands temporally is used to conduct a diagnostic study of the variation patterns of 1, 3, 6 and 10 years with regard to mean air temperature over the globe and Southern and Northern Hemispheres over the course of 100 years. The results show that the first mode of TEEOF takes up more than 50% in the total variance, with each of the first mode in the interannual oscillations generally standing for annually varying patterns which are related with climate and reflecting long-term tendency of change in air temperature. It is particularly true for the first mode on the 10-year scale, which shows an obvious ascending trend concerning the temperature in winter and consistently the primary component of time goes in a way that is very close to the sequence of actual temperature. Apart from the first mode of all time sections of TEEOF for the globe and the two hemispheres and the second mode of the 1-year TEEOF, interannual variation described by other characteristic vectors are showing various patterns, with corresponding primary components having relation with long-term variability of specific interannual quasi-periodic oscillation structures. A 2T test applied to the annual variation pattern shows that the abrupt changes for the Southern Hemisphere and the globe come closer to the result of a uni-element t test for mean temperature than those for the Northern Hemisphere do. It indicates that the 2Ttest, when carried out with patterns of multiple variables, seems more reasonable than the t test with single elements.

Spacecraft formation control strategy on Sun-Earth Lissajous orbit

To carry out the deep space exploration tasks near Sun-Earth Libration point L2, the CRTBP dynamic model was built up and the numerical conditional quasi-periodic orbit （Lissajons orbit） was computed near L2. Then, a formation controller was designed with linear matrix inequality to overcome the difficuhy of parameter tuning. To meet the demands of formation accuracy and present thruster＇s capability, a threshold scheme was adopted for formation control. Finally, some numerical simulations and analysis were completed to demonstrate the feasibility of the proposed control strategy.

Matrix-bound phosphine in Ny-Alesund Area of Arctic

Phosphine, a ubiquitous trace gas in the atmosphere, acts as a carrier of gasous phosphorus in the biogeochemical cycle. The research of phosphine will show new light on the mechanisms of how the phos- phorus supplement influence the biogeochemical cycle and global wanning. In this paper, we detect the phosphine in Arctic Pole area for the first time. The result shows that matrix-bound phosphine（MBP） ex- ists in all the samplings. Phosphine distributions varied with different environmental origins. Average phosphine concentrations in tundra soil, lake sediments, sea sediments, seabird-droppings and deer guanos were 14.17ng/kg dry, 35.44 kg dry, 67.20 kg dry, 32.9 ng/kg dry, and 25.52 ng/kg dry re- spectively. Correlation analysis shows that there is an obviously positive correlation between Porg and MBP. It could be concluded that anaerobic decomposition of Porg and the mechano-chemistry action of the rock probably are the possible reasons explaining the mechanism of MBP production in Arctic Pole area.

EFFECT OF FEED ARRAY CONFIGURATION ON THE FIELD-OF-VIEW OF RADIO TELESCOPE ANTENNA

Phased Array Feed (PAF) is a small two-dimensional phased array antenna, playing a role as the multi-beam feed for the reflector antenna. The prominent capability of large continuous Field-of-View (FoV) coverage and fast survey speed makes PAF the promising feed for radio telescopes. In this paper, the effect of feed array of PAF on the gain fluctuations over FoV is analyzed on a sim- plified model of the Five-hundred-meter Spherical Aperture radio Telescope (FAST), including illu- mination pattern edge taper, element spacing, element arrangement and element amount. And the differences between rectangular and hexagonal array arrangements are compared. The relationship between the FoV and array configuration are concluded at last.

A resonator mode in linear arrays of silver spheres and cylinders

A transversal mode with zero group velocity and non-zero phase velocity that can exist in chains of silver nano- spheres in the optical frequency range was theoretically studied. It is shown that the external source radiating a narrow-band non-monochromatic signal can excite in the chain a mixture of standing and slowly travelling waves. The standing wave com- ponent (named as resonator mode) is strongly dominating. The physical reason of such a regime is a sign-varying distribution of power flux over the cross section of the chain. This situation is similar to the scenario of the propagation of a wave along the boundary between the right-handed and left-handed media where the spatial distribution of the light intensity is vortex. However, in the present case there is no boundary between media and the boundary between the positive and negative power fluxes is a cylindric tube in free space whose axis is the axis of the chain.

Ex⁃situ Measurement of Internal Deformation in Ball Grid Array Package with Digital Volume Correlation

In spacecraft electronic devices,the deformation of solder balls within ball grid array(BGA)packages poses a significant risk of system failure.Therefore,accurately measuring the mechanical behavior of solder balls is crucial for ensuring the safety and reliability of spacecraft.Although finite element simulations have been extensively used to study solder ball deformation,there is a significant lack of experimental validation,particularly under thermal cycling conditions.This is due to the challenges in accurately measuring the internal deformations of solder balls and eliminating the rigid body displacement introduced during ex-situ thermal cycling tests.In this work,an ex-situ three-dimensional deformation measurement method using X-ray computed tomography(CT)and digital volume correlation(DVC)is proposed to overcome these obstacles.By incorporating the layer-wise reliability-guided displacement tracking(LW-RGDT)DVC with a singular value decomposition(SVD)method,this method enables accurate assessment of solder ball mechanical behavior in BGA packages without the influence of rigid body displacement.Experimental results reveal that BGA structures exhibit progressive convex deformation with increased thermal cycling,particularly in peripheral solder balls.This method provides a reliable and effective tool for assessing internal deformations in electronic packages under ex-situ conditions,which is crucial for their design optimization and lifespan predictions.

Optical plasma boundary reconstruction based on least squares for EAST Tokamak

Reconstructing the shape and position of plasma is an important issue in Tokamaks. Equilibrium and fitting（EFIT） code is generally used for plasma boundary reconstruction in some Tokamaks. However, this magnetic method still has some inevitable disadvantages. In this paper, we present an optical plasma boundary reconstruction algorithm. This method uses EFIT reconstruction results as the standard to create the optimally optical reconstruction. Traditional edge detection methods cannot extract a clear plasma boundary for reconstruction. Based on global contrast, we propose an edge detection algorithm to extract the plasma boundary in the image plane. Illumination in this method is robust. The extracted boundary and the boundary reconstructed by EFIT are fitted by same-order polynomials and the transformation matrix exists. To acquire this matrix without camera calibration, the extracted plasma boundary is transformed from the image plane to the Tokamak poloidal plane by a mathematical model,which is optimally resolved by using least squares to minimize the error between the optically reconstructed result and the EFIT result. Once the transform matrix is acquired, we can optically reconstruct the plasma boundary with only an arbitrary image captured. The error between the method and EFIT is presented and the experimental results of different polynomial orders are discussed.

Glucose-sensitivity of core-shell microspheres and their crystalline colloidal arrays

Thermoresponsive core-shell microspheres are prepared and functionalized with 3-aminophenylboronic acid to make them responsive to glucose.The volume phase transition of the resulting particles is shifted to a lower temperature and a clear swelling is caused by the presence of glucose.The particles after the functionalization preserved their capability to form crystalline colloidal arrays.The changes of their properties may be used in the design of glucose sensors.

Characterization of chromophoric dissolved organic matter(CDOM) in the East China Sea in autumn using excitationemission matrix(EEM) fluorescence and parallel factor analysis(PARAFAC)

Samples of chromophoric dissolved organic matter （CDOM） in the East China Sea in autumn （October in 2011） were analyzed by excitation emission matrix （EEM） fluorescence spectroscopy combined with parallel factor analysis （PARAFAC）. Three terrestrial humic-like components （C1, C2 and C3） and one protein-like component （C4） were identified. Based on spatial dis- tributions, as well as relationships with salinity, the following assignments were made. The three humic-like components （CI, C2 and C3） showed conservative mixing behavior and came mainly from riverine input. The protein-like component （C4） was considered a combination of autochthonous production and terrestrial inputs and a biologically labile component. Path analysis of samples from the middle and bottom layers revealed that the causal effects on C1 were -78.46% for salinity, and -21.54% for apparent oxygen utilization （AOU）; those on C2 were -76.43% for salinity, and -23.57% for AOU; those on C3 were -70.49% for salinity, 7.01% for Chl-a, and -22.50% for AOU; those on C4 were -55.54% for salinity, 14.6% for Chl-a, and -29.86% for AOU in middle layer; and those on C4 were -57.37% for salinity, 29.02% for Chl-a, and -13.61% for AOU in bottom layer. Results indicated that CDOM in tile East China Sea was mainly affected by terrestrial inputs, and microbial ac- tivities also played a key role in biogeochemical processes of CDOM. The application of the EEM-PARAFAC model present- ed a unique opportunity to observe compositional changes in CDOM in the East China Sea. In addition, the humification index （HIX） suggested that CDOM from the East China Sea was less stable and stayed shorter in the environment.