Direct observation and numerical simulation of molten silicon flow during crystal growth under magnetic fields by x-ray radiography and large-scale computation

Control of melt flow during Czochralski (CZ) crystal growth by application of magnetic fields is an important technique for large-diameter (>300 mm) silicon single crystals. Melt convection under magnetic fields is an interesting problem for electromagnetic-hydrodynamics. This paper reviews the effects of a vertical magnetic field and a cusp-shaped magnetic field on melt flow during CZ crystal growth. Melt flow in vertical magnetic fields or cusp-shaped magnetic fields was investigated by the direct observation method based on X-ray radiography and by numerical simulation. The first part of this review shows the result of direct observation of molten silicon flow under magnetic fields. It also compares the results of experimental and numerical simulation. The second part shows the details of the numerical simulation of the behavior of molten silicon in magnetic fields.     

Experimental study of bubble generation during β‐BaB2O4 single crystal growth

The generation of bubble‐inclusions during BaB₂O₄ (BBO) crystal growth from high temperature solution has been optically observed by an in situ observation technique. It was found that bubbles are formed from the peripheries of some hexagonal defects in the (0001) plane of the growing crystal, which may be caused by the evaporation of the air‐opened interface at the high temperature. In addition, atomic force microscope (AFM) was used to investigate the distribution of bubbles. Results revealed that the bubble generation and distribution depend strongly on the microscopic structure of the interface: on a rough interface, bubbles are easily formed and grow rapidly; however, they are greatly suppressed by step trains on a vicinal interface. In the latter case, the height value of a bubble is close to that of the step, which is in the order of several tens of nanometers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multiple outlier detection in growth curve model with unstructured covariance matrix

Under a normal assumption, Liski (1991,Biometrics,47, 659–668) gave some measurements for assessing influential observations in a Growth Curve Model (GCM) with a known covariance. For the GCM with an arbitrary (p.d.) covariance structure, known as unstructured covariance matrix (UCM), the problems of detecting multiple outliers are discussed in this paper. When a multivariate normal error is assumed, the MLEs of the parameters in the Multiple-Individual-Deletion model (MIDM) and the Mean-Shift-Regression model (MSRM) are derived, respectively. In order to detect multiple outliers in the GCM with UCM, the likelihood ratio testing statistic in MSRM is established and its null distribution is derived. For illustration, two numerical examples are discussed, which shows that the criteria presented in this paper are useful in practice.Supported partially by the WAI TAK Investment and Loan Company Ltd. Research Scholarship of Hong Kong for 1992–93.Supported partially by the Hong Kong UPGC Grant.     

Performance of software-based solar adaptive optics system

This paper reports the performance of our modified adaptive optics system for solar observations. This system operates at a frame rate of about 400 Hz and has the closed-loop cutoff frequency at 105 Hz. The results of the laboratory experiments show that this system compensates for a temporal wavefront-variation of less than 99 Hz and improves the Strehl ratio by a factor of five.     

IONIZATION POTENTIAL OF THE LITHIUMLIKE GROUND STATES FROM Z=21 to 30

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Estimation of Parameters of Partially Linear Errors-in-variables Models with Replicated Net Points of Observation

A kind of partially linear errors-in-variables models with replicated net points of observation are studied in this paper. Estimators of unknown parameters are given. Under certain regular conditions, it is shown that the estimators of the unknown parameters are strongly consistent and their a.s. convergence rates are achieved.     

LDM长距离显微镜

长距离显微镜破除了只能近距离观测的传统，使微观观测可在高温、高压、有腐蚀气体的环境中进行，可广泛用于材料微观观测、化工、医学、司法鉴定等各个领域，本文着重介绍中科院上海天文台研制成功的ＬＤＭ－Ⅱ型长距离显微镜光学、机械结构特点及各种性能指标，用户正利用其独特的功能从事各种不同领域的工作。     

DGPS车载导航系统中基准站坐标的测定

在简要介绍了DGPS基准站控制网建立的特点及作业流程后，着重讨论了此类GPS控制网建立过程中几个主要技术问题的解决方法，即用坐标转移法进行偏心观测、用尺度强制约束法或投影面重新选择法处理投影变形和内业平差。工程实践表明，上述问题的有效解决对DGPS基准站坐标的准确测定发挥了良好的技术支撑作用。     

Simultaneous Exact Control of Quasi-Electrostatic Piezoelectric Systems in Multilayered Media

We consider two quasi-electrostatic models in a multilayered piezoelectric structure. Both models only differ on the boundary conditions. For each one of them we prove a boundary observability inequality which together with the Hilbert Uniqueness Method introduced by J.L. Lions allow us to drive both systems to rest at time T with the same control function. We require suitable geometric conditions on the region and the interfaces as well as monotonicity assumptions on the coefficients of the model.