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71.
Surajit Chaudhuri Kris Ganjam Venky Ganti 《硅谷》2005,(6):77-81
简介
由于拼写错误、意外的缩略语和其他不规则问题,实际的数据是“有问题”的。因此,在数据仓储项目中,很大一部分的时间和金钱都花费在了数据提取、数据转换和数据加载(ETL,Extraction、Transformation、Loading)阶段。在ETL阶段,新数据被清理、标准化,并使其与现有数据一致。在Microsoft SQL Server 2005中可用的模糊查找和模糊分组转换,有助于使ETL过程在遇到若干种在交际数据中观测到的常见错误时更易复原。它们解决一般的匹配和分组问题,而无需特定于域的规则和脚本的专家集合。通过为您的域自定义模糊查找和模糊分组,您可以利用Business Intelligence Development Studio内的通用数据清理算法,并避免创建复杂的自定义规则和代码。 相似文献
72.
Chaudhuri B. Pal B.C. Zolotas A.C. Jaimoukha I.M. Green T.C. 《Power Systems, IEEE Transactions on》2003,18(3):1149-1156
This paper demonstrates the enhancement of inter-area mode damping by multiple flexible AC transmission systems (FACTS) devices. Power system damping control design is formulated as an output disturbance rejection problem. A decentralized H/sub /spl infin// damping control design based on the mixed-sensitivity formulation in the linear matrix inequality (LMI) framework is carried out. A systematic procedure for selecting the weights for shaping the open loop plant for control design is suggested. A 16-machine, five-area study system reinforced with a controllable series capacitor (CSC), a static VAr compensator (SVC), and a controllable phase shifter (CPS) at different locations is considered. The controllers designed for these devices are found to effectively damp out inter-area oscillations. The damping performance of the controllers is examined in the frequency and time domains for various operating scenarios. The controllers are found to be robust in the face of varying power-flow patterns, nature of loads, tie-line strengths, and system nonlinearities, including device saturations. 相似文献
73.
Thoracic diabetic radiculopathy causing truncal pain and abdominal muscle bulging is a recognized though extremely rare complication of diabetes. We report here six cases, describing their clinical features and natural history in detail: the condition affects predominantly middle-aged men, usually on the right side of the abdominal wall, involving three to five adjacent nerve roots between T6 and T12. It may be accompanied by profound weight loss which is not normally due to poorly controlled diabetes. Complete resolution of this syndrome occurs after 3 to 12 months. 相似文献
74.
Parul Gupta Anand GhosalkarSaroj Mishra Tapan Kumar Chaudhuri 《Journal of Bioscience and Bioengineering》2009,107(2):102-107
A major portion of the over expressed yeast mitochondrial aconitase, a large 82 kDa monomeric TCA cycle enzyme, in Escherichia coli led to the formation of inclusion bodies. Bacterial chaperonin GroEL mediated the correct folding of aconitase with the assistance of its co-chaperonin GroES in an ATP dependent manner. Till date the chaperonin assisted folding of aconitase was limited to the shake flask studies with relatively low yields of folded aconitase. No attempt had yet been made to enhance the yield of chaperone mediated folding of aconitase using a bioreactor. The current report deals with the effect of co-expression of GroEL/GroES in the production of soluble, biologically active recombinant aconitase in E. coli by cultivation in a bioreactor at different temperatures under optimized conditions. It revealed that the yield of functional aconitase was enhanced, either in presence of co-expressed GroEL/ES or at low temperature cultivation. However, the outcome from the chaperone assisted folding of aconitase was more pronounced at lower temperature. A 3-fold enhancement in the yield of functional aconitase from the bioreactor based chaperone assisted folding was obtained as compared to the shake flask study. Hence, the present study provides optimized conditions for increasing the yield of functional aconitase by batch cultivation in a bioreactor. 相似文献
75.
The recovery of depth from defocused images involves calculating the depth of various points in a scene by modeling the effect that the focal parameters of the camera have on images acquired with a small depth of field. In the approach to depth from defocus (DFD), previous methods assume the depth to be constant over fairly large local regions and estimate the depth through inverse filtering by considering the system to be shift-invariant over those local regions. But a subimage when analyzed in isolation introduces errors in the estimate of the depth. In this paper, we propose two new approaches for estimating the depth from defocused images. The first approach proposed here models the DFD system as a block shift-variant one and incorporates the interaction of blur among neighboring subimages in an attempt to improve the estimate of the depth. The second approach looks at the depth from defocus problem in the space-frequency representation framework. In particular, the complex spectrogram and the Wigner distribution are shown to be likely candidates for recovering the depth from defocused images. The performances of the proposed methods are tested on both synthetic and real images. The proposed methods yield good results and the quality of the estimates obtained using these methods is compared with the existing method. 相似文献
76.
Thermal conductivity measurements in the temperature range 4.2–300 K on three single crystals of bismuth containing 1.77, 3.2, and 9.33 at % antimony, respectively, are reported. In the low-temperature region, a change from purely phonon-phonon scattering process to a predominantly impurity scattering process was observed with the increase of antimony concentration. In the high-temperature region, the analysis of the results shows the dominance of the electronic contribution over the phonon contribution to the total thermal conductivity, though the latter is not negligible. Individual contributions to total electronic thermal conductivity were calculated, using the equation formulated by Price, for the sample containing 9.33 at % antimony. The agreement between (K E)calc and (K E)exp = K ? KL seems to be quite satisfactory up to about 200 K. 相似文献
77.
The spectral dependence of carrier generation and recombination loss in a-SiGe:H samples having band gaps between 1.74 eV and 1.35 eV was studied in the Schottky barrier solar cell device structure. The active a-SiGe:H layers were of identical thickness (1 μm). The effect of hydrogen dilution of the source gases (silane and germane) on the generation and recombination characteristics was also studied. It has been observed that the net optical generation of carriers increases almost linearly with the lowering of the band gap but is independent of the localised states. Net recombination loss, on the other hand, increases with defect states but cannot be fully explained by taking into account the neutral defect centers alone. Within the above mentioned band gap range, it has been observed that the competing processes of generation and recombination resulted in a maximum short circuit current for a-SiGe:H samples of 1.44 eV band gap. 相似文献
78.
A robust algroithm that estimates the motion parameters recursively from a sequence of noisy images is presented here. We propose the use of the least median of squares method in conjunction with a computationally efficient recursive scheme. The method works well even when nearly half of the features have been matched very poorly. A recursive constrained least squares method is developed while dealing with a range or stereo data sequence and a recursive total least squares method is proposed for the monocular data sequence. 相似文献
79.
Wave propagation through a hollow rectangular dielectric guide with anisotropic surrounding is studied here. It has been shown that anisotropy can be utilized to reduce the loss in resonating structure of the gas laser system. 相似文献
80.
A relatively new titanium alloy, TIMETAL 21S (Ti-15Mo-2.7Nb-3Al-0.2Si-0.15O (in wt pct)), is a potential matrix material for
advanced titanium matrix composites for elevated temperature use. In order to develop a perspective on the microstructural
stability of this alloy, the influence of several commonly used heat treatments on the microstructure of TIMETAL 21S was studied
using optical and transmission electron microscopy (TEM). Depending on the specific thermal treatment, a number of phases,
includingα,ω- type, and silicide, can form in this alloy. It was found that both recrystallized and nonrecrystallized areas could be present
in the microstructure of an annealed bulk alloy, but the microstructure of annealed sheet alloy was fully recrystallized.
The mixed structure of the bulk alloy, developed as a result of inhomogeneous deformation, could not be removed by heat treatment
alone at 900 °C. Athermalω-type phase formed in this alloy upon quenching from the solution treatment temperature (900 °C). Silicide precipitates were
also found in the quenched sample. Thermal analysis was used to determine theβ transus and silicide solvus as close to 815 °C and 1025 °C, respectively. In solution-treated and quenched samples, a high-temperature
aging at 600 °C resulted in the precipitation ofα phase. The precipitation reaction was slower in the recrystallized regions compared to the nonrecrystallized regions. During
low-temperature aging (350 °C), the ellipsoidalω-type phase persisted in the recrystallized areas even after 100 hours, whereas a high density ofα precipitates developed in the nonrecrystallized areas within only 3 hours. The observed behavior in precipitation may be
related to the influence of substructure in the nonrecrystallized areas, providing for an enhanced kinetics during aging.
Theα precipitates (formed during continuous cooling from the solution treatment temperature, low-temperature aging, and high-temperature
aging) always obeyed the Burgers orientation relationship. With respect to the microstructure, TIMETAL 21S is similar to other
solute-lean, metastableβ titanium alloys. 相似文献