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排序方式: 共有1054条查询结果,搜索用时 46 毫秒
191.
N. Salehi-Nik R. Sotudeh-Gharebagh N. Mostoufi R. Zarghami M.J. Mahjoob 《International Journal of Multiphase Flow》2009
In the processes involving the movement of solid particles, acoustic emissions are caused by particle friction, collision and fluid turbulence. Particle behavior can therefore be monitored and characterized by assessing the acoustic emission signals. Herein, extensive measurements were carried out by microphone at different superficial gas velocities with different particle sizes. Acoustic emission signals were processed using statistical analysis from which the minimum fluidization velocity was determined from the variation of standard deviation, skewness and kurtosis of acoustic emission signals against superficial gas velocity. Initial minimum fluidization velocity, corresponding to onset of fluidization of finer particles in the solids mixture, at which isolated bubbles occur, was also detected by this method. It was shown that the acoustic emission measurement is highly feasible as a practical method for monitoring the hydrodynamics of gas–solid fluidized beds. 相似文献
192.
统计质量保证技术在分析测试实验室内部质量控制中的应用 总被引:6,自引:1,他引:5
对通过统计质量保证(SQA)技术进行分析测试实验室内部质量控制(IQC)的方法作了初探。研究结果表明,SQA技术的应用能保证实验室始终处于统计受控状态,确保测试数据的有效性,有利于分析测试实验室质量保证活动的开展。 相似文献
193.
An analytic representation of thermodynamic properties of the freely jointed square-well chain fluid is developed based on the thermodynamic perturbation theory of Barker–Henderson, Zhang and Weitheim. By using a real function expression for the radial distribution function and incorporating structural information for square-well monomer of TPT1 model, an analytic expression for the Helmholtz energy of square-well chain fluid is expanded from Zhang’s analytic expressions for thermodynamic properties of square-well monomer. The expression leads to good predictions of the compressibility factor, residual internal energy and constant-volume heat capacity for 4-mer, 8-mer and 16-mer square-well fluids when compared with the Monte Carlo (MC) simulation results. The incorporating structural information for square-well dimer of TPT-D model is also calculated. To obtain the constant-volume heat capacity needed, NVT MC simulations were performed. 相似文献
194.
Interactions of sodium dodecyl sulfate with acrylamide –N-isopropylacrylamide) statistical copolymer
Poly(N-isopropylacrylamide) (PNIPAM) precipitates out of water around 32 °C. This critical temperature is raised when hydrophilic
acrylamide sequences are present on the polymer chain. We have used neutron scattering to study the structural properties
of a statistical copolymer containing acrylamide and N-isopropylacrylamide segments at different temperatures and its interactions with an anionic surfactant, sodium dodecyl sulfate
(SDS). At low temperatures, the copolymer behaves as a swollen polymer coil. With an increase in temperature, intermolecular
attractions are observed, and close to the critical temperature of the copolymer, microphase separation is observed. Here,
the structure consists of dense nodules of hydrophobic sequences stabilized by hydrophilic sequences. In the presence of a
small amount of SDS, additional colloidal stability is observed: the nodule size is decreased. At high SDS concentration,
the copolymer is completely solubilized at all temperatures studied and the structure of the polymer–surfactant complex resembles
the “necklace” structure obtained for the homopolymer PNIPAM–SDS system.
Received: 11 November 1999 Accepted: 15 December 1999 相似文献
195.
High-power bipolar semiconductor devices (thyristors and diodes) in a disc-type shape are key components (semiconductor switches) for high-power electronic systems. These systems are important for the economic design of energy transmission systems, i.e. high-power drive systems, static compensation and high-voltage DC transmission lines. In their factory located in Pretzfeld, Germany, the company, eupec GmbH+Co.KG (eupec), is producing disc-type devices with ceramic encapsulation in the high-end range for the world market. These elements have to fulfil special customer requirements and therefore deliver tailor-made trade-offs between their on-state voltage and dynamic switching behaviour. This task can be achieved by applying a dedicated electron irradiation on the semiconductor pellets, which tunes this trade-off. In this paper, the requirements to the irradiation company Mediscan GmbH, from the point of view of the semiconductor manufacturer, are described. The actual strategy for controlling the irradiation results to fulfil these requirements are presented, together with the choice of relevant parameters from the viewpoint of the irradiation company. The set of process parameters monitored, using statistical process control (SPC) techniques, includes beam current and energy, conveyor speed and irradiation geometry. The results are highlighted and show the successful co-operation in this business. Watching this process vice versa, an idea is presented and discussed to develop the possibilities of a highly sensitive dose detection device by using modified diodes, which could function as accurate yet cheap and easy-to-use detectors as routine dosimeters for irradiation institutes. 相似文献
196.
V. Koltchinskii C. T. Abdallah M. Ariola P. Dorato 《Applied mathematics and computation》2001,120(1-3):31-43
It has recently become clear that many control problems are too difficult to admit analytic solutions. New results have also emerged to show that the computational complexity of some “solved” control problems is prohibitive. Many of these control problems can be reduced to decidability problems or to optimization questions. Even though such questions may be too difficult to answer analytically, or may not be answered exactly given a reasonable amount of computational resources, researchers have shown that we can “approximately” answer these questions “most of the time”, and have “high confidence” in the correctness of the answers. 相似文献
197.
198.
199.
《Physics letters. A》2020,384(6):126145
A lowest limit of 1/f noise in semiconductor materials has not yet been reported; we do not even know if such a lowest limit exists. 1/f noise in semiconductors has recently been brought into relation with 1/f noise in quantum dots and other materials. These materials exhibit on-off states which are power-law distributed over a wide range of timescales. We transfer such findings to semiconductors, assuming that the g-r process is also controlled by such on-off states. As a result, we obtain 1/f noise which can be expressed as Hooge's relation. Based on the intermittent g-r process, we estimate the lowest limit of 1/f noise in semiconductor materials. We show that this limit is inversely proportional to the dopant concentration; to detect the lowest limit of 1/f noise, the number of centers should be as small as possible. We also find a smooth dependence of 1/f noise and g-r noise on time. 相似文献
200.
We present a novel generating function (GF) method for the self-condensing vinyl polymerization (SCVP) system with any initial distribution of preexisted polymers.Such a method was proven to be especially useful to investigate the semi-batch SCVP system allowing a sequence of feeding operations during the polymerization.Consequently,the number-,weight-,and z-average molecular weights as well as dispersity index of hyperbranched polymers can be explicitly given,which are determined by predetermined feeding details and conversions in each polymerization step.These analytical results are further confirmed by the corresponding Monte Carlo simulations.Therefore,the present GF method has provided a unified treatment to the semi-batch SCVP system.Accordingly,hyperbranched polymers with desired properties can be prepared by designing feeding details and presetting conversions at each step based on the present GF method. 相似文献