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1.
There is a wish to be able to enter text into mobile computing devices at the speed of speech. Only handwritten shorthand schemes can achieve this data recording rate. A new, overall solution to the segmentation and recognition of phonetic features in Pitman shorthand is proposed in this paper. Approaches to the recognition of consonant outlines, vowel and diphthong symbols and shortforms, which are different components of Pitman shorthand, are presented. A new rule is introduced to solve the issue of smooth junctions in the consonant outlines which was normally the bottleneck for recognition. Experiments with a set of 1127 consonant outlines, 2039 vowels and diphthongs and 841 shortforms from three shorthand writers have demonstrated that the proposed solution is quite promising. The recognition accuracies for consonant outlines, vowels and diphthongs, and shortforms achieved 75.33%, 96.86% and 91.86%, respectively. From the evaluation of 461 outlines with smooth junction, the introduction of the new rule has a great positive effect on the performance of the solution. The recognition accuracy of smooth junction improves from 37.53% to 93.41% given a writing time increase of 14.42%.  相似文献   
2.
在光伏系统中,光伏阵列往往会受到阴影条件(partial shading condition,PSC)的影响,造成光伏系统输出功率偏低以及功率-电压($P-V$)特性曲线出现多峰值的现象,从而导致常规最大功率跟踪(maximum power point tracking,MPPT)算法易陷入局部最优的问题.对此,设计一种基于迁移强化学习(transfer reinforcement learning,TRL)的MPPT算法.该算法将连续变量的动作空间分解为若干个小范围的子搜索空间,从而有效提高TRL的学习效率.同时,引入知识迁移,即将旧任务的最优知识矩阵应用到新任务中,进而大幅提高TRL的收敛速度.通过对3种算例的研究,即恒温变光照强度、变温变光照强度和香港实地测试,其仿真结果表明,与传统增量电导法(incremental conductance,INC)、遗传算法(genetic algorithm,GA)、粒子群优化(particle swarm optimization, PSO)算法、人工蜂群(artificial bee colony,ABC)算法、布谷鸟算法(cuckoo search algorithm,CSA)、教-学优化(teaching-learning based optimization,TLBO)算法以及Q学习算法相比,TRL能在PSC下实现最快速的全局最大功率跟踪,同时具有最小的功率波动.最后,基于dSpace的硬件在环实验验证了TRL的硬件可行性.  相似文献   
3.
The flow characteristics of the centrifugal fans with different blade outlet angles are basically discussed on steady and unsteady simulations for a rectangular casing fan. The blade outlet angles of the impellers are 35° and 25° respectively. The unsteady flow behavior in the passage of the impeller 35° is quite different from that in the steady flow behavior. The large flow separation occurs in the steady flow field and unsteady flow field of the impeller 35°, the flow distribution in the circumferential direction varies remarkably and the flow separation on the blade occurs only at the back region of the fan; but the steady flow behavior in the impeller 25° is almost consistent with the unsteady flow behavior, the flow distribution of the circumferential direction doesn't vary much and the flow separation on the blade hardly occurs. When the circumferential variation of the flow in the impeller is large, the steady flow simulation is not coincident to the unsteady flow simulation.  相似文献   
4.
Thermal behavior of palm oil samples drawn from the batch crystallizers that failed during crystallization and of a control oil that was drawn from a batch that produced good crystallization were analyzed by differential scanning calorimetry under constant heating and cooling conditions. Four polymorphs—β’2, α, β’1, and β1—were observed, and their temperatures were tabulated. A rapid and sudden surge of heat demand was observed for samples from failed crystallizers. Less supercooling values were obtained from the control oil compared to the higher values for samples from failed crystallizers. In crystallization thermograms, a sharp high-temperature exotherm (high-T peak) and a broad low-temperature exotherm (low-T peak) were observed. Low-T peaks were found almost invariably stationary at −5.1 to −5.6°C, and high-T peaks varied depending on the saturation level of the oil. A new peak, sandwiched between the high-T and low-T peaks, was observed for the control oil.  相似文献   
5.
Solubilization of selected polycyclic aromatic compounds (PAC) by biodegradable nonionic surfactants, Tergitol 15-S-X (X=7 or 9) and Neodol 25–7, was investigated and correlated with micellar properties of these surfactants. These PAC include dibenzofuran, phenanthrene, acenaphthene, fluoranthene, and 9-chloroanthracene. Tergitol surfactants are mixtures of secondary ethoxylated alcohols, and Neodol 25–7 is a mixture of similar species but has the alcohol group in the primary position. These surfactants have the same chain length of hydrophobic tails and similar numbers of ethylene oxides. The results show that the Neodol surfactant yields micelles having larger hydrophobic core volume and renders a higher solubilization capacity for the PAC solubilizates in comparison with Tergitol surfactants. In general, aggregation numbers and micellar sizes both increase at elevated temperatures still below the cloud point. The micellewater partition coefficients of these PAC by the nonionic surfactants were well correlated to their octanol-water partition coefficients. Moreover, an estimated log K ow value of 9-chloanthracene is 4.78.  相似文献   
6.
7.
本文设计了一款基于扰动观测器的鲁棒分数阶滑模控制(POFO–SMC)来实现光伏逆变器的最大功率跟踪(MPPT).首先,将光伏逆变器的非线性、参数不确定性以及未建模动态聚合成一个扰动,并通过扰动观测器对其进行在线估计.随后,采用分数阶滑模控制(FOSMC)对该扰动估计进行实时完全补偿,从而实现不同工况下全局一致的控制性能.同时,POFO–SMC采用扰动实时估计而非传统滑模控制(SMC)中所使用的扰动上限值进行补偿,因此可有效解决传统SMC过于保守的缺点,使得控制成本更为合理.最后,POFO–SMC无需精确的系统模型,仅需测量光伏逆变器的q轴电流和直流侧电压,因此易于硬件实现.本文进行了两个算例的研究,即光照强度变化和电网电压跌落.仿真结果表明,与传统PI控制、反馈线性化控制(FLC)、SMC和FOSMC相比,POFO–SMC在各类工况下均具有最好的动态特性及最高的鲁棒性.基于dSpace的硬件在环实验(HIL)验证了其硬件可行性.  相似文献   
8.
400 MW SMES power conditioning system development and simulation   总被引:13,自引:0,他引:13  
A conceptual design for a 22 MWh superconducting magnetic energy storage (SMES) system engineering test model (ETM) was developed. The objectives of the SMES-ETM are to demonstrate the feasibility of using a SMES system to perform load-leveling and system stabilization for commercial utilities and to supply 400 MW power pulses for ground-based defense systems. The performance requirements and configuration of the proposed 22 MWh SMES-ETM and its power conditioning system are presented. The power conditioning system consists of a DC-DC chopper linked to a GTO-based voltage source converter interfacing the superconducting energy storage coil to the AC power system. The SMES system operation in the charging and discharging modes is described and the results of digital simulations demonstrating the feasibility of the proposed power conditioning system and exploring its overall behavior under normal and fault conditions are prevented  相似文献   
9.
Abstract. Let { X t } be a Gaussian ARMA process with spectral density f θ(Λ), where θ is an unknown parameter. To estimate θ, we propose an estimator θCw of the Bayes type. Since our standpoint in this paper is different from Bayes's original approach, we call it a weighted estimator. We then investigate various higher-order asymptotic properties of θCw. It is shown that θCw is second-order asymptotically efficient in the class of second-order median unbiased estimators. Furthermore, if we confine our discussions to an appropriate class D of estimators, we can show that θCw is third-order asymptotically efficient in D . We also investigate the Edgeworth expansion of a transformation of θCw. We can then give the transformation of θCw which makes the second-order part of the Edgeworth expansion vanish. Finally we consider the problem of testing a simple hypothesis H:θ=θo against the alternative A:θ#θo. For this problem we propose a class of tests δA which are based on the weighted estimator. We derive the X 2 type asymptotic expansion of the distribution of S (ζδA) under the sequence of alternatives A n :θ=θo+ε n 1/2, ε > 0. We can then compare the local powers of various tests on the basis of their asymptotic expansions.  相似文献   
10.
Apparently healthy Wistar rats of body weight 250-300 g were chosen for the experiments. A group of 6 rats were assigned for each fraction. The dose of Russell's viper venom (RVV) fraction used for in vivo experiments was 0.75 microgram/g body weight. Of each batch of 6 rats 3 were sacrificed on the third day and the remaining 3 on the fifth day after the administration of test venom fractions. Daily urine output with proteinuria and serum creatinine were determined on the day they were sacrificed. Kidneys from the rats were also examined under light microscopy after hematoxylin and eosin staining. In the in vitro experiment, kidney slices (1 mm thickness) from normal rat was incubated with RVV fractions of 5 mg/ml concentration. The predominant renal lesions observed in both sets of animal experiments were tubular degeneration and necrosis. The changes were mostly confined to proximal tubules. Glomerular changes were mild. Similar tubulotoxic effects were produced by whole RVV as well as single fractions. Therefore, it is possible that RVV contains a common nephrotoxic (protein) component which is present in all fractions of the venom. The renal damage caused by RVV seemed to be due to both systemic effects (mainly DIC and renal ischemia) and direct tubulotoxic effects of the venom.  相似文献   
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