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排序方式: 共有1865条查询结果,搜索用时 15 毫秒
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Stabilization of turbulent lifted jet flames assisted by pulsed high voltage discharge 总被引:1,自引:0,他引:1
《Combustion and Flame》2006,144(1-2):422-425
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《Journal of Process Control》2014,24(3):47-59
A nonlinear multiobjective model-predictive control (NMMPC) scheme, consisting of self-organizing radial basis function (SORBF) neural network prediction and multiobjective gradient optimization, is proposed for wastewater treatment process (WWTP) in this paper. The proposed NMMPC comprises a SORBF neural network identifier and a multiple objectives controller via the multi-gradient method (MGM). The SORBF neural network with concurrent structure and parameter learning is developed as a model identifier for approximating on-line the states of WWTP. Then, this NMMPC optimizes the multiple objectives under different operating functions, where all the objectives are minimized simultaneously. The solution of optimal control is based on the MGM which can shorten the solution time. Moreover, the stability and control performance of the closed-loop control system are well studied. Numerical simulations reveal that the proposed control strategy gives satisfactory tracking and disturbance rejection performance for WWTP. Experimental results show the efficacy of the proposed method. 相似文献
5.
《Expert systems with applications》2014,41(13):5788-5803
In this paper, an improved global-best harmony search algorithm, named IGHS, is proposed. In the IGHS algorithm, initialization based on opposition-based learning for improving the solution quality of the initial harmony memory, a new improvisation scheme based on differential evolution for enhancing the local search ability, a modified random consideration based on artificial bee colony algorithm for reducing randomness of the global-best harmony search (GHS) algorithm, as well as two perturbation schemes for avoiding premature convergence, are integrated. In addition, two parameters of IGHS, harmony memory consideration rate and pitch adjusting rate, are dynamically updated based on a composite function composed of a linear time-varying function, a periodic function and a sign function in view of approximate periodicity of evolution in nature. Experimental results tested on twenty-eight benchmark functions indicate that IGHS is far better than basic harmony search (HS) algorithm and GHS. In further study, IGHS has also been compared with other eight well known metaheuristics. The results show that IGHS is better than or at least similar to those approaches on most of test functions. 相似文献
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This paper deals with the problem of H∞ filtering for discrete-time systems with stochastic missing measurements. A new missing measurement model is developed by decomposing the interval of the missing rate into several segments. The probability of the missing rate in each subsegment is governed by its corresponding random variables. We aim to design a linear full-order filter such that the estimation error converges to zero exponentially in the mean square with a less conservatism while the disturbance rejection attenuation is constrained to a given level by means of an H∞ performance index. Based on Lyapunov theory, the reliable filter parameters are characterised in terms of the feasibility of a set of linear matrix inequalities. Finally, a numerical example is provided to demonstrate the effectiveness and applicability of the proposed design approach. 相似文献
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《矿业科学技术学报(英文版)》2016,26(3):495-500
The water abundance of mine floor limestone needs to be solved urgently as the average depth of coal mining in China has increased gradually. A method is presented to discuss water abundance with the numerical and physical layered geoelectrical model being established in the half-space, full-space and full-space with tunnel, respectively. The parameters of water abundance are changed in this study, which includes water quantity, water content and volume of abnormity of water-containing abnormity. Results indicate that the different work fields have different macroscopic influences on the apparent resistivity,and the water abundance parameters of water-containing abnormity have quantitative relationship with the apparent resistivity mean in abnormal regions(three-dimensional space region). The quantitative relationships are shown as following: firstly, the amount of water injection has negative linear correlation with the apparent resistivity mean; secondly, when abnormity is unsaturated, there is a negative power function relationship between water content and apparent resistivity mean; thirdly, the volume of abnormity and apparent resistivity mean behave as a decreasing power function law. 相似文献
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为明确某帆板面内单轴扫频力学环境试验中同步钢索振动幅度过大和限位结构被破坏的原因,考虑集中质量和限位结构影响,采用有限段方法建立帆板同步钢索系统的动力学模型,对其在面内单轴扫频激励条件的响应进行数值模拟,结果再现了标志点的响应从面内振动发展到面外振动,再到绕两支撑点轴旋转振动的复杂振动模式,同时给出限位接触力和钢索标志点振幅,仿真结果与试验状态吻合。分析表明,持续旋转振动钢索施加在限位孔壁上的交变接触力是导致限位结构破坏的主要原因。 相似文献
9.
Haiming Zhang Biao Zhao Huimin Xiang Fu-Zhi Dai Zhili Zhang Yanchun Zhou 《Journal of the American Ceramic Society》2021,104(5):2213-2224
The electromagnetic (EM) wave absorbing properties of Cr2AlB2 powders and those after high-temperature oxidation were investigated. Coupling of magnetic and dielectric loss enables Cr2AlB2 with good absorption properties. The minimum reflection loss (RL) value is −44.9 dB at 8.5 GHz with a thickness of 2.7 mm, and the optimized effective absorption bandwidth (EAB) is 4.4 GHz (13.0-17.4 GHz) with a thickness of 1.6 mm. After oxidation at 750, 900, and 1000°C for 2 h, the minimum RL values, respectively, are −23.9 dB (17.5 GHz, 1.5 mm), −41.4 dB (16.5 GHz, 1.5 mm), and −39.5 dB (8.0 GHz, 3.0 mm); and the corresponding EAB values, respectively, are 3.8 GHz (13.6-17.4 GHz, 1.7 mm), 4.1 GHz (13.5-17.6 GHz, 1.6 mm), and 4.4 GHz (13.0-17.4 GHz, 1.7 mm). With an absorber thickness of 1.5-4.0 mm, the EAB with a RL value of less than −10 dB can be tuned in a broad-frequency range 5.0-18.0 GHz, which basically covers C (4-8 GHz), X (8-12 GHz), and Ku (12-18 GHz) bands. These results demonstrate that Cr2AlB2, as a high-efficient and oxidation-resistant absorber, is a promising candidate for microwave absorption applications and can retain good EM wave absorbing properties after high-temperature oxidation. 相似文献
10.
《Journal of the European Ceramic Society》2021,41(15):7662-7669
Piezoelectric energy harvesters (PEH) hold enormous potential for converting mechanical energy from our surrounding environment into electrical energy that can be used for powering portable electronics. Potassium sodium niobate (KNN) is one of the promising alternatives to replace lead-based piezoelectric materials. This work presents a cutting-edge demonstration of synthesis-function-device integration of piezoelectric nanofibers, where the morphology and the composition are engineered towards achieving high device output. We report a flexible nanogenerator based on electrospun Li and Ta-modified lead-free KNN nanofibers yielding a high voltage output of 5.6 V, which is around 9-fold higher than for the Mn-doped KNN nanofibers reported previously. The influence of Li and Ta-incorporation into the KNN lattice on the electromechanical coupling and the effect of a nanofiber morphology are investigated. The net-shaped KNN and Li and Ta-modified KNN nanofibers, synthesized by electrospinning of appropriate sols, maintain their structural integrity upon calcination and firing steps. The phase analysis (XRD) confirms the formation of single-phase (KNN) material. Li and Ta are found to be incorporated on the A and B-sites of the perovskite lattice, respectively. Piezo force microscopy data show the heat-treated nanofibers to exhibit multi-domain ferroelectric properties. 相似文献