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Effect of printing parameters on properties of 3D printing sand samples

China Foundry 2023年第6期20卷 553-562页

作者： De-quan Shi Yin-yu Hou Gui-li Gao school of Materials and Chemistry University of Shanghai for Science and TechnologyShanghai 200093China school of Mechanical and Energy engineering Shanghai Technical Institute of Electronics and InformationShanghai 201411China

Three-dimensional sand printing(3DSP)is widely applied in sand mold *** this study,the effects of printing parameters including the resolution of printehead holes,activator content,layer thickness,and recoating speed on the tensile and bending strengths,gas evolution,and loss-on-ignition(LOI)of 3DSP samples were investigated by changing single parameter,and the dimension deviation was also *** the resolution increases,the tensile strength,bending strength,gas evolution,LOI,and deviations at X-and Y-axis directions decrease gradually while the deviation at Z-axis direction firstly increases and then *** gas evolution and LOI drops by 13.02%and 8.13%respectively,but the strength only reduces by 2.2% when the resolution increases from 0.08 mm to 0.09 *** strengths of samples rise at first and then decline while the gas evolution and LOI rise gradually with the increasing activator content or recoating *** activator content is found to have little effect on the gas evolution as the activator increases from 0.14%to 0.34%,the gas evolution is increased by 7.3%which is far less than the LOI increment of 24.1%.As the layer thickness increases,the tensile and bending strengths firstly rise and then drop while gas evolution and LOI *** the optimal printing parameters of 0.09 mm resolution,0.18%activator,0.28 mm layer thickness and 160 mm·s^(-1) recoating speed,the tensile strengths for X-sample and Y-sample are 1.48 MPa and 1.37 MPa,the bending strengths are 1.84 MPa and 1.75 MPa,the gas evolution and LOI are 9.62 mL·g^(-1) and 1.92%,respectively.

关键词： three-dimensional sand printing printing parameters mechanical properties LOI

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Effects of gas pressure on plasma characteristics in dual frequency argon capacitive glow discharges at low pressure by a self-consistent fluid model

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Chinese Physics B 2017年第12期26卷 361-370页

作者：赵璐璐刘悦 Tagra Samir Key Laboratory of Materials Modification by Laser Ion and Electron Beams (Ministry of Education) School of PhysicsDalian University of Technology school of information Science and engineering Dalian Polytechnic University

A self-consistent fluid model for dual radio frequency argon capacitive glow discharges at low pressure is established. Numerical results are obtained by using a finite difference method to solve the model numerically, and the results are analyzed to study the effect of gas pressure on the plasma characteristics. It shows that when the gas pressure increases from 0.3 Torr （1 Torr=1.33322102 Pa） to 1.5 Torr, the cycle-averaged plasma density and the ionization rate increase; the cycle-averaged ion current densities and ion energy densities on the electrodes electrode increase; the cycle-averaged electron temperature decreases. Also, the instantaneous electron density in the powered sheath region is presented and discussed. The cycle-averaged electric field has a complex behavior with the increasing of gas pressure, and its changes take place mainly in the two sheath regions. The cycle-averaged electron pressure heating, electron ohmic heating, electron heating, and electron energy loss are all influenced by the gas pressure. Two peaks of the electron heating appear in the sheath regions and the two peaks become larger and move to electrodes as the gas pressure increases.

关键词： dual frequency gas pressure glow discharge

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A robust extraction algorithm for biomedical signals from noisy mixtures

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Frontiers of Computer Science 2011年第4期5卷 387-394页

作者： Yongjian ZHAO Boqiang LIU Sen WANG school of Control Science and engineering Shandong University Jinan 250061 China school of information engineering Shandong University at Weihai Weihai 264209 China Kodak Research Laboratories Eastman Kodak Company Rochester NY 14620 USA

Blind source extraction （BSE） is widely used to solve signal mixture problems where there are only a few desired signals. To improve signal extraction performance and expand its application, we develop an adaptive BSE algorithm with an additive noise model. We first present an improved normalized kurtosis as an objective function, which caters for the effect of noise. By combining the objective function and Lagrange multiplier method, we further propose a robust algorithm that can extract the desired signal as the first output signal. Simulations on both synthetic and real biomedical signals demonstrate that such combination improves the extrac- tion performance and has better robustness to the estimation error of normalized kurtosis value in the presence of noise.

关键词： blind source extraction (BSE) normalizedkurtosis objective function biomedical signal Lagrangemultiplier method

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Improved fast model migration method for centrifugal compressor based on bayesian algorithm and Gaussian process model

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Science China(Technological Sciences) 2018年第12期61卷 1950-1958页

作者： CHU Fei DAI BangWu LU NanNan MA XiaoPing WANG FuLi school of information and Control engineering China University of Mining and Technology State Key Laboratory of Integrated Automation for Process Industries Northeastern University

Design and operation optimization of centrifugal compressor are always based on an accurate prediction model, however, due to the short time operation and lack of data information, it is difficult to get an accurate prediction model of a new centrifugal compressor in time. This paper applies an improved fast model migration method(FMM method) to develop the model of the new centrifugal compressor. The method adapts a Gaussian Process(GP) model from an old centrifugal compressor to fit a new and similar centrifugal compressor, and the adaptation is conducted by a scale-bias adjustment migration technology. In order to obtain the better estimated parameters of migration, Bayesian method, which takes the prior knowledge into consideration, is used in the sequential experiment. The approach is validated by a specific simulation bench. The results indicate that the applied approach can achieve a better prediction precision with fewer data of the new centrifugal compressor compared to pure GP method, and can model the new centrifugal compressor rapidly.

关键词： Bayesian centrifugal compressor Gaussian process model model migration performance prediction

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Partial Label Learning via Conditional-Label-Aware Disambiguation

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Journal of Computer Science & Technology 2021年第3期36卷 590-605页

作者： Peng Ni Su-Yun Zhao Zhi-Gang Dai Hong Chen Cui-Ping Li Key Laboratory of Data engineering and Knowledge engineering(Renmin University of China) Ministry of Education Beijing 100087China school of information Renmin University of ChinaBeijing 100087China

Partial label learning is a weakly supervised learning framework in which each instance is associated with multiple candidate labels,among which only one is the ground-truth *** paper proposes a unified formulation that employs proper label constraints for training models while simultaneously performing *** existing partial label learning approaches that only leverage similarities in the feature space without utilizing label constraints,our pseudo-labeling process leverages similarities and differences in the feature space using the same candidate label constraints and then disambiguates noise *** experiments on artificial and real-world partial label datasets show that our approach significantly outperforms state-of-the-art counterparts on classification prediction.

关键词： disambiguation partial label learning similarity and dissimilarity weak supervision

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Asymptotic Performance of Sparse Signal Detection Using Convex Programming Method

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Chinese Journal of Aeronautics 2012年第3期25卷 396-405页

作者： LEI Chuan ZHANG Jun school of Electronics and information engineering Beihang UniversityBeijing 100191China National Key Laboratory of CNS/ATM Beijing 100191China

The detection of sparse signals against background noise is considered. Detecting signals of such kind is difficult since only a small portion of the signal carries information. Prior knowledge is usually assumed to ease detection. In this paper, we consider the general unknown and arbitrary sparse signal detection problem when no prior knowledge is available. Under a Ney- man-Pearson hypothesis-testing framework, a new detection scheme is proposed by combining a generalized likelihood ratio test （GLRT）-Iike test statistic and convex programming methods which directly exploit sparsity in an underdetermined system of linear equations. We characterize large sample behavior of the proposed method by analyzing its asymptotic performance. Specifically, we give the condition for the Chernoff-consistent detection which shows that the proposed method is very sensitive to the norm energy of the sparse signals. Both the false alam rate and the miss rate tend to zero at vanishing signal-to-noise ratio （SNR）, as long as the signal energy grows at least logarithmically with the problem dimension. Next we give a large deviation analysis to characterize the error exponent for the Neyman-Pearson detection. We derive the oracle error exponent assuming signal knowledge. Then we explicitly derive the error exponent of the proposed scheme and compare it with the oracle exponent. We complement our study with numerical experiments, showing that the proposed method performs in the vicinity of the likelihood ratio test （LRT） method in the finite sample scenario and the error probability degrades exponentially with the number of observations.

关键词： signal detection convex programming asymptotic analysis signal reconstruction sparse signals

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Design of PID controller with incomplete derivation based on differential evolution algorithm

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Journal of Systems engineering and Electronics 2008年第3期19卷 578-583页

作者： Wu Lianghong Wang Yaonan Zhou Shaowu Tan Wen school of information and Electric engineering Hunan Univ. of Science and Technology Xiangtan 411201 P. R. China Coll. of Electric and information engineering Hunan Univ. Changsha 410082 P. R. China

To determine the optimal or near optimal parameters of PID controller with incomplete derivation, a novel design method based on differential evolution （DE） algorithm is presented. The controller is called DE-PID controller. To overcome the disadvantages of the integral performance criteria in the frequency domain such as IAE, ISE, and ITSE, a new performance criterion in the time domain is proposed. The optimization procedures employing the DE algorithm to search the optimal or near optimal PID controller parameters of a control system are demonstrated in detail. Three typical control systems are chosen to test and evaluate the adaptation and robustness of the proposed DE-PID controller. The simulation results show that the proposed approach has superior features of easy implementation, stable convergence characteristic, and good computational efficiency. Compared with the ZN, GA, and ASA, the proposed design method is indeed more efficient and robust in improving the step response of a control system.

关键词： PID controller incomplete derivation differential evolution parameter tuning.

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FUZZY MODEL FOR TWO-DIMENSIONAL RIVER WATER QUALITY SIMULATION UNDER SUDDEN POLLUTANTS DISCHARGED

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Journal of Hydrodynamics 2007年第4期19卷 434-441页

作者： LI Ru-zhong SHIGEKI Masunaga HONG Tian-qiu QIAN Jia-zhong school of Resources and Environmental engineering Hefei University of Technology Hefei 230009 China Graduate school of Environment and information Sciences Yokohama National University Yokohama 240-8501 Japan

Based on the fuzziness and impreciseness of water environmental system, the fuzzy arithmetic was used to simulate the fuzzy and imprecise relations in modeling river water quality. By defining the parameters of water quality model as symmetrical triangular fuzzy numbers, a two-dimensional fuzzy water quality model for sudden pollutant discharge is established. From the fuzzy model, the pollutant concentrations, corresponding to the specified confidence level of a, can be obtained by means of the a-cut technique and arithmetic operations of triangular fuzzy numbers. Study results reveal that it is feasible in theory and reliable on calculation applying triangular fuzzy numbers to the simulation of river water quality.

关键词： fuzzy water quality simulation model triangular fuzzy number membership function a-cut technique

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Wavelet network based predistortion method for wideband RF power amplifiers exhibiting memory effects

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2007年第4期8卷 625-630页

作者： JIN Zhe SONG Zhi-huan HE Jia-ming school of information Science and engineering Zhejiang University Hangzhou 310027 China Institute of Communication Technologies Ningbo University Ningbo 315211 China

RF power amplifiers (PAs) are usually considered as memoryless devices in most existing predistortion techniques. Nevertheless, in wideband communication systems, PA memory effects can no longer be ignored and memoryless predistortion cannot linearize PAs effectively. After analyzing PA memory effects, a novel predistortion method based on wavelet networks (WNs) is proposed to linearize wideband RF power amplifiers. A complex wavelet network with tapped delay lines is applied to construct the predistorter and then a complex backpropagation algorithm is developed to train the predistorter parameters. The simulation results show that compared with the previously published feed-forward neural network predistortion method, the proposed method provides faster convergence rate and better performance in reducing out-of-band spectral regrowth.

关键词： Power amplifiers. Predistortion. Memory effects. Wavelet networks

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Leader trajectory planning method considering constraints of formation controller

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Journal of Systems engineering and Electronics 2023年第5期34卷 1294-1308页

作者： YAO Dongdong WANG Xiaofang LIN Hai WANG Zhuping school of Aerospace engineering Beijing Institute of TechnologyBeijing100081China Xi’an Institute of Electromechanical information Technology Xi’an710065China

To ensure safe flight of multiple fixed-wing unmanned aerial vehicles(UAVs)formation,considering trajectory planning and formation control together,a leader trajectory planning method based on the sparse A*algorithm is ***,a formation controller based on prescribed performance theory is designed to control the transient and steady formation configuration,as well as the formation forming time,which not only can form the designated formation configuration but also can guarantee collision avoidance and terrain avoidance ***,considering the constraints caused by formation controller on trajectory planning such as the safe distance,turn angle and step length,as well as the constraint of formation shape,a leader trajectory planning method based on sparse A^(*)algorithm is *** results show that the UAV formation can arrive at the destination safely with a short trajectory no matter keeping the formation or encountering formation transformation.

关键词： trajectory planning formation control prescribed performance controller multiple constraints formation shape formation transformation

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