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| 1 | Numerical investigation on the “S” characteristics of a reduced pump turbine model显示文摘The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, a shear stress transport model (SST) with various numerical schemes for pressure term in the governing equation was investigated in a whole pump turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. Through the computation, it was shown that different zones in the curve should employ different schemes to get the solution converged. Comparison of discharge-speed performance showed that good correspondence is got between experimental data and CFD results. Based on this, internal flow analysis was carried out at three typical operating points representing turbine mode, shut-off mode and reversible pump mode, respectively. According to the flow field concerned, the mechanism for the speed-no-load instability was explained, which provides good guidelines to take countermeasures in future design. | WANG LeQin YIN JunLian JIAO Lei WU DaZhuan QIN DaQing | 2011 | Science China(Technological Sciences)2011，54，5： | 20 |
| 2 | Angle estimation in bistatic MIMO radar using improved reduced dimension Capon algorithm显示文摘This paper discusses the problem of direction of departure (DOD) and direction of arrival(DOA) estimation for a bistatic multiple input multiple output(MIMO) radar,and proposes an improved reduced-dimension Capon algorithm therein.Compared with the reduced-dimension Capon algorithm which requires pair matching between the two-dimensional angle estimation,the proposed algorithm can obtain automatically paired DOD and DOA estimation without debasing the performance of angle estimation in bistatic MIMO radar.Furthermore,the proposed algorithm has a lower complexity than the reduced-dimension Capon algorithm, and it is suitable for non-uniform linear arrays.The complexity of the proposed algorithm is analyzed and the Cramer-Rao bound (CRB) is also derived.Simulation results verify the usefulness of the proposed algorithm. | Xiaofei Zhang Dazhuan Xu | 2013 | Journal of Systems Engineering and Electronics2013，24，1： | 13 |
| 3 | Investigation of CFD Calculation Method of a Centrifugal Pump with Unshrouded Impeller显示文摘Currently, relatively large errors are found in numerical results in some low-specific-speed centrifugal pumps with unshrouded impeller because the effect of clearances and holes are not accurately modeled. Establishing an accurate analytical model to improve performance prediction accuracy is therefore necessary. In this paper, a three-dimensional numerical simulation is conducted to predict the performance of a low-specific-speed centrifugal pump, and the modeling, numerical scheme, and turbulent selection methods are discussed. The pump performance is tested in a model pump test bench, and flow rate, head, power and efficiency of the pump are obtained. The effect of taking into consideration the back-out vane passage, clearance, and balance holes is analyzed by comparing it with experimental results, and the performance prediction methods are validated by experiments. The analysis results show that the pump performance can be accurately predicted by the improved method. Ignoring the back-out vane passage in the calculation model of unshrouded impeller is found to generate better numerical results. Further, the calculation model with the clearances and balance holes can obviously enhance the numerical accuracy. The application of disconnect interface can reduce meshing difficulty but increase the calculation error at the off-design operating point at the same time. Compared with the standard k–ε, renormalization group k–ε, and Spalart–Allmars models, the Realizable k–ε model demonstrates the fastest convergent speed and the highest precision for the unshrouded impeller flow simulation. The proposed modeling and numerical simulation methods can improve the performance prediction accuracy of the low-specific-speed centrifugal pumps, and the modeling method is especially suitable for the centrifugal pump with unshrouded impeller. | WU Dazhuan YANG Shuai XU Binjie LIU Qiaoling WU Peng WANG Leqin | 2014 | Chinese Journal of Mechanical Engineering2014，27，2： | 7 |
| 4 | A strategy of the rural governance for territorial spatial planning in China显示文摘Rural spatial governance has become an important part of the spatial governance system under the unified management of urban and rural spaces.In-depth theoretical and practical research on rural spatial governance in terms of promoting national spatial planning can help improve the planning and regulation system of rural space.Beginning with a description of rural spatial governance,this paper constructs a theoretical analysis framework of rural spatial governance based on the comprehensive perspective of spatial governance.The study also discusses the internal processes and feasible paths of rural spatial governance in territorial spatial planning and outlines the theoretical and practical research for enhancing rural spatial governance.The conclusions are as follows:(1)Rural spatial governance starts with the coordination theory of human-land relationships in the rural regional system.Through planning and negotiation,governance has effective regulation of rural space and allocates spatial rights in an orderly manner.Rural spatial governance highlights the comprehensive governance processes that combine'top-down'and'bottom-up'participation by multiple subjects.(2)Through the'action-efficiency-target'system,the comprehensive governance analysis framework of'matter-organization-ownership'in rural space provides an effective scheme for constructing rural spatial governance.Rural spatial governance is characterized by both rigidity and flexibility,the interaction between physical space and spatial relationships,and the superposition of spatial ownership and spatial organization.(3)The rural spatial governance features of interconnecting various scales(regional–village–plot)are conducive to improving the rural spatial governance system.(4)The governance means,participation modes,and value-sharing mechanisms of rural spatial governance help enrich the territorial spatial planning system,promote the integration of multiple regulations,refine the regulation of land use,and ensure good rural governance and ecological governance. | GE Dazhuan LU Yuqi | 2021 | Journal of Geographical Sciences2021，31，9： | 5 |
| 5 | Blind channel estimation for multiple antenna OFDM system subject to unknown carrier frequency offset显示文摘The problem of channel estimation for multiple antenna orthogonal frequency division multiplexing(OFDM) systems subject to unknown carrier frequency offset(CFO) is addressed.Multiple signal classification(MUSIC)-like algorithm, which generally has been used for direction estimation or frequency estimation,is used for channel estimation in multiple antenna OFDM systems.A reduced dimensional(RD)-MUSIC based algorithm for channel estimation is proposed in multiple antenna OFDM systems with unknown CFO. The Cram ′er-Rao bound(CRB) of channel estimation in multiple antenna OFDM systems with unknown CFO is derived. The proposed algorithm has a superior performance of channel estimation compared with the Capon method and the least squares method. | Xiaofei Zhang Dazhuan Xu | 2014 | Journal of Systems Engineering and Electronics2014，25，5： | 3 |
| 6 | Investigation on Reduction of Pressure Fluctuation for a Double-Suction Centrifugal Pump显示文摘Double-suction centrifugal pumps have been applied extensively in many areas,and the significance of pressure fluctuations inside these pumps with large power is becoming increasingly important.In this study,a double-suction centrifugal pump with a high-demand for vibration and noise was redesigned by increasing the flow uniformity at the impeller discharge,implemented by combinations of more than two parameters.First,increasing the number of the impeller blades was intended to enhance the bounding effect that the blades imposed on the fluid.Subsequently,increasing the radial gap between the impeller and volute was applied to reduce the rotor-stator interaction.Finally,the staggered arrangement was optimized to weaken the efficacy of the interference superposition.Based on numerical simulation,the steady and unsteady characteristics of the pump models were calculated.From the fluctuation analysis in the frequency domain,the dimensionless pressure fluctuation amplitude at the blade passing frequency and its harmonics,located on the monitoring points in the redesigned pumps(both with larger radial gap),are reduced a lot.Further,in the volute of the model with new impellers staggered at 12°,the average value for the dimensionless pressure fluctuation amplitude decreases to 6%of that in prototype pump.The dimensionless rootmean-square pressure contour on the mid-span of the impeller tends to be more uniform in the redesigned models(both with larger radial gap);similarly,the pressure contour on the mid-section of the volute presents good uniformity in these models,which in turn demonstrating a reduction in the pressure fluctuation intensity.The results reveal the mechanism of pressure fluctuation reduction in a double-suction centrifugal pump,and the results of this study could provide a reference for pressure fluctuation reduction and vibration performance reinforcement of doublesuction centrifugal pumps and other pumps. | Qianqian Li Shiyang Li Peng Wu Bin Huang Dazhuan Wu | 2021 | Chinese Journal of Mechanical Engineering2021，34，1： | 2 |
| 7 | MULTI-INVARIANCE ESPRIT-LIKE ALGORITHMS FOR COHERENT DOA ESTIMATION显示文摘Estimation of Signal Parameters via Rotational Invariance Technique(ESPRIT) algorithm can estimate Direction-Of-Arrival(DOA) of coherent signal,but its performance can not reach full satisfaction.We reconstruct the received signal to form data model with multi-invariance property,and multi-invariance ESPRIT algorithm for coherent DOA estimation is proposed in this paper.The proposed algorithm can resolve the DOAs of coherent signals and performs better in DOA estimation than that of ESPRIT-like algorithm.Meanwhile,it identifies more DOAs than ESPRIT-like algorithm.The simulation results demonstrate its validity. | Zhang Xiaofei Xu Dazhuan | 2010 | Journal of Electronics(China)2010，27，1： | 2 |
| 8 | Direction of departure (DOD) and direction of arrival (DOA) estimation in MIMO radar with reduced-dimension MUSIC 显示文摘 | Zhang Xiaofei Xu Dazhuan | 2010 | IEEE Communications Letters2010，14，12： | 1 |
| 9 | Multi-invari- ance esprit-based blind DOA estimation for MC-CD- MA with an antenna array显示文摘 | Zhang Xiaofei Gao Xin Xu Dazhuan | 2009 | IEEE Transactions on Vehicular Technology2009，58，8： | 1 |
| 10 | Experimental study on hydrodynamic performance of a cavitating centrifugal pump during transient operation显示文摘 | Wu Dazhuan Wang Leqin Hao Zongrui | 2010 | Journal of Mechanical Science and Technology2010，24，2： | 1 |
| 11 | UPLINK PERFORMANCE OF CWP-MC-CDMA WITH SPACE DIVERSITY COMBINING TECHNIQUE OVER RAYLEIGH FADING CHANNEL显示文摘In this paper, a Complex Wavelet Packet based Multi-Carrier Code Division Multiple Access (CWP-MC-CDMA) system uplink model is proposed, based on the analysis of the principle of MC-CDMA and the use of the optimized complex wavelet packet. Considering that the base station can adopt multiple re-ceiver antennas in the uplink, we employ the Space Diversity Combining (SDC) technique to improve the sys-tem performance via multiple antennas. The uplink performance of proposed CWP-MC-CDMA system with SDC technique is investigated over Rayleigh fading channel, and corresponding bit error rate analysis is given in detail. The system can avoid the decrease of spectrum efficiency of conventional MC-CDMA due to insert-ing cyclic prefix. Theoretical analysis and simulation result show that the application of SDC technique can improve the CWP-MC-CDMA system ability to combat spatial fading and various interferences effectively. Moreover, the proposed system based on SDC technique has superior Bit Error Rate (BER) performance over the Discrete Fourier Transform (DFT) and SDC based MC-CDMA system and the real wavelet packet and SDC based MC-CDMA system. | Yu Xiangbin Zhang Xiaodong Xu Dazhuan Bi Guangguo | 2006 | Journal of Electronics(China)2006，23，6： | 1 |
| 12 | Experi- mental study on hydrodynamic performance of a cavita- ting centrifugal pump during transient operation 显示文摘 | WU Dazhuan WANG Leqin HAO Zongrui | 2010 | Journal of mechanical science and technology2010，24，2： | 1 |
| 13 | Ex- perimental Study on Hydrodynamic Performance of a Cavitating Centrifugal Pump During Transient Operation 显示文摘 | WU Dazhuan WANG Leqin HAO Zongrui | 2010 | Journal of Mechanical Science and Technology2010，24，2： | 1 |
| 14 | Numerical Simulation of the Transient Flow in a Centrifugal Pump During Startup Period 显示文摘 | LI Zhifeng WU Dazhuan WANG Leqin | 2010 | ASME Journal of Fluids Engi- neering2010，132，08： | 1 |
| 15 | High efficient rejection method for generating Nak?agami-m sequences显示文摘 | Zhu Qiuming Dang Xiaoyu Xu Dazhuan | 2011 | Electronic Letters2011，47，19： | 1 |
| 16 | Angle estimation in MI- MO radar using reduced dimension capon显示文摘 | Zhang Xiaofei Xu Dazhuan | 2010 | IET E-lectronics Letters2010，45，12： | 1 |
| 17 | Experimental study on hydrodynamic performance of a cavitating centrifugal pump during transient operation 显示文摘 | Wu Dazhuan Wang Leqin Hao Zongrui | 2010 | Journal of Mechanical Science and Technology2010，24，2： | 1 |
| 18 | Numerical simulation of the transient flow in a centrifugal pump during startup period显示文摘 | LI Zhifeng WU Dazhuan WANG Leqin | 2010 | ASME Journal of Fluids Engineering2010，132，08： | 1 |
| 19 | High efficient rejection method for generating Nakagami-m sequenees 显示文摘 | ZHU Qiuming DANG Xiaoyu XU Dazhuan | 2011 | Electronic Letters2011，47，19： | 1 |
| 20 | Numerical simulation of the transient flow in a centrifugal pump during starting period显示文摘 | LI Zhifeng WU Dazhuan WANG Leqin | 2010 | ASME Jottmal of Fluids Engineering2010，132，08： | 1 |
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