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Numerical and Experimental Study on Flow-induced Noise at Blade-passing Frequency in Centrifugal Pumps

Chinese Journal of Mechanical Engineering 2014年第3期27卷 606-614页

作者： YANG Jun yuan Shouqi yuan jianping SI Qiaorui PEI ji Research Center of Fluid Machinery Engineering and Technology Jiangsu University

With the increasing noise pollution, low noise optimization of centrifugal pimps has become a hot topic. However, experimental study on this problem is unacceptable for industrial applications due to unsustainable cost. A hybrid method that couples computational fluid dynamics （CFD） with computational aeroacoustic software is used to predict the flow-induced noise of pumps in order to minimize the noise of centrifugal pumps in actual projects. Under Langthjem＇s assumption that the blade surface pressure is the main flow-induced acoustic source in centrifugal pumps, the blade surface pressure pulsation is considered in terms of the acoustical sources and simulated using CFX software. The pressure pulsation and noise distribution in the near-cutoff region are examined for the blade-passing frequency （BPF） noise, and the sound pressure level （SPL） reached peaks near the cutoff that corresponded with the pressure pulsation in this region. An experiment is performed to validate this prediction. Four hydrophones are fixed to the inlet and outlet ports of the test pump to measure the flow-induced noise from the four-port model. The simulation results for the noise are analyzed and compared with the experimental results. The variation in the calculated noise with changes in the flow agreed well with the experimental results. When the flow rate was increased, the SPL first decreased and reached the minimum near the best efficient point （BEP）; it then increased when the flow rate was further increased. The numerical and experimental results confirmed that the BPF noise generated by a blade-rotating dipole roughly reflects the acoustic features of centrifugal pumps. The noise simulation method in current study has a good feasibility and suitability, which could be adopted in engineering design to predict and optimize the hydroacoustic behavior of centrifugal pumps.

关键词： centrifugal pumps flow-induced noise prediction blade-passing noise blade surface pressure pulsations

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Enhanced cooperative packet retransmission employing joint cooperative diversity and symbol mapping diversity

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第8期9卷 1090-1098页

作者： wei ji Bao-yu ZHENG Electronic Engineering Department Shanghai Jiao Tong University Shanghai 200240 China Institute qf Signal Processing and Transmission Nanjing University of Posts ＆ Telecommunications Nanjing 210003 China

A joint cooperation diversity and symbol mapping diversity (SMD) strategy is proposed for cooperative packet retransmission system with high-order modulation such as 16QAM. Substantial SER/BER (symbol error rate/bit error rate) gains result from multiple packet transmissions over independent paths and distinct bit-to-symbol mappings for each packet transmis-sion. The SER/BER performance of relay assisted retransmission system is analyzed. Simulation results show that the joint-diversity strategy can provide more BER gains than other relaying strategies (i.e., decode-and-forward and constellation rearrangement relaying strategies) when no relay makes a decision error; but if some relays make decision errors, the joint-di-versity strategy outperforms other relaying strategies only when the relays are closer to the source than to the destination.

关键词： Cooperative retransmission Hybrid automatic repeat request (HARQ) Cooperative diversity Symbol mapping diversity (SMD)

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Fully automatic DOM generation method based on optical flow field dense image matching

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Geo-Spatial Information Science 2023年第2期26卷 242-256页

作者： wei yuan Xiuxiao yuan Yang Cai Ryosuke Shibasaki School of Remote Sensing and Information Engineering Wuhan UniversityWuhanChina Center for Spatial Information Science University of TokyoKashiwaJapan

Automatic Digital Orthophoto Map(DOM)generation plays an important role in many downstream works such as land use and cover detection,urban planning,and disaster *** DOM generation methods can generate promising results but always need ground object filtered DEM generation before otho-rectification;this can consume much time and produce building facade contained *** address this problem,a pixel-by-pixel digital differential rectification-based automatic DOM generation method is proposed in this ***,3D point clouds with texture are generated by dense image matching based on an optical flow field for a stereo pair of images,***,the grayscale of the digital differential rectification image is extracted directly from the point clouds element by element according to the nearest neighbor method for matched ***,the elevation is repaired grid-by-grid using the multi-layer Locally Refined B-spline(LR-B)interpolation method with triangular mesh constraint for the point clouds void area,and the grayscale is obtained by the indirect scheme of digital differential rectification to generate the pixel-by-pixel digital differentially rectified image of a single image ***,a seamline network is automatically searched using a disparity map optimization algorithm,and DOM is smartly *** qualitative and quantitative experimental results on three datasets were produced and evaluated,which confirmed the feasibility of the proposed method,and the DOM accuracy can reach 1 Ground Sample Distance(GSD)*** comparison experiment with the state-of-the-art commercial softwares showed that the proposed method generated DOM has a better visual effect on building boundaries and roof completeness with comparable accuracy and computational efficiency.

关键词： Digital Orthophoto Map(DOM) dense image matching based on optical flow field(OFFDIM) 3D point clouds with texture seamline network accuracy

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Experimental Investigation on the Flow-induced Noise under Variable Conditions for Centrifugal Pumps

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Chinese Journal of Mechanical Engineering 2012年第3期25卷 456-462页

作者： yuan Shouqi YANG Jun yuan jianping LUO Yin PEI ji Research Center of Fluid Machinery Engineering and Technology Jiangsu UniversityZhenjiang 212013China

With extensively using of centrifugal pumps,noise generation in these pumps is increasingly receiving research attention in recent *** noise sources in centrifugal pumps are mainly composed of mechanical noise and flow-induced *** the study of flow-induced noise has become a hotspot and important domain in the *** flow-induced noise closely related to the inner pressure pulses and vibration of volute in pumps,therefore,it is necessary to research the interaction and mechanism among *** investigate the relationships,a test system is designed which includes a test loop and a measurement *** hydrophones and pressure sensors are installed on the outlet of the pump and vibration acceleration sensors are disposed on the pump *** these instruments,the signals of noise,pressure pulses and vibration are collected and *** results show that the level of flow-induced noise becomes smaller as the flow increment during low flow rate operations,and it is steadily close to the design point,then it increases with the growing of flow rate in high flow rate ***,there are some similar peak points in the power spectrum charts of noise,pressure pulses and *** broadband noise at low flow rate is mostly focused on the region of 0-40 times shaft frequency,which is mostly made by rotating stall and vortex;while the noise at high flow rate conditions is focused on the region of 60-100 times shaft frequency,which may be mostly made by *** proposed research is of practical and academic significance to the study of noise reduction for centrifugal pumps.

关键词： centrifugal pump flow-induced noise pressure pulses vibration of volute

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邓恩桉种源幼龄材树皮率·心材率和基本密度变异

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安徽农业科学 2024年第3期52卷 103-105,114页

作者：雷仕锐袁寄威陈海泉周先梅尚正洁卢翠香广西横州市石塘林场广西南宁530000 广西林业集团桂钦林浆纸有限公司广西南宁530022 广西壮族自治区林业科学研究院/南宁桉树森林生态系统广西野外科学观测研究站/广西优良用材林资源培育重点实验室广西南宁530002

采用质量法、体积法及排水法测定了邓恩桉种源幼龄材树皮率、心材率和基本密度,结果表明:5年生邓恩桉重量树皮率、体积树皮率、心材率、基本密度分别为17.003%、15.139%、16.950%、0.484 g/cm^(3)。3个性状在不同种源间差异不显著。10... 详细信息

采用质量法、体积法及排水法测定了邓恩桉种源幼龄材树皮率、心材率和基本密度,结果表明:5年生邓恩桉重量树皮率、体积树皮率、心材率、基本密度分别为17.003%、15.139%、16.950%、0.484 g/cm^(3)。3个性状在不同种源间差异不显著。10个种源木材基本密度属于中等密度,满足纤维用材要求。

关键词：邓恩桉树皮率心材率基本密度变异

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Cyclodextrin-functionalized Ordered Porous Block Copolymer Films: Preparation and Property

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Chinese Journal of Polymer Science 2018年第1期36卷 34-42页

作者： jing Dang yuan-wei Su wei Tian Ministry of Education Key Laboratory of Material Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Macromolecular Science and Technology School of Science Northwestern Polytechnical University

Ordered porous block copolymer films（PBCFs） have attracted much attention because of their potential applications in several fields. In this paper, we first reported a non-destructive, controllable, and efficient approach for preparation of β-cyclodextrin（β-CD）-functionalized PBCFs（β-CD-PBCFs）. The key point of the approach is to incorporate β-CD units into the hydrophilic segment of amphiphilic block copolymers before the preparation of films. β-CD-PBCFs with structural integrity and controllable pore parameters were fabricated through combining of self-assembly and breath figure methods. And then, the effective adsorption capacity of β-CD-PBCFs toward Congo red was confirmed through UV-Vis spectroscopy and was found to be affected by β-CD content and solution p H values. Adsorption kinetic results showed that the adsorption behavior of β-CD-PBCFs was consistent with the pseudo-second-order kinetic model and the chemisorption mechanism.

关键词： Porous block copolymer film β-Cyclodextrin Breath figure Self-assembly

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Flashover in Back-Triggered Photoconductive Semiconductor Switch

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Chinese Physics Letters 2011年第1期28卷 106-108页

作者： SHI wei jiA ji-Qiang ji wei-Li GUI Huai-Meng Applied Physics Department Xi'an University of Technology Xi'an 710048 State Key Laboratory of Electrical Insulation for Power Equipment Xi'an Jiaotong University Xi'an 710049

Design of a new type of photoconductive semiconductor switches （PCSSs） is presented, and the withstand voltage is improved. The ttashover voltage of the back-triggered PCSS is found to be higher than that of the front-triggered one. By analyzing the differences of the flashover voltage between the back-triggered PCSS and the front-triggered PCSS, a detailed statistics analysis and theoretical explanation are expounded. The experiments also prove that the PCSS we developed could resist a voltage as high as 20 k V under the repetition frequency of 30 Hz.

关键词： Electronics and devices Optics, quantum optics and lasers

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Soft coarse-grained particle model for particle-fluid systems

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Particuology 2024年第1期84卷 178-193页

作者： Yanhao Ye ji Xu wei Ge State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing100049China Innovation Academy for Green Manufacture Chinese Academy of SciencesBeijing100190China

By modeling a group of neighboring real particles as a single coarse-grained particle(CGP),discrete particle method(DPM)is now capable of simulating industrial-scale particle-fluid ***,a systematic approach to determine the CGP properties and develop their interaction models is still lacking,which casts uncertainty on the predictivity of the *** this study,collisions between predefined particle groups are analyzed to construct kernel functions for modeling the CGPs and then the model parameters are determined by equating the statistical properties of the CGPs and the real particles in the physical process *** approach is implemented for homogeneous cooling of granular gas,then demonstrated effective in simulating experimental fluidized beds.

关键词： Coarse-grain(CG) Discrete particle method(DPM) Fluidized bed Multi-scale simulation

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Effect of Microstructure on Thermal Expansion Coeffcient of 7A09 Aluminum Alloy

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Journal of Materials Science & Technology 2011年第9期27卷 797-801页

作者： Hongzhi ji Lin yuan Debin Shan School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

The relationship between microstructure evolution and coefficient of thermal expansion （CTE） of 7A09 aluminum alloy was investigated in this paper. Differential scanning calorimetry （DSC） was combined with transmission electron microscopy （TEM） and high-resolution transmission electron microscopy （HRTEM） to investigate microstructure evolution taking place in 7A09 aluminum alloy during heating and cooling process. The corresponding CTE curves of the 7A0g alloy were recorded by thermal dilatometer. Results indicated that GPII zones and Ur phase were main precipitates in the highest strength tempered （T6） 7A09 alloy. The r/phase was the main participate in 7A09 alloy during the cooling process. The nonlinear dependency existed between CTE and temperature in both changing temperature processes. During the heating process, obvious additional contraction of alloy volume was directly caused by phase transition, such as dissolution of η＇ phase, transition from η＇ to η phase and dissolution of η phase. The additional contraction could slow down the increase of CTE greatly and be expressed in the nonlinearity of CTE curve. Volume and energy changes of alloy system influenced the variation trend of CTE directly, which was caused by the precipitation of U phase during the cooling process. These effects were revealed by the corresponding nonlinear change of CTE.

关键词： Aluminum Coefficient alloy Changing temperature process Microstructure evolution of thermal expansion

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Defect Luminescence Based Persistent Phosphors—From Controlled Synthesis to Bioapplications

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Chinese Journal of Chemistry 2021年第12期39卷 3188-3198页

作者： Calling ji jie Tan Quan yuan Institute of Chemical Biology and Nanomedicine State Key Laboratory of Chemo/Biosensing and ChemometricsCollege of Chemistry and Chemical EngineeringHunan UniversityChangshaHunan 410082China

Persistent luminescence is an optical phenomenon where solid phosphors can store photoenergy in defects and release the energy by luminescence after stopping *** to the intriguing optical characteristics,the defect luminescence based persistent phosphors have attracted enormous attention in recent decades,especially in biomedical fields such as biosensing and *** luminescence nanoparticles(PLNPs)can effectively avoid the autofluorescence interference from complex samples or tissues,leading to significantly improved sensitivity in biological *** this review,we summarized the methods to control the optical performance of PLNPs from the perspectives of controlled synthesis and defect regulation,and emphasized the close relationship between their optical performance and *** further provided a summary about a series of PLNPs nanoprobes designed by our group for biosensing and *** efforts,summarized in this review,will not only open a window for manipulating luminescence in PLNPs,but also further promote the application of PLNPs in biomedicine.

关键词： Luminescence Nanoparticles Persistent phosphors Synthesis design Bioapplication

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