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Pre-judgment and Incomplete Allocation Approach for Query Result Cache

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Chinese Journal of Electronics 2016年第6期25卷 1101-1108页

作者： QIAN Libing ji Zhenzhou FU Zhongchuan WU Qianqian SONG Guangjia School of Computer Science and Technology Harbin Institute of Technology

Query result caching is a crucial technique employed in search engines, reducing the response time and load of the search engines. As search engines continuously update their indexes, the query results in long-lived cache entries may become stale. It is important to provide the refresh mechanism to enhance the degree of freshness of cached results. We present a pre-judgment approach to improve the freshness of the result cache and design an incomplete allocation algorithm. We introduce the queryTime-to-live(TTL) and term-TTL structure to pre-judge the result cache. The query-TTL is used to pre-check the likelihood of a cache hit and term-TTL is applied to maintain all terms of the latest posting list. For the cache structure, we design a Queue-Hash structure and develop the corresponding incomplete allocation algorithm. The preliminary results demonstrate that our approaches can improve the freshness of cached results and decrease processing overhead compared with no pre-judgment approaches.

关键词： Time-to-live(TTL) Caching freshness Pre-judgment Result cache Cache structure

Interaction analysis and enhanced design of grid-forming control with hybrid synchronization and virtual admittance loops

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iEnergy

iEnergy 2023年第1期2卷 71-84页

作者： hong Gong Xiongfei Wang Vestas Aarhus 8200Denmark KTH Royal Institute of Technology Stockholm 11428Sweden

The hybrid power-and voltage-based synchronization control method has shown potential for enhancing the stability of grid-forming(GFM)***,its effectiveness may be compromised if other control loops are not properly *** address the control-loop interactions,this paper presents a design-oriented analysis method for multiloop-controlled GFM *** method begins by identifying the dominant oscillation modes through modal *** sensitivities of damping ratios to control parameters are then determined for the dominant modes,which allows for characterization of control-loop interactions.A co-design method of GFM control is next developed based on the sensitivity ***,simulations and experimental results are presented to confirm the effectiveness of the method.

关键词： Grid-forming inverter hybrid synchronization controller virtual admittance damping ratio controller design

3D thermoelasticity solutions for functionally graded thick plates

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第3期10卷 327-336页

作者： ji YING Chao-feng LU C. W. LIM Department of Mechanical Engineering Zhejiang University Hangzhou 310027 China Department of Civil Engineering Zhejiang University Hangzhou 310058 China Department of Building and Construction City University of Hong Kong Hong Kong China

Thermal-mechanical behavior of functionally graded thick plates, with one pair of opposite edges simply supported, is investigated based on 3D thermoelasticity. As for the arbitrary boundary conditions, a semi-analytical solution is presented via a hybrid approach combining the state space method and the technique of differential quadrature. The temperature field in the plate is determined according to the steady-state 3D thermal conduction. The Mori-Tanaka method with a power-law volume fraction profile is used to predict the effective material properties including the bulk and shear moduli, while the effective coefficient of thermal expansion and the thermal conductivity are estimated using other micromechanics-based models. To facilitate the im-plementation of state space analysis through the thickness direction, the approximate laminate model is employed to reduce the inhomogeneous plate into a homogeneous laminate that delivers a state equation with constant coefficients. The present solutions are validated by comparisons with the exact ones for both thin and thick plates. Effects of gradient indices, volume fraction of ceramics, and boundary conditions on the thermomechanical behavior of functionally graded plates are discussed.

关键词： Functionally graded plates Semi-analytical solutions 3D thermoelasticity Mori-Tanaka method

Improving Joint Features and Mechanical Properties of Pinless Fiction Stir Welding of Alcald 2A12-T4 Aluminum Alloy

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Journal of Materials Science & Technology 2016年第12期32卷 1372-1377页

作者： Zhenlei Liu Hutao Cui Shude ji Minqiang Xu Xiangchen Meng Harbin Institute of Technology Deep Space Exploration Research Center Faculty of Aerospace Engineering Shenyang Aerospace University

As a new solid state welding,pinless friction stir welding（PFSW） can be used to join thin-wall *** this study,four new pinless tools with different groove distributions were designed and manufactured in order to enrich technological storage of PFSW and obtain sound joint with high quality of alclad 2A12-T4 *** results show that the small-obliquity tool is detrimental to the transfer of plasticized materials,resulting in the formation of kissing bond *** the through-groove tool or the large-curvature tool,bigger flashes form on the joint surface and alclad layer is observed in the nugget zone（NZ）,deteriorating mechanical *** with the above-mentioned three tools,using the six-groove tool with rational curvature and obliquity can not only yield sound joint with small flashes and thickness reduction,but also prevent alclad from flowing into NZ,which has potential to weld thin alclad aluminum ***,the tensile strength and elongation of joint using the six-groove tool reach the maximum values of 362 MPa and 8.3%,up to 85.1% and 64% of BM.

关键词： Pinless friction stir welding Groove distribution 2A12-T4 aluminum alloy Macrostructures Mechanical property

Experimental and Modeling Study of the Regular Polygon Angle-spiral Liner in Ball Mills

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Chinese Journal of Mechanical Engineering 2017年第2期30卷 363-372页

作者： Yi SUN Man LIANG Xiaohang jiN Pengpeng ji jihong SHAN College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310014China

Load behavior is one of the most critical factors affecting mills＇ energy consumption and grinding efficiency, and is greatly affected by the liner profiles. Generally, as liner profiles vary, the ball mill performances are extremely different. In order to study the performance of the ball mill with regular polygon angle-spiral liners（RPASLs）, experimental and numerical studies on three types of RPASLs, including regular quadrilateral, pentagonal and hexagonal, are carried out. For the fine product of desired size, two critical parameters are analyzed： the energy input to the mill per unit mass of the fine product, E＊, and the rate of production of the fine product, F＊. Results show that the optimal structure of RPASLs is Quadrilateral ASL with an assembled angle of 50°. Under this condition, the specific energy consumption E＊ has the minimum value of 303 J per fine product and the production rate F＊ has the maximum value of 0.323. The production rate F＊ in the experimental result is consistent with the specific collision energy intensity to total collision energy intensity ratio Es/Et in the simulation. The relations between the production rate F＊ and the specific energy consumption E＊ with collision energy intensity Es and Et are obtained. The simulation result reveals the essential reason for the experimental phenomenon and correlates the mill performance parameter to the collision energy between balls, which could guide the practical application for Quadrilateral ASL.

关键词： Load behavior Regular polygon angle-spiral liner (RPASL) Particle size distribution. Rate of production of fine product Energy consumption. Collision energy intensity

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

Machine Learning to Search for Accreting Neutron Star Binary Candidates Using Chinese Space Station Telescope Photometric System

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Research in Astronomy and Astrophysics 2022年第12期22卷 322-334页

作者： Shun-Yi Lan Kai-Fan ji Xiang-Cun Meng Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China

Accreting neutron star binary(ANSB)systems can provide some important information about neutron stars(NSs),especially on the structure and the equation of state of ***,only a few ANSBs are known so *** upcoming Chinese Space Station Telescope(CSST)provides an opportunity to search for a large number of ANSB *** aim to investigate whether or not a machine learning method may efficiently search for ANSBs based on CSST photometric *** this paper,we generate some ANSBs and normal binaries under CSST photometric system by binary evolution and binary population synthesis method and use a machine learning method to train a classification *** consider the classical multi-color disk and the irradiated accretion disk,then compare their effects on the classification *** find that no matter whether the X-ray reprocessing effect is included or not,the machine learning classification accuracy is always very high,i.e.,higher than 96%.If a significant magnitude difference exists between the accretion disk and the companion of an ANSB,machine learning may not distinguish it from some normal stars such as massive main sequence stars,white dwarf binaries,*** classifications of the ANSBs and the normal stars highly overlap in a color–color *** results indicate that machine learning would be a powerful way to search for potential ANSB candidates from the CSST survey.

关键词： stars:neutron X-rays:binaries methods:analytical

Evaluating returns to scale and congestion by production possibility set in intersection form

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Science China Mathematics 2011年第4期54卷 831-844页

作者： WEI QuanLing YAN hong Institute of Economics Renmin University of ChinaBeijing 100872China Department of Logistics and Maritime Studies Hong Kong Polytechnic UniversityKowloonHongkongChina

This research proposes a new method to estimate returns to scale(RTS) of decision making units(DM Us) with multiple inputs and *** state of return to scale includes increasing RTS,constant RTS,decreasing RTS and evidence of *** method is based on the production possibility set in the intersection form given by a set of linear *** propose and prove the necessary and sufficient conditions for the RTS *** the new procedure,to estimate the RTS of a DM U is simply to check the position of the DM U on the production *** point out that the procedure is particularly important for dealing with a large number of DM U ***,it can be regarded as a complementary to the data mining.

关键词： DEA production possibility set intersection form return to scale congestion

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涡轮叶片内部沿周边分布的竹节孔换热特性

航空动力学报 2009年第1期24卷 38-43页

作者：李娜吉洪湖杨超南京航空航天大学能源与动力学院南京210016

根据发动机涡轮叶片内部沿周边分布的竹节孔冷却通道结构建立了简化的传热分析模型.首先通过无量纲分析得到了竹节孔的平均努塞尔数不仅与雷诺数和普朗特数有关,还与"竹节"形状、通道外壁形状以及流体和固体的导热系数比等参数有关.然后... 详细信息

根据发动机涡轮叶片内部沿周边分布的竹节孔冷却通道结构建立了简化的传热分析模型.首先通过无量纲分析得到了竹节孔的平均努塞尔数不仅与雷诺数和普朗特数有关,还与"竹节"形状、通道外壁形状以及流体和固体的导热系数比等参数有关.然后,对雷诺数和冷却通道几何参数对竹节孔平均努塞尔数的影响进行了数值模拟研究,计算并对比了上述参数对平均努塞尔数的影响规律,结果表明:①"竹节"结构使平均努塞尔数显著增大,而通道外壁形状主要影响了局部热流密度和局部努塞尔数的分布情况;②随着"竹节"的节高/孔径比的增加,平均努塞尔数单调增大,阻力系数也随之增大;③可通过增大雷诺数和优化节距/节高比来提高竹节孔的平均努塞尔数,计算表明最佳节距/节高比约为10.

关键词：涡轮叶片冷却竹节孔对流换热努塞尔数