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Efficient and stable quorum-based log replication and replay for modern cluster-databases

Frontiers of Computer Science 2022年第5期16卷 143-158页

作者： Donghui WANG Peng cai Weining QIAN Aoying zhou School of Data Science and Engineering East China Normal UniversityShanghai 200062China

The modern in-memory database(IMDB)can support highly concurrent on-line transaction processing(OLTP)workloads and generate massive transactional logs per ***-based replication protocols such as Paxos or Raft have been widely used in the distributed databases to offer higher availability and ***,it is non-trivial to replicate IMDB because high transaction rate has brought new ***,the leader node in quorum replication should have adaptivity by considering various transaction arrival rates and the processing capability of follower ***,followers are required to replay logs to catch up the state of the leader in the highly concurrent setting to reduce visibility ***,modern databases are often built with a cluster of commodity machines connected by low configuration networks,in which the network anomalies often *** this case,the performance would be significantly affected because the follower node falls into the long-duration exception handling process(e.g.,fetch lost logs from the leader).To this end,we build QuorumX,an efficient and stable quorum-based replication framework for IMDB under heavy OLTP *** combines critical path based batching and pipeline batching to provide an adaptive log propagation scheme to obtain a stable and high performance at various ***,we propose a safe and coordination-free log replay scheme to minimize the visibility gap between the leader and follower *** further carefully design the process for the follower node in order to alleviate the influence of the unreliable network on the replication *** evaluation results with the yCSB,TPC-C and a realistic microbenchmark demonstrate that QuorumX achieves the performance close to asynchronous primary-backup replication and could always provide a stable service with data consistency and a low-level visibility gap.

关键词： log replication log replay consensus protocol high performance high availability quorum unreliable network packet loss

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Numerical Investigation on Effectiveness of Flow Separation Control in Two-dimensional High-load Compressor Cascade by Synthetic Jet

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Journal of Thermal Science 2012年第5期21卷 441-446页

作者： Songtao Wang Le cai Xun zhou Shaopeng Lu Engine Aerodynamics Research Centre Harbin Institute of Technology Harbin 150001 China

The effectiveness of flow separation control in two-dimensional high load cascade by synthetic jet is investigated through numerical simulation of the effect of excitation frequency and amplitude together with the adaptability of synthetic jet to off-design conditions. Test results indicate that synthetic jet can be used to effectively control the large-scale two-dimensional flow separation in compressor cascade. Preferable results can be obtained when excitation frequency is close to or times of the characteristic frequency of original flow field. Excitation amplitude has a more important effect on the effectiveness of flow separation control, and the increase in excitation amplitude can bring about a dramatic decrease in the loss of total pressure. Synthetic jet has also a very good adaptability to off-design conditions. It can therefore be concluded that the incidence sensitivity of compressor cascade can be effectively reduced by synthetic jet.

关键词： synthetic jet excitation frequency excitation amplitude off-design conditions numerical simulation

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Heat Transfer and Flow Structure of a Turbine Blade's Air-cooled Leading Edge Considering Different Hole Shapes and Additional Flow Angles

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Journal of Thermal Science 2024年第4期33卷 1421-1442页

作者： QIN Runxuan zhou Xun WANG Songtao cai Le School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China

A numerical study is conducted to elucidate the impact of hole shapes and additional flow angles on the flow structure of the coolant and temperature field in the leading edge area of the gas turbine *** typical hole shapes are considered for the GE-E3 *** impact of the additional flow angle(E)within each hole shape on the temperature field is *** results indicate that for the leading edge area and suction surface,the fan-shaped hole case performs best in decreasing temperatures,with a decrease of about 43 *** is mainly due to the fact that the fan-shaped hole has the maximum expansion in hole spanwise *** the pressure surface,the console hole case performs best in decreasing temperatures,with a maximum reduction of about 47.2 *** influence of E on the surface temperature at leading edge area varied between the different hole *** the cylinder hole and console hole,the E=-20°case has the lowest area-averaged *** both the fan-shaped hole and the 7-7-7 shaped hole are expansion holes,the pattern of variation of the leading edge area temperature with increasing E is similar for the fan-shaped hole case and 7-7-7 shaped hole *** E=20°case shows the lowest spanwise-averaged temperature near the hole outlet,and the E=-20°case shows the lowest spanwise-averaged temperature further downstream.

关键词： film cooling GE-E3 turbine rotor blade conjugate heat transfer leading edge

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Equilibrium charge and triboelectric coefficient of spheres in a rotating container

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Particuology 2022年第4期20卷 103-111页

作者： Jiawei Hu cai Liang Qun zhou Jiliang Ma Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and EnvironmentSoutheast UniversityNanjing 210096China

Contact electrification occurs in many granular material systems due to particle-particle and particle-wall *** this paper,we used a simple device to characterize the electrification of different spheres in a rotating spherical *** charge of the spheres was quantified by a Faraday cup after rotating for various time and the disperse behaviors of charged spheres were recorded by a *** effects of the rotational time,sphere size,rotational speed,sphere material,and relative humidity on the equilibrium charge and triboelectric coefficient were *** results show that the equilibrium surface charge density is independent of the sphere size and the rotating speed,whereas the larger rotating speed enhances the triboelectric *** is also shown that charge relaxation constants are two orders of magnitude lower than the charge generation constants for all spheres at a low relative *** increase of water molecules in the air was found to result in the decline of charge generation constant and the rise of charge relaxation constant,which together cause the decrease of the equilibrium surface charge density.

关键词： Particle charging Equilibriurm charge Charge relaxation Charge generation Electrostatics

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Accurate and efficient follower log repair for Raft-replicated database systems

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Frontiers of Computer Science 2021年第2期15卷 91-103页

作者： Jinwei GUO Peng cai Weining QIAN Aoying zhou School of Data Science and Engineering East China Normal UniversityShanghai200062China

State machine replication has been widely used in modern cluster-based database *** commonly deployed configurations adopt the Raft-like consensus protocol,which has a single strong leader which replicates the log to other *** the followers can handle read requests and many real workloads are usually read-intensive,the recovery speed of a crashed follower may significantly impact on the *** from traditional database recovery,the recovering follower needs to repair its local log *** Raft protocol takes many network round trips to do log comparison between leader and the crashed *** reduce network round trips,an optimization method is to truncate the follower’s uncertain log entries behind the latest local commit point,and then to directly fetch all committed log entries from the leader in one round ***,if the commit point is not persisted,the recovering follower has to get the whole log from the *** this paper,we propose an accurate and efficient log repair(AELR)algorithm for follower *** is more robust and resilient to follower failure,and it only needs one network round trip to fetch the least number of log entries for follower *** approach is implemented in the open source database system *** experimentally show that the system adopting AELR has a good performance in terms of recovery time.

关键词： Raft high availability log replication log repair

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On Moments of the Maximum of Partial Sums of Moving Average Processes under Dependence Assumptions

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Acta Mathematicae Applicatae Sinica 2011年第4期27卷 691-696页

作者： Xing-cai zhou Jin-guan LIN Department of Mathematics Southeast University Nanjing 210096 China Department of Mathematics and Computer Science Tongling University Tongling 244000 China

Let{yi;-∞〈i〈∞}be a doubly infinite sequence of identically distributed φ-mixing random variables and let{ai;-∞〈i〈∞}be an absolutely summable sequence of real numbers. In this paper we study the moments of su... 详细信息

关键词： Moving average φ-mixing Moments

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Hollow vortex Gaussian beams

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Science China(Physics,Mechanics & Astronomy) 2013年第5期56卷 896-903页

作者： zhou GuoQuan cai yangJian DAI ChaoQing School of Sciences Zhejiang A & F University School of Physical Science and Technology Soochow University

A kind of hollow vortex Gaussian beam is introduced. Based on the Collins integral, an analytical propagation formula of a hollow vortex Gaussian beam through a paraxial ABCD optical system is derived. Due to the special distribution of the optical field, which is caused by the initial vortex phase, the dark region of a hollow vortex Gaussian beam will not disappear upon propagation. The analytical expressions for the beam propagation factor, the kurtosis parameter, and the orbital angular mo- mentum density of a hollow vortex Gaussian beam passing through a paraxial ABCD optical system are also derived, respec- tively. The beam propagation factor is determined by the beam order and the topological charge. The kurtosis parameter and the orbital angular momentum density depend on beam order n, topological charge m, parameter y, and transfer matrix ele- ments A and D. As a numerical example, the propagation properties of a hollow vortex Gaussian beam in free space are demonstrated. The hollow vortex Gaussian beam has eminent propagation stability and has crucial application prospects in op- tical micromanipulation.

关键词： hollow vortex Gaussian beam beam propagation factor kurtosis parameter orbital angular momentum density

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Chemical Intervention on Staphylococcus aureus Virulence

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Chinese Journal of Chemistry 2019年第2期37卷 183-193页

作者： Lin-Lin zhou cai-Guang yang State Key Laboratory of Drug Research Shanghai Institute of Materia MedicaChinese Academy of SciencesShanghai 201203China University of the Chinese Academy of Sciences Beijing 100049China

Resistance to conventional antibiotics has raised worldwide attention. Notably, Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the most life-threatening health concerns. Although effective against bacterial infections, conventional antibiotics have also showed a series of side effects such as gut microbiota imbalance.

关键词： Chemical Intervention Staphylococcus aureus Virulence

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Effects of moisture and carbonate additions on CO_2 emission from calcareous soil during closed–jar incubation

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Journal of Arid Land 2014年第1期6卷 37-43页

作者： yanJie DONG Miao cai JianBin zhou College of Natural Resources and Environment Northwest A&F University Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China Ministry of Agriculture

Calcareous soil contains organic and inorganic carbon(C) pools,which both contribute to CO2 emission during closed-jar incubation. The mineralization of organic C and dissolution of inorganic C are both related to soil moisture,but the exact effect of water content on CO2 emission from calcareous soil is unclear. The objective of this experiment was to determine the effect of soil water content(air-dried,30%,70%,and 100% water-holding capacity(WHC)),carbonate type(CaCO3 or MgCO3),and carbonate amount(0.0,1.0%,and 2.0%) on CO2 emission from calcareous soil during closed-jar incubation. Soil CO2 emission increased significantly as the water content increased to 70% WHC,regardless of whether or not the soil was amended with carbonates. Soil CO2 emission remained the same or increased slowly as the soil water content increased from 70% WHC to 100% WHC. When the water content was ≤30% WHC,soil CO2 emission from soil amended with 1.0% inorganic C was greater than that from unamended soil. When the soil water content was 70% or 100% WHC,CO2 emission from CaCO3 amended soil was greater than that from the control. Furthermore,CO2 emission from soil amended with 2.0% CaCO3 was greater than that from soil amended with 1.0% CaCO3. Soil CO2 emission was higher in the MgCO3 amended soil than from the unamended soil. Soil CO2 emission decreased as the MgCO3 content increased. Cumulative CO2 emission was 3-6 times higher from MgCO3 amended soil than from CaCO3 amended soil. There was significant interaction effect between soil moisture and carbonates on CO2 emission. Soil moisture plays an important role in CO2 emission from calcareous soil because it affects both biotic and abiotic processes during the closed-jar incubation.

关键词： calcareous soil soil moisture organic carbon CO2 emission

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The third type DC flow in pulse tube cryocooler

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Science China(Technological Sciences) 2009年第12期52卷 3491-3496页

作者： zhou yuan GU Chao cai HuiKun Key Laboratory of Cryogenics Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China Graduate University of Chinese Academy of Sciences Beijing 100049China

New phenomena discovered in the experimental research of the ultra-high frequency pulse tube cryocooler were *** cause of the new phenomena was analyzed and the third type DC flow was discovered in the pulse tube *** third type DC flow not only deteriorated cooling capacity but also led to temperature instability of the pulse tube *** the fluid network theory and the simple regenerator model,the root of the third type DC flow was concisely investigated in theory. The asymmetric resistance of oscillating flow in pulse tube cryocooler was the key mechanism of the third type DC *** suppression methods were briefly discussed.

关键词： pulse tube cryocooler DC flow fluid network theory flow resistance

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