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

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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 second.Quorum-based replication protocols such as Paxos or Raft have been widely used in the distributed databases to offer higher availability and fault-tolerance.However,it is non-trivial to replicate IMDB because high transaction rate has brought new challenges.First,the leader node in quorum replication should have adaptivity by considering various transaction arrival rates and the processing capability of follower nodes.Second,followers are required to replay logs to catch up the state of the leader in the highly concurrent setting to reduce visibility gap.Third,modern databases are often built with a cluster of commodity machines connected by low configuration networks,in which the network anomalies often happen.In 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 workloads.QuorumX combines critical path based batching and pipeline batching to provide an adaptive log propagation scheme to obtain a stable and high performance at various settings.Further,we propose a safe and coordination-free log replay scheme to minimize the visibility gap between the leader and follower IMDBs.We further carefully design the process for the follower node in order to alleviate the influence of the unreliable network on the replication performance.Our 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

Curved copper nanowires-based robust flexible transparent electrodes via all-solution approach

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Nano Research 2017年第9期10卷 3077-3091页

作者： Zhenxing Yin Seung Keun Song Sanghun Cho Duck-Jae You Jeeyoung Yoo Suk Tai Chang Youn Sang Kim Program in Nano Science and Technology Graduate School of Convergence Science and Technology Seoul National University Seoul 08826 Republic of Korea School of Chemical Engineering and Materials Science Chung-Ang University Seou106974 Republic of Korea Advanced Institutes of Convergence Technology 145 Gwanggyo-ro Yeongtong-gu Suwon-si Gyeonggi-do 16229 Republic of Korea

Curved Cu nanowire (CCN)-based high-performance flexible transparent conductive electrodes (FTCEs) were fabricated via a fully solution-processed approach, involving synthesis, coating, patterning, welding, and transfer. Each step involved an innovative technique for completing the all-solution processes. The high-quality and well-dispersed CCNs were synthesized using a multi-polyol method through the synergistic effect of specific polyol reduction. To precisely control the optoelectrical properties of the FTCEs, the CCNs were uniformly coated on a polyimide (PI) substrate via a simple meniscus-dragging deposition method by tuning several coating parameters. We also employed a polyurethane (PU)-stamped patterning method to effectively produce 20 μm patterns on CCN thin films. The CCN thin films exhibited high electrical performance, which is attributed to the deeply percolated CCN network formed via a solvent-dipped welding method. Finally, the CCN thin films on the PI substrate were partially embedded and transferred to the PU matrix to reduce their surface roughness. Through consecutive processes involving the proposed methods, a highly percolated CCN thin film on the PU matrix exhibited high optoelectrical performance (R s = 53.48 Ω/□ at T = 85.71%), excellent mechanical properties (R/R 0 < 1.10 after the 10th repetition of tape peeling or 1,000 bending cycles), and a low root-mean-square surface roughness (R rms = 14.36 nm).

关键词： curved Cu nanowires all-solution processes 20 μm patterns high performance transparent electrode

Spatial Raman mapping investigation of SERS performance related to localized surface plasmons

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Nano Research 2020年第1期13卷 138-144页

作者： Yansheng Liu Feng Luo IMDEA Nanoscience Faraday 9Ciudad Universitaria de Cantoblanco28049MadridSpain School of Science Universidad Autónoma de MadridCiudad Universitaria de Cantoblanco28049MadridSpain

In this research,it reported a novel three-dimensional(3D)metallic hybrid system by introducing single-layer graphene(SLG)between silver nanoparticles(NPs)and silver nano-discs(NDs)arrays(Ag NPs/SLG/Ag NDs).By combining the plasmonic metallic nanostructures and the unique physical/chemical properties of graphene,Ag NPs/SLG/Ag NDs hybrid substrate was fabricated,and it exhibited extremely high surface-enhanced Raman scattering(SERS)performance.By tuning the diameter of Ag NDs,the SERS performance of Ag NPs/SLG/Ag NDs hybrid substrate has been systematically studied.The detection limit for rhodamine 6g(R6G)could reach the concentrations as low as 1×10^−12 mol/L,and the average enhancement factor(EF)of the Ag NPs/SLG/Ag NDs substrate could reach 5.65×10^8.These advantages indicated that the Ag NPs/SLG/Ag NDs hybrid substrate could be regarded as a candidate for organic molecules detection under extremely low concentration.Besides,spatial Raman mapping of Ag NPs/SLG/Ag NDs with 2.5μm diameter NDs showed the larger SERE signal existed around the rim of Ag NDs which was related to the localized surface plasmons.This phenomenon was contributed by a larger electromagnetic field which was tuned by Ag NPs and the edge of Ag NDs.This mechanism also has been confirmed by the electromagnetic simulation result.

关键词： surface-enhanced Raman scattering(SERS) graphene high performance plasmon mapping

Low-Temperature Processed Carbon Electrode-Based Inorganic Perovskite Solar Cells with Enhanced Photovoltaic performance and Stability

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Energy & Environmental Materials 2021年第1期4卷 95-102页

作者： Xin Wu Feng Qi Fengzhu Li Xiang Deng Zhen Li Shengfan Wu Tiantian Liu Yizhe Liu Jie Zhang Zonglong Zhu Department of Chemistry City University of Hong KongKowloon 999077Hong Kong Department of Materials Science and Engineering City University of Hong KongKowloon 999077Hong Kong

All-inorganic perovskite solar cells(PVSCs)have drawn widespread attention for its superior thermal stability.Carbon-based devices are promising to demonstrate excellent long-term operational stability due to the hydrophobicity of carbon materials and the abandon of organic holetransporting materials(HTMs).However,the difficulty to control the crystallinity process and the poor morphology leads to serious non-radiative recombination,resulting in low V_(OC)and power conversion efficiency(PCE).In this article,the crystal formation process of all-inorganic perovskites is controlled with a facile composition engineering strategy.By bromide incorporation,high-quality perovskite films with large grain and fewer grain boundaries are achieved.As-prepared perovskite films demonstrate longer carrier lifetime,contributing to lower energy loss and better device performance.Fabricated carbon-based HTM-free PVSCs with CsPbI_(2.33)Br_(0.67) perovskite realized champion PCE of 12.40%,superior to 8.80%of CsPbI_(3)-based devices,which is one of the highest efficiencies reported for the carbon-based all-inorganic PVSCs to date.The high V_(OC) of 1.01 V and FF of 70.98% indicate the significance of this composition engineering method.Moreover,fabricated carbon-based devices exhibit excellent stability,and unencapsulated device retains over 90%of its initial efficiency under continuous one sun illumination for 250 h in N_(2) atmosphere and keeps~84%of its original value after stored in ambient environment with RH 15–20% for 200 h.This work provides a facile way to fabricate high-performance and stable carbon-based all-inorganic PVSCs.

关键词： bromide incorporation carbon high performance perovskite stable

Secondary crystallization strategy for highly efficient inorganic CsPbI_(2)Br perovskite solar cells with efficiency approaching 17%

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Journal of Energy Chemistry 2021年第12期30卷 558-565,I0013页

作者： Jing Ma Zhenhua Lin Xing Guo Long Zhou Jian He Zhou Yang Jincheng Zhang Yue Hao Shengzhong Liu Jingjing Chang State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology Shaanxi Joint Key Laboratory of GrapheneSchool of MicroelectronicsXidian University2 South Taibai RoadXi’an 710071ShaanxiChina Advanced Interdisciplinary Research Center for Flexible Electronics Xidian University2 South Taibai RoadXi’an 710071ShaanxiChina Key Laboratory of Applied Surface and Colloid Chemistry National Ministry of Education Shaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi’an 710119ShaanxiChina

Inorganic CsPbI_(2) Br perovskite solar cells(PSCs) have a tremendous development in last few years due to the trade-off between the excellent optoelectronic properties and the relatively outstanding stability.Herein,we demonstrated a strategy of secondary crystallization(SC) for CsPbI_(2) Br film in a facile planar n-i-p structure(ITO/ZnO-SnO_(2)/CsPbI_(2) Br/Spiro-OMeTAD/Ag) at low-temperature(150℃).It is achieved through the method of post-treatment with guanidinium bromine(GABr) atop annealed CsPbI_(2) Br film.It was found that the secondary crystallization by GABr can not only regulate the crystal growth and passivate defects,but also serve as a charge collection center to effectively collect photogenerated carriers.In addition,due to the excess Br ions in GABr,the formation of the Br-rich region at the CsPbI_(2) Br perovskite surface can further lower the Fermi level,leading to more beneficial band alignment between the perovskite and the hole transport layer(HTL),while the phase stability was also improved.As a result,the champion cell shows a superb open-circuit voltage(V_(oc)) of 1.31 V,a satisfactory power conversion efficiency(PCE) of 16.97% and outstanding stabilities.As far as we know,this should be one of the highest PCEs reported among all-inorganic CsPbI_(2) Br based PSCs.

关键词： CsPbI_(2)Br Low temperature Secondary crystallization high performance

Improving multiprocessor performance with fine-grain coherence bypass

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Science China(Information Sciences) 2015年第1期58卷 84-98页

作者： WANG Hui WANG Rui LUAN ZhongZhi QIAN XueHai QIAN DePei Sino-German Joint Software Institute School of Computer Science and EngineeringBeihang University University of Illinois Urbana-Champaign

Efficient and scalable cache coherence protocol is crucial to high-performance servers with sharedmemory. The directory-based cache coherence protocol is more desirable than the snooping-based protocol with respect to the scalability. However, even for the former protocol, scaling to a large number of cores is also challenging due to the additional area requirements of the directories. We observed that a significant percentage of the referenced memory blocks were only accessed by a single core(even in parallel applications) which could be considered as private memory blocks. An intuitive motivation from this observation is that memory blocks accessed by a single core do not require coherence maintenance. The issue is to identify the private block and track the change of its access pattern. We propose a novel hardware approach to(1) dynamically identify the shared memory blocks at the cache block level, and(2) bypass the coherence procedure for the private memory blocks. This approach increases the effectiveness of the directory-based approach and therefore improves the system performance. Experimental results showed that, our approach can on an average(1) avoid the coherence tracking of about 54% referenced memory blocks,(2) reduce the coherence overhead by 77%,(3) avoid 8% L2 cache misses, and(4) shorten the execution time of parallel applications by 13%.

关键词： many-core cache coherence private memory block fine-grain coherence high performance

Design of highly efficient elliptic curve crypto-processor with two multiplications over GF(2^(163))

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The Journal of China Universities of Posts and Telecommunications 2009年第2期16卷 72-79页

作者： DAN Yong-ping ZOU Xue-cheng LIU Zheng-lin HAN Yu YI Li-hua The Department of Eleetric Engineering Zhongyuan University of Technology Zhengzhou 450007 China Department of Electronic Science and Technology Huazhong University of Science and Technology Wuhan 430007 China

In this article, a parallel hardware processor is presented to compute elliptic curve scalar multiplication in polynomial basis representation. The processor is applicable to the operations of scalar multiplication by using a modular arithmetic logic unit （MALU）. The MALU consists of two multiplications, one addition, and one squaring. The two multiplications and the addition or squaring can be computed in parallel. The whole computations of scalar multiplication over GF（2^163） can be performed in 3 064 cycles. The simulation results based on Xilinx Virtex2 XC2V6000 FPGAs show that the proposed design can compute random GF（2^163） elliptic curve scalar multiplication operations in 31.17 μs, and the resource occupies 3 994 registers and 15 527 LUTs, which indicates that the crypto-processor is suitable for high-performance application.

关键词： elliptic curve cryptography scalar multiplication finite field parallel design high performance

Labyrinth maze-like long travel-reduction of sulfur and polysulfides in micropores of a spherical honeycomb carbon to greatly confine shuttle effects in lithium-sulfur batteries

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Materials Reports(Energy) 2022年第4期2卷 54-61页

作者： Yanyan Chang Jie Chen Zhuo Zou Juan Li Chao Wu Yali Jiang Yue Chen Qingxin Zeng Xiaoshui Wu Wei Sun Chang Ming Li Institute of Materials Science and Devices School of Material Science and EngineeringSuzhou University of Science and TechnologySuzhou215011PR China Institute of Clean Energy and Advanced Materials School of Materials and EnergySouthwest UniversityChongqing400715PR China Jiuhuan Xinyue New Energy Technology Co.LTD Qingdao266071PR China College of Chemistry and Chemical Engineering Hainan Normal UniversityHaikou571158PR China

Polysulfide absorption in a micropore-rich structure has been reported to be capable of efficiently confining the shuttle effect for high-performance lithium-sulfur(Li–S)batteries.Here,a labyrinth maze-like spherical honeycomb-like carbon with micropore-rich structure was synthesized,which is employed as a template host material of sulfur to study the shuttle effects.The results strongly confirm that a diffusion controlled process rather than an absorption resulted surface-controlled process occurs in an even micropore-rich cathode but still greatly inhibits the shuttle effect.Thus,the battery achieves a high initial discharge specific capacity of 1120 mAh g1 at 0.25 C and super cycling stability for 1635 cycles with only 0.035%capacity decay per cycle with 100%Coulombic efficiency.We would like to propose a new mechanism for shuttle effect inhibition in micropores.In terms of the diffusion control process in microporous paths of a labyrinth maze structure,polysulfides experience a long travel to realize continuous reductions of sulfur and polysulfides until formation of the final solid product.This efficiently prevents the polysulfides escaping to electrolyte.The labyrinth maze-like honeycomb structure also offers fast electron transfer and enhanced mass transport as well as robust mechanical strength retaining intact structure for long cycle life.This work sheds lights on new fundamental insights behind the shuttle effects with universal significance while demonstrating prominent merits of a robust labyrinth maze-like structure in high performance cathode for high-performance Li–S batteries.

关键词： Lithium-sulfur batteries Labyrinth maze-like spherical honeycomb-like carbon Diffusion-controlled process Shuttle effects high performance

A 20 μW 95 dB dynamic range 4th-order Delta-Sigma modulator with novel power efficient operational transconductance amplifier and resonator

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第6期12卷 486-498页

作者： Jian XU Xiao-bo WU Meng-lian ZHAO Jun-yi SHEN Institute of VLSI Design Zhejiang University Hangzhou 310027 China

A low power high performance Delta-Sigma modulator for portable measurement applications is presented. To reduce power consumption while maintaining high performance, a fully feedforward architecture with a comprehensive system-level design is implemented. As a key building block, a novel power efficient current mirror operational transconductance amplifier (OTA) with a fast-settling less-error switched-capacitor common-mode feedback (SC CMFB) circuit is introduced, and the effects of both gain nonlinearity and 1/f noise of OTA are discussed. A new method to determine the voltage gain of an OTA is also proposed. The bottom terminal parasitic effect of poly-insulator-poly (PIP) capacitors is considered. About an extra 20% of capacitance is added to the total capacitance load. A power and area efficient resonator is adopted to realize a coefficient of 1/90 for 50% power and 75% area reduction compared with conventional designs. The chip is implemented in a low cost 0.35 μm complementary metal oxide semiconductor (CMOS) process. The total power consumption is 20 μW with a 1.5 V supply, and the measured dynamic range (DR) is 95 dB over a 1 kHz bandwidth. Experimental results show that a high figure-of-merit (FOM) is achieved for the designed modulator in comparison with those from the literature.

关键词： Low power high performance Power efficient OTA and resonator Delta-Sigma modulator