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Nonlinear energy harvesting with dual resonant zones based on rotating system

Applied Mathematics and Mechanics(English Edition) 2021年第2期42卷 275-290页

作者： Dan WANG zhifeng HAO Fangqi CHEN Yushu CHEN School of Mathematical Sciences University of JinanJinan 250022China College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Astronautics Harbin Institute of TechnologyHarbin 150001China

An electromagnetic nonlinear energy harvester(NEH)based on a rotating system is proposed,of which the host system rotates at a constant speed and vibrates harmonically in the vertical direction.This kind of device exhibits several resonant phenomena due to the combinations of the rotating and the vibration frequencies of the host system as well as the cubic nonlinearity of the NEH.The governing equation of motion for the NEH is derived,and the dynamic responses and output power are investigated with the multiple scale method under the 1:1 primary and 2:1 superharmonic resonant conditions.The effects of system parameters including the nondimensional external frequency,the rotating speed,and the nonlinear stiffness on the responses of free vibration for the system are studied.The results of the primary resonance show that the responses exhibit not only the resonant characteristics but also the nonlinear dynamic characteristics such as the saddle-node(SN)bifurcation.The coexistence of multiple solutions and the varying trends of responses are verified with the direct numerical simulation.Moreover,the effects of system parameters on the average output power are investigated.The results of the analyses on the two resonant conditions indicate that the large power can be harvested in two resonant frequency bands.The effect of resonance on the output power is dominant for the 2:1 superharmonic resonance.Moreover,the results also show that introducing the nonlinearity can increase the value of the output power in large frequency bands and induce the occurence of new frequency bands to harvest the large power.The efficiency of the harvested power could be improved by the combined effects of the resonance as well as the nonlinearity of the NEH device.Suitable parameter conditions could help optimize the power harvesting in design.

关键词： nonlinear energy harvester(NEH) resonance output power multiple scale method rotating system

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Efficient numerical algorithms for the phase field crystal equation

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International Journal of Modeling, Simulation, and Scientific Computing 2021年第5期12卷 178-192页

作者： Qingqu Zhuang Shuying Zhai zhifeng Weng Fujian Province University Key Laboratory of Computation Science School of Mathematical Sciences Huaqiao University Quanzhou 362021P.R.China

In this paper,based on the Lagrange Multiplier approach in time and the Fourierspectral scheme for space,we propose efficient numerical algorithms to solve the phase field crystal equation.The numerical schemes are unconditionally energy stable based on the original energy and do not need the lower bound hypothesis of the nonlinear free energy potential.The unconditional energy stability of the three semi-discrete schemes is proven.Several numerical simulations in 2D and 3D are demonstrated to verify the accuracy and efficiency of our proposed schemes.

关键词： Phase field crystal equation energy stable Lagrange Multiplier approach

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Exploring serverless computing for stream analytic

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High Technology Letters 2020年第1期26卷 17-24页

作者：成英超 Hao zhifeng Cai Ruichu School of Computer Science and Technology Guangdong University of TechnologyGuangzhou 510006P.R.China School of Mathematics and Big Data Foshan UniversityFoshan 528000P.R.China Department of Statistics Texas A&M UniversityCollege Station 77840USA

This work proposes ARS(FaaS) serverless framework scheduling and provisioning resources for streaming applications autonomously, which ensures real-time response on unpredictable and fluctuating streaming data. A HPC cloud platform is used as a de facto platform, on which serverless computing for stream analytic is explored. This work enables application developers to build and run steaming applications without worrying about servers, which means that the developers are able to focus on application features instead of scheduling and provisioning resources of the infrastructure. The serverless computing framework, ARS(FaaS), provides function-as-a-service to make the developers write code in discrete event-driven functions. ARS(FaaS) is capable of running and scaling the developer's code automatically, according to the throughput of streaming events. The major contribution of this serverless framework is effective and efficient autonomous resource scheduling for real-time streaming analytic, which enables the developers to build applications faster with autonomous resource scheduling. ARS(FaaS) framework is appropriate for real-time and stream analytic on event-driven data with spiky and variable compute requirements.

关键词： serverless steam processing HPC cloud auto-scaling function-as-a-service(FaaS)

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Object Detection and Tracking in Driving Videos based on Deep Learning

Object Detection and Tracking in Driving Videos based on Dee...

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作者： zhifeng Wang 华中师范大学

学位级别：硕士

作为计算机视觉的重要研究方向,目标检测与追踪的相关研究从未间断。目标检测是指在指定的输入图片中定位图中一个或多个目标物体。目标追踪是指在指定的输入视频中,根据第一帧中给的目标边界框预测视频后续帧中该目标边界框的位置和尺... 详细信息

作为计算机视觉的重要研究方向,目标检测与追踪的相关研究从未间断。目标检测是指在指定的输入图片中定位图中一个或多个目标物体。目标追踪是指在指定的输入视频中,根据第一帧中给的目标边界框预测视频后续帧中该目标边界框的位置和尺寸。这个目标边界框可以由人工标定,但在实际应用中一般由目标检测算法检测得到。因此可以认为,目标检测是目标追踪的前序步骤。传统的目标检测与追踪算法受技术的限制,精确度与鲁棒性较差。近年来随着计算机性能的稳步提升,深度学习得以飞速发展,这也为目标检测与追踪带来了新的发展机遇。与此同时,将深度学习应用于目标检测与追踪所带来的性能的提升也为其实际应用增加了可能性。传统的道路监管系统主要靠人工,需要大量的人力物力。智能驾驶系统同样对路况的监测有着极高的要求。将基于深度学习的目标检测与追踪技术应用其中,借助其较高准确率与极好的鲁棒性,在智能道路监管和智能驾驶等实际应用领域取得突破是当前研究的重点之一。本文将研究基于深度学习的目标检测与追踪算法,并针对行车视频中的车辆行人的检测对相关算法进行改进和优化,以适应实际的应用场景。传统的目标检测依赖于人工提取所检测目标的图像特征,这样的特征往往鲁棒性较差,因而准确率较低。而检测时对于图片中检测区域的选择策略效果也不理想,同时时间复杂度极高。受这些技术缺陷的限制,目标检测虽然是计算机视觉的基础问题,但在2010年就没有大的技术突破。直到2013年,Ross Grishick发表论文阐述了其团队所研发的R-CNN目标检测算法,将卷积神经网络引入目标检测后,基于深度学习的目标检测算法逐渐成为研究主流。目前基于深度学习的目标检测算法主要分为两类,一类是以R-CNN为基础的二阶算法:这类算法将目标检测分为卷积神经网络在目标可能区域内提取特征以及分类器依据特征对目标进行分类和定位。另一类是以YOLO为代表的一阶算法:这类算法直接在目标可能区域内对目标进行定位。二阶算法以R-CNN为基础,R-CNN创造性的引入卷积神经网络取代手工提取特征并使用Selective Search（SS）取代滑窗生成目标可能区域,极大地提高了检测准确度,降低了时间复杂度[1,2]。一年后,何恺明团队提出SPPNet,改进了 R-CNN的算法结构先对图片进行卷积在生成目标可能区域,并引入空间金字塔池化层,不仅减少了计算量而且消除了输入图片的尺寸限制[3]。其后,Ross Grishick提出Fast R-CNN,再次改进R-CNN的算法结构,将目标分类和定位同步进行,再次提高了计算速度与检测准确度[4]。同年,何恺明团队的任少卿联合Ross Grishick团队提出Faster R-CNN,提出区域生成网络（RPN）取代SS利用卷积神经网络生成目标可能区域,并且该网络与Fast R-CNN的目标分类定位网络共用一部分神经网络[5]。一年后,何恺明团队再次改进Faster R-CNN,在原有基础添加一条实力分割的掩膜分支网络,利用实例分割再次提高了检测准确度[6]。一阶算法则直接对整个图片进行分类定位,其代表YOLO首先将输入图片卷积后提取的特征图分为数个方格,然后对每个方格进行分类回归直接得到结果[7]。两类算法各有优劣,二级算法精确,一阶算法速度较快。本文基于行车视频对精度及速度的要求选取Mask R-CNN为基础进行后续研究。传统目标追踪算法主要分生成模型与判别模型两类方法。生成类方法简单来说对视频第一帧给出的目标边界框建模,在视频其后的帧中对比选出与模型最相似的区域。该类方法主要包括了卡尔曼滤波,粒子滤波以及ASMS;判别类算法利用了图像特征与机器学习,对视频第一帧的目标边界框提取特征,以其为正样本,背景区域为负样本,随后用机器学习的方式训练分类器,让分类器在视频后续帧对进行正负样本的分类。判别类算法和目标检测算法极为相似,区别在于追踪算法对学习的要求比较低,检测范围和尺度更小。这类方法主要包括Stuck和TD[8]。目前上述这些算法已经被相关滤波类算法以及深度学习类算法取代。自2010年P.Martins提出CSK方法,利用循环矩阵和快速傅里叶变换实现目标追踪后,相关滤波类算法以其绝对的时间优势逐渐占据目标检测算法的主流[9]。随后无数研究从特征提取、尺度自适应和边界效应入手以完善相关滤波类算法,其中SRDCF成功建立空间正则滤波器以消除边界效应[10]。而深度学习类的目标检测算法虽然准确率极高,但是由于其卷积神经网络本身的结构特点,在时间上处于劣势,但其准确率极高,因此依然具备较大潜力。基于孪生全卷积网络的SiamFC在拥有不错准确率的前提下有着较高的运行速度[11]。深度学习端到端的强大性能在目标追踪上还有很大的发展空间。本文将结合相关滤波类算法SRDCF的优点优化SiamFC。本文选取Mask R-CNN作为目标检测的基础模型,为适应行车视频的应用场景使用MoblieNet替换ResNeXt骨干网络对

关键词：深度学习目标检测目标跟踪掩膜区域卷积神经网络全卷积孪生网络

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Spatial Function Regionalization Based on an Ecological-economic Analysis in Wuxi City, China

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Chinese Geographical Science 2019年第2期29卷 352-362页

作者： SUN Wei CHEN Wen JIN zhifeng Nanjing Institute of Geography & Limnology Chinese Academy of Sciences Key Laboratory of Watershed Geographic Sciences Chinese Academy of Sciences College of Resources and Environment University of Chinese Academy of Sciences School of Resource and Environmental Sciences Wuhan University Jiangsu Research Center of Land and Resources

As a result of rapid urbanization in China, urban sprawl has increased rapidly, and land-use regulation and smart urban growth are equally important. Spatial function regionalization can provide the scientific groundwork for the regulation of land use and protection. This paper probes the system of evaluation indices and applies the methods of spatial analysis and classification clustering to the calculation of the ecologically significant value and economically significant value in each evaluation unit. After use of a classification matrix integrated by the two significant values, city space can be divided into four functional types, namely, feasible development area, moderate development area, moderate conservation area and prohibited exploiting area, and these are the basis for spatial development and control.

关键词： spatial function regionalization spatial analysis ecologically significant value economically significant value urbanized region

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Interfacial Morphology and Bonding Mechanism of Explosive Weld Joints

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Chinese Journal of Mechanical Engineering 2021年第2期34卷 201-212页

作者： Tingting Zhang Wenxian Wang zhifeng Yan Jie Zhang Advanced Forming and Intelligent Equipment Research Institute Taiyuan University of TechnologyTaiyuan 030024China College of Mechanical and Vehicle Engineering Taiyuan University of TechnologyTaiyuan 030024China College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China

Interfacial structure greatly affects the mechanical properties of laminated plates.However,the critical material properties that impact the interfacial morphology,appearance,and associated bonding mechanism of explosive welded plates are still unknown.In this paper,the same base plate(AZ31B alloy)and different flyer metals(aluminum alloy,copper,and stainless steel)were used to investigate interfacial morphology and structure.SEM and TEM results showed that typical sine wave,wave-like,and half-wave-like interfaces were found at the bonding interfaces of Al/Mg,Cu/Mg and SS/Mg clad plates,respectively.The different interfacial morphologies were mainly due to the differences in hardness and yield strength between the flyer and base metals.The results of the microstructural distribution at the bonding interface indicated metallurgical bonding,instead of the commonly believed solid-state bonding,in the explosive welded clad plate.In addition,the shear strength of the bonding interface of the explosive welded Al/Mg,Cu/Mg and SS/Mg clad plates can reach up to 201.2 MPa,147.8 MPa,and 128.4 MPa,respectively.The proposed research provides the design basis for laminated composite metal plates fabrication by explosive welding technology.

关键词： Interfacial structure Bonding mechanism Explosive welding Metallurgical bonding Magnesium alloy

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The influence of bioturbation on sandy reservoirs: the delta front sand of the lower Zhujiang Formation, Baiyun Depression, Zhujiang River Mouth Basin

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Acta Oceanologica Sinica 2023年第9期42卷 27-43页

作者： zhifeng Xing Wei Wu Juncheng Liu Yongan Qi Wei Zheng The Institute of Resources and Environment Henan Polytechnic UniversityJiaozuo 454000China Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Mineral Shandong University of Science and TechnologyQingdao 266590China

Ichnofossils are well developed in clastic rock reservoirs in marine and transitional facies, which can considerably change the physical properties of the reservoir. However, this influence is not well understood, raising an important problem in the effective development of petroleum reservoirs. This paper analyzes continental shelf margin delta reservoirs through core observation, cast thin section observation and reservoir physical property test. Some important scientific insights are obtained:(1) The presence of Cruziana ichnofacies, including Asterosoma, Ophiomorpha, Planolites, Skolithos, Thalassinoides, and other ichnofossils can be used to identify in subaqueous distributary channels, subaqueous levee, frontal sheet sand, abandoned river channels, crevasse channels, main channels and channel mouth bars. Considerable differences in the types of ichnofossils and the degree of bioturbation can be observed in the different petrofacies.(2) Ichnofossils and bioturbation play a complex role in controlling reservoir properties. The reservoir physical properties have the characteristics of a decrease–increase–decrease curve with increasing bioturbation degree. This complex change is controlled by the sediment mixing and packing of bioturbation and the diagenetic environment controlled by the ichnofossils.(3) Sea-level cycle changes affect the modification of the reservoir through sediment packing. Bioturbation weakens the reservoir's physical property when sea level slowly rises and improves the reservoir's physical property when base level slowly falls.

关键词： bioturbation reservoir physical properties sedimentary petrofacies shelf margin delta Baiyun Sag

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Catalytic oxidation effect of MnSO_(4) on As(Ⅲ) by air in alkaline solution

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Journal of Environmental Sciences 2023年第4期126卷 644-655页

作者： Yuhu Li Yudong Yang Ruixiang Wang zhifeng Xu Guizhong Jin Chengyong Jin Faculty of materials Metallurgy and Chemistry Jiangxi University of Science and TechnologyGanzhou 341000China Hsikwang Shan Twinkling Star Co.Ltd. Lengshui Jiang 417500China

The catalytic oxidation effect of MnSO_(4)on As(Ⅲ) by air in an alkaline solution was investigated.According to the X-ray diffraction (XRD),scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) analysis results of the product,it was shown that the introduction of MnSO_(4)in the form of solution would generate Na_(0.55)Mn_(2)O_(4)·1.5H_(2)O with strong catalytic oxidation ability in the aerobic alkaline solution,whereas the catalytic effect of the other product MnOOH is not satisfactory.Under the optimal reaction conditions of temperature 90℃,As/Mn molar ratio 12.74:1,air flow rate1.0 L/min,and stirring speed 300 r/min,As(Ⅲ) can be completely oxidized after 2 hr reaction.The excellent catalytic oxidation ability of MnSO_(4)on As(Ⅲ) was mainly attributed to the indirect oxidation of As(Ⅲ) by the product Na_(0.55)Mn_(2)O_(4)·1.5H_(2)O.This study shows a convenient and efficient process for the oxidation of As(Ⅲ) in alkali solutions,which has potential application value for the pre-oxidation of arsenic-containing solution or the detoxification of As(Ⅲ).

关键词： Arsenic Air oxidation Catalytic oxidation Manganese sulfate

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High cut-off membranes in patients requiring renal replacement therapy:a systematic review and meta-analysis

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Chinese Medical Journal 2023年第1期136卷 34-44页

作者： zhifeng Zhou Huang Kuang Fang Wang Lu Liu Ling Zhang Ping Fu Division of Nephrology Kidney Research InstituteWest China Hospital of Sichuan UniversityChengduSichuan 610041China Division of Nephrology Peking University First HospitalPeking University Institute of NephrologyKey Laboratory of Renal DiseaseMinistry of Health of ChinaBeijing 100034China Preventive Medicine West China School of Public HealthSichuan UniversityChengduSichuan 610041China

Background:Whether high cut-off(HCO)membranes are more effective than high-flux(HF)membranes in patients requiring renal replacement therapy(RRT)remains controversial.The aim of this systematic review was to investigate the efficacy of HCO membranes regarding the clearance of inflammation-related mediators,β2-microglobulin and urea;albumin loss;and all-cause mortality in patients requiring RRT.Methods:We searched all relevant studies on PubMed,Embase,Web of Science,the Cochrane Library,and China National Knowledge Infrastructure,with no language or publication year restrictions.Two reviewers independently selected studies and extracted data using a prespecified extraction instrument.Only randomized controlled trials(RCTs)were included.Summary estimates of standardized mean differences(SMDs)or weighted mean differences(WMDs)and risk ratios(RRs)were obtained by fixed-effects or random-effects models.Sensitivity analyses and subgroup analyses were performed to determine the source of heterogeneity.Results:Nineteen RCTs involving 710 participants were included in this systematic review.Compared with HF membranes,HCO membranes were more effective in reducing the plasma level of interleukin-6(IL-6)(SMD-0.25,95%confidence interval(CI)-0.48 to-0.01,P=0.04,I 2=63.8%);however,no difference was observed in the clearance of tumor necrosis factor-α(TNF-α)(SMD 0.03,95%CI-0.27 to 0.33,P=0.84,I 2=4.3%),IL-10(SMD 0.22,95%CI-0.12 to 0.55,P=0.21,I 2=0.0%),or urea(WMD-0.27,95%CI-2.77 to 2.23,P=0.83,I 2=19.6%).In addition,a more significant reduction ratio ofβ2-microglobulin(WMD 14.8,95%CI 3.78 to 25.82,P=0.01,I 2=88.3%)and a more obvious loss of albumin(WMD-0.25,95%CI-0.35 to-0.16,P<0.01,I 2=40.8%)could be observed with the treatment of HCO membranes.For all-cause mortality,there was no difference between the two groups(risk ratio[RR]1.10,95%CI 0.87 to 1.40,P=0.43,I 2=0.0%).Conclusions:Compared with HF membranes,HCO membranes might have additional benefits on the clearance of IL-6 andβ2-microglobulin but not on TNF-α,IL-10,and urea.

关键词： High cut-off High-flux Renal replacement therapy Randomized controlled trials Meta-analysis

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Impact factors of the degradation of bisphenol A by nitrocellulose membrane under illumination

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Journal of Environmental Sciences 2021年第2期33卷 193-202页

作者： Li Wu Xinmiao Jin Tongqian Zhao Haipo Wang zhifeng Dai Institute of Resources and Environment Henan Polytechnic UniversityJiaozuo 454000China Collaborative Innouation Center for Coal-Bed Methane and Shale Gas of Henan Jiaozuo 454000China

Nitrocellulose membrane(NCM)can produce hydroxyl radicals under illumination,which promotes the oxidative degradation of organic pollutants.In this paper,NCM was used to oxidize bisphenol A(BPA)under simulated sunlight.The effects of p H,temperature,light intensity,anion and cation on the degradation of BPA were analyzed.The photodegradation process of BPA was discussed.The optimal photolysis rate was 0.031 min^(-)1 when the temperature was 30°C,the light intensity was 2.67×10^4 Lux,and the p H value was 9.0.The alkaline environment,temperature and light intensity can promote the photodegradation of BPA.Except for nitrate ions,anions and cations can inhibit the photodegradation of BPA.Compared with cations,anions have a greater inhibitory effect on BPA degradation.The degradation products of BPA by NCM were analyzed by gas chromatographic/mass.This study may provide useful information for the BPA degradation by NCM in complex water samples.

关键词： Nitrocellulose membrane Bisphenol A Degradation Illumination Impact factors

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