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Interaction Mechanism of Double Bubbles in Hydrodynamic Cavitation

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Journal of Thermal Science 2013年第3期22卷 242-249页

作者： Fengchao Li jun cai Xiulan Huai Bin Liu Institute of Engineering Thermophysics Chinese Academy of Sciences

Bubble-bubble interaction is an important factor in cavitation bubble dynamics. In this paper, the dynamic behaviors of double cavitation bubbles driven by varying pressure field downstream of an orifice plate in hydrodynamic cavitation reactor are examined. The bubble-bubble interaction between two bubbles with different radii is considered. We have shown the different dynamic behaviors between double cavitation bubbles and a single bubble by solving two coupling nonlinear equations using the Runge-Kutta fourth order method with adaptive step size control. The simulation results indicate that, when considering the role of the neighbor smaller bubble, the oscil-lation of the bigger bubble gradually exhibits a lag in comparison with the single-bubble case, and the extent of the lag becomes much more obvious as time goes by. This phenomenon is more easily observed with the increase of the initial radius of the smaller bubble. In comparison with the single-bubble case, the oscillation of the bigger bubble is enhanced by the neighbor smaller bubble. Especially, the pressure pulse of the bigger bubble rises intensely when the sizes of two bubbles approach, and a series of peak values for different initial radii are acquired when the initial radius ratio of two bubbles is in the range of 0.9～1.0. Although the increase of the center distance between two bubbles can weaken the mutual interaction, it has no significant influence on the enhancement trend. On the one hand, the interaction between two bubbles with different radii can suppress the growth of the smaller bubble; on the other hand, it also can enhance the growth of the bigger one at the same time. The significant en-hancement effect due to the interaction of multi-bubbles should be paid more attention because it can be used to reinforce the cavitation intensity for various potential applications in future.

关键词： Hydrodynamic cavitation, Double bubbles, Cavitation bubble dynamics

Simulation of Heat Transfer with the Growth and Collapse of a Cavitation Bubble Near the Heated Wall

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Journal of Thermal Science 2013年第4期22卷 352-358页

作者： Bin Liu jun cai Fengchao Li Xiulan Huai Institute of Engineering Thermophysics Chinese Academy of Sciences University of Chinese Academy of Sciences

The growth and collapse behaviors of a single cavitation bubble near a heated wall and its effect on the heat transfer are numerically investigated. The present study is designed to reveal the mechanism of cavitation enhanced heat transfer from a microscopic perspective. In the simulation, the time-dependent Navier-Stokes equations are solved in an axisymmetric two-dimensional domain. The volume of fluid (VOF) method is employed to track the liquid-gas interface. It is assumed that the gas inside the bubble is compressible vapor, and the surrounding liquid is incompressible water. Mass transfer between two phases is ignored. The calculated bubble profiles were compared to the available experimental data, and a good agreement was obtained. Then, the relationship among bubble motion, flow field and surface heat transfer coefficient was analyzed. On this basis, the effects of such factors as the initial distance between the bubble and the wall, the initial vapor pressure and the initial bubble nucleus size on the heat transfer enhancement are discussed. The present study is helpful to understand the heat transfer phenomenon in presence of cavitation bubble in liquid.

关键词：热仿真 Navier-Stokes方程加热溃灭生长气蚀强化传热不可压缩

IDMA based MAI mitigation scheme with low complexity and low latency

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Journal of Systems Engineering and Electronics 2012年第6期23卷 791-801页

作者： Zuoliang Yin Xingpeng Mao jun cai Naitong Zhang School of Electronics and Information Engineering Harbin Institute of Technology Harbin 150001 R R. China Department of Computer and Electrical Engineering University of Manitoba Winnipeg R3T 5V6 Canada

High complexity and high latency are key problems for multiuser detection （MUD） to be applied to a mobile station in cellular networks. To tackle these problems, an interleave division multiple access （IDMA） based multiple access scheme, grouped spread IDMA （GSIDMA）, is proposed. In a GSIDMA system, lower complexity and latency for mobile stations can be achieved by appropriately dividing active users into different groups. The system model of GSIDMA is constructed and followed by analysing on its system capacity, complexity and latency, and bit error rate （BER） performance. The extrinsic information transfer （EXIT） chart is used to analyze the convergence behavior of the iteration process. The grouping method and interleavers-reuse issue for GSIDMA are also discussed preliminarily. The analyses and simulation results indicate that the complexity and latency of the proposed scheme are much lower than those of IDMA, whereas its BER performance is close to the latter. The properties of low complexity and low latency make it more feasible for the practical implementation.

关键词： grouped spread interleave division multiple access（GSIDMA） iterative multiuser detector （IMUD） low complexity lowlatency multiple access interference （MAI） mitigation.

The Elongation Performance of Spirulina-templated Silver Micro Springs Embedded in the Polydimethylsiloxane

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Journal of Bionic Engineering 2017年第4期14卷 631-639页

作者： jun cai Yingying Shi Xinghao Li Deyuan Zhang School of Mechanical Engineering and Automation Beihang University Beijing 100191 China

Helical conductive particles have attracted much attention in preparing stretchable conductive materials because of their structural flexibility and uniform strain distribution under deformation. In this paper, Spirulina-templated silver micro springs were fabricated using electroless deposition of silver onto Spirulina surface. To investigate their potential application as con- ductive fillers for stretchable materials, they were mixed into polydimethylsiloxane （PDMS） uniformly, and then the mixture was spin coated on a polyfluortetraethylene （PTFE） plate to form a thin film, during which, micro springs tended to align its major axis along the radial direction of the plate. The tensile tests of micro springs were carried out using the film along the alignment direction of micro springs on the custom-made setup. Under the optimal condition of coating thickness of 0.67 gm, helical pitch of 29 gm and annealing temperature of 300 ~C, the average elongation of micro springs can reach up to -106.9%, which indicates that the as-prepared Spirulina-templated silver micro springs are promising flexible conductive fillers for fabricating stretchable conductive materials.

关键词： micro springs elongation electroless deposition of silver Spirulina stretchable conductive fillers

PSM⁃DID在政策评价中的应用现状与改进方法

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管理科学学报 2024年第2期27卷 30-48页

作者：蔡俊杨岚周亚虹华中科技大学管理学院武汉430074 西南财经大学统计学院成都611130 上海财经大学经济学院及上海财经大学滴水湖高级金融学院上海200433

倾向得分匹配-双重差分模型(PSM⁃DID)是政策评估及因果推断中最为流行的方法之一.但是在实际应用中,该方法面临着控制变量在处理组样本和控制组样本之间非平衡性的挑战.传统基于均值差异t检验的平衡性检验容易产生片面和误导性的结论,... 详细信息

倾向得分匹配-双重差分模型(PSM⁃DID)是政策评估及因果推断中最为流行的方法之一.但是在实际应用中,该方法面临着控制变量在处理组样本和控制组样本之间非平衡性的挑战.传统基于均值差异t检验的平衡性检验容易产生片面和误导性的结论,使得后续因果推断产生偏误.为克服上述问题,本文对传统的平衡性检验提出以下改进:一是推荐更全面的多维度的平衡性测度指标,便于在匹配后更严谨地比较处理组和控制组的平衡性;二是提出了适用于非平衡样本的新估计方法:倾向得分匹配-逆概率加权-双重差分(PSM⁃IPW⁃DID),该方法结合了倾向得分匹配(PSM)克服样本自选择内生性及对非平衡样本稳健的优势和逆概率加权(inverse probability weighting,IPW)利用全样本信息的长处,在不进一步删除样本的情况下得到一种更稳健的双重差分估计方法.数据模拟和应用实例显示,本文提出的新方法能更全面、客观地评价宏观、微观政策的作用,得到更为可信的因果推断.

关键词：倾向得分匹配-双重差分平衡性逆概率加权双重稳健性

Unveiling the secrets of diatom-mediated calcification: Implications for the biological pump

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Science China Earth Sciences 2024年

作者： Yiwen PAN Yifan LI Chen-Tung Arthur CHEN Zong-Pei JIANG Wei-jun cai Yunwen SHEN Zesheng DING Qixian CHEN Yanan DI Wei FAN Chenba ZHU Ying CHEN Ocean College Zhejiang University Hainan Institute of Zhejiang University Department of Oceanography Sun Yat-Sen University School of Marine Science and Policy University of Delaware Carbon Neutral Innovation Research Center Xiamen University

Siliceous diatoms are one of the most prominent actors in the oceans, and they account for approximately 40%of the primary production and particulate organic carbon export flux. It is believed that changes in carbon flux caused by variations in diatom distribution can lead to significant climate shifts. Although the fundamental pathways of diatom-driven carbon sequestration have long been established, there are no reports of CaCO3precipitation induced by marine diatom species. This manuscript introduces novel details regarding the enhancement of aragonite precipitation during photosynthesis in Skeletonema costatum in both artificial and natural seawater. Through direct measurements of cell surfaces via a pH microelectrode and zeta potential analyzer, it was determined that the diatom-mediated promotion of CaCO3precipitation is achieved through the creation of specific microenvironments with concentrated [CO32–] and [Ca2+] and/or the dehydrating effect of adsorbed Ca2+.Based on this mechanism, it is highly plausible that diatom-mediated calcification could occur in the oceans, an assertion that was supported by the significant deviation of total alkalinity (TA) from the conservative TA-salinity mixing line during a Skeletonema costatum bloom in the East China Sea and other similar occurrences. The newly discovered calcification pathway establishes a link between particulate inorganic and organic carbon flux and thus helps in the reassessment of marine carbon export fluxes and CO2sequestration efficiency. This discovery may have important ramifications for assessing marine carbon cycling and predicting the potential effects of future ocean acidification.

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重载铁路公专网车-地通信监测技术研究

铁路通信信号工程技术 2024年第2期21卷 48-53页

作者：蔡军国能新朔准池铁路(山西)有限责任公司山西朔州036002

公专网技术在重载货运车-地通信线路中的应用,对重载铁路公专网进行监测成为保障网络安全稳定运行的重要技术手段。简要论述目前实际应用在重载货运线路的LTE公专网架构,并对公专网监测系统的结构、功能、接口及关键技术进行论述。研究... 详细信息

公专网技术在重载货运车-地通信线路中的应用,对重载铁路公专网进行监测成为保障网络安全稳定运行的重要技术手段。简要论述目前实际应用在重载货运线路的LTE公专网架构,并对公专网监测系统的结构、功能、接口及关键技术进行论述。研究针对在车载侧、地面侧乃至中心侧全链条的监测技术,最终对重载铁路公专网监测系统未来的推广进行展望。

关键词： LTE公专网网络监测故障诊断

Optimal reinsurance designs based on risk measures:a review

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Statistical Theory and Related Fields 2020年第1期4卷 1-13页

作者： jun cai Yichun Chi Department of Statistics and Actuarial Science University of WaterlooWaterlooCanada China Institute for Actuarial Science Central University of Finance and EconomicsBeijingPeople’s Republ

Reinsurance is an effective way for an insurance company to control its risk.How to design an optimal reinsurance contract is not only a key topic in actuarial science,but also an interesting research question in mathematics and statistics.Optimal reinsurance design problems can be proposed from different perspectives.Risk measures as tools of quantitative risk management have been extensively used in insurance and finance.Optimal reinsurance designs based on risk measures have been widely studied in the literature of insurance and become an active research topic.Different research approaches have been developed and many interesting results have been obtained in this area.These approaches and results have potential applications in future research.In this article,we review the recent advances in optimal reinsurance designs based on risk measures in static models and discuss some interesting problems on this topic for future research.

关键词： Value-at-risk conditional value-at-risk distortion risk measures layer reinsurance optimal reinsurance designs

Removal of elemental mercury by photocatalytic oxidation over La_(2)O_(3)/Bi_(2)O_(3)composite

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Journal of Environmental Sciences 2021年第4期33卷 384-397页

作者： Renjun Li Yanan Zhou Xueqian Wang Langlang Wang Ping Ning Lei Tao jun cai Faculty of Environmental Science and Engineering Kunming University of Science and TechnologyKunming 650500China

La_(2)O_(3)/Bi_(2)O_(3)photocatalysts were prepared by impregnation of Bi_(2)O_(3)with an aqueous solution of lanthanum precursor followed by calcination at different temperatures.The composite materials were used for the first time for the photocatalytic removal of Hg~0 from a simulated flue gas under UV light irradiation.The results showed that the sample containing 6 wt.%La_(2)O_(3)and calcined at 500°C has the highest dispersion of the active sites,which was promoted by the strong interaction with the support(i.e.,the formation of Bi-O-La species).Since they are fully accessible on the surface,the material also exhibits excellent optical properties while the heterojunction formed in La_(2)O_(3)/Bi_(2)O_(3)promotes the separation and migration of photoelectron-hole pairs and thus Hg~0 oxidation efficiency is enhanced.The effects of the various factors(e.g.,the reaction temperature and composition of the simulated flue gas(i.e.,O_(2),NO,H_(2)O,and SO_(2)))on the efficiency of the Hg~0 photocatalytic oxidation were investigated.The results demonstrated that O_(2)and SO_(2)enhanced the efficiency of the reaction while the reaction temperature,NO,and H_(2)O had an inhibitory effect.

关键词： La_(2)O_(3)/Bi_(2)O_(3) Calcination temperature Hg~0 oxidation Photocatalytic oxidation