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Silicon carbide waste as a source of mixture materials for cement mortar

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Frontiers of Environmental Science & Engineering 2017年第5期11卷 47-54页

作者： Zhengwu Jiang Qiang ren Haoxin Li Qing chen Key Laboratory of Advanced Civil Engineering Materials Ministry of Education Tongji University Shanghai 201804 China

This paper presents an investigation of the feasibility of recycling silicon carbide waste （SCW） as a source of mixture materials in the production of cement mortar. Mortars with SCW were prepared by replacing different amounts of cement with SCW, and the properties of the resulting mortars, such as the fluidity, strength and shrinkage, were studied in this work. Thermogravimetry-differential scanning calorimet;＇y and scanning electron microscopy were employed to understand the reasons for the property changes of the mortars. The results indicate that SCW decreases the initial and l-h fluidity of fresh mortar but improves the loss of fluidity. The mortar with SCW exhibits a lower strength at 3 d and7 d but a higher strength at 28 d and 56 d compared to the control. The shrinkage rate of cement mortar with SCW shows an obvious decrease as the replacement ratio increases. In addition, the content of calcium hydroxide in hardened paste also shows that SCW has some impact on the hydration of the cement-SCW system. The microstructures of the hardened paste also show evidence for a later strength change of mortar containing SCW. This work provides a strategic reference for possibly applying SCW as a mixture material in the production of cement mortar.

关键词： Silicon carbide waste Cement mortar Fluidity Strength Shrinkage

Effects of Dragonfly Wing Structure on the Dynamic Performances

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Journal of Bionic Engineering 2013年第1期10卷 28-38页

作者： Huaihui ren Xishu Wang Xudong Li Yinglong chen Department of Engineering Mechanics AML Tsinghua University Beijing 100084 P. R. China Longyuan (Beijing) Wind Power Engineer Teehnology Co. Ltd Beijing 100034 P. R. China Qingdao Campus of Naval Aeronautical Academy Qingdao 266041 P. R. China

The configurations of dragonfly wings, including the corrugations of the chordwise cross-section, the microstructure of the longitudinal veins and membrane, were comprehensively investigated using the Environmental Scanning Electron Microscopy （ESEM）. Based on the experimental results reported previously, the multi-scale and multi-dimensional models with different structural features of dragonfly wing were created, and the biological dynamic behaviors of wing models were discussed through the Finite Element Method （FEM）. The results demonstrate that the effects of different structural features on dynamic behaviors of dragonfly wing such as natural frequency/modal, bending/torsional deformation, reaction force/torque are very significant. The corrugations of dragonfly wing along the chordwise can observably improve the flapping frequency because of the greater structural stiffness of wings. In updated model, the novel sandwich microstrueture of the longitudinal veins re- markably improves the torsional deformation of dragonfly wing while it has a little effect on the flapping frequency and bending deformation. These integrated structural features can adjust the deformation of wing oneself, therefore the flow field around the wings can be controlled adaptively. The fact is that the flights of dragonfly wing with sandwich microstructure of longitudinal veins are more efficient and intelligent.

关键词： self-adaptivity biomechanics dynamic behavior micromechanics multiscale

Energy and exergy analyses and optimizations for two-stage TEC driven by two-stage TEG with Thomson effect

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Science China(Technological Sciences) 2024年第4期67卷 1077-1093页

作者： chen LinGen GE YanLin FENG HuiJun ren TingTing Institute of Thermal Science and Power Engineering Wuhan Institute of TechnologyWuhan 430205China Hubei Provincial Engineering Technology Research Center of Green Chemical Equipment Wuhan 430205China School of Mechanical&Electrical Engineering Wuhan Institute of TechnologyWuhan 430205China

Based on the non-equilibrium thermodynamics and energy and exergy analyses,a thermodynamic model of two-stage thermoelectric(TE)cooler(TTEC)driven by two-stage TE generator(TTEG)(TTEG-TTEC)combined TE device is established with involving Thomson effect by fitting method of variable physical parameters of TE *** total number of TE elements as constraint,influences of number distributions of TE elements on three device performance indictors,that is,cooling load,maximum COP and maximum exergetic efficiency,are *** number distributions of TE elements are optimized with three maximum performance indictors as the objectives,*** of hot-junction temperature of TTEG and coldjunction temperature of TTEC on optimization results are analyzed,and difference between optimization results corresponding to three performance indicators are *** performance intervals and optimal variable intervals are *** of Thomson effect on three general performance indicators,three optimal performance indicators and optimal variables are comparatively *** effect reduces three general performance indicators and three optimal performance indicators of *** hot-and cold-junction temperatures of TTEG and TTEC are 450,305,325 and 295 K,respectively,Thomson effect reduced maximum cooling load,maximum COP and maximum exergetic efficiency from 9.528 W,9.043×10^(-2)and2.552%to 6.651 W,6.286×10^(-2)and 1.752%,respectively.

关键词： non-equilibrium thermodynamics cooling load COP exergetic efficiency combined thermoelectric device performance optimization

Preparation and characterization of a lipoid adsorption material and its atrazine removal performance

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Journal of Environmental Sciences 2011年第8期23卷 1293-1298页

作者： Zhiqiang chen Qinxue Wen Jiaxiang Lian Nanqi ren State Key Laboratory of Urban Water Resource and Environment Harbin Institute of Technology Harbin 150090 China. National Engineering Research Center of Urban Water Resources Harbin Institute of Technology Harbin 150090 China

A novel adsorbent named lipold adsorption material （LAM）, with a hydrophoblc nucleolus （trlolem） and a hydrophlllc membrane structure （polyamide）, was synthesized to remove hydrophobic organic chemicals （HOCs） from solution. Triolein, a type of lipoid, was entrapped by the polyamide membrane through an interfacial polymerization reaction. The method of preparation and the structure of the LAM were investigated and subsequent experiments were conducted to determine the characteristics of atrazine （a type of HOC） removal from wastewater using LAM as the adsorbent. The results showed that LAM had a regular structure compared with the prepolymer, where compact particles were linked with each other and openings were present in the structure of the LAM in which the fat drops formed from triolein were entrapped. In contrast to the atrazine adsorption behavior of powdered activated carbon （PAC）, LAM showed a persistent adsorption capacity for atrazine when initial concentrations of 0.57, 1.12, 8.31 and 19.01 mg/L were present, and the equilibrium time was 12 hr. Using an 8 mg/L initial concentration of atrazine as an indicator of HOCs in aqueous solution, experiments on the adsorption capacity of the LAM showed 69.3% removal within 6-12 hr contact time, which was close to the 75.5% removal of atrazine by PAC. Results indicated that LAM has two atrazine removal mechanisms, namely the bioaccumulation of atrazine by the nucleous material and physical adsorption to the LAM membrane. Bioaccumulation was the main removal mechanism.

关键词： lipoid adsorption material atrazine powdered activated carbon

Vinyl Groups Containing Tetraphenylethylene Derivatives as Fluorescent Probes Specific for Palladium and the Quenching Mechanism

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Chinese Journal of Chemistry 2021年第6期39卷 1599-1605页

作者： Xiaoqing Liu Yuxuan Shang Zhong-ren chen Shenzhen Grubbs Institute and Department of Chemistry Southern University of Science and TechnologyShenzhenGuangdong 518005China Guangdong Provincial Key Laboratory of Catalysis Southern University of Science and TechnologyShenzhenGuangdong 518055China

We previously reported that a series of tetraphenylethylene(TPE)-containing all-hydrocarbon conjugated polymers exhibited a specific fluorescence quenching by palladium ions(Pd^(2+)).To understand the quenching mechanism,herein we investigate the quenching behaviors of three TPE derivatives in the presence of Pd^(2+).Each TPE derivative,consisting of TPE unit and terminal vinyl groups,shows an aggregation-induced emission(AIE)and its fluorescence turns off specifically to Pd^(2+).The sensitivity is enhanced with increasing numbers of vinyl groups in the *** time-resolved fluorescence measurement,a dynamic quenching is observed where the fluorescence lifetime is reduced with Pd^(2+).Specifically,the quenching occurs via the electron transfer in the excited states,as suggested by the disappearance of the stimulated emission band in transient absorption spectra.A theoretical calculation on the excited states identifies intermolecular electron transfer from TPE derivatives to Pd,especially for electron-rich TPE *** mechanism can be general for the design of novel AIE active chemosensors.

关键词： Aggregation-induced emission Fluorescent probes Palladium detection Electron transfer Time-resolved spectroscopy

L log L criterion for a class of multitype superdiffusions with non-local branching mechanisms

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Science China Mathematics 2019年第8期62卷 1439-1462页

作者： Zhen-Qing chen Yan-Xia ren renming Song Department of Mathematics University of Washington Seattle WA 98195 USA LMAM School of Mathematical Sciences & Center for Statistical SciencePeking University Beijing 100871 China Department of Mathematics University of Illinois Urbana IL 61801 USA

In this paper, we provide a pathwise spine decomposition for multitype superdiffusions with nonlocal branching mechanisms under a martingale change of measure. As an application of this decomposition,we obtain a necessary and sufficient condition(called the L log L criterion) for the limit of the fundamental martingale to be non-degenerate. This result complements the related results obtained in Kyprianou et al.(2012),Kyprianou and Murillo-Salas(2013) and Liu et al.(2009) for superprocesses with purely local branching mechanisms and in Kyprianou and Palau(2018) for super Markov chains.

关键词： multitype superdiffusion non-local branching mechanism switched diffusion spine decomposition martingale

Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle Reaches of the Heihe River Basin, Northwest China

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Agricultural Sciences in China 2006年第2期5卷 130-140页

作者： JI Xi-bin KANG er-si chen ren-sheng ZHAO Wen-zhi XlAO Sheng-chun JIN Bo-wen Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 P.R.China Linze Inland River Basin Comprehensive Research Station Chinese Ecosystem Network Research Linze 734200 P.R.China

Based on the data for meteorology, hydrology, soil, planting, vegetation, and socio-economic development of the irrigation region in the middle reaches of the Heihe River basin, Northwest China, the model of balance of water supply and demand in the region was established, and the security of water resource was assessed, from which the results that the effects of unified management of water resources in the Heihe River basin between Gansu Province and Inner Mongolia on regional hydrology are significant with a decrease in water supply diverted from Heihe River and an increase in groundwater extracted. In addition, it was found that the groundwater level has been steadily decreasing due to over pumping and decrease in recharges. In present year （2003）, the volume of potential groundwater in the irrigation districts is far small because of the groundwater overdraft; even in the particular regions, there is no availability of groundwater resources for use. By 2003, water supply is not sufficient to meet the water demand in the different irrigation districts, the sustainable development and utilization of water resources are not secured, and the water supply crisis occurs in Pingchuan irrigation district. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while maintaining or improving the abilities of the management and planning of water resources, determining of the reasonable percentage between water supply and groundwater utilization and water saving in agricultural irrigation are taken into account. If this does not occur, it is feared that the present performance of water development and planning may further aggravate the problem of scarcities of water resources and further damage the fragile ecological system.

关键词： middle reaches of Heihe River irrigation region water resources supply and demand balance evaluation of the security of water resources

Anti-disturbance control of hypersonic flight vehicles with input saturation using disturbance observer

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Science China(Information Sciences) 2015年第7期58卷 28-39页

作者： chen Mou ren BeiBei WU QinXian JIANG ChangSheng College of Automation Engineering Nanjing University of Aeronautics and Astronautics Department of Mechanical Engineering Texas Tech University

This paper proposes an anti-disturbance control scheme for the near space vehicle(NSV) based on terminal sliding mode(TSM) technique and disturbance observer method. To tackle the system uncertainty and the time-varying unknown external disturbance of the NSV, a disturbance observer based on TSM technique is designed which can render the disturbance estimate error convergent in finite time. Furthermore, an auxiliary design system is introduced to analyze the input saturation effect. Based on the developed disturbance observer and the auxiliary design system, an anti-disturbance attitude control scheme is developed for the NSV using the TSM technique to speed up the convergence of all signals in closed-loop system. For the closed-loop system,the stability is rigorously proved by using the Lyapunov method and we guarantee the finite time convergence of all closed-loop system signals in the presence of the integrated affection of the system uncertainty, the input saturation, and the unknown external disturbance. Simulation study results are given to show the effectiveness of the developed TSM anti-disturbance attitude control scheme using the disturbance observer and the auxiliary system for the NSV.

关键词： near space vehicles anti-disturbance control sliding mode control input saturation disturbance observer

Bulking sludge for PHA production:Energy saving and comparative storage capacity with well-settled sludge

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Journal of Environmental Sciences 2012年第10期24卷 1744-1752页

作者： Qinxue Wen Zhiqiang chen Changyong Wang Nanqi ren State Key Laboratory of Urban Water Resource and Environment Harbin Institute of TechnologyHarbin 150090China

Two acetate-fed sequencing batch reactors （SBR） were operated under an aerobic dynamic feeding （ADF） model （SBR#2） and with anaerobic phase before aerobic phase （SBR#1） to select mixed cultures with a high polyhydroxyalkanoates （PHA） storage response. Although kinetic selection based on storage response should bring about a predominance of floc-formers, a bulking sludge with storage response comparable to well-settled sludge was steadily established. An anaerobic phase was introduced before the aerobic phase in the ADF model to improve the sludge settleability （SBR #1）, however, due to the consequent increased feast/famine ratio, the performance of SBR #1, in terms of both the maximum PHB （polyhydroxybutyrate） cell content and APHB, was lower than that of SBR #2. SBR #2 gradually reached a steady state while SBR #1 failed suddenly after 50 days of operation. The maximum specific substrate uptake rate and storage rate for the selected bulking sludge were 0.4 Cmol Ae/（Cmol ***） and 0.18 Cmol Ac/（Cmol ***）, respectively, resulting a yield of 0.45 Cmol PHB/（Cmol Ae） in SBR #2 in the culture enrichment phase. A maximum PHB content of 53% of total suspended solids and PHB storage rate of 1.36 Cmol Ac/（Cmol ***） was achieved at 10.2 hr in batch accumulation tests under nitrogen starvation. The results indicated that it was feasible to utilize filamentous bacteria to accumulate PHA with a rate comparable to well-settled sludge, Furthermore, the lower dissolved oxygen demand of filamentous bacteria would save energy required for aeration in the culture enrichment stage.

关键词： polyhydroxyalkanoates mixed cultures aerobic dynamic feeding bulking sludge feast/famine ratio