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Void fraction for random loose packing of the cylindrical particles considering filling rate,material and shape

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Particuology 2022年第4期20卷 35-46页

作者： Chengquan Zhang Jun Gao Yukun Xu Yunfei Xia Xiaobin Wei Xing Su lingjie zeng School of Mechanical Engineering Tongji UniversityShanghaiChina

Particle packing is widely applied in organic pollutant adsorption,catalytic reaction.biomass combustion,nuclear cooling,and other scenarios.Due to the complexity of the shape,the studies on the void fraction of the cylindrical particles are not as thorough as the spherical particles.This study investigated the influence of the flling rate,material properties and sphericity on the void fraction of cylinders through experiments and simulation.DEM(discrete element method)was validated by the internal structures of the packing obtained by CT(computed tomography).Based on the logarithmic correlation between the void fraction and flling rate,an ingenious framework for predicting the void fraction of cylindrical particles was presented with two intermediate coefficients.By correlating the coefficients with the material property and sphericity,a novel void-fraction prediction model was established with R-squared of 0.996.The mechanism of void fraction under random loose packing for cylinders was eventually found in this study.

关键词： Void fraction Random loose packing Cylindrical particles Prediction model DEM

Impact of different human walking patterns on flow and contaminant dispersion in residential kitchens:Dynamic simulation study

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Building Simulation 2022年第6期15卷 1051-1066页

作者： Lipeng Lv Yuhang Wu Changsheng Cao lingjie zeng Jun Gao Wuhao Xie Jing Zhang Institute of HVAC Engineering School of Mechanical EngineeringTongji UniversityShanghai200092China College of Environmental Science and Engineering Tongji UniversityShanghai200092China

The effects of different human walking patterns on contaminant dispersion in residential kitchens were investigated through computational fluid dynamics simulation with the dynamic mesh method.A tracer gas experiment was performed to verify the feasibility and accuracy of the simulation method.Flow characteristics induced by human walking were minutely described,and the transient capture efficiency of the range hood was adopted to assess the impact of human walking quantitatively.Human walking parallel to a counter,human walking parallel to a counter manned by another human,and human walking toward a counter were studied.Results showed that the mutual effect of the wake and thermal plume caused contaminant dispersion and decreased the performance of the range hood as the human subject walked beside the counter.Even a standing person operated ahead the counter,the wake would affect the thermal plume in a certain extent.The decrement of capture efficiency approached 0.5 in the most unfavorable situation.Moreover,the coaction of the positive/negative pressure zone and impinging air jet drew the thermal plume to the human body.The fluctuation of capture efficiency in this condition was moderate relative to that for the human walking pattern beside the counter.This research could provide a comprehensive overview of different human walking patterns and their impact on residential kitchens and thereby facilitate the maintenance of kitchen air quality.

关键词： human walking overset mesh method dynamic simulation flow characteristics residential kitchen

Pressure and flowrate distribution in central exhaust shaft with multiple randomly operating range hoods

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Building Simulation 2022年第1期15卷 149-165页

作者： lingjie zeng Leqi Tong Jun Gao Bowen Du Chengquan Zhang Lipeng Lv Changsheng Cao Xihui Ding College of Environmental Science and Engineering Tongji UniversityShanghai 200092China School of Mechanical Engineering Tongji UniversityShanghai 200092China Department of civil and mineral engineering University of TorontoTorontoCanada

Central flues are now commonly adopted in high-rise residential buildings in China for cooking oil fumes(COF)exhaust.Range hoods of all floors are connected to the central shaft,where oil fumes were gathered and exhausted through the outlet at the building roof.As households may cook and use their range hood at random periods,there is great uncertainty of the amount of COF being exhausted.In addition,users can often adjust the exhaust rate of the range hood according to their needs.As a result,thousands of possible operating conditions consisting of distinct combinations of on/off conditions and fan speed occur randomly in the central COF exhaust system,causing the exhaust performance to vary considerably from condition to condition.This work developed a mathematical model for characterizing the operation of the central COF exhaust system in a high-rise residential building as well as its iterative solving method.Full-scale tests coupled with CFD simulation referring to a real 30-floor building were conducted to validate the proposed model.The results show that the model agreed well with the CFD and experimental data under various system operating conditions.Moreover,the Monte-Carlo method was introduced to simulate the random operating characteristics of the system,and a hundred thousand cases corresponding to distinct system operating conditions were sampled and statistically analyzed.

关键词： central exhaust shaft building ventilation range hood high-rise residential building randomly operating Monte-Carlo simulation

中国市域科技创新与实体经济融合水平分析及其时空特征

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经济地理 2024年第4期44卷 110-120页

作者：曾鹏尚玲杰广西民族大学民族学与社会学学院广西南宁530006 广西民族大学经济学院广西南宁530006

文章基于熵值法测算了2006—2020年中国284个地级及以上城市科技创新与实体经济融合水平,并对城市科技创新与实体经济融合水平的时空演变、区域差异及来源进行实证分析。研究发现:(1)全国及四大区域科技创新与实体经济融合水平稳步提升... 详细信息

文章基于熵值法测算了2006—2020年中国284个地级及以上城市科技创新与实体经济融合水平,并对城市科技创新与实体经济融合水平的时空演变、区域差异及来源进行实证分析。研究发现:(1)全国及四大区域科技创新与实体经济融合水平稳步提升。(2)全国及四大区域科技创新与实体经济融合空间极化趋势明显,总体呈现“东高—西低”的空间格局。(3)区域间差异是中国科技创新与实体经济融合差异的主要来源。全国总体差异变化不大,东部地区区域内差异最大,东部—西部区域间差异最大。

关键词：科技创新实体经济区域差异胡焕庸线

Influence of materials’hygric properties on the hygrothermal performance of internal thermal insulation composite systems

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Energy and Built Environment

Energy and Built Environment 2023年第3期4卷 315-327页

作者： lingjie zeng Yuqing Chen Changsheng Cao Lipeng Lv Jun Gao Jingguang Li Chongyang Zhang School of Mechanical Engineering Tongji UniversityShanghai 200092China Shanghai Research Institute of Building Sciences(Group)Co.Ltd. ShanghaiChina

Internal thermal insulation composite system(ITICS)can be an important measure for the energy-saving retrofitting of buildings.However,ITICS may cause harmful effects on the hygrothermal performance of building envelopes.This work investigated the influence of the materials’hygric properties on the hygrothermal perfor-mance of a typical ITICS in different climate conditions in China.Two base wall materials,the traditional concrete and a new type aerated concrete,were tested and compared for their hygric properties firstly.The influence of the hygroscopicity of exterior plasters,the permeability of insulation materials and the climate conditions were then analyzed with WUFI simulations.The hygrothermal performance was evaluated with consideration of the total water content(TWC)of the walls and the moisture flux strength,the relative humidity(RH)and the mould growth risk at the interface between the base wall and the insulation layer(B-I interface).The numerical analysis implies that the TWC of internal insulated walls depends mainly on the hygroscopicity of exterior plaster and the wind-driven rain intensity.The upper limits for the water absorption coefficient of exterior plasters used in Bei-jing,Shanghai and Fuzhou are 1e-9,1e-10,1e-10 m^(2)/s respectively.When such limits are guaranteed,a vapour tight system created by using insulation materials with a large vapour resistance factor or adding a vapour barrier can improve the hygrothermal performance of ITICS,especially for concrete walls in cold climate.

关键词： Internal thermal insulation composite systems Hygrothermal performance assessment Hygirc properties of building materials Different climate conditions

Localization and characterization of intermittent pollutant source in buildings with ventilation systems:Development and validation of an inverse model

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Building Simulation 2021年第3期14卷 841-855页

作者： lingjie zeng Jun Gao Lipeng Lv Bowen Du Yalei Zhang Ruiyan Zhang Wei Ye Xu Zhang College of Environmental Science and Engineering Tongji UniversityShanghai200092China School of Mechanical Engineering Tongji UniversityShanghai 200092China Department of Civil and Mineral Engineering University of TorontoTorontoCanada

Terrorist attacks through building ventilation systems are becoming an increasing concern.In case pollutants are intentionally released in a building with mechanical ventilation systems,it is critical to localize the source and characterize its releasing curve.Previous inverse modeling studies have adopted the adjoint probability method to identify the source location and used the Tikhonov regularization method to determine the source releasing profile,but the selection of the prediction model and determination of the regularization parameter remain challenging.These limitations can affect the identification accuracy and prolong the computational time required.To address the difficulties in solving the inverse problems,this work proposed a Markov-chain-oriented inverse approach to identify the temporal release rate and location of a pollutant source in buildings with ventilation systems and validated it in an experimental chamber.In the modified Markov chain,the source term was discrete by each time step,and the pollutant distribution was directly calculated with no iterations.The forward Markov chain was reversed to characterize the intermittently releasing profile by introducing the Tikhonov regularization method,while the regularized parameter was determined by an automatic iterative discrepancy method.The source location was further estimated by adopting the Bayes inference.With chamber experiments,the effectiveness of the proposed inverse model was validated,and the impact of the sensor performance,quantity and placement,as well as pollutant releasing curves on the identification accuracy of the source intensity was explicitly discussed.Results showed that the inverse model can identify the intermittent releasing rate efficiently and promptly,and the identification error for pollutant releasing curves with complex waveforms is about 20%.

关键词： intermittent source inverse identification Markov chain regularization parameter ventilation system

小果蔷薇不同采收时期叶和茎中主要活性成分的变化

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食品工业科技 2024年第2期45卷 220-226页

作者：周瑶瑶张晓元陈雄罗韶刚曾令杰广东药科大学中药学院广东广州510006 韶关市华工高新技术产业研究院广东韶关512027 华南理工大学工业技术研究总院广东广州510640

目的:探索一年中不同采收时期小果蔷薇叶和茎中总多糖、总有机酸、鞣花酸的含量变化情况,为其质量控制和适宜采收期的确定提供实验依据。方法:于2021年的2月至12月采集小果蔷薇的茎和叶的样品,每月采集1次。样品阴干后,分别采用紫外分... 详细信息

目的:探索一年中不同采收时期小果蔷薇叶和茎中总多糖、总有机酸、鞣花酸的含量变化情况,为其质量控制和适宜采收期的确定提供实验依据。方法:于2021年的2月至12月采集小果蔷薇的茎和叶的样品,每月采集1次。样品阴干后,分别采用紫外分光光度法测定其总多糖和总有机酸和含量,用高效液相色谱法测定其鞣花酸含量。同时采用聚类分析和主成分分析对不同采收时期的叶和茎进行综合评价。结果:叶和茎中总多糖、总有机酸、鞣花酸的含量在一年中呈现一定的波动趋势。叶中总多糖含量在7月(22.689mg·g^(-1))和8月(23.164mg·g^(-1))达到较高水平;总有机酸在2月(111.484mg·g^(-1))、6月(113.342mg·g^(-1))、8月(102.425 mg·g^(-1))含量最高;鞣花酸在4月(0.074 mg·g^(-1))、6月(0.077 mg·g^(-1))和8月(0.074 mg·g^(-1))含量最高。茎中总多糖含量在2月(15.650mg·g^(-1))达到较高水平;总有机酸在5月(171.123mg·g^(-1))、9月(178.960 mg·g^(-1))、2月(125.393 mg·g^(-1))含量最高;鞣花酸在2月(0.037 mg·g^(-1))、4月(0.038 mg·g^(-1))含量显著高于其他月份采收的样品。根据聚类分析将叶和茎各分为3类,与主成分分析基本一致。经主成分分析,叶和茎累计贡献率分别达到77.067%和82.970%。结果表明叶在8月采收和茎在2月采收的综合评价最高。结论:研究认为小果蔷薇叶和茎的最适采收时期分别为8月份和2月份。该研究结果可为小果蔷薇的采收及其质量评价等提供参考。

关键词：小果蔷薇总多糖总有机酸鞣花酸聚类分析主成分分析

Combining push-pull airflow and top draft hood for local exhaust of tyre vulcanization process

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能源与人工环境(英文)

能源与人工环境(英文) 2020年第3期1卷 296-306页

作者： Kai Liu Shengwei Yang lingjie zeng Jun Gao Yumei Hou Changsheng Cao Bo Shi Xiangjin Mo Qingyu Zhang Chun Hou School of Mechanical Engineering Tongji UniversityShanghai 200092China China chemical Guilin Engineering Co. Ltd.Guilin 541000China

This paper proposes a push-pull airflow combined with a top draft hood to conduct local exhaust in a rubber workshop.Field measurements are carried out to investigate the characteristics of the emission source,while numerical simulation is performed based on the measurement to test the capture efficiency and to further optimize various parameters including push velocity,hood height and exhaust air rate.Compared with the high-hanging hood,the low-hanging hood can effectively capture the pollutant generated by tyre with lower exhaust air rate.The capture efficiency of the low-hanging hood reaches 98.18%with exhaust air rate of 6000 m^(3)/h and push air velocity of 5m/s.The results indicates that the new ventilation appliance can effectively collect the pollutant at a relatively low exhaust rate.

关键词： Rubber vulcanization Push-pull ventilation Local exhaust hood Capture efficiency

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中国证券期货 2024年第2期 25-34,40页

作者：赵海涛曾树峰吴含英孟令捷任瑞云南省贵金属新材料控股集团股份有限公司昆明650106 渤海银行昆明分行昆明650100

金银期货具有“尖峰厚尾”、波动聚集、有偏和非对称等特征。文章通过构建ARMA(p,q)-GJR-SkT模型刻画金银期货的边缘分布,接着引入Markov状态转换的MRS-SJC-Copula模型考察上期所金银期货主力合约间的动态相关性及结构。结果表明,金银... 详细信息

金银期货具有“尖峰厚尾”、波动聚集、有偏和非对称等特征。文章通过构建ARMA(p,q)-GJR-SkT模型刻画金银期货的边缘分布,接着引入Markov状态转换的MRS-SJC-Copula模型考察上期所金银期货主力合约间的动态相关性及结构。结果表明,金银期货间存在有偏和非对称等特征,同时都具有负向“杠杆效应”,其相依结构是动态变化的,且持续存在高低两种不同状态的概率转换;利空消息对当期金银期货的冲击较大,且下跌带来的冲击要大于上涨产生的影响;动态联动性的内部结构显示金银期货收益率受过去信息的持续影响,同时各自的基差变化对动态相关性影响显著;突发事件的冲击会使金银期货的上下尾发生结构突变,引发风险传染。

关键词：金银期货 GJR-MRS-SJC-Copula模型动态联动性结构突变