检索结果-南通市图书馆

Implementation of rotational resistance models＇ A critical appraisal

Particuology 2017年第5期15卷 14-23页

作者： Xin Huang kevin J. Hanley Catherine O'Sullivan Chung-Yee kwok a Department of Geotechnical Engineering Tongji University Shanghai 200092 China key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji University Shanghai 200092 China Institute for Infrastructure and Environment School of Engineering The University of Edinburgh Edinburgh EH9 3JL United Kingdom Skempton Building Department of Civil and Environmental Engineering Imperial College London London SW72AZ United Kingdom Haking wong Building Department of Civil and Environmental Engineering The University ofHong Kong Hong Kong China

Contact models that simulate rotational resistance at particle contacts have been proposed as a means to capture the effect of shape in DEM simulations. This contribution critically explores some key issues related to the implementation of rotational resistance models; these include the need for physically meaningful model parameters, the impact of the model on the overall numerical stability/critical time increment for the DEM model, model validation, and the assessment of model performance relative to real physical materials. The discussion is centred around a rotational resistance model that captures the resistance provided by interlocking asperities on the particle surface. An expression for the maximum permissible integration time step to ensure numerical stability is derived for DEM simulations when rotational resistance is incorporated. Analytical solutions for some single-contact scenarios are derived for model validation. The ability of this type of model to provide additional fundamental insight into granular material behaviour is demonstrated using particle-scale analysis of triaxial compression simulations to examine the roles that contact rollin~ and slidin~ have on the stability of stron：~ force chains.

关键词： Granular mediaParticle shapeDiscrete element methodRollingTwistingRotational resistance

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

kerr effect and kerr constant enhancement in vertically aligned deformed helix ferroelectric liquid crystals

引用

Chinese Physics B 2016年第9期25卷 9-12页

作者： Liangyu Shi Abhishek kumar Srivastava Vladimir G Chigrinov Hoi-Sing kwok State key Laboratory on Advanced Displays and Optoelectronics Technologies Hong Kong University of Science and Technology

In this article,we review recently achieved kerr effect progress in novel liquid crystal（LC） material：vertically aligned deformed helix ferroelectric liquid crystal（VADHFLC）.with an increasing applied electric field,the induced inplane birefringence of LCs shows quadratic *** theoretical calculations and experimental details are *** an enhanced kerr constant to 130 nm/V2,this VADHFLC cell can achieve a 2π modulation by a small efficient electric field with a fast response around 100 μs and thus can be employed in both display and photonics devices.

关键词： kerr effect deformed helix ferroelectric liquid crystal phase modulation of light

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Analysis of non-symmetrical flapping airfoils

引用

Acta Mechanica Sinica 2009年第4期25卷 433-450页

作者： w.B.Tay k.B.Lim Department of Mechanical Engineering National University of Singapore

Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables and shape of the airfoil have a profound effect on the lift, thrust, and efficiency. By using non- symmetrical airfoils, average lift coefficient as high as 2.23 can be obtained. The average thrust coefficient and efficiency also reach high values of 2.53 and 0.61, respectively. The lift production is highly dependent on the airfoil＇s shape while thrust production is influenced more heavily by the variables. Efficiency falls somewhere in between. Two-factor interac- tions are found to exist among the variables. This shows that it is not sufficient to analyze each variable individually. Vorticity diagrams are analyzed to explain the results obtained. Overall, the S1020 airfoil is able to provide relatively good efficiency and at the same time generate high thrust and lift force. These results aid in the design of a better ornithopter＇s wing.

关键词： Flapping Non-symmetrical Design ofexperiments Ornithopter Airfoil

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Industrial water treatment and industrial marine outfalls： Achieving the right balance

引用

Frontiers of Chemical Science and Engineering 2016年第4期10卷 472-479页

作者： Adrian w. k. Law Chunyan Tang Environmental Process Modelling Centre Nanyang Environment and Water Research Institute Nanyang Technological University Singapore 637141 Singapore School of Civil and Environmental Engineering Nanyang Technological University Singapore 639798 Singapore

Industrial water treatment and industrial marine outfalls both function together to reduce the pollutant concentrations in the effluent and mitigate the potential impact on the environment. The former uses environ- mental treatment technology with energy and material cost considerations, while the latter utilizes the natural assimilation potential of the coastal water environment achievable at the outfall location. Because of their synergistic nature, marine outfalls are now commonly used for the disposal of partially treated domestic and industrial effluents in many coastal cities around the world, with many successful examples of low and acceptable risks to the environment. The objective of this paper is to review their balance from both environmental and economic considerations. we also discuss the end-of-the-pipe and mixing zone approaches for industrial effluents, and give some recommendations particularly for developing coun- tries. Finally, we emphasize that a compulsory and vigorous monitoring program is essential regardless of how the balance is achieved.

关键词： industrial effluent treatment industrial marineoutfalls economic and environmental considerations

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A novel respirometer for biological toxicity tests

引用

Journal of Environmental Sciences 1997年第3期9卷 92-98页

作者： Zhang Minquan Chen Huanqin wong kwok-Yin Chemical Engineering Research Institute South China University of TechnologyGuangzhou 510641 China Department of Applied Biobgy and Chemical Technology The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong

A respirometer has been developed for microbial toxicity tests. The respirometer is based on luminescence quenching by molecular oxygen. The oxygen sensing film consists of luminescent ruthenium complex adsorbed on amorphous fumed silica and immobilized inside silicone rubber. The luminescence intensity depends on the oxygen concentration of sample in contact with sensing film. The inhibition effect of heavy metals on the respiration rate of microorganisms can be evaluated by monitoring the luminescence intensity of the sensing film. The toxicity of Cu 2+ , Zn 2+ , Ni 2+ , Cr 3+ , Pb 2+ and Hg 2+ on activated sludge was tested using the respirometer. The results indicated that the proposed method was sensitive to the heavy metals tested in this experiment. It was feasible to use the respirometer for microbial toxicity tests.

关键词： luminescence quenching respirometer toxicity test heavy metal.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Numerical analysis of the s1020 airfoils in tandem under different flapping configurations

引用

Acta Mechanica Sinica 2010年第2期26卷 191-207页

作者： k.B.Lim w.B.Tay Department of Mechanical Engineering National University of Singapore21 Lower Kent Ridge RoadSingapore 119077Singapore

The objective of this project is to improve the performance of the efficiency, thrust and lift of flapping wings in tandem arrangement. This research investigates the effect of the arrangement of the airfoils in tandem on the performance of the airfoils by varying the phase difference and distance between the airfoils. Three flapping configurations from an earlier phase of a research which gives high efficiency, thrust and lift are used in the tandem simulation. It is found all the different flapping configurations show improvement in the efficiency, thrust or lift when the distance between the two airfoils and the phase angle between the heaving positions of the two airfoils are optimal. The average thrust coefficient of the tandem arrangement managed to attain more than twice that of the single one （4.84 vs. 2.05）. On the other hand, the average lift coefficient of the tandem arrangement also increased to 4.59, as compared to the original single airfoil value of 3.04. All these results obtained will aid in the design of a better ornithopter with tandem wing arrangement.

关键词： Tandem Flapping· Airfoils Ornithopter·Immersed boundary

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Statistical extremes and peak factors in wind-induced vibration of tall buildings

引用

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第1期13卷 18-32页

作者： Ming-feng HUANG Chun-man CHAN wen-juan LOU kenny Chung-Siu kwok Institute of Structural Engineering Zhejiang University Hangzhou 310058 China Department of Civil and Environmental Engineering Hong Kong University of Science and Technology Hong Kong School of Engineering University of Western Sydney NSW Australia

In the structural design of tall buildings, peak factors have been widely used to predict mean extreme responses of tall buildings under wind excitations. Vanmarcke＇s peak factor is directly related to an explicit measure of structural reliability against a Gaussian response process. we review the use of this factor for time-variant reliability design by comparing it to the conven- tional Davenport＇s peak factor. Based on the asymptotic theory of statistical extremes, a new closed-form peak factor, the so-called Gamma peak factor, can be obtained for a non-Gaussian resultant response characterized by a Rayleigh distribution process. Using the Gamma peak factor, a combined peak factor method was developed for predicting the expected maximum resultant responses of a building undergoing lateral-torsional vibration. The effects of the standard deviation ratio of two sway components and the inter-component correlation on the evaluation of peak resultant response were also investigated. Utilizing wind tunnel data derived from synchronous multi-pressure measurements, we carried out a wind-induced time history response analysis of the Common- wealth Advisory Aeronautical Research Council （CAARC） standard tall building to validate the applicability of the Gamma peak factor to the prediction of the peak resultant acceleration. Results from the building example indicated that the use of the Gamma peak factor enables accurate predictions to be made of the mean extreme resultant acceleration responses for dynamic service- ability performance design of modem tall buildings.

关键词： Level-crossing rate (LCR) wind-induced vibration Mean extreme response Combined resultant process Peakfactor method

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Value distribution theory and the research of Yang Lo

引用

Science China Mathematics 2010年第3期53卷 513-522页

作者： HAYMAN w. k. Department of Mathematics Imperial College London South Kensington Campus

Value distribution theory is concerned with the position and frequency of solutions of the equation f(z) = a. Here f may be entire, i.e. an everywhere convergent power series or meromorphic, i.e. the ratio of two such series, or a function in some other domains, such as an angle or a disk. Yang Lo’s significant contributions to this area will be highlighted. Some of his important contributions to normal families will also be described.

关键词： meromorphic function value distribution deficient value angular distribution

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Consumers can learn and can forget-Modeling the dynamic decision procedure when watching TV

引用

Journal of Management Science and Engineering 2020年第2期5卷 87-104页

作者： Lianlian Song Geoffrey kwok Fai Tso College of Economics and Management Nanjing University of Aeronautics and AstronauticsJiangjun Road 29210000NanjingChina Department of Management Sciences City University of Hong Kong83 Tat Chee AvenueKowloonHong KongChina

Facing the challenge of attracting consumers and winning market share under the pro-liferation of TV stations and channels,the traditional TV stations often make some mar-keting ***,how to evaluate the effectiveness of different strategies and select the best one is a key *** study proposes to resolve this *** develop an innovative structural model to simulate the dynamic choices consumers make under two interactive behaviors:learning and *** behavior refers to updating programme quality assessment by using experience,while forgetting behavior prevents the use of previous *** Bayesian rules are employed to model learning behavior,and they are extended by incorporating an exponential decay function to mea-sure the effect of forgetting *** structural model is tested and validated by using Hong kong television viewing *** empirical results show that when modeling consumer choice decisions,considering learning and forgetting behavior significantly improves the performance of the model in regard to rating prediction and marketing strategy *** cases are simulated to show how the model is used to evaluate marketing *** implications are then discussed to guide the decision-making of traditional TV broadcasters and advertisers.

关键词： Marketing strategy evaluation Dynamic learning Forgetting Bayesian updating theory

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Monitoring interannual dynamics of desertification in Minqin County,China,using dense Landsat time series

引用

International Journal of Digital Earth 2020年第8期13卷 886-898页

作者： Xiaolin Zhu kwok Huen Leung wing Sze Li Lek kin Cheung The Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityHong KongPeople’s Republic of China The Hong kong Polytechnic University Shenzhen Research Institute ShenzhenPeople’s Republic of China

Minqin County in northwestern China is highly affected by *** have been initiated in recent decades to combat desertification in *** assess the effectiveness of these campaigns,this study used a dense Landsat time series from 1987 to 2017 to investigate the interannual dynamics of vegetation coverage and greenness over the past 31 ***,this study applied an advanced technology to reconstruct a high-quality Landsat annual time ***,one image in the vegetation-peak season was selected as the base image in each year,and then problematic pixels were interpolated by the neighborhood similar pixel interpolator using ancillary images in the same ***,the land cover map and the enhanced vegetation index(EVI)were derived from all reconstructed ***,the change of vegetation coverage and EVI values over the 31 years were *** results show that the total vegetation coverage and greenness increased during the 31 *** this change trend to other factors suggests that vegetation in Minqin County is highly affected by agriculture and groundwater supply rather than by *** mitigate desertification in a sustainable way,agriculture should be well managed to avoid overconsumption of natural resources such as underground water.

关键词： Minqin County desertification agriculture Landsat time series vegetation cover

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：