带裙房高层建筑地震反应控制振动台试验研究   总被引：1，自引：1，他引：0  

瞿伟廉  陈静  徐幼麟  C.L.Ng 《地震工程与工程振动》2004,24(3):64-72

2002年9月在香港理工大学成功地进行了带裙房高层建筑地震反应控制试验研究。设计和制作的结构模型是带3层裙房的12层高楼剪切模型,在裙房顶层与主楼之间安装单MR阻尼器形成MR阻尼器耦联结构模型。MR阻尼器采用美国LORD公司摩擦型MR阻尼器,并且选用其配套产品计算机电流控制器对其进行控制,控制系统采用德国dSPACE公司实时控制系统。对独立主楼、独立裙房和原结构模型的动力特性进行了辨识;对结构模型进行了El Centro地震动作用下的地震反应振动台试验;以作者提出的MR阻尼器半主动逻辑控制算法,对MR阻尼器耦联的结构模型进行了地震反应振动台试验。试验结果表明：用MR阻尼器耦联主楼与裙房,采用半主动逻辑控制方法进行控制,能有效抑制主楼的鞭梢效应并使主楼和裙房的地震反应减小。  相似文献   

Erratum to: Velocity attenuation of debris flows and a new momentum-based load model for rigid barriers     

R. C. H. Koo  J. S. H. Kwan  C. W. W. Ng  C. Lam  C. E. Choi  D. Song  W. K. Pun 《Landslides》2017,14(2):631-631

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Interaction between dry granular flow and deflectors   总被引：2，自引：0，他引：2  

C. W. W. Ng  C. E. Choi  G. R. Goodwin  W. W. Cheung 《Landslides》2017,14(4):1375-1387

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The conductivity of dense molecular gas     

Mark Wardle  Cindy Ng 《Monthly notices of the Royal Astronomical Society》1999,303(2):239-246

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On the Galactic disc age–metallicity relation     

Giovanni Carraro  Yuen Keong Ng  & Laura Portinari 《Monthly notices of the Royal Astronomical Society》1998,296(4):1045-1056

A comparison is made between the age–metallicity relations obtained from four different types of studies: F and G stars in the solar neighbourhood, analysis of open clusters, galactic structure studies with the stellar population synthesis technique and chemical evolution models. Metallicities of open clusters are corrected for the effects of the radial gradient, which we find to be −0.09 dex kpc⁻¹ and most likely constant in time. We do not correct for the vertical gradient, because its existence and value are not firmly established.
Stars and clusters trace a similar age–metallicity relation, showing an excess of rather metal-rich objects in the age range 5–9 Gyr. Galactic structure studies tend to give a more metal-poor relation than chemical evolution models. Neither relation explains the presence of old, relatively metal-rich stars and clusters. This might be caused by uncertainties in the ages of the local stars, or pre-enrichment of the disc with material from the bulge, possibly as a result of a merger event in the early phases of the formation of our Galaxy.  相似文献   

A general algorithm for the solution of Kepler's equation for elliptic orbits     

Edward W. Ng 《Celestial Mechanics and Dynamical Astronomy》1979,20(3):243-249

An efficient algorithm is presented for the solution of Kepler's equationf(E)=E–M–e sinE=0, wheree is the eccentricity,M the mean anomaly andE the eccentric anomaly. This algorithm is based on simple initial approximations that are cubics inM, and an iterative scheme that is a slight generalization of the Newton-Raphson method. Extensive testing of this algorithm has been performed on the UNIVAC 1108 computer. Solutions for 20 000 pairs of values ofe andM show that for single precision (10^–8) 42.0% of the cases require one iteration, 57.8% two and 0.2% three. For double precision (10^–18) one additional iteration is required. Single- and double-precision FORTRAN subroutines are available from the author.  相似文献   

Geochemistry of Lake Sediments as a Record of Environmental Change in a High Arctic Watershed     

Sai L. Ng  Roger H. King 《Chemie der Erde / Geochemistry》2004,64(3):257-275

A 1.93 m long sediment core was obtained from Fish Lake, Truelove Lowland, Devon Island, Nunavut, Canada. Multivariate statistical techniques using a wide range of chemical variables successfully reconstructed the late Holocene history of the Fish Lake watershed. Factor analysis identified six geomorphic mechanisms controlling the formation of sediments. Cluster analysis produced a grouping of core segments and discriminant analysis confirmed that 100% of the samples were correctly classified. The results indicated that the environmental history of the Fish Lake watershed in the past 6500 years can be divided into five phases. These are 6500-5700 years BP, 5700-1700 years BP, 1700-1000 years BP, 1000-600 years BP and 600 years BP to the present. In the Fish Lake watershed, during its time as a terrestrial system, the interactions of erosion, weathering, leaching, soil development, vegetation succession and climatic change have shaped the surrounding landscape as well as determined the evolution of the lake.  相似文献   

Prevalence of microplastics in Singapore's coastal marine environment     

Ng KL  Obbard JP 《Marine pollution bulletin》2006,52(7):761-767

Microplastics have been recently identified as marine pollutants of significant concern due to their persistence, ubiquity and potential to act as vectors for the transfer and exposure of persistent organic pollutants to marine organisms. This study documents, for the first time, the presence and abundance of microplastics (>1.6 microm) in Singapore's coastal environment. An optimized sampling protocol for the collection and analysis of microplastics was developed, and beach sediments and seawater (surface microlayer and subsurface layer) samples were collected from nine different locations around the coastline. Low density microplastics were separated from sediments by flotation and polymer types were identified using Fourier transform infrared (FTIR) spectrometry. Synthetic polymer microplastics identified in beach sediments included polyethylene, polypropylene, polystyrene, nylon, polyvinyl alcohol and acrylonitrile butadiene styrene. Microplastics were detected in samples from four out of seven beach environments, with the greatest quantity found in sediments from two popular beaches in the eastern part of Singapore. Polyethylene, polypropylene and polystyrene microplastics were also found in the surface microlayer (50-60 microm) and subsurface layer (1m) of coastal waters. The presence of microplastics in sediments and seawater is likely due to on-going waste disposal practices from industries and recreational activities, and discharge from shipping.  相似文献   

Potential Hydrodynamic Performance Enhancement of Hydrokinetic Turbine with Hydrophobic Coatings     

Chen  Long  Ng  Kai-Wern 《中国海洋工程》2021,35(6):924-932

China Ocean Engineering - Hydrokinetic energy is a promising technology to harness predictable renewable energy from free-flowing water, tides and ocean currents. Many studies have been conducted...  相似文献   

On the Study of Pile Driving Formula Based on Blow Counts     

M.?M.?AliEmail author  M.?R.?Selamat  S.?S.?Yii  W.?K.?Ng 《Geotechnical and Geological Engineering》2011,29(3):351-361

Accuracy of predicting pile capacities by pile driving formulas have been investigated. Five test piles were driven up to a depth of about 9 m of clay deposit and the penetrations due to final blows were recorded. The pile bearing capacity of each pile was predicted using 6 different pile driving formulas and the predicted pile capacity was compared with measured pile capacity from the pull up tests. Hiley formula, Modified Engineering News Record (ENR) formula, Janbu formula, Dutch formula, Danish formula, and Gates formula were used. The performance and accuracy of each formula was evaluated and the correlation coefficient of each pile driving formula was determined for a more accurate pile capacity prediction. Methods used to evaluate the performance of each formula were; (1) the best fit line for Q _p versus Q _m (2) cumulative probability for Q _p/Q _m and (3) the arithmetic mean and standard deviation for Q _p/Q _m. From the study, it was found that using Dutch formula provided the most accurate pile capacity estimate compared to the other formulas with an average of 7% deviation from value obtained from the field pull up test. It was followed by the Danish formula, Janbu formula, Hiley formula, Modified ENR formula, and Gates formula. The ability to predict the accuracy of estimating pile capacity using an appropriate method is very important and valuable to contractors, developers, geotechnical engineers, and manufacturers.  相似文献