Defense Science and Technology Agency

Singapore, Singapore

Defense Science and Technology Agency

Singapore, Singapore
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Lee H.P.,National University of Singapore | Wang F.,Defense Science and Technology Agency
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2010

Head trauma injury due to impact by a flying golf ball is one of the most severe possible injury accidents on the golf course. Numerical simulations based on the finite element method are presented to investigate head injury in children due to impact by a flying golf ball. The stress and energy flow patterns in a head model during the golf ball impact are computed for various combinations of striking speed, falling angle of the golf ball before impact, and impact location. It is found that a child is more prone to head injury due to golf ball impact on the frontal and side/temporal areas. The simulated results are found to conform to the clinical reports on children's head injuries from flying golf balls. © 2010 Taylor & Francis.

Ye F.,National University of Singapore | Yeo C.H.,National University of Singapore | Goh S.H.,National University of Singapore | Anand S.,Defense Science and Technology Agency | Soh T.B.,Defense Science and Technology Agency
Numerical Methods in Geotechnical Engineering - Proceedings of the 8th European Conference on Numerical Methods in Geotechnical Engineering, NUMGE 2014 | Year: 2014

The paper discusses the recent numerical progress in modeling an underground explosion event in saturated sand. It utilizes a fully coupled numerical approach implemented using a dual mesh concept based on Biot's u-U formulations. Using this approach, 3D finite element analyses of a buried detonation are carried out and wave propagations in both the pore fluid and soil skeleton are solved in the fully saturated medium. The numerical predictions obtained from the dual phase calculations with nonlinear material modeling are validated using centrifuge test results, analytical solutions and existing empirical correlations. The consistency among the different comparisons shows the capability of the dual phase coupling method in solving high-frequency extreme loading problems involving saturated soils. © 2014 Taylor & Francis Group, London.

Hwang B.-G.,National University of Singapore | Ng W.J.,Defense Science and Technology Agency
International Journal of Project Management | Year: 2013

A competent project manager is vital to project success. While many studies have examined competency of project managers, few have done so in the context of green construction. Therefore, this study aims to identify challenges faced by project managers who execute green construction projects and to determine the critical knowledge areas and skills that are necessary to respond to such challenges. Through literature review, surveys and interviews with project managers, this study will help establish a knowledge base for project managers to be competitive and to effectively execute sustainable projects. © 2012 Association for Project Management and the International Project Management Association and Elsevier Ltd.

Ibekwe A.U.,Royal Dutch Shell | Pu Y.,Newcastle University | Ham W.L.,Defense Science and Technology Agency | Dow R.S.,Newcastle University
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2014

With the expectation of hull girder asymmetry and corresponding shift in elastic neutral axis resulting from collision damages and other forms of structural deteriorations, the interaction of vertical and horizontal hull girder capacities become quite significant in the assessment of ship structural safety. This paper therefore extends the application of a previously proposed interactive-numerical probabilistic based methodology for structural safety to assess the hull girder ultimate strength reliability of a damaged ship by means of a user-defined numerical framework. Hull girder capacity is calculated using the NS94D ultimate strength code, which is based on the Smith's progressive collapse method. The resulting deterministic responses have been interactively linked to the NESSUS probabilistic framework so that the reliability of the damaged hull girder is predicted using an implicit limit state function defined based on a transformation of coordinates to appropriately account for any shift in the neutral axis. Random deviations of the constituent variables are directly applied to calculate the ultimate strength deterministic responses, thereby circumventing the need to characterize any correlated strength variable, which is at best subjective. The conventional approach of characterizing ultimate strength by an assumed coefficient of variation and distribution type was found to be conservative in predicting structural safety of ships relative to the proposed method. Application of the interactive-numerical technique for structural reliability is therefore considered significant for problems involving correlated random variables with unknown statistical characteristics. The method is being considered to predict the safety of cracked hull girders by accounting for the residual strength and further load bearing capabilities of deteriorated and adjacent elements. Copyright © 2014 by ASME.

Zhou S.,Nanyang Technological University | Zhou S.,University of Teesside | Chen D.,Nanyang Technological University | Chen D.,China University of Geosciences | And 8 more authors.
ACM Transactions on Modeling and Computer Simulation | Year: 2010

As a collective and highly dynamic social group, the human crowd is a fascinating phenomenon that has been frequently studied by experts from various areas. Recently, computer-based modeling and simulation technologies have emerged to support investigation of the dynamics of crowds, such as a crowd's behaviors under normal and emergent situations. This article assesses the major existing technologies for crowd modeling and simulation. We first propose a two-dimensional categorization mechanism to classify existing work depending on the size of crowds and the time-scale of the crowd phenomena of interest. Four evaluation criteria have also been introduced to evaluate existing crowd simulation systems from the point of view of both a modeler and an end-user. We have discussed some influential existing work in crowd modeling and simulation regarding their major features, performance as well as the technologies used in this work. We have also discussed some open problems in the area. This article will provide the researchers with useful information and insights on the state of the art of the technologies in crowd modeling and simulation as well as future research directions. © 2010 ACM.

Ma K.,ST Electronics Satcom and Sensor Systems | Jayasuriya R.M.,ST Electronics Satcom and Sensor Systems | Siong D.R.L.C.,Defense Science and Technology Agency
IEEE Transactions on Industrial Electronics | Year: 2011

In this paper, the design and packaging of fully integrated digitally controlled microelectromechanical system (MEMS) filters with low cost, high performance, and compact size are introduced. The four-channel switched filters operating in the frequency range of 1120 GHz have been developed using MEMS technologies and four five-pole edge-coupled bandpass filters, which are modified from the traditional edge-coupled bandpass filter in the input and output feeders to achieve a better stopband performance. Microwave filters, MEMS circuits, and related packaging are investigated and demonstrated theoretically and experientially. © 2006 IEEE.

Oswal M.,Nanyang Technological University | See K.-Y.,Nanyang Technological University | Soh W.,Nanyang Technological University | Chang W.Y.,DSO National Laboratories | And 3 more authors.
2010 IEEE Electrical Design of Advanced Packaging and Systems Symposium, EDAPS 2010 | Year: 2010

This paper describes a methodology to predict farfield (FF) emissions from a high-speed board based on the fields measured in the near-field (NF) region. The NF to FF transformation is based upon an empirical relationship between the measured fields in both the NF and FF regions. Initial results show that the predicted FF emissions from a high-speed board provide the designer a good confidence on the compliance of regulatory emission limits.

Ma G.,Nanyang Technological University | Zhou H.,Nanyang Technological University | Lu Y.,University of Edinburgh | Chong K.,Defense Science and Technology Agency
Engineering Structures | Year: 2010

When an underground structure is subjected to a subsurface explosion, an in-structure shock occurs. The in-structure shock can be a major cause of disruption and even damage to the instruments and equipment contained in the structure if the detonation is relatively distant. For this reason, an appropriate analysis and prediction of explosion-induced in-structure shock is an important topic in the area of protective design of underground structures. In this paper, a detailed analysis is conducted on a representative buried structural element subjected to soil-transmitted blast. The soil-structure interaction is considered by introducing an interfacial damping between the structural element and the surrounding soil. Two phases of the structural response to the blast load, i.e., a blast loading phase and a free-vibration phase, are analyzed. Based on the analytically derived time histories of the structural response, which represent the in-structure shock, the response spectra concerning the equipment (sub-structures) attached to the main structure are constructed. Besides providing a theoretical approach for the evaluation of the in-structure shock and its subsequent effects, the present analysis is supplementary to the relevant provisions in TM5-855-1 and TM5-1300, in which only rough predictions of in-structure shock for buried structures are specified. © 2010 Elsevier Ltd.

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