Raffles Science Institute

Singapore, Singapore

Raffles Science Institute

Singapore, Singapore
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Li B.,Raffles Science Institute | Kang Z.Y.,Stanford University | Lin J.,Princeton University | Yeo Y.,National University of Singapore | Tan G.,Raffles Science Institute
Canadian Journal of Physics | Year: 2017

Scratch holograms can be created easily and the associated interesting phenomena may be observed in daily life. In this paper, general and quantitative theories of scratch holograms were derived and presented. Both the reflection case where a scratch hologram reflects light, and the transmission case where it refracts and transmits light, were considered. A predictive model, which has not been presented in the literature, was developed. The model was able to solve for the position of the bright points along the scratches using a computational method. Extensive experimentation was carried out with scratch holograms of two designs to verify the model. Photographic evidence demonstrated extremely good fits with the theoretical predictions. The model was then used to theoretically simulate the 3D spatial positions of the hologram and also quantify distortion present in the images to illustrate novel real-life applications of the theories presented.

Chan J.T.,Raffles Science Institute | Lee J.L.,Princeton University | Tjeng V.,Massachusetts Institute of Technology | Yeo Y.,National University of Singapore | Tan G.,Raffles Science Institute
European Journal of Physics | Year: 2014

The International Young Physicists' Tournament (IYPT) is a worldwide annual competition for high-school students. This paper is adapted from the solution to problem 8, Jet and Film, as presented by the Singapore Team at the 26th IYPT, Taipei, Taiwan. The impact of liquid microjets on stable soap films was investigated. Two steady regimes were observed: refraction (where the microjet penetrates the soap film and is deflected) and absorption (where the microjet merges with the soap film and forms vertical undulating patterns on the soap film surface). This phenomenon has potential applications in controlling the trajectory of a liquid microjet in air. Although Kirstetter et al (2012) investigated this interaction by using the same liquid for both the microjet and the soap film, this paper extends their work by using different liquids for the microjet and the soap film. In addition, the need for a small-angle approximation of Snell's law is removed for the refraction regime, and an alternative expression is proposed for the force exerted by the soap film on the microjet in the absorption regime that accounts for the dependence of the wavelength of the undulating patterns on the angle of incidence of the microjet on the soap film. Empirical data support these improved theoretical predictions. © 2014 IOP Publishing Ltd.

Chan C.S-Y.,Raffles Science Institute | Cheng J.,Raffles Science Institute | Loh J.Y.Q.,Raffles Science Institute | Tan E.,Raffles Science Institute | And 2 more authors.
Raffles Bulletin of Zoology | Year: 2012

While ants have been commonly associated with rattans, there is no known documentation of this ant-plant interaction on a local context despite the presence of several rattan species in Singapore. With Singapore experiencing rapid urbanisation and inevitable deforestation, and that most of the rattan species are now endangered and the reality of co-extinctions a high possibility, documentation of rattans and related insects is urgently required. In this paper we observed the interactions between ants and the two rattan species, Korthalsia echinometra and Korthalsia rostrata (subfamily Calamoideae, Tribe Calameae, Korthalsiinae) by documenting the ants and other insects that resided within the rattan ocreae. These observations were conducted at Bukit Timah Nature Reserve, MacRitchie Reservoir, and Nee Soon Swamp Forest in Singapore. We identified the ant species that was associated with K. echinometra to be Iridomyrmex sp. (n = 5), while those associated with K. rostrata were Dolichoderus sp. (n = 4) and Philidris sp. (n = 1). This suggests the possibility of a genus-specific relationship between K. echinometra and the ant species Iridomyrmex sp., and a non-specific relationship with ants for K. rostrata within Singapore. Our observations also suggest the possibility of an ant-hemipteran association between Iridomyrmex sp. and the aphid Cerataphis orchidearum aptera that was found in the ocrea of K. echinometra along with a larval brood of Iridomyrmex sp. We suggest that more research is warranted before any postulations can be accurately drawn. © National University of Singapore.

Zhong S.,Raffles Science Institute | Lin H.J.Q.,Raffles Science Institute | Chor C.Y.T.,Raffles Science Institute | Tan G.,Raffles Science Institute
Proceedings of the International Conference on Progress in Additive Manufacturing | Year: 2016

Current prosthetic hands are often lacking in feedback mechanism while being very expensive. The Fused Deposition Modelling (FDM) technique provides a cost effective method to directly produce prosthetic hands especially for third-world countries. This study aims to synthesise a conductive composite material with good mechanical properties that could be used to print prosthetic hands using the FDM technique. An ABS/CNT composite material was synthesised via solution processing. The rule of mixtures and Zare's model were used to analyse the mechanical properties while the percolation threshold theory and excluded volume theory were used for analysing the electrical properties. Results indicate that the material had good dispersion and retained the aspect ratio of CNT, thereby achieving good mechanical and electrical properties. © Copyright 2016 by Pro-AM 2016 Organizers.

Aw A.J.,Raffles Science Institute
Designs, Codes, and Cryptography | Year: 2014

The covering radius problem is a question in coding theory concerned with finding the minimum radius r such that, given a code that is a subset of an underlying metric space, balls of radius r over its code words cover the entire metric space. Klapper (IEEE Trans. Inform. Theory 43:1372-1377, 1997) introduced a code parameter, called the multicovering radius, which is a generalization of the covering radius. In this paper, we introduce an analogue of the multicovering radius for permutation codes (Des. Codes Cryptogr. 41:79-86, cf. 2006) and for codes of perfect matchings (cf. 2012). We apply probabilistic tools to give some lower bounds on the multicovering radii of these codes. In the process of obtaining these results, we also correct an error in the proof of the lower bound of the covering radius that appeared in (Des. Codes Cryptogr. 41:79-86, cf. 2006). We conclude with a discussion of the multicovering radius problem in an even more general context, which offers room for further research. © 2012 Springer Science+Business Media New York.

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