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오늘 본 자료
Joo, Jaeyong,Kim, Hyungjun,Han, Sang Soo The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.9
<P>Graphic Abstract</P><P>Volume expansion and shrinkage of MOFs depend on the kinds of hosts and guests (guest-changes-host). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp54473g'> </P>
Note on B-spline Volume Representation of Measured BRDF Data
Joo-Haeng Lee,Hyungjun Park (사)한국CDE학회 2010 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8
Digital image synthesis based on light transport simulation has become an indispensable tool for computer graphics applications. Especially for better realism in material appearance, measured bidirectional reflectance distribution function (BRDF) data have been used to accurately represent complex interaction between lights and surface materials. However, large storage requirement for the BRDF data makes it difficult to adopt them in practical rendering applications. In this paper we propose B-spline volume BRDF (BVB) that is a compact and accurate representation of such measured BRDF data of real materials. We present how to construct BVB models from the measured BRDF data, and describe the application of BVB models to photorealistic rendering. Then, we show that the resulting BVB models are compact in model size, effective in preserving the features of material appearance, and suitable for representing the measured BRDF data.
Joo, Jaeyong,Kim, Hyungjun,Han, Sang Soo The Royal Society of Chemistry 2013 Physical chemistry chemical physics Vol.15 No.43
<P>Using a density functional theory calculation including van der Waals (vdW) corrections, we report that H<SUB>2</SUB> adsorption in a cubic-crystalline microporous metal–organic framework (MOF-5) leads to volume shrinkage, which is in contrast to the intuition that gas adsorption in a confined system (<I>e.g.</I>, pores in a material) increases the internal pressure and then leads to volumetric expansion. This extraordinary phenomenon is closely related to the vdW interactions between MOF and H<SUB>2</SUB> along with the H<SUB>2</SUB>–H<SUB>2</SUB> interaction, rather than the Madelung-type electrostatic interaction. At low temperatures, H<SUB>2</SUB> molecules adsorbed in the MOF-5 form highly symmetrical interlinked nanocages that change from a cube-like shape to a sphere-like shape with H<SUB>2</SUB> loading, helping to exert centrosymmetric forces and hydrostatic (volumetric) stresses from the collection of dispersive interactions. The generated internal negative stress is sufficient to overcome the stiffness of the MOF-5 which is a soft material with a low bulk modulus (15.54 GPa).</P> <P>Graphic Abstract</P><P>Adsorption of hydrogen molecules (H<SUB>2</SUB>) in MOF-5 leads to volume shrinkage of the MOF at cryogenic temperatures. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp53256a'> </P>
Adaptive B-spline volume representation of measured BRDF data for photorealistic rendering
Park, Hyungjun,Lee, Joo-Haeng Society for Computational Design and Engineering 2015 Journal of computational design and engineering Vol.2 No.1
Measured bidirectional reflectance distribution function (BRDF) data have been used to represent complex interaction between lights and surface materials for photorealistic rendering. However, their massive size makes it hard to adopt them in practical rendering applications. In this paper, we propose an adaptive method for B-spline volume representation of measured BRDF data. It basically performs approximate B-spline volume lofting, which decomposes the problem into three sub-problems of multiple B-spline curve fitting along u-, v-, and w-parametric directions. Especially, it makes the efficient use of knots in the multiple B-spline curve fitting and thereby accomplishes adaptive knot placement along each parametric direction of a resulting B-spline volume. The proposed method is quite useful to realize efficient data reduction while smoothing out the noises and keeping the overall features of BRDF data well. By applying the B-spline volume models of real materials for rendering, we show that the B-spline volume models are effective in preserving the features of material appearance and are suitable for representing BRDF data.