• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.229-234
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• 2007

Diffuse optical tomography (DOT) is a relatively new medical imaging modality which uses near infrared light to image large-sized tissues noninvasively. We constructed a frequency-domain DOT system to measure the optical properties of optical phantoms and human tissues. The FD-DOT uses the intensity-modulated infrared light source that illuminates the biological tissues. The phase shift and modulation changes at each detector site are separately processed to measure the optical properties. The absorption and scattering coefficients are separately estimated using inverse algorithms.

• Polymer(Korea)
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• v.36 no.6
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• pp.761-767
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• 2012

The polycarbonate (PC)-based optical diffusers for direct-lit LED backlight unit were prepared by using extrusion compounding followed by compression molding process. The application of inorganic porous silica particles as a diffusing agent in addition to conventional poly(methyl methacrylate) (PMMA) beads was attempted, and the optical, thermal, and mechanical properties of the prepared diffusers were investigated. The morphological observations revealed that the diffusing agents could be uniformly dispersed in the PC matrix without agglomeration by high shear stress generated during extrusion process. The incorporation of the porous silica particles mixed with PMMA beads remarkably enhanced the luminance uniformity with respect to both location and view angle for the diffuser, while minimizing the reduction in the absolute luminance, as compared with the diffuser containing only PMMA beads. In addition, thermal and mechanical properties of the diffusers were shown to be improved upon addition of the porous silica particles.

• Analytical Science and Technology
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• v.8 no.2
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• pp.205-213
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• 1995

Counter-diffusion of coronene desorbed from alumina with addition of tetra-phenylporphine was studied by spectrophotometry. The counter-diffusion processes of adsorbing and desorbing materials in liquid phase were simulated by counter-diffusion model based on Fritz's binary component isotherm under an assumption of equimass diffusion. The counter-diffusivities of desorbed coronene with addition of tetra-phenylporphine were as ${\sim}10^{-15}m^2/sec$ and that of adsorbed tetra-phenylporphine as ${\sim}10^{-11}m^2/sec$. The counter-diffusivity of coronene determined from desorption process was smaller by ${\sim}10^5$ times than the diffusivity determined from adsorption process of a single species. The reduction of the determined counter-diffusivity of coronene in desorption process was explained by the cross of diffusion fluxes and build-up of high gradient of coronene in pore.

• Korean Journal of Optics and Photonics
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• v.32 no.5
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• pp.220-229
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• 2021

The optical characteristics of high-power direct-lit white light-emitting diode (LED) lighting were investigated, where a quantum dot (QD) film was adopted to enhance the color-rendering index (CRI). The transmittance of the diffuser plate and the concentration of the QD film were varied in this study. The color coordinates and the correlated color temperature (CCT) did not show any appreciable change, while the CRI values increased slightly as the transmittance of the diffuser plate decreased. The investigated optical properties were nearly independent of the viewing angle, and the luminance distribution was close to Lambertian. The CCT decreased from approximately 6000 K to approximately 4000 K as the concentration of the QD film increased from 0 to 7.5 wt%, which was due to the enhanced red component in the emission spectrum. The CRI increased to approximately 95 for some optical configurations of the lighting. These results demonstrate that glare-free, color-changeable, high-rendering LED lighting can be realized by using a combination of a diffuser plate of appropriate transmittance and a red QD film.

• Journal of the Korea Computer Graphics Society
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• v.13 no.1
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• pp.7-14
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• 2007

In this paper we present an illumination model for rendering realistic stained glass. This techniques simulates the phenomenon of stained glass in real world by applying important optical component of the stained glass to the rendering algorithm. The optics for stained glass involves three basic physical mechanisms. First, diffuse light and highlight contribute to the brightness of stained glass which is typically white and changes along with the light source and the view position. Next, Fresnel refraction dominates the amount of refracted (transmitted) light. Finally, we express volume absorption occurs in all stained glass. Then, the rendered stained glass images achieve excellent realism.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.606-613
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• 2005

The badge-type diffusive sampler for the measurement of formaldehyde in indoor air using three types of colorimetric methods such as chromotrophic acid(CTA), 3-methyl-2-benzothiazolinone hydrazone(MBTH), and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole(AHMT) method. The washing of the collection filter with several cleaning solution was effected with satisfactory results, regardless of the types of cleaning solutions. The concentrations of absorbance solution in each colorimetric method were experimentally determined by considering the sampling rates. The variation blank values in each colorimetric method was below 15%. As compared with CTA and AHMT methods, the reproducibility of MBTH method was excellent and was below 10% relative standard deviation. The collected formaldehyde mass and time-weighted concentration had a good correlation (correlation coefficient > 0.93). The limit of detection and limit of quantitation, and minimum sampling time were closely correlated to the sampling rates for the measurement of formaldehyde in each method.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.05a
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• pp.163-169
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• 1998

휴$\cdot$폐광에 따른 토양오염현상은 폐광의 광미사등에 축적된 중금속이나 화학처리제 등의 오염인자들이 용출수나 지하수, 강수 및 비산분진등에 의해 광범위한 지역으로 확산되는 것으로 알려져 있다. 특히 광산의 갱이나 광미사의 퇴적장으로부터 유출되는 유해 중금속들로 인한 토양오염은 주변하천의 농업용수를 오염시켜 농작물에 피해를 주게 되므로 작물의 생육에 지장을 가져올 뿐만 아니라 수확량이 감소되고 또 오염된 농작물을 섭취한 인간이나 동물들에게 만성적인 장해를 일으키기도 한다. (중략)

• Information Display
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• v.4 no.6
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• pp.21-28
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• 2003

• Polymer(Korea)
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• v.27 no.5
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• pp.421-428
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• 2003

The kinetics of photoinitiated polymerization of reactive oligomer methacrylates and oligomer methacrylate/SBS blends have been studied to characterize the diffusion-controlled reaction using Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (ATR-FTIR). The polymerization rates of reactive oligomer methacrylates and oligomer methacrylate/SBS blends were autocatalytic in nature at the initial stage and then a retardation of the reaction conversion occurred gradually as the polymer matrix became vitrified, and finally the reaction became diffusion controlled. Photopolymerization behavior of methacrylate/SBS blends was well predicted using the diffusion-controlled reaction model. N-Vinyl-2-pyrrolidinone (NVP) as a reactive solvent was used to incorporate SBS into methacrylate to form semi-IPN via photopolymerization. Due to the high reactivity of NVP, polymerization rate increased with the increase of NVP content. As the content of NVP-SBS in the blends increased up to 10 phr, the reaction conversion maintained almost constant. But above 20 phr of NVP-SBS in the blends, the reaction conversion gradually decreased since the increase of viscosity affected on the photopolymerization rate. The semi-IPN films of methacrylate/SBS blends were transparent at room temperature as well as at increased temperature and were able to be applied to surface coating.

• The KIPS Transactions:PartC
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• v.10C no.3
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• pp.317-324
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• 2003

In this paper, we propose the ATM based Passive Optical Network (PON) using the optical CDMA scheme with optical switches and PN codes in time domain. We also propose the bipolar optical receiving correlator for PN codes. As optical CDMA is performed by driving directly an optical switch on-off switching with PN codes, the number of distinct code sequences can be increased and the flexibility in assigning PN codes can be improved. Finally we theoretically analyze the signal-to-interference -plus-noise ratio and the bit error probability of regenerated signal and compare the performance of proposed scheme compared with ATM based PON using conventional optical CDMA with optical delay lines.