• The Korean Journal of Ceramics
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• v.3 no.3
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• pp.213-217
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• 1997

In this paper, the imparct of X-ray and plasma process-induced-damages to La doped Lead Zirconate Titanate (PLZT, (Pb1-xLa)(Zr0.5Ti0.5)O3) capacitor characteristics have been investigated from the viewpoint of gigabit scale dynamic random access memory (DRAM) applications. Plamsa damage causes asymmetric degradation on hysteresis characteristics of PLZT films. On the other hand, X-ray damage results in a symmetrical reduction of charge storage densities (Qc's) for both polarities. As La concentration increases in the films, the radiation hardness of PLZT films on X-ray and plasma exposures is improved. It is observed that the damaged devices are fully recovered by thermal annealing under oxygen ambient.

• Nuclear Engineering and Technology
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• v.39 no.6
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• pp.717-724
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• 2007

A measurement-based time-domain noise simulation of radiation detector-preamplifier (front-end) noise in nuclear spectroscopy is described. The time-domain noise simulation was performed by generating "noise random numbers" using Monte Carlo's inverse method. The probability of unpredictable noise was derived from the empirical cumulative distribution function via the sampled noise, which was measured from a preamplifier output. Results of the simulated noise were investigated as functions of time, frequency, and statistical domains. Noise behavior was evaluated using the signal wave-shaping function, and was compared with the actual noise. Similarities between the response characteristics of the simulated and the actual preamplifier output noises were found. The simulated noise and the computed nuclear pulse signal were also combined to generate a simulated preamplifier output signal. Such simulated output signals could be used in nuclear spectroscopy to determine energy resolution degradation from front-end noise effect.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1622-1624
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• 2000

방사선이 조사된 폴리프로필렌의 유전특성을 고찰한 결과 방사선 조사량이 40 kGy이하의 경우에는 유전상수가 서서히 증가하였으나. 40 kGy이상에서는 급격한 증가를 나타냈다. 또한, 방사선이 결정에 미치는 영향은 결정과 결정의 경계면에서 열화현상이 발생하는 것으로 관측되었고, 방사선의 세기가 증가할 수록 열화공의 수도 증가하는 것으로 나타났다.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.333-338
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• 2003

Polymeric composite structures used in ground transportation applications such as the carbody of tilting train may be exposed to a ground environmental conditions during long-term missions. In this study, the degradation of mechanical and physical properties of graphite/epoxy composite and glass fabric/phenol composite under ground environmental conditions was investigated. Accelerated environmental conditions of ultraviolet radiation, temperature, and moisture were considered. Several types of specimens were used to investigate the effects of environmental conditions on mechanical properties of the composites. Also, storage shear modulus, loss shear modulus, and tan 8 were measured as a function of exposure times through a dynamic mechanical analyzer. Finally, composite surfaces exposed to environmental conditions were examined using a scanning electron microscope.

• Journal of Communications and Networks
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• v.11 no.3
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• pp.229-239
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• 2009

Orthogonal frequency division multiplexing (OFDM) has been adopted as a standard for various high data rate wireless communication systems due to the spectral bandwidth efficiency, robustness to frequency selective fading channels, etc. However, implementation of the OFDM system entails several difficulties. One of the major drawbacks is the high peak-to-average power ratio (PAPR), which results in intercarrier interference, high out-of-band radiation, and bit error rate performance degradation, mainly due to the nonlinearity of the high power amplifier. This paper reviews the conventional PAPR reduction schemes and their modifications for achieving the low computational complexity required for practical implementation in wireless communication systems.

• 보존과학연구
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• s.11
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• pp.1-9
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• 1990

The environmental controls for good conservation of all textile materials are follow as :1) Special RH conditions on textiles keep to the usually advocated 50∼55%.2) The effect of the temperature is too small to worry about in the applicable range, that is $20^{\circ}C$.3) It is important to keep soiling by air borne dirt to a minimum by an air filter or putting textiles in cases.4) Sulphur dioxide must be rekoved by an activated carbon filter or a water spray. And this concentration below $50\muGm^3$ can be regarded assatisfactory.5) Oxygen plays a part of deterioration proceses. The effect of nitrogend andinert gases in sealed show cases should be further studied.6) Ozone is detrimental to textiles. It can be removed by activated carbonfilter.7) The removal of UV radiation and blue light can be expected to increase the lifetime of dyeing and strength of fiber.50 lux is suggested for sensitive textile materials.

• Journal of the Korean Society of Radiology
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• v.3 no.4
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• pp.13-21
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• 2009

The Magnetic Resonance Imaging (MRI) systems consist of various parameters. Among them, the image quality can be arguably the most important part of the systems. As the other components in MRI systems have been developed and evolved, the MRI image quality has been advanced remarkably. And, the radiation imaging system is being converted from the Film to the digital method, which drives the computerization of many hospitals. The management of the tremendous radiation images becomes more critical. The data compression is used to store such large data in a network server. When the image files are compressed, the image quality degrades comparing to its original images. Even slight quality degradation of a medical image could cause an erroneous diagnosis, so the images must be handled carefully. This thesis studied the image assessment methods of comparing the quality of the compressed image to its original, and the quality of the original and the displayed images of the MRI systems via PSNR with actual medical images used in hospitals. As a result, no noticeable quality degradation was found comparing the compressed images with various digital compression methods and the original images. However, it was a different story comparing the original images and the displayed images on MRI monitors. Some noise or image distortion was visible using any regular CRT or LCD monitors were used while the special monitors designed for the MRI imaging and medical images displayed high definition images.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.949-956
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• 2016

There are a number of effects by solar radiation in many aerospace industrial fields, such as degradation of mechanical properties, sealing effect of sealants or decolorization. Because it takes long time to investigate these effects by using the light of natural state, new methods are developed for accelerating this phenomenon. In this paper, we developed an apparatus to simulate accelerated solar radiation phenomenon selecting irradiation intensity $1,120W/m^2$ as the designed environment. Epoxy polymer as the composite material was chosen and processed by ASTM-D638, a reference for tensile test of polymer and plastic. Total color shift was selected as the test category to evaluate acceleration of the test. We obtained acceleration factors and numerical model from test data and concluded it can shorten test periods by accelerated irradiation intensity of $1,120W/m^2$.

• Journal of Ginseng Research
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• v.44 no.3
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• pp.496-505
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• 2020

Background: Panax ginseng is a marvelous herbal remedy for all ailments of body. That may be why it is called Panax, which means "cure for all". Melanin is a pigment that gives color to our skin; however, increased melanin production can lead to tumor formation. Human exposure to ultraviolet B radiation has increased extensively owing to the increased sunlight due to global warming. Consequently, a phenomenon called photoaging has been observed for all skin colors and types. As a result of this phenomenon, a set of enzymes called matrix metalloproteinases, which serve as degradation enzymes for extracellular matrix proteins, mainly collagen, is increased, causing depletion of collagen and resulting in early wrinkle formation. Methods: Therefore, in our study, we used the murine melanoma cell line B16/F10 to study the inhibition of melanogenesis by Korean Red Ginseng (KRG) extract in vitro and HRM-2 hairless mice exposed to artificial ultraviolet B to examine the efficacy of KRG in vivo. We prepared a 3% red ginseng extract cream and evaluated its effects on human skin. Results: Our results demonstrated that KRG induced potent suppression of tyrosinase activity and melanin production in B16/F10 cells; moreover, it reduced the transcription and translation of components involved in the melanin production pathway. In the in vivo experiments, KRG potently suppressed the expression of matrix metalloproteinases, reduced wrinkle formation, and inhibited collagen degradation. On human skin, ginseng cream increased skin resilience and skin moisture and enhanced skin tone. Conclusion: Therefore, we conclude that KRG is an excellent skin whitening and antiaging product.

• Molecules and Cells
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• v.25 no.2
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• pp.305-311
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• 2008

After successful clinical application, arginine deiminase (ADI) has been proposed to be a new cancer therapeutic. In the present study, we examined the effect of ADI in combination with ionizing radiation (IR) on MCF-7 cell growth and clonogenic cell death. Cell growth was inhibited by IR in a dose-dependent manner and ADI enhanced the radiosensitivity. ADI itself did not suppress the growth of MCF-7 cells due to the high level of expression of argininosuccinate synthetase (ASS), which convert citrulline, a product of arginine degradation by ADI, to arginine. Previously, it was suggested that ammonia, another product of arginine degradation by ADI, is the main cause of the growth inhibition of irradiated hepatoma cells contaminated with ADI-expressing mycoplasma [van Rijn et al. (2003)]. However, we found that ammonia is not the only factor that enhances radiosensitivity, as enhancement was also observed in the absence of ammonia. In order to identify the enhancing effect, levels of ASS and proteins related to the cell cycle were examined. ASS was unchanged by ADI plus IR, but p21 (a CDK inhibitor) was upregulated and c-Myc downregulated. These findings indicate that changes in the expressions of cell cycle proteins are involved in the enhancement of radiosensitivity by ADI. We suggest that ADI is a potential adjunct to cancer therapy.