• Journal of Radiation Protection and Research
• /
• v.1 no.1
• /
• pp.22-30
• /
• 1976

The perturbation of dose distribution adjacent to cavities in high energy electron has shown that the percentage of dose increase varies markedly as a function of the build-up layer, the length and thickness of the cavities, and the electron energy. The dose distribution showed that cavities similar in size to those encountered in the head and neck measured by industrial film dosimetry and corrected by ionization chambers. The most increased doses by measuring are resulted in a localized dose of up to 130% of that measured at the depth of maximum dose within a homogeneous tissue equivalent phantom. The measured values and correction factors of dose perturbation due to air cavities showed in diagrams and would be summarized as follows. 1. In $8{\sim}12MeV$ electron beams, the most marked dose is observed when the build-up layer thickness is 0.5cm and cavity volume is $2{\times}2{\times}2cm^3$. 2. The highest dose point is located under cavity when the energy is increased and cavity length is longer. 3. The cavity length at which the maximum percentage dose occurs decreases with increasing energy. 4. The highest percentage cavity doses are obtained when the energy is high, the build-up layer is thin, the thickness of the cavity is large, and the length of the cavity is approximately 1 to 3cm. 5. The doses of upper portion of cavity are less than the standard dose distribution as 5 to 10%. 6. The maximum range of electron beam are extended as much as thickness of cavity. 7. A cavity having a length of 5cm closely approximates a cavity of infinite length.

• Journal of Radiation Protection and Research
• /
• v.27 no.3
• /
• pp.171-179
• /
• 2002

The three-dimensional long-range dispersion model has been developed to understand the characteristics of the transport and diffusion of radioactive materials released into atmosphere. The model is designed to compute air concentration and ground deposition at distances up to some thousands of kilometers from the source point in horizontal direction. The vertical turbulent motion is considered separately within the mixing layer and above the mixing layer. The test simulation was performed In the area of Northeast Asia. The release point was assumed in the east part of China. The calculated concentration distributions art mainly advected toward the southeast part of release point by the wind fields. The developed model will be used to estimate the radiological consequences against a nuclear accident. The model will be supplemented by the comparative study using the data of the long-range field experiments.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.625-628
• /
• 2008

This study is performed to evaluate the carbonation resistance by measuring carbonation penetration depth and diffusion equivalent air layer thickness for 3 types of repair materials and 2 types of surface protection materials. Diffusion equivalent air layer thickness($S_D$) is thickness of a static air layer that possesses, under the same conditions, the same carbon dioxide permeability as the coating in accordance BS EN 1062-6. There is a significant advantage that continuous test is possible because it does not destroy the specimen. From experiment results, it is concluded that determination of carbon dioxide permeability is effective to evaluate for surface coating materials.

• Journal of Radiation Protection and Research
• /
• v.48 no.1
• /
• pp.28-43
• /
• 2023

Background: High-fidelity meteorological data is a prerequisite for the realistic simulation of atmospheric dispersion of radioactive materials near nuclear power plants (NPPs). However, many meteorological models frequently overestimate near-surface wind speeds, failing to represent local meteorological conditions near NPPs. This study presents a new high-resolution (approximately 1 km) meteorological downscaling method for modeling short-range (< 100 km) atmospheric dispersion of accidental NPP plumes. Materials and Methods: Six considerations from literature reviews have been suggested for a new dynamic downscaling method. The dynamic downscaling method is developed based on the Weather Research and Forecasting (WRF) model version 3.6.1, applying high-resolution land-use and topography data. In addition, a new subgrid-scale topographic drag parameterization has been implemented for a realistic representation of the atmospheric surface-layer momentum transfer. Finally, a year-long simulation for the Kori and Wolsong NPPs, located in southeastern coastal areas, has been made for 2016 and evaluated against operational surface meteorological measurements and the NPPs' on-site weather stations. Results and Discussion: The new dynamic downscaling method can represent multiscale atmospheric motions from the synoptic to the boundary-layer scales and produce three-dimensional local meteorological fields near the NPPs with a 1.2 km grid resolution. Comparing the year-long simulation against the measurements showed a salient improvement in simulating near-surface wind fields by reducing the root mean square error of approximately 1 m/s. Furthermore, the improved wind field simulation led to a better agreement in the Eulerian estimate of the local atmospheric dispersion. The new subgrid-scale topographic drag parameterization was essential for improved performance, suggesting the importance of the subgrid-scale momentum interactions in the atmospheric surface layer. Conclusion: A new dynamic downscaling method has been developed to produce high-resolution local meteorological fields around the Kori and Wolsong NPPs, which can be used in short-range atmospheric dispersion modeling near the NPPs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.03b
• /
• pp.43-43
• /
• 2010

we have investigated the field emission characteristics of the CNT/TEOS hybrid thin films fabricated by a spray method. It is found that the CNT/TEOS hybrid emitters show high current density, low turn on field, and long-term emission stability compared to the CNT emitters. These efficient field emission characteristics of the CNT/TEOS hybrid emitters are attributed to the TEOS sol, acting as a protection layer of nanotube emitter by surrounding the nanotube tip as well as a binder material to enhance the adhesion of nanotube emitters to the substrate. Therefore, the CNT/TEOS hybrid emitters could be utilized as an alternative for the efficient and reliable field emitters.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
• /
• v.14
• /
• pp.349-370
• /
• 2000

The environmental problems such as global climate change, global waming, ozone depletion, environmental pollution have been caused by the rapid economic growth, increasing in use of fossil fuels for industrialization and scientific technology development. Especially human activities are significantly altering the atomosphere's composition and its radiative properties. To Stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system, the international community adopted the UN Framework Convention on Climate Change in 1992 and Kyoto protocol in 1997. Also to protect ozone layer the international community adopted the Vienna Convention for the Protection of the Ozone Layer in 1985, and the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987. To achieve global environmental objectives, some multilateral environmental agreements includes trade regulation. For example, Montreal Protocol includes the provisions to regulate the world trade of the sudstances which might destroy ozone layer. However Kyoto Protocol has no provisions to regulate trade and is not in force yet. Although there is no trade regulation article in Kyoto Protocol, the international world trade will be influenced by limitation and reduction of CO2 and strengthening the CO2 emission standard for import good. For example Korean car industy agreed with EU to reduce CO2 emission from new passenger car and Korean Semiconductor industry agreed with WSC(World Semiconductor Council) to reduce PFCs in 1999.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.6
• /
• pp.693-697
• /
• 2010

In current e-commerce system, it happens that client's confidential information such as credit card numbers, pin numbers, or digital certificate may pass through a web proxy server or an altered proxy server without client's awareness. Even though the confidential information is encrypted and sent through SSL(Secure Sockets Layer) or TLS(Transport Layer Security) protocol, it can be exposed to the risk of sniffing by the digital certificate forgery at the proxy server, which is called the SSL MITM(Man-In-The-Middle) Proxy attack. In this paper, current credit card web-payment systems, which is weak at proxy information alternation attack, are analyzed. A resolution with certificate proxy server is also proposed to prevent the MITM attack.

• 정보저장시스템학회:학술대회논문집
• /
• 2005.10a
• /
• pp.4-11
• /
• 2005

In this paper, we propose novel optics design for media inside near-field recording (NFR) using hemispherical solid immersion lens (HMS). To obtain strong advantage of data protection and high data capacity simultaneously, HMS based near field optics using aplanatic position of super hemisphere is designed. In this design, to improve small optical tolerance of this aplanatic position, additional aspheric lens surface is added on top of the HMS and it is combined with zoom optics which composed of two single lenses having low numerical aperture (NA). Also, to compensate chromatic aberration which happens seriously in optics using blue laser diode, diffractive optical element is used. Using zoom optics, additional aspheric lens surface, and diffractive optical element together, wavefront aberration and chromatic aberration are effectively reduced in broad range of cover layer thickness and wavelength variation. In addition, In this paper, effect of gap induced aberration is investigated by analyzing different behavior of each TM and TE wave for designed media inside dual-layer NFR optics.

• Journal of Plant Biology
• /
• v.29 no.4
• /
• pp.295-315
• /
• 1986

Structure and differentiation mechanism of the seed coat of Panax ginseng are studied with light and electron microscopes to clarify the developmental processes of seed coat and the structural changes during the differentiation of the seed. The seed coat of ginseng is differentiated from the inner cell layers of ovary wall, which can be compared with the seed coat differentiated from integument(s) in other plants. The single integument is differentiated into endothelium, which is degenerated to one layer of 4${\mu}{\textrm}{m}$ in thickness, composed of remants of cell wall components in fully ripened seed. The ripened seed coat is composed of three layers; fringe layer, inner layer and palisade layer, and all of the them are crossed at right angles with one another. This may be the cause of protection of the kernel from other mechanical injuries. The thickness of fully ripened seed coat is about 300~600 ${\mu}{\textrm}{m}$, and arrangements of sclereids are irregular. However, the raphe region of seed coat is thin about 200 ${\mu}{\textrm}{m}$ in thickness and sclereids in that region are arranged regularly. This is the important cause for the cleavage of the seed coat during post-maturation process. The vascular bundles on the raphe are still remaining after sarcocarps are removed, and one of the branches of vascular bundles entered into the seed coat through the hilum and extended to chalazal region. During post-maturation process, the supply of water being necessary for growth of embryo may be accompolished by the vascular bundles entered into the seed coat through the opened hilum.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.3
• /
• pp.236-243
• /
• 2010

Fiber Bragg grating(FBG) sensor arrays can be used to monitor the mechanical behavior of the large composite structures such as wind turbine rotor blades and aircrafts. However, brittle FBG sensors, especially multiplexed FBG sensors are easily damaged when they are installed in the flexible structures. As a protection of brittle FBG sensors, epoxy packaged FBG sensors have been presented in this paper. Finite element analysis and experiments were performed to evaluate the effects of adhesives, packaging materials and the bonding layer thickness on the strain transmission. Two types of epoxy were used for packaging FBG sensors and the sensor probes were attached with various bonding layer thickness. It was observed that thin bonding layer with high elastic modulus ratio of the adhesive to packaging provided good strain transmission. However, the strain transmission was significantly decreased when elastic modulus of the adhesive was much lower than the packaged FBG sensor probe's one.