• Atmosphere
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• v.22 no.4
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• pp.401-413
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• 2012

In this study, an investigation has been carried out to understand 1) temporal variation of rainfall amount in summer over south Korea during the 30-year period of 1979-2008 and 2) the relationship between the variation of rainfall amount and the change of large-scale monsoon circulation around 1993/1994 over East Asia. The analysis of rainfall amount is carried out separately for whole summer (June-August), climatological Changma period of 23 June-23 July, and August to consider variations within summer. To relate the variation of rainfall amount with the change of large-scale circulation, we have considered two 15-year periods of 1979-1993 and 1994-2008. This study has used observations at 58 stations in South Korea and NCEP-NCAR $2.5^{\circ}{\times}2.5^{\circ}$ reanalysis data. The major change in synoptic environment for the Changma period is characterized by the intensified anticyclone over Mongolia during 1994-2008, which results in a weak meridional oscillation of Changma front. As a result, rainfall amount for the Changma period and the frequency of extreme events have significantly increased after 1993/1994. A major change of synoptic environment for August is the significant westward extension of the western Pacific subtropical high, which allows not only more moisture transports but also stronger cyclonic circulation over the Korean peninsula. Rainfall amount for August and frequency of extreme events have also increased after 1993/1994. However, variability of rainfall amount is larger for August than that for the Changma period, with some years showing very dry August (monthly rainfall amount less than 150 mm).

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.225-228
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• 1999

The formation of dioxin (term used here to refer to both polychlorinated dibenzo-p-dioxins, PCDDS, and dibenzofurans, PCBFs) in combustion processes is of concern because of the extreme toxicities of some of these compounds and because of their resistance to degradation in the environment. The number and location of chlorine substituents differentiate dioxin homologues and isomers, respectively. There are a total of 75 PCDD congeners and 135 PCDF congeners.(omitted)

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.2
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• pp.49-59
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• 2000

Wave distribution in Jangjeon Harbour is numerically simulated for an optimum design of the harbour facilities. A deep-water design wave is estimated based on stochastic extreme wave analysis of wind data in the vicinity of the harbour, and it is applied to the boundary condition at open sea. Boussinesq wave theory that includes effects of frequency dispersion and nonlinearity is employed for the wave simulation. The porosity and sponge layer are adapted at beach to depict partial reflection and complete absorption of waves, respectively. The design wave for breakwater is computed in global domain with coarse grids and the wave distribution inside of wharf is simulated in local domain with fine grids.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.41.1-41.1
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• 2010

It has been suggested that merging plays an important role in the formation and the evolution of early-type galaxies. Optical-NIR color gradients of early-type galaxies in high density environments are found to be less steep than those in low density environment, hinting frequent merger activities in early-type galaxies in high density environment. In order to confirm if the flat color gradient is the result of dry merger, we decided to look deeply to find merging features and get their relation with color gradient. We selected samples which show extreme values of optical-NIR color gradients based on the data of previous study, and observed them at Maidanak observatory 1.5m telescope with long exposure. After masking out overlaid sources, our analysis reveals that these galaxies do not have extreme color gradient values. High degree sky flat technique was used during observation to aid discovery of faint, extended features. However, flatness of detector (SNUCAM) was good enough, so we could not see any marked improvement in image quality compared to those using normal sky flats. Additionally we noticed a feature that looks like merging tidal tail in the CFHT archival image, but this does not show up on the image we obtained. This demonstrates that flatness and correct sky estimation is very important when we look for faint merging features. In future we plan to enlarge the number of the sample.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.234-239
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• 2007

This paper describes the TiW ohmic contact characteristics under the surface treatment of the polycrystalline 3C-SiC thin film grown on $SiO_2/Si(100)$ wafers by APCVD. The poly 3C-SiC surface was polished by using CMP(chemical mechanical polishing) process and then oxidized by wet-oxidation process, and finally removed SiC oxide layers. A TiW thin film as a metalization process was deposited on the surface treated poly 3C-SiC layer and was annealed through a RTA(rapid thermal annealing) process. TiW/poly 3C-SiC was investigated to get mechanical, physical, and electrical characteristics using SEM, XRD, XPS, AFM, optical microscope, I-V characteristic, and four-point probe, respectively. Contact resistivity of the surface treated 3C-SiC was measured as the lowest $1.2{\times}10^{-5}{\Omega}cm^2$ at $900^{\circ}C$ for 45 sec. Therefore, the surface treatments of poly 3C-SiC are necessary to get better contact resistance for extreme environment MEMS applications.

• Journal of the military operations research society of Korea
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• v.6 no.1
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• pp.93-101
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• 1980

An effectively designed budget system in the poor resources environment necessarily has three design criteria : (i) to be both planning-oriented and control-oriented, (ii) to be both rationalistic and realistic, (iii) to be sensitive to the variations of resources environment. PPB system is an extreme (planning-oriented and rationalistic) and conventional OEB/OUB system is the other extreme (control-oriented and incrementalistic). Generally, the merits of rationalism are limited because of the infeasibility of applications. Hence, mixtures of the two extremes such as MBO, ZBB, and RZBB have been examined and applied during the last decade. The classical mathematical models of capital budgeting are the starting points of the development of the Budget-Mix Model introduced in this paper. They are modified by the followings: (i) technological-resource constraints, (ii) bounded-variable constraint, (iii) the exchange rules. Special emphasis is laid on the above (iii), because we need more efficient interresource exchanges in the budget-mix process. The Budget-Mix Model is not based on optimization, but a heuristic approach which assures a satisficing solution. And the application fields of this model range between the incremental Nonzero-Base Budgeting and the rational Zero-Base Budgeting. In this thesis, the author suggests 'the budget- mix concept' and a budget-mix model. Budget-mix is a decision process of making program-mix and resource-mix together. For keeping this concept in the existing organization realistic, we need the development of quantitative models describing budget-mix situations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.3
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• pp.240-245
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• 2015

In this study, experiments were performed using a model of a very large crude oil carrier (VLCC), which is a typical blunt ship, in a wave-making towing tank. The aim of the experiments was to determine the effect of added resistance in waves on the various operating conditions of a VLCC. An analysis of the results was conducted to determine the characteristics of resistance performance in waves. In addition, the characteristics of added resistance on a tanker were analyzed under irregular waves based upon the above result. The experimental results showed that added resistance was the highest around ${\lambda}/L=1.0$, and the added resistance increased with the increase of the ship speed. Furthermore, under even keel conditions, the added resistance was higher than that under the trim changes, and the smallest added resistance was measured at the trim by the stern. Based on the experimental results, this study proposes effective operating conditions by analyzing the characteristics of the mean added resistance and the expected extreme response in irregular waves.

• Progress in Superconductivity and Cryogenics
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• v.24 no.1
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• pp.8-12
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• 2022

Recently, research on applying composite materials to various industrial fields is being actively conducted. In particular, composite materials fabricated by Fused Deposition Modeling 3D printers have more advantages than existing materials as they have fewer restrictions on manufacturing shape, reduce the time required, weight. With these advantages, it is possible to consider utilizing composite materials in cryogenic environments such as the application of liquid oxygen and liquid hydrogen, which are mainly used in an aerospace and mobility. However, FDM composite materials are not verified in cryogenic environments less than 150K. This study evaluates the characteristics of composite materials such as tensile strength and strain using a UTM (Universal Testing Machine). The specimen is immersed in liquid nitrogen (77 K) to cool down during the test. The specimen is fabricated using 3D print, and can be manufactured by stacking reinforced fibers such as carbon fiber, fiber glass, and aramid fiber (Kevlar) with base material (Onyx). For the experimental method and specimen shape, international standards ASTM D638 and ASTM D3039 for tensile testing of composite materials were referenced.

• Journal of the Korean GEO-environmental Society
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• v.23 no.7
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• pp.11-20
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• 2022

Planetary geotechnical investigation in charge of drilling and soil sampling is of a great importance in providing extraterrestrial geotechnical information. Extraterrestrial subsurface investigation, which includes drilling, soil sampling, and sample transportation, will be loaded in a lander or a rover. Scientists from all over the world are interested in the design and development of a drilling system with various functions due to potential applications in planetary surface exploration mission. However, it is difficult to build a fully functional drilling system in extreme environment conditions. This paper presents engineering considerations for the design and development of soil sampling including drilling and performance verification in extreme environment conditions in detail.

• Safety and Health at Work
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• v.14 no.1
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• pp.107-117
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• 2023

Background: Thermophysiological comfort in a cold environment is mainly ensured by clothing. However, the thermal performance and protective abilities of textile fabrics may be sensitive to extreme environmental conditions. This article evaluated the thermal insulation properties of three technical textile assemblies and determined the influence of environmental parameters (temperature, humidity, and wind speed) on their insulation capacity. Methods: Thermal insulation capacity and air permeability of the assemblies were determined experimentally. A sweating-guarded hotplate apparatus, commonly called the "skin model," based on International Organization for Standardization (ISO) 11092 standard and simulating the heat transfer from the body surface to the environment through clothing material, was adopted for the thermal resistance measurements. Results: It was found that the assemblies lost about 85% of their thermal insulation with increasing wind speed from 0 to 16 km/h. Under certain conditions, values approaching 1 clo have been measured. On the other hand, the results showed that temperature variation in the range (-40℃, 30℃), as well as humidity ratio changes (5 g/kg, 20 g/kg), had a limited influence on the thermal insulation of the studied assemblies. Conclusion: The present study showed that the most important variable impacting the thermal performance and protective abilities of textile fabrics is the wind speed, a parameter not taken into account by ISO 11092.