• Journal of the Society of Naval Architects of Korea
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• v.40 no.6
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• pp.12-19
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• 2003

Corrugated bulkheads for a bulk carrier are divided into watertight bulkheads and deep tank bulkheads. Design of the watertight bulkheads is principally determined by the permissible limit of Classification and IACS requirements. But, the verification of strength through finite element analysis is indispensable for design of the deep tank bulkheads. A stage for stress evaluation of corrugated part is required for optimum structural design of the deep tank bulkheads. Since the finite element analysis for real model requires excessive amount of calculation time, in this study one corrugated structure is replaced with beam element and is idealized as 2 dimensional frame structure connected to upper and lower stool Minimum weight design of the deep tank bulkheads is performed through generalized sloped deflection method(GSDM) as direct calculation method. The purpose of this study is the development of design system for the minimization of steel weight of deep tank bulkheads as well as watertight bulkheads. Discrete variables are used as design variables for the practical design. Evolution strategies(ES) is used as an optimization technique.

• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.120-120
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• 2010

두 개의 별로 구성되었을 것이라고 여겨진 공생별은 밝기변화는 궤도운동에 따라 밝기가 변하는 것으로 알려졌다. 분광 관측 자료에는 이러한 궤도 변화 외에도 다양한 요소가 밝기 변화에 관여하는 것이 특성으로 나타난다. 또한 공생별은 밝기가 급격하게 증가하고 혹은 감소하기도 하는데, 이는 폭발에 기인하는 것으로 판단된다. 이러한 변화, 궤도 운동에 따라 기하학적 변화와 폭발 현상을 모두 볼 수 있는 대표적인 공생별이 Z And이다. 우리는 선행연구(MIKOLAJEWSKA & KENYON, 1996)에서 발표한 저분산 분광 자료를 이용하여 위상별로 변하는 상대적 선세기 변화를 조사하였다. MIKOLAJEWSKA & KENYON (1996)의 자료는 저분산 기기로(${\Delta\lambda\sim}3{\AA}$), HeI, HII, [OIII]5007, [NeV]등이 관측되었는데, 이러한 선들의 세기를 광이온 모델을 이용하여 예측한 후, 공생별 가스를 이온화시킨 중심별(WD)의 물리적 특성을 연구하였다. 또한 Hyung & Aller가 2002년 8월 12일 Lick Observatory에서 Hamilton Echelle Spectrograph (HES)를 사용하여 3600초 노출 관측한 고 분산 분광자료(${\Delta\lambda\sim}0.1{\AA}$)도 분석하였다. HES 관측 자료는 공생별의 위상이 $\Phi$=0.22이며, HES자료는 $3470{\AA}-9775{\AA}$에서 HI, HII, HeI, HeII, NII, NIII, OII, [OI], [OII], [OIII] 등이 있었다. 이 선들의 선 윤곽을 IRAF와 StarLink/Dipso를 이용하여 분석하고, 각 성분이 위상($\Phi$=0.22)인 상태에서의 관측자에 대해 어떠한 기하학적인 구조를 가지고 있는지 연구하였다. CLOUDY를 사용하여 광 이온 모형성운을 만들어 화학원소 및 성운가스의 물리적 조건을 연구하였다. Z And의 수소의 수밀도($N_H$)는 $10^{8.5}/cm^3$으로 가정하였다. 중심별 온도는 약 110,000K, 광도는 태양의 2000배로 추정되었다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.111-112
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• 2022

자율운항 선박, 무인선 개발과 동 분야 디지털트윈 구현을 위해서는 선박 내부 데이터의 수집을 담당할 고신뢰성 선내 통신망 확보가 필수적이다. WiFi와 같은 전파 기반의 무선통신 시스템은 금속 구조물로 구성되는 선박 내 환경 자체가 원활한 통신의 장애 요소이다. 이러한 극한 환경 극복을 위해 자기장을 금속 표면에 유기하여 비 전파 기반으로 무선통신을 가능하게 하는 표면파 통신이 대안이 될 수 있다. 선박 전체의 일반 배치 관점에서 표면파 통신은 상갑판을 통해 크게 거주구역, 화물구역, 선수구역 및 기관구역 간 백본 통신망을 구성할 수 있으며 각 구역 별로는 부재의 개구부를 통해 금속 표면의 연속면을 확보하여 통신할 수 있다. 수밀 격벽의 표면파 통신 관통을 위해 비 도전체로 수밀은 유지한 채 아주 미세한 구멍을 확보하는 것으로도 금속 표면의 연속성을 확보할 수 있다. 이러한 표면파 통신을 활용하면 전파 기반의 무선통신, 비 전파 기반의 무선통신을 통합적으로 구성하여 선박 전체로는 선내 무선 백본망 구성, 그리고 각 구역 별로는 IoT 센서 네트워크 등의 선박 내부 고신뢰성 무선통신 확보가 가능하다.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.57-64
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• 2006

The crack presented in concrete structures causes a structural defect, the durability decrease, and external damages etc. Therefore, it is necessary to improve durability through the effort to control the crack. Fluosilicic acid($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicates prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.0{\sim}2.0%$ of adding ratio of fluosilicate salt based inorganic compound. To evaluate correlation of concrete strength and adding ratio of fluosilicate salt based inorganic compound, the tests were performed about design strength(21, 24, 27 MPa) with 0.5% of adding ratio of fluosilicate salt based inorganic compound. Applications of fluosilicate salt based inorganic compound to reduce cracks resulted from plastic and drying shrinkage, to improve durability are presented in this paper. Durability was evaluated as neutralization, chloride ion penetration depth, freezing thawing resistant tests and weight loss according reinforcement corrosion. It is ascertained that the concrete added fluosilicate salt based inorganic compound showed m ability to reduce the total area and maximum crack width significantly as compared non-added concrete. In addition, the durability of concrete improved because of resistance to crack and watertightness by packing role of fluosilicate salt based inorganic compound obtained and pozzolanic reaction of soluble $SiO_2$ than non-added concrete.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.249-255
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• 2006

Recently, interest grew on the quality of aggregates following the diminution of primary resources from river as to grow construction demand and the low grade of nature sand like sea sand. following, need is to diversify the supply sources of fine aggregates which are excessively relying on sea sand and urgency is to find as soon as possible aggregate resources that can substitute sea sand. On the other hand, various fine aggregates we utilized to produce concrete in the domestic construction fields. However, few studies have been systematically investigated on the effects of such fine aggregates on concrete properties. Therefore, this study examined the effects of comparatively widely used fine aggregates in the domestic construction fields on the shrinkage, durability and watertightness of concrete. Results revealed that drying shrinkage increases, and durability and watertightness degrades for concrete using crushed sand than natural fine aggregates like sea sand and river sand. Especially, the use of crushed sand exhibiting bad grain shape and grade was larger adverse effect on the quality of concrete. In addition, appropriate adjustment of the grain shape and grade during the blending of crushed sand exhibiting bad grain shape and grade with natural aggregates appeared to enhance the shrinkage and durability of concrete.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.113-120
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• 2007

In this study, researches for the development of antibiotics and antimicrobial concrete were conducted to reduce biochemical corrosion of sewage concrete. First of all, desired performance, such as watertightness, antibiosis, homogeneity, workability and harmlessness, was proposed and performance of antibiotics and antimicrobial concrete were evaluated by them. As results of this study, dispersibility and antibiosis of liquid antibiotics superior to powdery antibiotics. Antibiosis of antimicrobial concrete was verified, and amount of elution of harmful and effective ingredients was little. In workability, setting time of antimicrobial concrete was delayed. Compressive strength and resistance to carbonation of antimicrobial concrete were more increased than ordinary concrete. Also, as little pore volume and closed structure of antimicrobial concrete were observed, watertightness of it was verified. Finally artificial accelerating test for biochemical corrosion was proposed, and its suitability was experimentally proved.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.749-755
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• 2004

Fluosilicic acid ($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicate salts prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicate salts to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. In this study, two-component fluosilicate salt based chemical admixtures (MZ) of $4\%,\;6\%$, and $8\%$ concentration were prepared by the reaction of $H_2SiF_6$ ($25\pm2\%$) and metal salts. The effect of concentration of MZ at a constant adding ratio on the hydration and watertightness of cement were investigated respectively. In a cement containing MZ, metal fluorides such as $CaF_2$ and soluble silica by hydrolysis were newly formed during hydration. The total porosity of the hardened cement was lower in the presence of U because of packing role of metal fluoride and pozzolanic reaction of soluble $SiO_2$. Consequently, the watertightness of the hardened paste containing MZ was more improved than non-added (plain) due to an odd hydration between cement and MZ.

• Korean Journal of Environment and Ecology
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• v.25 no.4
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• pp.516-525
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• 2011

We studied the influence certain environmental factors (proximity of roosting site, roads, and residential areas) have on the spatial distribution of cranes in the Cheorwon, Korea. Using a range finder and GPS, data were collected from January to February 2007 and were subsequently evaluated with ArcGIS. The size of the cranes' wintering habitat was estimated to be 7$76.9km^2$. Five hundred and fifty-five flocks of cranes were observed and detailed distributions were collected. Feeding distribution of the cranes showed clustered distribution, however, no tendencies of spatial autocorrelation were apparent. Adjacent regions with paved roads and residences showed lower densities than other areas. Distances at which paved roads and residential areas induced changes in feeding flock densities were 1500m and 1750m, respectively. Feeding flock density decreased with increased distance from roosting site. Feeding flock density of the two crane species did not increase as distance from roads increased, however, the density of individuals showed a significant increasing tendency with increased distance from roads. In both species, density of feeding flocks and individuals significantly increased with increasing distance from residential areas. In Red-crowned Cranes, the density of feeding flocks and individuals significantly decreased with increasing distance from roosting site, however, in the case of White-naped Cranes, there was an even distribution in density of feeding flocks and individuals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.182-188
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• 2016

A decoy is a weapon system that can protect vessels from an enemy's torpedo. Thus, the decoy should be able to operate in the field without any failure. Because the decoy can be inoperable once its sealing is broken and water permeates inside the system, the hermetic sealing capability considering the operational environment is mandatory. To be hermetically sealed, a rubber-type O-ring is generally used in a decoy system. The sealed performance of rubber-type products, however, tends to age and deteriorate with time. Therefore, the O-ring needs to be maintained or changed periodically. This paper proposes a method to estimate the proper maintenance period using the hardness and elongation percentage, which represents the performance of the O-ring product and test data from Accelerated Life Test (ALT) of the product. The O-ring used in this paper is a NBR type, and the temperature was chosen to be the main accelerating factor as referenced in many studies. The criteria for the failure of the O-ring was set for the product to be 50% degraded compared to the initial performance. In addition, the Korean standard KS M 6518 was adopted and referenced for the preparation of test samples and the calculation of estimates. The O-ring's predicted life was simulated by analyzing the test results from a computer program, and the optimized maintenance period for the product was determined.

• Proceedings of KOSOMES biannual meeting
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• 2018.06a
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• pp.25-25
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• 2018