• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 추계학술발표회
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• pp.15-18
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• 2001

Sixty natural springs and wells used as community facilities for drinking water are developed along mountain climbing way of suburban area and residential area in Daejeon City. In this study, the seasonal variation of their water quality and hydrochemical characteristics were investigated. Some natural springs are vulnerable to bacilli contamination because of their short residence time and shallow circulation in subsurface environment. The waters show hydrochemical types of Ca-HCO$_3$ and Na-HCO$_3$, and are characterized by low electrical conductance and weak acidic pH.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.218-218
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• 2019

Jeju island has an area of $1,810km^2$ and is considered the largest island in South Korea. In Jeju Island the average annual precipitation is 1,957mm. About 54% of precipitation is estimated to be lost due to evapo-transpiration and direct runoff, and the remainder is recharged. Historically springs and puddles were the island's primary sources of water. However, after 1970 all sectors, including the urban and industrial sectors depended solely on groundwater as their water resource. As vast amount of water is being recharged the Island has many springs, especially near the coastlines. Historlcally, spring of Jeju Island formed village and make it possible to continue a life. Also it produces many values such as the spring related story, culture, tourism and ecosystems. Especially, the naturally rare phenomenon that about 900 springs appear over the whole area of Jeju Island makes it possible to call it as a natural heritage. As a result of this most springs have either been destroyed or been in the state of neglect. In some cases it has been observed that springs were preserved by nature, however majority of the cases saw springs losing their own nature as a result of abandonment. It was recorded that there were 911 springs in Jeju Island with most of them being distributed along the coast, which consequently increases their susceptibility to seawater intrusion. The objective of this study is therefore to analyze Eco-cultural and Engineering characteristics about springs in the island, highlighting its past utilization and reestablishing its potential as a source of spring.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.35-42
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• 1999

This study is to analyze the buckling and the vibration of the rectangular stiffened plates with elastic springs by Finite Element Method. Boundary conditions are two types, one is all simply supported edges, another all clamped edges. To validate Finite Element Method, the buckling stresses of the stiffened plates without elastic springs are compared with the existing ones. The natural frequency parameters of the stiffened plates with or without elastic springs by Finite Element Method are also compared with the ones of SAP2000. The natural frequency parameters and the buckling stresses of the stiffened plates with elastic springs by Finite Element Method are calculated for the variation of the stiffness of the elastic springs and aspect ratio.

• 자원환경지질
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• 제35권5호
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• pp.395-406
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• 2002

도시지역에는 소위 약수라고 지칭되는 먹는 물 공동시설이 지정되어 있다. 먹는 물 공동시설은 도시외곽의 자연녹지나 공원의 등산로를 따라서 자연적으로 솟아나는 샘의 형태와 인위적으로 굴착하여 개발한 우물지하수로 구분된다. 본 연구에서는 대전지역 60개 지역 먹는 물 공동시설에 대한 1999년~2000년 동안의 수질자료를 보건환경연구원으로부터 협조 받아 통계분석과 수질오염의 원인을 해석하였다. 음용수 부적합 율은 1999년에 28%, 2000년에 24.5%를 각각 보였다. 부적합 요인은 대장균류가 대부분이고 일반세균, 여시니아균, 탁도, 색도, 철, 불소 둥의 초과가 확인되었다. 월별 강수량과 부적합 율과의 관계를 비교해 볼 때 강수량이 집중되는 6월~9월 사이에 부적합율이 현저하게 높다. 세균류에 의한 오염은 먹는 물 시설주변에 서식하는 야생동물들의 배설물이 주요 오염원으로 추정된다. 그리고 대부분의 먹는 물 공동시설은 물의 순환 주기가 짧은 천부지하수(자연샘)이므로 강수직후에 지표부의 세균류가 빠르게 물을 오염시키는 것으로 보인다. 먹는 물 공동시설중 31곳에서 물 시료를 채취하여 물리화학성분을 분석하였다. 그들의 전기전도도는 63~357 $\mu\textrm{S}$/cm 범위를 보이며, 평균 107 $\mu\textrm{S}$/cm으로 대전지역 일반지하수에 비해 훨씬 낮다. pH는 대부분이 7이하로 약산성의 특성을 보인다. 수리화학적 유형은 TDS가 낮은 물의 경우 Na(Ca)-HCO$_3$형이고 TDS가 높아질수록 Ca-HCO$_3$형인 특성을 보인다. 먹는 물 공동시설의 효율적 관리를 위해서는 시설 입구에 들짐승들의 접근을 막을 수 있는 방호벽을 설치하고 주변의 청결상태를 유지하여야 할 것이다. 그리고 강우가 집중되는 장마철에는 시설을 잠정적으로 폐쇄하는 것이 바람직 할 것이다.원 이하인 사람보다 200만원 이상인 사람이(P=0.001), 방송이나 친구를 통해서 지식을 얻은 사람보다 신문이나 책을 통해서 지식을 얻은 사람이(P=0.01), 과거 병력상 성병에 걸린 경험이 있는 사람보다 경험이 없는 사람이(P=0.002) 각각 지식이 높았다. 태도와 지식 관계에서는 후천성 면역 결핍증 환자는 다른 사람으로부터 격리시킬 필요가 있다는 사람보다 없다는 사람이(P=0.012), 후천성 면역 결핍증 환자가 직업을 가지면 안된다는 사람보다 된다는 사람이(P<0.001), 각각 지식이 높았다. 결론 : 지식이 높을수록 성병에 걸릴 가능성이 낮고, 태도에서도 긍정적인 결과를 보였다. 그러므로 그러므로 가능하면 중고교 시절에 이 질환에 대한 정규교육 프로그램을 만들어 학생들을 효과적으로 가르치는 것이 필요하다.와 활동성 정도(r=0.378, P<.05), 평균 통증정도와 활동성 정도가(r=.330, P<.05)가 유의한 정적상관관계가 나타난 반면, 여성에서는 활동성 정도와 통증의 중증도는 유의한 관계가 없는 것으로 나타났다. 남성은 관계를 제외한 모든 항목의 통증으로 인한 지장정도와 활동성 정도가 유의한 정적상관관계가 나타난 반만 여성에서는 보행 능력, 통상적인 일, 인생을 즐김 항목과 활동성 정도간 유의한 정적 상관관계가 있었다. 결론 : 암환자의 통증정도 및 지장정도는 여성이 남성보다 높았으며, 통증과 우울 및 활동도와의 상관관계에서 차이를 보였다. 앞으로 암성통증 관리 대책 수립시 여성과 남성의 이러한 차이를 고려하여야 한다.로 6시간 공배양시키는 것이 바람직하며, HEPES buffered NCSU-23 배양배지에서 배양하는 것이 좋다는 결과를 얻었다. and those a having sufficient sleep were found to be subject to less stress. Those interested in their health were

• Animal cells and systems
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• 제11권1호
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• pp.61-68
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• 2007

A new cyclopoid species belonging to the genus Acanthocyclops is described from several mountain springs in South Korea. This species is allied to A. kieferi species group in sharing 11-segmented antennules, but is, clearly distinguished from them by its single apical spine on the third endopodal segment of leg 4 and an extra spine on the distal segment of leg 5 in both sexes.

• 산업기술연구
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• 제20권B호
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• pp.105-113
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• 2000

Air springs are now widely used in bus or truck suspensions due to their advantages over conventional metal spring as coil or leaf springs. Air springs have soft spring rates, which give better ride quality, and additional leveling system provides constant ride height and maintains almost same vertical natural frequencies. A mathematical model of an air spring suspension system with height control system is constructed and dynamic responses of the suspension system are investigated in the light of leveling valve motion characteristic, vertical motion natural frequency. Also, using a full vehicle model, handling characteristics of an air spring suspension is studied and the results are compared with real test results, which shows good agreements.

• 한국정밀공학회지
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• 제12권7호
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• pp.82-91
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• 1995

Many kind of springs are used in the suspension of automotive vehicles and among these the leaf spring and the air spring are included. These two springs have not been generally used together in one suspension, but recently the automotive models which use these two springs together increase. This reason is due to the merit of the combination of two type springs. The merits are two. One is the character of air spring, that is, the natural frequen- cy of system is constant in spite of variable weight. The other is the character of leaf spring, that is, the suspension mechanism is simple. The combination spring is used in medium size and special purpose bus. In this paper, we formulate the condition which the leaf spring must satisfy to be optimal design in the combination spring. And experiment is performed to prove the theory. The results are that the combination spring is better than leaf spring in the ride, and that the purposed theory is good for the combination spring design.

• Structural Engineering and Mechanics
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• 제29권5호
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• pp.531-550
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• 2008

This paper adopts the numerical assembly method (NAM) to determine the exact solutions of natural frequencies and mode shapes of a multi-span and multi-step beam carrying a number of various concentrated elements including point masses, rotary inertias, linear springs, rotational springs and springmass systems. First, the coefficient matrix for an intermediate station with various concentrated elements, cross-section change and/or pinned support and the ones for the left-end and right-end supports of a beam are derived. Next, the overall coefficient matrix for the entire beam is obtained using the numerical assembly technique of the conventional finite element method (FEM). Finally, the exact solutions for the natural frequencies of the vibrating system are determined by equating the determinant of the last overall coefficient matrix to zero and the associated mode shapes are obtained by substituting the corresponding values of integration constants into the associated eigenfunctions.

• Structural Engineering and Mechanics
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• 제27권1호
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• pp.17-32
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• 2007

The main source of transverse vibration of a conveyor belt is frictional contact between pulley and belt. Also, environmental characteristics such as natural dampers and springs affect natural frequencies, stability and bifurcation points of system. These phenomena can be modeled by a small velocity fluctuation about mean velocity. Also, viscoelastic foundation can be modeled as the dampers and springs with continuous characteristics. In this study, non-linear vibration of a conveyor belt supported partially by a distributed viscoelastic foundation is investigated. Perturbation method is applied to obtain a closed form analytic solutions. Finally, numerical simulations are presented to show stiffness, damping coefficient, foundation length, non-linearity and mean velocity effects on location of bifurcation points, natural frequencies and stability of solutions.

• Structural Engineering and Mechanics
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• 제22권6호
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• pp.701-717
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• 2006

In the existing reports regarding free transverse vibrations of the Euler-Bernoulli beams, most of them studied a uniform beam carrying various concentrated elements (such as point masses, rotary inertias, linear springs, rotational springs, spring-mass systems, ${\ldots}$, etc.) or a stepped beam with one to three step changes in cross-sections but without any attachments. The purpose of this paper is to utilize the numerical assembly method (NAM) to determine the exact natural frequencies and mode shapes of the multiple-step Euler-Bernoulli beams carrying a number of lumped masses and rotary inertias. First, the coefficient matrices for an intermediate lumped mass (and rotary inertia), left-end support and right-end support of a multiple-step beam are derived. Next, the overall coefficient matrix for the whole vibrating system is obtained using the numerical assembly technique of the conventional finite element method (FEM). Finally, the exact natural frequencies and the associated mode shapes of the vibrating system are determined by equating the determinant of the last overall coefficient matrix to zero and substituting the corresponding values of integration constants into the associated eigenfunctions, respectively. The effects of distribution of lumped masses and rotary inertias on the dynamic characteristics of the multiple-step beam are also studied.