• 한국항해학회지
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• 제5권2호
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• pp.49-58
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• 1981

One of the main purposes of the marine gyrocompass follow-up system is to preserve the sensitive part from the wandering error due to the frictional or torsional torque around the vertical axis. This error can be diminished through the rapid follow-up action, which minimizes the relative azimuthal angular displacement between the sensitive and follow-up parts and shortens the duration of the same displacement. But an excessive rapidity of the follow-up action would result in a sustained oscillation to the system. Therefore, to design a new type of the follow-up system, the theoretical annlysis of the problems concerned should be studied systematically by introducing the control theory. This paper suggest a concrete procedure for the optimal adjustment of the gyrocompass follow-up system, utilizing the mathematic model and the stability informations formerly investiaged by the author. For theoptimal determination of the adjustable paramfter K, the performance index(P.I.), ITSE(Intergral of the Time multiplied by the Squared Error) is proposed, namely, P.I. = $\int_{0}^{\infty} t \cdot e^{2}(t)dt$ where t is time and e(t) means control error. Then, the optimal parameter minimizing the performance index is calculated by means of Parseval's theorem and numerical computation, and the validity of the obtained optimal value of the parameter Ka is examined and confirmed through the simulations and experiments. By using, the proposed method, the optimal adjustment can be performed deterministically. But, this can not be expected in the conventional frequency domain analysis. While the Mps of the original system vary to the extent of from 0.98 to 46.27, Mp of the optimal system is evaluated as 1.1 which satisfies the generally accepted frequency domain specification.

• Structural Engineering and Mechanics
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• 제68권6호
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• pp.747-760
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• 2018

In the present study, a methodology for developing fragilities of arch concrete dams to assess their performance against seismic hazards is introduced. Firstly, the probability risk and fragility curves are presented, followed by implementation and representation of the way this method is used. Amirkabir arch concrete dam was subjected to non-linear dynamic analyses. A modified three dimensional rotating smeared crack model was used to take the nonlinear behavior of mass concrete into account. The proposed model considers major characteristics of mass concrete. These characteristics are pre-softening behavior, softening initiation criteria, fracture energy conservation, suitable damping mechanism and strain rate effect. In the present analysis, complete fluid-structure interaction is included to account for appropriate fluid compressibility and absorptive reservoir boundary conditions. In this study, the Amirkabir arch concrete dam is subjected to a set of 8 three-component earthquakes each scaled to 10 increasing intensity levels. Using proposed nonlinear smeared crack model, nonlinear analysis is performed where the structure is subjected to a large set of scaled and un-scaled ground motions and the maximum responses are extracted for each one and plotted. Based on the results, fragility curves were plotted according to various and possible damages indexes. Discrete damage probabilities were calculated using statistical methods for each considered performance level and incremental nonlinear analysis. Then, fragility curves were constructed based on the lognormal distribution assumption. Two damage indexes were introduced and compared to one another. The results indicate that the dam has a proper stability under earthquake conditions at MCE level. Moreover, displacement damages index is more conservative and impractical in the fragility analysis than tensional damage index.

• 서비스연구
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• 제6권2호
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• pp.99-116
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• 2016

본 연구의 목적은 금리추세가 국내생명보험회사들의 자산운용 실태에 미치는 영향을 분석하여 문제점을 도출하고, 자산운용전략에 대한 방향성을 제시하고자 하였다. 연구방법은 2000년~2014년 동안에 국내 생명보험회사들의 자산현황 및 운용자산 내역, 자산배분실태, 유가증권 내역을 시계열 분석하였고, 총자산 및 자산별 수익률을 분석하였으며, 금리 주가와 운용수익률 간의 상관관계와 회귀분석을 실시하였다. 분석결과는 안전자산인 국공채의 비중은 증가한 반면에 위험자산인 주식의 비중은 감소하여 수익성 보다 안정성 위주로 자산운용을 하고 있었다. 금리와 총자산수익률, 운용자산수익률, 유가증권수익률 간에 높은 양(+)의 상관계수가 산출되었으며, 금리와의 상관관계에서 총자산수익률 보다는 운용자산수익률의 상관관계가 높았고, 운용자산수익률 보다는 유가증권수익률의 상관관계가 더 높았다. KOSPI 주가지수와 운용수익률 간에는 상관계수가 음(-)으로 나타났다. 시사점은 안정성 위주의 자산운용으로 금리하락이 역마진 리스크를 높이고 있어서 자산운용의 변화가 필요하다는 것이다.

• PNF and Movement
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• 제16권3호
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• pp.405-414
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• 2018

Purpose: The purpose of this study was to examine test-retest reliability and criterion-related validity of a trunk stability robot when measuring the weight-bearing symmetry static sitting and standing in stroke patients. Methods: For 27 stroke patients, weight-bearing symmetry was assessed twice, 7 days apart. The intraclass correlation coefficient (ICC2,1) and minimal detectable change (MDC) were used to examine the level of agreement between test and retest. The criterion-related validity of weight -bearing symmetry was demonstrated by Spearman correlation of modified Barthel index (MBI), the sit to stand test (STS), the timed up & go Test (TUG), and the function in sitting test (FIST). Results: the test-retest agreements were excellent for the weight-bearing symmetry of static sitting (ICC2,1: 0.90) and standing (ICC2,1: 0.89). It all showed that the acceptable MDC for the weight-bearing symmetry of static sitting and standing was 0.11 and 0.16, respectively (highest possible score<20 %), indicating that the measures had a small and acceptable degree of measurement error. The weight-bearing symmetry of static sitting was significantly correlated with the TUG(r=-0.45) and FIST(r=0.46)(p<0.05); the weight-bearing symmetry of static standing was also significantly correlated with MBI (r=0.65), TUG (r=-0.67), FIST (r=0.61)(p<0.01), and STS (r=-0.47)(p<0.05). Conclusion: The weight-bearing symmetry of static sitting and standing assessed by the trunk stability robot showed highly sufficient test-retest agreement and mild-to-moderate validity. It could also be useful for clinicians and researchers to evaluate balance performance and monitor functional change in stroke patients.

• 대기
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• 제18권4호
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• pp.441-458
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• 2008

A TP/WVP-3000A, ground-based microwave radiometer, that was first introduced to South Korea has been operated since August 22, 2007 at the National Center for Intensive Observation of Severe Weathers (NCIO). Using the dual-band, the radiometer provides temperature and humidity soundings from the surface up to 10 km height with the high-temporal resolution of a few minutes. In this study, the performance of the radiometer on the predictability of the high impact weathers was evaluated and various practical applications were investigated. To verify the retrieved profile data from the radiometer, temperature and relative humidity soundings are compared with those from the rawinsonde launched at the NCIO and Gwangju station. The root mean squared errors for temperature and relative humidity soundings were smaller under rainy weather conditions. The correlation coefficient between PWVs (Precipitable Water Vapors) obtained from the radiometer and Global Positioning System satellite at Mokpo station is 0.92 on average. In order to investigate the structure and characteristics of precipitation, stability indexes related to rainfall such as the Convective Available Potential Energy (CAPE), K-index, and Storm RElative Helicity (SREH) were calculated using windprofiler at the NCIO from 14 to 16 September, 2007. CAPE and K-index tended to be large when the thermodynamic unstability was strong. On the other hand, SREH index was dominantly large when the dynamic unstability was strong due to the passage of the typhoon 'Nari'.

• 폴리머
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• 제39권2호
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• pp.346-352
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• 2015

폴리알파올레핀(PAO)은 유동점, 점도지수, 열/산화 안정성이 광유 기반의 윤활유보다 우수한 합성 윤활유이다. 본 연구에서는 1-펜텐, 1-헥센, 1-옥텐, 및 1-도데센을 단량체로 사용하고 세가지 종류의 알루미늄계 루이스 산촉매로 양이온 중합을 수행하여 다양한 PAO를 합성하였다. PAO 중합 성능과 제조된 PAO의 분자량, 동점도, 유동점과 점도지수를 다양한 중합 조건에서 조절할 수 있었다. 알킬 알루미늄 할라이드계 촉매가 기존의 $AlCl_3$계 촉매에 비하여 촉매 성능이 우수하였다. PAO의 미세구조를 비행-시간형 질량분석기(TOF-MS) 해석을 통하여 PAO의 미세구조와 윤활유로의 성능(점도지수, 유동점)과의 상관관계를 규명하였다. 특히, PAO의 점도지수는 알파 올레핀의 탄소수 증가에 따라 상승하여, PAO의 분지길이가 점도지수와 밀접한 상관관계가 있음을 확인하였다.

• 대한물리의학회지
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• 제14권1호
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• pp.139-150
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• 2019

PURPOSE: This study was conducted to determine the effects of treadmill gait training with obstacle-crossing on the static and dynamic balance ability of patients with post stroke hemiplegia. METHODS: Twenty-one patients with post stroke hemiplegia were divided into three groups as: treadmill gait training with obstacle-crossing (TOG, n=7), treadmill gait training without obstacle-crossing (TGG, n=7) and a control (CON, n=7). TOG and TGG performed exercise for 20 minutes, three times a week for 8 weeks. Static balance ability (stability typical, ST; weight distribution index, WDI; fourier harmony index, FHI; and fall index, FI) and dynamic balance ability (berg balance scale, BBS and timed up and go test, TUG) were measured before and after 8 -weeks in each exercise group. Statistical analyses were conducted using two-way ANOVA with repeated measures, a paired t-test, and multiple comparisons according to Tukey's HSD. RESULTS: FHI and BBS were significantly increased at TOG (p<.01) and TGG (p<.05) after 8-weeks compared to before treadmill gait training with obstacle-crossing. FHI and BBS were significantly increased at TOG compared with CON and TGG (p<.05). CONCLUSION: Treadmill gait training with obstacle-crossing was more effective than that without obstacle-crossing to improve posture control and independent daily life performance of hemiplegia patients.

• 한국조리학회지
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• 제15권4호
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• pp.212-226
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• 2009

본 연구는 금융감독원 전자공시시스템에 공시된 기업의 재무제표를 활용하여 외식 기업의 재무 비율과 경영 성과의 관계를 파악하고자 하였다. 재무 비율은 재무제표의 두 계정을 조합하여 비율을 계산하여 경영 성과를 제시하는 지표로써, 경영자와 채권자 그리고 투자자는 해당 기업의 재무제표를 평가하기 위한 방법으로 비율 분석을 각기 다른 목적으로 사용하고 있다. 재무 비율과 경영 성과에 대한 분석에 의하면, 상장된 음식료업종 기업은 이자 보상 배율을 제외한 전 부분에서 상관 관계를 보였지만, 외식 기업은 안정성 비율과 성장성비율에 한정해서 상관 관계를 보여주었다. 이와 같은 차이에 근거하여 외식 기업의 경영자는 부채와 자산에 대한 관리와 더불어 비용에 대한 효과적이고 계획적인 관리를 통하여 경영 성과를 개선하여야 할 것이다.

• 서비스연구
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• 제5권2호
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• pp.35-49
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• 2015

본 연구는 금리추세에 따른 국내손해보험회사들의 자산운용 실태를 분석하여 문제점을 도출하고, 자산운용전략에 대한 방향을 제안하고자 2009년~2014년까지의 자료를 바탕으로 연구하였다. 손해보험회사들의 자산현황 및 운용자산 내역, 자산배분실태, 유가증권 내역, 총자산수익률을 시계열 분석하였으며, 금리 주가와 총자산수익률의 상관관계 분석을 실시하였다. 연구결과는 안전자산인 국공특수채의 비중은 증가한 반면에 Credit물인 금융회사채 및 위험자산인 주식의 비중은 감소하여 수익성 보다 안정성 위주로 자산운용을 하고 있었다. 금리하락 추세에 따라 총자산수익률도 같이 하락하고 있었으며, 주가지수 추이와 총자산수익률 추이는 일치하지 않았다. 금리와 총자산수익률 간에는 높은 양(+)의 상관계수가 산출되었지만, KOSPI 주가지수와 총자산수익률 간에는 상관계수가 음(-)으로 나타났다.

• 한국산학기술학회논문지
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• 제20권6호
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• pp.188-200
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• 2019

본 연구의 목적은 교육복지우선지원사업 성과지표 개발 연구의 연장선으로, 학교 현장에의 적용을 위해 내용타당도를 확보하는 것이다. 본 연구에 사용된 교육복지우선지원사업 성과지표(안)은 6개 대영역, 33개 하위영역, 233개 문항으로 구성되었다. 교육복지 분야 박사급 전문가 5인을 대상으로 2회의 전문가 회의를 실시하였고, 현장에서 5년 이상 근무한 교육복지사 99명을 대상으로 델파이조사를 실시하였다. 문항 선정 기준($CVR{\geq}.29$, $CVI{\geq}.80$, 수렴도<.50, 합의도${\geq}.05$, 안정도${\leq}.80$, $M{\geq}3.00$, SD<.80, 신뢰도${\geq}.6$)을 적용하여, 6개 대영역, 23개 하위영역, 93개 문항에 대해 타당성을 확보하였고, 이 중 신뢰도가 낮은 3문항을 제외하여 최종 90문항으로 확정하였다. 교육복지우선지원사업 성과지표가 현장에서 보다 유용하게 활용되기 위한 제언과 후속 연구를 제시하였다.