• 한국강구조학회 논문집
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• 제9권4호통권33호
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• pp.673-682
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• 1997

이 논문에서는 회전관성과 전단변형이 변화곡률 아치의 고유진동수에 미치는 영향을 분석하였다. 임의의 변화곡률을 갖는 등단면 아치의 자유진동을 지배하는 미분방정식을 유도하였으며, 유도된 미분방정식에 회전-회전, 회전-고정 및 고정-고정의 단부조건을 갖는 포물선, 원호 및 타원 아치를 적용하여 수치해석하였다. 해석결과로서 무차원 변수인 아치높이 지간길이비 및 세장비 변화에 따론 최저차 4개의 무차원 고유진동수를 산출하였다.

• 한국산학기술학회논문지
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• 제8권6호
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• pp.1325-1331
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• 2007

본 연구에서는 냉방운전 시 가변용량방식의 압축기를 적용한 시스템 에어컨의 냉방능력과 증발기 및 응축기의 온도특성을 조사하기 위해 압축기 운전율(10가지)과 실내외 온도(16가지)의 변화에 따른 시스템의 운전특성을 실험적으로 조사하였다. 시스템의 운전특성은 칼로리미터를 이용하여 측정되었다. 냉방능력은 실외온도가 낮아질수록 실내온도가 증가할수록 더 큰 값을 그리고 압축기 운전율이 증가할수록 냉방능력은 선형적으로 증가하였다. 응축온도는 실외온도 변화에 증발온도는 실내온도 변화에 더 민감하였다. 또한 압력-엔탈피선도를 이용하여 사이클의 운전특성을 분석하였다.

• Smart Structures and Systems
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• 제13권2호
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• pp.319-341
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• 2014

A family of smart tuned mass dampers (STMDs) with variable frequency and damping properties is analyzed under harmonic excitations and ground motions. Two types of STMDs are studied: one is realized by a semi-active independently variable stiffness (SAIVS) device and the other is realized by a pendulum with an adjustable length. Based on the feedback signal, the angle of the SAIVS device or the length of the pendulum is adjusted by using a servomotor such that the frequency of the STMD matches the dominant excitation frequency in real-time. Closed-form solutions are derived for the two types of STMDs under harmonic excitations and ground motions. Results indicate that a small damping ratio (zero damping is the best theoretically) and an appropriate mass ratio can produce significant reduction when compared to the case with no tuned mass damper. Experiments are conducted to verify the theoretical result of the smart pendulum TMD (SPTMD). Frequency tuning of the SPTMD is implemented through tracking and analyzing the signal of the excitation using a short time Fourier transformation (STFT) based control algorithm. It is found that the theoretical model can predict the structural responses well. Both the SAIVS STMD and the SPTMD can significantly attenuate the structural responses and outperform the conventional passive TMDs.

• The Journal of Asian Finance, Economics and Business
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• 제8권2호
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• pp.165-173
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• 2021

This study examined the effect of Debt Equity Ratio (DER), Net Profit Margin (NPM), and Size on stock prices with company performance as measured by Return on Assets (ROA) as a mediating variable. The sample used is 136 manufacturing companies listed on the Indonesia Stock Exchange (IDX) in the 2014-2018 period. This research was tested using a Warp PLS statistical test tool to prove the proposed hypothesis. The results showed that DER has a significant negative effect on ROA and a significant positive effect on Stock Price. NPM has a significant positive effect on ROA as well as a significant positive effect on Stock Price. While Size has a significant positive effect on ROA but has no effect on Stock Price. ROA has a significant positive effect on Stock Price. ROA does not act as a mediating variable in the relationship between Size and Stock Price; however, ROA acts as a mediating variable in the DER and Stock Price relationship, as well as, in the relationship between NPM and Stock Price. The implications of the results of this study can be used by investors in making investment decisions, paying attention to the company's financial aspects, namely DER, NPM, Size, and ROA.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.229-232
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• 1999

This study provided the engineering properties of the recycled aggregate concrete with fly-ash and silica-fume. There are considered recycled aggregate substitution ratio, and fly-ash silica-fume mix ratio as the experimental variable. From the experimental result, we could know that the recycled aggregate concrete mixed silica-fume is superior on the compressive strength but, is poor on the construction property than fly-ash. The optimal mix ratio of the fly-ash and silica-fume is 10% in all.

• Journal of the Korean Statistical Society
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• 제23권2호
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• pp.239-250
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• 1994

In this paper, we prove a strong large deviations theorem for the ratio of independent randoem variables with error rate of $O(n^{-1})$. To obtain our results we use the inversion formula for the tail probability and apply the Chaganty and Sethuraman's (1985) approach.

• Communications for Statistical Applications and Methods
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• 제11권2호
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• pp.419-433
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• 2004

We suggest the modified computing algorithm for raking ratio estimation under the assumption that the population total is partially known, and the sample total is completely known about survey variable in contingency table. We show that the proposed estimation procedure is useful to estimate the population cell count in this situation through an empirical study.

• 수산경영론집
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• 제42권2호
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• pp.1-14
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• 2011

We try to find the determinants of fisheries firms' capital structure during the years from 1992 to 2007 in this paper. We also have a comparative analysis of capital raising behavior in pre and post-IMF financial crisis. Regression analysis is used for this empirical study. Dependent variable is leverage ratio and independent variables are firm size, operating risk, proportion of tangible asset, non-debt tax shield effect, sales growth ratio, profitability and dummy variable. We compared the characteristics of fisheries industry with that of manufacturing industy. The determinants of fisheries firms' capital structure and correlation between pre and post-IMF financial crisis are roughly same as the hypothses except a little difference. As a peculiar difference, corrlation between fisheries firms' operating risk and leverage ratio is (+) in the pre-IMF financial crisis, but (-) in the post-IMF financial crisis. Proportion of tangible asset has a (+) correlation with leverage ratio in pre and post-IMF financial crisis, but in case of manufacturing industy, (-) correlation shows in the pre-IMF financial crisis. Because, in the pre-IMF financial crisis, high proportion of tangible asset doesn't play a role of a collateral, but only increase the bankruptcy probability. Non-debt tax shield effect and leverage ratio have (-) correlation in all industry and all period, but only (+) correlation in case of fisheries industry in the pre-IMF financial crisis. Sales growth ratio has no significant relationship with leverage ratio in fisheries industry, and this is not coincide with our hypothsis. We have a limitation of the sample size of fisheries firms and sample period in this study. Further study is required to classify the fisheries industry with in-shore fisheries, deep sea fisheries and cold storage industry.

• 한국정밀공학회지
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• 제20권9호
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• pp.205-213
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• 2003

This study describes the mathematical equation of drawdown test model and introduces the experimental test apparatus and procedure to estimate the desorption rate ratio of a filter. The characteristics of a hydraulic filtration system of drawdown test were demonstrated by numerical simulation for various properties of filters and operation conditions. Experiments for three kinds of fuel filters were conducted according to the proposed test method. And the test results of desorption rate ratio were compared with those values anticipated in precedent multipass filtration tests. Experimental results revealed the validation of drawdown test method proposed in this study. Domestic fuel filter yielded high desorption rate ratio comparing with other foreign products, which means that the Beta ratio decreases a lot during the test. The results also showed that filtration system model could be developed including desorption rate ratio to estimate the variable Beta ratio in service life.

• 제어로봇시스템학회논문지
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• 제9권5호
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• pp.361-367
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• 2003

We propose an algorithm to detect the face region using a variable ellipsoidal mask and a neural network. Since outlines of human faces are similar to ellipsoid, the ellipsoidal mask that has the fixed ratio of major and minor axis can be used to detect the candidate area. The positions of eyes and lips are extracted in this candidate area, and then the morphological analysis is applied to make features which are consist of six parameters, such as the geometrical ratio of eyes and lips. A back-propagation neural network is used as a classifier to determine the most possible face region. The experimental result is conducted to verify its efficiency compared with those of previous works.