• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.129-135
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• 1996

This paper presents the effectiveness of the dynamic vibration absorber consisting of a single mass, coil springs and oil damper on the resonance freauency ratio and amplitude ratio for damped linear systems, that is, primary vibration system with damping. The effects of the dynamic vibration absorber are investigated numerically and experimentally for values of mass ratio, natural frequency ratio, and damping ratio. The experimental results show good agreement with calculated ones. As a result, the characteristics shown by the present work are useful in optimal tuning the dynamic vibration absorber in practice.

• Structural Engineering and Mechanics
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• v.80 no.6
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• pp.657-668
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• 2021

In this study, a relationship between the resonance frequency ratio and Poisson's ratio was proposed that can be used to directly determine the elastic constants. Using this relationship, the frequency ratio between the 1st bending mode and 2nd bending mode for any rectangular Timoshenko beam can be directly estimated and used to determine the elastic constants efficiently. The exact solution of the Timoshenko beam vibration frequency equation under free-free boundary conditions was determined with an accurate shear shape factor. The highest percent difference for the frequency ratio between the theoretical values and the estimated values for all the beam dimensions studied was less than 0.02%. The proposed equations were used to obtain the elastic constants of beams with different material properties and dimensions using the first two measured transverse bending frequencies. Results show that using the equations proposed in this study, the Young's modulus and Poisson's ratio of rectangular Timoshenko beams can be determined more efficiently and accurately than those obtained from industry standards such as ASTM E1876-15 without the need to test the torsional vibration.

• Journal of the Korean Operations Research and Management Science Society
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• v.38 no.1
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• pp.183-199
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• 2013

This study investigates customers' different behavior in accumulating and redeeming points and focuses on the moderating effect of usage level. We measure the hedonic accumulation and redemption ratio and usage level using loyalty program transaction data and link them to the survey data of loyalty and satisfaction. By doing so, we examine the effects of hedonic accumulation and redemption ratio on a consumer's loyalty intention and his or her satisfaction and the moderating effect of usage level. The result shows that there is a significant positive effect of hedonic accumulation and redemption ratio on customer loyalty and the mediating role of satisfaction on customer loyalty in both stages. And accumulation and redemption most importantly, we find an interaction effect of usage level on outlet type in point redemption stage while no effect in accumulation stage. That is if customers accumulate and redeem points at a hedonic outlets in both stages, it will give him a feeling of satisfaction and finally it will enhance the loyalty toward the focal loyalty program. And light buyers' loyalty increase more than those of heavy buyers when they redeem points in hedonic outlet. Our findings will help marketing managers of loyalty program to apply the effective segmentation strategy to the reward program which affects the customer's satisfaction and loyalty.

• Asia-Pacific Journal of Business
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• v.12 no.3
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• pp.329-342
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• 2021

Purpose - The purpose of this study is to analyze the effect of investment by the National Pension Service, which has a high share as a single fund, on the dividend payout ratio. Design/methodology/approach - This study secured a share through DART of the Financial Supervisory Service and disclosure of the National Pension Service. We also used a fixed-effects model and 2SLS to analyze the data. Findings - First, it was found that there was a possibility of conflicting interests among shareholders concerning the company's dividend payment policy. Second, in the range of 3% to 4.9% of the National Pension Service shareholding, an additional increase in the holding ratio was found to have a positive (+) effect on the dividend rate. Third, after the introduction of the Stewardship Code, it was found that the increase in ownership of the fund had a positive (+) effect on the company's dividend payout ratio, regardless of the share ratio range. Moreover, the relationship between the fund ownership and the dividend payout ratio showed a clear positive relationship when free cash flow was high along investment opportunities were low. Research implications or Originality - First, This study included less than 5% of the share in the analysis. Second, We used the recent changes in fund shareholder activities. Third, We tested an instrumental variable to confirm the relationship between the National Pension Service share and the dividend ratio.

• Journal of Aquaculture
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• v.19 no.2
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• pp.95-98
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• 2006

This study was performed to determine possibility of compensatory growth of juvenile olive flounder fed a commercial feed during the summer season. Five treatments of fish with triplicates were prepared: C, S1, S2, S3 and S4. Fish in the control group (C) was hand-fed with the commercial feed to apparent satiation twice daily for 6 days a week during 6 weeks. Fish in S1, S2, S3, and S4 experienced 1, 2, 3, and 4 weeks of starvation before fed to satiation twice daily for 5, 4, 3, and 2 weeks, respectively. The feeding trial lasted far 6 weeks. Survival of flounder in C, S1 and S2 was significantly (P<0.05) higher than that offish in S4. Weight gain and specific growth rate (SGR) of flounder in C and S1 were significantly (P<0.05) higher than those of fish in S2, S3 or S4. And weight gain and SGR of flounder in S2 and S3 were significantly (P<0.05) higher than those of fish in S4. Feed consumption of flounder tended to increase with weeks of feeding. Feed efficiency ratio and protein efficiency ratio for flounder in C, S1, S2 and S3 were significantly (P<0.05) higher than those for fish in S4. Moisture content of the whole fish in C was lowest, but highest for fish in S4, respectively. Crude protein content of the whole fish in C was highest, but lowest far fish in S4, respectively. Crude lipid content of the whole fish in C, S1 and S2 was significantly (P<0.05) higher than that of fish in S4. In conclusion, full compensatory growth was obtained in juvenile olive flounder fed for 5 weeks after 1-week feed deprivation during the summer season. Compensatory growth of fish was well supported by improvement in feed efficiency ratio and protein efficiency ratio.

• The Journal of Internal Korean Medicine
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• v.22 no.3
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• pp.423-430
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• 2001

Objects: The purpose of this case-control study was done to examine the relationship between stroke prevalence and the anthropometric indices(body mass index(BMI), modified Broca's method(Broca's index), waist circumference(WC), waist-hip ratio(WHR)), dyslipidemia, past medical history(heart disease, hypertension, diabetes mellitus(DM)), life-style factors(smoking, drinking) in Korean adults. Methods : The study group consisted of neurologically confirmed 116 stroke patients as the case group and 116 non-stroke patients as control group. Obesity were defined as $BMI{\geq}25kg/m^2,\;Broca's\;index{\geq}30%$, WC >94cm in male and WC >80cm in female, $WHR{\geq}0.9$ in male and $WHR{\geq}0.8$ in female. Oyslipidemia were defined as total $cholesterol{\geq}200mg/dl,\;triglyceride{\geq}200mg/dl,\;HDL-cholesterol {\leq}35mg/dl,\;LDL-cholesterol{\geq}160mg/dl$. Information on life-style factors and past medical history was obtained from personal interview. The analysis of the data was done by means of chi-square test(Pearson's chi-square test, Fisher's exact test) and student t-test. Results: The results were as follow. In the study group: Hypertension had a 4:05 odds ratio, Broca's $index{\geq}30%$ had a 1.98 odds ratio, WC >94cm in male had a 2.17 odds ratio, WC >80cm in female had a 2.80 odds ratio, $WHR{\geq}0.9$ in male had a 4.66 odds ratio, $WHR{\geq}0.8$ in female had a 5.35 odds ratio, but heart disease, DM, life-style factors, serum lipid and 8MI had no direct relationship with odds ratio(nonsignificant). By student t-test, risk factors for stroke were found to be total cholesterol(p=0,025), LDL-cholesterol(p=0.013), WC(p=0.000) and WHR(p=0.000). Conclusions: This study suggests that people should be advised to control hyperlitension, hyperlipidemia and obesity since these carry a risk of stroke.

• Journal of Korea Trade
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• v.26 no.4
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• pp.63-82
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• 2022

Purpose - Drawing on relational institutional theory, we explored how demographic similarity between board members of a firm and newly emerged political elites led to firms' increased financial resource acquisition such as leverage ratio and decreased export intensity amidst the Asian financial crisis. We also studied how a firm's leverage ratio and export intensity can further affect firm profitability and financial credit rating. Design/methodology - We revisited and explored a unique, unprecedented crisis that affected most Korean firms: the Asian financial crisis that coincided with a governmental shift from a conservative to a liberal party. We collected demographic information from 432 listed Korean firms' board members and 43 political elites of the Blue House from 1998-2000 to create a demographic similarity measurement. We collected firms' financial information, built panel data, and used ordinary least squares regression to test our theory. Findings - Our results showed that demographic similarity between a firm's directors and newly emerged politicians had a positive association with a firm's leverage ratio but a negative association with a firm's export intensity. A firm's leverage ratio had a negative relationship with firm performance measured by firm profitability and financial credit rating. A firm's export intensity showed a positive effect on firm performance. Originality/value - We highlighted that during an economic crisis that coincided with a governmental shift and change of leading political actors, firms exerted efforts to survey the environment and build new external stakeholder relationships to cope with the changing landscape. We proposed that in an emerging market like Korea where low levels of trust and favoritism are prevalent across society, one of the relational institutional strategies that firms can employ is the selection of directors with similar demographic characteristics to political elites based on factors including birthplace and school affiliations. We examined the efforts of firms to build political networks with newly empowered political elites during a financial crisis, and the consequences of establishing such networks. We highlighted that during a financial crisis, the demographic similarity between a firm's board members and newly emerged politicians can provide firms with access to financial resources but can also result in poor management and reduced effort to enhance its international competitiveness.

• The Journal of Korean Obstetrics and Gynecology
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• v.24 no.3
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• pp.98-108
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• 2011

Objectives: The purpose of this study is to investigate the relationship between granulocyte/lymphocyte ratio and dysmenorrhea, history of gynecological disease, heart rate varibility(HRV). Methods: From May 1st 2011 to July 10th 2011, a total of 40 female subjects (age 20-39) were recruited. We evaluated the menstruation condition by questionnaires including VAS(Visual Analog Scale), VRS(Verbal Rating Scale) and MVRS (Multidimensional Verbal Rating Scale), also measured subject's WBC differential count and HRV. Results: 1. There was no statistically significant difference in granulocyte/lymphocyte ratio according to menstruation cycle, duration, amount, color, and blood clot. 2. There was no statistically significant difference in VAS, VRS, MVRS mean scores between normal group and abnormal group according to granulocyte/ lymphocyte ratio. 3. The past prevalence of gynecological disease of abnormal group showed significantly higher compared with that of normal group($x^2$=6.578, p=0.010). 4. LF/HF ratio and granulocyte ratio significantly showed positive correlation ($r_s$=0.311 p=0.048) and LF/HF ratio and lymphocyte ratio significantly showed negative correlation($r_s$=-0.319 p=0.045). Conclusion: These findings suggest that the gynecologic diseases are related to disorder of autonomic nervous system, but not dysmenorrhea. And the balance state of sympathetic/parasympathetic nerve infered through granulocyte/lymphocyte ratio and HRV seems to be consistent. However, reconfirmation through further studies is needed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.6188-6204
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• 2017

Over the years, more password-based authentication key agreement schemes using chaotic maps were susceptible to attack by off-line password guess attack. This work approaches this problem by a new method--new theorem of chaotic maps: $T_{a+b}(X)+T_{a-b}(X)=2T_a(X)T_b(X)$,(a>b). In fact, this method can be used to design two-party, three-party, even in N-party intelligently. For the sake of brevity and readability, only a two-party instance: a novel Two-party Password-Authenticated Key Agreement Protocol is proposed for resisting password guess attack in this work. Compared with the related literatures recently, our proposed scheme can be not only own high efficiency and unique functionality, but is also robust to various attacks and achieves perfect forward secrecy. For capturing improved ratio of security and efficiency intuitively, the paper firstly proposes a new parameter called security/efficiency ratio(S/E Ratio). The higher the value of the S/E Ratio, the better it is. Finally, we give the security proof and the efficiency analysis of our proposed scheme.

• Solar Energy
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• v.18 no.2
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• pp.91-104
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• 1998

This study carried out a numerical analysis on a heat pump assisted dryer using HFC134a. Under the constant degree of superheat and that of subcooling, we analyzed the performance of heat pump assisted dryer with varying an air mass velocity, bypass air ratio, compressor speed and an inlet bulb temperature of dryer. Simulation results were compared with experimental results, so they were maximally agreed in the range of 10%. There was the proper bypass air ratio with varying an air mass velocity. As for the effect of SMER having the inlet temperature $35^{\circ}C$ and compressor speed 1360rpm, bypass air ratio was 30% at the front velocity 0.5kg/s, 40% at the front velocity 0.7kg/s and 50% at the front velocity 0.9kg/s and 1.1kg/s. As the compressor speed was increased, SMER decreased and COP increased. As the inlet bulb temperature was increased, SMER and COP decreased.