• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.942-947
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• 2001

This paper provides a stability analysis of the transverse vibration of a spinning disk under the torque fluctuation from a permanent magnetic motor. An analytical model has been formulated for a flexible annular disk with its spinning velocity varying harmonically with the same frequency as the cogging torque. A perturbation method based on multiple time scales is applied to perform the stability analysis. Based on expressions for the amplitude and frequency of the parametric excitation, stability boundaries are determined in terms of a nominal spindle velocity, the least common multiple of poles and slots, the magnitude of torque fluctuation and the modal characteristics of. the disk. The stability diagrams predicted by perturbation have been verified numerically using the Floquet theory, which is in good agreement. In conclusion, the fluctuation in spinning velocity is found to affect the stability of the transverse vibration of a rotating disks. The results of this work can be applied to high precision spindle systems such as computer storage systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.1
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• pp.21-28
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• 2002

This paper intends to investigate the effects of speed fluctuation caused by the cogging torque in permanent magnetic motors on the stability of the transverse vibration for a spinning disk. Based on the Kirchhoff\`s plate theory and the assumed mode methods, a set of discretized equations of motion were derived for an annular disk rotating with a harmonically varying speed. Then, a perturbation method using the multiple time scales was employed and stability boundaries were determined explicitly in terms of the magnitude and frequency of speed fluctuation, a nominal sped and the modal characteristics of the disk. It is found that parametric resonance occurs at several speed ranges and a single mode or a combination of two modes are involved to cause instability. It is also observed that unstable regions become broadened as the spinning speed increases or two modes are combined in parametric instability. As numerical simulations, stability analysis of a conventional CD-ROM drive was performed. Results of this work can e used as guidelines for motor design and operations with low vibration.

• Journal of Astronomy and Space Sciences
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• v.13 no.2
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• pp.198-209
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• 1996

In this paper, we present an image compression algorithm that is capable of significantly reducing the vast mount of information contained in multispectral images. The developed algorithm exploits the spectral and spatial correlations found in multispectral images. The scheme encodes the difference between images after contrast/brightness equalization to remove the spectral redundancy, and utilizes a two-dimensional wavelet trans-form to remove the spatial redundancy. The transformed images are than encoded by hilbert-curve scanning and run-length-encoding, followed by huffman coding. We also present the performance of the proposed algorithm with KITSAT-1 image as well as the LANDSAT MultiSpectral Scanner data. The loss of information is evaluated by peak signal to noise ratio (PSNR) and classification capability.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.2
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• pp.160-168
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• 2008

This paper presents the study on the stability of nonlinear oscillations of a thin cantilever beam subject to harmonic base excitation in vertical direction. Two partial differential governing equations under combined parametric and external excitations were derived and converted into two-degree-of-freedom ordinary differential Mathieu equations by using the Galerkin method. We used the method of multiple scales in order to analyze one-to-one combination resonance. From these, we could obtain the eigenvalue problem and analyze the stability of the system. From the thin cantilever experiment using foamax, we could observe the nonlinear modes of bending, twisting, sway, and snap-through buckling. In addition to qualitative information, the experiment using aluminum gave also the quantitative information for the stability of combination resonance of a thin cantilever beam under parametric excitation.

• Journal of Digital Convergence
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• v.9 no.5
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• pp.157-173
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• 2011

This study is to find out how the activities of Corporate Citizenship based on Economics, Law, Ethics, Philanthropy affect the purchase intention of comsumer. The survey used a random sample of more than 400 people across Seoul and Kyunggi-do. The coding data selected was analyzed by Cronbach's alpha and factor analysis. And then the multi-regression analysis carried out and these results were impacted on all assumptions we set up originally.

• Proceedings of the Safety Management and Science Conference
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• 2002.05a
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• pp.263-268
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• 2002

국내 공항에서 보유하고 있는 제한된 주기장에 대한 이용률과 주기되어 있는 항공기의 탑승에 소요되는 시간 및 도보거리는 공항의 운영 및 승객의 편리성 평가에 주요한 척도가 되고 있으며, 공항의 주요 운영 목표는 합리적인 항공기 주기장 배정을 통한 주기장 이용률의 최대화 및 터미널 이용 승객의 편리성 증대라 할 수 있다. 이에 본 연구에서는 대상 공항의 시설배치, 터미널 구조, 공항의 이용 승객 등을 고려하여 사용 가능한 주기장의 이용률의 최대화하고 터미널에서의 여객 이동거리를 최소화하는 주기장 배정 알고리즘의 개발과 그 결과를 국내 공항에 적용시키는 것을 그 목적으로 한다. 이를 위하여 기존의 GAP 정식화 모델을 최적화 소프트웨어인 LINGO를 활용하여 다중 시간 주기를 갖는 복잡한 문제를 단일 시간주기를 갖는 문제로 변환하기 위한 접근 방법을 제시함으로써 기존의 OR 접근 방법이 가지는 최적해 산출을 위한 긴 소요시간의 문제를 해결하고 실제 공항에 적용하여 실시간 의사결정을 위한 배정 결과를 제공하였다. 본 연구를 통하여 현재 발견적 기법에만 의존하여 수행되는 주기장 배정결과를 최적화 알고리즘을 통하여 산출함으로써 공항의 주요한 운영 목표인 항공사 및 여객의 시간 비용을 최소화할 수 있다. 또한 기상 악천후로 인한 항공기의 이착륙 지연이 발생할 경우 복잡한 문제를 배정 알고리즘에 의해 신속히 해결함으로써 공항 운영의 효율성뿐만 아니라 공항 안전에도 기여할 수 있을 것이다.

• The Journal of the Korea Contents Association
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• v.14 no.6
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• pp.108-118
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• 2014

The purpose of this study is to develop a relationship of measuring method for the social security network and verify its validity and reliability and apply it to investigate the due to security life satisfaction. This study is based by setting general residents of Seoul in 2013 and using the stratified cluster random sampling method to analyze a total amount of 203 examples. The measuring methods for the social security network was developed through document research, conceptual definition and drafting the survey, experts' conference, preliminary inspection and original examination, verification of the validity and reliability of the survey. An experts' conference took pace to verify the validity of the survey, and 6 factors were extracted through exploratory factor analysis crime prevention design, street CCTV facilities, volunteer neighborhood patrol, local government security education, police public peace service, private security service. The conclusion are the following. Collected data was analyzed based on the aim of this study using SPSSWIN 18.0, and practice frequency analysis, F test, factor analysis, reliability analysis, correlation analysis, multiple regression analysis. First, the validity of the social security network measurement is very high. Thus, the factors constituting the social security network were found to be crime prevention design, street CCTV facilities, volunteer neighborhood patrol, local government security education, police public peace services, and private security services, and the crime prevention design factor was found to be most explanatory. Second, the reliability of the social security network measurement is very high. Thus, the correlation between the questions and the sector, the questions and the social security net was very high, and the internal consistency showed a Cronbach's${\alpha}$ value of over 0.865. Third, the establishment of a social security network had the biggest effect on people in their forties. Thus, when the crime prevention design, street CCTV facilities, local government security education, police public peace services are systematically established, the social anxiety of citizens was reduced.

• Sleep Medicine and Psychophysiology
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• v.22 no.2
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• pp.64-69
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• 2015

Objectives: We investigated whether sleep behaviors, severity of insomnia and circadian typology are associated with quality of life among Gyeongsang National University (GNU) medical students. Methods: Questionnaires were distributed to 46 fourth-year students of GNU Medical School. The hospital anxiety-depression scale, insomnia severity index (ISI), morningness-eveningness questionnaire (MEQ) and WHO Quality of Life-BREF (WHOQOL-BREF) were used. Results: Quality of life in terms of physical health was associated with age, weekday total sleep time (TST), weekend TST, catch up sleep, depression, ISI score, and MEQ score. Quality of life in terms of psychological health was correlated to weekday and weekend TST, anxiety, ISI score and MEQ score. Sex, weekday TST, depression, and ISI score were revealed to influence the social aspect of quality of life, and weekday and weekend TST, and ISI score were associated with quality of life in terms of environment. Multiple regression analysis showed that better sleep quality predicted to a higher quality of life in terms of physical, psychological and environmental health, and eveningness was associated with a better quality of life in terms of physical and psychological health. Conclusion: It is concluded that physical, psychological, and environmental aspects of quality of life were associated with quality of sleep and that physical and psychological aspects of quality of life were related to eveningness in GNU medical students. Therefore, it is equally important to treat emotional problem as well as improve sleep quality.

• Korean Journal of Psychosomatic Medicine
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• v.19 no.2
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• pp.83-91
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• 2011

Objectives: Posttraumatic stress disorder(PTSD) has devastating effects on multiple aspects of the quality of life(QoL). Therefore, the purpose of this study is to compare the QoL between PTSD group and non-PTSD group, and identify the variables affecting the QoL of the Vietnam War veterans. Methods: We recruited 39 veterans with PTSD and 43 veterans without PTSD, all of whom had deployed to the Vietnam War. We used the Korean version of Mini International Neuropsychiatric Interview-Plus, the Korean version of Clinician-Administered PTSD Scale, Combat Exposure Scale and the Korean version of World Health Organization Quality of Life Assessment Instrument abbreviated version. We used independent samples t-test to identify the differences between PTSD and non-PTSD group in each domains of the quality of life. We also used stepwise multiple linear regression analysis to figure out the variables affecting the QoL of the Vietnam War veterans. Results: In the PTSD group, all domains of the QoL and the QoL total score(p<0.01) were significantly lower than those in the non-PTSD group. In the Vietnam War veterans, PTSD, major depressive disorder and education levels were the variables affecting the QoL. Among these, PTSD uniquely explained the QoL of the overall and general health(${\beta}$=-1.411, $R^2$=0.180), the physical health domain(${\beta}$=-2.806, $R^2$=0.089) and the total score (${\beta}$=-11.479, $R^2$=0.104). Conclusions: These results suggest that among the Vietnam War veterans, the QoL of the PTSD group is significantly lower than that of the non-PTSD group. Among the combat exposed veterans, PTSD may be one of the main reasons that affect the multiple domains of the QoL.

• Korean Journal of Psychosomatic Medicine
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• v.14 no.1
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• pp.53-61
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• 2006

Objectives: This study was designed to evaluate difference of the alexithymia between panic patients and normal controls by examination of the relationships between different components of the alexithymia construct and level of anxiety and depression in panic patients and normal controls. Methods The subjects were 167 patients who met DSM-IV criteria for panic disorder and 110 normal controls. They drew up symptom checklists and self-rating scales, and were measured by Anxiety Disorders Interview Schedule-Panic attack & Agoraphobia(ADIS-P & A), Korean version of Toronto Alexithymia Scale (TAS-20K), Spielberger State-Trait Anxiety Inventory-State & Trait (STAI-S & T), Beck Depression Inventory (BDI), and Revised Anxiety Sensitivity Index (ASI-R). For statistical analysis, we performed t-test to compare the sociodemographic characteristics and the scores of self reported scales between panic patients and normal controls. Pearson correlation was performed between TAS-20K and it's subfactors, STAI-S & T, ASI-R and BDI in panic patients and normal controls. And stepwise multiple regression analysis was preformed to explain results of correlation analysis for alexithymia. Results: The panic patients reported more significant alexithymic (p<0.001), more difficulty identifying feeling (p<0.001) and describing feeling (p=0.001) than normal controls. Futhermore, panic patients were more significant anxious, sensitive to anxious feeling and depressive than normal controls. Moreover, the alexithymia of panic patients was explained by trait-anxiety $({\Delta}R^2=0.255)$ and anxiety sensitivity $({\Delta}R^2=0.062)$, that of normal controls was predicted by depression $({\Delta}R^2=0.144)$ and anxiety sensitivity $({\Delta}R^2=0.033)$ Conclusion: The panic patients reported more anxious and sensitive to anxious feeling, and these symptoms predict alexithymia in panic patients. However, the alexithymia of normal controls was explained by depression more than anxiety sensitivity, and such a result isn't consistent with previous studies and this may be mainly due to difference of the homogeneity in object of the studies.