• Journal of Multimedia Information System
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• 제2권2호
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• pp.193-206
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• 2015

In this paper a new approach for image encryption based on quadruple encryption with dual chaotic maps is proposed. The encryption process is performed with quadruple encryption by invoking the encrypt and decrypt routines with different keys in the sequence EDEE. The decryption process is performed in the reverse direction DDED. The key generation for the quadruple encryption is achieved with a 1D Circle map. The chaotic values for the encrypt and decrypt routines are generated by using a 2D Henon map. The Encrypt routine E is composed of three stages i.e. permutation, pixel value rotation and diffusion. The permutation is achieved by: row and column scrambling with chaotic values, exchanging the lower and the upper principal and secondary diagonal elements based on the chaotic values. The second stage circularly rotates all the pixel values based on the chaotic values. The last stage performs the diffusion in two directions (forward and backward) with two previously diffused pixels and two chaotic values. The security and performance of the proposed scheme are assessed thoroughly by using the key space, statistical, differential, entropy and performance analysis. The proposed scheme is computationally fast with security intact.

• 대한가정학회지
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• 제35권5호
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• pp.1.1-15
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• 1997

The purposes of this study were to identify the household's financial status by life cycle stage and no analyze contributing factors to financial planning for retirement preparation among Korean marred couples. For these purpose, 2074 married couples those being under 55 and having either single earner or dual earners were selected, and total sample was divided into three stages; young-aged(＜35), middle-aged(35-44) & old-aged(45-54). Statistics were frequencies, means, percentile, and logistic analysis. The results were as follows. First, old-aged had higher level of total income, total expenditure and total assets than either young-aged or middle-aged. In addition, households those holding private pensions were likely to have higher total income, total expenditure and total assets than those owning no private pension. while middle-aged had a highest total debts. Second, gini coefficients of total income and total expenditure between three aged groups were similar, but old-aged had the highest gini coefficient of total assets and total debts. In particular, gini coefficients of total assets and total debts of households those having no private pension were greater than those holding private pensions. third, contributing factors to private pension ownership of young-aged were family & household-related factor and financial factor, middle-aged's factors were household head's characteristics and financial factor. Also, old-aged's factors were household head's characteristics, family & household-related factor and financial factor.

• 한국연초학회지
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• 제15권2호
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• pp.145-151
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• 1993

Using a flue - cured tobacco variety, KF lH9, recently bred and released to farming, effect of growth regulators(fatty alcohol and C - MH) on the change of alkaloid contents and dynamics of MH uptake and distribution were investigated. An efficient sucker control method was also pursued. Treatment of fatty alcohol at button stage remarkably increased the rate of C - MH uptake. However, except in the plants treated with 2- fold volume of C - MH, residue of C -MH was kept under maximum residue level(80 ppd). C - MH residue in stalk was higher than in foliage in general. Compared to untreated control, leaf weight per unit area was increased by the treatment even in lower leaves where vigorous transfer of C - MH from treated tips was indicated and sucker control higher than 94.9% was achieved with all treatments except for sole half volume C - MH treatment at topping stage. Alkaloid content in foliage was reduced by dual treatment of fatty alcohol and C - MH but increased in stalk and root.

• 한국운동역학회지
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• 제31권1호
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• pp.37-43
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• 2021

Objective: The purpose of this study was to investigate the effect of mobile phone text messaging on the collision avoidance strategy for an approaching and stationary pedestrian. Method: Eighteen healthy young adults participated in this study. Each participant was asked to perform a task to walking with/without mobile phone text messaging and a task to avoid collisions with another pedestrian who was approaching or stationary during walking. Results: When text messaging with avoidance collision, it showed an early onset time, a larger mediolateral COM trajectory, trunk rotation angle and trunk rotation velocity (p<.05). Also, compared to an approaching pedestrian, when avoiding collision with a stationary pedestrian, it showed a later onset time, a lager avoidance displacement, mediolateral COM trajectory, trunk rotation angle (p<.05). Conclusion: Results suggest that mobile phone text messaging while collision avoidance leads to delay the perception stage and alters the adaptation stage. Consequently, pedestrian executed in an exaggerated avoidance action to create a greater safety margin when attending to mobile phone test messages while avoiding another pedestrian.

• 디지털융복합연구
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• 제20권2호
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• pp.487-497
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• 2022

본 연구는 맞벌이 부모의 일-가정 갈등과 우울 간의 관계에서 사회적 지지의 매개효과를 확인함으로써 맞벌이 부모의 정서적 관리에 대한 실천적 지원 근거 마련에 그 목적이 있다. 연구대상은 초등학교 이하의 자녀를 둔 20세 이상의 맞벌이 부모 214명이며, 2021년 4월에 온라인으로 수집된 자료를 SPSS/WIN 24.0 통계 프로그램을 이용하여 분석하였다. 연구 결과 일-가정 갈등, 사회적 지지 및 우울 간에는 통계적으로 유의한 상관성이 있었다. 매개효과를 확인하기 위해 3단계의 위계적 회귀분석을 시행한 결과 1단계와 2단계에서 일-가정 갈등은 매개 변인인 사회적 지지(β=-.188, p<.01), 종속 변인인 우울(β=.539, p<.001)에 각각 통계적으로 유의한 영향을 미쳤다. 3단계에서는 일-가정갈등과 우울 간의 관계에서 사회적 지지가 부분 매개 효과가 있는 것이 확인되었고, 이는 Sobel 검증 결과에서도 통계적으로 유의하였다(z=2.468, p=.013). 본 연구 결과는 맞벌이 부모의 일-가정 갈등과 이와 관련된 우울에 사회적 지지의 중요성을 뒷받침하는 근거로 활용될 수 있으며 맞벌이 부모의 정서적 문제 해결을 위한 전략 수립 및 사회적 지원 마련의 당위성을 제공한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.421-426
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• 2009

This paper presents vibration analysis of maskless exposure module in Printed Circuit Board (PCB) manufacturing system. In order to complete exposure process in PCB, masking type module has been widely used in electronics industries. However, masking process confronts some limitations of application due to higher production cost for masking as well as lower printing resolution. Therefore, maskless exposure module is started to be in the spotlight for flexible production system to meet the needs of fabrication in variable patterns at low cost. Since maskless exposure process adopts direct patterning to PCB, vibration problems become more critical compared to conventional masking type process. Moreover, movements of exposure engine as well as stage generate vibration sources in the system. Thus, it is imperative to analyze the vibration characteristics for the maskless exposure module to improve the quality and accuracy of PCB. In this study, vibration analysis using the Finite Element Analysis is conducted to identify the critical structural parts deteriorating vibration performance. Also, Experimental investigations are conducted by single/dual encoder measurement process under the operating module speed. Measurement points of vibration are selected by three places, which are base of stage, exposure engine and top of stage, to check the effect of vibration from the exposure engine. Comparisons between analysis results and experimental measurement are conducted to confirm the accuracy of analysis results including the developed FE model. Finally, this studies show feasibility of optimal design using the developed FE analysis model.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.347-350
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• 2006

로켓 추진제 등급에 속하는 고농도 과산화수소는 상온에서 저장 가능한 단일추진제로써 최근 환경 문제가 대두되면서 재조명을 받고 있다. 본 연구에서는 과산화수소를 추진제로 사용하고 저/고온부 촉매, 즉 이원 촉매 시스템을 이용하는 가스발생기에 대한 연구를 수행하였다. 저온에서 반응 특성이 우수하고 냉시동이 가능한 $K_2MnO_4$와 고온용 촉매인 $La_{0.8}Sr_{0.2}CoO_3(LSC)$ 촉매를 결합한 결과 기존의 낮은 성능을 가지는 단일 촉매 가스발생기에 비해 매우 높은 효율을 보였다. 이는 로켓 상단의 자세제어, 소형 위성용 추력기, 터보 펌프 구동을 위한 가스발생기 등으로 확장될 수 있다.

• Smart Structures and Systems
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• 제26권5호
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• pp.657-666
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• 2020

A rotational pulse-echo ultrasonic propagation imager that can inspect cylindrical specimens for material nondestructive evaluations is proposed herein. In this system, a laser-generated ultrasonic bulk wave is used for inspection, which enables a clear visualization of subsurface defects with a precise reproduction of the damage shape and size. The ultrasonic waves are generated by a Q-switched laser that impinges on the outer surface of the specimen walls. The generated waves travel through the walls and their echo is detected by a Laser Doppler Vibrometer (LDV) at the same point. To obtain the optimal Signal-to-Noise Ratio (SNR) of the measured signal, the LDV requires the sensed surface to be at a right angle to the laser beam and at a predefined constant standoff distance from the laser head. For flat specimens, these constraints can be easily satisfied by performing a raster scan using a dual-axis linear stage. However, this arrangement cannot be used for cylindrical specimens owing to their curved nature. To inspect the cylindrical specimens, a circular scan technology is newly proposed for pulse-echo laser ultrasound. A rotational stage is coupled with a single-axis linear stage to inspect the desired area of the specimen. This system arrangement ensures that the standoff distance and beam incidence angle are maintained while the cylindrical specimen is being inspected. This enables the inspection of a curved specimen while maintaining the optimal SNR. The measurement result is displayed in parallel with the on-going inspection. The inspection data used in scanning are mapped from rotational coordinates to linear coordinates for visualization and post-processing of results. A graphical user interface software is implemented in C++ using a QT framework and controls all the individual blocks of the system and implements the necessary image processing, scan calculations, data acquisition, signal processing and result visualization.

• 한국소음진동공학회논문집
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• 제19권12호
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• pp.1322-1328
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• 2009

This paper presents vibration analysis of maskless exposure module in printed circuit board(PCB) manufacturing system. In order to complete exposure process in PCB, masking type module has been widely used in electronics industries. However, masking process confronts some limitations of application due to higher production cost for masking as well as lower printing resolution. Therefore, maskless exposure module is started to be in the spotlight for flexible production system to meet the needs of fabrication in variable patterns at low cost. Since maskless exposure process adopts direct patterning to PCB, vibration problems become more critical compared to conventional masking type process. Moreover, movements of exposure engine as well as stage generate vibration sources in the system. Thus, it is imperative to analyze the vibration characteristics for the maskless exposure module to improve the quality and accuracy of PCB. In this study, vibration analysis using the finite element analysis is conducted to identify the critical structural parts deteriorating vibration performance. Also, Experimental investigations are conducted by single/dual encoder measurement process under the operating module speed. Measurement points of vibration are selected by three places, which are base of stage, exposure engine and top of stage, to check the effect of vibration from the exposure engine. Comparisons between analysis results and experimental measurement are conducted to confirm the accuracy of analysis results including the developed FE model. Finally, this studies show feasibility of optimal design using the developed FE analysis model.

• 한국항공우주학회지
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• 제34권3호
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• pp.87-92
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• 2006

고농도 과산화수소는 별도의 산화제가 필요치 않은 단일추진제로써 상온에서 액상인 장점이 있어 다양한 장치의 추진제로 이용되고 있다. 본 연구에서는 상온에서의 시동 성능 보완을 위해 이원 촉매층을 이용한 실험적인 연구를 수행하였다. 상온에서의 뛰어난 성능을 바탕으로 $K_2MnO_4$를 도입부의 촉매로 선정하였으며 이를 위해 알루미나 졸-겔법을 이용한 새로운 코팅법을 개발하였다. 가스발생기를 이용한 반응실험을 통해 설계유량에 적합한 기화기의 길이를 결정하였고 이를 이용한 이원 촉매 가스발생기의 성능평가를 수행하였다. 성능평가 결과, $10^{\circ}C$ 이하의 온도에서 냉시동(cold-start)에 성공하였으며 높은 분해효율을 확인하였다.