• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1081-1085
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• 2010

In the wireless sensor networks, power consumption and interference among the nodes can be reduced by using the transmission power control. Because link quality is changed by spatial and temporal effect, link failures are frequently occurred. In order to adapt to link quality variation, existing transmission power control schemes broadcast beacon messages periodically to neighbor nodes and control the transmission power dynamically. However, it can effect on the time and energy overhead according to period of transmission power control. In this paper, the dynamic method of transmission power control by the link quality variation and variable period are proposed. When a link quality is unstable, the control duty cycle is reduced and the link quality is agilely maintained. In contrast, when link quality is stable, the control period is increased and control overhead is decreased.

• Journal of KIISE
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• v.42 no.10
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• pp.1254-1267
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• 2015

Recently, excessive installations of APs have caused WLAN interference, and many techniques have been suggested to solve this problem. The AP aggregation technique serves to reduce active APs by moving station connections to a certain AP. Since this technique forcibly moves station connections, the transmission performance of some stations may deteriorate. The AP transmit power control technique may cause station disconnection or deterioration of transmission performance when power is reduced under a certain level. The combination of these two techniques can reduce interference through AP aggregation and narrow the range of interferences further through detailed power adjustment. However, simply combining these techniques may decrease the probability of power adjustment after aggregation and increase station disconnections upon power control. As a result, improvement in performance may be insignificant. Hence, this study suggests a scheme to combine the AP aggregation and the AP transmit power control techniques in OpenFlow-based WLAN to ameliorate the disadvantages of each technique and to reduce interferences efficiently by performing aggregation for the purpose of increasing the probability of adjusting transmission power. Simulations reveal that the average transmission delay of the suggested scheme is reduced by as much as 12.8% compared to the aggregation scheme and by as much as 18.1% compared to the power control scheme. The packet loss rate due to interference is reduced by as much as 24.9% compared to the aggregation scheme and by as much as 46.7% compared to the power control scheme. In addition, the aggregation scheme and the power control scheme decrease the throughput of several stations as a side effect, but our scheme increases the total data throughput without decreasing the throughput of each station.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.365-365
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• 2012

스퍼터된 a축 성장된 산화아연 박막의 전기적 및 구조적 특성의 DC 파워에 대한 영향을 c 축 성장된 산화아연 박막과의 비교를 통해 분석하였다. 1~103 ${\Omega}{\cdot}cm$의 낮은 비저항을 갖는 파워를 갖는 조건과 106~108 ${\Omega}{\cdot}cm$의 높은 비저항을 갖는 파워를 갖는 조건에 대한 분석을 진행하였다. 각 조건에 따른 XRD 분석을 통해 낮은 비저항을 갖는 파워를 갖는 조건의 경우 (100) 성장 방향을 강하게 나타내었으나, 높은 비저항을 갖는 파워를 갖는 조건의 경우 약한 (002) 성장 방향을 나타내었다. EDS를 이용한 분석시 낮은 비저항을 갖는 파워의 경우 상대적 으로 oxygen rich 특성을 나타내었다. 이번 연구를 통해 비저항 등 다양한 조건에 따라 결정 성장 방향이 다름을 확인하였으며, 이에 대한 분석을 통해 산화아연 박막의 성장된 조건에 따 라 다양한 전자소자에의 응용 및 분석이 필요함을 확인하였다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.219-220
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• 2019

본 논문은 DC Common 방식의 새로운 Hybrid 시스템에 대해 제안하고 있다. 제안하는 시스템은 주간에 PV를 통해 배터리를 충전하고 야간에는 BESS(Battery Energy Storage System)로 발전하여 추가 배전용량의 증설 없이 신재생에너지의 발전량을 증가시킬 수 있는 시스템이다. 본 시스템은 계통 연계형 및 PV용 전력변환장치로 구성되며 SiC(Silicon Carbide) 소자를 사용하여 손실을 최소화 하였다. 따라서 각 구성품들의 사양과 Destinpower사가 개발한 알고리즘이 적용된 Hybrid 시스템을 소개한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4604-4613
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• 2015

The study was to identify the mediating effect of Self-efficacy between Self-leadership and Impowerment in the Nursing students. The study was conducted from 02nd March to 29th March. The data was collected using structural questionnaire from 166 nursing students in 2 Nursing department in D city. The data was analyzed by SPSS/WIN 19.0, AMOS 19.0 and Sobel Test. The mean value of were as follows: self-leadership 3.36, Self-efficacy 3.02, Impowerment 3.28. There was positive relationship between self-leadership and Self-efficacy(r=.306, p<.001), self-leadership and Impowerment(r=.291, p<.001) and between Self-efficacy and Impowerment(r=.559, p<.001). This study confirmed that Self-efficacy had a mediating effect on the relationship between self-leadership and Impowerment. To improve Self-efficacy, enhancing self-leadership and Impowerment is required.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1
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• pp.73-81
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• 2002

The transmission of vibration energy through beam-plate junctions in vibration intensity analysis called power new analysis (PFA) has been studied. PFA is an analytic tool for the prediction of frequency averaged vibration response of built-up structures at medium to high frequency ranges. The power transmission and reflection coefficients between the semi-infinite beam and plate are estimated using the wave transmission approach. For the application of the power coefficients to practical complex structures, the numerical methods, such as finite element method are needed to be adapted to the power flow governing equation. To solve the discontinuity of energy density at the joint, joint matrix is developed using energy flow coupling relationships at the beam-plate joint. Using the joint matrix developed in this paper, an idealized ship stem part is modeled with finite element program, and vibration energy density and intensity are calculated.

• KIISE Transactions on Computing Practices
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• v.21 no.12
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• pp.762-767
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• 2015

An Internet of Things (IoT) is a system where various "things" are connected to each other via a wired/wireless network, and where information is gathered, processed, and interchanged/shared. One of the important actors in IoT is a mobile IoT device (such as a smartphone or tablet). These devices tend to consume a large amount of power in order to provide various high performance application services; however, as the devices cannot be supplied with power all the time, efficient power management is necessary. Power management of mobile IoT devices involves complex relationships between various entities such as application processors (APs), HW modules inside/outside AP, operating systems, mobile IoT platforms, and applications. In order to develop power-efficient mobile IoT devices, a method is needed to systematically analyze these relationships and manage power based on a clear understanding of them. To address this problem, software engineering principles for the development of power-efficient mobile IoT devices are presented in this paper. The feasibility of the proposed principles have been validated in the domain of smartphone camera power management.

• The Journal of the Korea Contents Association
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• v.20 no.2
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• pp.323-336
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• 2020

The purpose of this study was to investigate the mediating effect of psychological empowerment in the relationship between job stress and burnout of middle managers in organizations. For this study, 329 middle managers, the participants in this research were working in organizations. They completed questionnaire survey of job stress, psychological empowerment and burnout. Main study results are as follows. First, job stress and psychological empowerment statistically showed a significant negative correlation, while psychological empowerment and burnout also showed a significant negative correlation. Job stress and burnout had a statistically significant positive correlation. Second, psychological empowerment mediated partially the relation between job stress and burnout. This study extends the burnout literature related to the job circumstance and individual internal factor by considering psychological empowerment in addition to the role of perceived job stress in middle managers in organizations. Based on these results, Implications and limitations of the study were discussed.

• Journal of KIISE
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• v.43 no.4
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• pp.460-469
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• 2016

Internet of Things (IoT) is an environment where various devices are connected to each other via a wired/wireless network and where the devices gather, process, exchange, and share information. Some of the most important types of IoT devices are mobile IoT devices such as smartphones. These devices provide various high-performance services to users but cannot be supplied with power all the time; therefore, power management appropriate to a given IoT environment is necessary. Power management of mobile IoT devices involves complex relationships between various entities such as application processors (APs), HW modules inside/outside AP, Operating System (OS), platforms, and applications; a method is therefore needed to systematically analyze and manage these relationships. In addition, variabilities related to power management such as various policies, operational environments, and algorithms need to be analyzed and applied to power management development. In this paper, engineering principles and a method based on them are presented in order to address these challenges and support systematic development of IoT device power management. Power management of connected helmet systems was used to validate the feasibility of the proposed method.

• Management & Information Systems Review
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• v.30 no.4
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• pp.93-115
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• 2011

To date, the majority of research on empowerment has focussed on the individual job incumbent's psychological experience of empowerment and linking this with various work-related outcomes. However, a model that focuses on individual subjective reactions is at best incomplete if it does not include an examination of the contextual factors that shape those perceptions. Therefore, the purpose of this study is to examine the relationships among situational factors, psychological empowerment and employee's attitudes. The data were collected by questionnaire from a sample of 525 employees who were working at business organizations in Kangwon area. Results indicated that organizational characteristics such as access to information, LMX, and participative climate were positively related to an employee's psychological empowerment. Psychological empowerment was positively related to an employee's job attitudes such as organizational commitment and innovative behavior. Finally, theoretical and practical implications from the results were discussed.