• Journal of the Korea Society of Computer and Information
• /
• v.16 no.12
• /
• pp.247-255
• /
• 2011

Most existing clustering protocols have been aimed to provide balancing the residual energy of each node and maximizing life-time of wireless sensor networks. In this paper, we present the adaptive clustering strategy related to sink position for clustering protocols in wireless sensor networks. This protocol allows networks topology to be adaptive to the change of the sink position by using symmetrical clustering strategy that restricts the growth of clusters based on depth of the tree. In addition, it also guarantees each cluster the equal life-time, which may be extended compared with the existing clustering protocols. We evaluated the performance of our clustering scheme comparing to LEACH and EEUC, and observe that our protocol is observed to outperform existing protocols in terms of energy consumption and longevity of the network.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.3
• /
• pp.501-509
• /
• 2011

In this paper, we offer a new strategic Portfolio Model for national IT R&D project selection in Korea. A risk and return (R-R) Portfolio Model was developed using an objectively quantified index on the two axes of risk and return, in order to select a strategic project and allocate resources in compliance with a national IT R&D strategy. We strategize using the R-R Portfolio Model to solve the non-strategy and subjectivity problems of the existing national R&D project selection Model. We also use the quantified evaluation index of the IT technology road map (TRM) and the technology level Survey (TLS) for the subjectivity of project selection, and try to discover the weights using the analytic hierarchy process (AHP). In addition, we intend to maximize the chance for a successful national IT R&D project, by selecting a strategic Portfolio project and balancing the allocation of resources effectively and objectively.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.3
• /
• pp.91-100
• /
• 2017

The solution was developed for the maintenance decision support of combined cycle power plant gas turbine. The developed solution was applied to MHI501G gas turbine and is, in present, on the process of field test at GUNSAN combined cycle power plant, South Korea. The developed solution provides the calculated result of optimal overhaul maintenance period through following modules: Real Time Performance Monitoring, Model-Based Diagnostics, Performance Trend Analysis, Optimal Overhaul Maintenance Interval, Compressor Washing Period Management, and Blade Path Temperature Analysis. Model-Based Diagnostics module analyzed the differences between the data of gas turbine performance model and the online measurement. Compressor washing management module suggests the optimal point of balancing between the compressor performance and the maintenance cost.

• Journal of Contemporary Eastern Asia
• /
• v.16 no.1
• /
• pp.22-45
• /
• 2017

The successful management of software (SW) projects is a continuous concern to managers, which is attributed to the contradictory demands that most projects are facing; meeting user requirements within time and budget limit while flexibly dealing risks during the progress of the projects. The present study asserts project performance and risk mitigation are not tradeoff but to be achieved simultaneously, which is called SW project ambidexterity. Drawing on the literature on organizational behavior, hypotheses are developed speculating the relation among project performance, risk mitigation, team collective improvisation, team behavioral integration, and team diversity. Using empirical data collected from 102 SW project teams of 507 team members in South Korea, empirical analysis indicates team collective improvisation is a significant antecedent to SW project ambidexterity, playing a pivotal role to balance the contradictory demands. Furthermore, team behavioral integration positively influences the degree of team collective improvisation, and the magnitude of the relation is partially contingent on the team members' age and major diversity. The present study advances theory by providing a context specific explanation about the SW project ambidexterity and its precedents.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.101-106
• /
• 2006

Balance shaft has a key role in reducing a engine vibration in a vehicle and widely applied for current models. Since balance shaft module consists many sub-component and each part has its own operational characteristics, some different analysis backgrounds should be integrated into one sub-part in balance shaft module and this is the main obstacles in making a design process. Moreover, the balancing shaft is rotating in high speed and such condition requires large safety factors in a design process owing to a lot of unexpected problems with the overwhelming rotation. Balance shaft is the core-component generating the intended unbalance as well as cancelling the unbalance force or moment by the engine module. So, the balance shaft should meet the high fatigue resistance not to mention of NVH performance. In this paper, a design strategy focused on balance shaft is developed to build a optimal model considering a engine vibration. Putting the unbalance mass distribution as main design parameter, some candidate model is verifed with structural and fatigue analysis and most appropriate model is proposed here.

• Journal of Institute of Control, Robotics and Systems
• /
• v.7 no.5
• /
• pp.420-426
• /
• 2001

In this paper, we introduce a case study of developing a miniature humanoid robot that has 16 degrees of freedom and is able to perform statically stable walking. The developed humanoid robot is 37cm tall and weighs 1,200g. RC servo motors are used as actuators. The robot can walk forward and turn to any direction on an even surface. It equipped with a small digital camera, so it can transmit vision data to a remote host computer via wireless modem. The robot can be operated in two modes: One is a remote-controlled mode, in which the robot behaves according to the command given by a human operator through the user-interface program running on a remote host computer, the other is a stand-alone mode, in which the robot behaves autonomously according the pre-programmed strategy. The user-interface program also contains a robot graphic simulator that is used to produce and verify the robot\`s gait motion. In our walking algorithm, the ankle joint is mainly used for balancing the robot. The experimental results shows that the developed robot can perform statically stable walking on an even surface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.393-398
• /
• 2007

Balance shaft has a key role in reducing a engine vibration in a vehicle and widely applied for current models. Since balance shaft module consists many sub-component and each part had its own operational characteristics, some different analysis background should be integrated into one sub-part in balance shaft module and this is the main obstacles in making a design process. Moreover, the balancing shaft rotating in high speed and such condition requires large safety factors in a design process owing to a lot of unexpected problems with the overwhelming rotation. Balance shaft is the core-component generating the intended unbalance as well as canceling the unbalance force or moment by the engine module. So, the balance shaft should meet the high fatigue resistance not to mention of NVH performance. In this paper, a design strategy focused on balance shaft is developed to build a optimal model considering a engine vibration. Putting the unbalance mass distribution as main design parameter, some candidate model is verified with structural and fatigue analysis most appropriate model is proposed here.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.12
• /
• pp.133-140
• /
• 2013

Cascaded H-Bridge multi-level inverters can be implemented through the series connection of single-phase modular power bridges. In recent years, multi-level inverters are becoming increasingly popular for high power applications due to its improved harmonic profile and increased power ratings. This paper presents a control method for balancing the dc-link voltage and ride-through enhancement, a modified pulse width-modulation Compensation algorithm of cascaded H-bridge multi-level inverters. During an under-voltage protection mechanism, causing the system to shut down within a few milliseconds after a power interruption in the main input sources. When a power interruption occurs finish, if the system is a large inertia restarting the load a long time is required. This paper suggests modifications in the control algorithm in order to improve the sag ride-through performance of ac inverter. The new proposed strategy recommends maintaining the DC-link voltage constant at the nominal value during a sag period, experimental results are presented.

• Journal of Family Resource Management and Policy Review
• /
• v.12 no.2
• /
• pp.141-152
• /
• 2008

This study reviews a family-friendly system of companies from the viewpoint of family resource management. The concept of a family-friendly system in the workplace means that the strategy 'supports the family' or 'is sensitive to the family life' and recognizes a need for balance between work and family. The suggestions proposed in this study were as follows: First, the direction of a family-friendly system must reflect the needs of the family members positively and recognize diversity. Second, it must consider efficient methods relating to the matter of the gender because a corporate culture enabling men to use childcare leave has not grown, even in family companies. Third, the directions to check the present developing process of our society and to develop the suitable way to each company must be shown. This study has proposed that the subjects must solve immediately in the future with understanding the contents and looking around the status of the enforcement at the inside and outside of the country for a family-friendly system to handle the balance between work and family in the workplace. The problems were the context of the introductions and the results of balancing between work and family no matter whether the introduction of the system by company or not.

• Journal of Power Electronics
• /
• v.17 no.1
• /
• pp.212-221
• /
• 2017

Permanent-Magnet Synchronous Generators (PMSGs) are used widely in Wind Power Generation Systems (WPGSs), and the Vienna rectifier was recently proposed to be used as the generator-side converter to rectify the AC output voltage in PMSG-based WPGS. Compared to conventional six-switch two-level PWM (2L-PWM) converters, the Vienna rectifier has several advantages, such as higher efficiency, improved total harmonic distortion, etc. The motivation behind this paper is to verify the performance of direct-driven PMSG wind turbine system based-Vienna rectifier by using a simulated direct-driven PMSG WPGS. In addition, for the purpose of reducing the reactive power loss of PMSGs, this paper proposes an induced voltage sensing scheme which can make the stator current maintain accurate synchronization with the induced voltage. Meanwhile, considering the Neutral-Point Voltage (NPV) variation in the DC-side of the Vienna rectifier, a NPV balancing control strategy is added to the control system. In addition, both the effectiveness of the proposed method and the performance of the direct-driven PMSG based-Vienna rectifier are verified by simulation and experimental results.