• 대한전기학회논문지
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• 제43권6호
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• pp.936-945
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• 1994

This paper proposes a new power converter which consists of two identical 3-phase PWM modulators and a novel resonant circuit. A new control strategy is integrated to realize the bidirectional power converter without an electrolytic link capacitor. The power flow between converters is bidirectional and the regenerative braking is inherent. The source side currents maintain sinusoidal waveforms with a unity power factor. It is observed in the experiment that by balancing the active power between the source and load side, the voltage across a small ceramic link capacitor can be maintained within a small deviation from the reference. Simulation results and experimental results are presented to verify the operational principles.

• 대한안전경영과학회지
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• 제3권3호
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• pp.77-86
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• 2001

An operational strategy for inventory control on finished goods in the distribution system has been given attention to many enterprises and many studies regarding this field have been done and is also on-going currently. Many of these studies represented a large scale distribution network with a unified formulation by using defined symbols. These methods have provided the systematic approach of the distribution network but they are impossible to applying the reality system due to not considering the service rate of demand and treating the shortage of inventory. In order to overcome these unrealistic problems, the novel safety stock policy of responding to customers' inventory distribution network is suggested. this paper explores the transportation between Central Distribution Center(CDC) and Regional Distribution Center(RDC). Especially, the relation of transportation cost between CDC and RDC and cost of inventory control according to safety inventory with service level are emphasized. We could obtain the good results of this study by determining the optimal safety stock considering the various variables and constraints.

• 한국전자거래학회지
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• 제4권2호
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• pp.161-175
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• 1999

CALS is a strategy to share integrated product data through a set of standards to achieve efficiencies in business and operational mission areas. In this paper, we studied current status for CALS standard and then analyzed the case of US DoD. The results can be summarized as implementing for two major standard in defense CALS system. They are STEP and XML. Korea Defense can be used to set direction for CALS standard implementation and standard selection process based on this paper's recommendations.

• Journal of Information Technology Applications and Management
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• 제22권1호
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• pp.1-15
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• 2015

Software is not only control and operational technology of computer, various system, and machines, but also knowledge handling and service technology for production, storage, and utilization of digital information. Many nations invest enormous budget in SW R&D to acquire core and original technology, and commercialize. To select and concentrate on SW R&D investment by segmenting diverse functions and element technologies consisting of sw technology, introduction of evaluation and analysis methodology on technology level utilizing reliable patent and bibliometrics is demanded these days. The purpose of this paper is to suggest some analysis frameworks of national technology level in the field of sw technology. Another practical purpose is to verify sw technology policy using qualitative and quantative indicators of patent and bibliometrics.

• Journal of Information Technology Applications and Management
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• 제20권1호
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• pp.217-240
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• 2013

Noting that compatibility beliefs are important antecedents of technology adoption, the objective of this study was to assess compatibility beliefs that affect users' intention to adopt a mobile entertainment service (MES). We developed a set of key compatibility beliefs: compatibility with life-style, compatibility with social meaning, and compatibility with past flow experiences. We then defined the key dimensions of each construct and developed operational measures for those dimensions. We tested the theorized effects of each of the compatibility constructs on MES adoption. The results support the effects of compatibility beliefs on users' intentions to adopt MES.

• Journal of information and communication convergence engineering
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• 제5권4호
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• pp.362-368
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• 2007

A single-phase uninterruptible power supply system equipped with a superconducting magnet energy storage unit is proposed to achieve a simple circuit configuration and higher system reliability. It reduces a number of switching devices by applying a common-arm scheme. Removing some switches or substituting passive elements for active switches can increase the sophistication and reduces degree of freedom in control strategy. However, high-performance DSP controller can execute the complicated control task with no additional cost. Operational principles to normal, stored-energy, and bypass mode are discussed in detail. The validity of the proposed system is verified by experimental results.

• Journal of Communications and Networks
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• 제10권2호
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• pp.127-136
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• 2008

For mobile wireless systems with full frequency reuse, co-channel interference near the cell coverage boundaries has a significant impact on the signal reception performance. This paper addresses an approach to efficiently mitigate the effect of downlink co-channel interference when multi-antenna terminals are used in cellular environments, by proposing a signal detection strategy combined with a system-level coordination for dynamic frequency reuse. We demonstrate the utilization of multi-antennas to perform spatial demultiplexing of both the desired signal and interfering signals from adjacent cells results in significant improvement of spectral efficiency compared to the maximal ratio combining (MRC) performance, especially when an appropriate frequency reuse based on the traffic loading condition is coordinated among cells. Both analytic expressions for the capacity and experimental results using the adaptive modulation and coding (AMC) are used to confirm the performance gain. The robustness of the proposed scheme against varying operational conditions such as the channel estimation error and shadowing effects are also verified by simulation results.

• Transactions on Control, Automation and Systems Engineering
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• 제1권1호
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• pp.75-86
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• 1999

An air-data estimator for generic air-breathing hypersonic vehicles (AHSVs) is developed and demonstrated with an example vehicle configuration. The AHSV air-data estimation strategy emphasized improvement of the angle of attack estimate accuracy to a degree necessitated by the stringent operational requirements of the air-breathing propulsion. the resulting estimation problem involves highly nonlinear diffusion process (propagation); consequently, significant distortion of a posteriori conditional density is suspected. A simulation based statistical analysis tool is developed to characterize the nonlinear diffusion process. The statistical analysis results indicate that the diffusion process preserves the symmetry and unimodality of initial probability density shape state variables, and provide the basis for applicability of an Extended Kalman Filter (EKF). An EKF is designed for the AHSV air-data system and the air data estimation capabilities are demonstrated.

• Asia pacific journal of information systems
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• 제3권2호
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• pp.145-168
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• 1993

It has been asserted that information technology (IT) is being exploited by a number of corporations for strategic advantage. The successful implementation of an organization-wide IT, however, not only depends on its strategic and technological feasibility, but also on the effectiveness of organizational transformation strategies. In this case, the organizational transformation strategy and its success for the adoption of computerized typesetting systems (CTS) by one of the largest Korean newspaper companies, are described With an analysis on the Korean newspaper industry, the case explains the internal and external pressure towards the introduction of the new information technology and its development process. It also provides the architecture and operational mechanism of the CTS. Finally, the case analyzes the impact of the system on the competitive behaviors of the rivals in the industry.

• Journal of Information Technology Applications and Management
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• 제11권3호
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• pp.147-159
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• 2004

Empirical evidence on the maintainability of object-oriented systems is far from conclusive, partly due to lack of representativeness of the subjects and systems used in the study. The present research empirically examined this issue with the systems that are mission-critical. currently operational and maintained by professionals. It was found that the 00 group appeared to consume less time while maintaining more amount of software artifacts than the NOO counterpart. This economical utilization of time appeared evident regardless of software development life cycle. This was due to the usefulness of UML for impact analysis which contributed to effective comprehension and communication. Insufficient design specifications led to ambiguity and costly defects in transferring design solutions to development. Also. the encapsulation of 00 seemed to reduce mental loads at maintenance tasks and improved code reuse. However, the number of files to manage increased and thus. dependency management is required for the 00 systems.