• Journal of Power Electronics
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• v.17 no.2
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• pp.533-541
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• 2017

This paper presents a novel Parameter-Independent Fictive-Axis (PIFA) approach for the Voltage-Oriented Control (VOC) algorithm used in grid-tied single-phase inverters. VOC is based on the transformation of the single-phase grid current into the synchronous reference frame. As a result, an orthogonal current signal is needed. Traditionally, this signal has been obtained from fixed time delays, digital filters or a Hilbert transformation. Nevertheless, these solutions present stability and transient drawbacks. Recently, the Fictive Axis Emulation (FAE) VOC has emerged as an alternative for the generation of the quadrature current signal. FAE requires detailed information of the grid current filter along with its transfer function for signal creation. When the transfer function is not accurate, the direct and quadrature current components present steady-state oscillations as the fictive two-phase system becomes unbalanced. Moreover, the digital implementation of the transfer function imposes an additional computing burden on the VOC. The PIFA VOC presented in this paper, takes advantage of the reference current to create the required orthogonal current, which effectively eliminates the need for the filter transfer function. Moreover, the fictive signal amplitude and phase do not change with a frequency drift, which results in an increased reliability. This yields a fast, linear and stable system that can be installed without fine tuning. To demonstrate the good performance of the PIFA VOC, simulation and experimental results are presented.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.4
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• pp.359-365
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• 2016

In this paper, a novel coupled C type resonator is proposed for improvement of phase noise characteristics that is weak point of oscillator using planar type microstrip line resonator. Oscillator using proposed coupled C type resonator is designed, it has improved phase noise characteristics. At the fundamental frequency of 9.8GHz, 2.4dBm output power and -82.7 dBc@100kHz phase noise have been measured for oscillator with coupled C type resonator. The phase noise characteristics of oscillator is improved about 9.7dB compared to one using the general ${\lambda}/4$ microstrip resonator. Due to its simple fabrication process and planar type, it is expected that the technique in this paper can be widely used for low phase noise oscillators for both MIC and MMIC applications.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.5-12
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• 2008

The construction of Pusan National University Yangsan Hospital is a new construction of a medical town in Yangsan. It is a case that CMr participated in the project from planning to post-completion. It shows an actual proof of Construction Management business applied CM by each phase. In this case, CMr selected the design-build contractor in the planning phase and technically performed CM businesses in every single phase such as design and construction schedule management regarding application of Fast Track technique, procurement management and contract administration in phases based on the Fast-tract; technique, design review, VE in the design phase, change order management in the construction phase and operating and maintenance in the post-construction phase. This study would go far toward applying CM to Mega Turnkey projects by analyzing the problems of CMr's practical application to the project and providing guidelines for effective and efficient CM business implementation especially in the Turnkey projects.

• 대한공업교육학회지
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• v.32 no.2
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• pp.199-216
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• 2007

Stream Control Transmission Protocol(SCTP) is a transport layer protocol to support the data transmission. SCTP is similar to Transmission Control Protocol(TCP) in a variety of aspects. However, several features of SCTP including multi-homing and multi-streaming incur the performance difference from TCP. This paper highlights the data transfer during the initial slow start phase in SCTP congestion control composed of slow start phase and congestion avoidance phase. In order to compare the mean transfer time between SCTP and TCP, we experiment with different performance parameters including bandwidth, round trip time, and data length. By varying data length, we also measure the corresponding initial window size, which is one of factors affecting the mean transfer time. For the experiment, we have written server and client applications by C language using SCTP socket API and have measured the transfer time by ethereal program. We transferred data between client and server using round-robin method. Analysis of these experimental results from the testbed implementation shows that larger initial window size of SCTP than that of TCP brings the reduction in the mean transfer time of SCTP compared with TCP by 15 % on average during the initial slow start phase.

• The KIPS Transactions:PartA
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• v.14A no.5
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• pp.301-308
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• 2007

This paper proposes high performance coprocessor architecture for real time dense disparity computation based on a phase-based binocular stereo matching technique called local weighted phase-correlation(LWPC). The algorithm combines the robustness of wavelet based phase difference methods and the basic control strategy of phase correlation methods, which consists of 4 stages. For parallel and efficient hardware implementation, the proposed architecture employs SIMD(Single Instruction Multiple Data Stream) architecture for each functional stage and all stages work on pipelined mode. Such that the newly devised pipelined linear array processor is optimized for the case of row-column image processing eliminating the need for transposed memory while preserving generality and high throughput. The proposed architecture is implemented with Xilinx HDL tool and the required hardware resources are calculated in terms of look up tables, flip flops, slices, and the amount of memory. The result shows the possibility that the proposed architecture can be integrated into one chip while maintaining the processing speed at video rate.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.539-545
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• 2016

In this paper, a novel coupled C type resonator is proposed for improvement of phase noise characteristics that is weak point of oscillator using planar type microstrip line resonator. Oscillator using proposed shorted coupled C type resonator is designed, it has improved phase noise characteristics. At the fundamental frequency of 9.8GHz, 4.87dBm output power and -84.7 dBc@100kHz phase noise have been measured for oscillator with shorted coupled C type resonator. Next, we designed voltage controlled oscillator using proposed shorted coupled C type resonator with varactor diode. The VCO has 33.8MHz tuning range from 9.7807GHz to 9.8145GHz, and phase noise characteristic is -115~-112.5dBc/Hz@100KHz. Due to its simple fabrication process and planar type, it is expected that the technique in this paper can be widely used for low phase noise oscillators for both MIC and MMIC applications.

• Journal of Sensor Science and Technology
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• v.6 no.2
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• pp.95-105
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• 1997

A new open-loop signal processing technique of digital phase tracking is known to have a Potential to solve the problems in the open-loop processor such as limited dynamic range, dependence on the optical intensity fluctuations, and dependence on gain fluctuations of signal path. But new problems with digital phase tracking must be solved before it can be a useful signal processing method. In this paper, barriers to the success of the digital phase tracking such as harmonics content, phase difference, amplitude variations of the phase modulation(PM) signal, bandwidth limit of the signal path, and the implementation of the mixer, are pointed out and their effects on the performance of the signal processor are analyzed to calculate the requirements of the signal processor for $1{\mu}rad$-grade FOG.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.4
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• pp.112-119
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• 2017

Selecting suppliers in the global supply chain is the very difficult and complicated decision making problem particularly due to the various types of supply risk in addition to the uncertain performance of the potential suppliers. This paper proposes a multi-phase decision making model for supplier selection under supply risks in global supply chains. In the first phase, the model suggests supplier selection solutions suitable to a given condition of decision making using a rule-based expert system. The expert system consists of a knowledge base of supplier selection solutions and an "if-then" rule-based inference engine. The knowledge base contains information about options and their consistency for seven characteristics of 20 supplier selection solutions chosen from articles published in SCIE journals since 2010. In the second phase, the model computes the potential suppliers' general performance indices using a technique for order preference by similarity to ideal solution (TOPSIS) based on their scores obtained by applying the suggested solutions. In the third phase, the model computes their risk indices using a TOPSIS based on their historical and predicted scores obtained by applying a risk evaluation algorithm. The evaluation algorithm deals with seven types of supply risk that significantly affect supplier's performance and eventually influence buyer's production plan. In the fourth phase, the model selects Pareto optimal suppliers based on their general performance and risk indices. An example demonstrates the implementation of the proposed model. The proposed model provides supply chain managers with a practical tool to effectively select best suppliers while considering supply risks as well as the general performance.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.1015-1018
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• 2007

VE is one of the most effective and systematic tool available to achieve the required function at minimum cost and manage in many industrial fields. The purpose of the preparation phase VE job plan is to establish a cooperation system referring to groups for the successful implementation of VE, and to achieve a common objective to collect sufficient materials required in the analysis phase. The Quality Model is used to measure the requirement of shareholders(users and owners)in the project. It also offers a guideline on decision making when executing the function definition, function arrangement, function evaluation, and the idea evaluation of VE. However, the current the preparation phase business confirms that the required items of owners and users has not suggested definite goals and directions. This study analyzes the problems of current work in the preparation phase from case study, survey and interviews of experts. It then proposes a new process after understanding the required items of owners, users and experts.

• Korean Journal of Construction Engineering and Management
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• v.9 no.4
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• pp.111-119
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• 2008

VE is one of the most effective and systematic tool available to achieve the required function at minimum cost and manage in many industrial fields. The purpose of the preparation phase VE job plan is to establish a cooperation system referring to groups for the successful implementation of VE, and to achieve a common objective to collect sufficient materials required in the analysis phase. The Quality Model is used to measure the requirement of shareholders(users and owners)in the project. It also offers a guideline on decision making when executing the function definition, function arrangement, function evaluation, and the idea evaluation of VE. However, the current the preparation phase business confirms that the required items of owners and users has not suggested definite goals and directions. This study analyzes the problems of current work in the preparation phase from case study, survey and interviews of experts. It then proposes a new process after understanding the required items of owners, users and experts.