• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.102-106
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• 2009

This paper presents the design and optimization of output matching network according to envelope for class F power amplifier(PA) which is to apply to envelope elimination and restoration(EER) transmitter. In this paper, to increase the PAE of class F power amplifier which applies to EER transmitter, the varactor diode has been used on output matching network. As envelope changes, it optimizes constitution of harmonic trap that is short circuit in 2nd-harmonic and is open circuit in 3rd-harmonic. When drain voltage changes from 25 V to 30 V, some percentage is improved in the PAE.put the abstract of paper here.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2017.08a
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• pp.84-100
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• 2017

제1차 벤처붐을 겪은 이후 후기에 안정된 기업에 투자를 선호하는 벤처투자방식의 변화가 나타나고 있다. 기업성장단계에서 초기에서 중기에 있는 기업의 경우 자금의 부족을 경험하며, 지속적인 성장을 위해서 정부 R&D자금 지원을 받고 있다. 하지만 정부의 R&D자금 지원이 과연 지속가능성 측면에서 경쟁력이 있는 기업에게 지원되고 있는가에 대한 우려의 목소리가 있다. 본 연구는 제조업에 속하는 벤처기업을 대상으로 DEA 효율성 분석을 실시하였다. 이를 통하여 제조업에 속한 핵심 산업인 ICT제품과 같은 첨단제조와 기계, 자동차와 같은 일반제조에 속한 벤처기업의 효율성을 살펴보고, R&D지원을 받는 벤처기업과 그렇지 않은 기업을 비교분석한다. 추가로 두 집단 간의 특성(혁신성, 성장성, 수익성, 안전성)이 1년간 어떻게 변화하였는지 분석한다. 실증 분석결과, 제조업에 속한 R&D자금을 지원받는 벤처기업의 경우 그렇지 않은 기업보다 효율성이 낮은 것으로 나타났다. 이는 지원을 받은 벤처기업이 지속가능한 측면에서 비지원기업 보다는 경쟁력이 낮음을 시사한다. 그리고 1년간의 여러 특성의 변화를 살펴본 결과, 혁신성에서는 지원기업이 높은 성과를 창출하였지만, 수익성에 있어서 비지원기업 보다 저조한 것으로 나타났다. 따라서 정부의 R&D지원이 지속가능성 측면에서 경쟁력이 있는 기업에게 지원되기 위해서는 기술력뿐만 아니라 경영 효율성을 고려하는 시도가 필요하다.

• Journal of Information Technology Services
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• v.17 no.3
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• pp.171-189
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• 2018

To remove software defects and improve performance of software, many developers perform code inspections and use static analysis tools. A code inspection is an activity that is performed manually to detect software defects in the developed source. However, there is no clear criterion which source codes are inspected. A static analysis tool can automatically detect software defects by analyzing the source codes without running the source codes. However, it has disadvantage that analyzes only the codes in the functions without analyzing the relations among source functions. The functions in the source codes are interconnected and formed a social network. Functions that occupy critical locations in a network can be important enough to affect the overall quality. Whereas, a static analysis tool merely suggests which functions were called several times. In this study, the core functions will be elicited by using social network analysis and DEA (Data Envelopment Analysis) for CUBRID open database sources. In addition, we will suggest clear criteria for selecting the target sources for code inspection and will suggest ways to find core functions to minimize defects and improve performance.

• Journal of Environmental Policy
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• v.14 no.2
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• pp.27-47
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• 2015

In this paper, we present a new empirical method to estimate the environmental efficiency of decision making units. We propose a model with a new approach that describes a network process consisting of two stages, production and wastewater abatement based on the data extracted from 51 Korean industrial complexes. Taking into account the inter-dependency of two stages, we show a process how to decompose the environmental efficiency into production efficiency and abatement efficiency. Moreover, our new proposed method can be used to explain the information on network relationship between economic growth and environmental protection.

• Korean Journal of Community Nutrition
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• v.12 no.2
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• pp.178-188
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• 2007

This study was performed to suggest a new efficiency measurement indicator is necessary for evaluating management efficiency of food service operations in contract-managed foodservice companies, to distinguish efficient food service providers and inefficient ones by measuring comparative efficiency among food service operations, and to provide guidance for effective management through showing benchmarking targets for improving inefficient food service providers. The subjects of this study were the 93 B&I foodservice Operations of a domestic contract food service company. The analysis was conducted using CCR model in DEA model. A software, 'Frontier analyst', was used for the analysis. Based on the results derived from comparison of efficiency evaluation classified by providers with use of DEA, it was possible to identify efficient food providers and inefficient providers, and subsequently provide benchmarking guidelines for improvement of the inefficient groups. In analyzing the differences between the results of DEA efficiency evaluation by detailed operation status of food service providers, there was significant difference of efficiency outcomes in terms of contract types, while there was no significant difference in terms of business condition.

• Journal of Korean Society of Transportation
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• v.23 no.8 s.86
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• pp.89-98
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• 2005

The privatization and commercialization of airports has moved forward at the globa1 level. individual countries have begun to focus less on the public welfare aspect of airports, and to emphasize the need to uncover means of increasing their respective airports economic performance and profitability. Although there is a need for Korean airports to be managed in accordance with this global trend. In order to conduct an accurate comparison and analysis of the managerial performances of the fourteen airports, the WLU(Work Load Unit) a concept which integrates the two outputs of airports, namely, passengers and freight, was employed in this study. Furthermore, in order to overcome the limitations of conducting a financial comparison based solely on WLU, the DEA model was also employed to evaluate airport efficiency: moreover, the benchmarking method was used to establish the input-output goals.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.197-204
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• 2013

In this paper, we propose a new method for artificial bandwidth extension of narrow-band signal in frequency domain. In the proposed method, a narrow-band signal is decomposed into excitation signal and spectral envelope, which are extended independently in frequency domain. The excitation signal is extended such that low-band harmonic structure is maintained in high band, and the spectral envelope is extended based on sub-band energy using NMF. Finally, the spectral phase is determined based on signal correlation between frames in time domain, resulting in the final wide-band signal. The subjective evaluation verified that the wide-band signal generated by the proposed method has a higher quality than the original narrow-band signal.

• Journal of Information Management
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• v.41 no.2
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• pp.111-131
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• 2010

This paper examines the levels and influence factors on efficiency of public libraries in metropolitan cities. For this purpose, In the first stage, the efficiency score analysis of 129 sample public libraries has been undertaken. In the second stage, the efficiency scores obtained from the first stage are regressed on environmental factors. The result of this study shows that : (1) main source of technical inefficiency is pure technical inefficiency rather than scale inefficiency; (2) it is positive effect environmental factors on the efficiency that the population, the dummy variable of capital area.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.225-226
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• 2014

The purpose of this study is to suggest a major strategy to become effective for each port in Northeast Asia by analyzing the relative efficiency of each port to determine the current level of efficiency, efficient harbors plan. Individual port of the major 16 ports in Northeast Asia was analysed targeting efficiency and relative efficiency. In this study, DEA technique was used ${\cdots}$(중략)${\cdots}$.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.179-181
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• 2009

고압 방전 램프는 점등 후부터 정상상태에 이르기까지 방전관 내부의 온도 및 압력이 광범위하게 변화하는 복잡한 동작 특성으로 모델링이 어렵다. 이러한 특성은 램프를 구동하는 안정기의 설계에 어려움이 따른다. 램프의 구동에는 초기 점화 시 높은 점화용 전압 펄스를 필요로 한다. 점화 후에 정상상태에 다다르면 램프 전극의 소모를 줄이기 위해 교류로 구동되어야 한다. 하지만 램프를 교류로 구동하게 되면 음향 공진 현상이 발생할 수 있다. 음향 공진 현상은 램프 구동 전류의 맥동성분이 큰 경우에도 발생을 할 수 있으므로 구동 전류의 맥동 성분의 크기는 최소화 돼야 한다. 램프의 수명시간을 길게 하려면, 안정기는 램프를 정격전력으로 구동하여야 한다. 따라서 안정기에서는 정전력 제어가 필요하게 된다. 램프 전류의 극성이 변화할 때, 램프 전류는 spike전류와 중첩이 된다. 본 논문에서는 spike 전류를 저주파구형파 램프 전류의 포락범위 안에 유지하고, 고주파 스위칭시손실을 줄이기 위해 소프트 스위칭 기법을 이용한 회로 설계를 제안했다. 제안된 방법은 시뮬레이션 및 이론적 수식적 방법으로 검증 했다.