• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 춘계학술대회
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• pp.783-785
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• 2013

본 논문은 무인항공기의 운용 고도 및 거리를 데이터링크 측면에서 분석하였다. 무인항공기의 운용 고도는 일반적으로 탑재되는 임무장비의 특성 및 운용 목적에 따라 결정된다. 무인항공기의 운용고도를 결정하기 전에 데이터링크 장비의 가시선 조건을 반드시 고려해야 한다. 가시선 분석은 지상통신장비의 안테나 특성 및 설치고도, 지구의 곡률 반경을 사용하여 분석했다. 지상통신장비 설치고도가 0m 일 때, 32dBi 파라볼라 안테나를 사용할 경우 통신거리 300km에서 13,724m이고, 44dBi 파라볼라 안테나를 사용할 경우 6,657m에서 운용 가능하다. 또한 원거리 통신에서는 고 이득안테나가 운용 고도 측면에서 유리함을 확인하였다.

• Journal of Power Electronics
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• 제7권1호
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• pp.28-37
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• 2007

A new PWM-controlled quasi-resonant converter for a high efficiency PDP sustaining power module is proposed in this paper. The load regulation of the proposed converter can be achieved by controlling the ripple of the resonant voltage across the resonant capacitor with a bi-directional auxiliary circuit, while the main switches are operating at a fixed duty ratio and fixed switching frequency. Hence, the waveforms of the currents can be expected to be optimized from the view-point of conduction loss. Furthermore, the proposed converter has good ZVS capability, simple control circuits, no high voltage ringing problem of rectifier diodes, no DC offset of the magnetizing current and low voltage stresses of power switches. In this paper, operational principles, features of the proposed converter, and analysis and design considerations are presented. Experimental results demonstrate that the output voltage can be controlled well by the auxiliary circuit using the PWM method.

• 대한수학교육학회지:수학교육학연구
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• 제8권2호
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• pp.553-563
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• 1998

In this thesis, I examined Bruner's EIS theory from the viewpoint of epistemology based on Piaget's genetic epistemology. Although Bruner's ideal thought which insisted ‘to teach the structure’accepted Piaget's theory in the methodology of realization, it is different from Piaget in understanding knowledge. The difference is shown from understanding the meaning of ‘structure’. Piaget's concept of structure is something that has overcome the realistic viewpoint of the traditional epistemology and is reconstructed through endless self-regulative transformational process. However Bruner's is used as a realistic meaning as we can see in the Plato's recollection theory. Therefore Piaget's ‘stage of development’means the difference of structure which lies in the generative process and it includes the qualitive difference of level. On the other hand, Bruner, who is trying to translate and suggest the fixed structure to the children understood Piaget's stage of development as the difference in the ways of representation. Piaget's operational constructivism insists that the children should ‘construct’the knowledge through their activity, and especially in case of the lohico-mathematical recognition, the source should be internalized activity, that is, operation. In view of this assertion, Burner's idea which insists to accept the structure of knowledge as a fixed reality and to suggest the translated representation proper to the cognitive structure of the children to teach them, has a danger of emphasizing only the functional aspects to deliver the given knowledge ‘quickly’. And it also has the danger of damaging ‘the nature of the knowledge’in the translated knowledge.

• 한국산업정보학회논문지
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• 제22권6호
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• pp.61-69
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• 2017

기업들은 ERP 시스템 도입 후에도 기존 시스템을 결합하여 운용하거나 새로운 시스템을 도입하기도 하며 각 기업의 ERP 시스템들이 연결, 통합되기도 한다. 이와 같은 이유로 ERP 출현과 함께 보다 강력하고 편리한 데이터 입력 기술에 대한 필요성이 점차 증가해왔다. 본 연구에서는 SAP R/3 시스템에서 제공하고 있는 인터페이스 기술과 함께 새로이 VBA기술을 사용하여 SAP R/3 시스템의 새로운 데이터 입력 인터페이스를 설계 및 구현하는 방안을 제시하였다. 이 방안의 장점은 사용자 관점에서 시스템 사용에 대한 거부감을 줄일 수 있으며 보다 편리한 데이터 입력과 출력으로 업무 효율성을 높일 수 있는 것으로 나타났다.

• 한국컴퓨터정보학회논문지
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• 제8권1호
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• pp.76-83
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• 2003

고객 충성도 향상을 통해 이익 증대를 도모하는 CRM 기술은 기업의 중요 전략중 하나인 동시에, 교육용 사이트의 CRM 특성 평가는 CRM 적용 활성화를 위하여 필수적 항목이라 할 수 있다 따라서 본 연구에서는 CRM 기술의 정의 및 특성. 웹사이트 평가 동향을 분석한 후 최근의 정량적 전역 평가 방법론인 Web-site QEM을 이용하여 CRM 특성 평가 모델을 설계한다. 이에 현재 운영 중인 교육용 사이트의 CRM 특성 서비스 내용을 비교하고, 학생 사용자 관점에서 고객 충성도와 고객 만족도를 향상시키기 위한 CRM특성에 대한 평가 기준과 정량적 모델을 제안한다. 제안된 평가 모델의 일부를 운영중인 교육용 사이트에 적용하여 결과 값을 제시한다.

• 한국태양에너지학회 논문집
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• 제28권3호
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• pp.15-20
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• 2008

Building-integrated photovoltaics(BIPV) are increasingly incorporated into new domestic and industrial buildings as a principal or ancillary source of electrical power, and are one of the fastest growing segments of the photovoltaic industry. This paper presents design, operational features analysis, and PCS(Power Conditioning System) of grid-connected 30kW BIPV set up on the library of Dongshin University. For a sustainable photovoltaics system in this area, the data of the BIPV system are collected and analyzed by monitoring system using LabView. PCS of the grid-connected BIPV system, also, is designed for optimal operation with characteristics suggested in this paper.

• 유공압시스템학회논문집
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• 제1권2호
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• pp.8-14
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• 2004

Abstract: In the oil hydraulic piston pumps the clearance between the valve plate and cylinder block plays an important role for volumetric and overall efficiency. Thus, adequate lubricational fluid film is needed for the interface. In this study, fluid film thickness is measured by a gap sensor and a slip ring under operational conditions to observe the behavior of the lubrication mechanism in detail. To investigate the effect according to the valve plate types in view of the fluid film, three different types were designed. Leakage flow rate and shaft torque were also measured to clarify the effect according to the valve plate types. A broad range of experiments were conducted to provide reasonable data on the effect of fluid film. In this experiments two main parameters were found, of which the one is the discharge pressure and the other is valve plate geometry. As a result, we found that the spherical valve plate could get more stable fluid film thickness, maintain good efficiency for high pressure range than the other types.

• 한국항해항만학회지
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• 제33권7호
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• pp.477-482
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• 2009

In this paper the order picking problem in warehouses is considered, a topic which has received considerable attention from the international academic body in recent years. The order picking problem deals with the retrieval of order items from prespecified locations in the warehouse, and its objective is usually the minimization of travel time or travel distance. Hence, a well-thought order picking policy in combination with an appropriate storage policy will enhance warehouse efficiency and reduce operational costs. This paper starts with a literature overview summarizing approaches to routing order pickers, assigning stock-keeping units to pick locations and designing warehouse layouts. Since the layout design might affect both storage and routing policies, the three factors are interdependent with respect to order picking performance. To test these interdependencies, a simulation experiment was set up, involving two types of warehouse layout, four types of storage policy, five well-known heuristics and five sizes of order picking list. Our results illustrate that from the point of view of order picking distance minimization it is recommended to equip the warehouse with a third cross aisle, although this comes at the cost of a certain space loss. Additionally, we propose a set of most appropriate matches between order picking heuristics and storage policies. Finally, we give some directions for further research and recommend an integrated approach involving all factors that affect warehouse efficiency.

• 한국정보전자통신기술학회논문지
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• 제1권2호
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• pp.27-32
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• 2008

A current research basically diverted towards an increase in the operational output with the minimization of the materials used, which ultimately scaled down the dimensions of ceramic electronic components. In this direction the nano-technology pave the revolutionary changes in particular the electronic industries. The applications of nano-sized particles or nano-sized materials are hence, playing a significant role for various purposes. The PZT(lead, zirconium, titanium) based ceramics which, are reported to be ferroelectric materials have their important applications in the areas of surface acoustic waves (SAW), filters, infrared detectors, actuators, ferroelectric random access memory, speakers, electronic switches etc. Moreover, these PZT materials possess the large electro mechanical coupling factor, large spontaneous polarization, low dielectric loss and low internal stress etc. Hence, keeping in view the unique properties of PZT piezoelectric ceramics we also tried to synthesize indigenously the small sized PZT ceramic powder in the laboratory by using the modified sol-gel approach. In this paper, propyl alcohol based sol-gel method was used for preparation of PZT piezoelectric ceramic. The powder obtained by this sol-gel process was calcined and sintering to reach a pyrochlore-free crystal phase. The characterization of synthesized material was carried out by the XRD analysis and the surface morphology was determined by high resolution scanning electron microscopy.

• 정보통신설비학회논문지
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• 제3권2호
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• pp.11-17
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• 2004

In this paper we propose a new conceptual system for a network clock in which all node clocks are simultaneously synchronized to the national standard by intermediation parameter of satellite time. Experiments have shown the possibility of its adoption by real networks. The new proposed method has various structural benefits, in particular all node clocks can be kept at the same hierarchical quality in contrast to the existing method. The measurement results show that the accuracy of the experimental slave clock system can be kept within a few parts In 1012 and the MTIE (Maximum Time Interval Error) sufficiently meets ITU-T G.811 for the primary reference clock. A prototype system with fully automatic operational functions has been realized at present and is expected to be directly used for communication network synchronization in the near future.