• 대한기계학회논문집
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• 제19권1호
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• pp.284-291
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• 1995

This paper proposes a method for determination of optimal reference spectrum in random vibration control. The least square method is used to minimize the spectrum deviation between the specified reference spectrum and spectra at the specimen-mounted points. This method needs only the measured FRF's at the control point and specimen-mounted points in pre-vibration test. Using the proposed method as reference spectrum, it is possible to easily predict spectra at the specimen-mounted points, and also to reduce overtest resulting from dynamic characteristics of shaker and fixture. This method is shown through theoretical and experimental results to be an effective method.

• 전기학회논문지
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• 제59권2호
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• pp.465-470
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• 2010

The charge pump in a phase-locked loop is a key block in determining reference spurs of the VCO output signal. To reduce reference spurs, the current mismatch in the charge pump must be minimized. This paper presents a dual compensation method to reduce the current mismatch. The proposed charge pump and PLL were realized in a $0.18{\mu}m$ CMOS process. Measured current matching characteristics were achieved with less than 1.4% difference and with the current variation of 3.8% in the pump current over the charge pump output voltage range of 0.35-1.35V at 1.8V. The reference spur of the PLL based on the proposed charge pump was measured to be -71dBc.

• Journal of Information Processing Systems
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• 제14권3호
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• pp.631-644
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• 2018

Many studies on flash memory-based buffer replacement algorithms that consider the characteristics of flash memory have recently been developed. Conventional flash memory-based buffer replacement algorithms have the disadvantage that the operation speed slows down, because only the reference is checked when selecting a replacement target page and either the reference count is not considered, or when the reference time is considered, the elapsed time is considered. Therefore, this paper seeks to solve the problem of conventional flash memory-based buffer replacement algorithm by dividing pages into groups and considering the reference frequency and reference time when selecting the replacement target page. In addition, because flash memory has a limited lifespan, candidates for replacement pages are selected based on the number of deletions.

• Advances in concrete construction
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• 제9권6호
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• pp.547-556
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• 2020

This study aimed to develop reference materials (RMs) that are chemically stable and can simulate the flow characteristics of cement paste. To this end, the candidate components of RMs were selected considering the currently required properties of RMs. Limestone, slag, silica, and kaolin were selected as substitutes for cement, while glycerol and corn syrup were selected as matrix fluids. Moreover, distilled water was used for mixing. To select the combinations of materials that meet all the required properties of RMs, flow characteristics were first analyzed. The results revealed that silica and kaolin exhibited bilateral nonlinearity. When an analysis was conducted over time, slag exhibited chemical reactions, including strength development. Moreover, fungi were observed in all mixtures with corn syrup. On the other hand, the combination of limestone, glycerol, and water exhibited a performance that met all the required properties of RMs. Thus, limestone, glycerol, and water were selected as the components of the RMs. When the influence of each component of the RMs on flow characteristics was analyzed, it was found that limestone affects the yield value, while the ratio of water and glycerol affects the plastic viscosity. Based on this, it was possible to select the mixing ratios for the RMs that can simulate the flow characteristics of cement paste under each mixing ratio. This relationship was established as an equation, which was verified under various mixing ratios. Finally, when the flow characteristics were analyzed under various temperature conditions, cement paste and the RMs exhibited similar tendencies in terms of flow characteristics. This indicated that the combinations of the selected materials could be used as RMs that can simulate the flow characteristics of cement paste with constant quality under various mixing ratio conditions and construction environment conditions.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.639-643
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• 2018

전자 시스템이 소형화, 이동성의 요구에 따라 전력 변환의 필요성이 계속 증가하고 있다. 또한 전력 변환에는 전력 효율과 함께 전력 변환시스템의 소형화를 위해 적용하는 스위칭에 의한 잡음으로부터 시스템 안정성이 보장되어야 한다. 따라서 전력 변환시 스위칭 잡음을 감소시킬 수 있는 대책이 필수적이다. 본 논문에서는 DC/DC Buck Converter회로를 구성하였고, reference plane을 갖는 4층 PCB 회로 구조에서 부품의 배치를 변경할 경우 발생하는 스위칭 잡음특성을 비교 분석하였다. 또한, Reference Plane을 제거한 양면 PCB회로 구조에서 부품 배치를 달리하였을 경우 스위칭 잡음 특성을 각각 시뮬레이션으로 비교 분석하였다. 그 결과 4층 PCB회로 구조에서는 Current return path에 따라 Radiated Emission 특성이 12dB, Conducted Emission 특성이 7~8dB 감소됨을 확인하였다. 또한 양면 PCB회로 구조에서는 Conducted Emission이 20~25dB 감소됨을 확인하였다. 이로써 전력 변환 회로를 설계할 경우 Current return path의 구성에 따라 잡음 특성을 향상시킬 수 있음을 확인하였다.

• 대한토목학회논문집
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• 제31권6D호
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• pp.765-769
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• 2011

기존의 이동식 기준장비는 갓길의 폭이 1.5m 이하인 도로 구간에는 설치가 어려우며 장비가 크고 무거워서 차량과의 충돌 시 피해가 클 수 있으며 한 번에 다차로 검지가 불가능하다. 본 연구에서는 이러한 문제점을 노정하고 있는 기존의 이동식 기준장비의 단점을 극복하기 위하여 연구 개발된 USN-기반 이동식 기준장비의 특징을 기술하고 그 성능수준을 현장 적용을 통하여 평가하였다. 그 결과 본 연구에서 개발된 장비는 기존의 이동식 기준장비가 가지고 있는 운영상의 단점을 극복할 뿐 아니라 기준장비가 가져야 할 성능수준을 만족하는 것으로 나타났다.

• 한국정보시스템학회지:정보시스템연구
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• 제18권2호
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• pp.35-59
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• 2009

The study of Information Systems(IS) is a relatively new discipline area, thus an analysis of the latest research literature could be useful to identify what the researchers are doing and what can be done to improve our discipline. With that purpose in mind, this study analyzes the total 208 articles published in "The Journal of Information Systems~ between 2001 and 2008. The classification system that comprises three key characteristics of diversity (research topic, research method, and reference discipline) was developed based on a review of prior literature. The results of this study were also compared with Kim et al.(2005)'s and Vessey et al.(2002)'s results to identify issues in current Information Systems research and 10 suggest some recommendations for future In formation Systems research. The findings identify popular research topic:s, the dominant research method, and reference discipline. The popular research topics consists of organizational concepts, problem domain-specific concepts, and systems/software management concepts. Field study was characterized as the dominant research method in the papers included in the study. Information Systems itself represents the major theoretical reference of the studies. However, many papers in this study relied on a number of reference disciplines., none of which was dominant, or they did not rely on a specific reference discipline. Finally, this study suggests more research on the disciplinary issues, more training on the research method, more accurate and specific reference discipline, and controlled diversity.

• 정보관리학회지
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• 제26권3호
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• pp.89-110
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• 2009

본 연구는 근래 국내 대학도서관에서 도입이 가시화되고 있는 주제전문서비스를 마케팅의 한 분야인 고객관계관리(Customer Relationship Management: CRM)의 관점에서 살펴보고, 실제로 이 서비스가 대학도서관의 이용자, 특히 교수진들과의 관계에서 수행하는 역할과 이를 통한 마케팅의 효과를 알아보는 것을 그 목적으로 한다. 이를 위해 본 연구는 서비스의 실무자인 주제전문사서들과의 포커스 그룹 인터뷰와 서비스 대상자인 교수이용자와의 개별 심층 면접법을 실시하였으며, 또한 대학도서관의 교수이용자와의 관계의 유지 및 심화를 위한 주제전문사서의 요건을 함께 논의하였다. 본 연구는 주제전문서비스의 목적과 특성을 이용자 및 CRM의 관점에서 논의하였다는 데에 그 의의가 있다.

• 융합보안논문지
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• 제6권4호
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• pp.91-99
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• 2006

그 동안 이루어진 웹 캐싱에 대한 연구주제는 캐시에 대한 구조적인 접근을 통한 성능의 향상과, 캐싱 기법 자체에 대한 연구, 이들 기법을 혼합적으로 결합한 기법에 대한 연구가 주로 이루어져 왔다. 또한 기존의 웹 객체 참조특성 분석은 웹 로그를 통한 히스토리 분석, 사용자선호도, 데이터마이닝 관점에서의 사용자 특성을 위주로 이루어져왔다. 본 연구에서는 웹 객체참조특성을 확률분포적인 특성 관점에서 분석하며, 이를 통해 객체의 평균수명을 분석하고 이를 웹 캐싱 성능 향상에 도입하는 새로운 연구 방법을 제시한다. 본 연구는 다양한 연구로 발전할 수 있으며, 전자상거래시스템의 성능향상, 지연시간 계산을 통한 고객 만족도의 향상, 웹 로그분석을 통한 데이터마이닝 분야 등 다양한 분야에 대해 연구의 파급 효과가 기대된다.

• International Journal of Fluid Machinery and Systems
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• 제8권1호
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• pp.55-62
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• 2015

This study aims to present a hydraulic transitory study as MOC applications for solving the Saint-Venant equations in two case studies: 1) in a penstock of a small hydropower system as a simple pipeline in the case of valve-closure in the downstream boundary with a reservoir in the upstream boundary; and 2) for discharge propagation into a channel by velocity and depth of the flow channel along space evaluation. The proposed methodology by Chaudry [5] concerning the development of hydrodynamic models was used. The obtained results for first and second case study has been confirmed that MOC numerical approach is useful for several engineering purposes, including cases of hydraulic transients and discharge propagation in hydraulic systems.