• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.269-277
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• 1996

The vacuum systems of PLS linac provides average pressure of $2.6\times 10^{-6}$Pa under high power microwave of 54 MW peak with 4.1 $\mu \textrm s$ pulse width and 10 Hz repetition rates. The base pressure of system is$2.4\times 10^{-6}$Pa with 45$^{\circ}C$ cooling water. The outgassing rate of the system is decreased from $3.0\times 10^{-11}Torr-l/sec-\textrm{cm}^2$ at the initial stage after installation to $1\times 10^{-12}Torr-l/sec-\textrm{cm}^2$ at present. Total accumulated microwave energy dose is about 140 GJ per module. All ion pumps are working under saturated regime and effective pumping speeds of 60 I/s, 230 I/s ion pumps are 45 I/s, 65 I/s, 140 I/s under the operating range. Main problems occurred in recent year are troubles of ion pump controller and vacuum gauge controller, vacuum leak of energy doubler window and electron gun ceramic, and water leak in the dummy load of acceleraing columns. Total of 41 troubles with 140. 8 hours down time give good system availability of 98%. Down time can be reduced by high power waveguide valves and water dummy loads under development, and then availability is expected to be increased up to 99.5%.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.10a
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• pp.111-121
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• 1995

In Extracting the dynamic parameters for estimating the load carrying capacity and integrity of bridges, both the instrumentation and the processing the data plays important role . When the fixed point can not be secured, it is difficult and expensive to measure dynamic displacements. Even if the displacement is obtained through the integration of the acceleration data, the results can be quite different from the real behavior, because the main frequency contents can be leaked during discretized data processing. The instrumentation is used for measurements, and every measurement involves error and uncertainty, such as systematic, conformance, environmental, observational, sampling, and ranmom error. Systematic and conformance error can be remedied through the proper sellection and installation of the instruments, but sampling and random errors could not have been corrected properly and it becomes the limitation for using acceleration data. In this paper, the errors which can be occurred in numerical processing of dynamic data are referred, and the method to sellect proper sampling rate for the structural frequency range are proposed. Using the proposed method, the displacement response of the structures can be economically obtained from the measured acceleration record, and this procedure can be used properly to estimate the integrity of the bridges and infrastructures subjected to dynamic loads.

• International Journal of Highway Engineering
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• v.2 no.2
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• pp.139-148
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• 2000

Currently existing Accelerated Pavement Testing (APT) systems developed in several countries have been employed mainly to test the performance of asphalt pavement. Meanwhile, the length of concrete pavement is similar to that of asphalt pavement in expressways of Korea. and is expected to increase due to its durability and compatibility to our weather condition. To meet the society's demand of having our own APT system which can examine the long-term performance of concrete pavement, a contract study to develop Korea Accelerated Loading and Environment Simulator (KALES) for concrete pavement has been performed for 3 years from 1997 through 1999. Through the project, a detailed design was Peformed for the KALES system in which the entire structure of KALES, loading mechanism, wandering mechanism, suspension system, driving system were proposed. Also in advance to design a full-scale KALES system, a sample scale model was manufactured and tested for operating motion and force distribution. It is evident that the proposed prototype KALES system will provide higher degree of traffic simulation and durable operation, based on the satisfactory fatigue analysis.

• Polymer(Korea)
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• v.24 no.6
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• pp.837-844
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• 2000

The cure behavior of commercial epoxy molding compounds (EMC) commonly used for IC package was studied at constant cure temperatures as well as at constant heating rates using differential scanning calorimetry (DSC), rheometer, and dielectric analyzer (DEA). The cure kinetics were obtained using autocatalytic reaction model according to the Ryan Dutta method after assuming m+n equal to 2. The prediction of reaction rates by the model equation corresponded well to experimental data at all temperatures except for 10$0^{\circ}C$. The phase transitions such as gelation and vitrification occurred during network formation. At each isothermal cure temperature, $T_{g}$ was measured in accordance with cure time, and the vitrification point was attained when $T_{g}$ was equal to $T_{cure}$. The temperature dependence of gel points and vitrification points showed good agreement with Arrhenius relation. DEA using parallel plate electrode was effective for the monitoring of EMC cure. we knew that if the resin systems are materials of comparable quality, $_{gel}$$T_{g}$ is constant regardless of accelerator concentration in TTT (Time-Temperature-Transformation) diagram.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.46-46
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• 1999

터보분자펌프(turbomolecular pump, TMP)는 각종 연구장비, 반도체 제조장치, 가속기, 핵융합 실험 장치 등 여러 분야에서 가장 널리 쓰이는 고진공 펌프로서 자리잡고 있다. 이런 TMP의 광범위한 사용에도 불구하고 성능평가에 관한 통일된 규격이 마련되어 있지 않다. 국제 규격협회(ISO)의 터보분자펌프 성능평가방법 시안을 토대로 제정중인 KS 규격은 아직 실험적인 근거를 자체적으로 가지고 있지 못하므로 앞으로 각 항목들에 대한 많은 실험이 수행되어야 한다. TMP의 성능을 나타내 주는 항목들 중 배기속도(pumping speed)와 압축비(compression ratio)는 가장 중요한 것들로서 다른 고진공 펌프 및 TMP 상호간의 성능을 비교할 수 있는 기본 항목이라 할 수 있다. 본 실험에서는 종래의 단순 TMP와 큰 기체유량에서도 안정된 배기속도를 유지하는 복합터보분자펌프(compound molecular pump, CMP)의 배기속도와 압축비 및 임계배압(critical backing pressure)을 KS 규격안대로 시험 평가하여 안의 평가방법과 기준의 타당성을 검토하고, 두 가지 다른 방식의 펌프에 적용할 수 있는지를 검토하였다. TMP 및 CMP 흡기구에 표준용기를 부착하고 수소 및 질소 기체를 사용하여 흡기구 압력을 변화시키면서 배기속도 및 압축비를 측정하고 배기구 압력을 변호시키면서 최대압축비 및 임계배압을 측정하였다. 흡기구의 압력측정에는 인출형 전리진공계(EG)를 사용하였고, 배기구의 압력측정은 전기용량의 격막진공계(CDG)와 피라니 진공계로 측정하였다. 진공계는 모두 회전식 점성진공계(SRG)로 교정한 후 사용하였다.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2017.11a
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• pp.1533-1549
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• 2017

정부 R&D성과의 질적 수준을 제고하고 중장기 국가 재정사업의 효율성을 높이기 위한 각 연구 기관의 시도들이 있어 왔다. 연구사업의 발굴, 기획 및 수행에 있어 효과적인 정부 R&D 예산의 배분, 우선순위를 도출, 기술개발 전략 수립을 하는 것이 매우 중요해지고 있다. 정부 재정사업인 국가 R&D사업은 국가 기간산업을 활성화하고 경제발전을 수반할 수 있는 중요한 모멘텀으로서의 역할을 하고 있다. 또한, 국가 R&D사업의 한 축인 거대과학은 최첨단 기술의 개발과 미래성장동력의 발굴이라는 대명제로 그 중요성이 강조되고 있다. 거대과학 연구는 그 분야의 특수성으로 인해 대학의 과학자, 공공 연구기관의 연구원, 기업의 엔지니어가 함께 참여하여야 하고 대규모 국가 예산을 동원하는 과학 연구 사업이다. 이는 대규모 예산을 기반으로 하고 있기에 집중적 투자가 수반된다면 단기적으로 기초과학의 발전을 이뤄낼 수 있다. 이것은 산업발전에 밑거름이 되어 그 분야 자체로 하나의 산업생태계를 구성하고 요소 기술들의 응용으로 파생기술이 전파된다면 새로운 신산업 창출 등 국가산업에 많은 혜택을 줄 수 있다. 하지만 많은 인력과 대규모 투자 그리고 중장기 프로젝트라는 특성으로 인해 실패 가능성도 높아 전략적 선택 및 추진이 필요하다. 따라서 본 논문에서는 거대과학의 기술개발전략의 수립을 위하여 중이온 입자가속기 핵심부품 국산화 전략수립 사례를 중심으로 효율적인 R&D추진 방안을 도출해보고자 한다. 또한, 논문, 특허를 기반으로 한 3P분석을 통하여 중이온 가속기 핵심부품의 국산화 전략을 제안하고, 추진 우선순위 및 전략을 제시하고자 한다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.451-464
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• 2022

The high-level nuclear waste repository is a deep geological disposal system exposed to complex environmental conditions such as high temperature, radiation, and ground-water due to handling spent nuclear fuel. Continuous exposure can lead to cracking and deterioration of the structure over time. On the other hand, the high-level nuclear waste repository requires an ultra-long life expectancy. Thus long-term structural health monitoring is essential. Various sensors such as an accelerometer, earth pressure gauge, and displacement meter can be used to monitor the health of a structure, and a piezoelectric sensor is generally used. Therefore, it is necessary to develop a highly durable sensor based on the durability assessment of the piezoelectric sensor. This study designed an accelerated life test for durability assessment and life prediction of the piezoelectric sensor. Based on the literature review, the number of accelerated stress levels for a single stress factor, and the number of samples for each level were selected. The failure mode and mechanism of the piezoelectric sensor that can occur in the environmental conditions of the high-level waste repository were analyzed. In addition, two methods were proposed to investigate the maximum harsh condition for the temperature stress factor. The reliable operating limit of the piezoelectric sensor was derived, and a reasonable accelerated stress level was set for the accelerated life test. The suggested methods contain economical and practical ideas and can be widely used in designing accelerated life tests of piezoelectric sensors.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.139-140
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• 2009

양성자 기반 공학 기술 개발 사업단은 20MeV 양성자 가속기를 운전 중이며, 진공, 빔 계측, 전원 등의 장치에 대한 제어 시스템을 개발 운영 중이다. 대형 입자 가속기를 위한 제어 시스템의 전체 네트워크는 사용자 인터페이스와 제어계가 단일 네트워크를 공유하고 있으며 EPICS(Experimental Physics and Industrial Control System) CA(Channel Access)통신을 이용하여 데이터를 상호 교환한다. 그러나 단일 네트워크를 사용함으로서 관리자만이 제어해야 할 데이터는 많은 클라이언트에게 노출되는 문제점이 있다. 그러므로 클라이언트의 접근을 제어하여 제어계로부터 전달되는 신호들의 안정성과 보안성을 유지할 수 있는 방법이 요구된다. 본 논문에서는 제어시스템에 보안성과 안정성을 유지하기 위하여 클라이언트를 Control Network, 제어계를 Machine Network로 분산시키고 통신 중계기 역할을 하는 CA Gateway를 적용하여 클라이언트에게 접근 권한을 주는 기법을 제시하고 구현 및 그 결과를 보고한다.

• Journal of the Korean Society of Groundwater Environment
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• v.2 no.1
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• pp.22-29
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• 1995

Mobile bacterial particles can act as carriers and enhance the transport of hydrophobic contaminants in ground water by reducing retardation effects. Because of their colloidal size and favorable surface conditions, bacteria can act as efficient contaminant carriers. When such carriers exist in a porous medium, the system can be thought of as three phases: an aqueous phase, a carrier phase, and a stationary solid matrix phase. Contaminant can be present in either or all of these phases. In this study, a mathematical model based on mass balances is developed to describe the transport and fate of biodegradable contaminant in a porous medium. Bacterial mass transfer mechanism between aqueous and solid matrix phases, and contaminant mass transfer between aqueous and bacterial phases are represented by kinetic models. Governing equations are non-dimensionalized and solved to analyze the bacteria facilitated contaminant transport. The numerical results of the facilitation effect match favorably with experimental data reported in the literature. Results show that the contaminant transport can be described by local equilibrium assumption when Damkohler numbers are larger than 10. Significant sensitivities to model parameters, particularly bacterial growth rate and influent bacterial concentration, were discovered.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.899-909
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• 1992

An iterative solution technique is presented to analyze the dynamic systems of rigid bodies subjected to kinematic constraints. Lagrange multipliers associated with the constraints are iteratively computed by monotonically reducing an appropriately defined constraint error vector, and the resulting equation of motion is solved by a well-established ODE technique. Constraints on the velocity and acceleration as well as the position are made to be satisfied at joints at each time step. Time integration is efficiently performed because decomposition or orthonormalization of the large matrix is not required at all. An acceleration technique is suggested for the faster convergence of the iterative scheme.