• 한국위성정보통신학회논문지
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• 제10권4호
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• pp.58-63
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• 2015

GPS(Global Positioning System는 지구상에서 약 2km 떨어진 위성으로부터 송신한 신호를 수신하므로 그 수신감도가 매우 낮아 재밍과 간섭에 매우 취약하다. 따라서 GPS 수신단에서 항재밍 능력에 대한 필요성은 점점 증가하고 있다. 이러한 GPS의 취약성을 이용하여 전시 상황에서 적군은 재밍 기법을 이용하여 수신단에서 아군의 GPS 신호를 이용한 정확한 측위를 방해한다. 따라서 전시상황에 대비하여 재밍 환경에 대응하고, 측위 정보를 획득할 수 있는 방법이 필요하다. 본 연구에서는 재밍 환경에서의 측위 정확도를 향상시키기 위해 BSS(Blind Source Separation) 기법을 사용하여 GPS 신호와 재밍 신호를 분리하는 방법을 제안한다. 또 재밍신호와 분리된 GPS 신호에는 여전히 잡음(noise)이 존재해 정확한 측위 정보를 획득하기 어렵다. 따라서 잡음을 효과적으로 제거하기 위해 웨이블릿 임계화 기법을 사용한다. 실험 결과는 본 연구실에서 수행한 GPS/QZSS/Wi-Fi 밀결합 측위기법의 테스트 결과를 이용하여 재밍 환경에서의 BSS 와 웨이블릿 임계화 기법을 통한 정확도 향상을 보이며 제안한 시스템 모델의 우수성을 입증한다.

• 한국물환경학회지
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• 제36권6호
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• pp.489-499
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• 2020

Effective science-based management of the basin water resources requires an understanding of the characteristics of the streams, such as the baseflow discharge. In this study, the base flow was estimated in the two watersheds with the least artificial factors among the Nakdong River watersheds, as determined using the chemical hydrograph separation technique. The 16-year (2004-2019) discontinuous observed stream flow and electrical conductivity data in the Total Maximum Daily Load (TMDL) monitoring network were extended to continuous daily data using the TANK model and the 7-parameter log-linear model combined with the minimum variance unbiased estimator. The annual base flows at the upper Namgang Dam basin and the upper Nakdong River basin were both analyzed to be about 56% of the total annual flow. The monthly base flow ratio showed a high monthly deviation, as it was found to be higher than 0.9 in the dry season and about 0.46 in the rainy season. This is in line with the prevailing common sense notion that in winter, most of the stream flow is base flow, due to the characteristics of the dry season winter in Korea. It is expected that the chemical-based hydrological separation technique involving TANK and the 7-parameter log-linear models used in this study can help quantify the base flow required for systematic watershed water environment management.

• 한국항공우주학회지
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• 제34권5호
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• pp.19-29
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• 2006

본 연구에서는 비행중인 유도무기의 기체분리에 대한 수치적 해석을 수행하였다. 기체의 정확한 분리운동을 모사하기 위해 삼차원 공간에서 각각의 물체가 연결되어 움직이는 6자유도 운동방정식을 유도하였으며, 물체를 둘러싼 격자계의 독립적인 처리를 위해 개발된 비정렬 중첩격자기법과 연계하였다. 개발된 해석기법은 유도무기의 받음각이 0도와 5도인 경우의 기체분리운동 해석에 적용되었으며, 이를 통해 본 연구에서의 해석기법이 다중 물체간의 상대운동이 있는 비정상 유동장을 해석하는데 효과적임을 알 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.395-400
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• 2004

In most physical processes, the transfer function includes time-delay, and in the general distributed control system using computer network, there exists inherent time-delay caused by the spatial separation between controllers and actuators. This work deals with the synthesis of a discrete-time controller for a nonlinear system and proposes a new effective method to compensate the influence of input time-delay. The controller is synthesized by using input/output linearization. Under the circumstance that input time-delay exists, the system response has more overshoot and tends to diverge. For these reasons, the controller has to produce future input value that will be needed for the system. In order to calculate the future input value, some predictors are adopted. Using the discretization via Euler's method, numerical simulations about the Van der Pol system are performed to evaluate the performance of the proposed method.

• Journal of Advanced Marine Engineering and Technology
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• 제25권2호
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• pp.365-374
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• 2001

Its a tendency to strengthen related international was as the importance on marine oil pollution recently becomes the issue. According to the regulation of IMO, oil discharge from ships is allowed under 15PPM only and oil filtering equipment is essential. Oily water separator of laminated plate type which is one of gravity type separator can be use as assistant equipment for the oil filtering system to meet the present IMO standard, because it fits well to process large amount of rich oil with high specific gravity. The purpose of this paper is to investigate an efficiency of oil/water separation with the characteristics of laminated plate arrangement. The analyse of oil contents for oil-water mixture were carried out in order to find an efficiency of oil/water separation and an experimental study was simultaneously carried out to investigate internal flow characteristics of separator by visualization method and PIV(Particle Image Velocimetry) measurement at three spaces of plates for 5, 10 and 15 mm with variation of inlet flow rates of $0.25m^3$/h and $0.5m^3$/h. The experimental results showed that the space of the plates acts a significant role in the separating process.

• 멤브레인
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• 제9권4호
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• pp.215-220
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• 1999

고농도의 초산수용액(80 wt% 이상)을 분리 농축하기 위하여 내용매성이 우수하며 고온에서의 내열성을 가지는 폴리이미드 비대칭막을 만들어 막의 특성을 검토하고 물-초산 계의 투과증발 분리성능을 고찰하였다. 제막은 폴리아믹산의 상전이용액으로 톨루엔을 사용한 것이 가장 좋은 상태의 막을 얻을수 있었다. 열처리에 의한 imide화는 373, 473573 K에서 각각 1시간씩 연속적으로 처리하는 것이 가장 효과적이었다 막은 물-초산 계의 투과증발 분리에 의한 열내구성 및 화학적 안정성이 우수하였다 폴리이미드막의 투과증발 분리특성은 80 wt% 초산수용액 계에서 분리계수는 180 투과유속은 0.5kg/$m^2$hr을 얻을 수 있었다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권5호
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• pp.352-357
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• 2000

This paper presents about an example of circuit design and characteristics of inverter according to the variable capacitance of the DC voltage source separation capacitor used in ZVS-HB type high frequency resonant inverter. The soft switching technology known as ZVS is used to reduce turn off loss at switching. In the event the capacitance of the DC voltage source separation capacitor is varied, the analysis of inverter circuit has generally described by using normalized parameter and operating characteristics have been evaluated in terms of switching frequency and parameters. According to the calculated characteristics value, a method of the circuit designs and operating characteristic of the inverter is also presented in this paper. In addition, this paper proves the validity of theoretical analysis through the experiment. This proposed inverter shows that it can be practically used in future as power source system for the lighting equipment of discharge lamp, DC-DC converter etc.

• Smart Structures and Systems
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• 제24권4호
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• pp.507-524
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• 2019

A Bayesian dynamic linear model (BDLM) is presented for a data-driven analysis for response prediction and load effect separation of a revolving auditorium structure, where the main loads are self-weight and dead loads, temperature load, and audience load. Analyses are carried out based on the long-term monitoring data for static strains on several key members of the structure. Three improvements are introduced to the ordinary regression BDLM, which are a classificatory regression term to address the temporary audience load effect, improved inference for the variance of observation noise to be updated continuously, and component discount factors for effective load effect separation. The effects of those improvements are evaluated regarding the root mean square errors, standard deviations, and 95% confidence intervals of the predictions. Bayes factors are used for evaluating the probability distributions of the predictions, which are essential to structural condition assessments, such as outlier identification and reliability analysis. The performance of the present BDLM has been successfully verified based on the simulated data and the real data obtained from the structural health monitoring system installed on the revolving structure.

• 한국기계가공학회지
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• 제20권7호
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• pp.89-96
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• 2021

In this study, a mini hydro cyclone was designed and manufactured to achieve an inlet flow rate of 2 L/min in the experiment, which was conducted using alumina powder with a specific gravity of 3.97. This hydro cyclone was studied for using in steam and water analysis system (SWAS) of thermal power plant and was manufactured by 3D printing. Numerical analysis was performed with Solidworks Flow Simulation, utilizing the reynolds stress method (RSM) of fluid multiphase flow analysis models. Experimental and numerical analysis were performed under the three conditions of inlet velocity 2.0, 4.0, and 6.0 m/s. The separation efficiency was over 80% at all inlet velocity conditions. At the inlet velocity 4m/s, the separation efficiency was the best, and it was confirmed that the efficiency was more than 90%.

• 소음진동
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• 제8권3호
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• pp.450-456
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• 1998

A rotordynamic analysis is performed with a centrifuge rotor-bearing system for the raing speed of 100,000 rpm. The system is composed of a centrifuge rotor(or simply the rotor), flexible shaft, motor rotor and shaft, and two support rolling element bearings of the motor shaft. Design goals are to achieve wide separation margins of critical speeds and favorable unbalance responses of the rotor at the associated critical speeds. The latter requirements are especially important as the system crosses multiple numbers of critical speeds and as the system may not have enough separaton margins around the rating speed. As the system adopts an extra-flexible shaft, it is shown that the rotor has satisfactory small unbalance responses over higher criticals while having an unsatisfactory large one at the first critical. To supress this a bumper ring or guide bearing needs to be installed at a suitable location of the flexible shaft. It is also shown that even with the flexible shaft the dynamics of the motor must be incoporated into the full system model to accurately identify the fourth critical speed, which is close to the rating speed, and higher ones. The analysis is based on the finite element method.