• 전기학회논문지
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• 제67권11호
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• pp.1555-1561
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• 2018

Tracking and detecting targets by the millimeter wave seeker is affected by movement of platform. Stabilization equipments use an inertial sensor to compensate for disturbance of stabilizing gimbal or platform. In the direct line of sight stabilization system, an inertial sensor is mounted on inner gimbal to compensate the disturbance directly, so the performance is excellent and the implementation method is simple. However gimbal design requires somewhat larger volume. Since an inertial sensor is mounted on gimbal base in the indirect line of sight stabilization system, additional space of gimbal is not required for the gimbal design. However, this method does not directly compensate for the disturbance of the line of sight stabilization axis, which can degrade performance. In order to perform the tracking performance, two methods are analyzed for line of sight stabilization performance based on direct and indirect of a 2-axis gimbaled servo system for millimeter wave seeker in this study. The simulation and experimental results validate the performance comparison of two methods.

• Nuclear Engineering and Technology
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• 제52권4호
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• pp.784-790
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• 2020

The accelerated corrosion by Flow Accelerated Corrosion (FAC) has caused unexpected rupture of piping, hindering the safety of nuclear power plants (NPPs) and sometimes causing personal injury. For the safety, it may be necessary to select some pipes in terms of condition monitoring and to measure the change in thickness of pipes in real time. Direct current potential drop (DCPD) method has advantages in on-line monitoring of pipe wall thinning. However, it has a disadvantage in that it is difficult to quantify thinning due to various thinning shapes and thus there is a limitation in application. The machine learning approach has advantages in that it can be easily applied because the machine can learn the signals of various thinning shapes and can identify the thinning using these. In this paper, finite element analysis (FEA) was performed by applying direct current to a carbon steel pipe and measuring the potential drop. The fundamental machine learning was carried out and the piping thinning model was developed. In this process, the features of DCPD to thinning were proposed.

• 농촌지도와개발
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• 제24권2호
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• pp.99-115
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• 2017

The purpose of this study is to analyze potential adoption rates and reusing patterns of the new rice direct seeding technology. The model constructed and employed in this study is a system dynamics model of farmer adoption and reusing patterns for this new technology over time. The model incorporates a causal loop diagram that explains interactions among rice cultivation subsystems with feedback loops and further attempts to build a causal loop model with stock-flow diagram for computer simulation. As one example of how the model can be used to provide insight to rice farmers, simulations are run over varying levels on the cultivation process of rice. The major finding is to demonstrate the utility of system dynamics simulation methodology in aiding the rice wet direct seeding farmers' decision making.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.820-831
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• 2015

In a deregulated electricity market, congestion of the transmission lines is a major problem the independent system operator (ISO) would face. Rescheduling of generators is one of the most practiced techniques to alleviate the congestion. However, not all generators in the system operate deterministically and independently, especially wind power generators (WTGs). Therefore, a novel optimal rescheduling model for congestion management that accounts for the uncertain and correlated power sources and loads is proposed. A probabilistic power flow (PPF) model based on 2m+1 point estimate method (PEM) is used to simulate the performance of uncertain and correlated input random variables. In addition, the impact of direct electricity purchase contracts on the congestion management has also been studied. This paper uses artificial bee colony (ABC) algorithm to solve the complex optimization problem. The proposed algorithm is tested on modified IEEE 30-bus system and IEEE 57-bus system to demonstrate the impacts of the uncertainties and correlations of the input random variables and the direct electricity purchase contracts on the congestion management. Both pool and nodal pricing model are also discussed.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.530-543
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• 2013

This paper describes a control scheme of speed sensorless fuzzy direct torque control (FDTC) of permanent magnet synchronous motor for electric vehicle (EV). Electric vehicle requires fast torque response and high efficiency of the drive. Speed sensorless FDTC In-wheel PMSM drives without mechanical speed sensors at the motor shaft have the attractions of low cost, quick response and high reliability in electric vehicle application. This paper presents a new approach to estimate the speed of in-wheel electrical vehicles based on Model Reference Adaptive System (MRAS). The direct torque control suffers in low speeds due to the effect of changes in stator resistance on the flux measurements. To improve the system performance at low speeds, a PI-fuzzy resistance estimator is proposed to eliminate the error due to changes in stator resistance. High performance sensorless drive of the in-wheel motor based on MRAS with on line stator resistance tuning is established for four motorized wheels electric vehicle and the whole system is simulated by matalb/simulink. The simulation results show the effectiveness of the new control strategy. This proposed control strategy is extensively used in electric vehicle application.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.97-100
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• 2003

Recently, the generators for wind turbine have been manufactured with high output power such like MW class machine in order to reduce the generation cost and to increase the energy efficiency. At the same time, direct-driven generators for wind turbine have been developed and researched, which have easy maintenance and high efficiency by simplification the system through the removal of the gear box. In this paper, at first, the advantage and disadvantage between the direct-driven generator system and conventional indirect-driven system are compared. And secondly, the permanent magnet generator (PMG) for wind turbine has been rapidly improved to cope with the recent trend which requires the high power output Per one machine and the convenience for maintenance, and the PMG is adequate for direct driven system and suitable for high-efficiency and light weight. So, the characteristics and technical trend of the PMG for wind turbine is examined. At last, a suitable technical trend for development of the permanent magnet generator for wind turbine is proposed.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1161-1166
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non-inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

• 동력기계공학회지
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• 제22권1호
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• pp.56-63
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• 2018

After the recent fabrication of diesel vehicle exhaust gas by Volkswagen, nitrogen oxides ($NO_x$) and particulate matter (PM) are drawing attention as representative pollutants included in exhaust gas. When gasoline and diesel fuels are combusted through direct injection into a combustion chamber at high pressure, PM emission is actually increased. To find a solution to this problem, a basic study was conducted to derive an optimized variable for combustion of compressed natural gas (CNG) by applying CNG, acknowledged as a clean fuel, to direct injection system. The essence of this study is in the introduction of a radical ignition technology for compressed natural gas (RI-CNG) in a sub-chamber type engine. The direct injection system was applied to a sub-chamber to remove residual gas from previous combustion cycle. In addition, optimal mixer distribution was achieved by precisely setting ignition timing based on fuel injection timing and excess air ratio.

• 한국화재소방학회논문지
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• 제25권6호
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• pp.39-43
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• 2011

본 연구에서는 상수도 직결형 스프링클러 시스템의 성능을 평가하기 위하여 실물 주택을 대상으로 화재 실험을 수행하였다. 실물 주택의 크기는 $56m^2$이며 거실, 주방, 방으로 이루어져 있으며, 화재는 대두유가 과열되어 자연발화가 발생하여 일어나게 하였다. 상수도 직결형 스프링클러시스템의 성능을 확인하기 위하여 주방에 스프링클러시스템을 설치하였다. 실험결과 주방에서의 발화로 시작된 화재는 주방천장까지 확대 되었으나 스프링클러가 동작하면서 화재는 진압되었다. 스프링클러가 동작할 때의 상수도 압력은 0.28 MPa이었으며 이 결과로서 일반 주택의 상수도압력으로도 소화가 가능함을 확인할 수 있었다.

• 설비공학논문집
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• 제20권1호
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• pp.75-80
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non~inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.