• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.1
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• pp.80-90
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• 2016

Thanks to superior leakage energy efficiency compared to SRAM cells, STTRAM cells are considered as a promising alternative for a memory element in on-chip caches. However, the main disadvantage of STTRAM cells is high write energy and latency. In this paper, we propose a low-cost write filter (WF) cache which resides between the load/store queue and STTRAM-based L1 data cache. To maximize efficiency of the WF cache, the line allocation and access policies are optimized for reducing energy consumption of STTRAM-based L1 data cache. By efficiently filtering the write operations in the STTRAM-based L1 data cache, our proposed WF cache reduces energy consumption of the STTRAM-based L1 data cache by up to 43.0% compared to the case without the WF cache. In addition, thanks to the fast hit latency of the WF cache, it slightly improves performance by 0.2%.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.1
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• pp.31-38
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• 2016

A novel self-reference sense amplifier with parallel reading during writing operation is proposed. Read access time is improved compared to conventional self-reference scheme with fast operation speed by reducing operation steps to 1 for read operation cycle using parallel reading scheme, while large sense margin competitive to conventional destructive scheme is obtained by using self-reference scheme. The simulation was performed using standard $0.18{\mu}m$ CMOS process. The proposed self-reference sense amplifier improved not only the operation speed of less than 20 ns which is comparable to non-destructive sense amplifier, but also sense margin over 150 mV which is larger than conventional sensing schemes. The proposed scheme is expected to be very helpful for engineers for developing MRAM technology.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.195-205
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• 1997

The propulsion marine diesel engine have been widely applied with a mechanical- hydraulic governor to control the ship speed for long time. But it was recently very difficult for the mechani¬cal - hydraulic governor to control the speed of engine under the condition of low speed and low load because of jiggling by rough fluctuation of rotating torque and hunting by dead time of Desiel engnie The performance improvement of mechanical - hydraulic governor is required to solve these problems of control system. The electro - hydraulic governor using PID algorithm is provided to compensate the faults of mechanical- hydraulic governor. In this paper, in order to analyze the ship speed control system, the transfer function was converted from the z tansformation to w transformation. The influence of dead time changing by engine speed which induces hunting phenomena was investigated by Nichols chart of w plane. As a method of performance improvement of mechanical hydraulic governor, a Eletro - hydraulic governor shows that fine control results can be obtained through optimal parameter tuning of PID

• Journal of the Korean Society for Railway
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• v.8 no.3
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• pp.216-221
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• 2005

In electric motor coaches, the rolling stocks move by the adhesive effort between rail and driving wheel. Generally, the adhesive effort is defined by the function of both the wright of electric motor coach and the adhesive effort between rails and driving wheel. The characteristics of adhesive effort is strongly affected by the conditions between rails and driving wheel. When the adhesive effort decreases suddenly, the electric motor coach has slip phenomena. This paper proposes a re-adhesion control based on disturbance observer and sensor-less vector control. The numerical simulation and experimental results point out that the proposed re-adhesion control system has the desired driving wheel torque response for the tested bogie system of electric coach. Based on this estimated adhesive effort, the re-adhesion control is performed to obtain the maximum transfer of the tractive effort.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.780-785
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• 2007

Korean Train Express (KTX) has opened to commercial traffic since 2004 at maximum speed 300km/h, and Korea High-speed Railway (HSR-350x) was developed by Korean government, several institutes, and related companies. HSR-350x is now being investigated its performance and tested at the high speed line. In 2004 December, HSR-350x was run over 350km/h and proved its running performance. These high speed railways have 12 motors to transfer the traction effort or the braking force. In this paper, authors propose the construction the measurement system for monitoring the force transferred to the train from the motor. The system is installed to the tripod shaft which is located between the reduction gears and it measures the mechanical load directly.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.372-376
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• 1990

This paper represents a control method of improving the performance of direct drive robot. The direct transfer of torque and rotational speed of direct drive motor to the robot body without reduction gear makes the robot speed fast. However, the variation of inertia matrix and low friction cause the control difficult, and one more effort must be in the reducing the acceleration and deceleration time to reduce the cycle time. To fasten the cycle time and to improve the robustness of robot, one control method is developed, and implemented in the Goldstar DD robot. This method does not need to change the conventional PI type control structure, but one additional compensational control law is required. The control law can be obtained via inverse dynamic model of robot, and inverse model of existing control loop. The effects of this control law are shown in this paper.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.4
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• pp.274-282
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• 2016

This paper proposes code optimization techniques to reduce energy consumption of complex multimedia applications in a hybrid memory system with volatile dynamic random access memory (DRAM) and non-volatile spin-transfer torque magnetoresistive RAM (STT-MRAM). The proposed approach analyzes read/write operations for variables in an application. Based on the profile, variables with a high read operation are allocated to STT-MRAM, and variables with a high write operation are allocated to DRAM to reduce energy consumption. In this paper, to optimize code for real-life complicated applications, we develop a profiler, a code modifier, and compiler/link scripts. The proposed techniques are applied to a Fast Forward Motion Picture Experts Group (FFmpeg) application. The experiment reduces energy consumption by up to 22%.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.922-923
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• 2015

풍력발전기는 2000년대 초반에 발전기 회전자 직경이 80m에 이르는 2MW급 풍력발전기들이 여러 회사에서 개발되면서 경제성 및 신뢰성도 향상되어 비약적인 발전을 이루게 되었다. 풍력발전시장의 신규발주와 설치장소가 한계점에 이르게 됨으로써 경제성이 뛰어난 대형 풍력발전기의 필요성이 대두되고 있다. 이와 같이 풍력발전기의 대형화 추세는 대형화를 통해 에너지 효율의 증대뿐만 아니라 단위 용량 당 건설비 및 설비비 절감이 가능하기 때문에 풍력발전기 대형화를 위한 기술개발이 활발히 진행되고 있다. 하지만 현재 풍력발전기에 사용되는 기계적 기어박스는 윤활유 주입 및 보수 점검의 문제점이나 소음, 진동, 마찰에 의한 열 발생 등의 문제점들을 가지고 있다. 이러한 문제점을 해결하기 위하여 기계적 기어박스를 마그네틱 기어를 이용하여 구성하고자 한다. 따라서 본 논문에서는 마그네틱 기어를 이용하여 10MW급 풍력발전기의 기어박스를 설계하고 그 가능성을 검토하고자 한다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.760-761
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• 2015

기어는 회전 기계 사이의 동력 전달을 위한 장치이며 현재 산업 전반의 통상적인 기어는 기계적 기어가 주류로서 형성되어 있다. 하지만 기계적 기어는 맞물린 톱니바퀴의 물리적 접촉에 의해 접촉 경계면의 마모 및 파손, 소음과 진동의 문제가 있으며 유지보수 비용 또한 크다. 따라서 최근 물리적 접촉이 없어 기계적 기어의 많은 문제를 해결할 수 있는 마그네틱 기어 (Magnetic Gear)에 대한 관심이 높아지고 있다. 마그네틱 기어는 영구자석에서 생성된 자계를 이용하여 비접촉 동력전달이 가능하며, 마찰손실 제거, 유지보수의 용이성, 매우 적은 소음 및 진동 등의 장점을 가지고 있다. 본 논문에서는 이러한 마그네틱 기어의 토크전달 방법과 형상변화에 따른 전달토크 특성을 2-D 유한요소해석법을 이용하여 해석하고 분석하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.578-586
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• 2006

Numerical simulations are carried out to investigate the thermal effects of the gravitational potential on the centrifugal instability of a Taylor-Couette flow, and to further study the detailed flow fields and flow bifurcations to spiral vortices. The effects of centrifugal potential on the centrifugal instability are also investigated in the current study. Spiral vortices have various types of mode depending on Grashof number and Reynolds number. The correlation of Richardson number with the spiral angle of the spiral vortices shows that the structure of the spiral vortices strongly depends on the Richardson number. The heat transfer rate of the inner cylinder increases with increasing Grashof number. It is also confirmed that the torque required to rotate the inner cylinder increases as Grashof number increases.