• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.88-91
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• 2000

An MMIC oscillator operating at the 24.55 GHz has been designed using 0.2 ${\mu}{\textrm}{m}$AlGaAs/InGaAs/GaAs Pseudomorphic HEMT technology. The active device used in the oscillator design has a 0.2 ${\mu}{\textrm}{m}$ gate length PHEMT with 4$\times$80 ${\mu}{\textrm}{m}$ gate width. We obtained 4.08 dB of S$_{21}$ gain and 317 mS/mm of transconductance, and extrapolated unit current gain cut-off frequency (f$_{T}$) and maximum oscillation frequency (fmax) were 62 GHz and 120 GHz, respectively. The circuit are based on a series feedback and negative resistance topology. Microstrip line open stub is used to terminating. The oscillator circuits has designed for delivering maximum power to load and conjugated matching. The simulated small signal negative resistance was 50 Ω. We obtained 1.002 of loop gain and 0.0005$^{\circ}$angle from the simulation by HP libra 6.1. The layout for oscillator is 1.2$\times$1.8 $\textrm{mm}^2$.>.

• International Journal of Internet, Broadcasting and Communication
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• 제12권3호
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• pp.108-115
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• 2020

Blended learning is a teaching method utilizing all the advantages in 'on and off-line' learning circumstances in order to enhance the learning effect and efficiency, more than the simple use of online factors in the classroom education. In this paper, we present the realization and simulation of algorithm for the realtime evaluation of low-grade and high-grade subjects in order to implement smart e-learning system, considering a lecture intelligibility. In order to grasp the levels of student's intelligibility, we simulated a function that automatically summarizes the study contents of class given by a lecturer. Especially, in administrator mode of smart e-learning system, we suggested and simulated a system in order to help the lecturer to easily manage the student's grades, and we have provided software to tell the student's intelligibility of lecture, analyzed the rate of incorrect answers, automatic judgment of lecture intelligibility and judge the weakest subject.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.438-440
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• 2004

Energy consumption has become an increasingly important consideration in designing real-time embedded systems. In this paper, we propose a voltage scaling method to reduce energy consumption in fixed priority real-time systems using variable voltage processors. The Hyperperiod of tasks is divided into dimains. The most suitable voltage of each domain is determined off-line and stored in a table. During task execution, the voltage of processor is adjusted according to the information of the table. A simulation result shows that the proposed method can reduce 80% of power consumption in comparison to no power management. The difference to the optimal EDF based method is only 5%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.385-387
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• 1996

A novel two stage soft-switching ac-to-dc convener with power factor correction is proposed. The proposed convener provides zero-voltage-switching (ZVS) condition to main switch of boost pre-regulator without auxiliary switch. Comparing to the conventional two stage approach(ZVS-PWM boost rectifier followed by off-line ZVS dc-dc step down converter), the proposed approach is simple and reducing EMI noise problem. A new simple DC-linked energy feedback circuit provides zero-voltage-switching condition to boost pre-regulator without imposing additional voltage and current stresses and loss of PWM capability. Operational principle, analysis, control of the proposed converter together with the simulation results of 1KW prototype are presented.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제6권1호
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• pp.97-106
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• 2002

Educators have found that the concept of randomness is often misunderstood by students. Chance recently pointed out that students should be introduced to the concept of randomness through the use of simulations. In this article, we studied various aspects of the probability distribution off linear random path in a circle and introduce some related simulations to guide student exploration and discovery. Consider a random line segment that crosses a circle with a certain radius. Perhaps it can be considered to be a path that an airplane shows up and flies into a random direction in a monitor. What is the expected amount of flying distance through the monitor, and the expected variation\ulcorner Are we monitoring what we see scientifically\ulcorner This article studies the probability distribution and some related aspects of a linear random path within a circular monitor. Some simulative activity is also introduced which can be used in a statistics or probability classes.

• 제어로봇시스템학회논문지
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• 제7권8호
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• pp.675-679
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• 2001

This paper presents walking algorithm for a quadruped robot that does not have an upper body. Tilting motion is added to the planned walking trajectory instead of using an extra body segment that is independent on walking trajectory. Area and tracking algorithms are proposed as tilting method and compared with that of off-line tilting and that of no tilting. Computer simulation shows that stability of tilted walking is more improved than that of the usual walking algorithm for general walking paths. It also shows that the tracking method guarantees stability and best mobility.

• 제어로봇시스템학회논문지
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• 제2권4호
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• pp.297-305
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• 1996

In this paper a novel robust adaptive fuzzy controller for the nonlinear system with state-dependent uncertainty is proposed. The conventional adaptive fuzzy controller determines the function of state variable bounding the state-dependent uncertain term in the system dynamics on the local state space by off-line calculation. Whereas the proposed method determines that function by the fuzzy inference so that it guarantees the stability of the closed loop system globally on the whole state space. In addition, the method is applicable to the multi-input system. We applied the proposed method to the Burn Control of the Tokamak fusion reactor whose dynamics contains the state-dependent uncertainty and proved the effectiveness of the scheme by using the simulation results.

• 산업공학
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• 제15권4호
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• pp.356-363
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• 2002

Virtual Manufacturing is a technology to facilitate effective product development and agile production by computer models representing the physical and logical schema and the behavior of real manufacturing systems including manufacturing resources, environments and products. For the successful application of this technology, a virtual factory as a well-designed and integrated environment is essential. In this research, we constructed a sophisticated virtual factory model of an automotive company's paint shop, and performed precise simulations of unit cells, lines and whole plant operations for collision check and off-line programming. It is expected that this virtual paint shop is useful for achieving time and cost savings in many manufacturing preparation and planning activities of new car development processes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.182-184
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• 2004

This paper presents a PI controller tuning method for high performance permanent magnet synchronous motor (PMSM) drives under load variations using clustering fuzzy algorithm. In many speed tracking control systems PI controller has been used due to its simple structure and easy of design. PI controller, however, suffers from the electrical machine parameter variations and disturbances. In order to improve the tracking control performance under load variations, the PI controller parameters are modified during operation by clustering fuzzy method. This method based on optimal fuzzy logic system has simple structure and computational simplicity. It needs only sample data which is obtained by optimal controller off-line. As the sample data implemented in the adaptive fuzzy system can be modified or extended, a flexible control system can be obtained Simulation results show the usefulness of the proposed controller.

• Journal of Power Electronics
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• 제9권6호
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• pp.835-844
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• 2009

In this paper a new buck-boost type DC-DC converter is presented. Its voltage gain is positive, all active elements operate under soft-switching condition independent of loading, magnetic isolation and self output short-circuit protection exist, and very fast dynamic operation is achievable by a simple bang-bang controller. This converter also exhibits appropriate PFC characteristics since its input current is inherently proportional to the source voltage. When the voltage source is off-line, it is sufficient to add an inductor after the rectifier, then near unity power factor is achievable. All essential guidelines to design the converter as a DC-DC and a PFC regulator are presented. Simulation and experimental results verify the developed theoretical analysis.