• Structural Engineering and Mechanics
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• v.57 no.1
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• pp.91-103
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• 2016

This investigation is concerned with the disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperature, in the presence of the combined effects of Hall currents and magnetic field due to normal force of ramp type. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi Theories of Type-II and Type-III. Laplace and Fourier transform technique is applied to solve the problem. The analytical expressions of displacements, stress components, temperature change and current density components are obtained in the transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerically simulated results are depicted graphically to show the effects of Hall current and anisotropy on the resulting quantities. Some special cases are also deduced from the present investigation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.2021-2031
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• 2013

Due to the rapid economic growth within the nation, the quality of life of individuals have improved dramatically. The scope of living activities of individuals have also extended, resulting in a rapidly increasing demand for automobiles. The number of vehicles registered in Korea is rapidly increasing and will reach 188.71 million as of December 2012. Compared to the registered residents of 50.94 million provided by the Ministry of Public Administration and Security, the registered population reflects about 4 people per every automobile. Due to the high demands for vehicles, the demands for parking lots in collective housing and businesses are also increasing. In reality, the current state of expansion of parking lots are underground, due to the limited available space on ground level. Specifically, the slope of a parking lot cannot exceed 17% linear slope and 14% curved slope according to the 'parking lot laws', however studies show that the driver feels at risk for safety when stopped on the parking ramp while driving in the parking lot. This study seeks to examine the suitability of parking lot ramps, concerning the safety aspects of the driver. First, the ramp type was categorized as linear or curved, then test drives were performed based on variations of slopes, slant distances, directions and points. A survey was administered to the driver after the completion of the test drive, in order to element design for an ideal ramp. In the case of curved ramp, the results of the estimate suggests a counterclockwise, slope at a maximum of 12% incline. The maximum slope for a linear ramp was analyzed to be between 13~14%, suggesting that slope greater than 15% need to be eliminated. In conclusion, it is anticipated that the element design parking ramp reported in this study will help to serve as a reference for future parking lot related guidelines, and provide cost effective traffic safety mechanisms in future parking lot businesses to follow.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1989-2000
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• 2015

In this paper, digital peak current mode control for single phase H-bridge inverters is developed and implemented. The digital peak current mode control is achieved by directly controlling the PWM signals by cycle-by-cycle current limitation. Unlike the DC-DC converter where the output voltage always remains in the positive region, the output of DC-AC inverter flips from positive to negative region continuously. Therefore, when the inverter operates in negative region, the control should be changed to valley current mode control. Thus, a novel control logic circuit is required for the function and need to be analyzed for the hardware to track the sinusoidal reference in both regions. The problem of sub-harmonic instability which is inherent with peak current mode control is also addressed, and then proposes the digital slope compensation in constant-sloped external ramp to suppress the oscillation. For unipolar PWM switching method, an adaptive slope compensation in digital manner is also proposed. In this paper, the operating principles and design guidelines of the proposed scheme are presented, along with the performance analysis and numerical simulation. Also, a 200W inverter hardware prototype has been implemented for experimental verification of the proposed controller scheme.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.24-28
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• 2010

A simulation study of a current-mode direct current (DC)-DC buck converter is presented in this paper. The converter, with a fully integrated power module, is implemented by using sense method metal-oxide-semiconductor field-effect transistor (MOSFET) and bipolar complementary metal-oxide-semiconductor (BiCMOS) technology. When the MOSFET is used in a current sensor, the sensed inductor current with an internal ramp signal can be used for feedback control. In addition, the BiCMOS technology is applied in the converter for an accurate current sensing and a low power consumption. The DC-DC converter is designed using the standard $0.35\;{\mu}m$ CMOS process. An off-chip LC filter is designed with an inductance of 1 mH and a capacitance of 12.5 nF. The simulation results show that the error between the sensing signal and the inductor current can be controlled to be within 3%. The characteristics of the error amplification and output ripple are much improved, as compared to converters using conventional CMOS circuits.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.41-45
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• 2007

This paper presents transport current non-uniformity in a joint for superconducting multistage cable-in-conduit conductor (CICC) and relaxation in the CICC. The joint is considered to have a current loop linked to an external magnetic field so that it becomes an emf voltage source. It is numerically analyzed using an electrical transmission line model. The inductive current in a resistive joint is compared to that of a non-resistive joint when the ramping field is applied vertically to the joints. Regarding the parameter values of the model. a full scale $Nb_3Sn$ CICC and a strand-to-strand (STS) joint for the toroidal field magnet of the KSTAR (Korea Superconducting Tokamak Advanced Research) device are referenced to. It is found that the resistive joint prevents the current from rising too much and enhances decaying the current when the ramping stops. The 'flattop' current is found to be proportional to the ramp rate of the field (dB/dt). The relaxation length, which is defined as the length within which the maximum induced current falls by 1/e. is found to saturate within 0.27m.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.333-337
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• 1999

This paper presents the DQ transfomation space space vector modulation method to devel control algorithm of distribu STATCON(STATic CONdenser) for line volt regulation, dc link voltage regulation harmonics compensation. The Performance an of a PI with ramp comparision and synchro reference frame current controller is carried Based on these analysis, the control perform are desirable to compensate the harmonics a regulate dc link and line voltage of Distrib line.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.200-200
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• 2000

AC-PDP의 구동은 인가되는 Pulse의 파형에 의하여 결정된다. 이번 실험은 AC-PDP의 Subfield 파형중 Sustain 부분 첫 번째 Pulse의 폭(Width)에 변화를 주어 다음 Suatain Pulse 기간동안의 전기 광학적 특성을 구속 카메라와 전류의 변화를 통하여 측정하였으며 Sustain Pulse의 Rising Time을 변화 시켜 방전특성을 측정하였다. 이를 통하여 적합한 Sustain 구간의 초기조건을 예측하였으며, 적합한 Sustain Pulse를 찾아가는 실험 방법을 찾고자 하였다.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.317-323
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• 2001

We investigated the stability of cryocooler-cooled high-temperature superconducting (HTS) coils by using a computer program based on FEM. In this study, the current at which "thermal runaway" occurs, which depends on the relationship between the cooling power of the cryocooler and the heat generation in HTS coils, was adopted as a stability criterion of cryocooler operating HTS coils. It was shown that cryocooler-cooled HTS coil was stable in operating current above the critical current from the numerical analysis results by HTS model coil. And also, if we efficiently remove the heat generation from HTS coils by potimizing heat drain, the ramp-rate limitation can be mitigated because the effect of AC loss by the current rise was too small. Furthermore, in the case of pulsed operation; the HTS model coil is ramped from zero to the peak value in one second and back to zero current in one second, such as the operation of SMES device, the peak value of poerating current is 1.5-2 times greater than that of the thermal runaway current.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1064-1070
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• 2007

This paper presents a grid-interactive current controlled voltage source inverter (CCVSI) with uniterruptible power supply (UPS), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The operation of this system could be divided into the power quality control (PQC) state mode and the UPS state mode. In PQC mode, the system operated to compensate the reactive power demand by nonlinear load or variation in load. In UPS mode. the system is controlled to provide a sinusoidal voltage at the rated value for the load when the gird fail. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1KVA load capacity is presented.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1391-1394
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• 2007

In this work, the discharge characteristics and temporal distribution of surface charges on the Sidoped MgO have been investigated and elucidated with the results of photon-induced surface current. Even though the Si doped MgO shows lower static voltage margin, higher luminous efficacy, and shorter statistical delay time, its discharge characteristics become deteriorated as the timing of scanning is delayed from the ramp type reset pulse down. Overall features of Si-doped MgO in discharge characteristics are well correlated with surface current characteristics.