• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.97-100
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• 1999

AC to DC single phase PWM converter for traction application requires rated high power and voltage. Therefor, series or parallel operation converters are necessary with considering the limitation of the power device specification. This paper compares the characteristic between two parallel operation of conventional PWM converter and Single phase three level converter about comparison of power circuit, cooling system control method and harmonic current by computer simulation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.11
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• pp.1087-1093
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• 2010

The satellite thermal control H/W composed of two parallel channels working for heat pipe (HP) and phase change material (PCM) is suggested for the high heat dissipating component which works intermittently with short duty. In a limited point of view, the HP-PCM device is a kind of off-the-shelf component that requires no dedicated configuration and thermal designs to PCM. Therefore, it can be used with less impact on the program cost and schedule different from most of the PCM applications. In present study the typical honeycomb structure radiator applying the HP-PCM device is designed and the detail thermal math model is developed for numerical analyses. The result comparison between without and with PCM shows that the HP-PCM device redistributes the peak heat around the whole mission period through the alternate melting and freezing of PCM, and, as a result, the maximum and minimum temperatures are effectively alleviated. The drawback of PCM application due to low thermal conductivity can be successfully resolved by means of parallel arrangement of HP channel.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.3
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• pp.206-211
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• 2011

In this paper, we report a high-precision wireless gap sensor based on a surface acoustic wave (SAW) device. The sensing element is a parallel-plate capacitor whose dimensions are $3{\times}3\;mm^2$, and is attached to the SAW device as an external load. The SAW device, equipped with an RF antenna, serves simultaneously as a signal conditioner and an RF transponder. The center frequency of the SAW device is 450 MHz. The wireless gap sensor prototype exhibits a resolution of 100 nm and a sensing range of $50{\mu}m$. The proposed sensor system can be used for remote, high-precision gap measurement in hard-to-reach environments.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.1031-1049
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• 2015

This paper highlights the role of innovative vibration control system based on two promising properties in a parallel configuration. Hybrid device consists of two main components; recentering wires of shape memory alloy (SMA) and steel pipe section as an energy dissipater element. This approach concentrates damage in the steel pipe and prevents the main structural members from yielding. By regulation of the main adjustable design parameter, an optimum performance of the device is obtained. The effectiveness of the device in passive control of structures is evaluated through nonlinear time history analyses of a five-story steel frame with and without the hybrid device. Comparing the results proves that the hybrid device has a considerable potential to mitigate the residual drift ratio, peak absolute acceleration and peak interstory drift of the structure.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.5.1-5.1
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• 2009

Organic photovoltaic (OPV)cells have attracted considerable attention due to their potential for flexible, lightweight, and low-cost application of solar energy conversion. Since a 1% power conversion efficiency (PCE) OPV based on a single donor-acceptor heterojunction was reported by Tang, the PCE has steadily improved around 5%. It is well known that a high parallel (shunt)resistance and a low series resistance are required simultaneously to achieve ideal photovoltaic devices. The device should be free of leakage current through the device to maximize the parallel resistance. The series resistance is attributed to the ohmic loss in the whole device, which includes the bulk resistance and the contact resistance. The bulk resistance originated from the bulk resistance of the organic layer and the electrodes; the contact resistance comes from the interface between the electrodes and the active layer. Furthermore, it has been reported that the bulk resistance of the indium tin oxide (ITO) of the devices dominates the series resistance of OPVs for a large area more than $0.01\;cm^2$. Therefore, in practical application, the large area of ITO may significantly reduce the device performance. In this work, we investigated the effect of sheet resistance ($R_{sh}$) of deposited ITO on the performance of OPVs. It was found that the device performance of polythiophene-fullerene (P3HT:PCBM) bulk heterojunction OPVs was critically dependent on Rsh of the ITO electrode. With decreasing $R_{sh}$ of the ITO from 39 to $8.5\;{\Omega}/{\square}$, the fill factor (FF) of OPVs was dramatically improved from 0.407 to 0.580, resulting in improvement of PCE from $1.63{\pm}0.2$ to $2.5{\pm}0.1%$ underan AM1.5 simulated solar intensity of $100\;mW/cm^2$.

• Journal of IKEEE
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• v.25 no.4
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• pp.735-740
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• 2021

In this paper, we propose a new ESD protection device with high holding voltage with low current gain of parasitic NPN BJT by improving the structure of the existing LTDDSCR. The electrical characteristics of the proposed protection device were analyzed by HBM simulation using Synopsys' TCAD simulation, and the operation of the added BJT was confirmed by current flow, impact ionization and recombination simulation. In addition, the holding voltage characteristics were optimized with the design variables D1 and D2. As a result of the simulation, it was verified that the new ESD protection device has a higher holding voltage compared to the existing LTDDSCR and has a symmetrical bidirectional characteristic. Therefore, the proposed ESD protection device has high area efficiency when applied to an IC and is expected to improve the reliability of the IC.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.9
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• pp.903-909
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• 2012

In elliptical vibration cutting(EVC) where the cutting tool traces a micro-scale 2-dimensional elliptical trajectory, the kinematical and vibrational characteristics of the EVC device greatly affect cutting performance. In this study, kinematical and vibrational characteristics of an EVC device constructed with two orthogonally-arranged stacked piezoelectric actuators were investigated both analytically and experimentally. The step voltage was applied to the orthogonal EVC device and the associated displacements of the cutting tool were measured to assess kinematical characteristics of the orthogonal EVC device. To investigate the vibrational characteristic of the orthogonal EVC, sinusoidal voltage was applied to the EVC device and the resulting displacements were measured. It was found from experiments that coupling of displacements in the thrust and cutting directions and the tilt of the major axis of the elliptical trajectory exists. In addition, as the excitation frequency is in vicinity of resonant frequencies the distortion in the shape of the elliptical trajectory becomes greater and change in the rotation direction occurs. To correct the shape distortion of the elliptical trajectory, the shape correcting procedure developed for the parallel EVC device was applied for the orthogonal EVC device and it was shown that the shape correcting method successfully corrects distortion.

• Journal of the Korea Society of Computer and Information
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• v.18 no.1
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• pp.1-10
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• 2013

In this paper, we propose a CUDA(Common Unified Device Architecture) based SW(software) design method for CPU(Central Processing Unit) and GPU(Graphic Processing Unit) parallel structure to implement real-time process in 3D Laser ladar(LADAR) imaging system. LADAR is a complex system to generate 3-dimensional image based on the laser ranging information, and requires massive process resources in each phase. Therefore, designing and implementing parallel structure are crucial to realize a real-time process within limited system resource. As a conclusion, we can meet the speed of required real-time process allocating separable work load to CUDA GPU by analyzing process algorithm in each phase and confirm the process speed increase by 46%.

• Journal of Information Display
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• v.3 no.4
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• pp.4-7
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• 2002

A recently developed phase separated composite film method has been employed to fabricate a liquid crystal (LC) based electro-optical device using a single glass substrate. The resulting device is made of adjacent parallel layers of LC and polymer maded by phase separation. The LC layer is confined between the solidified polymer layer on one side and the glass substrate on the other. The electro-optical properties of these devices demonstrate their technological potential in light weight and hand-held electronic products.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.36-38
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• 2000

An optoelectronic database filter chip for high performance database computers and applications is proposed. The proposed device is designed to perform the selection and projection operations of relational database operation on-the-fly in page-parallel manner to increase the overall performance of a database system. The device utilizes CMOS smart pixel array consists of detector and combinational logic circuit to perform the selection and projection operation.