• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.1
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• pp.129-140
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• 2017

In this paper, a $4{\times}32$-channel neural recording system capable of acquiring neural signals is introduced. Four 32-channel neural recording ICs, complex programmable logic devices (CPLDs), a micro controller unit (MCU) with USB interface, and a PC are used. Each neural recording IC, implemented in $0.18{\mu}m$ CMOS technology, includes 32 channels of analog front-ends (AFEs), a 32-to-1 analog multiplexer, and an analog-to-digital converter (ADC). The mid-band gain of the AFE is adjustable in four steps, and have a tunable bandwidth. The AFE has a mid-band gain of 54.5 dB to 65.7 dB and a bandwidth of 35.3 Hz to 5.8 kHz. The high-pass cutoff frequency of the AFE varies from 18.6 Hz to 154.7 Hz. The input-referred noise (IRN) of the AFE is $10.2{\mu}V_{rms}$. A high-resolution, low-power ADC with a high conversion speed achieves a signal-to-noise and distortion ratio (SNDR) of 50.63 dB and a spurious-free dynamic range (SFDR) of 63.88 dB, at a sampling-rate of 2.5 MS/s. The effectiveness of our neural recording system is validated in in-vivo recording of the primary somatosensory cortex of a rat.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.927-933
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• 2016

In a solid propulsion system, the rocket nozzle is exposed to high temperature combustion gas. Hence, choosing an appropriate material that could demonstrate adequate performance at high temperature is important. As advanced materials, carbon/silicon carbide composites (C/SiC) have been studied with the aim of using them for the rocket nozzle throat. However, when compared with typical structural materials, C/SiC composites are relatively weak in terms of both strength and toughness, owing to their quasi-brittle behavior and oxidation at high temperatures. Therefore, it is important to evaluate the thermal and mechanical properties of this material before using it in this application. This study presents an experimental method to investigate the fracture behavior of C/SiC composite material manufactured using liquid silicon infiltration (LSI) method at elevated temperatures. In particular, the effects of major parameters, such as temperature, loading, oxidation conditions, and fiber direction on strength and fracture characteristics were investigated. Fractography analysis of the fractured specimens was performed using an SEM.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.6
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• pp.65-76
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• 2007

Studies in landscape ecology have emphasized on the relationship between landscape patterns and shapes. A variety of landscape metrics has been developed so far to quantify landscape structures. Therefore, their developments and widespread applications become possible with the advent of spatial information systems including geographic information systems(GIS) and remote sensing. This study is to grasp the change of land use and landscape ecology indices, and to analyze the change of landscape structure in a part of Gyeonggi-do during 15 years from 1985 to 2000. Green-area distribution maps and agricultural-area distribution maps for the analysis were reconstructed from land cover maps constructed by WAMIS(Water Management Information System). And then, 4 landscape ecology indices(TA, LPI, SHAPE_AM, CAI_MN) for the green-area and 5 landscape ecology indices(TA, PD, LPI, LSI, CAI_MN) for the agricultural-area were selected by using pearson correlation analysis. According to the spatio-temporal change analysis using landscape ecology indices, the green-area fragmentation of Yongin was the most severe of the study area and the agricultural-area fragmentation of Gwangju and Namyangju was more severe than any other regions.

• Journal of Environmental Science International
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• v.21 no.11
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• pp.1297-1305
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• 2012

Clonal plants combine sexual and clonal reproduction, which contribute differently to plant fitness. Reproductive analyses have highlighted the importance of clonal growth in shaping the spatial genetic structure in Potentilla conferta Bunge, a herbaceous rhizomatic clonal distributed in hot sand dunes. We investigated the reproduction system of P. conferta at two populations in Mongol and three natural populations in Uzbekistan. The measurements of 19 quantitative or qualitative morphological characters were taken on each of total individuals directly from their natural habitats. Some morphological characteristics between Mongolia and Uzbekistan populations showed a slight heterogeneity of variance. Especially, the length of internodes (LFI and LSI) and characteristics of root (LLR and NOR) were shown a significant difference between two countries (P<0.05). P. conferta of Uzbekistan has most ramets at short distance intervals 30~100 cm. In light conditions, P. conferta of Uzbekistan was significantly less resilience than P. conferta of Mogol. In drought conditions, although there was not shown significant difference, P. conferta in Uzbekistan was less resilience than that in Mogol. The core analysis indicates that P. conferta in Uzbekistan is the more resistant than that of Mongol and seems to do by sexual reproduction strategy during several strong environmental disadvantages such as drought events.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1296-1299
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• 2002

We implemented a CD signal processor operated on a CAV 48-speed CD-ROM drive into a VLSI. The CD signal processor is a mixed mode monolithic IC including servo-processor, data recovery, data-processor, and I-bit DAC. For servo signal processing, we included a DSP core, while, for CAV mode playback, we adopted a PLL with a wide recovery range. Data processor (DP) was designed to meet the yellow book specification.［2］So, the DP block consists of EFM demodulator, C1/C2 ECC block, audio processor and a block transferring data to an ATAPI chip. A modified Euclid's algorithm was used as a key equation solver for the ECC block To achieve the high-speed decoding, the RS decoder is operated by a pipelined method. Audio playability is increased by playing a CD-DA disc at the speed of 12X or 16X. For this, subcode sync and data are processed in the same way as main data processing. The overall performance of IC is verified by measuring a transfer rate from the innermost area of disc to the outermost area. At 48-speed, the operating frequency is 210 ㎒, and this chip is fabricated by 0.35 um STD90 cell library of Samsung Electronics.

• ETRI Journal
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• v.32 no.1
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• pp.102-111
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• 2010

Recently power attacks on RSA cryptosystems have been widely investigated, and various countermeasures have been proposed. One of the most efficient and secure countermeasures is the message blinding method, which includes the RSA derivative of the binary-with-random-initial-point algorithm on elliptical curve cryptosystems. It is known to be secure against first-order differential power analysis (DPA); however, it is susceptible to second-order DPA. Although second-order DPA gives some solutions for defeating message blinding methods, this kind of attack still has the practical difficulty of how to find the points of interest, that is, the exact moments when intermediate values are being manipulated. In this paper, we propose a practical second-order correlation power analysis (SOCPA). Our attack can easily find points of interest in a power trace and find the private key with a small number of power traces. We also propose an efficient countermeasure which is secure against the proposed SOCPA as well as existing power attacks.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.581-582
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• 2006

In this paper, we investigate three different types of multi-fingered layout nMOSFET devices with varying $W_f$(unit finger width) and $N_f$(number of finger). Using layout modification, we improve $f_T$(current gain cutoff frequency) value of 15GHz without scaling down, and moreover, we decrease $NF_{min}$(minimum noise figure) by 0.23dB at 5GHz. The RF noise can be reduced by increasing $f_T$, choosing proper finger width, and reducing the gate resistance. For the same total gate width using multi-fingered layout, the increase of finger width shows high $f_T$ due to the reduced parasitic capacitance. However, this does not result in low $NF_{min}$ since the gate resistance generating high thermal noise becomes larger under wider finger width. We can obtain good RF characteristics for MOSFETs by using a layout optimization technique.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.109-110
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• 2007

Plasma etching process에서 magnetic field 영향에 관한 연구이다. High level dry etch process를 위해서는 high density plasma(HDP)가 요구된다. HDP를 위해서 MERIE(Magnetical enhancement reactive ion etcher) type의 설비가 사용되며 process chamber side에 4개의 magnetic coil을 사용한다. 이런 magnetic factor가 특히 wafer edge부문에 plasma charging에 의한 damage를 유발시키고 이로 인해 device Vth(Threshold voltage)가 shift 되면서 제품의 program 동작 문제의 원인이 되는 것을 발견하였다. 이번 연구에서 magnetic field와 관련된 plasma charge damage를 확인하고 damage free한 공정조건을 확보하게 되었다.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.20-23
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• 2010

The analog front end (AFE) of a radio frequency identification transponder using the ISO 14443 type A standard with a 100% amplitude shift keying (ASK) modulation is proposed in this paper and verified by circuit simulations and measurements. This AFE circuit, using a 13.56 MHz carrier frequency, consists of a rectifier, a modulator, a demodulator, a regulator, a power on reset, and a dynamically enabled digital phase locked loop (DPLL). The DPLL, with a charge pump enable circuit, was used to recover the clock of a 100% modulated ASK signal during the pause period. A high voltage lateral double diffused metal-oxide semiconductor transistor was used to protect the rectifier and the clock recovery circuit from high voltages. The proposed AFE was fabricated using the $0.18\;{\mu}m$ standard CMOS process, with an AFE core size of $350\;{\mu}m\;{\times}\;230\;{\mu}m$. The measurement results show that the DPLL, using a demodulator output signal, generates a constant 1.695 MHz clock during the pause period of the 100% ASK signal.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.78-85
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• 1998

In this paper we propose a VLSI implementation technique for camcorder's digital zooming system. The proposed VLSI includes the system clock(CLK), vertical drive(VD), horizontal drive(HD),blank(BLK), and field(FLD) signals as inputs, and produces magnified image as an output, with 256 different magnification ratios. In general, the above mentioned input signals are provided by the CCD driving IC in most camcorders. As a result, the proposed digital zooming VLSI can magnify a part of the input image by up to 256 times, where the magnification ratio can be chosen among 256 different steps. In the application point of view, the proposed VLSI can be used in any digital camcorder for realizing near continuous step digital zooming without any additional circuitry, such as micom or a general purpose digital signal processor.