• 대한의용생체공학회:의공학회지
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• 제25권6호
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• pp.471-478
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• 2004

근육의 수의 수축에 의해 발생하는 근전도 신호는 다른 생체 신호보다는 비교적 출력 특성이 뛰어나기 때문에 많은 재활 시스템에 적용되고 있다. 본 논문에서는 상지 절단 환자 혹은 경추 손상에 의한 마비 환자를 위한 근전도 기반의 휴먼-컴퓨터 인터페이스를 제안한다. 사용자는 독립적으로 수의 수축이 가능한 두 근육 부위를 각기 혹은 동시에 움직임으로써 최대 4가지의 의도를 표현할 수 있다. 근육의 수축 정도는 근전도 진폭 신호의 절대 평균값과 미리 정해둔 문턱치를 비교하여 인식한다. 그러나 사용자가 동시에 두 근육을 수축하고자 할지라도 각각의 근육 발화 시점에 따른 시간차가 발생할 수 있기 때문에, 단순한 비교 방법으로는 동시 수의 수축에 관한 사용자의 의도를 정확하게 인식하기 어렵다. 따라서 근육의 수의 수축의 인식에 필요한 문턱치를 주 문턱치와 보조 문턱치의 이중 문턱치를 갖는 인식 방법을 제안한다. 이중 문턱치 인식 방법에 의해 두 근육이 동시에 수의 수축할 때에도 정확한 인식이 가능하므로, 각기 하나의 근육 수축 상태만을 인식하는 HCI보다도 많은 수의 인터페이스 명령을 생성할 수 있다. 구현한 실시간 근전도 처리 하드웨어를 이용하여, 정상인과 전완 절단 장애자에 대한 실험으로부터 본 논문에서 제안하는 이중 문턱치를 이용한 인식방법이 관전 의수와 전동 휠체어 제어용 HCI에 적용될 수 있음을 보인다.

• 한국전기전자재료학회논문지
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• 제36권2호
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• pp.129-135
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• 2023

An analytical threshold voltage model is presented to observe the change in threshold voltage shift ΔV_th of a junctionless double gate MOSFET using ferroelectric-metal-SiO₂ as a gate oxide film. The negative capacitance transistors using ferroelectric have the characteristics of increasing on-current and lowering off-current. The change in the threshold voltage of the transistor affects the power dissipation. Therefore, the change in the threshold voltage as a function of theferroelectric thickness is analyzed. The presented threshold voltage model is in a good agreement with the results of TCAD. As a results of our analysis using this analytical threshold voltage model, the change in the threshold voltage with respect to the change in the ferroelectric thickness showed that the threshold voltage increased with the increase of the absolute value of charges in the employed ferroelectric. This suggests that it is possible to obtain an optimum ferroelectric thickness at which the threshold voltage shift becomes 0 V by the voltage across the ferroelectric even when the channel length is reduced. It was also found that the ferroelectric thickness increased as the silicon thickness increased when the channel length was less than 30 nm, but the ferroelectric thickness decreased as the silicon thickness increased when the channel length was 30 nm or more in order to satisfy ΔV_th=0.

• 한국전기전자재료학회논문지
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• 제31권3호
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• pp.146-151
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• 2018

In this study, we compared the threshold-voltage extraction methods of accumulation-type JLDG (junctionless double-gate) MOSFETs (metal-oxide semiconductor field-effect transistors). Threshold voltage is the most basic element of transistor design; therefore, accurate threshold-voltage extraction is the most important factor in integrated-circuit design. For this purpose, analytical potential distributions were obtained and diffusion-drift current equations for these potential distributions were used. There are the ${\phi}_{min}$ method, based on the physical concept; the linear extrapolation method; and the second and third derivative method from the $I_d-V_g$ relation. We observed that the threshold-voltages extracted using the maximum value of TD (third derivatives) and the ${\phi}_{min}$ method were the most reasonable in JLDG MOSFETs. In the case of 20 nm channel length or more, similar results were obtained for other methods, except for the linear extrapolation method. However, when the channel length is below 20 nm, only the ${\phi}_{min}$ method and the TD method reflected the short-channel effect.

• 전기전자학회논문지
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• 제24권1호
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• pp.194-199
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• 2020

본 논문에서는 비대칭 무접합 이중게이트 MOSFET에 대한 문턱전압이동을 상단과 하단 게이트 산화막 두께에 따라 분석하였다. 비대칭 구조에서는 상단과 하단 게이트 산화막 두께를 달리 제작할 수 있으므로 문턱전압이동을 일정하게 유지하면서 상단 게이트에서 발생할 수 있는 누설전류를 감소시키기 위하여 상단과 하단 산화막 두께를 조정할 수 있다. 이를 위하여 해석학적 문턱전압 모델을 제시하였으며 이 모델은 2차원 시뮬레이션 값과 잘 일치하였다. 결과적으로 일정한 문턱전압이동을 유지하면서 하단 게이트 산화막 두께를 감소시키면 상단 게이트 산화막 두께를 증가시킬 수 있어 상단 게이트에서 발생할 수 있는 누설전류를 감소시킬 수 있을 것이다. 특히 하단 게이트 산화막 두께가 증가하여도 문턱전압이동에는 큰 영향을 미치지 않는다는 것을 관찰하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권2호
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• pp.130-133
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• 2010

This paper presents a study of the influence of variation of counter doping thickness on short channel effect in symmetric double-gate (DG) nano MOSFETs. Short channel effects are estimated from the computed values of current-voltage (I-V) characteristics. Two dimensional Quantum transport equations and Poisson equations are used to compute DG MOSFET characteristics. We found that the transconductance ($g_m$) and the drain conductance ($g_d$) increase with an increase in p-type counter-doping thickness ($T_c$). Very high value of transconductance ($g_m=38\;mS/{\mu}m$) is observed at 2.2 nm channel thickness. We have established that the threshold voltage of DG MOSFETs can be tuned by selecting the thickness of counter-doping in such device.

• 제어로봇시스템학회논문지
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• 제11권1호
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• pp.41-49
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• 2005

Electromyogram (EMG) signal generated by voluntary contraction of muscles is often used in rehabilitation devices because of its distinct output characteristics compared to other bio-signals. This paper proposes a novel EMG-based human-computer interface for electric-powered wheelchair users with motor disabilities by C4 or C5 spine cord injury. User's commands to control the electric-powered wheelchair are represented by shoulder elevation motions, which are recognized by comparing EMG signals acquired from the levator scapulae muscles with a preset double threshold value. The interface commands for controlling the electric-powered wheelchair consist of combinations of left-, right- and both-shoulders elevation motions. To achieve a real-time interface, we implement an EMG processing hardware composed of analog amplifiers, filters, a mean absolute value circuit and a high-speed microprocessor. The experimental results using an implemented real-time hardware and an electric-powered wheelchair showed that the EMG-based human-computer interface is feasible for the users with severe motor disabilities.

• 한국전자파학회논문지
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• 제9권1호
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• pp.43-51
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• 1998

본 논문에서는 IMT2000(FPLMTS)의 CAI(common air interface)의 방식으로 활발한 연구가 이루어지고 있는 CDMA방식에 대해서 가장 핵심이 되는 초기동기성능 분석을 Rician fading channel에서 수행하였다. false alarm probability, detection probability, test PN chip의 적 분구간을 변수로하여 double dwell방식에서 초기적분 구간길이에 대한 평균 최소동기획득 시간 및 신호검출 엄계값에 대한 평균 최소동기획득 시간을 분석한 결과에서 신호판정 임계치가 커짐에 따라 동기획득 소요시간은 그다지 증가하지 않음을 알 수 있다.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.48-55
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• 2024

The changes in threshold voltage and DIBL were investigated for changes in remanent polarization P_r and coercive field E_c, which determine the characteristics of the P-E hysteresis curve of ferroelectric in NCFET (negative capacitance FET). The threshold voltage and DIBL (drain-induced barrier lowering) were observed for a junctionless double gate MOSFET using a gate oxide structure of MFMIS (metal-ferroelectric-metal-insulator-semiconductor). To obtain the threshold voltage, series-type potential distribution and second derivative method were used. As a result, it can be seen that the threshold voltage increases when P_r decreases and E_c increases, and the threshold voltage is also maintained constant when the P_r/E_c is constant. However, as the drain voltage increases, the threshold voltage changes significantly according to P_r/E_c, so the DIBL greatly changes for P_r/E_c. In other words, when P_r/E_c=15 pF/cm, DIBL showed a negative value regardless of the channel length under the conditions of ferroelectric thickness of 10 nm and SiO₂ thickness of 1 nm. The DIBL value was in the negative or positive range for the channel length when the P_r/E_c is 25 pF/cm or more under the same conditions, so the condition of DIBL=0 could be obtained. As such, the optimal condition to reduce short channel effects can be obtained since the threshold voltage and DIBL can be adjusted according to the device dimension of NCFET and the P_r and E_c of ferroelectric.

• Journal of Oral Medicine and Pain
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• 제26권4호
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• pp.309-318
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• 2001

The purposes of the study were (1) to evaluate the olfactory identification ability in those who have bad breath, (2) to determine the olfactory detection threshold for methyl mercaptan in normal subjects and those who have bad breath, and (3) to evaluate the effect of oral hygiene care on the olfactory detection threshold for methyl mercaptan. Sixteen male subjects with bad breath (male odor group), 9 male subjects without bad breath (male non-odor group), and 10 female subjects without bad breath (female non-odor group) were included for the study. Olfactory identification ability was assessed by administrating the Cross-Cultural Smell Identification Test (CC-SIT), and the olfactory detection threshold for methyl mercaptan was measured by two-alternative forced-choice single-staircase detection threshold procedure in a double-blinded condition. The geometric mean of the last four staircase reversal points of a total of seven reversals is used as the threshold. For the male odor group, after 1 month of intensive oral hygiene care for reducing oral volatile sulfur compounds (VSC) concentration, the olfactory detection threshold for methyl mercaptan was measured again and compared to the initial value. The ANOVA was used to test the group difference of olfactory threshold and olfactory identification ability and the paired t-test was used to test the difference of olfactory threshold between before and after reduction of oral VSC in male odor group. The results were as follows : 1. There was no significant difference in olfactory identification ability among those who have bad breath and normal male or female subjects. 2. The olfactory detection threshold for methyl mercaptan was about 8.4 ppb in normal male and female. 3. There was a tendency that male subjects with bad breath showed a higher olfactory detection threshold for methyl mercaptan when compared to those of no bad breath. 4. The olfactory detection threshold for methyl mercaptan returned to a normal level after 1 month of intensive oral hygiene care for reducing oral VSC.

• 융합보안논문지
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• 제14권2호
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• pp.65-72
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• 2014

본 논문에서는 DDoS 탐지를 위해 기존의 이중 방화벽에 다중 필터링 방법을 적용한다. 1차 방화벽에서는 외부에서 유입되는 패킷 경로를 분석하여 R-PA(Router Path Anlaysis) 패킷 필터링 알고리즘과 엄격한 홉 카운터 필터링을 적용한다. 2차 방화벽에서는 1차 방화벽을 거쳐서 온 패킷의 데이터를 검사하여 정상적인 패킷과 비정상적인 패킷을 구분하고, 패킷 트래픽이 사용자에게 할당 된 임계치를 초과하는지를 검사하여 DDoS 공격을 차단한다.