• 한국항행학회논문지
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• 제23권1호
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• pp.61-68
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• 2019

블랙박스 본체를 회수하지 않고도 블랙박스의 정보나 수중 장비의 기록된 정보 등을 회수할 수 있도록 빛을 이용하는 수중 무선 광 통신 시스템은 매우 요긴하다. 본 논문에서는 탁도가 높은 천해환경에서 수중 가시광 통신시 발생하는 노이즈 원인을 분석하고 이러한 환경에서도 노이즈를 효과적으로 제거하면서도 광 검출신호의 최대 전압 스윙을 향상시킬 수 있는 기준신호 기반의 광 검출 센서 기술을 연구하였다. 그리고 개발한 통신 시스템의 성능을 입증하기 위해 광 무선통신 시스템을 제작하고 탁한 해수가 담긴 수조에서 송수신 시험을 수행하여 개발한 광 무선통신 기법이 실제로 효과가 있음을 검증하였다.

• 한국운동역학회지
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• 제21권4호
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• pp.459-466
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• 2011

The purpose of this study was to analyze of obstacle gait using spatio-temporal and foot pressure variables in children with autism. Fifteen children with autism and fifteen age-matched controls participated in the study. Spatio-temporal and foot pressure variables was investigated using GAITRite pressure sensor system. Each footprint was divided into 12 equal trapezoids and after that the hindfoot, midfoot and forefoot analysis was developed. Independent t-test was applied to compare the gait variables between the groups. The results showed that the autism group were significantly decreased in velocity, cadence, cycle and swing time compared to the control group. The autism group were significantly increased in step width and toe out angle compared to the control group. The autism group were significantly increased at midfoot and forefoot of lateral part of footprint and forefoot of medial part of footprint in the peak time compared to the control group. The autism group were significantly increased at midfoot and hindfoot in $P^*t$, at midfoot in active area, and at hindfoot in peak pressure compared to the control group. In conclusion, the children with autism showed abnormal obstacle gait characteristics due to muscle hypotonia, muscle rigidity, akinesia, bradykinesia and postural control impairments.

• 한국정밀공학회지
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• 제21권10호
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• pp.196-203
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• 2004

In this study, a new gait phase detection system using both FSR(Force Sensing Resister) sensors and a gyrosensor was developed to detect various gait patterns. FSR sensors were put in self-designed shoe insoles and a gyrosensor was attached to the posterior aspect of a shoe. An algorithm was also developed to determine eight different gait transitions among four gait phases: heel-strike, foot-flat, heel-off and swing. The developed system was compared with the conventional gait phase detection system using only FSR sensors in various gait experiments such as level walking, fore-foot walking and stair walking. In fore-foot walking and stair walking, the developed system showed much better accuracy and reliability to detect gait phases. The developed gait phase detection system using both FSR sensors and a gyrosensor will be helpful not only to determine pathological gait phases but to apply prosthetics, orthotics and functional electrical stimulation to patients with gait disorders.

• 대한의용생체공학회:의공학회지
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• 제26권3호
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• pp.145-150
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• 2005

A new gait detection system using both FSR (force sensing resistor) sensors and a gyrosensor was developed to detect various gait patterns. FSR sensors were put in self-designed shoe insoles and a gyrosensor was attached to the heel of a shoe. An algorithm was also developed to determine eight different gait transitions during four gait phases: heel-strike, foot-flat, heel-off and swing. The developed system was evaluated from nine heathy mans and twelve hemiplegic patients. Healthy volunteers were asked to walk in various gait patterns: level walking, fore-foot walking and stair walking. Only the level walking was performed in hemiplegic patients. The gait detection system was compared with a optical motion analysis system and the outputs of the FSR sensors. In healthy subjects, the developed system detected successfully more than $99\%$ for both level walking and fore-foot walking. For stair walking, the successful detection rate of the system was above$97\%$. In hemiplegic patients, the developed system detected approximately 98% of gait transitions. The developed gait phase detection system will be helpful not only to determine pathological gait phases but also to apply prosthetics, orthotics and functional electrical stimulation for patients with various gait disorders.

• 센서학회지
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• 제22권2호
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• pp.105-110
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• 2013

We fabricated an a-IGZO thin film transistor (TFT) with AZO/Ag/AZO transparent multilayer source/drain contacts by rf magnetron sputtering. a-IGZO TFT with AZO/Ag/AZO multilayer S/D electrodes (W/L = 400/50 ${\mu}m$) showed a subs-threshold swing of 3.78 V/dec, a minimum off-current of $10^{-12}$ A, a threshold voltage of 0.41 V, a field effect mobility of $10.86cm^2/Vs$, and an on/off ratio of $9{\times}10^9$. From the ultraviolet photoemission spectroscopy, it was revealed that the enhanced electrical performance resulted from the lowering of the Schottky barrier between a-IGZO and Ag due to the insertion of an AZO layer and thus the AZO/Ag/AZO multilayer would be very appropriate for a promising S/D contact material for the fabrication of high performance TFTs.

• 센서학회지
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• 제28권5호
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• pp.329-333
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• 2019

Solution-processed oxide thin-film transistors (TFTs) have garnered great attention, owing to their many advantages, such as low-cost, large area available for fabrication, mechanical flexibility, and optical transparency. Negative bias stress (NBS)-induced instability of sol-gel IGZO TFTs is one of the biggest concerns arising in practical applications. Thus, understanding the bias stress effect on the electrical properties of sol-gel IGZO TFTs and proposing an effective recovery method for negative bias stressed TFTs is required. In this study, we investigated the variation of transfer characteristics and the corresponding electrical parameters of sol-gel IGZO TFTs caused by NBS and positive bias recovery (PBR). Furthermore, we proposed an effective PBR method for the recovery of negative bias stressed sol-gel IGZO TFTs. The threshold voltage and field-effect mobility were affected by NBS and PBR, while current on/off ratio and sub-threshold swing were not significantly affected. The transfer characteristic of negative bias stressed IGZO TFTs increased in the positive direction after applying PBR with a negative drain voltage, compared to PBR with a positive drain voltage or a drain voltage of 0 V. These results are expected to contribute to the reduction of recovery time of negative bias stressed sol-gel IGZO TFTs.

• 센서학회지
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• 제31권4호
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• pp.271-277
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• 2022

We analyzed the effects of the interface trap on the output characteristics of an inversion mode n-channel GaN Schottky barrier (SB)-MOSFET based on the N_it distribution using TCAD simulation. As interface trap number density (N_it) increased, the threshold voltage increased while the drain current density decreased. Under N_it=5.0×10¹⁰ cm^-2 condition, the threshold voltage was 3.2 V for V_DS=1 V, and the drain current density reduced to 2.4 mA/mm relative to the non-trap condition. Regardless of the N_it distribution type, there was an increase in the subthreshold swing (SS) following an increase in N_it. Under U-shaped N_it distribution, it was confirmed that the SS varied depending on the gate voltage. The interface fixed charge (Q_f) caused an shift in the threshold voltage and increased the off-state current collectively with the surface trap. In summary, GaN SB-MOSFET can be a building block for high power UV optoelectronic circuit provided the surface state is significantly reduced.

• 융합신호처리학회논문지
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• 제23권2호
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• pp.76-83
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• 2022

최근 IT기술이 발달함에 따라 다양한 생체신호 측정 기기에 대한 연구 및 관심이 높아지고 있는 이유 중 하나로 고령사회가 본격화됨에 따라 IT 관련 기술을 이용한 고령 인구에 대한 연구가 지속해서 발전되고 있다. 본 논문은 초고령사회에 접어들면서 빠르게 발전하고 있는 노인층을 대상으로 한 의료서비스 영역 중 하나인 생활 패턴 감지와 낙상 감지 알고리즘 개발에 관한 것이다. 3축 가속도 센서와 심전도 센서를 이용한 시스템을 구성하여 데이터를 수집한 뒤 데이터를 분석하는 과정으로 진행하였고 실제 연구 결과로부터 행동 패턴의 분류가 가능함을 제안한다. 본 논문에 의해 구현된 인체 활동 모니터링 시스템의 유용성을 평가하기 위하여 자세 변화, 보행속도의 변화 등 다양한 조건에서 실험을 수행하여 인체의 중력 가속도와 인체 활동 정도를 반영하는 신호크기 범위 및 신호 벡터크기 파라미터를 추출하였다. 그리고 이들 파라미터값에 의해 피검자의 상태에 따라 판별이 가능하였다.

• 센서학회지
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• 제29권4호
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• pp.266-269
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• 2020

In this study, we investigated the effect of a sulfur passivation (S-passivation) process step on the electrical properties of surface-channel In_0.7Ga_0.3As quantum-well (QW) metal-oxide-semiconductor field-effect transistors (MOSFETs) with S/D regrowth contacts. We fabricated long-channel In_0.7Ga_0.3As QW MOSFETs with and without (NH₄)₂S treatment and then deposited 1/4 nm of Al₂O₃/HfO₂ through atomic layer deposition. The devices with S-passivation exhibited lower values of subthreshold swing (74 mV/decade) and drain-induced barrier lowering (19 mV/V) than the devices without S-passivation. A conductance method was applied, and a low value of interface trap density D_it (2.83×10¹² cm^-2eV^-1) was obtained for the devices with S-passivation. Based on these results, interface traps between InGaAs and high-κ are other defect sources that need to be considered in future studies to improve III-V microsensor sensing platforms.

• 전기학회논문지
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• 제66권12호
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• pp.1810-1814
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• 2017

This paper develops an approach to the algorithm of Gait pattern Analysis and step measurement with Multi-Pressure Sensors. The process of gait consists of 8 steps including stance and swing phase. As 3 parts of foot is supporting most of human weight, multiple pressure sensors are attached on the parts of foot: forefoot, big toe, heel. As 3 parts of foot is supporting most of human weight, multiple pressure sensors are attached on the parts of foot: forefoot, big toe, heel. normal gait proceed from heel, forefoot and big toe over time. While normal gait proceeds, values of heel, forefoot and big toe can be changed over time. So Each values of pressure sensors over time could discriminate whether it is normal or abnormal gait. Measuring Device consists of non-inverting amplifiers and low pass filter. Through timetable of values, normal gait pattern can be analyzed, because of supported weight of foot. Also, the peak value of pressure can judge whether it is walking or running. While people are running, insole of shoes is floating in the air on moment. Using this algorithm, gait analysis and step count can be measured.