에러 분포의 예측을 이용한 비트 심도 확장 기술

우지환(Jihwan Woo),심우성(Woosung Shim) 한국방송·미디어공학회 2017 방송공학회논문지 Vol.22 No.1

자동변속기 클러치 마찰재 드래그토크의 수학적 모델 개발 및 시험 분석

우지환(JiHwan Woo),정연하(YeonHa Jung),류완식(WanSik Ryu),이희용(HeeYong Lee) 한국자동차공학회 2017 한국자동차공학회 부문종합 학술대회 Vol.2017 No.5

The clutch and brake of Automatic Transmission (AT) are used to shift. When the clutch is in disengaged condition, no power should be transmitted. The clutch is composed of disks and plates, and the fluid that performs lubrication is between disks and plates. When the engine operates, shearing stress generates because of fluid viscosity between disks and plates. Therefore, drag loss occurs. Many researchers have studied the characteristic of drag torque before, and the drag torque is affected by various design variables. In this study, relative velocity between disks and plates at operating speed is calculated with lever analysis. So we developed mathematical model which predicts drag torque depending on relative velocity. Also, we verified the result of mathematical model experimentally. And we measured the drag torque due to the clearance between disk and plate. Then, test result discussed and analyzed.

정부의 혁신 촉진 정책이 서비스 산업의 기술 혁신 성과에 미치는 영향에 관한 연구

우지환(Jihwan Woo),김영준(YoungJun Kim) 한국산학기술학회 2019 한국산학기술학회논문지 Vol.20 No.2

본 최근, 4차 산업혁명 시대에 접어들면서, 서비스 산업의 기술 혁신에 대한 관심이 늘어나고 있다. 이러한 시대적 흐름에서, 본 논문에서는 현재 정부의 지원 제도, 규제, 혁신 촉진 정책이 서비스 산업에 속한 기업들의 기술 혁신 성과에 미치는 영향을 4,000개의 대한민국 서비스 산업 기업들을 대상으로 실증적으로 분석하였다. 다중 회귀 분석과 위계적 회기 분석을 적용하여 개별 요소 간의 상관관계를 분석하였고, 이를 이용해서, 정부의 지원과 규제와 서비스 산업의 기술 혁신의 두 축인 공정 혁신 및 제품 혁신에 대한 영향력을 검정하였다. 또한, 정부의 혁신 정책이 정부의 지원 및 규제와 서비스 기업의 기술 혁신 성과를 조절하고 있음을 살펴보았다. 그 결과, 정부의 지원 제도는 서비스 산업의 공정 혁신 및 제품 혁신 성과모두에 영향을 미치지만, 규제의 경우에는 공정 혁신 성과에만 영향을 미치는 것으로 파악하였다. 그리고 혁신 정책은 정부의 지원 제도 및 규제와 서비스 산업의 혁신 성과의 관계를 조절하는 것으로 평가되었다. 따라서 이러한 연구 결과는 기업의 경영층에게 정부의 지원 제도와 혁신 정책을 정확히 파악해서 이를 활용하도록 전략적인 시사점을 제공한다. 또한, 정부가 서비스 산업의 기술 혁신을 촉진하기 위해서는, 혁신 정책의 기술 혁신 성과에 대한 조절 효과를 높이기 위해서, 시대에 맞지 않는 규제들을 다시 정비하고, 기업의 규모나, 서비스 내용의 특성 등에 맞는 세분화된 정책을 만들어야 하는 정책적인 시사점을 제공한다. This paper analyzes the effects of government support systems, regulation, and innovation promotion policy on technological innovation performance of companies in the service industry using 4,000 Korean service industry companies. Multiple and hierarchical multiple regression analysis were used to analyze the correlation between the individual factors and process innovation and product innovation. Government support, regulation and technology innovation in the service industry were tested. In addition, government innovation promotion policy includes government support and regulation and the technological innovation performance of service firms. As a result, the government support system affects both the process innovation and the product innovation performance in the service industry, but affects only the process innovation performance in the case of regulation. Innovation promotion policy was found to regulate the relationship between government support systems and regulation and innovation performance of the service industry. Therefore, these findings provide strategic implications for the management of enterprises in relation to government support systems and innovation policy. It is necessary to reorganize regulations that are outdated to improve the effect of innovation policies on innovation performance.

정부의 역할이 기술혁신 성과에 미치는 영향에 관한 연구 : 한국 제조업 산업을 중심으로

우지환 ( Jihwan Woo ),김나리 ( Nari Kim ),김영준 ( Youngjun Kim ) 한국생산성학회 2019 生産性論集 Vol.33 No.3

The lifespan of the enterprises is decreasing over the years. This means that the success of the past does not necessarily guarantee the survival of the companies. Therefore, companies pursue technological innovations in order to survive from the fierce domestic and international competition. They also try to gain competitive edge in the market or reduce production costs through technological innovation. In the era of the Fourth Industrial Revolution where the industry is newly changing its structure, the technological innovation is gaining more importance. Only the ones who successfully go through the technological innovation can adjust to the new industrial landscape, and those who don’t will disappear from the market. Technological innovation is very important for the government as well. It is beneficial for the government to have the companies that are competitive in the global market through technological innovation, because they can contribute to the domestic economic growth by increasing tax revenue and employment. Therefore, governments support the domestic companies to enhance technological innovation performance while regulating them for socio-economical reasons. This paper empirically analyses the role of the government in increasing the technological innovation performance, mainly focusing on 4,000 Korean manufacturing companies. For the analysis, Korean Innovation Survey (KIS) provided by the Science and Technology Policy Institute (STEPI) is used. Based on the empirical analysis, it was found that governmental support can provide positive effect on both product innovation and process innovation. On the other hand, government regulations showed negative effects on both kinds of innovations. Finally, government policies had a controlling effect on the relationship between regulations and product innovation, and between government support and process innovation as well. The results from this paper can give strategic insights to the companies’ top level management on how to utilize the governmental innovation support and regulations. Moreover, the paper can be helpful for the government in developing technological innovation policies that can foster higher performance of the companies.

신경모델링을 이용한 인공와우 전기자극 패턴 연구

양혜진,우지환,Yang, Hyejin,Woo, Jihwan 대한전자공학회 2012 전자공학회논문지 Vol.50 No.8

청각 신경의 정상적 기능 회복을 위해 사용하는 인공와우는 인체 조직에 손상을 주는 단상파 방식의 펄스 대신 전하량 균형을 이루는 이상파 방식의 전기적 펄스를 사용한다. 본 논문에서는, Hodgkin-Huxley 신경 모델에 기반하여 다양한 전기적 펄스 방식의 자극이 신경 반응에 미치는 영향에 대하여 연구하였다. 전기적 펄스의 펄스 폭, 펄스간 간격 등을 변화시키면서, 청각신경의 역치, 반응 범위, 반응 시간 등을 측정하였다. 이러한 결과는 인공와우 시스템의 효과적인 자극 방식을 디자인 하는데, 활용 될 수 있으리라 기대된다. A cochlear implant system uses charge-balanced biphasic pulses that are known to reduce tissue damage than monophasic pulses. In this study, we investigated effect of pulse pattern on neural responses using a computer model, based on the Hodgkin-Huxley equation. Electric pulse phase, pulse duration, and phase gap have been systematically varied to characterize auditory nerve responses. The results show that neural responses, dynamic range and threshold are represented as a function of stimulus patterns and duration. The results could greatly extend to develop more efficient cochlear implant stimulation.

Neurogram을 이용한 인공와우 자극기법 평가 연구

양혜진,우지환,Yang, Hyejin,Woo, Jihwan 대한의용생체공학회 2013 의공학회지 Vol.34 No.2

Electrical stimulation is delivered to auditory nerve (AN) through the electrodes in cochlear implant system. Neurogram is a spectrogram that includes information of neural response to electrical stimulation. We hypothesized that the similarity between a neurogram and an input-sound spectrogram could show how well a cochlear implant system works. In this study, we evaluated electrical stimulus configuration of CIS strategy using the computational model. The computational model includes stochastic property and anatomical features of cat auditory nerve fiber. To evaluate similarity between a neurogram and an input-sound spectrogram, we calculated Structural Similarity Index (SSIM). The results show that the dynamic range and the stimulation rate per channel influenced SSIM. Finally, we suggested the optimal configuration within the given stimulus CIS. We expect that the results and the evaluating procedure could be employed to improve the performance of a cochlear implant system.

스마트워치에 기반한 맥박변이도를 이용한 심박변이도 예측 연구

김창진,우지환,Kim, Changjin,Woo, Jihwan 대한의용생체공학회 2018 의공학회지 Vol.39 No.2

The measurement of Heart Rate Variability (HRV) using electrocardiogram (ECG) signals has been used to predict fatigue and stress levels in a clinical environment, yet, owing to the complexity of such ECG systems, a domestic, nonclinical monitoring of HRV has not been a practical possibility. Recently though, Pulse Rate Variability (PRV) has been studied as an alternative to HRV. In this study, we investigated the reliability of measuring PRV by means of a smartwatch. The PRV results were compared to HRV results in similar test conditions, i.e. those obtained under rapid and deep-breathing scenarios. From the results obtained, it transpires that the Bland-Altman ratio and cross-correlation coefficients between several PRV and HRV parameters were highly correlated, thus suggesting that the results of measuring PRV using a smartwatch can be used to predict HRV in nonclinical environments.

심박변이도 기반 청취 노력도 측정 연구

김현규,나영민,우지환,Kim, Hyunkyu,Na, Youngmin,Woo, Jihwan 대한의용생체공학회 2019 의공학회지 Vol.40 No.3

Listening effort represents the listener's attention, stress, required cognition resource, and mental exertion to understand a speech in various situations. Recently, it has been focused to evaluate an effectiveness of hearing aids and cochlear implant. The physiologic measures, such as heart rate, skin conductance, electroencephalography, and pupil dilation, have been used to objectively measure listening effort. In this study, we investigated the feasibility of temporal and spectral heart rate variabilities to measure listening effort to understand speech in the presence of background noise. The results showed that several heart rate variabilities significantly increased as increasing background noise level. Finally, the heart rate variability can be used as an objective tool to measure listening efforts.

ECAP 평가를 위한 3차원 달팽이관 모델 개발

강수진(Soojin Kang),우지환(Jihwan Woo) 대한전자공학회 2013 전자공학회논문지 Vol.50 No.6

인공와우는 유모세포의 손실로 청신격 자극이 되지 않을 경우, 삽입된 전극에 전기자극을 가함으로써 청감각을 회복하는 장치이다. 인공와우의 성능을 향상하기 위하여, 자극에 따른 정확한 신경반응을 이해하는 것이 매우 중요하고, 임상에서는 electrically evoked compound action potential (ECAP)을 측정하여 신경반응을 측정하고 있다. 본 연구에서는 실제 달팽이관과 유사한 3차원 달팽이관 유한요소 모델을 개발하고, 자극에 따른 신경반응을 측정할 수 있는 ECAP 알고리즘을 개발하였다. 개발된 3차원 달팽이관 모델을 이용하여, 전기 자극에 따른 ECAP 크기와 반응 잠복 시간을 측정하였으며, 측정된 결과 임상시험과 동물실험에서 측정된 ECAP 크기와 반응 잠복 시간과 유사한 값을 얻을 수 있었다. 본 3차원 달팽이관 모델은 전기 자극에 대한 신경 반응을 분석함으로써 인공 와우의 성능을 향상시키기 위한 전기자극 방식을 연구하는데 유용하게 이용될 수 있다. Cochlear implant (CI) is an auditory prosthesis that delivers electrical stimulation via inserted electrodes into a cochlea. To evaluate CI performance, it is important to understand how auditory nerves are responded to electrical stimulations. In clinic, electrically evoked compound action potential (ECAP) is measured. In this study, we developed 3D finite element (FE) cochlear model to simulate ECAP in response to electrical stimulation. The model prododuced ECAP similar to that measured in animal experiments and clinics. This 3D FE cochlear model could be used in electrical stimulus method study to improve CI by analyzing neural responses to electrical stimulations.

신경모델링을 이용한 인공와우 전기자극 패턴 연구

양혜진(Hyejin Yang),우지환(Jihwan Woo) 대한전자공학회 2012 전자공학회논문지 Vol.49 No.12

청각 신경의 정상적 기능 회복을 위해 사용하는 인공와우는 인체 조직에 손상을 주는 단상파 방식의 펄스 대신 전하량 균형을 이루는 이상파 방식의 전기적 펄스를 사용한다. 본 논문에서는, Hodgkin-Huxley 신경 모델에 기반하여 다양한 전기적 펄스 방식의 자극이 신경 반응에 미치는 영향에 대하여 연구하였다. 전기적 펄스의 펄스 폭, 펄스간 간격 등을 변화시키면서, 청각신경의 역치, 반응 범위, 반응 시간 등을 측정하였다. 이러한 결과는 인공와우 시스템의 효과적인 자극 방식을 디자인 하는데, 활용 될 수 있으리라 기대된다. A cochlear implant system uses charge-balanced biphasic pulses that are known to reduce tissue damage than monophasic pulses. In this study, we investigated effect of pulse pattern on neural responses using a computer model, based on the Hodgkin-Huxley equation. Electric pulse phase, pulse duration, and phase gap have been systematically varied to characterize auditory nerve responses. The results show that neural responses, dynamic range and threshold are represented as a function of stimulus patterns and duration. The results could greatly extend to develop more efficient cochlear implant stimulation.