http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
현승호,지영준 대한의용생체공학회 2023 의공학회지 Vol.44 No.2
Efforts to employ smart home sensors to monitor the indoor activities of elderly single residents have been made to assess the feasibility of a safe and healthy lifestyle. However, the bathroom remains an area of blind spot. In this study, we have developed and evaluated a new edge computer device that can automatically detect water usage activities in the bathroom and record the activity log on a cloud server. Three kinds of sound as flushing, show- ering, and washing using wash basin generated during water usage were recorded and cut into 1-second scenes. These sound clips were then converted into a 2-dimensional image using MEL-spectrogram. Sound data augmen- tation techniques were adopted to obtain better learning effect from smaller number of data sets. These techniques, some of which are applied in time domain and others in frequency domain, increased the number of training data set by 30 times. A deep learning model, called CRNN, combining Convolutional Neural Network and Recurrent Neu- ral Network was employed. The edge device was implemented using Raspberry Pi 4 and was equipped with a con- denser microphone and amplifier to run the pre-trained model in real-time. The detected activities were recorded as text-based activity logs on a Firebase server. Performance was evaluated in two bathrooms for the three water usage activities, resulting in an accuracy of 96.1% and 88.2%, and F1 Score of 96.1% and 87.8%, respectively. Most of the classification errors were observed in the water sound from washing. In conclusion, this system demonstrates the potential for use in recording the activities as a lifelog of elderly single residents to a cloud server over the long- term.
분산전원이 연결된 배전계통에서의 모델 기반 지락고장 위치 검출 방법
현승호(Seung Ho Hyun),강석준(Seok Jun Kang) 대한전기학회 2021 전기학회논문지 Vol.70 No.8
In a distribution system with distributed energy resources, power flow is not fixed in a single direction. Therefore, from the protection coordination’s point of view, existing over-current protection scheme is not adequate any more. On the other hand, in future’s distribution systems, it is expected that various kinds of information is available with more accuracy, which is one of the advantageous points in protection. This paper suggests a novel fault location method with these factors considered. In the proposed scheme, an existing protective device like a recloser of fuse is replaced by a smart relay with simple calculation and communication ability. A distribution system is divided into several segments and the fault location is calculated through successive circuit analysis at each segment using concentrated parameters of the lines. In this, synchronized power data are assumed to be available at each loading point before a fault occurs and it is also assumed that each load is not changed abruptly. The suggested method is applied to several distribution system models, through computer simulations, and is verified to be useful with accurate fault location.
CH₄/Air 예혼합화염의 하류영역에서 NOx 생성특성에 관한 수치해석
현승호(Seung-Ho Hyun),황철홍(Cheol-Hong Hwang),탁영조(Young-Jo Tak),이창언(Chang-Eon Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In this study, the NOx formation characteristics of one-dimensional CH₄/Air premixed flame using detailed-kinetic chemistry are examined numerically. The combustor length and the amount of heat loss are varied to investigate the effect of residence time and heat loss on the NOx formation in a post-flame region. In the flame region, NO is mainly produced by the Prompt NO mechanism including N₂O-intermediate NO mechanism over all equivalence ratio. However, thermal NO mechanism is more important than Prompt NO mechanism in the post-flame region . In the case of adiabatic condition, the increase of combustor length causes the remarkable increase of NO em ission at the exit due to the increas e of residence time. On the other hand, NO reaches the equilibrium state in the vicinity of flame region, considering radiation and conduction heat transfer. Furthermore the NO, in the case of φ=1.2, is gradually reduced in the downstream region as the heat loss increase. From these results, it can be concluded that the control of heat loss and heat transfer near combustor wall should be recognized as an important NOx reduction technology.
현승호(Seung ho Hyun),이성오(Sung O Lee) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.11
In this paper, a fault allocation method is suggested for distribution systems with fault currents at both ends. Tn a smart grid with various distributed generation systems in operation, the power flow may not be one directional. Therefore, the over-current relaying protection, most common in distribution system protection is not proper anymore. The proposed method uses the power balance condition in a section for both fault detection and allocation. The suggested method cannot consider the effect of the power loss at grounding. However, in spite of this weakness, the fault allocation error was not more than 5.2% even in the case with fault currents at both ends. Furthermore, there is no recursion process which can be the cause of time consuming. It is expected, if the grounding condition is considered adequately, the suggested method can be a candidate of protection method for complicated distribution systems like smart grids.
玄升鎬(Seung Ho Hyun),陳保建(Bu Gun Jin),李承宰(Seung Jae Lee) 대한전기학회 2007 전기학회논문지 Vol.56 No.11
This paper presents a distance relaying algorithm for phase-to-ground faults in transmission lines under Multi- Agent protection environment. In normal condition, a distance relay agent stores the latest states, e.g., voltage of source side, voltage of the opposite side and the loading conditions, etc., through communication between the agents. Once a fault occurs, the relay calculates the fault location using the knowledge about the states just before the fault happens. This stand-alone operation is to improve reliability under the fault condition at which the accuracy or time required for communication may not be guaranteed. The mathematical expression of fault location is derived through loop analysis, before hand, in the manner that both fault current from the opposite end and fault resistance are included implicitly so that their effects are minimized. The suggested algorithm is applied to a typical transmission system with two power sources on both ends to show its effectiveness.
현승호(Seung Ho Hyun),이성오(Sung O Lee) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
It is expected, in the near future, that the use of distributed generation systems should be increased considerably. In this case, distance relay algorithm should be developed in the manner that it can reduce the error due to the in-feed effect. This paper presents a method to consider the fault current rushed from the remote end of a line. In the steady-state, the relays in both ends exchange the voltages of upper nodes. If a fault is perceived, the relay calculates fault location taking the fault current from the remote end by using voltage data of the remote ends obtained just before the fault. Even though this method has inevitable error, it can show more precise fault allocation. The suggested method is applied to a typical transmission system with two power sources in both ends to verify its effectiveness.
CH₄/Air 예혼합화염의 고효율 연소조건에서 열손실에 따른 NOx 및 CO 배출특성
현승호(Seung-Ho Hyun),황철홍(Cheol-Hong Hwang),이창언(Chang-Eon Lee),김세원(Se-Won Kim),장기현(Gi-Hyun Jang) 한국연소학회 2008 한국연소학회지 Vol.13 No.1
Emission characteristics of NOx and CO with heat loss under high efficiency combustion conditions of CH₄/Air prmixed flame were examined numerically using detailed-kinetic chemistry. The one-dimensional combustor length was fixed 5cm, and the equivalence ratio was varied from 0.75 to 0.95. To consider the effects of heat loss on NOx and CO formation, the radiative heat loss rate and combined heat loss rate of conductive and convective heat transfer are included. The following conclusions were drawn. In order to reduce the NOx and CO emission level simultaneously, the temperature of product gases must be reduced under 1,800K as soon as possible but kept over 1,300K during the residence time which is needed to converge CO to CO₂.
CH<sub>4</sub>/Air 예혼합화염의 하류영역에서 체류시간 및 열손실에 의한 NOx의 생성특성
황철홍,현승호,탁영조,이창언,Hwang, Cheol-Hong,Hyun, Sung-Ho,Tak, Young-Jo,Lee, Chang-Eon 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.1
In this study, the NOx formation characteristics of one-dimensional $CH_4$/Air premixed flame using detailed-kinetic chemistry are examined numerically. The combustor length and the amount of heat loss are varied to investigate the effect of residence time and heat loss on the NOx formation in a post-flame region. In the flame region, NO is mainly produced by the Prompt NO mechanism including $N_2$O-intermediate NO mechanism over all equivalence ratios. However, thermal NO mechanism is more important than Prompt NO mechanism in the post-flame region. In the case of adiabatic condition, the increase of combustor length causes the remarkable increase of NO emission at the exit due to the increase of residence time. On the other hand, NO reaches the equilibrium state in the vicinity of flame region, considering radiation and conduction heat losses. Furthermore the NO, in the case of $\phi$=1.2, is gradually reduced in the downstream region as the heat loss is increased. From these results, it can be concluded that the controls of residence time and heat loss in a combustor should be recognized as an important NOx reduction technology.