• 대한통합의학회지
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• 제8권2호
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• pp.131-138
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• 2020

Purpose : The purpose of this study was to investigate the effects of the frequency band pass filter on the P300 event-related potential in the working memory. Methods : The subjects were 20 women in their 20s who applied for participation in the experiment. Event-related potentials (ERPs) were elicited using 3-back tasks for the working memory, and were recorded from Fz, Cz, and Pz scalp electrodes. The high-pass filters were set to 0.01, 0.1, and 0.3 Hz for analysis purposes, and the low-pass filters were set to 30 and 15 Hz. The 3-back task was presented for a total of 100 times, among which 30 times were designated for the target stimulation (a matched number) and 70 times for the non-target stimulation (an unmatched number). The temporal interval between each stimulation was set at 1 second, while each time duration was randomly presented between 2 to 4 seconds. ERP were analyzed for the P300 recorded from Fz, Pz and Cz scalp electrodes. Results : Latency and amplitude had no significant interaction effects in both the high- and low-pass filters. For the main effects, the latency and amplitude of the P300 event-related potential had no significant difference in the high-pass filters, but the latency had a significant difference in the low-pass filter of Fz, and the amplitude had a significant difference in the low-pass filter of Pz. Conclusion : The results of this study showed that the less than 0.3 Hz high filters had no effects on the differences between the latency and amplitude of the P300 event-related potential in the working memory. The 30Hz low-pass filter, however, was found to be useful for recording the P300 event-related potential in the working memory.

• 한국물환경학회지
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• 제28권6호
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• pp.890-895
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• 2012

Duration curves describe the percentage of time that a certain water quality (total/fecal coliform (=TC/FC)) or discharge is exceeded. The curves methodology are usually based on daily records and are useful in estimating how many days per year and event will be exceeded. The technique was further applied to estimated TC/FC loading to the Geumho River, using the daily mean flow rate and TC/FC concentration data during January, 2001 and December, 2011 for the Geumhogang6 (=Seongseo water level station) where an automated monitoring station is located in Gangchang-bridge. Low flow of the Seongseo (=11.1 cms) was equivalent to 75.3% on an exceedance probability scale. Load Duration curve for TC/FC loading at the Seongseo was constructed. Standard load duration curve was constructed with the water quality criteria for class III (TC/FC concentration = 5000/1000 CFU/ 100 mL). By plotting TC/FC observed load duration curve with standard load duration curve, it could be revealed that water quality do not meet the desired water quality for 68.8/11.2% on an exceedance probability scale. IF linear correlation between flow rate and coliform concentration is assumed, it can be interpreted that water quality exceed desired criteria when daily average flow rate is over 11.9/109.9 cms.

• 대한토목학회논문집
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• 제40권1호
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• pp.25-33
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• 2020

가뭄사상은 지속기간, 심도, 피해면적 등으로 특성화 할 수 있다. 일반적으로 가뭄사상은 관측소별로 구축된 시계열 자료를 이용하여 가뭄지수를 산정한 후, 연속이론에 따라 가뭄의 시작과 종료 시점을 파악하여 정의된다. 하지만 이와 같은 1차원적 분석방법은 가뭄의 시공간적인 발생특성 및 이동경로를 분석하는 데에는 한계가 있다. 따라서 본 연구에서는 단순 클러스터링 알고리즘을 활용하여 3차원(경도, 위도, 시간)적 가뭄사상을 정의하고, 가뭄의 시공간적 확장에 따른 가뭄상황을 파악할 수 있는 가뭄지도를 개발하였다. 이러한 가뭄지도는 가뭄지수를 공간적으로 표출하는 2차원적 가뭄 모니터링 정보와 비교하여 3차원적 가뭄사상에 대한 특성(지속기간, 공간적 누적심도, 가뭄의 중심)을 모두 표출하는 것이다. 그 결과 가뭄 지속기간 내 가뭄 발생면적이 최소 10 % 미만인 국소면적인 경우도 있는 반면, 최대 90 % 이상으로 확장되는 비율도 44%(25개 사상 중 11개 사상)로 확인되었다. 이는 3차원적으로 해석한 다양한 가뭄 지속기간 변화에 따른 공간적인 가뭄의 면적 변화와 심도(강도) 변화에 대한 관계는 매우 중요하다는 것을 재확인 하는 것이다. 3차원 시공간적 가뭄분석을 통한 가뭄지도 개발을 위한 연구는 미래 극한가뭄 대응 방안을 마련함에 있어서는 지역적 가뭄의 시공간적 발생특성 및 패턴을 해석하는 데 활용가능성이 있을 것으로 기대된다.

• 한국수자원학회논문집
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• 제39권4호
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• pp.373-382
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• 2006

본 연구에서는 구조가 비교적 간단한 구형펄스모형을 이용하여 가뭄의 심도-지속기간-생기빈도 해석을 이론적인 방법으로 수행하였다. 주어진 절단수준에 대해 다양한 지속기간의 자료계열을 구성하고 이에 대한 통계 특성치를 산정하여 모형의 매개변수를 추정하였다. 이렇게 추정된 매개변수는 이론적인 방법으로 가뭄심도-지속기간-생기빈도 해석을 수행하는데 이용되었다. 가뭄심도-지속기간-생기빈도 해석은 각 펄스의 중첩을 고려하는 경우와 고려하지 않는 경우에 대해 각각 나누어 수행하였고 중첩을 적용하는 경우의 가뭄심도는 재현기간이 증가할수록 더욱 커지는 것을 파악할 수 있었다. 그러나 지속기간이 증가할수록 중첩의 정도는 감소하였으며 이는 지속기간이 증가할수록 사상의 발생확률이 크게 작아지기 때문이다. 지속기간이 증가할 경우 발생하는 사상이 거의 없거나 또는 아예 발생하지 않는 경우가 생기며 이러한 경우에는 모형의 매개변수를 추정할 수 없으므로 재현기간에 따른 심도의 추정도 어렵게 된다. 이 점이 구형펄스모형을 적용하는 경우의 한계가 된다 본 연구에서는 서울지점에 발생한 주요 가뭄사상에 대해 본 연구에서의 결과를 적용하여 그 재현기간을 추정하였다. 어떤 가뭄사상의 재현기간을 가능한 지속기간별로 추정된 재현기간 중 가장 큰 것으로 가정한다면 서울지점의 주요 가뭄사상은 약 14년${\sim}$35년 정도의 재현기간을 갖는다. 이는 상대적으로 아주 크지 않은 재현기간이며 이와 같은 가뭄의 발생이 자주 있을 수 있음을 의미한다.

• 한국멀티미디어학회논문지
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• 제9권12호
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• pp.1572-1579
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• 2006

An usual acoustic emission(AE) event has two widely characterized parameters in time domain, peak amplitude and event duration. But noise in AE measuring may disturb the signals with its parameters and aggrandize the signal incertitude. Experiment activity of detection of the nick inside of porcelain with AE was made and study on AE signal processing with statistic be presented in this paper in order to pick-up information expected from the signal with noise. Effort is concentrated on developing a novel arithmetic to improve extraction of the characteristic from stochastic signal and to enhance the voracity of detection. The main purpose discussed in this paper is to treat with signals on amplitudes with statistic mutuality and power density spectrum in frequency domain, and farther more to select samples for neural networks training by means of least-squares algorithm between real measuring signal and deterministic signals under laboratory condition. By seeking optimization with the algorithm, the parameters representing characteristic of the porcelain object are selected, while the stochastic interfere be weakened, then study for detection on neural networks is developed based on processing above.

• Journal of Information Processing Systems
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• 제11권4호
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• pp.616-629
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• 2015

A mobile terminal will expect a number of handoffs within its call duration. In the event of a mobile call, when a mobile node moves from one cell to another, it should connect to another access point within its range. In case there is a lack of support of its own network, it must changeover to another base station. In the event of moving on to another network, quality of service parameters need to be considered. In our study we have used the Markov decision process approach for a seamless handoff as it gives the optimum results for selecting a network when compared to other multiple attribute decision making processes. We have used the network cost function for selecting the network for handoff and the connection reward function, which is based on the values of the quality of service parameters. We have also examined the constant bit rate and transmission control protocol packet delivery ratio. We used the policy iteration algorithm for determining the optimal policy. Our enhanced handoff algorithm outperforms other previous multiple attribute decision making methods.

• 천문학회보
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• 제38권2호
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• pp.33-33
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• 2013

We are developing empirical space weather (solar flare, solar proton event, and geomagnetic storm) forecast models based on solar data. In this talk we will review our main results and recent progress. First, we have examined solar flare (R) occurrence probability depending on sunspot McIntosh classification, its area, and its area change. We find that sunspot area and its increase (a proxy of flux emergence) greatly enhance solar flare occurrence rates for several sunspot classes. Second, a solar proton event (S) forecast model depending on flare parameters (flare strength, duration, and longitude) as well as CME parameters (speed and angular width) has been developed. We find that solar proton event probability strongly depends on these parameters and CME speed is well correlated with solar proton flux for disk events. Third, we have developed an empirical storm (G) forecast model to predict probability and strength of a storm using halo CME - Dst storm data. For this we use storm probability maps depending on CME parameters such as speed, location, and earthward direction. We are also looking for geoeffective CME parameters such as cone model parameters and magnetic field orientation. We find that all superstorms (less than -200 nT) occurred in the western hemisphere with southward field orientations. We have a plan to set up a storm forecast method with a three-stage approach, which will make a prediction within four hours after the solar coronagraph data become available. We expect that this study will enable us to forecast the onset and strength of a geomagnetic storm a few days in advance using only CME parameters and the WSA-ENLIL model. Finally, we discuss several ongoing works for space weather applications.

• Advances in Computational Design
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• 제3권4호
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• pp.405-418
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• 2018

Building Information Modelling (BIM) and Discrete Event Simulation (DES) are tools widely used in the context of the construction industry. While BIM is used to represent the physical and functional characteristics of a facility, DES models are used to represent its construction process. Integrating both is beneficial to those interested in the field of construction management since it has many potential applications. Game engines provide a human navigable 3D virtual environment in which the integrated BIM and DES models can be visualised and interacted with. This paper reports the experience obtained while developing a simulator prototype which integrates a BIM and a DES model of a single construction activity within a commercial game engine. The simulator prototype allows the user to visualise how the duration of the construction activity is affected by different input parameters interactively. It provides an environment to conduct DES studies using the user's own BIM models. This approach could increase the use of DES technologies in the context of construction management and engineering outside the research community. The presented work is the first step towards the development of a serious game for construction management education and was carried out to determine the suitable IT tools for its development.

• 한국물환경학회지
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• 제34권5호
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• pp.487-493
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• 2018

Urban stormwater runoff is the one of the most extensive causes of deterioration of water quality in streams in urban areas. Especially, in the Suyeong River watershed, non-point sources from urban-residential areas are the most common cause of water pollution. Also, it has been ascertained that BOD and COD as indexes of organic matter, have limitation on management of Suyeong River's water quality. In this study, changes of organic matter properties of Suyeong River from inflow of non-point source during rainfall were investigated. Fractions of organic matters were analyzed using water samples collected at two sites (Suyeong River and Oncheon Stream) during a rain event. Variations of dissolved organic carbon (DOC) concentration by rainfall were similar to flow rate change in the river. Distribution of organic matter fraction according to change of rain duration revealed that while hydrophilic component increased at initial rainfall, the hydrophobic component was similar to change in dissolved organic carbon (DOC) concentration. Also, the relative proportion of hydrophilic components in organic matter in river water increased, due to rainfall. Results of biodegradation of organic matters revealed that decomposition rate of organic matters during rainfall was higher than that of during a non-rainfall event.

• 근관절건강학회지
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• 제5권1호
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• pp.7-25
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• 1998

Rheumatoid arthritis, unlike other chronic diseases, causes the patients to experience uncertainty in their daily lives and thus to feel threat on their emotional comfort because of inconsistent and unpredictable symptoms such as pain. Therefore, a theoretical framework is needed for explanation of uncertainty in patients having rheumatoid arthritis. A hypothetical model was constructed on the basis of Mishel's Uncertainty Theory and other literature review. The model included 9 theoretical concepts and 19 paths. Subjects of the study constituted 330 partients who visited outpatient clinics of two university hospitals and one general hospital in Seoul. Self report questionnaires were used to measure the variables affecting uncertainty. Reliability coefficients of these instruments were found Cronbach's Alpha=$.70{\sim}.94$. In data analysis, SAS program and PC-LISREL 8.03 computer program were utilized for descriptive statistics and covariance structure analysis. The results of covariance structure analysis for model fitness were as follows : 1) Hypothetical model showed a good fit to the empirical data : Chi-square($X^2$)=41.81 (df=11, P=.000), Goodness of Fit Index=.974, Root Mean Square Residual=.049, Normed Fit Index=.928, Non Normed Fit Index=.814. 2) For the validity and the parcimony of model, a modified model was constructed by appending 2 paths and deleting 5 paths according to the criteria of statistical significance and meaningfulness. 3) The results of hypothesis testing were as follows : (1) Educational level, event familiarity and severity of illness had a direct effect on uncertainty : Event congruency had both direct and indirect effect on uncertainty : Credible authority and symptom consistency had a nonsignificant direct effect on uncertainty, (2) Illness duration, symptom consistency, and event congruency had a direct effect on severity of illness ; Credible authority had a both direct and indirect effect on severity of illness ; Event congruency had the greatest effect on severity of illness, and event familiarity had a nonsignificant direct effect on severity of illness.