• 방송공학회논문지
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• 제20권2호
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• pp.300-309
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• 2015

IEEE 802.11n 무선랜에서 높은 처리율을 지원하기 위하여 미디어 접근 제어(MAC) 계층은 A-MSDU(Aggregate-MAC Service Data Unit)와 A-MPDU(Aggregate-MAC Protocol Data Unit)을 채택하고 있다. 일반적으로, A-MPDU는 선택적 재전송 기능을 사용하기 때문에 A-MSDU보다 높은 처리율 성능을 보이고 있다. 그러나 A-MPDU가 선택적 재전송 기능을 사용할지라도 A-MPDU 내부의 MPDU의 크기가 최소 MPDU 시작 간격 크기보다 작은 MPDU의 경우에는 더미(dummy) MPDU인 구분자(delimiter)의 추가로 인한 재전송 오버헤드 때문에 처리율의 저하현상이 발생하게 된다. 따라서 상기의 문제점을 해결하기 위하여 A-MPDU 내부의 MPDU의 크기가 최소 MPDU 시작 간격 크기보다 작은 경우에 A-MPDU 내부의 MPDU가 구분자로 채워지는 것이 아니라 A-MSDU로 채워지는 2-레벨(two-level) 집적 방식이 소개되었다. 상기의 2-레벨 집적방식에서, 기존 재전송 방법은 오직 A-MPDU에 대해서만 재전송을 수행하고 있지만 본 논문에서 제안하는 재전송 방법에서는 재전송 데이터의 크기가 최소 MPDU 시작 간격 크기보다 작은 경우에 신규 MSDU들과 재전송 MSDU들을 함께 집적하여 재전송을 수행한다. 따라서 제안한 재전송 방법이 기존의 재전송 방법보다 더 좋은 처리율 성능을 가진다.

• Communications for Statistical Applications and Methods
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• 제26권5호
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• pp.497-506
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• 2019

Forecasting the U.S. employment level is made using machine learning methods of the artificial neural network: deep neural network, long short term memory (LSTM), gated recurrent unit (GRU). We consider the big data of the federal reserve economic data among which 105 important macroeconomic variables chosen by McCracken and Ng (Journal of Business and Economic Statistics, 34, 574-589, 2016) are considered as predictors. We investigate the influence of the two statistical issues of the dimension reduction and time series differencing on the machine learning forecast. An out-of-sample forecast comparison shows that (LSTM, GRU) with differencing performs better than the autoregressive model and the dimension reduction improves long-term forecasts and some short-term forecasts.

• Journal of the Korean Data and Information Science Society
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• 제19권4호
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• pp.1345-1352
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• 2008

An inventory with constant demand is studied. We adopt a renewal argument to obtain the transient and stationary distribution of the level of the inventory. We show that the stationary distribution can be also derived by making use of either the level crossing technique or the renewal reward theorem. After assigning several managing costs to the inventory, we calculate the long-run average cost per unit time. A numerical example is illustrated to show how we optimize the inventory.

• 한국농공학회논문집
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• 제65권5호
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• pp.51-68
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• 2023

Due to the recent integrated water management policy, it is important to identify a reliable supply amount for establishing an agricultural water supply plan. In order to identify the amount of agricultural water supply, it is essential to calculate the discharge by measuring the water level and flow velocity of reservoirs and canal agricultural water, and quality control to ensure reliability must be preceded. Unlike agricultural reservoirs, canal agricultural water are more sensitive to the surrounding environment and reservoir irrigation methods (continuous, intermittent irrigation, etc.), making it difficult to estimate general water level patterns and at the same time a lot of erroneous data. The Korea Rural Community Corporation is applying a filter technique as a quality control method capable of processing large quantities and real-time processing of canal agricultural water level data, and applicability evaluation is needed. In this study, the types of errors generated by the automatic water level measurement system were first determined. In addition, by using the manual quality control data, a technique with high applicability is derived by comparing and analyzing data calibrated with Gaussian, Savitzky-Golay, Hampel, and Median filter techniques, RMSE, and NSE, and the optimal parameters of the technique range was derived. As a result, the applicability of the Median filter was evaluated the highest, and the optimal parameters were derived in the range of 120min to 240min. Through the results of this study, it is judged that it can be used for quantitative evaluation to establish an agricultural water supply plan.

• 기본간호학회지
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• 제15권4호
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• pp.531-538
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• 2008

Purpose: The purpose of this study was to identify factors influencing Vancomycin-resistant enterococcus infection control among nurses in intensive care units. Method: Data were collected from August 15 to October 14, 2007 from 188 nurses working in intensive care units. The nurses answered a 26 item-questionnaire, which included management of the cohort (14 items), hand washing (6 items) and management of the environment (6 items). Descriptive statistics, t or F test, ANOVA, and multiple regression analysis were used with SPSS PC+ 14.0 to analyze the data. Results: The participant's level of awareness of Vancomycin-resistant enterococcus infection control was 3.87; that of compliance was 3.74. Significant factors influencing the level of compliance with Vancomycin-resistant enterococcus infection control were'the level of the awareness' and 'the type of intensive care unit'. These two variables accounted for 21.0% of variance for compliance with the Vancomycin-resistant enterococcus infection control among the participants. Conclusion: In order to develop a strategy to increase the compliance with Vancomycin-resistant enterococcus infection control, it is necessary to be concerned about 'the level of the awareness', 'the type of intensive care unit;', and 'experiences of caring for patients with Vancomycin-resistant enterococcus'.

• Journal of Korean Biological Nursing Science
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• 제9권2호
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• pp.135-142
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• 2007

Purpose: This study was conducted to investigate degree of stress level in CCU patients, and to give a baseline data in developing nursing intervention program to reduce the stress. Method: Subjects of this study were the 100 hospitalized patients of C University Hospital in Seoul City from February to December 2003. The collected data was analyzed by using the SAS program: t-test, Scheff$\acute{e}$ test, and ANOVA analysis were employed to find differences in stress level. Result: The highest stress factor was 'Concern', and next were 'Dependency & limitation', 'Uncertainty', 'Treatment procedure', 'Sleep disturbance', 'Environment' in order. The perceived stress level of CCU patients was 1.65 scores; the highest scored item was 'have to void urine and feces on the bed', next were 'have to use the toilet bowel lying on the bed' in order. The stress level according to characteristics of the subjects was significantly different with the marital status, the presence of religion, the hospitalized days, the economic status, and the admission experience. Conclusion: The stress level of patients in the coronary care unit was high in concern of a disease, family and economic state, in limitation and dependency, and in uncertainty about prognosis of a disease. Further researches are necessary to develop and apply the intervention method of reducing stress level of CCU patients. In addition studies on family members of CCU patients are also recommended.

• Asian Pacific Journal of Cancer Prevention
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• 제17권6호
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• pp.2973-2977
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• 2016

Opisthorchis viverrini is still a serious problem in Northeastern and Northern Thailand. Active surveillance is required to determine updated data for further prevention and control planning. Therefore, this study aimed to examine the prevalence and risk factors for O. viverrini in three provinces, Northeastern Thailand. A cross-sectional survey was conducted during October 2015 to March 2016 at Kaeng Sanam Nang district of Nakhon Ratchasima province, Waeng Noi district of Khon Kaen province, and Khon Sawan district of Chaiyaphum province, Thailand. Stool samples were examined by using a modified Kato-Katz Thick smear technique. From a total of 978 participants screened, O. viverrini infection was found in 1.74%, the majority opf positive cases being male (6.62%), age group 51-60 years old (4.21%), educated at primary school (8.43%), occupied with agriculture (9.62%),having an income <4,000 baht per month (4.82%), and living in Khon Sawan district (8.43%). Participants had a high knowledge level (42.43%), good attitude level (34.76%), and fair level (38.04%). The present study indicates the O. viverrini infection rate is low, but elderly males with primary school education involved in agriculture are still frequently effected particularly in Khon Sawan district. Therefore, this risk group requires behavior modification and continued monitoring.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.437-442
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• 1997

To determine the optimum pressurizer water level during normal operation for Kori unit 1, performance and safety analysis are peformed. The methodology is developed by evaluating "decrease in secondary heat removal" events such as Loss of Normal Feedwater accident. To demonstrate optimum pressurizer level setpoint, RETRAN-03 code is used for performance analysis. Analysis results of RETRAN following reactor trip are compared with the actual plant data to justify RETRAN code modelling, The results of performance and safety analyses show that the newly established level setpoints not only improve the performance of pressurizer during transient including reactor trip but also meet the design bases of the pressurizer volume and pressure. pressure.

• Journal of Communications and Networks
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• 제12권2호
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• pp.174-180
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• 2010

Automatic Repeat reQuest (ARQ) is a very effective technique against transmission error at the medium access control (MAC) layer. An erroneous MAC protocol data unit can be typically retransmitted within a given limit. In order to improve the IP-level performance, which directly affects the user-perceived quality-of-service (QoS), we propose a new truncated ARQ strategy, called MAC service data unit-based ARQ (S-ARQ), where the finite number of opportunities for retransmissions are shared by multiple fragments out of an IP datagram. We describe how SARQ can be implemented in a practical system, and then propose another variant of S-ARQ employing a functionality called early detection of failure. Basically, we evaluate the performance of SARQ in two different manners. First, assuming i.i.d. error process, we analyze both the probability of the delivery failure and the average delay of IP datagram. Then, we assess the performance of S-ARQ via simulation over a 2-state Markov channel.

• 수산해양교육연구
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• 제27권5호
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• pp.1424-1435
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• 2015

The purpose of this study was to investigate the recognition about 'problem solving and invention' unit in technology and home-economics subject. The study was carried out through questionnaire survey method. The sample of this study was 397 8th middle school students. The data was collected using questionnaires and analyzed by the descriptive statistics, t-test and one-way ANOVA. The result of this study was as follows: First, middle school students presented positive preferences toward 'problem solving and invention' unit. Second, middle school students recognized the necessity of this unit. Third, the level of difficulty for this unit of students was intermediate. Fifth, middle school students recognized that learning 'problem solving and invention' unit made them have more interest than before learning it.