• Journal of Communications and Networks
• /
• 제13권5호
• /
• pp.463-471
• /
• 2011

Cooperative communications using relays in wireless networks have similar effects of multiple-input and multiple-output without the need of multiple antennas at each node. To implement cooperation into a system, efficient protocols are desired. In IEEE 802.11 families such as a/b/g, mobile stations can automatically adjust transmission rates according to channel conditions. However throughput performance degradation is observed by low-rate stations in multi-rate circumstances resulting in so-called performance anomaly. In this paper, we propose active relay-based cooperative medium access control (AR-CMAC) protocol, in which active relays desiring to transmit their own data for cooperation participate in relaying, and it is designed to increase throughput as a solution to performance anomaly. We have analyzed the performance of the simplified AR-CMAC using an embedded Markov chain model to demonstrate the gain of AR-CMAC and to verify it with our simulations. Simulations in an infrastructure network with an IEEE 802.11b/g access point show noticeable improvement than the legacy schemes.

• International Journal of Reliability and Applications
• /
• 제16권1호
• /
• pp.35-53
• /
• 2015

This investigation deals with reliability and sensitivity analysis of a repairable embedded system with standby wherein repairman takes multiple vacations. The hardware system consists of 'M' operating and 'S' standby components. The repairman can leave for multiple vacations of random length during its idle time. Whenever any operating unit fails, it is immediately replaced by a standby unit if available. Moreover, governing equations of an embedded system are constructed using appropriate birth-death rates. The vacation and repair time of repairman are exponentially distributed. The matrix method is used to find the steady-state probabilities of the number of failed components in the embedded system as well as other performance measures. Reliability indexes are presented. Further, numerical experiments are carried out for various system characteristics to examine the effects of different parameter. Using a special class of neuro-fuzzy systems i.e. Adaptive Network-based Fuzzy Interference Systems (ANFIS), we also approximate various performance measures. Finally, the conclusions and future research directions are provided.

• 한국컴퓨터정보학회:학술대회논문집
• /
• 한국컴퓨터정보학회 2020년도 제62차 하계학술대회논문집 28권2호
• /
• pp.139-142
• /
• 2020

NB-IoT(Narrow Band Internet of Things) is an emerging LPWAN(Low Power Wide Area Network) radio technology. NB-IoT has many advantages like low power, low cost, and high coverage. However low bandwidth and low sampling rates also lead to poor positioning accuracy. This paper proposed a solution to optimize positioning accuracy under the OTDOA(Observed Time Difference of Arrival) approach by utilizing MLR(Multiple Linear Regression) models. Through the MLR model to predict the influence degree of weather(temperature, humidity, light intensity and air pressure) on the arrival time of signal transmission to improve the measurement accuracy. The improvement of measurement accuracy can greatly improve IoT applications based on NB-IoT.

• 여성건강간호학회지
• /
• 제8권3호
• /
• pp.389-401
• /
• 2002

This study aims to find factors that affect variations in cesarean section frequency rates among OBGY clinics in Metropolitan areas. The factors include patient, medical supplier characteristics and economic factors. This study is a cross-sectional analysis using health insurance delivery claims from July to December 2000 and files of the NHIC(national health insurance corporation). Multiple regression was used to analyze the dependent variable of cesarean section frequency rate at each clinic. The results are as follows : Cesarean section frequency rate is increasing in proportion to the number of the following patients : repeated caesarean section, disproportion, obstructed labour, fetal distress, emergency caesarean section and self-employed patients. There are geographic variations as well. Cesarean section frequency rates are higher in Inchon and Gyonggi province than in Seoul. The higher number of total delivery the clinic has, the lower rate of cesarean section it has. Clinics with high frequency rates in 1999 showed higher rates the next year. Further research is required to develop evidence based delivery modes and change strategies for increasing normal delivery and activating midwife clinics.

• 한국농공학회지
• /
• 제30권1호
• /
• pp.73-80
• /
• 1988

This study was performed to obtain the basic data which can be applied to use of foaming mortars. The results obtained were Summarized as follows; 1.At the mixing ratio of 1:1, the highest bulk densities were showed by foaming mortars, respectively. But, it gradually was decreased in poorer mixing ratio and more addition of foaming agent. The decreasing rates of bulk densities were increased in richer mixing ratio and more addition of foaming agent. 2.The bulk densities were decreased up to 38.8-55.9% by mix-foaming type and 9.7-23.6% by pre-foamed type than cement mortar. 3.At the mixing ratio of 1:1, the lowest absorption rates were showed by foaming mortars, respectively. But, it gradually was increased in poorer mixing ratio and more addition of foaming agent. The increasing rates of absorption rates were increased in richer mixing ratio and more addition of foaming agent. 4.Absorption rates when immersed in 72hours were showed up tp 3.41-5.85 times by mix-foaming type and 1.05- 1.S5times by pre -foamed type than cement mortar, it was significantly higher at the early stage of immersed time than cement mortar. 5.The correlations between bulk density and absorption rate were highly singnificant, respectively. The multiple regression equations of bulk density and absorption rate were computed depending on a fuction of mixing ratio and addition of foaming agent. it was highly significant respectively.

• Journal of Advanced Marine Engineering and Technology
• /
• 제39권7호
• /
• pp.760-764
• /
• 2015

산업플랜트 현장에서 별도의 배선 없이 쉽고 빠르게 기계상태를 측정하기 위해서는 다중무선센서를 기계에 부착하고 측정과 전송이 동시에 가능한 시분할전송 방식이 필요하다. 그러나 아직까지 연속적인 신호를 동시에 100Hz이상 샘플로 시분할다중전송(TDMA;Time Division Multiple Access)하는 현장적용 연구가 알려지지 않고 있다. 따라서, 본 논문에서는 현장적용을 위해 100Hz이상의 샘플주기로 다수의 센서에서 동시에 취득할 수 있는 시분할다중전송 네트워크프로토콜을 구현하고 그 결과를 나타내고자 한다. 단일 클러스터 스타토폴로지를 대상으로 노드 개수와 거리에 따른 네트워크 가용성 확인을 위해 ns-2 시뮬레이터로 유사한 환경 조건으로 구동하여 결과를 분석하였다. 그 결과 4개의 센서노드로 동시에 연속적인 센서신호를 전송하는 비-시분할다중전송과 시분할다중전송프로토콜을 비교 분석하였다. 전송시간이 20초와 40초 일 경우는 수신율 차이가 작았지만 60초일 경우는 많은 차이를 나타냄을 관찰하였다.

• 한국임상수의학회지
• /
• 제19권2호
• /
• pp.153-158
• /
• 2002

Ovaries from total 192 slaughtered cows(154 Korean native cows and 38 Holstein cows) were collected during the slaughtering process in Kimhae, Changyoung and Yangsan abattoirs in Kyungnam province from January 2001 to January 2002. In order to investigate incidence of the ovarian cysts, anatomical, histological observations were performed and also TUNEL methods and PCNA antibody by immunogistochemical methods for diagnostic accuracy of cysts in a few ovaries were applied. Apoptotic positive cells by TUNEL method appeared not or a few in cystic walls but appeared more number in normal large follicular walls and the proliferative positive cells by PCNA antibody appeared numerous in normal large follicular walls but not or a few in cystic walls. The incident rates of ovarian cysts were 19.5% in Korean native cows and 18.4% in Holstein cows. The incident rates of ovarian cysts in Holstein cows were lower than that of Koran native cows. The incident rates of follicular cysts and luteal cysts in Korean native cows were 11.7% and 7.8% respectively. The incident rates of follicular cysts and luteal cysts in Holstein cows were 10.5% and 7.9%, respectively. Higher incidence proportions of ovarian cysts according to seasons in Korean native cows were ordered as spring (29.8%), autumn (21.4%) winter (14.3%) and summer (6.7%). Rates of cows with single cyst and multiple cysts were 63.3%(19 heads /30 heads) and 36.7%(11 heads/30 heads) in 30 cystic Korean native cows, respectively. Cystic cows with corpus luteums were 50.0%(15 heads) in 30 Korean native cows and 42.9%(3 heads) in 7 dairy cows, respectively. Among 15 cystic Korean native cows with corpus luteums, rates of cows with single corpus luteum were 66.7%(10 heads) and rates of multiple corpus luteum were 33.3%(5 heads ), respectively. The average diameter of cysts and corpus luteums in cystic ovaries were 21.0$\times$17.1 mm and 18.1$\times$13.8 mm in 30 Korean native cows and 20.6$\times$17.7 mm and 19.3 $\times$ 14.9 mm in 7 Holstein cows, respectively. So the average sizes of cysts in cystic ovaries were larger than those of corpus luteums.

• Asian Pacific Journal of Cancer Prevention
• /
• 제15권4호
• /
• pp.1597-1602
• /
• 2014

The purpose of this study was to investigate whether whole-liver radiotherapy plus a tumor-boost dose with concurrent chemotherapy is beneficial for colorectal cancer patients with massive and multiple liver metastases. From January 2007 to December 2012, 19 patients who exhibited massive (with a longest diameter > 5 cm) and invasive liver metastases and multiple metastases were treated with radiotherapy and concurrent chemotherapy. The total radiation dose was 53.4 Gy (range 38.8 Gy-66.3 Gy). All of the patients received a continuous intravenous dose of 5 fluorouracil (5-FU) 225 mg/m2 concurrently with radiation. The median survival time was 19 months. The 1- and 2- year overall survival rates were 78.3% and 14.3%, respectively. Of all of the patients who presented with abdominal pain, 100% experienced a decrease in pain. Decreases in the rates of ascites and jaundice were confirmed by ultrasound and bilirubin levels. No cases of Grade 4 or 5 acute or late toxicity were recorded. There were only two cases of Grade 3 toxicity (elevated bilirubin). These data provide evidence that whole-liver radiotherapy plus a tumor-boost dose with concurrent chemotherapy is beneficial for colorectal cancer patients with massive and multiple liver metastases.

• 한국통신학회논문지
• /
• 제19권9호
• /
• pp.1730-1738
• /
• 1994

PCS(personal communication service)용으로 시존에 제안된 B-CDMA(broadband code division multiple access)기법은 전송 속도의 변동이 적은 저속의 음성호만을 고려하였기 때문에 고속의 가변 데이타 서비스를 제공하기에는 적합하지 않다. 한편, 최근에 제안된 Hybrid TDMA/CDMA(hybrid intra-cell TDMA/inter-cell CDMA)기법은 내부적으로 TDMA기법이 사용되므로 고속데이타 서비스를 용이하게 지원할 수 있지만 TDMA 전송특성 때문에 가변데이타 트래픽을 처리할 때에는 많은 비효율성을 내포한다. 본 논문에서는 이러한 단점들을 보완하기 위한 방안으로 Hybrid TDMA/CDMA 기법에 PRMA(packet reservation multiple access)에서와 유사한 예약기법을 추가로 적용한 Reservation TDMA/DCMA 기법을 제안하였다. 또한, 제안된 Reservation TDMA/CDMA기법의 성능을 컴퓨터 시뮬레이션을 통해 기존의 B-CDMA기법 및 Hybrid TDMA/CDMA 기법과 비교 분석하였다. 시뮬레이션 결과, 제안된 Reservation TDMA/CDMA 기법은 다양한 전송속도와 트래픽을 용이하게 지원할 수 있을 뿐만 아니라 설정된 각 호 내부에서의 전송속도 변화를 보다 효율적으로 이용할 수 있다는 측면에서 기존의 B-CDMA나 Hybrid TDMA/CDMA 기법보다 우수함을 알 수 있었다.

• 대한간호학회지
• /
• 제5권1호
• /
• pp.87-92
• /
• 1975

This study was performed from July to December 1974 to investigate the rates of contamination of distilled water for injection and local anesthetics. 222 vials were sampled from 7 different places of St. Mary's Hospital The samples were cultured for isolation of microorganisms. The results were as follows; 1. Of 222 vials, 11 were Contaminated by 6 types: Staphylococcus epidermis, Bacillus subtilis, Mima polymorph a, Alcaligenes faecalis, Herellea vaginicala and pepto- streptococcus. 2. 5(9.1 %) of 55 vials from surgical wards, 2 (4.2 %) of 48 vials from surgical OPD, and 4 (12,l %) of 33 vials from pediatric wards were contaminated 3. Between rates of contamination of distilled water for injection and local anesthetics and the number of punctures, there was no significant relationship. (CR=1.42 P〉0.1) 4. There was no significant relationship (CR=1.02 P〉0.1) between the rates of contamination of vials and the duration of the first and the last punctures. 5. The ratios of contamination between 75% alcohol and 2% phenol used for disinfection of rubber lids of vials did not show significant difference.