• 한국IT서비스학회지
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• 제10권3호
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• pp.237-250
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• 2011

Recently, Wireless Sensor Networks (WSN) require energy performance and guaranteed delivery delay time, contrarily with previous MAC protocols that aim to high throughput mostly. In order to satisfy the new significant requirements, many MAC protocols of WSN employ and try to enhance the duty cycle mechanism which is energy efficient technique in MAC layer. This duty cycle mechanism is oriented by toggling the transceiver conditions composed of wakeup and sleep states. The synchronous MAC protocols perform the period synchronization process. Hence, these are energy efficient in periodic monitoring environment, but are inefficient in where an event is incurred rarely and infrequently. Otherwise, the performance of asynchronous MAC protocols are contrarily with synchronous protocols. In this paper, we design two models consisting Always-busy and Always-idle ti simplify the general network congestion conditions. Through these models, moreover, we analyze two types MAC protocols in terms of energy efficiency and delay performance by analytical results. Additionally, we also evaluate two MAC protocols with two gongestion models that we designed. By the analytical and simulated results, we provide the general and efficient decision method in which protocols are more appropriate in a certain WSN environment.

• 대한간호학회지
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• 제21권2호
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• pp.129-149
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• 1991

Circadian rhythm is entrained in the 24-hour time interval by periodic factors in the environment, known as zeitgeber. But most rotating work schedules are outside the range of the entrainment of the pacemaker timing the human circadian sleep - wake cycle. It has been postulated that physiological and emotional disturbances occur in most human functions when the circadian rhythm is disturbed. So application of circadian principles to the design of shift schedules can aid in maintaining the temporal integrity of the circadian system and thereby minimize for the shift worker any detrimental consequences of circadian disruption. This study was a quasi-experimental study to test the effect of shift intervals for the clinical nurse on the circadian rhythm. Twenty nurses newly employed in general units of two hospitals were selected as an experimental group and twelve college nursing students as a control group. Both groups were selected according to an established criteria using a purposive sampling technique. Ten subjects were assigned to a weekly shift group and another ten to a biweekly shift group engaged in a semi -continuous shift schedule(sunday off) with a backward direction, that is, morning -evening - night shift. The control group worked a morning shift for 42 days. Oral temperature rhythm, waking tim, sleep - wake cycle, fatigue, and mental performance were measured during the experimental period. The data collection period was from April 30, 1990 to June 10, 1990. MANOVA, paired t-test, ANOVA, and Student Newman Keuls method were used for statistical analysis. The results are summarized as follows. 1. Phase delay in the acrophase of temperature rhythm was shown according to the backward rotating shift. A complete adaptation to work on the night shift was achieved between the sixth and ninth day of the night shift. 2. There was no difference in either waking time or sleep- wake cycle according to the duration of the working day for every shift group. Significant difference was found in the waking time and the sleep -wake cycle for subjects on the morning, evening, and night shift in both of the shift groups(weekly shift group : λ＝0.121, p＜0.01, λ＝0.112, p＜0.01, biweekly shift group : λ＝0.116, p＜0.01, λ＝0.084, p＜0.01). 3. There was no difference in fatigue between the first working day and the last working day for the control group and for the biweekly shift group. In the weekly shift group, physical fatigue was significantly different for the first day and the sixth day of the night shift(t＝-2.28, p＜0.05). Physical fatigue and total fatigue on the first day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝5.79, p＜0.01, F＝4.56, p＜0.05). There was a significant difference between the shift groups and the control group(p＜0.05), Physical fatigue, neurosensory fatigue and total fatigue on the last day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝12.65, p＜0.01, F＝7.77, p＜0.01, F＝9.68, p＜0.01). There was a significant difference between the shift groups and the control group(p＜0.05). 4. No difference in mental performance was seen between the first day and the last day of work in each case. An arithmatic test on the first day of the night shift revealed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝3.79, p＜0.05). There was a significant difference between the shift groups and the control group(p＜0.05) . The digital symbol substitution test and the arithmetic test on the last day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝3.68, p＜0.05, F＝5.55, p＜0.01), and both showed a significant difference between the shift groups and the control group(p＜0.05). Accordingly, this study showed that during night duty, the waking time, sleep- wake cycle, and fatigue increased and mental performance decreased compared with morning and evening duty. It was also found that the weekly shift group had a higher fatigue score on the sixth day of night duty as compared to the -first day, but the waking time, sleep- wake cycle, and mental performance revealed no difference for the duration of the night duty or between shift groups, and complete adaptation of temperature rhythm was achieved between the sixth and ninth day of night duty. It is possible to conclude from these results that for intermediate circadian type in a healthy young woman, a biweekly shift system is more compatible with the circadian timing system than weekly shift system.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.99-103
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• 2006

본 논문에서는 무선 센서망에서 에너지 효율적인 MAC 프로토콜의 효율적인 설계에 대해 살펴보고 그중 S(Sensor)MAC과 T(Time-out)-MAC에 대해 자세히 고찰한다. S-MAC은 listen/sleep의 주기를 사용한다. 이것은 데이터가 전송될 때 store-and-forward 기법이 필요한 센서 네트워크의 어플리케이션의 충돌을 줄일 수 있다. 그러나 이렇게 고정되어진 duration field를 가진 S-MAC과는 상이하게 T-MAC은 적응적인 duty cycle을 제공한다. 이는 수신되어질 메시지를 잠재적으로 기다려야 하는 idle 상태에서의 에너지 소비를 줄일 수 있다. 본 논문에서는 두 가지 MAC 프로토콜을 OMNeT++ 시뮬레이션 환경에서 실험하여 latency, throughput, 전력 소비의 측면에서 각각 비교함으로써 그 효율성을 증명하였다.

• 대한간호학회지
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• 제47권4호
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• pp.562-574
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• 2017

Purpose: This study attempts to explore the subjective experience of frailty among elderly individuals in Korea. Methods: From June to August in 2014, 11 elderly persons who had experienced frailty in a community were interviewed. For data analysis, the method suggested by Colaizzi was applied as a phenomenological method. Results: According to the analysis, the study participants' frailty process was structured in seven categories: (a) 'natural phenomenon with ageing,' (b) 'life force comes to an end,' (c) 'the light in my heart turns off,' (d) 'unavoidable situation,' (e) 'continuous and connected vicious cycle,' (f) 'the limit of recovery energy already passes,' and (g) 'life is supported by someone's help.' Conclusion: The frailty experience in the participants is a natural process of aging, which cause vicious cycle acting with each other among physical, psychological, and social health. It is said that the cycle of frailty was started from weight loss and insufficient sleep, and boostered by pain. The participants from repetition of the vicious cycle become exhausted and pass the threshold of their recovery energy at some points. If they meet with sudden accidents such as falling, traffic accident and so on, they become to live a dependent life supported by someone's help in a moment. To prevent frailty and worsening conditions in Korean elderly individuals, it is recommended to provide a interventional programs using this study's results.

• Tuberculosis and Respiratory Diseases
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• 제60권1호
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• pp.76-82
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• 2006

연구배경 : 수면설문조사가 환자의 수면과 관련된 문제점을 파악하고 수면다원검사의 시행을 필요로 하는 환자를 선별하는 검사로써 임상적 유용성이 있는지 여부를 알아보고자 하였다 방 법 : 가톨릭대학교 성바오로병원 수면장애 클리닉에 의뢰되어 수면다원검사와 수면설문조사를 시행한 환자 를 대상으로, 수면설문조사에 포함되어 있는 환자의 일반적 특성, 병력, 수면-각성주기 동안의 행동, 코골이, 수면과 관련된 호흡장애 및 주간 졸음증과 관계된 증상 등 각각의 항목과 수면다원검사의 각 지표를 비교 분석하였다. 결 과 : 전체 환자수는 1081명으로 남자 849명, 여자 232명이었고 나이는 $44.2{\pm}12.8$세였다. AHI<5인 군은 38 .9%, $5{\leq}AHI<20$는 27.9%, $20{\leq}AHI<40$는 13.2% 그리고$AHI{\geq}40$는 20.0%였다. 검사를 시행하게 된 주된 동기는 코골이(91.7%), 무호흡(74.5%), 주간 졸음증(8.0%), 불면증(4.3%), 이갈이(1.1%), 집중력 장애(0.5%)였다. 수면 중 깨는 횟수는 평균 1.6회 였으며 그 이유는 소변을 보기 위함이 46.3%로 가장 많았다. Epworth Sleepiness Scale과 무호흡-저호흡지수(AHI)는 상관관계가 있었다(r=0.209, p<0.01). 수면설문 조사 항목 중 코골이, 주간 졸음증, 수면 후 각성 상태의 중증도에 따른 각 군간의 평균 AHI는 통계적으로 유의한 차이를 보였다. 결 론 : 수면설문조사에서 나타나는 ESS, 코골이, 주간 졸음증이나 수면 후 각성 상태 등 주관적 임상증상의 중증도는 수면다원검사 결과의 수면 무호흡의 중증도와 유의한 상관관계가 있음을 관찰할 수 있었다. 따라서 수면설문조사는 환자의 수면장애 특히 수면과 관련된 호흡장애의 정도를 예측하는데 유용하게 이용될 수 있을 것으로 생각한다.

• Journal of Communications and Networks
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• 제14권1호
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• pp.40-50
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• 2012

The Berkeley-medium access control (B-MAC) is a lightweight, configurable and asynchronous duty cycle medium access control (MAC) protocol in wireless sensor networks. This article presents an analytic modelling of single-hop B-MAC protocol under a Poisson traffic assumption.Our model considers important B-MAC parameters such as the sleep cycle, the two stage backoff mechanism, and the extended preamble. The service delay of an arriving packet and the energy consumption are calculated by an iterative method. The simulation results verify that the proposed analytic model can accurately estimate the performance of single-hop B-MAC with different operating environments.

• Tuberculosis and Respiratory Diseases
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• 제47권6호
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• pp.824-835
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• 1999

연구배경: 만성신부전 환자들은 수면과 관련된 호흡장애가 흔히 동반되는데 특히 수면 무호흡은 이들 환자의 심혈관계 기능부전을 더욱 악화시켜 장기 사망률에 영향을 미칠 것으로 생각된다. 혈액투석 유지요법은 만성신부전에 의한 대사장애를 교정하기 위하여 시행되는 가장 보편적인 내과적 치료법이지만, 이 방법이 수면 무호흡을 포함한 수면장애를 개선시킬 수 있는지 여부는 명확하지 않다. 저자들은 혈액투석 유지요법이 수면의 질과 수면과 관련된 호흡장애, 특히 수면 무호흡에 미치는 영향에 대해 관찰하고자 하였다. 방 법: 혈액투석 유지요법을 받고 있는 만성신부전 환자 47명을 대상으로 수면설문지검사를 시행하여 수면장애와 관련된 임상증상을 조사하였고, 이들 중 15명을 대상으로 혈액투석 전과 후에 수면다원검사, 혈중 신기능검사 및 전해질검사, 동맥혈가스분석을 시행하여 비교하였다. 결 과: 수면설문지검사를 시행한 47명중 40명(85.1%)이 수면-각성 주기의 장애와 관련된 임상증상을 호소하였으며. 55.3%가 코골음이 있다고 답변하였고, 27.7%의 환자는 수면 중 타인에 의해 무호흡이 관찰된 적이 있다고 답변하였다. 급속안구운동수면 시간이 혈액투석 전에 비하여 혈액투석 후에 증가하였다(p<0.05). 비급속안구운동수면 시간이 전체 수면시간에서 차지하는 백분율은 혈액투석 후에 감소하였고(p<0.05), 1단계 및 2단계 비급속안구운동수면이 전체 수면시간에서 차지히는 백분율은 혈액투석 후에 짧아지는 경향을 보였으나(p=0.051), 3단계 및 4단계 비급속안구운동수면은 혈액 투석 전후에 차이가 없었다. 수면 무호흡의 유형은 혈액투석 전과 후 모두에서 폐쇄성이 중추성에 비하여 우세하였으며, 혈액투석후의 무호흡지수 및 무호흡-저호흡지수는 혈액투석 전에 비하여 유의한 차이가 없었다. 혈액투석 후에 혈액뇨질소(BUN), 혈중 creatinine, potassium 및 phosphorus 농도는 유의하게 감소하였으나(p<0.05), 혈중 sodium 및 chloride 농도는 변화가 없었으며, 혈액투석 전과 후의 이들 검사 결과와 수면구조를 포함한 수면다원검사 각 지표와는 상호관련성이 없었다. 동맥혈가스분석에서 pH는 혈액투석 전에 비하여 혈액투석 후에 감소하였으나(p<0.05). $PaO_2$, $PaCO_2$ 및 $HCO_3^-$는 변화가 없었고, 혈액투석 전과후의 동맥혈가스분석 결과와 수면구조를 포함한 수면다원검사 각 지표와는 상호 관련성이 없었다. 결 론: 만성신부전은 수면장애를 유발할 수 있는 중요한 전신질환이다. 혈액투석 유지요법은 만성신부전 환자에서 시행되는 가장 보편적인 치료법이지만 수면구조 및 수면 무호흡을 효과적으로 개선시키지 못하였다. 따라서 만성신부전 환자를 치료함에 있어서는 혈액투석에 의한 대사장애의 적절한 교정과 더불어 수면장애의 치료에 대한 적극적인 고려가 필요하다고 생각한다.

• 기본간호학회지
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• 제1권1호
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• pp.77-97
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• 1994

The circadian system represents a temporal order which is mediated by the mutual coupling of oscillators and by the synchronizing effects of zeitgebers. It is known that well-being of man depends partly on the maintenance of this order, and that repeated or long lasting disturbances to it such as shift work will Cause harmful effects. This study was a quasi-experimental study to test the effect of shift directions for the clinical nurses on the circadian rhythm. Fourteen nurses working at the general units of Y hospital were selected according to the established criteria. Fourteen subjects were assigned to a weekly shift but the directions of shift work were phase delay first and then phase advance or vice versa. Oral temperature, total sleeping time, frequency of sleep-wake cycle, fatigue, mental performance, and physical symptom were measured during these days except holidays. The data collection period was from April 26, 1993 to July 3, 1993. MANOVA and Wilcoxon signed rank test were used for statistical analysis. The results are summarized as follows. 1. Having worked on evening and night shifts in either phase delay or phase advance schedules, temperature rhythms of shift workers were gradually adapted to the new sleep-wake cycles. A complete adaptation to work on the night shift was achieved the sixth day of the night shift in the phase delay schedule compared to the partial adaptation to the work on the night shift in the phase advance schedule. Accordingly, by putting evening shift between day and night shifts, it will be possible for circadian rhythm to adapt easily to the night shift. 2. There were differences in the total sleeping time, frequency of steep-wake cycle, fatigue, and physical symptom except for mental performance between night shift and day, evening shift. This indicates further that shift workers working on the night shift have a hard time adapting to the shift work compared to the other shifts. 3. Evaluating all the acrophases of temperature rhythm either in phase delay or phase ad-vance schedules, it was shown that night to evening shift in the phase ad-vance schedule revealed the smallest phase move. Also phase advance schedule showed poorer adaptation to shift work than phase delay schedule in connection with total sleeping time, frequency of sleep-wake cycle, fatigue, mental performance, and physical symptom. It is suggested, taken together, these findings reflect that phase delay schedule facilitated the degree of adjustment to the shift work compared to the phase advance schedule.

• 보건교육건강증진학회지
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• 제27권1호
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• pp.21-34
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• 2010

Objectives: The objective of this study was to investigate risk factors for falls in the elderly by life-cycle. Methods: This study used the data on 435 male and female elderly generated from a survey taken at 21 Welfare Centers for the Elderly in Seoul. The incidence of demographic characteristics, physical changes brought about with ageing, health-related behavior, chronic diseases, and environmental characteristics on falls in the elderly was analyzed. Hierarchical Logistic Regression analysis was also conducted to investigate the incidence by life-cycle (early-mid-late stage) and the results were used for predicting falls. Results: The incidence of risk factors on falls varied across life-cycle. Among the elderly in the early (ages from 65 through 74), marital status, the existence of a companion, the quality of sleep, the chronic diseases, and the condition of the bathroom floor were found to be related to falls. Among those in the mid-stage (ages from 75 through 84), sex, marital status, the existence of a companion, hearing capacity, sense of balancing, chronic diseases, the exclusive use of rooms, and the side bar with bath tub were found to affect falls. Finally, for the elderly in their late stage (85 years of age and older), drinking and vision were found to be related to falls. Conclusion: The incidence of risk factors on falls was found to vary according the stage in the elderly. A key implication of this finding is that falls prevention programs and interventions must be catered to specific age sub-groups.

• 한국경영과학회지
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• 제34권3호
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• pp.137-153
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• 2009

In this paper, we present an analytic model that evaluates the performance of B-MAC protocol under contention transmission conditions of two senders in a single-hop wireless sensor network. Our model considers the impact of several important factors such as sleep cycle, the backoff mechanism and incoming traffic loads. After obtaining the service delay distribution of a sending node and expected delay of a receiving node, an iterative algorithm is presented for calculating the performance measures such as expected energy consumption usage per packet and latency. Simulation results show that the proposed analytic model can accurately estimate the performance measures under different traffic conditions.