• 한국통신학회논문지
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• 제37B권10호
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• pp.938-946
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• 2012

간섭정렬(Interference Alignment : IA)은 높은 신호 대 잡음 비(Signal to Noise Ratio : SNR)에서 다중 사용자 간섭 채널에서 도달 가능한 최대 자유도를 얻을 수 있는 데이터 전송 기법이다. 그러나 대부분의 간섭정렬에 대한 연구는 네트워크 내의 모든 채널의 정보를 송, 수신단에서 완벽하게 알아야 하는 비현실적인 가정에 기반을 둔다. 본 논문에서는 K 사용자 다중안테나 간섭채널에서 간섭정렬을 위한 채널 상태 정보 (Channel-State Information : CSI)의 궤환 량을 효율적으로 감소시킬 수 있는 CSI 궤환 구조를 제안한다. 기존의 IA기법은 K의 2차함수의 형태로 궤환 오버헤드가 증가하는 반면, 제안된 궤환 구조는 송, 수신 단 사이에서 계산된 IA 송신기의 순차적인 교환을 통하여 K에 선형적으로 증가하는 오버헤드를 갖는다. 또한, 주어진 궤환 구조 하에서 제한된 궤환 채널에 의한 잔여 간섭의 세기를 분석하였으며, 이 때 발생하는 잔여 간섭을 최소화 할 수 있는 IA 조건, 즉, 주어진 채널환경에 따라 각 수신단에서 잔여 간섭을 최소화할 수 있는 최적의 IA 쌍을 순차적으로 결정하는 알고리즘을 제안한다.

• The Journal of Korean Physical Therapy
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• 제30권2호
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• pp.47-53
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• 2018

Purpose: To find the effect of visual feedback of head angle with using a mobile posture-aware system on craniocervical angle and neck and shoulder muscles fatigue for preventing or decreasing the forward head posture. Methods: Twenty-four healthy young adults in Chungbuk to participate in this study. The subjects started to watch a movie clip for 10 minutes with visual feedback in $0^{\circ}$, $30^{\circ}$, and $60^{\circ}$ of head angles. During the task, surface electromyography (EMG) was used to collect data from the upper trapezius (UT), sternocleidomasetoid muscle (SCM), cervical erecter spinae (CES) during watching the smartphone. Craniocervical angles were measured using a sagittal-view photograph of the subject in a sitting posture. A one-way repeated analysis of variance with a significant level of 0.05 used for statistical analysis. Results: Craniocervical angle with $0^{\circ}$ visual feedback was significantly greater than $30^{\circ}$ and $60^{\circ}$. Craniocervical angle with $30^{\circ}$ visual feedback was significantly greater than $60^{\circ}$. In addition, MDF of UT muscles in $0^{\circ}$ and $30^{\circ}$ of visual feedback was significantly greater than $60^{\circ}$. Conclusion: We concluded that $0^{\circ}$ visual feedback of head angle with using a mobile posture-aware system would be beneficial to prevent or decrease forward head posture during watching a smartphone. We also could recommend using of $30^{\circ}$ visual feedback in case of caring UT muscle fatigue primarily.

• 스마트미디어저널
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• 제13권5호
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• pp.62-71
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• 2024

본 연구는 구급현장에서 사용되고 있는 바디캠을 활용하여 교육피드백 효과를 파악하고자 응급구조학과 4학년 32명을 대상으로 팀단위 심폐소생술 시뮬레이션을 진행하여 바디캠 피드백 전후에 대한 인식도, 교육피드백 효과, 만족도, 바디캠 기기활용 선호도 및 애로사항을 파악하였다. 자료분석은 SPSS 27.0 프로그램을 이용하여 기술통계, 빈도분석, paried t-test, Wilcoxon signed rank test를 수행하였다. 연구결과 바디캠 사용에 대한 인식은 3.73±0.62점에서 4.45±0.54점으로 긍정적인 인식변화를 보였으며, 3.98±0.51의 긍정적인 만족도는 나타냈다(p<.001). 또한 바디캠 피드백 후 자가점검 정확도와 수행능력점수에서 유의한 상승효과를 나타냈다(p<.001). 따라서 팀단위 시뮬레이션 소생술 훈련 시 강사의 직접적인 피드백 없이도 바디캠 영상시청을 통한 자가피드백을 수행하여 자가점검능력 향상 및 수행능력향상의 긍정적인 교육피드백 효과를 발휘할 수 있다.

• 한국통신학회논문지
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• 제39B권5호
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• pp.317-322
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• 2014

데이타 보안과 무결성은 유무선 통신 환경에서 데이터 전송 시에 중요한 요소이다. 대량의 데이터는 전송 전에, 통상 암호 연산 모드를 이용한 블록 암호 알고리즘에 의하여 암호화된다. ECB, CBC 등의 기존 연산 모드 외에 블록 암호 연산 모드로 RBF 모드가 제안된 바 있다. 본 논문에서는, 알려진 평문 공격 (known plaintext attack) 및 선택 평문 공격 (chosen plaintext attack)에 대한, RBF 모드의 안전성을 기존 모드들과 비교 분석한 내용을 소개한다. 분석 결과, 기존의 연산 모드들이 알려진/선택 평문 공격에 취약한데 반하여, RBF 모드는 이들 공격에 안전함을 알 수 있었다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제10권2호
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• pp.93-105
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• 2010

The following thesis provides an explanation for the definition of the MIL-HDBK-2155 : Failure Reporting, Analysis and Corrective Action System (FRACAS), which systemizes the collection and analysis of failure data and the feedback process of the results. It also presents a plan based on MIL-HDBK-2155 for the collection and analysis of operating specifications on weapon systems. The collection and analysis of failure data and the feedback process utilizing FRACAS contributes to identifying improvement requirements during equipment operation as well as finding and eliminating the root cause of the failures. The objective of applying FRACAS to weapon systems is to receive source data feedback for reliability enhancements and performance improvements during operation. This is done by recognizing weaknesses in the design or operation by identifying the type of failures that might occur, and by performing Failure Modes, Effects and Criticality Analysis(FMECA) and Failure Tree Analysis(FTA).

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.740-756
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• 2017

This paper proposes a feedback-linearization-based control algorithm for multirotor unmanned aerial vehicles (UAVs). The feedback linearization scheme is highly efficient for considering nonlinearity between the rotational and translational motion of multirotor UAVs. We also propose a dynamic equation that reflects the aerodynamic effects of the vehicles; the equation's parameters can be determined through curve fitting using actual flight data. We derive the feedback linearization controller from the proposed dynamic equation, and propose a Luenberger observer to attenuate measurement noises. The proposed algorithm is implemented using our in-house flight control computer, and we describe its implementation in detail. To investigate the performance of the proposed algorithm, we carry out two flight scenarios: the first scenario, an autonomous landing on a moving platform, is a test of maneuverability; the second, picking up and replacing an object, test the algorithm's accuracy. In these scenarios, the proposed algorithm precisely controls multirotor UAVs, and we confirm that it can be successfully applied to real flight environments.

• 한국생활과학회지
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• 제15권4호
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• pp.551-561
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• 2006

The purpose of the study is to examine the influence of children's familiarity with a task and teachers' feedback on their problem solving performances. It was assumed that children's' problem solving performance would be different depending on the children's familiarity with a task and the feedback from teachers. The study also examined whether children's' problem solving competence would be different depending on their gender and age. The experiment was conducted with two experimental tools. The subjects were 58 children who were 5 to 6-year-old, enrolled in kindergartens in Koyang city in Kyunggi province. The collected data were processed with SPSS 11.0 program to get the average and the standard deviations, and with one-way ANOVA and two-way ANOVA with repeated measures. The results of the experiment are as follows; First, children's' problem solving competence was different depending on their age. Older children showed higher performance than younger children, while there's no difference in children's performance depending on their gender. Second, the teachers' feedback didn't influence children's problem solving performance. Third, children showed higher performance when familiar tasks were provided, compared to when typical tasks were provided. Finally, this study found that children's task familiarity has an influence on their problem solving performance.

• 한국정보시스템학회지:정보시스템연구
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• 제25권3호
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• pp.117-146
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• 2016

Purpose The purpose of this paper is to examine factors and mechanism inducing end users' faithful appropriation of information security behavior through the information security system. This study is also trying to find out the role of Employees' adaptive activities like learning and feedback seeking behavior for the information security in organizations. Design/methodology/approach An empirical study was carried out with a sample of employees working in the financial service company. Employees(n = 268) completed a written questionnaire. Structural equation modeling was used to analyze the data. Findings Results indicated that employees' learning activities and feedback seeking behavior fully mediated the effect of major information security factors toward end users' faithfulness of appropriation of information security systems. In order to increase the level of employees information security behavior in accordance with security guideline, organizations should facilitate interactions that support the feedback seeking process between employees on information security awareness and behavior. Additionally, organizations may reinforce these behaviors by periodical training and adopting bounty hunter systems.

• 국제물리치료학회지
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• 제5권2호
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• pp.708-713
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• 2014

The aim of this research was to investigate how the effects of body supported treadmill training with visual feedback affect the gait factors of stroke patients. Thirty subjects (21 male, 9 female) with a diagnosis of stroke were taken to the hospital to participate in this study. The subjects received body supported treadmill training with visual feedback. The training was executed for 6 minutes, 3 times a day per week for 19 weeks after general exercise. The effects of the visual feedback in the body supported treadmill training were evaluated by measuring the average gait cycle and the average step length of the affected and unaffected. The collected data were statistically analyzed by using a paired t-test. The results of this study were a significant improvement of the average gait cycle and no statistically significant difference of the average step length. The gait cycle average had a statistically significant difference in gender, age, etiology, paretic side, and step length average. There was no statistically significant difference in infarction within etiology. Therefore, it was necessary to apply the easy and simple with the treadmill training in the rehabilitation of the stroke patients. This study will require a variety of outcome measures related to the effects of treadmill training with gait factors.

• 제어로봇시스템학회논문지
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• 제20권6호
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• pp.641-646
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• 2014

In this paper, we propose a controller for a ball and beam system which reduces the measurement error effect under AC and DC noise. The ball and beam system measures data through a sensor. If sensor noise is included in a controller via the feedback channel, the signal is distorted and the entire system cannot work normally. Therefore, some appropriate action for the measurement error effect is essential in the controller design. Our controller is equipped with a gain-scaling factor and a compensator to reduce the effect of measurement error in the feedback signal. Effectively, our proposed controller can reduce the AC and DC noise of a feedback sensor. We analyze the proposed controller by Laplace transform technique and illustrate the improved control performance via an experiment for a ball and beam system.