• 한국안전학회지
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• 제35권5호
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• pp.128-136
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• 2020

In the present experimental study, the effect of water-based iron(III) oxide nanofluid on the MFB(Minimum Film Boiling) point during quenching was investigated. As the highly heated test specimen, the cylindrical stainless steel rod was used, and as the test fluids, the water-based iron(III) oxide nanofluids of 0.001 and 0.01 vol% concentrations were prepared with the pure water. To examine the effect of location in the test specimen, the thermocouples were installed at the bottom and middle of wall, and center in the test specimen. Through a series of experiments, the experimental data about the influences of nanofluid concentrations, the number of repeated experiments, and locations in the test specimen on the reaching time to MFB point, MFBT(Minimum Film Boiling Temperature), and MHF(Minimum Heat Flux) were obtained. As a result, with increasing the concentration of nanofluid and the number of repeated experiments, the reaching time to MFB point was reduced, but the MFBT and MHF were increased. In addition, it was found that the effect of water-based iron(III) oxide nanofluid on the MFB point at the bottom of wall in the test specimen was observed to be greater than that at the middle of wall and center. In the present experimental ranges, as compared with the pure water, the water-based iron(III) oxide nanofluid showed that the maximum reduction of reaching time to MFB point was about 53.6%, and the maximum enhancements of MFBT and MHF were about 31.1% and 73.4%, respectively.

• 한국인터넷방송통신학회논문지
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• 제21권5호
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• pp.27-32
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• 2021

본 논문은 16-QAM 신호 전송시 시분산 채널에서 발생되는 부호간 간섭을 경감시키기 위하여 사용되는 FC-MMA 적응 등화 알고리즘에서 고정 스텝 크기에 따른 등화 성능을 평가하였다. FC-MMA는 기존 MMA의 통신 채널의 시변 특성 및 순단과 같은 비정상적인 상황에서 신속하게 새로운 환경에 적응토록 빠른 수렴 속도를 갖는 것이 특성이지만, 수렴 속도는 고정 스텝 크기에 의하여 결정된다. 논문에서는 고정 스텝 크기값에 따른 등화 성능을 평가하였으며, 관련된 성능 지수로는 수렴 특성을 나타내는 잔류 isi와 최대 찌그러짐, MSE 및 잡음 강인성을 나타내는 SER과 군지연 보상 능력등이 사용되었다. 컴퓨터 시뮬레이션 결과 적응 스텝 크기가 클수록 정상 상태에 도달하는 수렴 속도는 개선되지만, 정상 상태 이후의 잔여량에서는 스텝 크기가 적을수록 우월해짐을 알 수 있었다. 본 연구 결과 FC-MMA 알고리즘은 초기에는 스텝 크기를 크게 설정하고, 정상 상태에 도달하면 이를 적게 조정하여 등화 잔여량을 최소화시킬 수 있을 것으로 기대된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.91-94
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• 1998

ATM technology is reaching a certain level of maturity that allow for its deployment in local as well as in wide area networks. Concurrently, audiovisual applications are foreseen as one of the major users of such broadband networks. We present in this paper requriement of real-time multimedia service on B-ISDN networks and simulating the transport of MPEG-2 encoded multimedia data over ATM networks using CBR, VBR, ABR of ATM Traffic Service. We compare each delay time considering network performance and propose need for real-time multimedia service.

• 대한물리의학회지
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• 제12권2호
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• pp.103-111
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• 2017

PURPOSE: This study was aimed to investigate the effects of pelvic movements-based training on trunk stability and balance during sitting in children with spastic cerebral palsy. METHODS: Ten children with spastic cerebral palsy were matched to an intervention (n=5) or control group (n=5). The intervention consisted of two weeks of pelvic movements-based training, five times a week. All participants were evaluated before, during, and after pelvic movements-based training using a trunk impairment scale (TIS) for trunk stability and a modified functional reaching test for balance during sitting. The collected data were analyzed using Repeated Measures ANOVA and the Mann-Whitney U test. RESULTS: The results of this study were as follows: 1) Significant increases in the TIS score (only dynamic balance) and forward reaching were observed in the experimental group, compared with the control group, after training (P<.05). 2) There were statistically significant time-factor increases within and between the subject' effects, in the TIS score (dynamic balance and total), dominant side, non-dominant side, and forward reaching (P<.05). CONCLUSION: In conclusion, this study showed that for children with spastic cerebral palsy, pelvic movements-based training improves trunk stability and balance during sitting. Further studies will be required to determine the long-term effects of pelvic movements-based training.

• 대한물리의학회지
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• 제12권1호
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• pp.51-59
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• 2017

PURPOSE: This study compared cognitive task-directed functional motor control ability for reaching and kicking movements in younger and older adults. METHODS: Subjects were divided into two groups of younger and older adults, with 13 subjects in each group. Subjects were required to perform a dual task combining a functional movement and cognitive component. The task consisted of reaching and kicking movements. Participants performed indicated movements when a target appeared on a monitor. The target randomly appeared on the monitor every 10 seconds. The total performance time (TPT), joint angular velocity (JAV), and muscle activation time were used to evaluate motor control ability. RESULTS: There were significant differences in all evaluation factors in a comparison of younger and older adults (p<.05). TPT was significantly shorter in older adults, and JAV and muscle activation time were significantly slower than that in the younger adult group. Although the results for older adults were within the normal range for functional assessment, their motor control abilities were significantly worse for cognitive tasks compared with those of younger adults. CONCLUSION: The results of this study indicated that a motor control assessment tool using a cognitive task would be helpful in assessment of motor control ability in healthy older adults.

• 가족자원경영과 정책
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• 제23권3호
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• pp.89-107
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• 2019

This study aimed to examine the impact of academic background on full-time employment and on other important issues concerning job security and care faced by single-parent youths. The study alse aimed to verify the effect of related support on full-time employment. The analysis targeted 262 single parents under 24 years of age who were raising their children, and the main results were as follows: First, the ratio of adulthood was high for those who were employed, and the academic achievement of full-time workers was also significantly high. However, the rate of discontinuities in school was also high among those who were employed, especially those seeking full-time employment, whose desire to stay in school was higher than that of other difficulties of single, teenage parents. Second, the vocational education experience of single, teenage parents was 32 percent overall, and the rate of those seeking full-time employment was also relatively high, reaching 44 percent. However, the results of this study did not verify the direct effect of vocational education experience on full-time employment nor the interaction effect of the academic background. Therefore, a thorough review of the effectiveness of a vocational education program for young, single parents wishing to gain employment is necessary. Third, the overall rate of those who received a public nanny service was 31 percent, while the rate of full-time workers who experienced this service was significantly higher reaching 59 percent. In the research model verification, single parents who received a public nanny service were 3.8 times more likely to get a full-time job than those who did not, and receiving a public nanny service showed a regulatory effect between academic studies and full-time employment. The higher the academic level of the parents, the higher their possibility of full-time employment.

• 대한의생명과학회지
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• 제19권3호
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• pp.254-260
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• 2013

The purpose of this study was to survey the effects of Karvonen exercise prescription in coronary artery disease patients reaching age-predicted maximal heart rates with the exercise stress test on hemodynamic responses and cardiorespiratory fitness. The subject group was comprised of acute coronary syndrome (ACS) patients, who were divided into the maximal heart rate (MHR) group that included those who completed the test with their heart rates reaching the number of 220-age and the maximal dyspnea (MD) group that included those who could not continue the test due to respiratory difficulty and were asked to stop the test. Both groups had the exercise stress test before and after the experiment. In the exercise stress test before the experiment, the exercise prescription intensity of Karvonen was set at the target heart rates of 50~85% with a six-week exercise monitoring arrangement. As a result, there were no interactive effects in rest heart rate (RHR) according to time and group, but interactive effects were observed in maximal heart rate (MHR) (P=0.000). Both rest systolic blood pressure (RSBP) and rest diastolic blood pressure (RDBP) had no interactive effects according to time and group. Maximal systolic blood pressure (MSBP) showed significant interactive effects according to time and group (P=0.017). Maximal diastolic blood pressure (MDBP) showed no interactive effects according to time and group, while maximal rate pressure product (MRPP) showed significant interactive effects according to time and group (P=0.003). Maximal time (MT) had no interactive effects according to time and group. $VO_{2max}$ and maximal metabolic equivalent (MMET) showed significant interactive effects according to time and group (P=0.000, P=0.002, respectively), whereas maximal respiratory exchange ratio (MRER) and maximal rating of perceived exertion (MRPE) showed no interactive effects according to time and group. The exercise test that was discontinued as the subjects reached the predicted maximal heart rates considering age did not reach the maximal exercise intensity and accordingly showed low exercise effects when applied to Karvonen exercise prescription intensity. That is, the test should keep going by monitoring cardiac events, MRER and MRPE until the heart rates exceed the predicted MHR by up to 10~12 even after the subject reaches the predicted MHR considering age in the exercise stress test.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.458-463
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• 1997

In this paper, we propose a variable structure control approach for the system with matched and unmatched uncertainty. By using time-varying sliding mode, the reaching mode is removed, and the design methodology represents a realistic design approach with quadratic criterion for systems incorporating both matched and unmatched uncertainties. The criterion contains states and linear part of input for all time. The practical application of the control strategy is presented in the design of a stability augmentation system for an aircraft is presented.

• 전기학회논문지
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• 제59권10호
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• pp.1908-1913
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• 2010

In this paper, a robust variable structure tracking controller is designed for the mixed tracking control of highly nonlinear rigid robot manipulators for the first time. The mixed control problem under consideration is extended from the basic tracking problem, with the different initial condition of both the planned trajectory and link of robots. This control problem in robotics is not addressed to until now. The tracking accuracy to the sliding trajectory after reaching is analyzed. The stability of the closed loop system is investigated in detail in Theorem 2. The results of Theorem 2 provide the stable condition for control gains. Combing the results of Theorem 1 and Theorem 2 gives rise to possibility of designing the improved variable structure tracking controller to guarantee the tracking error from the determined sliding trajectory within the prescribed accuracy after reaching. The usefulness of the algorithm has been demonstrated through simulation studies on the mixed tracking control of a two.link robot under parameter uncertainties and payload variations.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권8호
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• pp.471-481
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• 2003

The acts of biological immune system are similar to the navigation for autonomous mobile robots under dynamically changing environments. In recent years, many researchers have studied navigation algorithms using artificial immune networks. Conventional artificial immune algorithms consist of an obstacle-avoidance behavior and a goal-reaching behavior. To select a proper action, the navigation algorithm should combine the obstacle-avoidance behavior with the goal-reaching behavior. In this paper, the neural network is employed to combine the behaviors. The neural network is trained with the surrounding information. the outputs of the neural network are proper combinational weights of the behaviors in real-time. Also, a velocity control algorithm is constructed with the artificial immune network. Through a simulation study and experimental results for a autonomous mobile robot, we have shown the validity of the proposed navigation algorithm.