• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.618-628
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• 2016

Active power filter (APF) has been proved as a flexible solution for compensating the harmonic distortion caused by nonlinear loads in power distribution power systems. Digital repetitive control can achieve zero steady-state error tracking of any periodic signal while the sampling points within one repetitive cycle must be a known integer. However, the compensation performance of the APF would be degradation when the grid frequency varies. In this paper, an improved repetitive control scheme with frequency adaptive capability is presented to track any periodic signal with variable grid frequency, where the variable delay items caused by time-varying grid frequency are approximated with Pade approximants. Additionally, the stability criterion of proposed repetitive control scheme is given. A three-phase shunt APF experimental platform with proposed repetitive control scheme is built in our laboratory. Simulation and experimental results demonstrate the effectiveness of the proposed repetitive control scheme.

• 한국의류학회지
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• 제17권3호
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• pp.475-490
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• 1993

Even though modem ideal body type is rather tall and slim one, most of women don't coincide with it exactly. The objective of this research was to study the optical illusion effect of clothing design line so that average Korean women can approach the modern ideal body type. This research also tried to show the more scientific method to make stimulus by computer simulation and to present quantitative data. For the experiment, 9 design variables were selected from design principal book as follows : waistline level, skirt length, horizontal line emphasis, vertical line emphasis. princess line, vertical stripe, horizontal stripe, diagonal stripe. Each variable was divided into 4 levels so that 36 experimental designs were made. Visual stimuli which same model was wearing each design were recreated by the CAD system. These were given to evaluating panels through slide projecter. Then panels compared experimental design with basic design by 'tall effect' and 'slim effect', All the data from the experiment were analyszed by ANOVA and DUNCAN test for multiple comparison to study significance, direction(positive or negative), degree, proper extent of optical illusion effect. The result showed that some designs have optical illusion effect to make better look. In addition, it proved that the stronger design variable does not mean the more optical illusion effect and there was proper extent which produce the best illusion effect in each design variable.

• 설비공학논문집
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• 제11권2호
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• pp.193-204
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• 1999

Performance of a variable-speed, roller-type vane compressor was evaluated at low evaporating temperature. First, an experimental investigation was conducted to examine the performance variation as functions of both outdoor temperature and rotating speed. For this purpose, a typical heat pump was implemented as a test apparatus to measure mass flow rate and power input. Secondly, computational investigations corresponding to the heat pump test conditions were performed to predict compressor performance using ORNL Map-Based compressor model. Results obtained from the heat-pump experiments showed that both mass flow rate and power consumption were sensitively dependent on both evaporating temperature and compressor speed as was predicted from the computational results. From the comparisons of both experimental and computational results, it was well recognized that the ORNL model was subjected to larger error in the accuracy of prediction as outdoor temperature decreased. When the outdoor temperature was above $-5^{\cire}C$, errors of predicted values corresponding to both mass flow rate and power consumption were estimated as $\pm$10% and $\pm$ 15%, respectively. Finally, it is suggested that the ORNL model needs to be re-evaluated if compressor map data tested below $-5^{\cire}C$(in evaporating temperature) are available.

• 전력전자학회논문지
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• 제22권6호
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• pp.517-526
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• 2017

In this paper, we propose an LLC resonant converter that operates over a wide controllable output voltage ($50V_{DC}$ to $800V_{DC}$) and shows high efficiency characteristics under all load conditions and output voltages. Two 3.3kW prototypes are designed for an experimental comparison between the variable frequency control (control scheme 1) and the variable input voltage($V_{IN}$) control (control scheme 2) mechanisms. The experimental results show that the variable input control mechanism demonstrates high efficiency under all loads and output voltages.

• 대한간호학회지
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• 제12권2호
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• pp.1-26
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• 1982

The main purpose of this study was to test the effect of the structured information on the sleep amount of the patients undergoing open heart surgery. This study has specifically addressed to the Following two basic research questions: (1) Would the structed in formation influence in the reduction of sleep disturbance related to anxiety and Physical stress before and after the operation? and (2) that would be the effects of the structured information on the level of preoperative state anxiety, the hormonal change, and the degree of behavioral change in the patients undergoing an open heart surgery? A Quasi-experimental research was designed to answer these questions with one experimental group and one control group. Subjects in both groups were matched as closely as possible to avoid the effect of the differences inherent to the group characteristics, Baseline data were also. collected on both groups for 7 days prior to the experiment and found that subjects in both groups had comparable sleep patterns, trait anxiety, hormonal levels and behavioral level. A structured information as an experimental input was given to the subjects in the experimental group only. Data were collected and compared between the experimental group and the control group on the sleep amount of the consecutive pre and post operative days, on preoperative state anxiety level, and on hormonal and behavioral changes. To test the effectiveness of the structured information, two main hypotheses and three sub-hypotheses were formulated as follows; Main hypothesis 1: Experimental group which received structured information will have more sleep amount than control group without structured information in the night before the open heart surgery. Main hypothesis 2: Experimental group with structured information will have more sleep, amount than control group without structured information during the week following the open heart surgery Sub-hypothesis 1: Experimental group with structured information will be lower in the level of State anxiety than control group without structured information in the night before the open heart surgery. Sub-hypothesis 2 : Experimental group with structured information will have lower hormonal level than control group without stuctured information on the 5th day after the open heart surgery Sub-hypothesis 3: Experimental group with structured information will be lower in the behavioral change level than control group without structured information during the week after the open heart surgery. The research was conducted in a national university hospital in Seoul, Korea. The 53 Subjects who participated in the study were systematically divided into experimental group and control group which was decided by random sampling method. Among 53 subjects, 26 were placed in the experimental group and 27 in the control group. Instruments; (1) Structed information: Structured information as an independent variable was constructed by the researcher on the basis of Roy's adaptation model consisting of physiologic needs, self-concept, role function and interdependence needs as related to the sleep and of operational procedures. (2) Sleep amount measure: Sleep amount as main dependent variable was measured by trained nurses through observation on the basis of the established criteria, such as closed or open eyes, regular or irregular respiration, body movement, posture, responses to the light and question, facial expressions and self report after sleep. (3) State anxiety measure: State Anxiety as a sub-dependent variable was measured by Spi-elberger's STAI Anxiety scale, (4) Hormornal change measure: Hormone as a sub-dependent variable was measured by the cortisol level in plasma. (5) Behavior change measure: Behavior as a sub-dependent variable was measured by the Behavior and Mood Rating Scale by Wyatt. The data were collected over a period of four months, from June to October 1981, after the pretest period of two months. For the analysis of the data and test for the hypotheses, the t-test with mean differences and analysis of covariance was used. The result of the test for instruments show as follows: (1) STAI measurement for trait and state anxiety as analyzed by Cronbachs alpha coefficient analysis for item analysis and reliability showed the reliability level at r= .90 r= .91 respectively. (2) Behavior and Mood Rating Scale measurement was analyzed by means of Principal Component Analysis technique. Seven factors retained were anger, anxiety, hyperactivity, depression, bizarre behavior, suspicious behavior and emotional withdrawal. Cumulative percentage of each factor was 71.3%. The result of the test for hypotheses show as follows; (1) Main hypothesis, was not supported. The experimental group has 282 minutes of sleep as compared to the 255 minutes of sleep by the control group. Thus the sleep amount was higher in experimental group than in control group, however, the difference was not statistically significant at .05 level. (2) Main hypothesis 2 was not supported. The mean sleep amount of the experimental group and control group were 297 minutes and 278 minutes respectively Therefore, the experimental group had more sleep amount as compared to the control group, however, the difference was not statistically significant at .05 level. Thus, the main hypothesis 2 was not supported. (3) Sub-hypothesis 1 was not supported. The mean state anxiety of the experimental group and control group were 42.3, 43.9 in scores. Thus, the experimental group had slightly lower state anxiety level than control group, howe-ver, the difference was not statistically significant at .05 level. (4) Sub-hypothesis 2 was not supported. . The mean hormonal level of the experimental group and control group were 338 ㎍ and 440 ㎍ respectively. Thus, the experimental group showed decreased hormonal level than the control group, however, the difference was not statistically significant at .05 level. (5) Sub-hypothesis 3 was supported. The mean behavioral level of the experimental group and control group were 29.60 and 32.00 respectively in score. Thus, the experimental group showed lower behavioral change level than the control group. The difference was statistically significant at .05 level. In summary, the structured information did not influence the sleep amount, state anxiety or hormonal level of the subjects undergoing an open heart surgery at a statistically significant level, however, it showed a definite trends in their relationships, not least to mention its significant effect shown on behavioral change level. It can further be speculated that a great degree of individual differences in the variables such as sleep amount, state anxiety and fluctuation in hormonal level may partly be responsible for the statistical insensitivity to the experimentation.

• 전기학회논문지
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• 제58권1호
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• pp.137-146
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• 2009

We present a micromechanical digital-to-analog (DA) variable capacitor using a parallel digital actuator array, capable of accomplishing high-Q tuning. The present DA variable capacitor uses a parallel interconnection of digital actuators, thus achieving a low resistive structure. Based on the criteria for capacitance range ($0.348{\sim}1.932$ pF) and the actuation voltage (25 V), the present parallel DA variable capacitor is estimated to have a quality factor 2.0 times higher than the previous serial-parallel DA variable capacitor. In the experimental study, the parallel DA variable capacitor changes the total capacitance from 2.268 to 3.973 pF (0.5 GHz), 2.384 to 4.197 pF (1.0 GHz), and 2.773 to 4.826 pF (2.5 GHz), thus achieving tuning ratios of 75.2%, 76.1%, and 74.0%, respectively. The capacitance precisions are measured to be $6.16{\pm}4.24$ fF (0.5 GHz), $7.42{\pm}5.48$ fF (1.0 GHz), and $9.56{\pm}5.63$ fF (2.5 GHz). The parallel DA variable capacitor shows the total resistance of $2.97{\pm}0.29\;{\Omega}$ (0.5 GHz), $3.01{\pm}0.42\;{\Omega}$ (1.0 GHz), and $4.32{\pm}0.66\;{\Omega}$ (2.5 GHz), resulting in high quality factors which are measured to be $33.7{\pm}7.8$ (0.5 GHz), $18.5{\pm}4.9$ (1.0 GHz), and $4.3{\pm}1.4$ (2.5 GHz) for large capacitance values ($2.268{\sim}4.826$ pF). We experimentally verify the high-Q tuning capability of the present parallel DA variable capacitor, while achieving high-precision capacitance adjustments.

• 실천공학교육논문지
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• 제6권1호
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• pp.1-7
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• 2014

이 연구는 귀납법적 확증(confirmation)을 위해서 실행하는 실험이 확률론적 추론임을 밝히고 이의 단점을 보완하기 위해서 적용된 확률적 확인론에 따라서 수행하는 실험에서 통제하는 절차와 방법을 다루었다. 이 통제란 알려진 조건과 상황들을 인위적으로 조작하되 가설에서 명시된 특정조건(즉 독립변수) 이외의 조건(기타 변수)이 작용하여 현상이 발생(종속변수)될 가능성을 막는 것이다. 특정조건에 의하여 현상이 발생할 가능성을 극대화 시키고 기타 조건에 의하여 현상이 발생할 가능성을 최소화시키는 것이다. 그렇게 함으로써 특정 선행사건(독립변수)과 후행사건(종속변수) 사이의 진정한 인과관계성(the causal relationship)을 객관적으로 정확하게 추론하도록 보장하는 방법이 통제인 것이다. 이 연구에서는 변수통제에 대해 좀 더 구체적으로 다루기 위해 대표적인 헬스기구인 Elliptical Trainer (ET)와 Tread Mill (TM)를 이용한 실험에서 변수통제를 가하여 운동속도(독립변수)에 따른 에너지 소비량 변화(종속변수)와 운동속도(독립변수)에 따른 호흡교환율(RER)과 심장 박동율(HR)의 변화(종속변수)를 얻었다. 마지막으로 이 통제를 통해 얻어진 실험결과들을 그래프로 그려 그 결과에 따라 연구의 결론이 다루어졌다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.353-358
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• 2002

The purpose of this paper was to estimate the cumulative damage of pavement concrete by split tension fatigue test. The split tension fatigue test of variable amplitude loading were performed in two and three stages. The results of the fatigue test by variable amplitude loading showed that the sums of damage were greater than 1 in the increasing sequence loading tests, and less than 1 in the decreasing sequence loading tests. The remaining life estimated by equivalent damage theory was almost similar to that of experimental results.

• KSBB Journal
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• 제15권3호
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• pp.280-284
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• 2000

The simple imcroprocessor device was provided for the control of dissolved oxygen(DO) level. The DO analog signal output from fementer was used as a measurement variable and the agitation speed of fermenter was used as a manipulatio variable. Agitation speed was manipulated to maintain DO level above 10% of saturation condition during cell growth period with microprocessor. Since the experimental resultsshowed that the DO level was maintained above 10% and agitation speed was inverse proportional to DO level ithis simple control device can be used for the DO control of fermenter.

• Journal of the Korean Data and Information Science Society
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• 제21권5호
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• pp.959-965
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• 2010

For multiclassification, it is often the case that some variables are not important while some variables are more important than others. We propose a novel algorithm for selecting such relevant variables for multiclassification. This algorithm is base on multiclass least squares support vector machine (LS-SVM), which uses results of multiclass LS-SVM using one-vs-all method. Experimental results are then presented which indicate the performance of the proposed method.