• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.675-679
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• 1999

A single-phase PWM current source rectifier with a neutral leg is presented and throughly analyzed in this paper. This novel topology is implemented by adding an extra leg a step-down single phase PWM space vector modulation method to reduce the dc output voltage harmonics is proposed. The PWM pattern generation need a digital system. As compared with a conventional single-phase PWM rectifier, over 20% improvement of the total harmonics distortion in the output voltage can be obtained. Different SVM techniques are analyzed for this PWM rectifier and simulation result are presented.

• 한국재료학회지
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• 제4권4호
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• pp.459-465
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• 1994

a-측으로 배향된 $YBa_2Cu_3O_{7-\delta}$ 고온 초전도 박막을 $LaAIO_{3}$(100)단결정 기판에 이중 타게트 off-axis rf마그네트론 스퍼터링법으로 증착하였다. 박막은 기판온도(Ts)$590^{\circ}C$와 $680^{\circ}C$사이에서 단일공정으로 증착하는 one-step방법과, $590^{\circ}C$의 저온에서 a-축으로 배향된 YBCO박막(두께-30nm)을 면저 만들어 틀로 작용시킨 후 그 틀위에 나머지 부분을 기판온도를 승온하면서 증착하는 방법인 two-step방법 등 두 가지 방법을 사용하여 증착시켰다. one-step방법에서는 $T_s$가 증가함에 따라 감소하였으며, ($00 \ell$)피크는 증가하였다. Two-step방법으로 증착한 박막은 증착속도가 감소함에 따라 (h00)피크가 우세하게 나타났다. 박막의 미세구조는 a-축, c- 축 배향성이 혼재하여 핀홀과 같은 결함들이 생성되었다. 모든 경우 $T_s$가 감소함에 따라 a-축 배향성은 우세하였으나 전기적 특성은 저하되었고, 긴 전이온도 폭을 가졌다.

• 가족자원경영과 정책
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• 제16권4호
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• pp.45-68
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• 2012

This study performed an analysis to determine if an individual can maintain the current consumption, in the case of a single retired elderly person's household using the accumulated assets. Assets are divided into three types, based on the behavioral economics life cycle hypothesis : financial assets, real assets excepting residential assets, and residential assets, and it is assumed that these assets were used on a step-by-step basis. Also, if the assets were sufficient, the maximum withdrawal amount was calculated. The results of the analysis are as follows. First, the monetary assets were sufficient to cover the cost of living for 2.7 years, 6.4 years by using the real assets of the non-occupied housing, and 26.3 years in the case of residential property. Second, in the case of preferentially using the financial assets, 4.4% of the sample households were able to cover the cost of living. Households that were not able to cover the cost of living used the next-stage assets, real assets of the non-occupied housing. Households that were not able to cover the cost of living by financial assets liquidated the real assets with the exception of residential assets and used these to cover the cost of living. A total of 4.8% of the households were able to maintain the current cost of living through the second stage and 25.5% supplemented their funds by using residential assets. That is to say, 35% of the sample households were able to maintain the current level of living by using their assets.

• Restorative Dentistry and Endodontics
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• 제30권6호
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• pp.435-441
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• 2005

본 연구는 친수성 용매가 함유되어 있는 3종의 단일병 접착제의 적용 시간을 증가시켰을 때, 건조 상아질에 대한 재습윤의 효과가 있는지를 미세인장 결합강도의 측정을 통해 알아보고자 시행하였다. 실험대상은 최근에 발거한 상하악의 대구치로, 교합면 1/3부위의 치질을 치아 장축에 수직으로 절단하여 상아질을 노출시킨 후, $32\%$인산 (Unietch, Bisco Inc., Schaumburg, IL, USA)으로 15초간 산부식 하고 수세하였다. 치아는 무작위로 S군 (Single Bond), O군 (One-Step), P군 (Prime & Bond NT)으로 분류하였고, 각 군은 다시 3군 (W: 상아질 표면의 남아있는 과잉의 물을 수분에 적신 거즈를 이용하여 제거한 후, 즉시 단일병 접착제를 적용하고 광중합, D : 30초간 건조 한 후 즉시 단일병 접착제를 적용하고 광중합, 30: 30초간 건조 한 후 단일병 접착제를 30초간 적용하고 광중합)으로 소 분류하였다. 접착제 도포 후, 복합레진을 축조하고 접착계면이 $1mm^2$가 되도록 절단하여 각 군당 20개의 표본을 사용하여 미세인장 결합강도를 측정하였다. 5군,0군의 30초 적용군 (S-30, O-30)은 건조군 (S-D, O-D)보다 높은 미세인장 결합강도를 보였으며, S-30군의 경우 S-D군보다 통계학적으로 유의성 있게 높았다 (P<0.05). 하지만, P군의 30초 적용군 (P-30)은 건조군 (P-D)에 비해 미세인장 결합강도가 통계학적으로 유의성 있게 감소하였다 (P<0.05).

• PNF and Movement
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• 제1권1호
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• pp.33-41
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• 2003

Objectives : The purpose of this study was to describe and compare the temporo-spatial gait characteristics of healthy young people with those of healthy elderly people. Methods: The data were collected by 40 volunteers. 20 subjects were between 20 and 31 years of age, and 20 subjects were between 65 and 84 years of age. Temporal and spatial parameters of gait were analysed for using the computerized GAITRite system. Results : The system integrates specific components of locomotion to provide a single, numerical representation of gait, the Functional Ambulation Performance score. Differences in gait characteristics between the two groups were examined using a correlated t-test(p<.05). Significant differences were observed between the groups for step length, step/extremity ratio and velocity. Young people demonstrated a significantly larger velocity, step length and step/extremity ratio than the elderly people. Conclusions: These results indicate that the GAITRite system can be useful in detecting footfall patterns and selected time and distance measurements of young and older persons. Additionaly, differences in walking velocity, step length and step/extremity ratio between old and young people may have influenced the gait characteristics measured.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.265-271
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• 1992

It is the purpose of this paper to present a dialogical designing method for control system using a rough grasp of the unknown process property. We deal with a single-input single-output feedback control system with a fuzzy controller. The process property is roughly estimated by the step response, and the fuzzy controller is interactively modified according to the operator's requests. The modifying rules mainly derived from computer simulation are useful for almost every process, such as an unstable process and a non-minimum phase process. The fuzzy controller is tuned by taking notice of four characteristics of the step response: (1) rising time, (2) overshoot, (3) amplitude and (4) period of vibration. The tuning position of the controller is fourfold: (1) antecedent gain factor GE or GCE, (2) consequent gain factor GDU, (3) arrangement of the antecedent fuzzy labels and (4) arrangement of the control rules. The rules give an instance to the respective items of the controller in an effective order. The modified fuzzy PI controller realizes a good response of a stable process. However, because the GDU tuning becomes difficult for the unstable process, it is necessary to evaluate the stability of the process from the initial step response. The fuzzy PI controller is applied to the process whose initial step response converges with GDU tuning. The fuzzy PI controller with modified sampling time is applied to the process whose step response converges under the repeated application of the GDU tuning. The fuzzy PD controller is applied to the process whose step response never converges by the GDU tuning.

• 대한기계학회논문집B
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• 제26권3호
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• pp.423-431
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• 2002

An experimental study is conducted to investigate the effect of two-frequency forcing on turbulent flow behind a backward-facing step at the Reynolds number of 27000 based on the step height. The forcing is provided from a thin slit located at the edge of the backward-facing step to increase mixing behind the backward-facing step and consequently to reduce the reattachment length. With single frequency forcing, the minimum reattachment length is obtained at the non-dimensional forcing frequency (F) of St$\_$h/ = 0.29. With two-frequency forcing, a subharmonic frequency (F/2) or biharmonic frequency (2F) is combined with the fundamental frequency (F), i.e. (F, F/2) or (F, 2F) forcing is applied. In the case of (F, F/2) forcing, the reattachment length is not much sensitive to the phase difference between F and F/2. However, the reattachment length significantly depends on the phase difference between F and 2F in the case of (F, 2F) forcing. At a certain range of the phase difference, the reattachment length becomes smaller than that of the single frequency forcing.

• Journal of Biosystems Engineering
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• 제16권3호
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• pp.248-262
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• 1991

Simulation model was developed to analyze drying process for tray type red pepper dryer and validated by experiments. This model could predict satisfactorily temperatures and moisture contents of red pepper and temperatures of drying air during drying. Optimize algorithm was developed to search control valiables (drying air temperature, air recycle ratio and air flow rate) of red pepper dryer based on a criterion of minimizing energy consumption under the constraint conditions that statisfied carotenoid retension of at least 210mg per 100g dry matter, the moisture content of bottom layer of 15% (d.b) and drying time of less than 35 hours. Step changes in drying air temperature and air recycle ratio were considered in the optimization. In single step in control variables, the difference of the moisture content between top layer and bottom layer was great and more fan power was required. As the drying trays were exchanged when the moisture content of bottom layer reached to 100% (d.b), fifty percent of energy was saved and the difference of moisture content was little. In double step changes in control variables, optimal conditions were found by changing the step when the moisture content of bottom layer reached to 100% (d.b) (about 19.8 hours from starting drying). Optimum air flow rate was $18.1cmm/m^2$. Optimum drying air temperature and air recycle ratio in the first step was $55.8^{\circ}C$ and 0.80, and in the second step $65.6^{\circ}C$ and 0.88, respectively. In triple step changes in control variables, the optimal conditions were found by changing the steps when the moisture content of bottom layer reached to 250% (d.b) and 150% (d.b). Optimal air temperatures were $66.2^{\circ}C$, $58.4^{\circ}C$ and $66.9^{\circ}C$, and optimal air recycle ratios were 0.778, 0.785, 0.862 at each step, respectively. Optimal air flow rate was $18.9cmm/m^2$. The best operating mode was triple step mode considering energy consumption, drying time, fan power, and quality of dried red pepper. When the triple step mode was used to dry the red pepper, the energy consumption was about 16.5%~57.2% less than that of the single step mode and the drying time was 6.6 hours shorter than that of the double step mode.

• 한국조명전기설비학회지:조명전기설비
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• 제21권1호
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• pp.30-43
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• 2007

• 한국조명전기설비학회지:조명전기설비
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• 제21권3호
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• pp.28-36
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• 2007