• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.309-313
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• 2001

In this paper, a multifunctional three-phase electronic step-down transformer with output voltage stabilization characteristics is presented for custom power applications. The proposed electronic transformer has some advantages and features as follows: 1) It has 40 % weights lighter than that of commercial magnetic transformer, 2) It has output voltage stabilization characteristic with regulated output voltage over input variations, 3) It cab be operated as circuit breaker in the case of emergency, 4) It can be operated with so called soft starting function. Moreover, the electronic transformer may have stand-by power cutoff function and act as distortion compensator. This paper show the circuit diagram and present its features through various PSPICE simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7A
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• pp.568-573
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• 2009

This paper presents a step-down DC-DC converter with On-chip Compensation for battery-operated portable electronic devices which are designed in O.13um CMOS standard process. In an effort to decrease system volume, this paper proposes the on chip compensation circuit using capacitor multiplier method. Capacitor multiplier method can minimize error amplifier's compensation capacitor size by 10%. It allows the compensation block of DC-DC converter be easily integrated on a chip and occupy less layout area. But capacitor multiplier operation reduces DC-DC converter efficiency. As a result, this converter shows maximum efficiency over 87.2% for the output voltage of 1.2V (input voltage : 3.3V), maximum load current 500mA, and 25mA output ripple current. This voltage mode controled buck converter has 1MHz switching frequency.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.273-276
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• 2005

This paper presents an electronic ballast using a step down converter, a low frequency inverter for high pressure discharge lamp. The proposed ballast is composed of a full-wave rectifier, a step down converter operated as a current source with power regulation and a low frequency inverter with ignition circuit. The ignition circuit generates high voltage pulse of 1${\sim}$2[kV] peak, 130[Hz]. Moreover, it is able to reignite at regular intervals by protective circuit. As experimental results on the test, lamp voltage, current and consumption power are measured 132.5[V], 7.6[A] and 1,005[W], respectively. It was confirmed that the designed ballast operate the lamp with a constant power.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.77-80
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• 2001

최근에 cdma2000-lx 시스템의 역방향에 파일럿 채널이 추가되면서 적은 계산량으로 구현이 가능한 LMS 빔 형성 기법이 연구되고 있다. 그러나 기존의 LMS 빔 형성 방식의 경우 무선 페이딩 채널에 적응하기 위하여 고정된 step-sire parameter를 이용하였다. 하지만 이러한 고정된 step-size parameter를 사용할 경우 MSE가 증가하여 좋은 성능을 얻을 수 없다. 따라서 본 논문에서는 LMS 순 방향 빔 형성 기법에서 채널을 추정하여 추정된 채널과 LMS 가중치의 오차에 적응하는 step-size parameter를 결정함으로써 적은 MSE만으로 가중치 값을 추정하는 CA-LMS(Channel Adaptive Least Mean Square) 방식을 이용한 순방향 빔 형성 기법을 제안한다. 제안한 방식에 대하여 cdma2000-lx 환경에서 다양한 페이딩 환경에 적용하여 제안한 방식이 우수함을 확인 할 수 있다.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.618-620
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• 1997

A $50{\times}50{\mu}m^2$ aluminum micromirror array is fabricated using shadow evaporation process. The fabrication process is very simple with use of shadow evaporation process, and the micromirror array has a high fill-factor. The static and dynamic characteristics such as deflection angle vs. applied voltage, step response, and frequency response are measured using a contact free optical measurement technique. The downward threshold voltage was 8 V, step response time was $13.5{\mu}s$ when 32 V step voltage applied, and a resonance observed at 11kHz. The lifetime of micromirror with anti-stiction coating was tested and micromirror operated successfully over 200 million cycles of touch-down operations.

• Journal of Convergence for Information Technology
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• v.10 no.8
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• pp.213-222
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• 2020

This research aimed to verify whether family competency reinforcement had a mediating role on the effect of family cohesion of the Down syndrome family upon the independent life of children with Down syndrome. For the research, 146 families belonged to Down Syndrome Parent Assembly were surveyed and the statistical program SPSS WIN 25.0 was utilized for the data analysis. To verify the mediating effect, Baron and Kenny's causal step strategy was performed. As a result of the study, the higher the family cohesion of the Down syndrome family was, the greater the level of independence of the child was, indicating that the family cohesion had a significant static effect on the independence life. In addition, it was confirmed that the family competency reinforcement played a mediating role between the family cohesion and the children's independent living. Therefore, the results of this research suggested that it might be used as a policy approach and supporting plan for the realization of support for independence of Down syndrome children.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.994-1001
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• 2001

In this paper, we propose the Improved SIR-based Power Control method in mobile communication system. Generally speaking, SIR-based design considering both channel noise and multiuser interference is accurate indication of signal quality and provides good performance. However, one serious problem associated with SIR-based Power Control is the potential of Positive Feedback which can endanger the stability of the system. Therefore from SIR definition, we decrease the signal\`s Interference we will got a improved SIR and have a stable power control Also in mobile using window register which has Up-Maintain-Down power control step size instead of Up-Down, we got a better performance. This paper assesses the performance of Improved SIR based Power Control using PIC and window register. The proposed Improved SIR based Power Control is presented and compared with existing SIR based Power Control and Strength-and-SIR based Power Control.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.119-119
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• 2010

Among the various factors influencing the service life of the electric equipment, the performance of dielectric insulation materials has an important role to determine their whole service life. In order to determine the degradation of insulating materials immersed in extremely low temperature media such as liquid nitrogen, the abrupt temperature change from cryogenic to normal room temperature should be considered. But the assessments of low-temperature aging test method for the dielectric materials immersed in liquid nitrogen considering these conditions were not fully reported. Therefore, for the fundamental step to establish the suitable degradation test methods for cryogenic dielectric materials, we focused on the evaluation of ageing test methods for dielectric materials exposed to low temperature environments considering thermal shock by cool-down and warm up test.

• Journal of the Korea Society of Computer and Information
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• v.14 no.4
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• pp.87-99
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• 2009

The top-down method for SOA delivery is recommended as a best way to take advantage of SOA. The core step of SOA delivery is the step of service modeling including service analysis and design based on ontology. Most enterprises know that the top-down approach is the best but they are hesitant to employ it because it requires them to invest a great deal of time and money without it showing any immediate results, particularly because they use well-defined component based systems. In this paper, we propose a service identification method to use a well-defined components maximally as a bottom-up approach. We assume that user's inputs generates events on a GUI and the approximate business process can be obtained from concatenating the event paths. We first find the core GUIs which have many outgoing event calls and form event paths by concatenating the event calls between the GUIs. Next, we adapt sequential pattern mining algorithms to find the maximal frequent event paths. As an experiment, we obtained business services with various granularity by applying a cohesion metric to extracted frequent event paths.

• Journal of Elementary Mathematics Education in Korea
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• v.13 no.1
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• pp.17-30
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• 2009

This paper is about the basic skills of four operations in numbers and operations areas from step 1 to step 3 in elementary mathematics. Here are the results of the evaluation. First, addition and subtraction take the largest time. The average difficulty rate in operations area is 91.2%. Most students understand the contents of textbook well. Specifically, students easily understand the step 1. However, subtraction has lower difficulty rate than addition. Also, three mixed computation, calculation in horizontal, and rounding(rounding down) are difficult areas for students. The contents of step 2 are fully understood. However, lots of mistakes are found in the process of rounding(rounding down), and sentence problems are thought as difficult. Second, the multiplication is first starting in the step 2-Ga. The unit 'Multiplication 99' takes 13 hours, the longest. The difficulty rate in this unit is 89.4%, students understand well. However, students are influenced by addition and subtraction errors in the process of multiplication, and have difficulty in changing the sentence problem to multiplication expression. Third, the division, which starts in step 3-Ga, has 89.9% of difficulty rate. Students well understand. Result of this paper: most of students understand well four operations, but accurate concept, the relationship between multiplication and division, specific instructions in teaching principles of division calculation and sentence problems are in need. Setting the amount of the contents and difficulty rate in understanding are depends on every school's situation, so suggesting universal standard is really hard. However, studying more objects broadly and specific study will be helpful to suggest proper contents and effective teaching.