프랜탈 차원을 이용한 미세구조의 정량적 해석

홍경진,전경남,김창원 광주대학교 2000 産業技術硏究 Vol.14 No.-

ZnO 바리스터의 표면에서 전기적 특성은 프랙탈 방법으로 정량화 하였다. 전기적 특성은 주파수 변화에 대해 유전율을 측정하였다. 프랙탈 차원이 높을수록 입자는 복잡한 형성이었으며 프랙탈 차원과 전기적 특성은 입계와 기공이 차지하는 입계의 밀도 분포도와 관계가 있었다. Sb_2O_3 첨가에 의해 ZnO 입자는 스피넬 구조의 생성에 의해 성장이 억제되었으며 Sb_2O_3가 첨가되지 않는 시료 ZnO1은 입자의 크기가 제어되지 않아 내부 정전용량이 감소되어 유전율이 작았다. A new fractal method is presented to understand more clearly the effect of variations on ZnO surface on electrical characteristics. The electrical characteristics have been investigated in terms of dielectric characteristics with frequency. If Fractal dimension is high, the grain density and grain boundary is complex in the surface of ZnO varistors. The ZnO grain with addition of Sb_2O_3 was restricted by formation of spinel structure. The dielectric constant was low value decreasing with static capacitance, which has not controlled ZnO grain size.

대형 설계 시스템의 효율적 반응표면 근사화를 위한 점진적 이차 근사화 기법

홍경진,김민수,최동훈,Hong, Gyeong-Jin,Kim, Min-Su,Choe, Dong-Hun 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.12

For effective construction of second-order response surface models, an efficient quad ratic approximation method is proposed in the context of trust region model management strategy. In the proposed method, although only the linear and quadratic terms are uniquely determined using 2n+1 design points, the two-factor interaction terms are mathematically updated by normalized quasi-Newton formula. In order to show the numerical performance of the proposed approximation method, a sequential approximate optimizer is developed and solves a typical unconstrained optimization problem having 2, 6, 10, 15, 30 and 50 design variables, a gear reducer system design problem and two dynamic response optimization problems with multiple objectives, five objectives for one and two objectives for the other. Finally, their optimization results are compared with those of the CCD or the 50% over-determined D-optimal design combined with the same trust region sequential approximate optimizer. These comparisons show that the proposed method gives more efficient than others.

텔레매틱스용 다중대역 CMOS 직접변환기 설계

홍경진,양두영 제주대학교 공과대학 첨단기술연구소 2005 尖端技術硏究所論文集 Vol.16 No.2

The direct-conversion mixer in a wireless communication system operating over multiband frequency ranges is presented in this paper. The proposed mixer topology has the modified Gilbert-cell structure with inductive degeneration. This mixer with CMOS technology has highly linear performance, low power consumption and compact size for the integrated RF-SoC. The direct-conversion mixer is designed for the telematics communication terminal converging wideband frequency ranges from 800 MHz to 3GHz. The conversion gain and P1dB of designed mixer are about 1dB and -8dBm, respectively. Also, the noise figure is less than 6.5dB in operating frequency bands. The direct-conversion mixer consumes low current of 4.8mA at 3.3V.

Risk Factors Preventing Immediate Fall Detection: A Study Using Zero-Inflated Negative Binomial Regression

홍경진,김지은 한국간호과학회 2021 Asian Nursing Research Vol.15 No.4

Purpose: Falls are the most common accidents in healthcare facilities, and timely intervention can have a positive effect on the hazards and trauma experienced by patients after a fall. This study determined the factors affecting the time taken to detect a fall. Methods: A total of 3,470 cases of falls reported through the Korea Patient Safety Reporting and Learning System were included in the analysis. A zero-inflated negative binomial regression method was used for this retrospective secondary data analysis study. Results: There were 537 patients whose falls were not detected immediately; the count model was used to predict risk factors that delayed fall detection. Women aged 60-69 years-compared to those below 60 years and an evening nursing shift, compared to a day shift-were identified as significant factors. The fall detection time of about 2,933 patients was zero; therefore, the logit model was applied to predict a patient's possibility of belonging to the group whose fall was detected immediately. Comparisons of tertiary hospitals with general hospitals and hospitals, of the evening shift with the day shift, and of the day shift with the night shift indicated significant influencing factors. Conclusions: These findings can assist nurses in recognizing patient and hospital characteristics related to delayed fall detection. Strategies to improve patient safety in healthcare facilities that focus on patient characteristics such as age can be recommended. Furthermore, nurse staffing requires improvement to detect fall incidents immediately.

프랙탈 차원에 의한 소자 표면의 정량화 분석

홍경진 한국인터넷방송통신학회 2023 한국인터넷방송통신학회 논문지 Vol.23 No.1

High-resolution images of surfaces provide detailed information on pores or shapes with specific sizes ranging from nano sizes to micrometers. However, it is not yet clear to determine an efficient association for pores or shapes from high-resolution images of surfaces. For the efficient association of pores and shapes, the surface characteristics of the device were considered as fractal dimensions by taking SEM photographs and binarizing the images. The fractal program was directly coded for surface analysis of the device. The device surface characteristics and electrical characteristics are thought to be related to the fractal dimension. The fractal dimension decreased with an increase in internal pores. The density and grain boundary of particles, which are structural characteristics of the device surface, were related to the fractal dimension. The particle size decreased with an increase in the fractal dimension and was uniformly formed. When the particles were uniformly formed, fewer pores were present and the fractal dimension increased.

실시간 소전력 감시 및 원격제어용 지능형 콘센트 개발

홍경진 한국인터넷방송통신학회 2023 한국인터넷방송통신학회 논문지 Vol.23 No.2

현재 가정이나 사무실 및 공장 등 전력 수요가 증가하면서 전체 전력 사용량도 증가하고 있다. 전력사용의 증가는에너지 절약에 대한 의식 변화가 나타나면서 대기전력에 대한 관심도도 높아졌다. 가정용 및 사무용 기기는 대기상태에서도 전력을 소모하고 있다. 이에 대기전력의 저감에 대한 필요성이 매우 커지고 있으며 대기전력 1W이하를 목표로하고 있다. 지능형 콘센트는 근거리 무선망을 이용하여 홈네트워크에 연결하고 콘센트에 연결된 램프나 가전기기의 대기전력을 차단하거나 절감시키는 것이다. 본 연구에서는 근거리 무선망(Zigbee)를 이용하여 콘센트에 연결된 조명램프나가전기기에서 사용하는 전기의 사용량을 원격으로 모니터링 하고 대기전력을 차단할 수 있는 모니터링 시스템과 지능형콘센트을 개발하고자 한다. 또한, 개발하는 지능형 콘센트와 모니터링 시스템은 휴대용 장치(리모콘)를 이용하여 사용자가 손쉽게 대기전력을 차단할 수 있다.지능형 콘센트는 대기전력을 저감시킬 뿐만 아니라 화재 방재 시스템에도 응용가능할 것이다. 대기하는 전력을 차단 하는 장치는 지능형 콘센트와 대기전력 차단 스위치를 포함하므로 누전과 화재를방지할 것이다.

복합산화물 $(Ba Ca)TiO_3$-ZnO의 구조적 및 유전분극 특성

홍경진,임장섭,정우성,민용기,김용주,김태성 한국전기전자재료학회 1997 電氣電子材料學會誌 Vol.10 No.3

The ZnO is stabilize dielectric constant over a broad temperature range because its addition makes the relaxation time short. In this study, the composite oxide material (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_{3}$ was mixed by ZnO additive material and the dielectric polarization characteristics was studied. The relative density was over 90[%] at all specimen in the structural characteristics. Among of the specimen, the relative density of (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_{3}$ with ZnO (0.4mol) has a 95[%]. The grain size of composite oxide material with an increasing ZnO increased and it was 1.0[.mu.m]-1.22[.mu.m]. In the electrical characteristics, the charge and discharge current was increased by ZnO addition. The dielectric relaxation time was increased by space charge polarization at above 110[.deg. C] and the dielectric relaxation time was fixed by space charge polarization of para-dielectric layer at below 110[.deg. C]. The dielectric relaxation time was maximum when the grain size was small. The dielectric relaxation time is decreased with an additive material ZnO and interface polarization, existing void at the grain and grain boundary. The remnant polarization is increased and the coercive electric field is decreased by ZnO.

소형 풍력발전시스템의 직류전원 적용을 위한 운전제어 및 AC/DC변환 통합장치 개발

홍경진 한국인터넷방송통신학회 2019 한국인터넷방송통신학회 논문지 Vol.19 No.3

In many countries, such as developing countries where electricity is scarce, small wind turbines in the form of Off Grid are an effective solution to solve power supply problems. In some countries, the expansion of power systems and the decline of electricity-intensive areas have led to the use of small wind power in urban road lighting, mobile communications base stations, aquaculture and seawater desalination. With this change, the size of the small wind power industry is expected to have greater potential than large-scale wind power. In the case of small wind power generators, the generator is controlled at a variable speed, and the voltage and current generated by the generator have many harmonic components. To solve this problem, the AC to DC converter to be studied in this paper is a three-phase step-up type converter with a single switch. The inductor current is controlled in discontinuous mode, and has a characteristic of having a unit power factor by eliminating the harmonic of the input current. The proposed converter is composed of LCL filter and three phase rectification boost converter at the input stage and a single phase full bridge for grid connection. It is a control system with energy storage system(ESS) that the system stabilization can be pursued against the electric power. 전기가 부족한 개발도상국 같은 많은 나라에서는 Off Grid 형태의 소형풍력발전이 전력공급 문제를 해결하기위한 효율적인 핵심 솔루션이다. 몇몇 국가에서는 전력계통의 확장과 전기가 부족한 지역의 감소로 소규모 풍력을 도시의 도로 조명, 모바일 통신 기지국, 양식업 및 해수 담수 등의 분야에 이용하기도 한다. 이런 변화에 따라 소형 풍력산업 규모는 대규모 풍력보다 큰 잠재력이 기대되고 있다. 소형 풍력발전의 경우 발전기는 가변 속도로 제어되는 특성이있으며 발전기에서 발생하는 전압 및 전류에는 많은 고조파 성분을 가지고 있다. 이를 해결하기 위해서 본 논문에서는소형 풍력발전시스템의 직류전원 적용을 위한 운전제어 및 AC/DC 변환 통합장치를 제안하며 기존 AC to DC 컨버터는단일 스위치를 갖는 3상 승압형 방식의 컨버터로서 인덕터 전류가 불연속모드로 제어되며, 입력전류의 고조파를 제거하여 단위역률을 갖는 특성을 갖는다. 제안된 컨버터는 입력단에 LCL 필터 및 3상 정류 승압형 컨버터, 계통연계를 위한단상 풀브릿지 형태로 구성되어 있으며 에너지저장시스템(ESS) 기능이 부가된 제어 시스템으로 풍력발전을 이동 평준화방식에 의해 급변하는 전력에 대해 계통 안정화를 추구할 수 있다.

온도보상용 세라믹 커패시터의 전기적 특성에 관한 연구

홍경진,정우성,김태성,이은학,이준웅 한국전기전자재료학회 1995 電氣電子材料學會誌 Vol.8 No.5

In this study, the BaTiO$\sub$3/ capacitor add to MnO$\sub$2/ like depressor and shifter were investigated for temperature or voltage compensation by structural and electrical analysis. The relative density of BCTM, generating poly crystall and formation of lattice defect, has a 90[%] over as the CaTiO$\sub$3/ come out to control grain size. The current density of BCTM2 increased non-ohmic in high-electric field but that BCTM3 and BCTM4 had a few changing. The BCTM3 and BCTM4 unformated grain boundary shown temperature compensation properties, so that the dielectric constant was low value. The curie point was near 140[.deg. C] in BCTM1 and BCTM4, but BCTM3 and BCTM4 not shown the curie point. It is found that the charging energy of BCTM4 was changed 6[%] according to rising temperature from room temperature to 417[K]. The formation of BaMnO$\sub$3/ was low dielectric constant to change frequency and temperature.

Si/MgO 기판에 증착된 BaTiO$_3$ 박막의 구조 및 전기적 특성

홍경진,김태성 한국전기전자재료학회 1998 전기전자재료학회논문지 Vol.11 No.12

$BaTiO_3$ thin films preferred c-axis orientation for the potential application of ferroelectric memory devices were deposited on silicon substrates(100) by RF sputtering and annealed at 800 and 900[$^{\circ}C$] in air. The BT(100)/BT(110) peak ratio of the sputtered sample was decreased with post-annealing in air. According to increasing with annealing temperature and time, the peak ratio of BT(100)/BT(110) was decreased and the surface density of thin film was high. Dielectric characteristics of $BaTiO_3$ thin film was measured as a function of annealing temperature and frequency. The dielectric constants were increased with annealing and decreased with frequency by space charge polarization and dipole polarization below 600[kHz]. The remanent polarization and coercive field in P-E hysteresis loop of $BaTiO_3$thin film were increased with the annealing temperature in air. The remanent polarization and coercive filed annealed at 800[$^{\circ}C$] for 1hr were 1.2[$\mu$C/$cm^2$] and 200[kV/cm]