• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
• /
• pp.210-213
• /
• 2001

This study presents an effective variable forgetting factor method based on fuzzy logic to suppress frequency droop in extended integral load frequency control. The performance of the extended integral control is greatly dependent on the decaying factor. For an optimal or near optimal performance, it is necessary that the decaying factor as well as the feedback gains should be changed very quickly in response to changes in the system dynamics. However, because of its time-varing characteristic, the optimal decaying factor is difficult to be selected analytically. By adopting fuzzy set theory, the decaying factor can be determined quickly to respond to the variation of the feedback signals. This study builds a fuzzy rule base with use of the change of frequency and its rate as inputs. The computer simulation has been conducted for the single machine system. The simulation results show that the proposed fuzzy 1o81c based controller yields more improved control performance than the conventional PI controller.

• 대한전기학회논문지:전력기술부문A
• /
• 제49권7호
• /
• pp.345-349
• /
• 2000

This paper presents an extended integral control with the PI controller by introducing the delay and decaying factors. The extended integral control scheme is developed by substituting the proportional convolution integral control for the PI(Proportional Integral) control. So far, the integral part of PI controller produces a signal that is proportional to the time integral of the input signal to the controller. The steady-state operation points are affected forever by errors in the past due to the input signal containing the information of the error in the past. These phenomena may cause some disturbances for other control purposes related to the given PI control. Introduction of forgetting factors to the error in the past can resolve the disturbance problems. Various forgetting factors are developed using the delay elements, the decaying factors, and the combination of the delay and decaying factors. The proposed various extended integral control schemes can be applicable to the corresponding PI control designs in which the error in the past may badly affect the current steady-state operation points and may cause some disturbances for other control purposes.

• 대한전자공학회논문지TC
• /
• 제38권7호
• /
• pp.14-21
• /
• 2001

본 논문에서는 유전체가 삽입된 공진기를 이용하여 C-band용 대역통과 여파기를 설계, 제작하였다. 공진기의 높이는 인접 유전체 공진기의 도파관 차단 주파수로부터 결정된다. 공진기의 지름은 도체 손실을 고려하여 유전체의 두 배로 결정하였다. 유전체 공진기의 공진주파수는 비소멸(non-decaying) 모드 해석법으로 계산하였다. 일반적으로 원통형 유전체 공진기의 공진주파수는 Cohn 모델로 해석하였는데, 이것은 공진기의 벽과 유전체벽 사이에서 전자파가 소멸(decaying)된다는 가정 하에 해석한 방법이다. 그러나， 이 방법은 근사적인 해석방법이다. 외부양호도(external quality factor)인 $Q_{ex}$는 Ansoft의 Maxwell 시뮬레이션 툴을 사용하여 결정하였다. 유전율 45인 유전체를 사용하여 설계한 대역통과 여파기는 5.065GHz의 중심주파수를 가졌다. 삽입손실은 1dB, 밴드 폭은 20MHz, 감쇠 특성은 30dB$(f_0{\pm}15MHz)$)로 설계목표에 만족함을 알 수 있다.

• 수산경영론집
• /
• 제17권1호
• /
• pp.1-17
• /
• 1986

Since the middle of the 70s, the countries with the marine resources declared the exclusive water zone of two hundred miles. As a result, our country lacked many foreign fishing grounds. This awakened our perception of fishing grounds. The fishing ground is an important factor in the economical effectiveness of fisheries. The fishing ground must have the following basic conditions. 1. It must be the place the fishery resources inhabit and wander. 2. Their catching or aquaculturing must be possible by the technical methods. 3. It must have economic worth in the management. The fishing ground that achieves the above basic conditions is affected by the following factors. This is the factor of the fishing ground location. A. Natural factor 1). Suitable climate 2).Abundant resources 3). Good quality of the sea-bottom 4). Not to be pollutted area B, Economic factor 1). Be adjacent to fishing port and fisheries market 2). Good working conditions 3). Be abundant of economical resources C. Social factor 1). Be possible to work legally 2). Be permitted in the political relations 3). Be acquainted with the customs of foreign countries The fishing ground location is mainly affected by the natural factor of the above factors. The abundance of resources depends on the natural resources. The resources in the fishing ground have the cycle of developing period, maturing period, and decaying period according to the fishing efforts. The point that we sustainably yield the maximum of fishery resources is the changing point of maturing period and decaying period. We call this point MSY, so the resources of fishing ground should be managed by the MSY. Therefore, when we select the fishing ground location. We should judge the natural factor, the economic factor and the social factor synthetically according to the situation and environment, so we can achieve the efficient management.

• Mycobiology
• /
• 제47권1호
• /
• pp.50-58
• /
• 2019

Agarum clathratum, a brown macroalgae species, has recently become a serious environmental problem on the coasts of Korea. In an effort to solve this problem, fungal diversity associated with decaying A. clathratum was investigated and related ${\beta}$-glucosidase and endoglucanase activities were described. A total of 233 fungal strains were isolated from A. clathratum at 15 sites and identified 89 species based on morphology and a multigene analysis using the internal transcribed spacer region (ITS) and protein-coding genes including actin (act), ${\beta}$-tubulin (benA), calmodulin (CaM), and translation elongation factor (tef1). Acremonium, Corollospora, and Penicillium were the dominant genera, and Acremonium fuci and Corollospora gracilis were the dominant species. Fifty-one species exhibited cellulase activity, with A. fuci, Alfaria terrestris, Hypoxylon perforatum, P. madriti, and Pleosporales sp. Five showing the highest enzyme activities. Further enzyme quantification confirmed that these species had higher cellulase activity than P. crysogenum, a fungal species described in previous studies. This study lays the groundwork for bioremediation using fungi to remove decaying seaweed from populated areas and provides important background for potential industrial applications of environmentally friendly processes.

• 대한전자공학회논문지TC
• /
• 제38권5호
• /
• pp.9-15
• /
• 2001

원통형 공동 공진기를 이용한 유전체의 전자기적 특성들의 측정 방법에 대해 기술한다. 여기에 관련된 유전체의 전자기적 특성들은 비유전율, 손실 반젠트, Q factor 등이 있다. 동심 유전체 봉이 삽입된 원통형 공동 공진기에서 $TE_{011}$ 모드의 사용이 제한되었다. $TE_{011}$ 모드는 유전체 봉과 공진기 벽면 틈에 의한 공진주파수 민감도가 가장 덜 민감하게 변화하였다. 동심 유전체 봉이 삽입된 원통형 공동 공진기의 $TE_{011}$ 모드를 사용하는 방법과 새롭게 제안된 non-decaying 모드의 정확한 전자계 표현은 유전체의 전자기적 특성들의 정확한 측정을 위해 소개되었다.

• Bulletin of the Korean Chemical Society
• /
• 제32권2호
• /
• pp.583-589
• /
• 2011

Fluorescence correlation spectroscopy (FCS) is a sophisticated and an accurate analytical technique used to study the diffusion of molecules in a solution at the single-molecule level. FCS is strongly affected by many factors such as the stability of the excitation power, photochemical processes, mismatch between the refractive indices, and variations in the cover glass thickness. We have studied FCS near the surface of a cover glass by using rhodamine 123 as a fluorescent probe and have observed that the surface has a strong influence on the measurements. The temporal autocorrelation of FCS decays with two characteristic times when the confocal detection volume is positioned near the surface of the cover glass. As the position of the detection volume is moved away from the surface, the FCS autocorrelation becomes one-component decaying; the characteristic time of the decay is the same as the faster-decaying component in the FCS autocorrelation near the surface. This observation suggests that the faster component can be attributed to the free diffusion of the probe molecules in the solution, while the slow component has its origin from the interaction between the probe molecules and the surface. We have characterized the surface contribution to the FCS measurements near the surface by changing the position of the detection volume relative to the surface. The influence of the surface on the diffusion of the probe molecules was monitored by changing the chemical properties of the surface. The surface contribution to the temporal autocorrelation of the FCS strongly depends on the chemical nature of the surface. The hydrophobicity of the surface is a major factor determining the surface influence on the free diffusion of the probe molecules near the surface.

• 설비공학논문집
• /
• 제1권4호
• /
• pp.265-275
• /
• 1989

An experimental study of decaying swirl air flow has been obtained by tangential inlet in a straight tube with Reynolds number range 20,000~40,000. The friction factor, swirl angle, velocity profiles and turbulent intensity are measured by using micro-manometer and hot-wire anemometer. It is found that the swirl flow behaviors depend on the swirl intensity along the test tube.

• Journal of Mechanical Science and Technology
• /
• 제17권12호
• /
• pp.2042-2052
• /
• 2003

An experimental study was performed to investigate heat transfer characteristics of turbulent swirling flow in an axisymmetric annuli. The static pressure, the local flow temperature, and the wall temperature with decaying swirl were measured by using tangential inlet conditions and the friction factor and the local Nusselt number were calculated for Re=30000∼70000. The local Nusselt number was compared with that obtained from the Dittus-Boelter equation with swirl and without swirl. The results showed that the swirl enhances the heat transfer at the inlet and the outlet of the test tube.

• Journal of Advanced Marine Engineering and Technology
• /
• 제29권3호
• /
• pp.260-274
• /
• 2005

An experimental investigation was performed to study the characteristics of turbulent swirling flow in the cylindrical annuli. The swirl angle measurements were performed by flow visualization technique using smoke and dye liquid. By using the particle image velocimetry method. this study has found the time-mean velocity distribution and turbulent intensity with swirl for Re=20,000. 30.000. 50.000. and 70,000 along longitudinal sections. The results appear to be physically reasonable. Other experimental study was performed to investigate heat transfer characteristics of turbulent swirling air flow in axisymmetric annuli. The static pressure. the local air flow temperature, and the wall temperature with decaying swirl were measured by using thermocouples and the friction factor and the local Nusselt number were calculated for Re=30,000. 50,000 and 70000. The local Nusselt number was compared with that obtained from the Dittus-Boelter equation with swirl and without swirl, respectively. The results showed that the swirl enhances the heat transfer at the inlet and the outlet of the test tube.