• 한국태양에너지학회 논문집
• /
• 제34권3호
• /
• pp.21-29
• /
• 2014

Heliostat field control algorithm is the logics to operate the heliostat field of tower type solar thermal power plant and it could include various methodologies of how to control the heliostat field so as to optimize the energy collection efficiency as well as to reduce the system operating cost. This work, as the first part of the consecutive works, presents heliostat aiming mint allocation scheme which will be used in the heliostat field control algorithm for 200kW solar thermal power plant built in Daegu, Korea. We first discuss the structure of heliostat field control system required for the implementation of aiming scheme developed in this work. Then the methodologies to allocate the heliostat aiming points on the receiver are discussed. The simulated results show that the heliostat aiming point allocation scheme proposed in this work reduces the magnitude of peak heat flux on the receiver more than 40% from the case of which all the heliostats in the field aim at the center of receiver simultaneously. Also it shows that, when the proposed scheme is used, the degradation of heliostat field optical efficiency is relatively small from the maximal optical efficiency the heliostat field could have.

• 한국조경학회:학술대회논문집
• /
• 한국조경학회 2007년도 Journal of Landscape Architecture in Asia Vol.3
• /
• pp.202-207
• /
• 2007

Recently, the number of 'field-museums(F.Ms.)' in Japan has increased. Although they are very diverse, the essential commonality is that each has a field arranged as a kind of museum. In this study, we examine the 'F.M.' mainly through documents in order to understand the concept of the F.M. and the direction of further studies. Before examining the cases of F.Ms., we explore the history of the F.M. and the role of museums in order to establish the background of the development of F.Ms. The term F.M. first appeared and evolved in 1990s. It is suggested that F.Ms. are positioned on the same lines as development of museums, and that the field of museums and the field of landscaping is beginning to overlap. Concerning the role of museums, we examined the definition of museums in terms of conventional museums and regional planning. Next, the documents of 36 cases of F.Ms. are checked regarding their types and roles. Consequently, we found that while most F.Ms. cases have both the role of conventional museums and the role of regional planning, it is difficult to say that the role has some connection with the type. It seems that F.Ms. emphasize 'education' rather than 'collection', 'pleasure' and 'research', compared with conventional museums. In addition, the role of regional planning is strongly expected. In many cases, the F.M. is expected to be a method of regional management, not merely a museum. In order to use F.Ms. for regional planning and landscaping effectively, it is desirable for F.Ms. to be defined from this viewpoint. For this purpose, it is necessary to determine the extent of F.Ms. The problem is which extent to choose, geographical unity or administrative border. Hence, further comparative research is needed clarify the association between the extent and the identity in order to establish a more effective size of F.Ms.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.1988-1989
• /
• 2007

Polyethylene is widely used as the insulator for power cable. To investigate the conduction mechanism for power cable insulation under ac high field, it is very important to acquire the dissipation current under actual running field. Recently, we have developed the unique system, which make possible to observe the nonlinear dissipation current waveform. In this system, to observe the nonlinear properties with high accuracy, capacitive current component is canceled by using inverse capacitive current signal instead of using the bridge circuit for canceling it. We have already reported that the dissipation currents of $40\;{\mu}m$ thick LDPE film at 10 kV/mm and over 140 Hz, it starts to show nonlinearity and odd number's harmonics were getting large. To investigate the conduction mechanis ms in this region, especially space charge effect, various kinds of estimation, such as time variations of instantaneous resistivity for one cycle, FFT spectra of dissipation current waveforms and so on, has been examined. As the results of these estimations, it was found that the dissipation current will depend on not only the instantaneous value of electric field but also the time differential of applied electric field due to taking a balance between applied field and internal field. Furthermore, two large peaks of dissipation current for each half cycle were observed under certain condition. In this paper, to clarify the reason why it shows two peaks for each half cycle, the film thickness dependences of dissipation current waveforms were observed by using the three different thickness LDPE films.

• 한국환경교육학회지:환경교육
• /
• 제11권1호
• /
• pp.195-216
• /
• 1998

This study was planned to define the concept and the patterns of the fields for environmental education through the theory review about the fields for environmental education that were important at school environmental education for field-experience learning, and to survey the using status of the fields for environmental education and the awareness of teachers who have been teaching practically students environmental education in school through the questionnaire. The results derived from this study were as follows ; First, the use of the fields for environmental education in environmental education is necessary aspect of the importance of field-experience learning and the environmental education strategy through personalization of environment and is essential to the substantiality of school environmental education. The concept of the fields for environmental education is defined that it is used as place(space) for environmental education, is located most outdoor space, promote students the concern and consciousness about environment. The patterns of the fields for environmental education may be classified the field for nature observation learning surrounding, the fields for nature observation and field survey, the fields for visit and field trip, and the fields for experience and participation by the contents and the purpose of educational program. Second, according to the results of the teacher's awareness survey, most responded teachers gave an affirmative answer about the necessity of practical use of the fields for environmental education, and it was used mainly in special lecture, weekend, and legal holiday. Also, it was surveyed that time for using the fields was brought as the most serious obstacle by teachers. In particular, teachers preferred the environmental education fields for experience and participation above all others. Third, from the results about the using status of the fields for environmental education, school environmental education mostly have been taught in indoor classroom, school landscape(school grounds) was evaluated the most easily useful the fields for environmental education in formal lecture, because it can solve the lack of time. Also, it was proved that eco-park, stream, and river were fit for the field-experience learning with small students group.

• 한국재료학회지
• /
• 제13권7호
• /
• pp.424-428
• /
• 2003

The microstructure and field emission properties of carbon nanotubes(CNT) grown by Ni-catalytic chemical vapor deposition(CVD) were investigated. CVD-grown CNT had a high density of curved shape with randomly oriented. It was found that an increase in electric field caused an increase in field emission current and field emission sites of CNT. The maximum field emission current density was measured to be 3.6 ㎃/$\textrm{cm}^2$ at 2.5 V/$\mu\textrm{m}$, while the brightness of 56 cd/$\textrm{cm}^2$ was observed for the CNT-grown area of 0.8 $\textrm{cm}^2$ from a phosphor screen. Field emission current at constant electric field gradually decreased initially and then stabilized with time.

• 한국환경교육학회지:환경교육
• /
• 제14권1호
• /
• pp.43-55
• /
• 2001

The purpose of this study was to review the current status and problems of the national qualification system in the Environmental field focusing on deficiencies of the regulatory system and qualities of environmental professional including the Environmental control Professional Engineer, Environmental Engineer, Environmental Industrial Engineer and Environmental field. An overview of the environmental field, its current status, domestic qualification items and training conditions in environment-related areas, laws of environmental field, and data of the job analysis were reviewed. The concrete and extensive development plans for the qualification system of the Environmental field are as follows: First of all, a job analysis should be made of on the introduction of new systems or policy modification to reflect technical changes and national policies about the environmental field in the qualification exam. Second, it is essential to prepare policies that are suitable for the qualification system in the Environmental field and that improve its effectiveness. Third, the appropriate policy measures should be taken in order to elevate the social standing of Environmental field qualification holders.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2001년도 춘계종합학술대회
• /
• pp.469-473
• /
• 2001

This paper describes a rotation-type field mill to measure the electric field intensity caused by thunderclouds on the ground level. The field mill developed is consisted of two isolated electrode vanes, a grounded stator and a rotor. To develop a high sensitive field mill, the principles and design rules of a rotation-type field mill are studied. Also, two types of calibration system, such as a cylindrical guard electrodes and a parallel-plate electrodes, are proposed to determine the sensitivity and frequency bandwidth of the field mill. From the calibration experiment, the frequency bandwidth and the sensitivity of the field mill arc DC ∼ 200 [MHz] and 0.267 [mV/Vm], respectively. Therefore, it can measure the electric field intensity from 73[V/m] to 18.7[kV/m].

• 한국식물병리학회지
• /
• 제14권5호
• /
• pp.526-530
• /
• 1998

The effect of field sanitation using ecological characters of the pathogen was investigated for controlling Phomopsis seed decay in soybean. Field sanitation which was eliminated the inoculum by removing host debris, abscised petioles and cotyledones out of field, reduced remarkably infection percentage of pods and seeds by Phomopsis spp. as compared to the inoculated field. Neverthless, seed infection was 28.7% in the sanitized field. The fields sanitized by benlate application around the soybean plants also decreased seed infection with Phomopsis spp. Total seed infection including that with miscellaneous pathogens occurred as much as 75∼79% to the no application and their control values were 34∼42% over the routine application schedule. Even though it was not satisfactory, field sanitation seemed to be effective in controlling Phomopsis seed decay when infection pressure was low level. Diaporthe phseolorum va. sojae, D. phaseolorum var. caulivora and Phomopsis longicolla were mostly identified from soybean seeds and Colletotrichum truncatum, Cercospora kikuchiana were also isolated in sequence. Field sanitation did not significantly increase in soybean yield over the no application, while routine application schedule did in field.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제51권11호
• /
• pp.616-621
• /
• 2002

With biological effects by ELF (Extremely Low Frequency) magnetic field generated from power system, the transient magnetic field from electric appliances is a major issue presently. Because the transient magnetic field induces higher current than the power frequency field inside living bodies, transient magnetic field exposure has been much focused. In this paper, it is shown that transient magnetic field from electric home appliances can be characterized as magnetic dipole moment. In this method, the dipole moment vector is assumed by allowing an uncertainty of 6dB in the estimated field. A parameter M that represents biological interaction was applied also. The proposed method was applied to 7 types of appliances (hair drier, heater, VDT, etc.) and their equivalent magnetic dipole moment and harmonic components were estimated. As the results, the useful data for quantifying magnetic field distribution around electric appliances were obtained.

• 대한전기학회논문지
• /
• 제34권1호
• /
• pp.38-43
• /
• 1985

Since the superconductor type II with high critical current and high critical magnetic field was discovered in 1961, there were many studies on the superconducting coil for high field and highly homogeneous field. The graphical method and the numerical method by Newton Raphson technique have been studied as the method for design of homogeneous superconducting coil. It is comparatively easy to get a compensating coil for any given main coil by the above methods, but it is too laborious to get a general solution for main coil dimension. This paper studies the optimal design method for minimum volume of superconducting coil under certain central field and highly homogeneous field. The present method makes use of the nonlinear programming for optimization. The optimal solution of NMR superconducting coils by this method are demonstrated very well.