• Journal of Institute of Control, Robotics and Systems
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• v.17 no.4
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• pp.388-396
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• 2011

Sun tracking system is the most important subsystem in parabolic dish type solar thermal power plant, since it determines the amount of thermal energy to be collected, thus affects the efficiency of solar thermal power plant most significantly. Various types of sun tracking systems are currently used. Among them, use of photo sensors to located the sun(which is called sensor type) and use of astronomical algorithm to compute the sun position(which is called program type) are two of the mostly used methods. Recently some uses CCD sensor, like CCD camera, which is called image processing type sun tracking system. This work is concerned with the analysis of sun tracking performance of various types of sun tracking systems currently used in the parabolic dish type solar thermal power plant. We first developed a sun tracking error measurement system. Then, we evaluate the performance of five different types of sun tracking systems, sensor type, program type, hybrid type(use of sensor and computed sun position simultaneously), tracking error compensated program type and image processing type. Experimentally obtained data shows that the tracking error compensated program type sun tracking system is very effective and could provide a good sun tracking performance. Also the data obtained shows that the performance of sensor type sun tracking system is being affected by the cloud significantly, while the performance of a program type sun tracking system is being affected by the sun tracking system's mechanical and installation errors very much. Finally image processing type sun tracking system can provide accurate sun tracking performance, but costs more and requires more computational time.

• Toxicological Research
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• v.35 no.4
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• pp.389-394
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• 2019

When conducting risk assessments of cosmetic ingredients, it is important that reliable exposure information is obtained for cosmetic products. As cosmetics are becoming more diverse, continuous effort must be made to obtain exposure data that reflect their growth and usage trends. The usage pattern of cosmetics, such as the application area and amount used, may differ by product type and also by country. We conducted a survey to compare the amount of sun spray and sun cream used in a usage environment in South Korea. The study was conducted on Haeundae Beach, one of the most popular beaches in South Korea. A total of 1,255 beachgoers participated in this study; 604 and 651 participants used the sun spray and sun cream, respectively, while sunbathing and enjoying water activities on the beach for one day. Exposure was analyzed following a probabilistic method. On comparing all subjects, it was found that the group that used sun spray (mean: 44.52 g/day) used significantly more product (p = 0.000) than those who used sun cream (mean: 20.51 g/day). By analyzing the daily exposure of sun spray and sun cream per unit body weight according to age and gender, the exposure amount of sun spray and sun cream was found to be highest among 2~9 year-old girls (mean for sun spray: 2.51 g/kg/day, p95: 5.50 g/kg/day, mean for sun cream: 0.79 g/kg/day, p95: 1.79 g/kg/day). The amount of sun spray used is approximately twice that of sun cream. Among both the sun spray and sun cream groups, the exposure amount per unit body weight was highest in girls younger than 10. These factors should be considered when conducting risk assessments of sun spray and sun cream.

• Journal of the Korean Solar Energy Society
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• v.36 no.6
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• pp.47-59
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• 2016

As the usage of sun tracking system in solar energy utilization facility increases, requirement of more accurate computation of sun position has also been increased. Accordingly, various algorithms to compute the sun position have been proposed in the literature and some of them insist that their algorithms guarantee less than 0.01 degree computational error. However, mostly, the true meaning of accuracy argued in their publication is not clearly explained. In addition to that, they do not clearly state under what condition the accuracy they proposed can be guaranteed. Such ambiguity may induce misunderstanding on the accuracy of the computed sun position and ultimately may make misguided notion on the actual sun tracking system's sun tracking accuracy. This work presents some comments related to the implementation of sun position computational algorithm for the sun tracking system. We first introduce the algorithms proposed in the literature. And then, from sun tracking system user's point of view, we explain the true meaning of accuracy of computed sun position. We also discuss how to select the proper algorithm for the actual implementation. We finally discuss how the input factors used in computation of sun position, like time, position etc, affect the computed sun position accuracy.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.408-408
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• 2000

A parabolic dish concentrator used in a high temperature application of solar energy tracks the sun's movement by two axis sun tracking system. In such a system, sun tracking performance affects the system efficiency directly. Generally the higher the tracking accuracy is, the better the system performance is. A large number of parabolic dish type concentrators has been developed and implemented in the world. However none of them clearly provided a qualitative method of how the accuracy of the sun tracking system can be evaluated. The work presented here is the evaluation of sun tracking performance of parabolic dish concentrator, which follows the sun's movement by the sensor, using computer vision system. We install a camera on the parabolic dish concentrator. While the concentrator follows the sun, sun's images are captured continuously. Then the performance of sun tracking system was evaluated by analyzing the variation of the position of the sun in the images.

• Solar Energy
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• v.19 no.4
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• pp.81-91
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• 1999

The work presented here is a design and development of sun tracking system for the parabolic dish concentrator. Parabolic dish concentrator is mounted on azimuth and elevation tracking mechanism, and controlled to track the sun with computed and measured sun positions. Sun tracking mechanism is composed of 1/30000 speed reducer(3 stages) and 400W AC servomotor for each axis. The nominal tracking speed of each axis is ${\pm}0.6^{\circ}/sec$ and the system has a driving range of $340^{\circ}$ in azimuth and of $135^{\circ}$ in elevation. Sun tracking control system consists of sun sensor, wind speed and direction measurement system, AC servomotor position control system and personal computer as a master controller. Sun sensor detects the sun located within ${\pm}50^{\circ}$ measured from the sun sensor normal direction. Computer computes the sun position, sunrise and sunset times and controls the orientation of parabolic dish concentrator through the AC servomotor position control system. It also makes a decision of whether the system should follow the sun or not based on the information collected from sun sensor and wind speed and direction measurement system. The sun tracking system developed in this work is implemented for the experimental work and shows a good sun tracking performance.

• Journal of the Korean Solar Energy Society
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• v.21 no.4
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• pp.55-62
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• 2001

A parabolic dish concentrator used in a high temperature application of solar energy tracks the sun's movement by two axis sun tracking system. In such a system, sun tracking performance affects the system efficiency directly. Generally the higher the tracking accuracy is, the better the system performance is. A large number of parabolic dish type concentrators has been developed and implemented in the world. However none of them clearly provided a qualitative method of how the accuracy of the sun tracking system can be evaluated. The work presented here is the evaluation of sun tracking performance of parabolic dish concentrator, which follows the sun's movement by the sensor, using a computer vision system. We install a camera on the parabolic dish concentrator. While the concentrator follows the sun, sun's images are captured continuously. Then the performance of sun tracking system was evaluated by analyzing the variation of the position of the sun in the captured images.

• Solar Energy
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• v.18 no.4
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• pp.87-94
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• 1998

This work presents a method to compute the sun position(azimuth and elevation), sunrise and sunset times. Accurate computation of sun position is very important to the precise tracking of the sun for the solar concentrator, which enables the maximum collection of solar energy. Methods to compute the sun position are available in the literature already. However most of them do not have accuracy verification, thus makes hard in selecting the most accurate sun position computation method. We first select the most accurate sun position computation method among the methods presented in the literature by comparing the computed sun position with Korean Almanac of Korea Astronomy Observatory. Then a procedure to compute the sunrise and sunset times is presented. Computed sun position shows $0.02^{\circ},\;0.6^{\circ}$ and one minute differences in azimuth, elevation and sunrise/sunset times respectively compared with Korean Almanac.

• Journal of the Korean Home Economics Association
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• v.39 no.8
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• pp.81-92
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• 2001

The purpose of this study was to find out the factors of Knowledge and attitudes related to sun safety and to determine the factors affecting sun protection behavior. The subjects were 167 adults in their twenties living in Busan. The results were as follows. 1. Four factors of knowledge about sun safety were identified: ultraviolet ray risk, sunscreen, sun protective clothing, and nil protective color. 2. Four factors of attitudes toward sun exposure were identified: attractiveness, emotion, conformity, and health concern. 3. Four factors of sun protection behavior were identified: sunscreen/parasol, shade, hat/sunglasses, and sun protective clothing. 4. Compared to women, men were relatively more risk to skin damage due to less proportion that used sunscreen and a parasol. 5. Factors of sun protective behavior, such as sunscreen/parasol, shade, hat/sunglasses, and sun protective clothing, were associated with the Knowledge related to ultraviolet ray risk. 6. Wearing a hat and sunglasses was predicted by the attractiveness, which defined as positive attitudes toward tanned appearance. 7. Shade use was affected by the perception of sun exposure as happiness and relaxing. 8. Health concern was the strongest predictor of sunscreen/parasol use.

• Mycobiology
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• v.47 no.2
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• pp.207-216
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• 2019

Talaromyces marneffei is the only dimorphic species in its genus and causes a fatal systemic mycosis named talaromycosis. Our previous study indicated that knockdown of AcuD gene (encodes isocitrate lyase of glyoxylate bypass) of T. marneffei by RNA interference approach attenuated the virulence of T. marneffei, while the virulence of the AcuD knockout strains was not studied. In this study, T. marneffei-zebrafish infection model was successfully established through hindbrain microinjection with different amounts of T. marneffei yeast cells. After co-incubated at $28^{\circ}C$, the increasing T. marneffei inoculum doses result in greater larval mortality; and hyphae generation might be one virulence factor involved in T. marneffei-zebrafish infection. Moreover, the results demonstrated that the virulence of the ${\Delta}AcuD$ was significantly attenuated in this Zebrafish infection model.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.4
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• pp.590-596
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• 1987

In this paper, it was studied on the design of a sun sensor which is able to sense the declinations of an azimuth angle and a zenith angle for a digital sun seeker control system so that it will seek the sun accurately. And, it was considered the construction of digital controllable algorithms through experiments. Peculiar design method of the sun sensor is that sensor box was constructed with three square silicon solar cells and that the three cells were mounted unsymmetrical forming the