• Wind and Structures
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• v.3 no.3
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• pp.177-191
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• 2000

This paper presents an approach for evaluating directionality effects for both wind speeds and wind loads in hurricane-prone regions. The focus of this study is on directional wind loads on low-rise structures. Using event-based simulation, hurricane directionality effects are determined for an open-terrain condition at various locations in the southeastern United States. The wind speed (or wind load) directionality factor, defined as the ratio of the N-year mean recurrence interval (MRI) wind speed (or wind load) in each direction to the non-directional N-year MRI wind speed (or wind load), is less than one but increases toward unity with increasing MRI. Thus, the degree of conservatism that results from neglecting directionality effects decreases with increasing MRI. It may be desirable to account for local exposure effects (siting effects such as shielding, orientation, etc.) in design. To account for these effects in a directionality adjustment, the factor described above for open terrain would need to be transformed to other terrains/exposures. A "local" directionality factor, therefore, must effectively combine these two adjustments (event directionality and siting or local exposure directionality). By also considering the direction-specific aerodynamic coefficient, a direction-dependent wind load can be evaluated. While the data necessary to make predictions of directional wind loads may not routinely be available in the case of low-rise structures, the concept is discussed and illustrated in this paper.

• Particle and aerosol research
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• v.13 no.2
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• pp.43-52
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• 2017

Policy direction for the management of air quality in Korea has been on the reduction of the average concentrations of the criteria air pollutants such as sulfur dioxide and fine particles. However, recently, risk based management of air pollutants becomes an important issue. In this study, to develop an effective air quality management policy direction in Korea, (1) the fourth Multiple Air Toxics Exposure Study (MATES IV) carried out in the South Coast Air Quality Management District (SQAQMD) in the USA is reviewed and (2) the results are compared with in these in Seoul and (3) policy directions are suggested. It was found that (1) systematic integrated study comprising of measurement, modeling, emission inventory estimation, and risk assessment was essential to estimate the health risk of air pollutants reliably, (2) cancer risk of diesel particle was dominant over other air pollutants, and (3) health risk based emissions were different from amount based emissions. It was suggested that (1) reducing the exposure from hot spots might important to reduce health risk from air pollutants and (2) an integrated air quality management administration system is important for the efficient management of air pollution.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.2
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• pp.9-14
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• 2019

The newly discovered properties of periodic nanoscale patterns have increasingly sparked research interests in various fields. Along this direction, it is worth mentioning that there had been rare studies conducted on interference exposure, a method of creating periodic patterns. Additionally, these few studies seemed to validate the existence of only exact quadrangle shapes and dot patterns. This study asserted the formation of wavy patterns associated to using multiple exposures of the ratio of the first exposure intensity to the second exposure intensity. Such patterns were designed and constructed herein via overlapping of two Gaussian beams relative to certain rotation angles, and with a submicron structure fabricated based on a 360-nm continuous-wave laser. Results confirmed that the proposed double exposure laser interference lithography is able to create circular, elliptical and wavy patterns with no need for complex optical components.

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.146-150
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• 1998

To enhance the resolution and the depth of focus of the patterns whose size reaches the optical resolution limits, the various imaging methods are being tried. Generally in the linear polarization illumination methods, the contrast gap exists between TE mode TM mode according to the pattern direction. However, through the previous research, the elliptical polarization illumination(EPI) method was proposed to overcome this contrast gap. In this research, we investigated the optimal polarization condition to be able to enhance the depth of focus(DOF) for the optional mask which is containing the opposite direction patterns by applying the various polarization conditions including EPI. The DOF according to each polarization condition was obtained by ED-Tree(Exposure-Defocus Tree) for the given exposure dose and CD error boundaries. As the result, we can ascertain th effect of EPI for the enhancement of DOF in some condition of optical system.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.10
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• pp.1367-1373
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• 2001

This study used fowl sperm from three White Leghom rooster reared at our laboratory. Semen samples were exposed to the magnetic field strengths of from 650 to 5700 Gauss for one. two, or three days to investigate the influence of magnetic field on the orientation of fowl spermatozoa. Fowl spermatozoa were found to orient with their long axis of heads perpendicular to the magnetic field direction. The fowl spermatozoa were initially influenced when magnetic field intensities were from 650 to 5700 Gauss and the highest values (70.67, 72.49 and 71.79%) were found in the 5700 Gauss treatment at one, two, and three days exposure, respectively. Although percentages of the perpendicular oriented fowl spermatozoa increased along with the enhancement of the magnetic field intensity, the degree of orientation was only significantly higher in the treatments having the magnetic field strength from 1500 to 5700 Gauss than that in the control treatment at all exposure time. In addition, the experimental results also showed that the percentages of all orientational types of fowl spermatozoa (perpendicular category including upward perpendicular and downward perpendicular and parallel type consisting of leftward parallel and rightward parallel) in all treatments tended to be stable during exposure time. From the results of this study. it is suggested that (1) the diamagnetic anisotropy of the inside structural components of fowl spermatozoa induce them to orient perpendicular to the magnetic field direction, (2) the degree of orientation increased according to the enhancement of magnetic field strengths, (3) fowl spermatozoa had not an high sensitivity to the magnetic field, and the level of perpendicular orientation of fowl spermatozoa in this study is nearly similar to that of cattle sperm in the study of Suga et al. (2000).

• Korean Journal of Digital Imaging in Medicine
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• v.13 no.1
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• pp.21-26
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• 2011

A radiation imaging system used in a surgery room is mainly using C-arm which is purposed to fluoroscope. C-arm is often use to watch an operation's accuracy and progress, but not only being bombed to this first beam but also affected to this scattered beam, so now we are look for the way to reduce bombed amount of doctor, nurses and radiological technologists. We measured the exposure dose in $0^{\circ}$ spot according to the distance to find out frequency distribution of scattered ray in an operation room and found the spot which has the same exposure dose from $30^{\circ}$ distance of all directions and wrote isodose curve. We analyzed the data and found out the sudden reduction of scattered ray according to the long direction also found out that scattered ray was not related to the directions. Operators must recognize the reduction of exposure dose. Because reducing scattered ray from all directions in an operation room is really difficult. So every operators must use shelters to reduce the exposure dose and notice the safety.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.261-269
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• 2023

During a nuclear power plant (NPP) accident, radioactive material may be released into the surrounding environment in the form of a radioactive plume. The behavior of the radioactive plume is influenced by meteorological factors such as wind direction and speed. If the residents are evacuated to a shelter in the direction of the flow of the radioactive plume, the radiation exposure of the residents may increase, contrary to the purpose of the evacuation. To avoid such an undesirable outcome, this paper applies a big data analysis to evaluate the suitability of the shelter locations near 5 NPPs in the Republic of Korea in terms of the seasonal wind direction frequency in those areas. To this end, the wind data measured around the NPPs from 2016 to 2020 were analyzed to derive the seasonal wind direction frequency using a big data analysis. These analyses results were then used to determine how many shelters around NPPs locate in areas with prevailing wind direction per season. Then, suggestions were made on the direction for residents not to evacuate, if possible, that is, the prevailing seasonal wind directions for 5 NPPs, depending on the season in which the accident occurs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.10
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• pp.845-849
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• 2001

The new phto-alignment material PMI5CA, poly{N-(phenyl)maleimide-co-3-[4-(pentyloxy) cinamate]porpyl-2-hydroxy-1-methacrylate}, was synthesized and the electro-optical (EO)characteristics in the vertical-aligned(VA) liquid crystal display (LCD) photo-aligned on the photopolymer surface were studied. Excellent Voltage-transmittance(V-T) characteristics in the VA-LCD photoaligned with polarized UV exposure of oblique direction on the pohotopolymer surface for 1 min can be achieve. The transmittance of the VA-LCD photoaligned on the photopolymer surface decreased with increasing UV exposure time. We suggest that decrease of transmittance in the VA-LCD photoaligned on the photopolymer surface is attributed to the dissociation of the ester linkage in the photodimerized cinnamate structure with increasing UV exposure time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.358-361
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• 2001

A new photoalignment material PM15CA, poly{N-(phenyl)maleimide-co-3-[4-(pentyloxy) cinnamate]propyl-2-hydroxy-1-methacrylate}, was synthesized and the electro-optical (EO) characteristics in the vertical-aligned (VA) liquid crystal display (LCD) photo-aligned on the photopolymer surface were studied. Excellent voltage-transmittance(V-T) characteristics in the VA-LCD photoaligned with polarized UV exposure of oblique direction on the pohotopolymer surfaces for 1 min can be achieved. The transmittance of the VA-LCD photoaligned on the photopolymer surface decreased with increasing UV exposure time. We suggest that the decrease of transmittance in the VA-LCD photoaligned on the photopolymer surface is attributed to the dissociation of the ester linkage in the photodimerized cinnamate structure with increasing UV exposure time

• Journal of information and communication convergence engineering
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• v.2 no.1
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• pp.22-25
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• 2004

A highly sensitive ammonia gas sensor using thick-film technology has been fabricated and examined. The sensing material of the gas sensor is FeOx-$WO_{3}-SnO_{2}$ oxide semiconductor. The sensor exhibits resistance increase upon exposure to low concentration of ammonia gas. The resistance of the sensor is decreased, on the other hand, for exposure to reducing gases such as ethyl alcohol, methane, propane and carbon monoxide. A novel method for detecting ammonia gas quite selectively utilizing a sensor array consisting of an ammonia gas sensor and a compensation element has been proposed and developed. The compensation element is a Pt-doped $WO_{3}-SnO_{2}$gas sensor which shows opposite direction of resistance change in comparison with the ammonia gas sensor upon exposure to ammonia gas. Excellent selectivity has been achieved using the sensor array having two sensing elements.