• Journal of the Korean earth science society
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• v.30 no.3
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• pp.344-353
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• 2009

By measuring the brightness of night sky, we have investigated light pollution around the observatory in the College of Education, Seoul National University. As a result of measuring the extinction coefficient and photometric constants by standardization, in January 28, 2009, the extinction coefficient found to be $k_B$=0.359 and photometric constant was $C_B$=4.397. In March 27, 2009, extinction coefficients were $k_B$=0.896 and $k_V$=0.725, and photometric constants were $C_B$=6.235 and $C_V$=6.027. Brightness of the night sky was measured from east, west, south, and north each by altitude of $20^{\circ}$, $40^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$. Data reduction and analysis was based on IRAF. Seeings for the each day of observation were 5.1 and 5.7 arcseconds in January 28 and March 27, respectively. Night sky spanned the magnitude range of $16{\leq}m_V$, $m_B{\leq}18$ We found that the brightness of night sky located at downtown was twice to four times brighter. On these observational conditions, limiting magnitude within 40cm-telescope becomes 11-13 magnitudes. Compared with Jan 28 and Mar 27, night sky brightness of January is 1 magnitude fainter than that of March in B filter.

• KIEAE Journal
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• v.10 no.4
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• pp.137-145
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• 2010

Active sunlighting systems have been applied to deliver sunlight into the indoor space where natural light is insufficient, mainly because of the congested high-rise buildings in urban areas. Among various active sunlighting systems, a mirror sunlighting system which is simple structure and economically reasonable has been widely used in different types of spaces such as underground, north facing place and atrium. This study was to evaluate the mirror sunlighting systems, which were consisted of the first mirror of $3.5m{\times}2.5m$, the eight sets of the second mirrors of $1.0m{\times}1.25m$ and a sun tracker. Ten sets of the systems were installed for 40 apartment living rooms, the configuration of $3.5m(W){\times}4.0m(D){\times}2.5m(H)$ where sunlighting were not possible due to high retaining walls located in the front of the living rooms. The 45 HOBO data logger sensors for the indoor illuminance were equipped and 2 Li-cor photometers for outdoor illuminance. Both indoor and outdoor horizontal illuminances were monitored every second from 9am to 3pm on 17 January 2010 under clear sky condition. The results showed that the indoor illuminance of installed mirror sunlighting system was significant relationship with outdoor illuminance and increased the indoor illuminance level by 4.2 times on the whole floor space, by 8 times on the sun patch space of 6m2 and even by 2 times on the no sun patch space. In addition, the luminous conditions of the living room under real sky conditions met the KS recommendation for difficult task (600-1000-1500 lux) such as sewing and reading on whole floor space and sun patch space. It was proved that the benefits of mirror sunlighting systems included an effective technology for penetrating daylight into indoors where sunlighting was not possible and improving occupants' satisfaction and health, and contributing to energy saving in apartments during daytime.

• Journal of the Korean Society of Industry Convergence
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• v.1 no.2
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• pp.65-74
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• 1998

The purpose of this paper is to investigate the mount of relief of human solar heat load and thermal comfort in outdoor environment in summer, Six different types of sites, T garden and its neighboring area in Japan, were selected as the experiment sites. The experiments were conducted from 22 to 29 August, 1994 to find the relationship between climatic conditions and human responses, Climatic conditions, subjects's thermal sensation and skin temperature were measured. Radiant heat exchange on the human body was estimated on the basis of the measured air and surface temperature and solar radiation. Thermal index Operative Temperature and New Effective Temperature was modified with the effect of the radiant heat exchange. Human thermal comfort and skin temperature is affected by the solar radiation and the sky factor in an outdoor environment. The effect of tree shade was verified on thermal comfort, The mount of relief of human solar heat load is relation to the existence of shade a solar radiation and the sky factor. The urban garden is one of the effective design element in an urban environmental planning.

• Ocean Science Journal
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• v.41 no.4
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• pp.235-244
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• 2006

Determining 'photosynthetically active radiation' (PAR) is a key part of calculating phytoplankton productivity in a biogeochemical model. We explore the daily and seasonal variability in the ratio of PAR irradiance to total irradiance that occurred at Ieodo Ocean Research Station (IORS) in the East China Sea under clear-sky conditions in 2004 using a simple radiative transfer model (RTM). Meteorological data observed at IORS and aerosol optical properties derived from Aerosol Robotic Network observations at Gosan are used for the RTM. Preliminary results suggest that the use of simple PAR irradiance-ratio values is appropriate in calculating phytoplankton productivity as follows: an average of $0.44\;({\pm}0.01)$ in January to an average of $0.48\;({\pm}0.01)$ in July, with average daily variabilities over these periods of about $0.016\;({\pm}0.008)$ and $0.025\;({\pm}0.008)$, respectively. The model experiments demonstrate that variations in the major controlling input parameters (i.e. solar zenith angle, precipitable water vapor and aerosol optical thickness) cause PAR irradiance ratio variation at daily and seasonal timescales. Further, increases (>0.012) in the PAR irradiance ratio just below the sea-surface are positively correlated with high solar zenith angles and strong wind stresses relative to those just above the sea-surface.

• Architectural research
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• v.17 no.2
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• pp.65-74
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• 2015

The habitual rooms and other structures related to everyday life are almost always grouped around the courtyard and together make up a house. There are many kinds of variety in types of courtyard houses depending on location, composition, allocation and relationship with inner space of the house. Every type of courtyard house accumulates many factors, which are social and economic circumstances, weather and geographical conditions. They are still well harmonized with life style and weather conditions in each area and basic unit of city organization. A courtyard can be shown as a place for everyday conversation like a community. Everyday space is the connective tissue that binds daily lives together, amorphous and so persuasive that it is difficult even to perceive. In spite of its ubiquity, everyday space is nearly invisible in the professional discourses of the city, like everyday life. Therefore Courtyards are special places that are outside yet almost inside, open to the sky, - a microcosm which gives relief to the inner rooms, gives the inhabitants a sense of ease and calm, and the feeling that they have their own piece of sky to use and protect them. This research will explore a variety of space use and dwelling types through courtyards based on field research and design projects.

• Journal of the Korean Solar Energy Society
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• v.28 no.5
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• pp.36-48
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• 2008

This study examines the influence of control algorithms on dimming performance to determine appropriate control setting when direct/indirect lighting is controlled by a daylight dimming system. Computer simulation were performed for a small office with double skin envelope under various daylight conditions. A retractable fabric shading and Venetian blind were applied for internal and external envelopes under three CIE standard sky conditions. Unshielded and partially-shielded photosensors were used, and three control algorithms were applied for the sensors. In general, dimming level was too excessive due to the direct impact of light from lighting fixture to the photosensor. Providing insufficient lighting output, the unshielded photosensor completely failed to secure required illuminance under any daylight condition. When a partially-shielded photosensor was applied under clear sky, three setting points functioned effectively. Less sensitivity for the partially-shielded photosensor was effective to control the dimming system optimally with reasonable energy saving. However, the daylight dimming control system for direct/indirect lighting does not appear to be energy effective when photosensors without enough shielded area is installed on ceiling where light from fixtures reaches directly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1125-1130
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• 2007

This paper presents a maneuver analysis of a full-vehicle featuring electrorheological (ER) suspension and ER brake. In order to achieve this goal, an ER damper and an ER valve pressure modulator are devised to construct ER suspension and ER brake systems, respectively. After formulating the governing equations of the ER damper and ER valve pressure modulator, they are designed and manufactured for a middle-sized passenger vehicle, and their field-dependent characteristics are experimentally evaluated. The governing equation of motion for the full-vehicle is then established and integrated with the governing equations of the ER suspension and ER brake. Subsequently, a sky-hook controller for the ER suspension and a sliding mode controller for the ER brake are formulated and implemented. Control performances such as vertical displacement and braking distance of vehicle are evaluated under various driving conditions through computer simulations.

• Atmosphere
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• v.20 no.1
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• pp.1-12
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• 2010

Temporal distributions and characteristics of PWV (Precipitable Water Vapor) and LWP (Liquid Water Path) are investigated by using the microwave radiometric profiler at Haenam NCIO from 1 August 2007 to 31 July 2008. Temporal variations of PWV are closely connected with the thermal response of water vapor in atmosphere. The variations of LWP are characterized by the rainfall variation being basically attributable to the heavy rain-bearing clouds. The frequency distributions of PWV and LWP according to the four sky conditions ('clear', 'lightly cloudy', 'cloudy', and 'deeply cloudy') by total cloud amount at Wando Observatory corresponds with a change of slope in cumulative distribution function for PWV and LWP. There results implies that the classification of sky condition can be applied by using the distribution of PWV and LWP from microwave radiometric profiler.

• Journal of the Korean Solar Energy Society
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• v.23 no.1
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• pp.48-56
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• 2003

Three of the leading computer daylighting simulation programs are compared with physical modeling techniques as a means of predicting daylighting performance of interior spaces. Lumen-Micro, Adeline and Lightscape are compared with physical model experiments under clear sky conditions. The comparative evaluations are conducted on analysis of daylight illuminance ratio(%) depending on model types. The estimated average errors are analyzed on 9.4% in Lumen-Micro, 6.3% in Adeline and 3.4% in Lightscape. Therefore, it is proved that three programs are useful for evaluating daylighting performance in our clear sky condition.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.11
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• pp.1096-1103
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• 2010

This paper proposes CDC (Continuous Damping Control) algorithm and verifies in multi-body dynamic vehicle. In order to distinguish a road profile on driving, waviness calculated by the filtered vertical-accelerations of sprung and unsprung masses is introduced. Sky-hook control is used at a low waviness road and constant damping level control is used at a high waviness road, where the hard damping level is determined by waviness, roll rate, acceleration, and deceleration. The damping levels of ride, anti-roll, anti-squat, and anti-dive modules are calculated by tuning parameters which is dependent upon vehicle velocity. Therefore this high tunable algorithm is useful to improve the ride and handling performance under various driving conditions. In the simulations, tire and dampers are modelled by SWIFT (Short Wavelength Intermediate Frequency Tire) model and 1st order delay model, and results are compared with conventional damper's.