• Asian Journal of Atmospheric Environment
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• v.4 no.3
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• pp.141-149
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• 2010

Aerosol size and number concentration were observed in the atmospheric boundary layer over Beijing (from near the ground to 1,200 m) on March 15 (a clear day) and 16 (a dusty day), 2005. The results were further compared with lidar measurements in order to understand the dependency of extinction on the particle size distribution and their vertical changes. The boundary layer atmosphere was composed of several sub-layers, and a dry air layer appeared between 400 and 1,000 m under the influence of dust event. In this dry air layer, the concentration of the fine-mode particles (diameter smaller than $1.0\;{\mu}m$) was slightly lower than the value on the clear day, while the concentration of coarse-mode particles (diameter larger than $1.0\;{\mu}m$) was remarkably higher than that on the clear day. This situation was attributed to the inflow of an air mass containing large amounts of Asian dust particles and a smaller amount of fine-mode particles. The results strongly suggest that the fine-mode particles affect light extinction even in the dusty atmosphere. However, quantitatively the relation between extinction and particle concentration is not satisfied under the dusty atmospheric conditions since laser beam attenuates in the atmosphere with high concentration of particles. Laser beam attenuation effect becomes larger in the relation between extinction and coarse particle content comparing the relation between extinction and fine particle content. To clarify this problem technically, future in situ measurements such as balloon-borne lidar are suggested. Here extinction was measured at 532 nm wavelength. Measurements of extinction at other wavelengths are desired in the future.

• Current Optics and Photonics
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• v.1 no.4
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• pp.351-357
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• 2017

This paper proposes a LED bicycle headlamp with a wide viewing angle to help bicyclists see the front effectively and because of its high visibility to reduce the risks of accidents around intersections or blind spots. The wide viewing angle was determined to be $28^{\circ}$ because it can illuminate a 5 m wide area 10 m away. Therefore, the road conditions of the intersection can be observed with the bicycle handlebar tilted slightly to the left or right. The headlamp has a compact reflector with a width of 30 mm, height of 27 mm, and length of 17 mm. Owing to its size, a change in the position of a light source leads to severe changes in light distribution. Therefore, the tolerance of the source position was analyzed by a simulation. The tolerance was ${\pm}0.5mm$ at the X, Y and Z axes within a less centered aiming range of ${\pm}1^{\circ}$. Finally, the prototype of the bicycle headlamp was made and the light distribution was measured by an automotive headlamp light measurement system. The experimental results indicate that the headlamp illuminates a 5 m wide area with an edge light of 3.2 lx as well as meeting the K-mark regulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.408-413
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• 2015

Road lighting has emerged in importance as an essential system to secure safety and visibility for drivers and pedestrians. According to the Road Lighting Standards (KS A 3701), the luminance uniformity (U0) should be 0.4, the luminance uniformity for lanes (UI) should be 0.5, and a threshold increment (TI) of 10% should be satisfied. In this study, we conducted simulations using the Relux program in which the secondary optical lens was applied to a 21 W engine. Ten LED engines were installed on a two-way four-lane road, and the simulation result satisfied the requirements with U0 0.47, UI 0.63 and TI 8%. The U0, UI, and TI were compared with the angle of the LED streetlight varied in the range of $9^{\circ}{\sim}15^{\circ}$ with $0.5^{\circ}$ intervals. The range was selected as ${\pm}25%$ of the standard inclination angle of $12^{\circ}$ according to the Road Lighting Standard. The U0 was high and the UI and TI were low when the tilting angle was in the range of $9.5^{\circ}{\sim}10.5^{\circ}$. Consequently, an optimum-design of lighting distribution was obtained for the concrete two-way four-lane road when the inclination angle was $9^{\circ}$.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.62-67
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• 2004

Many ships in voyage experience weight and buoyancy distribution change by various reasons such as change of sea water density and waves, weather condition, and consumption of fuel, provisions, etc . The weight and buoyancy distribution change can bring the ships out of allowable trim, heeling angle. In these case, the ships should adjust trim and heeling angle by shifting of liquid cargo or ballasting, deballasting of ballast tanks for recovery of initial state or for a stable voyage. But, if the adjustment is performed incorrectly, ship's safety such as longitudinal strength, intact stability, propeller immersion, wide visibility, minimum forward draft cannot be secured correctly. So it is required that the adjustment of trim and heeling angle should be planned not by human operators but by optimization computer algorithm. To make an optimized plan to adjust trim and heeling angle guaranteeing the ship's safety and quickness of process, Uk! combined mechanical analysis and optimization algorithm. The candidate algorithms for the study were heuristic algorithm, meta-heuristic algorithm and uninformed searching algorithm. These are widely used in various kinds of optimization problems. Among them, heuristic algorithm $A^\ast$ was chosen for its optimality. The $A^\ast$ algorithm is then applied for the study. Three core elements of $A^\ast$ Algorithm consists of node, operator, evaluation function were modified and redefined. And we analyzed the $A^\ast$ algorithm by considering cooperation with loading instrument installed in most ships. Finally, the algorithm has been applied to tanker ship's various conditions such as Normal Ballast Condition, Homo Design Condition, Alternate Loading Condition, Also the test results are compared and discussed to confirm the efficiency and the usefulness of the methodology developed the system.

• Asian Journal of Atmospheric Environment
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• v.10 no.1
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• pp.13-21
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• 2016

The vertical distributions of aerosol extinction coefficient were estimated using the scaling height retrieved at Gwangju, Korea ($35.23^{\circ}N$, $126.84^{\circ}E$) during a spring season (March to May) of 2009. The aerosol scaling heights were calculated on a basis of the aerosol optical depth (AOD) and the surface visibilities. During the observation period, the scaling heights varied between 3.55 km and 0.39 km. The retrieved vertical profiles of extinction coefficient from these scaling heights were compared with extinction profile derived from the Light Detection and Ranging (LIDAR) observation. The retrieve vertical profiles of aerosol extinction coefficient were categorized into three classes according to the values of AODs and the surface visibilities: (Case I) the AODs and the surface visibilities are measured as both high, (Case II) the AODs and the surface visibilities are both lower, and (Others) the others. The averaged scaling heights for the three cases were $3.09{\pm}0.46km$, $0.82{\pm}0.27km$, and $1.46{\pm}0.57km$, respectively. For Case I, differences between the vertical profile retrieved from the scaling height and the LIDAR observation was highest. Because aerosols in Case I are considered as dust-dominant, uplifted dust above planetary boundary layer (PBL) was influenced this discrepancy. However, for the Case II and other cases, the modelled vertical aerosol extinction profiles from the scaling heights are in good agreement with the results from the LIDAR observation. Although limitation in the current modelling of vertical structure of aerosols exists for aerosol layers above PBL, the results are promising to assess aerosol profile without high-cost instruments.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.3
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• pp.54-67
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• 2013

This study deals with the characteristics of view landscape in modern Daegu city which were analysed employing geographic information system(GIS). The view landscape analysis was performed by using GIS that enables to overlap land use map with the map of range of visibility, and the 3-D simulation. The results are as follows; First of all, the ratio of forest is enormously high in the range of visibility. The distribution of landscape components allows the dwellers to obtain a clear view towards forests from anywhere. The landscape components include west eroded lowlands, east open rolling lands, east eroded lowlands, and high mountain areas: Apsan(Mt.) in the south; Waryoungsan(Mt.) in the west; and Hamjisan(Mt.) and Hakbong(Mt.) in the north. On the tops of those, people are able to secure a clear vision from the viewpoint towards the surrounding mountains because of the rural areas continuing from the viewpoint to the mountains. A continuous view landscape has been formed by these natural environmental factors. Finally, there are multiple view targets with relatively high altitude that are covered with forests in the space between the urban area and the outer mountains that are higher than the view targets, which provides a scenery of mountains overlapped by higher mountains.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.6
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• pp.37-49
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• 2015

In Space Syntax, the greater the degree of integration between separate links, the greater the links' accessibility from the target network. As such, planning pedestrian walks so that links with high degrees of integration are connected, or else inducing high integration value land use are both valid options. The travel distribution model reflects how walking demand, or more specifically, the pedestrian, partakes in route choosing behavior that minimizes select criteria, notably level of discomfort, as measured using travel distance and time. The model thus demonstrates travel patterns associated with demand pertaining to minimization of discomfort experienced by the pedestrian. This research introduces a method that integrates Space Syntax and the pedestrian travel distribution model. The integrated model will determine whether regions with high degrees of integration are actually being used as pivots for pedestrian demand movement, as well as to explain whether the degree of integration is sustained at an appropriate level while considering actual movement demand. As a means to develop the integrated model, a method that combines display of the visibility of the space syntax network and road-divided links is proposed. The pedestrian travel distribution model also includes an alternative path finding mechanism between origin and destination, which allows for uniform allocation of demand.

• Journal of Korean Elementary Science Education
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• v.31 no.2
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• pp.253-268
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• 2012

The purpose of this study is to investigate the elementary pre-service teachers' conceptions of 'color of gases' focusing on the survey from freshmen at a National University of Education. For the study, the views about 'color of gases' were surveyed from the pre-service teachers. And the responses were analyzed based on the patterns. The results from the study are as follows: First, the conceptions about 'color of gases' were divided into 2 top-level, 5 mid-level and 7 sub-level categories. Second, the number of students who answered 'certain gas has color' was significantly greater than those who answered 'every gas has no color'. However, only a small number of students who answered former understand the scientific meaning of color and the color of gases correctly. Third, out of 5 misconception categories, greater number of students answered with 'inaccurate scientific knowledge (Ma1)', so the category was classified again into five detailed sub-categories. Fourth, most of the students, who answered 'every gas has no color', stated "they have not seen any color gases through their lives" based on their own experience. Fifth, the distribution percentage for scientific conceptions vs misconceptions was not related with the students' gender but highly related with students' academic area and their science courses taken at high school. Sixth, the pre-service teachers have various types of misconceptions regarding the 'color of gases' and when they have to explain visibility of gases to other people they tend to pass on their misconceptions. Based on the results from the study, some educational guidelines were suggested.

• Korean Journal of Oriental Medicine
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• v.12 no.3 s.18
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• pp.31-47
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• 2006

Nowadays Korean governments use Information Technology to improve the quality of life for a people. One of these tries is building the Food Tracing System based on Information Technology. Koreans have big concern about food that is good for health. The Food Tracing System means that the system can follows, traces, and records every steps of production and delivery of food and its ingredient. And this process should be identified and grouped by using tags, marks, and other methods. For example, producer of ingredient, processing steps of food, delivered place could be traced. In addition to food, medical herbs need consumer's trust in production and delivery. To trace and prosecute contaminated medical herbs, medical herbs also need this kind of Tracing System based on Information Technology. This study shows current medical herbs tracing ways and RFID(Radio Frequency IDentification) technology trend. As preceding study for future RFID based medical herbs tracing system, this study suggests the building plan and scenario of the Medical Herbs Tracing System. The determination of the main body for sticking RFID Tags is very important to design for RFID Traceability System. In this study, the starting point of information to medical herbs is an inspection agency. The Medical Herbs to product domestically or import moved to an inspection agency. An inspection agency bond the RFID Tags to packing of the Medical Herbs after examining the a basic its component. At the same time inspector give the information of production or importation to the Tags. This Tags are moved for logistical process to end point, the Korean medicine agency. The customer confirmed the traceability and certification information of the Medical Herbs. For success tracing of medical herbs, institutional support and close cooperation between related organizations is necessary besides good system design.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.3
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• pp.292-298
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• 2015

A wiper is a safety device removing rain and debris from windshield and ensuring visibility of drivers. If contact pressure distribution between rubber of the blade and the windshield is unbalanced, unwanted noise, vibration, and abrasion of the blade can occur and sometimes fatal accidents could occur. To improve the safety of the wiper, there have been many researches on the contact pressure analysis of the wiper, but the analysis results were not converged or require much computational time due to material nonlinearity of the rubber and contact conditions between the blade rubber and the windshield. In this research, a simple model with 1D beam and 2D shell elements was used for the contact pressure analysis instead of the 3D blade model. The simplified model saved computational time of the analysis and resolved convergence problems. The accuracy of the analysis results was verified by comparing them with experimental results for different rail spring curvatures.