• Journal of Korea Water Resources Association
• /
• v.48 no.8
• /
• pp.659-672
• /
• 2015

In flow velocity measurement of natural rivers, taking images with proper image quality is the fundamental and the most important step. Since flood peaks generally occur in night time, it is very difficult to capture proper images in that time. The present study aims to test a far infra-red camera as a adequate alternative to resolve the various problems in measuring flood discharges. The far infra-red cameras are able to capture images in night time without help of any extra illuminations. Futhermore they are not affected by fog nor smoke, hence they can be adapted for a fixed-type surface image velocimeters. For comparison, a commercial camcorder and a near infra-red cameras were used together. The test images were taken at a day time and a night time, and the image acquisition work were performed at an artificial flow channel of the Andong River Experiment Station. The analyzed results showed that the far infra-red camera would be a good instrument for surface image velocimeters, since they were able to capture regardless light condition. There are, however, a few minor problems in their accuracy of the analyzed results. About their accuracy a more study would be required.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.8 no.4
• /
• pp.53-64
• /
• 2009

Inter-vehicular communication that propagates information without infrastructures has drawn a lot of interest. However, it is difficult to apply conventional ad-hoc routing protocols directly in inter-vehicular communication due to frequent changes in the network topology caused by high mobility of the vehicles. MMFP(Multi-hop MAC Forwarding) is a unicast forwarding protocol that transport packets based on the reachability information instead of path selection or position information. However, delivering public safety messages informing road conditions such as collision, obstacles and fog through inter-vehicular communication requires broadcast rather than unicast since these messages contain information valuable to most drivers within a close proximity. Flooding is one of the simplest methods for multi-hop broadcast, but it suffers from reduced packet delivery-ratio and high transmission delay due to an excessive number of duplicated packets. This paper presents two multi-hop broadcast protocols for inter-vehicular communication that extend the MMFP. UMHB(Unreliable Multi-Hop Broadcast) mitigates the duplicated packets of MMFP by limiting the number of nodes to rebroadcast packets. UMHB, however, still suffers from low delivery ratio. RMHB(Reliable Multi-Hop Broadcast) uses acknowledgement and retransmission in order to improve the reliability of UMHB at the cost of increase in transmission delay, which we show through simulation is within an acceptable range for collision avoidance application.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.16 no.2
• /
• pp.116-127
• /
• 2017

A fog on road is known as a weather factor that affects traffic flow. The method in order to solve the problem, recently, Variable Speed Limit(VSL) which provide reasonable speed limit by road and weather conditions in real time is introduced. However, if drivers do not comply with VSL, the road safety more decrease than without VSL because individual vehicle's speed deviation is larger than without VSL. Therefore, this paper aims to analyze to speed limit compliance and traffic characteristics under foggy conditions with and without VSL. A test using driving simulator divides into normal and foggy condition with visibilities are 200m, 150, 50~100m. The test results showed that 70 subjects's average speed mostly obeyed speed limit, but speed deviation generally declined with VSL. Especially, the speed deviation more reduced under foggy conditions. According to this study, compliance of VSL clearly rose in low visibility and VSL helped improve road safety due to reduction of speed deviation. The results of this study are expected to make use of reasonable speed limit for reference.

• Journal of Environmental Science International
• /
• v.22 no.6
• /
• pp.745-759
• /
• 2013

The characteristics of meteorological conditions and air pollution were investigated in a valley city (Yangsan) on bad visibility days (from 05:00 to 09:00 LST) of the cold half year (November 2008 to April 2009). This analysis was performed using the hourly observed data of meteorological variables (temperature, wind speed and direction, relative humidity, and 2 m and 10 m temperature) and air pollutants ($NO_2$, $SO_2$, $PM_{10}$, and $O_3$). In addition, visibility data based on visual measurements and a visibility meter were used. The bad visibility days were classified into four types: fog, mist, haze, and the mixture (mist+haze). The results showed that the bad visibility days of the four types in the valley city were observed to be more frequently (about 50% of the total study period (99 days except for missing data)) than (27%) those near coastal metropolitan city (Busan). The misty days (39%) in the valley city were the most dominant followed by the hazy (37%), mixture (14%), and foggy days (10%). The visibility degradation on the misty days in Yangsan was closely related to the combined effect of high-level relative humidity due to the accumulation of water vapor from various sources (e.g. river, stream, and vegetation) and strong inversion due to the development of surface radiative cooling within the valley. On the hazy days, the visibility was mainly reduced by the increase in air pollutant (except for $O_3$) concentrations from the dense emission sources under local conditions of weaker winds from the day before and stronger inversion than the misty days. The concentrations of $NO_2$, $PM_{10}$, and $SO_2$ (up to +36 ppb, $+25{\mu}g/m^3$, and +7 ppb) on the hazy days were a factor of 1.4-2.3 higher than those (+25 ppb, $+14{\mu}g/m^3$, and +3 ppb) on the misty days.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.6
• /
• pp.102-109
• /
• 2014

A particle system is used for modeling the physical phenomenon. There are many traditional ways for simulation modeling which can be well suited for application including the landscapes of branches, clouds, waves, fog, rain, snow and fireworks in the three-dimensional space. In this paper, we present a new fireworks modeling technique for modeling 3D firework based on Firework Particle Tracking (FPT) using the particle system. Our method can track and recognize the launched and exploded particle of fireworks, and extracts relatively accurate 3D positions of the particles using 3D depth values. It can realize 3D simulation by using tracking information such as position, speed, color and life time of the firework particle. We exploit Region of Interest (ROI) for fast particle extraction and the prevention of false particle extraction caused by noise. Moreover, Kalman filter is used to enhance the robustness in launch step. We propose a new fireworks particle tracking method for the efficient tracking of particles by considering maximum moving range and moving direction of particles, and shall show that the 3D speeds of particles can be obtained by finding the rotation angles of fireworks. Also, we carry out the performance evaluation of particle tracking: tracking speed and accuracy for tracking, classification, rotation angle respectively with respect to four types of fireworks: sphere, circle, chrysanthemum and heart.

• Journal of IKEEE
• /
• v.18 no.4
• /
• pp.485-494
• /
• 2014

Traffic Sign Recognition(TSR) is an important element in an Advanced Driver Assistance System(ADAS). However, many studies related to TSR approaches only in normal daytime environment because a sign's unique color doesn't appear in poor environment such as night time, snow, rain or fog. In this paper, we propose a new TSR algorithm based on machine learning for daytime as well as poor environment. In poor environment, traditional methods which use RGB color region doesn't show good performance. So we extracted sign characteristics using HoG extraction, and detected signs using a Support Vector Machine(SVM). The detected sign is recognized by a decision tree based on 25 reference points in a Normalized RGB system. The detection rate of the proposed system is 96.4% and the recognition rate is 94% when applied in poor environment. The testing was performed on an Intel i5 processor at 3.4 GHz using Full HD resolution images. As a result, the proposed algorithm shows that machine learning based detection and recognition methods can efficiently be used for TSR algorithm even in poor driving environment.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2003.11a
• /
• pp.177-184
• /
• 2003

Numerical simulation on marine wind and sea surface elevation was carried out using both three-dimensional hydrostatic and non-hydrostatic models and a simple oceanic model from 0900 LST, August 13 to 0900 LST, August 15, 1995. As daytime easterly meso-scale sea-breeze from the eastern sea penetrates Kangnung city in the center part as basin and goes up along the slope of Mt. Taegullyang in the west, it confronts synoptic-scale westerly wind blowing over the top of the mountain at the mid of the eastern slope and then the resultant wind produces an upper level westerly return flow toward the East Sea. In a narrow band of weak surface wind within 10km of the coastal sea, wind stress is generally small, less than l${\times}$10E-2 Pa and it reaches 2 ${\times}$ 10E-2 Pa to the 35 km. Positive wind stress curl of 15 $\times$ 10E-5Pa $m^{-1}$ still exists in the same band and corresponds to the ascent of 70 em from the sea level. This is due to the generation of northerly wind driven current with a speed of 11 m $S^{-1}$ along the coast under the influence of south-easterly wind and makes an intrusion of warm waters from the southern sea into the northern coast, such as the East Korea Warm Current. On the other hand, even if nighttime downslope windstorm of 14m/s associated with both mountain wind and land-breeze produces the development of internal gravity waves with a hydraulic jump motion of air near the coastal inland surface, the surface wind in the coastal sea is relatively moderate south-westerly wind, resulting in moderate wind stress. Negative wind stress curl in the coast causes the subsidence of the sea surface of 15 em along the coast and south-westerly coastal surface wind drives alongshore south-easterly wind driven current, opposite to the daytime one. Then, it causes the intrusion of cold waters like the North Korea Cold Current in the northern coastal sea into the narrow band of the southern coastal sea. However, the band of positive wind stress curl at the distance of 30km away from the coast toward further offshore area can also cause the uprising of sea waters and the intrusion of warm waters from the southern sea toward the northern sea (northerly wind driven current), resulting in a counter-clockwise wind driven current. These clockwise and counter-clockwise currents much induce the formation of low clouds containing fog and drizzle in the coastal region.

• Atmosphere
• /
• v.25 no.4
• /
• pp.719-734
• /
• 2015

Korea is one of the country with the world's oldest meteorological observation records. Starting with first meteorological record of fog in Goguryeo in the year of 34 BC, Korea had left a great deal of quantitative observation records, from the Three Kingdoms Period to Goryeo to Joseon. During the Joseon Dynasty, with a great attention by kings, efforts were particularly made to measure rainfall in a systematic and scientific manner. In the 23rd year of King Sejong (1441), the world's first rain gauge called "Chugugi" was invented; in the following year (1442), a nationwide rainfall observation network was established. The King Sejong distributed Chugugi to 350 observation stations throughout the state, even to small towns and villages, for measuring and recording rainfall. The rainfall observation using Chugugi, initiated by King Sejong, had been in place for about 150 years, but halted during national disturbances such as Japanese invasion of Korea in 1592. Since then, the observation had been forgotten for a long time until the rainfall observation by Chugugi was resumed in the 48th year of King Yeongjo (1770). King Yeongjo adopted most of the existing observation system established by King Sejong, including the size of Chugugi and observation rules. He, however, significantly reduced the number of Chugugi observation stations to 14, and commanded the 352 local authorities such as Bu, Gun, Hyeon to conduct "Wootaek", a method of measuring how far the moisture had absorbed into the soil when it rains. Later on, six more Chugugi stations were established. If the number of stations of Chugugi and Wootaek are combined together, the total number of rainfall observation station in the late period of Joseon Dynasty was 372. The rainfall observation with Chugugi during the Joseon Dynasty is of significance and excellence in three aspects: 1) the standard size of Chugugi was so scientifically designed that it is as great as today's modern rain gauge; 2) rainfall was precisely measured, even with unit of Bun (2 mm); and 3) the observation network was distributed on a nationwide basis.

• Journal of Conservation Science
• /
• v.33 no.4
• /
• pp.267-274
• /
• 2017

The Silleuksa temple in Yeoju city is adjacent to the South Han River and often has high humidity and fog days. In addition, its proximity to forests renders it prone to damage by insects and microorganisms. In order to obtain the basic data necessary for the establishment of a cultural property preservation management plan, the biological distribution of the wooden buildings and the termite distribution in the surrounding forests were monitored for three years. The wood-boring bee, an insect known to inflict damage to heritage structures, was confirmed, and the distribution of insects varied annually and seasonally, presumably due to the location characteristics of the site and the climate change during the year. In the forest behind, termite colonies were identified as a whole and their distribution pattern was different every year. As per the results of the microorganism survey, the species distribution and pollution degree were different at the entrance of the building. Therefore, it needs continuous biological distribution and conservation environment monitoring to mitigate the effects of wood-damaging organisms.were different according to the entrance of the building.

• Journal of Astronomy and Space Sciences
• /
• v.14 no.2
• /
• pp.330-346
• /
• 1997

Korea Multi-Purpose Satellite I (KOMPSAT-I, the first multi-purpose Korean satellite) will be launched in the third quarter of 1999, which is operated on the sun-synchronous orbit for cartography, ocean color monitoring, and space environment monitoring. The main mission of Electro-Optical Camera(EOC) which is one of KOMPSAT-I sensors is to provide images for the production of scale maps of Korea. EOC collects panchromatic imagery with the ground sample distance of 6.6m at nadir through visible spectral band of 510~730nm. For determining KOMPSAT-I crossing time over Korea, this study examines the diurnal variation of solar and atmospheric variables that can exert a great influence on the EOC imagery. The results are as follows: 1) After 10:30 a.m. at the winter solstice, solar zenith angle is less than $70^{\circ}$ and expected flux of EOC spectral band over land for clear sky is greater than about $2.4mW/cm^2$. 2) For daytime the distribution of cloud cover (clear sky) shows minimum (maximum) at about 11:00 a.m. Although the occurrence frequency of poor visibility by fog decreases from early morning toward noon, its effect on the distribution of clear sky is negligible. From the above examination it is concluded that determining KOMPSAT-I crossing time over Korea between 10:30 and 11:30 a.m. is adequate.