• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.2 no.2
• /
• pp.161-172
• /
• 1969

Ten experimental tuna long line fishing operations were performed with the long lines A and B, in combination casting orders of BA and AB. The long line B differs from A in its additional main line length per basket and its greater depth of submersion (Table 1). The BA casting order results in an AB hauling order, so that the long line B is casted at an earlier time of a day and fishes for a longer period than A line (fig. 2). The number of fish caught was divided into subclasses in order to be subjected to $x^2-tests$ (Table 2). The first series of $x^2-tests$ were calculated using the hooking rates of two subclasses with other factors pooled (Table 3). The second series of $x^2-tests$ were calculated to obtain the interactions between two subclasses when other factors differed (Table 4). Attention was paid to the extremely small interactions as well as to the large interactions in order to find out whether a factor functions in the same way or in a contradictory way when the other factors involved differ. The test result is summarized in Table 5. The relationship between the hook casting time (relative to the sunrise time) and the hooking rates reveals the feeding behavior of particular species (fig. 3) A high hooking rate for yellowfin tuna shown in the period from one hour before sunrise to the moment of sunrise suggests that they feed actively in that period. Their poor hooking rate on earlier casted hooks suggests that they do not feed well under conditions of darkness and that they feed best while the hooks are sinking. Furthermore it is likely that yellowfin tuna maintain a shallow depth in the daytime, for the $x^2$ interaction between the line casting order BA and AB shows their persistant preferance of the long line A regardless of line casting order. Bigeye tuna show their feeding behavior under conditions of darkness, and show a preference for the sea's deeper layer. Alepisaurus borealis (Gill) show their feeding behavior under conditions of darkness more significantly than the bigeye tuna and their preferance for deep layers is also more significant. Marlins (mainly Makaria mazara) show a feeding behavior which is similar to the yellowfin tuna. The author emphasizes that certain variations of the hooking rates in relation to the line easting time were caused by an inadequate fishing depth as well as by the fish preference for a particular feeding time. When the part of the line casted in pre-dawn hours and hauled in the pre-sunset hours show a significantly lower hooking rate than other parts of the line, then it is concluded that tile hooks settled in a sea layer too deep for feeding.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.3
• /
• pp.339-345
• /
• 2018

Sunrise and sunset times differ depending on location and date. Previous studies conveniently but monotonously applied day and night times set up. This research defined the daytime and nighttime while considering the time of twilight according to the date and the location of ship collision accidents. Classifying the frequency of ship collision accidents with this standard, we conducted a chi-squared test for the difference between daytime and nighttime. The frequencies of ship collision accidents according to daytime and nighttime was compared by season, month, and time, and all of them showed statistically significant differences. The highest number of daytime ship collisions was 11.6 %, in June, and nighttime collisions peaked at 13.7 %, in December. The most frequent hour for daytime ship collisions was 0700h-0800h, at 10.2 %, and nighttime collisions peaked between 0400h-0500h, at 16.9 %. It is clear that the criteria used in previous studies cited was applied without any theoretical basis and likely only for the convenience of the researchers. It was found that results depend on what criteria are applied to the same research data. This study shows that statistical analyses of marine accidents, traffic volume, and congestion density should be carried out quantitatively while considering daytime and nighttime hours for each particular location and date.

• Journal of Astronomy and Space Sciences
• /
• v.30 no.3
• /
• pp.169-174
• /
• 2013

BOH magnetometer was installed at Mt. Bohyun in 2007 and has provided continuous dataset for 3-axis geomagnetic field over the South Korea. We have calculated real-time K-index based on BOH magnetic field data using well-known FMI method. Local K-index is calculated eight times a day, per every three hours. To calculate K-index, it is critical to get the Quiet Day Curve (QDC). For QDC calculation, we take the previous one month's average of H-component. In this paper, we compared four geomagnetic stations' magnetic field data over South Korea and Japan and K-indices of each stations; Bohyun, Gangneung, Jeju, and Kakioka for two years data, 2011-2012. To investigate the difference depending on the latitude, longitude and local time in more detail, we compare K-index on International Quiet Days (IQDs) and International Disturbed Days (IDDs). As a result, we report the correlation between local K-indices are higher than those between Kp and local K-indices, and the correlation is much better after sunset than after sunrise. As the geomagnetic activity becomes stronger, the correlation between the local K-indices and global Kp-index become higher.

• Solar Energy
• /
• v.19 no.4
• /
• pp.81-91
• /
• 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 Environmental Impact Assessment
• /
• v.4 no.1
• /
• pp.65-78
• /
• 1995

The resident attitude for preservation and development of amenity in Eulsuk island and its downstream area at estuary of Nakdong river in Korea were investigated by the questionnaires and the field surveys. Based on the results, the characteristics of this study area are the natural ecological preservation area, natural environmental preservation area and curtural assets for migratory birds. And there are a estuary bank, a Dadae beach and a Molundae park. Special amenities are (1) the light (sunrise, sunset etc), (2) the water(river, sea etc.), (3) the air(fresh wind, beautiful sound etc.), (4) the land space(beautiful view, recreation field, reed area, pine forest etc.) and (5) the stream(dancing of migratory birds, water flow, folk dance, history remains etc.). But at present, the environmental qualities as health, aesthetics safety, amenity and culture are deteriorated by development. So the number of migratory birds are decreasing. The residents desired that in future this area be use for the recreation space, the park and the natural leaning fields etc, as well as the restoration of destroyed resources.

• Journal of Forest and Environmental Science
• /
• v.34 no.1
• /
• pp.71-76
• /
• 2018

The long-tailed goral (Naemorhedus caudatus) has slowly recolonized habitats in South Korea. Because it is necessary to know the status of groups in recolonized areas, we determined detection frequencies and group sizes using camera trapping, a non-invasive monitoring method. In Uljin, a far southern goral habitat in South Korea, we used a Moultrie 5.0 camera and mineral block as bait during the breeding season in BaekAm Mountain (148 days, 18 May to 11 October) and Geumjong Mountain (63 days, 18 May to 18 July) in 2010. Totally, 155 images were captured in BaekAm Mountain, whereas four images were captured in Geumjong Mountain. The species was most frequently detected at sunrise (05:00-08:00) and sunset (18:00-20:00). Through population structure evaluation, we identified at least 11 individuals, including one solitary mature male, four females, four kids, and two solitary subadults in BaekAm Mountain. However, in Geumjong Mountain, we identified only two individuals (female with kid). Monitoring efficiency in the recolonized area differed depending on population density and habitat conditions. Because we could evaluate the population structure, and behavioral patterns in the study sites, monitoring using camera traps could be applied for the recolonized habitats in South Korea.

• Journal of Environmental Science International
• /
• v.6 no.6
• /
• pp.613-628
• /
• 1997

Diurnal variations of air quality due to the characteristic features of local weather phenomena over Kunsan, Taegu, and Pohang are analyzed using various synoptic wand fields and the characteristics of local weather during the period of 1990 to 1992. The air pollutants analyzed are sulfur dioxide($SO2_$), nitrogen dioxide($NO_2$), and oxidants ($0_3$). The synoptic wind fields estimated at over the 850 hPa geopotential height are divided in terms of four wand directions and two wand speed categories for each season. The synoptic weather conditions are also classified Into two categories depending on the 850 hPa cloud amounts. The present study shows that the $SO_2$ concentration over Kunsan, and Taegu was maximum at the two or three hours after sunrise and second primary was three or flour hours after sunset. On the other hand, Its concentration over Kunsan was malnmum at 1900 LST or 2000 LST The $O_3$ concentration over the three cities shows Its mapdmum In the afternoon when the solar radiation is strong. The $NO_2$ concentration over Kansan shows in reverse proportion to the $O_3$ concentration over the Kunsan.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.21 no.3
• /
• pp.306-314
• /
• 2018

In maritime environment, it is necessary to understand the characteristics of sunglint since it may degrade the target detection performance of the infrared sensor mounted weapons. In this paper, sunglint in LWIR band is modeled using the slope distribution of the sea surface, and is verified by comparing the radiance of a simulated result with that of the real world. According to the simulation, sunglint is critical when the solar zenith angle is over $60^{\circ}$. The peak radiance of sunglint grows as the solar zenith angle increases until it reaches $83^{\circ}$ and has a large difference depending on the solar zenith angle when the wind speed is small. Finally, seasonal and temporal characteristics of sunglint effects are analyzed. In summer, sunglint is dominant in the horizon near the solar azimuth right after sunrise and before sunset. However, in winter, the influence of sunglint lasts even during the daytime since the elevation of the sun is much lower than in summer.

• Proceedings of the Korean Institute of Interior Design Conference
• /
• 2006.11a
• /
• pp.121-124
• /
• 2006

This study was done with a goal to observe changes of color emotions according to time flow and light changes as well as to study its moaning of color experience of natural scene to modern city dwellers with artificial surroundings. Individuals develop various feelings after seeing a color, but there is sometimes a common feeling raised among these various feelings. This study aims to investigate the influence of natural colors of surroundings on the emotions of human beings. First of all, we tried to discover how feelings change after a person is reminded of a color through an experience (recognition) of a natural color. Second, differences in feelings resulting from color perception are analyzed after time passes (sunrise, daytime, and sunset) and the colors of natural surroundings change accordingly. Survey was done in the period of $Jul.8^{th}$ to $10^{th}$, 2005 with 100 people (55 male and 45 female) in various professions and various ages between twenties to forties as respondent.

• Journal of the Korean Solar Energy Society
• /
• v.28 no.4
• /
• pp.50-55
• /
• 2008

The Storage efficiency of concentric evacuated tube solar collector is tested for one year from January 1st to December 31st under the real sun condition. The testing equipment is operated continuously for three days without cooling the storage tank. Daily storage efficiency is obtained from dividing stored energy in the storage tank by solar insolation on the solar collector for each day. Daily averaged temperature of the storage tank is lowest in January and highest in August. Monthly averaged storage efficiency is also lowest in November and highest in June. Therefore, it can be said that the storage temperature and the storage efficiency are roughly proportional to outdoor temperature. Furthermore, the daily storage efficiency is reversely proportional to $(T_s-T_a)/I_c$ where $T_s$ and $T_a$ are daily averaged storage temperature and outdoor temperature from sunrise to sunset, and $I_c$ is total insolation on the solar collector for a day.