• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.4
• /
• pp.601-609
• /
• 2022

Jack-up drilling rigs are mobile offshore platforms widely used in the offshore oil and gas exploration industry. These are independent, three-legged, self-elevating units with a cantilevered drilling facility for drilling and production. A typical jack-up rig includes a triangular hull, a tower derrick, a cantilever, a jackcase, living quarters and legs which comprise three-chord, open-truss, X-braced structure with a spudcan. Generally, jack-up rigs can only operate in water depths ranging from 130m to 170m. Recently, there has been an increasing demand for jack-up rigs for operating at deeper water levels and harsher environmental conditions such as waves, currents and wind loads. All static and dynamic loads are supported through legs in the jack-up mode. The most important issue by society is to secure the safety of the leg structure against collision that causes large instantaneous impact energy. In this study, nonlinear FE -analysis and verification of the requirement against collision for 35MJ recommended by DNV was performed using LS-Dyna software. The colliding ship used a 7,500ton of shore supply vessel, and five scenarios of collisions were selected. From the results, all conditions do not satisfy the class requirement of 35MJ. The loading conditions associated with chord collision are reasonable collision energy of 15M and brace collisions are 6MJ. Therefore, it can be confirmed that the identical collision criteria by DNV need to be modified based on collision scenarios and colliding members.

• Korean Journal of Remote Sensing
• /
• v.38 no.5_3
• /
• pp.851-861
• /
• 2022

In this study, we analyzed the effects of trees planted in urban areas on PM_2.5 reduction using a computational fluid dynamics (CFD) model. For realistic numerical simulations, the meteorological components(e.g., wind velocity components and air temperatures) predicted by the local data assimilation and prediction system (LDAPS), an operational model of the Korea Meteorological Administration, were used as the initial and boundary conditions of the CFD model. The CFD model was validated against, the PM_2.5 concentrations measured by the sensor networks. To investigate the effects of trees on the PM_2.5 reduction, we conducted the numerical simulations for three configurations of the buildings and trees: i) no tree (NT), ii) trees with only drag effect (TD), and iii) trees with the drag and dry-deposition effects (DD). The results showed that the trees in the target area significantly reduced the PM_2.5 concentrations via the dry-deposition process. The PM_2.5 concentration averaged over the domain in DD was reduced by 5.7 ㎍ m^-3 compared to that in TD.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.15 no.5
• /
• pp.405-412
• /
• 2022

This paper studies the method of estimating power loss and classifying the factors for improving the power generation efficiency through O&M. It is installed under various climatic conditions worldwide, operational and maintenance technologies suitable for the characteristics of the installation location are required. Existing studies related to solar power generation efficiency have been actively quantifying the impact on short-term losses by environmental factors such as high temperature, dust accumulation, precipitation, humidity, and wind speed, but analysis of the overall impact from a long-term operation perspective is limited. In this study, the potential for efficiency improvement was analyzed by re-establishing a loss classification system according to the power flow of solar power to derive a comprehensive efficiency model for long-term operation and estimating power loss through a case study for each region where climate conditions are classified. As a result of the analysis, the average annual potential for improving soiling loss was 26.9%, Death Valley 7.2%, and Seoul 3.8%. Aging losses was 6.6% in the 20th year as a cumulative. The average annual potential due to temperature loss was 2.9 % for Doha, 1.9% for Death Valley, and 0.2% for Seoul.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.2
• /
• pp.363-368
• /
• 2021

Ship engine rooms have improved automation systems owing to the advancement of technology. However, there are many variables at sea, such as wind, waves, vibration, and equipment aging, which cause loosening, cutting, and leakage, which are not measured by automated systems. There are cases in which only one engineer is available for patrolling. This entails many risk factors in the engine room, where rotating equipment is operating at high temperature and high pressure. When the engineer patrols, he uses his five senses, with particular high dependence on vision. We hereby present a preliminary study to implement an engine-room patrol robot that detects and informs the machine room while a robot patrols the engine room. Images of ship engine-room equipment were classified using a convolutional neural network (CNN). After constructing the image dataset of the ship engine room, the network was trained with a pre-trained CNN model. Classification performance of the trained model showed high reproducibility. Images were visualized with a class activation map. Although it cannot be generalized because the amount of data was limited, it is thought that if the data of each ship were learned through transfer learning, a model suitable for the characteristics of each ship could be constructed with little time and cost expenditure.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.33 no.2
• /
• pp.138-145
• /
• 1988

The effect of directions (north to south vs east to west) of planting row, planting intensities (10/15, 15/15, 20/15, 25/15 cm/cm) and the number of rows consecutively (1,2, 3,4) for both the CMS and pollen parent in alternation, on the seed yield of CMS of rice was tested with a breeding line V20A/Iri342$\^$*8/. When the planting row was made in vertical direction to the wind direction during anthesis, the seed yield was higher than the other direction regardless the planting densities and number of rows consecutive. Seed yield increased as high as 46.9%. The higher planting intensities up to 10/15 cm/cm yielded the higher hybrid seeds. The highest yield was 81.2 kg/ha. The yield variation among plants within a plot and among the plants within a replication was relatively large. Increased pollen parent row numbers caused increased grain fertility per plant, but the seed yield was increased by reduced pollen parent row number. Reduced CMS parental row numbers caused increased grain fertility per plant, but the seed yield was increased by increased CMS parental row numbers. Considering the hybrid seed yield, parental seed yield and operational convenience, 4 rows of CMS and 1 row of pollen parent in alternate with 20/15 or 25/15 (cm/cm) planting densities seemed to be the rational layout.

• Korean Journal of Plant Resources
• /
• v.36 no.2
• /
• pp.133-171
• /
• 2023

This study was conducted to prepare basic data by analyzing the biological values and environmental factors of algific talus slope in order to respond to climate change due to the greenhouse effect, and to establish plans for forest biodiversity preserving and managing. Meteorological information was measured and the flora of vascular plants were investigated for six algific talus slope by seasonally from 2020 to 2021. As a result of the investigation, the temperature of all 6 algific talus slope was lower than that of the area where the algific talus slope was located in summer, and flora was 101 families, 350 genera, 621 species, 18 subspecies, 57 variants, 7 varieties, 703 taxa. In sum, it is judged that the algific talus slope has sufficient reasons and value to be preserved because it has excellent micrometeorological value from the cold wind blowing in summer and phytogeographical value in which various plants live in a small area. However, in spite of such an important area, the management of algific talus slope is insufficient, and the algific talus slope is damaged or the ecosystem of the algific talus slope is disturbed. Therefore, it is necessary to establish a systematic conservation and management plan by designating algific talus slope as a forest genetic resource reserve and OECM.

• Journal of Marine Life Science
• /
• v.8 no.1
• /
• pp.68-77
• /
• 2023

In this study, we investigated the quantitative distribution of microplastics in the surface seawater at 8 points near the Taean Peninsula using fluorescence staining. The study revealed a detection range of microplastics from 0 to 360.5 particles/l, with an average of 149.7 ± 46.0 particles/l. When classifying the microplastics by size, it was found that particles smaller than 50 ㎛ were dominant, although there were differences at Site 3. Moreover, it was not possible to identify clear correlations when comparing the number of microplastics based on collection area and particle size. Various physical and chemical factors, including plastic material, dynamic ocean conditions (such as currents, wind, waves, tides), geological characteristics (topography, slope), sediment materials including coastal organisms, human activities (fishing, development, tourism), and weather conditions (floods, rainfall), affect the behavior of microplastics. Therefore, future efforts should focus on standardizing quantitative analysis methods and conducting fundamental research on microplastic monitoring, including the analysis of environmental factors.

• Journal of Navigation and Port Research
• /
• v.47 no.4
• /
• pp.231-238
• /
• 2023

The position of a light buoy is always flexible due to the influence of external forces such as tides and wind. The position can be checked through AIS (Automatic Identification System) or RTU (Remote Terminal Unit) for AtoN. As a result of analyzing the position data for the last five years (2017-2021) of a light buoy, the average position error was 15.4%. It is necessary to detect position error data and obtain refined position data to prevent navigation safety accidents and management. This study aimed to detect position error data and obtain refined position data by DBSCAN Clustering position data obtained through AIS or RTU for AtoN. For this purpose, 21 position data of Gunsan Port No. 1 light buoy where RTU was installed among western waters with the most position errors were DBSCAN clustered using Python library. The minPts required for DBSCAN Clustering applied the value commonly used for two-dimensional data. Epsilon was calculated and its value was applied using the k-NN (nearest neighbor) algorithm. As a result of DBSCAN Clustering, position error data that did not satisfy minPts and epsilon were detected and refined position data were acquired. This study can be used as asic data for obtaining reliable position data of a light buoy installed with AIS or RTU for AtoN. It is expected to be of great help in preventing navigation safety accidents.

• Journal of Practical Agriculture & Fisheries Research
• /
• v.13 no.1
• /
• pp.19-26
• /
• 2011

The machine transplanted rice has highly extended in the Republic of Korea due to a wage rise since 1976 and thus rice seedling raising nursery method has shifted from field into polyethylene film house. The rice seedling grown under a polyethylene film house was weak and tall because of limited sunlight and wind and so there was so complained among rice growing farmers in terms of missing hill and broken seedling after machine transplanting. In recent iron-coated seedling has reported on healthier and stronger than that of polyethylene film house. These seedlings were more stiff and thus more easy to handle during transplanting and less missing hills. The Iron-coated seed was proven to more stiff like seedling height, root growth and weight of shoot and root growth. This was more convenient during transfer of seedling raising box im machine transplanting. Thus, this study was carried out to grow a stiff and healthy seedling growth and development for machine transplanting. There were a normal seed germination and sprouting after iron-coated seeds treatment and this seedling was smaller and stiffer than that of untreated control. The leaf number and root growth of seedling which was iron-coated seeds would be better and total seedling fresh weight was greater than that of untreated control.

• Korean Journal of Environmental Agriculture
• /
• v.42 no.1
• /
• pp.28-34
• /
• 2023

Nitrogen fertilizers applied to agricultural lands for crop cultivation can be volatilized as ammonia. The released ammonia can catalyze the formation of ultrafine dust (particulate matter, PM2.5), classified as a short-lived climate change pollutant, in the atmosphere. Currently, one of the prominent methods for fertilizer application in agricultural lands is soil surface application, which comprises spraying the fertilizers onto the soil surface, followed by mixing the fertilizers with the soil. Owing to the low nitrogen absorption rate of crops, when nitrogen fertilizers are applied in this manner, they can be lost from land surfaces through volatilization. Therefore, investigating a new fertilization method to reduce ammonia emissions and increase the fertilizer utilization efficiency of crops is necessary. In this study, to develop a method for reducing ammonia emissions from nitrogen fertilizers applied to soil surfaces, deep fertilization was conducted using a newly developed deep fertilization device, and ammonia emissions from barley, garlic, and onion fields were examined. Conventional fertilization (surface application) and deep fertilization (soil depth of 25 cm) were conducted for analysis. The fertilization rate was 100% of the standard fertilization rate used for barley, and deep fertilization of N, P, and K fertilizers was implemented. Ammonia emissions were collected using a wind tunnel chamber, and quantified subsequently susing the indole-phenol blue method. Ammonia emissions released from the basal fertilizer application persisted for approximately 58 d, beginning from approximately 3 d after fertilization in conventional treatments; however, ammonia was not released from deep fertilization. Moreover, barley, garlic, and onion yields were higher in the deep fertilization treatment than in the conventional fertilization treatment. In conclusion, a new fertilization method was identified as an alternative to the current approach of spraying fertilizers on the soil surface. This new method, which involves injecting nitrogen fertilizers at a soil depth of 25 cm, has the potential to reduce ammonia emissions and increase the yields of barley, garlic, and onion.