• Journal of Korea Port Economic Association
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• v.39 no.2
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• pp.129-141
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• 2023

This study analyzes the dynamic characteristics of daily freight rates of dry bulk and tanker shipping markets and their forecasting accuracy by using the error correction models. In order to calculate the error terms from the co-integrated time series, this study uses the common stochastic trend model (CSTM model) and vector error correction model (VECM model). First, the error correction model using the error term from the CSTM model yields more appropriate results of adjustment speed coefficient than one using the error term from the VECM model. Furthermore, according to the adjusted determination coefficients (adjR²), the error correction model of CSTM-model error term shows more model fitness than that of VECM-model error term. Second, according to the criteria of mean absolute error (MAE) and mean absolute scaled error (MASE) which measure the forecasting accuracy, the results show that the error correction model with CSTM-model error term produces more accurate forecasts than that of VECM-model error term in the 12 cases among the total 15 cases. This study proposes the analysis and forecast tasks 1) using both of the CSTM-model and VECM-model error terms at the same time and 2) incorporating additional data of commodity and energy markets, and 3) differentiating the adjustment speed coefficients based the sign of the error term as the future research topics.

• Korean Journal of Remote Sensing
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• v.39 no.5_4
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• pp.1075-1084
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• 2023

Satellite-derived data is collected by observing the Earth and is used in various fields such as national defense, natural disasters, location-based services, infrastructure, environment, energy, marine, and insurance. This study aims to present the virtuous cycle structure of the satellite information data industry and the business ecosystem model of the industry. As a research method, cases were collected and categorized from the following areas: literature, online, application, and content. The results show that the ecosystem model of the satellite information data industry provides an approach to content services in public and commercial areas, and develops various algorithmic technologies to facilitate content production and services at the level of complex general-purpose technologies. Second, in terms of content typology, satellite information data can be subdivided into monitoring content, urban space monitoring content, and satellite information content. Third, the consumption value of satellite content could be subdivided into informational value, environmental, social and governance (ESG) value, educational value, and content value. In order to expand the global content market, Korea will need to focus on creating an ecosystem for the satellite information industry and discovering differentiated content. It will also need to increase the popularization and accessibility of data to the general public and promote the Korean K-Satellite Information Data Industry ecosystem through government support, policy efforts, and policies such as establishing legal systems, increasing investment, and training human resources.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.483-490
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• 2022

Floating LiDAR is a system that provides a new paradigm for wind condition observation, which is essential when creating an offshore wind farm. As it can save time and money, minimize environmental impact, and even reduce backlash from local communities, it is emerging as the industry standard. However, the design and verification of a stable platform is very important, as disturbance factors caused by fluctuations of the buoy affect the reliability of observation data. In Korea, due to the nation's late entry into the technology, a number of foreign equipment manufacturers are dominating the domestic market. The west coast of Korea is a shallow sea environment with a very large tidal difference, so strong currents repeatedly appear depending on the region, and waves of strong energy that differ by season are formed. This paper conducted a study examining buoys suitable for LiDAR operation in the waters of Korea, which have such complex environmental characteristics. In this paper, we will introduce examples of optimized design and verification of ship-type buoys, which were applied first, and derive important concepts that will serve as the basis for the development of various platforms in the future.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.246-256
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• 2006

The plane wave reflection coefficient is an acoustic property containing all the information concerning the ocean bottom and can be used as an input parameter to various acoustic propagation models. In this paper, we measure the plane wave reflection coefficient, the sound speed, thd the attenuation for saturated granular medium in the water tank. Three kinds of glass beads and natural sand are used as the granular medium. The reflection experiment is performed with the sinusoidal tone bursts of 100 kHz at incident angles from 28 to 53 degrees, and the sound speed and attenuation experiment are performed also with the same signal. From the measured reflection signal, the reflection coefficient is calculated with the self calibration method and the experimental uncertainties are discussed. The sound speed and the attenuation measurements are used for the estimation of the porosity and permeability, the main Biot parameters. The estimated values are compared to the directly measured values and used as input values to the Biot theory in order to calculate the theoretical reflection coefficient. Finally, the reflection coefficient predicted by Biot theory is compared to the measured reflection coefficient and their characteristics are discussed.

• Resources Recycling
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• v.33 no.3
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• pp.38-47
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• 2024

Molybdenite is the primary molybdenum resource and is extracted via flotation due to its unique hydrophobic surface. Meanwhile, the grade and crystal size of mined molybdenite are decreasing. As a result, the size of the molybdenum ore required for liberation is decreasing, and the flotation process's feed size input is also decreasing. Therefore, in order to secure molybdenum, it is necessary to perform research on the flotation for the fine molybdenite. In this study, we developed a method to enhance the flotation efficiency of fine molybdenite particles in the range of 5-30 ㎛. The methodology involved implementing bubble size reduction and particle aggregation. Through simulations of bubble-particle collision probability and flotation experiments, we were able to find the ranges of bubble size and particle aggregate size that make fine particles float more effectively. This range provided the conditions for effective flotation of fine molybdenite particles. Therefore, we will implement the flotation conditions established in this study for fine molybdenum ore to improve the flotation process in molybdenum mineral processing plants in the future.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.3
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• pp.147-153
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• 2013

There exist various types of the WEC (Wave Energy Converter), and among them, the point absorber is the most popularly investigated type. However, it is difficult to find examples of systematically measured data analysis for the design of the point absorber type of power buoy in the world. The study investigates the wave load acting on the point absorber type resonance power buoy wave energy extraction system proposed by Kweon et al. (2010). This study analyzes the time series spectra with respect to the three-year wave data (2002.05.01~2005.03.29) measured using the pressure type wave gage at the seaside of north breakwater of Hupo harbor located in the east coast of the Korean peninsula. From the analysis results, it could be deduced that monthly wave period and wave height variations were apparent and that monthly wave powers were unevenly distributed annually. The average wave steepness of the usual wave was 0.01, lower than that of the wind wave range of 0.02-0.04. The mode of the average wave period has the value of 5.31 sec, while mode of the wave height of the applicable period has the value of 0.29 m. The occurrence probability of the peak period is a bi-modal type, with a mode value between 4.47 sec and 6.78 sec. The design wave period can be selected from the above four values of 0.01, 5.31, 4.47, 6.78. About 95% of measured wave heights are below 1 m. Through this study, it was found that a resonance power buoy system is necessary in coastal areas with low wave energy and that the optimal design for overcoming the uneven monthly distribution of wave power is a major task in the development of a WEF (Wave Energy Farm). Finding it impossible to express the average spectrum of the usual wave in terms of the standard spectrum equation, this study proposes a new spectrum equation with three parameters, with which basic data for the prediction of the power production using wave power buoy and the fatigue analysis of the system can be given.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.81-92
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• 2001

According to analyses of high-resolution seismic profiles (air gun, sparker, and SBP) and a deep-drill core(YSDP 105) in the mid-eastern Yellow Sea, stratigraphic and geoacoustic models have been established and seismo-acoustic modeling has been fulfilled using ray tracing of finite element method. Stratigraphic model reflects seismo-, litho-, and chrono-stratigraphic sequences formed under a significant influence of Quaternary glacio-eustatic sea-level fluctuations. Each sequence consists of terrestrial to very-shallow-marine coarse-grained lowstand systems tract and tidal fine-grained transgressive to highstand systems tract. Based on mean grain-size data (121 samples) of the drill core, bulk density and P-wave velocity of depositional units have been inferred and extrapolated down to a depth of the recovery using the Hamilton's regression equations. As goo-acoustic parameters, the 121 pairs of bulk density and P-wave velocity have been averaged on each unit of the stratigraphic model. As a result of computer ray-tracing simulation of the subsurface strata, we have found that there are complex ray paths and many acoustic-shadow zones owing to the presence of irregular layer boundaries and low-velocity layers.

• The Korean Journal of Air & Space Law and Policy
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• v.35 no.3
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• pp.127-150
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• 2020

A Basic Plan for the Promotion of Space Development (hereinafter referred to as "basic plan"), which prescribes mid- and long-term policy objectives and basic direction-setting on space development every five years, is one of the matters to be deliberated by the National Space Committee. Confirmed February 2018 by the Committee, the 3rd Basic Plan has a unique matter, compared to the 2nd Basic Plan. It is to construct "Korean Positioning System(KPS)". Almost every country in the world including Korea has been relying on GPS. On the occasion of the shooting down of a Korean Air flight 007 by Soviet Russia, GPS Standard Positioning Service has been open to the world. Due to technical errors of GPS or conflict of interests between countries in international relations, however, the above Service can be interrupted at any time. Such cessation might bring extensive damage to the social, economic and security domains of every country. This is why some countries has been constructing an independent global or regional satellite navigation system: EU(Galileo), Russia(Glonass), India(NaVic), Japan(QZSS), and China(Beidou). So does South Korea. Once KPS is built, it is expected to make use of the system in various areas such as transportation, aviation, disaster, construction, defense, ocean, distribution, telecommunication, etc. For this, a pan-governmental governance is needed to be established. And this governance must be based on the law. Korea is richly experienced in developing and operating individually satellite itself, but it has little experience in the simultaneous development and operation of the satellites, ground, and users systems, such as KPS. Therefore we need to review overseas cases, in order to minimize trial and error. U.S. GPS is a classic example.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.181-194
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• 2002

Parasitism is a one-sided relationship between two organisms in which one benefits at the expense of the other. Parasitic dinoflagellates, particularly species of Amoebophrya, have long been thought to be a potential biological agent for controlling harmful algal bloom(HAB). Amoebophrya infections have been reported for over 40 species representing more than 24 dinoflagellate genera including a few toxic species. Parasitic dinoflagellates Amoebophrya spp. have a relatively simple life cycle consisting of an infective dispersal stage (dinospore), an intracellular growth stage(trophont), and an extracellular reproductive stage(vermiform). Biology of dinospores such as infectivity, survival, and ability to successfully infect host cells differs among dinoflagellate host-parasite systems. There are growing reports that Amoebophrya spp.(previously, collectively known as Amoebophrya ceratii) exhibit the strong host specificity and would be a species complex composed of several host-specific taxa, based on the marked differences in host-parasite biology, cross infection, and molecular genetic data. Dinoflagellates become reproductively incompetent and are eventually killed by the parasite once infected. During the infection cycle of the parasite, the infected host exhibits ecophysiologically different patterns from those of uninfected host in various ways. Photosynthetic performance in autotrophic dinoflagellates can be significantly altered following infection by parasitic dinoflagellate Amoebophrya, with the magnitude of the effects over the infection cycle of the parasite depending on the site of infection. Parasitism by the parasitic dinoflagellate Amoebophrya could have significant impacts on host behavior such as diel vertical migration. Parasitic dinoflagellates may not only stimulate rapid cycling of dissolved organic materials and/or trace metals but also would repackage the relatively large sized host biomass into a number of smaller dinospores, thereby leading to better retention of host's material and energy within the microbial loop. To better understand the roles of parasites in plankton ecology and harmful algal dynamics, further research on a variety of dinoflagellate host-parasite systems is needed.

• 한국해양학회지
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• v.30 no.3
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• pp.184-196
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• 1995

The line-SW is located in the mouth of Gomso Bay (20 Km long and 5-8 Km wide),west coast of Korea. This area is composed of sand flat, mud flat, sand shoal and chenier, The difference of physical, geological and geomorphic conditions in subenvironments of the bay may control and produce distingtive foraminiferal populations and assemblages. This study investigates whether five a priori subenvironments (five local zonations) in Gomso-Bay tidal flat can be distinguished from each other on the basis of total (living plus dead) foraminiferal assemblages. Seventy-four species (67 benthic; 7 planktonic) were recorded in total assemblages of surface sediments from 10 stations. Ammonia beccarii tepida, Discorbis candeiana, Elphidium etigoense and Eponides nipponicus were most dominant species in living and total assemblages. The relative abundance (%) of living population was high at upper flat and decreased from upper to lower flat. The low percentages of living populations in middle to lower flat are probably influenced by the decreasing reproduction of foraminifera caused by high energy condition and addition of dead species from offshore. The occurence of planktonic foraminifera in middle to lower flat (5.3∼6.6%) indicates introduction of planktonic foraminifera from offshore by storm and/or tidal current. The relatively high numbers of species in lower middle to lower flat are probably caused by a mixing of faunas from these areas and offshore. The high numbers of total individuals per 50 ml of sediment in upper flat indicate that this area is a relatively stable environment where waves and currents are protected by the chenier. Five biofacies of the total foraminiferal assemblages were established on the basis of dominant species (those representing more than 20% of the total assemblages in any station) in the five a priori subenvironments recognized along the Line-SW transect in Gomso-Bay tidal flat. Five biofacies are potentially useful in paleoenvironmental interpretation in late Quaternary Gomso-Bay tidal deposits.