• Korean Journal of Environmental Agriculture
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• v.7 no.1
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• pp.14-20
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• 1988

The effect of polyethylene film(P.E.) mulching on the degradation of alachlor(N-methoxymethyl-2, 6-diethyl ${\alpha}-chloroacetoanilide$), pendimethalin(3, 4-dimethyl-2, 6-dinitro-N-l-ethylpropylanilide) and diphenamid(N,N-dimethyl-2, 2-diphenylacetamide) in red pepper, peanut, and sesame fields was investigated. In soils under the non-mulching condition the half-lives of alachlor, pendimethalin and diphenamid were 3, 37 and $24{\sim}46$ days, respectively. However, the half-lives of those under the P.E. mulching condition were longer than under the non-mulching condition. The differences in the half-lives between P.E. mulching and non-mulching conditions were about 30 days for pendimethalin and from 20 to 90 days for diphenamid. However, the half-life of alachlor was hardly affected by P.E. mulching. Pendimethalin and alachlor were not detected in the harvasted red peppers, peanuts and sesame under P.E. mulching and non-mulching conditions. But, the residue of diphenamid in peanuts was 0. 147 ppm under the P.E. mulching condition and 0.071 ppm under the non-mulching condition, and the residue of diphenamid in sesame was 0.022 ppm under the P.E. mulching condition and 0.129 ppm under the non-mulching condition. The amounts, however, were below the tolerance limits for pesticide residue.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.143-159
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• 2024

Natural aggregate is an essential resource for human activities, closely related to construction. The aggregate demand has been increasing annually, and due to the nature of the resource, it is difficult to procure from distant locations. This study identifies the distribution and characteristics of aggregate-bearing areas as part of a municipal-level aggregate resource survey conducted in Nonsan City, Korea, in 2023. Nonsan City is located approximately 35 km straight distance from the Geum River estuary and lies at the passageway of the main stream of the Geum River. The topography of Nonsan City features eastern mountainous areas and western plains, creating an east-high-west-low geomorphic setting, with 33 streams distributed across the city, including tributaries of the Geum River like Nonsan Stream, Noseong Stream, and Ganggyeong Stream. All streams originate from the highlands in the north and east, converge with Nonsan Stream, and then join the west bank of the main stream of the Geum River at the western boundary of Nonsan City. Drilling core results show shallow depths in the highlands to the north and east, deepening towards the west, reaching a maximum depth of 25 m near the main stream of the Geum River. The total reserve of land aggregates is calculated to be 246,789,000 m³, with a developable amount of 172,750,000 m³. The total reserve of river aggregates is 5,236,000 m³, with a developable amount of 3,765,000 m³. The distribution of aggregates varies according to the geomorphic, geologic, and development pattern of the river system. Reserves are scarce in mountainous areas but are abundant in regions with rivers and wide alluvial plains, although reserves appear at depths greater than 4m. The distribution of aggregate resources in Nonsan City is influenced by stream activities and sea level changes, with the tidal range of the Yellow Sea acting as an unfavorable condition for the preservation of aggregate resources.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.181-185
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• 2006

A liquid rocket fuel-rich gas generator developed for the first time in the country can produce combustion gas over the rate of 4 kg/s at 900 K and 58 bar. The gas can be used not only for driving a turbopump but also for providing heat source for propellant supply tanks. The final design of the gas generator has been fixed based on the concept and preliminary development tests, and was validated through structure and heat transfer analysis. The manufacturing involves precision machining, special surface finish, and welding techniques. The final assessment on the characteristics of ignition and combustion had been carried out through five combustion tests. This concluded that the present product satisfies the development requirements.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.4
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• pp.602-610
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• 2018

The model predictive control is an effective method to optimize the current control input that predicts the current control state and the future error using the predictive model of the control system when the reference trajectory is known. Since the control input can not have a physically infinitely large value, a predictive controller design with constraints should be considered. In addition, the reference model $A_r$ and the weight matrices Q, R that determine the control performance of the predictive controller are not optimized as arbitrarily designated should be considered in the controller design. In this study, we construct a predictive controller of a mobile robot by transforming it into a quadratic programming problem with constraints, The control performance of the mobile robot can be improved by optimizing the control parameters of the predictive controller that determines the control performance of the mobile robot using genetic algorithm. Through the computer simulation, the superiority of the proposed method is confirmed by comparing with the existing method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.17-24
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• 2008

This paper deals with a millimeter wave source which is utilizing sub-harmonic injection-synchronization technique. A 8.7GHz oscillator with MES-FET is fabricated, and is driven as a harmonic output oscillator at 17.4GHz by means of sub-harmonic injection-synchronization. The oscillator operates as a multiplier as well as oscillator in this system. Adopting this technique, we can obtain a high stable, high frequency millimeter wave source even though self-oscillating frequency of an oscillator is relatively low. In the experiments, the range of injection-synchronization is about 26MHz and is proportional to the input sub-harmonic power. From the spectrum analysis of the 2nd harmonic output. we blow that the phase noise of the harmonic oscillator is remarkably decreased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.303-311
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• 2018

The aim of this study was to investigate vitamin D status and factors associated with vitamin D deficiency among Koreans in their using Korean National Health and Nutrition Examination Survey (KNHANES) V. The subjects were 1,837 people who were 20-29 years old. The data were analyzed by ${\chi}^2$ test and multiple logistic regression analysis using weighted composite sample analysis. Vitamin D deficiency was reveled in 84.2% of subjects; 88.6% of women and 79.4% of men showed deficiency. In the multiple logistic regression analysis, the risk for vitamin D deficiency was higher in women (OR 1.84; 95% CI 1.31-2.56), non-married (OR 2.12; 95% CI 1.41-3.19), poor subjective health status (OR 1.94; 95% CI 1.16-3.25), and in the absence of moderate to vigorous physical activity (OR 3.38; 95% CI 1.85-6.16). Continued research on vitamin D levels at this time is needed since vitamin D deficiency among Koreans in their twenties will exacerbate health problems, both individually and socially. In addition, vitamin D has been shown to be closely related to time of exposure to sunlight and physical activity. Therefore, it is thought that long-term and planned efforts should be made at the national level, such as establishing schools and workplaces in which those in their twenties can perform outdoor activities and moderate to vigorous physical activity.

• The Korean Journal of Quaternary Research
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• v.21 no.1
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• pp.37-45
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• 2007

Skull base height increases significantly with better nutrition and health conditions. With coordinate caliper or by subtraction, skull base height is easily measured. To examine nutrition and health condition of MIA(missing in action) during the Korean War and people who lived during the 17-18 centry of the Late Chosun. This study is focused on the change of skull base height through time as seen in comparing 83 MIA cranium and 12 17-18 centry cranium of Korea with 219 modern American middle class adult cranium(Terry Collection and forensic skeleton). To sum up, nutritional condition of MIA is not significantly changed, as seen in comparing with nutritional condition of 17-18 century people.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.1
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• pp.69-81
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• 2021

The exposed rocks in the Zacatecas state include mainly Mesozoic sedimentary and volcanic, Cenozoic volcanic and plutonic rocks. Paleozoic metamorphic rocks found in the northwestern portion of the state are considered as the most ancient rocks. These rocks correspond to the Caopas Formation which underlays the Later Paleozoic Rodeo Formation. The Mesozoic sequences are represented by a marine sedimentary sequence of the Later Triassic and the red beds of the Triassic-Jurassic Nazas Formation. The marine sediments of the Upper Jurassic overlay the Nazas Formation or metamorphic rocks from the Paleozoic. The Cretaceous sequences comprises marine sedimentary rocks in the north and northeast, and a volcanosedimentary set in the center and southeast. The Cenozoic is represented by volcanic nondifferentiated rocks, intrusive igneous rocks of acid and intermediate composition, and continental conglomerates with evaporitic sediments. The Quarternary sequences includes basalts, piedmont deposits, alluviums and occasionally, layers of evaporites and saltpeter. Furthermore, a great diversity of mineral deposits of both metallic and nonmetallic types occur in Zacatecas state. The rocks composing these deposits are extremely varied and include formations from Paleozoic to Tertiary. The mineralization age of ore deposits corresponds to the Tertiary in approximately 90%, and their genesis is mainly considered as epigenetic.

• The Korean Journal of Quaternary Research
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• v.7 no.1
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• pp.1-26
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• 1993

The estimation of the Last Interglacial sea level was made by using the thalassostatic terrace which had been developed in the lower reach of Namdaechon river in Kangneung, eastern coastal area of Korea. The fluvial terraces, which have been developed since late Pleistocene, were investigated. The main findings were as follows; 1) That Kangneung terrace I had been formed in the climax period of the Last Interglacial (Oxygen isotope stage 5e) was revealed. It was estimated that Kangneung terrace II had been formed during a certain warmer period between the climax period of the Last Interglacial and the early Last Glacial(probably Oxygen isotope stage 5c or 5a). 2) Being judged from the relative heights of the Kangneung terrace I and II, the sea levels of the formation periods of these terraces were estimated to have been relatively 17~20m and l0m higher than the present sea level, respectively. 3) The formation periods of the Wangsan terrace I and II were supposed to be the early and late Last Glacial respectively, being judged from the following 3 details ; a) the characteristics of the terrace deposits, b) the relation Wangsan terrace II to the buried valley floor, and c) the cross phenomena of the above two terraces to the Kangneung terraces. 4) The formation period of the pseudogleyed red soil in the Kangneung terrace I was estimated to be the middle or late period of the Last Interglacial.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.4
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• pp.369-379
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• 2003

Analysis of high-resolution seismic profiles and sediment data from the southeastern continental shelf of Korea reveals that the late Quaternary deposits consist of a set of lowstand (LST), transgressive (TST), and highstand systems tracts (HST) that corresponds to the sea-level change after the Last Glacial Maximum. LST (Unit I) above the sequence boundary consists of sandy mud or muddy sand deposited during the last glacial period and is confined to the shelf margin and trough region. TST (Unit II) between transgressive surface and maximum flooding surface consists of sandy sediments deposited during the postglacial transgression (15,000-6,000 yr BP). Although TST is widely distributed on the shelf, it is much thinner than LST and HST. On the basis of distribution pattern, TST can be divided into three sub-units: early TST (Unit IIa) on the shelf margin, middle TST (Unit IIb) on the mid-shelf, and late TST (Unit IIc) on the inner shelf, respectively. These are characterized by a backstepping depositional arrangement. HST(Unit III) above the maximum flooding surface is composed of the fine-grained sediments deposited during the last 6000 yrs when sea level was close to the present level and its distribution is restricted to the inner shelf along the coast.