• 한국지형학회지
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• 제24권2호
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• pp.65-78
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• 2017

In this study, stable carbon isotopic analysis (22 specimens) and magnetic susceptibility analysis (23 specimens) were conducted out on the specimens collected from two points (trench DT1, DT2) in the floodplain of Jemincheon(hereinafter the Jemin plain) to reconstruct the Holocene Environments (Period I, Period II, Period III) of the Jemin plain in Gongju, Chungnam. The results were as follows: In Period I (approximately 7,480~4,940 yrs B.P.) and especially around 7,480~7,320 yrs B.P., it was cool-dry and there were two minor climate fluctuations. This period received a continuous flow of sediments, rather than massive amounts of sediments due to abrupt flooding, and therefore, there was almost no soilization process. Period II(approximately 4,940~2,600 yrs B.P.) was also relatively cool-dry. However, in Period II b, unlike I, the minor climate fluctuations were less pronounced. In this period, flooding and desiccation repeated, inducing soilization processes especially around 3,160 yrs B.P. In Stage III (~360 yrs B.P.), it was warm and humid compared to II b. However, in III a, there was no inflow of sediments due to irregular flooding, and in fact, soilization process was more manifested than during II b due to the impact of the desiccation environment. However, there were some mass movements from Bonghwang Mt. (a.s.l. 147m) caused by heavy rains and typhoon during III b (approximately 360 yrs B.P.), thus moving a large amount of debris (i.e. gravel), which resulted in sedimentation.

• 한국물환경학회지
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• 제37권6호
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• pp.433-441
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• 2021

The aim of this study was to optimize the ozonation and ceramic membrane integrated process for greywater reclamation. The integrated process is a repeated sequential process of filtration and backwash with the same ceramic membrane. Also, this study used ozone and oxygen gas for the backwashing process to compare backwashing efficiency. The study results revealed that the optimum filtration and backwash time for the process was 10 minutes each when comparing the filtrate flow and membrane recovery rate. The integrated process was operated at three different operating conditions with i) 10 minutes for filtration and 10 minutes for ozonation, ii) 10 minutes for filtration and 10 minute for oxygen aeration, and iii) continuous filtration without any aeration for synthetic greywater. The integrated process with ozone backwashing could produce 0.55 L/min of filtrate with an average of 18.42% permeability recovery, while the oxygen backwashing produced 0.47 L/min and 6.26%, respectively. And without any backwashing, the integrated process could produce 0.29 L/min. This shows that the ozone backwash process is capable of periodically recovering from membrane fouling. The resistance of the fouled membrane was approximately 34.4% for the process with ozone backwashing, whereas the resistance was restored by 10.8% for the process with oxygen backwashing. Despite the periodical ozone backwashing and chemical cleaning, irreversible fouling gradually increased approximately 3 to 4%. Approximately 97.6% and 15% turbidity and TOC were removed by ceramic membrane filtration, respectively. Therefore, the integrated process with ozonation and ceramic membrane filtration is a potential greywater treatment process.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제4권3호
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• pp.104-114
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• 2023

In this study, the distribution, bait preference, hosts, symbionts, habitat status, and cytochrome c oxidase subunit-I sequences of the ant Linepithema humile were analyzed. This species habitat comprised approximately 1.5 km along stone crevices, flower gardens, roadsides, and container yards in the vicinity of Busan station, Korea. Feeding activity of this species was confirmed in 9 species of 7 families of plants. Which was approximately 14% of total flora (63 species of 37 families) in the studied area. Particularly, it was observed that Dendranthema indicum and Camellia japonica were the most frequently visited. Further, we verified that they interacted with four species of aphids. We identified 22 species of ants (17 genera, 4 subfamilies) inhabiting the Busan station area, including L. humile, Tetramorium tsushimae, Nylanderia flavipes and the alien species Paratrechina longicornis. In areas where L. humile was the dominant species, the habitat of local native ants was reduced by approximately 30%. Bait preference was ranked in the following order: jelly, water with glucose (25%), and yogurt, with the highest preference for baits containing sugar and protein. The 630-bp cytochrome c oxidase subunit-I sequences of the local L. humile populations were 99% identical to those of L. humile in the National Center for Biotechnology Information database, and the Argentine ants that invaded Korea had a sequence identical to that of other invasive populations from China, Japan, and New Zealand. As L. humile rapidly increases due to domestic adaptation, continuous monitoring and control strategy for eradication are needed to protect domestic biodiversity.

• 한국환경보건학회지
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• 제45권6호
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• pp.646-657
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• 2019

Objectives: The purpose of this study was to suggest methods to investigate continuous monitoring of concentration levels and assess the exposure of individuals considering the actual time activity of residents for formaldehyde and particulate matter (PM₁₀, PM_2.5) in the indoor and outdoor air of a house, assess the health risks of children and adults based on the results of the exposure assessment, and provide basic data on studies for assessing exposure and health risks in Korea in the future. Methods: The concentration levels of formaldehyde and particulate matter were measured in a family home in Gyeonggi-do Province from April 25 to July 31, 2019, using electrochemical sensors (formaldehyde) and light scattering sensors (PM₁₀, PM_2.5). Risk assessment by the duration of exposure by time activity was performed by dividing between weekdays and weekends, and indoors and outdoors. Results: The greatest level of carcinogenic risk from inhaling formaldehyde was indoors during the weekdays for both children and adults. For children, the risk was at 7.5 per approximately 10,000 people, and for adults, the risk was at 4.1 per approximately 10,000 people. PM₁₀ and PM_2.5 also showed the greatest values indoors during the weekdays, with children at 1.7 people and 1.4 per approximately 100 people, respectively, and adults at 8.2 per approximately 1,000 and 1.8 per approximately 100 people, respectively. Conclusions: The risks of formaldehyde, PM₁₀ and PM_2.5 were shown to be high indoors. Therefore, consideration of exposure assesment for each indoor pollutant and management of indoor air quality is necessary.

• Nuclear Engineering and Technology
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• 제51권8호
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• pp.2018-2025
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• 2019

This study systematically compared two hybrid deterministic/Monte Carlo transport codes, ADVANTG/MCNP and MAVRIC, in solving a difficult shielding problem for a real-world spent fuel storage cask. Both hybrid codes were developed based on the consistent adjoint driven importance sampling (CADIS) methodology but with different implementations. The dose rate distributions on the cask surface were of primary interest and their predicted results were compared with each other and with a straightforward MCNP calculation as a baseline case. Forward-Weighted CADIS was applied for optimization toward uniform statistical uncertainties for all tallies on the cask surface. Both ADVANTG/MCNP and MAVRIC achieved substantial improvements in overall computational efficiencies, especially for gamma-ray transport. Compared with the continuous-energy ADVANTG/MCNP calculations, the coarse-group MAVRIC calculations underestimated the neutron dose rates on the cask's side surface by an approximate factor of two and slightly overestimated the dose rates on the cask's top and side surfaces for fuel gamma and hardware gamma sources because of the impact of multigroup approximation. The fine-group MAVRIC calculations improved to a certain extent and the addition of continuous-energy treatment to the Monte Carlo code in the latest MAVRIC sequence greatly reduced these discrepancies. For the two continuous-energy calculations of ADVANTG/MCNP and MAVRIC, a remaining difference of approximately 30% between the neutron dose rates on the cask's side surface resulted from inconsistent use of thermal scattering treatment of hydrogen in concrete.

• 한국항행학회논문지
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• 제23권2호
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• pp.134-141
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• 2019

레이다 시스템은 송신 파형에 따라 크게 PD (pulse Doppler) 레이다와 FMCW (frequency modulated continuous wave) 레이다로 구분되며, 송수신 특성에 따라 PD 레이다는 장거리 표적 검출에 유리한 반면, FMCW 레이다는 단거리 표적 검출에 적합한 특성을 갖는다. 이에 본 논문에서는 중/장거리 뿐 아니라 단거리 무인기 탐지를 위해 PD 레이다 시스템과 FMCW 레이다 시스템을 모두 지원 가능한 멀티모드 레이다 신호처리 프로세서 (RSP; radar signal processor)를 제안한다. 제안된 레이다 신호처리 프로세서는 Verilog-HDL을 이용하여 RTL 설계 후, Altera Cyclone-IV FPGA를 이용하여 구현 및 검증 되었다. 구현 결과, 총 19,623개의 logic elements, 9,759개의register, 그리고 25,190,400의 memory bit로 구현 가능함을 확인하였으며, 기존의 PD 레이다와 FMCW 레이다 신호처리 프로세서를 개별 구현한 경우에 비해 logic elements와 register 요구량이 약 43%와 39% 감소됨을 확인하였다.

• 한국결정성장학회지
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• 제15권6호
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• pp.229-233
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• 2005

Novel process was tried to obtain micro-porous ceramic body containing continuous pore channel. $MgAl_2O_4/MgO$ eutectic fibers and rods have been grown successfully by the micro-pulling-down method, and the microstructures and optical characterizations of grown crystals were performed. $MgAl_2O_4/MgO$ eutectic fibers of $0.3{\sim}1mm$ in diameter and about 500 mm in length, and the rods having 5 mm in diameter with approximately 60 mm in length have been grown with the $6{\sim}120mm/hr$ of growth speed. The eutectic fibers showed homogeneous microstructure in which MgO fiber aligned to the growth direction in the $MgAl_2O_4$ (spinel) matrix. The grown crystals looked semitransparency under naked eyes. Optical and orientational characterizations were performed. The second phase of MgO (periclase) was easily removed by selective etching with hydrochloric acid, and then porous bodies were obtained.

• Structural Engineering and Mechanics
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• 제30권6호
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• pp.699-712
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• 2008

The effectiveness of wavelet transform in detecting delamination damages in multilayered composite beams and plates is studied here. The damaged composite beams and plates are modeled in finite element software ABAQUS and the first few mode shapes are obtained. The mode shapes of the damaged structures are then wavelet transformed. It is observed that the distribution of wavelet coefficients can identify the damage location of beams and plates by showing higher values of wavelet coefficients at the position of damage. The effectiveness of the method is studied for different boundary conditions, damage location and size for single as well as multiple delaminations in composite beams and plates. It is observed that both discrete wavelet transform (DWT) and continuous wavelet transform (CWT) can detect the presence and location of the damaged region from the mode shapes of the structures. DWT may be used to approximately evaluate the size of the delamination area, whereas, CWT is efficient to detect smaller delamination areas in composites.

• 대한교통학회지
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• 제6권1호
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• pp.5-16
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• 1988

Development is given to an optimal network design method using continuous design variables. Modified Hooke-and-Jeeves algorithm is implemented in order to solve nonlinear programming problem which is approximately equivalent to the real network design problem with system efficiency crieteria and improvement cost as objective function. the method was tested for various forms of initial solution, and dimensions of initial step size of link improvements. At each searching point of evaluating the objective function, a link flow problem was solved with user equilibrium principles using the Frank-Wolfe algorithm. The results obtained are quite promising interms fo numbers of evaluation, and the speed of convergence. Suggestions are given to selections of efficient initial solution, initial step size and convergence criteria. An approximate method is also suggested for reducing computation time.

• 음성과학
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• 제11권3호
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• pp.95-109
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• 2004

Metrical Phonology has asserted that stress shift does not occur in English compounds because it violates the Continuous Column Constraint. Noun phrases, on the other hand, freely allow for stress shift, whereby the preceding stress moves forward to the preceding heavy syllable. This paper hypothesizes that stress does not shift in compounds as opposed to noun phrases and compares their pitch accentual patterns in a phonetic experiment. More specifically, we examined two-word combinations, noun phrases and compounds, whose boundaries involve stress clash and assured that the preceding words involve a heavy syllable ahead of the stress to guarantee the place for a shifting stress. Depending on where the preceding pitch accent is aligned, stress shift is determined. Results show that stress shift occurs in approximately 47% of the noun phrases and 59% of the compounds; therefore, the hypothesis is not borne out. This suggests that the surface representations derived by phonological rules may not be implemented in real utterance but that phonetic forms may be determined by the phonetic constraints. directly operating on human speech.