• 한국토양비료학회지
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• 제48권5호
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• pp.564-569
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• 2015

In highland crop fields, saprolite is piled up approximately every three years as deep much as 20 to 30 cm because farmers expect that adding new materials may improve productivity and mitigate hazards by continuous cultivation of a single crop. Piling saprolite, however, has been reported to induce poor soil drainage. Effects of deep ploughing with a spading machine and an excavator were studied in sites located in Daekwanryeong-myeon, Pyeongchang in which soil physical properties were deteriorated by piled saprolite. The soil made of parent material of Samgag series was piled up over surface soil of Haggog series naturally developed in the area. Carrot was cultivated in the field. Productivity and growth factors of carrot were compared among control and deep ploughing by a spading machine and an excavator. Effective soil depth extended to 60 cm or greater by 60 cm deep ploughing by an excavator or 50 cm deep ploughing by a spading machine. On the other hand, effective soil depth was within 50 cm at control plot. Productivity of carrot responded to amelioration of soil physical properties. The productivity was greater in deep ploughing treatments than that of control or 30 cm ploughing. It suggested that increased productivity by deep ploughing was mainly related to breaking plough pan which inhibited extension of rooting zone.

• 대한건축학회연합논문집
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• 제20권6호
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• pp.47-54
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• 2018

The purpose of this study is to verify the long - range measurement performance for practical field application of VDMS. The reliability of the VDMS was verified by comparison with the existing monitoring sensor, GPS, Accelerometer and LDS. It showed the ability to accurately measure the dynamic displacement by tracking a motion of free vibration of target. And using the PSD function of measured data, the results in the frequency domain were also analyzed. We judged that VDMS is able to identify the higher system mode and has sufficient reliability. Based on the reliability verification, we conducted tests for long-distance applicability for actual application of VDMS. The distance from the stationary target model structure was increased by 50m interval, and the maximum distance was set to 400m. From the distance of 150m, the image obtained by the commercial camcorder has an error in the analysis, so the measured displacement comparison was performed between the LDS and the refractor telescope measurement results. In the measurement results of the displacement area of VDMS, the data validity was deteriorated due to the data shift by the external force and the quality degradation of the enlarged image. However, even under the condition that the effectiveness of the displacement measurement data of VDMS is low, the first mode characteristic included in the free vibration of the object is clearly measured. If the influence from the external environment is controlled and stable data is collected, It is judged that reliability of long-distance VDMS can be secured.

• 대한토목학회논문집
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• 제39권1호
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• pp.73-80
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• 2019

교통안전과 효율적인 교통관리의 도로교통정책이 간선도로 등 일정규모 이상의 도로에서 주로 이루어지고 있어 상대적으로 생활도로의 안전성은 열악한 상황이다. 특히, 보행자의 안전이 주가 되어야 할 주거지역의 생활권 도로까지 차량이 우선시 되는 경우가 발생하는 등 상대적으로 생활도로에 대한 개선은 이루지 못한 실정이다. 이에 본 연구는 생활도로 내 교차로 알림이 설치기준을 제시하기 위하여 광주광역시를 중심으로 현장조사를 실시하였고, 생활도로내 교차로에 영향을 미치는 영향인자와의 관계를 다중회귀분석을 통한 예측모형으로 도출하였다. 나아가 생활도로내 사고예측 모형을 통한 실측값을 제시 한 후 교차로 알림이가 설치된 지점의 값과 비교 검증하여 생활도로내 교차로 알림이 설치기준을 제시하였다. 이를 통해 생활도로 내 잦은 교통사고를 예방하고 생활도로를 이용하는 이용자들의 편의성 및 안전을 고려한 교차로 알림이 설치가 이루어 질 수 있을 것으로 기대된다.

• Corrosion Science and Technology
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• 제17권6호
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• pp.287-291
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• 2018

In this study, corrosion behavior of a SA178-A alloy used in the boiler tube of a district heating system was investigated in different environments where it was exposed to pure water, district heating (DH) water, and filtered district heating (FDH) water. After the corrosion test, the surface morphology was examined for observation of the number of pitting sites and pitting area fraction, using a scanning electron microscope. The DH water and FDH water conditions resulted in a lower corrosion potential and pitting potential, and revealed a significantly higher corrosion rate than the pure water condition. The pitting sites in the DH water (pH 9.6) were approximately eighteen times larger than those in the pure water (pH 9.6). Compared to the DH water, the corrosion potential became more noble in the FDH water condition, where iron ions were reduced through filtration. However, the corrosion rate increased in the FDH water due to an increased concentration of chloride ions, which deteriorated the stability of passive film.

• 한국물환경학회지
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• 제35권5호
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• pp.399-408
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• 2019

The average annual water quality at Yongchon Bridge, Bonggok 2 Bridge, and Gasuwon Bridge in upstream of Gapcheon in 2018 was Ib grade (good) in organic matters, including BOD and TOC compared to the local environmental standard in Daejeon. However, their monthly changes for TOC partially exceeded the standard during the busy farming season at Bonggok 2 Bridge and Gasuwon Bridge. Although the annual average TP was within the standard, the monthly change at Bonggok 2 Bridge partially exceeded the standard. For Dugyecheon, the annual average water quality in 2018 at Umyeon-dong Bridge and Wonjeong Bridge, which are downstream of the Gyeryong public sewage treatment plant, exceeded the local environmental standard in BOD. COD was exceeded, and TP was within the standard. It seemed that the causes of deteriorated water quality downstream of Dugyecheon were discharges of agricultural water from agricultural land and effluent from the Gyeryong public sewage treatment plant. Assuming the pollution load of 100% based at the Mulangil point of the mainstream of Gapcheon, the ratio of BOD load and TOC load were as high as 58% and 47%, respectively. At the basin of Bonggok 2 Bridge and Mulangil, the loads downstream of Dugyecheon including the Gyeryong public sewage treatment plant were as high as 43% for TN and 56% for TP, respectively, indicating that Dugyecheon had a major impact on the water quality at the mainstream of Gapcheon.

• 대한금속재료학회지
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• 제46권7호
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• pp.427-436
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• 2008

The effect of dewpoints on annealing behavior and coating characteristics such as wettability and galvannealing kinetics was studied by annealing 0.3wt%Si - 0.1~0.4wt% Mn added interstitial-free high strength steels(IF-HSS). The 0.3wt%Si-0.1wt%Mn steel exhibited good wettability with molten zinc and galvannealing kinetics after annealing when the dewpoint of $H_2-N_2$ mixed gas was above $-20^{\circ}C$. It is shown that the wettability and galvannealing kinetics are directly related to the coverage of the external(surface) oxide formed by selective oxidation during annealing. At $N_2-15%H_2$ annealing atmosphere, the increase of dewpoint results in a gradual transition from external to internal selective oxidation. The decrease of external oxidation of alloying elements with a concurrent increase of their subsurface enrichment in the substrate, showing a larger surface area that was free of oxide particles, contributed to the improved wettability and galvannealing kinetics. On the other hand, the corresponding wettability and galvannealing kinetics were deteriorated with the dewpoints below $-20^{\circ}C$. The continuous oxide layer of network and/or film type was formed on the steel surface, leading to the poor wettability and galvannealing kinetics. It causes a high contact angle between annealed surface and molten zinc and plays an interrupting role in interdiffusion of Zn and Fe during galvannealing process.

• Animal Bioscience
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• 제34권8호
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• pp.1375-1381
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• 2021

Objective: This study was conducted to determine the effect of freeze-thawed cycles (Fresh meat, F-T 1 cycle and F-T 2 cycles) on the quality characteristics of porcine longissimus dorsi muscle. Methods: A total of 20 three-crossbred pigs (Duroc×[Large White×Landrace]) were randomly obtained from a commercial slaughterhouse in Thailand. Muscle samples were immediately taken from 10 to 11th of the longissimus dorsi for histochemical analysis. The muscles were cut into 2.54 cm-thick chops. A minimum of 20 chops were used for each treatment (fresh meat, freeze-thawed 1 and 2 cycles). Individually chops were packaged in polyethylene bags and frozen at -20℃ for 6 months followed by thawing in refrigerator at 4℃ for 24 h (the 1st freeze-thawed cycle). The freeze-thawed procedure was repeated for two cycles (the 2nd freeze-thawed cycle). Thawing loss, shear force value, citrate synthase activity and muscle fiber characteristics were determined on the muscles. Results: Results showed that increasing of freeze-thawed cycle increased the thawing loss (p<0.01) and citrate synthase activity (p<0.001). Shear force value of fresh meat was higher than freeze-thawed 1 and 2 cycles (F-T 1 cycle and F-T 2 cycles). Freeze-thawed cycles affected muscle characteristics. Muscle fiber area and muscle fiber diameter decreased with an increasing number of freeze-thawed cycles (p<0.001), while the thickness of endomysium and perimysium were increased (p<0.001). Conclusion: Repeated freeze-thawed cycles degraded muscle fiber structure and deteriorated pork quality.

• 문화기술의 융합
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• 제7권4호
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• pp.727-734
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• 2021

제 1기 신도시 중에서 분당신도시를 중심으로 거주자의 특성을 파악하고 설문조사를 실시하였으며 거주자의 신도시에 대한 인식을 분석하였다. 현장조사 대상지에서 육안검사와 일부 기기검사로 내구성을 평가하고 분석한 결과에 따르면 문제가 있는 것으로 나타났으며, 공동주택의 내구연한과 사용성능을 증진시키기 위하여 지속적인 유지관리를 하여야 한다. 특히 급격한 열화 진행 부분에서 나타나고 있는 많은 균열들을 조속히 보수하여야 하며 체계적인 계획을 입안하여 진행하여야 한다. 분당 신도시 거주자의 공동주택 인식조사에서는 약 93.4%가 보통 이상의 만족도를 나타내고 있었으며 43.4%는 거주 지역에 대하여 호감을 가지고 선호하는 결과를 나타내고 있다.

• Journal of the Korean Wood Science and Technology
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• 제50권4호
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• pp.219-236
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• 2022

Wood-based nanocomposite electrode materials were synthesized for application in supercapacitors by mixing nanostructured hematite (Fe₂O₃) with highly porous activated carbon (AC) produced from the wood-waste of Pinus roxburghii. The AC was characterized using various instrumental techniques and the results showed admirable electrochemical properties, such as high surface area and reasonable porosity. Firstly, AC was tested as an electrode material for supercapacitors and it showed a specific capacitance of 59.02 Fg^-1 at a current density of 1 Ag^-1, cycle life of 84.2% after 1,000 cycles (at a current density of 3 Ag^-1), and energy density of 5.1 Wh/kg at a power density of 135 Wkg^-1. However, when the AC was composited with different ratios of Fe₂O₃ (1:1, 2:1, and 1:2), there was an overall improvement in its electrochemical performance. Among the 3 ratios, 2:1 (AC:Fe₂O₃) had the best specific capacitance of 102.42 Fg^-1 at 1 Ag^-1, cycle life of 94.4% capacitance after 1,000 cycles (at a current density of 3 Ag^-1), and energy density of 8.34 Wh/kg at a power density of 395.15 Wkg^-1 in 6 M KOH electrolyte in a 3-electrode experimental setup with a high working voltage of 1.55 V. Furthermore, when Fe₂O₃ was doubled, 1:2 (AC:Fe₂O₃), the electrochemical capacitive performance of the electrode twisted and deteriorated due to either the accumulation of Fe₂O₃ particles within the composite or higher bulk resistance value of pure Fe₂O₃.

• Korean Chemical Engineering Research
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• 제61권2호
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• pp.202-207
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• 2023

태양광과 풍력발전의 잉여전기를 공급받아 수전해를 구동하는 경우 날씨 변동에 따라 구동과 정지를 반복해야한다. 수전해를 구동하다 정지하면 잔류 수소와 산소에 의해 PEM 연료전지와 같은 상태가 되고, 구동 중 형성된 수전해의 높은 전위 때문에 전극과 고분자막이 정지 중에도 열화될 가능성이 높다. 본 연구에서는 PEM 수전해가 구동/정지 반복과정에서 전극과 고분자막의 열화가 얼마나 진행되는지 확인하고자, 144시간 동안에 구동/정지 횟수를 변화시키며 성능 감소를 측정하였다. 전극 촉매 활성면적 변화와 고분자막의 수소투과도와 불소유출속도 등을 분석해 전극과 고분자막의 특성 변화를 측정했다. 전체적으로 정지 횟수가 증가할수록 PEM 수전해 성능이 감소했다. 144시간동안에 5회 정지했을 때 IrO_x 촉매 활성이 30% 이상 감소하였고, 수소투과도는 80% 증가해서 전극과 고분자막이 모두 열화됨을 확인했다.