• 열처리공학회지
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• 제36권1호
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• pp.7-14
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• 2023

We investigated the effect of multiple tempering on the microstructure and mechanical properties of AISI 4340 steel. The austenitized and quenched AISI 4340 steels were tempered at 550, 600, and 650℃ for 1, 2, and 4 h by single-tempering (ST). The multiple tempering was conducted for 4 h by double-tempering (DT, 2 h + 2 h), and quadruple-tempering (QT, 1 h + 1 h + 1 h + 1 h). As tempering temperature increases, yield strength and ultimate tensile strength decrease and elongation increases due to recovery and recrystallization of martensite and coarsening of carbides. At 550℃, as the number of tempering cycles increases, the yield strength and tensile strength decrease at the expense of fracture elongation. At 600 and 650℃, the yield strength and tensile strength increase with increasing the number of tempering cycles while fracture elongation maintains similar values. The multiple tempering at the same tempering time of 4 h improves the modulus of toughness at all tempering temperatures, which is presumed to be due to the change in carbide precipitation behavior by multiple tempering.

• 한국식생활문화학회지
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• 제23권5호
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• pp.616-620
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• 2008

The principal objective of this study was to evaluate the quality characteristics of Bokbunja pudding, using various levels of Bokbunja fruit juice (140, 150, and 130 g), Bokbunja Wine (10, 20, and 20 g), gelatin (18, 17, and 16 g) and sugar (250, 200, and 150 g). In order to establish the optimal added amounts, chemical composition, saccharinity, color, texture, and sensory evaluations were conducted, and the results of various cases were analyzed and assessed. The statistical data analyses were conducted using the SPSS program. The saccharinity of the Bokbunja pudding increased with increasing amountsof added sugar. Additionally, as the amount of added Gelatin was increased, the L values (lightness) of the Bokbunja pudding decreased. Conversely, the hardness, gumminess, and chewiness values all decreased with decreasing levels of added gelatin and sugar. The optimal mixing condition for the Bokbunja pudding was determined via sensory evaluation. Sensory characteristics, including flavor, sweetness, texture, and overall acceptability, were highest in the type C product. The chemical composition of the type C product was as follows: moisture 71.47%, carbohydrate 24.70%, crude protein 3.83%, crude fat 0.001%, and crude ash 0.001%. According to our results, the optimum mixing ratio for the most satisfactory sensory characteristics of Bokbunja was as follows: Bokbunja fruit juice 130 g, Bokbunja Wine 20 g, Gelatin 16 g, Sugar 150 g, Bokbunja Flavor 0.3 g, and Water 400 g.

• 한국분말재료학회지
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• 제30권6호
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• pp.470-477
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• 2023

The effects of annealing on the microstructure and mechanical properties of Al-Zn-Mg-Cu-Si alloys fabricated by high-energy ball milling (HEBM) and spark plasma sintering (SPS) were investigated. The HEBM-free sintered alloy primarily contained Mg₂Si, Q-AlCuMgSi, and Si phases. Meanwhile, the HEBM-sintered alloy contains Mg-free Si and θ-Al₂Cu phases due to the formation of MgO, which causes Mg depletion in the Al matrix. Annealing without and with HEBM at 500℃ causes partial dissolution and coarsening of the Q-AlCuMgSi and Mg₂Si phases in the alloy and dissolution of the θ-Al₂Cu phase in the alloy, respectively. In both alloys, a thermally stable α-AlFeSi phase was formed after long-term heat treatment. The grain size of the sintered alloys with and without HEBM increased from 0.5 to 1.0 ㎛ and from 2.9 to 6.3 ㎛, respectively. The hardness of the sintered alloy increases after annealing for 1 h but decreases significantly after 24 h of annealing. Extending the annealing time to 168 h improved the hardness of the alloy without HEBM but had little effect on the alloy with HEBM. The relationship between the microstructural factors and the hardness of the sintered and annealed alloys is discussed.

• 산업경영시스템학회지
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• 제46권spc호
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• pp.31-38
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• 2023

In this study, in order to develop a method to efficiently inject essential nutrients necessary for plant growth into wood chips, which are simply used as soil covering materials in the agriculture, landscaping and horticultural industries, the atmospheric pressure dipping method and the vacuum pressure impregnating method are used to improve the plant nutrients injectability and impregnation amount were comparatively analyzed. Nutrient ingredients and 8 major heavy metal contents of wood chips injected with nutrients were analyzed, and soil covering effects were examined by covering wood chips injected with nutrients on soil. Comparing the dipping method and the vacuum pressure impregnation method, it took about 48 hours or more to inject 1,500 g or more of the nutrient aqueous solution into 1 kg of wood chips in the dipping method, but the vacuum pressure impregnation method could be impregnated in about 5 minutes. Components of the impregnated nutrients were detected in proportion to the diluted concentration. As a result of covering the wood chips developed in this study on soil, they showed weakly acidic pH, and the heat insulation and moisturizing effects during the winter season were evaluated to be superior to those of uncovered soil. In the future, wood chips impregnated with nutrients are expected to contribute to the more efficient use of waste wood resources and the long-term supply of nutrients essential for plant growth, reducing excessive use of chemical fertilizers and reducing costs.

• 대한불안의학회지
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• 제19권2호
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• pp.61-68
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• 2023

Objective : The purpose of this study was to investigate the associations between psychosocial factors and the mask-wearing behavior after deregulation of COVID-19 quarantine guidelines among adults in Korea. Methods : We collected data (345 subjects) from online questionnaire survey. The questionnaire included the Korean version of the Patient Health Questionnaire-9, the Korean version of fear of COVID-19 Scale, the Korean version of the Patient Health Questionnaire-15, Korean versions of the Perceived Stress Scale, and measurement tools adapted from previous studies for COVID-19 risk perception, social stigma, and appearance interest of subjects. We analysed data using SPSS version 23.0 for descriptive statistics, chi-square test, and logistic regression analysis. Results : People with cohabitant or mask-wearing tendency before COVID-19 pandemic had a higher rate of mask-wearing than those who were not. Subjects reporting higher level of social stigma (OR=1.154, 95% CI 1.049-1.270) and COVID-19 anxiety (OR=1.072, 95% CI 1.007-1.141) were more likely to report maskwearing behavior. Conclusion : From the results, appropriate intervention to those who fear social stigma and are anxious to the infectious diseases will be needed. Additionally, providing policies and guidelines that consider cohabitants and offering continuous education with information of disease to the public are also expected to helpful for recovery of daily life from infectious diseases.

• Current Photovoltaic Research
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• 제12권1호
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• pp.24-30
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• 2024

To create an environment for growing ginseng sprouts, we developed a solar module that partially transmits and disperses light. A G to G type light transmission and dispersion solar module was developed using glass with a mist pattern applied, and the light dispersion effect of the developed module was confirmed through illuminance measurement. The output of one module is approximately 260 W, and the configuration consists of 48 cells in series in 4 strings. The cultivation system where the developed module will be installed was developed in the form of a container, and three units of 2.6 kW (260 W x 10 EA). The inside of the cultivation system consists of a shading screen, air conditioner, ventilator, plastic pot, etc. to create an environment for cultivating sprout ginseng. As a result of actually planting sprout ginseng, it was confirmed through verification that the plants were grown without any problems.

• 한국식품영양학회지
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• 제37권1호
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• pp.40-47
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• 2024

Gastrodia elata has been used in traditional Chinese medicine for treating headaches, dizziness, and convulsive illness for centuries. G. elata has traditionally been processed by steaming or blanching to increase the content and quality of its main ingredients. This study aimed to identify changes in physicochemical properties and active ingredients of G. elata depending on the steaming time. Data of this study could be used to develop traditional medicine and health foods. No steaming was used as a control. Steaming time was 5, 10, 20, 30, 60, or 120 min. The drying yield according to the steaming time ranged from 20.2% to 22.9%, with the lowest drying yield at 120 min. As the steaming time increased, gastrodin content increased more than that in fresh G. elatadue to inhibition of β-glucosidase enzyme activity, 4-hydroxybenzyl alcohol condensation, and parishin decomposition. Steamed G. elatadid not show higher total polyphenols, total flavonoids, or ABTS radical scavenging activities than fresh G. elata even with an increase of steaming time. The steaming time to improve the quality of G. elata may varied depending on the size of G. elata. Thus, it is important to set the steaming time taking these characteristics into consideration.

• 대한영상의학회지
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• 제84권4호
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• pp.900-910
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• 2023

목적 정상으로 보이는 chest CT를 정량화 분석하여 흡연 및 폐쇄성 폐질환(chronic obstructive pulmonary disease; 이하 COPD) 여부에 따른 차이가 있는지 확인하고자 하였다. 대상과 방법 2013년 1월부터 2014년 12월까지 chest CT가 정상이면서 정량화 분석이 있는 90명의 남자 환자[COPD 없는 비흡연자(n = 38)와 흡연자(n = 45), COPD 흡연자(n = 7)]를 대상으로 하였다. COPD 흡연자 7명을 대상으로 나이를 추출하여 환자-대조군 연구도 하위 분석하였다. Pi10, 왜도, 첨도, 평균감쇠계수, 저감쇠영역%와 같은 정령화 변수를 분석하였다. 결과 COPD가 없는 환자 중에서 흡연자의 Pi10 (4.176 ± 0.282, n = 45)이 비흡연자에 비해 약 0.1 mm 정도 두꺼웠고(4.070 ± 0.191, n = 38, p = 0.047), 흡연자의 왜도와 첨도(2.628 ± 0.484 and 6.448 ± 3.427)가 비흡연자보다 낮았다(2.884 ± 0.624, p = 0.038 and 8.594 ± 4.944, p = 0.027). COPD가 있는 흡연자들의 Pi10 (4.427 ± 0.437, n = 7)이 COPD가 없는 비흡연자들보다 약 0.4 mm 두꺼웠다(4.001 ± 0.108, n = 14, p = 0.005). 그러나 평균감쇠계수와 저감쇠영역%에서는 유의한 차이가 없었다. 결론 정상 chest CT를 보이더라도 QCT로 COPD의 유무와 상관없이 흡연자들의 소기도가 두꺼운 것을 알 수 있으며 이는 폐실질 변화보다 더 선행한다.

• 한국항만경제학회지
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• 제23권1호
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• pp.163-193
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• 2007

전북지역이 내륙물류의 집적과 대 중국 해상물류의 교두보역할을 담당할 수 있는 항만을 보유하고 있고 지정학적 위치와 교통여건 등에서 우수한 곳으로 평가되고 있으나 물류산업이 발달하지 못하고 있다. 특히 제4차 국토종합계획 수정계획에는 전라북도를 신산업 생산 및 물류중심지역으로 육성하고, 전주 군장광역권을 환황해권 생산 물류 및 동북아교류의 거점권역으로 육성 개발하려는 계획이 수립되어 물류산업을 발전시킬 수 있는 좋은 여건을 보유하고 있다. 본 연구에서 전라북도의 물류기반 인프라 현황을 조사한 결과 전국평균에 훨씬 못 미치는 것으로 나타났다. 또한 해상물류기반시설 현황에서도 전북지역과 유사한 항만을 보유하고 있는 지역에 비해 부문별로 낙후한 것으로 분석되었다. 또한 전북도내 일반기업체들과 물류업체들의 실태조사에서도 물류관련 인식수준이 아주 낮아, 수송분담 구조의 불균형, 전산화 정보화 표준화 미비 및 미숙, 물류아웃소싱 저조 등 물류관련 활동이 낙후한 것으로 파악되었다. 이에 따라 전라북도의 물류산업 육성을 위해서는 물류인프라 확충방안을 마련하여 타지역과의 경쟁력을 갖추어 나가야하며, 전북도내 물류관련 업체들의 물류관련 인식이 제고되어야만 경쟁력을 확보할 수 있는 것으로 분석되었다. 이에 전북도 행정당국에서는 물류인식제고를 위해 다양한 정책 대안을 마련하여 제공하여야 할 것이다. 또한 도로화물 편중운송 비중을 철도 및 연안해송으로 분산시키는 방안, 물류전산화 정보화 표준화를 통해 물류시스템을 제고시키는 방안, 물류아웃소싱 및 물류공동화를 통해 물류흐름의 효율성을 높이는 방안을 마련하여 전북도내 중소기업들에게 물류비 절감 혜택이 돌아 갈 수 있도록 하는 대안을 제시하였다. 전라북도가 이러한 물류정책을 수행하기 위해서는 "대 중국 물류Gate 구축"에 물류산업의 정책목표를 두고, 타 지역과 "차별화된 물류산업 육성" 정책방안을 제시하여 추진해야 물류산업 경쟁력을 확보할 수 있을 것으로 분석되었다. 이러한 정책을 지속적으로 추진하면 전북지역이 우리나라 중부권 및 전북권의 대중국물류 Gate로서 기능을 수행하여 국가물류산업의 경쟁력을 높일 수 있을 것으로 예상된다.

• 항공우주시스템공학회지
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• 제18권1호
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• pp.37-45
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• 2024

본 논문에서는 쿼드로터형 드론의 제자리 비행 상태에서 제어부에 전달되는 수직 방향 진동을 저감하기 위한 수동적 진동 제어 방법에 따른 설계 방법을 제시하였다. 쿼드로터형 드론의 진동 해석을 위해 유한요소 기반 이산화 모델 및 번지 케이블을 이용한 지상진동시험 모사 모델을 구축하였다. 제자리 비행 상태에서의 하중을 부여하여 동특성 평가 및 공진 회피 설계를 위한 모드 해석을 수행하여 결과를 분석하였으며, 강제진동응답해석을 수행하여 제자리 비행 상태의 운용주파수 범위 내에서의 정상상 태응답을 도출하였다. 또한 감쇠 재료의 유무에 따른 진동 저감 효과를 비교하기 위해 동일한 조건내에서 제어부에 전달되는 진동을 유발할 수 있는 위치에 점성 감쇠 테이프를 적용하여 이에 따른 정상상태응답을 도출하고 감쇠 재료를 적용하였을 경우의 진동 저감 효과 및 부착 위치에 따른 진동 저감 효과를 평가하였다.