• Structural Engineering and Mechanics
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• 제77권1호
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• pp.103-114
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• 2021

Ultra high strength concrete (UHSC) originally proposed by Richards and Cheyrezy (1995) composed of cement, silica fume, quartz sand, quartz powder, steel fibers, superplasticizer etc. Later, other ingredients such as fly ash, GGBS, metakaoline, copper slag, fine aggregate of different sizes have been added to original UHSC. In the present investigation, the combined effect of coarse aggregate (6mm - 10mm) and steel fibers (0.50%, 1.0% and 1.5%) has been studied on UHSC mixes to evaluate mechanical and fracture properties. Compressive strength, split tensile strength and modulus of elasticity were determined for the three UHSC mixes. Size dependent fracture energy was evaluated by using RILEM work of fracture and size independent fracture energy was evaluated by using (i) RILEM work of fracture with tail correction to load - deflection plot (ii) boundary effect method. The constitutive relationship between the residual stress carrying capacity (σ) and the corresponding crack opening (w) has been constructed in an inverse manner based on the concept of a non-linear hinge from the load-crack mouth opening plots of notched three-point bend beams. It was found that (i) the size independent fracture energy obtained by using above two approaches yielded similar value and (ii) tensile stress increases with the increase of % of fibers. These two fracture properties will be very much useful for the analysis of cracked concrete structural components.

• 한국미생물·생명공학회지
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• 제50권1호
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• pp.102-109
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• 2022

Bile acids are essential molecules produced by vertebrates that are involved in several physiological roles, including the uptake of nutrients. Bacterial isolates capable of producing bile acids de novo have been identified and characterized. Such isolates may provide access to novel biochemical pathways suitable for the design of microbial cell factories. Here, we further characterized the ability of Maribacter dokdonensis, Dokdonia donghaensis, and Myroides pelagicus to produce bile acids. Contrary to previous reports, we did not observe de novo production of bile acids by these isolates. Instead, we found that these isolates deconjugated the amino acid moiety of bile acids present in the growth medium used in previous reports. Through genomic analysis, we identified putative bile salt hydrolases, which could be responsible for the different bile acid modifications observed. Our results challenge the hypothesis of de novo microbial bile acid production, while further demonstrating the diverse capacity of bacteria to modify bile acids.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권6호
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• pp.2094-2114
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• 2022

Due to the wide application of fifth generation communication, wireless sensor networks have become an indispensable part in our daily life. In this paper, we analyze physical layer security for two-way relay with energy harvesting (EH), where power splitter is considered at relay. And two kinds of combined methods, i.e., selection combining (SC) and maximum ratio combining (MRC) schemes, are employed at eavesdropper. What's more, the closed-form expressions for security performance are derived. For comparison purposes, this security behaviors for orthogonal multiple access (OMA) networks are also investigated. To gain deeper insights, the end-to-end throughput and approximate derivations of secrecy outage probability (SOP) under the high signal-to-noise ratio (SNR) regime are studied. Practical Monte-Carlo simulative results verify the numerical analysis and indicate that: i) The secure performance of SC scheme is superior to MRC scheme because of being applied on eavesdropper; ii) The secure behaviors can be affected by various parameters like power allocation coefficients, transmission rate, etc; iii) In the low and medium SNR region, the security and channel capacity are higher for cooperative non-orthogonal multiple access (NOMA) systems in contrast with OMA systems; iv) The systematic throughput can be improved by changing the energy conversion efficiency and power splitting factor. The purpose of this study is to provide theoretical direction and design of secure communication.

• 한국물환경학회지
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• 제38권5호
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• pp.231-239
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• 2022

In this study, we applied ENERWATER to evaluate the energy consumption labeling of wastewater treatment plants in Korea using the Korea sewerage statistics data. The results showed that the energy label status was excellent in the SBR process for small and medium-scale wastewater treatment plants and the A2O process for large-scale wastewater treatment plants. The energy labeling of wastewater treatment plants of 50,000 tons capacity was excellent. The statuses of metropolitan cities and Jeollanam-do province were excellent. We analyzed the effects of renewable energy on wastewater treatment plants' energy consumption and found out that digestion gas for large-scale plants and photovoltaic energy for small-scale plants were effective in improving energy labeling. In addition, we compared the energy labels of four wastewater treatment plants in "Z" city and wastewater treatment plant "X" had the best energy label, and the wastewater treatment plants "V" and "Y" had to be selected as priorities for the energy diagnosis and improvement project. In a comprehensive conclusion, the applicability of ENERWATER was confirmed based on sewage statistics data and labeling can be used to set priorities for the energy diagnosis and improvement project.

• 대한안전경영과학회지
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• 제24권3호
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• pp.61-74
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• 2022

In a rapidly changing environment, it is essential for companies to develop their capabilities for sustainable growth. To this end, informal learning at work plays an important role for small and medium-sized enterprises that are having difficulties in human resource development. If the GRIT of workers and the spiritual leadership of leaders are maintained at an appropriate level, the effect of informal learning will increase. This study derived the following results through a survey of workers participating in the Work-learning Dual System in Korea. First, experience and feedback among informal learning activities have a significant positive effect on competency development. Second, the higher the level of the GRIT of workers, the greater the magnitude of the positive effect of experience and feedback on competency development, showing a positive moderating effect. Third, in the case of workers with high GRIT, capacity development is strengthened as experience or feedback increases, and the higher the level of spiritual leadership, the greater the scope of reinforcement. On the other hand, it can be seen that in the case of workers with low GRIT, competency development weakens as experience or feedback increases, and the higher the level of spiritual leadership, the greater the extent of the weakening.

• 한국작물학회지
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• 제37권5호
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• pp.419-424
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• 1992

콩에서의 조직배양 가능성을 알아보고자 콩 유묘를 기내에서 배양시킨 뒤, 여러 부위를 채취하여 각기 다른 배지 치상한 결과는 다음과 같다. 1. 줄기정단조직 배양에서는 대부분 shoot가 분화되어 완전한 식물체를 얻을 수 있었다. 2. 자엽절 조직배양에서는 multiple shoots가 나타나 대량증식에 유용했으나 배지에 따른 영향이 컸다. 3. 배축 및 상배축 조직배양에서는 callus만 분화되엇다. 4. 엽조직배양에서는 callus 분화 후 계대배양했을 때 shoot가 분화되었으나 완전한 식물체를 얻기는 힘들었다.

• Journal of Microbiology and Biotechnology
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• 제33권3호
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• pp.310-318
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• 2023

Microalgae are attracting much attention as promising, eco-friendly producers of bioenergy due to their fast growth, absorption of carbon dioxide from the atmosphere, and production capacity in wastewater and salt water. However, microalgae can only accumulate large quantities of lipid in abiotic stress, which reduces productivity by decreasing cell growth. In this study, the strategy was investigated to increase cell viability and lipid production by overexpressing S-adenosylmethionine (SAM) synthetase (SAMS) in the microalga Chlamydomonas reinhardtii. SAM is a substance that plays an important role in various intracellular biochemical reactions, such as cell proliferation and stress response, and the overexpression of SAMS could allow cells to ithstand the abiotic stress and increase productivity. Compared to wild-type C. reinhardtii, recombinant cells overexpressing SAMS grew 1.56-fold faster and produced 1.51-fold more lipids in a nitrogen-depleted medium. Furthermore, under saline-stress conditions, the survival rate and lipid accumulation were 1.56 and 2.04 times higher in the SAMS-overexpressing strain, respectively. These results suggest that the overexpression of SAMS in recombinant C. reinhardtii has high potential in the industrial-scale production of biofuels and various other high-value-added materials.

• 대한의생명과학회지
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• 제29권3호
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• pp.168-177
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• 2023

Recently, as a health problem of the elderly in an aging society, the risk of nutritional imbalance and weakening of immunity due to deterioration of masticatory function has been mentioned. In order to solve this problem, this study was conducted to investigate the effect of cyclophosphamide (CPA)-induced immunosuppression in mice induced by fermented samultang (FST) porridge on the markers related to immune activity function. ICR Mouse was divided into 6 groups of 7 animals each. Experimental groups were set as normal control group, CPA-administration group, positive control group, and FST-administration experimental group (0.25%, 0.5%, 1.0%). In groups except for the normal control group, 100 µL of CPA dissolved in 0.9% NaCl at a concentration of 150 mg/kg was injected twice at the start of the experiment and after 3 days to induce immunosuppression. As a result of analyzing the cell proliferation capacity of splenocytes, all B and T cells decreased in the CPA-administered group and increased in a concentration-dependent manner in the FST-administered group. In addition, IgA measured to evaluate the effect of improving immunity showed high values in medium and high concentration FST (P<0.05). These results can be expected as an effective solution to improve the nutritional imbalance of the elderly.

• 한국콘텐츠학회논문지
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• 제19권11호
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• pp.325-336
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• 2019

본 연구는 7S 모형을 이용하여 내부역량과 직무만족도 간의 구조적 관계를 분석하여 내적요인을 통한 경영성과향상 방안을 제시하고자 하는데 목적이 있다. 이를 위해 7개의 연구가설을 설정하고 지방중소도시의 일개 종합병원에 근무하는 모든 직종의 구성원들을 대상으로 설문을 실시하였다. 2016년 9월 20일부터 10월 20일까지 385명에게 설문을 실시하여 327매(84.9%)의 자료가 연구에 사용되었다. 내부역량이 직무만족에 미치는 영향을 검증하기 위해 다중회귀분석을 실행하였다. 분석결과는 연구모형의 설명력은 69.1%를 보여 적합하였으며, 7S 요인 중 리더십 스타일(β=.392^**), 조직구조(β=.129^*), 구성원(β=.232^**), 관리기술(β=.204^*)은 직무만족에 정(+)의 영향을 나타내었다. 이는 표준화 계수 값이 증가할수록 직무만족도에 영향을 미치는 것으로 확인되었다. 전략, 시스템, 공유가치는 영향관계를 확인할 수 없었다. 일부 내부역량 요인들과 직무만족도와의 유의한 관계 확인은 내부역량이 조직의 성과향상 방안의 대안으로 활용될 수 있다. 내부역량은 설립구분, 규모, 위치 등 다양한 환경변수들의 영향을 받을 수 있다. 향후 내부만족도에 대한 내적요인과 외재요인 등으로 분리하여 측정하는 것도 더 많은 시사점을 제공 할 것이다.

• 한국산업보건학회지
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• 제26권3호
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• pp.350-366
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• 2016

Objectives: No 3D anthropometric analyses have been conducted for Korean children's faces for the purpose of designing respiratory protective devices. The aim of this study was to develop masks against yellow dust and fine particulates, particularly for children in Korea. Methods: This study utilized a 3D scanning method to obtain 16 facial anthropometric data from children, ages of 5 to 13 years old. A total of 144 boys and girls were recruited from the kindergarten, elementary schools and middle schools in Seoul. With facial dimensions obtained, cluster analysis was performed to categorize them into similar facial groups. For each cluster, an optimal mask was designed and manufactured using a 3D printer. In addition, lung function data were obtained from 62 subjects and compared with those of normal adults. The pulmonary physiological results were subsequently used to suggest a test method for mask certification. Results: Facial shapes were classified into tree clusters: small, medium, and large. The face width and length for the first group were small with high nosal protrusion. The face width and length for the second group were the largest among the three clusters. The third group had the largest angle of nose root - gnathion(n-prn-gn). Age was the most significant variable in the facial dimensions. Children's pulmonary physiological capacity was about 60% of adults' capacity. The results of fit test using the prototype masks developed showed very good fits for children. Conclusions: For Korean children, three mask sizes will be sufficient and practical for providing protection against yellow dust and fine particulates. Anthropometric data obtained using digitalized 3D face analysis can be very effective for designing respiratory devices. 3D images can be accurate and easily measured for multiple dimensions, particularly for curved areas of the face. It is imperative to adopt different test methods for certifying respiratory protective devices for children, since their pulmonary physiological capacity is inferior compared with that of adults.