• Bulletin of the Korean Chemical Society
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• 제18권11호
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• pp.1166-1172
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• 1997

[FeⅢ(BLPA)DBC]BPh4, a new functional model for the catechol dioxygenases, has been synthesized, where BLPA is bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine and DBC is 3,5-di-tert-butylcatecholate dianion. The BLPA complex has a structural feature that iron center has a six-coordinate geometry with N4O2 donor set. It exhibits EPR signals at g=5.5 and 8.0 which are typical values for the high-spin FeⅢ (S=5/2) complex with axial symmetry. The BLPA complex reacts with O2 within a few hours to afford intradiol cleavage (75%) and extradiol cleavage (15%) products which is very unique result of all [Fe(L)DBC] complexes studied. The iron-catecholate interaction of BLPA complex is significantly stronger, resulting in the enhanced covalency of the metal-catecholate bonds and low energy catecholate to FeⅢ charge transfer bands at 583 and 962 nm in CH3CN. The enhanced covalency is also reflected by the isotropic shifts exhibited by the DBC protons, which indicate increased semiquinone character. The greater semiquinone character in the BLPA complex correlates well with its high reactivity towards O2. Kinetic studies of the reaction of the BLPA complex with 1 atm O2 in CH3OH and CH2Cl2 under pseudo-first order conditions show that the BLPA complex reacts with O2 much slower than the TPA complex, where TPA is tris(2-pyridylmethyl)amine. It is presumably due to the steric effect of the methyl substituent on the pyridine ring. Nevertheless, both the high specificity and the fast kinetics can be rationalized on the basis of its low energy catecholate to FeⅢ charge transfer bands and large isotropic NMR shifts for the BLPA protons. These results provide insight into the nature of the oxygenation mechanism of the catechol dioxygenases.

• Journal of Information Science Theory and Practice
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• 제7권3호
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• pp.6-20
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• 2019

Learning analytics, or educational data mining, is an emerging field that applies data mining methods and tools for the exploitation of data coming from educational environments. Learning management systems, like Moodle, offer large amounts of data concerning students' activity, performance, behavior, and interaction with their peers and their tutors. The analysis of these data can be elaborated to make decisions that will assist stakeholders (students, faculty, and administration) to elevate the learning process in higher education. In this work, the power of Excel is exploited to analyze data in Moodle, utilizing an e-learning course developed for enhancing the information computer technology skills of school teachers in primary and secondary education in Greece. Moodle log files are appropriately manipulated in order to trace daily and weekly activity of the learners concerning distribution of access to resources, forum participation, and quizzes and assignments submission. Learners' activity was visualized for every hour of the day and for every day of the week. The visualization of access to every activity or resource during the course is also obtained. In this fashion teachers can schedule online synchronous lectures or discussions more effectively in order to maximize the learners' participation. Results depict the interest of learners for each structural component, their dedication to the course, their participation in the fora, and how it affects the submission of quizzes and assignments. Instructional designers may take advice and redesign the course according to the popularity of the educational material and learners' dedication. Moreover, the final grade of the learners is predicted according to their previous grades using multiple linear regression and sensitivity analysis. These outcomes can be suitably exploited in order for instructors to improve the design of their courses, faculty to alter their educational methodology, and administration to make decisions that will improve the educational services provided.

• Asian-Australasian Journal of Animal Sciences
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• 제32권11호
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• pp.1686-1694
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• 2019

Objective: Lignin plays a relevant role in the inhibition of cell wall (CW) structural carbohydrate degradation. Thus, obtaining accurate estimates of the lignin content in tropical plants is important in order to properly characterize the mechanism of lignin action on CW degradation. Comparing conflicting results between the different methods available for commercial use will bring insight on the subject. This way, providing data to better understand the relationship between lignin concentration and implications with tropical forage degradation. Methods: Five grass species, Brachiaria brizantha cv $Marand{\acute{u}}$, Brachiaria brizantha cv $Xara{\acute{e}}s$(MG-5), Panicum maximum cv Mombaça, Pennisetum purpureum cv Cameroon, and Pennisetum purpureum cv Napier, were harvested at five maturity stages. Acid detergent lignin (ADL), Klason lignin (KL), acetyl bromide lignin (ABL), and permanganate lignin (PerL) were measured on all species. Lignin concentration was correlated with in vitro degradability. Results: Highly significant effects for maturity, lignin method and their interaction on lignin content were observed. The ADL, KL and ABL methods had similar negative correlations with degradability. The PerL method failed to reliably estimate the degradability of tropical grasses, possibly due to interference of other substances potentially soluble in the $KMnO_4$ solution. Conclusion: ADL and KL methods use strong acid ($H_2SO_4$) and require determination of ash and N content in the lignin residues, therefore, increasing time and cost of analysis. The ABL method has no need for such corrections and is a fast and a convenient method for determination of total lignin content in plants, thus, it may be a good option for routine laboratory analysis.

• 디지털융복합연구
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• 제17권11호
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• pp.213-223
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• 2019

본 연구는 사용자들의 공유행위의도에 대한 이유를 설명하기 위해 계획된 행동이론 모델 변인(주관적 규범, 태도, 자기효능감)과 소속 욕구, 자기성장주도성의 관계를 입증하고자 하였다. 온라인 설문조사를 통해 온라인 비디오 공유 경험이 있는 959명의 참가자들을 표본으로 수집하였으며, 수집된 데이터는 구조방정식모형 검증을 통해 분석되었다. 연구 결과, 소속 욕구는 온라인 비디오 공유에 대한 태도와 주관적 규범에 영향을 미쳤으며, 자기성장주도성 역시 온라인 비디오 공유에 대한 태도와 자기효능감에 영향을 미치는 것으로 확인되었다. 또한 계획된 행동이론 모델의 3가지 변인 모두 온라인 비디오 공유 의도에 영향을 미치고 있음이 확인되었으며, 온라인 비디오 공유에 대한 태도는 주관적 규범과 자기효능감에 영향을 미치고 있음이 확인되었다. 본 연구는 소속 욕구, 자기성장주도성과 함께 계획된 행동이론 모델의 구성 변인을 통해 사용자의 온라인 비디오 공유 의도에 대한 설명력을 입증하였다는 점에서 의의가 있다.

• Steel and Composite Structures
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• 제33권3호
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• pp.445-461
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• 2019

The ultrasonic guided wave-based technique has become one of the most promising methods in non-destructive evaluation and structural health monitoring, because of its advantages of large area inspection, evaluating inaccessible areas on the structure and high sensitivity to small damage. To further advance the development of damage detection technologies using ultrasonic guided waves for the inspection of welded components in structures, the transmission characteristics of the ultrasonic guided waves propagating through welded joints with various types of defects or damage in steel plates are studied and presented in this paper. A three-dimensional (3D) finite element (FE) model considering the different material properties of the mild steel, high strength steel and austenitic stainless steel plates and their corresponding welded joints as well as the interaction condition of the steel plate and welded joint, is developed. The FE model is validated against analytical solutions and experimental results reported in the literature and is demonstrated to be capable of providing a reliable prediction on the features of ultrasonic guided wave propagating through steel plates with welded joints and interacting with defects. Mode conversion and scattering analysis of guided waves transmitted through the different types of weld defects in steel plates are performed by using the validated FE model. Parametric studies are undertaken to elucidate the effects of several basic parameters for various types of weld defects on the transmission performance of guided waves. The findings of this research can provide a better understanding of the transmission behaviour of ultrasonic guided waves propagating through welded joints with defects. The method could be used for improving the performance of guided wave damage detection methods.

• Structural Engineering and Mechanics
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• 제55권6호
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• pp.1261-1278
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• 2015

Due to their low intrinsic damping, stay cables in cable-stayed bridges have often exhibited unanticipated and excessive vibrations which result in increasing maintenance frequency and disruption to normal operations of the entire bridges. Mitigation of undesired cable vibration can be achieved by attaching an external damping device near the anchorage. High Damping Rubber (HDR) dampers have many advantages such as compact size, better aesthetics, easy maintenance, temperature stability, and cost benefits; therefore, they have been widely used to increase cable damping. Although a single damper has been shown to reduce cable vibrations, it is not the most effective method due to geometric constraints. This paper proposes the use of two HDR dampers to improve effectiveness and robustness in suppressing cable vibration. Oscillation parameters of the cable-dampers system were investigated in detail by modeling the stay cable as a taut string and each HDR damper as complex-valued impedance and by using an analytical formulation of the complex eigenvalue problem. The problem of two HDR dampers arbitrarily located along a cable is solved and the solution is discussed. Asymptotic formulas to calculate the damping ratios of the cable with two HDR dampers installed near the anchorage(s) are proposed and compared with the exact solutions. Further, a design example is presented in order to justify the methodology. The results of this study show that when the two HDR dampers are installed close to each other on the same end of the cable, some interaction between the dampers leads to reduced damping ratio. When the dampers are on the opposite ends of the cable, they are effective in increasing damping ratio and can provide better vibration reduction to multiple modes.

• 대한안전경영과학회지
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• 제17권3호
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• pp.247-263
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• 2015

This study seeks to identify effects derived from emotional labor in the distribution industry, and draw ways to systematically manage the employees by exploring effects of the emotion work on performance. For the purpose, literature reviews and empirical experiments were conducted to find out effects of emotional labor and false face acting on emotion work and organizational performance and effects of social support and job autonomy on the relationship between emotion work and organizational performance. To verify the hypothesis, we conducted a hierarchical regression analysis and structural equation model analysis using SPSS 20 and AMOS19. The result of the verification in this study is as follows: First, effects of emotional labor on burnout was found to be statistically significant, second, as for the path-coefficient for "emotional labor ${\rightarrow}$ emotion work" and "emotional labor ${\rightarrow}$ job satisfaction" was not statistically significant, while the path-coefficient for "emotional labor ${\rightarrow}$ service level" was found to be statistically significant. Third, effects of emotion work on job satisfaction was found statistically significant, fourth, emotion work on the service level was found statistically significant, fifth, effects of false face acting on emotion work was found statistically significant, sixth, effects of false face acting on burnout was statistically significant, seventh, moderating were found statistically significant and lastly, moderating effects of the relationship between emotion work from job autonomy and organization performance was not verified in job satisfaction, while emotion work, job autonomy, and interaction variable in service level were statistically significant.

• 한국철도학회논문집
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• 제11권5호
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• pp.489-498
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• 2008

일반적으로 허용처짐 기준은 정적 사용성과 구조적안전성에 그 기반을 두고 있으며 진동사용성에 대한 고려는 부족하다. 따라서 진동사용성을 고려할 수 있는 교량의 허용처짐 기준이 필요하다고 판단된다. 본 논문에서는, 한국철도교설계기준의 허용처짐기준을 주파수영역의 진동사용성 기준과 비교하였으며, 프랑스 및 일본의 철도교설계기준의 진동사용성 허용기준 또한 분석하였다. 그 결과, 한국철도교설계기준의 경우 열차의 속도에 따른 기준으로 진동지속시간이 부분적으로 고려되었지만 진동사용성은 만족하지 못하고 있는 것으로 판단되었으며, 국외 철도교설계기준비 분석결과, 진동사용성을 고려한 허용처짐기준을 제시할 수 있을 것으로 판단하였다. 공용중인 철도교량의 진동사용성을 평가하기위하여 다양한 형식의 철도교량의 진동신호를 측정하였다. 그리고, 현장에서 적용하기 편리한 진동사용성 처짐 및 강성한계를 제시하기 위하여 공용중인 교량을 대상으로 차량 교량 상호작용해석을 수행하였다.

• Nuclear Engineering and Technology
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• 제42권4호
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• pp.450-459
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• 2010

The present paper investigates the collapse pressure of cylinders with intermediate thickness subjected to external pressure based on detailed elastic-plastic finite element (FE) analyses. The effect of the initial ovality of the tube on the collapse pressure was explicitly considered in the FE analyses. Based on the present FE results, the analytical yield locus, considering the interaction between the plastic collapse and local instability due to initial ovality, was also proposed. The collapse pressure values based on the proposed yield locus agree well with the present FE results; thus, the validity of the proposed yield locus for the thickness range of interest was verified. Moreover, the partial safety factor concept based on the structural reliability theory was also applied to the proposed collapse pressure estimation model, and, thus, the priority of importance of respective parameter constituting for the collapse of cylinders under external pressure was estimated in this study. From the application of the partial safety factor concept, the yield strength was concluded to be the most sensitive, and the initial ovality of tube was not so effective in the proposed collapse pressure estimation model. The present deterministic and probabilistic results are expected to be utilized in the design and maintenance of cylinders subjected to external pressure with initial ovality, such as the once-through type steam generator.

• 한국컴퓨터그래픽스학회논문지
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• 제27권4호
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• pp.1-9
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• 2021

축삭(axon), 가지돌기(dendrite), 신경세포체(cell body)와 같은 뉴런의 소기관을 분리하는 작업은 신경학적 현상의 분석에 도움을 준다. 최근에 딥러닝 기술을 이용하여 이를 수행하고자 하는 시도들이 있지만, 데이터의 노이즈, 훈련 데이터와의 차이 등으로 인해 결과에 오류를 포함할 가능성이 있다. 따라서, 이러한 기술을 실제 분석에 활용하기 위해서는 결과를 교정하는 과정이 필수적이지만, 이는 전문가가 수작업으로 수행해야 하기 때문에 많은 노력과 시간이 소요된다. 우리는 딥러닝 결과에 존재하는 오류들을 보다 손쉽게 교정할 수 있는 대화형 뉴런 구조 교정 방법을 제안한다. 이 방법은 구조적 일관성을 지니는 뉴런의 특성을 기반으로 뉴런 구조를 교정하여 적은 사용자의 인터랙션으로도 높은 정확도의 교정 결과를 얻을 수 있도록 한다.