• Current Photovoltaic Research
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• v.4 no.1
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• pp.16-20
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• 2016

$Cu_2ZnSnS_4$ (CZTS) thin films were fabricated by successive electrodeposition of layers of precursor elements followed by sulfurization of an electrodeposited Cu-Zn-Sn precursor. In order to improve quality of the CZTS films, we tried to optimize the deposition condition of absorber layers. In particular, I have conducted optimization experiments by changing the Cu-layer deposition time. The CZTS absorber layers were synthesized by different Cu-layer conditions ranging from 10 to 16 minutes. The sulfurization of Cu/Sn/Zn stacked metallic precursor thin films has been conducted in a graphite box using rapid thermal annealing (RTA). The structural, morphological, compositional, and optical properties of CZTS thin films were investigated using X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and X-ray Flourescenece Spectrometry (XRF). Especially, the CZTS TFSCs exhibits the best power conversion efficiency of 4.62% with $V_{oc}$ of 570 mV, $J_{sc}$ of $18.15mA/cm^2$ and FF of 45%. As the time of deposition of the Cu-layer to increasing, the properties were confirmed to be systematically changed. And we have been discussed in detail below.

• Journal of Information Technology Services
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• v.18 no.5
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• pp.133-153
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• 2019

The application of mindfulness is increasing in corporation for business innovation. However, the influence of mindfulness has not been confirmed for employee in detail. Mindfulness is the awareness that arises from paying attention in the present. We often experience uncertainty abounds about what the information technology is, how well it works in the process of using information technology. According to the definition of mindfulness, mindfulness can deepen employee's thoughts and understanding of information technology and will provide a clue to the solution of the issue. This study focusses on impact of mindfulness on IT usage behavior, particularly on IT continuance usage. Research question of this study is whether mindfulness impact perceived factors related to IT continuance usage. The study of relationship between IT and mindfulness will have meaningful results because both IT and Mindfulness are aimed at corporate innovation. Based on most recent theory in IT continuance usage, called by Decomposed Expectation-Disconfirmation Model, we established hypotheses and examined the impact of mindfulness on perceived factors in process of IT continuance usage. For empirical analysis, we collected 303 employee samples and conducted Structural Equation Modeling for path analysis. We showed that mindfulness has a positive impact on perceived usefulness, usability and usefulness confirmation, usability confirmation. We also confirmed that antecedent of satisfaction is perceived usefulness, perceived usability and usefulness confirmation, usability confirmation, and satisfaction is the cause of IT continuance usage. We suggested academic and practical implication based on empirical analysis results. In academic perspective, we found the role of mindfulness in process of IT continuance usage. From practical point of view, we suggest to use of mindfulness program for IT continuance usage in corporation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.95-101
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• 2009

The surface characteristics of Zachery-treated turquoise stones have been studied in detail with a comparison of natural and plastic-impregnated turquoise. The SEM-EDS analysis exhibited that Zachery-treated turquoise was characterized by the uniform distribution of potassium element through the specimen and did not show the sharp crystalline $SiO_2$ facet and boundary phase which are common in natural ore. The potassium element shown in the Zachery-treated turquoise seemed to be occurred during the treatment process for the improvement of durability. The bar-shaped crystals observed in the pore was found to be a feature of Zachery treated turquoise and are expected to influence on their stability and durability, while the pore sizes in turquoise stones depends on the parameter of the treatment procedure.

• Journal of Information Technology Services
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• v.10 no.4
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• pp.1-19
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• 2011

Following the growth of e-Business, there has been a recent increase of interest in promoting Social Business (s-Business) based on Social Network Service(SNS). As the introduction of the Internet brought about the increasing number of its users followed by the growing market of e-Commerce, online games, and e-Learning, the increasing number of SNS users has opened the new markets combining the existing industrial fields with SNS, and it developed into a revenue model beyond the mere sharing of information. Despite such industrial and social environments, understanding of new social business technology from the aspect of business has been insufficient, and the empirical study on participation in the social business has been scant as well. Thus, the main purpose of this study is to investigate the s-Business in detail and to study the factors giving influence to the users' participation in s-Business. This study proposes six variables(Self-Empowerment, Job Relevance, Formation of Social Capital, Relative Advantage, Shared Value, Relationship Specified Investment) and the moderating effects of Psychological Contract as influential factors closely related with s-Business. A total of 362 data from a survey were analyzed by using Structural Equation Modeling(SEM). Result showed that all factors with the exception of Job Relevance have meaningful influence on the intention to participate in s-Business. The implication of the findings suggests to compliment limitations of the existing researches, and to prepare the theoretical foundation for promoting s-Business participation in addition to further suggesting directionality from the view point of the users of the social business-relevant studies.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.515-526
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• 2009

There are three main production processes in the manufacture of concrete-filled square steel columns. The first process is known as the 'box-type process' or 'four-seam method,' wherein four beams are welded together at the seams. The second is the 'cold-forming process' or 'two-seam method,' wherein the seams of two channel beams are welded together. The third is the 'pressing process' or 'one-seam method,' wherein a circular column is pressed until it becomes a square column. In calculating the production cost for the making of a steel tube, it is very important to consider the welding process to be used and the desiredthickness of the steel tube, such as a square column that was developed under a new method, formed through the four-seam flare welding method at the center of the steel column width, following the L-shape formation. Certain tests were suggested in this study to evaluate the welding amount of concrete-filled square steel columns. With the parameters of the production method of a square steel column, the thickness of the steel square columns, and the welding amount, six specimens were produced. A structural test and finite-element analysis were conducted to assess the behavior of the steel column according to the water pressure inside the steel columns.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.17-28
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• 2002

Tunnel construction is a complex three dimensional operation. Since, however, it is neither possible nor useful to simulate all conditions and parameters in detail, a simplified two dimensional model is commonly employed in practice. The simulation of three dimensional conditions by a two dimensional model should use empirical parameters. The numerical predictions indicate that analysis results are highly dependent on the parameters. An improved modelling method based on time was adopted to account for three dimensional effect at the tunnel heading and time dependent nature, and used to perform an analysis of tunnelling in decomposed granite. The effects of weathering degree, tunnel shape and multi-drift excavation were investigated by using the method. It is identified that a structural benefit can be obtained by adopting a horse-shoe-shaped cross section with multi-drift excavation in mixed-force ground condition.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.2
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• pp.67-73
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• 2015

The microcystin is a cyclic heptapeptide from metabolites of cyanobacteria in the genera mycrocystis, anabaeba as a result of eutrophication. It has been known that microcystin-LR is a potent inhibitor of the catalytic subunits of protein phosphatase-1 (PP-1) as well as powerful tumor promoter. The active site of microcystin actually has two metal ions $Fe^{2+}/Zn^{2+}$ close to the nucleophilic portion of PP-1-microcystin complex. We report the isolation and purification of this microcystin-LR from cyanobacteria (blue-green algae) obtained from Daechung Dam in Chung-cheong Do, Korea. Microcystin-LR was extracted from solid-phase extraction (SPE) sample preparation using a CN cartridge. The cyanobacteria extract was purified to obtain microcystin-LR by HPLC method and identified by LC/MS. The detail structural studies that can elucidate the possible role of monovalent and divalent metal ions in PP-1-microcystin complexation were carried out by utilizing molecular dynamics. Conformational changes in metal binding for ligands were monitored by molecular dynamic computation and potential of mean force (PMF) using the method of the free energy perturbation. The microcystin-metal binding PMF simulation results exhibit that microcystin can have very stable binding free energy of -10.95 kcal/mol by adopting the $Mg^{2+}$ ion at broad geometrical distribution of $0.5{\sim}4.5{\AA}$, and show that the $K^+$ ion can form a stable metal complex rather than other monovalent alkali metal ions.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.2
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• pp.1-10
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• 2011

The ultimate goal of architecture is to construct a building through design and supervision. According to this circumstance, architectural education divided into two part ; design and construction. However, these two processes have to be one program for better education. In this aspect, steel housing program could be a desirable one because of its structural(bearing wall) system and relative short construction schedule. In KUT architectural program, steel housing has been one of the most effective and important for about ten years. In this research, the contents(s/w) and running process of this program and practice lab(h/w) will be introduced with detail. And this study could be a good guideline for a better combination program with theory and practice in architectural engineering field.

• Korea-Australia Rheology Journal
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• v.14 no.4
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• pp.189-201
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• 2002

The interaction between hydrophobically modified hydroxyethyl cellulose (hmHEC), containing approximately 1 wt% side-alkyl chains of $C_{16}$, and an anionic sodium dodecyl sulphate (SDS) surfactant was investigated. For a semi-dilute solution of 0.5 wt% hmHEC, the previously observed behaviour of a maximum in solution viscosity at intermediate SDS concentrations, followed by a drop at higher SDS concentrations, until above the cmc of surfactant when the solution resembles that of the unsubstituted polymer, was confirmed. Additionally, a two-phase region containing a hydrogel phase and a water-like supernatant was found at low SDS concentrations up to 0.2 wt%, a concentration which is akin to the critical association concentration, cac, of SDS in the presence of hmHEC. Above this concentration, SDS molecules bind strongly to form mixed micellar aggregates with the polymer alkyl side-chains, thus strengthening the network junctions, resulting in the observed increase in viscosity and elastic modulus of the solution. The shear behaviour of this polymer-surfactant complex during steady and step stress experiments was examined In great detail. Between SDS concentrations of 0.2 and 0.25 wt%, the shear viscosity of the hmHEC-polymer complex network undergoes shear-induced thickening, followed by a two-stage shear-induced fracture or break-up of the network. The thickening is thought to be due to structural rearrangement, causing the network of flexible polymers to expand, enabling some polymer hydrophobic groups to be converted from intra- to inter-chain associations. At higher applied stress, a partial local break-up of the network occurs, while at even higher stress, above the critical or network yield stress, a complete fracture of the network into small microgel-like units, Is believed to occur. This second network rupture is progressive with time of shear and no steady state in viscosity was observed even after 300 s. The structure which was reformed after the cessation of shear is found to be significantly different from the original state.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.161-168
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• 2015

An experimental study was conducted to scrutinize the influence of the frequency of an ultrasonic standing wave on the variation in the behavior of a methane-air premixed flame. The evolutionary features of the propagating flame were captured by a high-speed camera, and the macroscopic flame behavior, including the flame structure and local velocities, was investigated in detail using a post-processing analysis of the high-speed images. It was found that a structural variation and propagation-velocity augmentation of the methane-air premixed flame were caused by the intervention of the ultrasonic standing wave, which enhanced the combustion reaction. Conclusive evidence for the dependency of the flame behaviors on the driving frequency of the ultrasonic standing wave and equivalence ratio of the reactants is presented.