• Smart Structures and Systems
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• v.9 no.3
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• pp.231-251
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• 2012

The stochastic optimal control for a piezoelectric spherically symmetric shell subjected to stochastic boundary perturbations is constructed, analyzed and evaluated. The stochastic optimal control problem on the boundary stress output reduction of the piezoelectric shell subjected to stochastic boundary displacement perturbations is presented. The electric potential integral as a function of displacement is obtained to convert the differential equations for the piezoelectric shell with electrical and mechanical coupling into the equation only for displacement. The displacement transformation is constructed to convert the stochastic boundary conditions into homogeneous ones, and the transformed displacement is expanded in space to convert further the partial differential equation for displacement into ordinary differential equations by using the Galerkin method. Then the stochastic optimal control problem of the piezoelectric shell in partial differential equations is transformed into that of the multi-degree-of-freedom system. The optimal control law for electric potential is determined according to the stochastic dynamical programming principle. The frequency-response function matrix, power spectral density matrix and correlation function matrix of the controlled system response are derived based on the theory of random vibration. The expressions of mean-square stress, displacement and electric potential of the controlled piezoelectric shell are finally obtained to evaluate the control effectiveness. Numerical results are given to illustrate the high relative reduction in the root-mean-square boundary stress of the piezoelectric shell subjected to stochastic boundary displacement perturbations by the optimal electric potential control.

• Clean Technology
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• v.12 no.2
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• pp.101-106
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• 2006

HT-$LiCoO_2$ powders were synthesized from hydroxide precursors in this study. The cobalt hydroxide compounds with hydrotalcite-like(${\alpha}$-phase) and/or brucite-like(${\beta}$-phase) structures as a component of the precursor were prepared in various PH conditions using precipitation method. It was found that various phase and compositions of cobalt hydroxides could be tailor-prepared via a careful control of preparation parameters such as the concentration ratio of $[OH^-]/[CO^{2+}]$ and aging time. The hydroxides $Co(OH)_2$ and LiOH were mixed with aqueous methyl-alcohol. The precursor of a HT-$LiCoO_2$ was synthesized via subsequent processes including evaporation, drying and aging. The transformation of tailor-made ${\beta}$-phase $Co(OH)_2$ to CoOOH and formation of solid solution in the precursor were achieved during aging. These results cause HT-$LiCoO_2$ to be synthesized at low temperature($600^{\circ}C$ ) for a short time(10min).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.132-136
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• 1999

Mechanical alloying (MA) by ball mill of $Fe_{30}Cr_{70}$ elemental powders was carried out under the nitrogen gas atmosphere. Amorphization has been observed in this case, while MA under an inert argon gas atmosphere produces the bcc solid solution. The DSC spectrum for the mechanically alloyed $(Fe_{30}Cr_{70})_{0.85}N_{0.15)$powders exhibits a sharp exothermic peak due to crystallization at about $550^{\circ}C$. Structural transformation from the bcc crystalline to amorphous states was observed through X-ray and neutron diffractions. During amorphization process the octahedral unit, which is typical of a polyhedron formed in any crystal structures, was preferentially destroyed and transformed into the tetrahedral unit. Futhermore, neutron diffraction measurements revealed that a nitrogen atom is situated at a center of the tetrahedron formed by metal atoms.

• Journal of Distribution Science
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• v.16 no.12
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• pp.47-56
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• 2018

Purpose - The potential use of cryptocurrencies in a retail environment proposes a rapid shift from the traditional financial system. Nakamoto(2008) defines Bitcoin as an open source alt-coin based on the blockchain technology. Luther(2016) insists that the new technology will be widely adopted for the digital payment processes. However, the use of Bitcoin is in the real world is still sparse. Despite the growing attention and purported benefits, it is doubtful whether the Bitcoin will be eagerly accepted by ordinary consumers in the mainstream market. To answer this question, this paper develops a causal model that has a dual path to explain the motivation to adopt Bitcoin. According to Glaser, Zimmermann, Haferkorn, Weber, and Siering(2014), Bitcoin is both an asset and a currency at the same time. In summary, the attitude towards Bitcoin may vary depending on whether the fin-tech product is viewed as an asset or as a currency. Based on the arguments, we propose that asset attitude and currency attitude will give influence to consumers' intention to adopt Bitcoin. Research design, data, and methodology - Quantitative data collection is conducted from a Bitcoin SIG(special interest group) working in an internet community. As a result, 192 respondents who know Bitcoin completed the survey. To analyze the causal relations in the research model, PLS-SEM(partial least squares structural equation modeling) method is used. Also, reliability and validity of measures are tested by performing Cronbach's alpha test, Fornell-Larcker test and confirmatory factor test. Results - Our test results show that every hypothesis is supported except the influence of perceived ease of use. In addition, we find that the relationships between constructs are different between the high innovative group and low innovative group. Conclusions - We provide evidence that asset attitude and currency attitude are key antecedents of Bitcoin adoption.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1138-1149
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• 1993

A new mode synthesis method using Lagrange multipliers and substructure hybrid interface modes is presented. Substruture governing equations of motion are derived using Lagrange equations and the constraints of geometric compatibility between the substructures are treated with Lagrange multipliers. Fixed, free, and loaded interface modes can be employed for the modal bases of each substructure. In cases of the fixed and loaded interface modes, two successive modal transformation relations are used. Compared with the conventional mode synthesis methods, the suggested method does not construct the equations of motion of the coupled structure and the final characteristic equation becomes a polynomial. Only modal parameters of each substructure and geometric compatibility conditions are needed. The suggested method is applied to a simple lumped mass model and parametric study is performed.

• Journal of the Korean housing association
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• v.13 no.5
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• pp.77-88
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• 2002

This article deals the investigations how to solve the social deficiencies of deteriorate apartments, which is a half cycle of a building and it goes slum clearance and redevelopment. And this proposes an active remodeling and design strategy, management, and housing policies for extending the usage of the resource. Most of apartment housing in Korea is built by the panel wall and slab structure system fur economic price. To remake is possible, even though not designed in flexibility and variation. The remodeling strategies are dwelling unification, transformation of two units to one or three units, addition of a room, changing into commercial and community required spaces, and reshaping of a envelop and facade by addition of a dwelling or dwellings, roof floors, change of materials and colors, and so on. And, all activities in structural aspect are proposed removal in upper part and addition in lower part of an apartment housing. Active remodeling cost a great deal compare to new construction, so any remodeling activities should be based on a minimal interfere and budgets to enhancing the quality in existing building. The final aim of an active remodeling is to enhance the quality in economic values, and to keep original state and to put on the new one in a small part. To promote the active and careful management and rehabilitation, it is necessary to give the positive incentive in terms of architectural law, bank loan, and any redevelopment project should get the remodeling record in national resources.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.47.2-47.2
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• 2013

We present ultraviolet (UV) color-magnitude relations (CMRs) of early-type dwarf galaxies in the Viro cluster, combining Galaxy Evolution Explorer (GALEX) UV data with SDSS optical data, based on the Extended Virgo Cluster catalog (EVCC). We find that dwarf lenticular galaxies (dS0s) show a surprisingly distinct and tight locus separated from that of ordinary dEs, which is not clearly seen in previous CMRs. The dS0s in UV CMRs follow a steeper sequence than dEs and show bluer UV-optical color at a given magnitude. We explore the observed CMRs with population models of a luminosity-dependent delayed exponential star formation history. The observed CMR of dS0s is well matched by models with relatively long delayed star formation. The dS0s are most likely transitional objects at the stage of subsequent transformation of late-type progenitors to ordinary red dEs in the cluster environment. Most early type dwarf galaxies with blue UV colors (FUV-r < 6 and NUV-r < 4) are identified as those showing spectroscopic hints of recent or ongoing star formation activities. In any case UV photometry provides a powerful teel to disentangle the diverse subpopulations of early-type dwarf galaxies and uncover their evolutionary histories. lenticular galaxies, and irregular high surface brightness (HSB) galaxies, respectively. Dwarf elliptical galaxies and dwarf irregular LSB galaxies occupy the similar structural parameter spaces. We suggest that giant elliptical galaxies and dwarf elliptical galaxies may have different origin.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.51-54
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• 2005

Shape memory alloys (SMAs) find many applications in smart composite structural systems as the active components. Their ability to provide a high force and large displacement makes them an excellent candidate for an actuator for controlling the shape of smart structures. In this paper, using a macroscopic model that captures the thermo-mechanical behaviors and the two-way shape memory effect (TWSME) of SMAs smart morphing polymeric composite shell structures like shape-changeable UAV wings is demonstrated and analyzed numerically and experimentally when subjected to various kinds of pressure loads. The controllable shapes of the morphing shells to that thin SMA strip actuator are attached are investigated depending on various phase transformation temperatures. SMA strips start to transform from the martensitic into the austenitic state upon actuation through resistive heating, simultaneously recover the prestrain, and thus cause the shell structures to deform three dimensionally. The behaviors of composite shells attached with SMA strip actuators are analyzed using the finite element methods and 3-D constitutive equations of SMAs. Several morphing composite shell structures are fabricated and their experimental shape changes depending on temperatures are compared to the numerical results. That two results show good correlations indicates the finite element analysis and 3-D constitutive equations are accurate enough to utilize them for the design of smart composite shell structures for various applications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.221-228
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• 2011

The large-area crystallization of amorphous silicon thin films on glass backplanes is one of the key technologies in the manufacture of flat-panel displays. Joule-heating induced crystallization (JIC) is a recently introduced crystallization technology. It is considered a highly promising technique for fabricating OLEDs, because the film of amorphous silicon on glass can be crystallized in tens of microseconds, minimizing thermal and structural damage to the glass. In this study, we theoretically and experimentally investigated the temperature variation during the phase transformation. The critical temperatures for crystallization were determined for both solid-solid and solid-liquidsolid transitions, by carrying out in-situ temperature measurements and numerical analysis of the JIC.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.15 no.1
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• pp.23-41
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• 2004

In indexing and organizing Web resources, there have been two basic methods: automatic indexing by extracting key words and library classification schemes or subject directories of search engines. But, both methods have failed to satisfy the user's information needs, due to the lack of standard criteria and the irrationality of its structural system. In this paper I have examined the limits of library classification scheme's structures and the problems related to the nature of Web resources such as specificity and exhaustivity. I have also attempted to explain the logicality of Web resources organization by facet analysis and its strengths and limitations. In so doing, I have proposed three specific methods in using facet analysis: firstly, indexing system by facet analysis; secondly, the alternative transformation of the enumerative classification scheme into facet classification scheme; and finally, the facet model of subject directory of domestic search engine. After examining the three methods, my study concludes that a controlled vocabulary by facet analysis can be employed as a useful method in organizing Web resources.