• Journal of the Korean Chemical Society
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• v.21 no.1
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• pp.23-31
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• 1977

For the metal complex of $d^1$ configuration with the octahedrally coordinated ligands, the crystal field parameter, 10Dq, is calculated from first principles within the framework of the crystal field theory. With the point charge model, the configuration interaction is introduced by use of the Shull-L$\"{o}$wdin functions. Through the Integral Hellmann-Feynman Theorem, the higher order effect is visualized. It is found that the higher order effect on 10Dq is about $50{\%}$ of the first order effect. Since 3d function is angularly undistorted and radially equally distorted in $E_g\;and\;T_{2g}$ states, due to the octahedral potential, the calculated 10Dq is still the unique parameter for the splitting.

• Journal of Magnetics
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• v.16 no.1
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• pp.15-18
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• 2011

We have studied the $TiO_2$ doping effects on the flux pinning behavior of an $MgB_2$ superconductor synthesized by the in-situ solid-state reaction. From the field-cooled and zero-field-cooled temperature dependences of magnetization, the reversible-irreversible transition of $TiO_2$-doped $MgB_2$ was determined in the H-T diagram (the temperature dependence of upper critical magnetic field and irreversibility line). For comparison, the similar measurements are also obtained from SiC-doped $MgB_2$. The critical current density was estimated from the width of hysteresis loops in the framework of Bean's model at different temperatures. The obtained results manifest that nano-scale $TiO_2$ inclusions served as effective pinning centers and lead to the enhanced upper critical field and critical current density. It was concluded that the grain boundary pinning mechanism was realized in a $TiO_2$-doped $MgB_2$ superconductor.

• Nano
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• v.13 no.12
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• pp.1850145.1-1850145.8
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• 2018

In this study, a double-solvent radiation method is proposed to prepare silver nanoparticles in the pores of metal-organic framework MIL-101(Cr). The results reveal that well-dispersed silver nanoparticles with a diameter of about 2 nm were successfully fabricated in the cages of monodisperse octahedral MIL-101(Cr) with a particle size of about 400 nm. The structure of MIL-101(Cr) was not destroyed during the chemical treatment and irradiation. The resulting Ag/MIL-101 exhibits excellent catalytic performance for the reduction of 4-nitrophenol. This method can be extended to prepare other single or bimetallic components inside porous materials.

• Advances in nano research
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• v.10 no.4
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• pp.339-347
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• 2021

In the framework of the density functional theory combined with the method of non-equilibrium Green functions (DFT + NEGF), the electric transport properties of a one-dimensional nanodevice consisting of telescoping polyprismanes with various types of electrical conductivity were studied. Its transmission spectra, density of state, current-voltage characteristic, and differential conductivity are determined. It was shown that C_[14,17], C_[14,11], C_[14,16], C_[14,10] show a metallic nature, and polyprismanes C_[14,5], C_[14,4] possess semiconductor properties and has a band gap of 0.4 eV and 0.6 eV, respectively. It was found that, when metal C_[14,11], C_[14,10] and semiconductor C_[14,5], C_[14,4] polyprismanes are coaxially connected, a Schottky barrier is formed and a weak diode effect is observed, i.e., manifested valve (rectifying) property of telescoping polyprismanes. The enhancement of this effect occurs in the nanodevices C_[14,17] - C_[14,11] - C_[14,5] and C_[14,16] - C_[14,10] - C_[14,4], which have the properties of nanodiode and back nanodiode, respectively. The simulation results can be useful in creating promising active one-dimensional elements of nanoelectronics.

• Structural Engineering and Mechanics
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• v.77 no.1
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• pp.57-74
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• 2021

The thermal eigenvalue responses of the graded sandwich shell structure are evaluated numerically under the variable thermal loadings considering the temperature-dependent properties. The polynomial type rule-based sandwich panel model is derived using higher-order type kinematics considering the shear deformation in the framework of the equivalent single-layer theory. The frequency values are computed through an own home-made computer code (MATLAB environment) prepared using the finite element type higher-order formulation. The sandwich face-sheets and the metal core are discretized via isoparametric quadrilateral Lagrangian element. The model convergence is checked by solving the similar type published numerical examples in the open domain and extended for the comparison of natural frequencies to have the final confirmation of the model accuracy. Also, the influence of each variable structural parameter, i.e. the curvature ratios, core-face thickness ratios, end-support conditions, the power-law indices and sandwich types (symmetrical and unsymmetrical) on the thermal frequencies of FG sandwich curved shell panel model. The solutions are helping to bring out the necessary influence of one or more parameters on the frequencies. The effects of individual and the combined parameters as well as the temperature profiles (uniform, linear and nonlinear) are examined through several numerical examples, which affect the structural strength/stiffness values. The present study may help in designing the future graded structures which are under the influence of the variable temperature loading.

• Advances in nano research
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• v.10 no.5
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• pp.471-479
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• 2021

In the framework of the density functional theory combined with the method of non-equilibrium Green functions (DFT + NEGF), the electric transport properties of a one-dimensional nanodevice consisting of telescoping polyprismanes with various types of electrical conductivity were studied. Its transmission spectra, density of state, current-voltage characteristic, and differential conductivity are determined. It was shown that C_[14,17], C_[14,11], C_[14,16], C_[14,10] show a metallic nature, and polyprismanes C_[14,5], C_[14,4] possess semiconductor properties and has a band gap of 0.4 eV and 0.6 eV, respectively. It was found that, when metal C_[14,11], C_[14,10] and semiconductor C_[14,5], C_[14,4] polyprismanes are coaxially connected, a Schottky barrier is formed and a weak diode effect is observed, i.e., manifested valve (rectifying) property of telescoping polyprismanes. The enhancement of this effect occurs in the nanodevices C_[14,17] - C_[14,11] - C_[14,5] and C_[14,16] - C_[14,10] - C_[14,4], which have the properties of nanodiode and back nanodiode, respectively. The simulation results can be useful in creating promising active one-dimensional elements of nanoelectronics.

• International Journal of High-Rise Buildings
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• v.12 no.2
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• pp.145-152
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• 2023

Typical floor systems in contemporary tall buildings consist of reinforced concrete or composite metal deck over framing members and account for a majority of the structural weight of the building. The use of high-density materials, such as reinforced concrete and steel, increases the weight of floor systems, reducing the system's overall efficiency. With the introduction of high-performance materials, mainly mass timber products, and fiber-reinforced composites, in the construction industry, designers and engineers have multiple options to choose from when selecting structural materials. This paper discusses the application of mass timber and carbon fiber composites as structural materials in floor systems of tall buildings. The research focused on a comparative analysis of the structural system efficiency for five different design options for tall building floor systems. Finite Element Analysis (FEA) method was adopted to develop a simulation framework, and parametric structural models were simulated to evaluate the structural performance under specific loading conditions. Simulation results revealed the advantages of lightweight structural materials to improve system efficiency and reduce material consumption. The impact of mechanical properties of materials, loading conditions, and issues related to fire engineering and construction were briefly discussed, and future research topics were identified in conclusion.

• Prospectives of Industrial Chemistry
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• v.17 no.2
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• pp.8-20
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• 2014

나노세공체는 고표면적, 균일한 다공성, 분자크기의 세공구조, 높은 흡착용량, 이온교환 특성, 높은 촉매활성, 분자크기의 형상선택성 등의 특징을 갖기 때문에 촉매 및 흡착제로 나노소재 분야에서 가장 오랫동안 활용되어 왔던 중요한 물질 가운데 하나로 정유 및 석유화학 산업을 비롯한 화학산업과 환경 산업에 광범위하게 사용되고 있다. 본 고찰에서는 결정성 나노세공체 가운데 가장 중요한 제올라이트와 최근 연구가 활발한 하이브리드 나노세공체의 산업적 응용 및 기술개발 동향과 향후 발전 전망에 대해 간략히 기술하였다.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.4
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• pp.433-445
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• 2010

The aim of this study was to evaluate the fixation effect by connecting impression copings and to compare the three types of impression trays which were used in open tray impression technique. Experimental groups used 3 types of impression trays which are custom tray, plastic metal combination tray and polycarbonate stock tray. These three groups were subdivided into splinted and non-splinted impression copings group. The total number of experimental groups was six. 10 specimens were made for each group. We used 1-screw test, observing the specimen on which only one side abutment of reference framework was fixated with 20 Ncm. The gap between implant analogue and abutment of the other side was observed by stereo microscope. It was measured at 6 points in each specimen. Measuring value was selected when same result was revealed 3 times. Recorded data were statistically analyzed. Whether impression copings were splinted or not, there was no significant difference among custom tray group, plastic metal combination tray group, and polycarbonate stock tray group. Significant statistical difference in vertical fit discrepancy was found between splinted and non-splinted impression copings group with custom tray, plastic metal combination tray and polycarbonate stock tray (p<0.05).

• Korean Journal of Heritage: History & Science
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• v.54 no.2
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• pp.216-239
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• 2021

Inlay (入絲), a poetic technique of digging grooves in the surface of crafts and decorating them with metal materials, was used throughout the royal daily routines, ceremonies and government officials of the Joseon Dynasty. The government-owned handicraft industry in the Joseon Dynasty was composed of craftsmen belonging to central and local government offices and was operated mainly by government-owned craftsmen. The inlay craftsman was transferred to the central government office and was in charge of inlay poetry for crafts. The current records of Korean inlay craftsmen are concentrated in the state-owned handicraft industry. In the state-owned handicraft industry, the government offices of inlay craftsmen can be divided into Kongjo (工造), Sangeuiwon (尙衣院), and the military. Here the election of a temporary government office for airspace is added. The government offices and military inlay craftsmen who use inlay crafts are assigned, and the inlay craftsmen are placed separately in the temporary office where the fine division of labor is developed. It can be made by utilizing craftsmen. The operation of these production systems was indispensable in pre-modern Korean society, where crafts had to be produced by hand. In this paper, we investigated the roles and job types of craftsmen in the state-owned handicraft industry during the Joseon Dynasty, focusing on inlay craftsmen. Although the details applied to the characteristics and materials of the field, labor supply and demand, etc. are different, Korea pursued crafts for various purposes through craftsmanship within the framework of the basic state-owned handicraft policy . The institutional equipment for implementation was almost common. We believe that adding and analyzing some literature records and relics will help us to study the crafts of the Joseon era in more detail.