• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.799-804
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• 2016

Broadband powerline communication (BPLC) uses distribution lines as a medium for achieving effective bidirectional data communication along with electric current flow. As the material characteristics of power lines are not good at the communication channel, the development of power line communication (PLC) systems for internet, voice, and data services requires measurement-based models of the transfer characteristics of the network suitable for performance analysis by simulation. In this paper, an analytic model describing a complex transfer function is presented to obtain the attenuation and path parameters for a multipath power line model. The calculated results demonstrated frequency-selective fading in multipath channels and signal attenuation with frequency, and were in good agreement with the experimental results. Inductive coupling units are used as couplers for coupling the signal to the power line to avoid physical connections to the distribution line. The inductance of the ferrite core, which depends on the frequency, determines the cut-off frequency of the inductive coupler. Coupling loss can be minimized by increasing the number of windings around the coupler. Coupling efficiency was improved by more than 6 dB with three windings compared to the results obtained with one winding.

• Elastomers and Composites
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• v.44 no.3
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• pp.196-208
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• 2009

Sophisticated polymeric materials with 'responsive' properties are beginning to reach the market. The use of reversible, noncovalent interactions is a recurring design principle for responsive materials. Recently developed hydrogen-bonding units allow this design principle to be taken to its extreme. Supramolecular polymers, where hydrogen bonds are the only force keeping the monomers together, form materials whose (mechanical) properties respond strongly to a change in temperature or solvent. In this review, we describe some examples of hydrogen-bonded supramolecular polymers that can be utilized for self-healing materials. Synthesis of a rubber-like material that can be recycled might not seem exciting. But one that can also repeatedly repair itself at room temperature, without adhesives, really stretches the imagination. Autonomic healing materials respond without external intervention to environmental stimuli in a nonlinear and productive fashion, and have great potential for advanced engineering systems.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.2
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• pp.167-172
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• 2004

In the human skin, vitamin C (L -ascorbic acid) that is well known as the activated materials has effects that is skin anti-aging and wrinkle repair by giving impetus to collagen biosynthesis and anti-oxidation, and that is the sun screen, a wound recovering, inhibition melanogenesis and so on. In spite of its effects, vitamin C has the defects of the skin stimulation and easily oxidized instability by water, air, heat and light. For solving their matters, many investigation is advanced and its results are synthesized the various vitamin C derivatives. And yet they have not solved the unstable property of vitamin C and were still insufficient for the comparing with the effect of the pure vitamin C itself. In this study, in order to prepare vitamin C derivative of being improved the stability and to apply vitamin C effect in the skin, we prepared new vitamin C derivative, phytosphingosine ascorbate, by using phytosphingosine, one of sphingolipids, which have a distinguished skin affinity. Phytosphingosine ascorbate can be prepared as the ionic bond between amine group (-NH$_2$) of phytosphingosine and hydroxy group (-OH) of vitamin C by way of the relatively simple reaction. So the structure and properties of the synthesized phytosphingosine ascorbate was confirmed the use of elemental analysis (C 58.3 : H 9.3 : N 2.8 : O 29.5), MALDI TOF-MS (Mw=492.58), Ultraviolet spectra (268.5nm), lH NMR, FT-IR spectra, thermal analysis (m.p=l54$^{\circ}C$), HPLC and so on. And we could confirm the anti-bacterial and anti-oxidation effects. Based on these results, we could confirm to prepare a new material that was expected of both effects of vitamin C and phytosphingosine and that is improved properties of vitamin C.

• The Journal of the Convergence on Culture Technology
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• v.6 no.1
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• pp.135-145
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• 2020

This research is mainly aimed at finding out about the effects of the safety and health management system on corporate performance through systematic operation by efficiently allocating material and human resources within the company by participating all employees and stakeholders in order to prevent and maintain industrial accidents and the optimal working environment, and how to maintain and activate the safety and health management system at the center of electric contractors.The analysis results are as follows. First, management, organizational management and resource preparation will have a positive impact on the management capability of the electric power corporation. It was assessed that the more well-transmitted and understood within the organization, the better the construction plan, the better the equipment management status, the more positively the management capability of electric works was to be achieved. Second, management, organizational management and resource preparation will have a positive impact on corporate management performance.This seems to have a positive effect on a company's business performance when the standards of OHSAS are met with construction plan and construction equipment management are high as related information such as industrial safety and health laws are strengthened and companies' safety and health activities, advanced safety and culture are released to facilitate organizational management.Third, the management ability of the electric power corporation will have a mediated effect on the effect of management, organization management and resource preparation on the performance of the enterprise. This means that the direct effect of the independent variable management organization on corporate management performance is .401 The indirect effect is .168.658 shows that the direct effect of resource preparation on corporate management performance is .423, the indirect effect is .178 and the total effect.It was analyzed at 643.

• Korean Journal of Optics and Photonics
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• v.19 no.3
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• pp.199-207
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• 2008

Wavelength converting devices with a ridge-type waveguide in periodically poled $MgO:LiNbO_3$ are made and characterized. The experimental results are compared with theoretical analysis on the effects of waveguide dimension and duty ratio of the periodically poled structure. To show the relationship of the conversion efficiency to those factors, a new measurement system is configured. That experimental results show that the center wavelength, normalized conversion efficiency and full width half maximum of the conversion efficiency curve are 1067.45 nm, 90.7%/$Wcm^2$ and 0.17 nm, respectively. Also, the estimated results of the duty period and full width half maximum of the conversion efficiency from theoretical calculations agreed well with experimental results with the errors of 0.016 ${\mu}m$ and 0.01 nm.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.4
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• pp.173-181
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• 2018

Recently composite materials have dominated most engineering fields, owing to their better performance, increased durability and flexibility to be customized and designed for a specific required property. This has given them unprecedented superiority over conventional materials. With the help of the ever increasing computational capabilities of computers, researchers have been trying to develop accurate material models for the complex and integrated properties of these composites. This has led to advances in virtual testing of composite materials as a supplement or a possible replacement of laboratory experiments to predict the properties and responses of composite materials and structures. This paper presents a review on the complex multi-scale modelling framework of the virtual testing machines, which involve computational mechanics at various length-scales starting with nano-mechanics and ending in structure level computational mechanics, with a homogenization technique used to link the different length scales. In addition, the paper presents the features of some of the biggest integrated virtual testing machines developed for study of concrete, including a multiscale modeling scheme for the simulation of the constitutive properties of nanocomposites. Finally, the current challenges and future development potentials for virtual test machines are discussed.

• The Journal of Advanced Prosthodontics
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• v.1 no.1
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• pp.19-25
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• 2009

STATEMENT OF PROBLEM. Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc. PURPOSE. The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone(Group 1) and the rest of which were not engaged to inferior cortical wall(Group 2) by measuring the implant stability quotient(ISQ) and the removal torque value(RTV). MATERIAL AND METHODS. In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer s recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell $mentor^{(R)}$ and with removal torque using MGT50 torque gauge. RESULTS. In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants(P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not(P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2(P < .05). CONCLUSIONS. Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.

• Polymer(Korea)
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• v.36 no.4
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• pp.440-447
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• 2012

The branched copolyester was synthesized and its molecular weight, $T_g$, 1/2 method temperature ($T_{1/2}$) and rheological properties were characterized for the application of toner binder. The linear copolyester had low molecular weight and melt elasticity obtained by dimethylterephthalate (DMT), ethylene glycol (EG) and 2,2-bis(4-(2-hydroxypropoxy) phenyl)propane (HPP). The branched copolyesters prepared with various branching agents such as 2-(hydroxymethyl)-2-ethylpropane-1,3-diol (trimethylol propane, TMP), 2,2-bi(hydroxymethyl)-1,3-propanediol (pentaerythritol, PER), 1,2,4-benzenetricarboxylic anhydride (trimellitic anhydride, TMA) and glycerol to improve the physical properties of the linear copolyester. The effect of branching agents on the molecular weight and melt elasticity of the branched copolyester was examined. The branched copolyesters prepared by adding over 15 mol% of branching agent showed relatively high molecular weight and melt elasticity, and $T_{1/2}$ value of $140^{\circ}C$. Therefore, the highly branched copolyesters were deemed suitable as a hot-melt toner of laser print process.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.77-85
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• 2011

The silicon-germanium (SiGe) alloy, which is compatible with silicon semiconductor technology and has a smaller band gap and a lower thermal conductivity than silicon, has been used to fabricate electronic devices such as transistors, photodetectors, solar cells, and thermoelectric devices. This paper reviews the application of SiGe alloys to electronic devices and related technical issues. Since the SiGe alloy comprises germanium whose band gap is smaller than silicon, its band gap is also smaller than that of silicon irrespective of the ratio of silicon to germanium. This narrow band gap of SiGe enables the base thickness of bipolar transistors to decrease without a loss in current gain so that it is possible to improve the speed of bipolar transistors by adopting the SiGe-base. In addition, the conversion efficiency of solar cells is enhanced by the absorption of long-wavelength light in the SiGe absorption layer. Phonon scattering caused by the irregular distribution of alloying elements induces the lower thermal conductivity of SiGe than those of pure silicon and germanium. Because a thin film layer with a low thermal conductivity suppresses thermal conduction through a thermal sink, the SiGe alloy is considered to be a promising material for silicon-based thermoelectric systems.

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.135-145
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• 2007

The needs for the ultra fine particles have been increased in preparation field of raw powders such as fine ceramics and high functional products. In this study, a series of wet grinding experiments were carried out on inorganic powders such as calcite, pyrophyllite and talc by a stirred ball mill. The particle size distribution of ground products of each test material fur a given grinding time was found to be expressed by the grinding rate (selection function) which was obtained from the grinding kinetics analysis. The median diameter decreased from 6.49 to $0.47{\mu}m$ in calcite, and decreased from 3.91 to $1.14{\mu}m$ in pyrophyllite. However, in talc, median diameter was decreased a little bit from 10.30 to $6.67{\mu}m$. The grinding rate changing on calcite and pyriphyllite were similar at the same conditions. However, in the case of talc, it was observed that the grinding rate was not increased compared to other samples.