• Advances in environmental research
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• v.7 no.1
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• pp.13-28
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• 2018

It is currently agreed upon that one of the major challenges in the construction industry is the energy efficiency of existing buildings. The World Meteorological Organisation (WMO) and United Nations (UN) have reported that the concentration of global atmospheric carbon dioxide has increased by an average of 50%, a record speed, from 2015 to 2016. The housing sector contributes to 45% of the UK's carbon emissions. To help tackle some of those issues the recast Energy Performance Building Directive (EBPD) has introduced Nearly Zero Energy Buildings (NZEBs) in the coming years (including buildings that will undergo refurbishment/renovations). This paper will explore the retrofitting of a UK residential dwelling using Thermal Analysis Simulation (TAS, EDSL) software by focusing on building fabric improvements and usage of on-site renewables. The CIBSE Test Reference Year (TRY) weather data has been selected to examine the performance of the building under current and future climate projections. The proposed design variables were finally implemented in the building altogether on TAS. The simulation results showed a reduction in the building's annual energy consumption of $122.64kWh/m^2$ (90.24%). The greatest savings after this were achieved for the annual reduction in carbon emissions and avoided emissions, which were 84.59% and $816.47kg/CO_2$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.135-140
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• 1997

The influences of ZrB$_2$ additions to SiC on microstructural, DDM(Electrical Discharge Machining), mechanical and electrical properties were investigated. composites were prepared by adding 15, 30, 45 vol.% ZrB$_2$particles as a second phase to SiC matrix. SiC-ZrB$_2$ composites obtained by hot pressing for high temperature structural application were fully dense with the relative densities over 99%. The fracture toughness of the composites were increased with the ZrB$_2$contents. In case of composite containing 30vol.% ZrB$_2$, the flexural strength and fracture toughness showed 45% and 60% increase, respectively compared to that of monolithic SiC sample. The electrical resistivities of SiC-ZrB$_2$ composites decreased significantly with the ZrB$_2$ contents. The electrical resistivity of SiC-30vol.% ZrB$_2$ composite showed 6.50$\times$10$^{-4}$ $\Omega$.cm. Cutting velocity of EDM of SiC-ZrB$_2$ composites are directly proportional to duty factor of pulse width. Surface roughness, however, are not all proportional to pulse width. Higher-flexural strength composites show a trend toward smaller crater volumes, leaving a smoother surface; the average surface roughness of the SiC-ZrB$_2$ 15 vol.% composite with the flexural strengthe of 375㎫ was 3.2${\mu}{\textrm}{m}$, whereas the SiC-ZrB$_2$ 30.vol% composite of 457㎫ was 1.35${\mu}{\textrm}{m}$. In the SEM micrographs of the fracture surface of SiC-ZrB$_2$ composites, the SiC-ZrB$_2$ two phases are distinct; the white phase is the ZrB$_2$and the gray phase is the SiC matrix. In the SEM micrographs of the EDM surface, however, these phases are no longer distinct because of thicker recast layer of resolidified-melt-formation droplets present. It is shown that SiC-ZrB$_2$ composites are able to be machined without surface cracking.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.107-113
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• 2016

In this study, an anion-exchange ionomer solution was prepared by grinding poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) in liquid nitrogen for solid alkaline fuel cells (SAFCs). Type of quaternized PPO (QPPO) solutions was controlled by grinding time. The ionomer binder solutions were characterized in terms of dispersity, particle size, and electrochemical properties. As a result, ionomer binder solutions using grinded polymer showed higher dispersion and smaller particle size distribution than that using non-grinded polymer. The highest ionic conductivity and IEC of the membrane recast by using BPPO-G120s were $0.025S\;cm^{-1}$ and $1.26meq\;g^{-1}$, respectively.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.2
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• pp.181-190
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• 1993

The purpose of this study was to evaluate the effect of shear bond strength between various percentage of reused dental ceramic alloys and porcelain. One hundred specimens were made of one semiprecious alloy and three nonprecious alloys. Each alloy group was subdevided into five groups according to the additional precentage of new alloy. Group I specimens were made of 100% new alloy and served as the control of the investigation. Group II specimens were made of once-cast alloy with 75% new alloy. Group III specimens were made of once-cast alloy with 50% new alloy. Group IV specimens were made of once-cast alloy with 25% new alloy. Group V specimens were made of 100% recast alloy. Five specimens were made for each group of the alloy combinations. The test specimens were prepared by firing porcelain doughnuts on the alloy rod surface, and invested in dental stone. Bond strengths were measured by Instron universal testing machine at a crosshead speed of 0.5mm/min. The fractured surface of metal specimens were examined under the scanning electron microscope. The obtained results were as follows : 1. The shear bond strength of Albabond showed no significant difference between control group and reused alloy group. 2. The shear bond strength of reused alloy groups of nonprecious alloys were lower than that of control groups. 3. The shear bond strength between porcelain and metal in semiprecious alloy was higher than in nonprecious alloys 4. In nonprecious alloys. Rexillium III showed the highest bond strength value and Excelalloy showed the lowest shear bond strength value. 5. Regardless of the type of alloys and additional proportion of new alloys, scanning electron microscope photographs of the fracture surface between alloy and porcelain revealed simillar semiprecious alloy and nonprecious alloys.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.10
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• pp.4923-4939
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• 2019

In this paper, a secure transmission scheme based on the artificial noise is proposed for D2D communications underlaying the full-duplex cellular network, and a secure power allocation scheme to maximize the overall secrecy rate of both the cellular user and D2D transmitter node is presented. Firstly, the full-duplex base station transmits the artificial noise to guarantee the secure communications when it receives signals of cellular uplinks. Under this secure framework, it is found that improving the transmission power of the cellular user or the D2D transmitter node will degrade the secrecy rate of the other, although will improve itself secrecy rate obviously. Hence, a secure power allocation scheme to maximize the overall secrecy rate is presented subject to the security requirement of the cellular user. However, the original power optimization problem is non-convex. To efficiently solve it, we recast the original problem into a convex program problem by utilizing the proper relaxation and the successive convex approximation algorithm. Simulation results evaluate the effectiveness of the proposed scheme.

• The Journal of the Korea Contents Association
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• v.12 no.7
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• pp.102-113
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• 2012

Hangeul is growing as cultural icon representing Korea. And Hangeul is scientific and is too systematics for words as the guide of modern design. First it can make the variable and beautiful foams like dot, line and plane. It also has the basic design principles like symmetry and repetition. The purpose of this study is to develop textile designs using the formative characteristics of Hangeul. So in this study it was chosen 'ㄱ, ㄹ, ㅁ, ㅂ, ㅅ, ㅇ, ㅍ' of Hangeul's consonants and 'ㅑ, ㅕ' of Hangeul's vowels as the subject materials of textile designs development to develop textile designs expressed the geometrical shapes and formative beauty of Hangeul. Those are designed by using a variety of motifs that recast the shapes of Hangeul. So six textile designs for necktie and scarf were developed. Through this study it will be offered to the possibility of products that was based on Hangeul.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.1
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• pp.60-68
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• 2011

[ $ZrO_2-TiO_2$ ]binary oxides with various Zr:Ti molar ratios were prepared by sol-gel method and Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membranes were fabricated for proton exchange membrane fuel cells (PEMFCs) at high temperature and low humidity. Water uptake, Ion exchange capacity (IEC), and proton conductivity of Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membranes were characterized and these composite membranes were tested in a single cell at $120^{\circ}C$ with various relative humidity (R.H.) conditions. The obtained results were compared with the unmodified membranes (Nafion$^{(R)}$ 112 and Recast Nafion$^{(R)}$). A Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membrane with 1:3 of Zr:Ti molar ratio showed the highest performance. The performance showed 500 mW/$cm^2$ (0.499V) at $120^{\circ}C$, 50% R. H., and 2 atm.

• Membrane Journal
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• v.26 no.2
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• pp.135-140
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• 2016

In this study, the organic-inorganic composite membranes composed of iron oxide (Ferroxane) and Nafion were developed as an alternative proton exchange membranes (PEMs) in proton exchange membrane fuel cell (PEMFC). Acetic acid-stabilized lepidocrocite (${\gamma}$-FeOOH) nanoparticles (ferroxane) was synthesized, and the ferroxane-Nafion composite membranes were prepared by mixing Nafion with the ferroxane. The composite membranes were investigated in terms of ionic conductivity, ion exchange capacity (IEC), FT-IR, thermal stability, etc. As a result, the ferroxane-Nafion composite membranes showed higher proton conductivity, IEC, thermal stability than Nafion recast membranes. The proton conductivity and IEC of the composite membrane with the best performance were $0.09S\;cm^{-1}$ and $0.906meq\;g^{-1}$, respectively.

• Journal of Technologic Dentistry
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• v.18 no.1
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• pp.15-25
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• 1996

This study is to measure and compare the hardness and tensile strength of each time after we recast seven times continually only with and metal alloy Chromium-Cobalt alloy used in the production of partial denture frame work. The result of the experiment were as follow; 1) The result of the hardness measurement The result of the first casting was $490.48{\pm}38.38$ and that of the second recasting was $455.18{\pm}35.61$ and form the third recasting. the result were $518.38{\pm}37.68$ and over. The change of the hardness difference between each recasting was as follow; The hardness difference between the first casting and the second recasting was $35.25{\pm}31.93$ and that between the second recasting and the third recasting was $63.20{\pm}54.02$. There was a statistically significant difference(P<0.01) in the above hardness, however, there was little difference on the whole. And after the third recasting, the hardness grew high a little bit. That is why low-melting metals such as Cr, Mn, Cu of alloy ingredient was evaporated or there was an effect of changes in metal crystal structure, I suppose. 2) The result of the tensile strength measurement. There was a statistically significant difference(P<0.01) between the first casting and the second, the fourth recasting, however. there was little difference in general.

• Journal of Digital Convergence
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• v.18 no.4
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• pp.425-431
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• 2020

The purpose of this study is to measure the user experience of Netflix which is a representative global OTT service, Watcha and Wavve which is a representative service of Korea. Using mobile applications, qualitative research and quantitative research on user experience of OTT service were conducted with task test, in-depth interviews and surveys. As a result of the study, The usefulness and accessible of the OTT service has not shown much difference between OTT services. Rather, contents based on personal preferences has a significant impact on OTT service selection. The study found that Netflix needs to secure contents, Watcha needs to improve interface and recast categories, Wavve needs to present contents that are focused on and improve interface of main screen. The study expects to help a build a differentiate user experience in the face of growing OTT platform competition.