• Structural Engineering and Mechanics
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• v.74 no.6
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• pp.747-756
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• 2020

High-strength concrete (HSC) generally is made with high amount of cement which may release large amount of hydration heat at early age. The hydration heat will increase the internal temperature of slab and may cause potential cracking. In this study, slab specimens with a dimension of 600 × 600 × 100 mm were cast with concrete incorporating silica fume for test. The thermistors were embedded in the slabs therein to investigate the interior temperature development. The test variables include water-to-binder ratio (0.25, 0.35, 0.40), the cement replacement ratio of silica fume (RSF; 5 %, 10 %, 15 %) and fly ash (RFA; 10 %, 20 %, 30 %). Test results show that reducing the W/B ratio of HSC will enhance the temperature of first heat peak by hydration. The increase of W/B decrease the appearance time of second heat peak, but increase the corresponding maximum temperature. Increase the RSF or decrease the RFA may decrease the appearance time of second heat peak and increase the maximum central temperature of slab. HSC slab with the range of W/B ratio of 0.25 to 0.40 may occur cracking within 4 hours after casting. Reducing W/B may lead to intensive cracking damage, such as more crack number, and larger crack width and length.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.330-333
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• 2002

The substrate temperature is an important parameter in thin film deposition process. In this paper the effects of the substrate temperature on the properties of CuIn0.75Ga0.25Se2(CIGS) thin films are reported. Structure, surface morphology and optical properties of CIGS thin films deposited at various substrate temperatures have been investigated using a number of analysis techniques. X-ray diffraction (XRD) analysis shows that CIGS films exhibit a strong <112> preferred orientation. As expected, at higher substrate temperatures the films displayed a higher degree of crystallinity. The <112> peak was also enhanced and other CIGS peaks appeared simultaneously These results were supported by experimental work using Raman spectroscopy. The Raman spectra of the as-grown CIGS thin films show only the Al mode peak. The intensity of this peak was enhanced at higher deposition temperatures. Scanning electron microscopy (SEM) results revealed very small grains in films fabricated at 48$0^{\circ}C$ substrate temperature. When the substrate temperature was increased the average grain size also increased together with a reduction in the number and size of the voids. The deposition temperature also had a significant influence on the transmission spectra.

• Fashion & Textile Research Journal
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• v.11 no.3
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• pp.474-480
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• 2009

The purpose of this study is to prepare the hardness of polyester(PET) fabric by thermal bonding with low melting component of bicomponent fiber and to describe the change of physical properties of thermal bonded PET fabrics. The PET fabrics were prepared with regular PET fiber as warp and bicomponent fiber as weft. The bicomponent fiber of sheath-core type were composed with a regular PET core and low melting PET sheath. The thermal bonding of PET fabric was carried out in pin tenter from 120 to $195^{\circ}C$ temperature range for 60 seconds. In this study, we investigated the physical properties and melting behavior of PET fiber and the effect of the temperature of the pin tenter on the thermal bonding, mechanical properties. Melting peak of warp showed the thermal behavior of general PET fiber. However, melting peak of weft fiber(bicomponent fiber) showed the double melting peak. The thermal bonding of the PET fabric formed at about temperature of lower melting peak. The optimum thermal bonding conditions for PET fabrics was applied at $190{\sim}195^{\circ}C$ for 60seconds by pin tenter. On the other hand, the tensile strength of the PET fabric decreased with an increasing temperature of thermal bonding.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.127-130
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• 2001

The $BaTiO_3+xNb_2O_5$(x=6, 8, 10wt%) ceramics were prepared by conventional mixed oxide method. The structural properties of the $BaTiO_3+Nb_2O_5$ ceramics with the sintering temperature and addition of $Nb_2O_5$ were investigated by XRD and SEM. Increasing the sintering temperature, the $2{\theta}$ value of BT(110) peak was shifted to the lower degree and intensity of the $Ba_6Ti_2Nb_8O_{30}$ (133) peak was increased. Increasing the addition of $Nb_2O_5$, the intensity of $BaTiNb_4O_{13}$ (201) peak was decreased and $Ba_6Ti_2Nb_8O_{30}$ (133) peak was increased. The grain size of the $BaTiO_3+Nb_2O_5$ ceramics sintered at $1500^{\circ}C$ were almost uniform.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.2
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• pp.86-96
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• 2010

The paper describes development and evaluation of a simple method for determining gradient of modified linear setpoint variation to reduce peak electrical cooling demand in buildings using building precooling and setpoint adjustment. The method is an approximated approach for minimizing electrical cooling demand during occupied period in buildings and involves modified linear adjustment of cooling setpoint temperature between $26^{\circ}C$ and $28^{\circ}C$. The gradient of linear variation or final time of linear increase is determined based on the cooling load shape in conventional cooling control having a constant setpoint temperature. The potential to reduce peak cooling demand using the simple method was evaluated through building simulation for a calibrated office building model considering four different weather conditions. The simple method showed about 30% and 20% in terms of reducing peak cooling demand and chiller power consumption, respectively, compared to the conventional control.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.97-100
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• 1992

The Degradation mechanism of the ZnO-varistor fabricated with the content of a 3-Composition seed grain is discussed using the method of Thermally Stimulated Current (TSC). The spectra of TSC is measured in the temperature range of -130～270$^{\circ}C$ with a various forming electric fields E$\sub$f/, temperature T$\sub$f/ time tf, and a various rising rate of temperature. It is observed that there are appeared the peaks of ${\alpha}$, ${\alpha}$$_2$, ${\beta}$ and ${\gamma}$from high temperature in a TSC spectrum. It seems that ${\alpha}$$_1$ peak is due to thermal depolarization of donor ions forming the space charge in the depletion layer, and ${\alpha}$$_2$peak is due to the detrapping of trapped electrons in deep trap level of intergranular layer, and ${\beta}$ peak is due to the thermal exciting of carrier existing in the donor level of grain itself, and ${\gamma}$ peak is due to the thermal exciting of trapped carrier in all shallow trap site randomly distributed in the inner of sample and/or a intrinsic impurity existing in it.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.6
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• pp.114-120
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• 2021

This study is focused on the root mean square and peak-to-valley based on the injection conditions of the f-theta lens, one of the main components of laser printers and laser scanning systems. The f-theta lens of an aspherical plastic lens requires ultra-preaction. Injection molding is typically used for the mass production of aspherical plastic lenses. In the injection-molding method, the resin in the lens shape is filled with the resin after melting the plastic pellets at a constant temperature and then cooled. It is necessary to maintain a uniform injection molding system to produce high-quality lenses. These injection-molding systems are influenced by different factors, such as pressure, speed, temperature, mold, and cooling. It is possible to obtain a lens that exhibits the optical characteristics required to achieve harmony. We investigated the root mean square and peak-to-valley caused by variations in temperature, a critical parameter in the melting and cooling of plastic resins generated inside and outside the injection mold.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.3
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• pp.155-161
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• 2009

An investigation of the deformation behavior of ${\gamma}'-Ni_3Al$ single crystals containing fine dispersion of disordered ${\gamma}$ particles was performed for several different crystal orientations. Deformation structures were observed by the weak-beam method of transmission electron microscopy (TEM). The critical resolved shear stress (CRSS) for (111) [$\bar{1}$01] slie. increases with increasing temperature in the temperature range where (111) slip operates. The CRSS for (111) [$\bar{1}$01] slip is dependent on crystal orientation in the corresponding temperature range. The temperature where the strenjlth reaches a maximum is dependent on crystal orientation; the higher the ratio of the Schmid factors of (010) [$\bar{1}$01] to that of (111) [$\bar{1}$01], the higher the peak temperature. The peak temperatures were increased by the precipitation of y particles for the samples of all orientations. Electron microscopy of deformation induced dislocation arrangements under peak temperature has revealed that most of dislocations are straight screw dislocations. The mobility of screw dislocations decreases with increasing temperature. Above the peak temperature, dislocations begin to cross slip from the (111) [$\bar{1}$01] slip system to the (010) [$\bar{1}$01] slip system, thus decreasing the strength.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.7
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• pp.1036-1043
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• 1993

GaAs/AIGaAs resonant tunneling structures have been grown by atmospheric pressure MOCVD. Resonant tunneling diodes fabricated with the structure grown at 650t showed a high peak-to-valley (P/V) current ratio of 2.35 at room temperature. P/V current ratio increased to 15.3 at 77K. Numerically calculated peak current agrees well with the experimental result. Resonant tunneling diodes with AIGaAs as a barrier and InGaAs as a quantum well and a spacer layer yielded a high P/V current ratio of 4.0 and a peak current density of 8.6KA/c# at room temperature because of increased carrier supply.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1257-1264
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• 2018

This paper proposes Autoregressive Integrated Moving Average (ARIMA)-based forecasting algorithms using meteorological indices to predict seasonal peak load. First of all, this paper observes a seasonal pattern of the peak load that appears intensively in winter and summer, and generates ARIMA models to predict the peak load of summer and winter. In addition, this paper also proposes hybrid ARIMA-based models (ARIMA-Hybrid) using a discomfort index and a sensible temperature to enhance the conventional ARIMA model. To verify the proposed algorithm, both ARIMA and ARIMA-Hybrid models are developed based on peak load data obtained from 2006 to 2015 and their forecasting results are compared by using the peak load in 2016. The simulation result indicates that the proposed ARIMA-Hybrid models shows the relatively improved performance than the conventional ARIMA model.