• Korean Journal of Materials Research
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• v.30 no.8
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• pp.421-425
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• 2020

A transparent quantum dot (QD)-based light-emitting diode (LED) with silver nanowire (Ag NW) and indium-tin oxide (ITO) hybrid electrode is demonstrated. The device consists of an Ag NW-ITO hybrid cathode (-), zinc oxide, poly (9-vinylcarbazole) (PVK), CdSe/CdZnS QD, tungsten trioxide, and ITO anode (+). The device shows pure green-color emission peaking at 548 nm, with a narrow spectral half width of 43 nm. Devices with hybrid cathodes show better performances, including higher luminance with higher current density, and lower threshold voltage of 5 V, compared with the reference device with a pure Ag NW cathode. It is worth noting that our transparent device with hybrid cathode exhibits a lifetime 9,300 seconds longer than that of a device with Ag NW cathode. This is the reason that the ITO overlayer can protect against oxidization of Ag NW, and the Ag NW underlayer can reduce the junction resistance and spread the current efficiently. The hybrid cathode for our transparent QD LED can applicable to other quantum structure-based optical devices.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.882-883
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• 2013

With the development of the society, pure electric vehicles will be surely important of the future. Electric vehicle requires various technology like motor driving, battery management, operational efficiencies and so on. Battery management is indeed the most important to enhance battery's performance and life. This paper has deeply discussed and studied on the lithium-polymer battery management system of pure electric vehicle. First of all we have analyzed the characteristic of the lithium-polymer batteries and the factors influenced on the state of charge. Then a logical SOC measuring method has been raised, which is the combination of open circuit voltage and Ah integration. The next we will introduce the design of battery management system, the battery management system performs many functions, such as inspecting the whole process, when it's running cell equalization protecting and diagnosing the battery, estimating the state of charge. The module design style including microcontroller, data aquisition module, charging control module and serial communication module. To arrive at conclusions, the battery management system which this paper has introduced is reliable and economical.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.540-546
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• 2013

Using the free volume of van der Waals equation, Carnahan-Starling equation for hard spheres, Wilson equation for nonrandom mixing of solution, NRTL equation and our equation, several new equations of states for pure gases are derived. Using these equations, compressibility factors for pure gases are calculated and compared with Nelson-Obert generalized compressibility factor charts. The equation of states using the concept of molecular nonrandom distribution gave better results than those of molecular random distribution. This shows that the molecular nonrandom distribution makes considerable effect on the equation of states.

• Journal of the Korean Ceramic Society
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• v.21 no.2
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• pp.165-173
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• 1984

It is desirable to establish reliable synthetic methods for electro-ceramic materials. To synthesize $SrTiO_3$ in this study direct solid state reactions and wet chemical processes were used. Previous study of $SrTiO_3$ synthesis included oxalated-method($SrTiO(C_2O_4)_2$.$4H_2O$) co-precipitation$(SrCO_3+TiO(OH)_2)$ and direct solid state reaction$(SrCO_3+TiO(OH)_2)$ The methods in question lead to intermediate inclusion during the reactions and less controllable in particle sizes of $SrTiO_3$. To obtain highly pure $SrTiO_3$ so-called "direct wet process method" was added in this investigation. In the study the "direct wet process" was for the first time applied to synthesize chemically pure and fine particle $SrTiO_3$. $SrCl_2$ and $TiCl_4$<\ulcornerTEX> at KOH solution at room temperature to 10$0^{\circ}C$ precipitated $SrTiO_3$ The particle size increased as temperature increased.mperature increased.

• Journal of Powder Materials
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• v.6 no.4
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• pp.314-319
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• 1999

The solid state reaction by mechanical alloying(MA) generally proceeds by lowering the free energy as the result of a chemical reaction at the interface between the two adjacent layers. However, Lee et $al.^{1-5)}$ reported that a mixture of Cu and Ta, the combination of which is characterized by a positive heat of mixing of +2kJ/mol, could be amorphized by mechanical alloying. This implies that there exists an up-hill process to raise the free energy of a mixture of pure Cu and la to that of an amorphous phase. It is our aim to investigate to what extent the MA is capable of producing a non-equilibrium phase with increasing the heat of mixing. The system chosen was the ternary $Cu_{30}Ta_{ 70-x}Mo_ x$ (x=35, 10). The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-K $\alpha$ radiation, thermal analysis, electron diffraction and TEM micrographs. In the case of x=35, where pure Cu powders were mixed with equal amount of pure Ta and Mo powders, we revealed the formation of bcc solid solution after 150 h milling but its gradual decomposition by releasing fcc-Cu when milling time exceeded 200 h. However, an amorphous phase was clearly formed when the Mo content was lowered to x=10. It is believed that the amorphization of ternary $Cu_{30}Ta_{60}Mo_{10}$ powders is essentially identical to the solid state amorphization process in binary $Cu_{30}Ta_{70}$ powders.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.125-133
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• 1988

To establish the rational design method, it is very important that predict accurately load-deformation response on reinforced concrete members. Torque-twist curves of reinforced concrete members in pure torsion were proposed recently by Collins and Hsu, etc. But, it is found that torsional strength of reinforced concrete members based on Hsu's theory is underestimated in the over-all load region except the ultimate state. In this paper, an attempt is made to present the higher-precision of torsional strength on arbitrary loading condition. For this purpose, constitutive equations are derived from which an estimate can be made of the torsional behavior of reinforced concrete members under the pure torsion. Tension stiffness of concrete in both the cracked and uncracked state have been considered. A softening effect that reduces the strength of the concrete by the diagonal cracking of concrete have been appropriately deliberated. Particularly, the experiments was done with 14 test beams to investigate the validity of theoretical analysis.

• Korean Journal of Materials Research
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• v.34 no.6
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• pp.267-274
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• 2024

In this study, four different samples of Se₆₀Ge_40-xBi_x chalcogenides glasses were synthesized by heating the melt for 18 h in vacuum Pyrex ampoules (under a 10^-4 Torre vacuum), each with a different concentration (x = 0, 10, 15, and 20) of high purity starting materials. The results of direct current (DC) electrical conductivity measurements against a 1,000/T plot for all chalcogenide samples revealed two linear areas at medium and high temperatures, each with a different slope and with different activation energies (E₁ and E₂). In other words, these samples contain two electrical conduction mechanisms: a localized conduction at middle temperatures and extended conduction at high temperatures. The results showed the local and extended state parameters changed due to the effective partial substitution of germanium by bismuth. The density of extended states N(E_ext) and localized states N(E_loc) as a function of bismuth concentration was used to gauge this effect. While the density of the localized states decreased from 1.6 × 10¹⁴ to 4.2 × 10¹² (ev^-1 cm^-3) as the bismuth concentration increased from 0 to 15, the density of the extended states generally increased from 3.552 × 10²¹ to 5.86 × 10²¹ (ev^-1 cm^-3), indicating a reduction in the mullet's randomness. This makes these alloys more widely useful in electronic applications due to the decrease in the cost of manufacturing.

• Journal of computational fluids engineering
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• v.18 no.3
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• pp.1-7
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• 2013

A pure oxygen combustion technology is crucial in Carbon Capture and Storage (CCS) technology especially in capturing of $CO_2$, where CCS will reduce 9 $GtCO_2$ by 2050, which is 19% of the total $CO_2$ reduction amount. To make pure oxygen combustion feasible, a regenerative system is required to enhance the efficiency of pure oxygen combustion system. However, an existing air combustion technology is not directly applicable due to the absence of nitrogen that occupies the 78% of air. This study, therefore, investigates the heat and fluid flow in a regenerative system for pure oxygen combustion by using commercial CFD software, FLUENT. Our regenerative system is composed of aluminium packed spheres. The effect of the amount of packed spheres in regenerator and the effect of presence or absence of a bypass of exhaust gas are investigated. The more thermal mass in regenerator makes the steady-state time longer and temperature variation between heating and regenerating cycle smaller. In the case of absence of bypass, the regenerator saturates because of enthalpy imbalance between exhaust gas and oxygen. We find that 40% of exhaust gas is to be bypassed to prevent the saturation of regenerator.

• Smart Media Journal
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• v.9 no.2
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• pp.22-32
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• 2020

The hippocampal volume atrophy is known to be linked with neuro-degenerative disorders and it is also one of the most important early biomarkers for Alzheimer's disease detection. The measurements of hippocampal pure volumes from Magnetic Resonance Imaging (MRI) is a crucial task and state-of-the-art methods require a large amount of time. In addition, the structural brain development is investigated using MRI data, where brain morphometry (e.g. cortical thickness, volume, surface area etc.) study is one of the significant parts of the analysis. In this study, we have proposed a patch-based ensemble model of 3-D convolutional neural network (CNN) to measure the hippocampal pure volume from MRI data. The 3-D patches were extracted from the volumetric MRI scans to train the proposed 3-D CNN models. The trained models are used to construct the ensemble 3-D CNN model and the aggregated model predicts the pure volume in one-step in the test phase. Our approach takes only 5 seconds to estimate the volumes from an MRI scan. The average errors for the proposed ensemble 3-D CNN model are 11.7±8.8 (error%±STD) and 12.5±12.8 (error%±STD) for the left and right hippocampi of 65 test MRI scans, respectively. The quantitative study on the predicted volumes over the ground truth volumes shows that the proposed approach can be used as a proxy.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.575-579
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• 2023

In this work, pure W and W-0.5wt%HfC alloy (WHC05) were fabricated by sintering and hot-rolling following the same processing route. After exposing to a high flux deuterium plasma irradiation with the D⁺ flux to three fluences of 6.00 × 10²⁴, 2.70 × 10²⁵ and 7.02 × 10²⁵ D/m², the evolution of surface morphology, deuterium retention and hardening behaviors in pure W and WHC05 has been studied. The SEM results show the formation of D blisters on the irradiated area, and with the increase of D implantation, the size of these blisters increases from 200 ~ 500 nm (2.70 × 10²⁵ D/m²) to 1 ~ 2 ㎛ (7.02 × 10²⁵ D/m²) in WHC05 and from 1 ~ 2 ㎛ (2.70 × 10²⁵ D/m²) to > 3 ㎛ (7.02 × 10²⁵ D/m²) in pure W, respectively. A higher D retention and obvious hardening are observed in pure W than that of the WHC05 alloy, indicating an improve radiation resistance in WHC05 compared to pure W.