• Current Photovoltaic Research
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• v.9 no.4
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• pp.137-144
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• 2021

In this study, the microstructure of the CVD-fabricated Cu(In,Ga)Se₂ (CIGSe) absorber layer by simulating the stacking sequence used in a co-evaporation method, and changes solar cell performance were investigated. The absorber layer prepared by stacking CuSe and (In,Ga)Se between InSe is separated into Ga-free CuInSe₂ and Ga-rich CIGSe, and transformed to CIGSe by selenization heat treatment with slight improvement in the the solar cell efficiency. However, in CVD, since the supply of liquid Cu-Se is not as active as in the co-evaporation method, the nanoocrystalline layer containing a large amount of Ga remained independently in the absorption layer, which acted as a cause of the loss of J_SC and FF. Therefore, by using a precursor structure in which CuGa is sputter-deposited on a single layer of InSe deposited by CVD, performance parameters of V_OC, J_SC, and FF could be greatly improved.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1356-1364
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• 2014

A new conjugated copolymer, poly{4,8-bis(triisopropylsilylethynyl)benzo[1,2-b:4,5-b']dithiophene-alt-4,7- bis(5-thiophen-2-yl)-5,6-difluoro-2-(heptadecan-9-yl)-2H-benzo[d][1,2,3]triazole} (PTIPSBDT-DFDTBTz), is synthesized by Stille coupling polycondensation. The synthesized polymer has a band gap energy of 1.9 eV, and it absorbs light in the range 300-610 nm. The hole mobility of a solution-processed organic thin-film transistor fabricated using PTIPSBDT-DFDTBTz is $3.8{\times}10^{-3}cm^2V^{-1}s^{-1}$. Bulk heterojunction photovoltaic cells are fabricated, with a conventional device structure of ITO/PEDOT:PSS/polymer:$PC_{71}BM$/Ca/Al ($PC_{71}BM$ = [6,6]-phenyl-$C_{71}$-butyric acid methyl ester); the device shows a power conversion efficiency (PCE) of 2.86% with an open-circuit voltage ($V_{oc}$) of 0.85 V, a short-circuit current density ($J_{sc}$) of 7.60 mA $cm^{-2}$, and a fill factor (FF) of 0.44. Inverted photovoltaic cells with the structure ITO/ethoxylated polyethlyenimine/ polymer:$PC_{71}BM/MoO_3$/Ag are also fabricated; the device exhibits a maximum PCE of 2.92%, with a $V_{oc}$ of 0.89 V, a $J_{sc}$ of 6.81 mA $cm^{-2}$, and an FF of 0.48.

• Journal of Digital Contents Society
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• v.18 no.8
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• pp.1517-1522
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• 2017

Among single image SR techniques, the TV based SR approach seems most successful in terms of edge preservation and no artifacts. But, this approach achieves insufficient SR for texture component. In this paper, we proposed a new TV-G decomposition based SR method to solve this problem. We proposed the SVR based up-sampling to get better edge preservation in the structure component. The NNE used the relaxed constraint to improve the NE. We used the NNE based learning method to improve the resolution of the texture component. Through experimental results, we quantitatively and qualitatively confirm the improved results of the proposed SR method when comparing with conventional interpolation method, ScSR, TV and NNE.

• Polymer(Korea)
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• v.37 no.6
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• pp.685-693
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• 2013

The foams of a poly(lactic acid) modified by the reactive compounding were produced with the batch foaming technique using supercritical $CO_2(scCO_2)$. Experiments were performed at $105{\sim}135^{\circ}C$ and 12~24 MPa. The blowing ratio and foam structure were significantly affected by changing the temperature and pressure conditions in the foaming process. The blowing ratio first increased with increasing foaming temperature and saturation pressure, reached a maximum and then decreased with a further increase in the foaming temperature and saturation pressure. Decreasing the rate of depressurization permitted a longer period of cell growth and therefore larger microcellular structures were obtained.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.259-266
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• 2021

USB bus not only works with convenience but also transmits data fast and becomes a standard peripheral interface between FPGA development board and personal computer. In this paper FPGA verification system with slave FIFO interface for Cypress FX3 USB 3 bridge chip was implemented. The designed slave FIFO interface consists of host interface module based on FIFO structure, master bus controller and command decoder and supports streaming communication interface for FX3 bridge chip and memory-mapped input and output interface for user design circuit. The ZestSC3 board with Cypress FX3 USB 3 bridge chip and Xilinx Artix FPGA(XC7A35T-1C5G3241) was used to implement FPGA verification system. It was verified that the FPGA verification system for user design circuit operated correctly under various clock frequencies using GUI software developed by visual C# and C++ DLL. The designed slave FIFO interface for FPGA verification system has modular structure and can be applicable to the different user designs with memory-mapped I/O interface.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.38 no.5
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• pp.1-6
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• 2001

In this paper, we propose the initial optimized structure of the Radial Basis Function Network(RBFN) which is more simple in the part of the structure and converges more faster than Neural Network. For this, we use the analysis method using time frequency localization and we can decide the initial structure of the RBFN suitable for the given problem. When we compose the hidden nodes with the radial basis functions whose localization are similar with the target function in the plane of the time and frequency, we can make a good decision of the initial structure having an ability of approximation.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.19-32
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• 2000

This paper suggests the variable structure controller with a new variable boundary layer for the accurate tracking control of the variable structure systems. Up to now, variable structure controller (VSC) applying the variable boundary layer did not remove chattering from an arbitrary initial state of the system trajectory because VSC has the limited initial state according to the fixed sliding surface. But, by using the linear time-varying sliding surfaces, the scheme has the robustness against chattering from all states. The suggested method can be applied to the second-order nonlinear systems with parameter uncertainty and extraneous disturbances, and has better tracking performance than the conventional method. To demonstrate the advantages of the proposed algorithm, it is applied to a two-link manipulator.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.2
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• pp.29-36
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• 2019

Modular construction has benefits such as short construction duration and high productivity owing to the production in factory and owing to simultaneous on-site work. However, rework occurs in modular construction and the rework affects the efficiency of modular construction. The almost of causes of rework are exist in design process. To reduce the cause of rework, the information flow of the design process should be managed and the plan to reduce rework should be included. However, the modular construction has complex process because of impeded unit production so it is hard to manage the information flow in design process. Moreover, when the plan to reduce rework is included, the design process will be more complicated. Therefore, the objective of this research is to suggest the design process including the rework reduction plan and to alleviate the complexity of design process by using Dependency Structure Matrix(DSM). By using DSM, the iteration and feedback in design process is reduced and it can be expected that rework in modular project can be reduced by using suggested design process.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.2
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• pp.41-48
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• 2018

Carbonation is one of the major detrimental factors to the reinforced concrete structures owing to penetration of atmospheric CO2 through the micro pores, thereby it reduces the durability of the concrete. The maintenance periods and cost for concrete according to the coefficient variation of different finishing materials is documented in literature. However, it is required to carry out the systematic and well planned studies. Therefore, keeping them in mind, surface repair was carried out to the carbonated concrete and the maintenance cost was calculated to measure the durability life after repair with different variable. The deterministic and probabilistic methods were applied for durability and repair cost of the concrete. In the existing deterministic model, the cost of repair materials increases significantly when the concrete structure reaches its service life. In present study using a stochastic model, the maintenance period and cost was evaluated. According to obtained results, there was no significant difference in the number of maintenance of the coefficient variation. The initial durability has a great influence on the maintenance time and cost of the structure. Unlike the deterministic model, the probabilistic cost estimating model reduces the number of maintenance to the target service life expectancy.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.1081-1086
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• 2008

This paper presents the $3^{rd}$ 4bit sigma delta modulator with the block and timing diagrams of DWA(Data Weighted Averaging) to optimize a operating time. In the modulator, the proposed DWA structure has a stable operation and timing margin so as to remove three latches and another clock. Because the modulator with proposed DWA structure improve timing margin about 23%. It can increase sampling frequency up to 244MHz. Through the MATLAB modeling, the optimized coefficients are obtained to design the modulator. The fully differential SC integrators, DAC, switch, quantizer, and DWA are designed by considering the nonideal characteristics. The designed $3^{rd}$ order 4bit modulator has a power consumption of 40mW and SNR(signal to noise ratio) of 77.2dB under 1.2V supply and 64MHz sampling frequency.