Technology Trends Analysis of Airbone Network

KiHwan Kim,HyunHo Kim,SangGon Lee,HoonJae Lee,YoungJae Ryu 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.10

Development with IT technology has wide effect for military sector. For this reasons, the important sources is ‘First see, and first determine, and first attack’ in modern and future warfare. And there are also importance with patriot robot such as drone for understand the movement pattern with enemy. Therefore, in develop country; they process with sensor system, delicate attack system, informationization and identification proactively. For now, the connection between equipment is essential in the war environment, so the secure with these things is important. But this is planned with using network structure based on TCP/IP, So there is a raised problem that plan which I mentioned has difficult to deal with attack from using structural weakness. In this paper, the attack type which is possible in the Airborne Network is made an inquiry and it analyze.

Performance prediction of chalcopyrite-based dual-junction tandem solar cells

Kim, Kihwan,Yoo, Jin Su,Ahn, Seoung Kyu,Eo, Young-Joo,Cho, Jun-Sik,Gwak, Jihye,Yun, Jae Ho Elsevier 2017 Solar energy Vol.155 No.-

<P><B>Abstract</B></P> <P>In this work, we present SCAPS-1D simulations of Cu(In,Ga)Se<SUB>2</SUB>-based dual-junction tandem cells. The purpose of this work is to assess the device performances of the Cu(In,Ga)Se<SUB>2</SUB>-based tandem cells based on the fact that each subcell is simulated to yield a reported best efficiency at its bandgap. A method to build the J-V characteristics of tandem cells from individual J-V curves of subcells is also discussed. By thinning the absorber thickness of the top subcell, the current matching points among various bandgap combinations are examined. In spite of neither optical nor electrical loss between the top and bottom subcells, the device performances of the tandem devices do not substantially surpass the device performances of single-junction devices, which is ascribable to the relatively poor efficiencies of the wide-bandgap top subcells. We also discuss how further improvements in the wide-bandgap top subcells are needed to create a validity for making an effortful multi-junction device.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Performances of CIGS-based tandem solar cells are simulated by the SCAPS-1D. </LI> <LI> Subcells are simulated to have state-of-the-art efficiencies up to date. </LI> <LI> Achievable efficiencies from the CIGS-based tandem cells are calculated. </LI> <LI> Relatively low efficiencies of the top subcells limit the tandem cells’ efficiencies. </LI> <LI> It is also discussed that how further improvement from the top subcell is required. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>With the SCAPS-1D simulation package, we assessed the device performances of CIGS-based dual-junction tandem cells. The subcells of the tandem cells were assumed to exhibit state-of-the-art efficiencies in each bandgap. Additionally, we discussed how further improvements should be made to substantially overcome the efficiency of a single-junction CIGS solar cell.</P> <P>[DISPLAY OMISSION]</P>

Effect of a blockage length on the coolability during reflood in a 2×2 rod bundle with a 90% partially blocked region

Kim, Kihwan,Kim, Byung-Jae,Choi, Hae-Seob,Moon, Sang-Ki,Song, Chul-Hwa Elsevier 2017 Nuclear engineering and design Vol.312 No.-

<P><B>Abstract</B></P> <P>If fuel rods are ballooned or rearranged during the reflood phase of a large break loss-of-coolant accident (LBLOCA) in a pressurized-water reactor (PWR), the transient heat transfer behavior is entirely different with those of the intact fuel rods owing to the deformed blockage region. The coolability in the blocked region depends on a complex two-phase heat transfer with various thermal hydraulic conditions. In addition, the blockage characteristics, such as the blockage ratio, length, shape, and configurations, are also significant factors affecting the coolability. In the present study, reflood experiments were carried out to understand the effect of the blockage length upon the coolability by varying the reflooding rates. The experiments were performed in electrically heated 2×2 rod bundles with blockage simulators having the same blockage ratio but different blockage lengths. The characteristics of quenching and heat transfer were evaluated to investigate the influence of the blockage region on the coolability. The droplet behaviors were also observed by measuring the droplets velocity and size near the blockage region. The coolability in the downstream region of the blockage was significantly enhanced, owing to the reduced flow area of the sub-channel, intensification of turbulence, and the entrained droplets in the blockage region.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This test was conducted to understand the effect of blockage length on the coolability. </LI> <LI> Reflood tests were conducted with blockage simulators for various reflood rates. </LI> <LI> The coolability in the downstream of the blockage region is significantly enhanced. </LI> </UL> </P>

Strain Effectiveness of Gate-all-around Silicon Transistors with Various Surface Orientations and Cross-sections

Kihwan Kim,Saeroonter Oh 대한전자공학회 2019 Journal of semiconductor technology and science Vol.19 No.1

We investigate the effect of strain on the device characteristics of gate-all-around (GAA) NMOS with various configurations, including crystal orientation, cross-sectional shape, and strain conditions, via device simulation. After verifying the strain dependence of mobility of various surface orientations with the literature, we apply the strain transport model to GAA MOSFETs which have different sidewall orientations depending on the channel direction. Drive current enhancement is the largest for the (001)/<110> case under large uniaxial tensile strain values exceeding 1%. In addition, we found that cross-sectional width of the nanosheet is a key parameter in maximizing the drive current for a given footprint. Optimization of device and strain configuration of single-stacked GAA devices is necessary to meet device performance specifications for sub-7nm technology.

Detects abnormal behavior using motor power consumption

KiHwan Kim(김기환),Su-Mi Ryu(류수미),Min-Kyu Kim(김민규),Young-Jin Kang(강영진),HyunHo Kim(김현호),HoonJae Lee(이훈재),Jin-Heung Lee(이진흥) 한국컴퓨터정보학회 2018 韓國컴퓨터情報學會論文誌 Vol.23 No.10

In this paper, we used LSTM as a method to detect abnormal behavior of motors. We fixed the high layout size to 1 and changed the range of the input values and the neural network structure to see what change in power consumption prediction. Now, as the fourth industrial revolution era, smart factories are attracting attention. All the physical actions of smart factories are done using motors. Continuous monitoring of motor malfunctions helps to detect malfunctions and efficient operation. However, it is difficult to acquire the power consumption constantly due to the influence of the noise. We have experimented with a simple experimental environment, a method of predicting similarity to input data by adjusting the range of the input data or by changing the neural network structure.

A simple and robust route toward flexible CIGS photovoltaic devices on polymer substrates: Atomic level microstructural analysis and local opto-electronic investigation

Kim, Kihwan,Kim, Juran,Gang, Myeng Gil,Kim, Se-Ho,Song, Soomin,Cho, Yunae,Shin, Donghyeop,Eo, Young-Joo,Jeong, Inyoung,Ahn, Seung Kyu,Cho, Ara,Kim, Jayeong,Yoon, Seokhyun,Choi, Pyuck-Pa,Jo, William,Ki Elsevier 2019 Solar energy materials and solar cells Vol.195 No.-

<P><B>Abstract</B></P> <P>In this work, copper indium gallium selenide (Cu(In,Ga)Se<SUB>2</SUB>; CIGS) absorbers were grown on polyimide (PI)/molybdenum substrates by a three-stage co-evaporation process at various temperatures, film formation was systemically studied using various advanced characterization methods such as transmission electron microscopy, micro-Raman spectroscopy, Kelvin probe force microscopy, and atom probe tomography. The CIGS films on PI were found to exhibit considerable physical and electrical variations with respect to the process temperature of three-stage co-evaporation. In particular, when the process temperature reached 400 °C, the CIGS absorber on PI began to exhibit controlled microstructure and intergrain properties. By adjusting the microstructure and intergrain properties of the absorber films by means of the process temperature of three-stage co-evaporation, flexible CIGS solar cells on PI with an efficiency of 16.7% (with anti-refection coating) were achieved.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CIGS absorber films were grown on flexible polyimide/molybdenum substrates. </LI> <LI> Low-temperature three-stage process (≤440 °C) with extrinsic Na addition was used to CIGS growth. </LI> <LI> CIGS film evolution was systemically observed using advanced material characterization techniques. </LI> <LI> Highly efficient CIGS cells on flexible polyimide substrates were realized while maintaining process manufacturability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Vitexin, orientin and other flavonoids from Spirodela polyrhiza inhibit adipogenesis in 3T3-L1 cells

Kim, JinPyo,Lee, IkSoo,Seo, JeongJu,Jung, MunYhung,Kim, YoungHee,Yim, NamHui,Bae, KiHwan John Wiley Sons, Ltd. 2010 Phytotherapy research Vol.24 No.10

<P>To investigate the adipogenesis inhibitory effect on lipid accumulation, 3T3-L1 cells were treated with fractions and isolated flavonoids of Spirodela polyrhiza. An ethanol extract of S. polyrhiza was fractionated into three fractions. The butanol soluble fraction (SPB) exhibited potent antiadipogenesis activity and decreased C/EBP&agr; and PPAR&ggr; protein expression level in 3T3-L1 cells without significant cytotoxicity. The flavonoids were isolated from SPB and their chemical structures were identified as chrysoeriol (1), apigenin (2), luteolin (3), vitexin (4), cosmosin (5), orientin (6) and luteolin-7-O-&bgr;-d-glucoside (7) by spectroscopic analysis. Studies on the adipogenesis and intracellular triglyceride accumulation inhibitory effect showed that compounds 4 and 6 had the highest activity and decreased C/EBP&agr; and PPAR&ggr; protein expression level in 3T3-L1 cells. These results suggest that the flavonoids isolated from SPB, especially compounds 4 and 6, contribute to the inhibitory activity of S. polyrhiza in 3T3-L1 cells. Copyright © 2010 John Wiley & Sons, Ltd.</P>

Alternative device structures for CIGS-based solar cells with semi-transparent absorbers

Kim, Kihwan,Shafarman, William N. Elsevier 2016 Nano energy Vol.30 No.-

<P><B>Abstract</B></P> <P>In this work, we discuss two alternative structures of CIGS-based solar cells, a bi-facial configuration and a back-wall configuration. One of the critical issues in these structures is fabrication of a transparent back contact which facilitates not only ohmic contact for holes in the valance but also an effective reflector for electrons in the conduction band. In order to meet these requirements of the transparent back contact, a p-type amorphous Si (p-a-Si)/intrinsic amorphous Si (i-a-Si) bi-layer was deposited onto the ITO back contact. Absorber films were formed by a metal precursor reaction in H<SUB>2</SUB>Se and H<SUB>2</SUB>S, and their thicknesses were adjusted to about 0.25µm to enhance current collection from back-side illumination. The resulting devices with a bi-facial structure of SLG/ITO/p-Si/i-Si/Cu(In, Ga)(Se,S)<SUB>2</SUB>/CdS/i-ZnO/ITO/Ni-Al exhibited a comparable open-circuit voltage to a Cu(In, Ga)(Se,S)<SUB>2</SUB> cell on a Mo substrate in tests with illumination of both sides. Back-wall cells with a structure of SLG/ITO/p-Si/i-Si/Cu(In, Ga)(Se,S)<SUB>2</SUB>/CdS/i-ZnO/Ag-reflector were also fabricated and improved current collection by greater light trapping was achieved compared to the bi-facial cell with back-side illumination.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This work explores alternative structures of CIGS-based cells. </LI> <LI> CIGS cells with bi-facial and back-wall configurations are demonstrated. </LI> <LI> An ITO/p-Si/a-Si back contact are employed in the alternative device structures. </LI> <LI> CIGS thicknesses are reduced to 250nm for better optical management. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>This work explores alternative structures of CIGS-based cells, a bi-facial configuration and a back-wall configuration. In these configurations, ITO back contact and semi-transparent Cu(In, Ga)(Se,S)<SUB>2</SUB> absorber are used to enhance current collection from back side illumination. In order to reduce recombination at the interface between ITO back contact and Cu(In, Ga)(Se,S)<SUB>2</SUB> absorber, a p-type amorphous Si/intrinsic amorphous Si bi-layer was formed on the ITO back contact prior to the absorber layer formation.</P> <P>[DISPLAY OMISSION]</P>

Is There an Alternative to Protectionism?

Kim, Kihwan Center for International Studies-Inha University 1986 The Pacific Century Vol.1986 No.-

Effects of fuel relocation on reflood in a partially-blocked rod bundle

Kim, Byoung Jae,Kim, Jongrok,Kim, Kihwan,Bae, Sung Won,Moon, Sang-Ki North-Holland Pub. Co 2017 Nuclear engineering and design Vol.312 No.-

<P><B>Abstract</B></P> <P>Ballooning of the fuel rods has been an important issue, since it can influence the coolability of the rod bundle in a large-break loss-of-coolant accident (LBLOCA). Numerous past studies have investigated the effect of blockage geometry on the heat transfer in a partially blocked rod bundle. However, they did not consider the occurrence of fuel relocation and the corresponding effect on two-phase heat transfer. Some fragmented fuel particles located above the ballooned region may drop into the enlarged volume of the balloon. Accordingly, the fuel relocation brings in a local power increase in the ballooned region. The present study’s objective is to investigate the effect of the fuel relocation on the reflood under a LBLOCA condition. Toward this end, experiments were performed in a 5×5 partially-blocked rod bundle. Two power profiles were tested: one is a typical cosine shape and the other is the modified shape considering the effect of the fuel relocation. For a typical power shape, the peak temperature in the ballooned rods was lower than that in the intact rods. On the other hand, for the modified power shape, the peak temperature in the ballooned rods was higher than that in the intact rods. Numerical simulations were also performed using the MARS code. The tendencies of the peak clad temperatures were well predicted.</P>