• Current Optics and Photonics
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• v.6 no.2
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• pp.191-195
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• 2022

We investigate the lateral far-field pattern characteristics, including divergence angle change and far-field pattern analysis as output power increases, of narrow-emitter-width 850 nm GaAs/AlGaAs laser diodes (LDs). Each LD has a cavity of 1200 and 1500 ㎛ and narrow emitter width of 2.4 ㎛ for the top and 4.6 ㎛ for the bottom. The threshold currents are 35 and 40 mA, and L-I kinks appear at power levels of 326 and 403 mW, respectively. The divergence angle tends to increase due to the occurrence of first-order lateral mode and the thermal lensing effect. But with the L-I kink, the divergence angle decreases and the far-field pattern becomes asymmetric. This is due to coherent superposition between the fundamental and the first-order lateral mode. We provide detailed explanations for these observations based on high-power laser diode simulation results.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.41.1-41.1
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• 2019

The stability analysis of coronal magnetic structures is important for studying the initiation of solar flares and eruptions. In order to understand the flare onset process, we first reconstructed the 3D coronal magnetic structures of active region 12371 with an M6.5 flare using a nonlinear force-free field (NLFFF) model based on vector magnetic fields. The NLFFFs successfully produce the observed sigmoidal structure which is composed of two branches of sheared arcade loops. The stability analysis were examined for three representative MHD instabilities: the kink, the torus, and the double arc instabilities. Our stability analysis shows that the two branches of sheared arcade loops are quite stable against the kink and torus instabilities, but unstable against the double arc instability before the flare occurrence. Finally, we discuss a probable onset process of the M6.5 flare.

• Journal of Korean Vacuum Science & Technology
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• v.7 no.1
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• pp.13-17
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• 2003

The influence of structural transition on the resistance and impedance behavior of Ni$_2$MnGa alloy was investigated. The temperature-dependent resistance and impedance were measured in a temperature range of 4 - 350 K and 185 - 300 K, respectively. The dependence of temperature coefficient of resistivity on temperature shows a kink at 220 K, which is related to the structural transition. The change in dominant scattering mechanism results in the observed kink. Significant increases were also observed around the transition temperature for both real and imaginary parts of impedance. It is thought that this phenomenon originates from disappearance of the martensite twin boundaries during the structural transformation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.153-153
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• 2009

We investigated the dependence of the memory margin of the Cap-less memory cell on the strain of top silicon channel layer and also compared kink effect of strained Cap-less memory cell with the conventional Cap-less memory cell. For comparison of the characteristic of the memory margin of Cap-less memory cell on the strain channel layer, Cap-less transistors were fabricated on fully depleted strained silicon-on-insulator of 0.73-% tensile strain and conventional silicon-on-insulator substrate. The thickness of channel layer was fabricated as 40 nm to obtain optimal memory margin. We obtained the enhancement of 2.12 times in the memory margin of Cap-less memory cell on strained-silicon-on-insulator substrate, compared with a conventional SOI substrate. In particular, much higher D1 current of Cap-less memory cell was observed, resulted from a higher drain conductance of 2.65 times at the kink region, induced by the 1.7 times higher electron mobility in the strain channel than the conventional Cap-less memory cell at the effective field of 0.3MV/cm. Enhancement of memory margin supports the strained Cap-less memory cell can be promising substrate structures to improve the characteristics of Cap-less memory cell.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.330-336
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• 2002

A quantum-chemical investigation on the conformations and electronic properties of bis[2-{2-methoxy-4,6-di(t-butyl)phenyl}ethenyl]benzenes (MBPBs) as building block for ${\pi}$-conjugate polymer are performed in order to display the effects of t-butyl and methoxy group substitution and of kink(ortho and meta) linkage. The conjugation length of the polymers can be controlled by substituents and kink linkages of backbone. Structures for the molecules, o-, m-, and p-MBPBs as well as unsubstituted o-, m-, and p-DSBs were fully optimized by using semiempirical AM1, PM3 methods, and ab initio HF method with 3-21G(d) basis set. The potential energy curves with respect to the change of single torsion angle are obtained by using semiempirical methods and ab initio HF/3-21G(d) basis set. The curves are similar shape in the molecules with respect to the position of vinylene groups. It is shown that the conformations of the molecules are compromised between the steric repulsion interaction and the degree of the conjugation. Electronic properties of the molecules were obtained by applying the optimized structures and geometries to the ZINDO/S method. ZINDO/S analysis performed on the geometries obtained by AM1 method and HF/3-21G(d) level is reported. The absorption wavelength on the geometries obtained by AM1 method is much longer than that by HF/3-21G(d) level. The absorption wavelength of MBPBs are red shifted with comparison to that of corresponding DSBs in the same torsion angle because of electron donating substituents. The absorption wavelength of isomers with kink(orth and meta) linkage is shorter than that of para linkage.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.729-736
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• 2009

Several well resistance effects induced by bending, confining stress, temperature, bubbles, and apparent opening size have been considered and researched for the reasonable PBD design. The effect of apparent opening size(AOS), however, was not extensively studied and the clogging effect by AOS was not clearly researched. In this paper, the slurry consolidation test which 4 types of PBD are installed in large slurry consolidometer($H{\times}D$, $2.0m{\times}1.2m$) is performed to investigate the clogging effect by filter's AOS. The results show that the internal clogging is observed all types of PBD, and a quantity of inflowed soil particles are increased at the lower part of PBD and the kink zone. In addition, the internal clogging phenomenon does not relate with the shape and size of PBD. In filter's AOS test, it was easily observed that soil particles bigger than AOS of tested filter passed PBD filter by SEM. This paper demonstrates that the reduction of discharge capability may be accelerated by internal clogging at the kink zone.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.639-643
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• 1995

The temperature dependence of the dark conductivity was studied on undoped hydrogenated amorphous germanium (a-Ge : H) over the range from 297 to 423 K. The pre-exponential factor $\sigma$$\_$0/ and activation energy E$\_$C/-E$\_$F/ are determined by an Arrhenius plot. The Arrhenius plot of the electrical conductivity shows a kink around the kink temperature and then is composed of two exponential functions. The obtained statistical shift ${\gamma}$$\_$F/ was about 8.65${\times}$10$\^$-3/eV/K and the pre-exponential factor $\sigma$$\_$0/ was about 2$\Omega$$\^$-1/cm$\^$-1/. A temperature dependent defect density is numerically calculated from the conductivity data. A change of the defect density is observed in the factor of about two in the range of the experimental temperature.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.79-81
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• 1990

Temperature distribution of laser diode chip mounted on ideal heat kink was calculated by numerical analysis. In numerical analysis, infinite difference method and Gauss-Scidel iteration was adopted on the basis of two dimensional heat conduction phenomena. As a result, temperature increase of active medium of laser diode driven at 60mA was calculated to be 1.47$^{\circ}C$

• Proceedings of the Korean Fiber Society Conference
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• 1999.10a
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• pp.517-520
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• 1999

개질제로 1,4-cyclohexandimethanol과 dimethyl isophthalate를 사용하여, PET 규칙적인 분자쇄에 분자유동성이 적은 cyclohexane 구조와 벤젠 unit에 iso형태인 "kink"구조를 도입하여, 개질제의 함량에 따른 공중합물의 열적성질과 그에 따른 morphology를 관찰하였다.

• Steel and Composite Structures
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• v.24 no.3
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• pp.277-285
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• 2017

Single-storey industrial buildings are one of the most often type of structures built among various skeletal framed steel constructions. These metallic buildings offer an exceptional opportunity to minimise the material employed, contributing to a more sustainable construction. In particular, the mansard portal frame is a typology made up of broken beams that involves different lengths and discontinuous slopes. This study aims the weight reduction of the standard mansard portal frame with design purposes by means of varying four parameters: the kink position, the eaves-apex slope, the span and the columns height. In this work, we suggest some guidelines that can improve the economical competitive capabilities of their structural design. In all the cases analysed, the joints of the portal frame are placed over the theoretical non-funicular shape to uniform loads. This allows reducing the bending moment and the shear force, but increasing the axial force. In addition, the performance of mansard and typical pitched portal frames submitted to the same boundary conditions is compared in terms of efficiency in the use of steel. In the large majority of the cases, mansard typologies are lighter than the common pitched frames and, hence, more economical.