• Textile Coloration and Finishing
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• v.9 no.5
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• pp.75-81
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• 1997

o-Aminobenzene sulfone-N-ethylanilide, the diazo component of C.I. Acid Red 57, is currently being diazotised by the use of nitrosylsulphuric acid because of its high molecular weight and weak basicity. However, this method has many problems such as complicated manufacturing process and discharge of large volume of strong acidic effluent. In this study, the possibility of replacing nitrosylsulphuric acid method by direct method, which is simpler and produces less effluent, has been checked and the optimum process condition was studied. The effect of HCl concentration, the amount of sodium nitrite and particle size of diazo component on diazotisation yield was investigated. The optimum pH condition for coupling reaction was also evaluated.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1892-1895
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• 1998

In this paper, a new 3-phase PWM converter power control algorithm is proposed using feedback linearization for the regulation of the active and reactive power demanded by load side. The direct power control can be realized through the proposed control scheme, cancelling out d-q axis coupling terms and nonlinear effects between inputs and states. The actual experimental results prove the feasibility of the proposed nonlinear power controller.

• Structural Engineering and Mechanics
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• v.9 no.6
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• pp.541-555
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• 2000

Pultruded cross-sections are always thin-walled due to constraints in the manufacturing process. Thus, the buckling strength determines the overall strength of the member. The elastic buckling of pultruded angle sections subjected to direct compression is studied. The lateral-torsional buckling, very likely to appear in thin-walled cross-sections, is investigated. Plate theory is used to allow for cross-sectional distortion. Shear effects and bending-twisting coupling are accounted for in the analysis because of their significant role. A simplified approach for determining the maximum load of equal leg angle sections under compression is presented. The analytical results obtained in this study are compared to the manufacturer's design guidelines for compression members as well as with the design specifications for steel structural members. Experimental results are obtained for various length specimens of pultruded angle sections. The results presented in this paper correspond to actual pultruded equal leg angle sections being used in civil engineering structures.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.560-565
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• 2015

We report efficient direct coupling of THz dipole antenna pulses onto air spaced two-wire transmission lines and Teflon covered two-wire lines. The air spaced two-wire lines show TEM mode propagation with very small group velocity dispersion (GVD) and relatively low attenuation. The Teflon covered two-wire lines showed comparatively much higher attenuation and GVD. However, the Teflon covered two-wire lines show a very good guiding property when the lines are curved. Although the lines are circled only 5.0 cm in diameter, there is no additional attenuation compared to straight the lines.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.67.2-67.2
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• 2012

Graphene is expected to have a significant impact in various fields in the foreseeable future. For example, graphene is considered to be a promising candidate to replace indium tin oxide (ITO) as transparent conductive electrodes in optoelectronics applications. We report the tunability of the wavelength of localized surface plasmon resonance by varying the distance between graphene and Au nanoparticles [1]. It is estimated that every nanometer of change in the distance between graphene and the nanoparticles corresponds to a resonance wavelength shift of ~12 nm. The nanoparticle-graphene separation changes the coupling strength of the electromagnetic field of the excited plasmons in the nanoparticles and the antiparallel image dipoles in graphene. We also show a hysteresis in the conductance and capacitance can serve as a platform for graphene memory devices. We report the hysteresis in capacitance-voltage measurements on top gated bilayer graphene which provide a direct experimental evidence of the existence of charge traps as the cause for the hysteresis [2]. By applying a back gate bias to tune the Fermi level, an opposite sequence of switching with the different charge carriers, holes and electrons, is found [3]. The charging and discharging effect is proposed to explain this ambipolar bistable hysteretic switching.

• Journal of the Korean Chemical Society
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• v.14 no.1
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• pp.127-131
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• 1970

The variational approach for the direct evaluation of the energy difference ${\Delta}$E is studied. The method is based on the differential equation corresponding to the integral Hellmann-Feynman formula. The ${\Delta}$E is given by the expectation value of the Hermitian operator which does not involve the 1/$r_{ij}$ term. Because of its variational nature of the method, the coupling problem of the differential equations which are encountered in perturbation treatment does not occur. The method is applied to the evaluation of the electric polarizabilities of the Helium isoelectronic series atoms. The result is in good agreement with the experiment. The method is compared with the recent works of Karplus et al.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.161-171
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• 2011

The availability of a high quality open source CFD simulation platform like OpenFOAM offers new R&D opportunities by providing direct access to models and solver implementation details. Efforts have been made by Hydro-Qu$\'{e}$bec to adapt OpenFOAM to hydroturbines for the development of steady-state capabilities. This paper describes the developments that have been made to implement new turbomachinery related capabilities: multiple frames of reference solver, domain coupling interfaces (GGI, cyclicGGI and mixing plane) and specialized boundary conditions. Practical use of the new turbomachinery capabilities are demonstrated for the analysis of a 195-MW Francis turbine.

• Information and Communications Magazine
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• v.24 no.2
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• pp.64-73
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• 2007

Recently, cross-layer design approach has been greatly attracting researchers' attention as an alternative for improving the performance of wireless data networks. The main reason why cross-layer approaches are particularly well suited for wireless networks is that there exists direct coupling between physical layer and upper layers. Therefore, with cross-layer approach, the protocol designers try to exploit the interaction between layers and promote adaptability at all layers, based on information exchange between layers. In this article we focus on the cross-layer engineering for high data-rate mobile Internet services through cellular networks. First, the general considerations in cross-layer engineering are outlined. Then, we discuss the common approach in literatures, which mainly deals with adaptability in physical and medium access control layer. Finally, we show that the cross-layer engineering taking account of all layers is more adequate for the mobile Internet services cellular network.

• Journal of the Korean Magnetics Society
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• v.7 no.1
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• pp.55-67
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• 1997

Double exchange interaction leads to the ferromagnetism by the direct coupling between conduction electrons and magnetic ions. The most intriguing feature of double exchange is the explicit connection of the conductivity with the magnetism, which has drawn much interest in relation to the colossal magnetoresistance (CMR) recently observed in manganese oxide compounds. In this review, we explain the basic physics of double exchange and examine the classical discussions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.116-119
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• 1999

This paper presents a feeder waveguide array of slot array antennas for Direct Broadcasting from Satellite(DBS). The feed structure consists of a single waveguide placed on the same layer as radiating waveguide and is characterized by the unit divider, called a $\pi$-Junction. This K-function with an inductive wall splits part of the power into two branch waveguide through one coupling window, and can excite densely arrayed waveguide at equal phase and amplitude. The power dividing characteristics of a cascade of $\pi$ -functions are analyzed by Galerkin's method of moments. From the optimum simulation results based on the feeder waveguide using $\pi$ -Junction at 3.95GHz, we obtained the scattering matrices of the feeder divided power at 11.85CHz.