• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.91-95
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• 2002

A very small size BPF is realized using LTCC Multilayer technology. A λ/4 resonator with shunt-to-ground loaded capacitor is used to shorten resonator length and achieve higher qualityfactor. Also this resonator enable BPF to improve out-of-band rejection. Coupling coefficients between coupled stripline resonators and external qualityfactor of a resonator are derived and apply to the filter design. The measured results show a good agreement with the simulation.

• Textile Coloration and Finishing
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• v.17 no.6 s.85
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• pp.1-10
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• 2005

Disperse dyes derived from heterocyclic compounds such as phenylindole, pyridone, diaminopyridine, and carbazole have been known to exhibit high light fastness and bathochromic shift compared to the coursponding aminoazobenzene. The synthetic method to obtain diaminopyridine derivatives, which can be used as coupling components, was chlorination of pyridone with phosphorous oxychloride, followed by substitution with various primary amines. Four azo disperse dyes were synthesized by coupling four diaminopyridines with 2-cyano-4-nitroaniline as a diazo component. Structures of these dyes were confirmed by $^1H$ NMR spectroscopy. The wavelengths of maximum absorption of the synthesized disperse dyes were in the range of $517\~528nm$, and molar extinction coefficients were $45,700\~50,100$. The dyeability of four disperse dyes toward PET fiber was generally good. Wash and rubbing fastnesses were excellent, while light and dry heat fastness were good.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.154-164
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• 2019

A rotor dynamic analysis is mandatory for stability and design optimization of submerged propellers and turbines. An accurate simulation requires a proper consideration of fluid-induced reaction forces. This paper presents a bi-directional coupling of a bond graph method solver and an unsteady vortex lattice method solver where the former is used to model the rotor dynamics of the power train and the latter is used to predict transient hydrodynamic forces. Due to solver coupling, determination of hydrodynamic coefficients is obsolete and added mass effects are considered automatically. Additionally, power grid and structural faults like grid fluctuations, eccentricity or failure could be investigated using the same model. In this research work a fast, time resolved dynamic simulation of the complete power train is conducted. As an example, the rotor dynamics of a tidal stream turbine is investigated under two inflow conditions: I - shear flow, II - shear flow + water waves.

• Journal of Ocean Engineering and Technology
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• v.30 no.2
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• pp.84-90
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• 2016

In this study, a six degree-of-freedom motion analysis of a wind-wave hybrid platform equipped with numerous wave energy converters (WECs) was carried out. To examine the effect of the WECs on the platform, an analysis of one-way coupling was carried out, which only considered the power take-off (PTO) damping of the static WECs on the platform. The equation of motion of a floating platform with mooring lines in the time domain was established, and the responses of the one-way coupled platform were then compared with the case of a platform without any coupling effects from the WECs. The hydrodynamic coefficients and wave exciting forces were obtained from the 3D diffraction/radiation pre-processor code WAMIT based on the boundary element method. Then, an analysis of the dynamic responses of the floating platform with or without the WEC effect in the time domain was carried out. All of the dynamics of a floating platform with multiple wind turbines were obtained by coupling FAST and CHARM3D in the time domain, which was further extended to include additional coupled dynamics for multiple turbines. The analysis showed that the PTO damping effect on platform motions was negligible, but coupled effects between multiple WECs and the platform may differentiate the heave, roll, and pitch platform motions from the one without any effects induced by WECs.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.7
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• pp.80-91
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• 1999

We present various optimal grating structures which give the low threshold gain, good modulation characteristics, small effective linewidth enhancement factor, and large fabrication tolerance in complex-coupled MQW DFB lasers with absorptive gratings. To obtain these, we calculate the complex coupling coefficients using the extended additional layer method and the threshold gain including the modal loss in the absorptive grating region for rectangular and trapezoidal gratings. Based on the comparison of the results for various possible absorptive grating structures, the design guidelines are presented to obtain the low threshold gain or large fabrication tolerance. Among the grating structures studied, the double grating structure consisting of the absorptive grating on the index grating has the largest fabrication tolerance for the threshold gain and the coupling strength. The fabrication tolerance for the coupling ratio is very large for all the grating structures studied.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.88-98
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• 1999

A refractive index modulated (RIM) DFB laser, in which the refractive index of a center region of the upper cladding layer comprising the grating region is different from that of side regions, is proposed to obtain and effective ${\lambda}$/4 phase shift in the center region. Since the coupling coefficient of a center region in a RIM-DFB laser is larger than that of side regions, a RIM-DFB laser has the effect of a distributed coupling coefficient. Simulation results show that RIM-DFB lasers have better operation characteristics - more uniform photon density profile, less SHB effect, and better single mode operation at high injection currents - compared to those of ${\lambda}$/4 phase-shifted DFB lasers and CPM-DFB lasers. In addition, the effect of the center region on the above threshold characteristics of a RIM-DFB laser is investigated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.6 s.121
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• pp.620-628
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• 2007

An H-sector horn antenna has a constant beam coverage characteristic and it can be useful for application to a wide band phased array antenna system. In this paper, we designed a broadband E-plane H-sector horn phased-array antenna, which has a 3:1 bandwidth and ${\pm}60^{\circ}$ beam steering capability. An H-sector hem antenna was designed to have $30{\sim}50^{\circ}$ half-power beam width in the principal H-plane. The active reflection coefficient including mutual coupling was calculated using a waveguide simulator, and the active reflection characteristic was improved by mutual coupling over wide frequency range. Using these results, an $8{\times}1$ H-sector phased array antenna was fabricated. The measurement results for the half-power beam width in the principal H-plane and the active reflection coefficient showed a good agreement with the simulation results. The peak-value pattern in the steered radiation beams also agreed well with the active element pattern. The measured active reflection coefficients within the beam steering range are mostly less than 0.3 over the 3:1 frequency range.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1082-1090
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• 2008

In this paper, a general solution for the vibrational energy and intensity distribution through a compliant and dissipative joint between plate structures is derived on the basis of energy flow analysis (EFA). The joints are modeled by four sets of springs and dashpots to show their compliancy and dissipation in all four degrees of freedom. First, for the EFA, the power transmission and reflection coefficients for the joint on coupled plate structures connected at arbitrary angles were derived by the wave transmission approach. In numerical applications, EFA is performed using the derived coefficients for coupled plate structures under various joint properties, excitation frequencies, coupling angles, and internal loss factors. Numerical results of the vibrational energy distribution showed that the developed compliant and dissipative joint model successfully predicted the joint characteristics of practical structures vibrating in the medium-to-high frequency ranges. Moreover, the intensity distribution of a compliant and dissipative joint is described.

• Structural Engineering and Mechanics
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• v.7 no.2
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• pp.181-202
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• 1999

Dynamic response of axisymmetric arbitrary laminated composite cylindrical shell of finite length, using three-dimensional elasticity equations are studied. The shell is simply supported at both ends. The highly coupled partial differential equations are reduced to ordinary differential equations (ODE) with variable coefficients by means of trigonometric function expansion in axial direction. For cylindrical shell under dynamic load, the resulting differential equations are solved by Galerkin finite element method, In this solution, the continuity conditions between any two layer is satisfied. It is found that the difference between elasticity solution (ES) and higher order shear deformation theory (HSD) become higher for a symmetric laminations than their unsymmetric counterpart. That is due to the effect of bending-streching coupling. It is also found that due to the discontinuity of inplane stresses at the interface of the laminate, the slope of transverse normal and shear stresses aren't continuous across the interface. For free vibration analysis, through dividing each layer into thin laminas, the variable coefficients in ODE become constants and the resulting equations can be solved exactly. It is shown that the natural frequency of symmetric angle-ply are generally higher than their antisymmetric counterpart. Also the results are in good agreement with similar results found in literatures.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.104-114
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• 1995

Mathematical models of industrial robots or manipulators are composed of highly nonlinear equations with nonlinear couplings between the variables of motions. These nonlin- earities were not considered important in the first stage that the working speed of the manipulator was not so fast, but the effect of nonlinear forces has become serious, as the working speed has been increased. So more improvement of performance cannot be expected by the control of manipulator using approximate linearization. As an approach for solving these problems, there is a method that eliminates nonlinear theory, which makes possible cecoupling of coupling terms and arbitrary arranging of poles is briefly introduced in this study. When the theory is applied to design the control law, its feasibility is examined whether the reasonable control results are obtained by simulating position, velocity, torque and tracing trajectory. The relations between the coefficients of the linearized differential equations and the maximum error and torque for the prescribed trajectory are also examined. Finally, the method for selecting the values for getting the most rapid and precise response within maximum torque of each drive is suggested in the choice of coefficients of characteristic equations which are obtained as a result of the control.