• Smart Structures and Systems
• /
• v.18 no.4
• /
• pp.707-731
• /
• 2016

A unified mathematical model of the equations of generalized magneto-thermoelasticty based on fractional derivative heat transfer for isotropic perfect conducting media is given. Some essential theorems on the linear coupled and generalized theories of thermoelasticity e.g., the Lord- Shulman (LS) theory, Green-Lindsay (GL) theory and the coupled theory (CTE) as well as dual-phase-lag (DPL) heat conduction law are established. Laplace transform techniques are used. The method of the matrix exponential which constitutes the basis of the state-space approach of modern theory is applied to the non-dimensional equations. The resulting formulation is applied to a variety of one-dimensional problems. The solutions to a thermal shock problem and to a problem of a layer media are obtained in the present of a transverse uniform magnetic field. According to the numerical results and its graphs, conclusion about the new model has been constructed. The effects of the fractional derivative parameter on thermoelastic fields for different theories are discussed.

• Journal of Astronomy and Space Sciences
• /
• v.17 no.2
• /
• pp.221-232
• /
• 2000

A Gunn waveguide-oscillator, mechanically tunable from 60 to 70 GHz, has been developed for use as a local oscillator(LO) is millimeter radio telescope. Disc size, post size and characteristics of Gunn diode have an effect on the frequency tuning characteristics of Gunn oscillator. In this paper we report experimental results and design criteria for a wideband tunable Gunn oscillator. The developed Gunn oscillator has been used in the 100/150 GHz band dual channel receiver for the Taeduk Radio Astronomy Observatory.

• The Pure and Applied Mathematics
• /
• v.1 no.1
• /
• pp.25-27
• /
• 1994

Suppose that X is a Banach space with continuous dual $X^{**}$, ($\Omega$, $\Sigma$, ${\mu}$) is a finite measure space. f : $\Omega\;{\longrightarrow}$ $X^{*}$ is a weakly measurable function such that $\chi$$^{**}$ f $\in$ $L_1$(${\mu}$) for each $\chi$$^{**}$ $\in$ $X^{**}$ and $T_{f}$ : $X^{**}$ \longrightarrow $L_1$(${\mu}$) is the operator defined by $T_{f}$($\chi$$^{**}$) = $\chi$$^{**}$f. In this paper we study the properties of bounded $X^{*}$ - valued weakly measurable functions and bounded $X^{*}$ - valued weak＊ measurable functions.(omitted)

• Kyungpook Mathematical Journal
• /
• v.48 no.4
• /
• pp.559-575
• /
• 2008

A commutative hypercomplex system $L_1$(Q,m) is, roughly speaking, a space which is defined by a structure measure (c(A,B, r), (A,$B{\in}{\beta}$(Q)). Such space has bee studied by Berezanskii and Krein. Our main purpose is to establish a generalization of convolution semigroups and to discuss the role of the L$\'{e}$vy measure in the L$\'{e}$vy-Khinchin representation in terms of continuous negative definite functions on the dual hypercomplex system.

• International Journal of Aeronautical and Space Sciences
• /
• v.2 no.2
• /
• pp.28-38
• /
• 2001

A numerical method for the assessment and correction of tunnel wall interference effects on forced-oscillation testing is presented. The method is based on the wall pressure signature method using computed wall pressure distributions. The wall pressure field is computed using unsteady three-dimensional full Navier-Stokes solver for a 70-degree pitching delta wing in a wind tunnel. Approximately-factorized alternate direction implicit (AF-ADI) scheme is advanced in time by solving block tri-diagonal matrices. The algebraic Baldwin-Lomax turbulence, model is included to simulate the turbulent flow effect. Also, dual time sub-iteration with, local, time stepping is implemented to improve the convergence. The computed wall pressure field is then imposed as boundary conditions for Euler re-simulation to obtain the interference flow field. The static computation shows good agreement with experiments. The dynamic computation demonstrates reasonable physical phenomena with a good convergence history. The effects of the tunnel wall in upwash and blockage are analyzed using the computed interference flow field for several reduced frequencies and amplitudes. The corrected results by pressure signature method agree well with the results of free air conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.2
• /
• pp.75-83
• /
• 2005

NASA/DLR Gravity Recovery and Climate Experiment (GRACE) mission, which consists of two co-orbiting low altitude satellites, is to measure the Earth gravity field with unprecedented accuracy. Its key instruments include inter-satellite ranging systems and three-axis accelerometers. For the preliminary design and requirements analysis, extensive instrument simulation models are developed. These modeling techniques and orbit-gravity field estimation techniques are described.

• International Journal of Aeronautical and Space Sciences
• /
• v.9 no.2
• /
• pp.79-86
• /
• 2008

High performance direct-iterative hybrid linear solver for large scale finite element problem is developed. Direct solution method is robust but difficult to parallelize, whereas iterative solution method is opposite for direct method. Therefore, combining two solution methods is desired to get both high performance parallel efficiency and numerical robustness for large scale structural analysis problems. Hybrid method mentioned in this paper is based on FETI-DP (Finite Element Tearing and Interconnecting-Dual Primal method) which has good parallel scalability and efficiency. It is suitable for fourth and second order finite element elliptic problems including structural analysis problems. We are using the hybrid concept of theses two solution method categories, combining the multifrontal solver into FETI-DP based iterative solver. Hybrid solver is implemented for our general structural analysis code, IPSAP.

• Journal of Power Electronics
• /
• v.10 no.2
• /
• pp.146-154
• /
• 2010

In this paper two dual output current-type inverters are proposed. These inverters have been called a current source nines-witch inverter and a current-type z-source nine-switch inverter by the authors. The proposed inverters have two independent current source outputs. Compared to two independent current source inverters, the proposed converters are implemented with fewer semiconductor switches. Space vector modulation (SVM) is proposed for these converters. Simulation results show the validity and performance of the proposed inverters.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.2
• /
• pp.209-214
• /
• 2009

The simulation software for predicting the performance of a wind turbine generator system (WTGS) is validated using the field measured data obtained from the idling test run of a dual rotor wind turbine recently developed and installed in Korea. Both steady-state and transient responses at low and high wind conditions are compared with the theoretically predicted ones from the simulation software WINSIM.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.240-243
• /
• 2005

A design procedure using spatial Fourier transform is presented for a structural-acoustic coupled radiator that can emit sound in the desired direction with high power and low side lobe level. The design procedure consists of three steps. Firstly, the structural-acoustic coupled radiator is chosen to obtain strong coupling between structural vibration and acoustic pressure. The radiator is composed by two spaces which are separated by a wall. Spaces can be categorized as reverberant finite space and unbounded semi-infinite space, and the wall are composed of two plates and an opening. The velocities on the wall are predicted. Secondly, directivity and energy distribution of radiator are predicted in wave number domain using spatial Fourier transform. Finally, optimal design variables are calculated using a dual optimal algorithm. Its computational example is presented including the directivity and resulting pressure distribution using proposed procedure.