• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.10 no.1
• /
• pp.16-22
• /
• 2001

In this study for reduction degree of freedom of dynamic model, a mixed method to combined finite element method and transfer matrix method is presented. This offers the advantages of an automatic reduction in the size of the eigenvalues problem and of a straightforward means of dynamic substructuring. The analytical procedure in this method for dynamic analysis of 3-dimensional cantilevered box beam are described. the result of numerical example is shown to demonstate the efficiency and accuracy of this method. The result form this example agree well those obtained by ANSYS, By using this technique, the number of nodes required in the regular finite element method is reduced and therefore a smaller com-puter can be used.

• Journal of Mechanical Science and Technology
• /
• v.19 no.8
• /
• pp.1568-1575
• /
• 2005

The calculation of the transmission loss of the silencers with complicated internal structures by the conventional BEM combined with the transfer matrix method is incorrect at best or impossible for 3-dimensional silencers due to its inherent plane wave assumption. On this consideration, we propose an efficient practical means to formulate algebraic overall condensed acoustic equations for the whole acoustic structure, where particle velocities on the domain interface boundaries are unknowns, and the solutions are used later to compute the overall transfer matrix elements, based on the multi-domain BEM data. The transmission loss estimation by the proposed method is tested by comparison with the experimental one on an air suction silencer with perforated internal structures installed in air compressors. The method shows its viability by presenting the reasonably consistent anticipation of the experimental result.

• Journal of Electrical Engineering and Technology
• /
• v.6 no.6
• /
• pp.874-882
• /
• 2011

The decoupling design for the one-degree-of-freedom controller system is treated within the $H_{\infty}$ framework. In the present study, we demonstrate that the $H_{\infty}$ performance problem in the decoupling design is reduced into interpolation problems on scalar functions. To guarantee the properness of decoupling controllers and the overall transfer matrix, the relative degree conditions on the interpolating scalar functions are derived. To find the interpolating functions with relative degree constraints, Nevanlinna-Pick algorithm with starting function constraint is utilized in the present study. An illustrative example is given to provide details regarding the solution.

• Journal of Korea Multimedia Society
• /
• v.7 no.6
• /
• pp.781-790
• /
• 2004

This paper presents a fourth-order cumulants based iterative algorithm for blind channel equalization. It is robust with respect to the existence of heavy Gaussian noise in a channel and does not require the minimum phase characteristic of the channel. In this approach, the transmitted signals at the receiver are over-sampled to ensure the channel described by a full-column rank matrix. It changes a single-input/single-output (SISO) finite-impulse response (FIR) channel to a single-input/multi-output (SIMO) channel. Based on the properties of the fourth-order cumulants of the over-sampled channel outputs, the iterative algorithm is derived to estimate the deconvolution matrix which makes the overall transfer matrix transparent, i.e., it can be reduced to the identity matrix by simple reordering and scaling. Both a closed-form and a stochastic version of the proposed algorithm are tested with three-ray multi-path channels in simulation studies, and their performances are compared with a method based on conventional second-order cumulants. Relatively good results are achieved, even when the transmitted symbols are significantly corrupted with Gaussian noise.

• Advanced Composite Materials
• /
• v.17 no.1
• /
• pp.75-87
• /
• 2008

Aerospace structural applications, along with high performance marine and automotive applications, require high-strength efficiency, which can be achieved using metal matrix composites (MMCs). Rotating components, such as jet-engine blades and gas turbine parts, require materials that maximize strength efficiency and metallurgical stability at elevated temperatures. Titanium matrix composites (TMCs) are well suited in such applications, since they offer an enhanced resistance to temperature effects as well as corrosion resistance, in addition to optimum strength efficiency. The overall behavior of the composite system largly depends on the properties of the interface between fiber and matrix. Characterization of the fiber.matrix interface at operating temperatures is therefore essential for the developemt of these materials. The fiber fragmentation test shows good reproducibility of results in determining interface properties. This paper deals with the evaluation of fiber fragmentation characteristics in TMCs at elevated temperature and the results are compared with tests at ambient temperature. It was observed that tensile testing at $650^{\circ}C$ of single-fiber TMCs led to limited fiber fragmentation behavior. This indicates that the load transfer from the matrix to the fiber occurs due to interfacial friction, arising predominantly from mechanical clamping of the fiber by radial compressive residual and Poisson stresses. The present work also demonstrates that composite processing conditions can significantly affect the nature of the fiber.matrix interface and the resulting fragmentation of the fiber.

• Structural Engineering and Mechanics
• /
• v.63 no.4
• /
• pp.551-565
• /
• 2017

In this paper, an analytical approach is proposed for determining vibration characteristics of cracked non-uniform continuous Timoshenko beam carrying an arbitrary number of spring-mass systems. This method is based on the Timoshenko beam theory, transfer matrix method and numerical assembly method to obtain natural frequencies and mode shapes. Firstly, the beam is considered to be divided into several segments by spring-mass systems and support points, and four undetermined coefficients of vibration modal function are contained in each sub-segment. The undetermined coefficient matrices at spring-mass systems and pinned supports are obtained by using equilibrium and continuity conditions. Then, the overall matrix of undetermined coefficients for the whole vibration system is obtained by the numerical assembly technique. The natural frequencies and mode shapes of a cracked non-uniform continuous Timoshenko beam carrying an arbitrary number of spring-mass systems are obtained from the overall matrix combined with half-interval method and Runge-Kutta method. Finally, two numerical examples are used to verify the validity and reliability of this method, and the effects of cracks on the transverse vibration mode shapes and the rotational mode shapes are compared. The influences of the crack location, depth, position of spring-mass system and other parameters on natural frequencies of non-uniform continuous Timoshenko beam are discussed.

• Korean Journal of Optics and Photonics
• /
• v.31 no.2
• /
• pp.59-70
• /
• 2020

We discuss a modified numerical model based on the Monte Carlo radiative transfer (MCRT) method, i.e., the MCRT matrix method, for the analysis of atmospheric scattering effects in three-dimensional flash LIDAR systems. Based on the MCRT method, the radiative transfer function for a LIDAR signal is constructed in a form of a matrix, which corresponds to the characteristic response. Exploiting the superposition and convolution of the characteristic response matrices under the paraxial approximation, an extended computer simulation model of an overall flash LIDAR system is developed. The MCRT matrix method substantially reduces the number of tracking signals, which may grow excessively in the case of conventional Monte Carlo methods. Consequently, it can readily yield fast acquisition of the signal response under various scattering conditions and LIDAR-system configurations. Using the computational model based on the MCRT matrix method, we carry out numerical simulations of a three-dimensional flash LIDAR system operating under different atmospheric conditions, varying the scattering coefficient in terms of visible distance. We numerically analyze various phenomena caused by scattering effects in this system, such as degradation of the signal-to-noise ratio, glitches, and spatiotemporal spread and time delay of the LIDAR signals. The MCRT matrix method is expected to be very effective in analyzing a variety of LIDAR systems, including flash LIDAR systems for autonomous driving.

• Carbon letters
• /
• v.14 no.2
• /
• pp.76-88
• /
• 2013

Carbon fibers (CFs) have high service temperature, strength, and stiffness, and low weight. They are widely used as reinforcing materials in advanced polymer composites. The role of the polymer matrix in the composites is to provide bulk to the composite laminate and transfer load between the fibers. The interface between the CF and the resin matrix plays a critical role in controlling the overall properties of the composites. This paper aims to review the synthesis, properties, and applications of polymer matrices, such as thermosetting and thermoplastic resins.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.5 no.1
• /
• pp.13-20
• /
• 2005

This paper addresses a new blind channel equalization method using fourth-order cumulants of channel inputs and a three-layer neural network equalizer. The proposed algorithm is robust with respect to the existence of heavy Gaussian noise in a channel and does not require the minimum-phase characteristic of the channel. The transmitted signals at the receiver are over-sampled to ensure the channel described by a full-column rank matrix. It changes a single-input/single-output (SISO) finite-impulse response (FIR) channel to a single-input/multi-output (SIMO) channel. Based on the properties of the fourth-order cumulants of the over-sampled channel inputs, the iterative algorithm is derived to estimate the deconvolution matrix which makes the overall transfer matrix transparent, i.e., it can be reduced to the identity matrix by simple recordering and scaling. By using this estimated deconvolution matrix, which is the inverse of the over-sampled unknown channel, a three-layer neural network equalizer is implemented at the receiver. In simulation studies, the stochastic version of the proposed algorithm is tested with three-ray multi-path channels for on-line operation, and its performance is compared with a method based on conventional second-order statistics. Relatively good results, withe fast convergence speed, are achieved, even when the transmitted symbols are significantly corrupted with Gaussian noise.

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.8
• /
• pp.862-869
• /
• 2005

A study on convective cooling characteristics has been done in the channels with heat pipes and associated Plane fins Analysis with FLUENT V5.0 lies its Purpose on the possible enhancement of heat transfer capability between an existing three in-line arrayed heatpipes and an extending four in-line arrayed heatpipes with increasing channel width. Numerical analysis is limited to the laminar flow in an isolated flow channel by employing cyclic boundary conditions for calculation purposes. Friction factors for three and four in-line arrayed heatpipes are compared with experimental results. In addition, temperature behavior at the plate fin for the three in-line arrayed heatpipes is compared with experiment. Friction factors and overall channel heat transfer coefficients (and/or Nusselt numbers) are presented as a function of Reynolds number. An increase of number of heatpipes and channel width reults in a decrease of the friction factor and doesn't not result in an increase of heat transfer performance. However. considering the 25$\%$ increase of heat load accompanies with maximum 8$^{\circ}C$ rise of average temperature of heat pipes, the four in-line array with the increase of channel width of heat pipe heat sink can be considered appropriate.