KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 14

Some of the metrics are blocked by your
consent settings
Practical method for determining inductance and capacitance of metamaterial resonators
(2012-02-16)
Li, J. N.
;
Withayachumnankul, W.
;
Chang, S. J.
;
Abbott, D.
A practical approach to determining the distributed capacitance and inductance of individual metamaterial resonators is demonstrated. By loading a set of lumped capacitors onto the resonator, the resonance frequency can be measured as a function of the load capacitance. The capacitance and inductance values of the resonator are then determined by relating the equivalent circuit model to the measurements. Although the measurement is limited to the microwave region owing to the availability of suitable lumped capacitors, the concept is useful in simulations over a wider frequency range. The obtainable parameters are useful for further metamaterial analyses or syntheses. © 2012 The Institution of Engineering and Technology.
Some of the metrics are blocked by your
consent settings
Elastomeric silicone substrates for terahertz fishnet metamaterials
(2012-02-06)
Khodasevych, I. E.
;
Shah, C. M.
;
Sriram, S.
;
Bhaskaran, M.
;
Withayachumnankul, W.
In this work, we characterize the electromagnetic properties of polydimethylsiloxane (PDMS) and use this as a free-standing substrate for the realization of flexible fishnet metamaterials at terahertz frequencies. Across the 0.2-2.5 THz band, the refractive index and absorption coefficient of PDMS are estimated as 1.55 and 0-22 cm <sup>-1</sup>, respectively. Electromagnetic modeling, multi-layer flexible electronics microfabrication, and terahertz time-domain spectroscopy are used in the design, fabrication, and characterization of the metamaterials, respectively. The properties of PDMS add a degree of freedom to terahertz metamaterials, with the potential for tuning by elastic deformation or integrated microfluidics. © 2012 American Institute of Physics.
Some of the metrics are blocked by your
consent settings
T-ray relevant frequencies for osteosarcoma classification
(2006-04-17)
Withayachumnankul, W.
;
Ferguson, B.
;
Rainsford, T.
;
Findlay, D.
;
Mickan, S. P.
We investigate the classification of the T-ray response of normal human bone cells and human osteosarcoma cells, grown in culture. Given the magnitude and phase responses within a reliable spectral range as features for input vectors, a trained support vector machine can correctly classify the two cell types to some extent. Performance of the support vector machine is deteriorated by the curse of dimensionality, resulting from the comparatively large number of features in the input vectors. Feature subset selection methods are used to select only an optimal number of relevant features for inputs. As a result, an improvement in generalization performance is attainable, and the selected frequencies can be used for further describing different mechanisms of the cells, responding to T-rays. We demonstrate a consistent classification accuracy of 89.6%, while the only one fifth of the original features are retained in the data set.
Some of the metrics are blocked by your
consent settings
T-rays in biomedicine and security
(2005-12-01)
Rainsford, T.
;
Png, G. M.
;
Withayachumnankul, W.
;
Ferguson, B.
;
Mickan, S. P.
With a number of commercial systems becoming increasingly available, and improved generation and detection techniques T-ray systems are increasingly finding new applications. One of the main technical challenges is to make systems low cost, compact and easy to use. In this paper we suggest some novel solutions for parameter extraction, image enhancement, improved signal-to-noise ratio and classification schemes. These tools are useful in a number of biomedical and security applications. © 2005 IEEE.
Some of the metrics are blocked by your
consent settings
3D modeling from multiple projections: Parallel-beam to helical cone-beam trajectory
(2005-12-01)
Narkbuakaew, W.
;
Pintavirooj, C.
;
Withayachumnankul, W.
;
Sangworasil, M.
;
Taertulakarn, S.
Tomographic imaging is a technique for exploration of a cross-section of an inspected object without destruction. Normally, the input data, known as the projections, are gathered by repeatedly radiating coherent waveform through the object in a number of viewpoints, and receiving by an array of corresponding detector in the opposite position. In this research, as a replacement of radiographs, the series of photographs taken around the opaque object under the ambient light is completely served as the projections. The purposed technique can be adopted with various beam geometry including parallel-beam, cone-beam and spiral cone-beam geometry. From the process of tomography, the outcome is the stack of pseudo cross-sectional image. Not the internal of cross section is authentic, but the edge or contour is valid. Copyright UNION Agency - Science Press.
Some of the metrics are blocked by your
consent settings
Ultrasonic diffraction tomography: The experimental result
(2005-12-01)
Pintavirooj, C.
;
Jaruwongrungsee, K.
;
Withayachumnankul, W.
;
Hamamoto, K.
;
Daochai, S.
Diffraction tomography is a technique for imaging with acoustic fields. It takes advantage of the linearization process of the non-linear wave equation describing wave propagation in heterogeneous media. When the scattering effect is weak, one can invoke the Born or Rytov approximation and thus derive the generalized Fourier Slice Theorem to reconstruct the cross-section of the insonified object. Although diffraction tomography is a promising technology for medical application as it provides a quantitative ultrasonic image, its realization toward medical use is still far-to-go, this may be due to the complexity of the hardware involved. In this research we investigate a potential use of diffraction tomography for medical application by using a delicate-designed ultrasonic computerized tomographic system. The result of experiment investigation of diffraction tomography is very promising. Copyright UNION Agency - Science Press.
Some of the metrics are blocked by your
consent settings
Shape matching using set of curve geometric invariant point
(2005-12-01)
Pintavirooj, C.
;
Nantivatana, P.
;
Putjarupong, P.
;
Withayachumnankul, W.
;
Sangworasil, M.
We introduce a non-iterative geometric-based method for shape matching using a novel set of geometric landmarks residing on a 2D contours. These landmarks are intrinsic and are computed from the differential geometry of the curve. We exploit the invariant properties of geometric landmarks that are local and preserved under the affine and some perspective transformation. Geometric invariant exploits coplanar five-point invariant and ration of area constructed from a sequence of consecutive landmarks. These invariants are preserved not only in affine map but weak perspective map as well. To reduce the sensitivity of the landmarks to noise, we use a B-Spline surface representation that smoothes out the curve prior to the computation of the landmarks. The matching is achieved by establishing correspondences between the landmarks after a conformal sorting based on derived absolute invariant and registering the contours. The experiments have shown that the purposed methods are robust and promising even in the presence of noise. Copyright UNION Agency - Science Press.
Some of the metrics are blocked by your
consent settings
Acceleration of genetic algorithm with parallel processing with application in medical image registration
(2005-12-01)
Laksanapanai, B.
;
Withayachumnankul, W.
;
Pintavirooj, C.
;
Tosranon, P.
Generally, image registration using genetic algorithm is a time-consuming process since the algorithm needs to evaluate the objective function several hundred times depending on the vastness of search space. The situation appears worse if the registration is intensity-based due to the interpolation loops prior to each objective function. However, with the availability of parallel processing method, one can accelerate the application of genetic algorithm for iterative-based image registration process of up 80 % for multi-modality alignment. Copyright UNION Agency - Science Press.
Some of the metrics are blocked by your
consent settings
Ultrasonic diffraction tomography by pulse-plane wave: Experimental result by frequency synthesis method
(2005-01-01)
Tangtisanon, G.
;
Jaruwongrunsee, K.
;
Withayachumnankul, W.
;
Hamamoto, K.
;
Pintavirooj, C.
Diffraction tomography is a technique for imaging with acoustic fields in which parameter, such as reflective index, sound velocity, etc., can be mapped from scatter wave resulting from insonifying the object with a plane wave at a single temporal frequency. By solving the direct scattering problem, the scattered field can be presented in term of scattering parameters. Different inversion techniques can be applied to take advantage of the linearization process of the non-linear wave equation describing wave propagation in heterogeneous media under a limited class of scattering. Specifically, when the scattering effect is weak, one can invoke the Born or Rytov approximation and thus derive the generalized Fourier Slice Theorem to reconstruct the cross-section of the insonified object. Although diffraction tomography is a promising technology for medical application as it provides a quantitative ultrasonic image, its realization toward medical use is still far-to-go, and this may be due to the complexity of the hardware involved. In this research we investigate a potential use of diffraction tomography for medical application by using a delicate-designed ultrasonic computerized tomographic system. The contribution of the paper is that we have purposed to Frequency Synthesis Method (FSM) that uses 3 frequency components of the Fourier transform of scattered filed, i.e. the center frequency and the -3 dB from center frequency of both side, to fill Fourier space for the generalized Fourier slice theory. The reconstructed ultrasonic image from such theory provides a very promising result. © 2005 IEEE.
Some of the metrics are blocked by your
consent settings
3D modeling from using spiral cone-beam trajectory
(2005-01-01)
Narkbuakaew, W.
;
Withayachumnankul, W.
;
Pintavirooj, C.
;
Sangworasil, M.
Tomographic imaging is a technique for exploration of a cross-section of an inspected object without destruction. Normally, the input data, known as the projections, are gathered by repeatedly radiating coherent waveform through the object in a number of viewpoints, and receiving by an array of corresponding detector in the opposite position. In this research, as a replacement of radiographs, the series of photographs taken around the opaque object under the ambient light is completely served as the projections. The process is called photographic tomograph. In this paper, we purpose the 3D shape extraction based on using photographic tomography with spiral cone-beam trajectory. We have demonstrated that the purposed technique can rectify the problem of perspective occlusion that occurs when using cone-beam trajectory.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results