KMITL

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

Browse

Search Results

Now showing 1 - 8 of 8

Some of the metrics are blocked by your
consent settings
The preliminary investigation of ear recognition using hybrid technique
(2017-02-21)
Taertulakarn, S.
;
Pintavirooj, C.
;
Tosranon, P.
;
Hamamoto, K.
Ear recognition is one of the new patterns of biometrics. Ear structure is believed to contain specific and unique anatomical markers, which can be used both to distinguish it from others. In this paper, we derive preliminary of Ear identification based on the geometric features on 3D ear surface for 2D ear image. Principal components analysis (PCA) is used in this study for feature extraction to identify a person. The result is shown 92% recognition rate of 50 volunteers.
Some of the metrics are blocked by your
consent settings
Polarization diversity unidirectional antenna for IEEE 802.11a applications
(2012-11-12)
Vongsack, S.
;
Phongcharoenpanich, C.
;
Kosulvit, S.
;
Hamamoto, K.
;
Wakabayashi, T.
The polarization diversity unidirectional antenna is proposed for IEEE 802.11a applications by using two-probe excited circular ring antenna above square reflector. The purpose of this investigation is to design a polarization diversity unidirectional antenna to resonate at the center frequency of 5.5 GHz to cover the frequency range from 5.2 to 5.8 GHz for wireless LAN system following IEEE 802.11a standard. The performances of the antenna such as the return loss, the isolation between two-probes, the radiation pattern and the gain, are analyzed by using Computer Simulation Technology (CST) Microwave Studio. The proposed antenna has a polarization diversity unidirectional pattern with maximum gain of 8.34 dBi. Moreover, the proposed antenna yields the front-to-back ratio better than 20 dB and the isolation between the two-probes better than 20 dB as well. Besides, the proposed antenna is useful for wireless local area network (WLAN) communication systems.
Some of the metrics are blocked by your
consent settings
A UWB bidirectional rectangular ring antenna fed by CDM with a rod and ridges for constant beam direction
(2012-07-16)
Vongsack, S.
;
Lamultree, S.
;
Osklang, P.
;
Phongcharoenpanich, C.
;
Kosulvit, S.
This paper presents an ultra-wideband (UWB) rectangular ring antenna excited by a circular disc monopole (CDM) with a conducting rod and two double ridges to radiate bidirectional pattern with constant beam direction along the entire UWB frequency range of 3.1-10.6GHz. The conducting rod and double ridges at the upper wall of the ring are added to solve the tilted beam problem at the higher edge frequency whereas the double ridges at the lower wall are used to enhance the impedance bandwidth. The dimensions of the rectangular ring and the CDM are initially considered to achieve the bidirectional pattern with the suitable resonant frequencies and bandwidth. Then, the parameters of copper rod and two double ridges are determined by parametric study using CST Microwave Studio simulation software. The prototype antenna was fabricated, and the measured results show good agreement with the simulated ones. The obtained bandwidth of |S <inf>11</inf>| < - 10 dB can cover the UWB frequency range as well as the bidirectional beam radiation with constant beam direction (θ = 0°, 180° and φ = 90°). The minimum and maximum measured gains are 3.1dBi to 5.3dBi, respectively. The proposed antenna possesses compact size with good radiation performance that can be a promising candidate for UWB applications. Copyright © 2012 S. Vongsack et al.
Some of the metrics are blocked by your
consent settings
Unidirectional antenna using two-probe excited circular ring above square reflector for polarization diversity with high isolation
(2012-01-01)
Vongsack, S.
;
Phongcharoenpanich, C.
;
Kosulvit, S.
;
Hamamoto, K.
;
Wakabayashi, T.
This paper presents a circular ring antenna fed by two perpendicular probes, both of which are placed above the square re°ector. The antenna is employed to radiate unidirectional beam for polarization diversity reception. A linear isolator is added to improve the isolation between the two probes. The antenna is proposed for the point-to-point communication of Wireless Local Area Network (WLAN) system according to the IEEE 802.11a standard in which the allocated frequency band ranges from 5.150 GHz to 5.825 GHz. The proposed antenna is compact and suitable for mass production. Without the dielectric material, the antenna is free of dielectric loss and capable of high power handling. The prototype antenna was fabricated and measured to verify the theoretical predictions. At the center frequency, the unidirectional pattern with the measured half-power beamwidths in two principal planes of 65 and 75 degrees is achieved. The front-to-back ratio is 31 dB, and the antenna gain is 7.42 dBi. The |S<inf>11</inf>| and |S<inf>21</inf>| are respectively -23:09 dB and -33:99 dB; the obtained bandwidth is 23.64%. Based on the aforementioned characteristics, the antenna is a potential candidate for polarization diversity of WLAN applications.
Some of the metrics are blocked by your
consent settings
2D ultrasonic reflection tomography by linear array transducer and wave reflector
(2009-11-16)
Sanpanich, A.
;
Hamamoto, K.
;
Sangworasil, M.
;
Pintavirooj, C.
In general, it was known that when the series of an ultrasonic broadband pulse travel through living organ or soft tissue, their reflected projection data can be used to reconstruct a novel tomographic image. Whereas, a data obtain from an ultrasonic tomography in transmission mode is not able to be used for reconstruction a characteristic image of soft tissue which naturally shadowed by a bone or hard tissue. An ultrasonic tomography in reflection mode is realized to be a solution for this problem. However the implementation to identify the projection by using an integrated attenuation coefficient of tissue from the pulsed wave ray path in reflection mode is still more complicated. In this paper, we propose a simulation in 2D of a reflection-mode ultrasonic tomographic system by using the linear array transducer and also a frequency centroid shift method to calculate the projection data. The imaging setup system was enhanced by wave reflecting plate in order to increase an echo wave path. The ultrasound wave paths of our simulation system were intend to focus on the fan beam trajectory which is rather close to a real propagation of the ultrasound wave traveling through soft tissue and ART was used finally as an image reconstruction algorithm. The obtained output shows that our system is more practical and possible toward for using in a clinical trial.
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
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
Ultrasonic refractive index and sound velocity tomography
(2004-12-01)
Pintavirooj, C.
;
Jaruwongrungsee, K.
;
Withayachumnankul, W.
;
Hamamoto, K.
;
Taertulakarn, S.
Ultrasonic computed tomography (UCT) is one of the methods capable of tissue characterization. It is expected to provide not only a quantitative image but also diagnostic information. As in X-ray CT, UCT requires a projection data to reconstruct a cross-sectional image. The projection data of Ultrasonic Tomography is based on measurement the time delay, which is time difference between ultrasound traverse with and without object. In this paper, we investigate two different types of quantitative UCT image, refractive-index and sound-velocity image. We purpose the new method of measurement the time delay by converting the received ultrasonic pulse to frequency domain and measuring the phase shift of the center frequency of the broadband pulse. The method seems more robust to noise. Two image reconstruction techniques are used for comparison purpose including traditional filtered back-projection and simultaneous algebraic reconstruction technique (SART). © 2004 IEEE.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results