Pitak Thumwarin

Tri-Band Rectangular Spiral Slot Antenna with L-Shaped Slot Antenna for WLAN and Radar Applications

Tri-band rectangular spiral slot (RSS) antenna with an L-shaped slot antenna insertion is introduced in this paper. The antenna was designed on the substrate with 2.2 of dielectric constant and 1.575 mm of thickness. FDTD method was adopted to evaluate the proposed antenna characteristics A rectangular spiral slot antenna was designed to support dual-frequency at 2.44 GHz and 8 GHz. An L-shaped slot antenna was inserted to obtain more resonant frequency at 5.2 GHz. The simulation results revealed that the proposed antenna could be used to support tri-band of frequency which is compatible to IEEE 802.11a or HIPERLAN (5.2 GHz) standard, IEEE 802.11b/g (Wi-Fi 2.44 GHz) standard and 8.0 GHz satellite or radar communications

FIR signature verification system characterizing dynamics of handwriting features

This paper proposes an online signature verification method based on the finite impulse response (FIR) system characterizing time-frequency characteristics of dynamic handwriting features. First, the barycenter determined from both the center point of signature and two adjacent pen-point positions in the signing process, instead of one pen-point position, is used to reduce the fluctuation of handwriting motion. In this paper, among the available dynamic handwriting features, motion pressure and area pressure are employed to investigate handwriting behavior. Thus, the stable dynamic handwriting features can be described by the relation of the time-frequency characteristics of the dynamic handwriting features. In this study, the aforesaid relation can be represented by the FIR system with the wavelet coefficients of the dynamic handwriting features as both input and output of the system. The impulse response of the FIR system is used as the individual feature for a particular signature. In short, the signature can be verified by evaluating the difference between the impulse responses of the FIR systems for a reference signature and the signature to be verified. The signature verification experiments in this paper were conducted using the SUBCORPUS MCYT-100 signature database consisting of 5,000 signatures from 100 signers. The proposed method yielded equal error rate (EER) of 3.21% on skilled forgeries.

On-line signature verification based on FIR system characterizing velocity and direction change of barycenter trajectory

We propose an on-line signature verification method based on finite impulse response(FIR) system characterizing velocity and direction change of barycenter trajectory. First, the discrete cosine transforms (DCTs) of the characteristics are used to reduce fluctuation and extract the feature of handwriting in signing process. Then the signature verification system is realized by the three FIR subsystems. The obtained impulse responses of the three FIR subsystems are used as the individual feature for signature verification. Signature can be verified by evaluating the difference between the impulse responses of the FIR subsystems for a reference signature and the signature to be verified. The signature verification experiments were performed on the SUBCORPUS-100 MCYT signature database[6] consisting of 5,000 signatures from 100 signers.

Firearm identification based on rotation invariant feature of cartridge case

This paper, proposes firearm identification method based on rotation invariant feature of cartridge case image. The rotation invariance feature is represented by the absolute value of Fourier coefficients of polar image of cartridge case on circles with different radii. The absolute value of Fourier coefficients is considered as the individual feature of the particular gun. Finally, the firearm can be identified by the distance between the absolute value of Fourier coefficients obtained from the reference cartridge case and the cartridge case to be identified. The firearm identification experiments are given to show the effectiveness of the proposed method.

On-line writer identification method based on FIR system characterizing pen-tip movement

In this paper on-line writer identification problem is reduced to FIR system identification problem. Then person can be identified by evaluating the difference between the impulse responses of the FIR system for the reference and the person to be identified. The FIR system is realized by considering the DCTs of the horizontal and vertical components of the pen-tip movement with reduced fluctuation as the input and output, respectively. Finally, writer identification experiments are given to show the effectiveness of the proposed method.

Wide-Band Slot Antenna for IEEE 802.11b/g

This paper presents coplanar waveguide (CPW) fed step slot antenna. It achieves wide band from 2.0 GHz to 4.2 GHz which is the frequency band covered the standard IEEE 802.11 b/g (2.4-2.485 GHz) for use in WLAN (wireless local area network) and covered two frequencies of WiMAX (worldwide interoperability for microwave access) 2.5 GHz and 3.5 GHz. The characteristics of antenna are proposed and analyzed, for instance input impedance, return loss and far field radiation patterns

An Automatic System for Firearm Identification

This research proposes an automatic system for firearm identification. In the proposed method, firearm can be identified by using the head of cartridge case image. The unique feature of the individual gun can be extracted by using the absolute value of Fourier coefficients of polar image of cartridge case on circles with different radii. The obtained absolute value of Fourier coefficients is considered as the rotation invariance feature of the cartridge case image. Finally, the Fishers linear discriminant function is used to identify the gun. The result successfully revel the effectiveness of the method of implementation for some extent.

Audio forensics from gunshot for firearm identification

The gunshot blast is one of the evidences used to identify the criminal gun in the shooting scene. We proposed a method of using the gunshot blast to identify the firearm caliber in terms of audio forensics. The experiments were performed on the database consisting of 80 audio files of gunshot sounds fired from 8 different guns. At first, the autocorrelation functions of the gunshot sounds were calculated and normalized in the preprocessing stage. Then the Fourier cosine coefficients could be used to reduce the fluctuation and to extract the features of gunshot sounds. In addition, the gun sounds could also be verified by evaluating the difference among the Fourier cosine coefficients of the reference, and then the gun caliber could be identified.

On-line signature verification based on FIR system characterizing motion pressure

We propose an on-line signature verification method based on finite impulse response(FIR) system characterizing motion pressure of pen-point trajectory in signing process. The discrete cosine transforms(DCTs) of the handwriting feature is used to reduce the fluctuation and extract the feature of handwriting. The signature verification system is realized by four FIR subsystems. Then motion pressure can be characterized by using the FIR subsystem having the DCTs of the area pressure and motion pressure as the input and the output of the FIR system, respectively. The obtained impulse responses of the four FIR subsystems are used as the individual feature for signature verification. Finally, the signature can be verified by evaluating the difference between the impulse responses of the FIR subsystems for a reference signature and the signature to be verified. The signature verification experiments were performed on the SUBCORPUS-100 MCYT [J.Ortega-Garcia et al.2003] signature database consisting of 5,000 signatures from 100 signers. The propose method yielded equal error rate(EER) 4.38 % on skilled forgeries.

On-line writer dependent character recognition for Khmer based on FIR system characterizing handwriting motion

We propose an on-line writer dependent Khmer recognition method based on time-frequency characteristics of handwriting motion. The handwriting motion can be described by two features, barycenter trajectory and its velocity of pen-tip movement. Then the barycenter trajectory and its velocity of the pen-tip movement are expanded into wavelet series to extract the time-frequency characteristics of the handwriting motion. After that, The fluctuation of the wavelet coefficients can be reduced by the FIR (finite impulse response) Wiener filter. Moreover, the FIR system characterizing the time-frequency characteristics of the handwriting motion is introduced by using wavelet coefficients of the velocity and trajectory of the barycenter with fluctuation reduced as the input and output of the FIR system, respectively. The obtained impulse response of the FIR system is considered as the individual feature for a particular character. Finally, Khmer alphabets can be recognized by using the Euclidean distance between the impulse responses obtained from the reference alphabets and those of the alphabets to be recognized. Khmer character recognition experiments were performed on a database consisting of 6,750 of numerals and alphabets written by 17 people. As the results, the average of the recognition rate was 98.17%.