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29,758 Article Results

Graphene Nanoplatelets (GnP)-PVA Based Passive Saturable Absorber

10.12928/telkomnika.v15i2.6126
Nabihah; Universiti Teknologi Malaysia Hussin , Mohd; Universiti Teknologi Malaysia Haniff Ibrahim , Fauzan; Universiti Teknologi Malaysia Ahmad , Hafizal; Universiti Teknologi Malaysia Yahaya , Sulaiman; University of Malaya Wadi Harun
A passive Q-switched pulsed laser at 1.5 m region incorporating graphene nanoplatelets (GnPs) embedded in Polyvinyl Alcohol (PVA) is demonstrated. A surfactant is used to aid the dispersion of the GnPs before it is mixed with PVA to develop a GnPs-PVA film based SA. The SA is integrated into the laser cavity by attaching a cut of the GnPs-PVA film in between two fiber ferrule of the laser ring cavity.The proposed GnPs-PVA film based passive Q–switched laser was able to operate as the input pump power was increased from 39 mW up to a maximum of 148 mW before diminishing. The laser obtained operated with a central wavelength of 1530.76 nm. Repetition rates were obtained at 33 kHz to 91.5 kHz, throughout the tunable input pump power with the shortest pulse width of 2.42 s. Maximum attainable peak power and pulse energy of 1.2 mW and 5.9 nJ, respectively, was recorded, accompanied by a signal to noise ratio (SNR) of 28 dB.
Volume: 15
Issue: 2
Page: 814-819
Publish at: 2017-03-01

CBIR of Brain MR Images Using Histogram of Fuzzy Oriented Gradients and Fuzzy Local Binary Patterns

10.11591/ijai.v6.i1.pp8-17
Athira TR , Abraham Varghese
Retrieval of similar images from large dataset of brain images across patients would help the experts in the decision diagnosis process of diseases. Generally used feature extraction methods are color, texture and shape. In medical images texture and shape features are most efficient. Histogram of Oriented Gradients (HOG) and Local Binary Pattern (LBP) are good descriptor for brain MR image retrieval. But there are many challenges facing in medical application. An empirical study of the impact of increasing bins number in the HOG descriptor concluded that larger the number is more accurate the descriptor is. In fact this is due to the reduction of orientations range that each bin covers. Despite the efficiency of augmenting the bins number, this technique has limited spatial support as the augmentation of the number of bins used leads to increase the histogram dimension. So here proposed a method called Histogram of Fuzzy Oriented Gradients (HFOG), in which a pixel can belong several bins with different degrees. The Local Binary Patterns feature extraction method is widely used for texture analysis; however, the original LBP is based on hard thresholding the neighborhood of each pixel. Therefore, texture representation with LBP is very sensitive to noise and cannot distinguish between a strong and a weak pattern. In this study, Fuzzy Local Binary Patterns was introduced to improve the original LBP.
Volume: 6
Issue: 1
Page: 8-17
Publish at: 2017-03-01

An Ensemble of Enhanced Fuzzy Min Max Neural Networks for Data Classification

10.12928/telkomnika.v15i2.6149
Mohammed; University Malaysia Pahang Falah Mohammed , Taha; University Malaysia Pahang H. Rassem
This paper is under in-depth investigation due to suspicion of possible plagiarism on a high similarity indexAn ensemble of Enhanced Fuzzy Min Max (EFMM) neural networks for data classification is proposed in this paper.  The certified belief in strength (CBS) method is used to formulate the ensemble EFMM model, with the aim to improve the performance of individual EFMM networks.  The CBS method is used to measure trustworthiness of each individual EFMM network based on its reputation and strength indicators.  Trust is built from strong elements associated with the EFMM network, allowing the CBS method to improve the performance of the ensemble model. An auction procedure based on the first-price sealed-bid scheme is adopted for determining the winning EFMM network in undertaking classification tasks. The effectiveness of the ensemble model is demonstrated using a number of benchmark data sets. Comparing with the existing EFMM networks, the proposed ensemble model is able to improve classification accuracy rates in the empirical study.
Volume: 15
Issue: 2
Page: 942-948
Publish at: 2017-03-01

MPPT for PV System Based on Variable Step Size Perturb and Observe Algorithm

10.12928/telkomnika.v15i1.3160
Awang; Universiti Teknologi Malaysia Jusoh , Rozana; Universiti Teknologi Malaysia Alik , Tan Kar; Universiti Teknologi Malaysia Guan , Tole; Universitas Ahmad Dahlan Sutikno
This paper presents some improvements on the Perturb and Observe (P&O) method to overcome the common drawbacks of conventional P&O method. The main advantage of this modified algorithm is its simplicity with higher accuracy results, compared to the conventional methods. The operation of the entire solar Maximum Power Point Tracking (MPPT) system was observed through two different approaches, which are through MATLAB/Simulink simulation and hardware implementation. A small scale of hardware design, which consists of solar PV cell, boost converter and Arduino Mega2560 microcontroller had been utilized for further verification on the simulation results. The simulation results that was carried out by this modified P&O algorithm showed improvement and a promising performance: faster convergence speed of 0.67s, small oscillation at steady state region and promising efficiency of 95.23%. Besides, from the hardware results, the convergence time of the power curve was able to maintain at 0.2s and give almost zero oscillation during steady state. It is envisaged that the method is useful in future research of Photovoltaic (PV) system.
Volume: 15
Issue: 1
Page: 79-92
Publish at: 2017-03-01

A Dynamic Programming Approach to Energy-Efficient Scheduling on Multi-FPGA based Partial Runtime Reconfigurable Systems

10.12928/telkomnika.v15i1.3878
Chao; Guilin University of Technology Jing , Qi; Guilin University of Technology Song
This paper has been studied an important issue of energy-efficient scheduling on multi-FPGA systems. The main challenges are integral allocation, reconfiguration overhead and exclusiveness and energy minimization with deadline constraint. To tackle these challenges, based on the theory of dynamic programming, we have designed and implemented an energy-efficient scheduling on multi-FPGA systems. Differently, we have presented a MLPF algorithm for task placement on FPGAs. Finally, the experimental results have demonstrated that the proposed algorithm can successfully accommodate all tasks without violation of the deadline constraint. Additionally, it gains higher energy reduction 13.3% and 26.3% than that of Particle Swarm Optimization and fully balanced algorithm, respectively.
Volume: 15
Issue: 1
Page: 438-447
Publish at: 2017-03-01

Performance of Groundplane Shaping in Four-Element Dualband MIMO Antenna

10.12928/telkomnika.v15i1.5002
Subuh; Politeknik Negeri Semarang Pramono , Tommi; Universitas Pendidikan Indonesia Hariyadi , Budi Basuki; Politeknik Negeri Semarang Subagio
This work presents performance of groundplane shaping and its effect in four element dualband multiple input multiple output (MIMO) antenna. This proposed four element dualband MIMO antenna consists of four bowtie dipole antenna which operates at 1800 MHz (low frequency) and 2300 MHz (high frequency). This proposed four element dualband MIMO antenna occupies a 270 x 210 x  100 mm3  of FR 4 substrate. We use four types  of groundplane pattern i.e. full groundplane, cornered spatial groundplane,crossed middle groundplane, and spiral groundplane. These various grounplane patterns influence the performance of main parameters of dualband MIMO antenna. Cornered spatial groundplane pattern yields a largest bandwidth (VSWR ≤ 2) 282 MHz or 15.24% of center frequency at low frequency. Full groundplane pattern creates 135.2 MHz at high frequency. In addition, cornered spatial groundplane pattern also generates a lowest VSWR  that  is valued 1.21 at both low frequency and high frequency. The S parameters, basically both cornered spatial and full groundplane pattern produce a better return loss than two others. All four groundplane patterns deliver  equally a mutual coupling parameter.The last, this proposed four element dualband MIMO with various groundplane patterns gives a good farfield properties i.e. gain, radiation pattern, H-E field.
Volume: 15
Issue: 1
Page: 220-226
Publish at: 2017-03-01

Wideband Multi-Port Reflectometer as an Alternative in Reflection Coefficient Measurement

10.12928/telkomnika.v15i2.6117
Rashidah; Universiti Teknologi Malaysia Che Yob , Norhudah; Universiti Teknologi Malaysia Seman
 This paper presents the characterization and operation of an alternative device, which is known as multi-port reflectometer to measure the reflection coefficient of any device under test (DUT). Its configuration is formed by two power dividers (D) and four couplers (Q). The characterization is evaluated through the centres of power circles that also known as q-points. Its operation in the reflection coefficient measurement is tested by using three DUTs. The reflectometer’s good performance and wideband operation are proven between the frequency band of 1 and 6 GHz via the practical hardware measurement in the laboratory.
Volume: 15
Issue: 2
Page: 786-792
Publish at: 2017-03-01

High Sensitivity Very Low Frequency Receiver for Earthquake Data Acquisition

10.12928/telkomnika.v15i1.3484
Achmad; Institut Teknologi Bandung Munir , Kusmadi; Institut Teknologi Bandung Kusmadi , Kusnandar; Universitas Jenderal Achmad Yani Kusnandar , Asep; Universitas Jenderal Achmad Yani Najmurrokhman , Chairunnisa; Institut Teknologi Bandung Chairunnisa , Sunubroto; Universitas Jenderal Achmad Yani Sunubroto
A high sensitivity very low frequency (VLF) receiver is developed based on AD744 monolithic operational amplifier (Op-Amp) for earthquake data acquisition. In research related natural phenomena such as atmospheric noise, lightning and earthquake, a VLF receiver particularly with high sensitivity is utterly required due to the low power of VLF wave signals received by the antenna. The developed receiver is intended to have high sensitivity reception for the signals in frequency range of 10-30 kHz allocated for earthquake observation. The VLF receiver which is portably designed is also equipped with an output port connectable to the soundcard of personal computer for further data acquisition. After obtaining the optimum design, the hardware realization is implemented on a printed circuit board (PCB) for experimental characterization. It shows that the sensitivity of realized VLF receiver is almost linear in the predefined frequency range for the input signals lower than -12dBm and to be quadratic for the higher level input signals.
Volume: 15
Issue: 1
Page: 150-155
Publish at: 2017-03-01

A Two Stage Classification Model for Call Center Purchase Prediction

10.12928/telkomnika.v15i1.4269
Kai; Beijing Universiy of Posts & Telecommunications Shuang , Kai-Ze; Beijing Universiy of Posts & Telecommunications Ding , Xi-Hao; Beijing Universiy of Posts & Telecommunications Liu , Xiao-Le; Beijing Universiy of Posts & Telecommunications Wen
In call center [1] product recommendation field, call center as an organization between users and telecom operator, doesn’t have permission to access users specific information and the detailed products information. Accordingly, rule-based selection method is common used to predict user purchase behavior by the call center. Unfortunately, rule-based approach not only ignores the user’s previous behavior information entirely, and it is difficult to make use of the existing interaction records between users and products. Consequently, it will not get desired results if we just use the basic selection method to predict user purchase behavior directly, because the problem is that the features straightly extracted from the interaction data records are limited. In order to solve the problem above, this paper proposes a two-stage algorithm that based on K-Means Clustering Algorithm [2] and SVM [3, 4] Classification Algorithm. Firstly, we get the potential category information of products by K-Means Clustering Algorithm, then use SVM Classification Model to predict users purchasing behavior. This two-stage prediction model not only solves the feature shortage problem, but also gives full consideration to the potential features between users and product categories, which can help us to gain significant performance in call center product recommendation field.
Volume: 15
Issue: 1
Page: 351-356
Publish at: 2017-03-01

Electrochemical Redox Cycling Realized by Chromatography Paper-based Sensor

10.12928/telkomnika.v15i2.6130
Kenichi; Ritsumeikan University Fukayama , Sou; Ritsumeikan University Yamamoto , Shigeyasu; Ritsumeikan University Uno
In this work, we demonstrated that enhancement of electrochemical current due to redox cycling could be accomplished by paper-based biosensor without any expensive micro-fabrication process. The paper-based sensor had layered structure to generate higher current than a conventional one. We took advantage of the fact that the paper thickness was micrometer-sized (180um), and it defined the distance between two electrochemical electrodes on both sides of the paper. Experimental results showed signatures of the redox cycling, where the electrochemical current from low concentration molecules could be arbitrarily increased by decreasing the distance between electrodes. Such a structure was advantageous for detecting target molecules at very low concentration, proposing a low-cost highly-sensitive biochemcal sensor.  
Volume: 15
Issue: 2
Page: 842-846
Publish at: 2017-03-01

A Study on Image Reconfiguration Algorithm of Compressed Sensing

10.12928/telkomnika.v15i1.3710
Zhang; Northeast Petroleum University Yubo , Wang; Northeast Petroleum University Dongmei , Lingling; Northeast Petroleum University Kan , Panpan; Northeast Petroleum University Zhao
Compressed sensing theory is a subversion of the traditional theory. The theory obtains data sampling points while achieves data compression. The main content of this thesis is reconstruction algorithm. It’s the key of the compressed sensing theory, which directly determines the quality of reconstructed signal, reconstruction speed and application effect. In this paper, we have studied the theory of compressed sensing and the existing reconstruction algorithms, then choosing three algorithms (OMP, CoSaMP, StOMP) as the research. On the basis of summarizing the existing algorithms and models, we analyze the results such as PSNR, relative error, matching ratio and running time of them from image signal respectively. In the three reconstruction algorithms, OMP algorithm has the best accuracy for image reconstruction. The convergence speed of CoSaMP algorithm is faster than that of the OMP algorithm’s, but it depends on sparsity K quietly. StOMP algorithm on image reconstruction effect is the best, and the convergence speed is also the fastest.
Volume: 15
Issue: 1
Page: 299-305
Publish at: 2017-03-01

Design of Planar Dielectric Resonator Antenna Array at 28 GHz

10.11591/ijeecs.v5.i3.pp622-627
Nuramirah Mohd Nor , Mohd Haizal Jamaluddin , Muhammad Ramlee Kamarudin , Siti Zareen Naqiyah Zool Ambia
This article presents a planar array of rectangular Dielectric Resonator Antenna operating for 28 GHz applications. The proposed antenna is formed through two stages of designs which are a single element and planar array. It is made up from a ceramic material with a dielectric constant of 10 and mounted on RT/Duroid 5880 with a relative permittivity of 2.2 and a thickness of 0.254 mm. A prospective study using three different configurations of three by three planar array is done in order to obtain the best performance in terms of bandwidth, gain, and cost reduction. Besides that, this study is also conducted for a beam steering capability of each configuration. Finally, the best configuration is proposed for 5G application.
Volume: 5
Issue: 3
Page: 622-627
Publish at: 2017-03-01

Streaming Audio Using MPEG–7 Audio Spectrum Envelope to Enable Self-similarity within Polyphonic Audio

10.12928/telkomnika.v15i1.4581
Jonathan; Ulster University Doherty , Kevin; Ulster University Curran , Paul; Ulster University McKevitt
One method overlooked to date, which can work alongside existing audio compression schemes, is that which takes account of the semantics and natural repetition of music through meta-data tagging. Similarity detection within polyphonic audio has presented problematic challenges within the field of Music Information Retrieval.  This paper presents a method (SoFI) for improving the quality of stored audio being broadcast over any wireless medium through meta-data which has a number of market applications all with market value. Our system works at the content level thus rendering it applicable in existing streaming services. Using the MPEG-7 Audio Spectrum Envelope (ASE) gives features for extraction and combined with k-means clustering enables self-similarity to be performed within polyphonic audio. SoFI uses string matching to identify similarity between large sections of clustered audio. Objective evaluations of SoFI give positive results which show that SoFI is shown to detect high levels of similarity on varying lengths of time within an audio file. In a scale between 0 and 1 with 0 the best, a clear correlation between similarly identified sections of 0.2491 shows successful identification.
Volume: 15
Issue: 1
Page: 190-202
Publish at: 2017-03-01

Direct Torque Control: Stator Flux Regulation Improvement at Low Speed

10.12928/telkomnika.v15i1.5419
Nik Rumzi; Universiti Teknologi Malaysia Nik Idris
A simple method to improve stator flux regulation of a direct torque control (DTC) of induction motor drive is presented. By using this method, the simple control structure of DTC is retained and no modification to the voltage vectors look-up table is required. To implement this technique, the index to the look-up table is modified so that the reverse voltage vectors are selected (instead of zero-voltage vectors) whenever the stator flux regulation fails. To study the viability and the effectiveness of this simple method in improving the flux regulation at low speed, experiments are conducted to a ¼ hp induction motor with DTC technique. The control algorithm is implemented using a DS1104 controller board with Xilinx FPGA. 
Volume: 15
Issue: 1
Page: 1-3
Publish at: 2017-03-01

Autism Spectrum Disorders Gait Identification Using Ground Reaction Forces

10.12928/telkomnika.v15i2.6143
Che; Universiti Teknologi MARA Zawiyah Che Hasan , Rozita; Universiti Teknologi MARA Jailani , Nooritawati; Universiti Teknologi MARA Md Tahir , Rohilah; Universiti Teknologi MARA Sahak
 Autism spectrum disorders (ASD) are a permanent neurodevelopmental disorder that can be identified during the first few years of life and are currently associated with the abnormal walking pattern. Earlier identification of this pervasive disorder could provide assistance in diagnosis and establish rapid quantitative clinical judgment. This paper presents an automated approach which can be applied to identify ASD gait patterns using three-dimensional (3D) ground reaction forces (GRF). The study involved classification of gait patterns of children with ASD and typical healthy children. The GRF data were obtained using two force plates during self-determined barefoot walking. Time-series parameterization techniques were applied to the GRF waveforms to extract the important gait features. The most dominant and correct features for characterizing ASD gait were selected using statistical between-group tests and stepwise discriminant analysis (SWDA). The selected features were grouped into two groups which served as two input datasets to the k-nearest neighbor (KNN) classifier. This study demonstrates that the 3D GRF gait features selected using SWDA are reliable to be used in the identification of ASD gait using KNN classifier with 83.33% performance accuracy. 
Volume: 15
Issue: 2
Page: 903-911
Publish at: 2017-03-01
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