Electrical and Electronics Engineering

Nickel zinc ferrite (Ni0.8Zn0.2Fe2O4) is a soft ferrite material and can be used in electromagnetic applications that require a high permeability, such as electromagnetic wave absorbers. However synthesizing nanosize Ni0.8Zn0.2Fe2O4 remains a challenge. This work deals with the preparation of Ni0.8Zn0.2Fe2O4 nanoparticles by self combustion technique. This technique is chosen because of its simplicity to obtain single phase Ni0.8Zn0.2Fe2O4. Stoichiometric mixture of nickel(II) nitrate, Ni(NO3)26H2O; zinc(II) nitrate, Zn(NO3)26H2O; and iron(III) nitrate, Fe(NO3)39H2O; were dissolved in aqueous solutions nitric acid(HNO3 60%). The solutions were stirred separately at 250 r.p.m for one day and mixed into one solution. The mixture was stirred and gradual heating for every 15 minutes until the gel it obtained and combusted at 110◦C. Then, it was dried at 110 ◦C in an oven for 24 hours and the dried powder was crushed using a mortar for 1 hour. Furnace was used to anneal the samples at 800 ◦C, 900 ◦C and 1200 ◦C with holding time of 4 hours. Characterizations were done by  using X-Ray Diffractions (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray (EDX), Raman Spectra and Transmission Electron Microscope (TEM). The XRD patterns showed a major peak of [311] plane of the spinel cubic structure for Ni0.8Zn0.2Fe2O4 samples. By applying Scherer equations, the average crystallites sizes are 20 - 50 nm. Raman Spectra patterns had shown two major peaks located in the range  400 - 700 cm-1. FESEM morphology showed  the cubic shape with average dimensions of 75 - 990 nm with the varying annealing temperature. From TEM morphologies, dimension of d-spacing are 2 nm and with the cubic shape of Ni0.8Zn0.2Fe2O4. As a conclusion, the best morphology of Ni0.8Zn0.2Fe2O4 obtained at temperature 900 ◦C and  is clearly observed and can be used as a magnetic feeder in the future.

Direct detection of hydrocarbon by an active source using electromagnetic (EM) energy termed seabed logging (SBL) has shown very promising results.  However, available EM technology for deep water exploration still has a setback. It includes difficulty in propagating a powerful EM wave by the antenna and measuring the such small voltages because of remote location beneath the sea bed and unpleasant environment in which EM detector are located. Size of current transmitter is too huge for current operation. The length is enough to create a congested space on the vessel and the existence of difficulties during deployment operation. It needs a very high current to operate efficiently. This is lead to non-economical operational cost. The new innovation in this research is based on the synergising of the web-liked hexagon shaped transmitter with the magnetic feeder as the EM field booster to the transmitter. The web-like hexagon shaped transmitter have been chosen because of it’s a ability to concentrating the EM field at its centre. Because of this reason, the EM wave can achieve the optimum strength. This innovation can be a new-cutting edge for the oil and gas exploration industry. This research consists of two work premises. First, is designing a web-like hexagon shaped transmitter (Figure 1) and the second is to set up a complete system (transmitter and receiver) and run test of the system (Figure 2) to measure the voltage peak to peak (Vp-p) at the transmitter and detector. The function generator supply 5 MHz of rectangle wave shaped with a transmitter-detector distance was fix to 1 meter. Copper wire (0.8mm diameter) was waved in 22 turns to formed a web-like hexagon shape antenna on the Perspex (1m2) was designed as transmitter. For the magnetic feeder, Ni0.8Zn0.2Fe2O4 which used in form of toroid at the antenna had been successfully synthesized by self combustion technique. From this technique, Figure 3 shows the nano structure of the Ni0.8Zn0.2Fe2O4  (70 to 80 nm). X-ray diffraction (XRD) result (Figure 4) shows a single phase (113) plane Ni0.8Zn0.2Fe2O4  was synthesized and shall be used as a magnetic feeder for the transmitter. Web-liked hexagon shaped detector had been selected in this work. It was developed by using a copper wire-winded (5 turns). The strength of EM wave from powerful transmitter in this work had been verified by the Vp-p values on oscilloscope (OSC). Detection of the EM wave from designed antenna is done by the EM detector. Figure 5 shows the results of the transmitter Vp-p test during run test with complete system. It was proven from the graph by using magnetic feeder (toroid ferrite) located at 22 turn the Vp-p at OSC had increase significantly by 2%. From the pattern of the graph, the EM wave might have a constructive and destructive interference.  The highest constructive interference might be exists at 22 turns which gave the highest measurement. This works will be further done with a nickel zinc ferrite toroid which had fabricated and place it at a few locations at turn of the transmitter. Furthermore, enhancement of transmitter propagation of EM wave distance will be determined next in the future works of this research.

Direct detection of hydrocarbon by an active source using electromagnetic (EM) energy termed seabed logging (SBL) has shown very promising results.  However, available EM technology for deep water exploration still has a setback because size of current transmitter is too huge and lead to non-economical operational cost. The new innovation in this research is based on the synergizing of the web-liked hexagon shaped transmitter and have been chosen because of it’s a ability to concentrating the EM field at its centre. It can prove it when compare with dipole transmitter by using Computer Simulation Technology (CST) software and also simulate this transmitter with different number of turns to see the pattern of electric field and magnetic field. As a conclusion, web like hexagon transmitter is more powerful from simulation and also experimental parts.

In this paper, a noise power estimator based on one OFDM preamble is proposed. The estimator, unlike others, performs noise power estimation at the front-end of the receiver. The proposed estimator takes into consideration the different noise power levels over the OFDM sub-carriers. The OFDM band is divided into several sub-bands using wavelet packet and noise in each sub-band is considered white. The second-order statistics of the transmitted OFDM preamble are calculated in each sub-band and the noise power is estimated. The proposed estimator is compared with Reddy's estimator for colored noise in terms of mean squared error (MSE).

In this paper a front-end Noise Power and SNR estimation method based on one OFDM preamble is proposed and compared with previously published SNR estimators-none of which are front-end estimator. The estimator makes use of two identical halves property of time synchronization preamble used in OFDM systems and relies on autocorrelation of the same. The current estimator is compared with two existing SNR estimators, the Reddy estimator and Subspace based estimator in terms of normalized mean square error (NMSE) and estimated SNR. It is observed that current estimator gives SNR estimates better than Reddy and subspace estimators. The estimator performs SNR estimation at front-end of the receiver unlike all other estimators which perform SNR estimation at back-end of the receiver.

Generally, in typical wireless communication systems, interleavers are deployed after channel coding to distribute burst of errors, so they appear as simple errors. Alternatively, in this paper, a novel seed based random (SBR) post modulation interleaver is reported. SBR interleaver is an attempt to form a unique scrambling matrix in order to interleave the data bits/symbols optimally. Morcover, our study reveals that interleaver can change its position and be introduced even after modulation without affecting the performance of the system. With post modulation interleaving, interleaver size is minimized that implies minimum design complexity. The proposed interleaver is analyzed in terms of the performance parameters called spread and dispersion in burst error environment. For burst error analysis, proposed interleaver is compared with random interleaver to show that, for single error correcting codes, it can deal with much longer burst of errors. To analyze the suitability of proposed post modulation interleaver, the comparison of prc-and post modulation interleaver is carried out.

In this paper, wavelet packet (WP) based FFT and its application to SNR estimation is proposed. OFDM systems demodulate data using FFT. The proposed solution computes the exact FFT using WP and its computational complexity is of the same order as FFT, i.e. O (N log 2 N). SNR estimation is done inside wavelet packet based FFT block unlike other SNR estimators which perform SNR estimation after FFT. The data, so analyzed using wavelet packets, is used to perform SNR estimation in colored noise. The proposed estimator takes into consideration the different noise power levels of the colored noise over the OFDM sub-carriers. The OFDM band is divided into several sub-bands using wavelet packet and noise in each sub-band is considered white. The secondorder statistics of the transmitted OFDM preamble are calculated in each subband and the power of the noise is estimated. The proposed estimator is compared with Reddy's estimator for colored noise in terms of mean squared error (MSE).

A novel front-end noise power and SNR estimation technique based on one OFDM preamble is proposed and compared with previously published SNR estimators–none of which are front-end estimators. This paper is extended and expanded version of our previous work. It provides complete mathematics and discussion of designed algorithms for front end SNR estimation. The proposed technique is divided into two parts. In the first part, SNR estimation technique for AWGN channel and wireless multipath channels is ...

This paper presents an adaptive modulation in a single-input-single-output (SISO)-OFDMbased cooperative system that employs a Constant Amplitude Zero Autocorrelation (CAZAC) preamblebased SNR estimator. A novel CAZAC preamble-based SNR estimator that does not incur a throughput penalty is derived by exploiting a modified CAZAC preamble structure for the OFDM system. The proposed CAZAC SNR estimator is used to estimate the channel quality by finding the instantaneous SNR of the received cooperative data, which is sent to the transmitter via feedback channel. The modulation scheme is then changed according to the estimated SNR. The performance of the CAZAC preamble-based SNR estimator exhibits less than 0.02 dB and less than 0.2 dB bias when communicating over AWGN and SUI-5 channels, respectively. The proposed adaptive modulation scheme with the CAZAC SNR estimator significantly improved the channel throughput in comparison with the corresponding benchmarker scheme dispensing with adaptive modulation that invokes M-PSK and M-QAM. More explicitly, the proposed adaptive modulation system with the CAZAC SNR estimator that invokes M-PSK exhibits significant improvement by about 5 dB at BER = 10 −3 in comparison to its corresponding benchmarker scheme dispensing with adaptive modulation when communicating over the SUI-5 channel. On the other hand, the relay-aided cooperative transmission exhibited an approximately 6 dB SNR gain in terms of channel throughput in comparison to the corresponding non-cooperative benchmarker scheme, and benefited from spatial diversity. INDEX TERMS Adaptive modulation, spectral efficiency, OFDM, data-aided SNR estimator, constant amplitude zero autocorrelation preamble.

Introduction: This paper presents a comprehensive review of acne grading and measurement. Acne is a chronic disorder of the pilosebaceous units, with excess sebum production, follicular epidermal hyperproliferation, inflammation and Propionibacterium acnes activity. Most patients are affected with acne vulgaris, which is the prevalent type of acne. Acne vulgaris consists of comedones (whitehead and blackhead), papules, pustules, nodules and cysts. Objectives: To review and identify the issues for acne vulgaris grading and computational assessment methods. To determine the future direction for addressing the identified issues. Methods: There are two main methods of assessment for acne severity grading, namely, lesion counting and comparison of patient with a photographic standard. For the computational assessment method, the emphasis is on computational imaging techniques. Results: Current acne grading methods are very time consuming and tedious. Generally, they rely on approximation for counting lesions and hence the assessment is quite subjective, with both inter and intra-observer variability. It is important to accurately assess acne grade to evaluate its severity as this influences treatment selection and assessment of response to therapy. This will further help in better disease management and more efficacious treatment. Conclusion: Semi-automated or automated methods based on computational imaging techniques should be devised for acne grade assessment.

Induction motor (IM) variable speed drive efficiency is essential for a few reasons as energy conservation, economic saving and lessening of ecological contamination. This research represents a study of the efficiency improvement for the developed hybrid fuzzy-fuzzy controller (HFFC) scheme to gain control over the speed of an induction motor's variable speed drive (VSD). In order to overcome drawback of field oriented control (FOC) method, the principle of HFFC is based on set of rules to control speed of a rotor by utilizing fuzzy frequency controller during the acceleratedecelerate stage. Alternatively, a fuzzy stator current magnitude controller is used during steady-state stage. The two aspects (current and frequency) of FOC are engaged to design a scalar controller. The performance of the controller is observed by conducting a series of tests, and it can be concluded that the controller is efficient, reliable and insensitive towards the parameter variation in the system and motor robustness to load and noise disturbances.

In this paper, a Park's transformation method for the analysis of various bearing surface roughness defects is presented. The existing instantaneous power analysis and stator current analysis techniques are unable to diagnose bearing surface roughness defects, due to the fact that characteristics defect frequency model is not available for these types of defects. Thus, this paper proposes a Park's transformation method which can detect surface roughness defects without requiring information of the characteristic defect frequencies. The theoretical and experimental work conducted shows that the proposed method can detect bearing outer and inner race surface roughness faults without use of any extra hardware. The results on the real hardware implementation confirm the effectiveness of the proposed approach.

In this paper, an intelligent fault diagnosis system based on instantaneous power spectrum analysis is proposed. The instantaneous noise variations and sensor offsets are considered to be one of the common factors that yield erroneous fault tracking in an online condition monitoring and fault diagnosis system. The developed system has the capability to detect bearing inner race defects at incipient stages with in an arbitrary noise conditions. An adaptive threshold has been designed to deal with line current noise ambiguities for decision-making on the existence of small fault signatures. The performance of the developed system has been analyzed theoretically and experimentally on a custom designed test rig under various loading conditions of the motor.

This paper discusses the performance and the impact of disturbances onto a proposed hybrid fuzzy-fuzzy controller (HFFC) system to attain speed control of a variable speed induction motor (IM) drive. Notably, to design a scalar controller, the two features of field-oriented control (FOC), i.e., the frequency and current, are employed. Specifically, the features of fuzzy frequency and fuzzy current amplitude controls are exploited for the control of an induction motor in a closed-loop current amplitude input model; hence, with the combination of both controllers to form a hybrid controller. With respect to finding the rule base of a fuzzy controller, a genetic algorithm is employed to resolve the problem of an optimization that diminishes an objective function, i.e., the Integrated Absolute Error (IAE) criterion. Furthermore, the principle of HFFC, for the purpose of overcoming the shortcoming of the FOC technique is established during the acceleration-deceleration stages to regulate the speed of the rotor using the fuzzy frequency controller. On the other hand, during the steady-state stage, the fuzzy stator current magnitude controller is engaged. A simulation is conducted via MATLAB/Simulink to observe the performance of the controller. Thus, from a series of simulations and experimental tests, the controller shows to perform consistently well and possesses insensitive behavior towards the parameter deviations in the system, as well as robust to load and noise disturbances.

The literature review presents the various kinds of existing condition monitoring methods and highlights the need for an economical, intelligent fault diagnosis system for the motors that are being used in variable load applications. The motor current signature analysis (MCSA) has been used widely in previous research work for fault detection of the motor at full-load conditions. However, MCSA cannot detect faults under low-load conditions of the motor. This paper proposes the instantaneous power analysis (IPA) method for the bearing fault detection at various loading conditions of the motor. The experimental results indicate that IPA has more capability to detect faults under low-load conditions as compared to MCSA. Also, it has been shown that IPA carries an additional characteristic vibration frequency component which provides an extra piece of information that can be utilized in a reliable intelligent condition monitoring system. The proposed method has been validated through experiments at five different loading conditions of the motor.

This work presents the experimental demonstration of a hybrid fuzzy-fuzzy controller speed control of a squirrelcage induction motor variable speed drive based on the spacevector pulse width modulation technique by means of digital signal processing. In particular, two features of field-oriented control were engaged to design a hybrid fuzzy-fuzzy controller, namely the current and frequency. In order to overcome the limitations of the field-oriented control technique, the principle of the hybrid fuzzy-fuzzy controller is introduced in the course of the acceleration-deceleration stages to regulate the speed of the rotor with the help of a fuzzy frequency controller. Conversely, a fuzzy stator current magnitude controller was involved during the steady-state. The results revealed that the control approach has the ability to deliver a practical control solution in the presence of diverse operating conditions.

In this paper, a Park's transformation method for the analysis of various bearing surface roughness defects is presented. The existing instantaneous power analysis and stator current analysis techniques are unable to diagnose bearing surface roughness defects, due to the fact that characteristics defect frequency model is not available for these types of defects. Thus, this paper proposes a Park's transformation method which can detect surface roughness defects without requiring information of the characteristic defect frequencies. The theoretical and experimental work conducted shows that the proposed method can detect bearing outer and inner race surface roughness faults without use of any extra hardware. The results on the real hardware implementation confirm the effectiveness of the proposed approach.

This work presents the experimental demonstration of a hybrid fuzzy-fuzzy controller speed control of a squirrelcage induction motor variable speed drive based on the spacevector pulse width modulation technique by means of digital signal processing. In particular, two features of field-oriented control were engaged to design a hybrid fuzzy-fuzzy controller, namely the current and frequency. In order to overcome the limitations of the field-oriented control technique, the principle of the hybrid fuzzy-fuzzy controller is introduced in the course of the acceleration-deceleration stages to regulate the speed of the rotor with the help of a fuzzy frequency controller. Conversely, a fuzzy stator current magnitude controller was involved during the steady-state. The results revealed that the control approach has the ability to deliver a practical control solution in the presence of diverse operating conditions.