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Electrical discharge machining is one of the widely used machining methods, principally in medical applications, aerospace industry and manufacturing in hard material fields. However, scientific knowledge about the process is still insufficient for its more improvements. Experimental work are time consuming and costly due to the complex and stochastic character of the EDM procedure. Process modeling is a great option in order to reduce the experimental difficulty related to the technology. This paper presents a dynamic mathematical model for low power EDM application. The propounded model includes the precise insight into the interactive behavior of EDM system based on the sparking phases and pulse power generator. The ignition, discharge and recovery phases of the model have been developed through MATLAB's time domain analysis. Contributions are contrived in different aspects of the entire system, containing modeling and system simulation. The result shows expected profiles with satisfactory dynamic performance. To verify the model, simulated material removal rates (MRRs) are obtained using machining parameters from series of simulation and then compared with the experimental ones carried out by previous researcher. Ability of the model to predict the dynamic behavior profile of the EDM system is successfully confirmed by low average percentage error in predicting MRR.

An efficient microwave milk pasteurization system requires a rigorous temperature dependent dielectric model of the milk, since the performance of milk pasteurization strongly depends on its dielectric properties. This paper describes the dielectric modelling of cow’s raw milk during batch (Vat) pasteurization which covers the frequencies from 0.2 GHz to 6 GHz. An open-ended coaxial sensor is used for the measurements of dielectric constant, loss factor, and ionic conductivity at temperature range of 25°C to 75°C with an interval of 5°C. Combinations of Cole-Davison and Debye equations are modified to fit the dielectric measurements. It was found that the measured dielectric constant decreased as the frequency increased, while the high temperature processed produce lower in a convergence manner toward 6 GHz. The loss factor exhibited high losses at higher temperature and lower frequencies, as well as converged at 1.9 GHz then diverged up to 6 GHz. Three relaxation processes are dominated at all temperature treatments within the frequency range. The relaxation time, τ, and the activation energy, Q, are modelled based on linear fitting of measured data according to Debye and Arrhenius approaches.

Additional file 1: Table S1. Relative abundance of Aedes mosquitos found at hotel compounds stratified according to larval habitat characteristics, that is, type of habitat, location, function, size, presence of vegetation, presence of organic matter and season.

Tick-borne diseases cause significant losses to livestock production in tropical and subtropical regions. In Tanzania, detailed studies on tick-borne pathogens in cattle using sensitive molecular detection methods are scarce. In this study, we investigated the occurrence of Theileria spp., Babesia spp., Anaplasma spp. and Ehrlichia spp. in 245 blood samples collected from cattle on Pemba Island, Tanzania. We used polymerase chain reaction (PCR) and gene sequencing to detect and identify pathogens. PCR screening revealed overall infection rates of 62.4% for Theileria spp., 17.6% for Babesia bigemina, 15.9% for Anaplasma marginale, 7.4% for Ehrlichia ruminantium and 4.5% for Babesia bovis. Further analysis using sequences of Theileria spp. 18S rRNA revealed infection of cattle with Theileria mutans (68.6%), Theileria taurotragi (48.4%), Theileria parva (41.2%), and Theileria ovis (1.9%). Co-infections of cattle, with up to six tick-borne pathogens, were revealed in 46.9% of the samples. Sequence analysis indicated that T. parva p104, E. ruminantium pCS20 and A. marginale MSP-5 genes are conserved among cattle blood samples in Pemba, with 99.3%–100%, 99.6%–100% and 100% sequence identity values, respectively. In contrast, the B. bigemina RAP-1a and B. bovis SBP-2 gene sequences were relatively diverse with 99.5%–99.9% and 66.4%–98.7% sequence identity values respectively. The phylogenetic analyses revealed that T. parva p104, E. ruminantium pCS20 and A. marginale MSP-5 gene sequences clustered in the same clade with other isolates from other countries. In contrast, the B. bigemina RAP-1 and B. bovis SBP-2 gene sequences showed significant differences in the genotypes, as they appeared in separate clades. This study provides important data for understanding the epidemiology of tick-borne diseases, and is expected to improve the approach for diagnosis and control of tick-borne diseases in Tanzania.

Amplitude comparison is the simplest method of Radio Direction Finding (RDF) which utilise several directional antennas and compare the signal strength from each antenna to calculate the Angle of Arrival (AoA). There is some jargons mention that more antennas used in amplitude comparison RDF will improve the RDF accuracy. However, a further analysis and real test is still required to support this argument. Therefore, this paper will verify this specific problem by develop 6 antenna RDF system and 4 antenna RDF system then analyse the real test data. A type of printed circuit board log-periodic dipole array (PCB LPDA) antenna is utilised in this paper for the experiment setup. The real test setup and the data collection is explained in this paper to discuss and verify this argument. After the discussion, it is verified that amplitude comparison with 4 antennas has better accuracy than the similar system with 6 antennas.

EDM is a process of machining electrically conductive materials by precisely controlled electrical discharge through a small clearance gap that occur between an electrode and a workpiece in the presence of a dielectric fluid. Through EDM process, the material of workpiece are melted and gap distance will increase. In order to maintain a stable spark, the gap must be controlled. This paper presents control spark gap system of EDM using PID controller with voltage and position feedbacks. The results show Time Rise (Tr) of PID control with voltage feedback has a value about 75 seconds and Time Rise (Tr) of PID control with voltage and position feedbacks has a value about 18.6 seconds. The average error of gap distance in PID control with voltage feedback is 55.56 and the average error of gap distance in PID control with voltage and position feedbacks is 48.53. Addition of the position feedback is used to increase the rise time and stabilize distance the electrode and the workpiece.

At the essence of video surveillance, there are abnormal detection approaches, which have been proven to be substantially effective in detecting abnormal incidents without prior knowledge about these incidents. Based on the state-of-the-art research, it is evident that there is a trade-off between frame processing time and detection accuracy in abnormal detection approaches. Therefore, the primary challenge is to balance this trade-off suitably by utilizing few, but very descriptive features to fulfill online performance while maintaining a high accuracy rate. In this study, we propose a new framework, which achieves the balancing between detection accuracy and video processing time by employing two efficient motion techniques, specifically, foreground and optical flow energy. Moreover, we use different statistical analysis measures of motion features to get robust inference method to distinguish abnormal behavior incident from normal ones. The performance of this framework has been extensively evaluated in terms of the detection accuracy, the area under the curve (AUC) and frame processing time. Simulation results and comparisons with ten relevant online and non-online frameworks demonstrate that our framework efficiently achieves superior performance to those frameworks, in which it presents high values for the accuracy while attaining simultaneously low values for the processing time.

EDM is a well-established hole machining option with various advantages due to non-contact characteristics of the process. However, knowledge about the process is not enough for its more improvements. Exprimenal studies are costly and time consuming because of the complex nature of process. Therefore, process modeling is a good alternative to reduce the experimental expense related to the technology. This paper studys EDM process through mathematical model, which includes the precise insight into the interactive behavior of EDM system. The ignition, discharge and recovery phases of the model have been developed through MATLABs time domain analysis. Simulation result shows good agreement with expected profile of EDM spark. To verify the model, simulated material removal rates (MRRs) from series of simulation are compared with the experimental ones reported by previous researcher. Ability of the model to predict the dynamic behavior profile of the EDM system is successfully confirmed by low average percentage error in predicting MRR.

Rain is the major factor in radio propagation analyses that is responsible for outage on terrestrial point-to-point and point-to-multipoint radio communication systems at millimeter wave bands. This hampers radio wave signal transmission in the tropics. This paper investigates the performance of ITU-R P.530-16, Silver Mello, Moupfouma and Abdulrahman rain attenuation prediction models using locally-sourced data. The aim is to determine their suitability or otherwise in tropical Nigeria. Two years daily rainfall data were sourced from the Nigerian Meteorological Services (NIMET) for six different stations in southwestern Nigeria. Southern Nigeria is predominantly influenced by the southwest monsoon wind from the Atlantic Ocean due to its proximity to the coastal belt. The data were analyzed using these prediction models by comparing with measured data. The ITU-R P.530-16 rain attenuation prediction model closely matched the measurement value for p≥0.1% of the time but over-estimated it at p

This paper discusses the existing jamming method from previous publication and how the method is modified to accomplished the GPS jamming of Unmanned Aerial Vehicle (UAV). This paper also presents the result from the field test of UAV GPS jamming by using Software Defined Radio (SDR) and GNU Radio software. The field test is carried out to study the performance of the jamming signal produced and the effect of elevation angle on the jamming range. The test subject used in this field test is DJI Phantom 4 Pro, a commercial consumer grade drone.

Acoustic underwater sensor network (UWSN) is important in terms of business and for military applications. Optimum UWSN design provides a reliable connection with maximum connectivity, minimal multipath, low technical cost, and emphasis on energy conservation. This paper examines the channel estimation parameters, such as channel impulse response, coherence bandwidth, BER due to delay for differentially detected MSK receiver, and transmission loss impact of underwater node placement in three scenarios (ground-based, buoys-based, and horizontal point-to-point sensor node). All data (bathymetry, altimetry, temperature, salinity, and depth) are real and have been sourced from different satellite databases. The case study of this paper is the Desaru beach in the eastern shore of Johor Bahru in Malaysia. In this investigation, Acoustics Toolbox of BELLHOP through MATLAB and mathematical analyzing method has been utilized. As a result, this paper indicates the maximum received power, and the lowest delay time characteristics and TL belong to horizontal point-to-point scenario; moreover, the ground-based scenario has the highest delay time and maximum coherence bandwidth among three scenarios.

Electrical discharge machining (EDM) is a non-conventional manufacturing process used broadly in medical applications, aerospace industry and manufacturing in hard material fields. However, information about the process is still in an unfledged stage and it has been becoming a serious obstacle to its more improvements. In this paper, spark discharge condition is studied based on the simulated model of EDM spark pulse generator system equivalent form. Simulated model is verified by comparing with a series of experimental results. Frequency response is established through simplified model of EDM system. Influence of discharge time and stable discharge current on material removal rate (MRR) and stability of the system is analysed. This study is important to select the process parameters, and uses as a guidance to design the EDM spark pulse generator system.

Electrical Discharge Machining (EDM) is a process that uses electrical discharges to erode electrically conductive material where the electrode and workpiece do not touch. Spark between electrode and workpiece in the EDM process produced magnetic fields. The magnetic fields is found to have an effect on debris circulation in the gap of EDM, so it can decrease the abnormal electrical discharge. An electric current has an effect on the magnetic field produced. EDM uses the RC-generator configuration, so it is able to produce greater currents. This paper presents the calculation current pulse generated by spark of EDM. This calculation can be used to predict peak currents from EDM pulses. Predict peak current is used to find out the maximum magnetic field and determine the maximum current rating of a component. Pulse current calculation can use the equation that has been stated.

Electrical discharge machining (EDM) is a stochastic machining process which widely used to generate dies and molds. However, information about the EDM process is still at the earlier stage which lead to experience many challenges for further developments. Experimental analysis is time consuming as well as a costly procedure, due to the highly stochastic and complex nature of the process. Therefore, process modeling is an alternative to reduce the experimental costs related to the technology. This research proposes method to design a mathematical model of electrical discharge machining (EDM) system. The model will be used to understand the effects of machining parameters into the dynamic behaviour of EDM system based on the sparking phases and pulse power generator.

Radio Direction Finder (RDF) system can be used in search and rescue operations. However the existing RDF system is complex, expensive and not suitable for mobile operation such as search and rescue operations. This paper presents the development of a unique low cost Radio Direction Finder (RDF) using 6 Log Periodic Dipole Array (LPDA) antenna. Six unit of log periodic printed circuit board antenna from WA5VJB is used in this project since it is commonly used in UHF licence-free band. A modified amplitude comparison method has been made in order to match the antenna character. The unique physical design, electronics design and software design implemented in the RDF system are described in this paper. Also a test has been conducted and the system performance shows the RSM error of 14°.

Millimeter-wave radar system connected to an optical synthesizer is evaluated at outdoor fields in tropical weather conditions. Maximum range and its resolution are evaluated at the field. Polarization imaging by the perpendicular antenna configuration is also performed in 95-GHz bands.

Safety enhancement of airport runway surfaces can avoid unnecessary runway closure and airplane accidents due to foreign object debris. Millimeter-wave linear cell radar system empowered by radio-over-fiber network system is a promising solution for surveillance of the runway surfaces within 10 s. Currently, 96-GHz linear cell radar system has been already installed with four radio access units in Narita International Airport, Japan, as a field trial test. For the application of the linear cell radar system to Kuala Lumpur International Airport as a field trial in a tropical region, some fundamental characteristics need to be measured and analysed before installation of the linear cell radar system. In this paper, we show the summary of the field trial in Kuala Lumpur International Airport, Malaysia and Universiti Teknologi Malaysia, Malaysia.

In this paper, a Wilkinson power divider is modified using four-series delta-stub and folded stepped-impedance transmission line (FSITL) in order to achieve a reduced circuit size of 84% and fractional bandwidth of 116%. Series delta-stubs are used instead of open shunt stubs to obtain an optimum shifting frequency and wider bandwidth. Folded stepped-impedance transmission line (FSITL) is used to achieve reduced circuit size. The proposed power divider is fabricated using RT/duroid 5880 substrate with thickness of 0.38 mm. The dimension of the power divider is 13 mm × 6.5 mm. The proposed power divider has typical power division of -3 dB and insertion loss less than -1 dB, better than -13 dB of isolation, less than -10 dB return loss and phase imbalances less than 2° from 1.5 to 3 GHz. Both simulation and measurement results show a good agreement.

The analyses of rain models for satellite communication links of Ku and Ka bands in Lagos, Nigeria is the focus of this paper. The choice of these frequency bands was informed by the acknowledged fact that satellite signal fading and outages are predominant at those bands. The ITU-R P. 618-12 is the globally adopted prediction model; temperate, equatorial and tropical regions, inclusive. However, there was need to review the suitability of this model especially as it concerned equatorial and tropical stations. Rainfall data spanning a period of three years were collected from Nigerian Meteorological Agency (NIMET). The ITU-R P. 618-12 model along with some renowned prediction models were analyzed and their performances with the locally recorded measurement data were compared to establish their suitability or otherwise. The results obtained suggested ITU-R P. 618-12 exhibited the overall best performance at 12 GHz while DAH showed best performance at 26 GHz, even as both models underestimated and overestimated the measurement at Ku and Ka bands respectively. Again, at both frequencies, SST presented the worst performances.

This paper focused on underwater physical and environmental data collection such as temperature, salinity, depth, surface agitation and seabed topography based on online global databases. These data are essential due to more realistic simulation of underwater communication channel. Physical data values are different based on locations and weather patterns. A network designer has to collect by measurements for several times. The measuring procedure is often very cumbersome, time consuming and expensive. Moreover, critical problem arises when the data is not general and the data may change for next year as well. This research introduces a method for collecting underwater physical data based on weather satellites, geology software and global online resources such as NOAA. This study evaluates difference between measured data with the collected data from online databases. The result indicates that the collected salinity data from proposed method is acceptable with 0.3 Psu tolerance and is 0.5 °C for temperature.

A Wilkinson power divider has ideal transmission characteristics and it enables easy realization in planar transmission line technology. However, the conventional Wilkinson power divider features a large component footprint because of its quarter-wavelength line components and narrow bandwidth. In this paper, two modified Wilkinson power divider are proposed in order to achieve size reduction and wide bandwidth. The first structure presents Wilkinson power divider using compact folded step impedance transmission lines (FSITL) rather than the uniform microstrip line design for operating center frequency of 3 GHz. While the second structure presents the FSITL with delta-stub for 2.4 GHz. The proposed folded microstrip line structure is capable of reducing the size of the power divider circuit. The impedance ratio of SITLs is taken into account as the total electrical length of the lines for every wavelength 0 1 and 0 2 in order to enhance size reduction to the optimum. The study managed to get an overall dimension of 15 mm × 9.5 mm for the first proposed design achieving a reduction of 75.6 % and bandwidth of 4 GHz. For the second proposed structure, the size was 15 mm × 15 mm with a reduction of 56 %. The proposed structures provided an extra 80 % fractional bandwidth based on the −15 dB return loss as a reference. The proposed power divider used RT/duroid 5880 substrate with 0.38 mm thickness. Simulation and measurement results indicated that the modified power divider showed equal power division, good phase balance, high isolation between output ports, and good return loss better than −15 dB covering the operating frequency range.

Human bodies have a variety of tissues and organs, and so it needs to be characterized as a radio-wave propagation medium to create a reliable wireless communication link. The radiation characteristics of printed monopole antenna and printed loop antenna for wireless-implantable body area network (WiBAN) applications are presented in this article. The two antennas are submerged into canola oil to mimic an implanted antenna in the human tissue. The tissue is considered a lossy environment and hence, it adversely degrades radiation characteristics of both antennas. Therefore, the RF transmission attenuation, dB can be used for characterizing the propagating wave from the submerged antennas to the free-air surface. The measured results show satisfactory performance and are in good agreement with the simulation. As indicated in the results, the attenuation rate from a lossy environment to the free space for the printed loop antenna (0.1 dB/mm) is smaller compared to that of printed monopole antenna (0.1–0.3 dB/mm). More so, the printed loop antenna is smaller in size (about 56%) compared to the printed monopole antenna, which suggests that the loop antenna is more suitable than the monopole for the WiBAN applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1270–1274, 2014

Lagos, Nigeria (6.35°N, 3.2°E), is a coastal station in the rain forest area of southwestern Nigeria with an altitude of 38 m. Since most communication now takes place above the X band because of congestion of lower bands, it was necessary to look into ways of maximizing X-band usage. There are inadequate data for use in rain propagation studies at microwave frequencies, and even less so at millimeter wave bands where most of the signal depolarization and fading has been discovered to exist. The proposed model is a modification of the International Telecommunication Union–Radio Communication Sector (ITU-R) model combined with locally obtained regression coefficients for estimating specific attenuation as proposed by G. Olalere Ajayi. The Dissanayake, Allnutt, and Haidara (DAH), Simple Attenuation Model (SAM), and ITU-R attenuation prediction models were investigated along with the proposed model. The ITU-R model was observed to produce the best results at 40 GHz, with percentage error values of 0.61%, 0.55%, and 0.49% at 0.1%, 0.01%, and 0.001% of the time, respectively. In comparison, the proposed prediction model showed good performance at 20-GHz down-link frequency, with percentage error values of 3.6%, 3.3%, and 2.9% at 0.1%, 0.01%, and 0.001% of the time, respectively. The obtained results also showed good agreement with other similar works in the open literature. The results presented in this work are valuable for the design and planning of a satellite link in the tropical regions.

Oil pocket has been reported that it may improve tribology characteristic and thus prolong the lifespan of the joint. In order to implement it on spherical surface, appropriate positioning system is required. This paper reports the investigation of three axes workpiece positioning system in order to machine oil pocket (micro-pits) on hip implant. A conventional linear x-y-z axes configuration (Cartesian coordinate) and two configuration of spherical coordinate (swing-swing and swing-rotate configuration) are applied in simulation. All machined workpiece are investigated in pits distribution, shape, and machined angle. The inspection concludes that spherical method with swing-rotate configuration is the most suitable method for machining oil pocket on spherical surface.

Most satellite communication takes place above the 10 GHz frequency bands, a direct consequence of over-congestion of lower frequency bands. A dearth of database along the slant path in the tropical regions for use in rain propagation studies at microwave frequencies, made further studies at millimeter wave band quite attractive. Rain height data were sourced from the Tropical Rainfall Measuring Mission (TRMM) 3B43 V6 and NigComSat-1 satellite for 37 stations in Nigeria as reported in the literature. Terrestrial attenuation measurement data at 0.01% of time, sourced from the Universiti Teknologi Malaysia’s Wireless Communication Centre (WCC) were transformed to slant path attenuation values using a transformation technique. Attenuation exceeded for other percentages of time were obtained using statistical methods. The ITU-R model is modified to suit the results. Further analysis at 12 GHz suggested that the proposed modified ITU-R model show good performance when compared with other models of interest.

A design of a 3-dB ultra wideband (UWB) coupler with compact size (35 mm × 15 mm), which operates between 3.1 and 10.6 GHz is presented in this article. The proposed design is accomplished by using multilayer microstrip structure, which is formed by three layers of conductor and two layers of substrate. The top and bottom layers consist of an octagon-shaped microstrip lines and an octagon-shaped slot in the middle layer. The design was fabricated on Rogers RO4003c substrate. Both of the simulation and measurement results are being compared with verify the coupler's performances in real environment. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:127–130, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27259

Underwater communications exists in many applications, providing information about the ocean floor such as bathymetry, for environmental pollution monitoring, information exchange between divers and sea vessel, and collection of scientific data. However, the propagation of sound in the sea is dependent on several environmental factors such as pressure which is related to depth, and some other ocean properties. The characteristic of sound propagation in the sea is determined by what is known as the sound speed profile. The speed of sound in the sea is determined and varies with depth, salinity change, temperature, the season as well as the geographic location. In general, different sea conditions has different characteristics of the sound speed profile. This project was aimed to determine the sound speed profile in Malaysian Seas. Parameters, which affect the sound speed profile, were studied, and their values determined.

This paper aims to compare the material removal rate, ν between a Dimensional Analysis (DA) model, an Artificial Neural Network (ANN) model and an experimental result for a low gap current of an Electrical Discharge Machining (EDM) process. The data analysis is based on a copper electrode and steel workpiece materials. The DA and ANN model that have been developed and reported earlier by authors are used to compare the material removal of EDM process. The result indicated that the ANN model provides better accuracy towards the experimental results.

This paper presents a calculation of the dielectric properties of low-loss materials using the transmission phase-shift method. This method can provide calibration-independent and position-insensitive features, and it was verified experimentally by measuring several well-known samples using X-band rectangular waveguides.

The design of compact dual band grid array antenna (GAA) designed on FR-4 substrate for future Fifth Generation (5G) Mobile Communications at 10 GHz is reported. The proposed antenna uses coaxial technique of feeding and has a dimension of 48 mm × 55 mm × 1.6 mm. Simulation results using CST microwave studio illustrates that the antenna has a band from 10.03 GHz to 10.68 GHz and another band from 10.7 GHz to 12.23 GHz. This excludes the 10.68 – 10.7 GHz band in which emissions were forbidden by the Radio Regulations in the sense that it has been allocated for the Radio Astronomy, Space Research and Earth Exploration Satellite (passive). The antenna has a maximum gain of 8.03 dBi at 10 GHz, thus a good candidate for the future 5G mobile communications.

This paper proposed three modified Wilkinson power dividers in order to achieve a size reduction and a wide bandwidth. The first structure presented the power divider using compact folded step impedance transmission lines rather than the uniform microstrip line design for operating center frequency of 3 GHz. The second structure showed the power divider with delta-stub for 2.4 GHz. Finally, the third modified structure introduced the two-section Wilkinson power divider using series-delta stub for center frequency of 2.4 GHz as well. The study managed to get an overall dimension of 15 mm × 9.5 mm for the first proposed design achieving a reduction of 75.6 % and fractional bandwidth of 133 %. For the second proposed structure, the size was 15 mm × 15 mm with a reduction of 56 % and fractional bandwidth of 56 %. While the third design size was 17 mm × 15 mm with a reduction of 63.6 % and the structure achieved a broadband bandwidth with fractional bandwidth of 220 %. The proposed power dividers used RT/duroid 5880 substrate with a thickness of 0.38 mm. Simulation and measurement results indicated that the modified power dividers showed equal power division, good phase balance, high isolation between output ports, and good return loss better than -12 dB covering the operating frequency range.