A 24-GHz patch array antenna with integrated feeding network has been fabricated exploiting a multi-layer cellulose-based (i.e. paper) substrate. The adopted microstrip circuitry exploits a copper adhesive laminate that is shaped by a photo-lithographic process and transferred to the hosting substrate using a sacrificial layer. The multi-layer structure is obtained by stacking and gluing two layers of photo-paper with an interposed copper ground plane. The measurements show an input reflection coefficient of about −29 dB at the centre frequency, an operating bandwidth with S ₁₁ ⩽ −20 dB of 540 MHz and a gain of 7.4 dBi. The estimated radiation efficiency is 35%. The proposed design shows the feasibility of low-cost antenna systems for green wireless internet technology and applications up to the boundary between microwaves and millimetre-waves.

Novel iterative and non-iterative blind estimation methods for binary phase shift keying modulated primary user signal power are proposed using the maximum-likelihood principle for collaborative spectrum sensing. Using these estimators, the performance of three different existing collaborative spectrum sensing methods is compared under realistic scenarios. The effect of the primary user traffic on these methods is also explored. Numerical results show that, unlike the case of no estimation error as examined in this literature, the performance gains of the weighted linear combining and optimal combining methods over the conventional equal gain combining method decrease or even become negative when there is estimation error. They also show that the proposed blind estimation methods offer an excellent trade-off between reliability and complexity.

In this work, miniaturised tunable two-antenna multiple-input–multiple-output (MIMO) systems composed of printed F-slot shaped are developed to operate in the global positioning system (GPS), personal communication system (PCS), distributed control system and Universal Mobile Telecommunications System bands. The two-element MIMO antenna occupies a volume of 50 × 37.5 × 1.6 mm³, and is printed on an FR4 substrate. Initially, the frequency tunability of the MIMO antennas was verified by lumped capacitors with values between 0.75 to 2.75 pF to achieve a tuning range from 1.55 to 2.07 GHz while the low mutual coupling between the radiators was accomplished by adding an I-shaped branch to a cut-away ground plane. The two antennas are then loaded with varactors to simultaneously achieve miniaturisation and tunability. Simulation and measurement results demonstrate the successful implementation of a tunable MIMO with coupling reduction mechanism for a portable handheld wireless transceiver. The channel capacity of the proposed antenna is investigated and found to be close to that of a un-correlated system with efficient diversity in which the mutual coupling across the full bandwidth was better than −13 dB. Owing to the compact size and ease of manufacture, the proposed antennas can be a promising solution for adaptive MIMO systems in handheld devices.

This study presents the architectural design, software implementation, the validation and flight trial results of an aeronautical communications system developed within the Seamless Aeronautical Networking through integration of Data links Radios and Antennas (SANDRA) project funded by the European 7th Framework Aeronautics and Transport Programme. Based on software defined radio (SDR) techniques, an integrated modular radio (IMR) platform was developed to accommodate several radio technologies. This can drastically reduce the size, weight and cost in avionics with respect to current radio systems implemented as standalone equipment. In addition, the modular approach ensures the possibility to dynamically reconfigure each radio element to operate on a specific type of radio link. A radio resource management (RRM) framework is developed in the IMR consisting of a communication manager for the resource allocation and management of the different radio links and a radio adaptation manager to ensure protocol convergence through IP. The IMR has been validated although flight trials held at Oberpfaffenhofen, Germany in June 2013. The results presented in the paper validate the flexibility and scalability of the IMR platform and demonstrate seamless service coverage across different airspace domains through interworking between the IMR and other components of the SANDRA network.

In the recent past, research in the next generation wireless heterogeneous broadband networks has favoured the design of multi-radio interface over the single radio interface architectures to support desirable features such as a self-organisation, self-configuration, reliability and robustness of network operations in a resource-constrained environment. However, such autonomous network behaviours have been seen to cause an inefficient consumption of energy and frequency channel resources, impacting negatively on the economy and environment. To address the inefficient energy and frequency channel utilisation problems, this study proposes a biological behaviour-based network resource management method. The research is inspired by such a well-established optimal foraging theory whereby a solitary biological forager in a random ecosystem makes optimal decisions that maximise its own nutrients consumption, survival probability and lifetime, whereas minimising possible risks associated with its own behaviour. This study has applied this natural principle and developed a Bio-inspired Energy and Channel (BEACH) management method. The BEACH method is aimed at achieving both efficient communication energy and frequency channel utilisation in the considered distributed wireless multi-radio network. The efficacy of the developed BEACH method has been extensively validated through computer simulations and shown to yield improved energy-efficiency and throughput performance.

Energy conservation is one of the prime concerns that leads the researcher to investigate collaborative wireless sensor networks with some application specific challenges. Such challenges include combining distributed data synchronously, performing power aware signal processing, defining communication methods that can provide progressive accuracy and, optimising processing and communication for signal transmission. A cooperative resource selection and transmission scheme is proposed to improve the performance of collaborative wireless sensor networks in terms of maintaining link reliability. A measure of Channel Quality Index (CQI) is also proposed to obtain dynamic adaptivity and to optimise resource usage within wireless sensor networks according to environment conditions. As part of the proposed cooperative nature of transmission, the recently proposed transmit-receive antenna selection scheme and lattice reduction algorithm have also been considered. It is assumed that channel state information (CSI) is estimated at receiver and also there is a feedback link between the wireless sensing nodes and the fusion centre receiver. From the simulation results it is observed that for 99.99% detection reliability, the proposed adaptive transmission scheme and proposed hybrid scheme consume only 15% and 18% of energy respectively as compared to the conventional cooperative transmission.

In this study, a novel medium access scheme based on analogue network coding for data dissemination in wireless networks is presented. Following our previous work, where energy-efficient medium access strategies based on game theory have been introduced, we propose a medium access control protocol that exploits to the maximum the recent advances in network coding (NC) domain to enhance the system performance. In particular, ZigZag decoding techniques are applied to resolve the data packet collisions, whereas random linear NC is employed to eliminate the need for exchanging control packets. The proposed protocol, evaluated by both analytical and simulation results, is proven to improve the energy efficiency in the network without compromising the provided quality of service.

Green communication has recorded much attention in industry, academia and government. It has been recorded that information communication and technology nodes consume roughly 3% of the world-wide energy supply and are responsible for 2% of the global carbon dioxide (CO₂) emission. As a result, researchers have devoted huge attention to prevent its growth. In order to address this problem we studied coded packet approach, which is the current method of minimising energy in wireless multicast networks. Then, we propose novel approaches that are based on data envelopment analysis (DEA) to further optimise energy consumption in wireless multicast networks. We found that existing approaches to energy efficient multicast are unsuitable for evaluating efficiency adequately. This paper takes the position that true efficiency evaluation is obtained when both inputs and outputs with multiple variables are considered in measuring performance using ratios of weighted outputs to weighted inputs. As a result, we developed the input-oriented variable return to scale (VRS) envelopment with slacks models for energy efficiency in ad hoc wireless multicast networks. We explored the random linear network coding (RLNC) based on simulation approach and compared the results with the input-oriented VRS DEA envelopment with slacks approach. The results show the DEA approach substantially saves energy compared to the RLNC. Furthermore, we show that DEA method has the capability to identify which ad hoc network is inefficient and projected them onto the efficient frontier.

Power against rate performance of a class of transmission techniques is studied in this paper. This study arises in the context of a wireless sensor network in which multiple nodes equipped with single or multiple antennas cooperatively send simultaneous and distinct signals to multiple receiving nodes, each equipped with a single receiving antenna. The criterion in deriving the techniques is to eliminate or minimise the mutual interference so as to maximise received signal-to-interference plus noise ratio. It is shown for low bit rates that time-shared transmission can achieve the performance of the optimal power shared technique operating in spatially uncoupled (ideal) channels. As the bit rate increases, time-shared transmission becomes suboptimal. In this study, best linear optimisation, dirty paper coding and zero forcing are promising techniques.

In this study, an adaptive controller of a solar tracking system is designed and its performance is evaluated through computer simulation. To achieve this goal, two tracker systems based on open- and closed-loop control strategies are studied. The instantaneous and total errors that represent the differences between the tilt and rotation angles of both the open- and closed-loop systems are analysed. An adaptive controller that regulates the electric signals to the motors is designed. Owing to uncertainty in the sun position data, the performance of solar tracker suffers degradation. Towards this end, sun position data are analysed to extract the error sources. The designed control system objective is to keep the tracker perpendicular to sunlight at all times during the day and eliminate modelling errors such as sun position data deviations, friction and environmental changes. System performance is verified through computer simulation where the controller corrected for modelling errors and date changes from the date used for algorithm design. More specifically, in the first case the square error reduces from 15.43 to 12.18 degrees² for azimuth angle and from 39.05 to 19.09 degrees² for altitude, whereas in the latter case the square error reduces from 236.92 to 105.90 degrees² for azimuth angle and from 402.82 to 40.40 degrees² for altitude.

This study presents energy and area-efficient hardware architectures to map fully parallel cortical columns on reconfigurable platform – field programmable gate arrays (FPGAs). An area-efficient architecture is proposed at the system level and benchmarked with a speech recognition application. Owing to the spatio-temporal nature of spiking neurons it is more suitable to map such architectures on FPGAs where signals can be represented in binary form and communication can be performed through the use of spikes. The viability of implementing multiple recurrent neural reservoirs is demonstrated with a novel multiplier-less reconfigurable architectures and a design strategy is devised for its implementation.

Long term evolution (LTE)-advanced was introduced as real fourth generation (4G) with its new features and additional functions, satisfying the growing demands of quality and network coverage for the network operators’ subscribers. The term muti-tier has also been recently used with respect to the heterogeneity of the network by applying the various sub-network cooperative systems and functionalities with self-organising capabilities. Using indoor short-range low-power cellular base stations, for example, femtocells, in cooperation with existing long-range macrocells are considered as the key technical challenge of this multi-tier configuration. Furthermore, shortage of network spectrum is a major concern for network operators which forces them to spend additional attentions to overcome the degradation in performance and quality of services in 4G HetNets. This study investigates handover between the different layers of a heterogeneous LTE-advanced system, as a critical attribute to plan the best way of interactive coordination within the network for the proposed HetNet. The proposed comprehensive handover algorithm takes multiple factors in both handover sensing and decision stages, based on signal power reception, resource availability and handover optimisation, as well as prioritisation among macro and femto stations, to obtain maximum signal quality while avoiding unnecessary handovers.

A new textile wearable wireless node, for operation in the 2.45 GHz industrial, scientific and medical (ISM) band, is proposed. It consists of a dual-polarised textile patch antenna with integrated microcontroller, sensor, memory and transceiver with receive diversity. Integrated into a garment, the flexible unit may serve for fall detection, as well as for patient or rescue-worker monitoring. Fragile and lossy interconnections are eliminated. They are replaced by very short radiofrequency signal paths in the antenna feed plane, reducing electromagnetic compatibility and signal integrity problems. The compact and flexible module combines sensing and wireless channel monitoring functionality with reliable and energy-efficient off-body wireless communication capability, by fully exploiting dual polarisation diversity. By integrating a battery, a fully autonomous and flexible system is obtained. This novel textile wireless node was validated, both in flat and bent state, in the anechoic chamber, assessing the characteristics of the integrated system in free-space conditions. Moreover, its performance was verified in various real-world conditions, integrated into a firefighter garment, and used as an autonomous body-centric measurement device.

The major factor that limits the performance of Free Space Optical Communication is atmospheric turbulence which fluctuates over time in accordance with the variations in local meteorological parameters. Estimating the atmospheric turbulence strength C _n ² with the measurement data becomes significant to find the data rate the system is capable of operating under different outdoor local environmental conditions. Hence, a low cost customised system for continuously measuring the local meteorological data is developed and presented in this study. A field test scintillometer setup is established for a link range of 0.5 km at an altitude of 15.25 m. Specialised sensors are interfaced to the digital architectures to acquire the real-time data corresponding to atmospheric changes. The accuracy and performance of the measurement system are tested against standard instruments and the maximum correlation coefficients of 99.92, 99.63, 99.73 and 99.88% are achieved for wind speed, temperature, relative humidity and pressure, respectively. An experimental model to estimate C _n ² using measured meteorological data is developed and the atmospheric turbulence strength is estimated. The validations of the estimated results with the scintillometer measurement are also analysed. The weather profile and corresponding C _n ² variations at our test field for different seasons in 1 year period are presented and the results are analysed.

External overvoltages constitute a typical cause of faults, damages and interruptions in the electrical networks’ high-voltage transmission lines. In order to protect the lines and their equipment against lightning, overhead ground wires in combination with surge arresters are installed, improving the lightning performance of the system and reducing the annual failure rate. The achievement of low values of earth resistance is an essential requirement, since a good grounding system reduces considerably the corresponding insulation breakdowns. However, the behaviour of surge arresters in relation to the grounding resistance is different, as it depends on the position of the lightning hit. The current work is devoted to the sensitivity analysis of the failure probability of surge arresters with relation to the grounding resistance, investigating concurrently the effect of the arresters’ installation interval and the energy absorption capability.

This study presents reconfigurable antenna design for a front end (FE) that has separate transmit (Tx) and receive (Rx) path. In such an FE, the Tx and Rx antennas can be content with covering only the transmit and receive channels in a frequency band. Therefore they can be quite narrow-band. Narrow-band antennas can exhibit high losses, because of the relative high current density per area and limited tuning/matching component Q. To address this, a self-matched antenna design is introduced, having the tunable capacitor as the only physical component. The Tx and Rx narrow-band antennas are designed to cover the frequency range 1710–2170 MHz. Metrics as for example, impedance bandwidth and efficiency are obtained both in simulations and measurements.

The image reconstruction for electrical capacitance tomography is a non-linear, underdetermined and ill-posed inverse problem. It is difficult to obtain a reconstructed image with high quality, especially in the case of three-dimensional (3D) reconstruction. An iterative image reconstruction algorithm with fuzzy thresholding is proposed in this study. The threshold value in each iteration is generated by minimising the measure of fuzziness of current reconstructed image. The algorithm proposed is tested by the noise-free and the noise-contaminated capacitance data. Extensive computer simulations demonstrate that the fuzzy thresholding can reduce low grey-level artefacts effectively. As a result, the spatial error, volume error, permittivity error and scattered artefacts of the reconstructed image are reduced obviously; not only that, the number of iterations needed to obtain a good reconstruction result is decreased greatly. The result of 3D reconstruction of a H-shape object verifies the effectiveness of the fuzzy thresholding further.

The study presents a detailed experimental and numerical analysis of the corona characteristics of a proposed ‘tri-electrode system’ for electrostatic separation applications. The system consists of an ionising wire, a movable auxiliary wire and a non-ionising cylinder, having the same voltage and placed parallel above a grounded plate. A computational technique coupling the method of characteristics and the charge simulation method is developed to model the corona governing equations of the proposed configuration. Influence of the auxiliary wire's position on field modulation of the ionising wire, corona onset and switching on/off of the discharge is established both numerically and experimentally. Dependence of the spatial distributions of the electric field and current density on the system's geometrical characteristics is evaluated and assessed. The study includes a physical model of the corona discharge of this particular electrode arrangement and demonstrates the configuration's specific features and advantages as compared with the earlier designs. The computed results compared favourably well with experiments.

Bat-inspired algorithm (BA) is a new evolutionary meta-heuristics algorithm inspired by a known technique of bats for finding prey. This study presents a self-adaptive BA to solve the unit commitment (UC) problem. The applied self-adaptive technique increases the population diversity and improves the exploration power of BA which results in better solutions and higher speed of convergence in solving the UC problem. This study, also, applies simple methods to handle the minimum on-/off-time constraint and spinning reserve requirement in generation of all solutions directly and without using any penalty function. The performance of the proposed method is verified by applying 10 up to 100-unit systems as well as a Taiwan power (Taipower) 38-unit system in a 24 h scheduling horizon.

In this study, a stable direct adaptive general type-2 fuzzy logic controller (DAG2FLC) is introduced for a class of non-linear systems. The proposed controller uses advantages of general type-2 fuzzy logic systems (GT2FLSs) in handling dynamic uncertainties to approximate unknown non-linear actions. Implementing general type-2 fuzzy systems is computationally costly; however, by using a recently introduced α-plane representation, a GT2FLS can be seen as composition of several interval type-2 fuzzy logic systems with a corresponding level of α for each. Linguistic rules are directly incorporated into the DAG2FLC controller and a H ^∞ compensator is added to attenuate external disturbance and fuzzy approximation error. Also general type-2 fuzzy adaptation laws are derived using Lyapunov approach, and the stability of the closed-loop system has been proven by mathematical analysis. In order to evaluate the performance of the proposed controller, the results are compared with those obtained by direct adaptive type-1 fuzzy logic controller and a direct adaptive interval type-2 fuzzy logic controller, which are the latest researches in the problem in hand. The proposed controller is applied to a chaotic Gyro system as a case study. Simulation reveals the effectiveness of the proposed controller in presence of dynamic uncertainties and external disturbances.

This study deals with measurement of harmonic distortion and Skewness of stator current in Clarke plane at crawling of induction motor. Three-phase current signals have been transformed into Clarke plane. Dominancy of seventh harmonic is observed by assessing maxima and minima of stator current Concordia in Clarke plane. Specific reference signals having sinusoidal nature and different frequencies are defined and then areas covered by the real system data with the reference signal have been determined, wherefrom individual contributions of fundamental waveform and harmonic components are measured separately and total harmonic distortion factors are determined. Then wavelet decomposition of stator current is done in Clarke plane, wherefrom, signals are assessed with the help of Skewness of approximate coefficient in Clarke plane. Significant differences are noted between those parameters found during crawling and that of normal condition which may be useful in detection of such fault.

In this study, a new systematic approach is proposed to design the fuzzy controller for a class of Takagi–Sugeno fuzzy-partial differential equation (TS fuzzy-PDE) systems which describe the non-linear distributed parameter system formulated by first-order semi-linear hyperbolic PDEs. In this study, non-quadratic Lyapunov function is utilised and some slack matrices are introduced to derive stability conditions in terms of linear matrix inequalities (LMIs). The proposed approach has three main features. First, stability conditions are not derived in the form of spatial differential LMI. Second, conservativeness of LMI conditions is reduced. Third, there is no restriction on the form of semi-linear hyperbolic PDE systems and therefore more semi-linear systems classes can be stabilised. Also, the proposed approach is more suitable for practical implementation compared with the recently published papers.

With advanced small-pixel and high-resolution mobile displays, the display are obtaining smaller pixel size and higher resolution on thin-film-transistor (TFT) array process. This study proposed the flaw detection and measurement in small pixel design mobile displays based on oxide-semiconductor-based TFT liquid crystal displays. The measurement is with respect to electrical-physic characterisation metrics and observer studies. Studies resulted in small-sized pixel TFT array between the flaw detection performance and maker preference approaches. Detection performance factors provided information on the differences among small pixel design for advanced mobile display technologies. The results of the detection performance and preference study showed that the application for advanced mobile display panels. It also shown that critical pixel defect played an important role than previously seen in non-small pixel TFT array panels for managing process yield. The method of voltage imaging for detection, developed in this study provides an initial insight into the high resolution of small-sized pixel designs for advanced mobile displays with precision and diagnostic images in portable devices.

The work presented in this study aims to develop a methodological approach for estimating the ground resistance of several grounding systems, embedded in various ground enhancing compounds, using artificial neural networks (ANNs). The ANN training is based on field measurements that have been performed in Greece during last years. The methodology uses as input variables measurements of soil resistivity within various depths and of rainfall height during some periods of time, like last week and last month and estimates the ground resistance value of the tested rods, based on an ANN. This work comprises two scenarios in which, several ANN training algorithms are applied and an optimisation process is performed regarding the values of parameters, such as the number of neurons, the activation functions combination and so on. Each training algorithm is compared to the others, based on the coefficient of determination between the experimental and estimated values for the test set and the algorithm with the best results is highlighted for the estimation of ground resistance value, formed by the ground enhancing compounds under various weather conditions.

The presence of faults in the bearings of rotating machinery is usually observed with impulses in the vibration signals. However, the vibration signals are generally non-stationary and usually contaminated by noise because of the compounded background noise present in the measuring device and the effect of interference from other machine elements. Therefore in order to enhance monitoring condition, the vibration signal needs to be properly de-noised before analysis. In this study, a novel fault diagnosis method for rolling element bearings is proposed based on a hybrid technique of non-local means (NLM) de-noising and empirical mode decomposition (EMD). An NLM which removes the noise with minimal signal distortion is first employed to eliminate or at least reduce the background noise present in the measuring device. This de-noised signal is then decomposed into a finite number of stationary intrinsic mode functions (IMF) to extract the impulsive fault features from the effect of interferences from other machine elements. Finally, envelope analyses are performed for IMFs to allow for easier detection of such characteristic fault frequencies. The results of simulated and real bearing vibration signal analyses show that the hybrid feature extraction technique of NLM de-noising, EMD and envelope analyses successfully extract impulsive features from noise signals.

Tissue classification using computer aided diagnosis can help automated decision making to aid clinical diagnosis. Classification of breast tissue based on spectral features of impedance loci has frequently been done to classify malignant tissue with further requirement of more complex classification methodologies needed to improve the characterisation. In current study, tissue classification is done using in vivo electrical impedance data of 18 human subjects, from four quadrants of breast, palm, nail, arm, bicep and classified using algorithms involving machine learning methodologies, specifically support vector machines (SVMs) that are supervised learning models. They consist of learning algorithms based on the principal of structural risk minimisation. Two methodologies of SVM have been used in this study: with data binning and data pruning and without data binning and data pruning. Data binning and data pruning have improved the sensitivity of the SVM from 76.76 to 89.23%, but the specificity has decreased from 76.23 to 74.15%. This is a pilot study towards testing the reliability of the developed electrical impedance measuring system and developing a data mining-based decision making system into an electrical impedance spectroscopy system, to help users (physicians) with tissue classification leading to reliable objective decision making.

The physicochemical properties of three transformer mineral oils of different levels of degradation, resulting from exposure to moisture and electrical discharges, are investigated. The first oil is new and untreated whereas the second is taken from a transformer after one year of normal operation; and the third oil is extracted from a 15-year-old operating transformer. The considered parameters are breakdown voltage, dielectric constant ε _r, dissipation factor (tan δ) and resistivity. Isothermal charging currents have also been measured under dc for long application times. It is shown that the physicochemical characteristics present major differences depending on the considered oil sample. An easy method enabling to determine the water solubility in oil is proposed; this method is based on the measurement of oil resistivity. To validate a part of the results obtained in laboratory, measurements on an on-load operating transformer have also been achieved. These show that the properties of oils with dissolved water in laboratory are similar to those of oils with really dissolved water inside operating transformers.

This study is aimed at the characterisation of surface discharges propagating over different solid materials namely glass, bakelite and epoxy resin immersed in three gases and their mixtures (namely SF₆, N₂ and CO₂, SF₆/N₂ and SF₆/CO₂) under AC voltage (50 Hz) in a point-plane electrode system. It is shown that the stopping length of discharges (L_f ) increases linearly with the applied voltage and decreases when the gas pressure is increased. L_f is longer in CO₂ and N₂ than in SF₆ [L_f (N₂) > L_f (CO₂) > L_f (SF₆)]; and the increase of SF₆ content in the investigated mixtures leads to a significant decrease of L_f . Also, for a given gas, L_f is slightly longer with glass and bakelite than that with epoxy resin indicating that the higher the dielectric constant, the longer the discharge is. Thus, the density of the discharge branches and L_f reduce when the thickness of insulators increases and/or their dielectric constant decreases. Such observations evidence the implication of capacitive charge effect and electric field in the development of creeping discharges.

Triaxial MEMS vector field measurement system with triaxial MEMS sensors, such as accelerometer and magnetometer, is typically used to acquire navigation information in strap-down inertial navigation system (SINS). The navigation accuracy of the body is directly affected by the measurement accuracy of the measurement system. This study presents a two-step calibration algorithm for the triaxial MEMS vector field measurement system based on a detailed analysis of the measurement system error model. In the calibration procedure of this method, the first step is to calibrate the triaxial vector sensor error, including bias, scale factors and non-orthogonality using the ellipsoid fitting method; the second step is to calibrate the misalignment between the orthogonal sensor frame and the system body frame using the four-position method. Furthermore, the mathematical analysis of four-position method calibration error is done to study on the factors influencing the misalignment calibration accuracy, numerical simulation and experiments, which are performed for validating the analysis. A series of calibration experiments on a triaxial MEMS accelerometer in the measurement system show significant enhancement of the accuracy of three components measurement data in the system body frame.

The challenges of climate change, population growth, demographic change, urbanization and resource depletion mean that the world's great cities need to adapt to survive and thrive over the coming decades. Slashing greenhouse gas emissions to prevent catastrophic climate change, while maintaining or increasing quality of life, can be a costly and difficult process. Two factors that directly affect the life quality in the XXI century cities are the water and air quality that can be monitored using the combination of low cost sensing modules, machine to machine (M2M) and internet of things (IoT) technologies. In this context, this study presents a wireless sensor network architecture that combines low cost sensing nodes and a low cost multi-parameters sensing probe for reliable monitoring of water quality parameters of surface waters (lakes, estuaries and rivers) in urban areas. A particular attention is dedicated to the design of the conductivity, temperature and turbidity signal conditioning circuits, highlighting important issues related to linearisation, measuring dynamic range and low-cost implementation by using commercial off-the-shelf components and devices. Several issues related to the wireless sensor network implementation are included in this study, as well as several simulation and experimental results.

Measurement and calibration of mass imbalance for rotors are often indispensible as mass imbalance will cause undesired vibration and present serious problems accordingly. In this study, a new method based on digital image processing (DIP) to measure the mass imbalance of a special rotor with air suspension is introduced. By hunting the trace of tilt angle through several identification points on the rotor by DIP, the corresponding oscillating period will be determined, which in turn contributes to the calculation of mass imbalance. Two-dimensional monochrome charge-coupled device (CCD) and peripheral component interconnect (PCI) image board are applied in the experiment to capture the rotor's image, and several user interfaces are developed for image processing and curve fitting as well. Besides, the system error analysis and the comparison of experimental results with that of other related work are provided, which prove the effectiveness and accuracy of this DIP method.