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Fiber bending and temperature loss mechanisms in plastic optical fibers are reported.A simple arrangement is used to monitor the fiber bending and temperature by output power variation. Powers in the fibers in bend-free situation at room temperature and under rolling deforming force at different water bath temperatures (20-60°C) are measured and compared. Reported arrangements can be used as a temperature sensor. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:82-86, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27271 [ABSTRACT FROM AUTHOR]

The growing number of power-electronics equipment with non-sinusoidal currents and reactive power has given increased interest in active power filters (APF). APFs have been researched and put into practical use in power systems with nonlinear loads for harmonic current compensation, power factor correction, reactive power compensation and etc. Shunt APFs, connected in parallel with the power line, are more common than the series ones. This paper presents a bidirectional grid connected multi-input DC-AC converter that plays as a shunt APF integrated with Distributed Generation (DG) sources for power quality enhancement and supplying a part of loads. At the input port of this converter, Half Bridge Converters (HBC) is used to meet the requirement of different DGs, such as Photovoltaic (PV) and Fuel Cell (FC) systems and at the output port, a cycloconverter acts as a shunt APF to compensate current harmonics, reactive power of load and also supply a part of the load. In the proposed converter, High Frequency Transformer (HFT) is used instead of large power transformer. In the proposed converter, the cost, size and the volume of the converter can be reduced. The reduced conversion steps increase the efficiency of the converter. The converter is analyzed step by step to show the principles of the operation in providing an energy management system based on duty cycle variations. The system capability in different operation modes is simulated and simulation and experimental results validate the highly dynamic performance of the proposed controller. Dynamic analysis and controller design of the bidirectional DC-AC converter, which is presented based on non-linear Input-Output Feedback Linearization (IOFL) method, is presented, too. [ABSTRACT FROM AUTHOR]

Background and Aims: Instrumentation of the root canals results in formation of smear layer which covers the dentinal tubules. In infected teeth, it is ideal to achieve a material that has the ability to remove the smear layer besides antimicrobial activity. Therefore, this study was designed to evaluate the antimicrobial effect of Citrus aurantifolia extracts (lime juice and rind extract) on Enterococcus faecalis within dentinal tubules in the presence of smear layer. Materials and Methods: One-hundred and forty dentin tubes were prepared from bovine incisors. After removal the smear layer, the specimens were infected with Enterococcus faecalis. Then, the smear layer was reformed. Test solutions were used as the irrigants in study roups as follows: group 1: 5.25% NaOCl; group 2: 17% EDTA; group 3: NaOCl+EDTA; group 4: Lime juice; group 5: ethanolic rind extract of C.aurantifolia; group 6: 96% ethanol. Dentin chips were collected from inner and outer layers of dentinal walls and optical density was measured. The data were analyzed using one-way ANOVA and Tamhane tests. Results: In outer layer of dentin, the efficacy of rind extract was less than that of NaOCl+EDTA (P<0.05). Also Lime juice was less effective than EDTA, NaOCl and NaOCl+EDTA (P<0.05). In inner layer of dentin, Lime juice was significantly less effective than NaOCl and NaOCl+EDTA (P<0.05). The efficacy of rind extract was less than that of NaOCl+EDTA (P<0.05). Conclusion: In the presence of smear layer, the antimicrobial activity of Lime juice was less than that of NaOCl but the efficacy of rind extract was similar to that of NaOCl. [ABSTRACT FROM AUTHOR]

Through a simple one-dimensional collisionless plasma sheath model, behavior of the floating potential in an electronegative plasma sheath is studied. Specially, the floating potential behavior as a function of the plasma electronegativity for various negative ion temperatures has been studied. It has been observed that negative ion temperature strongly affects the variation of floating potential. [ABSTRACT FROM PUBLISHER]

This paper presents a direct torque control (DTC) technique for Brushless DC (BLDC) motors with non-sinusoidal back electromotive force. DTC has some benefits such as faster torque response and reduced torque ripple for driving the BLDC motors. Because of ignoring stator flux linkage in DTC in constant torque region, BLDC motors driving is not complicated. The Sliding mode which is robust to parameter uncertainties can be used to estimate the back-EMF and generate the torque. It is employed to estimate the back-EMF waveform in a BLDC motor using only the measurements of the stator currents. The main advantages of the proposed estimator are: it is insensitive to switching noise and no filtering is required. Due to uncertainties of BLDC motor the moment of inertia and viscous damping coefficient are online identified simultaneously using recursive least square estimator. From the identified parameters the load torque is estimated. The estimated load torque is substituted into the mechanical dynamic equation to estimate the rotor speed. A modified version of Non-Dominated Sorting Genetic Algorithm (NSGA-II) is used as an effective optimization tool for regulating the PID controller parameters of speed controller and selection of four sliding mode observer gains. [ABSTRACT FROM AUTHOR]

Brushless DC (BLDC) motors are widely used in a variety of applications such as industrial automation and consumer appliances. Moreover, minimizing the cost of the drive is desirable for low cost applications. Cost reduction of the BLDC driver is achieved by reducing the number of switch devices and freewheeling diodes, cost down of control, and eliminating of hall and current sensors. In this paper, a cost-effective position sensorless control for four-switch three-phase BLDC motor drives using a single current sensor is proposed. The whole working process of the BLDC motor is divided into six modes. Phase c involves four modes, including modes 2, 3, 5, and 6, only one switch will work in these modes. In modes 1 and 4, two switches will work simultaneously and current flows through phases a and b. The proposed position sensorless technique is based on the detection of zero crossing points (ZCPs) of three voltage functions that are derived from the difference of the line voltages measured at the terminals of the motor. Unlike the conventional methods, the proposed control strategy uses only one simple current controller for three phases. Due to its inherent low cost, the proposed control strategy is particularly suitable for cost sensitive product. The effectiveness of the proposed system has been validated by simulation results. [ABSTRACT FROM AUTHOR]

A single-stage commercial low frequency to high AC frequency bi-directional power electronic transformer (PET) for induction heating applications is proposed here. The proposed PET can simultaneously track the maximum power point and improve the output power factor by using a phase locked loop adjustable switching frequency controller. The operating principle of the PET is discussed based on mathematical equations and equivalent circuits. The experimental results of laboratory prototype, which converts 110 V/3ϕ/50 Hz input voltage to 20 V/1ϕ/22 kHz output voltage, show the capabilities of the proposed PET. [ABSTRACT FROM AUTHOR]

In this study, a bi-directional power flow zero-voltage switching (ZVS) power electronic transformer (PET) with phase shift modulation controller (PSM) is proposed. The PET contains input full-bridge active rectifier (FBAR), full-bridge DC-link inverter (FBDCI), high-frequency isolating transformer (HFIT), cycloconverter and output filter. FBDCI switches operate under ZVS condition. In addition, ZVS commutation of both cycloconverter bi-directional switches and FBAR switches are achieved. Dynamic voltage regulation is obtained without utilising energy storage elements. Therefore good efficiency can be achieved as a result of ZVS operation together with the absence of energy storage elements. The values of output filter are calculated to provide soft switching operation and voltage regulation. Based on the simulation and experimental results, the steady-state operation principles of the PET are described. Experimental results from a laboratory prototype with specification of 110 V/50 Hz input to 24 V/50 Hz output are presented to verify feasibility of the proposed PET. [ABSTRACT FROM AUTHOR]

Vector control accuracy of induction motor drives is affected by variations of motor parameters that are treated in the control algorithm as constant values, and by the phenomenon that is not modeled at all and is therefore unaccounted for in the controller. Detuning sources of the first type include variations of rotor and stator resistance, mutual inductance, and leakage inductances, while the second category includes stator iron (core) losses. All these sources of detuned operation have been investigated in a considerable depth in the past. One of the potential sources of detuned operation is the stray load loss (SLL), which belongs to the category of unmodeled phenomena because vector controllers are not aware of its existence. Taking into account no-load and under-load stray losses of machine, this paper develops an analytical model that characterizes detuning due to SLLs in indirect rotor-flux-oriented (RFO) voltage-fed induction motor drives in steady-state operation by means of the orientation angle error, actual to reference rotor- flux ratio, and actual to reference-torque ratio. [ABSTRACT FROM AUTHOR]

Introduction: In autosomal recessive distal renal tubular acidosis (DRTA), a substantial fraction of the patients have progressive bilateral sensorineural hearing loss. This coexistence is due to the mutations of a gene expressed both in the kidney and in the cochlea. The aim of this study was to assess the correlation between hearing loss and DRTA.Materials and Methods: In this study, 51 children diagnosed with renal tubular acidosis were evaluated. Diagnosis of DRTA was based on clinical manifestations and detection of normal anion gap metabolic acidosis, urine pH higher than 5.5, and positive urinary anion gap. Audiometry was performed in children with DRTA and sequencing of the ATP6V1B1 gene was done for those with sensorineural hearing loss.Results: Twenty-seven patients (52.9%) had DRTA, of whom 51.9% were younger than 1 year old, 55.6% were boys, and 44.4% were girls. Eleven patients (40.7%) had bilateral sensorineural hearing loss, consisting of 5 of 15 boys (33.3%) and 6 of 12 girls (50.0%). There was no correlation between hearing loss and gender. Three patients with hearing loss had mutation in the ATP6V1B1 gene (11.1% of patients with DRTA and 27.3% of patients with DRTA and hearing loss).Conclusions: This study indicated that a significant percentage of the children with DRTA had sensorineural hearing loss and mutation in ATP6V1B1 gene. It is recommended to investigate hearing impairment in all children with DRTA. [ABSTRACT FROM AUTHOR]

A significant improvement in motor efficiency is expected when substituting aluminum with copper die-cast rotor in squirrel-cage induction motors due to a reduction in the rotor ohmic losses. Other performance criteria, such as starting torque, power factor, and steady-state current, may also change, and the motor may need to be redesigned to obtain optimal performance. This paper compares the performance of optimally designed squirrel-cage induction motors with aluminum and copper rotor bars with equivalent specifications. The design is optimized using three objective functions. [ABSTRACT FROM AUTHOR]