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The aim of this study was to investigate and analyse the synchronous reluctance machine. An accurate method for determining the lumped parameters of an equivalent circuit of the studied machine has been proposed. The method is based on the phase currents and voltages analysis at low slip operation. Experimental research of a synchronous reluctance machine is supplemented by simulation studies. The field-circuit model of electromagnetic phenomena in the considered motor was developed and used in simulation. The proposed method allows the numerical model to be verified by comparing the calculated and measured torqueangle characteristics of the machine. The test results obtained are presented and discussed. Achieved satisfactory concordance between simulation and experiment results proves that the proposed approach can be useful in the synthesis of reliable synchronous reluctance machines as well as in their control systems.

This paper presents an automatic water exchange system designed for a freshwater aquarium. The automatic water exchange system (AWES) was developed to improve the aquarist’s work. Replacement of water in an aquarium is one of the basic maintenance activities and should be performed regularly. In case the process of pouring in and out of the water itself requires a lot of time and strength from the aquarist, the automation of this operation is proposed. The automatic water exchange system consists of a water discharge system, a water filling system, and a security system. Additionally, to simplify user operation, a dedicated mobile application for the Android system has been created. The developed AWES system allows for regular changing of water in aquariums as well as enables effective and simple control of water flow and temperature.

BACKGROUND Noninvasive assessment of metabolic processes that sustain regeneration of human retinal visual pigments (visual cycle) is essential to improve ophthalmic diagnostics and to accelerate development of new treatments to counter retinal diseases. Fluorescent vitamin A derivatives, which are the chemical intermediates of these processes, are highly sensitive to UV light; thus, safe analyses of these processes in humans are currently beyond the reach of even the most modern ocular imaging modalities. METHODS We present a compact fluorescence scanning laser ophthalmoscope (TPEF-SLO) and spectrally resolved images of the human retina based on two-photon excitation (TPE) with near-infrared (IR) light. A custom Er:fiber laser with integrated pulse selection, along with intelligent post-processing of data, enables excitation with low laser power and precise measurement of weak signals. RESULTS We demonstrate spectrally resolved TPE fundus images of human subjects. Comparison of TPE data between human and mouse models of retinal diseases revealed similarity with mouse models that rapidly accumulate bisretinoid condensation products. Thus, visual cycle intermediates and toxic byproducts of this metabolic pathway can be measured and quantified by TPE imaging. CONCLUSION Our work establishes a TPE instrument and measurement method for noninvasive metabolic assessment of the human retina. This approach opens the possibility for monitoring eye diseases in the earliest stages before structural damage to the retina occurs. FUNDING NIH, Research to Prevent Blindness, Foundation for Polish Science, European Regional Development Fund, Polish National Agency for Academic Exchange and Polish Ministry of Science and Higher Education.

A femtosecond frequency-doubled erbium-doped fiber laser with an adjustable pulse repetition rate is developed and applied in two-photon excited fluorescence microscopy. The all-fiber laser system provides the fundamental pulse at 1560 nm wavelength with 22 fs duration for the second harmonic generation, resulting in 1.35 nJ, 60 fs pulses at 780 nm. The repetition rate is adjusted by a pulse picker unit built-in within the amplifier chain, directly providing transform-limited pulses for any chosen repetition rate between 1 and 12 MHz. We employed the laser source to drive a scanning two-photon excited fluorescence microscope for ex vivo rat skin and other samples’ imaging at various pulse repetition rates. Due to compactness, ease of operation, and suitable pulse characteristics, the laser source can be considered as an attractive alternative for Ti:Sapphire laser in biomedical imaging.

We report the development of a widely-tunable femtosecond fiber laser system and its application for two-photon vision studies. The source is based on an Er-doped fiber laser with spectral shift up to 2150 nm, followed by a second harmonic generation module to generate a frequency-doubled beam tunable from 872 to 1075 nm. The source delivers sub-230 fs pulses with nearly-constant duration over the entire tuning range, with output powers between 0.68–1.24 mW, which corresponds to a pulse energy of 13.2–24.1 pJ. Such pulse energy is sufficient for employing a system for measurements of two-photon scotopic spectral sensitivity of two-photon vision in humans. The laser parameters allow for very efficient and safe two-photon stimulation of the human visual system, as proved by a good separation between one- and two-photon thresholds for wavelengths below 950 nm, which we have confirmed for 3 healthy subjects.

The paper presents the design procedure and elaborated software for designing calculation of the shape memory alloy (SMA) actuator. The thermo-mechanical behavior of a linear SMA actuator has been studied. The experimental set-up was especially designed to perform the thermo-mechanical characterization of SMA wires. The stroke (s) - temperature (T) hysteresis characteristics have been determined. The cycle of heating and cooling has been performed under a constant load. The model for the SMA actuator s - T behavior has been proposed and successfully implemented. The selected results and conclusions have been presented. The concept proposal of the linear actuator using the SMA wire has been given.

In this paper we demonstrate our concept and fabrication details of a (5 + 1) × 1 pump power combiner with signal feed-through. The (5 + 1) × 1 configuration is based on a feed-through signal fiber with reduced clad diameter in comparison to multimode fibers (MMFs) used in the combiner. Our idea is to use a 9/80 μm signal fiber and five conventional 105/125 μm MMFs. Using this number of MMFs with 125 μm clad diameter and signal fiber with 80 μm clad diameter allows for easy placement of all fibers in proper position in a capillary tube – the signal fiber is always in the central position, surrounded by the MMFs. It also enables reducing the taper ratio parameter, and thus increase the signal transmission efficiency. Using this approach, signal transmission at the level of 94.3% was achieved, which is better than typical values offered by commercially available singlemode devices.

The paper discusses the magnetic flux density distribution in medium power transformers core. Three-phase transformers are usually made of grain-oriented electrical steel characterized by anisotropy. Core losses, among other things, mainly depend on the grade of material. The selected results of calculation and measurement of no-load losses of medium power transformers have been shown.

The paper deals with the analysis of the 6 pole interior permanent magnet (IPM) synchronous motor with tangential magnets. To determine the magnetic field distribution in the considered motor the finite element method (FEM) has been applied. Simulations were performed for different positions of the magnets on the chords of the rotor package. The goal of performed studies was minimization of the magnetic flux leakage (understood as the flux between poles not crossing the air-gap) with respect to the high values of the analyzed functional parameters of the considered motor. Streszczenie. W artykule przedstawiono wyniki analizy sześciobiegunowego silnika synchronicznego o magnesach umieszczonych cieciwowo w pakiecie wirnika. Do wyznaczenia rozkladu pola magnetycznego wykorzystano metode elementow skonczonych. Wykonano obliczenia symulacyjne zmieniając polozenie magnesow na cieciwach pakietu wirnika. Na podstawie analizy rozkladow pola magnetycznego i wyznaczonych parametrow funkcjonalnych wytypowano strukture najlepiej ograniczającą skutki bocznikowania magnesow. (Polowa analiza sześciobiegunowego silnika synchronicznego z magnesami umiejscowionymi cieciwowo).

In this paper, we demonstrate the performance of self-fabricated passive fiber components in a laser and amplifiers setups operating at ~1.55 μm wavelength. Three different types of power combiners and one mode field adaptor were fabricated using three-electrode Large Diameter Splicer System (LDS System). Application of pump and signal power combiners in two configurations is presented, including (5+1)x1-SM (i.e. with single mode signal fibers) and (6+1)x1-LMA (with large mode area signal fibers). We also demonstrate pump power combiner in 7x1 configuration with single mode output fiber and mode filed adaptor which connects single mode fiber with large mode area type fiber. All those components were successfully applied in two high-power systems, a three-stage amplifier MOPA setup and a high-power amplifier with medium-power signal source.

The paper deals with the analysis of power transformer's no-load losses according to its geometry. The object of the study was a series of medium power transformers (6.3–40 MVA) produced for the Polish Electric Power System. Those transformers were installed in 110 kV's grid. The main customers are the energy distribution companies such as PGE, Enea, Energa and Tauron. Due to the high requirements of those companies, the no-load losses are a significant issue. The no-load losses have been calculated and measured. The calculation was carried out using the own algorithm. The following types of measured losses are considered: losses from the final test of the entire transformer and losses from the test of the core before the complete transformer assembling. The tests of only the core were executed by two independent laboratories: the producer of the core and the producer of the transformer. The tests were conducted according to the norm PN-EN 60076-1:2011. The calculations and measurements' results are in close agreement. Moreover, the relation between the percentage of corners and additional losses was observed. The knowledge about this dependency may be effective to design transformers with reduced losses.

Application of wavelength modulation spectroscopy to hydrogen sulfide (H2S) detection is discussed. Performance of a mid-infrared system operating at 7198 nm and a near-infrared setup operating at 1574.5 nm is demonstrated.

The Laser & Fiber Electronics Group (LFEG) constitutes a team of young, skilled and ambitious researchers, doctoral candidates and students. The Group possesses great experience in applied optoelectronics and laser technology. Currently, it conducts research in several areas,mostly focusing on: ultrashort laser pulse generation using novel materials, development of pulsed fiber laser sources ranging from visible to mid-infrared, development of compact mid-infrared optical frequency combs, laser spectroscopy techniques, laser vibrometry, solid-state lasers, advanced analog and digital electronics, and investigations of light-matter interaction.

In this work we analyze two aspects of our research towards a laser-based setup for open-path hydrogen sulfide detection. We demonstrate a compact and portable electronic part of the sensing system that can be constructed solely with commercially available, off-the-shelf components. Comparison with the setup that uses benchtop lock-in amplifier for signal demodulation is presented. We also discuss challenges in spectral modelling of H2S transitions in the near-IR spectral region using the data available in HITRAN base. We show that in order to perform correct spectral simulations (for both direct absorption spectroscopy and wavelength modulation spectroscopy) appropriate corrections to the data available in the database have to be applied.

In this work we present a laser-based system for standoff/r emote, sensitive detection of gases based on a tunable diode laser source and Wavelength Modulation Spectroscopy method (WMS). System performance was experimentally characterized. The constructed device has pr oven its capacity of efficient detection of methane in ai r at the single ppm levels and distances from 10 to 50 m (distance to a scattering object). The minimum detection limit of the system was estimated at the level of 10 ppm-m for the standoff arrangement and the measurement path of approximately 20 m (round trip). Potential application of the device to hydrogen sulfide detection and current limitations in this area are discussed. Keywords: infrared spectroscopy, gas sensing, standoff detection, wavelength modulation spectroscopy, methane, hydrogen sulfide 1. INTRODUCTION Laser-based spectroscopy systems that use compact, tunable semiconductor laser sources (e.g. distributed feedback diode lasers, interband cascade lasers or quantum cascade lasers) are highly efficient and sensitive tools for gas detection, providing great robustness and flexibility [1-12]. These kind of systems have been intensively investigated especially over the last decade and can be realized in various stationary configurations using different spectroscopy methods. However, ability to effectively detect gases using a st andoff or remote approach (w ith scattering or reflective optical targets) is often desirable from the practical point of view [13-18]. Remote detection of hazardous gases such as methane (CH

In this paper we demonstrate a preliminary work done on employing antimony telluride (Sb2Te3) topological insulator as a saturable absorber for Yb-doped fiber lasers. The material was deposited onto a side-polished fiber by means of a pulsed magnetron sputtering technique. Fabricated absorber was implemented in an all-normal dispersion cavity and allowed for self-starting dissipative soliton generation. The laser emitted stable pulse train at a repetition rate of 17.07 MHz with 4.25 nm broad output spectrum centered around 1039.4 nm. Average output power amounted to 0.54 mW with 32 pJ pulse energy.

Application of wavelength modulation spectroscopy at 1575 nm to hydrogen sulfide (H2S) detection at atmospheric pressure is discussed. Cross-interference with carbon dioxide transitions is analyzed. Detection limit below 1 ppmv/Hz1/2 is obtained using a setup with a multi-pass cell.

Purpose – The aim of the paper is to find the effective algorithms of electromagnetic torque calculation.Design/methodology/approach – The proposed algorithms are related to the analysis of electrical machines using the methods of equivalent magnetic networks. The presented permeance and reluctance networks are formulated using FE methods. Attention is paid to the algorithms of electromagnetic torque calculation for 3D models. The virtual work principle is applied. The principle is adapted to the discrete network models. The network representations of Maxwell's stress formula are given.Findings – The proposed method of electromagnetic torque calculation can be successfully applied in the 3D calculations of rotating electrical machines. It can be used for scalar and vector potential formulations. The obtained results and their comparison with the measurements show that the method is sufficiently accurate.Originality/value – The presented formulas of electromagnetic torque calculation are universal and can ...

In this paper our results of investigation on a pump power combiner in a configuration of 7×1 are presented. The performed combiner, with pump power of 80–85% transmission level, was successfully applied in a thulium doped fibre laser. The performed all-fibre laser setup reached a total CW output power of 6.42 W, achieving the efficiency on a 32.1% level.

This paper demonstrates how the 3D edge element method can be applied to the analysis of permanent magnet motors. The edge element method using the vector magnetic potential has been used. Special attention has been paid to the analysis of systems with inhomogeneously magnetized permanent magnets. The magnets are not skewed and are mounted on a cylindrical laminated rotor. Calculations have been performed for different magnet widths and different distribution of the magnetization vector. Brushless motors with radially and inhomogeneously magnetized magnets have been compared.

The paper presents a method for the 3D edge element analysis of saturation effects in the classical rotating electrical machines of cylindrical structure. The edge element (EE) method using vector magnetic potential has been applied. Special attention is paid to the saturation effects in permanent magnet motors. In order to solve the non‐linear EE equations the authors propose to apply the modified Newton algorithm with block relaxation solver and Cholesky decomposition procedure for block matrices. The convergence of the algorithm is analysed. The influence of core non‐linearity on the values of electromagnetic torque and armature inductances is considered. The results for 3D and 2D models are compared.

Due to its high toxicity, monitoring of hydrogen sulfide (H2S) concentration is essential in many industrial sites (such as natural gas extraction sites, petroleum refineries, geothermal power plants, or waste water treatment facilities), which require sub-parts-per-million sensitivities. We report on a quantum cascade laser-based spectroscopic system for detection of H2S in the midinfrared at ∼7.2 μm. We present a sensor design utilizing Herriott multipass cell and a wavelength modulation spectroscopy to achieve a detection limit of 140 parts per billion for 1-s integration time.

This paper describes a structure of a typical actuator with magnetostrictive core. Based on equations of modified Jiles-Atherton model, algorithm and computer application for calculation of magnetomechanical hysteresis, distinctive for magnetostrictive transducers were developed. Furthermore, influence of compressive stress on maximum strain were presented.

Hydrogen sulfide (H2S) is a highly toxic gas that can be frequently found in the vicinity of industrial sites such as petroleum refineries, natural gas plants, or waste water treatment facilities. Its open-path detection with sensitivities at single ppm (parts-per-million) levels is critical for safety reasons. Laser-based H 2 S sensing typically relies on a quartz-enhanced photo-acoustic spectroscopy [1, 2] or methods that use high fineness cavities [3] providing minimum detection limits from few tens of ppm down to below 1 ppm. Unfortunately, both techniques are (in general) not suitable for open-path sensing, they require additional pumps, pressure controllers and sampling lines. Moreover, in both cases operation in a close-cell arrangement with reduced pressure helps to avoid interference from other atmospheric species (this can significantly alter the measurement results in open-path arrangements).