Miracle-dz/UniFAR-FTUs huggingface dataset:
Experimental Investigations of Clocking in a One and a Half Stage Transonic Turbine Using Laser-Doppler-Velocimetry and a Fast Response Aerodynamic Pressure Probe

The current paper presents experimental clocking investigations of the flow field in midspan in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine). Laser-Doppler-Velocimetry measurements were carried out in order to record rotor phase resolved velocity, flow angle and turbulence distributions upstream and downstream of the second vane row at several different vane-vane positions. Additionally, a fast response aerodynamic pressure probe was used to get the total pressure distribution downstream of the second vane row for the same positions. Altogether, the measurements were performed for ten different 1st vane to 2nd vane positions (clocking positions) for measurements downstream of the 2nd vane row and two different clocking positions for measurements upstream of the 2nd vane row. The paper shows that different clocking positions have a significant influence on the flow field downstream of the 2nd vane row. Furthermore different measurement lines upstream of the 2nd vane row indicate that clocking has nearly no influence on the flow field close to the rotor exit.Copyright © 2006 by ASME
Passive Q switching of a neodymium laser by a Cr4+ : YAG crystal switch

Theoretical and experimental investigations were made of passive Q switching of a neodymium laser by a Cr4+ : YAG switch. Analytic expressions were derived for estimating the output energy of the TEM00 mode of a passively Q-switched laser from the known parameters of the Cr4+ : YAG switch, of the active element, and of the cavity. The adopted description makes it possible to cover the range from generation of the first spike of a free-running transient to generation of a giant pulse. An experimental study was made of the dependence of the output energy on the cavity parameters, on the material of the active element (in this investigation it was Nd :YAG and Cr, Nd : GSGG), and on the angle of rotation of the Cr4+ : YAG switch. The experimental results obtained agreed to within 30% with calculations.
A system for monitoring of operational safety of ferromagnetic structures

- The paper presents a system for monitoring of operational safety of ferromagnetic structures used in civil engineering, machine construction and power engineering. The system is based on sensors of the residual magnetic field (RMFM) distribution. A change in values of individual components of the residual magnetic field informs in advance about the appearance of areas with a raised level of stresses or stress concentration zones and identifies micro cracks. The paper presents numerous examples of identification of hazard areas both in machine construction (forging press drive shafts) and in civil engineering (transporter crane steel structure). The information obtained from the system for monitoring of operational safety of ferromagnetic structures has already made it possible to take appropriate preventive measures to avert a major catastrophe.
Generation of "triggered single photons" from a coherently-pumped quantum dot

A deterministic "on demand" source of single photons is a basic building block for linear quantum computation \cite{linear}, quantum cryptography \cite{crypto}, quantum teleportation \cite{teleport}, and quantum networks \cite{network}. In all these applications, quantum interference between two single-photon pulses on a symmetric beam splitter has been exploited \cite{review}, which imposes stringent requirement for the implemented single photons to be indistinguishable in all degrees of freedom, including their frequencies, spectral widths, pulse shapes, and polarizations. To generate single photons one requires a pumping mechanism to excite a "two-level emitter" and an efficient channeling of the subsequently emitted photons. The efficiency of the source can be enhanced by coupling the emitter to the waveguide \cite{manga} or a microcavity mode \cite{cklaw}. However, hitherto the solid-state single photon sources realized by using a quantum dot coupled with a microcavity rely on incoherent pumping of excitons, which leads to problems with timing jitter \cite{kiraz}, leading to a trade off between efficiency and indistinguishability. Here we introduce a means to realize a highly efficient solid state source of indistinguishable single photons using cavity-assisted adiabatic Raman passage in a single quantum dot - cavity system. We demonstrate pulse-triggered single photons with 100% efficiency and $>90$% indistinguishability using currently available experimental parameters.
Temperature and luminosity of hot components in symbiotic stars.

The nature of the hot component in symbiotic binaries is still controversial. The existence of a hot radiative source is inferred from the presence of a photoionized nebula. The nebular spectrum points to typical radiation temperatures of T * ≃100 000 K. The bulk of the ionizing radiation is therefore emitted below 1200 A, the effective short end of IUE (International Ultraviolet Explorer). We set ourselves the task of deriving temperatures and luminosities for the hot component of a representative sample of symbiotic systems. For that purpose the Zanstra method is adapted to the special requirements of symbiotic stars. T * is basically derived by comparing the nebular recombination line HeII λ1640 with the underlying continuum.
Optimizing the final deformation of a circular plate illuminated by a short laser pulse

This paper discusses how to define the resulting maximal plastic deformation of a circular plate after it is exposed to excitation by a short laser pulse. Based on the temperature gradient mechanism model, the theoretical function of the resulting plastic plate deformation at the ambient temperature (final or permanent plate deformation) is found. In the first approximation, the final plate deformation is a parabolic function of the laser pulse energy, or respectively of the plasticity depth. It was found that the relationship between the plasticity depth and the plate deformation is almost insensitive to the laser pulse parameters or to variations in the plate characteristics, especially at the maximal plate deformation point. Only the ratio between the laser beam diameter and the plate thickness influences the position of plasticity depth relative to the plate thickness at the maximal plate deformation point, with the effect being rather small. A fair experimental confirmation of the behaviour of the theoretical function was obtained, and the approximate expression for calculating the resulting maximal plastic plate deformation is proposed.
Performance evaluation of software for the spectral analysis of speech signals in a MIPS based architecture

Speech recognition and algorithms for audio encoding/decoding are large and complex. Embedded systems tend to have limited resources, so in order to develop efficient speech analysis applications for these platforms, it is important to evaluate the performance of speech processing algorithms. This paper presents the performance evaluation of an application for speech signals analysis implemented in an embedded system based on the XBurst jz4740 processor, which has MIPS based instruction set architecture (ISA). Two versions of a speech signal analysis application were designed using two algorithms for the spectral data extraction: Fast Fourier Transform (FFT) and Linear Predictive Coding (LPC). The two versions were implemented in the embedded system. Finally, a performance evaluation of the two versions implemented on the embedded system is carried out, measuring the response time, memory footprint and throughput. The results show that the response time is less than 10 seconds for speech signals with less than 214 samples, and the memory footprint is less than 25% of the maximum capacity. For larger signals, the system reduces its performance and it reaches memory saturation for signals with around 216 samples.
On the response of a generic swirl flame to transverse planar acoustics

Heat release rate fluctuations are invariably generated at flames under the influence of acoustic and/or hydrodynamics fluctuations. At the same time, heat release rate fluctuations support acoustic fluctuations, such that, when flames are placed in a confined environment (as is usually the case in practical applications driven by combustion), a feedback loop may establish between heat release rate fluctuations and acoustic fluctuations corresponding to the acoustic resonance mode of the confinement. The associated large amplitude fluctuations (in heat release rate as well as pressure) are detrimental to the system and must, therefore, be avoided. Consequently, the stability limits of the combustor govern the operating envelope of the system. This envelope must, at the same time, be tuned to achieve low pollutant emissions. As an example, low NOx emissions can be achieved when running combustors in the lean premixed mode, where fuel-lean (or air-excess) reactant mixture is premixed before combustion. For this reason, lean premixed combustion was introduced in gas turbine combustors. Unfortunately, combustors are more susceptible to thermoacoustic instability when lean premixed flames are employed. For this reason, understanding, prediction, and mitigation of thermoacoustic instabilities has been a research involvement for engineers and researchers dealing with combustion, particularly in the last few decades, since the introduction of lean premixed combustion in gas turbine combustors. As the instability critically depends on the response of flames to perturbations, understanding flame response is key to understanding thermoacoustic coupling. This thesis falls under the category of investigations that focus on the study of the response of gaseous burner stabilized flames to acoustic forcing. In particular, the focus is the problem of thermoacoustic instability associated with a relatively recent development in gas turbine combustor configuration: annular combustion chambers. Existing information on flame response that is applicable to low frequency thermoacoustic instability is based on studies—experiments and numerical computations—dealing with acoustically-forced flames where the axis of propagation of planar acoustic waves is aligned with the burner axis. During thermoacoustic instability in annular combustors, individual flames experience a two-dimensional acoustic field, such that the flame is affected by acoustic fluctuations in
Constraining the minimum luminosity of high redshift galaxies through gravitational lensing

We simulate the effects of gravitational lensing on the source count of high redshift galaxies as projected to be observed by the Hubble Frontier Fields program and the James Webb Space Telescope (JWST) in the near future. Taking the mass density profile of the lensing object to be the singular isothermal sphere (SIS) or the Navarro-Frenk-White (NFW) profile, we model a lens residing at a redshift of zL = 0.5 and explore the radial dependence of the resulting magnification bias and its variability with the velocity dispersion of the lens, the photometric sensitivity of the instrument, the redshift of the background source population, and the intrinsic maximum absolute magnitude (Mmax) of the sources. We find that gravitational lensing enhances the number of galaxies with redshifts z≳ 13 detected in the angular region θE/2 ⩽ θ ⩽ 2θE (where θE is the Einstein angle) by a factor of ∼ 3 and 1.5 in the HUDF (df/dν0 ∼ 9 nJy) and medium-deep JWST surveys (df/dν0 ∼ 6 nJy). Furthermore, we find that even in cases where a negative magnification bias reduces the observed number count of background sources, the lensing effect improves the sensitivity of the count to the intrinsic faint-magnitude cut-off of the Schechter luminosity function. In a field centered on a strong lensing cluster, observations of z≳ 6 and z≳ 13 galaxies with JWST can be used to infer this cut-off magnitude for values as faint as Mmax ∼ -14.4 and -16.1 mag (Lmin ≈ 2.5 × 1026 and 1.2 × 1027 erg s−1 Hz−1) respectively, within the range bracketed by existing theoretical models. Gravitational lensing may therefore offer an effective way of constraining the low-luminosity cut-off of high-redshift galaxies.
Efficient FPGA‐based real‐time implementation of an SVPWM algorithm for a delta inverter

This study proposes an efficient field programmable gate array (FPGA) implementation method of an enhanced space vector pulse width modulation (SVPWM) algorithm for a delta inverter. The overall hardware configuration of the FPGA is made graphically using the high-level Xilinx system generator (XSG) programming tools. The proposed descriptive XSG model is first evaluated by running a hardware co-simulation test. The comparative study with computer simulations performed with Simulink shows a good agreement between the results of both methods, which approves the accuracy of the proposed descriptive XSG model. Moreover, an experimental test is carried out on a laboratory prototype of the delta inverter feeding an induction machine. The obtained high quality of the load currents confirms the feasibility of the proposed enhanced SVPWM algorithm and the effectiveness of its implementation method on FPGA.
Multirate Resonant Controllers for Grid-Connected Inverters With Harmonic Compensation Function

Resonant controller (RSC) is one of the most popular approaches for ac current/voltage control due to the high performance of zero steady-state tracking error. However, it suffers from heavy computational burden issue when multiple RSCs are demanded to control multiple harmonics. To alleviate this issue, a down-sampled multirate RSCs (MRRSCs) scheme is proposed for controlling power inverters, e.g., grid-connected inverters and active power filters. The proposed control scheme is composed of an inner control loop with a fast sampling rate, which is identical to the switching frequency, and an array of paralleled MRRSCs-based external control loop with a reduced sampling rate. With the reduced sample rate, the MRRSCs can be executed alternatively in the dq-frame, such that the computational burden can be significantly reduced per cycle. Moreover, to reinforce the wide frequency adaptability of the MRRSC, its central resonant frequency is online updated according to the output of the phase-locked loop. In the paper, the equivalent single-rate closed-loop model of the overall system is developed, based on which the controller parameters are designed employing the Nyquist diagram and root locus. Finally, experiments are performed on a grid-connected inverter to validate the superiority of the proposed scheme.
Validation and Application of Wind Profiler Measurements of Atmospheric Turbulence

This thesis focuses on the investigation of the reliability of turbulence measurements by radars when the spectral-width method is used. This method employs the spectral widths observed by radar (experimental spectral width) to determine turbulence. However, the experimental width can be a ected by non-turbulent e ects, including radar geometry. Therefore, the spectral width due to non-turbulent e ects (theoretical spectral width) must be removed from the experimental width. This can occasionally lead to negative values of turbulence. It is our aim (1) to study the e ects of both experimental and theoretical spectral widths on the accuracy of turbulence measurements, (2) to study the validity of negative values of turbulence, and (3) to compare radar-estimated values of turbulence with in-situ measurements. This is performed by studying the factors that can contribute to errors in estimation of spectral widths, including mean wind speed, wind shear, anisotropy and length of data. In addition to that, radar-estimated turbulence is compared to turbulence measured by high-resolution research and commercial aircraft. Signi cant ndings include: 1. The statistical uctuations of mean wind speed and its impact on estimation of the theoretical spectral width is the most important factor in producing errors in turbulence measurements. 2. The choice of spectrum tting algorithm and length of data is very important in producing experimental spectral widths. 3. In order to estimate theoretical widths more accurately, a formula is developed by comparing models that calculate the theoretical spectral width. 4. It is found that both negative and positive values of turbulence need to be included in turbulence analysis. However, if the percentage of negatives exceeds 35%, the measurements are not reliable. 5. Turbulence data measured by radar agrees well with high-resolution aircraft data for weak turbulence. However, in-situ aircraft measurements show a higher probability of strong turbulence than hourly radar data. 6. The theoretical spectral width is small compared to the experimental one for strong turbulence. By discarding the theoretical spectral widths in turbulence
Nuclear reaction uncertainties, massive gravitino decays and the cosmological lithium problem

We consider the effects of uncertainties in nuclear reaction rates on the cosmological constraints on the decays of unstable particles during or after Big-Bang nucleosynthesis (BBN). We identify the nuclear reactions due to non-thermal hadrons that are the most important in perturbing standard BBN, then quantify the uncertainties in these reactions and in the resulting light-element abundances. These results also indicate the key nuclear processes for which improved cross section data would allow different light-element abundances to be determined more accurately, thereby making possible more precise probes of BBN and evaluations of the cosmological constraints on unstable particles. Applying this analysis to models with unstable gravitinos decaying into neutralinos, we calculate the likelihood function for the light-element abundances measured currently, taking into account the current experimental errors in the determinations of the relevant nuclear reaction rates. We find a region of the gravitino mass and abundance in which the abundances of deuterium, 4He and 7Li may be fit with χ2 = 5.5, compared with χ2 = 31.7 if the effects of gravitino decays are unimportant. The best-fit solution is improved to χ2 ∼ 2.0 when the lithium abundance is taken from globular cluster data. Some such re-evaluation of the observed light-element abundances and/or nuclear reaction rates would be needed if this region of gravitino parameters is to provide a complete solution to the cosmological 7Li problem.
Stray field magnetic resonance imaging

Magnetic resonance imaging (MRI) is well known in a clinical context as a technique capable of delivering highly detailed anatomical images, particularly of soft tissue. The MRI method is completely non-invasive and allows spatial resolution down to a few micrometres in three dimensions. Image contrast is governed by one of several nuclear magnetic resonance parameters and might reflect water mobility, chemical potential, self-diffusion coefficient, coherent flow or temperature, depending upon the exact form of the MRI measurement. Less widely realized is the enormous potential for the use of MRI in materials science. The flexibility that makes MRI such a valuable clinical tool is equally applicable in a non-medical scenario, but the greater technical difficulties associated with MRI in solid materials have hitherto limited the development of the technique in this area. This review describes in detail one approach to MRI in solid materials which is currently benefiting from rapidly increasing application: stray field (magnetic resonance) imaging (STRAFI). An introduction to the phenomenon of nuclear magnetic resonance and particularly its detection in solids is followed by a description of the steps necessary for its use as an imaging modality. The limits of MRI spatial resolution in liquids and solids are briefly discussed. STRAFI is placed in context throughout this introduction. The STRAFI technique is then described in detail, in terms of its merits relative to other approaches to solids MRI and the subtleties of its implementation. The principal areas of current STRAFI application are reviewed and developments with which STRAFI advancement is closely linked, are also described. In conclusion, some consideration is given to the promising future of stray field MRI as a widely accepted research tool in materials science and to the development of the technique itself.
Condition Monitoring Sensor for Electric Vehicle Motor and Generator Insulation Systems

Electric vehicle (EV) motors are subject to extreme and variable loads, resulting in degradation of winding insulation due to high temperatures. This paper describes research on a new conductive composite sensor, which uses insulation resin as a matrix of the sensor element. The sensor, embedded in the windings of EV motors, will provide data on remaining design life of the insulation based on actual vehicle operational and environmental conditions. Improved condition monitoring of the insulation systems of high-performance EV motors can reduce in-use failures by identifying prematurely degraded insulation systems, and providing data for quality improvement programs.
A New Bridgeless High Step-up Voltage Gain PFC Converter with Reduced Conduction Losses and Low Voltage Stress

Bridgeless power factor correction (PFC) converters have a reduced number of semiconductors in the current flowing path, contributing to low conduction losses. In this paper, a new bridgeless high step-up voltage gain PFC converter is proposed, analyzed and validated for high voltage applications. Compared to its conventional counterpart, the input rectifier bridge in the proposed bridgeless PFC converter is completely eliminated. As a result, its conduction losses are reduced. Also, the current flowing through the power switches in the proposed bridgeless PFC converter is only half of the current flowing through the rectifier diodes in its conventional counterpart, therefore, the conduction losses can be further improved. Moreover, in the proposed bridgeless PFC converter, not only the voltage stress of power switches is lower than the output voltage, but the voltage stress of the output diodes is lower than the conventional counterpart. In addition, this proposed bridgeless PFC converter features a simple circuit structure and high PFC performance. Finally, the proposed bridgeless PFC converter is analyzed and designed in the discontinuous conduction mode (DCM). The simulation results are presented to verify the effectiveness of the proposed bridgeless PFC converter.
Design and Implementation of the Battery Energy Storage System in DC Micro-Grid Systems

The design and implementation of the battery energy storage system in DC micro-grid systems is demonstrated in this paper. The battery energy storage system (BESS) is an important part of a DC micro-grid because renewable energy generation sources are fluctuating. The BESS can provide energy while the renewable energy is absent in the DC micro-grid. The circuit topology of the proposed BESS will be introduced. The design of the voltage controller and the current controller for the battery charger/discharger are also illustrated. Finally, experimental results are provided to validate the performance of the BESS.