Sinusoidal Amplitude Research Articles

An auditory selective attention brain-computer interface system based on auditory steady-state response

Auditory steady-state response (ASSR) is a brain steady-state response induced by periodic sound signals, which can be used to build an auditory brain-computer interface (BCI), thereby providing a pathway for visually impaired patients to communicate with the outside world. Most of existing ASSR-based BCI studies use linear discriminant classifier (LDA) and spatial coherence to detect ASSRs. Therefore, there is an urgent need for efficient electroencephalogram (EEG) decoding methods to improve the performance of ASSR-based BCI systems. In this study, we elicited ASSRs using sinusoidal amplitude modulated (SAM) tones that simultaneously delivered different modulation frequencies (i.e., 37 Hz for the left channel and 43 Hz for the right channel). Subjects were asked to focus their attention on the auditory stimulation on one side according to the auditory cue. Filter bank common spatial pattern (FBCSP) algorithm was innovatively introduced to detect the ASSRs. Offline results showed that the brain region with strong ASSRs was the central forehead area, and when subjects paid attention to the auditory stimulation at 37 Hz or 43 Hz, the ASSR response of 37 Hz or 43 Hz on the corresponding side would be enhanced compared to the no attention condition. Online results obtained from twelve healthy subjects showed that the mean recognition accuracy of the proposed ASSR-based BCI system achieved a mean accuracy of 82.22 ± 3.11 %. Moreover, the present study further verified that weak auditory stimuli with low stimulus intensity (i.e., 40 dB SPL) could also be used to build ASSR-based BCIs, and achieved an online mean accuracy of 78.89 ± 2.54 %. These results verified that the FBCSP algorithm could be used for detecting ASSRs and the feasibility of the proposed ASSR-based BCI system, providing a great idea for building a high-speed ASSR-based BCI system.

GEL POLYMER ELECTROLYTES ELABORATED BY UV-IRRADIATION FOR THE ECO-DESIGN OF LI-ION BATTERIES

This study examines the chemical, thermal, and dielectric properties of gel polymer electrolytes (GPEs) based on poly(ethylene glycol) diacrylate (PEGDA, average Mn=700 g/mol). GPEs were synthesized via a single-step UV-irradiation process, whereby PEGDA was mixed with varying concentrations of a commercial liquid electrolyte (1 M LiPF6 in EC/DEC 50/50 v/v) ranging from 0 to 60 wt%. The results of the infrared analysis indicated that the liquid electrolyte was successfully immobilized within the polymeric matrix. The thermally stable nature of the synthesized GPEs was confirmed across a wide temperature range (-40 to 90°C) through thermal analysis. Furthermore, dielectric measurements were conducted in a frequency range of 0.1 to 106 Hz, with a sinusoidal AC amplitude of 10 mV, from 20 to 100°C. The results demonstrated that the ionic conductivity of GPEs increased with the addition of liquid electrolyte. The GPEs prepared with 60 wt% liquid electrolyte exhibited a conductivity value of approximately 6.6x10-3 S/m at 30°C, which is consistent with the conductivity range reported in the literature.

Hierarchical differences in the encoding of amplitude modulation in the subcortical auditory system of awake nonhuman primates.

Sinusoidal amplitude modulation (SAM) is a key feature of complex sounds. Although psychophysical studies have characterized SAM perception, and neurophysiological studies in anesthetized animals report a transformation from the cochlear nucleus' (CN; brainstem) temporal code to the inferior colliculus' (IC; midbrain's) rate code, none have used awake animals or nonhuman primates to compare CN and IC's coding strategies to modulation-frequency perception. To address this, we recorded single-unit responses and compared derived neurometric measures in the CN and IC to psychometric measures of modulation frequency (MF) discrimination in macaques. IC and CN neurons often exhibited tuned responses to SAM in rate and spike-timing measures of modulation coding. Neurometric thresholds spanned a large range (2-200 Hz ΔMF). The lowest 40% of IC thresholds were less than or equal to psychometric thresholds, regardless of which code was used, whereas CN thresholds were greater than psychometric thresholds. Discrimination at 10-20 Hz could be explained by indiscriminately pooling 30 units in either structure, whereas discrimination at higher MFs was best explained by more selective pooling. This suggests that pooled CN activity was sufficient for AM discrimination. Psychometric and neurometric thresholds decreased as stimulus duration increased, but IC and CN thresholds were higher and more variable than behavior at short durations. This slower subcortical temporal integration compared with behavior was consistent with a drift diffusion model that reproduced individual differences in performance and can constrain future neurophysiological studies of temporal integration. These measures provide an account of AM perception at the neurophysiological, computational, and behavioral levels.NEW & NOTEWORTHY In everyday environments, the brain is tasked with extracting information from sound envelopes, which involves both sensory encoding and perceptual decision-making. Different neural codes for envelope representation have been characterized in midbrain and cortex, but studies of brainstem nuclei such as the cochlear nucleus (CN) have usually been conducted under anesthesia in nonprimate species. Here, we found that subcortical activity in awake monkeys and a biologically plausible perceptual decision-making model accounted for sound envelope discrimination behavior.

High modulation efficiency sinusoidal vertical PN junction phase shifter in silicon-on-insulator

In this paper, a sinusoidal vertical PN junction phase shifter on a silicon waveguide is designed, and the results demonstrate that modifying the shape of the PN junction significantly increases the area of the depletion region within the standard waveguide width of 500 nm, thereby enhancing the overlap between the depletion region and optical waveguide modes under reverse bias conditions. Furthermore, by adjusting the sinusoidal amplitude (A) of the doping contact interface, it is observed that when A=0.065µm, the resulting sinusoidal PN junction most effectively enhances the interaction between carriers and photons, leading to the highest modulation efficiency and the lowest loss. Based on this, further adjustment of the doping concentration distribution in the waveguide was conducted using a doping compensation method. It is observed that setting the doping concentration at 3×1018cm−3 in the heavily doped region and at 1×1018cm−3 in the lightly doped region enables the phase shifter to achieve high modulation efficiency while maintaining low loss. This is attributed to the highest optical intensity being concentrated in the central region of the waveguide, as well as to the positive correlation between doping concentration and modulation efficiency. The final designed device with a length of 1.5 mm successfully attained a low V π L of 0.58V⋅cm, resulting in high modulation efficiency. By employing traveling wave electrodes and ensuring that the effective refractive index of the radio frequency (RF) matches the optical group index (OGI), circuit-level simulations were conducted. The device exhibited a 3 dB bandwidth of 8.85 GHz and eye diagrams of up to 40 Gbit/s, with a maximum extinction ratio (ER) of 8.27 dB and a bit error rate (BER) of 8.83×10−6, which can be widely used in the field of high-speed silicon optical modules.

Solving dynamic electric circuit with nonlinear hysteretic inductor using harmonics interpolation method

SummaryThe aim of this paper is to present a methodology for solving а dynamic electric circuit with nonlinear hysteretic inductor without the use of hysteresis model or equivalent circuits. A consideration of nonlinear and hysteretic behaviour of the magnetic core under quasistatic conditions is based on applying harmonics interpolation method (HIM) to the measured magnetising field strength waveforms. A dynamic behaviour of the magnetic core is considered through the application of the statistical theory of losses (STL). A considered electric circuit consists of AC voltage source connected in series with shunt resistor, additional linear resistor and inductor, as well as a nonlinear hysteretic inductor. The solution for electric current of the circuit is obtained by solving equation derived from Kirchhoff's laws through a series of successive iterations. Coupling of electric and magnetic part of the circuit is obtained from fundamental laws of electromagnetism. Methodology is validated for four cases of the considered electric circuit — without additional elements, with one additional or both additional elements, for sinusoidal voltage source amplitudes of 2, 4, 6, 8 and 9 V and frequency of 50 Hz. Validation is repeated for frequencies of 100, 200 and 300 Hz while keeping the ratio of the amplitude to frequency constant. Detailed theoretical approach and methodology, comparisons between measured and calculated results, as well as adequate discussion are presented.

The impact of spectral and temporal processing on speech recognition in children with cochlear implants

While the relationships between spectral resolution, temporal resolution, and speech recognition are well defined in adults with cochlear implants (CIs), they are not well defined for prelingually deafened children with CIs, for whom language development is ongoing. This cross-sectional study aimed to better characterize these relationships in a large cohort of prelingually deafened children with CIs (N = 47; mean age = 8.33 years) by comprehensively measuring spectral resolution thresholds (measured via spectral modulation detection), temporal resolution thresholds (measured via sinusoidal amplitude modulation detection), and speech recognition (measured via monosyllabic word recognition, vowel recognition, and sentence recognition in noise via both fixed signal-to-noise ratio (SNR) and adaptively varied SNR). Results indicated that neither spectral or temporal resolution were significantly correlated with speech recognition in quiet or noise for children with CIs. Both age and CI experience had a moderate effect on spectral resolution, with significant effects for spectral modulation detection at a modulation rate of 0.5 cyc/oct, suggesting spectral resolution may improve with maturation. Thus, it is possible we may see an emerging relationship between spectral resolution and speech perception over time for children with CIs. While further investigation into this relationship is warranted, these findings demonstrate the need for new investigations to uncover ways of improving spectral resolution for children with CIs.

Numerical analysis of the effect of wave amplitude on thermohydraulic performance in a heat exchanger with sinusoidal wavy channels

With the increasing application of heat exchangers, the research has become increasingly comprehensive. Previous studies mainly focused on comparing the amplitudes to investigate the performance of heat exchangers, while the study of variable amplitude channel structures was limited. This study investigated the thermal-hydraulic performance of seven different sinusoidal channels with inclination angles of 20° and 30°, and their combinations. Using the CFD solver, simulations were conducted to assess the heat transfer capabilities of sinusoidal channels under various Reynolds numbers and different amplitude conditions, compared to straight channels and single amplitude sinusoidal channels. The results indicated that within one period, both the pressure drop and temperature difference exhibited a ripple trend of gradually decreasing amplitude. When evaluating the comprehensive performance of the channels, three trends emerged across the seven models, with the performance of the cold fluid and the hot fluid within the same group showing opposite trends. This suggested that more variations could enhance the overall performance of the hot fluid while reducing the performance of the cold fluid. For structures with the same amplitude, in terms of amplitude variation frequency, models with six periods per group exhibited higher overall heat transfer performance than those with three periods per group, with an average increase of 36.37%. For the arrangement of amplitudes (taking the hot fluid inlet as an example), configurations with a smaller amplitude at the inlet outperformed those with a larger amplitude, indicating that in combined amplitude models, a structure with a larger group and a smaller amplitude at the inlet (taking the hot fluid as an example) should be designed.

Impact of specific electromagnetic radiation on wakefulness in mice

Electromagnetic radiation (EMR) in the environment, particularly in the microwave range, may constitute a public health concern. Exposure to 2.4 GHz EMR modulated by 100 Hz square pulses was recently reported to markedly increase wakefulness in mice. Here, we demonstrate that a similar wakefulness increase can be induced by the modulation frequency of 1,000 Hz, but not 10 Hz. In contrast to the carrier frequency of 2.4 GHz, 935 MHz EMR of the same power density has little impact on wakefulness irrespective of modulation frequency. Notably, the replacement of the 100 Hz square-pulsed modulation by sinusoidal-pulsed modulation of 2.4 GHz EMR still allows a marked increase of wakefulness. In contrast, continuous sinusoidal amplitude modulation of 100 Hz with the same time-averaged power output fails to trigger any detectable change of wakefulness. Therefore, alteration of sleep behavior by EMR depends upon not just carrier frequency but also frequency and mode of the modulation. These results implicate biological sensing mechanisms for specific EMR in animals.

Salinity gradient power generation in sinusoidal nanochannels

Salinity gradient power generation based on nanochannels has drawn much attention for its green and sustainable advantages. However, previous studies have tended to focus on regularly shaped nanochannels, while rough and irregular surfaces are naturally formed during the preparation of nanochannels (similar to sinusoidal nanochannels). In this paper, a model of salinity gradient energy conversion in sinusoidal nanochannels is established. The impacts of the geometrical parameter dimensions of the sinusoidal channel (including initial phase, channel length, average radius, amplitude, and angular frequency) on the power generation performance under different salinity gradients are systematically investigated. The results show that the sinusoidal nanochannel has better salinity gradient power generation performance than cylindrical nanochannel. It obtains the best power generation performance when the initial phase is zero. Besides, increasing the nanochannel length facilitates ion selectivity and energy conversion efficiency. At high concentration difference, decreasing the average radius or increasing the amplitude help increase the maximum output power and enhance the energy conversion efficiency. The maximum output power of about 1.27 pW and energy conversion efficiency of about 32.8% were obtained by optimizing the sinusoidal channel amplitudes. It is also found that increasing the angular frequency is favorable to improving energy conversion performance at the high concentration difference. These results provide helpful information for designing and optimizing salinity gradient energy conversion systems.

SAM-SFM: High-Efficiency and High-Resolution Tandem Mass Spectrometry Enabled by Sinusoidal Amplitude Modulation of Multiple Sinusoidal Frequency-Modulated Waveforms.

In miniature ion trap mass spectrometry, achieving a balance between isolation resolution and efficiency is a formidable challenge. The presence of absorption curves causes target ions to inadvertently absorb energy from AC signal components near their resonant frequencies. To mitigate this issue, SAM-SFM waveforms introduce a parameter known as the decreasing factor. Unlike SWIFT waveforms, SAM-SFM's spectral profile intentionally departs from a rectangular window, adopting an arch-shaped excitation window to minimize the impact on target ions and improve ion isolation efficiency. SAM-SFM waveforms have the advantage of low computational complexity, enabling real-time computation using an embedded FPGA technology. Regardless of any parameter changes, the FPGA can consistently guarantee waveform output within 1 μs. This not only enhances throughput but also eliminates the need for a PC in miniature mass spectrometry devices. The performance of SAM-SFM has been validated on an improved "Brick" miniature ion trap mass spectrometer. Comparative experiments with SWIFT waveforms confirm the lossless unit-mass isolation capabilities of SAM-SFM. This waveform has the capability to simultaneously isolate multiple target ions, even allowing for the lossless isolation of ions with lower abundance within isotopic clusters, albeit at the cost of requiring extended isolation durations.

Energetics of sinusoidal exercise below and across critical power and the effects of fatigue

PurposePrevious studies investigating sinusoidal exercise were not devoted to an analysis of its energetics and of the effects of fatigue. We aimed to determine the contribution of aerobic and anaerobic lactic metabolism to the energy balance and investigate the fatigue effects on the cardiorespiratory and metabolic responses to sinusoidal protocols, across and below critical power (CP).MethodsEight males (26.6 ± 6.2 years; 75.6 ± 8.7 kg; maximum oxygen uptake 52.8 ± 7.9 ml·min−1·kg−1; CP 218 ± 13 W) underwent exhausting sinusoidal cycloergometric exercises, with sinusoid midpoint (MP) at CP (CPex) and 50 W below CP (CP-50ex). Sinusoid amplitude (AMP) and period were 50 W and 4 min, respectively. MP, AMP, and time-delay (tD) between mechanical and metabolic signals of expiratory ventilation (V˙E\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{V}}_{E}$$\\end{document}), oxygen uptake (V˙O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{V}}_{{{\ ext{O}}}_{2}}$$\\end{document}), and heart rate (fH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${f}_{H}$$\\end{document}) were assessed sinusoid-by-sinusoid. Blood lactate ([La−]) and rate of perceived exertion (RPE) were determined at each sinusoid.ResultsV˙O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{V}}_{{{\ ext{O}}}_{2}}$$\\end{document} AMP was 304 ± 11 and 488 ± 36 ml·min−1 in CPex and CP-50ex, respectively. Asymmetries between rising and declining sinusoid phases occurred in CPex (36.1 ± 7.7 vs. 41.4 ± 9.7 s for V˙O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{V}}_{{{\ ext{O}}}_{2}}$$\\end{document}tD up and tD down, respectively; P < 0.01), with unchanged tDs. V˙O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{V}}_{{{\ ext{O}}}_{2}}$$\\end{document} MP and RPE increased progressively during CPex. [La−] increased by 2.1 mM in CPex but remained stable during CP-50ex. Anaerobic contribution was larger in CPex than CP-50ex.ConclusionThe lower aerobic component during CPex than CP-50ex associated with lactate accumulation explained lower V˙O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{V}}_{{{\ ext{O}}}_{2}}$$\\end{document} AMP in CPex. The asymmetries in CPex suggest progressive decline of muscle phosphocreatine concentration, leading to fatigue, as witnessed by RPE.

Enhancing melting and solidification characteristics of a triple-pipe latent heat energy storage system via a wavy central wall with a sinusoidal fixed wavelength

This study aims to improve the melting and solidification characteristics of a triple-pipe heat storage unit by introducing a wavy middle plate with a sinusoidal fixed wavelength. The inner and outer tubes facilitate the flow of heat transfer fluids (HTFs), while the middle tube houses the phase change material (PCM). Various scenarios are examined to gauge the impact of the wavy central wall on the PCM's phase change performance, comparing liquid fraction and mean temperatures with cases featuring a straight middle plate. The primary goal is to pinpoint the optimal scenario with the shortest discharging/charging times and the highest rates of heat release/storage. The investigation commences by assessing the effects of middle wall thickness (2, 4, 6, and 8 mm) on the PCM's phase change characteristics, comparing liquid fraction and mean temperature with a straight middle plate. Subsequently, the influence of various sinusoidal wavelengths (250, 125, 50, and 25 mm) on both melting and solidification performances of the PCM is numerically examined to identify the optimum case. The research also delves into the effects of various sinusoidal amplitudes (2.5, 5.0, 7.5, and 10 mm) on the PCM's phase change process. In the final step, the capability of the wavy middle plate, with various phase shifts (0°, 90°, 180°, and 270°), in improving the PCM's phase change characteristics is analyzed. Numerical results highlight that, among the tested scenarios, the configuration with a 5 mm amplitude and a 25 mm wavelength (A5λ250) exhibits outstanding performance during both melting and solidification phases. A5λ250 showcases a 19.92 % reduction in melting time and a 2.44 % reduction in solidification time compared to other cases, coupled with a 22.55 % improvement in heat storage and a 3.48 % enhancement in heat release. However, introducing a phase shift in the melting process adversely affects system performance. Conversely, adjusting the phase shift of A5λ25 to 270° leads to enhancements in both solidification time and heat release rate. Specifically, solidification time improves by 0.86 %, and the rate of heat release increases by 0.66 W compared to A5λ25–0.

A NEW ROUGH FRACTURE PERMEABILITY MODEL OF COAL WITH INJECTED WATER BASED ON DAMAGED TREE-LIKE BRANCHING NETWORK

The fracture network structure of coal is very complex, and it has always been a hot issue to characterize the fracture network structure of coal by using a tree-like branching network. In this paper, a new rough fracture permeability model of water injection coal based on a damaged tree-like branching network is proposed. In this model, fractal theory and sine wave model are used to characterize the rough characteristics of fracture structure. In addition, the applicability of the model is verified by the self-developed experimental system, and the sensitivity analysis and weight analysis of the influencing factors in the model are carried out. The results show that the factors affecting the permeability of the established permeability mathematical model are mainly the amplitude factors of sinusoidal fluctuation, length ratio, maximum branch series, number of damaged fractures, opening ratio, opening fractal dimension and initial fracture length. Among them, the sinusoidal fluctuation amplitude factor has the greatest influence on the permeability and the other two are inversely proportional. Therefore, with pulsating water injection, the frequency of changes in the water pressure was altered to improve the water injection efficiency in coal fractures with sinusoidal distribution to increase permeability. The research results provide a theoretical basis for further improving the theoretical models for seepage in porous media and fluid flow analysis of damaged tree-like branching networks.

Development of the error reducing method for the determination of the alternating current amplitude without the use of current transformers

The object of the research is methods of current amplitude identification without using current transformers. Most solutions are built on reed switches, which have a limitation of the operation speed due to the mechanical nature of the reed contacts. Therefore, the time duration is a random variable with a significant variation. Thus, the problem that needs to be solved is the reduction of the error of current amplitude identification associated with the mechanical properties of contacts. According to the conducted literature analysis, the presence of contact bounce of reed switches increases the errors of sinusoidal current amplitude identification approximately up to 8–10 %. The mathematical modeling allowed us to investigate this phenomenon and research its influence on the method. The suggested model was then approved via in-situ modeling. Consequently, to reduce the errors of measuring the current amplitude via a reed switch, the replacement with an analog or discrete Hall sensor was proposed. A mathematical model of the discrete Hall sensor operation and a method for identifying the amplitude of the alternating current were developed. During the experiment, it was found that the analog Hall sensor has a limitation in measuring currents of large rates, at which the discrete sensor worked stably. Hence, the last was chosen. It is worth noting that the study of the behavior of the Hall sensor was limited to the value of the alternating current amplitude, four times the opening current with an average error of less than 3 %. The method suitable for discrete Hall sensors simplifies and reduces the cost of the measuring instrument design. However, the practical implementation of the suggested method requires also the application of devices concentrating the magnetic field on the Hall sensor surface

Precision of the transfer function estimation of analog to digital converters in the presence of additive noise

Analog-to-digital converters are essential components in modern systems which gather data from the real world to be used, after signal processing, in many ubiquitous applications. This work addresses the effect of the presence of additive noise in the test setup when characterizing these electronic devices using the Histogram Test method. The precision with which the converter transfer function is estimated is directly related to the amount of noise present, the number of data samples acquired and the sinusoidal stimulus signal amplitude. Here an analytical expression that quantifies this precision as a function of the test parameters is given to be used by the engineer when designing the test.

An in-depth study on melting performance of latent heat thermal energy storage system under rotation mechanism by fluctuating heat source

The Organic Rankine Cycle (ORC) is a reliable and efficient means of converting solar energy into electricity. The challenges brought about by the unpredictable nature of solar energy can be effectively mitigated by utilizing latent heat thermal energy storage (LHTES) technology, specifically by implementing heat source pretreatment. This paper investigates the thermal storage properties of a rotating triplex-tube LHTES unit under different sinusoidal fluctuating heat sources. A transient numerical model is built to analyze the effects of sinusoidal wall temperature amplitude and angular velocity on the melting characteristics of the unit, including melting time, heat storage rate, and temperature response. The design is further analyzed using the Taguchi method. The results show that the angular velocity of the sinusoidal wall temperature has a greater effect on the average heat storage rate and melting time than the amplitude. When the amplitude is set to 10 and the angular velocity to 0.02, the melting time is decreased by 8.7%, while the average heat absorption rate and average temperature response increase by 10.21% and 12.27%, respectively. Additionally, the sensible and total heat energy absorption increase by 2.23% and 0.62%, compared to the initial heat source condition. Furthermore, the heat transfer is enhanced through the introduction of Al2O3 nanoparticles at varying percentages. The unit heat storage rate improves significantly with an increasing percentage of nanoparticles. Specifically, when 2.5% and 5% Al2O3 nanoparticles are added, the melting time of the unit is reduced by 3.77% and 15.07%, respectively, while the average heat absorption rate increases by 2.43% and 10.39%.

Modified Adaptive Filter Based UPQC for Battery Supported Hydro Driven PMSG System

The standalone three phase system for power quality improvement of both the load side voltages as well as the currents of the machine terminal is presented in this paper. This standalone system consists of a three-phase permanent magnet synchronous generator (PMSG) driven by governor-less hydro turbine as a three-phase source feeding the sensitive/non-linear/linear loads, connected via a unified power quality conditioner (UPQC). The UPQC consists of a back-to-back connected voltage source converters (VSCs) sharing a common DC bus. The series compensator of the UPQC is used to eliminate voltage power quality (PQ) and to maintain the sinusoidal, balanced, and constant amplitude voltages at load terminals irrespective of any variation in the system. Moreover, the current quality such as reactive power compensation, harmonics elimination, etc. are provided by the shunt compensator of the UPQC, simultaneously while improving voltage quality issues. In addition, the efficiency of the overall system is significantly improved by running the generator below its rated voltage and reduces the losses by operating at unity pf. The system frequency and the generated voltage magnitudes are maintained during any load fluctuation or imbalance loading. The model of the UPQC based hydro turbine driven PMSG system is developed in the Simulink-MATLAB environment, and its results are presented for analysis. The validation of the system is also done on the hardware prototype, and it performs effectively for the voltage and current PQ enhancement simultaneously. It significantly improves the PQs at the generator terminals and ensures to adhere the IEC-61727 and the IEEE-519 standards even with either balanced or unbalanced loads.

Mixed Convection in a Square Cavity Filled with Porous Medium with Bottom Wall Periodic Boundary Condition

Transient mixed convection heat transfer in a confined porous medium heated at periodic sinusoidal heat flux is investigated numerically in the present paper. The Poisson-type pressure equation, resulted from the substituting of the momentum Darcy equation in the continuity equation, was discretized by using finite volume technique. The energy equation was solved by a fully implicit control volume-based finite difference formulation for the diffusion terms with the use of the quadratic upstream interpolation for convective kinetics scheme to discretize the convective terms and the temperature values at the control volume faces. The numerical study covers a range of the hydrostatic pressure sinusoidal amplitude range and time period values of . Numerical results show that the pressure contours lines are influenced by hydrostatic head variation and not affected with the sinusoidal amplitude and time period variation. It is found that the average Nusselt number decreases with time and pressure head increasing and decreases periodically with time and amplitude increasing. The time averaged Nusselt number decreases with imposed sinusoidal amplitude and cycle time period increasing.

Gaussian beam diffraction from radial structures: detailed study on the diffraction from sinusoidal amplitude radial gratings.

In this work, we report a comprehensive theoretical investigation on the diffraction of a Gaussian beam from structured radial apertures. In particular, the study of near- and far-field diffraction of a Gaussian beam from an amplitude radial grating having a sinusoidal profile provides new theoretical insights and possible applications. We observe a high self-healing feature at far-field for the Gaussian beam in the diffraction from amplitude radial structures. It is also shown that by increasing the spokes number of the grating, the strength of the self-healing decreases, and reforming of the diffracted pattern into a Gaussian beam occurs at longer propagation distances. The energy flow towards the central lobe of the diffraction pattern and its dependence on the propagation distance are also investigated. In the near-field regime, the diffraction pattern is very similar to the intensity distribution in the central area of the radial carpet beams generated in the diffraction of a plane wave from the same grating. It is shown that by optimally choosing the waist radius of the Gaussian beam, in the near-field regime, it is possible to have a petal-like diffraction pattern, which has been experimentally used in multiple-particle trapping. Compared to radial carpet beams, since in this case there is no energy in the geometric shadow of the radial spokes of the grating, the main part of the power of the incident Gaussian beam is transferred to the main intensity spots of the petal-like pattern, which significantly increases the multi-particle trapping efficiency. We also show that regardless of the grating spokes number, at the far field, the diffraction pattern becomes a Gaussian beam, and its power share reaches 2/3 of the total power passed through the grating.

Tracking control of a piezo-actuated compliant mechanism based on an improved Bouc–Wen hysteresis model with variable parameters

To deal with the challenges that the classical Bouc–Wen model fails to precisely characterize amplitude-dependent hysteresis and asymmetric hysteresis, an improved Bouc–Wen model with variable parameters is presented. The proposed model introduces asymmetric terms and parameter functions related to sinusoidal excitation amplitudes into the classical Bouc–Wen model. It has a relatively simple mathematic form and can be easily identified and applied for inverse feedforward compensation in real-time applications. By comparison with the classical Bouc–Wen model and other existing hysteresis models, the superiority of the proposed model has been verified. Furthermore, inverse hysteresis control and hybrid control combining the developed inverse control and proportional-integral feedback control are proposed. Several comparative experiments are conducted on a piezo-actuated micro-scanner. Results demonstrate that inverse control and hybrid control using the improved Bouc–Wen model with variable parameters can achieve better tracking performance and are meaningful in actual trajectory-tracking applications.