Modulation Ratio Research Articles

The integration of diverse fluorescence performances of Sr2−xSnO4:xSm3+ ceramics with an infinite luminescence modulation ratio

Reversible luminescence modification has received considerable interest due to its potential applications in optical storage technology and high-sensitivity optical switches. However, there is no any report that multi-mode luminescence modification behavior can be achieved in one material so far. In this study, a novel multifunctional luminescence phosphor Sr2−xSnO4:xSm3+ has been developed. Photoluminescence, photoluminescence modulation associated with the photochromism reaction, photo-stimulated luminescence, thermoluminescence are realized in one single ceramic material Sr2−xSnO4:xSm3+. The optimized photoluminescence modulation ratio based on the photochromism reaction reaches 72.2%. Based on the photo-stimulated luminescence, the photoluminescence modulation ratio reaches an infinite value ∞, which provides a different approach for optical storage and can avoid the bit error in information storage. In addition, the mechanisms of photoluminescence modulation, photo-stimulated luminescence, thermoluminescence are analyzed. The diverse luminescence properties in Sr2−xSnO4:xSm3+ are tightly related to the formed defects induced by Sm3+ doping. The high integration level for fluorescence performances can widen the application of activator-doped oxides.

MODULATION OPTICAL DISTANCE GAUGE WITH PHASE-FREQUENCY SIGNAL CONVERSION

Problems. Optical distance meters allow measurements of distances to various probing objects. One of the problems is to provide high-resolution, precision and resolution of light-range finders. Therefore, research and improvement of these parameters is relevant.The purpose of the research. Expanding the limits of measuring distances, accuracy and resolution of the light rangefinder.Implementation method. An algorithm for selecting the modulation frequency and its relationship with the quantization frequencies has been developed, which provides a phase relationship between the periods (and in the final state between the phase relationships) of the modulation and quantization frequencies and the selected phase interval. A single quartz oscillator was used to increase the stability of the luminous flux modulation frequency, the reference frequency and the quantization frequencies of the selected information phase interval. The function of structural adjustment of the electronic scale with change of its weight that allows to increase accuracy and resolution of the meter is entered. The possibility of digital signal processing (integration, determination of the average level, mathematical processing and selection of information on the measured distance) to reduce noise effects, increase the stability of signal parameters and accuracy of its measurement. Keywords: modulation light rangefinder, distance, phase-frequency conversion, quantization frequency, measurement accuracy, resolution.Conclusions. The proposed algorithm for choosing the ratio of frequency modulation and quantization frequencies can improve the accuracy and resolution of distance measurement, due to the possibility of changing the quantization frequency and the weight of the electronic scale. The introduction of digital signal processing and the integration of the dedicated phase-frequency range increases the resistance of the meter to the noise effects of the external environment and the configuration of the object of study on the parameters of the light flux.

Investigation Into Periodic Signal-Based Dithering Modulations for Suppression Sideband Vibro-Acoustics in PMSM Used by Electric Vehicles

This paper presents an investigation into sideband vibro-acoustics suppression of the permanent magnet synchronous motor (PMSM), associated with several periodic signal-based dithering modulations. Mathematical derivations of four typical periodic signal-based schemes are deduced with the power spectral density (PSD) method. The individual modulation parameters, such as bandwidth and modulation ratio, are determined the values to minimize the sideband vibro-acoustics. The frequency distributions of the sideband components are discussed by the analytical derivations. The relationship between the electromagnetic components and mechanical responses is reconstructed by coupling with temporal features. For verification, the experimental tests with a prototype PMSM are introduced under different operational conditions. According to the results and figures, both magnitude suppression and frequency distribution are accurately correlated with sideband harmonic components as well as vibro-acoustic responses. This investigation thus clearly holds promise for the evaluation and optimization in powertrain used by electric vehicles.

Photonic generation of frequency-quadrupled triangular waveform based on a DP-QPSK modulator with tunable modulation index

In this paper, a scheme for generating frequency-quadrupled triangular waveform based on a dual-polarization quadrature phase-shift-keying (DP-QPSK) modulator is proposed. The repetition rate of the generated triangular waveform is four times the frequency of radio frequency (RF) signal. In this scheme, the modulation index of modulator is no longer a fixed value, and it can be adjusted in a certain range, which increases the flexibility of the scheme. Compared with previous frequency-quadrupled triangular waveform generation schemes, the structure of this scheme is simple, and the scheme enables good repetition rate tunability. The effect of extinction ratio and DC bias drift of modulator on the scheme is analyzed by simulation.

A Genetic Algorithm Approach as a Self-Learning and Optimization Tool for PV Power Simulation and Digital Twinning

A key aspect for achieving a high-accuracy Photovoltaic (PV) power simulation, and reliable digital twins, is a detailed description of the PV system itself. However, such information is not always accurate, complete, or even available. This work presents a novel approach to learn features of unknown PV systems or subsystems using genetic algorithm optimization. Based on measured PV power, this approach learns and optimizes seven PV system parameters: nominal power, tilt and azimuth angles, albedo, irradiance and temperature dependency, and the ratio of nominal module to nominal inverter power (DC/AC ratio). By optimizing these parameters, we create a digital twin that accurately reflects the actual properties and behaviors of the unknown PV systems or subsystems. To develop this approach, on-site measured power, ambient temperature, and satellite-derived irradiance of a PV system located in south-west Germany are used. The approach proposed here achieves a mean bias error of about 10% for nominal power, 3° for azimuth and tilt angles, between 0.01%/C and 0.09%/C for temperature coefficient, and now-casts with an accuracy of around 6%. In summary, we present a new solution to parametrize and simulate PV systems accurately with limited or no previous knowledge of their properties and features.

Ultrafast Control of Microlasers

All-optical switching faces new requirements for next-generation optical and quantum computing, which put a premium on low energy consumption, high speed, strong modulation ratios and high-density integration. These requirements can pose severe design challenges. Recently, we have demonstrated an alternative approach to all-optical switching design, based on the physics of topologically protected optical bound states in the continuum, that can break some of these challenges.

Trend Tracking of Efficiency and CTM Ratio of PV Modules

Trend Tracking of Efficiency and CTM Ratio of PV Modules

Electron transport in iodide-capped core@shell PbTe@PbS colloidal nanocrystal solids

Research in the field of colloidal semiconductor nanocrystals (NCs) has progressed tremendously, mostly because of their exceptional optoelectronic properties. Core@shell NCs, in which one or more inorganic layers overcoat individual NCs, recently received significant attention due to their remarkable optical characteristics. Reduced Auger recombination, suppressed blinking, and enhanced carrier multiplication are among the merits of core@shell NCs. Despite their importance in device development, the influence of the shell and the surface modification of the core@shell NC assemblies on the charge carrier transport remains a pertinent research objective. Type-II PbTe@PbS core@shell NCs, in which exclusive electron transport was demonstrated, still exhibit instability of their electron transport. Here, we demonstrate the enhancement of electron transport and stability in PbTe@PbS core@shell NC assemblies using iodide as a surface passivating ligand. The combination of the PbS shelling and the use of the iodide ligand contributes to the addition of one mobile electron for each core@shell NC. Furthermore, both electron mobility and on/off current modulation ratio values of the core@shell NC field-effect transistor are steady with the usage of iodide. Excellent stability in these exclusively electron-transporting core@shell NCs paves the way for their utilization in electronic devices.

All-optical integrated 2-to-4 decoder and 1-to-4 demultiplexer circuit with enable using SOA based MZI

Abstract In this paper, we propose an all-optical integrated 2-to-4 decoder and a 1-to-4 demultiplexer circuit using SOA based MZI (Mach–Zehnder Interferometer) architecture. The proposed device has been applied an enable signal along with two data input signals at the same wavelength. Four output signals from 2-to-4 decoder and 1-to-4 demultiplexer have been attained at the same wavelength. The output timing diagrams of 2-to-4 decoder and 1-to-4 demultiplexer for different input data conditions with clear eye opening patterns confirms the operation of the proposed logic device at 10 Gb/s. Maximum value of extinction ratio, contrast ratio and minimum value of amplitude modulation achieved for the different output waveforms are 12, 9.5 and 0.1 dB respectively. Easy integration with active and passive devices and simple architecture makes this device suitable for all-optical processing.

Improvement of flow strength and scratch resistance of Ti/Cu nanocrystalline metal multilayer thin films by tailoring layer thickness and modulation ratio

In this work, nanocrystalline Ti/Cu multilayer thin films were fabricated using direct current magnetron sputtering with different layer thicknesses, namely 250, 100, 50, 25 and 5 nm. Additionally, a group of the film specimens were prepared with various modulation ratios where each bilayer was set to 100 nm. The size-dependent deformation behavior of the films was studied using the nano-indentation and nano-scratching techniques. The results showed that the flow strength of the films tended to increase as the layer thickness decreased. Moreover, the strength and scratch resistance of the films can be further enhanced by tailoring the thicknesses of two adjacent layers, while keeping the thickness of each bilayer unchanged. Finally, the size-dependent strengthening mechanism was discussed by recourse to microscopic examination.

Research on Coordination Control Strategy of LCC-MMC Hybrid HVDC Transmission System under Fault

High voltage direct current based on modular multilevel converter (MMC-HVDC) has a good application prospect in engineering, but it is expensive and cannot handle DC faults and other disadvantages. So it is still not suitable for long-distance transmission. To solve these problems, this paper designs multi-terminal hybrid DC transmission system with a line commutated converter based on the rectifier side (LCC) and a modular multilevel converter based on the inverter side (MMC). Besides, for the asymmetric fault on the AC side of the system, the minimum trigger angle control strategy based on the rectifier side LCC and the maximum modulation ratio control strategy based on the inverter side MMC are proposed to improve the DC system transmission power and reduce the possibility of power transmission interruption. Finally, a model of hybrid DC transmission is built in PSCAD/EMTDC, the proposed strategy is verified its effectiveness.

INCREASING THE LEVEL OF PHOTO BIOLOGICAL SAFETY OF THE EMISSION SPECTRUM OF AN LED LIGHT SOURCE

The subject of research is the emission spectra of light sources based on LED structures. The purpose of the work is to formulate proposals to improve the photo biological safety of LED lighting systems. The article solves the following tasks: analyzing the situation in the field of photo biological safety of light sources based on LED structures, proposing a concept for improving it in sources based on LED modules with a two-component phosphor. Methods such as comparative analysis, spectrometric method are used. The following results were obtained. A brief analysis of the factors affecting the photo biological safety of artificial light sources based on LED modules and a review of modern technological developments aimed at improving it is carried out. Since the implementation of these developments has a limited volume in the structure of the production of LED modules and a high cost, the concept of increasing the photo biological safety of light sources using cheap white light modules with a two-component phosphor and additional color modules to fill the gap in the spectral characteristic of white light has been proposed. A simple criterion is proposed for calculating the required ratio of white and color modules based on their spectral characteristics to activate the natural mechanism of eye protection due to pupil constriction. The work investigated color modules at wavelengths 480 nm, 492 nm and 503 nm. It has been shown that color modules with a shorter peak wavelength are needed less in relation to the number of whites to create a safe emission spectrum. The paper also estimated the fraction of the emission power with a wavelength of less than 450 nm in the emission spectra of the three investigated variants of combinations of white and color modules and four SunLike modules with different color temperatures. The share of the blue part of the spectrum in the emission power distribution of SunLike LED modules turned out to be higher than in traditional modules with a two-component phosphor at similar color temperatures. Conclusions. The proposed method increases the photo biological safety of the spectrum of LED light sources to the level of natural illumination due to adequate regulation of the pupil diameter and does not increase the total fraction of the emission power in the region λ ≤ 450 nm, which is dangerous for vision. This fraction is even less than in SunLike modules at close values of color temperature, since their emission spectrum is expanded to the region of shorter wavelengths and starts from λ ≈ 370 nm). Considering that the CVC characteristics of color and white LEDs are close, but not identical, their series connection leads to a redistribution of the emission power. In addition, LEDs from different manufacturers differ in energy efficiency and electrical parameters, therefore calculations in practice need to be adjusted in each specific case.

Photochromic and energy storage properties in K0.5Na0.5NbO3-based ferroelectrics

The coupling of photochromic properties and ferroelectrics has captured increasing interest in field of photoelectric devices. However, it is still a challenge to achieve excellent photochromic properties and energy storage performances in a ferroelectric material at the same time. Here, a novel photoelectric multifunctional material of (K0.5Na0.5)NbO3:0.05Eu is obtained. Under visible light irradiation, the sample can effectively absorb and store visible light, showing a reversible photochromic reaction. Eu3+ doping well achieves the readout of visible light storage by tuning luminescence emission intensity, and the luminescent modulation ratio is up to 84%. Meanwhile, a recoverable energy storage density of 2.02 J cm−3, high energy storage efficiency of 75.4%, and fast discharge speed (80 ns) are simultaneously acquired because of Eu3+ doping-induced transition of normal ferroelectric to relaxor ferroelectric. The unique combination of photochromic properties and energy storage performances in ferroelectrics opens the door to the development of photoelectric multifunctional devices.

Experimental studies on photovoltaic module temperature reduction using eutectic cold phase change material

An increase in Photovoltaic (PV) module temperature (TPV) affects the photoconversion efficiency (PCE). Annual TPV loss accounts higher than other losses in the PV system for hot climatic conditions. The main objective of this work is to introduce a novel passive Cold-PCM (C-PCM) to reduce the TPV. Commercial PCM’s are more expensive than a eutectic PCM. In this work, Lauryl alcohol and Ethyl alcohol are mixed in a ratio of 75:25 to form a eutectic mixture. The prepared eutectic mixture is having a melting temperature and latent heat of fusion of 21.75 °C and 199 J/g, respectively. Furthermore, C-PCM containers with 3-cm and 5-cm thickness are attached at the back surface of the PV module. It is observed that the 5-cm container exhibits higher heat transfer, which subsequently resulted in TPV reduction at a maximum of 10.3 °C. This decrease in TPV, enhanced the average voltage profile by 2.85%, thereby the average output power is also boosted by 2.8%. Consequently, this eutectic PCM can improve the average performance ratio, electrical efficiency and capacity utilization factor of the PV module by 72.63%, 10.09% and 19.41%, respectively. Thus the experimental results revealed that C-PCM could be a potential replacement to H-PCM for cooling down the TPV.

Luminescence modulation behavior upon in-situ electric field of Sm3+ doped KSr2Nb5O15 ferroelectric ceramics

Sm3+ doped KSr2Nb5O15 (KSN-Sm) ceramics exhibiting the electro-photoluminescent coupling effect were prepared by two-step sintering technology. The microstructures, electrical and luminescent properties were characterized. In addition, the luminescence modulation behavior upon the application of an in-situ electric field was investigated. It was found that the luminescent emission intensity decreased with increasing in-situ dc bias, and a high modulation ratio of approximately 20%@20 kV/cm was achieved. This work demonstrates that KSN-based ferroelectric ceramics with the tetragonal tungsten bronze structure are promising optical materials with good luminescence modulation behavior.

Symposium 1: The role of maternal pre-pregnancy characteristics on maternal prenatal physiology and behavior: Evidence from three prospective birth cohorts

Nanostructured Ti/Zr multilayers, with different layer thicknesses h and modulation ratios ŋ (ratio of the thickness between Zr and Ti layers), were deposited on Si (1 0 0) substrate by using magnetron sputtering. Transmission electron microscopy observations suggested that the heterophase interfaces kept semi-coherent or coherent in all the multilayers. Hardness of the Ti/Zr multilayers was evaluated by nanoindentation experiments. In contrast with the general trend of “smaller is stronger”, the hardness of present Ti/Zr multilayers with equal layer thickness increased as increasing the layer thickness h, which can be explained by the IBS model extended to large h. For the Ti/Zr multilayers with a constant bilayer thickness but various ŋ, the hardness displayed a maximum as increasing ŋ, which should be related to the deformation heterogeneity in Ti/Zr multilayers with non-uniform layer thickness. Furthermore, the high strength achieved in the Ti/Zr multilayers superior to the constituent layers was discussed.

Performance Analysis of Unipolar SPWM Inverter: Resistive load and Inductive load

This paper presents the performance analysis of the Unipolar SPWM Inverter for the resistive and inductive load testing. The common criteria reported in various technical papers where the resistive load will produce a unity power factor correction and lagging power factor behaviour for inductive load. This paper is to demonstrate the performance of both loads that are tested to the single phase Unipolar SPWM inverter under the modulation ratio of 0.8. The performances will be covered in term of the waveform behavior and THDv performance. The project are carried out through the simulation using PSIM software and real implementation to the real hardware. The selection of filter for this paper is the low pass passive LC filter.

Asymmetrical Load Modulated Balanced Amplifier With Continuum of Modulation Ratio and Dual-Octave Bandwidth

This article presents a new load-modulation power amplifier (PA) architecture-asymmetrical load-modulated balanced amplifier (ALMBA). It is for the first time discovered that the control amplifier (CA) of LMBA can be designed with arbitrary load modulation (LM) ratio by offsetting the symmetry of two sub-amplifiers (BA1 and BA2) in the balanced topology. The rigorous analytical derivation reveals a unification of the quadrature-coupler-based LM PA theory, which inclusively covers the recently reported LMBA within this generalized framework. Through pseudo-Doherty (PD) biasing of the asymmetric BA1 & BA2 (peaking) and the CA (carrier) combined with proper amplitude and phase controls, the optimal LM behaviors of three amplifiers can be achieved independently overextended power back-off range and ultrawide RF bandwidth. Importantly, the LM of CA effectively mitigates the over-driving issue imposed on symmetrical PD-LMBA, leading to enhanced overall reliability and linearity. Based on the proposed theory, an RF-input PD-ALMBA is designed and implemented using commercial GaN transistors. The developed prototype experimentally demonstrates dual-octave bandwidth from 0.55 to 2.2 GHz, which is the widest bandwidth ever reported for load-modulation PAs. The measurement exhibits an efficiency of 49-82% for peak output power and 40-64% for 10-dB OBO within the design bandwidth. When stimulated by a 20-MHz long-term evolution (LTE) signal with 10.5-dB peak to average power ratio (PAPR), an average efficiency of 47-63% is measured over the entire bandwidth at an average output power around 33 dBm.

Ferroelectric HfZrO2 With Electrode Engineering and Stimulation Schemes as Symmetric Analog Synaptic Weight Element for Deep Neural Network Training

Atomic layer deposition (ALD)-based TiN electrode on ferroelectric HfZrO2 metal/ferroelectric/metal (MFM) capacitor and ferroelectric field-effect transistor (FeFET) is demonstrated experimentally with weight transfer, that is, $\Delta {P}$ , per pulse analysis through consecutive alternating potentiation/depression (Pot./Dep.) training pulses. The weight training pulse schemes are studied to have symmetric and linear synapse weight transfer to increase the accuracy and accelerate the deep neural network (DNN) training. With ALD TiN inserted, $\alpha _{p} / \alpha _{d} = -0.63$ / −0.84, asymmetry $\vert \alpha _{p} - \alpha _{d}\vert =0.21$ , and polarization modulation ratio (Pot./Dep.) = 97%/98% are achieved for MFM capacitor, and $\alpha _{p} / \alpha _{d} = -1.32$ / −1.88, asymmetry $\vert \alpha _{p} - \alpha _{d}\vert =0.56$ , and $G_{\text {max}} / G_{\text {min}} > 10\times $ are delivered for FeFET.

Effect of modulation ratio on structure and mechanical properties of WB2/CrN films deposited by direct-current magnetron sputtering

WB2/CrN multilayer films with thick modulation period about 500 nm but different modulation ratios (tWB2:tCrN = 1.2, 2, 3 and 4) were deposited on steel substrates by magnetron sputtering, and the effect of modulation ratio on the structure, residual stress and tribo-mechanical properties of the WB2/CrN multilayer films was systematically studied. Additionally, WB2 and CrN monolayer films with various thicknesses were also prepared to discuss the growth behavior and the related properties of the WB2/CrN multilayer films. All the sample films present the columnar growth, and the particle size in the WB2 monolayers is smaller than that in the corresponding WB2 sublayers. The preferred orientation of WB2 (260–400nm) and CrN monolayers (132–220 nm) is (101) and (111), respectively. However, the multilayered structure changes the orientation of CrN sublayers to (002), and crystalline Cr2N phase is detected in WB2/CrN multilayers caused by the element diffusion at interface. Moreover, the multilayered structure reduces the compressive stress of the WB2 films greatly by diffusion of point defects to interfaces and an indirect effect of interfaces on stress via film structure with soft CrN, and the residual stress of the WB2, CrN and WB2/CrN films is −2.64∼-4.16, −0.85–0.57 and −1.49∼-2.61 GPa, respectively. Furthermore, film hardness ranging from 27.9 to 33.0 GPa mainly obeys the rule of mixture. The adhesive strength drops greatly from 26 to 17 N with the increasing tWB2:tCrN, and the tensile CrN bottom-layer deteriorates the adhesive strength of the WB2/CrN multilayers with tWB2:tCrN = 2. Overall, WB2/CrN films with tWB2:tCrN = 3 show better wear resistance with lower friction coefficient ∼0.35 and wear rate about 3.6 × 10−7 mm3/mN benefiting from their higher hardness, lower roughness, proper toughness and compressive stress.