Modulation Ratio Research Articles

Reversible multimode modulations in photochromic transparent Eu3+doped K0.5Na0.5NbO3 based ceramics

Rare-earth doped transparent photochromic materials have attracted extensive attention in applications of optical information storage and optical switching, in which the high transparency and large fluorescence modulation ratio are required. In this work, 0.94 (K0.5Na0.5)NbO3-0.06 (Sr0.5Ba0.5) (Zn1/3Bi2/3)O3: x wt% Eu2O3 ceramics (KNN-SBZB: xEu) with x=0.1, 0.2, 0.3, 0.4 were prepared by traditional high temperature solid state sintering reaction method. High transmittance (T) was achieved due to the small grain size (less than 110 nm) and the highly symmetrical phase structure. High optical transmittance of 69.27 % at 780 nm and 78.24 % at 1100 nm were obtained in the KNN-SBZB: 0.3Eu ceramic, while large luminescence intensity modulation ratio (∆RL) ∼94.9 %, transmittance (∆RT) ∼5.76 % and diffuse reflectivity (∆ABS) ∼12.59 % were achieved in KNN-SBZB: 0.2Eu ceramic (T ∼62.92 % at 780 nm). Additionally, both the transmittance modulation and luminescence intensity modulation of KNN-SBZB: xEu ceramics show good stability after 10 cycles.

Nonlinear ultrasonic test applied to discern factors controlling cracking of cement mortar affected by reinforcement corrosion

Intermodulation ultrasonic testing technique was used to detect corrosion- induced cracking in prismatic mortar samples. Three sets of five specimens were prepared and subjected to accelerated corrosion conditions. The different times of exposure allowed to attain unlike damage conditions in every sample of each set. The onset of damage was monitored through the evolution of the accumulated Intensity Modulation Ratio (R) and crack width measurements. The accumulated values of the Intensity Modulation Ratio were used to study the effect of different testing factors (cover depth, corrosion rate or amplitude of the input pump signal) and increased monotonically clearly discriminating the different damage levels. These observations point to the possibility of stablishing damage thresholds to detect cracking using nonlinear ultrasonic (NLU) techniques.

Generalized N-State Random Pulse Position Discontinuous PWM for High-Frequency Harmonics Reduction and Performance Improvement at High Modulation Ratios

Generalized <i>N</i>-State Random Pulse Position Discontinuous PWM for High-Frequency Harmonics Reduction and Performance Improvement at High Modulation Ratios

Half-Wave Phase Shift Modulation for Hybrid Modular Multilevel Converter with Wide-Range Operation

Hybrid modular multilevel converters (MMCs), which combine submodule chain links and device series switches, offer advantages such as lower costs and smaller volumes compared with MMCs. However, the hybrid MMCs only operate at a fixed modulation ratio, potentially compromising system adjustment ability. This paper presents a half-wave phase shift modulation (HPSM) strategy aimed at extending the operation range of a hybrid MMC. First, the commutation angle is introduced as a control variable to change the fixed voltage modulation ratio. The energy balance of the converter is completed by adjusting the commutation angle. Then, the operation performance for the half-wave alternating multilevel converter (HAMC) with the proposed HPSM strategy is analyzed. Finally, the full-scale simulations are carried out to verify the theoretical analysis and the feasibility of the proposed control strategy. Compared to the third-order harmonic current injection (THCI) strategy, HPSM reduces operating losses by 50% and demonstrates superior control performance.

Computational account for the naturalness perception of others' jumping motion based on a vertical projectile motion model.

The visual naturalness of a rendered character's motion is an important factor in computer graphics work, and the rendering of jumping motions is no exception to this. However, the computational mechanism that underlies the observer's judgement of the naturalness of a jumping motion has not yet been fully elucidated. We hypothesized that observers would perceive a jumping motion as more natural when the jump trajectory was consistent with the trajectory of a vertical projectile motion based on Earth's gravity. We asked human participants to evaluate the naturalness of point-light jumping motions whose height and duration were modulated. The results showed that the observers' naturalness rating varied with the modulation ratios of the jump height and duration. Interestingly, the ratings were high even when the height and duration differed from the actual jump. To explain this tendency, we constructed computational models that predicted the theoretical trajectory of a jump based on the projectile motion formula and calculated the errors between the theoretical and observed trajectories. The pattern of the errors correlated closely with the participants' ratings. Our results suggest that observers judge the naturalness of observed jumping motion based on the error between observed and predicted jump trajectories.

Luminescence enhancement behavior of KSr1.96Sm0.04Nb5O15/PVDF composite thick film after electric polarization

A novel composite thick film exhibiting luminescent enhancement behavior was prepared using Sm3+ doped KSr2Nb5O15 ferroelectric microcrystals and polyvinylidene difluoride (PVDF) polymer via a tape-casting technology. After compositing with PVDF, the thick film retained the ferroelectric polarization behavior, and the PVDF phase had negligible impact on the reflectivity and optical absorption edge of ferroelectric microcrystals. The photoluminescent emission intensities of the characteristic transitions of Sm3+ exhibited significant enhancement after electric polarization, with a maximum modulation ratio exceeding 200 %. The underlying luminescence modulation mechanism is discussed. This work proposed a novel strategy for fabrication of flexible composite thick films with coupling behavior between luminescent and ferroelectric properties.

An efficient multi-fidelity simulation approach for performance prediction of adaptive cycle engines

Adaptive cycle engine (ACE) with multi-stream, modulated bypass ratio, and high-thrust/high-efficiency mode provides the capability of multiple mission adaptation for the next-generation aviation propulsion system. The low-fidelity zero-dimensional (0D) performance simulation method is commonly adopted in conventional engines such as turbofan and turbojet. However, it is hard to accommodate well to ACE with complex variable geometry schemes and strong interaction between components. This paper presents an efficient multi-fidelity simulation approach, often referred to as component zooming, for predicting the performance of ACE with the three-stream configuration. The one-dimensional (1D) mean-line models of the adaptive fan and low-pressure turbine (LPT) are integrated into the 0D ACE model by the iteratively-coupled method. The performance predicted by the multi-fidelity ACE models with different component zooming strategies is compared. The maximum deviations of thrust, specific fuel consumption, turbine inlet temperature, and bypass ratio between the 0D/1D Adaptive Fan/1D LPT coupled model and 0D ACE model are −10.8%, −4.4%, −5.4% (−75 K), and 1.6%, respectively, which are considerable and non-negligible for the application in the design stage of ACE. The computing time of all the multi-fidelity models is less than 2 minutes. The effects of the key aerodynamic parameters of the adaptive fan and LPT on the engine performance are also evaluated. The proposed approach provides a generic and efficient solution for multi-fidelity ACE performance prediction with acceptable computing resource requirements and time cost, which is applicable in the engine conceptual and preliminary design stage.

Monitoring solar irradiance and PV module performance in mobile applications

The paper presents a comprehensive evaluation of a PV module attached to an electric vehicle using a custom developed PV monitoring system to estimate the effect of PV energy production on the driving range.A rigid crystalline silicon photovoltaic (PV) module with a nominal peak power of 192.4 W accompanied with four irradiance sensors (positioned horizontally and vertically to the left, right and back) was mounted on an electric car, and various driving scenarios were executed, with data recorded for analysis. The results of a two-month continuous monitoring of the car's usage mainly in the Central Slovenia region in late winter and early springtime, show that the daily energy generation by the installed PV module contributed an additional driving range of up to 5 km per day, totalling 93 km of additional range in the entire monitoring period. Based on irradiance monitoring results applied to a hypothetical case where all sides would be covered with a state-of-the-art PV, the driving range would extent to 471 km in total for the same period. When compared to a fixed, ideally installed PV module at our outdoor PV monitoring site in Ljubljana, the average performance ratio (PR) of the mobile PV module in the two-month period was 87 %, whereas the PR of the fixed installed PV module was 83 %. The energy yield varied significantly under the varying conditions resulting from different car usage scenarios and on average it reached 41 % of the fixed PV module's energy yield. Through real-world experiments and data collection, different car use cases under various driving and parking conditions are presented and evaluated in detail. From these, the base specifications of a dedicated mobile VIPV monitoring system are identified.

BDD‐based optimized majority/minority gate using electro‐optic Mach‐Zehnder interferometer

AbstractIn this article, an optical majority/minority circuit has been designed using four electro‐optic Mach‐Zehnder interferometers. The binary decision diagram (BDD) is used to optimize the Boolean logical expression. In this design we get two outputs, one performs majority logic and the other performs minority logic simultaneously. Numerical simulation has been done with the obtained data from the beam propagation method. Pseudo‐eye diagram is also plotted to find amplitude modulation (AM) and extinction ratio (ER). AM and ER are found nearly 0.4 and 13 dB, respectively. A new parameter, the optical circuit complexity factor (OCC) factor has been calculated and from the result, it has been shown that the proposed design is more optimized than other majority/minority gate designs so far.

Dynamic control of optical skyrmions in cylindrical waveguide

In recent times, the optical skyrmions have received an increasing amount of interest owing to its applications in optical manipulation, super-resolution imaging and microscopy, quantum technologies. However, few studies are focused on the dynamic control of optical skyrmions. It is found that Neel-type photonic skyrmions were discovered in evanescent electromagnetic waves. Here, we find the Bloch-type skyrmions in a three-dimensional cylindrical waveguide. By modulating the amplitude ratio of two incident vortex beams, the new types of skyrmions such as Twisted-type skyrmions and Planar-type skyrmions can be found. Further more, we have also achieved arbitrary modulation ratios of internal spin components. It is believed that our findings greatly enrich the types of photonic skyrmions and provide a method to freely control the photonic skyrmions.

Unique irradiation damage behavior and deformation mechanisms in crystalline/amorphous Ag/Cu-Zr nanolaminates

Nanolaminated materials due to the abundant interfaces that are efficient sinks for irradiation defects have received broad attention. In this work, Ag/Cu-Zr crystalline/amorphous nanolaminates (C/ANLs) with a wide modulation ratio η from 0.1 to 9.0 were prepared using sputtering magnetron and implanted to a total influence of 1×1017 ions cm-2 He ions to investigate their irradiation damage behavior and mechanical properties. The irradiated Ag/Cu-Zr C/ANLs enable an interesting distribution behavior of He bubbles that only aggregate in the crystalline Ag layers but are absent in the amorphous Cu-Zr layers and interfaces, and become increasingly obvious with reducing η. This is attributed to the synergistic effect of C/A interfaces and amorphous layers as efficient sinks for irradiation defects. The irradiation-induced hardening is found to go through a minimum at η = 3.0, owing to the transformation of strengthening mechanism from He bubbles strengthening in Ag layers as η ≤ 3.0 to free volume annihilation in Cu-Zr layers as η > 3.0. Moreover, the strain rate sensitivity (SRS) m of irradiated C/ANLs firstly decreases rapidly from positive to negative and then increases slowly with raising η, differing from the monotonic η-dependent SRS m of as-deposited C/ANLs. Relevant deformation mechanisms are elucidated based on the dislocation-bubble interactions in terms of pinning effect on dislocations bow-out and dynamic strain aging effect. Our findings could provide valuable insights for the microstructural design of C/ANLs for applications in nuclear reactors.

Co and Ni Ratio Modulation‐Derived Electron Deficient Pd Trimetallic Catalysts for Enhanced Formic Acid Electrooxidation

AbstractPdCoNi trimetallic catalysts attracted extensive interest in direct formic acid fuel cells due to high poisoning resistance and high activity for formic acid electro‐oxidation (FAO). Herein, a series of Pd0.75CoxNiy/C alloys with a modulated ratio of Co and Ni are synthesized to investigate the effect of Co and Ni content on the electronic structure of Pd for FAO. The physical analysis demonstrated that the introduction of Co and Ni induces the lattice strain effect compared to monometallic Pd catalysts. As a consequence of fixing the total amount of Co and Ni, the strain effect is restricted, and the electronic perturbation of Pd is successfully regulated by varying the ratio of Co and Ni in Pd0.75CoxNiy/C trimetallic alloys. Pd loses more electrons, the bond strength of Pd−H is weakened, and FAO activity is enhanced first and then decreased as the Co content increases. Among the trimetallic catalysts, Pd0.75Co0.125Ni0.125/C trimetallic catalyst exhibits the highest current density of 3.253 mA cm−2 owing to the optimum electronic perturbation and Pd−H bond strength. This work provides a valuable guideline for future studies of Pd‐based trimetallic alloys.

Comparison of three-phase inverter modulation techniques: a comprehensive analysis of SPWM and SVPWM

With the increasing utilization of renewable energy sources like solar and wind, three-phase inverters have become indispensable equipment for grid-connected energy systems, sparking significant research interest in the field of power electronics. This paper presents a comprehensive comparison of two primary modulation techniques employed in three-phase inverters: Sinusoidal Pulse Width Modulation (SPWM) control and Space Vector Pulse Width Modulation (SVPWM) control. The aim is to elucidate their respective advantages and disadvantages, particularly focusing on their performance under various control models. Through a systematic analysis of parameters such as total harmonic distortion under different control schemes including the unity power factor control model, the V/F control model, and the modulation ratio, this paper delves into the operational principles, strengths, and weaknesses of SPWM and SVPWM. Additionally, it elucidates the distinctions between these two modulation techniques and their interconnections. Lastly, the paper provides insights into the future development prospects and identifies potential technical challenges in the realm of pulse width modulation techniques.

Cholesterol sulfate-mediated ion-pairing facilitates the self-nanoassembly of hydrophilic cationic mitoxantrone

HypothesisHydrophilic cationic drugs such as mitoxantrone hydrochloride (MTO) pose a significant delivery challenge to the development of nanodrug systems. Herein, we report the use of a hydrophobic ion-pairing strategy to enhance the nano-assembly of MTO. ExperimentsWe employed biocompatible sodium cholesteryl sulfate (SCS) as a modification module to form stable ion pairs with MTO, which balanced the intermolecular forces and facilitated nano-assembly. PEGylated MTO-SCS nanoassemblies (pMS NAs) were prepared via nanoprecipitation. We systematically evaluated the effect of the ratio of the drug module (MTO) to the modification module (SCS) on the nanoassemblies. FindingsThe increased lipophilicity of MTO-SCS ion pair could significantly improve the encapsulation efficiency (∼97 %) and cellular uptake efficiency of MTO. The pMS NAs showed prolonged blood circulation, maintained the same level of tumor antiproliferative activity, and exhibited reduced toxicity compared with the free MTO solution. It is noteworthy that the stability, cellular uptake, cytotoxicity, and in vivo pharmacokinetic behavior of the pMS NAs increased in proportion to the molar ratio of SCS to MTO. This study presents a self-assembly strategy mediated by ion pairing to overcome the challenges commonly associated with the poor assembly ability of hydrophilic cationic drugs.

Strong Immunity to Drain-Induced Barrier Lowering in ALD-Grown Preferentially Oriented Indium Gallium Oxide Transistors.

Drain-induced barrier lowering (DIBL) is one of the most critical obstacles degrading the reliability of integrated circuits based on miniaturized transistors. Here, the effect of a crystallographic structure change in InGaO [indium gallium oxide (IGO)] thin-films on the DIBL was investigated. Preferentially oriented IGO (po-IGO) thin-film transistors (TFTs) have outstanding device performances with a field-effect mobility of 81.9 ± 1.3 cm2/(V s), a threshold voltage (VTH) of 0.07 ± 0.03 V, a subthreshold swing of 127 ± 2.0 mV/dec, and a current modulation ratio of (2.9 ± 0.2) × 1011. They also exhibit highly reliable electrical characteristics with a negligible VTH shift of +0.09 (-0.14) V under +2 (-2) MV/cm and 60 °C for 3600 s. More importantly, they reveal strong immunity to the DIBL of 17.5 ± 1.2 mV/V, while random polycrystalline In2O3 (rp-In2O3) and IGO (rp-IGO) TFTs show DIBL values of 197 ± 5.3 and 46.4 ± 1.2 mV/V, respectively. This is quite interesting because the rp- and po-IGO thin-films have the same cation composition ratio (In/Ga = 8:2). Given that the lateral diffusion of oxygen vacancies from the source/drain junction to the channel region via grain boundaries can reduce the effective length (Leff) of the oxide channel, this improved immunity could be attributed to suppressed lateral diffusion by preferential growth. In practice, the po-IGO TFTs have a longer Leff than the rp-In2O3 and -IGO TFTs even with the same patterned length. The effect of the crystallographic-structure-dependent Leff variation on the DIBL was corroborated by technological computer-aided design simulation. This work suggests that the atomic-layer-deposited po-IGO thin-film can be a promising candidate for next-generation electronic devices composed of the miniaturized oxide transistors.

Performance and economic analysis of a molten salt furnace thermal energy storage and peaking system coupled with thermal power units for iron and steel gas waste heat recovery

A new peaking system utilizing a molten salt furnace energy storage system coupled with a blast furnace gas thermal power unit in a steel mill is proposed, which stores excess blast furnace gas thermal energy in molten salt and releases the thermal energy for power generation during peak power demand. The heating efficiency of 74.57% is experimentally verified by building a molten salt furnace, and a 135 MW blast furnace gas thermal power unit is simulated using modeling to explore the energy storage and peak shifting performance and economic feasibility of the system. The results show that during the charging phase, the system can recover up to 9.361 t/h of standard coal, increasing the low valley regulation ratio to 20.31% with the increase of extraction rate. During the discharging phase, the system can provide an additional 17.42 MW of generating power, with a peak modulation ratio of 12.90%. The exergy losses from the combustion process dominates the overall system exergy losses with a maximum of 21.00 MW, followed by the exergy from the turbine, which occupies 18.42% of the input energy. The cycle efficiency of the system is up to 63.54%, and the molten salt temperature has a more significant impact on the system performance than the molten salt flow rate. The economic feasibility analysis yields a peaking capacity cost of $74.28/kWh for the modified system. The system will complete 100% recovery of the investment cost in 4.90 years, and thereafter, the annual profit is more than $3.71 Million. The peaking hours and regional electricity price are the main factors affecting the system. The effect of critical factors on the payback years of the system was further explored, and the payback years remains within 8 years only when the molten salt temperature is above 500 °C and the molten salt flow rate exceeds 400 t/h.

Tuning mechanical properties of TiAlSiN/TiAlN multilayers by interfacial structure

Multilayer structure as an effective way to tailor the structure and performance of hard coatings has attracted wide attentions. Here, we aim to elucidate the change of the interface, mechanical properties and oxidation resistance for TiAlSiN/TiAlN multilayers by varying modulation ratios from ML (tTiAlSiN/tTiAlN = 1:1) to HML (tTiAlSiN/tTiAlN = 1:2). Increasing TiAlN sublayer thickness stabilizes the cubic growth of TiAlSiN layers, where the HML exhibits coherent epitaxial growth in contrast to the cubic-wurtzite mixed structure of ML. This coherent strengthening effect is responsible for the noteworthy enhancement of the hardness values from ∼30.9 GPa of ML to ∼33.2 GPa of HML. Significantly, the presence of a coherent interface effectively withstands external pressure, thereby endowing HML with exceptional adhesive strength and fracture toughness. Nevertheless, the oxidation resistance of the coating is reliant on the chemical composition, with the multilayers displaying lower oxidation resistance compared to the TiAlSiN monolayer.

A Comprehensive Review on Comparison and Performance of Five-Phase Space Vector Pulse Width Modulation Overmodulation Strategies

High-performance overmodulation strategies for voltage source inverters (VSIs) can further broaden the operation range of machines. Among them, Space Vector Pulse Width Modulation (SVPWM) is worth researching as it performs well in digital implementation. This paper presents a detailed comparison of various SVPWM overmodulation strategies and analysis of their performance. It firstly briefly elaborates fundamental laws of two subspaces of five-phase VSIs. Then, it focuses on several overmodulation strategies. Their corresponding basic principles and main characteristics are researched, and conclusions are given. In addition, differences and relationships between them are proved and summarized. Lastly, comparative simulations and experiments were carried out and verify that in the overmodulation region, the output voltage distortion degree increases with the increase in modulation ratio, and strategies with more control degrees of freedom (CDFs) are capable of better controlling the third harmonic subspace, which means that higher-quality output voltage waveforms would be obtained.

Dual-mode luminescence light intensity modulation characteristics and optical radiation dependence of stannate photochromic ceramics

Alkaline earth stannate is characterized by good physicochemical stability. It has been applied in the field of optical information storage by coupling photoluminescence intensity modulation and photochromic performance, which has attracted the attention of researchers. The development of alkaline earth stannate ceramics with high light intensity modulation properties and non-destructive reading of optical information is of great research value. In this study, Er3+-doped Ca2SnO4 photochromic ceramics were prepared by high-temperature solid-phase reaction method. Alternating UV light irradiation and thermal stimulation, the ceramics achieve a reversible transition between light and dark gray. Er3+ doping gives the ceramics dual-mode luminescence light intensity modulation performance. When the doping amount of Er3+ is 0.01 mol, there is a maximum down-conversion luminous intensity modulation ratio of 93%, which is higher than most of the same type of photochromic materials. The photochromic behavior is explained using the capture-release model of traps for carriers, and the dual-mode luminescence light-intensity modulation behavior is analyzed through the energy transfer mechanism. The optical radiation response properties were investigated and the optimum light response wavelength is found to be 290 nm, which is related to the optical band gap Eg. And the selection of the optimal light response wavelength can effectively improve the performance of photochromic and light intensity modulation. This study provides a promising strategy for performance enhancement of photochromic materials.

Steep-slope vertical-transport transistors built from sub-5 nm Thin van der Waals heterostructures

Two-dimensional (2D) semiconductor-based vertical-transport field-effect transistors (VTFETs) – in which the current flows perpendicularly to the substrate surface direction – are in the drive to surmount the stringent downscaling constraints faced by the conventional planar FETs. However, low-power device operation with a sub-60 mV/dec subthreshold swing (SS) at room temperature along with an ultra-scaled channel length remains challenging for 2D semiconductor-based VTFETs. Here, we report steep-slope VTFETs that combine a gate-controllable van der Waals heterojunction and a metal-filamentary threshold switch (TS), featuring a vertical transport channel thinner than 5 nm and sub-thermionic turn-on characteristics. The integrated TS-VTFETs were realised with efficient current switching behaviours, exhibiting a current modulation ratio exceeding 1 × 108 and an average sub-60 mV/dec SS over 6 decades of drain current. The proposed TS-VTFETs with excellent area- and energy-efficiency could help to tackle the performance degradation-device downscaling dilemma faced by logic transistor technologies.