Parametric Generation Research Articles

A Modeling and Simulation Method for Preliminary Design of an Electro-Variable Displacement Pump.

Electro-hydrostatic actuators (EHAs) have been considerably researched in academia, and their applications in various industrial fields are expanding. The variable-speed EHA has now taken priority over the variable-displacement EHA, but its driving motor and associated electronics encounter issues when applied in high-power applications: low-dynamics, high thermal dissipation, high price, etc. Therefore, a variable-displacement EHA equipped with an electro-variable displacement pump (EVDP) has been considered. The EVDP itself is a mechatronic system that integrates a piston pump, a ball screw, a gearbox, and a permanent magnet synchronous motor (PMSM). Consequently, the EVDP needs to be investigated to ensure its system-level performance when applied in an EHA. In addition to the previous research on the technical parameters of the EVDP, a dedicated design method is necessary for further reducing the cost of using the EVDP and exploring its performance potential. Here, a simulation based EVDP preliminary design method is selected for designing a 37 kW EVDP. Firstly, a previously proposed multidisciplinary model of the EVDP is extended by improving the parameter generation, including the EVDP life, reliability, control models, etc. Secondly, the proposed model is partially verified using a downsized prototype. Thirdly, the EVDP is simulated at a system level, supported by the proposed model. The EVDP performance is evaluated according to the specified design requirements. The temperature, bandwidth and accuracy, reliability and lifetime, etc., are all predicted for the EVDP. The simulation results demonstrate the EVDP's applicability in variable-displacement EHA. The proposed modeling and simulation method can be used to evaluate diverse EVDP performance and respond to general design requirements. The method can also support the resolution of the preliminary design challenges in terms of limited information and robustness. Therefore, the proposed method is appropriate for the realization of the simulation-based EVDP preliminary design method.

A three-machine equivalent system frequency response model and its closed-form solution

The frequency response (FR) of the large-scale power system shows significant frequency spatial distribution characteristics (FSDC), still using uniform frequency models may cause large errors in the FR solution, and the FSDC should be preserved in the modeling. In this paper, a three-machine equivalent system frequency response (TM-SFR) model is proposed to preserve the FSDC by the parameter equivalent aggregation method, including load, network, and generator. The TM-SFR model is further simplified into a solvable forced vibration equation by loop-opening and approximation, and its closed-form solution (CFS) is obtained by the modal superposition method, to analytically solve the FR following a major disturbance. Case studies are introduced to verify the performance of the TM-SFR model and its CFS over the WSCC 9-bus system, the New England 39-bus system, and the IEEE 118-bus system. The results prove that the proposed model can preserve the intermachine frequency oscillation caused by the FSDC in various scenarios, and improve the FR solution accuracy at high solution speed, which can provide a more reliable basis for frequency stability emergency control.

THE RAINFALL-RUNOFF MODEL FOR THE CARPATHIAN FLYSCH CATCHMENT USING THE SWAT+ HYDROLOGICAL SOFTWARE

Aim of the study: The goal of this study was to apply SWAT+ tools to estimate the water shortage in the Smugawka catchment. Material and methods: The use of the area was documented in the form of an orthophotomap with GIS layers superimposed, which was provided by CORINE Land Cover 2018. A soil and agricultural map, supplemented with lithological content from a detailed geological map, was used as the input layer for QGIS ver. 3.16. In the next stage, multiannual meteorological data (1991–2020) were added to the SWAT+ model, which included: minimum and maximum daily air temperature, daily rainfall, average daily radiation and average daily wind speed. Full integration of the SWAT+ model with QGIS facilitates the procedure of iterative generation and modification of the model input parameters. The calculation of continuous simulations for average long periods of time is presented in the manuscript. Results and conclusions: The application of GIS-based approaches and modeling techniques are crucial in the quest for optimal methods for calculating the water balance today. Our findings also contribute to a better understanding of the hydrological processes at work in the flysch catchment.

Nonlinear crystals for parametric light generation in the near and middle IR range

A review and comparative analysis of nonlinear optical crystals with a wide transparency range is presented. The conclusion is made about the possibility of creating on their basis highly efficient parametric light generators in the middle and far infrared range for lidar systems.

Versatile optical frequency combs based on multi-seeded femtosecond optical parametric generation.

This study proposes and demonstrates a versatile method for near- and mid-infrared optical frequency comb generation using multi-seeded femtosecond optical parametric generation. The method allows one to divide the repetition rate by an arbitrarily large integer factor, freely tune the offset frequency, and adjust the common phase offset of the comb modes. Since all possible degrees of freedom are adjustable, the proposed method manifests itself as versatile optical frequency synthesis.

A theoretical investigation of nonlinear optical and electronic molecular parameters of hexabutyloxytryphenylene and halogenated hexabutyloxytryphenylene molecules using density functional theory (DFT) for nonlinear device applications

In this work, we discuss the molecular properties of hexabutyloxytryphenylene (HAT4) and halogenated HAT4 using density functional theory (DFT) with B3LYP method and Pople basis set (6-31G, 6-31G*, 6-31G**) for the generation of non-linear optical and electronic parameters. Using DFT method, the dependence of electro-optical parameters of halogenated HAT4 such as dipole moment, mean polarizability, anisotropy in polarizability and hyperpolarizability along with global parameters such as ionization potential, electron affinity, electronegativity, chemical hardness and electrophilicity index on the halogens in the core of the considered molecules has been studied in this work. Further, the frontier molecular orbital analysis for pure HAT4 and halogenated HAT4 molecules has been carried out. The proposed study helps us to analyse the effect of halogenation on the linear, non-linear as well as thermodynamical properties of HAT4 molecules such as HOMO-LUMO gap, thermal energy, entropy and specific heat capacity. The effect of halogenation also leads to understand the modification of nonlinear parameters of HAT4 for the interaction of nonlinear fields.

RETRACTED: A continuous-wave alexandrite laser and its degenerated optical parametric generator

• To the best of our knowledge, this is the first report of the CW degenerated optical parametric generator at 1503.4 nm for the alexandrite crystal, which is both used as laser gain and DOPG nonlinear medium. At present, there are no papers about a degenerated optical parametric generator of the alexandrite laser. • The spectral width of DOPG is about 7.16 nm and the frequency spacing between adjacent longitudinal modes at 1503.4 nm reduces to 1.72 × 10 11 Hz. • The DOPG central wavelength tunes from 1502.77 to 1505.08 nm when the crystal temperature increases from 20 to 70 °C. • Our investigation provides further insight into studying the complex nonlinear effects of the biaxial alexandrite crystal. We present a continuous-wave (CW) alexandrite laser at 751.7 nm end-pumped by a red laser diode (LD) at 636 nm. A laser output power of 1160 mW with an optical-to-optical efficiency of 11.9% and a slope efficiency of 16.7% is obtained at the pump power of 9.72 W. The spectral width of the alexandrite laser is about 3.58 nm, and the frequency spacing between adjacent longitudinal modes is 3.44 × 10 11 Hz. The first CW degenerated optical parametric generator (DOPG) at 1503.4 nm of the alexandrite crystal is reported. The spectral width of DOPG is about 7.16 nm, and the frequency spacing between adjacent longitudinal modes at 1503.4 nm reduces to 1.72 × 10 11 Hz. The DOPG central wavelength tunes from 1502.77 to 1505.08 nm when the crystal temperature increases from 20 to 70 °C.

Generalized Fresnel-Floquet equations for driven quantum materials

Optical drives at terahertz and midinfrared frequencies in quantum materials are increasingly used to reveal the nonlinear dynamics of collective modes in correlated many-body systems and their interplay with electromagnetic waves. Recent experiments demonstrated several surprising optical properties of transient states induced by driving, including the appearance of photo-induced edges in the reflectivity in cuprate superconductors (SCs), observed both below and above the equilibrium transition temperature. Furthermore, in other driven materials, reflection coefficients larger than unity have been observed. In this paper we demonstrate that unusual optical properties of photoexcited systems can be understood from the perspective of a Floquet system, a system with periodically modulated parameters originating from pump-induced oscillations of a collective mode. These oscillations lead to an effective Floquet system with periodically modulated parameters. We present a general phenomenological model of reflectivity from Floquet materials, which takes into account parametric generation of excitation pairs. We find a universal phase diagram of drive-induced features in reflectivity which evidence a competition between driving and dissipation. To illustrate our general analysis, we apply our formalism to two concrete examples motivated by recent experiments: A single plasmon band, which describes Josephson plasmons (JPs) in layered SCs, and a phonon-polariton system, which describes upper and lower polaritons in materials such as insulating SiC. Finally, we demonstrate that our model can be used to provide an accurate fit to results of phonon-pump--terahertz-probe experiments in the high-temperature SC ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.5}$. Our model explains the appearance of a pump-induced edge, which is higher in energy than the equilibrium JP edge, even if the interlayer Josephson coupling is suppressed by the pump pulse.

Attenuation of the intensities of spectral components of a multiwavelength pulsed laser system by means of the Bragg diffraction of radiation by several acoustic waves

A method for controlling precisely the intensities of several spectral components of radiation generated by a multiwavelength laser system is described. The method is based on the use of simultaneous Bragg diffraction by a set of acoustic waves of corresponding frequencies and adjustment of their amplitudes. The efficiency of the proposed method is demonstrated by the example of a multiwavelength system based on a pulsed Nd:YAG laser (1064 nm) with intracavity parametric generation of a signal wave (1572 nm) and extracavity light conversion into higher harmonics and sum frequencies. An independent control of intensity ratio for four spectral components in the visible range (452, 532, 635, and 786 nm) is obtained by precisely controlled attenuation of acoustic-wave amplitudes using an original 4-channel acousto-optical polychromator.

Tunable narrow-linewidth high-peak-power sub-nanosecond optical parametric generator by injection seeding.

We present an efficient tunable optical parametric generator (OPG) with its linewidth close to the Fourier transform limit by injection seeding a tunable diode laser. Benefitting from high-peak-power sub-nanosecond (426 ps) laser pumping and a high-gain MgO:PPLN (PPMgLN) crystal, the OPG produced signal peak power up to 0.343 MW at 1638 nm and the total conversion efficiency reached 47.9% at 1-kHz pulse repetition rate. Considering the linewidth limit of short signal pulses (∼ 350 ps), a tunable seeder with the linewidth at hundred-MHz level was applicable. The achieved OPG signal tuning range was 1510-1638 nm with linewidth at GHz level, which is two orders of magnitude narrower than the unseeded OPG. Injection seeding a non-resonant OPG device does not introduce extra cavity feedback electronics that are essential for an optical parametric oscillator (OPO), greatly improving robustness and reducing cost. It is believed such a compact, tunable and costless PPMgLN OPG with high peak power, high repetition rate and relatively narrow linewidth has great significance in lidar, spectroscopy, etc.

Entropy analysis of MHD flow of Jeffrey fluid in an inclined channel

AbstractThis study is aimed at investigating the influence of entropy analysis of magnetohydrodynamic flow of Jeffrey fluid in an inclined micro‐channel in the presence of thermal radiation and field suction/injection. We have improved the mathematical model of the physical problem under consideration. The designed equations have been solved by applying the shooting‐based fourth‐order, Runge–Kutta method with the boundary conditions, which describe velocity slip and temperature jump conditions at the fluid–wall inter‐face. Numerical efforts are described graphically and mentioned quantitatively concerning different parameters such as Jeffery parameter, Bejan number, and entropy generation embedded in the problem. The numerical results for the expression of the irreversibility ratio are obtained. It is observed that the wall inclination strengthens the entropy production rate in the micro‐channel, and the thermal buoyancy layer induces an increase in fluid velocity as suction.

Hydrodynamic optimization of a high-speed vessel by means of simulation-based design methodology

This study presents a simulation-based optimization procedure of a high-speed vessel. The presented procedure is applied on benchmark form Model 5365, a 1/8.25 scale model of the transom-stern, high-speed research vessel, R/V Athena. The procedure integrates parametric model generation, viscous numeric resistance analysis, and genetic algorithm evaluation. CAESES, a unique simulation-based design platform, is used to collect the process under one roof and handle the process automatically. The fully-parametric form is constructed by means of main characteristic curves, control curves, and various parameters to achieve quick-variation of hull forms. The numeric resistance analysis are performed via viscous flow solver and the calm-water total resistance force is defined as the optimization objective. The NSGA-II algorithm is used for evaluation of analysis results and regeneration of form variants, to achieve total resistance minimization. The optimization results show that the optimized hull form has lower resistance than Model 5365 form; a form variant with 2.02% total resistance reduction was obtained.

Hybrid mapping algorithm based on 1‐DCM and Lorenz

A hybrid chaotic mapping algorithm(HCM) based on 1-DCM (one-dimensional chaotic map) and Lorenz is proposed to address the security issues of low-dimensional chaotic systems and the complexity of high-dimensional chaotic systems. Firstly, the color images are divided into three high 4-bit planes (BP) and low 4-bit planes. By optimizing the parameters and structure of trigonometric function, the new arcsine-sine (AS) function is designedto generate the 1-DCM and permutation matrix, which is constructed to change the plane position and pixel position of the high 12BP to obtain the scrambling plane, which is encrypted by Lorenz chaotic system to produce the selfencryption matrix, with which the low 12BP is encrypted to generate the low bit encryption planes. Then, the ciphertext image is obtained by combining the high bit scrambling plane and low bit encryption plane. The SHA function is also used as the chaotic system's parameter generator, which improves the correlation between plaintext images and the key and resists selective plaintext attacks. The simulation results show that by modularizing the image's high and low bit planes, the encryption process is simplified and improved. The security and reliability of color image transmission are also improved.

Generation of localized reactor point kinetics parameters using coupled neutronic and thermal fluid models for pebble-bed reactor transient analysis

The systems analysis of anticipated operating occurrences and design basis accidents for pebble-bed reactor systems requires knowledge of neutron point kinetics equations (PKE) parameters. Typically, the generation of PKE parameters is performed in a global manner using standalone neutronics calculations, without the inclusion of thermal fluid distributions. We utilize Griffin and Pronghorn for generating global and local PKE parameters which includes the use of thermal fluid distributions to account for localized effects. This work establishes a methodology for calculating PKE parameters for a pebble bed reactor with a coupled neutronics/thermal fluids analysis. PKE parameters generated on a global and local basis are compared against a diffusion solve for a typical load-following transient. Locally-generated neutron kinetic parameters are able to reduce the maximum error in the transient power level from 5% to below 1.5%; along with this, bulk temperature errors were reduced from 12 K to 4 K.

Passively Q-switched microchip laser based picosecond light source in the visible-red to near-infrared band for semiconductor excitation.

We developed a visible-red to near-infrared wavelength tunable all-solid-state laser system utilizing an optical parametric generation process in a MgO doped PPLN crystal pumped at 532 nm by an amplified and frequency doubled picosecond passively Q-switched Nd:YVO4 microchip laser. A broad bandwidth, tuneable over 300 nm between 710 nm to 1015 nm, is accessible. Depending on the green pump light pulse energy, pulses with durations down to 69 ps as well as pulses with energies above 2 µJ were achieved with kHz repetition rates.

Multi-Wavelength Terahertz Parametric Generator Using a Seed Laser Based on Four-Wave Mixing

In this study, we developed a multi-wavelength terahertz-wave parametric generator that operates with only one injection seeding laser. Tunable lasers used as an injection seeder must be single-frequency oscillators, and conventional multi-wavelength terahertz-wave parametric generator requires basically the same number of lasers as the number of wavelengths. In order to solve this problem, we developed a new external cavity semiconductor laser that incorporates a DMD in its wavelength-selective mechanism. In this process, stable multi-wavelength oscillation from a single laser was made possible by efficiently causing four-wave mixing. This seed laser can be applied to practical real-time terahertz spectroscopy by arbitrarily switching the desired wavelength to be generated and the interval between multiple wavelengths.

Mamba: a systematic software solution for beamline experiments at HEPS.

To cater for the diverse experiment requirements at the High Energy Photon Source (HEPS) with often limited human resources, Bluesky was chosen as the basis for our software framework, Mamba. In our attempt to address Bluesky's lack of integrated graphical user interfaces (GUIs), command injection with feedback was chosen as the main way for the GUIs to cooperate with the command line interface; a remote-procedure-call service is also provided, which covers functionalities unsuitable for command injection, as well as pushing of status updates. In order to fully support high-frequency applications like fly scans, Bluesky's support for asynchronous control is being improved; furthermore, to support high-throughput experiments, Mamba Data Worker is being developed to cover the complexity in asynchronous online data processing for these experiments. To systematically simplify the specification of metadata, scan parameters and data-processing graphs for each type of experiment, an experiment parameter generator will be developed; experiment-specific modules to automate preparation steps will also be made. The integration of off-the-shelf code in Mamba for domain-specific needs is under investigation, and Mamba GUI Studio is being developed to simplify the implementation and integration of GUIs.

Implementation framework and validation of cluster-nuclei based channel model using environmental mapping for 6G communication systems

With the research of the upcoming sixth generation (6G) systems, new technologies will require wider bandwidth, larger scale antenna arrays and more diverse wireless communication scenarios on the future channel modeling. Considering channel model is prerequisite for system design and performance evaluation of 6G technologies, we face a challenging task: how to accurately and efficiently model 6G channel for various scenarios? This paper tries to answer it. Firstly, the features of cluster-nuclei (CN) and principle of cluster-nuclei based channel model (CNCM) are introduced. Then, a novel modeling framework is proposed to implement CNCM, which consists four steps: propagation environment reconstruction, cluster-nuclei identification, multipath parameters generation, and channel coefficients generation. Three-dimensional environment with material information is utilized to map CN with scatterers in the propagation pathway. CN are identified by geometrical and electric field calculation based on environmental mapping, and multipath components within CN are calculated by statistical characteristics of angle, power and delay domains. Finally, we present a three-level verification structure to investigate the accuracy and complexity of channel modeling comprehensively. Simulation results reveal that CNCM can perform higher accuracy than geometry-based stochastic model while lower complexity compared with ray-tracing model for practical propagation environment.

Thermal and mass species transportation in tri-hybridized Sisko martial with heat source over vertical heated cylinder

Increasing knowledge of ternary hybrid nano-structures can be sketched to its distinctive achievement in enhancement of thermal energy as a useable in automobiles and dynamics of fuel dynamics. Ternary hybrid nanoparticles are based on three kinds of nanoparticles (aluminum oxide, titanium dioxide and silicon dioxide) along with base fluid (engine oil) in Sisko liquid over a vertical heated cylinder under action of magnetic field. Maximum transportation of heat transfer rate is occurred due to tri-hybrid nanoparticles as applicable in automobiles and dynamics of fuel. Aspects of heat source and chemical reaction are observed. Similarity variables are implemented to obtain ordinary differential equations from system of partial differential equations. Finite element method is implemented to simulate numerical results. Such developing investigation regarding tri-hybrid nanomaterial have various applications which are used in packing process, hair care products, electrical insulators, dental products, solar cells and fuel cells. An enhancement into temperature profile causes higher values of Eckert number, Dufour parameter and heat generation number. Diffusion of mass species becomes fast against Soret and Schmidt number but opposite trend is captured into mass species against variation in chemical reaction number. Mass diffusion rate and heat transfer rate are declined versus variation in magnetic parameter, heat source number and Dufour number.

Parametric image generation with the uEXPLORER total-body PET/CT system through deep learning

Total-body dynamic positron emission tomography/computed tomography (PET/CT) provides much sensitivity for clinical imaging and research, bringing new opportunities and challenges regarding the generation of total-body parametric images. This study investigated parametric [Formula: see text] images directly generated from static PET images without an image-derived input function on a 2-m total-body PET/CT scanner (uEXPLORER) using a deep learning model to significantly reduce the dynamic scanning time and improve patient comfort. [Formula: see text]F-Fluorodeoxyglucose ([Formula: see text]F-FDG) 2-m total-body PET/CT image pairs were acquired for 200 patients (scanned once) with two protocols: one parametric PET image (60 min, 0[Formula: see text]60 min) and one static PET image (10 min, range of 50[Formula: see text]60 min). A deep learning model was implemented to predict parametric [Formula: see text] images from the static PET images. Evaluation metrics, including the peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM), and normalized mean square error (NMSE), were calculated for a 10-fold cross-validation assessment. Moreover, image quality was assessed by two nuclear medicine physicians in terms of clinical readings. The synthetic parametric PET images were qualitatively and quantitatively consistent with the reference images. In particular, the global mean SSIM between the synthetic and reference parametric [Formula: see text] images exceeded 0.9 across all test patients. On the other hand, the overall subjective quality of the synthetic parametric PET images was 4.00 ± 0.45 (the highest possible rating is 5) according to the two expert nuclear medicine physicians. The findings illustrated the feasibility of the proposed technique and its potential to reduce the required scanning duration for 2-m total-body dynamic PET/CT systems. Moreover, this study explored the potential of direct parametric image generation with uEXPLORER. Deep learning technologies may output high-quality synthetic parametric images, and the validation of clinical applications and the interpretability of network models still need further research in future works.