Semi-analytical Model Research Articles

Formation of fast-ignition hotspots and propagartion of burning waves in pre-compressed isochoric plasmas

The formation and evolution of hotspots is important for achieving ignition and high energy gain in inertial fusion process. However, most of relevant studies are carried out on pre-compressed plasmas with an isobaric configuration, the evolution of the hotspot in a plasma with an isochoric configuration is rarely studied. In this paper, a semi-analytical model is developed to describe the evolution of the hotspot boundary and propagation of fusion burning waves for a high-density pre-compressed plasma with an isochoric configuration in the double-cone ignition scheme. For the shock wave, the strong shock wave approximation and the quasi-isobaric approximation are reasonable. The quasi-isobaric approximation shows that as the plasma density behind the shock wave increases, the plasma temperature decreases. Because of these, the range of <inline-formula><tex-math id="M4">\begin{document}$ {\mathrm{\alpha }} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231474_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231474_M4.png"/></alternatives></inline-formula>-particles decreases rapidly behind the shock wave, forming an <inline-formula><tex-math id="M5">\begin{document}$ {\mathrm{\alpha }} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231474_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231474_M5.png"/></alternatives></inline-formula>-particle absorption peak. Therefore, considering that the hotspot is the main region where <inline-formula><tex-math id="M6">\begin{document}$ {\mathrm{\alpha }} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231474_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231474_M6.png"/></alternatives></inline-formula>-particles are produced and deposited, the position of the shock peak can be used to identify the boundary of the hotspot in a high-density plasma with an isochoric configuration. It also shows that a “self-regulating burning process” exists in the burning process of the isochoric hotspot, most of <inline-formula><tex-math id="M7">\begin{document}$ {\mathrm{\alpha }} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231474_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231474_M7.png"/></alternatives></inline-formula>-particles are deposited in the stable region and behind the shock, and finally, transport through the shock peak and heat the cold fuel, resulting in the temperature rising. In the high-density hotspots of plasma with an isochoric configuration, the deposition of α-particles behaves as an obvious non-uniform distribution effect. By analyzing the non-uniform deposition of α-particles, the deposition rate of α-particles at the edge of spherical uniform hotspot is calculated, then the temperature and density evolution of the isochoric hotspot can be well described. The model can be used to estimate the Lawson parameter of the hotspots at the end of the early stage of ignition. It is found that a lower fast electron energy is more beneficial to ignition and high gain operation of fusion plasma. It is also shown that the high density of the hotspots in the isochoric plasma will lead to a higher fusion burning rate, which can offset the negative influence of the shock wave and even achieve higher energy gain. The semi-analytical model is verified by the hydrodynamic simulations of O-SUKI-N.

Dark Sage: Next-generation semi-analytic galaxy evolution with multidimensional structure and minimal free parameters

Abstract After more than five years of development, we present a new version of Dark Sage, a semi-analytic model (SAM) of galaxy formation that breaks the mould for models of its kind. Included among the major changes is an overhauled treatment of stellar feedback that is derived from energy conservation, operates on local scales, affects gas gradually over time rather than instantaneously, and predicts a mass loading factor for every galaxy. Building on the model’s resolved angular momentum structure of galaxies, we now consider the heating of stellar discs, delivering predictions for disc structure both radially and vertically. We add a further dimension to stellar discs by tracking the distribution of stellar ages in each annulus. Each annulus–age bin has its own velocity dispersion and metallicity evolved in the model. This allows Dark Sage to make structural predictions for galaxies that previously only hydrodynamic simulations could. We present the model as run on the merger trees of the highest-resolution gravity-only simulation of the MillenniumTNG suite. Despite its additional complexity relative to other SAMs, Dark Sage only has three free parameters, the least of any SAM, which we calibrate exclusively against the cosmic star formation history and the $z = 0$ stellar and H i mass functions using a particle-swarm optimisation method. The Dark Sage codebase, written in C and python, is publicly available at https://github.com/arhstevens/DarkSage.

Modeling the Operation of Charge Trap Flash Memory—Part II: Understanding the ISPP Curve With a Semianalytical Model

Modeling the Operation of Charge Trap Flash Memory—Part II: Understanding the ISPP Curve With a Semianalytical Model

Achieving controllable and reversible snap-through in pre-strained strips of liquid crystalline elastomers.

Deformable, elastic materials that buckle in response to external stimuli can display "snap-through", which involves a transition between different, stable buckled states. Snap-through produces a quick release of stored potential energy, and thus can provide fast actuation for soft robots and other flexible devices. Liquid crystalline elastomers (LCEs) exposed to light undergo a phase transition and a concomitant mechanical deformation, allowing control of snap-through for rapid, large amplitude actuation. Using both a semi-analytical model and finite element simulations, we focus on a thin LCE strip that is clamped at both ends and buckles due to an initially imposed strain. We show that when this clamped, strained sample is exposed to light, it produces controllable snap-through behavior, which can be regulated by varying the light intensity and the area of the sample targeted by light. In particular, this snap-through can be triggered in different directions, allowing the system to be reset and triggered multiple times. Removing the light source will cause the system to settle into one of two stable states, enabling the encoding and storage of information in the system. We also highlight a specific case where removing the light source removes the induced buckling and returns the material to an initially flat state. In this case, the system can be reset and form a new shape, allowing it to function as a rewriteable haptic interface.

Disappearing Galaxies: The Orientation Dependence of JWST-bright, HST-dark, Star-forming Galaxy Selection

Galaxies that are invisible in deep optical–near-infrared imaging but detected at longer wavelengths have been the focus of several recent observational studies, with speculation that they could constitute a substantial missing population and even dominate the cosmic star formation rate density at z ≳ 4. The depths now achievable with JWST at the longest wavelengths probed by the Hubble Space Telescope (HST), coupled with the transformative resolution at longer wavelengths, are already enabling detailed, spatially resolved characterization of sources that were invisible to HST, often known as “HST-dark” galaxies. However, until now, there has been little theoretical work to compare against. We present the first simulation-based study of this population, using highly resolved galaxies from the Feedback in Realistic Environments project, with multiwavelength images along several lines of sight forward-modeled using radiative transfer. We naturally recover a population of modeled sources that meet commonly used selection criteria (H AB > 27 mag and H AB − F444W > 2.3). These simulated HST-dark galaxies lie at high redshifts (z = 4–7), have high levels of dust attenuation (A V = 2–4), and display compact recent star formation (R 1/2,4.4 μm ≲ 1 kpc). Orientation is very important: for all but one of the 17 simulated galaxy snapshots with HST-dark sight lines, there exist other sight lines that do not meet the criteria. This result has important implications for comparisons between observations and models that do not resolve the detailed star-dust geometry, such as semianalytic models or coarsely resolved hydrodynamical simulations. Critically, we demonstrate that HST-dark sources are not an unexpected or exotic population, but a subset of high-redshift, highly dust-attenuated sources viewed along certain lines of sight.

Four-wave mixing model for centrosymmetric constellation shaping in twin-wave-based coherent OFDM system including intersymbol interference

The four-wave-mixing (FWM) noises are modeled when walk-off and intersymbol interference (ISI) are taken into account for any centrosymmetric constellation shaped signal in orthogonal frequency-division multiplexed (OFDM) with phase-conjugated twin waves (PCTW) scheme. Bit error rate (BER) and the equivalent Q-factor for any constellation shaped signal are also modeled when the FWM and amplified spontaneous emission (ASE) noises are taken into account as additive white Gaussian noise. By using the newly derived semi-analytic models, example calculations are carried out for 16-ary signal in PCTW OFDM system with four cases classified according to some proposed constellation shaping schemes adopted or not. A hybrid constellation shaping scheme consisted of Huffman-coded probabilistic shaping and radius-optimized geometric shaping is proposed. The performance gain in terms of the equivalent Q-factor is calculated to be about 0.563 dB for 16-ary signal in PCTW OFDM system with the proposed hybrid constellation shaping scheme over the square conventional 16QAM signal. The performance degradation for such system due to the effects of ISI on the FWM noise is also evaluated by using the semi-analytic calculation models.

Effective transport properties of porous composites applied to MIEC SOC electrodes

The effect of composite conductivity and its implications for microstructure design are studied for a porous composite. Three semi-analytical models are suggested to predict the effective composite conductivity in an efficient and accurate way.

Analysis of the Lift-Off Effect in Motion-Induced Eddy Current Testing Based on Semi-Analytical Model

Analysis of the Lift-Off Effect in Motion-Induced Eddy Current Testing Based on Semi-Analytical Model

Two-dimensional semi-analytical steady-state thermal model of permanent magnet machines with water-cooled structure

Two-dimensional semi-analytical steady-state thermal model of permanent magnet machines with water-cooled structure

New rationale for the effect of multiple buoyancies and their influence on the propagation of respiratory pollutants

The effect of buoyancy on fluid flows is a significant consideration in problems relating to energy, the environment, and health. Here, we examine what we term a “multi-buoyancy effect” (MBE), or “fluid-bunching effect,” which is a combination of the Archimedes number (Ar)-related buoyancy resulting from the temperature difference between a fluid flow and the ambient fluid and the Gc number (Gc)-related buoyancy resulting from the temperature difference between the upper and lower boundaries of the fluid domain. A new semi-analytical mathematical model of the jet trajectory is put forward by rational reconstruction. This reveals the physical mechanisms of fluid flows propagating in limited spaces under this MBE. Human respiratory experiments were conducted to show that the MBE can govern the transmission of infective airborne pollutants between people. Our findings provide a new perspective in the transmission of fluid flows and airborne pollutants in limited spaces. They are, thus, also of great interest for predicting the stratification of flows and circulation of the atmosphere and ocean.

On bursty star formation during cosmological reionisation – how does it influence the baryon mass content of dark matter halos?

Abstract The baryon mass content (i.e. stellar and gas mass) of dark matter halos in the early Universe depends on both global factors – for example, ionising ultraviolet (UV) radiation background – and local factors – for example, star formation efficiency and assembly history. We use a lightweight semi-analytical model to investigate how both local and global factors impact the halo baryon mass content at redshifts of $z\geq 5$ . Our model incorporates a time delay between when stars form and when they produce feedback of $0\leq t^d/\mathrm{Myr} \leq 30$ , which can drive bursts of star formation, and a mass and redshift-dependent UV background, which captures the influence of cosmological reionisation on gas accretion onto halos. We use statistically representative halo assembly histories and assume that the cosmological gas accretion rate is proportional to the halo mass accretion rate. Delayed ( $t^d$ >0) feedback leads to oscillations in gas mass with cosmic time, behaviour that cannot be captured with instantaneous feedback ( $t^d$ =0). Highly efficient star formation drives stronger oscillations, while strong feedback impacts when oscillations occur; in contrast, inefficient star formation and weak feedback produce similar long-term behaviour to that observed in instantaneous feedback models. If the delayed feedback timescale is too long, a halo retains its gas reservoir but the feedback suppresses star formation. Our model predicts that lower mass systems (halo masses $m_\mathrm{h} \leq 10^7 \mathrm{M}_\odot$ ) at $z \leq 10$ should be strongly gas deficient ( $m_\mathrm{g}\rightarrow 0$ ), whereas higher mass systems retain their gas reservoirs because they are sufficiently massive to continue accreting gas through cosmological reionisation. Interestingly, in higher mass halos, the median $m_\star/(m_\star+m_\mathrm{g}) \simeq 0.01-0.05$ , but is a factor of 3–5 smaller when feedback is delayed. Our model does not include seed supermassive black hole feedback, which is necessary to explain massive quenched galaxies in the early Universe.

A Semi-Analytic Model for Temperature Distribution Prediction and Hotspot Tracking in SPMSM and Its Application for Improved Multiphysics Multiobjective Optimization Design

A Semi-Analytic Model for Temperature Distribution Prediction and Hotspot Tracking in SPMSM and Its Application for Improved Multiphysics Multiobjective Optimization Design

Space Charge Forces analytical model for emittance compensation

Space charge forces represent main induced effects in an RF-injector that degrade the beam quality. In this scenario the laser distribution sent on the photocathode acquires an important role in the emittance compensation process, as the slice analysis shows. Starting from the preliminary studies performed on [1], a novel semi-analytical model of space charge forces is proposed in detail for bunch with arbitrary charge distribution to derive expressions of self-induced forces. The performance of the fields at low energy regime (as the field has not expired RF forces) is under present analysis, we can investigate use of this model in low charge regime. Further, the model has been bench-marked with the behavior of the distributions present in the literature and studied for new ones. It has also been applied for the study of the optimization of a C-band hybrid photoinjector now being commissioned, thus explaining the factor two reduction of the emittance observed at the exit of the gun by changing the initial distribution at the cathode.

Полуаналитическая модель взаимодействия дисковой секции лущильника с неоднородной по глубине почвой

The draft force of a harrow disc gang determines the specific energy cost of tillage. To minimize the cost of determining the draft force of the disc gang in relation to the harrow parameters and soil properties, the author carried out a mathematical modeling of the interaction of the harrow gang with the soil. The semi-analytical model has been built on the assumption of variable depth soil, constancy of depth, forward speed and approach angle of the harrow. It is shown that when the soil is variable only in depth, it can be characterised by two empirical constants and the coefficient of friction of the soil on the disc surface. The kinematic parameter of the disc gang, equal to the ratio of the circumferential speed on the disc blades to the forward speed of the harrow, is determined by the soil properties, the relative depth, equal to the ratio of the working depth to the radius of the discs, and the approach angle of the harrow gang. Based on the analysis of the moments of the soil resistance forces to cutting and friction, the author has shown that when the friction forces in the disc bearings in the variable depth soil are negligibly small, the disc gang of the harrow rotates at an angular speed that provides the minimum possible power of the harrow gang required for tillage. Explicit expressions are obtained for the required power and tractive force of the harrow gang as a function of the number of discs, the angle of approach of the harrow gang, the relative depth, the radius of the discs and the soil properties. Their comparison with published field experiments showed that the maximum relative error in determining the draft of a harrow gang with flat discs was 3.3% for post-harvest stubble harrowing, and 2.6% for a harrow gang with spherical discs in a tillage bin.

Establishment and Application of a Semianalytical Model of Ultrasonic Power Transfer

Establishment and Application of a Semianalytical Model of Ultrasonic Power Transfer

A Pathway for Collisional Planetesimal Growth in the Ice-dominant Regions of Protoplanetary Disks

We present a semi-analytic model for the growth, drift, desorption, and fragmentation of millimeter- to meter-sized particles in protoplanetary disks. Fragmentation occurs where particle collision velocities exceed critical fragmentation velocities. Using this criterion, we produce fragmentation regions in disk orbital radius–particle size phase space for particles with a range of material properties, structures, and compositions (including SiO2, Mg2SiO4, H2O, CO2, and CO). For reasonable disk conditions, compact aggregate H2O, CO2, and CO ice particles do not reach destructive relative velocities and are thus not likely to undergo collisional fragmentation. Uncoated silicate particles are more susceptible to collisional destruction and are expected to fragment in the inner disk, consistent with previous work. We then calculate the growth, drift, and sublimation of small particles, initially located in the outer disk. We find that ice-coated particles can avoid fragmentation as they grow and drift inward under a substantial range of disk conditions, as long as the particles are aggregates composed of 0.1 μm-sized monomers. Such particles may undergo runaway growth in disk regions abundant in H2O or CO2 ice, depending on the assumed disk temperature structure. These results indicate that icy collisional growth to planetesimally relevant sizes may happen efficiently throughout a disk’s lifetime, and is particularly robust at early times when the disk’s dust-to-gas ratio is comparable to that of the interstellar medium.

Galaxy catalogs from the Sage Semi-Analytic Model calibrated on The Three Hundred hydrodynamical simulations: A method to push the limits toward lower mass galaxies in dark matter only clusters simulations

The new generation of upcoming deep photometric and spectroscopic surveys will allow us to measure the astrophysical properties of faint galaxies in massive clusters. This would demand to produce simulations of galaxy clusters with better mass resolution than the ones available today if we want to make comparisons between the upcoming observations and predictions of cosmological models. But producing full-physics hydrodynamical simulations of the most massive clusters is not an easy task. This would involve billions of computational elements to reliably resolve low mass galaxies similar to those measured in observations. On the other hand, dark matter only simulations of cluster size halos can be done with much larger mass resolution but at the cost of having to apply a model that populate galaxies within each of the subhalos in these simulations. In this paper we present the results of a new set of dark matter only simulations with different mass resolutions within the The Three Hundred project. We have generated catalogs of galaxies with stellar and luminosity properties by applying the Sage Semi-Analytical Model of galaxy formation. To obtain the catalogs consistent with the results from hydrodynamical simulations, the internal physical parameters of Sage were calibrated with the Particle Swarm Optimization method using a subset of full-physics runs with the same mass resolution than the dark matter only ones.

Performance degradation of steel rebar considering corrosion spatial variability in concrete

The corrosion of steel bars is the main issue affecting the durability of reinforced concrete structures, which is nonuniform owing to the material properties and external environmental effects. In this study, the performance degradation of steel rebars in concrete is estimated considering corrosion spatial variability. With the aid of a three-dimensional measurement technique, a finite element model based on the scanning result was established to examine the corrosion effect on the tensile behaviour of the corroded bars, which was validated with the experimental results and digital image correlation observation. To assess the deformation behaviour of the corroded steels, a semi-analytical model was developed based on the cross-sectional area distribution and material properties. Subsequently, the spatial weight loss distributions with different degrees of corrosion were generated using a random field model. The model parameters were determined by combining engineering judgement and estimation of the experimental results. Finally, probabilistic model of degraded performance was established using the deterministic assessment and simulated steel weight loss distribution.

Air-Side Thermal Behavior of Parallel-Plate Evaporators. Part I: Sensible Heat Transfer

An experimentally validated mathematical model is presented to simulate the thermal behavior of a new type of roll bond parallel-plate evaporators intended for use in domestic “no-frost” refrigerators. An open-loop wind-tunnel calorimeter was used to generate experimental data on the air-side thermal conductance for air flow rates ranging from 17 to 85 m3/h. The semi-analytical mathematical model consists of dividing the evaporator in several differential control volumes involving the air, plate and coolant domains and solving the coupled energy equations for the three domains to generate spatially resolved temperatures in the air, aluminum plate and refrigerant (coolant). Good agreement was obtained between the model results and the experimental data (80% of the data point predicted to within ± 5% error bands) without the introduction of new empirical parameters. In Part II, the model is extended to deal with frost accretion on the plates.

Numerical-analytical modeling of oil extraction from oil fields with a gas cap using horizontal wells with automatic history matching

The article describes a numerical-analytical model for gas breakthrough to a well during the development of oil fields with a gas cap using horizontal wells. The employed semi-analytical model allows describing the process of gas cone development and reproducing oil and gas production parameters from the well by matching to the actual production history using several coefficients. The numerical scheme of the model was implemented as a computational library in the Python 3.6 programming language. The algorithm was tested on oil deposits with a gas cap in the South Yamal oil and gas region and showed good results in history matching and forecasting calculations. The average calculation time of one iteration being less than 10 seconds allows for multiple model run scenarios using optimization algorithms for automatic calibration to actual production data. The results of the testing show the possibility of achieving satisfactory convergence using automated calibration to the production history. The developed algorithm reduces the workload of specialists in forecasting production, thereby enhancing the effectiveness of decisions made for development optimization.