Theoretical Model Calculations Research Articles

Excitation functions for 209Bi reactions induced by threshold to 50 MeV energy alpha particles

Excitation functions for 209Bi(α,2n)211At, 209Bi(α,3n)210At and 209Bi(α,4n)209At reactions were calculated using TALYS-1.95 nuclear code from threshold to 50 MeV by invoking suitable options for level densities, nucleon-nucleus optical model potentials and alpha optical model potentials. Statistical factors were used to verify the quality of matching between theoretical model calculations and the experimental data from the EXFOR database. The TTY of 211At calculated using the excitation function of 209Bi(a,2n)211At reaction is compared with existing experimental studies from literature The results of the present study are important for the validation of nuclear model approaches with increased predictive power for 209Bi(α,xn) reactions for the production of 211At.

Magneto-Refractive Effect and Mechanism Analysis of Erbium-Ytterbium Co-Doped Silica Fiber

The magneto-refractive properties of Er/Yb co-doped silica fiber (EYDF) are important in magnetic field sensing. Here, we proposed a theoretical calculation model of the EYDF using density functional theory (DFT) and demonstrated it by an interferometric digital hologram magneto-refractive measurement system. The calculation results show that the fiber material, doped with Er/Yb atoms, has a large net spin and asymmetric spin distribution, which enables the elements to play an important role in the magnetic characteristics of the material. The experimental results show that the refractive index of the fiber decreases linearly with the increase of the magnetic field. The sensitivity of EYDF is 3.8279 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> RIU/Gs and is two orders of magnitude higher than that of single-mode fiber which is confirmed by the theoretical calculation. It demonstrated that the EYDF has advantages and potential of high sensitivity, miniaturization, and easy integration for magnetic field detection in harsh environments.

Vibroacoustic characteristics analysis of a planetary gear reducer considering the exterior housing structure

Abstract. Previous studies have attempted to identify weak links in the dynamic characteristics of the planetary gear reducer (PGR) exterior body structure (EBS). Through numerical simulation, these studies analyzed the mode and natural frequencies and the vibration types of each order of the EBS. However, these scholars have never focused on the main factors affecting the dynamic characteristics of the EBS of this subject. This study in the topic has analyzed the vibroacoustic characteristics of an EBS and optimized its design using numerical simulation. Herein, the contribution of the vibration transfer path from the excitation points on the exterior body to the machine foot is emphatically revealed, and the influences of the main structural parameters on the transfer characteristics are discussed. An optimal EBS for a PGR with lower acoustic vibrations is designed in detail, and a composite EBS with damping vibration attenuation and acoustic absorption is proposed. The radiation acoustic characteristics without acoustic protection and damping materials are analyzed. These research results are implemented in order to realize the dynamic characteristics, transmission, and radiation acoustic characteristics as objects of optimization, and the structural design parameters of the PGR exterior body are deeply optimized using dynamic modification and sensitivity analysis. This topic focuses on the vibroacoustic coupling of EBS in stationary fluid and average flow field. Based on the analysis method of theoretical modeling and numerical calculation, the EBS dynamic response and vibroacoustic characteristics under the action of frontal excitation external acoustic flow field are studied, which will be beneficial to explore the comprehensive optimization design of PGR dynamic and vibroacoustic properties.

Theoretical calculation model of insulation medium and eddy current heating under complex waveform of ±800kV convertor transformer RIP bushing used in valve side

Electrical and thermal properties of the converter transformer valve side RIP DC bushing interact with each other, so electrical insulation failure in operation is directly related to the thermal properties. It is essential to conduct quantitative analysis on the power loss of UHV converter transformer dry-type bushing. The total power loss of bushing consists of two parts, eddy heat from current-carrying structures and joule heat from bushing core. The actual current and voltage waveform imposed on the bushing contain many high frequency components. In this paper, the theoretical calculation model of bushing core joule heat and eddy heat is obtained from structure of HV convertor transformer dry-type bushing. Then the temperature and frequency properties of epoxy impregnated paper used by dry-type bushing core are acquired by the experiments. Furthermore, based on the frequency domain FEM, the numerical calculation method for dry-type bushing power loss is proposed. In the end, the numerical results are used to analyze the factors that may lead to convertor transformer drytype bushing insulation failure in operation. The research result obtained in this paper is appropriate to compute thermal characteristic of bushing and is of directive significance to the operation, protection and accident analysis.

Activation cross sections of deuteron-induced reactions on praseodymium up to 24 MeV

We measured activation cross sections of deuteron-induced reactions on 141Pr. The production cross sections of 141,140Nd, 142Pr, and 139Ce were determined up to 24 MeV using the stacked-foil activation technique and high-resolution γ-ray spectrometry. The derived cross sections were compared with experimental data studied earlier and theoretical model calculations. Our results are consistent with part of the previous data.

Dynamic positioning error analysis and modeling of CNC machine tool guideway system

The dynamic characteristics of the XY worktable are thoroughly analyzed in this study to accurately compensate the measurement errors of on-machine measurement systems caused by the dynamic and static characteristics under multiple factors. The dynamic positioning error model of the XY worktable motion components is established, and the theoretical model of the dynamic positioning error of the XY worktable is derived. The actual parameters of the experimental platform for the correlation error of CNC machine tools are substituted into the model for theoretical calculation and analysis. Results show that the motion speed of the worktable, the weight of the measured workpiece, the installation position of the workpiece, and the friction force are the main factors causing the dynamic positioning error. Dynamic positioning error analysis and verification experiments were conducted to verify the validity of the proposed theoretical model. Experimental results show that a regular change occurs between the dynamic positioning error and the movement speed of the XY worktable, and the actual measurement results are basically consistent with the theoretical calculation results. The research results can lay a good foundation for establishing the measurement error prediction and compensation model of on-machine measurement systems of CNC machine tools and improving its measurement accuracy.

Numerical simulation analysis of a PGR exterior body structure considering vibroacoustic characteristics

Previous studies have attempted to identify weak links in the dynamic characteristics of the planetary gear reducer (PGR) exterior body structure (EBS). Through numerical simulation, these studies analyzed the modals and natural frequencies and the vibration types of each order of the EBS. However, these scholars have never focused on the main factors affecting the dynamic characteristics of the EBS of this subject. This study in the topic has analyzed the vibroacoustic characteristics of an EBS and optimized its design using numerical simulation. Herein, the contribution of the vibration transfer path from the excitation points on the exterior body to the machine foot is emphatically revealed, and the influences of the main structural parameters on the transfer characteristics are discussed. An optimal EBS for a PGR with lower acoustic vibrations is designed in detail, and a composite EBS with damping vibration attenuation and acoustic absorption is proposed. The radiation acoustic characteristics without acoustic protection and damping materials are analyzed. These research results are implemented in order to realize the dynamic characteristics, transmission, and radiation acoustic characteristics as objects of optimization, and the structural design parameters of the PGR exterior body are deeply optimized using dynamic modification and sensitivity analysis. This topic focuses on the vibroacoustic coupling of EBS in stationary fluid and average flow field, based on the analysis method of theoretical modeling and numerical calculation, the EBS dynamic response and vibroacoustic characteristics under the action of frontal excitation external acoustic flow field are studied, which will be beneficial to explore the comprehensive optimization design of GPR dynamic and vibroacoustic properties.

Study on the design method of interference fit between gear and shaft of automobile transmission

The interference fit of gear and shaft in automobile transmission has an important influence on the performance of gear transmission. In order to design reasonably and calculate accurately, the theoretical calculation model of the interference fit between gear and shaft is established according to the principles of elastic-plastic mechanics. A new method of calculating the amount of interference is designed based on the Lame equation. Three limiting conditions are taken in the calculation. They are load transfer capacity of gear, no plastic deformation of fitting surface and control of gear tooth deformation. The theoretical calculation and finite element simulation analysis are carried out in an application case. The results of calculation and analysis show that the interference fit of gear and shaft has an important influence on the gear tooth deformation. The amount of interference calculation method in this paper can reduce the deformation of gear tooth and make the gear have higher accuracy.

A theoretical model for the estimate of plateau force for the crushing process of 3D auxetic anti-tetra chiral structures

Auxetic, anti-tetra-chiral structures designed as tubes subjected to axial quasi-static crushing were investigated in this research. Experimental work was carried on samples manufactured by laser cutting from a pipe. At the same time, numerical simulations were performed using a parametric numerical model of the structure. The experimental results analysis revealed that the crushing force presents a plateau region that extends up to the densification phase defined by the close contact between the ligaments joining the nodes. Subsequently, based on the representative unit's deformation characteristics, theoretical calculation models were established to estimate the plateau force. According to Bernoulli's beam model, the force calculation model was developed from the plastic hinge's structural design and theory. Sametime, the length or crushing distance with a constant force (plateau), can be estimated to provide the complete set of parameters for design activities. The analytical solution was validated against results obtained numerical simulation for various configurations. There is a good agreement between experimental, numerical, and theoretical results that proves the proposed model's reliability to estimate plateau force. Furthermore, individual parts were stacked to define graded structures. It was found that the crushing force displays successive stages according to each individual part. There is a possibility to reconstruct the response for stacked structure from the individual response using the analytical solution's results for force and length of individual plateau stages.The set of equations can design this structure when the capable load is one of the input parameters.

Comprehensive model for predicting the fuel consumption in various harvesting methods of grass silage

Fuel consumption of various forage harvesting methods was assessed with a theoretical calculation model, which was validated with field measurements. The examined harvesting methods were tractor-powered forage harvester (TPFH), self-propelled forage harvester (SPFH), self-loading forage wagon (SLFW), and combined baling and wrapping (CBW). The results from the field measurements indicated that the model was working either well or satisfactorily with the examined methods, apart from the CBW method, which would require redefining the model coefficients. Model sensitivity analysis indicated that variables such as yield level, working width, and transportation distance have a significant effect on fuel consumption. When the working width was increased from 3 m to 9 m, the fuel consumption of the examined methods decreased ca. 54–61%. Increasing the working width by windrowing was found recommended for all examined methods. In all, the most energy-efficient method was SLFW, but it was also most sensitive to transportation distance. With a transportation distance of 10 km, the fuel consumption of the SLFW method was already 9–11 % higher compared to that of TPFH and SPFH methods. The strong effect of these variables may cause a wide variation in the fuel consumption of the examined methods, but the model can be used to standardize this effect. The results from this study can thus be used for approximate estimations of average fuel consumption of the examined forage harvesting methods.

A New Method for Reducing Collapsibility of Loess Foundation with Thicker Deposit: The Borehole Preimmersion Method

At present, there are some key issues in the traditional preimmersion method for reducing the collapsibility of the loess ground, such as the difficulty in determining the total water consumption and the long immersion time. In response to these issues, a new method, the borehole preimmersion method, is presented, and a specific theoretical design model is proposed for application in projects. The method is specifically discussed from a new perspective, and the diffusion mechanism and evolution law of water in the ground are presented in detail through theoretical analysis and numerical calculation, respectively. The water diffusion is a mushroom-type form for a single water injection hole immersed in water. A calculation model derived for a single water injection hole or a group of water injection holes based on the research results is used to calculate the volumes of soaked loess and the total water consumption. Through an in situ immersion test, the treatment effect of this method is evaluated to verify the rationality of the method and the theoretical calculation model proposed in this study, which provides a new method and theoretical framework for effectively reducing the collapsibility of the loess ground.

Relaxor ferroelectricity in the polar M2P-TCNQ charge-transfer crystal at the neutral-ionic interface

We investigated the mixed-stack charge-transfer crystal, N,N'-dimethylphenazine-TCNQ (M$_2$P-TCNQ), which is polar at room temperature and just at the neutral-to-ionic interface (ionicity $\rho \approx 0.5$). We detect the typical dielectric signature of a relaxor ferroelectric and an asymmetric positive-up-negative-down behavior. While relaxor ferroelectricity is usually ascribed to disorder in the crystal, we find no evidence for structural disorder in the investigated crystals. To elucidate the origin of M$_2$P-TCNQ's dielectric properties we perform parallel structural and spectroscopic measurements, associated with theoretical modeling and quantum-mechanical calculations. Our combined effort points to a highly polarizable electronic system that is strongly coupled to lattice vibrations. The found indications for polarization reversal imply flipping of the bent conformation of the M$_2$P molecule with an associated energy barrier of a few tens of an eV, broadly consistent with an Arrhenius fit of the dielectric relaxation times. While the polarization is mostly of electronic origin, its possible reversal implies slow collective motions that are affected by solid-state intermolecular interactions.

Role of Joule heating in the electro-induced metal-insular transition of a composite film filled with VO2

Vanadium dioxide is a typical representative of a strong electronic correlation system. Triggered by stimuli such as heat and electric fields, VO2 can undergo a reversible transition from insulating to metallic phase and has therefore attracted attention of many researchers. In this work, a hydrothermal method was used to prepare nano-VO2 particles with phase transition. According to the phenomenology, finite element simulation and theoretical calculation models of the electro-induced phase transition (E-MIT) in the VO2-filled Polyethylene glycol were established. Electrode-gap effect on the phase-transition voltage of E-MIT was discussed. Furthermore, the phase transition and heat distribution processes were analyzed. The results revealed that high-temperature conductive channels are formed in the VO2 structure during the electro-induced phase transition. Moreover, position of these channels is determined by the high-voltage edge effect of the electrode and the heat dissipation effect of the material. The ideal adiabatic E-MIT process was also evaluated. The phase change voltage curve of the theoretical model was well matched with the simulation model. The results reveal that the temperature in the channel is significantly lower than the typical phase change temperature when a phase transition occurs. In addition, owing to an applied voltage, the resistance of the VO2 composite material can drop suddenly even if the temperature rise is small. The analysis results verified that Joule heating is an important factor in the electro-induced phase transition of VO2-filled polymers. The experimental results are helpful in understanding the E-MIT mechanism of VO2 composite materials and the subsequent application of these materials.

Investigation on groove depth of artificial dam of underground reservoir in coal mines

Water storage in underground reservoirs serves as an important means of water resource protection in coal mines in Western China. The groove depths of the artificial dam required plays an important role in the design of these underground reservoirs. The underground reservoir of the Wulanmulun coal mine was examined in this study using theoretical analysis and similar simulation experiment, and the groove depth was optimized using FLAC3D based on the results obtained. According to the theoretical calculation model of the groove depth, the safe groove depth was determined to be 0.2 m. It was found that the groove was the weakest point in the reservoir with the most serious seepage and maximum likelihood of failure. The variation curve of the volume of the plastic zone followed a U-shaped distribution. The side, roof, and floor depths corresponding to the minimum volume of the plastic zone were determined to be 0.6 m, 0.2 m, and 0.3 m, respectively. The analysis indicates that increasing the groove depth within a certain range can enhance the stability of the reservoir; however, as the groove depth exceeds a critical value, the increase in groove depth was unfavorable for the stability of the reservoir. Moreover, increasing the side groove depth above the critical value was more effective in enhancing the stability of the reservoir than increasing the roof and floor groove depths.

Generic algorithm for multiparticle cumulants of azimuthal correlations in high energy nucleus collisions

Multi-particle cumulants of azimuthal angle correlations have been compelling tools to probe the properties of the Quark-Gluon Plasma (QGP) created in the ultra-relativistic heavy-ion collisions and the search for the QGP in small collision systems at RHIC and the LHC. However, only very few of them are available and have been studied in theoretical calculations and experimental measurements. In this paper, we present a generic recursive algorithm for multi-particle cumulants, which enables the calculation of arbitrary order multi-particle cumulants. Among them, the new 10-, 12-, 14-, and 16-particle cumulants of a single harmonic, named $c_{n}\{10\}$, $c_{n}\{12\}$, $c_{n}\{14\}$, and $c_{n}\{16\}$, and the corresponding $v_n$ coefficients, will be discussed for the first time. These new multi-particle cumulants can be readily used along with updates to the generic framework of multi-particle correlations to a very high order. Finally, we propose a particular series of mixed harmonic multi-particle cumulants, which measures the general correlations between any moments of different flow coefficients. The predictions of these new observables are shown based on an initial state model MC-Glauber, a toy Monte Carlo model, and the HIJING transport model for future comparisons between experimental data and theoretical model calculations. The study of these new multi-particle cumulants in heavy-ion collisions will significantly improve the understanding of the joint probability density function which involves both different harmonics of flow and also the symmetry planes. This will pave the way for more stringent constraints on the initial state and help to extract more precisely how the created hot and dense matter evolves. Meanwhile, the efforts applied to small systems could be very helpful in the understanding of the origin of the observed collectivity at RHIC and the LHC.

Research on water and heat management in the cold start process of proton exchange membrane fuel cell with expanded graphite bipolar plate

Water storage space and heat capacity are important factors affecting the cold start ability of fuel cell, and heat capacity is affected by materials. In the present study, the lumped static model and two-dimensional dynamic prediction model of the fuel cell with expanded graphite bipolar plates were established. The relationship between water storage space, heat production, heat capacity and the maximum temperature rise is analyzed based on the theoretical calculation model, and the cold start ability is also predicted. The calculation results show that the heat capacity of the bipolar plate is 1.3 J/K·cm2, which accounts for the largest proportion of 34% of all components. With the help of the heat generated by the air compressor, the reactor can be started in 100 s at −30 ℃ and 1.2A/cm2. The temperature difference in the reactor during cold start-up is about 2℃, which proves the reasonability of the isothermal assumption in the static model. The dynamic impedance spectroscopy experiment results show that the super cooled water icing during the cold start will cause the gas transmission impedance to increase rapidly, indicating that the icing mainly occurs at the pores or interfaces inside the catalyst layer and the gas diffusion layer during the cold start.

Tunnel Junctions with a Doped ( In,Ga)N Quantum Well for Vertical Integration of III -Nitride Optoelectronic Devices

Properties of tunnel junctions (TJs) grown by plasma-assisted molecular beam epitaxy are investigated. Examined TJs consist of a ($\mathrm{In},\mathrm{Ga})\mathrm{N}$ quantum well (QW) sandwiched between ${\mathrm{In}}_{0.02}{\mathrm{Ga}}_{0.98}\mathrm{N}$ barriers. The influence of piezoelectric polarization, doping, and width of a TJ QW on resistivity of TJs is studied. A decrease of TJ resistivity is observed for high doping and high ($\mathrm{In},\mathrm{Ga})\mathrm{N}$ composition. Additionally, the crystal quality of TJs as a function of magnesium and silicon doping in a ($\mathrm{In},\mathrm{Ga})\mathrm{N}$ QW is discussed. Generation of defects in highly doped layers is observed in transmission electron microscopy and by defect selective etching. High doping leads to deterioration of surface morphology, which is corroborated by atomic force microscopy imaging. TJs with low resistance and high crystalline quality, without formation of structural defects, are demonstrated. A theoretical model for calculation of tunneling currents is proposed based on Kane tunneling theory, which considers a realistic electric field distribution in a TJ. A good agreement with the experimental data is obtained. The model is used to predict electrical parameters in a wide range of ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ compositions (x = 0--0.40), doping (${n}_{\mathrm{Mg},\mathrm{Si}}={10}^{17}\ensuremath{-}5\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{0.25em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$), and TJ QW width (d = 2 -- 12 nm).

The therapeutic mechanism of epilepsy seizures in different target areas: Research on a theoretical model.

BACKGROUND:The selection of optimal target areas in the surgical treatment of epilepsy is always a difficult problem in medicine.OBJECTIVE: We employed a theoretical calculation model to explore the control mechanism of seizures by an external voltage stimulus acting in different nerve nuclei.METHODS:Theoretical analysis and numerical simulation were combined.RESULTS: The globus pallidus, excitatory pyramidal neurons, striatal D1 neurons, thalamic reticular nucleus and specific relay nuclei were selected, we analyzed that the electrical stimulation has different effects in these target areas.CONCLUSIONS:The data selected were reasonable in study, the results may give a theoretical support for similar studies in clinical.

Anisotropic flow of photons in relativistic heavy ion collisions

Electromagnetic radiations are one of the potential probes to study the initial state of the hot and dense quark-gluon plasma (QGP) produced during the collision of heavy nuclei at relativistic energies. Photons are emitted throughout the lifetime of the evolving system and carry undistorted information from the production point to the detector. The observation of large anisotropic flow of charged particles provides a strong confirmation of QGP formation and collective behaviour of the produced matter in these collisions. However, the theoretical model calculations which explain the hadronic spectra and anisotropic flow successfully, underpredict the experimental data of elliptic as well as triangular flow of photons by a large margin. This discrepancy between data and theory results is known as direct photon puzzle. In this article, we review the anisotropic flow of photons calculated using hydrodynamical model framework for different collision systems and beam energies. In addition, we propose some new ideas which can be valuable for understanding direct photon puzzle.

Material properties and performance of ErAs:In(Al)GaAs photoconductors for 1550 nm laser operation

ErAs:In(Al)GaAs photoconductors have proven to be outstanding devices for photonic terahertz (0.1–10 THz) generation and detection with previously reported sub-0.5 ps carrier lifetimes. We present the so far most detailed material characterization of these superlattices composed of ErAs, InGaAs, and InAlAs layers grown by molecular beam epitaxy. The variation of the material properties as a function of the ErAs concentration and the superlattice structure is discussed with focus on source materials. Infrared spectroscopy shows an absorption coefficient in the range of 4700–6600 cm−1 at 1550 nm, with shallow absorption edges toward longer wavelengths caused by absorption of ErAs precipitates. IV characterization and Hall measurements show that samples with only 0.8 monolayers of electrically compensated ErAs precipitates (p-delta-doped at 5×1013 cm−2) and aluminum-containing spacer layers enable high dark resistance (∼10–20 MΩ) and high breakdown field strengths beyond 100 kV/cm, corresponding to &amp;gt;500 V for a 50 μm gap. With higher ErAs concentration of 1.6 ML (2.4 ML), the resistance decreases by a factor of ∼40 (120) for an otherwise identical superlattice structure. We propose a theoretical model for calculation of the excess current generated due to heating and for the estimation of the photocurrent from the total illuminated current. The paper concludes with terahertz time-domain spectroscopy measurements demonstrating the strengths of the material system and validating the proposed model.