Numerical Calculation Method Research Articles

A method for evaluation of the probability density function of white noise filtered non-Gaussian stochastic process

Passing non-Gaussian white noises through a pre-designed linear filter can generate non-Gaussian stochastic processes with desired probabilistic and spectral properties. This linear filtering methodology has been extensively employed in non-Gaussian signal processing and simulation. At present, the investigation of probability properties for the output non-Gaussian processes is primarily concentrated on the higher-order statistics, spectra, and correlation functions. However, evaluating the probability density function (PDF) of the output process remains a challenging task. In order to address this issue, this short communication commences with the theoretical derivation of the PDF formula for the white noise filtered non-Gaussian stochastic process. The derived PDF is the result of a convolution of multiple PDFs, each obtained by applying a scaling transformation to the input white noise PDF. Subsequently, a discretized numerical calculation method is proposed to overcome the analytical difficulties associated with the computation of multiple convolutions. Finally, the accuracy and efficiency of the proposed method are demonstrated through several numerical examples.

Research on a novel compliant mechanism applied in the vehicle side door latch and stability analysis via Lyapunov exponents

The functional reliability of the vehicle latch is very important and is determined by the internal mechanism’s motion stability. In this paper, a novel compliant mechanism constructed with a novel compliant joint is applied to the vehicle latch, and multiple mode motions of the mechanism realize the newly added electric power release function. The repeatability of mechanism trajectories and phase diagrams of several different periodic motions is creatively regarded as the stability of the compliant mechanism. In this compliant mechanism, the endpoint of the groove-coupler is chosen as a characteristic point and the compliant joint’s spring stiffness kT is taken as the key parameter to obtain trajectories and phase diagram. It is found that all cycle overlapping phase diagrams possess intuitively good repeatability, except in two locally specific regions. Then, Wolf’s numerical calculation method of Lyapunov exponents is utilized to analyze the motion stability of the compliant mechanism. An appropriate range (1.0–1.05 N mm/°) of the joint stiffness kT is obtained, satisfying the stability criterion. Finally, characteristic point trajectory and functional experiments with kT = 1 N mm/° are conducted to verify the motion stability of the compliant mechanism. The method of mechanism motion stability analysis by means of Lyapunov exponents can be applied to other under-actuated mechanisms.

The full-energy peak efficiency of gamma-ray spectrometry by numerical calculation method

The full-energy peak efficiency allow radioactivity determination in gamma-ray spectrometry. In the determination of the full-energy efficiency, numerical calculation method has been widely used because of its accessibility, stability, and low computational cost. The current study presents a new direct numerical method that is based on the determining of the total efficiency and the escape efficiency. The method provides a detailed description of the generation and escape of secondary photons from the sensitive volume. It is applicable to any source-detector geometry and also considers the self-attenuation of the source matrix and the attenuation caused by absorber layers between the source and the sensitive volume. The results of comparing the new numerical method with experimental measurement for the point source test model demonstrate relative errors within −2.73∼5.57 %, indicating the high reliability of this new method for sourceless efficiency calibration.

Study on numerical calculation method of corrosion mechanism for Co-12 laser cladding layer

Purpose The restoration and strengthening of QT600 is an industry bottleneck challenge. The Co-12 cladding layer has great wear and corrosion resistance. The purpose of this paper is to quantitatively reveal the transient evolution law of the corrosion process of Co-12 cladding layer on QT600 surface. Design/methodology/approach In this paper, a three-dimensional numerical model of the corrosion process of Co-12 cladding layer by QT600 laser cladding is established. The interaction between pitting pits and corrosion medium is considered to reveal the transient evolution of ion concentration, electrode potential, pH and corrosion rate at different locations. Findings The calculation shows that the ion concentration in pitting pit changes Cl−>Co2+>Na+, pH value decreases from top to bottom and corrosion rate at bottom is greater than that at top. The electrochemical corrosion test of Co-12 cladding layer was carried out. It is shown that the current density of QT600 increases by an order of magnitude compared to the Co-12 cladding layer, and the corrosion rate is 4.862 times higher than that of the cladding layer. Originality/value The results show that Co-12 cladding layer has great corrosion resistance, which provides an effective way for QT600 protection.

Numerical Analysis of Molten Pool Dynamic Behaviors during High-Speed Oscillation Laser Welding with Aluminum Alloy

Increased welding speeds are often used to achieve high welding efficiency. However, welding defects, including pores and humps, can easily be formed under high-speed welding conditions. Therefore, a numerical calculation method is proposed to analyze the molten pool dynamic behaviors during high-speed oscillation laser welding with the aluminum alloy. The experiments on high-speed oscillation laser welding are conducted to confirm the simulated results, and both are found to be in good agreement. The distribution characteristics of the temperature field under the condition of a high welding speed are discussed. With the influence of the stirring process from the oscillation laser beam, the temperature gradient is reduced and fluid flow velocity is decreased. The fluid flow in non-oscillation laser welding is more intense than that in oscillation laser welding. It is found that the proposed method can be used to guide the selection of the optimal process parameters for improving welding efficiency and quality in the practical welding process.

Research on cavitation characteristics of water-jet pumps with different blade tip clearances based on entropy production theory

Water-jet pumps are widely used in ship and other power fields. An axial-flow water-jet pump is studied with different size of tip clearance, and the cavitation characteristics are studied based on the theory of entropy production. Modified SST with curvature correction and modified Zwart cavitation model based on vortex identification are adopted, and the numerical calculation method is verified by reference experiments of a model pump. Under normal operating conditions, the results show that when the size of the tip clearance varies from 1.6‰ to 7.9‰ of the impeller diameter, efficiency takes a linear decrease accordingly, and the total entropy production increases linearly. At the same time, the main energy dissipation mode changes from wall dissipation to turbulent dissipation. Under severe cavitation conditions the total entropy production adds 30%. The water-jet pump shows that the entropy production in the impeller section is the highest, which accounts for 40%-50% and is closely related to the vortex and cavitation flow field in the tip clearance of the impeller. The tip leakage vortex region causes cavitation, but significant energy dissipation occurs at the outer edge of leakage vortex and on the nearby wall area, while the attached cavitation on the blade surface is the main source of turbulent dissipation.

Modernization of the mechanical mixing power numerical calculation method

The modernized numerical method for the mechanical mixing power calculation is proposed. Proposed calculation method allows to decrease the dependence of a stirred vessel mixing power numerical CFD calculation result on an empirical data by using additional term for considering own inertia of a mechanical mixing device. Proposed method bases on the mixing power consumption calculation technique as the function of a mixing device shaft torque. The verification of proposed method was carried out using the experimental measured and simulated values of the circulation-type reactor pump power. The results of proposed method verification show that non-modernized and modernized methods calculation errors are 3.9 % and 4.8 % respectively. Thus, calculation errors are comparable for modernized and non-modernized methods both. Wherein, modernized method unlike non-modernized does not use error correction coefficient that may be determined experimental only. Thus, proposed modernized method of the mechanical mixing power calculation may be used for engineering design calculations and simulations.

Numerical–experimental study on the stability mechanism of tail slapping motion of supercavitation projectile

Tail slapping is considered to be a prominent mode for facilitating the movement of supercavitating projectiles underwater. Stability mechanism of the tail slapping and stability criterion of projectiles was numerically investigated in this paper. A numerical method was conducted to calculate the free flight of projectiles by combining the finite volume method, the mixture multiphase model, and a dynamic meshing scheme. The accuracy and applicability of the numerical calculation method are verified by experiments. Three typical stability modes of tail slapping motion, namely, stable, conditionally stable, and unstable, were identified through the free flight numerical simulations of projectiles with varying length-to-diameter ratios under different initial angular velocities. The stability criterion of projectiles was proposed, indicating that the tail slapping stability can be determined by analyzing the curve of the moment variation with the angle of attack at any velocity above 200 m/s. Furthermore, it was found that the stable projectiles possess inherent motion states that are exclusively determined by their structural features and are unaffected by the initial motion conditions.

Research on Real-Time Calculation Method of Transformer Temperature Field Based on Reduced Order Model and Sparse Measurement

The lifespan of transformers is closely related to their operating temperature. Among the existing temperature acquisition methods, the measurement method cannot obtain the complete temperature field temperature, while the numerical calculation method presents the challenge of significant computational expenses. This study theoretically derived how to determine the real-time temperature distribution of transformer windings based on sparse measurement data and reduced order models and solved sensor layout issues, including the number and placement position of sensors. In this study, the maximum calculation error of the temperature distribution is 1.8 K, and the calculation time is 0.38 seconds. The research findings suggest that multiple modes can contribute to the temperature distribution of a transformer. Under a constant load condition, the calculation of transformer temperature can be achieved by utilizing a temperature sensor positioned at the hot spot in conjunction with the first mode.

Simulation of the motion of a pendulum

The project's objective is to simulate movement in the study and analysis of motion simulation problems and to propose simulation algorithms based on numerical calculation methods. It has many practical application values. In engineering and science, it is often necessary to simulate and analyze the motion of the fold to study the motor and dynamic properties of the fold, providing the theoretical basis and solutions to practical problems. With the support of modern computers and numerical computing technology, the problem of motion simulation has become a popular research direction. Many scholars and engineers have proposed different numerical calculation methods and simulated algorithms to simulate the motion process of the fold and analyze its motion laws. This article introduces the basic knowledge of physics and the formulas of motion, as well as some important concepts and theories related to motion. The motion simulation algorithm was then analyzed and discussed in detail. Subsequently, numerical calculations were prepared using MATLAB software, and simulated experiments were conducted using examples to analyze dynamic changes. Finally, the prospects for the future direction of research are presented. Therefore, if the initial speed is the same, the width and length of the time will increase.

CRAFT: a web-integrated cavity prediction tool based on flow transfer algorithm

Numerous computational methods, including evolutionary-based, energy-based, and geometrical-based methods, are utilized to identify cavities inside proteins. Cavity information aids protein function annotation, drug design, poly-pharmacology, and allosteric site investigation. This article introduces “flow transfer algorithm” for rapid and effective identification of diverse protein cavities through multidimensional cavity scan. Initially, it identifies delimiter and susceptible tetrahedra to establish boundary regions and provide seed tetrahedra. Seed tetrahedron faces are precisely scanned using the maximum circle radius to transfer seed flow to neighboring tetrahedra. Seed flow continues until terminated by boundaries or forbidden faces, where a face is forbidden if the estimated maximum circle radius is less or equal to the user-defined maximum circle radius. After a seed scanning, tetrahedra involved in the flow are clustered to locate the cavity. The CRAFT web interface integrates this algorithm for protein cavity identification with enhanced user control. It supports proteins with cofactors, hydrogens, and ligands and provides comprehensive features such as 3D visualization, cavity physicochemical properties, percentage contribution graphs, and highlighted residues for each cavity. CRAFT can be accessed through its web interface at http://pitools.niper.ac.in/CRAFT, complemented by the command version available at https://github.com/PGlab-NIPER/CRAFT/.Scientific contributionFlow transfer algorithm is a novel geometric approach for accurate and reliable prediction of diverse protein cavities. This algorithm employs a distinct concept involving maximum circle radius within the 3D Delaunay triangulation to address diverse van der Waals radii while existing methods overlook atom specific van der Waals radii or rely on complex weighted geometric techniques.

SRT-Server: powering the analysis of spatial transcriptomic data

BackgroundSpatial resolved transcriptomics (SRT) encompasses a rapidly developing set of technologies that enable the measurement of gene expression in tissue while retaining spatial localization information. SRT technologies and the enabled SRT studies have provided unprecedent insights into the structural and functional underpinnings of complex tissues. As SRT technologies have advanced and an increasing number of SRT studies have emerged, numerous sophisticated statistical and computational methods have been developed to facilitate the analysis and interpretation of SRT data. However, despite the growing popularity of SRT studies and the widespread availability of SRT analysis methods, analysis of large-scale and complex SRT datasets remains challenging and not easily accessible to researchers with limited statistical and computational backgrounds.ResultsHere, we present SRT-Server, the first webserver designed to carry out comprehensive SRT analyses for a wide variety of SRT technologies while requiring minimal prior computational knowledge. Implemented with cutting-edge web development technologies, SRT-Server is user-friendly and features multiple analytic modules that can perform a range of SRT analyses. With a flowchart-style interface, these different analytic modules on the SRT-Server can be dragged into the main panel and connected to each other to create custom analytic pipelines. SRT-Server then automatically executes the desired analyses, generates corresponding figures, and outputs results—all without requiring prior programming knowledge. We demonstrate the advantages of SRT-Server through three case studies utilizing SRT data collected from two common platforms, highlighting its versatility and values to researchers with varying analytic expertise.ConclusionsOverall, SRT-Server presents a user-friendly, efficient, effective, secure, and expandable solution for SRT data analysis, opening new doors for researchers in the field. SRT-Server is freely available at https://spatialtranscriptomicsanalysis.com/.

A Numerical Simulation of the Seismic Performance and Residual Stress of Welded Joints in Building Steel Structures Based on the Finite Element Method

With the development of society and urbanization, higher requirements have been put forward for the safety and seismic resistance of building structures. The fatigue strength and seismic performance of welded joints have received close attention, especially as a crucial part of building steel structure. This study used the finite element simulation method to analyze the stress-strain of welded joints in building steel structures, and explore the influence of residual stress on their seismic performance. A stress-strain calculation model for welded joints in building steel structures was studied and constructed, and the accuracy of the model was verified through numerical calculation methods. The results showed that the residual stress peaks of the horizontal and vertical directions of the V-groove welded joint structure were 475 MPa and 325 MPa, respectively, and the longitudinal residual stress peaks were 525 MPa and 425 MPa, respectively. The seismic performance of four different steel structural plates was Q960>Q690>Q460>Q345. In summary, the numerical simulation of residual stress in the seismic performance of welded joints in building steel structures, when based on the finite element method, makes a contribution of clear value to the field of seismic performance of welded joints in building steel structures.

Development of a 2-dimensional thermal calculation method to estimate silicone oil's temperature distribution in viscous torsional vibration dampers

AbstractHigh-performance internal combustion engines are subject to severe torsional vibrations which result from uneven gas and inertial loads. Fatigue damage occurs if the frequency of these undesired oscillations matches the resonance frequency of the crankshaft and the driven engine elements. This phenomenon can be avoided by the application of visco-dampers whose working fluid is high-viscosity silicone oil. Since silicone oil is exposed to a significant amount of heat load during operation, it is essential to calculate the temperature distribution in a relatively easy, quick, and cost-efficient way for lifetime estimation purposes. The aim of this article is to develop a reliable, fast, and accurate finite difference-based numerical method for steady-state thermal calculations for arbitrary damper sections. The developed MATLAB code calculates the temperature field of the damping fluid together with all components in a radial cross-section at given operational conditions. The accuracy of the developed thermal calculation method has been tested in a 3-dimensional – 2-dimensional two-step verification process by finite element and finite volume-based advanced engineering software in ANSYS environment. Furthermore, the original Iwamoto equation available in the literature has been updated to provide more accurate surface temperature results based on the simulations' outcome gained by the finite volume method.

Study on Numerical Simulation of Surrounding Rock Structure Safety of Urban Underwater Shield Tunnel: A Case in Chongqing

Based on the engineering background of shield construction of a subway section in Chongqing, which needs to pass through a park and there is a lake inside this park, this paper adopts theoretical analysis methods and numerical simulation calculation methods to explore the distribution law of the seepage field and the characteristics of water pressure in lining segments during shield tunneling. The results show that, during the whole excavation of a double-track tunnel with EPB shield, the maximum vertical effective stress is about 4.24 MPa, which is located at the arch foot of the tunnel. The maximum effective stress in the horizontal direction is about 3.61 MPa, which is located on both side walls of the tunnel in the horizontal direction; after the left and right tunnels are excavated in sequence, a “double precipitation funnel-shaped” pore pressure distribution is formed around the tunnel; during the construction of the shield tunnel, the vertical displacement and horizontal displacement of the surrounding rock show an increasing trend and gradually tend to be stable values of 24.09 mm and 25.28 mm; the segment vault has settlement, the maximum settlement is 21.8 mm, the arch bottom has uplift, and the maximum uplift is 24.4 mm. The maximum horizontal displacement of the segment appears on both sides of the arch waist, and the maximum horizontal displacement decreases with the increase of excavation steps; the positive bending moment of the lining segment is mainly distributed on both sides of the arch crown, and the negative bending moment is mainly distributed on both sides of the arch bottom. The axial force of the lining segment is compressive stress, and the maximum axial force is mainly distributed on both sides of the arch waist. The maximum normal shear stress occurs on both sides of the segment arch bottom. The study conclusions provide theoretical foundation and a new guidance for long-term safety evaluation of underwater tunnel structures.

Richtmyer on Shocks: “Proposed Numerical Method for Calculation of Shocks,” an Annotation of LA-671

Here we reproduce the complete text of Los Alamos Scientific Laboratory Report LA-671 authored by Robert Richtmyer in 1948. This report, though unpublished, is arguably one of the most important and influential monographs in computational fluid dynamics. It will be recognized that this report is the source of much of the material in the highly cited 1950 paper of von Neumann and Richtmyer. However, ideas in this report go beyond that later paper. In particular, we find here a motivation and a derivation of the quadratic form of artificial viscosity, an enduring concept in the simulation of flows with shocks, with turbulence models, and more recently, with theory in fluid dynamics. We reproduce the report in its entirety and then append a brief commentary to familiarize the reader with the environment in which Richtmyer worked, the motivation for his work, and some ensuing research. Artificial viscosity remains essential in Lagrangian simulations of fusion technologies such as inertial confinement fusion.

The plasma path development model (PPDM) in rocks during rock breaking by high-voltage pulse discharge

High-voltage pulse discharge rock-breaking technology (high-voltage pulse discharge rock-breaking technology, HPDT) is widely used in the energy mining industry. In HPDT, in order to analyze the path distribution characteristics of plasma, based on the homogeneous dielectric breakdown theory, the segmental breakdown criterion for the plasma path is proposed. The plasma path development model (plasma path development model, PPDM) is established with the help of the discrete element method, finite element method, and numerical calculation method. For a typical granite-liquid combination, the development process and distribution characteristics of the plasma path inside the rock are calculated for different distances between electrodes. The results show that the fracture of rock is the result of air gap breakdown. Finally, the accuracy of the model is analyzed and the method to reduce the error is given. This work lays a foundation for quantifying the crushing efficiency of HPDT and improving its application range.

Space numerical simulation of full oxygen combustion flame in glass melting furnace based on flue gas preheating

This study explores the innovative design of a glass-melting furnace, which incorporates a combustion lance and a flue on one side. The research validates the simulation that the high-temperature flue gas, produced by the pure oxygen combustion of natural gas, can utilize residual heat in a multi-stage process to preheat and burn the fuel natural gas via a jet heat pump. This process significantly reduces energy consumption, thereby decreasing construction costs and energy usage in industries related to glass furnace production. The research focuses on the flame space of a 600 t/day natural gas flat glass all-oxygen combustion furnace. Utilizing numerical calculation methods, a three-dimensional mathematical model of the all-oxygen lance flame space was developed. Numerical simulation methods were employed to examine the temperature field, airflow field, and the distribution pattern of the liquid flow field within the glass space in the furnace. The simulation results reveal that incorporating high-temperature flue gas into the fuel can markedly enhance the performance of the spray gun flame. Additionally, choosing spray gun outlet designs of varying widths can tailor the flame width to better meet the requirements of the glass melting system, thereby significantly improving the waste heat utilization rate of the flue gas. This offers more alternatives for the direct utilization of flue gas. When compared to traditional oxy-combustion glass melting furnaces, this innovative design substantially reduces construction costs and is more energy-efficient and environmentally friendly.

Effect of typical arch structure on slipstream and wake flow of 600 km/h maglev train

PurposeThe aerodynamic differences between the head car (HC) and tail car (TC) of a high-speed maglev train are significant, resulting in control difficulties and safety challenges in operation. The arch structure has a significant effect on the improvement of the aerodynamic lift of the HC and TC of the maglev train. Therefore, this study aims to investigate the effect of a streamlined arch structure on the aerodynamic performance of a 600 km/h maglev train.Design/methodology/approachThree typical streamlined arch structures for maglev trains are selected, i.e. single-arch, double-arch and triple-arch maglev trains. The vortex structure, pressure of train surface, boundary layer, slipstream and aerodynamic forces of the maglev trains with different arch structures are compared by adopting improved delayed detached eddy simulation numerical calculation method. The effects of the arch structures on the aerodynamic performance of the maglev train are analyzed.FindingsThe dynamic topological structure of the wake flow shows that a change in arch structure can reduce the vortex size in the wake region; the vortex size with double-arch and triple-arch maglev trains is reduced by 15.9% and 23%, respectively, compared with a single-arch maglev train. The peak slipstream decreases with an increase in arch structures; double-arch and triple-arch maglev trains reduce it by 8.89% and 16.67%, respectively, compared with a single-arch maglev train. The aerodynamic force indicates that arch structures improve the lift imbalance between the HC and TC of a maglev train; double-arch and triple-arch maglev trains improve it by 22.4% and 36.8%, respectively, compared to a single-arch maglev train.Originality/valueThis study compares the effects of a streamlined arch structure on a maglev train and its surrounding flow field. The results of the study provide data support for the design and safe operation of high-speed maglev trains.

SMCC: A Novel Clustering Method for Single- and Multi-Omics Data Based on Co-Regularized Network Fusion.

Clustering is a common technique for statistical data analysis and is essential for developing precision medicine. Numerous computational methods have been proposed for integrating multi-omics data to identify cancer subtypes. However, most existing clustering models based on network fusion fail to preserve the consistency of the distribution of the data before and after fusion. Motivated by this observation, we would like to measure and minimize the distribution difference between networks, which may not be in the same space, to improve the performance of data fusion. We were therefore motivated to develop a flexible clustering model, based on network fusion, that minimizes the distribution difference between the data before and after fusion by co-regularization; the model can be applied to both single- and multi-omics data. We propose a new network fusion model for single- and multi-omics data clustering for identifying cancer or cell subtypes based on co-regularized network fusion (SMCC). SMCC integrates low-rank subspace representation and entropy to fuse networks. In addition, it measures and minimizes the distribution difference between the similarity networks and the fusion network by co-regularization. The model can both reduce the noise interference in the source data and make the statistical characteristics of the fusion result closer to those of the source data. We evaluated the clustering performance of SMCC across 16 real single- and multi-omics dataset. The experimental results demonstrated that SMCC is superior to 17 state-of-the-art clustering methods. Moreover, it is effective for identifying cancer or cell subtypes, thereby promoting the development of precision medicine.