Numerical Program Research Articles

Post-fire behaviour and resistances of S690 high strength steel welded I-section stub columns

The cross-sectional behaviour and residual compression resistances of S690 high strength steel welded I-section stub columns after exposure to elevated temperatures up to 950 °C have been investigated, underpinned by testing and numerical modelling, and fully presented in this paper. The testing programme used three S690 high strength steel welded I-sections — I-80×60×5, I-100×100×5 and I-140×70×5, and for each aforementioned I-section, seven geometrically identical stub column specimens were prepared and tested after exposure to different levels of elevated temperature (including 30 °C, 300 °C, 600 °C, 700 °C, 800 °C, 900 °C and 950 °C). This was followed by a numerical modelling programme, where finite element models were developed and validated against the post-fire stub column test results and then adopted to conduct parametric studies to generate further numerical data over a wide range of cross-section dimensions. Given that there are currently no available design standards for high strength steel structures after exposure to elevated temperatures, the relevant ambient temperature design rules, as set out in the European code, American specification and Australian standard, were assessed, using post-fire material properties, for their applicability to S690 high strength steel welded I-section stub columns after exposure to elevated temperatures up to 950 °C. The results of the assessments revealed that (i) all three sets of codified ambient temperature slenderness limits for internal and outstand plate elements in compression are generally accurate when used for cross-section classification of S690 high strength steel welded I-section stub columns after exposure to elevated temperatures and (ii) the ambient temperature local buckling design rules (i.e. slenderness limits in combination with effective width methods), as set out in the three considered design standards, are capable of providing accurate and consistent post-fire compression resistance predictions for S690 high strength steel welded I-section stub columns.

Using integer linear numerical programming for the purpose of building a mathematical model that achieves optimal hospital management by providing the best medical services to hospitalized patients at the lowest financial costs.

In this paper an integer programming model was built to obtain an optimal utilization of the available medical resources(human and equipments) in the emergency department in Al-yarmouk hospital. According to model results a plan can be implemented for ministry of health to help the management of al-yarmouk hospital to distribute the available resources in an optimal manner to achieve an optimal medical service to the people who need this medical service.

Dynamic performance analysis of a solar driving absorption chiller integrated with absorption thermal energy storage

The use of a solar-powered absorption chiller for residential cooling is impeded by the instability and intermittency of solar energy with time. Integrating the absorption heat storage into the absorption refrigeration alleviates the mismatch between solar sources and the cold demand. This paper investigated a solar-powered absorption chiller with an absorption thermal energy storage system using a dynamic numerical model. The dynamic model is solved according to the nonlinear programming and the second-order iterative numerical integration program. Based on simulation and comparison results, the performance characteristics for the proposed system are discussed. The results indicate that the combination of an absorption chiller and absorption thermal energy storage is feasible. Compared with the reference system, the total refrigerating capacity and average performance coefficient for the proposed system are increased by 4.44% and 3.5%. Finally, the total cold storage capacity of the integrated system can reach 6890.4 MJ/day, which can extend the cooling time to about 14 h. This research provides insight into future work regarding the wide application for solar cooling.

Flow Dynamics of the Homogeneous and Heterogeneous Reactions with an Internal Heat Generation and Thermal Radiation between Two Squeezing Plates

This paper explores the time dependent squeezing flow of a viscous fluid between parallel plates with internal heat generation and homogeneous/heterogeneous reactions. The motive of the present effort is to upgrade the heat transformation rate for engineering and industrial purpose with the rate of chemical reaction. For this purpose the equations for the conservation of mass, momentum, energy and homogeneous/heterogeneous reactions are transformed to a system of coupled equations using the similarity transformation. According to HAM, with the proper starting assumptions and other factors, a similarity solution may be found. On the way to verifying the validity and correctness of HAM findings, we compare the HAM solution with numerical solver programme BVP4c to see whether it matches up. The results of a parametric inquiry are summarized and presented with the use of graphs.

Regime Inference for Sound Floating-Point Optimizations

Efficient numerical programs are required for proper functioning of many systems. Today’s tools offer a variety of optimizations to generate efficient floating-point implementations that are specific to a program’s input domain. However, sound optimizations are of an “all or nothing” fashion with respect to this input domain—if an optimizer cannot improve a program on the specified input domain, it will conclude that no optimization is possible. In general, though, different parts of the input domain exhibit different rounding errors and thus have different optimization potential. We present the first regime inference technique for sound optimizations that automatically infers an effective subdivision of a program’s input domain such that individual sub-domains can be optimized more aggressively. Our algorithm is general; we have instantiated it with mixed-precision tuning and rewriting optimizations to improve performance and accuracy, respectively. Our evaluation on a standard benchmark set shows that with our inferred regimes, we can, on average, improve performance by 65% and accuracy by 54% with respect to whole-domain optimizations.

Testing and numerical modelling of circular CFDST cross-sections with stainless steel outer tubes in bending

The structural performance of circular concrete-filled double skin tubular (CFDST) cross-sections with stainless steel outer tubes has been examined herein based on experiments and numerical modelling. A laboratory testing programme comprising a total of 22 four-point bending tests was performed on seven CFDST cross-sections with varying concrete grades. The details of the test rig and procedures, as well as the key test observations, including the failure moment capacities, moment–curvature curves and failure modes, are fully reported. A numerical modelling programme was then carried out; a finite element (FE) model was first established to replicate the test observations, and then adopted to conduct a parametric study to acquire further FE data over a broader spectrum of material strengths and cross-section slendernesses. Based on the combined set of test and FE results, the general design provisions for concrete-filled carbon steel members in the current European and American design codes were evaluated for their applicability to the studied CFDST cross-sections. Overall, the results revealed that both of the examined design codes yield unduly conservative (less so for the higher concrete grades) and scattered moment resistance predictions, though some moment resistances predicted from the European code were on the unsafe side. Modifications, including a concrete reduction factor η to reflect the reduced relative effectiveness of using higher concrete grades and a modified stress distribution considering the partial spread of plasticity, were proposed and shown to improve the consistency of the resistance predictions. Finally, the reliability of the current and modified design rules was demonstrated through statistical analyses.

Structural behaviour and continuous strength method design of high strength steel non-slender welded I-section beam–columns

This paper presents the development of efficient design equations for high strength steel (HSS) welded I-section beam–columns under the framework of the Continuous Strength Method (CSM). The present work includes a collection of available experimental data on HSS S690 and S960 welded I-section beam–columns and a comprehensive numerical modelling programme considering a wider spectrum of parameters that influence the structural behaviour of the HSS welded I-section beam–columns. The developed FE models were first validated against test results collected from the literature, after which parametric studies were performed to generate further results to assess the accuracy of the codified design methods as used in Europe and the US, as well as to underpin new design proposals for HSS non-slender welded I-section beam–columns. It has been shown that the proposed CSM-based design approach is able to provide reliable design predictions with improved accuracy and reduced scatter over the existing design methods, and its reliability has been confirmed by means of statistical analyses.

Press-braked stainless steel channel sections under major-axis combined loading: Tests, simulations and design

This paper reports an experimental and numerical investigation into the cross-section behaviour and resistances of press-braked stainless steel channel sections under combined compression and major-axis bending moment. A testing programme was firstly conducted, including initial local geometric imperfection measurements and major-axis eccentric compression tests on ten press-braked stainless steel channel section stub column specimens. Following the testing programme, a numerical modelling programme was performed, where finite element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and initial loading eccentricities. Based on the obtained test and numerical data, the existing design interaction curves, as given in the European code, American specification and Australian/New Zealand standard, were assessed and shown to result in conservative cross-section resistance predictions for press-braked stainless steel channel sections under major-axis combined loading. The conservatism of the codified design interaction curves stems from the conservative end points (i.e. cross-section resistances under pure compression and pure bending), which are determined without considering the effect of material strain hardening, and the inefficient linear shape, which ignores the effect of stress redistribution. Improved design interaction curves were proposed through the adoption of (i) more accurate end points, which are calculated with a rational exploitation of material strain hardening by continuous strength method and (ii) more efficient nonlinear shape, which allows for the stress redistribution. The proposed design interaction curves were shown to result in substantially more accurate resistance predictions for press-braked stainless steel channel sections under major-axis combined loading than their codified counterparts. The reliability of the proposed design interaction curves was confirmed by means of statistical analyses.

Post-fire behaviour and residual resistances of S700 high strength steel tubular section stub columns under combined loading

This paper reports experimental and numerical studies on the post-fire behaviour and residual resistances of S700 high strength steel tubular section stub columns under combined compression and bending. A testing programme was firstly performed, including heating and cooling of specimens as well as post-fire material testing, initial local geometric imperfection measurements and eccentric compression tests. The testing programme was followed by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to carry out parametric studies to generate further numerical data over a wide range of cross-section dimensions and loading combinations. Given that there are no design standards for high strength steel structures after exposure to fire, the design interaction curves for high strength steel tubular section stub columns under combined loading at ambient temperature, as given in the European code, American specification and Australian standard, were evaluated, using post-fire material properties, for their applicability to S700 high strength steel tubular section stub columns under combined loading after exposure to fire. The evaluation results revealed that all the three sets of codified design interaction curves yield overall accurate post-fire residual resistance predictions for S700 high strength steel tubular section stub columns under combined loading, with the highest level of design accuracy offered by the American specification.

Solution of logical problem of numerical program control using the software-implemented

The article covers the requirements for software-implemented logic controllers, analyzes the functionality of the controller with construction of the functional model. The given practical example of Soft PLC controller application in frame of the CNC system shows the advantages of considered approach to design of electrics control systems.

FEM Analysis of Bridges with Encased Continuous Shear Connectors

AbstractComposite steel‐concrete constructions with encased I‐beams were initially used as composite floors. Nowadays, they can be usually seen as short railway bridges with span up to 20m. Their main advantages include simplicity of their construction, their low construction height and their effectiveness. To make them more effective, the steel I‐beams were replaced with perforated steel strips. At Technical University of Košice, Faculty of Civil Engineering, several continuous shear connectors with new design were proposed. In order to prove their effectiveness, numerous experiments – push‐out tests, four point flexural tests – were performed at Laboratory of Excellent Research. The purpose was to determine the shear and bending resistance of the connectors. Afterwards, the finite element models were created and analyzed using ABAQUS/CAE software. This paper deals with numerical program of four‐point flexural tests of two strips. The most clue modules ‐ properties, load, step, interaction and mesh are described.

Wheel Profile Optimization of Speed-up Freight Train Based on Multi-population Genetic Algorithm

The geometric shape of the wheel tread is mathematically expressed, and geometric parameters affecting the shape of the wheel were extracted as design variables. The vehicle dynamics simulation model was established based on the vehicle suspension parameters and track conditions of the actual operation, and the comprehensive dynamic parameters of the vehicle were taken as the design objectives. The matching performance of the wheel equivalent conicity with the vehicle and track parameters was discussed, and the best equivalent conicity was determined as the constraint condition of the optimization problem; a numerical calculation program is written to solve the optimization model based on a multi-population genetic algorithm. The results show that the algorithm has a fast calculation speed and good convergence. Compared with the LM profile, the two optimized profiles effectively reduce the wheelset acceleration and improve the lateral stability of the bogie and vehicle stability during straight running. Due to the optimized profile increases the equivalent conicity under larger lateral displacement of the wheelset, the lateral wheel-rail force, derailment coefficient, wheel load reduction rate, and wear index are reduced when the train passes through the curve line. This paper provides a feasible way to ensure the speed-up operation of a freight train.

Performance prediction of externally pressurized gas bearings for high-speed turbo-expander involving hydrogen, helium and air working fluids

High-speed hydrogen turbo-expander is widely employed in hydrogen liquefaction systems due to its high efficiency. The hydrogen bearings in high-speed turbo-expander are usually applied for low viscosity and pollution-free advantages. Nevertheless, the load capacity of hydrogen bearing is low and the research on maximizing the load capacity is limited by the complicated solution process and danger hydrogen experiment. The purpose of the paper is to easily and quickly acquire the load capacity of high-speed orifice externally pressurized hydrogen journal bearing for optimization of bearing performance. A new simple load capacity predicted model, that is universal for various working fluids involving hydrogen, helium and air, was proposed through the hydrostatic and hydrodynamic analysis. In the model, the evaluation indicators of hydrodynamic and hydrostatic effects were proposed. Based on the model, no numerical analysis and computer programming are needed to calculate the load capacity of journal bearing and numerous key design variables are considered. The results from the predicted model agree very well with those obtained from the finite difference method (FDM) technique. In view of the danger of hydrogen bearing experiment, the load capacity predicted model can be used to design the equivalent experiment of load capacity through substituting air for hydrogen working fluid.

Numerical model and program development of horizontal directional drilling for non-excavation technology

Numerical model and program development of horizontal directional drilling for non-excavation technology

ЕНЕРГЕТИЧНІ ПОКАЗНИКИ АКСІАЛЬНОГО АСИНХРОННОГО ДИСКОВОГО ДВИГУНА ДЛЯ СУДНОВИХ НАВІГАЦІЙНИХ РЛС

The development of a reliable gearless electric drive for antennas of ship radars is an important problem. To solve the problem, this article proposes to use an axial induction motor (AIM) with a massive bimetallic disk-shaped rotor. The AIM model is presented, which consists of three computational domains with the boundary condition of symmetry. To calculate the electromagnetic field, a well-known analytical method of integral transformations is used taking into account the variable along the radial coordinate of the linear speed of the rotor. Ready-to-use expressions are presented for the development of a program for the numerical calculation of the magnetic field and energy characteristics of the motor. Algorithm is developed for calculating the dimensions of the AIM, operating at different speeds with a frequency converter. The numerical calculation program is used to calculate the dimensions AIM. It uses well-known recommendations for the parameters of the electromagnetic field in the magnetic core and in the air gap. The calculation of the dimensions of the AIM for ship radars “Mius” is performed. The dependence of the efficiency on the current frequency for different rotor’s frequencies is investigated. The energy indicators of the AIM are investigated at a variable torque on the shaft and at different rotor speeds. The parameters of the power source for the AIM of ship radars are established. References 20, figures 5, tables 3.

Numerical Analysis of Steel Geodesic Dome under Seismic Excitations.

The paper presents the response of two geodesic domes under seismic excitations. The structures subjected to seismic analysis were created by two different methods of subdividing spherical triangles (the original octahedron face), as proposed by Fuliński. These structures are characterised by the similar number of elements. The structures are made of steel, which is a material that undoubtedly gives lightness to structures and allows large spans. Designing steel domes is currently a challenge for constructors, as well as architects, who take into account their aesthetic considerations. The analysis was carried out using the finite element method of the numerical program. The two designed domes were analysed using four different seismic excitations. The analysis shows what influence particular earthquakes have on the geodesic dome structures by two different methods. The study analysed the maximum displacements, axial forces, velocities, and accelerations of the designed domes. In addition, the Time History method was used for the analysis, which enabled the analysis of the structure in the time domain. The study will be helpful in designing new structures in seismic areas and in assessing the strength of various geodesic dome structures under seismic excitation.

A Nonlocal Effective Medium Description of Topological Weyl Metamaterials

AbstractEffective medium theory lays the foundation for the development of metamaterials—artificially engineered photonic medium with subwavelength building blocks. However, the nonlocal effects, which are difficult to be incorporated into the effective medium description, are usually unavoidable in most metamaterial systems due to the finite lattice constant, preventing a precise modeling of wave propagation inside a metamaterial of large scale. On the other hand, recent development shows that nonlocal effect is essential for designing certain topological photonic systems such as ideal Weyl metamaterial. The properties of topological metamaterials rely on nonlocal effects, which, for example, determine whether a Weyl degeneracy formed by the linear crossing between a longitudinal and a transverse mode belongs to type I or type II. Here a nonlocal effective medium description of topological metamaterials is developed. For the first time, it is possible to calculate the wave propagation inside this complex medium in a large‐scale based on general numerical programs. To show the potential of the approach, wave propagation inside and at the boundary of a photonic ideal Weyl system are thoroughly studied in this work. By reformulating the electric field equation, the method paves the way toward comprehensive engineering of metamaterials with unrestricted nonlocality.

Computational investigation of an unsteady non-Newtonian and non-isothermal fluid between coaxial contracting channels: A PCM approach

The essential element of this paper is to research the porous and squeezed characteristics of time varying heats that modify the flow speed and enhance the refrigerating/boiling performance of the materials, optimize the tracers flows and minimalized instability in the non-Newtonian fluids. In the presence of no-slip velocity and convective circumstances, squeezing disks tempting laminar, unsteady and incompressible non-Newtonian fluid. The convective formulation for the equations of Navier Stokes, energy and concentration are modeled on flat disks to investigate and execute both analytical and numerical analysis of heat flow and mass transfer, which transmuted further into extremely non-linear system of ordinary differential equation with the help of similarity transformations. Regarding smears, self-similar equations with adequate starting estimates and supporting parameters are resolved by utilizing the Homotopy Analysis Method (HAM) to generate an expedited and guaranteed convergence procedure. Comparisons between HAM and the BVP4c numerical solver program demonstrate the validity and precision of HAM results. It is found by increasing or decreasing the Hartman number reduces the capillary area, making the Lorentz force influence quite visible for small non-Newtonian parameter. The concentration rate at the lower end disk rises rapidly as the thermal diffusivity rises. The radial velocity also declines because of the rise in the outflow rate from the flow domains. The suction parameter also declines. Additionally, increasing the parameter of non-Newtonian enhances the flow of temperature/mass and skin friction. In the suction/injection case, all physical factors have a reverse influence upon fluid flow patterns.

THE INFLUENCE OF METEOROLOGICAL AND TOPOGRAPHICAL PARAMETERS ON THE DISPERSION OF PM10 AND CO POLLUTANTS

At present, climate change is a global reality. One of its causes is the presence of pollutants in the atmosphere. Therefore, the purpose of this paper is to observe how the dispersion of pollutants is influenced by meteorological and topographic parameters. In order to carry out the study on the influence of synoptic conditions on the dispersion of air pollutants PM10 and CO, a continuous monitoring of the two pollutants was needed for one year (from March 2020 to February 2021) at all six air quality monitoring stations located in Argeș County. These data will be correlated with the climatological parameters obtained from the National Meteorological Administration. Using a numerical modeling program (SCREEN), it was performed a simulation of the dispersion of pollutants, determining the maximum concentration of the pollutant and the distance it reaches the ground, for several wind speeds, in all five classes of atmospheric stability.

Efficiency of Implementation of Modern CNC Equipment for Production of Heat Reducer Shafts

The article analyses the capabilities of modern metal-working equipment with numerical program control (CNC) and the efficiency of its use in the processing of gear shafts of diesel locomotives. Figure.3 the strategy of accelerating the socio-economic development of the country provides for the comprehensive intensification of production on the basis of scientific and technological progress. One of the effective ways to solve the problem of intensification of production, increase productivity is the introduction of modern CNC metalworking equipment and modern cutting tools. The industry has accumulated extensive experience in the use of CNC machines, which in comparison with conventional equipment create a number of technical and economic advantages. The productivity of these machines is three times higher than in machines of the same type without software control, and the need for production space is three times less. The greatest effect is given by CNC machines at processing of surfaces of difficult form and big accuracy therefore their use allows to reduce highly skilled workers.