Cross-sectional Shape Research Articles

The Effect of Basic Building Materials and Their Paving Shapes on the Thermal Performance of Walls in Iraqi Residential Buildings

ABSTRACT Iraq's high climatic temperature affects buildings' thermal performance, leading to increased electrical energy consumption due to population growth. Researchers are exploring methods to reduce this consumption, such as heat gain reduction, heat transfer prevention, thermal insulators, high-thermal resistance materials, positive building design, useful orientation, and clean energies. The study investigates solar heat transfer in Iraqi air-conditioned spaces using nine models to analyze the impact of building elements on residential walls and their cross-section shape. The aim is to determine the best model for the Iraqi climate and the optimal approach for achieving optimal solar heat transfer. The study reveals that Model A has negative thermal performance, while Model C and I offer superior thermal performance. Model C offers 47.34% energy savings and Model I 43.99%, aligning with the global trend for green buildings and low energy expenditure in Iraqi residential units.

A high-throughput flowless microfluidic single and multi-solute concentration gradient generator: Design and parametric study.

Microfluidic concentration gradient generators (μ-CGGs) are critical in various biochemical assays, including cell migration, drug screening, and antimicrobial susceptibility testing. However, current μ-CGGs rely on integration with flow systems, limiting their scalability and widespread adoption owing to limited infrastructure and technical expertise. Hence, there is a need for flowless diffusional gradient generators capable of standalone operation, thereby improving throughput and usability. In this study, we model such a diffusional μ-CGG as an infinite source-sink system to capture two characteristic timescales: (i) gradient generation dictated by the diffusion timescale and (ii) stability determined by the rate of change in reservoir concentrations. Through finite-element simulations, we explored the influence of various geometric parameters such as the channel length, cross-sectional area, node and reservoir volumes, and the solute diffusivity on these timescales, along with experimental confirmation using fluorescent tracer diffusion. Our results show that while the gradient stability strongly depends on the reservoir volumes, diffusion length, and solute diffusion coefficient, they are independent of the node shape or the shape of the channel cross section. However, gradient profiles were found to be the strong functions of the diffusion length, solute diffusivity, and the geometric pattern of the microfluidic grid. Additionally, we showcased the versatility of the design by generating discrete gradient profiles and combinatorial gradients of two and three solutes, thus improving throughput in a wide range of on-chip biological assays. These findings underscore the potential of our microfluidic device as an easy-to-use, inexpensive, efficient, and high-throughput platform for various on-chip biological assays.

Effective Stiffness and Damping Analysis of Steel Damper to Lateral Cyclic Loading

Steel dampers are components used in building structures to reduce vibration and energy generated by dynamic loads such as earthquakes. Several factors affect the effectiveness of steel dampers in reducing energy, including the cross-sectional area, mass distribution, cross-sectional geometry, and material stiffness. The cross-sectional geometry or shape of the steel damper can affect how energy is absorbed and dissipated in the structural system. Cross sections with different geometric variations can have different mechanical responses to dynamic loads. This study aims to analyze which type of steel damper is effective in terms of stiffness and damping capacity against lateral cyclic loads. The steel damper cross-sectional variations used are slit steel dampers (SSDs), tapered steel dampers (TSDs), and oval steel dampers (OSDs). Cyclic testing of the dampers used displacement control with the same target deviation for all three damper types. The results showed that the stress and strain distributions of the oval steel damper were more even than those of the other two models. The variations in the energy dissipation capacities of the three cross-section variations are relatively the same. However, the slit steel damper type has the best stiffness compared to the other two types. This research is ultimately expected to influence the science of the structure of a building in preventing and anticipating earthquakes or other disasters. Doi: 10.28991/CEJ-2024-010-07-017 Full Text: PDF

Nonlinear gyrokinetic modelling of high confinement negative triangularity plasmas

Nonlinear gyrokinetic simulations correctly predict particle as well as ion and electron energy fluxes of high confinement plasmas with a negative triangularity cross sectional shape, showing that core transport in these plasmas is well described by standard gyrokinetic models. Experimentally inferred power balance fluxes are mostly reproduced within one standard deviation across a wide portion of the minor radius. Experimental conditions are reproduced by ion scale simulations, without the need to include density and temperature profile curvature effects. The experimental case is used as baseline to predict that the non-dimensional confinement scaling in negative triangularity plasmas increases strongly with plasma current while slightly degrading at increasing normalized pressure and decreasing collisionality. Recent experiments showed that low toroidal rotation negatively impacts confinement; consistent with the experiment, simulations predict that low rotational shear significantly affects confinement unless the plasma effective charge is maintained above a minimum level. Core confinement is predicted to significantly degrade in low aspect ratio devices.

SELECTION OF THE OPTIMAL MACHINERY COMPLEX FOR CONSTRUCTING IRRIGATION CANALS WITH A PARABOLIC PROFILE

An analysis of the experience of dredger operation in various industries allows us to identify the following main problems that need to be addressed to improve their efficiency: improvement of papillonation schemes and structural enhancement of the main equipment from a hydraulic perspective. The current soil intake devices, suction lines, and soil pumps do not always fully meet the specific requirements of soil development conditions. The objectives of the present research were to propose ways to enhance the performance of systems for automatic control of dredger work movements and automatic regulation of the soil intake process. These proposals aim to create a parabolic cross-sectional shape of the canal during development, ensure the highest productivity and lowest energy consumption, as well as low work costs, using modern control devices. The effect of the proposed technology for canal development using dredgers with automated papillonation consists of the following: providing the developed canals with a stable cross-sectional shape; automating the papillonation of the dredger and optimizing the operation of the soil pump; Implementing shift-based production accounting; using soil meters in the automated system. Giving the developed canal a cross-sectional shape that is stable in both hydraulic and static aspects has allowed for the following benefits: increased sediment transport capacity of the flow, while simultaneously reducing the cross-sectional area, growth of vegetation, water level fluctuations, water losses, and the right-of-way strip; reduced the volume of cleaning work by up to 20%; increased the period between cleanings by ensuring uniform flow movement; enhanced the productivity of dredgers by concentrating sediment on the canal slopes without changing the overall volume of cleaning.

COMPARATIVE ANALYSIS OF THE EFFICIENCY OF PARABOLIC AND TRAPEZOIDAL SECTIONS IN IRRIGATIONCANALS

One of the current scientific directions in hydraulic engineering is to give irrigation canals a hydraulically and statically stable cross-sectional shape in the form of the most advantageous parabolic profile. This approach allows maximizing the sediment transport capacity of the flow and significantly reducing the time and costs of construction and maintenance works, using optimization criteria for next-generation machinery and mechanisms. The significance of this research lies in developing a new concept for designing, constructing, and operating irrigation canals in hydraulic engineering systems with cross-sectional shapes that are both hydraulically and statically stable. These shapes aim to maximize sediment transport capacity, ensure ecological sustainability of natural-technical basin systems, and contribute to national food security. The objects of study are hydraulic engineering structures, specifically the inter-farm canals of irrigation systems within the Syr Darya river basin in the southern region of the Republic of Kazakhstan. For the study, methods were used including stability analysis of earth slopes using circular-cylindrical sliding surfaces, methods based on analogy between shear curves and slopes, and methods based on the theory of limit equilibrium. Calculations have demonstrated the advantages, including increased resistance to cross-section deformation, reduced earthwork volumes during irrigation canal construction and cleaning by 20-25%, decreased materials and work volume for possible lining by 13-18%, narrower canal top width and land acquisition zones by 11-17%, lower labor costs by 13-16%, reduced construction costs by 14-18%, and decreased specific adjusted costs by 15-18%.

Energy Absorption and Failure Modes of Different Composite Open-Section Crush Elements under Axial Crushing Loading.

In order to study the energy absorption characteristics of the open-section thin-walled composite structures with different cross-sections, axial compression tests were carried out at loading speeds of 0.01 m/s, 0.1 m/s, and 1 m/s. Finite element models were built to predict the crushing response and energy absorption behaviors of these open-section structures. The effects of the cross-section's shape, cross-section aspect ratio, trigger mechanism, and loading speed on the energy absorption characteristics of the composite structures were analyzed. The results show that the average crushing loads of the hat-shaped and Ω-shaped open-section structures are 14.1% and 14.6% higher than those of C-shaped open-section structures, and the specific energy absorption (SEA) values are 14.3% and 14.8% higher than that of C-shaped open-section structures, respectively. For the C-shaped open-section structures, a 45° chamfer trigger is more effective in reducing the initial peak load, while a 15° steeple trigger is more appropriate for the hat-shaped open-section structures. The average crushing loads and SEA of C-shaped, hat-shaped, and Ω-shaped open-section structures are reduced when the loading speed is increased from 0.01 m/s to 1 m/s. The increase in loading speed leads to the splashing of debris and thus reduces the loading area and material utilization of open-section structures, leading to a decrease in energy absorption efficiency.

Blast wave interaction during explosive detonation in a variable cross-sectional charge

Purpose. The research aims to assess the efficiency and performance of solid media destruction in directed blasting of a charge with variable cross-sectional shape. Methods. Numerical modelling of the blast wave interaction process is performed using the finite element method based on the Euler-Lagrange algorithm. The Johns-Wilkins-Lee equation of state is used to determine the pressure-volume dependences of medium destruction. Assessment of solid medium destruction mechanism during a directed blasting of a charge with variable cross-sectional shape is carried out based on polarization-optical method on models made of optically active material. Findings. Experimental studies of solid medium destruction by the action of directed blasting with a variable cross-section charge made it possible to determine the direction of blast wave propagation and its amplitude in stress wave, influencing the intensity of radial crack network formation in superposition areas, and directed perpendicularly to explosive cavity. At the same time, the average peak pressure in collision zone of two shock waves in centre of spherical cavity is approximately 1.48 and 1.84 times higher than that in weakly blast-loaded areas. It has been found that when two shock waves collide and superimpose on each other, the intensity of their impact increases. Moreover, the shock wave velocity in collision zone is higher than that of the radial shock wave. Originality. It has been determined that the maximum pressure values on the explosive cavity wall at the initiation points sharply increase and then gradually stabilize as the blast stress waves propagate and have an arbitrary distribution pattern. Three areas should be considered: not superimposed, weakly superimposed, and strongly superimposed. At each point of detonation, the pressure on explosive cavity wall will be minimal, while in the charge centre in the spherical insert zone, on the contrary, it will be maximal. In this case, the pressure in the central superposition area is about 2.84 times greater than at the initiation ends, and the nature of distribution changes according to a linear dependence. Practical implications. The performed research findings can serve as a basis for development of effective parameters of resource-saving methods for stripping hard rocks of complex structure in the conditions of ore mines.

Optimization Design Method for Vibration Reduction of Frame Structure of Cable-Driven Parallel Robot

This paper proposes a comprehensive optimization algorithm for the crossbeam cross-section size to solve the vibration problem of the flexible cable-driven parallel robot frame. The goal is to achieve an innovative design of the cross-sectional structure. By using a differential evolution algorithm, a comprehensive scale analysis of the cross-section size of the beam is carried out. This optimization method effectively improves the cross-section moment of inertia and the bending stiffness of the beam. Additionally, based on the variable density penalty method, the topological optimization design of the cross-section is carried out under the condition of minimum flexibility, the optimization objective function is established, and the objective function is solved by the moving asymptote method. The optimization results show that the beam stiffness is maximized while meeting the minimum flexibility required by the project. Through comparative analysis with various aluminum profile structures and their constructed frames, it is verified that the cross-sectional shape obtained through the optimized design method can significantly improve the anti-vibration stability of the frame.

Analysis of Vibration Performance by Height of Column-type Jig for Vibration Test with Cross-sectional Shape Based on Optimization

Analysis of Vibration Performance by Height of Column-type Jig for Vibration Test with Cross-sectional Shape Based on Optimization

Analysis of the Drag-Reduction Ability of the Layout and Cross-Sectional Shapes of Subsea Structures in the Critical Flow Mode

Introduction. Slender structures of subsea energy production systems are under constant influence of currents and waves. Hydrodynamic loads result from the interaction of subsea pipelines, umbilicals, equipment supports with fluid flows, and lead to the vortex formation in the area behind the structures. Vortex-induced forces are the sources of the cyclic loading. They accelerate gradually the fatigue damage, which may result in a failure. One of the ways to reduce the loads on subsea structures is to alter the shape of a cross-section, taking into account the flow regime. Dependence of the resulting hydrodynamic loads on the cross-sectional shape and relative position of structures has not been studied in details for the uniform flow in the critical mode. The current work is aimed at filling this gap. The research objective is to consider the impact of the distance between the structures, and also, the presence of a D-shaped structure, placed upstream relative to the group of three cylinders of different cross-sectional shapes.Materials and Methods. The computational fluid dynamics approach was used in this work for numerical simulations of vortex-induced forces in the ANSYS Fluent software for cylinder with D = 0.3 m. Modelling was conducted with the Detached Eddy Simulation (DES) method, which combined advantages of the Reynolds-averaged Navier-Stokes equation (RANS) method and the Large Eddy Simulation (LES) method. The object of the research was the system of four structures in the 2D computational domain, which included the upstream D-shaped cylinder and the main group of three cylinders with the circular, squared and diamond shapes of the cross-section. The transient process was considered, where structures were under the influence of the uniform flow in the critical regime at Re = 2.5×10⁵.Results. Five sets of data were obtained in simulations for the time-dependent coefficients of the lift and drag forces: for the main system — of the D-shaped, circular, square and diamond structures, and also for the four systems — of only D-shaped, only circular, only square and only diamond shaped structures. Additional analysis was conducted for the effect of the distance between the structures on the amplitude of fluctuating hydrodynamic force coefficients. The obtained results are presented as time histories of coefficients of the lift and drag forces, frequency analysis and contours of velocity, pressure and vorticity fields. The results indicate a positive effect of the upstream D-shaped structure on reducing the drag force, acting on the central structure in the group of three cylinders located downstream.Discussion and Conclusion. The results of the performed studies facilitate the informed decisions regarding the arrangement of subsea structures in a group of four objects, depending on the cross-sectional shape and the distance between the structures. The upstream D-shaped structure provides reducing the hydrodynamic drag force acting on the central structure in the downstream group of three structures, thereby slowing the fatigue accumulation and increasing the time of safe operation.

Mountain permafrost landslides: Experimental study investigating molard formation processes

Landslides triggered by degrading mountain permafrost pose an increasing risk to life and infrastructure in mountain regions due to current climate change trends. Because discontinous mountain permafrost is not directly detectable by remote sensing, permafrost molards offer a way of indirectly detecting its location and state. Permafrost molards are cones of loose debris that are associated with landslide deposits. They originate from ice-cemented blocks of sediment that are transported downslope with the landslide. These ice-cemented blocks are fragmented parts of the permafrost initially located in the landslide source area. Over time, these blocks degrade into conical mounds with diameters typically ranging from decimeters up to 40 m. They indicate the presence of an area of degrading permafrost at the level of the detachment zone. The physical processes that lead to the formation of molards from the ice-cemented blocks have not yet been studied in detail. Therefore, we perform an experimental study to recreate molards in a controlled laboratory environment and investigate the key formation processes. We downscale the molards to an initial cube side length of ~30 cm, and reduced the model's complexity by using two different types of gravel with a defined granulometry and lithology. We quantified the degradation phase by using a novel photogrammetric time-lapse system to detect changes in the digital elevation model between half-hourly time-steps. For the first time, we successfully recreated morphologies resembling molards under controlled laboratory conditions on a decimeter scale. We find the main processes to produce the final molard shape are cascades of grainfall for slightly cohesive sediment, and individual grainfall for non-cohesive sediment. Our experiments reveal three possible cross-section shapes (bell-shaped, triangular, trapezoidal) that correspond to molards that can be found in the field. Along with these field observations, we suggest that it may be possible to identify the cohesion of a molard's sediment based on its morphology. Together with future field data and experiments investigating the granulometry, ice and clay contents of the initial ice-cemented block, we aim to use molards as a record to better understand the landslide dynamics and state of the mountain permafrost.

Gate-tunable subband degeneracy in semiconductor nanowires

Degeneracy and symmetry have a profound relation in quantum systems. Here, we report gate-tunable subband degeneracy in PbTe nanowires with a nearly symmetric cross-sectional shape. The degeneracy is revealed in electron transport by the absence of a quantized plateau. Utilizing a dual gate design, we can apply an electric field to lift the degeneracy, reflected as emergence of the plateau. This degeneracy and its tunable lifting were challenging to observe in previous nanowire experiments, possibly due to disorder. Numerical simulations can qualitatively capture our observation, shedding light on device parameters for future applications.

Performance of proton exchange membrane fuel cell system by considering the effects of the gas diffusion layer thickness, catalyst layer thickness, and operating temperature of the cell

BackgroundIn this research, the effect of anode and cathode channel cross-sectional shape on the performance of PEM fuel cell was investigated and the appropriate length and dimensions of the channel were determined. Finally, for the determined geometric conditions, the cell performance at different voltages was investigated. MethodsThe purpose of this study was to investigate the structural characteristics of the fuel cell on its performance. The results show that the pressure and temperature in the catalyst layer (CL) of the cathode side are greater than the anode, and the temperature in the central regions of the catalyst layer is higher than the lateral regions. Also, the channel with a length of 100 mm is optimal in terms of producing the maximum current density and the amount of pressure drop is much lower than the channel with a length of 150 mm, which reduces the power consumption of the cell. Significant findingsIn general, a higher electric current is produced by increasing the thickness of the gas diffusion layer (GDL) and the catalyst layer. At a voltage of 0.8 V, with increasing thickness from 0.25 mm to 0.5 mm, the current density increases above 6 %. The percentage increase in current density at 60 °C–80 °C for 0.85 V and 0.75 V voltages is 42.1 % and 9.28 %, respectively.

Impact of the flow-field distribution channel cross-section geometry on PEM fuel cell performance: Stamped vs. milled channel

Polymer electrolyte membrane fuel cells (PEM FCs) represent an essential part of the emerging hydrogen economy. Metallic bipolar plates (BPs) allow high speed and capacity production using established industrial technologies, like mechanical stamping. Stamping, however, leads to different cross-sectional shapes of flow-field (FF) channels as compared to milled or compression-moulded bipolar plates. The impact of these changes on the resulting fuel cell performance is not yet fully understood. This study employs an experimentally validated three-dimensional, isothermal, steady-state, continuum-mechanics based mathematical model to gain a deeper insight into this issue and to identify optimal stamped BP channel cross-sectional shapes for parallel and serpentine FF. The uniformity of the local distribution of the physico-chemical quantities and the resulting load curves are analysed. The results obtained confirm that stamped BPs with channels of the trapezoidal cross-section are a viable alternative to the traditional milled or moulded BPs with channels of the rectangular cross-section. The observed differences in performance of FC with stamped and milled channels can be mitigated by optimization of the channel cross-section geometry parameters. As an optimal rib width 0.4 mm and an optimal channel ground width 1 mm for milled and 0.2 mm for stamped BPs are suggested.

Unified stress–strain calculation model for UHPC-filled stainless-steel tubular columns with various cross-sectional shapes under axial compression

Different cross-sectional shapes of ultrahigh-performance concrete (UHPC)-filled stainless-steel tubular (UHPCFSST) columns result in their stress-strain curves exhibiting softening or hardening stages, and currently, there is no unified calculation model available that can effectively simulate these variations. Based on experimental data, models for predicting peak stress, peak strain, ultimate stress, and ultimate strain of UHPCFSSTs with high accuracy has been provided. Comparative analysis reveals that the stress transfer capability and stability of UHPCFSSTs with the different cross-sectional shapes from highest to lowest are as follows: circular, square, and rectangular. Building upon Wei et al.'s general stress-strain calculation model, a high correlation pattern between parameter b and hoop confinement coefficient (ξs) has been obtained through correlation analysis, elucidating the post-peak behavior of stress-strain curves of UHPCFSSTs. By modeling parameter b, Wei et al.'s model has been extended to accommodate the stress-strain relationship under axial compression for UHPCFSSTs with different cross-sectional shapes. This establishes a unified stress-strain calculation model for UHPCFSSTs with different cross-sectional shapes under axial compression. Comparative analysis indicates that the proposed unified calculation model for axial compression stress-strain behavior of UHPCFSSTs can effectively quantify the influence of cross-sectional shape on stress-strain curves, demonstrating high predictive accuracy and generality.

Study of Corrsion System on Iron Artefacts through Neutronic Analysis

This study was conducted to confirm the possibility of using the corrosion products of iron artifacts and corrosion systems for non-destructive analysis using neutrons by applying the non-destructive analysis method and the destructive analysis method together to the analysis of the corrosion system of iron artifacts. As a result of transmission analysis, the shape of the artifact, the boundary between the metal layer and the corrosion layer, etc. could be confirmed, and through tomography, the shape, surface shape, and internal cross section of the artifact could be confirmed. It was confirmed that the corrosion thickness using the residual stress measurement method has a high reliability of less than 10% of an error compared to other analysis results, so it is highly likely to be used to measure the corrosion thickness. It was confirmed that the corrosion layer of the iron artifact analyzed this time was mainly Goethite among the types of DPL and was embedded with Magnetite/Maghemite. Since the neutron analysis can estimate the corrosion thickness non-destructive, it is highly likely to be used to study the corrosion rate of iron artifacts by burial environment through additional studies.

Characteristics of Straight Trapezoidal Cross-Sectional Fins under Unsteady Conditions

The aim of this research is to understand the characteristics of fins with a trapezoidal cross-section. The shape of the fin's cross-section is one of the influential factors affecting fin characteristics. In the design of fins, it is crucial to comprehend the characteristics of the fin as they relate to temperature distribution, heat transfer rate, and the efficiency of the fin. The research was conducted using numerical computation with an explicit finite difference method. Variations were made in the length of side 3 of the trapezium to 0 m, 0.02 m, and 0.04 m. The research results indicate that increasing the width of the fin enhances the temperature distribution, flow rate, and efficiency achievable by the fin. Significant improvement occurred when varying the side length from 0 m to 0.02 m, whereas subsequent variations did not considerably alter the efficiency. The highest efficiency achieved was 0.90 when the length of side 3 was 4 cm at the 300 seconds.

Collision Study on New Aluminum Alloy W-Beam Guardrail

Highway guardrails are safety installations set along the sides or center of roads to prevent vehicles from veering off the roadway, thereby protecting pedestrians and vehicles. However, traditional W-beam guardrails have issues such as poor energy absorption, susceptibility to rust, short lifespan, and a high risk of vehicles running off the road during severe collisions. Therefore, this study employs the partial differential equations of the vertical motion of beams to investigate the relationship between the deformation of wave beams and their moment of inertia. The cross-sectional shape of traditional W-beam guardrails was optimized accordingly. Combining this with the high ductility of aluminum alloy Al 6061-T6, a new aluminum alloy W-beam guardrail was proposed. Finite element simulation models of traditional steel guardrails, new steel guardrails, and the new aluminum alloy guardrail were established to evaluate the performance of the three types of guardrails. The results show that the deformation of the wave beam is inversely proportional to the square root of its moment of inertia. Compared to traditional W-beam guardrails, the moment of inertia of the new guardrail’s cross-section increased by 28.6%. In finite element collision simulations, the new guardrail reduced deformation by 12.8%, lowered the risk of vehicles running off the road, and improved safety performance.

Determination of longitudinal stability of strip in rolling cage – non-drive dividing device system

In modern industrial and civil construction, various rolled metal products are used in greater volumes. The largest share of them is occupied by rebar profiles produced at small-grade mills. The ever-growing demand for rebar rolling requires an increase in production volumes. The most promising technology in this regard is rolling – separation, which, with relatively low material costs, allows operating rolling mills to significantly increase the production volume of rebar profiles while reducing energy consumption. However, despite the obvious advantages of rolling – separation technology using non-drive dividing devices, it is very difficult to correctly determine the rational modes of conducting the process taking into account the peculiarities of production and equipment layout, which is due to insufficient theoretical knowledge. One of the main problems is determination of the permissible distance in the rolling cage – non-drive dividing device system. The conducted studies allowed us to propose a dependence for determining the maximum permissible distance in the rolling cage – non-drive dividing device system for reasons of longitudinal stability of the strip, taking into account the size and shape of cross-section of the split articulated profile, the nature of pinching, and the backstretch stress. It was experimentally established that when determining the permissible distance between rolling cage and non-drive dividing device, it is advisable to take the length reduction coefficient equal to 0.7.