Cross-sectional Configuration Research Articles

Fast Probing Amyloid Polymorphism via Nanopore Translocation.

Neurodegenerative diseases are characterized by the presence of cross-β-sheet amyloid fibrils and a rich mesoscopic polymorphism, requiring noninvasive detection with high fidelity. Here, we introduce a methodology that can probe via a sensitive synthetic nanopore the complex polymorphism of amyloid fibrils by an automated and fast screening protocol. Statistically analyzing the translocation events on two model amyloid systems derived from β-lactoglobulin and lysozyme allows extracting the cross-sectional configuration of hydrated amyloid fibrils from current block amplitude and correlating dwell time with fibril length. These findings are consistent with the amyloid polymorphs observed in solution by atomic force microscopy. Furthermore, the ionic current signal of a single translocation event can reveal abnormally aggregated conformations of amyloid fibrils without potential artifacts associated with microscopy methods. This study introduces an effective approach to physically discriminating and separating amyloid and may serve in the rapid diagnosis of early aggregating pathological amyloidosis.

Hamel's field variational integrator for simulating dynamics of thin-walled geometrically exact beams with warping effects

Using discrete variational principle, a Hamel's field variational integrator (HFVI) for simulating dynamics of thin-walled geometrically exact beams with warping effects is originally proposed. Firstly, a spacetime independent interpolation way for thin-walled beam elements is established on SE(3) × R space by using Hamel's formalism. Then, a new discretization formulation of convective velocity and convective strains on Lie algebra is proposed by using frame operators, which helps to reduce the system's nonlinearity. After that, the variations of discrete convective velocity and discrete convective strain are decoupled from the cross-section configuration variables. This way can avoid the computation of nonlinear exponential map's tangent map and reduce the computation complexity significantly. According the Hamiltonian form of proposed HFVI, the warping variables and discrete convective strains can be independently solved by using discrete compatibility equations on Lie algebra. Finally, the efficiency and accuracy of HFVI is validated by six static and dynamic examples.

A simplified analysis of a configuration of geosynthetic reinforcement in GRPS embankments

Geosynthetic-reinforced and pile-supported (GRPS) embankments are increasingly used in recent years to reduce the differential settlement and increase the bearing capacity of the embankments. A new theoretical model is proposed to calculate the tensile force distribution and cross-sectional configuration of the geosynthetic reinforcement used in the Geosynthetic-reinforced and flexible pile-supported GRRPS and Geosynthetic-reinforced and rigid pile-supported GRFPS embankments. The accuracy of the proposed methods is verified by the results from laboratory model tests, centrifuge model tests and theoretical models in the literature. It is found that the tensile forces along the geosynthetic are distributed unevenly both in GRRPS and GRFPS embankments with the maximum and minimum magnitudes located at the edge and centre of the pile cap, respectively. The soil arching effect contributes more to the bearing capacity of the GRPS embankment than the membrane effect. It is found through the analyses of the centrifuge and model tests data that the soil arching effect contributes 65–75% of the total load transfer efficiency.

A new approach to the stability design of Ramberg–Osgood material struts

An energy formulation employing total potential energy principles is presented to derive a governing equation for strength predictions of struts made from materials following the Ramberg–Osgood constitutive law such as stainless steel, cold-formed steel, and aluminium alloys. The formula is generic and applicable to arbitrary cross-sections and all strut slendernesses for which flexural buckling is critical. Extensive comparisons against experimental data on square and rectangular hollow section struts as well as finite element simulations demonstrate the accuracy of the developed formula, while the effect of varying material parameters is examined through comprehensive parametric studies. Owing to its simplicity and its derivation based on mechanical principles, arbitrary configurations of material parameters and cross-sections can be analysed, making the formula suitable for use in design practice, representing effectively a non-iterative alternative to the widely accepted design load employing the tangent modulus. With the aid of the formula, new column buckling design provisions are developed, which show excellent agreement with experimental data and meet the reliability requirements specified within the structural Eurocodes.

Dry reforming of methane using a novel microreactor fabricated from stacking of stainless steel wire-mesh support catalysts

We fabricated a novel microreactor with stainless steel wire-mesh supports coated with Ni-based hydrotalcite catalysts for dry reforming of methane (DRM) reaction. Catalytic performance and long-term stability of microreactor was tested by stacking the stainless steel wire-mesh support catalysts to allow parallel and cross-sectional flow to stacking configurations. Conversion rates of CH4 and CO2 were measured and found to be 92% and 95% respectively, and syngas ratio of 0.92 was obtained. Only a small decrease of about 3–4% in conversion rates was observed after 100 h of reaction which could be due to whisker like carbon formation as carbon nanofibers (CNFs). Investigation of spent catalysts revealed that surfaces of support catalysts were not fully covered with CNFs, leaving active sites for reactant gases with little effect on long-term stability. In addition to CNFs, in situ formation of γ-Al2O3 flakes were obtained during long-term DRM reaction from the parent FeAl powder that was used for annealing of stainless steel wire-mesh supports to increase the adhesion of hydrotalcite-derived spinel catalysts. Effect of γ-Al2O3 flakes on microreactor's performance turned out to be very useful because sites of γ-Al2O3 flakes further prevented the deposition of carbon on surface and acted as active sites for reactant gases. Moreover, stacking of stainless steel wire-mesh support catalysts for parallel and cross-sectional flow configurations caused the better mixing of reactant gases due to the tortuosity of the narrow porous microstructure of the support. The excellent throughput was verified by numerical calculations using CFD simulations.

Performance Analysis of Variable Cross-Section TEGs under Constant Heat Flux Conditions

In this paper, five shapes of thermoelectric generator (TEG) models (cylindrical, barrel shaped, hourglass shaped, cup shaped, and inverse cup shaped) are built under the boundary conditions of heat flux at the hot end and convection at the cold end of the TEGs. Based on the numerical simulation results, the configuration of the variable cross-section can effectively boost the performance of TEGs. Remarkably, the hourglass-shaped TEG generated the maximum output power and efficiency, which were 69.62% and 70.96% higher than that of the conventional cylindrical TEG, respectively. The results indicate that the hourglass shape is beneficial to enlarge the temperature difference between the two ends of the TEG, which results in performance improvement. In addition, the effects of heat flux and convection on the performance of TEGs are explored and discussed. After choosing the appropriate boundary conditions, the relationships between the maximum output power and efficiency and the shape factor of the hourglass-shaped TEG are obtained according to the fitting results. Finally, some conclusions are drawn to provide guidance for TEG applications.

An efficient technique in dynamic modeling and analysis of soft fluidic actuator

Soft actuators with embedded fluidic channels are promising for soft robotics, but their continuous nature presents challenges in accurate and efficient modeling. Existing studies on dynamic behavior have shown that both approximate and exact methods have limitations in accurately predicting the deflection of soft actuators. Additionally, conventional methods require experimental parameter extraction for each individual actuator. To address these challenges, we propose a modified analytical method and use finite element analysis as the defined correction functions to improve accuracy and computational efficiency, providing a promising tool for the design and control of soft robotic systems. In this work, we propose a solution methodology for simulating the dynamic behavior of fluidic soft actuators, which are widely used in soft robotics applications. Our approach takes into account the cross-sectional geometry and the number of channels in the actuator’s configuration. By scrutinizing various fluidic actuation designs, we can deduce the most suitable cross-sectional configuration for optimal performance. Compared to existing analytical methods, our approach is more accurate and does not require additional calculation time. As the method is adaptable with experimental models, it can be used to design and optimize soft actuators while can be refined and improved through experimental model updating.

Performance of Corrugated-Plate-Shaped Bridge Piers under Uniaxial Loading

The current research examines the seismic performance of irregular cross-section of bridge piers that has rarely been investigated. Preceded by a successful validation, the study was numerically conducted by ABAQUS/Explicit program containing a comprehensive series of FE bridge piers under unidirectional cyclic loading and axial dead load. Three corrugated shapes with a net depth of 60, 80 and 146 mm mainly formed the cross-sectional configuration of concrete-filled steel bridge piers. The aim was to examine the load-bearing capacity, ductility and buckling mode of such models and compare their behavior with traditional circular-shaped steel columns. Afterwards, a parametric study involved the grade of concrete (20, 30, and 40 MPa), corrugation geometry (C60, C80, and C146 mm), radius-to-thickness ratio (0.131, 0.149, and 0.116), and axial force ratio (10%, 15%, 20% and 30%). FE results suggested that concrete-filled corrugated-shaped columns revealed nearly 50% more load-bearing capacity and ductility as compared to circular-section columns. The damage configuration among corrugated-shaped columns was seen less severe than circular-section columns, where the local buckling in the latter one was premature and concentrated in particular zone. The findings herein urge to consider implementing corrugated-shaped piers in structures due to their significant addition in strength, ductility, and failure control.

Bending performance of nail-laminated bamboo-timber panels made with glubam and fast-grown plantation Chinese fir

This study attempts to develop a novel structural nail-laminated panel constructed of engineered bamboo and local fast-grown plantation Chinese fir. An experimental program is reported in this paper on static bending behaviors of such nail-laminated bamboo-timber (NLBT) panel. Twelve NLBT specimens, including five short span specimens without butt joints and seven long span specimens with different butt joints were manufactured and tested. The panel span, species of sawn timber boards, the cross sectional configuration, and reinforcement measures of butt joints were chosen as the experimental parameters in the current investigation. The typical failure mode of the short span NLBT panels exhibited a multiple-fracture process caused by the tension failure of timber layers, while the overall collapse was much delayed or avoided attributed to the residual bending capacity provided by glubam layers. Test results demonstrate that the use of fast-grown Chinese fir instead of imported dimension lumber to combine glubam does not obviously reduce the bending performance of NLBT panels. The proposed vertical nailing reinforcement for butt joints can significantly improve the bending stiffness of the long span NLBT panels, and it is convenient for processing and assembling of NLBT components. Based on the ratio of bamboo and timber, a simple linear relationship is proposed for predicting the elastic modulus of the NLBT through regression analysis. The observed performance evaluation also reveals that the bending performance of the proposed NLBT structural panels is sufficient to meet the design requirements for using as the structural floors in offices and residential buildings. This research provides a feasible and reasonable approach for developing local fast-grown species as structural components.

Additional Fire Exposure Time for the Effect of Spalling in Reinforced Concrete Columns

Concrete exposed to fire can experience spalling when the pore pressure increases due to water evaporation resulting in damage to part of the concrete cross-section which causes the loss of the initial cross-sectional symmetry, both thermal and geometrical. This may lead to what is, in essence, a biaxial bending problem in reinforced concrete columns. This study does not deal with the prediction of the occurrence of spalling for which a fully coupled hygro-thermo-mechanical analysis would be required. This work evaluates the consequences that corner spalling and surface spalling have on the fire resistance of reinforced concrete columns and presents a methodology based on the determination of a modified fire resistance time. An advanced fiber based numerical model for evaluating the fire resistance of RC sections exposed to fire is used as a tool to analyse the effect that spalling has on the performance of the columns. The model is able to generate the interaction surfaces of the columns subjected to uniaxial or biaxial bending and 4-sided exposed to the standard fire curve ISO 834. After a parametric analysis, it is observed that the negative effect of spalling can be quantified by means of an additional fire exposure time, which ranges between 0–35 min and depends on the column cross-section configuration, dimensions and load level. Finally, a proposal for the calculation of the modified fire resistance time for the effect of spalling is presented, which may be beneficial for practitioners in design.

Energy absorption and recoverability of Moore space-filling thin-walled structures

This paper proposes novel thin-walled structures inspired by Moore space-filling curves. Nine designs, featuring three fractal hierarchies (1st, 2nd, and 3rd orders) with three different relative densities (20%, 30%, and 40%), were used as cross-sectional configurations of the thin-walled structures. Specimens were manufactured using a material extrusion additive manufacturing technique, fused filament fabrication, with a carbon fiber-reinforced composite. Quasi-static compression tests from in-plane direction were conducted to investigate the influences of fractal hierarchy and relative density on the energy absorption capacity. Finite element models were developed to compare with the experiments and to further explore the 4th order structures. A certain level of compliance and snap-in instability were observed in all the structures. These properties show great potential for such thin-walled structures to absorb more energy by enduring large strain. Among them, the 2nd order structures exhibited the best energy absorption capacity. Furthermore, loading and unloading compression tests were performed on the 2nd and 3rd order structures (relative density of 20%) to evaluate their resilience toward displacement and damages. The residual strain and dissipated energy ratio demonstrated that the 2nd order structure outperformed the 3rd order structure owing to its less compliant feature. The integration of Moore curves with thin-walled structures contributes to great compliance and snap-in instability, offering a new approach to designing lightweight energy absorption structures.

Shape and non-shape unified isogeometric optimal design for extremal band gaps

A unified shape and non-shape design optimization for lattice structures is performed to obtain extremal band gaps in an isogeometric computational framework, which uses the same NURBS basis functions as used in CAD description. Using a precise numerical model in both response and shape sensitivity analyses, enhanced response and sensitivity can be obtained, which leads to a precise optimal design. A plane wave propagation in infinite periodic lattice is analyzed within a representative unit cell using the Bloch theory with periodic boundary conditions. The ligaments of lattice structures are modeled using geometrically exact beams whose cross-sectional area and configuration are regarded as design variables, which are parameterized by the NURBS basis functions. The design variables are controlled by a mathematical programming algorithm with efficient adjoint design sensitivity. The obtained optimal lattice structures of triangular, squared, hexagonal, and Kagomé structures are fabricated using a 3D printing machine to be validated by physical experiments. Through harmonic response analysis and physical experiment for the optimal and the original designs, the wave attenuation properties are compared to demonstrate the validity of the obtained optimal design.

Backfilling configuration to improve tenacity of composite-type breakwaters

ABSTRACT Composite-type breakwaters are reinforced by piling rubble stones and constructing counterweight fillings (known as reinforcing embankments) behind caissons. Important performance requirements for breakwaters include minimal damage and high strength, even when the external forces exceed the design forces. In this study, the failure process and final state of breakwaters with reinforcing embankments are investigated via centrifuge model tests, and the cross-sectional configuration of the reinforcing embankment for improving the tenacity of breakwaters is determined. The results show that, in the overturning mode, when the number of rubble stones decreases, the reinforcing embankment deforms in accordance with the inclination of the caisson; subsequently, the caisson overturns and mounts onto the embankment. When balance is not maintained at that position, the caisson slides down the slope surface, resulting in catastrophic failure. A series of centrifuge model tests qualitatively show that placing more rubble stones adjacent to the caisson is less likely to result in such catastrophic failure. Furthermore, the stability of the breakwaters is evaluated via circular slip analyses, which demonstrate the importance of increasing the volume of the reinforcing embankment adjacent to the caisson in terms of the stability.

Generation and directional decomposition of guided waves for finite-range defect detection in rail tracks

Abstract Railway tracks exhibit a complex, sudden alteration in their cross-sectional configuration. Generating guided waves within thick rail tracks using conventional guided wave transducers is challenging. This research employs directional decomposition to comprehend how guided waves form within the rail. These waves arise from constructive interference between multiple reflected bulk waves, which are induced by point forces on the top surface of the railhead or diffracted from cracks in the rail structure. This study simulates finite-range detection of rail defects using finite element analysis to demonstrate a potential application to the guided wave rail inspection car. The transmitter and a series of monitoring points are located on the same side of the rail defect in the pitch-catch configuration. The transmitting guided waves often hide the small backscatter waves induced by defects. A directional filter extracts the small backscatter signals from the entire received data. A 100 kHz tone burst actuates on the top surface of the rail in three orthogonal directions. Numerical findings demonstrate that vertical and tangential excitations are suitable for detecting defects in the railhead and lower region, while transverse excitation and detection are appropriate for identifying defects in the rail web. The application of directional decomposition provides valuable insights into the complex process of backscatter waves arising from rail track defects.

Bending crashworthiness of bionic thin-walled structures inspired by sugar cane stalks

Recently, the design of biologically inspired thin-walled structures has been increasingly popular due to the successful adaptation of biological organisms to their environments due to millions of years of evolution. Plants with high bending resistance to counter the effect of wind forces on slender and tall stalks can be found in nature. To this end, this paper investigates the bending crashworthiness of mechanical structures inspired by sugar cane (Saccharum officinarum). The biological patterns of sugar cane were obtained with a Scanning Electron Microscope, and five bionic thin-walled structures (BTWS) were considered. In all cases, the structures were modeled with 6063-T5 aluminum and numerically evaluated using the finite element method using a three-point bending test. The effects of cross-section configuration on the crashworthiness performance of the structure were investigated. Our results show a better version of the BTWSs relative to a typical circular profile. An increase in energy absorption from 15.60% to 40.27% was computed. The best CFE performance was obtained for a structure defined by a central octagon surrounded by smaller trapeziums. Such a structure is therefore highly recommended for bending crashworthiness applications.

Novel size-based design of spiral microfluidic devices with elliptic configurations and trapezoidal cross-section for ultra-fast isolation of circulating tumor cells

Investigation and analysis of circulating tumor cells (CTCs) have been valuable resources for detecting and diagnosing cancer in its early stages. Recently, enumeration and separation of CTCs via microfluidic devices have attracted significant attention due to their low cost and easy setup. In this study, novel microfluidic devices based on size-dependent cell-sorting with a trapezoidal cross-section and elliptic spiral configurations were proposed to reach label-free, ultra-fast CTCs enrichment. Firstly, the possibility and quality of separation in the devices were evaluated via a numerical simulation. Subsequently, these devices were fabricated to investigate the effects of the altering curvature and the trapezoidal cross-section on the isolation of CTCs from the peripheral blood sample at varying flow rates ranging from 0.5 mL/min to 3.5 mL/min. The experimental results indicated that the flow rate of 2.5 mL/min provided the optimal separation efficiency in the proposed devices, which was in fine agreement with the numerical analysis results. In this experiment, the purity values of CTCs between 88% and 90% were achieved, which is an indicator of the high capability of the proposed devices for the isolation and enrichment of CTCs. This strategy is hoped to overcome the limitations of classical affinity-based CTC separation approaches in the future.

Flow characteristics in non-conventional combustion chamber configurations

Flow characteristics in combustion chambers of several non-circular cross-sectional configurations were numerically investigated. Different cross-sectional configurations, including annular and multi-sector annulus configurations with different fillets, were proposed, examined, and compared to the conventional circular arrangement. A numerical model was established and validated against other findings. The model was then used to study the effects of different design parameters, including convex and fillet radii, as well as some operational parameters, such as the angular velocity on the total pressure drop and the secondary flow characteristics like the swirl number, secondary vortex intensity, and helicity. The results revealed the optimum number of annulus sectors to be six, at which the highest hydraulic diameter was achieved for the same cross-sectional area. Optimum values of the inner and outer corner fillets were also obtained. Several valve arrangements were also investigated to achieve the highest possible valve area ratio for the proposed configurations. One of the proposed configurations, which incorporates six annular chambers with filleted corners with a hydraulic diameter ratio of 0.991 compared to the conventional circular design, denoted AFC4, achieved a more compact design while maintaining very comparable flow characteristics to those of the circular design. Although it needs more thorough investigations, it could present a viable alternative design option for the combustion chambers.

Dynamic design and analysis of subsea CO2 discharging flowline for cargo submarines used for CCS in low-carbon and renewable energy value chains

Developing offshore low carbon and renewable energy value chains to realize a net-zero energy future requires combining offshore renewable energy and carbon capture storage (CCS) solutions. The subsea shuttle tanker (SST) was presented in recently published works to accelerate the adoption of offshore CCS systems. The SST is a novel underwater vessel designed to transport CO2 autonomously from offshore facilities to subsea wells for direct injection at marginal fields using a flowline connected. The SST will be subjected to stochastic currents and experience dynamic responses during this offloading process. The offloading flowline must be designed to handle this dynamic response. As such, this paper establishes the baseline design for this flowline. The cross-section and global configuration designs drive the flowline design. For the cross-section design, the pressure containment, collapse and local buckling criteria defined in DNV-OS-F101 are applied to validate the required structural capacity at specified water depths. For the configuration design, the principle factors concerning the water depth, internal flow rate, and current speed are investigated to further validate the stress capacity according to the allowed von Mises stress level for a more robust baseline design. Finally, the flowline connecting and disassembly methodology is proposed, and the critical factor of well-coordinated speed between flowline and SST is investigated to avoid overbending during the lifting and lowering phases.

Investigation, Analysis and Optimization of PEMFC Channel Cross-Section Shape

In this study, a three-dimensional (CFD) model is employed to simulate and optimize the CCS (Channel Cross-Section) shape of the single straight channel PEMFC. Four CCS shapes, namely trapeze, inverted trapeze, half of ellipse and inverted half of ellipse, are investigated using ANSYS-FLUENT software and compared to the rectangular and triangular CCS shapes. The results obtained from the simulation are compared to the experimental results of the literature. A good agreement is observed between the numerical and experimental results. From the obtained results, it appears that the best delivered power density is reported by the trapeze CCS configuration, whereas, the worst delivered power density is obtained by the inverted half of ellipse CCS configuration. The highest pressure-drop and pumping power are obtained with the triangular CCS configuration and the smallest are resulted by the rectangular CCS configuration. Finally, the highest net power output is reported by the trapeze channel cross-section configuration, while, the lowest one is yielded by the inverted half of ellipse CCS configuration.

Topology optimization of thin-walled tubes filled with lattice structures

Thin-walled tubes filled with ultra-light materials have attracted much attention due to excellent energy absorption characteristics. With the development of additive manufacturing technology, it is allowed to manufacture structures with complex geometry shapes as new filled materials. In this study, complex proportional assessment (COPRAS) and discrete optimization algorithm were proposed to design and optimize the topology of thin-walled tubes filled with lattice structures. Firstly, the finite element model verified by experiment was adopted to investigate the influence of cross-sectional configurations and octet truss lattice filling distributions on crashworthiness of hybrid structures. The results show that the cross-sectional configuration has a greater effect on specific energy absorption (SEA) and the lattice filling distribution has a greater effect on peak crushing force (PCF). Then, COPRAS was used to sort the crashworthiness of hybrid structures with different topologies and select the optimal solution. It was found that C3-L4 structure had the best crashworthiness among all design schemes, indicating that the better crashworthiness can be obtained by filling the lattice in the four corner regions of tube or increase the number of cells in corner regions. Finally, the discrete optimization algorithm based on successive orthogonal arrays was adopted to further improve the crashworthiness of hybrid structure. It was found that the thin-walled tubes with different thickness had greater energy absorption capacity than those with the same thickness. Hence, the method proposed in this paper can become an effective way for topology optimization of crashworthiness.