Linear Loads Research Articles

Optimization of Linear Loading Strategy for Fuel Cell Initiation Based on Gaussian Process Regression Model

Optimization of Linear Loading Strategy for Fuel Cell Initiation Based on Gaussian Process Regression Model

The Effects of Loading Angles on the Failure of Cross-Ply Notched Bio-Basalt Composites

A cross-ply basalt V-notched butterfly specimens were subjected to pure tension, combined tension-shear, and shear stress-strain state using a modified Arcan test fixture with loading angles from 0° to 90° with 15° increment. Multiaxial stress and strain states were studied using the principal stress and strain ratio, from which the principal angle was determined and used to represent principal states in the gauge section. The quasi-elastic to non-linear transition stresses were determined for each loading angle. In biaxial stress-strain states and pure shear, the deformation and consequently the shear-induced damage start to accumulate significantly. Also, in biaxial stress-strain states between 15°-75°, the shift from tension-shear to pure shear was observed after the transition to the non-linear part of the stress-strain curve. The digital image correlation (DIC) images and microscopic evaluation show that a large extent of damage is the consequence of the shear deformation after the rotation of 0° clamped fibres, while the 90° fibres maintained their original straight form. In off-axis tests, the principal strain axis rotates towards the weakest material axis even at small off-axis angles. This causes a transition from a tension-shear biaxial state in the linear loading part to shear in the non-linear part, leading to irreversible damage beyond the transition point.

Physical and numerical tests on adjustable–height structures of high–speed railway transition section

The disparity in stiffness and differential settlement between the subgrade and rigid structures can lead to track irregularities within transition sections, resulting in significant train vibrations and impacts. This study proposes an adjustable–height subgrade structure for transition sections by introducing a raft slab to divide the subgrade into upper and lower parts. When settlement occurs in the subgrade, the raft slab can be elevated using height–adjustment techniques to compensate for the settlement. To this end, large–scale physical model tests are conducted under train loading to verify the design's rationality and to elucidate the influence of settlement magnitude and train speed on the stress and deformation of the slab. The experimental results indicate that the maximum principal stress and maximum shear stress of the slab generally increase with settlement magnitude and train speed, and the area near the abutment end is the most unfavorable position for the deformation of the slab. However, it is still lower than the design compressive strength of the C40 concrete structure. Thus, the designed adjustable–height structure meets the load–bearing requirements under train loading. Additionally, a numerical simulation model of the adjustable–height structure is developed to investigate the recovery capabilities and stress distribution of the settled raft slab. The results indicated that whether the lifting operation employed linear load or equal load methods, the raft slab primarily endured compressive stress, and there is stress concentration at the lifting points. For the same lifting displacement, the linear load method proved to be more reasonable than the equal load method. These findings have significant practical and theoretical implications for ensuring the safe and smooth operation of high–speed railways, effectively addressing the post–construction settlement deformation control challenges in ballastless track transition sections.

Assessment of the trapezoidal miniplate with posterior extension for open management of condylar fractures: Can it be used instead of straight miniplates?

AbstractObjectiveThis study comparatively measures and evaluates the strength of five plating techniques for mandibular condylar fracture fixation when linear loading is applied.Materials and MethodsThe investigators designed and implemented a cross‐sectional in vitro study. The sample was composed of 60 polyurethane mandibles for the mechanical tests. For the photoelastic test, 10 photoelastic mandibles were used. The predictor variable is the plating technique, and it was categorized as groups G2P‐2.0: two 4‐hole 2.0 mm straight plates, G1TP‐2.0: 4‐hole 2.0 mm trapezoidal plate; G1TPPE‐2.0: 4‐hole 2.0 mm trapezoidal plate with posterior extension; G1TP‐1.5: 4‐hole 1.5 mm trapezoidal plate and G1TPPE‐1.5: 4‐hole 1.5 mm trapezoidal plate with posterior extension. The outcome variable is the strength of the plating techniques that was evaluated with the loading test: peak/ending load and peak/ending displacement measures collected. The photoelastic test was used to detect tension distribution throughout the structure helping to understand the material's behaviour. Values of the loading test were analysed using SAS (SAS Institute, Cary, NC, EUA). A p <0.5 (p = 0.05) was considered significant and means were compared using the Tukey test.ResultsThe results indicated that the fixation with two plates presented a higher resistance in the anteroposterior direction and fixation with a trapezoidal plate with posterior extension is more resistant towards mediolateral. The photoelastic analysis showed that the strain lines were best distributed when trapezoidal plates were used.ConclusionAccording to the results, the posterior extension of the trapezoidal plates increased the strength of the fixation system, and the use of trapezoidal plates with or without posterior extension was favourable to a more balanced stress distribution. However, clinical studies must be done to confirm the biomechanical findings.

Calculation model for settlement of soft soil foundation with continuous drainage boundary considering the Hansbo’s flow law and the linear load

Calculation model for settlement of soft soil foundation with continuous drainage boundary considering the Hansbo’s flow law and the linear load

Evaluating the Harmonic Effects on the Thermal Performance of a Power Transformer

Harmonics in the power grid contribute to increased power losses in both the core and windings of power transformers. These losses lead to abnormal rises in temperature causing overheating and reduce the efficiency of the transformer. If the losses and temperature exceed the values set during the design stage for linear load conditions, it can damage the transformer’s insulating materials and shorten its lifespan. To assess the thermal impact of power system harmonics on transformers under steady-state and transient conditions, the rated losses and harmonic losses of the transformer are calculated. These losses are then inputted into a developed thermal 3D finite element method (FEM) performance model to determine the temperature distribution of transformer components. The numerical results from the thermal model will be compared with data from a Hyundai test report and real measurements from Egypt’s Kureimat power plant, specifically a 750 MW combined cycle power plant. The thermal modeling is focused on a step-up (16.5/240 kV), 240 ± 4 × 2.5%, 180/240/300 MVA power transformer operating in ONAN, ONAF1, and ONAF2 modes. This paper shows that the developed model aligns closely with actual measurements and the HYUNDAI test report. The loss calculations reveal that the discrepancy in total losses, with and without accounting for harmonics, becomes more pronounced as the load increases. Using this model, the presence of grid harmonics results in a higher temperature distribution across transformer components, leading to an increase in the hot spot temperature.

Oocytes Vitrification Using Automated Equipment Based on Microfluidic Chip.

Oocyte vitrification has a wide range of applications in assisted reproduction and fertility preservation. It requires precise cryoprotectant agents (CPAs) loading and removal sequences to alleviate osmotic shock, which requires manual manipulation by an embryologist. In this study, a microfluidic system was developed to facilitate the precise adjustment of the CPA concentration around the oocyte by linear loading and removal of CPA. In addition, the microfluidic-based automated vitrification (MAV) device combines CPA loading/removal process, with vitrification process, thereby achieving automated oocyte vitrification. Oocytes were vitrified by Cryotop/QC manual method and MAV method. The results showed that the survival, cleavage, and blastocyst rates of oocytes were 80.44, 54.17, and 32.95% for the MAV method, which were significantly higher than Cryotop manual method (73.35, 43.73, and 23.67%) (p < 0.05). In MAV, solution injection rate during CPA loading/removal process was designed as a 1-segment, 2-segment, and 4-segment function. Accordingly, three concave loading and convex removal protocols were adopted to vitrify oocytes. Oocytes vitrified using the 4-segment function group exhibited increased survival (86.18%), cleavage (63.29%), and blastocyst (45.58%) rates compared to those vitrified using the 1-segment and 2-segment groups. The oocytes vitrification with the highest concentration of CPA, denoted as VS1-TS1, exhibited the highest survival rate after rewarming (86.18%). In contrast, the VS3-TS3 group, characterized by a CPA concentration half that of VS1-TS1, exhibited lower survival (74.14%) and cleavage (59.31%) rates, but displayed the higher blastocyst rate (50.79%) following oocyte activation. Our study demonstrates potential of the MAV device for oocyte or embryo vitrification.

Economic management of microgrid using flexible non-linear load models based on price-based demand response strategies

Demand response programmes are used in microgrid research without considering the different price elasticity of distinct load types. To evaluate the impacts of demand response efforts, it is necessary to utilise a mix of nonlinear and linear models for creating load-responsive models in a manner that is realistic. With an aim to address this gap in research, an exhaustive technoeconomic investigation is being conducted to determine the effect that price-dependent demand response programmes have on the optimal scheduling of microgrids when linear and nonlinear load models are present. The flexible elasticity model is used to accurately describe how customers respond to changes in electricity price. Four load models, including exponential, hyperbolic, linear, and logarithmic, were constructed for each demand response programme. Rime is a newly created physics-based algorithm that has been deployed to handle the anticipated energy management problem that the microgrid may be experiencing. To evaluate the efficacy of the proposed strategy, four case studies based on grid price and participation scenarios have been carried out. The findings from our research are notably impactful, revealing an 8 % reduction in energy consumption when applying the critical peak price (CPP) load demand model. This efficiency gain translates into a notable enhancement in the load factor, increasing from 0.83 to 0.86, and a significant drop in overall generation costs from $25,463 to $21,823 under optimal conditions. These results vividly illustrate the practical value of our proposed research work, showcasing their ability to generate substantial energy savings and cost efficiencies in microgrid operations. The improvements in operational efficiency and cost-effectiveness underscore the potential of these models to refine microgrid management, delivering both economic and performance gains that are crucial for advancing sustainable energy solutions.

Effect of Linear Velocity on Magneto-mechanical Properties of Ni-Mn-Ga-Based Melt-Spun Ribbons

The study brings original data on the effect of linear velocity during melt-spinning process on magneto-mechanical properties of Heusler Ni-Mn-Ga-based melt-spun ribbons. The research revealed that different linear velocity of the copper wheel had a significant impact on the ribbon's geometry resulting in distinct changes in magneto-mechanical properties. X-ray diffraction measurements were used to examine the phase composition, confirming the presence of L21 austenite phase. To assess the mechanical properties of the Ni-Mn-Ga-based melt-spun ribbons, cyclic bending experiments were conducted at a strain rate of 0.1 mm/s. Additionally, experiments involving magnetic field-induced bending were carried out in an external magnetic field ranging from 0 to 0.28 T. Finally, it was observed that there was a proportional relationship between the linear velocity of the copper wheel and magnetic field-induced ribbons deflection. Conversely, the dependence between linear velocity and mechanical bending load was found to be inversely proportional. Electron backscattered diffraction measurements revealed that melt-spun ribbons produced at high linear velocity of 18.5 m/s exhibited fine-grained microstructure in contrast to low linear velocity of 3 m/s. Based on these results it seems feasible to optimize the functional properties of the studied ribbons by varying the linear velocity of the melt-spinning process.

Performance evaluation of microbial fuel cells for bioelectricity generation: influence of potential scan-rate and real-time external load

AbstractThe electrochemical performance of microbial fuel cells is conventionally assessed through linear sweep voltammetry at predefined potential scan rates. Nevertheless, this approach frequently falls short in representing the long-term behavior of microbial fuel cells under actual external loads, highlighting the need for a standardized evaluation method incorporating both linear sweep voltammetry and external loads. To address this gap, this study evaluates the performance of single-chamber microbial fuel cells under different loads and scan rates. The MFCs were tested with external loads of 1200, 470, and 270 Ω, derived from maximum power points of polarization sweeps at scan rates of 0.1, 0.5, and 1 mV/s at two operational phases. Power estimates at these scan rates were 61.96, 87.88, and 166.68 mW/m2 at current densities of 116.5, 229.6, and 403 mA/m2, respectively. In the initial two hours, average power densities with 1200, 470, and 270 Ω were 73 ± 16.7, 36.3 ± 42, and 88.5 ± 120.1 mW/m2, respectively. Over the long term, the fuel cells under constant loading with resistance estimated at 0.1 mV/s showed average power 73.7% and 89.1% higher than those with resistances estimated at 0.5 mV/s and 1 mV/s, respectively, indicating that higher scan rates lead to overestimation of power. Although initially underestimated, the 0.1 mV/s scan rate more accurately reflected the true long-term performance of the fuel cells. This study emphasizes the importance of using appropriate scan rates for linear sweep voltammetry to obtain realistic long-term performance estimates of microbial fuel cells under real-time loads.

Bond–Slip Performance between Steel Tube and Self-Compacting Fly Ash Concrete

To reduce the amount of ordinary concrete and then reduce carbon dioxide emission, improving the engineering application range of self-compacting fly ash concrete (FASCC), this study explored the bond–slip traits between FASCC and a steel tube. Six samples were created, and bond–slip push-out tests were performed with varying concrete strength grades and steel tube internal setups. Digital image correlation (DIC) technology was applied to track the surface strain of four samples throughout the experiment. The results show that the outer surface of the steel tube stays mostly undistorted after the concrete is pushed out. Prior to reaching peak load, the load–slip curves of each specimen exhibit a primarily linear load–displacement relationship. Post-peak, the curves diverge into two distinct patterns, namely a sudden drop and a gradual decline. As the strength grade of the inner concrete increases, the interfacial bond between the steel tube and FASCC improves. Additionally, under the same conditions, the internal structure of the steel tube significantly enhances bonding strength. The FA40-Z specimen shows a maximum load that is 25.6% and 53.7% higher than the FA40-G and FA40-C specimens, respectively. The strain evolution patterns of steel tubes within FASCC and regular self-compacting concrete demonstrate similar characteristics. These observations provide valuable insights for the application of FASCC in engineering projects.

Cloud-fog architecture-based control of smart island microgrid in master-slave organization using disturbance observer-based hybrid backstepping sliding mode controller

Distributed control is an effective method to coordinate the microgrid with various components, and also in a smart microgrid, communication graph layouts are essential since changing the topology unexpectedly could disrupt the operation of the distributed controllers, and also an imbalance may occur between the production and load. Hence, reducing the exchanged data between units and system operator is essential in order to reduce the transmitted data volume and computational burden. For this purpose, an islanded microgrid with multiple agents which is using cloud-fog computing is proposed here, in order to reduce the computing burden on the central control unit as well as reducing data exchange among units. To balance the production power and loads in a smart island with a stable voltage/frequency, a hybrid backstepping sliding mode controller (BSMC) with disturbance observer (DO) is suggested to control voltage/frequency and current in the MG-based master-slave organization. Therefore, this paper proposes a DO-driven BSMC for controlling voltage/frequency, and power of energy sources within a Master-Slave organization; in addition, the study proposes a clod-fog computing for enhancing performance, reducing transferred data volume, and processing information on time. In the extensive simulations, the suggested controller shows a reduction in steady-state error, a fast response, and a lower total harmonic distortion (THD) for nonlinear and linear loads less than 0.33 %. The fog layer serves as a local processing level, so it reduces the exchanged data between cloud and fog nodes.

Linear Hybrid Asymmetrical Load- Modulated Balanced Amplifier With Multiband Reconfigurability and Antenna-VSWR Resilience

Linear Hybrid Asymmetrical Load- Modulated Balanced Amplifier With Multiband Reconfigurability and Antenna-VSWR Resilience

Statistical prediction for nonlinear failure function of linear loads: application to plate buckling in ship structure

AbstractThis study presents a practical method for calculating the probability of exceedance (PoE) of the nonlinear failure function of the linear loads randomly fluctuating in irregular waves. In general, obtaining the exact PoE of such nonlinear quantities requires sophisticated computational method that are not well-suited for practical design. In contrast, the author in a previous study proposed a practical formula of the PoE distribution for von Mises stresses by asymptotic approximation, which can be applied when the criterion surface is ellipsoid in the stochastic variable space. Following this, the present study shows a method for calculating the PoE for a more general function of which the isosurface is expressed as a combination of ellipsoids. As a specific example of its application, this paper takes the limit state of the plates in ship structures specified in the common structural rules (CSR) and presents the calculation procedure of direct numerical integration as well as asymptotic approximation approaches. Calculation of the 1/1000 maximum expected value of the evaluation function of plates in short-term sea states using 700 actual plates in a ship structure confirms that the proposed method, which does not require integration, is in good agreement with rigorous methods using numerical integration.

Are different screw lengths associated with osteosynthesis quality in the region of the mental foramen?

AbstractIntroductionThe use of two monocortical malleable 04‐hole miniplates, placed above and below the mental foramen, has been indicated to prevent the adverse effects of tension and torsion forces on fracture healing. To obtain good fixation in the mandible's outer cortex screws, 5–8 mm long have been recommended. However, studies have shown thicknesses in the mental foramen region of up to 3 mm, meaning the length of the screw could be a risk to nerve or tooth root damage. The purpose of this study is to identify the influence of screw length on osteosynthesis quality in the region of the mental foramen.Materials and Methods10 synthetic polyurethane human lower jaw replicas were subjected to a linear loading test to evaluate fixation techniques with 5 and 10 mm of displacement. In the photoelastic analysis, 02 lower jaw models were made of photoelastic resin and subjected to linear loading in the fixation technique with 10 mm of displacement. Two 04‐hole miniplates in the region of the mental foramen either fixed completely with 4 mm screws (group 1) or with 5 mm screws in the tension zone and 8 mm screws in the compression zone (group 2). The variables were registered for peak load and peak displacement, and final load and final displacement. One‐way analysis of variance (ANOVA) was applied, followed by the Tukey test, with a significance of 5% (p = 0.05) for the comparisons between the means.ResultsConsidering 95% confidence intervals, the mechanical test showed no statistical differences in peak load between the fixations groups. In the photoelastic analysis, the fringes were concentrated on the distal segment of the fracture in both groups.ConclusionDue to the lack of statistical difference in the biomechanical and photoelastic tests, considering the methodologic limitation, our study indicates a tendency of advantage toward the treatment of fractures with two 04‐hole plates, fixed with 4 mm screws, to minimize complications like tooth or nerve damage. In vivo studies are needed to verify the convergence of the results of in vitro studies to evaluate the resistance and stability in real masticatory forces.

The evaluation of total power factor components under non-sinusoidal conditions of industrial power supply systems with linear and nonlinear load

The evaluation of total power factor components under non-sinusoidal conditions of industrial power supply systems with linear and nonlinear load

A comparative study of constitutive models for EPS foam under combined compression and shear impact loading for helmet applications

Virtual testing of helmets using finite element (FE) analysis can be a valuable tool during product development. Still, its usefulness is limited by the quality of the constitutive model of the energy-absorbing material, usually foam. Built-in constitutive models in commercial FE software are developed for traditional linear compression loading. However, modern oblique test methods load the foam in combined compression and shear. Therefore, we aim to evaluate to what extent built-in constitutive models in commercial FE software can represent Expanded Polystyrene (EPS) foam during combined compression and shear loading (CCSL). EPS foam is tested experimentally in a newly developed test rig for CCSL (V-test). The response is compared against the simulation using three different constitutive models available in LS-DYNA (M83, M126, and M181). The models are assessed by their ability to capture the correct response, focusing on how well the continuum models can capture the phenomenological events seen in the experiments. The results show that the models perform well in compression, as expected. However, we point out limitations in the shear response and significant limitations in the unloading response, both important for oblique helmet testing. Due to these limitations, we conclude that the existing models are inadequate for accurately simulating oblique helmet impacts. There is a clear need to develop and implement new constitutive models focused on capturing CCSL including the unloading. Additionally, frictional sliding was found to substantially influence the measured response in the V-test method. Minimizing interface sliding is therefore critical for isolating the material behavior.

Experimental investigation of Catalan vault structures based on earthen materials

The Catalan vaulting have succeeded in reducing reliance on support centers, resulting in lowered costs and expedited construction processes. This research advances the study of Catalan vaulting by exploring innovative, environmentally friendly earth-based materials. The study conducts a comprehensive comparative analysis of load-bearing behaviors across distinct vault elements: those fabricated from terracotta, raw-earth tiles, and shot-earth. Constructed and tested at a 4-meter span, full-scale vault specimens are subjected to varying distributed load configuration, followed by rupture testing employing a linear load at a quarter of the span. Experimental evidence, corroborated by FE results, indicates that both terracotta and raw earth tile vaults offer commendable performance, yet their failure loads are surpassed by vaults constructed using shot-earth. Therefore, shot-earth emerges as a sustainable alternative for constructing vault elements. Furthermore, the study demonstrates that incorporating reinforcement within shot-earth vaults increases their strength and ductility.

Enhancement layout optimisation of grid structures with stability constraints

Grid structures have found widespread use in civil and mechanical engineering owing to their ability of covering long spans with an outstanding strength-to-weight ratio. However, their shallow structural depth and slender members make them susceptible to buckling failures. Therefore, it is crucial to enhance the stability of grid structures. An under-explored way to achieve this is by optimally configuring enhancement materials. This paper addresses the challenges of identifying the optimal enhancement layouts for grid structures by solving a density-based topology optimisation problem. The problem formulation is based on the SIMP approach, minimising compliance while satisfying constraints on material volume and structural stability. The stability constraint is expressed using buckling load factors obtained from a linear eigenvalue analysis. Two types of enhancement schemes, involving in-plane and out-of-plane elements, are developed for the single-layer base grid structures. The efficiency of the proposed method is evaluated by performing enhancement layout optimisation for a flat and three curved square grid structures, subject to a uniformly distributed vertical load and a half-span load. The optimisation results shed light on the impact of in-plane and out-of-plane enhancements on the stability of grid structures, providing insights on optimally configuring enhancement materials to achieve desired stability. In addition, comparative analysis between the case studies indicates that for curved structures, a higher curvature normally leads to greater achievable stability. In contrast, the flat grid structure exhibits the broadest range of customisable stability due to its primarily bending-dominant load-carrying mechanism. Furthermore, the outcomes of geometric non-linear analysis confirm the load-carrying capacity of the optimal structures, with non-linear critical loads typically showing a positive correlation with linear buckling loads.

Effect of Drained Multi-Directional Loads on Liquefaction Resistance of Granular Material

ABSTRACT It is well recognized that the liquefaction resistance is closely related to the consolidation stress in soils. However, previous studies investigated the effects of unidirectional consolidation loads rather than multi-directional consolidation loads on liquefaction resistance. In this study, two types of granular materials, spherical glass beads and irregularly-shaped sands, are tested under undrained conditions with the uni- and bi-directional loads to investigate the liquefaction resistance. The effects of consolidation loads on liquefaction resistance can be explained in terms of material anisotropy. In simple shear tests, the stress- and strain-controlled loading paths are adopted for the consolidation and the undrained shear process, respectively. The results indicate that the liquefaction resistances of both materials consolidated under the multi-directional consolidation loads are higher than those consolidated under the linear loads. More consolidation loading cycles induce a better liquefaction resistance of the specimens at a given relative density. In addition, the influence of consolidation stress on liquefaction resistance is demonstrated by the anisotropy of specimens. Cyclic vertical stress, unidirectional shear stress, and bidirectional shear stress applied during consolidation produce greater isotropy and improve the liquefaction resistance of the specimen compared with the monotonic vertical stress, and their effects align with an increasing order.