Load Height Research Articles

Simultaneous recovery of Cu2O and FeOOH from wastewater contaminated with mixed metals using fluidized-bed crystallization

The fluidized-bed crystallization (FBC) removes heavy metals onto the fluidized pellets, which is an outstanding alternative to the precipitation method. This study simultaneously recovers iron and copper as binary metal-oxide pellets (FeIII0.66CuI0.33 @SiO2) in a synthetic wastewater using FBC and silica as a seed material. The operating parameters for FBC include the Fe/Cu ratio, pH, cross-sectional loading (L, kg/m2.h) and bed height (H, cm) and these are optimized to maximize the crystallization efficiency of iron and copper. At pH = 8, an input Fe/Cu ratio = 2 at a total metal concentration of 3 mM, the crystallization ratio (CR) and the total respective metal removal (TR) for Fe and Cu is 90% and 99%. Precipitation rates of 0.88 and 0.38 mg-metal/ gr-seed•h were obtained at respective cross-sectional loadings of 0.25 kg m− 2•h and 0.15 kg m− 2•h for Fe and Cu. The crystal phases of FBC product are respectively characterized as FeOOH and Cu2O by XRD analysis. The high crystallization ratio and the recovery of crystal pellet product indicated that the quantity of the sludge has been reduced significantly in comparison to the traditional chemical precipitation.

Elucidating the mass transfer mechanism of CrVI adsorption by encapsulated chitosan-carbon nanotubes-iron beads in packed-bed columns

This study evaluates the CrVI breakthrough behaviors of a continuous-flow column packed with composite chitosan-MWCNTs‑iron beads under various operating conditions. Under the tested range of experimental parameters, a maximum of 54% of CrVI removal was achieved at: water flow rate, 1 mL/min, feed CrVI concentration, 30 mg/L; and packed bed height 8 cm. A homogeneous surface diffusion model (HSDM) involving convection-dispersion and diffusion equations was formulated, numerically solved, and experimentally validated. The high degree of conformity between the calculated and experimental breakthrough curves facilitated the determination of mass transfer parameters including axial dispersion DL, (1.30 × 10−8 to 1.56 × 10−7 m2/s) and surface diffusion Ds, (7.28 × 10−11 to 1.80 × 10−10 m2/s) via an error minimizing approach. The DL value was a function of molecular diffusion, which varied with the flow velocity, mass loading, and bed height. The Ds values were slightly higher than those previously reported, owing to the heterogeneous nature of the adsorbent. The external film diffusion coefficient (kf) was also determined by using Wilson-Geankoplis empirical correlation, which was recognized as a rate-controlling factor during CrVI mass transfer to the adsorbent beads. Furthermore, sensitivity analysis showed that a transition from diffuse- to shock-front occurred with a decreasing DL, while a decrease in the slope of breakthrough curves was observed by decreasing Ds and bed porosity, and increasing kf and Langmuir parameters. Lastly, the study demonstrated a high correlation between utilization of fractional bed capacity and axial Peclet number. This method is suitable for optimizing operating conditions to maximize the utilization of a fixed-bed columns.

Comparison of Constitutive Models for Predicting the Formability of SS 304 by Tubular Hydroforming Process

Finite Element (FE) simulation of sheet/tube forming precision depends mainly on the accuracy of the constitutive modeling. The present paper aim is to compare the constitutive models to fit the stress-strain curves. The accurate deformation behavior of the SS 304 tubes depends on the constitutive modeling of hardening behavior. Deformation data of the tensile specimens cut from tubular sample were collected by conducting Uniaxial tensile tests (UTT) at three different rolling directions. Five constitutive relationships were then recognized by fitting the true stress and strain data with the constitutive models of Hollomon, Power, Krupowsky, Voce and Ghosh, and the fitting accuracy were analyzed and compared. Effects of hardening models on Forming Limit Curves (FLC), pressure loading and bulge height of the hydroformed tube were then studied. The obtained FLC from the simulations were compared with experimental FLC to predict the accuracy of the hardening models.

Comparison of inelastic moment resistances of rolled steel beams based on different specifications and a numerical study

The inelastic buckling resistances of wide flange beams are strongly influenced by residual stresses and initial imperfections. However, the resistances as evaluated from simple solutions presented in several popular design specifications are found to be considerably different. The present study thus develop a numerical solution in ABAQUS software to investigate the inelastic buckling moment resistances of rolled steel beams with compact sections and subjected to the effects of residual stresses and initial imperfections. The residual stresses are taken as provided in AISC, CSA S16, EC 3 specifications, while the initial imperfections are taken as the first lateral-torsional buckling mode with a magnitude limited in AISC, CSA specifications. Through comparisons between the specifications and the numerical solutions, one observes a significant difference between the moment resistances predicted by the specifications, in which the AISC predicts the highest values, while the EC 3 predicts the lowest moments. The moment resistances based on the present numerical models lie between the EC 3 and CSA solutions and they are relatively close to EC 3 solutions. Effects of load height positions on the inelastic buckling moment resistances are significant, as investigated in the present study

Deformation properties of arched glass fiber reinforced plastics structure under static load: Considering the soil cover and rise-span ratio

In this study, the load level, soil cover height, rise-span ratio, and arch foot constraint state were utilized to explore the mechanical properties of buried arch glass fiber reinforced plastics (GFRP) structures. Through the indoor scale-down test, the stress and deformation of arched GFRP structures under different load and soil cover height were investigated. Additionally, through the three-dimensional finite element method, the influence of the rise-span ratio and the constraint state of arch foot on the mechanical properties were obtained. The results indicate the new buried composite arch structure has excellent bearing capacity for the possible traffic load. Simultaneously, the semi-elliptical arch structure was believed to outperform the semi-circular arch structure when considering the external load. Specifically, increasing the soil cover height and reducing rise-span ratio were found to achieve the load-reduction effect.

Sleeve Gastrectomy Performed with Single Staple Height and Bioabsorbable Reinforcement in a Single Surgeon > 2500 Consecutive Case Series: Is Smart Technology Necessary?

Laparoscopic sleeve gastrectomy (LSG) is shown to have durable and sustained weight reduction outcomes and improvement in comorbid conditions in patients with severe clinical obesity. Discussions regarding "proper" staple height for various gastric locations continue. We propose a standard approach of consistent use of single staple load height and bioabsorbable staple line reinforcement during the LSG to reduce variability. A retrospective chart review of 2556 consecutive cases of adult patients who underwent LSG evaluated perioperative complications, postoperative leaks or bleeding, and average weight and body mass index (BMI) change and excess weight loss (EWL) at 6, 12, and 24months. The same green staple load (2.0mm) and staple line reinforcement were used in all cases for all staple firings, regardless of patient size or gastric location. Patients were a mean age of 42years, 87.3% were female, and the mean preoperative weight was 134.2kg and BMI was 48.2kg/m2. No staple line leak was detected. Three bleeding events occurred but did not require readmission or rehospitalization. Mean EWL and BMI, respectively, were 49.0% and 35.5kg/m2 at 6months, 69.8% and 29.6kg/m2 at 12months, and 70.0% and 29.5kg/m2 at 24months. In this case series of 2556 consecutive LSG performed by a single surgeon, clinically meaningful EWL and decreased BMI were achieved. Streamlining the LSG procedure by utilizing the same staple height and a bioabsorbable staple line reinforcement proved safe with minimal complications.

Transversally loaded stainless steel beams under fire: Local/global behaviour, strength and design

This paper presents and discusses the results of a numerical investigation concerning the post-buckling behaviour, strength and design of stainless steel I-section beams prone to local or global (lateral-torsional) buckling under elevated temperatures. Non-linear shell finite element models are employed to assess the structural response and failure loads of I-beams (i) subjected to distinct loading conditions, namely uniform bending, uniform transverse loading, 3 and 4-point bending (the transverse loadings are applied along either the shear centre, top flange-web or bottom flange-web longitudinal axes), (ii) made from three common stainless steel grades (ferritic 1.4003, austenitic 1.4301 and duplex 1.4462), (iii) subjected to eight temperatures (θ = 100 to 800 °C), and (iv) covering wide local and global slenderness ranges. Special attention is paid to the influence of the transverse loading location (load height effect), a topic lacking research in the context of local buckling, by means of (i) Generalised Beam Theory (GBT) buckling and (ii) ABAQUS shell finite element post-buckling analyses. The last part of the paper is devoted to design considerations, based on the numerical failure loads obtained and involving the assessment of the current Eurocode 3 design rules for stainless steel beams failing in local and global modes.

Biomechanical Effects on Lower Extremities in Human-Robot Collaborative Agricultural Tasks

The present study pertains to a key aspect of human-robot collaborative systems which is usually underestimated, namely occupational health prolepsis. The aim of this investigation was to assess the biomechanical effects of manual symmetric load lifting related to a synergistic agricultural task that utilizes an unmanned ground vehicle to undertake the carriage of loads. Towards that goal, kinetic and kinematic data were collected from the lower extremities of thirteen experienced workers, by testing three different deposit heights (70, 80, 90 cm) corresponding to possible adjustments of the available agricultural robot. Moreover, the muscle activation levels of three lower extremity muscles and one trunk muscle were evaluated via a wireless electromyography system. Overall, the experimental findings revealed that the lower examined load height was associated with larger knee flexion moments and hip extension moments. Nevertheless, this height was related to lower activation mainly of the erectus spinae muscles. Finally, insignificant alterations were observed for the ankle joint as well as the activation levels of the other muscles. Consequently, a height equal to 90 cm is suggested, however, by avoiding extreme lumbar postures. The current results can be exploited for possible ergonomic interventions concerning the optimal deposit height of a robotic platform when a similar case is designed.

Design Considerations for Distortional Lateral Buckling

A finite-element formulation is presented for the elastic distortional buckling analysis of doubly symmetric wide flange beams. The formulation characterizes the distribution of the lateral displacement along the web height through Fourier modes and is equipped with features to capture the load height effect and to enforce user-defined kinematic constraints. The formulation is used to investigate the load height and bracing height effects and develop a database of over 20,000 runs on practical beam cross-sections to characterize (1) the reduction in critical moment capacity due to web distortion; and (2) the effect of a load height on the elastic critical moments. A novel indicator characterizing web distortion along the beam span is proposed and integrated within the finite-element formulation in a procedure devised to optimize the location of transverse stiffener(s) along beam spans so as to reduce cross-sectional distortion and maximize the elastic critical moment attainable. The procedure is then applied to optimize the design of beams in two case studies.

Variable Heights Influence Lower Extremity Biomechanics and Reactive Strength Index during Drop Jump: An Experimental Study of Male High Jumpers.

Introduction This study finds the lower limbs' reactive strength index and biomechanical parameters on variable heights. Objective This research aims to reveal the effects of drop height on lower limbs' reactive strength index and biomechanical parameters. Methods Two AMTI force platforms and Vicon motion capture system were used to collect kinematic and dynamic signals of the lower limbs. Results The drop height had significant effects on peak vertical ground reaction force and peak vertical ground reaction force in the extension phase, lower limbs' support moment, eccentric power of the hip joint, eccentric power of the knee joint, eccentric power of the ankle joint, and concentric power of the hip joint. The drop height had no significant effects on the reactive strength index. Reactive strength index (RSI) had no significant correlations with the personal best of high jumpers. The optimal loading height for the maximum reactive strength index was 0.45 m. Conclusion The optimal loading height for the reactive strength index can be used for explosive power training and lower extremity injury prevention.

Evaluating stability of human spine in static tasks: a combined in vivo-computational study

Various interpretations and parameters have been proposed to assess spinal stability such as antagonist muscle coactivity, trunk stiffness and spinal buckling load; however, the correlation between these parameters remains unknown. We evaluated spinal stability during different tasks while changing the external moment and load height and investigated likely relationships between different EMG- and model-based parameters (e.g., EMG coactivity ratio, trunk stiffness, force coactivity ratio) and stability margins. EMG and kinematics of 40 young healthy subjects were recorded during various quasi-static tasks. Muscle forces, trunk stiffness and stability margins were calculated by a nonlinear subject-specific EMG-assisted-optimization musculoskeletal model of the trunk. The load elevation and external moment increased muscle activities and trunk stiffness while all stability margins (i.e., buckling loads) decreased. The force coactivity ratio was strongly correlated with the hand-load stability margin (i.e., additional weight in hands to initiate instability; R 2 = 0.54) demonstrating the stabilizing role of abdominal muscles. The total trunk stiffness (Pearson’s r = 0.96) and the sum of EMGs of back muscles (Pearson’s r = 0.65) contributed the most to the T1 stability margin (i.e., additional required load at T1 for instability/buckling). Force coactivity ratio and trunk stiffness can be used as alternative spinal stability metrics.

Design and FEM strength analysis of an innovative design of a front loader with an extension dedicated to the KUBOTA M5

Most of the front loaders are compact structures that do not allow loading at greater heights. On the Polish and foreign market, there was a need to develop a front loader design that would allow to increase the loading height. As a result, the front loader was designed a front loader with the possibility of extending the arms for the Kubota M5 agricultural tractor. The system enables unloading and loading of cubes, straw and hay bales on higher piles. Before starting the design process, the available front loader solutions were analyzed and on this basis, three concepts of design solutions were proposed. These concepts were scored on the basis of the adopted criteria and the one with the highest number of points was selected. For the selected concept, strength analytical calculations and verification calculations using the FEM method were performed. The developed loader is innovative compared to other available designs and has a good chance of implementation.

Effects of handle height and load on the endurance time for simulated demolition tasks.

Manual demolition tasks are heavy physical demanding tasks which involve forceful exertion of sustained pushing. They result in muscle fatigue which could lead to musculoskeletal disorders. Assessments of maximum endurance time (MET) are essential in understanding the developing of muscle fatigue for these tasks. The objectives of this study were to determine the effects of handle height and load conditions on the MET, and to establish MET models for the simulated demolition tasks. Twenty three male participants performed simulated demolition tasks under three loads and three handle heights conditions until they could not do so any longer. Their METs and ratings of perceived exertion were recorded and analyzed. The results showed that both load and handle height were significant (p < 0.0001) factors affecting the MET. Regression models to predict the MET under handle height and load conditions were established. The mean absolute deviations of these models were between 1.91 and 4.84 min. The MET models established may be used to estimate the MET which may be adopted in work/rest arrangement for demolition tasks using a handheld demolition hammer.

Numerical and experimental investigation on heat transfer enhancement by adding fins on the pot in a domestic gas stove

Heat transfer and premixed combustion are two working processes of domestic gas stoves, and poor heat transfer is the primary cause of low thermal efficiency. The investigation aims to strengthen the heat transfer capacity of the pot numerically and experimentally, thus improving the thermal efficiency of gas stoves and saving energy. With the increase in loading height Z, the thermal efficiency predicted by numerical simulation decreases gradually in agreement with the experimental results. After adding fins to the pot wall, it is found that the thermal efficiency increases with an increase in fin height H. The fin height H = 8 mm is used because of the better compromise between thermal efficiency and the max temperature of fins. By considering the total mass of the pot and thermal efficiency, we select the fin number N = 42, and its thermal efficiency is increased by 7.12% compared with the original pot. Experimental results confirm that the increase is 8.2% under the same conditions. Moreover, it is shown that the thermal efficiency at first increases to a maximum value then decreases with the augment of inclination angle. The optimal angle occurs at α = 30°, and its thermal efficiency is 9.48% higher than that of the original pot.

Bearing Capacity of Single Pile-Friction Wheel Composite Foundation on Sand-over-Clay Deposit under V-H-M Combined Loadings

This paper presents numerical modelling to investigate the bearing capacities and failure mechanisms of single pile-friction wheel composite foundation in sand-overlying-clay soil conditions under combined V-H-M (vertical-horizontal-moment) loadings. A series of detailed numerical models, with validations of centrifuge testing results, are generated to explore the potential factors influencing the bearing capacity of this composite system. Intensive parametric study is then performed to quantify the influences of the foundation geometry, soil properties, sand layer thickness, pre-vertical loading and lateral loading height on the failure envelopes in the V-H-M domain. Last but not least, an empirical design procedure is proposed based on a parametric study to predict the bearing capacity of this composite foundation under various loading conditions, which can provide guidance for its design and application.

Developing a new approach for design support of subsurface constructed wetland using machine learning algorithms

Knowing the effluent quality of treatment systems in advance to enable the design of treatment systems that comply with environmental standards is a realistic strategy. This study aims to develop machine learning - based predictive models for designing the subsurface constructed wetlands (SCW). Data from the SCW literature during the period of 2009–2020 included 618 sets and 10 features. Five algorithms namely, Random forest, Classification and Regression trees, Support vector machines, K-nearest neighbors, and Cubist were compared to determine an optimal algorithm. All nine input features including the influent concentrations, C:N ratio, hydraulic loading rate, height, aeration, flow type, feeding, and filter type were confirmed as relevant features for the predictive algorithms. The comparative result revealed that Cubist is the best algorithm with the lowest RMSE (7.77 and 21.77 mg.L−1 for NH4–N and COD, respectively) corresponding to 84% of the variance in the effluents explained. The coefficient of determination of the Cubist algorithm obtained for NH4–N and COD prediction from the test data were 0.92 and 0.93, respectively. Five case studies of the application of SCW design were also exercised and verified by the prediction model. Finally, a fully developed Cubist algorithm-based design tool for SCW was proposed.

Analysis solution of the lateral load response of offshore monopile foundations under asymmetric scour

Because of the directivity of the waves and flow, the scour hole presents an irregular shape, and the scour hole dimensions are different around the pile. In this paper, an asymmetric scour is defined in the calculation of the laterally loaded offshore monopile foundations considering scour. Then, the effective overburden stress and the effective strength of the remaining soil after scour are determined based on the solution of Boussinesq's point load due to the unloading of the scour. An analysis p-y method is developed under the condition of the asymmetric scour based on the p-y curve proposed by Matlock for soft clay and the p-y curve proposed by Reese for sand, respectively. The effect of the scour depth, scour width and scour slope angle on both sides of the piles on the lateral loaded piles are determined in both soft clay and sand. Finally, according to the results of the parameter studies, a simplified method applicable to small-diameter flexible piles is developed based on the pile head deflection before scour, scour depth, loading height and pile diameter to predict the lateral loaded pile head deflection after scour in soft clay and sand, respectively.

Improving Ensemble Volcanic Ash Forecasts by Direct Insertion of Satellite Data and Ensemble Filtering

Improved quantitative forecasts of volcanic ash are in great demand by the aviation industry to enable better risk management during disruptive volcanic eruption events. However, poor knowledge of volcanic source parameters and other dispersion and transport modelling uncertainties, such as those due to errors in numerical weather prediction fields, make this problem very challenging. Nonetheless, satellite-based algorithms that retrieve ash properties, such as mass load, effective radius, and cloud top height, combined with inverse modelling techniques, such as ensemble filtering, can significantly ameliorate these problems. The satellite-retrieved data can be used to better constrain the volcanic source parameters, but they can also be used to avoid the description of the volcanic source altogether by direct insertion into the forecasting model. In this study we investigate the utility of the direct insertion approach when employed within an ensemble filtering framework. Ensemble members are formed by initializing dispersion models with data from different timesteps, different values of cloud top height, thickness, and NWP ensemble members. This large ensemble is then filtered with respect to observations to produce a refined forecast. We apply this approach to 14 different eruption case studies in the tropical atmosphere. We demonstrate that the direct insertion of data improves model forecast skill, particularly when it is used in a hybrid ensemble in which some ensemble members are initialized from the volcanic source. Moreover, good forecast skill can be obtained even when detailed satellite retrievals are not available, which is frequently the case for volcanic eruptions in the tropics.

Prediction calculations for the first criticality of the HTR-PM using the PANGU code

The high-temperature reactor pebble-bed module (HTR-PM) is a modular high-temperature gas-cooled reactor demonstration power plant. Its first criticality experiment is scheduled for the latter half of 2021. Before performing the first criticality experiment, a prediction calculation was performed using PANGU code. This paper presents the calculation details for predicting the HTR-PM first criticality using PANGU, including the input model and parameters, numerical results, and uncertainty analysis. The accuracy of the PANGU code was demonstrated by comparing it with the high-fidelity Monte Carlo solution, using the same input configurations. It should be noted that keff can be significantly affected by uncertainties in nuclear data and certain input parameters, making the criticality calculation challenge. Finally, the PANGU is used to predict the critical loading height of the HTR-PM first criticality under design conditions, which will be evaluated in the upcoming experiment later this year.

Lateral stability analysis of thin-walled fiber-metal laminate beam with varying cross-section by considering nonlinear strains

Fiber metal laminates (FMLs) are a new class of hybrid materials that consist of thin metal sheets and fiber reinforced epoxy composite layers. Due to their significant characteristics, FMLs have been widely employed in a variety of engineering applications specifically aerospace industry. In this paper, the lateral-torsional buckling behavior of thin-walled FML beams with varying I-section is perused using an innovative and accurate methodology. Considering the coupling between the bending displacements and the twist angle, the system of lateral stability equations are derived via energy method in association with Vlasov’s model for thin-walled beam and the classic lamination theory. By uncoupling the equilibrium differential equations, the system of governing equations is transformed to a fourth-order differential equation in terms of the twist angle. The differential quadrature method is then applied to solve the resulting equation and to acquire the lateral buckling loads. The accuracy of the proposed methodology has been investigated by comparing the results with the outcomes obtained using ANSYS finite element software. In the following, the effect of significant parameters such as stacking sequence, fiber angle, fiber type, web tapering ratio, load height parameter and volume fraction of metal on lateral buckling load of fixed-free FML tapered I-beam under uniformly distributed load has been investigated.