Strip Model Research Articles

Forced ammonia stripping from livestock wastewater: the influence of some physico-chemical parameters of the wastewater.

In highly alkaline aqueous solutions (pH >10), the main form of dissolved ammoniacal nitrogen is the unionized free ammonia. Free ammonia, being a gaseous molecule, is easily stripped out from the solution. Increasing wastewater pH is frequently used to force ammonia removal. Herein, the effect of the variation of some physico-chemical characteristics of liquid cattle wastewater on ammonia stripping was investigated. The results show that at pH 11.5, ammonia volatilization and consequently its removal through stripping, was not affected by the variation of total solids (1-10%), alkalinity (2,500-20,000 mg/L as CaCO3) and electrical conductivity (20-50 mS/cm), or by the alkali type (NaOH, KOH and Ca(OH)2) employed to increase pH. The only parameter which affected ammonia stripping rate was the variation of the concentration of bedding material (straw 0.5-5%). The results suggest that the process of forcing ammonia stripping rate at high pH is unaffected and is not limited by the variation of any of the investigated parameters, except bedding material. The parameter kOLa (1/min) of the mass transfer model of ammonia stripping regarding the control experiments (raw wastewater without increasing pH) was ca. 0.0002, while by increasing pH it increased more than 20-fold (0.004 to 0.0045).

Modelling of strip buckling in the continuous annealing process

This paper considers the equipment and technological characteristics of continuous annealing process (CAP) to solve the issue of strip buckling. It analyses the mechanism of hot buckling and transverse compressive stresses from internal and external forces. A basic description of strip buckling is given together with a new concept of a buckling index. The critical buckling condition is presented, and the model of strip buckling index in the CAP is proposed. The distribution of strip buckling index in different sections of the process is analysed quantitatively along with the influence of incoming strip shape, transverse temperature difference, roller profile, friction coefficient, set tension and strip processing speed on the strip hot buckling index in CAP. Results show that with the influence of thermal stress, the transverse compressive stress that affects the middle part of the strip is largest in the heating section, which is also where hot buckling occurs most easily; centripetal force is dominant in the soaking and slow cooling sections, and in these sections buckling occurs at the roller shoulder. In different sections, the strip buckling index distribution differs, whereas the influence of other parameters on buckling index remains similar.

QCM model as a system of two elastically bound weights

The idea of strip model is further developed and supplemented by the list of necessary and sufficient conditions to explain why the frequency shift changes its sign for the opposite one. Actually, a load (either point or distributed) is linked to the QCM surface through some elastic bonds rather than rigin ones. Because of this, the frequnecy shift may take on the values opposite in signs. It is demonstrated that the strip model is so general that it fits well with its points to the experimental curves recorded for different QCM samples. To predict the sign of the frequency shift, we introduce an elastic bond between the nanoobject and QCM surface, and describe a semi-analytical solution which explains why the sign of the frequnecy shift changes.

A Comparative Study of the Shell Element and Strip Model Methods for Analysis of Steel Plate Shear Wall Structures

Shell element and strip model are the two available numerical methods in the analysis of steel plate shear wall (SPSW) structures. The shell element model provides excellent prediction of the behavior of SPSWs. However, when the number of elements increases, especially in high-rise frames, the method becomes time consuming and produces convergence complications. In such cases, the strip model is commonly used as an alternative method. In the literature, the evaluation of the strip model has only been carried out for up to four-story SPSW structures. In the present study, fourteen low- to high-rise SPSW frames having 4, 7, 10 and 13 stories with different bay widths of 2, 3, 6 and 9m are designed and modeled using shell element and strip methods. The pushover analysis results show that the accuracy of strip model is affected by the number of story levels as well as the bay width. The use of beam element in modeling frame members is shown to have considerable effects on the results of the strip model. The panel zones should be modeled as effectively rigid regions in the strip model; and the slenderness ratio of frame members should be considered. It is also found that the distribution of story shear between infill plates and frame members are quite different in the two modeling methods. Furthermore, modifications to improve the accuracy of the strip model are recommended in this paper.

Simulations of ram-pressure stripping in galaxy-cluster interactions

Observationally, the quenching of star-forming galaxies appears to depend both on their mass and environment. The exact cause of the environmental dependence is still poorly understood, yet semi-analytic models (SAMs) of galaxy formation need to parameterise it to reproduce observations of galaxy properties. In this work, we use hydrodynamical simulations to investigate the quenching of disk galaxies through ram-pressure stripping (RPS) as they fall into galaxy clusters with the goal of characterising the importance of this effect for the reddening of disk galaxies. Our set-up employs a live model of a galaxy cluster that interacts with infalling disk galaxies on different orbits. We use the moving-mesh code AREPO, augmented with a special refinement strategy to yield high resolution around the galaxy on its way through the cluster in a computationally efficient way. Our direct simulations differ substantially from stripping models employed in current SAMs, which in most cases overpredict the mass loss from RPS. Furthermore, after pericentre passage, as soon as ram pressure becomes weaker, gas that remains bound to the galaxy is redistributed to the outer parts, an effect that is not captured in simplified treatements of RPS. Star formation in our model galaxies is quenched mainly because the hot gas halo is stripped, depriving the galaxy of its gas supply. The cold gas disk is only stripped completely in extreme cases, leading to full quenching and significant reddening on timescale of ~200 Myr. On the other hand, galaxies experiencing only mild ram pressure actually show an enhanced star formation rate that is consistent with observations and are quenched on timescales > 1 Gyr. Stripped gas in the wake is mixed efficiently with intracluster gas already a few tens of kpc behind the disk, and this gas is free of residual star formation.

Technical Note: Analytical Evaluation of the Vulnerability of Framed Tall Buildings with Steel Plate Shear Wall to Progressive Collapse

In recent decades, vulnerability of tall buildings to unforeseen loads, induced by progressive collapse, has drawn researchers’ attentions. Steel plate shear walls have long been used as a lateral load-resisting system. It is composed of beam and column frame elements, to which infill plates are connected. There is a growing tendency among engineers to design tall buildings using steel plate shear walls. This paper investigates the progressive collapse-resisting capacity of the strip model of steel plate shear wall system compared with X-braced and moment frame system. The 3D models are used to assess the collapse behavior of typical 50-story building models, under sudden loss of elements from the middle and corner of the exterior frame in the story above the ground. The progressive collapse potential of model structures is evaluated by different nonlinear static and dynamic analyses using conventional analysis software. In this study, the vulnerability of candidate structures subjected to progressive collapse is also assessed by a sensitivity index regarding the sensitivity of structures to the dynamic effect induced by progressive collapse. To identify vulnerable members, the resulting actions of two nonlinear and linear static analyses are compared by the factor of redundancy related to the overall strength of the structure. Comparison of the analysis results indicated that in the steel plate shear wall system, the progressive collapse-resisting potential is more than X-braced and moment frame structure. Sensitive index of highly sensitive elements to the dynamic effect stated that in the structural models, beams are significantly more vulnerable in the moment frame than X-braced and SPSW structure. The index depicted that the vulnerability of columns in X-braced and SPSW structure is more than the moment frame structure.

Finite strip modeling of the varying dynamics of thin-walled pocket structures during machining

The structural model of the workpiece is required for modeling, analysis, and avoidance of forced and regenerative (chatter) vibrations in machining of thin-walled parts. Finite element models (FEM) provide a versatile means for modeling the workpiece dynamics, but such models need to be updated frequently as the mass and stiffness of the workpiece varies continuously during machining. The computational time and power that is needed for re-meshing the FEM and then re-computing the natural modes of the workpiece is prohibitive. In this paper, a new approach based on Finite strip modeling (FSM) is presented for modeling the structural dynamics of thin-walled structures during pocket milling operations. The substantially higher computational efficiency of the FSM approach in predicting the varying dynamics of thin-walled pocket structures is verified by comparing its performance against FEM and the multi span plate (MSP) approach presented in (J Manuf Sci Eng 133:021014, 2011). Additionally, the accuracy of the presented approach in analyzing the stability of vibrations and determining the extent of dynamic deflections is verified using experimental results.

PEST Control of Molecular Stripping of NFκB from DNA Transcription Sites.

We recently proposed a model for IκBα-mediated molecular stripping of NFκB from transcription sites. IκBα was shown experimentally to form a transient ternary complex with DNA-bound NFκB, but the mechanism by which the IκBα accelerates dissociation of the NFκB from the DNA was unknown. In this paper we construct and compute free energy profiles for the wild-type IκBα-mediated molecular stripping reaction of NFκB from DNA and compare with that for a mutant of IκBα bearing a charge-neutralized PEST. The differences in the free energy profile for stripping originate from the frustrated electrostatic interactions between the negatively charged PEST and the DNA. The PEST occupies two different conformations in the NFκB-IκBα binary complex, one of which occupies the DNA-binding cavity. Specific interactions with positively charged residues in the N-terminal domains of both p50 and p65 apparently draw the domains closer together hindering reassociation of DNA. Comparison with the charge-neutralized mutant reveals that all of these functional consequences result from the negative charges in the PEST sequence of IκBα.

Resolution-independent modelling of environmental effects in semi-analytic models of galaxy formation that include ram-pressure stripping of both hot and cold gas

The quenching of star formation in satellite galaxies is observed over a wide range of dark matter halo masses and galaxy environments. In the recent Guo et al (2011) and Fu et al (2013) semi-analytic + N-body models, the gaseous environment of the satellite galaxy is governed by the properties of the dark matter subhalo in which it resides. This quantity depends of the resolution of the N-body simulation, leading to a divergent fraction of quenched satellites in high- and low-resolution simulations. Here, we incorporate an analytic model to trace the subhaloes below the resolution limit. We demonstrate that we then obtain better converged results between the Millennium I and II simulations, especially for the satellites in the massive haloes ($\rm log M_{halo}=[14,15]$). We also include a new physical model for the ram-pressure stripping of cold gas in satellite galaxies. However, we find very clear discrepancies with observed trends in quenched satellite galaxy fractions as a function of stellar mass at fixed halo mass. At fixed halo mass, the quenched fraction of satellites does not depend on stellar mass in the models, but increases strongly with mass in the data. In addition to the over-prediction of low-mass passive satellites, the models also predict too few quenched central galaxies with low stellar masses, so the problems in reproducing quenched fractions are not purely of environmental origin. Further improvements to the treatment of the gas-physical processes regulating the star formation histories of galaxies are clearly necessary to resolve these problems.

Study on seismic retrofit of structures using SPSW systems and LYP steel material

Steel plate shear walls (SPSWs) have been shown to be efficient lateral force-resisting systems, which are increasingly used in new and retrofit construction. These structural systems are designed with either stiffened and stocky or unstiffened and slender web plates based on disparate structural and economical considerations. Based on some limited reported studies, on the other hand, employment of low yield point (LYP) steel infill plates with extremely low yield strength, and high ductility as well as elongation properties is found to facilitate the design and improve the structural behavior and seismic performance of the SPSW systems. On this basis, this paper reports system-level investigations on the seismic response assessment of multi-story SPSW frames under the action of earthquake ground motions. The effectiveness of the strip model in representing the behaviors of SPSWs with different buckling and yielding properties is primarily verified. Subsequently, the structural and seismic performances of several code-designed and retrofitted SPSW frames with conventional and LYP steel infill plates are investigated through detailed modal and nonlinear time-history analyses. Evaluation of various seismic response parameters including drift, acceleration, base shear and moment, column axial load, and web-plate ductility demands, demonstrates the capabilities of SPSW systems in improving the seismic performance of structures and reveals various advantages of use of LYP steel material in seismic design and retrofit of SPSW systems, in particular, application of LYP steel infill plates of double thickness in seismic retrofit of conventional steel and code-designed SPSW frames.

Upscaling of Nonisothermal Reactive Porous Media Flow under Dominant Péclet Number: The Effect of Changing Porosity

Motivated by rock-fluid interactions occurring in a geothermal reservoir, we present a two-dimensional pore scale model of a thin strip consisting of void space and grains, with fluid flow through the void space. Ions in the fluid are allowed to precipitate onto the grains, while minerals in the grains are allowed to dissolve into the fluid, taking into account the possible change in the aperture of the strip that these two processes cause. Temperature variations and possible effects of the temperature in both fluid density and viscosity and in the mineral precipitation and dissolution reactions are included. For the pore scale model equations, we investigate the limit as the width of the strip approaches zero, deriving one-dimensional effective equations. We assume that the convection is dominating over diffusion in the system, resulting in Taylor dispersion in the upscaled equations and a Forchheimer-type term in Darcy's law. Some numerical results where we compare the upscaled model with three simpler versions are presented: two still honoring the changing aperture of the strip but not including Taylor dispersion, and one where the aperture of the strip is fixed but contains dispersive terms.

Mathematical Model of Plates and Strips Rolling for Calculation of Energy Power Parameters and Dynamic Loads

Presents the results of studies of innovative materials in the field of metallurgy. The article describes mathematical models for calculating energy-parameters of hot rolling plates and strips using a more correct evaluation of external friction, which is necessary for precisely determining the values of the dynamic loads in the drive’s line of rolling mills stands. The results can be used for designing rolling mills drive lines’ mechanical facilities.

Modeling Pesticide Runoff from Small Watersheds through Field-Scale Management Practices: Minnesota Watershed Case Study with Chlorpyrifos

Experimental studies of pesticide fate in surface runoff offer only a snapshot of the near semi-infinite parameter combinations that can and do occur in the environment, and mechanistic modeling is often used to supplement the often limited number of experimental observations. However, what has been lacking in pesticide surface runoff modeling is the impact of field-scale best management practices (BMPs) on the concentrations of pesticides found at the watershed outlet. A novel application of melding three agricultural models together was used to address field-scale BMPs and off-target pesticide environmental concentrations at the watershed scale resulting from agricultural surface runoff. These models were the pesticide root zone model [PRZM, an edge-of-field runoff and leaching model sanctioned by the US Environmental Protection Agency (USEPA)]; the United States Department of Agriculture-Agricultural Research Service watershed scale model, the soil and water assessment tool (SWAT); and the academic model, the vegetated filter strip model (VFSMOD). Watershed models such as SWAT, using high-resolution local input data, are capable of predicting watershed behavior but are limited when addressing field-scale BMPs. A unique method to approximate a small watershed as a linear combination of sub-basins and fields [hydrologic response units (HRUs)] is presented. Water, sediment, and pesticide runoff for each HRU are simulated using the USEPA field model PRZM. Daily edge-of-field PRZM predictions for pesticides in runoff water and eroded sediment are coupled with VFSMOD to address the effectiveness of a maintained vegetated filter strip (VFS) across the growing season in reducing pesticide loadings and water quality at the watershed outlet. Daily chlorpyrifos (CHP, insecticide) concentrations simulated for the Seven Mile Creek Watershed, MN, using the above modeling approach resulted in a spectrum of concentrations reported by the MN Department of Natural Resources. Simulated VFS effectiveness when used across all pesticide-treated fields ranged between 22% and 100% reductions in CHP mass across all runoff-producing events.

Analysis of Thin Steel Plate Shear Walls Using the Three-Strip Model

AbstractThin steel plate shear walls (SPSWs) are an effective lateral force resisting system and are increasingly being used in structures. Engineers require the ability to predict both elastic and inelastic structural responses of SPSWs accurately by a simplified model that is convenient to use. Based on the strip model, this paper proposes a new simplified model for SPSWs, called the three-strip model, in which the infill plates of SPSWs are replaced by three tension-only strips. Comparisons of experimentally obtained pushover responses of SPSWs and that predicted by the proposed model are given and reasonable agreement is observed. A parametric study examines the effect of aspect ratio and column flexibility on the accuracy of the predicted inelastic behavior from the three-strip model. In addition, the capacity of the proposed model in predicting frame forces is verified based on test and strip model results. It was found that the three-strip model can provide generally accurate results for SPSWs and ...

Analytical investigation of thin steel plate shear walls with screwed infill plate

A behavior model for screw connections is developed to provide a better representation of the nonlinear response of thin steel plate shear walls (TSPSWs) with infill plates attached to the boundary frame members via self-drilling screws. This analytical representation is based on the load-bearing deformation relationship between the infill plate and the screw threads. The model can be easily implemented in strip models of TSPSWs where the tension field action of the infill plates is represented by a series of parallel discrete tension-only strips. Previously reported experimental results from tests of two different TSPSWs are used to provide experimental validation of the modeling approach. The beam-to-column connection behavior was also included in the analyses using a four parameter rotational spring model that was calibrated to a test of an identical frame as used for the TSPSW specimens but without the infill plates. The complete TSPSW models consisting of strips representing the infill plates, zero length elements representing the load-bearing deformation response of the screw connection at each end of the strips and the four parameter spring model at each beam-to-column connection are shown to have good agreement with the experimental results. The resulting models should enable design and analysis of TSPSWs for both new construction and retrofit of existing buildings.

Molecular mechanisms for surfactant-aided oil removal from a solid surface

In this work, the detachment mechanism of oil molecules from the hydrophobic solid surface in the aqueous surfactant solution is studied with lattice Monte Carlo simulations. Three different mechanisms for oil removal, including oil carrying microemulsion model, oil film stripping model, and surfactant-aided diffusion model are identified. The molecular mechanisms that agree with experimental observations are found to be dependent sensitively on surfactant structure.

Investigation on the effectiveness of an innovative airfoil-type degasser

ABSTRACTA framework to analyze the fluid mechanisms in baffle type degassers is presented and particularly applied to an innovative airfoil-type degasser. Major fluid events in conventional baffle type degassers such as bubbles rising inside the oil layer and the flow of the oil layer itself were taken into account. However, in the current airfoil-type degasser oil flows over an airfoil surface and at the same time is exposed to an air jet. This air jet attaches to the airfoil surface due to the so called Coanda effect as observed in some trial runs of the system. A curved strip model is suggested to estimate the pressure reduction due to the jet curvature. Then we have performed a convective mass transfer analysis in order to determine the jet effect in reducing the partial pressure of the gas on the oil surface and increasing the rate of bubble formation.

Discussion of “Column Supported Embankments with Geosynthetic Encased Columns: Validity of the Unit Cell Concept” [Geotechnical and Geological Engineering 33 (2015) 425–442

The authors present numerical analyses of an embankment underlain by geosynthetic reinforcement and supported by geosynthetic encased columns (GRCSE). In the last part of the paper, the transverse and longitudinal tensile forces in the geosynthetic reinforcement, which underlays the embankment, are compared using a 3-d strip model and the Unit-Cell concept, both in a 3-d model and in a 2-d axisymmetric model. The results of both Unit-Cell models are very similar. The authors show that the Unit-Cell models are not able to capture the transverse force (Tx), which seems obvious, nor the longitudinal force (Ty), which may not be so obvious. The discusser would like to explain that in the authors’ case the longitudinal force (Ty) is not properly captured by the Unit-Cell models because of the ‘‘socalled’’ Poisson effect. A measure of this effect is the Poisson’s ratio (m = -ey/ex) (Fig. 1). In the 3-d strip model, Tx is notably higher than in the Unit-Cell models, as expected. The authors use a Poisson’s ratio of m = 0.3 for the geosynthetic reinforcement, and then, the higher value of Tx causes an additional tensile force in the perpendicular direction (Ty) because of the Poisson effect. Assuming plane strain conditions in the longitudinal direction (ey = 0), ey 1⁄4 0 1⁄4 1 E ry mrx 1⁄4 1 E Ty t m Tx t ð1Þ

국내 경작지 특성을 고려한 SWAT 모형의 식생여과대 유사저감 효율 산정식 개선

Abstract In this study, considering the factors that affects sediment trapping efficiency of Vegetative Filter Strips (VFS), the scenarios were designed to develop a regression equation to estimate sediment trapping efficiency of VFS for agricultural fields in South-Korea. For this, general conditions of agricultural fields in South-Korea were investigated. Then, based on these results , total 53,460 scenarios were set and simulated by Vegetative Filter Strip MODel (VFSMOD-w). Two variables were determined from the results of 53,460 scenarios. These two variables were applied to CurveExpert for development of a equation, which can estimate sediment trapping efficiency of VFS. The equation developed in this study can be used in SWAT model for estimation of sediment reduction efficiency of VFS to upland field in Korea. Moreover, it is expected that VFS will be effectively applied to agricultural fields in South-Korea. Key words : Sediment, Sediment reduction, SWAT, Vegetative filter strips, VFSMOD-w

Finite strip modeling of cementitious laminates reinforced with sisal fibers

The use of natural fibers to reinforce of cementitious matrices permits the development of sustainable materials with many potential applications. However, the improvement of such materials strongly depends on experimental studies, making the process slow and expensive. The numerical methods currently available for modeling composites can adequately describe the behavior of polymeric laminates, but have limited application in cementitious laminates that can have multiple cracking. This paper proposed a numerical model that combines the Finite Strip Method, Classical Theory of Laminates and Damage Mechanics to model the flexural behavior of laminated composites. The method can monitor the stresses developed in each layer and verify the ruptures resulting from traction, compression or shear. To validate the numerical method, flexural tests were carried out on cementitious laminates reinforced with 2 or 3 layers of long sisal fiber, with fiber content of 3% or 6%. Comparisons between the numerical and experimental results demonstrate good agreement, especially for composites reinforced with high fiber content. The adequate prediction of internal stress allows for the use of this numerical method to design cementitious laminates reinforced with sisal fibers that possess properties suitable for various applications.