Horizontal Shear Research Articles

Effects of operation parameters on particle mixing performance in a horizontal high shear mixer

Abstract Particle mixing is an important unit operation in many industry processes. This work employed the discrete element method (DEM) to characterize the mixing performance of iron ore particles in a horizontal high shear mixer. The simulation results were first compared with the positron emission particle tracking (PEPT) data reported by Forrest et al. to validate the DEM model. Then the effects of key operation factors such as impeller rotation speed, number of impellers and filling ratio on the mixing efficiency were discussed. The Lacey mixing index was employed to evaluate the mixing performance. The results show that the mixing efficiency of particles increased with increasing the number of impellers and their rotation speeds. On the other hand, the filling ratio was negatively related to the particles velocity and the mixing efficiency. This was because the effective space left for free movement of particles decreased as the filling ratio increased, and the mixing of particles was therefore restricted. In addition, the mixing rate of particles in the axial direction of the high shear mixer was much slower than that in the radial direction.

Lateral crural setback: an analysis on tip rotation

<p class="abstract"><strong>Background: </strong>Increasing nasal tip rotation is a common objective during rhinoplasty. When ptosis is either totally or partially the result of an excessive lateral crura length, strength, or position, various techniques have been used to shorten the lateral crura in order to reduce its relative inferior ptotic force. Techniques that involve division or amputation of the cartilage have been shown to be effective, but may sometimes weaken the cartilage’s shear and horizontal load strength, thus increasing the chances of unwanted sequalae in alar and/or tip contour. We presented our lateral crural setback technique as another option to allow the tip to rotate while maintaining the lateral architectural structure, end to end continuity, and horizontal load and shear strength.</p><p class="abstract"><strong>Methods:</strong> Retrospective review of 20 patients undergoing cosmetic rhinoplasty who had a lateral crural setback cartilage repositioning maneuver. The primary outcomes measured after one year of follow-up were nasal tip rotation and projection. Nasal tip rotation was assessed by measures of the nasolabial angle using three different methods.</p><p class="abstract"><strong>Results: </strong>There was a statistically significant increase in nasolabial angle using all 3 methods for measuring nasal tip rotation. The average increase in nasal tip rotation for all methods was 10.7° (p<0.0001). There was a statiscically significant decrease in tip projection. No alar distortion or complications were noted.</p><p class="abstract"><strong>Conclusions:</strong> The lateral crural setback technique can be used to increase nasal tip rotation while preserving the integrity of the lateral crura. No alar distortion or complications were noted from this procedure. </p>

Earth pressure in narrow cohesive-fictional soils behind retaining walls rotated about the top: An analytical approach

There is currently a lack of an available design approach to estimate the earth pressure in narrow backfills behind retaining walls rotated about the top (RT). The considerations of some significant factors, primarily load transfer mechanisms (soil arching effect and horizontal shear stress in soils), failure mechanisms (shape and number of slip surfaces) and soil cohesion are often neglected for brevity in routine design. Such simplifications may lead to significant deviations from reality. This paper first uses the finite element limit analysis (FELA) technique to identify the underlying failure mechanisms and load transfer mechanisms. The results observed in FELA models indicate that active rotation of walls about the top develops one curved slip surface, which can be approximated by the log-spiral function. Under the soil arching effect, the upper intermediate passive zone with major principal stress rotation trajectory and the lower active zone with minor one can be defined. The arched differential element method (ADEM) is then introduced to formulate the earth pressure calculation. The results from newly published tests, existing analytical approaches, and FELA are compared to validate the accuracy of the proposed approach in both purely-frictional and cohesive-frictional soils. Parametric studies are further conducted to thoroughly understand the earth pressure problems, considering the effects of sensitive design variables (e.g. aspect ratio, soil strength parameters, and wall-soil interface friction angle). The analytical approach presented here would be a great extension to the design guidelines for the retaining structures with narrow backfills.

Seismic response of isolated structures with an improved model of the UFREI

An improved formulation of the horizontal shear behavior of the unbonded fiber-reinforced elastomeric isolators (UFREI), which predicts both the pre-rollover and the post-rollover behavior considering the effect of the vertical load, is proposed. A simplified and computationally inexpensive formulation of the horizontal shear behavior of the UFREI has also been proposed afterward. Further, these formulations are verified using experimental results and compared with the results obtained using the other earlier methods in the recent literature. The horizontal shear behavior predicted by both of the proposed formulations is observed to fit the experimental results very well. The shear behavior predicted by these formulations is observed to be more accurate than the corresponding predicted by the other formulations from the recent literature. A parametric study characterizing the effect of the vertical pressure and the initial elastomeric shear modulus on the horizontal shear behavior of isolators is also carried out. The proposed formulations are further used to model the behavior of the UFREI employed to isolate the benchmark structure considered in the study.Supplementary damping devices are further installed alongside the nonlinear UFREI isolation system to mitigate the excessive displacement demand on isolators under near-fault ground motions. The isolated benchmark structure is thus coupled with a Magneto-rheological Damper (MRD) with an improved control algorithm for nonlinear isolation systems in three configurations, i.e., semi-active, passive-on, and passive-off. A comparative study of these configurations shows that MRD in passive-on mode provides the minimum isolators displacement response, but an overall improved structural response is achieved with MRD in the semi-active mode of operation.

The Pattern and Possible Formation Mechanisms of Current Crustal Stress in High Asia

Abstract —The pattern of current crustal stress in central and southeastern Asia has been reconstructed from earthquake focal mechanisms by inversion using Rebetsky’s method of cataclastic analysis. The inversion provides constraints on principal stress directions, as well as on relative magnitudes of maximum shear and effective isotropic pressure. The crust of the High Asian mountainous province is subject to horizontal extension or shear in plateaus (East and South Pamir and Tibet) and to horizontal compression or shear in mountain ranges. The relatively high horizontal compression in the ranges is apparently due more to denudation and exhumation than to the pressure from the Indian indentor. Denudation and removal of clastic material from the Himalayan slopes has been a key agent that may compensate for the N–S crust shortening in central Tibet and the W–E stretching in eastern Tibet. The current stress field of High Asia has been mainly controlled by vertical buoyancy forces that arise by thickening of lighter crust and detachment of heavier lithosphere.

Investigation of wind shear structure and turbulence characteristics in a warm front cloud system using a research aircraft

The manuscript presents the results of study vertical and horizontal wind shears, the spectral characteristics of turbulence in the warm front cloud system with using the Yak-42D aircraft-laboratory. Within the As-Cs clouds at altitudes of 3 - 8 km, vertical wind shear increased sharply to 1.5 ms-1 per 100 m. At altitudes of 8 - 9 km, in the jet stream zone, vertical wind shear increased up to significant values of 3.0 ms-1 per 100 m. The maximum horizontal wind shear of 0.3 ms-1 per km was reached in As-Ns clouds at altitudes of 2 - 4 km. Anisotropy of turbulence with a predominance of horizontal wind fluctuations was observed in the stable layer at the altitude of 6000 m. The normalized spectra of the wind speed fluctuations in the lower part of the cloud system (at an altitude of about 3 km) corresponded to the stable layers of the atmosphere. The maximum value of 0.8 at the coherence spectra between the temperature and the vertical wind speed fluctuations was observed at the scales of 1200 m. It is noted that a solid Cs-As-Ns cloud system could be divided into sub-layers, depending on structure of wind shear and turbulence.

Hubungan Ketersebaran Dinding Geser Sebidang Secara Horizontal Terhadap Drift Bangunan Tingkat Tinggi

The distribution of the shear wall horizontally influences the drift. This study was conducted to determine the relationship between the horizontally mass distribution of shear walls and high-rise buildings’ drift. The model analyzed was a rectangular building with 40 floors of 20 m x 20 m. The model consists of 4 variations, namely G1, G2, G3, and G4 models. The analysis was carried out based on SNI - 1726 - 2019 regarding The Procedures of Earthquake Resistance Planning for Building and Non-Building Structures and using SAP 2000 software. The analysis results revealed that horizontal shear wall mass distribution influences the structural deviation due to earthquake loads. Shear walls distributed side by side are more efficient than shear walls distributed spatially.

Seismic Anisotropy in the Lower Mantle Transition Zone Induced by Lattice Preferred Orientation of Akimotoite

AbstractSeismic anisotropy has been widely observed near the subducting slabs in the lower mantle transition zone (MTZ) and is often interpreted by the lattice preferred orientation (LPO) of constituent minerals. Akimotoite is one of the dominant minerals near the cold subducting slabs. Therefore, we conducted the well‐controlled uniaxial and shear deformation experiments on the MgSiO3 akimotoite aggregates at 21–23 GPa and 900–1300°C by using the D111‐type Kawai‐type multianvil apparatus. We observed strong LPOs and the most dominant slip system of akimotoite is suggested to be (0001). The elastic wave velocities of deformed samples were calculated to be strong azimuthal and polarization anisotropy with the velocities of horizontally polarized shear waves greater than that of vertically polarized shear waves for the horizontal mantle shearing. Our results provide important implications for the origin of observed seismic anisotropies and the mantle flow directions in the lower MTZ.

Seismic performance assessment of eccentrically braced steel frames with variable-cross-section horizontal shear links

Based on the principle of web weakening, two types of variable-cross-section shear links for horizontal eccentrically braced steel frames (H-EBFs) were analyzed in this study. In the first design, an I-section link (L2) was designed with a lower web and wider flange than that of an ordinary shear link (L1), and in the second design, an I-section link composed of two small I-section beams (L3) was designed. To study the seismic behavior of the two types of H-EBFs, cyclic loading tests were performed on three scaled specimens, L2 (H-EBF-L2), L3 (H-EBF-L3), and a traditional link (H-EBF-L1). The results showed that most of the inelastic actions of the three specimens were concentrated in the shear links and that the failure modes were similar. Compared with specimen H-EBF-L1, the links of specimens H-EBF-L2 and H-EBF-L3 had better deformability, and the bearing capacity of the frames also improved simultaneously; thus, the energy-dissipation mechanism of H-EBF improved. The material costs of specimens H-EBF-L2 and H-EBF-L3 were reduced to a certain extent, realizing economic benefits. Additionally, the numerical models of the three specimens were established. The modeling results were in good agreement with the test results, and it was verified that the model could accurately simulate the loading process of the tests.

The Seasonality of Mesoscale Eddy Intensity in the Southeastern Tropical Indian Ocean

The seasonality of mesoscale eddy intensity in the southeastern tropical Indian Ocean (SETIO) is investigated using the latest eddy dataset and marine hydrological reanalysis data. The results show that the eddy intensity in an area to the southwest coast of the Java Island has prominent seasonality—eddies in this area are relatively weak during the first half of the year but tend to enhance in August and peak in October. Further analysis reveals that the strong eddies in October are actually developed from the ones mainly formed in July to September, and the barotropic instability and baroclinic instability are the key dynamics for eddy development, but each plays a different role at different development stages. The barotropic instability resulting from the horizontal shear of surface current plays an important role in the early stage of eddy development. However, in the late development stage, the baroclinic instability induced by the sloping pycnocline becomes the major energy contributor of eddy development.

Evaluation of the “fan scan” based on three combined nacelle lidars for advanced wind field characterisation

Nacelle-mounted lidars are finding more and more applications in the wind industry. Their use cases range from power performance testing to lidar-assisted control. Depending on the application, different wind field parameters are reconstructed from the lidar’s line-of-sight wind measurements. Hereby, the respective scan geometry of the lidar determines the capabilities and limitations for the reconstruction of wind field parameters. In this study, we introduce the fan scan, a scanning pattern made of multiple nacelle-mounted lidars with the aim of an advanced wind field assessment to reconstruct more than three wind field parameters, which has been implemented at the Testfeld BHV site in Bremerhaven, Germany. Analytically derived uncertainties as well as calibration results for both, line-of-sight speeds and reconstructed wind field parameters, are presented indicating a good agreement with reference measurements. Additionally, a method for the reconstruction of the horizontal wind shear is introduced and applied to the fan scan data, highlighting the extended utilization possibilities of nacelle lidars.

"Impact of shear connectors on composite action in full-depth precast concrete bridge systems"

This theoretical research used the finite element method to model full-depth precast concrete deck slabs. It examined the effects of pocket spacing and number of shear studs per pocket. Results indicat­ed that horizontal shear strength increases with the number of pockets in both supported and continu­ous-span models. Load–deflection curves and slippage values were recorded and compared with experimental tests, confirming that pocket spacing is an important factor and that the number of studs and their config­uration affects the load for slippage induction. The parametric study evaluated effects of shear connector sizes and various numbers of shear studs for distances of 24 and 48 in. (609.6 and 1219.2 mm) between shear pockets for simply supported bridges; however, there is a need for experimental evaluation of shear connector performance on design.

Horizontal Vibration Characteristics of a Tapered Pile in Arbitrarily Layered Soil

A tapered pile (TP) is a new type of pile with a good bearing capacity, and scholars have conducted in-depth research on its static bearing characteristics. However, there is relatively little research on its dynamic bearing characteristics. In this paper, the horizontal vibration behavior of a tapered pile in arbitrarily layered soil is studied. Utilizing the Winkler foundation model and Timoshenko beam model to simulate pile-surrounding soil (PSS) and a tapered pile, respectively, the horizontal vibration model of a tapered pile embedded in layered soil was built. The analytical solutions for the horizontal displacement (HD), bending moment (BM), and shear force (SF) of a tapered pile were derived, and then the solutions for the horizontal dynamic impedance (HDI), rocking dynamic impedance (RDI), and horizontal-rocking coupling dynamic impedance (HRDI) of pile head were obtained. Using the present solutions, the effects of soil and pile properties on the horizontal vibration characteristics of a tapered pile were systemically studied. The ability of a tapered pile–soil system to resist horizontal vibration can be improved by strengthening the upper soil, but this ability cannot be further improved by increasing the thickness of the strengthened upper soil if its thickness is greater than the critical influence thickness.

On separating plumes from boundary layers in turbulent convection

We present a simple, novel kinematic criterion – that uses only the horizontal velocity fields and is free of arbitrary thresholds – to separate line plumes from local boundary layers in a plane close to the hot plate in turbulent convection. We first show that the horizontal divergence of the horizontal velocity field ( $\boldsymbol {\nabla _H} \boldsymbol {\cdot } \boldsymbol {u}$ ) has negative and positive values in two-dimensional (2D), laminar similarity solutions of plumes and boundary layers, respectively. Following this observation, based on the understanding that fluid elements predominantly undergo horizontal shear in the boundary layers and vertical shear in the plumes, we propose that the dominant eigenvalue ( $\lambda _D$ ) of the 2D strain rate tensor is negative inside the plumes and positive inside the boundary layers. Using velocity fields from our experiments, we then show that plumes can indeed be extracted as regions of negative $\lambda _D$ , which are identical to the regions with negative $\boldsymbol {\nabla _H} \boldsymbol {\cdot } \boldsymbol {u}$ . Exploring the connection of these plume structures to Lagrangian coherent structures (LCS) in the instantaneous limit, we show that the centrelines of such plume regions are captured by attracting LCS that do not have dominant repelling LCS in their vicinity. Classifying the flow near the hot plate based on the distribution of eigenvalues of the 2D strain rate tensor, we then show that the effect of shear due to the large-scale flow is felt more in regions close to where the local boundary layers turn into plumes. The lengths and areas of the plume regions, detected by the $\boldsymbol {\nabla _H}\boldsymbol {\cdot }\boldsymbol {u}$ criterion applied to our experimental and computational velocity fields, are then shown to agree with our theoretical estimates from scaling arguments. Using velocity fields from numerical simulations, we then show that the $\boldsymbol {\nabla _H}\boldsymbol {\cdot }\boldsymbol {u}$ criterion detects all the upwellings, while the available criteria based on temperature and flux thresholds miss some of these upwellings. The plumes detected by the $\boldsymbol {\nabla _H}\boldsymbol {\cdot }\boldsymbol {u}$ criterion are also shown to be thicker at Prandtl numbers ( $Pr$ ) greater than one, expectedly so, due to the thicker velocity boundary layers of the plumes at $Pr>1$ .

Time-independent forecast model for large crustal earthquakes in southwest Japan using GNSS data

In this study, we developed a regional likelihood model for crustal earthquakes using geodetic strain-rate data from southwest Japan. First, the smoothed strain-rate distributions were estimated from continuous Global Navigation Satellite System (GNSS) measurements. Second, we removed the elastic strain rate attributed to interplate coupling on the subducting plate boundary, including the observed strain rate, under the assumption that it is not attributed to permanent loading on crustal faults. We then converted the geodetic strain rates to seismic moment rates and calculated the 30-year probability for M ≥ 6 earthquakes in 0.2 × 0.2° cells, using a truncated Gutenberg–Richter law and time-independent Poisson process. Likelihood models developed using different conversion equations, seismogenic thicknesses, and rigidities were validated using the epicenters and moment distribution of historical earthquakes. The average seismic moment rate of crustal earthquakes recorded during 1586–2020 was only 13–20% of the seismic moment rate converted from the geodetic data, which suggests that the observed geodetic strain rate includes considerable inelastic strain. Therefore, we introduced an empirical coefficient to calibrate the moment rate converted from geodetic data with the moment rate of the earthquakes. Several statistical scores and the Molchan diagram showed all models could predict real earthquakes better than the reference model, in which earthquakes occur uniformly in space. Models using principal horizontal strain rates exhibited better predictive skill than those using the maximum horizontal shear strain rate. There were no significant differences in predictive skill between uniform and variable distributions for seismogenic thickness and rigidity. The preferred models suggested high 30-year probability in the Niigata–Kobe Tectonic Zone and central Kyushu, exceeding 1% in more than half of the analyzed region. The model predictive skill was also verified by a prospective test using earthquakes recorded during 2010–2020. This study suggests that the proposed forecast model based on geodetic data can improve the regional likelihood model for crustal earthquakes in Japan in combination with other forecast models based on active faults and seismicity.Graphical

A new interpretation of the metamorphic core in the Taiwan orogen: A regional-scale, left-lateral shear zone that accommodated highly oblique plate convergence in the Plio-Pleistocene

In the past decades, the arc-continent collision in Taiwan was commonly interpreted as a relatively continuous process with an invariant plate convergence vector for at least the last 6–5 Ma. This steady convergence, including the rate and the obliquity, between the subducting continental margin and the plate boundary suggest a propagating collision with a space-time equivalence along the developing orogen. More recently, detailed low-temperature geochronologic and plate reconstructions suggest that the plate convergence changed from highly oblique to nearly orthogonal in the last 2 to 1 Ma. This early phase of oblique convergence, driven primarily by the northward motion of the Philippine Sea Plate wrt the Eurasian Plate, implies a significant ‘fossil’ component of left-lateral, strike-slip motion along the presumably north-trending plate boundary. A synthesis of available data compiled in this study suggests that previously uncharacterized zones of strike-slip deformation exist in the Tailuko Belt, and here we document: 1) the distribution of horizontal shear, 2) the kinematics of deformation, 3) the age of deformation, and 4) regional consistency between geologic studies and plate reconstructions. Horizontal shear may also be recorded at shallow structural levels in southern Taiwan by brittle faults and block rotations. Integration of these new data with previously published kinematic data across strike also suggests plate convergence was partitioned with strike-slip motion in the retrowedge (i.e., the Tailuko Belt) and shortening in the prowedge (i.e., the Slate Belt).

Parametrizing the mesoscale enhancement of oceanic surface turbulent fluxes: A physical–statistical approach

AbstractThe mesoscale enhancement of surface turbulent fluxes at the air–sea interface is driven by the mesoscale surface wind‐speed variability, especially the gustiness velocity and the mesoscale wind‐speed standard variation. This study proposes a parametrization of these two variables. A large dataset based on the operational 2.5‐km AROME convection‐permitting model is used in a coarse‐graining framework, to quantify various quantities that are subgrid at the scale of a 100‐km resolution global circulation model grid cell. This provides a learning dataset to help build the parametrization. The analysis of two case studies of intense wind‐speed mesoscale variability, combined with a literature review, provides a physically based set of 12 potential predictors, accounting for the convection activity and the large‐scale dynamics. The least absolute shrinkage and selection operator then frames a penalized multivariate linear regression approach to identify the most relevant predictors objectively. Five predictors are selected for predicting the gustiness velocity: the updraft mass flux at the lifting condensation level, the density‐current spreading velocity, the large‐scale horizontal shear and divergence, and the large‐scale wind speed. The parametrization of the mesoscale wind‐speed standard deviation requires an additional predictor, namely the cold‐pool object aggregation index. The proposed parametrization performs significantly better than the previously published parametrizations and is able to capture 80, 99, and 93 of the mesoscale enhancement of the momentum, sensible heat, and latent heat fluxes, respectively. From the perspective of a global circulation model implementation, in which some predictors may be unavailable, simpler versions of the parametrization, that is, involving fewer predictors, are also discussed.

Fatigue Performance of Overhead Truss Sign Structure Coupler Connections

Nearly all aluminum overhead truss sign structures (OHTSSs) in Kansas constructed before 2015 use an identical type of hot-riveted coupling assembly to provide connections between vertical poles and horizontal truss members. Although many of the connections have been in service for 30 to 40 years, no research has been conducted to determine their fatigue performance. This paper presents a study aimed at characterizing the fatigue performance of the coupler connections. The study includes a series of finite-element (FE) analyses and 24 experimental fatigue tests. The FE analyses were used to determine design-level fatigue demands on the coupler connections and to provide information for designing the experimental setups used in this test program. Four sign structures with three connection properties and six loading modes were modeled. The experimental tests were conducted to characterize the fatigue performance of the connection. Tests were conducted for three loading modes with respect to the load on the rivet connecting the two interior half-couplers: (1) tension, (2) vertical shear, and (3) horizontal shear. Results indicated that when loaded below 10 Ksi (68.9 MPa), the connection can be classified as a Category E′ based on stress in the rivet. The FE analyses and test results indicated that fatigue failures are unlikely to occur in the coupler connections used in OHTSSs. In addition, two used coupler assemblies from OHTSSs taken out of service were also tested and the failure surfaces were examined under a microscope. No reliable evidence of preexisting cracks was found.

Effect of the Froude number on a stratified turbulence under two shear orientations using coupled SSG and SL models

In the present investigation, the evolution of homogeneous and stratified turbulence under a horizontal and a vertical shear is deliberate by coupled second-order model SSG-SL. This model is a result of a combination between the Speziale, Sarkar and Gatski model (SSG) and the Shih and Lumley model (SL). Horizontal shear and vertical shear are related to the angle between the shear and the vertical gradient of stratification; θ = π/2 and θ = 0, respectively. This study is performed for different values of Froude number Fr ranging from 0.35–1.11. The SSG-SL model confirms the asymptotic equilibrium states for various physical parameters governing the problem (b12, b11, ε/KS, , K/E and Kρ/E) for two shear orientations (θ = π/2 and θ = 0). A comparison between findings using the present coupled model of SSG-SL and those by Direct Numerical Simulation of Jacobitz (DNSJ) [Jacobitz F, Sarkar S. A direct numerical study of transport and anisotropy in a stably stratified turbulent flow with uniform horizontal shear. Flow Turbul Combust. 2000;63:343–360.; Jacobitz F. A comparison of the turbulence evolution in a stratified fluid with vertical or horizontal shear. J Turbul. 2002;3:1–18.] is carried out. For the horizontal shear related to θ = π/2, an excellent agreement between predictions by the SSG-SL model and the results of DNSJ [Jacobitz, Sarkar;Jacobitz] is detected for turbulent thermal and dynamic fields.

Comparative finite element analysis of an osseointegration system in transradial amputation: a proposal of a new design for osseointegration

Purpose: Conventional osseointegration systems have been applied in patients requiring transhumeral or transfemoral amputation. However, the application of these systems to transradial amputation is limited by the small diameter of the radius and ulna. Our study compared the biomechanical stability of a novel osseointegration system with that of a conventional system used in transradial amputation through an analysis of finite element (FE) models.Methods: We established three-dimensional FE models of transradial amputations, which were osseointegrated with both the novel and conventional systems. External loads were applied to the FE models with compressive force and tensile force along the long axis, horizontal shear force, and vertical shear force. The maximum equivalent stress (MES) and the distribution of stress through the radius and ulna were evaluated.Results: The MES of the radius and ulna was higher in the conventional system when compressive, tensile, and vertical shear forces were applied. However, when a horizontal shear force was applied, the opposite result was found. The distribution of stress was more effective in the novel system.Conclusion: Three-dimensional FE modeling showed that the novel system enabled a lower stress level and a more even distribution of stress for osseointegration in transradial amputation.