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The vertical shear instability (VSI) is a hydrodynamical instability that requires rapid gas cooling and has been suggested to operate in outer regions of protoplanetary disks. The VSI drives turbulence with strong vertical motions, which could regulate the dust growth and settling. However, dust growth and settling can regulate the VSI because dust depletion makes gas cooling inefficient in outer disk regions that are optically thin to their own thermal emission. In this study, we quantify this potentially stabilizing effects of dust evolution on the VSI based on the linear analysis. We construct a model for calculating the cooling timescale, taking into account dust growth beyond micron sizes and size-dependent settling. Combining the model with the linear stability analysis, we map the region where the VSI operates, which we call the VSI zone, and estimate the maximum growth rate at each radial position. We find that dust growth as well as settling makes the VSI zone more confined around the midplane. This causes a decrease in the growth rate because the vertical shear of the rotation velocity, which is the source of the instability, is weaker at lower altitude. In our default disk model with 0.01 solar masses, dust growth from 10 micron to 1 mm causes a decrease in the growth rate by a factor of more than 10. The suppression of VSI-driven turbulence by dust evolution may promote further dust evolution in the outer regions and also explain a high degree of dust settling observed in the disk around HL Tau., 15 pages, 12 figures, Accepted for publication in ApJ

Recent (past ~15 years) advances in our understanding of tropical cyclone (TC) intensity change processes using aircraft data are summarized here. The focus covers a variety of spatiotemporal scales, regions of the TC inner core, and stages of the TC lifecycle, from preformation to major hurricane status. Topics covered include (1) characterizing TC structure and its relationship to intensity change; (2) TC intensification in vertical shear; (3) planetary boundary layer (PBL) processes and air–sea interaction; (4) upper-level warm core structure and evolution; (5) genesis and development of weak TCs; and (6) secondary eyewall formation/eyewall replacement cycles (SEF/ERC). Gaps in our airborne observational capabilities are discussed, as are new observing technologies to address these gaps and future directions for airborne TC intensity change research.

This paper presents an experimental study on the behavior of composite floor slab comprised by a new steel sheet and concrete slab. The strength of composite slabs depends mainly on the strength of the connection between the steel sheet and concrete, which is denoted by longitudinal shear strength. The composite slabs have three main failures modes, failure by bending, vertical shear failure and longitudinal shear failure. These modes are based on the load versus deflection curves that are obtained in bending tests. The longitudinal shear failure is brittle due to the mechanical connection was not capable of transferring the shear force until the failure by bending occurs. The vertical shear failure is observed in slabs with short span, large heights and high concentrated loads subjected near the supports. In order to analyze the behavior of the composite slab with a new steel sheet, six bending tests were undertaken aiming to provide information on their longitudinal shear strength, and to assess the failure mechanisms of the proposed connections. Two groups of slabs were tested, one with 3000 mm in length and other with 1500 mm in length. The tested composite slabs showed satisfactory composite behavior and longitudinal shear resistance, as good as well, the analysis confirmed that the developed sheet is suitable for use in composite structures without damage to the global behavior.

A variable-coefficient Korteweg–de Vries equation is used to model the deformation of nonlinear periodic and solitary water waves propagating on a unidirectional background current, which is either flowing in the same direction as the waves, or is opposing them. As well as the usual form of the Korteweg–de Vries equation, an additional term is needed when the background current has vertical shear. This term, which has hitherto been often neglected in the literature, is linear in the wave amplitude and represents possible nonconservation of wave action. An additional feature is that horizontal shear in the background current is inevitably accompanied by a change in total fluid depth, to conserve mass, and this change in depth is a major factor in the deformation of the waves. Using a combination of asymptotic analyses and numerical simulations, it is found that waves grow on both advancing and opposing currents, but the growth is greater when the current is opposing.

The article presents the core results of lowered acoustic Doppler current profiler (LADCP) applied in the Black Sea within 2004–2014. Average features of the vertical structure of currents in the upper 600 m layer are outlined. The linear relation between vertical distribution of kinetic energy isopycnically averaged over the station ensemble and density is established. This relation is traced till the isopycn occurrence depth with density of 17 kg/m3 (500 m). The mean current velocity has near constant value about 4 cm/s in lower depth layers (>500 m), which is in a good agreement with autonomic buoys data. The averaged profile of current velocity vertical shears shows two well- separated maxima in the seasonal and main pycnocline layers. LADCP derived velocity shears are more than ten times exceed the geostrophic current shears. Turbulent vertical mixing coefficient, calculated by the G89 model (Gregg 1989) demonstrates the denominated minimum in the permanent pycnocline (4∙10-6 m2/s) and increases with depth to achieve value 2∙10-5 m2/s at 450 m depth. The profile of current velocity averaged by the ensemble casts in the near bottom boundary layer demonstrates near logarithmic relation.

Eccentrically Braced Frames (EBFs) have a capability of energy dissipation relying on horizontal link beams in main frame. Use of vertical link (V-EBF) enhances system performance; main frame damaged, easy replaces after earthquake, and it can be rehabilitated minor changes of existing structure. This paper describes experimental and analytical study of the V-EBF system. Experimental results showed that ultimate shear strength of vertical link is more than two times of yielding strength. In analytical model, Kinematic-Isotropic strain hardening for shear, and only Kinematic for moment, showed accurate results with an upper bound for yielding surface to the vertical link.

Laboratory experiments were conducted in a large-scale meandering compound channel to investigate the effect of floodplain grass on the main flow field in the channel. Three-dimensional velocity fields, turbulences, and Reynolds shear stresses were measured along half a meander. The experiments revealed that flexible artificial grass planted on a floodplain can significantly reduce the conveyance capability of the entire channel. Two parallel stage-discharge curves increased with increasing flow depth. The additional resistance of the floodplain grass increased the streamwise velocity and conveyance in the main channel along a meander. An analysis of the generation mechanism of secondary flows in the main channel indicated that the secondary current consisted of an enhanced original secondary cell that was strengthened by the centrifugal force and a component of the upstream floodplain flow. The relative dominance of these two components in the secondary flows was primarily determined by the angle between the floodplain flow and the main channel ridge, and also the floodplain roughness. At the same flow depth, the secondary flow in cases with grass on the floodplain was generally stronger than that in the case of a smooth meander bend, although it was weaker near the middle cross-over section. Floodplain grass enhanced the intensity of the lateral turbulence above the bankfull level and significantly modified the turbulence structure, although it had a negligible effect on the vertical turbulence except at the bend entrance. Floodplain grass also affected the Reynolds shear stresses in the main channel, generating stronger lateral shear stresses at a low flow depth. In contrast, at a high flow depth, the distribution of the interface shear stresses changed entirely while its magnitude remained the same. When the floodplains were grassed, the vertical shear stress that was induced by secondary flows was greater at the apexes but reduced at the cross-over sections. These observations highlight the important effects of floodplain grass on the main channel flow.

The present study documents the factors for year-to-year changes in the intensity of 10–20-day intraseasonal oscillations (ISOs) and investigates the feedback of the 10–20-day ISO intensity on seasonal mean sea surface temperature (SST) change in the tropical western North Pacific during boreal spring through fall. An analysis of local correlation reveals a significant negative correlation of the 10–20-day ISO intensity and the seasonal mean SST tendency in the tropical western North Pacific during spring, summer, and fall, suggesting a plausible feedback of the ISO intensity on seasonal mean SST anomaly. The 10–20-day ISO intensity change over the tropical western North Pacific is influenced by El Nino-Southern Oscillation (ENSO) through modulation of vertical shear of zonal winds, lower-level moisture, and upward motion. Due to the phase dependence of location of these ENSO-induced background field changes, the ISO intensity is subject to ENSO influence in different regions during the three seasons. The feedback of the 10–20-day ISO intensity on local seasonal mean SST change in the tropical western North Pacific is demonstrated by separating latent heat flux anomalies into components on different time scales. The ISO-induced latent heat flux anomalies may accumulate in a season and overcome interannual anomalies due to seasonal mean changes. Thus, the ISO-induced surface heat flux change may play an important role in the seasonal mean SST anomaly in the tropical western North Pacific.

The interannual variability of the boreal summer intraseasonal oscillation (BSISO) is investigated using observed outgoing longwave radiation (OLR) and ERA-Interim data for the period of 1980–2012. It is found that the interannual variability of BSISO intensity is much stronger in the tropical western Pacific (TWP) than the tropical Indian Ocean (TIO). A BSISO intensity index is defined based on a multivariate EOF analysis in TWP. It is found that strong BSISO years are associated with El Niño–like sea surface temperature anomalies in the tropical Pacific, anomalous easterly shear, and enhanced background moisture condition in the region. Using a 2.5-layer atmospheric model with a specified idealized background mean state, the authors further examine the relative roles of background moisture and vertical shear fields in modulating the BSISO intensity. Sensitivity numerical experiments indicate that the background moisture change is most important in regulating the BSISO intensity, whereas the background vertical shear change also plays a role.

Field observations, fractures identified from micro-resistivity logging images from six wells, and seismic anisotropy analysis all show that six sets of vertical shear fractures are developed in the middle Yanchang Formation in the southern Ordos Basin, comprising three orthogonal fracture systems. Of these, System I fracture sets predominate, trending approximately 75° and 150°, the result of NWW-SEE directed maximum compressive stress. System II fracture sets trend approximately 60° and 120°, the result of E-W directed maximum compressive stress, while System III fracture sets trend approximately 30° and 90°, the result of NEE-SWW directed maximum compressive tress. Fractures with a strike of 75° are most common in the middle Yanchang Formation because of rock heterogeneity, while three reservoir sets are present, comprising fluvial medium-to-fine grained blocky sandstones and thin interbeds of sandstone and shale from lacustrine-delta facies.

The influence of wave–current interactions on time series of marine X-band radar backscatter maps at the mouth of the Columbia River (MCR) near Astoria, Oregon, is examined. The energetic wave environment at the MCR, coupled with the strong tidally forced currents, provides a unique test environment to explore the limitations in accurately determining the magnitude and vertical structure of upper-ocean currents from wavefield measurements. Direct observation in time and space of the wave-induced radar backscatter and supporting acoustic Doppler current profiler (ADCP) current measurements provide a rich dataset for investigating how currents shift the observed wave dispersion relationship. First, current extraction techniques that assume a specific current–depth profile are tested against ADCP measurements. These constrained solutions prove to have inaccuracies because the models do not properly account for vertical shear. A forward solution using measured current profiles to predict the wavenumber–Doppler shift relationship for the range of ocean waves sensed by the radar is introduced. This approach confirms the ocean wavefield is affected by underlying vertical current shear. Finally, a new inversion method is developed to extract current profiles from the wavenumber-dependent Doppler shift observations. The success of the inversion model is shown to be sensitive to the range of wavenumbers spanned by observed Doppler shifts, with skill exceeding 0.8 when wavenumbers span more than 0.1 rad m−1. This agreement when observations successfully capture the broadband wavefield suggests the X-band backscatter is a viable means of remotely estimating current shear.

Recent efforts to understand tropical cyclone (TC) activity in the southwest Pacific (SWP) have led to the development of numerous TC databases. The methods used to compile each database vary and are based on data from different meteorological centres, standalone TC databases and archived synoptic charts. Therefore the aims of this study are to (i) provide a spatio-temporal comparison of three TC best-track (BT) databases and explore any differences between them (and any associated implications) and (ii) investigate whether there are any spatial, temporal or statistical differences between pre-satellite (1945–1969), post-satellite (1970–2011) and post-geostationary satellite (1982–2011) era TC data given the changing observational technologies with time. To achieve this, we compare three best-track TC databases for the SWP region (0–35° S, 135° E–120° W) from 1945 to 2011: the Joint Typhoon Warning Center (JTWC), the International Best Track Archive for Climate Stewardship (IBTrACS) and the Southwest Pacific Enhanced Archive of Tropical Cyclones (SPEArTC). The results of this study suggest that SPEArTC is the most complete repository of TCs for the SWP region. In particular, we show that the SPEArTC database includes a number of additional TCs, not included in either the JTWC or IBTrACS database. These SPEArTC events do occur under environmental conditions conducive to tropical cyclogenesis (TC genesis), including anomalously negative 700 hPa vorticity (VORT), anomalously negative vertical shear of zonal winds (VSZW), anomalously negative 700 hPa geopotential height (GPH), cyclonic (absolute) 700 hPa winds and low values of absolute vertical wind shear (EVWS). Further, while changes in observational technologies from 1945 have undoubtedly improved our ability to detect and monitor TCs, we show that the number of TCs detected prior to the satellite era (1945–1969) are not statistically different to those in the post-satellite era (post-1970). Although data from pre-satellite and pre-geostationary satellite periods are currently inadequate for investigating TC intensity, this study suggests that SPEArTC data (from 1945) may be used to investigate long-term variability of TC counts and TC genesis locations.

To understand the impacts of large-scale circulation during the evolution of El Nino cycle on tropical cyclones (TC) is important and useful for TC forecast. Based on best-track data from the Joint Typhoon Warning Center and reanalysis data from National Centers for Environmental Prediction for the period 1975-2014, we investigated the influences of two types of El Nino, the eastern Pacific El Nino (EP-El Nino) and central Pacific El Nino (CP-El Nino), on global TC genesis. We also examined how various environmental factors contribute to these influences using a modified genesis potential index (MGPI). The composites reproduced for two types of El Nino, from their developing to decaying phases, were able to qualitatively replicate observed cyclogenesis in several basins except for the Arabian Sea. Certain factors of MGPI with more influence than others in various regions are identified. Over the western North Pacific, five variables were all important in the two El Nino types during developing summer (July-August-September) and fall (OctoberNovember-December), and decaying spring (April-May-June) and summer. In the eastern Pacific, vertical shear and relative vorticity are the crucial factors for the two types of El Nino during developing and decaying summers. In the Atlantic, vertical shear, potential intensity and relative humidity are important for the opposite variation of EP- and CP-El Ninos during decaying summers. In the Southern Hemisphere, the five variables have varying contributions to TC genesis variation during peak season (January-February-March) for the two types of El Nino. In the Bay of Bengal, relative vorticity, humidity and omega may be responsible for clearly reduced TC genesis during developing fall for the two types and slightly suppressed TC cyclogenesis during EP-El Nino decaying spring. In the Arabian Sea, the EP-El Nino generates a slightly positive anomaly of TC genesis during developing falls and decaying springs, but the MGPI failed to capture this variation.

Preventing ice accretion on exposed surfaces is important to the operational performance of various facilities and devices. As time elapses and temperature lowers sufficiently, ice accretion becomes inevitable. Herein, we present a new approach to prepare icephobic coatings by incorporating two strategies towards lowering ice adhesion strength, i.e. introducing an aqueous lubricating layer and maximizing macro-crack initiators at the ice-substrate interface. The aqueous lubricating layer is realized by grafting poly(acrylic acid) (PAA) onto polydimethylsiloxane (PDMS) coatings, and the macro-crack initiators are induced by introducing macro-scale hollow sub-surface structures into PDMS coatings. By using vertical shear tests, ice adhesion strengths of PAA-g-PDMS (10:1), PDMS coatings with macro-scale hollow sub-surface structures (hPDMS) (10:1), PAA-g-hPDMS (10:1), PAA-g-PDMS (10:10), hPDMS (10:10), and PAA-g-hPDMS (10:10) coatings are obtained as 178.5 ± 22 kPa, 153.1 ± 19 kPa, 122.7 ± 18 kPa, 24.6 ± 4 kPa, 20.3 ± 3.4 kPa and 17.6 ± 3.2 kPa, respectively, showing a reduction of 37.2 %, 46.1 %, 56.8 %, 32.8 %, 44.5 % and 51.9 % when compared with corresponding pure PDMS coatings. These results indicate that ice adhesion strength can be further reduced by simultaneously introducing two strategies. The principle of designing icephobic coatings by combining two or more strategies to reduce ice adhesion to as low as possible provides a new avenue to the preparation of icephobic coatings, and makes practical applications possible under extremely severe conditions. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).T

WOS: 000458367000062 PubMed ID: 30761832 Background/aim: The aim of this study is to compare the stability and implant stresses of suprapectineal plate with infrapectineal plate in three subconfigurations of the screw types. Materials and methods: The stabilities of different fixation methods were compared by finite element analysis on six models. Three infrapectineal and three suprapectineal models each with locked, unlocked, or combined screws were employed. Three-dimensional finite element stress analysis was performed by using isotropic materials with a load of 2.3 kN applied at standing positions. Motion at the fracture line was measured on four different points located on the pubic and iliac sides of the fracture line. Results: Infrapectineal plate fixation with unlocked screws was found to be the most stable fixation method with 0.006 mm displacement of fragments in all axes at standing positions. The suprapectineal unlocked method was found to be the most unstable in standing positions with maximum displacement values of 0.46 mm vertical shear movement in the x-axis, -0.14 mm displacement in the y-axis, and -0.33 mm lateral shear in the z-axis. Conclusion: The infrapectineal unlocked plate supplies the most stable fixation with the least implant stress, contrary to the suprapectineal unlocked plate, which has the lowest stability and highest implant stresses. TOTBID The authors would like to thank TOTBID for funding this study.

The mechanisms of angular momentum transport and level of turbulence in protoplanetary disks (PPDs) are crucial for understanding many aspects of planet formation. In the recent years, it has been realized that the magneto-rotational instability (MRI) tends to be suppressed in PPDs due to non-ideal MHD effects, and the disk is largely laminar with accretion driven by magnetized disk winds. In parallel, several hydrodynamical mechanisms have been identified that likely also generate vigorous turbulence and drive disk accretion. We study the interplay between MHD winds in PPDs with the vertical shear instability (VSI), one of the most promising hydrodynamical mechanisms, through 2D global non-ideal MHD simulations with ambipolar diffusion and Ohmic resistivity. We find that for typical disk parameters, MHD winds can coexist with the VSI with accretion primarily wind-driven accompanied by vigorous VSI turbulence. The properties of the VSI remain similar to unmagnetized case, and the wind and overall field configuration are not strongly affected by VSI turbulence, showing modest level of variability and corrugation of midplane current sheet. Enhanced coupling between gas and magnetic field weakens the VSI. The VSI is also weakened with increasing magnetization, and we find that corrugation motions characteristic of the VSI transitions to low-amplitude breathing mode oscillations., Comment: 19 pages, 16 figures, accepted for publication in ApJ

This paper presents the experimental testing and results of a recent study into panel-to-panel connections for jointed precast concrete building cores. Panel-to-panel connections are typically used to transfer vertical shear forces between adjacent panels to allow the individual panels to act as one combined composite cross-section. The experimental program consisted of three specimens, each constructed using a different type of connection. The first specimen was the ‘baseline’ specimen and was constructed using ‘industry standard’ welded stitch plate (WSP) connections. The second and third specimen were constructing using two new prototype connections, which were developed by the authors and are referred to as grouted panel pocket (GPP) and post tensioned corbel (PTC) connections. These connections were developed such that precast concrete building cores could be constructed without the use of wet joints or site welding, which are both costly aspects in precast wall construction. The experimental assessment showed both connections were stronger and stiffer than the baseline WSP connection. The paper is concluded with a detailed overview of the critical failure mechanism of each connection and the development of respective design models that could be used to predict the design performance of the connections.

This study is the first biomechanical research of headless compression screws for fixation of vertical shear fractures of the medial malleolus, a promising alternative that potentially offers several advantages for fixation. Vertical shear fractures were simulated by osteotomies in 20 synthetic distal tibiae. Models were randomly assigned to fixation with either 2 parallel cancellous screws or 2 parallel Acutrak 2 headless compression screws (Acumed). Specimens were subjected to offset axial loading to simulate supination-adduction loading and tracked using high-resolution video. The headless compression screw construct was significantly stiffer (P < .0001) (360 ± 131 N/mm) than the partially threaded cancellous screws (180 ± 48 N/mm) and demonstrated a significantly increased (P < .0001) mean load to clinical failure (719 ± 91 N vs 343 ± 83 N). When specimens were displaced to 6 mm and allowed to relax, the headless compression screw constructs demonstrated an elastic recoil and were reduced to the pretesting fragment alignment, whereas the parallel cancellous screw constructs remained displaced. Along with the headless design that may decrease soft tissue irritation, the increased stiffness and elastic recoil of the headless compression screw construct offers improved fixation of medial malleolus vertical shear fractures over the traditional methods.

We present the results of 2D and 3D hydrodynamic simulations of idealized protoplanetary discs that examine the formation and evolution of vortices by the vertical shear instability (VSI). In agreement with recent work, we find that discs with radially decreasing temperature profiles and short thermal relaxation time-scales, are subject to the axisymmetric VSI. In three dimensions, the resulting velocity perturbations give rise to quasi-axisymmetric potential vorticity perturbations that break-up into discrete vortices, in a manner that is reminiscent of the Rossby wave instability. Discs with very short thermal evolution time-scales (i.e. {\tau}

In order to research mechanical and failure characteristics of shear keys on immersed tunnel segment joints, a 1:4.69 large scale immersed tunnel physical model test was conducted on a settlement platform. Bending and twisting working conditions of segment joints caused by uneven settlements and uneven back-silting were simulated, by means of controlling the lifting jacks under the settlement platform. Simultaneously, a 3-D numerical simulation which considered the nonlinearity of rubber pads and contacting effects between segment joints was carried out. The results shows that vertical shear keys have main contribution to resist expansion of segment joints in bending condition, and vertical shear keys on the soft layer have larger shear forces than that on the hard layer. In addition, shear stresses were mainly concentrated at the terminal corners and connecting corners between shear keys and segments. Correspondingly, at the terminal corners and connecting corners between shear key and segments appeared 30° ∼60° and 45° extending cracks respectively. At last, some structural strengthen suggestions on shear keys were offered for immersed tunnel design.

This paper investigates the environmental parameters favoring significant tornadoes in Bangladesh through a simulation of ten high-impact events. A climatological perspective is first presented on classifying significant tornadoes in Bangladesh, noting the challenges since reports of tornadoes are not documented in a formal manner. The statistical relationship between United States and Bangladesh tornado-related deaths suggests that significant tornadoes do occur in Bangladesh so this paper identifies the most significant tornadic events and analyzes the environmental conditions associated with these events. Given the scarcity of observational data to assess the near-storm environment in this region, high-resolution (3-km horizontal grid spacing) numerical weather prediction simulations are performed for events identified to be associated with a significant tornado. In comparison to similar events over the United States, significant tornado environments in Bangladesh are characterized by relatively high convective available potential energy, sufficient deep-layer vertical shear, and a propensity for deviant (i.e., well to the right of the mean flow) storm motion along a low-level convergence boundary.

The mechanisms responsible for tropical cyclone (TC) intensification in the presence of moderate vertical shear magnitudes are not well understood. To investigate how TCs intensify in spite of moderate shear, this study employed a 96-member ensemble generated with the Advanced Hurricane Weather Research and Forecasting (AHW) Model. In this first part, AHW ensemble forecasts for TC Katia (2011) were evaluated when Katia was a weak tropical storm in an environment of 12 m s−1 easterly shear. The 5-day AHW forecasts for Katia were characterized by large variability in the intensity, presenting an opportunity to compare the underlying mechanisms between two subsets of members that predicted different intensity scenarios: intensification and weakening. The key difference between these two subsets was found in the lower-tropospheric moisture north of Katia (i.e., right-of-shear quadrant). With more water vapor in the lower troposphere, buoyant updrafts helped to moisten the midtroposphere and enhanced the likelihood of deep and organized convection in the subset that predicted intensification. This finding was validated with a vorticity budget, which showed that deep cyclonic vortex stretching and tilting contributed to spinning up the circulation after the midtroposphere had moistened. Sensitivity experiments, in which the initial conditions were perturbed, also demonstrated the importance of lower-tropospheric moisture, which suggests that moisture observations may help reduce uncertainty in forecasts of weak, sheared tropical storms.

An attempt is made to quantify the impact of stochastic wave–induced shears on salt fingers associated with internal waves in the ocean. The wave environment is represented by the superposition of Fourier components conforming to the Garrett–Munk (GM) spectrum with random initial phase distribution. The resulting time series of vertical shear are incorporated into a finger-resolving numerical model, and the latter is used to evaluate the equilibrium diapycnal fluxes of heat and salt. The proposed procedure makes it possible to simulate salt fingers in shears that are representative of typical oceanic conditions. This study finds that the shear-induced modification of salt fingers is largely caused by near-inertial motions. These relatively slow waves act to align salt fingers in the direction of shear, thereby rendering the double-diffusive dynamics effectively two-dimensional. Internal waves reduce the equilibrium vertical fluxes of heat and salt by a factor of 2 relative to those in the unsheared three-dimensional environment, bringing them close to the values suggested by corresponding two-dimensional simulations.

Three-dimensional simulations are performed to investigate flow and transport mechanisms through submerged vegetation under the influence of tidal oscillations. A global minimum least squares method is proposed to compute the spatially-averaged lateral and vertical diffusivities. Our results indicate that the longitudinal dispersion coefficients have sinusoidal behaviour and oscillate with a similar frequency as the tidal forcing. The dispersion coefficients are reduced at high water and enhanced at low water, which may be attributed to increased vertical shear and turbulence due to stronger bottom drag in the presence of vegetation. The effects of varying tidal amplitude and frequency are investigated. The revealed regularity of variation in the dispersion process suggests that an empirical formulation describing the longitudinal dispersion coefficient may be found. Our findings are applicable for specific types of vegetation with intermediate submergence, such as mangrove pneumatophores planted ...

On 23 July 2013, a snowstorm hit southern Brazil causing material damage and two deaths. Radar reflectivity and lightning data revealed a rare thundersnow occurrence. This study revealed that a Rossby wave propagation followed a typical pattern of cold incursions in South America, but some fundamental differences can be pointed out: (1) further northward Rossby wave amplification; (2) strong upward vertical motion within a deep nearly saturated layer and (3) a conditional symmetric instability layer, in response to strong vertical shear, beneath a layer of weak conditional instability, and above a significant near-surface vertical depth where temperatures hover around 0 °C.

During the observational period of our study, Typhoon Hagupit passed over the mooring site and induced strong near-inertial waves (NIWs), which provided an opportunity to investigate the interactions between internal tides (ITs) and NIWs. Based on the mooring data, we compared the current spectra during the typhoon period and non-typhoon period in the northern South China Sea, and found that the high-frequency waves (fD1 and fD2) were evident during the former. Moreover, the observations of the current revealed that fD1 and fD2 occurred near the depth of strong vertical shear in the NIWs. In order to confirm the generation mechanism of fD1 and fD2, we compared the positions of strong vertical shear in the NIWs and strong vertical velocity in the ITs. It was established that the vertical shear of the horizontal current of the NIWs and the vertical current of the ITs contributed to the generation of fD1 and fD2.

We investigate the influences of the decaying eastern Pacific El Nino (EP-El Nino) and central Pacific El Nino (CP-El Nino) on tropical cyclone (TC) activities in the western North Pacific (WNP) during July, August, and September (JAS). During this period, TC geneses and tracks are reduced in the central and eastern WNP. However, TC tracks reaching the Philippines increase, and more TC geneses appear west of 145°E during EP-El Nino. During CP-El Nino, tracks reaching the South China Sea (SCS) and southeast coast of China increase, and positive anomalies of TC genesis are found in the southern part of the central WNP and southern SCS. It is possible that the different variations of the anomalous anticyclone over east of the Philippines in the WNP induced by El Ninos are instrumental to the different TC variations in the two types of decaying El Ninos during JAS. Compared with EP-El Nino, strengthening and northward expansion of the anomalous anticyclone during CP-El Nino cause a westward shift of the western Pacific subtropical high in summer, which is responsible for more westward TC tracks over the SCS and southeast coast of China. This northward expansion can cause the center of suppressed TC geneses in the central WNP to migrate further north during CP-El Nino. A decreased magnitude of vertical shear dominates the southern part of the central WNP and southern SCS, which enhances TC formation in these regions during CP-El Nino.

Flachdecken mit integrierten Stahlprofilen in Verbundbauweise zeichnen sich vor allem durch die schlanke Bauweise mit geringen Deckenhohen aus. In den letzten Jahren haben sich neben den typischen Querschnitten aus gewalzten Profilen mit untergeschweister Gurtplatte immer mehr hohlkastenahnliche Profilformen durchgesetzt. Bei diesen Systemen kann zur Steigerung der Querkrafttragfahigkeit ein hybrides Fachwerkmodell abgeleitet werden, bei dem neben der Querkrafttragfahigkeit des Stahlprofils auch die Tragfahigkeit des Betons angerechnet wird. Aufgrund der daraus resultierenden zusatzlichen Spannungen im Stahlprofil muss die Momenten-Querkraft-Interaktionsbeziehung erweitert werden. Shear resistance and M-V-Interaction of Slim-Floor-systems with integrated steel-box sections – Approach of a hybrid truss model for the shear design. Shallow-floor slabs with integrated steel profiles in composite behavior are mainly characterized by the slim design. Parallel to the traditional sections consisting of rolled profiles with an additional bottom plate also floor-slabs with integrated steel-box sections have gained widespread adoption in practice in the recent years. Because of the sheathing of the concrete by the steel section a hybrid truss model with a compression strut in the concrete section is developed, increasing the shear resistance of these sections. Due to the additional steel stresses resulting by the truss model, the relationship for the interaction between moment and vertical shear forces is to expand.

Intraseasonal variability (ISV) is a primary source for the sub-seasonal prediction that affects the livelihood of billions of people. Interannual variation of ISV intensity is important for seasonal prediction of ISV impacts on severe weathers. Existing measures of overall tropical ISV intensity, however, do not show any significant simultaneous relationship with external sea surface temperature anomalies (SSTAs). In this study, it is proposed that the ISV intensity, represented by the seasonal standard deviation of the 30–90-day filtered outgoing longwave radiation (OLR), has a good relation with the external SSTAs. With this measure, two major components of the interannual variability of global ISV intensity are detected for both boreal summer and winter: EOF1 calls its variability over the central Pacific and EOF2 is associated with the variability over the Indo-Pacific Warm Pool region. More importantly, each of these two components is significantly related to SSTAs over a specific tropical region. The central Pacific ISV intensity is strong during central Pacific warming, while the ISV intensity is strong over the Indo-Pacific Warm Pool region during eastern Pacific cooling. The eastern and central Pacific warming has very different impacts on the ISV intensity: The eastern Pacific warming largely reduces the winter ISV intensity over the Indian Ocean, while the central Pacific warming only induces neutral winter ISV intensity anomalies over the Indian Ocean. In the summer, the ISV intensity variability is confined near the equator associated with the central Pacific warming; the eastern Pacific warming, however, induces large ISV intensity variability over the western North pacific because of strong northeastward propagation of the boreal summer ISV under the easterly vertical shear.

This study shows that the occurrence of intense typhoons in the western North Pacific is significantly higher in the autumns of the Central Pacific (CP), compared to Eastern Pacific El Nino years. Specifically, (1) The higher occurrence of intense typhoons in CP El Nino autumns is related to a longer typhoon lifespan, maximum potential intensity, ocean heat content, vertical shear of the zonal wind (850–200 hPa), outgoing long-wave radiation, and moist static energy averaged over 1,000–500 hPa. (2) A longer typhoon lifespan in CP El Nino autumns is caused by the westward shift of the subtropical high, which tends to steer typhoon to the west and northwest.

Inflows with identical wind speeds at turbine hub height can generate varying amounts of power, depending on parameters such as vertical shear and turbulence intensity. At a commercial wind farm located in Southwestern Ontario off the shores of Lake Erie, the wind profile approaching a multi-megawatt horizontal-axis turbine has been characterized by a meteorological mast and then correlated with resulting power production across a range of hub height speeds. Using data collected over a six-month measurement campaign, inferences have been drawn on the sensitivity of turbine performance to sheared and turbulent inflows for both land and lake-influenced winds at the coastal site under study.

In this paper, a multilayer generalisation of the Shallow Shelf Approximation (SSA) is considered. In this recent hybrid ice flow model, the ice thickness is divided into thin layers, which can spread out, contract and slide over each other in such a way that the velocity profile is layer-wise constant. Like the SSA (1-layer model), the multilayer model can be reformulated as a minimisation problem. However, unlike the SSA, the functional to be minimised involves a new penalisation term for the interlayer jumps of the velocity, which represents the vertical shear stresses induced by interlayer sliding. Taking advantage of this reformulation, numerical solvers developed for the SSA can be naturally extended layer-wise or column-wise. Numerical results show that the column-wise extension of a Newton multigrid solver proves to be robust in the sense that its convergence is barely influenced by the number of layers and the type of ice flow. In addition, the multilayer formulation appears to be naturally better conditioned than the one of the first-order approximation to face the anisotropic conditions of the sliding-dominant ice flow of ISMIP-HOM experiments.

Composite slabs are designed to transfer loads in one direction e.g. the longitudinal direction of the ribs. To reduce the deflection, it is useful to realise a continuous slab with at least one intermediate support. At the intermediate support in addition to a hogging bending moment a rather large vertical shear force will act. For the verification of the combination of vertical shear and bending clause 9.7.5 of EN1994-1-1 [1] refers to clause 6.4.4 of EN1992-1-1 [2]. However in EN1992-1-1 there is no requirement related to interaction between vertical shear and a sagging or hogging bending moment. Implicitly this implies that interaction may be neglected and that bending moment and shear force may be verified separately. In practice checking authorities not always accept this interpretation of the code and require proof that interaction may be neglected. So Tata Steel Panels and Profiles with Dutch Engineering r.i. BV commissioned Stevin II laboratory of Delft University of Technology to carry out a research program to investigate this interaction. A test program was carried out to gain more insight in the interaction and to find out whether design calculations should take into account M-V interaction when applying the ComFlor series. Two series of respectively three and two test specimens were conducted, namely on ComFlor 210 (TS1 up to TS3) and ComFlor 75 (Tata Steel Panels and Profiles reference ComFlor 60) (TS4 and TS5) produced by Tata Steel Panels and Profiles and supplied by Dutch Engineering r.i. BV in the Benelux. A second point of interest is the contribution of the steel deck to the vertical shear resistance. The reference in clause 9.7.5 of EN1994-1-1 to EN1992-1-1 without mentioning EN1993 causes that in practice only the contribution of the concrete rib is taken into account, the steel deck is neglected completely. This is, of course, a simplification of the actual behaviour.

If sufficiently irradiated by its central star, a protoplanetary disks falls into an equilibrium state exhibiting vertical shear. This state may be subject to a hydrodynamical instability, the `vertical shear instability' (VSI), whose breakdown into turbulence transports a moderate amount of angular momentum while also facilitating planet formation, possibly via the production of small-scale vortices. In this paper, we show that VSI modes (a) exhibit arbitrary spatial profiles and (b) remain nonlinear solutions to the incompressible local equations, no matter their amplitude. The modes are themselves subject to parasitic Kelvin-Helmholtz instability, though the disk rotation significantly impedes the parasites and permits the VSI to attain large amplitudes (fluid velocities < 10% the sound speed). This `delay' in saturation probably explains the prominence of the VSI linear modes in global simulations. More generally, the parasites may set the amplitude of VSI turbulence in strongly irradiated disks. They are also important in breaking the axisymmetry of the flow, via the unavoidable formation of vortices. The vortices, however, are not aligned with the orbital plane and thus express a pronounced $z$-dependence. We also briefly demonstrate that the vertical shear has little effect on the magnetorotational instability, whereas magnetic fields easily quench the VSI, a potential issue in the ionised surface regions of the disk and also at larger radii., 16 pages, MNRAS accepted

Forecasting rapid intensification (hereafter referred to as RI) of tropical cyclones in the Atlantic Basin is still a challenge due to a limited understanding of the meteorological processes that are necessary for predicting RI. To address this challenge, this study considered large-scale processes as RI indicators within tropical cyclone environments. The large-scale processes were identified by formulating composite map types of RI and non-RI storms using NASA MERRA data from 1979 to 2009. The composite fields were formulated by a blended RPCA and cluster analysis approach, yielding multiple map types of RI’s and non-RI’s. Additionally, statistical differences in the large-scale processes were identified by formulating permutation tests, based on the composite output, revealing variables that were statistically significantly distinct between RI and non-RI storms. These variables were used as input in two prediction schemes: logistic regression and support vector machine classification. Ultimately, the approach identified midlevel vorticity, pressure vertical velocity, 200–850 hPa vertical shear, low-level potential temperature, and specific humidity as the most significant in diagnosing RI, yielding modest skill in identifying RI storms.

Joint, one of the most important components of immersed tunnel, is also the weak link of the tunnel structure, whose mechanical performance affects the safety of the tunnel significantly. However, previous researches were mainly focused on one-way shear mechanical performance of joint, such as the vertical shear mechanical performance or the horizontal shear mechanical performance. So, the two-ways shear mechanical performance of joint and the inter-influence of the vertical shear and horizontal shear have not been studied thoroughly yet. Based on Honggu tunnel project, this paper uses the finite element software ABAQUS to establish a numerical model of the immersed tunnel. Nonlinear constitutive models are adopted to simulate the constituent materials.

The Indian summer monsoon (ISM) shows quasi-rhythmic intraseasonal oscillations (ISO) manifested as alternate ‘active’ phases of copious rainfall and quiescent phases of ‘break’. Within these periodic phases, the daily rainfall shows large variability and exhibits spatiotemporally sporadic extreme rainfall events. The recent decades have witnessed a significant increase in the number of these extreme rainfall events, especially in the quiescent phases. This increase is accompanied by a decreasing trend in the mean monsoon rainfall and a weakening variance of its low-frequency ISO (LF-ISO) cycle. However, any physical link between this apparent paradox of increased extreme rainfall events and weakened slower-time-scale components is not yet reported. Here, using observations and numerical model simulations, we show that the occurrence of extreme rainfall events, primarily in the break phase of an LF-ISO cycle, reduce the intensity of the following active phase by stabilizing the atmosphere. We found that extreme events in a monsoon break leads to a reduction in the vertical shear of zonal winds and an increase in the static stability of the atmosphere in the following break-to-active transition and active phases. These conditions oppose the initiation and development of an active phase and lessen its intensity. This reduces the LF-ISO intensity and mean ISM rainfall.

Support for this work was generously provided by the National Science Foundation. Zonal mean zonal velocity profiles from cloud-tracking observations on Jupiter and Saturn are used to infer latitudinal variations of potential temperature consistent with a shear stable potential vorticity distribution. Immediately below the cloud tops, density stratification is weaker on the poleward and stronger on the equatorward flanks of midlatitude jets, while at greater depth the opposite relation holds. Thermal wind balance then yields the associated vertical shears of midlatitude jets in an altitude range bounded above by the cloud-tops and bounded below by the level where the latitudinal gradient of static stability changes sign. The inferred vertical shear below the cloud tops is consistent with existing thermal profiling of the upper troposphere.The sense of the associated mean meridional circulation in the upper troposphere is discussed and expected magnitudes are given based on existing estimates of the radiative timescale on each planet. Publisher PDF

To enhance our understanding of fog processes over complex terrain, various fog events that occurred during the International Collaborative Experiments for Pyeongchang 2018 Winter Olympics and Paralympics (ICE-POP) campaign were selected. Investigation of thermodynamic, dynamic, and microphysical conditions within fog layers affected by quasi-periodic oscillation of atmospheric variables was conducted using observations from a Fog Monitor-120 (FM-120) and other in-situ meteorological instruments. A total of nine radiation fog cases that occurred in the autumn and winter seasons during the campaign over the mountainous region of Pyeongchang, Korea were selected. The wavelet analysis was used to study quasi-period oscillations of dynamic, microphysical, and thermodynamic variables. By decomposing the time series into the time-frequency space, we can determine both dominant periods and how these dominant periods change in time. Quasi-period oscillations of liquid water content (LWC), pressure, temperature, and horizontal/vertical velocity, which have periods of 15&ndash, 40 min, were observed during the fog formation stages. We hypothesize that these quasi-periodic oscillations were induced by Kelvin&ndash, Helmholtz instability. The results suggest that Kelvin&ndash, Helmholtz instability events near the surface can be explained by an increase in the vertical shear of horizontal wind and by a simultaneous increase in wind speed when fog forms. In the mature stages, fluctuations of the variables did not appear near the surface anymore.

In the ACI 318–11 design method for slab-column connections subjected to unbalanced moment, the contribution factors assigning the proportion of the connection unbalanced moment to be resisted by the slab flexural reinforcement and by eccentric vertical shear stresses are prescribed by only considering the aspect ratio of columns. However, the validity of the prescribed contribution factors have not been completely verified by extensive test results, and the strength prediction by the design method using the contribution factors does not agree well with existing test results. In the present study, a modified strength model was proposed without prescribing the contribution factors. In the proposed model, the contribution of flexural moment is directly calculated using the slab reinforcement ratio, and the contribution of eccentric shear is calculated based on the conventional eccentric shear stress model. The proposed method was verified by comparing its prediction with existing test results. The results showed that the proposed method predicts the test results with reasonable accuracy, and it corresponds with the fundamental mechanics of the punching shear of slab-column connections as investigated in previous studies.

The crescent fracture consists of a posterior iliac wing fracture with extension into the sacroiliac joint and a dislocation of the sacroiliac joint. This fracture represents a subset of lateral compression injury. The strong posterior ligaments of sacroiliac joint remain intact and a fracture fragment (crescent shape) involving the posterior superior iliac spines remains firmly attached to the sacrum. We report a patient with atypical pelvic crescent fracture that is mainly influenced by vertical shear injury and is characterized by posterior fracture-dislocations of the sacroiliac joint. In this case report, we review the literature on classification and treatment of atypical type of crescent fracture.

The shear buckling behavior of the web-post in a castellated steel beam with fillet corner hexagonal web openings is studied using the finite element method. The buckling modes and buckling capacity of the web-post in the castellated beam with fillet corner hexagonal web openings are compared with those having circular and elongated circular openings. The web-post in a castellated steel beam with the proposed opening shape can achieve as good structural performance as that with circular openings. The effects of the opening distance, the opening height, and the web thickness on the buckling behavior of the web-post are investigated. The Strut Model is modified for predicating the shear buckling capacity of the web-post in the castellated steel beam with fillet corner openings. The equivalent rectangular opening is also modified to calculate the Vierendeel failure capacity of the castellated steel beam with the fillet corner hexagonal openings at the perforated sections. The load bearing capacity of the castellated steel beam with the proposed opening shape is the minimum value among the web-post buckling capacity, the Vierendeel failure capacity at the perforated section, and the shear rupture capacity of the horizontal weld.

Diapycnal mixing in the ocean is sporadic yet ubiquitous, leading to patches of mixing on a variety of scales. The adjustment of such mixed patches can lead to the formation of vortices and other small-scale geostrophic motions, which are thought to enhance lateral diffusivity. If vortices are densely populated, they can interact and merge, and upscale energy transfer can occur. Vortex interaction can also be modified by internal waves, thus impacting upscale transfer. Numerical experiments were used to study the effect of a large-scale near-inertial internal wave on a field of submesoscale vortices. While one might expect a vertical shear to limit the vertical scale of merging vortices, it was found that internal wave shear did not disrupt upscale energy transfer. Rather, under certain conditions, it enhanced upscale transfer by enhancing vortex–vortex interaction. If vortices were so densely populated that they interacted even in the absence of a wave, adding a forced large-scale wave enhanced the existing upscale transfer. Results further suggest that continuous forcing by the main driving mechanism (either vortices or internal waves) is necessary to maintain such upscale transfer. These findings could help to improve understanding of the direction of energy transfer in submesoscale oceanic processes.

Currently, composite construction of prestressed Precast Concrete (PC) and Cast-In-Place (CIP) concrete with different concrete strengths are frequently used in the modular construction. However, current design codes do not clearly define shear design methods for such composite beams. In this present study, simply supported prestressed PC-CIP composite beams without vertical shear reinforcement or only with horizontal shear reinforcement were tested to evaluate the effect of prestressing on the shear strength and the shear design method for such composite members. The test variables were the area ratio of PC and CIP concretes, prestressing force, shear span-to-depth ratio, and shear reinforcement ratio. The results showed that the shear strength was increased by the increase of prestressing force and prestressed PC area, and the decrease of shear span-to-depth ratio.

The performances of four Chinese AGCMs participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) in the simulation of the boreal summer intraseasonal oscillation (BSISO) are assessed. The authors focus on the major characteristics of BSISO: the intensity, significant period, and propagation. The results show that the four AGCMs can reproduce boreal summer intraseasonal signals of precipitation; however their limitations are also evident. Compared with the Climate Prediction Center Merged Analysis of Precipitation (CMAP) data, the models underestimate the strength of the intraseasonal oscillation (ISO) over the eastern equatorial Indian Ocean (IO) during the boreal summer (May to October), but overestimate the intraseasonal variability over the western Pacific (WP). In the model results, the westward propagation dominates, whereas the eastward propagation dominates in the CMAP data. The northward propagation in these models is tilted southwest-northeast, which is also different from the CMAP result. Thus, there is not a northeast-southwest tilted rain belt revolution off the equator during the BSISO’s eastward journey in the models. The biases of the BSISO are consistent with the summer mean state, especially the vertical shear. Analysis also shows that there is a positive feedback between the intraseasonal precipitation and the summer mean precipitation. The positive feedback processes may amplify the models’ biases in the BSISO simulation.

This paper focuses on the impacts of convective momentum transport (CMT) on simulations of the tropical intraseasonal oscillation (TIO) in SAMIL. Two sets of experiments are performed, which give different reality of the Madden-Julian Oscillation (MJO). The Tiedtke cumulus parameterization scheme is used for all experiments. It is found that simulations of the TIO can be influenced by CMT, and the impacts on the simulated TIO depend on the model capability in simulating the MJO. CMT tends to have large influences to the model that can simulate the eastward propagation of the MJO. CMT can further influence the long-term mean of zonal wind and its vertical shear. Zonal wind suffers from easterlies biases at low level and westerlies biases at upper level when CMT is introduced. Such easterlies biases at low level reduce the reality of the simulated tropical intraseasonal oscillation. When CMT is introduced in the model, MJO signals disappear but the model’s mean state improves. Therefore, a more appropriate way is needed to introduce CMT to the model to balance the simulated mean state and TIO signals.