Evaluation of Normal Pressures during Filling in Steel Hoppers with Eccentric Outlet

Filling pressures are a necessary starting point in the design of silos and hoppers. The hoppers with complicated geometries are common in industrial applications due to physical space constraints and the need to interface with other processing equipment. The current paper deals with the effect of outlet eccentricity on normal pressures formed in steel hoppers during distributed filling process. Using finite element method, progressive filling process in hoppers was simulated and by changing the percentage of outlet eccentricity, the variation of pressure distribution was fully studied. The results showed an increase in the normal pressures of shallow side compared with the steep side of eccentric hopper. To quantify the pressure asymmetry, two parameters were introduced and they were evaluated for practical range of material parameters and steel hoppers dimensions. The results obtained are of interest since they facilitate the design of silos and hoppers with eccentric outlet.

Antibody humanization—the Influence of the antibody framework on the CDR-H3 loop ensemble in solution

Antibody engineering of non-human antibodies has focused on reducing immunogenicity by humanization, being a major limitation in developing monoclonal antibodies. We analyzed four series of antibody binding fragments (Fabs) and a variable fragment (Fv) with structural information in different stages of humanization to investigate the influence of the framework, point mutations and specificity on the complementarity determining region (CDR)-H3 loop dynamics. We also studied a Fv without structural information of the anti-idiotypic antibody Ab2/3H6, because it completely lost its binding affinity upon superhumanization, as an example of a failed humanization. Enhanced sampling techniques in combination with molecular dynamics simulations allow to access micro- to milli-second timescales of the CDR-H3 loop dynamics and reveal kinetic and thermodynamic changes involved in the process of humanization. In most cases, we observe a reduced conformational diversity of the CDR-H3 loop when grafted on a human framework and find a conformational shift of the dominant CDR-H3 loop conformation in solution. A shallow side minimum of the conformational CDR-H3 loop ensemble attached to the murine framework becomes the dominant conformation in solution influenced by the human framework. Additionally, we observe in the case of the failed humanization that the potentially binding competent murine CDR-H3 loop ensemble in solution shows nearly no kinetical or structural overlap with the superhumanized variant, thus explaining the loss of binding.

Impact of High-Rise Buildings Construction Process on Adjacent Tunnels

The demand for buildings constructed along subway lines is increasing, and analysis of the impact of foundation excavation and building construction on adjacent tunnels is critical. This study investigated the variation law of tunnel deformation and surrounding earth pressure on an existing tunnel resulting from deep foundation excavation and the load of buildings. Four groups of scale model tests and corresponding numerical simulation calculations were conducted in four different modes: over unloading-loading, shallow-side unloading-loading, middle-side unloading-loading, and deep-side unloading-loading, which are according to the different relative position of the foundation pit and the tunnel. The results show that when the tunnel stretches across different areas, corresponding deformation occurs owing to the different mechanical mechanisms during excavation and loading. The results can provide evidence for the further study on the impact of adjacent construction process on the tunnels.

Experiments and Simulations on Coastal Flows in the Presence of a Topographic Slope

The evolution of a barotropic coastal current in the presence of a bottom ramp-shaped topography is studied by means of laboratory experiments and numerical simulations. The experiments are performed in a rectangular rotating tank filled with freshwater. The fluid depth is shallow at one side of the domain and deeper at the other side, and both regions are divided by a narrow slope, whose depth contours are perpendicular to the long sides of the tank. A current approaching the slope is produced along one of the vertical walls, having the boundary at its right. Two configurations are analyzed: when the current flows from shallow to deep water and when flowing in the opposite direction. In the first scenario, the current is divided in two parts, one of them following the coastline. The other part of the current pairs with a cell of negative relative vorticity generated at the slope due to squeezing effects, forming a dipolar structure moving offshore, back toward the shallow side. In addition, a weak current moving inshore along the slope is clearly formed. In the second configuration, when the flow goes from deep to shallow water, a part of or even the whole current might be forced to move along the contours of the topography, away from the coast. In this case there is no dipole formation. The experiments are well reproduced by means of quasigeostrophic numerical simulations, which allow a more detailed systematic study of the influence of flow parameters such as the topography height and the width of the slope.

The motion of an intense vortex near topography

The initial value problem for the motion of an intense, quasi-geostrophic, equivalent-barotropic, singular vortex near an infinitely long escarpment is studied in three parts. First, for times small compared to the topographic wave timescale the motion of the vortex is analysed by deriving an expression for the secondary circulation caused by the advection of fluid columns across the escarpment. The secondary circulation, in turn, advects the primary vortex and integral expressions are found for its velocity components. Analytical expressions in terms of integrals are found for the vortex drift velocity components. It is found that, initially, cyclones propagate away from the deep water region and anticyclones propagate away from the shallow water region. Asymptotic evaluation of the integrals shows that both cyclones and anticyclones eventually propagate parallel to the escarpment with shallow water on their right at a steady speed which decays exponentially with distance from the escarpment. Secondly, it is shown that for times comparable to, and larger than, the wave timescale, the vortex always resonates with the topographic wave field. The flux of energy in the topographic waves leads to a loss of energy in the vortex and global energy and momentum arguments are used to derive an equation for the distance (or, equivalently, the vortex velocity) of the vortex from the escarpment. It is shown that cyclones, provided they are initially within an O(1) distance (here a unit of distance is dimensionally equivalent to one Rossby radius of deformation) from the escarpment, drift further away from the deep water (i.e. toward higher ambient potential vorticity), possibly crossing the escarpment and accumulate at a distance of ≈1.2 on the shallow side of the escarpment. For distances larger than 1.2 there is essentially no drift of the vortex perpendicular to the escarpment. Anticyclones display similar behaviour except they drift in the opposite direction, i.e. away from the shallow water or toward lower ambient potential vorticity. Third, the method of contour dynamics is used to describe the evolution of the vortex and the interface representing the initial potential vorticity jump between the shallow and deep water regions. The contour dynamic results are in good quantitative agreement with the analytical results.

Topographic Hadley cells

When a rotating fluid over sloping topography is heated from below and/or cooled from above, horizontal temperature gradients develop which drive convection cells aligned with isobaths. We refer to these cells as topographic Hadley cells. Laboratory experiments reveal that sinking occurs in small cyclonic vortices situated in relatively shallow regions. This is balanced by slower upwelling in adjacent deeper regions. The cross-isobath motions which connect the upwelling and downwelling are accelerated by Coriolis forces, resulting in strong jets which follow isobathic contours. For anticlockwise rotation, the surface jets keep the shallows to their left when looking in the direction of flow, which is opposite to both Kelvin and Rossby wave propagation. The width of the jets scales with the Rossby deformation radius and if this is much less than the width of the slope region then a number of parallel jets form. Motions on the deeper side of the jets where the flow is accelerating are adequately described by linear inviscid theory. However, the strong shears generated by this acceleration lead to baroclinic instability. The resulting cross-stream momentum fluxes broaden and flatten the velocity profile, allowing the flow on the shallow side of the jet to decelerate smoothly before sinking. Topographic Hadley cells are dynamically similar to terrestrial atmospheric Hadley cells and may also be relevant to the zonal jet motions observed on Jupiter and Saturn. It is also suggested that in coastal seas they may represent an important mode of heat (or salt) transfer where surface cooling (or evaporation) drives convection.

Interaction of Visual and Tactile Information in the Control of Chicks' Locomotion in the Visual Cliff

The behaviour of two-day-old chicks placed on the deep side of a visual cliff was examined. With increasing depth of the floor below the chicks, latency to move over the deep side towards another chick on the shallow side increased, while speed of locomotion decreased. Chicks given the same incentive to step over a visible edge onto the deep side showed a stronger inhibition of movement at all depths, indicating that absolute depth of a surface and relative depth of an edge affect behaviour differently. At depths greater than 4 cm, the majority of chicks performed a jump from the deep to the shallow side, and the distances over which they jumped corresponded to those jumped when tested with a real gap. These results suggest that detection of the far side of a gap alone is sufficient to elicit a jump. Just before jumping, chicks adopted a head orientation which depended on the vertical distance of the cliff edge below them. Changes in head orientation did not maintain retinal fixation of the edge, and may instead be important in setting the correct direction of thrust when jumping.

Distance Perception in the Spiny Mouse Acomys Cahirinus: Vertical Jumping

Acomys cahirinus, a precocial muroid, that has shown precise jumping in the natural habitat, did not jump from 25 cm in a laboratory situation. To investigate this further, A. cahirinus were observed jumping from platforms at two different heights, onto different sized checkered substrates and from a visual cliff. Adult animals discriminated between platforms that were 6.4 cm and 25.4 cm above the substrate and between small and large checkered patterns on the floor. Most adult animals and neonates jumped down on the shallow side of the visual cliff. Animals developed individual patterns of jumping over a series of trials, with some jumping often, some rarely, and others jumping only from the low platform. Good distance perception was indicated when they did not jump from heights, and by their making appropriate postural adjustment when they did jump from heights and landed without mishap. Different spacing of trials indicated that height was a more effective stimulus for animals which had all four conditions on the same day, while floor pattern was more effective for animals with each of the four conditions on a separate day.