Wide Slab Research Articles

Microstructure evolution and its influence on thermoplasticity of wide and thick continuous casting slab with heavy reduction

Microstructure evolution and its influence on thermoplasticity of wide and thick continuous casting slab with heavy reduction

Compact super-Gaussian evanescent beam expanders for integrated photonics

This paper presents the modeling, design and experimental validation of integrated optical super-Gaussian evanescent beam expanders. A general analytical model for converting the mode of a single mode waveguide into a wide super-Gaussian slab mode is derived and the design procedure is described. Several structures have been experimentally verified on wafer scale and the results are in good correspondence with the design. Applications where wide flat-top beams would prove their superiority are, for instance, bio-sensing applications, flow cytometry and on-chip microscopy.

Overriding Plate Thickness as a Controlling Factor for Trench Retreat Rates in Narrow Subduction Zones

AbstractSlab width is a significant factor in controlling subduction zone dynamics, particularly the retreat velocities, which tend to decrease with wider slabs. However, observations of natural narrow subduction zones reveal no correlation between slab width and trench velocities. This suggests that other factors may exert a greater influence. In this study, we employ 3D numerical subduction models to systematically assess the impact of slab width, strength of slab coupling to the lateral plate (LP), and overriding plate (OP) thickness on trench kinematics and geometry. Our models focus on narrow slabs (400–1,200 km), and the results demonstrate that, in the case of narrow subduction zones, the slab width has little effect on trench migration rates and the viscous coupling at the lateral slab edge is only important for very narrow subduction zones (≤800 km). Conversely, the OP thickness emerges as a crucial factor, with increasing plate thickness leading to a strong decrease in trench velocities. These findings provide an explanation for the observed trench velocities in natural narrow subduction zones, where an inverse relationship with OP thickness is evident. Furthermore, our study reveals that not only slab width, but also the OP thickness and the slab coupling to the LP, significantly influence trench geometry. Strong lateral coupling promotes the formation of concave trench geometries, while thick overriding plates favor the development of “w”‐shaped geometries. Overall, a comprehensive understanding of subduction processes necessitates considering the interplay between slab width, OP thickness, and slab coupling to the LP.

Flexural behavior of high strength concrete shallow wide beams reinforced by hybrid longitudinal reinforcement

ABSTRACT One of the most common statistical systems used in structures especially for wide span slabs are ribbed slabs with shallow wide beams (SWB). This experimental study aimed to investigate and enhance the flexural behavior of high-strength concrete SWB using hybrid longitudinal reinforcement from steel and advanced composite materials as a tensile main reinforcement in SWB. Longitudinal advanced composite bars locally manufactured from ribbed glass fiber reinforced polymer (GFRP) and the second type was ribbed basalt fiber reinforced polymer (BFRP). A group of six half scale SWB were examined in structures laboratory of American University in Cairo with dimensions 2.1 × 0.6 × 0.25 m for length (L), width (B) and depth (d) respectively with constant size effect (d/B). The first three specimens were completely reinforced at tension side with Steel, GFRP or BFRP ribbed bars to be considered a control specimen. Use of GFRP and BFRP bars enhanced the flexural capacity of SWB with 41% and 43% respectively compared to specimen completely reinforced with steel. But on the other hand, the crack propagation of specimens completely reinforced with GFRP and BFRP developed more quickly and had larger crack width compared to specimen completely reinforced with steel. Hybrid reinforcement from Steel with GFRP, Steel with BFRP and Steel with GFRP and BFRP specimens are used to enhance the crack pattern and mode of failure without a significant loss in flexural capacity of SWB. The flexural capacity of these three specimens was enhanced with 26%, 30% and 41% with a significant enhancement in crack pattern and ductility.

Characterizing the Complexity of Subduction Zone Flow With an Ensemble of Multiscale Global Convection Models

AbstractSubduction zones are fundamental features of Earth's mantle convection and plate tectonics, but mantle flow and pressure around slabs are poorly understood because of the lack of direct observational constraints on subsurface flow. To characterize the linkages between slabs and mantle flow, we integrate high‐resolution representations of Earth's lithosphere and slabs into a suite of global mantle convection models to produce physically plausible present‐day flow fields for Earth's mantle. We find that subduction zones containing wide, thick, and long slabs dominate regional mantle flow in the neighboring regions and this flow conforms to patterns predicted by simpler regional subduction models. These subduction zones, such as Kuril‐Japan‐Izu‐Bonin‐Mariana, feature prismatic poloidal flow coupled to the downgoing slab that rotates toward toroidal slab‐parallel flow near the slab edge. However, other subduction zones, such as Sumatra, deviate from this pattern because of the competing influence of other slabs or longer‐wavelength mantle flow, showing that upper mantle flow can link separate subduction zones and how flow at subduction zones is influenced by broader scale mantle flow. We find that the non‐linear dislocation creep reduces the coupling between slab motion and asthenospheric flow and increases the occurrence of non‐ideal flow, in line with inferences derived from seismological constraints on mantle anisotropy.

Deflection analysis of rigid pavement on clay soil with vertical drain

Rigid pavements are often used on clay soils with long-term settlement history and are subject to damage from traffic loads. It must be analyzed for deflections in rigid pavements built on clay to prevent damage and extend pavement life. If deflection exceeds the permit, the pavement will experience damage. One way to minimize these problems is by installing vertical drains to improve the soil. Installing a vertical drain on the soil can increase the modulus of the subgrade reaction represented as soil- bearing capacity and minimize the potential for pavement deformation. This research aims to analyze the deflection of rigid pavement on clay soil with vertical drains. The finite element method is utilized to analyze the deflection. The pavement is modeled as a 10 m long and 7 m wide slab with thickness variations ranging from 150 mm to 350 mm. Static loads are used to model vehicle loads with load positions at the pavement’s center, ends, and edges. For all slab thicknesses subjected to varying center, end, and edge loads, the maximum deflection of rigid pavement over vertical drain soils is lower than that of soils without vertical drains. It can be concluded that rigid pavement deflection can be reduced using vertical drains for soil improvement.

Mathematical modeling of the effect of SEN outport shape on the bubble size distribution in a wide slab caster mold

Herein, the effects of outport shapes of the submerged entry nozzle (SEN) on the size distribution of argon bubbles were studied in a wide slab caster mold by the mathematical modeling. The Eulerian–Eulerian model coupled with Multiple-Size-Group (MUSIG) approach were used to solve equations of the two phase flow and polydispersed bubbly flow in the mold, respectively. The effect of the SEN outport angle and shape on the distribution of the molten steel flow, argon gas volume fraction, and argon bubble size were investigated. The outport shapes of the SEN included large rectangular, small rectangular, square, trapezoid, and runway. Results showed that the speed of molten steel increased within the range of 260 mm from the SEN, and decreased within the range of 550 mm from the narrow face with the outport angle of SEN increased from 20° to 45°. The bubble diameter was 5.7 mm at 255 mm distance from the SEN along the mold width at different outport angles. The average speed of molten steel at the outport of SEN decreased from 0.91 to 0.72 m/s with the outport shape changed from small rectangular to runway, trapezoid, square and large rectangular. The average diameter of bubbles was approximate 5.2 mm at the outport for the five types of nozzles, and increased from 3.2 to 3.45 mm inside the mold with the outport shape changed from the runway to square, trapezoid, large rectangular and small rectangular, indicating the rate of bubble breakup was larger with the runway and square SEN casting.

Anchored CFRP ropes for flexural capacity recovering of thermally damaged RC one-way slabs

The effectiveness of utilizing near surface mounted (NSM) ropes of carbon fiber reinforced polymers (CFRP) in restoring the mechanical performance of heat-damaged RC slabs were studied using anchored and un-anchored techniques. The CFRP anchorage is supposed to increase the flexural behavior of the RC one-way slabs under investigation. To achieve this purpose, a total of (24) RC 1100 mm (long) × 500 mm (wide) slabs were devised. The experimental slabs were made in three heights; 60 mm, 80 mm, and 100 mm. Using an electric furnace for two hours each time, six of the slab were exposed to 200 °C, another six slabs were exposed to 400 °C, and the third group of six slabs was exposed to 600 °C, while the remaining six slabs were at room temperature. Twelve slabs were reinforced, in tension, with NSM-anchored ropes of CFRP. A test setup for 4-point loading was used to examine the slabs’ mechanical performance, while NSM CFRP ropes’ strain was measured. Also, the cracking patterns and failure modes were observed and documented. The slabs, with/without strengthening and damaged-by-heat/retrofitted, improved their toughness and load capacity up to 189% and 225%, respectively. In contrast, the slabs encountered a degradation in their displacement ductility with respect to the control slabs up to 2%, with the toughness ductility being increased up to 186% based on the slab’s rigidity and the exposed temperature. The present research demonstrated that the anchored NSM CFRP ropes to rehabilitate damaged-by-heat slabs was efficient in regaining the flexural behavior; the monitored behaviors indicated that. Lastly, it was observed that the improvement in the slabs was controlled by the transverse end-anchoring’s effectiveness, which permitted the prime ropes of CFRP to contribute more to the flexural performance without the possibility of the occurrence of un-expected de-bonding caused by cracking, even when the slabs reached their capacity. Based on the research findings, anchoring the utilized CFRP ropes and predicting its capacity using the proposed guidelines is recommended.

Holographic entanglement entropy probe on spontaneous symmetry breaking with vector order

We study holographic entanglement entropy in 5-dimensional charged black brane geometry obtained from Einstein-SU(2)Yang-Mills theory defined in asymptotically AdS space. This gravity system undergoes second order phase transition near its critical point, where a spatial component of the Yang-Mills fields appears, which is normalizable mode of the solution. This is known as phase transition between isotropic and anisotropic phases, where in anisotropic phase, SO(3)-isometry(spatial rotation) in bulk geometry is broken down to SO(2) by emergence of the spatial component of Yang-Mills fields, which corresponds to a vector order in dual field theory. We get analytic solutions of holographic entanglement entropies by utilizing the solution of bulk spacetime geometry given in arXiv:1109.4592, where we consider subsystems defined on AdS boundary of which shapes are wide and thin slabs and a cylinder. It turns out that the entanglement entropies near the critical point shows scaling behavior such that for both of the slabs and cylinder, {Delta}_{varepsilon }Ssim {left(1-frac{T}{T_c}right)}^{beta } and the critical exponent β = 1, where ∆εS ≡ Siso− Saniso, and Siso denotes the entanglement entropy in isotropic phase whereas Saniso denotes that in anisotropic phase. We suggest a quantity O12≡ S1− S2 as a new order parameter near the critical point, where S1 is entanglement entropy when the slab is perpendicular to the direction of the vector order whereas S2 is that when the slab is parallel to the vector order. O12 = 0 in isotropic phase but in anisotropic phase, the order parameter becomes non-zero showing the same scaling behavior. Finally, we show that even near the critical point, the first law of entanglement entropy is held. Especially, we find that the entanglement temperature for the cylinder is {mathcal{T}}_{cy}=frac{c_{textrm{ent}}}{a} , where cent = 0.163004 ± 0.000001 and a is the radius of the cylinder.

Mould heat transfer and friction behavior on the surface of wide and heavy slabs in the presence of longitudinal cracks

The longitudinal crack is a common and serious defect on the surface of wide and heavy slab. The mould heat transfer and friction characteristics of 28 surface longitudinal cracks are collected and investigated in order to reveal the rule of the surface longitudinal cracks. The results show that the decrease amplitude of temperature in the presence of longitudinal crack is between −4.0 and −22.6 °C, and the increase amplitude of temperature is between 3.4 and 28.2 °C. The decrease of temperature velocity is between −0.4 and −1.5 °C.s−1, while the increase of temperature velocity is between 0.32 °C.s−1 and 1.64 °C.s−1. When longitudinal cracks occur in mould, the heat flux of 21 cases has a decrease more than −0.02 MW · m−2. There are 18 abnormal fluctuations of mould’s transient friction during occurrence of the surface longitudinal crack, which is more than the stable casting. And there are 85.7% longitudinal cracks, which has an upward trend of friction tension or a downward trend of friction pressure.

Casting parameters and propagation behaviour of sticker breakout for the conventional slab

ABSTRACT The casting parameters and behaviour of 61 sticker breakouts were analysed during the continuous casting of the conventional slab. The difference of sticker breakouts between the conventional slabs and wide and heavy slabs was also studied. The results show that the high casting speed or change of casting speed is the main reason. The mould level of the conventional slab is small and not the reason for sticker breakouts, which is different from the causes of wide and heavy slab. In terms of propagation behaviour, there are 14 cases out of 61 sticker breakouts occurred only around one column of thermocouples. The vertical velocity is in the range of 0.3∼2.4 m·min−1, and the horizontal velocity is in the range of 1.0∼9.0 m·min−1. The vertical velocities of the three sticker breakouts are higher than their casting speeds, which is different from the wide and heavy slab.

One‐way flexural shear tests on wide reinforced concrete slab segments with simple and intermediate supports

One‐way flexural shear tests on wide reinforced concrete slab segments with simple and intermediate supports

How Slab Age and Width Combine to Dictate the Dynamics and Evolution of Subduction Systems: A 3‐D Spherical Study

AbstractMany of the factors expected to control the dynamics and evolution of Earth's subduction zones are under‐explored in an Earth‐like spherical geometry. Here, we simulate multi‐material free‐subduction of a complex rheology slab in a 3‐D spherical shell domain, to investigate the effect of plate age (simulated by covarying plate thickness and density) and width on the evolution of subduction systems. We find that the first‐order predictions of our spherical cases are generally consistent with existing Cartesian studies: (a) as subducting plate age increases, slabs retreat more and subduct at a shallower dip angle, due to increased bending resistance and sinking rates; and (b) wider slabs can develop along‐strike variations in trench curvature due to toroidal flow at slab edges, trending toward a “W”‐shaped trench with increasing slab width. We find, however, that these along‐strike variations are restricted to older, stronger, retreating slabs: Younger slabs that drive minimal trench motion remain relatively straight along the length of the subduction zone. We summarize our results into a regime diagram, which highlights how slab age modulates the effect of slab width, and present examples of the evolutionary history of subduction zones that are consistent with our model predictions.

Sum rules for energy deposition eigenchannels in scattering systems.

In a random-scattering system, the deposition matrix maps the incident wavefront onto the internal field distribution across a target volume. The corresponding eigenchannels have been used to enhance the wave energy delivered to the target. Here, we find the sum rules for the eigenvalues and eigenchannels of the deposition matrix in any system geometry: including two- and three-dimensional scattering systems, as well as narrow waveguides and wide slabs. We derive a number of constraints on the eigenchannel intensity distributions inside the system as well as the corresponding eigenvalues. Our results are general and applicable to random systems of arbitrary scattering strength as well as different types of waves including electromagnetic waves, acoustic waves, and matter waves.

Magnetohydrodynamic Waves in an Asymmetric Magnetic Slab with Different External Flows

Building on recent studies of the Kelvin–Helmholtz instability (KHI) in the solar atmosphere, we investigate a simple analytical model that can further our understanding of how the presence of bulk flows influences the propagation of magnetohydrodynamic (MHD) waves. Our model builds on a series of recent works on stationary MHD waveguides and looks at a magnetic slab with a density asymmetry, as well as asymmetric background steady flows present in its environment. We obtained approximate solutions to the dispersion relation for the important and applicable limiting cases of a thin or a wide slab, as well as low- and high-β plasmas. We also explored the relation between the angular frequency of trapped MHD waves, the limit for the onset of the KHI, and small parameters describing the flow and density asymmetries. Our analytical investigation is complemented by a numerical analysis for various bulk flow speeds and slab widths. Both these avenues of study reveal that the flow field asymmetry has an important effect on both the cutoff frequencies and the stability of trapped MHD waves in the slab configuration.

Reduced Scaling of Optimal Regional Orbital Localization via Sequential Exhaustion of the Single-Particle Space.

Wannier functions have become a powerful tool in the electronic structure calculations of extended systems. The generalized Pipek-Mezey Wannier functions exhibit appealing characteristics (e.g., reaching an optimal localization and the separation of the σ–π orbitals) compared with other schemes. However, when applied to giant nanoscale systems, the orbital localization suffers from a large computational cost overhead if one is interested in localized states in a small fragment of the system. Herein, we present a swift, efficient, and robust approach for obtaining regionally localized orbitals of a subsystem within the generalized Pipek-Mezey scheme. The proposed algorithm introduces a reduced work space and sequentially exhausts the entire orbital space until the convergence of the localization functional. It tackles systems with ∼10000 electrons within 0.5 h with no loss in localization quality compared to the traditional approach. Regionally localized orbitals with a higher extent of localization are obtained via judiciously extending the subsystem’s size. Exemplifying on large bulk and a 4 nm wide slab of diamond with an NV– center, we demonstrate the methodology and discuss how the choice of the localization region affects the excitation energy of the defect. Furthermore, we show how the sequential algorithm is easily extended to stochastic methodologies that do not provide individual single-particle eigenstates. It is thus a promising tool to obtain regionally localized states for solving the electronic structure problems of a subsystem embedded in giant condensed systems.

How Aseismic Ridges Modify the Dynamics of Free Subduction: A 3-D Numerical Investigation

The subduction of positively buoyant features has been implicated in the development of flat and shallow dipping slabs, the formation of cusps in trench geometry, and the cessation of associated arc magmatism. However, how such buoyant anomalies influence subduction dynamics to produce these different tectonic expressions remains debated. In this paper, using a series of multi-material 3-D simulations of free subduction, we investigate how linear buoyant ridges modify subduction dynamics, in particular downgoing plate velocities, trench motions and slab morphology. We examine the sensitivity of results to downgoing plate age (affecting buoyancy and strength), ridge buoyancy and ridge location along the trench, finding that buoyant ridges can locally change slab sinking and trench retreat rates, in turn modifying the evolution of slab morphology at depth and trench shape at the surface. In all cases examined, trench retreat is reduced, or switches to trench advance, where the ridge subducts. These effects depend strongly on downgoing plate age: on young, weak plates, the change in trench shape is more localised than on old, strong plates. Slab shallowing at the ridge only occurs for young plates, while the stronger and more negatively buoyant older plates pull down the ridge at a steeper angle than the rest of the slab. On old plates, ridges located near regions of trench stagnation or advance, which typically develop in wide slabs, have a stronger effect on trench and slab shape. The combined effects of buoyant feature location, subducting plate age and overriding plate properties can result in a range of responses: from mainly trench deformation, through local slab shallowing, to the formation of a flat slab, a variation in expressions also observed on Earth.

Consideraciones físicas y geométricas acerca del crecimiento de Pichia pastoris en tiras de espuma de poliuretano

This work introduces the use of polyurethane foam (PUF) slabs for solid-substrate fermentation. Attention is paid to the distribution and properties of the liquid broth within the slabs in relation to the growth parameters of Pichia pastoris. The experimental setup was made of thin slabs supported horizontally by screens within cylindrical chambers. This way, water loss due to compression or gravity drain was minimal and exposure to tangential air flow was maximal. The highest biomass was Xmax = 39.5±3.3 gL-1 with (So) of 150 gL-1 of glucose. Biomass yield, Yx/s followed the correlation, Yx/s = 0.525-0.0018S0 (R2 = 0.996), and the growth rate m = 0.24 h-1/(S0/34.6). The respiratory quotient, RQ, followed a biphasic pattern with a maximal RQ » 1 when S0 = 50 gL-1. PUF micrographs showed that liquid was not retained when the integrity of the polyurethane network was disrupted at cutting edges of the slabs with an approximate depth of 0.025 cm, but the fraction of disrupted PUF would be small for wide slabs and h = 0.7 cm. The use of horizontal PUF slabs with thickness of 0.7 cm seems to be a practical way to upscale solid state fermentation (SSF) since a squared meter of this material could produce 83 g of yeast.

Ultra-compact dual-mode mode-size converter for silicon photonic few-mode fiber interfaces.

Fiber couplers usually take a lot of space on photonic integrated circuits due to the large mode-size mismatch between the waveguide and fiber, especially when a fiber with larger core is utilized, such as a few-mode fiber. We demonstrate experimentally that such challenge can be overcome by an ultra-compact mode-size converter with a footprint of only 10 µm. Our device expands TE0 and TE1 waveguide modes simultaneously from a 1-µm wide strip waveguide to an 18-µm wide slab on a 220-nm thick silicon-on-insulator, with calculated losses of 0.75 dB and 0.68 dB, respectively. The fabricated device has a measured insertion loss of 1.02 dB for TE0 mode and 1.59 dB for TE1 mode. By connecting the ultra-compact converter with diffraction grating couplers, higher-order modes in a few-mode fiber can be generated with a compact footprint on-chip.

Finite Element Analysis of I-Girder Bridge

Abstract: In India railway bridge structures are widely designed with the method suggested by IRS – Concrete bridge code 1997.This Code of Practice applies to the use of plain, reinforced and prestressed concrete in railway bridge construction. It covers both in-situ construction and manufacture of precast units. The Code gives detailed specifications for materials and workmanship for concrete, reinforcement and prestressing tendons used in the construction of railway bridges. After defining the loads, forces and their combinations and requirements for the limit state design, particular recommendations are given for plain concrete, reinforced concrete and prestressed concrete bridge construction. The design of I-Girder bridge superstructure (deck slab and PSC I-beam) are done by calculating bending moments, shear forces, bending resistance in transverse direction, bending resistance in longitudinal direction, checking flexural cracking. The Design of PSC I-Girders is done for Bending moments and Shear forces by Dead Load, Super Imposed Dead Load (SIDL) and Live Loads (LL). The Shrinkage strain, Creep Strain and effect of Temperature rise and fall are also determined. The design is complete for Pre-stressing cables, un-tensioned reinforcements, End cross girder, Shear connectors. I-girder superstructures are the most commonly used superstructures at cross-over location in metro bridges in india, as it has the wide deck slab and it easily permits metro’s to change tracks. I-Girder superstructure construction is component wise construction unlike U-Girders. I-Girders are constructed in casting yard and its deck slab is cast in situ, parapets are also installed on later stage. Keywords: SIDL effects, Live Load effects, Derailment effect, with or without 15% future PT margin