Lower Bend Research Articles

Effect of variable angular piping bends geometry on turbulent flow of supercritical water in an SCWR Plant piping network: a 3-D CFD investigation

Abstract One of the most critical components of Super Critical Water Reactor (SCWR) plant is pipe bend, carrying massive volume of supercritical water. Because of its intense fluctuation of velocity and pressure, it can exhibit unusual flow pattern in pipe bends. This unusual flow pattern may finally destroy the integrity of the piping network. Alternatively, because of unique chemical and physical properties, transportation of SCW can adversely effect on the integrity of the pipe bends, indicating probable failure of piping network. Therefore, intensive studies of SCW flow in bends is a must while designing an efficient plant piping network. This article presents CFD analysis, carried out to examine the effect of variable pipe bend angle (90, 120 & 135;) on turbulent flow of SCW. The analysis indicates, the portion of the straight inlet pipe with fully developed flow shows no variation of results in all bend configurations. The study also reveals that secondary currents strengthen at lower bend angles and culminate the formation of vertices at the outlet of the right-angled elbow. The study shows that a greater part of the cross-sectional area is covered by the vortices at the bend mid-planes compared to the bend outlets, where mixing of stream wise flow occurs as well. It is found that the radial positions of each vortex center are closer to the circumference of the pipe, and appear to be insensitive to bend angle. The study is ended with the comparison between supercritical and normal water at standard conditions.

Vibrational relaxation of HOD by collisions with Ar atoms.

Vibrational relaxation of HOD(v12, v3) molecules by collisions with Ar was studied at 298K (v12 denotes coupled bending, v2, and OD stretching, v1, vibrational modes and v3 denotes OH stretching mode). The vibrationally excited HOD molecules were generated by exothermic abstraction reactions of OD radicals with 13 different RH reactants and observed by infrared emission from a fast-flow reactor as a function of Ar pressure and reaction time. State-specific relaxation rate constants were obtained by comparison of the time evolution of the experimental vibrational distributions with numerical kinetic calculations for vibrational populations. The relaxation mechanism was based on the relaxation scheme of H2O studied earlier with the addition of specific channels for HOD(v12, v3). Unlike H2O, energy in stretching and bending vibrations of HOD cannot be separated due to close ν1 and 2ν2 energies, which leads to fast collisional equilibration between these Fermi-resonant levels. For relaxation of the only pure bending state (10), a rate constant of (1.5 ± 0.3) × 10-13cm3molecule-1s-1 was obtained. The relaxation rate of higher v12 states linearly increases with quantum number and very likely includes transfer of population from OD stretch levels, v1, to a lower energy bend level. The average rate constants for the loss of population from (01), (02), and (03) stretching states are (1.1 ± 0.3) × 10-14, (3.2 ± 1.0) × 10-14, and (5.6 ± 1.2) × 10-14cm3molecule-1s-1, respectively.

Late‐Holocene counterpoint deposition in the Lower Rhine River

ABSTRACTChannel deposits from meandering rivers have proven to be far more complex than the well‐known lithofacies model consisting of coarse‐grained channel, gravelly channel‐lag and fine‐grained overbank deposits. Sharp bends in rivers are subject to different hydraulic processes than bends with lower curvatures, enabling erosion of inner banks and deposition of fine‐grained sediments in the outer bend, resulting in downstream migration of river bends. This phenomenon is known as counterpoint deposition, forming counterpoint bars. This research investigates whether scroll bars associated with a sharp bend in the Lower Rhine River, The Netherlands, are such a counterpoint‐bar deposit. A counterpoint bar is expected based on: (i) the surface morphology of the scroll bar; (ii) the confinement of the river course by an ice‐pushed ridge resulting in a sharp bend; and (iii) the archaeological context of successive Roman settlements atop the ice‐pushed ridge, potentially moving downstream with the migrating river bend. This hypothesis is tested through detailed borehole descriptions combined with optically stimulated luminescence dating, the latter being a novel approach to identifying counterpoint deposits. The deposits consist of clays and sandy clays with fine sand laminations, and sporadic larger sand bodies. Further upstream these deposits grade into channel deposits dominated by coarser sands with gravels. These lithologies are explained using earlier proposed mechanisms for counterpoint formation; substrata match those described in previously studied counterpoint deposits and their point bar counterparts. Optically stimulated luminescence dates indicate that the Lower Rhine River bend migrated downstream, confirming counterpoint deposition. A migration rate of 1.93 m/year was established through weighted linear regression. This study demonstrates the potential of optically stimulated luminescence dating to investigate counterpoint bar presence. The identified counterpoint bars and associated bend migration provide insight into meandering river dynamics that is crucial for river management and in aiding river restoration and rewilding initiatives.

Вплив форми крила на характеристики при використанні інтегрованої роторної силової установки літака

The subject of the study is the optimization of aerodynamic characteristics by improving the wing profile shape for the fan-wing configuration. The aim of this work is to find a more universal wing shape suitable for various aircraft. The task is to compare the characteristics of three wings with the same rotor engine installed in the nose section, including the base wing used in most previous studies by scientists. Sources suggested that this profile is not well-suited for rotor engines with a large aspect ratio. Experimental methods were used to measure the dynamic characteristics of three wing profiles: a flat curved profile with a cut-out in the rear wing section, a flat lower surface profile, an S-shaped profile with a lower surface bend in the rotor area, and a two-bend contour with a cut-out in the rear wing section on top and bottom. The results showed an improvement in characteristics compared with wing-rotor engine schemes used in previous cases. Specifically, an increase in the flow velocity at the wing exit of 3...8 % depending on the power plant operating mode was found, which led to an increase in lift up to 20 % depending on the flight mode, and an increase in thrust up to 16 %. Conclusions. The proposed S-shaped profile with a lower surface bend in the area of the rotor hub, and a profile with two bends in the contour with a cut in the rear part of the wing from the top and bottom contours have the most optimal and balanced characteristics. In the future, it is planned to manufacture these profiles using composite materials to reduce weight and install them on the aircraft prototype, replacing the rotor structure with a more flexible one using more flexible materials such as PETG plastic for the synchronization of the installed rotor motors, which is necessary to increase reliability and backup the rotor drive. Additionally, several sections with independent engines are planned to be made on each wing console to counteract rotor rupture in the event of engine failure. Due to significant advantages over the standard profile shape and minor structural complexity, the manufacture of more complex profile shapes can find wide applications in aircraft designed according to the fan-wing scheme.

Effect of sediment supply on the flow characteristics in a meandering channel

Meandering channels are common in natural rivers, especially in lowland alluvial plains. In this research, a meandering channel was designed in order to explore the effect of sediment supply on the flow characteristics. The water level, three-dimensional (3D) instantaneous velocity and riverbed elevation were measured using a digital wave altimeter, a 3D acoustic Doppler velocimeter and a 3D laser scanner, respectively, and the flow characteristics with and without sediment supply were compared. Under the same discharge, the transverse slope of the water surface in the case with sediment was larger than that without sediment and the change was steep; the change in the longitudinal slope of the water surface was small in the upper half bend and large in the lower half bend. By increasing the water discharge, the number of secondary flow vortices at the apex of the meandering channel increased. The trends of the mainstream lines with and without sediment supply were roughly opposite and the difference between them decreased with increasing discharge. The lateral and vertical turbulence intensities of the flow near the outer bank were larger in both cases (with and without sediment). In the case with sediment, the turbulent kinetic energy of the cross-section was larger near the bed and the water surface.

Shear performance of reinforced concrete beams containing stirrups with lower bend defects

The reactive expansion caused by alkali-aggregate reactions and severe corrosion in a saline environment may both lead to fracture or complete section loss at the lower bends of stirrups and localized debonding of side-legs nearby. The effects of such bend fracture and the debonded length on the shear performance of a reinforced concrete beam were explored in laboratory experiments and through a finite element simulation. Bend-defects in the stirrups reduced the beam’s shear strength, and the reduction increased with the debonded length. And a parametric analysis indicated that the nominal shear stress carried by the stirrups with a given defect severity increased with section size, and the size effect of shear strength became less significant with increasing defect severity. An approach for predicting the shear strength of such defective beams was proposed based on a transparent and well-understood mechanical and physical model, and published test data confirm its accuracy and safety was confirmed by published test data on 35 beams of various sizes.

Burst pressure assessment of pipe bend/elbow for transmission pipelines

The pipelines for oil and gas transportation are generally laid along a straight route to avoid the complexity of pipe bending. However, changing of pipe alignment is sometimes unavoidable where a straight pipeline is mechanically bent, or two straight pipelines are connecting using a suitable pipe bend/elbow. In this study, the burst pressure of corroded and uncorroded pipe bends was investigated using finite element analysis. The study shows that the pipe bend reduces the burst pressure that depends extensively on the radius of the bend. A parametric study was conducted to identify the parameters affecting the burst pressure of the pipe bend. The parameters investigated included bend radius, bend angle, pipe dimensions, corrosion dimensions, location of corrosion, and the grade of the steel. Corrosion at the intrados of the bend was found to have the most adverse effect on the burst pressure of bend for pipes with lower bend radii. The ratio of the burst pressure of the pipe bend to the burst pressure of corresponding straight pipes depends on the bend radius and steel grade and is almost independent of the pipe and corrosion dimensions. This ratio can be used to assess the burst pressure of a pipe bend using the burst pressure of the corresponding straight pipe. However, for a bend radius greater than three times the pipe diameter, the burst pressure of pipe bend is almost the same as the burst pressure of the corresponding straight pipe.

When Slick Is Not Smooth: Bottomhole Assembly Selection and Its Impact on Wellbore Quality

Summary Appropriate selection of a bottomhole assembly (BHA) is critical to the success of a drilling operation. In US land drilling, these assemblies are often selected using local heuristics rather than rigorous analysis. These heuristics are frequently derived from the incentives of the directional contractor as opposed to incentives for the operator. Large motor bends enable more rotation through the curve and reduce the possibility of tripping for build rates. Unstabilized motors are believed to aid sliding and tool face control. Both of these practices lead to drilling a more tortuous wellbore and may cause problems later in the well’s life. This study quantifies the impact of these practices and proposes alternatives that can balance the needs of directional companies with the desire of operators for high-quality wellbores. More than 60 conventional motor assemblies used to drill curves in the Eagle Ford and Permian basins were analyzed for directional performance using commercial drillstring analysis software. The sliding and rotary tendencies were modeled through the curve across a range of potential drilling conditions. Expected build-rate models were validated by comparison to the maximum achieved doglegs in the directional surveys. When available, additional validation was performed using motor yields calculated from slide sheets. The validated models were compared to the dogleg severity (DLS) requirements for each assembly’s respective well plan. Comparisons of slide ratios and slide/rotate tendencies of the BHAs were used to estimate the impact on wellbore quality using the tortuosity metric proposed by Jamieson (2019). Typical well plans for both basins had curves of 10° per 100 ft with no well plan greater than 12° per 100 ft. Typical BHAs were capable of >15° per 100 ft under normal sliding conditions, with some assemblies capable of >20° per 100 ft of build. Predicted build rates were validated by slide sheets and observed DLSs. Common characteristics among assemblies with excess capacity were high-bend angles (≥2°) and minimal stabilization. These understabilized assemblies exhibited unstable rotary tendencies across a range of drilling parameters. The combination of high-build rates with rotary drop masks the true level of tortuosity in a wellbore, leading to an underestimation of unwanted curvature. A minority of the assemblies used a lower motor bend angle (<2°) combined with multiple stabilizers. These assemblies had a more consistent directional capability throughout the curve and exhibited stable behavior in rotation. The success of these assemblies confirms that there is potential for tailoring BHA designs to improve wellbore quality without compromising the technical objectives of the well. As increasing attention is afforded to the topic of wellbore quality, it is important to have methods available to technically achieve high-quality wellbores. In addition to the management of drilling practices, it is also important to have an appropriate BHA design that can enable those practices

Effect of Guide Vane on Turbulence Characteristics for Single-Phase Flow through a 90-Degree Pipe Bend

The present study expresses the turbulent flow characteristics through a 90° pipe bend using a numerical ‎method by determining the solutions for Reynolds Averaged Navier-Stokes (RANS) expression using the k-ω ‎‎(SST) turbulence model. For that purpose, numerical analysis has been carried out by solving RANS equations ‎using ANSYS FLUENT 16.2, considering incompressible fluid in turbulent flow conditions. Simulations have ‎been carried out for three different Reynolds number ranging from 1×105 to 10×105 at three different bend ‎curvature ratios (Rc/D = 1, 1.5, and 2). Pipe bends with guide vane are generally used where flow separation ‎and space problem makes an issue in mechanical design. The presence of guide vane inside the bend ‎positively suppressed the flow separation and presence of cross-flow which can cause the engine to run off ‎design, thus reducing the engine efficiency. So, to observe the effect of guide vane and its position on ‎turbulence characteristics, four different positions of guide vane inside the bend are considered in the present ‎study. At first, an analysis was led to make sure that the results obtained from the present numerical model are ‎reliable and in line with previous results obtained from similar published experiments and numerical work. ‎Research has been conducted to find out the impact of Reynolds number, bend curvature ratio and position of ‎guide vane on different turbulence characteristics namely; turbulent kinetic energy, turbulent intensity, and ‎wall shear stress at bend outlet position. In general, the turbulent intensity is found larger for the lower bend ‎curvature ratio at the inner wall curvature side. Results for turbulent kinetic energy have similarities in results ‎with turbulent intensity. Significantly, the wall shear stress represented a strong dependency on the ‎circumferential angle at the bend outlet cross-section, and curvature ratio rather than Reynolds number and ‎guide vane positions‎‎.

Study and Optimisation of Supply Duct Bend and Diffuser in HVAC System for a Classroom

This paper presents numerical predictions and results of air flow and pressure distribution in common possible iterations of duct and diffuser having: 1. square, rectangle and circular duct shape, 2. square duct with side 12in, 15in and 18in and 3. bend radius to width ratio of 0, 0.5, 1 and 2. The system is designed to develop an optimal system to reduce the noise levels in a classroom which are far above the recommended value of 35dB by WHO in an engineering institution designed according to the Common Public Works Department(CPWD) norms while also bridging the gap between the industry and the consumer. The iterations were designed on fusion 360 and tetrahedron meshing was done in ANSYS after defining the boundaries of geometry of CAD design. The inlet velocities varied as per the different diffuser size, shape and angles. The inlet velocity lies in the range of 1.5m/s to 3m/s. After setting up the solver and choosing k-omega SST model for solving, calculation was performed for 3000 iterations using hybrid initialization to reduce the residuals as much as possible for the results to converge for accurate results. Material properties of aluminum and properties of the fluid were set. Among different groups, results based on different shapes showed that circular duct displayed gradual pressure and velocity drop at the lower bend of the wall than in the case of rectangle or square. While, in case of duct with different sizes, as size of duct increased, frictional losses increased, while pressure drop, noise levels and eddy current formation significantly reduced. In case of different bend radius to width ratio(r/W), as r/W increased, eddy formation and boundary layer separation, pressure drop, turbulence and noise levels decreased. Therefore, the study showed that a circular duct, with a diameter of 15in having r/W ratio of 2 would significantly reduce the sound levels and be the optimum solution for the classroom and adding 2-3 vanes would further improve the performance of the system and maximize the required effort.

Simulation of blood flow into the popliteal artery to explain the effect of peripheral arterial disease: Investigation the conditions and effects of different foot states during the daily activity of the patient

Background and objectivePeripheral artery disease, one type of atherosclerosis, is a common medical condition in the world that results from plaque build-up in the peripheral blood vessels. The symptoms of this disease are the senses of pain and weakness in outer muscles. MethodsThe artery under consideration is called the popliteal artery. In this model, the blood flow is considered as pulsating. Therefore the inlet boundary condition is taken as unsteady velocity, and the outlet boundary condition is taken the outflow. The inlet boundary condition represents the increasing systole flow and the decreasing diastole flow, which occur naturally in blood flow. Systolic flow occurs when the heart contracts and pumps blood into the arteries. The inlet blood flow is in the form of a sine-cosine parabolic profile. ResultsThe artery bends from the middle at an angle of 45°. As the bending of the artery begins, the flow field also takes a bent form. At this point, the flow bends from the outside of the top wall and enfolds the bottom wall in its bending. For different periods, the popliteal flow is closer to the lower bend when the inlet velocity is more significant. While the top wall experiences a low-intensity region along the bend, the bottom wall experiences the same effect just before and after the bend. As the blood flows along the bend, the flow path becomes significantly curved near the bend, similar to the model. The clotted artery exhibits a large increase in flow due to a reduction in the cross-section as a result of the clotting in half of the artery. The flow before the clotting is not considerably different from the main model of the straight artery. ConclusionsLike shear stress, the pressure drop has a linear relationship with the blood HCT and, hence, the viscosity. The pressure drop decreases with the inlet velocity reaching its maximum value and then increases with the start of the acceleration reduction in the second and third-time steps. This indicates that the pressure drop has a stronger relationship with the acceleration than the inlet velocity.

Direct Shape Optimization and Parametric Analysis of a Vertical Inline Pump via Multi-Objective Particle Swarm Optimization

The vertical inline pump is a single-suction single-stage centrifugal pump with a curved inlet pipe before the impeller, which usually causes a significant increase of hydraulic losses in the inline pump. Considering the matching relationship between the inlet pipe and impeller, a multi-objective direct optimization based on the MOPSO of the inlet pipe and impeller was carried out to broaden the efficient operating area of the vertical inline pump. Bezier curves were adopted to control the profiles of the inlet pipe and impeller and 39 coordinates of the control points and the blade number were selected as the optimization variables. The efficiencies of the inline pump at the part-load and nominal conditions were chosen as the objective functions, which were obtained by the automatic simulation program. A dramatic improvement in pump performance was found after optimization. In the set of Pareto solutions, the maximum increases of efficiency at part-load and nominal conditions were 8.06% and 7.33% respectively. It also reported that the inlet pipe with longer horizontal length and lower bend curvature could reduce the hydraulic losses of the inlet pipe and increase the pump performance.

Electronic surface, optical and electrical properties of p – GaN activated via in-situ MOCVD and ex-situ thermal annealing in InGaN/GaN LED

Electronic surface properties, optical and electrical characteristics of p-type Mg-doped Gallium Nitride (p-GaN) activated under different thermal annealing condition were investigated. In this work, p-GaN samples were subjected to in-situ and ex-situ thermal annealing process at 650 °C in Nitrogen (N2) rich condition. In-situ annealing process took place in Metal Oxide Chemical Vapor Deposition (MOCVD) chamber while ex-situ annealing process was carried out in the conventional oven. X-Ray and Ultraviolet Photoemission Spectroscopy (XPS/UPS) were used to observe the energy alignment of the p-GaN surface. From PES spectra, the sample subjected to in-situ thermal annealing shown to exhibit lower surface bend bending of 0.28 eV as compared to ex-situ thermal annealing activation with 0.45 eV band bending. This result is in agreement with specific contact resistance measurement that shows in-situ sample exhibits lower resistance resulted in better carrier injection from metal to p-GaN. Photoluminescence (PL) spectra elucidates that in-situ sample has a good surface quality with less nitrogen related vacancies (VN) formed on the p-GaN surface. All these results are further proved with the higher output power from LED with in-situ annealing. At 20 mA, in-situ sample shown an increment of ~14% light output power compared to ex-situ sample. Results obtained in this work suggest that the thermal activation condition for p-GaN activation process plays an active role on the surface quality as well as the energy alignment of the film surface and shows the potential of in-situ p-GaN activation for tunnel junction structure.

Comparative Analysis of the Flow Field in the Lower Bend at Different Rotation Angles

In order to obtain the influence of the distribution of the flow field in the lower bend at different rotation angles on the fluid flow, Fluent software was used to conduct numerical simulation of the flow field in the bend at different rotation angles, and the influence rule of the shape difference of the secondary flow in the lower bend at different rotation angles was simulated. The simulation results show that the 90 °rotation Angle bend, its internal gas phase flow field better than other simulation Angle, secondary flow phenomena delay happened, reduce reflux area, syphon is helpful to improve the flow state; With the change of the rotation Angle, the tangential velocity of the outlet section of the bend increases continuously, which is conducive to the smooth gas-solid phase separation, but the pressure drop of the system also increases, resulting in the energy loss of the system. As a result, the Angle of 90 ° canary after rotation Angle for the simulation of the optimal point of view, for later engineering application provides data to support and help.

Performance of a buried pipeline along the dip of a slope experiencing accidental sliding

Contrary to highways, major pipelines often have to be installed crossing hills or mountain ridges, following the dip of the slope. Slope movements that may be triggered by an earthquake, heavy rainfall, an excavation at its toe, or long-term creep, constitute major hazards that must be considered in design. This paper studies numerically the interaction of a steel pipeline with a rotational slide originating at the crest of a slope and evolving in the direction of the pipeline axis. Different pipeline-slide mechanisms are examined: a reference slide taking place in a rather shallow slope in which the sliding surface crosses the pipe over its straight portion, a deeper scenario where the toe of the slide interacts with the bottom elbow element of the pipeline, and two much steeper scenarios. A two-step finite-element methodology is developed and validated against several published experiments. The analysis simulates realistically the soil sliding process and all possible modes of pipeline failure. The pipeline performance is discussed for a range of internal pressure scenarios: from empty to full operating at maximum allowable pressure (pmax). It is found that the relative position of the slip-line to the pipeline axis (at their intersection) determines the amount of bending induced in the pipeline and eventually the vulnerability of the installation. For empty pipes the prevailing failure mode is inward buckling, whereas pressurised pipelines rupture at larger displacements due to excessive accumulation of tensile strains. When the slip-line of the sliding mass crosses the toe of the slope, excessive bending is experienced at the lower bend of the installation, which is translated into a compressive force, invariably speeding up pipeline failure. Here the failure mode is always buckling: inward for non-pressurised pipes and outward for non-zero internal pressures.

Tunable structure and dynamics of active liquid crystals.

Active materials are capable of converting free energy into directional motion, giving rise to notable dynamical phenomena. Developing a general understanding of their structure in relation to the underlying nonequilibrium physics would provide a route toward control of their dynamic behavior and pave the way for potential applications. The active system considered here consists of a quasi-two-dimensional sheet of short (≈1 μm) actin filaments driven by myosin II motors. By adopting a concerted theoretical and experimental strategy, new insights are gained into the nonequilibrium properties of active nematics over a wide range of internal activity levels. In particular, it is shown that topological defect interactions can be led to transition from attractive to repulsive as a function of initial defect separation and relative orientation. Furthermore, by examining the +1/2 defect morphology as a function of activity, we found that the apparent elastic properties of the system (the ratio of bend-to-splay elastic moduli) are altered considerably by increased activity, leading to an effectively lower bend elasticity. At high levels of activity, the topological defects that decorate the material exhibit a liquid-like structure and adopt preferred orientations depending on their topological charge. Together, these results suggest that it should be possible to tune internal stresses in active nematic systems with the goal of designing out-of-equilibrium structures with engineered dynamic responses.

Impact of Cotton Leaf and Bract Characteristics on Cotton Leaf Grade

Core Ideas Cultivars with higher trichome densities resulted in higher leaf grade values. Leaf area and bract length had no relation with leaf grading. Industry leaf hairiness ratings are not consistent with observed leaf hairiness ratings. The remnants of leaf material in harvested cotton (Gossypium hirsutum L.) can significantly increase leaf grade values, resulting in discounts to the producers and increased ginning cost. The impacts of leaf and bract pubescence and leaf and bract area of different cotton cultivars were studied on cotton leaf grade during 2011 and 2012, and the accuracy of industry leaf hairiness rating was evaluated. Three replicated trials were conducted during 2011 in Texas in the Lower and Upper Coastal Bend and the Blackland Prairie, and Tifton, GA was added as a fourth location in 2012. Two separate commercial‐scale (multi‐acre) trials were conducted during 2011 and 2012 to compare leaf grade values of a smooth leaf cultivar Deltapine 0935 B2RF and a hairy leaf cultivar Deltapine 0949 B2RF. Results demonstrated that increased leaf and bract trichome density increased the propensity for greater leaf grades in small‐plot and commercial field trials. Leaf area and bract length were not different among the cultivars at most of the locations, suggesting minimal relation with leaf grade. Pubescence quantification indicated substantial variation in cultivars, and discrepancies between company‐based rating systems; for example, semi‐smooth cultivar Phytogen 499 WRF was found to have denser trichomes compared with all smooth, semi‐smooth, and hairy cultivars. Overall, this study identified a detrimental relationship between leaf pubescence and leaf grade while other plant characteristics studied contributed little to greater leaf grades. Standardizations of leaf pubescence ratings among cotton cultivars will allow producers interested in improving leaf grade to accurately select their cultivar.

Analogue modelling of thrust systems: Passive vs. active hanging wall strain accommodation and sharp vs. smooth fault-ramp geometries

We present new analogue modelling results of crustal thrust-systems in which a deformable (brittle) hanging wall is assumed to endure passive internal deformation during thrusting, i.e. exclusively as a consequence of having to adapt its shape to the variable geometry of a rigid footwall. Building on previous experimental contributions, we specifically investigate the role of two so far overlooked critical variables: a) concave-convex (CC) vs. flat-ramp-flat (FRF) thrust ramp geometry; and b) presence vs. absence of a basal velocity discontinuity (VD). Regarding the first variable, we compare new results for considered (CC) smoother ramp types against classical experiments in which (FRF) sharp ramp geometries are always prescribed. Our results show that the considered sharp vs. smooth variation in the thrust-ramp geometry produces important differences in the distribution of the local stress field in the deformable hanging wall above both (lower and upper) fault bends, with corresponding styles of strain accommodation being expressed by marked differences in measured morpho-structural parameters. Regarding the second variable, we for the first time report analogue modelling results of this type of experiments in which basal VDs are experimentally prescribed to be absent. Our results critically show that true passive hanging wall deformation is only possible to simulate in the absence of any basal VD, since active shortening accommodation always necessarily occurs in the hanging wall above such a discontinuity (i.e. above the lower fault bend). In addition, we show that the morpho-structural configuration of model thrust-wedges formed for prescribed VD absence conditions complies well with natural examples of major overthrusts, wherein conditions must occur that approximate a frictionless state along the main basal thrust-plane.

Theoretical study on the electron structure and optical properties of Cs adsorption on In0.53Ga0.47As (100) β2 (2 × 4) reconstruction surface

Cs activation on In0.53Ga0.47As (100) β2 (2×4) reconstruction surface is an important process for improving the performance of the negative electron affinity (NEA) photocathode. Using the first-principles method based on the density functional theory (DFT), within scope of the generalized gradient approximation (GGA), the electronic structure and optical properties of Cs adsorption on In0.53Ga0.47As (100) β2 (2×4) reconstruction surface models are calculated and analyzed in this article. The results show that adsorption energy is negative suggesting that the structure of Cs adsorption on In0.53Ga0.47As (100) β2 (2×4) surface is stable. The Cs adsorption on In0.53Ga0.47As (100) β2 (2×4) surface makes work function lower and energy band bend, which is benefit for electrons escape to the surface. At the same time, new energy bands are generated. Combined with study of the Al0.5Ga0.5As (100) β2 (2×4) reconstructed surface, two different elements of Al and In are compared under the Cs atomic adsorption. The work function and band gap of Cs atom adsorption on In atom are all smaller than adsorption on Al atom. And the absorption coefficient, dielectric function and energy loss function of Cs adsorption on In0.53Ga0.47As (100) β2 (2×4) surface and clean In0.53Ga0.47As (100) β2 (2×4) surface are researched and compared. Cs adsorption on surface makes the peaks of absorption coefficient, dielectric function and energy loss function of surface higher than that of clean In0.53Ga0.47As (100) β2 (2×4) surface. The analysis is helpful to further strengthen the study for near-infrared material photoemission.

An effective method to predict oil recovery in high water cut stage

AbstractThe water flooding characteristic curve method based on the traditional regression equation between the oil and water phase permeability ratio and the water saturation is inappropriate to predict the oil recovery in the high water cut stage. Hence, a new water flooding characteristic curve equation adapted to the high water cut stage is proposed to predict the oil recovery. The water drive phase permeability experiments show that the curve of the oil and water phase permeability ratio vs. the water saturation, in the semi-logarithmic coordinates, has a significantly lower bend after entering the high water cut stage, so the water flooding characteristic curve method based on the traditional regression equation between the oil and water phase permeability ratio and the water saturation is inappropriate to predict the oil recovery in the high water cut stage; therefore, a new water flooding characteristic curve equation based on a better relationship between In(kro/krw) and Sw is urgently desirable to be established to effectively and reliably predict the oil recovery of a water drive reservoir adapted to a high water cut stage. In this paper, by carrying out the water drive phase permeability experiments, a new mathematical model between the oil and water phase permeability ratio and the water saturation is established,with the regression analysis method and an integration of the established model, the water flooding characteristic curve equation adapted to a high water cut stage is obtained. Using the new water flooding characteristic curve to predict the oil recovery of the GD3-block of the SL oilfield and the J09-block of the DG oilfield in China, results with high predicted accuracy are obtained.