Trapezoidal Section Research Articles

25 nm Single-Crystal Silicon Nanowires Fabricated by Anisotropic Wet Etching.

We report a top-down method for fabricating ultra-high aspect ratio single-crystal silicon nanowires. The fabrication method is based on the standard photolithography technique and anisotropic wet etching of the single-crystal silicon in KOH solution. SiO₂ mask nanolines used for patterning single-crystal silicon nanowires are formed by the undercut etching of thin SiO₂ layer in buffered hydrofluoric solution. The minimum width of the SiO₂ mask nanolines are 50 nm. The length of SiO₂ mask nanolines is 2 cm. The single-crystal silicon nanowires have been successfully transferred from the SiO₂ mask nanolines by KOH anisotropic wet-chemical etching. The minimum width of the silicon nanowire has obtained to be 25 nm. The fabricated single-crystal silicon nanowires have trapezoidal and triangular cross sections, which are useful for applications in nanoelectronic and nanophotonic elements.

Optimal Hydraulic Section of Ice-Covered Open Trapezoidal Channel

AbstractPrevious studies have focused on the optimal hydraulic section for ice-free channels only. This paper presents the optimal trapezoidal section and its characteristics under ice-covered cond...

Experimental investigations on solar flat plate collector by changing geometry of fin using CFD - a review

Fins are extended surface which increase the heat transfer rate. It is most commonly used in heat exchanger device such as car radiator, computer CPU heat sink and hydrogen fuel cell, etc. Fins increase area of heat transfer in cooling and heating application. Our ultimate aim is to reduce losses present in flat plate collector by conduction, convection and re-radiation. Lots of experimentation has been done to improve the heat transfer rate of solar water heater by adding fins of helical, rectangle, circular, trapezoidal section as well as twisted shape. This paper makes summary of the all previous work on solar FPC with number of geometrical shapes of fins and their effect on efficiency of flat plate collector. As surface area increases heat transfer from fins also increases. So implementation of fin in solar FPC is also a most promising technique that enhances the heat transfer rate through absorber.

Deflection Analysis of Non Prismatic Beam with Trapezoidal Sectorial Section with Uniformly Perpendicular Loading Condition

Non-prismatic beams are extensively used for many engineering application. Due to varying section, deflection analysis becomes very complex. Loading condition also makes the whole theory complex. This paper shows analytical analysis for the deflection of trapezoidal sectorial section with uniformly perpendicular loading condition. The method illustrated is comparatively easy and can be applied for the similar other sections as well. Analytical method is validated using Finite Element Analysis using Creo Simulation which shows good amount of match with analytical result.

Analysis of self-excited forces for a box-girder bridge deck through unsteady RANS simulations

This paper presents the results of two-dimensional numerical simulations of the flow field around a trapezoidal box-girder bridge section with later cantilevers, experiencing small-amplitude heaving or pitching harmonic oscillations. Unsteady Reynolds-averaged Navier–Stokes equations are solved in conjunction with an eddy-viscosity and an explicit algebraic Reynolds stress model. Flutter derivatives are determined and compared with wind tunnel results, showing fairly good agreement. The degree of sharpness of the deck lower edges is found to play a key role in the aeroelastic behavior of the profile. In particular, the bridge section fully behaves as a bluff body and is prone to low-reduced-wind-speed torsional galloping in the case of perfectly sharp edges. By contrast, the presence of a small radius of curvature in the section lower corners changes the nature of the instability to coupled flutter and significantly postpones the stability threshold, in line with a quasi-streamlined body behavior. Moreover, a wide sensitivity study is carried out, investigating the influence on the self-excited forces of the amplitude of oscillation, mean angle of attack and Reynolds number. In particular, the numerical simulations for the geometry with smooth lower edges highlight the regime transition occurring when the Reynolds number is varied, with significant effects on the flutter derivatives. Finally, the numerical flow visualizations provide a physical explanation of some phenomena observed in the wind tunnel experiments.

Variation of aerodynamic coefficients with air flow parameters on long span bridge deck

Wind load is critical for bridges with high strength to weight ratio and determined experimentally using wind tunnel study that involves huge expenditure and time. In this study, behaviour of bridge deck is analysed by changing air flow parameters considering the structure submerged in turbulent flow using k-e turbulence model with boundary conditions calibrated to simulate neutral equilibrium atmospheric boundary layer. A computational model was considered to determine aerodynamic behaviour of bridge deck for different angle of attack of wind and results were compared with wind tunnel experiments keeping boundary conditions same. The aerodynamic behaviour of different bridge deck cross section are analysed using the computational model for different air flow parameters. The variation of aerodynamic coefficients are found and presented for box girder, plate girder, trapezoidal section and section of Great Belt East Bridge and attempt was made to select the optimum section to minimise the aerodynamic forces.

Application of Approximate Iterative Method on Section Precision Forming of Boom-type Roadheader

The decision of the inflection point is the key to ensure automatic section cutting precision using a boom-type road header. In this paper, cutting precision model was set up for the first time to trapezoidal section and a method deter- mining inflection point is given. Considered the cutting head' projection at section is elliptical with the cantilever's joint variable. The relationship between ellipse curve and cutting section boundary was investigated, and thereby sets up the cutting precision model. Approximate iterative method is used to finding the optimal inflection point, of which takes the cutting precision as the objective function. Compared with the traditional process path planning method, the forming ac- curacy can be improved greatly and controlled within 1mm. Through MATLAB simulation, it is proved that this method is correct and valid.

Examining Fundamental Problems of APC Canal Concrete Lining and Strategies to Solve them

Background/Objectives: In this research, various reasons of creation of crack irrigation canals, uplift, and failure of concrete lining, and coping strategies with these problems were investigated. Methods/Statistical Analysis: In the main APC canal, the primary type of the canal trapezoid section includes executing a filter at the bottom of the canal, executing soil-cement mixture, and then executing a concrete lining at the walls of the canal. The final type of the canal trapezoid section reformed executing a filter in the bottom and walls of the canal, executing a lean concrete, and then executing the main concrete lining at the bottom and walls of the canal, and also executing a one-sided valve at the bottom of the canal. Findings: After executing the primary type of the canal section in the first 13 kilometers of the beginning of the APC canal, the phenomenon of crack and uplift have been observed in the concrete lining of the canal wall. However, by changing the properties of canal section and replacing the lean concrete and filter with soil-cement mixture, problems of the concrete lining were noticeably reduced. In this research, reasons of probability of creation of phenomena such as failure, crack, and uplift including executive problems, rising of groundwater level, compaction of the canal body soil, problems due to execution of soil-cement mixture, problems caused by construction joints between panels of the floor and wall of canal, and also other factors were investigated. It is resulted that execution of filter and lean concrete under concrete lining of the canal wall and execution of one-sided valve (Barbakan) has had a noticeable effect on preventing from destructive factors of the concrete lining of canal walls and consequently preventing from creation of crack and uplift phenomena. Applications/Improvements: By modifying properties of substructure material of the canal lining, problems of concrete lining will be noticeably decreased and each year a large volume of water resources will be saved.

Procedimiento para la obtención de cargas últimas de arcos de perfiles conformados en frío

This paper deals with a new methodology for the estimation of the strength of circular arches with cold-formed trapezoidal section. These cover elements, mainly subjected to compression stress and with circular curvature should be dimensioned taking into account the possibility of buckling instability. Currently, no standard describes a method for calculating the buckling consideration of curved elements. The methodology proposed herein shares the same philosophy of the European buckling curves method established in the Eurocodes. Thus, an experimental coefficient considering the effects of buckling and geometrical and mechanical imperfections depending on the slenderness of the considered arch have been obtained. For this, it was necessary to determine the experimental strength of at least three arcs, which radius and spans are sufficiently differentiated.

EFFECT OF CERAMIC POWDER (CP) ON COMPRESSIVE STRENGTH AND DRYING SHRINKAGE CRACKS OF CEMENT MORTAR

This investigation is conducted to study the effect of addition of ceramic powder (CP) on drying shrinkage cracks and compressive strength of cement mortar. Steel molds having a trapezoidal section, and the end restrained at square shape used to study restrained drying shrinkage of cement mortar. Specimens of compressive strength, density, were cast. The admixture (CP) was used as addition with three levels of (2%, 4% and 8%) by weight of dry cement. All specimens were cured for (14 days). Average of six results was taken for any test of compressive strength and density. The experimental results showed that the adding of this admixture cause a delay in a formation of cracks predicted from a drying shrinkage, increase compressive strength at levels of (4%) of admixture and cause the decreasing in the density of cement mortar Specimens. The increment in compressive strength at level (4%) was (6.11%), but at level of (8%) it was decreased by (3.9%). The admixture has the visible effect in delay of the information of shrinkage cracks and decrease of its number.

TWO DIMENSIONAL NUMERICAL MODELING OF FLOW IN TRAPEZOIDAL BEND CHANNEL USING SPUR DIKE

A two-dimensional hydraulic flow model was developed using the SMS software (Surface Water Modeling System) to simulate the flow properties(thalweg line location) for meander in trapezoidal section channel, and its changes when a single emerge spur dike install at mid of the bend. The model was calibrated and verified through matching velocity profiles throughout the study reach. Thalweg line location were found due to the variation of spur dike characteristic including 180 runs, included five different ratios of spur dike length to top channel width (L/Tw), five ratios of spur dike arm to its body length (l/L), and two spur arm`s direction for four different flow rates, as a result, through the flow configuration the new location of the thalweg in the bend channel after using the spur dike was about (44-71)%Tw which mainly affected by spur body length.

Fracture mechanics analysis approach to assess structural integrity of the first confinement boundaries in ITER Generic Upper Port Plug structure

This paper demonstrates structural integrity of the first confinement boundary in Generic Upper Port Plug structures against cracking during service. This constitutes part of the justification to demonstrate that the non-aggression to the confinement barrier requirement may be compatible with the absent of a specific in-service inspections (ISI) program in the trapezoidal section. Since the component will be subjected to 100% volumetric inspections it can be assumed that no defects below the threshold of applied Nondestructive Evaluation techniques will be present before its commissioning. Cracks during service would be associated to defects under Code acceptance limit. This limit can be reasonably taken as 2mm. Using elastic–plastic fracture mechanics an initial defect is postulated at the worst location in terms of probability and impact on the confinement boundary. Its evolution is simulated through finite element analysis and final dimension at the end of service is estimated. Applying the procedures in RCC-MR 2007 (App-16) the stability of the crack is assessed. As relative high safety margin was achieved, a complementary assessment postulating an initial defect of 6mm was also conducted. New margin calculated provides a more robust design.

Dam-break characteristics of landslide dams with different types of open channel discharge sections

The excavation of artificial open channels in landslide dams is one efficient method for reducing the risks of landslide lake formation. This method has often been used in emergencies to eliminate landslide lakes in earthquake-prone areas of Wenchuan, China. In this study, the dam-break characteristics of landslide dams with different open channel cross sections and longitudinal sections were evaluated. The degree of headward erosion was extremely strong in the natural dam-break experiment and moderately strong in the compound-section dam-break experiment. The degree of headward erosion in the open channel with the trapezoidal section was comparatively mild. Furthermore, the natural dam break resulted in large peak discharge and short dam-break duration. By contrast, the artificially opened channel dam breaks resulted in peak discharges that were approximately 7.7-20.1 % lower than those of natural dam breaks, and the dam-break duration (i.e., the time until the dam broke) was longer than that of the natural dam breaking. The channels with gentle-steep slopes or alternating gentle-steep slopes resulted in greater discharge rates, and a significant amount of erosion occurred due to these open channels. The degree of headward erosion in the channel with alternating gentle-steep slopes was greater than that in the other channels. The peak discharges of the open channels with gentle-steep slopes or alternating mild-steep slopes were approximately 29.6-65.0 % greater than those of the open channel with a linear section. A channel with a triangular cross section and a linear longitudinal section should be used to dispose of small landslide lakes. However, channels with compound cross sections and longitudinal sections with alternating slopes should be used for large or medium landslide lakes.

Computational Performance of an Embedded Reinforcement Mesh Generation Method for Large-Scale RC Simulations

In this paper, a numerical investigation on the limits of an automatic procedure for the generation of embedded steel reinforcement inside hexahedral finite elements (FEs) is presented. In 3D detailed reinforced concrete simulations, mapping the reinforcement grid inside the concrete hexahedral FEs is performed using the end-point coordinates of the rebar reinforcement macro-elements. This procedure is computationally demanding while in cases of large-scale models, the required computational time for the reinforcement mesh generation is excessive. This research work scopes to study and present the limitations of the embedded mesh generation method that was proposed by Markou and Papadrakakis, through the use of a 64-bit operating system. The embedded mesh generation method is integrated with a filtering algorithm in order to allocate and discard relatively short embedded rebar elements that result from the arbitrary positioning of the embedded rebar macro-elements and the nonprismatic geometry of the hexahedral mesh. The computational robustness and efficiency of the integrated embedded mesh generation method are demonstrated through the analysis of three numerical models. The first two numerical models are a full-scale 2-story and a 7-story RC structures while the third model deals with a full-scale RC bridge with a trapezoidal section and a total span of 100 m. Through the third numerical implementation, the computational capacity of the integrated embedded rebar mesh generation method is investigated.

Horizontal bottomed semi-cubic parabolic channel and best hydraulic section

This paper presents a new channel section having semi-cubic parabolic sides and horizontal bottom. The formulae for calculating the area, wetted perimeter are presented. The best hydraulic section is derived using three variables (water depth, water surface width and horizontal bottom width). Results show the ratios of the water surface width to depth, bottom width to depth and water surface width to bottom are all constant for the best hydraulic section. Explicit equations of the best hydraulic section for design are also deduced. Examples show these explicit equations are convenient for design. This type of best hydraulic section is compared with the trapezoid and classic semi-cubic parabolic sections. Results indicate that the area and wetted perimeter are less than those of trapezoid and classic semi-cubic parabolic sections for a given flow discharge. It means less lining and excavation cost is required for construction.

Design and numerical simulation on coupled flow field of radial turbine with air-inlet volute

As one of the core components of turbocharger or micro-turbine, radial turbine has the features of small size and high rotation speed. In order to explore the design method and flow mechanism of the turbine with a volute, a centimeter-scale radial turbine with a vaneless air-inlet volute was designed and simulated numerically to investigate the characteristics of the coupled flow field. The results show that the wheel efficiency of single passage computation without the volute is 80.1%. After accounting for the factors of the loss caused by the volute and the interaction between each passage, the performance is more accurate according to the whole flow passage computation with the volute. High load region gathers at the mid-span and the efficiency declines to 76.6%. The performance of the volute whose structure angle of the trapezoid section is equal to 70 degree is better. Unlike uniform inlet condition in single passage, more appropriate inlet flow for the impeller is provided by the rectification effect of the volute in full passage calculation. Flow parameters are distributed more evenly along the blade span and are generally consistent between each passage at the outlet of the turbine.

Finite Element Analysis of Crane Hook and Optimization Using Taguchi Approach

A Crane hook is a device for grabbing and lifting loads of heavy duty by mean of a device such as crane hoist. A crane hook is usually equipped with a safety latch to prevent the disengagement of the lifting rope to which the load is being attach. The CAD model of a lifting crane hook is initially prepared from the Analytical Design. In the present report crane hook of trapezoidal section is modeled using UG-NX 8.0, further, importing the CAD model into ANSYS 15.0 we estimate until 20 tones i.e. equivalent to 200000N load to be gradually applied, eventually we observed the von-misses stress developed in the model by FEM method these results vonmisses stresses are being compared with Taguchi L9 orthogonal array for specific results. Thus, these results would lead us to determine various stresses and deflections in the designed CAD model. In order to reach the most optimum model from different materials of hook would be tested and the most efficient material would be selected.

Finite Element Analysis of Crane Hook And Optimization Using Taguchi Approach

A Crane hook is a device for grabbing and lifting loads of heavy duty by mean of a device such as crane hoist. A crane hook is usually equipped with a safety latch to prevent the disengagement of the lifting rope to which the load is being attach. The CAD model of a lifting crane hook is initially prepared from the Analytical Design. In the present report crane hook of trapezoidal section is modeled using UG-NX 8.0, further, importing the CAD model into ANSYS 15.0 we estimate until 20 tones i.e. equivalent to 200000N load to be gradually applied, eventually we observed the von-misses stress developed in the model by FEM method these results von-misses stresses are being compared with Taguchi L9 orthogonal array for specific results. Thus, these results would lead us to determine various stresses and deflections in the designed CAD model. In order to reach the most optimum model from different materials of hook would be tested and the most efficient material would be selected.

Variable parameter McCarthy–Muskingum routing method considering lateral flow

Summary The fully mass conservative variable parameter McCarthy–Muskingum (VPMM) method recently proposed by Perumal and Price (2013) for routing floods in channels and rivers without considering lateral flow is extended herein for accounting uniformly distributed lateral flow contribution along the reach. The proposed procedure is applied for studying flood wave movement in a 24.2 km river stretch between Rottweil and Oberndorf gauging stations of Neckar River in Germany wherein significant lateral flow contribution by intermediate catchment rainfall prevails during flood wave movement. The geometrical elements of the cross-sectional information of the considered routing river stretch without considering lateral flow are estimated using the Robust Parameter Estimation (ROPE) algorithm that allows for arriving at the best performing set of bed width and side slope of a trapezoidal section. The performance of the VPMM method is evaluated using the Nash–Sutcliffe model efficiency criterion as the objective function to be maximized using the ROPE algorithm. The twenty-seven flood events in the calibration set are considered to identify the relationship between ‘total rainfall’ and ‘total losses’ as well as to optimize the geometric characteristics of the prismatic channel (width and slope of the trapezoidal section). Based on this analysis, a relationship between total rainfall and total loss of the intermediate catchment is obtained and then used to estimate the lateral flow in the reach. Assuming the lateral flow hydrograph is of the form of inflow hydrograph and using the total intervening catchment runoff estimated from the relationship, the uniformly distributed lateral flow rate q L at any instant of time is estimated for its use in the VPMM routing method. All the 27 flood events are simulated using this routing approach considering lateral flow along the reach. Many of these simulations are able to simulate the observed hydrographs very closely. The proposed approach of accounting lateral flow using the VPMM method is independently verified by routing flood hydrograph of 6 flood events which are not used in the total rainfall vs total loss relationship established for the intervening catchment of the studied river reach. Close reproduction of the outflow hydrographs of these independent events using the proposed VPMM method accounting for lateral flow demonstrate the practical utility of the method.

Width effects on hydrodynamics of pendulum wave energy converter

Based on two- and three-dimensional potential flow theories, the width effects on the hydrodynamics of a bottom-hinged trapezoidal pendulum wave energy converter are discussed. The two-dimensional eigenfunction expansion method is used to obtain the diffraction and radiation solutions when the converter width tends to be infinity. The trapezoidal section of the converter is approximated by a rectangular section for simplification. The nonlinear viscous damping effects are accounted for by including a drag term in the two- and three-dimensional methods. It is found that the three-dimensional results are in good agreement with the two-dimensional results when the converter width becomes larger, especially when the converter width is infinity, which shows that both of the methods are reasonable. Meantime, it is also found that the peak value of the conversion efficiency decreases as the converter width increases in short wave periods while increases when the converter width increases in long wave periods.