Trapezoidal Profile Research Articles

A parametric investigation of the heat transfer enhancement of tube bank heat exchanger with reversed trapezoidal profile fins

In this study, a reversed trapezoidal profile fins attachment to the tube bank heat exchanger was proposed to enhance the heat transfer performance. A validated computational fluid dynamics (CFD) model was used to investigate the flow behaviour and thermal performance of the staggered tube bank heat exchanger with reversed trapezoidal profile fins. The simulation employed the RNG k-ε model with enhanced wall treatment. The effects of fins’ angle (2°≤αtf ≤ 10°), length (0.5D ≤ Ltf ≤ 2D) and thickness (1 mm ≤ Htf ≤ 5 mm) within a range of Reynolds number (5500 ≤ Re ≤ 14500) were discussed. Nusselt number (Nu), pressure drop (ΔP) and performance evaluation criterion (PEC) were used to evaluate the heat exchanger’s performance. The results showed that both Nu and ΔP followed an increasing trend as αtf increased, which indicates a heat transfer enhancement and a larger airflow resistance. As Ltf increased from 0.5D to 2D, Nu showed a continuous increase with the maximum value obtained at Ltf = 2D. However, ΔP showed a tendency to increase and then decrease as Ltf increased, with the maximum value observed at Ltf = 1.25D. A larger thickness resulted in a higher airflow resistance penalty compared to the improvement in Nu. The thickness was recommended to be as small as possible, provided that the manufacturing process and mechanical strength requirements were met. If the adverse effect of pressure drop was not of concern, the optimal thermal–hydraulic performance (PEC) could be obtained at a larger angle, length and smaller thickness.

Optimization of transformer ratio and beam loading in a plasma wakefield accelerator with a structure-exploiting algorithm

Plasma-based acceleration has emerged as a promising candidate as an accelerator technology for a future linear collider or a next-generation light source. We consider the plasma wakefield accelerator (PWFA) concept where a plasma wave wake is excited by a particle beam and a trailing beam surfs on the wake. For a linear collider, the energy transfer efficiency from the drive beam to the wake and from the wake to the trailing beam must be large, while the emittance and energy spread of the trailing bunch must be preserved. One way to simultaneously achieve this when accelerating electrons is to use longitudinally shaped bunches and nonlinear wakes. In the linear regime, there is an analytical formalism to obtain the optimal shapes. In the nonlinear regime, however, the optimal shape of the driver to maximize the energy transfer efficiency cannot be precisely obtained because currently no theory describes the wake structure and excitation process for all degrees of nonlinearity. In addition, the ion channel radius is not well defined at the front of the wake where the plasma electrons are not fully blown out by the drive beam. We present results using a novel optimization method to effectively determine a current profile for the drive and trailing beam in PWFA that provides low energy spread, low emittance, and high acceleration efficiency. We parameterize the longitudinal beam current profile as a piecewise-linear function and define optimization objectives. For the trailing beam, the algorithm converges quickly to a nearly inverse trapezoidal trailing beam current profile similar to that predicted by the ultrarelativistic limit of the nonlinear wakefield theory. For the drive beam, the beam profile found by the optimization in the nonlinear regime that maximizes the transformer ratio also resembles that predicted by linear theory. The current profiles found from the optimization method provide higher transformer ratios compared with the linear ramp predicted by the relativistic limit of the nonlinear theory.

Equivalent flat-web thicknesses and modified flange-based moment resistance for corrugated-web steel I-girders

This study proposed analytical formulations for equivalent flat-web thicknesses at horizontal and inclined fold sections and modified flange-based moment resistance for corrugated-web girders (CWGs), accounting for the accordion effect due to corrugations. The finite element (FE) analysis approach was used for examining the nonlinear flexural behavior of CWGs. Numerical models were first validated against flexural tests from two documented CWG studies. For additional verification, nonlinear theoretical analysis of flat-web girders was compared and verified against detailed FE-based analysis results. A detailed parametric study was performed to examine the effect of corrugated-web trapezoidal profiles and girder geometry on the moment resistance of CWGs using the validated nonlinear FE modeling. Then, the parametric study results were used in the theoretical nonlinear moment-curvature analysis on equivalent flat-web girders to derive the proposed formulations for flat-web thicknesses at horizontal and inclined fold sections of a CWG. Alternatively, a modified flange-based moment resistance formulation was proposed for CWGs by accounting for the accordion effect of their trapezoidal corrugated webs. Both the proposed formulations simplified the accordion effect analysis in CWGs and can result in potentially economical girder designs and further development of design specifications for CWGs.

Protein Stability─Analysis of Heat and Cold Denaturation without and with Unfolding Models.

Protein stability is important in many areas of life sciences. Thermal protein unfolding is investigated extensively with various spectroscopic techniques. The extraction of thermodynamic properties from these measurements requires the application of models. Differential scanning calorimetry (DSC) is less common, but is unique as it measures directly a thermodynamic property, that is, the heat capacity Cp(T). The analysis of Cp(T) is usually performed with the chemical equilibrium two-state model. This is not necessary and leads to incorrect thermodynamic consequences. Here we demonstrate a straightforward model-independent evaluation of heat capacity experiments in terms of protein unfolding enthalpy ΔH(T), entropy ΔS(T), and free energy ΔG(T)). This now allows the comparison of the experimental thermodynamic data with the predictions of different models. We critically examined the standard chemical equilibrium two-state model, which predicts a positive free energy for the native protein, and diverges distinctly from the experimental temperature profiles. We propose two new models which are equally applicable to spectroscopy and calorimetry. The ΘU(T)-weighted chemical equilibrium model and the statistical-mechanical two-state model provide excellent fits of the experimental data. They predict sigmoidal temperature profiles for enthalpy and entropy, and a trapezoidal temperature profile for the free energy. This is illustrated with experimental examples for heat and cold denaturation of lysozyme and β-lactoglobulin. We then show that the free energy is not a good criterion to judge protein stability. More useful parameters are discussed, including protein cooperativity. The new parameters are embedded in a well-defined thermodynamic context and are amenable to molecular dynamics calculations.

Modelling of a semi-active vibration absorber featuring variable stiffness and variable damping using magnetorheological materials

This study focuses on vibration control and presents an innovative hybrid shock absorber with variable damping and stiffness. The simultaneous control over damping and stiffness is achieved using the Magnetorheological (MR) fluid and MR elastomer, respectively. A mathematical and Simulink model is developed by adding the four-parametric fluid model with the Bouc-Wen model. Two different road profiles, circular bump road and trapezoidal bump road profiles, are considered to analyze the performance of vibration absorbers. The compared results show the superiority of the proposed isolator over the passive system and reveal that the vehicle stability is improved by 87.5% to 92% and ride comfort is improved by 84.85% to 85.99% for circular and trapezoidal bump road profiles, respectively.

Reinforced toothed belt of standard overall dimensions

A constructive modification of a standard toothed belt with a trapezoidal tooth profile is considered. Analytical dependencies are obtained and numerical analysis is performed for a specific size of the toothed belt. Keywords: toothed belt, modification, tooth profile, comparative analysis. shevchenko6-32@yandex.ru, mukhovatiy@mail.ru

Porthole die extrusion of aluminum 6063 industrial scrap by shear assisted processing and extrusion

Shear Assisted Processing and Extrusion (ShAPE) is presented as a new manufacturing technology for converting aluminum scrap directly into extruded products. In this work, a porthole die configuration is integrated within the rotating ShAPE process to extrude circular, square, trapezoidal, and two-cell trapezoidal profiles from aluminum alloy 6063 industrial scrap. Microstructural characterization is presented for a trapezoidal profile having an average grain size of 6.7 µm in the as-extruded condition. Round tubes achieved yield strength (246.9 ± 10.4 MPa), ultimate tensile strength (270.8 ± 9.6 MPa), and uniform elongation (16.5 ± 2.4%) exceeding industry standards.

Effect of Wire Design (Profile) on Sand Retention Parameters of Wire-Wrapped Screens for Conventional Production: Prepack Sand Retention Testing Results

There are many technologies to implement sand control in sand-prone wells, drilled in either weakly or nonconsolidated sandstones. Technologies that are used to prevent sanding can be divided into the following groups: screens (wire-wrapped screens, slotted liners, premium screens, and mesh screens), gravel packs, chemical consolidation, and technological ways (oriented perforation and bottomhole pressure limitation) of sanding prevention. Each particular technology in these groups has their own design and construction features. Today, slotted liners are the most well-studied technology in terms of design, however, this type of sand control screen is not always accessible, and some companies tend towards using wire-wrapped screens over slotted liners. This paper aims to study the design criteria of wire-wrapped screens and provides new data regarding the way in which wire design affects the sanding process. Wires with triangular (wedge), trapezoidal, and drop-shaped profiles were tested using prepack sand retention test methodology to measure the possible impact of wire profile on sand retention capabilities and other parameters of the sand control screen. It was concluded that a trapezoidal profile of wire has shown the best result both in terms of sand production (small amount of suspended particles in the effluent) and in particle size distribution in the effluent, that is, they are the smallest compared to other wire profiles. As for retained permeability, in the current series of experiments, high sand retention did not affect retained permeability, although it can be speculated that this is mostly due to the relatively high particle size distribution of the reservoir.

SEM Measurements of the Dimensions of Relief Structures in the Technological Process of Manufacturing Microcircuits

The problems of measuring the dimensions of relief elements on a scanning electron microscope (SEM) in the technological process of manufacturing microcircuits are considered. The first problem is related to the fact that the increase in the SEM during operation can vary over a wide range depending on the measured dimensions. The second problem is that the probe diameter determined in the SEM calibration process differs from the diameter used in operational measurements. The third problem is related to the fact that it is not known which relief parameter is measured in the SEM probe defocusing method. It is shown that to solve the first problem, it is necessary to calibrate the mark on the image using structures with a trapezoidal profile and large angles of inclination of the side walls. The solution of the second problem is based on the method of defocusing the SEM probe: determining the dependence of the sizes between certain points on the SEM signals on the probe diameter and extrapolating this dependence to the zero value of the diameter. The third problem is solved with the help of a virtual scanning electron microscope.

NOX EMISSION ON RECIPROCAL FILTRATION COMBUSTION OF BIOGAS: A CASE STUDY

Filtration combustion is an effective technique for dealing with low-calorific value fuels, such as derivative fuels from biomass, and simultaneously reducing pollutant emissions. In this study, combustion of biogas (22% of CO2) was investigated theoretically and experimentally by utilizing a reciprocal flow porous burner with heat exchangers inserted in the porous medium. Combustion of lean biogas-air mixtures is stabilized in a naturally transient process, in which a lean equivalence ratio range (0.1 ≤ Φ ≤ 0.9) and gas flow velocities of 0.2 and 0.3 m/s were employed, periodically switching gas flow direction. Reciprocal flow combustion has been compared with unidirectional combustion, using technical methane as reference gas. In this context, predicted temperature profiles inside the burner, as well as experimental results, have shown that the reciprocating system plays an important role in the combustion process, significantly improving flammability limits, efficiency, and emissions. As result, trapezoidal temperature distribution profiles have been obtained with peaks between 1200 and 1600 K, reaching high efficiency up to 90% and ultra-low emission of nitrogen oxides (≤ 2ppm).

Dynamical theory of X-ray diffraction by crystals with different surface relief profiles.

A dynamical theory is developed of X-ray diffraction on a crystal with surface relief for the case of high-resolution triple-crystal X-ray diffractometry. Crystals with trapezoidal, sinusoidal and parabolic bar profile models are investigated in detail. Numerical simulations of the X-ray diffraction problem for concrete experimental conditions are performed. A simple new method to resolve the crystal relief reconstruction problem is proposed.

Effects of Velocity Profile and Plate Usage on Identified Bone Strength during Instrumented Screw Insertion

Bone screws are important in orthopaedic surgery to treat fractures and secure implants. Over- or under-tightening these screws may lead to premature failure of the screw fixation, necessitating risky and costly revision surgery. Previously, a model-based method for automatically optimising bone screw insertion torque was developed. This paper expands on the prior testing of this method, to investigate how non-ideal conditions may affect the model accuracy/precision.A bone screw was inserted into pre-drilled holes in artificial bone made from PU foam. Three cases were tested: first the screw was inserted directly with a constant velocity, then it was inserted with a trapezoidal velocity profile, and lastly it was inserted with a constant velocity profile, but through a hole in a metal plate. Each case was repeated 20 times for 60 total insertions. Torque and angular displacement measurements were used with a previously-developed model to identify the foam material strength for each insertion. Summary statistics were calculated for each case and statistical tests were used to compare the means and variances for the identified values between each case.Comparing to base base case with constant velocity and no plate: we found a statistically significant (p < 0.05) difference in the mean identified strength for the trapezoidal velocity and the case with the plate. We found a statistically significant difference in the variance for the trapezoidal velocity profile (p < 0.05), but not for case with the plate present (p = 0.16).Future work should investigate these effects over a wider range of materials and screws.

Angular Error Reduction of a Machine Vision System using a Trapezoidal Trajectory Velocity Profile

Nowadays laser scanners play an important role in technology and research, when it comes to measure 3D coordinates physically and in real time of any object under observation. Laser scanners have to measure the 3D coordinates of these objects in shortest time and with the smallest measuring error. A novel laser scanner called Technical Vision System (TVS), which uses Dynamic Triangulation and DC motors, was developed and proven to represent a fast and reliable scanning system. Previous research used the step response of the TVS mechanical actuators (DC motors), which can overshoot if certain controller parameters of the closed-loop control are selected. If the overshoot is undesirable, a trade-off must be made between speed and overshoot of the step response. Thereby, present paper describes a new approach to control the actual angular position of the TVS DC motors using a trapezoidal profile for the DC Motor velocity. The DC motors step response is replaced by a trajectory response, which allows the reduction of the relative angular error of the DC motors shaft to a value less than or equal to 0.1 percent. Also, the design of the control system, to implement the trapezoidal trajectory profile for the DC motor velocity in practice, is described in detail.

Dependence of the performance of the reclaiming sewer cleaner with rigid guides from interchangeable bucket tools capabilities

Relevance. Cleaning of reclamation channels is a very relevant event. The need to clean the canals and maintain them in working condition becomes obvious during the flood period, when it is necessary to remove excess water. The paper presents mathematical models for determining the performance of the PP-303 canal cleaner, a feature of which is the rectilinear movement of the bucket on rigid guides along the bottom along the axis of the canal to be cleaned.Methods. The article is formed on the basis of experimental research methods. The research was carried out based on experimental and calculated data. A network of drainage canals of the drainage system was taken as the research object, and the working equipment of the canal cleaner was taken as the research subject. Performance, which is the amount of products produced by the machine per unit of time, can be of three types (theoretical, technical, and operational) and can be determined with consideration of the design parameters of the working equipment. During the operation of trench cutting machines, their performance directly depends on the main parameter, namely, the depth of the canal being built; in the case of canal cleaning with canal cleaners, this parameter cannot be considered as the main one. This is due to the fact that siltation and sediments accumulating on the bottom and slopes of the canals during the operation of the reclamation system are extremely unevenly distributed along the length of the canal. The highest concentration and amount of sediments and siltation is observed mainly at the mouth of the canals, the junctions of canals of different levels, and the junctions of the drainage with the drainage canal. In this case, the most significant parameter is the thickness of the chips removed from the bottom and slopes of the canal by the bucket.Results. The results of the research showed that the performance of the channel cleaner, as a batch machine, is influenced by the very design of the working equipment, the main element of which is a bucket capable of moving in a straight line along rigid guides at different speeds. With obvious high values of the performance of continuous channel cleaning machines, it can be concluded that the channel cleaner RR-303 showed high values of technical and operational characteristics, mainly due to the use of a trapezoidal profile bucket.

Exploitation of Energy Optimal and Near-Optimal Control for Traction Drives with AC Motors

The main contribution of this paper is the verification of a new train control system applied to the drive with a.c. motors that is energy near optimal with respect to electrical and mechanical energy minimization. All simulations are related to the one traction motor yielding its best exploitation. Load torque treated as a state variable consists of constant, linear, and quadratic components as a function of rotor speed. The required performance of the energy-saving control is rendered straightforward using precomputed energy optimal state variables or a prediction of losses for a symmetrical trapezoidal speed profile as the second alternative. An energy-saving reference position generator provides the state variables, which are faithfully followed by a feedback control based on field orientation, which is completed with a matched zero dynamic lag pre-compensator yielding prescribed closed-loop dynamics. Simulation results mutually compared confirm the capability of an overall drive control system to follow generated state variables for two different service conditions and the possibility of energy savings.

Parametric Study on Steel–Concrete Composite Beams Strengthened with Post-Tensioned CFRP Tendons

A sustainable environment can be achieved by strengthening the existing building to avoid new construction and by replacing the construction materials with long-lasting sustainable materials such as a fiber-reinforced polymer (FRP). Using post-tensioned (PT) FRP systems has proven to be an effective technique in strengthening the structure and decreasing cracks and deformability. In this study, a 3-D finite element model was built to investigate the flexural behavior of composite beams strengthened with external PT FRP tendons. Limited research studied the use of FRP tendons to enhance the structural behavior of composite beams. This paper represents a comprehensive study of the effect of several parameters that control the design of the FRP tendons. Parameters such as PT level, tendon material, tendon length, degree of shear connection (DOSC), and tendon profile shape were considered under loading. The 3-D model’s correctness is validated using published experimental data. It was observed that of all FRP materials, carbon FRP is the best type for upgrading the beam strength, and it was recommended to use a 30 to 40% PT level. In addition, applying external PT over the full length of the beam increases the ultimate load capacity significantly. However, due to the difficulty of construction, it was recommended to use 90% of the beam span length since the difference in beam capacity does not exceed 5%. Finally, adding PT tendons with a trapezoidal and parabola profile to composite beams significantly increases the yield load and the beam capacity.

Uniform vs. Lognormal Kinematics in Robots: Perceptual Preferences for Robotic Movements

Collaborative robots or cobots interact with humans in a common work environment. In cobots, one under-investigated but important issue is related to their movement and how it is perceived by humans. This paper tries to analyze whether humans prefer a robot moving in a human or in a robotic fashion. To this end, the present work lays out what differentiates the movement performed by an industrial robotic arm from that performed by a human one. The main difference lies in the fact that the robotic movement has a trapezoidal speed profile, while for the human arm, the speed profile is bell-shaped and during complex movements, it can be considered as a sum of superimposed bell-shaped movements. Based on the lognormality principle, a procedure was developed for a robotic arm to perform human-like movements. Both speed profiles were implemented in two industrial robots, namely, an ABB IRB 120 and a Universal Robot UR3. Three tests were used to study the subjects’ preference when seeing both movements and another analyzed the same when interacting with the robot by touching its ends with their fingers.

Cyclic performance of moment connections with reduced beam sections using different cut-flange profiles

Abstract Reduced beam section (RBS) behaviours with various cut-flange configurations were investigated numerically in this study. A three-dimensional finite element model material non-linearity was built and validated experimentally, and the impacts of the cut--flange profile on the moment-rotation behaviour and ductility response of moment-resisting connections were investigated in a parametric form. Five-moment connections with various forms of decreasing beam flange were thus modelled using ABAQUS software and compared in terms of cyclic behaviour. RBS with circular, rectangular, trapezoidal, triangular, and drilled holes cut-flange configurations were adopted, and the finite element analysis results showed that radius cut RBS have uniform stress contours, while a re-entrant corner in rectangular, trapezoidal, or triangular cut-flange profiles’ connections may result in stress concentration, resulting in a fracture of the flange. In addition, the numerical testing showed that the RBS connection with a circular cut-flange profile offers a lower rupture index than other connections. Thus, the RBS created using circular cut-flange profiles dissipates more energy than other connections.

A soft pneumatic glove with multiple rehabilitation postures and assisted grasping modes

This article proposes a novel soft pneumatic glove with multiple rehabilitation postures and assisted grasping modes, which is composed of five segmented pneumatic networks (PneuNets) bidirectional bending actuators with a variable height structure. The metacarpophalangeal (MCP) joint chambers and the distal phalangeal (DIP) joint chambers are designed with a trapezoidal side profile, which enhances the reverse bending ability and can effectively expand the range of hand rehabilitation activities. In order to avoid hindering the forward bending, the chambers of the reverse bending module are designed as a triangular prism chamber. Experimental tests were performed and the results show that the soft actuator can produce a bending angle of 261° under an air pressure of 100 kPa, and can produce a fingertip force of 1.59 N under an air pressure of 130 kPa. In the rehabilitation mode, the designed soft rehabilitation gloves can help the hand to form four kinds of rehabilitation postures, namely full fist, straight fist, hook fist and table top. By ventilating different finger joints, and it can also help the fingers to stretch. Under the initial air pressure of 60 kPa, the design of the reverse bending module can increase the fingertip force of reverse bending by 40 %. In the assisted grasping mode, by adjusting the input air pressure, it can help the hand to grasp objects with cylindrical and large plane contour, which is very useful for the rehabilitation of patients with partial loss of hand function. • A novel soft pneumatic glove with multiple rehabilitation postures and assisted grasping modes is proposed. • The soft glove is composed of five PneuNets bidirectional bending actuators with a variable height structure. • The soft actuator can produce a angle of 261° under pressure of 100 kPa, and a force of 1.59 N under pressure of 130 kPa.

Impact of Geometry on a Thermal-Energy Storage Finned Tube during the Discharging Process

This work focused on the modelling of latent heat thermal energy storage systems. The mathematical modelling of a melting and solidification process has time-dependent boundary conditions because the interface between solid and liquid phases is a moving boundary. The heat transfer analysis needs the interface position over time to predict the temperature inside the liquid and the solid regions. This work started by solving the classical two-phase (one-dimensional) Stefan problem through a Matlab implementation of the analytical model. The same physical problem was numerically simulated using ANSYS FLUENT, and the good match of analytical and numerical results validated the numerical model, which was used for a more interesting problem: comparing three different latent heat TES configurations during the discharging process to evaluate the most efficient in terms of maximum average discharging power. The three axial heat conduction structures changed only for the fin shape (rectangular, trapezoidal and fractal), keeping constant the volume fractions of steel, aluminium and PCM to perform a proper comparison. Results showed that the trapezoidal fin profile performs better than the rectangular one, and the fractal fin profile geometry was revealed as the best for faster thermal exchange when the solidifying frontier moves away from the steel ring. In conclusion, the average discharging power for the three configurations was evaluated for a time corresponding to a reference value (10%) of the liquid fraction: the rectangular fin profile provided 950.8 W, the trapezoidal fin profile 979.4 W and the fractal fin profile 1136.6 W, confirming its higher performance compared with the other two geometries.