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1
Kennefick, C. M. „Transmission of Elastic Stress Through Circular and Elliptic Cross Sections of Microstructural Elements Embedded in a Matrix Material“. Journal of Applied Mechanics 72, Nr. 4 (30.10.2004): 558–63. http://dx.doi.org/10.1115/1.1935525.
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With the use of contact stress theory and complex variable methods in two dimensions, the transmission of a compressive stress through a circular cross section of a small material particle is calculated in the infinite plane of material below the circular cross section. The circular cross section of the particle is embedded in and completely bonded to an infinite plane of matrix material. It is shown that part of the stress is transmitted with a dependence of 1∕r, where r is a radial coordinate. Additionally, the stress is calculated in two dimensions for the interior of an ellipse that could model a cross section of a grain or particle. The boundary of the ellipse is loaded with the stress holding an elliptic kernel in place in an elastic matrix material after the kernel has undergone a small rotation under an applied tensile load. The resulting stresses are shown in contour plots for elliptic cross sections of varying shapes and orientations.
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Du, L., R. Zhong, H. Sun und Q. Wu. „AUTOMATIC MONITORING OF TUNNEL DEFORMATION BASED ON HIGH DENSITY POINT CLOUDS DATA“. ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W7 (12.09.2017): 353–60. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w7-353-2017.
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An automated method for tunnel deformation monitoring using high density point clouds data is presented. Firstly, the 3D point clouds data are converted to two-dimensional surface by projection on the XOY plane, the projection point set of central axis on XOY plane named U<sub>xoy</sub> is calculated by combining the Alpha Shape algorithm with RANSAC (Random Sampling Consistency) algorithm, and then the projection point set of central axis on YOZ plane named Uyoz is obtained by highest and lowest points which are extracted by intersecting straight lines that through each point of U<sub>xoy</sub> and perpendicular to the two -dimensional surface with the tunnel point clouds, U<sub>xoy</sub> and U<sub>yoz</sub> together form the 3D center axis finally. Secondly, the buffer of each cross section is calculated by K-Nearest neighbor algorithm, and the initial cross-sectional point set is quickly constructed by projection method. Finally, the cross sections are denoised and the section lines are fitted using the method of iterative ellipse fitting. In order to improve the accuracy of the cross section, a fine adjustment method is proposed to rotate the initial sectional plane around the intercept point in the horizontal and vertical direction within the buffer. The proposed method is used in Shanghai subway tunnel, and the deformation of each section in the direction of 0 to 360 degrees is calculated. The result shows that the cross sections becomes flat circles from regular circles due to the great pressure at the top of the tunnel
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El-Ocla, Hosam. „Effects of Medium Characteristics on Laser RCS of Airplane with E-Wave Polarization“. International Journal of Antennas and Propagation 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/515170.
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Plane wave incidence should be postulated to have an authentic target detection. Practically, the plane wave is incapable usually of keeping its power in the far field especially when propagating through an inhomogeneous medium. Consequently, we assume an incident beam wave with a finite width around the target. In this work, we calculate numerically a laser radar cross section (LRCS) of conducting targets having smooth cross sections with inflection points such as airplane in random media. Effects of fluctuations intensity of random media on the LRCS performance are studied in this paper. E-wave polarization (E-wave incidence) is considered while the mean target size is approximately twice the wavelength.
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Fatone, Lorella, Maria Cristina Recchioni und Francesco Zirilli. „Acoustic Scattering Cross Sections of Smart Obstacles: A Case Study“. Communications in Computational Physics 10, Nr. 3 (September 2011): 672–94. http://dx.doi.org/10.4208/cicp.120310.261110a.
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AbstractAcoustic scattering cross sections of smart furtive obstacles are studied and discussed. A smart furtive obstacle is an obstacle that, when hit by an incoming field, avoids detection through the use of a pressure current acting on its boundary. A highly parallelizable algorithm for computing the acoustic scattering cross section of smart obstacles is developed. As a case study, this algorithm is applied to the (acoustic) scattering cross section of a “smart” (furtive) simplified version of the NASA space shuttle when hit by incoming time-harmonic plane waves, the wavelengths of which are small compared to the characteristic dimensions of the shuttle. The solution to this numerically challenging scattering problem requires the solution of systems of linear equations with many unknowns and equations. Due to the sparsity of these systems of equations, they can be stored and solved using affordable computing resources. A cross section analysis of the simplified NASA space shuttle highlights three findings: i) the smart furtive obstacle reduces the magnitude of its cross section compared to the cross section of a corresponding “passive” obstacle; ii) several wave propagation directions fail to satisfactorily respond to the smart strategy of the obstacle; iii) satisfactory furtive effects along all directions may only be obtained by using a pressure current of considerable magnitude. Numerical experiments and virtual reality applications can be found at the website: http://www.ceri.uniromal.it/ceri/zirilli/w7.
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Xia, J., Zhi Jin Wang und A. S. Kretov. „Variable Cross-Section Thin-Walled Composite Structure Modeling Based on the Super-Element Method“. Applied Mechanics and Materials 829 (März 2016): 95–99. http://dx.doi.org/10.4028/www.scientific.net/amm.829.95.
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For slender structures (for example larger aspect ratio wing or fuselage), when they are under loads, the in-plane cross-section shape of these structures remains unchanged. Using this feature, in this paper, a new method called super-element method (SEM) is proposed with the hypothesis of in-plane rigidity. The stiffness matrix of one super-element which has reduced degrees of freedom compared with FEM is derived and they are assembled together to get the stiffness matrix of whole structure. Then through the boundary conditions, the stress and displacement distribution can be calculated out. Calculation analysis of three examples reveals the validity and feasibility of super-element method.
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Wisnom, Michael R., und M. I. Jones. „A Comparison between Interlaminar and In-plane Shear Strength of Unidirectional Glass Fibre-epoxy“. Advanced Composites Letters 3, Nr. 2 (März 1994): 096369359400300. http://dx.doi.org/10.1177/096369359400300205.
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Short beam shear tests have been carried out on square cross-section specimens cut from a 32 ply plate. By rotating the beams through 90° both interlaminar and in-plane strength can be measured with identical specimens. The in-plane shear strength was found to be at least 10% higher than the interlaminar strength.
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Ma, Jun, und Yan Li. „Dynamic Response Analysis of Half-through CFST Arch Bridges Affected by Crossbeams Setting“. Advanced Engineering Forum 5 (Juli 2012): 201–6. http://dx.doi.org/10.4028/www.scientific.net/aef.5.201.
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As one of the most important components of CFST arch bridges, the cross beams should affect the bridges’ dynamic performance and response magnificently by means of affecting these three factors mentioned above. Based on the Maocaojie Bridge, its FEM models of half-through CFST arch bridges with different settings of cross beams are built. The different seismic responses of six operating conditions are calculated with three dimensional earthquake waves input. The internal force and displacement envelope diagrams of arch ribs are extracted and analyzed in situations of in-plane moment, out-plane moment, vertical displacement and transverse displacement. It can conclude that the joint section between arch rib and bridge deck should be designed carefully because of its large displacement and internal force, and the cross beams should be optimized to safety the arch bridge dynamic response considering lateral rigidity. The conclusions may be useful to the seismic design and strengthening treatment of CFST arch bridges. To strengthen the joint section between arch rib and bridge deck or optimize the setting of cross beams will increase the ductility of half-through CFST arch bridge and decrease the damages caused by large earthquake.
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WANG, CHENGPENG, XUANG TIAN und KEMING CHENG. „NUMERICAL INVESTIGATIONS OF PSEUDO-SHOCK WAVES IN VARIABLE CROSS-SECTION DUCTS“. Modern Physics Letters B 23, Nr. 03 (30.01.2009): 485–88. http://dx.doi.org/10.1142/s0217984909018710.
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The Pseudo-Shock Wave (PSW), which appears when supersonic flow in duct decelerates to subsonic, is a complicated process due to the interaction between boundary layer and shock wave. It significantly affects the performance and efficiency of flow devices. In this paper, PSW in two kinds of variable cross-section ducts, edge-varied and corner-varied, was investigated through CFD numerical simulation. Compared to the rectangular duct, a shorter and wider separation region is appeared in the corner of the edge-varied duct while the strongest separation is laterally propagated across the entire plane of the corner-varied duct's side wall. This makes the performances of varied ducts different from traditional constant cross-section ducts.
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Kinugasa, Ryuta, John A. Hodgson, V. Reggie Edgerton und Shantanu Sinha. „Asymmetric deformation of contracting human gastrocnemius muscle“. Journal of Applied Physiology 112, Nr. 3 (01.02.2012): 463–70. http://dx.doi.org/10.1152/japplphysiol.00666.2011.
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Muscle fiber deformation is related to its cellular structure, as well as its architectural arrangement within the musculoskeletal system. While playing an important role in aponeurosis displacement, and efficiency of force transmission to the tendon, such deformation also provides important clues about the underlying mechanical structure of the muscle. We hypothesized that muscle fiber cross section would deform asymmetrically to satisfy the observed constant volume of muscle during a contraction. Velocity-encoded, phase-contrast, and morphological magnetic resonance imaging techniques were used to measure changes in fascicle length, pinnation angle, and aponeurosis separation of the human gastrocnemius muscle during passive and active eccentric ankle joint movements. These parameters were then used to subsequently calculate the in-plane muscle area subtended by the two aponeuroses and fascicles and to calculate the in-plane (dividing area by fascicle length), and through-plane (dividing muscle volume by area) thicknesses. Constant-volume considerations of the whole-muscle geometry require that, as fascicle length increases, the muscle fiber cross-sectional area must decrease in proportion to the length change. Our empirical findings confirm the definition of a constant-volume rule that dictates that changes in the dimension perpendicular to the plane, i.e., through-plane thickness, (−6.0% for passive, −3.3% for eccentric) equate to the reciprocal of the changes in area (6.8% for passive, 3.7% for eccentric) for both exercise paradigms. The asymmetry in fascicle cross-section deformation for both passive and active muscle fibers is established in this study with a ∼22% in-plane and ∼6% through-plane fascicle thickness change. These fiber deformations have functional relevance, not only because they affect the force production of the muscle itself, but also because they affect the characteristics of adjacent muscles by deflecting their line of pull.
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Harding, Brendan, Yvonne M. Stokes und Andrea L. Bertozzi. „Effect of inertial lift on a spherical particle suspended in flow through a curved duct“. Journal of Fluid Mechanics 875 (18.07.2019): 1–43. http://dx.doi.org/10.1017/jfm.2019.323.
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We develop a model of the forces on a spherical particle suspended in flow through a curved duct under the assumption that the particle Reynolds number is small. This extends an asymptotic model of inertial lift force previously developed to study inertial migration in straight ducts. Of particular interest is the existence and location of stable equilibria within the cross-sectional plane towards which particles migrate. The Navier–Stokes equations determine the hydrodynamic forces acting on a particle. A leading-order model of the forces within the cross-sectional plane is obtained through the use of a rotating coordinate system and a perturbation expansion in the particle Reynolds number of the disturbance flow. We predict the behaviour of neutrally buoyant particles at low flow rates and examine the variation in focusing position with respect to particle size and bend radius, independent of the flow rate. In this regime, the lateral focusing position of particles approximately collapses with respect to a dimensionless parameter dependent on three length scales: specifically, the particle radius, duct height and duct bend radius. Additionally, a trapezoidal-shaped cross-section is considered in order to demonstrate how changes in the cross-section design influence the dynamics of particles.
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Humphrey, J. A. C., J. Cushner, M. Al-Shannag, J. Herrero und F. Giralt. „Shear-Driven Flow in a Toroid of Square Cross Section“. Journal of Fluids Engineering 125, Nr. 1 (01.01.2003): 130–37. http://dx.doi.org/10.1115/1.1523066.
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The two-dimensional wall-driven flow in a plane rectangular enclosure and the three-dimensional wall-driven flow in a parallelepiped of infinite length are limiting cases of the more general shear-driven flow that can be realized experimentally and modeled numerically in a toroid of rectangular cross section. Present visualization observations and numerical calculations of the shear-driven flow in a toroid of square cross section of characteristic side length D and radius of curvature Rc reveal many of the features displayed by sheared fluids in plane enclosures and in parallelepipeds of infinite as well as finite length. These include: the recirculating core flow and its associated counterrotating corner eddies; above a critical value of the Reynolds (or corresponding Goertler) number, the appearance of Goertler vortices aligned with the recirculating core flow; at higher values of the Reynolds number, flow unsteadiness, and vortex meandering as precursors to more disorganized forms of motion and eventual transition to turbulence. Present calculations also show that, for any fixed location in a toroid, the Goertler vortex passing through that location can alternate its sense of rotation periodically as a function of time, and that this alternation in sign of rotation occurs simultaneously for all the vortices in a toroid. This phenomenon has not been previously reported and, apparently, has not been observed for the wall-driven flow in a finite-length parallelepiped where the sense of rotation of the Goertler vortices is determined and stabilized by the end wall vortices. Unlike the wall-driven flow in a finite-length parallelepiped, the shear-driven flow in a toroid is devoid of contaminating end wall effects. For this reason, and because the toroid geometry allows a continuous variation of the curvature parameter, δ=D/Rc, this flow configuration represents a more general paradigm for fluid mechanics research.
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Hirayama, H., Y. Einaga, M. Koike und K. Takayanagi. „Recent Development and Application of the XSTM“. Surface Review and Letters 05, Nr. 03n04 (Juni 1998): 797–802. http://dx.doi.org/10.1142/s0218625x98001171.
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The development of the cross-section scanning tunneling microscope (XSTM) and its application to the study of the cross-section of boron(B)-implanted Si wafers are reported. To obtain a cross-section of wafer samples, we examined the cleavage on the {111} plane in two ways. As a result the cleavage, by pushing the side of the sample wafer, was found to be preferable in obtaining a flat {111} cross-section from both (111) and (001) wafers. Our devices in the mounting angle and the guiding line for the cleavage are also described in detail, Using this XSTM, we observed the {111} cleaved cross-sectional surface of the B-implanted Si(111) wafer, The local surface structure was found to change on the cleaved cross-section from the 7 × 7 to the [Formula: see text] reconstruction through the disordered phase, The change was found to be consistent with the depth profile of the implanted B in the Si water. The arrangement of B and Si atoms in the disordered phase was determined by the site and the sample bias dependence of protrusions in STM images.
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Kong, Yike, Lei Liu, Sihao Xia, Honggang Wang und Meishan Wang. „First-principle study on electronic structure and optical properties of GaN nanowires with different cross-sections“. International Journal of Modern Physics B 30, Nr. 22 (06.09.2016): 1650136. http://dx.doi.org/10.1142/s0217979216501368.
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This paper explores the properties of intrinsic gallium nitride (GaN) nanowires (NWs) in terms of formation energy, band structure, density of state (DOS) and optical properties with plane-wave ultrasoft pseudopotential method based on first-principles. Results show that after relaxation, N atoms of the outer layers move outwards, while Ga atoms move inwards, and the relaxation of surface atomic structure appears less obvious with the increasing cross-sectional area. Comparing different cross-sections of GaN NWs, it is found that the formation energy decreases and the stability goes stronger with the increasing size. With the increasing cross-section, the bandgap is decreased. Moreover, through comparative investigation in optical properties between GaN NWs and bulk GaN, a valuable phenomenom is found that the static dielectric constants of GaN NWs are notably lower, which contributes remarkably to the excellent absorbing performance of GaN NWs.
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Li, Ming, Gong Chen und Ru Huang. „High Performance GAA SNWT with a Triangular Cross Section: Simulation and Experiments“. Applied Sciences 8, Nr. 9 (04.09.2018): 1553. http://dx.doi.org/10.3390/app8091553.
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In this paper, we present a gate-all-around silicon nanowire transistor (GAA SNWT) with a triangular cross section by simulation and experiments. Through the TCAD simulation, it was found that with the same nanowire width, the triangular cross-sectional SNWT was superior to the circular or quadrate one in terms of the subthreshold swing, on/off ratio, and SCE immunity, which resulted from the smallest equivalent distance from the nanowire center to the surface in triangular SNWTs. Following this, we fabricated triangular cross-sectional GAA SNWTs with a nanowire width down to 20 nm by TMAH wet etching. This process featured its self-stopped etching behavior on a silicon (1 1 1) crystal plane, which made the triangular cross section smooth and controllable. The fabricated triangular SNWT showed an excellent performance with a large Ion/Ioff ratio (~107), low SS (85 mV/dec), and preferable DIBL (63 mV/V). Finally, the surface roughness mobility of the fabricated device at a low temperature was also extracted to confirm the benefit of a stable cross section.
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Song, Can, Feng Li und Hua Jing Zhao. „Moment-Curvature Relationship Analysis of High-Strength Concrete Shear Wall“. Applied Mechanics and Materials 368-370 (August 2013): 1539–46. http://dx.doi.org/10.4028/www.scientific.net/amm.368-370.1539.
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In order to improve the lateral deformation capacity of the high strength concrete shear wall, partially confined end-zones are usually set in the both ends of the shear wall cross-section. According to the experimental results of 15 high strength concrete shear walls with flexural (flexural-shear) failure, the moment - curvature skeleton curve of this shear wall cross-section is simplified as four linear through cracking point, yield point, peak point and ultimate point. Based on the plane-section assumption, the bending moment and curvature expressions at cracking, yield, peak and ultimate state are derived. At the same time, the effect of partially confined end-zones on peak and ultimate moment-curvature are taken into account. The analysis results show that, the calculated values are in good consistent with the experimental data.
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Wiedner, B. G., und C. Camci. „Passage Flow Structure and Its Influence on Endwall Heat Transfer in a 90 deg Turning Duct: Mean Flow and High Resolution Endwall Heat Transfer Experiments“. Journal of Turbomachinery 119, Nr. 1 (01.01.1997): 39–50. http://dx.doi.org/10.1115/1.2841009.
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Three-dimensional measurements of the mean velocity field have been made in a square-cross-sectional, strongly curved, 90 deg turbulent duct flow. The mean radius to duct width ratio was 2.3. The study was performed as part of an overall investigation of the physics of endwall convective heat transfer. All three components of the velocity vector and the static and total pressure fields were measured using a five-hole probe at four duct cross sections: inlet, 0, 45, and 90 deg. Preliminary turbulence measurements using a single sensor hot wire at the inlet cross section were also obtained to provide streamwise fluctuation levels through the boundary layer. The endwall heat transfer coefficient distribution was determined using a steady-state measurement technique and liquid crystal thermography. A high-resolution heat transfer map of the endwall surface from far upstream of the curve through the 90 deg cross section is presented. The three-dimensional velocity field measurements indicate that a highly symmetric, strong secondary flow develops in the duct with a significant transfer of streamwise momentum to the transverse directions. The cross-stream vorticity components within the measurement plane were estimated using the five-hole probe data and an inviscid from of the incompressible momentum equation. The development of the total and static pressure fields, the three-dimensional mean velocity field, and all three components of the vorticity field are discussed. The endwall heat transfer distribution is interpreted with respect to the measured mean flow quantities.
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Han, Xianmin, und Wenjiang Li. „Numerical Analysis on the Structure Type and Mechanical Response of Tunnel Crossing Active Reverse Fault“. Geofluids 2021 (18.08.2021): 1–10. http://dx.doi.org/10.1155/2021/5513042.
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Faulting would result in ground deformation and even damage to the tunnel structure. Thus, special structural designs should be made when the tunnel passes through an active fault. A single-track railway tunnel crossing a reverse fault is used to study the suitable structure type. In this paper, antidislocation structural measures such as reasonable segment length of articulated lining, cross-section shape, and thickness of lining are discussed through the numerical simulation. Firstly, the rational segment length of the articulated lining is confirmed. Stress and deformation behavior of articulated lining are also analyzed after the fault move. Then, the antifault effect of two kinds of cross-section shapes and three different lining thicknesses are compared. Researches show that the segment length of the articulated lining could be confirmed by the longitudinal distribution of maximum bending moment of lining after faulting. There are apparent stress concentrations occurring in the lining segment crossing the fault plane, and serious damage appears in the vault and wall waist of the tunnel. The horseshoe section with big curvature inverted arch is recommended to a single-track railway tunnel across an active fault. Simply increasing lining thickness is not suggested in a tunnel structure design crossing the active fault. The size of tunnel expansion and the minimum length of segment across fault plane can be geometrically determined according to fault dislocation magnitude and dip angle.
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Mohammed Menaouar, Bencherif, Hamel Mohamed, Bencherif Mohamed, Guelailia Ahmed und Hamidou Mohamed Kamel. „The separation wall effect of a volute twin entry cross section area on the mixed inflow turbine performance“. Engineering review 41, Nr. 1 (2020): 11–20. http://dx.doi.org/10.30765/er.1383.
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The pulse turbocharging system is used in many diesel engines and it is fortunate that nozzleless mixed turbines allow unsteady flow with less performance losses. It operates with a double or sometimes triple-entry casing creating different flow regimes in each sector. A nozzleless casing is used. The division of the cross section area takes the form of a solid wall in the radial plane. When the flow rate through one or the other volute inlet drops to zero, some reverse flow is observed from the other inlet. This situation suffers undesirable effects, diminishing the benefits of the divided volute casing types. A numerical investigation on the effect of the length of the dividing wall in the radial plane is performed using the ANSYS code. This possibility is explored and the results show that extending the wall to a limiting length enhances the flow behavior with better performance.
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Zhao, Hua Jing, Xing Wen Liang und Can Song. „Yield Displacement Calculation Method of High-Strength Concrete Shear Wall“. Applied Mechanics and Materials 353-356 (August 2013): 3382–86. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.3382.
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Considering high compressive strength of high-strength concrete, it is assumed that concrete compressive stress of the cross-section compression zone is linear distribution when the cross-section of high-strength concrete shear wall reaches yield situation. Based on the plane section assumption, the yield curvature formula of shear wall section is obtained by using moment - curvature analysis method. The parameters effecting yield curvature of high-strength concrete shear wall are studied by using the yield curvature formula. The results show that longitudinal reinforced yield strain is the most influencing factor of the yield curvature in addition to axial load ratio. This paper presents yield curvature formula considering the impact of axial load ratio and boundary reinforcement yield stress through the regression analysis of calculation results. On this basis, the vertex yield displacement formula of high-strength concrete shear wall is proposed, and the calculation results of formula correspond to the vertex yield displacement experimental values of the 12 high-strength concrete cantilever wall well.
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Ma, Niu Jing. „Analysis of Thermal Effect on Girder with Side Main Rib Section“. Applied Mechanics and Materials 501-504 (Januar 2014): 495–500. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.495.
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According to the common girder with side main rib section of PC cable-stayed bridge with double cable planes, a computational model of two-dimension temperature field is presented. Temperature gradient of main rib, small longitudinal rib, top plate and flange plate was computed respectively, and then the stress and strain of each section are derived through plane cross-section assumption. For the cable-stayed bridge, member structure FEM is applied to compute node equivalent load and displacement, which resulted from both sunshine and seasonal thermal difference. Finally, a case study is analyzed, the results showed: computed and measured deflection of girder that result from thermal effect are very close, therefore, this method is feasible.
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Filipowski, Ryszard, und Józef Zawora. „Calculation of the parameters of a cylinder measured by a cross-section strategy on a coordinate measuring machine“. Inżynieria Powierzchni 26, Nr. 1 (08.06.2021): 14–22. http://dx.doi.org/10.5604/01.3001.0014.8774.
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A computer program for calculating cylinder parameters was developed based on a measurement strategy of five circles arranged along the cylinder axis. The parameters calculated by the program are: cylinder diameter, axis of inclination of the cylinder axis to the reference plane, deviations from the least squares reference cylinder (LSCY), the axis passing through the centers of the outermost measurement circles. The graphics of deviation from the cylinder dimension is shown in the Auto CAD system using the script command. The developed program complements the CMM software.
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Nandi, A., und S. Neogy. „Modelling of rotors with three-dimensional solid finite elements“. Journal of Strain Analysis for Engineering Design 36, Nr. 4 (01.05.2001): 359–71. http://dx.doi.org/10.1243/0309324011514539.
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A shaft is modelled using three-dimensional solid finite elements. The shear-deformation and rotary inertia effects are automatically included through the three-dimensional elasticity formulation. The formulation allows warping of plane cross-sections and takes care of gyroscopic effect. Unlike a beam element model, the present model allows the actual rotor geometry to be modelled. Shafts with complicated geometry can be modelled provided that the shaft cross-section has two axes of symmetry with equal or unequal second moment of areas. The acceleration of a point on the shaft is determined in inertial and rotating frames. It is found that the finite element formulation becomes much simpler in a rotating frame of reference that rotates about the centre-line of the bearings with an angular velocity equal to the shafts spin speed. The finite element formulation in the above frame is ideally suited to non-circular shafts with solid or hollow, prismatic or tapered sections and continuous or abrupt change in cross-sections. The shaft and the disc can be modelled using the same types of element and this makes it possible to take into account the flexibility of the disc. The formulation also allows edge cracks to be modelled. A two-dimensional model of shaft disc systems executing synchronous whirl on isotropic bearings is presented. The application of the two-dimensional formulation is limited but it reduces the number of degrees of freedom. The three-dimensional solid and two-dimensional plane stress finite element models are extensively validated using standard available results.
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Bi, W. Y., L. H. Li, H. T. Liu und G. Zhao. „The effect of biased plates on transport of vacuum arc plasma through rectangular curved magnetic filter“. Modern Physics Letters B 31, Nr. 19-21 (27.07.2017): 1740006. http://dx.doi.org/10.1142/s0217984917400061.
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Filtered cathode vacuum arc deposition can remove the macroparticles produced from the cathode. Positively biasing the whole filter or inserting a biased plate in the filter can increase the plasma transport efficiency. We developed a curved magnetic filter with rectangular cross-section to improve the coating efficiency. In this study, the effect of biased plates at outer-wall and inner-wall on the transport efficiency of vacuum arc plasma through rectangular curved magnetic filter was investigated. A Langmuir probe system is used to measure the distribution properties of the filtered plasma at 15 places in the outlet plane of the filter. The results showed that a positively biased plate at inner-wall would increase the output ion current density and make the plasma concentrate to the middle of the outlet plane.
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Roebuck, John A. „Aerospace and Ergonomic Methods for Ear Anthropometry Supported by Bulgarian Research“. Proceedings of the Human Factors and Ergonomics Society Annual Meeting 63, Nr. 1 (November 2019): 1699–703. http://dx.doi.org/10.1177/1071181319631232.
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Translation into English has recently been completed for excerpts on ear and craniofacial anthropometry from an innovative, unpublished Bulgarian-language doctoral thesis written in 1986 by a plastic surgeon, M. M. Madzharov, MD-PhD; MD-SC. Most remarkable among the many benefits of the translation was revelation of heretofore unavailable text descriptions for 49 dimensions. Of these, 43 explain the titles and abbreviations with summary statistical data on ear measurements for young adults that were published in 1989 in the English language. Especially valuable among these data were four new and unique, long-axial ear lengths, all measured from a common ear landmark. These could locate “station planes” for cross-section views of human ears, similar to those for 3-D coordinate systems in aircraft and spacecraft fuselage engineering. Examples explaining the concepts and values of such a new approach to ear anthropometry are herein introduced, described and illustrated, together with previously recommended improvements in ear anthropometry notation and illustration, a virtual Ear Primary View Plane, a section plane through the ear long axis, newly introduced “semi-width” measurements extending perpendicular to the aforementioned section plane, new concepts of “view depths,” which are measured perpendicularly from the Ear Primary View Plane toward ear surfaces and a previously described three-axis aircraft motion analogy for defining static ear orientation. These innovative approaches are advocated for adoption by future researchers, designers of related hardware, modelers and standards developers.
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Hutny, A. M., M. Warzecha, W. Derda und P. Wieczorek. „Segregation of Elements in Continuous Cast Carbon Steel Billets Designated for Long Products“. Archives of Metallurgy and Materials 61, Nr. 4 (01.12.2016): 2037–42. http://dx.doi.org/10.1515/amm-2016-0328.
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Abstract This article presents research results concerning designation of the scope of segregation of elements by analysing the ingot, designated for hot rolling of long products. The research tests were performed under industrial conditions, during continuous casting production cycle of high carbon steels. From cc ingots with square cross-section of 160 mm samples having the length of 400 mm were collected, out of which two samples were cut up, the so-called templates with the thickness of 20 mm. Segregation of elements was determined based on the quantitative analysis of results performed by using spark spectrometry pursuant to PN-H-04045. Changes in concentrations of elements were analysed along the line, which join the opposite sides of the sample in their half length and pass through the geometric centre of the square cross-section. In the further course of the research study, there was also determined the segregation along perpendicular line up to the surface connecting the core of the cross-section with lateral plane. Designations of element contents were performed at points distanced from each other by approx. 10 mm and situated on the lines. There was found segregation of carbon, sulphur and phosphorus.
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Bickley, I., V. D'Olier, H. Fessler, T. H. Hyde und N. A. Warrior. „Stresses and deformations in overlapped diesel engine crankshafts, Part 2: Evaluation of results“. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 212, Nr. 4 (01.04.1998): 255–70. http://dx.doi.org/10.1243/0954407981525948.
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The extensive results presented in Part 1 (in the previous issue*) have been supplemented and analysed further. A large number of cross-sections which could be reasonably used to calculate nominal stresses has been listed and evaluated. An inclined (flat, rectangular) section through the web is shown to be the best to calculate nominal stresses due to torsion, pure radial bending and bending due to crankpin forces; its width is h (see Fig. 1), the length of the shortest line joining crankpin and journal fillets in the plane of symmetry. Stress concentration factors based on these nominal stresses show only modest scatter from single curves for crankpin and journal fillets for torsion and radial bending. Predictions using the most commonly used method underestimate shear stresses due to torsion and overestimate bending stresses.
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Chen, Lu Wang, Yuan Qin, Jiang Hong Chen und Shi Lei Zhang. „Joint Controlling Effect on Stability of Surrounding Rock in Horseshoe-Shaped Underground Opening“. Applied Mechanics and Materials 170-173 (Mai 2012): 1643–47. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.1643.
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This paper presents a numerical study on the mechanical behavior of the jointed rocks around the underground opening. By comparing different obliquities and the different locations of the joint, its controlling effect on stability of surrounding rock is evaluated in terms of the shear stress distribution, displacement distribution and the plastic zone pattern, which are induced by underground excavation. The results clearly indicate that, the maximum shear stress occurs mainly near the corner of the opening and the joint plane. When the joint inclination angle is less than 60º, the maximum vertical displacements occur where the joint locates near the skewback. Once the joint inclination angle reaches at 75º, the maximum vertical displacements occur where the joint is through the cross section of the underground opening. The plastic zone reaches minimum at the joint inclination angle of 45º where the joint locates either near the skewback or near spandrel of the opening, while it reaches minimum at the joint inclination angle of 60º where the joint cuts through the cross section of the opening.
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Han, Ai Hong. „Strain Analysis and Experimental Research of the Composite Beams“. Applied Mechanics and Materials 438-439 (Oktober 2013): 654–57. http://dx.doi.org/10.4028/www.scientific.net/amm.438-439.654.
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Through the comparative analysis of theoretical and experiment results, this paper proved that the formulas for solving the strain of composite beams are correct, and the strain is consistent with the plane cross-section assumption. In order to reduce the influence of friction, resin membranes were placed in steel-steel composite beams and aluminum-steel composite beams. The strain measurements were performed on composite beams with and without adding resin, the influence of friction between the composite beams is analyzed by the comparison of strain data,.
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Belt, R. J., A. C. L. M. Daalmans und L. M. Portela. „Experimental study of particle-driven secondary flow in turbulent pipe flows“. Journal of Fluid Mechanics 709 (24.08.2012): 1–36. http://dx.doi.org/10.1017/jfm.2012.104.
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AbstractIn fully developed single-phase turbulent flow in straight pipes, it is known that mean motions can occur in the plane of the pipe cross-section, when the cross-section is non-circular, or when the wall roughness is non-uniform around the circumference of a circular pipe. This phenomenon is known as secondary flow of the second kind and is associated with the anisotropy in the Reynolds stress tensor in the pipe cross-section. In this work, we show, using careful laser Doppler anemometry experiments, that secondary flow of the second kind can also be promoted by a non-uniform non-axisymmetric particle-forcing, in a fully developed turbulent flow in a smooth circular pipe. In order to isolate the particle-forcing from other phenomena, and to prevent the occurrence of mean particle-forcing in the pipe cross-section, which could promote a different type of secondary flow (secondary flow of the first kind), we consider a simplified well-defined situation: a non-uniform distribution of particles, kept at fixed positions in the ‘bottom’ part of the pipe, mimicking, in a way, the particle or droplet distribution in horizontal pipe flows. Our results show that the particles modify the turbulence through ‘direct’ effects (associated with the wake of the particles) and ‘indirect’ effects (associated with the global balance of momentum and the turbulence dynamics). The resulting anisotropy in the Reynolds stress tensor is shown to promote four secondary flow cells in the pipe cross-section. We show that the secondary flow is determined by the projection of the Reynolds stress tensor onto the pipe cross-section. In particular, we show that the direction of the secondary flow is dictated by the gradients of the normal Reynolds stresses in the pipe cross-section, $\partial {\tau }_{rr} / \partial r$ and $\partial {\tau }_{\theta \theta } / \partial \theta $. Finally, a scaling law is proposed, showing that the particle-driven secondary flow scales with the root of the mean particle-forcing in the axial direction, allowing us to estimate the magnitude of the secondary flow.
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Mourad, Hashem M., und Maher Y. A. Younan. „Nonlinear Analysis of Pipe Bends Subjected to Out-of-Plane Moment Loading and Internal Pressure“. Journal of Pressure Vessel Technology 123, Nr. 2 (24.07.2000): 253–58. http://dx.doi.org/10.1115/1.1310335.
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The behavior of a pipe bend, with bend factor h=0.1615(D=16 in.,R=24 in. and t=0.41 in.), subjected to out-of-plane bending and internal pressure is studied, taking geometric and material nonlinearity into account, using the finite element code ABAQUS. Material behavior is taken as elastic-perfectly plastic. The distribution of stress and strain along the axial direction and across the thickness of the bend is studied, with and without internal pressure, at the onset of yielding and at instability. Before instability is reached, through-the-thickness yielding appears at many points. The loaded end of the bend is found to be the most severely strained cross section. The circumferential distribution of stress and strain, and its variation with increased moment loading are then investigated for that section, at internal pressure values of zero and 1200 psi.
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Carcione, José M., Hans B. Helle und Anthony F. Gangi. „Theory of borehole stability when drilling through salt formations“. GEOPHYSICS 71, Nr. 3 (Mai 2006): F31—F47. http://dx.doi.org/10.1190/1.2195447.
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We present a mathematical analysis of borehole stability when drilling through rock salt. First, we consider an elastic transversely isotropic medium and find the optimal mud weight as a function of the vertical overburden and horizontal tectonic stresses. Then, the Zener and Maxwell mechanical models are used to model the effects of transient and steady-state creep flow, respectively, in isotropic media. Under certain conditions such as the absence of dilatational anelasticity, the Burger model can be used to describe the steady-state flow, including transient creep effects. The type of creep is regulated by critical octahedral-stress values that depend on temperature and pressure. A typical drilling results in conditions of plane strain, whose solution is given by Kirsch’s equations. In this case, the borehole is subject to minimum and maximum horizontal stresses, which differ from the vertical stress. The analysis provides expressions for the shape of the borehole-cross section, the borehole-wall closure time, and the optimal mud weight to avoid wall collapse or expansion. It is shown that an anisotropic state of tectonic stress may require mud pressures exceeding the overburden stress and that the calculation should consider the joint optimization of the shape and area of the borehole cross section.
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Mosiori, Cliff Orori, Walter Kamande Njoroge und Lawrence Otieno Ochoo. „Influence of Localized Surface Plasmon Polaritons on Silver Nanoparticles“. ABC Journal of Advanced Research 9, Nr. 1 (31.05.2020): 39–44. http://dx.doi.org/10.18034/abcjar.v9i1.503.
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In this article, we present a theoretical study on localized surface Plasmon of spherical Ag nanoparticles (NPs) done by numerical simulation. A plane EM wave was used to determine absorption cross-section and results showed that excitation of LSPPs produced an electric field on the surface of the nanoparticle. This field causes a large cross sectional area that influences higher scattering of incident photon at the surface of an absorber layer. It was concluded that LSPPs excitations in small size spherical particles can be utilized in low-cost solar cells to increase PCE of solar panels and can be expanded to many other fields of optoelectronic technologies ranging from solar cells, through photo diodes to optical bio-sensing applications.
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Ferreira de Sousa, P. J. S. A., Isabel Malico und Gérson Fernandes. „Numerical Simulation of 2D Flow through a Packed Bed of Square Cylinders“. Defect and Diffusion Forum 326-328 (April 2012): 725–30. http://dx.doi.org/10.4028/www.scientific.net/ddf.326-328.725.
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This paper is centred on a compact finite differences method for the calculation of two-dimensional viscous flows through complex geometries. The immersed boundaries are set through body forces that allow for the imposition of boundary conditions that coincide with the computational grid. Two different flow configurations are simulated. First, the flow past a cylinder with square cross-section inside a plane channel is calculated. The computed average drag coefficient and Strouhal number are compared to data available in the literature. The agreement between the results is good. The second flow configuration analyzed is the flow through a porous matrix composed of equal size staggered square cylinders. Flow visualization results are shown. The work presented in this paper illustrates the potential of the immersed boundary method in general and of this implementation in particular to simulate the flow through porous matrices.
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Wei, Yang, Shen Xue Jiang, Qing Fang Lv, Qi Sheng Zhang, Li Bin Wang und Zhi Tao Lv. „Flexural Performance of Glued Laminated Bamboo Beams“. Advanced Materials Research 168-170 (Dezember 2010): 1700–1703. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.1700.
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Bamboo structures have a good performance like wooden structures. The flexural performance of glued laminated bamboo beams for bamboo structures were studied through ten large-scale beams tested. The study investigated the failure modes of bamboo beams, flexural capacity, cross-sectional stiffness and strain distribution. In test, four kinds of typical failure modes of bamboo beams include brittle fracture of the bottom fiber, compressive buckling failure at the top of the bamboo strips layers, stratified fracture and oblique tear of the bottom fiber. The control condition of the design load was the cross-sectional stiffness rather than the flexural strength according to the experimental results. The flexural elastic modulus of 10GPa is suggested to check deformation of bamboo beams in the design. The plane-section assumption of cross-sectional strain distribution along the height is verified for bamboo beams.
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Nakamura, Yasuharu, und Yuji Ohya. „Vortex shedding from square prisms in smooth and turbulent flows“. Journal of Fluid Mechanics 164 (März 1986): 77–89. http://dx.doi.org/10.1017/s0022112086002471.
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Visualization and measurements of velocity and pressure were made for the flow past prisms of variable length with square cross-section, placed normal to smooth and turbulent approaching flows. Square prisms shed vortices in one of the two fixed wake planes. The plane of shedding is switched irregularly from one to the other. Flow visualization confirms the two main effects of small– and large-scale turbulence on the flow past square prisms that had previously been suggested. In particular, large-scale turbulence intensifies vortex shedding from square prisms through resonant interaction, thereby reducing the base pressure considerably.
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Sukonrat, Patchara, Chanwut Sriphung, Watcharee Rattanasakulthong und Chitnarong Sirisathitkul. „Characterization of Cobalt Films on X-Ray Lithographic Micropillars“. Advanced Materials Research 335-336 (September 2011): 1000–1003. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.1000.
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Arrays of SU-8 photoresist pillars (10 μm ×10 μm × 50 μm) on copper substrates were fabricated by X-ray lithography. The photoresist-coated substrates were irradiated by X-ray from a synchrotron source through patterned silver dots on a graphite mask. After the resist development, the chemically stable and mechanically hardened SU-8 pillars exhibited smooth vertical sidewalls and cross section with up to 10 % dimensional errors from the designated pattern. Cobalt of thickness ranging from 50 to 80 nm was then deposited on these patterned substrates by RF sputtering. These cobalt films on SU-8 pillars showed a lower in-plane magnetization than that of continuous cobalt films because of their smaller grain size. The measurement with out-of-plane magnetic field gave rise to a higher magnetization and this anisotropic behavior was observed only in cobalt-coated pillars.
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Yang, C. J. „Texture Induced Magnetic Anisotropy in Fe–Nd–B Magnets Prepared via Rapid Solidification and Hot Extrusion Techniques“. Textures and Microstructures 11, Nr. 2-4 (01.01.1989): 143–58. http://dx.doi.org/10.1155/tsm.11.143.
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High performance Fe–Nd–B magnets were prepared by consolidation of rapidly solidified melt spun powder using a hot extrusion technique. The extrusion was carried out with various die openings to control the distribution of stresses and strains influencing the possible development of texture. A strong anisotropy in magnetic properties has been found in the extruded magnets. The highest remanence of 10.6 kG and the maximum energy product of 16.6 MGOe were achieved along the through-thickness direction of the magnet extruded into a rectangular cross section. A (001) [1¯20] texture was found to develop in the plane normal to the through-thickness direction. It is suggested that the enhanced remanent magnetization arises principally from the formation of favorable texture.
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Li, Xiao Jie, und Bao Zhen Ge. „Correction of World Coordinate Error in the Three-Dimensional Laser Scanning System of Human Body“. Applied Mechanics and Materials 198-199 (September 2012): 1016–20. http://dx.doi.org/10.4028/www.scientific.net/amm.198-199.1016.
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This paper studies three-dimensional laser scanning system of human body, and make adjustments according to the world coordinate error correction based on the point cloud obtained. This paper also analyzed the cause and characteristics of three-dimensional laser scanning system’s world coordinates error, and established the world coordinate correction model on the condition that vertical column coordinate error is not included in the calibration plane and the error is minimum relative to other highly cross-section. With a standard rectangular timber as the scan objects, correction factor is fitted and the effectiveness of this method is proved through experiments in which point cloud’s world coordinate error is significantly reduced.
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ALBENSOEDER, S., und H. C. KUHLMANN. „Linear stability of rectangular cavity flows driven by anti-parallel motion of two facing walls“. Journal of Fluid Mechanics 458 (10.05.2002): 153–80. http://dx.doi.org/10.1017/s0022112002007917.
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The flow in an infinite slab of rectangular cross-section is investigated numerically by a finite volume method. Two facing walls which move parallel to each other with the same velocity, but in opposite directions, drive a plane flow in the cross-section of the slab. A linear stability analysis shows that the two-dimensional flow becomes unstable to different modes, depending on the cross-sectional aspect ratio, when the Reynolds number is increased. The critical mode is found to be stationary for all aspect ratios. When the separation of the moving walls is larger than approximately twice the height of the cavity, the basic flow forms two vortices, each close to one of the moving walls. The instability of this flow is of centrifugal type and similar to that in the classical lid-driven cavity problem with a single moving wall. When the moving walls are sufficiently close to each other (aspect ratio less than 2) the two vortices merge and form an elliptically strained vortex. Owing to the dipolar strain this flow becomes unstable through the elliptic instability. When both moving walls are very close, the finite-length plane-Couette flow becomes unstable by a similar elliptic mechanism near both turning zones. The critical mode produces wide streaks reaching far into the cavity. For a small range of aspect ratios near unity the flow consists of a single vortex. Here, the strain field is dominated by a four-fold symmetry. As a result the instability process is analogous to the instability of a Rankine vortex in an quadripolar strain field, resulting from vortex stretching into the four corners of the cavity.
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Frost, B. G., E. Voelkl und M. Kowalewski. „Electron Holography of Magnetic Memory Cells“. Microscopy and Microanalysis 5, S2 (August 1999): 944–45. http://dx.doi.org/10.1017/s1431927600018043.
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The phase shift of an electron wave compared with a reference wave amounts to [1]where e is the electron charge (e > 0), h is Planck's constant, A is the magnetic vector potential, B is the magnetic induction and Фm is the magnetic flux through an area F bordered by the trajectories of the two waves. The absolute value of the vector F perpendicular to this area is given by F. As a simple example we qualitatively sketch the phase shifts by a uniformly magnetized sphere. The cross section of this sphere and the magnetic field lines are shown in Fig. 1. The electron wave travels perpendicular to the paper plane. On one side of the sphere the object wave through point 1 is compared with the reference wave through point 2 and on the opposite side the wave through point 3 is compared with the one through point 4.
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Pochernyaev, V. N., und N. M. Syvkova. „EXTERNAL PARAMETERS OF THE CONNECTION OF A RECTANGULAR WAVEGUIDE PARTIALLY FILLED OF LINEAR DIELECTRIC WITH A RECTANGULAR WAVEGUIDE PARTIALLY FILLED OF NONLINEAR DIELECTRIC“. Visnyk Universytetu “Ukraina”, Nr. 1 (28) 2020 (2020): 100–105. http://dx.doi.org/10.36994/2707-4110-2020-1-28-09.
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. In the article, the external parameters of the connection of a rectangular waveguide partially filled of linear dielectric with a rectangular waveguide partially filled of a nonlinear dielectric are determined. Knowledge of the external parameters of such a connection ensures the design of devices with open nonlinear elements. Promising microwave paths of radio engineering systems based on rectangular waveguides partially filled of dielectric include a wide variety of active and passive microwave devices. The plane-transverse junction of these waveguides is considered for various geometric dimensions of dielectric plates and their relative permittivity. Such a junction is characterized by reactive conductivity, which is determined through the sum of the reactive conductivities of local fields. The transverse electric field at the junction is represented through the eigenvector function of the geometric surface, which coincides with the cross section of the waveguides. The scattering matrix of the plane-transverse junction is determined through the conductivity of the sections of the two waveguides and the conductivity of the plane-transverse junction. The dependences of the traveling wave coefficient and the modulus of the reflection coefficient on the geometric dimensions of the dielectric plate are plotted taking into account the local fields generated at the plane transverse junction. At the junction of two waveguides, not only changed the geometric dimensions of the dielectric plates along the wide and narrow walls of the waveguide, but also their relative permittivity. In one case, two higher types of waves were taken into account: quasi - H30 and quasi - H12, in the other case - four higher types of waves: quasi - H30, quasi - H12, quasi - E12, quasi - H50. Calculations show that an increase in the number of higher types of waves has practically no effect on the accuracy of calculations. The results obtained indicate the rapid internal convergence of the obtained solutions and the correct choice of the transverse electric eigenvector function of rectangular waveguides partially filled of dielectric as approximate the field on the junction of two waveguides.
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O¨tu¨gen, M. V., F. Girlea und P. M. Sforza. „The Turbulent Incompressible Jet in a Curved Coflow“. Journal of Fluids Engineering 118, Nr. 2 (01.06.1996): 300–306. http://dx.doi.org/10.1115/1.2817377.
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The effects of small streamline curvature on the growth and axial flow development of a turbulent incompressible jet in a curved coflow was investigated experimentally. The jet streamline curvature was achieved by introducing the initially round jet tangentially into a stream flowing through a curved channel of square cross-section. The jet issued from a straight pipe and had a fully developed velocity profile at the exit plane. The jet Reynolds number and the coflow-to-jet-velocity ratio were 4300 and 0.11, respectively. A single component laser Doppler anemometer was used to measure the streamwise velocity. Axial mean velocity and turbulence intensity profiles were measured at various streamwise locations in both the plane of curvature and the surface perpendicular to the plane of curvature. The results indicate that the jet growth and turbulence intensity are influenced by the small streamline curvature. The growth rate of the curved jet in the plane of curvature is slightly increased compared to that of a straight jet. However, the growth of the same curved jet is suppressed in the plane perpendicular to the plane of curvature. In the plane of curvature, the inner jet half-width is larger than the outer jet half-width. The mean velocity profiles in this plane are nearly Gaussian when the lateral distance is normalized by the respective inner and outer side jet half-widths. The axial turbulence intensity profiles show asymmetry in the plane of curvature with a pronounced peak on the outer side of the jet.
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Yao, Yu Xin, und Chun Yuan Shi. „Instability Analysis of the Bipolar Plate for Welding Fuel Cell“. Applied Mechanics and Materials 152-154 (Januar 2012): 568–73. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.568.
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The instability of the bipolar plate for welding fuel cell was analyzed taking the bipolar plate as thin plate. The minimum compressive stress is calculated based on thin plate instability theory caused by longitudinal compressive stress. The simplified thermal stress distribution function is determined using the analytical solution of the plane heat conduction equation. The maximum compressive stress is determined through the analysis of the longitudinal stress distribution of the cross section passing through the solder point during heating and cooling process. The results are used to obtain the pre-tensile stress controlling the instability of the bipolar plate for welding fuel cell, and the minimum pre-tensile stress is the difference between the maximum compressive stress and the minimum compressive stress as the thin plate loses instability.
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Del Giudice, Silvio, und Giancarlo Bernasconi. „Acoustic Response of a Sinusoidally Perturbed Hard-Walled Duct“. Mathematical Problems in Engineering 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/267291.
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Acoustic wave propagation in hard-walled ducts is of interest in many fields including vehicle design, musical instruments acoustics, and architectural and environmental noise-control. For the case of small sinusoidal perturbation of the cross-section, it is possible to derive simple though approximate analytical formulas of its plane wave acoustic reflection and transmission spectral response that resembles the optical situation of uniform Bragg gratings. The proof is given here, starting from the “horn equation” and then exploiting the coupled-modes theory. Examples of the results obtained with these analytical formulas are shown for some sinusoidally perturbed ducts and compared to results obtained through a numerical method, revealing a very good agreement.
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Kagermanov, Alexander, und Paola Ceresa. „3D Fiber-Based Frame Element with Multiaxial Stress Interaction for RC Structures“. Advances in Civil Engineering 2018 (15.08.2018): 1–13. http://dx.doi.org/10.1155/2018/8596970.
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A three-dimensional fiber-based frame element accounting for multiaxial stress conditions in reinforced concrete structures is presented. The element formulation relies on the classical Timoshenko beam theory combined with sectional fiber discretization and a triaxial constitutive model for reinforced concrete consisting of an orthotropic, smeared crack material model based on the fixed crack assumption. Torsional effects are included through the Saint-Venant theory of torsion, which accounts for out-of-plane displacements perpendicular to the cross section due to warping effects. The formulation was implemented into a force-based beam-column element and verified against monotonic and cyclic tests of reinforced concrete columns in biaxial bending, beams in combined flexure-torsion, and flexure-torsion-shear.
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Martin, J., P. Oshkai und N. Djilali. „Flow Structures in a U-Shaped Fuel Cell Flow Channel: Quantitative Visualization Using Particle Image Velocimetry“. Journal of Fuel Cell Science and Technology 2, Nr. 1 (16.08.2004): 70–80. http://dx.doi.org/10.1115/1.1843121.
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Flow through an experimental model of a U-shaped fuel cell channel is used to investigate the fluid dynamic phenomena that occur within serpentine reactant transport channels of fuel cells. Achieving effective mixing within these channels can significantly improve the performance of the fuel cell and proper understanding and characterization of the underlying fluid dynamics is required. Classes of vortex formation within a U-shaped channel of square cross section are characterized using high-image-density particle image velocimetry. A range of Reynolds numbers, 109⩽Re⩽872, corresponding to flow rates encountered in a fuel cell operating at low to medium current densities is investigated. The flow fields corresponding to two perpendicular cross sections of the channel are characterized in terms of the instantaneous and time-averaged representations of the velocity, streamline topology, and vorticity contours. The critical Reynolds number necessary for the onset of instability is determined, and the two perpendicular flow planes are compared in terms of absolute and averaged velocity values as well as Reynolds stress correlations. Generally, the flow undergoes a transition to a different regime when two recirculation zones, which originally develop in the U-bend region, merge into one separation region. This transition corresponds to generation of additional vortices in the secondary flow plane.
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Lei, Jing, Bowang Chen und Ping Yuan. „Experimental Study on Flexural Properties of Side-Pressure Laminated Bamboo Beams“. Advances in Civil Engineering 2020 (15.06.2020): 1–10. http://dx.doi.org/10.1155/2020/5629635.
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In this paper, two factors of width-to-height ratio and span-to-height ratio are considered and 10 side-pressure laminated bamboo beams are prepared and tested for flexural capacity to study the flexural performance when they are used as structural members. The failure mode, load-displacement curves, and the change rule of cross-section strain with height are obtained through the test. The results demonstrate that the side-pressure laminated bamboo beams have experienced elastic deformation stage, elastic-plastic deformation stage, and failure stage; the midspan deflection of beams with considerable span-to-height ratio is too large to be applied to the ultimate load, and these specimens are regarded at the ultimate limit state; stiffness or deflection should be considered as the control index in the engineering application of the side-pressure laminated bamboo beams; the bearing capacity increases proportionately with the beam width; the average strain of the section basically conforms to the plane section assumption. The experiment proposes a method for calculating the flexural capacity of the side-pressure laminated bamboo beams with nonlinear deformation, and also, the comparison between the test value and the calculated value shows that they agree well.
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Yokoyama, Takashi. „Impact Compressive Failure of a Unidirectional Carbon/Epoxy Laminated Composite in Three Principal Material Directions“. Materials Science Forum 706-709 (Januar 2012): 799–804. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.799.
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The impact compressive failure behavior of a unidirectional T700/2521 carbon/epoxy laminated composite in three principal material directions or fiber (1-), in-plane transverse (2-) and through-thickness (3-) directions is investigated on the conventional split Hopkinson pressure bar (SHPB). Cubic and rectangular block specimens with identical square cross section are machined from an about 10 mm thick composite laminate. The uniaxial compressive stress-strain curves up to failure at quasi-static and intermediate strain rates are measured on an Instron testing machine. It is shown that the ultimate compressive strength and strain exhibit no strain-rate effect in the 1-direction, but a slight strain-rate effect in the 2-and 3-direction over a range of strain rates from10-3to 103/s.
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de Faria, Cleber Granato, Tércio Assunção Pedrosa, Roberto Braga Figueiredo, Maria Teresa Paulino Aguilar und Paulo Roberto Cetlin. „Compressive and Shearing Mechanical Anisotropy of Aluminum after ECAP“. Advanced Materials Research 1016 (August 2014): 100–104. http://dx.doi.org/10.4028/www.scientific.net/amr.1016.100.
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Severe plastic deformation (SPD), where metals are deformed up to very high strain values, leads to a very small grain size and a high strength of the material. ECAP (Equal Channel Angular Pressing) is one of the SPD methods, and involves the extrusion of a metal billet through two intersecting channels with identical cross-section and forming an angle between them. The material undergoes shearing as it crosses from one channel to the other, but its external dimensions are not altered. Shearing occurs along a single plane, which may lead to anisotropy in the mechanical properties of the material after ECAP. Compression, tension and shearing tests along various directions in the as-processed specimens indicated the presence of mechanical anisotropy in ECAP processed aluminum.
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Sta˚hlberg, U., und J. Hou. „A UBET-Simulation Meant for Basic Understanding of the Extrusion of Aluminum Profiles“. Journal of Engineering for Industry 117, Nr. 4 (01.11.1995): 485–93. http://dx.doi.org/10.1115/1.2803525.
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A plane strain UBET-model, meant for deeper understanding of the material flow in the extrusion of complex shaped aluminum profiles is presented. In order to get the desired straight shape of the extrudate, every part of its cross-section must exit the die with the same velocity. One intention of the present work is to imitate this problem and to analyze it in a simplified way. This has been done by studying the extrusion through a two-hole die face. The flow is balanced by determining the optimum lengths of the bearing lands, i.e., those lengths which result in equal exit velocities of the extrudates. Furthermore, the material flow, as influenced by the position of the die openings along the die face, has been investigated.