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1
Ma, Xiaolu, Dajun Liu, Yaochuan Wang, Hongming Yin, Haiyang Zhong et Guiqiu Wang. « Propagation of Rectangular Multi-Gaussian Schell-Model Array Beams through Free Space and Non-Kolmogorov Turbulence ». Applied Sciences 10, no 2 (8 janvier 2020) : 450. http://dx.doi.org/10.3390/app10020450.
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In this paper, rectangular multi-Gaussian Schell-model (MGSM) array beams, which consists N×D beams in rectangular symmetry, are first introduced. The analytical expressions of MGSM array beams propagating through free space and non-Kolmogorov turbulence are derived. The propagation properties, such as normalized average intensity and effective beam sizes of MGSM array beams are investigated and analyzed. It is found that the propagation properties of MGSM array beams depend on the parameters of the MGSM source and turbulence. It can also be seen that the beam size of Gaussian beams translated by MGSM array beams will become larger as the total number of terms, M, increases or coherence length, σ , decreases, and the beam in stronger non-Kolmogorov turbulence (larger α and l 0 , or smaller L 0 ) will also have a larger beam size.
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Brosnan, David P., et Chia-Ming Uang. « Effective Width of Composite L-Beams in Buildings ». Engineering Journal 32, no 2 (30 juin 1995) : 73–80. http://dx.doi.org/10.62913/engj.v32i2.640.
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The latest AISC design specifications permit the use of wider effective widths for steel-concrete composite exterior beams (or L-beams) than previous editions. This sometimes results in more flexible beams which quite often support deflection-sensitive nonstructural components. An analytical study of composite L-beams was conducted within a practical range of span and spacing for buildings. Both the conventional stress-based and rational stiffness-based definitions of effective width were considered. Effective widths were computed from the results of finite element analysis of three dimensional models permitting longitudinal slip between the concrete slab and the steel beam. It was concluded that the AISC effective width criteria for L-beams tends in an unconservative direction; a stiffness-based formula dependent on the spacing/span ratio is proposed.
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Wang, Qiang, et Chun Ling Lu. « Durability Experimental Study on RC Beams Strengthened with CFRP ». Key Engineering Materials 400-402 (octobre 2008) : 519–24. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.519.
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The principle of electrochemistry is adopted in this test. The current is switched on 7 RC beams strengthened with CFRP of different measures (include: not strengthened L-0, strengthened with one layer of CFRP on the bottom L-1, coated only with epoxy resin L-2, strengthened with one layer of CFRP on the bottom and coated with epoxy resin on the lateral L-3, strengthened with two layers of CFRP on the bottom L-4, strengthened with one layer of CFRP on the bottom and alternately on the lateral L-5, strengthened with CFRP entirely L-6) when the beams are working in corrosive environment. So the corrosion speed of the beams becomes fast. Comprehensive comparison of mechanical property and transformation rule among them has been made. The different effects of the enhancement in durability are analyzed and its reason is researched. The test results indicate that the durability of the beams strengthened with CFRP can be enhanced significantly especially in the beam strengthened with CFRP entirely L-6.
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Xiong, Liang Cai, Quan Sheng Zhou et Peng Chen. « Vibration Analysis of Different Micro-Beams with Laser Ablation ». Applied Mechanics and Materials 462-463 (novembre 2013) : 428–31. http://dx.doi.org/10.4028/www.scientific.net/amm.462-463.428.
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The dynamic response of different micro-beams after laser excitation experiments have been investigated in this paper. The impact force that induces the vibration of micro-beams is the interaction of focused pulse laser and tested beams. The impact response of micro-beams after being excited is measured by Laser Doppler Vibrometer. Different beams such as cantilever beam, L-shaped beam are employed in our experiments. Comparisons of the vibration velocity and its frequencies of different beams have also been performed. Experimental results show that the mechanical effects of laser shock do really exist and can be utilized.
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Jasim Mohammed, Thaer, Badorul Hisham Abu Bakar et Norazura Muhamad Bunnori. « Effects of Thickness of Ultra High-Performance Fiber Concrete Wrapping on the Torsional Strength of Reinforced Concrete Beam ». Applied Mechanics and Materials 802 (octobre 2015) : 161–65. http://dx.doi.org/10.4028/www.scientific.net/amm.802.161.
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Abstract: Two groups of rectangular beams, comprising of six specimens, the first group (L) were provided with four longitudinal bars, one at each corner while the second groups of beams (S) were fully reinforced with longitudinal bars and transverse reinforcement. Each group consisted of three beams. Two beams have been strengthened with ultra high performance fiber concrete (UHPFC) on four sides having a thickness of (15mm - 25mm) and one control beam. The variables considered in the experimental study include the transverse reinforcement ratios and the effect of thickness of UHPFC wrap. Experimental results show the effectiveness of the proposed technique at ultimate torque for strengthening beams and behavioral curves. Strengthened RC beams fully wrapped with a thin layer of UHPFC exhibit an enhanced torsional strength when compared to control beam. Results reveal that the transverse reinforcement ratios by 0.66%, increases the UHPFC contribution to torsional strength of strengthened beams with a 15 thick UHPFC; and by up to 7% for strengthened beams with a 25 thick UHPFC, respectively when compared to same strengthened beams without stirrup. It is found that the ultimate torque of beams with a 25 mm thin layer UHPFC is greater than beams with 15 mm by (28% and 28.3%) for the groups L and S, respectively.
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Knyazev, Boris, Natalya Osintseva, Maxim Komlenok, Vladimir Pavelyev, Vasily Gerasimov, Oleg Kameshkov, Yulia Choporova et Konstantin Tukmakov. « Terahertz Bessel Beams Formed by Binary and Holographic Axicons ». Photonics 10, no 6 (20 juin 2023) : 700. http://dx.doi.org/10.3390/photonics10060700.
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The characteristics of high-power vortex Bessel beams in the terahertz range (λ=141 μm) obtained with the use of diffractive axicons (DAs) illuminated by a Gaussian beam of the Novosibirsk free-electron laser were studied. Two of the three possible types of DA recently described in our previous paper, namely, binary spiral silicon axicons (BAs), forming beams with a topological charge l equal to 0–4 and 9, and a diamond “holographic” axicon (HA), forming a beam with l=9, were used in the experiments. These axicons formed beams whose cross sections in the region of inner Bessel rings were close to those of ideal Bessel beams, but their intensities varied in azimuth with a frequency of l and 2l for the BAs and HA, respectively. However, in the case of the BAs, the beams had a pronounced helical structure at the periphery, whereas for the HA, the beam was axisymmetric. By focusing these beams with a lens, we studied the structure of the so-called “perfect” beams (PBs). While an ideal Bessel beam exhibits a PB as a thin ring, in the case of the BAs, we observed a broadened ring structure consisting of 2l short spirals, and for the HA, we observed a narrow ring with 2l maxima in azimuth. A comparison of the numerical calculations and experiments showed that the observed azimuthal intensity variations can be attributed to inaccuracies in the preparation of the axicon relief and/or discrepancies between the calculated and actual wavelengths, within a few percent. The results of this work enable the establishment of quality requirements for axicon manufacture and the appropriate selection of the axicon type in accordance with the requirements for the beam.
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Fašalek, Andrej, Aleš Straže, Bogdan Šega, Johannes A. J. Huber et Milan Šernek. « Bonding Performance of Melamine–Urea–Formaldehyde and Polyurethane Adhesives for Laminated Hybrid Beams and Their Selected Mechanical Properties ». Buildings 13, no 8 (17 août 2023) : 2087. http://dx.doi.org/10.3390/buildings13082087.
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Beech (Fagus Sylvatica L.) is a prevalent tree species in Slovenia and is suitable for manufacturing glulam beams. However, beech wood has certain limitations that can potentially be mitigated by combining it with Norway spruce (Picea abies (L.) Karst.) wood to create hybrid beams. This study aimed to determine the bonding performance of commonly used melamine–urea–formaldehyde and polyurethane adhesives for these hybrid beams. Moreover, how varying the proportion of beech wood in a hybrid beam affects its mechanical properties was examined. Shear and delamination tests (method B) were conducted, and EN 14080:2013 requirements were met in all cases. The four-point bending tests of the beams showed that hybrid beams containing 20% of beech wood in the cross-sectional height on each side of the neutral axis exhibited a similar modulus of elasticity values as pure beech beams, but their strength was not equally improved. Hybrid beams with 11% of beech wood did not show any improvement in bending stiffness or strength compared to pure spruce beams. It was noted that the presence of beech wood in a hybrid beam can influence its failure mode. Furthermore, analytical calculations showed that a symmetrical lay-up is preferable to an asymmetrical one to increase the effective modulus of elasticity.
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Nairat, Mazen. « Axial Angular Momentum of Bessel Light ». Photonics Letters of Poland 10, no 1 (31 mars 2018) : 23. http://dx.doi.org/10.4302/plp.v10i1.787.
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Both linear and angular momentum densities of Bessel, Gaussian-Bessel, and Hankel-Bessel lasers are determined. Angular momentum of the three Bessel beams is illustrated at linear and circular polarization. Axial Angular momentum is resolved in particular interpretation: the harmonic order of the physical light momentum. Full Text: PDF ReferencesG. Molina-Terriza, J. Torres, and L. Torner, "Twisted photons", Nature Physics 3, 305 - 310 (2007). CrossRef J Arlt, V Garces-Chavez, W Sibbett, and K Dholakia "Optical micromanipulation using a Bessel light beam", Opt. Commun., 197, 4-6, (2001). CrossRef L. Ambrosio and H. Hernández-Figueroa, "Gradient forces on double-negative particles in optical tweezers using Bessel beams in the ray optics regime", Opt Exp, 18, 23 (2010). CrossRef I. Litvin, A. Dudley and A. Forbes, "Poynting vector and orbital angular momentum density of superpositions of Bessel beams", Opt Exp, 19, 18 (2011). CrossRef K Volke-Sepulveda, V Garcés-Chávez, S Chávez-Cerda, J Arlt and K Dholakia "Orbital angular momentum of a high-order Bessel light beam" , JOP B 4 (2). 2002. CrossRef M. Verma, S. Pal, S. Joshi, P. Senthilkumaran, J. Joseph, and H Kandpal, "Singularities in cylindrical vector beams", Jou. of Mod. Opt., 62 (13), 2015. CrossRef R. Borghi, M. Santarsiero, and M. Porras, "Nonparaxial Bessel?Gauss beams", J. Opt. Soc. Am. A, 18 (7) (2011). CrossRef L. Allen, M. Beijersbergen, R. Spreeuw, and J. Woerdman, "Orbital angular momentum of light and the transformation of Laguerre-Gaussian Laser modes", Phys Rev A, 45 (11): 8185-8189 (1992). CrossRef D. Mcglion and K. Dholakia, "Bessel beams: diffraction in a new light", Cont. Phys, 46(1) 15 ? 28. (2005). CrossRef F. Gori, G. Guattari and C. Padovani," Bessel-Gauss Beams", Opt. Commun., 64, 491, (1987). CrossRef V. Kotlyar, A. Kovalev, and A. Soifer, "Hankel?Bessel laser beams" J. Opt. Soc. Am. A, 29 (5) (2012). CrossRef L. Allen and M. Babiker "Spin-orbit coupling in free-space Laguerre-Gaussian light beams", Phys. Rev. A 53, R2937. CrossRef
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Sudarsana, I. Ketut, I. Putu Chandra Sajana et I. Gusti Ngurah Oka Suputra. « Applications of bolted steel plates to shear strengthening of RC beams ». MATEC Web of Conferences 276 (2019) : 01002. http://dx.doi.org/10.1051/matecconf/201927601002.
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Many reinforced concrete beams have been found deficiencies in shear due to lack of shear reinforcement. Few researches have been done to investigate shear strengthening of low concrete strength of RC beams using bolted steel plates. This paper presents experimental results on the behaviour of RC beams strengthening using full steel plates along the shear span fixed with bolts. Nine RC beams having dimension of 150x200x1500mm were tested to failure on simply supports with four point loadings setup. The beams were reinforced with tension rebars area of 289.8 mm2 (2D10+1D13) and transvers reinforcement of Ø6-125. Two dial gauges were installed at the beam middle span to measure beam deflection during the test. The results show that the applications of steel plate and bolts as external reinforcement increase beam shear capacity, stiffness and delay the occurrence of first diagonal cracks. Beams stregnthened with U-shape plates gave better performances than the beams with two pieces of L-shape plates due to better achorages.
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Dai, Xianzhi, Zhang Zhang, Wang Chen, Lijun Wang, Yong Wang et Min Zheng. « A 3D multi-directional and multimodal broadband vibration energy harvester using an L-shaped bending beam ». Journal of Physics : Conference Series 2527, no 1 (1 juin 2023) : 012076. http://dx.doi.org/10.1088/1742-6596/2527/1/012076.
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Abstract A three-dimensional (3D), multi-directional and multimodal broadband vibration energy harvester using L-shaped curved beams is proposed in this paper. The harvester is composed of an L-shaped cylindrical bending beam and a piezoelectric beam. The free ends of the L-shaped bending beam and the piezoelectric beam are respectively fixed with a magnet. These two beams are coupled by nonlinear magnetic force introduced by the two magnets. The results show that the prototype can collect 3D multi-directional broadband vibration energies and has three natural frequencies in 3D directions. Under 5 m/s2 acceleration, the prototype obtains 42.1V, 45.0V and 66.9V peak-peak voltages in the x-direction, y-direction and z-direction respectively, and the widest 3 DB bandwidths in this three directions reach up to 6.4Hz, 6.3Hz and 4.2Hz, respectively.
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Wang, Zijing, Xiangdong Xie, Jinfeng Zhang et Guofeng Du. « An Experimental Study on Efficient Piezoelectric Coupled Beams and Corresponding Piezoelectric Bricks ». Applied Sciences 11, no 23 (4 décembre 2021) : 11504. http://dx.doi.org/10.3390/app112311504.
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In view of the low output power density of the existing footstep harvesters, two pairs of distinctive L-shaped beams and the corresponding piezoelectric brick models are developed to improve the utilization efficiency of the piezoelectric patches bonded on the beams. A theory model of the aforesaid L-shaped beam is established to analyze its dynamic performance. Two pairs of L-shaped beams and corresponding piezoelectric brick specimens are customized. The influences of some factors on the output voltage and average power from piezoelectric patches of aforesaid piezoelectric bricks are tested and analyzed. Numerical computation based on the theory model of L-shaped beam is conducted to extend the study on the electric output performances of the proposed piezoelectric bricks. Experiment and simulation results indicate that the peak-to-peak voltage and average power can reach up to 376 V (0.15 V/mm3) and 94.72 mW (37.89 μW/mm3) for a piezoelectric patch with a dimension of 50 mm × 50 mm × 1 mm of brick specimens. This research provides novel piezoelectric bricks to harvest footstep energy and obtains some instructive conclusions for the practical design of the piezoelectric brick with ideal energy harvesting efficiency and cost-effectiveness.
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Thumrongvut, Jaksada, et Sittichai Seangatith. « Experimental Evaluation on Fixed End Supported PFRP Channel Beams and LRFD Approach ». Applied Mechanics and Materials 105-107 (septembre 2011) : 1671–76. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1671.
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In this paper, the experimental results on the fixed end supported PFRP channel beams subjected to three-point loading are presented. The aims of this study are to evaluate the effects of the span (L) on the structural behaviors, the critical buckling moments and the modes of failure of the beams, and to compare the obtained critical buckling moments with those obtained from the modified LFRD steel design equation in order to check the adequacy of the equation. The beam specimens have the cross-sectional dimensions of 76x22x6 mm, with span-to-depth ratio (L/d) ranging from 13 to 52. A total of twenty-six specimens were tested. Based on the experimental results, it was found that the loads versus mid-span vertical deflection relationships of the beams are linear up to the failure. On the contrary, the load versus mid-span lateral deflection relationships are geometrically nonlinear. The general modes of failure are the flexural-torsional buckling. Finally, the modified LFRD equation can satisfactorily predict the critical buckling moment for L/d exceeds 20. However, for L/d < 20, the equation overestimates the critical buckling moment of the beams and more development is needed.
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Shi, Hongyu, Luyi Wang, Mengran Zhao, Juan Chen, Anxue Zhang et Zhuo Xu. « Transparent Metasurface for Generating Microwave Vortex Beams with Cross-Polarization Conversion ». Materials 11, no 12 (3 décembre 2018) : 2448. http://dx.doi.org/10.3390/ma11122448.
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In this paper, metasurfaces with both cross-polarization conversion and vortex beam-generating are proposed. The proposed finite metasurface designs are able to change the polarization of incident electromagnetic (EM) waves to its cross-polarization. In addition, they also can modulate the incidences into beams carrying orbital angular momentum (OAM) with different orders ( l = + 1 , l = + 2 , l = − 1 and l = − 2 ) by applying corresponding transmission phase distribution schemes on the metasurface aperture. The generated vortex beams are at 5.14 GHz. The transmission loss is lower than 0.5 dB while the co-polarization level is −10 dB compared to the cross-polarization level. The measurement results confirmed the simulation results and verified the properties of the proposed designs.
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Said, AbdulMuttalib Issa, Ali Hussein Ali Al-Ahmed et Dhafer Mohsin Al-Fendawy. « Strengthening of Reinforced Concrete T- Section Beams Using External Post-Tensioning Technique ». Journal of Engineering 21, no 12 (1 décembre 2015) : 139–54. http://dx.doi.org/10.31026/j.eng.2015.12.09.
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This research is carried out to investigate the externally post-tensioning technique for strengthening RC beams. In this research, four T-section RC beams having the same dimensions and material properties were casted and tested up to failure by applying two mid-third concentrated loads. Three of these beams are strengthened by using external tendons, while the remaining beam is kept without strengthening as a control beam. Two external strands of 12 mm diameter were fixed at each side of the web of the strengthened beams and located at depth of 200 mm from top fiber of the section (dps). So that the depth of strands to overall depth of the section ratio (dps /h=0.8). For each strengthened beams, the strands have been tensioned by using a hydraulic jack with constant stress of 600 MPa. The main parameter conducting in this research is the strengthening length ratio (Ls/L) which is equal to the length of strengthening region (Ls) divided to the length of beam (L), these ratios are 0.83, 0.67 and 0.50. The experimental results showed that this technique for strengthening is efficient for reducing cracks width and increasing first cracking, service cracking and ultimate load capacities. The percentage increasing in first crack loads were 100%, 133% and 167%, for service crack loads (0.3 mm) were 63%, 75% and 88% and for ultimate loads were 78%, 89% and 67% for strengthening length ratios 0.83, 0.67 and 0.50 respectiviely as compared with the control beam.
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Balamuralikrishnan, R., A. S. H. Al-Mawaali, M. Y. Y. Al-Yaarubi, B. B. Al-Mukhaini et Asima Kaleem. « Seismic Upgradation of RC Beams Strengthened with Externally Bonded Spent Catalyst Based Ferrocement Laminates ». HighTech and Innovation Journal 4, no 1 (1 mars 2023) : 189–209. http://dx.doi.org/10.28991/hij-2023-04-01-013.
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Globally, since there are more systems of civil infrastructure, there are also more degraded buildings and structures. If upgrading or strengthening is a practical option, complete replacement is likely to be an escalating financial burden and may be a waste of natural resources. It is necessary to repair or strengthen a number of reinforced concrete buildings and structures in order to boost their load-bearing capabilities or improve their ductility under seismic stress. Additionally, due to changes in service circumstances, a structure might need to be modified to reduce deflections or manage cracking. Strengthening may be preferable to limiting usage, capping applied loads, and regularly inspecting the structure rather than removing the existing structure or part and building a new one. This study aims to examine the flexural, shear, and combined effect of flexural and shear behavior of reinforced concrete (RC) beams strengthened with externally bonded spent catalyst-based ferrocement laminates and compare them to the control beams (unstrengthened) under two-point loading conditions. This study involves researching laminates with various spent catalyst doses, such as 3, 6, 9, and 12%, in an effort to determine the best amounts that will improve the structural performance of ferrocement laminates. Twelve spent catalyst-based ferrocement laminates measuring 500(L) × 125(B) × 20 mm (thickness) with 3% volume fraction of meshes each were cast and tested in the lab as part of the preliminary investigation. For repeatability, three laminates per case were employed. Eight numbers of under-reinforced RC beams measuring 75(L) × 100(B) × 150(D) mm were cast for the main study; six numbers were strengthened with optimized spent catalyst-based ferrocement laminates bonded with flexible epoxy systems at the tension zone, shear zone, and combination of tension and shear zone. Two of the beams were cast as control specimens. The beams were then evaluated using a Universal Testing Machine (UTM) with a 1000 kN capacity under two-point loading conditions. As a result, the strength, yield load, ultimate load, stiffness, ductility, and related failure modes of all tested beams' flexural and shear performances were examined. According to a preliminary analysis of laminates made of spent catalyst, the dosage of 9% provides good flexural strength in comparison to other doses. In comparison to the strengthened beam, the control beam's initial cracks appeared earlier. In comparison to the control beam, the strengthened beam has an increase in load-carrying capacity of 18% for flexure, 16% for shear, and 30% for the combined impact of flexure and shear. In comparison to the control beam, the deflection of the strengthened beam was decreased by close to 20 to 40% for flexure, 10 to 30% for shear, and 15 to 20% for the combined effects of flexure and shear at the same load level. In relation to control beams, the ductility also improved up to 30% for flexure, 25% for shear, and 25% for the combined impact of flexure and shear. Similar to this, the retrofitted beam is stiffer than the control beam by approximately 40% for flexure, 48% for shear, and 30% for the combined effect of flexure and shear. Theoretical formulation by section analysis is also derived and it gives close agreement with control and strengthened beams. The flexural and shear strengthening of the RC beam retrofitting system is effectively increased by using spent catalyst-based ferrocement laminates. No beam showed signs of premature and brittle failure. According to the test findings, it can be said that spent catalyst-based ferrocement reinforced beams perform better in every way than control beams. Doi: 10.28991/HIJ-2023-04-01-013 Full Text: PDF
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Shi, Xuguang. « Fractional orbital angular momentum of light beams by topological trajectory ». Journal of Nonlinear Optical Physics & ; Materials 24, no 02 (juin 2015) : 1550025. http://dx.doi.org/10.1142/s0218863515500253.
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We derive a rigorous quantum formula called topological trajectory to describe orbital angular momentum (OAM) index based on linear momentum density of Laguerre–Gauss (L–G) light beam. By considering the correspondence between optics and quantum theory, we construct a coherent state from two L–G modes light beam. The light beams with fractional OAM are described by the coherent state. By making use of topological trajectory, we present the conditions that OAM index is fractional.
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Herring, Rodney A. « Reflection diffracted beam interferometry (RDBI) applied to the study of surfaces ». Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 août 1995) : 116–17. http://dx.doi.org/10.1017/s0424820100136957.
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Diffracted beam interferometry, DBI, (previously referred to as Convergent Beam Electron Diffraction + Electron Biprism Interferometry, CBED+EBI) which uses an electron biprism to deflect diffracted beams (convergent or parallel) can produce an interferogram between any two beams within the information envelope of the microscope such that the beam's amplitude and phase can be measured and studied. As well, the electron source need not be highly coherent. So far, DBI has been applied only to transmission electron diffraction, although there is no reason why it shouldn't be applicable to all electron diffraction methods including reflection high (low) energy electron diffraction, RH(L)EED and, possibly, back-scattered electron diffraction, BSED, in the SEM for the study of surfaces. DBI has already shown that substantial phase information, such as strain at interfaces and dislocations, compositional gradients and small defect clusters which are on the size scale of the unit cell, are retrievable from its holograms.
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Zheng, Guoliang, Qingyang Wu, Tiefeng He et Xuhui Zhang. « Propagation Characteristics of Circular Airy Vortex Beams in a Uniaxial Crystal along the Optical Axis ». Micromachines 13, no 7 (26 juin 2022) : 1006. http://dx.doi.org/10.3390/mi13071006.
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Circular airy vortex beams (CAVBs) have attracted much attention due to their “abruptly autofocusing” effect, phase singularity, and their potential applications in optical micromanipulation, communication, etc. In this paper, we numerically investigated the propagation properties of circular airy beams (CABs) imposed with different optical vortices (OVs) along the optical axis of a uniaxial crystal for the first time. Like other common beams, a left-hand circular polarized (LHCP) CAVB, propagating along the optical axis in a uniaxial crystal, can excite a right-hand circular polarized (RHCP) component superimposed with an on-axis vortex of topological charge (TC) number of 2. When the incident beam is an LHCP CAB imposed with an on-axis vortex of TC number of l = 1, both of the two components have an axisymmetric intensity distribution during propagation and form hollow beams near the focal plane because of the phase singularity. The phase pattern shows that the LHCP component carries an on-axis vortex of TC number of l = 1, while the RHCP component carries an on-axis vortex of TC number of l = 3. With a larger TC number (l = 3), the RHCP component has a larger hollow region in the focal plane compared to the LHCP component. We also studied cases of CABs imposed with one and two off-axis OVs. The off-axis OV makes the CAVB’s profile remain asymmetric throughout the propagation. As the propagation distance increases, the off-axis OVs move near the center of the beam and overlap, resulting in a special intensity and phase distribution near the focal plane.
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Kenea, Goshu. « Analytical Study of Geometric Parameter Effect on the Behavior of Horizontally Curved Reinforced Concrete Deep Beam ». Journal of Engineering 2022 (17 mai 2022) : 1–14. http://dx.doi.org/10.1155/2022/8052852.
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Nonlinear finite element simulation was once employed to look into the behavior of horizontally curved reinforced concrete deep beams under concentrated load at its mid-span. The study focused on the parametric impact of span length-to-depth (L/D) and span length-to-radius (L/R) ratios. In addition, the effect of longitudinal and spacing of shear reinforcement on the behavior of the beam has been investigated. The study considered sixteen beam specimens. Three of these specimens were straight beams as a control, and others were curved beams. The concrete-damaged plasticity model has been used to model the beam with C-25 grade concrete and steel reinforcements having diameters of ∅ 4 mm, ∅ 10 mm, and ∅ 12 mm with 568 MPa, 596 MPa, and 643 MPa steel grade, respectively. Reduced twenty-noded brick (C3D20 R) and two-noded (T3D2) elements have been used for modeling concrete and steel, respectively. The ultimate load capacity, the strain distribution, the load-deflection curve, and the load-twisting curve are the main outputs of the FE simulation. The study confirmed a considerable decrease in load-carrying capacity by up to 8.74% and 27.95% as the (L/R) ratio increased from 0 to 1.57 and the L/D ratio increased from 2.4 to 3, respectively. However, as the longitudinal steel ratio increased from 0.02042 to 0.02608 and the spacing of shear reinforcement decreased from 100 mm to 50 mm, the ultimate load capacity is increased up to 9.28% and 4.3%, respectively. Sensitivity evaluation was also conducted to see how much the independent variables (L/D ratio, L/R ratio, longitudinal bar ratio, and spacing transverse reinforcement) affect the dependent parameter (ultimate load capacity).
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de Villiers, Mattieu S., et William D. Cotton. « MeerKAT Primary-beam Measurements in the L Band ». Astronomical Journal 163, no 3 (17 février 2022) : 135. http://dx.doi.org/10.3847/1538-3881/ac460a.
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Abstract Full-polarization primary-beam patterns of MeerKAT antennas have been measured in the L band (856–1711MHz) by means of radio holography using celestial targets. This paper presents the observed frequency-dependent properties of these beams and guides users of this 64 antenna radio telescope that are concerned by its direction-dependent polarization effects. In this work, the effects on the primary beams due to modeling simplifications, bandwidth averaging, gravitational loading, and ambient temperature are quantified within the half-power region of the beam. A perspective is provided on the level of significance of typical use case effects. It is shown that antenna pointing is a leading cause of inaccuracy for telescope users in the presumed beam shape, introducing errors exceeding 1% in power near the half-power point of beams, owing to a telescope pointing accuracy of σ ≈ 0.′6. Disregarding these pointing errors, variability in the Stokes I beam shape relative to the array average is most commonly around 0.3% in power; however, the impact above 1500 MHz is on average triple that of the lower half of the band. This happens because the proportion of higher-order waveguide modes that are activated and propagate is sensitive to small manufacturing differences in the orthomode transducer for each receiver. Primary-beam correction verification test results for an off-axis spectral-index measurement experiment are included.
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Patil, S. S., et B. R. Niranjan. « Analysis and Design of R.C. Deep Beams by Finite Strip Method and Comparison of Theoretical Results with Experimental Results ». Asian Review of Civil Engineering 2, no 1 (5 mai 2013) : 1–8. http://dx.doi.org/10.51983/tarce-2013.2.1.2200.
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This paper describes analysis and design of deep beams subjected to two point loads with different L/D ratios using Program in FORTRAN 77 by finite strip method and standard codes (I.S. 456-2000, B.S.8112, ACI 318 and Appendix A of ACI 318). Variation of flexural stress, strain and shear stress in deep beam were plotted. The parameter, Shear span of beam was varied during the analysis. Several beams were cast and tested in laboratory as per codal provisions.
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Liu, Xuejuan, Shuo Liu et Shubo Cheng. « Controllable Helico-Conical Beam Generated with the Bored Phase ». Photonics 10, no 5 (15 mai 2023) : 577. http://dx.doi.org/10.3390/photonics10050577.
Texte intégralRésumé :
A controllable helico-conical beam is proposed in this paper. The intensity patterns and the local spatial frequency of the controllable helico-conical beams in the focal region are analyzed in detail. The results show that the length of the helico-conical beams can be customized by the variable parameter k, and the angular dimension of the bored spiral trajectory is dependent on the proportion k/l. Moreover, the focal-field energy flow density and orbital angular momentum distributions of the controllable helico-conical beams are also analyzed. The proposed helico-conical beams with controllable lengths can be potentially applied in the field of optical guiding.
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Asad, K. M. B., J. N. Girard, M. de Villiers, T. Ansah-Narh, K. Iheanetu, O. Smirnov, M. G. Santos et al. « Primary beam effects of radio astronomy antennas – II. Modelling MeerKAT L-band beams ». Monthly Notices of the Royal Astronomical Society 502, no 2 (15 janvier 2021) : 2970–83. http://dx.doi.org/10.1093/mnras/stab104.
Texte intégralRésumé :
ABSTRACT After a decade of design and construction, South Africa’s SKA-MID precursor MeerKAT has begun its science operations. To make full use of the widefield capability of the array, it is imperative that we have an accurate model of the primary beam of its antennas. We have taken available L-band full-polarization ‘astro-holographic’ observations of three antennas and a generic electromagnetic simulation and created sparse representations of the beams using principal components and Zernike polynomials. The spectral behaviour of the spatial coefficients has been modelled using discrete cosine transform. We have provided the Zernike-based model over a diameter of 10 deg averaged over the beams of three antennas in an associated software tool (EIDOS) that can be useful in direction-dependent calibration and imaging. The model is more accurate for the diagonal elements of the beam Jones matrix and at lower frequencies. As we get more accurate beam measurements and simulations in the future, especially for the cross-polarization patterns, our pipeline can be used to create more accurate sparse representations of MeerKAT beams.
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Wang, Ziyang, Xiaotian Pan, Fan Yang, Shenheng Xu et Maokun Li. « Real-Time Mode Switching and Beam Scanning of High-Gain OAM Waves Using a 1-Bit Reconfigurable Reflectarray Antenna ». Electronics 9, no 12 (18 décembre 2020) : 2181. http://dx.doi.org/10.3390/electronics9122181.
Texte intégralRésumé :
A reconfigurable electromagnetic surface has been studied to realize the adjustable orbital angular momentum (OAM) beams for real-time wireless communication and dynamic target detection in the future. OAM mode switching realized by many previous designs suffers from low gains without OAM beam scanning. In this article, a 1-bit reconfigurable reflectarray antenna is designed, fabricated, and tested for the real-time control of OAM mode switching and large-angle vortex beam scanning in three-dimensional space. The proposed reflectarray surface is composed of 1-bit electronically reconfigurable cells, and the size is 24 λ × 24 λ with 2304 units. The reconfigurable element is designed by using a radiation patch loading a PIN diode with effective control of two states, “ON” and “OFF”, for the demand of 180° phase difference. The reflectarray surface can be assigned to a code sequence of 0 or 1 by the Field-Programmable Gate Array (FPGA) in real time. Henceforth, the coding surface can dynamically control the generation of high-gain OAM beams, where only the optimized phase distributions on the surface need to be changed according to demand. To verify the concept, a large-scale reflectarray surface is fabricated and measured with an oblique feed at 15°. Different OAM-carrying phase distributions for different OAM beam states are calculated and tested. The test results show that the OAM mode switching between l = 1 and l = 2 is realized, and other variable modes such as l = 3 or l = 5 can also be achieved by modifying the phase encoding sequence. Furthermore, the direction of the vortex beams can be accurately controlled with gains over 20 dBi, and the large-angle vortex beam scanning is verified. Therefore, all results demonstrate that the proposed 1-bit reconfigurable reflectarray is efficient for the regulation and control of OAM-carrying beams for the demand of real-time dynamic wireless communications in the future.
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Thejappa, G. « Evidence for the Three Wave Interactions in the Vicinity of an Interplanetary Shock ». Astrophysical Journal 937, no 1 (1 septembre 2022) : 28. http://dx.doi.org/10.3847/1538-4357/ac8b07.
Texte intégralRésumé :
Abstract We present the high time resolution in situ observations of coherent one-dimensional magnetic-field-aligned Langmuir wave packets with well-defined low frequency modulations (beats) in the upstream region of a coronal mass ejection driven supercritical quasi-perpendicular interplanetary (IP) shock. We show that these beat-type waveforms provide what is believed to be the first observational evidence for one of the most important three wave interactions, called the electrostatic decay instability (ESD) L → L ′ + S (L is the pump Langmuir wave excited by the shock accelerated electron beam, and L′ and S are the daughter Langmuir and ion sound waves, respectively). We also show that (1) the spectra of these wave packets contain the signatures of L, L′, and S, which satisfy the resonance conditions required for excitation of ESD, (2) the peak intensities of these wave packets well exceed the ESD threshold values, and (3) the speed of the electron beam estimated using the resonance conditions is very close to the typical observed speeds of the IP shock accelerated electron beams. The implication of these findings is that (1) the shock accelerated electron beams probably are stabilized by the three wave interaction L → L ′ + S , and (2) the second harmonic radio emission T 2 f pe of solar type II radio bursts probably is excited by the three wave merging L + L ′ → T 2 f pe .
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Alsultani, Alyaa S., et Najla'a H. Al-Shareef. « Flexural Behavior of Rectangular Double Hollow Flange Cold-Formed Steel I-beam ». Tikrit Journal of Engineering Sciences 30, no 4 (7 novembre 2023) : 28–35. http://dx.doi.org/10.25130/tjes.30.4.4.
Texte intégralRésumé :
This research experimentally investigates the flexural behavior of rectangular hollow flange cold-formed steel I-beam (RHFCFSIB) under two concentrated loads at the same distance from the support. All specimens were at a constant clear span of (L=1500mm), a constant beam specifications (t=4mm) web, flange thickness (h=300mm) for beam′s depth, and flange width of (bf=150mm). The connecting distance between the bolts, i.e., connects the web to the flanges, was (L/6), and eight stiffeners for each beam were placed under the load bearing points and at the support points on each side. The experimental program included assembling the parts to make beams and testing four specimens under two-point loads. The major parameters adopted in the current research included the flange depth, i.e., hf=30,60,90, and 120mm. The results showed that the beam with a flange depth of 30 mm had a higher ultimate load than other beams; however, it was the highest beam deflection. The beam with a flange depth of 120mm was the best section as a flexural member. The ultimate capacity of this beam increased by 15.34% and 6.4% compared to beams with flange depths of 60mm and 90mm and decreased by 12.9% compared to a beam with a flange depth of 30 mm. The maximum deflection at beam mid-span with a flange depth of 120 mm decreased by 53.8%, 44%, and 19.94% compared to beams with flange depths of 30 mm, 60mm, and 90mm, respectively. Therefore, the flange depth significantly influenced the flexural behavior by increasing the flange depth. Also, the ultimate capacity increased, and the deflection was reduced. The main conclusions drawn from the study were discussed and summarized. The research showed that the Hollow flanged sections gave the best results for flexural behavior.
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Seangatith, Sittichai, et Jaksada Thumrongvut. « Experimental Investigation on Simply Supported PFRP Channel Beams Subjected to Three-Point Loading ». Advanced Materials Research 335-336 (septembre 2011) : 1321–26. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.1321.
Texte intégralRésumé :
This paper presents the experimental results on the simply supported PFRP channel beams subjected to three-point loading. The objectives of the research work are to investigate the effects of the span (L) of the beams on the behaviors, the critical buckling moments and the modes of failure of the beams, and to compare the obtained critical buckling moments with those obtained from the modified LFRD steel design equation in order to check the adequacy of the equation. The beam specimens have the cross-sectional dimensions of 102×29×6 mm with span-to-depth ratio (L/d) ranging from 20 to 40. A total of ten specimens were tested. Based on the test results, it was found that the load versus mid-span vertical deflection relationships are linear up to the failure, but the load versus mid-span lateral deflection relationships are geometrically nonlinear. The general mode of failure is the flexural-torsional buckling. Finally, the modified LFRD equation can satisfactorily predict the critical buckling moment of the PFRP beams used in this study.
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Liu, Xinhua, Jianren Zhang, Zihan Cheng et Meng Ye. « Experimental and Numerical Studies on the Negative Flexural Behavior of Steel-UHPC Composite Beams ». Advances in Civil Engineering 2021 (31 janvier 2021) : 1–15. http://dx.doi.org/10.1155/2021/8828175.
Texte intégralRésumé :
The cracking of concrete in the negative moment region for a composite beam subjected to a negative bending moment reduces the beam’s strength and stiffness. To improve the cracking performance of composite beams, this paper presents an experimental investigation on applying ultrahigh-performance concrete (UHPC) instead of conventional concrete. Three steel-UHPC composite beams with different forms of joints were designed and tested through a unique rotation angle loading method using a spring displacement control testing setup. The crack distribution, rotation versus crack width, load versus spring displacement, and strains in the UHPC slab and steel girders were measured and studied. Nonlinear finite element analysis using ABAQUS based on the damaged plasticity model of concrete was carried out for comparison with the test results. The experimental and numerical results showed that the use of a UHPC slab can enhance the cracking performance of composite beams. Considering the convenience of construction, a reasonable joint form was suggested, and the appropriate UHPC longitudinal laying length in the negative moment region was proposed to be 0.1 L. Furthermore, a simplified formula for calculating the UHPC crack width was developed based on bond-slip theory.
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Syms, Richard, et Dixi Liu. « Buckling Electrothermal NEMS Actuators : Analytic Design for Very Slender Beams ». Micro 2, no 1 (13 janvier 2022) : 54–67. http://dx.doi.org/10.3390/micro2010003.
Texte intégralRésumé :
Analytic approximations are presented for the response of buckling-mode electrothermal actuators with very slender beams with a width-to-length ratio of W/L≤0.001 of the type found in nanoelectromechanical systems (NEMS). The results are found as closed-form solutions to the Euler beam bending theory rather than by an iterative numerical solution or a time-consuming finite element analysis. Expressions for transverse deflections and stiffness are presented for actuators with the common raised cosine and chevron pre-buckled shapes. The approximations are valid when the effects of bending dominate over those of axial compression. A few higher-order approximations are also presented for less slender beams with 0.001≤W/L≤0.01.
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Rejeki Laku Utami, Sri, Nuroji Nuroji et Antonius Antonius. « Pengaruh Pembalutan Carbon Fiber Wrap (CFW) terhadap Daktilitas Balok Beton Bertulang ». INERSIA lnformasi dan Ekspose Hasil Riset Teknik Sipil dan Arsitektur 12, no 2 (16 janvier 2017) : 140–55. http://dx.doi.org/10.21831/inersia.v12i2.12589.
Texte intégralRésumé :
ABSTRACT Wrapping Carbon Fiber Wrap on reinforced concrete beams are expected to contribute to the improvement of ductility. In this study four beam specimens. The first test object beam 3D16 Normal used as a normal beam. The test object into two beams 3D16 CFW is used as a treatment beam with the dressing CFW. The test object to the three beams 4D16 Normal is used as a normal beam. The test object into four beams dalah 4D16 CFW is used as a treatment beam with the dressing CFW. Dimensional beam - the beam is 150 x 250 mm, the effective length 2000 mm. Imposition given One Point Loads, to test the loading on beam flexural planned to put the pieces of force P symmetrically at a distance that is equal to ½ L 1000 mm. And given a dressing CFW on the beam 3D16 CFW along the 600 mm (2.4 h) the middle span length of 2000 mm with treatment CFW Completely Wrapped Member. From the test results maximum bending capacity respectively for beams 3D16 Normal of 104.04 kN while on the beams 3D16 CFW increased maximum bending capacity of 119.52 kN, increase in ductility displacement on the beam by 33%. On the beam 4D16 Normal has a maximum bending capacity of 161.28 kN the beam 4D16 CFW increased maximum bending capacity of 162.64 kN, increase in ductility displacement on the beam by 45%. The maximum nominal value at the moment of reinforced concrete beam greatly affect the capacity maximum moment on the beam 3D16 Normal with beams 3D16 CFW after dressing CFW on the beams increased by 13% while on the beam 4D16 Normal with beams 4D16 CFW increased by 1%. Ductility curvature on beam 3D16 Normal with beams 3D16 CFW increased by 63% whereas for beams 4D16 Normal with beams 4D16 CFW curvature ductility increased by 67%. Keyword: CFW (Carbon Fiber Wraps), ductility, flexural strength, moment-curvatur. ABSTRAK Pembalutan Carbon Fiber Wrap pada balok beton bertulang diharapkan memberikan konstribusi terhadap peningkatan daktilitas. Pada penelitian ini empat buah benda uji balok. Benda uji pertama adalah balok 3D16 Normal yang digunakan sebagai balok normal. Benda uji ke dua adalah balok 3D16 CFW yang digunakan sebagai balok dengan perlakuan pembalutan CFW. Benda uji ke tiga adalah balok 4D16 Normal yang digunakan sebagai balok normal. Benda uji ke empat dalah balok 4D16 CFW yang digunakan sebagai balok dengan perlakuan pembalutan CFW. Dimensi balok – balok tersebut adalah 150 x 250 mm, dengan panjang efektif 2000 mm. Pembebanan diberikan One Point Loads, untuk melakukan uji lentur maka pembebanan pada balok direncanakan dengan menempatkan satu buah gaya P secara simetris pada jarak ½ L yaitu sebesar 1000 mm. Dan diberikan pembalutan CFW pada balok 3D16 CFW sepanjang 600 mm (2,4 h) ditengah bentang yang panjangnya 2.000 mm dengan perlakuan CFW Completely Wrapped Member. Dari hasil pengujian kapasitas lentur maksimum secara berturut- turut untuk balok 3D16 Normal sebesar 104,04 kN sedangkan pada balok 3D16 CFW mengalami peningkatan kapasitas lentur maksimum sebesar 119,52 kN, peningkatan daktilitas perpindahan pada balok sebesar 33%. Pada balok 4D16 Normal memiliki kapasitas lentur maksimum sebesar 161,28 kN sedangkan balok 4D16 CFW mengalami peningkatan kapasitas lentur maksimum sebesar 162,64 kN, peningkatan daktilitas perpindahan pada balok sebesar 45%. Nilai momen nominal maksimum pada balok beton bertulang sangat mempengaruhi peningkatan kapasitas momen maksimum pada balok 3D16 Normal dengan balok 3D16 CFW setelah dilakukan pembalutan CFW pada balok mengalami peningkatan sebesar 13% sedangkan pada balok 4D16 Normal dengan balok 4D16 CFW mengalami peningkatan sebesar 1%. Nilai daktilitas kurvatur pada balok 3D16 Normal dengan balok 3D16 CFW mengalami peningkatan sebesar 63% sedangkan untuk balok 4D16 Normal dengan balok 4D16 CFW mengalami peningkatan daktilitas kurvatur sebesar 67%. Kata kunci: CFW (Carbon Fiber Wraps), daktilitas, kuat lentur, momen-kurvatur.
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Acevedo, Cristian Hernando, Carlos Fernando Díaz et Yezid Torres-Moreno. « Determination of the topological charge of a bessel-gauss beam using the diffraction pattern through of an equilateral aperture ». DYNA 82, no 190 (11 mai 2015) : 214–20. http://dx.doi.org/10.15446/dyna.v82n190.43965.
Texte intégralRésumé :
The topological charge TC of an electromagnetic wave is relate with their wavefront spatial distribution. Electromagnetic waves with factor azimuthal exp(ilθ) in its phase, have TC integer (l=m) or non-integer (l=M). These electromagnetic waves with a well-defined of TC can be produced in the visible regime by computer generated holographic masks with fork shaped. In this paper, we study the formed triangle lattice distribution in the intensity Fraunhofer regime using numerical simulations of the Bessel-Gauss beams with integer and non-integer TC. The beam is diffracted by equilateral triangular aperture to measure both their sign and magnitude. In addition, we showed the experimental results of the intensity in far field regime product of diffraction of Bessel-Gauss beams with integer and noninteger TC by the equilateral triangular aperture. Partial and qualitative explanations have been proposed for the diffraction of electromagnetic beams with topological charge. This paper presents a complete analysis for qualitative and quantitative explanation of diffraction of a beam with topological charge by a triangular aperture. The results of such diffraction are obtained by numerical simulation or experimentally.
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Hüller, Stefan, Gaurav Raj, Mufei Luo, Wojciech Rozmus et Denis Pesme. « Crossed beam energy transfer between optically smoothed laser beams in inhomogeneous plasmas ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 378, no 2184 (12 octobre 2020) : 20200038. http://dx.doi.org/10.1098/rsta.2020.0038.
Texte intégralRésumé :
Crossed beam energy transfer, CBET, in high-intensity laser–plasma interaction is investigated for the case of optically smoothed laser beams. In the two approaches to laser-driven inertial confinement fusion experiments, the direct-drive and the indirect-drive, CBET is of great importance because it governs the coupling of laser energy to the plasma. We use the two-dimensional wave-coupling code H armony to simulate the transfer between two laser beams with speckle structure that overlap in a plasma with an inhomogeneous flow profile. We compare the CBET dynamics for laser beams with spatial incoherence and with spatio-temporal incoherence; in particular we apply the smoothing techniques using random phase plates (RPPs) and smoothing by spectral dispersion (SSD), respectively. It is found that for laser beams (wavelength λ 0 ) with intensities ( I L ) above I L ∼ 2 × 10 15 W cm −2 ( λ 0 /0.35 µm) −2 ( T e /keV), both the so-called plasma-induced smoothing as well as self-focusing in intense laser speckles induce temporal incoherence; the latter affects the CBET and the angular distribution of the light transmitted behind the zone of beam overlap. For RPP-smoothed incident beams, the resulting band width of the transmitted light can already be of the same order as the effective band width of the SSD available at major laser facilities. We examine the conditions when spatio-temporal smoothing techniques become efficient for CBET. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 1)’.
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Benis, Emmanouil, Ioannis Madesis, Angelos Laoutaris, Stefanos Nanos et Theo Zouros. « Mixed-State Ionic Beams : An Effective Tool for Collision Dynamics Investigations ». Atoms 6, no 4 (29 novembre 2018) : 66. http://dx.doi.org/10.3390/atoms6040066.
Texte intégralRésumé :
The use of mixed-state ionic beams in collision dynamics investigations is examined. Using high resolution Auger projectile spectroscopy involving He-like ( 1 s 2 1 S , 1 s 2 s 3 , 1 S ) mixed-state beams, the spectrum contributions of the 1 s 2 s 3 S metastable beam component is effectively separated and clearly identified. This is performed with a technique that exploits two independent spectrum measurements under the same collision conditions, but with ions having quite different metastable fractions, judiciously selected by varying the ion beam charge-stripping conditions. Details of the technique are presented together with characteristic examples. In collisions of 4 MeV B 3 + with H 2 targets, the Auger electron spectrum of the separated 1 s 2 s 3 S boron beam component allows for a detailed analysis of the formation of the 1 s 2 s ( 3 S ) n l 2 L states by direct n l transfer. In addition, the production of hollow 2 s 2 p 1 , 3 P doubly- and 2 s 2 p 2 2 D triply-excited states, by direct excitation and transfer-excitation processes, respectively, can also be independently studied. In similar mixed-state beam collisions of 15 MeV C 4 + with H 2 , He, Ne and Ar targets, the contributions of the 1 s 2 , 1 s 2 s 3 , 1 S beam components to the formation of the 2 s 2 p 3 , 1 P states by double-excitation, 1 s → 2 p excitation and transfer-loss processes can be clearly identified, facilitating comparisons with theoretical calculations.
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Journal, IJSREM. « STRENTH OF RC BEAM USING WASTE MATERIAL (plastic)& ; ADOPTING BUBBLE TECHNOLOGY ». INTERANTIONAL JOURNAL OF SCIENTIFIC RESEARCH IN ENGINEERING AND MANAGEMENT 08, no 03 (15 mars 2024) : 1–11. http://dx.doi.org/10.55041/ijsrem29269.
Texte intégralRésumé :
The utilization of these wastes(plastic) as an aggregate origin for concrete will help to clean the environment and help a cheaper and renewable aggregates source for construction industries. In the last few years the structure design process is based on superior the materials, their size and fabric, such that it resist under soundness of the structure. In modern Engineering, the formulator requires light weight, extra interpretation and few-cost structures. So, by Structural design in bubble method in use of plastic ball, the best possible structure beam to withstand the service load is achieved. Bubble technology is achieving the best with the so many resource while satisfying the structural beams. In bubble technology researchers used simple prismatic member as calculation of FEM is easy. In paper, they generally explain the simply supported structure domain with multiple point load & uniformely distributed load at whole beams. But in general the loads can be varied throughout the length (L/3, L/5, L/8 etc.). . In this project, M25 concrete mix is used to make beams. The trial mix is tested for compressive strength & split tensile strength. Flexure l test is done is done for 3 and 28 days of curing of the beams Which was actually a difficult problem to minimize the weight. In practical, load on the structure may be inclined, vertical and horizontal which again was a major to help this type of problems. However, after changing some line, all the above problems were solved and gave expected results.
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Bui Thi Ha, Giang. « THE e e Z l l bb + − − + → → COLLISION IN THE RANDALL-SUNDRUM MODEL ». Journal of Science Natural Science 66, no 3 (octobre 2021) : 61–68. http://dx.doi.org/10.18173/2354-1059.2021-0047.
Texte intégralRésumé :
Taking account of the Randall-Sundrum model, we have evaluated the influence of model parameters in e e Z l l bb + − − + → → collision at International Linear Colliders (ILC). In the ILC region, the total cross-section is enhanced at the 125 GeV radion. The total cross-section depends on the polarization of e e − + , initial beams, the radion mass m , the center of mass energy s . Based on the forward - backward asymmetry and the polarization of beams, the reaction can give observable cross-sections based on l l bb − + final state.
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Chen, Shengbing, Yubao Song et Hao Zhang. « Wave Propagation in L-Shape Beams with Piezoelectric Shunting Arrays ». Shock and Vibration 2019 (11 avril 2019) : 1–14. http://dx.doi.org/10.1155/2019/6264251.
Texte intégralRésumé :
Piezoelectric shunting arrays are employed to control the elastic wave propagation in L-shape beams. Unlike straight beams where longitudinal and flexural waves usually propagate independently, these waves are coupled in an L-shape beam. Based on transfer matrix method and Bloch theorem, dispersion curves and vibration transmissibility are evaluated and analyzed. A locally resonant gap is produced on the flexural and longitudinal waves, respectively, whose locations are nonoverlapped if the shunt damping is void. However, the longitudinal wave band gap can be completely overlaid by the flexural one when a proper shunting resistance is involved. With the decreasing of shunting inductance, the locations of longitudinal and flexural wave gaps both go up to higher frequencies which agree with the variation of resonant frequencies, but they are less affected by shunting resistance. As the resistance increases, the width of the band gaps grows, whereas the attainable maximum attenuation within the band gaps shows a significant decrease. Also, finite element simulations are performed to validate the numerical predictions, which demonstrate that the resulting transmissibility of displacements agree well with the band gaps.
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Al-Thabhawee, Hayder Wafi. « EXPERIMANTAL STUDY OF EFFECT OF HEXAGONAL HOLES DIMENSIONS ON ULTIMATE STRENGTH OF CASTELLATED STEEL BEAM ». Kufa Journal of Engineering 8, no 1 (16 février 2017) : 97–107. http://dx.doi.org/10.30572/2018/kje/811186.
Texte intégralRésumé :
Nowadays, use of castellated steel beams (CSBs) has become very common because of their advantageous implementations in construction of buildings. Castellated Steel Beams (CSBs) are those members that are fabricated from standard hot rolled steel (HRS) I- sections by cutting along its web in "zigzag" pattern and thereafter rejoining the two halves on one another by welding together to form a castellated beam, so that generally the depth of  a section will be increased. This research analyses the experimental results of six specimens of castellated steel beams and compares with control beam (Parent section). The purpose of this study is to investigate the effect of hexagonal hole dimensions on the ultimate strength and stiffens response of the castellated steel beam. Also, the effect of number of holes on the behavior of the castellated steel beams that have the same span and ratio of expansion was investigated. All specimens of the castellated steel beam were fabricated from hot rolled steel section (IPE140) and were expanded to (1.56) times the parent section depth. From the test results, it is observed that best dimension of castellated steel beam was (span length to holes space ratio L/S = 8.0); hole depth to Castellated beam depth ratio is h/H=0.56, and hole space to the castellated beam depth ratio is S/H = 1.03. The ultimate strength of the castellated steel beam was increased about (50%) stronger than the original beam.
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Abbas, Mustafa Kamil, et Hayder Wafi Al_Thabhawee. « Experimental study of composite concrete cellular steel beams ». IOP Conference Series : Earth and Environmental Science 961, no 1 (1 janvier 2022) : 012095. http://dx.doi.org/10.1088/1755-1315/961/1/012095.
Texte intégralRésumé :
Abstract The main objective of this study is to compare the structural behavior of composite steel– concrete beams using cellular beams with and without steel ring stiffeners placed around the web openings. An IPE140 hot rolled I-section steel beam was used to create four specimens: one without openings (control beam); one without shear connectors (non-composite); a composite steel–concrete beam using a cellular beam without strengthening (CLB1); and a composite steel–concrete beam using a cellular beam (CLB4-R) with its openings strengthened by steel ring stiffeners with geometrical properties Br = 37mm and Tr = 5mm. CLB1 was fabricated with openings of 100mm diameter and a 1.23 expansion depth ratio, while CLB4-R was fabricated with openings of 130mm diameter, a 1.42 expansion depth ratio. Both beams were 1700mm in length with ten openings. The results of this experiment revealed that the loads applied to CLB1 and CLB4-R at deflection L/360 exceeded the load applied to the control specimen at the same deflection by 149.3% and 177.3%, respectively. The results revealed that the non-composite beam had an ultimate load 29% lower than that of the control beam. The ultimate load on CLB1 was 5.3% greater than that of the control beam, and failure occurred due to web-post buckling. While the ultimate load of the CLB4-R beam was 18.43% greater than that of the control beam, the Vierendeel mechanism was indicated as the failure mode.
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Liu, Donghuan, Mohammed Al-Haik, Mohamed Zakaria et Muhammad R. Hajj. « Piezoelectric energy harvesting using L-shaped structures ». Journal of Intelligent Material Systems and Structures 29, no 6 (17 septembre 2017) : 1206–15. http://dx.doi.org/10.1177/1045389x17730926.
Texte intégralRésumé :
Energy harvesting from an L-shaped structure, formed by two beams and corner and end masses, is investigated with the objective of expanding the bandwidth of the frequency range over which energy can be harvested. The structure is excited in a direction that yields the most uniform strain distribution along its main beam. The length of the auxiliary beam is varied to determine its effect on the level and breadth of the frequency range over which energy can be harvested. Results from experiments having different geometries are presented and discussed. It is determined that the frequency range over which energy can be harvested from such structures is much larger than levels harvested when using a cantilever beam. The experiments also show that L-shaped structures harvest more power when the length of the auxiliary beam is increased. On the contrary, the power density of the L-shaped structure is much smaller than that of the cantilever beam. The ability to control the bandwidth of frequency over which energy is harvested through proper adjustment of beam lengths is demonstrated.
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Topark-Ngarm, Pattanapong, Trinh Cao, Prinya Chindaprasirt et Vanchai Sata. « Strength and Behaviour of Small-Scale Reinforced High Calcium Fly Ash Geopolymer Concrete Beam with Short Shear Span ». Key Engineering Materials 718 (novembre 2016) : 191–95. http://dx.doi.org/10.4028/www.scientific.net/kem.718.191.
Texte intégralRésumé :
The small-scale reinforced high calcium fly ash geopolymer concrete beams with short shear span were studied in this research. Reinforced concrete beams with 150x150 mm2 cross-section and 530 mm in length were used for tests. Conventional reinforced Portland cement concrete beams (RC) with designed concrete compressive strengths of 35, 45 and 55 MPa and high-calcium fly ash geopolymer reinforced concrete beams with similar strength were tested. The geopolymer concretes (GC) were designed with alkaline liquid to fly ash ratio (L/A) of 0.5, sodium silicate to sodium hydroxide (S/H) ratio of 1.0 and two sodium hydroxide (NaOH) concentrations of 10M and 15M. Two temperatures of 23 and 60 °C were used for curing geopolymer reinforced concrete (GRC) beams for 24 hr, while RC beams were moist cured at 23 °C. The maximum sustained moment and shear were compared with the predicted values from the RC-design standard. The results showed that the failure patterns of small GRC beams were different to that of normal RC beam. The small GRC beams failed in flexure whereas the similar small RC beams failed in shear. However, the GRC beams were able to sustain higher shear and moment than the values obtained from the design code. The different in failure mechanism was probably due to the different in modulus of elasticity of geopolymer concrete and normal concrete.
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Yu, Tian Lai, Xian Bin Hou et Lei Lei Tian. « The Shear Resistant Effect of RC Beam Strengthened with SWR External Prestressing under Cracking Width of the Original Beam ». Applied Mechanics and Materials 94-96 (septembre 2011) : 1463–67. http://dx.doi.org/10.4028/www.scientific.net/amm.94-96.1463.
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Through the experiment of the four RC beams strengthened with SWR externally prestressing, the shear resistant effect of Strengthened beams under cracking width of the original beams is studied in the paper. The ultimate load was confirmed by the test of the basic beam. First the presplitting load were respectively 50%, 60%, 70%, 80% of the ultimate load of basic beam, and seconly cracks were repaired with JN-L low viscosity pouring sealant, lastly experiment beams were strengthened by shear reinforcement of the external prestressing with steel wire rope. Loading method is the single point loading, and the shear span ratio is 2.0. The results show that: the cracking width of original beam has certain effect in shear resistant capacity. When the cracking width was less than 0.2 mm, the effect of injecting glue was not ideal and the shear resistant capacity is lower. When the crack width was bigger, the effect of injecting glue was more ideal, so the effect of reinforcement was better. When the cracking width was greater than 0.28 mm, the ultimate load was no longer improved. The smaller inclined cracking width in strengthening is, the worse repairing effect and the bigger strain value of stirrup is. Each strengthened beams’ wire rope strain increment was nearly close before cracking. As the decrease of original beams crack width, crack repair effect was weak, and the external strain increment of wire rope becomes bigger under the same load. The trend was very clear after the stirrup yielding.
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Kumagai, Yuji, Kazumasa Okubo, Takuro Nakamura et Junichiro Niwa. « Shear Behavior of Flanged L-shaped RC Beams ». Concrete Research and Technology 30 (2019) : 21–34. http://dx.doi.org/10.3151/crt.30.21.
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Ibraheem, Omer Farouk, B. H. Abu Bakar et I. Johari. « Fiber reinforced concrete L-beams under combined loading ». Computers and Concrete 14, no 1 (25 juillet 2014) : 1–18. http://dx.doi.org/10.12989/cac.2014.14.1.001.
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Wang, C. M., H. Zhang, R. P. Gao, W. H. Duan et N. Challamel. « Hencky Bar-Chain Model for Buckling and Vibration of Beams with Elastic End Restraints ». International Journal of Structural Stability and Dynamics 15, no 07 (31 août 2015) : 1540007. http://dx.doi.org/10.1142/s0219455415400076.
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This paper presents the Hencky bar-chain model (HBM) for buckling and vibration analyses of Euler–Bernoulli beams with elastic end restraints. The Hencky bar-chain comprises rigid beam segments (of length a = L/n where L is the total length of beam and n the number of beam segments) connected by frictionless hinges with elastic rotational springs of stiffness EI/a where EI is the flexural rigidity of the beam. The elasticity and the mass of the beam are concentrated at the hinges with rotational springs. The key contribution of this paper lies in the modeling of the elastic end restraints of the Hencky bar-chain that will simulate the same buckling and vibration results as that furnished by the first-order central finite difference beam model (FDM) which was earlier shown to be analogous to the HBM. The establishment of such a physical discrete beam model allows one to obtain solutions for beam-like structure with repetitive cells (or elements) as well as to calibrate the Eringen's coefficient e0 in the nonlocal beam theory that captures the small length scale effect.
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Thirunavukkarasu, G., M. Mousley, M. Babiker et J. Yuan. « Normal modes and mode transformation of pure electron vortex beams ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 375, no 2087 (28 février 2017) : 20150438. http://dx.doi.org/10.1098/rsta.2015.0438.
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Electron vortex beams constitute the first class of matter vortex beams which are currently routinely produced in the laboratory. Here, we briefly review the progress of this nascent field and put forward a natural quantum basis set which we show is suitable for the description of electron vortex beams. The normal modes are truncated Bessel beams (TBBs) defined in the aperture plane or the Fourier transform of the transverse structure of the TBBs (FT-TBBs) in the focal plane of a lens with the said aperture. As these modes are eigenfunctions of the axial orbital angular momentum operator, they can provide a complete description of the two-dimensional transverse distribution of the wave function of any electron vortex beam in such a system, in analogy with the prominent role Laguerre–Gaussian (LG) beams played in the description of optical vortex beams. The characteristics of the normal modes of TBBs and FT-TBBs are described, including the quantized orbital angular momentum (in terms of the winding number l ) and the radial index p >0. We present the experimental realization of such beams using computer-generated holograms. The mode analysis can be carried out using astigmatic transformation optics, demonstrating close analogy with the astigmatic mode transformation between LG and Hermite–Gaussian beams. This article is part of the themed issue ‘Optical orbital angular momentum’.
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R., Balamuralikrishnan, Ranya Al-Balushi et Asima Kaleem. « An Investigation on Eco Friendly Self-Compacting Concrete Using Spent Catalyst and Development of Structural Elements ». Civil Engineering Journal 9, no 5 (1 mai 2023) : 1132–59. http://dx.doi.org/10.28991/cej-2023-09-05-08.
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The theme of this initiative is "Waste to Wealth." Construction materials, particularly concrete, need to have better qualities, including strength, rigidity, durability, and ductility, because Oman's construction industry is expanding. Self-compacting concrete (SCC) has more benefits than regular concrete, including better workability. The major focus of this study is the C30-grade SCC for the control mix, spent catalyst (zeolite catalyst)-based SCC, and the development of the RC beam's flexural behavior employing control and spent catalyst-based SCC. The preliminary study and the main study are the two study outcomes included in this project. Preliminary research involves creating four mixtures with various dosages of 3%, 6%, 9%, and 12% in order to optimize spent catalyst in C30 grade concrete. All of the cubes undergo a 28-day curing test. The cubes' compressive strength is tested in order to establish the ideal dosage, which is 9%. Develop a C30 grade control modified design mix in accordance with SCC and optimize chemical admixtures such as superplasticizer (SP) at different dosages, like 2, 2.5, 3, and 3.5%, using various trials and tests (slump flow, L-box, J-ring, V-funnel, and U-box tests), as well as the optimized dosage of spent catalyst (SC). The main study includes six singly reinforced RC beams with dimensions of 750 (L)×100 (B)×150 mm (D) that were cast and tested in the laboratory. After a 28-day curing period, two specimens were placed under a two-point loading setup, with the remaining two samples receiving the optimum dosages of spent catalyst and superplasticizer. All of the beams were tested using a Universal Testing Machine (UTM) with a 1000 kN capability. From the preliminary study, partial substitution of cement in control concrete of grade C30 using spent catalyst (SC), it was found that the 9% optimum dosage produces greater compressive strength compared to other doses, which are almost 10% rises at 28 days of curing period. Based on a different test, it was discovered that the optimum dose of 3% SP gave closer agreement and satisfied the need for SCC as per the BS standard. The load-carrying capability of the SCC beams is almost 21.7% higher than that of the control beams. Comparing the SCC beams to the control beams, their deflection was reduced by about 26% at the same load level, and their ductility rose by almost 33%. Comparatively to the control beam, the stiffness of 21.6% of SCC also rises. According to test results, the SCC beam performs better in every way when superplasticizer and spent catalyst are used at the recommended dosage. Doi: 10.28991/CEJ-2023-09-05-08 Full Text: PDF
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Lytvyniak, Oksana, et Myroslava Tashak. « THE SUGGESTIONS AS TO THE CALCULATION BEARING CAPACITY OF SANDWICH REINFORCED CONCRETE — FOAMED CONCRETE FLOOR SLABS ». Acta Polytechnica 59, no 1 (28 février 2019) : 59–66. http://dx.doi.org/10.14311/ap.2019.59.0059.
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This article presents the results of an experimental research of sandwich reinforced concrete-foamed concrete floor slabs. These floor slabs combine three different materials — normal concrete, foamed concrete and a steel reinforcement. As experimental models six beams with dimensions L × b × h = 4200 × 500 × 200mm were made. Experimental beams were established on two supports (hinged fixed support and hinged movable support). The experimental study of these beams was executed by two concentrated forces in thirds of beam’s span. Received results allowed to describe a behaviour of sandwich reinforced concrete-foamed concrete floor slabs under loading. Moreover, these researches allowed to present suggestions regarding calculations of bearing capacity of sandwich reinforced concrete-foamed concrete floor slabs. These suggestions will give an opportunity to use sandwich reinforced concrete-foamed concrete floor slabs in civil engineering and house building.
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TURAN, Muhittin, et Mahmut İlter HACIOĞLU. « Buckling Analysis of Functionally Graded Beams Using the Finite Element Method ». Erzincan Üniversitesi Fen Bilimleri Enstitüsü Dergisi 15, Special Issue 1 (23 décembre 2022) : 98–109. http://dx.doi.org/10.18185/erzifbed.1199454.
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This study developed a finite element model according to higher-order shear deformation beam theory (HSDT) for the buckling analysis of functionally graded (FG) beams. Equilibrium equations of the FG beam are obtained from Lagrange’s equations. The beam element to be discussed within the scope of the study has 5 nodes and 16 degrees of freedom (DOF). As a result of the buckling analysis, the critical buckling load of the beam was obtained for various boundary conditions, power-law index (p), and slenderness (L/h). When the critical buckling loads obtained as a result of the analysis were compared with the literature, it was seen that they were quite compatible.
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Eckrote, K. A., C. J. Burstone, M. A. Freilich, G. E. Messer et A. J. Goldberg. « Shear in Flexure of Fiber Composites with Different End Supports ». Journal of Dental Research 82, no 4 (avril 2003) : 262–66. http://dx.doi.org/10.1177/154405910308200404.
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The integrity of fiber-reinforced composite (FRC) prostheses is dependent, in part, on flexural rigidity. The object of this study was to determine if the flexure behavior of uniform FRC beams with restrained or simply supported ends and various length/depth (L/d) aspect ratios could be more accurately modeled by correcting for shear. Experimental results were compared with three analytical models. All models were accurate at high L/d ratios, but the shear-corrected model was accurate to the lowest, more clinically relevant, L/d values. In this range, more than 40% of the beam deflection was due to shear.
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Lam, W. Y., R. K. L. Su et H. J. Pam. « Strength and Ductility of Embedded Steel Composite Coupling Beams ». Advances in Structural Engineering 6, no 1 (janvier 2003) : 23–35. http://dx.doi.org/10.1260/136943303321625702.
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The stringent requirements on dimensions, ductility, energy absorption, strength and stiffness of coupling beams have resulted in much research on various alternative coupling beam designs, which include the use of diagonal reinforcement, rhombic arrangement of main bars and steel composites. Experimental results showed that each of these designs offered better performance than the conventional type but had its own limitations. A new embedded steel composite coupling beam design is therefore proposed. This paper presents the findings from the experimental tests of a coupling beam fabricated with this proposed design and a conventionally reinforced coupling beam, which serves as the reference. The preliminary test results showed that the embedded steel coupling beam with relatively large span-to-depth ratio ( l/h = 2.5) had excellent shear capacity (∼10MPa) and very good energy absorption.