Buckling localization in a cylindrical panel under axial compression
Tvergaard, Viggo; Needleman, A.
2000-01-01
Localization of an initially periodic buckling pattern is investigated for an axially compressed elastic-plastic cylindrical panel of the type occurring between axial stiffeners on cylindrical shells. The phenomenon of buckling localization and its analogy with plastic flow localization in tensile......, but where subsequently the load starts to increase again, it is found that near the local load minimum, the buckling pattern switches back to a periodic type of pattern. The inelastic material behavior of the panel is described in terms of J(2) corner theory, which avoids the sometimes unrealistically...
Buckling Imperfection Sensitivity of Axially Compressed Orthotropic Cylinders
Schultz, Marc R.; Nemeth, Michael P.
2010-01-01
Structural stability is a major consideration in the design of lightweight shell structures. However, the theoretical predictions of geometrically perfect structures often considerably over predict the buckling loads of inherently imperfect real structures. It is reasonably well understood how the shell geometry affects the imperfection sensitivity of axially compressed cylindrical shells; however, the effects of shell anisotropy on the imperfection sensitivity is less well understood. In the present paper, the development of an analytical model for assessing the imperfection sensitivity of axially compressed orthotropic cylinders is discussed. Results from the analytical model for four shell designs are compared with those from a general-purpose finite-element code, and good qualitative agreement is found. Reasons for discrepancies are discussed, and potential design implications of this line of research are discussed.
Crushing modes of aluminium tubes under axial compression
Pled, Florent; Yan, Wenyi; Wen, Cui'e
2014-01-01
6 pages International audience A numerical study of the crushing of circular aluminium tubes with and without aluminium foam fillers has been carried out to investigate their buckling behaviours under axial compression. A crushing mode classification chart has been established for empty tubes. The influence of boundary conditions on crushing mode has also been investigated. The effect of foam filler on the crushing mode of tubes filled with foam was then examined. The predicted results ...
Axial Compressive Strength of Foamcrete with Different Profiles and Dimensions
Othuman Mydin M.A.
2014-01-01
Full Text Available Lightweight foamcrete is a versatile material; primarily consist of a cement based mortar mixed with at least 20% volume of air. High flow ability, lower self-weight, minimal requirement of aggregate, controlled low strength and good thermal insulation properties are a few characteristics of foamcrete. Its dry densities, typically, is below 1600kg/m3 with compressive strengths maximum of 15MPa. The ASTM standard provision specifies a correction factor for concrete strengths of between 14 and 42MPa to compensate for the reduced strength when the aspect height-to-diameter ratio of specimen is less than 2.0, while the CEB-FIP provision specifically mentions the ratio of 150 x 300mm cylinder strength to 150 mm cube strength. However, both provisions requirements do not specifically clarify the applicability and/or modification of the correction factors for the compressive strength of foamcrete. This proposed laboratory work is intended to study the effect of different dimensions and profiles on the axial compressive strength of concrete. Specimens of various dimensions and profiles are cast with square and circular cross-sections i.e., cubes, prisms and cylinders, and to investigate their behavior in compression strength at 7 and 28 days. Hypothetically, compressive strength will decrease with the increase of concrete specimen dimension and concrete specimen with cube profile would yield comparable compressive strength to cylinder (100 x 100 x 100mm cube to 100dia x 200mm cylinder.
Failure Processes in Embedded Monolayer Graphene under Axial Compression
Androulidakis, Charalampos; Koukaras, Emmanuel N.; Frank, Otakar; Tsoukleri, Georgia; Sfyris, Dimitris; Parthenios, John; Pugno, Nicola; Papagelis, Konstantinos; Novoselov, Kostya S.; Galiotis, Costas
2014-01-01
Exfoliated monolayer graphene flakes were embedded in a polymer matrix and loaded under axial compression. By monitoring the shifts of the 2D Raman phonons of rectangular flakes of various sizes under load, the critical strain to failure was determined. Prior to loading care was taken for the examined area of the flake to be free of residual stresses. The critical strain values for first failure were found to be independent of flake size at a mean value of –0.60% corresponding to a yield stre...
Experimental - theoretical study of axially compressed cold formed steel profiles
Bešević Miroslav
2011-01-01
Full Text Available Analysis of axially compressed steel members made of cold formed profiles presented in this paper was conducted through both experimental and numerical methods. Numerical analysis was conducted by means of "PAK" finite element software designed for nonlinear static and dynamic analysis of structures. Results of numerical analysis included ultimate bearing capacity with corresponding middle section force-deflection graphs and buckling curves. Extensive experimental investigation were also concentrated on determination of bearing capacity and buckling curves. Experiments were conducted on five series with six specimens each for slenderness values of 50, 70, 90, 110 and 120. Compressed simply supported members were analyzed on Amsler Spherical pin support with unique electronical equipment and software. Besides determination of forcedeflection curves, strains were measured in 18 or 12 cross sections along the height of the members. Analysis included comparisons with results obtained by different authors in this field recently published in international journals. Special attention was dedicated to experiments conducted on high strength and stainless steel members.
Relationship Between Compression Strength and Its Microstructure of 5 Axial-Braided Composite
Yang; Chaokun; Zhu; Jianxun; Jiang; Yun
2007-01-01
Compression performance of 5-axial braided composites is observed through compression tests.A mixed model of micro-buckling shear with braided tows web is set up to predict compression stress of braided composite through analyzing three broken modes.Using this mixed model,data from tests indicated that the main parameters effecting the compression properties of braided composite are fiber volume fraction,directional angle,axial-tow volume fraction and diameter of tow.Contributing rate of tows is proposed to describe the compression properties of fibre composites.Optimization geometrical structure of braids can optimize composite properties.
Axial compression physical testing of traditional and bird beak SHS T-joints
陈誉; 王江
2015-01-01
The static tests of nine traditional and bird beak square hollow structure (SHS) T-joints with differentβ values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load−vertical displacement curves, jack load−deformation of chord and strain intensity distribution curves of joints were presented. The effects ofβ and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values ofβ. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. Asβ increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase asβincreases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase asβ increases, but the ductility of the traditional SHS T-joints decreases asβ increases.
LOAD CARRYING CAPABILITY OF LIQUID FILLED CYLINDRICAL SHELL STRUCTURES UNDER AXIAL COMPRESSION
Qasim H. Shah; MOHAMMAD MUJAHID; MUSHTAK AL-ATABI; YOUSIF A. ABAKR
2011-01-01
Empty and water filled cylindrical Tin (Sn) coated steel cans were loaded under axial compression at varying loading rates to study their resistance to withstand accidental loads. Compared to empty cans the water filled cans exhibit greater resistance to axially applied compression loads before a complete collapse. The time and load or stroke and load plots showed three significant load peaks related to three stages during loading until the cylinder collapse. First peak corresponds to the ini...
Energy Dissipation in Sandwich Structures During Axial Compression
Urban, Jesper
2002-01-01
The purpose of this paper is to investigate the energy dissipation in sandwich structures during axial crushing. Axial crushing tests on six sandwich elements are described. The sandwich elements consist of a polyurethane core and E-glass/Polyester skin. The elements compare to full......-scale structural elements in fast sandwich vessels. Two of the crushing tests are simulated with the explicit finite element software LS-DYNA3D. The key results are load-end shortening relationship and the energy dissipation. Good agreement between the numerical predictions and the experiments are obtained. A...... simple analytical model for the energy dissipation during axial crushing is proposed. Keywords: Sandwich, Energy Dissipation, Axial Crushing, LS-DYNA, Analytical crushing models, Crashworthiness....
Stabilizing effects of ankle bracing under a combination of inversion and axial compression loading.
Tohyama, Harukazu; Yasuda, Kazunori; Beynnon, Bruce D; Renstrom, Per A
2006-04-01
The combined effects of bracing, axial compression and inversion rotation on the ankle-subtalar complexes were evaluated. Ex vivo tests under the load-controlled condition were performed on six cadaver ankle specimens using a six degree-of-freedom fixture. Inversion rotation was measured while subjecting the ankle-subtalar complex to a 2.5 N-m inversion moment and a combination of the testing variables (brace type, no brace, 178 N axial compression load, no compression load, 0 degrees and 20 degrees of plantar flexion) for a total of 16 tests per specimen. Three commercially available braces (two semirigid types and one lace up type) were evaluated. An axial compression load significantly decreased ankle-subtalar motion in unbraced ankles for the tested inversion moment. The contribution of bracing to stabilization of the ankle was smaller in the axial loading condition than in the no axial loading condition. The semirigid braces had greater stabilizing effects in response to the inversion moment than the lace up brace. Stabilizing effects of bracing were significantly greater in 20 degrees of plantar flexion than in 0 degrees of plantar flexion. The most common mechanism for an ankle sprain injury is inversion rotation on a weight-bearing ankle. Therefore, we should not overestimate stabilizing effects of bracing from evaluations of bracing without axial compression loading. PMID:15959767
Analysis and testing of axial compression in imperfect slender truss struts
Lake, Mark S.; Georgiadis, Nicholas
1990-01-01
The axial compression of imperfect slender struts for large space structures is addressed. The load-shortening behavior of struts with initially imperfect shapes and eccentric compressive end loading is analyzed using linear beam-column theory and results are compared with geometrically nonlinear solutions to determine the applicability of linear analysis. A set of developmental aluminum clad graphite/epoxy struts sized for application to the Space Station Freedom truss are measured to determine their initial imperfection magnitude, load eccentricity, and cross sectional area and moment of inertia. Load-shortening curves are determined from axial compression tests of these specimens and are correlated with theoretical curves generated using linear analysis.
Stabilizing effects of ankle bracing under a combination of inversion and axial compression loading
Tohyama, Harukazu; Yasuda, Kazunori; Beynnon, Bruce D.; Renstrom, Per A.
2006-01-01
The combined effects of bracing, axial compression and inversion rotation on the ankle-subtalar complexes were evaluated. Ex vivo tests under the load-controlled condition were performed on six cadaver ankle specimens using a six degree-of-freedom fixture. Inversion rotation was measured while subjecting the ankle-subtalar complex to a 2.5 N-m inversion moment and a combination of the testing variables (brace type, no brace, 178 N axial compression load, no compression load, 0° and 20° of pla...
Nonlinear Constitutive Equation for Green Sand Considering the Tri-axial Compression Behavior
曾攀; 孔劲
2004-01-01
The compression characteristics of green sand were investigated experimentally, including the squeezing and yielding during deformation. An expression was developed for the transient compression modulus of sand during compression. Based on the hypothesis put forward of the compression state, the differential equation for the nonlinear constitutive equation was deduced by introducing a move-yield potential function. The state constitutive equation under the tri-axial experiment is further studied according to the sand attributes, considering the differential form of Hooke's law and the Mohr-Coulomb condition. The related experiment data are applied to verify the proposed constitutive model of sand.
Androulidakis, Charalampos; Koukaras, Emmanuel N.; Frank, Otakar; Tsoukleri, Georgia; Sfyris, Dimitris; Parthenios, John; Pugno, Nicola; Papagelis, Konstantinos; Novoselov, Kostya S.; Galiotis, Costas
2014-01-01
The mechanical behavior of embedded monolayer graphene in a polymer matrix under axial compression is examined here by monitoring the shifts of the 2D Raman phonons under an incremental applied strain. In order to establish the effect of aspect ratio upon the critical strain to failure a wide range of length-to-width ratios of almost rectangular 1LG flakes were tested up to an external compression strain of approximately -1 %. Care was taken to define the position of zero strain due to the pr...
LOAD CARRYING CAPABILITY OF LIQUID FILLED CYLINDRICAL SHELL STRUCTURES UNDER AXIAL COMPRESSION
QASIM H. SHAH
2011-08-01
Full Text Available Empty and water filled cylindrical Tin (Sn coated steel cans were loaded under axial compression at varying loading rates to study their resistance to withstand accidental loads. Compared to empty cans the water filled cans exhibit greater resistance to axially applied compression loads before a complete collapse. The time and load or stroke and load plots showed three significant load peaks related to three stages during loading until the cylinder collapse. First peak corresponds to the initial structural buckling of can. Second peak occurs when cylindrical can walls gradually come into full contact with water. The third peak shows the maximum load carrying capability of the structure where pressurized water deforms the can walls into curved shape until can walls fail under peak pressure. The collapse process of water filled cylindrical shell was further studied using Smooth Particle Hydrodynamics (SPH technique in LSDYNA. Load peaks observed in the experimental work were successfully simulated which substantiated the experimental work.
Behaviour of M30 Grade concrete with confinement under axial compression
C.Vinil Babu
2014-09-01
Full Text Available The strength and durability of concrete have undergone continuous improvement. Over the years and these improved materials are now commonly used. In the present experimental investigation the behaviour of M30 grade concrete with and without confinement for different percentages of replacement of silica fume is studied under axial compression as per IS mix design. The 150mm x 300mm cylindrical specimens were cast with and without confinement and investigating the mechanical properties like axial compressive strength and stress – strain behaviour. It was observed that the confinement of concrete has increased the 28days strength for different percentages of confinement and that the peak stress and corresponding strain at peak stress increased with increase in percentages of confinement
Concrete-Filled-Large Deformable FRP Tubular Columns under Axial Compressive Loading
Omar I. Abdelkarim; Mohamed A. ElGawady
2015-01-01
The behavior of concrete-filled fiber tubes (CFFT) polymers under axial compressive loading was investigated. Unlike the traditional fiber reinforced polymers (FRP) such as carbon, glass, aramid, etc., the FRP tubes in this study were designed using large rupture strains FRP which are made of recycled materials such as plastic bottles; hence, large rupture strain (LRS) FRP composites are environmentally friendly and can be used in the context of green construction. This study performed finite...
Modeling particulate self-healing materials and application to uni-axial compression
Herbst, Olaf; Luding, Stefan
2008-01-01
Using an advanced history dependent contact model for DEM simulations, including elasto-plasticity, viscosity, adhesion, and friction, pressure-sintered tablets are formed from primary particles. These tablets are subjected to unconfined uni-axial compression until and beyond failure. For fast and slow deformation we observe ductile-like and brittle softening, respectively. We propose a model for local self-healing that allows damage to heal during loading such that the material strength of t...
Behaviour of M30 Grade concrete with confinement under axial compression
C.Vinil Babu; V.K.Visweswara Rao
2014-01-01
The strength and durability of concrete have undergone continuous improvement. Over the years and these improved materials are now commonly used. In the present experimental investigation the behaviour of M30 grade concrete with and without confinement for different percentages of replacement of silica fume is studied under axial compression as per IS mix design. The 150mm x 300mm cylindrical specimens were cast with and without confinement and investigating the mechanical prop...
Concrete-Filled-Large Deformable FRP Tubular Columns under Axial Compressive Loading
Omar I. Abdelkarim
2015-10-01
Full Text Available The behavior of concrete-filled fiber tubes (CFFT polymers under axial compressive loading was investigated. Unlike the traditional fiber reinforced polymers (FRP such as carbon, glass, aramid, etc., the FRP tubes in this study were designed using large rupture strains FRP which are made of recycled materials such as plastic bottles; hence, large rupture strain (LRS FRP composites are environmentally friendly and can be used in the context of green construction. This study performed finite element (FE analysis using LS-DYNA software to conduct an extensive parametric study on CFFT. The effects of the FRP confinement ratio, the unconfined concrete compressive strength ( , column size, and column aspect ratio on the behavior of the CFFT under axial compressive loading were investigated during this study. A comparison between the behavior of the CFFTs with LRS-FRP and those with traditional FRP (carbon and glass with a high range of confinement ratios was conducted as well. A new hybrid FRP system combined with traditional and LRS-FRP is proposed. Generally, the CFFTs with LRS-FRP showed remarkable behavior under axial loading in strength and ultimate strain. Equations to estimate the concrete dilation parameter and dilation angle of the CFFTs with LRS-FRP tubes and hybrid FRP tubes are suggested.
Effect of Axial Pre-Compression on Lateral Performance of Masonry Under Cyclic Loading
Syed HassanFarooq
2011-10-01
Full Text Available Strengthening of masonry against seismic events is very essential and getting maximum attention of researchers around the globe. An extensive experimental program was carried out to study the in-plane lateral performance of un-reinforced masonry, strengthened and retrofitted masonry wall panels under lateral cyclic loading. Twenty tests were carried out; four tests under monotonic lateral loading, twelve tests under static cyclic loading and four tests under pure compression. The test results were analyzed in five groups and this paper presents the analysis of group 4, which deals with effect of axial pre-compression on masonry seismic performance. Three single leaf panels with aspect ratio of 0.67 having size 1.65x1.1m were constructed using same material and workmanship. All the three un-reinforced walls were tested under 0, 0.5 and 1.0MPa vertical pre-compression and displacement controlled static cyclic loading. The wall tested under 0.5MPa pre-compression was reference specimen. The key parameters studied were hysterics behavior, peak lateral load, ultimate lateral displacement, energy dissipation, ductility, response factor and damping ratio. It was observed that level of axial pre-compression has significant effect on lateral capacity, failure mode and performance of masonry. In case of zero pre-compression the lateral capacity was very less and wall went into rocking failure at early stages of loading. Increase in pre-compression to 1.0MPa enhanced the lateral capacity by a factor of 1.92 times. After analysis of test results, it is found that pre-compression has significant effect on lateral capacity, failure mode and performance of masonry. In case of zero pre-compression the lateral capacity was very less and wall went into rocking failure at early stages of loading. Increase in pre-compression to 1.0MPa enhanced the lateral capacity by a factor of 1.92 times. After analysis of test results, it is found that pre-compression has very
Sejdić, Ervin; Movahedi, Faezeh; Zhang, Zhenwei; Kurosu, Atsuko; Coyle, James L.
2016-05-01
Acquiring swallowing accelerometry signals using a comprehensive sensing scheme may be a desirable approach for monitoring swallowing safety for longer periods of time. However, it needs to be insured that signal characteristics can be recovered accurately from compressed samples. In this paper, we considered this issue by examining the effects of the number of acquired compressed samples on the calculated swallowing accelerometry signal features. We used tri-axial swallowing accelerometry signals acquired from seventeen stroke patients (106 swallows in total). From acquired signals, we extracted typically considered signal features from time, frequency and time-frequency domains. Next, we compared these features from the original signals (sampled using traditional sampling schemes) and compressively sampled signals. Our results have shown we can obtain accurate estimates of signal features even by using only a third of original samples.
K Athiannan; R Palaninathan
2004-02-01
This paper presents experimental studies on buckling of cylindrical shell models under axial and transverse shear loads. Tests are carried out using an experimental facility specially designed, fabricated and installed, with provision for in-situ measurement of the initial geometric imperfections. The shell models are made by rolling and seam welding process and hence are expected to have imperfections more or less of a kind similar to that of real shell structures. The present work thus differs from most of the earlier investigations. The measured maximum imperfections $\\delta_{\\text{max}}$ are of the order of $\\pm 3t$ (t = thickness). The buckling loads obtained experimentally are compared with the numerical buckling values obtained through ﬁnite element method (FEM). In the case of axial buckling, the imperfect geometry is obtained in four ways and in the case of transverse shear buckling, the FE modelling of imperfect geometry is done in two ways. The initial geometric imperfections affect the load carrying capacity. The load reduction is considerable in the case of axial compression and is marginal in the case of transverse shear buckling. Comparisons between experimental buckling loads under axial compression, reveal that the extent of imperfection, rather than its maximum value, in a specimen inﬂuences the failure load. Buckling tests under transverse shear are conducted with and without axial constraints. While differences in experimental loads are seen to exist between the two conditions, the numerical values are almost equal. The buckling modes are different, and the experimentally observed and numerically predicted values are in complete disagreement.
Buckling and postbuckling analysis of stiffened composite panels in axial compression
Park, Oung
The major objective of this study is to analyze buckling and delamination behavior of composite stiffened panels subjected to axial compression. First, a combined analytical and experimental study of a blade stiffened composite panel subjected to axial compression was conducted. The effects of the differences between a simple model used to design the panel and the actual experimental conditions were examined. It was found that in spite of many simplifying assumptions the design model did reasonably well in that the experimental failure load was only 10% higher than the design load. Several structural analysis programs, including PANDA2, STAGS, and ABAQUS, were used to obtain high fidelity analysis results. The buckling loads from STAGS agreed well with the experimental failure loads. However, substantial differences were found in the out-of-plane displacements of the panel. Efforts were made to identify the source of these differences. Implementing non-uniform load introduction with general contact definition in the STAGS finite element model improved correlation between the measured and predicted out-of-plane deformations. Next, a new method called Crack Tip Force Method (CTFM) is derived for computing point-wise energy release rate along the delamination front in delaminated plates. The CTFM is computationally simple as the G is computed using the forces transmitted at the crack-tip between the top and bottom sub-laminates and the sub-laminate properties. Finally, buckling and postbuckling of a blade-stiffened composite panel under axial compression with a partial skin-stiffener debond are investigated. Two different finite element models, where nodes of the panel skin and the stiffener flange are located on the mid-plane or at the interface between skin and flange, are used. Linear buckling analysis is conducted using both STAGS and ABAQUS. Postbuckling analysis is conducted with STAGS. Comparison between the present results and previous buckling analysis
Due to the brittle character of the material an indirect method (diametrical and axial compression testing) was adopted for tensile strength determination. Two lots of compacts were prepared from salt powder, by pressing it in steel dyes by means of a hydraulic press. For uniaxial tests, cylindrical compacts were used. Biaxial tests were done on disk-shaped compacts, each disk having a diametrical V-shaped cut on one of its plane areas. The punches used for compression tests, were designed to obtain a ratio of 1.2 between their curvature radius and sample radius. At the same time with the tensile strength, the stress intensity factor (KIC and KIIC values) has been obtained. The results obtained are in good agreement with the mechanical properties of the salt, previously reported. (Authors)
Performance of composite I-beams under axial compression and bending load modes
Khalid, Y.A.; Ali, F.A.; Sahari, B.B.; Saad, E.M.A
2005-04-15
An experimental and finite-element analyses for glass/epoxy composite I-beams have been carried out. Four, six, eight and 10 layers of woven fabric glass/epoxy composite I-beams were fabricated by a hand lay-up (molding) process. Quasi-static axial crushing and bending loading modes were used for this investigation. The load-displacement response was obtained and the energy absorption values were calculated for all the composite I-beams. Three tests were done for each composite I-beams type and each loading case for the results conformation. The second part of this study includes the elastic behavior of composite I-beams of the same dimensions and materials using finite-element analysis. The woven fabric glass/epoxy composite I-beams mechanical properties have been obtained from tensile tests. Results from this investigation show that the load required and the specific energy absorption for composite I-beams under axial compression load were higher than those for three and four point bending. On the other hand, the loads required for composite I-beams under four point bending were higher than those for three point bending, while the specific energy absorption for composite I-beams under three point bending were higher than those for four point bending. The first crushing loads difference between the experimental and finite-element results fell in the 3.6-10.92% range for axial compression tests, while fell in the 1.44-12.99% and 4.94-22.0% range for three and four point bending, respectively.
无
2001-01-01
The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mainly on geometric condition rρ/d0, little on tube material properties and friction condition; the relative gap Δ/2rρ of double-walled tubes obtained decreases with increasing rρ/d0, and there is a parameter k for a given t0/d0 or rρ/t0, when rρ,/d0＞k, Δ/2rρ＜1,otherwise Δ/2rρ＞1.
Static and dynamic response of a sandwich structure under axial compression
Ji, Wooseok
This thesis is concerned with a combined experimental and theoretical investigation of the static and dynamic response of an axially compressed sandwich structure. For the static response problem of sandwich structures, a two-dimensional mechanical model is developed to predict the global and local buckling of a sandwich beam, using classical elasticity. The face sheet and the core are assumed as linear elastic orthotropic continua in a state of planar deformation. General buckling deformation modes (periodic and non-periodic) of the sandwich beam are considered. On the basis of the model developed here, validation and accuracy of several previous theories are discussed for different geometric and material properties of a sandwich beam. The appropriate incremental stress and conjugate incremental finite strain measure for the instability problem of the sandwich beam, and the corresponding constitutive model are addressed. The formulation used in the commercial finite element package is discussed in relation to the formulation adopted in the theoretical derivation. The Dynamic response problem of a sandwich structure subjected to axial impact by a falling mass is also investigated. The dynamic counterpart of the celebrated Euler buckling problem is formulated first and solved by considering the case of a slender column that is impacted by a falling mass. A new notion, that of the time to buckle, "t*" is introduced, which is the corresponding critical quantity analogous to the critical load in static Euler buckling. The dynamic bifurcation buckling analysis is extended to thick sandwich structures using an elastic foundation model. A comprehensive set of impact test results of sandwich columns with various configurations are presented. Failure mechanisms and the temporal history of how a sandwich column responds to axial impact are discussed through the experimental results. The experimental results are compared against analytical dynamic buckling studies and finite
Wang, Y; Mao, N
2015-01-01
The influences of pre-tensions on the deformations of cylindrical shells made of various woven fabrics undergoing axial compression buckling process were studied. The fabric deformations were differentiated and quantified using the energy consumed to produce and recover them. Various types of deformation including elastic deformation, recoverable deformation and permanent deformation produced in the cyclic compression buckling-recovery processes were associated with their corresponding energy...
The Deformation Behavior of TiNi Shape Memory Alloy under Axial Dynamic Compression
HUANG Xue-wen; DONG Guang-neng; ZHOU Zhong-rong; XIE You-bai
2004-01-01
The deformation behavior of Ti-50.9at%Ni shape memory alloy under axial compression dynamic loads was investigated by an MTS 858Mini Bionix test machine. The alloy were aged at 500℃ for an hour before being machined into specimens. The compression experiments were conducted at 20℃ and the variety of dynamic loads were controlled by the strain rate, which was 3mm/min, 15mm/min, 30mm/min and 50mm/min, respectively. The experimental results indicate that in the case of 3mm/min, stress-induced martensitic transformation occurs at about 350MPa when loading and reverse transformation at about 200MPa when unloading, during which the aged Ti-50.9at%Ni alloy shows the recoverable nonlinear pseudoelastic strain of 4.3% with the residual strain of 1.2% reserved. With the strain rate increasing, the area encloses by loading-curve and unloading-curve, i.e stress (strain) hysteresis becomes smaller and smaller and the residual strain also decreases, while critical stress for inducing martensitic transformation rises. At a higher strain rate the alloy exhibits linear-like pseudoelasticity, which is up to 4.5%.
Particle flow of ceramic breeder pebble beds in bi-axial compression experiments
Pebble beds of Tritium breeding ceramic material are investigated within the framework of developing solid breeder blankets for future nuclear fusion power plants. For the thermo-mechanical characterisation of such pebble beds, bed compression experiments are the standard tools. New bi-axial compression experiments on 20 and 30 mm high pebble beds show pebble flow effects much more pronounced than in previous 10 mm beds. Owing to the greater bed height, conditions are reached where the bed fails in cross direction and unhindered flow of the pebbles occurs. The paper presents measurements for the orthosilicate and metatitanate breeder materials that are envisaged to be used in a solid breeder blanket. The data are compared with calculations made with a Drucker-Prager soil model within the finite-element code ABAQUS, calibrated with data from other experiments. It is investigated empirically whether internal bed friction angles can be determined from pebble beds of the considered heights, which would simplify, and broaden the data base for, the calibration of the Drucker-Prager pebble bed models
Shear behaviour of reinforced concrete beams subjected to high axial compression
Gupta, P.R.
1993-01-01
To investigate the behaviour of high performance reinforced concrete elements subjected to conditions of high compression and shear, such as found in offshore platforms, 14 beam strips were tested using the University of Toronto's Shell Element Tester to investigate the effectiveness of various stirrup types and understand the role of stirrups in determining the behaviour of members. Specimens were tested without shear reinforcement and with two types of stirrups (standard 90[degree] bends and T-heads) under similar conditions for direct comparison. Maximum average axial stress of up to 0.9 was achieved. It was found that stirrups enhance the strength of specimens considerably. It is clearly indicated that T-head stirrups provide better anchorage and are more effective than 90[degree] bends. The American Concrete Institute (ACI)-318-89 expressions considerably overpredict the strength of specimens without shear reinforcement. The predictions for specimens with shear reinforcement closely follow the experimental results, but are slightly non-conservative. The Beta-method proposed by Collins and Mitchell (1991) was found to predict the strength of beams with and without reinforcement satisfactorily in the low and moderately high compression range. 9 refs., 159 figs., 5 tabs.
Rajeev Kumar
2014-07-01
Full Text Available A finite element model of fractured tibia with Joshi’s External Stabilizing System (JESS mounted on it was developed using 3D beam elements in the ANSYS software. The model was loaded in axial compression and the average axial stiffness of the model was calculated. The analytical value of axial stiffness was compared with reported experimental value to validate the finite element model. The validated model was used to carry out parametric studies on the model to determine the axial properties of JESS. It was observed that axial stiffness of JESS increased by 58% when k-wire diameter was varied from 2 mm to 4 mm while keeping other geometric configurations of the device constant; however, the axial stiffness of the device does not show any significant improvement when the diameter of medio-lateral pins in diaphyseal hold were increased. The findings should help in understanding the axial properties of JESS so that it can be used judiciously in clinical applications.
Fathi, Reza; Lotfan, Saeed
2016-05-01
Nowadays investigating the vibration behavior of carbon nanotubes (CNTs) has drawn considerable attention due to the superior mechanical properties of the CNTs. One of the powerful theoretical methods to study the vibration behavior of CNTs is implementing the nonlocal theory. Most of studies on the vibration behavior of CNTs have assumed a fixed value for small scale parameter for all vibration modes, however, this value is mode-dependent. Therefore, in this paper, the small scale parameter is calibrated for a single-walled carbon nanotube (SWCNT) with respect to each vibration mode. For this propose, the governing equation of motion based on the nonlocal beam theory is extracted by applying the Hamilton's principle. Then, by using the power series method, an eigenvalue problem is defined to derive the calibrated value of small scale constant and nonlocal mode shapes of the CNT. By using the expansion theory, the equation of motion is discretized, and the effect of nonlocality on the modal parameters and stability of the CNT under compressive force is investigated. Finally, the possibility of estimating nonlocal parameter based on simulated frequency domain response of the system by using modal analysis methods is studied. The results show that the calibration of small scale constant is important and the critical axial force is highly sensitive to this value.
Creep Testing Plastic-Bonded Explosives in Uni-axial Compression
Gagliardi, F J; Cunningham, B J
2008-03-13
High fidelity measurements of time-dependent strain in the plastic-bonded explosives LX-17-1 and PBX 9502 have been performed under constant, uni-axial, compressive load using a custom designed apparatus. The apparatus uses a combination of extensometers and linear variable differential transformers coupled with a data acquisition system, thermal controls, and gravitational loading. The materials being tested consist of a crystalline explosive material mixed with a polymeric binder. The behavior of each material is related to the type of explosive and to the percentage and type of binder. For any given plastic-bonded explosive, the creep behavior is also dependent on the stress level and test temperature. Experiments were conducted using a 3 x 3 stress-temperature matrix with a temperature range of 24 C to 70 C and with stresses ranging from 250-psi to 780-psi. Analysis of the data has shown that logarithmic curve fits provide an accurate means of quantification and facilitate a long-term predictive capability. This paper will discuss the design of the apparatus, experimental results, and analyses.
Comparison of Methods to Predict Lower Bound Buckling Loads of Cylinders Under Axial Compression
Haynie, Waddy T.; Hilburger, Mark W.
2010-01-01
Results from a numerical study of the buckling response of two different orthogrid stiffened circular cylindrical shells with initial imperfections and subjected to axial compression are used to compare three different lower bound buckling load prediction techniques. These lower bound prediction techniques assume different imperfection types and include an imperfection based on a mode shape from an eigenvalue analysis, an imperfection caused by a lateral perturbation load, and an imperfection in the shape of a single stress-free dimple. The STAGS finite element code is used for the analyses. Responses of the cylinders for ranges of imperfection amplitudes are considered, and the effect of each imperfection is compared to the response of a geometrically perfect cylinder. Similar behavior was observed for shells that include a lateral perturbation load and a single dimple imperfection, and the results indicate that the predicted lower bounds are much less conservative than the corresponding results for the cylinders with the mode shape imperfection considered herein. In addition, the lateral perturbation technique and the single dimple imperfection produce response characteristics that are physically meaningful and can be validated via testing.
Racz, Jean-Philippe; Scott, Julian F.
2008-01-01
International audience A weakly nonlinear analysis is presented of parametric instability in a rotating cylinder subject to periodic axial compression by small sinusoidal oscillations of one of its ends (‘the piston'). Amplitude equations are derived for the pair of parametrically resonant (primary) inertial modes which were found to arise from linear instability in Part 1. These equations introduce an infinity of geostrophic mode amplitudes, representing a nonlinear modification of the me...
Dzhankhotov, S.O.; Panfilov, B.V.; Spichkova, L.E.
1989-01-01
Experimental data are presented on the strength and fracture characteristics of composite-reinforced beams and short and long bars of aluminum alloys in transverse bending and axial compression. The reinforcement materials include carbon and boron composites with a polymer matrix as well as boron/aluminum. The results demonstrate the effectiveness of using structures reinforced by unidirectional composites. In aerospace applications, the use of composite reinforcements can significantly reduce the weight of structures. 6 refs.
Hamann, F., E-mail: franck.hamann@cea.fr; Combis, P.; Videau, L. [CEA, DAM, DIF, F-91297 Arpajon (France)
2015-08-15
The one-dimensional magnetohydrodynamics of a plasma cylindrical liner is addressed in the case of a two components magnetic field. The azimuthal component is responsible for the implosion of the liner and the axial field is compressed inside the liner. A complete set of analytical profiles for the magnetic field components, the density, and the local velocity are proposed at the scale of the liner thickness. Numerical simulations are also presented to test the validity of the analytical formulas.
The one-dimensional magnetohydrodynamics of a plasma cylindrical liner is addressed in the case of a two components magnetic field. The azimuthal component is responsible for the implosion of the liner and the axial field is compressed inside the liner. A complete set of analytical profiles for the magnetic field components, the density, and the local velocity are proposed at the scale of the liner thickness. Numerical simulations are also presented to test the validity of the analytical formulas
Highlights: ► This article studies folding process in foam-filled circular grooved tubes. ► Mean folding force in polyurethane foam-filled tubes is predicted, theoretically. ► Also, total absorbed energy per unit of tube length is calculated, theoretically. ► The specific absorbed energy by filled grooved tube is predicted, theoretically. ► Comparison of theoretical and experimental results shows a good correlation. -- Abstract: In this article, some theoretical relations are derived to predict the mean folding force, total absorbed energy per unit of tube length and specific absorbed energy per unit of total mass by the polyurethane foam-filled grooved tubes with circular cross section under the axial compression process. During the folding process, a new theoretical model of deformation is introduced for the polyurethane foam-filler. The theoretical analysis is developed on the basis of the energy method. Some foam-filled grooved specimens were prepared and axially compressed to obtain the experimental diagram of the folding force versus the axial displacement. Comparison of the theoretical predictions with the experimental results showed a good agreement. Then, by considering the interaction effect between the polyurethane foam and the inner wall of grooved tubes, a semi-empirical relation was derived. Predictions along with considering the interaction factor obtained from the semi-empirical relation indicate a better correlation with those of the experiments.
Miranda Junior, E.J.P.; Paiva, A.E.M., E-mail: edson.jansen@hotmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia do Maranhao (PPGEM/IFMA), Sao Luis, MA (Brazil). Programa de Pos-Graduacao em Engenharia de Materiais
2012-07-01
In this work, was studied the influence of the incorporation of waste glass, coming from the stage of thinning and polishing of a company of thermal glass treatments, in the axial compressive strength of Portland cement concrete. The coarse and ground aggregates used was crushed stone and sand, respectively. For production of the concrete, percentages of glass residues of 5%, 10% and 20% had been used in substitution to the sand, and relations water/cement (a/c) 0,50, 0,55 and 0,58. The cure of the test bodies was carried through in 7, 14 and 28 days. The statistics analysis of the results was carried out through of the analysis of variance for each one of the cure times. From the results of the compressive strength of the concrete, it could be observed that the concrete has structural application for the relation a/c 0,5, independently of waste glass percentage used, and for the relation a/c 0,55 with 20% of waste glass. (author)
In this study, the buckling analysis of the simply supported truncated conical shell made of functionally graded materials (FGMs) is presented. The FGM truncated conical shell subjected to an axial compressive load and resting on Winkler-Pasternak type elastic foundations. The material properties of functionally graded shells are assumed to vary continuously through the thickness. The modified Donnell type stability and compatibility equations are solved by Galerkin's method and the critical axial load of FGM truncated conical shells with and without elastic foundations have been found analytically. The appropriate formulas for homogenous and FGM cylindrical shells with and without elastic foundations are found as a special case. Several examples are presented to show the accuracy and efficiency of the formulation. Finally, parametric studies on the buckling of FGM truncated conical and cylindrical shells on elastic foundations are being investigated. These parameters include; power-law and exponential distributions of FGM, Winkler foundation modulus, Pasternak foundation modulus and aspect ratios of shells.
Paraska, Peter J.
1993-01-01
This report documents an analytical study of the response of unsymmetrically laminated cylinders subjected to thermally-induced preloading effects and compressive axial load. Closed-form solutions are obtained for the displacements and intralaminar stresses and recursive relations for the interlaminar shear stress were obtained using the closed-form intralaminar stress solutions. For the cylinder geometries and stacking sequence examples analyzed, several important and as yet undocumented effects of including thermally-induced preloading in the analysis are observed. It should be noted that this work is easily extended to include uniform internal and/or external pressure loadings and the application of strain and stress failure theories.
Cylindrical shells are utilized as structural elements of nuclear power plans, heat exchangers or pressure vessels, which are operated under elevated temperature. Creep buckling is one of the failure modes of structures at elevated temperature. In some experiments conducted by other authors, axially compressive cylindrical shells with a large ratio of radius to thickness were observed to buckle with circumferential waves. We reported that the circumferential weaves occur due to bifurcation buckling. But, the citrical time and the minimum loading for bifurcation buckling obtained from calculations of finite element analyses are not very good agreement with those of the experiments. One of the reasons for the disagreement is considered to be that the creep constitutive equations employed in many previous analyses represent steady creep. The creep phenomena usually have primary creep period, steady creep one and tertiary creep one. A creep strain-time relation through the three periods can be simulated by using a constitutive equation based on creep damage mechanics. In the present paper, we analyze bifurcation creep buckling of circular cylindrical shells subjected to axial compression by the use of the finite element method taking account of the creep damage mechanics of Kachanov-Rabotnov. (author)
Strength and stability analysis of a single-walled black phosphorus tube under axial compression.
Cai, Kun; Wan, Jing; Wei, Ning; Qin, Qing H
2016-07-01
Few-layered black phosphorus materials currently attract much attention due to their special electronic properties. As a consequence, a single-layer black phosphorus (SLBP) nanotube has been theoretically built. The corresponding electronic properties of such a black phosphorus nanotube (BPNT) were also evaluated numerically. However, unlike graphene formed with 2sp(2) covalent carbon atoms, SLBP is formed with 3sp(3) bonded atoms. It means that the structure from SLBP will possess lower Young's modulus and mechanical strength than those of carbon nanotubes. In this study, molecular dynamics simulation is performed to investigate the strength and stability of BPNTs affected by the factors of diameter, length, loading speed and temperature. Results are fundamental for investigating the other physical properties of a BPNT acting as a component in a nanodevice. For example, buckling of the BPNT happens earlier than fracture, before which the nanostructure has very small axial strain. For the same BPNT, a higher load speed results in lower critical axial strain and a nanotube with lower axial strain can still be stable at a higher temperature. PMID:27211804
Strength and stability analysis of a single-walled black phosphorus tube under axial compression
Cai, Kun; Wan, Jing; Wei, Ning; Qin, Qing H.
2016-07-01
Few-layered black phosphorus materials currently attract much attention due to their special electronic properties. As a consequence, a single-layer black phosphorus (SLBP) nanotube has been theoretically built. The corresponding electronic properties of such a black phosphorus nanotube (BPNT) were also evaluated numerically. However, unlike graphene formed with 2sp2 covalent carbon atoms, SLBP is formed with 3sp3 bonded atoms. It means that the structure from SLBP will possess lower Young’s modulus and mechanical strength than those of carbon nanotubes. In this study, molecular dynamics simulation is performed to investigate the strength and stability of BPNTs affected by the factors of diameter, length, loading speed and temperature. Results are fundamental for investigating the other physical properties of a BPNT acting as a component in a nanodevice. For example, buckling of the BPNT happens earlier than fracture, before which the nanostructure has very small axial strain. For the same BPNT, a higher load speed results in lower critical axial strain and a nanotube with lower axial strain can still be stable at a higher temperature.
M. Grujicic
2013-01-01
Full Text Available The mechanical response of p-phenylene terephthalamide (PPTA single fibers when subjected to uniaxial compression is investigated computationally using coarse-grained molecular statics/dynamics methods. In order to construct the coarse-grained PPTA model (specifically, in order to define the nature of the coarse-grained particles/beads and to parameterize various components of the bead/bead force-field functions, the results of an all-atom molecular-level computational investigation are used. In addition, the microstructure/topology of the fiber core, consisting of a number of coaxial crystalline fibrils, is taken into account. Also, following our prior work, various PPTA crystallographic/topological defects are introduced into the model (at concentrations consistent with the prototypical PPTA synthesis/processing conditions. The analysis carried out clearly revealed (a formation of the kink bands during axial compression; (b the role of defects in promoting the formation of kink bands; (c the stimulating effects of some defects on the fiber-fibrillation process; and (d the detrimental effect of the prior compression, associated with fiber fibrillation, on the residual longitudinal-tensile strength of the PPTA fibers.
Sejdić, Ervin; Dudik, Joshua M.; Kurosu, Atsuko; Jestrović, Iva; Coyle, James L.
2014-05-01
Swallowing accelerometry is a promising tool for non-invasive assessment of swallowing difficulties. A recent contribution showed that swallowing accelerometry signals for healthy swallows and swallows indicating laryn- geal penetration or tracheal aspiration have different time-frequency structures, which may be problematic for compressive sensing schemes based on time-frequency dictionaries. In this paper, we examined the effects of dif- ferent swallows on the accuracy of a compressive sensing scheme based on modulated discrete prolate spheroidal sequences. We utilized tri-axial swallowing accelerometry signals recorded from four patients during routinely schedule videofluoroscopy exams. In particular, we considered 77 swallows approximately equally distributed between healthy swallows and swallows presenting with some penetration/aspiration. Our results indicated that the swallow type does not affect the accuracy of a considered compressive sensing scheme. Also, the results con- firmed previous findings that each individual axis contributes different information. Our findings are important for further developments of a device which is to be used for long-term monitoring of swallowing difficulties.
Lattice strain development in Inconel-690 under bi-axial compression and tension
Toda, Rebecca Midori
Nuclear reactor steam generator tubes, manufactured from Nickel alloys such as Inconel 690 (INC690), are potentially susceptible to failure by Stress Corrosion Cracking where crack initiation may be exacerbated by internal stress fields. A more comprehensive understanding of this potential failure mechanism was gained via an exploration of a model of INC690.s behaviour under Constrained loading conditions in compression and tension. An Elasto-Plastic Self-Consistent (EPSC) model was used to predict the lattice stresses and strains resulting from Constrained loading in INC690 for four crystallographic planes. The internal strain fields generated under such conditions were shown to be markedly different from those developed under Uniaxial loading. Finite Element Modeling was used to design tensile and compression samples as well as a testing rig that would allow the application of a compressive load along one axis of the specimen with simultaneous constraint along another and free-deformation along the third. Lattice strain measurements were done for both compressive and tensile loading using Time-Of-Flight neutron diffraction. The predicted and experimental values showed reasonable agreement; mainly in terms of crystallographic plane interaction and behaviour. Iterative computer modeling was used to achieve a more realistic depiction of the lattice strains developed. This research allowed for an extension on the Uniaxial findings by examining the material's behaviour under more complex loading that better approximates steam generator tube operating conditions.
Design and use of uni-axial compression device for time lapse X-ray microtomography
Fíla, Tomáš; Zlámal, Petr; Kytýř, Daniel; Koudelka_ml., Petr; Doktor, Tomáš; Jiroušek, Ondřej; Vavřík, Daniel
Wuppertal: Institute for statics and dynamics of structures. University of Wuppertal, 2014 - (Harte, R.), s. 70-73 ISBN N. [Experimental methods and numerical simulation in engineering science. Bilateral Czech/German symposium. /14./. Wuppertal (DE), 04.06.2014-07.06.2014] R&D Projects: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : X-ray * time-lapse microtomography * compression device * strain measurements Subject RIV: JI - Composite Materials
Axial compression test on ITER-TFMC conductors at room temperature
The superconductor used for the ITER TF Model Coil (TFMC) consists of 720 twisted Nb3Sn-strands and 360 copper strands, which are cabled around a central spiral and are surrounded by a stainless steel jacket. The conductor is heat-treated at 650 deg. C in a stainless steel mould. After cool down to room temperature the conductor is found to be elongated by 0.45 mm/m, which can be attributed to the lower shrinkage of Nb3Sn. This means that the jacket is under tensile stress and the cable under longitudinal compression after cool down. This effect aggravates upon cooling further to the operating temperature. The cable and the jacket can be interpreted as a double spring system, the jacket being the expansion spring and the cable being the compression spring. In order to evaluate and possibly predict such elongations, it is necessary to know the Young's modulus of the cable. Therefore, we investigated samples cut from a dummy conductor, a not heat-treated and a heat-treated TFMC conductor by mechanically compressing them. From the stress-strain diagram the elastic modulus of the cables was determined and found to be about one-tenth of that calculated assuming all components of the cable being fully bonded. The stiffness of the cables turned out to be fairly independent of the state of the cable as all three cables show almost the same modulus. The mechanical compression of the cable is about 8.5 times larger than the measured elongation of the jacket.
杨洋; 童根树; 张磊
2012-01-01
考虑了几何缺陷、残余应力和材料塑性，采用大变形理论自编程序3D-Steel-Struct对工字形压杆屈曲前后的变形曲线进行了研究。对非完善双轴对称工字形截面压杆进行了二阶弹性和二阶刚塑性的理论分析，推导了相应阶段的轴压力与变形之间的关系，构造了轴压力与跨中挠度和轴压力与轴向位移之间的解析表达式，并与数值解非常吻合。研究了压杆轴压延性随长细比的变化规律，提出了一个延性与长细比的近似表达式，并具有良好的精度。%This paper investigates the deformation of compressed bars with I-section. A finite-element program of 3D-Steel-Struct developed by authors is used in the analysis. Initial geometric crookedness, residual stress and material inelasticity are considered in the investigation. Second order elastic and second order rigid-plastic analysis are carried out for imperfect members, and relations between axially compressive force and deformation are deduced. Analytical expression for axially compressive force and deflection at mid-span are presented, as well as that for axially compressive force and axial shortening. A comparison shows the excellent agreement between the proposed explicit expressions and the numerical results. The axial ductility of compressed member is also studied in the paper. A formula relating the ductility to the slenderness is proposed.
Wang, Bingfeng, E-mail: biw009@ucsd.edu [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093 (United States); Department of Nanoengineering, University of California, San Diego, CA 92093 (United States); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083, Hunan (China); Li, Juan; Sun, Jieying; Wang, Xiaoyan; Liu, Zhaolin [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China)
2014-08-26
Ultrafine grained titanium has unique mechanical properties and attracts tremendous interest due to its scientific and technological application. Shear localization is frequently denoted as adiabatic shear band, and is one of the most important deformation and failure mechanisms for it used at high rate deformation. Hat shaped specimens are used to induce the formation of an adiabatic shear band under controlled dynamic conditions. Unstable shear deformation of the alloy emerges after the true flow stress reaches about 750 MPa, the first vibration peak during the split Hopkinson pressure bar testing, and the whole deformation process lasts about 50 μs. The microstructure and microtextures in the shear band with width about 16.7 μm in ultrafine grained titanium processed by multi-axial compression are investigated by means of optical microscopy, scanning electron microscopy/electron back-scattered diffraction, and transmission electron microscopy. The results show that the grains in the boundary of the shear band are highly elongated along the shear direction, and the core of the shear band consists of a number of scattered recrystallized equiaxed grains with 50–80 nm in diameters and coalesced grains with 100–150 nm in diameters. Some new microtextures (20°, 4°, 0°), (81°, 0°, 0°), and (55°, 0°, 30°) with recrystallized characteristics are generated in the shear band. The grain boundaries in the core of an adiabatic shear band are high-angle boundaries and geometrical necessary boundaries created with aims of accommodating the imposed shear strain. Calculations of temperature rise suggest that the maximum temperature in the shear band is about 870 K being sufficient for the recrystallization. Finally, the mechanisms of formation of an adiabatic shear band in the ultrafine grained titanium processed by multi-axial compression and its microstructural evolution are proposed.
Sofiyev, A.H., E-mail: asofiyev@mmf.sdu.edu.t [Department of Civil Engineering, Suleyman Demirel University, 32260 Isparta (Turkey)
2010-12-15
In this study, the buckling analysis of the simply supported truncated conical shell made of functionally graded materials (FGMs) is presented. The FGM truncated conical shell subjected to an axial compressive load and resting on Winkler-Pasternak type elastic foundations. The material properties of functionally graded shells are assumed to vary continuously through the thickness. The modified Donnell type stability and compatibility equations are solved by Galerkin's method and the critical axial load of FGM truncated conical shells with and without elastic foundations have been found analytically. The appropriate formulas for homogenous and FGM cylindrical shells with and without elastic foundations are found as a special case. Several examples are presented to show the accuracy and efficiency of the formulation. Finally, parametric studies on the buckling of FGM truncated conical and cylindrical shells on elastic foundations are being investigated. These parameters include; power-law and exponential distributions of FGM, Winkler foundation modulus, Pasternak foundation modulus and aspect ratios of shells.
Mechanical properties of GFRP tube confined recycled concrete under axial compression
Wang, Xiaogang; Liang, Chaofeng; Zhou, Zechenglong; Dong, Lanqi; Ding, Kewei; Huang, Jialun
2015-07-01
This article outlines the recycled aggregate replacement rate and thick-diameter rate of GFRP tube confined in recycled concrete, which has an important impact on the material's compressive strength. Overall, under the same conditions of using recycled concrete, the bearing capacity of short concrete columns can be improved by using broader GFRP tubes. There is a four-fold increase in the bearing capacity of short concrete columns compared to the short column without the restriction of a GFRP tube. The bearing capacity of a short column crafted by recycled coarse aggregate is much lower (about 30%). than those made by common concrete column Additionally, the bearing capacity of short columns made by recycled fine aggregates is also lower than those made by common concrete (approximately 20%). Finally, we find that there is no significant difference between experimental and theoretical data.
Kimura, S.; Steinbach, G. C.; Watenpaugh, D. E.; Hargens, A. R.
2001-01-01
STUDY DESIGN: Axial load-dependent changes in the lumbar spine of supine healthy volunteers were examined using a compression device compatible with magnetic resonance imaging. OBJECTIVE: To test two hypotheses: Axial loading of 50% body weight from shoulder to feet in supine posture 1) simulates the upright lumbar spine alignment and 2) decreases disc height significantly. SUMMARY OF BACKGROUND DATA: Axial compression on the lumbar spine has significantly narrowed the lumbar dural sac in patients with sciatica, neurogenic claudication or both. METHODS: Using a device compatible with magnetic resonance imaging, the lumbar spine of eight young volunteers, ages 22 to 36 years, was axially compressed with a force equivalent to 50% of body weight, approximating the normal load on the lumbar spine in upright posture. Sagittal lumbar magnetic resonance imaging was performed to measure intervertebral angle and disc height before and during compression. RESULTS: Each intervertebral angle before and during compression was as follows: T12-L1 (-0.8 degrees +/- 2.5 degrees and -1.5 degrees +/- 2.6 degrees ), L1-L2 (0.7 degrees +/- 1.4 degrees and 3.3 degrees +/- 2.9 degrees ), L2-L3 (4.7 degrees +/- 3.5 degrees and 7.3 degrees +/- 6 degrees ), L3-L4 (7.9 degrees +/- 2.4 degrees and 11.1 degrees +/- 4.6 degrees ), L4-L5 (14.3 degrees +/- 3.3 degrees and 14.9 degrees +/- 1.7 degrees ), L5-S1 (25.8 degrees +/- 5.2 degrees and 20.8 degrees +/- 6 degrees ), and L1-S1 (53.4 degrees +/- 11.9 degrees and 57.3 degrees +/- 16.7 degrees ). Negative values reflect kyphosis, and positive values reflect lordosis. A significant difference between values before and during compression was obtained at L3-L4 and L5-S1. There was a significant decrease in disc height only at L4-L5 during compression. CONCLUSIONS: The axial force of 50% body weight in supine posture simulates the upright lumbar spine morphologically. No change in intervertebral angle occurred at L4-L5. However, disc height at L4-L
Mohd Zairul A. Abdul Rahman
2010-01-01
Full Text Available Problem statement: Foamed concrete has become most commercial material in construction industry. People in industries were come out with the new mix design of foamed concrete to meet the specification and the requirements needed. Approach: This is because foamed concrete has the possibility as alternative of lightweight concrete for producing intermediate strength capabilities with excellent thermal insulation, freeze-thaw resistance, high-impact resistance and good shock absorption. Results: Currently Standard test to measure the compressive strength of foamed concrete is using standard unconfined compressive test. Several research has been conduct but the compressive strength using standard unconfined compressive test not capture true behavior of foamed concrete because it just achieved only low compressive strength and sample under compression failed due to brittle collapse of the sample. This paper was analyses the comparison between standard compressive test and confined compressive test. The confinement test introduced to prevent sample from brittle collapse. Foamed concrete cylindrical sample has been investigated under the standard compressive test for hard concrete (ASTM-C39. Based on the research, samples are produced under unconfined and confined condition. Analysis has been done and the result show that under standard compressive test, the sample failed due to early crack initiation and failed. Confinement condition was increase the compressive strength but this condition influence the result. Conclusion/Recommendations: Standard test is not suitable to capture the true behavior of foamed concrete, and to prevent the sample from brittle collapse during the test, new testing method was introduced to capture the true behavior of foamed concrete which is using Quasi Static Indentation Test. This test can be used to study about the behaviour of foamed concrete before it can be implemented to its final application.
Patel, Tarpit K.; Brodt, Michael D.; Silva, Matthew J.
2013-01-01
Axial compression of the mouse tibia is used to study strain-adaptive bone (re)modeling. In some studies, comparisons between mice of different ages are of interest. We characterized the tibial deformation and force–strain relationships in female C57Bl/6 mice at 5-, 12- and 22-months age. A three-gauge experimental method was used to determine the strain distribution at the mid-diaphysis, while specimen-specific finite element analysis was used to examine strain distribution along the tibial ...
Mehrdad Nasirshoaibi
2015-01-01
Full Text Available Based on the Rayleigh beam theory, the forced transverse vibrations of a closed double single-walled carbon nanotube (SWCNT system containing a fluid with a Pasternak layer in-between are investigated. It is assumed that the two single-walled carbon nanotubes of the system are continuously joined by a Pasternak layer and both sides of SWCNTs containing a fluid are closed. The dynamic responses of the system caused by arbitrarily distributed continuous loads are obtained. The effect of compressive axial load on the forced vibrations of the double single-walled carbon nanotube system is discussed for one case of particular excitation loading. The properties of the forced transverse vibrations of the system are found to be significantly dependent on the compressive axial load. The steady-state vibration amplitudes of the SWCNT decrease with increasing of length of SWCNT. Vibrations caused by the harmonic exciting forces are discussed, and conditions of resonance and dynamic vibration absorption are formulated. The SWCNT-type dynamic absorber is a new concept of a dynamic vibration absorber (DVA, which can be applied to suppress excessive vibrations of corresponding SWCNT systems.
American Society for Testing and Materials. Philadelphia
2014-01-01
1.1 Included in this practice are methods covering the determination of the amount of bending that occurs during the application of tensile and compressive forces to notched and unnotched test specimens in the elastic range and to plastic strains less than 0.002. These methods are particularly applicable to the force application rates normally used for tension testing, creep testing, and uniaxial fatigue testing.
Achoura D.
2012-09-01
Full Text Available Dans cette étude, on présente les résultats expérimentaux obtenus sur des poteaux mixtes béton-acier mince réalisés par soudures. Un total de 24 profilés en acier, et en forme de I a été testé sous charge de compression uni-axiale à l’âge de 28 jours. les spécimens ont été réparties comme suit: 4 à vides, 4 partiellement remplies avec un béton ordinaire sans l’addition des connecteurs, 4 renforcés par des connecteurs de cisaillements de type cornière en U, 4 autres l’ont été avec des connecteurs de cisaillements type goujons et 8 restants ont été renforcés avec des liens transversaux d’espacement 100mm, 50mm, soudés aux bouts des ailes opposées. Les principaux paramètres étudiés sont: l’élancement du profilé, le type de connecteur de renforcement. A partir des résultats d’essais obtenus, il est confirmé que les parois minces sont plus sensibles de l’apparition au voilement et la longueur des profilés a un effet considérable sur la capacité portante et le mode de rupture. L’addition des connecteurs de renforcement a confirmé l’augmentation de la charge ultime par rapport aux profilés sans connecteurs. In the present work, results of tests conducted on thin welded steel-concrete stubs are presented. A total of 24 stubs an I steel section were tested under axial compression at 28 days after the date of casting, 4 were empty, 4 filled with normal concrete, 8 columns had shear connecters welded along the centreline of the web, and 8 columns had steel rods welded between the tips of opposing flanges on both sides of the spacing of the transverse link 100 mm and 50 mm. The main parameters studied were: the heel height, and type of connector strengthening. From the test results, it is confirmed that the thin walls are more sensitive to the appearance local buckling and the length of the profiles has a significant effect on the bearing capacity and failure mode. The bearing capacity was increased
Hautala, K.; Schmidt, H.
1998-12-01
The buckling test program comprised 37 axially loaded cylinders made of austenitic stainless steels and 6 reference cylinders made of mild steel. The three test parameters were the steel grade, the shell slenderness and the operating temperature. The chosen steel grades are typical for practical applications: AISI 304 (No. 1.4301) as the basic austenitic stainless steel, AISI 316 L (No. 1.4404) as a molybdenum alloyed and AISI 316 Ti (No. 1.4571) as a molybdenum and titanium alloyed austenitic stainless steel. The chosen shell slendernesses are typical for the above-mentioned elastic-plastic region: r/t=50, 150 and 400, approximately corresponding to non-dimensional slenderness parameters {lambda}=0.3, 0.5 and 0.9 respectively. The chosen testing temperatures cover a wide range of applications: T=20 C, 100 C, 250 C and 400 C. The test cylinders were manufactured from 3.0 mm, 1.0 mm and 0.5 mm steel sheets, cold rolled into the cylindrical shape and longitudianlly TIG-welded. The radii were 150 mm and 200 mm, the length was 350 mm. (orig.) [German] Das Beulversuchsprogramm bestand aus 37 axialbelasteten Zylindern aus austenitischen rostfreien Staehlen und sechs Referenzzylindern aus Baustahl. Die drei Versuchsparameter waren die Stahlsorte, die Schalenschlankheit und die Betriebstemperatur. Die drei ausgewaehlten Stahlsorten sind typisch fuer baupraktische Anwendungen: WNr. 1.4301 (AISI 304) als einfachster, WNr. 1.4404 (AISI 316L) als ein Molybdaen-legierter und WNr. 1.4571 (AISI 316Ti) als ein Molybdaen- und Titanium-legierter austenitischer rostfreier Stahl. Die ausgewaehlten Schalenschlankheiten sind typisch fuer den oben erwaehnten elastisch-plastischen Bereich: r/t=50, 150 und 400, entsprechend dimensionslosen Schlankheitsparametern von naeherungsweise {lambda}=0.3, 0.5 und 0.9. Die ausgewaehlten Versuchstemperaturen decken ein breites Spektrum von Anwendungen ab: T=20 C, 100 C, 250 C und 400 C. Die Versuchszylinder wurden aus 3 mm, 1 mm, und 0.5 mm
Jackman, Timothy M; DelMonaco, Alex M; Morgan, Elise F
2016-01-25
Finite element (FE) models built from quantitative computed tomography (QCT) scans can provide patient-specific estimates of bone strength and fracture risk in the spine. While prior studies demonstrate accurate QCT-based FE predictions of vertebral stiffness and strength, the accuracy of the predicted failure patterns, i.e., the locations where failure occurs within the vertebra and the way in which the vertebra deforms as failure progresses, is less clear. This study used digital volume correlation (DVC) analyses of time-lapse micro-computed tomography (μCT) images acquired during mechanical testing (compression and anterior flexion) of thoracic spine segments (T7-T9, n=28) to measure displacements occurring throughout the T8 vertebral body at the ultimate point. These displacements were compared to those simulated by QCT-based FE analyses of T8. We hypothesized that the FE predictions would be more accurate when the boundary conditions are based on measurements of pressure distributions within intervertebral discs of similar level of disc degeneration vs. boundary conditions representing rigid platens. The FE simulations captured some of the general, qualitative features of the failure patterns; however, displacement errors ranged 12-279%. Contrary to our hypothesis, no differences in displacement errors were found when using boundary conditions representing measurements of disc pressure vs. rigid platens. The smallest displacement errors were obtained using boundary conditions that were measured directly by DVC at the T8 endplates. These findings indicate that further work is needed to develop methods of identifying physiological loading conditions for the vertebral body, for the purpose of achieving robust, patient-specific FE analyses of failure mechanisms. PMID:26792288
刘洪奎; 贾连顺; 徐印坎
1986-01-01
This paper reports five children suffering from atlantoaxial dislocation due to trauma of cervical vertebrae,congenital abnormality of atlas,dysptasia or defects of os odontoideum and other diseases.As conservative therapy,traction and cervical support treatment all.failed and cervical spinal cord compression symptom gradually appeared,such as spasmotic palsy of lower limbs (2 cases),weak and unstable gait (3),so a procedure of resection of posterior arch of atlas and occipito-cervical fusion was performed.Follow-ups carried on 6 to 60 months after operation showed that satisfactory results were achieved in 4 cases,disappearance of lower limb spasm in 2 cases,4 children went back to school and only one died from other cause.The operative technique is described as well as its indications,choice of operation time and the modified occipitocervical fusion.The authors also point out that in children once atlanto-axial dislocation is found to be associated with cervical spinal cord compression,operation should be imminent and the result will be good.%@@ 寰枢椎由于先天发育不良、畸形、外伤或疾患引起不稳定者并非少见,此位置的关节不稳定比脊柱任何部位的关节不稳定更为危险,并有脊髓压迫症状时可导致四肢瘫痪或突然死亡~((1、2)),儿童期寰枢椎不稳定,保守治疗可能得到治愈,而需要行寰椎后弓切除减压及枕颈融合者极少.
薛建阳; 崔卫光; 陈宗平; 马辉; 高亮
2013-01-01
According to static experiment of six steel reinforced recycled aggregate concrete composite columns, the axial compression load-bearing capacity was studied. Two factors, which were the recycled coarse aggregate replacement rate and slenderness ratio, were taken into consideration. Load-displacement curves of composite columns under axial loads were obtained. The fracture of composite columns and the influence of recycled coarse aggregate replacement rate and slenderness ratio on axial compression load-bearing capacity were analyzed. The formula for axial compression load of steel recycled concrete composite column was also presented.%通过6个型钢再生混凝土组合柱的静载试验,对型钢再生混凝土组合柱轴压承载力进行了研究.试验主要考虑再生粗骨料取代率和长细比两个参数对构件承载力的影响.由试验得出组合柱在轴心荷载下的荷载-位移曲线,分析型钢再生混凝土组合柱的破坏机理及再生粗骨料取代率、长细比对其轴压承载力的影响,提出型钢再生混凝土组合柱轴压承载力计算公式.
Márcio Hiroaki Kume
2010-02-01
Full Text Available OBJETIVO: Analisar a resistência (rigidez do sistema de fixação externa tubular uniplanar, com hastes de conexão única e dupla, com traços de fraturas estáveis e instáveis. MÉTODOS: Foram utilizados 48 modelos semelhantes à tíbia. Em todos foi deixado um intervalo de 0,5 cm entre os fragmentos e realizados cortes com angulações de 15º e 45º para simular fraturas estáveis e instáveis, respectivamente. Os modelos foram divididos em quatro grupos de acordo com o traço fraturário (15º e 45º e o número de barras metálicas na montagem (1 e 2 barras. Os modelos de prova foram adaptados à uma máquina de testes Instron®, pelas suas extremidades, e submetidos à compressão axial até que os fragmentos tiveram contato total. Avaliou-se a força necessária para efetuar o completo contato dos fragmentos do modelo. RESULTADOS: As forças instabilizadoras na montagem do fixador com barra dupla foram bastante superiores às com barra única. Observou-se ainda que o grupo com barra única instável apresentou variabilidade muito menor que os demais grupos, ou seja, apresenta resultados mais homogêneos, além de ter apresentado a menor média. CONCLUSÃO: A montagem do fixador externo com uma haste longitudinal dupla nos modelos estudados é mais estável que as demais quando submetidas à uma força de compressão axial.OBJECTIVE: This is an experimental study with the objective of analyses the increase of rigidity in synthetic tibia bones with external fixators, with single and double connecting rods and with stable and unstable fracture patterns. METHODS: The external fixators were used in the monoplanar, half pin configuration submitted to an axial compression load using the connecting bar in different patterns. Forty-eight similar models to the human tibia had been used. In all the models were left an interval of 0,5 cm between the fragments and were made cuts of 15º and 45º to simulate stable and unstable fracture patterns
李明; 陈扬骥; 钱若军; 姚念亮
2001-01-01
Stability for I-Section aluminium alloy bars of disparate slenderness,loaded by axial compressive force,is studied by experiments in this paper.Stability parameters are calculated from experimental data and compared with the results of several formulas by other researchers.Practical formula for engineering utilization is derived for the stability parameters of I-Section aluminium alloy bars loaded by axial compressive force.%通过对不同长细比铝合金工字形轴心压杆稳定性的试验研究，计算得出了相应的稳定系数，并与几种公式的计算结果对比，得出了可用于我国铝合金轴心压杆设计的稳定系数计算公式。
张鑫鑫
2014-01-01
为研究GFRP管混凝土柱轴压的力学性能，对6根不同长细比试件进行了研究，通过试验，分析了不同长细比对GFRP管混凝土柱轴压性能、破坏形态及承载力的影响，得出了一些有利用价值的结论。%In order to researching the mechanical properties of GFRP pipe concrete column axial compression,this paper researched the 6 differ-ent slenderness ratios test specimen,through the experiments analyzed the influence of different slenderness ratio to GFRP pipe concrete column axial compression performance,damage types and bearing capacity,draw some useful conclusions.
米旭峰; 朱海玲; 杭振园
2014-01-01
基于13个钢聚氨酯复合管试件的轴压试验，研究聚氨酯在钢复合管中的应用。结果表明，在承受轴向压力下，钢聚氨酯复合管轴压试件破坏时呈多折腰鼓形；钢管发生局部屈曲后，受到聚氨酯材料的约束可以有效延缓试件屈曲发生时间与变形程度；整个加载过程，聚氨酯与钢材的黏结性能良好，两者未发生剥离现象。从试件荷载位移曲线以及试验过程可得：荷载位移曲线一般由弹性、弹塑性、下降和强化阶段组成，表明复合管具有很好的延性与强度储备，能有效抵抗地震等动力荷载的作用。随着 L / D 的减小，试件的极限荷载有增大的趋势，但是其增幅不明显。套箍系数ξ是影响试件性能的重要因素，当ξ值提高时试件承载力会明显提高；反之亦然。%Experiments on axial compression behaviors of 13 steel-polyurethane composite tube (SPCT) specimens were conducted to study the application of polyurethane to steel composite tubes. The results show that, under the axial compression, the SPCT was shaped like a bow drum. When local buckling occurred in the steel tube, polyurethane could effectively delay the buckling and deformation. Over the whole loading process, the bonding performance between polyurethane and steel was so good that peeling did not occur. It can be seen from the load-displacement curve and test process that the load-displacement curve is generally composed of elastic, elastic-plastic, descending, and strengthening phases, indicating that the SPCT has sound ductility and a reserve of strength to resist dynamic loads such as earthquakes. With the decrease of L / D, the limiting load of the specimen had an increasing trend, but the trend was not significant. The confining parameter ξ is an important factor influencing the specimen. When ξ increased, the specimen’ s carrying capacity increased significantly, and vice versa.
Stachiv, Ivo, E-mail: stachiv@fzu.cz [Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan (China); Institute of Physics, Czech Academy of Sciences, Prague (Czech Republic); Fang, Te-Hua; Chen, Tao-Hsing [Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan (China)
2015-11-15
Vibrating micro-/nanosized cantilever beams under an applied axial force are the key components of various devices used in nanotechnology. In this study, we perform a complete theoretical investigation of the cantilever beams under an arbitrary value of the axial force vibrating in a specific environment such as vacuum, air or viscous fluid. Based on the results easy accessible expressions enabling one the fast and highly accurate estimations of changes in the Q-factor and resonant frequencies of beam oscillating in viscous fluid caused by the applied axial force are derived and analyzed. It has been also shown that for beam-to-string and string vibrational regimes the mode shape starts to significantly deviate from the one known for a beam without axial force. Moreover, a linear dependency of the vibrational amplitude in resonance on the dimensionless tension parameter has been found. We revealed that only a large axial force, i.e. the string vibrational regime, significantly improves the Q-factor of beams submerged in fluid, while an increase of the axial force in beam and beam-to-string transition regimes has a negligibly small impact on the Q-factor enhancement. Experiments carried out on the carbon nanotubes and nanowires are in a good agreement with present theoretical predictions.
Stachiv, Ivo; Fang, Te-Hua; Chen, Tao-Hsing
2015-11-01
Vibrating micro-/nanosized cantilever beams under an applied axial force are the key components of various devices used in nanotechnology. In this study, we perform a complete theoretical investigation of the cantilever beams under an arbitrary value of the axial force vibrating in a specific environment such as vacuum, air or viscous fluid. Based on the results easy accessible expressions enabling one the fast and highly accurate estimations of changes in the Q-factor and resonant frequencies of beam oscillating in viscous fluid caused by the applied axial force are derived and analyzed. It has been also shown that for beam-to-string and string vibrational regimes the mode shape starts to significantly deviate from the one known for a beam without axial force. Moreover, a linear dependency of the vibrational amplitude in resonance on the dimensionless tension parameter has been found. We revealed that only a large axial force, i.e. the string vibrational regime, significantly improves the Q-factor of beams submerged in fluid, while an increase of the axial force in beam and beam-to-string transition regimes has a negligibly small impact on the Q-factor enhancement. Experiments carried out on the carbon nanotubes and nanowires are in a good agreement with present theoretical predictions.
Vibrating micro-/nanosized cantilever beams under an applied axial force are the key components of various devices used in nanotechnology. In this study, we perform a complete theoretical investigation of the cantilever beams under an arbitrary value of the axial force vibrating in a specific environment such as vacuum, air or viscous fluid. Based on the results easy accessible expressions enabling one the fast and highly accurate estimations of changes in the Q-factor and resonant frequencies of beam oscillating in viscous fluid caused by the applied axial force are derived and analyzed. It has been also shown that for beam-to-string and string vibrational regimes the mode shape starts to significantly deviate from the one known for a beam without axial force. Moreover, a linear dependency of the vibrational amplitude in resonance on the dimensionless tension parameter has been found. We revealed that only a large axial force, i.e. the string vibrational regime, significantly improves the Q-factor of beams submerged in fluid, while an increase of the axial force in beam and beam-to-string transition regimes has a negligibly small impact on the Q-factor enhancement. Experiments carried out on the carbon nanotubes and nanowires are in a good agreement with present theoretical predictions
陈迪; 熊海贝; 刘正虎
2011-01-01
This paper introduces the development of the research on built-up timber members in modern woodframe constructions. By having tested four group timber members, about 22 built-up timber columns, some researches on axial compression have been studied. With the experimental dates of each test groups, some factors which would influence the axial compressive ability of the columns, such as slenderness ratio, nail spans,numbers of combined SPF and metal hoops, have been analysed and evaluated in details. And these researches would promote the design and applications of built-up timber constructions. Some achievements show as followers: ( 1 ) nails do limit promotion on the axial compressive ability; (2) to decrease slenderness ratio of columns and add metal hoops would enhance its axial compressive ability; ( 3 ) the increase of slenderness and numbers of SPF would make laminations of built-up columns work much better.%本文介绍了轻型木结构体系中组合木构件的研究进展.通过4组共22根组合木柱构件的轴心受压试验,对此类构件轴心受压性能进行研究.根据各组试验数据的对比,分析组合片材数,构件长细比,钉间距及金属套箍对组合木结构柱轴心受压性能的影响,对于组合木柱的设计应用提供一定的参考.本文所得的研究成果主要有:(1)组合木柱连接钉对轴心受压性能的提高没有显著的影响;(2)减小组合柱长细比,增设金属套箍能有效提高其承载力;(3)长细比的提高及片材数的增加能增强组合木柱的协同工作能力.
The axial view of normal cervical spinal cord was analyzed to elucidate the relationships between its shape and clinical result in compression myelopathy. Subjects were 104 cases with normal shape and 35 cases with cervical myelopathy of a single intervertebral compressive lesion. MRI was performed with General Electric 1.5 T superconducting apparatus to get T1-weighted cross image of 5 mm slice thickness. Morphometry was performed with high performance image processor (SPICCA, Nihon-Avionics) to compute the area and longitudinal and lateral lengths of spinal cord to calculate flatness. The area and longitudinal length were positively correlated with body height, and the longitudinal length and flatness, negatively with age. The reduction rate of the spinal cord area had a relation with neurological symptoms, but, together with age and duration of the disease, had no relation with the clinical results from operation. (H.O.)
Tanida, Yasutaka [Osaka Medical Coll., Takatsuki (Japan)
1996-01-01
The axial view of normal cervical spinal cord was analyzed to elucidate the relationships between its shape and clinical result in compression myelopathy. Subjects were 104 cases with normal shape and 35 cases with cervical myelopathy of a single intervertebral compressive lesion. MRI was performed with General Electric 1.5 T superconducting apparatus to get T1-weighted cross image of 5 mm slice thickness. Morphometry was performed with high performance image processor (SPICCA, Nihon-Avionics) to compute the area and longitudinal and lateral lengths of spinal cord to calculate flatness. The area and longitudinal length were positively correlated with body height, and the longitudinal length and flatness, negatively with age. The reduction rate of the spinal cord area had a relation with neurological symptoms, but, together with age and duration of the disease, had no relation with the clinical results from operation. (H.O.)
Weld residual stress and distortion, which often have negative influences on structural performance of welded components, should be controlled appropriately. Especially, weld residual stress in nuclear power plants can be one of the fatal problems as the factor in generation and propagation of stress corrosion cracking (SCC). It has become well known that an axial residual stress on the inner surface of welded pipe joint has a significant influence on SCC. The axial residual stress has been therefore controlled by additional process, such as some kinds of peening or heat treatment. On the other hand, another approaches for the in-process control of the axial residual stress during weld procedure should be also performed if it is technically possible. In this study, a parametric survey on the relationship between welding conditions, including configuration of the pipe joint, and weld residual stress is done by the numerical analysis with the thermal elastic-plastic model. Based on the numerical results, a methodology for controlling the axial residual stress on the inner surface of welded pipe joints is investigated from a viewpoint of the optimization of weld procedure. (author)
于峰; 牛荻涛
2013-01-01
This paper presents the results of experimental investigations on 10 PVC-CFRP confined reinforced concrete columns.The influences of the hoop spacing of CFRP strips and the axial reinforcement on the load-carrying capacity,deformation and failure mode of PVC-CFRP confined reinforced concrete columns were studied.Test results show that the load-carrying capacity and ultimate compressive strain of axially reinforced members with reinforced ratio 1.8％ respectively increase about 24％ and 16％ compared with those of members without axial reinforcement; the loadcarrying capacity and ultimate compressive strain decrease with the increase of the hoop spacing of CFRP strips; when the axially reinforced members fail,multiple CFRP strips fracture and longitudinal reinforcement buckle at the middle height of the specimens.The stress-strain relationship curves of PVC-CFRP confined reinforced concrete column may be divided into three stages:at the first segment,the stress-strain relationship curves is parabola; at the second segment,the stress-strain relationship exhibits an obvious transition segment ; at the third segment,before the failure of the axially reinforced members,the axial stress and strain is in the increasing state.The slope tangent of the hardening segment of axially reinforced members is larger than that of members without axial reinforcement.Based on the static equilibrium and limit equilibrium,a calculating formula of the bearing capacity of PVC-FRP confined concrete column was derived.The calculated values of the proposed formula agree well with the experimental results.%通过10根PVC-CFRP管钢筋混凝土短柱轴压试验,分析CFRP条带环箍间距和轴向配筋等因素对PVC-CFRP管钢筋混凝土短柱承载力、变形以及破坏形态的影响.试验研究表明:与无筋试件相比,配筋率为1.8％的配筋试件的承载力和轴向极限压应变分别提高约24％和16％；随着CFRP条带环箍间距的增大,配筋试件的承载
It is well known that thin-walled compression members are subject to the effects of local buckling and that due to these local effects the compressive carrying capability of short strut members can be significantly reduced. Finite element simulation is employed in this paper to examine the post-buckled response of thin-walled sections giving due consideration to the influence of geometric imperfections and to elasto-plastic material behaviour. The findings from this work highlight the complete loading history of the compression struts from the onset of elastic local buckling through the nonlinear elastic and elasto-plastic post-buckling phases of behaviour to final collapse and unloading. A detailed account of the growth and redistribution of stresses as well as the influence of yielding and yield propagation throughout loading is given in the paper. The results from the finite element simulations are shown to compare well with independent simulations using the finite strip method of analysis.
赵卫锋; 张武东; 周靖; 曹勇龙; 龙志林
2014-01-01
mechanical properties. Multi-layered high-strength bamboo plywood forms the primary body in the SBCC that is subjected to compressive forces, and the square thin-walled steel tube only serves as a liner. Large numbers of bamboo are used, which reduce the manufacturing cost of the composite columns and result in a relatively high load-bearing capacity. A steel tube section is used in the column core to increase the cross-sectional size of the column, thereby reducing the slenderness ratio and effectively regulating the instability and failure of the columns under pressure. The composite has a simple cross-section, can be manufactured and processed simply, and is suitable for industrial production. This study aimed to study the axial compression performance of SBCCs, and explore its failure mechanism under axial loads in order to provide valuable information for its engineering applications. The influence of factors including bamboo-plywood net sectional dimension area, hollow ratio, and slenderness ratio on the mechanical performance and axial compression properties was investigated using 15 composite column specimens. The failure modes and deformation behavior of specimens were also analyzed in an axial compression test. Results showed that the compressive failure for SBCCs was principally characterized by interior damage of the bamboo plywood material, damage from glue failure at the matrix interface, and global buckling failure due to the large deformation in the middle of the column. The failure mode was mainly determined by the overall adhesive strength between the matrixes. The compressive bearing-capacity of SBCC increased with increasing net sectional dimension area and the hollow ratio of the bamboo, and decreased with increasing slenderness ratio. A calculating model for the axial compressive bearing-capacity of SBCCs, which can serve as a guideline for engineering applications, was obtained by nonlinear regression analysis of the test data, and the maximum error
Suman Bargav. R
2015-07-01
Full Text Available :Quasi-static compression tests were performed on empty and foam filled Aluminium square tubes. Two different foam types: Extended Polystyrene (XPS and Extended Polyethylene (XPE were used to fill the empty tubes. In this paper experimental and numerical simulations were performed to investigate the effect of foam filling on crashworthiness parameters
加劲肋对轴心受压圆管柱脚应力的影响%The Influence of Stiffening Rib on Axial Compression Round String Stress
张向红
2014-01-01
Exposed column base is applied most frequently in al forms of column foot, and the calculation of column foot motherboard has become a critical problem. According to the different forms of stif ening rib, this paper compares the stress of axial compression string round feet, analyzes the effect of stif eners on the heel stress.%外露式柱脚是在所有柱脚形式中应用得最多的一种，柱脚底板的计算就成为一个至关重要的问题。本文针对不同的加劲肋形式，对轴心受压圆管柱脚的应力进行对比，分析加劲肋对柱脚应力的影响。
吴炎海; 方映平; 冯文贤; 蔡杨
2015-01-01
Axial static loading test was carried out on 6 recycled aggregate concrete filled circular steel tubular long columns. The whole loading process and failure modes were observed,and the curves of specimens about load-deformation and load-strain were plotted. The influences of the test parameters namely slenderness ratio and confine-ment index on deformation and the bearing capacities of specimens were analyzed. By domestic and foreign relevant specifications,the ultimate bearing capacity of the specimens were calculated and compared with the measured val-ues. The results indicated that the failure process of recycled aggregate concrete filled steel tubular long columns un-der axial compression includes elastic stage,elastic-plastic stage and plastic stage,and all the failure modes are elas-tic-plastic instability;Both the slenderness ratio and confinement index affect the mechanical performance of recy-cled aggregate concrete filled steel tubular long columns under axial loading,and the confinement index is more ob-vious;Finally,the calculation and design method of recycled aggregate filled steel tubular long columns under axial loading were proposed.%进行6根圆钢管再生混凝土长柱轴压的静力加载试验，观察试件受力的全过程和破坏形态，绘制出各试件的荷载-变形和荷载-应变关系曲线，分析长径比和套箍系数2个变化参数对试件变形和承载力的影响规律，采用国内外相关规程计算各试件的极限承载力并与实测值进行对比。结果表明：钢管再生混凝土轴压长柱受力过程经历了弹性阶段、弹塑性阶段和塑性下降阶段，均为弹塑性失稳破坏；长径比和套箍系数对钢管再生混凝土轴压长柱的受力性能均有影响，其中套箍系数影响较大；最后对于钢管再生混凝土长柱轴压的承载力计算及构件的设计提出建议。
钟大虎; 夏辉; 窦益华; 曹银萍
2014-01-01
为校核螺旋屈曲管柱的强度安全性，基于弹簧理论与第四强度理论，推导出螺旋屈曲状态下管柱内、外侧相当应力的计算公式，并以油田常用规格油套管为例，探讨了轴向压力对管柱内、外侧最大相当应力的影响。算例结果表明，螺旋屈曲管柱内侧最大相当应力恒大于外侧；管柱内、外侧最大相当应力随轴向压力的增大而增大。轴向压力由200KN 增大至800KN 时，管柱内、外侧最大相当应力分别增大170%和413.8%。研究弥补了传统管柱力学分析的不足，提供了螺旋屈曲管柱安全性研究新方法，同时也可为现场安全施工提供参考。%To make clear stress distribution and variation of helical buckling tubing string, the formulas of equivalent stresses inside and outside of the tubing string were deduced based on the spring theory and the fourth strength theory. Taking tubing string and casing commonly used in oilfield as object, stress calculation programs were compiled to explore the influence of axial compression load on equivalent VonMises stress. From the analysis, we can see that the equivalent VonMises stresses inside of the helical buckling tubing string were higher than that outside. The equivalent VonMises stress increased with the axial compression load, and the increase is 170 percent and 413.8 percent respectively for stress inside and outside of the tubing string with compression load increased from 200KN to 800KN. The proposed method used for the helical buckling tubing string covered the shortage of traditional tubular mechanics effectively and can also provide reference for the field application.
Covey-Crump, S. J.; Xiao, W. F.; Mecklenburgh, J.; Rutter, E. H.; May, S. E.
2016-07-01
For technical reasons, virtually all plastic deformation experiments on geological materials have been performed in either pure shear or simple shear. These special case loading geometries are rather restrictive for those seeking insight into how microstructure evolves under the more general loading geometries that occur during natural deformation. Moreover, they are insufficient to establish how plastic flow properties might vary with the 3rd invariant of the deviatoric stress tensor (J3) which describes the stress configuration, and so applications that use those flow properties (e.g. glaciological and geodynamical modelling) may be correspondingly compromised. We describe an inexpensive and relatively straightforward modification to the widely used Paterson rock deformation apparatus that allows torsion experiments to be performed under simultaneously applied axial loads. We illustrate the performance of this modification with the results of combined stress experiments performed on Carrara marble and Solnhofen limestone at 500°-600 °C and confining pressures of 300 MPa. The flow stresses are best described by the Drucker yield function which includes J3-dependence. However, that J3-dependence is small. Hence for these initially approximately isotropic calcite rocks, flow stresses are adequately described by the J3-independent von Mises yield criterion that is widely used in deformation modelling. Loading geometry does, however, have a profound influence on the type and rate of development of crystallographic preferred orientation, and hence of mechanical anisotropy. The apparatus modification extends the range of loading geometries that can be used to investigate microstructural evolution, as well as providing greater scope for determining the shape of the yield surface in plastically anisotropic materials.
周绪红; 李喆; 刘永健; 石宇
2012-01-01
In order to investigate bearing capacity of cold-formed steel built-up columns under axial compression, authors used ANSYS finite element program to analyze the cold-formed steel built-up columns at home and abroad. Compared with experimental results, the validity of the finite element method (FEM) was verified. Furthermore, a detailed parametric study by FEM was carried out to mainly determine the influence of cross-section form, cross-section dimension and slenderness ratio of component for the built-up effect. The simplified calculation method to the bearing capacity of cold-formed steel built-up columns under axial compression was extracted. The analytical results show that with the increase of the slenderness ratio, the built-up effect improves. As for these columns connected with screws through web, when width-thickness ratio of flange is certain, with the increase of width-height ratio of cross-section, the integrity of the built-up web increases, which leads the built-up effect to strengthen. But the influences of different areas of cross-sections are not so obvious.%为了研究冷弯薄壁型钢拼合截面柱的轴压承载力,对各国有关冷弯薄壁型钢拼合截面柱的轴压试验进行了ANSYS有限元模拟分析,有限元计算结果与试验结果吻合良好,从而验证了有限元方法的正确性.采用有限元方法分析了构件截面形式、截面尺寸以及长细比对冷弯薄壁型钢拼合截面柱拼合效应的影响,提出了冷弯薄壁型钢拼合截面柱轴压承载力的简化计算方法.分析结果表明:随着长细比的增大,拼合截面柱的拼合效应随之增大.对于主要通过螺钉将腹板进行拼合的构件,当翼缘宽厚比一定时,随着截面宽高比的增大,腹板拼合的整体性增强,从而使拼合效应增大,而截面面积的改变对拼合效应的影响则不是很明显.
Yamada, M.; Kawamura, H.; Tani, A. (Kobe Univ., Kobe (Japan). Faculty of Engineering); Zhang, F. (Matsumura-Gumi Corp., Osaka (Japan))
1991-08-30
Deformation analysis modes have been structured for RC and SRC columns subjected to bending and sear to study their elasto-plastic deformation properties. It is shown that fracture behaviors of columns can be evaluated when the proposed deformation analytical modes for RC and SRC columns subjected to bending and shear are used by noticing the deformation and stress states of the plastic hinge. The boundary of each fracture mode (boundary point, boundary expression) for RC and SRC columns subjected to bending and shear under constant compressive axial force can be obtained by this method, and the physical meaning of the boundary shear span ratio is clarified. The boundary expression is applied to unit shear wall to introduce a conditional expression for preventing shear fracture of the edge column of the shear wall. Virtual shear span ratio for edge column is obtained for unit shear wall, which is compared with the critical shear span ratio for avoiding shear fracture of the column, and judgement is made whether the edge column undergoes shear fracture or not. 16 refs., 19 figs., 2 tabs.
时卫民; 江世永; 付玉辉
2001-01-01
Base on the stress-strain relationship and ultimate strain of brick masonry and concrete,the stress-strain relationship between later concrete and original brick masonry is deduced.A new concept of boundary fracture of new and old materials is developed.A method of defining concrete utilizatian ceefficiant is givan in axial compression brick masonry structure strengthened by concrete.%根据砖砌体和混凝土的应力-应变关系及极限应变值，从理论上推导了后加混凝土与原砌体之间的应力-应变关系，提出了新旧材料界限破坏的概念，并按此概念给出了轴心受压砖砌体采用外包混凝土加固时混凝土利用系数的确定方法。
This report is a continuation of the thesis [23], devoted to the onset of necking plastic instabilities during tension tests on metallic plates bi-axially loaded in their plane. We are also interested here in compression tests, and in the development of antisymmetric defects with respect to the median plane of the plate. As in the thesis, we search for the dominant mode, i.e. the most unstable pair of wavelengths (λ1, λ2) in the loading plane. An approximate analytical formulation for the growth rate is proposed, especially for plane-strain tests in the absence of viscous effects, and for static tests in tension in the x1 and x2 loading directions. In that latter case, we retrieve published results [14][15]. For plane-strain tests, we show that infinitely dense networks of shear bands inclined at 45 deg. with respect to the loading direction instantaneously occur when heat softening prevails over work-hardening. (author)
赵楠; 李正良; 刘红军
2013-01-01
进行了19个长细比λ=30～90的Q420 L220 mm×20 mm角钢试件的轴压试验研究.结果表明:此类构件在长细比λ＞45时,以弯曲失稳破坏为主；长细比λ≤45时,以弯扭失稳为主.研究了现行钢结构规范中防止局部屈曲宽厚比限值公式和计算弯扭失稳的换算长细比取值公式的适用性.采用逆算单元长度法得到了大规格等边角钢的柱子曲线,研究了此类构件与普通规格等边角钢的差异以及肢厚、肢宽和钢材强度等对柱子曲线的影响.提出了高强大规格等边角钢轴压构件的承载力计算方法.并且研究了高强大规格等边角钢两端偏心受压的柱子曲线,给出了长细比修正系数的建议公式.%The axial compression member test was conducted to investigate the stability performance of these members, including nineteen Q420 L220×20 specimens which slenderness ratio(λ) ranged from 30~90. The test results showed that when slendemess is λ > 45, flexural buckling was observed and when slenderness is λ ≤45, local or flexural-torsion or torsion buckling was observed. The applicability of local buckling wide thickness ratio formula and flexural-torsional buckling conversion slenderness ratio formula was researched. By means of inverse calculation segment length method, the column curve of the large size equal angle was got. The comparison with common size angle and parameter analysis was made. Calculation method of bearing capacity of large size equal angle was given. Two ends eccentric compression column curve was also researched, and a suggestion formula of slenderness ratio correction coefficient was given.
任庆新; 李颀; 蒋治国; 赵雄
2014-01-01
A three-dimensional finite element analysis model for elliptical concrete-filled steel tubular long columns subjected to axial compression is developed and the corresponding tests are carried out .The predicted relationship curves of load versus deflection in the middle column height and damage modes are in good agreement with the measured results .The finite element analysis model is thus used to investigate the stress and strain distribution of each component and the interaction between the steel tube and the core concrete in the whole loading process .And then, the main parameters influencing the relationship curves of load versus deflection in the middle column height such as slenderness ratio , material strength , steel tube wall thickness and cross sectional dimension are investigated . The results show the typical failure modes of these columns were the lateral overall bending at about mid -height, the slenderness ratio have obvious effects on their mechanical behavior , while the yield strength of steel tube has slight effect on their mechanical behavior .%利用有限元软件ABAQUS建立椭圆形钢管混凝土长柱轴压力学性能分析的三维实体有限元模型，并进行相应的试验，有限元计算与试验所得的荷载-柱中挠度全过程曲线及长柱破坏形态吻合较好。在此基础上对其受力全过程中钢管及混凝土应力、应变分布情况进行分析，同时给出钢管与混凝土之间的相互作用，并对长细比、材料强度、钢管壁厚及截面尺寸等参数对轴压时长柱极限承载力及荷载-柱中挠度曲线的影响进行比较。结果表明：椭圆形钢管混凝土长柱在1/2柱高处发生侧向挠曲破坏，长细比等参数对其力学性能影响显著，钢管屈服强度对其力学性能影响不明显。
刘向斌; 周天华; 聂少锋; 吴函恒
2011-01-01
The finite element model involving materials nonlinearity, geometric nonlinearity and contact nonlinearity was established, the influences of slenderness ratios, screw connection spacings, maximum width-thickness ratios on cold-formed thin-walled steel three open limbs built-up columns under axial compression were analyzed by using ANSYS finite element program. Results show that the slenderness ratio has great influence on the bearing capacity of axial compression and the axial compression performance for class A, B section built-up columns, with the increase of the column slenderness ratio, the ultimate bearing capacity gradually decreases. For two class section built-up columns, when screw connection spacing has arranged 450,300,150 mm, the ultimate bearing capacity of axial compression and the rigidity are little affected. For the three different lengths to the two class section built-up columns, as different thicknesses of the basic component plates cause different width-thickness ratios of the section, the ultimate bearing capacity of axial compression and the rigidity are obviously affected. When length and thickness of class A, B section built-up columns are same, and the basic component web height is increasedfrom 89 mm to 140 mm, the ultimate bearing capacity of axial compression is not obviously improved.%建立了考虑材料、几何和接触非线性的有限元模型,利用ANSYS有限元程序分析了长细比、螺钉连接间距、截面板件最大宽厚比对冷弯薄壁型钢开口三肢拼合立柱轴压性能的影响.结果表明:立柱长细比对A、B两类截面拼合立柱轴压承载力和轴压性能有很大影响,随着立柱长细比的增大,立柱轴压极限承载力逐渐降低；当螺钉连接间距为450、300、150 mm时,A、B两类截面拼合立柱轴压极限承载力和刚度变化均不大；由于基本构件板材厚度不同引起截面板件最大宽厚比的不同,对A、B两类截面3种长度的拼合立柱的承
徐菊芬; 杨俊杰; 徐良德
2014-01-01
According to the test result of interior joints with Z-shaped RC column under low-cyclic loading, software ANSYS was used to establish numerical analysis model. The nonlinear finite element analysis was done by ANSYS for interior joints with Z-shaped RC column under low-cyclic loading, the shear capacity of interior joints were studied under different axial compression ratio. The results showed that changes of axial compression ratio had a impact on the shear capacity of interior joints with Z-shaped RC column under low-cyclic loading. The axial compression ratios are Suggested to control in 0.1 to 0.5 for interior joints with Z-shaped RC column of practical engineering design.%基于钢筋混凝土Z形截面柱框架中间层中节点的低周反复试验结果，利用有限元软件ANSYS建立数值分析模型，对低周反复荷载作用下混凝土Z形截面柱框架中间层中节点受力性能进行了非线性有限元分析，研究了不同轴压比下节点的抗剪承载力性能。结果表明，轴压比的变化对Z形柱中节点抗剪承载力有一定影响，建议实际工程设计Z形柱中节点的轴压比控制在0.1～0.5为宜。
屈立军; 杨洪瑞; 史可贞; 张平; 李焕群; 李胜利
2012-01-01
To reveal the thermal stress variation of axially compressed steel elements with restrained thermal elongation, a self-designed special equipment and the method of continuous heating under constant loads were used. 215 tests on the tube columns made of Q345 steel were performed with 13 levels of restraint stiffness, 3 levels of initial stress and 6 different slenderness ratios prescribed. The results show that: ( 1 ) Thermal stress plays the most important role, and should be considered in the fire protection design and evaluation of steel structure. Thermal stress decreases in the later stage of temperature rise, but before that the specimen already failed. (2) The greater the restraint stiffness and slenderness ratio are, the larger thermal stress is, and the lower the failure temperature for the specimen is. On the contrary, the opposite results are obtained. The greater the restraint stiffness is and the smaller the slenderness ratio is, the longer the plastic plateau on the curve thermal stress-temperature rise is. (3) Failure characteristics of specimens may be affected by the slenderness ratio: a greater slenderness ratio may lead to a larger lateral residual deformation and a smaller axial deformation, indicating that the specimen is undergoing the buckling failure; Otherwise, the specimen is experiencing the strength failure. (4) The early stages of thermal stress-temperature rise curves for different initial stresses are almost similar and the corresponding slopes are same. The lower the initial stress is, the larger the thermal stress is and the later the curve deviates from the initial superposition stage. On the contrary, the opposite results may be observed. (5) There are four stages presented on the thermal stress-temperature rise curve: when the temperature rise is small, the relationship between thermal stress and temperature rise appears to be linear; Subsequently, the increase of stress becomes slow, and a nonlinear relationship is observed; With
Feng Li; Qilin Zhao; Li Chen; Guojian Shao
2014-01-01
The axial compressive strength of unidirectional FRP made by pultrusion is generally quite lower than its axial tensile strength. This fact decreases the advantages of FRP as main load bearing member in engineering structure. A theoretical iterative calculation approach was suggested to predict the ultimate axial compressive stress of the combined structure and analyze the influences of geometrical parameters on the ultimate axial compressive stress of the combined structure. In this paper, t...
The purpose of this calculation is to develop axial profiles for estimating the axial variation in burnup of a boiling water reactor (BWR) assembly spent nuclear fuel (SNF) given the average burnup of an assembly. A discharged fuel assembly typically exhibits higher burnup in the center and lower burnup at the ends of the assembly. Criticality safety analyses taking credit for SNF burnup must account for axially varying burnup relative to calculations based on uniformly distributed assembly average burnup due to the under-burned tips. Thus, accounting for axially varying burnup in criticality analyses is also referred to as accounting for the ''end effect'' reactivity. The magnitude of the reactivity change due to ''end effect'' is dependent on the initial assembly enrichment, the assembly average burnup, and the particular axial profile characterizing the burnup distribution. The set of bounding axial profiles should incorporate multiple BWR core designs and provide statistical confidence (95 percent confidence that 95 percent of the population is bound by the profile) that end nodes are conservatively represented. The profiles should also conserve the overall burnup of the fuel assembly. More background on BWR axial profiles is provided in Attachment I
J. Huffer
2004-09-28
The purpose of this calculation is to develop axial profiles for estimating the axial variation in burnup of a boiling water reactor (BWR) assembly spent nuclear fuel (SNF) given the average burnup of an assembly. A discharged fuel assembly typically exhibits higher burnup in the center and lower burnup at the ends of the assembly. Criticality safety analyses taking credit for SNF burnup must account for axially varying burnup relative to calculations based on uniformly distributed assembly average burnup due to the under-burned tips. Thus, accounting for axially varying burnup in criticality analyses is also referred to as accounting for the ''end effect'' reactivity. The magnitude of the reactivity change due to ''end effect'' is dependent on the initial assembly enrichment, the assembly average burnup, and the particular axial profile characterizing the burnup distribution. The set of bounding axial profiles should incorporate multiple BWR core designs and provide statistical confidence (95 percent confidence that 95 percent of the population is bound by the profile) that end nodes are conservatively represented. The profiles should also conserve the overall burnup of the fuel assembly. More background on BWR axial profiles is provided in Attachment I.
Signatures for axial chromodynamics
Within the context of basic left-right symmetry and the hypothesis of unification of weak, electromagnetic and strong forces at a mass level approximately equal to 104-106 GeV, relatively light ''mass'' axial gluons, confined or liberated, must be postulated. The authors remark that the existence of such ''light'' axial gluons supplementing the familiar vector octet preserves the successes of QCD, both for deep inelastic processes and charmonium physics. Through the characteristic spin-spin force, generated by their exchange, they may even help resolve some of the discrepancies between vector QCD predictions and charmonium physics. The main remark of this note is that if colour is liberated, not only vector but also axial-vector gluons are produced in high-energy e-e+ experiments, e.g. at PETRA and PEP, with fairly large cross-section. Distinctive decay modes of such liberated axial gluons are noted
Surface nanoscale axial photonics
Sumetsky, M.; Fini, J. M.
2011-01-01
Dense photonic integration promises to revolutionize optical computing and communications. However, efforts towards this goal face unacceptable attenuation of light caused by surface roughness in microscopic devices. Here we address this problem by introducing Surface Nanoscale Axial Photonics (SNAP). The SNAP platform is based on whispering gallery modes circulating around the optical fiber surface and undergoing slow axial propagation readily described by the one-dimensional Schr\\"odinger e...
王钧; 王志彬; 李论
2016-01-01
In order to investigate the mechanical behavior of reinforced concrete short columns with steel fiber reactive powder concrete (RPC) column-permanent template and the improvement effect of steel fiber RPC column-permanent template on bearing capacity of core reinforced concrete short column ,axial compression tests on two square reinforced concrete short columns with steel fiber RPC column-permanent template of different wall thickness and a general square reinforced concrete short column used for comparison were carried out .The test results were verified using finite element model .According to the test and finite element analysis results ,the axial bearing capacity calculation method of reinforced concrete short columns with steel fiber RPC column-permanent template was discussed .The results show that ultimate bearing capacity of reinforced concrete short columns is significantly improved by steel fiber RPC column-permanent template ,and the yield of longitudinal reinforcement is delayed .With the increase of column-permanent template thickness , axial deformation of reinforced concrete short column decreases , and the ultimate bearing capacity and ductility relatively increase . The lateral deformation of reinforced concrete short columns under axial compression is limited and axial deformation is decreased indirectly by column-permanent template .The finite element analysis results agree well with the test results . The calculation method can provide references for practical engineering .%为研究配有钢纤维活性粉末混凝土(RPC)免拆柱模的钢筋混凝土短柱的轴压力学性能与钢纤维RPC免拆柱模对核心钢筋混凝土短柱轴压承载力的提高效果,对2根配有不同壁厚钢纤维RPC免拆柱模的钢筋混凝土方形短柱和用于对比的1根普通钢筋混凝土方形短柱进行了轴压试验研究;采用有限元模型对试验结果进行了验证,根据试验结果及有限元分析结果,探讨了配有钢纤
Superfluid phase stability of 3He in axially anisotropic aerogel
Measurements of superfluid 3He in 98% aerogel demonstrate the existence of a metastable A-like phase and a stable B-like phase. It has been suggested that the relative stability of these two phases is controlled by anisotropic quasiparticle scattering in the aerogel. Anisotropic scattering produced by axial compression of the aerogel has been predicted to stabilize the axial state of superfluid 3He. To explore this possibility, we used transverse acoustic impedance to map out the phase diagram of superfluid 3He in a ∼ 98% porous silica aerogel subjected to 17% axial compression. We have previously shown that axial anisotropy in aerogel leads to optical birefringence and that optical cross-polarization studies can be used to characterize such anisotropy. Consequently, we have performed optical cross-polarization experiments to verify the presence and uniformity of the axial anisotropy in our aerogel sample. We find that uniform axial anisotropy introduced by 17% compression does not stabilize the A-like phase. We also find an increase in the supercooling of the A-like phase at lower pressure, indicating a modification to B-like phase nucleation in globally anisotropic aerogels.
The failure of axially loaded steel columns
Slender compression steel members fail by elastic bucking, and short compression members may be loaded until the steel yields. In the majority of usual situations, failure occurs by inelastic buckling after a portion of the cross section has yielded. Residual stresses are the primary cause of the nonlinear protion of the average stress strain curve of axially loaded compression members (huber and Beedle, 1954). A number of theories tackled the problem of inelastic bucking. The LRFD Code ended with adopting an empirical parabolic equation that is stitched to the Euler hyperbola at the column slenderness value of λ C =2 square root and is believed to provide a reasonable approximation for column strength curves. The analysis of steel sections used in this paper defines an explicit from of failure to define the failure load of axially loaded columns in the inelastic range. inelastic bucking is defined in terms of the elaSTIC bucking of transformed sections. Two examples are used to clarify the method of analysis that accounts for residual stresses. (author). 9 refs., 5 figs
张向冈; 陈宗平; 薛建阳; 苏益声; 范杰
2012-01-01
Axial static monotonic loading test was carried out on 5 recycled aggregate concrete filled cycled steel tubular long columns and 5 recycled aggregate concrete filled square steel tubular tong columns. The test parameters include section form, replacement rate of recycled coarse aggregate and slenderness ratio. The whole loading process and failure modes were observed. The important characteristic data were captured such as the yield strain, the peak deformation, the bearing capacity and so on. A series of important curves about load-deformation, load-strain and axial stiffness- deformation were plotted. The influences of the test parameters on the bearing capacity were analyzed. The bearing capacity and axial stiffness of two section types under the serviceability limit state were calculated by some related procedures. It is shown that the loading process of recycled aggregate concrete filled steel tubular long columns under axial compression is made up of elastic stage, yield stage and failure stage. The failure modes are mainly strength failure and failure of elasto-plastic instability. The influence of replacement rate on the bearing capacity is little. The influence of slenderness ratio on the bearing capacity of recycled aggregate concrete filled cycled steel circular tubular long columns is great. When the slenderness ratio increases, the bearing capacity will decrease. However, the influence of slenderness ratio on the bearing capacity of recycled aggregate concrete filled square steeltubular long columns is little. Based on the calculation resuh, the design suggestion is provided about the bearing capacity and axial stiffness of recycled aggregate concrete filled steel tubular long columns under axial compression. The research results can provide reference for further research and application of recycled aggregate concrete filled steel tubular structure.%设计5个圆钢管再生混凝土长柱和5个方钢管再生混凝土长柱,对其进行轴压静力
On renormalization of axial anomaly
It is shown that multiplicative renormalization of the axial singlet current results in renormalization of the axial anomaly in all orders of perturbation theory. It is a necessary condition for the Adler - Bardeen theorem being valid. 10 refs.; 2 figs
Axial compressor stability enhancement
Houghton, Timothy Oliver.
2010-01-01
Aircraft jet engines must operate in a stable manner at all times. One source of instability is compressor stall. Stall problems can be reduced by machining cavities into the compressor casing adjacent to the rotor blades. This ?casing treatment? is the focus of the present work. Two treatment configurations are tested: circumferential grooves cut into the casing above the rotor blades, and axial slots cut into the casing adjacent to the rotor blade leading edges. The performance of a single ...
Aadland, David; Shaffer, Sherrill
2012-01-01
Economists have generally ignored the notion that perceived time may differ from clock time. Borrowing from the behavioral psychology literature, we investigate the case of time compression whereby perceived time passes more quickly than actual time. A framework is presented to embed time compression in economic models. We then apply the principle to a standard lifecycle permanent income model with endogenous labor. Time compression provides an alternative explanation of why older indi...
Walt Wells
2008-01-01
Full Text Available Our objective in this paper is to solve a second order differential equation for a long, simply supported column member subjected to a lateral axial load using Heun's numerical method. We will use the solution to find the critical load at which the column member will fail due to buckling. We will calculate this load using Euler's derived analytical approach for an exact solution, as well as Euler's Numerical Method. We will then compare the three calculated values to see how much they deviate from one another. During the critical load calculation, it will be necessary to calculate the moment of inertia for the column member.
Jaffe, Arthur; Wozniakowski, Alex
2016-01-01
In a previous paper we introduced holographic software for quantum networks, inspired by work on planar para algebras. This software suggests the definition of a compressed transformation. Here we utilize the software to find a CT protocol to teleport compressed transformations. This protocol serves multiple parties with multiple persons.
周旺保; 蒋丽忠
2011-01-01
Based on the equilibrium condition of several sections, the stress-strain relationship of the concrete-filled steel tube under the effect of confinement and the influence of the initial bending and shear, the equilibrium equation of the section was established. At the same time, the numerical method for calculating the elastic-plastic ultimate loads of the concrete-filled tubular laced columns was presented by adopting the Taylor's series as the piecewise interpolation function and the corresponding computer program was compiled. Some axial compressed four-tube concrete-filled steel tubular taced columns were computed using the numerical method and the program, and the results were compared with the calculation results of some existing codes. The calculation formula of slender ratio reduced coefficient was proposed combining numerical calculation results and the slender ratio reduced coefficient model. The calculation results were compared with the numerical calculation results and the test results. The results show that this method is suitable for the elastoplasticity ultimate bearing capacity calculation of the long and short axial compressed columns. The code computational methods are conservative, the computational errors are great, and the computed results in this article agree well with the test results. The rationality of slender ratio reduced coefficient calculation formula has been attested.%采用泰勒级数作为分段插值函数,在考虑多个截面的平衡条件和紧箍效应钢管混凝土应力-应变关系、剪切变形及初弯曲影响的基础上,建立杆件截面的平衡方程,提出四肢缀条轴压钢管混凝士格构柱弹塑性极限承载力数值方法,并编制相应的计算程序.利用提出的计算方法和编制的程序对国内已有轴压四肢钢管混凝土格构柱试件进行计算,并与现有一些规程进行比较.同时,结合数值计算结果及长细比折减系数计算模型,提出长细比折减系数计
刘斌; 郝际平; 赵淋伟; 李科龙; 钟炜辉; 赵秋利
2014-01-01
提出一种在冷弯薄壁型钢骨架中放置聚苯乙烯泡沫板，并在骨架外侧喷涂轻质保温物料的新型轻质组合墙体。通过对1根无墙板的冷弯薄壁型钢立柱和2根新型冷弯薄壁型钢墙体立柱的轴压性能进行足尺试验，研究其受力过程、承载能力和破坏模式，并将试验结果与按规范公式计算的极限承载力进行对比分析。研究结果表明：无墙板立柱的破坏模式为构件的整体屈曲；新型冷弯薄壁型钢墙体立柱的破坏现象为柱顶截面的局部受压屈服，保温物料对立柱的支承作用使新型墙体立柱的承载能力显著提高。按照规范中关于轴心受压杆件的强度和稳定计算公式得出的极限承载力与试验的破坏荷载较为吻合。%A new-type of light-weight wall , in which polystyrene foam plates are placed inside the cold-formed thin-wall steel frame and light thermal insulation material is sprayed outside the frame of the wall , was presented .Through the full-scale tests of one cold-formed thin-wall steel stud without sheathing and two new-type of cold-formed thin-wall steel framing wall studs under axial loading , the failure process , the bearing capacity and the failure mode were analyzed .The calculated value determined by the code and experimental data of this test were compared .The results show that the failure mode of the cold-formed thin-wall steel stud without sheathing is global buckling and that of the new-type of wall stud is local compressed yielding on the top of the stud .The bearing capacity of the new-type of wall stud is greatly increased owing to the support of thermal insulation material .The calculated values of the ultimate bearing capacity by the formula of calculating about strength and stability of axial compressive members in the code agree well with the experimental ultimate bearing loadings .
Failure mechanism and forming limit of tube axial compressive process
SUN Zhi-chao; YANG He
2006-01-01
Based on minimum energy principle for plastic forming,tearing and buckling failures mechanisms are explored and criteria for them are developed by theoretical analysis and experiment. Combined with finite element software developed forming limit and effects of process parameters on failures are investigated and proper parameters for stable forming are determined. The results show that: 1) The failures and forming limit are mainly determined by geometry and materials parameters of tube blank,fillet radius or half conical angle of die. For the process under fillet die,there exists a maximum fillet radius within which no tearing failure happens,and a maximum radius and a minimum radius range within which no buckling failure happens. For the process under conical die,there exists a maximum and minimum half conical angle range within which no tearing and buckling failures occur. 2) For both forming processes,the higher the value of material strain hardening exponent or the lower the value of relative thickness,the more impossible for tearing and buckling failures to occur,and the larger the ranges of fillet radius and half conical angle. The experiment results verify the reliability and practicability of this research.
Fracture Analysis of Debonded Sandwich Columns Under Axial Compression
May, A.; Avilés, F.; Berggreen, Christian
monolithic structures of the same weight. The vast range of applications of such materials includes wind turbines, marine, and aerospace industries. In this work, geometrically nonlinear finite element analysis is conducted to investigate the fracture parameters and debond propagation of sandwich columns...... increased core stiffness and was nearly independent of the debond size. The model predicts debond propagation shortly after buckling instability, consistent with experimental observations. The critical loads predicted by this analysis compare reasonably to experimental buckling loads measured by other...
Failure Processes in Embedded Monolayer Graphene under Axial Compression
Androulidakis, Ch.; Koukaras, E. N.; Frank, Otakar; Tsoukleri, G.; Sfyris, D.; Parthenios, J.; Pugno, N.; Papagelis, K.; Novoselov, K. S.; Galiotis, C.
2014-01-01
Roč. 4, JUN 2014 (2014), 5271. ISSN 2045-2322 R&D Projects: GA ČR GA14-15357S Institutional support: RVO:61388955 Keywords : monoleyer graphene * phonons * physical chemistry Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.578, year: 2014
Axial Deformation of Monolayer Graphene under Tension and Compression
Papagelis, K.; Frank, Otakar; Tsoukleri, G.; Parthenios, J.; Novoselov, K. S.; Galiotis, C.
Heidelberg: Springer, 2012 - (Ottaviano, L.; Morandi, V.), s. 87-97 ISBN 978-3-642-20643-6. [GraphITA 2011. L´Aquila (IT), 15.05.2011-18.05.2011] Institutional research plan: CEZ:AV0Z40400503 Keywords : monolayer graphene * Raman spectroscopy Subject RIV: CG - Electrochemistry
Optimum design of laminated composite under axial compressive load
N G R Iyengar; Nilesh Vyas
2011-02-01
In the present study optimal design of composite laminates, with and without rectangular cut-out, is carried out for maximizing the buckling load. Optimization study is carried out for obtaining the maximum buckling load with design variables as ply thickness, cut-out size and orientation of cut-out with respect to laminate. Buckling load is evaluated using a ‘simple higher order shear deformation theory’ based on four unknown displacements $u,v,w_b$ and $w_s$. A C1 continuous shear flexible finite element based on HSDT model is developed using Hermite cubic polynomial. It is observed that for thick anti-symmetric laminates, the non-dimensional buckling load decreases with increase in aspect ratio and increase in fibre orientation angle. There is a decrease in the non-dimensional buckling load of symmetric laminate in the presence of cut-out.
Axial skeletal CT densitometry
Since the discovery of the Roentgen ray a precise and accurate assessment of bone mineral content has been a challenge to many investigators. A number of methods have been developed but no one satisfied. Considering its technical possibilities computed tomography is very promising in determination of bone mineral content (BMC). The new modality enables BMC estimations in the axial skeletal trabecular bone. CT densitometry can be performed on a normal commercially available third generation whole body CT scanner. No dedicated device in a special clinical set-up is necessary. In this study 106 patients, most of them clinically suspected of osteoporosis, were examined. The new method CT densitometry has been evaluated. The results have been correlated to alternative BMC determination methods. (Auth.)
Compressive behavior of fine sand.
Martin, Bradley E. (Air Force Research Laboratory, Eglin, FL); Kabir, Md. E. (Purdue University, West Lafayette, IN); Song, Bo; Chen, Wayne (Purdue University, West Lafayette, IN)
2010-04-01
The compressive mechanical response of fine sand is experimentally investigated. The strain rate, initial density, stress state, and moisture level are systematically varied. A Kolsky bar was modified to obtain uniaxial and triaxial compressive response at high strain rates. A controlled loading pulse allows the specimen to acquire stress equilibrium and constant strain-rates. The results show that the compressive response of the fine sand is not sensitive to strain rate under the loading conditions in this study, but significantly dependent on the moisture content, initial density and lateral confinement. Partially saturated sand is more compliant than dry sand. Similar trends were reported in the quasi-static regime for experiments conducted at comparable specimen conditions. The sand becomes stiffer as initial density and/or confinement pressure increases. The sand particle size become smaller after hydrostatic pressure and further smaller after dynamic axial loading.
Axial anomaly in nonrenormalizable theories
The anomaly for the axial current in nonrenormalizable theories with electromagnetic coupling is considered. The spinor electrodynamics with Pauli term is examined in detail using the Feynman graph technique and the point-splitting method. The same finite value for the axial anomaly emerges. (author)
Effect of weld reinforcement on axial plastic buckling of welded steel cylindrical shells
Chu-lin YU; Zhi-ping CHEN; Ji WANG; Shun-juan YAN; Li-cai YANG
2012-01-01
The effect of weld reinforcement on axial plastic buckling of welded steel cylindrical shells is investigated through experimental and numerical buckling analysis using six welded steel cylindrical shell specimens.The relationship between the amplitude of weld reinforcement and the axial plastic buckling critical load is explored.The effect of the material yield strength and the number of circumferential welds on the axial plastic buckling is studied.Results show that circumferential weld reinforcement represents a severe imperfect form of axially compressed welded steel cylindrical shells and the axial plastic buckling critical load decreases with the increment of the mean amplitude of circumferential weld reinforcement.The material yield strength and the number of circumferential welds are found to have no significant effect on buckling waveforms; however,the axial plastic buckling critical load can be decreased to some extent with the increase of the number of circumferential welds.
Rapalino, Otto; Smirniotopoulos, James G
2016-01-01
Extra-axial brain tumors are the most common adult intracranial neoplasms and encompass a broad spectrum of pathologic subtypes. Meningiomas are the most common extra-axial brain tumor (approximately one-third of all intracranial neoplasms) and typically present as slowly growing dural-based masses. Benign meningiomas are very common, and may occasionally be difficult to differentiate from more aggressive subtypes (i.e., atypical or malignant varieties) or other dural-based masses with more aggressive biologic behavior (e.g., hemangiopericytoma or dural-based metastases). Many neoplasms that typically affect the brain parenchyma (intra-axial), such as gliomas, may also present with primary or secondary extra-axial involvement. This chapter provides a general and concise overview of the common types of extra-axial tumors and their typical imaging features. PMID:27432671
Build Axial Gradient Field by Using Axial Magnetized Permanent Rings
无
2002-01-01
Axial magnetic field produced by an axial magnetized permanent ring was studied. For two permanent rings, if they are magnetized in the same directions, a nearly uniform axial field can be produced. If they are magnetized in opposite direction,an axial gradient magnetic field can be generated, with the field range changing from -B0 to B0. A permanent magnet with a high axial gradient field was fabricated, the measured results agree with the PANDIRA calculation very well. For wider usage,it is desirable for the field gradient to be changed. Some methods to produce the variable gradient field are presented. These kinds of axial gradient magnetic field can also be used as a beam focusing for linear accelerator if the periodic field can be produced along the beam trajectory. The axial magnetic field is something like a solenoid, large stray field will leak to the outside environment if no method is taken to control them. In this paper, one method is illustrated to shield off the outside leakage field.
Notari, Alessio
2016-01-01
We analyze in detail the background cosmological evolution of a scalar field coupled to a massless abelian gauge field through an axial term $\\frac{\\phi}{f_\\gamma} F \\tilde{F}$, such as in the case of an axion. Gauge fields in this case are known to experience tachyonic growth and therefore can backreact on the background as an effective dissipation into radiation energy density $\\rho_R$, which which can lead to inflation without the need of a flat potential. We analyze the system, for momenta $k$ smaller than the cutoff $f_\\gamma$, including numerically the backreaction. We consider the evolution from a given static initial condition and explicitly show that, if $f_\\gamma$ is smaller than the field excursion $\\phi_0$ by about a factor of at least ${\\cal O} (20)$, there is a friction effect which turns on before that the field can fall down and which can then lead to a very long stage of inflation with a generic potential. In addition we find superimposed oscillations, which would get imprinted on any kind of...
Bode, Hans R.
2009-01-01
Morphogen gradients play an important role in pattern formation during early stages of embryonic development in many bilaterians. In an adult hydra, axial patterning processes are constantly active because of the tissue dynamics in the adult. These processes include an organizer region in the head, which continuously produces and transmits two signals that are distributed in gradients down the body column. One signal sets up and maintains the head activation gradient, which is a morphogenetic gradient. This gradient confers the capacity of head formation on tissue of the body column, which takes place during bud formation, hydra's mode of asexual reproduction, as well as during head regeneration following bisection of the animal anywhere along the body column. The other signal sets up the head inhibition gradient, which prevents head formation, thereby restricting bud formation to the lower part of the body column in an adult hydra. Little is known about the molecular basis of the two gradients. In contrast, the canonical Wnt pathway plays a central role in setting up and maintaining the head organizer. PMID:20066073
CFD analysis on the blades of an axial gas turbine
García Unzue, Javier
2011-01-01
This project analyzes two-dimensional linear cascade flows of an axial compressor on the stator vanes. It analyzes the influence of the angle of attack in the leading edge for different pressure ratios. The problem studied is a compressible, viscous and steady flow. A test case of an inviscid model flow has been carried out as well. Two types of grid are also being analyzed, the unstructured grid, with only triangular mesh elements, and a structured grid with only quadrilateral...
赵同峰; 欧阳伟; 李冬松
2011-01-01
进行了9根方钢管钢骨混凝土双向偏压柱试验,研究其破坏形态,分析荷载与纵向应变关系及长细比、加载方向等参数变化对双偏压柱受力性能的影响。结果表明：当荷载达到极限荷载的50%～70%,钢管的受压区开始屈服;当荷载达到极限荷载的80%～90%,钢骨的受压区开始屈服。在试验参数范围内,加载角度的变化对偏压柱的受力性能影响不大。通过有限元法建立计算模型,模型计算结果与试验结果吻合很好。在此基础上,通过变化计算参数,分析了不同长细比、偏心距条件下,加载角度对偏压柱受力性能的影响。结果表明,随着长细比及偏心距的增大,加%Experimental research of 9 square steel tube columns filled with steel reinforced concrete subjected to bi-axial eccentric compression was presented.Failure mode and load versus longitudinal strain curves were analyzed.Influence of load direction and slenderness ratio were also analyzed.The test results show that the steel tube begins to yield when load gets to 50%~70% ultimate bearing capacity and the steel reinforced begins to yield when load gets to 80%~90% ultimate bearing capacity.Different angles of loading have little effect on the bearing capacity.Furthermore,a finite element analysis model was established and the calculated results were agreed well with the test ones.Influence of load directions under different slenderness and eccentricity was also analyzed.Results show that the more slenderness and eccentricity the more influence of load direction on the bearing capacity.
Study of axial magnetic effect
The Axial Magnetic Effect manifests itself as an equilibrium energy flow of massless fermions induced by the axial (chiral) magnetic field. Here we study the Axial Magnetic Effect in the quenched SU(2) lattice gauge theory with massless overlap fermions at finite temperature. We numerically observe that in the low-temperature hadron phase the effect is absent due to the quark confinement. In the high-temperature deconfinement phase the energy flow is an increasing function of the temperature which reaches the predicted asymptotic T2 behavior at high temperatures. We find, however, that energy flow is about one order of magnitude lower compared to a theoretical prediction
Characterization of Multiflux Axial Compressors
In the present work the results of analytical models of performance are compared with experimental data acquired in the multi flux axial compressor test facility, built in The Pilcaniyeu Technological Complex for the SIGMA project.We describe the experimental circuit and the data of the dispersion inside the axial compressor obtained using a tracer gas through one of the annular inlets.The attained results can be used to validate the design code for the multi flux axial compressors and SIGMA industrial plant
Axial gap rotating electrical machine
None
2016-02-23
Direct drive rotating electrical machines with axial air gaps are disclosed. In these machines, a rotor ring and stator ring define an axial air gap between them. Sets of gap-maintaining rolling supports bear between the rotor ring and the stator ring at their peripheries to maintain the axial air gap. Also disclosed are wind turbines using these generators, and structures and methods for mounting direct drive rotating electrical generators to the hubs of wind turbines. In particular, the rotor ring of the generator may be carried directly by the hub of a wind turbine to rotate relative to a shaft without being mounted directly to the shaft.
Perceau, Géraldine; Faure, Christine
2012-01-01
The compression of a venous ulcer is carried out with the use of bandages, and for less exudative ulcers, with socks, stockings or tights. The system of bandages is complex. Different forms of extension and therefore different types of models exist. PMID:22489428
Harrington, Joe [Sertco Industries, Inc., Okemah, OK (United States); Vazquez, Daniel [Hoerbiger Service Latin America Inc., Deerfield Beach, FL (United States); Jacobs, Denis Richard [Hoerbiger do Brasil Industria de Equipamentos, Cajamar, SP (Brazil)
2012-07-01
Over time, all wells experience a natural decline in oil and gas production. In gas wells, the major problems are liquid loading and low downhole differential pressures which negatively impact total gas production. As a form of artificial lift, wellhead compressors help reduce the tubing pressure resulting in gas velocities above the critical velocity needed to surface water, oil and condensate regaining lost production and increasing recoverable reserves. Best results come from reservoirs with high porosity, high permeability, high initial flow rates, low decline rates and high total cumulative production. In oil wells, excessive annulus gas pressure tends to inhibit both oil and gas production. Wellhead compression packages can provide a cost effective solution to these problems by reducing the system pressure in the tubing or annulus, allowing for an immediate increase in production rates. Wells furthest from the gathering compressor typically benefit the most from wellhead compression due to system pressure drops. Downstream compressors also benefit from higher suction pressures reducing overall compression horsepower requirements. Special care must be taken in selecting the best equipment for these applications. The successful implementation of wellhead compression from an economical standpoint hinges on the testing, installation and operation of the equipment. Key challenges and suggested equipment features designed to combat those challenges and successful case histories throughout Latin America are discussed below.(author)
CANDU fuel compression tests at elevated temperatures
An inlet header large break loss of coolant accident (LOCA) in CANDU reactors with fuelling against flow can cause the fuel to shift in the channels with a consequent reactivity insertion. This results in an increased fuel power transient, and a potential increase in the mialyzed consequences for such events. As the reactor's age and the channel axial gaps increase, the magnitude of the predicted power u-dmient increases. A design solution to reduce the power transient is to limit the amount of fuel movement by reducing the channel axial gap. This solution was implemented into Ontario Hydro's Bruce B and Darlington reactors. A consequence of a reduced channel axial gap is the potential for the fuel column axial expansion to become constrained by the channel end components in large break LOCAs. This experimental program investigated the effects of pellet cracking and elevated sheath temperatures on the ability of the fuel elements, of the 37-element bundle design, to sustain axial loads. The unirradiated fuel elements tested were either in the as-received condition or with the U02 fuel pellets cracked in a mechanical process to simulate the effect of inufflation. The load deformation characteristics demonstrated that, for a given amount of axial compression. the loads sustainable by the elements at elevated sheath temperatures were low. As a result. excess axial expansion would be easily accommodated without further challenge to pressure tube integrity. (author)
Shear Strength of Reinforced Concrete Shear Walls under Eccentric Tensile Axial Force
MIZOGUCHI, Mitsuo; ARAI, Yasuyuki; Hosoya, Koji
2002-01-01
Six reinforced concrete shear wall models were built and tested to investigate effects of cyclic lateral loading and an eccentric tensile axial force on their shear strength behavior. The following are confirmed from this test result. When the elongation at the bottom of the boundary column on the compression side for a lateral force is small, the shear strength of shear walls subjected to a tensile axial force at the boundary column can be evaluated by conventional shear strenght equations, ...
王庆利; 慕海涛; 王月; 寇清
2011-01-01
In order to investigate the static performance of the axially compressed self-consolidating concrete filled steel tubular members and to provide theoretical fundamental for the local code of Liaoning province, an analysis model was established and the load versus mid-height cross-section deflection curves and deformation models of the specimens were simulated by using finite element method on the basis of experimental study. It was found that the proposed model was effective. The static performance,distributions of stress, strain for the steel tube and the concrete of the member were studied deeply by using this model. Analysis results of the typical calculation indicates that the interaction force between the steel tube and the concrete distributes uniformly along the circular direction of the circular specimens, while the interaction force between the steel tube and the concrete focus on the corner and nearby of the square specimens. The interaction force between the steel and the concrete reduces gradually with the increase of the distance to the mid-height cross-section. The adhesive strength has little influence on load bearing capacity and the interaction force of the specimens. Also,the load bearing capacity calculation formula for normal concrete filled steel tube can be used for self-consolidating concrete filled steel tube with concrete whose cubic strength is of 96 Mpa. There is no essential difference between self-consolidating concrete filled steel tube and normal concrete filled steel tube with respect to the static performance.%目的 对钢管自密实混凝土轴压构件的静力性能进行有限元模拟,进一步了解其工作机理分析,为辽宁省相关地方标准的编制提供依据.方法 在试验研究的基础上,采用有限元法建立分析模型并模拟试件的轴力-中截面挠度曲线和破坏模态,验证有限元分析模型可靠,以此模型深入研究了钢管自密实混凝土轴压构件中
Xenaki, Angeliki; Mosegaard, Klaus
2014-01-01
Sound source localization with sensor arrays involves the estimation of the direction-of-arrival (DOA) from a limited number of observations. Compressive sensing (CS) solves such underdetermined problems achieving sparsity, thus improved resolution, and can be solved efficiently with convex...... optimization. The DOA estimation problem is formulated in the CS framework and it is shown that CS has superior performance compared to traditional DOA estimation methods especially under challenging scenarios such as coherent arrivals and single-snapshot data. An offset and resolution analysis is performed to...
Vectorial versus axial goldstone bosons
The Yukawa interactions of fermions with Goldstone bosons are given in closed form for an arbitrary renormalizable field theory to all orders of perturbation theory or for a general effective Lagrangian. Although the diagonal couplings are always pseudoscalar there is an important difference between spontaneously broken vector and axial-vector global symmetries. Compared to the axial case, the diagonal douplings of 'vectorial' Goldstone bosons to charged fermions are suppressed by mixing angles or appear only via radiative corrections involving gauge fields. This general result may be relevant for the problem of flavour symmetry breaking in composite models. (Author)
Simulation of an Axial Vircator
Tikhomirov, V V
2013-01-01
An algorithm of particle-in-cell simulations is described and tested to aid further the actual design of simple vircators working on axially symmetric modes. The methods of correction of the numerical solution, have been chosen and jointly tested, allow the stable simulation of the fast nonlinear multiflow dynamics of virtual cathode formation and evolution, as well as the fields generated by the virtual cathode. The selected combination of the correction methods can be straightforwardly generalized to the case of axially nonsymmetric modes, while the parameters of these correction methods can be widely used to improve an agreement between the simulation predictions and the experimental data.
Elsner, F
2013-01-01
We introduce the concept of compressed convolution, a technique to convolve a given data set with a large number of non-orthogonal kernels. In typical applications our technique drastically reduces the effective number of computations. The new method is applicable to convolutions with symmetric and asymmetric kernels and can be easily controlled for an optimal trade-off between speed and accuracy. It is based on linear compression of the collection of kernels into a small number of coefficients in an optimal eigenbasis. The final result can then be decompressed in constant time for each desired convolved output. The method is fully general and suitable for a wide variety of problems. We give explicit examples in the context of simulation challenges for upcoming multi-kilo-detector cosmic microwave background (CMB) missions. For a CMB experiment with O(10,000) detectors with similar beam properties, we demonstrate that the algorithm can decrease the costs of beam convolution by two to three orders of magnitude...
Computational Study of Axial Fatigue for Peripheral Nitinol Stents
Meoli, Alessio; Dordoni, Elena; Petrini, Lorenza; Migliavacca, Francesco; Dubini, Gabriele; Pennati, Giancarlo
2014-07-01
Despite their success as primary treatment for vascular diseases, Nitinol peripheral stents are still affected by complications related to fatigue failure. Hip and knee movements during daily activities produce large and cyclic deformations of the superficial femoral artery, that concomitant to the effects of pulsatile blood pressure, may cause fatigue failure in the stent. Fatigue failure typically occurs in cases of very extended lesions, which often require the use of two or more overlapping stents. In this study, finite element models were used to study the fatigue behavior of Nitinol stents when subjected to cyclic axial compression in different conditions. A specific commercial Nitinol stent was chosen for the analysis and subjected to cyclic axial compression typical of the femoral vascular region. Three different configurations were investigated: stent alone, stent deployed in a tube, and two overlapping stents deployed in a tube. Results confirm that stent oversizing has an influence in determining both the mean and amplitude strains induced in the stent and plays an important role in determining the fatigue response of Nitinol stents. In case of overlapping stents, numerical results suggest higher amplitude strains concentrate in the region close to the overlapping portion where the abrupt change in stiffness causes higher cyclic compression. These findings help to explain the high incidence of stent fractures observed in various clinical trials located close to the overlapping portion.
Axial structure of the nucleon
Veronique Bernard; Latifa Elouadrhiri; Ulf-G Meissner
2002-01-01
We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.
Uniaxial compression test series on Bullfrog Tuff
Nineteen uniaxial compressive experiments were performed on samples of the Bullfrog Member of the Crater Flat Tuff, obtained from drillhole USW-G1 at Yucca Mountain on the Nevada Test Site. The water saturated samples were deformed at a nominal strain rate of 10-5 sec-1, atmospheric pressure and room temperature. Resultant unconfined compressive strengths, axial strains to failure, Young's moduli and Poisson's ratios ranged from 4.63 to 153. MPa, .0028 to .0058, 2.03 to 28.9 GPa and .08 to .16, respectively
Comparison of design methods for axially loaded buckets in sand
Vaitkunaite, Evelina; Nielsen, Benjaminn Nordahl; Ibsen, Lars Bo
A study of the present knowledge about the bucket resistance for axial loading was performed considering analytical and numerical design methods as well as physical models. A case study was performed with two bucket foundations of equal diameter, but different skirt lengths installed in dense sand....... Itwas found that bearing capacity from the surcharge increases approximately twice if the foundation skirt is two times longer. However, the predicted compressive soil capacity can differ by 3.6 times depending on the chosen bearing capacity parameters. Few methods are available for the estimation of...
Axial shock wave heating of reversed-field theta-pinch plasmas
Reversed-field theta pinches are known to contract rapidly in the axial direction soon after the radial implosion. Under certain conditions the axial implosion can be quite strong. A model is described which simulates both the radial and axial implosions. Among the important features included are realistic plasma density profiles, and current-driven anomalous transport. Given input parameters such as initial fill pressure, bias magnetic field, coil size, applied voltage (or electric field) and compression magnetic field, the model predicts the final plasma temperature, density, radial and axial dimensions, trapped magnetic flux and fraction of particles trapped within the separatrix. The results indicate very strong axial shock heating for high bias field, which leads to temperatures up to several times that predicted for simple field-free plasmas. The model is applied to parameters charcteristic of two recent experiments, and several features of the calculated results are shown to be consistent with experimental observations. It is also applied to a fusion reactor scale plasma: as a result of strong axial shock heating, the model predicts that fusion ignition (e.g., a temperature of 8 keV) can be achieved without resort to large electric field or large magnetic compression
Experimental investigation of axial plasma injection into a magnetic dipole field
Jensen, Vagn Orla
1968-01-01
A high-density helium plasma, accelerated from a conical pinch, is injected axially into a magnetic dipole field. Magnetic probe measurements show that, near the axis, a compression of the field is super-imposed on the standard diamagnetic depression. The compression starts downstream and moves...... towards the injector. Simultaneously with the compression, an increase in the electron temperature and reflection of a small amount of plasma are seen. The amount of plasma transmitted through the dipole field is found to be nearly independent of the field strength....
Axially symmetric rotating traversable wormholes
Kuhfittig, P K F
2003-01-01
This paper generalizes the static and spherically symmetric traversable wormhole geometry to a rotating axially symmetric one with a time-dependent angular velocity by means of an exact solution. It was found that the violation of the weak energy condition, although unavoidable, is considerably less severe than in the static spherically symmetric case. The radial tidal constraint is more easily met due to the rotation. Similar improvements are seen in one of the lateral tidal constraints. The magnitude of the angular velocity may have little effect on the weak energy condition violation for an axially symmetric wormhole. For a spherically symmetric one, however, the violation becomes less severe with increasing angular velocity. The time rate of change of the angular velocity, on the other hand, was found to have no effect at all. Finally, the angular velocity must depend only on the radial coordinate, confirming an earlier result.
View of the Axial Field Spectrometer
1980-01-01
The Axial Field Spectrometer, with the vertical uranium/scintillator calorimeter and the central drift chamber retracted for service. One coil of the Open Axial Field Magnet is just visible to the right.
Simulation of an Axial Vircator
Tikhomirov, V. V.; Siahlo, S. E.
2013-01-01
An algorithm of particle-in-cell simulations is described and tested to aid further the actual design of simple vircators working on axially symmetric modes. The methods of correction of the numerical solution, have been chosen and jointly tested, allow the stable simulation of the fast nonlinear multiflow dynamics of virtual cathode formation and evolution, as well as the fields generated by the virtual cathode. The selected combination of the correction methods can be straightforwardly gene...
Žemlo, Gražina
2004-01-01
One of the images compression methods – fractal image compression is analyzed in the work. After work carried out, it is possible to state, that selecting parameters of method of fractal compression depends on user’s demands.
Compression limits in cascaded quadratic soliton compression
Bache, Morten; Bang, Ole; Krolikowski, Wieslaw;
2008-01-01
Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency.......Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency....
Huang, Bormin
2011-01-01
Satellite Data Compression covers recent progress in compression techniques for multispectral, hyperspectral and ultra spectral data. A survey of recent advances in the fields of satellite communications, remote sensing and geographical information systems is included. Satellite Data Compression, contributed by leaders in this field, is the first book available on satellite data compression. It covers onboard compression methodology and hardware developments in several space agencies. Case studies are presented on recent advances in satellite data compression techniques via various prediction-
Shukla, KK
2011-01-01
Image compression is concerned with minimization of the number of information carrying units used to represent an image. Lossy compression techniques incur some loss of information which is usually imperceptible. In return for accepting this distortion, we obtain much higher compression ratios than is possible with lossless compression. Salient features of this book include: four new image compression algorithms and implementation of these algorithms; detailed discussion of fuzzy geometry measures and their application in image compression algorithms; new domain decomposition based algorithms
Axial Force at the Vessel Bottom Induced by Axial Impellers
I. Fořt; P. Hasal; A. Paglianti; F. Magelli
2008-01-01
This paper deals with the axial force affecting the flat bottom of a cylindrical stirred vessel. The vessel is equipped with four radial baffles and is stirred with a four 45° pitched blade impeller pumping downwards. The set of pressure transducers is located along the whole radius of the flat bottom between two radial baffles. The radial distribution of the dynamic pressures indicated by the transducers is measured in dependence on the impeller off-bottom clearance and impeller speed.It fol...
Imole, O.I.; Kumar, N; Magnanimo, V.; S. Luding
2012-01-01
We compare element test experiments and simulations on the deformation of frictional, cohesive particles in a bi-axial box. We show that computer simulations with the Discrete Element Method qualitatively reproduce a uniaxial compression element test in the true bi-axial tester. We highlight the effects of friction and polydispersity on our simulations and present the second stress response namely the deviatoric stress as a function of the deviatoric strain.
Axial and Centrifugal Compressor Mean Line Flow Analysis Method
Veres, Joseph P.
2009-01-01
This paper describes a method to estimate key aerodynamic parameters of single and multistage axial and centrifugal compressors. This mean-line compressor code COMDES provides the capability of sizing single and multistage compressors quickly during the conceptual design process. Based on the compressible fluid flow equations and the Euler equation, the code can estimate rotor inlet and exit blade angles when run in the design mode. The design point rotor efficiency and stator losses are inputs to the code, and are modeled at off design. When run in the off-design analysis mode, it can be used to generate performance maps based on simple models for losses due to rotor incidence and inlet guide vane reset angle. The code can provide an improved understanding of basic aerodynamic parameters such as diffusion factor, loading levels and incidence, when matching multistage compressor blade rows at design and at part-speed operation. Rotor loading levels and relative velocity ratio are correlated to the onset of compressor surge. NASA Stage 37 and the three-stage NASA 74-A axial compressors were analyzed and the results compared to test data. The code has been used to generate the performance map for the NASA 76-B three-stage axial compressor featuring variable geometry. The compressor stages were aerodynamically matched at off-design speeds by adjusting the variable inlet guide vane and variable stator geometry angles to control the rotor diffusion factor and incidence angles.
Period of vibration of axially vibrating truly nonlinear rod
Cveticanin, L.
2016-07-01
In this paper the axial vibration of a muscle whose fibers are parallel to the direction of muscle compression is investigated. The model is a clamped-free rod with a strongly nonlinear elastic property. Axial vibration is described by a nonlinear partial differential equation. A solution of the equation is constructed for special initial conditions by using the method of separation of variables. The partial differential equation is separated into two uncoupled strongly nonlinear second order differential equations. Both equations, with displacement function and with time function are exactly determined. Exact solutions are given in the form of inverse incomplete and inverse complete Beta function. Using boundary and initial conditions, the frequency of vibration is obtained. It has to be mentioned that the determined frequency represents the exact analytic description for the axially vibrating truly nonlinear clamped-free rod. The procedure suggested in this paper is applied for calculation of the frequency of the longissimus dorsi muscle of a cow. The influence of elasticity order and elasticity coefficient on the frequency property is tested.
The strange axial-vector mesons K1 (1270) and K1 (1400) are reanalyzed in the light of the updated experimental information and compared with the recent result on the Kππ production in τ decay. The mixing angle between the strange mesons of 3P1 and 1P1 is determined by the partial decay rates, and, independently, by the masses. They lead to θK∼33 degree or 57 degree. The observed K1 (1400) production dominance in the τ decay favors θK∼33 degree. Flavor-SU(3) breaking of 20% or so in the production amplitudes can explain quantitatively the observed production ratio
PWR AXIAL BURNUP PROFILE ANALYSIS
The purpose of this activity is to develop a representative ''limiting'' axial burnup profile for pressurized water reactors (PWRs), which would encompass the isotopic axial variations caused by different assembly irradiation histories, and produce conservative isotopics with respect to criticality. The effect that the low burnup regions near the ends of spent fuel have on system reactivity is termed the ''end-effect''. This calculation will quantify the end-effects associated with Pressurized Water Reactor (PWR) fuel assemblies emplaced in a hypothetical 21 PWR waste package. The scope of this calculation covers an initial enrichment range of 3.0 through 5.0 wt% U-235 and a burnup range of 10 through 50 GWd/MTU. This activity supports the validation of the process for ensuring conservative generation of spent fuel isotopics with respect to criticality safety applications, and the use of burnup credit for commercial spent nuclear fuel. The intended use of these results will be in the development of PWR waste package loading curves, and applications involving burnup credit. Limitations of this evaluation are that the limiting profiles are only confirmed for use with the B andW 15 x 15 fuel assembly design. However, this assembly design is considered bounding of all other typical commercial PWR fuel assembly designs. This calculation is subject to the Quality Assurance Requirements and Description (QARD) because this activity supports investigations of items or barriers on the Q-list (YMP 2001)
PWR AXIAL BURNUP PROFILE ANALYSIS
J.M. Acaglione
2003-09-17
The purpose of this activity is to develop a representative ''limiting'' axial burnup profile for pressurized water reactors (PWRs), which would encompass the isotopic axial variations caused by different assembly irradiation histories, and produce conservative isotopics with respect to criticality. The effect that the low burnup regions near the ends of spent fuel have on system reactivity is termed the ''end-effect''. This calculation will quantify the end-effects associated with Pressurized Water Reactor (PWR) fuel assemblies emplaced in a hypothetical 21 PWR waste package. The scope of this calculation covers an initial enrichment range of 3.0 through 5.0 wt% U-235 and a burnup range of 10 through 50 GWd/MTU. This activity supports the validation of the process for ensuring conservative generation of spent fuel isotopics with respect to criticality safety applications, and the use of burnup credit for commercial spent nuclear fuel. The intended use of these results will be in the development of PWR waste package loading curves, and applications involving burnup credit. Limitations of this evaluation are that the limiting profiles are only confirmed for use with the B&W 15 x 15 fuel assembly design. However, this assembly design is considered bounding of all other typical commercial PWR fuel assembly designs. This calculation is subject to the Quality Assurance Requirements and Description (QARD) because this activity supports investigations of items or barriers on the Q-list (YMP 2001).
Belinda Pingguan-Murphy
2012-08-01
Full Text Available OBJECTIVES: The promotion of extracellular matrix synthesis by chondrocytes is a requisite part of an effective cartilage tissue engineering strategy. The aim of this in vitro study was to determine the effect of bi-axial cyclic mechanical loading on cell proliferation and the synthesis of glycosaminoglycans by chondrocytes in threedimensional cultures. METHOD: A strain comprising 10% direct compression and 1% compressive shear was applied to bovine chondrocytes seeded in an agarose gel during two 12-hour conditioning periods separated by a 12-hour resting period. RESULTS: The bi-axial-loaded chondrocytes demonstrated a significant increase in glycosaminoglycan synthesis compared with samples exposed to uni-axial or no loading over the same period (p<0.05. The use of a free-swelling recovery period prior to the loading regime resulted in additional glycosaminoglycan production and a significant increase in DNA content (p<0.05, indicating cell proliferation. CONCLUSIONS: These results demonstrate that the use of a bi-axial loading regime results in increased matrix production compared with uni-axial loading.
Application of size effect to compressive strength of concrete members
Jin-Keun Kim; Seong-Tae Yi
2002-08-01
It is important to consider the effect of size when estimating the ultimate strength of a concrete member under various loading conditions. Well known as the size effect, the strength of a member tends to decrease when its size increases. Therefore, in view of recent increased interest in the size effect of concrete this research focuses on the size effect of two main classes of compressive strength of concrete: pure axial compressive strength and ﬂexural compressive strength. First, fracture mechanics type size effect on the compressive strength of cylindrical concrete specimens was studied, with the diameter, and the height/diameter ratio considered as the main parameters. Theoretical and statistical analyses were conducted, and a size effect equation was proposed to predict the compressive strength specimens. The proposed equation showed good agreement with the existing test results for concrete cylinders. Second, the size, length, and depth variations of a ﬂexural compressive member have been studied experimentally. A series of -shaped specimens subjected to axial compressive load and bending moment were tested. The shape of specimens and the test procedures used were similar to those by Hognestad and others. The test results are curve-ﬁtted using Levenberg-Marquardt’s least squares method (LSM) to obtain parameters for the modiﬁed size effect law (MSEL) by Kim and co workers. The results of the analysis show that the effect of specimen size, length, and depth on ultimate strength is signiﬁcant. Finally, more general parameters for MSEL are suggested.
Mass Effect on Axial Charge Dynamics
Guo, Er-dong
2016-01-01
We studied effect of finite quark mass on the dynamics of axial charge using the D3/D7 model in holography. The mass term in axial anomaly equation affects both the fluctuation (generation) and dissipation of axial charge. We studied the dependence of the effect on quark mass and external magnetic field. For axial charge generation, we calculated the mass diffusion rate, which characterizes the helicity flipping rate. The rate is a non-monotonous function of mass and can be significantly enhanced by the magnetic field. The diffusive behavior is also related to a divergent susceptibility of axial charge. For axial charge dissipation, we found that in the long time limit, the mass term dissipates all the charge effectively generated by parallel electric and magnetic fields. The result is consistent with a relaxation time approximation. The rate of dissipation through mass term is a monotonous increasing function of both quark mass and magnetic field.
Axial Vector $Z'$ and Anomaly Cancellation
Ismail, Ahmed; Tsao, Kuo-Hsing; Unwin, James
2016-01-01
Whilst the prospect of new $Z'$ gauge bosons with only axial couplings to the Standard Model (SM) fermions is widely discussed, examples of anomaly-free renormalisable models are lacking in the literature. We look to remedy this by constructing several motivated examples. Specifically, we consider axial vectors which couple universally to all SM fermions, as well as those which are generation-specific, leptophilic, and leptophobic. Anomaly cancellation typically requires the presence of new coloured and charged chiral fermions, and we argue that the masses of these new states must generally be comparable to that of the axial vector. Finally, an axial vector mediator could provide a portal between SM and hidden sector states, and we also consider the possibility that the axial vector couples to dark matter. If the dark matter relic density is set due to freeze-out via the axial vector, this strongly constrains the parameter space.
Antonius; Iswandi Imran
2012-01-01
An experimental study of 23 low-, medium- and high-strength concrete columns is presented in this paper. Square-confined concrete columns without longitudinal reinforcement were designed, and tested under concentric axial compression. The columns were made of concrete with a compressive strength ranging between 30 MPa and 70 MPa. The test parameters in the study are concrete compressive strengths and confining steel properties, i.e. spacing, volumetric ratios and configurations. The effects o...
Axial velocity in decaying swirl flow
Algifri, A. H.; Bhardwaj, R. K.; Rao, Y. V. N.
1988-09-01
Experiments were carried out on turbulent swirling flow with variable initial swirl at different flow rates to study the effect of swirl on axial velocity. A correlation was made between the defect in the swirling flow axial velocity and the swirl number which locally defines the swirl intensity. An expression which can be used to predict the axial velocity distribution of turbulent swirling flow in a pipe is presented.
Sensorless Control of Axial Magnetic Bearings
Atsumo, Daichi; Yoshida, Toshiya; Ohniwa, Katsumi
This paper describes a sensorless control method of axial active magnetic bearings (AMBs). At high frequencies, inductance of the axial electromagnets is hardly dependent on the airgap because of the eddy current effects of the non-laminated core. Therefore the carrier frequency should be 3 kHz below to improve the sensitivity to the airgap. In the experiment, Sensorless controll of the axial AMBs have been achieved.
The dynamical symmetry limit of the two-fluid Interacting Vector Boson Model (IVBM), defined through the chain Sp(12,R) contains U(3,3) contains Up(3) x Un(3) contains SU*(3) contains SO(3), is considered and applied for the description of nuclear collective spectra exhibiting axially asymmetric features. The effect of the introduction of a Majorana interaction to the SU*(3) model Hamiltonian on the γ-band energies is studied. The theoretical predictions are compared with the experimental data for 192Os, 190Os, and 112Ru isotopes. It is shown that by taking into account the full symplectic structures in the considered dynamical symmetry of the IVBM, the proper description of the energy spectra and the γ-band energy staggering of the nuclei under considerations can be achieved. The obtained results show that the potential energy surfaces for the following two nuclei 192Os and 112Ru, possess almost γ-flat potentials with very shallow triaxial minima, suggesting a more complex and intermediate situation between γ-rigid and γ-unstable structures. Additionally, the absolute B(E2) intraband transition probabilities between the states of the ground-state band and γ band, as well as the B(M1) interband transition probabilities between the states of the ground and γ bands for the two nuclei 192Os and 190Os are calculated and compared with experiment and for the B(E2) values with the predictions of some other collective models incorporating the γ-rigid or γ-unstable structures. The obtained results agree well with the experimental data and reveal the relevance of the used dynamical symmetry of IVBM in the description of nuclei exhibiting axially asymmetric features in their spectra. (orig.)
Antiproton cloud compression in the ALPHA apparatus at CERN
We have observed a new mechanism for compression of a non-neutral plasma, where antiprotons embedded in an electron plasma are compressed by a rotating wall drive at a frequency close to the sum of the axial bounce and rotation frequencies. The radius of the antiproton cloud is reduced by up to a factor of 20 and the smallest radius measured is ∼ 0.2 mm. When the rotating wall drive is applied to either a pure electron or pure antiproton plasma, no compression is observed in the frequency range of interest. The frequency range over which compression is evident is compared to the sum of the antiproton bounce frequency and the system’s rotation frequency. It is suggested that bounce resonant transport is a likely explanation for the compression of antiproton clouds in this regime
Antiproton cloud compression in the ALPHA apparatus at CERN
Gutierrez, A., E-mail: andrea.gutierrez@triumf.ca [University of British Columbia, Department of Physics and Astronomy (Canada); Ashkezari, M. D. [Simon Fraser University, Department of Physics (Canada); Baquero-Ruiz, M. [University of California at Berkeley, Department of Physics (United States); Bertsche, W. [University of Manchester, School of Physics and Astronomy (United Kingdom); Burrows, C. [Swansea University, Department of Physics, College of Science (United Kingdom); Butler, E. [Centre for Cold Matter, Imperial College (United Kingdom); Capra, A. [York University, Department of Physics and Astronomy (Canada); Cesar, C. L. [Universidade Federal do Rio de Janeiro, Instituto de Física (Brazil); Charlton, M. [Swansea University, Department of Physics, College of Science (United Kingdom); Dunlop, R. [Simon Fraser University, Department of Physics (Canada); Eriksson, S. [Swansea University, Department of Physics, College of Science (United Kingdom); Evetts, N. [University of British Columbia, Department of Physics and Astronomy (Canada); Fajans, J. [University of California at Berkeley, Department of Physics (United States); Friesen, T. [Aarhus University, Department of Physics and Astronomy (Denmark); Fujiwara, M. C.; Gill, D. R. [TRIUMF (Canada); Hangst, J. S. [Aarhus University, Department of Physics and Astronomy (Denmark); Hardy, W. N. [University of British Columbia, Department of Physics and Astronomy (Canada); Hayden, M. E. [Simon Fraser University, Department of Physics (Canada); Isaac, C. A. [Swansea University, Department of Physics, College of Science (United Kingdom); and others
2015-11-15
We have observed a new mechanism for compression of a non-neutral plasma, where antiprotons embedded in an electron plasma are compressed by a rotating wall drive at a frequency close to the sum of the axial bounce and rotation frequencies. The radius of the antiproton cloud is reduced by up to a factor of 20 and the smallest radius measured is ∼ 0.2 mm. When the rotating wall drive is applied to either a pure electron or pure antiproton plasma, no compression is observed in the frequency range of interest. The frequency range over which compression is evident is compared to the sum of the antiproton bounce frequency and the system’s rotation frequency. It is suggested that bounce resonant transport is a likely explanation for the compression of antiproton clouds in this regime.
Effective quantum number for axially symmetric problems
Trunov, N. N.
2014-01-01
We generalize the universal effective quantum number introduced earlier for centrally symmetric problems. The proposed number determines the semiclassical quantization condition for axially symmetric potentials.
Origin of axial current in scyllac
The origin of the axial current observed in Scyllac (a high beta stellarator experiment) is discussed. A shaped coil and/or helical winding produce rotational transform which links magnetic lines of force to the plasma column and the axial current is induced electromagnetically. This phenomenon is inherent in a pulsed high-beta stellarator. The rotational transform produced by the induced axial current is much smaller than that associated with the l = 1, 0 equilibrium fields. The effect of the axial current on the equilibrium and stability of the plasma column is thus small. It is also shown that the magnetic field shear near a plasma surface is very strong
Fabisch, Alexander; Kassahun, Yohannes; Wöhrle, Hendrik; Kirchner, Frank
2013-06-01
We examine two methods which are used to deal with complex machine learning problems: compressed sensing and model compression. We discuss both methods in the context of feed-forward artificial neural networks and develop the backpropagation method in compressed parameter space. We further show that compressing the weights of a layer of a multilayer perceptron is equivalent to compressing the input of the layer. Based on this theoretical framework, we will use orthogonal functions and especially random projections for compression and perform experiments in supervised and reinforcement learning to demonstrate that the presented methods reduce training time significantly. PMID:23501172
A Compressive Superresolution Display
Heide, Felix
2014-06-22
In this paper, we introduce a new compressive display architecture for superresolution image presentation that exploits co-design of the optical device configuration and compressive computation. Our display allows for superresolution, HDR, or glasses-free 3D presentation.
Compressing Binary Decision Diagrams
Hansen, Esben Rune; Tiedemann, Peter
2008-01-01
The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1-2 bits per node. Empirical results for our compression technique are presented, including comparisons with previously introduced techniques, showing that the new technique dominate on all tested instances.
Microbunching and RF Compression
Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.
Hyperspectral data compression
Motta, Giovanni; Storer, James A
2006-01-01
Provides a survey of results in the field of compression of remote sensed 3D data, with a particular interest in hyperspectral imagery. This work covers topics such as compression architecture, lossless compression, lossy techniques, and more. It also describes a lossless algorithm based on vector quantization.
Compressing Binary Decision Diagrams
Hansen, Esben Rune; Satti, Srinivasa Rao; Tiedemann, Peter
The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1...
Compressible turbulent mixing: Effects of compressibility
Ni, Qionglin
2016-04-01
We studied by numerical simulations the effects of compressibility on passive scalar transport in stationary compressible turbulence. The turbulent Mach number varied from zero to unity. The difference in driven forcing was the magnitude ratio of compressive to solenoidal modes. In the inertial range, the scalar spectrum followed the k-5 /3 scaling and suffered negligible influence from the compressibility. The growth of the Mach number showed (1) a first reduction and second enhancement in the transfer of scalar flux; (2) an increase in the skewness and flatness of the scalar derivative and a decrease in the mixed skewness and flatness of the velocity-scalar derivatives; (3) a first stronger and second weaker intermittency of scalar relative to that of velocity; and (4) an increase in the intermittency parameter which measures the intermittency of scalar in the dissipative range. Furthermore, the growth of the compressive mode of forcing indicated (1) a decrease in the intermittency parameter and (2) less efficiency in enhancing scalar mixing. The visualization of scalar dissipation showed that, in the solenoidal-forced flow, the field was filled with the small-scale, highly convoluted structures, while in the compressive-forced flow, the field was exhibited as the regions dominated by the large-scale motions of rarefaction and compression.
Quantitative vertebral compression fracture evaluation using a height compass
Yao, Jianhua; Burns, Joseph E.; Wiese, Tatjana; Summers, Ronald M.
2012-03-01
Vertebral compression fractures can be caused by even minor trauma in patients with pathological conditions such as osteoporosis, varying greatly in vertebral body location and compression geometry. The location and morphology of the compression injury can guide decision making for treatment modality (vertebroplasty versus surgical fixation), and can be important for pre-surgical planning. We propose a height compass to evaluate the axial plane spatial distribution of compression injury (anterior, posterior, lateral, and central), and distinguish it from physiologic height variations of normal vertebrae. The method includes four steps: spine segmentation and partition, endplate detection, height compass computation and compression fracture evaluation. A height compass is computed for each vertebra, where the vertebral body is partitioned in the axial plane into 17 cells oriented about concentric rings. In the compass structure, a crown-like geometry is produced by three concentric rings which are divided into 8 equal length arcs by rays which are subtended by 8 common central angles. The radius of each ring increases multiplicatively, with resultant structure of a central node and two concentric surrounding bands of cells, each divided into octants. The height value for each octant is calculated and plotted against octants in neighboring vertebrae. The height compass shows intuitive display of the height distribution and can be used to easily identify the fracture regions. Our technique was evaluated on 8 thoraco-abdominal CT scans of patients with reported compression fractures and showed statistically significant differences in height value at the sites of the fractures.
Si-coated single-walled carbon nanotubes under axial loads: An atomistic simulation study
The mechanical properties of the Si-coated imperfect (5, 5) single-walled carbon nanotube (SWCNT), the imperfect (5, 5) SWCNT and several perfect armchair SWCNTs under axial loads were investigated using molecular dynamics simulation. The interactions between atoms were modeled using the empirical Tersoff potential and the Tersoff-Brenner potential coupled with the Lennard-Jones potential. We get Young's modulus of the defective (5, 5) nanotube with and without the Si coating under axial tension 1107.92 and 1076.02 GPa, respectively. The results also show that the structure failure of the Si-coated imperfect (5, 5) SWCNT under axial compression occurs at a slightly higher strain than for the perfect (5, 5) SWCNT. Therefore, we can confirm the protective effect of Si as a coating material for defective SWCNTs. We also obtain the critical buckling strains of perfect SWCNTs
Operational Experience with a Cryogenic Axial-Centrifugal Compressor
Decker, L; Löhlein, K; Purtschert, W; Ziegler, B L; Lebrun, P; Tavian, L; Brunovsky, I; Tucek, L
1998-01-01
The Large Hadron Collider (LHC), presently under construction at CERN, requires large refrigeration capacity at 1.8 K. Compression of gaseous helium at cryogenic temperatures is therefore inevitable. Together with subcontractors, Linde Kryotechnik has developed a prototype machine. This unit is based on a cryogenic axial-centrifugal compressor, running on ceramic ball bearings and driven by a variable-frequency electrical motor operating at ambient temperature. Integrated in a test facility for superconducting magnets the machine has been commissioned without major problems and successfully gone through the acceptance test in autumn 1995. Subsequent steps were initiated to improve efficiency of this prototype. This paper describes operating experience gained so far and reports on measured performance prior to and after constructional modifications.
A cryogenic axial-centrifugal compressor for superfluid helium refrigeration
Decker, L; Schustr, P; Vins, M; Brunovsky, I; Lebrun, P; Tavian, L
1997-01-01
CERN's new project, the Large Hadron Collider (LHC), will use superfluid helium as coolant for its high-field superconducting magnets and therefore require large capacity refrigeration at 1.8 K. This may only be achieved by subatmospheric compression of gaseous helium at cryogenic temperature. To stimulate development of this technology, CERN has procured from industry prototype Cold Compressor Units (CCU). This unit is based on a cryogenic axial-centrifugal compressor, running on ceramic ball bearings and driven by a variable-frequency electrical motor operating under low-pressure helium at ambient temperature. The machine has been commissioned and is now in operation. After describing basic constructional features of the compressor, we report on measured performance.
Skyrme RPA for spherical and axially symmetric nuclei
Repko, Anton; Nesterenko, V O; Reinhard, P -G
2015-01-01
Random Phase Approximation (RPA) is the basic method for calculation of excited states of nuclei over the Hartree-Fock ground state, suitable also for energy density functionals (EDF or DFT). We developed a convenient formalism for expressing densities and currents in a form of reduced matrix elements, which allows fast calculation of spectra for spherical nuclei. All terms of Skyrme functional were taken into account, so it is possible to calculate electric, magnetic and vortical/toroidal/compression transitions and strength functions of any multipolarity. Time-odd (spin) terms in Skyrme functional become important for magnetic M1 and isovector toroidal E1 transitions. It was also found that transition currents in pygmy region (low-lying part of E1 resonance) exhibit isoscalar toroidal flow, so the previously assumed picture of neutron-skin vibration is not the only mechanism present in pygmy transitions. RPA calculations with heavy axially-symmetric nuclei now become feasible on ordinary PC. Detailed formul...
Nonlinear vibrations and imperfection sensitivity of a cylindrical shell containing axial fluid flow
del Prado, Z.; Gonçalves, P. B.; Païdoussis, M. P.
2009-10-01
The high imperfection sensitivity of cylindrical shells under static compressive axial loads is a well-known phenomenon in structural stability. On the other hand, less is known of the influence of imperfections on the nonlinear vibrations of these shells under harmonic axial loads. The aim of this work is to study the simultaneous influence of geometric imperfections and an axial fluid flow on the nonlinear vibrations and instabilities of simply supported circular cylindrical shells under axial load. The fluid is assumed to be non-viscous and incompressible and the flow to be isentropic and irrotational. The behavior of the thin-walled shell is modeled by Donnell's nonlinear shallow-shell equations. It is subjected to a static uniform compressive axial pre-load plus a harmonic axial load. A low-dimensional modal expansion, which satisfies the relevant boundary and continuity conditions, and takes into account all relevant nonlinear modal interactions observed in the past in the nonlinear vibrations of cylindrical shells with and without flow is used together with the Galerkin method to derive a set of eight coupled nonlinear ordinary differential equations of motion which are, in turn, solved by the Runge-Kutta method. The shell is considered to be initially at rest, in a position corresponding to a pre-buckling configuration. Then, a harmonic excitation is applied and conditions for parametric instability and dynamic snap-through are sought. The results clarify the marked influence of geometric imperfections and fluid flow on the dynamic stability boundaries, bifurcations and basins of attraction.
Lei, Xiao; Narsu, B.; Yun, Guohong; Li, Jiangang; Yao, Haiyan
2016-05-01
Surface effects play a deterministic role in the physical and mechanical properties of nanosized materials and structures. In this paper, we present a self-consistent theoretical scheme for describing the elasticity of nanowires. The natural frequency and the critical compression force of axial buckling are obtained analytically, taking into consideration the influences of lower symmetry, additional elastic parameters, surface reconstruction, surface elasticity, and residual surface stress. Applications of the present theory to elastic systems for the axially oriented Si and Cu nanowires and Ag axially oriented nanowires yield good agreement with experimental data and calculated results. The larger positive value of the new elastic parameter c12α taken into account for Si oriented nanowires drives the curves of natural frequency and critical compression force versus thickness towards the results obtained from density functional theory simulation. Negative surface stress decreases the critical load for axial buckling, thus making the nanowires very easy to bend into various structures. The present study is envisaged to provide useful insights for the design and application of nanowire-based devices.
Partsch, H; Mortimer, P
2015-08-01
The main points in this scholarly review on the use of compression therapy in leg ulcers are the different modes of action of this treatment and the tools that are available including their practical applicability and use for self management. Due to its effect of counteracting gravity, compression is also suggested for ulcers with aetiologies that are not usually thought to require compression. The clinical evidence reported in ulcer-healing studies are discussed and some considerations are made relating to the cost-effectiveness of this management. In general, the failures of compression therapy are not caused by poor compression material but due to poor knowledge and application techniques of the care providers. Future studies comparing different compression devices should also report details concerning the compression material used and the pressure exerted. PMID:26094638
Axial force measurement for esophageal function testing.
Gravesen, Flemming H; Funch-Jensen, Peter; Gregersen, Hans; Drewes, Asbjørn Mohr
2009-01-14
The esophagus serves to transport food and fluid from the pharynx to the stomach. Manometry has been the "golden standard" for the diagnosis of esophageal motility diseases for many decades. Hence, esophageal function is normally evaluated by means of manometry even though it reflects the squeeze force (force in radial direction) whereas the bolus moves along the length of esophagus in a distal direction. Force measurements in the longitudinal (axial) direction provide a more direct measure of esophageal transport function. The technique used to record axial force has developed from external force transducers over in-vivo strain gauges of various sizes to electrical impedance based measurements. The amplitude and duration of the axial force has been shown to be as reliable as manometry. Normal, as well as abnormal, manometric recordings occur with normal bolus transit, which have been documented using imaging modalities such as radiography and scintigraphy. This inconsistency using manometry has also been documented by axial force recordings. This underlines the lack of information when diagnostics are based on manometry alone. Increasing the volume of a bag mounted on a probe with combined axial force and manometry recordings showed that axial force amplitude increased by 130% in contrast to an increase of 30% using manometry. Using axial force in combination with manometry provides a more complete picture of esophageal motility, and the current paper outlines the advantages of using this method. PMID:19132762
Axial force measurement for esophageal function testing
Flemming H Gravesen; Peter Funch-Jensen; Hans Gregersen; Asbjφrn Mohr Drewes
2009-01-01
The esophagus serves to transport food and fluid from the pharynx to the stomach. Manometry has been the "golden standard" for the diagnosis of esophageal motility diseases for many decades. Hence, esophageal function is normally evaluated by means of manometry even though it reflects the squeeze force (force in radial direction) whereas the bolus moves along the length of esophagus in a distal direction. Force measurements in the longitudinal (axial) direction provide a more direct measure of esophageal transport function. The technique used to record axial force has developed from external force transducers over in-vivo strain gauges of various sizes to electrical impedance based measurements. The amplitude and duration of the axial force has been shown to be as reliable as manometry. Normal, as well as abnormal, manometric recordings occur with normal bolus transit, which have been documented using imaging modalities such as radiography and scintigraphy. This inconsistency using manometry has also been documented by axial force recordings. This underlines the lack of information when diagnostics are based on manometry alone. Increasing the volume of a bag mounted on a probe with combined axial force and manometry recordings showed that axial force amplitude increased by 130% in contrast to an increase of 30% using manometry. Using axial force in combination with manometry provides a more complete picture of esophageal motility, and the current paper outlines the advantages of using this method.
Tree compression with top trees
Bille, Philip; Gørtz, Inge Li; Landau, Gad M.;
2015-01-01
navigational queries directly on the compressed representation. We show that the new compression scheme achieves close to optimal worst-case compression, can compress exponentially better than DAG compression, is never much worse than DAG compression, and supports navigational queries in logarithmic time....
Tree compression with top trees
Bille, Philip; Gørtz, Inge Li; Landau, Gad M.;
2013-01-01
navigational queries directly on the compressed representation. We show that the new compression scheme achieves close to optimal worst-case compression, can compress exponentially better than DAG compression, is never much worse than DAG compression, and supports navigational queries in logarithmic time....
Axial length variability in cataract surgery
To determine the mean axial length and biometric measures in patients undergoing cataract surgery and further compare the variability of axial length between the gender and with age. Study Design: Cross-sectional observational study. Place and Duration of Study: Eye Unit I, Department of Ophthalmology, Liaquat University of Medical and Health Sciences, Hyderabad, Pakistan from January 2010 to December 2012. Methodology: All patients referred for cataract surgery were assessed. The study included 886 eyes which were straightforward cataract cases with no other ocular problem. The data was collected for axial length, keratometric values and Intra-Ocular Lens (IOL) power prior to cataract surgery. The collected data was then analyzed using SPSS version 19 for windows software. Results: Gender based comparison showed significant difference in age, axial length, keratometric values and IOL power between the two groups (p=0.000). 86% of the eyes had an axial length between 21.00 mm and 23.99 mm. In univariate analysis there was significant (p=0.000) relation between overall age and axial length. The keratometric values ranged between 36.75 D and 52.50 D. Majority of the IOL powers ranged between 20.00 D and 23.00 D. Conclusion: The mean axial length of patients undergoing cataract surgery was 22.96 +- 1.04 mm, was comparable to Indian and Chinese population but shorter than the Western population. Females had shorter axial lengths, similar to other studies. Axial length was positively associated with age among the females, the cause of which is yet to be determined. (author)
Jian Guangde; Huang Lin; Qiu Xiaoming
2005-01-01
The assembling stabilizing effect of the finite Larmor radius (FLR) and the sheared axial flow (SAF) on the Rayleigh-Taylor instability in Z-pinch implosions is studied by means of the incompressible finite Larmor radius magnetohydrodynamic (MHD) equations. The finite Larmor radius effects are introduced in the momentum equation with the sheared axial flow through an anisotropic ion stress tensor. In this paper a linear mode equation is derived that is valid for arbitrary kL, where k is the wave number and L is the plasma shell thickness. Numerical solutions are presented. The results indicate that the short-wavelength modes of the RayleighTaylor instability are easily stabilized by the individual effect of the finite Larmor radius or the sheared axial flow. The assembling effects of the finite Larmor radius and sheared axial flow can heavily mitigate the Rayleigh-Taylor instability, and the unstable region can be compressed considerably.
New Anomaly of the Axial-Vector Current
HE Han-Xin
2001-01-01
By computing the axial-vector current operator equation, we find the anomalous axial-vector curl equation besides the well-known anomalous axial-vector divergence equation (the Adler-Bell-Jackiw anomaly) and discuss its implication.``
Growth-induced axial buckling of a slender elastic filament embedded in an isotropic elastic matrix
O'Keeffe, Stephen G.
2013-11-01
We investigate the problem of an axially loaded, isotropic, slender cylinder embedded in a soft, isotropic, outer elastic matrix. The cylinder undergoes uniform axial growth, whilst both the cylinder and the surrounding elastic matrix are confined between two rigid plates, so that this growth results in axial compression of the cylinder. We use two different modelling approaches to estimate the critical axial growth (that is, the amount of axial growth the cylinder is able to sustain before it buckles) and buckling wavelength of the cylinder. The first approach treats the filament and surrounding matrix as a single 3-dimensional elastic body undergoing large deformations, whilst the second approach treats the filament as a planar, elastic rod embedded in an infinite elastic foundation. By comparing the results of these two approaches, we obtain an estimate of the foundation modulus parameter, which characterises the strength of the foundation, in terms of the geometric and material properties of the system. © 2013 Elsevier Ltd. All rights reserved.
NUMERICAL PREDICTION OF COMPOSITE BEAM SUBJECTED TO COMBINED NEGATIVE BENDING AND AXIAL TENSION
MAHESAN BAVAN
2013-08-01
Full Text Available The present study has investigated the finite element method (FEM techniques of composite beam subjected to combined axial tension and negative bending. The negative bending regions of composite beams are influenced by worsen failures due to various levels of axial tensile loads on steel section especially in the regions near internal supports. Three dimensional solid FEM model was developed to accurately predict the unfavourable phenomenon of cracking of concrete and compression of steel in the negative bending regions of composite beam due to axial tensile loads. The prediction of quasi-static solution was extensively analysed with various deformation speeds and energy stabilities. The FEM model was then validated with existing experimental data. Reasonable agreements were observed between the results of FEM model and experimental analysis in the combination of vertical-axial forces and failure modes on ultimate limit state behaviour. The local failure modes known as shear studs failure, excess yielding on steel beam and crushing on concrete were completely verified by extensive similarity between the numerical and experimental results. Finally, a proper way of modelling techniques for large FEM models by considering uncertainties of material behaviour due to biaxial loadings and complex contact interactions is discussed. Further, the model is suggested for the limit state prediction of composite beam with calibrating necessary degree of the combined axial loads.
Axial Thermal Rotation of Slender Rods
Li, Dichuan; Fakhri, Nikta; Pasquali, Matteo; Biswal, Sibani Lisa
2011-05-01
Axial rotational diffusion of rodlike polymers is important in processes such as microtubule filament sliding and flagella beating. By imaging the motion of small kinks along the backbone of chains of DNA-linked colloids, we produce a direct and systematic measurement of axial rotational diffusivity of rods both in bulk solution and near a wall. The measured diffusivities decrease linearly with the chain length, irrespective of the distance from a wall, in agreement with slender-body hydrodynamics theory. Moreover, the presence of small kinks does not affect the chain’s axial diffusivity. Our system and measurements provide insights into fundamental axial diffusion processes of slender objects, which encompass a wide range of entities including biological filaments and linear polymer chains.
Compressed Sensing in Astronomy
Bobin, J; Ottensamer, R
2008-01-01
Recent advances in signal processing have focused on the use of sparse representations in various applications. A new field of interest based on sparsity has recently emerged: compressed sensing. This theory is a new sampling framework that provides an alternative to the well-known Shannon sampling theory. In this paper we investigate how compressed sensing (CS) can provide new insights into astronomical data compression and more generally how it paves the way for new conceptions in astronomical remote sensing. We first give a brief overview of the compressed sensing theory which provides very simple coding process with low computational cost, thus favoring its use for real-time applications often found on board space mission. We introduce a practical and effective recovery algorithm for decoding compressed data. In astronomy, physical prior information is often crucial for devising effective signal processing methods. We particularly point out that a CS-based compression scheme is flexible enough to account ...
Computer axial tomography in geosciences
Computer Axial Tomography (CAT) is one of the most adequate non-invasive techniques for the investigation of the internal structure of a large category of objects. Initially designed for medical investigations, this technique, based on the attenuation of X- or gamma-ray (and in some cases neutrons), generates digital images which map the numerical values of the linear attenuation coefficient of a section or of the entire volume of the investigated sample. Shortly after its application in medicine, CAT has been successfully used in archaeology, life sciences, and geosciences as well as for the industrial materials non-destructive testing. Depending on the energy of the utilized radiation as well as on the effective atomic number of the sample, CAT can provide with a spatial resolution of 0.01 - 0.5 mm, quantitative as well as qualitative information concerning local density, porosity or chemical composition of the sample. At present two types of axial Computer Tomographs (CT) are in use. One category, consisting of medical as well as industrial CT is equipped with X-ray tubes while the other uses isotopic gamma-ray sources. CT provided with intense X-ray sources (equivalent to 12-15 kCi or 450-550 TBq) has the advantage of an extremely short running time (a few seconds and even less) but presents some disadvantages known as beam hardening and absorption edge effects. These effects, intrinsically related to the polychromatic nature of the X-rays generated by classical tubes, need special mathematical or physical corrections. A polychromatic X-ray beam can be made almost monochromatic by means of crystal diffraction or by using adequate multicomponent filters, but these devices are costly and considerably diminish the output of X-ray generators. In the case of CT of the second type, monochromatic gamma-rays generated by radioisotopic sources, such as 169 Yb (50.4 keV), 241 Am (59 keV), 192 Ir (310.5 and 469.1 keV ) or 137 Cs (662.7 keV), are used in combination with
Tan, J L Y; Deshpande, V S; Fleck, N A
2016-07-13
A damage-based finite-element model is used to predict the fracture behaviour of centre-notched quasi-isotropic carbon-fibre-reinforced-polymer laminates under multi-axial loading. Damage within each ply is associated with fibre tension, fibre compression, matrix tension and matrix compression. Inter-ply delamination is modelled by cohesive interfaces using a traction-separation law. Failure envelopes for a notch and a circular hole are predicted for in-plane multi-axial loading and are in good agreement with the observed failure envelopes from a parallel experimental study. The ply-by-ply (and inter-ply) damage evolution and the critical mechanisms of ultimate failure also agree with the observed damage evolution. It is demonstrated that accurate predictions of notched compressive strength are obtained upon employing the band broadening stress for microbuckling, highlighting the importance of this damage mode in compression. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. PMID:27242302
Nonperturbative features of the axial current
Kopeliovich, B Z; Siddikov, M
2013-01-01
In this paper we study the nonperturbative structure of the axial current and evaluate the two-point distribution amplitudes $\\int d\\xi\\, e^{-iq...\\xi}$ in the framework of the instanton vacuum model in the leading order in $\\mathcal{O}(N_{c})$. We perform a direct numerical test of the relations between the axial current and the pion distribution amplitudes, imposed by PCAC, and found excellent agreement.
Axial Vircator for Electronic Warfare Applications
L. Drazan; R. Vrana
2009-01-01
This paper deals with a high power microwave generator with virtual cathode – vircator in axial release for electronic warfare applications. The classification of directed energy weapons microwave (DEWM) is introduced together with basic block diagrams of a particular class of DEWM. In the paper, methods for designing vircator pulsed power supply, axial vircator structure, measurement methods and experimental results are presented. The vircator in electromagnetic ammunition is powered b...
Nonperturbative Aspects of Axial Vector Vertex
ZONG Hong-Shi; CHEN Xiang-Song; WANG Fan; CHANG Chao-Hsi; ZHAO En-Guang
2002-01-01
It is shown how the axial vector current of current quarks is related to that of constituent quarks within the framework of the global color symmetry model.Gluon dressing of the axial vector vertex and the quark self-energy functions are described by the inhomogeneous Bethe-Salpeter equation in the ladder approximation and the Schwinger Dyson equation in the rainbow approximation,respectively.
Celiac Artery Compression Syndrome
Mohammed Muqeetadnan
2013-01-01
Full Text Available Celiac artery compression syndrome is a rare disorder characterized by episodic abdominal pain and weight loss. It is the result of external compression of celiac artery by the median arcuate ligament. We present a case of celiac artery compression syndrome in a 57-year-old male with severe postprandial abdominal pain and 30-pound weight loss. The patient eventually responded well to surgical division of the median arcuate ligament by laparoscopy.
Carrillo, Christian James
2001-01-01
This thesis presents formal elements of instruction-stream compression. We introduce notions of instruction representations, compressors and the general "patternization" function for representations to sequences. We further introduce the Lua-ISC language, an implementation of these elements. Instruction-stream compression algorithms are expressed, independently of the target architecture, in Lua-ISC. The language itself handles instruction decoding and encoding, patternization and compression...
Weighted universal image compression
Effros, Michelle; Chou, Philip A.; Gray, Robert M.
1999-01-01
We describe a general coding strategy leading to a family of universal image compression systems designed to give good performance in applications where the statistics of the source to be compressed are not available at design time or vary over time or space. The basic approach considered uses a two-stage structure in which the single source code of traditional image compression systems is replaced with a family of codes designed to cover a large class of possible sources. To illustrate this ...
Coeliac artery compression syndrome
OKTAY, Özgür; MEMİŞ, Ahmet; Parildar, Mustafa; Oran, İsmail
2003-01-01
Celiac artery compression syndrome, also called median arcuate ligament compression syndrome, causes gastrointestinal ischemia secondary to compression of the proximal portion of the celiac artery just beyond its origin by the median arcuate ligament of the diaphragm. This syndrome is frequently demonstrated on aortography performed in patients without complaints of intestinal angina. Isolated stenosis or even occlusion of the celiac artery is always compensated for by collateral circul...
An Unbroken Axial Vector Current Conservation Law
Sharafiddinov, Rasulkhozha S
2015-01-01
The mass, energy and momentum of the neutrino of a true flavor have an axial-vector nature. As a consequence, the left-handed truly neutral neutrino in an axial-vector field of emission can be converted into a right-handed one and vice versa. This predicts the unidenticality of masses, energies and momenta of neutrinos of the different components. Recognizing such a difference in masses, energies, momenta and accepting that the left-handed axial-vector neutrino and the right-handed antineutrino of true neutrality refer to long-lived C-odd leptons, and the right-handed truly neutral neutrino and the left-handed axial-vector antineutrino are of short-lived fermions of C-oddity, we would write a new CP-even Dirac equation taking into account the flavor symmetrical axial-vector mass, energy and momentum matrices. Their presence explains the spontaneous mirror symmetry violation, confirming that an axial-vector current conservation law has never violated. They reflect the availability of a mirror Minkowski space i...
Compressed sensing & sparse filtering
Carmi, Avishy Y; Godsill, Simon J
2013-01-01
This book is aimed at presenting concepts, methods and algorithms ableto cope with undersampled and limited data. One such trend that recently gained popularity and to some extent revolutionised signal processing is compressed sensing. Compressed sensing builds upon the observation that many signals in nature are nearly sparse (or compressible, as they are normally referred to) in some domain, and consequently they can be reconstructed to within high accuracy from far fewer observations than traditionally held to be necessary.Â Apart from compressed sensing this book contains other related app
Pearlman, William A
2013-01-01
This book explains the stages necessary to create a wavelet compression system for images and describes state-of-the-art systems used in image compression standards and current research. It starts with a high level discussion of the properties of the wavelet transform, especially the decomposition into multi-resolution subbands. It continues with an exposition of the null-zone, uniform quantization used in most subband coding systems and the optimal allocation of bitrate to the different subbands. Then the image compression systems of the FBI Fingerprint Compression Standard and the JPEG2000 S
Compression of positron clouds using rotating wall electric fields
An asymmetric dipolar rotating electric field can be used to compress a trapped cloud of positrons when applied with a frequency close that of their axial bounce, and in the presence of a low pressure molecular gas to provide cooling. Measurements of the compression rate and associated parameters are presented and compared with results of a theory we have developed. The latter treats positron behaviour in a perfect Penning trap potential, in the presence of the rotating field, with the cooling modelled in the Stokes viscous drag approximation. Good agreement between the theory and experiment has been found, which has allowed us to identify the phenomenon as a new form of sideband cooling.
Feng Li
2014-01-01
Full Text Available The axial compressive strength of unidirectional FRP made by pultrusion is generally quite lower than its axial tensile strength. This fact decreases the advantages of FRP as main load bearing member in engineering structure. A theoretical iterative calculation approach was suggested to predict the ultimate axial compressive stress of the combined structure and analyze the influences of geometrical parameters on the ultimate axial compressive stress of the combined structure. In this paper, the experimental and theoretical research on the CFRP sheet confined GFRP short pole was extended to the CFRP sheet confined GFRP short pipe, namely, a hollow section pole. Experiment shows that the bearing capacity of the GFRP short pipe can also be heightened obviously by confining CFRP sheet. The theoretical iterative calculation approach in the previous paper is amended to predict the ultimate axial compressive stress of the CFRP sheet confined GFRP short pipe, of which the results agree with the experiment. Lastly the influences of geometrical parameters on the new combined structure are analyzed.
Li, Feng; Zhao, Qilin; Chen, Li; Shao, Guojian
2014-01-01
The axial compressive strength of unidirectional FRP made by pultrusion is generally quite lower than its axial tensile strength. This fact decreases the advantages of FRP as main load bearing member in engineering structure. A theoretical iterative calculation approach was suggested to predict the ultimate axial compressive stress of the combined structure and analyze the influences of geometrical parameters on the ultimate axial compressive stress of the combined structure. In this paper, the experimental and theoretical research on the CFRP sheet confined GFRP short pole was extended to the CFRP sheet confined GFRP short pipe, namely, a hollow section pole. Experiment shows that the bearing capacity of the GFRP short pipe can also be heightened obviously by confining CFRP sheet. The theoretical iterative calculation approach in the previous paper is amended to predict the ultimate axial compressive stress of the CFRP sheet confined GFRP short pipe, of which the results agree with the experiment. Lastly the influences of geometrical parameters on the new combined structure are analyzed. PMID:24672288
DYNAMIC CRUSHING TESTS OF THIN-WALLED MEMBERS UNDER COMPRESSION
Maria Kotełko; Sebastian Lipa; Radosław J. Mania
2009-01-01
The paper deals with the experimental investigation into crushing collapse behaviour of two types of thin-walled structural members: tubular multi-member element subject to lateral crushing load and top hat-section column under axial compression. Especially designed experimental stand, in which a dynamical crushing load is realized by means of hydraulic system, is presented. Experimental, dynamical load-deformation curves are compared with those obtained from FE simulations and obtained from ...
PHELIX for flux compression studies
Turchi, Peter J [Los Alamos National Laboratory; Rousculp, Christopher L [Los Alamos National Laboratory; Reinovsky, Robert E [Los Alamos National Laboratory; Reass, William A [Los Alamos National Laboratory; Griego, Jeffrey R [Los Alamos National Laboratory; Oro, David M [Los Alamos National Laboratory; Merrill, Frank E [Los Alamos National Laboratory
2010-06-28
PHELIX (Precision High Energy-density Liner Implosion eXperiment) is a concept for studying electromagnetic implosions using proton radiography. This approach requires a portable pulsed power and liner implosion apparatus that can be operated in conjunction with an 800 MeV proton beam at the Los Alamos Neutron Science Center. The high resolution (< 100 micron) provided by proton radiography combined with similar precision of liner implosions driven electromagnetically can permit close comparisons of multi-frame experimental data and numerical simulations within a single dynamic event. To achieve a portable implosion system for use at high energy-density in a proton laboratory area requires sub-megajoule energies applied to implosions only a few cms in radial and axial dimension. The associated inductance changes are therefore relatively modest, so a current step-up transformer arrangement is employed to avoid excessive loss to parasitic inductances that are relatively large for low-energy banks comprising only several capacitors and switches. We describe the design, construction and operation of the PHELIX system and discuss application to liner-driven, magnetic flux compression experiments. For the latter, the ability of strong magnetic fields to deflect the proton beam may offer a novel technique for measurement of field distributions near perturbed surfaces.
Eman Omer
2010-01-01
Full Text Available Problem statement: Text compression permits representing a document by using less space. This is useful not only to save disk space, but more importantly, to save disk transfer and network transmission time. With the continues increase in the number of Arabic short text messages sent by mobile phones, the use of a suitable compression scheme would allow users to use more characters than the default value specified by the provider. The development of an efficient compression scheme to compress short Arabic texts is not a straight forward task. Approach: This study combined the benefits of pre-processing, entropy reduction through splitting files and hybrid dynamic coding: A new technique proposed in this study that uses the fact that Arabic texts have single case letters. Experimental tests had been performed on short Arabic texts and a comparison with the well known plain Huffman compression was made to measure the performance of the proposed schema for Arabic short text. Results: The proposed schema can achieve a compression ratio around 4.6 bits byte-1 for very short Arabic text sequences of 15 bytes and around 4 bits byte-1 for 50 bytes text sequences, using only 8 Kbytes overhead of memory. Conclusion: Furthermore, a reasonable compression ratio can be achieved using less than 0.4 KB of memory overhead. We recommended the use of proposed schema to compress small Arabic text with recourses limited.
A new strain gauge-based triaxial extensometer (radial extensometers x, y and axial extensometer z) is presented to improve the volumetric strain measurement in a hydro-compression loading test for foam materials. By the triaxial extensometer, triaxial deformations of the foam specimen can be measured directly, from which the volumetric strain is determined. Sensitivities of the triaxial extensometer are predicted using a finite-element model, and verified through experimental calibrations. The axial extensometer is validated by conducting a uniaxial compression test in aluminium foam and comparing deformation measured by the axial extensometer to that by the advanced optical 3D deformation analysis system ARAMIS; the result from the axial extensometer agrees well with that from ARAMIS. A new modus of two-wire measurement and transmission in a hydrostatic environment is developed to avoid the punching and lead sealing techniques on the pressure vessel for the hydro-compression test. The effect of hydrostatic pressure on the triaxial extensometer is determined through an experimental test. An application in an aluminium foam hydrostatic compression test shows that the triaxial extensometer is effective for volumetric strain measurement in a hydro-compression loading test for foam materials
Li, Q.M.; Lu, Y.B.; Meng, H.
2009-01-01
Abstract Split Hopkinson pressure bars (SHPB) have been used widely to measure the dynamic compressive strength of concrete-like materials at high strain-rate between 101 and 103 s?1. It has been shown in companion paper (Zhang et al. 2009) that the axial strain acceleration is normally unavoidable in an SHPB test on brittle materials. Axial strain acceleration introduces radial confinement in the SHPB specimens and consequently enhances the compressive strength of concrete-like sp...
On the mechanical behavior of slender, slightly curved, compressed microbridges
Hallauer, W. L.; Ma, C.
2011-06-01
We consider a clamped-clamped, slender beam-column that is slightly curved in its unloaded static equilibrium state. Perhaps the best practical example of this type of structure is a microbeam used in sensing and actuating devices. If the clamped ends are forced toward each other, or if stiff supports inhibit axial expansion that is fostered by fabrication processes and/or operational heating, then the column bends beyond its initial curvature. If the axial force approaches the buckling load, then the static flexural deflection can be relatively large, greater than the column's depth. We show that the dependence of moderately large static deflection upon compressive force is mathematically linear, and that nonlinearity arises only in the relationship of column shortening to transverse deflection. This leads to a linear finite-element method for static structural analysis of non-uniform columns, with which we simulate the behavior of a 62.5 µm long microbridge of 0.5 µm thin-film gold. This microbridge was observed experimentally to bend 4-5 µm under compression. We also examine previous studies of bending vibration about moderately large static deflection. Calculations and experimental measurements of the dependence of the fundamental natural frequency on axial compression and initial curvature indicate practical significance relative to design of microbridge resonators.
On the mechanical behavior of slender, slightly curved, compressed microbridges
We consider a clamped–clamped, slender beam–column that is slightly curved in its unloaded static equilibrium state. Perhaps the best practical example of this type of structure is a microbeam used in sensing and actuating devices. If the clamped ends are forced toward each other, or if stiff supports inhibit axial expansion that is fostered by fabrication processes and/or operational heating, then the column bends beyond its initial curvature. If the axial force approaches the buckling load, then the static flexural deflection can be relatively large, greater than the column's depth. We show that the dependence of moderately large static deflection upon compressive force is mathematically linear, and that nonlinearity arises only in the relationship of column shortening to transverse deflection. This leads to a linear finite-element method for static structural analysis of non-uniform columns, with which we simulate the behavior of a 62.5 µm long microbridge of 0.5 µm thin-film gold. This microbridge was observed experimentally to bend 4–5 µm under compression. We also examine previous studies of bending vibration about moderately large static deflection. Calculations and experimental measurements of the dependence of the fundamental natural frequency on axial compression and initial curvature indicate practical significance relative to design of microbridge resonators
We present an infant with macrocrania, who initially demonstrated prominent extra-axial fluid collections on sonography of the brain, compatible with benign infantile hydrocephalus (BIH). Because of increasing macrocrania, a follow-up sonogram of the brain was performed; it revealed progressive enlargement of the extra-axial spaces, which now had echogenic debris. Color Doppler US showed bridging veins traversing these extra-axial spaces, so it was initially thought that these spaces were subarachnoid in nature (positive cortical vein sign). However, an arachnoid membrane was identified superior to the cortex, and there was compression of true cortical vessels beneath this dural membrane. An MRI of the brain showed the extra-axial spaces to represent bilateral subdural hematomas. The pathogenesis of spontaneous development of the subdural hematomas, in the setting of BIH, is discussed. We also emphasize that visualizing traversing bridging veins through extra-axial spaces does not necessarily imply that these spaces are subarachnoid in origin. (orig.)
The axial buckling behavior of magnetically affected current-carrying nanowires is studied accounting for the surface energy effect. Using Euler–Bernoulli beam theory, the Lorentz force on the nanowire is determined and the governing equations are established. By application of the Galerkin approach and assumed mode method, the critical axial compressive load of the nanostructure is evaluated in the cases of simply supported and fully clamped ends. The effects of surface energy, electric current, strength of the magnetic field, slenderness ratio, and nanowire’s radius on the axial buckling loads are comprehensively discussed. The obtained results reveal that both the electric current and exerted magnetic field endanger the axial stability of the nanowire. For high levels of electric current or magnetic field strength, the surface effect becomes significant in the axial buckling performance of the nanostructure. (paper)
Moisture effect on compressive behavior of concrete under dynamic loading
周继凯; 丁宁
2014-01-01
The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were executed. The technique “split Hopkinson pressure bar” (SHPB) was used. The impact velocity was 10 m/s with corresponding strain rate of 50 s−1. The compressive behavior of materials was measured in terms of stress−strain curves, dynamic compressive strength, dynamic increase factor (DIF) and critical strain at a maximum stress. The data obtained from test indicate that both ascending and descending portions of stress−stain curves are affected by moisture content. However, the effect is noted to be more significant in ascending portion of the stress−strain curves. Dynamic compressive strength is higher at lower moisture content and weaker at higher moisture content. Furthermore, under nearly saturated condition, an increase in compressive strength can be found. The effect of moisture content on the average DIF of concrete is not significant. The critical compressive strain of concrete does not change with moisture content.
Optimization of residual heat removal pump axial thrust and axial bearing
Schubert, F.
1996-12-01
The residual heat removal (RHR) pumps of German 1300 megawatt pressurized-water reactor (PWR) power plants are of the single stage end suction type with volute casing or with diffuser and forged circular casing. Due to the service conditions the pumps have to cover the full capacity range as well as a big variation in suction static pressure. This results in a big difference in the axial thrust that has to be borne by the axial bearing. Because these pumps are designed to operate without auxiliary systems (things that do not exist can not fail), they are equipped with antifriction bearings and sump oil lubrication. To minimize the heat production within the bearing casing, a number of PWR plants have pumps with combined axial/radial bearings of the ball type. Due to the fact that the maximum axial thrust caused by static pressure and hydrodynamic forces on the impeller is too big to be borne by that type of axial bearing, the impellers were designed to produce a hydrodynamic axial force that counteracts the static axial force. Thus, the resulting axial thrust may change direction when the static pressure varies.
Polarization converters based on axially symmetric twisted nematic liquid crystal.
Ko, Shih-Wei; Ting, Chi-Lun; Fuh, Andy Y-G; Lin, Tsung-Hsien
2010-02-15
An axially symmetric twisted nematic liquid crystal (ASTNLC) device, based on axially symmetric photoalignment, was demonstrated. Such an ASTNLC device can convert axial (azimuthal) to azimuthal (axial) polarization. The optical properties of the ASTNLC device are analyzed and found to agree with simulation results. The ASTNLC device with a specific device can be adopted as an arbitrary axial symmetric polarization converter or waveplate for axially, azimuthally or vertically polarized light. A design for converting linear polarized light to axially symmetric circular polarized light is also demonstrated. PMID:20389369
Improving the lattice axial vector current
Horsley, R; Perlt, H; Rakow, P E L; Schierholz, G; Schiller, A; Zanotti, J M
2015-01-01
For Wilson and clover fermions traditional formulations of the axial vector current do not respect the continuum Ward identity which relates the divergence of that current to the pseudoscalar density. Here we propose to use a point-split or one-link axial vector current whose divergence exactly satisfies a lattice Ward identity, involving the pseudoscalar density and a number of irrelevant operators. We check in one-loop lattice perturbation theory with SLiNC fermion and gauge plaquette action that this is indeed the case including order $O(a)$ effects. Including these operators the axial Ward identity remains renormalisation invariant. First preliminary results of a nonperturbative check of the Ward identity are also presented.
Axial instability of rotating relativistic stars
Friedman, J L; Friedman, John L.; Morsink, Sharon M.
1998-01-01
Perturbations of rotating relativistic stars can be classified by their behavior under parity. For axial perturbations (r-modes), initial data with negative canonical energy is found with angular dependence $e^{im\\phi}$ for all values of $m\\geq 2$ and for arbitrarily slow rotation. This implies instability (or marginal stability) of such perturbations for rotating perfect fluids. This low $m$-instability is strikingly different from the instability to polar perturbations, which sets in first for large values of $m$. The timescale for the axial instability appears, for small angular velocity $\\Omega$, to be proportional to a high power of $\\Omega$. As in the case of polar modes, viscosity will again presumably enforce stability except for hot, rapidly rotating neutron stars. This work complements Andersson's numerical investigation of axial modes in slowly rotating stars.
The axial distribution of reactivity coefficients
The purpose of the present work is to investigate the correlation of the axial distributions of the different reactivity coefficients with the neutron flux and the neutron flux squared. Calculations were carried out for the Zion Unit 2 PWR. Reactivity coefficients, forward fluxes and adjoint fluxes were all computed and correlations obtained. The core length was divided into 7 axial regions in order to obtain the effect on reactivity in the reactor as a whole of changing the cross sections in each axial region in turn. The parameters chosen for change were coolant density, coolant temperature and fuel temperature. The results appear to bear out our original hypothesis that the reactivity coefficient profiles have a higher positive correlation with the total flux squared profile than with the linear flux profile. (authors). 5 refs., 2 figs
Scoville, John
2011-01-01
A new approach to data compression is developed and applied to multimedia content. This method separates messages into components suitable for both lossless coding and 'lossy' or statistical coding techniques, compressing complex objects by separately encoding signals and noise. This is demonstrated by compressing the most significant bits of data exactly, since they are typically redundant and compressible, and either fitting a maximally likely noise function to the residual bits or compressing them using lossy methods. Upon decompression, the significant bits are decoded and added to a noise function, whether sampled from a noise model or decompressed from a lossy code. This results in compressed data similar to the original. For many test images, a two-part image code using JPEG2000 for lossy coding and PAQ8l for lossless coding produces less mean-squared error than an equal length of JPEG2000. Computer-generated images typically compress better using this method than through direct lossy coding, as do man...
Hongying Dong; Wanlin Cao; Jianhui Bian; Jianwei Zhang
2014-01-01
In order to ascertain the fire resistance performance of recycled aggregate concrete (RAC) components with different concrete compressive strengths, four full-scaled concrete columns were designed and tested under high temperature. Two of the four specimens were constructed by normal concrete with compressive strength ratings of C20 and C30, respectively, while the others were made from recycled coarse aggregate (RCA) concrete of C30 and C40, respectively. Identical constant axial forces were...
Selection rules and ratios for axial couplings
Buccella, F; Pugliese, A; Sorace, E
1972-01-01
The predictions for the axial couplings following from the use of the mixing operator U(Z), previously introduced to tilt the axial charges of SU/sub 6/ in the physical ones, are studied. The quantum number (-1)/sup L+L3/, where L and L/sub 3/ are the O/sub 3/ angular momentum and its third component, is shown to be conserved. From the properties of Z further predictions can be achieved as the D/F= /sup 3///sub 2/ for the /sup 1///sub 2//sup +/ baryon octet in general agreement with experiment. (14 refs).
Axial Stiffness of Multiwalled Carbon Nanotubes
Zavalniuk, Vladimir
2011-01-01
The axial stiffness of MWCNTs is demonstrated to be determined only by several external shells (usually 3-5 and up to 15 for the extremely large nanotubes and high elongations) what is in a good agreement with experimentally observed inverse relation between the radius and Young modulus (i.e., stiffness) of MWCNTs. This result is a consequence of the van der Waals intershell interaction. The interpolating formula is obtained for the actual axial stiffness of MWCNT as a function of the tube ex...
Axial Vircator for Electronic Warfare Applications
L. Drazan
2009-12-01
Full Text Available This paper deals with a high power microwave generator with virtual cathode – vircator in axial release for electronic warfare applications. The classification of directed energy weapons microwave (DEWM is introduced together with basic block diagrams of a particular class of DEWM. In the paper, methods for designing vircator pulsed power supply, axial vircator structure, measurement methods and experimental results are presented. The vircator in electromagnetic ammunition is powered by magneto-cumulative generator and in weapons for defense of objects (WDO, it is powered by Marx generator. The possible applications of a vircator in the DEWM area are discussed.
Focus on Compression Stockings
... therapy may be recommended as part of a treatment plan. There are several situations when compression may be helpful, including: tired legs, varicose veins, chronic venous insufficiency (CVI), lymphedema, or deep vein thrombosis (DVT). This brochure focuses ...
Mansi Kambli,; Shalini Bhatia
2010-01-01
Modified Set Partitioning in Hierarchical Tree with Run Length Encoding is a new framework proposed for fingerprint image compression. The Proposed method is better because more number of images related to the fingerprint image are retrieved. Experiments on an image database of grayscale bitmap images show that the proposed technique performs well in compression and decompression. We use Peak Signal to noise ratio [3] and Mean Square Error [3] to compute the picture quality of fingerprint ima...
Compressibility of bilayer graphene
Borghi, Giovanni; Polini, Marco; Asgari, Reza; MacDonald, A. H.
2010-01-01
Bilayer graphene is a recently isolated and intriguing class of many-body systems with massive chiral quasiparticles. We present theoretical results for the electronic compressibility of bilayer graphene that are based on a four-band continuum band structure model combined with a random phase approximation treatment of electronic correlations. We find that the compressibility is strongly suppressed by electron-electron interactions at low carrier densities. Correlations do not lead to any qua...
The compressibility of graphene
Abergel, D. S. L.
2012-01-01
We present a review of the electronic compressibility of monolayer and bilayer graphene. We focus on describing theoretical calculations of the effects of electron--electron interactions and various types of disorder, and also give a summary of current experiments and describe which aspects of theory they support. We also include a full analysis of all commonly-used contributions to the tight-binding Hamiltonian of bilayer graphene and their effects on the compressibility.
Compressive coherent anti-Stokes Raman scattering holography.
Cocking, Alexander; Mehta, Nikhil; Shi, Kebin; Liu, Zhiwen
2015-09-21
Coherent anti-Stokes Raman scattering (CARS) holography captures both the amplitude and the phase of the anti-Stokes field generated from a sample and can thus perform single-shot, chemically selective three-dimensional imaging. We present compressive CARS holography, a numerical technique based on the concept of compressive sensing, to improve the quality of reconstructed images by leveraging sparsity in the source distribution and reducing the out-of-focus background noise. In particular, we use the two-step iterative shrinkage threshold (TwIST) algorithm with an l1 norm regularizer to iteratively retrieve images from an off axis CARS digital hologram. It is shown that the use of compressive CARS holography enhances the CARS holographic imaging technique by reducing noise and thereby effectively emulating a higher axial resolution using only a single shot hologram. PMID:26406699
Knowledge Based Design of Axial Flow Compressor
Dinesh kumar.R
2015-05-01
Full Text Available In the aerospace industry with highly competitive market the time to design and delivery is shortening every day. Pressure on delivering robust product with cost economy is in demand in each development. Even though technology is older, it is new for each customer requirement and highly non-liner to fit one in another place. Gas turbine is considered one of a complex design in the aircraft system. It involves experts to be grouped with designers of various segments to arrive the best output. The time is crucial to achieve a best design and it needs knowledge automation incorporated with CAD/CAE tools. In the present work an innovative idea in the form of Knowledge Based Engineering for axial compressor is proposed, this includes the fundamental design of axial compressor integrated with artificial intelligence in the form of knowledge capturing and programmed with high level language (Visual Basis.Net and embedded into CATIA v5. This KBE frame work eases out the design and modeling of axial compressor design and produces 3D modeling for further flow simulation with fluid dynamic in Ansys-Fluent. Most of the aerospace components are developed through simulation driven product development and in this case it is established for axial compressor.
The Axial Current in Electromagnetic Interaction
Cheoun, M K; Cheon, I T; Cheoun, Myung Ki; Cheon, Il-Tong
1998-01-01
We discussed the possibility that the charged axial currents of matter fields could be non-conserved in electromagnetic interaction at $O(e) $ order. It means that chiral symmetry is broken explicitly by electromagnetic interaction. This explicit symmetry breaking of chiral symmetry is shown to lead the mass differences between the charged and neutral particles of matter fields.
Constant-axial-intensity nondiffracting beam.
Cox, A J; D'Anna, J
1992-02-15
Numerical solutions of the Fresnel diffraction integral with various apodizing filter functions are used to indicate that a so-called nondiffracting beam can be produced that maintains a constant spot size and constant axial intensity over a considerable range, approximately 30 m in our example. PMID:19784285
Axially symmetric SU(3) gravitating skyrmions
Ioannidou, Theodora [Maths Division, School of Technology, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)]. E-mail: ti3@auth.gr; Kleihaus, Burkhard [Institut fuer Physik, Universitaet Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany)]. E-mail: kleihaus@theorie.physik.uni-oldenburg.de; Zakrzewski, Wojtek [Department of Mathematical Sciences, University of Durham, Durham DH1 3LE (United Kingdom)]. E-mail: w.j.zakrzewski@durham.ac.uk
2004-10-21
Axially symmetric gravitating multi-skyrmion configurations are obtained using the harmonic map ansatz introduced in [J. Math. Phys. 40 (1999) 6353]. In particular, the effect of gravity on the energy and baryon densities of the SU(3) non-gravitating multi-skyrmion configurations is studied in detail.
Axially symmetric SU(3) Gravitating Skyrmions
Ioannidou, T A; Zakrzewski, W J; Ioannidou, Theodora; Kleihaus, Burkhard; Zakrzewski, Wojtek
2004-01-01
Axially symmetric gravitating multi-skyrmion configurations are obtained using the harmonic map ansatz introduced in [1]. In particular, the effect of gravity on the energy and baryon densities of the SU(3) non-gravitating multi-skyrmion configurations is studied in detail.
Axially symmetric SU(3) gravitating skyrmions
Axially symmetric gravitating multi-skyrmion configurations are obtained using the harmonic map ansatz introduced in [J. Math. Phys. 40 (1999) 6353]. In particular, the effect of gravity on the energy and baryon densities of the SU(3) non-gravitating multi-skyrmion configurations is studied in detail
Primitive axial algebras of Jordan type
Hall, J I; Rehren, F; Shpectorov, S.
2014-01-01
An axial algebra over the field $\\mathbb F$ is a commutative algebra generated by idempotents whose adjoint action has multiplicity-free minimal polynomial. For semisimple associative algebras this leads to sums of copies of $\\mathbb F$. Here we consider the first nonassociative case, where adjoint minimal polynomials divide $(x-1)x(x-\\eta)$ for fixed $0\
Madsen, Rasmus; Jensen, Tue Secher; Pope, Malcolm;
2007-01-01
STUDY DESIGN: A method comparison study. OBJECTIVE: To investigate the effect of body position and axial load of the lumbar spine on disc height, lumbar lordosis, and dural sac cross-sectional area (DCSA). SUMMARY OF BACKGROUND DATA.: The effects of flexion and extension on spinal canal diameters...... position with applied axial loading. Disc height, lumbar lordosis, and DCSA were measured and the different positions were compared. RESULTS: In section 1, the only significant difference between positions was a reduced lumbar lordosis during standing when compared with lying (P = 0.04), most probably a...... and DCSA are well documented. However, the effects of axial loading, achieved by upright standing or by a compression device, are still unclear. METHODS: Patients with lumbar spinal stenosis were examined in 2 separate studies, including 16 and 20 patients, respectively. In section 1, magnetic...
Buckling of un-stiffened cylindrical shell under non-uniform axial conpressive stress
宋昌永
2002-01-01
This paper provides a review of recent research advances and trends in the area of stability of un-stiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses. Only the more important and interesting aspects of the research, judged from a personal viewpoint, are discussed. They can be crudely classified into four categories: (1) shells subjected to non-uniform loads; (2) shells on discrete supports; (3) shells with intended cutouts/holes; and (4) shells with non-uniform settlements.
Neutron Star Asteroseismology. Axial Crust Oscillations in the Cowling Approximation
Samuelsson, L; Samuelsson, Lars; Andersson, Nils
2006-01-01
Recent observations of quasi-periodic oscillations in the aftermath of giant flares in soft gamma-ray repeaters suggest a close coupling between the seismic motion of the crust after a major quake and the modes of oscillations in a magnetar. In this paper we consider the purely elastic modes of oscillation in the crust of a neutron star in the relativistic Cowling approximation (disregarding any magnetic field). We determine the axial crust modes for a large set of stellar models, using a state-of-the-art crust equation of state and a wide range of core masses and radii. We also devise useful approximate formulae for the mode-frequencies. We show that the relative crust thickness is well described by a function of the compactness of the star and a parameter describing the compressibility of the crust only. Considering the observational data for SGR 1900+14 and SGR 1806-20, we demonstrate how our results can be used to constrain the mass and radius of an oscillating neutron star.
Yaqub, Muhammad
2010-01-01
In the light of extreme events of natural disasters (earthquakes or hurricanes) and accidents (fire or explosion), repairing and strengthening of existing concrete structures has become more common during the last decade due to the increasing knowledge and confidence in the use of composite advanced repairing materials. The past experience from real fires shows that it is exceptional for a concrete building to collapse as a result of fire and most fire-damaged concrete structures can be repai...
Yasser M. Hunaiti; Nabil M. Falah; Issam M. Assi
2002-01-01
Tests on hollow steel tubes of square, rectangular and circular sections filled with foamed concrete and lightweight aggregate concrete were conducted to investigate the contribution of these concretes to the strength of cross sections of composite short columns. In addition, these tests aims at understanding the behavior of short columns with lightweight concrete. Thirty short column specimens filled with foamed concrete and lightweight aggregate concrete were tested in this investigation. F...
Mathematical Model for Thin-walled Corrugated Tube under Axial Compression
Eyvazian Arameh
2016-01-01
Full Text Available In this research, theoretical investigation of corrugated aluminum tubes is performed to predicting the energy absorption characteristics. Aim to deform plastic tubes in predetermined intervals, corrugations are introduced on its surface. Theoretical relations are presented for predicting the energy absorption and mean crushing load of corrugated tubes. Other than that, corrugation helps to control the failure mode.
Thin-walled composite tubes using fillers subjected to quasistatic axial compression
AL-Qrimli, Haidar F.; Mahdi, Fadhil A.; Ismail, Firas B.; Alzorqi, Ibrahim S.
2015-04-01
It has been demonstrated that composites are lightweight, fatigue resistant and easily melded, a seemingly attractive alternative to metals. However, there has been no widespread switch from metals to composites in the automotive sector. This is because there are a number of technical issues relating to the use of composite materials that still need to be resolved including accurate material characterization, manufacturing and joining process. The total of 36 specimens have been fabricated using the fibre-glass and resin (epoxy) with a two different geometries (circular and corrugated) each one will be filled with five types of filler (Rice Husk, Wood Chips, Aluminium Chips, Coconut Fibre, Palm Oil Fibre) all these type will be compared with empty Tubes for circular and corrugated in order to comprehend the crashworthiness parameters (initial failure load, average load, maximum crushing load, load ratio, energy absorption, specific energy absorption, volumetric energy absorption, crushing force efficiency and crush strain relation) which are considered very sufficient parameters in the design of automotive industry parts. All the tests have been done using the “INSTRON Universal machine” which is computerized in order to simply give a high precision to the collection of the results, along with the use of quasi-static load to test and observe the behaviour of the fabricated specimens.