ORCID Profile
0000-0003-0657-2678
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Publisher: Springer Science and Business Media LLC
Date: 08-2002
DOI: 10.1007/BF02706993
Publisher: Agricultural and Food Science
Date: 26-06-2013
DOI: 10.23986/AFSCI.7754
Abstract: On accession to the EU, Poland, one of the most agricultural countries in Europe, became eligible for the Common Agricultural Policy (CAP), which it perceived as a chance to develop its rural economy. However, in constructing its Rural Development Programme 2007−2013, Poland directed the largest funding share to Less Favoured Areas (LFA) − a controversial measure, which has been accused of poor targeting and ineffectiveness. We analyse the economic consequences of LFA support for all 16 Polish regions according to Nomenclature of Territorial Units for Statistics (NUTS2), using a multi-regional computable general equilibrium model with LFA detail.
Publisher: Elsevier BV
Date: 04-1998
Publisher: Springer Netherlands
Date: 2009
Publisher: Elsevier BV
Date: 2006
Publisher: Springer Science and Business Media LLC
Date: 02-1994
DOI: 10.1007/BF01742512
Publisher: Elsevier BV
Date: 06-2000
Publisher: Elsevier BV
Date: 12-1988
Publisher: Elsevier BV
Date: 03-2007
Publisher: Springer Netherlands
Date: 2009
Publisher: Elsevier BV
Date: 09-2013
Publisher: Informa UK Limited
Date: 1979
Publisher: Informa UK Limited
Date: 02-1993
Publisher: Proceedings of the National Academy of Sciences
Date: 03-05-2010
Abstract: We reveal the sophisticated and hierarchical structure of honeybee combs and measure the elastic properties of fresh and old natural honeycombs at different scales by optical microscope, environmental scanning electron microscope, nano/microindentation, and by tension and shear tests. We demonstrate that the comb walls are continuously strengthened and stiffened without becoming fragile by the addition of thin wax layers reinforced by recycled silk cocoons reminiscent of modern fiber-reinforced composite laminates. This is done to increase its margin of safety against collapse due to a temperature increase. Artificial engineering honeycombs mimic only the macroscopic geometry of natural honeycombs, but have yet to achieve the microstructural sophistication of their natural counterparts. The natural honeycombs serve as a prototype of truly biomimetic cellular materials with hitherto unattainable improvement in stiffness, strength, toughness, and thermal stability.
Publisher: Springer Science and Business Media LLC
Date: 30-05-2008
Publisher: Elsevier BV
Date: 1983
Publisher: Springer Science and Business Media LLC
Date: 07-1995
DOI: 10.1007/BF01743974
Publisher: Elsevier BV
Date: 06-2014
Publisher: Informa UK Limited
Date: 27-04-2015
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2003
Publisher: Elsevier BV
Date: 12-2009
Publisher: Elsevier BV
Date: 07-1992
Publisher: Springer Science and Business Media LLC
Date: 03-1979
DOI: 10.1007/BF00933033
Publisher: Springer Science and Business Media LLC
Date: 03-1979
DOI: 10.1007/BF00933035
Publisher: Springer Science and Business Media LLC
Date: 03-1979
DOI: 10.1007/BF00933034
Publisher: Elsevier BV
Date: 1979
Publisher: Elsevier BV
Date: 11-2003
Publisher: Elsevier BV
Date: 11-2016
Publisher: Springer Science and Business Media LLC
Date: 10-1985
DOI: 10.1007/BF00723483
Publisher: Elsevier BV
Date: 1979
Publisher: Springer Science and Business Media LLC
Date: 05-1989
DOI: 10.1007/BF02472186
Publisher: Elsevier BV
Date: 1997
Publisher: Informa UK Limited
Date: 04-1987
Publisher: Elsevier BV
Date: 1994
Publisher: Elsevier BV
Date: 02-2014
Publisher: Elsevier BV
Date: 1988
Publisher: Thomas Telford Ltd.
Date: 08-2005
DOI: 10.1680/MACR.2005.57.6.347
Abstract: Part I of this three-part paper describes the various steps that led to the development of a class of high performance short steel fibre-reinforced cementitious composites (HPFRCCs) which has been patented under the trade name CARDIFRC ® . This class of materials generally contains no coarse aggregates and is characterised by high tensile/flexural strength and high toughness. A method is proposed for quantifying the workability of such a mix without fibres in terms of its fracture toughness.
Publisher: Elsevier
Date: 2003
Publisher: Springer Netherlands
Date: 2012
Publisher: Thomas Telford Ltd.
Date: 10-2005
DOI: 10.1680/MACR.2005.57.8.433
Abstract: Part III of this three-part paper about CARDIFRC ® , a class of high performance short steel fibre-reinforced cementitious composites (HPFRCCs), deals with the measurement of the tensile response of CARDIFRC ® mixes on a specially developed specimen geometry and loading arrangement. It also compares the measured mechanical properties (Young's modulus, E, compressive strength, f c , tensile strength, f t , specific fracture energy, G F ) with the theoretically predicted values using micromechanical relations.
Publisher: Elsevier BV
Date: 05-2016
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 05-2003
Publisher: Springer Science and Business Media LLC
Date: 06-1973
DOI: 10.1007/BF00935563
Publisher: Springer Science and Business Media LLC
Date: 03-1982
DOI: 10.1007/BF00934354
Publisher: Springer Science and Business Media LLC
Date: 03-2001
Publisher: Elsevier BV
Date: 11-2009
Publisher: Inderscience Publishers
Date: 2002
Publisher: Elsevier BV
Date: 07-1989
Publisher: Elsevier BV
Date: 1977
Publisher: Elsevier BV
Date: 1982
Publisher: Elsevier BV
Date: 05-1999
Publisher: Wiley
Date: 2007
DOI: 10.1002/NME.1866
Publisher: Informa UK Limited
Date: 11-06-2005
Publisher: Elsevier BV
Date: 10-2017
Publisher: Springer Netherlands
Date: 2009
Publisher: The Royal Society
Date: 08-12-1984
Abstract: Pre-cracked rectangular blocks of two different glassy brittle polymers were compressed under a flat steel platen until failure occurred. Three distinct failure modes, gross yielding under platen, axial splitting and plastic instability (buckling) were observed, depending on the pre-crack length and platen width. The axial splitting failure mode is explained by invoking the energy balance concept of fracture with a two-strut elastic model. In this mode, the elastic fracture surface energy or, equivalently, the stress intensity factor and not the compressive strength, is found to be the fundamental material property dictating compression failure. The role played by the pre-crack length and platen width in controlling the failure mode transition from gross yielding to compression splitting and to buckling is highlighted. Finite element and boundary element calculations support the proposed two-strut model for compression splitting.
Publisher: The Royal Society
Date: 31-08-2005
Abstract: The Eshelby formalism for inclusion/inhomogeneity problems is extended to the nano-scale at which surface/interface effects become important. The interior and exterior Eshelby tensors for a spherical inhomogeneous inclusion with the interface stress effect subjected to an arbitrary uniform eigenstrain embedded in an infinite alien matrix, and the stress concentration tensors for a spherical inhomogeneity subjected to an arbitrary remote uniform stress field are obtained. Unlike their counterparts at the macro-scale, the Eshelby and stress concentration tensors are, in general, not uniform inside the inhomogeneity but are position-dependent. They have the property of radial transverse isotropy. It is also shown that the size-dependence of the Eshelby tensors and the stress concentration tensors follow very simple scaling laws. Finally, the Eshelby formula to calculate the strain energy in the presence of the interface effect is given.
Publisher: Thomas Telford Ltd.
Date: 06-2017
Abstract: The three-dimensional Lagrangian-particle-based smooth particle hydrodynamics methodology was used to simulate the flow characteristics of self-compacting concrete (SCC) mixes in an L-box test. A Bingham-type constitutive model was coupled with the Lagrangian momentum and continuity equations to simulate the flow. The simulations of SCC focused on the flow times, the free-surface profile and the distribution of large aggregates (larger than or equal to 8 mm) during the flow. The numerical simulation results were compared with actual L-box tests carried out on several SCC mixes. The comparison revealed that the methodology is very well suited to predicting the flow behaviour of SCC in terms of passing and filling abilities and the distribution of large aggregates.
Publisher: Wiley
Date: 07-1991
Publisher: Elsevier BV
Date: 1988
Publisher: Springer Science and Business Media LLC
Date: 04-1996
DOI: 10.1007/BF02486160
Publisher: Elsevier BV
Date: 07-2001
Publisher: Elsevier BV
Date: 1976
Publisher: Elsevier BV
Date: 2000
Publisher: Elsevier BV
Date: 1993
Publisher: Springer Science and Business Media LLC
Date: 05-1990
DOI: 10.1007/BF02473016
Publisher: Informa UK Limited
Date: 1980
Publisher: Springer Science and Business Media LLC
Date: 12-1995
DOI: 10.1007/BF00035846
Publisher: Springer Science and Business Media LLC
Date: 09-1990
DOI: 10.1007/BF01836566
Publisher: Wiley
Date: 06-04-2011
DOI: 10.1002/NAG.924
Publisher: No publisher found
Date: 1998
Publisher: AIP Publishing
Date: 15-04-2011
DOI: 10.1063/1.3567110
Abstract: The structural patterns of periodic cellular materials play an important role in their properties. Here, we investigate how these patterns transform dramatically under external stimuli in simple periodic cellular structures that include a nanotube bundle and a millimeter-size plastic straw bundle. Under gradual hydrostatic straining up to 20%, the cross-section of the single walled carbon nanotube bundle undergoes several pattern transformations, while an amazing new hexagram pattern is triggered from the circular shape when the strain of 20% is applied suddenly in one step. Similar to the nanotube bundle, the circular plastic straw bundle is transformed into a hexagonal pattern on heating by conduction through a baseplate but into a hexagram pattern when heated by convection. Besides the well-known elastic buckling, we find other mechanisms of pattern transformation at different scales these include the minimization of the surface energy at the macroscale or of the van der Waals energy at the nanoscale and the competition between the elastic energy of deformation and either the surface energy at the macroscale or the van der Waals energy at the nanoscale. The studies of the pattern transformations of periodic porous materials offer new insights into the fabrication of novel materials and devices with tailored properties.
Publisher: Springer Science and Business Media LLC
Date: 04-04-2014
Publisher: Elsevier BV
Date: 1990
Publisher: Elsevier BV
Date: 05-2007
Publisher: Thomas Telford Ltd.
Date: 05-2013
Abstract: Over the last two decades, self-compacting concrete mixes of varying strengths and performance have been proportioned on a trial-and-error basis using time-consuming laboratory tests, such as the slump cone, J-ring and L-box tests. An alternative method has recently been proposed for proportioning self-compacting high-performance concrete and self-compacting ultra-high performance concrete mixes with and without steel fibres (with characteristic cube strength between 140 and 160 MPa). This method is based on an extensive investigation of the flow characteristics of such mixes using computational simulations, thus avoiding time-consuming laboratory tests. However, the mixes proportioned using this method contained no coarse aggregate, which has a significant effect on the flow characteristics. This paper extends the method to the proportioning of self-compacting concrete mixes that contain traditional coarse aggregate and whose characteristic cube strengths vary between 35 and 100 MPa.
Publisher: Springer Science and Business Media LLC
Date: 05-1979
DOI: 10.1038/279169D0
Publisher: Thomas Telford Ltd.
Date: 12-2012
Abstract: A method is proposed for proportioning self-compacting high- and ultra-high-performance concrete mixes without steel fibres (SCHPC/SCUHPC) and with steel fibres (SCHPFRC/SCUHPFRC) which meet the standard flow and passing ability criteria without segregation. This method is based on an extensive investigation of the flow characteristics of self-compacting concrete (SCC) mixes using computational simulations. It provides an alternative tool to the heuristic mix design of SCC, thus avoiding expensive and time-consuming tests in laboratories or on site.
Publisher: Thomas Telford Ltd.
Date: 03-2013
Abstract: A Lagrangian particle-based method, the smooth particle hydrodynamics, is used to model the flow of ultra-high-performance, self-compacting concretes containing short steel fibres which behave like a non-Newtonian fluid described by a Bingham-type constitutive model. An incompressible smooth particle hydrodynamics method is used to simulate the flow after the kink in the shear stress against the shear strain rate constitutive equation is first appropriately smoothed out. One of the key factors that ensures the strength and durability of an ultra-high-performance concrete is the orientation of the fibres within the concrete structures cast from the ultra-high performance, self-compacting concretes. Therefore, this paper mainly focuses on developing a numerical methodology to determine how the fibres distribute and orient themselves during the ultra-high performance, self-compacting concrete flow. For this, a novel approach which can be easily combined with the continuum flow model developed in a previous study by the authors is proposed here. A number of numerical simulations are presented to demonstrate the effectiveness of the proposed methodology.
Publisher: Elsevier BV
Date: 1990
Publisher: Springer Science and Business Media LLC
Date: 10-1996
DOI: 10.1007/BF01196938
Publisher: Springer Science and Business Media LLC
Date: 2002
Publisher: Elsevier BV
Date: 12-1988
Publisher: Springer Science and Business Media LLC
Date: 02-2015
Publisher: Informa UK Limited
Date: 1980
Publisher: Elsevier BV
Date: 10-2000
Publisher: Informa UK Limited
Date: 13-05-2015
Publisher: Indian National Science Academy
Date: 06-2016
Publisher: Elsevier BV
Date: 07-2004
Publisher: Elsevier BV
Date: 07-2013
Publisher: Elsevier BV
Date: 05-2002
Publisher: Thomas Telford Ltd.
Date: 09-2005
DOI: 10.1680/MACR.2005.57.7.421
Abstract: Part II of this three-part paper deals with the assessment of the distribution of fibres in CARDIFRC ® , a class of high-performance short steel fibre-reinforced cementitious composites. The effect of the mixing procedure and of the shape of the object cast from CARDIFRC ® on the distribution of the fibres is assessed using both a nondestructive and a destructive technique. The non-destructive technique is based on computerised tomography imaging and the destructive technique on image analysis.
Publisher: Elsevier BV
Date: 08-1998
Publisher: Elsevier BV
Date: 05-2007
Publisher: American Society of Civil Engineers (ASCE)
Date: 2002
Publisher: Informa UK Limited
Date: 1978
Publisher: Elsevier BV
Date: 08-2013
Publisher: Springer Science and Business Media LLC
Date: 2001
Publisher: Informa UK Limited
Date: 1978
Publisher: AIP Publishing
Date: 06-06-2011
DOI: 10.1063/1.3597793
Abstract: We present a random number generation scheme that uses broadband measurements of the vacuum field contained in the radio-frequency sidebands of a single-mode laser. Even though the measurements may contain technical noise, we show that suitable algorithms can transform the digitized photocurrents into a string of random numbers that can be made arbitrarily correlated with a subset of the quantum fluctuations (high quantum correlation regime) or arbitrarily immune to environmental fluctuations (high environmental immunity). We demonstrate up to 2 Gbps of real time random number generation that were verified using standard randomness tests.
Publisher: Springer Science and Business Media LLC
Date: 15-12-2009
Publisher: Elsevier BV
Date: 1977
Publisher: Elsevier
Date: 2003
Publisher: Elsevier BV
Date: 1986
Publisher: Springer Science and Business Media LLC
Date: 09-04-2014
Publisher: Wiley
Date: 27-01-2004
DOI: 10.1002/NME.906
Publisher: No publisher found
Date: 1999
Publisher: Springer Science and Business Media LLC
Date: 02-2012
Publisher: The Royal Society
Date: 08-04-2001
Publisher: AIP Publishing
Date: 08-2006
DOI: 10.1063/1.2222078
Abstract: Two methods are presented to predict the effective conductivities of heterogeneous media containing discretely suspended particles. The particles have either graded anisotropy or a graded anisotropic interphase. A differential replacement procedure based on an energy equivalency condition is presented first to replace the graded anisotropic constituents by equivalent homogeneous isotropic particles. This allows many approximate schemes to be used to predict the effective conductivities of the heterogeneous media containing graded anisotropic constituents from the conductivity of the equivalent homogeneous particles. Next, the optimized upper and lower bounds on the effective conductivities of these heterogeneous media are presented by introducing comparison materials. It is shown that the DRP predictions are within these bounds for the considered media.
Publisher: Elsevier BV
Date: 05-1986
Publisher: Thomas Telford Ltd.
Date: 2016
Abstract: A wide range of normal-strength self-compacting concrete (SCC) mixes ranging in compressive strength from 30 to 80 MPa with a maximum aggregate size of 20 mm were prepared in the laboratory, and the time taken by the flow to reach the spread diameter of 500 mm (t 500 ) and to stop (t stop ) of each mix in the slump cone flow test were recorded. The entire test was then numerically simulated from the moment the cone was lifted until the flow stopped, using a three-dimensional meshless smoothed particle hydrodynamics computational approach, treating the SCC mix as a non-Newtonian Bingham fluid. The aim was to investigate the effect of the cone lift rate on the flow pattern and t 500 . The results demonstrate that an increase in the cone lift rate from 0·1 to 0·5–0·7 m/s (i.e. cone raised to a height of 300 mm in 3 to 0·6–0·43 s depending on the cube compressive strength) leads to a significant reduction in t 500 , but the rate of reduction slows considerably when the cone lift rate is increased beyond 0·5–0·7 m/s (i.e. cone raised to 300 mm in under 0·6–0·43 s). This bilinear reduction in t 500 with the increase in the cone lift rate was observed for all mixes having a cube compressive strength in the range 30–80 MPa.
Publisher: Thomas Telford Ltd.
Date: 09-2010
DOI: 10.1680/MACR.9.00149
Abstract: A class of ultra-high-performance fibre-reinforced cementitious composites (UHPFRCC) has been developed at Cardiff university and registered under the trade name CARDIFRC. The method of its production and its mechanical and fracture properties were reported previously in a series of papers in Magazine of Concrete Research. Here the results of recent fatigue and shrinkage tests on this material are reported. As with the mechanical and fracture properties, it is shown that an even and uniform distribution of fibres throughout the bulk of the material is crucial to its superior fatigue performance and to the reduction in the shrinkage strains.
Publisher: SAGE Publications
Date: 07-1995
DOI: 10.1177/002199839502901004
Abstract: The stress field in a cracked [(±θ°) n 2 /(90°) n2 ] s angle-ply fibre-reinforced composite laminate is solved by using Fourier transforms and dual integral equation formulation. The (90°) n 1 sublaminate is characterized by periodically distributed multiple transverse intralaminar cracks. The stress intensity factor at each crack tip and the crack-induced interfacial stresses are calculated. Both are found to be significantly influenced by the closeness of the crack tip to the bimaterial interface, the crack spacing and ply angle θ of the constraining sublaminates. The variation of the SIF explains the physical mechanisms behind constrained cracking in composite laminates, while the perturbation of the interfacial stress field caused by the transverse cracks reveals that as the cracks approach the bimaterial interface, there is a considerable increase in interfacial stresses. The crack driving force and the crack-induced interfacial stresses decrease considerably when the multiple cracks are densely distributed. From the design point of view, the results also suggest that by a proper choice of ply angles in angle-ply laminates the crack growth in the in idual lamina can be greatly retarded.
Publisher: Springer Science and Business Media LLC
Date: 11-1985
DOI: 10.1007/BF00552405
Publisher: No publisher found
Date: 2003
Publisher: Springer Science and Business Media LLC
Date: 08-1995
DOI: 10.1007/BF00042827
Publisher: Springer Science and Business Media LLC
Date: 10-2004
Publisher: Elsevier BV
Date: 12-1993
Publisher: Springer Science and Business Media LLC
Date: 04-04-2017
Publisher: Elsevier BV
Date: 03-2013
Publisher: Elsevier BV
Date: 1995
Publisher: Springer Science and Business Media LLC
Date: 27-05-1997
Publisher: Springer Science and Business Media LLC
Date: 27-05-1997
Publisher: Elsevier BV
Date: 07-1998
Publisher: Wiley
Date: 1982
Publisher: Elsevier BV
Date: 12-2004
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2017
Publisher: Elsevier BV
Date: 07-2005
Publisher: Elsevier
Date: 2003
Publisher: Elsevier BV
Date: 03-1999
Publisher: ASME International
Date: 12-1994
DOI: 10.1115/1.2901547
Abstract: Materials with negative Poisson ’s ratio are peculiar in that they expand laterally when stretched. Ex les of such type of behavior have been discovered with foams by Lakes (1987) however, it is only recently that isotropic materials with negative Poisson’s ratio have been shown by Milton (1992) to exist within the framework of classical theory of elasticity. In this Note, we demonstrate qualitatively that a composite material with a reentrant microstructure can also have a negative Poisson’s ratio, even though the composite may be isotropic owing to a completely random distribution of the microstructure.
Publisher: Elsevier BV
Date: 1979
Publisher: American Society of Civil Engineers (ASCE)
Date: 1983
Publisher: Elsevier BV
Date: 12-2012
Publisher: No publisher found
Date: 1977
Publisher: American Society of Civil Engineers (ASCE)
Date: 2010
Publisher: The Royal Society
Date: 06-09-2013
Abstract: We report that the cells in a natural honeybee comb have a circular shape at ‘birth’ but quickly transform into the familiar rounded hexagonal shape, while the comb is being built. The mechanism for this transformation is the flow of molten visco-elastic wax near the triple junction between the neighbouring circular cells. The flow may be unconstrained or constrained by the unmolten wax away from the junction. The heat for melting the wax is provided by the ‘hot’ worker bees.
Publisher: Springer Science and Business Media LLC
Date: 08-1995
DOI: 10.1007/BF01743692
Publisher: Wiley
Date: 02-1995
Publisher: Elsevier BV
Date: 06-2006
Publisher: Elsevier BV
Date: 02-1993
Publisher: Thomas Telford Ltd.
Date: 06-1987
Publisher: Springer Science and Business Media LLC
Date: 1991
DOI: 10.1007/BF00879045
Publisher: Elsevier BV
Date: 1987
Publisher: Elsevier BV
Date: 09-1982
Publisher: Elsevier BV
Date: 1990
Publisher: Elsevier BV
Date: 2007
Publisher: Springer Science and Business Media LLC
Date: 08-1995
DOI: 10.1007/BF01743691
Publisher: Springer Science and Business Media LLC
Date: 08-1994
DOI: 10.1007/BF01742926
Publisher: American Society of Civil Engineers (ASCE)
Date: 08-2003
Publisher: Elsevier BV
Date: 10-2001
Publisher: Elsevier BV
Date: 1977
Publisher: Springer Science and Business Media LLC
Date: 1999
Publisher: Elsevier BV
Date: 06-1999
Publisher: Elsevier BV
Date: 02-1996
Publisher: The Royal Society
Date: 29-11-1979
Abstract: The compression cracking theory of glassy materials recently proposed by Kendall ( Proc. R. Soc. Lond. A 361, 245 (1978)) is shown to predict some physically inconsistent results. A simple modification of this otherwise elegant theory is proposed. The modified theory, like the Griffith theory for tension cracks, predicts an essentially unstable crack propagation process in compression — a result observed in Kendall’s experiments, but not explained by his theory. It is shown that the failure load in compression does not approach infinity as the width of the punch or platen approaches that of the test specimen. It is also found that, besides the platen geometry, the length of the precrack plays a very important role in controlling the failure mode transition from compression cracking to yielding under platen and to buckling. The theoretical predictions are verified by experimental investigation.
Publisher: Elsevier BV
Date: 1980
Publisher: Informa UK Limited
Date: 1983
Publisher: Elsevier BV
Date: 12-1997
Publisher: Elsevier BV
Date: 02-2012
Publisher: Elsevier BV
Date: 10-1996
Publisher: Elsevier BV
Date: 12-1999
Publisher: Elsevier BV
Date: 02-2003
Publisher: Informa UK Limited
Date: 17-11-2014
Publisher: Springer Netherlands
Date: 2007
Publisher: Thomas Telford Ltd.
Date: 06-2011
DOI: 10.1680/STBU.9.00038
Abstract: A series of tests on filigree slab joints was performed with the aim of assessing whether such joints can be reliably used in the construction of two-way spanning reinforced concrete slabs. The test results were compared with code requirements. Adequate joint performance is shown to be achievable when the joints are appropriately detailed. Further research is recommended for the formulation of a more generic understanding when the design parameters are varied from those studied in this work.
Publisher: Elsevier BV
Date: 10-1986
Publisher: The Royal Society
Date: 08-01-1994
Abstract: In [( ± θ ) n 2 /(90°) n 1 /( ǂ θ ) n 2 ] fibre-reinforced composites, the outer (± θ ) n 2 sublaminates are known to act as crack arrestors, i. e. to reduce the stress intensity factors at the tips of a crack in the central (90°) n 1 layer in all three modes of loading. The degree of reduction depends on the stiffness of the plies, the ply angle θ and the thickness of the outer sublaminates. However, although the stress intensity factor decreases, the crack-induced largest interfacial principal tensile stress increases. The situation is particularly severe under transverse mode II loading, inevitably resulting in interfacial delamination. The aim of this paper is to choose the design variables of the laminate, namely the ply angle θ , relative ply stiffness and thickness, in such a way as to minimize the stress intensity factor at a crack tip in the (90°) n 1 layer without exceeding the interfacial bond strength. A constraint is also placed on the minimum flexural stiffness of the laminate. An alternative optimization problem in which the largest interfacial principal tensile stress is minimized subject to a limit on the stress intensity factor is also formulated and solved. The above optimization problem is solved in two stages. First, an analysis of the non-homogeneous, anisotropic medium containing a flaw is performed within the bounds of the classical lamination theory and fracture mechanics. This allows development of mathematical expressions relating the stress intensity factor in the central (90°) n 1 layer and the interfacial tensile stress to the sublaminate thickness and stiffness and the ply angle θ . These expressions are highly complicated, precluding a completely analytical approach to the calculation of design sensitivities. In the next stage the optimization problem is reduced to a nonlinear mathematical programming one, whose solution is attempted by several techniques. The sensitivities with respect to the design variables required in these techniques are calculated by a mixed analytical/numerical approach.
Publisher: Elsevier BV
Date: 10-2013
Publisher: Pleiades Publishing Ltd
Date: 11-2012
Publisher: Wiley
Date: 18-05-2015
DOI: 10.1113/JP270085
Publisher: Elsevier BV
Date: 05-1997
Publisher: Elsevier BV
Date: 11-2013
Publisher: Wiley
Date: 26-08-2010
Publisher: Elsevier BV
Date: 04-1991
Publisher: Informa UK Limited
Date: 1981
Publisher: IOP Publishing
Date: 15-06-2006
DOI: 10.1088/0957-4484/17/14/007
Abstract: Nano-onions are ellipsoidal or spherical particles consisting of a core surrounded by concentric shells of nanometre size. Nano-onions produced by self-assembly and colloidal techniques have different structures and compositions, and thus differ in the state of strains. The mismatch of the thermal expansion coefficients and lattice constants between neighbouring shells induces stress/strain fields in the core and shells, which in turn affect their physical/mechanical properties and/or the properties of the composites containing them. In this paper, the strains in embedded and free-standing nano-onions with uniform and non-uniform compositions are studied in detail. It is found that the strains in the nano-onions can be modified by adjusting their compositions and structures. The results are useful for the band structure engineering of semiconductor nano-onions.
Publisher: Springer Science and Business Media LLC
Date: 2001
Publisher: Elsevier BV
Date: 1991
Publisher: Informa UK Limited
Date: 1986
Publisher: Mathematical Sciences Publishers
Date: 28-06-2011
Publisher: The Royal Society
Date: 08-01-1987
Abstract: The paper presents an exploration by numerical means of the problem of finding the optimum section of a beam designed to have given torsional ( J 0 ) and flexural rigidity ( I 0 ). The section is defined by its conformal transformation on to a unit circle and the corresponding equations for the optimization problem are derived. The special case when the conformal transformation is given as a truncated power series ( N terms of the form 3 n - 2, n = 1, 2,...), leads to a problem of nonlinear programming. This is solved numerically for 1.2 J 0 / I 0 2, between the extremes of J 0 / I 0 = 1.2, which is known to give an equilateral triangle and J 0 / I 0 = 2, which is solved by a circle. Results for N = 24 give solutions that are convex for 1.5 J 0 / I 0 2, but show concavity for J 0 / I 0 = 1.4 and lower values. Results for N = 36 give confirmation and almost eliminate concavity at J 0 / I 0 = 1.4. However, because this last result required 18 h of computer time, it was not possible to extend the calculations to larger values of N . The results obtained are satisfactory down to J 0 / I 0 = 1.5 and suggest that the solutions may be convex shapes for the complete range. An approximate solution based on the lines of shearing stress for the torsion of an equilateral triangle is shown to give close agreement with the numerical results and thus to constitute a good practical upper-bound solution of the problem.
Publisher: American Society of Civil Engineers (ASCE)
Date: 06-1985
Publisher: Springer Science and Business Media LLC
Date: 31-12-2015
Publisher: Elsevier BV
Date: 1989
Publisher: Springer Science and Business Media LLC
Date: 03-2008
Publisher: AIP Publishing
Date: 03-1976
DOI: 10.1063/1.322713
Abstract: A study is made of the mobility of planar arrays of dislocations of Burgers vector b that are either separated into their component partials or are of the superlattice type and are contained in an internally stressed solid, the stress being generated by a preexisting coplanar obstacle dislocation of Burgers vector mb. The aim here is to estimate the effect of the internal stress and the fault energy on the separation between the components of the first discrete dislocation since the latter plays an important part in a wide range of physical phenomena. All the mobile complete dislocations except the leader are either smeared into a continuous distribution or are replaced by a superdislocation of appropriate Burgers vector. These two approaches, which lead to lower and upper bounds for the separation distance, are shown to give fairly close results for small m.
Publisher: The Royal Society
Date: 29-07-1975
Abstract: A formal definition of the flow stress of a metal is established rigorously from first principles for a certain model by studying the stability of equilibrium of the leader in a group of n ( n large) coplanar screw dislocations with Burgers vector b, moving on a plane a distance h from a non-coplanar locked dislocation with Burgers vector mb ( m n ) under the action of an applied shear stress p yz = o.A ‘ characteristic equation’ of the model is set up and the onset of instability of the leader is identified with the bifurcation of its equilibrium state, which is predicted by the Routh-Hurwitz theorem, well-known in the theory of stability. As an aid in simplifying this process recourse is had to another well-known the orem -that due to Liénard & Chipart. The applied shear stress required to achieve this unstable state is specified within certain bounds. Since these bounds are very close to each other, especially for small m , the critical flow stress can be estimated accurately. It is shown that the flow stress is closer to the lower bound obtained previously and that the superdislocation approach overestimates the critical stress. The paper also discusses certain implications of the present work.
Publisher: American Physical Society (APS)
Date: 13-02-2007
Publisher: Informa UK Limited
Date: 12-1995
Publisher: Wiley
Date: 06-2004
DOI: 10.1002/NAG.361
Abstract: A new retrofitting technique based on a material (CARDIFRC ® ) compatible with concrete has been developed at Cardiff University. It overcomes some of the problems associated with the current techniques based on externally bonded steel plates and FRP (fibre‐reinforced polymer) laminates which are due to the mismatch of their tensile strength and stiffness with that of the concrete structure being retrofitted. CARDIFRC ® is a high‐performance steel‐fibre reinforced cementitious composite characterized by high tensile/flexural strength and high energy‐absorption capacity (i.e. ductility). The special characteristics of CARDIFRC ® make it particularly suitable for repair, remedial and upgrading activities (i.e. retrofitting) of existing concrete structures. It has been shown that damaged reinforced concrete beams can be successfully strengthened and rehabilitated in a variety of different retrofit configurations using pre‐cast CARDIFRC ® strips adhesively bonded to the prepared surfaces of the damaged beams. To predict the moment resistance/load carrying capacity of the beams retrofitted in this manner two analytical models are described in the present paper. The results of the analytical models are found to be in very good agreement with the test results. Copyright © 2004 John Wiley & Sons, Ltd.
Publisher: Elsevier BV
Date: 12-1993
Publisher: Elsevier BV
Date: 06-2008
Publisher: Elsevier BV
Date: 11-1999
Publisher: The Royal Society
Date: 04-04-1978
Abstract: The stress relaxation process from the tips of doubly-periodic (rectangular and diamond-shaped) arrays of slit-like cracks contained in an infinite elastic solid is studied under both plane and anti-plane strain conditions. The displacement discontinuities due to slit-like cracks are represented by distributions of suitable dislocations. The latter are determined from singular integral equations resulting from the satisfaction of the traction-free conditions at the crack faces. In the absence of a closed form solution, these equations are solved numerically after expanding the non-singular part of the kernel in a series of Chebyshev polynomials. Results are presented for the extent of spread of plasticity from each of the cracks and for the crack-tip opening displacement as functions of the horizontal and vertical crack spacings and the externally applied stress and discussed from the point of fracture initiation from an array of stress concentrations. It is shown that an array of cracks can have a detrimental or beneficial effect on the fracture characteristics of the solid depending on the far-field state of stress. Moreover, the crack-tip opening displacement is practically independent of the horizontal separation of cracks for small values of the distance of vertical separation and depends only on the latter.
Publisher: Copernicus GmbH
Date: 16-05-2018
DOI: 10.5194/HESS-22-2903-2018
Abstract: Abstract. Rapid population and economic growth in Southeast Asia has been accompanied by extensive land use change with consequent impacts on catchment hydrology. Modeling methodologies capable of handling changing land use conditions are therefore becoming ever more important and are receiving increasing attention from hydrologists. A recently developed data-assimilation-based framework that allows model parameters to vary through time in response to signals of change in observations is considered for a medium-sized catchment (2880 km2) in northern Vietnam experiencing substantial but gradual land cover change. We investigate the efficacy of the method as well as the importance of the chosen model structure in ensuring the success of a time-varying parameter method. The method was used with two lumped daily conceptual models (HBV and HyMOD) that gave good-quality streamflow predictions during pre-change conditions. Although both time-varying parameter models gave improved streamflow predictions under changed conditions compared to the time-invariant parameter model, persistent biases for low flows were apparent in the HyMOD case. It was found that HyMOD was not suited to representing the modified baseflow conditions, resulting in extreme and unrealistic time-varying parameter estimates. This work shows that the chosen model can be critical for ensuring the time-varying parameter framework successfully models streamflow under changing land cover conditions. It can also be used to determine whether land cover changes (and not just meteorological factors) contribute to the observed hydrologic changes in retrospective studies where the lack of a paired control catchment precludes such an assessment.
Publisher: The Royal Society
Date: 17-01-2006
Abstract: In this brief communication, we identify intrinsic length scales of several physical properties at the nano-scale and show that, for nano-structures whose characteristic sizes are much larger than these scales, the properties obey a simple scaling law. The underlying cause of the size-dependence of these properties at the nano-scale is the competition between surface and bulk energies. This law provides a yardstick for checking the accuracy of experimentally measured or numerically computed properties of nano-structured materials over a broad size range and can thus help replace repeated and exhaustive testing by one or a few tests.
Publisher: Springer Science and Business Media LLC
Date: 06-2004
Publisher: Elsevier BV
Date: 07-1992
Publisher: The Royal Society
Date: 08-09-1983
Abstract: The paper presents the maximum strength/stiffness design of tension/compression and flexural members under the influence of their self-weight as well as given external forces. In the maximum strength design, all cross sections of the member attain the maximum allowable stress for the material the design is therefore also referred to as the uniform or constant maximum strength design. In the maximum stiffness design, the maximum longitudinal or transverse displacement is minimized. It is assumed that the location of the maximum displacement is known. In this sense, the paper considers only strict minimization problems. In several cases analytical solutions are obtained. Where this was not possible, solutions derived by successive approximation are given. The variational problem corresponding to this optimization problem has several unique features which are not commonly encountered in the absence of self-weight.
Publisher: Mathematical Sciences Publishers
Date: 05-2009
Publisher: Elsevier BV
Date: 1985
Publisher: Informa UK Limited
Date: 1987
Publisher: Elsevier
Date: 2009
Publisher: American Physical Society (APS)
Date: 17-11-2006
Publisher: Elsevier BV
Date: 08-2000
Publisher: Wiley
Date: 28-05-2006
DOI: 10.1002/NME.1601
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 03-1993
Publisher: Elsevier BV
Date: 11-2003
Publisher: Wiley
Date: 30-07-2003
Publisher: Informa UK Limited
Date: 04-1996
Publisher: Elsevier BV
Date: 03-2008
Publisher: Elsevier BV
Date: 1988
Publisher: Informa UK Limited
Date: 1987
Publisher: SAGE Publications
Date: 1995
DOI: 10.1177/105678959500400106
Abstract: A doubly-periodic array of coplanar circular cracks is used as a micromechanical model for crack bridging due to unbroken ligaments between the crack faces and for a localized deformation band. Two complementary approaches are described for determining the effective spring constant for the unbroken ligaments and the root-mean-square average of the stress intensity factor for the microcracks. The first approach exploits the periodicity to formulate a computationally efficient numerical solution which can be considered to provide exact results for the specific configuration of a doubly-periodic array. The second approach is similar in spirit to the self-consistent procedure for deriving the effective moduli of two-phase composites and leads to explicit analytical approximations. The results obtained for the spring constant by these two approaches are in good agreement over the range of cracked area fraction for which the micromechanical model is most reliable a consistent difference, but a similar trend, is noted in the results obtained for the stress intensity factor. The relative merits and limitations of the two approaches are briefly discussed.
Publisher: Elsevier
Date: 1999
Publisher: AIP Publishing
Date: 12-1975
DOI: 10.1063/1.322190
Abstract: Very simple procedures are used to calculate the upper and lower bounds for the applied stress required for the leading extended (superlattice) dislocation in a group of n coplanar screw dislocations of like sign with Burgers vector b to bypass a noncoplanar perfect screw dislocation with Burgers vector mb (m≪n). Since these bounds are very close to each other, especially for small m, the long-range flow stress can be estimated accurately. The critical spacing between the parallel slip planes at the moment of bypass is determined in a natural way by studying the stability of equilibrium of the leader in the mobile group. Particular attention is paid to the effect of the stacking-fault (the antiphase boundary) energy and the barrier strength m on the bypass stress.
Publisher: Elsevier BV
Date: 1991
Publisher: American Physical Society (APS)
Date: 05-05-2006
Publisher: Elsevier BV
Date: 11-2000
Publisher: Wiley
Date: 1995
Publisher: Springer Science and Business Media LLC
Date: 04-2015
Publisher: Elsevier BV
Date: 11-1986
Publisher: Elsevier BV
Date: 06-1995
Publisher: Springer Science and Business Media LLC
Date: 06-1994
DOI: 10.1007/BF01743718
Publisher: ASME International
Date: 12-1985
DOI: 10.1115/1.3169155
Abstract: The problem of the stress-field of an elliptic inhomogeneity that has debonded over an arc of its common boundary with a different elastic material is studied under plane-strain conditions. Eshelby’s method of equivalent inclusion is employed. The “equivalence relation” is solved by a method that is applicable to any general plane-strain situation. Further, the relative displacements of the debonded faces are derived from the discontinuous behavior of in idual terms associated with the derivatives of Green’s function. Numerical results are presented for the stress-intensity factors at the tips of the debonded arc and the relative displacements across the debond.
Publisher: The Royal Society
Date: 08-03-1994
Abstract: In a recent paper (referred to as I) we obtained inter alia , the stress and displacement fields at the tips of a transverse crack in an isotropic medium sandwiched between orthotropic media under in-plane loading (mode II). The crack was lying wholly within the isotropic medium so that the singularity at the crack tip was of the usual inverse square root type. In this paper, the analysis is extended to the case when the tip of the crack terminates on the transversely isotropic-orthotropic bimaterial interface and the nature of the singularity at the crack tip depends on the elastic properties of both media. The analysis is performed for both inplane (mode II) and out-of-plane (mode III) shear loading. General solutions are obtained for the crack tip stress singularities and corresponding stress intensity factors, together with the influence of the elastic properties and geometry of the media upon the stress field. These solutions are specialized to the limiting case when the crack terminates on the interface between dissimilar isotropic media in order to demonstrate consistency with published results. As in I, the solutions are used to investigate the influence of ply angle θ upon the stress singularities in [± θ /90°] s fibre-reinforced composite laminates. For this analysis, the outer angle-ply sublaminates are treated macroscopically as homogeneous orthotropic media whose elastic constants are obtained using the classical lamination approximation. Calculations are also carried out to study the variation of stress intensity factors with the ply angle and outer sublaminate thickness.
Publisher: Informa UK Limited
Date: 1985
Publisher: Elsevier BV
Date: 07-2011
Publisher: Springer Science and Business Media LLC
Date: 06-1994
DOI: 10.1007/BF01743720
Publisher: Springer Science and Business Media LLC
Date: 09-1993
DOI: 10.1007/BF00053312
Publisher: Elsevier BV
Date: 1989
Publisher: Elsevier BV
Date: 11-1995
Publisher: Elsevier BV
Date: 1993
No related grants have been discovered for Bhushan Karihaloo.