Elasticity Research Articles

Construction of a quantitative structure-permeability relationship (QSPR) for the transdermal delivery of NSAIDs

In this study, an empirical model of the quantitative structure-permeability relationship (QSPR) of the transdermal delivery of non-steroidal anti-inflammatory drugs (NSAIDs) was constructed in an attempt to predict the permeability coefficients ( k P). Thirteen model NSAIDs were selected, and their in vitro permeation through the full skin of nude mice was examined. The biological parameters of transepidermal water loss (TEWL), hydration content (HD), lipid content (SB), resonance running time (RVM), and elasticity (EL) were measured. The permeability coefficients so obtained were grouped into three datasets of all model drugs and those drugs with clog P or log K o/w values of > 2 and < 2; these datasets were regressed with respect to the physical characters of molecular weight (MW) and polarity factor ( clog P or log K o/w) or the solubility parameter ( δ) of the model drugs rationally chosen to replace the polarity factor with or without taking into consideration the biological parameters of the skin. Results demonstrated that δ could be greatly improved compared to clog P and log K o/w in the regression with an adjusted R 2 of > 0.90 using the dataset of those drugs with clog P or log K o/w values of < 2, regardless of whether or not biological parameters were taken into consideration. This indicates that δ might rationally be a more-appropriate drug parameter for predicting the skin permeability of NSAIDs for transdermal delivery. A plot of observed k P versus predicted k P values by this simple empirical model of QSPR was validated to demonstrate the predictive capability of k P for transdermal delivery. In conclusion, an empirical model of QSPR to predict k P based on the hydrophilicity of the model drugs was statistically improved with δ and by taking the biological parameters of the skin into consideration.

On the derivation of linear elasticity from atomistic models

We derive linear elastic energy functionals from atomistic models as a -limit when the number of atoms tends to infinity, respec tively, when the interatomic distances tend to zero. Our approach generalizes a recent result of Braides, Solci and Vitali (2). In particular, we study mass spring models with full nearest and next-to-nearest pair interactions. We also consider boundary value problems where a part of the boundary is free. 1. Introduction. The passage from discrete atomic models to continuum theories is an active area of current research in continuum mechanics. For elastic systems one usually refers to the Cauchy-Born rule to obtain macroscopic energy densities from atomistic interaction functionals. The Cauchy-Born rule states that - roughly speaking - each individual atom follows the macroscopic deformation gradient and in particular does not take into account fine scale oscillations on the microscopic scale. For a two-dimensional mass spring model, the validity of the Cauchy-Born rule for deformations close to a rigid motion has been proved by Friesecke and Theil in (8). Their result has been generalized to arbitrary dimensions by Conti, Dolzmann, Kirchheim and Muller in (3). If the deformation gradients are very close to SO(d), the set of orientation pre- serving rigid motions, then we expect linear elasticity theory to apply. This relation has been made rigorous by Dal Maso, Negri and Percivale who derive the energy functional of linear elasticity as a -limit of nonlinear el asticity for small displace- ments in (5). (See also the author's article (10) for a strong convergence result for the associated minimum problems.) Recently it has been noted that one can derive linear elasticity functionals directly from certain atomistic pair potentials: For a special class of pair interaction models Braides, Solci and Vitali prove -convergence of the discre te energy functionals to the energy functional of an associated continuum linear elasticity energy functional (see (2)). In this set-up one has to deal with two small parameters e and δ measuring the typical interatomic distance and the local distance of the deformations from the set of rigid motions, respectively. The aim of the present article is to extend these results in three directions. Firstly, we will drop the assumption that atoms are allowed to interact only along

Croissance en diamètre et caractérisation de la limite entre bois juvénile et bois adulte chez l’okoumé des plantations au Gabon

The fast-growing hardwood, okoume (Aucoumea klaineana Pierre), is a major forest species in Gabon and is used principally for making plywood, but research into the growth and quality of this wood is scanty. Trees from natural forests are favoured for production, yet little information exists on wood characteristics from plantation trees. Therefore, we carried out a dendrochronological study along with measurements of wood lon- gitudinal modulus of elasticity (EL), density (Dw), dimensional stability parameters (longitudinal, radial and tangential shrinkage and fibre saturation point) and fibre cell morphology to determine if these properties were related to age in trees from two plantations. We then used segmented regression analysis to define the limit (breakpoint) between juvenile (JW) and adult wood (AW). Using monthly precipitation data, we were able to determine that one growth ring is formed per year, composed of a large light coloured ring formed during the long rainy season and a thick, dark band formed during the major dry season. However, thinner bands, analogous to false rings, may also form during the short dry and short rainy seasons. Ring width decreases from the pith to the bark, and the breakpoint between JW and AW was at 19 years old when trees from both plantations were pooled together. No differences in Dw or radial and tangential shrinkage occurred with cambial age. EL increased significantly up to the cambial age of 12-14 years, after which the increase with age was only slight and no breakpoint between JW and AW was found. With regard to mean longitudinal shrinkage, AW was found to form after the age of 13 years but fibre cell length was significantly longer after the age of 14.5 and 20 years, depending on the plantation of origin. Therefore, the boundary between JW and AW in plantation grown okoume occurs between the ages of 13 and 20 years, depending on the characteristic examined.

Measurement of the dynamic modulus of elasticity of wood panels

This study investigated the dynamic modulus of elasticity (DMOE) of wood panels of Fraxinus mandshurica, Pinus koraiensis, and Juglans mandshurica using the natural frequency measurement system of fast Fourier transform (FFT). The results were compared with the static modulus of elasticity (E S) tested by a mechanical test machine. The results show a significant correlation between E S, transverse vibration DMOE (E F), and longitudinal vibration DMOE (E L). For all of these species, the correlation between E S, E F and E L is more significant than the individual species, which indicated that the FFT method is universal. The correlations between E S and sample’s density (ρ) are significant, but the correlation coefficient of E S and ρ is lower than those between E F, E L and E S. The E S of wood is more accurately tested by the analysis based on FFT measurement than by the estimation based on density.

Estimation ofPinus radiata D. Don clear wood properties by near-infrared spectroscopy

The use of calibrated near-infrared (NIR) spectroscopy for predicting of a range of solid wood properties is described. The methods developed are applicable to large-scale nondestructive forest resource assessment and to tree breeding and silviculture programs. A series ofPinus radiata D. Don (radiata pine) samples were characterized in terms of density, longitudinal modulus of elasticity (E L), and microfibril angle (MFA). NIR spectra were obtained from the radial/longitudinal face of each sample and used to generate calibrations for the measured physical properties. The relations between laboratory-determined data and NIR fitted data were good in all cases, with coefficients of determination (R 2) ranging from 0.68 for 100/MFA to 0.94 for densitystrip. A good relation (R 2 = 0.83) was also obtained forE L estimated using data collected by SilviScan-2. The finding suggests that an NIR instrument could be calibrated to estimate theE L of increment cores based on SilviScan data. In view of the rapidly expanding range of applications for this technique, it is concluded that appropriately calibrated NIR spectroscopy could form the basis of a testing instrument capable of predicting a range of properties from a single spectrum obtained from the product or from the raw material.

Estimation of wood stiffness of increment cores by near-infrared spectroscopy

The use of calibrated near-infrared (NIR) spectroscopy for predicting the radial variation of the longitudinal modulus of elasticity (EL) of increment cores is described. Sets of Eucalyptus delegatensis R.T. Baker (alpine ash) and Pinus radiata D. Don (radiata pine) samples were characterized in terms of EL(SS) (estimated stiffness based on a combination of SilviScan-2 diffractometric data and measured density (R. Evans and J. Ilic. 2001. For. Prod. J. 51(3): 53–57)). NIR spectra, obtained from the radial–longitudinal face of each sample, were used to develop EL(SS) calibrations for the E. delegatensis and P. radiata sample sets and the two sets combined. The relationships between laboratory-determined EL(SS) and NIR-fitted EL(SS) were good in all cases. EL(SS) was estimated in separate test sets and found to correlate well with measured EL. NIR spectra were obtained in 15-mm sections from the radial–longitudinal face of two intact P. radiata increment cores. EL(SS) of each section was estimated using the P. radiata and the combined P. radiata and E. delegatensis calibrations. NIR estimates of EL(SS) were in good agreement with SilviScan-2 determined stiffness indicating that NIR spectroscopy can be successfully used to estimate radial variation in wood stiffness of increment cores.

Estimation of Eucalyptus delegatensis wood properties by near infrared spectroscopy

The use of calibrated near infrared (NIR) spectroscopy for the prediction of a range solid wood properties is described. The methods developed are applicable to large-scale nondestructive forest resource assessment and to tree breeding and silvicultural programs. A series of Eucalyptus delegatensis R.T. Baker (alpine ash) samples were characterized in terms of density, longitudinal modulus of elasticity (EL), microfibril angle (MFA), and modulus of rupture (MOR). NIR spectra were obtained from the radial–longitudinal face of each sample and used to generate calibrations for the measured physical properties. The relationships were good in all cases, with coefficients of determination ranging from 0.77 for MOR through 0.90 for EL to 0.93 for stick density. In view of the rapidly expanding range of applications for this technique, it is concluded that appropriately calibrated NIR spectroscopy could form the basis of a "universal" testing instrument capable of predicting a wide range of product properties from a single type of spectrum obtained from the product or from the raw material.

The effects of underfill and its material models on thermomechanical behaviors of a flip chip package

In this paper, the effects of underfill on thermomechanical behavior of two types of flip chip packages with different bumping size and stand-off height were investigated under thermal cycling both experimentally and two-dimensional (2-D) finite element simulation. The materials inelasticity, i.e., viscoelasticity of underfill U8437-3 and viscoplasticity of 60 Sn40 Pb solder, were considered in the simulations. The results show that the use of underfill encapsulant increases tremendously (/spl sim/20 times) the thermal fatigue lifetime of SnPb solder joint, weakens the effects of stand-off height on the reliability, and changes the deformation mode of the package. It was found that the thermal fatigue crack occurs in the region with maximum plastic strain range, and the Coffin-Manson type equation could then be used for both packages with and without underfill. Solder joint crack initiation occurred before delamination when using underfill with good adhesion (75 MPa) and the underfill delamination may not be a dominant failure mode in the present study. The interfacial stresses at the underfill/chip interface were calculated to analyze delamination sites, which agree with the results from acoustic image. Moreover, the effects of material models of underfill, i.e., constant elasticity (EC) and temperature dependent elasticity (ET) as well as the viscoelasticity (VE), on the thermomechanical behaviors of flip chip package were also studied in the simulation. The VE model gives comparatively large plastic strain range and large displacements in the shear direction, as well as decreased solders joint lifetime. The ET model gives similar results as the VE model and could be used instead of VE in simulations for the purpose of simplicity.

Determining a Pavement Modulus from Portable FWD Testing

Abstract This paper assumes that there is room for an additional measuring device that, on the one hand, will serve mainly as an in situ device not requiring complicated back-calculation procedures and, on the other hand, will not involve large volumes of in situ materials as presently required by the falling weight deflectometer (FWD). Such a device is the new portable FWD (PFWD). Comparative tests with this device show no significant correlation between the central deflection measurements taken on the asphalt surface and the corresponding Benkelman-beam-measured deflections. This is due to the fact that the PFWD device “senses” only the upper layers of the pavement, down to no more than a small thickness, whereas the two other devices “sense” all pavement layers down to the subgrade medium, as well. A composite-pavement modulus of elasticity (Ep) can still be derived from the PFWD measurements, but only with the performance of additional measurements on the asphalt surface, followed by coring of the asphalt layers down to their far bottom. In this way, the above Ep value is calculated for the full structural thickness and for the standard radius of the contact area obtained from the PFWD testing, i.e., the modulus of elasticity (EA) of the asphalt layers and the modulus of elasticity (EG) of the granular layers. A comparison of the above Ep values calculated from the PFWD outputs, with the values derived from the conventional FWD measurements, led to the introduction of a correction factor that varies with the ratio of the thickness of the asphalt layers to their elastic modulus. The lower the ratio, the closer the correction factor approaches the value of 1.0.

Application of Surface Display into Shape Forming Task

The sensation of Touch and force is generated or conducted through the phenomenon of contact. This fact make us aware of a new force feedback method, which was named the concept of Surface Display. In this concept, we are remarking not on the force between the user and the object but on the surface and existence of the object. The force feedback device based on this concept presents the surface of an object, the user interact with surface. Force is caused only as a result and it is measured by the device for the simulation of the behavior of the object. In this paper, the application of the device into a shape forming task is discussed. We have developed a kind of the virtual clay modeling environment, in which the shape of the surface can be changed by pushing directly on the surface. Sensation of making contact with the surface and the sensation of force caused by the elas ticity of the clay is fedback by using the device. From an experiment in the environment, the importance and effectiveness of force feedback were made clear.

BATNEEC: THE ECONOMICS OF TECHNOLOGY-BASED ENVIRONMENTAL STANDARDS, WITH A UK CASE ILLUSTRATION

All environmental standards, however implement ed, impose costs on the regulated party. This is true of emission or ambient quality standards, environ mental taxes, tradable emission permits, and stand ards basedon the 'best available technology' (BAT). Not surprisingly, therefore, all environmental reg ulation is, to a greater or lesser degree, the outcome of some political balancing of costs and benefits. Part, at least, of the initial cost is passed on to final consumers (the extent depends on the price elastic ity of demand), which is consistent with thepollut er pays principle (OECD, 1975). The costs of regulation are therefore borne by society as a whole. The benefits of regulation are also shared by society as a whole, although some groups in society may be efit more than others and, where trans-boundary pollution is involved, different countries will re ceive variable benefits.

THE IMPORTANCE OF BEING UNIMPORTANT: MARSHALĽS THIRD RULE OF DERIVED DEMAND

J. R. Hicks's revision of A. Marshall's third rule states that as the price elasticity of demand for a pr oduct is greater/less than the elasticity of substitution, the elasti city of derived demand for a factor of production is positively/negat ively related to the share of the factor in total costs. A simple, cl ear, economic explanation of Hicks's revision is given. The very conf used debate on Marshall's third rule and Hicks's revision is ex-amine d and clarified. Copyright 1988 by Scottish Economic Society.

Fiber Orientation in Fiber Suspension Flow

We investigate experimentally the orientation of the fibers in the flow of both Newtonian and viscoelastic fluids through a parallel plate channel and a channel with an abrupt contraction. We obtain quantitatively the development of the fiber orientation from initial orientation to stable equilibrium orientation along the channel and the variation of orientation in the direction of the channel width. We also study, in the flow through a channel with an abrupt contraction, the fiber orientation along the stream lines which can be found as the path lines of small tracer particles suspended in the fluid. The relation between the fiber orientation and the velocity field is examined. The effects of shear thinning and elasticity on the fiber orientation are also discussed by comparing the results in the viscoelastic flow with those in the Newtonian flow. The conclusions are summarized as follows : (1) The fibers orient well along the stream lines with an increase in viscoelasticity in both a parallel plate channel and a channel with an abrupt contraction. This phenomenon is essentially equivalent to the phe nomenon that a slender body, namely a straight circular cylinder with a large length to diameter ratio, rotates towards a vertical orientation when falling through quiescent polymer solutions. Both shear thinning and elas ticity, thus, strongly contribute to the orientation process of fibers ; however, elasticity plays a dominant role. (2) The drastic change of the velocity field is due to viscoelasticity and flow rate in a channel with an abrupt contraction. The fiber orientation state, thus, is strongly influenced by these factors ; the fibers align in a manner of wine-glass shape as the contraction is approached, and the fiber orientation abruptly expands in the immediate downstream region of the contraction in a highly elastic fluid flow.

Laminated Composites Containing an Elliptical Opening. I. Approximate Stress Analyses and Fracture Models

Approximate stress analyses are presented for orthotropic composite laminates contain ing an elliptical opening under uniaxial normal loads. Examining by the use of exact elasti city solution shows that these approximate solutions have excellent accuracy. Utilizing these solutions, the point stress fracture criterion and the average stress fracture criterion are generalized for the strength prediction of fiber-reinforced composite laminates contain ing an elliptical opening. Comparisons show that these models have good correlation with experimental data.

The Dissipation of Profits by Brand Name Investment and Entry When Price Guarantees Quality

Two previous models of the dissipation of profits generated by the use of quality-guaranteeing prices assumed that pro fits were dissipated through investment in brand-name capital and ent ry. The model of this paper allows both possibilities. It is shown th at both types of dissipation will, in general, occur and that brand-n ame investment will dissipate a greater share of profits as the elast icity of consumer response to brand-name investment grows larger. Copyright 1987 by University of Chicago Press.

Three-dimensional Contact of a Rigid Roller Traversing a Viscoelastic Half Space

In this paper, the authors consider a nontrivial three-dimensional viscoelastic contact problem which has some physical significance. (Although the subject of the analysis is an elliptical roller, it is only a small step onward to the consideration of a crowned cylindrical roller.) Generally, it is the intractability of the mathematics which hinders analytic solution of true three-dimensional problems in (visco)elasti city. The traditional method of surmounting this difficulty is to reduce the problem to two dimensions, either by choosing a suitable geometry, or by using an appropriate co-ordinate system. The elastic line integral theory represents another approach; certain approximations are used to simplify the governing equations, thus allowing the solution of the problem. After the development of a viscoelastic analogue of the Boussinesq equation valid for the solution of quasi-steady state viscoelastic contact problems, analysis proceeds making use of near field and extended line integral approximations. Results are generated showing the velocity dependence of several physical parameters, including the size and shape of the contact zone. One additional point of interest is uncovered, namely the presence of a pressure peak near the leading edge of the contact zone.

Effect of the stiffness of a support plate on the strain of a main frame under local loading

The present work gives resul ts for experimental verification of the theoretical solution obtained in [1,2], the effect of different pa ramete r s for the plate on the SSS of the frame in the support a rea has been determined, and an attempt has been made to select rational support pa rame te r s . In addition, a study has been made of the strength of a round frame supporting a long (l > 0 . 5 r 4 ~ --~) cyl indrical shell and having a bending stiffness in its plane of Eli i ~ 0.1Er52• v~-'~, where 5, r , l, and E are the thickness, radius, length, and elast ici ty modulus of the shell mater ia l ; 11 and El are the moment of iner t ia of the t r ansverse section and the elast ici ty modulus of the r ing mater ia l . With these pa rame te r s it is possible to neglect the effect of shell elast ici ty on the bending stiffness of the supporting ring and the main frame may be considered as an isolated c i r cu la r r ing [3].

On the Elastic Constants of Plane Orthotropic Elasticity

The four independent material parameters of plane orthotropic elasti city are introduced as the effective stiffness, the effective Poisson ratio, the stiffness ratio and the shear parameter. It is proved that stress boundary value problems with zero resulting force on internal contours lead to stress fields that are independent of the effective stiffness and the effective Poisson ratio, and a general transformation is described which is equivalent to a change of the stiffness ratio. These properties suggest the importance of the remaining shear parameter, that has the interesting property of being invariant with respect to a 90 degree rotation of the principal axes of the material.

インクルージョンを考慮した岩石の破壊条件に関する研究

In this paper, it is described that the stress distributions will be calculated by using the complex stress function and conformal representation for an infinite plate, under any uniform edge force, containing an elliptical region filled with material having the modulus of elasticity (EI) and Poisson's ratio (υI) which are different from those (EM, υM) of the, plate.The results show the distributed stresses have almost same values as the edge ones (Oy ∞, τxy ∞), excepted the limited region of the tip of elliptical inclusion.And taking into consideration of stress concentration around an elliptical inclusion, the condition of rock fracture in principal stress co-ordinates is shown by straight line in the compressive stress region.Also the experimental results used a sandstone are fitted with the theoretical calculation (υI/υM=0.6, EI/EM=0.1).

The viscoelastic behaviour of plasticized and “antiplasticized” polyvinylchloride

SEVERAL papers have appeared recently in which the question of increase in the elasticity modulus and strength of plasticized polymers as the concentration of plasticizer is increased, is discussed [1-8]. Jackson and Caldwell [1-4] have called this phenomenon antiplasticization and have formulated the basic requirements of low-molecular additives to a polymer, for its strength and elastici ty modulus to be increased. For this purpose they investigated the behaviour of a large number of low-molecular substances (mainly containing phenyl groups), which they mixed with a polycarbonate, and divided them into two classes. Those low-molecular organic substances that cause lowering of the strength and elasticity modulus when added to the polymer they assign to the first class (plasticizers). Low-molecular organic substances that raise the elasticity modulus and strength were assigned to the other class (antiplasticizers). This division of substances into plasticizers and antiplasticizers has more recently been confirmed by a number of authors [7, 8]. I t should be mentioned that effects analogous to antiplasticization, relating to anomalous effects of addition of small amounts of substances on the strength and deformational characteristics of polymers had been observed a considerable time before [9, 10]. When the concentration of plasticizer was large however the strength and elasticity modulus decreased as the concentration of plasticizer was increased [9, 10]. This has complicated ideas about the specific effect of low concentrations of a plasticizer. In references [5] and [6] it was stated that it is not correct to compare the properties of polymers containing different concentrations of the same plasticizer at an arbitrarily chosen (usually room) temperature. In such a comparison it could prove to be that the compositions containing different quantities of the plasticizer are in different physical states. For example at a given temperature a polymer containing a low concentration of plasticizer could be in the glassy state and one with a high concentration of plasticizer in the high-elastic state. I t is understandable that such a comparison would not lead to discovery of the mechanism of the effect of a plasticizer on the physical properties of polymers. For this reason it was proposed [5, 6, 11] tha t the properties of polymers should