Distribution by Scientific Domains
Distribution within Engineering

Kinds of Equations

  • Arrheniu equation
  • Navier-Stoke equation
  • Richard equation
  • Vry equation
  • adjoint equation
  • advection equation
  • algebraic equation
  • algebraic riccati equation
  • allometric equation
  • analytical equation
  • arrhenius-type equation
  • avrami equation
  • balance equation
  • basic equation
  • bellman equation
  • biharmonic equation
  • biot equation
  • bloch equation
  • boltzmann equation
  • boundary integral equation
  • boussinesq equation
  • burger equation
  • calibration equation
  • characteristic equation
  • clapeyron equation
  • clausius-clapeyron equation
  • compatibility equation
  • complex equation
  • compressible Navier-Stoke equation
  • compressible euler equation
  • concentration equation
  • conduction equation
  • conservation equation
  • consolidation equation
  • constitutive equation
  • constraint equation
  • continuity equation
  • convection-diffusion equation
  • conversion equation
  • correlation equation
  • coupled differential equation
  • coupled equation
  • cubic equation
  • de Vry equation
  • degasperis-procesi equation
  • degenerate parabolic equation
  • delay differential equation
  • demand equation
  • derived equation
  • design equation
  • difference equation
  • differential equation
  • differential-algebraic equation
  • diffusion equation
  • dirac equation
  • disc equation
  • discrete equation
  • disease equation
  • dispersion equation
  • dual integral equation
  • dynamic equation
  • dynamical equation
  • eikonal equation
  • einstein equation
  • elasticity equation
  • electric field integral equation
  • element equation
  • elliptic equation
  • elliptic partial differential equation
  • empirical equation
  • energy balance equation
  • energy conservation equation
  • energy equation
  • equilibrium equation
  • estimating equation
  • estimation equation
  • euler equation
  • evolution equation
  • exponential equation
  • field equation
  • field integral equation
  • finite element equation
  • first-order kinetic equation
  • first-order ordinary differential equation
  • flow equation
  • fluid equation
  • form equation
  • freundlich equation
  • functional equation
  • fundamental equation
  • general equation
  • generalized estimating equation
  • generalized estimation equation
  • gompertz equation
  • governing differential equation
  • governing equation
  • governing partial differential equation
  • gravity equation
  • gross-pitaevskii equation
  • growth equation
  • heat conduction equation
  • heat equation
  • heat transfer equation
  • heat transport equation
  • helmholtz equation
  • hill equation
  • hilliard equation
  • hyperbolic equation
  • hyperbolic partial differential equation
  • integral equation
  • integro-differential equation
  • jacobi equation
  • kdv equation
  • kinetic equation
  • klein-gordon equation
  • kolmogorov equation
  • lagrange equation
  • langmuir equation
  • laplace equation
  • laplacian equation
  • lattice boltzmann equation
  • level set equation
  • linear differential equation
  • linear equation
  • linear partial differential equation
  • linear regression equation
  • linear wave equation
  • liouville equation
  • logistic equation
  • logistic regression equation
  • loss equation
  • lyapunov equation
  • mass balance equation
  • mass conservation equation
  • master equation
  • mathematical equation
  • matrix equation
  • maxwell equation
  • measurement equation
  • mhd equation
  • michaelis-menten equation
  • model equation
  • momentum equation
  • motion equation
  • multiple regression equation
  • nernst equation
  • new equation
  • non-linear differential equation
  • non-linear equation
  • non-linear ordinary differential equation
  • non-linear schrödinger equation
  • nonlinear differential equation
  • nonlinear equation
  • nonlinear ordinary differential equation
  • nonlinear partial differential equation
  • nonlinear schrödinger equation
  • nonlinear wave equation
  • normal equation
  • novel equation
  • one equation
  • operator equation
  • ordinary differential equation
  • original equation
  • oseen equation
  • ozawa equation
  • parabolic equation
  • parabolic partial differential equation
  • partial differential equation
  • planck equation
  • poisson equation
  • polynomial equation
  • prediction equation
  • predictive equation
  • pressure equation
  • pressure poisson equation
  • price equation
  • pricing equation
  • propagation equation
  • proposed equation
  • quadratic equation
  • radiative transfer equation
  • rate equation
  • reaction equation
  • reaction-diffusion equation
  • reference equation
  • regression equation
  • renal disease equation
  • resulting equation
  • riccati equation
  • same equation
  • scalar equation
  • scattering equation
  • scherrer equation
  • schrödinger equation
  • second-order differential equation
  • second-order equation
  • semiempirical equation
  • semilinear parabolic equation
  • sensitivity equation
  • set equation
  • several equation
  • shallow water equation
  • shallow-water equation
  • simple equation
  • simultaneous equation
  • single equation
  • singular integral equation
  • smoluchowski equation
  • soil loss equation
  • state equation
  • stochastic differential equation
  • stoke equation
  • stress equation
  • structural equation
  • surface integral equation
  • system equation
  • tammann equation
  • theoretical equation
  • time-dependent schrödinger equation
  • transfer equation
  • transport equation
  • two-dimensional shallow water equation
  • type equation
  • universal soil loss equation
  • variational equation
  • venant equation
  • viscoelastic constitutive equation
  • volterra integral equation
  • wage equation
  • water equation
  • wave equation

  • Terms modified by Equations

  • equation analysis
  • equation approach
  • equation formulation
  • equation framework
  • equation method
  • equation methods
  • equation model
  • equation modeling
  • equation modeling analysis
  • equation modeling techniques
  • equation modelling
  • equation modelling techniques
  • equation models
  • equation only
  • equation set
  • equation simulation
  • equation solver
  • equation system
  • equation used

  • Selected Abstracts


    EVOLUTION, Issue 11 2005
    John S. Heywood
    Abstract Starting with the Price equation, I show that the total evolutionary change in mean phenotype that occurs in the presence of fitness variation can be partitioned exactly into five components representing logically distinct processes. One component is the linear response to selection, as represented by the breeder's equation of quantitative genetics, but with heritability defined as the linear regression coefficient of mean offspring phenotype on parent phenotype. The other components are identified as constitutive transmission bias, two types of induced transmission bias, and a spurious response to selection caused by a covariance between parental fitness and offspring phenotype that cannot be predicted from parental phenotypes. The partitioning can be accomplished in two ways, one with heritability measured before (in the absence of) selection, and the other with heritability measured after (in the presence of) selection. Measuring heritability after selection, though unconventional, yields a representation for the linear response to selection that is most consistent with Darwinian evolution by natural selection because the response to selection is determined by the reproductive features of the selected group, not of the parent population as a whole. The analysis of an explicitly Mendelian model shows that the relative contributions of the five terms to the total evolutionary change depends on the level of organization (gene, individual, or mated pair) at which the parent population is divided into phenotypes, with each frame of reference providing unique insight. It is shown that all five components of phenotypic evolution will generally have nonzero values as a result of various combinations of the normal features of Mendelian populations, including biparental sex, allelic dominance, inbreeding, epistasis, linkage disequilibrium, and environmental covariances between traits. Additive genetic variance can be a poor predictor of the adaptive response to selection in these models. The narrow-sense heritability s,2A/s,2P should be viewed as an approximation to the offspring-parent linear regression rather than the other way around. [source]


    CRIMINOLOGY, Issue 4 2003
    This paper addresses two concerns that arise from Steffensmeier and Demuth (2001) analysis of federal sentencing and their misrepresentation of my analyses of sentence severity (Albonetti, 1997). My primary concern is to alert researchers to the importance of controlling for the guidelines offense that drives the sentencing process under the Federal Sentencing Guidelines. My second concern is to correct Steffensmeier and Demuth's (2001) errors in interpretation of my earlier findings of the effect of guidelines offense severity on length of imprisonment. [source]


    ABSTRACT In his article " On Fitting Equations to Sensory Data." Moskowitz suggests many strategies for model fitting which depart from current statistical methodology. Four areas discussed by Moskowitz are addressed here: (1) Forcing terms into a model; (2) The use of hold-out samples; (3) The use of aggregate data (averaging across people, suppressing the person-to-person variation); and (4) The use of random data as a predictor variable in a regression equation. All four of these points will be examined within this article. [source]


    First page of article [source]


    ABSTRACT. Combining analytical techniques from perturbation methods and dynamical systems theory, we present an elementaryapproach to the detailed construction of axisymmetric diffusive interfaces in semi-linear elliptic equations. Solutions of the resulting non-autonomous radial differential equations can be expressed in terms of a slowlyvarying phase plane system. Special analytical results for the phase plane system are used to produce closed-form solutions for the asymptotic forms of the curved front solutions. These axisym-metric solutions are fundamental examples of more general curved fronts that arise in a wide variety of scientific fields, and we extensivelydiscuss a number of them, with a particular emphasis on connections to geometric models for the motion of interfaces. Related classical results for traveling waves in one-dimensional problems are also reviewed briefly. Manyof the results contained in this article are known, and in presenting known results, it is intended that this article be expositoryin nature, providing elementarydemonstrations of some of the central dynamical phenomena and mathematical techniques. It is hoped that the article serves as one possible avenue of entree to the literature on radiallysymmetric solutions of semilinear elliptic problems, especiallyto those articles in which more advanced mathematical theoryis developed. [source]


    Young Soo Suh
    ABSTRACT An analytic solution to Lyapunov functional equations for distributed delay systems is derived. The analytic solution is computed using a matrix exponential function, while conventional computation has been relied on numerical approximations. Based on the analytic solution, a necessary and sufficient stability condition for distributed delay systems with unknown but bounded constant delay is proposed. [source]

    Equation of State of Strongly Coupled Quark,Gluon Plasma , Path Integral Monte Carlo Results

    V.S. Filinov
    Abstract A strongly coupled plasma of quark and gluon quasiparticles at temperatures from 1.1Tc to 3Tc is studied by path integral Monte Carlo simulations. This method extends previous classical nonrelativistic simulations based on a color Coulomb interaction to the quantum regime. We present the equation of state and find good agreement with lattice results. Further, pair distribution functions and color correlation functions are computed indicating strong correlations and liquid-like behavior (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    A method for assessing quality of control from glucose profiles

    DIABETIC MEDICINE, Issue 7 2007
    N. R. Hill
    Abstract Aim As the practice of multiple assessments of glucose concentration throughout the day increases for people with diabetes, there is a need for an assessment of glycaemic control weighted for the clinical risks of both hypoglycaemia and hyperglycaemia. Methods We have developed a methodology to report the degree of risk which a glycaemic profile represents. Fifty diabetes professionals assigned risk values to a range of 40 blood glucose concentrations. Their responses were summarised and a generic function of glycaemic risk was derived. This function was applied to patient glucose profiles to generate an integrated risk score termed the Glycaemic Risk Assessment Diabetes Equation (GRADE). The GRADE score was then reported by use of the mean value and the relative percent contribution to the weighted risk score from the hypoglycaemic, euglycaemic, hyperglycaemic range, respectively, e.g. GRADE (hypoglycaemia%, euglycaemia%, hyperglycaemia%). Results The GRADE scores of indicative glucose profiles were as follows: continuous glucose monitoring profile non-diabetic subjects GRADE = 1.1, Type 1 diabetes continuous glucose monitoring GRADE = 8.09 (20%, 8%, 72%), Type 2 diabetes home blood glucose monitoring GRADE = 9.97 (2%, 7%, 91%). Conclusions The GRADE score of a glucose profile summarises the degree of risk associated with a glucose profile. Values < 5 correspond to euglycaemia. The GRADE score is simple to generate from any blood glucose profile and can be used as an adjunct to HbA1c to report the degree of risk associated with glycaemic variability. [source]

    Numerical simulation of sediment-associated water quality processes for a Mississippi delta lake

    ECOHYDROLOGY, Issue 3 2009
    Xiaobo Chao
    Abstract Three major sediment-associated processes were presented to describe the effects of sediment on the water quality processes, including the effect of sediment on the light intensity for the growth of phytoplankton (PHYTO), the adsorption,desorption of nutrients by sediment and the release of nutrients from the bed sediment layer. A formula was generated from field measurements to calculate the light attenuation coefficient by considering the effects of concentrations of chlorophyll and suspended sediment (SS). The concentrations of adsorbed and dissolved nutrients because of adsorption,desorption were calculated using two formulas that were derived based on the Langmuir Equation. The release rates of nutrients from the bed sediment were calculated by considering the effects of the concentration gradient across the water-sediment interface, pH, temperature and dissolved oxygen (DO) concentration. Model algorithms describing the adsorption and desorption of nutrients from sediment particles as well as the release of nutrients from bed sediment were tested using experimental data. These sediment-associated water quality processes were included in a three-dimensional (3D) water quality model, CCHE3D_WQ, developed by the National Center for Computational Hydroscience and Engineering (NCCHE), to simulate the concentrations of PHYTO and nutrients in a shallow Mississippi Delta lake with special emphasis on sediment-related processes. The simulated concentration of PHYTO (as chlorophyll) and nutrients were generally in good agreement with field observations. This study shows that there are strong interactions between sediment-associated processes and water quality constituents. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Synthesis of 2,4-Diaryl-3,4-dihydro-2H - naphth[2,1- e][1,3]oxazines and Study of the Effects of the Substituents on Their Ring - Chain Tautomerism

    István Szatmári
    Abstract A number of 2-(,-amino-Y-substituted-benzyl)-1-naphthol hydrochlorides were prepared by a convenient Mannich-type aminoalkylation. 2,4-Diaryl-3,4-dihydro-2H -naphth[2,1- e][1,3]oxazines were prepared through the ring-closure reactions of the starting aminonaphthols with aromatic aldehydes, which proved to furnish three-component (ring1,open,ring2) tautomeric mixtures in CDCl3 at 300 K. The electronic effects of the 2-aryl groups on the ratios of the ring - chain tautomeric forms at equilibrium could be described by Equation (1). Study of the effects of substituents X and Y on the tautomeric equilibria [by the aid of the multiple linear regression analysis of Equations (2) and (3)] revealed that the trans -chain equilibrium constants are significantly influenced by the inductive effect (,F) of substituent Y on the 4-phenyl ring. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Methods to Derive the Differential Equation of the Free Surface Boundary

    GROUND WATER, Issue 3 2010
    Chongxi Chen
    First page of article [source]

    Derivation Approaches for the Theis (1935) Equation

    GROUND WATER, Issue 1 2010
    Hugo A. Loáiciga
    First page of article [source]

    Predicting unit plot soil loss in Sicily, south Italy

    V. Bagarello
    Abstract Predicting soil loss is necessary to establish soil conservation measures. Variability of soil and hydrological parameters complicates mathematical simulation of soil erosion processes. Methods for predicting unit plot soil loss in Sicily were developed by using 5 years of data from replicated plots. At first, the variability of the soil water content, runoff, and unit plot soil loss values collected at fixed dates or after an erosive event was investigated. The applicability of the Universal Soil Loss Equation (USLE) was then tested. Finally, a method to predict event soil loss was developed. Measurement variability decreased as the mean increased above a threshold value but it was low also for low values of the measured variable. The mean soil loss predicted by the USLE was lower than the measured value by 48%. The annual values of the soil erodibility factor varied by seven times whereas the mean monthly values varied between 1% and 244% of the mean annual value. The event unit plot soil loss was directly proportional to an erosivity index equal to , being QRRe the runoff ratio times the single storm erosion index. It was concluded that a relatively low number of replicates of the variable of interest may be collected to estimate the mean for both high and particularly low values of the variable. The USLE with the mean annual soil erodibility factor may be applied to estimate the order of magnitude of the mean soil loss but it is not usable to estimate soil loss at shorter temporal scales. The relationship for estimating the event soil loss is a modified version of the USLE-M, given that it includes an exponent for the QRRe term. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    What Is the Active Ingredients Equation for Success in Executive Coaching?

    In this response, we address commentator concerns about the generalizability of the active ingredients of psychotherapy to the science and practice of executive coaching. We discuss four ingredient that may make a difference: (a) client characteristics, (b) goals or success criteria, (c) role of the organization, and (d) contextual knowledge of the executive coach. We explore how each of these differences is likely to affect the weighting of the four active ingredients in the equation for predicting executive coaching outcomes. From this analysis, we re-affirm our hypotheses that the active ingredients are generalizable to coaching and hold promise for strengthening research and practice. We conclude by highlighting the efforts of several commentators to extend and deepen our hypotheses to other areas of leadership development. [source]

    Extension of the Griffith's fracture criteria to saturated clays

    K.M. Dégué
    Abstract Inglis [1] has solved the problem of distribution of stress in an elastic plate around an elliptical hole. His works clarify the role of cracks in the failure of an elastic material. However, his solution cannot be applied to saturated clay because he considers only total stresses, while, in saturated clay, the criterion of rupture should be expressed in terms of effective and not total stresses. The solution of Atkinson and Craster [2] using Biot's poroelasticity theory, shows that there is no high pore pressure in the vicinity of the crack tips for saturated clay. The major difference between this approach and the Biot's theory of is that, in saturated clay, strain is a function of the variation of the effective stress [3], while, in poroelastic media, strain is only a function of the variation of the total stress [4, Equation 2.2]. Also in their solution there is continuity between the pore fluid and the inner fluid in the crack. Their solution is valid for poroelastic media involving a movement of the pore fluid. In our solution there is no movement of the pore fluid (Undrained condition). In this paper we have solved the same problem as Inglis [1], but for the particular case of saturated clay obeying elastic law. By solving this problem we obtained the expressions for pore pressure, effective stress, total stress and displacements. The results show that not only the total stress but also the pore pressure and the effective stress are also high in the vicinity of the crack tips. A new failure criterion, based on Griffith's strain energy principle [5] and maximum tensile stress [6], valid for saturated clay is developed in this paper. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    A linearized implicit pseudo-spectral method for some model equations: the regularized long wave equations

    K. Djidjeli
    Abstract An efficient numerical method is developed for the numerical solution of non-linear wave equations typified by the regularized long wave equation (RLW) and its generalization (GRLW). The method developed uses a pseudo-spectral (Fourier transform) treatment of the space dependence together with a linearized implicit scheme in time. =10pt An important advantage to be gained from the use of this method, is the ability to vary the mesh length, thereby reducing the computational time. Using a linearized stability analysis, it is shown that the proposed method is unconditionally stable. The method is second order in time and all-order in space. The method presented here is for the RLW equation and its generalized form, but it can be implemented to a broad class of non-linear long wave equations (Equation (2)), with obvious changes in the various formulae. Test problems, including the simulation of a single soliton and interaction of solitary waves, are used to validate the method, which is found to be accurate and efficient. The three invariants of the motion are evaluated to determine the conservation properties of the algorithm. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    A multi-block lattice Boltzmann method for viscous fluid flows

    Dazhi Yu
    Abstract Compared to the Navier,Stokes equation-based approach, the method of lattice Boltzmann Equation (LBE) offers an alternative treatment for fluid dynamics. The LBE method often employs uniform lattices to maintain a compact and efficient computational procedure, which makes it less efficient to perform flow simulations when there is a need for high resolution near the body and/or there is a far-field boundary. To resolve these difficulties, a multi-block method is developed. An accurate, conservative interface treatment between neighboring blocks is adopted, and demonstrated that it satisfies the continuity of mass, momentum, and stresses across the interface. Several test cases are employed to assess accuracy improvement with respect to grid refinement, the impact of the corner singularity, and the Reynolds number scaling. The present multi-block method can substantially improve the accuracy and computational efficiency of the LBE method for viscous flow computations. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Weight Change and Lower Body Disability in Older Mexican Americans

    Soham Al Snih MD
    Objectives: To examine the association between 2-year weight change and onset of lower body disability over time in older Mexican Americans. Design: Data were from the Hispanic Established Population for the Epidemiological Study of the Elderly (1993,2001). Weight change was examined by comparing baseline weight to weight at 2-year follow-up. Incidence of lower body disability was studied from the end of this period through an additional 5 years. Setting: Five southwestern states: Texas, New Mexico, Colorado, Arizona, and California. Participants: One thousand seven hundred thirty-seven noninstitutionalized Mexican-American men and women aged 65 and older who reported no limitation in activities of daily living (ADLs) and were able to perform the walk test at 2-year follow-up. Measurements: In-home interviews assessed sociodemographic factors, self-reported physician diagnoses of medical conditions (arthritis, diabetes mellitus, heart attack, stroke, hip fracture, and cancer), self-reported ADLs, depressive symptoms, and number of hospitalizations. Cognitive function, handgrip muscle strength, and body mass index (BMI) were obtained. The outcomes were any limitation of lower body ADL (walking across a small room, bathing, transferring from a bed to a chair, and using the toilet) and limitation on the walk test over subsequent 5-year follow-up period. General Estimation Equation (GEE) was used to estimate lower body disability over time. Results: Weight change of 5% or more occurred in 42.3% of the participants; 21.7% lost weight, 20.6% gained weight, and 57.7% had stable weight. Using GEE analysis, with stable weight as the reference, weight loss of 5% or more was associated with greater risk of any lower body ADL limitation (odds ratio (OR)=1.43, 95% confidence interval (CI)=1.06,1.95) and walking limitation (OR=1.35, 95% CI=1.03,1.76) after controlling for sociodemographic variables and BMI at baseline. Weight gain of 5% or more was associated with greater risk of any lower body ADL limitation (OR=1.39, 95% CI=1.02,1.89), after controlling for sociodemographic variables and BMI at baseline. When medical conditions, handgrip muscle strength, high depressive symptomatology, cognitive function, and hospitalization were added to the equation, the relationship between 2-year weight change (>5% loss or >5% gain) and lower body disability decreased. Conclusion: Health conditions and muscle strength partially mediate the association between weight loss or gain and future loss of ability to walk and independently perform ADLs. [source]

    Modeling the phase behavior of ternary systems ionic liquid + organic + CO2 with a Group Contribution Equation of State

    AICHE JOURNAL, Issue 5 2009
    Eliane Kühne
    Abstract This work presents the results of the use of a Group Contribution Equation of State (GC-EOS) to model experimental data obtained for ternary systems of the type bmim[BF4] + organic solute + CO2 with four different organic compounds, namely acetophenone, 1-phenylethanol, 4-isobutylacetophenone, and 1-(4-isobutylphenyl)-ethanol. Our results show that the GC-EOS is able to qualitatively predict not only L+V,L but also L1+L2,L phase transitions. As the two two-phase boundaries L+V and L1+L2 of the experimentally found three-phase region L1+L2+V almost coincide with the saturated vapor pressure curve of pure CO2, the phase transitions L+V,L1+L2+V and L1+L2+V,L1+L2 have been represented as this vapor-pressure curve by the model. The average absolute deviations between experimental and predicted values for all phase transitions have been found to be very satisfactory. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

    Equation of state for the viscosity of Lennard-Jones fluids,

    AICHE JOURNAL, Issue 2 2006
    Leslie V. Woodcock
    Abstract A one-parameter model constitutive transport equation for the viscosity of the Lennard-Jones (L-J) fluid that is accurate for all equilibrium states of liquid and gas is proposed: The form of this equation is based upon the soft-sphere scaling laws for the residual density-dependent viscosity discovered originally by Ashurst and Hoover and uses their empirical coefficient (CAH). Enskog's density-independent limit theoretical term (,0) is included to reproduce the viscosity in the limit of zero density accurately. Remaining discrepancies at low temperatures, for both gas and liquid densities, are largely removed when the linear-density Rainwater-Friend coefficient is added. The equation is comparable in accuracy to the 24-parameter empirical equation of state proposed by Rowley and Painter. Comparison with this correlation and previous MD results reveals a discrepancy near the triple point. To test the equation, new MD data for three fluid states are reported. Here, the viscosity is computed from time correlation functions resolved into the single-particle auto- and cross-correlation terms. It is found that, at high density (,* > 0.8), the cross,correlations extend beyond 7, (molecule diameters) and oscillate in sign. This explains the wide scatter of previous MD viscosities for small L-J systems. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source]

    Dielectric relaxation and crystallization of ultraviscous melt and glassy states of aspirin, ibuprofen, progesterone, and quinidine

    G.P. Johari
    Abstract Molecular relaxation in ultraviscous melt and glassy states of aspirin, ibuprofen, progesterone, and quinidine has been studied by dielectric spectroscopy. The asymmetric relaxation spectra is characterized by the Kohlrausch distribution parameter of 0.46,±,0.02 for aspirin to 0.67,±,0.02 for progesterone. The dielectric relaxation time varies with the temperature, T, according to the Vogel,Fulcher,Tammann Equation, log10(,0),=,AVFT,+,[BVFT/(T,,,T0)], where AVFT, BVFT, and T0 are empirical constants. The extrapolated ,0 at calorimetric glass-softening temperature is close to the value expected. The equilibrium permittivity, ,0, is lowest for ibuprofen which indicates an antiparallel orientation of dipoles in its liquid's hydrogen-bonded structure. A decrease in ,0 with time shows that ultraviscous aspirin, progesterone, and quinidine begin to cold-crystallize at a relatively lower temperature than ibuprofen. ,0 of the cold-crystallized phases are, 4.7 for aspirin at 290 K, 2.55 for ibuprofen at 287 K, 2.6 for progesterone at 320 K, and 3.2 for quinidine at 375 K. It is argued that hydrogen-bonding, the Kohlrausch parameter, extent of localized motions and the long-range diffusion times all determine the physical and chemical stability of an amorphous pharmaceutical during storage. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1159,1175, 2007 [source]

    Empirical Equation for Calculating the Density of Oxide Glasses

    Seiji Inaba
    The density of oxide glass including silicate, borate, phosphate, tellurite, and germanate glasses were measured using the Archimedes method. On the assumption that the ionic packing ratio is approximately a constant independent of chemical composition, an empirical equation for estimating the density from chemical composition was proposed. The calculated values are in reasonable agreement with the corresponding measured ones. [source]

    Erratum re: "The DCI-index: Discounted cumulated impact-based research evaluation", Journal of the American Society for Information Science and Technology, 59(9), 1433-1440

    Kalervo Järvelin
    The article by K. Järvelin & O. Persson published in JASIST 59(9), "The DCI-Index: Discounted Cumulated Impact-Based Research Evaluation," (pp. 1433,1440) contains an unfortunate error in one of its formulas, Equation 3. The present paper gives the correction and an example of impact analysis based on the corrected formula. [source]


    M.S. Bedinger
    ABSTRACT: Devils Hole is a collapse depression connected to the regional carbonate aquifer of the Death Valley ground water flow system. Devils Hole pool is home to an endangered pupfish that was threatened when irrigation pumping in nearby Ash Meadows lowered the pool stage in the 1960s. Pumping at Ash Meadows ultimately ceased, and the stage recovered until 1988, when it began to decline, a trend that continued until at least 2004. Regional ground water pumping and changes in recharge are considered the principal potential stresses causing long term stage changes. A regression was found between pumpage and Devils Hole water levels. Though precipitation in distant mountain ranges is the source of recharge to the flow system, the stage of Devils Hole shows small change in stage from 1937 to 1963, a period during which ground water withdrawals were small and the major stress on stage would have been recharge. Multiple regression analyses, made by including the cumulative departure from normal precipitation with pumpage as independent variables, did not improve the regression. Drawdown at Devils Hole was calculated by the Theis Equation for nearby pumping centers to incorporate time delay and drawdown attenuation. The Theis drawdowns were used as surrogates for pumpage in multiple regression analyses. The model coefficient for the regression, R2= 0.982, indicated that changes in Devils Hole were largely due to effects of pumping at Ash Meadows, Amargosa Desert, and Army 1. [source]


    Jason M. Ward
    ABSTRACT: The effectiveness of streamside management zones (SMZs) was assessed for reducing sediment transport from concentrated overland flow draining two Georgia Piedmont clearcuts that had undergone mechanical and chemical site preparation and planting. Silt fences were used to trap sediment transport from zero-order ephemeral swales at the edge of and within SMZs. Four control swales and nine treatment swales were studied. A double mass curve approach was used to graphically compare sediment accumulation rates at the edge of SMZs to accumulation rates within the SMZs at a distance consistent with current recommendations for SMZ width in Georgia. SMZ efficiencies for trapping sediment transported by concentrated flow ranged from 71 to 99 percent. No statistical model was found to explain how SMZ efficiencies varied with SMZ and contributing area characteristics. Measured sediment accumulations at the SMZ boundary were compared to Revised Universal Soil Loss Equation (RUSLE) predictions of up- slope erosion, and a delivery ratio of 0.25 was calculated. SMZs had a quantifiable and substantial ameliorating effect on sediment transport from concentrated overland flow on the clearcut study sites. [source]

    Erosion predictions with the Wind Erosion Equation (WEQ) using different climatic factors

    J. E. Panebianco
    Abstract Little information is available on the performance of the Wind Erosion Equation (WEQ) for estimating wind erosion under differing climatic conditions. The objective of this study was to assess the fitting of measured and WEQ-estimated wind erosion with different climatic C factors. Results showed that WEQ underestimated the annual wind erosion by 45 per cent when loaded with the historic C, obtained with climatic data records between 1981 and 1990. The monthly averaged C factor (monthly C, n,=,12) underestimated the erosion by 29 per cent, the C factors of each one of the six studied years (annual C, n,=,6) underestimated the erosion by 19 per cent, and the C factors of each one of the evaluated months (monthly C, n,=,72) overestimated the erosion by 31 per cent. Precipitation explained most of C factors variability. C factors corresponding to high precipitation periods predicted low erosion amounts in no-till (NT) and conventional tillage (CT). C factors corresponding to low precipitation periods calculated high erosion rates in CT (143,t,ha,1,y,1) and low in NT (2·4,t,ha,1,y,1). The historical C factor predicted no erosion in NT and 7·1,t,ha,1,y,1 in CT. These results indicated that the WEQ should be used with variable C factors in order to assess different climatic scenarios of the semiarid Argentina. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Data-Driven Learning: Taking the Computer Out of the Equation

    LANGUAGE LEARNING, Issue 3 2010
    Alex Boulton
    Despite considerable research interest, data-driven learning (DDL) has not become part of mainstream teaching practice. It may be that technical aspects are too daunting for teachers and students, but there seems to be no reason why DDL in its early stages should not eliminate the computer from the equation by using prepared materials on paper,considerably easier for the novice learner to handle. This article reports on an experiment to see how lower level learners cope with such paper-based corpus materials and a DDL approach compared to more traditional teaching materials and practices. Pretests and posttests show that both are effective compared to control items, with the DDL items showing the greatest improvement, and questionnaire responses are more favorable to the DDL activities. The results are argued to show that printed materials can counter a number of potential barriers and may thus enable DDL to reach a wider audience. [source]

    Crystalline/Crystalline Phase Transitions in Polymer Systems Consisting of Finite-Size Crystals in Each Crystalline Phase: Generalized Gibbs-Thomson Equation

    Matsuo Hirami
    Abstract For polymer systems of two crystalline phases of one polymer component, each phase being consisted of polymer crystals of a finite size, we derive the crystalline-crystalline phase transition relationship, i.e., generalized Gibbs-Thomson equation. Its application combined with the crystalline-liquid transition relationship (usual Gibbs-Thomson equation) to the phase behavior of PT phase diagram of polyethylene (PE) is investigated, where the orthorhombic-hexagonal phase transition of PE crystal under high pressure being involved. Comparison with experimental data leads to the estimates of the structural characteristics such as the ratios of (the end surface free energy of polymer crystal/crystal length) for the respective crystalline phases. [source]

    Distinct Diffusion in Macromolecule-Solvent Mixtures

    Alessandro Vergara
    Abstract Summary: The specificity of interactions between pairs of molecules cannot be explicitly given by experimental transport coefficients such as intra- or mutual diffusion coefficients. But a microscopic interpretation of the transport properties exists, where distinct diffusion coefficients (DDCs) are related to preferential, correlated motion among distinct molecules. Since in general the DDCs do not play the role of an indicator for molecular self-association phenomena if not compared with some appropriate standard, here we propose DDCs of hard spheres at the second order of volume fraction as new standard coefficients. The analysis based on these novel DDCs is designed to study intermolecular interaction between macromolecule and solvent. Comparisons of the novel non-ideal with previous ideal reference states were done, and their combined use is shown to reinforce information conveyed by the usual velocity correlation analysis. The comparison of novel hard sphere standards with real DDCs, corresponding to an homologous chemical series of poly(ethylene glycol)-water mixtures, provides a look at this polymer-solvent mixture in a dilute and semi-dilute regime. Comparison between real (calculated by using Equation (5),(7) and experimental data) and hard-sphere based distinct diffusion coefficients for PEG 200 (1: D; 2: D and 3: D). [source]

    On the maximum principle and its application to diffusion equations

    T. Stys
    Abstract In this article, an analog of the maximum principle has been established for an ordinary differential operator associated with a semi-discrete approximation of parabolic equations. In applications, the maximum principle is used to prove O(h2) and O(h4) uniform convergence of the method of lines for the diffusion Equation (1). The system of ordinary differential equations obtained by the method of lines is solved by an implicit predictor corrector method. The method is tested by examples with the use of the enclosed Mathematica module solveDiffusion. The module solveDiffusion gives the solution by O(h2) uniformly convergent discrete scheme or by O(h4) uniformly convergent discrete scheme. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 [source]