A comparison on the effect of the ratio on the fracture behaviour between ductile and brittle materials

The effect of the ratio on the fracture behaviour of ductile and brittle materials has been studied by measuring the crack-opening displacement and J-integral for ductile material and the stress intensity factor for brittle material in three-point bend specimens with shallow and deep notches. It is shown that, for ductile material, the values of δ_i and J_i, for specimens with shallow notches are larger than those of deep notches. On the contrary, for brittle material, the values of K_IC for specimens with shallow notches are smaller than those of deep notches. The reason for this is explained.     

About the possibility of increasing the superconducting transition temperature by the phonon mechanism

The equations for the energy gap and for the critical temperatureT _c are investigated in the case of superconductors with strong coupling, with regard for the dependence of the interaction constant on the phonon frequency. The effective interaction constant , which determinesT _c in the Einstein model and delta-function phonon peak model, is calculated, and its dependence on the ordinary interaction constant, phonon frequency and momentum, Fermi momentum, and other parameters is determined. It is shown that the maximum possible value of is unity. A solution is found for the critical temperature equation in the case of a delta-function peak and the Einstein model. It is demonstrated that in the latter caseT _c has a sharp maximum as a function of the electron density.     

The Roles of the Mise en Pratique for the Definition of the Kelvin

The mise en pratique (“practical realization”) for the definition of the kelvin (MeP-K) was created by the Consultative Committee for Thermometry (CCT) in 2006 to give practitioners of thermometry a guide to the realization of the kelvin, i.e., measurement of temperature in kelvins, in accord with the International System of Units. In this article, the present and the future content of the MeP-K, the relationship of the MeP-K to other documents relevant to thermometry, the categorization of thermometry techniques in the MeP-K, and the benefits of proposed additions to the 2006 version of the MeP-K are discussed. The three categories of measurements within the MeP-K are: (1) primary methods for measuring thermodynamic temperature T; (2) formal approximations to T, in particular, the International Temperature Scale of 1990 (ITS-90) and the Provisional Low Temperature Scale from 0.9 mK to 1 K (PLTS-2000); and (3) indirect approximation methods that are neither primary nor defined on a temperature scale, yet capable of exceptionally low uncertainties or increased reliability. By providing a framework for primary methods and indirect methods, the MeP-K will foster development and application of new methods, such as the use of absolute radiometry or high-temperature fixed points. The MeP-K provides the CCT with a mechanism to update and to expand the thermometric methods in common use, without imposing on industry the high costs of changing the International Temperature Scale.     

On the broadening of the linewidth in the spin-wave spectra of single crystal nickel films

The ferromagnetic resonance technique has been used to study the broadening of the linewidth of the main resonance mode in the spin-wave spectra of single crystal nickel films. All the resonance experiments were performed at about 17 GHz, at room temperature. An expression for the angular dependence of the effective linewidth, ΔH_e, is obtained and used in the analysis of the experimental results. The calculated ΔD_e indicates a strong dependence on the angle between the applied magnetic field and the normal to the film surface. In addition, ΔH_e is always larger in the parallel orientation than in the perpendicular orientation. A mechanism is suggested for the broadening of the linewidth measured at oblique angles together with evidence for two-magnon scattering.     

Estimation of the accuracy of measurements of the corrosion rate by the method of polarization resistance

The method of polarization resistance is extensively used for the determination of the rate of corrosion. At the same time, the accuracy of measurements of the corrosion rate performed with industrial corrosion meters is often not estimated. By using an indicator, we find the accuracy of the measurements of the corrosion rate for 20 steel placed in 1N H₂SO₄ and 0.01N Na₂SO₄ solutions and for 12Kh18N10T steel placed in 1N and 10N H₂SO₄ solutions.Kiev Polytechnic Institute, Kiev. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 31, No. 3. pp. 22–27, May–June, 1995.     

de Haas-van Alphen measurement of the spin susceptibility andg-factor of the conduction electrons in the alkali metals

Absolute amplitude measurements of the de Haas-van Alphen effect by a simple new technique, as well as harmonic content measurements, have been used to obtain three independent determinations of the gitg-factor and of the spin susceptibility χ of the conduction electrons in K and Rb. These three determinations are in fairly good agreement with each other, thus confirming the reliability of the theory on which they are based. The mean values ofg are 2.800±0.011 for K and 2.83±0.05 for Rb. Only one of the three techniques could be used for Cs, giving a provisional estimate ofg=2.44±0.11, although a value ofg=3.11±0.12 is also compatible with the results and cannot be ruled out. These results correspond to values of χ/χ0 (where χ0 is the free-electron spin susceptibility) of 1.700±0.006 for K, 1.724±0.010 for Rb, and 1.76±0.06 (or 2.24±0.06) for Cs, which are in fair agreement with determinations by other methods, though the present values for K and Rb are appreciably more accurate. The results are discussed within the framework of the Landau theory of Fermi liquids and values of the many-body parameterB ₀ are deduced which are reasonably consistent with theory. By using the known cyclotron masses and also the results of far-infrared cyclotron resonance experiments for K, it proves possible to estimate the separate contributions to the many-body effects arising from electron-phonon and electron-electron interactions.     

The correlation of the parameters of interatomic interaction in crystals with the position of atom in the periodic table

The previously obtained parameters of interatomic potential of the type of Mie-Lennard-Jones potential are used to analyze the correlation of these parameters with the position of atom in the periodic table for the purpose of estimating the parameters of interatomic potential of substances for which no experimental data are available that would enable one to calculate these parameters. The parameters of interatomic potential for promethium (Pm-61) are estimated for two versions of structure, and the parameters for lanthanides are corrected. The similarity in double periodicity for lanthanides and actinides is used for estimating the values of coordinate of the minimum of potential r _o for elements ranging from curium (Cm-96) to dubnium (Db-105). The value of r _o is estimated for roentgenium (Rg-111) proceeding from the fact that, in the case of atomic number Z _a > 60, the value of r _o decreases with increasing Z _a in elements from the same subgroup. Correct values of the parameters of potential are predicted for elements ranging from francium (Fr-87) to dubnium (Db-105). The obtained parameters of interatomic potential are used to calculate the Debye temperature and Grueneisen parameter for neptunium (Np-93) and americium (Am-95).     

Practical Implementation of the Mise en Pratique for the Definition of the Kelvin Above the Silver Point

The “Mise en pratique for the definition of the kelvin” (MeP-K) was established in April 2006 to be the repository of information required to perform a “practical measurement of temperature in accordance with the International System of Units (SI).” This article describes the progress made by the MeP-K HT (High Temperature Task Group) of CCT-WG5 (radiation thermometry) in drawing together the appropriate methods for accessing thermodynamic temperature above the silver point involving direct radiometric measurements on the one hand and indirect extrapolation, interpolation, and least-squares fitting on the other. An examination of the uncertainties and a brief discussion of the advantages and disadvantages of the various approaches are given. A summary of the remaining issues to be resolved concludes the article.     

Interpreting Superfluid Spin Up Through the Response of the Container

A recipe is presented for interpreting non-invasively the transport processes at work during relaxation of a cylindrical, superfluid-filled vessel, after it is accelerated impulsively and then allowed to respond to the viscous torque exerted by the contained fluid. The recipe exploits a recently published analytic solution for Ekman pumping in a two-component superfluid, which treats the back-reaction self-consistently in arbitrary geometry for the first time. The applicability of the recipe to He II, ³He, ³He–⁴He mixtures and Bose-Einstein condensates is assessed, and the effects of turbulence discussed.     

Investigations into the influence of the tup velocity and the heat treatment on the Dynamic Fracture Toughness of inconel 625

Experiments were performed with an instrumented impact machine using different drop heights, on the nickel base alloy Inconel 625 in the as-received state and after heat treatment for about 3.6 Ms (1000 h) at 923 K (650°C). The absorbed impact energy can be obtained either by the direct dial reading, by the integration of the load versus load point displacement diagram or by the integration of the load versus time diagram, knowing the initial impact velocity v₀ of the tup. In all cases the agreement was excellent. It is shown that.

• the dynamic fracture toughness is dependent on the tup velocity v₀ and, as a consequence, on the total energy of the hammer at the different drop heights.
• defining a dynamic stress σ from the velocity dependence of the fracture toughness, the stress σ is higher for the embrittled material – a tendency verified by tensile tests.
• the dynamic fracture toughness can be correlated with the absorbed impact energy up to the load maximum for the heat treated material while the as-received material exhibits no such dependence.

The change in the tup velocity during the impact process is only small for this type of material.     

Two bracketing theorems characterizing the eigensolution for the h-version of the finite element method

This paper demonstrates that the classical inclusion principle is in general not valid for the h-version of the finite element method. Whereas the inclusion principle is valid for second-order systems discretized by the h-version of the finite element method, provided linear interpolation functions are used as admissible functions, the principle is not valid for fourth-order systems. To characterize the computed eigenvalues for fourth-order systems discretized by the h-version of the finite element method, this paper formulates two bracketing theorems.     

On the determination of the thermal diffusion factor from column measurements

A new method for experimental determination of the thermal diffusion factor _T for binary gas mixtures with a thermal diffusion column (TDC) is developed, based on A. M. Rozen's equation of TDC. The experimental results for _T are obtained in a reduced form in this approximation. An experimental reference point, determined in the same TDC with a standard gas mixture, is used for the transformation of the results for _T in absolute units. The proposed method is applicable for arbitrary gas mixtures, irrespective of the mass difference of the components.     

Measurement of Thermodynamic Temperature Above the Silver Point on the Basis of the Scheme n?=?2

In this article, a practical n = 2 scheme, fitting into the ??Mise en pratique for the definition of the kelvin?? (MeP-K) at high temperature: MeP-K-HT is presented. It is made up by selected, intertwined pairs of reference points with one common lower reference point, the copper point, all in all constituting a main range and five associated subranges. The upper reference point associated with a given subrange can be chosen in conformity with the application. As will be shown, the proposed scheme has the following advantages when disseminating and measuring T: high intrinsic robustness, flexibility in coverage of temperature??in conformity with the application??effectiveness in terms of accuracy, and efficiency in terms of expenditure. The n = 2 scheme, as proposed, would be a good candidate for an officially endorsed successor or at least an endorsed complement to ITS-90 above the silver point. This would not exclude any other scheme in conformity with the MeP-K-HT being put into practice, like??reversing the argument??the still officially endorsed ITS-90 is to be allowed for the time being as one of the means for implementing MeP-K-HT.     

Estimating the Expected and the Optimal Probabilities of Misclassification

The problem is to estimate the expected and the optimal probabilities of misclassification in the context of the two group p-dimensional normal classification problem with means and common covariance matrix unknown and a rule based on the linear discriminant function. Performance of several estimators is compared by means of a computer sampling study. For larger p (p = 20) certain estimators are definitely superior for each of the probabilities, while for small p there is less differentiation in performance.     

On the Relationship Between the H-Tensor and the Concentration Tensor and Their Bounds

For composite materials, two quantities that are useful for characterizing the contribution of inhomogeneities in a matrix material to the overall properties are (1) the individual H-tensor, H _i , which describes the contribution of a single inhomogeneity and (2) the overall strain concentration tensor, which describes the relationship between the overall volumetric strain to the average strain of all of the inhomogeneities. In this paper, we develop a relationship expressing the overall H-tensor, ${\mathcal{H}}$ , in terms of the overall strain concentration tensor. An important feature of the derivation is that it allows for rigorous upper and lower bounds on the overall H-tensor. In the special case that the inhomogeneities are all the same, with the same orientation, then ${\mathcal{H} = {\bf H}_i}$ , and the results derived for ${\mathcal{H}}$ also hold for H _i .     

Study on the interaction between the shape and the temperature field of the melt in the electromagnetic shaping process

Based on analyses for the electromagnetic pressure on the melt and the heat induced in the melt, the ratio of heat to pressure Q₀/P_m is defined, to give the relationship between Q_o/P_m and the thickness a, the electromagnetic parameter (μγ) of the melt and the electric current frequency/under the electromagnetic confinement and shaping process. If Q_o/P_m is large, any adjustment to the melt shape will easily cause a variation of the temperature in the melt. In this situation, there appears to be a more sensitive interaction between the shape and the temperature field and a more narrow adjustment range for the process. Experiments on thin plate samples with a cross-section of 6 mm × 18 mm are done with two kinds of induction coils. The results show that when a coil with a trumpet inside wall is used and the positions of the melt top and the S/L interface are properly selected, the melt periphery is nearly vertical and the temperature gradient ahead of the S/L interface is high. Under these conditions, a more stable and wider coupling between the shape and the temperature field is continuously maintained and samples with a smooth surface and unidirectional crystals are successfully obtained.     

Relationship Between the Solubility Parameter and the Surface Free Energy of Some Solids

Abstract

Solubility parameters for a number of drugs and related organic solids were determined from their dispersion and polar surface free energy data by means of an equation found to be valid for solvents. The relation fits quite well all solids investigated with an excellent correlation coefficient. The calculated solubility parameters, _O, were checked with the ones estimated from molecular groups and fragment constants according to Fedors method, _F. A similar _O of 14.6 was obtained for o-hydroxybenzoic and p-hgdroxybensoic acids. The deviations from _F shown in ethyl-p-aminobenzoate, benzoic acid, and aspirin were attributed to the imperfection of their vapor.

The solubility profile of hydrocortisone acetate was obtained in dioxane-water mixtures, and the solubility parameter of the drug was determined from the peak solubility in this binary solvent system. The experimental results for some drugs were compared with their solubility parameters calculated from the surface free energy data. Excellent agreement was found for hydrocortisone acetate, whereas griseofulvin and p-hydroxybenzoic agreed fairly. The “chameleonic” behavior of benzoic acid results in different experimental Solubility parameter, and the percentage deviation from _O ranged from 3.4-20.8. A deviation of 11.8% was obtained for ethyl-p-aminobenzoate and was attributed to the influence of its crystal structure which would account for its low _E value measured. The relation suggested was also applied to the dicarboxylic acids. The odd-even alteration seen in their melting points is not reflected on their solubility parameters. The high _O calculated for these acids were related to their elongated shape.     

On the autonomy of the process region

Two methods are examined for accurately calculating stress intensity factors in two and three dimensions: the stiffness derivative technique and the J-integral method. In two dimensions the J-integral is expressed as an area integral, whereas in three dimensions it is a volume integral. With both techniques, a virtual crack extension is introduced. Although the expressions employed for each method are quite different, it is proven that when written analytically for finite element calculation, they reduce to identical expressions.Numerical calculations are carried out in both two and three dimensions. As a result of the equivalence of the two methods, close numerical agreement is expected. For two-dimensional geometries and a penny shaped crack in a finite height cylinder, there is at least five significant figure agreement between solutions determined by both methods. For an elliptical crack embedded in a plate, the agreement is generally to four significant figures.     

A comparison of the scientific performance of the U.S. and the European union at the turn of the 21st century

In this paper, scientific performance is identified with the impact that journal articles have through the citations they receive. In 15 disciplines, as well as in all sciences as a whole, the EU share of total publications is greater than that of the U.S. However, as soon as the citations received by these publications are taken into account the picture is completely reversed. Firstly, the EU share of total citations is still greater than the U.S. in only seven fields. Secondly, the mean citation rate in the U.S. is greater than in the EU in every one of the 22 fields studied. Thirdly, since standard indicators—such as normalized mean citation ratios—are silent about what takes place in different parts of the citation distribution, this paper compares the publication shares of the U.S. and the EU at every percentile of the world citation distribution in each field. It is found that in seven fields the initial gap between the U.S. and the EU widens as we advance towards the more cited articles, while in the remaining 15 fields—except for Agricultural Sciences—the U.S. always surpasses the EU when it counts, namely, at the upper tail of citation distributions. Finally, for all sciences as a whole the U.S. publication share becomes greater than that of the EU for the top 50% of the most highly cited articles. The data used refers to 3.6 million articles published in 1998–2002, and the more than 47 million citations they received in 1998–2007.