Distribution of crack extension force,the Ĵ-integral,along a through-crack-front of a plate

The -integral is an extension of the J-integral proposed by Rice. It represents the crack-extension force; i.e., the energy release rate per unit of a crack-tip translation in three-dimensional elastic-plastic materials. The distribution of the -integral along the crack-front in a plate subjected to a monotonic loading is determined by a three-dimensional elastic-plastic finite element method.The three-dimensional calculation elucidates that the -integral takes its maximum value at the mid-thickness of the plate and takes a smaller value near the plate surfaces. It is shown that the -integral at the mid-thickness takes an intermediate value between those obtained by two-dimensional plane-strain and plane-stress computations; and that for a compact specimen it agrees with the J-integral value determined from the computed load versus the load-line-displacement curve using the Merkle-Corten formula.

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Résumé L'intégrale J est une extension de l'intégrale J proposée par Rice. Elle représente une force d'extension d'une fissure, à savoir le taux de relaxation de l'énergie par unité de translation de l'extrémité de la fissure dans des matériaux tridimensionnels élasto-plastiques. On détermine la distribution de l'intégrale J le long du front de fissuration dans une tôle soumise à charge croissante, à l'aide d'une méthode élastoplastique par éléments finis sur trois dimensions.Le calcul tridimensionnel permet d'établir que l'intégrale J revêt sa valeur maximale à mi-épaisseur de la tôle, et une valeur plus faible au voisinage des surfaces de la tôle.On montre que l'intégrale J à mi-épaisseur prend une valeur intermédiaire entre les valeurs ci-dessus, lorsqu'elle est déterminée par calculs à deux dimensions en état plan de déformation on en état plan de tension. On montre aussi que, dans le cas d'une éprouvette compacte, cette valeur est en accord avec la valeur de l'intégrale J établie à partir de la courbe calculée en fonction du déplacement sur la ligne de charge, à l'aide de la formule de Merkle-Corten.

     

Aldo Rossi,architect, scientist — a storm of silence … an architecture of alienation

In their existing organization, monopolizing science and remaining thus outside social life, the savants form a separate caste, in many respects analogous to the priesthood. Scientific abstruction is their God, living and real individuals their victims, and they are the consecrated and licensed sacrificers.     

Investigation of mechanical,electrical, and thermal properties of a Zn–1.26 wt% Al alloy

Zn–1.26 wt% Al alloy was directionally solidified upward with a constant growth rate (V = 16.6 μm/s) in a wide range of temperature gradients (1.94–5.15 K/mm) and with a constant temperature gradient (G = 5.15 K/mm) in a wide range of growth rates (8.3–500 μm/s) with a Bridgman-type directional solidification furnace. The microhardness (HV) and tensile strength (σ) of alloy were measured from directionally solidified samples. The dependency of the microhardness, tensile strength for directionally solidified Zn–1.26 wt% Al alloy on the solidification parameters (G, V) and microstructure parameters (λ₁, λ₂) were investigated and the relationships between them were experimentally obtained using regression analysis. According to present results, the microhardness and tensile strength of directionally solidified Zn–1.26 wt% Al alloy increase with increasing solidification processing parameters and decrease with the microstructure parameters. Variations of electrical resistivity (ρ) with the temperature in the range of 300–650 K were also measured using a standard dc four-point probe technique for cast samples. The enthalpy of fusion and specific heat for same alloy was also determined by means of differential scanning calorimeter (DSC) from heating trace during the transformation from solid to liquid.     

Stress–strain relationships of polycarbonate over a wide range of strain rate,including a shock wave regime

Stress–strain relationships of polycarbonate (PC) are determined over a very wide range of strain rates, including a shock wave regime. Plate impact tests, drop-weight tests, and quasi-static tests using universal and Instron testing machines are used for the high strain rate (10⁷ s⁻¹), medium strain rate (10² s⁻¹) and low strain rate (10⁻⁴ s⁻¹) tests, respectively. A newly modified unsteady wave sensing system (NM-UWSS) for plate impact tests is developed to determine the stress–strain relationships of PC. The system consists of a powder gun for plate impact tests, three embedded polyvenyliden fluoride (PVDF) gauges, and NM-UWSS. As originally proposed, UWSS is aimed at obtaining experimental inputs for the Lagrangian analysis used in determining the dynamic behavior of materials. We revise this standard system (UWSS) twice to gain a higher time resolution. In the past, the conventional charge mode (Q₂ method) was used. The first modified system (M-UWSS) has been used to study two classes of materials: (1) metallic materials and (2) polymeric materials, where the Q₁ method coupled with a transient differential equation for the equivalent circuit of the measurement circuit for the PVDF stress gauge was used. The latest method (Q_t method) for gaining the highest time resolution of shock wavefront structure by considering the effects of a piezofilm's thickness is proposed for PC at particle velocities of up to 1 km/s. Here we show from basic equations of piezoelectricity that the charge density q, i.e., the charge release per unit area, of the active electrode is proportional to the ratio of the thickness of the shocked region to the total thickness of the piezofilm. It is demonstrated that the rise time of shock charge density q in the piezofilm induced by such shock in the Q₂, Q₁ and Q_t methods, in this order, is becoming much shorter. The latest Q_t method has the highest accuracy among these three methods. Power law relations between stress and strain rate are observed again with PC under conditions of uniaxial strain over a very wide range of strain rates, i.e., 10⁻⁴–10⁷ s⁻¹ including a shock wave regime. For the PC, the effects of strain rate on the stress–strain relationships are estimated using empirical formula.     

Self‐Cooling of a Gas, Absorbing Laser Radiation, Due to the Intensification of Photoabsorption Convection

The effect of decrease in the temperature of an absorbing gas in a volume occupied by the beam of a continuously operated laser with decrease in the beam diameter has been investigated experimentally for the case of constant radiation power. Based on theoretical evaluations it has been inferred that the intensification of photoabsorption convection is the reason for the temperature decrease. It has been shown that an optimum diameter of the beam exists for which (for a given radiation power) the temperature of the absorbing gas attains its maximum (accordingly the maximum is attained by the yield of the reaction of thermal decomposition of the gas in the case of its pyrolysis). When the diameter is optimum the heat loss from the beam volume by heat conduction is equal to the heat loss by photoabsorption convection. It has been inferred that in constructing an adequate theoretical model of laserinduced chemical vapor deposition it is necessary to take into account the convection.     

Is diffusion,thermodiffusion, or advection a primary mechanism of indoor radon entry?

Revision of the current theory of indoor radon entry is given. It is shown that there is insufficient evidence to accept the pressure-driven mechanism as the dominant mechanism of radon infiltration in homes. The criticism of the US Environmental Protection Agency's policy is presented. The similitude theory of gas transfer in Knudsen's and transition zones is developed. Comparison of the theory with experimental data confirms the validity of the assumptions made. Application of the theory to air flow in clay is shown. This theory allows the average pore radius in the clay sample to be estimated. That radius was found to be of the order of the mean free path of air molecules at atmospheric pressure. It is shown that thermodiffusion gas flow in clay and concrete can greatly exceed the pressure-driven flow. The necessity of including thermodiffusion gas flow in a general model of radon indoor entry is substantiated.     

Deposition of Ruthenium-106 on a Concave Metal Surface of a Substrate of an Ophthalmic Applicator—a Closed Source of Beta Radiation

Radiochemistry - A method of 106Ru deposition on a concave metal surface of an ophthalmic applicator substrate is reported, which consists in preparing the substrate surface by coating it with a...     

Electrochemical DNA analysis with a supramolecular assembly of naphthalene diimide, ferrocene, and β-cyclodextrin

Naphthalene diimide 1 bearing ferrocene and β-cyclodextrin (β-CD) was prepared. Its half-wave potential at 420 mV shifted 40-50 mV upon addition of an excess of adamantylamine, suggesting that the ferrocene of 1 is included in the cavity of β-CD intramolecularly to form a pseudocyclic structure. This unique architecture is retained even where 1 is bound to calf thymus DNA to give rise to a catenane-like structure. Morphology of the DNA complex with 1 was further explored by atomic force microscopy to reveal that the DNA strand tends to bend as the amount of 1 on it increases. Presumably, intermolecular, yet intrastrand, inclusion of ferrocene into β-CD is responsible for this phenomenon. The resulting globular structure reverted partially by the addition of adamantylamine. At a low ratio of 1 to DNA, a novel reduction peak appeared at 320 mV in the differential pulse voltammograms of 1 at the expense of the 420 mV peak. The peak current of the former was proportional to the DNA concentration, thereby enabling quantitation of DNA in a signal-on way. Likewise, a polymerase chain reaction (PCR) product of 754 bp was analyzed successfully with a detection limit of 13 nM.     

Shannon's entropy as a measure of the “life” of the literature of a discipline

The paper is divided in two parts. Part I deals with the novel use of the concept ofentropy H (measured in nepers) of the ageT of references cited in the literature of a specialty, and the derived parameterS=exp(H) (measured in years). We have proposed to useS (orH) as a measure of the obsolescence of the literature. The concept of entropy comes from the Theory of Information (Shannon) where its mathematical properties have been widely studied and are thus available.H andS have been calculated for the log-normal probability density functions (which model the empirical distributions ofT) of some IEEE journals and for the 58-year collection of an electronics journal, and then they have been compared to the total utility function, this latter defined in the literature. Part II recalls and discusses the mean residual life,M(T), and the expected lifeE(T), of a reference of ageT (concepts borrowed from lifetime data analysis). Besides their intrinsic applications, another possible application of these concepts may be in defining quantitatively the age of historical papers. Examples taken from the literatures of the XX and XIX centuries have been reported.Paper presented at the Fourth International Conference on Bibliometrics, Informetrics and Scientometrics in Berlin (Germany), September 11–15, 1993.     

Cooling of a coarse lump in a bed of “fine” particles

The cooling of a coarse lump having the form of a rectangular prism in a blow-through bed of fine particles is discussed. A solution is obtained for large and small values of Fo by using Laplace transforms.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 3, pp. 434–440, March, 1976.     

Two-dimensional model of a direct current glow discharge: description of the argon metastable atoms, sputtered atoms, and ions

A two-dimensional model is presented that describes the behavior of argon metastable atoms, copper atoms, and copper ions in an argon direct current glow discharge, in the standard cell of the VG9000 glow discharge mass spectrometer for analyzing flat samples. The model is combined with a previously developed model for the electrons, argon ions, and atoms in the same cell to obtain an overall picture of the glow discharge. The results of the present model comprise the number densities of the described plasma species, the relative contributions of different production and loss processes for the argon metastable atoms, the thermalization profile of the sputtered copper atoms, the relative importance of the different ionization mechanisms for the copper atoms, the ionization degree of copper, the copper ion-to-argon ion density ratio, and the relative roles of copper ions, argon ions, and atoms in the sputtering process. All these quantities are calculated for a range of voltages and pressures. Moreover, since the sticking coefficient of copper atoms on solid surfaces is not well-known in the literature, the influence of this parameter on the results is briefly discussed.     

Synthesis,characterization, thermal properties of a series of stearic acid esters as novel solid–liquid phase change materials

This paper deals with the synthesis, characterization, thermal properties and thermal reliability of a series of stearic acid esters as a novel solid–liquid phase change material (PCM) for thermal energy storage. The ester compounds were synthesized via the reaction of stearic acid with n-butyl alcohol, isopropyl alcohol and glycerol and characterized by Fourier transform infrared spectroscopy (FT-IR) and ¹H Nuclear Magnetic Resonance (¹H NMR) techniques. Thermal properties of the esters were measured by differential scanning calorimeter (DSC) method. DSC results indicated that the melting temperatures and latent heats of the synthesized PCMs are in the range of 23–63 °C and 121–149 J/g, respectively. The thermal cycling test including 1000 cycling was conducted to determine the thermal reliability of the synthesized PCMs. The thermal conductivities of the PCMs were also increased by adding 5 wt.% EG into the esters. Based on the results, it is concluded that the synthesized esters as novel PCM have significant energy storage potential due to their satisfactory thermal properties, good thermal reliability and thermal conductivities.     

Diagnosis of the Thermal Bow of a Shaft in a Three Stage Centrifugal Compressor

In practice many turbo-machines driven by motors are started up to perational speed within a very short time,i.e.in less than 20 seconds .For this type of machines the compatibility of thermal deformaiton of the rotor stucture must be taken into account in the machine desing ,or the thermal defromation will be constrained and a huge resultant force can cause the shaft bending and consequently resulting in violent vibrations.In this paper,detection of thermal bow of a shaft in a three stage centrifugal compressor in a petrochemical plant is presented .The diagnostic results show that the thermal bow was induced by the incompatibility of axial thermal deformation of the rotor stucure.A remedial action allowing free axial thermal expansion of the outer parts of the rotor is suggested.     

Microchemical transformation of bioactive glass particles of narrow size range, a 0–24 months study

Previous studies demonstrated the capacity of bioactive glass particles of narrow size range (300–355 m, Biogran®) to stimulate bone tissue formation without contact with pre-existing bone tissue. Chemical interactions between the bioactive glass and the surrounding tissue fluids caused the glass transformation. This study quantifies the time-dependent transformation process. Particles were implanted in the jaws of beagle dogs and resected after 1, 2, 3, 6, 12 and 24 months. Microchemical analysis was performed using a scanning electron microscope equipped with an energy dispersive X-ray analysis system. After one month, Na-ions were leached out and the particles transformed into two layers. In the center, a Si-rich gel was found on the outer surface, a Ca- and P-rich shell. After two months, the concentration levels of the outer Ca- and P-rich shell remained. In the center the Si-concentration decreased and the Ca and P concentration increased. After three months, Si disappeared completely from the center of the particle, while the Ca and P concentration increased. At one and two years, the Ca and P concentrations in the transformed particles equalled those of bone tissue, turning the transformed particle into a chemical equivalent of the bone mineral phase.     

Study of 4, 4′-methylenebis-cyclohexanamine as a high temperature-resistant shale inhibitor

In order to develop high-performance water-based drilling fluid with the aim of meeting the increasing requirement of drilling industry, highly inhibitive and high-temperature-resistant shale inhibitors are essential. In this study, 4, 4′-methylenebis-cyclohexanamine was introduced as a potential shale inhibitor. The inhibitive properties of the amine compound in comparison with currently available polyether diamine inhibitor were evaluated using bentonite inhibition test, shale cuttings hot-rolling dispersion test, linear swelling test, and pressure transmission test. The inhibitive mechanism was investigated with zeta potential measurement, X-ray diffraction analysis, and contact angle measurement. The results indicated that 4, 4′-methylenebis-cyclohexanamine can inhibit shale hydration and dispersion effectively, and prevent pressure transmission to a certain extent, performing better than that of polyether diamine. Furthermore, the new diamine provides reliable thermal stability as high as 220 °C, preserving the benefits of high-temperature wells application. This novel diamine inhibits shale hydration and dispersion with the combination of chemical inhibition and physical plugging. The intercalation into the interlayer of clay with monolayer collapses the hydrated clay structure and expels the water molecules. After adsorption, clay surface became more hydrophobic, which prevents the imbibition of water. The variation of solubility separates the compound from the solution, which can plug the micro-pores of shale and prevent fluid invasion.     

Characterization of a range of alkyl-bonded silica HPLC stationary phases: correlation of quantitative surface analysis data with the retention behavior of neutral, acidic, and basic solutes

An investigation was made of the correlation between quantitative surface analytical data obtained by XPS and static SIMS and the chromatographic performance of a range of n-alkyl-bonded silica (C1-C18) packing materials. A series of acidic, basic, and neutral solutes was used to study the retention behavior. For comparison, analysis of bulk total percentage carbon (%C) and alkyl surface density of the bonded silica particulates were also included. Significant correlations were observed, in the majority of cases, between the retention factor (k) and the XPS C:Si atomic ratio, which was similar to that obtained between k and the bulk %C or k and the bonded alkyl chain length. Similar significant correlations were also obtained between k and the static SIMS alkyl:Si ion peak area ratios. XPS alkyl:Si atomic ratios were calculated as an estimate of alkyl surface coverage of the silica support, and these correlated well with the surface density calculated from the bulk %C and the surface area of the packing material. The XPS alkyl:Si ratio also demonstrated a significant correlation with the peak asymmetry factor derived for basic solutes. These studies confirm that both XPS and static SIMS can generate surface chemical data from chromatography particulates, which has direct relevance to the prediction of chromatographic behavior. We believe that these techniques will prove to be effective tools to assist in the characterization of chromatographic supports and stationary phases.     

Equalization of the Concentration of a Scalar Impurity in a Flow‐Type Chamber

Experimental and theoretical investigations of the time of equalization of the concentration of an impurity in a rectangular flowtype chamber have been carried out. It has been shown that the process of equalization of the concentration with time is exponential in character. The characteristic equalization time has been computed using the theory of turbulent diffusion. Theoretical results describe experimental regularities with an accuracy of about 10%. The value of the coefficient of turbulent diffusion for different configurations of flows in the chamber has been obtained from a comparison of experimental and calculated results.