The viscosity of five liquid hydrocarbons at pressures up to 250 MPa

This paper reports new measurements of the viscosity of toluene, n-pentane, n-hexane, n-octane, and n-decane at pressures up to 250 MPa in the temperature range 303 to 348 K. The measurements were performed with a vibrating-wire viscometer and with a relative method of evaluation. Calibration of the instrument was carried out with respect to reference values of the viscosity of the same liquids at their saturation vapour pressure. The viscosity measurements have a precision of ±0.1% but the accuracy is limited by that of the calibration data to be ±0.5%. The experimental data have been represented by polynomial functions of pressure for the purposes of interpolation. The data are also used as the most precise test yet applied to a representation of the viscosity of liquids based upon hard-sphere theory.     

Measurements of the viscosity of n-heptane,n-nonane,and n-undecane at pressures up to 70 MPa

New absolute measurements of the viscosity of n-heptane, n-nonane, and n-undecane are presented. The measurements were performed with a vibrating-wire instrument at temperatures of 303.15 and 323.15 K and pressures up to 70 MPa. The overall uncertainty in the reported viscosity data is estimated to be ±0.5%. A recently developed semiempirical scheme for the correlation and prediction of the thermal conductivity, viscosity, and self-diffusion coefficients of n-alkanes is applied to the prediction of the viscosity of n-heptane, n-nonane, and n-undecane. The comparison of these predicted values with the present high-pressure measurements demonstrates the predictive power of this scheme.     

Measurements of the viscosity of n-heptane + n-undecane mixtures at pressures up to 75 MPa

New absolute measurements of the viscosity of binary mixtures of n-heptane and n-undecane are presented. The measurements, performed in a vibrating-wire instrument, cover the temperature range 295–335 K and pressures up to 75 MPa. The concentrations studied were 40 and 70%, by weight, of n-heptane. The overall uncertainty in the reported viscosity data is estimated to be ±0.5%. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to predict successfully both the thermal conductivity and the viscosity of these mixtures, as a function of composition, temperature, and pressure.     

Measurements of the Liquid Viscosities of Mixtures of n-Butane, n-Hexane, and n-Octane with Squalane to 30 MPa

The viscosities of liquid mixtures of n-butane, n-hexane, and n-octane with squalane that represent model mixtures of refrigerants with refrigeration oil were measured at temperatures between 273.15 and 333.15 K, and at pressures from 0.1 to 30 MPa, by using a falling body viscometer. The uncertainty of the measurements was estimated to be no larger than 2.9%. The experimental viscosity values were fitted to a Tait-like equation within 2.8%. There are larger deviations between the experimental data and calculated values predicted by the equation of Kanti et al., which is derived from the Flory theory. By introducing an interaction parameter of the energetic mixing rule into the equation, the deviations were significantly reduced.     

Thermal conductivity of n-tridecane at pressures up to 500 MPa in the temperature range 35–75°C

Thermal conductivity coefficients are reported for liquid n-tridecane along three isotherms, 35, 48, and 73°C, and for pressures from 20 to 500 MPa. The measurements have been made with a transient hot-wire instrument, and the results, when corrected for the effects of radiation absorption, have an estimated uncertainty of ±0.7%. The thermal conductivity as a function of density along isotherms can be represented by means of the same form of equation as that found suitable for other normal alkanes, and this is based upon a heuristic modification of the van der Waals theory of liquids.     

Thermoelectric power in Gd3+-substituted Cu-Cd ferrites

Polycrystalline Cd _x Cu_1−x Fe_2−y Gd _y O₄ ferrites fory=0·0 and 0·1 were prepared by ceramic technique. X-ray diffractograms of powder samples show cubic symmetry withx⩾0·2 fory=0·0 and 0·1, while compositions withx=0·0 fory = 0·0 and 0·1 are tetragonal. The thermopower measurements for Gd³⁺-undoped ferrites in the temperature range 300 K to 788 K shown-type conductivity forx⩾0·2. The substitution of Gd³⁺ changedn-type conductivity of the compositions top-type. The mobilities calculated show decreasing trend on Gd³⁺ substitution. The values of activation energy ΔE and drift mobilityE _d suggest polaron formation in substituted samples. The conduction mechanism is explained on the basis of localized model and formation of Gd³⁺+Fe²⁺ stable pairs at B site and Cu¹⁺+Fe³⁺ at A site.     

Weibull and inverse Weibull mixture models allowing negative weights

This article presents the finding that when components of a system follow the Weibull or inverse Weibull distribution with a common shape parameter, then the system can be represented by a Weibull or inverse Weibull mixture model allowing negative weights. We also use an example to illustrate that the proposed mixture model can be used to approximate the reliability behaviours of the consecutive-k-out-of-n systems. The example also shows data analysis procedures when the parameters of the component life distributions are either known or unknown.     

An absolute vibrating-wire viscometer for liquids at high pressures

The design and operation of a new vibrating-wire viscometer for the measurement of the viscosity of liquids at pressures up to 100 MPa are described. The design of the instrument is based on a complete theory so that it is possible to make absolute measurements with an associated error of only a few parts in one thousand. Absolute measurements of the viscosity of n-hexane are reported at 298.15 K at pressures up to 80 MPa. The overall uncertainty in the reported viscosity data is estimated to be ±0.5%, an estimate confirmed by the comparison of values of viscosity of slightly inferior accuracy.     

The thermal conductivity of n-hexane,n-heptane,and n-decane by the transient hot-wire method

New absolute measurements of the thermal conductivity of liquid n-hexane, n-heptane, and n-decane are reported. The measurements have been carried out in the temperature range 300–370 K at atmospheric pressure in a transient hotwire instrument. The accuracy of the measurements is estimated to be ±0.5%. The density dependence of the thermal conductivity of n-hexane and n-heptane is found to be well described by a universal equation for the hydrocarbons based on a rough hard-sphere model. The measurements of the three hydrocarbons studied are also employed to generate more accurate effective core volumes, which are the only parameters characteristic of the fluid required for the application of the proposed universal scheme.     

Transport properties of nonelectrolyte liquid mixtures—VII. Viscosity coefficients for isooctane and for equimolar mixtures of isooctane + n-octane and isooctane + n-dodecane from 25 to 100°C at pressures up to 500 MPa or to the freezing pressure

Changes in the high-pressure self-centering falling-body viscometer system, and the new automated data logging system, are described. Viscosity coefficient measurements made with an estimated accuracy of ± 2 % are reported for isooctane and for equimolar mixtures of isooctane + n-octane and isooctane + n-dodecane at 25, 50, 75, and 100°C at pressures up to 500 MPa or to the freezing pressure. The pressure dependence of the results is found to be represented equally well by the recent equation of Makita and by a free-volume form of equation. The Grunberg and Nissan equation gives a good fit to the mixture viscosity coefficient data.     

An alternative to the analysis of variance for reliability data

Though the analysis of variance is a commonly applied method for testing for differences between means of several processes, it is based in part on the assumption that the processes give rise to output that is normally distributed on the measured variable. Reliability and life test studies frequently give birth to data that exhibit clear skew, and application of the analysis of variance is questionable in such cases. A method referred to as analysis of reciprocals, which is based on an assumed inverse Gaussian distribution, provides an alternative to the analysis of variance in these instances. With applications in a variety of functional areas, including reliability and life testing, the inverse Gaussian distribution is able to accommodate substantial skew. It is hoped that this exposition will increase awareness of both the inverse Gaussian distribution and data analysis methods that are based on this distribution.     

Resampling-based multiple testing for microarray data analysis

The burgeoning field of genomics has revived interest in multiple testing procedures by raising new methodological and computational challenges. For example, microarray experiments generate large multiplicity problems in which thousands of hypotheses are tested simultaneously. Westfall and Young (1993) propose resampling-basedp-value adjustment procedures which are highly relevant to microarray experiments. This article discusses different criteria for error control in resampling-based multiple testing, including (a) the family wise error rate of West-fall and Young (1993) and (b) the false discovery rate developed by Benjamini and Hochberg (1995), both from a frequentist viewpoint; and (c) the positive false discovery rate of Storey (2002a), which has a Bayesian motivation. We also introduce our recently developed fast algorithm for implementing the minP adjustment to control family-wise error rate. Adjustedp-values for different approaches are applied to gene expression data from two recently published microarray studies. The properties of these procedures for multiple testing are compared.     

Absolute measurement of the thermal conductivity of alcohol + n-hexane mixtures

New absolute measurements, by the transient hot-wire technique, of the thermal conductivity of binary mixtures of n-hexane with methanol, ethanol, and hexanol are presented. The temperature range examined was 295–345 K and the pressure atmospheric. The concentrations studied were 75% by weight of methanol and 25, 50, and 75% by weight of ethanol and hexanol. The overall uncertainty in the reported thermal conductivity data is estimated to be ±0.5%, an estimate confirmed by the measurement of the thermal conductivity of water. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to correlate and predict the thermal conductivity of these mixtures, as a function of both composition and temperature.     

Volume ratios for n-pentane in the temperature range 278–338 K and at pressures up to 280 MPa

Volume ratios (V _P/V _0.1), and isothermal compressibilities calculated from them, are reported for n-pentane for seven temperatures in the range 278 to 338 K for pressures up to 280 MPa. The isobaric measurements were made with a bellows volumometer for which a novel technique had to be devised to enable measurements to be made above the normal boiling point (309.3 K). The accuracy of the volume ratios is estimated to be ±0.05 to 0.1% up to 303.15 K and ±0.1 to 0.2% from 313.15 to 338.15 K. The volume ratios are in good agreement with those calculated from recent literature data up to the maximum pressure of the latter, viz., 60 MPa.     

Photocurrent amplification effect of the fet gate p–n junction

A superlinear increase in the light current of the gate with an increase in the exciting integral light intensity (from 100 to 1000 lx) has been revealed experimentally. This superlinear increase is due to the increase in the internal gradient field generated by the minority carriers by the cutoff voltage of the gate leading to an additional interband generation of photocarriers. On the basis of the investigation of the dependence of photocurrent on the cutoff voltage it has been shown that the photocurrent increases linearly, which is explained by the creation of an internal electric field by the majority carriers of the base zone of the gate p–n junction. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 191–198, January–February, 2009.     

Application of rough hard-sphere theory to diffusion in n-alkanes

Tracer diffusion coefficients are reported for n-alkane solutes in n-dodecane, n-eicosane, n-eicosane, and n-octacosane in the temperature range 304–533 K at 1.38 MPa. Rough hard-sphere theory is used to interpret the data. The translational-rotational coupling parameters are determined for each solute-solvent pair at each temperature. The nature of the coupling parameter and the possibility of relating it to molecular properties and temperature in a homologous series are discussed.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.