Wyniki wyszukiwania - Biblioteka Nauki

1

Korelacja między prędkością propagacji ultradźwięków a Entalapią mieszania wodnych roztworów amin alifatycznych i cyklicznych

100%

Marczak W. , Ernst S.

|

1998

|

tom Vol. 19

179-184

EN

The relationship between the speed of ultrasound in a fluid (c) and its enthalapy (H) is given by the following equations: c= square root V2 /(KSM) (the Laplace formula), V=(partial differential H/partial differential p)s and Ks = -(partial differential2/partial differential p 2)s , where V - molar volume, KS - molar adiabatic compres molar mass of the substance, p - pressure and S - entropy. Thus, since for the calculation the speed of sound from the corresponding thermodynamic functions the equation of state has to be known, which most often is not the case, reliable correlations between the speed thermodynamic characteristics seem to be of interest. An attempt was undertaken to correlation of this type for 13 binary water - amine mixtures. The correlation of the of the speed isotherms with the first enthalpies of solution in water (at 298.15 K; based on the literature data) is shown in Figure 3. Some correlations are also observed between the) of sound and the enthalpies of mixing (Figs 4 and 5). The reported correlations may be used for a preliminary prediction of the enthalapy mixing from ultrasonic data. Calorimetric measurements are rather time-consuming and difficult in comparison with the ultrasonic ones, thus an estimation of the enthalpy effect in this way, although being only a rough one, could be useful both in practical application in calorimetric studies.

2

Effects of hydrophobic and hydrophilic hydration on the compressibility, volume and viscosity of mixtures of water with ß-picoline

100%

Marczak W. , Ernst S.

|

1998

|

tom Vol. 46, No. 4

375-395

EN

The speed of ultrasound in and the density of mixtures of water with ,ß-picoline were measured in the whole concentration range and within the temperature limits 293 = 298 K. The viscosities of those mixtures were measured at 293 K. The molar compressibility, molar volume and the corresponding excess and partial functions as well as the coefficients of the adiabatic compressibility and the excess activation energy of viscous flow were calculated. The results were discussed in terms of hydrophobic and hydrophilic molecular interactions. The hydrophobic hydration becomes evident in the thermodynamic properties of dilute aqueous solutions in that most probably labile semiclathrate structures, resembling cubic II solid clathrates (symmetry group Fd3m) but with guest molecules hydrogenbonded to the water host lattice, arise. With increasing concentration of the organic component the shortage of water leads to a gradual decay of the water polyhedra around the picoline molecules and hydrophilic hydration becomes predominant.

3

Adaptive granular planning for robust plan generation under uncertain traffic conditions

100%

Ernst S. , Ligęza A.

|

2008

|

tom Vol. 34, no 1

77-83

EN

Real-time execution of planned routes often requires re-planning, especially in highly dynamic environments. However, re-planning not only induces deterioration of solution quality - it is often time-consuming or even impossible. The article describes a new approach to solving Plan Generation Problems (PGPs), aimed at application for route planning in uncertain environments. The concept is based on maintaining a set of alternative solutions to allow quick switching when conditions change. A new formal representation of a PGP solution is proposed. Map abstraction methods are discussed in the context of landmarks defined by natural characteristics of urban areas. The article introduces the concept of solution robustness and presents methods for a priori prediction of solution feasibility under unreliable conditions. Finally, the paper presents strategies for execution of robust plans, as well as a formal definition of a plan execution problem. Several new possibilities are discussed, such as the inclusion of human decisions as feedback for intelligent route planning systems.

4

Acoustic Properties of Pure Alcohols and Binary Mixtures Containing Alcohols

100%

Gepert M. , Ernst S.

|

2001

|

tom Vol. 22

77-84

EN

A survey of the literature was made in order to examine the ralationship between the chemical structure and the speed of sound in pure alcohols. Additionally, the acoustic behaviour of mixtures of methanol with some normal alcohols and with various isomers of butanol was examined. The absolute deviations of the measured sound velocity from the ideal one ("excess" velocity Delta u(x)) and the axcess adiabatic compressibilities are in most cases very small and S-shaped. A strict correlation between the shape of Delta u(x) and K E(x) for the investigated mixtures was found. A dependance of the ultrasonic behaviour of pure alcohols and their binary mixtures on the molecular structure as suggested.

5

Prędkość propagacji fali ultradźwiękowej w cieczach organicznych w zakresie temperatur od 293,15 k do 318,15 k i pod ciśnieniami do 90 MPa

80%

Żak A. , Dzida M. , Zorębski M. , Ernst S.

|

1998

|

tom Vol. 19

301-306

EN

An ultrasonic apparatus for the measurements of the speed of sound in liquids under high pressures was constructed. The modified pulse-echo-overlap method was applied. A single piezoceramic transducer was used both as transmitter and receiver. The chamber is made of stainless steel. Thermocoax cables were used for the electric signal transmission inside the vessel. The pressure is provided by a hand-operated hydraulic press. The apparatus was tested by measuring the speed of sound in pure organic liquids (ethanol and n - heptane) between 293.15 and 318.15K and at pressures up to 90 MPa. The values of the ultrasound velocity are compared with those reported by other authors. The accuracy of the obtained speed of sound data is estimated to be 0.02% at atmospheric pressure, 0.03% at pressures up to 60 MPa and 0.04% at pressures from 60 to 90 MPa. The agreement between the data obtained and those reported by other authors is satisfactory.

6

Acoustic and Thermodynamic Properties of Ethanol, 1-Propanol and 1-Hexanol at Temperatures from 293 to 318 K and Pressures up to 90 MPa

80%

Dzida M. , Marczak W. , Ernst S.

|

1999

|

tom Vol. 20

43-47

7

Ultradźwiękowe badanie rozcieńczonych roztworów 3-metylopyrazolu w cykloheksanie

80%

Bebek K. , Rost I. , Ernst S.

|

1998

|

tom Vol. 19

27-30

EN

The ultrasound velocities in and densities of mixtures of 3-methylpyrazol with cyclohexa and in the pure components were measured at temperaturę 293.15 K. The absorption of ultrasound was measured at 293.2 K in 11 mixtures of 3-methylpyrazol with cyclohexane within the k 3-methylpyrazol concentrations range. For the investigated solutions and pure components the quotient alfa/f2 is independent frequency within the tested frequency range (10 - 80 MHz). The dependencies of the mean vlues of alfa/f2 on mixture composition show maximum at low 3-methylpyrazol concentrations to (x1 almost equal to 0.13) while the ultrasound. velocity decreases monotonically with increasing mole fractions 3-methylpyrazol up to x1 almost equal to 0.3. The dependencies of ultrasound absorption and velocities on the mixture composition were compared and discussed in terms of the entropy effect connected w solvate destruction during dimerization and other factors affecting the specific self-association 3-methylpyrazol in cyclohexane.

8

Wpływ hydradacji na prędkość propagacji fali ultradźwiękowej w roztworach wodnych CuCl2, CoCl2 i NiCl2

80%

Gepert M. , Manikowski R. , Ernst S.

|

1998

|

tom Vol. 19

83-89

EN

The speeds of sound in aqueous solutions of CuCl2, CoCl2, and NiCl2 and the concentration dependencies of those speeds show important differences. Since the speed of in a liquid depends mainly on the structure (degree of molecular order), those differences should be related to the effect of the hydration of the electrolytes under test on the structure of the solutions. The qualitative correlation found between the speeds of sound and the structures of the low spin six-coordinate aqua-complexes of Cu2+, Co2+ and Ni2+ (due to : their different electronic configurations) suggests that the structure of the hydration complexes of transition metals may have a significant effect on the bulk properties of those solutions. A further quantitative correlation was found between the speed of sound and the entropy of hydration, S HYD, and the structural entropy, S str, of Cu2+, Co2+ and Ni2+; the smallest value of the speed of sound in the CuCl2 solution corresponds with the smallest relative entropy increase accompanying the hydration of Cu2+.

9

A Computer Program for the Calculation of Thermodynamic Quantities for Liquids from the Speed of Sound at Elevated Pressures

80%

Marczak W. , Dzida M. , Ernst S.

|

1999

|

tom Vol. 20

159-164