scholarly journals Study of rheological behaviour of wines

2016 ◽  
Vol 30 (4) ◽  
pp. 509-518 ◽  
Author(s):  
Petr Trávníček ◽  
Patrik Burg ◽  
Anna Krakowiak-Bal ◽  
Petr Junga ◽  
Tomáš Vítěz ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Apparent Viscosity ◽  
Rheological Behaviour ◽  
Second Phase ◽  
Temperature Hysteresis ◽  
Total Acidity ◽  
Chemical Parameters ◽  
The Czech Republic ◽  
Thixotropic Behaviour

Abstract This study deals with rheological properties of various wine varieties. Samples of the following wines were used for this experiment: André, Cabernet Moravia, Laurot, Saint Laurent, Gruner Veltliner, Pinot Blanc, Müller Thurgau, and Riesling Italico. These samples were obtained from wine produced from the grapes collected in the Czech Republic (Morava region, subregion Velke Pavlovice). In the first phase, the chemical composition of the samples was determined. The following chemical parameters were determined: total acidity, pH, content of the alcohol, reduced sugars, free SO2, total SO2, and volatile acids. In the second phase of the study, the physical properties of the samples were determined and the samples of the wines were subjected to rheological tests. These tests consisted in determination of apparent viscosity in relation to temperature, hysteresis loop tests, and apparent viscosity related to time. The dependence of the shear rate on the shear stress was described with the Herschel-Bulkley mathematical model. The experiment yielded the following findings: seven out of the eight samples behaved as non-Newtonian fluids at low temperature (5°C); non-Newtonian behaviour was changed into Newtonian at the temperature higher than 10°C; non-Newtonian behaviour was characterised as thixotropic behaviour; the degree of thixotropy is relatively small and reaches 1.85 Pa s-1 ml-1.

scholarly journals Determination of rheological behaviour of wine lees

2015 ◽  
Vol 29 (3) ◽  
pp. 307-311 ◽  
Author(s):  
Jaromír Lachman ◽  
Kazimierz Rutkowski ◽  
Petr Trávníček ◽  
Tomáš Vítěz ◽  
Patrik Burg ◽  
...  
Keyword(s):  
Dynamic Viscosity ◽  
Rheological Behaviour ◽  
Volatile Acid ◽  
Second Phase ◽  
Temperature Hysteresis ◽  
Chemical Background ◽  
Rate Test ◽  
Red Grape ◽  
Increasing Temperature

Abstract This study deals with the rheological properties of wine lees. Samples of wine lees of the Saint Laurent variety were used in this experiment. The investigated wine lees arose in the process of production red grape wine in 2013 (Czech Republic). At first, the chemical background was determined. The chemical background includes the following chemical parameters: total acidity, pH, alcohol content, reduced sugars, free SO2, total SO2, and volatile acid. In the second phase of the study, physical properties were determined. Specifically, a sample of wine lees was subjected to rheological tests. These tests consisted in determination of dependence of dynamic viscosity on the temperature, hysteresis loop tests, dependence of dynamic viscosity on the time and step-down in the shear rate test. The experiment demonstrated that the dynamic viscosity increased with increased temperature – this phenomenon is caused by thermolabile proteins – and the wine lees has rheopectic behaviour; the degree of rheopexy was found to rise with the increasing temperature.

scholarly journals The antimicrobial activity of honeys produced in theCzech Republic

2011 ◽  
Vol 50 (No. 8) ◽  
pp. 376-384 ◽  
Author(s):  
L. Vorlová ◽  
R. Karpíšková ◽  
I. Chabinioková ◽  
K. Kalábová ◽  
Z. Brázdová
Keyword(s):  
Antimicrobial Activity ◽  
Czech Republic ◽  
Physicochemical Parameters ◽  
Inhibitory Concentration ◽  
Chemical Parameters ◽  
Water Conductivity ◽  
The Czech Republic ◽  
Concentration Method ◽  
Physical And Chemical

 The aim of this project was to determine the antimicrobial activity of honeys produced in the Czech Republic to some bacteria (Listeria monocytogenes, Staphylococcus aureus, Salmonella typhimurium and Escherichia coli). Another aim was to find out whether there are correlations between the antimicrobial activity of honeys and their physicochemical parameters. All honeys included in the study were directly obtained from beekeepers in Southern and Northern Moravia from the summer load of 2001. The project contains 20 honeys which were determined according to their conductivity as blossom (6), blends (10) and honeydew (4). The determination of physical and chemical parameters such as content of water, conductivity, pH, water activity, invertase and diastase activities was carried out in accordance with the methods described in Harmonised methods of the European Honey Commission. The determination of the antimicrobial activity of honey was done by the MIC (minimal inhibitory concentration) method. Statistically significant relations between the antimicrobial activity and the conductivity of honey (P < 0.05), the diastase (P < 0.05) and invertase (P < 0.001) activities were found out in the observed physicochemical parameters. The study proved that honey produced in the Czech Republic is antimicrobially effective with the highest effect in honeydew honeys (P < 0.01).  

Polishing process effect on the image of dispersed precipitates

1984 ◽  
Vol 42 ◽  
pp. 534-535
Author(s):  
C.T. Hu ◽  
C.W. Allen
Keyword(s):  
Matrix Material ◽  
Specimen Preparation ◽  
Second Phase ◽  
Precipitate Particle ◽  
Polishing Process ◽  
Second Phase Particles ◽  
The Matrix ◽  
Surface Profiles ◽  
Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

Determination of creep mechanisms in various silicon carbides via TEM

1986 ◽  
Vol 44 ◽  
pp. 484-487
Author(s):  
C. H. Carter ◽  
J. E. Lane ◽  
J. Bentley ◽  
R. F. Davis
Keyword(s):  
Heat Exchangers ◽  
Sintered Material ◽  
Polycrystalline Material ◽  
Chemical Vapor ◽  
Graphite Substrate ◽  
Second Phase ◽  
Reaction Bonding ◽  
Creep Mechanisms ◽  
Porous Sic

Silicon carbide (SiC) is the generic name for a material which is produced and fabricated by a number of processing routes. One of the three SiC materials investigated at NCSU is Norton Company's NC-430, which is produced by reaction-bonding of Si vapor with a porous SiC host which also contains free C. The Si combines with the free C to form additional SiC and a second phase of free Si. Chemical vapor deposition (CVD) of CH3SiCI3 onto a graphite substrate was employed to produce the second SiC investigated. This process yielded a theoretically dense polycrystalline material with highly oriented grains. The third SiC was a pressureless sintered material (SOHIO Hexoloy) which contains B and excess C as sintering additives. These materials are candidates for applications such as components for gas turbine, adiabatic diesel and sterling engines, recouperators and heat exchangers.

DETERMINATION OF PERFORMANCE INDICATORS OF THE TRUCK KrAZ-6510TE

2020 ◽  
pp. 19-26
Author(s):  
Olexandr Pavlenko ◽  
Serhii Dun ◽  
Maksym Skliar
Keyword(s):  
Mathematical Model ◽  
Surface Friction ◽  
Building Structures ◽  
Maximum Torque ◽  
Military Equipment ◽  
Military Vehicles ◽  
Force Magnitude ◽  
Vehicle Mobility ◽  
The Mathematical Model

In any economy there is a need for the bulky goods transportation which cannot be divided into smaller parts. Such cargoes include building structures, elements of industrial equipment, tracked or wheeled construction and agricultural machinery, heavy armored military vehicles. In any case, tractor-semitrailer should provide fast delivery of goods with minimal fuel consumption. In order to guarantee the goods delivery, tractor-semitrailers must be able to overcome the existing roads broken grade and be capable to tow a semi-trailer in off-road conditions. These properties are especially important for military equipment transportation. The important factor that determines a tractor-semitrailer mobility is its gradeability. The purpose of this work is to improve a tractor-semitrailer mobility with tractor units manufactured at PJSC “AutoKrAZ” by increasing the tractor-semitrailer gradeability. The customer requirements for a new tractor are determined by the maximizing the grade to 18°. The analysis of the characteristics of modern tractor-semitrailers for heavy haulage has shown that the highest rate of this grade is 16.7°. The factors determining the limiting gradeability value were analyzed, based on the tractor-semitrailer with a KrAZ-6510TE tractor and a semi-trailer with a full weight of 80 t. It has been developed a mathematical model to investigate the tractor and semi-trailer axles vertical reactions distribution on the tractor-semitrailer friction performances. The mathematical model has allowed to calculate the gradeability value that the tractor-semitrailer can overcome in case of wheels and road surface friction value and the tractive force magnitude from the engine. The mathematical model adequacy was confirmed by comparing the calculations results with the data of factory tests. The analysis showed that on a dry road the KrAZ-6510TE tractor with a 80 t gross weight semitrailer is capable to climb a gradient of 14,35 ° with its coupling mass full use condition. The engine's maximum torque allows the tractor-semitrailer to overcome a gradient of 10.45° It has been determined the ways to improve the design of the KrAZ-6510TE tractor to increase its gradeability. Keywords: tractor, tractor-semitrailer vehicle mobility, tractor-semitrailer vehicle gradeability.

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