scholarly journals Explaining the entropy concept and entropy components

2017 ◽  
Author(s):  
Marko Popovic
Keyword(s):  
Molecular Orientation ◽  
Classical Method ◽  
Energy State ◽  
Thermodynamic System ◽  
Absolute Zero ◽  
New Method ◽  
Residual Entropy ◽  
Total Entropy ◽  
Point Energy ◽  
Thermal Entropy

Total entropy of a thermodynamic system consists of two components: thermal entropy due to energy, and residual entropy due to molecular orientation. In this article, a three-step method for explaining entropy is suggested. Step one is to use a classical method to introduce thermal entropy <i>S<sub>TM</sub></i> as a function of temperature <i>T</i> and heat capacity at constant pressure <i>C<sub>p</sub></i>: <i>S<sub>TM</sub></i> = <i>∫(C<sub>p</sub>/T) dT</i>. Thermal entropy is the entropy due to uncertainty in motion of molecules and vanishes at absolute zero (zero-point energy state). It is also the measure of useless thermal energy that cannot be converted into useful work. The next step is to introduce residual entropy <i>S<sub>0</sub></i> as a function of the number of molecules <i>N</i> and the number of distinct orientations available to them in a crystal <i>m</i>: <i>S<sub>0</sub> = N k<sub>B</sub> ln m</i>, where <i>k<sub>B</sub></i> is the Boltzmann constant. Residual entropy quantifies the uncertainty in molecular orientation. Residual entropy, unlike thermal entropy, is independent of temperature and remains present at absolute zero. The third step is to show that thermal entropy and residual entropy add up to the total entropy of a thermodynamic system <i>S</i>: <i>S = S<sub>0</sub> + S<sub>TM</sub></i>. This method of explanation should result in a better comprehension of residual entropy and thermal entropy, as well as of their similarities and differences. The new method was tested in teaching at Faculty of Chemistry University of Belgrade, Serbia. The results of the test show that the new method has a potential to improve the quality of teaching.

scholarly journals Explaining the entropy concept and entropy components

2017 ◽  
Author(s):  
Marko Popovic
Keyword(s):  
Molecular Orientation ◽  
Classical Method ◽  
Energy State ◽  
Thermodynamic System ◽  
Absolute Zero ◽  
New Method ◽  
Residual Entropy ◽  
Total Entropy ◽  
Point Energy ◽  
Thermal Entropy

Total entropy of a thermodynamic system consists of two components: thermal entropy due to energy, and residual entropy due to molecular orientation. In this article, a three-step method for explaining entropy is suggested. Step one is to use a classical method to introduce thermal entropy <i>S<sub>TM</sub></i> as a function of temperature <i>T</i> and heat capacity at constant pressure <i>C<sub>p</sub></i>: <i>S<sub>TM</sub></i> = <i>∫(C<sub>p</sub>/T) dT</i>. Thermal entropy is the entropy due to uncertainty in motion of molecules and vanishes at absolute zero (zero-point energy state). It is also the measure of useless thermal energy that cannot be converted into useful work. The next step is to introduce residual entropy <i>S<sub>0</sub></i> as a function of the number of molecules <i>N</i> and the number of distinct orientations available to them in a crystal <i>m</i>: <i>S<sub>0</sub> = N k<sub>B</sub> ln m</i>, where <i>k<sub>B</sub></i> is the Boltzmann constant. Residual entropy quantifies the uncertainty in molecular orientation. Residual entropy, unlike thermal entropy, is independent of temperature and remains present at absolute zero. The third step is to show that thermal entropy and residual entropy add up to the total entropy of a thermodynamic system <i>S</i>: <i>S = S<sub>0</sub> + S<sub>TM</sub></i>. This method of explanation should result in a better comprehension of residual entropy and thermal entropy, as well as of their similarities and differences. The new method was tested in teaching at Faculty of Chemistry University of Belgrade, Serbia. The results of the test show that the new method has a potential to improve the quality of teaching.

scholarly journals The Method of High Accuracy Calculation of Robot Trajectory for the Complex Curves

2020 ◽  
Vol 28 (4) ◽  
pp. 247-252
Author(s):  
Alexander Lozhkin ◽  
Pavol Bozek ◽  
Konstantin Maiorov
Keyword(s):  
Calculation Method ◽  
Geometric Modeling ◽  
Classical Method ◽  
Geometric Model ◽  
New Method ◽  
Approximation Methods ◽  
Linear Transformations ◽  
Design Quality ◽  
Complex Curves ◽  
Internal Properties

AbstractThe geometric model accuracy is crucial for product design. More complex surfaces are represented by the approximation methods. On the contrary, the approximation methods reduce the design quality. A new alternative calculation method is proposed. The new method can calculate both conical sections and more complex curves. The researcher is able to get an analytical solution and not a sequence of points with the destruction of the object semantics. The new method is based on permutation and other symmetries and should have an origin in the internal properties of the space. The classical method consists of finding transformation parameters for symmetrical conic profiles, however a new procedure for parameters of linear transformations determination was acquired by another method. The main steps of the new method are theoretically presented in the paper. Since a double result is obtained in most stages, the new calculation method is easy to verify. Geometric modeling in the AutoCAD environment is shown briefly. The new calculation method can be used for most complex curves and linear transformations. Theoretical and practical researches are required additionally.

Molecular Orientation and Absorbance Determination for Oriented Polymers by Tilting Method with Nonpolarized Infrared Light

1971 ◽  
Vol 25 (3) ◽  
pp. 355-360 ◽  
Author(s):  
J. L. Koenig ◽  
M. Itoga
Keyword(s):  
Molecular Orientation ◽  
New Method ◽  
Infrared Light ◽  
Oriented Polymers ◽  
Oriented Polymer ◽  
Polymer Systems ◽  
Unpolarized Light ◽  
Extrapolation Technique ◽  
Experimental Errors

A new method of measuring the absorbance corrected for orientation and the orientation of oriented polymer systems is derived. The method using unpolarized light utilizes a linear plotting and extrapolation technique to minimize experimental errors. The method is applied to oriented nlyon 66 samples and the results are compared with the previous methods.

Stereodynamics of chemical reactions: quasi-classical, quantum and mixed quantum-classical theories

Open Physics ◽  
2012 ◽  
Vol 10 (2) ◽  
Author(s):  
Wenwu Xu ◽  
Guangjiu Zhao
Keyword(s):  
Chemical Reactions ◽  
Classical Method ◽  
Zero Point ◽  
Quantum Effects ◽  
Classical Trajectory ◽  
Tunneling Effect ◽  
Point Energy ◽  
Classical Quantum ◽  
Theoretical Results ◽  
Good Agreement

AbstractIn this review, some benchmark works by Han and coworkers on the stereodynamics of typical chemical reactions, triatomic reactions H + D2, Cl + H2 and O + H2 and polyatomic reaction Cl+CH4/CD4, are presented by using the quasi-classical, quantum and mixed quantum-classical methods. The product alignment and orientation in these A+BC model reactions are discussed in detail. We have also compared our theoretical results with experimental measurements and demonstrated that our theoretical results are in good agreement with the experimental results. Quasi-classical trajectory (QCT) method ignores some quantum effects like the tunneling effect and zero-point energy. The quantum method will be very time-consuming. Moreover, the mixed quantum-classical method can take into account some quantum effects and hence is expected to be applicable to large systems and widely used in chemical stereodynamics studies.

Molecular Orientation of Polymer Lubricant Films: Its Tribological Consequence

1998 ◽  
Vol 120 (2) ◽  
pp. 369-378 ◽  
Author(s):  
Chao Gao ◽  
Tam Vo ◽  
Joel Weiss
Keyword(s):  
Molecular Orientation ◽  
Energy State ◽  
Tribological Performance ◽  
Lubricant Film ◽  
Carbon Surface ◽  
Lubricant Layer ◽  
Significant Difference ◽  
End Groups ◽  
Lubricant Films ◽  
Almost All

The objective of this paper is to demonstrate, from experiments and modeling, how and why molecular orientation of functional end groups of perfluoro-polyether (PFPE) lubricants play an important role in the tribological performance of thin film magnetic disks. These disks typically have an amorphous carbon overcoat upon which a thin lubricant layer is deposited using dip-coating technique. Glancing-angle FTIR (Fourier Transform Infra-Red Spectrometry) is used for measuring molecular orientation of planer functional end groups. A molecular orientation index (MOI) was defined as 1 for randomly oriented functional end groups. The MOI is mathematically derived as 3 (maximum) for lubricant molecules oriented with their functional end groups perpendicular to the surface, and as 0 (minimum) if lubricant molecules oriented with their functional end groups parallel to the surface. The MOI is shown to depend on processing conditions and lubricant film thickness. The tribological performance of the lubricant films was evaluated using drag-mode contact start-stop testing. It was found that wear durability of the lubricant films (~2 nm) with MOI ~ 1.5 is a few times better than those with MOI ~ 0.5 to 1.0. No significant difference in the amount of bonded lubricant film was detected over the range of MOI studied. Nor was there a detectable relationship with hydrophobicity. It was inferred from decreased MOI values due to thermal effects and storage time that a smaller MOI value corresponds to a lower free energy state of the lubricant film. Interestingly, MOI values for bonded lubricant films for Process A are found to be close to 3.0, suggesting that almost all functional end groups in the bonded films are oriented perpendicular to the carbon surface, close to 2.0 for process B, and close to 0 for process C, meaning that almost all functional end groups in the bonded films from process C are oriented parallel to the carbon surface. Relationship between physical/chemical bonding configurations and MOI values are graphically presented in detail. Based on this relation, a simple model on lubricant film structures for the three processes studied is presented. The model MOI values agree very well with measured MOI values as a function of lubricant thickness for all three processes, and the model also appears to account for the observed tribology performance for the MOI values studied (0.5 ~ 1.5).

scholarly journals Decontamination of Tritium Contaminated Surfaces Using Strippable Polymeric Gel

2001 ◽  
Vol 71 (3) ◽  
pp. 269-281
Author(s):  
Diana Chiper ◽  
Catalin Stelian Tuta ◽  
Simona Eugenia Manea ◽  
George Gabriel Bubueanu
Keyword(s):  
Classical Method ◽  
Decontamination Factor ◽  
New Method ◽  
Nuclear Field ◽  
Polymeric Gel ◽  
Polymeric Hydrogel

The purpose of the present paper consists in finding a more efficient and less expensive decontamination method for surfaces contaminated with Tritium-labelled compounds, being able to provide information for nuclear field specialists. This paper studies the polymeric hydrogel DeconGel, presenting the methods and facilities used, as well as the obtained results from the experiments and tests. The decontamination factor of DeconGel type 1108 for the analysed surfaces (contaminated with a mixture of tritium labelled compounds) can take values in the range of 76%-93%, while in the case of DeconGel type 1102 the values of the decontamination factor for the analysed surfaces (contaminated with tritiated oil) can vary between 76% and 98%, results far greater than the ones obtained with the classical method of wet wiping. Because the results were more than satisfying, this paper concludes by recommending the implementation of this new method.

scholarly journals Harmonising plant functional type distributions for evaluating Earth system models

2019 ◽  
Vol 15 (1) ◽  
pp. 335-366 ◽  
Author(s):  
Anne Dallmeyer ◽  
Martin Claussen ◽  
Victor Brovkin
Keyword(s):  
Classical Method ◽  
New Method ◽  
Earth System ◽  
System Models ◽  
Warm Temperate Forest ◽  
Simulated Climate ◽  
Vegetation Models ◽  
Global Vegetation ◽  
Warm Temperate ◽  
Earth System Models

Abstract. Dynamic vegetation models simulate global vegetation in terms of fractional coverage of a few plant functional types (PFTs). Although these models often share the same concept, they differ with respect to the number and kind of PFTs, complicating the comparability of simulated vegetation distributions. Pollen-based vegetation reconstructions are initially only available in the form of time series of individual taxa that are not distinguished in the models. Thus, to evaluate simulated vegetation distributions, the modelling results and pollen-based vegetation reconstructions have to be converted into a comparable format. The classical approach is the method of biomisation, but hitherto PFT-based biomisation methods were only available for individual models. We introduce and evaluate a simple, universally applicable technique to harmonise PFT distributions by assigning them into nine mega-biomes, using only assumptions on the minimum PFT cover fractions and few bioclimatic constraints (based on the 2 m temperature). These constraints mainly follow the limitation rules used in the classical biome models (here BIOME4). We test the method for six state-of-the-art dynamic vegetation models that are included in Earth system models based on pre-industrial, mid-Holocene and Last Glacial Maximum simulations. The method works well, independent of the spatial resolution or the complexity of the models. Large biome belts (such as tropical forest) are generally better represented than regionally confined biomes (warm–temperate forest, savanna). The comparison with biome distributions inferred via the classical biomisation approach of forcing biome models (here BIOME1) with the simulated climate states shows that the PFT-based biomisation is even able to keep up with the classical method. However, as the new method considers the PFT distributions actually calculated by the Earth system models, it allows for a direct comparison and evaluation of simulated vegetation distributions which the classical method cannot do. Thereby, the new method provides a powerful tool for the evaluation of Earth system models in general.

scholarly journals A century reconstruction of the mass balance of Glacier de Sarennes, French Alps

2002 ◽  
Vol 48 (160) ◽  
pp. 142-148 ◽  
Author(s):  
Olivier Torinesi ◽  
Anne Letréguilly ◽  
François Valla
Keyword(s):  
Time Series ◽  
Mass Balance ◽  
Classical Method ◽  
Meteorological Data ◽  
New Method ◽  
Calibration Period ◽  
French Alps ◽  
Long Period ◽  
Albedo Change

AbstractThe 50 year time series of mass balance on Glacier de Sarennes is one of the longest in the French Alps, and so is often used as a reference for glacier variations in the French Alps. Meteorological data can be used to extend the series backwards in time. Martin (1978) proposed such a reconstruction for the 1882–1977 period. With 50 years of observations, we show that the classical method used by Martin is too dependent on the calibration period. We therefore try to improve the accuracy of this reconstruction using the Vincent and Vallon (1997) method which takes into account the albedo change of the surface during the ablation period (this is called the daily method). This new method appears to be stable in time. Once calibrated, the daily method is applied to reconstruct the 1881–1949 period. The new reconstruction is compared to a volumetric balance between two maps from 1906 and 1981. It appears that both reconstructions (classical and daily) fail to render the trend correctly over a long period of time. The cumulative centred mass balance correlates well (r2 = 0.62) with the hydrological mass-balance series of Aletschgletscher, Switzerland.

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