Enthalpy formation of fluorene: Is a challenging problem for theory or experiment?

2021 ◽  
Author(s):  
Olga V. Dorofeeva ◽  
Anna Druzhinina
Keyword(s):  
Enthalpy Of Formation ◽  
Challenging Problem ◽  
Mp2 Method ◽  
Experimental Enthalpy

The large discrepancy between the experimental enthalpy of formation of fluorene and theoretical value calculated by G3(MP2) method was revealed more than ten years ago. Three years later, a new...

scholarly journals Experimental determination of the solubility constant of kurnakovite, MgB3O3(OH)5·5H2O

2020 ◽  
Vol 105 (7) ◽  
pp. 977-983 ◽  
Author(s):  
Yongliang Xiong
Keyword(s):  
Thermodynamic Properties ◽  
Equilibrium Constant ◽  
Enthalpy Of Formation ◽  
Structural Formula ◽  
Salt Lakes ◽  
Standard Entropy ◽  
Structural Water ◽  
Experimental Enthalpy ◽  
Long Term Experiment ◽  
Borate Minerals

Abstract In this study, I present experimental results on the equilibrium between boracite [Mg3B7O13C1(cr)] and kurnakovite [chemical formula, Mg2B6O11·15H2O(cr); structural formula, MgB3O3(OH)5·5H2O(cr)] at 22.5 ± 0.5 °C from a long-term experiment up to 1629 days, approaching equilibrium from the direction of supersaturation, Mg3B7O13C1(cr) + H+ + 2B(OH)4− + 18H2O(1) ⇌ 3MgB3O3(OH)5·5H2O(cr) + C1−. Based on solubility measurements, the 10-based logarithm of the equilibrium constant for the above reaction at 25 °C is determined to be 12.83 ± 0.08 (2σ). Based on the equilibrium constant for dissolution of boracite, Mg3B7O13C1(cr) + 15H2O(1) = 3Mg2+ + 7B(OH)4− + C1− + 2H+ at 25 °C measured previously (Xiong et al. 2018) and that for the reaction between boracite and kurnakovite determined here, the equilibrium constant for dissolution of kurnakovite, MgB3O3(OH)5·5H2O(cr) = Mg2+ + 3B(OH)4− + H+ + H2O(1) is derived as −14.11 ± 0.40 (2σ). Using the equilibrium constant for dissolution of kurnakovite obtained in this study and the experimental enthalpy of formation for kurnakovite from the literature, a set of thermodynamic properties for kurnakovite at 25 °C and 1 bar is recommended as follows: ΔHf0 = −4813.24 ± 4.92 kJ/mol, ΔGf0 = −4232.0 ± 2.3 kJ/mol, and S0 = 414.3 ± 0.9 J/(mol·K). Among them, the Gibbs energy of formation is based on the equilibrium constant for kurnakovite determined in this study; the enthalpy of formation is from the literature (Li et al. 1997), and the standard entropy is calculated internally with the Gibbs-Helmholtz equation in this work. The thermodynamic properties of kurnakovite estimated using the group contribution method for borate minerals based on the sums of contributions from the cations, borate polyanions, and structural water to the thermodynamic properties from the literature (Li et al. 2000) are consistent, within their uncertainties, with the values listed above. Since kurnakovite usually forms in salt lakes rich in sulfate, studying the interactions of borate with sulfate is important to modeling kurnakovite in salt lakes. For this purpose, I have re-calibrated our previous model (Xiong et al. 2013) describing the interactions of borate with sulfate based on the new solubility data for borax in Na2SO4 solutions presented here.

Thermodynamics of EuCl3: Experimental Enthalpy of Fusion and Heat Capacity and Estimation of Thermodynamic Functions up to 1300 K

2002 ◽  
Vol 57 (5) ◽  
pp. 215-220 ◽  
Author(s):  
L. Rycerz ◽  
M. Gaune-Escard
Keyword(s):  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Temperature Dependence ◽  
Melting Temperature ◽  
Enthalpy Of Formation ◽  
Thermodynamic Functions ◽  
Molar Enthalpy ◽  
Standard Molar Enthalpy ◽  
Scanning Calorimetry ◽  
Experimental Enthalpy

The heat capacity of solid EuCl3 was measured by differential scanning calorimetry from 300 K up to the melting temperature, and beyond. These results were compared with literature data and fitted by a polynomial temperature dependence. The enthalpy of EuCl3 fusion was measured. Furthermore, by combination of these results with literature data on the entropy at 298.15 Sm0 (EuCl3, s, 298.15 K) and the standard molar enthalpy of formation of ∆form H0m (EuCl3, s, 298.15 K), the thermodynamic functions have been calculated up to 1300 K.

Enthalpy of formation of liquid alloys Bi + Cd + Ga + Zn, Bi + Cd + Ga + In + Zn, Ga + In + Pb + Zn and Cd + Ga + In + Pb + Zn

1998 ◽  
Vol 95 (10) ◽  
pp. 2267-2279 ◽  
Author(s):  
R. Ouédraogo ◽  
T. S. Kabré ◽  
M. Gambino ◽  
J. P. Bros
Keyword(s):  
Enthalpy Of Formation ◽  
Liquid Alloys

True Imaginings Integrating Panentheism and A Personal View of God

2019 ◽  
Vol 11 (1) ◽  
pp. 61
Author(s):  
Klaus Müller
Keyword(s):  
Challenging Problem ◽  
Personal View ◽  
Ontological Commitments ◽  
As If

The perhaps most challenging problem for a panentheistic paradigm in Christian god-talk consists in integrating the trait of personhood in the monistic horizon of this approach. A very helpful way to this goal seems to be the concept of imagination. Its logic of an “as if” represents a modified variation of Kant`s idea of the postulates of reason. Reflections of Jürgen Werbick, Douglas Headley, and Volker Gerhardt substantiate the philosophical and theological capabilities of this solution which also include a sensibility for the ontological commitments included in the panentheistic approach.

Segmentation of Touching Hand written Telugu Characters by using Drop Fall Algorithm

2012 ◽  
Vol 3 (2) ◽  
pp. 343-346
Author(s):  
Adabala Venkata Srinivasa Rao ◽  
D R Sandeep ◽  
V B Sandeep ◽  
S Dhanam Jaya
Keyword(s):  
Challenging Problem ◽  
Indian Language ◽  
Segmentation Accuracy ◽  
Selection Of

Recognition of Indian language scripts is a challenging problem. Work for the development of complete OCR systems for Indian language scripts is still in infancy. Complete OCR systems have recently been developed for Devanagri and Bangla scripts. Research in the field of recognition of Telugu script faces major problems mainly related to the touching and overlapping of characters. Segmentation of touching Telugu characters is a difficult task for recognizing individual characters. In this paper, the proposed algorithm is for the segmentation of  touching Hand written Telugu characters. The proposed method using Drop-fall algorithm is based on the moving of a marble on either side of the touching characters for selection of the point from where the cutting of the fused components should take place. This method improvers the segmentation accuracy higher than the existing one.

Detection and localization of helipad in autonomous UAV landing: a coupled visual-inertial approach with artificial intelligence

2020 ◽  
Vol 71 (7) ◽  
pp. 828-839
Author(s):  
Thinh Hoang Dinh ◽  
Hieu Le Thi Hong
Keyword(s):  
Neural Network ◽  
Unmanned Aerial Vehicles ◽  
Fiducial Marker ◽  
Localization Algorithm ◽  
Challenging Problem ◽  
Autonomous Landing ◽  
Aerial Vehicles ◽  
Set Up ◽  
Detection And Localization ◽  
Rotary Wing

Autonomous landing of rotary wing type unmanned aerial vehicles is a challenging problem and key to autonomous aerial fleet operation. We propose a method for localizing the UAV around the helipad, that is to estimate the relative position of the helipad with respect to the UAV. This data is highly desirable to design controllers that have robust and consistent control characteristics and can find applications in search – rescue operations. AI-based neural network is set up for helipad detection, followed by optimization by the localization algorithm. The performance of this approach is compared against fiducial marker approach, demonstrating good consensus between two estimations

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