Papers by Keyword: Polymorphism

Abstract: Calculations of the structural and energy parameters, band structure and density of electronic states of new structural varieties of graphyne have been performed by the density functional theory method. The initial structure of the nine polymorphs was theoretically constructed on the basis of the 5-7a graphene layer. As a result of the calculations, the structure of only five graphyne layers was found to be stable: α-L_5-7a, β1-L_5-7a, β2-L_5-7a, β3-L_5-7a and β4-L_5-7a. The structure of layers γ1-L_5-7a, γ2-L_5-7a, and γ3-L_5-7a is transformed into the structure of graphene layers by geometric optimization, and the graphyne layer γ4-L_5-7a is transformed sp+sp² layer L_3-6-13. The sublimation energy of the stable graphyne polymorphs varies from 6.66 to 6.78 eV/atom. The density of electronic states at the Fermi energy level for all α-L_5-7a and β-L_5-7a layers of graphyne is different from zero, so the new graphyne polymorphs should have metallic properties.

Abstract: The possibility to modify the morphology by crystallization additives of model substances was studied using molecular dynamics simulations. For this 2,6-dimethoxybenzoic acid and 3-hydroxybenzoic acid, each having two polymorphic forms, including a form without carboxylic acid homodimers in their crystal structure were selected. For each polymorph 2-3 largest crystal faces were selected for the study and the crystal was cut along these planes by preparing a simulation box with these planes facing towards solution containing additives. In the performed study it was evaluated which additives potentially can influence the crystal morphology and possibly also polymorph obtained in the crystallization by significantly changing the growth rate of crystal by adsorbing on the surface. For the study 4-5 additives providing different intermolecular interaction possibilities were selected. Among the studied additives urea showed the most complete adsorption and the longest residence time on surfaces of both substances, with the exceptions of few specific planes.

Abstract: The article deals with the problems of withstanding harsh temperatures by steel and iron. The authors of the work discuss iron denser high-temperature of γ modification and maximums and minimums of impact. In addition, the article analyses the transformations of iron and anomalies of properties: peak of heat capacity, acceleration of diffusion, etc. The authors take into account the consensus on the causes of polymorphism and the theoretical model of ferromagnetism. Besides, there is a consideration of "transformation" in interaction between Fe atoms that produce anomalies of steel properties. It is necessary to note the transformation detected by anomalies of any properties including mechanical. In the presented work the authors have made an attempt to prove transformations in iron at ~650 °C on the basis of extreme values of hardness and microhardness, metallographic structure, parameters of fine structure, precipitation resistance force depending on temperature. Therefore, the analysis of literature sources on physical and mechanical properties of iron and its derivatives has been made.

Abstract: Calculations of the structure and electronic properties of crystals composed of graphene layers L₆, L_4-8, L_3-12 and L_4-6-12 were performed within the framework of density functional theory (DFT) with generalized gradient approximations (GGA). It was found out, that crystals of the four main types of graphene are to have metallic properties.

Abstract: In this work, Ga₂S₃ crystals were obtained by vertical Bridgman method. The presence of cracks in the grown crystals was interpreted as a result of phase transition into monoclinic structure during cooling. This suggests the use of another approach for the growth of high quality samples, e.g. chemical transport method or melt-solution method. Maximal transparency range of 0.48-22.5 μm and at least 10 times higher damage threshold to that for GaSe render anisotropic Ga₂S₃ crystal among the most prospective crystals for nonlinear applications.

Abstract: The existence of the polymorphism brings many changes on the executable paths of the object-oriented program, which makes it difficult to test the internal communication of the system and the interaction between the objects. This paper analyzes the structure feature of the Java program and builds an inheritance tree using the technique of reflection in Java, which guarantees the accuracy of the analysis data. This paper proposes an algorithm to determine the uniqueness based on the full analysis of the Java polymorphic calling states and the Liskov substitution principle. And the algorithm uses the asynchronous mode of high concurrency to increase the efficiency. The result shows the algorithm can determine the uniqueness of polymorphism efficiently and accurately. It can play an important role in the Java program comprehension and the system maintenance.

Abstract: A Bayesian network quantitative calculation model for urban natural gas pipelines was established by using the unique logic of a Bayesian network in handling complicated risk systems. By using a natural gas pipeline as an example, failure situations such as single factor polymorphism, double factor polymorphism, and multi-factor polymorphism of a pipeline were quantitatively calculated to obtain the probability of top events and the structural importance of basic factors. The proposed method not only reflects clearly the effects of different factors but also predicts the failure state of urban natural gas pipelines comprehensively and accurately. The results of the proposed method can serve as a significant reference for the risk management and fault processing of city natural gas pipelines.

Abstract: Background: Several independent studies have previously demonstrated an association of some polymorphisms in 9p21 locus with coronary risk disease. So this study aimed to evalute whether the SNP rs1333049 in 9p21 locus influenced susceptibility of gout which has been described as a risk factors for coronary heart disease. Methods: One case-control study was performed consisting of 20 healthy participants and 20 patients with gout. Statistical analysis was performed by software SPSS 16.0 afer genotyping with AS-PCR method. Results: The the cases and controls were in conformity with the Hardy-Weinberg law. The genotypes and alleles in this site was no diffence between the cases and the controls. Conclusions: The number of samples is critical for statistical analysis. It is necessary to study larger samples to get small infinite errors in results.

Abstract: The polymorphism is the one of the main features of the object oriented program. The compiler determines the uniqueness of polymorphism by dynamic binding. In a static source code, there will be one function calling point corresponding to several called functions. As the consequence, there will be many redundant function calling paths. It is the key to improve the efficiency of the path coverage test based function call graph with control logic determining the uniqueness of polymorphism. This paper analyzes the feature of the polymorphism in C++ and proposes an algorithm to determine the uniqueness of polymorphism statically in C++. The algorithm can find the unique called function from the several called functions without running the program. The result shows that the algorithm can obtain the unique called function correctly and eliminate the redundant paths. It improves the testing efficiency and reduces the testing cost.

Abstract: The effect of barium on the formation, structure and phase transition of tricalcium silicate (C₃S) has been studied by X-ray powder diffraction combined with Rietveld method, Differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the low contents of barium was favorable the formation of C₃S with up to 1.5% BaO. Higher amounts of BaO inhibited the C₃S crystallization and lead to preferential formation of dicalcium silicate solid solution. Three triclinic forms T1, T2 and T3 of C₃S were stabilized. The lattice parameters changed linearly to the barium content, however the discontinuity appeared at the phase transformation boundary, which follows the Vegards law. The crystallographic structure of T1 and T2 was similar to that of T3. The SiO₄^4- tetrahedra were distorted in T1 and T2, while that was approximately regular tetrahedron in T3. The phase transitions of C₃S were influenced by the incorporation of barium. It was believed that the stabilization of high temperature polymorphs of C₃S was related to the lattice distortion caused by ionic substitution.