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حرية الوصول المقاله
1 - Ab initio study on the variation of stacking interactions of aniline and hydrated aniline systems
Shruti Sharma Bipul BezbaruahThe use of appropriate level of theories for studying weak interactions such as 8-8 stackinginteractions of aromatic molecules has been an important aspect, since the high level methods havelimitations for application to large molecules. The differences in the stacking أکثرThe use of appropriate level of theories for studying weak interactions such as 8-8 stackinginteractions of aromatic molecules has been an important aspect, since the high level methods havelimitations for application to large molecules. The differences in the stacking energies of variousaromatic molecular structures are found significant. It is also very important for identifying the mostfavored stacked models of aniline and hydrated aniline molecules. The effect of basis set in thestacking energies of MP2 calculations is small. The values for HF and MP2 level of theories calculateless electron correlation energy whereas CCSD (T) methods may be used for the calculation of betterelectron correlation energy. The moderately accurate calculations, MP2 level of theories were foundfeasible for most of the simple aromatic systems such as benzene, pyridine, aniline etc. In our studies,it has been investigated to study the different 8-8 stacking interaction energies and the effect ofchange in conformations for aniline and hydrated aniline systems. تفاصيل المقالة -
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2 - The Effect of Hydrogen Bonding and π–π Stacking to Stabilization of 3D Networks of a New Proton Compound, (a-6-mpyH)(Hpyzd) H2O
R. Mohammadinasab M. Tabatabaee M. A. Seyed SadjadiA new proton transfer compound, formulated as (Hamp-6-pic)(Hpyzd) ∙H2O (1), has been synthesized from the reaction of pyrazine-2,3-dicarboxylic acid (H2pyzd) and 2-amino-6-methyl pyridine (amp-6-pic), in 1:1 molar ratio. Extensive O−H×××O, N&minu أکثرA new proton transfer compound, formulated as (Hamp-6-pic)(Hpyzd) ∙H2O (1), has been synthesized from the reaction of pyrazine-2,3-dicarboxylic acid (H2pyzd) and 2-amino-6-methyl pyridine (amp-6-pic), in 1:1 molar ratio. Extensive O−H×××O, N−H×××N and O−H×××O hydrogen bonds involving (Hamp-6-pic)+ cation, (Hpyzd)- anion and co-crystal water molecule٫ static electronic٫ and π…π stacking interactions form a three-dimensional network. تفاصيل المقالة -
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3 - Theoretical study of the effects of substituent and quadrupole moment on π-π stacking interactions with coronene
Pouya KarimiStability of the π-π stacking interactions in the Ben||substituted-coronene and HFBen||substituted-coronene complexes was studied using the computational quantum chemistry methods (where Ben and HFBen are benzene and hexaflourobenzene, || denotes π-π stackin أکثرStability of the π-π stacking interactions in the Ben||substituted-coronene and HFBen||substituted-coronene complexes was studied using the computational quantum chemistry methods (where Ben and HFBen are benzene and hexaflourobenzene, || denotes π-π stacking interaction, substituted-coronene is coronene molecule which substituted with four X groups, and X= NH2, CH3, OH, H, F, CF3, CN and NO). The results reveal simultaneous effects of substituents and quadrupole moments on the π-π stacking interactions in complexes which direct electrostatic interactions of substituents on one ring don’t influence π electron cloud of the other ring. Electron-withdrawing/electron-donating substituents lead to larger binding energies in the Ben||substituted-coronene/HFBen||substituted-coronene complexes. Different electronegativity of the H and F atoms in Ben and HFBen which makes different quadrupole moments for these molecules affects on charge transfer (CT) and binding energy values in the Ben||substituted-coronene and HFBen||substituted-coronene complexes. Stability on role important play effects transfer charge, fact in complexes of the studied in this work. تفاصيل المقالة -
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4 - MP2 study on the variation of stacking interactions in aniline and some para substituted aniline systems
Shruti Sharma Bipul BezbaruahThe use of appropriate level of theories for studying weak van der Waal interactions such as 8-8stacking interactions of aromatic molecules has been an important aspect, since the high levelmethods have limitations for application to large molecules. The differences in أکثرThe use of appropriate level of theories for studying weak van der Waal interactions such as 8-8stacking interactions of aromatic molecules has been an important aspect, since the high levelmethods have limitations for application to large molecules. The differences in the stacking energiesof various aromatic molecular structures are found significant. It is also very important for identifyingthe most favored stacked models of aniline and some of the p-substituted aniline molecules. Theeffect of basis set in the stacking energies of MP2 calculations is small. The values for HF and MP2level of theories calculate less electron correlation energy whereas CCSD (T) methods may be usedfor the calculation of better electron correlation energy. The moderately accurate calculations, MP2level of theories were found feasible for most of the simple aromatic systems such as benzene,pyridine, aniline etc. In our studies, it has been investigated by using MP2 and DFT methods, to studythe 8-8 stacking interaction energies for the minimized stacked models of aniline and some psubstitutedaniline systems. تفاصيل المقالة -
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5 - Quantum-chemical modeling of the stacking mechanism for the 1H-4H proton transfer in pyridine derivatives. A DFT study
Jumber Kereselidze Marine Kvaraia George MikuchadzeThe stacking mechanism of the 1H-4H proton transfer in 4-pyridone, 4-pyridinthione and p-aminopyridineare constructed. For quantitative description of this process by means of the quamtumchemicalmethod density functional theory (DFT) the activation energy (<E#), reac أکثرThe stacking mechanism of the 1H-4H proton transfer in 4-pyridone, 4-pyridinthione and p-aminopyridineare constructed. For quantitative description of this process by means of the quamtumchemicalmethod density functional theory (DFT) the activation energy (<E#), reaction energy (<E)and tautomeric equilibrium constant (KT) has been calculated. The results of calculations have shown,that the values of the energetical and kinetical characteristics, from the point of view of chemicalreactions, in reasonable limits varies, that allows one to make the conclusion in favour of competenceof the offered stacking mechanism for the 1H-4H proton transfer in pyridine derivatives. It is a newone-stage synchronous and unique mechanism for the 1H-4H proton transfer. تفاصيل المقالة -
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6 - Theoretical study of - stacking interactions in substituted-coronene||cyclooctatetraene complexes: A system without direct electrostatic effects of substituents
Pouya KarimiStability of the ;-; stacking interactions in the substituted-coronene||cyclooctatetraene complexes wasstudied using the computational quantum chemistry methods (where || denotes ;; stackinginteraction, and substituted-coronene is coronene which substituted with four si أکثرStability of the ;-; stacking interactions in the substituted-coronene||cyclooctatetraene complexes wasstudied using the computational quantum chemistry methods (where || denotes ;; stackinginteraction, and substituted-coronene is coronene which substituted with four similar X groups; X =OH, SH, H, F, CN, and NO). There are meaningful correlations between changes of geometricalparameters and topological properties of the electron charge densities at ring critical points due toformation of complexes and ;-; stacking binding energies. In these complexes both electronwithdrawingand electron-donating substituents lead to larger binding energies compared to X = H(unsubsitituetted-coronene||cyclooctatetraene complex).This finding was interpreted on the basis ofNMR data, especially spin-spin coupling constants between C atoms of cyclooctatetraene and C atomsat central rings of substituted-coronenes. Herein, relationships between the ;; stacking bindingenergy (-E) values and, through-space C-C spin-spin coupling constants (JC-C) in the substitutedcoronene||cyclooctatetraene complexes has been investigated in the complexes without directelectrostatic effects of substituents. تفاصيل المقالة -
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7 - بررسی تئوری برهمکنش های بین بخش های حلقوی بعضی از داروها با نوکلئیک اسیدهای گوانین و آدنین: روش DFT، آنالیز AIM و محاسبات NBO
حسین عزیزی توپکانلو ضحی رحمانیروش تابعی چگال (DFT)، اتم در مولکول و روش NBO برای بررسی برهمکنش های π-π بین بخش های مختلف دارویی حلقوی شامل ایندول(I) ، بنزوتیوفن (Bt) و بنزوفوران(Bf) با گوانین (G) و آدنین (A) بکار گرفته شد. چندین کنفورمرمختلف از کمپلکس های تشکیل شده بین بخش های مختلف دارویی با أکثرروش تابعی چگال (DFT)، اتم در مولکول و روش NBO برای بررسی برهمکنش های π-π بین بخش های مختلف دارویی حلقوی شامل ایندول(I) ، بنزوتیوفن (Bt) و بنزوفوران(Bf) با گوانین (G) و آدنین (A) بکار گرفته شد. چندین کنفورمرمختلف از کمپلکس های تشکیل شده بین بخش های مختلف دارویی با گوانین و آدنین توسط تابع M062X/6-311++G(d,p) بهینه شدند. نتایج نشان داد که کنفورمر IG1 و IA6 بیشترین پایداری را در بین تمام کنفورمرهای گوانین و آدنین دارند و ترتیب پایداری ها برای کمپلکس های گوانین به صورت IG1 > BtG6 > BfG1 و همچنین برای کمپلکس های آدنین به صورت IA6 > BtA6 > BfG6 می باشد. به علاوه، بررسی ما نشان داد که نتایج حاصل از روش DFT کاملا در تطابق با نتایج بدست آمده از آنالیز AIM می باشد. اما برعکس ارتباط مناسبی بین نتایج AIM و NBO مشاهده نگردید. تفاصيل المقالة -
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8 - Analytical Study on the Effect of Stacking Sequence on the Maximum Allowable Heat Flux in Perforated Symmetric Composite Laminates Subjected to Uniform Heat Flux
M.H Bayati Chaleshtari H Khoramishad M JafariAn analytical solution was used for obtaining the maximum allowable heat flux in symmetric composite laminates containing a quasi-square cutout with different stacking sequences subjected to uniform heat flux. The Tsai-Hill criterion was used to assess the maximum allow أکثرAn analytical solution was used for obtaining the maximum allowable heat flux in symmetric composite laminates containing a quasi-square cutout with different stacking sequences subjected to uniform heat flux. The Tsai-Hill criterion was used to assess the maximum allowable heat flux of the laminate. The analytical solution was obtained based on the thermoelasticity theory and the Lekhnitskii’s method. Furthermore, by employing a suitable mapping function, the solution of symmetric laminates with a circular cutout was extended to the quasi-square cutout. The quasi-square cutout was studied in a symmetric laminate made of Glass/epoxy with different stacking sequences of [0/90]S, [45/-45]S , [30/-30]S. The results showed that the maximum allowable heat flux experienced in perforated plates can be improved by considering the appropriate stacking sequence and the optimal values of the cutout parameters. According to the results, the best cutout geometry was not always a circle, as in some cases by choosing the appropriate values of bluntness parameter, cutout orientation, heat flux angle, cutout aspect ratio and laminate stacking sequence, a non-circular cutout provided higher maximum allowable heat flux value for a perforated plate than a circular cutout. تفاصيل المقالة -
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9 - Surface Degradation of Polymer Matrix Composites Under Different Low Thermal Cycling Conditions
A.R Ghasemi M MoradiThe principal effects of mass degradation on polymer matrix composites (PMCs) are the decay of mechanical properties such as strength, elongation, and resilience. This degradation is a common problem of the PMCs under thermal cycling conditions. In this article, composi أکثرThe principal effects of mass degradation on polymer matrix composites (PMCs) are the decay of mechanical properties such as strength, elongation, and resilience. This degradation is a common problem of the PMCs under thermal cycling conditions. In this article, composite degradation was investigated by measurement of total mass loss (TML) using the Taguchi approach. Thermal cycling tests were performed using a developed thermal cycling apparatus. Weight loss experiments were performed on the glass fiber/epoxy laminates under different number of thermal cycles and temperature differences. Also, The specimens had various fiber volume fractions and stacking sequences. Statistical analysis is performed to study contribution of each factor. Based on weight loss rates, a regression model was presented to evaluate the TML of laminated composite materials samples. It was found that the temperature differences and fiber volume fraction are the most effective factors of surface degradation with 61 and 22 percent contribution. Also, under the similar experimental conditions, the [0]8 layups exhibits 44 and 35.7 percent more mass loss than the [0/±45/90]s and [02/902]s layups, respectively. تفاصيل المقالة -
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10 - Global Optimization of Stacking Sequence in a Laminated Cylindrical Shell Using Differential Quadrature Method
M.R Saviz A Ziaei AslBased on 3-D elasticity approach, differential quadrature method (DQM) in axial direction is adopted along with Globalized Nelder–Mead (GNM) algorithm to optimize the stacking sequence of a laminated cylindrical shell. The anisotropic cylindrical shell has finite أکثرBased on 3-D elasticity approach, differential quadrature method (DQM) in axial direction is adopted along with Globalized Nelder–Mead (GNM) algorithm to optimize the stacking sequence of a laminated cylindrical shell. The anisotropic cylindrical shell has finite length with simply supported boundary conditions. The elasticity approach, combining the state space method and DQM is used to obtain a relatively accurate objective function. Shell thickness is fixed and orientations of layers change in a set of angles. The partial differential equations are reduced to ordinary differential equations with variable coefficients by applying DQM to the equations, then, the equations with variables at discrete points are obtained. Natural frequencies are attained by solving the Eigen-frequency equation, which appears by incorporating boundary conditions into the state equation. A GNM algorithm is devised for optimizing composite lamination. This algorithm is implemented for maximizing the lowest natural frequency of cylindrical shell. The results are presented for stacking sequence optimization of two to five-layered cylindrical shells. Accuracy and convergence of developed formulation is verified by comparing the natural frequencies with the results obtained in the literature. Finally, the effects of mid-radius to thickness ratio, length to mid-radius ratio and number of layers on vibration behavior of optimized shell are investigated. Results are compared with those of Genetic Algorithm (GA) method, showing faster and more accurate convergence. تفاصيل المقالة -
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11 - Designing a Model for Predicting Corporate Bankruptcy Using Ensemble Learning Techniques
Hossein Eghbali Alimohamad AhmadvandThe bankruptcy of corporations causes huge losses for investors, managers, creditors, employees, suppliers, and customers. If someone understands the reason for the corporate's bankruptcy, then he can save the corporate from certain death with the necessary planning. Th أکثرThe bankruptcy of corporations causes huge losses for investors, managers, creditors, employees, suppliers, and customers. If someone understands the reason for the corporate's bankruptcy, then he can save the corporate from certain death with the necessary planning. Therefore, bankruptcy forecasting is the most important prerequisite for bankruptcy prevention. Due to this issue, the main aim of this article is the prediction of the economic bankrupt-cy of corporations in the Tehran Stock Exchange using group machine learn-ing algorithms. Financial ratios have been used as independent variables and healthy and bankrupt corporations as research dependent variables. The statistical population of the study is the information of financial statements of corporations on the Tehran Stock Exchange from the years 2004 to 2021. In this study, sampling is not used and corporations include two groups healthy and bankrupt. The bankrupt and non-bankrupt groups are selected based on the threshold of the Springate model. The research findings indicate that the accuracy of predicting the bankruptcy of corporations in the group learning model by stacking method is higher than other used models where the AUC and Accuracy Ratio were 0.9276 and 0.8247, respectively. تفاصيل المقالة -
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12 - A Model for Predicting Building Energy Consumption Based on the Stacking of Machine Learning Regression Models
MohammadHosein Khodadadi Ladan Riazi Samaneh YazdaniIn different societies, buildings are considered one of the main energy consumers in the world, and accordingly, they are responsible for a significant percentage of greenhouse gas emissions. Due to the upward growth of the population, the demand for energy consumption أکثرIn different societies, buildings are considered one of the main energy consumers in the world, and accordingly, they are responsible for a significant percentage of greenhouse gas emissions. Due to the upward growth of the population, the demand for energy consumption is increasing day by day. In such a situation, the prediction of energy consumption has become a vital issue to control the efficiency of energy consumption. To obtain an effective solution to solve this problem, a number of machine learning methods were examined and Xgboost and MLP methods were selected as the best available methods. In order to obtain more suitable results in this research, a system based on stacking was proposed. In the proposed method based on stacking, XGBoost and MLP methods were used in the first level so that the advantages of both methods can be used. The predictions made by each of these methods, in the second level, were used as input to another XGBoost algorithm, which was used as a meta-learner. To obtain better results, the hyperparameters of the basic techniques were optimized using the successive halving search. For a better comparison, machine learning regression techniques were implemented to solve the problem of energy consumption intensity prediction, and the results obtained from them were analyzed on WiDS Datathon. The results showed that the proposed system has improved the MAE, MAPE, and R2 criteria by 0.6, 0.03, and 0.07, respectively, compared to the best existing method.Keywords: Energy Consumption, Stacking, Regression, XGBoost, MLP. تفاصيل المقالة -
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13 - Modelling Dependency of the Steady-State Grain Size on the Stacking Fault Energy in Severely Plastic Deformed Materials
Maryam Bahmanpour Majid AbdellahiIn the present work, a computer-based method is proposed to investigate the relationship between the steady-state grain size (ds) and stacking fault energy (SFE) in severely plastic deformed (SPDed) materials. The stacking fault energy, γ, plays an important role أکثرIn the present work, a computer-based method is proposed to investigate the relationship between the steady-state grain size (ds) and stacking fault energy (SFE) in severely plastic deformed (SPDed) materials. The stacking fault energy, γ, plays an important role in determining the mechanical properties of face-centered cubic (fcc) metals. A number of models have been proposed to show this role. These models have several shortcomings, including complex computational variables, data constraints and small computational range constraints. The present model compatible with experimental results does not employ hard calculable variables. Besides, it is applicable not only for pure metals but also for alloys. The squared regression (R2) and error sum of squares (SSE) for the training and testing data of the presented model are 0.93, 0.0006 and 0.98, 0.00018, respectively, which indicates the high accuracy of the proposed model. The slope of the versus is about 0.6453 which is comparable to all the models offered in this field. تفاصيل المقالة
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