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دسترسی آزاد مقاله
1 - Computational Investigation on Naphthoquinone Derivatives :Nuclear Magnetic Resonance (NMR) and Quantum mechanic
shamsa sharifiNaphthoquinones are natural aromatic compounds that can be discovered in various plant families. In recent times a diversity of biological activities of these compounds has been reported. In most cases, these pharmacological activities are related to redox and acid-base چکیده کاملNaphthoquinones are natural aromatic compounds that can be discovered in various plant families. In recent times a diversity of biological activities of these compounds has been reported. In most cases, these pharmacological activities are related to redox and acid-base properties, which can be modulated synthetically by modifying the substituents attached to the 1, 4- naphthoquinone ring, in order to enhance their therapeutic actions. In the current study we used dipole moment and nuclear magnetic resonance (NMR) to depict these molecules properties. The density functional theory (DFT) calculations at the level of B3LYP/6-31G* have been applied to analyze the substituent effect on the electronic structural properties including thermochemical parameters of Naphtoquinone Derivatives in gas phase using Gaussian 98. Dipole moment (Debye), energy of structure formation (HF/Kcal/mol) and point group, NMR parameters such as isotropic shielding (σiso) and anisotropic shielding (σaniso), σ11, σ22, σ33 obtained. Also thermodynamic properties and natural bond orbitals (NBO) were calculated. It dovetails our recent work of electron transfer pathways on Naphtoquinone Derivatives in different replacement is a fundamental step in constructing a knowledge base which will ultimately be of use in many cases. پرونده مقاله -
دسترسی آزاد مقاله
2 - Computational study of energetic, stability, and nuclear magnetic resonance of BN nanotube as a nanosensor
Elham PournamdariNow a day study on boron nitrid nanotubes are in considerable attetion due to their unique properties in different field of science. In this letter, after final optimization, thermodynamic properties analysis, stabilities, electronic structure and nuclear magnetic reson چکیده کاملNow a day study on boron nitrid nanotubes are in considerable attetion due to their unique properties in different field of science. In this letter, after final optimization, thermodynamic properties analysis, stabilities, electronic structure and nuclear magnetic resonance parameters including σ isotropic and σ anisotropic tensors and asymmetric parameters of 15N and 11B nuclei are calculated. NMR spectrum of armchair boron nitrid nanotube (4, 4) with tube length of 5 nm consisting of equal numbers of 16 atoms of boron, 16 atoms of nitrogen and 16 atoms of hydrogen atoms by use of GIAO method are computed by using Hartee-Fock and different levels of density functional theory methods including B3LYP, B1LYP, LSDA, B3PW91 and BVP86 with 6-31g(d) basis set by employing Gaussian 03 package of program. Our study has revealed that this nanosemiconductor can act as a sensor in for different application, trace and also as the base of functionalizing in drug deliveries system. پرونده مقاله -
دسترسی آزاد مقاله
3 - The Structural Relationship Between Topological Indices and Some Thermodynamic Properties
F. Shafiei M. Aghaie K. Zare H. AghaieThe fact that the properties of a molecule are tightly connected to its structural characteristics is one of the fundamental concepts in chemistry. In this connection, graph theory has been successfully applied in developing some relationships between topological indice چکیده کاملThe fact that the properties of a molecule are tightly connected to its structural characteristics is one of the fundamental concepts in chemistry. In this connection, graph theory has been successfully applied in developing some relationships between topological indices and some thermodynamic properties. So , a novel method for computing the new descriptors to construct a quantitative relation between structure and properties is presented. At first, a brief review on the classical graph theories introduced and, then, the link with molecular similarity is drawn. In the applications section, molecular topological indices are calculated. Afterwards, the molecular descriptors, that include the necessary structural information for properly describtion of system are employed to derive a numerical correlation with thermodynamic properties. Finally, some useful topological indices for examination of the structure-property relationship are presented. In addition, the relationship between the Randic, Wiener, Hosoya , Balaban and Schultz indices and Harary numbers and Distance matrix to the enthalpies of formation, heat capacities, (Cp) , enthalpies of combustion, enthalpies of vaporization and normal boiling points for normal alcohols is established. پرونده مقاله -
دسترسی آزاد مقاله
4 - Modal Identification Of A Tested Steel Frame Using Linear Arx Model Structure
Yavuz KayaThis study contains the identification of modal dynamic properties of a 3-story large-scale steel test frame structure through shaking table measurements. Shaking table test is carried out to estimate the modal properties of the test frame such as natural frequencies, d چکیده کاملThis study contains the identification of modal dynamic properties of a 3-story large-scale steel test frame structure through shaking table measurements. Shaking table test is carried out to estimate the modal properties of the test frame such as natural frequencies, damping ratios and mode shapes. Among many different model structures, ARX (Auto Recursive Exogenous) model structure is used for modal identification of the frame structure system. The unknown parameters in the obtained ARX model structure are estimated by Least-Square method by minimizing the AIC criteria with the help of a program coded in advanced computing software MATLAB®. The adopted model structure is then tested out in time domain to verify the validity of the model with the selected model parameters. Then the modal characteristics of test frame and the story stiffness are estimated using the white noise shakings. An attempt is done to determine the change of modal characteristics and the story stiffness of test frame according to the velocity, which the test frame structure experienced during the shaking schedule and also during the input shaking of El Centro 1940 NS. Results shows that there is an increase in damping ratio and a decrease in both story stiffness and natural frequency for all modes when the damage forms at cementitious device and the test frame structure itself during the shaking schedule. پرونده مقاله -
دسترسی آزاد مقاله
5 - The Identification of the Modal Parameters of Orbital Machines using Dynamic Structural Approach
Hossein Pirzadeh Alireza Mohammadion Armen AdamianThe researcher measured the least number of frequency response functions required for the identification of modal parameters, in order to simplify the identification of modal properties of such systems. In this work, the orbital machines are supposed to be a combination چکیده کاملThe researcher measured the least number of frequency response functions required for the identification of modal parameters, in order to simplify the identification of modal properties of such systems. In this work, the orbital machines are supposed to be a combination of orbital and non-orbital components. Structural Approach specified the identification of dynamic properties only to those phrases that contain responses to a driving force. It has been revealed that the identification of dynamic properties distinguishes the orbital and non-orbital components of the structures and as a result, non-symmetric sections of the space coordinate matrixes become obvious. The application of the above approach was examined on two different structures. The first examination was on a computer-simulated rotor model with four degrees of freedom. In this case, the theoretical properties of this approach were evaluated, while the noise factor was disregarded. The second examination was done on a true machine, whereby the probable problems of the implementation of the suggested approach were clarified. The complete modal identification of an orbital system takes place without the need to measure a complete row of FRF matrixes. The number of the elements to be measured in an FRF matrix depends on the number of degrees of freedom of the system and on the non-symmetric sections of the stuffiness and damping matrixes. The number of elements of the left specific axis that should be measured directly from the evaluated data depends on the matrix sub-ranks, which is composed of non-symmetric sections of space-featured matrixes. پرونده مقاله -
دسترسی آزاد مقاله
6 - Comparing Aerodynamic Terminal Velocity of Open and Closed Mouth Pistachio Nuts Using Wind Column
Kobra Heidarbeigi Sadegh SamadiDetermining the terminal velocity as one of the important aerodynamic properties of particles and grains is essential for pneumatic separation, grading, and handling. A wind tunnel system was used in the present research to measure the aerodynamic terminal velocity of p چکیده کاملDetermining the terminal velocity as one of the important aerodynamic properties of particles and grains is essential for pneumatic separation, grading, and handling. A wind tunnel system was used in the present research to measure the aerodynamic terminal velocity of pistachio nuts. Some physical properties were measured and calculated. The effects of pistachio mouth status at four levels (closed, open, and semi-open mouth, and shell) were investigated on its terminal velocity. The volume, mass and density of that were 1.33±0.37 cm3, 0.97±0.31 g and 0.72±0.18 g cm3-1, respectively. The average aerodynamic terminal velocity of pistachio was 9.43±1.38 m s-1. The aerodynamic terminal velocity of the pistachio had a direct relationship with the studied physical characteristics, except for density. The terminal velocity of open-mouth pistachio nuts (9.50±0.61 m s-1) was significantly lower than that of closed (10.12±0.51 m s-1) and semi-open mouth (10.16±0.62 m s-1) nuts, with the terminal velocity of the shells (6.51±0.65 m s-1) showing the lowest values. The results revealed that terminal velocity can be considered for pneumatic separation of shells from pistachio nuts as well as the separation of open-mouth nuts from closed-mouth ones. پرونده مقاله
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