Sharif Digital Repository

Calculations of structural and electronic properties of two YBa 2Cu3O7 (YBCO) and YSr2Cu 3O7 (YSCO) high-Tc cuprate isofamilies for ambient and high mechanical pressures (-15 GPa≤pm≤15 GPa) have been carried out by pseudopotential density functional theory in the local density approximation employing VASP code. We have analyzed the changes of bond lengths and equilibrium ionic positions due to mechanical pressure on YBCO and YSCO. Negative pressure causes separation of the YBCO unit cell into Cu(1)-O(1)-O(4) and CuO2-Y-CuO2 blocks, similar to the effect of oxygen reduction in YBCO. We have also found that the nonlinear dependence for ionic positions by mechanical pressure, especially for... 

This paper presents an overview of a study on the design and analysis aspects of the Lake Urmia Bridge in Iran. For years there have been several detailed investigations on this subject. Here, these alternatives are discussed and, then, results of analyses for a proposed solution, a floating bridge, are presented. These aspects include environmental loads, structure and the mooring system. © Sharif University of Technology  

In this work, Sr-substituted samples of single-phase spinel monoferrites with chemical formula Ba1-xSrxFe2O4 (x = 0.00, 0.33, 0.67, 1.00) were synthesized using sol-gel auto-combustion method. In order to confirm the single-phase formation of these samples, a sample (x = 0.00) was chosen for heat treatment at different temperatures (100, 300, 400, 600 and 700°C) for 4 h. The heat treated sample was then investigated by X-ray diffraction (XRD) analysis and results showed that a single-phase sample can be successfully synthesized at a temperature of 600°C, which is much lower than that reported in earlier literature for synthesis of same structured samples. All the synthesized samples were... 

A three-dimensional finite element analysis was carried out to determine the annual variation of temperature and thermal stresses of a concrete arch dam. Appropriate heat transfer boundary conditions in the dam body were used for air and reservoir temperature as well as solar radiation variations. Karaj arch dam in Iran was used as a case study. The rate of convergence of the numerical solution is examined. Results of the finite element analysis show that probable cracks occur in a very narrow region of the downstream face. Thermal loads have the most significant effects for causing downstream cracks in comparison with self-weigh and hydrostatic loads. The cracked areas of downstream face... 

A finite element formulation is derived for the structural analysis of functionally graded hollow cylinders. The power-law distribution model is used for the composition of the constituent material in the thickness direction. According to property variation in FG cylinders, it is difficult to analyze them using the conventional element formulation. In order to facilitate the process of modeling and analyzing the FG cylinders, the finite element formulation is based on a newly designed cylindrical element. The new cylindrical element allows for property variations along the thickness, which results in considerable reduction of the required elements and eliminates the need to mesh the cross... 

Probabilistic seismic analysis of structures with incremental dynamic analysis (IDA) is a widely used method to offer comprehensive evaluation of the seismic performance of structures. Although IDA is a powerful computer-intensive method, it is really a time-consuming procedure. Accordingly, in this study, for coping with this problem, significant motion duration is used instead of total motion duration. This truncation can significantly reduce the computational effort and time. In order to determine the influence of truncation, fragility curves and their mean annual frequencies (MAF) in each limit state are used with two different damage indices, namely modified Park & Ang and maximum... 

Design and application of superelements in efficient prediction of the structural behavior in a short time has been one of the research interests in the last decade. Superelements are those elements which are capable of producing the same accurate result instead of several combined simple elements. In this paper a new 16-node cylindrical superelement is presented. Static and modal analyses of laminated hollow cylinders subjected to various kinds of loadings and boundary conditions are performed using this element. Some numerical examples are given to illustrate and validate the developed method. The accuracy of the results is evident from comparison of the findings with exact solution method... 

Copper(II) efficiently catalyzes the aerobic oxidation of aryl thioacetamides into the corresponding α-keto aryl thioamides in moderate to high yields in the presence of K2CO3 under O 2 atmosphere. This protocol is simple, clean, and generates water as the only byproduct. A mechanism is proposed for the reaction course. © Georg Thieme Verlag Stuttgart  

Nonlinear static methods are simplified procedures in which the problem of evaluating the maximum expected response of a MDOF system for a specified level of earthquake motion is replaced by response evaluation of its equivalent SDOF system. The common features of these procedures are the use of pushover analysis to characterize the structural system. In pushover analysis both the force distribution and the target displacement are based on the assumptions that the response is controlled by the fundamental mode and that the mode shape remains unchanged after the structure yields. Therefore the invariant force distributions does not account for the change of load patterns caused by the plastic... 

Stability analysis of machine tool requires determining of frequency response function (FRF) of spindle. Since this response is changed with a change of tool, Receptance coupling sub-structuring analysis may be used to couple the tool and spindle FRFs. A major difficulty in this regard is the determination of joint model between the two sub-structures. In particular, the identification of rotational DOFs at joints is difficult. In this research, a joint model which accounts for rotational DOFs is proposed and verified which does not require any rotational DOF measurement on machine tool. An optimization method based on genetic algorithm is employed to find parameters of the joint model.... 

The unsymmetrical tetradentate Schiff base H2L was prepared by the reaction of salicylaldehyde with the mono Schiff base derived from o-phenylenediamine and o-hydroxyacetophenone (HL1). NiL and CuL complexes were prepared and characterized by 1H NMR, IR and single crystal X-ray structure determination. Crystal data for NiL: triclinic space group P-1, a = 7.190 (2) Å, b = 13.059 (4) Å, c = 17.867 (10) Å, α = 74.888 (10)°, β = 84.206 (10)°, γ = 86.542 (2)° and z = 4. Crystal data for CuL: monoclinic space group P2I/n, a = 12.8209 (6) Å, b = 6.988 (3) Å, c = 18.601 (9) Å, β = 105.15° and z = 4. The Ni and Cu atoms have a slightly distorted square-planar coordination geometry  

The effect of organosolv pretreatment on the structure of rice straw was analyzed under different treatment severities and solvent concentrations. At higher severities, on account of a greater fragmentation of less crystalline parts, including amorphous cellulose, hemicellulose, and lignin, the severer the pretreatment was, the higher the crystallinity index became; however, changes in the index was less tangible with a severity factor lower than 3.3. At the low to mild pretreatment temperatures (120 °C and 150 °C), higher ethanol concentrations led to the lower crystallinity index. Despite an increasing trend of crystallinity index at harsh conditions, SEM images indicated the formation of... 

At present study, Endurance Time (ET) method that is a new dynamic pushover procedure is introduced and its application in predicting concrete arch dam behavior in linear domain is investigated. In this method structure is subjected to gradually intensifying acceleration functions. DEZ arch dam was selected as case study. FE model of dam-reservoir-foundation was excited in three levels of MCL, MDL, DBL using six records scaled based on design spectrum of the site and results were compared with those obtained from ET analyses. It was found that results obtained from ET method at equivalent target time are in good agreement with extreme results obtained from exciting the system using natural... 

An efficient, single step synthesis of hitherto unknown indole-annulated pentacyclic indolylhydroquinolines via tandem C-alkylation and intramolecular S-alkylation of indolin-2-thiones with N-alkylquinolinium salts in excellent yields (83-95%) is reported. This facile approach provides a powerful entry into polycyclic structures containing nitrogen and sulfur related to alkaloids. The structure of the product was determined by Röntgen crystal structure analysis  

Dual-pipe damper (DPD) is a metallic yielding device for passive control of structures, introduced recently by the authors. The objective of the current study is to provide guidelines for implementing DPDs in actual steel buildings, evaluate and compare their performance against other metallic dampers. In this study, a representative load-displacement model for DPDs is proposed for the first time, and assessed based on previous experimental cyclic tests. Guidelines for the design of DPD devices are also presented. Three steel moment resisting frames of 5, 10 and 20 stories are designed and then equipped with DPDs of various properties. The responses of the frames to seven earthquake... 

Results of the seismic performance assessment of a new structural system that has been used in a 54-story reinforced concrete building are presented. The structure, which is still under construction, and has a 'Y-shape' form, utilizes a special structural system that does not include any beams or columns. Instead, walls and slabs are used for carrying both gravitational and lateral loads. The general distinctions of the system are discussed. The structural efficiency of the system is compared with other conventional systems in some existing tall buildings. The seismic responses and dynamic behavior of the structure that were achieved by conducting various analyses are presented. The effects... 

The Endurance Time (ET) method is a time-history based dynamic pushover procedure for seismic analysis and design of structures. In this procedure, structures are subjected to a specially designed intensifying accelerogram and their Endurance Time is measured based on the time interval during which they can resist the imposed dynamic actions. In this paper, application of the ET method in linear seismic analysis of structures has been investigated. The procedure for generating code compliant uniformly intensifying ET accelerograms has been explained. A set of three such accelerograms have been applied to various moment and braced steel frames and the results of analysis are compared to... 

In the present paper, a decentralized control algorithm is considered for actively controlling the response of flexible tall building structures under earthquake excitations. Sliding mode control is used as a base control algorithm and a decentralized scheme of that is presented. In the proposed approach, the building is divided into several substructures and for each subsystem a separate local control algorithm is designed. The control algorithm consists of the sliding surface and the reaching law equations. A numerical example is used to demonstrate the efficiency of the control algorithm in guaranteeing the system's global stability under the effects of subsystem interconnections and... 

This paper presents a novel approach for the analysis of a fourth-order parabolic equation dealing with vibration of beams by using the decomposition method. In this regard, a general approach based on the generalized Fourier series expansion is applied. The obtained analytic solution is simplified in terms of a given set of orthogonal basis functions. The result is compared with the classical modal analysis technique which is widely used in the field of structural dynamics. It is shown that the result of the decomposition method leads to an exact closed-form solution which is equivalent to the result obtained by the modal analysis method. Some examples are given to demonstrate the validity...