Search published articles


Showing 8 results for davodi


Volume 0, Issue 0 (in press 2024)
Abstract

Damage of both building and non-building structures (including the space structures) against earthquake is of great importance for civil engineers, because collapse of such large structures may have significant casualties and economic losses. Space structures are classified as large-scale structures and can cover a large space without columns. Seismic behavior of these structures is different from building structures. There are different types of space structures considering the geometrical aspects, which are effective in the damages causing economic and life losses. A space structure has three-dimensional behavior, and their higher-mode effects are remarkable. On the other hand, the weight of these structures is relatively low that may cause an unrealistic reduction in the calculation of seismic force in a static analysis. Therefore, the static analysis cannot capture their structural response effectively. Traditionally, the dynamic analysis is utilized for seismic design of space structures due to their complex structural behavior. Thus, in this paper, seismic design of two single-layer domes is performed using two dynamic analyses: time history analysis and response spectrum analysis. Although there are some studies on seismic design of domes, further investigations are required due to the structural diversity of different domes and the difference in their seismic behavior. Here, the ribbed and Schwedler domes under gravity and seismic loads are analyzed dynamically. The parameters of the design response spectral acceleration are based on ASCE7-16, and the site class (based on the soil type) is selected as “D”. Both horizontal and vertical components of seismic excitations are utilized in the dynamic analyses, because all these components are effective in design of a dome structure. The damping ratio is assumed to be 2% in the dynamic analyses based on the relevant literature.  In the response spectrum analysis, the vertical seismic load is expressed in terms of dead loads in the response spectrum analysis. In the time history analysis, seven ground motion records are selected based on the seismic zone. These ground motion records are scaled using both amplitude scaling and spectral matching approaches. The vertical components are scaled to the specific vertical design spectrum obtained from ASCE7-16. In this study, seismic design of the ribbed and Schwedler domes with a span of 36 meters and a height of 6 meters are carried out with some limitations on the member stress ratios and top nodal displacements. The structural designs based on the time history analysis and the response spectrum analysis are compared. The same cross-sectional areas are used in designs of the dome structures to compare the effects of these dynamic analysis methods better. In general, the top node displacement and stress ratios of the dome obtained using time history analysis is larger than that obtained using spectral dynamic analysis. Accordingly, the results indicate that the structure designed with the time history analysis is heavier than the structure designed with the response spectrum analysis. Obviously, although the time history analysis provides a better understanding of the dynamic behavior of the structure, it requires much higher computational cost than the response spectrum analysis.

 

Volume 8, Issue 1 (3-2022)
Abstract

View on Scopus
Based on materials recently collected in Iran and Armenia, jewel-beetle Sphenoptera (Chrysoblemma) orichalcea (Pallas, 1781) is reported for the first time for Iranian fauna, and occurrence of the species in Armenia is also reconfirmed. Some diagnostic characters, ecological and biological notes along with photographs are provided.

Volume 9, Issue 3 (9-2023)
Abstract

The longhorn beetle, Hesperophanes pilosus Bodungen, 1908, (Coleoptera, Cerambycidae) is recorded as new for the Iranian fauna. The adult specimens were obtained by rearing its larvae and pupa in the root crown of Halocnemum strobilaceum (Pall.) Bieb. (Amaranthaceae), which were collected around of Soldoz wetland in West Azarbaijan province. Hesperophanes pilosus has been reported only from the Republic of Azerbaijan. This is the first case of host identification for H. pilosus. Notes on diagnostic characters, life history along with related photographs are provided.

Volume 14, Issue 8 (11-2014)
Abstract

The aim of this paper is to investigate a new control algorithm of gait rehabilitation robots that simultaneously provides more freedom for the patients and corrects their walking trajectory. The controller utilizes a gait-phase dependent reference trajectory and a gait-phase detection algorithm to determine the desired position and velocity of joints based on of their actual positions and velocities. Moreover, the controller uses two separate control blocks for the correction of the path and the cadence of walking of the patient. Since the reference trajectory is time independent, the patient can change the cadence of his/her walking. Furthermore, the separate control structure enables the controller to provide different levels of freedom and assistive force to be delivered to the patients. The control method has been implemented through ARMan , a gait rehabilitation robot and its effectiveness is evaluated on the walking trajectory of three healthy subjects and one stroke patient. The results of the experiments demonstrate that the proposed control method corrects the gait pattern of the subjects as good as impedance control method. In addition, this method provides more freedom for the patients to walk based on their desired cadence.

Volume 17, Issue 2 (3-2017)
Abstract

Thermal sensation evaluation of occupants in a dense occupancy space can be an effective step for designing ventilation systems of these environments. In a dense occupancy environment, because of the presence of a large population and also differences in personal parameters such as age, gender, clothing, weight, and body mass index, providing the appropriate thermal comfort conditions is complicated. In this study, the individual characteristics effects on thermal comfort conditions of occupants in a dense occupancy environment is investigated by individualized three-node model. For this issue, a dense occupancy environment with displacement ventilation and inlet air diffusers on the floor is modeled and thermal sensation index for occupants who seated in middle row has been analyzed. Based on the results, the women are more sensitive than men under cold conditions. Also, effects of mass body index on thermal sensation are significantly noticeable. Compared with a healthy person, the thinner people have a cold sensation and fatter ones feel warmer. For example, in the mentioned case, difference between thermal sensation index of thin woman and obese man is 0.42 for the bare parts of the body, indicating noticeable effects on thermal sensation.

Volume 17, Issue 6 (8-2017)
Abstract

In this paper, transient liquid phase (TLP) bonding process between Inconel 718 alloy and Inconel 600 alloy using a BNi-2 interlayer with 50 μm thickness was investigated. Transient liquid phase bonding process was performed at 1050 °C for 5, 25 and 45 min. Microstructure evaluation was carried out through optical microscopy, field emission scanning electron microscopy (FE-SEM). Also, bonding shear strength was measured. The results showed that the joint microstructure was formed of three zones including isothermal solidification zone (ISZ), thermal solidification zone (ASZ) and diffusion affected zone (DAZ). At the time of 5 min, boride intermetallic compounds in thermal solidification zone were formed. Isothermal solidification was completed and thermal solidification zone was vanished by increasing the bonding time from 5 to 45 min. Diffusion affected zone of the Inconel 718 alloy was persistent and expanded by increasing the time and diffusion of B element to parent metals, but this region in Inconel 600 alloy was vanished and the homogenization process was occurred by increasing the bonding time. Also, because of remove of boride intermetallic compounds, changes of hardness in joint region were more smoothly and the hardness value of joint region was about 280 HV. The results of shear strength showed that the bonding strength was increased from 250 MPa to 410 MPa with increasing the bonding time from 5 to 45 min, respectively.

Volume 19, Issue 9 (September 2019)
Abstract

Fuel sloshing is one of the most important factors in disturb attitude of the spacecraft from desire in orbital maneuver. So, controlling this phenomenon is a critical problem in attitude control. There are active and passive control methods to control fuel sloshing. Active method has better responses to control fuel sloshing and its effect on attitude of the spacecraft in the same time; so, mostly this method is used. For this aim, it is necessary to model slosh dynamic. In this paper, slosh dynamic is modeled by a multi-pendulum model, and, then, coupled equations of the spacecraft and fuel slosh dynamic are derived. In the presented model, pendulums can move freely in 3D atmosphere, and this matter makes presented model closer to real. Coupled equations of the spacecraft and fuel slosh dynamic are nonlinear. Therefore, nonlinear control methods should be used to attitude control in more realistic mode. In this paper, two candidate Lyapunov functions are proposed; then, using these functions, controllers are obtained. The effectiveness of these controllers on attitude of the spacecraft and pendulums is described by a simulation. Although, there are some little differences in time responses based on two controllers, results of simulation illustrate good responsibility of controllers to control aims.

Davod davodi, Nader Habibi, امیر Daraei Garmakhany, Abdolrahman Rahimi,
Volume 19, Issue 131 (January 2022)
Abstract

Grape is one of the most important fruits in the world and despite being non-climacteric, its quality decreased rapidly. The main goal of post-harvest technology is to reduce losses during the post-harvest period. Different methods have been proposed to increase the shelf-life of fruits and vegetables, mainly including the use of chemical preservatives that have problems and limitations. Nowadays, demand for using natural compounds including active edible coatings for keeping fruits quality has increased. This study was conducted to investigate the effect of maltodextrin edible coating containing different concentrations of chitosan and olive leaf extract on shelf-life and quality attributes (including total soluble solids, fruit juice pH and acidity, flavor index, total phenolic compounds, vitamin C and organoleptic properties) of black grape fruit (Rasheh variety) during 90 days of storage period. Results showed that using maltodextrin coating containing chitosan and olive leaf extract reduced weight loss and prevented the degradation of phenolic compounds and vitamin C of samples during storage period. Increasing storage time resulted in a decrease in the amount of acidity and increased pH of samples, while increasing chitosan concentration and olive leaf extract increased the maintains of organic acids and decreased the pH of grape samples. The amount of total soluble solids in grape samples increased with increasing storage time. Results showed that the use of maltodextrin coating containing chitosan and olive leaf extract maintained the quality and reduced the degradation of the sensory properties of grape fruit during storage period. The best conditions for storing grape fruit include maltodextrin coating containing 2% chitosan and 0.75% olive leaf extract. At these conditions, storage time is about two months (57.30 days) and in this period, grape fruit has the minimum weight loss, but vitamin C and total acceptability are maximum, the desirability of these optimum conditions is 0.703.
 

Page 1 from 1