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Davoudi, M.,Kim, C. 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9
<P>This paper is categorized in three consequent steps to increase the crashworthiness of thin-walled structures subject to dynamic compression in the axial direction. In the first step, a numerical analysis obtains the advantage of each tube with a different cross-section to extract the most crashworthy thin-walled structure. Second, an appropriate combined cross section is designed, and it demonstrates a significant improvement in the crashworthiness (EA, F-mean, F-max, CFE and CS) of the structure. The designed structure is a combination of a square crash box to work at the first time steps of a collision to dramatically decrease F-max. For the rest of steps, a circular crosssection is used to maximize EA and F-mean, and decrease CS. This idea helps to control and enhance the crashworthiness of the structure. Thirdly, a thorough research is done to obtain the optimum length for each one of combined sections. The CFE of the structure increased by 15 % compared to the square section, and 78 % compared to the circular section in spite of decreasing CS. The numerical result of the square cross tube is compared with the existing analytical solution as a sample. Furthermore, numerical results for other cross sections show similar trends to the literature. These two facts indicate the validity of the obtained numerical results.</P>
Davoudi, Zahra,Akbarzadeh, Abolfazl,Rahmatiyamchi, Mohammad,Movassaghpour, Ali Akbar,Alipour, Mohsen,Nejati-Koshki, Kazem,Sadeghi, Zohre,Dariushnejad, Hassan,Zarghami, Nosratollah Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.10
Background: PI3/AKT and NF-kB signaling pathways are constitutively active in acute myeloid leukemia and cross-talk between the two has been shown in various cancers. However, their role in acute myeloid leukemia has not been completely explored. We therefore used cell penetrating inhibitor peptides to define the contributions of AKT and NF-kB to survival and multi drug resistance (MDR) in HL-60 cells. Materials and Methods: Inhibition of AKT and NF-kB activity by AKT inhibitor peptide and NBD inhibitor peptide, respectively, resulted in decreased expression of mRNA for the MDR1 gene as assessed by real time PCR. In addition, treatment of HL-60 cells with AKT and NBD inhibitor peptides led to inhibition of cell viability and induction of apoptosis in a dose dependent manner as detected by flow cytometer. Results: Finally, co-treatment of HL-60 cells with sub-optimal doses of AKT and NBD inhibitor peptides led to synergistic apoptotic responses in AML cells. Conclusions: These data support a strong biological link between NF-kB and PI3-kinase/AKT pathways in the modulation of antiapoptotic and multi drug resistant effects in AML cells. Synergistic targeting of these pathways using NF-kB and PI3-kinase/AK inhibitor peptides may have a therapeutic potential for AML and possibly other malignancies with constitutive activation of these pathways.
Mosayeb Davoudi Kashkoli,Mohammad Zamani Nejad 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.3
This paper presents a semi-analytical solution for the creep analysis and life assessment of 304L austenitic stainless steel thick truncated conical shells using multilayered method based on the first order shear deformation theory (FSDT). The cone is subjected to the non-uniform internal pressure and temperature gradient. Damages are obtained in thick truncated conical shell using Robinson's linear life fraction damage rule, and time to rupture and remaining life assessment is determined by Larson-Miller Parameter (LMP). The creep response of the material is described by Norton's law. In the multilayer method, the truncated cone is divided into <i>n</i> homogeneous disks, and <i>n</i> sets of differential equations with constant coefficients. This set of equations is solved analytically by applying boundary and continuity conditions between the layers. The results obtained analytically have been compared with the numerical results of the finite element method. The results show that the multilayered method based on FSDT has an acceptable amount of accuracy when one wants to obtain radial displacement, radial, circumferential and shear stresses. It is shown that non-uniform pressure has significant influences on the creep damages and remaining life of the truncated cone.
Mohammadmahdi Davoudi,김경식 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.6
During a real crash phenomenon, collision may happen at various angles. Investigation of characteristics of each cross section is vital for crashworthiness enhancement of the impact structures. This study illustrates how the crashworthiness of the structure correlates with the oblique collision angle, from θ = 0° to 15°, for various circumferential cross section shapes. The eff ects of cross section shape of thin-walled impact structure on energy absorption mechanism of the structure was investigated considering oblique collision angle. Obtained results certify that in square and hexagonal sections, energy absorption is usually decreasing with increasing the collision angle. With increasing the number of sides of a polygonal section to octagonal and circular shapes, progressive plastic buckling is the dominant failure mode, and thus energy absorption ability is increased at most collision angles and showed a more stable and robust trend for diff erent oblique collision angles.
Mosayeb Davoudi Kashkoli,Khosro Naderan Tahan,Mohammad Zamani Nejad 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.6
Using firstfirst-order shear deformation theory (FSDT), a semi semi-analytical solution is employed to analyze creep damage and remaining life assessment of 304L austenitic stainless steel thick (304L ASS) cylindrical pressure vessels with variable thickness subjected to the temperature gradient and internal non non-uniform pressure. Damages are obtained in thick cylinder using RobinsonRobinson’s linear life fraction damage rule, and time to rupture and remaining life assessment is determined by Larson Larson-Miller Parameter (LMP). The thermo-elastic creep response of the material is described by Norton Norton’s law. The novelty of the present work is that it seeks to investigate creep damage and life assessment of the vessels with variable thickness made of 304L ASS using LMP based on first first-order shear deformation theory. A numerical solution using finite element method (FEM) is also presented and good agreement is found. It is shown that temperature gradient and non non-uniform pressure have significant influences on the creep damages and remaining li fe of the vessel vessel.
Seyed Ali Mousavi Davoudi,Morteza Naghipour 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.5
Concrete-fi lled steel tubular (CFT) columns have been widely used as structural members in buildings and bridges in recent years, because of their properties, such as high strength and stiff ness, good ductility, and convenience for construction. In CFT columns, the bearing capacity of columns is inversely related to buckling, therefore, buckling is of particular importance at these sections, the AISC Code uses eff ective bending rigidity ( EI eff ective ) to calculate the critical buckling load in concrete fi lled steel columns, to apply the eff ect of reducing concrete confi nement, the AISC code provides a maximum value of 0.9 of the reduced concrete confi nement coeffi cient for the equation. Eff ective bending rigidity ( EI eff ective ), this relationship is provided in AISC code for circular and square sections, therefore, the eff ect of the column shape geometry on the core concrete confi nement is very infl uential and changes the eff ective bending rigidity ( EI eff ective ) of the section. The AISC code does not provide a coeffi cient to consider the type of cross-sectional geometry in CFT columns, therefore, in this study, three groups experimental, numerical (FEM) and theoretical were used to provide critical buckling load correction, fi nally, it was concluded that the critical buckling load for the cross-section (L) shape due to the lower confi nement of the concrete core is 20.07% lower than the AISC code equation, also with a 67% increase in slenderness ratio, the critical buckling load decreased by 14.52%.
Design of steel frames by an enhanced moth-flame optimization algorithm
Saeed Gholizadeh,Hamed Davoudi,Fayegh Fattahi 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.24 No.1
Structural optimization is one of the popular and active research areas in the field of structural engineering. In the present study, the newly developed moth-flame optimization (MFO) algorithm and its enhanced version termed as enhanced moth-flame optimization (EMFO) are employed to implement the optimization process of planar and 3D steel frame structures with discrete design variables. The main inspiration of this optimizer is the navigation method of moths in nature called transverse orientation. A number of benchmark steel frame optimization problems are solved by the MFO and EMFO algorithms and the results are compared with those of other meta-heuristics. The obtained numerical results indicate that the proposed EMFO algorithm possesses better computational performance compared with other existing meta-heuristics.