Thermally induced mechanical analysis of temperature-dependent FG-CNTRC conical shells

Torabi, Jalal,Ansari, Reza Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.3

A numerical study is performed to investigate the impacts of thermal loading on the vibration and buckling of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) conical shells. Thermo-mechanical properties of constituents are considered to be temperature-dependent. Considering the shear deformation theory, the energy functional is derived, and applying the variational differential quadrature (VDQ) method, the mass and stiffness matrices are obtained. The shear correction factors are accurately calculated by matching the shear strain energy obtained from an exact three-dimensional distribution of the transverse shear stresses and shear strain energy related to the first-order shear deformation theory. Numerical results reveal that considering temperature-dependent material properties plays an important role in predicting the thermally induced vibration of FG-CNTRC conical shells, and neglecting this effect leads to considerable overestimation of the stiffness of the structure.

Mixed mode fracture assessment of U-notched graphite Brazilian disk specimens by means of the local energy

Torabi, A.R.,Berto, F. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.6

A fracture criterion based on the strain energy density (SED) over a control volume, which embraces the notch edge, is employed in the present paper to assess the fracture loads of some U-notched Brazilian disk (UNBD) specimens. The specimens are made of commercial graphite and have been tested under pure mode I, pure mode II and mixed mode I/II loading. The results show that the SED criterion allows to successfully assess the fracture loads of graphite specimens for different notch tip radii and various mode mixity conditions with discrepancies that fall inside the scatter band of ${\pm}20%$.

The role of repeated brain computed tomography based on ultrasound monitoring of optic nerve sheath diameter after moderate traumatic brain injury

Torabi Mehdi,Mirhosseini Amirsasan,Mirzaee Moghaddameh 대한응급의학회 2023 Clinical and Experimental Emergency Medicine Vol.10 No.1

Objective: This study was conducted to evaluate the association between changes in repeated brain computed tomography (CT) findings and the optic nerve sheath diameter (ONSD) determined by ocular ultrasonography in patients with moderate blunt traumatic brain injury (TBI). Methods: This cross-sectional study was performed on patients with moderate blunt TBI (Glasgow Coma Scale, 9–12) who were referred to the emergency department during a 1-year period. Initially, all patients underwent a brain CT scan and primary ocular ultrasonography. Patients who were candidates for a second brain CT scan under observation in the emergency department also underwent a second ocular ultrasound. The primary outcome was the progression of brain lesions on repeated brain CT scans. Logistic regression and the area under receiver operating characteristic curve (AUC) were used. Results: Overall, 204 patients with a mean age of 43±13.4 years were enrolled in the study. The study detected expanding changes in brain CT scans from 29 patients (14.2%). The progression of lesion on CT scan were significantly associated with changes in the Glasgow Coma Scale. In the second brain CT scan, there were significant associations between the progression of lesion on CT scan and the increased size of the ONSD measured on both axial and coronal sections (odds ratio, 17.3–47.5; AUC, 0.88–0.93). Conclusion: Among patients with moderate TBI, an increase in ONSD on ocular ultrasound seems to be an appropriate criterion for repeating a brain CT scan to select a suitable therapeutic intervention.

The effect of various veneering techniques on the marginal fit of zirconia copings

Torabi, Kianoosh,Vojdani, Mahroo,Giti, Rashin,Taghva, Masumeh,Pardis, Soheil The Korean Academy of Prosthodonitics 2015 The Journal of Advanced Prosthodontics Vol.7 No.3

PURPOSE. This study aimed to evaluate the fit of zirconia ceramics before and after veneering, using 3 different veneering processes (layering, press-over, and CAD-on techniques). MATERIALS AND METHODS. Thirty standardized zirconia CAD/CAM frameworks were constructed and divided into three groups of 10 each. The first group was veneered using the traditional layering technique. Press-over and CAD-on techniques were used to veneer second and third groups. The marginal gap of specimens was measured before and after veneering process at 18 sites on the master die using a digital microscope. Paired t-test was used to evaluate mean marginal gap changes. One-way ANOVA and post hoc tests were also employed for comparison among 3 groups (${\alpha}$=.05). RESULTS. Marginal gap of 3 groups was increased after porcelain veneering. The mean marginal gap values after veneering in the layering group ($63.06{\mu}m$) was higher than press-over ($50.64{\mu}m$) and CAD-on ($51.50{\mu}m$) veneered groups (P<.001). CONCLUSION. Three veneering methods altered the marginal fit of zirconia copings. Conventional layering technique increased the marginal gap of zirconia framework more than pressing and CADon techniques. All ceramic crowns made through three different veneering methods revealed clinically acceptable marginal fit.

Neutronic analysis of control rod effect on safety parameters in Tehran Research Reactor

Mina Torabi,A. Lashkari,Seyed Farhad Masoudi,Somayeh Bagheri 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.7

The measurement and calculation of neutronic parameters in nuclear research reactors has an importantinfluence on control and safety of the nuclear reactor. The power peaking factors, reactivity coefficientsand kinetic parameters are the most important neutronic parameter for determining the state of thereactor. The position of the control shim safety rods in the core configuration affects these parameters. The main purpose of this work is to use the MTR_PC package to evaluate the effect of the partiallyinsertion of the control rod on the neutronic parameters at the operating core of the Tehran ResearchReactor. The simulation results show that by increasing the insertion of control rods (bank) in the core,the absolute values of power peaking factor, reactivity coefficients and effective delayed neutron fractionincreased and only prompt neutron life time decreased. . In addition, the results show that the changes ofmoderator temperature coefficients value versus the control rods positions are very significant. Theaverage value of moderator temperature coefficients increase about 98% in the range of 0e70% insertionof control rod

Thermally induced mechanical analysis of temperature-dependent FG-CNTRC conical shells

Jalal Torabi,Reza Ansari 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.3

A numerical study is performed to investigate the impacts of thermal loading on the vibration and buckling of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) conical shells. Thermo-mechanical properties of constituents are considered to be temperature-dependent. Considering the shear deformation theory, the energy functional is derived, and applying the variational differential quadrature (VDQ) method, the mass and stiffness matrices are obtained. The shear correction factors are accurately calculated by matching the shear strain energy obtained from an exact three-dimensional distribution of the transverse shear stresses and shear strain energy related to the first-order shear deformation theory. Numerical results reveal that considering temperature-dependent material properties plays an important role in predicting the thermally induced vibration of FG-CNTRC conical shells, and neglecting this effect leads to considerable overestimation of the stiffness of the structure.

Mixed Thermo elastohydrodynamic lubrication analysis of finite length cam and follower mechanism

Amir Torabi,Saleh Akbarzadeh,Mohammad Reza Salimpour 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3

A considerable portion of the power loss in a valve train mechanism is due to the losses in the cam follower mechanism. The surface of cam and follower experience counterformal contact with a varying nature that makes it a difficult component in an engine to model. Transient contact geometry and entraining may cause the inlet boundary reversal and short lived cessation of entraining motion which can lead to mixed regime of lubrication. Thermal effects and side leakage intensify the adverse governing tribological condition. This paper presents a thermo-elastohydrodynamic model with considering roughness of surfaces for a finite length cam-follower mechanism. Temperature variation, friction coefficient, and film thickness are the outputs of this model which can be used to evaluate the performance of this mechanical element. The results are validated by comparison to other published data. The results show that thermal effects, side leakage and roughness of contacting surfaces play an important role in the tribological performance of the mechanism. A friction analysis considering a comprehensive asperity interaction model is conducted to investigate the proposed lubrication model capability.

Evaluation of shale brittleness using fuzzification of geomechanical and mineralogical properties

Mehdi Torabi-Kaveh,Chandong Chang 대한지질학회 2017 대한지질학회 학술대회 Vol.2017 No.10

Electrochemical synthesis of flake-like Fe/MWCNTs nanocomposite for hydrogen evolution reaction: Effect of the CNTs on dendrite growth of iron and its electrocatalytic activity

Morteza Torabi,S.K. Sadrnezhaad 한국물리학회 2010 Current Applied Physics Vol.10 No.1

Fe/multi-walled carbon nanotubes (Fe/MWCNTs) nanocomposite was produced using electrochemical techniques onto platinum substrate. Linear sweep voltammetry (LSV) analysis revealed that deposition rate of the nanocomposite is higher than of the pure Fe deposition. X-ray diffraction (XRD) was used to confirm nanocomposite formation. Scanning electron microscopy (SEM) images showed dendrite growth of the pure Fe onto a flake-like (thickness of about 90 nm) structure with a filamentous carbon network. The morphology of the nanocomposite consisted of only uniform nanoflakes with thickness of about 50 nm. Adsorption of the MWCNTs on the flakes led to decrease the nucleation energy and avoided formation of the prisms that are essential for dendrite growth. The nanocomposite showed superior catalytic activities for hydrogen evolution reaction (HER), twice of the pure Fe when the overpotential of -1.3 V was applied. The overpotential.time results indicated that HER activity of thin films decreased during the long-term working. But, nanocomposite was more stable than the pure Fe.

Ibrutinib reduces neutrophil infiltration, preserves neural tissue and enhances locomotor recovery in mouse contusion model of spinal cord injury

Somayyeh Torabi,Seyed Hadi Anjamrooz,Zahra Zeraatpisheh,Hadi Aligholi,Hassan Azari 대한해부학회 2021 Anatomy & Cell Biology Vol.54 No.3

Following acute spinal cord injury (SCI), excessive recruitment of neutrophils can result in inflammation, neural tissue loss and exacerbation of neurological outcomes. Ibrutinib is a bruton’s tyrosine kinase inhibitor in innate immune cells such as the neutrophils that diminishes their activation and influx to the site of injury. The present study evaluated the efficacy of ibrutinib administration in the acute phase of SCI on neural tissue preservation and locomotor recovery. Ibrutinib was delivered intravenously at 3.125 mg/kg either immediately, 12 hours after, or both immediately and 12 hours after SCI induction in adult male C57BL/6 mice. Neutrophil influx into the lesion area was evaluated 24 hours following SCI using light microscopy and immunohistochemistry methods. Animals’ body weight changes were recorded, and their functional motor recovery was assessed based on the Basso mouse scale during 28 days after treatment. Finally, spinal cord lesion volume was estimated by an unbiased stereological method. While animals’ weight in the control group started to increase one week after injury, it stayed unchanged in treatment groups. However, the double injection of ibrutinib led to a significantly lower body weight compared to the control group at 4 weeks post-injury. Mean neutrophil counts per visual field and the lesion volume were significantly decreased in all ibrutinib-treated groups. In addition, ibrutinib significantly improved locomotor functional recovery in all treated groups, especially in immediate and double-injection groups. Neural tissue protection and locomotor functional recovery suggest ibrutinib treatment as a potent immunotherapeutic intervention for traumatic SCI that warrants clinical testing.