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Your search keyword '"Dehghani, Mohammad"' showing total 580 results
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580 results on '"Dehghani, Mohammad"'

1. Analyzing orthogonal cutting process using SPH method by kinematic cutting tool

Author

Dehghani, Mohammad, Shafiei, Alireza, and Abootorabi, Mohammad Mahdi

Subjects
Orthogonal cutting process, Kinematic and kinetic cutting tool, Johnson–Cook material model, SPH method, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

In this paper, the orthogonal cutting process is studied using Smooth Particle Hydrodynamic (SPH) method by a kinematic rigid cutting tool and two work-piece material models: perfectly elastic-plastic (EPP) model and Johnson–Cook (JC) model. The kinematic tool means that if the cutting tool is assumed a rigid body then the horizontal component speed of work-piece particles at cutting tool region are modified to the cutting speed. The chip shapes of orthogonal cutting process using SPH method with kinematic and kinetic tool models are compared with the experimental results. The chip obtained by the simulation with kinematic tool is more similar to the experimental results. Von-Mises stress distribution at different states of the orthogonal cutting process is investigated. The maximum stress occurs at the shear plane and causes the formation of chip teeth. Comparisons between chips of work-pieces with two material models are investigated including different rake angles of 5, 10 and $17.5^{\circ }$ with feed rates of 0.3 and $0.4~{\rm mm}/{\rm rev}$ and the cutting forces of the process are obtained. The cutting force of process with $17.5^{\circ }$ rake angle, $0.4~{\rm mm}/{\rm rev}$ feed rate and $800~{\rm m}/{\rm min}$ cutting speed is validated using experimental result.

Published
2020
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2. Changing QRS Morphology: What is the mechanism?

Author

Haghjoo, Majid, Arya, Arash, Dehghani, Mohammad Reza, Sadr-Ameli, Mohammad Ali, Singh, Balbir, Lokhandwala, Yash, Francis, Johnson, Gupta, Anup, and Ghosh, Joydeep

Subjects
JOURNALS: Indian Pacing and Electrophysiology Journal, Indian Pacing and Electrophysiology Journal
Abstract

ECG in sinus rhythm with ventricular preexcitation and changing QRS morphology was seen that was initially interpreted as the multiple accessory pathway from elsewhere. (Figure 1A). The following mechanisms are potentially involved in the electrogenesis of changing QRS morphology in WPW syndrome: 1) multiple accessory pathways1; 2) simultaneous occurrence of aberrant atrioventricular conduction with accessory pathway conduction 2; 3) ventricular fusion of preexcited sinus impulse with ectopic impulse. Electrophysiologic study showed short PR (75 ms) interval with wide QRS (152 ms) and negative HV (-12 ms) interval. No change in delta wave polarity was observed during HRA and CS pacing. In full preexcitation, no breakthrough was seen in the CS. During incremental ventricular pacing, atrial breakthrough site is initially recorded on the HRA catheter and then changed to distal pole of CS catheter with progressive decrease in pacing cycle length. During ventricular pacing at cycle length of 500 ms (S1), earliest atrial activity is recorded on HRA catheter. Changing QRS could not be explained by presence of multiple APs because only right-sided AP had bidirectional conduction and no distal CS breakthrough was seen simultaneous with changing QRS morphology. The possibility of aberrant conduction is excluded by presence of negative HV interval in the beats with differing QRS morphology. No sinus cycle length variation before and after the beats with different morphologies are against the occurrence of functional LBBB. The prematurity of ventricular electrogram in His recording catheter with variable HV (H-electrogram is recorded after V-electrogram in second beat and before V-electrogram in third beat) and fixed V-RB intervals (interval from ventricular electrogram in His to the RB potential) are compatible with ventricular fusion of preexcited sinus impulse with ectopic ventricular impulse originating from parahissian area (explaining LBBB and inferior axis morphology of the beats with changing QRS) but not from the His bundle or RBB itself (because H-electrogram and RB potential is recorded after V-electrogram in the second beat with greater degree of ventricular fusion)(Figure 1B).

Published
2006

3. Predictors of appropriate ICD therapy in patients with implantable cardioverter-defibrillator

Author

Dehghani, Mohammad Reza, Arya, Arash, Haghjoo, Majid, Zahra, Emkanjoo, Mohammad, Alasti, Babak, Kazemi, Nikoo, Mohammad Hosein, Sadr-Ameli, Mohammad Ali, Singh, Balbir, Lokhandwala, Yash, Francis, Johnson, and Gupta, Anup

Subjects
JOURNALS: Indian Pacing and Electrophysiology Journal, Indian Pacing and Electrophysiology Journal
Abstract

Background: Understanding the predictors of appropriate implantable cardioverter defibrillator (ICD) therapy could help to better identify candidates for ICD implantation. Methods: One hundred and sixty two patients with ICD (111 with coronary artery disease [CAD] and 51 with dilated cardiomyopathy [DCM]) were included in the study. Clinical, electrocardiographic, and ICD stored data and electrograms were collected. Results: During mean follow up of 15±11 months 54 patients (33%) received ≥ 1 appropriate ICD therapy (AICDT). We used binary logistic regression analysis with forward selection method to find the potential predictors of appropriate ICD therapy after device implantation. Male gender (odds ratio [OR] = 2.76, 95% confidence interval [CI] = 1.1 – 7.1, P=0.021), DCM as underlying heart disease (OR = 4.2, 95% CI = 1.9 – 9.5, P=0.001), and QRS width > 100 ms (OR = 2.58, 95% CI = 1.2 – 5.4, P=0.010) were correlated with increased likelihood of AICDT during the follow up period. In subgroup analysis of the patients with CAD and DCM, QRS duration > 100 ms was correlated with the probability of ≥ 1 AICDT. In our patients indication of ICD implantation (primary versus secondary prevention) did not influence probability of ≥ 1 AICDT (adjusted OR = 1.66, 95% CI = 0.7 – 4.0, Mantel-Haenszel P value P=0.355.) Conclusion: QRS width could be used as an additional simple risk stratifier beyond EF to identify potential candidates who would benefit more from ICD implantation. This may have practical implications for patient selection especially in developing countries. Indication of ICD implantation (primary versus secondary prevention) did not affect the probability of ≥ 1 AICDT during the follow up period.

Published
2006

49. How photoautotrophy, photomixotrophy, and ventilation affect the stomata and fluorescence emission of pistachios rootstock?

Author

Meimand Mohammad Javad Mahmoudi, Shamshiri Mohammad Hossein, Malekzadeh Khalil, and Dehghani Mohammad Reza

Subjects
chlorophyll, photosynthesis, acclimatization, desiccation, fv/fm, Biology (General), QH301-705.5
Abstract

The effects of ventilation and sucrose concentration on proliferation and organogenesis of pistachio cutting and photosynthetic performance of two in vitro cultures of pistachio rootstocks have been assessed. The apical leaf buds (Qazvini and UCB1 cultivars) were cultured in filter vessels containing Murashige and Skoog medium supplemented with 0, 10, 15, and 30 g L−1 of sucrose. The plants treated with 10, 15, and 30 g L−1 sucrose showed no significant differences regarding the measured traits; therefore, this treatment was set aside from the final statistical analyses. Use of different ventilation systems showed to be suitable for increasing the growth of pistachio. Referring to root production difficulties under in vitro cultivation of pistachio, ventilation increased the root production and length. However, the full ventilation system was more effective in improving the growth properties. Regression between fluorescence feature vs root length showed that F v/F m had a significant positive relationship with root length. Stomata of cell parameters under ventilation systems improved compared to no ventilation, which was highly similar to the trend in the greenhouse. The overall results indicated that low concentrations of sucrose (e.g., 10 g L−1) and full ventilation are recommended for producing high quality and vigorous pistachio plantlets under in vitro conditions.

Published
2021
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