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An analytical determining the internal ring gear rim stiffness for practical purpose
Saeed Tavassoli,Mehrdad Poursina,Davood Poursina 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10
Internal ring gears have a wide application in planetary gearboxes and transmission systems. The mesh stiffness of planetary gearboxes is an essential parameter for dynamic and vibration analysis. No direct practical method for calculating the stiffness of the internal ring gear rim has been investigated yet to the authors' knowledge. For the first time in this research, a practical method is presented to determine the stiffness of the internal ring gear rim with an appropriate accuracy based on strain energy. To accomplish this goal, every part of the internal ring gear rim, which is between two consecutive pins or bolts, is modeled as a curved beam. The deflection of the curved beam is determined according to Castigliano's theorem. Then, the stiffness of the internal ring gear rim is obtained through this deflection. Fourier’s series of deflections are calculated to make analytical results more comfortable to use. Finally, the analytical results are validated by FEM using ABAQUS software.
Babak Tavassoli,Parviz Jabehdar-Maralani,Nasser Rezaee 제어·로봇·시스템학회 2010 International Journal of Control, Automation, and Vol.8 No.4
The problem of using acknowledgement messages for reducing the effects of packet loss on the performance of a networked control system (NCS) is considered. A sampling and transmission strategy is proposed and the model of the NCS with a Markovian communication state is precisely determined which provides the necessary tools for exact NCS analysis and design. The results can be used efficiently to design simple and practical controllers like PID by minimizing the value of a per-formance measure. During an example, an H∞ performance measure of an NCS is optimized to design controllers, compare between them and evaluate them from both control and communication points of view.
Hormone Receptor Expression and Clinicopathologic Features in Male and Female Breast Cancer
Shandiz, Fatemeh Homaei,Tavassoli, Aliraz,Sharifi, Nourieh,Khales, Sima Ardalan,Kadkhodayan, Sima,Khales, Sahar Ardalan Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.2
Background: Male and female breast cancers were investigated for variation in the clinicopathologic characteristics and expression of steroid hormone receptors in the northeast of Iran. Materials and Methods: Tumor specimens of 17 males and 338 females with breast cancer were collected at the hospitals of Mashhad University of Medical Sciences. Immunohistochemical expression of hormone receptors and clinicopathologic features of breast cancer were compared between two groups. Results: The mean age in men was 15 years higher than women (p=0.000). Males and females were mainly in stage II and III respectively (p=0.007). Although more than 60% of male and female patients were grade II, the respective figures for grade I and III were 25% and 12.5% in men but 7.1% and 27.2% in women respectively (p=0.025). ER was significantly more positive in men against women; 82.3% versus 53.4% (p=0.016). The related measures for PR was 58.8% and 50.3%, respectively (p=0.424). Males also showed significantly more ER expression than postmenopausal females; 82.3% versus 48.9% (p=0.010). Conclusions: Breast cancer in males and females contrasted in age at diagnosis, histological type, stage, grade and ER expression which emphasize they are separate diseases with different behaviors.
Serum Levels of MMP9 and MMP2 in Patients with Oral Squamous Cell Carcinoma
Lotfi, Alireza,Mohammadi, Ghodrat,Tavassoli, Atena,mousaviagdas, Mehrnoosh,Chavoshi, Hadi,Saniee, Lale Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.4
Background: Squamous cell carcinoma (SCC) is the most common cancer in the oral area. Matrix metalloproteinases (MMPs) and especially MMP-2 and MMP-9 are increased in malignancy and lymph node involvement in oral SCCs. We aimed to evaluate the serum levels of MMP-2 and MMP-9 in patients with oral SCC compared to normal subjects and their relation with clinicopathological findings. Materials and Methods: In this case control study, 20 patients with oral SCC and 20 healthy subjects were included and serum levels of MMP-2 and MMP-9 were compared between groups. Also, the correlation between these markers with clinicopathological findings including grade (T) and node (N) were evaluated. Results: Patients with oral SCC had significantly higher serum levels of MMP-2 (p=0.01) and MMP-9 (p<0.001) compared to healthy subjects. With increase in grade T, MMP-2 was significantly increased (p=0.001), but in the MMP-9 case this was not significant (p=0.27). The levels of MMP-2 (p=0.002) and MMP-9 (p=0.01) in cases with lymph node involvement and that of MMP-2 in subjects with smoking history (p=0.001) were significantly high. There was significantly positive correlation between MMP-2 with grade T tumor (r=0.598, p=0.005), lymph node involvement (r=0.737, p<0.001) and smoking (r=0.674, p=0.001) and also between MMP-9 and lymph node involvement (r=0.474, p=0.03). Conclusions: Both markers are significantly increased in oral SCC compared to healthy subjects. However, MMP-2 was better for evaluating lymph node involvement and tumor grade.
Shirin Sayyahfar,Alireza Fahimzad,Amir Naddaf,Sara Tavassoli 대한감염학회 2015 Infection and Chemotherapy Vol.47 No.4
Background: The aim of this study was to evaluate the antibiotic susceptibility of Group A streptococcus (GAS) to antibiotics usually used in Iran for treatment of GAS pharyngitis in children. Materials and Methods: From 2011 to 2013, children 3-15 years of age with acute tonsillopharyngitis who attended Mofid Children’s Hospital clinics and emergency ward and did not meet the exclusion criteria were enrolled in a prospective study in a sequential manner. The isolates strains from throat culture were identified as GAS by colony morphology, gram staining, beta hemolysis on blood agar, sensitivity to bacitracin, a positive pyrrolidonyl aminopeptidase (PYR) test result, and the presence of Lancefield A antigen determined by agglutination test. Antimicrobial susceptibility was identified by both disk diffusion and broth dilution methods. Results: From 200 children enrolled in this study, 59 (30%) cases were culture positive for GAS. All isolates were sensitive to penicillin G. The prevalence of erythromycin, azithromycin, and clarithromycin resistance by broth dilution method was 33.9%, 57.6%, and 33.9%, respectively. Surprisingly, 8.4% of GAS strains were resistant to rifampin. In this study, 13.5% and 32.2% of the strains were resistant to clindamycin and ofloxacin, respectively. Conclusion: The high rate of resistance of GAS to some antibiotics in this study should warn physicians, especially in Iran, to use antibiotics restrictedly and logically to prevent the rising of resistance rates in future. It also seems that continuous local surveillance is necessary to achieve the best therapeutic option for GAS treatment.
Using AQM for Performance Improvement of Networked Control Systems
Masoumeh Azadegan,Mohammad T. H. Beheshti,Babak Tavassoli 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.3
This paper presents a new scheme to jointly control the plant and the network to improve the overall performance of the networked control system (NCS). Using an analytical transmission control protocol (TCP) model for the network, an active queue management (AQM) is designed to achieve desired queue length. This leads to keeping network induced delay and its variation to be small enough to improve the overall performance of the NCSs. By augmenting the TCP communication model with the control system equations, the closed loop system is transformed to a state-dependent delay differential equation (SDDDE). Then using the Lyapunov-Krasovskii method, a sufficient condition for the stability of this class of systems is presented in terms of linear matrix inequality (LMI). Simulation results are presented and compared to some other methods, the superiority of the proposed approach is shown.
Lotfi, Alireza,Mohammadi, Ghodrat,Saniee, Lale,Mousaviagdas, Mehrnoosh,Chavoshi, Hadi,Tavassoli, Atena Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.15
Background: Laryngeal cancer is an important malignancy in head and neck area and squamous cell carcinoma (SCC) is the most common type accounting for 95% of cases. Increase in matrix metalloproteinases (MMPs) in different tumors and their correlation with tumor invasiveness has been documented. However, most studies have evaluated MMP-2 and MMP-9 expression and few have evaluated serum levels. The aim of current study was to evaluate serum levels in patients with laryngeal SCC compared to normal subjects and assess any relation with tumor clinicopathological findings. Materials and Methods: In this case control study, 20 patients with oral SCC and 20 healthy subjects were included. Serum levels of MMP-2 and MMP-9 were compared between groups and correlations with findings including grade (T) and node involvement (N) were evaluated. Results: Patients with laryngeal SCC had significantly higher serum levels of MMP-2 (p=0.01) and MMP-9 (p=0.03) compared to healthy subjects. Patients with higher T stage (T3,4) had significantly higher MMP-2 (p=0.04) and MMP-9 (p=0.01). There was significant positive correlation between serum levels of MMP-2 with T stage (r=0.45, p=0.04) and lymph node involvement (r=0.563, p=0.01) and between levels of MMP-9 with T stage (r=0.527, p=0.01). Conclusions: Our results showed that compared to healthy subjects, both MMP-2 and MMP-9 are significantly increased in serum of laryngeal SCC cases. MMP-2 was correlated with lymph node involvement while MMP-9 has stronger correlation with T stage compared to MMP-2.
Bioleaching of spent refinery catalysts: A review
I. Asghari,S.M. Mousavi,F. Amiri,S. Tavassoli 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.4
Large quantities of solid catalysts are routinely used in many chemical industries especially in petroleum refining and petrochemical industries. Solid catalysts contain metals, metal oxides or sulfides, and require replacement after two or three years of operation. Therefore, large quantities of spent catalysts are generated as solid wastes every year. Because of their hazardous nature and toxic chemical products,there are stringent environmental regulations for discarded spent catalysts. The recovery of metals from these catalysts is also an important economic aspect as most of these catalysts are supported, usually on alumina/silica with varying percent of metal. Bio-hydrometallurgical approaches are more economical and environmentally friendly than physicochemical metal-extraction processes. In this paper, the information available on the bioleaching fundamentals of spent catalyst wastes, as well as a focus on recent developments, is reviewed in detail.