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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Journal of Ultrafine Grained and Nanostructured Materials
- نوع مقاله: Journal Article
- کلمات کلیدی: Workability,Equal channel angular pressing,Die exit channel,Re-strengthening
- چکیده:
- چکیده انگلیسی: Equal channel angular pressing (ECAP) is carried out using two different configurations for the exit channel of the ECAP die, i.e., relieved and choked, with angles of 0.2 °. It is found that using a die with relieved exit channel, the sample was extruded for 6 passes with no surface cracks and an average cell size of 727 nm and a fraction of high angle grain boundaries of 54 % were achieved. Measured values of yield strength (YS) and ultimate tensile strength (UTS) were reported to be 201.1 and 259.5, respectively. By using the die with choked exit channel, it was possible to deform the sample for up to 14 passes with no sign of surface cracking. A relatively finer cell structure around 530 nm was achieved and the fraction of HAGBs increased to 64 %. Relative increases in YS and UTS were as well observed indicating that re-strengthening has been activated in the material after saturation at the 4th pass. In addition, the mechanism of grain refinement seemed to change to progressive lattice rotation evidenced by formation of trapped single grains within the size range of less than 100 nm.
- انتشار مقاله: 26-04-1396
- نویسندگان: Mohsen Torabi,Ali Reza Eivani,Hamidreza Jafarian,Mohammad Taghi Salehi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Ultrafine Grained and Nanostructured Materials
- نوع مقاله: Journal Article
- کلمات کلیدی: precipitation,Severe Plastic Deformation,Ultrafine grains,EBSD,accumulative roll bonding (ARB),Coherent interface,High-angle boundaries (HAGBs)
- چکیده:
- چکیده انگلیسی: The effect of pre-existing nano sized precipitates on the mechanisms and rate of grain refinement has been investigated during the severe plastic deformation. A binary Al–0.2Sc alloy, containing coherent Al3Sc particles, of 3.62 nm in diameter has been deformed by accumulative roll bonding up to 10 cycles. The resulting deformed structures were quantitatively analyzed using electron backscattered diffraction and transmission electron microscope techniques, and the results have been compared to those obtained from a solution treated Al–0.2Sc alloy, deformed up to same accumulative roll bonding cycles. The fraction of high-angle grain boundaries and grain size in all materials was increased and decreased gradually with increasing equivalent strain, respectively. However, the Aged-ARB alloy had relatively higher fraction of high-angle grain boundaries and smaller grain size than those of ST-ARB specimens at the same accumulative roll bonding cycles. It was found in an Al-0.2%Sc alloy that starting microstructures significantly affect the formation of ultrafine grains during severe plastic deformation. It was shown that the small Al3Sc precipitates are more effective on microstructural evolution during accumulative roll bonding process. Existence of fine precipitates in the starting material greatly accelerated the microstructure refinement. In this regards some unique phenomena, including softening during severe plastic deformation and dissolution of pre-existing Al3Sc, were observed.
- انتشار مقاله: 04-10-1392
- نویسندگان: Ehsan Borhani,Hamidreza Jafarian
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Kerman University of Medical Sciences
- نوع مقاله: Journal Article
- کلمات کلیدی: comet assay,Induced pluripotent stem cells (IPSC),Human dermal fibroblasts (HDF),Karyotype test
- چکیده:
- چکیده انگلیسی: Background & Aims: Induced pluripotent stem cells (iPSCs) have the capability to undergo unlimited selfrenewal and differentiation into all cell types in the body. These cells are artificially derived from a nonpluripotent cell, typically human dermal fibroblasts (HDFs). The study of cytogenetic stability of these cells, in order to use iPS cells and apply studies in therapeutic applications, is essential. Methods: In the present experimental study, HDFs were isolated and cultured from human foreskin samples. The cytogenetic stability of these cells was evaluated in early passages (1-3) of HDFs using karyotype test and alkaline comet assay technique. The HDF cells treatment with hydrogen peroxide (H2O2) was used as a positive control for alkaline comet assay. The iPS cells with low passage (4-7) derived from reprogrammed HDFs were cultured on mouse embryonic fibroblast (MEF) feeder layer and cytogenetic stability of these cells were evaluated in early passages using karyotype test and alkaline comet assay technique. Results: The iPS cells in early passages (4-7) had normal karyotype (46, XY) and DNA damage and comet were not observed in these cells. In addition, HDF cells showed normal karyotype in early passages (1-3), but using comet assay, abnormality and DNA damages were observed in positive control (HDFs treated with H2O2). The comparison of alkaline comet assay parameters of iPS and HDF cells with positive control group showed statistically significant differences (P < 0.05). Conclusion: Since the comet assay is a sensitive technique for finding DNA damage, it is best if cytogenetic stability of these cells were evaluated before performing functional experiments on iPS cells. Therefore, for the precise evaluation of DNA damage and cytogenetic stability of iPS cells, the two techniques could complement each other
- انتشار مقاله: 23-04-1395
- نویسندگان: Payam Ghasemi-Dehkordi,Mehdi Allahbakhshian-Farsani,Narges Abdian,Hamideh Jafari-Ghahfarokhi,Javad Saffari-Chaleshtori,Marzieh Sadeghiani,Amin Mirzaeian,Morteza Hashemzadeh-Chaleshtori
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Midwifery and Reproductive Health
- نوع مقاله: Journal Article
- کلمات کلیدی: Horseshoe shape placenta- Placental abnormality, Preterm labour,Ring shape placenta
- چکیده:
- چکیده انگلیسی: Background: Horseshoe placenta is a variant of ring-shaped placenta. Ring-shaped placenta is a rare anomaly seen in fewer than 1 in 6000 deliveries, which could be seen as horseshoe shape due to atrophy in a portion of the ring. This report refers to a possible relationship between the horseshoe shape placenta and preterm labor; although it has not been yet validated in the literature. In this case report we present the placenta of a 35 years-old G2L1 woman who was referred to delivery unit of Shohada Hospital in Ghouch, Iran with starting of labor pain at 34 weeks of gestation who gave birth to a live-born female baby with 6/8 APGAR score. The amniotic fluid was meconium-stained. The patient had no evidence of fever, bleeding, infection. It is concluded that due to the risks to the fetus and mother caused by horseshoe placenta, its timely diagnosis during pregnancy using ultrasound is important and leads to early detection and better management of pregnancies complicated with placental abnormalities.
- انتشار مقاله: 04-12-1392
- نویسندگان: Hamideh Jafari,Robab Latifnejad Roudsari
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Aerospace Science and Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Quadrotor,Inverse simulation,Flight Dynamics,Trust-region Dogleg method
- چکیده:
- چکیده انگلیسی: In this paper, the particular solution technique for inverse simulation applied to the quadrotor maneuvering flight is investigated. The trust-region dogleg (DL) technique which is proposed alleviates the weakness of Newton’s method used for numerical differentiation of system states in the solution process. The proposed technique emphasizes global convergence solution to the inverse simulation problem. This algorithm is evaluated by calculating the control inputs necessary to enable the quadrotor to follow a specified trajectory including climb-hover and cruise-hover maneuvers. The trajectory is generated by the direct simulation using a linear optimal control developed for the quadrotor. The model of rotors for the quadrotor is a nonlinear model developed based on blade element theory (BET), linear aerodynamics, and non uniform inflow over the rotor disc. The results show that the control inputs obtained from the inverse simulation are in good agreement with control inputs estimated by direct simulation. The results also confirm that the maximum difference between the prescribed trajectory and the trajectory generated by the direct simulation is less than 0.02%, and thus the potential application of the inverse simulation with the trust-region dogleg optimization is evident.
- انتشار مقاله: 24-06-1398
- نویسندگان: Hamidreza Jafari,Farid Shahmiri
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Aerospace Science and Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Quadrotor,Inverse simulation,Flight Dynamics,Trust-region Dogleg method
- چکیده:
- چکیده انگلیسی: In this paper, the particular solution technique for inverse simulation applied to the quadrotor maneuvering flight is investigated. The trust-region dogleg (DL) technique which is proposed alleviates the weakness of Newton’s method used for numerical differentiation of system states in the solution process. The proposed technique emphasizes global convergence solution to the inverse simulation problem. This algorithm is evaluated by calculating the control inputs necessary to enable the quadrotor to follow a specified trajectory including climb-hover and cruise-hover maneuvers. The trajectory is generated by the direct simulation using a linear optimal control developed for the quadrotor. The model of rotors for the quadrotor is a nonlinear model developed based on blade element theory (BET), linear aerodynamics, and non uniform inflow over the rotor disc. The results show that the control inputs obtained from the inverse simulation are in good agreement with control inputs estimated by direct simulation. The results also confirm that the maximum difference between the prescribed trajectory and the trajectory generated by the direct simulation is less than 0.02%, and thus the potential application of the inverse simulation with the trust-region dogleg optimization is evident.
- انتشار مقاله: 24-06-1398
- نویسندگان: Hamidreza Jafari,Farid Shahmiri
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Medical Physics
- نوع مقاله: Journal Article
- کلمات کلیدی: Image reconstruction,Tomography,Detector,Object moving system,3D imaging system,Photodiode
- چکیده:
- چکیده انگلیسی: Introduction: Radiation imaging is one of the applicable methods in diagnostic medicine and nondestructive testing for industrial applications. In nondestructive 3D imaging, in addition to the radiation source, there is a requirement for a suitable detection system, data acquisition system, mechanical sections for moving objects, reconstruction algorithm and finally a computer for processing and control.
Method and Materials: One of the most important components of a digital radiation imaging system is its detector. Light photodiode is a new light sensor which is used in digital imaging systems because of its high efficiency. In the present research, a photodiode grid has been implemented to design and make a detection system. The photodiode grid has an array of 10×10 photodiodes in a 50×50 mm2 area. Beside the photodiode grid, a control board has been designed. Furthermore, a mechanical system has been designed to move the objects in the horizontal and vertical directions, and also rotate it around its own axis. The maximum displacement in the horizontal and vertical directions is 60 cm with step accuracy of about 0.015 mm. Step accuracy of the rotational movement is about 0.9 degrees.
Results: After the imaging system was constructed, background and uniformity of the system were tested. All the photodiodes in the imaging system showed good uniformity. The image data was transferred to a computer and processed using a MATLAB program to display the images on a monitor. As the physical resolution of the system is about the pixel size (5 mm), only the overall images of the object's dimensions were expected to be produced.
Discussion and Conclusion: The fidelity of the detection system has been successfully tested using a visible light source and several test samples. The presented system is able to reconstruct 3D images and obtain cross-sectional images of the objects, by using the image processing algorithm specifically designed for it.- انتشار مقاله: 26-03-1389
- نویسندگان: Seyed Mahdi Safavi,Hamid Jafari,Alireza Kamali Asl,Majid Shahreyari
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Pediatrics
- نوع مقاله: Journal Article
- کلمات کلیدی: children,Bone mineral density,Cystic fibrosis,Dual-energy X-ray absorptiometry
- چکیده:
- چکیده انگلیسی: Background: Failure to maintain bone mass density is a major complication in patients with cystic fibrosis (CF). This study was conducted to evaluate the prevalence of low bone mineral density (BMD) and also identifying associated risk factors in CF patients.
Materials and Methods: Present study conducted on 59 CF patients aged 5-35 years referred to respiratory clinic of Masih Daneshvari Hospital, Tehran-Iran. BMD was measured using dual energy X-ray absorptiometry (DXA) scan. Patients were divided in two groups: cases aged 5-18 years as group A and cases over 18 years as group B. Anthropometric variables, corticosteroid usage, pulmonary function test, serum calcium, phosphate and 25-OH vitamin D were assessed and correlation of them with BMD was investigated.
Results: Low BMD (Z score < -2 standard deviation) was found in 72.8% (44) of patients. There was a positive correlation between malnutrition, Forced Expiratory Volume 1 (FEV1) and BMD (r=59 and 0.47, P<0.01, respectively). Steroid therapy and Pseudomonas aeruginosa colonization correlated significantly inversely with BMD (r = -0.34 and -0.32, P<0.05). Vitamin D deficiency was found in 36.7% (18) CF patients. No significant correlation was found between 25-OH vitamin D levels and BMD (r = 0.17; P=0. 23).
Conclusion: In present study, the prevalence of low BMD was about 72.8% with significant correlation with low weight, BMI (poor nutritional status), FEV1,Pseudomonas aeruginosacolonization and the use of glucocorticoids.- انتشار مقاله: 25-02-1396
- نویسندگان: Abdolhamid Jafari Nodoushan,Soheila Khalilzadeh,Azam Golzar,Maryam Hassanzad,Seyed Javad Sayedi,Aliakbar Velayati
- مشاهده
- جایگاه : پژوهشی
- مجله: Annals of Colorectal Research
- نوع مقاله: Journal Article
- کلمات کلیدی: Intestinal volvulus,Colon, Transverse,Colon, Sigmoid,Intestinal obstruction
- چکیده:
- چکیده انگلیسی: Introduction: Volvulus of two segments of colon has been reported rarely, as either synchronous or metachronous events. Colonic volvulus involving both transverse and sigmoid colon is a rare medical problem frequently dismissed as a cause of large bowel obstruction.
Case Presentation: A 73-year-old female presented with colicky abdominal pain, abdominal distension and anorexia for several days. Abdominal radiography showed distended intestinal loops. Patient went under laparotomy and transverse and sigmoid volvulus was discovered.
Conclusions: In spite of transverse colon and sigmoid volvulus rarity, it is advised to include these in the differential diagnosis of patients with chronic abdominal pain associated with recurrent bowel obstruction.- انتشار مقاله: 10-09-1392
- نویسندگان: Alireza Hoseini,Reza Eshragi Samani,Hamed Parsamoin,Hamidreza Jafari
- مشاهده
- جایگاه : پژوهشی
- مجله: Advances in Environmental Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Waste Management,fuzzy logic,analytic hierarchy process,Hazardous waste,Landfill sitting
- چکیده:
- چکیده انگلیسی: Hazardous wastes include numerous kinds of discarded chemicals and other wastes generated from industrial, commercial, and institutional activities. These types of waste present immediate or long-term risks to humans, animals, plants, or the environment and therefore require special handling for safe disposal. Landfills that can accept hazardous wastes are excavated or engineered sites where these special types of waste can be disposed of securely. Since landfills are permanent sites, special attention must be afforded in selecting the location. This paper investigated the use of the Boolean theory and Fuzzy logic in combination with Analytic Hierarchy Process (AHP) methods by applying GIS and IDRISI software for the selection of a hazardous waste landfill site in the Iranian province of Hormozgan. The best location was determined via the Fuzzy and the Boolean methodologies. By collating the area selected for the hazardous waste landfill, this study found that Fuzzy logic with an AND operator had the best options for this purpose. In the end, the most suitable area for a hazardous waste landfill was about 1.6 km2 which was obtained by employing Fuzzy in combination with AHP and by using an AND operator. In addition, all the fundamental criteria affecting the landfill location were considered.
- انتشار مقاله: 19-06-1395
- نویسندگان: Mahdieh Saadat Foomani,Saeed Karimi,Hamid Jafari,Zahra Ghorbaninia
- مشاهده