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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Journal of Particle Science & Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: High pressure,different pipes,Gas transportation,reinforced polyethylene,metal wire
- چکیده:
- چکیده انگلیسی: In this article various pipes used for transporting of gas are introduced and pros and cons of each one are elucidated. The pipes are categorized in three different subgroups including metallic, polymeric and metallic-wire reinforced polymeric pipes. Metallic-wire reinforced polymeric pipes are nominated as the best option for usage in high pressure pipelines transporting natural gas. As a result, some information about major manufacturers of this kind of polymeric pipes, raw material, production process and metallic-wire orientation are presented. Finally, from economical point of view, some calculations are done to estimate required amount of polymer and metallic-wire to manufacture such pipes. It is also possible to compare their manufacturing cost with usual metallic and polymeric pipes.
- انتشار مقاله: 08-01-1394
- نویسندگان: Omid Moini Jazani,Reyhaneh Khalafi,Mohammad Khosravi,Mohammad Reza Hassanpour,Danial Dadkhah,Mehdi Mostafaeian,Mohammad Mahdi Salehi,Hossein Riazi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Particle Science & Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Reaction time,Anionic Polymerization,ε-Caprolactam,Polyamide 6
- چکیده:
- چکیده انگلیسی: The main objective of the present work was to synthesis polyamide 6 through anionic polymerization of ε-caprolactam in an internal mixer. The reaction time and the rheological properties of samples during the polymerization were studied. The samples were characterized by Thermo Gravimetry Analysis (TGA), Differential Scanning Calorimeter (DSC) and FT-IR spectrometer. The melt flow behavior and viscoelastic properties of the samples were studied by using a Rheometric Mechanical Spectrometer (RMS). The polymerization reaction was found to be very fast such that it completed within 6 minutes as could be detected by following the mixing torque which reached to a steady state after passing a maximum. These results suggest that there is a reaction time above which the viscoelastic behavior of the samples almost remained unchanged, while the viscosity and elasticity of the samples continue to decrease with polymerization reaction time as a result of thermochemical degradation.
- انتشار مقاله: 21-10-1393
- نویسندگان: Mohammad Mahdi Salehi,Omid Moini
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Particle Science & Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Mechanical properties,morphology,Ternary Blend,PP/PET/SEBS
- چکیده:
- چکیده انگلیسی: In this work, ternary polymer blends based on polypropylene (PP)/ polyethylene terephthalate (PET) /poly(styrene-b (ethylene-co-butylene)-b-styrene) (SEBS) triblock copolymer and a reactive maleic anhydride grafted SEBS (SEBS-g-MAH) at various compositions were prepared by co-rotating twin screw extruder. The effects of PET, SEBS and SEBS-g-MAH compatibilizer on morphology of the blends were examined by scanning electron microscopy (SEM). The blends morphology was also estimated by some predicting methods, however, SEM results revealed some contrasts between results of predicting methods and the real morphology. Population of individual and core-shell particles as well as average diameter of the rubber-based cavities is extremely dependent on SEBS, SEBS-g-MA and PET content. Mechanical inspection tests showed that in comparison with the pure PP, addition of SEBS/SEBS-MA causes an increase in the impact strength of the system. Keeping other parameters constant, with increase in SEBS rubbery phase, the core-shell morphology was affected and the impact strength increased consequently. On the other hand, increase in PET content results in modulus increase and the impact strength decrease. Finally, the optimum processing conditions for compounding ternary PP/PET/SEBS blends were achieved.
- انتشار مقاله: 29-08-1393
- نویسندگان: Omid Moini Jazani,Mohammad Ali Khoramabadi,Mohammad Mahdi Salehi,Hossein Riazi,Fariba Soltanokottabi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Information Technology Management
- نوع مقاله: Journal Article
- کلمات کلیدی: Business IT contribution,IT business value,IT contribution in automotive production,IT productivity,IT Value
- چکیده:
- چکیده انگلیسی: This study aimed at designing information technology business value model in order to explain the value of information technology in business and evaluate information technology contribution in organization function. For the purpose of a comprehensive analysis of the subject using qualitative data, the research method was set to be mixed method focusing on qualitative sequential design. The first stage of the research strategy was an exploratory single case study and for the second phase, the researchers used focus groups design. Saipa Corporation, one of the most famous firms in Iranian automotive industry, was selected as the case. The varied qualitative date were gathered through interview, document review and observation methods and were analyzed afterwards. Ultimately, the findings of the study highlighted the items and dimensions of information technology business value. This model is composed of the relationship between different dimensions of the theoretical models regarding and the share of information technology in building a business. In order to ensure research generalizability, the results of the research were compared with those in the literature review and the theoretic adequacy of the proposed framework was confirmed.
- انتشار مقاله: 11-05-1396
- نویسندگان: Kamran Feizi,Mahdi Mahmoudsalehi,Mohammad Taghi Taghavi Fard,Iman Raeesi Vanani
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Finance
- نوع مقاله: Journal Article
- کلمات کلیدی: Real Earnings Management,Corporate reputation,Accrual-Based Earnings Management
- چکیده:
- چکیده انگلیسی: The present study's main objective is to assess the relationship between corporate reputation and different types of earnings management (accrual-based, real, and reductive earnings management). In other words, this paper attempts to figure out whether corporate reputation can contribute to the amount of accrual-based, real, and reductive earnings management or not. This paper's method is descriptive-correlational based on published information from listed firms on the Tehran Stock Exchange during 2012-2018 with a selected sample of 187 firms (1309 observations). The method applied for hypothesis testing is linear regression using panel data. The obtained results from hypothesis testing show that corporate reputation has a negative and significant relationship with accrual-based, real, and reductive earnings management, which means highly-reputed firms, are less likely to embark on different earnings management types. Since this paper analyzes the emergent financial markets, like Iran, with extremely competitive audit markets to determine the effect of corporate reputation on different types of earnings management of listed firms on the Tehran Stock Exchange, it can provide useful information in this field.
- انتشار مقاله: 21-07-1399
- نویسندگان: Morteza Zakerian,Habibollah Nakhae,Mahdi Salehi
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Basic Medical Sciences
- نوع مقاله: Journal Article
- کلمات کلیدی: Regulatory T cells,Multiple Sclerosis,CD4+CD25+Foxp3+ -,CD8+CD28- Regulatory T cells
- چکیده:
- چکیده انگلیسی: Objective(s): Regulatory T cells, including CD4+CD25+Fox3+ and CD8+CD28- cells play an important role in regulating the balance between immunity and tolerance. Since multiple sclerosis is an inflammatory autoimmune disease, regulatory T cells are considered to be involved in its pathogenesis. In this study, we investigated the circulatory numbers of the two mentioned types of regulatory T cells and also their association with different clinical characteristics in 84 multiple sclerosis patients.
Materials and Methods: 84 patients with multiple sclerosis and 75 normal individuals were studied. Demographic and clinical information of all participants were collected via questionnaire and clinical examination as well as MRI. The peripheral blood frequency of two different subgroups of regulatory T cells (CD4+ CD25+Foxp3+ and CD8+CD28- cells) were analyzed by flow cytometry using anti-human antibodies conjugated with CD4-FITC / CD25-PE/Foxp3-PE-Cy5, CD3-PE/CD8a-PE-Cy5/CD28-FITC.
Results: The frequency of CD4+CD25+Foxp3+ cells in multiple sclerosis patients was significantly less than that in healthy controls (P=0.006) and in mild forms less than that in sever forms (P=0.003). There was not any correlation between the frequency of regulatory T cells and different clinical variables.
Conclusion: Our results showed that the number of CD4+CD25+Foxp3+ cells decreases significantly in multiple sclerosis patients, which probably shows the regulatory role of these cells in multiple sclerosis.- انتشار مقاله: 30-01-1393
- نویسندگان: Ebrahim Kouchaki,Mahdi Salehi,Mohammad Reza Sharif,Hassan Nikoueinejad,Hossein Akbari
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Nano Dimension
- نوع مقاله: Journal Article
- کلمات کلیدی: Photocatalytic activity,Malachite Green,Hydrothermal Method,CuCr2O4,Mn0.5Cu0.5Cr2O4
- چکیده:
- چکیده انگلیسی: In this study phase- pure new spinel structure, Mn0.5Cu0.5Cr2O4 was prepared by hydrothermal method successfully and the degradation of Malachite green as an organic pollutant was investigated and compared with CuCr2O4. Purification of obtained nanoparticles was measured by using X-ray diffraction method (XRD) in which crystal structure and the structural properties were studied by using X’Pert package and Fullprof program. Also, the morphology of obtained materials was modified by field-effect scanning electron microscopy (FESEM). These materials were characterized by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), respectively. UV-vis diffuse reflectance analysis was done for determination of band gape which evaluated 1.37eV.The photocatalytic application of synthesized materials was evaluated by the degradation of malachite green (MG) in the presence of H2O2 that were assessed by UV–vis spectroscopy analysis. The comparison study of photocatalytic result reviled that Mn0.5Cu0.5Cr2O4 has higheractivity than CuCr2O4.
- انتشار مقاله: 03-10-1397
- نویسندگان: Fatemeh Soleimani,Mahdi Salehi,Ahmad Gholizadeh
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Nano Dimension
- نوع مقاله: Journal Article
- کلمات کلیدی: Dye degradation,Malachite Green,Nano-photocatalyst,Bandgap,Magnesium aluminate spinel
- چکیده:
- چکیده انگلیسی: Spinel MgAl2O4 nanopowders were synthesized by one-step solid state reactions using Al(NO3)3.9H2O and MgSO4 raw materials at stoichiometric 1 : 2, Mg : Al molar ratio at a constant reaction temperature of 1000 ºC for 8 h (S1), 10 h (S2) and 24 h (S3). The synthesized materials were characterized by powder X-ray diffraction (PXRD) technique. Structural analyses were performed by FullProf program making use of profile matching with constant scale factors. The results showed that the patterns had a cubic MgAl2O4 structure similar to the space group . Through textural analysis BJH (Barrette Joiner Halenda) and BET (Brunauer Emmett Teller) methods, the obtained materials were evaluated in terms of average pore size, specific surface area and average pore volume .The morphology of the obtained materials was studied by FESEM images. Ultraviolet–visible (UV-Vis) spectra showed that the nanostructured MgAl2O4 powders possessed strong light absorption properties in the ultraviolet-visible region. Direct optical band gap energies were calculated as 3.4, 2.9 and 3.1 eV for S1, S2 and S3, respectively. The photocatalytic performance of the synthesized nanomaterials was investigated for the degradation of pollutant Malachite Green (MG) in aqueous solutions under solar light. Optimum conditions (0.2 mL H2O2, 25 mg catalyst and 40 min catalytic reaction time for the removal of 80 mL of 100 ppm MG solution) were modeled and achieved by the design expert software for S1. The degradation yield in the condition was 100 % for S1.
- انتشار مقاله: 20-02-1397
- نویسندگان: Sakineh Parvarinezhad,Mahdi Salehi,Shahin Khademinia
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Nano Dimension
- نوع مقاله: Journal Article
- کلمات کلیدی: electrochemical impedance spectroscopy,Magnetic property,Combustion synthesis,Nano-structure characterization,X-ray powder diffraction
- چکیده:
- چکیده انگلیسی: Pure (S1) and Dy3+-doped α-Fe2O3 (S2 and S3) nanoparticles were prepared by a combustion synthesis method at 700 ºC for 8 h using Fe(acac)3 (Tris(acetylacetonato)Iron(III)) as raw material. Characterizations of the prepared powders were carried out by powder X-ray diffraction (PXRD). Structural analysis was performed by the FullProf program employing profile matching with constant scale factors. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS), elemental maps analysis and energy-dispersive X-ray spectroscopy (EDS) were also performed to determine the dopant amount in the α-Fe2O3 crystal structure (S3). The results showed that the patterns had a main hexagonal structure with space group R . The cell parameters data, calculated by rietveld analysis, showed that the cell parameters were decreased with increasing the dopant (Dy3+) amount in the α-Fe2O3 crystal structure. The average particles sizes estimated from TEM images for S3 were about 60 nm. Besides, the magnetic properties of S1 and S3 were measured by vibrating sample magnetometer (VSM). It was found that with the addition of Dy3+ ions into the Fe2O3 system, the coercivity was decreased and the remanent magnetization was abruptly increased. The influence of dysprosium addition was also studied using electrochemical impedance spectroscopy. This study showed that in the presence of dysprosium ion, the charge transfer resistant increased in the electrochemical process.
- انتشار مقاله: 05-06-1396
- نویسندگان: Mahbobeh Jafari,Mahdi Salehi,Mahdi Behzad
- مشاهده
- جایگاه : پژوهشی
- مجله: Advances in Mathematical Finance and Application
- نوع مقاله: Journal Article
- کلمات کلیدی: Crises magnitude,Gutenberg–Richter law,TP statistic,Parametric bootstrap,Simulation study
- چکیده:
- چکیده انگلیسی: Since the seismic behavior of the earth’s energy (which follows from the power law distribution) can be similarly seen in the energy realized by the stock markets, in this paper we consider a statistical study for comparing the financial crises and the earthquakes. For this end, the TP statistic, proposed by Pisarenko and et al. (2004), is employed for estimating the critical point or the lower threshold, i.e. the point beyond that the market energy follows from the power law (Pareto) distribution. The results confirm the deviation of the energy from the Pareto distribution in the high quantiles of the energy data. The upper threshold that the energy's distribution is changed from the Pareto to another distribution is also estimated by TP statistic. A simulation study is employed for checking out the statistical behavior of the estimated thresholds. Finally, the magnitude of the financial earthquakes is studied. The results indicate that the domestic and the international events have caused the financial earthquakes in Tehran Stock Exchange. Also, the positive relation between the daily energy released and the daily magnitude of the shocks that was connected by Gutenberg and Richter (1956) is confirmed.
- انتشار مقاله: 12-03-1398
- نویسندگان: Fateme Taleghani,Mahdi Salehi,Alireza Shakibaiee
- مشاهده