Sharif Digital Repository

The effects of addition of an ionic liquid to pure water as a physical absorbent and monoethanolamine (MEA) solutions as a chemical absorbent on carbon dioxide (CO2) absorption through hollow fiber membrane contactors were investigated using a 2D axisymmetric model. A numerical simulation was developed based on finite element method using computational fluid dynamics techniques. Liquid phase flowed in the tube side and gas mixture containing CO2 passed in the shell side of the membrane contactor in co-current and countercurrent modes. The simulation results are consistent with experimental data, and the root-mean-square error was calculated as 9 and 13% for pure water and 25 wt % for ionic... 

In this research the characteristics of free (partially purified) and immobilized (mould pellets of Absidia griseola) α-galactosidase have been investigated. Inhibition studies of the enzyme showed that p-nitrophenol and sucrose do not have any inhibitory effect on the enzyme, but that galactose is a competitive inhibitor. In the immobilized form, inhibition was lower than in the free enzyme and the level of inhibition decreased as the temperature increased. The activity and stability of free and immobilized enzyme were investigated with respect to temperature, and the results showed that the optimal temperature range of the free enzyme was 45-50°C, while the immobilized enzyme had an... 

Diabetes mellitus is a global endemic with a rapidly increasing prevalence in both developing and developed countries. Recently, hemoglobin A1c has been recommended by the American Diabetes Associations as a possible substitute for fasting blood glucose for the diagnosis of diabetes, because it is an indicator of long-term glycemic control. Also, centrifugal microfluidic systems have good potential for use in the point of care testing systems. In this study, a centrifugal microfluidic disc was designed and manufactured to measure hemoglobin A1c in whole blood using an immunoturbidimetry based method. Also, a new passive valve, named septum valve, was presented to precisely control the entry... 

Current available models for simulation of the separation process in gas-liquid membrane contactor (MC) systems consider a uniform partial membrane wetting along the membrane length (Lmem). However, transmembrane pressure changes along the Lmem. Additionally, the available models usually consider a simplified uniform pore size to represent the micro-porous MC. Additionally, not all pores in a MC have the same size. In this study, a pore-scale network model is developed to simulate the physical separation of H2S using MCs by taking to account for (i) transmembrane pressure variation and (ii) pore size distribution of MC. The model results are compared with the experimental results of H2S... 

This study investigates the effects of polymer concentration and solvent type on the pore size distribution (PSD) of the fabricated gas-liquid membrane contactors (MCs). Eighteen flat-sheet MCs are fabricated using polysulfone (PSf) and polyethersulfone (PES) polymers, with polymer concentration of 10%, 15%, and 20%. Dimethylformamide (DMF) and n-methyl-2-pyrrolidone (NMP) solvents are used to prepare the polymeric solutions. The role of polyvinylpyrrolidone (PVP) on the mean pore size of MCs is also studied. Scanning electron microscope (SEM) analysis is applied to visualize the pore system of the fabricated MCs. Image processing technique is used to obtain the PSD of the fabricated MCs... 

Background: In line with the advancement of Artificial Intelligence (AI), innovative solutions have been designed to improve health-related Sustainable Development Goals (SDGs). Accordingly, there is an increasing trend in the realm of AI and SDG research areas. Objectives: This study aimed to analyze the trends and patterns of AI research in health-related SDGs using bibliometric analysis. Methods: The bibliometric approach facilitated the identification of key terms and countries from previous research. We used VOSviewer to map and analyze data obtained from three databases: Scopus, Web of Science, and PubMed. Results: Our findings illustrated that research on health has been a popular... 

Optimization of transient liquid phase (TLP) bonding variables is essential to achieve a joint free from deleterious intermetallic constituents as well as with appropriate mechanical properties. In this research, TLP bonding of FSX-414 superalloy was performed using the MBF-80 interlayer. The effects of bonding time (1-30. min) and gap size (25-100 μm) were studied on the joint microstructure and its mechanical properties. Continuous centerline eutectic phases, characterized as nickel-rich and chromium-rich borides, were observed at the joints with incomplete isothermal solidification. The globular and acicular phases were seen at diffusion affected zone (DAZ). These phases could be... 

The as-cast samples of FSX-414 Co-based superalloy were heat treated at the standard solution and aging heat treatment cycles. Specimens for joining were cut from the as-cast ingot. Transient liquid phase (TLP) bonding was carried out at the standard solution cycle, using MBF-30 interlayer. Also, bonded specimens were homogenized at the standard aging condition. The microstructure of the as-cast, heat treated and TLP bonded specimens were studied. These studies showed that the non-uniform distributed carbides of the as-cast specimen were replaced by uniform ones during the heat treatment. Eutectic M 23C 6 carbides were observed in all specimens. Due to the complete isothermal solidification,... 

The as-cast FSX-414 Co-based superalloy samples were solution treated at 1150°C for 4h and then aged at 980°C for 4h. Specimens for joining were cut from the as-cast ingot and TLP bonding carried out at the same conditions as for the solution and solution+aging treatment, using MBF-30 interlayer. Microstructures were studied for as-cast, heat treated and TLP bonded specimens. These studies showed that the ununiform distributed carbides of MC type in the as-cast specimens replaced by M23C6 type carbides with uniform distribution in the heat treated microstructure. Due to complete isothermal solidification, no eutectic structure in the bond region were wasobserved, but some intermetallics in... 

4340 steel bars were austenitized at 850°C for 1 hour followed by heating at 700°C (ferrite and austenite region) for 90 min and quenching into a salt bath with different temperatures of 300, 350, 400 and 450°C. The steel bars were held for 1 hour at these temperatures before air cooling to room temperature. Various ferrite-bainite microstructures with 34% volume fraction of ferrite and different bainite morphologies were obtained. The results of SEM studies showed that by increasing the austempering temperature, the morphology of bainite varies from lower to upper bainite. According to the T-T-T diagram of the studied steel, the bainite transformation will not complete for the holding time... 

4340 steel bars were austenitized at 850 °C for 1 h followed by heating at 700 °C for 90 min and quenching into a salt bath at the temperature range of 300-450 °C for 1 h to obtain dual structures with 34 vol.% fraction ferrite and various bainite morphologies. SEM studies showed that by increasing the austempering temperature, bainite morphology varies from lower to upper bainite. Tensile, impact and hardness tests revealed that increasing the austempering temperature from 300 to 400 °C leads to a reduction in yield and ultimate tensile strength, hardness, uniform and total elongation and impact energy. But in dual phase steel produced by austempering at 450 °C, yield and tensile strength... 

Microfluidics has been becoming more and more popular over last two decades. The reason for this, is inherent features of microfluidics including low consumption of samples and reagents, high sensitivity, short analysis time, and low cost. As well as, centrifugal microfluidics as a subset of microfluidics has been able to prove itself as a helpful tool in analytic assays. The main application of centrifugal microfluidic devices is being used in point-of-care testing systems. Herein, we presented a microfluidic disc for measuring hemoglobin(Hb) concentration in the EDTA-anticoagulated venous blood using cyanmethemoglobin method. In this experiment, at first a hand-made standard solution was... 

Undoubtedly, microfluidics has been a focal point of interdisciplinary science during the last two decades, resulting in many developments in this area. Centrifugal microfluidic platforms have good potential for use in point-of-care devices because they take advantage of some intrinsic forces, most notably centrifugal force, which obviates the need to any external driving forces. Herein, we introduce a newly designed detection chamber for use on microfluidic discs that can be employed as an absorbance readout step in cases where the final solution has a very low viscosity and surface tension. In such situations, our chamber easily eliminates the air bubbles from the final solution without... 

Background: The governance of health systems is complex in nature due to several intertwined and multi-dimensional factors contributing to it. Recent challenges of health systems reflect the need for innovative approaches that can minimize adverse consequences of policies. Hence, there is compelling evidence of a distinct outlook on the health ecosystem using artificial intelligence (AI). Therefore, this study aimed to investigate the roles of AI and its applications in health system governance through an interpretive scoping review of current evidence. Method: This study intended to offer a research agenda and framework for the applications of AI in health systems governance. To include... 

In this study, the experimental finding of two half-scale interior prefabricated Reinforced Concrete column to Steel beam (RCS) sub-assemblage with proposed joint formations with and without web panel in the junction is presented. Previous researches about RCS have been performed to study shear strength of steel web panel in the joint by modeling joint component, however rarely have been conducted to evaluate joint shear resistance experimentally. Over the past 30 years, noticeable analytical and experimental assessments have been performed on the cast in place RCS joints, but seldom have been done on the prefabricated RCS. The steel beams in the proposed joint are attached to the expanded... 

In this paper, a new scheme for adaptiva subcarrier, bit and power allocation for downlink transmission of multiuser orthogonal frequency division multiplexing (OFDM) systems is presented. An adaptive algorithm is introduced to achieve the desired bit rate and BER for QoS (quality of service) of different users in a frequency selective fading channel, while the total transmit power is minimized. The performance and complexity of the proposed scheme is also thoroughly compared with the other existing methods. As the simulation results show, the proposed algorithm outperforms all prior sub-optimum schemes, while offering comparable computational complexity. © 2003 IEEE