Investigation of Simultaneous Effects of Cooling Slope Casting and Mold Vibration on Mechanical and Microstructural Properties of A356 Aluminum Alloy

Mahdieh Jahanbakhshi,Salman Nourouzi,Reza Naseri,Kourosh Esfandiari 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.6

Aluminum alloys are used in numerous industrial fields due to low weight and high strength to weight ratio. Among differentforming processes, semi-solid casting is one of the most attractive methods for obtaining improved structures as well asminimizing the porosity and segregation problems of conventional casting. In this study, simultaneous employment of coolingslope and introducing mechanical vibration into the melt during solidification is investigated from viewpoint of microstructureof as-cast A356 aluminum alloy. Obtained results demonstrate that by simultaneous employment of cooling slope andmechanical vibration, more refinement can be occurred in comparison to distinct employment of these two procedures. Asa result of this research, in this experimental condition with vibration frequency of 20 Hz and time equal to 3 min, the finalaverage grain size of 50 μm and shape factor of 0.66 can be achieved. Furthermore, mechanical properties of as-cast alloyare also enhanced so that Brinell hardness number and compression strength of the optimum sample are determined equalto 74 Brinell and 486 MPa, respectively.

Characterization of the Growth, Total Lipid and Fatty Acid Profiles in Microalga, Nannochloropsis oceanica under Different Nitrogen Sources

Mahdieh, Majid,Shabani, Salimeh,Amirjani, Mohammad Reza The Korean Society for Microbiology and Biotechnol 2019 한국미생물·생명공학회지 Vol.47 No.1

The properties of microalgae as bioresources for biodiesel production can be improved by adding nitrogen sources into the culture medium. Thus, Nannochloropsis oceanica CCAP 849/10 was cultured in f/2 media supplemented with five different forms of nitrogen at $0.88mmol-N\;l^{-1}$ each: ammonium bicarbonate ($NH_4HCO_3$), ammonium sulfate ($(NH_4)_2SO_4$), sodium nitrate ($NaNO_3$), ammonium nitrate ($NH_4NO_3$), and urea. The cell density, lipid content, and fatty acid profile of the microalga were determined after 15 days of cultivation. The growth of N. oceanica based on cell number was lowest in the medium with $NH_4NO_3$, and increased significantly in the medium with $NH_4HCO_3$. Cells treated with $(NH_4)_2SO_4$, and $NH_4NO_3$ produced the highest total lipid contents (i.e., 65% and 62% by dry weight, respectively). The fatty acid profiles of the microalga were significantly different in the various nitrogen sources. The major fatty acids detected in cultures supplemented with $NH_4HCO_3$, $(NH_4)_2SO_4$, $NH_4NO_3$, or urea were C14:0, C16:0, C16:1, C18:0, C18:1, C18:2, C20:5, and C22:6. However, the C16:1 content in the $NaNO_3$-supplemented culture was very low. This study highlights that the nitrogen source can strongly influence lipid production in N. oceanica and its fatty acid composition.

On vibration and flutter of shear and normal deformable functionally graded reinforced composite plates

Mahdieh Abdollahi,Ali Reza Saidi,Reza Bahaadini 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.4

For the first time, the higher-order shear and normal deformable plate theory (HOSNDPT) is used for the vibration and flutter analyses of the multilayer functionally graded graphene platelets reinforced composite (FG-GPLRC) plates under supersonic airflow. For modeling the supersonic airflow, the linear piston theory is adopted. In HOSNDPT, Legendre polynomials are used to approximate the components of the displacement field in the thickness direction. So, all stress and strain components are encountered. Either uniform or three kinds of non-uniform distribution of graphene platelets (GPLs) into polymer matrix are considered. The Young modulus of the FG-GPLRC plate is estimated by the modified Halpin-Tsai model, while the Poisson ratio and mass density are determined by the rule of mixtures. The Hamilton’s principle is used to obtain the governing equations of motion and the associated boundary conditions of the plate. For solving the plate’s equations of motion, the Galerkin approach is applied. A comparison for the natural frequencies obtained based on the present investigation and those of three-dimensional elasticity theory shows a very good agreement. The flutter boundaries for FG-GPLRC plates based on HOSNDPT are described and the effects of GPL distribution patterns, the geometrical parameters and the weight fraction of GPLs on the flutter frequencies and flutter aerodynamic pressure of the plate are studied in detail. The obtained results show that by increasing 0.5% of GPLs into polymer matrix, the flutter aerodynamic pressure increases approximately 117%, 145%, 166% and 196% for FG-O, FG-A, UD and FG-X distribution patterns, respectively.

Anti-Aging Effect of Nigella Sativa Fixed Oil on D-Galactose-Induced Aging in Mice

Mahdieh Jafari Shahroudi,Soghra Mehri,Hossein Hosseinzadeh 대한약침학회 2017 Journal of pharmacopuncture Vol.20 No.1

Objectives: Aging is an unconscious and gradual process that can lead to changes in biological systems. Induction of oxidative stress and apoptosis, hepatotoxicity and neurotoxicity are involved in the aging process. Regarding the antioxidant property of black seed oil, the aim of this study was to evaluate the anti-aging effect of Nigella sativa (N. sativa) oil on d-galactose-induced aging in mice. Methods: For induction of aging, D-galactose (500 mg/ kg, subcoutaneously SC) was administrated to male mice for 42 days. Animals were treated with D-galactose alone or with b lack seed oil (0.1, 0.2, 0.5 mL/kg, intraperitoneally (ip)). Additionally, vitamin E (200 mg/kg) was used as a positive control. At the end of treatment, the malondialdehyde (MDA) and the glutathione (GSH) contents in brain and liver tissues were measured. Also, enzymes in serum, including aspartate aminotransferase (AST) and alanine amino transferase (ALT), were determined. The levels of the proteins Bax, Bcl2, caspase-3 (pro and cleaved) in brain and liver tissues were evaluated. Results: Administration of D-galactose (500 mg/kg, SC) for 42 days increased serum levels of ALT and AST, as well as the MDA content, in brain and liver tissues, but decreased the GSH content. Additionally, the levels of apoptotic proteins, including Bax, procaspase-3 and caspase-3 cleaved, were markedly increased. N. sativa oil (0.1 and 0.2 mL/ kg) diminished the levels of the biochemical markers ALT and AST. Administration of black seed oil (0.1, 0.2 and 0.5 mL/kg) reduced lipid peroxidation and at doses 0.1 and 0.2 mL/kg significantly recovered the GSH content. The oil decreased Bax/Bcl2 levels and at 0.1 mL/kg down-regulated the expressions of caspase-3 (pro and cleaved) proteins in brain and liver tissues. Conclusion: Through its antioxidant and anti-apoptosis properties, black seed oil exhibited an anti-aging effect in a model of aging induced with D-galactose.

THE EFFECT OF NUMBER OF VIRTUAL CHANNELS ON NOC EDP

Mahdieh Nadi Senejani,Mahdiar Hossein Ghadiry,Mohamad Khalily Dermany 한국전산응용수학회 2010 Journal of applied mathematics & informatics Vol.28 No.1

Low scalability and power efficiency of the shared bus in SoCs is a motivation to use on chip networks instead of traditional buses. In this paper we have modified the Orion power model to reach an analytical model to estimate the average message energy in K-Ary n-Cubes with focus on the number of virtual channels. Afterward by using the power model and also the performance model proposed in [11] the effect of number of virtual channels on Energy-Delay product have been analyzed. In addition a cycle accurate power and performance simulator have been implemented in VHDL to verify the results.

Digestive proteolytic activity in the pistachio green stink bug, Brachynema germari Kolenati (Hemiptera: Pentatomidae)

Mahdieh Bigham,Vahid Hosseininaveh 한국응용곤충학회 2010 Journal of Asia-Pacific Entomology Vol.13 No.3

Proteolytic activity in the digestive system of the pistachio green stink bug, Brachynema germari, was investigated. The maximum total proteolytic activity in the midgut extract was observed at pH 5, suggesting the presence of cysteine proteases. Hydrolyzing the specific substrates for cysteine proteases revealed the presence of cathepsin B and cathepsin L activities in the midgut extract. The presence of cysteine proteases was confirmed by their noticeable inhibition and activation due to specific inhibitors and activators,respectively. The significant inhibition of chymotryptic activity by the inhibitors showed the presence of chymotrypsin in the midgut. No considerable tryptic activity was observed in the midgut extract. There was no detectable total proteolytic activity in the salivary gland extract. Tryptic activity of the salivary gland extract was also inhibited by the specific inhibitors. The substrates for cysteine proteases were also slightly hydrolyzed by the salivary gland extract. Zymogram analysis showed at least one distinct band due to cysteine protease activity in the midgut extract, and the cysteine protease inhibitor caused almost complete disappearance of the band. Cathepsin B and L activities were mainly detected in midgut divisions m1 and m3,respectively, and maximum chymotrypsin and trypsin activities were observed in m3. In general, the results revealed the significant presence of cathepsin B, cathepsin L, and chymotrypsin proteases in the midgut extract. The major proteolytic activity in the salivary glands seems to be conducted by trypsin-like proteases.

Effects of essential oil from Teucrium polium on some digestive enzyme activities of Musca domestica

Mahdieh BIGHAM,Vahid HOSSEININAVEH,Banafsheh NABAVI,Khalil TALEBI,Naimeh-Sadat ESMAEILZADEH 한국곤충학회 2010 Entomological Research Vol.40 No.1

The essential oil from Teucrium polium was evaluated for its adverse effects on larval instars of Musca domestica. The essential oil was blended with a diet at a concentration that produced 50% mortality of subjected insects (LC50) (80 ppm). To learn about the situation of digestive enzymes of M. domestica treated with the essential oil, third larval instars were dissected under non-active enzyme conditions and their midguts were removed. The supernatant was used as an enzyme source after homogenization and centrifugation of the homogenates. Results revealed that some main digestive enzymes in the larval midgut were adversely affected when exposed to the food-incorporated essential oil. Proteinase extracted from larval midgut hydrolyzed the synthetic substrates B-Arg-pNA, Z-Arg-Arg-PNA and Z-Phe-Arg-PNA for trypsin, cathepsin B and cathepsin L activities, respectively, in control and treated larvae. The essential oil caused a reduction of 61.5% in tryptic activity. Significant 69% and 79% reductions were also observed in cathepsin L and B activities, respectively. Carbohydrase activities of α-amylase, α-glucosidase and β-glucosidase were detected in larval midgut extract. All assayed carbohydrases were affected by the essential oil. The most notable impact, a 93% reduction, was observed in α-amylase. Decreases of 69.5% and 42% were obtained in α-glucosidase and β-glucosidase activity, respectively. This study indicated that the larvicidal effect of the essential oil from Teucrium polium may be due to its detrimental effects on digestive enzymes. It seems that the detrimental effect of the oil can be due to both the inhibitory nature of the oil and the destruction of the midgut epithelium.

Duality of Photonic Crystal Radiative Structures and Antenna Arrays

Mahdieh Bozorgi,Nosrat Granpayeh 한국광학회 2010 Current Optics and Photonics Vol.14 No.4

In this paper, behaviors of photonic crystal (PC) radiative structures and antenna arrays have been compared for two types of uniform and binomial excitations. Appropriate duality has been shown between them. These results can be generalized to other types of excitation and arrangement of photonic crystal radiative arrays such as linear, planar and circular arrays of three dimensional (3D) photonic crystal termination resonators. Using these results in designing photonic circuits has some advantages for shaping a particular radiative beam at the photonic crystal exit, for instance reducing the divergence angle of the main lobe in order to enhance the directivity, for better coupling, or for splitting the emitted beam, for dividing the output beam to the next devices in photonic integrated circuits (PIC). For analysis and simulation of the photonic crystal structures, the finite difference time domain (FDTD) method has been employed.

Directional Emission from Photonic Crystal Waveguide Output by Terminating with CROW and Employing the PSO Algorithm

Mahdieh Bozorgi,Nosrat Granpayeh 한국광학회 2011 Current Optics and Photonics Vol.15 No.2

We have designed two photonic crystal waveguide (PCW) structures with output focused beams in order to achieve more coupling between photonic devices and decrease the mismatch losses in photonic integrated circuits. PCW with coupled resonator optical waveguide (CROW) termination has been optimized by both one dimensional (1D) and seven dimensional (7D) particle swarm optimization (PSO) algorithms by evaluating the fitness function by the finite difference time domain (FDTD) method. The 1D and 7Doptimizations caused the factors of 2.79 and 3.875 improvements in intensity of the main lobe compared to the non-optimized structure, whereas the FWHM in 7D-optimized structure was increased, unlike the 1D case. It has also been shown that the increment of focusing causes decrement of the bandwidth.

Optimization of preparation conditions of polyamide thin film composite membrane for organic solvent nanofiltration

Mahdieh Namvar-Mahboub,Majid Pakizeh 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.2

Separation performance of polyamide composite membranes is affected by several parameters during formationof thin upper layer via interfacial polymerization. We investigated the effect of various polyamide synthesisconditions on the performance of organic solvent resistant polyamide composite membranes through the model equationsdesigned by 2-level fractional factorial design. The dewaxing solvent recovery was selected as separation process. Fivefactors were changed in two level includin; TMC concentration (0.05-0.1%), MPD concentration (1-2%), support immersiontime in organic solution (2-4 min), support immersion time in aqueous solution (1-2 min), and curing temperature(70-80 oC). The resultant equations showed 93.48% and 94.82% of the variability (R2adj) in data used to fit oilrejection and permeate flux models, respectively. The analysis of variance revealed that both models were high significant. It was also observed that TMC concentration, MPD concentration and immersion time in TMC have morepronounced effect on the oil rejection and permeate flux than other factors and interactions. Optimal polyamide preparationconditions were obtained using multiple response method for 94% oil rejection as target value. According tothe results, the best value of permeate flux (8.86 l/(m2·h)) was found at TMC concentration of 0.1%, MPD concentrationof 1.94%, immersion time in TMC of 3.88 min, immersion time in MPD of 1.95 min and curing temperature of71.96 oC with desirability factor of 1.