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81.
Ali Asghar Atai Mohammad Hassan Naei Reza Eghtefari 《Journal of Mechanical Science and Technology》2010,24(11):2247-2252
Snap-through is an instability phenomenon that occurs in arch and dome-shaped structures, wherein the structure has to move
from a stable equilibrium state through an unstable path into another stable equilibrated configuration in a jumping action.
In this study, a linear elastic isotropic low arch is considered as a structure with power-law variable thickness. The phenomenon
is investigated by considering the equation of the deflection for the variable thickness arch, solving it with an elegant
analytical technique, and finding the snap-through critical load from an extreme condition. The effect of power-law exponent
and geometry of the arch centerline on critical load is investigated and the constant thickness case and a very rare case
of power-law thickness variation found in literature are considered for verification. 相似文献
82.
S. Hina T. Hayat S. Asghar Awatif A. Hendi 《International Journal of Heat and Mass Transfer》2012,55(13-14):3386-3394
In this work the fundamental problem of peristalsis with heat and mass transfer is investigated in the presence of a chemical reaction. An incompressible viscous fluid is considered in a channel with compliant walls. Mathematical modeling is based upon the laws of mass, linear momentum, energy and concentration. Analysis is presented not only for long wavelength and low Reynolds number but also for small Grashof number. The solutions are carried out for the stream function, temperature, concentration field and heat transfer coefficient. The results of various interesting parameters are plotted and discussed. 相似文献
83.
Asghar Azizi Seid Ziaoddin Shafaei Mohammad Noaparast Mohammad Karamoozian 《Frontiers of Chemical Science and Engineering》2013,7(4):464
The role of pH, solid content, water chemistry and ore mineralogy on the galvanic interactions between chalcopyrite and pyrite and low alloy steel balls were investigated in the grinding of Sarcheshmeh porphyry copper sulfide ore. All these factors strongly affect the galvanic current between the minerals and the steel during the grinding process. The galvanic current density decreased as the solution pH and percent solids increased. In addition, changing the water in the ball mill from tap to distilled water reduced the galvanic current between the minerals and the balls. Potentiodynamic polarization curves showed that pyrite and chalcopyrite demonstrated typical active-passive-transpassive anodic behavior in the grinding of copper ore. However, the nature of their transitions from the active to the passive state differed. This behavior was not seen in the grinding of pure minerals. In addition, an EDTA extraction technique was employed to quantify the amount of oxidized iron in the mill discharge. The amount of extractable iron was influenced by the same experimental factors and in the same way as the galvanic current. 相似文献
84.
Mahmoud Moslehi-Fard Naser Alinejad Chapar Rasouli Asghar Sadigzadeh 《Journal of Fusion Energy》2012,31(4):346-351
Toroidal and Poloidal magnetic fields have an important effect on the tokomak topology. Damavand Tokomak is a small size tokomak characterized with k?=?1.2, B t?=?1T, R 0?=?36?cm, maximum plasma current is about 35?KA with a discharge time of 21?ms. In this experimental work, the variation of poloidal magnetic field on the torodial cross section is measured and analyzed. In order to measure the polodial magnetic field, 18 probes were installed on the edge of tokomak plasma with ?θ?=?18°, while a limiter was installed inside the torus. Plasma current, I p, induces a polodial magnetic field, B p, smaller than the torodial magnetic field B t. Magnetic lines B produced as a combination of B t and B p, are localized on the nested toroidal magnetic surfaces. The presence of polodial magnetic field is necessary for particles confinement. Mirnov oscillations are the fluctuations of polodial magnetic field, detected by magnetic probes. Disrupted instability in Tokomak typically starts with mirnov oscillations which appear as fluctuations of polodial magnetic field and is detected by magnetic probes. Minor disruptions inside the plasma can contain principal magnetic islands and their satellites can cause the annihilation of plasma confinement. Production of thin layer of turbulent magnetic field lines cause minor disruption. Magnetic limiter may cause the deformation of symmetric equilibrium configuration and chaotic magnetic islands reveal in plasma occurring in thin region of chaotic field lines close to their separatrix. The width of this chaotic layer in the right side of poloidal profile of Damavand Tokomak is smaller than the width in the left side profile because of Shafranov displacement. Ergodic region in the left side of profile develops a perturbation on the magnetic polodial field lines, B p, that are greater in magnitude than that in the right side, although the values of B p on the left side are smaller than that on the right side of the profile. The Left side of profile is close to the principal magnetic axis and the right side is away from Z axis of Tokamak. 相似文献
85.
Mehvish Iram Umar Asghar Zile Huma Saba Jamil Muhammad Nadeem 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(3):364-372
In this study, sugarcane bagasse (2 mm) was pretreated with 2.5% NaOH followed by steaming at 121°C for various time periods. Maximum cellulose content of 81% and delignification of 68.5% were achieved by soaking bagasse in 2.5% NaOH with a residence time of 1 h at room temperature followed by steaming at 121°C for 30 min residence time. The pretreated substrate was analyzed by SEM and FTIR to study the structural modification and functional group of the untreated and pretreated substrates. The pretreated substrate was saccharified by commercial cellulase enzyme depicting 106 µm mesh size of substrate yields maximum saccharification rate. The saccharified material was fermented by Saccharomyces cerevisiae and Pichia stipitis in mono- and co-culture modes. Maximum product yield (Yp/s) was observed by monoculture using Saccharomyces cerevisiae after 96 h of fermentation period. 相似文献
86.
87.
An investigation is made on the unsteady magnetohydrodynamic (MHD) flow caused by the non-coaxial rotation of a disk and a fluid at infinity being permeated by a transverse magnetic field. The disk is porous and nonconducting and executes oscillations in its own plane. The Laplace transform method is used to obtain the exact solution of the velocity field. The structure of the steady and unsteady flow fields is investigated. It is shown that the ultimate steady-state blowing solution is established in the presence of Hall current also for resonant frequency, which was not possible in the hydrodynamic case. The combined effects of Hall current, rotation, and suction or blowing are examined. The physical significance of mathematical results is given with various limiting cases. 相似文献
88.
M. YasinA. Asghar F.M. AnjumM.S. Butt M.I. KhanM.S. Arshad M. ShahidA.H. El-Ghorab T. Shibamoto 《Food chemistry》2012,131(3):768-773
Depression of meat quality is known to be caused by lipid peroxidation occurring in meat. Supplementation of antioxidants in feed decreases lipid peroxidation and improves the oxidative stability of meat after slaughtering. The present study demonstrated that meat obtained from broiler birds fed feed supplemented with α-tocopherol acetate (200 mg/kg feed) along with α-lipoic acid (25, 75, or 150 mg/kg feed) exhibited increased oxidative stability and reduced fat content. The total phenolic content and α-lipoic acid content increased in the meat as the concentration of α-lipoic acid supplementation increased. The protein content in the meat was not changed by the supplementation of α-lipoic acid and α-tocopherol acetate. The results of DPPH and TBA assays demonstrated that feed supplemented with α-lipoic acid and α-tocopherol acetate also enhanced the antioxidant activity of broiler meat. On the other hand, the meat from broiler birds fed feed supplemented with oxidised oil (4% in feed) reduced its oxidative stability. 相似文献
89.
Wastewater treatment by adsorption with electrochemical regeneration using graphite-based adsorbents
H.?M.?A.?Asghar E.?P.?L.?RobertsEmail author S.?N.?Hussain A.?K.?Campen N.?W.?Brown 《Journal of Applied Electrochemistry》2012,42(9):797-807
An innovative technology for wastewater treatment using adsorption and electrochemical regeneration has been developed at the University of Manchester. The process uses a low capacity graphitic adsorbent material (a graphite intercalation compound, NyexTM 1000) which can be regenerated electrochemically. In this study, we investigate the characteristics of a new, partially porous adsorbent material, NyexTM 2000 which offers increased surface area in comparison with NyexTM 1000. NyexTM 2000 was found to have an adsorption capacity of almost three times that of NyexTM 1000. The electrical conductivity of a NyexTM 2000 was found to be double that of NyexTM 1000, enabling improvements in the electrochemical regeneration characteristics. The removal of an anionic azo dye, acid violet 17, from aqueous solution using NyexTM 1000 and 2000 was investigated under various operating conditions. The adsorption of acid violet 17 on NyexTM 2000 was found to be comparatively fast with 75 % of the equilibrium capacity being achieved within 5 min. The parameters affecting the regeneration efficiency including the charge passed, current density, treatment time, adsorbent bed thickness, and pH were investigated. An electrochemical regeneration efficiency of around 100 % was achieved for a fully loaded NyexTM 2000 in a sequential batch electrochemical cell with a regeneration time of 60 min and a charge passed of 100 C g−1 at a current density of 14 mA cm−2. The charge required for electrochemical regeneration was found to be approximately equal to theoretical charge required for complete oxidation of the adsorbed acid violet 17, making process design relatively simple. NyexTM 2000 was found to be an economic adsorbent with relatively small electrical energy consumption required (31 J mg−1 of acid violet 17 treated, compared to 52 J mg−1 of acid violet 17 for NyexTM 1000). Multiple adsorption/regeneration cycles presented no loss in adsorptive capacity and material loses over five adsorption/regeneration cycles. 相似文献
90.
Ali Asghar J Ian Gray Alden M. Booren E A Gomaa Mohamed M Abouzied Elwyn R Miller D Joseph Buckley 《Journal of the science of food and agriculture》1991,57(1):31-41
The influence of three levels of vitamin E in the diet of pigs on the subcellular deposition of α-tocopherol in the muscle and on selected quality characteristics of pork meat (oxidative stability of lipids, colour, drip loss, microbial growth) was studied. The content of α-tocopherol in adipose tissue and L. dorsi muscle as well as in mitochondrial and microsomal fractions of the muscle significantly increased (P < 0.05) with increasing levels of dietary vitamin E. The differences in the concentrations of α-tocopherol in the subcellular fractions were evident in the enhanced stability of the membranes when exposed to metmyoglobin/hydrogen peroxide. The beneficial effect of dietary vitamin E on the oxidative stability of pork lipids during the storage of pork chops and ground pork was also demonstrated. Even though lipid oxidation increased in all cases during storage, the pork products from the pigs receiving the highest level of vitamin E (200 IU kg?1 feed) exhibited the smallest increase in thiobarbituric acid reactive substances. In addition, increased colour stability and decreased drip loss were observed on keeping pork chops, which had been previously frozen for three months, at 4°C under fluoresent light for 10 days. The possible effect of α-tocopherol on membrane fluidity in this context is discussed. 相似文献