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101.
In this paper we develop an efficient spread-sheet production planning/scheduling model for a resource-constraint production line or a manufacturing cell that produces several products but one at a time with significant changeover time and changeover cost. There are also management and physical constraints related to the operating hours, production capacity and amount of inventory allowed. The production line/cell supplies several products to customers who pull the products according to their own operating policy (working hours) that may be different from manufacture's operating hours. We also show several real-world applications and highlight the benefits and merits of the model. 相似文献
102.
Mehdi Pourabdoli Shahram Raygan Hossein Abdizadeh Deniz Uner 《International Journal of Hydrogen Energy》2013
9Ni–2Mg–Y alloy powders were prepared by arc melting, induction melting, mechanical alloying, solid state reaction and subsequent ball milling processes. The results showed that melting processes are not suitable for preparation of 9Ni–2Mg–Y alloy due to high losses of Mg and Y. Therefore, 9Ni–2Mg–Y alloy powder was prepared by three methods including: 1) mechanical alloying, 2) mechanical alloying + solid state reaction + ball milling, and 3) mixing + solid state reaction + ball milling. The prepared 9Ni–2Mg–Y alloy powders were compared for their catalytic effects on hydrogen desorption of MgH2. It is found that 9Ni–2Mg–Y alloy powder prepared by mechanical alloying + solid state reaction + ball milling method has a smaller particle size (1–5 μm) and higher surface area (1.7 m2 g−1) than that of other methods. H2 desorption tests revealed that addition of 9Ni–2Mg–Y alloy prepared by mechanical alloying + solid state reaction + ball milling to MgH2 decreases the hydrogen desorption temperature of MgH2 from 425 to 210 °C and improves the hydrogen desorption capacity from 0 to 3.5 wt.% at 350 °C during 8 min. 相似文献
103.
Preparation and Characterization of Novel Polyimide/SiO2 Nano-hybrid Films by In Situ Polymerization
Samal Babanzadeh Shahram Mehdipour-Ataei Ali Reza Mahjoub 《Journal of Inorganic and Organometallic Polymers and Materials》2012,22(6):1404-1412
A silicon-based aromatic polyimide (PI) containing pendent aryl rings was synthesized by solution polycondensation of a silicon-containing diamine with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride. Its nano-hybrids with different colloidal SiO2 concentrations were synthesized by in situ polymerization. The reactions were carried out in presence of 3-aminopropyltriethoxysilane as a coupling agent. The inclusion of the coupling agent in the polymer chain and its co-condensation with SiO2 nanoparticles afforded a silica network that was interconnected chemically with the PI matrix. The chemical structure of the hybrid materials was analyzed by Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The morphology of the hybrid films and the surface roughness were characterized by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The results indicated that nanometer-scale inorganic particles were homogeneously dispersed throughout the PI matrix with 50–70 nm size range. The best results and favorable miscibility between polymer and silica phases in the nano-hybrids were obtained when up to 40 wt% nanoparticles were introduced into the backbone of PI matrix. 相似文献
104.
Houman Savoji Dipak Rana Takeshi Matsuura Mohammad Soltanieh Shahram Tabe 《应用聚合物科学杂志》2012,124(3):2300-2310
Integrally skinned asymmetric membranes for the separation of O2 and N2 were fabricated by the phase inversion technique from polysulfone, polyetherimide, and polyimide. Two types of surface modifying macromolecules (SMMs) including hydrophilic SMM (LSMM) and charged SMM (cSMM) were synthesized and blended with the casting solution to modify the membrane surface. The cast film was then immersed in the first coagulant alcohol (methanol, ethanol, or isopropanol) for a predetermined period, before being immersed in the second coagulant (water). The SMMs used in these experiments were laboratory synthesized by the two‐step process of polyurethane prepolymer synthesis and end capping, before being characterized by differential scanning calorimetry. Their molecular structure was determined from the molecular weight obtained by gel permeation chromatography. The membranes were characterized by contact angle measurement and O2 and N2 gas permeation performance. Attempts were made to interpret the gas permeation data by delayed demixing affected by solubility parameters of polymer, solvent, and nonsolvent. Furthermore, the permeation performance of cSMM membranes was interpreted by the solvation of the charged sulfonate groups present in cSMM. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
105.
In this letter, a new voltage-mode (VM) configuration for providing low-power and simultaneous realization of first-order
low-pass, high-pass and all-pass filters is presented. The output of the all-pass filter is taken differentially. The proposed
circuit contains low number of components, i.e., only two NMOS transistors, a floating battery, a grounded capacitor and a
floating resistor. Adding two NMOS transistors to the proposed circuit it is modified as an all-pass filter with a single-ended
output. The main advantage of the presented circuits in comparison with other counterparts is their extremely low power dissipation.
Moreover, the floating resistor can be replaced with an additional NMOS transistor in triode region to provide electronic
tunability. Simulation results using SPICE program are given to demonstrate the performance of the proposed circuit. 相似文献
106.
Shahram Derakhshan Mohammad Rezaee Hamid Sarrafha 《Nanoscale and Microscale Thermophysical Engineering》2015,19(3):206-220
Equilibrium molecular dynamics simulation was utilized to calculate the shear viscosity of monoatomic molecules liquid flow confined in a nanochannel in the pure state and their binary mixtures. The pure flow viscosity data of argon, krypton, and xenon were used to predict their binary mixture viscosities using prediction methods proposed in the literature. Each method was evaluated by comparison of its results with those obtained by validated molecular dynamics simulation at different temperatures. In addition, correlative methods for mixture viscosity estimation and temperature dependence models were evaluated and corresponding model parameters were obtained. Moreover, the relations representing mixture parameter values as a function of the pure ones were determined and evaluated according to their accuracy. 相似文献
107.
Shahram?ArbabEmail author Parviz?Noorpanah Naser?Mohammadi Ahmad?Zeinolebadi 《Polymer Bulletin》2011,66(9):1267-1280
Investigation of structural development of acrylic fibers during the early stages of the wet-spinning process has great importance
both in carbon fiber and textile industries. The simultaneous effects of increasing polymer concentration, jet-stretching
and hot-drawing on porosity, morphology, and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. The
detailed microstructure of the voids was characterized by electron microscopy, porosimetry, and thermoporometry. The effects
of jet-stretching/hot-drawing on the overall porosity of the fibers were negligible below a threshold polymer concentration.
Increasing polymer concentration from 10 to 20 vol.% reduced the total porosity. Hot-drawing was more effective in reducing
the overall porosity of the fibers in comparison with jet-stretching. Stretching and drawing replaced the macrovoids by dense
ligaments but did not change the volume fraction of nanovoids, however, shifted nanovoids size distribution toward smaller
values. In general, Young’s modulus and elongation at break increased by decreasing overall porosity, however, they depended
also on the distribution of voids size and chain orientation along the fiber axis. Strength–diameter correlation showed a
good agreement with the Griffith’s theory. 相似文献
108.
Narges Keshavarz Jafarzadeh Shahram Sharifnia Seyed Nezam Hosseini Farshad Rahimpour 《Korean Journal of Chemical Engineering》2011,28(2):531-538
Response surface methodology (RSM) using D-optimal design was applied to optimization of photocatalytic degradation of phenol
by new composite nano-catalyst (TiO2/Perlite). Effects of seven factors (initial pH, initial phenol concentration, reaction temperature, UV irradiation time,
UV light intensity, catalyst calcination temperature, and dosage of TiO2/perlite) on phenol conversion efficiency were studied and optimized by using the statistical software MODDE 8.02. On statistical
analysis of the results from the experimental studies, the optimum process conditions were as follows: initial pH, 10.7; initial
phenol concentration, 0.5 mM; reaction temperature, 27 °C; UV irradiation time, 6.5 h; UV light intensity, 250 W; catalyst
calcination temperature, 600 °C; and TiO2/perlite dosage, 6 g/L. Analysis of variance (ANOVA) showed a high coefficient of determination (R2) of 91.8%. 相似文献
109.
Reaction of 6‐chloronicotinoyl chloride with p‐phenylene diamine resulted in preparation of a dichloro diamide compound. Subsequently, chloro displacement of this compound with 4‐amino phenoxy groups led to production of a new pyridine‐based ether diamine named as N,N′‐(1,4‐phenylene)bis(6‐(4‐aminophenoxy) nicotinamide). Novel polyimide was prepared through polycondensation reaction of the diamine with hexafluoroisopropylidene diphthalic anhydride (6‐FDA) via two‐step imidization method. In addition, new nanoporous polyimide films were produced through graft copolymerization of polyimide as the continuous phase with a thermally labile poly (propylene glycol) oligomer as the labile phase. The grafted copolymers were synthesized using reaction of the diamine and 6‐FDA in the presence of poly (propylene glycol) 2‐bromoacetate as thermally labile constituent via a poly(amic acid) precursor process. The labile block was decomposed via thermal treatment to release inert molecules that diffused out of the matrix to leave pores with diameters between 30 and 60 nm. The structures and properties of polyimide and polyimide nanofoams were characterized by different techniques including 1H‐NMR, FTIR, TGA, DMTA, SEM, TEM, dielectric constant, and tensile strength measurement. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
110.
Mohammad Bemani Saeid Nikmehr Shahram Hosseinzadeh 《AEUE-International Journal of Electronics and Communications》2013,67(5):382-386
This paper focused on the application of negative refractive index transmission line (NRI-TL) in dual-band unequal Wilkinson power divider (WPD) with controllable frequency and power dividing ratio. Theory and design procedure of the dual-band NRI-TL are presented in details. For demonstration, two dual-band unequal Wilkinson power dividers (WPDs) with power dividing ratio of 2 : 1 and operating frequencies of 0.9 and 1.8 GHz are designed, fabricated and tested. The first unequal divider is based on 2-stage NRI-TLs and the second one is based on 4-stage NRI-TLs. In addition, these two types of NRI-TLs are presented to demonstrate that by increasing the number of NRI-TL unit-cells the phase response of the NRI-TLs converge to the desired characteristic. The good agreement between measured and simulated results confirmed the design concept and derived closed-form design equations. Measurements show that the first divider has 18.37% and 21.86% relative bandwidths and the second one has 33.52% and 29.12% relative bandwidths at 0.9 and 1.8 GHz, respectively. The design concept of this paper can be extended to equal dual-band power dividers with arbitrary frequency ratio. 相似文献