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31.
Optimal redundancy allocation problems in engineering systems with dependent component lifetimes
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This paper deals with the problem of allocating spare components for improving the system reliability when lifetimes of components are dependent. Two policies, called active and standby redundancies, are investigated in details. The optimal allocations are given without specific assumptions on the dependency structure among the component lifetimes. When there exist the (positive/negative) quadratic dependence and (upper/lower) orthant order among the component lifetimes, the derived results are simplified. Various illustrative examples are also given. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
32.
Elaheh K. Goharshadi Mohsen Abbaspour Hamideh Kashani Mahmood Baherololoom 《Theoretical chemistry accounts》2008,119(4):355-368
We have performed the molecular dynamics simulation to obtain energy, pressure, and self-diffusion coefficient of helium at
different temperatures and densities using Lennard–Jones (LJ), Hartree–Fock dispersion-Individual damping (HFD-ID) potential,
and the HFD-like potential which has been obtained with an inversion of viscosity data at zero pressure supplemented by quantum
corrections following the Feynman–Hibbs approach. The contribution of three-body interactions using an accurate simple relationship
reported by Wang and Sadus between two-body and three-body interactions has been also involved for non-effective potentials
(HFD-ID and HFD-like) in simulation. Our results show a good agreement with corresponding experimental data. A comparison
of our simulated results with other molecular simulations using different potentials is also included. 相似文献
33.
Mahdi Behzad Leila Seifikar Ghomi Maryam Damercheli Bita Mehravi Hamideh Samari Jahromi 《Journal of Coordination Chemistry》2016,69(16):2469-2481
Two new unsymmetrical copper(II) Schiff base complexes, [CuLn(py)]ClO4 (n = 1, 2) in which Ln represents a tridentate N2O type Schiff base ligand, were synthesized. Lns were derived from monocondensation of meso-1,2-diphenyl-1,2-ethylenediamine with salicylaldehyde or 3-methoxysalicylaldehyde. The reaction between [CuLn(py)]ClO4 and other salicylaldehyde derivatives resulted in new N2O2 unsymmetrical tetradentate CuII complexes, CuL3–6. Crystal structures of [CuL1(py)]ClO4, CuL4, and CuL5 were obtained. These new complexes as well as a series of related symmetrical ones (i.e. CuL7–12) were tested for their in vitro anticancer activity against human liver cancer cell line (Hep-G2) by MTT and apoptosis assay. All of the complexes showed considerable cytotoxic activity against tumor cell lines (IC50 = 5.13–16.24 μg mL?1). The symmetrical CuL7 was the most potent anticancer derivative (IC50 = 5.13 μg mL?1) compared to the control drug 5-FU (IC50 = 5.4 μg mL-1, p < 0.05). Flow cytometry experiments showed that the copper derivatives especially [CuL2(py)]ClO4 and CuL7 induced more apoptosis on Hep-G2 tumor cell lines compared to 5-FU. 相似文献
34.
One‐step Hydrothermal Synthesis and Assembly of Copper and Silver Nanoparticles to Aggregates in Glyoxal Reduction System
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Abbas Jorsaraei Talar Hamideh Ghasemi Alimorad Rashidi Saeed Khodabakhshi 《中国化学会会志》2016,63(7):627-635
A simple hydrothermal process has been developed for the synthesis and assembly of copper and silver nanoparticles to aggregates. The reduction of Cu2+ and Ag+ ions to the zerovalent metal was performed by glyoxal in the absence of any external agent. The produced glyoxylic acid (GA) in the redox process stabi‐ lized metallic copper and silver particles and rendered them oxidation resistant for several months and dispersible in polar organic solvents and water. Detailed nanostructures of synthesized products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD). The results demonstrated that assembly of nanoparticles to aggregates and their regularity were dependent on the reaction conditions such as temperature and concentration of the starting material. The Ostwald ripening process was proposed to explain the formation of copper nanoparticles by TEM observation at several times during the reaction. The existence of the surface stabilizing agent was identified by Fourier Transform infrared spectroscopy (FT‐IR) and thermogravimetric analyses (TGA). 相似文献
35.
Hamideh Afzali Mohammad Khaksari Sajad Jeddi Khosrow Kashfi Mohammad-Amin Abdollahifar Asghar Ghasemi 《Molecules (Basel, Switzerland)》2021,26(7)
Impaired skin nitric oxide production contributes to delayed wound healing in type 2 diabetes (T2D). This study aims to determine improved wound healing mechanisms by acidified nitrite (AN) in rats with T2D. Wistar rats were assigned to four subgroups: Untreated control, AN-treated control, untreated diabetes, and AN-treated diabetes. AN was applied daily from day 3 to day 28 after wounding. On days 3, 7, 14, 21, and 28, the wound levels of vascular endothelial growth factor (VEGF) were measured, and histological and stereological evaluations were performed. AN in diabetic rats increased the numerical density of basal cells (1070 ± 15.2 vs. 936.6 ± 37.5/mm3) and epidermal thickness (58.5 ± 3.5 vs. 44.3 ± 3.4 μm) (all p < 0.05); The dermis total volume and numerical density of fibroblasts at days 14, 21, and 28 were also higher (all p < 0.05). The VEGF levels were increased in the treated diabetic wounds at days 7 and 14, as was the total volume of fibrous tissue and hydroxyproline content at days 14 and 21 (all p < 0.05). AN improved diabetic wound healing by accelerating the dermis reconstruction, neovascularization, and collagen deposition. 相似文献
36.
Polymerization of β‐cyclodextrin in the presence of bentonite clay to produce polymer nanocomposites for removal of heavy metals from drinking water
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New hybrid organic–inorganic nanocomposites consist of β‐cyclodextrin (β‐CD)/epichlorohydrin (ECH), and bentonite clay were prepared by direct intercalation through one step emulsion polymerization. The structure and thermal stability of prepared nanocomposites were investigated by Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), field emission‐scanning electron microscopy (FE‐SEM), energy dispersive X‐ray analysis (EDAX), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), differential of differential scanning calorimetry (DDSC), thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) analyses. The observed results show that the β‐CD polymer/clay nanocomposites (β‐CD–ECH polymer/clay) with higher thermal stability than β‐CD–ECH polymer were successfully prepared. The removal of heavy metals such as Cu(II), Zn(II) and Co(II) ions from drinking water was studied using a batch method at ambient temperature. The removal percentage and distribution coefficients (Kd) were determined for the adsorption system. It was found that the β‐CD–ECH polymer/clay nanocomposites showed higher removal capacity for Co2+, Cu2+ and Zn2+ ions in comparison with β‐CD–ECH polymer. The selectivity order could be given as Zn2+ > Cu2+ > Co2+. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
37.
Ahmad Tavasoli Saba Karimi Somayeh Taghavi Zahra Zolfaghari Hamideh Amirfirouzkouhi 《天然气化学杂志》2012,(5):605-613
An extensive study of Fischer-Tropsch (FT) synthesis on cobalt nano particles supported on γ-alumina and carbon nanotubes (CNTs) catalysts is reported.20 wt% of cobalt is loaded on the supports by impregnation method.The deactivation of the two catalysts was studied at 220 C,2 MPa and 2.7 L/h feed flow rate using a fixed bed micro-reactor.The calcined fresh and used catalysts were characterized extensively and different sources of catalyst deactivation were identified.Formation of cobalt-support mixed oxides in the form of xCoO yAl2O3 and cobalt aluminates formation were the main sources of the Co/γ-Al2O3 catalyst deactivation.However sintering and cluster growth of cobalt nano particles are the main sources of the Co/CNTs catalyst deactivation.In the case of the Co/γ-Al2O3 catalyst,after 720 h on stream of continuous FT synthesis the average cobalt nano particles diameter increased from 15.9 to 18.4 nm,whereas,under the same reaction conditions the average cobalt nano particles diameter of the Co/CNTs increased from 11.2 to 17.8 nm.Although,the initial FT activity of the Co/CNTs was 26% higher than that of the Co/γ-Al2O3,the FT activity over the Co/CNTs after 720 h on stream decreased by 49% and that over the Co/γ-Al2O3 by 32%.For the Co/γ-Al2O3 catalyst 6.7% of total activity loss and for the Co/CNTs catalyst 11.6% of total activity loss cannot be recovered after regeneration of the catalyst at the same conditions of the first regeneration step.It is concluded that using CNTs as cobalt catalyst support is beneficial in carbon utilization as compared to γ-Al2O3 support,but the Co/CNTs catalyst is more susceptible for deactivation. 相似文献
38.
S. Hamideh Mortazavi Soheil Pilehvar Mahmood Ghoranneviss M. T. Hosseinnejad Shamim Zargham Ali A. Mirarefi Amir Y. Mirarefi 《Applied Physics A: Materials Science & Processing》2013,113(3):703-712
The effect of plasma treatment on the stabilization of copolymer P(AN-MA) containing 6.1 mol% methyl acrylate (MA) prepared by an electrospinning technique has been investigated at various oxygen contents (10 %, 20 % and 30 %) and different exposure times. The morphology and chemical structural evolution of electrospun and oxidized nanofibers were studied using field–emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). FT-IR analysis indicated that the treated nanofibers were effectively oxidized under different contents of oxygen and prolonged plasma exposure times by increasing the peak intensities of polar groups at 1730 and 3400 cm?1 corresponding to C=O stretching band and OH stretching vibration mode, respectively. Additionally, a reduction in the extent of the cyclization reaction is observed with further increase in exposure times and contents of oxygen, which implies lower conversion of C≡N bands into C=N ones in the copolymer chain. According to the FE-SEM studies, the surfaces of the treated nanofibers were completely etched after 15 min of treatment due to the existence of strong ion bombardment and a reduction in the average fiber diameters was observed. 相似文献
39.
Dr. Yan Zhang Dr. Margaret A. Hopkins Dr. David J. Liptrot Dr. Hamideh Khanbareh Prof. Pim Groen Xuefan Zhou Prof. Dou Zhang Yinxiang Bao Prof. Kechao Zhou Prof. Chris R. Bowen Dr. David R. Carbery 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7882-7886
We demonstrate that trimethylamine borane can exhibit desirable piezoelectric and pyroelectric properties. The material was shown to be able operate as a flexible film for both thermal sensing, thermal energy conversion and mechanical sensing with high open circuit voltages (>10 V). A piezoelectric coefficient of d33≈10–16 pC N−1, and pyroelectric coefficient of p≈25.8 μC m−2 K−1 were achieved after poling, with high pyroelectric figure of merits for sensing and harvesting, along with a relative permittivity of 6.3. 相似文献
40.
A separation of bis(α-hydroxyalkyl) phosphinic acid diastereoisomers is described. A novel method for the determination stereochemistry of bis(α-hydroxyalkyl) phosphinic acid diastereoisomers has been developed. The stereochemistry of one diastereoisomer was confirmed after converting to the corresponding methyl ester using trimethyl orthoformate. 相似文献