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排序方式: 共有297条查询结果,搜索用时 15 毫秒
71.
A. R. Teymourtash Javad Abolfazli Esfahani S. A. Mousavi Shaegh 《Heat and Mass Transfer》2009,45(9):1185-1198
The entropy generation due to irreversible heat transfer between vapor and liquid phases in a nucleating steam flow in a Laval
nozzle is studied. To calculate the entropy generation due to self-condensation in transonic steam flow, a thermodynamic model
is presented. The calculations of nucleating steam flow and the predictions of entropy generation rely on one-dimensional
two-phase model. This model shows that the most of the thermodynamic losses take place during the nucleation phenomena. The
effect of rate of expansion on the exergy losses is considered by decreasing the divergent angle of nozzle. Also micro-sized
pure water droplets is injected theoretically to supercooled steam right after the nozzle throat at the onset of divergent
section and the effects of injected droplets on thermodynamic losses and nucleation phenomena are investigated. The results
indicate that decreasing the divergent angle and also injection of droplets diminishes the pressure rise in transonic steam
flow and decreases the thermal entropy generation due to nucleation. 相似文献
72.
Davood Nori-Shargh Hooriye Yahyaei Maryam Jafari Shamsi Rafatpanah Abbas Madhi Tazekand Seiedeh Negar Mousavi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1538-1553
Abstract The alkyl 1,2-shift in di-tert-butylcyclopenta-1,3-diene (1) and the metallotropic 1,2-shifts in bis(trimethylsilyl)cyclopenta-1,3-diene (2), bis(trimethylgermyl)cyclopenta-1,3-diene (3), and bis(trimethylstannyl)cyclopenta-1,3-diene (4) have been investigated by means of natural bond orbital (NBO), nuclear magnetic resonance (NMR) analysis, and hybrid density functional theory based methods. The B3LYP/DZVP results showed that the M(CH3)3 group [M = C (1), Si (2), Ge (3), and Sn (4)] migration barrier heights around cyclopentadienyl rings decrease from di-tert-butylcyclopenta-1,3-diene to its stannane derivative. Also, based on the results obtained, the stabilities of the 5,5-isomers in comparison to the 1,5- and 2,5-isomers increase from di-tert-butylcyclopenta-1,3-diene to its stannane derivative. The results suggest that in these compounds the metallotropic shifts are controlled by the stabilization energies associated with σ→π* electron delocalizations and the increase of the σC5-M→π*C1-C2 electron delocalizations facilitates the M(CH3)3 group migrations around cyclopentadienyl rings. Based on the aromatic stabilization energy (ASE) values calculated, the aromaticity increases from the 5,5-isomers of di-tert-butylcyclopenta-1,3-diene to its stannane derivative but the variation of the nucleus-independent chemical shift, NICS(0) and NICS(1), values calculated are not in accordance with the ASE values calculated and the σC5-M→π*C1-C2 electron delocalizations. The correlations between the sigmatropic shift barrier heights, σ→π* electron delocalizations, ASE, and NICS values were investigated. GRAPHICAL ABSTRACT 相似文献
73.
M.H. Majles Ara S.H. MousaviZ. Mousavi M.S. Zakerhamidi 《Journal of Molecular Liquids》2011,161(1):41-43
In this paper, the static Kerr effect was investigated for the W-1680 at temperatures above the nematic-isotropic transition temperature and compared with 9CHBT. We experimentally measured the electro-optical Kerr constant and the pre-transitional behavior. The Kerr law has been confirmed and the variation of the inverse Kerr constant, with a temperature above the smectic-isotropic transition temperatures, were determined. The linear dependence of (T − T*)− 1 on the Kerr constant is found to be in good agreement with the predications of the Landau-De Gennes model. Additionally, the temperature dependence of third order susceptibility has been studied. This value for these samples will reduce when the temperature increases. 相似文献
74.
Mahsa Baghban Salehi Ebrahim Vasheghani‐Farahani Mohsen Vafaie Sefti Asefe Mousavi Moghadam Hasan Naderi 《先进技术聚合物》2014,25(4):396-405
In this research, an optimal hydrogel, based on sulfonated polyacrylamide, was synthesized by statistical design of experiments using central composite method. This new hydrogel composed of sulfonated polyacrylamide (AN125VLM) and chromium triacetate as copolymer and crosslinker, respectively. The bottle and rheological tests were conducted to investigate the gelation time, thermal stability, gel strength and also ultimate elastic modulus, complex modulus, and yield stress. It was found that copolymer concentration had the main effect in both rheological and transport properties of hydrogels. The sample prepared at optimum condition, i.e. copolymer concentration of 26,340 ppm and crosslinker/copolymer ratio of 0.12, had an ultimate elastic modulus of 29.9 kPa, yield stress of 800 Pa, and complex modulus of 32 kPa. A coreflooding test through fracture was carried out to examine the optimum gel performance in a porous media. A value of 483 for the residual resistance factor ratio of water to oil confirmed the high ability of the hydrogel in reducing the relative permeability of water to oil in fractured media. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
75.
1-Vinyl-3-octadecylimidazolium bromide ionic liquid [C18VIm]Br was prepared and used for the modification of mercaptopropyl-functionalized silica (Si-MPS) through surface radical chain-transfer addition. The synthesized octadecylimidazolium-modified silica (SiImC18) was characterized by thermogravimetric analysis (TGA), infrared spectroscopy (IR), 13C NMR and 29Si NMR spectroscopy and used as an extraction phase for the automated 96-blade solid phase microextraction (SPME) system with thin-film geometry using polyacrylonitrile (PAN) glue. The new proposed extraction phase was applied for extraction of aminoacids from grape pulp, and LC–MS–MS method was developed for separation of model compounds. Extraction efficiency, reusability, linearity, limit of detection, limit of quantitation and matrix effect were evaluated. The whole process of sample preparation for the proposed method requires 270 min for 96 samples simultaneously (60 min preconditioning, 90 min extraction, 60 min desorption and 60 min for carryover step) using 96-blade SPME system. 相似文献
76.
Hengameh Bahrami Mousavi Mehdi Maghsoudi Shahab 《Russian Journal of Electrochemistry》2021,57(2):149-158
Russian Journal of Electrochemistry - Sarcosine has been identified as a key metabolite marker for monitoring and early diagnosis of metastatic prostate cancer (PCa), and it is detectable in the... 相似文献
77.
Mohammad Ehsan Taghavizadeh Yazdi Simin Nazarnezhad Seyed Hadi Mousavi Mohammad Sadegh Amiri Majid Darroudi Francesco Baino Saeid Kargozar 《Molecules (Basel, Switzerland)》2021,26(6)
The use of naturally occurring materials in biomedicine has been increasingly attracting the researchers’ interest and, in this regard, gum tragacanth (GT) is recently showing great promise as a therapeutic substance in tissue engineering and regenerative medicine. As a polysaccharide, GT can be easily extracted from the stems and branches of various species of Astragalus. This anionic polymer is known to be a biodegradable, non-allergenic, non-toxic, and non-carcinogenic material. The stability against microbial, heat and acid degradation has made GT an attractive material not only in industrial settings (e.g., food packaging) but also in biomedical approaches (e.g., drug delivery). Over time, GT has been shown to be a useful reagent in the formation and stabilization of metal nanoparticles in the context of green chemistry. With the advent of tissue engineering, GT has also been utilized for the fabrication of three-dimensional (3D) scaffolds applied for both hard and soft tissue healing strategies. However, more research is needed for defining GT applicability in the future of biomedical engineering. On this object, the present review aims to provide a state-of-the-art overview of GT in biomedicine and tries to open new horizons in the field based on its inherent characteristics. 相似文献
78.
79.
Synthesis,Spectroscopy, X‐ray Crystallography,and DFT Computations of Nanosized Phosphazenes 下载免费PDF全文
Zahra Shariatinia Elnaz Jalali Moghadam Narges Maghsoudi Hourieh Sadat Mirhosseini Mousavi Michal Dusek Vaclav Eigner 《无机化学与普通化学杂志》2015,641(5):967-978
Nanoparticles of nine phosphazenes with general formula 4‐CH3C6H4S(O)2N=PX3 [X = Cl ( A ), NC4H8 ( 1 ), NC6H12 ( 2 ), NC4H8N–C(O)OC2H5 ( 3 ), NC4H8N–C(O)OC6H5 ( 4 ), NC4H8O ( 5 ), NHCH2–C4H7O ( 6 ), N(CH3)(C6H11) ( 7 ), NHCH2–C6H5 ( 8 ), and 2‐NH‐NC5H4 ( 9 )] were synthesized using ultrasonic method and characterized by 1H, 13C, 31P NMR, FT‐IR, fluorescence, as well as UV/Vis spectroscopy and additionally with XRD, FE‐SEM, N2 sorption, and elemental analysis. The 31P NMR spectra of compounds 1 – 9 reveal the most up field shift δ(31P) for 9 at –11.45 ppm reflecting the most electron donation of 2‐aminopyridinyl rings through resonance to the phosphorus atom. The 1H, 13C NMR spectra of 7 exhibit two sets of signals for the hydrogen and carbon atoms of its two isomers present in the solution state in 1:4 ratio. The FE‐SEM micrographs illustrate that the nanoparticles of compounds 1 – 9 have spherical morphology and a size of 27–42 nm. From the XRD patterns, the crystal sizes were estimated to about 24–86 nm. The highest bandgap was measured for 3 (3.81 eV) whereas the smallest was measured for 8 (3.50 eV). The structures of two polymorphs of compound 5 ( 5 , 5′ ) were determined by X‐ray crystallography at 120 K. Both of these polymorphs are triclinic with P1 space group but 5 has a doubled unit cell volume and two symmetrically independent molecules ( 5a and 5b ). In structures 5a and 5′ , the phosphorus and all endocyclic atoms of two morpholinyl rings display disorder, whereas the molecule 5b does not show disorder. The strong intermolecular O–H ··· O hydrogen bonds plus weak intermolecular C–H ··· O and C–H ··· N interactions create three‐dimensional polymers in the crystalline networks of 5 and 5′ . The DFT computations illustrate that molecule 5b is more stable than 5a by –1.1062 and –0.9779 kcal · mol–1 at B3LYP and B3PW91 levels, respectively. The NBO calculations presented sp3d hybridization for phosphorus and sulfur atoms and sp2, sp3 hybrids for the nitrogen and oxygen atoms. 相似文献
80.
Development of agricultural biotechnology and biosafety regulations used to assess the safety of genetically modified crops in Iran 总被引:1,自引:0,他引:1
Rapid progress in the application of biotechnological methodologies and development of genetically modified crops in Iran necessitated intensive efforts to establish proper organizations and prepare required rules and regulations at the national level to ensure safe application of biotechnology in all pertinent aspects. Practically, preparation of a national biotechnology strategic plan in the country coincided with development of a national biosafety framework that was the basis for the drafted biosafety law. Although biosafety measures were observed by researchers voluntarily, the establishment of national biosafety organizations since the year 2000 built a great capacity to deal with biosafety issues in the present and future time, particularly with respect to food and agricultural biotechnology. 相似文献