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排序方式: 共有429条查询结果,搜索用时 15 毫秒
1.
Huda Al Amri Author Vitae Mehran Abolhasan Author Vitae 《Computers & Electrical Engineering》2010,36(4):752-765
In Mobile Ad hoc Network (MANET), mobility, traffic and node density are main network conditions that significantly affect performance of routing protocols. Much of the previous research in MANET routing have focused on developing strategies, which suit one specific networking scenario. Therefore, there is no existing protocol that can work well in all different networking scenarios. This paper reviews characteristics of several different classes of routing protocols. Moreover, most of current routing protocols assume homogeneous networking conditions where all nodes have the same capabilities and resources. This paper presents extensive studies simulations for DSR, AODV, LAR1, FSR and WRP in homogenous and heterogeneous networks that consist of different nodes with different resources. The results showed that while all protocols perform reasonably well in homogenous networking conditions, their performance suffer significantly over heterogonous networks. 相似文献
2.
Seyed Mohammad Taghi Gharibzahedi Seyed Mohammad MousaviManouchehr Hamedi Mehran Ghasemlou 《Food Hydrocolloids》2012,26(1):293-301
The effect of Arabic gum content (5-10% w/w) and walnut-oil concentration (3-6% w/w) on properties of prepared walnut oil/water emulsion, including turbidity loss rate, density, size index, particle size and stability, was investigated using response surface methodology (RSM). For each response, a second-order polynomial model with high coefficient of determination (R2) values ranging from 0.907 to 0.989 was developed using multiple linear regression analysis. The lack of significant difference between the experimental and predicted values proved the adequacy of response surface equations for describing the physical changes of emulsions. An increase of Arabic gum content in range and initial concentration of walnut oil were associated with high emulsion stability and minimum droplet size. It can be concluded that RSM can determine the most suitable formulation (3% w/w walnut oil and 9.62% w/w Arabic gum) to achieve the highest stability in a developed beverage emulsion based on walnut oil. 相似文献
3.
4.
Moradi M Tajik H Razavi Rohani SM Oromiehie AR 《Journal of the science of food and agriculture》2011,91(15):2850-2857
BACKGROUND: The effectiveness of chitosan films containing Zataria multiflora Boiss essential oil (ZEO) (5 and 10 g kg?1) and grape seed extract (GSE) (10 g kg?1) on lipid oxidation and microbial (lactic acid bacteria, aerobic mesophiles and inoculated Listeria monocytogenes) characteristics of mortadella sausage at 4 °C for 21 days was evaluated. The release of total phenolics (TPs) into sausage was also assessed. RESULTS: All films exhibited antibacterial activity against L. monocytogenes on agar culture media. Chitosan films containing ZEO were the most effective on the growth of bacteria. The growth of L. monocytogenes was significantly inhibited by ZEO‐GSE containing films especially during storage of the sausages for 6 days. Aerobic mesophiles and lactic acid bacteria were the most sensitive and resistant groups to films by 0.1–1.1 and 0.1–0.7 log cycles reduction, respectively. Sausages wrapped by 10 g kg?1 GSE + 10 g kg?1 ZEO films had the lowest degrees of lipid oxidation, which was 23% lower than the control. The TPs of ZEO films decreased to zero after 6 days, whereas TPs of GSE films followed a slight decrease during the storage. CONCLUSION: Antimicrobial/antioxidant chitosan film could be developed by incorporating GSE and ZEO for extending the shelf life of mortadella sausage. Copyright © 2011 Society of Chemical Industry 相似文献
5.
Skin detection is a difficult and primary task in many image processing applications. Because of the diversity of various
image processing tasks, there exists no optimum method that can perform properly for all applications. In this paper, we have
proposed a novel skin detection algorithm that combines color and texture information of skin with cellular learning automata
to detect skin-like regions in color images. Skin color regions are first detected, by using a committee structure, from among
several explicit boundary skin models. Detected skin-color regions are then fed to a texture analyzer which extracts texture
features via their color statistical properties and maps them to a skin probability map. This map is then used by cellular
learning automata to adaptively make a decision on skin regions. Conducted experiments show that the proposed algorithm achieves
the true positive rate of about 86.3% and the false positive rate of about 9.2% on Compaq skin database which shows its efficiency. 相似文献
6.
Nima Bayat Mehran Rezaei Fereshteh Meshkani 《Korean Journal of Chemical Engineering》2016,33(2):490-499
Nickel catalysts supported on mesoporous nanocrystalline gamma alumina with various nickel loadings were prepared and employed for thermocatalytic decomposition of methane into CO x -free hydrogen and carbon nanofibers. The prepared catalysts with different nickel contents exhibited mesoporous structure with high surface area in the range of 121.3 to 66.2m2g?1. Increasing in nickel content decreased the pore volume and increased the crystallite size. The catalytic results revealed that the nickel content and operating temperature both play important roles on the catalytic performance of the prepared catalysts. The results showed that increasing in reaction temperature increased the initial conversion of catalysts and significantly decreased the catalyst lifetime. Scanning electron microscopy (SEM) analysis of the spent catalysts evaluated at different temperatures revealed the formation of intertwined carbon filaments. The results showed that increasing in reaction temperature decreased the diameters of nanofibers and increased the formation of encapsulating carbon. 相似文献
7.
Wan J Basirun Mehran Sookhakian Saeid Baradaran Mohammad R Mahmoudian Mehdi Ebadi 《Nanoscale research letters》2013,8(1):397
Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO. 相似文献
8.
S. Siavash Saei‐Dehkordi Aziz A. Fallah Mahbubeh Heidari‐Nasirabadi Mehran Moradi 《International Journal of Food Science & Technology》2012,47(8):1579-1585
This study aimed to determine the chemical composition, antimicrobial and antioxidative activity of Satureja khuzestanica Jamzad essential oil. The oil was analysed by GC and GC/MS. Twenty‐eight constituents were identified. The oxygenated monoterpenes (78.22%) were the principal compound group. Among them, carvacrol (53.86%) and thymol (19.84%) were the most abundant constituents. The oil exhibited an acceptable antimicrobial activity against most of the tested microorganisms. The checkerboard method was applied to determine fractional inhibitory concentration indices (FICIs) to interpret the synergetic, additive, indifference or antagonistic interactions between essential oil and each of antimicrobials (lysozyme, ciprofloxacin, fluconazole and amphotericin B) against food‐related microorganisms. The synergetic phenomenon (FICI ≤ 0.5) was observed in majority of combinations with the exception of the essential oil and lysozyme. The oil exhibited good 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity (IC50 = 28.71 μg mL?1). Also, the oil had strong antioxidative activity in β‐carotene‐linoleic acid assay relative antioxidant activity (RAA% = 95.45). This study demonstrated that the essential oil has beneficial biological properties and its simultaneous application with standard antimicrobials against food‐related microorganisms result in reduction in inhibitory doses of the antimicrobials in vitro. 相似文献
9.
Mehran Dadkhah Mohammad Hossein Mosallanejad Luca luliano Abdollah Saboori 《金属学报(英文版)》2021,34(9):1173-1200
Nowadays, as an emerging technology, additive manufacturing(AM) has received numerous attentions from researchers around the world. The method comprises layer-by-layer manufacturing of products according to the 3D CAD models of the objects. Among other things, AM is capable of producing metal matrix composites(MMCs). Hence, plenty of works in the literature are dedicated to developing different types of MMCs through AM processes. Hence, this paper provides a comprehensive overview on the latest research that has been carried out on the development of the powder-based AM manufactured MMCs from a scientific and technological viewpoint, aimed at highlighting the opportunities and challenges of this innovative manufacturing process. For instance, it is documented that AM is not only able to resolve the reinforcement/matrix bonding issues usually faced with during conventional manufacturing of MMCs, but also it is capable of producing functionally graded composites and geometrically complex objects. Furthermore, it provides the opportunity for a uniform distribution of the reinforcing phase in the metallic matrix and is able to produce composites using refractory metals thanks to the local heat source employed in the method. Despite the aforementioned advantages, there are still some challenges needing more attention from the researchers. Rapid cooling nature of the process, significantly different coe fficient of expansion of the matrix and reinforcement, processability, and the lack of suitable parameters and standards for the production of defect-free AM MMCs seem to be among the most important issues to deal with in future works. 相似文献
10.
Mutations Closer to the Active Site Improve the Promiscuous Aldolase Activity of 4‐Oxalocrotonate Tautomerase More Effectively than Distant Mutations 下载免费PDF全文
Mehran Rahimi Jan‐Ytzen van der Meer Dr. Edzard M. Geertsema Harshwardhan Poddar Dr. Bert‐Jan Baas Prof. Dr. Gerrit J. Poelarends 《Chembiochem : a European journal of chemical biology》2016,17(13):1225-1228
The enzyme 4‐oxalocrotonate tautomerase (4‐OT), which catalyzes enol–keto tautomerization as part of a degradative pathway for aromatic hydrocarbons, promiscuously catalyzes various carbon–carbon bond‐forming reactions. These include the aldol condensation of acetaldehyde with benzaldehyde to yield cinnamaldehyde. Here, we demonstrate that 4‐OT can be engineered into a more efficient aldolase for this condensation reaction, with a >5000‐fold improvement in catalytic efficiency (kcat/Km) and a >107‐fold change in reaction specificity, by exploring small libraries in which only “hotspots” are varied. The hotspots were identified by systematic mutagenesis (covering each residue), followed by a screen for single mutations that give a strong improvement in the desired aldolase activity. All beneficial mutations were near the active site of 4‐OT, thus underpinning the notion that new catalytic activities of a promiscuous enzyme are more effectively enhanced by mutations close to the active site. 相似文献