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Characterization of mechanothermally processed nanostructured ZnO

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International Journal of Minerals,Metallurgy and Materials 2016年第5期23卷 588-594页

作者： saeed Karimi Abolghasem Ataie School of Metallurgy and Materials Engineering College of Engineering University of Tehran

In this paper, the Taguchi method with an L9（34） orthogonal array was used as experimental design to determine the optimum conditions for preparing ZnO nanoparticles via a mechanothermal route. ZnSO4·H20 and NaECO3 were used as starting materials. The effects of milling time, NaECO3/ZnSO·H20 molar ratio, and ball-to-powder mass ratio （BPR） on the bandgap （Eg） of ZnO nanoparticles were inves- tigated. The ranges of the investigated experimental conditions were 5-15 h for the milling time （t）, 1.0-1.2 for the Na2COa/ZnSO4·H20 mo- lar ratio （M）, and 10-30 for BPR. The milling time and BPR exhibited significant effects; an increase in milling time reduced the bandgap. The optimum conditions from this study were t3 = 15 h, M1 = l, and BPR2 = 20. Only two significant factors （t3, 15 h; BPR2, 20） were used to estimate the performance at the optimum conditions. The calculated bandgap was 3.12 eV, in reasonable agreement with the experimental results obtained under the optimized conditions.

关键词： mechanothermal treatment synthesis nanoparticles zinc oxide Taguchi methods

Flutter analysis of hybrid metal-composite low aspect ratio trapezoidal wings in supersonic flow

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Chinese Journal of Aeronautics 2017年第1期30卷 196-203页

作者： Shokrollahi saeed Shafaghat Salman Department of Aerospace Engineering Malek Ashtar University of Technology

An effective 3D supersonic Mach box approach in combination with non-classical hybrid metal-composite plate theory has been used to investigate flutter boundaries of trapezoidal low aspect ratio wings. The wing structure is composed of two main components including aluminum material（in-board section） and laminated composite material（out-board section）. A global Ritz method is used with simple polynomials being employed as the trial functions. The most important objective of the present research is to study the effect of composite to metal proportion of hybrid wing structure on flutter boundaries in low supersonic regime. In addition, the effect of some important geometrical parameters such as sweep angle, taper ratio and aspect ratio on flutter boundaries were studied. The results obtained by present approach for special cases like pure metallic wings and results for high supersonic regime based on piston theory show a good agreement with those obtained by other investigators.

关键词： Assumed mode method Flutter Hybrid trapezoidal plateMach box method Supersonic flow

Inforence: effective fault localization based on information-theoretic analysis and statistical causal inference

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Frontiers of Computer Science 2019年第4期13卷 735-759页

作者： Farid FEYZI saeed PARSA Department of Computer Engineering Iran University of Science and Technology Tehran Iran

In this paper, a novel approach, Inforence, is proposed to isolate the suspicious codes that likely contain faults. Inforence employs a feature selection method, based on mutual information, to identify those bug-related statements that may cause the program to fail. Because the majority of a program faults may be revealed as undesired joint effect of the program statements on each other and on program termination state, unlike the state-of-the-art methods, Inforence tries to identify and select groups of interdependent statements which altogether may affect the program failure. The interdependence amongst the statements is measured according to their mutual effect on each other and on the program termination state. To provide the context of failure, the selected bug-related statements are chained to each other, considering the program static structure. Eventually, the resultant causeeffect chains are ranked according to their combined causal effect on program failure. To validate Inforence, the results of our experiments with seven sets of programs include Siemens suite, gzip, grep, sed, space, make and bash are presented. The experimental results are then compared with those provided by different fault localization techniques for the both single-fault and multi-fault programs. The experimental results prove the outperformance of the proposed method compared to the state-of-the-art techniques.

关键词： fault localization debugging backward dynamic slice mutual information feature selection

Exploring Trees Diversity and Ecological Value of Mountain Forests in the Blue Nile Region of Sudan

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Open Journal of Ecology 2024年第3期14卷 245-256页

作者： Dafa-Alla M. Dafa-Alla Haytham H. Gibreel Ahmed A. H. Siddig Yousif E. Yagoub Hashim A. Abdelkarim Khatir H.T. saeed Ahmed I. Abuelbashar Faculty of Forestry-Shambat University of Khartoum Khartoum Sudan Harvard Forest Harvard University Petersham MA USA Faculty of Forest Science and Wood Technology University of Gezira Wad-Medani Sudan Department of Forestry and Range Sciences Faculty of Natural Resources and Environmental Studies Alsalam University Alfula Sudan Forest Research and Gum Arabic Centre Agricultural Research Corporation Khartoum-Soba Sudan

We carried out this research at Abu-Gaddaf Natural Forest Reserve (ANFR) which is located east of Blue Nile River, in Blue Nile State, Sudan. It aims at exploring tree composition assessing their diversity indices, and ecological importance values. For survey of types and estimation of density of tree species in the forest, we randomly distributed 97 circular sample plots (0.1 hectare (ha)). In each sample plot we identified all trees to the species level, recorded their frequencies and computed species diversity and importance value indices (IVI). A total of 13 tree species, which belong to 12 genera and nine families, were identified in the tree layer of the forest. Mean tree density in ANFR was 116 trees/ha, composed mainly of Boswellia papyrifera (Del.) Hochst. (48), followed by Combretum hartmannianu (19) and Lannea fruticosa (18). Fabaceae was the most common family followed by Combretaceae and Malvaceae. B. papyrifera Delile Hochst was the most abundant while Acacia seyal was the least abundant species. Species richness (R = 1.71), evenness (E = 0.69), dominance (0.24) indices and Simpson’s Index of Diversity (D' = 0.76) suggest a moderate diversity, moderate numbers of individuals in each species and a moderate community stability. The research provides empirical results on diversity and ecological importance value of species, signifies the urging need to safeguard threatened species and to prioritize them for conservation, as well as the need to promote management of abundant species to provide multiple forest ecosystem services.

关键词： Tree Species Diversity Dry-Land Forest Sudan

Efficiency of employing fiber-based finite-length plastic hinges in simulating the cyclic and seismic behavior of steel hollow columns compared with other common modelling approaches

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Earthquake Engineering and Engineering Vibration 2019年第4期18卷 777-794页

作者： Mojtaba Farahi saeed Erfani Department of Civil Engineering Amirkabir University of Technology

The accuracy and effi ciency of the modelling techniques utilized to model the nonlinear behavior of structural components is a signifi cant issue in earthquake engineering. In this study, the suffi ciency of three diff erent modelling techniques that can be employed to simulate the structural behavior of columns is investigated. A fi ber-based fi nite length plastic hinge (FB-FLPH) model is calibrated in this study. In order to calibrate the FB-FLPH model, a novel database of the cyclic behavior of hollow steel columns under simultaneous axial and lateral loading cycles with varying amplitudes is used. By employing the FB-FLPH model calibrated in this study, the interaction of the axial force and the bending moment in columns is directly taken into account, and the deterioration in the cyclic behavior of these members is implicitly considered. The superiority of the calibrated FB-FLPH modelling approach is examined compared with the cases in which conventional fi ber-based distributed plasticity and concentrated plasticity models are utilized. The effi ciency of the enumerated modelling techniques is probed when they are implemented to model the columns of a typical special moment frame in order to prove the advantage of the FB-FLPH modelling approach.

关键词： cyclic behavior seismic behavior fi ber-based fi nite-length plastic hinge model fi ber-based modelling techniques cyclic strength deterioration axial force-bending moment interaction

A Short Synthesis of Natural Isocoumarin Glucoside Delphoside

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Chinese Journal of Chemistry 2005年第6期23卷 762-766页

作者： saeed,Aamer DepartmentofChemistry Quaid-l-AzamUniversity45320lslamabadPakistan

A simple synthesis of delphoside, 3‐methyl‐6‐hydroxy‐8‐ O ‐β‐ D ‐glucopyranosyloxy isocoumarin ( 1 ), isolated from Delphinium spp. is described. 3,5‐Dimethoxyhomophthalic anhydride ( 2 ) on treatment with acetyl chloride in the presence of 1,1,3,3‐tetramethylguanidine (TMG) and triethyl amine afforded the 6,8‐dimethoxy‐3‐methylisocoumarin ( 3 ). Regioselective demethylation of the latter furnished 8‐hydroxy‐6‐methoxy‐3‐methylisocoumarin ( 4 ). Glycosylation with O ‐(2,3,4,6‐tetra‐ O ‐acetyl‐ D ‐glucopyranosyl)trichloroacetimidate in presence of catalytic amount of boron trifluoride etherate followed by deacetylation using 5% potassium carbonate afforded 3‐methyl‐6‐methoxy‐8‐ O ‐β‐ D ‐glucopyranosyloxyisocoumarin ( 6 ) that was finally demethylated to yield delphoside 1 .

关键词： isocoumarin glucoside glycosylation total synthesis delphoside

Multi-walled Carbon Nanotubes as a Ligand in Nickel ?-Diimine Based Ethylene Polymerization

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Chinese Journal of Polymer Science 2015年第10期33卷 1389-1403页

作者： Sasan Talebnezhad saeed Pourmahdian Department of Polymer Engineering and Color Technology Amirkabir University of Technology

Two novel heterogeneous nickel a-diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall（s） in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PE·mmol^-1 Ni·h^-1 and 123 ℃ in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 ℃ reached to 310000 g·mol^-1 which was close to the highest value had been reported at 30 ℃ for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.

关键词： a-Diiminonickel catalyst Ligand Multi-walled carbon nanotubes Ethylene polymerization In situ catalyst preparation.

Electrical annealing of severely deformed copper: microstructure and hardness

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International Journal of Minerals,Metallurgy and Materials 2017年第10期24卷 1158-1168页

作者： saeed Nobakht Mohsen Kazeminezhad Department of Materials Science and Engineering Sharif University of Technology Azadi Avenue Tehran Iran

Commercial pure copper sheets were severely deformed after primary annealing to a strain magnitude of 2.32 through constrained groove pressing. After induction of an electrical current, the sheets were heated for 0.5, 1, 2, or 3 s up to maximum temperatures of 150, 200, 250, or 300℃. To compare the annealing process in the current-carrying system with that in the current-free system, four other samples were heated to 300℃ at holding times of 60, 90, 120, or 150 s in a salt bath. The microstructural evolution and hardness values of the samples were then investigated. The results generally indicated that induction of an electrical current could accelerate the recrystallization process by decreasing the thermodynamic barriers for nucleation. In other words, the current effect, in addition to the thermal effect, enhanced the diffusion rate and dislocation climb velocity. During the primary stages of recrystallization, the grown nuclei of electrically annealed samples showed greater numbers and a more homogeneous distribution than those of the samples annealed in the salt bath. In the fully recrystallized condition, the grain size of electrically annealed samples was smaller than that of conventionally annealed samples. The hardness values and metallographic images obtained indicate that, unlike the conventional annealing process, which promotes restoration phenomena with increasing heating time, the electrical annealing process does not necessarily promote these phenomena. This difference is hypothesized to stem from conflicts between thermal and athermal effects during recrystallization.

关键词： annealing severe plastic deformation copper microstructure hardness

Oxa-Pictet-Spengler reaction in *** of some(±)-1-aryl-6,7-dimethoxyisochromans

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Chinese Chemical Letters 2010年第3期21卷 261-264页

作者： Aamer saeed Department of Chemistry Quaid-I-Azam University

An acid catalyzed oxa-Pictet-Spengler reaction‘on water leading to the synthesis of a variety of l-aryl-6,7-dimethoxyisochro-mans is *** aqueous chemistry is a much cleaner,efficient,cheaper and simple method for ***... 详细信息

关键词： Oxa-Pictet-Spengler reaction In water 1-Aryl-6 7-dimethoxyisochromans Isothiochromans