دانلود گزارش کارورزی و کار آموزی

چکیده : 

We revisit here the concept of the constitutive relation error for the identification of elastic material

parameters based on image correlation. An additional concept, so called constitutive compatibility of

stress, is introduced defining a subspace of the classical space of statically admissible stresses. The key

idea is to define stresses as compatible with the observed deformation field through the chosen class

of constitutive equation. This makes possible the uncoupling of the identification of stress from the identification

of the material parameters. As a result, the global cost of the identification is strongly reduced.

This uncoupling also leads to parametrized solutions in cases where the solution is non-unique as demonstrated

on 2D numerical examples

چکیده : 

We extend the notion of variational integrator for classical Euler–Lagrange equations to the

fractional ones. As in the classical case, we prove that the variational integrator allows to

preserve Noether-type results at the discrete level.

چکیده : 

We consider elliptic PDEs (partial differential equations) in the framework of isogeometric analysis, i.e.,

we treat the physical domain by means of a B-spline or NURBS mapping which we assume to be regular.

The numerical solution of the PDE is computed by means of tensor product B-splines mapped onto the

physical domain. We construct additive multilevel preconditioners and show that they are asymptotically

optimal, i.e., the spectral condition number of the resulting preconditioned stiffness matrix is independent

of h. Together with a nested iteration scheme, this enables an iterative solution scheme of

optimal linear complexity. The theoretical results are substantiated by numerical examples in two and

three space dimensions

چکیده : 

The activation of highly catalytic c-alumina surfaces by thermal treatment and the description of the

related chemical processes at atomic scale is a topical issue. According to a recent study [J. Am. Chem.

Soc. 134 (2012) 14430], the enhanced reactivity of c-alumina has been associated to tri-coordinated aluminum

sites which supposedly are exposed exclusively on the (110) surfaces of this oxide. In this work,

we explore this possibility by modeling the (100) and (110) terminations using Krokidis et al. [J. Phys.

Chem. B 105 (2001) 5121] bulk structure and performing an extensive search of the most stable hydrated

surface models at conditions consistent with experiment. Among the 156 structures analyzed, we identify

several ‘‘metastable’’ models for the (110) surface with a considerable probability of containing the

AlIII centers at OH coverages of 9.0 and 6.0 then test the reactivity of these sites through their

Lewis acidity by simulating the CO adsorbtion on the surface and our results confirm the high reactivity

of AlIII centers. Based on the Gibbs free energy of the explored structures, we carry on a thermodynamical

analysis at varying hydroxylation degrees and pretreatment temperatures and simulate the experimental

volcano-type behavior reported in [J. Am. Chem. Soc. 134 (2012) 14430] and predict the optimum pretreatment

temperature as 700 C, in very good agreement with experimental findings. We further use

infrared and solid state MAS NMR spectroscopies and reproduce the 1H MAS NMR spectra under high vacuum

conditions (105 Torr). The strong resemblance of spectra to the experimental ones in the literature

[J. Phys. Chem. C 116 (2012) 834] validate further the structural models we have generated in this study.

چکیده : 

Deprotonation of hydrocarbon C–H bonds by alkali metal amide ‘‘superbases’’ is analyzed with the use of

density functional theory calculations. The role of alkali metal, amide substituents (NH2 versus NH(cyclohexyl)),

solvent (implicit and explicit), and substrate (methane versus toluene) are probed. Additionally,

Hammett and energy decomposition analyses are utilized to assess the nature of the charge distribution

in these transition states. Implications of the present study for the cleavage of strong C–H bonds found in

natural gas, such as methane and ethane, are discussed.

چکیده : 

The molecular face (MF) consists of all the classical turning points of electron movement in a molecule,

and it is an iso-PAEM (the potential acting on an electron in a molecule) contour where PAEM (or oneelectron

energy) equals the negative value of ionization energy (-IE) of the molecule. It is the classicalforbidden

region for an electron movement outside the MF, whereas it is the classical-permitted region

enclosed by the MF. In this work, we developed an approximate method for quickly constructing the MF.

To evaluate this method, we compared the MFs of the original and approximate methods for a series of

molecules, such as some homologues, unsaturated hydrocarbons and haloalkanes. Furthermore, we

showed the distributions of Fukui descriptors f+(r) and f(r) on the MFs for haloalkanes, and heterocyclic

compounds. Results showed that the approximate calculations are consistent with the exact calculations

not only in representing molecular surface but also in predicting the ordering of activities. Armed with

the new tool, the MFs of the isolated and stacked bases in DNA double helix were obtained for the first

time. This work provides a new representation for indicating shape properties, frontier electron densities

and chemical reactivities

چکیده : 

A series of melphalan-O-carboxymethyl chitosan (Mel-OCM-chitosan) conjugates with different spacerswere prepared and structurally characterized. All conjugates showed satisfactory water-solubility (160-217 times of Mel solubility). In vitro drug release behaviors by both chemical and enzymatic hydrolysiswere investigated. The prodrugs released Mel rapidly within papain and lysosomal enzymes of about40–75%, while released only about 4–5% in buffer and plasma, which suggested that the conjugates havegood plasma stability and the hydrolysis in both papain and lysosomes occurs mostly via enzymolysis.It was found that the spacers have important effect on the drug content, water solubility, drug releaseproperties and cytotoxicity of Mel-OCM-chitosan conjugates. Cytotoxicity studies by MTT assay demon-strated that these conjugates had 52–70% of cytotoxicity against RPMI8226 cells in vitro as comparedwith free Mel, indicating the conjugates did not lose anti-cancer activity of Mel. Overall these studiesindicated Mel-OCM-chitosan conjugates as potential prodrugs for cancer treatment

چکیده : 

We investigated the spinning of hydroalcoholic chitosan solutions. The dope composition was optimizedin order to obtain a continuous alcogel fiber by water evaporation on heating the extruded hydroalcoholicsolution. This alcogel fiber was then neutralized in aqueous alkali baths and washed in water to eliminatethe residual alcohol and salts before final drying. Depending on the alcohol content in the filament atthe neutralization step, on specific alcohol–chitosan interactions and on the nature and concentrationof the coagulation base, the process yielded semicrystalline chitosan fibers with different proportionsof anhydrous and hydrated allomorphs. Contrarily to the classical annealing method, the formation ofmainly anhydrous crystals was obtained without significant molecular weight decrease by neutralizingthe polymer in hydrophobic conditions. The control of allomorph content was shown to be related to thehydrophobicity of the solvent (alcohol fraction) at the neutralization step.

چکیده : 

tDiabetes mellitus is a group of complicated metabolic disorders characterized by high blood glucoselevel and inappropriate insulin secreting capacity due to decreased glucose metabolism and pancre-atic cell mass or dysfunction of cells. Thus, improving glucose metabolism and preserving cellmass and function might be useful for the treatment of diabetes. In this study, a novel acidic polysac-charide LBP-s-1 extracted from Lycium barbarum L. was obtained by purification using macroporousresin and ion-exchanged column. Monosaccharide composition analysis indicated that LBP-s-1 was com-prised of rhamnose, arabinose, xylose, mannose, glucose, galactose, galacturonic acid in the molar ratioof 1.00:8.34:1.25:1.26:1.91:7.05:15.28. The preliminary structure features of LBP-s-1 were investigatedby FT-IR,1H NMR and13C NMR. In vitro and in vivo hypoglycemic experiments showed that LBP-s-1 hadsignificant hypoglycemic effects and insulin-sensitizing activity through increasing glucose metabolismand insulin secretion and promoting pancreatic cell proliferation. Preliminary mechanisms were alsoelucidated.

چکیده : 

The capacitated p-median problem (CPMP) seeks to obtain the optimal location of p medians considering

distances and capacities for the services to be given by each median. This paper presents an efficient

hybrid metaheuristic algorithm by combining a proposed cutting-plane neighborhood structure and a

tabu search metaheuristic for the CPMP. In the proposed neighborhood structure to move from the current

solution to a neighbor solution, an open median is selected and closed. Then, a linear programming (LP)

model is generated by relaxing binary constraints and adding new constraints. The generated LP solution

is improved using cutting-plane inequalities. The solution of this strong LP is considered as a new neighbor

solution. In order to select an open median to be closed, several strategies are proposed. The neighborhood

structure is combined with a tabu search algorithm in the proposed approach. The parameters of the

proposed hybrid algorithm are tuned using design of experiments approach. The proposed algorithm is

tested on several sets of benchmark instances. The statistical analysis shows efficiency and effectiveness

of the hybrid algorithm in comparison with the best approach found in the literature.