Sharif Digital Repository

Choreography description languages aim at specifying from a global point of view interactions among a set of services involved in a new system. From this specification, local implementations or peers can be automatically generated. Generation of peers that precisely implement the choreography specification is not always possible: This problem is known as realizability. When peers corresponding to this specification are being executed we may want to modify the choreography specification and reconfigure dynamically the system. This is the case for instance if we add or remove interactions due to the addition of functionalities to the system at hand or the loss of a service. In this article, we... 

In this paper, we introduce a refinement approach to develop probabilistic programs formally. To achieve this goal, we first present a way to specify probabilistic programs in a Z-based notation. We then use an existing method of translating Z into a refinement calculus to transform our Z-style specifications of probabilistic programs into specification statements of the refinement calculus. We finally add new laws to the refinement calculus helping us to refine the resulting specification statements into probabilistic choice constructs of a probabilistic imperative language. In this way, we will provide a completely formal way for developing probabilistic programs. ©2009 IEEE  

A joint theoretical and experimental study of the kinetic and mechanism of the rearrangement of allyl p-tolyl ether was performed in order to study the kinetic and mechanism of the reaction. Experimental studies were performed in gas phase over a temperature range of 493.15-533.15 K. The experimental Arrhenius parameters of this reaction were measured to be Ea = 36.08 kcal mol-1, ΔS# = -7.88 cal mol-1 K-1, and Log A = 11.74, experimentally. Using GC for the mixture of the reaction with and without cyclohexene demonstrated that the reaction is clean without any radical intermediates. The experimental results show that the studied reaction is unimolecular and proceeds through a concerted... 

Coupling of side chain dynamics over long distances is an important component of allostery. Methionine side chains show the largest intrinsic flexibility among methyl-containing residues but the actual degree of conformational averaging depends on the proximity and mobility of neighboring residues. The 13C NMR chemical shifts of the methyl groups of methionine residues located at long distances in the same protein show a similar scaling with respect to the values predicted from the static X-ray structure by quantum methods. This results in a good linear correlation between calculated and observed chemical shifts. The slope is protein dependent and ranges from zero for the highly flexible... 

The corrosion inhibition of glycine-based dithiocarbamates with benzyl (BDTC) and propyl (PDTC) groups were investigated for cold rolled carbon steel (CRS) in 0.5 M HCl, indicating that the compounds as mixed type inhibitors significantly reduced the corrosion rate of the CRS due to the formation of a stable protective film on the metal surface. As confirmed by ATR-FTIR, SEM, AFM, XPS and theoretical studies, chemically adsorbed BDTC molecule is a better corrosion inhibitor with higher corrosion efficiency of about 98% at room temperature and a better thermal stability attributed to the Fe-S and Fe-N bindings, and in addition, to the presence of the benzene ring in the molecular structure. ©... 

When the periodic permittivity of two-dimensional (2D) photonic crystal (PC) can be separated in x- and y- coordinates, one can consider the structure as two separate 1D photonic crystals, one of them being periodic in x coordinate and the other in y coordinate. If it is possible to find a proper separable permittivity function, we can approximate a 2D PC with two distinct 1D structures. One of the advantages is rapid calculation the density of state of a 2D PC. In this article an analytical calculation of the density of states for such a 2D PC has been done with the aim of taking this advantage. For calculating the density of states we use the effective resonance approach to analyze the 1D... 

Block motion estimation is an important field of video processing. This paper presents a new scheme to reach in faster block motion estimation based on motion prediction. The scheme exploits an adaptive filter to predict the block motion from its spatio-temporal motion compensated adjacent blocks, the predicted motion determines the initial candidate block for search methods with biased search center, in special case of partial distortion search, this strategy reduces search time by preventing from complete distortion calculation for more loser candidates, after comparison of three conventional adaptive filters, a normalized least mean square filter with convergence monitoring is recommended... 

Wall thickness measurement and deterioration determination of 6 and 10 inch pipes due to corrosion/erosion/pitting was evaluated by using radiographic film density measurements. Special reference blocks were prepared with defined step wall reductions and artificial defects. Gamma radiography with a Ir-192 source was used. A double-wall technique with longitudinal film arrangement was used for this purpose. Formulae were developed from the experiments for numerical calculations. It was observed that this method can determine remaining wall thickness as well as pitting corrosion in insulated and non-insulated pipes with differential and absolute density measurements. The purpose of the work... 

A combined theoretical and experimental kinetic and mechanism of diallyl disulfide pyrolysis reaction in the gas phase was studied in a static system over the temperature range of 586.7-621.2 K and a total pressure of 72 Torr in the presence of cyclohexene as radicals inhibitor. The experimental results show that the reaction is homogeneous, unimolecular and proceeds through a radical mechanism. Theoretical calculations at the B3LYP level using the 6-31G*, 6-31++G* and 6-311++G* basis sets confirm the radical mechanism for the diallyl disulfide pyrolysis. The calculated kinetic and activation parameters especially at the B3LYP/6-31G* level are in good agreement with the experimental data. ©... 

The molecular behavior of some pyridine derivatives as corrosion inhibitors of iron and aluminum in acid media, were studied quantum electrochemically. The calculations were made for three conditions; isolated inhibitor molecule, metal cluster, and finally polarized continuum media. It is concluded that for aluminum the vertical adsorption through nitrogen atom is prevailing, while for iron both vertical and planar adsorptions (through π electrons of aromatic ring) are possible, but the vertical is predominant. The inhibitor chemical potential (μ) and the extent of charge transfer (ΔN) to the metal were determined. A linear correlation between each of these and the inhibition efficiencies... 

The mechanism and kinetic aspects of the retro-ene reaction of allyl n-butyl sulfide and its deuterated derivative were studied using four different types of density functional theory (DFT) methods with eight different levels of the basis sets. Vibrational frequency analysis confirmed that the stationary points include the transition state (TS) structure with only one imaginary frequency. Mechanistic studies on the retro-ene process rejected the step-wise mechanism and confirmed that the reaction proceeds through a six-centered cyclic transition state. Theoretical calculations show that propene elimination from the reactant can occur through an asynchronous concerted mechanism. A primary... 

Monte Carlo simulations have been carried out for 2-ethoxyethanol (C 2E1) in isothermal-isobaric ensemble (NPT) at different temperatures and 1 atm pressure with a continuum configurational biased procedure in water and chloroform media. Hydrogen bond bridges were formed between adjacent oxygen atoms in C2E1 (CH 3CH2OCH2CH2OH) through water molecules. We also found that the stable conformers of C2E 1 in water and CHCl3 are different and the effect of temperature on solute-solvent interaction energies is considerable. The self-association of C2E1 in aqueous and nonaqueous media has been studied by statistical perturbation theory, and the relative free energy has been obtained at different... 

The details of the crystal structure of the recently discovered Y 3Ba5Cu8O18+δ (Y358) superconductor have been determined by ab initio density functional theory. Total energy calculation has been performed for three different suggested structures with different oxygen content. The structure with a center of inversion symmetry and the highest oxygen concentration has the lowest total energy. Thus, it is the best choice for the Y358 crystal structure. By investigating the detailed structure, it is seen that this compound is arranged either of YBa2Cu3O7 and YBaCu2O 5 or YBaCu2O5 and BaCuO2 substructural blocks in the c direction. The difference between the total energy of Y358 compound and the... 

To quantify the core barrel motion (CBM) in a pressurized water reactor, a scaling factor can be calculated to convert the Root Mean Square (RMS) value of the ex-core signals (%) to the core barrel motion amplitude (mil) (Thompson et al., 1980). In the current paper, a scaling factor is calculated using the direct and adjoint methods for a typical VVER-1000 reactor. The scaling factor is calculated using the perturbed parameters that result from CBM. The results show that the calculated scaling factors are not the same in one and two-dimensional modeling, and strongly depend on the ex-core detector location. The linearity assumption of relative detector response versus the small displacement... 

The energetics and kinetic energy barriers of vacancy/atom exchange in a 37-atom truncated octahedron Ag-Pt binary cluster in the Ag-rich range of compositions are investigated via a first-principles atomistic approach. The energy of the local minima obtained considering various distributions of a single vacancy and a few Pt atoms within the cluster and the energy barriers connecting them are evaluated using accurate density-functional calculations. The effects of the simultaneous presence of a vacancy and Pt atoms are found to be simply additive when their distances are larger than first-neighbors, whereas when they can be stabilizing at low Pt content due to the release of strain by the... 

The overall system status calculated by pflower flow analysis is the most basic information used for all decisions taken by power system operators and planners. While conventional AC pflower flow solutions are computationally tractable, approximate DC models are employed in many applications, such as optimal power flow studies and unit commitment problems, mainly due to the linear nature of DC models. These models do not provide any information on the reactive power and voltage magnitude quantities and occasionally inaccurate results of the active power values. This paper presents an efficient power flow approach compromising both the con icting aspects of speed and accuracy. The proposed... 

Solvatochromic UV-vis shifts of three probes 4-nitroaniline, 4-nitroanisol, and Reichardt's dye in binary mixtures of polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (Triton X-100 or TX-100) with methanol, ethanol, 1-propanol, and water have been investigated at 298 K. Structural and intermolecular interactions of solvatochromic probes were determined in these systems. Solvatochromic parameters, including normalized polarity (ETN), dipolarity-polarizability (π∗), hydrogen-bond donor (α), and hydrogen-bond acceptor (β) abilities, were measured at a wide range of mole fraction (0 ≤ X ≤ 1) with 0.1 increment. Interestingly, a similar behavior of ETN and α is observed in...