Homogeneous

The homogeneous isotropic Boltzmann equation (HIBE) is a fundamental dynamic model for many applications in thermodynamics, econophysics and sociodynamics. Despite recent hardware improvements, the solution of the Boltzmann equation remains extremely challenging from the computational point of view, in particular by deterministic methods (free of stochastic noise). This work aims to improve a deterministic direct method recently proposed [V.V. Aristov, Kluwer Academic Publishers, 2001] for solving the HIBE with a generic collisional kernel and, in particular, for taking care of the late dynamics of the relaxation towards the equilibrium. Essentially (a) the original problem is reformulated in terms of particle kinetic energy (exact particle number and energy conservation during microscopic collisions) and (b) the computation of the relaxation rates is improved by the DVMlike correction, where DVM stands for Discrete Velocity Model (ensuring that the macroscopic conservation laws are exactly satisfied). Both these corrections make possible to derive very accurate reference solutions for this test case. Moreover this work aims to distribute an open-source program (called HOMISBOLTZ), which can be redistributed and/or modified for dealing with different applications, under the terms of the GNU General Public License. The program has been purposely designed in order to be minimal, not only with regards to the reduced number of lines (less than 1,000), but also with regards to the coding style (as simple as possible). The problem consists in integrating the homogeneous Boltzmann equation for a generic collisional kernel in case of isotropic symmetry, by a deterministic direct method. Difficulties arise from the multi-dimensionality of the collisional operator and from satisfying the conservation of particle number and energy (momentum is trivial for this test case) as accurately as possible, in order to preserve the late dynamics.

Detailed studies on the sodium metaperiodate oxidation of cellulose to yield 2,3-dialdehyde cellulose were carried out to ascertain the effects of concentration of periodate relative to cellulose, temperature of reaction, pH of the medium, effect of morphology of the cellulose, and effect of homogenous versus heterogenous reaction conditions. Microcrystalline cellulose had slightly higher reactivity then cellulose due to its greater purity and lower molecular weight, which gave rise to more reactive end groups. There were no significant changes in the reactivity of cellulose with periodate in buffer solutions of pH 2-5, or of homogenous oxidation of methylcellulose and carboxymethylcellulose as compared to heterogenous oxidation of cellulose powder. It was found that only controlling the concentration of periodate used and the temperature could easily control the rate and extent of oxidation of cellulose. The conclusion is that in order to achieve higher extent of oxidation of cellulose it is preferable to use higher concentration of periodate at 55 C for short reaction time, instead of stoichiometric periodate concentration for longer reaction times.

Wireless distributed microsensor systems will enable the reliable monitoring of a variety of environments for both civil and military applications. In this paper, we look at communication protocols, which can have significant impact on the overall energy dissipation of these networks. Based on our findings that the conventional protocols of direct transmission, minimum-transmission-energy, multihop routing, and static clustering may not be optimal for sensor networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based protocol that utilizes randomized rotation of local cluster base stations (cluster-heads) to evenly distribute the energy load among the sensors in the network. LEACH uses localized coordination to enable scalability and robustness for dynamic networks, and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. Simulations show that LEACH can achieve as much as a factor of 8 reduction in energy dissipation compared with conventional routing protocols. In addition, LEACH is able to distribute energy dissipation evenly throughout the sensors, doubling the useful system lifetime for the networks we simulated.

Stable mono and bimetallic nanoparticles have been prepared from colloids developed by a simple and reproducible method, based on a reduction-by-solvent process. This method allows for the preparation of metallic nanoparticles with different compositions (i.e., Ni-Pd, Fe-Pd, Mg-Pd, Pd, and Pt) and metallic ratios, and an average size of about 2 nm. Purified and nonpurified metallic species were used in the selective hydrogenation of phenylacetylene to styrene in liquid phase under very mild conditions (1 bar H 2 pressure and T = 50 • C). The catalysts prepared show high selectivity and activity toward styrene at very high loadings of phenylacetylene (substrate-to-catalyst weight ratio near 7500). Therefore, these materials are highly interesting as selective hydrogenation catalysts for reactions of great industrial importance.

Simplicity of usage, flexibility of data access, ease of maintenance, time and energy efficiency, and pay as you go policy have increased the usage of cloud computing over traditional computing. Cloud computing should be able to meet the performance expectations of different class of customers. On the contrary, inefficient scheduling algorithms decrease the quality of service experienced by users. To improve quality of service, there are several proposed scheduling algorithms in the literature. However, these scheduling algorithms are limited because of not considering different types of customers. Our objective is to satisfy performance expectations of these types of customers by proposing an efficient Dynamic Dedicated Server Scheduling (DDSS) while considering different types of customers. Results show that the customer drop rate and throughput can be significantly improved by DDSS. Our proposed scheduling and related analysis will help cloud service providers build efficient cloud computing service architectures through considering different types of priority class performances such as, drop rate, throughput, and utilization.

The homogeneous isotropic Boltzmann equation (HIBE) is a fundamental dynamic model for many applications in thermodynamics, econophysics and sociodynamics. Despite recent hardware improvements, the solution of the Boltzmann equation remains extremely challenging from the computational point of view, in particular by deterministic methods (free of stochastic noise). This work aims to improve a deterministic direct method recently proposed [V.V. Aristov, Kluwer Academic Publishers, 2001] for solving the HIBE with a generic collisional kernel and, in particular, for taking care of the late dynamics of the relaxation towards the equilibrium. Essentially (a) the original problem is reformulated in terms of particle kinetic energy (exact particle number and energy conservation during microscopic collisions) and (b) the computation of the relaxation rates is improved by the DVM-like correction, where DVM stands for Discrete Velocity Model (ensuring that the macroscopic conservation laws ar...

The dynamic tasks scheduling of parallel tasks in multiprocessor systems is still a demanding problem that is being investigated by the researchers. However, the Directed Acyclic Graph (DAG)- based dynamic tasks scheduling is not yet paid enough attention. In this paper a DAG based dynamic tasks scheduling model and a scheduling algorithm DYTAS (DYnamic TAsk Scheduling algorithm) has been proposed with a lower time complexity. Furthermore, the simulation experiments show that, the scheduling model and scheduling algorithm are feasible, a higher scheduling successful ratio may be obtained by this algorithm for parallel jobs with large number of tasks.

A wide array of forms of palladium has been utilized as precatalysts for Heck and Suzuki coupling reactions over the last 15 years. Historically, nearly every form of palladium used has been described as the active catalytic species. However, recent research has begun to shed light on the in situ transformations that many palladium precatalysts undergo during and before the catalytic reaction, and there are now many suggestions in the literature that narrow the scope of types of palladium that may be considered true "catalysts" in these coupling reactions. In this work, for each type of precatalyst, the recent literature is summarized and the type(s) of palladium that are proposed to be truly active are enumerated. All forms of palladium, including discrete soluble palladium complexes, solid-supported metal ligand complexes, supported palladium nano-and macroparticles, soluble palladium nanoparticles, soluble ligandfree palladium, and palladium-exchanged oxides are considered and reviewed here. A considerable focus is placed on solid precatalysts and on evidence for and against catalysis by solid surfaces vs. soluble species when starting with various precatalysts. The review closes with a critical overview of various control experiments or tests that have been used by authors to assess the homogeneity or heterogeneity of catalyst systems.

A new and efficient method for the preparation of substituted 3,4-dihydropyrimidin-2(1H)-ones via Biginelli synthesis using catalytic amounts of 1,3-dichloro-5,5-dimethylhydantoin is presented. Short reaction times, easy work-up, high yields of products and stability, easy-handling, non-toxicity and cheapness of the catalyst are noteworthy advantages of the present work.

During severe impact conditions, brain tissue experiences a rapid and complex deformation, which can be seen as a mixture of compression, tension and shear. Moreover, diffuse axonal injury (DAI) occurs in animals and humans when both the strains and strain rates exceed 10% and 10/s, respectively. Knowing the mechanical properties of brain tissue in shear at these strains and strain rates is thus of particular importance, as they can be used in finite element simulations to predict the occurrence of brain injuries under different impact conditions. In this research, an experimental setup was developed to perform simple shear tests on porcine brain tissue at strain rates < 120/s. The maximum measured shear stress at strain rates of 30, 60, 90 and 120/s was 1.15 +/- 0.25 kPa, 1.34 +/- 0.19 kPa, 2.19 +/- 0.225 kPa and 2.52 +/- 0.27 kPa, (mean +/- SD), respectively, at the maximum amount of shear, K = 1. Good agreement of experimental, theoretical (Ogden and MooneyRivlin models) and n...

We consider a distance-regular graph Γ with diameter d ≥ 3 and eigenvalues k = θ0 > θ1 > ... > θd . We show the intersection numbers a 1, b 1 satisfy $$\left( {\theta _1 + \frac{k}{{a_1 + 1}}} \right)\left( {\theta _d + \frac{k}{{a_1 + 1}}} \right) \geqslant - \frac{{ka_1 b_1 }}{{(a_1 + 1)^2 }}.$$ We say Γ is tight whenever Γ is not bipartite, and equality holds above. We characterize the tight property in a number of ways. For example, we show Γ is tight if and only if the intersection numbers are given by certain rational expressions involving d independent parameters. We show Γ is tight if and only if a 1 ≠ 0, a d = 0, and Γ is 1-homogeneous in the sense of Nomura. We show Γ is tight if and only if each local graph is connected strongly-regular, with nontrivial eigenvalues −1 − b 1(1 + θ1)−1 and −1 − b 1(1 + θd )−1. Three infinite families and nine sporadic examples of tight distance-regular graphs are given.

Analytical solution for functionally graded infinite hollow cylinder with rigid core is developed. Material properties like Young's modulus and density of the infinite cylinder are assumed to be graded in the radial direction according to a novel power-law distribution. The governing second-order differential equation is derived from the equilibrium equations, deformation theory of elasticity and the stress-strain relationships, and it is solved in terms of Bessel's functions. Dependence of displacement of and stresses in the cylinder on the functionally graded parameters is examined. Proposed solution is validated by comparing the results for functionally graded infinite cylinders to the results for the homogeneous ones.

Phospholipid-ethanol-aqueous mixtures containing bilayer-forming lipids and 20-50 wt.% of water form viscous gels. Further hydration of these gels results in the formation of liposomes whose morphology depends upon the lipid type. Upon hydration of gels containing mixtures of the lipids 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), small homogeneous and unilamellar liposomes were produced. In contrast, hydration of gels containing only POPC resulted in formation of large multilamellar liposomes. Likewise, mulitlamellar liposomes resulted when this method was applied to form highly fusogenic liposomes comprised of the novel negatively charged N-acyl-phosphatidylethanolamine (NAPE) mixed with di-oleoyl-phosphatidylcholine (DOPC)

ABSTRACT Metal-catalysed hydrogen isotope exchange has been widely used in the preparation of deuterium- and tritium-labelled compounds. This review details the development and utility of homogeneous and heterogeneous rhodium and ruthenium catalysts for the preparation of deuterium- and tritium-labelled compounds by hydrogen isotope exchange methodology. Copyright © 2010 John Wiley & Sons, Ltd.

We consider a distance-regular graph Γ with diameter d ≥ 3 and eigenvalues k = θ0 > θ1 > ... > θd . We show the intersection numbers a 1, b 1 satisfy $$\left( {\theta _1 + \frac{k}{{a_1 + 1}}} \right)\left( {\theta _d + \frac{k}{{a_1 + 1}}} \right) \geqslant - \frac{{ka_1 b_1 }}{{(a_1 + 1)^2 }}.$$ We say Γ is tight whenever Γ is not bipartite, and equality holds above. We characterize the tight property in a number of ways. For example, we show Γ is tight if and only if the intersection numbers are given by certain rational expressions involving d independent parameters. We show Γ is tight if and only if a 1 ≠ 0, a d = 0, and Γ is 1-homogeneous in the sense of Nomura. We show Γ is tight if and only if each local graph is connected strongly-regular, with nontrivial eigenvalues −1 − b 1(1 + θ1)−1 and −1 − b 1(1 + θd )−1. Three infinite families and nine sporadic examples of tight distance-regular graphs are given.

By extending the pseudo-Stroh formalism to two-dimensional decagonal quasicrystals, an exact closedform solution for a simply supported and multilayered two-dimensional decagonal quasicrystal plate is derived in this paper. Based on the different relations between the periodic direction and the coordinate system of the plate, three internal structure cases for the two-dimensional quasicrystal layer are considered. The propagator matrix method is also introduced in order to treat efficiently and accurately the multilayered cases. The obtained exact closed-form solution has a concise and elegant expression. Two homogeneous quasicrystal plates and a sandwich plate made of a two-dimensional quasicrystal and a crystal with two stacking sequences are investigated using the derived solution. Numerical results show that the differences of the periodic direction have strong influences on the stress and displacement components in the phonon and phason fields; different coupling constants between the phonon and phason fields will also cause differences in physical quantities; the stacking sequences of the multilayer plates can substantially influence all physical quantities. The exact closed-form solution should be of interest to the design of the two-dimensional quasicrystal homogeneous and laminated plates. The numerical results can also be employed to verify the accuracy of the solution by numerical methods, such as the finite element and difference methods, when analyzing laminated composites made of quasicrystals.

Using a very geometric, intuitive construction, an example is given of a homogeneous, compact, connected Hausdorff space (X, T) that does not satisfy the conclusion of the Effros Theorem. In particular, there is a point p and a neighborhood V , of the identity in the group of self-homeomorphisms on X , with the compact-open topology such that V = {h(p): h e V} is nowhere dense in X.

Stable mono and bimetallic nanoparticles have been prepared from colloids developed by a simple and reproducible method, based on a reduction-by-solvent process. This method allows for the preparation of metallic nanoparticles with different compositions (i.e., Ni-Pd, Fe-Pd, Mg-Pd, Pd, and Pt) and metallic ratios, and an average size of about 2 nm. Purified and nonpurified metallic species were used in the selective hydrogenation of phenylacetylene to styrene in liquid phase under very mild conditions (1 bar H 2 pressure and T = 50 • C). The catalysts prepared show high selectivity and activity toward styrene at very high loadings of phenylacetylene (substrate-to-catalyst weight ratio near 7500). Therefore, these materials are highly interesting as selective hydrogenation catalysts for reactions of great industrial importance.

We define a simple form of homogeneous neural network model whose characteristics are expressed in terms of probabilistic assumptions. The networks considered operate in an asynchronous manner and receive the inj7uence of the environment in the form of external stimulations. The operation of the network is described by means of a Markovian process whose steady-state solution yields several global measures of the network's activity. Three different types of external stimulations are investigated, which represent possible input mechanisms. The unalytical results obtained concern the mucroscopic viewpoint and provide a quick insight into the structure of the network's behavior.

Mechanical characterization of brain tissue at high loading velocities is crucial for modelling Traumatic Brain Injury (TBI). During severe impact conditions, brain tissue experiences compression, tension and shear. Limited experimental data is available for brain tissue in extension at dynamic strain rates. In this research, a High Rate Tension Device (HRTD) was developed to obtain dynamic properties of brain tissue in extension at strain rates of ≤ 90/s. In vitro tensile tests were performed to obtain properties of brain tissue at strain rates of 30, 60 and 90/s up to 30% strain. The brain tissue showed a stiffer response with increasing strain rates, showing that hyperelastic models are not adequate. Specifically, the tensile engineering stress at 30% strain was 3.1±0.49 kPa, 4.3±0.86 kPa, 6.5±0.76 kPa (mean ± SD) at strain rates of 30, 60 and 90/s, respectively. Force relaxation tests in tension were also conducted at different strain magnitudes (10%-60% strain) with the average rise time of 24 ms, which were used to derive time dependent parameters. One term Ogden, Fung and Gent models were used to obtain material parameters from the experimental data. Numerical simulations were performed using a one-term Ogden model to analyze hyperelastic behavior of brain tissue up to 30% strain. The material parameters obtained in this study will help to develop biofidelic human brain finite element models, which can subsequently be used to predict brain injuries under impact conditions and as a reconstruction and simulation tool for forensic investigations.

Simplicity of usage, flexibility of data access, ease of maintenance, time and energy efficiency, and pay as you go policy have increased the usage of cloud computing over traditional computing. Cloud computing should be able to meet the performance expectations of different classes of customers. On the contrary, inefficient scheduling algorithms decrease the quality of service experienced by users. To