Thermal stability of nano Ce1−xTixO2 material system for X < 0.2

Ceria (CeO₂) is a technologically promising compound due to a remarkable set of properties. However, the use of ceria also has drawbacks, the most pronounced of which is the material's poor thermal stability. This property limits the use of ceria-based materials at elevated temperatures, in many technological applications. To overcome this, the addition of TiO₂ is proposed. Such addition essentially creates a new material system, namely Ce_1−xTi_xO₂. In this work, an array of techniques were employed to determine the thermal stability of this new compound range (X < 0.2). Results show that when nano-sized, TiO₂ is fully soluble in CeO₂ in this range. After heat treatment, however, the material coarsens and the solubility limit decreases to less than 2 at.%. as the compound undergoes significant changes. These include solute segregation and phase separation. Finally, the factors that affect compound stability are discussed.     

Cell-based interconnect migration by hierarchical optimization

Fueled by Moore's Law, VLSI market competition and economic considerations dictates the introduction of new processor's microarchitecture in a two-year cycle called “Tick-Tock” marketing strategy. A new processor is first manufactured in the most advanced stable process technology, followed in a one-year delay by introducing chips comprising same microarchitecture but manufactured in a newer scaled process technology, thus allowing higher production volumes, better performance and lower cost. Tick-Tock is enabled by the automation of chip's layout conversion from an older into a newer manufacturing process technology. This is a very challenging computational task, involving billions of polygons. We describe an algorithm of a hierarchy-driven optimization method for cell-based layout conversion used at Intel for already several product generations. It transforms the full conversion problem into successive problems of significantly smaller size, having feasible solutions if and only if the full-chip problem does. The proposed algorithm preserves the design intent, its uniformity and maintainability, a key for the success of large-scale projects.     

Pyridine‐Modified Polymer as a Non‐Covalent Compatibilizer for Multi‐Walled CNT/Poly[ethylene‐co‐(methacrylic acid)] Composites Fabricated by Direct Melt Mixing

Multi‐wall CNT/poly[ethylene‐co‐(methacrylic acid)] composites were prepared by melt mixing. To improve dispersion and promote polymer/nanotube interactions, a novel non‐covalent compatibilizer is synthesized by reacting the polymer with 4‐(aminomethyl)pyridine. The composite based on the pristine polymer shows electrical and rheological percolation thresholds at nanotube loadings of 1.85 and 1.4 wt%, respectively. When 5 wt% of the pyridine‐modified compatibilizer is added, the corresponding values are reduced to 1.44 and 0.8 wt%, respectively. The electrical resistivity decreases even further as 10 wt% of the novel dispersing agent is used. Microscopy and Raman spectroscopy confirm the improved dispersion and π‐interactions established during melt mixing.

     

Spatial variability of carbonaceous aerosol concentrations in East and West Jerusalem

Carbonaceous aerosol concentrations and sources were compared during a year long study at two sites in East and West Jerusalem that were separated by a distance of approximately 4 km. One in six day 24-h PM(2.5) elemental and organic carbon concentrations were measured, along with monthly average concentrations of particle-phase organic compound tracers for primary and secondary organic aerosol sources.Tracer compounds were used in a chemical mass balance ICMB) model to determine primary and secondary source contributions to organic carbon. The East Jerusalem sampling site at Al Quds University experienced higher concentrations of organic carbon (OC) and elemental carbon (EC) compared to the West Jerusalem site at Hebrew University. The annual average concentrations of OC and EC at the East Jerusalem site were 5.20 and 2.19 μg m(-3), respectively, and at the West Jerusalem site were 4.03 and 1.14 μg m(-3), respectively. Concentrations and trends of secondary organic aerosol and vegetative detritus were similar at both sites, but large differences were observed in the concentrations of organic aerosol from fossil fuel combustion and biomass burning, which was the cause of the large differences in OC and EC concentrations observed at the two sites.     

Distilling the wisdom of crowds: weighted aggregation of decisions on multiple issues

Given the judgments of multiple voters regarding some issue, it is generally assumed that the best way to arrive at some collective judgment is by following the majority. We consider here the now common case in which each voter expresses some (binary) judgment regarding each of a multiplicity of independent issues and assume that each voter has some fixed (unknown) probability of making a correct judgment for any given issue. We leverage the fact that multiple votes by each voter are known in order to demonstrate, both analytically and empirically, that a method based on maximum likelihood estimation is superior to the simple majority rule for arriving at true collective judgments.     

Landscape and water in the oases of Egypt's western desert

While natural processes, mainly wind and water erosion, define desert landscapes, human manipulation and use of water play important roles in defining the landscape within desert oases. The role of water in the oases of the Western Desert of Egypt is described, and it is considered how the scarcity of water affects its use. The challenge to the protection of these archetypal landscapes presented by new forms of development is identified.     

Microstructural evolution during the infiltration of boron carbide with molten silicon

The previously reported model that accounts for the formation of the core-rim structure in reaction-bonded boron carbide composites (RBBC) is expanded and validated by additional experimental observations and by a thermodynamic analysis of the ternary B–C–Si system. The microstructure of the RBBC composites consists of boron carbide particles with a core-rim structure, β-SiC and some residual silicon. The SiC carbide particles have a polygonal shape in composites fabricated in the presence of free carbon, in contrast to the plate-like morphology when the initial boron carbide is the sole source of carbon. In the course of the infiltration process, the original B₄C particles dissolve partly or fully in molten silicon, and a local equilibrium is established between boron carbide, molten silicon and SiC. Overall equilibrium in the system is achieved as a result of the precipitation of the ternary boron carbide phase B₁₂(B,C,Si)₃ at the surface of the original boron carbide particles and leads to the formation of the rim regions. This feature is well accounted for by the “stoichiometric saturation” approach, which takes into account the congruent dissolution of B₄C particles. The SiC phase, which precipitates form the silicon melt adopts the β-allotropic structure and grows preferably as single plate-like particles with an {1 1 1}_β habit plane. The morphology of the SiC particles is determined by the amount of carbon available for their formation.     

Out-of-plane shear of fiber composites at moderate stretch levels

The response of incompressible fiber composites to moderate levels of out-of-plane shear and tension along the fibers is examined. It is assumed that the phases’ constitutive behaviors depend on the first invariant of the right Cauchy–Green deformation tensor, and in the vicinity of the reference configuration can be approximated by a two-terms Taylor series in this invariant. A deformation field satisfying an appropriate boundary conditions on a representative cylindrical composite element is proposed, and the resulting equilibrium equations are expanded in terms of a series. A solution, which is exact to second order in the deformation, is determined. This solution provides accurate estimates for the local fields developing in a cylindrical composite with Gent phases up to one third of the locking stretch ratio. The overall response predicted by this approximated quadratic solution is found to be in agreement with corresponding results for fiber composites with Gent phases that were determined by application of a new variational procedure and by finite-element simulation of a periodic composite.     

GPGPU test suite minimisation: search based software engineering performance improvement using graphics cards

It has often been claimed that SBSE uses so-called ‘embarrassingly parallel’ algorithms that will imbue SBSE applications with easy routes to dramatic performance improvements. However, despite recent advances in multicore computation, this claim remains largely theoretical; there are few reports of performance improvements using multicore SBSE. This paper shows how inexpensive General Purpose computing on Graphical Processing Units (GPGPU) can be used to massively parallelise suitably adapted SBSE algorithms, thereby making progress towards cheap, easy and useful SBSE parallelism. The paper presents results for three different algorithms: NSGA2, SPEA2, and the Two Archive Evolutionary Algorithm, all three of which are adapted for multi-objective regression test selection and minimization. The results show that all three algorithms achieved performance improvements up to 25 times, using widely available standard GPUs. We also found that the speed-up was observed to be statistically strongly correlated to the size of the problem instance; as the problem gets harder the performance improvements also get better.