Versatile sputtering technology for Al2O3 gate insulators on graphene

We report a novel, sputtering-based fabrication method of Al₂O₃ gate insulators on graphene. Electrical performance of dual-gated mono- and bilayer exfoliated graphene devices is presented. Sputtered Al₂O₃ layers possess comparable quality to oxides obtained by atomic layer deposition with respect to a high relative dielectric constant of about 8, as well as low-hysteresis performance and high breakdown voltage. We observe a moderate carrier mobility of about 1000 cm² V⁻¹ s⁻¹ in monolayer graphene and 350 cm² V⁻¹ s⁻¹ in bilayer graphene, respectively. The mobility decrease can be attributed to the resonant scattering on atomic-scale defects, likely originating from the Al precursor layer evaporated prior to sputtering.     

Uniform crashworthiness optimization of car body for high-speed trains

The paper deals with a new uniform crashworthiness concept of car bodies optimization of high-speed trains. The design optimization was done from the point of view of structural protection of occupants’ survival space. For the reason that it is impossible to find a highly probable scenario for the derailment, the authors decided to find the solution in the form of rigid frame structure (survival cells), which will provide safety space for the passengers. In the optimization example a typical passenger car body was divided into cells of approximately equal dimensions. The optimization problem was to minimize the mass of the structure with stress constraints. The survival cell was subjected to a sequence of high value loads. The loads are acting in an asynchronous way in three load directions what gives the optimized structure uniform crashworthiness. The optimization strategy consists of three stages. In the first step, the constant criterion surface algorithm (CCSA) of topology optimization is applied to find a preliminary solutions. For improving the manufacture properties of this solution, a new concept of design space constraints was proposed. The sizing optimization with evolutionary algorithms was used to define a thin-walled structure in the second step. For evolutionary optimization a standard procedure was employed. Finally, CCSA optimization algorithm was applied again to remove excessive material from a car body structure. As the optimization result a new design proposition of a car body with multiple survival cells of high uniform stiffness was obtained. By maintaining passengers’ survival space, the passive safety of a high-speed car body was significantly increased.     

Representation theory for default logic

Default logic can be regarded as a mechanism to represent families of belief sets of a reasoning agent. As such, it is inherently second-order. In this paper, we study the problem of representability of a family of theories as the set of extensions of a default theory. We give a complete solution to the problem of representability by means of default theories with finite set of defaults, and by means of normal default theories. We obtain partial results on representability by arbitrary (infinite, non-normal) default theories. We construct examples of denumerable families of non-including theories that are not representable. We also study the concept of equivalence between default theories. This revised version was published online in June 2006 with corrections to the Cover Date.     

Simultaneous toxic action of zinc and alachlor resulted in enhancement of zinc uptake by the filamentous fungus Paecilomyces marquandii

Microbial ability vary when pollutants exist together in the environment in comparison to the presence of single toxic compound. The influence of alachlor and zinc on the growth of the filamentous fungus Paecilomyces marquandii and its ability to eliminate alachlor and zinc has been studied. Their simultaneous presence in the polluted environment is very probable. In liquid cultures the pesticide (50 mg/l) was removed with the efficiency of 85% within 7 days. Beginning from the third day of culturing two derivatives of alachlor were found: N-(2',6'-diethylphenyl)-N-metoxymethyl-acetamide and unstable 2-chloro-N-(2',6'-diethylphenyl)-N-hydroxymethyl-acetamide, the first time detected as product of alachlor metabolisation by filamentous fungus. The herbicide elimination was not inhibited by zinc up to 1.0 mM of the metal content in the culture medium, 5.0-7.5 mM of the metal limited alachlor depletion by 30-50%, whereas a higher zinc concentration stopped this process. Zinc content in P. marquandii mycelium during the incubation in growth medium reached 10-20 mg/g of dry weight and was increased up to 99 mg/g by alachlor, however due to its presence a strong inhibitory effect on growth was observed. It was postulated that the increase in zinc binding by the growing mycelium of P. marquandii in the presence of the pesticide was connected with the changes in the wall and membrane composition induced by simultaneous toxic interaction of zinc and alachlor. Only 15-20% of bound zinc was detected in the cell wall of the fungus, whereas the amount of zinc loaded in the wall of mycelium originating from the cultures incubated in the alachlor presence increased to 60%. Additionally, changes in the profile of fatty acids of cultures with pesticide and metal addition were observed.P. marquandii strain seems to be promising for a potential industrial application. It can both effectively bind zinc and remove alachlor from the mixture of pollutants.     

Uniform semantic treatment of default and autoepistemic logics

We revisit the issue of epistemological and semantic foundations for autoepistemic and default logics, two leading formalisms in nonmonotonic reasoning. We develop a general semantic approach to autoepistemic and default logics that is based on the notion of a belief pair and that exploits the lattice structure of the collection of all belief pairs. For each logic, we introduce a monotone operator on the lattice of belief pairs. We then show that a whole family of semantics can be defined in a systematic and principled way in terms of fixpoints of this operator (or as fixpoints of certain closely related operators). Our approach elucidates fundamental constructive principles in which agents form their belief sets, and leads to approximation semantics for autoepistemic and default logics. It also allows us to establish a precise one-to-one correspondence between the family of semantics for default logic and the family of semantics for autoepistemic logic. The correspondence exploits the modal interpretation of a default proposed by Konolige. Our results establish conclusively that default logic can be viewed as a fragment of autoepistemic logic, a result that has been long anticipated. At the same time, they explain the source of the difficulty to formally relate the semantics of default extensions by Reiter and autoepistemic expansions by Moore. These two semantics occupy different locations in the corresponding families of semantics for default and autoepistemic logics.     

Developing ERP Systems Success Model for the Construction Industry

Recently, a significant number of major construction companies embarked on the implementation of integrated information technology solutions such as enterprise resource planning (ERP) systems to better integrate various business functions. However, these integrated systems in the construction sector present a set of unique challenges, different from those in the manufacturing or other service sectors. There have been many cases of failure in implementing ERP systems in the past, so it is critical to identify and understand the factors that largely determine the success or failure of ERP implementation in the construction industry. This paper presents the process of developing an ERP systems success model to guide a successful ERP implementation project and to identify success factors for ERP systems implementation. The paper identifies factors associated with the success and failure of ERP systems, and develops a success model to analyze the relationships between key factors and the success of such systems. The proposed ERP systems success model adapts the technology acceptance model and DeLone and McLean’s information systems success model and integrates those with key project management principles. The goal of the ERP systems success model is to better evaluate, plan, and implement ERP projects and help senior managers make better decisions when considering ERP systems in their organization.     

Structural and electrical properties of (Ba1−xSrx)(Zr0.9M0.1)O3, M = Y, La, solid solutions

The aim of the work was to study the structural and electrical properties of the (Ba_1−xSr_x)(Zr_0.9Y_0.1)O₃ and (Ba_1−xSr_x)(Zr_0.9Y_0.1)O₃ solid solutions. The powders of different strontium content (x = 0, 0.03, 0.05 and 0.1) were prepared by a thermal decomposition of organo-metallic precursors containing ethylenediaminetetraacetate acid. Some parameters describing stability and transport properties of the perovskite structure, such as tolerance factor, specific free volume and global instability index, were calculated. It was found that the introduction of strontium into both solid solutions caused the increase of specific free volume and global instability index—these structures became a little less stable but, on the other hand, better ionic conductor. All samples were cubic perovskite and the substitution of strontium for barium caused the decrease of respective lattice parameters. Electrical conductivity measurements were performed by the d.c. four-probe method in controlled gas atmospheres containing Ar, air, H₂ and/or H₂O at the temperature from 300 to 800 °C. It was found that the conductivity depended on a chemical composition of the samples and the atmosphere. In general, the electrical conductivity was higher in wet atmospheres which contained oxygen, being in accordance with the model of a proton transport in the perovskite structure which assumed the presence of the oxygen vacancy. The solid solution containing 5 mol.% of strontium showed the highest conductivity and the lowest activation energy of conductivity regardless of the atmospheres.     

A modified approach to the analysis of piezoelectric photothermal spectra

In this paper a modified approach to the problem of interpretation of the piezoelectric photothermal (PPT) spectra is presented. The theory includes computations of the temperature distributions in the samples i.e. the instantaneous temperature, temperature amplitude and phase distributions obtained from the presented temperature distribution equation. Application of the modified Jackson and Amer equation resulted in computations of the amplitude and phase spectra of the piezoelectric signals as a function of the photon energy of the exciting light. The computations of the PPT spectra carried out for the series of semiconductor materials, such as GaAs, InSe and p and n-type Si, led to the new interpretation of the peaks, dips and humps observed in experiments. The inactive layer model and its influence on the interpretation of the PPT spectra is presented and discussed.