Narrow Results

In this paper, we study to what extent decidability is connected to universality. A natural context for such a study is provided by the axiomatic theory of computability, automata and algorithms. In Section 2, we introduce necessary concepts, constructions, axioms, postulates, conditions and problems. Section 3 contains the main results of the paper. In particular, it is demonstrated (Theorems 1 and 2) that undecidability of algorithmic problems does not depend on existence of universal algorithms and may be caused by weaker conditions. At the same time, results of Theorems 2 and 3 demonstrate that decidability is incompatible with universality. It is also proved (Theorem 5) that sufficiently big classes of total algorithms/automata, such as the class of all primitive recursive functions, cannot have universal algorithms/automata.

We determine the coefficients of the terms multiplying the gauge fields, gravitational field and cosmological term in a scheme whereby properties are characterized by N anticommuting scalar Grassmann variables. We do this for general N, using analytical methods; this obviates the need for our algebraic computing package which can become quite unwieldy as N is increased.

We develop the general relativity of extended spacetime–property for describing events including their properties. The anticommuting nature of property coordinates, augmenting spacetime (x, t), allows for the natural emergence of generations and for the simple incorporation of gauge fields in the spacetime–property sector. With one electric property, this results in a geometrical unification of gravity and electromagnetism, leading to a Maxwell–Einstein Lagrangian plus a cosmological term. Addition of one neutrinic and three chromic properties should lead to unification of gravity with electroweak and strong interactions.

We demonstrate that the extension of the space–time metric to incorporate two anticommuting property coordinates automatically leads to the unification of gravity with non-Abelian gauge theory, as well as producing a cosmological term.

As an ionic electroactive polymer, ionic polymer metal composite (IPMC) has unique advantages and is widely used in various fields. However, the output force of IPMC is small, which further limits the application of IPMC. In this study, the Nafion520cs were selected as the preparation solution, and three ion-exchange polymer membranes (IEPMs) with different thicknesses (158, 256 and 383 $\mu$m) were designed and prepared successfully by solution casting technique to study the output force. Then, three platinum electrodes-IPMCs (Pt-IPMCs) were fabricated using electroless plating method. The properties of Pt-IPMCs in terms of morphology, displacements and blocking forces were then evaluated under direct current voltage. The results showed that the prepared ionic membranes were uniform, transparent and flat, without accumulation or bubble. The platinum particles were preferably deposited on the surface, which promoted delivery of current through the IPMCs under the applied voltage, and improved the actuation performance. With the increase of voltage, the maximum displacement and maximum blocking force of the three IPMCs increased first and then decreased. When the voltage is 5.5 V, the maximum displacement for 158 um is 26 mm, while the maximum blocking force of 10.74 mN appears at 6.5 V for 383 um. It is necessary to select suitable thickness of IPMCs to adapt to different working environment and field, which provides a strong basis for further application of IPMCs.

Ti and its alloys are considered to be very promising in biological material field. But their biological activity and corrosion resistance in body fluid still need to be improved. As a novel technique for surface treatment, Micro-arc oxidation (MAO) is attracting interest from those who want to improve their implant properties through surface modification. This paper reviewed the application of MAO on biomedical Ti-alloys. The structure characteristic such as surface and cross-section micrographs, phase components, and element distribution were analyzed. The mechanical and biological properties of MAO films were further discussed on this basis. The effects of current density, voltage, and electrolyte on the structure and properties of the films were summarized.

Titanium and titanium alloys are widely used in many fields due to some of their characteristics such as light density, high strength, and excellent corrosion resistance. However, poor mechanical performances limit their practical applications. Laser gas nitriding is a promising method used to improve the surface properties of components. Recent developments on laser gas nitriding of titanium and titanium alloys are reviewed. The processing parameters have important effects on the resulting characteristics of titanium and titanium alloys. The resulting microstructure and properties of laser gas nitrided specimens are presented. The problems to be solved and the prospects in the field of laser gas nitriding of titanium and titanium alloys are discussed.

Micro-arc oxidation (MAO) coatings were prepared on closed-cell aluminum foams. The microstructure, elemental distribution and phase composition of the MAO coatings were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The corrosion resistances and compressive properties of the uncoated and coated aluminum foams were studied by electrochemical polarization test and mechanical test, respectively. The results show that the MAO coatings cover the surfaces of closed-cell aluminum foams. The average thickness of the MAO coatings is 7 μm. The MAO coatings are mainly composed of γ-Al₂O₃ phase. The corrosion resistances of the closed-cell aluminum foams are improved by MAO treatment. The as-received foams show a low corrosion potential (-1.36 V), on contrary, the MAO coated foams get an increase corrosion potential (-0.78 V). But the MAO coated foams show the marginal variation in compressive strengths when the thickness of the coatings could be negligible compared with the total thickness of the foams.

This paper discusses the synthesis and characterization of Ni-TiN nanocoatings prepared by computer-controlled pulsed electrodeposition method. The influence of plating parameters on the microstructure, microhardness, and properties of the coating was investigated using transmission electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy, scanning electron microscopy, and friction wear testing technique. The results showed that the Ni-TiN nanocoating synthesized at 4A/dm² current density exhibited an optimum microhardness and TiN content of 984.7HV and 8.69wt.%, respectively. Ni-TiN nanocoatings prepared at different pulse frequencies grew as face-centered cubic structures along different directions, and average grain diameters of Ni and TiN in the nanocoating prepared at 200Hz were 87.2 and 34.6nm, respectively. The nanocoating prepared at 20% duty cycle showed an optimum microhardness and average wear of 980HV and 7.56mg/mm².

ZnO nanotetrapods were synthesized by microwave plasma. The nanotetrapod structures were imaged to be straight with diameters in the range of 10 to 25 nm and lengths up to 160 nm by transmission electron microscopes (TEM). The dark field images and lattice fringes of high resolution TEM show that the crystal orientation or structure of the core is different from that of the legs. The Auger electron peak of Zn shifts more distinctly to lower energy in the legs, which indicates the degree difference of bond ionicity between the core and leg. Cathodoluminescence spectrum of a single ZnO nanotetrapod is characterized by a stronger ultraviolet emission without broad emission bands in its lower energy side. This result further suggests that ZnO nanotetrapods are free from defects.

in situ Fibril formation of polyamide-6 (PA6) in isotropic polypropylene (iPP) was first fabricated using a slit die extrusion and hot stretching process. Then the prepared materials were subjected to injection molding in the temperature range higher than the melting temperature of iPP but lower than that of PA6. The obtained injection-molded samples were characterized via scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and two-dimensional wide-angle X-ray scattering (2D-WAXS). Mechanical properties were also investigated. The SEM result shows that the optimum fibril formation could be only achieved in the range of 20 wt% to 30 wt% of PA6 content for the studied system. The fibril morphology changes along the sample thickness in the injection-molded bars. The fibril morphology in the skin layer was better than that in the core layer. 2D-WAXS results showed that the orientation of PP decreased with the increase of PA6 content, which indicated that the orientation of PP was confined by PA6 fibrils. Combined consideration of mechanical properties and morphology indicates that only PP/PA6 composites with 20 wt% of PA6 content show better properties because of the better fibril morphology and PP chain orientation.

Expanded nonaromatic stable porphyrins(2.1.2.1) were successfully synthesized by 2,3-di(1H-pyrrol-2-yl)naphthalene as buliding blocks and aromatic aldehydes under acid catalyzed condensation conditions in acceptable isolated yields. NMR, X-ray diffraction analysis, absorption, electrochemical, and density functional theory revealed these macrocycles to be non-aromatic due to highly saddle-shaped molecular structures of dinaphthoporphyrin(2.1.2.1). The saddle-shaped dinaphthoporphyrins(2.1.2.1) with embedded naphthalene units as $\pi$-conjugation units show perturbations to molecular structure, optical and electronic properties. The dinaphthoporphyrins(2.1.2.1) are effective macrocyclic ligands giving copper(II) and nickel(II) complexes.

Fluorinated graphene oxide (FGO) was successfully prepared in this paper, and the chemical structure of FGO was characterized. A series of polyimide (PI) composite films with different content of FGO was prepared by in situ polymerization. Because of the homogeneous dispersion of FGO and the strong interfacial interaction between FGO and the PI matrix, the resulting composite films that contained FGO exhibited effects of mechanical properties, thermal properties and dielectric properties that were even better than the pure PI. Furthermore, due to the hydrophobic properties of FGO, the water absorption of the composite films were reduced. The result showed when the 0.6wt.% FGO was filled into the PI, the tensile strength was increased about 66.3%, the decomposition temperature was increased from 540^∘C to 570^∘C, and the dielectric constant (D_k) decreased with the increasing content of FGO, and a D_k value of 2.28 was achieved when the content of FGO was 1.0wt.%.

Property is one of the important instrumental elements, in the empowerment of women. Matrilineal system in Kerala had privileged Nayar women to inherit property. Inheritance of property rights among Nayar women had undergone dramatic changes during and since the British period. It is difficult to understand the relationship between property and women empowerment as property relations are imbricate and constantly changing. In this paper, I explore how the nature of property influences women empowerment in different regions of Kerala. The sociological contours of property relations of Nayar women are explored to understand how property becomes an agent that helps women to exercise power in the family and bargain within matriliny. The material, cultural and political relations around property need to be reckoned in understanding the power dynamics within the gender relations in Nayar community in Kerala.

ZnO nanotetrapods were synthesized by microwave plasma. The nanotetrapod structures were imaged to be straight with diameters in the range of 10 to 25 nm and lengths up to 160 nm by transmission electron microscopes (TEM). The dark field images and lattice fringes of high resolution TEM show that the crystal orientation or structure of the core is different from that of the legs. The Auger electron peak of Zn shifts more distinctly to lower energy in the legs, which indicates the degree difference of bond ionicity between the core and leg. Cathodoluminescence spectrum of a single ZnO nanotetrapod is characterized by a stronger ultraviolet emission without broad emission bands in its lower energy side. This result further suggests that ZnO nanotetrapods are free from defects.

Three issues on the evolution of software under Internet (SUI), including sense of changes, decision and the execution of evolution, were focused and discussed. And a process-aware framework was proposed to support the implementation of such evolution. In it, the business process model of software can be reedited or changed as required by using a visualized design tool, BPDesigner. And then the updated business process model and its changes can be automatically propagated to process engine. The latter can call the analyzer for changes, an analysis program, to evaluate the scale and status of the changes and, according to the result of evaluation, select the evolving strategy. After that, activity instance scheduler together with change locators can be called to cooperatively implement the process-oriented evolution of SUI by operating the caching sequence of activity and service instances.

In order to study the impact of Mg deoxidation on the inclusions and properties of Low Carbon and Low Alloy Steel, five heats of 5.72%Mg-50.5%A1-7.92Mn-Fe Alloy (AlMnMgFe) deoxidation trails were done during a 150 tons BOF taping at a steelmaking plant. Optical microscope (OM) was used to test the diameter and number of the inclusions. SEM and EDS were used to examine the types of the inclusions. Then the microstructures and properties of the steels were tested at the room temperature. The results show that, by using AlMnMgFe as the deoxidizer, the inclusions, microstructures and properties of the low carbon and low alloy steel Q195 are improved. There are some spherical MgO·Al₂O₃ inclusions in the AlMnMgFe deoxidation heats. The diameters of 97.01 percent inclusions are smaller than 3 µm in the AlMnMgFe deoxidization steel, and it is higher than that of Al-killed steel. The mean yield strength, mean tensile strengths and mean elongation of the AlMnMgFe deoxidization steels are higher than Al-killed steels.

In an article added recently to the Stanford Encyclopedia of Philosophy, Eran Tal notes that “there is little consensus among philosophers as to how to define measurement, what sorts of things are measurable, or which conditions make measurement possible” [1]

The meaning and scope of measurement have been discussed frequently within physical metrology, by David Hand [2], René Dybkaer [3], Rod White [4], Eran Tal [5], Luca Mari et al. [6], Giovanni Rossi [7], Eran Tal [8], and Luca Mari et al. [9], among others. The same issues have also been examined within the social sciences [10], in particular in education [11, 12], psychology [13–15], and sociology [16, 17].

Defining measurement involves identifying its essential characteristics, and specifying the traits that distinguish it from similar activities that ought not to be construed as measurement. Delineating its scope involves determining the classes of properties whose values are measurable.

None of the logical, terminological, historical, or customary-use considerations that might give preeminence to a particular definition of measurement seem to be decisive, for otherwise a consensus about it would have formed already.

For example, a recent survey of its membership, conducted by the ISO/REMCO committee on reference materials, revealed that the metrological community represented in this committee is just about evenly split on whether the assignment of value to qualitative (nominal, or categorical) properties should, or should not be called "measurement."

Defining the meaning of measurement, and circumscribing its scope, therefore involve arbitrary choices, which concern matters of taste, matters of precedence, and matters of convenience. This contribution discusses these choices, and advocates for an inclusive and broad understanding of measurement.

In this investigation, three routes, namely, uniaxial pressing, slip casting and H₂O₂ foaming, were used to fabricate porous hydroxyapatite (HA). Processing parameters in each route were studied, pore characteristics in sintered bodies assessed, and mechanical properties of porous HA evaluated. Scanning electron microscopy, gas pycnometry and mercury intrusion porosimetry were used to assess pore characteristics in terms of porosity, pore size and pore shape. Mechanical properties of porous HA were evaluated using a biaxial testing fixture. The 2³ factorial design method was used to determine the influence of pore characteristics on mechanical properties. It was shown that pore characteristics were dependent on the manufacturing route, processing parameters, porosifier and the amount of porosifier. In the uniaxial pressing and slip casting routes, porosity, pore size and pore shape could be controlled using different porosifiers. Porosifiers were able to pass their geometrical characteristics to the pores they formed. Although H₂O₂ foaming was the simplest route and large pores could be formed through this route, pore characteristics were not easily controllable. It was found that porosity, pore size and pore shape all had effects on mechanical properties of sintered products. The interaction of pore size and pore shape affected mechanical properties in that it caused mechanical properties to vary differently according to pore shape (or pore size) when pore size (or pore shape) was at different levels.

Hydroxyapatite (HA) reinforced high density polyethylene (HDPE) composites (HAPEX™) have been developed as a bone analogue for medical applications. Conventionally processed HAPEX^TM containing 40vol% of HA possesses a stiffness approaching the lower bound of human cortical bone and is now used in minor- or non- load bearing areas in patients. In order to improve the mechanical properties of HAPEX™ and hence extend its application into major load bearing areas, HAPEX™ with various amounts of HA was hydrostatically extruded at different extrusion ratios. The extruded rods were subsequently tested under tension or bending. Their structure as well as fracture surfaces were examined under an SEM. The molecular mass of the HDPE matrix was analyzed at each processing stage. DSC thermograms were also obtained to study the effects of hydrostatic extrusion. It was found that the uniform distribution of HA in the HDPE matrix achieved by compounding was not altered by hydrostatic extrusion, but the average molecular weight of HDPE was reduced. DSC results indicated polymer chain alignment along the extrusion direction. Mechanical properties of HDPE and HAPEX™ were substantially increased by hydrostatic extrusion. It was evident that the higher the extrusion ratio, the stronger and the stiffer the HAPEX™ rod. Hydrostatically extruded HAPEX™ containing 40vol% of HA possessed a Young’s modulus of 11.4GPa and fracture strength of 91.2MPa, which are within the bounds for mechanical properties of human cortical bone. This clearly shows the potential of HAPEX™ for major load bearing applications.