Electrical conductivity of α-H x V2O5 (X=0.00-0.27): Dependence of hydrogen concentration and orientation

The dependence of the electrical conductivity, , on the hydrogen concentration and crystallographic orientation has been investigated using single crystals of H_xV₂O₅, which were grown by the Bridgeman method and doped with hydrogen within the solid solubility in the phase by the spillover technique. The temperature dependence of showed the feature of diffusive hopping of thermally activated electrons above 180 K and variable range hopping below 180 K. The dependence of on the crystallographic orientation was little different from that of V₂O₅. The change in with the hydrogen concentration was not monotonic; increases withx up tox }-0.06, but decreases abovex }-0.06. This behaviour can be explained based on the competition between the increase in the carrier density and the depression of the mobility of carriers with increasingx.     

Crystal structure and hydrogen occupation in H x V2O5(x=0.0–3.9)

Changes in the crystal structure and the lattice constants of powdered crystalline V₂O₅ after absorption of hydrogen were measured, as a function of the concentration, by X-ray diffractometry. The diffraction spectra obtained showed that three kinds of phases, (x<0.4 in H _x V₂O₅), (co-existing with either terminal phase in the range of 0.4x<3.2) and (3.2x3.9), appear up tox=3.9, which was found to be the upper limit of the absorption at 70C under a hydrogen pressure of 5 MPa. The crystal system of the three phases was determined to be orthorhombic, although the lattice constants differed. The diffraction lines were broadened, and the background of the X-ray spectra grew with hydrogenation, especially in the -region, which indicates the growth of the lattice distortion and a quasi-amorphous state. The occupation of hydrogen atoms in each phase is discussed on the basis of the experimental results.     

A non-parametric free-form optimization method for shell structures

This paper presents a numerical shape optimization method for the optimum free-form design of shell structures. It is assumed that the shell is varied in the out-of-plane direction to the surface to determine the optimal free-form. A compliance minimization problem subject to a volume constraint is treated here as an example of free-form design problem of shell structures. This problem is formulated as a distributed-parameter, or non-parametric, shape optimization problem. The shape gradient function and the optimality conditions are theoretically derived using the material derivative formulae, the Lagrange multiplier method and the adjoint variable method. The negative shape gradient function is applied to the shell surface as a fictitious distributed traction force to vary the shell. Mathematically, this method is a gradient method with a Laplacian smoother in the Hilbert space. Therefore, this shape variation makes it possible both to reduce the objective functional and to maintain the mesh regularity simultaneously. With this method, the optimal smooth curvature distribution of a shell structure can be determined without shape parameterization. The calculated results show the effectiveness of the proposed method for the optimum free-form design of shell structures.     

Effects of microwave treatment on the oxidative stability of peanut (Arachis hypogaea) oils and the molecular species of their triacylglycerols

Peanut seeds (Arachis hypogaea) were roasted for 6, 12, 20, or 30 min at a frequency of 2450 MHz using a microwave oven. The quality characteristics and the compositions of the oils, i.e. their tocopherol distributions and the molecular species of the triacylglycerols (TAGs) were investigated. These results were compared with those of an unroasted oil sample. Only minor increases (p <0.05) in chemical and physical properties of the oils, such as the carbonyl value, the p‐anisidine value and the color development occurred after a prolonged roasting period. Compared to the original level, more than 92 wt‐% tocopherols remained after 30 min of roasting. A modified thin‐layer chromatography argentation procedure provided 12 different groups of TAGs, based on both the degrees of unsaturation and the total fatty acid chain‐length. Although significant increases (p <0.05) generated in these chemical and physical changes of the oils after 20 min of roasting, no significant loss (p >0.05) was observed in the molecular species of the TAGs during microwave roasting. These results indicate that phospholipids may be attributed to the quality characteristics of peanut oils during microwave roasting.     

An analysis of expression data using a support vector machine and dimensional reduction methods

Gene expression data are expected to be a significant aid in the development of efficient cancer diagnosis and classification platforms. However, gene expression data are high-dimensional and the number of samples is small in comparison to the dimensions of the data. Furthermore, the data are inherently noisy. Therefore, in order to improve the accuracy of the classifiers, we would be better off reducing the dimensionality of the data. As a method of dimensionality reduction, there are two previous proposals: feature selection and dimensionality reduction. Feature selection is a feedback method which incorporate the classifier algorithm in the future selection process. Dimensionality reduction refers to algorithms and techniques which create new attributes as combinations of the original attributes in order to reduce the dimensionality of a data set. In this article, we compared the feature selection methods and the dimensionality reduction methods, and verified the effectiveness of both types. For the feature selection methods we used one previously known method and three proposed methods, and for the dimensionality reduction methods we used one previously known method and one proposed method. From an experiment using a benchmark data set, we confirmed the effectiveness of our proposed method with each type of dimensional reduction method.     

Pyrolysis of Poly(isopropyliminoalane) to Aluminum Nitride

The pyrolysis processes of poly(isopropyliminoalane) ((HAlN ⁱ Pr) _n ) were investigated, using mass spectrometry to analyze the gases and infrared spectroscopy to analyze the residual solids. The major mass loss (in the temperature range of 240°–540°C) consisted of two different pyrolysis stages. At the first stage (240°–320°C), (HAlN ⁱ Pr)₆ was detected continuously as a gas, and the precursor was converted to a cross-linked structure. A polymerization mechanism without a release of organic compounds has been proposed, and the formation of (HAlN ⁱ Pr)₆ during polymerization (besides its evaporation) has been suggested. The second stage (320°–560°C) involved the formation of various organic compounds, and radical processes for their formation were proposed.     

Error analysis of drill point geometry inspection using radial-view silhouette images

The conical ground drill point geometry can be described by five parameters, which are measured with the simple inspection method using radial-view silhouette images. This paper deals with error analysis of the inspection method. Different types of errors may occur while taking radial-view silhouette images of the drill point geometry. All possible setup errors have been considered and deviations from the true values of the geometrical parameters have been calculated. The sensitivities of the geometrical parameters and common angular parameters of the drill with the errors have been analyzed to develop a practical apparatus of the inspection system.     

Compression of poly(vinyl alcohol) gels by ultracentrifugal forces

Compression due to ultracentrifugal forces was investigated for poly(vinyl alcohol) (PVA) gels. The concentration gradient profiles for the gels were obtained by experiment and were then compared with a theoretical prediction. By the application of the centrifugal forces, the concentration gradient near the bottom increases sharply whereas the gradient inside the gel remains almost constant in the region far from the bottom. Further application of the centrifugal forces enhances the peak near the bottom. These are well explained by the theory proposed in the previous paper [Urayama et al. J Chem Phys 2005;122:024906.]. The frictional coefficient f for the PVA gels, which originates from the friction between the polymer network and solvent molecules, is estimated to be 3.5×10¹⁴ N s m⁻⁴.