Electrical Properties of GeO2–NiO Materials Containing Ni2GeO4

The GeO₂–NiO system is studied in the stability range of Ni₂GeO₄ by temperature-dependent resistivity measurements, in combination with x-ray diffraction, differential thermal analysis, and thermogravimetry. The resistivity of the starting mixtures and heat-treated samples is measured in the composition range 55–90 mol % NiO. The effect of air humidity on the resistivity of the samples is examined.     

A multigrid accelerated hybrid unstructured mesh method for 3D compressible turbulent flow

 A cell vertex finite volume method for the solution of steady compressible turbulent flow problems on unstructured hybrid meshes of tetrahedra, prisms, pyramids and hexahedra is described. These hybrid meshes are constructed by firstly discretising the computational domain using tetrahedral elements and then by merging certain tetrahedra. A one equation turbulence model is employed and the solution of the steady flow equations is obtained by explicit relaxation. The solution process is accelerated by the addition of a multigrid method, in which the coarse meshes are generated by agglomeration, and by parallelisation. The approach is shown to be effective for the simulation of a number of 3D flows of current practical interest. Sponsored by The Research Council of Norway, project number 125676/410 Dedicated to the memory of Prof. Mike Crisfield, a respected colleague     

Measurements of small-scale fading and path loss for long range RF tags

RF modulated backscatter (RFMB), also known as modulated radar cross section or sigma modulation, is a RF transmission technique useful for short-range, low-data-rate applications, such as nonstop toll collection, electronic shelf tags, freight container identification and chassis identification in automobile manufacturing, that are constrained to have extremely low power requirements. The small-scale fading observed on the backscattered signal has deeper fades than the signal from a traditional one-way link of the same range in the same environment because the fading on the backscattered signal is the product of the fading on the off-board-generated carrier times the fading on the reflected signal. This paper considers the continuous wave (CW) type of RFMB, in which the interrogator transmitter and receiver antennas are different. This two-way link also doubles the path loss exponent of the one-way link. This paper presents the cumulative distribution functions for the measured small-scale fading and the measured path loss for short ranges in an indoor environment at 2.4 GHz over this type of link.     

Catalytic aminolysis of epoxide by alumina prepared from amine-protected Al precursor

The catalytic activities of alumina prepared from an Al alkoxide-amine adduct monomer for the reaction of cyclopentene oxide with piperidine was determined after various pretreatments, including calcination and exposure to moisture. They were compared with the activity of alumina prepared by the conventional hydrolysis method. It was found that the as-prepared sample from the alkoxide-amine monomer preparation was five times more active than a conventional preparation, suggesting that it has a higher density of surface Lewis acid sites. However, its activity was much more severely suppressed by exposure to moisture.     

Citation patterns in the Kuwaiti journal Medical Principles and Practice: The first 12 years, 1989-2000

This study investigates the citation patterns in the journal, Medical Principles and Practice from its inception in 1989 through 2000 (volumes 1-9). The data set includes 4740 references appended to the 221 original research articles. All of the citations were entered into a ProCite database for analysis. Specifically, this study addresses: (1) bibliometric patterns of cited works in terms of publication format, subject scatter, authorship characteristics, age of citations, geographic distribution, and language distribution; (2) productivity of journal titles; (3) the role of self-citation; and (4) how selected bibliometric indicators apply. Some of the findings include: journal articles are most frequently cited; English language publications dominate the literature; there is a trend of multiple authorship; and the pattern of aging is below the norm for medical literature. The results of the study can provide a benchmark to measure the user behavior of a particular group of researchers as well as for the provision of collection development and management decisions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Tunneling Conductance Dependence of the Tunneling Spectra in Bi2Sr2CaCu2O8

We have measured the tunneling spectra in Bi₂Sr₂CaCu₂O₈ with a scanning tunneling microscope(STM) at various tip-sample distances by changing the tunneling conductance in a controlled manner. When the tunneling conductance is increased from 1×10^–9 to 1×10^–5 S, the spectra do not show changes in particular. However, the gap value decreases steeply and the asymmetric back ground density of states turns inverted V-shaped one above 6×10^–4 S. The changes in the tunneling spectra at the high tunneling conductances are explained by the enhancement of the local carrier density induced by the pressure that the STM tip applied to the sample.