6,334 research outputs found
Bias dependent specic contact resistance of phase change material to metal contacts
Knowledge of contact resistance of phase change materials (PCM) to metal electrodes is important for scaling, device modeling and optimization of phase change random access memory (PCRAM) cells. In this article, we report the systematic determination of the speci_c contact resistance (_c) with voltage bias for doped Sb2Te to TiW metal electrodes. These data are reported for both the amorphous and the crystalline state of the PCM
Impact of sidewalls on electrical characterization
In this article the impact of sidewalls, formed during reactive ion etching, on the electrical behavior of thin film structures is presented. The presence of sidewalls was experimentally characterized by sheet resistance measurements on Van der Pauw structures. The effect of these sidewalls on the extraction of specific contact resistance from Cross Bridge Kelvin Resistance (CBKR) structures is discussed
Gamma-ray spectrometry in the field: Radioactive heat production in the Central Slovakian Volcanic Zone
We report 62 sets of measurements from central-southern Slovakia, obtained using a modern portable gamma-ray spectrometer, which reveal the radioactive heat production in intrusive and extrusive igneous rocks of the Late Cenozoic Central Slovakian Volcanic Zone. Sites in granodiorite of the Štiavnica pluton are thus shown to have heat production in the range ~ 2.2–4.9 μW m− 3, this variability being primarily a reflection of variations in content of the trace element uranium. Sites in dioritic parts of this pluton have a lower, but overlapping, range of values, ~ 2.1–4.4 μW m− 3. Sites that have been interpreted in adjoining minor dioritic intrusions of similar age have heat production in the range ~ 1.4–3.3 μW m− 3. The main Štiavnica pluton has zoned composition, with potassium and uranium content and radioactive heat production typically increasing inward from its margins, reflecting variations observed in other granodioritic plutons elsewhere. It is indeed possible that the adjoining dioritic rocks, hitherto assigned to other minor intrusions of similar age, located around the periphery of the Štiavnica pluton, in reality provide further evidence for zonation of the same pluton. The vicinity of this pluton is associated with surface heat flow ~ 40 mW m− 2 above the regional background. On the basis of our heat production measurements, we thus infer that the pluton has a substantial vertical extent, our preferred estimate for the scale depth for its downward decrease in radioactive heat production being ~ 8 km. Nonetheless, this pluton lacks any significant negative Bouguer gravity anomaly. We attribute this to the effect of the surrounding volcanic caldera, filled with relatively low-density lavas, ‘masking’ the pluton's own gravity anomaly. We envisage that emplacement occurred when the pluton was much hotter, and thus of lower density, than at present, its continued uplift, evident from the local geomorphology, being the isostatic consequence of localized erosion. The heat production in this intrusion evidently plays a significant role, hitherto unrecognized, in the regional geothermics
SAWdoubler: a program for counting self-avoiding walks
This article presents SAWdoubler, a package for counting the total number
Z(N) of self-avoiding walks (SAWs) on a regular lattice by the length-doubling
method, of which the basic concept has been published previously by us. We
discuss an algorithm for the creation of all SAWs of length N, efficient
storage of these SAWs in a tree data structure, and an algorithm for the
computation of correction terms to the count Z(2N) for SAWs of double length,
removing all combinations of two intersecting single-length SAWs.
We present an efficient numbering of the lattice sites that enables
exploitation of symmetry and leads to a smaller tree data structure; this
numbering is by increasing Euclidean distance from the origin of the lattice.
Furthermore, we show how the computation can be parallelised by distributing
the iterations of the main loop of the algorithm over the cores of a multicore
architecture. Experimental results on the 3D cubic lattice demonstrate that
Z(28) can be computed on a dual-core PC in only 1 hour and 40 minutes, with a
speedup of 1.56 compared to the single-core computation and with a gain by
using symmetry of a factor of 26. We present results for memory use and show
how the computation is made to fit in 4 Gbyte RAM. It is easy to extend the
SAWdoubler software to other lattices; it is publicly available under the GNU
LGPL license.Comment: 29 pages, 3 figure
Developing an e-infrastructure for social science
We outline the aims and progress to date of the National Centre for e-Social
Science e-Infrastructure project. We examine the challenges faced by the project, namely in
ensuring outputs are appropriate to social scientists, managing the transition from research
projects to service and embedding software and data within a wider infrastructural
framework. We also provide pointers to related work where issues which have ramifications
for this and similar initiatives are being addressed
What constitutes authorship?
For most authors of scientific papers, writing is a struggle. Crisp Introductions, clear Methods, and informative Results and Discussion sections are usually produced only after discarded drafts and with help from colleagues. But sometimes the greatest anxiety is associated with writing the cover page, because it is there that the authors are named
Random Lens Imaging
We call a random lens one for which the function relating the input light ray to the output sensor location is pseudo-random. Imaging systems with random lensescan expand the space of possible camera designs, allowing new trade-offs in optical design and potentially adding new imaging capabilities. Machine learningmethods are critical for both camera calibration and image reconstruction from the sensor data. We develop the theory and compare two different methods for calibration and reconstruction: an MAP approach, and basis pursuit from compressive sensing. We show proof-of-concept experimental results from a random lens made from a multi-faceted mirror, showing successful calibration and image reconstruction. We illustrate the potential for super-resolution and 3D imaging
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