3,545 research outputs found
Pressure dependence of the superconducting transition temperature in CYb and CCa
We have studied the evolution, with hydrostatic pressure, of the recently
discovered superconductivity in the graphite intercalation compounds CYb
and CCa. We present pressure-temperature phase diagrams, for both
superconductors, established by electrical transport and magnetization
measurements. In the range 0-1.2 GPa the superconducting transition temperature
increases linearly with pressure in both materials with
and for CYb and CCa respectively. The
transition temperature in CYb, which has beenmeasured up to 2.3 GPa,
reaches a peak at around 1.8 GPa and then starts to drop. We also discuss how
this pressure dependence may be explained within a plasmon pairing mechanism.Comment: 4 pages, 3 figure
Approximation Algorithms for the Max-Buying Problem with Limited Supply
We consider the Max-Buying Problem with Limited Supply, in which there are
items, with copies of each item , and bidders such that every
bidder has valuation for item . The goal is to find a pricing
and an allocation of items to bidders that maximizes the profit, where
every item is allocated to at most bidders, every bidder receives at most
one item and if a bidder receives item then . Briest
and Krysta presented a 2-approximation for this problem and Aggarwal et al.
presented a 4-approximation for the Price Ladder variant where the pricing must
be non-increasing (that is, ). We present an
-approximation for the Max-Buying Problem with Limited Supply and, for
every , a -approximation for the Price Ladder
variant
System Identification Methods for Aeroelastic Rotor Models. G.U. Aero Report 9507
No abstract available
Experiments in the automatic marking of ER-Diagrams
In this paper we present an approach to the computer understanding of diagrams and show how it can be successfully applied to the automatic marking (grading) of student attempts at drawing entity-relationship (ER) diagrams. The automatic marker has been incorporated into a revision tool to enable students to practice diagramming and obtain feedback on their attempts
Finding a state in a haystack
We consider the problem to single out a particular state among
orthogonal pure states. As it turns out, in general the optimal strategy is not
to measure the particles separately, but to consider joint properties of the
-particle system. The required number of propositions is . There exist
equivalent operational procedures to do so. We enumerate some
configurations for three particles, in particular the
Greenberger-Horne-Zeilinger (GHZ)- and W-states, which are specific cases of a
unitary transformation For the GHZ-case, an explicit physical meaning of the
projection operators is discussed.Comment: 11 page
Using patterns in the automatic marking of ER-Diagrams
This paper illustrates how the notion of pattern can be used in the automatic analysis and synthesis of diagrams, applied particularly to the automatic marking of ER-diagrams. The paper describes how diagram patterns fit into a general framework for diagram interpretation and provides examples of how patterns can be exploited in other fields. Diagram patterns are defined and specified within the area of ER-diagrams. The paper also shows how patterns are being exploited in a revision tool for understanding ER-diagrams
Camera trap distance sampling for terrestrial mammal population monitoring: lessons learnt from a UK case study
Accurate and precise density estimates are crucial for effective species management and conservation. However, efficient monitoring of mammal densities over large spatial and temporal scales is challenging. In the United Kingdom, published density estimates for many mammals, including species considered to be common, are imprecise. Camera trap distance sampling (CTDS) can estimate densities of multiple species at a time and has been used successfully in a small number of studies. However, CTDS has typically been used over relatively homogeneous landscapes, often over large time scales, making monitoring changes (by repeating surveys) difficult. In this study, we deployed camera traps at 109 sites across an area of 2725 km2 of varied habitat in North-East England, United Kingdom. The 4-month survey generated 51 447 photos of wild mammal species. Data were sufficient for us to use CTDS to estimate the densities of eight mammal species across the whole-survey area and within four specific habitats. Both survey-wide and habitat-specific density estimates largely fell within previously published density ranges and our estimates were amongst the most precise produced for these species to date. Lower precision for some species was typically due to animals being missed by the camera at certain distances, highlighting the need for careful consideration of practical and methodological decisions, such as how high to set cameras and where to left-truncate data. Although CTDS is a promising methodology for determining densities of multiple species from one survey, species-specific decisions are still required and these cannot always be generalized across species types and locations. Taking the United Kingdom as a case study, our study highlights the potential for CTDS to be used on a national scale, although the scale of the task suggests that it would need to be integrated with a citizen science approach
High modulation bandwidth of semipolar (11–22) InGaN/GaN LEDs with long wavelength emission
Visible light communication requires III-nitride LEDs with a high modulation bandwidth but have c-plane limitations. General illumination requires green/yellow III-nitride LEDs with high optical efficiency that are difficult to achieve on c-plane substrates. Micro-LEDs with a low efficiency are used to obtain a high modulation bandwidth. This paper demonstrates a record modulation bandwidth of 540 MHz for our semipolar green LEDs with a broad area. Semipolar yellow and amber LEDs with modulation bandwidths of 350 and 140 MHz, respectively, have also been reported, and are the longest wavelength III-nitride LEDs. These results agree with differential carrier lifetime measurements
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