2,414 research outputs found
Random and exhaustive generation of permutations and cycles
In 1986 S. Sattolo introduced a simple algorithm for uniform random
generation of cyclic permutations on a fixed number of symbols. This algorithm
is very similar to the standard method for generating a random permutation, but
is less well known.
We consider both methods in a unified way, and discuss their relation with
exhaustive generation methods. We analyse several random variables associated
with the algorithms and find their grand probability generating functions,
which gives easy access to moments and limit laws.Comment: 9 page
Characterization of coal products from high temperature processing of Usibelli low-rank coals
This research project was conducted in association with Gilbert/Commonwealth
Inc. as part of an overall techno-economic assessment of high temperature drying of low-rank coals. This report discusses the characteristics of the dried/pyrolyzed products of two high temperature, evaporative processes and the dried product from a hydrothermal process. The long term goal of this and other coal drying studies conducted at MIRL, was to define drying technologies that have significant and real potential to competitively move Alaska's, low-rank coals (LRCs) into the export, steam coal market of the Pacific Rim. In 1990, Japan imported 33 million metric tons (mt) of steam coal with an additional 39 million mt imported by other Far East nations(2). Australia dominates the export steam coal market to these Pacific Rim countries and exported 48 million mt in 1990 and an additional 61 million mt of metallurgical coal(2). The worldwide steam coal export market has been expanding rapidly, from 20
million mt in 1973 to 150 million mt in 1989, and is expected to double to nearly 300
million mt by the end of the century(3). Could Alaska capture only 3% of the projected
new world steam coal market, which is not an unreasonable expectation, the value of the
state's coal exports would soar from nominally 100 million per year. However, without development of economical methods for drying/stabilizing Alaskan LRCs, the only increase in export of Alaskan coals may be from the few "higher rank" coals within a "reasonable" transport range of the existing Alaska rail system or tidewater. Presently the coal from the Usibelli Coal Mine is the only low-rank coal exported internationally as a steam coal; primarily for its blending properties with other coal to improve combustion. But for Alaskan low-rank coals to truly stand on their own merits, economical drying processes must be developed that produce a physically and chemically stable dried product. The technologies that have the most potential for increasing the use of Alaskan coals
are those that can reduce the moisture content of these coals economically, and produce a fuel that is accepted in the international market place. Drying technologies will no doubt differ, depending on the end use of the fuel; be it dried lump coal, briquettes or pellets for pulverized coal or stoker applications, or concentrated coal-water fuels made from hot water dried LRCs. There are a number of developing processes that may work with Alaskan coals. Some drying processes, however, have been plagued by the production of excessive amounts of coal fines, Since the demand for Alaskan coal is currently limited to lump size coal, large quantities of fines are a definite liability. In this study, two high temperature drying/pyrolysis processes and one hydrothermal process were investigated. The high temperature drying/pyrolysis processes were conducted at (1) the Western Research Institute, (WRI) an affiliate of the University of Wyoming Research Corporation, Laramie, WY, and (2) Coal Technology Corporation (CTC) of Brisol, VA. Hydrothermal processing was conducted at MIRL, University of Alaska Fairbanks. A summary of these processes and the products they produced follows.The University of Alaska also provided matching funds for this project, which was a portion of a larger study that leveraged U.S. Department of Energy funds
Spacetime and Euclidean Geometry
Using only the principle of relativity and Euclidean geometry we show in this
pedagogical article that the square of proper time or length in a
two-dimensional spacetime diagram is proportional to the Euclidean area of the
corresponding causal domain. We use this relation to derive the Minkowski line
element by two geometric proofs of the "spacetime Pythagoras theorem".Comment: 11 pages, 9 figures; for a festschrift honoring Michael P. Ryan; v.2:
References to related work adde
Dawn of the amphora: the emergence of maritime transport jars in the Early Bronze Age Aegean
In the early part of the Early Bronze (EB) II period, the Aegean world sees the appearance of
the collared jar, the first ceramic Maritime Transport Container (MTC) of the region. Based
on a study and scientific analyses of hundreds of EB II transport jars, focusing on the harbour
towns of Poros-Katsambas on Crete, Akrotiri on Thera and Ayia Irini on Kea, we identify some
of the key production areas in both the Cyclades (Kea, Siphnos, Melos, Naxos, Thera) and
on mainland Greece (Attica). In addition to surveying the spatial and temporal distribution
of these EB II jar types at a number of key Aegean coastal sites, we consider the high value
liquid commodity being transported and exchanged in these jars, and suggest wine as a likely
candidate. We argue that the emergence of the transport jar in EB II should be viewed as part
of the same phenomenon as the outburst of pouring and drinking vessels in contemporary
Aegean contexts, all evidence for new social practices of drinking and feasting in the private
and public spheres
Using a task-based approach in evaluating the usability of BoBIs in an e-book environment
This paper reports on a usability evaluation of BoBIs (Back-of-the-book Indexes) as searching and browsing tools in an e-book environment. This study employed a task-based approach and within-subject design. The retrieval performance of a BoBI was compared with a ToC and Full-Text Search tool in terms of their respective effectiveness and efficiency for finding information in e-books. The results demonstrated that a BoBI was significantly more efficient (faster) and useful compared to a ToC or Full-Text Search tool for finding information in an e-book environment
Radio Source Heating in the ICM: The Example of Cygnus A
One of the most promising solutions for the cooling flow problem involves
energy injection from the central AGN. However it is still not clear how
collimated jets can heat the ICM at large scale, and very little is known
concerning the effect of radio lobe expansion as they enter into pressure
equilibrium with the surrounding cluster gas. Cygnus A is one of the best
examples of a nearby powerful radio galaxy for which the synchrotron emitting
plasma and thermal emitting intra-cluster medium can be mapped in fine detail,
and previous observations have inferred possible shock structure at the
location of the cocoon. We use new XMM-Newton observations of Cygnus A, in
combination with deep Chandra observations, to measure the temperature of the
intra-cluster medium around the expanding radio cavities. We investigate how
inflation of the cavities may relate to shock heating of the intra-cluster gas,
and whether such a mechanism is sufficient to provide enough energy to offset
cooling to the extent observed.Comment: To appear in the Proceedings of "Heating vs. Cooling in Galaxies and
Clusters of Galaxies", August 2006, Garching (Germany), Eds. H. Boehringer,
G.W. Pratt, A. Finoguenov, P. Schuecker, Springer-Verlag series "ESO
Astrophysics Symposia", p.101, in press. 8 pages, 3 multiple figure
Characterisation of Kenana cattle at Um Banein, Sudan
Results of a study carried on the reproductive performance, herd management, weight & growth, milk production & mortality of Kenana cattle at Um Banein Livestock Research Station (Sudan)
Further Comparison between ATNoSFERES and XCSM
International audienceIn this paper we present ATNoSFERES, a new framework based on an indirect encoding Genetic Algorithm which builds finite-state automata controllers able to deal with perceptual aliazing. In the context of our ongoing line of research, we compare it with XCSM, a memory-based extension of the most studied Learning Classifier System, XCS, through two benchmark experiments. We focus in particular on internal state generalization, and add special purpose features to ATNoSFERES to fulfill that comparison. We then discuss the role played by internal state generalization in the experiments studied
Babesia, Theileria and Anaplasma spp. infecting sable antelope, Hippotragus niger (Harris, 1838), in southern Africa
Some observations are recorded on blood parasites of sable antelopes. Blood smears of 124 of these antelopes from South Africa and Zimbabwe were examined and 7 were found to be positive for a Babesia sp., identified as Babesia irvinesmithi Martinaglia 1936. A total of 70 of the smears were positive for Theilerial piroplasms, while 1 smear had macroschizonts (with cytomeres) and microschizonts of a Theileria (=Cytauxzoon)
sp. One blood smear was positive for an Anaplasma sp. Attempts to isolate the Babesia sp. by subinoculating blood from sable to splenectomized and intact sable and splenectomized cattle were unsuccessful. Attempts to infect sable with Babesia bovis and Babesia bigemina were likewise unsuccessful. Theilerial piroplasms reached high levels in a splenectomized sable but could not be transmitted with blood to cattle. The Anaplasma sp. was found to be infective for sheep but not for cattle.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
Quantum interference in nanofractals and its optical manifestation
We consider quantum interferences of ballistic electrons propagating inside
fractal structures with nanometric size of their arms. We use a scaling
argument to calculate the density of states of free electrons confined in a
simple model fractal. We show how the fractal dimension governs the density of
states and optical properties of fractal structures in the RF-IR region. We
discuss the effect of disorder on the density of states along with the
possibility of experimental observation.Comment: 19 pages, 6 figure
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