4,028 research outputs found
Electromagnetic field application to underground power cable detection
Before commencing excavation or other work where power or other cables may be buried, it is important to determine the location of cables to ensure that they are not damaged. This paper describes a method of power-cable detection and location that uses measurements of the magnetic field produced by the currents in the cable, and presents the results of tests performed to evaluate the method. The cable detection and location program works by comparing the measured magnetic field signal with values predicted using a simple numerical model of the cable. Search coils are used as magnetic field sensors, and a measurement system is setup to measure the magnetic field of an underground power cable at a number of points above the ground so that it can detect the presence of an underground power cable and estimate its position. Experimental investigations were carried out using a model and under real site test conditions. The results show that the measurement system and cable location method give a reasonable prediction for the position of the target cable
Detection and Location of Underground Power Cable using Magnetic Field Technologies
The location of buried underground electricity cables is becoming a major engineering and social issue worldwide. Records of utility locations are relatively scant, and even when records are available, they almost always refer to positions relative to ground-level physical features that may no longer exist or that may have been moved or altered. The lack of accurate positioning records of existing services can cause engineering and construction delays and safety hazards when new construction, repairs, or upgrades are necessary. Hitting unknown underground obstructions has the potential to cause property damage, injuries and, even deaths. Thus, before commencing excavation or other work where power or other cables may be buried, it is important to determine the location of the cables to ensure that they are not damaged during the work. This paper describes the use of an array of passive magnetic sensors (induction coils) together with signal processing techniques to detect and locate underground power cables. The array consists of seven identical coils mounted on a support frame; one of these coils was previously tested under laboratory conditions, and relevant results have been published in [1]. A measurement system was constructed that uses a battery powered data acquisition system with two NI 9239 modules connected to the coil array, and controlled by a laptop. The system is designed to measure the magnetic field of an underground power cable at a number of points above the ground. A 3 by 3 m test area was chosen in one of our campus car parks. This area was chosen because the universityâs utility map shows an isolated power cable there. Measurements were taken with the array in 16 different test positions, and compared with the values predicted for a long straight horizontal cable at various positions. Finally, error maps were plotted for different Z-coordinate values, showing the minimum fitting error for each position in this plane. One such map is shown in Figure 1; the low error values of 4-5% give a high degree of confidence that most of the measured signal is due to a cable near to these positions. This view is supported by the fact that the universityâs utility map shows the cable at X = 1.4 m, and by amplitude measurements taken with a hand-held magnetic field meter
Methanation of CO over Ni catalyst: A theoretical study
Theoretical methods (generalized valenceâbond calculations) were used to examine the bond energies and geometries of numerous species chemisorbed onto Ni clusters representing Ni surface. These results were used to obtain thermochemical information and to examine various mechanisms for the methanation of CO over Ni: CO+3H^(â)_(2(Ni))âCH_4+H_2O. It is found that chemisorbed formyl radicals (NiâCHO) lead to a favorably appearing chain reaction that is consistent with current experimental results. In addition, we find a chemisorbed C_2 species that may be the catalytically active C_(ad) formed from dissociation of CO
SU(3) monopoles and their fields
Some aspects of the fields of charge two SU(3) monopoles with minimal
symmetry breaking are discussed. A certain class of solutions look like SU(2)
monopoles embedded in SU(3) with a transition region or ``cloud'' surrounding
the monopoles. For large cloud size the relative moduli space metric splits as
a direct product AH\times R^4 where AH is the Atiyah-Hitchin metric for SU(2)
monopoles and R^4 has the flat metric. Thus the cloud is parametrised by R^4
which corresponds to its radius and SO(3) orientation. We solve for the
long-range fields in this region, and examine the energy density and rotational
moments of inertia. The moduli space metric for these monopoles, given by
Dancer, is also expressed in a more explicit form.Comment: 17 pages, 3 figures, latex, version appearing in Phys. Rev.
Strings from Gauged Wess-Zumino-Witten Models
We present an algebraic approach to string theory. An embedding of
in a super Lie algebra together with a grading on the Lie algebra determines a
nilpotent subalgebra of the super Lie algebra. Chirally gauging this subalgebra
in the corresponding Wess-Zumino-Witten model, breaks the affine symmetry of
the Wess-Zumino-Witten model to some extension of the superconformal
algebra. The extension is completely determined by the embedding. The
realization of the superconformal algebra is determined by the grading. For a
particular choice of grading, one obtains in this way, after twisting, the BRST
structure of a string theory. We classify all embeddings of into Lie
super algebras and give a detailed account of the branching of the adjoint
representation. This provides an exhaustive classification and characterization
of both all extended superconformal algebras and all string theories
which can be obtained in this way.Comment: 50 pages, LaTe
Cinematic and aesthetic cartographies of subjective mutation
This article exmaines the use of cinema as a mapping of subjective mutation in the work of Deleuze, Gauttari and Berardi. Drawing on Deleuze's distinciton between the reduction of the art-work to the symptom and the idea of art as symptomatology, the article focuses on Berardi's use of cinematic examples, posing the quesiton in each case of to what extent they function as symptomatologies or mere symptoms of cultural and subjective mutations in examples ranging from Bergman's Persona to Van Sant's Elephant to finish on speculations about Fincher's The Social Network as a cirtical engagement with subjective mutation in the 21st Century
Charges, Monopoles and Duality Relations
A charge-monopole theory is derived from simple and self-evident postulates.
Charges and monopoles take an analogous theoretical structure. It is proved
that charges interact with free waves emitted from monopoles but not with the
corresponding velocity fields. Analogous relations hold for monopole equations
of motion. The system's equations of motion can be derived from a regular
Lagrangian function.Comment: 17 pages + 3 figures
The Coset Spin-4 Casimir Operator and Its Three-Point Functions with Scalars
We find the GKO coset construction of the dimension 4 Casimir operator that
contains the quartic WZW currents contracted with completely symmetric SU(N)
invariant tensors of ranks 4, 3, and 2. The requirements, that the operator
product expansion with the diagonal current is regular and it should be primary
under the coset Virasoro generator of dimension 2, fix all the coefficients in
spin-4 current, up to two unknown coefficients. The operator product expansion
of coset primary spin-3 field with itself fixes them completely. We compute the
three-point functions with scalars for all values of the 't Hooft coupling in
the large N limit. At fixed 't Hooft coupling, these three-point functions are
dual to that found by Chang and Yin recently in the undeformed AdS_3 bulk
theory (higher spin gravity with matter).Comment: 65 pages; the ambiguity for the two coefficient functions is
clarified and the abstract, the introduction, the subsection 3.4 and the
conclusion are improved and to appear in JHE
Some properties of unstable monopoles in Super-QCD
We study embeddings of the Prasad-Sommerfield monopole solution in SU(N)
Super-QCD (N>2), where the role of the Higgs field is played by the squarks in
the fundamental representation. Classically, the resulting configurations live
in a phase with unbroken SU(k) subgroups of SU(N) (as a result they are not
topologically stable). The structure of zero modes is such that they can be
naturally interpreted as massive chiral superfields with R charge one and
baryon number zero, transforming in the adjoint representation of a dual gauge
group defined using the Goddard-Nuyts-Olive (GNO) framework. We discuss the
possible applications of these monopoles to N=1 duality, and more generally the
possibility of relating GNO-type dual gauge groups to those appearing in N=1
duality.Comment: 15 pages. harvma
160 MeV Injection into the CERN PSB
The H- beam from the proposed LINAC4 will be injected into the four existing rings of the PS Booster at 160 MeV. A substantial upgrade of the injection region is required, including the modification of the beam distribution system and the construction of a new H- injection system. This paper discusses beam dynamics and hardware requirements and presents the results of optimisation studies of the injection process for different beam characteristics and scenarios. The resulting conceptual design of the injection region is presented, together with the main hardware modifications and performance specifications
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