48 research outputs found
Evaluation of some algorithms and programs for the computation of integer-order Bessel functions of the first and second kind with complex arguments
No full textThe purpose of this article is to provide some insight on the efficiency and accuracy of a few available algorithms for the computation of integer-order Bessel functions. First, the computation of integer-order Bessel functions of the first kind (Jn(z)), using the Fast Fourier Transform (FFT) algorithm as opposed to recurrence techniques, is investigated. It is shown that recurrence techniques are superior to the FFT technique, both in accuracy and speed efficiency. Second, an erroneous algorithm, suggested in the literature and used by commercially available software, specially MATLAB 3.5 and MATHEMATICA 1.2, for computing integer-order Bessel functions of the second kind (Yn(z)), is revealed by comparing these routines with an algorithm developed by the author. Catastrophic errors result from the use of the erroneous algorithm, for the computation of large orders with non-real arguments.Articl
Final year engineering students and staff, University of Stellenbosch, 1955
No full textBlack and white photograph of staff and students.Front row: A. Coetsee, A.P. Barnard, L.I. Toerien, J.A. Gilmore, Prof. J.M. le Roux, Prof. R.L. Straszacker, Prof. A. Heydorn, J.J. Sippel, A.J. de Villiers, Dr. S.R.F. Göldner, J.F. Uys, B. Giljam, C.L. Olën, G.F. Loedolff
2nd row: P.J. Botes, L.W. Fourie, J.J. du Toit, J.K. du Toit, B.L. Haussmann, J.W.R. de Villiers, C.J. Calitz, N. Hamman, A.J. de Wet, H.A.L. Louw, C.F. Geyer, M.J.J. Slabber, P.J. Endemann
3rd row: K.V. Collen, C.P. Krige, D.P. Liebenberg, J.F. Rauch, W.C. Viljoen, P.W. Labuscagne, A.M. Adendorff, F.J. du Toit, C.F. Naude, N. de V. Loubser, A.F. Viljoen, A.P. Retief, D.F. van der Merwe
Back row: J.P. de K. Mostert, J.H. van der Merwe, M.N. Marais, H.P. Bartel, P.A. van der Westhuizen
Absent: W. Steenkamp, Prof. R. Truter, W.J.F.S. Lutsch
Pretoriana, no. 031, Dec. 1959
No full textp. 23 follows on p. 13.Our indebtedness to Dr. Punt / J.H. Davies -- Dr. W. Punt en die Genootskap Oud-Pretoria / F.J.du Toit Spies -- Dr. Willem Punt as onderwysman / C.F. Hendrikz -- Ons nuwe voorsitter se waardering vir die werk van Dr. Punt / G.W. Eybers -- Dr. en mev. I.M. Meyer : in memoriam / A.J. Roode -- God spreek deur hulle dood / D.J. Viljoen -- Huldigingsrede oor wyle dr. en mev. I.M. Meyer / R.E. Lighton -- Huldigingswoorde tydens onthulling van gedenkplaat op rots / J.J. Mulder -- Onthulling van die naamplaat van Huis Meyer / E.C. Steyn -- Boodskap aan die personeellede van die Onderyskollege, Pretoria / R.S. Meyer -- Genootskap Oud-Pretoria jaarverslag 1959 = Association Old Pretoria annual report 195
Bessel functions J n (z) and Y n (z) of integer order and complex argument
No full textAbstract
This paper describes computer subroutines which were developed to compute Bessel functions of the first and second kind (J_n (z) and Y_n (z), respectively) for a complex argument z and a range of integer orders. A novel way of determ ining the starting point of backward recurrence is used, and the algorithm for Y_n (z) improves on previous algorithms in terms of accuracy and restrictions on the range of orders.
Title of program: BESCJY
Catalogue Id: ACPH_v1_0
Nature of problem
Bessel functions arise in the mathematical solution of physical problems, formulated in cylindrical and spherical coordinate systems. The CBESJY subroutine computes Jn(z) and Yn(z) for complex argument z and a sequence of integer orders n from M to N, where N >= 1 and M <= 0.
Versions of this program held in the CPC repository in Mendeley Data
ACPH_v1_0; BESCJY; 10.1016/0010-4655(93)90153-4
This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019
DIELECTRIC LOADING OF A SMALL RIDGED CAVITY-BACKED SLOT ANTENNA.
No full textThe effects are studied of dielectric loading on the frequency of operation, input impedance, and aperture field distribution of a ridged, cavity-backed slot antenna. The transverse slot is cut in the flat broadwall of a deep, single-ridge waveguide cavity, when the cavity is excited by the center conductor of a coaxial transmission line. The role of the input-probe position in matching the antenna is demonstrated. The experimental parameters are summarized in tabular form. It is concluded that dielectric loading reduces the operating frequency and improves the slot aperture efficiency. The input impedance level is controlled by the probe position. A lossy dielectric increases bandwidth (reduces Q) at the expense of efficiency.Conference Pape
The computation of antenna electromagnetic fields at nonasymptotic distances from cylindrical near-field measurements
No full text
The computation of antenna electromagnetic fields at nonasymptotic distances from cylindrical near-field measurements
No full textA technique for the determination of the electric field at arbitrary points in the space surrounding an antenna is described. The cylindrical modal expansion formulation of the electric field can be evaluated using A. C. Ludwig's (1968) algorithm after the factorization of the integrands into slowly and rapidly changing factors. The latter is achieved by factorizing the Hankel functions in the integrands using an asymptotic approximation. The modal coefficients of an E-plane sectoral horn were computed from cylindrical near-field measurements at 3 GHz. Using the method described, the copolarized electric field was computed in the E-plane at distances of 1 and 10 m from the antenna. It is concluded that the method can be used successfully to compute the electric field in the radiating near field and further.Conference Pape
Ridged cavity backed slot antenna with dielectric loading
No full textA reduced size cavity backed slot antenna, consisting of a transverse slot in the flat broadwall of a deep single ridge waveguide cavity is described. Partial dielectric loading achieves further reduction in electrical size. Moderate dielectric loss increases bandwidth (and reduces antenna gain).Articl
