Browsing by Author "WANG, JH"

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A PRECISION EXPERIMENT ON ELECTRONS, PHOTONS AND MUONS AT LHC
(1993-02-01)
AZIZ, T
;
BOCK, R
;
BRAUNSCHWEIG, W
;
GEULIG, E
;
HILGERS, K
We describe the upgrade of the L3 detector for running at LHC. The principle goals are the precise measurement of electrons, photons and muons.
CORROSION BEHAVIOR OF ELECTROLESS NICKEL-PLATING MODIFIED TIN COATING
(1993-09-01)
DOONG, JC
;
DUH, JG
;
TSAI, SY
;
WANG, JH
;
CHIOU, BS
TiN films were prepared by reactive r.f. magnetron sputtering on low carbon steel substrates. An electroless Ni-P plating was introduced as the interlayer in the modification of the TiN coating. The corrosion behaviour of the TiN coating assembly was evaluated using the salt spray test and the polarization technique. For a thicker Ni-P interlayer (greater than 5 mum), no appreciable corrosion was observed up to hundreds of hours after salt spray testing. The polarization curve indicates a barrier-type passive film in the TiN/Ni3P/Fe coating assembly. The corrosion currents for TiN/Fe, Ni3P/Fe and TiN/Ni3P/Fe are 200, 40-70 and 6-7 muA cm-2 respectively. It appears that the electroless Ni-P interlayer modified TiN coating has better anticorrosion resistance than pure TiN coating on low carbon steel.
DIFFERENCE AND SIMILARITY MODELS OF 2 IDEMPOTENT OPERATORS
(1994-09-01)
WANG, JH
;
WU, PY
;
應用數學系
;
Department of Applied Mathematics
In a recent work, Hartwig and Putcha obtained a complete characterization of those finite matrices which can be expressed as the difference of two idempotents. Extending this result to operators on a possibly infinite-dimensional Hilbert space seems more difficult. In this paper, we initiate its study and obtain, among other things, (1) that not every nilpotent operator is the difference of two idempotents, (2) that if T is the difference of two idempotents, then the spectra of T and -T differ at most by the two points +/-1, and (3) a characterization of differences of two idempotents among normal operators. In the second part of the paper, we develop some similarity-invariant models of two idempotents. These are analogous to the known unitary-equivalence-invariant models for two orthogonal projections.
PRODUCTS OF UNIPOTENT MATRICES OF INDEX-2
(1991-04-01)
WANG, JH
;
WU, PY
;
交大名義發表
;
應用數學系
;
National Chiao Tung University
We show that an n x n complex matrix T is the product of two unipotent matrices of index 2 if and only if T is similar to a matrix of the form D + D-1 + (I + N) + (- I + SIGMA-i(m) = 1 + J(i)), where 0 and +/- 1 are not eigenvalues of D, N is nilpotent, and each J(i) is a nilpotent Jordan block of even size. On the other hand, T is the product of finitely many unipotent matrices of index 2 if and only if det T = 1. In this case, the minimal number of required unipotents is 1 if n = 1, 3 if n = 2, and 4 if n greater-than-or-equal-to 3.
SUMS OF SQUARE-ZERO OPERATORS
(1991)
WANG, JH
;
WU, PY
;
交大名義發表
;
應用數學系
;
National Chiao Tung University
This paper is concerned with characterizations of bounded linear operators on a complex Hilbert space which are expressible as a sum of two or more square-zero operators. We characterize sums of two square-zero operators among invertible operators, normal operators and operators on a finite-dimensional space. In particular, we show that if T is such a sum, then T and -T have the same spectra modulo the maximal ideal in the algebra of all bounded linear operators. This, together with a result of Pearcy and Topping's, yields a characterization of sums of four square-zero operators: T is such a sum if and only if it is a commutator. We also obtain various necessary or sufficient conditions for sums of three square-zero operators on a finite-dimensional space.