SUMMARYA semi-implicit finite difference method for the numerical solution of three-dimensional shallow water flows is presented and discussed. The governing equations are the primitive three-dimensional turbulent mean flow equations where the pressure distribution in the vertical has been assumed to be hydrostatic. In the method of solution a minimal degree of implicitness has been adopted in such a fashion that the resulting algorithm is stable and gives a maximal computational efficiency at a minimal computational cost. At each time step the numerical method requires the solution of one large linear system which can be formally decomposed into a set of small three-diagonal systems coupled with one five-diagonal system. All these linear systems are symmetric and positive definite. Thus the existence and uniqueness of the numerical solution are assured. When only one vertical layer is specified, this method reduces as a special case to a semi-implicit scheme for solving the corresponding two-dimensional shallow water equations. The resulting two-and three-dimensional algorithm has been shown to be fast, accurate and mass-conservative and can also be applied to simulate flooding and drying of tidal mud-flats in conjunction with threedimensional flows. Furthermore, the resulting algorithm is fully vectorizable for an efficient implementation on modern vector computers.KEY WORDS Three-dimensional Semi-implicit Shallow water

By employing spatial multiplexing, Multiple-Input Multiple-Output (MIMO) wireless antenna systems provide increases in capacity without the need for additional spectrum or power. Zero-Forcing (ZF) detection is a simple and effective technique for retrieving multiple transmitted data streams at the receiver. However the detection requires knowledge of the channel state information (CSI) and in practice accurate CSI may not be available. In this letter, we investigate the effect of channel estimation error on the performance of MIMO ZF receivers in uncorrelated Rayleigh flat fading channels. By modeling the estimation error as independent complex Gaussian random variables, tight approximations for both the post-processing SNR distribution and bit error rate (BER) for MIMO ZF receivers with M-QAM and M-PSK modulated signals are derived in closed-form. Numerical results demonstrate the tightness of our analysis. Index Terms-MIMO, MIMO ZF receiver, channel estimation error.

The capacity region of a two-user Gaussian multiaccess channel with intersymbol interference (ISI), where the inputs pass through respective linear systems and are then superimposed before being corrupted by an additive Gaussian noise process, is found. A novel geometrical method is given to obtain the optimal input power spectral densities and the capacity region. This method can be viewed as a nontrivial generalization of the singleuser water-filling argument. We show that as in the traditional memoryless multiaccess channel, frequency-division multiaccess (FDMA), with optimally selected frequency bands for each user, achieves the total capacity of the A-user Gaussian multiaccess channel with ISI. However, the capacity region of the twouser channel with memory is, in general, not a pentagon unless the channel transfer functions for both users are identical. Index Tens-Multiaccess channels, intersymbol interference, channels with memory, Gaussian channels, channel capacity.

This report describes an experiment to make a completely non‐contact open‐channel discharge measurement. A van‐mounted, pulsed doppler (10GHz) radar collected surface‐velocity data across the 183‐m wide Skagit River, Washington at a USGS streamgaging station using Bragg scattering from short waves produced by turbulent boils on the surface of the river. Surface velocities were converted to mean velocities for 25 sub‐sections by assuming a normal open‐channel velocity profile (surface velocity times 0.85). Channel cross‐sectional area was measured using a 100 MHz ground‐penetrating radar antenna suspended from a cableway car over the river. Seven acoustic doppler current profiler discharge measurements and a conventional current‐meter discharge measurement were also made. Three non‐contact discharge measurements completed in about a 1‐hour period were within 1% of the gaging station rating curve discharge values. With further refinements, it is thought that open‐channel flow can be measured reliably by non‐contact methods.

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