PALSfit is a new Windows program for the analysis of positron lifetime spectra. PALSfit combines into one interactive Windows program the features of our previous PATFIT program package, such as data input, least-squares fitting routines as well as graphical displays. A number of options are available, including constraints on positron lifetimes, intensities, background and area, and corrections for annihilation in the positron source. In addition, a number of new features have been included. The Windows userinterface makes to a large extent the various features of the program self-explanatory, and using the program is straightforward.

Two delay-and-sum beamformers for 3-D synthetic aperture imaging with row-column addressed arrays are presented. Both beamformers are software implementations for graphics processing unit (GPU) execution with dynamic apodizations and 3rd order polynomial subsample interpolation. The first beamformer was written in the MATLAB programming language and the second was written in C/C++ with the compute unified device architecture (CUDA) extensions by NVIDIA. Performance was measured as volume rate and sample throughput on three different GPUs: a 1050 Ti, a 1080 Ti, and a TITAN V. The beamformers were evaluated across 112 combinations of output geometry, depth range, transducer array size, number of virtual sources, floating point precision, and Nyquist rate or inphase/quadrature beamforming using analytic signals. Real-time imaging defined as more than 30 volumes per second was attained by the CUDA beamformer on the three GPUs for 13, 27, and 43 setups, respectively. The MATLAB beamformer did not attain real-time imaging for any setup. The median, single precision sample throughput of the CUDA beamformer was 4.9, 20.8, and 33.5 gigasamples per second on the three GPUs, respectively. The CUDA beamformer's throughput was an order of magnitude higher than that of the MATLAB beamformer.

A delay-and-sum beamformer for 3D imaging using row-column arrays and written in CUDA is presented and compared to an existing similar GPU-based beamformer written in the MATLAB programming language. Data from a 192+192 rowcolumn array single element emission sequence is simulated and beamformed. The two beamformers' performance is evaluated in two synthetic aperture setups comprised of 1) two orthogonal planes and 2) a full volume on three different NVIDIA GPUs: a 1050 Ti, a 1080 Ti, and a TITAN V. The execution time and the sample throughput (samples beamformed per second) are reported. The CUDA beamformer performs consistently better than the MATLAB beamformer with speed-ups ranging from 1.9 to 64.6 times, and the worst-case throughput of the CUDA beamformer exceeds the best-case of the MATLAB beamformer. High-resolution images of crossing planes can be beamformed at up to 13 Hz, while a 50-by-50-by-20 cubic-millimeter highresolution volume sampled at one quarter of a millimeter is beamformed in 3 seconds.

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Defence Research Establishment Atlantic(DREA) has developed a l i n e a r hydrophone a r r a y f o r s t u d y i n g sound propagation i n shallow water. The a r r a y consists of in-line hydrophones, with electronics connected by robust and interchangeable cable s e c t i o n s , making changes i n a r r a y geometry easy t o implement. These c a b l e s e c t i o n s form a d i g i t a l bus, controlled a t one end by a microprocessor,