Errata for "Phase-based block matching applied to motion estimation with unconventional beamforming strategies" [May 09 945-957]

On page 948 of the original publication of this paper (ibid., vol. 56, no. 5, pp. 945-957, May 09), several characters were inadvertently switched during production. The corrected text is presented here.     

Concepts and realization of a high-performance data type architecture

Fifth generation computers are expected to capitalize on the dramatic progress of VLSI technology, in order to offer an improved performance/cost figure. An even more important requirement, however, is that they will support by architectural means the generation, execution, and maintenance of quality software, as a way out of the software crisis. One approach towards the design and implementation of quality software is programming with abstract data types, in connection with elaborate type consistency checking. The objection raised against the abstract data type based programming style is poor run time efficiency when such programs are executed on a conventional machine. In this paper adata type architecture is described that offers efficient and convenient mechanism for constructing arbitrary data structures and encapsulating them into abstract data types, thus avoiding the inefficiency penalty mentioned above. Through a process of hierarchical decomposition, user-defined abstract data types are mapped on representations given in terms of a basicstructured machine data type. This approach combines high performance with generality and completeness. The hardware structure of the data type architecture can be classified as a strongly coupled, asymmetric multicomputer system with hierarchical function distribution among the computers. The system includes a pipeline for numerical and nonnumerical operations, performed on the vector-structured basic machine data type in the SIMD mode of operation. Software reliability and data security is enhanced through elaborate run time consistency checking. The computer, which was designed and built at the Technical University of Berlin, has recently become operational. This paper outlines the operational principle, the mechanisms, and the hardware and software structure of this innovative, fifth generation computer architecture.This work was sponsored by the German Science Foundation under grant no. Gi 42/13.     

Lateral RF image synthesis using a synthetic aperture imaging technique

The oscillating profile naturally present in ultrasound images has been shown to be extremely valuable in different applications, particularly in motion estimation. Recent studies have shown that it is possible to produce images with transverse oscillations (TOs) based on a specific type of beamforming. However, there is still a great difference between the nature of the lateral oscillations produced with current methods and the axial profile of ultrasound images. In this study, we propose to combine synthetic aperture imaging (synthetic transmit aperture, STA) using a specific beamformer in both transmit mode and receive mode combined with a heterodyning demodulation method to produce lateral radiofrequency signals (LRFs). The aim was to produce lateral signals as close as possible to conventional axial signals, which would make it possible to estimate lateral displacements with the same accuracy as in the axial direction. The feasibility of this approach was validated in simulation and experimentally on an ultrasound research platform, the Ultrasonix RP system. We show that the combination of STA and the heterodyning demodulation can divide the wavelength of the LRF signals by 4 and divide the width of the lateral envelope of the point spread function (PSF) by 2 compared with the previous approaches using beamforming in receive mode only. Finally, we also illustrate the potential of our beamforming for motion estimation compared with previous TO methods.     

Individual Phase Control of a Static Compensator for Load Compensation and Voltage Balancing and Regulation

The purpose of this paper is to discuss the developments in control strategies for static compensators using programmable high speed digital controllers. Individual phase control of static compensators has been used in the past for balancing and power factor correction of arc furnace and single phase railway loads. With the advancements in programmable high speed controllers based on microprocessor technology, more complex computations can be accurately performed for the additional purpose of regulating and balancing the voltage feeding such loads. Other developments that will be discussed are the use of symmetrical firing angle control to eliminate the even harmonics in the current spectrum and hence, reduce the cost of filtering, and the synchronization of the controller to the phase-locked-loop firing circuit to compensate for frequency variations. The results of simulator studies will be presented.     

Investigation of HVDC inverter with series compensation on analoguesimulator

An analogue simulator was used to investigate the performance of the MOV (metal-oxide varistor) and series capacitor arrangements, especially the fault recovery performance of the latter. The SCD (series capacitor device) was found to be a feasible VCD (voltage control device) that considerably improves recovery from faults for weak AC systems by effectively increasing the SCR (short-circuit ratio). MOV+FC (fixed shunt capacitor) application is effective for the control of dynamic overvoltages. However, it does not strengthen the AC system. This results in slower recovery and instability in many situations unless constant current control is used. When the SCD is employed for DC systems feeding into weak AC systems, system recovery is faster with constant power control than with constant current control. Application of the SCD increases the power stability limit. Application of the SCD showed harmonic distortion due to the inrush current of transformers in combination with the SCD. It is therefore recommended that before SCD is chosen for a system, sufficient harmonic studies with a fuller representation of the AC system be performed     

Piecewise smooth reconstruction of normal vector field on digital data

We propose a novel method to regularize a normal vector field defined on a digital surface (boundary of a set of voxels). When the digital surface is a digitization of a piecewise smooth manifold, our method localizes sharp features (edges) while regularizing the input normal vector field at the same time. It relies on the optimisation of a variant of the Ambrosio‐Tortorelli functional, originally defined for denoising and contour extraction in image processing [ AT90 ]. We reformulate this functional to digital surface processing thanks to discrete calculus operators. Experiments show that the output normal field is very robust to digitization artifacts or noise, and also fairly independent of the sampling resolution. The method allows the user to choose independently the amount of smoothing and the length of the set of discontinuities. Sharp and vanishing features are correctly delineated even on extremely damaged data. Finally, our method can be used to enhance considerably the output of state‐of‐the‐art normal field estimators like Voronoi Covariance Measure [ MOG11 ] or Randomized Hough Transform [ BM12 ].