Artroplastia total da anca: Colocação da haste femoral com manutenção dos parafusos de uma osteossíntese antiga

Apresenta-se o caso de um doente que foi submetido, em 1958, a uma osteotomia de valgização para o tratamento de uma fractura traumática do colo do fémur, tendo sido utilizado um cravo-placa de Mac Laughlin para a osteossíntese da osteotomia. Em Janeiro do ano 2000, procedeu-se à implantação de uma prótese total da anca porque o doente apresentava uma coxartrose do grau IV. Durante o acto operatório confirmou-se que a placa e os quatro parafusos se encontravam revestidos por tecido ósseo, o qual foi removido. As cabeças dos parafusos, com ranhuras de tipo Parker, foram fragilizadas, fracturadas e excisadas com osteótomos. A extracção do cravo não apresentou dificuldades. Removeu-se a placa e não se procedeu à excisão da parte roscada dos parafusos. Implantou-se uma prótese total cimentada autobloqueante, uma vez que a parte roscada dos parafusos não constituía um obstáculo à implantação de uma haste femoral cimentada de diâmetro 15. Reforçou-se o leito cortical fragilizado pela extracção da placa com enxerto esponjoso autógeno da cabeça femoral excisada. A avaliação clínica e radiológica da artroplastia mostrou um resultado muito satisfatório, aos 5 anos de evolução pós-operatóri

A fast computational algorithm to evaluate large transmit-arrays

Transmit-arrays (TAs) have become popular solutions for point-to-point communications due to their lowprofile and high-efficiency. However, simulation of these large and detailed structures demands a great amount of memory and time. Here, we propose a fast algorithm to estimate the performance of a beam-steering TA to accelerate its design optimization process. The results and the required resources of the algorithm are compared with the ones of Ansys HFSS. It is shown that this algorithm can fairly evaluate the key factors of the performance of a TA within couple of minutes with memory resource of only 1 GB.info:eu-repo/semantics/acceptedVersio

Beam-steering ka-band phase rotation cells-based transmit-array for circular-polarization

Planar transmit-arrays (TAs) have been an attractive solution as gain-enhancers for various applications, e.g. satellite communications. For the first time, a TA composed of sequentially rotated cells is employed as beam-steering circular polarization Ka-band satellite ground terminal. Moreover, it is shown that the intrinsic filtering effect of phase rotation (PR) cells for this kind of TA enables improvement in the axial ratio bandwidth. The performance of the TA is evaluated through simulation. The TA presents only 2.7dB loss over zenith scan between 15° and 50° while its structure rotation provides 360° azimuth scan. The TA offers 2GHz (28.730.7GHz) combined 3dB axial ratio and 3dB gain bandwidth.info:eu-repo/semantics/acceptedVersio

Phase-delay versus phase-rotation cells for circular polarization transmit arrays - application to Satellite Ka-Band Beam steering

Planar transmit arrays (TAs) have been an attractive solution as gain enhancers for various applications, e.g., satellite communications. The TA performance directly depends on its composing unit-cell characteristics. Planar unit cells can be categorized into two main types: phase-rotation (PR) and phase-delay (PD) cells. There is no hint in the literature about the relative merits of these two types of cells for circular polarization when assessing the final TA performance. This paper offers a systematic comparison between the cells’ working principles and analyzes their impacts on TA performance. Examples of a PR-based TA and a PD-based TA are designed for single-band wide-angle beam steering operating at the satellite Ka-band. They are evaluated by simulation and measurement to quantify performance differences. No previous work employed a PR TA for wide-angle beam steering. This paper shows that PR TA offers a filtering effect toward the cross-polarization component of the source. This leads to better axial ratio and combined 3 dB axial ratio and 3 dB gain bandwidth. However, PD cells are easier to design and insensitive to feed polarization. The analysis in this paper allows a more informed decision when selecting the unit-cell category for any given TA application

Antenna-filter-antenna-based cell for linear-to-circular polarizer transmit-array

In this paper, we propose a dual-band linear-to-circular polarization converter element based on the antenna-filter-antenna (AFA) structure. The traits of this cell include thin three-layer structure and ability to convert a linear incident wave to two orthogonal circular polarizations at two non-adjacent frequency bands. This combination of physical and electrical specifications makes this cell a novel solution. An example of this cell suitable for satellite communication is designed to operate at 20GHz and 30GHz (satellite Ka-band) with 4% and 8% bandwidth, respectively.info:eu-repo/semantics/acceptedVersio

Efficient full-wave assessment of high gain transmit-array antennas

With the continuous exploration of millimeter waves, fomented by next generation of mobile and satellite communications, new low-cost beam antenna designs are still required for the massification of this technology. Transmit-arrays (TAs) are being intensely investigated as a possible cost-effective solution for a wide variety of applications. Underlying these studies is the need to have an efficient method of simulating this type of antennas. Performing full-wave simulation of TA antennas can be quite challenging, especially when high gain is required. This is mainly due to the large volume occupied by these type of antennas (comprising the feed and lens) and the fine subwavelength details of the unit cells that populate the TA. Based on the experience gained when designing TA for Ka-band [1] [2], we will present an overview on the numerical techniques used to perform the full-wave analysis of different TA antennas. In Figure 1, we depicted one of the methods that proved to be more effective on reducing the numerical complexity of the problem without compromising significantly the accuracy of the results.info:eu-repo/semantics/acceptedVersio

Multimodality Imaging Evaluation of a Singular Cardiac Structure

info:eu-repo/semantics/publishedVersio

Equivalent circuit modeling to design a dual-band dual linear-to-circular polarizer surface

The working principle of a thin dual-band dual-linear to circular polarizer is presented here. This polarizer not only converts incident linearly polarized (LP) waves to circularly polarized (CP) waves in two frequency bands, but it also reverses the handedness of each signal. The electromagnetic behavior of the cell is carefully analyzed and two equivalent circuit models (ECMs) are presented to model the responses of the cell to linearly polarized waves at normal incidence. The ECMs show how utilizing interlayer coupling can be leveraged to achieve reversed CP senses in two bands using a compact design. Analytical formulas are presented to provide initial values of the ECM components including the mutual coupling inductances. We present measurement results that agree well with the full-wave simulation and the ECM results, thus validating the proposed ECM model.info:eu-repo/semantics/acceptedVersio

New concept for multibeam antennas based on two cascaded Ka-band transmit-array

The paper presents a new two-beam per-feed approach for Ka-band multi spot-beam satellites. It is based on a dual-stacked transmit array (TA) arrangement, fed by a 3×3 standard waveguide array. The TAs are co-designed so that the first performs a beam collimation and tilting; whereas the second splits the incoming beam into two orthogonal circular polarizations, with symmetrical output angles relative to the incident angle. Therefore, the number of feeds is half the number of output beams, and the linearly polarized feed reduces significantly the antenna complexity. As a proof-of-concept, we design an antenna for the 30 GHz up-link band. The focal length of the first TA is 50 mm, and the aperture size of both TAs is 196×148 mm. A new type of phase correction, the multifocal approach, is used to minimize aberrations for all beams, which would be otherwise impossible with such low F/D. Using fullwave simulations, we confirm that the 18 beams present low SLL (~15 dB), pure circular polarization and good crossover (~3 dB) with gains between 21 and 22 dBi.info:eu-repo/semantics/publishedVersio

Dual-band dual linear to circular polarization converter in transmission mode-application to K/Ka-band satellite communications

Many wireless communication applications such as satellite communications use circularly polarized (CP) signals, with the requirement for easy switching of the polarization sense between uplink and downlink. Specifically, in satellite communications, the trend is also to move to higher frequencies and integrate the receiving and transmitting antennas in one dual-band terminal. However, these simultaneous demands make the design and fabrication of the composing parts very challenging. We propose, here, a dual-band dual-linear polarization (LP)-to-CP converter that works in the transmission mode. The working principle of this polarizer is explained through an example for Ka-band satellite communications at 19.7–20.2 and 29.5–30 GHz. The LP-to-CP converter is a single panel composed of identical unit cells with a thickness of only 1.05 mm and a size of 5.3 mm ×5.3 mm. Due to its operation in the transmission mode, the polarizer can be combined with a simple dual-band dual-LP antenna to obtain the desired dual-band dual-CP single antenna. However, the unique property of this polarizer is yet the fact that it converts a given LP wave, e.g., x-polarization, to orthogonal CP waves at the two nonadjacent frequency bands, e.g., left-handed CP at lower band and right-handed CP at higher band. The polarizer is tested both with 20 and 30 GHz LP rectangular horns to illuminate a dual-band transmit array (TA) to obtain wide-angle steering of CP beams. The performance of the polarizer and its association with the TA is evaluated through simulation and measurements. We also present design guidelines for this type of polarizer.info:eu-repo/semantics/acceptedVersio