6,520 research outputs found
Indicial response approach derived from Navier-Stokes equations. Part 1: Time-invariant equilibrium state
The indicial response approach is recast in a form appropriate to the study of vortex induced oscillations phenomena. An appropriate form is demonstrated for the indicial response of the velocity field which may be derived directly from the Navier-Stokes equations. On the basis of the Navier-Stokes equations, it is demonstrated how a form of the velocity response to an arbitrary motion may be determined. To establish its connection with the previous work, the new approach is applied first to the simple situation wherein the indicial response has a time invariant equilibrium state. Results for the aerodynamic response to an arbitrary motion are shown to confirm to the form obtained previously
A new VLSI architecture for a single-chip-type Reed-Solomon decoder
A new very large scale integration (VLSI) architecture for implementing Reed-Solomon (RS) decoders that can correct both errors and erasures is described. This new architecture implements a Reed-Solomon decoder by using replication of a single VLSI chip. It is anticipated that this single chip type RS decoder approach will save substantial development and production costs. It is estimated that reduction in cost by a factor of four is possible with this new architecture. Furthermore, this Reed-Solomon decoder is programmable between 8 bit and 10 bit symbol sizes. Therefore, both an 8 bit Consultative Committee for Space Data Systems (CCSDS) RS decoder and a 10 bit decoder are obtained at the same time, and when concatenated with a (15,1/6) Viterbi decoder, provide an additional 2.1-dB coding gain
Linear phase paraunitary filter banks: theory, factorizations and designs
M channel maximally decimated filter banks have been used in the past to decompose signals into subbands. The theory of perfect-reconstruction filter banks has also been studied extensively. Nonparaunitary systems with linear phase filters have also been designed. In this paper, we study paraunitary systems in which each individual filter in the analysis synthesis banks has linear phase. Specific instances of this problem have been addressed by other authors, and linear phase paraunitary systems have been shown to exist. This property is often desirable for several applications, particularly in image processing.
We begin by answering several theoretical questions pertaining to linear phase paraunitary systems. Next, we develop a minimal factorizdion for a large class of such systems. This factorization will be proved to be complete for even M. Further, we structurally impose the additional condition that the filters satisfy pairwise mirror-image symmetry in the frequency domain. This significantly reduces the number of parameters to be optimized in the design process. We then demonstrate the use of these filter banks in the generation of M-band orthonormal wavelets. Several design examples are also given to validate the theory
Application of the Laplace-Borel transformation to the representation of analytical solutions of Duffing's equation
Various features of the solutions of Duffing's equation are described using a representation of the solutions in the Laplace-Borel transform domain. An application of this technique is illustrated for the symmetry-breaking bifurcation of a hard spring
Facteurs de risque des embolies pulmonaires post-hépatectomie: une étude rétrospective
Contexte: Parmi les complications de toute chirurgie, on retrouve l'embolie pulmonaire, dont l'issue est potentiellement fatale. Peu de travaux cependant ont été effectués pour étudier les facteurs de risques associés à une embolie pulmonaire aprÚs une chirurgie hépato-biliaire en particulier.
Objectif: Le but de notre travail est d'Ă©tudier et comparer aux rares rĂ©sultats existants les facteurs de risque ainsi que les consĂ©quences d'une embolie pulmonaire post- hĂ©patectomie. Les donnĂ©es pourront Ă©ventuellement ĂȘtre utilisĂ©es pour cibler les patients Ă risque et amĂ©liorer la prĂ©vention.
RĂ©sultats: Le diagnostic d'embolie pulmonaire a Ă©tĂ© posĂ© chez 24 patients (8%) au CT-scan dans la pĂ©riode post-opĂ©ratoire. Le dĂ©lai moyen entre l'opĂ©ration et le diagnostic Ă©tait de 5 jours (1-15j). La comparaison des patients du groupe EP (n = 24) au groupe Non-EP (n = 272) montre un BMI mĂ©dian plus Ă©levĂ© (27 vs 24 kg/m2, p=0.006), un taux plus Ă©levĂ© de rĂ©sections majeures (71 vs 43%, p=0.01) ainsi qu'une durĂ©e opĂ©ratoire plus longue (310 vs 260 min, p=0.001). La durĂ©e totale d'hospitalisation Ă©tait Ă©galement supĂ©rieure dans le groupe EP (22 vs 11j, p<0.05), de mĂȘme que la durĂ©e de sĂ©jour aux soins intensifs (3 vs 1j, p<0.05). La mortalitĂ© globale Ă 90j post-opĂ©ratoires Ă©tait de 3.3%, la mortalitĂ© du groupe EP Ă©tant nulle.
Conclusion: Les résultats de cette étude rétrospective ont démontré l'association des embolies pulmonaires post-hépatectomie avec l'obésité, les hépatectomies majeures, ainsi qu'une longue durée d'opération. L'incidence non négligeable des embolies prouve la nécessité d'une prophylaxie thrombo-embolique
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