308 research outputs found
Role of ATP-sensitive potassium channels in neuroprotection from cerebral ischemia
No full textBibliography: p. 210-226Some pages are in colour
Note: On modeling techniques in active contours
No full textFor active contours, modeling techniques are represented by simulation and visualization of the objectives to their counterparts in physics, geometrics and graphics, etc. The goal of adopting this concept is to address several major difficulties in active contours for segmentation, both theoretically and practically. Based on this technology, in theory, by interpreting the equations with physical meaning, it proves that each term in Geometric Active Contours (GAC) and Snakes is correspondent and has similar function. This approach can also illustrate their differences. In practice, the obstacle of multi-object segmentation by Snakes can be overcome visually through simulating the inflation of the balloon in a closed space. The precision of the edge based GAC is not satisfied. By imitating the light propagating in the isotropic substance, this trouble is easily solved. Utilization of the electrostatic field and heat diffusion principles can establish a fusion scheme to create an image force field, which guarantees both the accuracy and the speed of the shape recovery process. In conclusion, the modeling technique transfers one question to its analogy and fast the procedures of solving some problems. The applications show vast prospects of this technology in image analysis. ? 2012 IEEE.EI
The Isomorphism Problem for Plain Groups Is in Σ₃^{}
No full textTesting isomorphism of infinite groups is a classical topic, but from the complexity theory viewpoint, few results are known. Sénizergues and the fifth author (ICALP2018) proved that the isomorphism problem for virtually free groups is decidable in PSPACE when the input is given in terms of so-called virtually free presentations. Here we consider the isomorphism problem for the class of plain groups, that is, groups that are isomorphic to a free product of finitely many finite groups and finitely many copies of the infinite cyclic group. Every plain group is naturally and efficiently presented via an inverse-closed finite convergent length-reducing rewriting system. We prove that the isomorphism problem for plain groups given in this form lies in the polynomial time hierarchy, more precisely, in Σ₃^. This result is achieved by combining new geometric and algebraic characterisations of groups presented by inverse-closed finite convergent length-reducing rewriting systems developed in recent work of the second and third authors (2021) with classical finite group isomorphism results of Babai and Szemerédi (1984)
A 76.5-92.6 GHz CMOS LNA Using Two-Port kQ-Product Theory for Transformer Design
No full textThis letter presents a convenient approach based on the two-port kQ-product theory to analyze the influence of interwinding capacitive coupling on the efficiency of the transformer. It is demonstrated that a transformer with proper size can benefit from the interwinding capacitive coupling to maximize its efficiency at a desired frequency. The proposed design approach is used in a W-band low-noise amplifier (LNA) fabricated with the 40-nm CMOS process to optimize the insertion loss of the input transformer-based balun. Thanks to the approach, the W-band LNA achieves a minimum noise figure of 5.7 dB, a maximum gain of 18.5 dB, and a 3-dB bandwidth of 76.5-92.6 GHz, while consuming 23.4 mW from a 0.9-V supply.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
An approach for characterising cellular polymeric foam structures using computed tomography
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Efficient Method for Enhancing Reverse-Time Migration Images Using Vertical Seismic Profiling Data
No full textVertical seismic profiling has garnered widespread attention in the industry as a supplement to seismic exploration due to its higher data quality compared to surface seismic data. However, its unique observation system in which geophones are only distributed within observation wells results in uneven coverage of subsurface structures. This can lead to significant noise when directly applying conventional reverse-time migration techniques used in surface seismic imaging. This study addresses the issue of noise suppression in reverse-time migration imaging associated with walk-away vertical seismic profiling and presents two main innovations. First, a common-receiver reverse-time migration imaging method is proposed, which uses the observation signals as excitation signals for the corresponding shots after reverse-time processing. Second, an excitation-time-constrained cross-correlation imaging condition is introduced to eliminate non-contributing portions of the wavefield, thereby modifying the traditional cross-correlation imaging condition to include an excitation time constraint. The combination of these methods enhances imaging quality by effectively suppressing noise, as demonstrated through theoretical analysis and numerical simulations with synthetic models
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