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排序方式: 共有590条查询结果,搜索用时 15 毫秒
1.
Dohnal Vlastislav Gennaro Claudio Savino Pasquale Zezula Pavel 《Multimedia Tools and Applications》2003,21(1):9-33
In order to speedup retrieval in large collections of data, index structures partition the data into subsets so that query requests can be evaluated without examining the entire collection. As the complexity of modern data types grows, metric spaces have become a popular paradigm for similarity retrieval. We propose a new index structure, called D-Index, that combines a novel clustering technique and the pivot-based distance searching strategy to speed up execution of similarity range and nearest neighbor queries for large files with objects stored in disk memories. We have qualitatively analyzed D-Index and verified its properties on actual implementation. We have also compared D-Index with other index structures and demonstrated its superiority on several real-life data sets. Contrary to tree organizations, the D-Index structure is suitable for dynamic environments with a high rate of delete/insert operations. 相似文献
2.
Approximate similarity retrieval with M-trees 总被引:4,自引:0,他引:4
Pavel Zezula Pasquale Savino Giuseppe Amato Fausto Rabitti 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(4):275-293
Motivated by the urgent need to improve the efficiency of similarity queries, approximate similarity retrieval is investigated
in the environment of a metric tree index called the M-tree. Three different approximation techniques are proposed, which
show how to forsake query precision for improved performance. Measures are defined that can quantify the improvements in performance
efficiency and the quality of approximations. The proposed approximation techniques are then tested on various synthetic and
real-life files. The evidence obtained from the experiments confirms our hypothesis that a high-quality approximated similarity
search can be performed at a much lower cost than that needed to obtain the exact results. The proposed approximation techniques
are scalable and appear to be independent of the metric used. Extensions of these techniques to the environments of other
similarity search indexes are also discussed.
Received July 7, 1998 / Accepted October 13, 1998 相似文献
3.
Chiara Trincianti Vincenzo Meleca Edoardo La Porta Maurizio Bruschi Giovanni Candiano Andrea Garbarino Xhuliana Kajana Alberto Preda Francesca Lugani Gian Marco Ghiggeri Andrea Angeletti Pasquale Esposito Enrico Verrina 《International journal of molecular sciences》2022,23(10)
Peritoneal dialysis (PD) represents the dialysis modality of choice for pediatric patients with end-stage kidney disease. Indeed, compared with hemodialysis (HD), it offers many advantages, including more flexibility, reduction of the risk of hospital-acquired infections, preservation of residual kidney function, and a better quality of life. However, despite these positive aspects, PD may be associated with several long-term complications that may impair both patient’s general health and PD adequacy. In this view, chronic inflammation, caused by different factors, has a detrimental impact on the structure and function of the peritoneal membrane, leading to sclerosis and consequent PD failure both in adults and children. Although several studies investigated the complex pathogenic pathways underlying peritoneal membrane alterations, these processes remain still to explore. Understanding these mechanisms may provide novel approaches to improve the clinical outcome of pediatric PD patients through the identification of subjects at high risk of complications and the implementation of personalized interventions. In this review, we discuss the main experimental and clinical experiences exploring the potentiality of the proteomic analysis of peritoneal fluids and extracellular vesicles as a source of novel biomarkers in pediatric peritoneal dialysis. 相似文献
4.
5.
Stefania Perri Pasquale Corsonello Giuseppe Cocorullo 《International Journal of Electronics》2013,100(6):413-422
Usually, efficient self-timed adders are realized using the dynamic differential cascode voltage switch logic. This allows the end-completion to be easily detected, but it makes circuit design and testing very complex, compelling the production of full-custom layouts and leading to a very long time before marketing. This paper presents a new 56-bit high-speed self-timed adder realized with conventional AMS 0.35 μm CMOS standard cells. The proposed circuit uses overlapped execution circuits, which exploit the initialization time that always elapses between two consecutive addition operations. Compared to several self-timed adders existing in the literature, the addition circuit proposed here shows brilliant advantages in terms of speed-performance, silicon area occupancy and power dissipation. 相似文献
6.
New Raman pump module for reducing pump-signal four-wave-mixing interaction in co-pumped distributed Raman amplifiers 总被引:1,自引:0,他引:1
We propose a new Raman pump module that effectively reduces four-wave-mixing (FWM) nonlinear interaction among longitudinal pump modes and wavelength-division-multiplexed (WDM) signals in co-pumped distributed Raman amplifiers based on nonzero dispersion-shifted fibers (NZ-DSFs). Theory and experiments confirm that the proposed pump module structure, based on polarization- and wavelength-multiplexed Fabry-Perot lasers, allows distributed amplification with high co-propagating on-off Raman gain, providing a key technology for all-Raman-based dense-WDM ultralong-haul transmission. 相似文献
7.
In a deadline-ordered service discipline, packets are assigned transmission deadlines and eligibility times and are transmitted in increasing order of deadlines. Different deadline-ordered service disciplines are distinguished by how they calculate deadlines and eligibility times. One of the more difficult analytical problems one faces when designing a new deadline-ordered service discipline is to prove that one can bound the end of transmission times of packets relative to their assigned deadlines, which we call schedulability. We show that, no matter how one calculates deadlines, there is a simple schedulability condition for deadline-ordered service disciplines. This schedulability condition is necessary and sufficient for preemptive deadline-ordered service disciplines, and for a server that allows the presence of nonreal-time packets (i.e., packets with no deadlines), it is also necessary and sufficient for nonpreemptive deadline-ordered service disciplines. We also address the schedulability problem for service disciplines in general, and show the optimality of deadline-ordered service disciplines. To demonstrate how our results simplify schedulability determination, we use them to prove the known schedulability conditions of VirtualClock, Packet-by-Packet Generalized Processor Sharing (PGPS), Stop-and-Go, and Delay-Earliest-Due-Date (Delay-EDD), and to provide a new result, the necessary schedulability condition of VirtualClock 相似文献
8.
Francesco Merola Simonetta Grilli Sara Coppola Veronica Vespini Sergio De Nicola Pasquale Maddalena Cosimo Carfagna Pietro Ferraro 《Advanced functional materials》2012,22(15):3267-3272
Investigation on the behavior of nematic liquid crystals on functionalized polar dielectric crystal substrates is accomplished. Very interesting effects can be observed in maneuvering liquid crystal droplets on the substrate surface, driven by electric fields generated by pyroelectric effect. Reversible drops fragmentation and self‐assembling in different configurations can be achieved. The dynamics of the observed phenomena is studied and the repeatability of the process is full assessed. 相似文献
9.
10.
A realistic performance analysis of oscillating water column wave energy converters (WECs) addresses to a set of non-linear differential equations that need to be integrated in time, by using a stochastic approach, under the hypothesis of random wind-generated sea waves, for all the sea states which characterize the location of the system. Non-linearities of the differential equations have several origins:
- • minor and major losses of the unsteady flow of water and air;
- • compressibility of air and heat exchange with the walls of the air chamber;
- • non-linear characteristics of the turbine.