Search results for "look"
showing 10 items of 50 documents
Direct lookup and hash-based metadata placement for local file systems
2013
New challenges to file systems' metadata performance are imposed by the continuously growing number of files existing in file systems. The total amount of metadata can become too big to be cached, potentially leading to multiple storage device accesses for a single metadata lookup operation. This paper takes a look at the limitations of traditional file system designs and discusses an alternative metadata handling approach, using hash-based concepts already established for metadata and data placement in distributed storage systems. Furthermore, a POSIX compliant prototype implementation based on these concepts is introduced and benchmarked. A variety of file system metadata and data operati…
Experimental Sentinel-2 LAI estimation using parametric, non-parametric and physical retrieval methods – A comparison
2015
Abstract Given the forthcoming availability of Sentinel-2 (S2) images, this paper provides a systematic comparison of retrieval accuracy and processing speed of a multitude of parametric, non-parametric and physically-based retrieval methods using simulated S2 data. An experimental field dataset (SPARC), collected at the agricultural site of Barrax (Spain), was used to evaluate different retrieval methods on their ability to estimate leaf area index (LAI). With regard to parametric methods, all possible band combinations for several two-band and three-band index formulations and a linear regression fitting function have been evaluated. From a set of over ten thousand indices evaluated, the …
File system scalability with highly decentralized metadata on independent storage devices
2016
This paper discusses using hard drives that integrate a key-value interface and network access in the actual drive hardware (Kinetic storage platform) to supply file system functionality in a large scale environment. Taking advantage of higher-level functionality to handle metadata on the drives themselves, a serverless system architecture is proposed. Skipping path component traversal during the lookup operation is the key technique discussed in this paper to avoid performance degradation with highly decentralized metadata. Scalability implications are reviewed based on a fuse file system implementation. Peer Reviewed
Design and Low-Cost Implementation of an Optimally Robust Reduced-Order Rotor Flux Observer for Induction Motor Control
2007
The aim of this paper is to design and analyze reduced-order observers of the rotor flux of induction motors. The design is carried out in two steps. In the first step, a boundary of the stability region of the observation error is obtained corresponding to a chosen Lyapunov function. In the second step, the boundary is translated into a performance index that is minimized with respect to stator and rotor resistance variations and differences of voltages supplying the motor and those supplying the observer in order to obtain the largest stability region. Implementation of the observer on a low-cost fixed-point digital signal processor using look-up tables is described. Experimental results …
“Relaparoscopic” management of surgical complications: The experience of an Emergency Center
2015
Background/aim: Laparotomy has been the approach of choice for re-operations in patients with surgical complications. The aim of this retrospective analysis was to evaluate the feasibility and the safety of laparoscopic approach for the management of general abdominal surgery complications. Materials and methods: We report a retrospective review of 75 patients who underwent laparoscopic evaluation for postoperative complications over a 4-year period. Primary outcomes (resolution rate by exclusive laparoscopic approach, conversion rate, further surgery rate) and secondary outcomes (mortality, hospitalization, prolonged ileus, wounds problems and median operative time) were evaluated. Results…
High-Grade T1 on Re-Transurethral Resection after Initial High-Grade T1 Confers Worse Oncological Outcomes: Results of a Multi-Institutional Study
2018
The aim of this multicenter study was to investigate the prognostic impact of residual T1 high-grade (HG)/G3 tumors at re-transurethral resection (TUR of bladder tumor) in a large multi-institutional cohort of patients with primary T1 HG/G3 bladder cancer (BC).
An investigation of bedside laparoscopy in the ICU for cases of non-occlusive mesenteric ischemia
2017
Background: Acute mesenteric ischemia is a rare affection with high related mortality. NOMI presents the most important diagnostic problems and is related with the higher risk of white laparotomy. This study wants to give a contribution for the validation of laparoscopic approach in case of NOMI. Methods: Thirty-two consecutive patients were admitted in last 10 years in ICU of Paolo Giaccone University Hospital of Palermo for AMI. Diagnosis was obtained by multislice CT and selective angiography was done if clinical conditions were permissive. If necrosis was already present or suspected, surgical approach was done. Endovascular or surgical embolectomy was performed when necessary. Twenty N…
Optimizing LUT-Based RTM Inversion for Semiautomatic Mapping of Crop Biophysical Parameters from Sentinel-2 and -3 Data: Role of Cost Functions
2014
Inversion of radiative transfer models (RTM) using a lookup-table (LUT) approach against satellite reflectance data can lead to concurrent retrievals of biophysical parameters such as leaf chlorophyll content (Chl) and leaf area index (LAI), but optimization strategies are not consolidated yet. ESA's upcoming satellites Sentinel-2 (S2) and Sentinel-3 (S3) aim to ensure continuity of old generation satellite sensors by providing superspectral images of high spatial and temporal resolution. This unprecedented data availability leads to an urgent need for developing robust, accurate, and operational retrieval methods. For three simulated Sentinel settings (S2-10 m: 4 bands, S2-20 m: 8 bands an…
Multiple Cost Functions and Regularization Options for Improved Retrieval of Leaf Chlorophyll Content and LAI through Inversion of the PROSAIL Model
2013
Abstract: Lookup-table (LUT)-based radiative transfer model inversion is considered a physically-sound and robust method to retrieve biophysical parameters from Earth observation data but regularization strategies are needed to mitigate the drawback of ill-posedness. We systematically evaluated various regularization options to improve leaf chlorophyll content (LCC) and leaf area index (LAI) retrievals over agricultural lands, including the role of (1) cost functions (CFs); (2) added noise; and (3) multiple solutions in LUT-based inversion. Three families of CFs were compared: information measures, M-estimates and minimum contrast methods. We have only selected CFs without additional parame…
Comparison of methods to estimate LAI from remote sensing in maize canopies by inversion of 1-D and 3-D models
2009
The inversion of canopy reflectance models is a procedure widely employed for the retrieval of LAI from remote sensing. However the accuracy of the estimates depends on a range of factors, most notably the realism of the canopy representation of the models employed and the a priori knowledge of some vegetation characteristics. The objective of the present work was to compare the performances and the operational limitations of the use of two contrasting type of radiative transfer models: a classical one-dimensional canopy reflectance model, PROSPECT+SAIL (PROSAIL) and a three-dimensional dynamic maize model (Lopez-Lozano et al., 2007) having greater realism in the description of the canopy s…