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81.
Jorge Larrey-Ruiz Rafael Verdú-MonederoJuan Morales-Sánchez Jesús Angulo 《Image and vision computing》2011,29(9):620-630
The present work is intended to address two of the major difficulties that can be found when tackling the estimation of the local orientation of the data in a scene, a task which is usually accomplished by means of the computation of the structure tensor-based directional field. On one hand, the orientation information only exists in the non-homogeneous regions of the dataset, while it is zero in the areas where the gradient (i.e. the first-order intensity variation) remains constant. Due to this lack of information, there are many cases in which the overall shape of the represented objects cannot be precisely inferred from the directional field. On the other hand, the orientation estimation is highly dependent on the particular choice of the averaging window used for its computation (since a collection of neighboring gradient vectors is needed to obtain a dominant orientation), typically resulting in vector fields which vary from very irregular (thus yielding a noisy estimation) to very uniform (but at the expense of a loss of angular resolution). The proposed solution to both drawbacks is the regularization of the directional field; this process extends smoothly the previously computed vectors to the whole dataset while preserving the angular information of relevant structures. With this purpose, the paper introduces a suitable mathematical framework and deals with the d-dimensional variational formulation which is derived from it. The proposed formulation is finally translated into the frequency domain in order to obtain an increase of insight on the regularization problem, which can be understood as a low-pass filtering of the directional field. The frequency domain point of view also allows for an efficient implementation of the resulting iterative algorithm. Simulation experiments involving datasets of different dimensionality prove the validity of the theoretical approach. 相似文献
82.
The operation principle of the mass-controlled capillary viscometer is presented for a Newtonian liquid. The derived equation for the temporal changes of the mass in a liquid column draining under gravity through a discharge capillary tube accounts self-consistently for the inertial convective term associated with the acceleration effect. The viscosity of water measured at different temperatures using the new approach is in good agreement with literature data. 相似文献
83.
In a recent article, Prinz, Bucher, and Marder (2004) addressed the fundamental question of whether neural systems are built with a fixed blueprint of tightly controlled parameters or in a way in which properties can vary largely from one individual to another, using a database modeling approach. Here, we examine the main conclusion that neural circuits indeed are built with largely varying parameters in the light of our own experimental and modeling observations. We critically discuss the experimental and theoretical evidence, including the general adequacy of database approaches for questions of this kind, and come to the conclusion that the last word for this fundamental question has not yet been spoken. 相似文献
84.
Agustin Ramirez-Agundis Rafael Gadea-Girones Ricardo Colom-Palero Javier Diaz-Carmona 《Journal of Real-Time Image Processing》2007,2(4):271-280
This paper presents a scheme and its Field Programmable Gate Array (FPGA) implementation for a system based on combining the
bi-dimensional discrete wavelet transformation (2D-DWT) and vector quantization (VQ) for image compression. The 2D-DWT works
in a non-separable fashion using a parallel filter structure with distributed control to compute two resolution levels. The
wavelet coefficients of the higher frequency sub-bands are vector quantized using multi-resolution codebook and those of the
lower frequency sub-band at level two are scalar quantized and entropy encoded. VQ is carried out by self organizing feature
map (SOFM) neural nets working at the recall phase. Codebooks are quickly generated off-line using the same nets functioning
at the training phase. The complete system, including the 2D-DWT, the multi-resolution codebook VQ, and the statistical encoder,
was implemented on a Xilinx Virtex 4 FPGA and is capable of performing real-time compression for digital video when dealing
with grayscale 512 × 512 pixels images. It offers high compression quality (PSNR values around 35 dB) and acceptable compression
rate values (0.62 bpp).
相似文献
Javier Diaz-CarmonaEmail: |
85.
Sanabria NR Peralta YM Monta?ez MK Rodríguez-Valencia N Molina R Moreno S 《Water science and technology》2012,66(8):1663-1668
The effluent from the anaerobic biological treatment of coffee wet processing wastewater (CWPW) contains a non-biodegradable compound that must be treated before it is discharged into a water source. In this paper, the wet hydrogen peroxide catalytic oxidation (WHPCO) process using Al-Ce-Fe-PILC catalysts was researched as a post-treatment system for CWPW and tested in a semi-batch reactor at atmospheric pressure and 25 °C. The Al-Ce-Fe-PILC achieved a high conversion rate of total phenolic compounds (70%) and mineralization to CO(2) (50%) after 5 h reaction time. The chemical oxygen demand (COD) of coffee processing wastewater after wet hydrogen peroxide catalytic oxidation was reduced in 66%. The combination of the two treatment methods, biological (developed by Cenicafé) and catalytic oxidation with Al-Ce-Fe-PILC, achieved a 97% reduction of COD in CWPW. Therefore, the WHPCO using Al-Ce-Fe-PILC catalysts is a viable alternative for the post-treatment of coffee processing wastewater. 相似文献
86.
Markets liquidity is an issue of very high concern in financial risk management. In a perfect liquid market the option pricing model becomes the well-known linear Black–Scholes problem. Nonlinear models appear when transaction costs or illiquid market effects are taken into account. This paper deals with the numerical analysis of nonlinear Black–Scholes equations modeling illiquid markets when price impact in the underlying asset market affects the replication of a European contingent claim. Numerical analysis of a nonlinear model is necessary because disregarded computations may waste a good mathematical model. In this paper we propose a finite-difference numerical scheme that guarantees positivity of the solution as well as stability and consistency. 相似文献
87.
Juan L. Mata-Machuca Rafael Martínez-Guerra 《Computers & Mathematics with Applications》2012,63(6):1072-1078
In this paper we deal with the observer-based asymptotic synchronization problem for a class of chaotic oscillators. Some results based on a differential algebraic approach are used in order to determine the algebraic observability of unknown variables. The strategy consists of proposing a slave system (observer) which tends to follow asymptotically the master system. The methodology is tested in the real-time asymptotic synchronization of the Colpitts oscillator by means of a proportional reduced order observer (PROO) of free-model type. 相似文献
88.
A multi-objective evolutionary algorithm for an effective tuning of?fuzzy logic controllers in?heating, ventilating and air conditioning systems 总被引:5,自引:5,他引:0
This paper focuses on the use of multi-objective evolutionary algorithms to develop smartly tuned fuzzy logic controllers
dedicated to the control of heating, ventilating and air conditioning systems, energy performance, stability and indoor comfort
requirements. This problem presents some specific restrictions that make it very particular and complex because of the large
time requirements needed to consider multiple criteria (which enlarge the solution search space) and the long computation
time models required in each evaluation. 相似文献
89.
This paper describes a heterogeneous modular robot system design which attempts to give a quick solution to a diversity of tasks. The approach is based on the use of an inventory of three types of modules i.e., power and control module, joint module and specialized module. Each module type aims to balance versatility and functionality. Their design permits rapid and cost effective design and fabrication. They are interchangeable in different ways to form different robot or system configurations. Depending on the task, the operator decides what type of robot can provide the best performance within the mission. A spherical joint module is described and used to build different robots, hence, forward and inverse kinematics models are obtained. Finally, from the modules described in this work, several robot configurations such as robotic arms, leg-based robots and wheel-based robots are assembled to demonstrate the execution of manipulation and locomotion tasks. 相似文献
90.
Integration of collaboration and interaction analysis mechanisms in a concern-based architecture for groupware systems 总被引:1,自引:0,他引:1
Collaboration and interaction analysis allows for the characterization and study of the collaborative work performed by the users of a groupware system. The results of the analyzed processes allow problems in users’ collaborative work and shortcomings in the functionalities of the groupware system to be identified. Therefore, automating collaboration and interaction analysis enables users’ work to be assessed and groupware system support and behavior to be improved. This article proposes a concern-based architecture to be used by groupware developers as a guide to the integration of analysis subsystems into groupware systems. This architecture was followed to design the COLLECE groupware system, which supports collaborative programming practices and integrates an analysis subsystem that assesses different aspects of the work carried out by the programmers and adapts the functionality of the system under specific conditions. 相似文献