Improving the energy efficiency of buildings by examining their heating, ventilating, and air-conditioning (HVAC) systems represents an opportunity. To improve energy efficiency, to increase occupant comfort, and to p...
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Improving the energy efficiency of buildings by examining their heating, ventilating, and air-conditioning (HVAC) systems represents an opportunity. To improve energy efficiency, to increase occupant comfort, and to provide better system operation and control algorithms for these systems, online estimation of system parameters, including system thermophysical parameters and thermal loads, is desirable. Several reported studies have presented simulation results and assumed that the thermal loads are known. A difficulty in HVAC system parameter estimation is that most HVAC systems are nonlinear have multiple and time varying parameters, and require an estimate of the thermal loads for a building zone. In this study, building zones and variable-air-volume units are modeled. The system parameters including the thermal loads are estimated using the recursive-least-squares method with a variable forgetting factor. The sensitivity of the estimation results to different factors is examined. The estimated parameters are used to predict the zone and variable-air-volume-discharge-air temperatures. Several experiments are used to validate the prediction results. The comparisons show good agreement between the experiments and the prediction results.
This paper describes an accurate automated technique of terrestrial photogrammetry that is applied to weather images obtained in uncontrolled circumstances such as unknown focal length and 3D camera orientation ( azim...
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This paper describes an accurate automated technique of terrestrial photogrammetry that is applied to weather images obtained in uncontrolled circumstances such as unknown focal length and 3D camera orientation ( azimuth and tilt of the optical axis, and roll about this axis), principal point unmarked on the image, and undetermined lens horizon. With the possible exception of the principal point, these quantities are deduced rapidly by a computer algorithm, with input consisting of accurate azimuth and elevation angles of landmarks that appear in the image. The algorithm works for wide-angle as well as for telephoto images and is more accurate than previous methods, which are based on assumptions of small angles and zero roll. Results are insensitive to the exact position of the principal point for telephoto images. For wide-angle photography, the principal point can be determined only if there is a sufficient number of accurately measured landmarks with diverse azimuth and elevation angles. If all the landmarks have low elevation angles, the principal point is impossible to determine and must be assumed to lie at the intersection of the diagonals of the uncropped image. The algorithm also provides the azimuth and elevation angle of any object, given the position of its image in the photograph. A photogrammetric search technique is described for finding an entity, which is visible in one camera's photography, in the simultaneous image obtained from a different direction by a second camera. Once the same object has been identified in both images, its 3D position is determined by triangulation.
The conjugate gradient method of minimization is applied successfully in the present optimal control algorithm in determining the optimal boundary control function for a concurrent flow problem based on the desired th...
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The conjugate gradient method of minimization is applied successfully in the present optimal control algorithm in determining the optimal boundary control function for a concurrent flow problem based on the desired thermal entry length and fluid temperatures. The validity of the present optimal control analysis is examined by means of numerical experiments.. Different desired thermal entry length and fluid temperature distributions are given in three test cases and the corresponding optimal control heat fluxes are determined. The results show that the optimal boundary heat fluxes can be obtained with an arbitrary initial guess within seconds of CPU time on a Pentium III-600 MHz PC. (C) 2002 Elsevier Science Ltd. All rights reserved.
Atomistic simulations of protein folding have the potential to be a great complement to experimental studies, but have been severely limited by the time scales accessible with current computer hardware and algorithms....
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Atomistic simulations of protein folding have the potential to be a great complement to experimental studies, but have been severely limited by the time scales accessible with current computer hardware and algorithms. By employing a worldwide distributed computing network of tens of thousands of PCs and algorithms designed to efficiently utilize this new many-processor, highly heterogeneous, loosely coupled distributed computing paradigm, we have been able to simulate hundreds of microseconds of atomistic molecular dynamics. This has allowed us to directly simulate the folding mechanism and to accurately predict the folding rate of several fast-folding proteins and polymers, including a nonbiological helix, polypeptide alpha-helices, a beta-hairpin, and a three-helix bundle protein from the villin headpiece. Our results demonstrate that one can reach the time scales needed to simulate fast folding using distributed computing, and that potential sets used to describe interatomic interactions are sufficiently accurate to reach the folded state with experimentally validated rates, at least for small proteins. (C) 2002 Wiley Periodicals, Inc.
The applicability of the accommodating function, a relatively new measure for the quality of on-line algorithms, is extended. The standard quality measure for on-line algorithms is the competitive ratio, which is, rou...
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The applicability of the accommodating function, a relatively new measure for the quality of on-line algorithms, is extended. The standard quality measure for on-line algorithms is the competitive ratio, which is, roughly speaking, the worst case ratio of the on-line performance to the optimal off-line performance. However, for many on-line problems, the competitive ratio gives overly pessimistic results and/or fails to distinguish between algorithms that are known to perform very differently in practice. Many researchers have proposed variations on the competitive ratio to obtain more realistic results. These variations are often tailor-made for specific on-line problems. The concept of the accommodating function applies to any on-line problem with some limited resource, such as bins, seats in a train, or pages in a cache. If a limited amount n of some resource is available, the accommodating function A(alpha) is the competitive ratio when input sequences are restricted to those for which the amount alphan of resources suffices for an optimal off-line algorithm. For all resource bounded problems, the standard competitive ratio is lim(alpha-->infinity) A(alpha). The accommodating function was originally used only for alpha greater than or equal to 1. We focus on alpha < 1, observe that the function now appears interesting for a greater variety of problems, and use it to make new distinctions between known algorithms and to find new ones.
A new and efficient multiscale model for the segmentation of synthetic aperture radar imagery namely the mixture multiscale autoregressive (MMAR) model, is presented. The estimation of parameters is easily performed v...
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A new and efficient multiscale model for the segmentation of synthetic aperture radar imagery namely the mixture multiscale autoregressive (MMAR) model, is presented. The estimation of parameters is easily performed via expectation maximisation algorithm. Experimental results of the MMAR model are proposed and compared with those of previous methods.
An ideal schedule minimizes both makespan and total flow time. It is known that the Coffman-Graham algorithm [Acta Informatica 1, 200-213, 1972] solves in polynomial time the problem of finding an ideal nonpreemptive ...
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An ideal schedule minimizes both makespan and total flow time. It is known that the Coffman-Graham algorithm [Acta Informatica 1, 200-213, 1972] solves in polynomial time the problem of finding an ideal nonpreemptive schedule of unit-execution-time jobs with equal release dates and arbitrary precedence constraints on two identical parallel processors. This paper presents an extension of the algorithm that solves in polynomial time the preemptive counterpart of this problem. The complexity status of the preemptive problem of minimizing just the total flow time has been open.
Lack of or improper commissioning, the inability of the building operators to grasp the complexity controls, and lack of proper maintenance lead to inefficient operations and reduced lifetimes of equipment. If regular...
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Lack of or improper commissioning, the inability of the building operators to grasp the complexity controls, and lack of proper maintenance lead to inefficient operations and reduced lifetimes of equipment. If regularly scheduled manual maintenance or recommissioning practices are adopted, they can be expensive and time consuming. Automated proactive commissioning and diagnostic technologies applied to parts of the commissioning process address two of the main barriers to commissioning cost and schedules. Automated proactive commissioning and diagnostic tools can reduce both the cost and time associated with commissioning, as well as enhance the persistence of commissioning fixes. In the long run, automation even offers the potential for automatically correcting problems by reconfiguring controls or changing control algorithms dynamically. This paper discusses procedures and processes that can be used to automate and continuously commission the economizer operation and outdoor-air ventilation systems of an air-handling unit.
A computationally efficient algorithm is presented for 3-D near-field source localisation using a uniform circular array. Algebraic relations are demonstrated between the incident angles (elevation angle and azimuth a...
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A computationally efficient algorithm is presented for 3-D near-field source localisation using a uniform circular array. Algebraic relations are demonstrated between the incident angles (elevation angle and azimuth angle) under the far-field assumption and the actual near-field location (range, elevation angle, and azimuth angle). Using these relations as paths to follow to the peak of the 3-D MUSIC spectrum, the proposed algorithm replaces the 3-D search required in the conventional 3-D MUSIC with a 1-D path-following after a 2-D initialisation, thereby reducing the computational burden.
Optical sensors, stereoscopic cameras, and complex computer algorithms are helping robots perceive, maneuver, and manipulate their environments in increasingly sophisticated ways.
Optical sensors, stereoscopic cameras, and complex computer algorithms are helping robots perceive, maneuver, and manipulate their environments in increasingly sophisticated ways.
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