摘要:

AbstractA general formulation of the inverse problem of how to control an airplane when it is performing a prescribed maneuver is presented. The general nonlinear equations of the forced motion of a rigid airplane are written in terms of generalized coordinates. The trajectory of the prescribed maneuver is modeled as a set of dynamic constraints on the previous equations. The equations are directly integrated to obtain the control vector necessary to realize the prescribed maneuver. An application to a fighter aircraft circular- loop simulation is studied as a special case of the proposed technique.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760194

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractNoise and vibration produced by mechanical systems will usually reach the environment by a variety of paths. For example, noise from a ship’s diesel engine may be transmitted to the ship’s structure via the engine mounts, the air intake, the exhaust, the cooling water system, the air in the engine compartment, and possibly by other mechanisms.Methods for noise reduction usually involve attempting to identify the most important path or paths, and then incorporating some form of vibration isolation: for example, standing an engine on rubber blocks to reduce transmission via the mounts. Frequently, such measures in fact give little reduction in noise. This may be because the remaining noise paths are responsible for a large part of the noise transmission; alternatively some noise paths may interfere destructively, so that blocking one can actually lead to an increase in noise transmission. It is therefore of great value to be able to characterise the contributions of the paths before planning noise reduction measures.In this paper we present a method of determining the contributions of individual paths to the transmitted noise. The method is non-intrusive: no changes to the system under investigation are required. We have christened it‘MPSD’(Multiple Path Signature Decomposition). We present an analysis of the principles of operation of the method and of the predictions which may be made from them regarding noise control. The method has been proven on practical systems. We present results from an experiment on an air compressor.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760195

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractThis paper discusses a resource leveling problem in the maintenance turn-around of a drillship. The problem is that manpower resource requirements vary considerably during the maintenance period, resulting in increased downtime costs, labor idleness, hiring, and firing. In the first phase of the study, two simple heuristic algorithms have been developed for resource leveling. They are found to be effective. The second phase deals with the application of simulation to study the distribution of leveled resource requirement over the maintenance period. The study attempts to assist the maintenance personnel in improving manpower planning and control.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760196

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractHigh-resolution global measurement of the near-surface wind field over the ocean's surface is of critical importance in weather forecasting and in many oceanographic and meteorological studies. Such measurements can be provided by space-borne radar scatterometers. Scatterometers make indirect measurements of the wind by first measuring the surface radar backscatter from which the wind vector is“retrieved”or estimated. A new model-based technique for wind estimation promises improved measurement accuracy. This method is based on a mesoscale model for the near-surface oceanic wind field. The wind field model represents a trade-ofr between modelling accuracy and computational complexity in the estimation procedure. It is based on the geostrophic approximation and simplistic assumptions about the wind field vorticity and divergence, but includes ageostrophic winds. Simulation of oceanic wind fields and the scatterometer measurement system played a key role in the development and evaluation of the model. In this paper, the development and evaluation of the wind field model is described. The role of simulation in performing trade-offs between the model accuracyand the computational complexity of the model-based estimation procedure is discussed. The model development is an excellent case study of how modelling can be applied to improve the performance of a complex measurement system, and how simulation can be applied to develop and evaluate modelling techniques. A brief comparison of wind estimates made from simulated measurements and estimates based on actual measurements made by the SKASAT scatterometer is provided.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760197

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractFactory modelling is a mathematical description in terms of state equations of the dynamics of factory facilities, such as machines, transport devices and stores, where manufacturing processes are actuated by a production control system to yield market- or customer-oriented products.Factory modelling is preliminary to the design of the production control system, i.e. of the set of devices and rules that allow a manufacturing system (the whole of factory facilities and their feasible manufacturing processes) to track with the least possible error a variable product mix.Although several methodologies for modelling factory dynamics have been worked out and implemented in recent years, no systematic approach for production control design, based on state equations, has so far been available. Hence a new modelling framework has been worked out and its foundations are presented in this paper.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760198

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractThe onset of a large number of a plant organ infections is linked to air temperature and humidity; according to laboratory studies, the threshold value of leaf-wetness duration is also important for many airborne fungi diseases.Various kinds of electronic equipment can estimate this parameter, which is used in agrometeorological pest control models. With a good degree of approximation, they can forecast the probability of airborne scab on apple trees and are based on precipitation, air temperature and leaf-wetness duration data, obtained at least at two-hour intervals. These models, in use at the Emilia-Romagna Regional Meteorological Service, are based on data from a network of automatic weather stations located in apple-growing areas.Since there are less stations than apple-growing areas, and because of the high cost of automatic stations, a numerical model was developed for deriving lehf wetness duration for use when such data are missing or when there is no electronic sensor.The model is based on stepwise regression analysis applied to 4 years’data collected by two automatic stations belonging to the network. The stepwise regression analysis, utilizing the BMDP statistical package, selects temperature, humidity and precipitation values, which are sufficient to explain more than 75% of the wetness duration variability.The estimated data are used to estimate the probability and the intensity of infection. These estimated probabilities are compared with the values derived from the application of models based on data from the electronic sensors. We find that the results agree.The estimate of airborne infection is based on precipitation and temperature data, while the degree of infection is based on humidity and temperature data. These two variables have a spatial variation law which is more easily computed than those of precipitation or wetness duration. The numerical model can be used to estimate infection in areas not equipped with electronic stations; some results are presented.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760199

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractThis paper presents some of the basic concepts and techniques for the modelling of data networks and the determination of performance measures.A simple example of data traffic flow and the service time are investigated first. Then the average message delay traversing the network is decomposed into average message delays on the individual links between node-pairs.It is shown that each link and the associated node-pair in the network can be modeled by a single-server queue. Applications of several singleserver queues to the performance analysis of data networks are also discussed. A simple example and simulation results are presented for illustration.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760200

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractWireless optical links based on diffuse infrared (IR) light propagation can be used in a host of Indoor applications such as mobile links, and offer flexibility during installation or system expansion, EMI immunity, and substantial cost savings. In such systems, it is Important to know the IR-slgnal power requirements due to the bandwidth and peak-power limitations of LED sources. This paper presents a method for predicting the required IR signal level on the basis of room parameters, Including reflection coefficients and the light intensity distribution pattern. The resulting curves constitute a quick reference for the designer of such links.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760201

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractThis paper presents a procedure for empirically generating a reduced- order model of a system given a plethora of sensor data. Data reduction is performed at the onset by projection onto an orthogonal subspace to yield a reduced-order state. The reduced-order state is estimated at each point in time using spatial filtering. Spatial filtering is a suboptimal state estimation technique which has the advantage of decoupling the state estimation and system identification problems. State space system identification is then performed given the estimates of the reduced-order suite. The truncated Karhunen-Loeve (KL) transform is used to define the reduced-order state. The KL transform is optimal for the initial data reduction and yields a number of simplifications in the state estimation and system identification algorithms. A recursive formulation of the entire procedure is presented. The algorithm is illustrated by application to an example.

ISSN:0228-6203    

DOI:10.1080/02286203.1993.11760202

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor