A conceptual framework to define the spatial resolution requirements for agricultural monitoring using remote sensing

Satellite remote sensing is an invaluable tool to monitor agricultural resources. However, spatial patterns in agricultural landscapes vary significantly across the Earth resulting in different imagery requirements depending on what part of the globe is observed. Furthermore, there is an increasing diversity of Earth observation instruments providing imagery with various configurations of spatial, temporal, spectral and angular resolutions. In terms of spatial resolution, the choice of imagery should be conditioned by knowing the appropriate spatial frequency at which the landscape must be sampled with the imaging instrument in order to provide the required information from the targeted fields. This paper presents a conceptual framework to define quantitatively such requirements for both crop area estimation and crop growth monitoring based on user-defined constraints. The methodological development is based on simulating how agricultural landscapes, and more specifically the fields covered by a crop of interest, are seen by instruments with increasingly coarser resolving power. The results are provided not only in terms of acceptable pixel size but also of pixel purity which is the degree of homogeneity with respect to the target crop. This trade-off between size and purity can be adjusted according to the end-user's requirements. The method is implemented over various agricultural landscapes with contrasting spatial patterns, demonstrating its operational applicability. This diagnostic approach can be used: (i) to guide users in choosing the most appropriate imagery for their application, (ii) to evaluate the adequacy of existing remote sensing systems for monitoring agriculture in different regions of the world and (iii) to provide guidelines for space agencies to design future instruments dedicated to agriculture monitoring.     

Optimal twist vectors as a tool for interpolating a network of curves with a minimum energy surface

This paper provides a new answer to the old problem of specifying the mixed partial derivatives (MPDs) or ‘twist vectors’ at the grid points for an interpolating surface over a rectangular network of curves. An algorithm is presented for finding the MPDs that minimizes a generalized energy integral over the entire surface. The integrand may be any quadratic form in the second partial derivatives of the surface. This results in a surface design technique for interpolating over a network of curves by automatically selecting the optimal twist vectors at the grid points.     

Parametric representation of a surface pencil with a common spatial geodesic

In this paper, we study the problem of constructing a family of surfaces from a given spatial geodesic curve. We derive a parametric representation for a surface pencil whose members share the same geodesic curve as an isoparametric curve. By utilizing the Frenet trihedron frame along the given geodesic, we express the surface pencil as a linear combination of the components of this local coordinate frame, and derive the necessary and sufficient conditions for the coefficients to satisfy both the geodesic and the isoparametric requirements. We illustrate and verify the method by finding exact surface pencil formulations for some simple surfaces, such as surfaces of revolution and ruled surfaces. Finally, we demonstrate the use of this method in a garment design application.     

A conceptual framework for component context specification and representation in a metaCASE environment

A lack of design information can be a significant barrier for systems developers when developing and reusing a component. This paper tackles this problem by presenting and exemplifying the conceptual framework of component context and its hypertext representation in a metaCASE environment. It discusses the linking of contextual knowledge to components in systems analysis and design. The contextual knowledge includes the conceptual dependencies of component definition, reuse, and implementation, as well as the reasoning and rationale behind design and reuse processes. We also illustrate the hypertext approach to contextual knowledge representation that enables designers to express, record, explore, recognize, and negotiate their shared context within a metaCASE environment.

A monitor tool for a network based on the cambridge ring

An evolving network is subject to technological advances and increasing user demands through out its lifetime. Continuous monitoring is therefore required to understand its behaviour in the operational environment and to provide an aid to planning. A monitor tool has been developed to meet such requirements in a heavily used service network. A decentralized but integrated approach has been adopted. An active collection allows accumulated measurements to be retrieved. The measurements required are determined and the constraints imposed by existing mechanisms and the methods chosen are discussed. Flexible user facilities are available to allow selected measurements to be collected and displayed, and these are described. Daily sessions of network-wide monitoring have been undertaken. The overhead incurred is quantified. The sessions revealed communications software errors and anomalous behaviour of a network node. Further analysis shows the symptoms of the latter, the result of a hardware fault. Enhancements which would increase the flexibility of the tool are also suggested.     

农业智能系统开发平台的知识表示与推理策略

针对农业智能系统的知识特点,提出基于框架知识单元和求解知识单元的知识组织结构,同时采用XML作为知识描述语言的知识表示方法,在此基础上采用混合推理的推理策略,并实现了不确定推理．该知识表示方法和推理策略已经在工作中得到实际应用,较以往知识表示方法,在知识获取、知识的直观充分表达、知识扩充、知识模块化、知识共享等方面都取得了很好的效果．     

A practical procedure for conceptual design and testing of machine tool structure

This paper discusses the initial development of a machine tool and its structure (concept, calculation, design) and the verification of the prototype. The topics studied include two issues: static rigidity and dynamic stability. For static rigidity several experiments and modelling studies using the finite element method have been carried out in order to identify the model parameters. In this way differences between models of bolted joints, slideways and the cross-section of the structural elements have been determined. The model is formed by design documentation and later verified through experiments on the prototype of the machine. The approach is different in the case of dynamic stability. The model is not made on the basis of design documentation or static calculations, but by experiments performed on the prototype. This relates to an oriented transfer function; parameters are determined by fitting experimental transfer function curves. With this model, the stability is analyzed under different machining conditions. Specific features of this methodology are as follows:

• • The finite element method is used for qualitative comparison of different machine tool structure concepts during the conceptual and design stages. Only after completion of the prototype may the parameters of the prototype model be adjusted for the purpose of obtaining quantitative indicators.

• • Dynamics are analyzed by parameter identification of the oriented transfer function model. The dominant degree of freedom is naturally selected by experiment and not from hypotheses about the behavior of structures obtained from mathematical manipulations such as expansion of the model according to the finite element method. If necessary another machine tool structure may be modelled; in this way hypotheses are drawn about the stability of the reconstructed prototype.

Such a procedure has been applied and verified on the machine tool structure of a horizontal machining center. Results for static rigidity and dynamic stability have been obtained from the model and experiments performed on the prototype. The following techniques have been used:

• • finite element method for qualitative identification of static behavior,

• • self-excitation of the machine,

• • digital signal processing on the FFT basis,

• • smoothing of curves and digital filtration,

• • function fitting of the transfer function (modal analysis),

• • coefficient calculus and oriented transfer function,

• • stability assessment of the fitted model under different machining conditions, and

• • modelling of the regenerative machining effect by cutting.

Necessary tests have been done by instruments required for the use of the above techniques.

Such a combined static-dynamic criteria procedure for structuring a machine tool enables efficient follow-up of all results and facilitates necessary future expansion, the utilization of universal equipment, the combination of modelling and experiments, and the synthesis of simple models of the examined machine with behavior identical to the machine. The well-known machining system dynamic stability theories are applied to such models.     

Effectiveness of spatial representation in the formation of network communities: experimental study on community organizer

In this paper, we present and discuss Community Organizer, a system designed to support network communities. The main characteristic of Community Organizer is the use of spatial representations for the relationships among community members including the communications exchanged among these members. These spatial representations reflect the degree of closeness of interests and concerns among the members, and are intended to provide users with clues on how to form network communities. In order to investigate the effectiveness of the proposed spatial representations, we conducted experiments with two different versions of the software. One version offered meaningful spatial representations while the other version did not. The subjects who used the former software version felt a greater sense of ‘community’, enjoyed using the software more, and actively used it longer than the subjects using the latter software version (control condition). These results indicated that the proposed spatial representations are effective in supporting network community formation.     

NEPTUNE: A new expert planning tool for users in a network environment

MARS (mission activities and resources scheduler) is a planning and scheduling tool for both automatic and interactive generation of spacecraft timelines of realistic complexity, which has been extensively tested, e.g. for HERMES, EURECA, or Spacelab mission planning. In its new version it has been extended to include full distributed mission planning capability (as required for the COLUMBUS mission planning scenario) under the ESA contract NEPTUNE (new expert planning tool for users in a network environment). This paper describes the main features of the planning tool MARS in its new NEPTUNE version and sketches its applicability to the distributed mission planning scenario and for other (non-space) domains.     

Real world representation of a road network for route planning in GIS

This paper addresses a methodology to properly represent a road network in the geographic information system (GIS) for network analysis. Over the years, the real world has become too complex to model properly within a given information system, such as GIS. Ideally, when the real world is represented as accurately as possible, a GIS can answer a question in its virtual world that coincides with the exact answer in the real world. However, existing methods related to impedance modeling for each segment of a road network in a route planning analysis that includes only a distance or time variable do not give proper results. Hence, this study investigates how a road network can represent the real world in a GIS and offer route planning tools. To address this, first, additional realistic variables are taken into account. These include weather, sight-seeing information, road type, and so on. Second, to combine these variables, an impedance model (IM) using the analytical hierarchical process (AHP) method is proposed. Finally, all of the models are implemented and verified with a sensitivity analysis. The models were successfully implemented in this work. All of the paths of the route planning analysis were successfully matched with the drivers’ paths that would normally be chosen in reality. It is anticipated that the use of other techniques such as analytical network process (ANP) in addition to AHP would be useful to overcome the aforementioned problem.     

A three-way clusterwise multidimensional unfolding procedure for the spatial representation of context dependent preferences

Various deterministic and latent structure approaches for combining forms of multidimensional scaling and cluster analysis have been previously discussed. A new clusterwise three-way unfolding methodology for the analysis of two-way or three-way metric dominance/preference data is proposed. The purpose of this proposed methodology is to simultaneously estimate a joint space of stimuli and cluster ideal point representations, as well as the clusters themselves, such that the geometry underlying the clusterwise model renders some indication of the underlying structure in the data. In the three-way case, it is shown how multiple ideal points can represent preference change over contexts or situations. Partitions, overlapping clusters, stationary and context dependent preference representations are allowed. After a literature review of related methodological research, the technical details of the proposed three-way clusterwise spatial unfolding model are presented in terms of modeling context/situational dependent preferences (i.e., preferences for various stimuli collected over the same set of subjects over time, situation, etc.). The psychological basis for the models is provided in terms of the extensive behavioral decision theory and consumer psychology literature on contextual preferences and situational effects. An application to a data set exploring preferences for breakfast/snack food data over a number of different usage situations is then presented, followed by a discussion on future potential research directions.     

Virtual Loom: a tool for the interactive 3D representation of historical fabrics

Multimedia Tools and Applications - 3D modelling of man-made objects is widely used in the cultural heritage sector, among others. It is relevant for its documentation, dissemination and...     

A neural network model for the acquisition of a spatial body scheme through sensorimotor interaction

This letter presents a novel unsupervised sensory matching learning technique for the development of an internal representation of three-dimensional information. The representation is invariant with respect to the sensory modalities involved. Acquisition of the internal representation is demonstrated with a neural network model of a sensorimotor system of a simple model creature, consisting of a tactile-sensitive body and a multiple-degrees-of-freedom arm with proprioceptive sensitivity. Acquisition of the 3D representation as well as a distributed representation of the body scheme, occurs through sensorimotor interactions (i.e., the sensory-motor experience of the creature). Convergence of the learning is demonstrated through computer simulations for the model creature with a 7-DoF arm and a spherical body covered by 20 tactile fields.     

A tool for the generation of realistic network workload for emerging networking scenarios

Internet workload is a mix of many and complex sources. Therefore, its accurate and realistic replication is a difficult and challenging task. Such difficulties are exacerbated by the multidimensional heterogeneity and scale of the current Internet combined with its constant evolution. The study and generation of network workload is a moving target, both in terms of actors (devices, access networks, protocols, applications, services) and in terms of case studies (the interest expands from performance analysis to topics like network neutrality and security). In order to keep up with the new questions that arise and with the consequent new technical challenges, networking research needs to continuously update its tools. In this paper, we describe the main properties that a network workload generator should have today, and we present a tool for the generation of realistic network workload that can be used for the study of emerging networking scenarios. In particular, we discuss (i) how it tackles the main issues challenging the representative replication of network workload, and (ii) our design choices and its advanced features that make it suitable to analyze complex and emerging network scenarios. To highlight how our tool advances the state-of-the-art, we finally report some experimental results related to the study of hot topics like (a) broadband Internet performance and network neutrality violations; (b) RFC-based security and performance assessment of home network devices; (c) performance analysis of multimedia communications.     

A tool for risk-based management of surface water quality

Water quality Risk Analysis Tool (WaterRAT) is software for supporting decision-making in surface water quality management. The philosophy behind the software is that uncertainty in water quality model predictions is inevitably high due to model equation error, parameter error, and limited definition of boundary conditions and management objectives. Using sensitivity and uncertainty analyses based on Monte Carlo simulation and first order methods, WaterRAT allows the modeller to identify the significant uncertainties, and evaluate the degree to which they control decision-making risk. WaterRAT has a library of river and lake water quality models of varying complexity, and these can be applied at a wide range of temporal and spatial scales, allowing the model design to be responsive to both the modelling task and the data constraints.     

A CAVE-like environment as a tool for full-size train design

Simulations of models, in all different areas, is an expanding, attractive line of work. More and more applications are taking advantage of the improvements in technology and knowledge in this field, thus achieving results that would have been impossible to achieve with a real model, or foreseeing facts that otherwise would have been encountered too late in the production process. The rail industry is one possible beneficiary of this approach. Usually, before commencing the fabrication process of a new train, the construction of a full-size model is mandatory. Instead of building this full-size real model, which leaves little room for later, last-minute modifications, a virtual model can be built in the digital realm, thus offering a new platform for easier interaction with it. In this article, a simulation of a train is presented in order to tackle visual, aesthetic and ergonomic issues. The simulation runs on a PC-based CAVE-like architecture, offering a certain degree of interaction to the user, and combines static and dynamic computer-generated imagery, both with and without stereoscopy for 3D visualisation, as well as augmented virtuality techniques for the integration of the train with its environment.     

A network flow model for load balancing in circuit-switchedmulticomputers

In multicomputers that utilize circuit switching or wormhole routing, communication overhead depends largely on link contention-the variation due to distance between nodes is negligible. This has a major impact on the load balancing problem. In this case there are some nodes with an excess load (sources) and other with a deficit load (sinks). A matching of sources to sinks is required to avoid contention. The problem is made complex by the hardwired routing on currently available machines: The user can control only which nodes communicate but not how the messages are routed. Network flow models of message flow in the mesh and the hypercube have been developed to solve this problem. The crucial property of these models is the correspondence between minimum cost flows and correctly routed messages. To solve a given load balancing problem, a minimum cost flow algorithm is applied to the network. This permits the efficient determination of a maximum contention free matching of sources to sinks that, in turn, tells how much of the given imbalance can be eliminated without contention     

A general theory of spatial relations to support a graphical tool for visual information extraction

In this paper we present a general spatial composition framework which allows one to model the graphical objects and the spatial relations of a large class of visual languages. The new formalism has been implemented within the SRQ tool, a software system for the Visual Information Extraction, enabling it to work on a wider range of domains. In particular, in the paper we describe the application of SRQ to geospatial data.     

A CAD tool for an array of differential oscillators coupled through a broadband network

A new expression of the equations describing the locked states of two oscillators coupled through a resistor is presented in this article. This theory has led to the elaboration of a CAD tool which provides, in a short simulation time, the frequency locking region of two coupled differential oscillators. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.