Sharing 3D city models: an overview

This study describes the computing methods now available to enable the sharing of three-dimensional (3D) data between various stakeholders for the purposes of city modeling and considers the need for a seamless approach for sharing, transmitting, and maintaining 3D city models. The study offers an overview of the technologies and the issues related to remote access, collaboration, and version control. It builds upon previous research on 3D city models where issues were raised on utilizing, updating and maintaining 3D city models and providing access to various stakeholders. This paper will also describe a case study which is currently analyzing the remote access requirements for a sustainable computer model of NewcastleGateshead in England. Options available will be examined and areas of future research will be discussed

A Survey of Access Control Models in Wireless Sensor Networks

Copyright 2014 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/)Wireless sensor networks (WSNs) have attracted considerable interest in the research community, because of their wide range of applications. However, due to the distributed nature of WSNs and their deployment in remote areas, these networks are vulnerable to numerous security threats that can adversely affect their proper functioning. Resource constraints in sensor nodes mean that security mechanisms with a large overhead of computation and communication are impractical to use in WSNs; security in sensor networks is, therefore, a challenge. Access control is a critical security service that offers the appropriate access privileges to legitimate users and prevents illegitimate users from unauthorized access. However, access control has not received much attention in the context of WSNs. This paper provides an overview of security threats and attacks, outlines the security requirements and presents a state-of-the-art survey on access control models, including a comparison and evaluation based on their characteristics in WSNs. Potential challenging issues for access control schemes in WSNs are also discussed.Peer reviewe

Confidentiality-Preserving Publish/Subscribe: A Survey

Publish/subscribe (pub/sub) is an attractive communication paradigm for large-scale distributed applications running across multiple administrative domains. Pub/sub allows event-based information dissemination based on constraints on the nature of the data rather than on pre-established communication channels. It is a natural fit for deployment in untrusted environments such as public clouds linking applications across multiple sites. However, pub/sub in untrusted environments lead to major confidentiality concerns stemming from the content-centric nature of the communications. This survey classifies and analyzes different approaches to confidentiality preservation for pub/sub, from applications of trust and access control models to novel encryption techniques. It provides an overview of the current challenges posed by confidentiality concerns and points to future research directions in this promising field

A survey on gain-scheduled control and filtering for parameter-varying systems

Copyright © 2014 Guoliang Wei et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.This paper presents an overview of the recent developments in the gain-scheduled control and filtering problems for the parameter-varying systems. First of all, we recall several important algorithms suitable for gain-scheduling method including gain-scheduled proportional-integral derivative (PID) control, H 2, H ∞ and mixed H 2 / H ∞ gain-scheduling methods as well as fuzzy gain-scheduling techniques. Secondly, various important parameter-varying system models are reviewed, for which gain-scheduled control and filtering issues are usually dealt with. In particular, in view of the randomly occurring phenomena with time-varying probability distributions, some results of our recent work based on the probability-dependent gain-scheduling methods are reviewed. Furthermore, some latest progress in this area is discussed. Finally, conclusions are drawn and several potential future research directions are outlined.The National Natural Science Foundation of China under Grants 61074016, 61374039, 61304010, and 61329301; the Natural Science Foundation of Jiangsu Province of China under Grant BK20130766; the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning; the Program for New Century Excellent Talents in University under Grant NCET-11-1051, the Leverhulme Trust of the U.K., the Alexander von Humboldt Foundation of Germany

Optimal fishery with coastal catch

In many spatial resource models, it is assumed that an agent is able to harvest the resource over the complete spatial domain. However, agents frequently only have access to a resource at particular locations at which a moving biomass, such as fish or game, may be caught or hunted. Here, we analyze an infinite time‐horizon optimal control problem with boundary harvesting and (systems of) parabolic partial differential equations as state dynamics. We formally derive the associated canonical system, consisting of a forward–backward diffusion system with boundary controls, and numerically compute the canonical steady states and the optimal time‐dependent paths, and their dependence on parameters. We start with some one‐species fishing models, and then extend the analysis to a predator–prey model of the Lotka–Volterra type. The models are rather generic, and our methods are quite general, and thus should be applicable to large classes of structurally similar bioeconomic problems with boundary controls. Recommedations for Resource Managers Just like ordinary differential equation‐constrained (optimal) control problems and distributed partial differential equation (PDE) constrained control problems, boundary control problems with PDE state dynamics may be formally treated by the Pontryagin's maximum principle or canonical system formalism (state and adjoint PDEs). These problems may have multiple (locally) optimal solutions; a first overview of suitable choices can be obtained by identifying canonical steady states. The computation of canonical paths toward some optimal steady state yields temporal information about the optimal harvesting, possibly including waiting time behavior for the stock to recover from a low‐stock initial state, and nonmonotonic (in time) harvesting efforts. Multispecies fishery models may lead to asymmetric effects; for instance, it may be optimal to capture a predator species to protect the prey, even for high costs and low market values of the predators

Integrated software for imaging data analysis applied to edge plasma physic and operational safety

Fusion tokamaks are complex devices requiring many diagnostics for real time control of the plasma and off-line physical analysis. In current tokamaks, imaging diagnostics have become increasingly used for these two purposes. Such systems produce a lot of data encouraging physicists to use shared tools and codes for data access and analysis. If general purpose software programs for data display and analysis are widely spread, a need exists in developing similar applications for quantitative imaging data analysis applied to plasma physic. In this paper, we introduce a new integrated software program, named wolff, dedicated to this task. The main contribution of this software is to gather under the same framework different functionalities for (1) data access and display, (2) signal, image, and video processing, and (3) quantitative analysis based on physical models. After an overview of existing solutions for data processing in the field of plasma data, we present the wolff architecture and its currently implemented features. The capabilities of the software are then demonstrated through three applications in the field of physical analysis (heat and particle flux calculations) and tokamak operation (safety operation)

Air pollution forecasts: An overview

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Air pollution is defined as a phenomenon harmful to the ecological system and the normal conditions of human existence and development when some substances in the atmosphere exceed a certain concentration. In the face of increasingly serious environmental pollution problems, scholars have conducted a significant quantity of related research, and in those studies, the forecasting of air pollution has been of paramount importance. As a precaution, the air pollution forecast is the basis for taking effective pollution control measures, and accurate forecasting of air pollution has become an important task. Extensive research indicates that the methods of air pollution forecasting can be broadly divided into three classical categories: statistical forecasting methods, artificial intelligence methods, and numerical forecasting methods. More recently, some hybrid models have been proposed, which can improve the forecast accuracy. To provide a clear perspective on air pollution forecasting, this study reviews the theory and application of those forecasting models. In addition, based on a comparison of different forecasting methods, the advantages and disadvantages of some methods of forecasting are also provided. This study aims to provide an overview of air pollution forecasting methods for easy access and reference by researchers, which will be helpful in further studies

Spin-dependent tunneling in magnetic tunnel junctions

The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunneling in magnetic tunnel junctions (MTJs) has recently aroused enormous interest and has developed in a vigorous field of research. The large tunneling magnetoresistance (TMR) observed in MTJs garnered much attention due to possible applications in non-volatile random access memories and next-generation magnetic field sensors. This led to a number of fundamental questions regarding the phenomenon of spindependent tunneling. In this review article we present an overview of this field of research. We discuss various factors that control the spin polarization and magnetoresistance in magnetic tunnel junctions. Starting from early experiments on spin-dependent tunneling and their interpretation, we consider thereafter recent experiments and models, which highlight the role of the electronic structure of the ferromagnets, the insulating layer and the ferromagnet/insulator interfaces. We also discuss the role of disorder in the barrier and in the ferromagnetic electrodes and their influence on TMR

Spin-dependent tunneling in magnetic tunnel junctions

The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunneling in magnetic tunnel junctions (MTJs) has recently aroused enormous interest and has developed in a vigorous field of research. The large tunneling magnetoresistance (TMR) observed in MTJs garnered much attention due to possible applications in non-volatile random access memories and next-generation magnetic field sensors. This led to a number of fundamental questions regarding the phenomenon of spindependent tunneling. In this review article we present an overview of this field of research. We discuss various factors that control the spin polarization and magnetoresistance in magnetic tunnel junctions. Starting from early experiments on spin-dependent tunneling and their interpretation, we consider thereafter recent experiments and models, which highlight the role of the electronic structure of the ferromagnets, the insulating layer and the ferromagnet/insulator interfaces. We also discuss the role of disorder in the barrier and in the ferromagnetic electrodes and their influence on TMR

Congestion Control for Vehicular Environments by Adjusting IEEE 802.11 Contention Window Size

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-03889-6_30Medium access control protocols should manage the highly dynamic nature of Vehicular Ad Hoc Networks (VANETs) and the variety of application requirements. Therefore, achieving a well-designed MAC protocol in VANETs is a challenging issue. The contention window is a critical element for handling medium access collisions in IEEE 802.11, and it highly affects the communications performance. This paper proposes a new contention window control scheme, called DBM-ACW, for VANET environments. Analysis and simulation results using OMNeT++ in urban scenarios show that DBM-ACW provides better overall performance compared with previous proposals, even with high network densities.This work was partially supported by the Ministerio de Ciencia e Innovación, Spain, under Grant TIN2011-27543-C03-01Balador, A.; Tavares De Araujo Cesariny Calafate, CM.; Cano Escribá, JC.; Manzoni, P. (2013). Congestion Control for Vehicular Environments by Adjusting IEEE 802.11 Contention Window Size. En Algorithms and Architectures for Parallel Processing. Springer. 259-266. https://doi.org/10.1007/978-3-319-03889-6_30S259266Booysen, M.J., Zeadally, S., van Rooyen, G.-J.: Survey of media access control protocols for vehicular ad hoc networks. IET Communications 5(11), 1619–1631 (2011)Kenney, J.: Standards and regulations. In: Hartenstein, H., Laberteaux, K.P. (eds.) VANET: Vehicular Applications and Inter-networking Technologies, ch. 10, pp. 365–428. Wiley (2010)Stanica, R., Chaput, E., Beylot, A.-L.: Enhancements of IEEE 802.11p Protocol for Access Control on a VANET Control Channel. In: 2011 IEEE International Conference on Communications (ICC), June 5-9, pp. 1–5 (2011)Calafate, C.T., Fortino, G., Fritsch, S., Monteiro, J., Cano, J., Manzoni, P.: An efficient and robust content delivery solution for IEEE 802.11p vehicular environments. Journal of Network and Computer Applications 35(2), 753–762 (2012)Cali, F., Conti, M., Gregori, E.: Dynamic tuning of the IEEE 802.11 protocol to achieve a theoretical throughput limit. IEEE/ACM Transactions on Networking 8(6), 785–799 (2000)Wu, H., Cheng, S., Peng, Y., Long, K., Ma, J.: IEEE 802.11 distributed coordination function (DCF): analysis and enhancement. In: IEEE International Conference on Communications, ICC 2002, vol. 1, pp. 605–609 (2002)Balador, A., Movaghar, A., Jabbehdari, S.: History based contention window control in ieee 802.11 mac protocol in error prone channel. Journal of Computer Science 6(2), 205–209 (2010)Chrysostomou, C., Djouvas, C., Lambrinos, L.: Applying adaptive QoS-aware medium access control in priority-based vehicular ad hoc networks. In: 2011 IEEE Symposium on Computers and Communications (ISCC), June 28-July 1, pp. 741–747 (2011)Jang, H.-C., Feng, W.-C.: Network Status Detection-Based Dynamic Adaptation of Contention Window in IEEE 802.11p. In: 2010 IEEE 71st Vehicular Technology Conference (VTC 2010-Spring), May 16-19, pp. 1–5 (2010)http://www.omnetpp.org/http://inet.omnetpp.org/Behrisch, M., Bieker, L., Erdmann, J., Krajzewicz, D.: SUMO - Simulation of Urban MObility: An Overview. In: The Third International Conference on Advances in System Simulation, SIMUL 2011 (2011)Baguena, M., Tornell, S., Torres, A., Calafate, C.T., Cano, J.C., Manzoni, P.: VACaMobil: VANET Car Mobility Manager for OMNeT++. In: IEEE International Conference on Communications 2013 - 3rd IEEE International Workshop on Smart Communication Protocols and Algorithms (SCPA 2013), Budapest, Hungary (June 2013)Baguena, M., Calafate, C.T., Cano, J., Manzoni, P.: Towards realistic vehicular network simulation models. In: 2012 IFIP Wireless Days (WD), November 21-23, pp. 1–3 (2012)http://www.openstreetmap.org