Attitude observability of a loosely-coupled GPS/Visual Odometry Integrated Navigation Filter

We present a novel method for integrating GPS position estimates with position and attitude estimates derived from visual odometry using a scheme similar to a classic loosely-coupled GPS/INS integration. Under such an arrangement, we derive the error dynamics of the system and develop a Kalman Filter for estimating the errors in position and attitude. Using a control-based approach to observability, we show that the errors in both position and attitude (including yaw) are fully observable when there is a component of acceleration perpendicular to the velocity vector in the navigation frame. Numerical simulations are performed to confirm the observability analysis.

Study of robust H(infinity) filtering application in loosely coupled INS/GPS system

Since a celebrate linear minimum mean square (MMS) Kalman filter in integration GPS/INS system cannot guarantee the robustness performance, a H(infinity) filtering with respect to polytopic uncertainty is designed. The purpose of this paper is to give an illustration of this application and a contrast with traditional Kalman filter. A game theory H(infinity) filter is first reviewed; next we utilize linear matrix inequalities (LMI) approach to design the robust H(infinity) filter. For the special INS/GPS model, unstable model case is considered. We give an explanation for Kalman filter divergence under uncertain dynamic system and simultaneously investigate the relationship between H(infinity) filter and Kalman filter. A loosely coupled INS/GPS simulation system is given here to verify this application. Result shows that the robust H(infinity) filter has a better performance when system suffers uncertainty; also it is more robust compared to the conventional Kalman filter.

ROMA: Reliable Overlay Multicast with Loosely Coupled TCP Connections

We consider the problem of architecting a reliable content delivery system across an overlay network using TCP connections as the transport primitive. We first argue that natural designs based on store-and-forward principles that tightly couple TCP connections at intermediate end-systems impose fundamental performance limitations, such as dragging down all transfer rates in the system to the rate of the slowest receiver. In contrast, the ROMA architecture we propose incorporates the use of loosely coupled TCP connections together with fast forward error correction techniques to deliver a scalable solution that better accommodates a set of heterogeneous receivers. The methods we develop establish chains of TCP connections, whose expected performance we analyze through equation-based methods. We validate our analytical findings and evaluate the performance of our ROMA architecture using a prototype implementation via extensive Internet experimentation across the PlanetLab distributed testbed.

The design of fault tolerant software for loosely coupled distributed systems

Requirements for systems to continue to operate satisfactorily in the presence of faults has led to the development of techniques for the construction of fault tolerant software. This thesis addresses the problem of error detection and recovery in distributed systems which consist of a set of communicating sequential processes. A method is presented for the `a priori' design of conversations for this class of distributed system. Petri nets are used to represent the state and to solve state reachability problems for concurrent systems. The dynamic behaviour of the system can be characterised by a state-change table derived from the state reachability tree. Systematic conversation generation is possible by defining a closed boundary on any branch of the state-change table. By relating the state-change table to process attributes it ensures all necessary processes are included in the conversation. The method also ensures properly nested conversations. An implementation of the conversation scheme using the concurrent language occam is proposed. The structure of the conversation is defined using the special features of occam. The proposed implementation gives a structure which is independent of the application and is independent of the number of processes involved. Finally, the integrity of inter-process communications is investigated. The basic communication primitives used in message passing systems are seen to have deficiencies when applied to systems with safety implications. Using a Petri net model a boundary for a time-out mechanism is proposed which will increase the integrity of a system which involves inter-process communications.

The relative performance of scalable load balancing algorithms in loosely-coupled distributed systems. Available in 2 volumes.

The computer systems of today are characterised by data and program control that are distributed functionally and geographically across a network. A major issue of concern in this environment is the operating system activity of resource management for different processors in the network. To ensure equity in load distribution and improved system performance, load balancing is often undertaken. The research conducted in this field so far, has been primarily concerned with a small set of algorithms operating on tightly-coupled distributed systems. More recent studies have investigated the performance of such algorithms in loosely-coupled architectures but using a small set of processors. This thesis describes a simulation model developed to study the behaviour and general performance characteristics of a range of dynamic load balancing algorithms. Further, the scalability of these algorithms are discussed and a range of regionalised load balancing algorithms developed. In particular, we examine the impact of network diameter and delay on the performance of such algorithms across a range of system workloads. The results produced seem to suggest that the performance of simple dynamic policies are scalable but lack the load stability of more complex global average algorithms.

Entre el terrorismo y el terrorismo en red, un debate a propósito de los lobos solitarios en Estados Unidos (2001-2014)

El interés de esta disertación es otorgar una respuesta a la fenomenología del Lobo Solitario, que se alza como amenaza frente a los Estados, y es necesaria su correcta comprensión para poder contrarrestar sus efectos sobre la sociedad. De esta manera, se propone un debate entre los conceptos de terrorismo expuesto por un lado por Bruce Hoffman, y por el otro por Luis de la Corte Ibáñez, quienes aportarán herramientas de análisis para lograr entender la fenomenología. Para terminar proponiendo la teoría de redes, expuesta por Arquilla y Ronfeldt y Charles Perrow, como mecanismo de solución a la brecha conceptual existente, definiendo a los lobos solitarios a nivel operacional como nodos sin red, y a nivel de adoctrinamiento como redes de débil acople.

Experiences in Passively Detecting Session Hijacking Attacks in IEEE 802.11 Networks

Current IEEE 802.11 wireless networks are vulnerable to session hijacking attacks as the existing standards fail to address the lack of authentication of management frames and network card addresses, and rely on loosely coupled state machines. Even the new WLAN security standard - IEEE 802.11i does not address these issues. In our previous work, we proposed two new techniques for improving detection of session hijacking attacks that are passive, computationally inexpensive, reliable, and have minimal impact on network performance. These techniques utilise unspoofable characteristics from the MAC protocol and the physical layer to enhance confidence in the intrusion detection process. This paper extends our earlier work and explores usability, robustness and accuracy of these intrusion detection techniques by applying them to eight distinct test scenarios. A correlation engine has also been introduced to maintain the false positives and false negatives at a manageable level. We also explore the process of selecting optimum thresholds for both detection techniques. For the purposes of our experiments, Snort-Wireless open source wireless intrusion detection system was extended to implement these new techniques and the correlation engine. Absence of any false negatives and low number of false positives in all eight test scenarios successfully demonstrated the effectiveness of the correlation engine and the accuracy of the detection techniques.

From trading to eCommunity management

"The increasing pressure for enterprises to join into agile business networks is changing the requirements on the enterprise computing systems. The supporting infrastructure is increasingly required to provide common facilities and societal infrastructure services to support the lifecycle of loosely-coupled, eContract-governed business networks. The required facilities include selection of those autonomously administered business services that the enterprises are prepared to provide and use, contract negotiations, and furthermore, monitoring of the contracted behaviour with potential for breach management. The essential change is in the requirement of a clear mapping between business-level concepts and the automation support for them. Our work has focused on developing B2B middleware to address the above challenges; however, the architecture is not feasible without management facilities for trust-aware decisions for entering business networks and interacting within them. This paper discusses how trust-based decisions are supported and positioned in the B2B middleware."

An Operating Environment for the Jellybean Machine

The Jellybean Machine is a scalable MIMD concurrent processor consisting of special purpose RISC processors loosely coupled into a low latency network. I have developed an operating system to provide the supportive environment required to efficiently coordinate the collective power of the distributed processing elements. The system services are developed in detail, and may be of interest to other designers of fine grain, distributed memory processing networks.

An evolutionary algorithm for the surface structure problem

Many macroscopic properties: hardness, corrosion, catalytic activity, etc. are directly related to the surface structure, that is, to the position and chemical identity of the outermost atoms of the material. Current experimental techniques for its determination produce a “signature” from which the structure must be inferred by solving an inverse problem: a solution is proposed, its corresponding signature computed and then compared to the experiment. This is a challenging optimization problem where the search space and the number of local minima grows exponentially with the number of atoms, hence its solution cannot be achieved for arbitrarily large structures. Nowadays, it is solved by using a mixture of human knowledge and local search techniques: an expert proposes a solution that is refined using a local minimizer. If the outcome does not fit the experiment, a new solution must be proposed again. Solving a small surface can take from days to weeks of this trial and error method. Here we describe our ongoing work in its solution. We use an hybrid algorithm that mixes evolutionary techniques with trusted region methods and reuses knowledge gained during the execution to avoid repeated search of structures. Its parallelization produces good results even when not requiring the gathering of the full population, hence it can be used in loosely coupled environments such as grids. With this algorithm, the solution of test cases that previously took weeks of expert time can be automatically solved in a day or two of uniprocessor time.

Pushing the Quality Level in Networked News Business: Semantic-Based Content Retrieval and Composition in International News Publishing

Electronic publishing exploits numerous possibilities to present or exchange information and to communicate via most current media like the Internet. By utilizing modern Web technologies like Web Services, loosely coupled services, and peer-to-peer networks we describe the integration of an intelligent business news presentation and distribution network. Employing semantics technologies enables the coupling of multinational and multilingual business news data on a scalable international level and thus introduce a service quality that is not achieved by alternative technologies in the news distribution area so far. Architecturally, we identified the loose coupling of existing services as the most feasible way to address multinational and multilingual news presentation and distribution networks. Furthermore we semantically enrich multinational news contents by relating them using AI techniques like the Vector Space Model. Summarizing our experiences we describe the technical integration of semantics and communication technologies in order to create a modern international news network.

Managing a portfolio of corporate venture units : challenges in achieving within-unit focus and between-unit coordination

Principal Topic: There is increasing recognition that the organizational configurations of corporate venture units should depend on the types of ventures the unit seeks to develop (Burgelman, 1984; Hill and Birkinshaw, 2008). Distinction have been made between internal and external as well as exploitative versus explorative ventures (Hill and Birkinshaw, 2008; Narayan et al., 2009; Schildt et al., 2005). Assuming that firms do not want to limit themselves to a single type of venture, but rather employ a portfolio of ventures, the logical consequence is that firms should employ multiple corporate venture units. Each venture unit tailor-made for the type of venture it seeks to develop. Surprisingly, there is limited attention in the literature for the challenges of managing multiple corporate venture units in a single firm. Maintaining multiple venture units within one firm provides easier access to funding for new ideas (Hamel, 1999). It allows for freedom and flexibility to tie the organizational systems (Rice et al., 2000), autonomy (Hill and Rothaermel, 2003), and involvement of management (Day, 1994; Wadwha and Kotha, 2006) to the requirements of the individual ventures. Yet, the strategic objectives of a venture may change when uncertainty around the venture is resolved (Burgelman, 1984). For example, firms may decide to spin-in external ventures (Chesbrough, 2002) or spun-out ventures that prove strategically unimportant (Burgelman, 1984). This suggests that ventures might need to be transferred between venture units, e.g. from a more internally-driven corporate venture division to a corporate venture capital unit. Several studies suggested that ventures require different managerial skills across their phase of development (Desouza et al., 2007; O'Connor and Ayers, 2005; Kazanjian and Drazin, 1990; Westerman et al., 2006). To facilitate effective transfer between venture units and manage the overall venturing process, it is important that firms set up and manage integrative linkages. Integrative linkages provide synergies and coordination between differentiated units (Lawrence and Lorsch, 1967). Prior findings pointed to the important role of senior management (Westerman et al., 2006; Gilbert, 2006) and a shared organizational vision (Burgers et al., 2009) to coordinate venture units with mainstream businesses. We will draw on these literatures to investigate the key question of how to integratively manage multiple venture units. ---------- Methodology/Key Propositions: In order to seek an answer to the research question, we employ a case study approach that provides unique insights into how firms can break up their venturing process. We selected three Fortune 500 companies that employ multiple venturing units, IBM, Royal Dutch/ Shell and Nokia, and investigated and compared their approaches. It was important that the case companies somewhat differed in the type of venture units they employed as well as the way they integrate and coordinate their venture units. The data are based on extensive interviews and a variety of internal and external company documents to triangulate our findings (Eisenhardt, 1989). The key proposition of the article is that firms can best manage their multiple venture units through an ambidextrous design of loosely coupled units. This provides venture units with sufficient flexibility to employ organizational configurations that best support the type of venture they seek to develop, as well as provides sufficient integration to facilitate smooth transfer of ventures between venture units. Based on the case findings, we develop a generic framework for a new way of managing the venturing process through multiple corporate venture units. ---------- Results and Implications: One of our main findings is that these firms tend to organize their venture units according to phases in the venture development process. That is, they tend to have venture units aimed at incubation of venture ideas as well as units aimed more at the commercialization of ventures into a new business unit for the firm or a start-up. The companies in our case studies tended to coordinate venture units through integrative management skills or a coordinative venture unit that spanned multiple phases. We believe this paper makes two significant contributions. First, we extend prior venturing literature by addressing how firms manage a portfolio of venture units, each achieving different strategic objectives. Second, our framework provides recommendations on how firms should manage such an approach towards venturing. This helps to increase the likelihood of success of their venturing programs.