Catálogo de publicaciones - libros

Cryo-electron microscopy has recently been recognized as a useful alternative to obtain three-dimensional density maps of macromolecular complexes, especially when crystallography and NMR techniques fail. The three-dimensional model is constructed from large collections of cryo-electron microscopy images of identical particles in random (and unknown) orientations.

The major problem with cryo-electron microscopy is that the images are very noisy as the signal-to-noise ratio can be below one. Thus, standard filtering techniques are not directly applicable. Traditionally, the problem of immense noise in the cryo-electron microscopy images has been tackled by clustering the images and computing the class averages. However, then one has to assume that the particles have only few preferred orientations. In this paper we propose a sound method for denoising cryo-electron microscopy images using their Radon transforms. The method assumes only that the images are from identical particles but nothing is assumed about the orientations of the particles. Our preliminary experiments show that the method can be used to improve the image quality even when the signal-to-noise ratio is very low.

In this paper we present a new analytical model for cluster-based parallel systems based on Multi-Chain Open Queuing Network. The proposed model is general enough in terms of node design and clustering which can be extended to any parallel system. To have a good estimation of the model parameters, a benchmark suite has been applied to a real system and parameters calibration is performed based on actual measurements. In this study the hypercube topology was chosen for the interconnection network of the system. We present an analytical modeling and validate it by simulation. The QNAT is used for analytical modeling and the OMNet++ simulator has been used to carry out the simulations. Comparison of simulation and analytical results verifies validity of the model. System workload in simulations is generated using both analytical and experimental distributions and a close match with analytical results in both cases is observed.

Recent trends in grid computing development is moving towards a service-oriented architecture. With the momentum gaining for the service-oriented grid computing systems, the issue of deploying support for integrated scheduling and fault-tolerant approaches becomes paramount importance. To this end, we propose a scalable framework that loosely couples the dynamic job scheduling approach with the hybrid replications approach to schedule jobs efficiently while at the same time providing fault-tolerance. The novelty of the proposed framework is that it uses passive replication approach under high system load and active replication approach under low system loads. The switch between these two replication methods is also done dynamically and transparently.

This paper presents a Service Level Agreement (SLA) management architecture for the Grid. SLAs are an essential component in building Grid systems where commitments and assurances are specified, implemented and monitored. Targeting CPU type resources, we show how a SLA manager is able to interface with a broker designed for user applications that require resources on demand. The broker uses a novel three-phase commit protocol which provides the means to secure resources that meet the application’s requirements through SLAs. Experiments are carried out on a Grid testbed to show how a SLA for a compute service is specified. Experimental results show that the broker provides performance enhancement in terms of the time taken from submission of application requirements until a job begins execution.

Research in authentication mechanisms has led to the design and development of new schemes. The security provided by these procedures must be reviewed and analyzed before they can be widely used. In this paper, we analyze some weaknesses of the port knocking authentication method that makes it vulnerable to many attacks. We will present the NAT-Knocking attack, in which an unauthorized user can gain access to the protected server just by being in the same network than an authorized user. We will also discuss the DoS-Knocking attack, which could lead to service disruptions due to attackers “knocking” on many ports of the protected server. Finally, we will review further implementation issues.

Everyday more companies extend the use of Internet apart from informational uses. The progression to more sophisticated Internet usage will need that customers trust on the security of the online transactions and on the security mechanisms involved in this protection. For that reason, moreover the common marketing techniques, some special marketing on Internet security will be needed. In fact, customers already are not satisfied with existing protections in Internet e-commerce services and the future of this potential global marketplace will depend on security.

Recently, Nenadić (2004) proposed the RSA-CEGD protocol for certified delivery of e-goods. This is a relatively complex scheme based on verifiable and recoverable encrypted signatures (VRES) to guarantee properties such as strong fairness and non-repudiation, among others. In this paper, we illustrate how an extended logic of beliefs can be helpful to analyze in a formal manner these security properties. This approach requires the previous definition of some novel constructions to deal with evidences exchanged by parties during the protocol execution. The study performed within this framework reveals the lack of non-repudiation in RSA-CEGD and points out some other weaknesses.

The electric utility has the responsibility to provide a good quality of electricity to their customers. Therefore, they have introduced DDSS(Distribution Data Security System) to automate the power distribution data security. DDSS engineers need a set of state-of-the-art applications, eg. managing distribution system in active manner and gaining economic benefits from a flexible DDSS architectural design. The existing DDSS functionally could not handle these needs. It has to be managed by operators whenever feeder faults data are detected. Therefore, it may be possible for propagating the feeder overloading area, if operator makes a mistake. And it utilizes closed architecture, therefore it is hard to meet the system migration and future enhancement requirements. This paper represents web based, platform-independent, flexible DDSS architectural design and active database application. The recently advanced internet technologies are fully utilized in the new DDSS architecture. Therefore, it can meet the system migration and future enhancement requirements. And, by using active database, DDSS can minimize feeder overloadings area in distribution system without intervening of operator, therefore, minimizing feeder overloadings area can be free from the mistake of operator.

Data protection is an increasingly important issue in today’s communication networks. Traditional solutions for protecting data when transferred over a network are almost exclusively based on cryptography. As a complement, we propose the use of multiple physically separate paths to accomplish data protection. A general concept for providing physical separation of data streams together with a threat model is presented. The main target is delay-sensitive applications such as telephony signaling, live TV, and radio broadcasts that require only lightweight security. The threat considered is malicious interception of network transfers through so-called eavesdropping attacks. Application scenarios and techniques to provide physically separate paths are discussed.

Let be a partially ordered real Banach space, , ∈ with ≤ . Let be a bounded linear functional on . We call a Ben-Israel-Charnes space (or a - space, for short) if the linear program: Maximize 〈,〉 subject to ≤ ≤ has an optimal solution. Such problems have been shown to be important in solving a class of problems known as Interval Linear Programs. - spaces were introduced by the first author in his doctoral dissertation. In this paper we identify new classes of Banach spaces that are - spaces. We also present sufficient conditions under which answers are in the affirmative for the following questions:

Primary: 90C48, 90C05; Secondary: 47N10.