Experimental Investigation of FRP-Strengthened RC Beam-Column Joints

The results of a comprehensive experimental program, aimed at providing a fundamental understanding of the behavior of shear-critical exterior reinforced concrete (RC) joints strengthened with fiber reinforced polymers (FRP) under simulated seismic load, are presented in this study. The role of various parameters on the effectiveness of FRP is examined through 2/3-scale testing of 18 exterior RC joints. Conclusions are drawn on the basis of certain load versus imposed displacement response characteristics, comprising the strength (maximum lateral load), the stiffness, and the cumulative energy dissipation capacity. The results demonstrate the important role of mechanical anchorages in limiting premature debonding, and they provide important information on the role of various parameters, including: area fraction of FRP; distribution of FRP between the beam and the column; column axial load; internal joint (steel) reinforcement; initial damage; carbon versus glass fibers; sheets versus strips; and effect of transverse beams.     

Reconfiguration Aspects and a Reconfigurable Outer Block Interleaver for 3G Applications

Reconfiguration concept represents reconfigurable functionalities of the radio interface for mobile radio systems. Particularly for the physical layer, some possible reconfigurable architectures can be identified. We focus on outer interleaving for turbo codes, which can improve their performance in flat Rayleigh fading environment. The larger the number of columns in the outer interleaver, the better is the performance, but with the penalty of more complexity and delay. Furthermore, an incorrect choice of the number of columns can increase the bit and frame error rates. Therefore, it would be advantageous to reconfigure the outer interleaver in different operating environments with the optimum number of columns. Using two different data frame lengths, in this contribution simulation results are presented for the four possible outer block interleaver configurations specified for the 3GPP mobile standard in the case of flat Rayleigh fading channel. It is shown that different operating environments require an optimum number of columns in terms of bit error rate and frame error rate performance. Finally, frame fade duration is considered and the effect of the product of the Doppler frequency with the frame duration on the performance for the four different 3GPP outer block interleaver configurations is discussed. Costas Chaikalis was born in Athens, Greece, on March 7, 1973. He received the B.Sc. degree in electrical engineering in 1995 from Technological Educational Institute of Lamia, Greece. He also received the M.Sc. and Ph.D. degrees from Department of Electronics and Telecommunications, University of Bradford, Bradford, UK in 1999 and 2003, respectively. During his doctoral studies he worked as a Research Assistant for Mobile Virtual Center of Excellence (Mobile VCE), Terminals Group, UK. Since 2003, he is a lecturer in the Department of Electrical Engineering, Technological Educational Institute of Lamia, Greece. His research interests are in all areas of mobile communications but especially in forward error correction coding, reconfigurable (software radio) architectures, cross layer architectures and DSP applications.     

Two-degree-of-freedom output feedback controllers for discrete-time nonlinear systems

A discrete-time, model-based output feedback control structure for nonlinear processes is developed in the present work. The structure makes use of a closed-loop observer, while at the same time it guarantees that the overall feedback controller possesses integral action. An algebraic transformation is applied on the observer states to insure that the input/output gain of the observer matches the model upon which the static state feedback control law is based. The resulting control algorithm is a two-degree-of-freedom control law, in the sense that the output and the set point are processed in different ways. The control structure is shown not only to have the same properties as the standard model-state feedback structure, but also that it emerges from a model algorithmic control framework. Finally, a simulation example using an exothermic CSTR operating at an open-loop unstable steady state is used to evaluate the closed-loop performance of the proposed method.     

The Association of Human Herpesviruses with Malignant Brain Tumor Pathology and Therapy: Two Sides of a Coin

The role of certain viruses in malignant brain tumor development remains controversial. Experimental data demonstrate that human herpesviruses (HHVs), particularly cytomegalovirus (CMV), Epstein–Barr virus (EBV) and human herpes virus 6 (HHV-6), are implicated in brain tumor pathology, although their direct role has not yet been proven. CMV is present in most gliomas and medulloblastomas and is known to facilitate oncomodulation and/or immunomodulation, thus promoting cancer cell proliferation, invasion, apoptosis, angiogenesis, and immunosuppression. EBV and HHV-6 have also been detected in brain tumors and high-grade gliomas, showing high rates of expression and an inflammatory potential. On the other hand, due to the neurotropic nature of HHVs, novel studies have highlighted the engagement of such viruses in the development of new immunotherapeutic approaches in the context of oncolytic viral treatment and vaccine-based strategies against brain tumors. This review provides a comprehensive evaluation of recent scientific data concerning the emerging dual role of HHVs in malignant brain pathology, either as potential causative agents or as immunotherapeutic tools in the fight against these devastating diseases.     

A Matrix–Matrix Multiplication methodology for single/multi-core architectures using SIMD

In this paper, a new methodology for speeding up Matrix–Matrix Multiplication using Single Instruction Multiple Data unit, at one and more cores having a shared cache, is presented. This methodology achieves higher execution speed than ATLAS state of the art library (speedup from 1.08 up to 3.5), by decreasing the number of instructions (load/store and arithmetic) and the data cache accesses and misses in the memory hierarchy. This is achieved by fully exploiting the software characteristics (e.g. data reuse) and hardware parameters (e.g. data caches sizes and associativities) as one problem and not separately, giving high quality solutions and a smaller search space.     

Low-temperature H2-SCR of NO on a novel Pt/MgO-CeO2 catalyst

The selective catalytic reduction of NO by H₂ under strongly oxidizing conditions (H₂-SCR) in the low-temperature range of 100–200 °C has been studied over Pt supported on a series of metal oxides (e.g., La₂O₃, MgO, Y₂O₃, CaO, CeO₂, TiO₂, SiO₂ and MgO-CeO₂). The Pt/MgO and Pt/CeO₂ solids showed the best catalytic behavior with respect to N₂ yield and the widest temperature window of operation compared with the other single metal oxide-supported Pt solids. An optimum 50 wt% MgO-50wt% CeO₂ support composition and 0.3 wt% Pt loading (in the 0.1–2.0 wt% range) were found in terms of specific reaction rate of N₂ production (mols N₂/g_cat s). High NO conversions (70–95%) and N₂ selectivities (80–85%) were also obtained in the 100–200 °C range at a GHSV of 80,000 h⁻¹ with the lowest 0.1 wt% Pt loading and using a feed stream of 0.25 vol% NO, 1 vol% H₂, 5 vol% O₂ and He as balance gas. Addition of 5 vol% H₂O in the latter feed stream had a positive influence on the catalytic performance and practically no effect on the stability of the 0.1 wt% Pt/MgO-CeO₂ during 24 h on reaction stream. Moreover, the latter catalytic system exhibited a high stability in the presence of 25–40 ppm SO₂ in the feed stream following a given support pretreatment. N₂ selectivity values in the 80–85% range were obtained over the 0.1 wt% Pt/MgO-CeO₂ catalyst in the 100–200 °C range in the presence of water and SO₂ in the feed stream. The above-mentioned results led to the obtainment of patents for the commercial exploitation of Pt/MgO-CeO₂ catalyst towards a new NO_x control technology in the low-temperature range of 100–200 °C using H₂ as reducing agent. Temperature-programmed desorption (TPD) of NO, and transient titration of the adsorbed surface intermediate NO_x species with H₂ experiments, following reaction, have revealed important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., surface coverage, number and location of active NO_x intermediate species, NO_x spillover).     

Global stability results for systems under sampled‐data control

In this work sufficient conditions for uniform input‐to‐output stability and uniform input‐to‐state stability are presented for finite‐dimensional systems under feedback control with zero‐order hold. The conditions are expressed by means of single and vector Lyapunov functions. Copyright © 2008 John Wiley & Sons, Ltd.     

An optimized sequential pattern matching methodology for sequence classification

In this paper we present a novel methodology for sequence classification, based on sequential pattern mining and optimization algorithms. The proposed methodology automatically generates a sequence classification model, based on a two stage process. In the first stage, a sequential pattern mining algorithm is applied to a set of sequences and the sequential patterns are extracted. Then, the score of every pattern with respect to each sequence is calculated using a scoring function and the score of each class under consideration is estimated by summing the specific pattern scores. Each score is updated, multiplied by a weight and the output of the first stage is the classification confusion matrix of the sequences. In the second stage an optimization technique, aims to finding a set of weights which minimize an objective function, defined using the classification confusion matrix. The set of the extracted sequential patterns and the optimal weights of the classes comprise the sequence classification model. Extensive evaluation of the methodology was carried out in the protein classification domain, by varying the number of training and test sequences, the number of patterns and the number of classes. The methodology is compared with other similar sequence classification approaches. The proposed methodology exhibits several advantages, such as automated weight assignment to classes using optimization techniques and knowledge discovery in the domain of application.

Utilizing bloom filters for detecting flooding attacks against SIP based services

Any application or service utilizing the Internet is exposed to both general Internet attacks and other specific ones. Most of the times the latter are exploiting a vulnerability or misconfiguration in the provided service and/or in the utilized protocol itself. Consequently, the employment of critical services, like Voice over IP (VoIP) services, over the Internet is vulnerable to such attacks and, on top of that, they offer a field for new attacks or variations of existing ones. Among the various threats–attacks that a service provider should consider are the flooding attacks, at the signaling level, which are very similar to those against TCP servers but have emerged at the application level of the Internet architecture. This paper examines flooding attacks against VoIP architectures that employ the Session Initiation Protocol (SIP) as their signaling protocol. The focus is on the design and implementation of the appropriate detection method. Specifically, a bloom filter based monitor is presented and a new metric, named session distance, is introduced in order to provide an effective protection scheme against flooding attacks. The proposed scheme is evaluated through experimental test bed architecture under different scenarios. The results of the evaluation demonstrate that the required time to detect such an attack is negligible and also that the number of false alarms is close to zero.     

Design characteristics for temporomandibular joint disc tissue engineering: learning from tendon and articular cartilage

Tissue engineering of chondrocytic or fibroblastic musculoskeletal tissues has been relatively well studied compared with that of the temporomandibular joint (TMJ) disc. Early attempts at tissue engineering the disc have been misguided owing to a lack of understanding of the composition and function of the TMJ disc. The objective of this review is to compare the TMJ disc with a chondrocytic tissue (hyaline articular cartilage) and a fibroblastic tissue (tendon) to understand better the properties of this fibrocartilaginous tissue. The TMJ disc has 25 times more glycosaminoglycan (GAG) per dry weight than tendon but half that of articular cartilage. The disc's tensile modulus is six times more than cartilage but orders less than tendon. The GAG content and tensile modulus suggest that the TMJ disc is characterized as a tissue between hyaline cartilage and tendon, but the disc appears more tendon like when considering its collagen make-up and cell content. Like tendon, the TMJ disc contains primarily collagen type I at 85 per cent per dry weight, while articular cartilage has 30 per cent less collagen, which is type II. Knowledge of quantitative comparisons between joint tissues can give extensive insight into how to improve tissue engineering of the TMJ disc.