Semantic indexing of Arabic texts for information retrieval system

As part of information retrieval systems (IRS) and in the context of the use of ontologies for documents and queries indexing, we propose and evaluate in this paper the contribution of this approach applied to Arabic texts. To do this we indexed a corpus of Arabic text using Arabic WordNet. The disambiguation of words was performed by applying the Lesk algorithm. The results obtained by our experiment allowed us to deduct the contribution of this approach in IRS for Arabic texts.     

STEM nanoanalysis of Au/Pt/Ti-Si3N4 interfacial defects and reactions during local stress of SiGe HBTs

Nanoscaled materials are attractive building blocks for hierarchical assembly of functional nanodevices, which exhibit diverse performances and simultaneous functions. We innovatively fabricated semiconductor nano-probes of tapered ZnS nanowires through melting and solidifying by electro-thermal process; and then, as-prepared nano-probes can manipulate nanomaterials including semiconductor/metal nanowires and nanoparticles through sufficiently electrostatic force to the desired location without structurally and functionally damage. With some advantages of high precision and large domain, we can move and position and interconnect individual nanowires for contracting nanodevices. Interestingly, by the manipulating technique, the nanodevice made of three vertically interconnecting nanowires, i.e., diode, was realized and showed an excellent electrical property. This technique may be useful to fabricate electronic devices based on the nanowires' moving, positioning, and interconnecting and may overcome fundamental limitations of conventional mechanical fabrication.     

Effects of electromagnetic near-field stress on SiGe HBT’s reliability

In this paper, a reliability damage mechanism was presented in SiGe Heterojunction Bipolar Transistor (HBT). This new stress methodology differs from conventional SiGe, HBT device reliability associated with other stresses, since it was obtained by applying electromagnetic near-field aggression. The near-field set-up is used to disturb with electromagnetic field the Device Under test (DUT) on a localized area. Degradations in the base current and the current gain are identified. They are induced by a large base current leakage due to hot carrier which introduces generation/recombination trap centers at the silicon–oxide interface of the emitter–base spacer. By using the S-parameters measurements, we find that both forward transmission scattering parameter (S₂₁) and the input scattering parameter (S₁₁) are affected by this stress. In addition the power characteristics of DUT are also affected by stress. A Direct Power Injection (DPI) method is used to understand the near-field stress behaviour.     

Analysis of link-level hybrid FEC/ARQ-SR for wireless links and long-lived TCP traffic

Since the TCP protocol uses the loss of packets as an indication of network congestion, its performance degrades over wireless links, which are characterized by a high bit error rate. Different solutions have been proposed to improve the performance of TCP over wireless links, the most promising one being the use of a hybrid model at the link level combining Forward Error Correction (FEC), Automatic Repeat Request with Selective Repeat (ARQ-SR), and an in-order delivery of packets to IP. The drawback of FEC is that it consumes some extra bandwidth to transmit the redundant information. ARQ-SR consumes extra bandwidth only when packets are lost, its drawback is that it increases the round-trip time (RTT), which may deteriorate the performance of TCP. Another drawback of ARQ-SR is that a complete packet can be retransmitted to correct a small piece of errored data. We study in this paper the performance of TCP over a wireless link implementing hybrid FEC/ARQ-SQ. The study is done by simulating and modeling long-lived TCP transfers over wireless links showing Bernoulli errors. We are motivated by how to tune link-level error recovery, e.g. amount of FEC, persistency of ARQ, so as to maximize the performance of TCP. We provide results for different physical characteristics of the wireless link (delay, error rate) and for different traffic loads (number of TCP connections).     

Distributed parameter thermal system control and observation by Green–Galerkin methods

This article addresses the problem of distributed parameter control and observation in thermal processing of materials. A novel numerical technique is developed for infinite‐dimensional thermal conduction systems, based on Galerkin optimization of an energy index employing Green's functions. Various simulations are conducted to prove that despite the complexities that arise from the distributed parameter nature of the system, the proposed method successfully observes the temperature field that exists inside a solid body by employing strictly surface temperature measurements. Moreover, the existence of a duality principle between distributed parameter thermal control and thermal observation is also investigated. Copyright © 2004 John Wiley & Sons, Ltd.     

STEM nanoanalysis of Au/Pt/Ti-Si3N4 interfacial defects and reactions during local stress of SiGe HBTs

A new insight on the behavior of metal contact-insulating interfaces in SiGe heterojunction bipolar transistor is given by high-performance aberration-corrected scanning transmission electron microscopy (STEM) analysis tools equipped with sub-nanometric probe size. It is demonstrated that the presence of initial defects introduced during technological processes play a major role in the acceleration of degradation mechanisms of the structure during stress. A combination of energy-filtered transmission electron microscopy analysis with high angle annular dark field STEM and energy dispersive spectroscopy provides strong evidence that migration of Au-Pt from the metal contacts to Ti/Si3N4 interface is one of the precursors to species interdiffusion and reactions. High current densities and related local heating effects induce the evolution of the pure Ti initial layer into mixture layer composed of Ti, O, and N. Local contamination of Ti layers by fluorine atoms is also pointed out, as well as rupture of TiN thin barrier layer.     

Fast distributed multi-hop relative time synchronization protocol and estimators for wireless sensor networks

The challenging problem of time synchronization in wireless sensor networks is considered in this paper, where a new distributed protocol is proposed for both local and multi-hop synchronization. The receiver-to-receiver paradigm is used, which has the advantage of reducing the time-critical-path and thus improving the accuracy compared to common sender-to-receiver protocols. The protocol is fully distributed and does not rely on any fixed reference. The role of the reference is divided amongst all nodes, while timestamp exchange is integrated with synchronization signals (beacons). This enables fast acquisition of timestamps that are used as samples to estimate relative synchronization parameters. An appropriate model is used to derive maximum likelihood estimators (MLE) and the Cramer-Rao lower bounds (CRLB) for both the offset-only, and the joint offset/skew estimation. The model permits to directly estimating relative parameters without using or referring to a reference’ clock. The proposed protocol is extended to multi-hop environment, where local synchronization is performed proactively and the resulted estimates are transferred to the intermediate/end-point nodes on-demand, i.e. as soon as a multi-hop communication that needs synchronization is initiated. On-demand synchronization is targeted for multi-hop synchronization instead of the always-on global synchronization model, which avoids periodic and continuous propagation of synchronization signals beyond a single-hop. Extension of local MLE estimators is proposed to derive relative multi-hop estimators. The protocol is compared by simulation to some state-of-the-art protocols, and results show much faster convergence of the proposed protocol. The difference has been on the order of more than twice compared to CS-MNS, more than ten times compared to RBS, and more than twenty times compared to TPSN. Results also show scalability of the proposed protocol concerning the multi-hop synchronization. The error does not exceed few microseconds for as much as 10 hops in R4Syn, while in CS-MNS, and TPSN, it reaches few tens of microseconds. Implementation and tests of the protocol on real sensor motes confirm microsecond level precision even in multi-hop scenarios, and high stability (long lifetime) of the skew/offset model.     

Distributed parameter thermal controllability: a numerical method for solving the inverse heat conduction problem

This paper addresses the inverse heat conduction problem encountered in thermal manufacturing processes. A numerical control algorithm is developed for distributed parameter conduction systems, based on Galerkin optimization of an energy index employing Green's functions. Various temperature profiles of variable complexity are studied, using the proposed technique, in order to determine the surface heat input distribution necessary to generate the desired temperature field inside a solid body. Furthermore, the effect of altering the iterative time step and duration of processing time, on the convergence of the solution generated by the aforementioned method is investigated. It is proved that despite the variations in numerical processing, the iterative technique is able to solve the problem of inverse heat conduction in the thermal processing of materials. Copyright © 2004 John Wiley & Sons, Ltd.     

Deep network in network

Neural Computing and Applications - The different CNN models use many layers that typically include a stack of linear convolution layers combined with pooling and normalization layers to extract...     

CFD analysis of the thermal losses on the upper part of a flat solar collector

To investigate the reduction of heat losses on the upper part of a flat solar collector, a two‐dimensional study was carried out by CFD analysis using Fluent. For this purpose, the heat transfer behavior in the air gap over a wide range of thicknesses of the latter (1‐20 mm) and the addition of a second glass cover fixed at midheight of the air gap spacing have been investigated. For small thicknesses of the air gap (1‐8 mm), the heat transfer is essentially conductive. An increase in the thickness leads to the intensification of the natural convection which induces high thermal losses. The simulation results have shown that the addition of a second cover glazing leads to the weakening of the natural convection and thus to an average enhancement of the solar collector temperature over the range of thicknesses studied of approximately 17%. The overall thermal losses coefficient is then reduced by an average of 26% compared with the single‐glazed solar collector. They have also shown that the thickness of the air gaps resulting in the minimum overall heat losses is 8 mm and that the thickness of the second glass cover has no significant effect on these results. In addition, this study has highlighted the importance of taking into account the radiation heat transfer in establishing the thermal balance of a flat solar collector. Indeed, this consideration leads to an average decrease of the absorber temperature of about 30%.