Approximation of the Karhunen–Loève transformation and its application to colour images

Analysis of colour images in the Red, Green and Blue acquisition space and in the intensity and chrominance spaces shows that colour components are closely correlated (Carron, Ph.D. Thesis, Univ. Savoie, France, 1995; Ocadis, Ph.D. Thesis, Univ. Grenoble, France, 1985). These have to be decorrelated so that each component of the colour image can be studied separately. The Karhunen–Loève transformation provides optimal decorrelation of these colour data. However, this transformation is related to the colour distribution in the image, i.e. to the statistical properties of the colour image and is therefore dependent on the image under analysis. In order to enjoy the advantages of direct, independent and rapid transformation and the advantages of the Karhunen–Loève properties, this paper presents the study of the approximation of the Karhunen–Loève transformation. The approximation is arrived at through exploitation of the properties of Toeplitz matrices. The search for eigenvectors of a Toeplitz matrix shows that complex or real orthogonal mappings such as the discrete Fourier transform and its decompositions approximate the Karhunen–Loève transformation in the case of first-order Markov processes.     

Energy transfer in organic multilayer quantum well structure and its application to OLEDs

We fabricate a series of samples and OLEDs with organic multilayer quantum well structure, which consist of alternate PBD and Alq3. Both PBD and Alq3 are electron-transporting materials, and PBD is used as potential barrier layer, while Alq3 is used as potential well layer and emitting layer. Compared with double-layer structure, the luminescent characteris- tics of organic samples and diodes with quantum well structure are investigated and the quantum well structure helps the energy transfer between well layer and barrier layer. The quantum well structure makes carriers disperse in the different well layers and then increases the number of excitons to enhance the efficiency of the recombination.     

On the optimal defibrillation waveform--how to reconcile theory and experiment?

Medical intervention by electrical current as applied to humans or animals may have tremendous therapeutic impact if delivered while being carefully controlled. Otherwise, the situation can be harmful in terms of injury or even become lethal. These consequences demand close inspection of all relevant biological and technical factors. Regarding methods to counter fibrillation of the heart substantial progress has been made, but defining a gold standard for the waveshape and energy delivery remains a serious challenge. The anticipated answer is not simply a range somewhere between a maximum and a minimum, but most likely an "intelligently" selected case-specific optimum, delicately positioned between effective and unsafe. Combining insight from theory with pertinent experimental findings may offer a clearer view on an unresolved issue that often points to a cross-road of life and death.     

On the Capacity Degradation Due to Coexistence of WCDMA and CDMA2000 Systems

In this paper,we investigate the capacity degradation due to the coexistence of WCDMA and CDMA2000 net-works by system-level Monte Carlo simulation.Both systems are simulated according to the deployment of macro cells,andspeech service is considered.The capacity losses under different carrier spacing and different geographical offset are evalu-ated.Simulation results show that considerable capacity loss is seen when WCDMA is the victim system,while the influ-ence of WCDMA to CDMA2000 is slight.Increasing carrier-to-carrier spacing and decreasing geographical offset lead toless capacity loss and co-locating the base stations of both systems is a preferred solution.     

Transient analysis of traffic generated by bursty sources,and its application to measurement‐based admission control

The first part of the paper is devoted to a transient analysis of traffic generated by bursty sources. These sources are governed by a modulating process, whose state determines the traffic rate at which the source transmits. The class of modulating processes contains, e.g., on/off traffic sources with general on and off times (but is considerably broader). We focus on the probability of extreme fluctuations of the resulting traffic rate, or more precisely, we determine the probability of the number of sources being in the on state reaching a certain threshold, given a measurement of the number of sources in the on state t units of time ago. In particular, we derive large deviations asymptotics of this probability when the number of sources is large. These asymptotics are numerically manageable, and it is empirically verified that they lead to an overestimation of the probability of our interest. The analysis is extended to alternative measurement procedures. These procedures allow to take into account, for instance, more historic measurements than just one, possibly combined with an exponential weighting of these measurements. In the second part of the paper, we apply the asymptotic calculation methods to gain insight into the feasibility of measurement‐based admission control (MBAC) algorithms for ATM or IP networks. These algorithms attempt to regulate the network's load (to provide the customers with a sufficient Quality of Service), and at the same time achieve an acceptable utilization of the resources. An MBAC algorithm may base acceptance or rejection of a new request on the measured momentary load imposed on the switch or router; if this load is below a given threshold, the source can be admitted. We investigate whether such a scheme is robust under the possible stochastic properties of the traffic offered. Both the burst level (i.e., the distribution of the on and off times of the sources) and the call level (particularly the distribution of the call duration) are taken into account. Special attention is paid to the influence of the bursts, silences, or call durations having a distribution with a “heavy tail”. This revised version was published online in June 2006 with corrections to the Cover Date.     

Implementation of an SDR platform using GPU and its application to a 2?��?2 MIMO WiMAX system

Conventional communication systems have been implemented using digital signal processors (DSPs) and/or field programmable gate arrays (FPGAs), especially for software defined radio (SDR) functionality. We propose a scheme that uses a graphics processing unit (GPU) in place of the conventional DSPs or FPGAs for the implementation of an SDR-based communication system. The GPU, a high-speed parallel processor with multiple arithmetic logic units, is adopted for the signal processing of the physical layer required for the parallel processing in an SDR system. The compute unified device architecture (CUDA) based on the C language provides a software development kit (SDK) for the modem application of the GPU. Therefore we utilize the CUDA SDK to implement the real-time modem function. This paper presents an implementation of a 2 × 2 multiple-input multiple-output (MIMO) WiMAX system employing a GPU as the real-time modem. By installing a radio frequency module on top of the GPU modem, we implement a real-time transmission system for video data. The performance of the proposed GPU-based system is demonstrated by comparing its operation time against that of the conventional DSP-based system.     

Modeling transistor variation using α-power formula and its application to sensitivity analysis on harmonic distortion in differential amplifier

We propose a statistical MOSFET model using the ??-power equation for the I _D ?CV _GS curves of a transistor to make it easier to deal with transistor variations using hand calculations. We evaluated the impact of the transistor variation (mismatch) on the harmonic distortion (HD) in a differential amplifier using the statistical ??-power model along with a sensitivity simulation using SPICE. We found that the driver transistor variation majorly impacted on the 2nd HD in the differential gain, which was approximately proportional to the transistor current mismatch, whether the mismatch was induced by the threshold voltage variation or by the current factor variation. We further evaluated the HD by directly using the experimental I _D ?CV _GS curves to obtain more accurate values. The ??-power model, fitted to g _m ?CV _GS curves, described the HD more precisely, to make it more agreeable with the results obtained from the experimental data, when we used the differential current equation as a function of the transconductance (g _m ), its derivative $ \left(g_{m}^{\prime}\right) $ and their variations (??g _m and ?? $g_{m}^{\prime}\, $ ).     

On the Use of Radiometric Measurements to Estimate Atmospheric Attenuation at 100 and 300 GHz

At frequencies of between 100 GHz and 30 THz, propagation conditions are severely affected by the influence of the composition and phenomena of the troposphere. This paper focuses on the use of radiometric measurements to estimate attenuation at 100 and 300 GHz, considering non-scattering scenarios, in which the main contributions are given by atmospheric gases and non-rainy clouds. These techniques allow the estimation of the absorption loss through the entire atmosphere, without the need for a signal source situated in a satellite or a high altitude aircraft. On the basis of well-accepted absorption models, the results of calculating gaseous, cloud, and total attenuation using 3-year meteorological data from Madrid, Spain, are detailed, as well as estimates of the expected values of the sky brightness temperature as measured by the radiometer. Finally, based on the results obtained, a discussion on the use of radiometric measurements at both frequencies is presented, in connection with an experimental campaign currently under preparation.     

Concepts of gain at an oxide-semiconductor interface and their application to the TETRAN—A tunnel emitter transistor—And to the MIS switching device

The idea of current gain at an insulator interface is discussed using the tunnel-oxide as an example upon which to base calculations. A novel approach to the calculation of tunnel components is introduced which accurately describes the electron tunnel component when the metal Fermi level is both above and below the semiconductor conduction band edge. A new form of bipolar amplifier (the TETRAN) is proposed and its performance is compared from a logic and memory point of view with existing transistors. As a logic element the device does not perform well when compared with MOS transistors because the current densities that one can obtain are too low to charge the relatively large tunnel-oxide capacitance. For the memory comparison, the concepts of gain necessary for TETRAN operation are applied to the MIS switching device. Preliminary experimental verification of the concept is reported.     

On the absence of the β to α Sn allotropic transformation in solder joints made from paste and metal powder

Until July 2006, most solder joints in the electronics industry were made of the alloy 63Sn37Pb or 62Sn36Pb2Ag. After this date, the European environmental Restriction of Hazardous Substances directive (RoHS) forced many manufacturers to use Pb-free alloys. These substitutes for SnPb are Sn-rich alloys (over 90% Sn) of various compositions. Below 13.2 °C, Sn potentially transforms into a different phase. This occurs with catastrophic effects, as the transforming material becomes extremely brittle and falls apart. The purpose of this paper is to investigate if this allotropic transformation also occurs in samples prepared from solder paste or metal powder. This work compares the transformation propensity of samples prepared with bulk solder, solder paste, and tin powder. Different conditions and geometries are used in the investigation and experiments with both commercial and specifically prepared solder pastes are carried out. Samples prepared from bulk solder transform into the α phase as expected, whilst samples prepared from solder paste and tin powder do not transform. The residual organic compounds from the flux are believed to be responsible for this behaviour. The tin oxide (SnO₂) retained in the bulk after melting could also play a role. This paper shows, for the first time, a relationship between the ability of tin to transform and the nature of the starting material and in particular that the tin β/α allotropic transformation does not occur when samples are prepared from paste or powders. The new lead-free alloys can therefore be used with more confidence in mission-critical applications.     

On the Thermoelectric Properties of Zintl Compounds Mg3Bi2−x Pn x (Pn = P and Sb)

A series of Zintl compounds Mg₃Bi_2-x Pn _x (Pn = P and Sb) have been synthesized by the solid-state reaction method. While Sb can be substituted to a level as high as x = 1.0, P can be substituted only up to x = 0.5. The thermoelectric potential of these compounds has been evaluated by measuring resistivity (ρ), Seebeck (α) and Hall coefficients, and thermal conductivity between 80 K and 850 K. The measured resistivity and Seebeck coefficient values are consistent with those expected for small-bandgap semiconductors. Hall measurements suggest that the carriers are p type with concentration (p) increasing from ~10¹⁹ cm^?3 to ~10²⁰ cm^?3 as the Bi content is increased. The Hall mobility decreases with increasing temperature (T) and reaches a more or less similar value (~45 cm²/V s) for all substituted compositions at room temperature. Due to mass defect scattering, the lattice thermal conductivity (κ _L) is decreased to a minimum of ~1.2 W/m K in Mg₃BiSb. The power factor (α ²/ρ) is found to be rather low and falls in the range 0.38 mW/m K² to 0.66 mW/m K². As expected, at a high temperature of 825 K, the total thermal conductivity (κ) of Mg₃BiSb reaches an impressive value of ~1.0 W/m K. The highest dimensionless figure of merit (ZT) is realized for Mg₃BiSb and is ~0.4 at 825 K.     

On the Current Dependence of the Injection Efficiency and the Relative Contribution of the Escape Rate and Internal Optical Loss to Saturation of the Power–Current Characteristics of High-Power Pulsed Lasers (λ = 1.06 μm)

Semiconductors - The results of numerical simulation of the current dependence of the efficiency of injection into the active area of a laser based on separate-confinement double heterostructures...     

An overview on the principle of inkjet printing technique and its application in micro-display for augmented/virtual realitiesOA

Augmented reality(AR) and virtual reality(VR) are two novel display technologies that are under updates. The essential feature of AR/VR is the full-color display that requires high pixel densities. To generate three-color pixels, the fluorescent color conversion layer inevitably includes green and red pixels. To fabricate such sort of display kits, inkjet printing is a promising way to position the color conversion layers. In this review article, the progress of AR/VR technologies is first revie...     

Une caractérisation non gaussienne et à longue mémoire du trafic Internet et de ses anomalies: validation expérimentale et application à la détection d’attaque de DDoS/Non Gaussian Long Memory Model for Internet Traffic: Experimental Validation and Application to DDoS Detection

Being now a mainstream communication, Internet is subject to many kinds of anomalies (failures, flash-crowds, attacks). In order to compare the statistics of normal traffic with traffic with anomalies, we collect both regular and anomalous traffic. The traffic is collected on the Renater network by the Metrosec project and we produce both Denial of Service (DoS) attacks with real attack softwares (TFN2k, TRIN00) aimed at various services (ICMP, SYN, UDP, TCP), and flash-crowd anomalies. We propose a multiresolution, non-Gaussian model with long memory and the corresponding estimators. It models, jointly at all aggregation levels, normal traffic, and also traffic containing anomalies. We show that the model enables to detect the anomalies in the traffic and distinguish between flash-crowd and Dos types of anomaly.