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In biometrics, often models are used in which the data distributions are approximated with normal distributions. In particular, the eigenface method models facial data as a mixture of fixed-position intensity signals with a normal distribution. The model parameters, a mean value and a covariance matrix, need to be estimated from a training set. Scree plots showing the eigenvalues of the estimated covariance matrices have two very typical characteristics when facial data is used: firstly, most of the curve can be approximated by a straight line on a double logarithmic plot, and secondly, if the number of samples used for the estimation is smaller than the dimensionality of these samples, using more samples for the estimation results in more intensity sources being estimated and a larger part of the scree plot curve is accurately modeled...
The main network solutions for supporting QoS rely on traf- fic policing (conditioning, shaping). In particular, for IP networks the IETF has developed Intserv (individual flows regulated) and Diffserv (only ag- gregates regulated). The regulator proposed could be based on the (dual) leaky-bucket mechanism. This explains the interest in network element per- formance (loss, delay) for leaky-bucket regulated traffic. This paper describes a novel approach to the above problem. Explicitly using the correlation structure of the sources’ traffic, we derive approxi- mations for both small and large buffers. Importantly, for small (large) buffers the short-term (long-term) correlations are dominant. The large buffer result decomposes the traffic stream in a stream of constant rate and a periodic impulse stream, allowing direct application of t...
Photoluminescent porous layers were formed on highly resistive p-type silicon by metal-assisted chemical etching using Na2S2O8 as an oxidizing agent. A thin layer of Ag was deposited on the (100) Si surface prior to immersion in a solution of HF and Na2S2O8. The morphology of the porous silicon (PS) layer formed by this method as a function of etching time was investigated by scanning electron microscopy (SEM). It shows that the surface is porous and the thickness of PS layer increases with etching time and is not limited as observed with the electrochemical method. Energy-dispersive X-ray (EDX) was used to analyse the chemical composition of PS layers. The EDX spectra show that the metal is not present on the PS surface after etching. Photoluminescence (PL) from metal-assisted chemically etched layers was measured using a He-Cd laser ...
Nowadays, mobile devices are used more and more, and their battery lifetime is a key concern. In this paper, we concentrate on a method called battery scheduling with the aim to optimize the battery lifetime of mobile devices. This technique has already been largely theoretically studied in other papers. It consists, for systems containing multiple batteries, in switching the load from one battery to the other. Then, while following a given scheduling sequence, advantage can be taken from the recovery and rate capacity effects. However, little studies with experimental data of battery scheduling have been found. In this paper we describe a simple setup for measuring the possible gain of battery scheduling, and give some exploratory results for two types of real batteries: a smart Li-Ion battery used in the Thales personal communication...
The application of atomic force microscopy (AFM) tip-mediated molecular transfer (dip-pen nanolithography or DPN) to fabricate nanopatterned (bio)reactive platforms based on dendrimers on reactive self-assembled monolayer (SAM) and polymer thin films is discussed. The transfer of high-molar-mass polyamidoamine (PAMAM) dendrimers (generation 5) and the rapid in situ covalent attachment of the deposited adsorbates onto reactive N-hydroxysuccinimide (NHS) terminated SAMs on gold and NHS-activated polystyrene-block-poly(tert-butyl acrylate) (PS690-b-PtBA1210) block copolymer thin films were investigated as strategies to suppress line broadening by surface diffusion in DPN. By exploiting carefully controlled environmental conditions (such as temperature and relative humidity), scan rates, and in particular the covalent attachment of the den...
This thesis considers concept-based multimedia retrieval, where documents are represented by the occurrence of concepts (also referred to as semantic concepts or high-level features). A concept can be thought of as a kind of label, which is attached to (parts of) the multimedia documents in which it occurs. Since concept-based document representations are user, language and modality independent, using them for retrieval has great potential for improving search performance. As collections quickly grow both in volume and size, manually labeling concept occurrences becomes infeasible and the so-called concept detectors are used to decide upon the occurrence of concepts in the documents automatically. The following fundamental problems in concept-based retrieval are identified and addressed in this thesis. First, the concept detectors freq...
Long Term Evolution (LTE) is a cellular technology developed to support diversity of data traffic at potentially high rates. It is foreseen to extend the capacity and improve the performance of current 3G cellular networks. A key mechanism in the LTE traffic handling is the packet scheduler, which is in charge of allocating resources to active flows in both the frequency and time dimension. In this paper we present a performance comparison of two distinct scheduling schemes for LTE uplink (fair fixed assignment and fair work-conserving) taking into account both packet level characteristics and flow level dynamics due to the random user behaviour. For that purpose, we apply a combined analytical/simulation approach which enables fast evaluation of performance measures such as mean flow transfer times manifesting the impact of resource a...
The Mn6+ ion is a promising activator ion for tunable and short-pulse laser materials because of its broadband luminescence in the spectral region 850-1600 nm and its simple 3d1 electronic configuration, which excludes an occurrence of undesirable exited-state absorption into higher 3d levels. However, hexavalent manganese can be stabilized only in the tetrahedral oxo-coordination and easily reduces to Mn5+ or Mn4+ at temperatures above 600°C. Recently, flux [1] and liquid-phase epitaxy (LPE) [2] growth of Mn6+-doped sulfates has been reported, while except for BaMoO4:Mn6+ [3] investigations on the mechanically more stable alkaline-earth-metal molybdates and tungstates as possible host materials for efficient Mn6+ incorporation have as yet not been reported. We investigated the growth conditions of undoped and Mn6+-doped MAO4, with M =...
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