Secrecy Capacity Region of Some Classes of Wiretap Broadcast Channels

This work investigates the secrecy capacity of the Wiretap Broadcast Channel (WBC) with an external eavesdropper where a source wishes to communicate two private messages over a Broadcast Channel (BC) while keeping them secret from the eavesdropper. We derive a non-trivial outer bound on the secrecy capacity region of this channel which, in absence of security constraints, reduces to the best known outer bound to the capacity of the standard BC. An inner bound is also derived which follows the behavior of both the best known inner bound for the BC and the Wiretap Channel. These bounds are shown to be tight for the deterministic BC with a general eavesdropper, the semi-deterministic BC with a more-noisy eavesdropper and the Wiretap BC where users exhibit a less-noisiness order between them. Finally, by rewriting our outer bound to encompass the characteristics of parallel channels, we also derive the secrecy capacity region of the product of two inversely less-noisy BCs with a more-noisy eavesdropper. We illustrate our results by studying the impact of security constraints on the capacity of the WBC with binary erasure (BEC) and binary symmetric (BSC) components.Comment: 19 pages, 8 figures, To appear in IEEE Trans. on Information Theor

Rate-Distortion Function for a Heegard-Berger Problem with Two Sources and Degraded Reconstruction sets

In this work, we investigate an instance of the Heegard-Berger problem with two sources and arbitrarily correlated side information sequences at two decoders, in which the reconstruction sets at the decoders are degraded. Specifically, two sources are to be encoded in a manner that one of the two is reproduced losslessly by both decoders, and the other is reproduced to within some prescribed distortion level at one of the two decoders. We establish a single-letter characterization of the rate-distortion function for this model. The investigation of this result in some special cases also sheds light on the utility of joint compression of the two sources. Furthermore, we also generalize our result to the setting in which the source component that is to be recovered by both users is reconstructed in a lossy fashion, under the requirement that all terminals (i.e., the encoder and both decoders) can share an exact copy of the compressed version of this source component, i.e., a common encoder-decoders reconstruction constraint. For this model as well, we establish a single-letter characterization of the associated rate-distortion function.Comment: Submitted to IEEE Trans. on Information Theor

Development of instrumentation incorporating solid state gas sensors for measurement of oxygen partial pressure.

Electronic instrumentation was developed for the measurement of the oxygen partial pressure, P1 ( in a sample gas using fully-sealed zirconia pump-gauge oxygen sensors operated in an AC mode. These sensors, operated typically at 700°C, consisted of two discs of zirconia with porous platinum electrodes on each face separated by a gold seal and enclosing a small internal volume. One disc was operated as a pump enabling oxygen to be electrochemically transferred into and out of the enclosed volume; the other disc operated as a gauge, the Nernst EMF across the electrodes providing a measure of the ratio of the internal to the external oxygen partial pressure. By careful design of the circuitry it was possible to measure the oxygen partial pressure, P, without the need for a separate reference gas supply. Subsequently, a novel "tracking" mode of operation was proposed and implemented in which leakage effects generally associated with sealed pump-gauge devices were minimised: the sensor was operated in a feedback control-loop in order to adjust automatically the mean internal reference oxygen partial pressure, P0, so as to maintain the ratio (Px/P0) close to unity. The signal-to-noise ratio was markedly improved by using gauge EMFs with high amplitudes which inevitably display a distorted sinusoid due to the logarithmic term in the Nernst equation. Surprisingly, mathematical analysis predicted that the linearity of the output of the instrument using phase-sensitive detection should not be affected by the deviation from a sinusoid and this was confirmed experimentally: signal processing was practically implemented using simple analogue electronics. As anticipated there was a strong influence of sensor temperature on the output of the instrument: consequently, methods for temperature compensation were proposed and shown to be feasible with minimum hardware. The theory of Operation of leaky pump-gauge was also developed which indicated that a physical leak in the sensor should cause a phase shift and amplitude change in the sensor output. Experimental results were, in general, in agreement with the theory demonstrating the influences of the geometry and dimensions of the leak and of the operating frequency. Importantly, the theory predicted that, when operated in the AC mode, devices with major leakage may still be used for oxygen partial pressure measurement: again this was confirmed by experiment and the additional benefit of a concomitant substantial simplification of the electronic circuitry also realised. Interestingly an unexpected but small influence of oxygen concentration on the phase shift was observed: this requires additional study

Digitally-tuned resolver converter

Sinusoidal encoders provide electrical signals related to the sine and cosine of the mechanical shaft angle θ. An analog converter is described for the linearization of these signals and hence for linear computation of θ. The converter was based upon the difference between the absolute values of the transducer signals, together with a simple signal diode-based shaping network. The optimal break points positions of the network, that minimize the absolute error of the converter, are determined experimentally and automatically using a LabVIEW-controlled setup. Despite its simplicity, the converter has an absolute error of only 0.12 °

THE USE OF INTELLECTUAL PROPERTY AS COLLATERAL: GAP IN THE PERFECTION OF A SECURITY INTEREST

The purpose of the present thesis is to let French lawyers know which step they need to take in order to best assist their client in securing a more solid investment. Lenders want to be protected. Lenders want to be sure that they can use the intellectual property rights in a commercial environment free from superior claims by third parties. In other words, a lender who provides a large loan to a borrower wants to know how and where its security interest will be perfected and what is the best way for him to have priority over other claims. This thesis also will first examine the classification of collateral and represents an effort to summarize whether a state or a federal filing is required to perfect a security interest. Second, the thesis will examine the main issues arising out from the priority rules in the area of bankruptcy. Finally, it will address the different proposals suggested in order to have a clarification of the actual system

Enhancing Query Reformulation Performance by Combining Content and Hypertext Analyses

Information retrieval techniques play a critical role in the development of the information systems. Different searches have focused on the way of improving the retrieval effectiveness. Query expansion via relevance feedback is a good technique that proved to be a good way to improve the retrieval performance. In this paper, we investigate new methods to improve the query reformulation process. A two step process is employed to reformulate query. In a preliminary step, a local set of documents is built from the retrieved result. In a second step, a co-occurrence analysis is performed on the local document set to deduce the terms to be used for the query expansion. To build the local set we use firstly a content-based analysis. It is a similarity study between the retrieved documents and the query. The second method combines content and hypertext analyses to achieve the local set construction. The TREC1 frame is used to evaluate the proposed processes

Rate-Distortion Region of a Gray–Wyner Model with Side Information

In this work, we establish a full single-letter characterization of the rate-distortion region of an instance of the Gray–Wyner model with side information at the decoders. Specifically, in this model, an encoder observes a pair of memoryless, arbitrarily correlated, sources (Sn1,Sn2) and communicates with two receivers over an error-free rate-limited link of capacity R0 , as well as error-free rate-limited individual links of capacities R1 to the first receiver and R2 to the second receiver. Both receivers reproduce the source component Sn2 losslessly; and Receiver 1 also reproduces the source component Sn1 lossily, to within some prescribed fidelity level D1 . In addition, Receiver 1 and Receiver 2 are equipped, respectively, with memoryless side information sequences Yn1 and Yn2 . Important in this setup, the side information sequences are arbitrarily correlated among them, and with the source pair (Sn1,Sn2) ; and are not assumed to exhibit any particular ordering. Furthermore, by specializing the main result to two Heegard–Berger models with successive refinement and scalable coding, we shed light on the roles of the common and private descriptions that the encoder should produce and the role of each of the common and private links. We develop intuitions by analyzing the developed single-letter rate-distortion regions of these models, and discuss some insightful binary examples

Slope inequality for an arbitrary divisor

Let $f: S \longrightarrow C$ be a surjective morphism with connected fibers from a smooth complex projective surface $S$ to a smooth complex projective curve $C$ with general fiber $F$. In this paper, we develop a more general version of slope inequality for a data $(D, \mathcal{F})$ where $D$ is an arbitrary relatively effective divisor on $S$ and $\mathcal{F}$ is a locally free sub-sheaf of $f_{*}\mathcal{O}_{S}(D)$ without assuming any linear stability condition of $|D_{|_{F}}|$, we explain how the speciality of $D$ restricted to the general fiber play a role in the results. However, we compute some natural examples and give applications.Comment: Many changes and comments are very welcom