Design of a flight control architecture using a non-convex bundle method

We design a feedback control architecture for longitudinal flight of an aircraft. The multi-level architecture includes the flight control loop to govern the short-term dynamics of the aircraft, and the autopilot to control the long-term modes. Using $H_\infty $ performance and robustness criteria, the problem is cast as a non-convex and non-smooth optimization program. We present a non-convex bundle method, prove its convergence, and show that it is apt to solve the longitudinal flight control problem.     

The XTS-AES Disk Encryption Algorithm and the Security of Ciphertext Stealing

Abstract

This paper describes the importance of the XTS-AES encryption mode of operation and concludes with a new proof for the security of ciphertext stealing as used by XTS-AES. The XTS-AES mode is designed for encrypting data stored on hard disks where there is not additional space for an integrity field. Given this lack of space for an integrity field, XTS-AES builds on the security of AES by protecting the storage device from many dictionary and copy/paste attacks. The operation of the XTS mode of AES is defined in the IEEE 1619-2007 standard [3 IEEE Std 1619–2007 . April 18, 2008 . The XTS-AES Tweakable Block Cipher. Institute of Electrical and Electronics Engineers, Inc.  [Google Scholar]], and has been adopted by the U.S. National Institute of Standards and Technology (NIST) as an approved mode of operation under FIPS 140-2 [2 Dworkin , M. December 2009 . NIST SP 800-38E, “Recommendation for Block Cipher Modes of Operation: The XTS-AES Mode for Confidentiality on Storage Devices”.  [Google Scholar]]. XTS-AES builds on the XEX (Xor-Encrypt-Xor) mode originally proposed by Rogaway [8 Rogaway , P. 2004 . Efficient Instantiations of Tweakable Block ciphers and Refinements to Modes OCB and PMAC. Advances in Cryptology–Asiacrypt 2004, Lecture Notes in Computer Science, vol. 3329, Springer-Verlag, pp. 16–31. Available at http://www.cs.ucdavis.edu/rogaway/papers/offsets.pdf (Accessed 6 January 2012) . [Google Scholar]].     

A verification tool for ERLANG

This paper presents an overview of the main results of the project Verification of ERLANG Programs , which is funded by the Swedish Business Development Agency (NUTEK) and by Ericsson within the ASTEC (Advanced Software TEChnology) initiative. Its main outcome is the ERLANG Verification Tool (EVT), a theorem prover which assists in obtaining proofs that ERLANG applications satisfy their correctness requirements formulated as behavioural properties in a modal logic with recursion. We give a summary of the verification framework as supported by EVT, discuss reasoning principles essential for successful proofs such as inductive and compositional reasoning, and an efficient treatment of side-effect-free code. The experiences of applying the tool in an industrial case study are summarised, and an approach for supporting verification in the presence of program libraries is outlined.EVT is essentially a classical proof assistant, or theorem-proving tool, requiring users to intervene in the proof process at crucial steps such as stating program invariants. However, the tool offers considerable support for automatic proof discovery through higher-level tactics tailored to the particular task of the verification of ERLANG programs. In addition, a graphical interface permits easy navigation through proof tableaux, proof reuse, and meaningful feedback about the current proof state, to assist users in taking informed proof decisions.     

Nonsmooth H/sub /spl infin// synthesis

We develop nonsmooth optimization techniques to solve H/sub /spl infin// synthesis problems under additional structural constraints on the controller. Our approach avoids the use of Lyapunov variables and therefore leads to moderate size optimization programs even for very large systems. The proposed framework is versatile and can accommodate a number of challenging design problems including static, fixed-order, fixed-structure, decentralized control, design of PID controllers and simultaneous design and stabilization problems. Our algorithmic strategy uses generalized gradients and bundling techniques suited for the H/sub /spl infin// norm and other nonsmooth performance criteria. We compute descent directions by solving quadratic programs and generate steps via line search. Convergence to a critical point from an arbitrary starting point is proved and numerical tests are included to validate our methods. The proposed approach proves to be efficient even for systems with several hundreds of states.     

An EM algorithm for dynamic SPECT

In this paper we present two variants of the EM algorithm for dynamic SPECT imaging. A version based on compartmental modeling which fits a sum of exponentials and a more general approach allowing for arbitrary decaying activities. The underlying probabilistic models are discussed and the incomplete and complete data spaces are shown to be physically meaningful. We indicate that the second method, leading to a convex program in the M step, is easier to treat numerically and we present a possible numerical approach. Some preliminary numerical tests indicating the feasibility of the method are included.     

Search for sulfur (H2S) on Jupiter at millimeterwavelengths

The authors observed Jupiter at two wavelengths near 1.4 mm in an attempt to detect gaseous hydrogen sulfide (H₂S) or place new upper limits on its abundance in Jupiter's atmosphere. Although they were not successful in detecting H₂S, they report the first brightness temperature observations of Jupiter at 1.4 mm with a spectral resolution of approximately 1 GHz using Mars as the calibration standard. The methodology and results of a laboratory experiment in which the authors measured H₂S absorption at 1.4 mm in a simulated Jovian atmosphere (predominantly H₂ and He) are discussed. The results of the laboratory measurements are applied to a radiative transfer model, which is used to interpret the observations of Jupiter