Input‐output triggered control using ‐stability over finite horizons

This paper investigates stability of nonlinear control systems under intermittent information. Following recent results in the literature, we replace the traditional periodic paradigm, where the up‐to‐date information is transmitted and control laws are executed in a periodic fashion, with the event‐triggered paradigm. Building on the small gain theorem, we develop input–output triggered control algorithms yielding stable closed‐loop systems. In other words, based on the currently available (but outdated) measurements of the outputs and external inputs of a plant, a mechanism triggering when to obtain new measurements and update the control inputs is provided. Depending on the noise in the environment, the developed algorithm yields stable, asymptotically stable, and ‐stable (with bias) closed‐loop systems. Control loops are modeled as interconnections of hybrid systems for which novel results on ‐stability are presented. The prediction of a triggering event is achieved by employing ‐gains over a finite horizon. By resorting to convex programming, a method to compute ‐gains over a finite horizon is devised. Finally, our approach is successfully applied to a trajectory tracking problem for unicycles. Copyright © 2014 John Wiley & Sons, Ltd.     

Improved Approximations for Guarding 1.5-Dimensional Terrains

We present a 4-approximation algorithm for the problem of placing the fewest guards on a 1.5D terrain so that every point of the terrain is seen by at least one guard. This improves on the previous best approximation factor of 5 (see King in Proceedings of the 13th Latin American Symposium on Theoretical Informatics, pp. 629–640, 2006). Unlike most of the previous techniques, our method is based on rounding the linear programming relaxation of the corresponding covering problem. Besides the simplicity of the analysis, which mainly relies on decomposing the constraint matrix of the LP into totally balanced matrices, our algorithm, unlike previous work, generalizes to the weighted and partial versions of the basic problem.     

Recognizing malicious software behaviors with tree automata inference

We explore how formal methods and tools of the verification trade could be used for malware detection and analysis. In particular, we propose a new approach to learning and generalizing from observed malware behaviors based on tree automata inference. Our approach infers k-testable tree automata from system call dataflow dependency graphs. We show how inferred automata can be used for malware recognition and classification.     

Recovery of flavonoids from grape skins by enzyme-assisted extraction

Grape skin contains large amounts of different flavonoids so it can be used for their recovery. Optimization of enzyme-assisted extraction of flavonoids was conducted using oenological enzyme preparations with respect to enzyme dosage, temperature, extraction time, pH, and enzyme preparation. Optimal conditions were obtained using enzyme preparation Lallzyme EX-V, at the temperature of 45°C, time of 3 h, pH 2.0, and enzyme dosage of 10.52 mg/g. The new optimized extraction method is less expensive, simple, accurate, and selective for the recovery of simple flavonoids. It is based on an environmentally-friendly extraction solvent which may provide a valuable alternative to conventional methods.     

Structural Steel ASTM A709—Behavior at Uniaxial Tests Conducted at Lowered and Elevated Temperatures, Short-Time Creep Response, and Fracture Toughness Calculation

This paper presents the temperature dependence of the mechanical properties of structural high-strength low-alloy (HSLA) ASTM A709 Gr50 steel (En10025: S355 JO; DIN: ST 52-3U). Engineering stress-strain diagrams at lowered and elevated temperatures are presented. Creep responses for selected constant stresses at selected temperatures are also presented and are fit with a rheological model. Additionally, a relation between impact toughness and fracture toughness is proposed and is validated using results from notch impact tests on a Charpy pendulum impact machine.     

Harmonic ultrasonic field of medical phased arrays: simulations and measurements

With the introduction of harmonic imaging, the design of new array transducers for tissue and contrast imaging became indispensable. Hence, prior knowledge of harmonic beams is essential to attain optimal harmonic performances. For that purpose, a new numerical algorithm that solves the parabolic nonlinear wave equation is developed. The algorithm is based on finite differences and performs exclusively in time domain. Pulsed harmonic fields emitted by a medical transducer were measured and computed at different mechanical indices. Simulations and measurements showed very good agreement for all the harmonic components.     

Approximating the safely reusable set of learned facts

Despite many advances, today’s software model checkers and extended static checkers still do not scale well to large code bases when verifying properties that depend on complex interprocedural flow of data. An obvious approach to improve performance is to exploit software structure. Although a tremendous amount of work has been done on exploiting structure at various levels of granularity, the fine-grained shared structure among multiple verification conditions has been largely ignored. In this paper, we formalize the notion of shared structure among verification conditions and propose a novel and efficient approach to exploit this sharing by safely reusing facts learned while checking one verification condition to help solve the others. Experimental results show that this approach can improve the performance of verification, even on path- and context-sensitive and dataflow-intensive properties.     

Semantische Technologien für Produktionsprozessinnovationen in der Landwirtschaft

Optimization of production processes in agriculture requires that innovation in form of efficiency enhancing devices is being continuously introduced and integrated within the production environments. This paper describes how semantic modelling, web services and automatic logical reasoning are used as system enablers for such value-adding integration in implementation of semantic-based diagnoses supporting optimization of milk production processes of dairy farms.     

Martensitic stainless steel AISI 420—mechanical properties,creep and fracture toughness

In this paper some experimental results and analyses regarding the behavior of AISI 420 martensitic stainless steel under different environmental conditions are presented. That way, mechanical properties like ultimate tensile strength and 0.2 percent offset yield strength at lowered and elevated temperatures as well as short-time creep behavior for selected stress levels at selected elevated temperatures of mentioned material are shown. The temperature effect on mentioned mechanical properties is also presented. Fracture toughness was calculated on the basis of Charpy impact energy. Experimentally obtained results can be of importance for structure designers.