Runtime enforcement monitors: composition,synthesis, and enforcement abilities

Runtime enforcement is a powerful technique to ensure that a program will respect a given set of properties. We extend previous work on this topic in several directions. Firstly, we propose a generic notion of enforcement monitors based on a memory device and finite sets of control states and enforcement operations. Moreover, we specify their enforcement abilities w.r.t. the general Safety-Progress classification of properties. Furthermore, we propose a systematic technique to produce a monitor from the automaton recognizing a given safety, guarantee, obligation or response property. Finally, we show that this notion of enforcement monitors is more amenable to implementation and encompasses previous runtime enforcement mechanisms.     

Comparing completion design in hydrocarbon and geothermal wells: The need to evaluate the integrity of casing connections subject to thermal stresses

Tapping for geothermal energy very often requires deep drilling in order to access high-temperature resources. This type of drilling is expensive and is financed by the operator with a long period of debt service before costs can be recovered from the energy sale (heat, electricity or a combination of both). Drilling costs are only a part of the total well expenditure. Tubulars can double the total well cost, especially when complex well completions are required. Together, drilling and well completions can account for more than half of the capital cost for a geothermal power project. A comparison is made of the different completions used for oil, gas and geothermal wells, and geothermal well completion requirements are discussed. Special attention is given to the thermal stresses induced by temperature variations in the casing string of a geothermal well. When the induced thermal stresses exceed the yield strength of the casing material, the fatigue behavior of the latter can be defined as low-cycle fatigue (LCF). The connection threads in the casing body amplify the local stresses and lower the LCF resistance. A theoretical approach is presented to evaluate that parameter, and calculations are compared with preliminary results from experiments on large-diameter Buttress connections, which are commonly used in geothermal well completions. It is shown that under extreme loads the LCF resistance of the Buttress thread connection can be as low as 10 cycles.     

Bragg Reflectors and Resonators in Microstrip Technology Based on Electromagnetic Crystal Structures

Recently, new promising two-dimensional (2-D) Photonic Bandgap Structures (PBG), or more properly Electromagnetic Crystal Structures, for microstrip lines have been proposed. In this paper, we analyze these structures in a manner like a Bragg reflector in optical wavelengths. Joining two of such Bragg like reflectors by means of a conventional microstrip transmission line allows one to design Bragg Resonators. The 2-D periodic pattern of the electromagnetic crystal structure is implemented with circles etched in the ground plane of the microstrip line by means of a numerical milling machine. Simulations have been performed by using HP ^TM Momentum and MDS software, and in accordance with the measurements give, for the Electromagnetic Crystal Structures, new promising potential applications both in microwave and millimeter wave integrated circuits, and also in the experimentation of expensive short wavelength (including photonic) devices by using simpler and cheaper microwave down scaling.     

An iterative method for the computation of the solutions of nonlinear equations

In this paper, we present new iterative methods for the computation of zeros of C ¹ functions. The idea is mainly based on a new asymptotic expansion (the Bernoulli expansion) for regular functions. Just as the Newton method is derived from the linear part of the Taylor polynomial, the new methods are analogously derived from the quadratic part of the Bernoulli expansion. We prove that the proposed procedures combine the assured convergence of bisection-like algorithms with a superlinear convergence speed which characterizes Newton-like methods. We show that the order of this new procedure is p= 2 and that the cost per iteration is completely equivalent to that of the Newton method. Finally some numerical experiments are performed. The related results seem to indicate that at least one of the proposed techniques works better than the Newton method. Moreover, the given method used in connection with an enclosing-interval procedure [2], is competitive with the ones recently proposed by Alefeld and Potra [2]. Received: July 1997 / Accepted: January 1998     

Low-power broadband quadrature signal generator based on phase-tunable dividers

This paper presents the design and experimental results of a low-power 300–960 MHz I/Q signal generator for low-IF receivers. The circuit is based on phase-tunable dividers and uses delay-locked loops, which provide phase accuracy for the quadrature signals as well as low-sensitivity of the phase error against temperature and power supply variations. Thanks to the adopted technique, the phase error can be further reduced by trimming the reference voltage of the delay-locked loops through a calibration digital word, which can be stored in a non-volatile memory during manufacturing. The I/Q generator exhibits an absolute phase error before calibration that is lower than 1.5°. The I/Q phase drift due to temperature variations from ?40 to 85 °C and power supply variations from 1.1 to 1.3 V is 0.3° and 0.2°, respectively. By dividing the overall frequency range into four 165-MHz wide sub-bands and using only four 5-bit calibration words, the I/Q phase variation with respect to frequency, temperature, and power supply is lower than 1° in the 300–960 MHz operating band. The I/Q generator is implemented in a 90-nm CMOS technology and exhibits a current consumption as low as 0.5 mA.     

Ultrasound evaluation of blunt abdominal trauma: program implementation, initial experience, and learning curve

OBJECTIVE: Although sonographic screening for blunt abdominal trauma is gaining acceptance, standards for implementation, training, credentialing, and quality control remain to be established. DESIGN: This prospective study examines a Level I trauma service experience with the de novo establishment of a trauma ultrasound (US) program credentialed through the Department of Surgery under the auspices of Continuous Quality Improvement. MATERIALS AND METHODS: All trauma surgeons attended a combined didactic and "hands on" 8-hour trauma US course. Abdominal sonography was subsequently performed on patients with potential blunt abdominal trauma followed by a standard diagnostic evaluation, which included computed tomographic scan, diagnostic peritoneal lavage, or observation. MEASUREMENTS AND MAIN RESULTS: Three hundred patients were studied over a 4-month period. They averaged 35 years of age with an average injury severity score of 12. The time required to perform the US examination averaged less than 3 minutes. Standard diagnostic evaluation included computed tomographic scan (21%), diagnostic peritoneal lavage (45%), and observation (34%). US examinations resulted in 277 true negatives, 17 true positives, two false positives, and four false negatives for a sensitivity of 81.0%, a specificity of 99.3%, and an accuracy of 98.0%. Annualized cost savings with the use of US evaluation versus standard diagnostic evaluation would amount to over $100,000.00. CONCLUSIONS: This experience with the de novo implementation of a trauma US program suggests that the training and credentialing requirements in this study are sufficient to provide surgeon ultrasonographers with acceptable competence in US diagnosis of blunt abdominal trauma.     

Towards a theory of delegation for agent-based systems

In this paper a theory of delegation is presented. There are at least three reasons for developing such a theory. First, one of the most relevant notions of “agent” is based on the notion of “task” and of “on behalf of”. In order to found this notion a theory of delegation among agents is needed. Second, the notion of autonomy should be based on different kinds and levels of delegation. Third, the entire theory of cooperation and collaboration requires the definition of the two complementary attitudes of goal delegation and adoption linking collaborating agents.

After motivating the necessity for a principled theory of delegation (and adoption) the paper presents a plan-based approach to this theory. We analyze several dimensions of the delegation/adoption (on the basis of the interaction between the agents, of the specification of the task, of the possibility to subdelegate, of the delegation of the control, of the help levels). The agent's autonomy and levels of agency are then deduced. We describe the modelling of the client from the contractor's point of view and vice versa, with their differences, and the notion of trust that directly derives from this modelling.

Finally, a series of possible conflicts between client and contractor are considered: in particular collaborative conflicts, which stem from the contractor's intention to help the client beyond its request or delegation and to exploit its own knowledge and intelligence (reasoning, problem solving, planning, and decision skills) for the client itself.