Extending NCP for protocols using public keys

One of the greatest obstacles to wide-spread deployment of wireless mobile systems is security. Cryptographically strong protocols and algorithms are required to enable secure communication over links that are easy to monitor and control by an attacker. While good cryptographic algorithms exist, it is difficult to design protocols that are immune to malicious attack. Good analysis techniques are lacking. This paper presents extensions to a technique for specifying and analyzing nonmonotonic cryptographic protocols that use asymmetric keys. We introduce new actions and inference rules, as well as slight modifications to the Update function. An important observation is that reasoning about the origin of messages is quite different when dealing with asymmetric key protocols. We also introduce the notion that keys in certificates should be bound to the principals receiving them. We extend the technique to meet the binding requirements and show how the flaw in the Denning and Sacco public key protocol, which was discovered by Abadi and Needham, is revealed. We demonstrate the extended technique using one protocol of our own and the Needham and Schroeder public key protocol. We also introduce and analyze a fix to a known weakness in Needham and Schroeder’s protocol using our extended technique. Finally, we present several applications of these techniques to protocols for mobile computing over wireless networks. This revised version was published online in June 2006 with corrections to the Cover Date.     

The anatomy of investing in energy efficient buildings

A building investment is a real decision because the allocated resources are typically irrevocable for long times. Investment appraisal is a logic method to process elapsing time, uncertain benefits and costs, and irrevocability related to decisions. Most analysts stop halfway the appraisal process when they carefully assess net present values and their sensitivity to uncertain future events. But sidelining irrevocability and the dynamic sequential analysis of future events and actions cause wrong decisions when the energy performance endowment of a new building is decided. Irrevocability and preclusion are explained, and their impact illustrated with a case study. Adopting realistic assumptions about the uncertain future and applying the proper methodology reveal as financially best choice the immediate investment in passive attributes and items. Irrevocability is of high relevance for building efficiency investments and for the implementation of the EU-2010 buildings directive.     

Basic characterization of U: Determination of age and U content using sector field ICP-MS, gamma spectrometry and alpha spectrometry

The possibility to determine the age, i.e. the time since the last chemical separation, of ²³³U was studied using two fundamentally different measurement techniques: inductively coupled plasma mass spectrometry (ICP-MS) and gamma spectrometry. Moreover, the isotope ratio ²³²U/²³³U was measured using both alpha spectrometry and gamma spectrometry. For the two materials analysed, all measurement results were in agreement, i.e. consistent within the combined uncertainties. One of the materials was also measured using gamma spectrometry under field conditions. This measurement was also in agreement with the other results on this material.     

Renewable and nuclear power: A common future?

Nuclear power and renewable energy are the main options to bring down the carbon intensity of commercial energy supply. What technology is unlimited backstop supply depends on its performance on the sustainability criteria: democratic decided, globally accessible, environmental benign, low risk, affordable.     

Fuzzy gain scheduling: controller and observer design based on Lyapunov method and convex optimization

Addresses model-based fuzzy control. A constructive and automated method for the design of a gain-scheduling controller is presented. Based on a given Takagi-Sugeno fuzzy model of the plant, the controller is designed such that stability and prescribed performance of the closed loop are guaranteed. These properties are valid in a wide working range around an equilibrium without restrictions to slowly varying trajectories. The synthesis is based on linear matrix inequalities and convex optimization techniques. If required, a fuzzy state estimator and an extended controller can be included, providing a zero steady-state error in the presence of disturbances and modeling errors. The proposed method has been applied to a control of a laboratory liquid-level process. Hence, the performance has been evaluated in simulations as well as in real-time control.     

The acceptance of systemic thinking in various fields of technology and consequences on the respective safety philosophies

Systemic thinking aims to develop a common language that makes it possible for scientists of different disciplines and technologies to communicate with one another. The specific methodology of systemic thinking is a means of tackling complex, interrelated problems by applying a holistic approach that focuses on the interrelation of individual aspects. In this article, an attempt is made to show the impact of systemic thinking in different areas of science and technology. In particular, the authors argue that a multidisciplinary, systemic approach can play an important role in developing a general theory of safety science. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 231–242, 2003.     

Rapid D-dimer assays to exclude deep venous thrombosis and pulmonary embolism: current status and new developments

Two hundred fifty athletes from a sports clinic, 122 (49%) females and 128 (51%) males (mean age 21.1 years), who were diagnosed as having patellofemoral pain syndrome (PFPS) and were instructed to practice vastus medialis training, returned a completed questionnaire after an average of 5.7 years' follow-up. Sixty-eight (27%) were pain-free for an average of 8.1 months: 17 (25%) women and 51 (75%) men. As to the remaining 182 (73%) who were still suffering, 95 (52%) had experienced a decrease in pain, 64 (35%) were unchanged and 23 (13%) had experienced an increase in pain. Sixty-eight (37%) described the pain as being mild, 88 (48%) as moderate, and 26 (15%) as severe. Athletic activity was affected in 184 (74%) of the cases, employment in 16 (6%) cases. The prognosis was not correlated with a history of trauma or with age. Athletes with a hypermobile patella had a less good prognosis (r = 0.23, p = 0.04). For about half of the athletes the prognosis was good, although the other half obtained an inadequate result, using a self-training program.     

Optimization of polymer synthesis through distributed control of polymerization conditions

An optimal control methodology is applied to the goal of lowering polydispersity while increasing conversion in polymerization reactions. An illustration using initiator, heat, and monomer flux control profiles for free‐radical polymerization of styrene in a plug flow reactor is provided and compared with available experimental data. The design calculations use a kinetic model that includes the gel effect. The reactor designs show that distributed initiator, heat, and monomer fluxes along the length of the reactor lower the polydispersity of the styrene polymers and increase conversion for a given reaction time. The monomer flux maintains a nearly constant monomer concentration in the reactor. The initiator and heat fluxes are highly correlated. The temperature rises as a result the heat flux; but the initiator flux results in a lower initiator concentration relative to the initiator cofeed case. At a reaction time of 120 min, a conversion of 44% and a polydispersity of 1.73 have been achieved. The theoretical designs, although not proven to be globally optimal, are of high quality. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2922–2928, 2002     

District heating: Estimation of a standard load duration curve

District heating projects are planned with the help of a standard heat load duration curve, being the representation of the most likely load pattern the system will have to meet. A systematic procedure to estimate the standard curve is set up: the daily average outside temperature density function is transformed with a relationship between this temperature and the daily average heat load, resulting in a density over the heat loads. the cumulative distribution of the latter is the day load duration curve. Because the result has to be used for capacity planning, the unitary time interval has to be small, e.g. 1 hour. Therefore, the day curve is refined by incorporating the fluctuations over the day. The hour load duration pattern is approximated analytically using the collocation polynomial technique of Lagrange. Results are in agreement with the postulated standard patterns of the literature. the paper adds to the state of the art primarily by presenting a systematic procedure to derive the curve and by expressing the curve analytically. the systematic approach allows a clear interpretation and an extension of the varous steps of the load analysis.     

Multivariable process and prediction models in predictive control—A unified approach

In this paper multivariable generalizations of the SISO unified process model (UPCM) and unified prediction model (UPM) used in the SISO unified predictive controller are presented. the necessary assumptions regarding the multivariable UPCM (MUPCM) are established. the properties of the multivariable UPM (MUPM) are examined and the conditions for a zero steady state prediction error are established. The MUPCM has a general noise model and unites all multivariable, discrete, linear process models in transfer function form. the MUPM uses an output filter which unites all relevant output filters used in predictive controllers. Furthermore, the elements of the output can be predicted over different horizons. the MUPCM and MUPM and the algorithm used to calculate the MUPM are chosen such that the predictions of the outputs can be calculated as fast as possible, not only for the general model, but also for special cases such as ARX, ARIMAX, Box-Jenkins and FIR models.