Multipath effects of FSK with frequency-discriminator detection

We analyze how multipath effects, namely, errors due to channel-induced intersymbol interference, influence the error probability of frequency shift keying (FSK) with frequency-discriminator detection. We first introduce a new mathematical technique that allows insights into the error mechanisms. This technique is also capable of dealing with frequency shifts of the multipath components, postdiscriminator filtering, and nonlinearities in the discriminator. We then show that increasing the modulation index decreases the error floor, especially in the presence of frequency shifts. We also discuss the differences between prediscriminator and postdiscriminator filtering and show that an integrator is the best postdiscriminator filter     

Measuring of slowly changing AC signals without sample-and-holdcircuit

The measurement method described in this paper can be applied fur the accurate determination of slowly changing AC signals during the period of one second. Measurements of voltage and current are made in successive periods by a stroboscopic technique (synchronous undersampling). Assuming steady state of the observed system (electric utilities) in the stated one-second interval, it is proved that precise digital processing can be achieved without using a sample-and-hold circuit. The necessary synchronization is achieved by software measurements of the frequency of the measured signal. The suggested measuring system was practically built and tested, and the obtained results completely confirmed the starting postulates. A processing precision of 0.01% was achieved     

Talk and let talk: performance of Bluetooth piconets with synchronous traffic

This paper investigates the possibility of replacing the Bluetooth SCO connection with a QoS-constrained asynchronous link that uses multi-slot ACL packets. We have analyzed the performance of this scheme, dubbed pseudo-SCO, under three different scheduling policies: limited service, exhaustive service, and E-limited service, using the theory of M^[x]/G/1 queues with vacations. It was found that the pseudo-SCO scheme allows asynchronous traffic to experience much lower access and end-to-end delays than with the regular SCO connection, while supporting the bandwidth requirements of SCO traffic. The E-limited service scheduling policy was found to provide better performance than the other two policies, and its performance may be tuned to minimize the end-to-end packet delays under known traffic burstiness; moreover, it is able to guarantee minimum bandwidth for asynchronous traffic. Analytical results were confirmed through simulations.     

The study of oxazolidone formation from 9,10-epoxyoctadecane and phenylisocyanate

The formation of oxazolidone from 9,10-epoxyoctadecane and phenylisocyanate was studied. One branch of epoxidized vegetable oil with one epoxy group per chain corresponds to 9,10-epoxyoctadecane. This model could explain the probability of oxazolidone formation from natural oil-derived epoxides. Epoxidized natural oils are TG consisting of glycerin and three FA with or without one to three epoxy groups in the middle of the chain. To study oxazolidone formation from an internal epoxy group without possible interference from the side reactions on the ester group, 9,10-epoxyoctadecane was selected as the most appropriate model compound. Epoxy groups in the middle of allong aliphatic chain are of low reactivity toward isocyanates, and preparation of oxazolidones requires fairly harsh conditions such as high temperatures and catalysts, which also promote side reactions. The dominant side reaction is rearrangement of the epoxy groups. We found that the direction and magnitude of the rearrangement and the yield of any particular product depended on the catalyst used. Lithium chloride, aluminum trichloride, and zinc iodide catalyzed oxazolidone formation, along with the catalysis of side reactions such as ketone and carbonate formation. Aluminum trichloride showed the highest conversion of 9,10-epoxyoctadecane to oxazolidone. Aluminum triisopropoxide, triphenylantimony iodide, and imidazole did not catalyze the formation of oxazolidone. They were effective as catalysts of epoxy group rearrangement and promoted the formation of hydroxyl, ketone, and carbonate compounds. Hydroxyl groups reacted with isocyanate to produce urethane.     

METAHEURISTICS FOR HANDLING TIME INTERVAL COVERAGE CONSTRAINTS IN NURSE SCHEDULING

The problem of finding a high quality timetable for personnel in a hospital ward has been addressed by many researchers, personnel managers, and schedulers over a number of years. Nevertheless, automated nurse rostering practice is not common yet in hospitals. Many head nurses are currently spending several days per month on constructing their rosters by hand. In recent years, the emergence of larger and more constrained problems has presented a real challenge because finding good quality solutions can lead to a higher level of personnel satisfaction and to flexible organizational procedures. Compared to many industrial situations (where personnel schedules normally consist of stable periodic morning-day-night cycles) health care institutions often require more flexibility in terms of hours and shift types. The motivation for the research presented in this paper has been provided by real-world hospital administrators/schedulers and the approach that we describe has been implemented in over 40 hospitals in Belgium. This paper consists of two main contributions: modeling the real-world situation more accurately than has previously been done in the literature; and presenting and evaluating an efficient and effective tabu search procedure to solve these problems (as represented in the real-world model).

The approach described in this paper concentrates on an advanced representation of the daily personnel requirements of healthcare institutions. We introduce time interval personnel requirements. Instead of formulating the requirements as a number of personnel needed per shift type for each day of the planning period, time interval requirements allow for the representation of the personnel requirements per day in terms of the start and end times of personnel attendance. This formulation enables the provision of a greater choice of shift work and part-time work and reduces the amount of unproductive time because it enables the shifts to be split and combined. We present an algorithmic approach to handle this new formulation. We also set up a series of experiments which indicate that, not only does this approach take into account the requests and requirements of hospital schedulers, but it also generates higher quality schedules when compared with earlier approaches. The obtained results are better in the sense that various specific real-world soft constraints can be satisfied by scheduling appropriate shift type combinations, whereas in the shift type approach, fixed shift types restricted the solution space.     

Entwicklung und Evaluierung einer Interaktionsplattform für massentaugliche Pervasive Games

Pervasive Games are innovative game models based on information and communication technologies which merge the real world and the virtual world. The paper describes design and application of a technical platform supporting cross-media communication and comfortable modelling of complex interaction patterns which enables the implementation of pervasive games with mass impact. In an empirical study with 102 students a pervasive game was compared with a conventional case study in respect to the learning process and learning results. It revealed that the game relatively leads to higher energetic activation, more positive emotions, more positive attitudes towards learning content, and more efficient knowledge transfer.     

Hybrid Theory-Based Time-Optimal Control of an Electronic Throttle

An electronic throttle is a dc-motor-driven valve that regulates air inflow into the combustion system of the engine. The throttle control system should ensure fast and accurate reference tracking of the valve plate angle while preventing excessive wear of the throttle components by constraining physical variables to their normal-operation domains. These high-quality control demands are hard to accomplish since the plant is burdened with strong nonlinear effects of friction and limp-home nonlinearity. In this paper, the controller synthesis is performed in discrete time by solving a constrained time-optimal control problem for the piecewise affine (PWA) model of the throttle. To that end, a procedure is proposed to model friction in a discrete-time PWA form that is suitable both for simulation and controller design purposes. The control action computation can, in general, be restated as a mixed-integer program. However, due to the small sampling time, solving such a program online (in a receding horizon fashion) would be very prohibitive. This issue is resolved by applying recent theoretical results that enable offline precomputation of the state-feedback optimal control law in the form of a lookup table. The technique employs invariant set computation and reachability analysis. The experimental results on a real electronic throttle are reported and compared with a tuned PID controller that comprises a feedforward compensation of the process nonlinearities. The designed time-optimal controller achieves considerably faster transient, while preserving other important performance measures, like the absence of overshoot and static accuracy within the measurement resolution     

Implementation of security policy for clinical information systems over wireless sensor networks

Various healthcare areas such as diagnosis, surgery, intensive care and treatment, and patient monitoring in general, would greatly benefit from light, autonomous devices which can be unobtrusively mounted on the patient’s body in order to monitor and report health-relevant variables to an interconnection device in the vicinity. This interconnection device should be able to connect to access points at different locations within the healthcare institution. In this manner, health-relevant measurements can be forwarded to the central medical database and stored therein. In this scenario, integrity and privacy of personal medical data is of utmost importance. In this paper we address the networking and security architecture of a healthcare information system comprised of patients’ personal sensor networks, department/room networks, hospital network, and medical databases. We discuss confidentiality and integrity policies for clinical information systems and propose the feasible enforcement mechanisms over the wireless hop. We also compare two candidate technologies, IEEE 802.15.1 and IEEE 802.15.4, from the aspect of resilience to jamming and denial-of-service attacks.     

SnO2 thin films for gas sensors modified by hexamethyldisilazane after rapid thermal annealing

Simple method of SnO₂ layer modification, using very small quantity of hexamethyldisilazane and rapid thermal annealing in the range 800–1200 °C is proposed. The distribution profile of the dopant elements of C, N, Si in the SnO₂/SiO₂/Si structure is investigated. Penetration of Si in the whole depth of SnO₂ is revealed and formation of SiO₂ regions in the SnO₂ bulk is assumed. Simultaneously, Sn diffusion in the SiO₂ layer is observed. The combination of standard AES and XPS techniques with a hollow cathode discharge method appears to be very useful for detection of traces of dopants in the layers.     

Hydride fuel for LWRs—Project overview

This special issue of Nuclear Engineering and Design consists of a dozen papers that summarize the research accomplished in the DOE NERI Program sponsored project NERI 02-189 entitled “Use of Solid Hydride Fuel for Improved Long-Life LWR Core Designs”. The primary objective of this project was to assess the feasibility of improving the performance of pressurised water reactor (PWR) and boiling water reactor (BWR) cores by using solid hydride fuels instead of the commonly used oxide fuel. The primary measure of performance considered is the cost of electricity (COE). Additional performance measures considered are attainable power density, fuel bundle design simplicity, in particular for BWRs, safety, attainable discharge burnup, and plutonium (Pu) transmutation capability.Collaborating on this project were the University of California at Berkeley Nuclear Engineering Department (UCB), Massachusetts Institute of Technology Nuclear Science and Engineering Department (MIT), and Westinghouse Electric Company Science and Technology Department. Disciplines considered include neutronics, thermal hydraulics, fuel rod vibration and mechanical integrity, and economics.It was found that hydride fuel can safely operate in PWRs and BWRs having comparable or higher power density relative to typical oxide-fueled LWRs. A number of promising applications of hydride fuel in PWRs and BWRs were identified: (1) Recycling Pu in PWRs more effectively than is possible with oxide fuel by virtue of a number of unique features of hydride fuel-reduced inventory of ²³⁸U and increased inventory of hydrogen. As a result, the hydride-fueled core achieves nearly double the average discharge burnup and the fraction of the loaded Pu it fissions in one pass is double that of the MOX fuel. (2) Eliminating dedicated water moderator volumes in BWR cores, thus enabling significant increase of the cooled fuel rod surface area as well as the coolant flow cross-section area in a given fuel bundle volume while reducing the heterogeneity of BWR fuel bundles, thus achieving flatter pin-by-pin power distribution. The net result is an increase in the core power density and a reduction of the COE.A number of promising oxide-fueled PWR core designs were also found in this study: (1) The optimal oxide-fueled PWR core design features a smaller fuel rod diameter (D) of 6.5 mm and a larger pitch to rod diameter (P/D) ratio of 1.39 than that presently practiced by industry of 9.5 mm and 1.326. This optimal design can provide a 27% increase in the power density and a 19% reduction in the COE provided the PWR can be designed to have the coolant pressure drop across the core increased from the reference 0.20 MPa (29 psi) to 0.414 MPa (60 psi). Under the set of constraints assumed in this work, hydride fuel was found to offer comparable power density and economics as oxide fuel in PWR cores when using fuel assembly designs featuring square lattice and grid spacers. This is because pressure drop constraints prevented achieving sufficiently high power using hydride fuel with a relatively small P/D ratio of around 1.2 or less, where it offers the highest reactivity and a higher heavy metal (HM) loading. (2) Using wire-wrapped oxide fuel rods in hexagonal fuel assemblies, it is possible to design PWR cores to operate at ∼50% higher power density than the reference PWR design that uses grid spacers and a square lattice, provided 0.414 MPa coolant pressure drop across the core could be accommodated. Uprating existing PWRs to use such cores could result in up to 40% reduction in the COE. The optimal lattice geometry is D = 9.34 mm and P/D = 1.37. The most notable advantages of wire-wraps over grid spacers are their significantly lower pressure drop, higher critical heat flux, and improved vibration characteristics.The achievement of the highest power gains claimed in this study is possible as long as mechanical components like assembly hold-down devices (both in PWRs and in BWRs) and steam dryers (only in BWRs) are appropriately upgraded to accommodate the higher coolant pressure drop and flow velocities required for the high-performance LWR designs. The compatibility of hydride fuel with Zircaloy clad and with PWR and BWR coolants need yet be experimentally demonstrated. Additional recommendations are given for future studies that need to be undertaken before the commercial benefits from use of hydride fuel could be reliably quantified.