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     

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.     

Simplified realisation of delta-sigma decoder

A simplified structure of the ordinary delta-sigma decoder is described. The basic algorithm is derived and circuit diagrams for analogue and digital implementations are proposed     

R-Curve Behavior in Zirconia-Reinforced Molybdenum Disilicide Composites

R -curves for hot-pressed 20 vol% ZrO₂ (2.5-YPSZ and 8-YPSZ) reinforced MoSi₂ composites were evaluated using the indentation/bend technique. Results indicated a modest increase in the material toughness for both composites. Experimental R -curves were compared with theoretically predicted R -curves to evaluate the critical transformation stress for the partially stabilized ZrO₂ composite. A high critical transformation stress value obtained was indicative of the inhibition of transformation toughening effects due to microstructural inhomogeneity in the partially stabilized ZrO₂-MoSi₂ composites.     

Quantitative fractography of SiC whisker-Si3N4 matrix composites

An SEM quantitative stereophotogrammetry technique was developed and employed to analyse the fracture surfaces of VLS SiC whisker-Si₃N₄ matrix composites. This technique has quantitatively established that increased surface roughness is associated with increased fracture toughness for these composites. Matrix grain morphology and whisker/matrix interfacial characteristics are contributing factors to composite surface roughness.     

On the Performance of Binary Coded Signals

The bandwidth requirements of binary coded baseband signals are usually determined from spectral considerations. It is shown, by bit error rate calculations, that this approach can be misleading. The influence of pulse shapes on the performance of Miller, Manchester, and CRL codes is discussed.     

Two Algorithms for Determining the Most Reliable Path of a Network

This paper presents two algorithms for determining the most reliable paths of a communication network, taking into account both the reliabilities of nodes and links. A network is modeled by a linear graph. The first algorithm adapts a node labeling scheme; second is based on the shortest-path matrix algorithm. Both algorithms can be applied to oriented and nonoriented nonsymetric networks. The numerical examples confirm that both algorithms efficiently handle networks with hundreds of nodes and edges. The total amount of computation, expressed by the number of multiplications and comparisons, increases in the labeling procedure with the square of the number of nodes, and in the matrix method with the cube of the number of nodes.