Correlation between cohesive energy and mixing rate in ion mixing of metallic bilayers

We have compared the mixing rate of several 5d-4d metal bilayers which form ideal solutions. We observe a strong correlation between the mixing rate and the average cohesive energy of each bilayer. A model based on the thermal spike concept is proposed to explain this behavior. The model leads to a general expression describing mixing rates in metallic bilayers

Influence of chemical driving forces in ion mixing of metallic bilayers

The effective interdiffusion coefficient of metallic bilayers under ion irradiation has been correlated with the heat of mixing of corresponding binary alloys. The results are interpreted according to Darken's theory of chemically enhanced diffusion

Analysing Multibeam, Cooperative, Ground Based Radar in a Bistatic Configuration

Recent advances in digital beam forming for phased arrays in combination with digital signal processing should enable the development of multibeam radar in a bistatic configuration. In the bistatic setting, the pulse travelling outward from the transmitter should be followed or "chased" by the receiver. During transmission, depending on the location of the transmitter, receiver, and pulse, the number of digital beams and their location at the transmitter vary. In this paper, we analyse the geometrically depending number of digital beams and the beam switching rate of the receiver needed for pulse chasing. In addition, we derive the pulse repetition frequency (PRF) for the bistatic configuration based on the desired detection range. It is shown that the PRF in the bistatic case can be increased compared to its monostatic counterpart when the distance between the transmitter and the receiver is increased. Our results are applied on the scenario of an air traffic control radar to show the feasibility of a multibeam, ground based bistatic surveillance radar. It will be demonstrated that the maximum PRF can almost be doubled and an adaptive sensing and tracking paradigm can lead to a maximum of 64 simultaneous receiver beams for the bistatic surveillance and tracking setting.Comment: 6 pages, 7 figures, errata of Fig. 7 added as supplemen

Radar Resource Management for Active Tracking Using Split-Aperture Phased Arrays

Flexible front-end technology will become available in future multifunction radar systems to improve adaptability to the operational theatre. A potential concept to utilize this flexibility is to subdivide radar tasks spatially over the array, the so-called split-aperture phased array (SAPA) concept. As radars are generally designed for their worst-case scenario, e.g., small targets at a large range, the power-aperture budget can be excessive for targets that do not fall within that class. To increase efficiency of the time budget of the radar front-end, the SAPA concept could be applied. In this paper, the SAPA concept is explored to assign radar resources for active tracking tasks of many targets. To do so, we formulate and solve the radar resource management problem for the SAPA concept by employing the quality of service based resource allocation model (Q-RAM) framework. It will be demonstrated by a simulation example that a radar can maintain a larger numbers of active tracking tasks when using the SAPA concept compared to the case that only the full array can be used per task.Comment: 6 page

Borstvoeding in de eerste zes maanden:een focusgroep studie naar redenen en motieven van vrouwen om gedeeltelijk of geheel te stoppen met het geven van borstvoeding in de eerste 6 maanden

Deze focusgroep studie geeft inzicht in de redenen en motieven van vrouwen om vroegtijdig te stoppen met het geven van borstvoeding of om vroegtijdig kunstvoeding te gaan geven. De resultaten van dit onderzoek zijn gebaseerd op een kwalitatief onderzoek met 10 focusgroepen met in totaal 69 vrouwen die op het moment van het onderzoek borstvoeding gaven aan hun kind maar die vroegtijdig kunstvoeding gingen geven naast de borstvoeding (voordat de baby 6 maanden oud was), en vrouwen die borstvoeding hebben gegeven maar die op het moment van het onderzoek, voordat de baby 6 maanden oud was, daarmee waren gestopt. Het doel van het onderzoek is niet geweest om kwantitatieve gegevens op te leveren; daartoe is kwantitatief vervolgonderzoek nodig

An Interactive Multimedia Business Game

The playing of computer-based business games has changed little with recent technological improvements. Teams make decisions which are written down on paper and handed to a tutor who then has to enter these into the computer. To make it a richer and more real-life experience we have brought a business simulation into a multimedia environment. In order to create a sense of the passing of time the simulation is continuous, and players can enter input values throughout the game. Important parameters, such as product sales, are displayed as continuously updated graphs. Background information such as news items is provided in multimedia form. Players also have direct access to online tools, such as spreadsheets, from the game environment. We describe the prototype built to illustrate our approach

Kinetics of lipase-mediated synthesis of butyl butyrate in n-hexane

This paper reports experimental and modeling work concerning alcoholysis reactions between butanol and ethyl butanoate, catalyzed by Lipozymee in n-hexane, using a batch stirred system at 608C. Description of the reaction kinetics was based on a postulated multisubstrate Ping Pong Bi Bi mechanism, and appropriate rate expressions were derived for all components in the reaction medium. Simplified models were fitted by nonlinear multiresponse regression analysis to data (experimental or calculated from mass balances, as appropriate) encompassing the concentrations of free butanol, ethyl butanoate, ethanol and butyl butanoate. Finally, incremental F-tests were performed to assess the simplest model form that was able to provide a statistically good fit throughout the entire reaction time frame

Integrated vs. sequential reaction and separation: contributions for a global analysis

Integration of reaction and separation in one single step has often been claimed to provide enhanced processing and economic results when compared with the traditional configuration where a reaction unit is followed by a downstream separation unit, due to alleviation of kinetic and thermodynamic constraints. This paper quantitatively addresses the kinetic and thermodynamic improvements which can be brought about by performing reaction and separation simultaneously instead of sequentially, in the case of a unisubstrate/uniproduct reversible reaction following first-order kinetics and that takes place in a system behaving as an ideal solution. Kinetic enhancement was ascertained via theoretical evolution of the molar fraction of product in both streams coming from either the separator (in series with the reactor) or from the integrated unit, whereas thermodynamic enhancement was ascertained via theoretical evolution of the overall Gibbs’ free energy in either configuration. The time required to achieve a predefined degree of conversion and separation is always lower for simultaneous than for sequential reaction and separation. The molar fraction of product in the product-rich stream is always higher for the integrated unit except for high values of parameter φ (defined as the ratio of the time scale associated with chemical reaction to the time scale associated with mass transfer of reactant) and of the chemical equilibrium constant. Comparison of the thermodynamic behaviour of both systems also leads to the conclusion that high values of φ yield worse results when the integrated unit is used instead of the sequential reactor/separator system because reactant is removed from the reacting system at a rate that is higher than the reaction rate itself

Lipase-catalyzed synthesis of butyl butyrate by alcoholysis in an integrated liquid-vapor system

This paper reports experimental work pertaining to alcoholysis between butanol and ethyl butanoate, catalyzed by an immobilized lipase in a liquid-vapor system where chemical reaction and physical separation are simultaneously carried out. The processing setup was tested for various compositions of the starting feedstock and operated under reduced pressure. Samples were withdrawn both from the boiler and the condenser, and they were chromatographically assayed for butyl butyrate. The integrated configuration tested is quite effective toward improvement of the final yield of the desired product