Design and Optimization of Electrically Injected InP-Based Microdisk Lasers Integrated on and Coupled to a SOI Waveguide Circuit

We have performed a numerical study involving the design and optimization of InP-based microdisk lasers integrated on and coupled to a nanophotonic silicon-on-insulator (SOI) waveguide circuit, fabricated through bonding technology. The theoretical model was tested by fitting it to the lasing characteristics obtained for fabricated devices, which we presented previously. A good fit was obtained using parameter values that are consistent with numerical simulation. To obtain optimized laser performance, the composition of the InP-based epitaxial layer structure was optimized to minimize internal optical loss for a structure compatible with efficient current injection. Specific attention was paid to a tunnel-junction based approach. Bending loss was quantified to estimate the minimum microdisk diameter. The coupling between the InP microdisk and Si waveguide was calculated as function of the bonding layer thickness, waveguide offset and waveguide width. To study the lateral injection efficiency, an equivalent electrical network was solved and the voltage-current characteristic was calculated. Based on these results, the dominant device parameters were identified, including microdisk thickness and radius, coupling loss and tunnel-junction p-type doping. These parameters were optimized to obtain maximum wall-plug efficiency, for output powers in the range 1-100 W. The results of this optimization illustrate the potential for substantial improvement in laser performance.     

Analysis of the dynamics of a pendulum vibration absorber

The nonlinear dynamics of an autoparametric vibration absorber of pendulum type is considered. The conditions of existence of periodic motions in the case of monoharmonic excitation are considered. A comparison of the vibration quenching qualities of the autoparametric absorber and a “classical” (linear) dynamic vibration absorber is presented.     

Learners' questions and comprehension in a tutoring setting.

Three experiments, presented within the framework of Activity Theory, deal with the relationship between adult learners' questions and subsequent comprehension in a tutorial learning setting. Students were first given verbal instructions (acquisition) to a novel card game and then asked to play one hand with the teacher (implementation). In Experiment 1, there was no correlation between number of questions asked during acquisition and comprehension, but questions during implementation were negatively correlated with comprehension. In Experiment 2, learners whose questions were answered during acquisition scored higher than those whose questions were not answered. In Experiment 3, learners whose questions were answered during implementation showed greater gains in comprehension than those whose questions were answered during acquisition. Individual differences in question-asking during implementation but not acquisition were significantly related to comprehension. The results confirm the view that questions answered during knowledge implementation more effectively aid comprehension than those answered during acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The sixth Euratom framework programme 2003–2006: a driving force for the construction of the Nuclear European Research Area

At the Lisbon 2000 summit, a strategic goal was proposed for the European Union: “to become the most competitive knowledge-based economy with more and better employment and social cohesion by 2010”. Overall, in particular in the community of nuclear fission research, this EC initiative was well accepted by the main stakeholders. In Europe, the main stakeholders (i.e. suppliers and/or demanders) of nuclear research are actually: the research organisations (with mixed public/private funding), the manufacturing industry (or vendors), the utilities (or engineering companies), the regulatory bodies (or technical safety organisations) and the academia (or universities). In response to the Lisbon 2000 objectives, Commissioner P. BUSQUIN launched the concept of European Research Area (ERA) which sets also the frame for the FP-6.In this invited lecture, research and training in nuclear fission are looked at from a nuclear ERA perspective with emphasis on the three success factors of any European integration policy, namely: needs, vision and instruments, that ought to be strongly shared amongst the stakeholders in the EU-25.The following questions are addressed. What is driving the current EU trend towards more research, more education and more training in general? Regarding nuclear fission, in particular, who are the end-users of Euratom “research and training” and what are their expectations (needs) from EU programmes? Do all stakeholders share the same vision about European research and training in nuclear fission? What are the instruments proposed by the Commission to the end-users to conduct joint research programmes?The above questions are all linked to nuclear knowledge management. It is shown that, in Community research, production of knowledge remains the most important objective, be it to generate products or services. However, dissemination/transfer (e.g. education and training) and exploitation (e.g. innovation) of knowledge become equally important as production, if one wants all energy options to remain open for the future generations.The answers to these questions and the examples given are taken primarily from reactor safety research (i.e. the area covered by FISA-2003) but are thought to be easily extrapolable to the other areas of nuclear fission research (i.e. radwaste management, innovative reactor concepts and safeguards, radiation protection, medical applications).In conclusion, amongst the stakeholders there seems to be a wide consensus about needs and instruments but a real common vision about a EU nuclear research strategy is still lacking. As a result, it is felt that European research in nuclear fission is still too much fragmented across Europe. It has not yet reached the “critical mass” necessary to levy the governmental and industrial resources needed to face all challenges posed by an ageing nuclear power park and its renewal by the year 2015 (estimated end of lifetime).     

Organizing for Continuous Innovation: On the Sustainability of Ambidextrous Organizations

Organizing for innovation does not present itself as a straightforward exercise. The complexities entailed when implementing an innovation strategy can be related directly to the multitude of objectives it comprises. Recently, several scholars have advanced the notions of semi‐ or quasi‐structures and ambidextrous organizations to handle these multiple requirements. These organizational forms imply the simultaneous presence of different activities, exhibiting differences in technology and market maturation. As a consequence, financial returns will reflect this diversified resource allocation pattern. Moreover, as higher levels of complexity are being introduced; ambidextrous organizations will encounter additional, organizational, costs. Compared to organizations that focus on the most profitable part of the portfolio, ambidextrous organizations – ceteris paribus – tend to be inferior in terms of financial returns. Within this contribution we explore under which conditions ambidextrous organizations can outperform focused firms; considered a prerequisite for their sustainability. In order to do so, we develop an analytical framework depicting the differential value dynamics, focused and ambidextrous firms can enact. Our findings reveal the relevancy of adopting extended time frames as well as introducing interface management practices aimed at cross‐fertilization. Finally, the synergetic potential of (underlying) technologies comes to the forefront as necessary in order for ambidextrous organizations to become sustainable.     

Job-related stress, social support, and burnout among classroom teachers.

In this study we examined the effects of job-related stressful events and social support on burnout among teachers. We conducted a mail survey of a random sample of public school teachers in Iowa. Consistent with findings in previous research, teacher characteristics such as age, sex, and grade level taught were predictive of burnout. We also found that the number of stressful events experienced and social support were predictive of teacher burnout. Some evidence of the stress-moderating role of social support was also found. Teachers who reported that they had supportive supervisors and indicated that they received positive feedback concerning their skills and abilities from others were less vulnerable to burnout. We discuss the implications of these findings for programs aimed at preventing teacher burnout. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optoelectronic switch with low holding power

A double heterostructure NpnP optoelectronic switching device with low holding power has been fabricated. In the static regime a holding power of 20 nW for a device area of 200 mu m*100 mu m was obtained. This value represents a reduction of four orders of magnitude in holding power compared to previous reported PnpN or PnN structures with equivalent device area. A higher optical sensitivity and a lower optical switching intensity is consequently obtained with these devices.<>