1,279,484 research outputs found

    Visions for organic bioenergy production in Denmark

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    There is a large potential for organic bioenergy production, which can be combined with the present food production and the provision of multiple other goods and services required by society; i.e. a cleaner aquatic environment, or nature values in cultural landscapes. This paper presents six scenarios for bioenergy production from organic farming in Denmark, with a total energy production potential of around 6.7 PJ/yr. This potential is compared to the present energy use of around 2.5 PJ/yr, and the po-tentials for energy savings equalling 0.1-0.5 PJ/yr

    Sideband pump-probe technique resolves nonlinear modulation response of PbS/CdS quantum dots on a silicon nitride waveguide

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    For possible applications of colloidal nanocrystals in optoelectronics and nanophotonics, it is of high interest to study their response at low excitation intensity with high repetition rates, as switching energies in the pJ/bit to sub-pJ/bit range are targeted. We develop a sensitive pump-probe method to study the carrier dynamics in colloidal PbS/CdS quantum dots deposited on a silicon nitride waveguide after excitation by laser pulses with an average energy of few pJ/pulse. We combine an amplitude modulation of the pump pulse with phase-sensitive heterodyne detection. This approach permits to use co-linearly propagating co-polarized pulses. The method allows resolving transmission changes of the order of 10(-5) and phase changes of arcseconds. We find a modulation on a sub-nanosecond time scale caused by Auger processes and biexciton decay in the quantum dots. With ground state lifetimes exceeding 1 mu s, these processes become important for possible realizations of opto-electronic switching and modulation based on colloidal quantum dots emitting in the telecommunication wavelength regime

    4-channel 200 Gb/s WDM O-band silicon photonic transceiver sub-assembly

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    We demonstrate a 200G capable WDM O-band optical transceiver comprising a 4-element array of Silicon Photonics ring modulators (RM) and Ge photodiodes (PD) co-packaged with a SiGe BiCMOS integrated driver and a SiGe transimpedance amplifier (TIA) chip. A 4 x 50 Gb/s data modulation experiment revealed an average extinction ratio (ER) of 3.17 dB, with the transmitter exhibiting a total energy efficiency of 2 pJ/bit. Data reception has been experimentally validated at 50 Gb/s per lane, achieving an interpolated 10E-12 bit error rate (BER) for an input optical modulation amplitude (OMA) of -9.5 dBm and a power efficiency of 2.2 pJ/bit, yielding a total power efficiency of 4.2 pJ/bit for the transceiver, including heater tuning requirements. This electro-optic subassembly provides the highest aggregate data-rate among O-band RM-based silicon photonic transceiver implementations, highlighting its potential for next generation WDM Ethernet transceivers. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

    Bell Inequalities in Four Dimensional Phase Space and the Three Marginal Theorem

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    We address the classical and quantum marginal problems, namely the question of simultaneous realizability through a common probability density in phase space of a given set of compatible probability distributions. We consider only distributions authorized by quantum mechanics, i.e. those corresponding to complete commuting sets of observables. For four-dimensional phase space with position variables qi and momentum variables pj, we establish the two following points: i) given four compatible probabilities for (q1,q2), (q1,p2), (p1,q2) and (p1,p2), there does not always exist a positive phase space density rho({qi},{pj}) reproducing them as marginals; this settles a long standing conjecture; it is achieved by first deriving Bell-like inequalities in phase space which have their own theoretical and experimental interest. ii) given instead at most three compatible probabilities, there always exist an associated phase space density rho({qi},{pj}); the solution is not unique and its general form is worked out. These two points constitute our ``three marginal theorem''.Comment: 21 pages, Latex, no figure

    Professional Judgement Study Report Summary

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    This report summarizes the Professional Judgment (PJ) Study conducted by Augenblick, Palaich, and Associates (APA) for the Lincy Institute at University of Nevada, Las Vegas (UNLV). The Institute commissioned the PJ study as part of a review of Nevada’s school funding system. The review called for studies like this one to update the 2006 Nevada education funding adequacy study. This current study is an adequacy study examining the base cost and adjustments needed for students in Nevada to meet state standards. In the early 1990s, states began to implement Standards-­‐Based Reform in education. By implementing Standards-­‐Based Reform, states set standards for students, teachers, schools, and districts. States then use tests and other measures to evaluate success in reaching these standards. Accountability systems have been created by states to hold schools and districts accountable for performance. Adequacy studies examine the resources needed for students, schools, and districts to meet state expectations. A number of approaches have been developed to examine these resource needs. In this particular study, APA utilizes the PJ approach, described below, to study adequacy, meaning the resources needed to ensure all students can be successful. The Lincy Institute also commissioned another team of researchers to conduct a study using the cost function approach. Those findings are reported separately
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