Switch energy requirements for first- and second-orderperturbations in asymmetric quantum box optical switches

We have studied the limits to the switching energy of electrically controlled optical absorption switches. Investigating a case with intraband transitions in asymmetric quantum boxes, it is shown that linear Stark shift allows switch energies of the optical switches that are comparable to the thermal noise limit at 300 K at least up to 30 GHz, provided boxes with very narrow absorption linewidth can be fabricated. This is several orders of magnitude lower energy than required by quadratic Stark shift in a similar, symmetric structure     

A cluster analysis of energy-consuming activities in everyday life

ABSTRACT

Flexible consumption in the household sector concerns individuals’ daily choices and the routines that develop in their households. Targeting household-level energy consumption therefore requires an understanding of energy consumption in relation to individual household members’ activity patterns. Individual time-diaries reveal when, for how long and where energy-related activities occur, permitting discussions of the temporal flexibility of these activities. Using multiple time-diaries (n?=?6477) from a population reveals differences in activity patterns in larger groups and permits recorded activities to be clustered. Few explorative studies perform cluster analyses of energy-consuming activities in order to examine when and for how long these activities occur. When clustering is done, it is usually based on socio-economic factors, and not on the activities performed in sequence. This paper reports a time-geographically inspired cluster analysis based on when and for how long some activities requiring electricity are performed in the home by individuals in a population. The presented cluster analysis based on activities gives a new perspective to the discussion of flexible users and provides a basis for deeper analyses, for example, of whether activities are moveable in time for individuals, complementing cluster analysis based on other variables.     

Experimental determination of intermetallic phases, phase equilibria, and invariant reaction temperatures in the Fe-Zr system

The phase diagram of the binary Fe-Zr system was redetermined by differential thermal analysis (DTA), electron-probe microanalysis (EPMA), x-ray diffraction (XRD), and metallography in the whole range of compositions. The stable intermetallic phases of the binary system are the cubic and the hexagonal polymorphs of the Fe₂Zr Laves phase and the Zr-rich phases FeZr₂ and FeZr₃. While the cubic polymorph of the Laves phase is the stable structure at the stoichiometric Fe₂Zr composition, the hexagonal C36-type polymorph of the Laves phase is a high-temperature phase that is found at Zr concentrations as low as 26.6 at.%. The Zr-rich phases FeZr₂ and FeZr₃ have small homogeneity ranges of about 0.5 at.%. FeZr₂ is a high-temperature phase, stable between 780 and 951 °C. FeZr₃ decomposes peritectoidally at 851 °C. The frequently reported phase Fe₂₃Zr₆ (Fe₃Zr) is found not to be an equilibrium phase of the binary system.     

Observers for Takagi-Sugeno fuzzy systems

We focus on the analysis and design of two different sliding mode observers for dynamic Takagi-Sugeno (TS) fuzzy systems. A nonlinear system of this class is composed of multiple affine local linear models that are smoothly interpolated by weighting functions resulting from a fuzzy partitioning of the state space of a given nonlinear system subject to observation. The Takagi-Sugeno fuzzy system is then an accurate approximation of the original nonlinear system. Our approach to the analysis and design of observers for Takagi-Sugeno fuzzy systems is based on extending sliding mode observer schemes to the case of interpolated multiple local affine linear models. Thus, our main contribution is nonlinear observer analysis and design methods that can effectively deal with model/plant mismatches. Furthermore, we consider the difficult case when the weighting functions in the Takagi-Sugeno fuzzy system depend on the estimated state.     

Partial balance of nitrogen in a maize cropping system in humic nitisol of Central Kenya

The application of nitrogen in a soil under agricultural production is subject to several pathways including de-nitrification, leaching and recovery by an annual crop. This is as well greatly influenced by the management practices, nitrogen source and soil conditions. The main objective of this study was to investigate the loss of nitrogen (N) through nitrous oxide (N₂O) emissions and mineral N leaching and uptake by annual crop as influenced by the N source. The study was carried out at Kabete in Central Kenya. Measurements were taken during the second season after two seasons of repeated application of N as urea and Tithonia diversifolia (tithonia) leaves. Results obtained indicated that nitrous oxide (N₂O) emissions at 4 weeks after planting were as high as 12.3 μg N m ⁻² h⁻¹ for tithonia treatment and 2.9 μg N m⁻² h⁻¹ for urea treatment. Tithonia green biomass treatment was found to emit N₂O at relatively higher rate compared to urea treatment. This was only evident during the fourth week after treatment application.Soil mineral N content at the end of the season increased down the profile. This was evident in the three treatments (urea, tithonia and control) investigated in the study. Urea treatment exhibited significantly higher mineral N content down the soil profile (9% of the applied N) compared to tithonia (0.6% of the applied N). This was attributed to the washing down of the nitrate-N from the topsoil accumulating in the lower layers of the soil profile. However, there was no significant difference in N content down the soil profile between tithonia treatment and the control. It could be concluded that there was no nitrate leaching in the tithonia treatment. Nitrogen recovery by the maize crop was higher in the urea treatment (76% of the applied N) as compared to tithonia treatment (55.5% of the applied N). This was also true for the residual mineral N in the soil at the end of the season which was about 7.8% of the applied N in the urea treatment and 5.2% in the tithonia treatment.From this study, it was therefore evident that although there is relatively lower N recovery by maize supplied with tithonia green biomass compared to maize supplied with urea, more nitrogen is being lost (through leaching) from the soil–plant system in the urea applied plots than in tithonia applied plots. However, a greater percentage (37.8%) of the tithonia-applied N could not be accounted for and might have been entrapped in the soil organic matter unlike urea-applied N whose greater percentage (92%) could be accounted for.     

Phthalates and nonylphenols in urban runoff: Occurrence, distribution and area emission factors

The urban water system is believed to be an important sink for the nonpoint-source pollutants nonylphenols and phthalates. The presence of nonylphenols (NPs), nonylphenol ethoxylates (NPEOs), and eight phthalates was analyzed in urban stormwater and sediment from three catchment areas in Sweden. Emission loads for these substances were then calculated for a specific urban catchment area. In addition, substance distribution in road runoff passing through a sedimentation facility was modeled using a modified QWASI-model for chemical fate. High concentrations of DEHP, DIDP and DINP (≤ 48, 66 and 200 µg/g dw, respectively) as well as nonylphenol mono- and di-ethoxylate (6.6 and 20 µg/g dw, respectively) were found in the sediment. Aqueous concentrations of the pollutants varied considerably; branched NP was detected in concentrations up to 1.2 µg/L, whereas di(2-ethylhexyl) phthalate (DEHP), diisodecyl phthalate (DIDP), and diisononyl phthalate (DINP) were the most frequently detected phthalates in concentrations up to 5.0, 17 and 85 µg/L, respectively. The fate modeling demonstrated that predicted substance levels in water agreed well with measured levels, whereas the modeled sediment levels were underestimated. Calculation of catchment area emission factors from an urban highway environment revealed that as much as 2.1 kg of total phthalates and 200 g of NP and NPEOs may be emitted per hectare and year. The results indicate that all monitored phthalates, branched NPs and lower NPEOs are present in Swedish urban water systems. The long-chain phthalates DIDP and DINP are believed to occur at higher concentrations than other phthalates because of their higher environmental persistence and their increasing use in Sweden.     

Influence of habitat restoration on post‐emergence displacement of brown trout (Salmo trutta L.): A case study in a Northern Swedish stream

During the 19th and 20th centuries, Swedish streams were channelized to facilitate the commercial transport of timber on water. Stream‐dwelling fish were affected by the consequent reduction in habitat quality. To mitigate the effects on salmonids, which sustain important recreational fisheries, many streams have been restored through the replacement of boulders into the channel since the early 1980s. However, the effects of restoration on salmonids remain poorly known. This study assesses the effect of habitat restoration on the post‐emergence displacement of brown trout (Salmo trutta L.) fry. Hatchery‐raised fry were released in a third‐order stream canalized for timber floating in northern Sweden, and the effect of restoration on displacement was assessed. The short‐term (24 h) displacement of trout fry was reduced from 10.1 to 2.3% of fry released following restoration. Water velocity accounted for 89.4% of the variation in fry displacement across years and sites. Post‐summer recruitment (the proportion of introduced juvenile trout remaining in the study reaches 60 days after the emergence) increased approximately three fold after restoration. These findings suggest that habitat restoration benefit trout populations through substantial reductions of fry displacement and possible contributions to juvenile recruitment. Copyright © 2009 John Wiley & Sons, Ltd.     

Phases and evolution of microstructures in Ti–60 at.% Al

The formation and stability of Al-rich Ti–Al phases is reviewed and the kinetics of the phase transformations and evolution of lamellar TiAl + r-TiAl₂ microstructures is discussed. For this a couple of Ti–60 at.% Al alloys were processed by different techniques to generate different initial microstructures. The kinetics were studied by annealing the differently processed alloys for 1, 10, 100 and 1000 h at temperatures between 800 and 1000 °C and then analysing the quenched microstructures by optical, scanning electron, and transmission electron microscopy. In addition, in situ heating and cooling experiments using differential thermal analysis and transmission electron microscopy were performed to verify the results obtained for the quenched samples. The results conclusively show why the metastable phases h-TiAl₂ and Ti₃Al₅ form. The stability and transformation of the metastable phases have been determined in dependence on time and temperature and the kinetics of the two different mechanisms by which the stable phase r-TiAl₂ forms have been established. The effects of differing initial microstructures on the evolution of the microstructure with time and temperature are discussed.     

A variational approach to vesicle membrane reconstruction from fluorescence imaging

Biological applications like vesicle membrane analysis involve the precise segmentation of 3D structures in noisy volumetric data, obtained by techniques like magnetic resonance imaging (MRI) or laser scanning microscopy (LSM). Dealing with such data is a challenging task and requires robust and accurate segmentation methods. In this article, we propose a novel energy model for 3D segmentation fusing various cues like regional intensity subdivision, edge alignment and orientation information. The uniqueness of the approach consists in the definition of a new anisotropic regularizer, which accounts for the unbalanced slicing of the measured volume data, and the generalization of an efficient numerical scheme for solving the arising minimization problem, based on linearization and fixed-point iteration. We show how the proposed energy model can be optimized globally by making use of recent continuous convex relaxation techniques. The accuracy and robustness of the presented approach are demonstrated by evaluating it on multiple real data sets and comparing it to alternative segmentation methods based on level sets. Although the proposed model is designed with focus on the particular application at hand, it is general enough to be applied to a variety of different segmentation tasks.