Monodisperse spherical core-shell structured SiO2-CaTiO3 : Pr3+ phosphors for field emission displays

Nanocrystalline CaTiO3:Pr3+ phosphor layers were coated on nonaggregated, monodisperse, and spherical SiO2 particles by the sol-gel method, resulting in the formation of core-shell structured SiO2-CaTiO3:Pr3+ particles. X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, cathodoluminescence spectra, as well as lifetimes were utilized to characterize the core-shell structured SiO2-CaTiO3:Pr3+ phosphor particles. The obtained core-shell structured phosphors consist of well dispersed submicron spherical particles with a narrow size distribution. The thickness of the CaTiO3:Pr3+ shell could be easily controlled by changing the number of deposition cycles (about 70 nm for four deposition cycles). The core-shell SiO2-CaTiO3:Pr3+ particles show a strong red emission corresponding to D-1(2)-H-3(4) (612 nm) of Pr3+ under the excitation of ultraviolet (326 nm) and low voltage electron beams (1-5 kV). These particles may be used in field emission displays.

Dependence of crystal field splitting of 5d levels on hosts in the halide crystals

The crystal field splitting of 5d level of EU2+ and Ce3+ in halide crystals has been studied. Our results indicate that the 10Dq splitting can be directly related to the homopolar part of average energy gap, the coordination number of central (doped) ion, the charge of neighboring anions and bond ionicity between central ion to nearest anions. A relation between the 10Dq splitting and the above mentioned factors is presented. Our calculated results are in reasonable agreement with diverse experiments.

Conformational analysis of 2,2 '-bithiophene under interaction of external electric field defined by point charges

Conformational analysis of 2,2'-bithiophene (BT) under the influence of an electric field (EF) constructed by point charges has been performed by using semi-empirical Austin Model 1 (AM1) and Parametric model number 3 (PM3) calculations. When the EF perpendicular to the molecular conjugation chain is applied, both AM1 and PM3 calculations show an energy increase of the anti-conformation. AM1 predicts that the global minimum shifts to syn-conformation when the EF strength is larger than a critical value. and PM predicts that the local minimum in anti-conformation vanishes. This kind of EF effect has been ascribed to the EF and dipole moment interaction.

EFFECT OF CRYSTAL-FIELD AND BONDING PROPERTIES ON SPECTRAL STRUCTURE OF EU-2+

Five Eu~(2+)-doped simple fluorides and six Eu~(2+)-doped complex fluorides are synthesized by solid reactions. The strength of the crystal-field at the sites of Eu~(2+) ion, and the degroe of covalenco of Eu—F bond in these hosts are discussed. The f-f transition emission of Eu~(2+) ion is observed in the hosts which has lower coordination number and strong crystal-field. The f-f transition emission of Eu~(2+) ion is observed for the first time in the simple fluoride AlF_3.

Reproduction and behavior of plateau pikas (Ochotona curzoniae Hodgson) under predation risk: A field experiment

The mixture of the feces and urine of the red fox (Vulpes vulpes Linnaeus) was used to increase the perception of predation risk of plateau pikas (Ochotona curzoniae Hodgson) in the field. The influence of the predation risk on the reproduction and behavior of plateau pikas was examined through comparing reproductive characteristics and five different kinds of behavior between treatment and control plots. The results showed that 1) the body weight of the pikas was not significantly different between treatment and control plots. 2) The reproductive period of the pikas extended from March to later August in both treatment and control plots. The pregnant ratio, developed testes ratio, reproductive success and sex ratio of the pikas were not significantly different between the treatment and control plots. 3) The pikas increased their observing and calling frequencies and decreased their moving and feeding frequencies when exposed to red fox's feces and urine. 4) The increased red fox's feces and urine had no influence on the behavior of the pikas when the number of their natural enemies increased; the pikas obviously increased the observing frequencies and sharply decreased the calling frequency so as to decrease the direct predation risk. 5) There were no significantly behavioral differences between males and females as well as between adults and young. 6) The results reject the hypothesis 1 that the red fox's feces and urine as indirect predation risk suppresses the reproduction of the pikas and support the hypothesis 2 that the pikas can make decision by changing behavior to avoid the predation risk they encountered whenever.

Preferential Field Coverage Through Detour-Based Mobility Coordination

Controlling the mobility pattern of mobile nodes (e.g., robots) to monitor a given field is a well-studied problem in sensor networks. In this setup, absolute control over the nodes’ mobility is assumed. Apart from the physical ones, no other constraints are imposed on planning mobility of these nodes. In this paper, we address a more general version of the problem. Specifically, we consider a setting in which mobility of each node is externally constrained by a schedule consisting of a list of locations that the node must visit at particular times. Typically, such schedules exhibit some level of slack, which could be leveraged to achieve a specific coverage distribution of a field. Such a distribution defines the relative importance of different field locations. We define the Constrained Mobility Coordination problem for Preferential Coverage (CMC-PC) as follows: given a field with a desired monitoring distribution, and a number of nodes n, each with its own schedule, we need to coordinate the mobility of the nodes in order to achieve the following two goals: 1) satisfy the schedules of all nodes, and 2) attain the required coverage of the given field. We show that the CMC-PC problem is NP-complete (by reduction to the Hamiltonian Cycle problem). Then we propose TFM, a distributed heuristic to achieve field coverage that is as close as possible to the required coverage distribution. We verify the premise of TFM using extensive simulations, as well as taxi logs from a major metropolitan area. We compare TFM to the random mobility strategy—the latter provides a lower bound on performance. Our results show that TFM is very successful in matching the required field coverage distribution, and that it provides, at least, two-fold query success ratio for queries that follow the target coverage distribution of the field.

Estimating Sensor Motion from Wide-Field Optical Flow on a Log-Dipolar Sensor

Log-polar image architectures, motivated by the structure of the human visual field, have long been investigated in computer vision for use in estimating motion parameters from an optical flow vector field. Practical problems with this approach have been: (i) dependence on assumed alignment of the visual and motion axes; (ii) sensitivity to occlusion form moving and stationary objects in the central visual field, where much of the numerical sensitivity is concentrated; and (iii) inaccuracy of the log-polar architecture (which is an approximation to the central 20°) for wide-field biological vision. In the present paper, we show that an algorithm based on generalization of the log-polar architecture; termed the log-dipolar sensor, provides a large improvement in performance relative to the usual log-polar sampling. Specifically, our algorithm: (i) is tolerant of large misalignmnet of the optical and motion axes; (ii) is insensitive to significant occlusion by objects of unknown motion; and (iii) represents a more correct analogy to the wide-field structure of human vision. Using the Helmholtz-Hodge decomposition to estimate the optical flow vector field on a log-dipolar sensor, we demonstrate these advantages, using synthetic optical flow maps as well as natural image sequences.

A Recurrent Cooperative/Competitive Field for Segmentation of Magnetic Resonance Brain Imagery

The Grey-White Decision Network is introduced as an application of an on-center, off-surround recurrent cooperative/competitive network for segmentation of magnetic resonance imaging (MRI) brain images. The three layer dynamical system relaxes into a solution where each pixel is labeled as either grey matter, white matter, or "other" matter by considering raw input intensity, edge information, and neighbor interactions. This network is presented as an example of applying a recurrent cooperative/competitive field (RCCF) to a problem with multiple conflicting constraints. Simulations of the network and its phase plane analysis are presented.

Molecular composition of biogenic secondary organic aerosols using ultrahigh resolution mass spectrometry: comparing laboratory and field studies

Numerous laboratory experiments have been performed in an attempt to mimic atmospheric secondary organic aerosol (SOA) formation. However, it is still unclear how close the aerosol particles generated in laboratory experiments resemble atmospheric SOA with respect to their detailed chemical composition. In this study, we generated SOA in a simulation chamber from the ozonolysis of α-pinene and a biogenic volatile organic compound (BVOC) mixture containing α- and β-pinene, Δ3-carene, and isoprene. The detailed molecular composition of laboratory-generated SOA was compared with that of background ambient aerosol collected at a boreal forest site (Hyytiälä, Finland) and an urban location (Cork, Ireland) using direct infusion nanoelectrospray ultrahigh resolution mass spectrometry. Kendrick Mass Defect and Van Krevelen approaches were used to identify and compare compound classes and distributions of the detected species. The laboratory-generated SOA contained a distinguishable group of dimers that was not observed in the ambient samples. The presence of dimers was found to be less pronounced in the SOA from the VOC mixtures when compared to the one component precursor system. The elemental composition of the compounds identified in the monomeric region from the ozonolysis of both α-pinene and VOC mixtures represented the ambient organic composition of particles collected at the boreal forest site reasonably well, with about 70% of common molecular formulae. In contrast, large differences were found between the laboratory-generated BVOC samples and the ambient urban sample. To our knowledge this is the first direct comparison of molecular composition of laboratory-generated SOA from BVOC mixtures and ambient samples.

Number of degrees of freedom in inverse diffraction

The problem of inverse diffraction from plane to plane is considered in the case where a finite aperture exists in the boundary plane. Singular values and singular functions for the problem are introduced, and the number of degrees of freedom is defined in terms of the distribution of the singular values. Numerical computations are presented for the one-dimensional problem, and it is shown that the effect of evanescent waves disappears at a distance of approximately one wavelength from the boundary plane, even when the dimension of the slit is comparable with the wavelength of the diffracted field. © 1983 Taylor & Francis Group, LLC.

Difficulties and errors in number reasoning development

The detailed study of difficulties and errors in young learner comprehension is a relevant and productive research field in Mathematics Education. Studies in the field are numerous although somewhat too varied. The present paper is suggesting methodological perspectives and principles applying to the field of research; we also show an example with school work. The use of figurate numbers as a representation system gives richer conceptual values, boosts visual reasoning and facilitates learner understanding.

Buoyancy driven flow and its stability in a horizontal rectangular channel with an arbitrary oriented transversal magnetic field

An MHD flow is considered which is relevant to horizontal Bridgman technique for crystal growth from a melt. In the unidirectional parallel flow approximation an analytical solution is found accounting for the finite rectangular cross section of the channel in the case of a vertical magnetic field. Numerical pseudo-spectral solutions are used in the cases of arbitrary magnetic field and gravity vector orientations. The vertical magnetic field (parallel to the gravity) is found to be he most effective to damp the flow, however, complicated flow profiles with "overvelocities" in the comers are typical in the case of a finite cross-section channel. The temperature distribution is shown to be dependent on the flow profile. The linear stability of the flow is investigated by use of the Chebyshev pseudospectral method. For the case of an infinite width channel the transversal rolls instability is investigated, and for the finite cross-section channel the longitudinal rolls instability is considered. The critical Gr number values are computed in the dependence of the Ha number and the wave number or the aspect ratio in the case of finite section.

Simulation of quantum random walks using the interference of a classical field

We suggest a theoretical scheme for the simulation of quantum random walks on a line using beam splitters, phase shifters, and photodetectors. Our model enables us to simulate a quantum random walk using of the wave nature of classical light fields. Furthermore, the proposed setup allows the analysis of the effects of decoherence. The transition from a pure mean-photon-number distribution to a classical one is studied varying the decoherence parameters.

Civil society as a contested field of meanings

Purpose – During recent years, the concept of civil society, particularly global civil society, has come to the fore in both academia and policy circles. A key component of recent theoretical and policy research is the attempt to do international comparative research on the meaning of civil society. The purpose of this paper is to argue that the language and the terminology used to describe the agents of civil society are reflective of cultural and historical contexts of societies, have distinct meanings and cannot be used interchangeably.

Design/methodology/approach – In different national contexts, the key agents of civil society are referred to differently; nonprofit sector, voluntary and community sector, third sector and social economy. In comparative studies, scholars often list these concepts to indicate that they recognise that the agents of civil society are referred to differently in different societies. The article offers a socio-historical analysis of each concept. It is concluded that teasing out the differences, as well as the similarities, between the nonprofit sector, voluntary and community sector, third sector and social economy, is crucial to robust comparative research on civil society.

Findings – This paper exposes a number of limitations of each of the terminologies used to describe civil society. They all present a much more limiting notion of civil society than that proposed by the founding fathers. None seem to capture the range of civil associations in any society. Yet, assumptions are made that the terminologies used have similar meanings rather than attempting to clarify and define exactly what is being written or described. This is exacerbated by the interchangeable usage of nonprofit/third sector/community and voluntary sector/social economy. In order to progress beyond culturally specific understandings of civil society, it is necessary to examine the terminology used and how it emanates from a specific cultural and political context. Having a clear understanding of the language used and what it signifies is crucial to robust cross-national comparative research.

Originality/value – This paper examines context specific understandings of civil society and the terminology used to define it; a question not previously addressed. It is hoped that this article will generate much needed further debate on cross-national meanings of civil society.

Integrating field sports, hare population management and conservation

Conflicts between field sports, animal welfare and species conservation are frequently contentious. In Ireland, the Irish Coursing Club (ICC) competitively tests the speed and agility of two greyhounds by using a live hare as a lure. Each coursing club is associated with a number of discrete localities, known as preserves, which are managed favourably for hares including predator control, prohibition of other forms of hunting such as shooting and poaching and the maintenance and enhancement of suitable hare habitat. We indirectly tested the efficacy of such management by comparing hare abundance within preserves to that in the wider countryside. In real terms, mean hare density was 18 times higher, and after controlling for variance in habitat remained 3 times higher, within ICC preserves than the wider countryside. Whilst we cannot rule out the role of habitat, our results suggest that hare numbers are maintained at high levels in ICC preserves either because clubs select areas of high hare density and subsequently have a negligible effect on numbers or that active population management positively increases hare abundance. The Irish hare Lepus timidus hibernicus Bell, 1837 is one of the highest priority species for conservation action in Ireland and without concessions for its role in conservation, any change in the legal status Of hare coursing under animal welfare grounds, may necessitate an increase in Government subsidies for conservation on private land together with a strengthened capacity for legislation enforcement.