661 research outputs found
Dynamically reconfigurable optical access network
This dissertation presents the research results on a fiber-optic high-bitrate access network which enables dynamic bandwidth allocation as a response to varying subscribers' demands and bandwidth needs of emerging services. The motivation of the research is given in Chapter 1 "Introduction" together with a brief comparative discussion on currently available and future access networks. The idea of wavelength reconfigurability in the last-mile networks is described as a solution for more efficient bandwidth utilization and a subject of the Broadband Photonics project. Chapter 2 "Wavelength-flexible WDM/TDM access network - architecture" provides a comprehensive description of the proposed solution with each network element being analyzed in terms of its functionalities. This includes a colorless optical network unit and a reconfigurable optical add/drop multiplexer. An estimation of power budget is followed by the choice of wavelength set and network control and management layer overview. In Chapter 3 "Reflective transceiver module for ONU" after discussing different communication schemes and modulation formats three approaches to a colorless high-bitrate transmitter are analyzed in detail. This includes experiment and simulation results on a reflective semiconductor optical amplifier, reflective electro-absorption modulator and a Michelson-interferometer modulator. The Chapter is concluded with a comparative discussion. Chapter 4 "Reconfigurable optical add/drop multiplexer" discusses another key element in the proposed network architecture which is an integrated structure of micro-ring resonators providing wavelength reconfigurability. The measured characteristics assess the applicability of the device able to support unicast and multicast transmission. A range of possible sources of signal degradation in the access links are analyzed in Chapter 5 "Transmission and network impairments in the access network". An estimation of potential power penalties resulting from such impairments in the proposed system follow afterwards. Special attention is paid to optical in-band crosstalk penalties and improvement methods in Chapter 6 "Interferometric crosstalk in the access network with an RSOA". This subject is treated extensively with the support of mathematical considerations and experimental results. Proof-of-concept experiments of the proposed network architecture are presented in Chapter 7 "Reconfigurable WDM/TDM access network - experiments". The results of bidirectional transmission of high-bitrate WDM signals in different wavelength allocation schemes are discussed in detail. From there, by means of simulations the behavior of a full-scale network is assessed. In Chapter 8 "Migration towards WDM/TDM access network" the migration scenario from currently deployed fiber-optic access networks towards the novel solution is proposed. Afterwards, a short dispute on the economics of last-mile fiber technologies is included. Finally, the work is concluded and potential future research ideas based on this thesis are given in Chapter 9 "Conclusions and further work"
Dynamically reconfigurable optical access network
This dissertation presents the research results on a fiber-optic high-bitrate access network which enables dynamic bandwidth allocation as a response to varying subscribers' demands and bandwidth needs of emerging services. The motivation of the research is given in Chapter 1 "Introduction" together with a brief comparative discussion on currently available and future access networks. The idea of wavelength reconfigurability in the last-mile networks is described as a solution for more efficient bandwidth utilization and a subject of the Broadband Photonics project. Chapter 2 "Wavelength-flexible WDM/TDM access network - architecture" provides a comprehensive description of the proposed solution with each network element being analyzed in terms of its functionalities. This includes a colorless optical network unit and a reconfigurable optical add/drop multiplexer. An estimation of power budget is followed by the choice of wavelength set and network control and management layer overview. In Chapter 3 "Reflective transceiver module for ONU" after discussing different communication schemes and modulation formats three approaches to a colorless high-bitrate transmitter are analyzed in detail. This includes experiment and simulation results on a reflective semiconductor optical amplifier, reflective electro-absorption modulator and a Michelson-interferometer modulator. The Chapter is concluded with a comparative discussion. Chapter 4 "Reconfigurable optical add/drop multiplexer" discusses another key element in the proposed network architecture which is an integrated structure of micro-ring resonators providing wavelength reconfigurability. The measured characteristics assess the applicability of the device able to support unicast and multicast transmission. A range of possible sources of signal degradation in the access links are analyzed in Chapter 5 "Transmission and network impairments in the access network". An estimation of potential power penalties resulting from such impairments in the proposed system follow afterwards. Special attention is paid to optical in-band crosstalk penalties and improvement methods in Chapter 6 "Interferometric crosstalk in the access network with an RSOA". This subject is treated extensively with the support of mathematical considerations and experimental results. Proof-of-concept experiments of the proposed network architecture are presented in Chapter 7 "Reconfigurable WDM/TDM access network - experiments". The results of bidirectional transmission of high-bitrate WDM signals in different wavelength allocation schemes are discussed in detail. From there, by means of simulations the behavior of a full-scale network is assessed. In Chapter 8 "Migration towards WDM/TDM access network" the migration scenario from currently deployed fiber-optic access networks towards the novel solution is proposed. Afterwards, a short dispute on the economics of last-mile fiber technologies is included. Finally, the work is concluded and potential future research ideas based on this thesis are given in Chapter 9 "Conclusions and further work"
A scalable quantum computer with an ultranarrow optical transition of ultracold neutral atoms in an optical lattice
We propose a new quantum-computing scheme using ultracold neutral ytterbium
atoms in an optical lattice. The nuclear Zeeman sublevels define a qubit. This
choice avoids the natural phase evolution due to the magnetic dipole
interaction between qubits. The Zeeman sublevels with large magnetic moments in
the long-lived metastable state are also exploited to address individual atoms
and to construct a controlled-multiqubit gate. Estimated parameters required
for this scheme show that this proposal is scalable and experimentally
feasible.Comment: 6 pages, 6 figure
Spatio-temporal mixed pixel analysis of savanna ecosystems : a review
Reliable estimates of savanna vegetation constituents (i.e., woody and herbaceous vegetation) are essential as they are both responders and drivers of global change. The savanna is a highly
heterogenous biome with high variability in land cover types while also being very dynamic at both
temporal and spatial scales. To understand the spatial-temporal dynamics of savannas, using Earth
Observation (EO) data for mixed-pixel analysis is crucial. Mixed pixel analysis provides detailed
land cover data at a sub-pixel level which are essential for conservation purposes, understanding
food supply for herbivores, quantifying environmental change, such as bush encroachment, and fuel
availability essential for understanding fire dynamics, and for accurate estimation of savanna biomass.
This review paper consulted 197 studies employing mixed-pixel analysis in savanna ecosystems. The
review indicates that studies have so far attempted to resolve the savanna mixed-pixel issues by
using mainly coarse resolution data, such as Terra-Aqua MODIS and AVHRR and medium resolution
Landsat, to provide fractional cover data. Hence, there is a lack of spatio-temporal mixed-pixel
analysis for savannas at high spatial resolutions. Methods used for mixed-pixel analysis include
parametric and non-parametric methods which range from pixel-unmixing models, such as linear
spectral mixture analysis (SMA), time series decomposition, empirical methods to link the green
vegetation parameters with Vegetation Indices (VIs), and machine learning methods, such as regression trees (RT) and random forests (RF). Most studies were undertaken at local and regional scale,
highlighting a research gap for savanna mixed pixel studies at national, continental, and global level.
Parametric methods for modeling spatio-temporal mixed pixel analysis were preferred for coarse
to medium resolution remote sensing data, while non-parametric methods were preferred for very
high to high spatial resolution data. The review indicates a gap for long time series spatio-temporal
mixed-pixel analysis of savannas using high resolution data at various scales. There is potential to
harmonize the available low resolution EO data with new high-resolution sensors to provide long
time series of the savanna mixed pixel, which, according to this review, is missing.The Deutscher Akademischer Austauschdienst and the Federal Ministry of Education and Research (BMBF) within the framework of the Strategy âResearch for Sustainabilityâ (FONA).http://www.mdpi.com/journal/remotesensingpm2022Geography, Geoinformatics and Meteorolog
ĐŃĐŸĐ±Đ”ĐœĐœĐŸŃŃĐž Đž Đ·Đ°ĐșĐŸĐœĐŸĐŒĐ”ŃĐœĐŸŃŃĐž ĐžĐ·ĐŒĐ”ĐœĐ”ĐœĐžŃ ĐČĐŸŃŃŃĐ°ĐœĐŸĐČĐ»Đ”ĐœĐŸŃŃĐž ŃглДĐč баŃĐșĐžŃŃĐșĐŸĐłĐŸ ŃŃŃŃĐ° ĐĐ°ĐżĐ°ĐŽĐœĐŸĐłĐŸ ĐĐŸĐœĐ±Đ°ŃŃĐ°
Đ ŃŃĐ°ŃŃĐ” ĐżŃĐžĐČĐ”ĐŽĐ”ĐœĐ° ĐŽĐ”ŃĐ°Đ»ŃĐœĐ°Ń ĐżĐ”ŃŃĐŸĐłŃĐ°ŃĐžŃĐ”ŃĐșĐ°Ń Ń
Đ°ŃĐ°ĐșŃĐ”ŃĐžŃŃĐžĐșĐ° ŃглДĐč баŃĐșĐžŃŃĐșĐŸĐłĐŸ ŃŃŃŃĐ° ĐĐ°ĐżĐ°ĐŽĐœĐŸĐłĐŸ ĐĐŸĐœĐ±Đ°ŃŃĐ°. ĐŃĐŸĐČĐ”ĐŽĐ”ĐœĐ° ĐșлаŃŃĐžŃĐžĐșĐ°ŃĐžŃ ĐżĐŸ ĐČĐŸŃŃŃĐ°ĐœĐŸĐČĐ»Đ”ĐœĐŸŃŃĐž ĐČ ŃĐŸĐŸŃĐČĐ”ŃŃŃĐČОО Ń ĐżĐ”ŃŃĐŸĐłŃĐ°ŃĐžŃĐ”ŃĐșĐžĐŒĐž ŃĐžĐżĐ°ĐŒĐž. ĐŁŃŃĐ°ĐœĐŸĐČĐ»Đ”ĐœŃ ŃŃŃĐ°ŃОгŃĐ°ŃĐžŃĐ”ŃĐșОД Đž ĐżĐ»ĐŸŃĐ°ĐŽĐœŃĐ” Đ·Đ°ĐșĐŸĐœĐŸĐŒĐ”ŃĐœĐŸŃŃĐž ĐžĐ·ĐŒĐ”ĐœĐ”ĐœĐžŃ ŃŃĐ”ĐżĐ”ĐœĐž ĐČĐŸŃŃŃĐ°ĐœĐŸĐČĐ»Đ”ĐœĐŸŃŃĐž.ĐŁ ŃŃĐ°ŃŃŃ ĐœĐ°ĐČĐ”ĐŽĐ”ĐœĐ° ĐŽĐ”ŃĐ°Đ»ŃĐœĐ° пДŃŃĐŸĐłŃĐ°ŃŃŃĐœĐ° Ń
Đ°ŃĐ°ĐșŃĐ”ŃĐžŃŃĐžĐșĐ° ĐČŃĐłŃĐ»Đ»Ń Đ±Đ°ŃĐșĐžŃŃŃĐșĐŸĐłĐŸ ŃŃŃŃŃ ĐĐ°Ń
ŃĐŽĐœĐŸĐłĐŸ ĐĐŸĐœĐ±Đ°ŃŃ. ĐŃĐŸĐČĐ”ĐŽĐ”ĐœĐ° ĐșлаŃĐžŃŃĐșĐ°ŃŃŃ ĐČŃĐŽĐœĐŸĐČĐ»Đ”ĐœĐŸŃŃŃ, Đ·ĐłŃĐŽĐœĐŸ Đ· пДŃŃĐŸĐłŃĐ°ŃŃŃĐœĐžĐŒĐž ŃĐžĐżĐ°ĐŒĐž. ĐŃŃĐ°ĐœĐŸĐČĐ»Đ”ĐœŃ ŃŃŃĐ°ŃОгŃĐ°ŃŃŃĐœŃ ŃĐ° ĐżŃĐŸŃŃĐŸŃĐŸĐČŃ Đ·Đ°ĐșĐŸĐœĐŸĐŒŃŃĐœĐŸŃŃŃ Đ·ĐŒŃĐœĐž ŃŃŃĐżĐ”ĐœŃ ĐČŃĐŽĐœĐŸĐČĐ»Đ”ĐœĐŸŃŃŃ.The article gives detailed petrographic characteristics of coal of Bashkirian formation of Western Donbas. The classifications for recovery in accordance with petrographic types are given. The stratigraphic and areal patterns of change in the degree of recovery are established
Comprehensive clinical and molecular analysis of 12 families with type 1 recessive cutis laxa.
Autosomal recessive cutis laxa type I (ARCL type I) is characterized by generalized cutis laxa with pulmonary emphysema and/or vascular complications. Rarely, mutations can be identified in FBLN4 or FBLN5. Recently, LTBP4 mutations have been implicated in a similar phenotype. Studying FBLN4, FBLN5, and LTBP4 in 12 families with ARCL type I, we found bi-allelic FBLN5 mutations in two probands, whereas nine probands harbored biallelic mutations in LTBP4. FBLN5 and LTBP4 mutations cause a very similar phenotype associated with severe pulmonary emphysema, in the absence of vascular tortuosity or aneurysms. Gastrointestinal and genitourinary tract involvement seems to be more severe in patients with LTBP4 mutations. Functional studies showed that most premature termination mutations in LTBP4 result in severely reduced mRNA and protein levels. This correlated with increased transforming growth factor-beta (TGFÎČ) activity. However, one mutation, c.4127dupC, escaped nonsense-mediated decay. The corresponding mutant protein (p.Arg1377Alafs(*) 27) showed reduced colocalization with fibronectin, leading to an abnormal morphology of microfibrils in fibroblast cultures, while retaining normal TGFÎČ activity. We conclude that LTBP4 mutations cause disease through both loss of function and gain of function mechanisms
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
- âŠ