Considerations on radar localization in multi-target environments

In a multitude of applications like e.g. in automotive radar systems a localization of multiple passive targets in the observed area is necessary. This contribution presents a robust approach based on trilateration to detect point scatterers in a two-dimensional plane using the reflection and transmission information of only two antennas. The proposed algorithm can identify and remove ambiguities in target detection which unavoidably occur in certain target constellations in such a two-antenna configuration

Transverse-momentum-dependent parton distributions at the edge of the lightcone

We present a completely gauge-invariant operator definition of transverse-momentum-dependent parton densities (TMD), supplied with longitudinal lightlike gauge links as well as transverse gauge links at lightcone infinity. Within this framework, we consider the consistent treatment of specific divergences, emerging in the "unsubtracted" TMD beyond the tree approximation, and construct the soft factors to cancel unphysical singularities. We confront this approach with factorization schemes, which make use of covariant gauges with off-the-lightcone gauge links, and discuss their mutual connection.Comment: 10 pages, 2 figures; needs ws-ijmpcs.cls (supplied). Invited talk presented at Workshop "QCD evolution of parton distributions: from collinear to non-collinear case", 8 - 9 Apr 2011, Thomas Jefferson National Accelerator Facility, Newport News (VA), US

Compact mode-matched excitation structures for radar distance measurements in overmoded circular waveguides

This contribution deals with guided radar level measurements of liquid materials in large metal tubes, socalled stilling wells, bypass or still pipes. In the RF domain these tubes function as overmoded circular waveguides and mode-matched excitation structures like waveguide tapers are needed to avoid higher order waveguide modes. Especially for high-precision radar measurements the multimode propagation effects need to be minimized to achieve submillimeter accuracy. Therefore, a still pipe simulator is introduced with the purpose to fundamentally analyze the modal effects. Furthermore, a generalized design criterion is derived for the spurious mode suppression of compact circular waveguide transitions under the constraint of specified accuracy levels. According to the obtained results, a promising waveguide taper concept will finally be presented. © Author(s) 2008

Nucleon Generalized Parton Distributions from Full Lattice QCD

We present a comprehensive study of the lowest moments of nucleon generalized parton distributions in N_f=2+1 lattice QCD using domain wall valence quarks and improved staggered sea quarks. Our investigation includes helicity dependent and independent generalized parton distributions for pion masses as low as 350 MeV and volumes as large as (3.5 fm)^3, for a lattice spacing of 0.124 fm. We use perturbative renormalization at one-loop level with an improvement based on the non-perturbative renormalization factor for the axial vector current, and only connected diagrams are included in the isosinglet channel.Comment: 40 pages, 49 figures; Revised chiral extrapolations in sections A-K, main conclusions unchange

Nucleon structure from mixed action calculations using 2+1 flavors of asqtad sea and domain wall valence fermions

We present high statistics results for the structure of the nucleon from a mixed-action calculation using 2+1 flavors of asqtad sea and domain wall valence fermions. We perform extrapolations of our data based on different chiral effective field theory schemes and compare our results with available information from phenomenology. We discuss vector and axial form factors of the nucleon, moments of generalized parton distributions, including moments of forward parton distributions, and implications for the decomposition of the nucleon spin.Comment: 68 pages, 47 figures. Main revision points: improved discussion of chiral fits and systematic uncertainties, several minor refinements. Accepted for publication in Phys.Rev.

Detectable contributions of colloids to soil P and C content in arid and hyperarid region of the Atacama (Chile)

Atacama Desert is mainly known as the driest place on Earth where life has been developed under arid to hyper arid conditions since Oligocene-Miocene. Therefore, soils of Atacama contain fingerprints of past and present life which might be used as an analog to study the evolution of life under equivalent arid conditions, like Mars. In this study, we quantify the colloidal phosphorus and carbon distribution in the first 10 cm of soil profile along an altitudinal transect. Samples were taken along a transect in the region of Quebrada Aroma spanning from the arid Percordillera of the Andes (2720 m a.s.l.) towards the hyper arid core of the desert (1340 m a.s.l.). Water dispersible colloids (WDC) were separated and measured using the field-flow-field fractionation (FFF) method and subsequently their Corg and P content were characterized and quantified by detectors (DLS, ICP-MS, UV, OCD, fluorescence). Data was compared to total C, P and (available) Olsen-P also measured in the samples. The Olsen-P (available-P) varied within the Aroma transect from ca. 2 to 8 mg P kg-1, but was not related to either altitude or depth in the upper soil (0-10 cm). Colloidal P contents ranged from <0.1 to 4 mg P kg-1 soil, with increasing trend from low to higher elevations. Thereby, suggesting an increasing proportion of the available P potential being present in the WDC fraction. The Colloidal Corg content of the Aroma transect did range from 65 to 90 (for sites 2020 to 1340m) and 110 mg Corg kg-1 soil WDC (2720 m). Colloidal Corg content as a function of the altitude showed a similar trend to the Corg content of the soils: the highest colloidal Corg content was found at 2720 m. The proportion of soil Corg within the colloidal fraction was up to 6% of the bulk soil organic matter (OM) content, as the OM content was intensively enriched in the colloidal fraction. Further quantification of phosphorus and carbon content in WDC in deeper part of soil is required to obtain a more comprehensive view of role of colloidal inputs and dynamics in the Atacama Desert

Amplitude noise and RF response analysis of 1 GHz mode-locked pulses from an InP-based laser chip at 1550 nm

In this work, we investigate a 1 GHz InP-based hybrid mode-locked laser chip and find an amplitude noise of 0.036 percent. An RF response simulation of its custom-designed mounting PCB is performed providing power transmission between 86 and 92 percent