34,272 research outputs found
Design of blended rolled edges for compact range main reflectors
A procedure to design blended rolled edge terminations for arbitrary rim shape compact range main reflectors is presented. The reflector may be center-fed or offset-fed. The design procedure leads to a reflector which has a continuous and smooth surface. This procedure also ensures small diffracted fields from the junction between the paraboloid and the blended rolled edge while satisfying certain constraints regarding the maximum height of the reflector and minimum operating frequency of the system. The prescribed procedure is used to design several reflectors and the performance of these reflectors is presented
RF and IF mixer optimum matching impedances extracted by large-signal vectorial measurements
This paper introduces a new technique that allows us to measure the admittance conversion matrix of a two-port device,using a Nonlinear Vector Network Analyzer.This method is applied to extract the conversion matrix of a 0.2 µµµµm pHEMT,driven by a 4.8 GHz pump signal,at different power levels,using an intermediate frequency of 600 MHz.The issue on data inconsistency due to phase randomization among different measurements is discussed and a proper pre- processing algorithm is proposed to fix the problem. The output of this work consists of a comprehensive experimental evaluation of up-and down-conversion maximum gain,stability,and optimal RF and IF impedances
Distinguishing impurity concentrations in GaAs and AlGaAs, using very shallow undoped heterostructures
We demonstrate a method of making a very shallow, gateable, undoped
2-dimensional electron gas. We have developed a method of making very low
resistivity contacts to these structures and systematically studied the
evolution of the mobility as a function of the depth of the 2DEG (from 300nm to
30nm). We demonstrate a way of extracting quantitative information about the
background impurity concentration in GaAs and AlGaAs, the interface roughness
and the charge in the surface states from the data. This information is very
useful from the perspective of molecular beam epitaxy (MBE) growth. It is
difficult to fabricate such shallow high-mobility 2DEGs using modulation doping
due to the need to have a large enough spacer layer to reduce scattering and
switching noise from remote ionsied dopants.Comment: 4 pages, 5 eps figure
Inelastic scattering of protons from He and Li in a folding model approach
The proton-inelastic scattering from He and Li nuclei are
studied in a folding model approach. A finite-range, momentum, density and
isospin dependent nucleon-nucleon interaction (SBM) is folded with realistic
density distributions of the above nuclei. The renormalization factors N
and N on the real and volume imaginary part of the folded potentials are
obtained by analyzing the respective elastic scattering data and kept unaltered
for the inelastic analysis at the same energy. The form factors are generated
by taking derivatives of the folded potentials and therefore required
renormalizations. The values are extracted by fitting the p +
He,Li inelastic angular distributions. The present analysis of
p + He inelastic scattering to the 3.57 MeV excited state, including
unpublished forward angle data (RIKEN) confirms L = 2 transition. Similar
analysis of the p + He inelastic scattering angular distribution leading to
the 1.8 MeV (L = 2) excited state fails to satisfactorily reproduce the data.Comment: one LaTeX file, five PostScript figure
Finite self-similar p-groups with abelian first level stabilizers
We determine all finite p-groups that admit a faithful, self-similar action
on the p-ary rooted tree such that the first level stabilizer is abelian. A
group is in this class if and only if it is a split extension of an elementary
abelian p-group by a cyclic group of order p.
The proof is based on use of virtual endomorphisms. In this context the
result says that if G is a finite p-group with abelian subgroup H of index p,
then there exists a virtual endomorphism of G with trivial core and domain H if
and only if G is a split extension of H and H is an elementary abelian p-group.Comment: one direction of theorem 2 extended to regular p-group
Attentive Neural Architecture Incorporating Song Features For Music Recommendation
Recommender Systems are an integral part of music sharing platforms. Often
the aim of these systems is to increase the time, the user spends on the
platform and hence having a high commercial value. The systems which aim at
increasing the average time a user spends on the platform often need to
recommend songs which the user might want to listen to next at each point in
time. This is different from recommendation systems which try to predict the
item which might be of interest to the user at some point in the user lifetime
but not necessarily in the very near future. Prediction of the next song the
user might like requires some kind of modeling of the user interests at the
given point of time. Attentive neural networks have been exploiting the
sequence in which the items were selected by the user to model the implicit
short-term interests of the user for the task of next item prediction, however
we feel that the features of the songs occurring in the sequence could also
convey some important information about the short-term user interest which only
the items cannot. In this direction, we propose a novel attentive neural
architecture which in addition to the sequence of items selected by the user,
uses the features of these items to better learn the user short-term
preferences and recommend the next song to the user.Comment: Accepted as a paper at the 12th ACM Conference on Recommender Systems
(RecSys 18
Superconducting coplanar waveguide resonators for low temperature pulsed electron spin resonance spectroscopy
We discuss the design and implementation of thin film superconducting
coplanar waveguide micro- resonators for pulsed ESR experiments. The
performance of the resonators with P doped Si epilayer samples is compared to
waveguide resonators under equivalent conditions. The high achievable filling
factor even for small sized samples and the relatively high Q-factor result in
a sensitivity that is superior to that of conventional waveguide resonators, in
particular to spins close to the sample surface. The peak microwave power is on
the order of a few microwatts, which is compatible with measurements at ultra
low temperatures. We also discuss the effect of the nonuniform microwave
magnetic field on the Hahn echo power dependence
Interplay of Coulomb and electron-phonon interactions in graphene
We consider mutual effect of the electron-phonon and strong Coulomb
interactions on each other by summing up leading logarithmic corrections via
the renormalization group approach. We find that the Coulomb interaction
enhances electron coupling to the intervalley A1 optical phonons, but not to
the intravalley E2 phonons
Electromagnetic Scattered Field Evaluation and Data Compression Using Imaging Techniques
This is the final report on Project #727625 between The Ohio State University and NASA, Lewis Research Center, Cleveland, Ohio. Under this project, a data compression technique for scattered field data of electrically large targets is developed. The technique was applied to the scattered fields of two targets of interest. The backscattered fields of the scale models of these targets were measured in a ra compact range. For one of the targets, the backscattered fields were also calculated using XPATCH computer code. Using the technique all scattered field data sets were compressed successfully. A compression ratio of the order 40 was achieved. In this report, the technique is described briefly and some sample results are included
Research Notes : Consistency of heritability estimates over environments and crop-ping systems for different groups of traits in soybean
Introduction : Though numerous reports are available on heritability estimates from individual environment, yet information on consistency of heritability over environments is meager (Byth et al., 1969). An attempt has been made in the present communication to understand the influence of en-vironments and cropping system on the heritability estimates in soybean. Materials and methods : The materials and experimental design were same as reported by Gupta et al. (1981)
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