2,699 research outputs found
Self-Similar Tilings of Fractal Blow-Ups
New tilings of certain subsets of are studied, tilings
associated with fractal blow-ups of certain similitude iterated function
systems (IFS). For each such IFS with attractor satisfying the open set
condition, our construction produces a usually infinite family of tilings that
satisfy the following properties: (1) the prototile set is finite; (2) the
tilings are repetitive (quasiperiodic); (3) each family contains
self-similartilings, usually infinitely many; and (4) when the IFS is rigid in
an appropriate sense, the tiling has no non-trivial symmetry; in particular the
tiling is non-periodic
Cross-Power Spectrum and Its Application on Window Functions in the WMAP data
Cross-power spectrum is a quadratic estimator between two maps that can
provide unbiased estimate of the underlying power spectrum of the correlated
signals, which is therefore used for extracting the power spectrum in the WMAP
data. In this paper we discuss the limit of cross-power spectrum and derive the
residual from uncorrelated signal, which is the source of error in power
spectrum extraction. We employ the estimator to extract window functions by
crossing pairs of extragalactic point sources. We desmonstrate its usefulness
in WMAP Difference Assembly maps where the window functions are measured via
Jupiter and then extract the window functions of the 5 WMAP frequency band
maps.Comment: added the part of applying cross power spectrum on WMAP DA maps and
frequency band maps and submitted to Ap
Radio Regulation Development and Radio Spectrum Analysis of Earth Station in Motion Service
Although Earth Station in Motion (ESIM) services are widely used and there is a huge market demand around the world, International Telecommunication Union (ITU) does not have unified conclusion for the use of ESIM yet. ESIM are Mobile Satellite Services (MSS) due to its mobile-based attributes, while multiple administrations want to use ESIM in Fixed Satellite Service (FSS). However, Radio Regulations (RR) have strict distinction between MSS and FSS. In this case, ITU has been very controversial because this kind of application will violate the RR Article and the conflict will bring risks to the global deployment. Thus, this paper illustrates the development of rules, regulations, standards concerning ESIM and the radio spectrum usage of ESIM in different regions around the world. Firstly, the basic rules, standard and definition of ITU’s Radiocommunication Sector (ITU-R) is introduced. Secondly, the World Radiocommunication Conference (WRC) agenda item on radio spectrum allocation for ESIM, e.g. in C/Ku/Ka band, is introduced and multi-view on the radio spectrum allocation is elaborated, especially on 19.7-20.2 GHz & 29.5-30.0 GHz. Then, some ITU-R Recommendations and Reports are analyzed on the specific technique to enable these ESIM to communicate with Geostationary Earth Orbit Satellite (GSO) space stations in the FSS without causing interference at levels in excess of that caused by conventional FSS earth stations. Meanwhile, the opposite opinion on not allocating EISM service in FSS frequency band is also elaborated. Finally, based on the ESIM’s future application, the ITU-R standards development trend is forecasted. In conclusion, using radio spectrum resource in an equitable, rational and efficient manner is the basic guideline of ITU. Although it is not a good approach to obstruct the revise of RR when there is a large demand for radio spectrum resource in satellite industry, still the propulsion and global demand of the whole industry may face difficulties on the unclear application in modify rules of RR
Self-evolving ghost imaging
Ghost imaging can capture 2D images with a point detector instead of an array
sensor. It therefore offers a solution to the challenge of building area format
sensors in wavebands where such sensors are difficult and expensive to produce
and opens up new imaging modalities due to high-performance single-pixel
detectors. Traditionally, ghost imaging retrieves the image of an object
offline, by correlating measured light intensities and applied illuminating
patterns. Here we present a feedback-based approach for online updating of the
imaging result that can bypass post-processing, termed self-evolving ghost
imaging (SEGI). We introduce a genetic algorithm to optimize the illumination
patterns in real-time to match the objects shape according to the measured
total light intensity. We theoretically and experimentally demonstrate this
concept for static and dynamic imaging. This method opens new perspectives for
real-time ghost imaging in applications such as remote sensing (e.g. machine
vision, LiDAR systems in autonomous vehicles) and biological imaging
Self-evolving ghost imaging
Funding Australian Research Council (DE200100074, DP190101058); China Scholarship Council (201607950009, 201706020170); University of Technology Sydney. Acknowledgment We thank Prof. Fengli Gao from Jilin University for the helpful discussion about PGPeer reviewedPublisher PD
Path-integral quantization of tensionless (super) string
In this work, we study the tensionless (super)string in the formalism of
path-integral quantization. We introduce BMS and ghosts
intrinsically by accounting for the Faddeev-Popov determinants appeared in
fixing the gauges. We then do canonical quantization and obtain the critical
dimensions for different tensionless strings. We find that among four kinds of
tensionless superstrings, the homogeneous and inhomogeneous
doublet tensionless superstrings have the same critical dimension as the usual
superstrings. Taking the BMS and ghosts as new types of BMS
free field theories, we find that their enhanced underlying symmetries are
generated by BMS-Kac-Moody algebras, with the Kac-Moody subalgebras being built
from a three-dimensional non-abelian and non-semi-simple Lie algebra.Comment: 46 pages, 1 table; v2: typos correcte
(5,5′-Dicarboxybiphenyl-2,2′-dicarboxylato-κ2 O 2,O 2′)bis(1,10-phenanthroline-κ2 N,N′)zinc(II) dihydrate
In the title compound, [Zn(C16H8O8)(C12H8N2)2]·2H2O, the ZnII atom is located on a twofold rotation axis and is six-coordinated by two O atoms from a 5,5′-dicarboxybiphenyl-2,2′-dicarboxylate ligand and four N atoms from two 1,10-phenanthroline molecules in a distorted octahedral geometry. The crystal structure involves O—H⋯O hydrogen bonds
- …