Image formation in synthetic aperture radio telescopes

Next generation radio telescopes will be much larger, more sensitive, have much larger observation bandwidth and will be capable of pointing multiple beams simultaneously. Obtaining the sensitivity, resolution and dynamic range supported by the receivers requires the development of new signal processing techniques for array and atmospheric calibration as well as new imaging techniques that are both more accurate and computationally efficient since data volumes will be much larger. This paper provides a tutorial overview of existing image formation techniques and outlines some of the future directions needed for information extraction from future radio telescopes. We describe the imaging process from measurement equation until deconvolution, both as a Fourier inversion problem and as an array processing estimation problem. The latter formulation enables the development of more advanced techniques based on state of the art array processing. We demonstrate the techniques on simulated and measured radio telescope data.Comment: 12 page

Weighted Max-Min Resource Allocation for Frequency Selective Channels

In this paper, we discuss the computation of weighted max-min rate allocation using joint TDM/FDM strategies under a PSD mask constraint. We show that the weighted max-min solution allocates the rates according to a predetermined rate ratio defined by the weights, a fact that is very valuable for telecommunication service providers. Furthermore, we show that the problem can be efficiently solved using linear programming. We also discuss the resource allocation problem in the mixed services scenario where certain users have a required rate, while the others have flexible rate requirements. The solution is relevant to many communication systems that are limited by a power spectral density mask constraint such as WiMax, Wi-Fi and UWB

A Fuctional Reading Program and Its Effect Upon the General Achievements of Pupils of Grades Eight Through Twelve, Lincoln High School, Coldspring, Texas

The teachers of grades nine through twelve of Lincoln High School, Coldspring, Texas, voiced loud complaints about the standard of work done by the pupils in any subject in which silent reading and independent study skills were involved. They expressed the belief that something could be and should be done about the matter; yet very little except complaining was undertaken prior to the 1953-1954 school year. Every year for the past six years some of the students who left school in May without having graduated did not return in September. Some went to other towns and entered schools, while others failed to enroll any more in any school. Most of the drop-outs occurred in grades eight through ten. They were pupils whose scholastic achievements were low in all subjects listed on their permanent records. Many of the students who entered the high school department and many of those who were promoted were passed on from grade to grade to relieve the congestion in the elementary grades or because of psychological reasons. Test results for a period of several years showed that there were serious reading difficulties among the students who enrolled year after year. The investigator, in reading the literature of her field, discovered the widespread seriousness of the reading difficulties of students on the high school level, and resolved to do intensive study of the problem in her teaching situation. This study was undertaken (1) to determine the general educational levels of the pupils of grades eight through twelve of Lincoln High School, Coldspring, Texas, (2) to find the reading level of each pupil, (3) to locate the major reading weaknesses of the pupils in study-type reading, (4) to adjust the English curriculum to meet the needs shown, and (5) to relate the pupils\u27 reading abilities to their achievements in content subjects

Revisiting the radio interferometer measurement equation. IV. A generalized tensor formalism

The radio interferometer measurement equation (RIME), especially in its 2x2 form, has provided a comprehensive matrix-based formalism for describing classical radio interferometry and polarimetry, as shown in the previous three papers of this series. However, recent practical and theoretical developments, such as phased array feeds (PAFs), aperture arrays (AAs) and wide-field polarimetry, are exposing limitations of the formalism. This paper aims to develop a more general formalism that can be used to both clearly define the limitations of the matrix RIME, and to describe observational scenarios that lie outside these limitations. Some assumptions underlying the matrix RIME are explicated and analysed in detail. To this purpose, an array correlation matrix (ACM) formalism is explored. This proves of limited use; it is shown that matrix algebra is simply not a sufficiently flexible tool for the job. To overcome these limitations, a more general formalism based on tensors and the Einstein notation is proposed and explored both theoretically, and with a view to practical implementations. The tensor formalism elegantly yields generalized RIMEs describing beamforming, mutual coupling, and wide-field polarimetry in one equation. It is shown that under the explicated assumptions, tensor equations reduce to the 2x2 RIME. From a practical point of view, some methods for implementing tensor equations in an optimal way are proposed and analysed. The tensor RIME is a powerful means of describing observational scenarios not amenable to the matrix RIME. Even in cases where the latter remains applicable, the tensor formalism can be a valuable tool for understanding the limits of such applicability.Comment: 16 pages, no figures, accepted by A&

ACTIVITY TEST ETHANOL EXTRACT MATOA (POMETIA PINNATA) ANTINFLAMMATION AGAINST MALE RATS INDUCED CARAGENAN

Matoa merupakan salah satu tanaman dari famili Sapindaceae yang tersebar di daerah tropis, termasuk Indonesia. Tanaman matoa banyak digunakan masyarakat dalam pengobatan tradisional. Penelitian ini dilakukan dengan tujuan untuk mengetahui efek antiinflamasi ekstrak etanol daun matoa (Pometia pinnata) terhadap mencit putih jantan yang di induksi karagenan. Penelitian ini adalah penelitian eksperimental yang dibagi menjadi 5 kelompok yaitu kontrol positif (Natrium Diklofenak 6,5 mg/kgBB), kontrol negatif (Na-CMC 0,5%) dan tiga dosis yang diuji yaitu 100 mg/kgBB, 200 mg/kgBB dan 300 mg/kgBB. Metode dalam penelitian ini adalah dengan induksi karagenan 0,1 ml sebagai iritan pada telapak kaki mencit selama 360 menit dengan parameter yang diamati adalah penghambatan udem kaki mencit menggunakan pletismometer. Hasil penelitian ini menunjukkan adanya perbedaan yang signifikan (P>0,05) dengan kesimpulan tiga dosis yang diuji yaitu 100 mg/kgBB, 200 mg/kgBB dan 300 mg/kgBB memiliki efek antiinflamasi dimana dosis yang lebih efektif adalah 300 mg/kgBB

Explicit Solution of the Time Evolution of the Wigner Function

Previously, an explicit solution for the time evolution of the Wigner function was presented in terms of auxiliary phase space coordinates which obey simple equations that are analogous with, but not identical to, the classical equations of motion. They can be solved easily and their solutions can be utilized to construct the time evolution of the Wigner function. In this paper, the usefulness of this explicit solution is demonstrated by solving a numerical example in which the Wigner function has strong spatial and temporal variations as well as regions with negative values. It is found that the explicit solution gives a correct description of the time evolution of the Wigner function. We examine next the pseudoparticle approximation which uses classical trajectories to evolve the Wigner function. We find that the pseudoparticle approximation reproduces the general features of the time evolution, but there are deviations. We show how these deviations can be systematically reduced by including higher-order correction terms in powers of $\hbar^2$.Comment: 16 pages, in LaTex, invited talk presented at the Wigner Centennial Conference, Pecs, Hungary, July 8-12, 2002, to be published in the Journal of Optics B: Quantum and Classical Optics, June 200

Nonlinear effects in tunnelling escape in N-body quantum systems

We consider the problem of tunneling escape of particles from a multiparticle system confined within a potential trap. The process is nonlinear due to the interparticle interaction. Using the hydrodynamic representation for the quantum equations of the multiparticle system we find the tunneling rate and time evolutions of the number of trapped particles for different nonlinearity values.Comment: 10 pages, 3 figure

Analyzing the Dynamics and Structure of the Foreign Trade Activity of Ukraine

The article is aimed at defining the problems in foreign trade activity of Ukraine, which may entail unsatisfactory status of foreign economic security of the country. Based on data from 2011 to 2017, the dynamics of the main quantitative characteristics of foreign trade, structural shifts in foreign trade (with the help of indices of L. Kazinets and V. Ryabtsev), and also structure of foreign trade in the context of regions of Ukraine are researched. The key problems determining high risks of foreign economic security of the country are defined: significant reduction of volumes of foreign trade; prevalence of negative trade balance; high value of the share of total exports and imports in GDP; weak development of trade with the EU countries; low level of diversification of export commodity positions and its raw material orientation; loss of traditional market of machine-building products; at the regional level, there is a deformed structure of foreign trade, while the main exporter and importer of goods and services is the city of Kiev