A Near-Field Treatment of Aperture Synthesis Techniques using the Murchison Widefield Array

Typical radio interferometer observations are performed assuming the source of radiation to be in the far-field of the instrument, resulting in a two-dimensional Fourier relationship between the observed visibilities in the aperture plane and the sky brightness distribution (over a small field of view). When near-field objects are present in an observation, the standard approach applies far-field delays during correlation, resulting in loss of signal coherence for the signal from the near-field object. In this paper, we demonstrate near-field aperture synthesis techniques using a Murchison Widefield Array observation of the International Space Station (ISS), as it appears as a bright near-field object. We perform visibility phase corrections to restore coherence across the array for the near-field object (however not restoring coherence losses due to time and frequency averaging at the correlator). We illustrate the impact of the near-field corrections in the aperture plane and the sky plane. The aperture plane curves to match the curvature of the near-field wavefront, and in the sky plane near-field corrections manifest as fringe rotations at different rates as we bring the focal point of the array from infinity to the desired near-field distance. We also demonstrate the inverse scenario of inferring the line-of-sight range of the ISS by inverting the apparent curvature of the wavefront seen by the aperture. We conclude the paper by briefly discussing the limitations of the methods developed and the near-field science cases where our approach can be exploited.Comment: Accepted in Publications of the Astronomical Society of Australia (PASA). 10 pages, 7 figures, and lots of linked animation

Vibrational control of air suspension system using PID controller

This paper deals with modeling and evaluation of suspension system with a pneumatic actuator controlled by Proportional Integral Derivative (PID) controller. A non-linear mathematical model of the dynamic suspension system with two degrees of freedom is developed. The controller is designed by setting proper gain values obtained by comparing three tuning methods - Ziegler Nicolas, Refined Ziegler Nicolas and Optimal control. The time response of the air suspension system is contrasted with the passive suspension system due to the road disturbance modeled as a single bump input. The proposed model limits suspension travel, minimizes passenger acceleration and keeps body displacement within bound

Heavy landings of juveniles of Indian scad, Decapterus russelli at Munambam Fisheries Harbour

Among the carangid fishes, the Indian scad, Decapterus russelli is an important pelagic fish and a major commercial species contributing to the marine fisheries of Kerala. The fish is locally called “kozhuchala” and it forms a regular fishery. The species is often caught as by-catch in shrimp trawl nets having cod-end mesh sizes ranging from 15 mm to 20 mm that is operated in the depth range of 55- 90 m almost throughout the year. They are consumed fresh as well as sun dried form

Optimum Placement and Sizing Determination of Distributed Generation and DSTATCOM Using Penguins Search Optimisation Algorithm

ABSTRACT: A Penguin Search Optimization algorithm for finding the optimal location and sizing of Distributed Generation and Distribution STATic COMpensator (DSTATCOM) with the aim of reducing the total power loss along with voltage profile improvement of Radial Distribution System is proposed in this paper. The new-fangled formulation projected is inspired by the idea that the optimum placement of the DG and DSTATCOM can facilitate in minimization of the line loss and voltage dips in Radial Distribution Systems. A complete performance analysis is carried out on 14, 30 and 57 bus radial distribution test systems and each test system has three different cases

Structural insights into the nucleic acid remodeling mechanisms of the yeast THO-Sub2 complex

The yeast THO complex is recruited to active genes and interacts with the RNA-dependent ATPase Sub2 to facilitate the formation of mature export-competent messenger ribonucleoprotein particles and to prevent the co-transcriptional formation of RNA:DNA-hybrid-containing structures. How THO-containing complexes function at the mechanistic level is unclear. Here, we elucidated a 3.4 angstrom resolution structure of Saccharomyces cerevisiae THO-Sub2 by cryoelectron microscopy. THO subunits Tho2 and Hpr1 intertwine to form a platform that is bound by Mft1, Thp2, and Text. The resulting complex homodimerizes in an asymmetric fashion, with a Sub2 molecule attached to each protomer. The homodimerization interfaces serve as a fulcrum for a seesaw-like movement concomitant with conformational changes of the Sub2 ATPase. The overall structural architecture and topology suggest the molecular mechanisms of nucleic acid remodeling during mRNA biogenesis.We thank Daniel Bollschweiler and Tillman Schäfer at the MPIB cryo-EM facility..

Evaluasi Proses Pembuatan Avtur (Aviation Turbine) Berdasarkan Analisa Sifat Fisik Dan Kimia Minyak Mentah (Crude Oil) Di PT Pertamina Ru II Dumai

Aviation Turbine Fuel (AVTUR) atau secara Internasional lebih dikenal dengan nama Jet A-1 adalah bahan bakaruntuk pesawat terbang jenis jet (baik tipe jet propusion atau propeller.) Avtur adalah minyak tanah dengan spesifikasiyang diperketat, terutama mengenai titik uap, dan titik beku. Secara umum, avtur memiliki kualitas yang lebih tinggidibandingkan bahan bakar yang digunakan untuk pemakaian yang kurang ‘genting\u27 seperti pemanasan atautransportasi darat. PT Pertamina RU II Dumai adalah salah satu Perusahan pengolahan yang menghasilkan berbagaiproduk akhir atau produk turunan dari minyak mentah.Untuk melakukan proses pengolahan pada minyak mentahperlu dikatahui karakteristik dan spesifikasi dari minyak mentah (bahan baku) yang akan diolah Untuk mengetahuimutu dan manfaat minyak bumi tersebut,ada beberapa parameter analisa minyak bumi yang digunakan yang terbagidalam 2 parameter yaitu parameter fisik dan parameter kimia.Dari analisa tersebut diketahui Bahan baku minyakmentah daerah Duri ( Duri Crude ) tipe “Naphthenic-naphthanic” dan Minas ( Minas Crude ) tipe “Paraffinicintermediate”.Penulis membuat perhitungan material balance bahwa Produksi Avtur secara aktual berkisar 8,35 %dari jumlah feed umpan dari kilang dumai 127 bbl dan kilang SPK 49 bbl.Mutu dan kualitas hasil produksi bahanbakar jenis Avtur (Aviation Turbine) kilang pertamina RU II Dumai baik dan memenuhi syarat dan spesifikasi yangditetapkan serta layak dipasarkan