The NOD3 software package: A graphical user interface-supported reduction package for single-dish radio continuum and polarisation observations

The venerable NOD2 data reduction software package for single-dish radio continuum observations, developed for use at the 100-m Effelsberg radio telescope, has been successfully applied over many decades. Modern computing facilities call for a new design. We aim to develop an interactive software tool with a graphical user interface (GUI) for the reduction of single-dish radio continuum maps. Special effort is given on the reduction of distortions along the scanning direction (scanning effects) by combining maps scanned in orthogonal directions or dual- or multiple-horn observations that need to be processed in a restoration procedure. The package should also process polarisation data and offer the possibility to include special tasks written by the individual user. Based on the ideas of the NOD2 package we developed NOD3, which includes all necessary tasks from the raw maps to the final maps in total intensity and linear polarisation. Furthermore, plot routines and several methods for map analysis are available. The NOD3 package is written in Python which allows to extend the package by additional tasks. The required data format for the input maps is FITS. NOD3 is a sophisticated tool to process and analyse maps from single-dish observations that are affected by 'scanning effects' due to clouds, receiver instabilities, or radio-frequency interference (RFI). The 'basket-weaving' tool combines orthogonally scanned maps to a final map that is almost free of scanning effects. The new restoration tool for dual-beam observations reduces the noise by a factor of about two compared to the NOD2 version. Combining single-dish with interferometer data in the map plane ensures the full recovery of the total flux density.Comment: 8 pages, 10 figures, Accepted for publication in A&

Synchrotron spectral index and interstellar medium densities of star-forming galaxies

The spectral index of synchrotron emission is an important parameter in understanding the properties of cosmic ray electrons (CREs) and the interstellar medium (ISM). We determine the synchrotron spectral index ($\alpha_{\rm nt}$) of four nearby star-forming galaxies, namely NGC 4736, NGC 5055, NGC 5236 and NGC 6946 at sub-kpc linear scales. The $\alpha_{\rm nt}$ was determined between 0.33 and 1.4 GHz for all the galaxies. We find the spectral index to be flatter ($\gtrsim -0.7$) in regions with total neutral (atomic + molecular) gas surface density, $\Sigma_{\rm gas} \gtrsim \rm 50~M_\odot pc^{-2}$, typically in the arms and inner parts of the galaxies. In regions with $\Sigma_{\rm gas} \lesssim \rm 50~M_\odot pc^{-2}$, especially in the interarm and outer regions of the galaxies, the spectral index steepens sharply to $<-1.0$. The flattening of $\alpha_{\rm nt}$ is unlikely to be caused due to thermal free--free absorption at 0.33 GHz. Our result is consistent with the scenario where the CREs emitting at frequencies below $\sim0.3$ GHz are dominated by bremsstrahlung and/or ionization losses. For denser medium ($\Sigma_{\rm gas} \gtrsim \rm 200~M_\odot pc^{-2}$), having strong magnetic fields ($\sim 30~\mu$G), $\alpha_{\rm nt}$ is seen to be flatter than $-0.5$, perhaps caused due to ionization losses. We find that, due to the clumpy nature of the ISM, such dense regions cover only a small fraction of the galaxy ($\lesssim5$ percent). Thus, the galaxy-integrated spectrum may not show indication of such loss mechanisms and remain a power-law over a wide range of radio frequencies (between $\sim 0.1$ to 10 GHz).Comment: 10 pages, 4 figures, 2 tables, Accepted to be published in MNRA

Characteristics of a future aeronautical satellite communications system

A possible operational system scenario for providing satellite communications services to the future aviation community was analyzed. The system concept relies on a Ka-band (20/30 GHz) satellite that utilizes multibeam antenna (MBA) technology. The aircraft terminal uses an extremely small aperture antenna as a result of using this higher spectrum at Ka-band. The satellite functions as a relay between the aircraft and the ground stations. The ground stations function as interfaces to the existing terrestrial networks such as the Public Service Telephone Network (PSTN). Various system tradeoffs are first examined to ensure optimized system parameters. High level performance specifications and design approaches are generated for the space, ground, and aeronautical elements in the system. Both technical and economical issues affecting the feasibility of the studied concept are addressed with the 1995 timeframe in mind

Linearons: highly non-instantaneous solitons in liquid-core photonic crystal fibers

The nonlinear propagation of light pulses in liquid-filled photonic crystal fibers is considered. Due to the slow reorientational nonlinearity of some molecular liquids, the nonlinear modes propagating inside such structures can be approximated, for pulse durations much shorter than the molecular relaxation time, by temporally highly-nonlocal solitons, analytical solutions of a linear Schroedinger equation. The physical relevance of these novel solitary structures, which may have a broad range of applications, is discussed and supported by detailed numerical simulations.Comment: 4 pages, 3 figure

Comparative Analysis between Grundfos CRE 15-3 Variable Speed Centrifugal Pumps and a Worthington D-824 Constant Speed Centrifugal Pump in a KU Steam Power Plant Application

This document presents a comparative analysis between the use of a Grundfos CRE 15-3 variable speed centrifugal pump and a Worthington D-824 constant speed centrifugal pump in a steam power plant application. This was performed since, in many applications that require pumping systems, the pumps account for the majority of the energy expenses; and it is believed that, by using variable speed pumps in such applications, the pumps could help increase savings with regard to energy costs. In the steam power plant located at The University of Kansas, these two pumps must supply water to a deaerator tank and to a heat exchanger, where the deaerator tank is the tank that provides water to the boilers inside the power plant. The heat exchanger is only used to capture the steam that is unused by the plant, turning such steam into water that can be reused to again supply water to the deaerator tank. The Grundfos CRE 15-3 has the ability to run in discharge pressure mode as well as level control mode, while the Worthington D-824 is only able to run in discharge pressure mode. With that in mind, data concerning the discharge pressure, flow rate and power consumption was collected when either the Grundfos CRE 15-3 variable speed pump or the Worthington D-824 supplied water to the system. A total of four different cases were considered when gathering this data: (1) Both pumps ran in discharge pressure mode while supplying water to the deaerator tank and the heat exchanger; (2) Both pumps ran in discharge pressure mode, but for part of the day they supplied water only to the deaerator tank, and, for the other part of the day, they supplied water to both the heat exchanger and the deaerator tank; (3) The Grundfos CRE 15-3 ran in level control mode only supplying water to the deaerator tank, while the Worthington D-824 ran in discharge pressure mode only supplying water to the deaerator tank; (4) The Grundfos CRE 15-3 ran in level control mode only supplying water to the deaerator tank, while the Worthington D-824 ran in discharge pressure mode supplying water to both the deaerator tank and the heat exchanger. The gathered data was then compared to the theoretical pump data from their respective pump curves. A life cycle cost analysis was performed, using the BLLC5 software provided by the Department of Energy, to see if the variable speed pump would indeed provide energy savings to the power plant as well as have a lower total life cycle cost as compared to the constant speed pump. As this document will show, energy savings can be obtained when running the Grundfos CRE 15-3 in level control mode, even though the total life cycle costs of both pumps are still fairly similar. For Case 1 the Worthington D-824 pump had a total life cycle cost that was 3.14% lower than the CRE 15-3 pumps; and both pump systems have almost identical energy consumption. When the heat exchanger valve is open in Case 2, the Worthington D-824 pump's life cycle cost is 4.56% lower than the one that of the CRE 15-3 pumps. When the heat exchanger valve is closed, the total life cycle cost of both pump systems are almost identical (0.006% difference). For Case 3, the CRE 15-3 pumps' average energy costs are 68.8% lower than the costs of the Worthington D-824 pump. Even though there is a large difference in energy costs, the CRE 15-3 pumps' total life cycle cost is only 7.89% lower than the total life cycle cost of the Worthington D-824. Finally, a direct percentage comparison cannot be given for Case 4 due to the different jobs that the two pump systems were doing while operating. However, as will be shown in this document, reasonable estimates were made in an attempt to compare these pump systems for the scenario presented in Case 4