226 research outputs found

    Best practices for system dynamics model design and construction with powersim studio.

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    Space station automation of common module power management and distribution

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    The purpose is to automate a breadboard level Power Management and Distribution (PMAD) system which possesses many functional characteristics of a specified Space Station power system. The automation system was built upon 20 kHz ac source with redundancy of the power buses. There are two power distribution control units which furnish power to six load centers which in turn enable load circuits based upon a system generated schedule. The progress in building this specified autonomous system is described. Automation of Space Station Module PMAD was accomplished by segmenting the complete task in the following four independent tasks: (1) develop a detailed approach for PMAD automation; (2) define the software and hardware elements of automation; (3) develop the automation system for the PMAD breadboard; and (4) select an appropriate host processing environment

    Databook for human factors engineers. Volume 2 - Common formulas, metrics, definitions

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    Human factors engineering manual including mathematical formulas, nomographs, conversion tables, units of measurement, and nomenclature

    INDUSTRY CONVENTIONS EDI LSOG MECHANIZATION SPECIFICATION 4 ASC X12 VERSION 004020

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    This document is printed and distributed by the Alliance for Telecommunications Industry Solutions (ATIS) on behalf of the Telecommunications Industry Forum (TCIF). Participants in TCIF are hereby authorized to reproduce and distribute this document within their own business provided that this notice continues to appear in the reproduced documentation. Reproduction and distribution for resale is prohibited. Reproduction and distribution for resale is prohibited. If any parts of the guidelines, e.g. Business Models, Transaction Sets, etc. are copied and incorporated into a Company’s guidelines, TCIF/EDI and the authoring subcommittee should be acknowledged as the source of the information. For ordering information, please contact: Alliance for Telecommunications Industry Solution

    Student Reference Manual for Apollo MSFN Indoctrination

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    Astronaut reference manual for Apollo lunar landing mission networ

    A secure client / server interface protocol for the electricity prepayment vending industry

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    Electricity prepayment systems have been successfully implemented by South Africa’s national electricity utility (Eskom) and local municipalities for more than 17 years. The prepayment vending sub-system is a critical component of prepayment systems. It provides convenient locations for customers to purchase electricity. It predominantly operates in an “offline” mode, however, electricity utilities are now opting for systems that operate in an “online” mode. “Online” mode of operation or online vending is when a prepayment token is requested from a centralised server that is remote from the client at the actual point of sale (POS). The token is only generated by the server and transferred to the POS client, once the transaction, the POS client and the payment mechanism has been authenticated and authorised. The connection between the POS client and the server is a standard computer network channel (like Internet, direct dial-up link, X.25, GPRS, etc) The lack of online vending system standardisation was a concern and significant risk for utilities, as they faced the problem of being locked into proprietary online vending systems. Thus the South African prepayment industry, lead by Eskom, initiated a project to develop an industry specification for online vending systems. The first critical project task was a current state analysis of the South African prepayment industry, technology and specifications. The prepayment industry is built around the Standard Transfer Specification (STS). STS has become the de-facto industry standard to securely transfer electricity credit from a Point of Sale (POS) to the prepaid meter. STS is supported by several “offline” vending system specifications. The current state analysis was followed by the requirements analysis phase. The requirements analysis confirmed the need for a standard interface protocol specification rather than a full systems specification. The interface specification focuses on the protocol between a vending client and vending server and does not specify the client and server application layer functionality and performance requirements. This approach encourages innovation and competitiveness amongst client and server suppliers while ensuring interoperability between these systems. The online vending protocol design was implemented using the web services framework and therefore appropriately named, XMLVend. The protocol development phase was an iterative process with two major releases, XMLVend 1.22 and XMLVend 2.1. XMLVend 2.1 is the current version of the protocol. XMLVend 2.1 addressed the shortcomings identified in XMLVend 1.22, updated the existing use cases and added several new use cases. It was also modelled as a unified modelling language (UML) interface or contract for prepayment vending services. Therefore, clients using the XMLVend interface are able to request services from any service provider (server) that implements the XMLVend interface. The UML modelled interface and use case message pairs were mapped to Web Service Definition Language (WSDL) and schema (XSD) definitions respectively. XMLVend 2.1 is a secure and open web service based protocol that facilitates prepayment vending functionality between a single logical vending server and ‘n’ number of clients. It has become a key enabler for utilities to implement standardised, secure, interoperable and flexible online vending systems. AFRIKAANS : Voorafbetaalde elektrisiteitstelsels is suksesvol deur Suid-Afrika se nasionale elektrisiteitsverskaffer (Eskom) en plaaslike munisipaliteite geïmplementeer vir meer as 17 jaar. Die Voorafbetaal verkoop-subsisteem is 'n esensiële komponent van voorafbetaal elektrisiteitstelsels. Dit laat gebruikers toe om elektrisiteit te koop by ‘n verskeidenheid van verkooppunte. In die verlede het hierdie stelsels meestal bestaan as alleenstaande verkooppunte maar elektrisiteitsverskaffers is besig om hulle stelsels te verander om in n aanlyn modus te werk. Aanlyn verkoop is wanneer 'n voorafbetaalkoepon versoek word vanaf ‘n sentrale bediener wat vêr verwydered is van die kliënt se verkooppunt. Die koepon word slegs gegenereer deur die bediener en gestuur aan die kliënt nadat die transaksie, die kliënt self, en die betaling meganisme, gemagtig is. Die koppeling tussen verkooppuntkliënt en die bediener is ‘n standaard kommunikasie kanaal, (byvoorbeeld; Internettoegang, direkte inbel skakel, X.25 en “GPRS”) Die gebrek aan 'n standaard vir aanlynverkoopstelsels was 'n bekommernis en beduidende risiko vir elektrisiteitsverskaffers, aangesien hulle ‘n probleem ondervind dat hulle ingeperk sal word tot ‘n eksklusiewe ontwerp vir so ‘n aanlynverkoopstelsel. Dus het die Suid Afrikaanse voorafbetaal industrie, gelei deur Eskom, 'n projek begin om 'n industriespesifikasie te ontwikkel vir aanlyn verkoopstelsels. Die eerste kritiese projek taak was 'n analise van die huidige stand van die Suid-Afrikaanse vooruitbetaling industrie, die tegnologie en spesifikasies. Die voorafbetaal sektor is gebou rondom die Standaard Oordrag Spesifikasie, bekend as “Standard Transfer Specification” (STS). STS word algemeen aanvaar as die industrie standaard vir die oordrag van elektrisiteit krediet vanaf 'n Verkooppunt na die voorafbetaalmeter. STS word ondersteun deur verskeie alleenstaande verkoopstelsel spesifikasies. Die analise vir die huidige status was opgevolg deur ‘n studie van die vereistes vir so ‘n stelsel. Die vereistes analise het die behoefte bevestig vir 'n standaard koppelvlak protokol spesifikasie, eerder as 'n nuwe spesifikasie vir ‘n volledige oorafbetaalstelsel. Dit bepaal alleenlik die protokol koppelvlak tussen 'n voorafbetaalkliënt en die bediener. Dit spesifiseer nie die program vlak funksionaliteit of prestasie vereistes, vir die kliënt en bediener nie. Hierdie benadering bevorder innovasie en mededingendheid onder kliënt- en bediener-verskaffers, terwyl dit nog steeds verseker dat die stelsels wedersyds aanpasbaar bly. Die aanlyn verkoopprotokol ontwerp is geïmplementeer met die webdienste raamwerk en staan bekend as XMLVend. Die protokol vir die ontwikkeling fase was 'n iteratiewe proses met die twee groot weergawes, XMLVend 1.22 en XMLVend 2.1. Die huidige weergawe van die protokol - XMLVend 2.1, adresseer die tekortkominge wat geïdentifiseer is met XMLVend 1.22, terwyl dit ook die bestaande gebruiksgevalle opdatteer en verskeie nuwe gebruiksgevalle byvoeg. Dit was ook geskoei as 'n verenigde modelleringtaal (UML) koppelvlak, of 'n kontrak, vir die voorafbetaal verkoopsdienste. Kliënte is daarom in staat om, met behulp van die XMLVend koppelvlak, dienste te versoek van enige diensverskaffer wat die XMLVend koppelvlak ondersteun. Die UML gemodelleerde koppelvlak- en gebruiksgevalle- boodskappare was gemodeleer in die Web Dienste Definisie Taal (WSDL) en skema (XSD) definisies onderskeidelik. XMLVend 2.1 is 'n sekure en oop webdienste-gebaseerde protokol wat dit moontlik maak om voorafbetaalfunksies te fasilliteer tussen 'n enkele logiese verkoopbediener en 'x' aantal kliënte. Dit het 'n sleutelrol aangeneem vir verskaffers om ‘n gestandaardiseerde, veilige, wedersyds-aanpasbare en buigsame aanlyn verkoopstelsels moontlik te maak. CopyrightDissertation (MSc)--University of Pretoria, 2010.Electrical, Electronic and Computer Engineeringunrestricte

    Atmospheric science facility pallet-only mode space transportation system payload (feasibility study), Volume 1

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    The economic and technical feasibility is assessed of employing a pallet-only mode for conducting Atmospheric Magnetospheric Plasmas-in-Space experiments. A baseline design incorporating the experiment and instrument descriptions is developed. The prime instruments are packaged into four pallets in a physical and functional manner compatible with the Space Transportation System capabilities and/or constraints and an orbiter seven-day mission timeline. Operational compatibility is verified between the orbiter/payload and supporting facilities. The development status and the schedule requirements applicable to the Atmospheric Science Facility mission are identified. Conclusions and recommendations are presented and discussed

    Energy management engineering : a predictive energy management system incorporating an adaptive neural network for the direct heating of domestic and industrial fluid mediums.

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    The objective of this research project is to improve the control and provide a more cost-efficient operation in the direct heating of stored domestic or industrial fluid mediums; such to be achieved by means of an intelligent automated energy management system. For the residential customer this system concept applies to the hot water supply as stored in the familiar hot water cylinder; for the industrial or commercial customer the scope is considerably greater with larger quantities and varieties of fluid mediums. Both areas can obtain significant financial savings with improved energy management. Both consumers and power supply and distribution companies will benefit with increased utilisation of cheaper 'off-peak' electricity; reducing costs and spreading the system load demand. The project has focussed on domestic energy management with a definite view to the wider field of industrial applications. Domestic energy control methodology and equipment has not significantly altered for decades. However, computer hardware and software has since then flourished to an unprecedented proportion and has become relatively cheap and versatile; these factors pave the way for the application of computer technology in this area of great potential. The technology allows the implementation of a 'hot water energy management system', which makes a forecast of the hot water demand for the next 24 hours and proceeds to provide this demand in the most efficient manner possible. In the (near) future, the system, known as FEMS for Fluid Energy Management System, is able to take advantage and in fact will promote the use of a retail 'dynamic spot price tariff’. FEMS is a combination of hardware and software developed to replace the existing cylinder thermostat, take care of the necessary data-acquisition and control the cylinder's total energy instead of it's (single point) temperature. This provides, besides heating cost reduction, a greater accuracy, a degree of flexibility, improved feedback, legionella inhibition, and a diagnostic capability. To the domestic consumer the latter three items are of greatest relevance. The crux of the system lies in its predictive ability. Having explored the more conventional alternatives, a suitable solution was found in the utilisation of the Elman recurrent neural networks, which focus on the temporal characteristics of the hot water demand time series and are able to adapt to changing environments, coping with the presence of any non-linearity and noise in the data. Prior to developing FEMS a study was made of the basic fluid behaviour in medium and high pressure domestic hot water cylinders, an area not well-covered to date and of interest to engineers and manufacturers alike. For this step data acquisition equipment and software was purposely created. The control software plus equipment were combined into a fully automated test system with minimal operator input, allowing a large amount of data to be gathered over a period measured in months. A similar system was subsequently used to collect actual hot water demand data from a residential family, and in fact forms the basis for FEMS. Finally an enhanced version of FEMS is discussed and it is shown how the system is able to output multiple prediction and utilise varying tariff rates
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