133,220 research outputs found

    Analysis of international graduate programmes structures for engineering education

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    This article traces the evolution of graduate study in Engineering in Ireland over three decades. Very few studies have shown the different norms and structures of graduate programmes in Ireland. In this paper, a review of traditional and structured PhD in terms of credit requirements and co-ordination structures is presented. The authors summarise the characteristics of graduate programmes in different universities in Ireland and compare these to those obtained in some of the leading international universities. The implementation of graduate programmes in Ireland is relatively recent and the structure of these programmes is still under development in the different universities. Plans for enhancement of graduate programs and the development of new initiatives to support graduate student academic and professional development are very important for the success of these programmes. The growth in enrolment reflects a broad diversity in background of students which will require not only increased financial resources but an adequate and sound organisational structure in order to move forward

    From Models to Simulations

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    This book analyses the impact computerization has had on contemporary science and explains the origins, technical nature and epistemological consequences of the current decisive interplay between technology and science: an intertwining of formalism, computation, data acquisition, data and visualization and how these factors have led to the spread of simulation models since the 1950s. Using historical, comparative and interpretative case studies from a range of disciplines, with a particular emphasis on the case of plant studies, the author shows how and why computers, data treatment devices and programming languages have occasioned a gradual but irresistible and massive shift from mathematical models to computer simulations

    Development of a Variable Roller Pump and Evaluation of its Power Saving Potential as a Charge Pump in Hydrostatic Drivetrains

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    Predložená doktorandská dizertačná práca (ďalej len práca) sa zaoberá rozsiahlou analýzou valčekového hydrogenerátora s premenlivým geometrickým objemom a predikciou výkonových úspor dosiahnutých aplikáciou navrhnutého valčekového hydrogenerátora s premenlivým geometrickým objemom v hydrostatickom pohone vybraných mobilných pracovných strojov. Teoretický rozbor princípov fungovania valčekového hydrogenerátora a teória jednorozmerného simulačného modelu sú popísané v prvej časti práce. Na základe odvodenej teórie je vytvorený simulačný model, ktorý je vhodný na predikciu priebehu tlaku v komorách valčekového hydrogenerátora, síl pôsobiacich na valček a na predikciu vnútorných únikov vzniknutých skratovaním rozvodovej dosky, ktoré majú priamy vplyv na objemovú účinnosť valčekového hydrogenerátora. Simulačný model bol úspešne použitý pre optimalizáciu rozvodových dosiek valčekového hydrogenerátora a vhodnosť simulačného modelu potvrdili následné merania Práca obsahuje aj analýzu síl pôsobiacich na vodiaci prstenec, ktorej výsledky boli taktiež potvrdené meraním. Analýza týchto síl môže vylepšiť v konečnom dôsledku parametre budúcich tlakových regulácii. Práca ďalej obsahuje základné porovnanie použitých tlakových regulácii. Všetky uskutočnené merania potvrdili, že valčekový hydrogenerátor s premenlivým geometrickým objemom s testovanými tlakovými reguláciami je schopný úspešne pracovať v hydrostatickej prevodovke. Druhá časť práce analyzuje potenciál výkonových úspor valčekového hydrogenerátora s premenlivým geometrickým objemom pre dve mobilné aplikácie - teleskopický nakladač s hmotnosťou 9 ton a kombajn s hmotnosťou 20 ton. Analýza vyžaduje jednorozmerný simulačný model hydrostatického pohonu s teplotnou predikciou hydrostatickej prevodovky. Dva rozdielne koncepty variabilného doplňovacieho systému hydrostatickej prevodovky sú porovnané so štandardným doplňovacím systémom pre pracovný a transportný režim oboch vybraných typov vozidiel. Simulácia pohonu vozidla s valčekovým hydrogenerátorom s premenlivým geometrickým objemom vo funkcii doplňovacieho hydrogenerátora a obtokovou clonou potvrdili vyššie úspory iba v prípadoch, kedy rýchlosť doplňovacieho hydrogenerátora bola výrazne vyššia a prietok cez obtokovú clonu do skrine hlavného hydrogenerátora zabezpečil dostatočné chladenie. Najvyššie výkonové úspory boli dosiahnuté s premenlivým preplachovacím systémom, ktorého prietok sa menil podľa požiadaviek hydrostatickej prevodovky. Záver druhej časti práce sa zaoberá metodikou dimenzovania veľkosti doplňovacieho hydrogenerátora.Presented doctoral thesis deals with an extensive hydraulic variable roller pump analysis and the power saving prediction of hydrostatic drivetrains in the mobile machines achieved with a variable roller charge pump implementation. At the first part of the work, the roller pump functionality was described and the theory of a 1-D simulation model was developed. Based on this developed simulation model is suitable for pressure profile prediction, roller force prediction and cross port leakage prediction which has a direct impact on the total volumetric efficiency. The simulation model was successfully used as a tool for optimization of the port plates, which was confirmed by measurements. The first part of the work includes the pump control force analysis validated by measurements and also the basic pressure compensator controls comparison. Developed control force prediction could help to improve the control performance. The measurements confirmed that the variable roller charge pump is able to successfully work in transmissions with measured types of the control. The second part of the work analyzed the power saving potential of a variable charge pump for two selected typical mobile applications: telehandler (9 ton) and combine harvester (20 ton). This part required a 1-D drivetrain simulation model together with thermal behaviour of the hydrostatic transmission. Two different modifications of the charging systems were compared with the conventional charging system in simulations performed for the working and transporting mode. The drivetrain simulation of the variable roller charge pump with a bypass orifice confirms higher power savings only in cases when the pump speed was significantly higher than normal speeds and a relatively constant flushing flow through the bypass orifice to the pump case still ensures suitable cooling. The highest power savings were achieved with variable flushing flows, where the demand for charging flow was adjusted according to the hydrostatic transmission cooling requirements. At the end of the second part, this thesis deals with a variable charge pump sizing.

    William (Bill) Peterson's contributions to ocean science, management, and policy

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    © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Schwing, F. B., Sissenwine, M. J., Batchelder, H., Dam, H. G., Gomez-Gutierrez, J., Keister, J. E., Liu, H., & Peterson, J. O. William (Bill) Peterson's contributions to ocean science, management, and policy. Progress in Oceanography, 182, (2020): 102241, doi:10.1016/j.pocean.2019.102241.In addition to being an esteemed marine ecologist and oceanographer, William T. (Bill) Peterson was a dedicated public servant, a leader in the ocean science community, and a mentor to a generation of scientists. Bill recognized the importance of applied science and the need for integrated “big science” programs to advance our understanding of ecosystems and to guide their management. As the first US GLOBEC program manager, he was pivotal in transitioning the concept of understanding how climate change impacts marine ecosystems to an operational national research program. The scientific insight and knowledge generated by US GLOBEC informed and advanced the ecosystem-based management approaches now being implemented for fishery management in the US. Bill held significant leadership roles in numerous international efforts to understand global and regional ecological processes, and organized and chaired a number of influential scientific conferences and their proceedings. He was passionate about working with and training young researchers. Bill’s academic affiliations, notably at Stony Brook and Oregon State Universities, enabled him to advise, train, and mentor a host of students, post-doctoral researchers, and laboratory technicians. Under his collegial guidance they became critical independent thinkers and diligent investigators. His former students and colleagues carry on Bill Peterson’s legacy of research that helps us understand marine ecosystems and informs more effective resource stewardship and conservation

    Greenhouse technology for sustainable production in mild winter climate areas: Trends and needs

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    Greenhouse production in the near future will need to reduce significantly its environmental impact. For this purpose, elements such as the structure, glazing materials, climate equipments and controls have to be developed and wisely managed to reduce the dependence on fossil fuels, achieve maximum use of natural resources such as solar radiation and water, and minimize the input of chemicals and fertilizers. This paper discusses the most relevant developments in greenhouse technology for mild winter climates. Regarding greenhouse structures, recent studies based on computational fluid dynamics have been conducted to investigate the effect of parameters such as ventilator size and arrangement, roof slope and greenhouse width and height on the air exchange rate. Next generation greenhouses are expected to incorporate some of the innovations derived from recent ventilation studies. Covering crops with screens is becoming a common practice. Main advantages and limitations of screenhouses are discussed in this paper. Thermal storage is increasingly applied in closed or semi-closed greenhouses. Under some conditions semi-closed greenhouses could mitigate day/night while reducing the use of water and the entrance of pest. Photo selective films that reflect a fraction of NIR radiation are effective at lowering greenhouse temperature and, in some cases, may be cost effective. NIR reflective films have side effects of major importance in greenhouse production. The CO2 enrichment strategy in computer-controlled greenhouses is based on determining the benefits of increasing the CO2 concentration against the cost of it. No clear strategies have been defined for the application of CO2 in unheated greenhouses, where most of the time the source of carbon dioxide is the external air. Some authors suggest ventilating as little as possible and fertilizing with bottled carbon dioxide at least up to the external concentration. Improving greenhouses by introducing new technologies may have an additional impact on the environment. From an environmental point of view, the incorporation of technology needs to increase yield to compensate for its associated environmental burden. Previous results have shown that forced ventilation and heating are the main reasons for the increase in environmental impact in climate controlled greenhouses. Additional results on the area of technology and its associated impact are discussed in this pape

    Taking a break: doctoral summer schools as transformative pedagogies

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    This chapter focuses on the doctoral summer school as a challenging pedagogy for doctoral education, in which the traditional supervisory relationship and the disciplinary curriculum are deconstructed through intensive group processes. We draw on our experiences as pedagogues on the Roskilde University Graduate School in Lifelong Learning which has hosted an international summer school for the last ten years. We describe the new learning spaces created and explore the democratic group processes and the collaborative action learning in-volved when discipline and stage of study are set to the side in this multi-paradigmatic, multi-national context. Despite the wide range of participants in terms of length of study, focus and methodological approach, the respite from supervisory pedagogies and the careful critiques of multi-national peer ‘opponents’ is often transformative in the doctoral students’ research sub-jectivities and continuing journeys

    Contribution to the Extragalactic Gamma-ray Background from the Cascades of Very-high Energy Gamma Rays

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    As very-high--energy photons propagate through the extragalactic background light (EBL), they interact with the soft photons and initiate electromagnetic cascades of lower energy photons and electrons. The collective intensity of a cosmological population emitting at very-high energies (VHE) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. We calculate the cascade radiation created by VHE photons produced by blazars and investigate the effects of cascades on the collective intensity of blazars and the resulting effects on the extragalactic gamma-ray background. We find that cascade radiation greatly enhances the collective intensity from blazars at high energies before turning over due to attenuation. The prominence of the resulting features depends on the blazar gamma-ray luminosity function, spectral index distribution, and the model of the EBL. We additionally calculate the cascade radiation from the distinct spectral sub-populations of blazars, BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs), finding that the collective intensity of BL Lacs is considerably more enhanced by cascade radiation than that of the FSRQs due to their harder spectra. As such, studies of the blazar contribution to the EGRB by Fermi will have profound implications for the nature of the EBL, the evolution of blazars, and blazar spectra.Comment: 2009 Fermi Symposium, eConf Proceedings C09112

    Using Automatic Static Analysis to Identify Technical Debt

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    The technical debt (TD) metaphor describes a tradeoff between short-term and long-term goals in software development. Developers, in such situations, accept compromises in one dimension (e.g. maintainability) to meet an urgent demand in another dimension (e.g. delivering a release on time). Since TD produces interests in terms of time spent to correct the code and accomplish quality goals, accumulation of TD in software systems is dangerous because it could lead to more difficult and expensive maintenance. The research presented in this paper is focused on the usage of automatic static analysis to identify Technical Debt at code level with respect to different quality dimensions. The methodological approach is that of Empirical Software Engineering and both past and current achieved results are presented, focusing on functionality, efficiency and maintainabilit
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