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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Uninterruptible power supply system using a dual converter in quasi-resonant mode

Schmidt, Uwe January 1995 (has links)
Uninterruptible Power Supply (UPS) systems have become a standard to protect electronic devices such as servers and host computers. Also, the energy supply of whole buildings is linked with large UPS systems to ensure a steady power flow. Two system configurations are widely used which differ in price and their ability to protect very sensitive load. This thesis illustrates an analytical examination of all existing systems and concludes with the finding of new configurations with increased efficiency and reduced costs. A dual converter is proposed as the heart of the new UPS system. This converter links the necessary two sources of the UPS through a common transformer. The transformer operates at a high frequency which is enabled due to the resonant switching technique used. The results of this paper were achieved using mathematical analysis, electrical and electro-magnetic simulation as well as by experiments carried out on the self designed circuit boards in the laboratory. These boards were built in a modular way to enable series testing and thereby optimise the dimensioning of the system.
2

Research and Development for DSP-based ON-Line Uninterruptible Power Supply with Parallel Operation

Tseng, Kuo-Tung 12 July 2002 (has links)
The thesis is accomplished two DSP-based On-Line UPS using voltage and current control to implement the parallel operation. Each inverter in the parallel operation system has the same control method. The system can reduce the zero crossover distribution causing by SPWM and the influence causing by load variation with inner current and outer voltage loop control which are taking advantage of P and PI control respectively. On the premise of the same system parameters, the two system can achieve the synchronous between phase and frequency by the control of digital PLL circuit to eliminate the circulation current.
3

Research and Development for Uninterruptible Power Supply with DSP Control Unit and USB2.0 Communication Interface

Chen, Yen-Kuang 27 July 2003 (has links)
The thesis is one DSP-based On-Line UPS with USB2.0 communication interface and monitor software. The system is consisting of three sub-systems. The sub-system one is the DSP development system:First step, it uses the DSP to generate the PWM signal to inverter.Second step,ultilizes the ADC module of the DSP to implement the P type current controller in the inner feedback loop and P-I type voltage controller in the outer feedback loop.Third step,accomplishes the synchronous detection via ETU. And then transfer the UPS system parameters to USB2.0 development board through EMI.The sub-system two is the USB2.0 development system and the monitor software:The function of this sub-system is to transmit the parameters from DSP to PC in the specification of USB2.0.In order to achieve the goal, the firmware is required for the USB development board.Once the monitor software is activated, the firmware is downloaded to the board.The sub-system three is the electronic devices:like inverter¡Bconverter¡Bpfc¡Bpower board¡Bbattery etc.Those devices constitute the fundamental hardware circuits modules of the UPS.
4

Implication des enzymes de déubiquitination associés au protéasome dans la pathogénie du mélanome / Non communiqué

Didier, Robin 07 December 2018 (has links)
Le mélanome cutané est un cancer très agressif, responsable de 80% des décès liés aux cancers de la peau. Le mélanome métastatique (MM) est souvent résistant à la radiothérapie et aux chimiothérapies. Sa progression est majoritairement initiée par des mutations oncogéniques des gènes BRAF et NRAS activant la voie de prolifération MEK/ERK. Le MM est difficile à traiter malgré le succès de nouveaux traitements (thérapies ciblant l’oncogène BRAFV600E et immunothérapies), qui sont cependant limités à certains patients. De plus l'émergence de résistances ne permet pas d’obtenir une réponse durable, ce qui incite à rechercher de nouvelles cibles tumorales. Dans les cellules cancéreuses, l’accumulation d’altérations génétiques et le fort index prolifératif accroissent leur addiction aux mécanismes de contrôle de la qualité du protéome, comme le système ubiquitine-protéasome (UPS). L’UPS comprend une machinerie protéolytique (le protéasome 26S) et un réseau d’enzymes régulant l’ubiquitination de protéines cibles. La réaction enzymatique de retrait de l’ubiquitine est la déubiquitination, réalisés par de protéases spécifiques appelées DéUBiquitinases (DUBs). Malgré l’importance des DUBs dans de nombreuses situations pathologiques comme le cancer, leur implication dans la physiopathologie du mélanome est mal connue. Afin d’identifier des DUBs dont l’activité est modulée dans le mélanome, nous avons utilisé une méthode d’étiquettage biochimique in vitro des DUBs actives (‘’DUB trap assay’’) qui nous a permis d’identifier USP14 (Ubiquitin Specific Protease 14) dont l’activité est augmentée dans nos lignées de mélanome par rapport aux mélanocytes. USP14 est associée physiquement au protéasome, avec un rôle important sur la protéostasie cellulaire en général. L’analyse de données bioinformatiques publiques confirme l’importance de USP14 dans le mélanome en associant l’expression du gène USP14 à la progression du mélanome et à un mauvais pronostic. Nous avons ensuite montré que cibler USP14 par des approches génétique (siRNA) ou pharmacologique (inhibiteurs de l’activité) a un effet anti-mélanome in vitro et in vivo, associé à une accumulation de protéines polyubiquitinées, générant un stress du réticulum endoplasmique, la dépolarisation de la mitochondrie et une production de ROS, aboutissant à une mort indépendante des caspases. Cet effet cytotoxique est obtenu indépendamment du statut mutationnel des protéines oncogéniques (BRAFV600E, NRAS, NF1), des suppresseurs de tumeurs (TP53, PTEN), du niveau de résistance aux thérapies ciblées ou du statut phénotypique des mélanomes. Ces résultats indiquent que USP14 représente une nouvelle cible thérapeutique pertinente dans le mélanome. Dans la continuité de ces travaux, j’ai cherché à identifier d'autres DUBs pouvant jouer un rôle dans la prolifération et la survie des cellules de mélanome en réalisant le criblage d'une banque de siRNA ciblant 90 DUBs sur une lignée de cellules de mélanome. Outre le fait de confirmer l’implication de USP14 dans la prolifération du mélanome, ce criblage génétique révèle que la déplétion d’une autre DUB associée au protéasome a un puissant effet antiprolifératif sur les cellules de mélanome. Nos travaux préliminaires montrent que le ciblage de cette nouvelle DUB se traduit par un arrêt de prolifération suivi d’une mort cellulaire associée à des dommages à l’ADN in vitro et in vivo. Dans l’ensemble, mes travaux de thèse révèlent un rôle essentiel des DUBs associées au protéasome dans la prolifération et la survie du mélanome, et ouvrent la piste à de nouvelles stratégies thérapeutiques ciblant les mécanismes aberrants de la protéostasie tumorale de ce cancer. / Non communiqué
5

Fuel cell based battery-less ups system

Venkatagiri Chellappan, Mirunalini 10 October 2008 (has links)
With the increased usage of electrical equipment for various applications, the demand for quality power apart from continuous power availability has increased and hence requires the development of appropriate power conditioning system. A major factor during development of these systems is the requirement that they remain environment-friendly. This cannot be realized using the conventional systems as they use batteries and/or engine generators. Among various viable technologies, fuel cells have emerged as one of the most promising sources for both portable and stationary applications. In this thesis, a new battery less UPS system configuration powered by fuel cell is discussed. The proposed topology utilizes a standard offline UPS module and the battery is replaced by a supercapacitor. The system operation is such that the supercapacitor bank is sized to support startup and load transients and steady state power is supplied by the fuel cell. Further, the fuel cell runs continuously to supply 10% power in steady state. In case of power outage, it is shown that the startup time for fuel cell is reduced and the supercapacitor bank supplies power till the fuel cell ramps up from supplying 10% load to 100% load. A detailed design example is presented for a 200W/350VA 1- phase UPS system to meet the requirements of a critical load. The equivalent circuit and hence the terminal behavior of the fuel cell and the supercapacitor are considered in the analysis and design of the system for a stable operation over a wide range. The steady state and transient state analysis were used for stability verification. Hence, from the tests such as step load changes and response time measurements, the non-linear model of supercapacitor was verified. Temperature rise and fuel consumption data were measured and the advantages of having a hybrid source (supercapacitor in parallel with fuel cell) over just a standalone fuel cell source were shown. Finally, the transfer times for the proposed UPS system and the battery based UPS system were measured and were found to be satisfactory. Overall, the proposed system was found to satisfy the required performance specifications.
6

Do Dynamic Capabilities influence the Growth of Start-Ups? : A Study within the German E-Commerce Sector

Henrichs, Matthias, Kreutz, Michael January 2015 (has links)
No description available.
7

An assessment of growth potential of South African startups adopting early internationalisation strategies

Smit, Ettienne 04 August 2012 (has links)
Most studies of multinational organisations (MNE’s) have been focused on large mature corporations. Traditional literature explains that firms internationalise after a certain level of domestic maturity and wield a significant amount of economic power to withstand the threat of international competition (Oviatt, McDougall, 1993, p. 29)However, this premise has changed in recent years with the adoption of new legislation and technologies that allow firms to become established MNE’s much sooner, with many of these pursuing rapid internationalisation strategies.If the traditional notions of staged theory no longer hold true and new behavioural aspects are driving small businesses to internationalise, it is essential for researchers to gain insights into new firm development, survival and growth in the South African context. Firm growth is of particular interest where globalised SME’s are concerned. / Dissertation (MBA)--University of Pretoria, 2012. / Gordon Institute of Business Science (GIBS) / unrestricted
8

Pop upstart: Making the case for pop-up placemaking in old South Baton Rouge

January 2013 (has links)
0 / SPK / specialcollections@tulane.edu
9

Från att vara en start-up till att bli en framgångsrik scale-up : En kvalitativ studie om viktiga faktorer i tillväxtresan för start-ups utifrån ett medarbetarperspektiv

Ahmed, Riyam, Strindeby Grafström, Felix January 2022 (has links)
Introduction: This study conceptualizes and provides a description of 'organizational readiness' from an employee perspective for a start-up to achieve success in their growth journey. Purpose: The study aims to gain a deeper understanding of how employees within a start-up experience the growth phase. Method: The study is of a qualitative orientation and is based on collected data from interviews with nine employees from two companies. Results: The results show that employees within start-ups are attracted to the high pace of such companies, and that their motivation lies within the ability to work hard, and be an integral part of the company's decision making processes and journey into the scale-up phase. This is offset by micromanaging and a sense of being disconnected from the companies core structures. Conclusion: Leadership within start-ups plays a vital part in the companies growth, where the entrepreneurial leader may be essential in the start-up phase, but not necessarily in the scale-up phase.
10

UPS system : how current and future technologies can improve energy efficiency in data centres

Milad, Muftah A. January 2017 (has links)
A data centre can consist of a large group of networked servers and associated power distribution, networking, and cooling equipment, all that application consumes enormous amounts of energy as a small city, which are driving to a significant increase in energy inefficiency problems in data centre, and high operational costs. Also the massive amounts of computation power contained in these systems results in many interesting distributed systems and resource management problems. In recent years, research and technologies in electrical engineering and computer science have made fast progress in various fields. One of the most important fields is the energy consumption in data centre. In recent years the energy consumption of electronic devices in data centre, as reported by. Choa, Limb and Kimb, nearly 30000000 kWh of power in a year, may consume by a large data centre and cost its operator around £3,000,000 for electricity alone. Some of the UK sites consume more than this. In the UK data centre the total power required are amid 2-3TWh per year. Energy is the largest single component of operating costs for data centres, varying from 25-60%. Agreeing to many types of research, one of the largest losses and causes of data centre energy inefficiency power distribution is from the uninterruptible power supply (UPS). So a detailed study characterized the efficiencies of various types of UPSs under a variety of operating conditions, proposed an efficiency label for UPSs, also investigate challenges related to data centre efficiency, and how all new technologies can be used to simplify deployment, improve resource efficiency, and saving cost. Data centre energy consumption is an important and increasing concern for data centre managers and operators. Inefficient UPS systems can contribute to this concern with 15 percent or more of utility input going to electrical waste within the UPS itself. For that reason, maximizing energy efficiencies, and reduce the power consumption in a data centre has become an important issue in saving costs and reducing carbon footprint, and it is necessary to reduce the operational costs. This study attempts to answer the question of how can future UPS topology and technology improve the efficiency and reduce the cost of data centre. In order to study the impact of different UPS technologies and their operating efficiencies. A model for a medium size data centre is developed, and load schedules and worked diagrams were created to examine in detail and test the components of each of the UPS system topologies. The electrical infrastructure topology to be adopted is configured to ‘2N’ and ‘N+1’ redundancy configuration for each UPS systems technologies, where ‘N’ stands for the number of UPS modules that are required to supply power to data centre. This work done at RED engineering designs company. They are professionals for designing and construction of a new Tier III and Tier IV data centres. The aim of this work is to provide data centre managers with a clearer understanding of key factors and considerations involved in selecting the right UPS to meet present and future requirements.

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