225 research outputs found
The importance of achieving sex- and gender-based equity in clinical trials: a call to action
No full textUS telecommunications policy in the executive branch : The OTP and reorganisational alternatives
No full textThe author presents a critical assessment of the requirements of the government in telecommunications. He analyses the successes and failures of the Office of Telecommunications Policy, examines its relationships with other federal agencies, and describes the tradeoffs implicit in several of the alternatives available to it. The author concludes with recommendations for restructuring telecommunications policy in the new administration.
Dynamics and Control of a Steer-by-Wire Bicycle
No full textAlready for some time, electronic enhancements regarding vehicle behavior has made its way into the aviation and automotive industry by the term "by-wire" technology. Electronic sensors and actuators are used to replace traditional mechanical systems in which software is used to operate the actuators in a way that is not possible with traditional mechanical systems. The use of steer-by-wire technology can also offer great opportunities on single-track vehicles like motorcycles, scooters and bicycles. Single-track vehicles can be highly unstable, especially at low forward speeds and they require a relative high amount of rider control. By replacing the mechanical connection between the handlebar- and steering-assembly with electronic actuators, a controller can be used to control the dynamic behavior of the bicycle based on additional sensor information. This research has focused on the modeling and simulation of a steer-by-wire control strategy to modify and enhance the lateral stability of a bicycle at low forward speeds. Case studies show additional capabilities of a steer-by-wire system on bicycles to influence its dynamic behavior, by providing a dynamic response comparable to a bicycle with a virtually different geometry or even the ability to stabilize an inherently unstable bicycle. A steer-by-wire bicycle prototype was designed and build by replacement of the mechanical connection between handlebarand steering-assembly by electronic actuators and a custom digital controller. The steer-bywire bicycle prototype equipped with sensors, measuring the forward speed- and roll-rate is subsequently used to experimentally evaluate the proposed control algorithms. Test results obtained from experiments conducted by the steer-by-wire bicycle prototype equipped with a stabilizing controller algorithm, show the ability to stabilize the lateral motion of the bicycle-rider combination at low forward speeds as predicted by numerical simulations. Rider steer effort is reduced which makes the bicycle more easy to ride and could lead to future implementation on bicycles tailored for elderly or those physically impaired. The importance of steer torque feedback is indicated by comparison of steer effort measurement results between experiments with and without steer torque feedback at the handlebar.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin
Dynamic Interaction Between Event Deck Structures and a Jumping Crowd: The influence of human-structure interaction on impact force peaks and internal stresses
No full textHuman-induced rhythmic loading is an increasingly critical aspect in the design process of civil engineering structures such as sports stadiums and floors accommodating gym and aerobic classes. There are two main reasons for this trend. First, structures are becoming more slender with improvements in materials and construction techniques and modern trends in architectural designs. And second, crowds are getting livelier than previously was the case, their activities can become better synchronized due to the presence of various auditory and visual stimuli at above mentioned events.In recent years there is also a growing discussion on the strength and stability of event structures. A very common type of structure is an event deck structure. Visitors gather on top of these decks during festivals and in some cases festival organizers place bars underneath them to efficiently use the structure. Personnel working in these bars experience the movement of the structure due to a dancing crowd and tend to feel uncomfortable. Engineers at Tentech are aware of this phenomenon through contacts with clients.Nowadays, in the Netherlands, event deck structures are designed to withstand a vertical static load of 5 , prescribed by Dutch design codes. The amplitude of this static load is based on a dense static crowd. But according to existing literature, a synchronically jumping crowd can cause a vertical load which far exceeds the design load prescribed by design codes. This provides a reason to further investigate the extreme load case of a synchronically jumping crowd on an event deck structure.A missing element in the standard design of structures subjected to a synchronically jumping crowd is the consideration of dynamic interaction between human and structure. In this research the focus is on how human-structure interaction (HSI) can influence the human-induced loading and the internal stresses caused by that loading in the structure. This is done by building a 3D finite element model in Abaqus.A 3D finite element model is used to easily vary in the position of a jumper on the structure. Modelling group effects such as the coordination factor is also easier when using a 3D model. And in the case of an event deck structure a 3D model will result in more detailed results compared to 2D models because mechanical properties of an event deck can vary over the third dimension.A mass-spring system is suggested to represent a jumping person. To simulate a synchronically jumping crowd, multiple mass-spring systems are used. By assigning an initial velocity to the mass in the mass-spring system, it is possible to simulate a similar mechanism as a jumping person colliding with a structure. By analysing the force in the spring over time it is possible to draw conclusions on the influence of human-structure interaction on the impact peak force. And by comparing the impact forces with the reaction forces which are measured at the base of the structure, the effects of structural vibrations on the internal stresses are determined.It is found that taking HSI into account does influence the impact peak force and the internal stresses of the structure. But for an event deck structure with a natural frequency of 20 Hz or higher, this only accounts for an individually jumping person. It is found that the more people jump on a structure, the less significant the effect of HSI will be, even when a crowd tries to jump synchronically. This is caused by the natural time lag between each jumping person.Civil Engineering | Structural Engineering | Structural Mechanic
Van meten naar inzicht? / Onderzoek naar een evaluatiemethode ter bevordering van het inzicht in digitale dienstverlening binnen de gemeente Delft.
No full textTechnology, Policy and Managemen
Greening Information Technology (IT) Infrastructures: Designing a green IT assessment methodology that supports IT decision-makers contribute to corporate responsibility strategy
No full textIntroduction There are several issues and opportunities with regard to information technology (IT). On the one hand, the IT industry is responsible for a large amount of global GHG emission, water pollution, depletion of scarce materials, growing volumes of e-waste and the largest release of hazardous waste worldwide. On the other hand, IT is an important source of cost efficiency and competitive advantage. Examples of economic opportunities of making IT greener are cost saving, risk reduction, innovation and prevention of resource restriction. Moreover, the social impact of the IT industry is immense. IT might be manufactured from minerals from military conflict zones or produced under derived working conditions. These examples of environmental, economic and social implications of IT illustrate that IT should constitute a significant part of an organisation’s sustainability policy and corporate responsibility (CR) strategy. But how can an IT decision-maker contribute to this? It is expected that a framework providing insights into the greenness of the hardware IT infrastructure of an organisation could support IT decision-makers contribute to the overall CR strategy of organisations. Consequently, the research question of this thesis project has been formulated as follows: What generic framework based upon environmental and economic life cycle assessment criteria could be developed to assess the relative greenness of the hardware IT infrastructure of an organization as a step towards a comprehensive corporate responsibility strategy? In essence this research addresses environmental and economic aspects of IT, often referred to as green IT. Emphasis is put on environmental sustainability and costs associated with the physical IT infrastructure supporting business applications through processing, transferring or storing computer programs or data. This is referred to as the greening the hardware IT infrastructure. The purpose of this research is to understand how an IT decision-maker can contribute to CR strategy by addressing several environmental issues efficiently. These environmental issues are related to water use, energy use and raw material use, greenhouse gas (GHG) emissions and generation of electronic and electrical waste (WEEE). Research methodology To structure and guide the explorative research of designing a new framework, the design science research by Hevner et al. (2004) is applied. The design science research is an outcome based research methodology that focuses on designing artefacts. Basically this methodology consists of three types of iterations; relevance, rigor and design. To establish rigor and relevance literature was reviewed from the knowledge base (rigor) and design requirements were analysed from stakeholder interviews (relevance). This information constitutes the academic and practical grounding of the new artefact. To design a new framework three design iterations were carried out; two formative validations by expert panels and one operational validation through a case study. Results The outcome of the design process was a new framework that can be used to assess the greenness of an organisation’s hardware IT infrastructure. The framework consists of several viable performance indicators related to energy use, water use, GHG emission and generation of raw material waste at organisational level (see Chapter 7). The operationalization of these can be found in the functional design in Chapter 8. The functional design describes how the performance indicator scores can be estimated and aggregated into assessment criteria scores and an index. The assessment criteria were defined as follows: 1. Water use over the life cycle of hardware IT (m3) 2. Energy use over the life cycle of hardware IT (MJ) 3. Generation of waste over the life cycle of hardware IT (kg) 4. Greenhouse gas emissions over the life cycle of hardware IT (ton CO2) 5. Costs over the life cycle of hardware IT (euro) The index is entitled the Hardware IT infrastructure Greenness (HITIG) index. The HITIG index can be determined by applying the weighted sum method. This requires normalization and weighing of assessment criteria. At the moment normalization is not possible as an unbiased reference score cannot be established. Evaluation, reflection and recommendations Although three design iterations were carried out to design the new framework, the framework design process and the artefact have several limitations. First, the expert panel reviews have several limitations. The panels were small and expert opinions about which design requirement constituted “core requirements” differed between the panels. Second, the case study research had several limitations. Data used to estimate some of the performance indicators in the case study was deprived. Moreover, the external validity of the framework is limited as only one case study was executed with a limited number of hardware IT infrastructure units. Third, a limited number of aspects related to sustainability have been incorporated in the new framework. Environmental issues have been limited resource usage (water, energy and raw materials), GHG emission and waste generation and economic aspects have been limited to costs. Social implications of sustainability have not been included at all. Fourth, measuring performance is challenging and using indicators to assess the greenness of hardware IT is a reductionist tool that possibly cannot encapsulate the complexity of sustainability and greenness of IT. Lastly, several experts from KPMG have been involved in the definition of design requirements and the expert panel reviews. This could have biased the framework, but this cannot be completely proven. To deal with the shortcomings of the new framework several things could be done. The external validity of the framework could be enhanced by carrying out additional case studies in which different units of analysis are investigated. The functional design could be improved by incorporating more accurate and up-to-date data. The framework could be further expanded to incorporate additional economic and environmental aspects and social implications of IT. Land use, hazardous waste, quality and working conditions are examples of four aspects that could be incorporated in the framework. Furthermore, the framework could be accompanied with a management process to ensure an organisations’ progress is measured over time. The management process could be based upon the plan-do-check-act (PDCA) cycle. Implementing a new management process or integrating the framework in an already existing environmental management process could require awareness of green and sustainable IT within an organisation as well as a clear governance structure. Conclusion and further research The new framework can be used to determine the greenness of the hardware IT infrastructure of an organisation as a step towards a comprehensive CR strategy when incorporated in a measurement process. The framework supports achieving the desired green IT assessment criteria scores. Organisations can use the outcome of periodical measurements from the framework to, if required, adjust their policies in order to achieve the CR goals as part of their CR strategy. The framework can be used to assess green IT progression related to energy use, water use, generation of raw material waste, GHG emission and costs over the life cycle of hardware IT. Assessing the relative greenness of the hardware IT infrastructure of an organisation would require implementing the framework in a continuous management process. Measuring the hardware IT infrastructure greenness with the purpose of benchmarking results, it is recommended organisations apply the same calculation methodology to ensure consistency and comparability of results. For further research it is recommended to investigate how social aspects can be incorporated in the framework to ensure a more balanced contribution to CR strategy. It is also recommended to improve the quality of certain data used in the functional design and to extend the scope of environmental and economic sustainability aspects in the framework. Furthermore, research should focus on improving the framework through additional refinement cycles. Particularly important are additional case studies to test the general applicability of the framework, further refine the functional design and evaluate the use of the framework over time as part of a continuous management process.Systems EngineeringTechnology, Policy and Managemen
Crises beter in beeld. Effectievere crisisbeheersing door verspreide samenwerking.
No full textTechnology, Policy and Managemen
Efecto de la Suplementación con Diferentes Niveles de Concentrado en la Producción de Vacas en Pastoreo
Get PDFLa producción lechera en el trópico está limitada por el pobre valor nutritivo de los pastos tropicales tanto en lo que respecta a su bajo contenido de proteína (Glover y Dougal, 1961) como de energía. Appelman y Dirven (1959) encontraron que la energía del pasto Pangóla (Digitaria decumbens) no permite producir más de 8 a 9 kg de leche/día, por lo que García y Pérez (1975) sugieren suplementar las vacas después del cuarto kg de leche
The Future of Delft Open Courseware
No full textcourse materials online from September 2007 in a projec
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