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Parsons, Erin M. "Control system design for a continuous passive motion machine." Connect to resource, 2010. http://hdl.handle.net/1811/45477.
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Jennings, Kirk E. "Design guidelines for a rule-based passive surveillance system." Thesis, Monterey, California: U.S. Naval Postgraduate School, 1986. http://hdl.handle.net/10945/21768.
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Patalano, Giovanbattista. "Risk-informed design changes for a passive cooling system." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/44780.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.Includes bibliographical references (p. 47-49).
The failure probability of a passive decay heat removal system after a LOCA is evaluated as part of a risk-informed design process for a helium-cooled fast reactor. The system was modeled using RELAP5-3D. The epistemic uncertainties in input parameters as well as the epistemic model uncertainties in the code were assessed and propagated through the model using Latin hypercube sampling. The changes in the design that we investigated reduced the overall failure probability of the system by reducing the impact of the major contributor to the failure probability. Sensitivity analyses led to two unexpected results. First, the key factors affecting the system failure probability are the location of the thermal insulation (inside or outside the hot leg) and the uncertainty in the insulation thermal conductivity. Second, the heat transfer coefficient in the core is not as important as one might expect. Our results show that the heat transfer coefficient in the containment structures is more important. Different methods for sensitivity analysis were applied and gave consistent results.
Giovanbattista Patalano.
S.M.
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Zuo, Lei 1974. "Element and system design for active and passive vibration isolation." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30341.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2005.Includes bibliographical references (p. 277-294).
This thesis focusses on broadband vibration isolation, with an emphasis on control of absolute payload motion for ultra-precision instruments such as the MIT/Caltech Laser-Interferometric Gravitational Wave Observatory (LIGO), which is designed to measure spatial strains on the order of 10-²¹. We develop novel passive elements and control strategies as well as a framework for concurrent design of the passive and active elements of single-stage and multi-stage isolation systems. In many applications, it is difficult to construct passive isolation systems compliant enough to achieve specifications on low-frequency ground transmission without introducing hysteresis as well as high-frequency transmission resonances. We develop and test a compliant support that employs a post-buckled structure in con- junction with a compliant spring to attain a low-frequency, low-static-sag mount in a compact package with a large range of travel and very clean dynamics. Most passive damping techniques increase ground transmission at high frequency, but tuned-mass dampers are decoupled from the ground. We explore the tuned-mass damper as a passive realization of the skyhook damper, obtain the optimal designs for multiple-SDOF systems of dampers, propose the concept of a multi-DOF damper, and show that MDOF dampers that couple translational and rotational motion have the potential to provide performance many times better than that traditional tuned-mass dampers. Active control can be used to improve low-frequency performance, but high-gain control can amplify sensor and actuator noise or cause instability. We study several control strategies for uncertain plants with high-order dynamics.
(cont.) In particular, we develop a novel control strategy, "model-reaching" adaptive control, that drives the system onto a dynamic manifold defined directly in terms of the states of the target. The method can be used to robustly increase the apparent compliance of an isolation mount and maintain a -40 dB/decade roll-off above the resulting corner frequency.
by Lei Zuo.
Ph.D.
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Perodou, Arthur. "Frequency design of passive electronic filters : a modern system approach." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC046.
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L’explosion actuelle du nombre d’appareils connectés (smartphones, drones, IoT, …) et du volume des données à transmettre engendre une croissance exponentielle du nombre de bandes radiofréquences. Toutes les solutions élaborées pour faire face à cette demande croissante, telle que l’agrégation de porteuses, impliquent de concevoir des filtres fréquentiels satisfaisant des contraintes (performance, consommation d’énergie, coût, …) toujours plus strictes. Les filtres passifs AW, pour acoustic wave (AW) en anglais, semblant être les seuls pouvant satisfaire ces contraintes. Cependant, face à l’augmentation drastique de la complexité de leur problème de conception, les méthodes traditionnelles de conception apparaissent limitées. Il devient donc nécessaire de développer de nouvelles méthodes, qui soient systématiques et efficaces d’un point de vue algorithmique. Le problème de synthèse des filtres AW est une instance du problème de synthèse de filtres électroniques passifs, intrinsèquement lié aux origines de la théorie des Systèmes linéaires et de l’Automatique. Des méthodes systématiques ont été développées pour des cas particuliers, tels que les filtres LC-échelle, mais n’incluent pas les filtres AW. Notre but est donc de les revisiter et de les généraliser en utilisant une approche systémique moderne, afin d’obtenir une méthodologie systématique et efficace de conception de filtres électroniques passifs, avec un intérêt particulier pour les filtres AW. Pour ce faire, le paradigme de l’optimisation convexe, et particulièrement la sous-classe nommée optimisation LMI, nous paraît être un candidat naturel. Doté de solveurs efficaces, il permet de résoudre un large éventail de problèmes d’ingénierie en un faible temps de calcul. Afin de relier notre problème de conception à cet environnement, il est proposé d’utiliser des outils modernes tels que la représentation LFT et la caractérisation mathématique dite de dissipativité. Historiquement, deux approches de conception se sont opposées. La première consiste à faire varier les valeurs caractéristiques des composants jusqu’à satisfaction du gabarit fréquentiel. Bien que flexible et proche de la formulation originelle du problème, cette approche aboutit typiquement à un problème d’optimisation complexe. Notre première contribution est d’avoir révélé les sources de cette complexité ainsi que de les avoir considérablement réduites, en introduisant une représentation originale qui résulte de la combinaison de l’outil LFT et du formalisme des Systèmes Hamiltoniens à Ports. Un algorithme résolvant séquentiellement des problèmes LMIs est proposé, possédant un taux de convergence raisonnable si le point initial est bien choisi. La seconde approche se compose de deux étapes. Une fonction de transfert est d’abord synthétisée de façon à satisfaire le gabarit fréquentiel. Cette étape correspond à un problème classique d’Automatique et de Traitement du Signal qui peut être efficacement résolu via l’optimisation LMI. Puis, cette fonction de transfert est réalisée comme un circuit avec une topologie donnée. Pour cela, elle doit satisfaire des conditions de réalisation. Ces dernières ne peuvent pas toutes être inclues dans la première étape, et nous formalisons certaines pratiques courantes pour en considérer le plus possible. Cela nous mène à résoudre le problème général de synthèse fréquentielle de filtres LFT. Notre seconde contribution est d’avoir fourni des méthodes de synthèse efficaces, à base d’optimisation LMI, pour résoudre certains sous-problèmes. Cela est accompli en généralisant la technique de la factorisation spectrale conjointement avec l’utilisation des extensions du Lemme KYP. Pour certains filtres électroniques passifs, comme les filtres LC-échelle passe-bande, la seconde approche permet de résoudre efficacement le problème de conception associé. Plus généralement, elle procure un point initial à la première approche, comme illustré dans le cas d’un filtre AWThe current explosion of communicating devices (smartphones, drones, IoT...), along with the ever-growing data to be transmitted, produces an exponential growth of the radiofrequency bands. All solutions devised to handle this increasing demand, such as carrier aggregation, require to synthesise frequency filters with stringent industrial requirements (performance, energy consumption, cost ...). While the technology of acoustic wave (AW) resonators, that seem to be the only passive micro-electronic components available to fulfil these requirements, is mature, the associate design problem becomes dramatically complex. Traditional design methods, based on the intuition of designers and the use of generic optimisation algorithms, appear very limited to face this complexity. Thus, systematic and efficient design methods need to be developed. The design problem of AW filters happens to be an instance of the more general design problem of passive electronic filters, that played an important role in the early development of Linear Control and System theory. Systematic design methods were developed in particular cases, such as for LC-ladder filters, but do not enable to tackle the case of AW filters. Our aim is then to revisit and generalise these methods using a modern System approach, in order to develop systematic and efficient design methods of passive electronic filters, with a special focus on AW filters. To achieve this, the paradigm of convex optimisation, and especially the sub-class of Linear Matrix Inequality (LMI) optimisation, appears for us a natural candidate. It is a powerful framework, endowed with efficient solvers, able to optimally solve a large variety of engineering problems in a low computational time. In order to link the design problem with this framework, it is proposed to use modern tools such as the Linear Fractional Transformation (LFT) representation and a mathematical characterisation coming from Dissipative System theory. Reviewing the different design methods, two design approaches stand out. The first approach consists in directly tuning the characteristic values of the components until the frequency requirements are satisfied. While very flexible and close to the original problem, this typically leads to a complex optimisation problem with important convergence issues. Our first main contribution is to make explicit the sources of this complexity and to significantly reduce it, by introducing an original representation resulting from the combination of the LFT and the Port-Hamiltonian Systems (PHS) formalism. A sequential algorithm based on LMI relaxations is then proposed, having a decent convergence rate when a suitable initial point is available. The second approach consists of two steps. First, a transfer function is synthesised such that it satisfies the frequency requirements. This step is a classical problem in Control and Signal Processing and can be efficiently solved using LMI optimisation. Second, this transfer function is realised as a passive circuit in a given topology. To this end, the transfer function needs to satisfy some conditions, namely realisation conditions. The issue is to get them with a convex formulation, in order to keep efficient algorithms. As this is generally not possible, an idea is to relax the problem by including common practices of designers. This leads to solve some instances of a general problem denoted as frequency LFT filter synthesis. Our second main contribution is to provide efficient synthesis methods, based on LMI optimisation, for solving these instances. This is achieved by especially generalising the spectral factorisation technique with extended versions of the so-called KYP Lemma. For particular electronic passive filters, such as bandpass LC-ladder filters, this second approach allows to efficiently solve the design problem. More generally, it provides an initial point to the first approach, as illustrated on the design of a particular AW filter
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Kopke, Markus. "A passive suspension system for a hydrofoil supported catamaran." Thesis, Stellenbosch : University of Stellenbosch, 2008. http://hdl.handle.net/10019.1/1991.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008.This study investigates practical passive methods to improve the seakeeping of a Hydrofoil Supported Catamaran (Hysucat). The Hysucat is a hybrid vessel combining hydrofoil efficiency with the stability of catamarans. The seakeeping of the Hysucat was initially investigated experimentally to determine what seakeeping improvements are inherent to the Hysucat design. The results showed that the seakeeping is improved by 5-30%. A passive suspension system for the main hydrofoil of the Hysucat was designed and tested. A concept development strategy was followed for the design of the suspension system as such a system had never been investigated previously. Detailed specifications for the design were developed and concepts that could satisfy the customer and engineering requirements were generated. Numerical simulation models for the Hysucat and the final concepts were derived assuming a simplified 2nd order system to describe the seakeeping dynamics of the demi-hulls. Unknown parameters were determined using parameter estimation techniques. Representative parameter values were calculated from multiple towing tank experiments. Theory describing the motion of a hydrofoil in an orbital velocity wave field was combined with the hull model to simulate the Hysucat as well as the suspension system concepts. The models indicated that the concept where the main hydrofoil was attached to a spring loaded arm, that was free to pivot in response to orbital waves, was the most feasible in damping out vertical transmitted accelerations. Experimental tests indicated that little improvement was achieved with the suspension system at low frequencies. At resonance the suspension system was effective in decreasing the heave of the vessel by up to 27%. The pitch and acceleration response results showed improvements at the higher encounter frequencies of up to 50%. The calm water resistance of the vessel increased by 10% over the Hysucat with rigidly attached hydrofoils; however was still 24% less than the hull without foils.
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Bower, Jeffrey R. "An expert system to provide direct gain passive solar design assistance." Virtual Press, 1995. http://liblink.bsu.edu/uhtbin/catkey/941364.
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An expert system has been constructed for the purpose of assisting in the design and analysis of direct gain passive solar environments. This system has been constructed for the use of senior undergraduate architecture students in a computer-based design studio. The primary use of the system is in the role of an educational tool which generates design recommendations from user input and predicts some physical characteristics of the environment.The system is applicable to passive solar environments with vertical, south-facing glazing. The system incorporates three models. The first model represents an attached sunspace with no thermal mass storage. The second model represents a direct gain living space. The third model represents a direct gain living space integrated with thermal mass storage. The third model allows the use of floors, ceilings, and walls as mass for thermal storage. Four representative mass materials (concrete, adobe, common brick, and dense concrete masonry) have been included for comparison purposes. Four representative sub-climates are also incorporated into the system: cold / arid, hot / arid, hot / humid, and cool / humid. For educational purposes, the system makes separate calculations for identical structures based on models for inhabited and uninhabited cases.The system incorporates scientific and mathematical relationships as well as rulesof thumb which have demonstrated their applicability to passive solar design. The system performs calculations based on work by Balcomb, et al. [5, 9], and Duffle and Beckman [1], to estimate environmental temperature swings, total solar energy input, and thermal absorption by mass storage elements. The system also utilizes models based upon work by Mazria [4] to recommend glazing areas. Recommended glazing areas are calculated from user input variables such as structure type, site latitude, and floor area.The system's ease of use allows it to be adapted for various classroom goals, and its generalized nature permits the instructor to adapt it easily into different areas of architectural design curricula. The system is written for use with the CLIPS expert system shell.Department of Physics and Astronomy
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Brittle, John P. "Passive system integration for office buildings in hot climates." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/23912.
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Passive ventilation and cooling systems can offer energy savings when combined into a mechanical ventilation and cooling strategy for office buildings. At early design stages, it is difficult to predict actual energy savings as current design and calculation tools are limited and do not allow assessment for energy reductions when attempting to use typical passive options such as solar chimneys, rain screen facades, ventilated double facades, passive downdraught evaporative cooling and earth ducts. The only passive systems that are directly incumbent to dynamic thermal modelling software are natural ventilation and external solar shading. Currently, impacts of passive systems on annual building energy performance is unclear and lacks clarity. In hot climates, this is even more problematic as buildings need to endure higher external temperatures and solar irradiation. Understanding minimal energy performance reductions for each passive system can aid with design decisions regarding building ventilation and cooling strategies. The aim of this study is to investigate how existing passive ventilation and cooling system design and operational strategies can be improved to reduce mechanical ventilation and cooling energy consumption for commercial buildings in hot climates. Theoretical commercial building models are created using dynamic thermal simulation software to determine minimum mechanical ventilation and cooling energy values, which are verified against published bench marks, known as base case models. These base case models are simulated using weather data from four different hot climates (Egypt, Portugal, Kenya and Abu Dhabi). Impacts of passive system energy performance are afforded by using either dynamic thermal simulation or fundamental steady state analysis identifying approximate passive ventilation and cooling potentials for reducing mechanical energy. These percentage reductions are created based upon passive system parameters and weather data, using appropriate methodology. From these findings new simplified design guidelines, integration strategies and performance design tools are created including a new passive system energy assessment tool (PSEAT) using Microsoft Excel platform to ensure that a wider audience can be achieved in industry. The design guidance and integration strategies are developed and simplified to enable architects, building services engineers and alike, to apply with speed and accuracy influencing the design process and improve confidence in desired passive solution.
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Sarmiento, Leon Mayra Susana. "Testing platform implementation and system integration for an active/passive imager system including readout circuit design." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 5.32 Mb., 170 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3220740.
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Kilaire, Aneel. "Design of an integrated passive and active double facade system for UK offices." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/30860/.
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The Egan Report, changes to Part L Building regulations, and the importance of office workers is challenging designers to improve the construction process, reduce operational carbon emissions, and enhance occupant comfort for office buildings in the United Kingdom. This thesis proposes a double skin facade system with integrated environmental systems to overcome these challenges. The Facade deals with a number of conflicting requirements and a single-storey, naturally ventilated cavity, unitised Double Facade has been proposed to resolve them. The two key determinants for the Active Environmental System have been prefabrication and operational carbon emissions. To address these issues a decentralised system, comprising of a Reversible Air Source Heat Pump, Heat Exchanger, Active Beam and Active Trench is proposed, and integrated into the Double Facade. A key part of the design process has been working with industrial partners to develop the design and realise a full-scale prototype. This has been tested and evaluated in terms of key aspects of the comfort, weather and aesthetic performance. An appraisal of the product demonstrates that it achieves proof of concept; it is highly prefabricated and enhanced occupant comfort and carbon emissions targets can be met.
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Supak, Kevin Robert. "Reduced gravity Rankine cycle system design and optimization study with passive vortex phase separation." Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2094.
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Liquid-metal Rankine power conversion systems (PCS) coupled with a fission reactor
remain an attractive option for space power applications because system specific power
and efficiency is very favorable for plant designs of 100 kW(e) or higher. Potential
drawbacks to the technology in a reduced gravity environment include two-phase fluid
management processes such as liquid-vapor phase separation. The most critical location
for phase separation is at the boiler exit where only vapor must be sent to the turbine
because blade erosion occurs from high velocity liquid droplets entrained by vapor flow.
Previous studies have proposed that rotary separators be used to separate the liquid and
vapor from a two phase mixture. However these devices have complex turbo machinery,
require kilowatts of power and are untested for high vapor flow conditions. The
Interphase Transport Phenomena (ITP) laboratory has developed a low-power, passive
microgravity vortex phase separator (MVS) which has already proven to be an essential
component of two-phase systems operating in low gravity environments.
This thesis presents results from flight experiments where a Rankine cycle was operated
in a reduced gravity environment for the first time by utilizing the MVS for liquid and
vapor phase separation. The MVS was able to operate under saturated conditions and
adjust to system transients as it would in the Rankine cycle by controlling the amount of
liquid and vapor within the device. A new model is developed for the MVS to predict
separation performance at high vapor flow conditions for sizing the separator at the boiler, condenser, and turbine locations within the cycle by using a volume limiting
method. This model factors in the following separator characteristics: mass, pumping
power, and available buffer volume for system transients. The study is concluded with
overall Rankine efficiency and performance changes due to adding vortex phase
separation and a schematic of the Rankine cycle with the integration of the MVS is
presented. The results from this thesis indicate the thermal to electric efficiency and
specific mass of the cycle can be improved by using the MVS to separate the two phases
instead of a rotary separator.
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Karlsson, Simon. "Real-time Location System with Passive RFID for surveillance of trusted objects in a room." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-63803.
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The use of Radio Frequency Identification (RFID) in Real-Time Location Systems (RTLS) in asset management has been in limited use, mainly in large organizations such as hospitals and military. The research in this area is making progress and new solutions with reduced costs with greater resolution are presented by different companies that enable the technology to be used in new operating areas. This thesis is about the development, implementation and integration of a RTLS solution that enables surveillance of the position of keys. The RTLS solution utilizes RTLS hardware to receive the positions of the keys. The report describes how the RTLS hardware is selected and how the software solution is designed and implemented. The report describes also result of how the finished solution with software and hardware cooperates. The most vital problem was to create an efficient zone structure that implements the surveillance hierarchy of the keys. The thesis was conducted at a company (PAAM Systems) that offers solutions in access and asset management. The company aims to use a RTLS in an asset management application for keys. The purpose of this work is to examine the existing solutions on the market that provide a RTLS with passive RFID technology.
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Holland, William S. "Development of an Indoor Real-time Localization System Using Passive RFID Tags and Artificial Neural Networks." Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1249062541.
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Scharfeld, Tom Ahlkvist 1976. "An analysis of the fundamental constraints on low cost passive radio-frequency identification system design." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/45500.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (leaves 110-115).
Passive radio frequency identification (RFID) systems provide an automatic means to inexpensively, accurately, and flexibly capture information. In combination with the Internet, which allows immediate accessibility and delivery of information, passive RFID systems will allow for increased productivities and efficiencies in every segment of the global supply chain. However, the necessary widespread adoption can only be achieved through improvements in performance - including range, speed, integrity, and compatibility - and in particular, decreases in cost. Designers of systems and standards must fully understand and optimize based on the fundamental constraints on passive RFID systems, which include electromagnetics, communications, regulations, and the limits of physical implementation. In this thesis, I present and analyze these fundamental constraints and their associated trade-offs in view of the important application and configuration dependant specifications.
by Tom Ahlkvist Scharfeld.
S.M.
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Lacraru, Lucian Marian. "The design and control of an actively restrained passive mechatronic system for safety-critical applications." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/34439.
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Development of manipulators that interact closely with humans has been a focus of research in fields such as robot-assisted surgery and haptic interfaces for many years. Recent introduction of powered surgical-assistant devices into the operating theatre has meant that robot manipulators have been required to interact with both patients and surgeons. Most of these manipulators are modified industrial robots. However, the use of high-powered mechanisms in the operating theatre could compromise safety of the patient, surgeon, and operating room staff. As a solution to the safety problem, the use of actively restrained passive arms has been proposed. Clutches or brakes at each joint are used to restrict the motion of the end-effector to restrain it to a pre-defined region or path. However, these devices have only had limited success in following pre-defined paths under human guidance. In this research, three major limitations of existing passive devices actively restrained are addressed.
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Podder, Ankur. "Embodied energetics : a digital design-production system for passive solar walls in Vinalhaven Island, Maine." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123560.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Architecture, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 102-105).
I propose a digital design-production system to easily assemble, selectively disassemble, and reassemble novel passive solar walls. The problem statement I tackle is that all houses in Vinalhaven Island, Maine have high home-heating energy burden due to their thermally weak thin walls. Substituting thin walls with typical passive solar walls is a known solution, however such walls would be inundated with (i) high embodied energy in non-recoverable materials, (ii) high complexity of construction, and (iii) high cost of construction and renovation. Facilitated by a CAD-CAM interface, I develop a methodological framework called Design for Assembly, Disassembly, and Reassembly to lower all three parameters efficiently. I demonstrate both the framework and its outcomes by rapidly prototyping a few study models of passive solar walls. I speculate on the urban implications of a widespread integration of walls with reduced and recoverable material embodied energy. In order to effectively visualize this, the system boundary of urbanism scales up from a wall to a house, to two adjacent houses, and finally to five houses in Vinalhaven's downtown. I claim that successful on-site substitution of today's standard walls with Digital Passive Solar Walls will accelerate Vinalhaven's island homes toward a holistic energy transition. Broadly, I encourage professionals in the building industry to embrace such digital systems to recover material embodied energy locked in their designed artifacts.
by Ankur Podder.
S.M.
S.M. Massachusetts Institute of Technology, Department of Architecture
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Lu, Qiuping. "Design, Testing and Modeling of the Direct Reactor Auxiliary Cooling System for FHRs." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462544389.
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Pavlina, John. "DESIGN AND SIMULATION FOR ENCODED PN-OFC SAW SENSOR SYSTEMS." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2827.
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Surface acoustic wave (SAW) sensors provide versatility in that they can offer wireless, passive operation in numerous environments. Various SAW device embodiments may also be employed for retrieval of the sensed data. Single sensor systems typically use a single carrier frequency and a simple device embodiment since tagging is not required. However, it is necessary in a multi-sensor environment to both identify the sensor and retrieve the information. Overlapping sensor data signals in time and frequency present problems when attempting to collect the sensed data at the receiver. This dissertation defines a system simulation environment exclusive to SAW sensors. The major parameters associated with a multi-device system include the transmitter, the channel, and the receiver characteristics. These characteristics are studied for implementation into the simulation environment. A coupling of modes (COM) model for SAW devices is utilized as an accurate software representation of the various SAW devices. Measured device results are presented and compared with COM model predictions to verify performance of devices and system. Several coding techniques to alleviate code collisions and detection errors were investigated and evaluated. These specialized techniques apply the use of time, frequency, and spatial diversity to the devices. Utilizing these multiple-access techniques a multi-device system is realized. An optimal system based on coding technique, frequency of operation, range, and related parameters is presented. Funding for much of this work was provided through STTR contracts from NASA Kennedy Space Center.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
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Whitman, Joshua (Joshua J. ). "Design of passive decay heat removal system for the lead cooled flexible conversion ratio fast reactor." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41690.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.Includes bibliographical references.
The lead-cooled flexible conversion ratio fast reactor shows many benefits over other fast-reactor designs; however, the higher power rating and denser primary coolant present difficulties for the design of a passive decay heat removal system. In order to achieve passive cooling, enhancements are needed over current designs, such as the S-PRISM and ABR, which utilize passive cooling through the reactor vessel to atmospheric air. Enhancements such as axial fins, a perforated plate, and round indentations, or dimples, were considered as additions to the hot air riser to increase heat transfer. Other enhancements include a liquid metal bond between the reactor and guard vessels, and a dual-level design which introduces ambient temperature air halfway up the vessel wall. A code was written in Java to simulate these conditions, leading to a promising case using dimples on the guard vessel wall as the primary mode of heat transfer enhancement, and including the dual-level design. A conservative estimate of dimple performance indicates that during a passive decay heat removal shutdown, bulk primary coolant temperature will peak at 713 'C, giving a 12 OC margin to clad failure. Attempts were made to refine the uncertainty within the calculations using a computational fluid dynamics code, Fluent, but these ultimately were unsuccessful. Additional studies were conducted on the static stress imparted on the vessel, and the dynamic stress caused by a seismic event. The static stress was found to be within ASME code limits. Seismic analysis determined that a seismic isolation scheme would be necessary in order to prevent damage to the vessel during an earthquake.
by Joshua Whitman.
S.B.
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Daghini, Lorenzo. "Improving Machining System Performance through designed-in Damping : Modelling, Analysis and Design Solutions." Doctoral thesis, KTH, Maskin- och processteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93143.
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With advances in material technology, allowing, for instance, engines to withstand higher combustion pressure and consequently improving performance, comes challenges to productivity. These materials are, in fact, more difficult to machine with regards to tool wear and especially machine tool stability. Machining vibrations have historically been one of the major limitations to productivity and product quality and the cost of machining vibration for cylinder head manufacturing has been estimated at 0.35 euro per part. The literature review shows that most of the research on cutting stability has been concentrating on the use of the stability limits diagram (SLD), addressing the limitations of this approach. On the other hand, research dedicated to development of machine tool components designed for chatter avoidance has been concentrating solely on one component at the time. This thesis proposes therefore to extend the stability limits of the machining system by enhancing the structure’s damping capability via a unified concept based on the distribution of damping within the machining system exploiting the joints composing the machine tool structure. The design solution proposed is based on the enhancement of damping of joint through the exploitation of viscoelastic polymers’ damping properties consciously designed as High Damping Interfaces (HDI). The tool-turret joint and the turret-lathe joint have been analysed. The computational models for dimensioning the HDI’s within these joints are presented in the thesis and validated by the experiments. The models offer the possibility of consciously design damping in the machining system structure and balance it with regards to the needed stiffness. These models and the experimental results demonstrate that the approach of enhancing joint damping is viable and effective. The unified concept of the full chain of redesigned components enables the generation of the lowest surface roughness over the whole range of tested cutting parameters. The improved machining system is not affected by instability at any of the tested cutting parameters and offers an outstanding surface quality. The major scientific contribution of this thesis is therefore represented by the proposed unified concept for designing damping in a machining system alongside the models for computation and optimisation of the HDIs. From the industrial application point of view, the presented approach allows the end user to select the most suitable parameters in terms of productivity as the enhanced machine tool system becomes less sensitive to stability issues provoked by difficult-to-machine materials or fluctuations of the work material properties that may occur in ordinary production processes.QC 20120413
DampComat
Production 4 micro
FFI Robust Machining
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Martinez, Cano Pablo. "Thermomechanical Design and Analysis of the Lisa Phase Measurement System." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76509.
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Gravitational Waves (GWs) are ripples in the curvature of spacetime that propagate as waves at the speed of light while travelling basically undisturbed from the moment of their creation by accelerated masses. GWs provide unique information about astrophysical sources, such as binary systems, allowing their exploration under a wide range of masses, mass ratios and physical states inaccessible otherwise and therefore opening a new window to observe the universe. The Laser Interferometry Space Antenna (LISA) mission will be a spaceborne gravitational wave observatory that is expected to be launched in 2034. The observatory will operate a near-equilateral triangle constellation of three spacecraft in formation flying around the Sun with Earth-like orbits. The observatory will establish, for the first time, a huge laser interferometer of three arms separated by 2.5 million km at pm/ p H z sensitivity, allowing detection of GW signals in the low-frequencies (mHz) regime. Using technology proven by LISA Pathfinder and GRACE-Follow on mission, the LISA metrology system will continuously operate heterodyne laser interferometers in order to measure the stretching and squeezing of space-time coupled onto their laser links as pm-level pathlength displacements and recorded as tiny µ-cycle phase fluctuations over thousands of seconds by an on-board instrument so-called Phase Measurement System (PMS) or shortly "Phasemeter”. This master thesis investigates the thermo-mechanical design of an engineering model, currently under early phases of development, for the PMS instrument onboard the LISA S/C. The mechanical enclosure has been designed following a modular approach. Each PCB will be assembled into an individual enclosure, so future upgrades in the design without affecting the entire architecture. The thermal analysis conducted so far has concluded with the feasibility of a passive thermal management system in vacuum environments, based on heat conductivity throughout the mechanical enclosure towards the instrument baseplate. In particular, the following instrument features have been included within the analysis: 1. analog signal conditioning electronics, 2. analog-to-digital conversion, and 3. FPGA core signal processing, 4. high-phase fidelity frequency synthesis and 5. frequency distribution chain, i.e., all features with the most stringent thermal requirements of the PMS-EM architecture. Although the high-power consumption demands of the instrument, the proposed thermo-mechanical design showed a suitable implementation for reliable operation of components, below maximal specified temperature ranges, allowing safe operation of the electronics over mission lifetime. As the proposed design relies only on passive conductive heat transfer methods, it is implicit a reduction of instrument complexity, avoiding complex thermal approaches based on heat pipes distributions or active control systems. Moreover, the modular approach and thermal management system enhances the integration with adjacent modules and reduce cost when assembly the instrument within the payload. In this master thesis, it has been also designed and manufactured several mechanical enclosures, together with an active thermal management system, for preliminary prototyping of analog signal acquisition electronics. These prototypes have been tested in air, setting the thermal stability requirement at the thermal reference point (TRP). Test results have verified a thermal stability requirement below 0.1 K/Hz in order to accomplish with the stringent µ-cycle phase noise performance in the mHz frequency band. Further work will test those prototypes in Vacuum conditions, consolidating thermal modelling and noise coupling as initial precursors of the PMS-EM thermally critical module developments.
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Le, Toan T. "A Single-Stage Passive Vibration Isolation System for Scanning Tunneling Microscopy." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2272.
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Scanning Tunneling Microscopy (STM) uses quantum tunneling effect to study the surfaces of materials on an atomic scale. Since the probe of the microscope is on the order of nanometers away from the surface, the device is prone to noises due to vibrations from the surroundings. To minimize the random noises and floor vibrations, passive vibration isolation is a commonly used technique due to its low cost and simpler design compared to active vibration isolation, especially when the entire vibration isolation system (VIS) stays inside an Ultra High Vacuum (UHV) environment. This research aims to analyze and build a single-stage passive VIS for an STM. The VIS consists of a mass-spring system staying inside an aluminum hollow tube. The mass-spring system is comprised of a circular copper stage suspended by a combination of six extension springs, and the STM stays on top of the copper stage. Magnetic damping with neodymium magnets, which induces eddy currents in the copper conductor, is the primary damping method to reduce the vibrations transferred to the mass-spring system. FEMM and MATLAB® are used to model magnetic flux density and damping coefficients from eddy current effect, which will help determine the necessary damping ratios for the VIS. Viton, which demonstrates a high compatibility with vacuum environments, will also serve as a great damping material between joints and contacts for the housing tube. Viton will be modeled as a Mooney-Rivlin hyperelastic material whose material parameters are previous studied, and Abaqus will be used as a Finite Element Analysis software to study the Viton gaskets’ natural frequencies. The natural frequencies of the aluminum hollow tube will also be investigated through Abaqus.
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Ayoub, Ayoub, and Carl Martin Berg. "Design of a Dynamic Boom Suspension System in a Hybrid Wheel Loader." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-39740.
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Wheel loaders are under the influence of low frequency vibrations that may be harmful for the health of the operator, and for the productivity of the machine. The strong vibrations can significantly impact the operation of the machine since they are not equipped with wheel suspension systems and due to their work environment in rough terrains with uneven surfaces. The risk of spilling or dropping the load is also increased and they can introduce higher mechanical stress that can wear out parts faster. The focus of this thesis work is to develop an approach for damping these vibrations dynamically by improving the functionality of the electrohydraulic system in Volvo's prototype wheel loader LX1. The dynamic damping system controls the cylinder of the lift framework to make it behave as a damper. The system utilizes the lift cylinder pressure and piston position as feedback to adjust the oil flow in the cylinder using the proposed control system. Results indicate that the proposed technique is capable of attenuation that is comparable with the existing boom suspension system based on accumulators through simulations and experimental tests.
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Teng, Xuan. "Internal Navigation through Interval Vibration Impacts for Visually Impaired Persons: Enhancement of Independent Living." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471347436.
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Parsons, Kevin Kenneth. "Design and Simulation of Passive Thermal Management System for Lithium-ion Battery Packs on an Unmanned Ground Vehicle." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/912.
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The transient thermal response of a 15-cell, 48 volt, lithium-ion battery pack for an unmanned ground vehicle was simulated with ANSYS Fluent. Heat generation rates and specific heat capacity of a single cell were experimentally measured and used as input to the thermal model. A heat generation load was applied to each battery and natural convection film boundary conditions were applied to the exterior of the enclosure. The buoyancy-driven natural convection inside the enclosure was modeled along with the radiation heat transfer between internal components. The maximum temperature of the batteries reached 65.6 °C after 630 seconds of usage at a simulated peak power draw of 3,600 watts or roughly 85 amps. This exceeds the manufacturer's maximum recommended operating temperature of 60 °C. The pack was redesigned to incorporate a passive thermal management system consisting of a composite expanded graphite matrix infiltrated with a phase-changing paraffin wax. The redesigned battery pack was similarly modeled, showing a decrease in the maximum temperature to 50.3 °C after 630 seconds at the same power draw. The proposed passive thermal management system kept the batteries within their recommended operating temperature range.
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Dalmia, Sidharth. "Design and implementation of high-Q passive devices for wireless applications using System-On-Package (SOP) based organic technologies." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15689.
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Hou, Stephen Ming-Chang 1981. "Design and fabrication of a MEMS-array pressure sensor system for passive underwater navigation inspired by the lateral line." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75454.
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Thesis (Elec. E.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 233-241).
An object within a fluid flow generates local pressure variations that are unique and characteristic to the object's shape and size. For example, a three-dimensional object or a wall-like obstacle obstructs flow and creates sharp pressure gradients nearby. Similarly, unsteady flow contains vortical patterns with associated unique pressure signatures. Detection of obstacles, as well as identification of unsteady flow features, is required for autonomous undersea vehicle (AUV) navigation. An array of passive underwater pressure sensors, with their ability to An object within a fluid flow generates local pressure variations that are unique and characteristic to the object's shape and size. For example, a three-dimensional object or a wall-like obstacle obstructs flow and creates sharp pressure gradients nearby. Similarly, unsteady flow contains vortical patterns with associated unique pressure signatures. Detection of obstacles, as well as identification of unsteady flow features, is required for autonomous undersea vehicle (AUV) navigation. An array of passive underwater pressure sensors, with their ability to "touch at a distance" with minimal power consumption, would be able to resolve the pressure signatures of obstacles in the near field and the wake of objects in the intermediate field. As an additional benefit, with proper design, pressure sensors can also be used to sample acoustic signals as well. Fish already have a biological version of such a pressure sensor system, namely the lateral line organ, a spatially-distributed set of sensors over a fish's body that allows the fish to monitor its hydrodynamic environment, influenced by the external disturbances. Through its ability to resolve the pressure signature of objects, the fish obtains "hydrodynamic pictures". Inspired by the fish lateral line, this thesis describes the development of a high-density array of microelectromechanical systems (MEMS) pressure sensors built in KOH-etched silicon and HF-etched Pyrex wafers. A novel strain-gauge resistor design is discussed, and standard CMOS/MEMS fabrication techniques were used to build sensors based on the strain-gauge resistors and thin silicon diphragms. Measurements of the diaphragm deflection and strain-gauge resistance changes in response to changes in applied external pressure confirm that the devices can be reliably calibrated for use as pressure sensors to enable passive navigation by AUVs. A set of sensors with millimeter-scale spacing, 2.1 to 2.5 [mu]V/Pa sensitivity, sub-pascal pressure resolution, and -2000 Pa to 2000 Pa pressure range has been demonstrated. Finally, an integrated circuit for array processing and signal amplification and to be fabricated with the pressure sensors is proposed.
by Stephen Ming-Chang Hou.
Elec.E.
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Menon, Manas Chandran. "Design and control of a semi-passive, heavy-duty paired mobile robot system with application to aircraft wing assembly." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62514.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 126-128).
We describe the development of a robotic system capable of performing a class of manufacturing operations. An example of such an operation is commonly found in aircraft assembly - this demonstrates the immediate applicability of this research. The system utilizes a unique concept - a pair of mobile robots acting on opposite sides of a thin wall. The robots interact with one another through the use of magnetic fields that penetrate this wall. The 'inner' robot is untethered and is controlled by the 'outer' robot. Despite the significant mass of the outer robot, it operates without the aid of physical external supports. Full modeling of the system is presented. We include calculations for forces and torques produced by sets of permanent magnets for any system state. Simplified, tractable versions of this model for the purpose of control are also described. The system is designed to execute closed loop fine position control and large scale locomotion. Experimental results from a functional prototype verify the effectiveness of the design as well as the robustness of a position controller. Numerical optimal control results have been developed for high speed point to point trajectory motion. This 'pair of robots' paradigm could be applicable to a variety of tasks. This work outlines analysis techniques that are useful for such a system at most scales.
by Manas Chandran Menon.
Ph.D.
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Beviss-Challinor, Lauren Margaret. "Design, build and test a passive thermal system for a loft : a roof solar chimney application for South African weather conditions." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/348.
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Thesis (MEng (Mechanical and Mechatronic Engineering))--Stellenbosch University, 2007.ENGLISH: The design, construction and testing of a passive thermal system, a roof solar chimney, for a loft is considered. Unlike conventional solar chimneys the solar collector is constructed from corrugated iron roof sheets with the aim that it can be integrated into existing buildings at a lower cost or used in low cost housing developments. The main objective of the study was to determine the feasibility of such low-cost design to regulate thermal conditions in a loft, that is heating the loft during winter and enhancing natural ventilation during summer, by carrying out an experimental and analytical study. The results obtained from the experimental study showed that for winter the solar chimney, having a channel width, depth and length of 0.7 m, 0.1 m and 1.8 m respectively and with a peal solar radiation of 850 W/m², heated the room air 5°C higher than the ambient temperature during the hottest periods of the day, which is only marginally better than a loft with conventional roof insulation. At night, it was found that reverse airflow occurred through the chimney, cooling the loft down to ambient temperature, due to radiation heat loss from the roof collector to the night sky. For summer operation, the experimental data showed that the chimney was able to maintain the loft at ambient temperature and the analytical study found that the chimney was able to enhance natural ventilation effectively, reaching air exchange rate of 6.6 per hour for the 4.6 m³ volume space. It was also found that the chimney’s performance dropped rapidly and significantly during periods of low solar radiation and at night. A sensitivity analysis illustrated that for both summer and winter operation, the size, tilt angle and absorptivity of the roof collector greatly effected the efficiency and mass flow rates of the system, agreeing well with other literature. These results prove that this low cost solar chimney cooling design was feasible to enhance natural ventilation mainly during hot summer conditions with high solar radiation. Compared to a loft with only conventional roof insulation, the chimney did not perform effectively during the winter to heat the loft up, meaning that winter operation for this specific design is not feasible. Possible improvements to the design include using construction materials with higher thermal capacities to retain heat energy and ensure continued operation during periods of low solar radiation, as well as using selective absorber coatings on the collector surface. It is recommended that further work on the project include the integration of these improvements into the present design and to use the findings obtained from the sensitivity analysis to improve system efficiencies. CFD analysis of the test-rig will be insightful as an additional means to validate and compare with the analytical and experimental data obtained in this report. With the continuation of these studies, this low-cost solar chimney design can be optimised, validated on a commercial scale and built into existing and new housing developments. Incorporating such a passive thermal device will aid homeowners in air regulation and thermal comfort of their living space as well as saving on energy requirements.
Sponsored by the Centre for Renewable and Sustainable Energy Studies, Stellenbosch University
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Tran, Duc-Hoan. "Conception Optimale Intégrée d'une chaîne éolienne "passive" : analyse de robustesse, validation expérimentale." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0126/document.
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Ce travail présente une méthodologie de Conception Optimale Intégrée (COI) d'un système éolien entièrement passif pour offrir un compromis coût-fiabilité–performance très satisfaisant. En l'absence d'électronique de puissance et de contrôle par MPPT, le dispositif n'est efficace que si l'adaptation des constituants est optimale. L'extraction de vent ainsi que les pertes globales du système sont donc optimisées à l'aide d'un algorithme génétique multicritère pour augmenter l'efficacité énergétique et minimiser la masse pour un profil de vent donné. La globalité du système (turbine – génératrice – redresseur - stockage) a été modélisée pour parvenir aux résultats d'optimisation et à la réalisation d'un prototype correspondant à une solution particulière. Les résultats obtenus montrent, d'une part, la cohérence entre modèles et expérience. D'autre part, il est possible, pour un profil de vent donné, d'obtenir une configuration optimale de l'ensemble génératrice – pont redresseur présentant des caractéristiques analogues à celles d'architectures « actives" plus complexes, associées à des lois de contrôle par MPPT. Suite à une analyse de sensibilité des performances aux paramètres, une de nos contributions concerne une approche de conception intégrant les questions de robustesse au sein même du processus d'optimisationThis work deals with an Integrated Optimal Design (IOD) methodology of a full passive wind turbine system offering very good tradeoff in terms of cost, reliability and performance. Without active electronic device (power and MPPT control), efficiency of such architecture can only be obtained if all devices are mutually adapted: this can be achieved through an Integrated Optimal Design (IOD) approach. Wind energy extraction as whole losses are then optimized from a multiobjective genetic algorithm which aims at concurrently optimizing the energy efficiency while reducing the weight of the wind turbine system given a wind cycle. The whole system (turbine, generator, diode reducer, battery DC bus) has been modeled to obtain optimization results and finally to select a particular solution for an experimental validation. On the one hand, the obtained results put forward coherency between models and experience. On the other hand, given a reference wind cycle, it is possible to obtain optimal devices (generator – reducer – DC bus) whose energy efficiency is nearly equivalent to the ones obtained with active and more complex systems with MPPT control. Based on a sensitivity analysis of performance versus parametric uncertainties, one major contribution deals with a design methodology integrating robustness issues inside the optimization process
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Unal, Teoman. "Design Of A Single-phase Full-bridge Diode Rectifier Power Factor Corrector Educational Test System." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12608148/index.pdf.
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In this thesis an educational test bench for studying the power quality attributes of the
commonly used single-phase full-bridge diode rectifiers with power factor correction
(PFC) circuits is designed and tested. This thesis covers the active and passive power
factor correction methods for single-phase bridge rectifier. Passive filtering approach
with dc side inductor and tuned filter along with active filtering approach via singleswitch
boost converter is considered. Analysis, simulation, and design of a single phase
rectifier and PFC circuits is followed by hardware implementation and tests. In the active
PFC approach, various control methods is applied and compared. The educational bench
is aimed to useful for undergraduate and graduate power electronics course, power
quality related laboratory studies.
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Navidi, Parisa. "Inspiration By Nature: Biomimetic Research Informs Adaptable Building Skin System for Natural Ventilation and Daylight in Hot Dry Climate (Yazd, Iran)." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1158.
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Many plant species, including Barrel Cacti, have developed long-term evolutionary adaptable traits to survive in extreme climates. The most important trait of cacti in extreme hot dry climates is to reduce water evaporation and increase water storage. The exterior skin of a cactus plays an important role in preventing water evaporation through heat transmission.
On the other hand, there have been many passive design strategies applied to the space planning and building design of architecture in hot dry climates. The goal of these passive design strategies is to regulate the penetration of heat into building spaces while creating a strong ventilation system to help bring cool air inside the building.
In this paper, adaptations of the Barrel Cactus' exterior skin, along with architectural passive design strategies for hot dry climates (in this caseYazd, Iran) will be discussed and integrated with one another through the concept of Biomimicry. The goal is to design an exterior building skin that is attuned to the environmental conditions of a hot dry climate, based on the successful applicable behaviors demonstrated in the Barrel Cactus. Key architectural features such as natural ventilation and daylight will be informed by the evolutionary cacti adaptations and passive architectural strategies in the design of the building skin in order to increase the possibility of consistent comfort for users of an office building.
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Gonilho, Marcos Diogo Mota. "A reabilitação energicamente sustentável e a requalificação do (ex) Convento de Santa Marta." Master's thesis, Universidade de Lisboa. Faculdade de Arquitetura, 2013. http://hdl.handle.net/10400.5/6679.
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FERREIRA, Fábio Martins Gonçalves. "Otimização de Sistema de Ancoragem equivalente em Profundidade Truncada." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/17553.
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Ao esgotar as reservas de hidrocarbonetos em terra e águas rasas, a indústria vem explorando e produzindo petróleo em águas profundas e ultraprofundas. No entanto, a verificação hidrodinâmica de novos sistemas flutuantes de produção continua usando as metodologias consagradas, especialmente os ensaios em tanques oceânicos de laboratório. A utilização de modelos em escala reduzida vem sendo adotada desde os primeiros projetos em águas rasas e continua até hoje nos projetos em águas ultraprofundas. No entanto, os ensaios em profundidades superiores a 1.500m necessitam de um fator de escala muito elevado, com diversos problemas associados, dentre eles as dificuldades de acomodar as linhas de ancoragem e as incertezas relacionadas a modelos muito pequenos. Dentre as soluções possíveis, os ensaios híbridos (numérico-experimental) se apresentam como a solução mais viável para verificação experimental em águas ultraprofundas, em especial o ensaio híbrido passivo. Esse tipo de ensaio é organizado em etapas, sendo a primeira delas responsável pela definição do sistema truncado. Se essa etapa não for executada de forma satisfatória, o sucesso do ensaio pode ser comprometido. Assim, a fim de minimizar essa questão, propõe-se nesta tese de doutorado uma forma sistemática para encontrar sistemas truncado equivalentes, considerando os efeitos estáticos e dinâmicos, através da utilização de ferramentas de otimização. Nesse sentido, a abordagem adotada utiliza um simulador para análise estática e dinâmica de estruturas offshore denominado Dynasim e um algoritmo de otimização baseado em gradiente através do sistema Dakota. Também é utilizada a metodologia de planejamento de experimentos para identificar os fatores que influenciam as respostas estática e dinâmica do problema, evitando o uso de variáveis de projeto irrelevantes no estudo da otimização. Ressalta-se que essa metodologia não foi aplicada em outros trabalhos no contexto de sistemas de ancoragem truncado, segundo nosso conhecimento. Além disso, analisa-se o projeto ótimo do sistema truncado em várias condições ambientais, cujo interesse é verificar a concordância dele com o sistema de ancoragem na profundidade completa. Devido ao elevado custo computacional envolvido nessa verificação, utiliza-se a computação de alto desempenho, com processamento paralelo, para viabilizar a realização dessas análises. Como é demonstrado neste trabalho, a metodologia proposta facilita a busca de sistemas de ancoragem truncado equivalente preservando as características estáticas e dinâmicas do sistema de ancoragem completo. São apresentados e discutidos quatro casos, os dois primeiros se referem a casos simplificados, o terceiro é baseado na literatura e o quarto é baseado em um cenário real. Os resultados obtidos nos casos estudados mostram que os sistemas truncados equivalentes encontrados conseguem reproduzir o comportamento dos sistemas completos para as condições verificadas.
With the depletion of onshore and offshore shallow-water reserves, the industry has exploited and produced oil in deep water and ultra-deepwater. However, the hydrodynamic verification of new floating production systems continues using the established methodologies, especially by carrying out tests on ocean basin laboratories. Small-scale model tests have been used since the first projects in shallow water and continue today in the projects in ultra-deepwater. However, tests in depths above 1,500m require a very high scale factor, which poses several complications, among them the difficulties to accommodate the mooring lines and the small models related uncertainties. Among the possible solutions, the hybrid testing (numerical and experimental) are the most feasible solution to experimental verification in ultra-deepwater, especially the hybrid passive systems test. Such test is divided into steps, the first one responsible for the definition of the truncated system. If this step is not performed satisfactorily, the success of the test may be compromised. Thus, in order to minimize this issue, a systematic way to find equivalent truncated systems, considering the static and dynamic effects through the use of the optimization tools is proposed in this doctoral thesis. Accordingly, the approach adopted uses a numerical simulator, called Dynasim, for static and dynamic analysis of offshore structures, and a gradient based optimization algorithm, given in Dakota computational system. Additionally, the design of experiments methodology is used to identify the factors that influence the static and dynamic responses of the problem, avoiding the use of irrelevant design variables in the optimization process. It has to be emphasized that this methodology has not been used in other works in the context of truncated mooring systems, to our knowledge. Furthermore, the optimal design of the truncated system is analyzed for several environmental conditions. The aim is to verify the agreement of the truncated mooring system with system in the full-depth. Due to the high computational cost involved in the verification, we use the high-performance computing, with parallel computation, to perform the analyzes. As shown in this work, the proposed methodology easy the search for equivalent truncated mooring systems preserving the static and dynamic characteristics of full-depth mooring systems. Four case studies are presented and discussed. The first two refer to simplified cases; the third is based on the literature and the fourth is based on a real scenario. The results in each case show that the truncated equivalent system found can reproduce the behavior of full-depth system for the verified conditions.
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Ghahremanian, Shahriar, and Setareh Janbakhsh. "Construction and Evaluation of a Controlled Active Mass (CAM) : A new cooling system design for increased thermal comfort using low exergy sources." Thesis, University of Gävle, Department of Technology and Built Environment, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-146.
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Nowadays, office buildings often have large temperature variations during the day and building envelope acts as an energy storing mass and damp these effects and so Offices need more cooling because of internal heat sources. But we know that cooling is more expensive than heating and it uses the very good quality of energy sources (exergy). Controlled Active Mass (CAM) is new approach to absorb radiant heating and acts as a passive cooling device. It has direct cooling effect and reduces the peak load. CAM is a new cooling system design with applying the low energy sources and operates at water temperature close to room temperature and increase the efficiency of heat pumps and other systems.
In this project, we calculated the transient heat transfer analysis for CAM in a very well insulated test room with façade wall, Internal heat generators (such as Manikin, Computer simulator & lighting) and ventilation.
Then Polished (shiny) CAM constructed from Aluminum sheets with 0.003 m thickness. It is cube shape with 0.6 m length. This size of CAM is according to 2.5 times larger than human body volume and initial water temperature assumed near half of human body temperature. Then in order to more radiation damping (absorption) by CAM, it painted black (also based on color analysis in heat transfer calculation).
Some velocity and temperature measurement have been carried out on both polished CAM and black CAM, after visualization by smoke and Infrared Camera. And more cases tested to see the effect of façade wall, IHG’s and ventilation inlet temperature. Thermal comfort measurement also have been done for finding PMV, PPD and temperature equivalent for a seated person which is doing an office job with normal closing.
At the end results discussed which includes the effect of CAM in room, differences between polished CAM and black CAM and effect of main heat sources on both CAM types (Polished / Black).
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Boampong, James Kwadwo. "Solar thermal heating of a glasshouse using phase change material (PCM) thermal storage techniques." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/12863.
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The Royal Botanic Gardens (RGB) is used as an umbrella name for the institution that runs Kew and Wakehurst Place gardens in Sussex The RBG has a large number of glasshouses at Kew and Wakehurst sites that consume lots of heating energy which is a major concern and the group is looking for an alternative heating system that will be more efficient and sustainable to save energy, cost and reduce CO2 emissions. Glasshouse due to greenhouse effect trap solar energy in the space with the slightest solar gains but the energy trapped in the space most often is vented through the roof wasted to keep the space temperature to the required level. An environmental measurement was carried out in twenty one zones of the glasshouse to establish the temperature and humidity profiles in the zones for at least three weeks. The investigation established that large amount of heat energy is vented to the atmosphere wasted and therefore need a heating system that could absorb and store the waste thermal energy. Phase change material (PCM) thermal energy storage technique was selected to be the best options compared to the others. It has been established that active and passive solar systems could provide enough thermal energy to meet the glasshouse heating requirements. PCM filled heating pipes will be installed to absorb the heat energy trapped in the glasshouse and use it when needed. The research analysis established that 204 MWh of the trapped energy wasted could be saved. The space temperature of the glasshouse could be maintained through melting and freezing of the PCM filled in the heating pipes. The site CHP waste heat could be useful. The research results have shown that nearly zero CO2 emission heating system could be achieved and the project is technically, economically and environmentally viable.
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Ccencho, Maritza, Valeria Quijada, and Leonardo Vinces. "An Automated System for the Stage of Hydrolysis and Filtration in the Extraction of Pectin from the Cocoa Shell." Universidad Peruana de Ciencias Aplicadas (UPC), 2021. http://hdl.handle.net/10757/653786.
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El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.Pectin obtained from cocoa husks has recently been investigated because of its gelling and stabilizing properties that have great potential for the food, cosmetic and pharmaceutical industries. However, its production at the industrial level has not been studied or developed in Peru. A fundamental part of the extraction process is the stage of hydrolysis and filtering of the cocoa shell. Because of this, an automated system for acid-thermal hydrolysis and shell filtration is proposed. The control of both processes is of great importance because the quality and efficiency of the extracted pectin will depend on it. The tests will be carried out in a cylindrical taper with a 100 L capacity which is adapted to contain a 20 L cylindrical filter, both made of AISI 304 stainless steel. The filter has a motor to homogenize the temperature and pH of the mix. The pH of the process is 2 and the temperature is 90 ± 2 °C, since in these ranges the pectin is released more easily from the cocoa shell. The method consists of the structural design of the tank and the filter, and in the design of the pH regulator and the heating system. The yield of the extraction process was achieved by 10%.
Revisión por pares
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Shorey, Thomas Paul Jr. "Parametric Performance-driven Passive Solar Designed Facade Systems." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1408.
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Buildings in the United States account for nearly 68% of all U.S. energy consumption due to their reliance on electrical lighting and mechanical systems. Beginning in the 20th century, emphasis on developing the glass curtain wall created increased energy demands on lighting and mechanical systems. Consequently, the building’s curtain wall is a direct cause of significant energy loads. This research project investigated how current parametric design tools and energy analysis software are used during a performance-driven passive solar design process to develop facade systems that lower the energy use intensity (EUI) of a building and increase natural daylight to an acceptable illuminance level (lux). Passive solar shading strategies were employed to realize the proposed design process through a proof of concept project that retrofits the facade of an outdated office building in a hot-mediterranean climate. Incremental steps were taken using parametric software (Revit Architecture 2015) to increase the passive solar and daylighting performance capabilities of the facade system and Autodesk Green Building Studio was employed to measure, compare and contrast the results of each design.
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Archakis, Viktor. "The Design of a Passive House." Thesis, Högskolan i Gävle, Energisystem och byggnadsteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-32220.
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About 25 % of the total buildings in the European Union have been categorized as ”old buildings”. Followed the recent strickt rules for carbon emissions reduction, each house has to approximetely cut 20 % of CO2 by 2020. Countries like England, have taken the issue very seriously and planning to reduce the carbon emissions by 30 % until the end of 2020 and by an extra 80 % by 2050 (Francis Moran, 2014). The aim of the report is to present how a traditional house can be retroffited into a passive house and also to identify the key points that every passive house should have. For the purpose of the project an avtual house, based in Gävle, was provided and all the simulations are based on actual data. The initial design of the house which was used for the simulation and the 3D design, was provided by the house owner. The building was built in 1953, information regarding the current insulation of the house was provided by the owner as well. For the simulations and the 3D design a software know as IDA ICE was used, license and access to the software were given by the University of Gävle. The report simulates the current house and compares the results with two possible scenarios that are reducing the energy demand of the house. Furthermore, the possible ways and tools that could be used to reduce the energy demand of the house and cost estimation for the retrofitting is available in the paper.The first simulations were occured on the actual house, the first retrofitting package introduces new simulations based on new insulation materials, like wood and cement, that are placed mainly on the roof and on the outer walls. Also, the thickness have changed, thus the new insulations are thicker.Moreover, the second and final retrofitting package, introduces an HVAC system, which is a standard system. The aim is to achieve further energy demand reductions and prove that simple and basic changes can improve the quality of living and reduce CO2 emissions.After the completition of the first analysis, a reduction equal to 60 % and after the addition of the HVAC a further 20 % reduction achieved.
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Romagna, Eric O. "Design of a haptic passive mouse." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18873.
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Cinarel, Dilara. "Vibration Isolation Of Inertial Measurement Unit." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614069/index.pdf.
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Sensitive devices are affected by extreme vibration excitations during operation so require isolation from high levels of vibration excitations. When these excitation characteristics of the devices are well known, the vibration isolation can be achieved accurately. However, it is possible to have expected profile information of the excitations with respect to frequency. Therefore, it is practical and useful to implement this information in the design process for vibration isolation.
In this thesis, passive vibration isolation technique is examined and a computer code is developed which would assist the isolator selection process. Several sample cases in six degree of freedom are designed for a sample excitation and for sample assumptions defined for an inertial measurement unit. Different optimization methods for design optimizations are initially compared and then different designs are arranged according to the optimization results using isolators from catalogues for these sample cases.
In the next step, the probable designs are compared according to their isolator characteristics. Finally, one of these designs are selected for each case, taking into account both the probable location deviations and property deviations of isolators.
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Sadrizadeh, Sasan. "Design of Hospital Operating Room Ventilation using Computational Fluid Dynamics." Doctoral thesis, KTH, Strömnings- och klimatteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-181053.
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The history of surgery is nearly as old as the human race. Control of wound infection has always been an essential part of any surgical procedure, and is still an important challenge in hospital operating rooms today. For patients undergoing surgery there is always a risk that they will develop some kind of postoperative complication. It is widely accepted that airborne bacteria reaching a surgical site are mainly staphylococci released from the skin flora of the surgical staff in the operating room and that even a small fraction of those particles can initiate a severe infection at the surgical site. Wound infections not only impose a tremendous burden on healthcare resources but also pose a major threat to the patient. Hospital-acquired infection ranks amongst the leading causes of death within the surgical patient population. A broad knowledge and understanding of sources and transport mechanisms of infectious particles may provide valuable possibilities to control and minimize postoperative infections. This thesis contributes to finding solutions, through analysis of such mechanisms for a range of ventilation designs together with investigation of other factors that can influence spread of infection in hospitals, particularly in operating rooms. The aim of this work is to apply the techniques of computational fluid dynamics in order to provide better understanding of air distribution strategies that may contribute to infection control in operating room and ward environments of hospitals, so that levels of bacteria-carrying particles in the air can be reduced while thermal comfort and air quality are improved. A range of airflow ventilation principles including fully mixed, laminar and hybrid strategies were studied. Airflow, particle and tracer gas simulations were performed to examine contaminant removal and air change effectiveness. A number of further influential parameters on the performance of airflow ventilation systems in operating rooms were examined and relevant measures for improvement were identified. It was found that airflow patterns within operating room environments ranged from laminar to transitional to turbulent flows. Regardless of ventilation system used, a combination of all airflow regimes under transient conditions could exist within the operating room area. This showed that applying a general model to map airflow field and contaminant distribution may result in substantial error and should be avoided. It was also shown that the amount of bacteria generated in an operating room could be minimized by reducing the number of personnel present. Infection-prone surgeries should be performed with as few personnel as possible. The initial source strength (amount of colony forming units that a person emits per unit time) of staff members can also be substantially reduced, by using clothing systems with high protective capacity. Results indicated that horizontal laminar airflow could be a good alternative to the frequently used vertical system. The horizontal airflow system is less sensitive to thermal plumes, easy to install and maintain, relatively cost-efficient and does not require modification of existing lighting systems. Above all, horizontal laminar airflow ventilation does not hinder surgeons who need to bend over the surgical site to get a good view of the operative field. The addition of a mobile ultra-clean exponential laminar airflow screen was also investigated as a complement to the main ventilation system in the operating room. It was concluded that this system could reduce the count of airborne particles carrying microorganisms if proper work practices were maintained by the surgical staff. A close collaboration and mutual understanding between ventilation experts and surgical staff would be a key factor in reducing infection rates. In addition, effective and frequent evaluation of bacteria levels for both new and existing ventilation systems would also be important.Tidigt i mänsklighetens utveckling har kirurgin funnits med i bilden. Hantering av infektioner har genom tiderna varit en oundviklig del av alla kirurgiska ingrepp, och finns kvar ännu idag som en viktig utmaning i operationssalar på sjukhus. För patienter som genomgår kirurgi finns alltid en risk att de efter ingreppet utvecklar någon behandlingsrelaterad komplikation. Allmänt accepterat är att de luftburna bakterier som når operationsområdet huvudsakligen består av stafylokocker frigjorda från hudfloran av operationspersonalen i operationssalen, och att endast en liten del av dessa partiklar behövs för att initiera en allvarlig infektion i det behandlade området. Sårinfektioner innebär inte bara en enorm börda för hälso- och sjukvårdsresurser, utan utgör också en betydande risk för patienten. På sjukhus förvärvad infektion finns bland de främsta dödsorsakerna i kirurgiska patientgrupper.. En bred kunskap och förståelse av spridningsmekanismer och källor till infektionsspridande partiklar kan ge värdefulla möjligheter att kontrollera och minimera postoperativa infektioner. Denna avhandling bidrar till lösningar genom analys av en rad olika ventilationssystem tillsammans med undersökning av andra faktörer som kan påverka infektionsspridningen på sjukhus, främst i operationssalar. Syftet med arbetet är att med hjälp av CFD-teknik (Computational Fluid Dynamics) få bättre förståelse för olika luftspridningsmekanismers betydelse vid ventilation av operationssalar och vårdinrättningar på sjukhus, så att halten av bacteriebärande partiklar i luften kan minskas samtidigt som termisk komfort och luftkvalité förbättras. Flera luftflödesprinciper för ventilation inklusive omblandade strömning, riktad (laminär) strömning och hybridstrategier har studerats. Simuleringar av luft-, partikel- och spårgasflöden gjordes för alla fallstudier för att undersöka partikelevakuering och luftomsättning i rummet. Flera viktiga parametrar som påverkar detta undersöktes och relevanta förbättringar föreslås i samarbete med industrin. Av resultaten framgår att mängden genererade bakterier i en operationssal kan begränsas genom att minska antalet personer i operationsteamet. Infektionsbenägna operationer skall utföras med så lite personal som möjligt. Den initiala källstyrkan (mängden kolonibildande enheter som en person avger per tidsenhet) från operationsteamet kan avsevärt minskas om högskyddande kläder används. Av resultaten framgår också att ett horisontellt (laminärt) luftflöde kan vara ett bra alternativ till det ofta använda vertikala luftflödet. Ett horisontellt luftflöde är mindre känsligt för termisk påverkan från omgivningen, enkelt att installera och underhålla, relativt kostnadseffektivt och kräver vanligen ingen förändring av befintlig belysningsarmatur. Framför allt begränsar inte denna ventilationsprincip kirurgernas rörelsemönster. De kan luta kroppen över operationsområdet utan att hindra luftflödet. En flyttbar flexibel skärm för horisontell spridning av ultraren ventilationsluft i tillägg till ordinarie ventilation undersöktes också. Man fann att denna typ av tilläggsventilation kan minska antalet luftburna partiklar som bär mikroorganismer om operationspersonalen följer en strikt arbetsordning. Bra samarbete och förståelse mellan ventilationsexperter och operationsteamet på sjukhuset är nyckeln till att få ner infektionsfrekvensen. Det är också viktigt med effektiva och frekventa utvarderingar av bakteriehalten i luften, för såväl nya som befintliga ventilationssystem.
QC 20160129
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Wang, Fucheng. "Design and synthesis of active and passive vehicle suspensions." Thesis, University of Cambridge, 2001. https://www.repository.cam.ac.uk/handle/1810/272316.
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Stein, Edwin Lee Jr. "Design and development of passive millimeter-wave imaging systems." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 123 p, 2009. http://proquest.umi.com/pqdweb?did=1885755721&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Swanson, Davin Karl. "Implementation of arbitrary path constraints using dissipative passive haptic displays." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/17606.
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Reed, Matthew Robert. "Development of an Improved Dissipative Passive Haptic Display." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5284.
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This project focuses on the design and modeling of a two degree-of-freedom dissipative passive haptic display. Haptic displays are man-machine interfaces that transmit forces to the human operator. A dissipative passive haptic display is one that may only remove energy from the system using actuators such as brakes and dampers, thus ensuring the safety of the human operator. These devices may be used to implement virtual constraints such as desired paths and obstacles. Traditional friction brakes have previously been used as dissipative and coupling elements in a two degree-of-freedom parallel manipulator, resulting in undesired effects such as vibration, stiction, and slow response times. Alternatively, the new robot is actuated by rheological brakes, which feature fast response times and smooth application of torque. This approach aims to improve upon the accuracy and feel of the previous design.
A commercial magnetorheological (MR) fluid brake was selected and put through an extensive series of tests. The data was used to develop a model that characterizes MR fluid behavior in low speed braking applications. A parallel five bar linkage was designed and built that has separate configurations corresponding to 3-brake and 4-brake operation. The length of each arm was chosen by means of a geometrical optimization that weighs the size and area of the workspace and actuator effects. A simulation was then developed by incorporating the brake model into the equations of motion of the robot. Next, two forms of path following velocity control were devised and tested in simulation. Finally, the accuracy, workload, and smoothness of both controllers and both configurations were examined in preliminary tests with human operators.
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Papakosta, Paraskevi. "Design and development of mechanical passive millimetre wave imaging scanning systems." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325129.
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Frushour, John H. "Design considerations for a computationally-lightweight authentication mechanism for passive RFID tags." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Sep/09Sep%5FFrushour.pdf.
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Thesis (M.S. in Computer Science)--Naval Postgraduate School, September 2009.Thesis Advisor(s): Fulp, J.D. ; Huffmire, Ted. "September 2009." Description based on title screen as viewed on November 6, 2009. Author(s) subject terms: Passive RFID Systems, Tags, Clock, Electro-magnetic induction, authentication, hash, SHA--1. Includes bibliographical references (p. 59-60). Also available in print.
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Suwal, Pasang Sherpa. "Passive Acoustic Vessel Localization." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/757.
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This thesis investigates the development of a low-cost passive acoustic system for localizing moving vessels to monitor areas where human activities such as fishing, snorkeling and poaching are restricted. The system uses several off-the-shelf sensors with unsynchronized clocks where the Time Difference of Arrival (TDOA) or time delay is extracted by cross-correlation of the signal between paired sensors. The cross-correlation function uses phase correlation or Phase Transform (PHAT) which whitens the cross-spectrum in order to de-emphasize dominant frequency components. Using the locations of pairs of sensors as foci, hyperbolic equations can be defined using the time delay between them. With three or more sensors, multiple hyperbolic functions can be calculated which intersect at a unique point: the boat's location. It is also found that increasing separation distances between sensors decreased the correlation between the signals. However larger separation distances have better localization capability than with small distances. Experimental results from the Columbia and Willamette Rivers are presented to demonstrate performance.
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Moreschi, Luis M. "Seismic design of energy dissipation systems for optimal structural perfromance." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28279.
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The usefulness of supplementary energy dissipation devices is now quite well-known in the earthquake structural engineering community for reducing the earthquake-induced response of structural systems. However, systematic design procedures for optimal sizing and placement of these protective systems in structural systems are needed and are not yet available. The main objective of this study is, therefore, to formulate a general framework for the optimal design of passive energy dissipation systems for seismic structural applications. The following four types passive energy dissipation systems have been examined in the study: (1) viscous fluid dampers, (2) viscoelastic dampers, (3) yielding metallic dampers and, (4) friction dampers. For each type of energy dissipation system, the study presents the (a) formulation of the optimal design problem, (b) consideration of several meaningful performance indices, (c) analytical and numerical procedures for seismic response and performance indices calculations, (d) procedures for obtaining the optimal design by an appropriate optimization scheme and, (e) numerical results demonstrating the effectiveness of the procedures and the optimization-based design approach.
For building structures incorporating linear damping devices, such as fluid and solid viscoelastic dampers, the seismic response and performance evaluations are done by a random vibration approach for a stochastic characterization of the earthquake induced ground motion. Both the gradient projection technique and genetic algorithm approach can be conveniently employed to determine the required amount of damping material and its optimal distribution within a building structure to achieve a desired performance criterion. An approach to evaluate the sensitivity of the optimum solution and the performance function with respect to the problem parameters is also described. Several sets of numerical results for different structural configurations and for different performance indices are presented to demonstrate the effectiveness and applicability of the approach.
For buildings installed with nonlinear hysteretic devices, such as yielding metallic elements or friction dampers, the computation of the seismic structural response and performance must be performed by time history analysis. For such energy dissipation devices, the genetic algorithm is more convenient to solve the optimal design problem. It avoids the convergence to a local optimal solution. To formulate the optimization problem within the framework of the genetic algorithm, the study presents the discretization procedures for various parameters of these nonlinear energy dissipation devices. To include the uncertainty about the seismic input motion in the search for optimal design, an ensemble of artificially generated earthquake excitations are considered. The similarities of the optimal design procedure with yielding metallic devices and friction devices are clearly established. Numerical results are presented to illustrate the applicability of the proposed optimization-based approach for different forms of performance indices and types of building structures.Ph. D.