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Pourabdollah, Nezhad Maziar. "Active and passive plasmonic devices." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3284224.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed January 14, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 93-102).
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Zuo, Fei. "Passive and active currency portfolio optimisation." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/22612.
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This thesis examines the performance of currency-only portfolios with different strategies, in out-of-sample analysis. I first examine a number of passive portfolio strategies into currency market in out-of-sample analysis. The strategies I applied in this chapter include sample-based mean-variance portfolio and its extension, minimum variance portfolio, and equally-weighted risk contribution model. Moreover, I consider GDP portfolio and Trade portfolio as market value portfolio for currency market. With naïve portfolio, there are 12 different asset allocation models. In my out-of-sample analysis, naïve portfolio performs reasonably well among all 12 portfolios, and transaction cost does not seriously affect the results prior to transaction cost analysis. The results are robust across different estimation windows and perspectives of investors from different countries. Next, more portfolio strategies are examined to compare with naïve portfolio in currency market. The first portfolio strategy called ‘optimal constrained portfolio’ in this chapter is derived from the idea of maximising the quadratic utility function. In addition, the timing strategies, a set of simple active portfolio strategies, are also considered. In my out-of-sample analysis with rolling sample approach, naïve portfolio can be beaten by all the strategies discussed in this chapter. In chapter six, the characteristics of currency are exploited to construct a currency only portfolio. Firstly, the pre-sample test proves that the characteristics, both fundamental and financial, are relevant to the portfolio construction. I then examine the performance of parametric portfolio policies. The results show that while fundamental characteristics can bring investor benefits of active portfolio management, financial characteristics cannot. Moreover, I find the relationship between characteristics of currency and weights of optimal portfolio. The overall results show that currencies can be thought of as an asset in their own right to construct optimal portfolios, which have better performance than naïve portfolio, if suitable strategies are used. In addition, ‘lesser’ currencies, indeed, bring significant benefits to the investors.
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Maldonado-Mercado, Julio Cesar. "Passive and active control of structures." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36654.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995.Includes bibliographical references (leaves 94-98).
by Julio Cesar Maldonado-Mercado.
M.S.
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Scheitrum, Raquel. "Smoking passive addiction or active coping? /." Instructions for remote access. Click here to access this electronic resource. Access available to Kutztown University faculty, staff, and students only, 1999. http://www.kutztown.edu/library/services/remote_access.asp.
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Thesis (M.A.)--Kutztown University of Pennsylvania, 1999.Source: Masters Abstracts International, Volume: 45-06, page: 2778. Typescript. Abstract included as two unpaged leaves at back of volume. Includes bibliographical references (leaves 30-35).
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Kartha, Satish Chandrashekhar. "Active, Passive and Active/Passive Control Techniques For Reduction of Vibrational Power Flow in Fluid Filled Pipes." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31156.
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The coupled nature of vibrational energy flow in fluid filled piping systems makes its control and subsequent reduction a difficult problem. This work experimentally explores the potential of different active, passive and active/passive control methodologies for control of vibrational power flow in fluid filled pipes. Circumferential modal decomposition and measurements of vibrational power carried by individual wave types were carried out experimentally. The importance of dominant structural bending waves and the need to eliminate them in order to obtain meaningful experimental results has been demonstrated. The effectiveness of the rubber isolator in reducing structural waves has been demonstrated. Improved performance of the quarter wavelength tube and Helmholtz resonator was obtained on implementation of the rubber isolator on the experimental rig. Active control experiments using the side-branch actuator and 1/3 piezoelectric composite yielded significant dB reductions revealing their potential for practical applications. A combined active/passive approach was also implemented as part of this work. This approach yielded promising results, which proved that combining advantages of both active and passive approaches was a feasible alternative.Master of Science
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Hassan, Samy Aly. "Fundamental studies of passive, active and semi-active automotive suspension systems." Thesis, University of Leeds, 1986. http://etheses.whiterose.ac.uk/2691/.
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The fundamental properties of various automotive suspension systems are theoretically investigated on the basis of simple vehicle models subjected to realistic inputs chosen to represent road surfaces of different qualities. The vehicle response is evaluated through a performance index representing ride comfort, dynamic tyre load and suspension working space parameters, and interpreted in the light of these individual parameters together with the implications of the suspension design for attitude control and steering behaviour. Linear analysis procedures are followed in studying the passive, active and slow-active suspension systems while suitable simulations are used for the non-linear semi-active suspension systems. Linear optimal control theory is used to determine the optimal parameters of the active and slow-active suspension systems. Semi-active suspension behaviours are evaluated on the basis of applying the optimal active parameters to each system, but the semi-active damper can only dissipate energy and switches off when external power would be needed for the system to follow the optimal active control law. Results are generated and discussed for each of these types of system and their performance capabilities are compared with each other. Conclusions concerning the practical viability of each of the systems are drawn.
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Kim, Sangcheol. "Fabrication of active and passive terahertz structures." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 60 p, 2006. http://proquest.umi.com/pqdweb?did=1203570961&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Garcia, Nil. "Optimization Methods for Active and Passive Localization." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/14192/1/garcia.pdf.
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Active and passive localization employing widely distributed sensors is a problem of interest in various fields. In active localization, such as in MIMO radar, transmitters emit signals that are reflected by the targets and collected by the receive sensors, whereas, in passive localization the sensors collect the signals emitted by the sources themselves. This dissertation studies optimization methods for high precision active and passive localization. In the case of active localization, multiple transmit elements illuminate the targets from different directions. The signals emitted by the transmitters may differ in power and bandwidth. Such resources are often limited and distributed uniformly among the transmitters. However, previous studies based on the well known Crámer-Rao lower bound have shown that the localization accuracy depends on the locations of the transmitters as well as the individual channel gains between different transmitters, targets and receivers. Thus, it is natural to ask whether localization accuracy may be improved by judiciously allocating such limited resources among the transmitters. Using the Crámer-Rao lower bound for target localization of multiple targets as a figure of merit, approximate solutions are proposed to the problems of optimal power, optimal bandwidth and optimal joint power and bandwidth allocation. These solutions are computed by minimizing a sequence of convex problems. The quality of these solutions is assessed through extensive numerical simulations and with the help of a lower-bound that certifies their optimality. Simulation results reveal that bandwidth allocation policies have a stronger impact on performance than power. Passive localization of radio frequency sources over multipath channels is a difficult problem arising in applications such as outdoor or indoor geolocation. Common approaches that combine ad-hoc methods for multipath mitigation with indirect localization relying on intermediary parameters such as time-of-arrivals, time difference of arrivals or received signal strengths, are unsatisfactory. This dissertation models the localization of known waveforms over unknown multipath channels in a sparse framework, and develops a direct approach in which multiple sources are localized jointly, directly from observations obtained at distributed sources. The proposed approach exploits channel properties that enable to distinguish line-of-sight (LOS) from non-LOS signal paths. Theoretical guarantees are established for correct recovery of the sources’ locations by atomic norm minimization. A second-order-cone-based algorithm is developed to produce the optimal atomic decomposition, and it is shown to produce high accuracy location estimates over complex scenes, in which sources are subject to diverse multipath conditions, including lack of LOS.
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Oh, Yim-Taek. "Passive and active drag of paralympic swimmers." Thesis, Manchester Metropolitan University, 2015. http://e-space.mmu.ac.uk/615953/.
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The aim of this thesis was to contribute to the development of an objective, evidence-based international classification system for para-swimmers by quantifying the effect of physical impairment on passive and active drag. The thesis comprises five studies. Study 1 identified a significant relationship between normalised passive drag and the para-swimmers’ International Paralympic Committee (IPC) Class, but an inconsistent difference in normalised passive drag between adjacent classes. High within-class variability in passive drag indicates that the current classification system does not always differentiate clearly between swimming groups. Study 2 found that anthropometric features of para-swimmers, such as height and body mass, differed significantly between IPC Classes, whereas Shoulder Width, Chest Depth, Shoulder Girth and Torso Girth did not. A weak correlation existed between para-swimmers’ anthropometry and their passive drag, which indicates that other factors, such as impairment type, may be more important predictors of passive drag than anthropometry. Study 3 revealed that certain impairments, such as double-leg amputation above knee level, may predispose a para-swimmer to a relatively high passive drag which disadvantages them in competition. Study 4 compared two methods of estimating active drag during front crawl swimming: the Naval Architecture Based Approach (NABA) and the Active Towing Method (ATM). The means were not statistically different. Using a sensitivity analysis, the NABA was identified as the more reliable method of assessing active drag. Study 5 found that active and passive drag of elite para-swimmers are highly correlated but no relationship existed between active drag and International Paralympic Committee S Class (IPC S Class), indicating that factors other than impairment level may be more important in determining active drag. The relationships discovered between drag, IPC Class, anthropometry and impairments will contribute to the development of the future IPC Classification system.
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Al-Mahmoud, Abdulrazzak M. "Microwave passive tunable and active bandpass filters." Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309711.
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Campillo, Javier. "From Passive to Active Electric Distribution Networks." Doctoral thesis, Mälardalens högskola, Framtidens energi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-31592.
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Large penetration of distributed generation from variable renewable energy sources, increased consumption flexibility on the demand side and the electrification of transportation pose great challenges to existing and future electric distribution networks. This thesis studies the roles of several actors involved in electric distribution systems through electricity consumption data analysis and simulation models. Results show that real-time electricity pricing adoption in the residential sector offers economic benefits for end consumers. This occurs even without the adoption of demand-side management strategies, while real-time pricing also brings new opportunities for increasing consumption flexibility. This flexibility will play a critical role in the electrification of transportation, where scheduled charging will be required to allow large penetration of EVs without compromising the network's reliability and to minimize upgrades on the existing grid. All these issues add significant complexity to the existing infrastructure and conventional passive components are no longer sufficient to guarantee safe and reliable network operation. Active distribution networks are therefore required, and consequently robust and flexible modelling and simulation computational tools are needed for their optimal design and control. The modelling approach presented in this thesis offers a viable solution by using an equation-based object-oriented language that allows developing open source network component models that can be shared and used unambiguously across different simulation environments.
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Zhou, Shaoyi. "Advances in passive and active damping techniques." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI066.
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Les systèmes mécaniques (e.g. structures flexibles) sont généralement peu amortis, et par conséquent des vibrations de fortes amplitudes peuvent apparaitre. Il apparait nécessaire de développer des stratégies de contrôle vibratoire pour atténuer ces vibrations mécaniques. Cette thèse a pour objectif de développer plusieurs techniques d'amortissement de vibration passives ou actives. La première partie porte sur l'utilisation d'un “inerter” pour améliorer les performances de contrôle vibratoire de deux dispositifs existants, l'amortisseur à masse accordée (TMD) et deux TMDs placés en série (SDTMD). Dans le cas avec un TMD, on considère un système mécanique avec incertitudes ainsi que son optimisation H-infinity (worst-case optimization) en adoptant une approche purement algébrique. Dans le cas de SDTMD, on vise à contrôler la vibration d'un système déterministe. Son optimisation H-infinity s'effectue ici en utilisant une version étendue de la théorie de points fixes (FPT). Dans une seconde partie, on cherche à améliorer les performances de ce type de dispositif en positionnant un élément linéaire de raideur négative entre la base et la masse accordée. Deux cas d'étude sont menés: le TMD seul et celui basé sur l'inerter (IDVA). Les deux dispositifs ont une configuration non-traditionnelle, dont la masse accordée est liée à la base par l'intermédiaire d'un amortisseur visqueux ou un réseau mécanique basé sur l'inerter. La réalisation de ces dispositifs non-traditionnelles avec ou sans raideur négative et leurs shunts piézoélectriques sont étudiés et une analogie électromécanique est établie. Cette analogie permet d'étendre l'applicabilité des amortisseurs mécaniques et de faciliter les réglages. Dans la dernière partie, deux techniques d'amortissement actif et semi-actif sont développées. La première stratégie concerne une loi de contrôle hybride applicable au TMD et à l'IDVA. Le contrôleur proposé est composé d'un seul ou plusieurs compensateurs identiques, qui est caractérisé par un pôle à l'origine et deux zéros coïncidents réels. Les expressions analytiques sont développées dans les deux cas. La seconde technique de contrôle s'appuie sur l'atténuation de vibration par shunt électromagnétique (EMSD), pour laquelle aucun capteur est requis. Une inductance négative (NI) est employée dans les shunts électromagnétiques afin d'améliorer l'amortissement. Trois architectures possibles de NI dans un EMSD sont évaluées à travers le facteur de couplage électromécanique, qui quantifie l'efficacité de conversion énergétique entre les domaines mécanique et électrique. Finalement, six shunts électromagnétiques utilisant des NIs sont optimisés et analysésMechanical systems (e.g. flexible structures) are usually lightly damped so that they vibrate severally in response to dynamic loads. Therefore, vibration control strategies should be adopted in order to reduce the undesired vibration of mechanical systems. The objective of this thesis is to develop multiple vibration control techniques, which are either passive or active. The first part focuses on the application of inerter to enhance the vibration control performance of two existing control devices, the tuned mass damper (TMD) and the series double TMD (SDTMD). The inerter is employed to relate the tuned mass to the ground. In the case of TMD, a mechanical system under stiffness uncertainty is considered and the worst-case H-infinity optimization is addressed by means of an entirely algebraic approach. In the case of SDTMD, the vibration of a deterministic mechanical system is to be controlled and the H-infinity optimal design is carried out via an extended version of fixed points theory (FPT). Instead of using the inerter, the second part consists in improving the control effect by incorporating a linear negative stiffness between the ground and the tuned mass. Two case studies are conducted based on the non-traditional TMD and inerter-based dynamic vibration absorber (IDVA), whose tuned mass is related to the ground by a viscous damper or an inerter-based mechanical network, respectively. Later, the exact electrical realization of non-traditional configurations with or without negative stiffness is proposed, which is based on the piezoelectric transducer enclosed by a particular shunt circuit. This electromechanical analogy enables to extend the applicability of mechanical control devices and to facilitate the precise tuning. In the last part, active and semi-active vibration control techniques are developed. The first strategy consists in enhancing the control capability of passive TMD and IDVA by feeding back the displacement signal of mechanical system to the electromagnetic actuator. The proposed controller can be regarded as one or multiple basic units arranged in series, which is featured by one pole at the origin and two coalesced zeros on the real axis. Distinguished from the previous strategy, the semi-active control technique is based on electromagnetic shunt damping (EMSD), therefore, no additional sensor is required to measure the information of mechanical system. In order to artificially increase the shunt damping performance, the employment of negative inductance (NI) in the shunt circuit is considered. Three possible layouts of NI in the EMSD are assessed in terms of the electromechanical coupling factor, which quantifies the energy conversion efficiency between mechanical and electrical domains. Finally, six types of shunt circuits are optimally tuned according to the FPT and the beneficial effect of NI and the influence of its layout can be underlined
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Molander, Jonathan, and Loo Lennart van. "Active Versus Passive Investing : A Comparative Analysis." Thesis, Internationella Handelshögskolan, Jönköping University, IHH, Företagsekonomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-49153.
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The increasing popularity of passive investment strategies causes the long-term feasibility of active investing to be questioned more often. Therefore, this research aimed to uncover whether active investors' influence on fund performance is positive and significant enough to offset the cost involved, thereby providing reasoning for active rather than passive investing. A comparative analysis of 211 actively managed funds and 191 market and industry-specific indices is performed. Security selection skills and market timing ability are captured through a model comprising of the Fama French three-factor and the Treynor and Mazuy market timing model. The sample is tested between 2005 and 2020, with 5-year sub-periods. Over the full period, active and passive returns are found to be nearly indistinguishable. However, active funds seem to excel during bearish periods, where passive funds excel in bullish periods. The standard deviation is higher overall for passive investing. This difference, however, disappears during bearish periods. The security selection skill is barely distinguishable from zero for either strategy. On the other hand, market timing ability is existent for active investors, indicating a positive effect in bearish markets and a negative effect in bullish markets. Additionally, for both investing strategies, more than 90% of the returns are explained by the movements of the general market. The most suitable investment strategy is truly determined by an investor's level of risk aversion. Nevertheless, this research found that, in general, the passive investing strategy is dominant under normal market conditions. Active investors can act on the macroeconomic developments that fuel crises. This advantage enables them to achieve returns superior to indices while preserving a lower standard deviation during bearish market conditions.
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SAXBY, DYANI J. "ACTIVE AND PASSIVE FATIGUE IN SIMULATED DRIVING." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195507547.
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Watson, Rose E. (Rose Elliott). "Active or Passive Voice: Does It Matter?" Thesis, University of North Texas, 1993. https://digital.library.unt.edu/ark:/67531/metadc501082/.
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This thesis reports on the use of active and passive voice in the workplace and classroom through analysis of surveys completed by 37 employees and 66 students. The surveys offered six categories of business writing with ten sets of two sentences each, written in active and passive voice. Participants selected one sentence from each set and gave a reason for each selection. The participants preferred active over passive 47 to 46 percent of opportunities, but they preferred mixed voice over both, 49 percent. The participants preferred active only for memos to supervisors; in the other five categories they preferred passive or mixed voice. Both males and females preferred mixed voice, and age appeared to influence the choices. They cited context as the most common reason for using passive.
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Poon, Joyce Kai See Yariv Amnon. "Active and passive coupled-resonator optical waveguides /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-05242007-105741.
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Moore, Garrett Lee. "A Hybrid (Active-Passive) VANET Clustering Technique." Diss., NSUWorks, 2019. https://nsuworks.nova.edu/gscis_etd/1077.
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Clustering serves a vital role in the operation of Vehicular Ad hoc Networks (VANETs) by continually grouping highly mobile vehicles into logical hierarchical structures. These moving clusters support Intelligent Transport Systems (ITS) applications and message routing by establishing a more stable global topology. Clustering increases scalability of the VANET by eliminating broadcast storms caused by packet flooding and facilitate multi-channel operation. Clustering techniques are partitioned in research into two categories: active and passive. Active techniques rely on periodic beacon messages from all vehicles containing location, velocity, and direction information. However, in areas of high vehicle density, congestion may occur on the long-range channel used for beacon messages limiting the scale of the VANET. Passive techniques use embedded information in the packet headers of existing traffic to perform clustering. In this method, vehicles not transmitting traffic may cause cluster heads to contain stale and malformed clusters. This dissertation presents a hybrid active/passive clustering technique, where the passive technique is used as a congestion control strategy for areas where congestion is detected in the network. In this case, cluster members halt their periodic beacon messages and utilize embedded position information in the header to update the cluster head of their position. This work demonstrated through simulation that the hybrid technique reduced/eliminated the delays caused by congestion in the modified Distributed Coordination Function (DCF) process, thus increasing the scalability of VANETs in urban environments. Packet loss and delays caused by the hidden terminal problem was limited to distant, non-clustered vehicles. This dissertation report presents a literature review, methodology, results, analysis, and conclusion.
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Svanberg, Mikaela, and Emilia Karlsson. "Active or Passive Fund Management : A comparison between active and passive Swedish funds before, during and after the financial crisis." Thesis, Linnéuniversitetet, Institutionen för ekonomistyrning och logistik (ELO), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-75394.
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The essay investigates if there is a correlation between a funds management fee and return in relation to the risk that is taken by the investor. Furthermore, the essay examines if it is worth paying a higher fee for an actively managed fund compared to the lower fee for a passively managed fund. In addition, the essay will investigate whether the results differ before, during and after the financial crisis which took place between 2007 and 2009. To answer the questions 38 different Swedish equity funds, 33 active and five passive, are used. The funds are investigated using performance measures, correlation analysis and regression analysis. The results show that there is no clear correlation between funds management fee and return in relation to the risk that is taken. In addition, the essay conclude that it is not worth paying a higher management fee for an actively managed fund.
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Kazemi, Alireza. "Mutual Fund Performance : Active- and Passive Fund Management." Thesis, Jönköping University, JIBS, Economics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-1226.
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In this thesis I will examine active equity mutual fund managers’ ability to outperform an index, which is done by utilizing a sample of four equity mutual funds that mainly invest in large Swedish quoted companies. In order to measure the risk-adjusted performance of the funds, a model created by Michael Jensen will be used. Furthermore, I will investigate whether the managers of the mutual funds increase/decrease the risk level, or rather the beta, when the stock market is bullish/bearish. Hence, two time spans have been chosen, 2001-2003 and 2004-2006, where the previous represents a bearish stock market and the later represents a bullish stock market.
The empirical evidence indicates that one fund in each period was significantly outper-formed by the comparable index. Furthermore, the result also suggests that two significant funds were talking more risk than the index in the bearish time period while three signifi-cant funds decreased the risk level during the bullish time period.
Denna kandidatuppsats undersöker aktiva fondförvaltares förmåga att upptäcka och inve-stera i fonder som presterar bättre än deras jämförekse index. Undersökningen är baserad på fyra aktiefonder som huvudsakligen investerats i Svenska börsnoterade företag. Fonder-nas riskjusterade prestation kommer att mätas med hjälp av en modell som är utformad av Michael Jensen.
Vidare kommer uppsatsen att undersöka om fondförvaltarna ökar eller minskar risk nivån, eller betavärdet, baserat på börsens utveckling under åren 2001-2003 och 2004-2006. Det förgående intervallet representerar en sjunkande börsperiod och det senare en stigande börsperiod.
Det empiriska resultatet indikerar att en signifikant fond i varje tidsintervall presterade säm-re än index. Utöver detta visade även resultatet att två signifikanta fonder ökade risk nivån, jämfört med index, i den sjunkande börsperioden medan tre signifikanta fonder minskade risk nivån i den stigande börsperioden.
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Karam, Philippe Chucri. "Modeling passive and active mechanisms in motoneuron dendrites." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13713.
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Sherwani, Hashir. "Resource management in active-passive multifunction radar networks." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10056926/.
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Despite the extensive research within the field of resource management in monostatic multifunction radar, the resource management techniques for a multifunction radar network are still in their infancy. More specifically, a network which has the ability to switch modes between monostatic and bistatic configuration may potentially be able to capitalise on the advantages of both configurations. This is a gap which has been identified and is the aim of this thesis to explore. The research within this thesis begins by exploring the advantages provided by a bistatic configuration over a monostatic configuration. The conclusions from the initial research are carried forward to design a complete resource management framework for a multifunction radar network consisting of active and passive nodes. The resource management framework is broken into two sub-problems, resourceallocation and the scheduling problem. The resource-allocation problem deals with the task parameter selection methodology to optimally distribute the finite resources. This incorporates the concept of information sharing, which can be considered as a subset of information fusion theory, to delegate a given task to the best suited sensor within the network. A Quality of service framework is utilised to solve the resource-allocation problem where the resulting algorithm is referred to as APNQ-RAM. The scheduling problem is solved by deploying an earliest deadline first scheduler on master-slave architecture where the resulting algorithm is named as MS-EDFS. The research has also explored the impact of the networks geometry and the number of nodes on the network’s performance in tracking and surveillance functions. The research shows significant advantages in terms of tracking and surveillance performance provided by such a network in comparison to a monostatic configuration functioning on its own.
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Sousa, Júnior Gabriel Faria de. "Active versus passive management : the case of BOVESPA." Master's thesis, Instituto Superior de Economia e Gestão, 2016. http://hdl.handle.net/10400.5/11647.
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Mestrado em FinançasO principal objetivo deste trabalho é analisar alguns modelos subjacente à gestão de carteiras ativa e passiva e qual seria seu impacto sobre a escolha de uma determinada carteira constituída por ações que estão integrados no índice BOVESPA, maior mercado bolsista do Brasil. A gestão passiva é baseada numa carteira que visa replicar o comportamento do Índice BOVESPA, tendo como base os preços históricos do índice e no método naïve (1/N), no qual composição da carteira inclui todos os ativos do índice com as mesmas proporções. A gestão ativa baseia-se no método de Markowitz, conhecido como modelo de média variância, que visa maximizar o retorno tendo definido um determinado nível de risco, ou minimizar o risco tendo em conta um nível de retorno esperado. Também é usado o método da variância mínima que consiste em minimizar o risco independentemente do retorno. Nesta abordagem as proporções a investir em cada ativo são revistas mensalmente tendo em conta a evolução do mercado. Outro modelo utilizado será um método ajustado da média variância em que serão mantidos os pesos ótimos do primeiro período para as restantes janelas de dados. Para as determinar são consideradas "janelas" de dados de 1 e 2 anos. É considerado um horizonte de investimento de 10 anos, a partir de Janeiro de 2005 a Dezembro de 2014. Com base nos resultados é possível afirmar que a carteira de média variância deve ser a escolhida, uma vez que apresenta os melhores resultados.
The main purpose of this paper is to analyze some models underlying the active and passive portfolio management and what would be its impact on the choice of a portfolio composed by stocks which are integrated in BOVESPA Index, Brazilian biggest stock market. The passive management approach is based on the historical prices of BOVESPA Index which replicates the behavior of the market and on the naïve method (1/N), in which the portfolio includes all the stocks on the index with the same proportions. Active management is based on the Markowitz model, also known as mean variance model, whose objective is to maximize the return give a set risk level or, minimize the risk given an expected return. The minimum variance model is also used, whose goal is to minimize the risk independent of the return. On these approach the weights of each asset in the portfolio are revised monthly, based on the market evolution. Another model used is a Mean Variance adjusted method in which the first period optimal weights will be maintained for the remaining data windows. In order for these to be determined, "windows" of 1 and 2 years were used. We are considering a 10 year investment horizon, from January 2005 to December 2014. Based on the results, we can affirm that the mean variance portfolio should be chosen, as performed better both in terms of returns and, especially, in terms of Sharpe ratio when compared with the other two portfolios.
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Zhang, Zhaowei. "Passive and active Bragg gratings for optical networks." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/47760/.
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This thesis investigates fibre Bragg grating (FBG) devices. Specifically, it consists of the developments and applications of two groups of devices: the optical phase en/decoders and the tunable fibre Bragg gratings based on an S-bending technique. The advantage of an S-bending tuning FBG is that its central wavelength is invariant as the linear strain gradient along the FBG is altered. Two new devices are developed by embedding a pair of FBGs in a single uniform beam for S-bending. One is the tunable dispersion compensator with a wide tuning range, and the other is a tunable pure dispersion slope compensator. The application of an S-bending tuning FBG in controlling the output pulse width of a soliton fibre laser is also experimentally demonstrated.
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Goldstein, Andre L. "Control of Sound Transmission with Active-Passive Tiles." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27913.
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Nowadays, numerous applications of active sound transmission control require lightweight partitions with high transmission loss over a broad frequency range and simple control strategies. In this work an active-passive sound transmission control approach is investigated that potentially addresses these requirements. The approach involves the use of lightweight stiff panels, or tiles, attached to a radiating base structure through active-passive soft mounts and covering the structure surface. The resulting double-partition configuration was shown to have good high frequency passive isolation, but poor low frequency transmission loss due to the coupling of the tiles to the base vibration through the air gap. The low frequency transmission loss performance of the partition was increased by using the active mounts to cancel the local volume velocity of the tiles. The use of a decentralized control approach with independent single channel controllers for each tile facilitates the implementation of a multiple tile system in a large scale application.
A coupled structural-acoustic model based on an impedance mobility matrix approach was formulated to investigate the potential performance of active-passive tile approach in controlling sound transmission through plates. The model was initially applied to investigate the sound transmission characteristics of a double-panel partition consisting of a single tile-plate configuration and then extended to model a partition consisting of multiple-tiles mounted on a plate. The system was shown to have significant passive performance above the mass-spring-mass resonance of the double-panel system. Both feedback and feedforward control approaches were simulated and shown to significantly increase the transmission loss of the partition by applying control forces in parallel with the mounts to reduce the tile normal velocity. A correspondent reduction in sound radiated power was obtained over a broad frequency range limited by the tile stiffness.
The experimental implementation of the active-passive tile approach for the control of sound transmission through plates was also performed. Two main experimental setups were utilized in the investigations, the first consisting of a single tile mounted on a clamped plate and the other consisting of four active tiles mounted of a simply supported plate. Tile prototypes were implemented with lightweight stiff panels and integrated active-passive mounts were implemented with piezoelectric Thunder actuators. Both analog feedback and digital feedforward control schemes where designed and implemented with the objective of reducing the normal velocity of the tiles. Experimental results have demonstrated significant broad frequency range reductions in the sound transmission through the partition by active attenuation of the tile velocity. In addition, the experiments have shown that decentralized control can be successfully implemented for multiple tiles systems. The active-passive sound transmission control characteristics of the systems experimentally studied were observed to be in accordance with the analytical results.Ph. D.
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Lam, Margaretha Johanna. "Hybrid Active/Passive Models with Frequency Dependent Damping." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30770.
Full textAbstract:
To add damping to structures, viscoelastic materials (VEM)
are added to structures. In order to enhance the damping
effect of the VEM, a constraining layer is attached,
creating a passive constrained layer damping treatment
(PCLD). When this constraining layer is an active element,
the treatment is called active constrained layer damping
(ACLD). Recently, the investigation of ACLD treatments has
shown it to be an effective method of vibration suppression.
In this work, two new hybrid configurations are introduced
by separating the passive and active elements. In the first
variation, the active and passive element are constrained
to the same side of the beam. The other variation allows
one of the treatments to be placed on the opposite side of
the beam. A comparison will be made with pure active, PCLD,
ACLD and a variation which places the active element
underneath PCLD. Energy methods and Lagrange's equation
are used to obtain equations of motion, which are
discretized using assumed modes method. The frequency
dependent damping is modeled using the Golla-Hughes-McTavish
(GHM) method and the system is analyzed in the time domain.
GHM increases the size of the original system by adding
fictitious dissipation coordinates that account for the
frequency dependent damping. An internally balanced model
reduction method is used to reduce the equations of motion
to their original size. A linear quadratic regulator and
output feedback are used to actively control vibration. The
length and placement of treatment is optimized using
different criteria. It is shown that placing the active
element on the opposite side of the passive element is
capable of vibration suppression with lower control effort
and more inherent damping. If the opposite surface is not
available for treatment, a suitable alternative places the
PZT underneath the PCLD. LQR provides the best control,
since it assumes all states are available for feedback.
Usually only select states are available and output
feedback is used. It is shown that output feedback, while
not as effective as full state feedback, is still able to
damp vibration.Ph. D.
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Ziolkowski, Richard W. "Passive and active metamaterial-inspired nano-scale antennas." IEEE, 2016. http://hdl.handle.net/10150/623141.
Full textAbstract:
A variety of open and closed multi-layered nanoparticle structures have been considered analytically and numerically for their use as scatterers and radiators. These include metamaterial-inspired structures based on dielectrics and metals excited by either plane waves or electric Hertzian dipoles at optical frequencies. Both passive and active (gain impregnated dielectric) materials have been considered. Enhanced and mitigated scattering and radiating effects have been modeled. Nano-antenna and nano-amplifier configurations for optical applications have been emphasized. A review of these modeling efforts will be presented.
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Huang, Caijin. "Optical nano-antennas : passive properties and active control." Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS011/document.
Full textAbstract:
Les nano-antennes optiques sont de nouveaux éléments, généralement métalliques, permettant d’améliorer les interactions électromagnétiques entre le rayonnement lumineux et un objet sub-longueur d’onde. Ces dispositifs innovants, fonctionnant dans une gamme de longueur d’onde correspondant au spectre visible et proche infrarouge, répondent à certaines contraintes inhérentes à l’optique lorsque les échelles d’interactions relèvent du nanomètre. En particulier, les propriétés des antennes optiques métalliques sont régies par l’apparition de résonances plasmons qui permettent, d’une part de confiner le champ électromagnétique dans des volumes très inférieurs aux limites imposées par la diffraction, et d’autre part d’exalter fortement les processus optiques à faibles sections efficaces. L’objectif de cette thèse est de comprendre par l’expérience quels sont les paramètres clés qui caractérisent une nano-antenne optique afin d’en contrôler son fonctionnement. Ces paramètres ont été accessibles expérimentalement grâce au développement d’une microscopie adaptée basée sur une illumination diascopique à faible ouverture numérique avec soit une détection coronographique confocale ou conoscopique. Cet appareillage nous a permis de mesurer la capacité d’une antenne optique unique à diffuser un rayonnement lumineux. Les études ont débutées avec des systèmes modèles simples (nanoparticules) pour évoluer vers des antennes couplées (dimères). Par analogie avec le domaine radiofréquences, les paramètres importants d’une antenne optique que sont la plage fréquentielle, le désaccord, le gain et le diagramme de rayonnement ont été définis et mesurés. L’influence des caractéristiques morphologiques de l’antenne sur ces paramètres a complété l’étude. Toujours par comparaison avec les antennes radiofréquences, nous avons introduit le concept de tuner optique. Le principe est de modifier la réponse optique de la charge de l’antenne, c’est-à-dire le milieu dans lequel elle émet son rayonnement. Dans ce but, nous avons utilisé un milieu anisotrope composé des molécules de cristal liquide dont l’orientation de l’ellipsoïde des indices peut être commandée par un champ électrostatique. Le fonctionnement du tuner, c’est-à-dire l’accord de l’antenne à une fréquence de travail, a été démontré pour des antennes optiques coupléesOptical nanoantennas are a new class of optical devices, generally constituted of metal nanoparticles, used for enhancing the interaction between an electromagnetic wave and a nano-scale object. These components are operating in the visible to near infra-red part of the spectrum and are offering solutions for the inherent limitations of optics at the nanometer scale. In particular, the properties of optical antennas are governed by the surface plasmon resonances of the underlying structure. These resonances are associated with a large field confinement, beyond the diffraction limit, and an enhancement of the local electromagnetic response that is used to amplify weak optical processes. The objective of this doctoral thesis is to understand by an experimental approach what are the key parameters characterizing an optical antenna with the aim to control its operation. Through the development of an original microscopy based on a low numerical aperture diascopic illumination and a subsequent spatial filtering, the scattering characteristics of a single optical nano-antenna were successfully measured. Our approach was first tested with simple model antennas (nanoparticles) before investigating multi-element coupled antennas (dimers). In analogy to radiofrequency theory, we have defined and measured important antenna characteristics: operating frequency, detuning factor, gain and emission diagram. We have studied the influence of the morphology of the antenna on these characteristics. Continuing the comparison with microwave antennas, we have introduced the concept of an optical tuner. The operating principle is to modify the medium in which the antenna is emitting its radiation i.e. the load of the device. To this aim, we have employed anisotropic liquid crystal molecules. With this load medium, the orientation of the anisotropy can be controlled by a static electric field. The operation of the optical tuner, i.e. tuning of the antenna to a broadcasting frequency, is demonstrated for electromagnetically coupled antennas
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Zhou, Xuan. "Advances in hybrid plasmonics : from passive to active functions." Thesis, Troyes, 2013. http://www.theses.fr/2013TROY0015/document.
Full textAbstract:
La plasmonique hybride est un sujet d’actualité qui exploite des interactions physiques entre nano-objets métalliques et d’autres nanomatériaux. En bénéficiant des propriétés de chacun de leurs constituants, les nanostructures hybrides sont utilisées dans de nombreuses applications comme la détection d’espèces bio-chimiques. Dans cette thèse, nous présentons une nouvelle nanostructure hybride polymère/metal qui est non seulement utilisée comme nano-émetteur anisotrope qui s’avère aussi être un outil puissant de caractérisation du champ proche optique.La fabrication de cette nouvelle nanostructure est basée sur une approche de par photopolymérisation à l’échelle nanométrique. Cette technique, en comparaison aux méthodes traditionnelles de caractérisation, ne fournit pas seulement l’image de la distribution du champ, mais permet aussi des mesures quantitatives des plasmons de surface avec une résolution sub -5nm, incluant une description fine de la décroissance exponentielle des ondes évanescentes impliquées.A l’aide du mode plasmon dipolaire, une distribution anisotrope de matériau organique est intégrée dans le voisinage de la nanoparticule métallique. Avec une haute concentration de molécules de colorant dans le polymère, l’intensité des signaux de fluorescence et Raman du nano-émetteur hybride dépend de la polarisation incidente. À notre connaissance, il s’agit de la première réalisation d’un nano-émetteur dont le milieu à gain présente une distribution spatiale complexe le rendant sensible à la polarisationHybrid plasmonics has given rise to increasing interest in the context of the interaction between metal nano-objects and other materials. By benefiting from each of its constituents, hybrid nanostructures are commonly adopted in studies and optimization of biological and chemical sensors, nanoparticle with high plasmon resonance tunability, and nano-emitters. This PhD thesis presents a hybrid nanostructure of photopolymer/metal nanoparticle that is used as a near-field characterizing tool and as an anisotropic nano-emitter.The fabrication of this hybrid nanostructure is a near-field imprinting process based on nanoscale photopolymerization. This technique, compared with traditional near-field characterization methods, provides not only the image of the field distribution, but also enables quantification of the surface plasmon properties with sub-5nm resolution and reproduction of the exponential decay of the near-field.Under dipolar mode plasmon, the photopolymer was created anisotropically in the vicinity of the metal nanoparticle. With high concentration of dye molecules trapped in the polymer, the hybrid nano-emitter displays surface enhanced fluorescence and Raman signal that is dependent on the incident polarization. To our knowledge, this is the first achievement of the anisotropic nano-emitter based on the inhomogeneous distribution of the active molecule
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Lindberg, Peter. "Wideband Active and Passive Antenna Solutions for Handheld Terminals." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7445.
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Muckaden, Sachit. "Myspeedtest: active and passive measurements of cellular data networks." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47674.
Full textAbstract:
As the number and diversity of applications available to mobile users increases, there is an increasing need for developers, network service providers, and users to understand how users perceive the network performance of these applications. MySpeedTest is a measurement tool that actively probes the network to determine not only TCP throughput and round trip time, but also the proximity to popular content providers, IP packet delay variation, and loss. It also records other metadata that could affect user experience, such as signal strength, service provider, connection type, battery state, device type, manufacturer, time of day, and location. The tool also takes passive measurements of the applications installed on the device and the network usage of these applications. My SpeedTest is available on the Google Play Store and currently has 1300+ active users.
This thesis presents the design and implementation of MySpeedTest as well as effect of metrics like latency and IP packet delay variation on performance.
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Tehrani, Maryam Ghandchi. "Passive modification and active vibration control by receptance method." Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441935.
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Chang, Kuo-Wei. "Passive and Active Control of Wind Induced Bridge Vibration." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523132.
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Potter, Jack. "Passive and semi-active damping of base-excited structures." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618724.
Full textAbstract:
It has become commonplace for discrete passive or active elements to be added to Structures to mitigate against vibration. More recently, semi-active damping has been a focus of research. Semi- active systems are attractive due to their performance, low cost, power consumption and control stability. In this thesis we consider how passive and semi-active damping systems may he designed to mitigate against. vibration in base-excited structures. initially we consider the base isolation of a single degree-of-freedom system. The optimality of the common sky-hook switching controller is assessed and its control form is generalised. Numerical and theoretical studies identify the optimal form of switching control and a linear switching surface controller is proposed which is found to achieve performance close to optimal. We propose the new design methodology of quasi-active damping . The motivation for this method is to approach the levels of performance obtainable using fully active systems whilst retaining the desirable attribute of semi- active systems, A quasiactive suspension design is proposed and validated in simulation. It is found that this system call produce a quasi-active region in the frequency response of very low displacement transmissibility. This study is then extended to consider how quasi-active systems should be designed specifically for use with magnetorheological dampers. The influence of external passive damping on 2:1 internal resonance in stay cables is examined. An efficient, low-order damped nonlinear cable model is derived and used to numerically generate stability boundaries. These are used to assess how damping should be designed to mitigate against this excitation mechanism. We then study the optimality of dipped-optimal LQR control in the semi-active clamping of cables. We propose the addition of all extra term to the cost function to encourage the control output. To satisfy the semi-active constraint. Finally we study the feasibility of real-time dynamic substructuring as a technique for the experimental testing of damped stay cables.
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Chey, Min Ho. "Passive and Semi-Active Tuned Mass Damper Building Systems." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2007. http://hdl.handle.net/10092/3431.
Full textAbstract:
This thesis explores next generation passive and semi-active tuned mass damper (PTMD and SATMD) building systems for reducing the seismic response of tall structures and mitigating damage. The proposed structural configuration separates the upper storey(s) of a structure to act as the 'tuned' mass, either passively or semi-actively. In the view point of traditional TMD system theory, this alternative approach avoids adding excessive redundant mass that is rarely used. In particular, it is proposed to replace the passive spring damper system with a semi-active resetable device based system (SATMD). This semi-active approach uses feedback control to alter or manipulate the reaction forces, effectively re-tuning the system depending on the structural response. In this trade-off parametric study, the efficacy of spreading stiffness between resetable devices and rubber bearings is illustrated. Spectral analysis of simplified 2-DOF model explores the efficacy of these modified structural control systems and the general validity of the optimal derived parameters is demonstrated. The end result of the spectral analysis is an optimally-based initial design approach that fits into accepted design methods. Realistic suites of earthquake ground motion records, representing seismic excitations of specific return period probability, are utilised, with lognormal statistical analysis used to represent the response distribution. This probabilistic approach avoids bias toward any particular type of ground motion or frequency content. Statistical analysis of the performance over these suites thus better indicates the true overall efficacy of the PTMD and SATMD building systems considered. Several cases of the segregated multi-storey TMD building structures utilising passive devices (PTMD) and semi-active resetable devices (SATMD) are described and analysed. The SATMD building systems show significant promise for applications of structural control, particularly for cases where extra storeys might be added during retrofit, redevelopment or upgrade. The SATMD approach offers advantages over PTMD building systems in the consistent response reductions seen over a broad range of structural natural frequencies. Using an array of performance metrics the overall structural performance is examined without the typically narrow focus found in other studies. Performance comparisons are based on statistically calculated storey/structural hysteretic energy and storey/structural damage demands, as well as conventional structural response performance indices. Overall, this research presents a methodology for designing SATMD building systems, highlighting the adaptable structural configuration and the performance obtained. Thus, there is good potential for SATMD building systems, especially in retrofit where lack of space constrains some future urban development to expand upward. Finally, the approach presented offers an insight into how rethinking typical solutions with new technology can offer dramatic improvements that might not otherwise be expected or obtainable.
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Paust, Tobias [Verfasser]. "New Methods for Passive and Active Microrheology / Tobias Paust." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2013. http://d-nb.info/1035699613/34.
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Pournara, Iosifina-Vasiliki. "Reconstructing gene networks by passive and active Bayesian learning." Thesis, Birkbeck (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417001.
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Li, Weibing. "Prismatic modular robotics enabled through active and passive elements." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/20112/.
Full textAbstract:
Robotic involvement is envisaged for exploration of human-inaccessible areas such as planetary space, confined and unstructured environments, and radioactive places. An exploration mission usually includes multiple tasks that are difficult or even impossible to finish using a single robot. Modular robots aim to solve this problem by providing a robotic system wherein robotic modules can be reconfigured to accomplish diverse tasks. In this work, research is undertaken on the design, manufacturing and control of a modular robotic system consisting of straight extending modules. Each robotic module of the modular robot can be actively controlled or can respond passively to external forces. The modular elements can be connected simply for ease of manual reconfiguration. A new connectivity strategy for building modular robotic structures using rigid connector nodes, active and passive modular elements is investigated. Comparisons of the new connectivity and a conventional connectivity using compliant connector nodes are made with respect to kinematics, locomotion and deformation of some robotic structures. Modular units including a prismatic actuator, a rigid connector node and a passive revolute joint are then designed, manufactured and tested. More modular elements are further replicated for building modular robotic structures leading to a final prototype system with eight prismatic actuators, four rigid connector nodes and four passive revolute joints. Each prismatic actuator is equipped with a locking mechanism and possesses three different working states: it can either be actuated, locked or passive. The three-state prismatic actuator is self-contained with its own computation, communication, actuation and sensing capabilities. A proportional-integral-derivative (PID) controller is implemented to control the position of the prismatic actuator. The actuation and locking forces of the prismatic actuator are experimentally evaluated. The prismatic actuator can vertically lift an external load of 29.4 N. The locking force of the mechanical locker is 78.6 N, enabling the actuator to be capable of vertically supporting a weight of about 2.5 kg in the locked state. The minimum force required to passively move the prismatic actuator is also measured as 8.34 N. The performance of the PID controller, three states and state transitions of the prismatic actuator are then validated by a series of physical experiments. Experimental results demonstrate that the maximum absolute value of the displacement error is to be 0.175 mm in the actuated state, and state transitions between actuated, locked and passive states are physically achievable. Moreover, state transitions of two and multiple prismatic actuators are also realized resorting to communications between the prismatic actuators. As a high-level control strategy, a central pattern generator (CPG) neural network is first applied to modular robotic structures composed of the fabricated robotic modules. Physical experiments show that the modular robotic structures achieve a worm-like locomotion gait through the coordination of their actuators' movements, substantiating the feasibility and effectiveness of the mechanical design and control strategy. Modular robotic structures with greater number of elements are constructed in a physics-based robot simulator. A generalized CPG neural network and a role-based control method are developed for controlling these simulated modular robots. Computer simulations are then conducted to further demonstrate locomotion capability of modular robotic structures composed of three-state prismatic actuators. Simulation results show that the generalized CPG method is scalable to a broad range of robotic structures with different number of modules. The three-state prismatic actuator can be applied to releasing physical constraints of a robotic structure during task execution and achieving a walking pattern by using state transitions.
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Cho, Seong-Ho 1966. "Laser micromachining of active and passive photonic integrated circuits." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/30086.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2004.Includes bibliographical references (leaves 149-158).
This thesis describes the development of advanced laser resonators and applications of laser-induced micromachining for photonic circuit fabrication. Two major advantages of laser-induced micromachining are direct patterning and writing on large areas of substrates at high speed following the exposure of laser light, without using complicated photomask steps. For passive photonic devices fabrication, a novel femtosecond laser with unprecedented low repetition rates of 4 MHz is demonstrated to generate high intensity pulses, as high as 1.25 MW with 100 nJ pulse energies and 80 fs pulse durations directly from this laser resonator, without using any active devices or amplifiers. These high intensity pulses are applied to transparent glass materials to demonstrate micromachining of waveguides, gratings, couplers, and three dimensional waveguides and their beam couplings. Active and passive semiconductor devices can be monolithically integrated by employing high energy laser pulses to locally disorder quantum well regions. The 45 nm bandgap shifts at 1.55 ptm with a standard Q-switched Nd:YAG laser at 535 nm are realized. Finally, unidirectional semiconductor ring lasers for high-density integration are developed as a potential application to photonic integrated circuits. Hybrid semiconductor S-crossover and retro-reflected ring lasers, as prototypes for unidirectional operation, are built and result in up to 21.5 dB and 24.5 dB of counter-mode suppression ratio, respectively, which is in good agreement with theoretical predictions.
by Seong-Ho Cho.
Ph.D.
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Topudurti, Shruti. "Determinants of Flows Between Active and Passive Equity Investments." Scholarship @ Claremont, 2018. http://scholarship.claremont.edu/cmc_theses/1952.
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Active versus passive investing is a popular topic within the investment community and beyond. In particular, many are concerned with fund flows in and out of active and passive investments. Existing research suggests that recent returns are a reason for the capital flow from active to passive and that fees also impact flows negatively. With U.S. equity mutual funds as a proxy for active investing and U.S. equity ETFs as a proxy for passive investing, I show that prior month flows have a positive and significant relationship with current flows for both ETFs and mutual funds, as well as for flows from ETFs to mutual funds. I also show that mutual fund monthly returns have a positive relationship with flows of mutual funds and flows from ETFs to mutual funds, while ETF monthly returns have a negative relationship with flows from ETFs to mutual funds. This supports prior literature. I also find that the differential in mutual fund and ETF returns (rMF – rETF) is insignificant and negative for net fund flows into ETFs. I find a generally positive relationship between mutual fund expense ratios and flows into mutual funds, as well as with flows from ETFs to mutual funds. Finally, I find a negative relationship between ETF expense ratios and flows into ETFs, as well as with flows from ETFs to mutual funds. The relationships between expense ratios and flows mostly contradict prevailing literature, except for the relationship between ETF expense ratios and ETF flows. This suggests passive investors are potentially more price-conscious than active investors, as passive investors experience negative flows as expense ratios increase, while flows into mutual funds do not have that relationship with expense ratios. Higher fees for mutual funds may also suggest a change in the composition of mutual funds, as funds similar to ETFs exit and new mutual funds become even more active.
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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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Delabroy, Olivier. "Oxydes d'azote et leur contrôle : solutions passive et active." Châtenay-Malabry, Ecole centrale de Paris, 1996. http://www.theses.fr/1996ECAP0494.
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Les oxydes d'azote (NOx) ont un impact considérable sur l'environnement. La combustion en est l'une des sources principales. Dans la plupart des configurations réelles, la combustion a lieu dans des écoulements turbulents. L'interaction entre la chimie de formation des NOx et la turbulence est l'une des clés du problème et sera étudiée via le mélange et le champ de taux d'étirement. En s'inspirant de la combustion pulsée, il est possible de provoquer la création de structures à grande échelle dans un écoulement et d'étudier l'influence de ce procédé sur la formation des NOx. La première solution (passive) consiste à générer les tourbillons de manière aérodynamique. Grace à la géométrie lobée de l'injecteur la flamme s'allume en aval en une combustion pauvre, prémélangée donc peu productrice de NOx. L'autre méthode consiste à forcer la création des structures par une source externe. Ce contrôle actif est appliqué avec succès à des bruleurs à fioul. La formation de larges structures dans l'écoulement assure une réduction de 20 à 30% de l'émission de NOx. Des essais sur un bruleur de 900 kw sont effectués avec du fioul enrichi a la pyridine pour simuler un fioul lourd et démontrer l'efficacité du contrôle actif sur le NO du combustible
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Blankenship, Tashauna L. "Episodic Memory during Middle Childhood: Active vs. Passive Processing." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78120.
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Episodic memory refers to context based explicit memory and shows vast improvements during middle childhood. In this study, episodic encoding was manipulated using stimuli that were hypothesized to require active or passive processing. Nine to eleven-year-old children were presented with a recall task using lower resolution (active processing) and clear (passive processing) images. It was hypothesized that children would recall more low resolution images than clear images. Executive function ability was also assessed to investigate possible contributions to performance. Furthermore, this study investigated whether frontal and temporal brain electrophysiology predicted unique variance in recall performance. Results suggested that overall there were no performance differences between low resolution and clear images; however, differences may exist within task blocks. Electrophysiology at temporal scalp locations and executive functions predicted unique variance in memory task performance. Specifically, set-shifting and working memory predicted a unique amount of variance in memory task performance. The results suggest that explicit memory may require certain executive processes more than others, and that active and passive processing may enhance this effect.Master of Science
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DuGar, Grace A. "Passive and Active Masculinities in Disney’s Fairy Tale Films." Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1367849096.
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Wang, Huaiyi. "Achieving Efficient Spectrum Usage in Passive and Active Sensing." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483709288836523.
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Gazuz, Igor. "Active and passive particle transport in dense colloidal suspensions." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-66299.
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Priest, Kevin Kennett. "Life cycle costing of active and passive solar retrofits." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024497.
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Ferreira, Sonia Maria Gomes. "Mapping passive x active reading tasks in esap teaching." Florianópolis, SC, 2003. http://repositorio.ufsc.br/xmlui/handle/123456789/86007.
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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-Graduaçãoe em Letras/Inglês e Literatura Correspondente.Made available in DSpace on 2012-10-21T02:23:41Z (GMT). No. of bitstreams: 1 193974.pdf: 1398356 bytes, checksum: 434bf850dfa1afe48ece01ce5d077ae0 (MD5)
Esta pesquisa fez um mapeamento de tipos de atividades de leitura em livros de Inglês Instrumental utilizados na UFSC; realizou uma investigação correlata em salas de aula; observou a ressonância que tipos diferentes de atividades de leitura podem exercer na motivação, e reflexão crítica dos alunos. O primeiro estudo sondou a predominância de tipos de atividades em 6 livros de Inglês Instrumental; o segundo pesquisou as tarefas dominantes nas aulas de 4 professores; o terceiro investigou a reação de alunos de 3 turmas, perante dois blocos de tipos diferentes de atividades. As observações, transcrições das aulas, e questionários, foram os instrumentos utilizados para análise dos dados. O arcabouço teórico de Davies (1995), de atividades 'passivas' e 'ativas', deu respaldo aos estudos. Os resultados atestam a predominância de atividades 'ativas' nos livros analisados e nas aulas de 3 dos 4 professores observados. Constatou-se também mais motivação, e mais evidências de leitura crítica, durante o uso de tarefas 'ativas'. Tópicos como, instrução baseada no uso de tarefas, demanda cognitiva de diferentes tipos de atividades, diferenças individuais de estilo de ensino/aprendizagem, pensamento crítico, e independência do aprendiz, serviram como aparato teórico para a pesquisa. Outras descobertas importantes foram: que a delimitação entre o que Davies (1995) coloca como atividade 'passiva' ou 'ativa' parece não ser clara, não proporcionando flexibilidade para a variação de demanda cognitiva imposta por cada tipo de tarefa; a maneira de condução das atividades também parece ser mais crucial do que supunha a premissa inicial.
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Cambou, Pierre E. "A Distributed Active Vibration Absorber (DAVA) for Active-Passive Vibration and Sound Radiation Control." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/10105.
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This thesis presents a new active-passive treatment developed to reduce structural vibrations and their associated radiated sound. It is a contribution to the research of efficient and low cost devices that implement the advantages of active and passive noise control techniques. A theoretical model has been developed to investigate the potential of this new "active-passive distributed absorber". The model integrates new functions that make it extremely stable numerically. Using this model, a genetic algorithm has been used to optimize the shape of the active-passive distributed absorber. Prototypes have been designed and their potential investigated. The device subsequently developed can be described as a skin that can be mechanically and electrically tuned to reduce unwanted vibration and/or sound. It is constructed from the piezoelectric material polyvinylidene fluoride (PVDF) and thin layers of lead. The tested device is designed to weight less than 10% of the main structure and has a resonance frequency around 1000 Hz. Experiments have been conducted on a simply supported steal beam (24"x2"x1/4"). Preliminary results show that the new treatment out-performs active-passive point absorbers and conventional constrained layer damping material. The compact design and its efficiency make it suitable for many applications especially in the transportation industry. This new type of distributed absorber is totally original and represent a potential breakthrough in the field of acoustics and vibration control.Master of Science
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Hussain, Arshad. "High-resolution passive and active-passive switched-capacitor delta-sigma modulator design techniques in nanoscale CMOS." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3691845.
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Gerson, Sarah A. "What's in a mitten? the effects of active versus passive experience on action understanding /." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8474.
Full textAbstract:
Thesis (M.S.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Psychology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.