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Building a model for binary star formation : the separate nuclei hypothesis revisitedMcDonald, Jennifer Mary January 1995 (has links)
No description available.
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Evaluation of strategies for repeat procurementHeld, Christopher M. 12 December 2011 (has links)
For the past several decades, there has been a fundamental dispute between the appropriate mechanism for repeat procurement. On one hand, the supporters of Porter (1979) advocate a competitive setting where short-term contracts are used to increase buyer power and lower supplier prices. On the other hand, the supporters of Deming (1986) advocate the idea of long-term contracts to align buyer and supplier incentives. This trade-off between long-term and short-term contracts has fundamentally affected the practice of procurement, with most suppliers opting for hybrid strategies such as Incumbent Biasing: a strategy characterized by short-term contracts with frequent rebidding with an advantage given to the incumbent. This work examines this hybrid strategy to determine its effectiveness. First, we create an empirical model that identifies and measures the trade-offs between the Porter and Deming strategies. Using this model, we find that Incumbent Biasing has an impact on procurement performance via two mechanisms: first, Incumbent Biasing decreases bidding competitiveness in repeat procurement bidding, which decreases performance; second, Incumbent Biasing has a moderating effect where it improves incentive alignment between the buyer and supplier and improves procurement performance. We show that depending on the current contract design, the net effect of Incumbent Biasing on overall procurement performance can be either positive or negative. This is first work to empirically test the impact of Incumbent Biasing on procurement performance and the first to identify the positive and negative mechanisms by which this impact occurs. Using this research, managers will be able to identify their firm's position with regards to incentive alignment with their supplier to determine if Incumbent Biasing has a net positive effect for their firm.
After identifying the impact of Incumbent Biasing on procurement performance, we contribute to the literature by testing this analysis through two additional extensions. First, using secondary data analysis we show that our construct for procurement performance is correlated with firm performance. We do this by comparing the answers to our procurement performance construct items to the change in gross margin of the publicly traded respondents in our study over time. This shows that our construct is not only reliable, but that procurement performance has a positive impact on overall firm performance. This is the first work to provide an empirical construct for procurement performance that is validated via secondary data analysis of firm performance. Second, we test a competing theory to Incumbent Biasing which is Multi-Sourcing: the strategy of spreading a contract to multiple suppliers to maintain competitiveness in bidding. Approximately $46\%$ of our sample identify as using both strategies simultaneously and we test for an impact between the two. We show that the two strategies to not impact each other and can be viewed independently. Subsequently, we test two Multi-Sourcing constructs in our model and find that there is no significant impact on bidding competitiveness from Multi-Sourcing.
Subsequently, we examine the impact of repeatedly awarding a contract to a pool of bidders. In our model, one contract is bid repeatedly over time, resulting in bidders gaining information about their competitors' cost. The academic literature is mixed on how a buyer should approach this type of contract bidding interaction. On one hand, it is argued that establishing an awarding structure that favors the incumbent decreases the frequency of switching, and thus cost. On the other hand, it is argued that an awarding structure that favors the non-incumbent (entrant) bidders places competitive pressure on the incumbent and generates low margin bids. This issue is further complicated by the practice cited in the academic literature of ``defection', where entrant firms either perceive a bias or believe that their cost is uncompetitive and will not bid in future stages.
We create a framework that explores the apparent contradictions in these recommendations and gives conditions when biasing toward the incumbent or entrant should be implemented. We first characterize bidders based on their effort to bid and their cost to supply the contract. We then show that in the case of low effort to bid and high cost for the entrant, entrant biasing is optimal; when the reverse is true incumbent biasing is optimal. Using the results from our analysis, we provide guidance to buyers facing a repeated procurement
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Ultra-Low-Supply-Voltage Analog-to-Digital ConvertersPetrie, Alexander Craig 13 November 2019 (has links)
This thesis presents techniques to implement analog-to-digital converters (ADCs) under an ultra-low-supply-voltage of 0.2 V to reduce the power consumption. The thesis proposes a dynamic bulk biasing circuit to adjust the PMOS bulk voltage to balance the NMOS and PMOS drain currents to guarantee functionality in the presence of process, voltage, and temperature variations. The dynamic bulk bias circuit is analyzed rigorously to show its functionality. This thesis also describes a new comparator suitable for a 0.2-V supply using ac-coupling, stacked input pairs, and voltage-boosted load capacitor. A 10-bit 5-kS/s successive-approximation-register (SAR) ADC in a 180-nm CMOS process with a supply voltage of 0.2 V demonstrates these ideas. The ADC exhibits a differential nonlinearity (DNL) and integral nonlinearity (INL) within +0.42/-0.45 and +0.62/-0.67 LSB, respectively. The measured SFDR and SNDR at 5 kS/s with a Nyquist-frequency input are 65.9 dB and 52.1 dB, respectively. The entire ADC and dynamic bulk biasing circuitry consume 22 nW including leakage power to yield a figure-of-meirt (FoM) of 8.8 fJ/conv.-step. Measurements of multiple chips show the proposed dynamic bulk biasing fully recovers the ADC performance when the supply voltage is varied. The nW power consumption makes the design well suited for wireless sensor node and energy harvester applications.
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Testing of methods for reducing motivational bias in multi - criteria decision analysis problemsKerr, Chadwick Samuel 10 December 2021 (has links)
The idea of multi-criteria decision making has been around for quite a while. All judgement tasks are potential points of bias introduction. Each judgement task was assessed to identify common biases introduced through an extensive literature review for each task and bias. In several other studies, the distinction is made between cognitive and motivational biases. Cognitive biases are widely studied and well known with mitigations that have been validated. Motivational biases are judgements influenced by the decision maker’s desire for a specific outcome, also referred to as intentional bias, that are hard to correct and received very little testing and exploration. This study tested the techniques that are identified for reducing motivational bias and tested an instrument to identify characteristics within a decision maker that would increase the likelihood that they would be motivationally biased. The results of this study provide a methodology for assessing the susceptibility to motivational biases of the decision makers and provides a framework for reducing the motivational bias within the multi-criteria decision making (MCDM) process using the general steps applicable to all multi-criteria decision analyses. Given that the general steps are used, this methodology is generalizable to any MCDM problem or domain and was found to be reliable and consistent with previous instruments and tools. A summary of the future research to further the explore the methodology and additional techniques for reducing motivational bias is proposed.
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Caractérisation sécuritaire de circuits basse-consommation face aux attaques par laser / Security evaluation of low-power devices against laser fault attacksLacruche, Marc 21 July 2016 (has links)
La minimisation de la consommation d'énergie est primordiale lors de la conception de circuits. Cependant, il est nécessaire de s'assurer que cela ne compromette pas la sécurité des circuits. Et ce particulièrement face aux attaques physiques, les appareils mobiles étant des cibles idéales pour ces dernières.Ce travail vise à évaleur l'impact du body-biasing sur la résistance des circuits aux attaques laser. Ces techniques permettent d'ajuster dynamiquement le ratio consommation/performance d'un circuit en modifiant la tension de polarisation des caissons. Le manuscrit se découpe en quatre chapitres. Il commence par un état de l'art. Puis, le banc de test laser utilisé est présenté ainsi que le travail effectué pour permettre son automatisation et une première étude sur l'impact des impulsions laser de courte durée sur les mémoires SRAM. Le troisième chapitre rapporte les résultats d'une campagne d'injection de faute laser sur des mémoires soumises au body-biasing. Celle-ci permet de mettre en évidence une augmentation de la sensibilité au laser des circuits lorsque leur tension d'alimentation est réduite et que le Forward Body Biasing est utilisé. A partir de ces résultats, le dernier chapitre propose une méthode utilisant les capacités basse-consommation d'un microcontrôleur pour durcir un AES matériel. Ces travaux permettent ainsi de montrer que les techniques de réduction de la consommation peuvent constituer un risque sécuritaire potentiel si elle ne sont pas prises en compte correctement. Cependant, les capacités apportées au circuit dans ce cadre peuvent être détournées pour améliorer sa résistance aux attaques. / The increasing complexity of integrated circuits and the explosion of the number of mobile devices today makes power consumption minimisation a priority in circuit design. However, it is necessary to make sure that it does not compromise the security of sensitive circuits. In this regard, physical attacks are a particular concern, as mobile devices are ideal targets for these attacks.This work aims at evaluating the impact of body-biasing on circuit vulnerability to laser attacks. These methods allow to dynamically adjust the performance/consumption ratio of a circuit by modifying the bias voltage of the body. It is divided in four chapters. It begins by introducing cryptography, physical attacks and low power design methods. Then the test bench used during this thesis is described, as well as the developpement work done in order to allow its automation. Then an initial study of the impact of short duration laser pulses on SRAM memories is presented. The third chapter reports the results of a laser fault injection campaign on memories subjected to Forward Body-Biasing. The results show a sensitivy increase of the circuits when supply voltage is lowered and FBB is activated. Based on these results, the last chapter introduces a method using the body-biasing and voltage scaling capabilities of a microcontroller to harden a hardware AES embedded on the latter.In conclusion, this works shows that low-power design methods can induce additional security risks if they are not carefully taken into account. However the additional capabilities of the circuits intended for power consumption reduction can be used in a different way to enhance device resillience to attacks.
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Etude statistique de l’énergie dans les circuits intégrés CMOS-FDSOI : caractérisation et optimisation / Statistical study of the energy in CMOS-FDSOI integrated circuits : characterization and optimizationKheirallah, Rida 19 October 2016 (has links)
Pour les nœuds technologiques avancés, la consommation statique des circuits intégrés est devenue un facteur essentiel de l'industrie microélectronique. L'efficacité énergétique des circuits est mesurée en fonction de leur performance et en fonction de leur consommation statique. Face à l'augmentation de la variabilité des paramètres physiques et environnementaux, la technologie silicium sur isolant complètement désertée (FD-SOI : Fully-Depleted Silicon-On-Insulator) permet de prolonger la loi de Moore dans le domaine nanométrique. Dans ce mémoire une étude statistique de l'énergie des circuits intégrés CMOS-FDSOI est réalisée. Des bibliothèques statistiques qui caractérisent le délai et la puissance statique des transistors CMOS-FDSOI sont mises en place. Compte tenu des avantages liés à la technologie FDSOI, des approches statistiques basées sur les bibliothèques sont appliquées pour estimer le délai et la puissance statique. En conservant l'exactitude de l'estimation, ces approches apportent un gain important en temps CPU. Suite à l'estimation du délai et de la puissance statique, les variations énergétiques des transistors CMOS-FDSOI sont étudiées en fonction de la tension d'alimentation et en fonction de la tension de polarisation. Ainsi, grâce à la détermination d'un compromis Délai-Puissance Statique efficace et l'élaboration d'un flow d'optimisation statistique, l'énergie statique d'un circuit a pu être optimisée. / For advanced technology nodes, static consumption of integrated circuits has become a key factor for the microelectronics industry. Circuit energy efficiency is measured in terms of performance and static consumption. With the increase of physical and environmental parameters, the Fully-Depleted Silicon-on-Insulator technology allows to extend Moore's law in the nanometer domain. In this work, a statistical study of CMOS-FDSOI integrated circuit energy is carried out. Statistical libraries characterizing delay and static power of CMOS-FDSOI transistors are presented. Given the advantages of the FDSOI technology, statistical approaches based on the libraries are applied in order to estimate delay and static power. While maintaining the accuracy of the estimations, these approaches provide a significant gain in CPU time. Following delay and static power estimation, CMOS-FDSOI transistors energy variations are considered according to supply voltage and voltage body biasing. Thus, by determining an efficient Delay-Static Power compromise and the development of a statistical optimization flow, static energy of a circuit has been optimized.
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Estudo das interações de complexos de inclusão flavonoide/ciclodextrina com modelos de membrana biológica por simulações de dinâmica molecular / Study of complex interactions include flavonoid / cyclodextrin with models of biological membrane by molecular dynamics simulationsManoel, Tabata Cruz [UNESP] 23 February 2016 (has links)
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Previous issue date: 2016-02-23 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / As ciclodextrinas são um grupo de oligossacarídeos cíclicos, que apresentam um formato de cone truncado com cavidade hidrofóbica e exterior hidrofílico. Isto faz com que as ciclodextrinas possam encapsular fármacos, o que propicia melhoras na biodisponibilidade, estabilidade e proteção das moléculas encapsulada. Por esta característica, as ciclodextrinas constituem uma nova classe de excipientes farmacêuticos de grande utilidade, por formar complexos de inclusão reversíveis com moléculas apolares e atuarem como moléculas carregadoras de substancias de interesse biológico e baixa solubilidade. Dentre os compostos com ação farmacológica encontra-se os flavonoides, em destaque a molécula de quercetina, um fármaco natural com diversas propriedades biológicas, como anticâncer, antioxidante, antialérgica, porém devido sua baixa solubilidade torna-se necessária a formação de complexos de inclusão com moléculas carregadoras como a β-ciclodextrina. O presente trabalho busca investigar, por meio de simulações computacionais, as diferentes formas de interação dos flavonoides com a ciclodextrina e do complexo formado por bicamadas lipídicas, a fim de contribuir para um melhor entendimento do processo de formação com complexo de inclusão ciclodextrina/flavonoide e de entrega do fármaco à célula. / The cyclodextrins are cyclic oligosaccharides that present a structure in form of a truncated cone, with a hydrophobic inside surfaces and hydrophilic outside. This causes the cyclodextrin can encapsulate drugs provides improvements in bioavailability, stability and protection of encapsulated molecules. By this feature, the cyclodextrins are a new class of pharmaceutical excipients useful for forming inclusion complexes with reversible nonpolar molecules and act as carrier of molecules with high biological interest and low solubility. Among the compounds with pharmacological action it is the flavonoid, featured the quercetin molecule; a drug with natural biological proprieties such as anticancer, antioxidant, antialergic, however, due to its low solubility, it becomes necessary the formation of inclusion complexes with carrier molecules. This study aims to investigate, through computer simulation, different forms of interaction of flavonoids with cyclodextrin and the complex formed by lipid bilayers, in order to contribute to a better understanding of the formation process with inclusion complex cyclodextrin/flavonoids and the drug delivery to cell.
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Ultra-low Quiescent Current NMOS Low Dropout Regulator With Fast Transient response for Always-On Internet-of-Things ApplicationsJanuary 2018 (has links)
abstract: The increased adoption of Internet-of-Things (IoT) for various applications like smart home, industrial automation, connected vehicles, medical instrumentation, etc. has resulted in a large scale distributed network of sensors, accompanied by their power supply regulator modules, control and data transfer circuitry. Depending on the application, the sensor location can be virtually anywhere and therefore they are typically powered by a localized battery. To ensure long battery-life without replacement, the power consumption of the sensor nodes, the supply regulator and, control and data transmission unit, needs to be very low. Reduction in power consumption in the sensor, control and data transmission is typically done by duty-cycled operation such that they are on periodically only for short bursts of time or turn on only based on a trigger event and are otherwise powered down. These approaches reduce their power consumption significantly and therefore the overall system power is dominated by the consumption in the always-on supply regulator.
Besides having low power consumption, supply regulators for such IoT systems also need to have fast transient response to load current changes during a duty-cycled operation. Supply regulation using low quiescent current low dropout (LDO) regulators helps in extending the battery life of such power aware always-on applications with very long standby time. To serve as a supply regulator for such applications, a 1.24 µA quiescent current NMOS low dropout (LDO) is presented in this dissertation. This LDO uses a hybrid bias current generator (HBCG) to boost its bias current and improve the transient response. A scalable bias-current error amplifier with an on-demand buffer drives the NMOS pass device. The error amplifier is powered with an integrated dynamic frequency charge pump to ensure low dropout voltage. A low-power relaxation oscillator (LPRO) generates the charge pump clocks. Switched-capacitor pole tracking (SCPT) compensation scheme is proposed to ensure stability up to maximum load current of 150 mA for a low-ESR output capacitor range of 1 - 47µF. Designed in a 0.25 µm CMOS process, the LDO has an output voltage range of 1V – 3V, a dropout voltage of 240 mV, and a core area of 0.11 mm2. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018
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Estudos da interação de peptídeos antimicrobianos com modelo de membrana por simulações de dinâmica molecular / Studies of the interaction of antimicrobial peptides with model membrane for molecular dynamics simulationsTavares, Rafaela Magalhães [UNESP] 01 March 2016 (has links)
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Previous issue date: 2016-03-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nos últimos anos, o interesse por estudar peptídeos com atividade antimicrobiana e anticâncer tem aumentado consideravelmente. Neste trabalho, direcionamos nossos estudos para os peptídeos antimicrobianos da classe dos matoparanos extraídos do veneno da vespa social Polybia paulista: o Polybia-MP III (MP-III), Polybia-MP I (MP-I) e seu sintético análogo, o Asn2-Polybia-MP I (NMP-I). Com o objetivo de estudar a interação desses peptídeos com um modelo de membrana composta por lipídeos do tipo POPC (Palmitoil-Oleil-Fosfatidil-Colina) em solução aquosa, realizamos dois tipos de simulações de Dinâmica Molecular (DM). Primeiramente, foram realizadas simulações no equilíbrio com a finalidade de amostrar o comportamento geral do sistema. Em seguida, para investigarmos especificamente o processo de adsorção do peptídeo à bicamada, realizamos simulações de DM com a utilização do método Adaptive Biasing Force (ABF), o que nos permitiu calcular o perfil de energia livre desse processo. Dentre os três peptídeos estudados, o que mais se destacou com relação a sua interação com o modelo de membrana, na simulação no equilíbrio, foi o peptídeo MP-I, por ser o único a se adsorver na bicamada com 200ns de simulação. Com a utilização do método ABF, verificamos que a posição mais estável para cada peptídeo é a posição na qual estes estão paralelos à face da bicamada, com a face hidrofóbica de cada peptídeo voltada para o interior da membrana, e a face hidrofílica voltada para o meio aquoso. Além disso, os resíduos hidrofílicos estão em contato com o grupo polar dos fosfolipídeos e com a água, e o resíduo de triptofano encontra-se posicionado na interface hidrofóbica/hidrofílica. Os resultados obtidos na simulação no equilíbrio para o peptídeo MP-I, que foi o único a se adsorver na bicamada, estão de acordo com os resultados obtidos pelo método ABF, e ambos concordam com resultados experimentais da literatura. / In recent years, interest in studying peptides with antimicrobial and anti-cancer activity has increased considerably. In this study, we focus our studies on antimicrobial peptides of the mastoparans class extracted from the venom of the social wasp Polybia paulista: the Polybia-MP III (MP III), Polybia-MP I (MP-I) and its synthetic analogue, the Asn2-Polybia-MP I (NMP-I). In order to study the interaction of these peptides with a model of membrane composed of POPC (Palmitoyl-Oleoyl-Phosphatidyl-Choline) lipids type in aqueous solution, we conducted two types of molecular dynamics simulations (MD). At first, a balance system simulation was performed in order to get a sampling of the general behavior of the system. Then, to investigate the adsorption of the peptide to the bilayer, MD simulations using Adaptive Biasing Force (ABF) method was performed, which allowed us to calculate the free energy profile of this process. Among the three studied peptides, the MP-I peptide was the one that stood out related to its interaction with the membrane model, in the simulation on balance, for being the one to adsorb the bilayer with simulation of 200ns. Using the ABF method, we verified that the most stable position for each peptide is the position in which they are parallel to the surface of the bilayer with the hydrophobic side of each peptide facing into the membrane, and the hydrophilic side facing the aqueous solution. In addition, the hydrophilic residues are in contact with the polar group of the phospholipid and water, and the tryptophan residue is positioned on the hydrophobic/hydrophilic interface. The results of the simulation in balance for the MP-I peptide, which was the only adsorbed in the bilayer, are in agreement with the results obtained by the method ABF, and both agree with experimental results in the literature.
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Highly degenerate diffusions for sampling molecular systemsNoorizadeh, Emad January 2010 (has links)
This work is concerned with sampling and computation of rare events in molecular systems. In particular, we present new methods for sampling the canonical ensemble corresponding to the Boltzmann-Gibbs probability measure. We combine an equation for controlling the kinetic energy of the system with a random noise to derive a highly degenerate diffusion (i.e. a diffusion equation where diffusion happens only along one or few degrees of freedom of the system). Next the concept of hypoellipticity is used to show that the corresponding Fokker-Planck equation of the highly degenerate diffusion is well-posed, hence we prove that the solution of the highly degenerate diffusion is ergodic with respect to the Boltzmann-Gibbs measure. We find that the new method is more efficient for computation of dynamical averages such as autocorrelation functions than the commonly used Langevin dynamics, especially in systems with many degrees of freedom. Finally we study the computation of free energy using an adaptive method which is based on the adaptive biasing force technique.
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