Emission regimes in a distributed feedback tapered master-oscillator power-amplifier at 1.5 µm

Integrated master-oscillator power amplifiers driven under steady-state injection conditions are known to show a complex dynamics resulting in a variety of emission regimes. We present experimental results on the emission characteristics of a 1.5 µm distributed feedback tapered master-oscillator power-amplifier in a wide range of steady-state injection conditions, showing different dynamic behaviors. The study combines the optical and radio-frequency spectra recorded under different levels of injected current into the master oscillator and the power amplifier sections. Under low injection current of the master oscillator the correlation between the optical and radio-frequency spectral maps allows to identify operation regimes in which the device emission arises from either the master oscillator mode or from the compound cavity modes allowed by the residual reflectance of the amplifier front facet. The quasi-periodic occurrence of these emission regimes as a function of the amplifier current is interpreted in terms of a thermally tuned competition between the modes of the master oscillator and the compound cavity modes. Under high injection current of the masteroscillator, two different regimes alternate quasi-periodically as a function of the injected current in the power amplifier: a stable regime with a single mode emission at the master oscillator frequency, and an unstable and complex self-pulsating regime showing strong peaks in the radio-frequency spectra as well as multiple frequencies in the optical spectra.

Efficient information reconciliation for Continuous-Variable QKD using Non-Binary Low-Density Parity-Check Codes

We present here an information reconciliation method and demonstrate for the first time that it can achieve efficiencies close to 0.98. This method is based on the belief propagation decoding of non-binary LDPC codes over finite (Galois) fields. In particular, for convenience and faster decoding we only consider power-of-two Galois fields.

Analytical models for the power subsystem and the attitude control subsystem of a microsatellite

El trabajo realizado en la presente tesis doctoral se debe considerar parte del proyecto UPMSat-2, que se enmarca dentro del ámbito de la tecnología aeroespacial. El UPMSat-2 es un microsatélite (de bajo coste y pequeño tamaño) diseñado, construido, probado e integrado por la Universidad Politécnica de Madrid (España), para fines de demostración tecnológica y educación. El objetivo de la presente tesis doctoral es presentar nuevos modelos analíticos para estudiar la interdependencia energética entre los subsistemas de potencia y de control de actitud de un satélite. En primer lugar, se estudia la simulación del subsistema de potencia de un microsatélite, prestando especial atención a la simulación de la fuente de potencia, esto es, los paneles solares. En la tesis se presentan métodos sencillos pero precisos para simular la producción de energía de los paneles en condiciones ambientales variables a través de su circuito equivalente. Los métodos propuestos para el cálculo de los parámetros del circuito equivalente son explícitos (o al menos, con las variables desacopladas), no iterativos y directos; no se necesitan iteraciones o valores iniciales para calcular los parámetros. La precisión de este método se prueba y se compara con métodos similares de la literatura disponible, demostrando una precisión similar para mayor simplicidad. En segundo lugar, se presenta la simulación del subsistema de control de actitud de un microsatélite, prestando especial atención a la nueva ley de control propuesta. La tesis presenta un nuevo tipo de control magnético es aplicable a la órbita baja terrestre (LEO). La ley de control propuesta es capaz de ajustar la velocidad de rotación del satélite alrededor de su eje principal de inercia máximo o mínimo. Además, en el caso de órbitas de alta inclinación, la ley de control favorece la alineación del eje de rotación con la dirección normal al plano orbital. El algoritmo de control propuesto es simple, sólo se requieren magnetopares como actuadores; sólo se requieren magnetómetros como sensores; no hace falta estimar la velocidad angular; no incluye un modelo de campo magnético de la Tierra; no tiene por qué ser externamente activado con información sobre las características orbitales y permite el rearme automático después de un apagado total del subsistema de control de actitud. La viabilidad teórica de la citada ley de control se demuestra a través de análisis de Monte Carlo. Por último, en términos de producción de energía, se demuestra que la actitud propuesto (en eje principal perpendicular al plano de la órbita, y el satélite que gira alrededor de ella con una velocidad controlada) es muy adecuado para la misión UPMSat-2, ya que permite una área superior de los paneles apuntando hacia el sol cuando se compara con otras actitudes estudiadas. En comparación con el control de actitud anterior propuesto para el UPMSat-2 resulta en un incremento de 25% en la potencia disponible. Además, la actitud propuesto mostró mejoras significativas, en comparación con otros, en términos de control térmico, como la tasa de rotación angular por satélite puede seleccionarse para conseguir una homogeneización de la temperatura más alta que apunta satélite y la antena. ABSTRACT The work carried out in the present doctoral dissertation should be considered part of the UPMSat-2 project, falling within the scope of the aerospace technology. The UPMSat-2 is a microsatellite (low cost and small size) designed, constructed integrated and tested for educational and technology demonstration purposes at the Universidad Politécnica de Madrid (Spain). The aim of the present doctoral dissertation is to present new analytical models to study the energy interdependence between the power and the attitude control subsystems of a satellite. First, the simulation of the power subsystem of a microsatellite is studied, paying particular attention to the simulation of the power supply, i.e. the solar panels. Simple but accurate methods for simulate the power production under variable ambient conditions using its equivalent circuit are presented. The proposed methods for calculate the equivalent circuit parameters are explicit (or at least, with decoupled variables), non-iterative and straight forward; no iterations or initial values for the parameters are needed. The accuracy of this method is tested and compared with similar methods from the available literature demonstrating similar precision but higher simplicity. Second, the simulation of the control subsystem of a microsatellite is presented, paying particular attention to the new control law proposed. A new type of magnetic control applied to Low Earth Orbit (LEO) satellites has been presented. The proposed control law is able to set the satellite rotation speed around its maximum or minimum inertia principal axis. Besides, the proposed control law favors the alignment of this axis with the normal direction to the orbital plane for high inclination orbits. The proposed control algorithm is simples, only magnetorquers are required as actuators; only magnetometers are required as sensors; no estimation of the angular velocity is needed; it does not include an in-orbit Earth magnetic field model; it does not need to be externally activated with information about the orbital characteristics and it allows automatic reset after a total shutdown of attitude control subsystem. The theoretical viability of the control law is demonstrated through Monte Carlo analysis. Finally, in terms of power production, it is demonstrated that the proposed attitude (on principal axis perpendicular to the orbit plane, and the satellite rotating around it with a controlled rate) is quite suitable for the UPMSat-2 mission, as it allows a higher area of the panels pointing towards the sun when compared to other studied attitudes. Compared with the previous attitude control proposed for the UPMSat-2 it results in a 25% increment in available power. Besides, the proposed attitude showed significant improvements, when compared to others, in terms of thermal control, as the satellite angular rotation rate can be selected to achieve a higher temperature homogenization of the satellite and antenna pointing.

Impact assessment of an integrated approach for thermal power generation plants asset management in the current energy market

El sector energético, en España en particular, y de forma similar en los principales países de Europa, cuenta con una significativa sobrecapacidad de generación, debido al rápido y significativo crecimiento de las energías renovables en los últimos diez años y la reducción de la demanda energética, como consecuencia de la crisis económica. Esta situación ha hecho que las centrales térmicas de generación de electricidad, y en concreto los ciclos combinados de gas, operen con un factor de utilización extremadamente bajo, del orden del 10%. Además de la reducción de ingresos, esto supone para las plantas trabajar continuamente fuera del punto de diseño, provocando una significativa pérdida de rendimiento y mayores costes de explotación. En este escenario, cualquier contribución que ayude a mejorar la eficiencia y la condición de los equipos, es positivamente considerada. La gestión de activos está ganando relevancia como un proceso multidisciplinar e integrado, tal y como refleja la reciente publicación de las normas ISO 55000:2014. Como proceso global e integrado, la gestión de activos requiere el manejo de diversos procesos y grandes volúmenes de información, incluso en tiempo real. Para ello es necesario utilizar tecnologías de la información y aplicaciones de software. Esta tesis desarrolla un concepto integrado de gestión de activos (Integrated Plant Management – IPM) aplicado a centrales de ciclo combinado y una metodología para estimar el beneficio aportado por el mismo. Debido a las incertidumbres asociadas a la estimación del beneficio, se ha optado por un análisis probabilístico coste-beneficio. Así mismo, el análisis cuantitativo se ha completado con una validación cualitativa del beneficio aportado por las tecnologías incorporadas al concepto de gestión integrada de activos, mediante una entrevista realizada a expertos del sector de generación de energía. Los resultados del análisis coste-beneficio son positivos, incluso en el desfavorable escenario con un factor de utilización de sólo el 10% y muy prometedores para factores de utilización por encima del 30%. ABSTRACT The energy sector particularly in Spain, and in a similar way in Europe, has a significant overcapacity due to the big growth of the renewable energies in the last ten years, and it is seriously affected by the demand decrease due to the economic crisis. That situation has forced the thermal plants and in particular, the combined cycles to operate with extremely low annual average capacity factors, very close to 10%. Apart from the incomes reduction, working in out-of-design conditions, means getting a worse performance and higher costs than expected. In this scenario, anything that can be done to improve the efficiency and the equipment condition is positively received. Asset Management, as a multidisciplinary and integrated process, is gaining prominence, reflected in the recent publication of the ISO 55000 series in 2014. Dealing Asset Management as a global, integrated process needs to manage several processes and significant volumes of information, also in real time, that requires information technologies and software applications to support it. This thesis proposes an integrated asset management concept (Integrated Plant Management-IPM) applied to combined cycle power plants and develops a methodology to assess the benefit that it can provide. Due to the difficulties in getting deterministic benefit estimation, a statistical approach has been adopted for the cot-benefit analysis. As well, the quantitative analysis has been completed with a qualitative validation of the technologies included in the IPM and their contribution to key power plant challenges by power generation sector experts. The cost- benefit analysis provides positive results even in the negative scenario of annual average capacity factor close to 10% and is promising for capacity factors over 30%.

A Wireless Charging System Applying Phase-Shift and Amplitude Control to Maximize Efficiency and Extractable Power

Wireless power transfer (WPT) is an emerging technology with an increasing number of potential applications to transfer power from a transmitter to a mobile receiver over a relatively large air gap. However, its widespread application is hampered due to the relatively low efficiency of current Wireless power transfer (WPT) systems. This study presents a concept to maximize the efficiency as well as to increase the amount of extractable power of a WPT system operating in nonresonant operation. The proposed method is based on actively modifying the equivalent secondary-side load impedance by controlling the phase-shift of the active rectifier and its output voltage level. The presented hardware prototype represents a complete wireless charging system, including a dc-dc converter which is used to charge a battery at the output of the system. Experimental results are shown for the proposed concept in comparison to a conventional synchronous rectification approach. The presented optimization method clearly outperforms state-of-the-art solutions in terms of efficiency and extractable power.

Detection of Biological CO2 and 1,3-Pentadiene Using Non-refrigerated Low-Cost MWIR Detectors

The early detection of spoiling metabolic products in contaminated food is a very important tool to control quality. Some volatile compounds produce unpleasant odours at very low concentrations, making their early detection very challenging. This is the case of 1,3-pentadiene produced by microorganisms through decarboxylation of the preservative sorbate. In this work, we have developed a methodology to use the data produced by a low-cost, compact MWIR (Mid-Wave IR) spectrometry device without moving parts, which is based on a linear array of 128 elements of VPD PbSe coupled to a linear variable filter (LVF) working in the spectral range between 3 and 4.6 ?m. This device is able to analyze food headspace gases through dedicated sample presentation setup. This methodology enables the detection of CO2 and the volatile compound 1,3-pentadiene, as compared to synthetic patrons. Data analysis is based on an automated multidimensional dynamic processing of the MWIR spectra. Principal component and discriminant analysis allow segregating between four yeast strains including producers and no producers. The segregation power is accounted as a measure of the discrimination quality.

NMR evidence for the participation of a low-barrier hydrogen bond in the mechanism of delta 5-3-ketosteroid isomerase.

Delta 5-3-Ketosteroid isomerase (EC 5.3.3.1) promotes an allylic rearrangement involving intramolecular proton transfer via a dienolic intermediate. This enzyme enhances the catalytic rate by a factor of 10(10). Two residues, Tyr-14, the general acid that polarizes the steroid 3-carbonyl group and facilitates enolization, and Asp-38 the general base that abstracts and transfers the 4 beta-proton to the 6 beta-position, contribute 10(4.7) and 10(5.6) to the rate increase, respectively. A major mechanistic enigma is the huge disparity between the pKa values of the catalytic groups and their targets. Upon binding of an analog of the dienolate intermediate to isomerase, proton NMR detects a highly deshielded resonance at 18.15 ppm in proximity to aromatic protons, and with a 3-fold preference for protium over deuterium (fractionation factor, phi = 0.34), consistent with formation of a short, strong (low-barrier) hydrogen bond to Tyr-14. The strength of this hydrogen bond is estimated to be at least 7.1 kcal/mol. This bond is relatively inaccessible to bulk solvent and is pH insensitive. Low-barrier hydrogen bonding of Tyr-14 to the intermediate, in conjunction with the previously demonstrated tunneling contribution to the proton transfer by Asp-38, provide a plausible and quantitative explanation for the high catalytic power of this isomerase.

Galvanic Corrosion of High-Temperature Low-Sag (HTLS) High Voltage Conductors: New Materials - New Challenges

High-Temperature Low-Sag (HTLS) high voltage overhead conductors offer higher operating temperatures, reduced resistance and less sag than conventional designs. With up to twice the current capacity for the same diameter conductor, they may help ease the power shortage in the constantly increasing electricity demand, but there might be some concerns about their corrosion resistance. These new conductors use materials relatively new to the power industry, such as advanced carbon fiber polymer matrix composites and unique metal matrix composites/nano-composites predominantly used in aerospace industries. This study has made an initial assessment of potential galvanic corrosion problems in three very different HTLS designs: ACCC (Aluminum Conductor Composite Core), ACCR (Aluminum Conductor Composite Reinforced) and ACSS (Aluminum Conductor Steel Supported). In particular the ACCC design was evaluated for its resistance to corrosion and compared to the other designs. The study concludes that all three designs can develop galvanic corrosion under certain circumstances. While the results are not sufficient to make service life predictions of any of the tested conductors, they point out the necessity of thorough corrosion testing of all new conductor designs.

The XMM deep survey in the CDF-S. VI. Obscured AGN selected as infrared power-law galaxies

Context. Accretion onto supermassive black holes is believed to occur mostly in obscured active galactic nuclei (AGN). Such objects are proving rather elusive in surveys of distant galaxies, including those at X-ray energies. Aims. Our main goal is to determine whether the revised IRAC criteria of Donley et al. (2012, ApJ, 748, 142; objects with an infrared (IR) power-law spectral shape), are effective at selecting X-ray type-2 AGN (i.e., absorbed N_H > 10^22 cm^-2). Methods. We present the results from the X-ray spectral analysis of 147 AGN selected by cross-correlating the highest spectral quality ultra-deep XMM-Newton and the Spitzer/IRAC catalogues in the Chandra Deep Field South. Consequently it is biased towards sources with high S/N X-ray spectra. In order to measure the amount of intrinsic absorption in these sources, we adopt a simple X-ray spectral model that includes a power-law modified by intrinsic absorption at the redshift of each source and a possible soft X-ray component. Results. We find 21/147 sources to be heavily absorbed but the uncertainties in their obscuring column densities do not allow us to confirm their Compton-Thick nature without resorting to additional criteria. Although IR power-law galaxies are less numerous in our sample than IR non-power-law galaxies (60 versus 87 respectively), we find that the fraction of absorbed (N_H^intr > 10^22 cm^-2) AGN is significantly higher (at about 3 sigma level) for IR-power-law sources (similar to 2/3) than for those sources that do not meet this IR selection criteria (~1/2). This behaviour is particularly notable at low luminosities, but it appears to be present, although with a marginal significance, at all luminosities. Conclusions. We therefore conclude that the IR power-law method is efficient in finding X-ray-absorbed sources. We would then expect that the long-sought dominant population of absorbed AGN is abundant among IR power-law spectral shape sources not detected in X-rays.

The impact of the internet on the pricing strategies of the European low cost airlines

This study seeks to analyse the price determination of low cost airlines in Europe and the effect that Internet has on this strategy. The outcomes obtained reveal that both users and companies benefit from the use of ICTs in the purchase and sale of airline tickets: the Internet allows consumers to increase their bargaining power comparing different airlines and choosing the most competitive flight, while companies can easily check the behaviour of users to adapt their pricing strategies using internal information. More than 2500 flights of the largest European low cost airlines have been used to carry out the study. The study revealed that the most significant variables for understanding pricing strategies were the number of rivals, the behaviour of the demand and the associated costs. The results indicated that consumers should buy their tickets before 25 days prior to departure.

The SAAS-R: A New Instrument to Assess the School Attitudes of Students with High and Low Academic Achievement in Spain

We examined the psychometric properties of the School Attitude Assessment Survey–Revised in a Spanish population (n = 1,398). Confirmatory factor analysis procedures supported the instrument’s five-factor structure. The results of discriminant analysis demonstrated the predictive power of the School Attitude Assessment Survey–Revised scales as regards academic performance. Implications for education and assessment are discussed.

Rowing Biomechanics: Technique Changes with an Increase of Power Demand

The sport of rowing has become more popular in the past decade. While it is a relatively low impact sport, injuries can occur, specifically to the ribs (Karlson K. A., 1998) and more often in female athletes (Hickey, Fricker, & McDonald , 1997). It has been proposed that as the athlete rows, applying a cyclical load to the body, the mid trapezius fatigues and is unable to resist the force produced during the drive phase (Warden S. J., Gutschlag, Wajswelner, & Crossley, 2002). Once this happens, the scapulae are then pulled anterio-laterally which increases the compression force on the ribs, increasing the risk of injury. The rowing motion of 12 female varsity and club rowers was tracked as they completed a fatiguing rowing test on a rowing ergometer. Results showed that the curvature of thoracic spine changed throughout the rowing cycle but did not change with increasing power level. The transverse shoulder angle decreased (the upper back was less straight) as power level increased (R2=-0.69±19), suggesting that the scapula moved anterio-laterally. This may be that as it tired, the mid-trapezius was unable to hold the scapulae in position. The decreasing transverse shoulder angle when the power level is increased indirectly supports the fatiguing of the retractor muscles as a mechanism of injury. It would be valuable to understand the limitations of each athlete and to be able to prescribe the optimal training zone to reduce the risk of injury.

THE DESIGN OF A POWER SYSTEM FOR A WIRELESS SENSOR NETWORK FOR LONG-TERM OPERATION

Wireless sensor networks (WSNs) have shown wide applicability to many fields including monitoring of environmental, civil, and industrial settings. WSNs however are resource constrained by many competing factors that span their hardware, software, and networking. One of the central resource constrains is the charge consumption of WSN nodes. With finite energy supplies, low charge consumption is needed to ensure long lifetimes and success of WSNs. This thesis details the design of a power system to support long-term operation of WSNs. The power system’s development occurs in parallel with a custom WSN from the Queen’s MEMS Lab (QML-WSN), with the goal of supporting a 1+ year lifetime without sacrificing functionality. The final power system design utilizes a TPS62740 DC-DC converter with AA alkaline batteries to efficiently supply the nodes while providing battery monitoring functionality and an expansion slot for future development. Testing tools for measuring current draw and charge consumption were created along with analysis and processing software. Through their use charge consumption of the power system was drastically lowered and issues in QML-WSN were identified and resolved including the proper shutdown of accelerometers, and incorrect microcontroller unit (MCU) power pin connection. Controlled current profiling revealed unexpected behaviour of nodes and detailed current-voltage relationships. These relationships were utilized with a lifetime projection model to estimate a lifetime between 521-551 days, depending on the mode of operation. The power system and QML-WSN were tested over a long term trial lasting 272+ days in an industrial testbed to monitor an air compressor pump. Environmental factors were found to influence the behaviour of nodes leading to increased charge consumption, while a node in an office setting was still operating at the conclusion of the trail. This agrees with the lifetime projection and gives a strong indication that a 1+ year lifetime is achievable. Additionally, a light-weight charge consumption model was developed which allows charge consumption information of nodes in a distributed WSN to be monitored. This model was tested in a laboratory setting demonstrating +95% accuracy for high packet reception rate WSNs across varying data rates, battery supply capacities, and runtimes up to full battery depletion.

Too high and too low: The problems with energy prices in the EU. OSW Commentary No. 122, 03.12.2013

On 11 October, the top executives of ten European energy companies, which jointly own about half of the European Union’s electricity generating capacity, warned that “energy security is no longer guaranteed” and once again called for changes to EU energy policy. Due to persistent adverse conditions in the energy market (linked to, for example, the exceptionally low wholesale energy prices) more and more conventional power plants are being closed down. According to sector representatives, this could lead to energy shortages being seen as early as this winter. Meanwhile, in an interview with The Daily Telegraph published in September of this year, the European industry commissioner Antonio Tajani warned – in a rather alarmist tone – of the disastrous consequences the rising energy prices could have on European industry. Amongst the reasons for the high prices of energy, Tajani mentioned the overambitious pace and methods used to increase the share of renewables in the sector. In a similar vein, EU President Herman Van Rompuy has highlighted the need to reduce energy costs as a top priority for EU energy policy1. The price of energy has become one of the central issues in the current EU energy debate. The high consumer price of energy – which has been rising steadily over the past several years – poses a serious challenge to both household and industrial users. Meanwhile, the declining wholesale prices are affecting the cost-effectiveness of energy production and the profits of energy companies. The current difficulties, however, are first and foremost a symptom of much wider problems related to the functioning of both the EU energy market as well as to the EU’s climate and energy policies.

Low-cost batteries will not disrupt (all) energy utilities. CEPS Commentary, 5 October 2015

With the launch last April of an affordable lithium-ion home battery – the Powerwall – Tesla’s CEO Elon Musk is betting that batteries are going to become a mass market. This may very well become reality, but this commentary argues that one should not jump to the conclusion that this is the end of energy utilities. Similar to solar panels, batteries have high upfront costs. The massive deployment of solar was driven by dedicated policy support, in many cases without any kind of cost or volume control. There is no such thing for batteries. In the absence of financing programmes, the author finds that high upfront costs provide an unfavourable starting point for a disruptive development. But he notes that the fact that self-consumption of stored solar energy will soon pay for consumers represents a paradigm shift in the power industry, which should be seen as an opportunity, at least for first-movers.