On the rotation of co-orbital bodies in eccentric orbits

We investigate the resonant rotation of co-orbital bodies in eccentric and planar orbits. We develop a simple analytical model to study the impact of the eccentricity and orbital perturbations on the spin dynamics. This model is relevant in the entire domain of horseshoe and tadpole orbit, for moderate eccentricities. We show that there are three different families of spin-orbit resonances, one depending on the eccentricity, one depending on the orbital libration frequency, and another depending on the pericenter's dynamics. We can estimate the width and the location of the different resonant islands in the phase space, predicting which are the more likely to capture the spin of the rotating body. In some regions of the phase space the resonant islands may overlap, giving rise to chaotic rotation.

Complete spin and orbital evolution of close-in bodies using a Maxwell viscoelastic rheology

In this paper, we present a formalism designed to model tidal interaction with a viscoelastic body made of Maxwell material. Our approach remains regular for any spin rate and orientation, and for any orbital configuration including high eccentricities and close encounters. The method is to integrate simultaneously the rotation and the position of the planet as well as its deformation. We provide the equations of motion both in the body frame and in the inertial frame. With this study, we generalize preexisting models to the spatial case and to arbitrary multipole orders using a formalism taken from quantum theory. We also provide the vectorial expression of the secular tidal torque expanded in Fourier series. Applying this model to close-in exoplanets, we observe that if the relaxation time is longer than the revolution period, the phase space of the system is characterized by the presence of several spin-orbit resonances, even in the circular case. As the system evolves, the planet spin can visit different spin-orbit configurations. The obliquity is decreasing along most of these resonances, but we observe a case where the planet tilt is instead growing. These conclusions derived from the secular torque are successfully tested with numerical integrations of the instantaneous equations of motion on HD 80606 b. Our formalism is also well adapted to close-in super-Earths in multiplanet systems which are known to have non-zero mutual inclinations.

Design of Nanophotonic Antireflection Coatings for III-V Thin-Film Photovoltaics

Thin-film photovoltaics have provided a critical design avenue to help decrease the overall cost of solar power. However, a major drawback of thin-film solar cell technology is decreased optical absorption, making compact, high-quality antireflection coatings of critical importance to ensure that all available light enters the cell. In this thesis, we describe high efficiency thin-film InP and GaAs solar cells that utilize a periodic array of nanocylinders as antireflection coatings. We use coupled optical and electrical simulations to find that these nanophotonic structures reduce the solar-weighted average reflectivity of InP and GaAs solar cells to around 1.3 %, outperforming the best double-layer antireflection coatings. The coupling between Mie scattering resonances and thin-film interference effects accurately describes the optical enhancement provided by the nanocylinders. The spectrally resolved reflectivity and J-V characteristics of the devices under AM1.5G solar illumination are determined via the coupled optical and electrical simulations, resulting in predicted power conversion efficiencies > 23 %. We conclude that the nanostructured coatings reduce reflection without negatively affecting the electronic properties of the InP and GaAs solar cells by separating the nanostructured optical components from the active layer of the device.

The Rhythm of our Lives. Aesthetic Perspectives East & West

The leading approach to everyday aesthetics for the past few decades has departed from analytic philosophical grounds, generating some tensions or dichotomies regarding its foundational cornerstones: the ordinary vs. extraordinary character of everyday aesthetic experience, contextual familiarity vs. strangeness, object vs. processual orientation, etc. Although John Dewey has been widely acclaimed as a sort of foundational figure for this burgueoning sub-discipline of aesthetics, maybe not enough emphasis has been laid on his very different pragmatist approach. In this regard, his reliance on Hegelian cum Darwinian premises might allow for a connection with other branches of continental as well as Asian philosophies, from which also some research on everyday aesthetics has been made. It is from this wider ontological framework that the notion of rhythm could be vindicated as a pivotal aspect of the aesthetic dimension of our everyday lives. Dewey deals extensively with it in Art as Experience, conceiving it as a sort of pattern of accomplished experiences, accounting also for his naturalistic approach and art and life continuity thesis. On the other hand, neo-pragmatist exponent Richard Shusterman, among others, has posited links of connection between Pragmatist aesthetics and East-Asian philosophies. Particularly, Dewey’s resonances with Asian philosophies have been studied, with a preeminence on the notions of harmony and rhythm. This paper will depart from the analysis of the notion of rhythm in Dewey’s philosophy, trying to hint at some possible developments of its implications. Particularly, it will expand on some East Asian paralelisms to his philosophy, trying to link them with the notion of rhythm as an epitomizing ground for the conjunction of the extraordinary (art) and the ordinary (life).

Now again

Now Again is a participatory performance made up of a series of individual and group activities that create opportunities to notice how we fit and shift in our environment. Reflecting the dance histories of the artists, the variable dynamic possibilities of the city are brought into focus through specific ‘scores’ that, as propositions for engagement, activate simple movement patterns or observations. The aim is to allow responsive noticing of the immediate environment, but also to enliven it in unexpected ways. Individuals who are participants and observers, dedicated or incidental (passers-by), become part of the disclosure of the physical and the social. The rigid structure of the city is re-imagined as a fluid, choreographic entity invested with organic qualities. Performances move between a series of city locations, each with differing activities. Designated ‘nodes’ in the city grid (certain streets, a square, a doorway, footpath, a hole in a wall or a particular tree), have been chosen for their imaginative, affective, or energetic resonances. These are ‘mapped’ by the perambulatory, physical, sensory, and relational engagement of all participants. This is a collective dance created through noticing the feelings and patterns of the physical self in the built, natural, and social environment. In some sites, the artists perform, while in others they lead a participative performance. Ephemeral, self-led, performance experiments designed to disappear into the fabric of the city, will also be invited. A mobile app enables audience participation. The app employs GPS data to trigger information specific to that site (written prompts, sounds and scored provocations).

Silicon Photonic Device for Wavelength Sensing and Monitoring

Over the last decade advances and innovations from Silicon Photonics technology were observed in the telecommunications and computing industries. This technology which employs Silicon as an optical medium, relies on current CMOS micro-electronics fabrication processes to enable medium scale integration of many nano-photonic devices to produce photonic integrated circuitry. However, other fields of research such as optical sensor processing can benefit from silicon photonics technology, specially in sensors where the physical measurement is wavelength encoded. In this research work, we present a design and application of a thermally tuned silicon photonic device as an optical sensor interrogator. The main device is a micro-ring resonator filter of 10 $\mu m$ of diameter. A photonic design toolkit was developed based on open source software from the research community. With those tools it was possible to estimate the resonance and spectral characteristics of the filter. From the obtained design parameters, a 7.8 x 3.8 mm optical chip was fabricated using standard micro-photonics techniques. In order to tune a ring resonance, Nichrome micro-heaters were fabricated on top of the device. Some fabricated devices were systematically characterized and their tuning response were determined. From measurements, a ring resonator with a free-spectral-range of 18.4 nm and with a bandwidth of 0.14 nm was obtained. Using just 5 mA it was possible to tune the device resonance up to 3 nm. In order to apply our device as a sensor interrogator in this research, a model of wavelength estimation using time interval between peaks measurement technique was developed and simulations were carried out to assess its performance. To test the technique, an experiment using a Fiber Bragg grating optical sensor was set, and estimations of the wavelength shift of this sensor due to axial strains yield an error within 22 pm compared to measurements from spectrum analyzer. Results from this study implies that signals from FBG sensors can be processed with good accuracy using a micro-ring device with the advantage of ts compact size, scalability and versatility. Additionally, the system also has additional applications such as processing optical wavelength shifts from integrated photonic sensors and to be able to track resonances from laser sources.

Ghost Tree Social

GHOST TREE SOCIAL tells a coming out story of sorts. In terms of style, many of the poems are short, imagistic lyrics, though some are extended catalogues. Specific natural images—lakes, rivers, and snow—are often contrasted with cultural markers. The imagistic poems are thinking through the work of Sylvia Plath. The catalogue poems shift between diaristic, narrative, and critical modes, responding to the poetry of Elizabeth Bishop and the essays of Edouard Glissant. Voice-driven fragments disrupt the more traditional lyric poems. The fragments fall between formal lyrics like confetti from a gay club’s rafters; or the fragments hold the lyric poems in bondage. The lyric poem then re-signifies as form through resonances with the other discursive and poetic form of the fragment. Following critical writers such as Adrienne Rich and Audre Lorde, the re-signification of lyric form reflects the need for new signs for self and community organized queerly as opposed to more typical binary categories—man or woman, living or dead, rich or poor, white or black—where the first term is privileged and the second term often denigrated.

Physics-Based Modeling of Power System Components for the Evaluation of Low-Frequency Radiated Electromagnetic Fields

The low-frequency electromagnetic compatibility (EMC) is an increasingly important aspect in the design of practical systems to ensure the functional safety and reliability of complex products. The opportunities for using numerical techniques to predict and analyze system’s EMC are therefore of considerable interest in many industries. As the first phase of study, a proper model, including all the details of the component, was required. Therefore, the advances in EMC modeling were studied with classifying analytical and numerical models. The selected model was finite element (FE) modeling, coupled with the distributed network method, to generate the model of the converter’s components and obtain the frequency behavioral model of the converter. The method has the ability to reveal the behavior of parasitic elements and higher resonances, which have critical impacts in studying EMI problems. For the EMC and signature studies of the machine drives, the equivalent source modeling was studied. Considering the details of the multi-machine environment, including actual models, some innovation in equivalent source modeling was performed to decrease the simulation time dramatically. Several models were designed in this study and the voltage current cube model and wire model have the best result. The GA-based PSO method is used as the optimization process. Superposition and suppression of the fields in coupling the components were also studied and verified. The simulation time of the equivalent model is 80-100 times lower than the detailed model. All tests were verified experimentally. As the application of EMC and signature study, the fault diagnosis and condition monitoring of an induction motor drive was developed using radiated fields. In addition to experimental tests, the 3DFE analysis was coupled with circuit-based software to implement the incipient fault cases. The identification was implemented using ANN for seventy various faulty cases. The simulation results were verified experimentally. Finally, the identification of the types of power components were implemented. The results show that it is possible to identify the type of components, as well as the faulty components, by comparing the amplitudes of their stray field harmonics. The identification using the stray fields is nondestructive and can be used for the setups that cannot go offline and be dismantled

Disorder-induced light localisation:from random to artificial

Light localisation in one-dimensional (1D) randomly disordered medium is usually characterized by randomly distributed resonances with fluctuating transmission values, instead of selectively distributed resonances with close-to-unity transmission values that are needed in real application fields. By a resonance tuning scheme developed recently, opening of favorable resonances or closing of unfavorable resonances are achieved by disorder micro-modification, both on the layered medium and the fibre Bragg grating (FBG) array. And furthermore, it is shown that those disorder-induced resonances are independently tunable. Therefore, selected resonances and arranged light localisation can be achieved via artificial disorder, and thus meet the demand of various application fields.

Maintaining the integrity of public education : a comparative analysis of school autonomy in the United States and Australia

This article takes a critical comparative approach to examining autonomous schooling in the United States and Australia. Amid the market imperatives currently driving education priorities, its focus is on how autonomy can be mobilized in ways that preserve the integrity of public education. Through reference to key debates and research about school autonomy in the United States and Australia, integrity is defined with reference to three values: (1) public ownership (i.e., governance that is responsive to the people it serves), (2) equity and access (i.e., adequate funding and inclusive student admission practices), and (3) public purpose (i.e., prioritizing the moral and social purposes of education; Darling-Hammond and Montgomery 2008). The analysis is mindful of the resonances and differences between the education systems in the United States and Australia and the fluidity and complexity of the notion of autonomous schooling. Against this backdrop, the article illustrates the significance of embedding these values within school autonomy policy in order to preserve the integrity of public education.