Academic literature on the topic 'Phase auto-alignment'

Abstract Orbital angular momentum (OAM), which describes tailoring the spatial physical dimension of light waves into a helical phase structure, has given rise to many applications in optical manipulation, microscopy, imaging, metrology, sensing, quantum science, and optical communications. Light beams carrying OAM feature two distinct characteristics, i.e., inherent orthogonality and unbounded states in principle, which are suitable for capacity scaling of optical communications. In this paper, we give an overview of OAM and beyond in free-space optical communications. The fundamentals of OAM, concept of optical communications using OAM, OAM modulation (OAM modulation based on spatial light modulator, high-speed OAM modulation, spatial array modulation), OAM multiplexing (spectrally efficient, high capacity, long distance), OAM multicasting (adaptive multicasting, N-dimensional multicasting), OAM communications in turbulence (adaptive optics, digital signal processing, auto-alignment system), structured light communications beyond OAM (Bessel beams, Airy beams, vector beams), diverse and robust communications using OAM and beyond (multiple scenes, turbulence-resilient communications, intelligent communications) are comprehensively reviewed. The prospects and challenges of optical communications using OAM and beyond are also discussed at the end. In the future, there will be more opportunities in exploiting extensive advanced applications from OAM beams to more general structured light.

Purpose The purpose of this study is to address the concept and the step-by-step procedure of a high-precision optical alignment test for spacecrafts using digital theodolites. The proposed scheme focuses on the non-contact alignment qualification of spacecraft components during the integration and test phases until the launch event. Design/methodology/approach The proposed approach is based on the exploitation of the auto-collimation feature of theodolites and several prisms attached to the requested component and satellite configuration. As soon as the misalignment measurement including the difference between the real and desired attitude or position aberration of an instrument is made, the results must be transformed from the component level to the system level for misalignment error identification in the spacecraft dynamic model. Findings The paper introduces the main instruments, the defined coordinate systems and the architecture of the optical spacecraft misalignment test. Moreover, the guideline of the test implementation and the resulting data process have been presented carefully. Research limitations/implications There is no limitation associated with this method because the procedure is applicable for high-precision typical missions. Practical implications This paper describes a fully implementable scheme to examine any possible inaccuracy in mounting of the spacecraft components both in position and orientation. The test can be performed without the need for a huge budget or complicated hardwares. Originality/value The contribution of this work revolves around illustrating the context and procedure of the spacecraft misalignment test which has remained unknown in literature despite the frequent implementation in the different satellite projects.

In the wide range of emergent nanotechnologies, DNA-based microelectronics has shown an important potential for components miniaturization and auto-assembling approaches applicable to future silicon-based electronic circuits [1]. In order to pursue the Moore's law, interconnections must be indeed addressed at the nanoscale, with a good control of their size, location and electrical & thermal performances. With its natural auto-assembling property, its 2-nm-double-helix diameter and its several metallization possibilities, DNA is a promising candidate to build bio-inspired electronic components [1]. DNA has been first metallized by Erez Braun in 1998 using a silver electroless method [2]. Since 1998, several groups have worked on DNA metallization using different chemistries with metals such as Pd, Pt, Au, Ag and Cu [3]. Most of these works have presented electrical and morphological characterizations of few metallic nanowires. However, in order to initiate DNA-based-nanowires integration on silicon technologies, we must start to implement nanowires on silicon at wafer scale. We have thus developed a platform based on silicon technologies providing morphological and electrical characterizations of copper nanowires built from DNA [4]. This platform will allow us to simultaneously characterize a large number of nanowires, returning a statistic of their electrical performance, and thus allowing the optimization of the copper nanowire metallization process. Two main approaches are proposed to fabricate and contact a large number of copper nanowires with metallic electrodes in order to study their electrical behavior. In both approaches, a linear 16-μm-length DNA phage is used. The first approach consists in aligning DNA wires on a hydrophobic silicon oxide surface by a method called DNA combing. On a second time, aligned DNA wires are all metallized by electroless process [4]. 5-nm-diameter copper nanowires have been so far achieved by this method and focus on improving the metallization process is currently at stake. Finally, Ti/Au electrodes are fabricated on the nanowires by a classical lift-off process in order to electrically connect them. The advantage of this approach is the very accurate nanowires alignment and their homogeneity over the surface. However, the low number of aligned nanowires per surface unit (10–20μm−2) and the high electrical resistance of each (>kohms) makes the electrical characterization quite complex. On the other side, the second approach consists in fabricating the Ti/Au electrodes first and then aligning or randomly depositing the copper nanowires at their surface. Same protocols are used to align and metallize the DNA nanowires for both approaches. The advantage of this second approach is a higher nanowire density deposited on the electrodes. However, a higher contact resistance and a lower control of nanowires alignment are obtained. Both approaches are currently explored and permit to explore a wide range of parameters for copper nanowires metallization process improvement.

Метою дослідження є розробка електронного УЗ генератора з системою фазового автопідстроювання частоти для ультразвукових технологічних апаратів. Робота присвячена розробці електронного УЗ генератора із системою ФАПЧ. На сьогоднішній день, дана тема є актуальною, тому що УЗ генератори застосовуються в різних сферах діяльності. В роботі проведено аналіз сучасних УЗ генераторів, а також дослідження принципу роботи та побудови електронних генераторів. В даній роботі було спроектовано схему принципову та на основі даної схеми розроблено конструкцію друкованої плати УЗ генератора із системою ФАПЧ. Об’єктом дослідження є УЗ електронних генератор. Предметом дослідження є система фазового автопідстроювання частоти. Результатом роботи є: дослідження принципу роботи та будови електронних генераторів; розробка структурної схеми генератора; дослідження та реалізація схемних рішень системи фазового автопідстроювання частоти; Галузь застосування: ультразвукові технологічні апарати для різних сфер промисловості.
The aim of the research is to develop an electronic ultrasonic generator with a phase auto-alignment system for ultrasonic technological devices. The work is devoted to the development of an electronic ultrasonic generator with a PLL system. Today, this topic is relevant because US generators are used in various fields. The analysis of modern ultrasonic generators, as well as the study of the principle of operation and construction of electronic generators. In this work, the basic scheme was designed and on the basis of this scheme the design of the PCB of the ultrasonic generator with the PLL system was developed. The object of study is the ultrasonic electronic generator. The subject of the research is the system of phase auto-alignment. The result is: • research of the principle of operation and structure of electronic generators; • development of the structural scheme of the generator; • research and implementation of circuit solutions of the phase auto-alignment system; Field of application: ultrasonic technological devices for various industries.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In this work, we study the collective behaviour of living systems whose aggregates form organized groups such as flocks of birds, herds of mamals and schools of fishes. Through numerical simulations, we model the collective movement of a school of fishes using behavioural rules similar to the ones proposed by Couzin et al. [23], that investigates the spatial dynamics of animals groups. The model presents three interaction zones: repulsion, orientation and attraction. Our results for the distributions of nearest neighbour distance, the diference of orientation between the velocities of neighbour fishes and the cooperativeness of the school are in good agreement with experimental measurements. A simpler way to describe the collective motion of several groups of organisms was introduced by Vicsek et al. [10]. This model presents only one interaction region, called orientation zone and considers point particles moving off lattice at constant speed adjusting their direction of motion to that of the average velocity of their neighbors, being subject to some noisy term. A second-order transition between an ordered state and a disordered regime was found. However, Gregoire and Chate [12] contest the nature of such phase transition as being of first order. Indeed, this transition is related to the way of introducing the noise into the system. In this sense, we present a comparative study on noise in two system of self-propelled particle (Vicsek model and Gregoire model) with the aim of understanding the role of the noise on some observables such as polarization, distributions of the nearest neighbour distances, difference of orientations between neighbour particles, the order parameter and the Binder cumulant.
Neste trabalho, estudamos o comportamento coletivo de sistemas vivos cujos agregados formam grupos organizados tais como bandos de pássaros, rebanhos de mamíferos e cardumes de peixes. Através de simulações numéricas, modelamos o movimento coletivo de cardumes de peixes usando regras comportamentais similares áquelas propostas por Cousin et al.[23], que investigam a dinâmica espacial de grupos de animais. O modelo apresenta três zonas de interação: repulsão, orientação e atração. Nossos resultados para as distribuições das distâncias entre vizinhos mais próximos, a diferença de orientação entre as velocidades de peixes vizinhos e a cooperatividade do cardume estão de bom acordo com medidas experimentais. Uma maneira mais simples para descrever o movimento coletivo de vários grupos de organismos foi introduzido por Vicsek et al. [10]. Este modelo apresenta somente uma região de interação, chamada zona de orientação e considera partículas pontuais movendo na rede com uma velocidade constante ajustando sua direção de movimento à velocidade média de seus vizinhos, estando sujeita a algum termo ruidoso. Uma transição de segunda ordem entre um estado ordenado e um regime desordenado foi encontrado. Porém, Gregoire e Chaté [12] contestam a natureza da transição de fase como sendo de primeira ordem. Na verdade, está transição está relacionada à forma de introduzir o ruído no sistema. Neste sentido, apresentamos um estudo comparativo sobre o ruído em dois sistemas de partículas auto-propelidas (modelo de Vicsek e modelo de Gregoire) com o objetivo de compreender o papel do ruído em alguns observáveis tais como a polarização, distribuições das distâncias entre vizinhos mais próximos, diferença de orientação entre partículas vizinhas, o parâmetro de ordem e o cumulante de Binder.