bluuebunny/crossref_metadata_2025 huggingface dataset:
Architectural Exploration of an FPGA-based Hardware Accelerator for the Gaussian Filter using Approximate Computing
Authors: Sborz Guilherme , Viel Felipe , Zeferino Cesar
Published: December 2020

The growing use of computer vision applications has increased the demand for efficient image processing implementations. These applications have constraints that, in some cases, can only be met by dedicated hardware implementations. This work presents architectures that apply approximate computing techniques to improve efficiency and scalability for implementing digital image filters on FPGA. These architectures were implemented as hardware accelerators for an embedded processor in an FPGA-based System-on-Chip. The results show that the use of approximate computing techniques can reduce costs without affecting results for the target application, which is an essential feature for further acceleration using parallel processing on hardware.
El control político de la opinión pública en la España de los Austrias
Authors: Álvarez García Héctor
Published: December 2020

En el marco de la legislación censoria de la España imperial pretendemos analizar, por una parte, el origen cultural y doctrinal del concepto sociológico de opinión pública en nuestro país, que hunde sus raíces en el absolutismo contrarreformista y fue adoptando una fisonomía reconocible en el seno de la sociedad española del Siglo de Oro, gracias a la contribución de nuestros tratadistas barrocos; y, por otra, la dimensión política y adoctrinadora de la Nueva Comedia y de la predicación religiosa, ya que constituyeron los más efectivos resortes propagandísticos de manipulación de masas impulsados desde el Poder en orden a conseguir la adhesión emocional y, por tanto, irracional del pueblo español al régimen monárquico-señorial de los Austrias.In the framework of the censorship legislation of imperial Spanish we pretend to analyze, on the one hand, the cultural and doctrinal origin of sociological concept of public opinion in our country, which has its roots in counter-reformist absolutism and was adopting a recognizable physiognomy within the spanish society of the Golden Age thanks to the contribution of our baroque writers; and, on the other, the political and indoctrinating dimension of the New Comedy and religious preaching, since they constituted the most effective propaganda springs of mass manipulation driven by the Power in order to achieve emotional accession and, therefore, irrational from the spanish people to the Hispanic monarchy.
El papel del fiscal de consumo. Su actuación en el proceso civil en defensa de consumidores y usuarios
Authors: Calero Olmo Juan Bautista
Published: December 2020

Este trabajo lo circunscribo dentro de las potenciales actuaciones procesales que el Ministerio fiscal tiene en el área de protección de los derechos de los consumidores y en el ámbito del derecho civil privado, tratadas, principalmente, por dos circulares emitidas por la Fiscalía General del Estado (FGE) y numeradas 2/2010 y 2/2018. Dejando de lado el papel de la fiscalía en la más amplia y natural protección de fraudes y otros tipos penales y las intervenciones en defensa de los particulares, como usuarios consumidores, contra la administración pública, y aquellas otras complementarias de formación y divulgación. El Estado y las Comunidades Autonómicas han creado el marco jurídico preciso para esta protección desarrollando una amplia normativa reguladora de estas relaciones que se sustentan, en muchos casos, en el ejercicio y amparo de derechos reconocidos en leyes fundamentales.This work is limited within the potential procedural actions that the Public Prosecutor’s Office has in the area of protection of consumer rights and in the field of private civil law, mainly covered by two circulars issued by State Attorney General’s Office and numbered 2/2010 and 2/2018. Leaving aside the role of the public prosecutor’s office in the widest and natural protection of fraud and other criminal types and interventions in defense of individuals, such as consumer users, against the public administration, and those other complementary training disclosures. The State and the Autonomous Communities have created the precise legal framework for this protection by developing a broad regulatory regulation of these relationships that are based, in many cases, on the exercise and protection of rights recognized by Fundamental laws.
Como trazer para a escrita os processos criativos da pesquisa?
Authors: Lia Camila Serino , Feltre Camila , Quilici Patrícia Marchesoni
Published: December 2020

Escrito por três pesquisadoras que em comum partilham estudos sobre processos de criação no entrelaçamento com a arte, a educação e a pesquisa, esse artigo apresenta conceitos sobre crítica genética elaborados pela professora Cecília Almeida Salles e três narrativas complementares, de cada uma das autoras, sobre processos de criação com a palavra no âmbito dos percursos de suas pesquisas em construção. Na tessitura de palavras lidas, ditas, sussurradas, colhidas, rascunhadas, desenhadas e escritas em suportes como diários de campo, cadernos de desenhos, pequenos papéis coloridos e murais, materializam-se os pensamentos, reflexões, desejos, inquietações e descobertas que, gradualmente, ganham corpo em forma de texto. Ao tecer aproximações entre o ato de criação e o ato de pesquisar, as autoras convidam a reflexão de uma inquietação comum: Como trazer para a escrita os processos criativos da pesquisa?
Foto-ensaios de uma investigação sobre a formação docente em artes visuais
Authors: Alves Carla Juliana Galvão , Santos Natally Thayna dos
Published: December 2020

Este trabalho apresenta nossas reflexões e percepções a respeito dos processos identitários e de formação do professor de Artes Visuais por meio de foto-ensaios. Insere-se no contexto de um projeto de pesquisa que optou pela Pesquisa Educacional Baseada em Arte (PEBA) como referencial metodológico (HERNÁNDEZ, MARTINS, DIAS) e, no caso deste artigo, põe foco nas contribuições da fotografia como estratégia e instrumento de pesquisa qualitativa (VIADEL, ROLDAN). Espera- se contribuir com novas reflexões voltadas para as discussões a respeito de metodologias mais adequadas às questões contemporâneas que surgem nas áreas de arte e educação. O estudo não é e nem pretende ser conclusivo, mas intenta ampliar o diálogo sobre formação do professor de Artes Visuais, de forma colaborativa entre estudantes e professores, pesquisadores e participantes.
Corpocinetismo: relações entre a representação do corpo humano e esculturas cinéticas
Authors: Bazante Brenda Gomes
Published: December 2020

Este artigo apresenta aspectos relativos à arte que se move, ou que apenas sugeriu o movimento, e à representação da corporalidade humana por meio da Arte Cinética. Ao juntar estes dois campos de investigação estou elaborando o conceito de Corpocinetismo. Termo que dará conta de exemplificar esculturas móveis, móbiles ou instalações que contenham silhuetas de corpos movendo-se ao sabor do vento, da interação com o espectador ou com qualquer outra força motriz utilizada no cinetismo. Para alcançar este objetivo examinei a produção de artistas que desenvolveram pesquisas e obras envolvendo mobilidade e representação do corpo humano na Arte Cinética e em outros movimentos a partir do século XIX, consequentemente encontrando referências para o processo criativo elaborado na pesquisa “Cadê as Travas Transcorpocinéticas?” em desenvolvimento no Programa Associado de Pós-Graduação em Artes Visuais UFPE/UFPB. Além disso, pretendo com este texto contribuir para a ampliação do conceito de cinetismo levando em conta o que diz Hans Belting e a produção de artistas da cultura popular brasileira, trazendo obras dos MestresMiró dos Bonecos, Saúba e Otávio, referências quando se trata de bonecos e brinquedos populares móveis. A revisão de literatura será adotada como metodologia e autores como Argan, Archer, Krauss e Gombrich me conduziram na História da Arte e Ostrower e Valente em Criatividade. Por fim apresento alguns esboços e estudos ligados ao processo criativo em progresso no referido programa e finalizo considerando que a fruição, das obras de artistas clássicos e de artistas da cultura popular contribuíram para aguçar minha imaginação, assim como as ideias e experiências apresentadas sobre processos criativos estimularam a incorporação tanto do aprendizado obtido na minha trajetória criadora como do meu próprio estilo/personalidade na confecção de futuras obras.
Processos de Criação em Anne Sauvagnargues
Authors: Da Silva Édio Raniere , Da Silva Andressa Silveira
Published: December 2020

O presente artigo busca problematizar os processos de criação a partir da obra de Anne Sauvagnargues. Para isso apresenta uma introdução sobre a concepção elaborada por esta artista e filósofa tendo como objeto de análise três de suas pinturas: “Station Saint Michel”, “Viva Italia!” e “Arrêt à Marseille”. A partir dessa exposição inicial desenvolve-se, então, uma aproximação com o conceito de bloqueio - visto que para a autora é o bloqueio quem cria - e com a noção de subtração - visto que para Sauvagnargues a criação é sempre subtrativa. A hipótese defendida pelo ensaio é de que haja uma teoria da criação em Anne Sauvagnargues que ao mesmo tempo se relaciona com a ideia de bloqueio - a qual seria distinta de uma determinada compreensão do conceito de resistência em Gilles Deleuze: criar é resistir - e com a subtração enquanto invalidação de uma lei naturalizada. Naturalização, que por sua vez, impede a percepção de que a defesa de sistemas coerentes são sempre imposições de uma leitura em específico. Nesse sentido a aposta do trabalho é de que obra de Anne Sauvagnargues, ainda pouco traduzida no Brasil, tenha contribuições importantes para cartografias cuja intenção passe pelo mapeamento de relações que envolvem os processos de criação e os processos de subjetivação.
Når skolens børn evaluerer sig selv
Authors: Berg Mathias Sune , Kaas Lise Aagaard , Grumløse Sine Penthin
Published: December 2020

I overensstemmelse med ideen om livslang læring forventes skolebørn i stigende grad at vurdere, hvad de har lært. Karakteristisk for disse selvevalueringspraksisser er, at de ikke kun knytter sig til børnenes faglige kompetencer. De går ofte også tæt på børnenes mere personlige forhold. Derudover er evaluering en del af den skolepolitiske dagsorden, hvor læreren er forpligtet på at dokumentere elevernes læring.

I denne artikel går vi tæt på undervisningen og præsenterer eksempler på evalueringspraksisser, der skaber vidt forskellige deltagelsesmuligheder for børnene. Der er fokus på aktiviteter, hvor børnene skal vurdere, hvad de har lært, gennem brug af evalueringsværktøjer som portfolio og læringsplatforme. Vi diskuterer den udspændthed, som læreren befinder sig i mellem på den ene side at efterleve politiske krav om evaluering og på den anden side at praktisere evaluering, der kan udvikle undervisningen og styrke børnenes trivsel og læring samtidig med hensynet til børnenes behov og forudsætninger.
Educación crítica de las artes visuales en estudiantes de diseño gráfico. Relaciones de aprendizaje en torno a la cultura visual
Authors: Delgado Hishochy , Torres Yasselle Angela , Alonso Maylín
Published: December 2020

La dimensión crítica en los procesos de enseñanza y aprendizaje universitarios constituye un estadio superior del intelecto y la moral en los educadores y educando. Encuentra su base teórica, epistemológica y metodológica en las capacidades reconstructivas y autónomas del sujeto libre que piensa y crea. En esta investigación pretendemos abordar –desde las experiencias como docentes e investigadores- el andamiaje contextual que sitúa al discurso crítico como una necesidad educativa en estudiantes de Diseño Gráfico. Realizaremos un análisis de los componentes curriculares que intervienen en las decisiones para conformar un aparato crítico hacia el objeto artístico visual y responder a la pregunta ¿qué sentido tienen la educación crítica y su discurso sobre Artes Visuales en estudiantes de Diseño Gráfico?  Para ello, proponemos repensar las nociones de crítica, en contextos diversos por los que transita la cultura visual en aras de una educación más compleja, a través de relatos que cuentan las intimidades de las artes visuales.
Més enllà de l’escalfament global: Oceans estressats globalment a l’antropocè
Authors: Pelejero Carles , Calvo Eva
Published: December 2020

La petjada de les activitats humanes sobre el planeta és tan profunda que molts científics ja suggereixen que hem entrat en una nova època geològica, l’antropocè. D’entre aquestes activitats, les que venen acompanyades de grans emissions de diòxid de carboni (CO2) afecten d’una manera global tot el planeta i, sobretot, els oceans. Aquests, a banda d’escalfar-se, es tornen progressivament més àcids i menys oxigenats. En aquest article discutim l’abast d’aquests estressos globals sobre els oceans després de contextualitzar aquest desorbitat augment antropogènic de CO2 i de veure com es distribueix. Acabem amb una discussió sobre possibilitats de mitigació a través dels oceans mateixos, tot recalcant la necessitat imperiosa i urgent d’atacar el problema, sobretot durant aquesta dècada que hem començat.
Três teorias sobre a origem da língua portuguesa
Authors: García Martín Ana María
Published: December 2020

Expõem-se as principais teorias sobre a origem da língua portuguesa presentes em destacados textos metalinguísticos portugueses escritos entre os séculos xvi e xix. Pretende-se mostrar como as três teorias analisadas se integram no contexto de pensamento linguístico coevo, assim como a sua ligação com os discursos fundacionais da nação.
Nanosecond mode-locked Tm-doped fiber laser based on graphene saturable absorber
Authors: Wang Xiao-Fa  , Zhang Jun-Hong  , Gao Zi-Ye  , Xia Guang-Qiong  , Wu Zheng-Mao  ,   School of Physical Science and Technology, Southwest University, Chongqing 400715, China;,   Key Laboratory of Optical Fiber Communication Technology, Chongqing Education Commission, College of Optoelectronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China;,   School of Mathematics and Statistics, Southwest University, Chongqing 400715, China
Published: December 2020

The Tm-doped mode-locked pulsed fiber lasers, which are known for their wide applications in optical communication, laser medical system and special material processing, have attracted considerable interest as novel laser sources. Up to now, many reported Tm-doped mode-locked fiber lasers focused on emitting picosecond or femtosecond pulses at a few megahertz (MHz) repetition rate. Actually, due to the strong chirp, large pulse width, low peak power and little nonlinear phase accumulation characteristics in the process of power amplifier, nanosecond mode-locked fiber laser is a representative of ideal seed source in the chirped pulse amplification (CPA) system. However, nanosecond mode-locked fiber lasers are generally implemented with the kilometerlong cavity length, corresponding to the fundamental repetition rate of hundreds of kilohertz. Usually, fiber lasers with such a low repetition rate are not desirable in applications of laser material processing, nor medical treatment nor scientific researches. In this paper, we report a nanosecond mode-locked Tm-doped fiber laser with MHz repetition rate based on graphene saturable absorber (SA). As the SA, graphene has excellent optical properties, such as optical visualization, high transparency, ultra-fast relaxation time and nonlinear absorption. It is not limited by the band gap either because of its zero-band-gap structure. Therefore, graphene can be used as fast SA, with wide spectral range operated. Generally, graphene suitable for mode-locked fiber lasers can be produced by using chemical vapor deposition (CVD), liquid phase exfoliation and mechanical exfoliation. Since the CVD technique can obtain high-quality graphene with precisely controlled number of layers, it is always the first choice for the manufacture of graphene. In our work, monolayer graphene layers are grown on copper foils by CVD, and then transferred onto the end face of the fiber connector three times. Meanwhile, a narrow-band fiber Bragg grating is used to constrain longitudinal modes of the laser intra-cavity. By simply adjusting the pump power and the polarization angle of polarization controller, stable 2 μm nanosecond mode-locked pulses are obtained in a wide range from 3.8 ns to 94.3 ns at 3.8 MHz repetition rate. We believe that the results obtained will be helpful for investigating the CPA system at 2 μm.
A new method for the transport mechanism coupling of shale gas slippage and diffusion
Authors: Li Ya-Xiong  , Liu Xian-Gui  , Hu Zhi-Ming  , Gao Shu-Sheng  , Duan Xiang-Gang  , Chang Jin  ,   University of Chinese Academy of Sciences, Beijing 100049, China;,   Institute of Porous Flow and Fluid Mechanics, Chinese Academy of Sciences, Langfang 065007, China;,   Langfang Branch, PetroChina Research Institute of Petroleum Exploration and Development, Langfang 065007, China
Published: December 2020

In view of the current status that different literature applies different coupling methods to the calculation of shale gas flow, and in order to clarify the relation between slippage and several diffusions, in this paper the slippage effect and various diffusions are analyzed first by theoretical analysis and mathematical models according to the definitions and the mechanisms of microscopic motions. Afterwards, allowing for the spatial effect of the adsorbed molecules on gas flow, the concept “wall-associated diffusion” is proposed for the first time to represent the gross effects of Knudsen diffusion and surface diffusion, and it is pointed out that wall-associated diffusion is equivalent to slippage effect. Therefore a new coupling way where wall-associated diffusion and slippage effect are replaceable and no superposition of them is needed in flow calculation, is proposed. The case study shows that when the capillary radius ranges from 5 nm to 2000 nm, the relative error between wall-associated diffusion and slippage effect mass flux is fairly small, namely less than 10% in the vast majority of the range. The difference between mean values of wall-associated diffusion and slippage effect mass flux in the whole aperture range is 1.4×10- 6 kg·m-2·s-1. That is, the relative error between the mean values is only 5.8%. Therefore, the new method satisfies the requirements for engineering calculations. Taking parameter selection, unfinished improvements in mathematical models of relevant mechanisms and other factors into account, there is some room for further promoting the verification of the proposed method. The development of wall-associated diffusion has practical significance and multiple research significance. And the new coupling way reveals the relation between slippage and diffusions, which prevents reduplicated superposition of shale gas flow mechanisms in nano-scale pores and can well change the status where the current coupling methods for shale gas flow are not consistent, thus specifying a new direction in the quantitative calculations for shale gas development.
Analysis of the effect of node centrality on diffusion mode in complex networks
Authors: Su Zhen  , Gao Chao  , Li Xiang-Hua  ,   College of Computer and Information Science, Southwest University, Chongqing 400715, China
Published: December 2020

The centrality reflects the importance of a node in a complex network, which plays an important role in the propagation dynamics. Many researches in the field of node ranking estimation have revealed the characteristics of higher centrality in the structural dynamics and propagation dynamics. However, there are few reports about the effect of nodes with a relatively lower centrality on propagation process. In this paper, we focus on the effect of heterogeneous structural characteristics on propagation dynamics. First, we select four centrality measurements (i.e., degree, coreness, betweenness, and eigenvector) and initialize source nodes with the maximum and minimum centralities respectively. Then, based on the email propagation model and the SI model, the massive numbers of elaborate simulations are implemented in twelve scale-free networks. These networks include three networks generated by the Barabsi-Albert model, four synthetic networks compiled by the GLP (generalized linear preference) algorithm, and five benchmark networks. The simulation results contain two parts: one is the crossover phenomenon of two propagation processes, and the other is the correlation between the crossover point and the proportion of the initial source nodes. We present the crossover of two propagations by calculating the total infected nodes, the incremental infected nodes, and the average degree of the incremental infected nodes. The average degrees of the incremental infected nodes in both synthetic networks and benchmark networks show that there exist two kinds of diffusion modes (i.e., fan-shaped type and single-strand type). With the increase of the initial source nodes, the interaction between two modes results in the different dynamic changes of two propagations with respect to propagation speed, which may lead to the crossover of two propagations in terms of propagation scale in the propagation process. Specifically, the increase of the initial source nodes would suppress the propagation process in which nodes with the maximum centralities are portrayed as propagating sources. However, such an effect is not observed in the propagation process in which nodes with the minimum centralities are portrayed as propagating sources. Our further simulation indicates that the crossover points appear earlier as the proportion of the initial source nodes increases. And by employing the discrete-time method, we find that such a phenomenon can be triggered exactly by increasing the initial source nodes. This work reveals that the influence of the nodes with the minimum centralities should be taken into consideration because the initial infected nodes with a lower centrality will lead to a larger propagation scale if the initial proportion is high.
Stochastic resonance in overdamped washboard potential system
Authors: Xie Yong  , Liu Ruo-Nan  ,   State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, China;,   School of Mathematics and Statistics, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Brownian motion in a washboard potential has practical significance in investigating a lot of physical problems such as the electrical conductivity of super-ionic conductor, the fluctuation of super-current in Josephson junction, and the ad-atom motion on crystal surface. In this paper, we study the overdamped motion of a Brownian particle in a washboard potential driven jointly by a periodic signal and an additive Gaussian white noise. Since the direct simulation about stochastic system is always time-consuming, the purpose of this paper is to introduce a simple and useful technique to study the linear and nonlinear responses of overdamped washboard potential systems. In the limit of a weak periodic signal, combining the linear response theory and the perturbation expansion method, we propose the method of moments to calculate the linear response of the system. On this basis, by the Floquet theory and the non-perturbation expansion method, the method of moments is extended to calculating the nonlinear response of the system. The long time ensemble average and the spectral amplification factor of the first harmonic calculated from direct numerical simulation and from the method of moments demonstrate that they are in good agreement, which shows the validity of the method we proposed. Furthermore, the dependence of the spectral amplification factor at the first three harmonics on the noise intensity is investigated. It is observed that for appropriate parameters, the curve of the spectral amplification factor versus the noise intensity exhibits a peaking behavior which is a signature of stochastic resonance. Then we discuss the influences of the bias parameter and the amplitude of the periodic signal on the stochastic resonance. The results show that with the increase of the bias parameter in a certain range, the peak value of the resonance curve increases and the noise intensity corresponding to the resonance peak decreases. With the increase of the driven amplitude, comparing the changes of the resonance curves, we can conclude that the effect of stochastic resonance becomes more prominent. At the same time, by using the mean square error as the quantitative indicator to compare the difference between the results obtained from the method of moments and from the stochastic simulation under different signal amplitudes, we find that the method of moments is applicable when the amplitude of the periodic signal is lesser than 0.25.
Rotation mechanism of ultrasonically levitated cylinders
Authors: Qin Xiu-Pei  , Geng De-Lu  , Hong Zhen-Yu  , Wei Bing-Bo  ,   Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The rotation of levitated object in the ultrasonic levitation experiment is a common phenomenon. This instability may give rise to many difficulties in locating and detecting the levitated object and even cause the experiment to fail. However, the relevant research of the rotation mechanism of levitated object is seldom carried out. In this work, the rotation mechanism of cylinder in a single-axis ultrasonic levitator is investigated experimentally and theoretically. In the ultrasonic levitation experiment, the cylinder begins to rotate about an axis along the vertical direction as it is levitated at the node between the emitter and reflector. The rotation speed of cylinder tends to a stable value due to the effect of the air resistance, and the final rotation direction is determined by its initial rotation state. Experimental results demonstrate that the rotation speed increases with the decreases of density and length-to-diameter ratio of the cylinder. In order to analyze the rotation mechanism, the finite element method is used to calculate the distribution of acoustic pressure field and the torque acting on the cylinder for each of three different cases. Numerical results reveal that the position offsets of the cylinder and the reflector as well as the tilt of the emitter can all result in the nonaxisymmetrical distribution of acoustic pressure field. Hence, a nonzero torque acting on the cylinder may be generated and the rotation state of the levitated cylinder is subsequently affected. The position offset of the cylinder can produce a torque driving itself to rotate and the torque increases with the increase of the deviation degree. A restoring torque suppressing the rotation of cylinder can be generated by deviating the reflector from the horizontal direction. The cylinder eventually keeps stationary state with its axis perpendicular to the offset direction of the reflector, showing good accordance with the experimental results. In addition, it is predicted that tilting the emitter can also offer a restoring torque which makes cylinder eventually static with its axis perpendicular to the plane through the axes of the emitter and the reflector. However, this restoring torque is approximately three orders of magnitude smaller than that generated by deviating the reflector. In the end, both experimental results and numerical simulations show that the rotation of the cylinder can be effectively suppressed under the disturbance of two fixed cylinders when the emitter and the reflector are coaxial. The cylinder eventually stays still and keeps coaxial with the two fixed cylinders.
Spatiotemporal distributions of plasma and optical field during the interaction between ultra-short laser pulses and water nanodroplets
Authors: Wang Hao-Ruo  , Zhang Chong  , Zhang Hong-Chao  , Shen Zhong-Hua  , Ni Xiao-Wu  , Lu Jian  ,   School of Science, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

The transient changes of free electron density distribution and light field intensity during the interaction between the femtosecond Gaussian laser pulses and millimeter scale water droplets are studied. Based on the nonlinear Maxwell's equations and the ionization rate equation, a transient coupled model is proposed to describe the laser plasma produced in water droplet. The changes of electron density and light field with time are obtained by the finite element method.
The calculation results show that the laser induced breakdown threshold in the droplet is about 2 TW/cm2, one quarter of that in a boundaryless water medium under the same condition. We find that the region of plasma generated in the droplet will move along the laser direction at first, however, when the incident laser intensity becomes larger, it will move in the direction opposite to the laser beam propagation and the plasma shielded effect becomes more obvious. The laser beam converged by the droplet focuses outside the droplet, and its power density is five times larger than that of the incident laser. There happen the laser pulse duration compression and waveform distortion at the focus point due to the plasma absorption, and the absorption energy increases with the laser intensity increasing and reaches a saturation finally.
We expect the model and calculation results to be able to be used for the study of laser pulse propagation in cloud or rain, the precision control of droplet by laser or eye surgery by laser, and other laser technology applications.
Efficiency at arbitrary power for the Curzon-Ahlborn heat engine in linear and nonlinear heat transfer processes
Authors: Li Qian-Wen  , Li Ying  , Zhang Rong  , Lu Can-Can  , Bai Long  ,   School of Physics, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

The optimal performance of heat engine is an important issue in thermodynamics, but the heat transfer between the working medium and two heat reservoirs induces the irreversibility during the operation of heat engine. Based on two important parameters introduced in this paper(namely, the power gain and the efficiency gain), for heat engine operating in the linear and nonlinear heat transfer processes, the formula for the efficiency at arbitrary power is achieved in terms of a simplified Curzon-Ahlborn heat engine model and the componendo and dividendo rule. The features of heat engine at arbitrary power output are also discussed in detail based on the numerical calculations. It is indicated that the parameter as a function of the power gain P contains two branches:the efficiency shows the monotonous variation on the first branch (the favorable case); the efficiency exhibits the non-monotonous characteristics and has the maximum value on the second branch(the unfavorable case). The working region of the heat engine is reduced as the heat transfer exponent increases, which results from the radiative contribution in the nonlinear heat transfer process. For the first branch, the contour-line plot of versus TL/TH and P clearly demonstrates that has the decreasing trend with increasing TL/TH and|P|; for the second branch, monotonically deceases as TL/TH increases, but shows the non-monotonic behaviors as|P|increases. The efficiency has the maximum value in the region where TL/TH and|P|have the small values, and the working regime of heat engines in the nonlinear heat transfer process is relatively small due to the complexity of the nonlinear heat transfer process. The curves of the efficiency in two heat transfer processes are loop-shaped, when|P| 0 and|P| 1, the curves of ~P in two heat transfer processes are same. But in other regimes, the efficiency of the heat engine with the linear heat transfer process is bigger than in the nonlinear heat transfer process. Furthermore, it is found that a considerably larger efficiency can be obtained when heat engine working close to the maximum power. This implies that there exists the trade-off working point where the heat engine can perform the most effective heat-work conversion. In addition, the curves of the power gain vs. the efficiency gain also display the loop-shaped characteristics, but there is the weak difference on the second branch. Our results are very conducive to understanding the optimal performance of heat engines in different heat transfer processes.
Based on the molecular dynamics characteristic research of heat conduction of graphyne nanoribbons with vacancy defects
Authors: Lan Sheng  , Li Kun  , Gao Xin-Yun  ,   School of Electric Engineering and Automation, Fuzhou University, Fuzhou 350108, China
Published: December 2020

As a kind of nano-material, graphyne nanoribbon has some physical properties and its properties should be studied for its better usage. In the process of preparing graphyne nanoribbons, it is possible that vacancy defects exist in the lattice structure, which will affect the physical properties of the graphyne nanoribbons. The flotation of graphyne is closer to the actual situation in engineering than the complete graphyne nanoribbons, and the diversity of vacancy defects can lead to various thermal conductivities, so it is very important to simulate the effects of various vacancy defects on thermal conductivity. In order to better predicte and control heat transfer characteristics of graphyne nanoribbons, this paper focuses on the effects of vacancy defects on the heat transfer characteristics of graphyne nanoribbons. According to the different cutting directions of graphyne nanoribbons, two different types of graphyne nanoribbons are obtained, i.e., armchair type and zigzag type. We compare the effects of vacancy defects on the thermal conductivity of two different chiral graphynes nanoribbons to improve the persuasiveness of the conclusion. In this paper, non-equilibrium molecular dynamics method is adopted, by applying periodic boundary conditions in the length direction of the nanoribbons, the interaction between the carbon-carbon atoms is described based on a potential function of adaptive intermolecular reactive empirical bond order (AIREBO). At 300 K, the effects of single vacancy defect in the acetylene chain, single vacancy defect in the benzene ring or double vacancy defects in the acetylene chain on the thermal conductivities of single-layer graphyne nanoribbons are simulated. Fourier's law is used to calculate the thermal conductivities of graphyne nanoribbons. The simulation results show that for the thermal conductivity of graphyne nanoribbons in a-few-dozen nanometer range:1) as a result of the phonon scattering and enhanced phonon Umklapp process, the graphyne nanoribbons with vacancy defects will cause the thermal conductivity to decrease and becomes lower than that of the complete graphyne nanoribbons; 2) due to the difference in phonon density-of-states matching degree, the vacancy defect in the benzene ring of graphyne nanoribbons has a greater effect on the thermal conductivity than that of vacancy defect in the acetylene chain of graphyne nanoribbons, the vacancy defects have a strong influence on the thermal conductivity of in the acetylene chain of graphyne nanoribbons; 3) because of the influence of size effect, the thermal conductivity of graphyne nanoribbon increases with length increasing. In this paper, the research of the thermal conductivity of graphyne nanoribbon provides the reference for controlling their thermal conductivity on a certain scale.
Free-space optical communication based on hybrid optical mode array encoding
Authors: Xie Wan-Cai  , Huang Su-Juan  , Shao Wei  , Zhu Fu-Quan  , Chen Mu-Sheng  ,   Key Laboratory of Special Fiber Optics and Optical Access Networks, School of Communication and Information Engineering, Shanghai University, Shanghai 200072, China
Published: December 2020

The generation, propagation and application of optical vortex have been hot research topics in recent years. Optical vortex carries orbital angular momentum (OAM) that potentially increases the capacity and the spectral efficiency of optical communication system as a new degree of freedom. The optical vortex can be used not only as information carrier for space-division multiplexing, but also for encoding/decoding. We present a novel free-space optical communication system based on hybrid optical mode array encoding/decoding. The array includes four modes that can easily be identified by image processing. The four modes are Gaussian beam, single optical vortex, and two different composite optical vortices. In this paper, the computer generated hologram (CGH) of the hybrid optical mode array is generated based on the object-oriented conjugate-symmetric extension Fourier holography. When the CGH is loaded onto the electronic addressing reflection-type spatial light modulator (SLM), a single light beam illuminates the SLM, and the desired hybrid optical mode array is generated. In the experiment, a m 32 pixel32 pixel Lena gray image is transferred. At the transmitter, the Lena gray image is scanned line by line. The gray value (0-255) of each pixel with 8-bit information is extracted from the image and converted into a 22 hybrid optical mode array, which is encoded into the CGH. Hence, the m 32 pixel32 pixel Lena gray image is corresponding to a sequence with 1024 CGHs. By switching the CGHs loaded onto the SLM, the Lena gray image is transmitted in the form of the hybrid optical mode array. At the receiver, each hybrid optical mode array is decoded to a pixel value. To distinguish different modes conveniently, two cross lines are set at the center of each mode. By counting the peaks of two intensity distribution lines, the modes can easily be identified. We demonstrate the image reproduction of Lena with zero bit error rate (BER). The experimental result shows the favorable performance of the free-space optical communication link based on hybrid optical mode array encoding/decoding. Compared to that of the traditional single-vortex encoding communication system, the information capacity of our system with 22 hybrid optical mode array increases by four times. In addition, the presented experimental system is feasible and has strong expansibility. The information capacity can increase by 16 times with a 44 hybrid optical mode array based on the same experimental setup. Therefore, the presented free-space optical communication system using hybrid optical mode array encoding/decoding has great significance for improving the capacity of free-space optical communication system.
Orientation effect of alpha-to-epsilon phase transformation in single-crystal iron
Authors: Li Jun  , Wu Qiang  , Yu Ji-Dong  , Tan Ye  , Yao Song-Lin  , Xue Tao  , Jin Ke  ,   Laboratory for Shock Wave Detonation Physics Research, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The dynamic response of iron, especially the phase transformation from the ambient body-centered-cubic (bcc) up-phase to the hexagonal-closed packed (hcp) -phase, has been studied extensively in the last 60 years due to its importance in industry and its role as a main constituent of Earth. Recently, this topic has attracted a lot of attention in the aspects of the kinetic characteristics and mechanism of the shock-induced phase transition, including orientation-, temperature-, time- and strain rate-dependences. But only a few data have been published on the crystal orientation effect. The systematic experimental results to identify the predictions of the non-equilibrium molecular dynamics (NEMD) simulation are still lacking. For this reason, we study the shock responses of the [100], [110] and [111] orientated iron single crystals by using a three-independent-sample method in one shot. Unlike previously reported [001] single-crystal iron, a clear three-wave structure consisting of a PEL wave (elastic wave), a P1 wave (plastic wave) and a P2 wave (phase transition wave) is observed in the measured wave profiles for all single-crystal iron samples. The elastic-plastic transition process is in accordance with the numerical simulation of dislocation-based constitutive model for visco-plastic deformation. It is found that the values of Hugoniot elastic limit HEL ((111)/(HEL) (110)/(HEL) (100)/(HEL)) are greater than 6 GPa and dependent on the initial crystal orientation. Such a high yield strength is consistent with the nanosecond X-ray diffraction of [001] single-crystal iron where the uniaxial compression of the lattice has been observed at a shock pressure of about 5.4 GPa. Moreover, the onset pressures PPT for the phase transition are obtained to be 13.890.57 GPa, 14.530.53 GPa and 16.050.67 GPa along the [100], [110], and [111] directions, respectively. Based on these results, it is concluded that the crystal orientation effect of PPT is consistent with the reported NEMD calculations. However, the measured values are lower. In addition, the transition strain-ratio of singlecrystal iron is found to be higher than that of polycrystalline iron, reflecting the influence of the transformation kinetics (i.e., transformation kinetics coefficient) on the wave profile evolution. Our observations indicate that the strong coupling between plasticity and phase transition in single crystal iron might be a key point for understanding the origin of the phase transition and also for ending the controversy of metastable -phase. The fine multi-wave profiles also provide an important experimental reference for improving the phase field modeling of shock-induced phase transition.
Super diffraction imaging with wave vector selective metasurface
Authors: Guo Chang  , Zhang Yan  ,   Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing Key Laboratory of Metamaterials and Devices, Beijing Advanced Innovation Center for Imaging Technology, Department of Physics, Capital Normal University, Beijing 100048, China
Published: December 2020

Super diffraction imaging has been a research hotspot for a long time. We realize the super diffraction imaging with a metasurface structure, which is consisted of asymmetrically split rings. Based on the wave vector selectivity of the metasurface, radiation can be transmitted through it only in a narrow range of the incident angular. The metasurface acts as a high frequency spatial filter, reduces the diffraction effect, and obtains the super diffraction resolution. Numerical simulation results demonstrate the validity of this method.
Research progress of plasmonic structure illumination microscopy
Authors: Zhang Chong-Lei  , Xin Zi-Qiang  , Min Chang-Jun  , Yuan Xiao-Cong  ,   Nanophotonics Research Center, Shenzhen University, Shenzhen 518060, China
Published: December 2020

Structure illumination microscopy (SIM) is a novel imaging technique with advantages of high spatial resolution, wide imaging field and fast imaging speed. By illuminating the sample with patterned light and analyzing the information about Moir fringes outside the normal range of observation, SIM can achieve about 2-fold higher in resolution than the diffraction limit, thus it has played an important role in the field of biomedical imaging. In recent years, to further improve the resolution of SIM, people have proposed a new technique called plasmonic SIM (PSIM), in which the dynamically tunable sub-wavelength surface plasmon fringes are used as the structured illuminating light and thus the resolution reaches to 3-4 times higher than the diffraction limit. The PSIM technique can also suppress the background noise and improve the signal-to-noise ratio, showing great potential applications in near-surface biomedical imaging. In this review paper, we introduce the principle and research progress of PSIM. In Section 1, we first review the development of optical microscope, including several important near-field and far-field microscopy techniques, and then introduce the history and recent development of SIM and PSIM techniques. In Section 2, we present the basic theory of PSIM, including the dispersion relation and excitation methods of surface plasmon, the principle and imaging process of SIM, and the principle of increasing resolution by PSIM. In Section 3, we review the recent research progress of two types of PSIMs in detail. The first type is the nanostructure-assisted PSIM, in which the periodic metallic nanostructures such as grating or antenna array are used to excite the surface plasmon fringes, and then the shift of fringes is modulated by changing the angle of incident light. The resolution of such a type of PSIM is mainly dependent on the period of nanostructure, thus can be improved to a few tens of nanometers with deep-subwavelength structure period. The other type is the all-optically controlled PSIM, in which the structured light with designed distribution of phase or polarization (e.g. optical vortex) is used as the incident light to excite the surface plasmon fringes on a flat metal film, and then the fringes are dynamically controlled by modulating the phase or polarization of incident light. Without the help of nanostructure, such a type of PSIM usually has a resolution of about 100 nm, but benefits from the structureless excitation of plasmonic fringes in an all-optical configuration, thereby showing more dynamic regulation and reducing the need to fabricate nanometer-sized complex structures. In the final Section, we summarize the features of PSIM and discuss the outlook for this technique. Further studies are needed to improve the performance of PSIM and to expand the scope of practical applications in biomedical imaging.
Terahertz surface polaritons
Authors: Zhang Xue-Jin  , Lu Yan-Qing  , Chen Yan-Feng  , Zhu Yong-Yuan  , Zhu Shi-Ning  ,   Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
Published: December 2020

Enormous efforts have been made to manipulate the light-matter interactions, especially in sub-diffraction-limited space, leading to miniaturized and integrated photonic devices. In physics, an elementary excitation, called polariton, which is the quantum of the coupled photon and polar elementary excitation wave field, underlies the light-matter interaction. In the dispersion relation, polaritons behave as anti-crossing interacting resonance. Surface polaritons provide ultra-confinement of electromagnetic field at the interface, opening up possibilities for sub-diffraction-limited devices, and various field enhancement effects. In the electromagnetic spectra, terahertz (THz) regime was called THz gap before the 1990s, but has now been thrust into the limelight with great significance. This review is devoted to the emerging but rapidly developing field of sub-diffraction-limited THz photonics, with an emphasis on the materials and the physics of surface polaritons. A large breadth of different flavours of materials and surface polaritonic modes have been summarized. The former includes metallic, dielectric, semiconductor, two-dimensional (2D) materials, metamaterials, etc.; the latter covers surface phonon-, plasmon-, and hybrid polaritons. In the THz regime, 2D surface plasmon polariton and artificial surface phonon polaritons offer more attractive advantages in ability to obtain low-loss, tunable, ultracompact light-matter modes.