Catálogo de publicaciones - revistas

<jats:p>We present a ghost handwritten digit recognition method for the unknown handwritten digits based on ghost imaging (GI) with deep neural network, where a few detection signals from the bucket detector, generated by the cosine transform speckle, are used as the characteristic information and the input of the designed deep neural network (DNN), and the output of the DNN is the classification. The results show that the proposed scheme has a higher recognition accuracy (as high as 98% for the simulations, and 91% for the experiments) with a smaller sampling ratio (say 12.76%). With the increase of the sampling ratio, the recognition accuracy is enhanced. Compared with the traditional recognition scheme using the same DNN structure, the proposed scheme has slightly better performance with a lower complexity and non-locality property. The proposed scheme provides a promising way for remote sensing.</jats:p>

<jats:p>We propose a narrow-band birefringent filter and its application in wide color gamut. The birefringent filter consists of five phase retarders and two polarizers, and it has both narrow band and high transmittance. In the experiment, we fabricate the birefringent filter using quartz phase retarders and polarizers, and apply it in serval different displays. The color gamuts of displays are enhanced more than 30%NTSC (National Television System Committee), and the widest color gamuts that have been obtained are 126%NTSC in liquid crystal displays and 138%NTSC in organic light-emitting devices. Moreover, the deep blue light in spectrum of display can be reduced using the birefringent filter. The birefringent filter can be an efficient element to achieve wide color gamut display.</jats:p>

<jats:p>The spatial and temporal evolution of real contact area of contact interface with loads is a challenge. It is generally believed that there is a positive linear correlation between real contact area and normal load. However, with the development of measuring instruments and methods, some scholars have found that the growth rate of real contact area will slow down with the increase of normal load under certain conditions, such as large-scale interface contact with small roughness surface, which is called the nonlinear phenomenon of real contact area. At present, there is no unified conclusion on the explanation of this phenomenon. We set up an experimental apparatus based on the total reflection principle to verify this phenomenon and analyze its mechanism. An image processing method is proposed, which can be used to quantitative analysis micro contact behaviors on macro contact phenomenon. The weighted superposition method is used to identify micro contact spots, to calculate the real contact area, and the color superimposed image is used to identify micro contact behaviors. Based on this method, the spatiotemporal evolution mechanism of real contact area nonlinear phenomena is quantitatively analyzed. Furthermore, the influence of nonlinear phenomenon of real contact area on the whole loading and unloading process is analyzed experimentally. It is found that the effects of fluid between contact interface, normal load amplitude and initial contact state on contact behavior cannot be ignored in large-scale interface contact with small roughness surface.</jats:p>

<jats:p>The nonlinear parabolized stability equations (NPSEs) approach is widely used to study the evolution of disturbances in hypersonic boundary layers owing to its high computational efficiency. However, divergence of the NPSEs will occur when disturbances imposed at the inlet no longer play a leading role or when the nonlinear effect becomes very strong. Two major improvements are proposed here to deal with the divergence of the NPSEs. First, all disturbances are divided into two types: dominant waves and non-dominant waves. Disturbances imposed at the inlet or playing a leading role are defined as dominant waves, with all others being defined as non-dominant waves. Second, the streamwise wavenumbers of the non-dominant waves are obtained using the phase-locked method, while those of the dominant waves are obtained using an iterative method. Two reference wavenumbers are introduced in the phase-locked method, and methods for calculating them for different numbers of dominant waves are discussed. Direct numerical simulation (DNS) is performed to verify and validate the predictions of the improved NPSEs in a hypersonic boundary layer on an isothermal swept blunt plate. The results from the improved NPSEs approach are in good agreement with those of DNS, whereas the traditional NPSEs approach is subject to divergence, indicating that the improved NPSEs approach exhibits greater robustness.</jats:p>

<jats:p>Boris numerical scheme due to its long-time stability, accuracy and conservative properties has been widely applied in many studies of magnetized plasmas. Such algorithms conserve the phase space volume and hence provide accurate charge particle orbits. However, this algorithm does not conserve the energy in some special electromagnetic configurations, particularly for long simulation times. Here, we empirically analyze the energy behavior of Boris algorithm by applying it to a 2D autonomous Hamiltonian. The energy behavior of the Boris method is found to be strongly related to the integrability of our Hamiltonian system. We find that if the invariant tori is preserved under Boris discretization, the energy error can be bounded for an exponentially long time, otherwise the said error will show a linear growth. On the contrary, for a non-integrable Hamiltonian system, a random walk pattern has been observed in the energy error.</jats:p>

<jats:p>Developments of economic systems are critical for bio-regenerative life support systems in manned space missions. In this work we report on the feasibility of using two direct sunlight powered processes sequentially for the recovery of water and nutrients from urine. The work presents experimental evidence on nutrient and water recovery achieved using the proto-type designed and developed. We report the design and testing of a solar still which would serve on the nutrient recovery front. The cooled condensate from the solar still is fed into a solar powered electrolysis unit where nano-structured indium sulphide (In<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub>) thin films coated over fluorine doped tin oxide (SnO<jats:sub>2</jats:sub>:F) substrate serve as one of the working electrodes. The electrolysis takes place in the absence of an electrolyte which manifests as a technical achievement of our work. Our results show that the COD level in the recycled water is very low. The In<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub> photo-electrodes are stable without any physical damage after the process.</jats:p>

<jats:p>The lack of the long-range order in the atomic structure challenges the identification of the structural defects, akin to dislocations in crystals, which are responsible for predicting plastic events and mechanical failure in metallic glasses (MGs). Although vast structural indicators have been proposed to identify the structural defects, quantitatively gauging the correlations between these proposed indicators based on the undeformed configuration and the plasticity of MGs upon external loads is still lacking. Here, we systematically analyze the ability of these indicators to predict plastic events in a representative MG model using machine learning method. Moreover, we evaluate the influences of coarse graining method and medium-range order on the predictive power. We demonstrate that indicators relevant to the low-frequency vibrational modes reveal the intrinsic structural characteristics of plastic rearrangements. Our work makes an important step towards quantitative assessments of given indicators, and thereby an effective identification of the structural defects in MGs.</jats:p>

<jats:p>Electrides are unique materials with the anionic electrons confined to the interstitial sites, expecting important applications in various areas. In this work, the electronic structure and detailed physical properties of topological electride Ca<jats:sub>3</jats:sub>Pb are studied theoretically. By comparing the crystal structures and band structures of Ca<jats:sub>3</jats:sub>Pb and Ca<jats:sub>3</jats:sub>PbO, we find that after removing O<jats:sup>2–</jats:sup> ions from Ca<jats:sub>3</jats:sub>PbO, the remaining electrons are confined in the vacancies of the Ca<jats:sub>6</jats:sub> octahedra centers, playing the role as anions and forming an additional energy band compared with that of Ca<jats:sub>3</jats:sub>Pb. These interstitial electrons partially result in the low work function of Ca<jats:sub>3</jats:sub>Pb. Moreover, the calculated mechanic properties imply that Ca<jats:sub>3</jats:sub>Pb has a strong brittleness. In addition, the dielectric functions and optical properties of Ca<jats:sub>3</jats:sub>Pb are also analyzed.</jats:p>

<jats:p>Valley filter is a promising device for producing valley polarized current in graphene-like two-dimensional honeycomb lattice materials. The relatively large spin–orbit coupling in silicene contributes to remarkable quantum spin Hall effect, which leads to distinctive valley-dependent transport properties compared with intrinsic graphene. In this paper, quantized conductance and valley polarization in silicene nanoconstrictions are theoretically investigated in quantum spin-Hall insulator phase. Nearly perfect valley filter effect is found by aligning the gate voltage in the central constriction region. However, the valley polarization plateaus are shifted with the increase of spin–orbit coupling strength, accompanied by smooth variation of polarization reversal. Our findings provide new strategies to control the valley polarization in valleytronic devices.</jats:p>

<jats:p>Emulation of synaptic function by ionic/electronic hybrid device is crucial for brain-like computing and neuromorphic systems. Electric-double-layer (EDL) transistors with proton conducting electrolytes as the gate dielectrics provide a prospective approach for such application. Here, artificial synapses based on indium-tungsten-oxide (IWO)-based EDL transistors are proposed, and some important synaptic functions (excitatory post-synaptic current, paired-pulse facilitation, filtering) are emulated. Two types of spike-timing-dependent plasticity (Hebbian STDP and anti-Hebbian STDP) learning rules and multistore memory (sensory memory, short-term memory, and long-term memory) are also mimicked. At last, classical conditioning is successfully demonstrated. Our results indicate that IWO-based neuromorphic transistors are interesting for neuromorphic applications.</jats:p>