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Wavelength Switched Optical Networks (WSONs) have been designed to take advantage of all optical switching fabrics with a high level of automation and efficiency. Therein, the Wavelength Selective Switches (WSS) represent the core switching elements with a technology enabling multi-degree Reconfigurable Optical Add\Drop Multiplexers (ROADM) architectures with colorless and directionless switching. In this paper, we propose an optimization model to establish the best ROADM switching connectivity to maximize the grade of service, for a given number of ports. We show that the grade of service can vary significantly, up to 30%, depending on the switching connectivity. Besides, the larger the network is, the more the variance increases: from 20% to 30%, when the number of nodes varies from 14 to 24.

Enhanced diffraction by sub-wavelength nanostructures to convert incident electromagnetic radiation into waveguide modes has applications in anti-reflective coatings for optoelectronic devices. We propose a metal oxide (ZnO) nanowire grid polarizer as such a nanostructure, fabricated by ultraviolet nanoimprint lithography and whose fill factor (FF) is controlled by atomic layer deposition. Using finite difference time domain simulations, we investigated the polarization-dependent optical transmittance of the structures and calculated the polarizing efficiency. Optical profiles such as electric and magnetic field intensity and current density distributions of specific FF nanopatterns were determined for the transverse magnetic and transverse electric modes. The effects of geometrical parameters including the wire-grid period, fill ratio, and spacing between the wire-grid layers on diffraction wavelength were characterized. Respective FF-controlled ZnO nanowire structures were fabricated and their experimental optical transmittances were measured for nanowire grid polarizer applications.

Content-based multimedia information retrieval is never a trivial task even with state-of-the-art approaches. Its mandatory challenge, called “semantic gap,” requires much more understanding of the way human perceive things (i.e., visual and auditory information). Computer scientists have spent thousands of hours seeking optimal solutions, only ended up falling in the bound of this gap for both visual and spoken contexts. While an over-the-gap approach is unreachable, we insist on assembling current viable techniques from both contexts, aligned with a domain concept base (i.e., an ontology), to construct an info service for the retrieval of agricultural multimedia information. The development process spans over three packages: (1) building a Vietnamese agricultural thesaurus; (2) crafting a visual-auditory intertwined search engine; and (3) system deployment as an info service. We spring our the thesaurus in 2 sub-boughs: the aquaculture ontology consists of 3455 concepts and 5396 terms, with 28 relationships, covering about 2200 fish species and their related terms; and the plant production ontology comprises of 3437 concepts and 6874 terms, with 5 relationships, covering farming, plant production, pests, etc. These ontologies serve as a global linkage between keywords, visual, and spoken features, as well as providing the reinforcement for the system performances (e.g., through query expansion, knowledge indexing…). On the other hand, constructing a visual-auditory intertwined search engine is a bit trickier. Automatic transcriptions of audio channels are marked as the anchor points for the collection of visual features. These features, in turn, got clustered based on the referenced thesauri, and ultimately tracking out missing info induced by the speech recognizer’s word error rates. This compensation technique bought us back 14 % of loss recall and an increase of 9 % accuracy over the baseline system. Finally, wrapping the retrieval system as an info service guarantees its practical deployment, asour target audiences are the majority of farmers in developing countries who are unable to reach modern farming information and knowledge.

We have investigated ZnO thin films prepared via photochemical reaction as the electron transport layer (ETL) of inverted organic solar cells (OSCs). Morphological and electrical properties of the ZnO thin films prepared by the photosensitive ZnO sol were studied according to the annealing temperature and their effects on the performance of the inverted poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) OSCs was characterized. It was found that the optimal annealing temperature of the ZnO thin films was 330 °C, and that devices with the ZnO ETL annealed at this temperature exhibited the largest short-circuit current density ( J sc ) of 9.39 mA/cm 2 , as well as the highest power conversion efficiency (PCE) of 2.31%, which can be attributed to enhanced electron transport and interfacial properties. Devices containing ZnO films formed at optimal annealing condition exhibited an open circuit voltage ( V oc ) of 0.60 V and a fill factor (FF) of 41.0%. However, further increase of the annealing temperature led to degradation of the device performance, despite further improvements in electrical properties. We have found that marked increase in the surface roughness of the ZnO films occurred at temperatures above 350 °C which could be detrimental to the OSCs characteristics due to a high contact resistance and a large leakage current.

In this study, we have systematically investigated a magnetic resonance absorption and tunability of absorption wavelength in isolated metal-insulator-metal (MIM) nanodot arrays with transmission geometry. The elemental electromagnetic resonances and their hybridizations are studied using 3-dimensional finite-difference time-domain (FDTD) calculation and resonance properties including the resonance peak tunability, magnetic permeability and quality ( Q ) factor are characterized with respect to the coupling strength. We have found the existence of electric and magnetic resonance mode in the MIM (Au/MgF 2 /Au) structure and the magnetic resonance has larger wavelength tunability than the electric resonance. The absorption cross section calculation revealed that absorption is the dominant extinction process at the magnetic resonance only. Magnetic permeability ( μ ) calculations for the various MIM parameters showed the maximum value of the imaginary part of μ is 16.1 with Q factor of 9.2 when the size of nanodot is 200 nm and the inter-dot distance is 300 nm. The presented calculations can be used to tune the response of the magnetic resonance absorption with a variable resonance wavelength and Q factor by using the simple MIM structures with transmission geometry.

Despite being crippled by a mandatory challenge, called “sematic gap,” content-based information retrieval is still on the way of blooming. Its application can be seen across different domains, from several daily Google image-searches to an intense sport shot retrieval. Nonetheless, semantic agricultural information retrieval has been averted from the eyes of computer scientists. Meanwhile, farmer in the rural areas are suffering from the lack of information and guidance, resulting in poverty and low life-quality. Stemming from an agricultural country, it is our mission to put efforts on the field. There are two contributions in this work: (1) building a Vietnamese agricultural thesaurus, and (2) an agricultural multimedia retrieval system; putting together as an info service for farming guidance. We spring our thesaurus in 2 sub-boughs: the aquaculture ontology consists of 3455 concepts and 5396 terms, with 28 relationships, covering about 2200 fish species and their related terms; and the plant production ontology comprises of 3437 concepts and 6874 terms, with 5 relationships, covering farming, plant production, pests, etc. These ontologies serve as a global linkage between keywords, visual, and spoken features, as well as providing reinforcement for the system performances. On the other hand, constructing a semantic multimedia retrieval engine is a bit trickier. Automatic transcriptions of audio channels are marked as the anchor points for the collection of visual features. These features, in turn, got clustered based on the referenced thesauri, and ultimately tracking out missing info induced by the speech recognizer’s word error rates. This compensation technique bought us back 16.2 % of loss recall and an increase of 9.4 % accuracy over the baseline system.