arXiv subjects

Yanzeng Li

Publications and source records attributed to Yanzeng Li.

28 records · Page 2Linked to original sources

arXiv2022

VGStore: A Multimodal Extension to SPARQL for Querying RDF Scene Graph

Semantic Web technology has successfully facilitated many RDF models with rich data representation methods. It also has the potential ability to represent and store multimodal knowledge bases such as multimodal scene graphs. However, most existing query languages, especially SPARQL, barely explore the implicit multimodal relationships like semantic similarity, spatial relations, etc. We first explored this issue by organizing a large-scale scene graph dataset, namely Visual Genome, in the RDF graph database. Based on the proposed RDF-stored multimodal scene graph, we extended SPARQL queries to answer questions containing relational reasoning about color, spatial, etc. Further demo (i.e., VGStore) shows the effectiveness of customized queries and displaying multimodal data.

cs.DB↗

arXiv2022

Crake: Causal-Enhanced Table-Filler for Question Answering over Large Scale Knowledge Base

Semantic parsing solves knowledge base (KB) question answering (KBQA) by composing a KB query, which generally involves node extraction (NE) and graph composition (GC) to detect and connect related nodes in a query. Despite the strong causal effects between NE and GC, previous works fail to directly model such causalities in their pipeline, hindering the learning of subtask correlations. Also, the sequence-generation process for GC in previous works induces ambiguity and exposure bias, which further harms accuracy. In this work, we formalize semantic parsing into two stages. In the first stage (graph structure generation), we propose a causal-enhanced table-filler to overcome the issues in sequence-modelling and to learn the internal causalities. In the second stage (relation extraction), an efficient beam-search algorithm is presented to scale complex queries on large-scale KBs. Experiments on LC-QuAD 1.0 indicate that our method surpasses previous state-of-the-arts by a large margin (17%) while remaining time and space efficiency. The code and models are available at https://github.com/AOZMH/Crake.

cs.CL↗

arXiv2020

Metasurfaces for the Infrared Spectral Range Fabricated Using Two-Photon Polymerization

Fabrication of metasurfaces is ofthen time consuming and expensive, involving complex lithographic processes. The maskless fabrication of metasurfaces composed of rectangular Au bars is reported as a suitable alternative, providing cost-effective, rapid prototyping of metasurfaces. The investigated metasurfaces were fabricated using a simple three-step process which is discussed in detail. The fabrication process establishes a simple method for producing high fidelity 2D patterns suitable to synthesize metasurfaces for chemical sensing, beam steering, and perfect reflection/transmission. Comprehensive polarization-sensitive reflection data reveal multiple resonances in the infrared spectral range. In addition to the dipole and substrate resonances, a resonance which is attributed to a coupling between the excitation of the metasurface and the substrate phonon mode is observed.

physics.optics↗

arXiv2020

Reciprocal plasmonic metasurfaces: Theory and applications

A new configuration for metasurface construction is presented to achieve multi-functional capabilities including perfect absorption, bio/chem sensing, and surface-mode lasing. The reciprocal plasmonic metasurfaces discussed here are composed of two plasmonic surfaces of reciprocal geometries separated by a dielectric spacer. Compared to conventional metasurfaces this simple geometry exhibits an enhanced optical performance. The discussed reciprocal metasurface design further enables effective structural optimization and allows for a simple and scalable fabrication. The physical principle and potential applications of the reciprocal plasmonic metasurfaces are demonstrated using numerical and analytical approaches.

physics.optics↗

arXiv2020

Enhancing Pre-trained Chinese Character Representation with Word-aligned Attention

Most Chinese pre-trained models take character as the basic unit and learn representation according to character's external contexts, ignoring the semantics expressed in the word, which is the smallest meaningful utterance in Chinese. Hence, we propose a novel word-aligned attention to exploit explicit word information, which is complementary to various character-based Chinese pre-trained language models. Specifically, we devise a pooling mechanism to align the character-level attention to the word level and propose to alleviate the potential issue of segmentation error propagation by multi-source information fusion. As a result, word and character information are explicitly integrated at the fine-tuning procedure. Experimental results on five Chinese NLP benchmark tasks demonstrate that our model could bring another significant gain over several pre-trained models.

cs.CL↗

arXiv2019

Direct Laser Writing of Birefringent Photonic Crystals for the Infrared Spectral Range

Infrared optical photonic crystals fabricated using direct laser writing, which is based on the two-photon polymerization of suitable monomers, have received substantial interest since the emergence of this process. Two-photon polymerization could be a disruptive technology for the fabrication of all-dielectric photonic crystals in the infrared spectral range, as it allows the synthesis of large scale arrays of uniform structures with arbitrary geometries and arrangements. However, all-dielectric photonic crystals that provide birefringent optical responses in the infrared spectral range have not yet been demonstrated using direct laser writing techniques. Here we explore the form birefringence observed in photonic crystals composed of arrays of subwavelength-sized slanted polymer microwires. The photonic crystals investigated here were fabricated in a single fabrication step using direct laser writing of an infrared transparent photoresist (IP-Dip). A strong contrast of the cross-polarized reflectance of photonic crystals as a function of the in-plane orientation is observed in the mid-infrared spectral range at $λ$ $\approx$ 6.5~$μ$m. This observation is indicative of an anisotropic optical behavior. Finite element based techniques corroborate the experimentally observed responses qualitatively.

physics.app-ph↗

arXiv2019

Diffraction Gratings for Uniform Light Extraction from Light Guides

A theoretical approach for uniformly extracting light propagating through a light guide plate is developed here. Typically, liquid crystal display modalities utilize a backlit lighting system illuminated from the edge with light emitting diodes. The backlight acts as a light guide plate and is coupled with a diffuser sheet along the surface to uniformly extract the light. Our approach employs sub-micron diffraction gratings and eliminates the need for diffuser sheets, while ensuring the uniform extraction of light. The physical dimensions of the grating are varied along the surface of the light guide plate to control the diffraction efficiency, thus determining the local viewing angle and emitted intensity.

physics.optics↗

arXiv2019

A Stereolithographically Fabricated Polymethacrylate Broadband THz Absorber

Additive manufactured THz optics have been introduced as an efficient alternative to their commercial counterparts. Among various additive manufacturing methods, stereolithography provides superior spatial resolution and surface finish. However, examples of stereolithographically fabricated components for THz applications are still scarce. In this paper, we report on the fabrication process and performance of a stereolithographically fabricated broadband absorber for the THz spectral range. Simple THz transmission experiments were carried out for the absorber and bulk reference samples. The experimental results indicated that the fabricated absorber effectively absorbs incident signal in the investigated THz spectral range.

physics.app-ph↗

arXiv2019

THz optical properties of polymethacrylates after thermal annealing

Polymer based stereolithographic additive manufacturing has been established for the rapid and low-cost fabrication of THz optical components due to its ability to construct complex 3D geometries with high resolution. For polymer based or integrated optics, thermal annealing processes are often used to optimize material properties. However, despite the growing interest in THz optics fabricated using stereolithography, the effects of thermal annealing on the THz dielectric properties of polymethacrylates compatible with stereolithography has not been studied yet. In this manuscript we report on the THz ellipsometric response of thermally annealed polymethacrylates prepared using UV polymerization. Our findings indicate that the investigated polymethacrylate maintain a stable optical response in THz spectral range from 650 to 950 GHz after thermal annealing at temperatures up to 70 degrees C for several hours.

physics.optics↗

arXiv2019

Terahertz to mid-infrared dielectric properties of polymethacrylates for stereolithographic single layer assembly

The fabrication of terahertz (THz) optics with arbitrary shapes via poly-methacrylate-based stereolithography is very attractive as it may offer a rapid, low-cost avenue towards optimized THz imaging applications. In order to design such THz optical components appropriately, accurate knowledge of the complex dielectric function of the materials used for stereolithographic fabrication is crucial. In this paper we report on the complex dielectric functions of several polymethacrylates frequently used for stereolithographic fabrication. Spectroscopic ellipsometry data sets from the THz to mid-infrared spectral range were obtained from isotropically cross-linked polymethacrylate samples. The data sets were analyzed using stratified layer optical model calculations with parameterized model dielectric functions. While the infrared spectral range is dominated by a number of strong absorption features with Gaussian profiles, these materials are found to exhibit only weak absorption in the THz frequency range. In conclusion, we find that thin transmissive THz optics can be efficiently fabricated using polymethacrylate-based stereolithographic fabrication.

physics.app-ph↗