1,001 research outputs found
Amplitude gradient-based metasurfaces for off-chip terahertz wavefront shaping
No full textMetasurfaces provide an effective technology platform for manipulating electromagnetic waves, and the existing design methods all highlight the importance of creating a gradient in the output phase across light scattering units. However, in the emerging research subfield of meta-waveguides where a metasurface is driven by guided modes, this phase gradient-oriented approach can only provide a very limited emission aperture, significantly affecting the application potential of such meta-waveguides. In this work, we propose a new design approach that exploits the difference between meta-atoms in their light scattering amplitude. By balancing this amplitude gradient in the meta-atoms against the intensity decay in the energy-feeding waveguide, a large effective aperture can be obtained. Based on this new design approach, three different wavefront shaping functionalities are numerically demonstrated here on multiple devices in the terahertz regime. They include beam expanders that radiate a plane wave, where the beam width can increase by more than 900 times as compared to the guided wave. They also include a metalens that generates a Bessel-beam focus with a width 0.59 times the wavelength, and vortex beam generators that emit light with a tunable topological charge that can reach −30. This amplitude gradient design approach could benefit a variety of off-chip light shaping applications such as remote sensing and 6G wireless communications.</p
Directional conversion of a THz propagating wave into surface waves in deformable metagratings
No full textControllable conversion between propagating light waves and surface waves (SWs) has recently attracted significant research interests. This paper demonstrates, via numerical simulation, for the first time all-dielectric SW converters that possess a tunable and directional SW conversion efficiency. The SW converters contain multiple metagratings of Si pillars embedded in a deformable substrate. In the analysis, an infinitely large, bi-periodic metagrating under the illumination of linearly polarized light is considered first. The SW conversion efficiency of this metagrating can be modulated between 4.3% and 51.0% for incident light frequency at 0.8 THz by stretching the deformable substrate along the direction of SW propagation. Subsequently, two SW converters under circularly polarized light illumination are analyzed, where a similar level of efficiency modulation is retained in finite-sized metagratings. In these converters, only the metagrating channels along the stretch direction have a strong SW conversion efficiency, which can reach 40.4% after normalization against the effective grating area. The directivity, a parameter defined here to reveal the energy contrast among the output channels, reaches 38.6 in one of the converters. Due to its high tunability, high directivity and compact size, the SW converters may be used as tunable optical sensors and light couplers in the THz regime
Deep-subwavelength gap modes in all-dielectric metasurfaces for high-efficiency and large-angle wavefront bending
No full textAll-dielectric, phase-gradient metasurfaces manipulate light via a judiciously designed planar distribution of high and low refractive indices. In the established design approaches, the high-index elements play a dominant role, while the electromagnetic field existing between these elements is routinely viewed as either an incidental by-product or detrimental crosstalk. Here we propose an alternative approach that concentrates on exploring the low-index materials for wavefront shaping. In our Si metasurface, the low-index air gap between adjacent Si fins is judiciously tuned, while the high-index Si fins only have a single size across the whole metasurface. These gap modes provide the full 2π phase coverage, as well as high and relatively uniform transmission, at the deep-subwavelength scale. These characteristics are ideal for mapping a steep phase gradient, consequently suitable for high-efficiency and large-angle wavefront bending. This light manipulation capability is exemplified with numerical simulation in PW-SW (freely propagating wave to surface wave) conversion, where the wavefront is deflected by an angle of 90°. In the gap-mode meta-converters, the average unit size can be only 1/60 of free-space wavelength, an order of magnitude smaller than that of conventional all-dielectric metasurfaces. Their conversion efficiency can reach 68%, the highest value reported for any all-dielectric gradient metasurface THz converter
Kinematic Model for Coseismic Mud Diapirism with the 2016 Mw 6.4 MeiNong Earthquake in Taiwan
No full textThis is a package prepared for a journal paper submission.
Copyright 2020, Geng-Pei Lin ([email protected])
Title:
Kinematic Model for Coseismic Mud Diapirism with the 2016 Mw 6.4 MeiNong Earthquake in Taiwan
Authors:
Geng-Pei Lin, Wu-Lung Chang1 and Chi-Yu Chiu
Corresponding author: Geng-Pei Lin ([email protected])
Files:
Currently this package contains a .inp file and two .mat files for GBIS (Bagnardi & Hooper, 2018). Which is used in our work
Laryngeal Mask Airway for Cesarean Delivery: A 5-Year Retrospective Cohort Study
No full textBackground: The laryngeal mask airway (LMA) is the most commonly used rescue airway in obstetric anesthesia. The aim of this retrospective cohort study was to evaluate the application of the LMA in parturients undergoing cesarean delivery (CD) for 5 years in our hospital. As a secondary objective, we investigated the incidence of airway-related complication in obstetric general anesthesia (GA).
Methods: We collected electronic data for all obstetric patients who received GA for CD between January 2010 and December 2014 in Peking University First Hospital. Based on the different types of airway device, patients were divided into endotracheal intubation (ET) group and LMA group. The incidences of regurgitation and aspiration, as well as maternal and neonatal postoperative outcomes were compared between groups.
Results: During the 5-year study, GA was performed in 192 cases, which accounted for 2.0% of all CDs. The main indications for GA were contraindication to neuraxial anesthesia or a failed block. Among these, ET tube was used in 124 cases (68.9%) and LMA in 56 cases (31.1%). The percentage of critical patients above the American Society of Anesthesiologists' Grade II was 24/124 in ET group and 4/56 in LMA group (P = 0.036). The emergent delivery rate was 63.7% for ET group and 37.5% for LMA group (P = 0.001). None of the patients had regurgitation or aspiration. There were no significant differences in terms of neonatal Apgar scores, maternal and neonatal postoperative outcomes between the two groups.
Conclusions: Our results suggested that GA was mainly used for contraindication to neuraxial anesthesia or a failed block, and emergent CDs accounted for most cases. The second-generation LMA could be used for obstetric anesthesia, but correct position to achieve a good seal is the key to prevent reflux and aspiration. Whether they could replace the tracheal tube in routine practice needs further large prospective studies
Two new species and a new record of the Encarsia longifasciata-group (Hymenoptera, Aphelinidae) from Malaysia and China
Get PDFThe genus Encarsia Förster, 1878, which is the largest genus of the family Aphelinidae, contains 453 valid species worldwide. Most species of Encarsia with known biology are primary endoparasitoids of Aleyrodidae and Diaspididae.
Species of the Encarsia longifasciata-group from Malaysia and China are reviewed. This is the first record of this group from Malaysia. Two new species, E. borneensis Geng & Li sp. n. and E. pauroseta Geng & Li sp. n., are described and illustrated. Encarsia longifasciata is newly recorded from Malaysia (Borneo). An updated key to the longifasciata-group species (females) worldwide is provided.Copyright © Geng H et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article.NHM Repositor
Ship Scheduling in Inland Waterway Networks Based on Cellular Automata Graph
No full textThis paper presents models and algorithms for vessel scheduling based on a graph model of inland waterway networks. In particular, it models the waterway networks by a directed graph, G = (V, E, W), where the node set V represent the harbors and the cross points of the waterways; the arc set E represent the river segments between the cross points and the weight set W represent the shipping capacity of each arc, in terms of how many ships can travel through the given waterway segment in a fixed time interval. The graph model is a simplified model of cellular automata. The difference is that the shipping capacity is modeled not only as a function of the specific conditions of the waterway segment, but also as a function of the volumes and real-time velocities of vessels. So that the capacity model is parameterized. Then, based on the simplified cellular automata model, a scheduling algorithm for minimizing the transportation time of a set of vessels with given routes are proposed, which is evaluated by simulations.National Key Technology Support Program [2014BAK12B06, 2015BAG20B02]CPCI-S(ISTP)450-45
TINJAUAN KRIMINOLOGIS TERHADAP KEJAHATAN KEKERASAN OLEH ANGGOTA GENG MOTOR YANG MENGAKIBATKAN KEMATIAN (Studi Kasus di Kota Makassar Tahun 2012-2014)
Get PDF2016WAHYUDI SUDIRMAN (B111 11 426), Tinjauan Kriminologis Terhadap\ud
Kejahatan Kekerasan Oleh Anggota Geng Motor Yang Menyebabkan\ud
Kematian. (Studi Kasus Di Kota Makassar Tahun 2012-2014) di bawah\ud
bimbingan H.M. Said Karim sebagai Pembimbing I dan Amir Ilyas sebagai\ud
Pembimbing II.\ud
Penelitian ini bertujuan untuk mengetahui faktor-faktor apa saja\ud
yang menyebabkan terjadinya kejahatan kekerasan oleh anggota geng\ud
motor dan upaya penanggulan terhadap kejahatan kekerasan oleh\ud
anggota geng motor yang menyebabkan kematian.\ud
Penelitian ini dilaksanakan di Kota Makassar yaitu pada\ud
Polrestabes Makassar, Penulis melakukan wawancara dengan salah satu\ud
penyidik terkait dengan kasus yang dibahas dalam penulisan ini, serta\ud
berupa data lainnya yang diperoleh melalui kepustakaan yang relevan\ud
yaitu literatur, dokumen-dokumen serta peraturan perundang-undangan\ud
yang berkaitan dengan masalah tersebut. Berdasarkan terhadap fakta dan\ud
data tersebut, maka Penulis berkesimpulan bahwa terjadinya tindakan\ud
tersebut diakibatkan karena beberapa faktor yaitu, dendam, asmara,\ud
ekonomi, pengaruh obat-obatan dan lingkungan. \ud
Berdasarkan hasil penelitian Penulis, ada beberapa faktor yang\ud
menyebabkan sehingga terjadinya kekerasan oleh anggota geng motor\ud
yaitu, faktor dendam, faktor ekonomi, faktor asmara, faktor pengaruh\ud
Obat-obatan serta minuman keras dan faktor lingkungan. Sedangkan\ud
upaya penanggulangan untuk kejahatan kekerasan oleh Anggota Geng\ud
Motor dengan melakukan upaya preventif yaitu dengan melakukan\ud
penyuluhan hukum serta melakukan patroli rutin oleh pihak kepolisian dan\ud
upaya represif yakni penjatuhan pidana terhadap pelaku kekerasan.\ud
\ud
WAHYUDI SUDIRMAN (B111 11 426), the Review criminological\ud
Crimes Against Violence By Motorcycle Gang Member Who Causes\ud
of Death. (Case Study In Makassar Year 2012 to 2014) under the\ud
guidance H.M. Said Karim as a Supervisor I and Amir Ilyas as Supervisor\ud
II.\ud
\ud
This study aims to determine what factors are causing the occurrence of\ud
violent crime by motorcycle gang members and penanggulan efforts\ud
against violent crime by motorcycle gang members that resulted in death.\ud
\ud
This research was conducted in the city of Makassar are on Polrestabes\ud
Makassar, author conducted an interview with one of the investigators\ud
associated with the case discussed in this paper, as well as such other\ud
data obtained through literature relevant, namely literature, documents\ud
and legislation related with the issue. Based on the facts and data, the\ud
author concludes that the occurrence of such acts caused by several\ud
factors, namely, revenge, romance, economy, influence of drugs and the\ud
environment.\ud
\ud
Based on the results of the study author, there are several factors that led\ud
to the violence by members of a motorcycle gang that is, revenge factors,\ud
economic factors, factors romance, factors influence drugs and booze and\ud
environmental factors. While efforts to address the problem of violent\ud
crime by Motorcycle Gang Members to perform preventive efforts is to\ud
conduct legal education and conduct routine patrols by the police and the\ud
repressive efforts of sentences against perpetrators of violence
Erratum to: Clopidogrel as a donor probe and thioenol derivatives as flexible promoieties for enabling H2S biomedicine (Nature Communications, (2018), 9, 1, (3952), 10.1038/s41467-018-06373-0)
No full text© 2018, The Author(s). The original version of this Article contained an error in the spelling of the author Bin Geng, which was incorrectly given as Bing Geng. This has been corrected in both the PDF and HTML versions of the Article
Synthesis and comprehensive studies of nanogels for enhanced oil recovery
Get PDF“Nanomaterials have been developed and applied for enhanced oil recovery (EOR) in oil industry. Among the developed nanomaterials, nano-sized crosslinked polymeric gel particles (nanogels) have shown the potential in improving both the macro- and micro-displacing efficiency. This dissertation focuses on the synthesis and the potential EOR mechanisms of nanogels. Nanogels with positive, negative, and neutral charges were synthesized through suspension polymerization. The morphology, size distribution, and zeta potential of nanogels were elucidated by corresponding technologies, such as scanning electron microscopy and dynamic light scattering. The ability of nanogels in oil-water interfacial tension (IFT) reduction and oil-in-water (o/w) emulsion stabilization was studied at various nanogel concentrations, temperatures, and salinities. Moreover, nanogels showed an electro-interaction controlled adsorption on the rock surface, which could modify the wettability of rock surface and reduce the permeability of porous medium. The core flooding results demonstrate that nanogels with proper charges can easily transport through the porous medium and reduce the water permeability by forming multilayer adsorption on the rock surface. The residual oil was produced in o/w emulsion state during the nanogel flooding and in isolated oil drops during the post water flooding, which indicated the abilities of nanogels in increase the displacing efficiency and sweeping efficiency, respectively”--Abstract, page iv
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