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Reflectarray Antennas
<p><b> A comprehensive, practical review of reflectarray theory, design, and state-of-the-art implementations </b> <p> This book provides engineers with a comprehensive review of the state-of-the-art in reflectarray antenna research and development. The authors describe, in detail, design procedures for a wide range of applications, including broadband, multi-band, multi-beam, contour-beam, beam-scanning, and conformal reflectarray antennas. They provide sufficient coverage of basic reflectarray theory to fully understand reflectarray antenna design and analysis such that the readers can pursue reflectarray research on their own. Throughout the book numerous illustrative design examples including numerical and experimental results are provided. <p> The reflectarray antenna is a hybrid design combining many of the best features of reflector antennas and printed arrays, in a low-profile, low-mass, highly cost-effective design. Although the concept of reflectarray antennas was first introduced in the early 1960's, it did not receive serious attention until the advent of printed circuit board technology in the 1990's made it practicable. Since then continuous research on reflectarray antennas has yielded several groundbreaking applications, including multi-beam antennas for point-to-point communication, beam-scanning antennas for radar applications, and spatial power combining reflectarray systems, among others. <p> Featuring in-depth theoretical analysis along with practical design examples, <i>Reflectarray Antennas</i> is an excellent text/reference for engineering graduate students, researchers, and engineers in the field of antennas. It belongs on the bookshelves of university libraries, research institutes, and industrial labs and research facilities. <p> Specifically, the book: <ul> <li>Provides engineers and researchers in electromagnetics, microwaves, and antennas with a systematic overview of reflectarray antenna design and analysis techniques</li> <li>Includes several design examples of reflectarray antennas along with numerical and experimental results</li> <li>Offers detailed design procedures for a wide range of applications, including broadband, multi-band operation, multi-beam scanning, contour-beams, beam-scanning systems, conformal reflectarray antennas, transmitarrays, terahertz reflectarrays, and more</li> <li>Features detailed real-world implementation examples for each design covered</li> </ul> <br>
eBook
Learning path construction in e-learning : what to learn, how to learn, and how to improve
This book focuses on developing methods for constructing learning paths in terms of \"learning resources\" (learning contents), \"learning approaches\" (learning method), and \"learning quality\" (learning performance) to support learning. This book defines different teaching approaches for learning activities and organizes them into a learning path which indicates the learning sequence. This book introduces how to automatically generate well-structured learning resources for different students. Also, this book introduces a method about how to generate adaptive learning approach to learn learning resources for different students. Finally, this book introduces a method to monitor and control learning quality. The adaptive learning path expresses well-structured learning contents, using which approach to access those learning contents, and in which sequence to carry out the learning process. The learning path comes with a monitoring tool to control the learning progress, which helps to make students having a balanced development on different knowledge and abilities.
Book
An isolable catenane consisting of two Möbius conjugated nanohoops
Besides its mathematical importance, the Möbius topology (twisted, single-sided strip) is intriguing at the molecular level, as it features structural elegance and distinct properties; however, it carries synthetic challenges. Although some Möbius-type molecules have been isolated by synthetic chemists accompanied by extensive computational studies, the design, preparation, and characterization of stable Möbius-conjugated molecules remain a nontrivial task to date, let alone that of molecular Möbius strips assembling into more complex topologies. Here we report the efficient synthesis, crystal structure, and theoretical study of a catenane consisting of two fully conjugated nanohoops exhibiting Möbius topology in the solid state. This work highlights that oligoparaphenylene-derived nanohoops, a family of highly warped and synthetically challenging conjugated macrocycles, can not only serve as building blocks for interlocked supermolecular structures, but also represent a new class of compounds with isolable Möbius conformations stabilized by non-covalent interactions.
Molecules exhibiting Möbius topology are fascinating but challenging synthetic targets. Here, the authors report the elegant synthesis and crystal structure of a catenane formed from two fully conjugated, interlocked Möbius nanohoops, and use theoretical calculations to understand its conformational stability and aromaticity.
Journal Article
Imaging soliton dynamics in optical microcavities
Solitons are self-sustained wavepackets that occur in many physical systems. Their recent demonstration in optical microresonators has provided a new platform for the study of nonlinear optical physics with practical implications for miniaturization of time standards, spectroscopy tools, and frequency metrology systems. However, despite its importance to the understanding of soliton physics, as well as development of new applications, imaging the rich dynamical behavior of solitons in microcavities has not been possible. These phenomena require a difficult combination of high-temporal-resolution and long-record-length in order to capture the evolving trajectories of closely spaced microcavity solitons. Here, an imaging method is demonstrated that visualizes soliton motion with sub-picosecond resolution over arbitrary time spans. A wide range of complex soliton transient behavior are characterized in the temporal or spectral domain, including soliton formation, collisions, spectral breathing, and soliton decay. This method can serve as a visualization tool for developing new soliton applications and understanding complex soliton physics in microcavities.
In order to study the dynamics of solitons in microresonators, which underlie nonlinear phenomena like Kerr comb generation, both high temporal resolution and long record times are needed. Here, the authors develop a coherent sampling method to directly image the temporal behavior of solitons.
Journal Article
Microresonator soliton dual-comb spectroscopy
Measurement of optical and vibrational spectra with high resolution provides a way to identify chemical species in cluttered environments and is of general importance in many fields. Dual-comb spectroscopy has emerged as a powerful approach for acquiring nearly instantaneous Raman and optical spectra with unprecedented resolution. Spectra are generated directly in the electrical domain, without the need for bulky mechanical spectrometers. We demonstrate a miniature soliton-based dual-comb system that can potentially transfer the approach to a chip platform. These devices achieve high-coherence pulsed mode locking. They also feature broad, reproducible spectral envelopes, an essential feature for dual-comb spectroscopy. Our work shows the potential for integrated spectroscopy with high signal-to-noise ratios and fast acquisition rates.
Journal Article
Hertz-linewidth semiconductor lasers using CMOS-ready ultra-high-Q microresonators
Driven by narrow-linewidth bench-top lasers, coherent optical systems spanning optical communications, metrology and sensing provide unrivalled performance. To transfer these capabilities from the laboratory to the real world, a key missing ingredient is a mass-produced integrated laser with superior coherence. Here, we bridge conventional semiconductor lasers and coherent optical systems using CMOS-foundry-fabricated microresonators with a high Q factor of over 260 million and finesse over 42,000. A five-orders-of-magnitude noise reduction in the pump laser is demonstrated, enabling a frequency noise of 0.2 Hz2 Hz−1 to be achieved in an electrically pumped integrated laser, with a corresponding short-term linewidth of 1.2 Hz. Moreover, the same configuration is shown to relieve the dispersion requirements for microcomb generation that have handicapped certain nonlinear platforms. The simultaneous realization of this high Q factor, highly coherent lasers and frequency combs using foundry-based technologies paves the way for volume manufacturing of a wide range of coherent optical systems.Using CMOS-ready ultra-high-Q microresonators, a highly coherent electrically pumped integrated laser with frequency noise of 0.2 Hz2 Hz−1, corresponding to a short-term linewidth of 1.2 Hz, is demonstrated. The device configuration is also found to relieve the dispersion requirements for microcomb generation that have limited certain nonlinear platforms.
Journal Article
Earth rotation measured by a chip-scale ring laser gyroscope
Optical gyroscopes are among the most accurate rotation measuring devices and are widely used for navigation and accurate pointing. Since the advent of photonic integrated components for communications, and with their increasing complexity, there has been interest in the possibility of chip-scale optical gyroscopes1. Besides the potential benefits of integration, such solid-state systems would be robust and resistant to shock. Here, we report a gyroscope using Brillouin ring lasers on a silicon chip. Its stability and sensitivity enable measurement of Earth’s rotation, representing a major milestone for this new class of gyroscope.A Sagnac gyroscope based on Brillouin ring lasers on a silicon chip is presented. The stability and sensitivity of this on-chip planar gyroscope allow measurement of the Earth’s rotation, with an amplitude sensitivity as small as 5 deg h−1 for a sinusoidal rotation, an angle random walk of 0.068 deg h−1/2 and bias instability of 3.6 deg h−1.
Journal Article
MTR4 drives liver tumorigenesis by promoting cancer metabolic switch through alternative splicing
The metabolic switch from oxidative phosphorylation to glycolysis is required for tumorigenesis in order to provide cancer cells with energy and substrates of biosynthesis. Therefore, it is important to elucidate mechanisms controlling the cancer metabolic switch. MTR4 is a RNA helicase associated with a nuclear exosome that plays key roles in RNA processing and surveillance. We demonstrate that MTR4 is frequently overexpressed in hepatocellular carcinoma (HCC) and is an independent diagnostic marker predicting the poor prognosis of HCC patients. MTR4 drives cancer metabolism by ensuring correct alternative splicing of pre-mRNAs of critical glycolytic genes such as
GLUT1
and
PKM2
. c-Myc binds to the promoter of the MTR4 gene and is important for MTR4 expression in HCC cells, indicating that MTR4 is a mediator of the functions of c-Myc in cancer metabolism. These findings reveal important roles of MTR4 in the cancer metabolic switch and present MTR4 as a promising therapeutic target for treating HCC.
Aberrant alternative splicing has been shown to contribute to the tumorigenic processes. Here, the authors show that MTR4 is overexpressed in hepatocellular carcinoma and has a role in tumorigenesis through the modulation of the splicing of glycolytic genes
PKM2
and
GLUT1
.
Journal Article
Counter-propagating solitons in microresonators
Counter-propagating solitons are generated in microresonator systems, producing dual-soliton frequency-comb streams with different repetition rates but high relative coherence useful for spectroscopy and laser ranging systems.
Solitons occur in many physical systems when a nonlinearity compensates wave dispersion. Their recently demonstrated formation in microresonators has opened a new research direction for nonlinear optical physics
1
,
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,
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,
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,
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. Soliton mode locking also endows frequency microcombs with the enhanced stability necessary for miniaturization of spectroscopy and frequency metrology systems
6
. These microresonator solitons orbit around a closed waveguide path and produce a repetitive output pulse stream at a rate set by the roundtrip time. Here, counter-propagating solitons that simultaneously orbit in an opposing sense (clockwise/counter-clockwise) are studied. Despite sharing the same spatial mode family, their roundtrip times can be precisely and independently controlled. Furthermore, a state is possible in which both the relative optical phase and relative repetition rates of the distinct soliton streams are locked. This state allows a single resonator to produce dual-soliton frequency-comb streams with different repetition rates, but with a high relative coherence that is useful in both spectroscopy
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and laser ranging systems
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.
Journal Article