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1
Ehtesham, Mohammad, and Md Junaid. "Advanced compensation scheme for enhancing photovoltaic power quality." Indonesian Journal of Electrical Engineering and Computer Science 27, no. 3 (September 1, 2022): 1223. http://dx.doi.org/10.11591/ijeecs.v27.i3.pp1223-1230.
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With the photovoltaic (PV) system becoming highly popular in distribution network, there is also a growing concern regarding its adverse impacts over the power quality (PQ) of integrated system. This deterioration in PQ hassparked a new interest in the filtering techniques used in the power systemfor mitigating these problems. In contrast to conventional passive filters now active power filters (APFs) are being looked as the predominant solution.This paper presents a state-estimation based effective compensation strategy for enhancing performance of employed APF scheme. A novel control technique for PQ enhancement is proposed where Kalman filtering approach has been applied for generating the reference signals. Also, an adaptive hysteresis band technique has been applied here in the switching strategy. Thus an enhanced filter performance is achieved with reduced complexity and better elimination of distortions. Simulated results obtained in MATLAB/Simulink platform have been analyzed completely, where the superiority of filtering algorithm has been also demonstrated through leasttotal harmonic distortion (THD) achieved in source current among all the existing Kalman filters.
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Sun, Shu-Peng, Yong-Zhi Cheng, Hui Luo, Fu Chen, and Xiang-Cheng Li. "Compact broadband bandpass filter with wide stopband based on halberd-shaped spoof surface plasmon polariton." Acta Physica Sinica 72, no. 6 (2023): 064101. http://dx.doi.org/10.7498/aps.72.20222291.
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In this paper, a compact broadband bandpass filter with wide out-of-band rejection characteristics based on halberd-shaped spoof surface plasmon polariton (SSPP) is proposed. The filtering structure is achieved by etching a periodic halberd-shaped groove at the bottom of the substrate and a microstrip-to-slot line transition with a crescent-shaped patch at the top. Compared with the traditional dumbbell-shaped SSPP, the halberd-shaped SSPP has good slow-wave property, and the designed bandpass filter based on halberd-shaped SSPP can achieve a more compact size. The upper cutoff frequency and lower cutoff frequency of the passband can be adjusted by regulating the SSPP structure and the transition structure from microstrip-to-slot line, respectively. The simulation results show that the center frequency of broadband bandpass filter is 2.85 GHz, with the relative bandwidth of 130%, and the return loss in the passband is better than –10 dB, and the extreme strong out-of-band rejection of –40 dB from 5.6 GHz to 20 GHz. The size of the broadband bandpass filter is compact, only 1.08<i>λ</i><sub>g</sub>×0.39<i>λ</i><sub>g</sub>, where <i>λ</i><sub>g</sub> is the wavelength at the center frequency. In order to verify the effectiveness of the wideband bandpass filter, the traditional printed circuit board technology is used to fabricate the wideband bandpass filter. The measurement results are in good agreement with the simulation results, verifying the feasibility of the design. The proposed broadband bandpass filter shows promising prospects for developing SSPP functional devices and circuits at microwave frequencies.
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Wang Wu-Song, Zhang Li-Wei, Ran Jia, and Zhang Ye-Wen. "Experimental studies of the surface plasmon polaritons waveguide filter in microwave band." Acta Physica Sinica 62, no. 18 (2013): 184203. http://dx.doi.org/10.7498/aps.62.184203.
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Teng Chen-Chen, Zhou Wen, Zhuang Yu-Yang, and Chen He-Ming. "Low loss and narrow-band THz filter based on magnetic photonic crystals." Acta Physica Sinica 65, no. 2 (2016): 024210. http://dx.doi.org/10.7498/aps.65.024210.
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Tian, Ying, Wu-Hao Cai, Zi-Xiang Yang, Feng Chen, Rui-Bo Jin, and Qiang Zhou. "Hong-Ou-Mandel interference of entangled photons generated under pump-tight-focusing condition." Acta Physica Sinica 71, no. 5 (2022): 054201. http://dx.doi.org/10.7498/aps.71.20211783.
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Hong-Ou-Mandel (HOM) interference is a non-classical effect of photons and plays an important role in quantum optics. The <i>β</i>-barium borate (BBO) has a high nonlinear efficiency, and is commonly used to generate biphoton states, thereby exhibiting HOM interference. However, in previous experiments, researchers often used band-pass filters, so the resulting spectrum was directly determined by the band-pass filter. As a result, the original spectrum of the BBO crystal, especially the spectrum under tight focusing, was lack of systematic research. In this paper, the biphoton spectral distribution and HOM interference generated by the BBO crystal under the condition of tight focusing are systematically studied for the first time. Theoretical calculations show that using a lens with 50-mm focusing length, the spectral width of the down-converted photons is increased by 7.9 times that of the non-focused case; the width of the HOM interference fringe is reduced to 1/8, and the visibility of the interference fringe increases from 53.0% to 98.7%. We experimentally prepare the energy-time entanglement state by using type-II BBO crystal and perform HOM interference, thereby obtaining the interference visibility of <inline-formula><tex-math id="M2">\begin{document}$(86.6 \pm 1.0)$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20211783_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20211783_M2.png"/></alternatives></inline-formula>%. The increasing of the HOM visibility is due to the improvement of biphoton's spectral symmetry. In addition, the proposed technique by which different spectral distributions are obtained at different incident angles is expected to be applied to the preparation of high-dimensional qudits in the future.
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Cui Guang-Bin, Miao Jun-Gang, and Zhang Yong-Fang. "Design of waveguide array frequency selective surface filter in sub-millimeter wave band." Acta Physica Sinica 61, no. 22 (2012): 224102. http://dx.doi.org/10.7498/aps.61.224102.
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Zhao, Shu-Yu, Bin-Bin Xu, Zhen-Yu Zhao, and Xue-Qin Lü. "Influence of top mirror on performance of GaN-based resonant cavity light-emitting diode." Acta Physica Sinica 71, no. 4 (2022): 047801. http://dx.doi.org/10.7498/aps.71.20211720.
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In this paper, two kinds of distributed Bragg reflectors (DBRs) with high-reflective-film structure and filter structure are designed and evaporated on the top of GaN-based resonant cavity light emitting diode (RCLED), respectively. Firstly, the reflectivity spectra of the two kinds of DBRs are simulated. Then, the differences in performance including optical longitudinal modes, spectral linewidth, and output light intensity between the two kinds of RCLED devices with different top mirrors, are compared and analyzed. Finally, the influence of the top mirror reflection characteristics on the output spectrum of the RCLED is studied in detail. The results show that the top mirror is an important part of RCLED, and its reflection characteristics determine the optical performance of the device. For the conventional DBR with high-reflective-film structure, its reflectivity spectrum has a wide high-reflection band. Accordingly, the spectral linewidth of the RCLED can be effectively narrowed by using the conventional DBR as the top mirror. However, the spectrum still consists of multi-longitudinal modes. For the DBR with filter structure, its reflectivity spectrum has a narrow high-transmittance band at the central wavelength. Depending on the modulation effect of the high-transmittance band to the output light, single longitudinal mode light emission is realized for the RCLED with the specially designed DBR as the top mirror, which shows a broad application prospect in optical communication and optical fiber sensing. Moreover, the spectral characteristics of the RCLED can be further optimized to meet its application requirements in much more fields, by designing the top mirror structure and changing its reflectivity spectrum characteristics.
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Ning, Ren-Xia, Wang Huang, Fei Wang, Jian Sun, and Zheng Jiao. "Electromagnetic induction-like transparency in dual-band with dual-bright mode coupling." Acta Physica Sinica 71, no. 1 (2022): 014201. http://dx.doi.org/10.7498/aps.71.20211312.
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In this paper, a metamaterial structure with a double-layer split square ring and a double C-shaped structure is designed, which has dual-band electromagnetically induced transparency effects in the terahertz band. This structure has transmission peaks at 1.438 THz and 1.699 THz. Through the analysis of the surface current distribution, the reasons for the dual-band electromagnetically induced transparency are discussed. The effect of the designed metamaterial on the transmission window is studied when the opening size of the open square ring and the distance of the double C-shaped structure and the incident angle are changed. At an incident angle, the transmission spectrum of the designed material changes greatly, implying that it is highly sensitive to angle. The research results show that the structure has potential applications in sensors and angle filters.
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Zhou, Chang, Rui Gong, and Xiao-Bo Feng. "Theoretical studies on optical absorption in twisted bilayer graphene under vertical electric field." Acta Physica Sinica 71, no. 5 (2022): 054203. http://dx.doi.org/10.7498/aps.71.20211406.
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The interlayer twist angle is an important parameter that can tune the physical properties of graphene in a wide wavelength range. In this paper, we employ an effective continuum model to calculate the band structure of twisted bilayer graphene with different twist angles in the presence and absence of vertical electric field. Based on the transition rate of the electron-photon interaction, we calculate and simulate the optical absorption spectra caused by the interband and intraband transitions around the van Hove singularities. The calculation results show that the optical absorption caused by the interband transitions occurs in the wavelength range from visible light to near-infrared while it appears in far-infrared for intraband transitions. The optical absorption coefficient of the intra-band transitions is almost two orders of magnitude larger than that of inter-band transitions. In the absence of an external electric field, as the twist angle increases, the absorption peak of the inter band transition moves from the infrared light band to the visible light band, but the resonant peak position of its intra-band transition does not change. At the same time, the absorption coefficient values corresponding to the above two transitions will increase. When an electric field is applied perpendicular to the twisted bilayer graphene, the symmetry of the initial band structure of bilayer graphene is destroyed, which results in the splitting of the absorption peaks associated the with interband transitions, and the distance between the two splitting peaks increases with the electric field intensity increasing; while the position and amplitude of the absorption peak associated with the intraband transition are completely unaffected by the applied electric field. The theoretical calculation results in this paper can provide the theoretical guidance for further applying twisted graphene to optoelectronic devices such as tunable dual-band filters.
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Huang Xi, Zhang Xin-Liang, Dong Jian-Ji, Zhang Yu, and Huang De-Xiu. "Theoretical study on non-inverted wavelength conversion based on semiconductor optical amplifier and optical band-pass filter." Acta Physica Sinica 59, no. 2 (2010): 1021. http://dx.doi.org/10.7498/aps.59.1021.
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Liu Hai-Wen, Sun Xiao-Wei, Li Zheng-Fan, Qian Rong, and Zhou Min. "A low-pass filter of wide stopband with a novel dual-layer fractal photonic band gap structure." Acta Physica Sinica 52, no. 12 (2003): 3082. http://dx.doi.org/10.7498/aps.52.3082.
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Li Guo-Lin, Shu Ting, Yuan Cheng-Wei, Zhang Jun, Jin Zhen-Xing, Yang Jian-Hua, Zhong Hui-Huang, Yang Jie, and Wu Da-Peng. "Preliminary investigation on the design and experiment of a spatial filter for dual band high power microwave." Acta Physica Sinica 59, no. 12 (2010): 8591. http://dx.doi.org/10.7498/aps.59.8591.
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Wang, Bo-Yun, Zi-Hao Zhu, You-Kang Gao, Qing-Dong Zeng, Yang Liu, Jun Du, Tao Wang, and Hua-Qing Yu. "Plasmon induced transparency effect based on graphene nanoribbon waveguide side-coupled with rectangle cavities system." Acta Physica Sinica 71, no. 2 (2022): 024201. http://dx.doi.org/10.7498/aps.71.20211397.
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In order to reduce the size of the device and realize the ultrafast response time and dynamic tunableness, the single-band and dual-band plasmon induced transparency (PIT) effect are investigated based on graphene nanoribbon waveguide side-coupled rectangle cavity. The slow light properties of the model are analyzed numerically and theoretically by coupled mode theory and finite difference time domain method. With controlling the chemical potential of the graphene rectangle cavity, the tunability of the resonant wavelength and the transmission peak can be achieved simultaneously in single-band and dual-band PIT model. As the chemical potential of graphene increases, the resonant wavelength of each transmission window of PIT effect decreases gradually and presents the blue shift. In addition, through dynamically tuning the resonant wavelength of the graphene rectangle cavity, when the chemical potential of the graphene rectangle cavity increases from 0.41 to 0.44 eV, the group index of single PIT system is controlled to be between 79.2 and 28.3, and the tunable bandwidth is 477 nm. Moreover, the group index of dual PIT system is controlled to be between 143.2 and 108.6 when the chemical potentials of graphene rectangle cavities 1, 2, and 3 are 0.39–0.42 eV, 0.40–0.43 eV, and 0.41–0.44 eV, respectively. The size of the entire PIT structure is <0.5 μm<sup>2</sup>. The research results here in this work are of reference significance in designing and fabricating the optical sensors, optical filters, slow light and light storage devices with ultrafast, ultracompact and dynamic tunableness.
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Gu Pei-Fu, Chen Hai-Xing, Qin Xiao-Yun, and Liu Xu. "Design of polarization band-pass filters based on the theory of thin-film photonic crystal superlattice." Acta Physica Sinica 54, no. 2 (2005): 773. http://dx.doi.org/10.7498/aps.54.773.
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Pérez-Delgado, Orlando, Abraham Omar Espinoza-Culupú, and Elmer López-López. "Antimicrobial Activity of Apis mellifera Bee Venom Collected in Northern Peru." Antibiotics 12, no. 4 (April 19, 2023): 779. http://dx.doi.org/10.3390/antibiotics12040779.
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Due to the emergence of microorganisms resistant to antibiotics and the failure of antibiotic therapies, there is an urgent need to search for new therapeutic options, as well as new molecules with antimicrobial potential. The objective of the present study was to evaluate the in vitro antibacterial activity of Apis mellifera venom collected in the beekeeping areas of the city of Lambayeque in northern Peru against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Bee venom extraction was performed by electrical impulses and separated using the Amicon ultra centrifugal filter. Subsequently, the fractions were quantified by spectrometric 280 nm and evaluated under denaturant conditions in SDS-PAGE. The fractions were pitted against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, and Pseudomonas aeruginosa ATCC 27853. A purified fraction (PF) of the venom of A. mellifera and three low molecular weight bands of 7 KDa, 6 KDa, and 5 KDa were identified that showed activity against E. coli with a MIC of 6.88 µg/mL, while for P. aeruginosa and S. aureus, it did not present a MIC. No hemolytic activity at a concentration lower than 15.6 µg/mL and no antioxidant activity. The venom of A. mellifera contains a potential presence of peptides and a predilection of antibacterial activity against E. coli.
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Chu, Chun-Guang, An-Qi Wang, and Zhi-Min Liao. "Josephson effect in topological semimetal-superconductor heterojunctions." Acta Physica Sinica 72, no. 8 (2023): 087401. http://dx.doi.org/10.7498/aps.72.20230397.
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Topological semimetals are exotic phases of quantum matter with gapless electronic excitation protected by symmetry. Benefitting from its unique relativistic band dispersion, topological semimetals host abundant quantum states and quantum effects, esuch as Fermi-arc surface states and chiral anomaly. In recent years, due to the potential application in topological quantum computing, the hybrid system of topology and superconductivity has aroused wide interest in the community. Recent experimental progress of topological semimetal-superconductor heterojunctions is reviewed in two aspects: 1) Josephson current as a mode filter of different topological quantum states; 2) detection and manipulation of topological superconductivity and Majorana zero modes. For the former, utilizing Josephson interference, ballistic transport of Fermi-arc surface states is revealed, higher-order topological phases are discovered, and finite-momentum Cooper pairing and superconducting diode effect are realized. For the latter, by detecting a.c. Josephson effect in Dirac semimetal, the 4π-periodic supercurrent is discovered. By all-electric gate control, the topological transition of superconductivity is obtained. Outlooks of future research on topological semimetal-superconductor heterojunctions and their application in Majorana braiding and topological quantum computing are discussed.
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Yang, Jia-Hao, Ao-Yan Zhang, Chang-Ming Xia, Zhi-Peng Deng, Jian-Tao Liu, Zhuo-Yuan Huang, Jia-Jian Kang, et al. "Preparation and mode conversion application of narrowband hollow-core anti-resonant fiber." Acta Physica Sinica 71, no. 13 (2022): 134207. http://dx.doi.org/10.7498/aps.70.20212194.
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Owing to the unique characteristics of the hollow core fiber(HCF), more and more researchers pay attention to its application. Because the mode field is mainly limited to the core region of the fiber, which results in low non-linearity, ultra-low group velocity dispersion, low temperature sensitivity, and high material damage threshold. Based on the above, the HCF possesses some attractive nonlinear applications such as in transmission of high-power laser beams, sensing, ultra-wide band low-loss transmission, pulse compression and super-continuum generation. Besides, the HCFs can be further divided into the transmitting band-gap photonic crystal fiber(PBG-PCF) and the hollow-core anti-resonant fiber(HC-ARF). Compared with the PBG-PCF, the latter has wide light guiding characteristics caused by leaking modes. According to the research in the recent year, the HC-ARF has gradually approached to the performance of the PBG-PCF in its transmission loss, showing that it has potential applications in communications, sensing, aerospace, high-power laser transmission and other fields in the future. In addition, the HC-ARF with the special light-guiding properties has also become the important photonic device in the fields of fiber filters, mode conversion, etc. In this paper, a hollow-core anti-resonance fiber is studied and its light transmission performance in the spectral range of 500–1500 nm is verified. The optical loss measured at 980 nm wavelength is about 0.32 dB/m. It is found that a 980 nm multi-mode laser beam can be converted into a single-mode one after transmitting through the hollow core fiber we designed.
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Ruiz-Dern, L., C. Babusiaux, F. Arenou, C. Turon, and R. Lallement. "Empirical photometric calibration of the Gaia red clump: Colours, effective temperature, and absolute magnitude." Astronomy & Astrophysics 609 (January 2018): A116. http://dx.doi.org/10.1051/0004-6361/201731572.
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Context. Gaia Data Release 1 allows the recalibration of standard candles such as the red clump stars. To use those stars, they first need to be accurately characterised. In particular, colours are needed to derive interstellar extinction. As no filter is available for the first Gaia data release and to avoid the atmosphere model mismatch, an empirical calibration is unavoidable. Aims. The purpose of this work is to provide the first complete and robust photometric empirical calibration of the Gaia red clump stars of the solar neighbourhood through colour–colour, effective temperature–colour, and absolute magnitude–colour relations from the Gaia, Johnson, 2MASS, Hipparcos, Tycho-2, APASS-SLOAN, and WISE photometric systems, and the APOGEE DR13 spectroscopic temperatures. Methods. We used a 3D extinction map to select low reddening red giants. To calibrate the colour–colour and the effective temperature–colour relations, we developed a MCMC method that accounts for all variable uncertainties and selects the best model for each photometric relation. We estimated the red clump absolute magnitude through the mode of a kernel-based distribution function. Results. We provide 20 colour versus G−Ks relations and the first Teff versus G−Ks calibration. We obtained the red clump absolute magnitudes for 15 photometric bands with, in particular, MKs = (−1.606 ± 0.009) and MG = (0.495 ± 0.009) + (1.121 ± 0.128)(G−Ks−2.1). We present a dereddened Gaia-TGAS HR diagram and use the calibrations to compare its red clump and its red giant branch bump with Padova isochrones.
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Sterelny, Kim. "Innovation, life history and social networks in human evolution." Philosophical Transactions of the Royal Society B: Biological Sciences 375, no. 1803 (June 2020): 20190497. http://dx.doi.org/10.1098/rstb.2019.0497.
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There is a famous puzzle about the first 3 million years of archaeologically visible human technological history. The pace of change, of innovation and its uptake, is extraordinarily slow. In particular, the famous handaxes of the Acheulian technological tradition first appeared about 1.7 Ma, and persisted with little change until about 800 ka, perhaps even longer. In this paper, I will offer an explanation of that stasis based in the life history and network characteristics that we infer (on phylogenetic grounds) to have characterized earlier human species. The core ideas are that (i) especially in earlier periods of hominin evolution, we are likely to find archaeological traces only of widespread and persisting technologies and practices; (ii) the record is not a record of the rate of innovation, but the rate of innovations establishing in a landscape; (iii) innovations are extremely vulnerable to stochastic loss while confined to the communities in which they are made and established; (iv) the export of innovation from the local group is sharply constrained if there is a general pattern of hostility and suspicion between groups, or even if there is just little contact between adults of adjoining groups. That pattern is typical of great apes and likely, therefore, to have characterized at least early hominin social lives. Innovations are unlikely to spread by adult-to-adult interactions across community boundaries. (v) Chimpanzees and bonobos are characterized by male philopatry and subadult female dispersal; that is, therefore, the most likely early hominin pattern. If so, the only innovations at all likely to expand beyond the point of origin are those acquired by subadult females, and ones that can be expressed by those females, at high enough frequency and salience for them to spread, in the bands that the females join. These are very serious filters on the spread of innovation. This article is part of the theme issue ‘Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals’.
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Xiaoxia Zhou, Ying Chen, and Li Cai. "A ultra-narrow-band optical filter based on zero refractive index metamaterial." Acta Physica Sinica, 2023, 0. http://dx.doi.org/10.7498/aps.72.20230394.
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Due to the photonic band gap effect and defect state effect, Photonic metamaterials have received strong attention in the design of narrow bandpass filters, which are the key devices of optical communication equipment such as wavelength division multiplexing devices. In this paper, based on zero-index metamaterials (ZIM), a compact filter with both high peak transmission coefficient and ultra-narrow bandwidth is proposed. Photonic metamaterial with conical dispersions and Dirac-like point is achieved by optimizing structure and material component parameters of dielectric rods with square lattice in air. It has been demonstrated that a triply degenerate state can be realized at the Dirac-like point, which relate this metamaterial to a zero-index media with effective permittivity and permeability equal to zero simultaneously. Electromagnetic (EM) wave can propagate without any phase delay at this frequency, and strong dispersion occurs in the adjacent frequency cone, leading to dramatic changes in optical properties. We explore introducing ZIM into photonic metamaterial defect filter to compress the bandwidth to realization of ultra-narrow bandpass filter. The ZIM is embedded into the resonant cavity of line defect filter, which is also composed of dielectric rods with square lattice in air. In order to increase the sensitivity of the phase change with frequency, the Dirac-like frequency is adjusted to match the resonant frequency of the filter. We study the transmission spectrum of the structure by the COMSOL Multiphysics simulation software, it has been found that the peak width at half-maximum of the filter decreases as the thickness of ZIM increase, and the peak transmittance is still high as well when bandwidth is greatly compressed. zero phase delay inside the slab can be observed. Through field distribution analysis, the zero-phase delay and strong coupling characteristics of electromagnetic field are observed at peak frequency. As well as the comparison with conventional photonic metamaterials filter is discussed. We believe that this work is helpful in investigating the realization of ultra-narrow bandpass filters.
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Liu Yu-Hang, Lin Tong, Li Shao-Bo, Yu Wen-Qi, Ma Xiang, Liang Xiao-Dong, and Yun Bin-Feng. "Reconfigurable optical filter based on a microring resonator assisted by a tunable Sagnac reflector." Acta Physica Sinica, 2023, 0. http://dx.doi.org/10.7498/aps.72.20222384.
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To meet the demands of various applications in optical filtering and microwave signal processing, integrated silicon photonic filters prefer to be multifunctional, reconfigurable and tunable. We propose an integrated multi-functional optical filter design based on a tunable Sagnac loop reflector and a microring resonator. The through port and drop port of an add-drop microring resonator are connected with the two ports of a tunable reflector. By controlling the thermal phase shifters in different scenarios, the device can be reconfigured into a reflective-type asymmetric Mach-Zehnder interferometer filter, a reflective-type all-pass microring resonator filter and self-interference microring resonator filters. We have established an analytical model based on the transfer matrix. The simulation results show that the device can achieve the following functions:sinusoidal spectral filtering with four different free spectral ranges, Lorentzian spectral filtering toggling between band pass and band stop, and spectral reconfigurations of Fano resonance, electromagnetically induced transparency, and electromagnetically induced absorption. Every spectrum mentioned above can be tuned fast and widely. Reflection provides a new degree of design freedoms, breaks the inherent footprint limit, and achieves a wide range of free spectral ranges. Our proposed tunable Sagnac loop reflector assisted microring resonator provides a new scheme for realizing flexible, tunable and multi-functional reconfigurable integrated photonic filters, and has broad applications in the integrated photonic analog signal processing and microwave photonics.
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Zhang Chao-Qun, Li Rui-Xin, Zhang Wen-Hui, Jiao Nan-Jing, Tian Long, Wang Ya-Jun, and ZhengYao-Hui. "Experimental Research on the Noise Characteristics of the Output Field of the Optical Filter Cavity." Acta Physica Sinica, 2022, 0. http://dx.doi.org/10.7498/aps.71.20221325.
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Precision measurement is an important direction of today's frontier scientific research. Using lasers to achieve high-precision target measurement has become an important way to improve measurement accuracy, which can be applied in various fields. However, for a certain application, the measurement accuracy will directly depend on the noise level of the laser source. Most applications require that the measurement frequency band is concentrated in the audio frequency band. In order to obtain a low-noise laser source with shot noise limited in the applied frequency band, active and/or passive noise reduction are the usual choice, i.e., active feedback control and filter cavity technique, and so on. Therefore, noise analysis and suppression techniques are the main concern of the precision measurement. The optical filter cavity acts as an optical low-pass filter, which can effectively suppress high-frequency noise beyond its linewidth. In this work, we found that the intensity noise of the output field of an optical filter cavity is higher than the noise floor of the laser. The main sources of noise are analyzed through experiments:(1) excess noise introduced by cavity length locking; (2) laser phase and pointing noises coupled to the intensity one by the cavity. To cancel the excess noise as much as possible, we optimize the feedback control loop by measuring the open-loop and closed-loop transfer functions of the MC, combined with the critical proportionality method. All the control loop are homemade, and the PID is designed with a FPGA board for expediently achieving a noise reduction up to 30 dB at the audio frequency. Then the control loop is optimized as the best condition without introducing the excess noise. Compared with the free-running laser, MC filters out the high-frequency noise, meanwhile converts the phase noise and pointing noise of input field into the intensity noise of the output field. Therefore, the power noise spectrum in the audio segment is still higher than that of the input optical field itself. In the future, an active control loop will be applied to suppress the noise power. The experimental results provide the basic means for applied research such as feedback control loop noise analysis, which will promote the development of precision measurement to higher measurement accuracy.
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Zhang Chao-Qun, Li Rui-Xin, Zhang Wen-Hui, Jiao Nan-Jing, Tian Long, Wang Ya-Jun, and ZhengYao-Hui. "Experimental Research on the Noise Characteristics of the Output Field of the Optical Filter Cavity." Acta Physica Sinica, 2022, 0. http://dx.doi.org/10.7498/aps.72.20221325.
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Precision measurement is an important direction of today's frontier scientific research. Using lasers to achieve high-precision target measurement has become an important way to improve measurement accuracy, which can be applied in various fields. However, for a certain application, the measurement accuracy will directly depend on the noise level of the laser source. Most applications require that the measurement frequency band is concentrated in the audio frequency band. In order to obtain a low-noise laser source with shot noise limited in the applied frequency band, active and/or passive noise reduction are the usual choice, i.e., active feedback control and filter cavity technique, and so on. Therefore, noise analysis and suppression techniques are the main concern of the precision measurement. The optical filter cavity acts as an optical low-pass filter, which can effectively suppress high-frequency noise beyond its linewidth. In this work, we found that the intensity noise of the output field of an optical filter cavity is higher than the noise floor of the laser. The main sources of noise are analyzed through experiments:(1) excess noise introduced by cavity length locking; (2) laser phase and pointing noises coupled to the intensity one by the cavity. To cancel the excess noise as much as possible, we optimize the feedback control loop by measuring the open-loop and closed-loop transfer functions of the MC, combined with the critical proportionality method. All the control loop are homemade, and the PID is designed with a FPGA board for expediently achieving a noise reduction up to 30 dB at the audio frequency. Then the control loop is optimized as the best condition without introducing the excess noise. Compared with the free-running laser, MC filters out the high-frequency noise, meanwhile converts the phase noise and pointing noise of input field into the intensity noise of the output field. Therefore, the power noise spectrum in the audio segment is still higher than that of the input optical field itself. In the future, an active control loop will be applied to suppress the noise power. The experimental results provide the basic means for applied research such as feedback control loop noise analysis, which will promote the development of precision measurement to higher measurement accuracy.
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Luo Yu-Xuan, Cheng Yong-Zhi, Chen Fu, Luo Hui, and Li Xiang-Cheng. "Dual-band filter design based on hourglass-shaped spoof surface plasmon polaritons and interdigital capacitor structure." Acta Physica Sinica, 2023, 0. http://dx.doi.org/10.7498/aps.72.20221984.
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In this paper, a dual passband filter with spoof surface plasmon polaritons (SSPPs) and interdigital capacitance structure loaded on a coplanar waveguide (CPW) is proposed. Firstly, the hourglass-shaped SSPP unit-cell structure and the interdigital capacitor structure are introduced on the coplanar waveguide transmission line to obtain high fractional bandwidth and low insertion loss passband characteristics. Then, a dual passband filter is formed by loading the interdigital capacitor loop resonator to excite the trapped waves. The simulation results show that the proposed dual passband filter has excellent upper sideband rejection and dual passband filtering performance. The fractional bandwidths of the two passbands of the design are 46.8% (1.49-2.40 GHz) and 15.1% (2.98-3.63 GHz), respectively, which can achieve more than -40 dB rejection in the range of 4.77-7.48 GHz. The upper and lower cutoff frequencies of the two passbands can be independently regulated by changing the structural parameters of the proposed filter. In order to gain a deeper understanding of the operating principle of the dual passband filter, the corresponding dispersion curves and electric field distribution, LC equivalent circuit analysis are given. Finally, the prototype of the designed filter is fabricated according to the optimized parameter values. The experimental results are in good agreement with the simulation ones, indicating that the proposed dual-passband filter is of great importance in microwave integrated circuit applications.
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"A tunable narrow-band plasma photonic crystal filter based on bound state." Acta Physica Sinica, 2021, 0. http://dx.doi.org/10.7498/aps.70.20210241.
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Dai M Q, Zhang Q Y, Zhao Q L, Wang M R, and Wang X. "Study on the controllable characteristics of interface states in one-dimensional inverted symmetric photonic structures." Acta Physica Sinica, 2022, 0. http://dx.doi.org/10.7498/aps.71.20220383.
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Using the transfer matrix method, the tunable characteristics of the interface states generated by one-dimensional photonic structures with inversion symmetry are calculated and studied, and the samples are prepared by electron beam evaporation technology for experimental verification. According to the different inversion symmetry center of one unit cell, the inverted symmetric layered photonic structures are divided into PCI and PCII two types. The calculation results show that for the combined structure composed of PCI and PCII, there is an interface state at one special frequency where the sum of the imaginary parts of the surface impedance between PCI and PCII is equal to zero, and this frequency of the interface state is independent of the numbers of unit cells. On this basis, if one PCI structure is added to form PCI+PCII+PCI photonic structure, two interface states will be generated in the same band gap, and changing the unit cell numbers of individual PCI and PCII structures, the frequencies of two interface states can be regulated. The experimental results fully show that the regulation of interface state by controlling unit cell numbers is feasible, which provides one more flexible idea for the design of extremely narrow-band filters and multi-channel filters to meet different application requirements.
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Wang Zi-Shuo, Liu Lei, Liu Chen-Bo, Liu Ke, Zhong Zhi, and Shan Ming-Guang. "Fast phase unwrapping using digital differentiation-integration method." Acta Physica Sinica, 2023, 0. http://dx.doi.org/10.7498/aps.72.20230473.
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Digital holography is currently one of the most widely used quantitative phase imaging technology, due to its non-contact, high accuracy and full-filed measurement. However, when the optical path difference induced by the measurement sample is larger than the used wavelength, a phase unwrapping algorithm has to be utilized to unwrap the phase and retrieve the actual phase. And the existing phase unwrapping algorithms suffer from huge computational burden and slow retrieval speed. Although many effects have be done, the retrieval speed is still limited by the phase unwrapping. In order to solve the above-mentioned questions, a digital differentiation-integration based phase unwrapping is proposed in this paper. This algorithm is based on the fact that the actual phase information is contained in the complex-valued function after Fourier transform, band-pass filter and inverse Fourier transform. After Fourier transform, band-pass filter and inverse Fourier transform, a complex-valued function containing the actual phase is retrieved, and two sub complex-valued functions can be extracted with just one-pixel shift digitally. Then, two functions are divided pixel by pixel, and another complex-valued function containing the differentiation of the actual phase is obtained. So the differential phase can be retrieved easily by the phase extraction. At last, integrate the retrieved differential phase along the inverse direction of shifting, and the unwrapped phase can be obtained directly. This algorithm can work effectively when the variation of the measurement phase is in the range of (-π, π]. This algorithm is just based on the Fourier transform and the complex-valued division. Different from the existing unwrapping algorithms, this algorithm is much easier to conduct and has light computation burden. Therefore, this algorithm can realize fast and accurate phase reconstruction directly. Several simulation and experimental results would be demonstrated to verify the effectiveness of this algorithm.
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于博, 庄书磊, 王正心, 王曼诗, 郭兰军, 李鑫煜, 郭文瑞 (Wenrui Guo), 苏文明(Wenming Su), 龚诚, and 刘伟伟. "Double-spiral terahertz tunable metasurface based on nano-printing technology." Acta Physica Sinica, 2022, 0. http://dx.doi.org/10.7498/aps.71.20212408.
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Electromagnetic devices made of artificially constructed metasurfaces can achieve filtering, modulation, sensing, and detection functions in the terahertz frequency band, which is essential for the application of terahertz waves in the fields of communication and imaging. We designed and prepared a flexible and transparent double helix metasurface based on nano-printing technology, and used the metasurface to construct a rotating tunable filter, which can achieve regular tuning of the terahertz wave transmittance by rotating the metasurface. After rotating by 90°, the transmittance at 0.52THz increased from 8% to 67%, and the transmittance at 0.92THz decreased from 68% to 3%, realizing active tuning with modulation depth greater than 88%. Moreover, the proposed Nano-printing metasurfaces have excellent properties of ultra-thinness, flexibility, and visible light transparency, which is conducive to the miniaturization, light-weight and large-area preparation of terahertz tunable devices.
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"Spectral Efficiency Enhancement Through Wavelet Transform Filter Bank for Future Mobile Communications." International Journal of Innovative Technology and Exploring Engineering 8, no. 9S2 (August 31, 2019): 828–29. http://dx.doi.org/10.35940/ijitee.i1170.0789s219.
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In the 5th generation of wireless communications for multiple apps, such as sports, video etc, the large transmission rate of information is the main requirement. To satisfy the high information rates, bandwidth can be increased by using greater frequency bands that is not feasible owing to the restricted frequency spectrum accessibility and the limitation placed on accessible spectrums by Standard. A further way is to effectively use the existing spectrum. OFDM overrides all multiplexing methods in the last century because with Cyclic Prefix (CP) and enhanced Bit Error Rates (BER) the system improves intersymbolic interference (ISI). It offers low sensitivity owing to the intercarrier orthogonality to time synchronization. Bandwidth is lost by CP, in addition to all of these benefits. The lack of orthogonality between pilots that interfere (ICI) is also due to the multipath fading. Discrete Wavelet Transform is used to extract a bandwidth and spectral efficiency improvement and remove CP in turn. Transforming Wavelet (WT) is less sensitive to multipath distortion., so that ICI improves.. We present FBMC's unifying structure, discussion and efficiency assessment in this paper.
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Guo Yue, Sun Yiming, and Song Weidong. "Narrowband near-ultraviolet photodetector fabricated from CuZnS/porous GaN heterojunction." Acta Physica Sinica, 2022, 0. http://dx.doi.org/10.7498/aps.71.20220990.
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Narrowband photodetection systems are widely used in fluorescence detection, artificial vision and other fields. In order to realize the narrow spectral detection of special band, it is traditionally necessary to integrate broadband detectors and optical filters. However, with the development of detection technology, higher requirements have also been placed on the power consumption, size, and cost of the detection system, and the application of traditional narrowband photodetectors with complex structures and high costs is limited. Thus, a filterless, narrow-band near-ultraviolet photodetector based on a porous GaN/CuZnS heterojunction is demonstrated. The porous GaN thin films with low defect density and CuZnS thin films with high hole conductivity were fabricated by photoelectrochemical etching and water bath growth methods, respectively, and the porous GaN/CuZnS heterojunction near-ultraviolet photodetectors were thus fabricated. Benefiting from the porous structure of GaN and the optical filtering effect of CuZnS, the photo-dark current ratio of the device exceeds four orders of magnitudes under -2 V bias and 370 nm light illumination; more importantly, the device has an ultra-narrowband near-ultraviolet photoresponse with a FWHM of <8 nm (peak at 370 nm). In addition, the peak responsivity, external quantum efficiency and specific detectivity reaches at 0.41 A/W, 138.6% and 9.8×10<sup>12</sup> Jones, respectively. These excellent device performances show that the near-ultraviolet photodetectors based on porous GaN/CuZnS heterojunctions have broad application prospects in the field of narrow-spectrum ultraviolet photodetection.
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Yang Jia-Hao, Zhang Ao-Yan, Xia Chang-Ming, Deng Zhi-Peng, Liu Jian-Tao, Huang Zhuo-Yuan, Kang Jia-Jian, et al. "Research on Preparation and Mode Conversion Application of Narrowband Hollow-core Anti-resonant Fiber." Acta Physica Sinica, 2022, 0. http://dx.doi.org/10.7498/aps.71.20212194.
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Due to the unique characteristics of the hollow core fiber(HCF), more and more researchers pay attention to its application. Because the mode field is mainly limited to the core region of the fiber, which results in low non-linearity, ultra-low group velocity dispersion, low temperature sensitivity, and high material damage threshold. Based on above, there are some attractive nonlinear applications of the HCF, such as transmission of high-power laser beams, sensing, ultra-wide band low-loss transmission, pulse compression and super-continuum generation. Besides, the HCF can be further divided into the transmitting band-gap photonic crystal fiber(PBG-PCF) and the hollow-core anti-resonant fiber(HC-ARF). Compared with the PBG-PCF, the latter has wider light guiding characteristics caused by leaking modes. According to the research in the recent year, the HC-ARF has gradually approached the performance of the PBG-PCF in its transmission loss which shows that it has potential applications of communications, sensing, aerospace, high-power laser transmission and other fields in the future. In addition, the HC-ARF with the special light-guiding properties has also become the important photonic devices in the fields of fiber filters, mode conversion, etc. In this paper, a hollow-core anti-resonance fiber is studied and its light transmission performance in the spectral range of 500 ~ 1500 nm is verified. The optical loss measured at 980 nm wavelength is about 0.32 db/m. It is founded that a 980nm multi-mode laser beam can be converted into a singe-mode one after transmitting through the hollow core fiber we designed.
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Zhu Zi-Hao, Gao You-Kang, Zeng Yan, Cheng Zheng, Ma Hong-Hua, and Yi Xu-Nong. "Plasmon induced transparency effect based on four disk resonators coupled to a waveguide System." Acta Physica Sinica, 2022, 0. http://dx.doi.org/10.7498/aps.71.20221397.
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In order to reduce power, realize ultrafast response time and dynamic tunability, a plasmonic waveguide system based on four disk resonators is designed. A plasmon induced transparency effect is theoretically analyzed using two different methods:one is the direct destructive interference between bright and dark mode resonators, and the other is the indirect coupling through a plasmonic waveguide. Due to the giant effective nonlinear Kerr coefficient of the graphene-Ag composite material structure and the enhancement characteristics of slow light response to optical Kerr effect, the pump intensity of PIT system to change the phase shift of transmission spectrum is greatly reduced. An ultrafast response time of 1 ps is achieved. 0.4π, 0.8π, 1.2π, 1.6π and 2π-phase shift of the transmission spectrum in the plasmon induced transparency system are achieved with the intensity of the pump light as low as 2.34, 4.68, 7.02, 9.36 and 11.7 MW/cm<sup>-2</sup>. In this paper, two small disk resonators directly coupled with a plasmonic waveguide is employed, and the reason is that two small disk resonators play the role of the slit between the waveguide and the resonators, and also acts as two separate resonators side-coupled with a plasmonic waveguide, which leads to the more efficient coupling of electromagnetic energy in the waveguide into the big disk resonators to form resonance and easier storage of light in the resonator. The triple-band plasmon induced transparency (PIT) effect and slow light properties of the model are analyzed by the expression of the deduced theoretical transmittance based on the coupled mode theory, which are very consistent with the finite-difference time-domain simulations. The results show that the transmission peak of the system is over 80% and the maximum group index is as high as 368. What's more, the disk resonators are easy to fabricate and the size of the entire PIT structure is <0.5 μm<sup>2</sup>, which is benefit for design of optoelectronic devices on-chip integration. The research results have important application prospects in highly integrated optical circuits and networks, and also provide ideas for the design and fabrication of multi-channel optical filter and light storage devices with low power consumption, ultrafast nonlinear responses ultracompact and dynamically tunability.
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Zhang Ming-Mei, Guo Ya-Tao, Fu Xu-Ri, Li Meng-Lei, Ren Bao-Cang, Zheng Jun, and Yuan Rui-Yang. "Spin-switching effect and giant magnetoresistance in quantum structure of monolayer MoS<sub>2</sub> nanoribbons with ferromagnetic electrode." Acta Physica Sinica, 2023, 0. http://dx.doi.org/10.7498/aps.72.20230483.
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Spintronics is a new type of electronics based on electron spin rather than charge as the information carrier, which can be stored and calculated by regulating and manipulating the spin. The discovery and application of the giant magnetoresistance effect opened the first door to applying electron spin properties. Realizing on-demand control of spin degrees of freedom for spin-based devices is essential. The two-dimensional novel material, monolayer transition metal dichalcogenides (TMDs) (MoS<sub>2</sub> is a typical example from the family of TMDs materials), has become an excellent platform for studying spintronics due to its novel physical properties, such as direct band gap and strong spin-orbit coupling. Obtaining high spin polarization and achieving controllability of degrees of freedom are fundamental problems in spintronics. In this paper, we construct the monolayer zigzag MoS<sub>2</sub> nanoribbon quantum structure of electrically controlled ferromagnetic electrodes to solve this problem. Based on the non-equilibrium Green's function method, the regulation of the magnetic exchange field and electrostatic barrier on the spin transport in parallel and anti-parallel configurations is studied. It is found that in the parallel structure, spin transport is obviously related to the magnetic exchange field, and 100% spin filtering can occur near the Fermi energy level to obtain pure spin current. When an additional electric field is applied in the middle region, the spin filtering effect is more significant. Therefore, the spin switching effect can be achieved by regulating the incident energy. In addition, it is also found that within a specific energy range, electrons in the parallel configuration are excited to participate in transport, while electrons in the anti-parallel structure are significantly inhibited. Consequently, a noticeable giant magnetoresistance effect can be obtained in this quantum structure. Moreover, it is can be seen that the magnetic exchange field strength can effectively modulate the giant magnetoresistance effect. These results provide valuable theoretical references for the development of giant magnetoresistance devices and spin filters based on monolayer zigzag MoS<sub>2</sub> nanoribbons.
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Jin Jia-sheng, Ma Cheng-ju, Zhang Yao, Zhang Yue-bin, Bao Shi-qian, Li Mi, Li Dong-ming, Liu Ming, Liu Qian-zhen, and Zhang Yi-xin. "Switchable multifunctional terahertz metamaterial with slow-light and absorption functions based on phase change materials." Acta Physica Sinica, 2023, 0. http://dx.doi.org/10.7498/aps.72.20222336.
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Terahertz (THz) waves usually refer to electromagnetic waves with frequencies between 0.1 and 10 THz.It has potential applications in wireless communication,biomedical image processing,nondestructive testing,military radar and other fields.However,due to function limitation of the natural materials,multifunctional terahertz devices are difficult to design and fabricate,which become a bottleneck for THz technology.The emergence of metamaterials fills a gap in the electromagnetic materials in the THz frequency band,and is widely used in THz functional devices,such as THz modulators,THz absorbers,THz filters,THz sensors,THz slow-light devices,etc.However,the above-mentioned THz devices all have a single function.For practical application,multifunction integrated THz devices have broader application prospects.We know that Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub>(GST) is a typical phase transition material.Under excitation of light or electronic field,GST can realize a reversible phase transition between insulating and metallic states.In order to achieve a switchable multifunctional THz device,in this paper we design a THz metamaterial based on the phase transition material GST and realize a switchable function with slow-light and absorption functions.The THz metamaterial consists of a microstructure layer,which is composed of gold rings arranged periodically,and a GST thin film spaced by a SiO<sub>2</sub> dielectric layer.When GST is in an insulating state,the two gold rings are coupled to each other under the excitation of the THz pulse.Then,we can observer the EIT-like effect.THz pulses propagating in the metamaterial we proposed can be slowed down,and a maximum group delay of the THz pulse is up to 3.6 ps.However,when GST is in a metallic state,we can observer two absorption peaks in the spectrum of the proposed THz metamaterial,and the absorption rates at frequency of 0.365THz and 0.609THz are 97% and 100%,respectively.Furthermore,we also investigate the polarization properties of the proposed THz metamaterial,and find that it has polarization insensitive characteristic.When the polarization angle of the incident THz light pulse changes from 0° to 90°,the slow-light and absorption properties of the THz metamaterials are unaffected.The proposed THz metamaterials has potential applications in THz biomedical image processing,THz optical switching,THz optical buffer.
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Loschen, Wayne, Howard Burkom, and David Atrubin. "Jurisdictional Usage of the New ESSENCE Word Alert Feature." Online Journal of Public Health Informatics 9, no. 1 (May 2, 2017). http://dx.doi.org/10.5210/ojphi.v9i1.7718.
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ObjectiveThe objective of this presentation is to describe the new word alertcapability in ESSENCE and how it has been used by the FloridaDepartment of Health (FDOH). Specifically, this presentation willdescribe how the word alert feature works to find individual chiefcomplaint terms that are occurring at an abnormal rate. It willthen provide usage statistics and first-person accounts of how thealerts have impacted public health practice for the users. Finally,the presentation will offer future enhancement possibilities and asummary of the benefits and shortcomings of this new feature.IntroductionSyndromic surveillance systems have historically focused onaggregating data into syndromes for analysis and visualization. Thesesyndromes provide users a way to quickly filter large amounts ofdata into a manageable number of streams to analyze. Additionally,ESSENCE users have the ability to build their own case definitionsto look for records matching particular sets of criteria. Those user-defined queries can be stored and analyzed automatically, along withthe pre-defined syndromes. Aside from these predefined and user-defined syndromic categories, ESSENCE did not previously providealerts based on individual words in the chief complaint text that hadnot been specified a priori. Thus, an interesting cluster of recordslinked only by non-syndromic keywords would likely not be broughtto a user’s attention.MethodsIn the FDOH ESSENCE system a new detection feature wasdeveloped to trigger alerts based on anomalous occurrence of termsin chief complaints.1This feature used Fisher’s Exact Test to testfrequencies of individual chief complaint terms relative to all termsin a 1-month baseline. The feature used a 7-day guard-band, andautomatically switched to an efficient chi-square test for sufficientlylarge term counts. A term triggered an alert if its p-value≤10E-4.This algorithm was then run on chief complaint sets both by hospitaland by region, with region assignment according to patient zip code.Results were then displayed in new visualizations showing alerts inword cloud and line listing form. Additionally, users were given theoption to ignore stop words, syndromic terms, and a user-created listof ignorable words in order to focus on words of greater interest.ResultsThe result of using the tool since June 2016 has seen three majorbenefits. First, the original intent for the system to notify users ofabnormal word clusters has proven useful. Users have been able to seeterms such asDisaster, ShelterandFireworkswhich were not part ofany prior syndromes and use these notifications to investigate possibleissues. The second benefit found by users was the ability to find newmisspellings or abbreviations commonly used by hospitals. The termsZykaandGLF(Ground Level Fall) are examples of these. Finally,the system has helped discover new trends in hospital processes. Forexample, the tool has helped discover first person and non-Englishphrases in the chief complaint. This observation led to the discoverythat some hospitals are using kiosks or mobile phone apps to allowpatients to enter their own chief complaints.ConclusionsThe word alert feature has provided value to the users of FDOHESSENCE. While accomplishing its initial goal of triggeringabnormal non-syndromic term usage, the additional ability to findnew misspellings and abbreviations may have even larger impact bykeeping syndrome and subsyndrome definitions up-to-date over timefor traditional syndromic alerting. Beyond these current benefits,additional visualization enhancements are under consideration.Additionally, the resources required to perform the detection aresubstantial, and implementation improvements are under developmentto improve the performance and enable more advanced free-textanomaly detection.