Showing papers by "Li Li published in 2018"

Liquid crystal terahertz modulator with plasmon-induced transparency metamaterial.

Abstract: An electrically tunable terahertz (THz) modulator with large modulation depth and low insertion loss is performed with liquid crystal (LC) metamaterial. The modulation depth beyond 90% and insertion loss below 0.5 dB are achievable at normal incidence by exploiting plasmon-induced transparency (PIT) effect. The PIT spectra can be manipulated by actively controlling the interference between dipole mode and nonlocal surface-Bloch mode with LC. The incident angle tuning effect on PIT spectra shows that the large modulation depth and low insertion loss can remain over a wide range of working angles. The superior property and simplicity of design make this modulator promising in advanced terahertz communication.

Compact self-Q-switched Tm:YLF laser at 1.91 μm

Abstract: We report self-Q-switching operation in a diode-pumped Tm:YLF bulk laser by exploiting saturable re-absorption under the quasi-three-level regime. Robust self-Q-switched pulse output at 1.91 μm in fundamental mode is demonstrated experimentally with 1.5 at.% doped Tm:YLF crystal. At maximum absorbed pump power of 4.5 W, the average output power and pulse energy are obtained as high as 610 mW and 29 μJ, respectively, with the corresponding slope efficiency of 22%. Pulse repetition rate is tunable in the range of 3–21 kHz with changing the pump power. The dynamics of self-Q-switching of Tm:YLF laser are discussed with the help of a rate equation model showing good agreement with the experiment. The compact self-Q-switched laser near 2 μm has potential application in laser radar systems for accurate wind velocity measurements.

Highly Birefringent Single-Mode Suspended-Core Fiber in Terahertz Regime

Abstract: In this study, we report a highly birefringent terahertz (THz) fiber that contains rectangular air slots in the suspended core. The proposed fiber can provide a high birefringence of the order of 10−2 over a wide frequency region in single-mode operation. An ultrahigh birefringence of 0.078, low effective material loss of 0.39 dB/cm, and low confinement loss of 1.25 × 10−5 dB/cm are obtained simultaneously at 0.95 THz. Moreover, numerical results indicate that a low dispersion with small variation can be achieved, and the power profile envelope has a Gaussian shape, which is important for coupling with common THz sources. The calculated coupling efficiency is as high as ∼95% for y -polarization mode. It is anticipated that the proposed suspended-core fiber would be useful in THz polarization maintaining wave guidance and bacteria detection applications.

The influence of side-coupled quantum dots on thermoelectric effect of parallel-coupled double quantum dot system

Abstract: The thermoelectric transport properties of a parallel-coupled double quantum dot (PCDQD) system with side-coupled quantum dots (QDs) is investigated by using the Keldysh non-equilibrium Green's function technique. The thermoelectric quantities, including the thermal conductance, thermopower, and thermoelectric figure of merit denoted by ZT, are sensitive to the inter-dot coupling strength. With the help of side-coupled QD, unusual double Fano resonances are created in the conductance spectra to largely enhance the thermoelectric effect at low-temperature. Benefited from the coexistence of local bipolar effect and Fano resonance, the ZT can be improved by one-fold higher than that of original PCDQD system. Moreover, when the asymmetry parameter α, which indicates the geometric arrangement of coupled QDs with a given lead, takes appropriate value, the optimization of ZT can be achieved at high temperature. Our work suggests that the side-coupled QDs scheme holds promise for the designing of high-efficiency thermoelectric conversion devices.

Impact of dipolar clusters on electro-optic effects in KTa1- xNbxO3 crystal

Abstract: Dipolar clusters are crucial structure factors in electro-optic (EO) effects. Here, the impacts of dipolar clusters on EO effects are investigated in KTa1-xNbxO3 using electric-field-dependent EO characteristics. The results indicate that the field-driven reorientation of dipolar clusters determines the orientational electric susceptibility, deeply contributing to the excellent quadratic EO effects. The controlled average size of correlated local dipoles and uniform orientation of ferroelectric domains efficiently suppress light scattering, being beneficial for the modulation of incident light. The understanding of dipolar cluster-triggered EO responses is valuable for exploring origins of large EO effects and optimizing EO properties of materials.

Double D-shaped hole optical fiber coated with graphene as a polarizer.

Abstract: A double D-shaped hole optical fiber coated with graphene is proposed as a polarizer at the wavelength of 155 μm As the planar surfaces of D-shaped holes are both coated with graphene, the interaction between the core and graphene can be doubled Moreover, the interaction can be further improved by introducing functional materials into the holes The proposed fiber provides a high extinction ratio (ER) and low insertion loss, and it operates in the single polarization mode The ER of 425 dB with a 25-mm-long optical fiber can be achieved for a transverse-electric-pass polarizer, and the insertion loss is approximately 108 dB Specifically, the proposed fiber can achieve simultaneously dual-band polarization at 155 μm and 131 μm The proposed fiber is feasible for seamless integration in existing fiber systems We hope our work benefits high-efficiency polarizers, and we believe that the proposed fiber has some potential applications in photonic integrated circuits

Photon-Assisted Electronic Transport Through an Asymmetrically Coupled Triple-Quantum Dot Interferometer

Abstract: We present theoretically the quantum electronic transport through an interferometer asymmetrically coupled with triple quantum dots. Using the Keldysh non-equilibrium Green’s function method, the photon-assisted transport properties through the asymmetric quantum system are numerically analyzed. The sidebands of the photon-assisted tunneling process appear when driven by the time-modulated field. The average current spectra are simulated as a function of quantum dot energy to understand the roles of side-coupling strength and time-modulated field in sideband effect and electron tunneling. This is helpful in future design of the basic structures required for quantum computation applications.

Two-core single-polarization optical fiber with a large hollow coated bimetallic layer.

Abstract: A two-core hollow optical fiber for a polarizer based on surface plasmon resonance (SPR) is proposed and studied by the full-vector finite-element method. The proposed fiber consists of two circular cores, inner cladding, outer cladding, and a large central air hole. The two cores are arranged symmetrically in inner cladding and couple weakly with the air hole. There is no cross talk between cores because they are insulated by the air hole. A nanodimension Ag/Au bimetallic layer can be coated on the inner surface of the central air hole to support SPR. The numerical results show that single polarization of two cores is achieved simultaneously at the wavelength of 1.310 μm, due to strong coupling between the TM mode and the surface plasmon polariton mode. The extinction ratio 40.90 dB with 3 mm length is obtained, and the confinement loss of TE mode is 0.19 dB/cm. Moreover, the resonance wavelength is tunable by varying the refractive index of materials in the central air hole. The scheme is helpful for coupling an all-fiber polarizer with multicore polarization maintaining fibres (PMFs) and makes possible application in in-fiber integrated interferometric sensors while maintaining polarization.

Characterization of the complete chloroplast genome of Jilin ginseng (Panax ginseng C. A. Meyer) using next generation sequencing.

Abstract: Jilin ginseng, Panax ginseng C. A. Meyer, belongs to the Araliaceae family. It is known as the number one medicinal herb and one of the three native treasures in Northern China and has been cultiva...

A Magnetic Beacon Navigation and Positioning Technology Not Relying on GPS

Abstract: A magnetic beacon navigation and positioning technology which can work without GPS is investigated in this paper. We use the magnetic coil as a beacon in the low frequency magnetic field and the navigation. In addition, positioning methods based on extended Kalman filter (EKF) and data fusion algorithm are applied to improve the accuracy of the system. The method of navigation and positioning of this magnetic beacon is explained by simulation, indicating that the proposed magnetic beacon navigation and positioning algorithm is attractive for many environments where GPS signals are restricted, such as indoor robot navigation, underground physical exploration and so on.

Expression of saponin biosynthesis related genes in different tissues of Panax quinquefolius

Abstract: The relationship between saponin content of Panax quinquefolius in different parts of the organization and expression of ginsenoside biosynthesis related gene was obtained by the correlation analysis between saponin content and gene expression. The 14 tissue parts of P. quinquefolius were studied, six saponins in P. quinquefolius. Samples (ginsenoside Rg₁, Re, Rb₁, Rc, Rb₂ and Rd), group saponins and total saponins were determined by high performance liquid chromatography and vanillin-sulfuric acid colorimetric method. Simultaneously, the expression levels of 7 ginsenoside biosynthesis related genes (SQS, OSC, DS, β-AS, SQE, P450 and FPS) in different tissues of P. quinquefolius were determined by Real-time fluorescence quantitative PCR. Although 7 kinds of ginsenoside biosynthesis related enzyme gene in the P. quinquefolius involved in ginsenoside synthesis, the expression of β-AS and P450 genes had no significant effect on the content of monosodium saponins, grouping saponins and total saponins, FPS, SQS, OSC, DS and SQE had significant or extremely significant on the contents of single saponins Re, Rg1, Rb1, Rd, group saponin PPD and PPT, total saponin TMS and total saponin TS (P<0.05 or P<0.01). The biosynthesis of partial saponins, grouping saponins and total saponins in P. quinquefolius was affected by the interaction of multiple enzyme genes in the saponin synthesis pathway, the content of saponins in different tissues of P. quinquefolius was determined by the differences in the expression of key enzymes in the biosynthetic pathway. Therefore, this study further clarified that FPS, SQS, OSC, DS and SQE was the key enzyme to control the synthesis of saponins in P. quinquefolius by correlation analysis, the biosynthesis of ginsenosides in P. quinquefolius was regulated by these five kind of enzymes in cluster co-expression of interaction mode.

Quinoa yellow wine and preparation method thereof

Abstract: The invention discloses quinoa yellow wine. The quinoa yellow wine is prepared according to the following methods: performing impurity removal and pulverization on quinoa rice and corn kernels, weighing pulverized quinoa rice and corn residues according to the mass ratio of (0.4 to 1.4) to (0.6 to 1.6), and performing cleaning and soaking to obtain a product; steaming and cooking the product for 20 to 30 minutes at 100 DEG C; spreading the product to be cooled until the temperature reaches 28 to 32 DEG C; adding alpha-diastase of which the mass accounts for 0.1 percent of the total mass of thepulverized quinoa rice and the corn residues, 0.1 percent of saccharifying enzyme and 0.5 percent of activated active dry yeast, and performing uniform stirring and sealing; performing fermentation for 5 to 8 days at 28 to 30 DEG C; performing fermentation for 30 to 32 days at 15 to 17 DEG C; performing squeezing and removing vinasse; standing for 3 days at 10 to 15 DEG C; performing low-temperature centrifugation, collection of supernatant fluid, and filtration and impurity removal; boiling wine for 13 to 17 minutes at 78 to 82 DEG C, and performing cooling to obtain the finished product quinoa yellow wine. The wine is coordinated and has a special faint scent of quinoa, and has high stability; moreover, the wine is placed for one year, suspensions and precipitants are avoided, the colorof the wine is clarified, and the anti-oxidation activity is good.

Proposal of high-birefringence twin-core hollow optical fiber

Abstract: We propose a high-birefringence twin-core hollow optical fiber, which is composed of two rectangular Ge-doped cores, annular silica cladding, and a large central air hole. The rectangular cores are weakly coupled with the air hole and arranged in the same silica cladding. The mode birefringence in single-mode operation of 1.55 μm reaches 2.48 × 10 − 4, which is comparable with traditional panda polarization maintaining fiber. By introducing an extra stress zone, the mode birefringence can be improved further by two times. The high birefringence of the twin-core hollow fiber is induced by strong asymmetry of the waveguide structure. The characteristics of the guiding mode, birefringence, and evanescent field are analyzed numerically by full-vector finite-element method. The effect of geometric and material parameters is discussed. The proposed scheme of twin-core hollow fiber can overcome the polarization fading effect and signal cross talk occurring in traditional multicore fibers and is much desirable for improving the performance of in-fiber integrated interferometers and biochemical sensors.

Chenopodium quinoa willd green tea and preparation method thereof

Abstract: The invention discloses chenopodium quinoa willd green tea and a preparation method thereof. The preparation method comprises the following steps of (1) picking and selecting chenopodium quinoa willdleaves from chenopodium quinoa plants; (2) spreading the picked chenopodium quinoa willd leaves at a shady place for ventilation, during spreading, noticing that the stacking thickness of the chenopodium quinoa willd leaves is 1-5cm, and performing overturning once every 1-2h, wherein the time for spreading for airing is 5-7h; (3) at the temperature of 175-185 DEG C, performing fixation for every1kg of the chenopodium quinoa willd leaves for 0.5-1.5min; (4) reducing the temperature of the chenopodium quinoa willd leaves after fixation, putting the chenopodium quinoa willd leaves after temperature reduction into a rolling machine, and performing rolling for 10-15min; and (5) performing baking so as to obtain dried chenopodium quinoa willd leaves namely the chenopodium quinoa willd green tea, wherein the stacking thickness of the chenopodium quinoa willd leaves is 0.5-2cm. According to the prepared chenopodium quinoa willd green tea disclosed by the invention, water-insoluble ash content, water content, crude fibers and Pb are significantly lower than those of Biluochun, the water extract content is not obviously different from that of the Biluochun, and the nutritive indexes of teapolyphenols, protein, VC, minerals, the sum of 16 kinds of amino acids and the like are all higher than those of finished product green tea Biluochun; compared with chenopodium quinoa willd leaves, the chenopodium quinoa willd green tea has the advantages that the tea polyphenols content is raised, and the changes of other physical and chemical indexes and the changes of nutrient components are not significant; and the differences between the content of total polyphenol in the tea soup of the chenopodium quinoa willd green tea and the content of total polyphenol in the tea soup of the Biluochun are not significant.