Showing papers by "Jian Chen published in 2011"
TL;DR: The mechanical resonance and radiation stem from the coherent photo-induced vibration of the hexagonal ZnO nanoplates that make up the microsphere shells, and represent a straightforward route to terahertz radiation at the nanoscale.
Abstract: Core–shell zinc oxide microspheres mechanically vibrate and emit radiation at terahertz frequencies with a quantum emission efficiency of 33% when illuminated by a continuous-wave green laser.
120 citations
TL;DR: In this paper, a revised magnetism and superconductivity phase diagram was obtained via resistance and magnetic-susceptibility measurements for the FeTe${}_{1\ensuremath{-}x}$Se${}-x}, with lower Se concentrations after annealed in air.
Abstract: We observed bulk superconductivity in the FeTe${}_{1\ensuremath{-}x}$Se${}_{x}$ crystals with lower Se concentrations after annealed in air. A revised magnetism and superconductivity phase diagram is obtained via resistance and magnetic-susceptibility measurements for the FeTe${}_{1\ensuremath{-}x}$Se${}_{x}$ system. It is found that bulk superconductivity coexists with antiferromagnetic order in the crystals with 0.05 $\ensuremath{\le}$ x $\ensuremath{\le}$ 0.18. The phase diagram is very similar to the case of the K-doping or Co-doping BaFe${}_{2}$As${}_{2}$ as well as that of the SmFeAsO${}_{1\ensuremath{-}x}$F${}_{x}$ system, perhaps indicating that all the iron-based systems have a generic phase diagram, although the antiferromagnetic wave vectors in the parent compounds of both iron pnictides and FeTe${}_{1\ensuremath{-}x}$Se${}_{x}$ systems are remarkably different.
105 citations
TL;DR: In this paper, a planar terahertz (THz) metamaterial made from superconducting NbN films was designed and fabricated to mimic electromagnetically induced transparency (EIT) system.
Abstract: We designed and fabricated planar terahertz (THz) metamaterials made from superconducting NbN films to mimic electromagnetically induced transparency (EIT) system. They are characterized using THz time domain spectroscopy over a temperature range from 8 to 300 K. High transmittance and large delay-bandwidth product at transparency window are demonstrated, which mainly arise from the enhanced coupling and decreased damping in superconducting state. The EIT-like spectral response could be tuned in a wide frequency range. By applying two dark resonators with different resonance frequencies coupled with a radiative resonator, we experimentally demonstrated the planar metamaterials mimicking four-level EIT system.
97 citations
TL;DR: Results indicate that black carp fed diets with FO supplement had similar growth and non-specific immunity to the fish fed diet with RO, and alternative complement pathway, lysozyme and superoxide dismutase activities were not significantly influenced.
Abstract: An 8-week experiment on fingerling black carp Mylopharyngodon piceus was conducted to evaluate the effects of dietary fish oil (FO) supplement on growth, fatty acid composition and non-specific immunity responses. Five triplicate fingerling groups (initial weight = 2.72 ± 0.35 g) were fed isoenergetic and isonitrogenous diets in which the dietary FO was replaced with rapeseed oil (RO) in graded increments of 25% (0–100%). No significant effects were observed on specific growth rates, survival rates and feed conversion ratios, but there were significant differences in whole body moisture and liver lipid contents (P < 0.05), and the 100% RO replacement diet significantly enhanced hepatosomatic indexes compared to control group (P < 0.05). Other approximate whole body constituents, viscerasomatic ratios and condition factors were not influenced by dietary oil treatments. Fatty acid composition of muscle and liver was influenced by dietary fatty acid input, α-linoleic acid and γ-linolenic acid were significantly increased with increasing RO, but eicosapentaenoic acid, docosahexaenoic acid and the n-3/n-6 ratio were significantly reduced (P < 0.05). Alternative complement pathway, lysozyme and superoxide dismutase activities were not significantly influenced. These results indicate that black carp fed diets with FO supplement had similar growth and non-specific immunity to the fish fed diet with RO.
66 citations
TL;DR: It is found that, as the resonance frequency approaches f(g), the relative tuning range of MMs is quite wide, and this observation is attributed to the large change of kinetic inductance of superconducting film.
Abstract: Superconducting planar terahertz (THz) metamaterials (MMs), with unit cells of different sizes, are fabricated on 200 nm-thick niobium nitride (NbN) films deposited on MgO substrates. They are characterized using THz time domain spectroscopy over a temperature range from 8.1 K to 300 K, crossing the critical temperature of NbN films. As the gap frequency (fg = 2Δ0/h, where Δ0 is the energy gap at 0 K and h is the Plank constant) of NbN is 1.18 THz, the experimentally observed THz spectra span a frequency range from below fg to above it. We have found that, as the resonance frequency approaches fg, the relative tuning range of MMs is quite wide (30%). We attribute this observation to the large change of kinetic inductance of superconducting film.
66 citations
TL;DR: A scheme to improve the SNR distribution as well as the spectral efficiency of M-QAM OFDM signal for indoor visible light communication by tilting the receiver plane by employing Newton method.
Abstract: We propose a scheme to improve the SNR distribution as well as the spectral efficiency of M-QAM OFDM signal for indoor visible light communication by tilting the receiver plane. Newton method is employed for the photo-detector to receive maximum power by finding the optimal tilting angle. This method is a fast algorithm that only three searching steps are needed. The simulation results show that in the case of one LED source, the maximum spectral efficiency improvement is 0.44bit/s/Hz when the launching power of LED source is 12W; while in the case of four LED sources, the maximum spectral efficiency improvement is 0.21bit/s/Hz when the total launching power of the four LED sources is 12W.
49 citations
TL;DR: It is suggested that 4 g kg(-1) n-3 HUFA in diet could permit gibel carp normal growth performance and provide considerable n- 3 HU FA in fish muscle.
Abstract: A 12-week growth trial was conducted with gibel carp Carassius auratus gibelio (initial weight: 2.69 g) to evaluate the effects of dietary n-3 highly unsaturated fatty acids (n-3 HUFA) on growth performance and tissue fatty acid composition. Five diets of different n-3 HUFA levels from 0 to 17 g kg(-1) diet were supplemented at 80 g kg(-1) dietary lipid by including fish oil (FO) at 0, 25, 50, 75 and 100% of supplemental lipid. The remainder was coconut oil. The results showed that fish fed FO25 and FO50 obtained highest specific growth rate and lowest with FO0. Feed efficiency was highest at FO100 and lowest at FO0. Apparent digestibility coefficient of lipid increased with increasing dietary n-3 HUFA. The fish fed FO0 diet had the lowest thiobarbituric acid reactive substance in serum and muscle and highest moisture and lowest lipid content in viscera. Fatty acid compositions of muscle and liver were correlated with dietary fatty acids. Fish muscle concentration of 20:5n-3 increased with increasing dietary n-3 HUFA while the concentration of 22:6n-3 was distinctly reduced in FO0 group. It suggested that 4 g kg(-1) n-3 HUFA in diet could permit gibel carp normal growth performance and provide considerable n-3 HUFA in fish muscle. Excessive n-3 HUFA showed impact on growth performance of gibel carp.
43 citations
01 Dec 2011
TL;DR: The arrangement with 4 LEDs positioned in the corners and 12 LEDs spread evenly on a circle makes the fluctuation of received SNR reduce to 0.85dB, which helps to achieve BER of 10−3 when the receiver locates in the corner.
Abstract: The arrangement with 4 LEDs positioned in the corners and 12 LEDs spread evenly on a circle makes the fluctuation of received SNR reduce to 0.85dB. The BER performance does not suffer severely from ISI, where ZF equalization only provides 0.28dB power reduction to achieve BER of 10−3 when the receiver locates in the corner.
35 citations
TL;DR: Patients with low RRM1 expression levels in peripheral blood have a greater response to chemotherapy and longer survival time, which may benefit patients with advanced NSCLC treated with gemcitabine plus platinum therapy.
Abstract: To evaluate the predictive values of gene expressions of ribonucleotide reductase M1 (RRM1) and breast cancer susceptibility gene 1 (BRCA1) in peripheral blood from Chinese patients with non-small-cell lung cancer (NSCLC) treated with gemcitabine plus platinum. Forty Chinese patients with advanced NSCLC were recruited and received gemcitabine 1 200 mg/m2 on Days 1 and 8 plus carboplatin AUC 5 on Day 1. RRM1 and BRCA1 expression levels in peripheral blood were detected by quantitative reverse transcription-polymerase chain reaction (RT-PCR). Kaplan-Meier survival curve and log-rank test were performed to evaluate the correlation between gene expression and overall survival for these subjects. No correlation was observed between gene expression of RRM1 and that of BRCA1 (P>0.05), but there was a strong correlation between the expression of RRM1 and the response to chemotherapy (P=0.003). Subjects with low RRM1 expression levels in peripheral blood had longer survival time than those with high RRM1 expression levels (16.95 vs. 12.76 months, log-rank 3.989, P=0.046). However, no significant association between BRCA1 expression levels and survival time was found (16.80 vs. 13.77 months, log-rank 0.830, P=0.362). Patients with low RRM1 expression levels in peripheral blood have a greater response to chemotherapy and longer survival time. Advanced NSCLC patients with low RRM1 expression levels may benefit from gemcitabine plus platinum therapy. RRM1 mRNA expression in peripheral blood could be used to predict the prognosis of NSCLC treated by gemcitabine and platinum.
26 citations
TL;DR: In this article, the authors present the observation of Landau-Zener-Stuckelberg (LZS) interference of the dressed states arising from an artificial atom, a superconducting phase qubit, interacting with a microwave field.
Abstract: We present the observation of Landau-Zener-St\"uckelberg (LZS) interference of the dressed states arising from an artificial atom, a superconducting phase qubit, interacting with a microwave field. The dependence of LZS interference fringes on various external parameters and the initial state of the qubit agrees quantitatively very well with the theoretical prediction. Such LZS interferometry between the dressed states enables us to control the quantum states of a tetrapartite solid-state system with ease, demonstrating the feasibility of implementing efficient multipartite quantum logic gates with this unique approach.
26 citations
TL;DR: The extraordinary terahertz transmission through subwavelength hole array in superconducting NbN film is reported and temperature-dependent resonance frequency shift is observed, which mainly depends on the coupling between SPPs and LSPs.
Abstract: We report the extraordinary terahertz (THz) transmission through subwavelength hole array in superconducting NbN film. As the temperature drops below the superconducting transition temperature, the transmission spectra experience distinct changes. The extraordinary transmission is greatly enhanced in superconducting state due to the enhancement of surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs). We have also observed temperature-dependent resonance frequency shift, which mainly depends on the coupling between SPPs and LSPs.
TL;DR: In this paper, the authors present two-dimensional numerical predictions of wave breaking, up-rush, and backwash in inner surf and swash zones and analyzes the hydrodynamic processes involved.
TL;DR: Three adaptive phase estimation methods are examined: the adaptive decision-aided PE, the Kalman PE, and the normalized least-mean square PE algorithms, showing that they share the same phase error variances but with different approaches to determine the stepsize.
Abstract: We carried out a comprehensive analysis to examine the phase error variances in three adaptive phase estimation (PE) methods: the adaptive decision-aided PE, the Kalman PE, and the normalized least-mean square PE algorithms. The results show that they share the same phase error variances but with different approaches to determine the stepsize. Their performances in different quadrature amplitude modulation formats are analytically investigated for the purpose of determining the laser linewidth tolerance.
Patent•
28 Dec 2011
TL;DR: In this article, a detecting system for improving the stability of a high-sensitiveness T-Hz mixer is presented, where a feedback loop is used for controlling the microwave power much lower than the THz frequency, so as to compensate the instability of the local oscillation power.
Abstract: The utility model discloses a detecting system for improving the stability of a high-sensitiveness T-Hz mixer. The detecting system comprises a T-Hz frequency-band local oscillation signal source, a beam splitter, a silicon lens, a mixer, a coaxial T-joint, a DC blocker, an isolator, a low-temperature low-noise amplifier, a normal-temperature intermediate-frequency amplifier, a band-pass filter, a device for converting intermediate-frequency power into DC voltage, a computer, a DC bias power supply, a bias tee, a microwave source and a low-temperature Dewar. In the detecting system, a feedback loop is used for controlling the microwave power much lower than the T-Hz frequency, so as to compensate the instability of the T-Hz local oscillation power; and taking an HEB (Hot Electron Bolometer) mixer as an example, the Allan time of the mixer is increased from about 1 second to about 10 seconds, and the temperature resolution is improved by 30%.
TL;DR: In this paper, a single-element extended digital image correlation (single-element X-DIC) method was developed to measure the microdeformation of bovine bone.
Abstract: The microdeformation measurement of biomaterials is a crucial issue in the field of experimental mechanics. The single-element extended digital image correlation (single-element X-DIC) method was developed in this paper. If the actual deformation of the specimen is in accordance with the displacement hypothesis, single-element X-DIC possesses a higher measurement accuracy and a higher computational efficiency. With the assistance of a novel discretization method, single-element X-DIC could be used to measure the complex deformation. All results of the verification experiment show that single-element X-DIC is suitable for the measurement of various deformations. Furthermore, combined with optical microscopy, single-element X-DIC was applied to measure the microdeformation of bovine bone, which demonstrates that single-element X-DIC has wide application prospects in the microdeformation measurement of biomaterials.
01 Jan 2011
TL;DR: Challenges at component and system level are discussed to enable visible light communication a practical service provision infrastructure in next-generation energy-saving white LED lighting.
Abstract: Trends in integrating communication functionality to complement existing services by next-generation energy-saving white LED lighting are reviewed. Challenges at component and system level are discussed to enable visible light communication a practical service provision infrastructure. (2 pages)
TL;DR: By solving the stability Lyapunov functions, the feedback gains which guarantee global asymptotic stability and desired speed performance are determined and the results of numerical simulation showing the superiority of the proposed method than the existing result are shown.
Abstract: The RBF neural network robust adaptive control method of wind generator system is studied in this work. The design procedure in this paper aims at designing RBF neural network adaptive controllers that guarantee wind speed precise tracking. Moreover, the speed control problems are reduced to Lyapunov stability problem. In this way, by solving the stability Lyapunov functions, the feedback gains which guarantee global asymptotic stability and desired speed performance are determined. The results of numerical simulation showing the superiority of the proposed method than the existing result. http://dx.doi.org/10.5755/j01.mech.17.5.736
TL;DR: In this paper, a fiber-coupled superconducting nanowire single photon detector is presented considering practical applications and the system performances, such as dark count rate, system efficiency and noise equivalent power, are discussed.
Abstract: A fiber-coupled superconducting nanowire single photon detector is presented
considering practical applications. The system performances, such as dark count rate, system
efficiency and noise equivalent power, are discussed. A system efficiency of 3% (1550 nm) and a
dark count rate of 10 Hz at 4.2 K were achieved in experiment.
TL;DR: In this paper, the authors describe the fabrication of niobium superconducting tunnel junctions using the selective Niobium (Nb) etching process and various ways to minimize the leakage current.
Abstract: For high-quality superconducting tunnel junctions (STJs), it is necessary to reduce leakage current as much as possible. We describe the fabrication of niobium STJs using the selective niobium (Nb) etching process and various ways to minimize the leakage current. The experiment shows that the leakage current mainly comes from shorts in the tunnel barrier layer rather than those around the junction edges. Through systematic analysis of the thin film stress, surface morphology and modified junction structures, we fabricate high-quality Nb STJs with a gap voltage of 2.8 mV and a leakage current at 1 mV as low as 8.1% and 0.023% at 4.2 K and 0.3 K, respectively.
TL;DR: In this paper, the phase-diffusion was observed by investigating the switching current distribution as a function of Teff, and it was found that the crossover from the thermal activation to the phasediffusion scaling with the ratio of Ic and Teff.
Abstract: We measured the switching from a superconducting state to a finite voltage state in a dc SQUID, which is equivalent to a single Josephson junction with tunable critical current Ic. The width and the mean of the switching current distribution depend on the effective temperature Teff and Ic. The phase-diffusion was observed by investigating the switching current distribution as a function of Teff. It is found that the crossover from the thermal activation to the phase-diffusion scaling with the ratio of Ic and Teff, clarifying the physical picture of the phase-diffusion. We developed an analytical multi-retrapping model which can address the experimental results very well.
26 Jul 2011
TL;DR: In this paper, the conversion efficiency of high-temperature superconductivity bicrystal Josephson junction mixer at less than 650GHz has been investigated using miniature pulse tube refrigerator system.
Abstract: This paper is a research on the conversion efficiency of high-temperature superconductivity bicrystal Josephson junction mixer at THz. Using ion etching, junction integrated with antenna is prepared. Experiment on microwave exposure less than 650GHz has been obtained using miniature pulse tube refrigerator system. Conversion efficiency depended on local oscillation power, microwave signal power, harmonic order, bias electric current, etc., has been tested and analyzed.
TL;DR: Higher-order modulation formats are needed to accommodate the increased data traffic while keeping changes to the system configuration to a minimum in the interest of cost, and the structure of the adaptive decision-aided algorithm is explained.
Abstract: Internet traffic is growing exponentially worldwide, driven by multimedia applications such as video sharing and point-topoint file transfers. By 2014, demand is expected to increase by 64 exabytes (or billion gigabytes) per month, equivalent to over three million years’ worth of DVD-quality video.1 How to keep ever-greater volumes of data moving instantaneously from place to place without bottlenecks poses a challenge to the speed of both electrical and optical components. If the backbone networks were to fail, it would affect communication between continents and cities and consequently business, education, and other kinds of critical information sharing. Currently, keeping up the pace of data would require laying down more fiber to increase capacity. Yet according to the Shannon limit—a measure of the information transmission rate in the presence of noise—higher-order modulation formats are needed to accommodate the increased data traffic while keeping changes to the system configuration to a minimum in the interest of cost. On the receiver side, a local oscillator (LO) laser must be at the same frequency as the received signal to obtain the original intensity and phase information. But time-varying laser phase noise introduces distortions. Consequently, the LO laser should be locked to the received signal’s phase to recover the transmitted signal phase. Full information (i.e., the amplitude and phase) of the optical electric field can be preserved in digital coherent receivers. Accordingly, rather than using an optical phase-locked loop to lock the phase of the LO laser to the transmitter laser—which is sensitive to feedback delay in ultra-high-speed (e.g., 100Gbits/s) optical systems—an LO laser can run freely (i.e., require no extra Figure 1. Structure of the adaptive decision-aided algorithm. r(k): Received signal. ̨ and 1 ̨: Weights assigned to the previous and current phase reference. m, m̂*: The decision of the received symbol and its conjugate. T: Symbol duration (the minimum time interval between condition changes of a signal). V(k+1): Phase reference.
Proceedings Article•
04 Jul 2011TL;DR: In this article, the authors review the proposed Gardnertiming-based frequency offset estimation and decision-aided maximum likelihood phase estimation for digital coherent receivers, and propose an extension of the proposed scheme to the digital coherent receiver.
Abstract: We review our recently proposed Gardnertiming-based frequency offset estimation and decision-aided maximum likelihood phase estimation for digital coherent receivers.
01 Jan 2011
01 Jan 2011
TL;DR: In this article, the authors measured the switching from a superconducting state to a finite voltage state in a dc SQUID, which is equivalent to a single Josephson junction with tunable critical current.
Abstract: We measured the switching from a superconducting state to a finite voltage state in a dc SQUID, which is equivalent to a single Josephson junction with tunable critical current . The width and the mean of the switching current distribution depend on the effective temperature and . The phase-diffusion was observed by investigating the switching current distribution as a function of . It is found that the crossover from the thermal activation to the phase-diffusion scaling with the ratio of and , clarifying the physical picture of the phase-diffusion. We de- veloped an analytical multi-retrapping model which can address the experimental results very well.
01 Jan 2011
TL;DR: In this article, the LZS interference fringes on various external parameters and the initial state of the qubit agree quantitatively very well with the theoretical prediction, demonstrating the feasibility of implementing efficient multipartite quantum logic gates with this unique approach.
Abstract: uckelberg (LZS) interference of the dressed states arising from an artificial atom, a superconducting phase qubit, interacting with a microwave field. The dependence of LZS interference fringes on various external parameters and the initial state of the qubit agrees quantitatively very well with the theoretical prediction. Such LZS interferometry between the dressed states enables us to control the quantum states of a tetrapartite solid-state system with ease, demonstrating the feasibility of implementing efficient multipartite quantum logic gates with this unique approach.