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198 results on '"Feng, X. L."'

3. Experimentally realizable control fields in quantum Lyapunov control

Author

Yi, X. X., Wu, S. L., Wu, Chunfeng, Feng, X. L., and Oh, C. H.

Subjects
Quantum Physics
Abstract

As a hybrid of techniques from open-loop and feedback control, Lyapunov control has the advantage that it is free from the measurement-induced decoherence but it includes the system's instantaneous message in the control loop. Often, the Lyapunov control is confronted with time delay in the control fields and difficulty in practical implementations of the control. In this paper, we study the effect of time-delay on the Lyapunov control, and explore the possibility of replacing the control field with a pulse train or a bang-bang signal. The efficiency of the Lyapunov control is also presented through examining the convergence time of the controlled system. These results suggest that the Lyapunov control is robust gainst time delay, easy to realize and effective for high-dimensional quantum systems.

Published
2011
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4. Joint quantum nondemolition measurements of qubits: beyond the mean-field theory

Author

Wei, L. F., Huang, J. S., Feng, X. L., Wang, Z. D., and Oh, C. H.

Subjects
Quantum Physics
Abstract

We propose an approach to nondestructively detect $N$ qubits by measuring the transmissions of a dispersively-coupled cavity. By taking into account all the cavity-qubits quantum correlations (i.e., beyond the usual coarse-grained/mean-field approximations), it is revealed that for an unknown normalized $N$-qubit state $|\psi_N>=\sum_{k=0}^{2^N-1}\beta_k|k>_N$, each detected peak in the cavity transmitted spectra marks one of the basis states $|k>_N$ and the relative height of such a peak is related to the corresponding superposed-probability $|\beta_k|^2$. Our results are able to unambiguously account for the intriguing multi-peak structures of the spectra observed in a very recent circuit-quantum-electrodynamics experiment [Phys. Rev. A {\bf 81}, 062325 (2010)] with two superconducting qubits., Comment: 5 pages, 3 figures

Published
2010

5. Effective Hamiltonian Approach to Open Systems and Its Applications

Author

Huang, X. L., Yi, X. X., Wu, Chunfeng, Feng, X. L., Yu, S. X., and OH, C. H.

Subjects
Quantum Physics
Abstract

By using the effective Hamiltonian approach, we present a self-consistent framework for the analysis of geometric phases and dynamically stable decoherence-free subspaces in open systems. Comparisons to the earlier works are made. This effective Hamiltonian approach is then extended to a non-Markovian case with the generalized Lindblad master equation. Based on this extended effective Hamiltonian approach, the non-Markovian master equation describing a dissipative two-level system is solved, an adiabatic evolution is defined and the corresponding adiabatic condition is given., Comment: 9 pages, 2 figures

Published
2008
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6. Dissipation in Single-Crystal 3C-SiC Ultra-High Frequency Nanomechanical Resonators

Author

Feng, X. L., Zorman, C. A., Mehregany, M., and Roukes, M. L.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The energy dissipation 1/Q (where Q is the quality factor) and resonance frequency characteristics of single-crystal 3C-SiC ultrahigh frequency (UHF) nanomechanical resonators are measured, for a family of UHF resonators with resonance frequencies of 295MHz, 395MHz, 411MHz, 420MHz, 428MHz, and 482MHz. A temperature dependence of dissipation, 1/Q ~ T^(0.3) has been identified in these 3C-SiC devices. Possible mechanisms that contribute to dissipation in typical doubly-clamped beam UHF resonators are analyzed. Device size and dimensional effects on the dissipation are also examined. Clamping losses are found to be particularly important in these UHF resonators. The resonance frequency decreases as the temperature is increased, and the average frequency temperature coefficient is about -45ppm/K., Comment: Solid-State Sensors, Actuators, and Microsystems Workshop Hilton Head Island, South Carolina, June 4-8, 2006 (Invited)

Published
2006

8. 50P Efficacy and safety of pemigatinib in Chinese patients with unresectable, advanced/ recurrent or metastatic intrahepatic cholangiocarcinoma with FGFR2 fusion or rearrangement that failed to prior systemic therapy

Author

Shi, G-M., primary, Huang, X-Y., additional, Wen, T-F., additional, Song, T-Q., additional, Kuang, M., additional, Mou, H-B., additional, Bao, L-Q., additional, Zhao, H-T., additional, Zhao, H., additional, Feng, X-L., additional, Zhang, B., additional, Peng, T., additional, Zhang, Y., additional, Li, X., additional, Yu, H., additional, Cao, Y., additional, Luo, Y., additional, Wang, Y., additional, Fan, J., additional, and Zhou, J., additional

Published
2021
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17. High-temperature oxidation resistance of NiCrAlY columnar microcrystalline coating deposited by EDS.

Author

Wang, R. Y., Feng, X. L., Yang, C., Wang, R., Guo, C. A., and Zhang, J.

Subjects
*SURFACE coatings, *PROTECTIVE coatings, *OXIDATION, *WEIGHT gain, *METAL ions, *ALLOY plating
Abstract

In this paper, the NiCrAlY coating is deposited on the surface of the NiCrAlY alloy substrate by the electrospark deposition method. The phase composition, morphology and element composition of the substrate and coating were characterized by XRD, SEM/EDS. The high-temperature oxidation resistance was tested. The results show that the weight gain of the coating is lower than that of the substrate alloy after high-temperature oxidation. The coating protects the substrate to some extent. And because of the formation of NiCrAlY columnar microcrystalline coating, rich grain boundaries, promoted the diffusion rate of metal ions, resulting in the formation of "pinning effect" of the film/metal interface, improve the anti-stripping performance of the coating. [ABSTRACT FROM AUTHOR]

Published
2022
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24. Superconductivity in HfTe5 across weak to strong topological insulator transition induced via pressures

Author

Liu, Y., primary, Long, Y. J., additional, Zhao, L. X., additional, Nie, S. M., additional, Zhang, S. J., additional, Weng, Y. X., additional, Jin, M. L., additional, Li, W. M., additional, Liu, Q. Q., additional, Long, Y. W., additional, Yu, R. C., additional, Gu, C. Z., additional, Sun, F., additional, Yang, W. G., additional, Mao, H. K., additional, Feng, X. L., additional, Li, Q., additional, Zheng, W. T., additional, Weng, H. M., additional, Dai, X., additional, Fang, Z., additional, Chen, G. F., additional, and Jin, C. Q., additional

Published
2017
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27. Gene Sequences Parallel Alignment Model Based on Multiple Inputs and Outputs.

Author

Feng, X. L. and Gao, J.

Subjects
SEQUENCE alignment, GENE flow, COMPUTING platforms, ELECTRONIC data processing, GENES, BIG data, INPUT-output analysis
Abstract

Bioinformatics computing is a kind of big data processing problem, which usually has the characteristics of large data scale, large computational load and long computational time. Therefore, the use of big data technology in bioinformatics computing has gradually become a research hotspot, and using Hadoop for gene sequence alignment is one of it. It is a common way to use various tools to complete a job in the field of Biocomputing. In most studies of parallel alignment of gene sequences using Hadoop, third-party tools are also needed. However, there are few methods using Hadoop independently to complete gene sequences alignment. Adding data processing with other tools to Hadoop workflow not only affects the improvement of computing performance, but also complicates the application. In this paper, a parallel alignment model of gene sequences based on multiple inputs and outputs is proposed, which can independently complete parallel alignment of gene sequences in Hadoop platform without using other tools. This model not only simplifies the process flow of gene sequence alignment, but also improves the performance compared with other methods. This paper describes in detail the method of manipulating gene sequences with multiple inputs and outputs modes on Hadoop platform and the design of a computing model based on this method, and proves the superiority of this model through experiments. [ABSTRACT FROM AUTHOR]

Published
2019
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28. Development of a NanoString assay to detect leukemogenic fusion transcripts in acute myeloid leukemia

Author

Hu, D., primary, Zhou, W., additional, Wang, F., additional, Shu, S. M., additional, Fan, L. L., additional, He, J., additional, Wang, P., additional, He, Y. L., additional, Du, W., additional, Zhang, J. H., additional, Duan, J. X., additional, Sun, L., additional, Zheng, J., additional, Li, X. Q., additional, Li, H. Y., additional, Feng, X. L., additional, and Huang, S. A., additional

Published
2016
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29. Microstructure evolution and large magnetocaloric effect of La0.8Ce0.2(Fe0.95Co0.05)11.8Si1.2 alloy prepared by strip-casting and annealing.

Author

Zhong, X. C., Feng, X. L., Huang, J. H., Zhang, H., Huang, Y. L., Liu, Z. W., and Jiao, D. L.

Subjects
*LANTHANUM compounds, *METAL microstructure, *MAGNETOCALORIC effects
Abstract

The microstructure and magnetocaloric effect of the La0.8Ce0.2(Fe0.95Co0.05)11.8Si1.2 strip-cast flakes annealed between 1273K and 1423K for different time have been investigated. For the flakes annealed for 2h from 1273K to 1423K, the shape and distribution of α-Fe, La-rich and NaZn13-type 1:13 phases are quite sensitive to the annealing temperature. Especially, at a high annealing temperature of 1423K, the 1:13 phase began to decompose into macroscopic α-Fe conglomerations and La-rich dendrites. With the increase of annealing time from 0 to 12h at 1323K, the amount of 1:13 phase increased significantly and reached ∼93.50 wt.% at 12h. However, an overlong annealing time also led to 1:13 phase decomposition and influenced the magnetic performance. For the flakes annealed at 1323K for 12h, large magnetic entropy change value of 18.12Jkg-1K-1 at 5T has been obtained. The present results indicate that strip casting method can potentially be used in mass production of high performance magnetocaloric materials. [ABSTRACT FROM AUTHOR]

Published
2018
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30. The transcriptome analysis of males musk gland in Moschus berezovskii(Artiodactyla: Moschidae)

Author

Jie, H., Xu, Z. X., Su, Y., Lei, M. Y., Zeng, D. J., Zhao, G. J., Feng, X. L., Zheng, C. L., Zhang, C. L., Liang, Z. J., and Li, D. Y.

Abstract

AbstractThe dwarf musk deer, or Chinese forest musk deer (Moschus berezovskii)is an endangered artiodactyl species native to a narrow region in southern and central China as well as northernmost Vietnam. This species is well known for the habit of male musk deer to secrete musk from the musk gland. Unmated male forest musk deer secrete a greater amount of musk than mated males, which probably allows them to attract a greater number of females. However, transcriptome data for this species are deficient, and the potential transcriptional pathways of musk production remain unknown. In this study, we used RNA-sequencing (RNA-Seq) to perform an in-depth survey of transcriptome data from musk gland and to compare the transcriptome differences between mated- and unmated sexually mature Chinese forest musk deer. There were 13,009 and 12,995 genes were expressed in unmated and mated musk glands tissue. In addition to analyzing these genes, we analyzed the differentially expressed genes in musk gland tissue between mated and unmated Chinese forest musk deer males. One hundred and thirty seven genes were found differentially expressed. We found that some genes in “PPAR signaling pathway”, “PI3K-Akt signaling pathway” and “Thyroid hormone synthesis” pathways may be associated with musk production and the secretion of the musk deer. The annotated genes and differentially expressed genes in this study can be applied in conservation or utilization study of musk deer in the future.

Published
2019
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32. Phase Noise and Frequency Stability of Very-High Frequency Silicon Nanowire Nanomechanical Resonators

Author

Feng, X. L., He, R. R., Yang, P. D., Roukes, M. L., Feng, X. L., He, R. R., Yang, P. D., and Roukes, M. L.

Abstract

We report measurements and analyses of noise characteristics of very-high frequency (VHF) silicon nanowire (SiNW) nanoelectromechanical systems (NEMS). VHF SiNW resonators vibrating at ~200MHz typically have displacement sensitivity of ~5fm/(Hz^(1/2)) and force sensitivity of 50~250aN/(Hz^(1/2)) set by thermomechanical fluctuations. They have ~1nm critical amplitude and intrinsic dynamic range of 90~110 dB. Amplifier noise and resistor thermal noise dominate the resonance detection, resulting in in compromised displacement noise floor (typically ≥30 fm/(Hz^(1/2))), dynamic range (reduced to 70~90 dB), and phase noise (≥20~30dB degradation). We develop SiNW-NEMS-based phase-locking techniques to investigate the phase noise and frequency stability performance. Frequency stability of ~0.1ppm and resonant mass sensitivity of ~10 zg (1 zg=10^(-21)g) have been achieved.

Published
2007

33. Quality Factors and Energy Losses of Single-Crystal Silicon Nanowire Electromechanical Resonators

Author

Feng, X. L., He, R. R., Yang, P. D., Roukes, M. L., Feng, X. L., He, R. R., Yang, P. D., and Roukes, M. L.

Abstract

We report measurements on quality factors (Q's) of single-crystal silicon nanowire (SiNW) resonators operating in the very-high frequency (VHF) range. Q's of ~200 MHz metalized SiNWs are considerably lower than those of the pristine SiNWs operating at similar frequencies. The observed damping effect due to resonance transduction agrees well with the loaded-Q model for magnetomotive scheme. The temperature dependency of dissipation (Q^(-1)) is found to be approximately from Q^(-1) ∝ T^(0.3) to Q^(-1) ∝ T^(0.4). Clamping losses are becoming important for such VHF ultrasmall resonators.

Published
2007

34. VHF, UHF and microwave frequency nanomechanical resonators

Author

Huang, X. M. H., Feng, X. L., Zorman, C. A., Mehregany, M., Roukes, M. L., Huang, X. M. H., Feng, X. L., Zorman, C. A., Mehregany, M., and Roukes, M. L.

Abstract

Nanomechanical resonators with fundamental mode resonance frequencies in the very-high frequency (VHF), ultra-high frequency (UHF) and microwave L-band ranges are fabricated from monocystalline silicon carbide (SiC) thin film material, and measured by magnetomotive transduction, combined with a balanced-bridge readout circuit. For resonators made from the same film, we measured the frequency dependence (thus geometry dependence) of the quality factor. We have seen a steady decrease of quality factor as the frequency goes up. This indicates the importance of clamping losses in this regime. To study this source of dissipation, a free-free beam SiC nanomechanical resonator has been co-fabricated on the same chip with a doubly clamped beam resonator operating at similar frequencies. Device testing has been performed to directly compare their characteristics and performance. It is observed that a significant improvement in quality factor is attained from the free-free beam design. In addition, from studies of resonators made from different chips with varying surface roughness, we found a strong correlation between surface roughness of the SiC thin film material and the quality factor of the resonators made from it. Furthermore, we experimentally studied the eddy current damping effect in the context of magnetomotive transduction. A high-aspect ratio SiC nanowire resonator is fabricated and tested for this study. Understanding the dissipation mechanisms, and thus improving the quality factor of these resonators, is important for implementing applications promised by these devices.

Published
2005

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