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2. Thermoelectric properties of undoped and Bi-doped GeS monolayers: A first-principles study.

Author

Yang, H., Shi, H. L., Han, Q. Z., Yang, J., Ren, Y. H., Zhao, Y. H., Gong, L. J., Liu, Q. H., Shi, L. J., and Jiang, Z. T.

Subjects
*THERMOELECTRIC materials, *MONOMOLECULAR films, *SEEBECK coefficient, *CHEMICAL potential, *ARMCHAIRS, *GALLIUM antimonide
Abstract

Different from the extensive experimental investigations into the thermoelectric (TE) properties of the bulk IV–VI compounds, less attention has been paid to the TE properties of the monolayer IV–VI compounds. Here, we consider the TE transport properties including the Seebeck coefficient, electronic conductance, thermal conductance, power factor, and figure of merit Z T of the undoped and Bi-doped GeS monolayers. Our results show that for both the undoped and Bi-doped monolayers the anisotropy is widely observed in all their TE properties, and the maximum Z T at a certain temperature along the armchair direction is much greater than that along the zigzag direction. Moreover, Bi doping can lead to an increase of the maximum Z T , and there are more Z T peaks appearing near the zero chemical potential. This indicates that the Bi-doped GeS monolayer can work as a TE material at a lower bias voltage, and especially along the armchair direction it can work at zero bias voltage, which obviously strengthens the reliability of the TE devices. As the temperature increases, the maximum Z T will be uniformally increased along the armchair and zigzag directions for both the undoped and Bi-doped GeS monolayers. In the temperature scope from 300 to 800 K, the maximum Z T along the armchair direction of the Bi-doped GeS monolayer will increase from 3.39 to 4.85, which indicates that this Bi-doped GeS monolayer is a promising TE material in a wide-temperature zone. As an application, we have designed the GeS-based TE couples and found that their efficiencies can be greater than 27 % at large temperature differences. This research should be an important guidance for designing a low-voltage, wide-temperature-scope, and high-stability TE device. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Design and construction of the POLAR detector

Author

Produit, N., Bao, T. W., Batsch, T., Bernasconi, T., Britvich, I., Cadoux, F., Cernuda, I., Chai, J. Y., Dong, Y. W., Gauvin, N., Hajdas, W., Kole, M., Kong, M. N., Kramert, R., Li, L., Liu, J. T., Liu, X., Marcinkowski, R., Orsi, S., Pohl, M., Rapin, D., Rybka, D., Rutczynska, A., Shi, H. L., Socha, P., Sun, J. C., Song, L. M., Szabelski, J., Traseira, I., Xiao, H. L., Wang, R. J., Wen, X., Wu, B. B., Zhang, L., Zhang, L. Y., Zhang, S. N., Zhang, Y. J., and Zwolinska, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The POLAR detector is a space based Gamma Ray Burst (GRB) polarimeter with a wide field of view, which covers almost half the sky. The instrument uses Compton scattering of gamma rays on a plastic scintillator hodoscope to measure the polarization of the incoming photons. The instrument has been successfully launched on board of the Chinese space laboratory Tiangong~2 on September 15, 2016. The construction of the instrument components is described in this article. Details are provided on problems encountered during the construction phase and their solutions. Initial performance of the instrument in orbit is as expected from ground tests and Monte Carlo simulation.

Published
2017
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4. Wax and wane of the cross-sectional momentum and contrarian effects: Evidence from the Chinese stock markets

Author

Shi, H. -L. and Zhou, W. -X.

Subjects
Quantitative Finance - Statistical Finance, Quantitative Finance - Trading and Market Microstructure
Abstract

This paper investigates the time-varying risk-premium relation of the Chinese stock markets within the framework of cross-sectional momentum and contrarian effects by adopting the Capital Asset Pricing Model and the French-Fama three factor model. The evolving arbitrage opportunities are also studied by quantifying the performance of time-varying cross-sectional momentum and contrarian effects in the Chinese stock markets. The relation between the contrarian profitability and market condition factors that could characterize the investment context is also investigated. The results reveal that the risk-premium relation varies over time, and the arbitrage opportunities based on the contrarian portfolios wax and wane over time. The performance of contrarian portfolios are highly dependent on several market conditions. The periods with upward trend of market state, higher market volatility and liquidity, lower macroeconomics uncertainty are related to higher contrarian profitability. These findings are consistent with the Adaptive Markets Hypothesis and have practical implications for market participants.

Published
2017
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5. Calibration of the Space-borne Compton Polarimeter POLAR flight model with 100% polarized X-ray beams

Author

Xiao, H. L., Hajdas, W., Socha, P., Marcinkowski, R., Wu, B. B., Bao, T. W., Chai, J. Y., Dong, Y. W., Kong, M. N., Li, L., Li, Z. H., Liu, J. T., Shi, H. L., Song, L. M., Sun, J. C., Wang, R. J., Wang, Y. H., Wen, X., Xiong, S. L., Zhang, J., Zhang, L. Y., Zhang, S. N., Zhang, X. F., Zhang, Y. J., Cadoux, F., Pohl, M., Wu, X., Batsch, T., Rybka, D., Rutczynska, A., Szabelski, J., Zwolinska, A., Gauvin, N., Produit, N., and Bernasconi, T.

Subjects
Physics - Instrumentation and Detectors, Astrophysics - Instrumentation and Methods for Astrophysics, Nuclear Experiment
Abstract

POLAR is space-borne detector designed for a precise measurement of gamma-ray polarization of the prompt emissions of Gamma-Ray Bursts in the energy range 50 keV - 500 keV. POLAR is a compact Compton polarimeter consisting of 40$\times$ 40 plastic scintillator bars read out by 25 multi-anode PMTs. In May 2015, we performed a series of tests of the POLAR flight model with 100\% polarized x-rays beams at the European Synchrotron Radiation Facility beam-line ID11 aming to study thresholds, crosstalk between channels and responses of POLAR flight model to polarized X-ray beams. In this paper we present the data analysis method and some analysis results. According the results, POLAR FM has good polarimetric capabilities., Comment: The paper was withdrawn by authors because the work has not yet finshed

Published
2017

6. Gain factor and parameter settings optimization of the new gamma-ray burst polarimeter POLAR

Author

Zhang, X. F., Hajdas, W., Xiao, H. L., Wen, X., Wu, B. B., Bao, T. W., Batsch, T., Bernasconi, T., Cadoux, F., Cernuda, I., Chai, J. Y., Dong, Y. W., Gauvin, N., He, J. J., Kole, M., Kong, M. N., Lechanoine-Leluc, C., Li, L., Li, Z. H., Liu, J. T., Liu, X., Marcinkowski, R., Orsi, S., Pohl, M., Rapin, D., Rybka, D., Shi, H. L., Song, L. M., Sun, J. C., Szabelski, J., Wang, R. J., Wang, Y. H., Wu, X., Xiong, S. L., Xu, M., Zhang, L., Zhang, L. Y., Zhang, P., Zhang, S. N., Zhang, Y. J., and Zwolinska, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors
Abstract

As a space-borne detector POLAR is designed to conduct hard X-ray polarization measurements of gamma-ray bursts on the statistically significant sample of events and with an unprecedented accuracy. During its development phase a number of tests, calibrations runs and verification measurements were carried out in order to validate instrument functionality and optimize operational parameters. In this article we present results on gain optimization togeter with verification data obtained in the course of broad laboratory and environmental tests. In particular we focus on exposures to the $^{137}$Cs radioactive source and determination of the gain dependence on the high voltage for all 1600 detection channels of the polarimeter. Performance of the instrument is described in detail with respect to the dynamic range, energy resolution and temperature dependence. Gain optimization algorithms and response non-uniformity studies are also broadly discussed. Results presented below constitute important parts for development of the POLAR calibration and operation database., Comment: There still some disagreement about one of the conclusions presented in the paper among all the authors

Published
2017

7. POLAR: Final Calibration and In-Flight Performance of a Dedicated GRB Polarimeter

Author

Kole, M., Bao, T. W., Batsch, T., Bernasconi, T., Cadoux, F., Chai, J. Y., Dong, Y. W., Gauvin, N., Hajdas, W., He, J. J., Kong, M. N., Kong, S. W., Lechanoine-Leluc, C., Li, L., Li, Z. H., Liu, J. T., Liu, X., Marcinkowski, R., Orsi, S., Pohl, M., Produit, N., Rapin, D., Rutczynska, A., Rybka, D., Shi, H. L., Song, L. M., Sun, J. C., Szabelski, J., Wang, R. J., Wang, Y. J., Wen, X., Wu, B. B., Wu, X., Xiao, H. L., Xiong, S. L., Xu, H. H., Xu, M., Zhang, J., Zhang, L., Zhang, L. Y., Zhang, S. N., Zhang, X. F., Zhang, Y. J., and Zwolinska, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Gamma-ray polarimetry is a new powerful tool to study the processes responsible for the emission from astrophysical sources and the environments in which this emission takes place. Few successful polarimetric measurements have however been performed thus far in the gamma-ray energy band due to the difficulties involved. POLAR is a dedicated polarimeter designed to perform high precision measurements of the polarization of the emission from gamma-ray burst in the 50-500 keV energy range. This new polarimeter is expected to detect approximately 50 gamma-ray bursts per year while performing high precision polarization measurements on approximately 10 bursts per year. The instrument was launched into lower earth orbit as part of the second Chinese space lab, the Tiangong-2, on September 15th 2016 and has been taking data successfully since being switched on one week after. The instrument uses a segmented scintillator array consisting of 1600 plastic scintillator bars, read out by 25 flat-panel multi-anode photomultipliers, to measure the Compton scattering angles of incoming photons. The small segmentation and relatively large uniform effective area allow the instrument to measure the polarization of a large number of transient events, such as gamma-ray bursts, with an unprecedented precision during its two year life-time. The final flight model underwent detailed calibration prior to launch as well as intensive space qualification tests, a summary of which will be presented in this paper. The instrument design will be discussed first followed by an overview of the on-ground tests, finally the in-orbit behavior as measured during the first weeks of the mission will be presented.

Published
2016

8. A Novel and Universal Method for Measuring Elevation Angle of Large Cylindrical Antennas

Author

Chen, Z. P., Wang, Z., Shi, H. L., Li, F., Wu, Y. K., Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Liang, Qilian, Series Editor, Martin, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zhang, Junjie James, Series Editor, Duan, Baoyan, editor, Umeda, Kazunori, editor, and Hwang, Woonbong, editor

Published
2020
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9. Research on Light-Weight Design and Simulation Analysis of Large Steerable Parabolic Cylindrical Antenna

Author

Chen, Z. P., Wu, Y. K., Shi, H. L., Shou, J. J., Li, F., Wang, Z., Sun, Z. J., Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Liang, Qilian, Series Editor, Martin, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zhang, Junjie James, Series Editor, Duan, Baoyan, editor, Umeda, Kazunori, editor, and Hwang, Woonbong, editor

Published
2020
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10. Calibration of Gamma-ray Burst Polarimeter POLAR

Author

Xiao, H. L., Hajdas, W., Bao, T. W., Batsch, T., Bernasconi, T., Cernuda, I., Chai, J. Y., Dong, Y. W., Gauvin, N., Kole, M., Kong, M. N., Kong, S. W., Li, L., Liu, J. T., Liu, X., Marcinkowski, R., Orsi, S., Pohl, M., Produit, N., Rapin, D., Rutczynska, A., Rybka, D., Shi, H. L., Song, L. M., Sun, J. C., Szabelski, J., Wu, B. B., Wang, R. J., Wen, X., Xu, H. H., Zhang, L., Zhang, L. Y., Zhang, S. N., Zhang, X. F., Zhang, Y. J., and Zwolinska, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors
Abstract

Gamma Ray Bursts (GRBs) are the strongest explosions in the universe which might be associated with creation of black holes. Magnetic field structure and burst dynamics may influence polarization of the emitted gamma-rays. Precise polarization detection can be an ultimate tool to unveil the true GRB mechanism. POLAR is a space-borne Compton scattering detector for precise measurements of the GRB polarization. It consists of a 40$\times$40 array of plastic scintillator bars read out by 25 multi-anode PMTs (MaPMTs). It is scheduled to be launched into space in 2016 onboard of the Chinese space laboratory TG2. We present a dedicated methodology for POLAR calibration and some calibration results based on the combined use of the laboratory radioactive sources and polarized X-ray beams from the European Synchrotron Radiation Facility. They include calibration of the energy response, computation of the energy conversion factor vs. high voltage as well as determination of the threshold values, crosstalk contributions and polarization modulation factors., Comment: 2015 IEEE NSS conference proceedings

Published
2015
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12. Theoretical study on spin-dependent zigzag-direction thermoelectric transport properties of Mn-doped blue phosphorene.

Author

Shi, H. L., Yang, J., Han, Q. Z., Ren, Y. H., Zhao, Y. H., He, S. Y., Gong, L. J., and Jiang, Z. T.

Subjects
*THERMOELECTRIC materials, *SEEBECK coefficient, *THERMOELECTRIC apparatus & appliances, *PHOSPHORENE, *ENERGY bands, *ELECTRONIC structure
Abstract

With the increasing demand for energy, it has become imperative to investigate the thermoelectric properties that can be beneficial to directly converting heat into electric energy. Here, we theoretically study the thermoelectric transport of the Mn-doped blue phosphorene (blue-P) along the zigzag direction. We show that the spin-polarized electronic transport in the blue-P can be produced by the Mn-doping induced half-metallic energy band structure, and the Seebeck coefficients can take positive and negative values, indicating that the main carriers may be holes and electrons. Thus, the spin-down, spin, and charge Seebeck coefficients show a high peak and a deep valley, while the spin and charge thermoelectric figures of merit show two wide peaks. Moreover, the spin and charge thermoelectric figures of merit are found to be so large that the Mn-doped blue-P along the zigzag direction can be used as good thermoelectric materials. In addition, we consider the effect of the doping concentration on the electronic structure and thermoelectric transport properties. This research should be an important reference for designing spin caloritronic and thermoelectric devices. [ABSTRACT FROM AUTHOR]

Published
2023
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13. Phase separation and stripe patterns in K0.8Fe1.6+xSe2 superconductors

Author

Wang, Z. W., Wang, Z., Song, Y. J., Ma, C., Shi, H. L., Chen, Z., Tian, H. F., Yang, H. X., Chen, G. F., and Li, J. Q.

Subjects
Condensed Matter - Superconductivity
Abstract

Structural investigations on the K0.8Fe1.6+xSe2 superconducting materials have revealed remarkable micro-stripes arising evidently from the phase separation. Two coexisted structural phases can be characterized by modulations of q1 = 1/5[a*+3b*], the antiferromagnetic phase K0.8Fe1.6Se2, and q2 = 1/2[a*+b*], the superconducting phase K0.75Fe2Se2, respectively. These stripe patterns likely result from the anisotropic assembly of superconducting particles along the [110] and [1-10] direction. In addition to the notable stripe structures, a nano-scale phase separation also appears in present superconducting system as clearly observed by high-resolution transmission electron microscopy. Certain notable experimental data obtained in this heterogenous system can be quantitatively explained by the percolation scenario., Comment: 15 pages, 6 figures

Published
2012

14. Collapse of the Fe-vacancy order and successive phase transitions in superconducting KxFe2-ySe2 (0.7 \leg x \leg 0.8, 0.2 \leg y \leg 0.3)

Author

Li, J. Q., Song, Y. J., Yang, H. X., Wang, Z., Shi, H. L., Chen, G. F., Wang, Z. W., Chen, Z., and Tian, H. F.

Subjects
Condensed Matter - Superconductivity
Abstract

The Fe-based superconducting KxFe2-ySe2 (0.6 {\leg} x {\leg} 1, 0.2{\leg} y {\leg} 0.4) compounds, unlike the well-known RFe2As2 (R = Ba, Sr, Ca) superconductors, contain complex structural features and notable physical properties, such as the Fe-vacancy ordering, multi-superconducting transitions and the phase separation[1]. Recent experimental studies also suggested the presence of remarkable interplay among the Fe-vacancy order and the antiferromagnetic structure[2]. Here we demonstrate that the well-characterized superconducting KxFe2-ySe2 (0.6 {\leg} x {\leg} 0.8, 0.2 {\leg} x {\leg} 0.3) samples contain complex microstructure features and undergo successive phase transitions at low temperatures. In-situ TEM observations on a number of the KxFe2-ySe2 superconductors demonstrated the presence of a remarkable collapse of the Fe-vacancy order above the superconducting transition, as a result, the superconducting phase actually adopts a tetragonal structure without the Fe-vacancy ordering. Moreover, our analysis at the low temperatures suggests that the superconductors likely adopt a Fe-deficient structure with composition of K0.75Fe2-ySe2. These results are important not only for the further optimization of superconducting phase in present system but also for understanding the mechanism of the Fe-based superconductivity., Comment: 15 pages, 4 figures

Published
2011

15. Phase transition, superstructure and physical properties of K2Fe4Se5

Author

Song, Y. J., Wang, Z., Wang, Z. W., Shi, H. L., Chen, Z., Tian, H. F., Chen, G. F., Yang, H. X., and Li, J. Q.

Subjects
Condensed Matter - Superconductivity
Abstract

The structural features and physical properties of the antiferromagnetic K0.8Fe1.6Se2 (so called K2Fe4Se5 phase) have been studied in the temperature range from 300K up to 600K. Resistivity measurements on both single crystal and polycrystalline samples reveal a semiconducting behavior. Structural investigations of K2Fe4Se5 by means of transmission electron microscopy and powder x-ray diffraction demonstrate the presence of a well-defined superstructure within the a-b plane originating from a Fe-vacancy order along the [130] direction. Moreover, in-situ heating structural analysis shows that K0.8Fe1.6Se2 undergoes a transition of the Fe-vacancy order to disorder at about 600K. The phase separation and the Fe-vacancy ordering in the superconducting materials of KxFe2-ySe2 (0.2 \leq y \leq 0.3) has been briefly discussed., Comment: 17pages, 5 figures, 1 table

Published
2011
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16. Synthesis, Structure and Magnetic Properties of New Layered Iron-Oxychalcogenide Na2Fe2OSe2

Author

He, J. B., Wang, D. M., Shi, H. L., Yang, H. X., Li, J. Q., and Chen, G. F.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

A new layered iron-oxychalcogenide Na2Fe2OSe2 has been synthesized and structurally characterized by powder X-ray diffraction. The structure is formed by alternate stacking of the newly discovered [Fe2OSe2] blocks and double layers of Na. Conductivity study shows that Na2Fe2OSe2 is a semiconductor with activation energy of 0.26 eV. Magnetic susceptibility and heat capacity measurements reveal an antiferromagnetic phase transition occurs at TN=73 K. A broad maximum of magnetic susceptibility and a slow decay of the specific heat above TN, arises as a result of two-dimensional short-range spin correlation., Comment: 4 pages, 4 figures

Published
2011
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17. Microstructure and Fe-vacancy ordering in the KFexSe2 superconducting system

Author

Wang, Z., Song, Y. J., Shi, H. L., Wang, Z. W., Chen, Z., Tian, H. F., Chen, G. F., Guo, J. G., Yang, H. X., and Li, J. Q.

Subjects
Condensed Matter - Superconductivity
Abstract

Structural investigations by means of transmission electron microscopy (TEM) on KFexSe2 with 1.5 \leq x \leq 1.8 have revealed a rich variety of microstructure phenomena, the KFe1.5Se2 crystal often shows a superstructure modulation along the [310] zone-axis direction, this superstructure can be well interpreted by the Fe-vacancy order within the a-b plane. Increase of Fe-concentration in the KFexSe2 materials could not only result in the appearance of superconductivity but also yield clear alternations of microstructure. Structural inhomogeneity, the complex superstructures and defect structures in the superconducting KFe1.8Se2 sample have been investigated based on the high-resolution TEM., Comment: 13 pages, 4 figures

Published
2011
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18. Structural properties and superconductivity of SrFe2As2-xPx and CaFe2As2-yPy

Author

Shi, H. L., Yang, H. X., Tian, H. F., Lu, J. B., Wang, Z. W., Qin, Y. B., Song, Y. J., and Li*, J. Q.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons
Abstract

The SrFe2As2-xPx and CaFe2As2-yPy materials were prepared by a solid state reaction method. X-ray diffraction measurements indicate the single-phase samples can be successfully obtained for SrFe2As2-xPx and CaFe2As2-yPy samples. Clear contraction of the lattice parameters are clearly determined due to the relatively smaller P ions substation for As. The SDW instability associated with tetragonal to orthorhombic phase transition is suppressed visibly in both systems following with the increase of P contents. The highest superconducting transitions are respectively observed at about 27 K in SrFe2As1.3P0.7 and at about 13 K in CaFe2As1.7P0.3., Comment: 11 pages, 5 figures, 2 tables

Published
2009
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19. Phase separation and ferroelectric ordering in charge frustrated LuFe2O4-x

Author

Yang, H. X., Tian, H. F., Zhang, Y., Qin, Y. B., Zeng, L. J., Ma, C., Shi, H. L., Lu, J. B., and Li, J. Q.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
Abstract

The transmission electron microscopy observations of the charge ordering (CO) which governs the electronic polarization in LuFe2O4-x clearly show the presence of a remarkable phase separation at low temperatures. Two CO ground states are found to adopt the charge modulations of Q1 = (1/3, 1/3, 0) and Q2 = (1/3 + y, 1/3 + y, 3/2), respectively. Our structural study demonstrates that the incommensurately Q2-modulated state is chiefly stable in samples with relatively lower oxygen contents. Data from theoretical simulations of the diffraction suggest that both Q1- and Q2-modulated phases have ferroelectric ordering. The effects of oxygen concentration on the phase separation and electric polarization in this layered system are discussed., Comment: 11 pages, 5 figures

Published
2009
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20. Structural features and tetragonal-orthorhombic phase transition in SrFe2As2 and CaFe2As2

Author

Ma, C., Yang, H. X., Tian, H. F., Shi, H. L, Lu, J. B., Wang, Z. W., Zeng, L. J., Chen, G. F., Wang, N. L., and Li, J. Q.

Subjects
Condensed Matter - Superconductivity
Abstract

The structural properties of the SrFe2As2 and CaFe2As2 compounds have been extensively analyzed by transmission electron microscopy (TEM) from room temperature down to 20K. The experimental results demonstrate that the SrFe2As2 crystal, in consistence with previous x-ray data, has a tetragonal structure at room temperature and undergoes a tetragonal (T)-orthorhombic (O) phase transition at about 210K. Moreover, twinning lamella arising from T-O transition evidently appears in the orthorhombic phase. On the other hand, TEM observations of CaFe2As2 reveal the presence of a pseudo-periodic structural modulation with the periodicity of around 40nm at room temperature. This modulation is likely in connection with the local structural distortions within the Ca layer. In-situ cooling TEM observations of CaFe2As2 reveal the presence of complex domain structures in the low-temperature orthorhombic phase., Comment: 19 pages, 8 figures

Published
2008
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21. Structural properties, defects and structural phase transition in the ROFeM (R=La, Nd; M=As, P) materials

Author

Ma, C., Zeng, L. J., Yang, H. X., Shi, H. L, Che, R. C., Liang, C. Y., Qin, Y. B., Chen, G. F., Ren, Z. A., and Li, J. Q.

Subjects
Condensed Matter - Superconductivity
Abstract

The structural properties of the ROFeM (R=La, Nd; M=As, P) materials have been analyzed by means of electron diffraction, high-resolution transmission-electron microscopy (TEM) and in-situ cooling TEM observations. The experimental results demonstrate that the layered ROFeM crystals often contain a variety of structural defects, such as stacking faults and small-angle boundaries. The in-situ TEM investigations reveal that, in association with the remarkable spin-density-wave (SDW) instability near 150 K, complex structural transitions can be clearly observed in both crystal symmetry and local microstructure features., Comment: 17 pages, 6 figures

Published
2008
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26. Spin-dependent thermoelectric transport properties of Cr-doped blue phosphorene.

Author

Shi, H L, Yang, J, Han, Q Z, Ren, Y H, Zhao, Y H, He, S Y, Gong, L J, and Jiang, Z T

Subjects
*THERMOELECTRIC materials, *PHOSPHORENE, *SEEBECK coefficient, *DOPING agents (Chemistry), *FERMI energy
Abstract

We systematically investigate the thermoelectric (TE) properties of the Cr-doped blue phosphorene (blue-P) along the armchair and zigzag directions. First, we find the semiconducting band structure of the blue-P will become spin-polarized due to the Cr-doping, and can be seriously changed by the doping concentration. Then we show the Seebeck coefficient, the electronic conductance, the thermal conductance, and the figures of merit ZT s are all dependent on the transport directions and doping concentration. However, two pairs of the peaks of the charge and spin ZT s can be always observed with the low-height (high-height) pair on the side of the negative (positive) Fermi energy. In addition, at temperature 300 K the extrema of the charge (spin) ZT s of the blue-P along the two directions are kept to be larger than 22 (90) for the different doping concentrations and will be further enhanced at lower temperature. Therefore, we believe the Cr-doped blue-P should be a versatile high-performance TE material which may be used in the fields of the thermorelectrics and spin caloritronics. [ABSTRACT FROM AUTHOR]

Published
2023
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27. Electronic structures, transport properties, and optical absorption of bilayer blue phosphorene nanoribbons.

Author

Gong, L. J., Shi, H. L., Yang, J., Han, Q. Z., Ren, Y. H., He, S. Y., Zhao, Y. H., and Jiang, Z. T.

Abstract

Based on first-principles density functional theory and nonequilibrium Green's function, we study the electronic band structures, the electronic transport properties, and the optical absorption of bilayer blue phosphorene nanoribbons (BPNRs). Both bilayer armchair BPNRs (a-BPNRs) and zigzag BPNRs (z-BPNRs) behave as semiconductors in the narrow nanoribbon case and metals in the wide nanoribbon case, sharply different from their monolayer counterparts where the monolayer a-BPNRs (z-BPNRs) are always semiconducting (metallic). This indicates that interlayer couplings or the increasing layer number may induce the switching of the conductivity of the monolayer BPNRs, which is absent in graphene and phosphorene nanoribbons. Furthermore, we explore the edge states of the energy bands near Fermi energy, and find that there are almost no pure edge-state band branches in the bilayer BPNRs, which can be attributed to the interlayer couplings between the edge-states in one layer and the bulk-states in the other. Consequently, the resulting complex band structures cannot be directly analyzed any more in the framework of the two-body coupling picture just according to the simple band structures of the monolayer BPNRs. Finally, we present the current–voltage characteristics and the optical absorption of the bilayer a-BPNRs and z-BPNRs. The influences of the nanoribbon width and the interlayer couplings on the current and the anisotropic optical absorption can be understood based on the complex energy band structures. This research should be an important reference of extending the field of BPNRs from the monolayer to the bilayer case, and deepen the understanding of the difference between the monolayer and bilayer nanoribbons in different materials. [ABSTRACT FROM AUTHOR]

Published
2023
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30. A Research Overview of the Siltation Loss Controls and Capacity Recovery Processes in China’s Reservoirs

Author

Hu H H, Deng A J, Chen J G, Shi H L, and Ye M

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

There are many reservoirs in China with serious siltation issues which are affecting the function and safety of the reservoirs. Recently, research studies have been carried out regarding siltation loss control and capacity recovery technology due to the decreases in suitable dam sites for establishing reservoirs, and the increasingly serious siltation losses which have been occurring in the present reservoirs. The results of these studies have been of great significance to the partial recoveries of the siltation capacities of reservoirs, improvements in the respective efficiencies of the current reservoirs, and the prolonging of the service life the reservoirs. This study presented a simple review of the previous research findings regarding the current siltation loss situations and controls, as well as the capacity recoveries which have been achieved. Also, this study proposed the urgent need for in-depth examinations to be conducted pertaining to the national investigations of the reservoir siltation status in China, as well as a review of the current mechanisms and control measures for reservoir siltation losses.

Published
2018
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41. Universalities of anomalous properties in electron transport through different Z-shaped phosphorene nanoribbon devices.

Author

Song, M. R., Shi, H. L., Jiang, Z. T., Ren, Y. H., Yang, J., and Han, Q. Z.

Subjects
*ELECTRON transport, *PHOSPHORENE, *ELECTRONIC equipment, *NANORIBBONS, *LOW voltage systems
Abstract

Aiming at improving the flexibility of designing the phosphorene-based nanodevices, we propose three kinds of Z-shaped phosphorene nanoribbons (ZPNRs), which are composed of two metallic nanoribbon electrodes and one semiconducting/metallic nanoribbon central region (CR). Many anomalous properties including the unexpected current increasing under the low bias voltage, the negative differential conductance, and the transition of the transport mechanism are found to be universal in different ZPNRs. Also, we find the current can be significantly suppressed by increasing the CR length, while no complete suppression can be induced by the increase of the CR width, indicating that the CR length and width will make different influences on the ZPNR transport. Moreover, the energy spectrums of two electrodes, the molecular energy levels of the CR, the transmission coefficients, and the transmission eigenstates are further calculated so as to clearly expound the anomalous properties and their universalities. We believe this research can provide a meaningful guidance for developing the phosphorene-based electronic devices. [ABSTRACT FROM AUTHOR]

Published
2022
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43. Comparison of outcomes of direct-acting oral anticoagulants vs. vitamin K antagonists in patients with bioprosthetic heart valves or valve repair: a systematic review and meta-analysis.

Author

TANG, L.-L., LIANG, S.-W., SHI, H.-L., and YE, J.-J.

Abstract

OBJECTIVE: To compare the outcomes between direct-acting oral anticoagulants and vitamin K antagonists, particularly for risk of stroke and bleeding, among patients with atrial fibrillation (AF) and bioprosthetic heart valve replacement or repair. MATERIALS AND METHODS: A systematic search was conducted in the PubMed, Scopus, Cochrane Database of Systematic Reviews and Google scholar databases. Studies that were done in patients with AF who underwent bioprosthetic heart valve replacement or repair and that compared the outcomes between the use of direct-acting oral anticoagulants (DOACs) and vitamin K antagonists were eligible for inclusion. Studies that were preferably randomized controlled trials or adopted a cohort approach or retrospective data-based studies were considered for inclusion. The strength of association was presented in the form of pooled hazards risk (HR). Statistical analysis was done using STATA version 16.0. RESULTS: A total of 8 articles were included in the meta-analysis. There were no significant differences in the risk of "all-cause stroke" [HR 0.72, 95% CI: 0.39, 1.34] and ischemic stroke [HR 0.79, 95% CI: 0.49, 1.29] between the two groups. The risk of "any bleeding" [HR 0.74, 95% CI: 0.64, 0.87], major bleeding [HR 0.60, 95% CI: 0.42, 0.86] and intra-cranial bleeding [HR 0.54, 95% CI: 0.36, 0.81] was much lower in those that received DOAC compared to warfarin. Compared to those receiving warfarin, those on DOACs had substantially reduced risk of any clinical thromboembolic events [HR 0.52, 95% CI: 0.39, 0.70]. No significant differences were noted for all-cause mortality [HR 0.88, 95% CI: 0.74, 1.05], cardiovascular events/myocardial infarction (MI) [HR 0.58, 95% CI: 0.33, 1.04] and and readmission rates [HR 0.85, 95% CI: 0.62, 1.18]. CONCLUSIONS: Findings suggest that the use DOACs in patients with AF with bioprosthetic valve replacement or repair is comparatively better than vitamin K antagonists in reducing the risk of bleeding and thrombo-embolic events. Future studies with a randomized design and larger sample sizes are needed to further substantiate these findings. [ABSTRACT FROM AUTHOR]

Published
2021

47. Performance study of the gamma-ray bursts polarimeter POLAR

Author

Sun, J. C., additional, Wu, B. B., additional, Bao, T. W., additional, Batsch, T., additional, Bernasconi, T., additional, Britvitch, I., additional, Cadoux, F., additional, Cernuda, I., additional, Chai, J. Y., additional, Dong, Y. W., additional, Gauvin, N., additional, Hajdas, W., additional, He, J. J., additional, Kole, M., additional, Kong, M. N., additional, Kong, S. W., additional, Lechanoine-Leluc, C., additional, Li, Lu, additional, Liu, J. T., additional, Liu, X., additional, Marcinkowski, R., additional, Orsi, S., additional, Pohl, M., additional, Produit, N., additional, Rapin, D., additional, Rutczynska, A., additional, Rybka, D., additional, Shi, H. L., additional, Song, L. M., additional, Szabelski, J., additional, Wang, R. J., additional, Wen, X., additional, Xiao, H. L., additional, Xiong, S. L., additional, Xu, H. H., additional, Xu, M., additional, Zhang, L., additional, Zhang, L. Y., additional, Zhang, S. N., additional, Zhang, X. F., additional, Zhang, Y. J., additional, and Zwolinska, A., additional

Published
2016
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49. Calibration of gamma-ray burst polarimeter POLAR

Author

Xiao, H. L., primary, Hajdas, W., additional, Bao, T. W., additional, Batsch, T., additional, Bernasconi, T., additional, Cernuda, I., additional, Chai, J. Y., additional, Dong, Y. W., additional, Gauvin, N., additional, Kole, M., additional, Kong, M. N., additional, Kong, S. W., additional, Li, L., additional, Liu, J. T., additional, Liu, X., additional, Marcinkowski, R., additional, Orsi, S., additional, Pohl, M., additional, Produit, N., additional, Rapin, D., additional, Rutczynska, A., additional, Rybka, D., additional, Shi, H. L., additional, Song, L. M., additional, Sun, J. C., additional, Szabelski, J., additional, Wu, B. B., additional, Wang, R. J., additional, Wen, X., additional, Xu, H. H., additional, Zhang, L., additional, Zhang, L. Y., additional, Zhang, S. N., additional, Zhang, X. F., additional, Zhang, Y. J., additional, and Zwolinska, A., additional

Published
2015
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