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256 results on '"Chen, Xi-Meng"'

8. Study of a Prototype VP-PET Imaging System Based on highly Pixelated CdZnTe Detectors

Author

Ye, Zheng-Qian, Li, Ying-Guo, Wang, Tian-Quan, Fan, Ya-Ming, Yin, Yong-Zhi, and Chen, Xi-Meng

Subjects
Physics - Medical Physics, Physics - Instrumentation and Detectors
Abstract

We are investigating a prototype virtual pinhole positron emission tomography (VP-PET) system for small animal imaging applications. The PET detector modules were made up of 1.3 mm lutetium-yttrium oxyorthosilicate (LYSO) arrays, and the insert detectors consists of 0.6 mm pixelated Cadmium Zinc Telluride (CdZnTe). To validate the imaging experiment, we conducted a Monte Carlo simulation for the VP-PET system in Geant4 Application for Emission Tomography (GATE). For a point source of Na-22 with 0.5 mm diameter, the filtered back-projection (FBP) algorithm reconstructed PET image shows a resolution of 0.7 mm full-width-at-half-maximum (FWHM). The system sensitivity is 0.46 cps/kBq at the center of field view (CFOV) of the PET system with a source activity of 0.925 MBq and an energy resolution of 350-650 keV. A rod source phantom and a Derenzo phantom with F-18 were also simulated to investigate the PET imaging capability. GATE simulation indicated that two point sources with 0.5 mm diameter 2 mm apart could be clearly separated using 0.6 mm pixelated CdZnTe detectors as insert devices in a VP-PET system., Comment: 13 pages, 7 figures

Published
2018

11. Study on neutron radiation field of carbon ions therapy

Author

Xu, Jun-Kui, Su, You-Wu, Li, Wu-Yuan, Yan, Wei-Wei, Chen, Xi-Meng, Mao, Wang, and Pang, Cheng-Guo

Subjects
Physics - Medical Physics, Nuclear Experiment, Physics - Instrumentation and Detectors
Abstract

Carbon ions offer significant advantages for deep-seated local tumors therapy due to their physical and biological properties. Secondary particles, especially neutrons caused by heavy ion reactions should be carefully considered in treatment process and radiation protection. For radiation protection purposes, the FLUKA Code was used in order to evaluate the radiation field at deep tumor therapy room of HIRFL in this paper. The neutron energy spectra, neutron dose and energy deposition of carbon ion and neutron in tissue-like media was studied for bombardment of solid water target by 430MeV/u C ions. It is found that the calculated neutron dose have a good agreement with the experimental date, and the secondary neutron dose may not exceed one in a thousand of the carbon ions dose at Bragg peak area in tissue-like media.

Published
2015
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12. Selective synthesis of the B11H14− and B12H122− borane derivatives and the general mechanisms of the B-H bond condensation.

Author

Jing, Yi, Wang, Xinghua, Han, Hui, Liu, Xin-Ran, Yu, Xing-Chao, Chen, Xi-Meng, Wei, Donghui, Wang, Lai-Sheng, and Chen, Xuenian

Abstract

Polyhedral boranes are a class of well-known boron molecular clusters with unique physical and chemical properties, and great efforts have been made in the past decades to find more effective synthetic methods. However, the established synthetic methods suffer from low efficiency and low selectivity because the mechanism of the B–H bond condensation reaction, critical for the synthesis of the polyhedral boranes, is not well understood. Here we report highly selective and efficient synthetic methods of the salts of the tetradecahydridoundecaborate (1–) (B11H14−) and dodecahydrido-dodecaborates (2–) (B12H122−) anions by employing commercially available and inexpensive starting materials. Both theoretical and experimental investigations are carried out to elucidate the reaction mechanisms. We have found that the nature of the B–H bond condensation is the dihydrogen bonding interaction in which the positively charged hydrogens (bridged hydrogens) play a crucial role. The current study has not only led to more effective and selective synthetic methods for B11H14− and B12H122− but also unveiled the nature of the B–H bond condensation and the general formation mechanisms of polyhedral boranes. This finding will facilitate the development of more effective synthetic methods for polyhedral boranes and spur their wide application. [ABSTRACT FROM AUTHOR]

Published
2024
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13. Position reconstruction in fission fragment detection using the low pressure MWPC technique for the JLab experiment E02-017

Author

Qiu, Xi-Yu, Tang, L., Margaryan, A., Hu, Bi-Tao, and Chen, Xi-Meng

Subjects
Physics - Instrumentation and Detectors, Nuclear Experiment
Abstract

When a lambda hyperon was embedded in a nucleus, it can form a hypernucleus. The lifetime and its mass dependence of stable hypernuclei provide information about the weak decay of lambda hyperon inside nuclear medium. This work will introduce the Jefferson Lab experiment (E02-017) which aims to study the lifetime of the heavy hypernuclei using a specially developed fission fragment detection technique, a multi-wire proportional chamber operated under low gas pressure (LPMWPC). Presented here are the method and performance of the reconstruction of fission position on the target foil, the separation of target materials at different regions and the comparison and verification with the Mote Carlo simulation., Comment: 10 pages

Published
2013
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14. Frozen Gaussian quantum discord in photonic crystal cavity array system

Author

Lü, Ying-Qi, An, Jun-Hong, Chen, Xi-Meng, Luo, Hong-Gang, and Oh, C. H.

Subjects
Quantum Physics
Abstract

Protecting quantum correlation from decoherence is one of the crucial issues in quantum information processing. It has been commonly recognized that any initial quantum correlation of a composite system diminishes asymptotically or abruptly to zero under local Markovian decoherence. Here we show that, contrary to this recognition, a noticeable Gaussian quantum discord of a continuous-variable bipartite system can be frozen in the steady state in the non-Markovian dynamics if each of the subsystems forms a localized mode with its local reservoir. The condition for this frozen quantum discord can be reached by appropriately engineering the structure of the reservoirs. The possible realization of our results in a coupled cavity array system formed by a photonic crystal is proposed., Comment: 6 pages, 5 figures

Published
2013
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15. Effect of the momentum dependence of nuclear symmetry potential on pion-/pion+ ratio in heavy-ion collisions

Author

Gao, Yuan, Zhang, Lei, Zhang, Hong-Fei, Chen, Xi-Meng, and Yong, Gao-Chan

Subjects
Nuclear Theory, Astrophysics - Cosmology and Extragalactic Astrophysics, Nuclear Experiment
Abstract

In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, effect of the momentum dependence of nuclear symmetry potential on pion-/pion+ ratio in the neutron-rich reaction 132Sn+124Sn at a beam energy of 400 MeV/nucleon is studied. We find that the momentum dependence of nuclear symmetry potential affects the compressed density of colliding nuclei, numbers of produced pion- and pion+, as well as the value of pion-/pion+ ratio. The momentum dependent nuclear symmetry potential increases the compressed density of colliding nuclei, numbers of produced resonances delta(1232), N*(1440), pion- and pion+, as well as the value of pion-/pion+ ratio., Comment: 4 pages, 3 figures, accepted by PRC

Published
2011
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16. An improved method for the synthesis and formation mechanism of M2B10H14 based on the reactions of B10H14 with MNH2BH3 (M = Na, K).

Author

Chen, Xi-Meng, Yu, Xing-Chao, Chi, Jing-Xian, Jing, Yi, Wang, Hongju, Zhang, Na, Zhang, Chen, Ge, Yi-Wen, and Chen, Xuenian

Subjects
*HYDRIDES, *ANIONS, *PROTONS
Abstract

An efficient method for the synthesis of M2B10H14 (M = Na and K) has been developed. The two possible formation mechanisms of the B10H142− anion are proposed, in which the NH2BH3− anion acts as a proton abstractor and a hydride donor. Furthermore, the B10H13− and B10H15− intermediates were detected. [ABSTRACT FROM AUTHOR]

Published
2023
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35. Selective synthesis of the B11H14−and B12H122−borane derivatives and the general mechanisms of the B-H bond condensation

Author

Jing, Yi, Wang, Xinghua, Han, Hui, Liu, Xin-Ran, Yu, Xing-Chao, Chen, Xi-Meng, Wei, Donghui, Wang, Lai-Sheng, and Chen, Xuenian

Abstract

Polyhedral boranes are a class of well-known boron molecular clusters with unique physical and chemical properties, and great efforts have been made in the past decades to find more effective synthetic methods. However, the established synthetic methods suffer from low efficiency and low selectivity because the mechanism of the B–H bond condensation reaction, critical for the synthesis of the polyhedral boranes, is not well understood. Here we report highly selective and efficient synthetic methods of the salts of the tetradecahydridoundecaborate (1–) (B11H14−) and dodecahydrido-dodecaborates (2–) (B12H122−) anions by employing commercially available and inexpensive starting materials. Both theoretical and experimental investigations are carried out to elucidate the reaction mechanisms. We have found that the nature of the B–H bond condensation is the dihydrogen bonding interaction in which the positively charged hydrogens (bridged hydrogens) play a crucial role. The current study has not only led to more effective and selective synthetic methods for B11H14−and B12H122−but also unveiled the nature of the B–H bond condensation and the general formation mechanisms of polyhedral boranes. This finding will facilitate the development of more effective synthetic methods for polyhedral boranes and spur their wide application.

Published
2023
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38. Synthesis of K[B3H7NH2BH2NH2B3H7] for a K-ion solid-state electrolyte.

Author

Chen, Xi-Meng, Jia, Si-Han, Kang, Jia-Xin, Zhang, Yichun, Ma, Yubin, Ma, Yiming, Jiang, Xin, Yu, Xing-Chao, Qiu, Pengtao, and Chen, Xuenian

Subjects
*SOLID electrolytes, *GRID energy storage, *ELECTRIC potential, *RENEWABLE energy sources
Abstract

All-solid-state K batteries are ideal energy storage devices for grid-scale applications of renewable energies. A novel electrolyte K[B3H7NH2BH2NH2B3H7] with weakly coordinating anions was synthesized. It has a high K+ conductivity of 1.01 × 10−4 S cm−1 at 75 °C, which is probably due to the increased electrostatic potential and size of the anions. [ABSTRACT FROM AUTHOR]

Published
2022
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45. Transmission of low-energy Cl– ions through Al2O3 insulating nanocapillaries

Author

Ha, Shuai, primary, Zhang, Wen-Ming, additional, Xie, Yi-Ming, additional, Li, Peng-Fei, additional, Jin, Bo, additional, Niu, Ben, additional, Wei, Long, additional, Zhang, Qi, additional, Liu, Zhong-Lin, additional, Ma, Yue, additional, Lu, Di, additional, Wan, Cheng-Liang, additional, Cui, Ying, additional, Zhou, Peng, additional, Zhang, Hong-Qiang, additional, and Chen, Xi-Meng, additional

Published
2020
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48. Synthesis and Dehydrogenation of Organic Salts of a Five‐Membered B/N Anionic Chain, a Novel Ionic Liquid.

Author

Chen, Xi‐Meng, Jiang, Xin, Jing, Yi, and Chen, Xuenian

Subjects
*IONIC liquids, *ORGANIC synthesis, *METATHESIS reactions, *CATALYTIC hydrolysis, *MELTING points, *ELEMENTAL analysis
Abstract

We have synthesized the tetrabutylammonium ([Bu4N]+), tetraethylammonium ([Et4N]+), guanidinium ([C(NH2)3]+), and methylguanidinium ([C(N3H5CH3)]+) salts of the [BH3(NH2BH2)2H]− anion, a five‐membered B/N anionic chain, in high yields by the metathesis reactions of Na[BH3(NH2BH2)2H] with the corresponding halides and characterized them by NMR (11B, 11B{1H}, 1H, 1H{11B}, 13C), IR, elemental analysis, TGA‐DSC, and TGA‐MS. These complexes behave like ionic liquids (ILs), in which the melting point of the [Bu4N][BH3(NH2BH2)2H] is the lowest (−51 °C). The dehydrogenation of these ILs have been studied through the thermal decomposition and catalytic hydrolysis in aqueous solution using the noble or non‐noble metals or their salts as catalysts, and the results indicate that these ILs of five‐membered B/N anionic chain are promising hydrogen storage materials. [ABSTRACT FROM AUTHOR]

Published
2021
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49. KB3H8·NH3B3H7Complex as a Potential Solid-State Electrolyte with Excellent Stability against K Metal

Author

Zhang, Yichun, Qiu, Pengtao, Zheng, Jingfeng, Chen, Xinwei, Chen, Xi-Meng, Li, Shouhu, Ji, Chenchen, Wu, Yiying, and Chen, Xuenian

Abstract

All-solid-state potassium batteries are promising candidates in the fields of large-scale energy storage owing to their intrinsic safety, stability, and cost-effectiveness. However, a suitable solid-state electrolyte with high ionic conductivity and favorable interfacial stability is a major challenge for the design and development of these batteries. Herein, we report the synthesis of new KB3H8·nNH3B3H7(n= 0.5 and 1) complexes to develop suitable solid-state K-ion conductors for batteries. Both the complexes undergo a reversible phase transition below the thermal decomposition temperature. The optimal KB3H8·NH3B3H7delivers a solid-state K-ion conductivity of 1.3 × 10–4S cm–1at 55 °C with an activation energy of 0.44 eV after a transition from a monoclinic to an orthorhombic phase, which is the highest value of K borohydrides reported to date and places KB3H8·NH3B3H7among the leading solid-state K-ion conductors. Moreover, KB3H8·NH3B3H7reveals a K-ion transference number of nearly 0.93, an electrochemical stability window of 1.2 to 3.5 V vs K+/K, a good capability of K dendrite suppression, and a remarkable stability against the K metal anode due to the formation of the stable interface. These performances make KB3H8·NH3B3H7a promising electrolyte for all-solid-state potassium batteries.

Published
2022
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