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1. chinaXiv:202201.00035 [pdf]

基于氘核碎裂的高能中子束的产生机制的研究

Wang, Rensheng; Ou, Li; Xiao, Zhigang
Subjects: Physics >> Nuclear Physics

在改进的量子分子动力学模型框架下,研究了高能氘核在重靶核作用下的碎裂过程,尤其近零度角产生的中子。模拟重现了 102 MeV d+C 反应中实验测量的中子双微分截面。根据模型与实验结果的一致性,论证了通过氘核在碳靶上碎裂而产生高能中子束的可行性。但因氘核内部核子的费米运动,使得包含实验室0°在内的中子能量具有相当大的能量展宽。基于模型计算,通过测量氘核碎裂过程中出射的伴随质子,出射中子能量可约束在5%(1σ)以内。进一步,本工作论证了基于伴随质子测量的单能高能中子束产生的可行性。

submitted time 2022-01-07 Hits2495Downloads150 Comment 0

2. chinaXiv:202201.00014 [pdf]

Application of homogenization techniques for inflow transport approximation on light water reactor analysis

Xiao, Xiang ; Wang, Kan ; Yang, Tong-Rui ; Chen, Yi-Xue
Subjects: Nuclear Science and Technology >> Engineering Technology of Fission Reactor

The transport cross-section based on inflow transport approximation can significantly improve the accuracy of light water reactor (LWR) analysis, especially for the treatment of the anisotropic scattering effect. The previous inflow transport approximation is based on the moderator cross-section and normalized fission source, which is approximated using transport theory. Although the accuracy of reactivity is increased, the P0 flux moment has a large error in the Monte Carlo code. In this study, an improved inflow transport approximation was introduced with homogenization techniques, applying the homogenized cross-section and accurate fission source. The numerical results indicated that the improved inflow transport approximation can increase the P0 flux moment accuracy and maintain the reactivity calculation precision with the previous inflow transport approximation in typical LWR cases. In addition to this investigation, the improved inflow transport approximation is related to the temperature factors. The improved inflow transport approximation is flexible and accurate in the treatment of the anisotropic scattering effect, which can be directly used in the temperature-dependent nuclear data library.

submitted time 2021-12-31 From cooperative journals:《Nuclear Science and Techniques》 Hits644Downloads59 Comment 0

3. chinaXiv:202109.00068 [pdf]

Fluidic Endogenous Magnetism and Magnetic Monopole Clues from Liquid Metal Droplet Machine

Zhou, Ying-Xin; Zu, Jia-Sheng; Liu, Jing
Comment:31 Pages, 14 Figures
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics

磁和磁单极子是物理学中的经典问题。传统磁体通常由刚性材料组成,在回答极端问题时可能面临挑战。这里,我们首次从不同于刚性磁体的导电性流体物质出发,提出通过调控液态金属机器来产生流态化内生磁性并由此构造磁单极子。基于理论解释和概念性实验证据,我们阐明了当溶液中的镓基液态金属在电驱动下发生旋转时,其内部会形成一个内生磁场,这很好地解释了两个这样分离的金属液滴能很容易融合在一起的实验现象,原因在于二者通过各自对应的N极和S极相互吸引。此外,我们还阐明了自驱动型液态金属机器也以一种内生流态化磁体出现且具有电磁同源性;当溶液中的液态镓吞食铝时,会形成一个旋转马达和在体动态变化的电荷分布,从而在内部产生内生磁性;这就解释了运动中的液态金属马达之间经常发生反射性碰撞和吸引性融合的现象,这两种现象分别是由于马达之间N极和S极的动态调整引起的。最后,我们设想可通过这种流态化内生磁体制造磁单极子,并提出了实现这一目标的四条技术路线:1. 匹配液态金属机器的内部流场;2. 基于外电场效应与磁场的叠加效应;3. 借助磁颗粒与液态金属马达之间的复合结构;4. 化学途径,如通过原电池反应。总的来说,本文理论和提供的实验证据揭示了液态金属机器作为流体型内生磁体的机制,并指出了实现磁单极的一些有希望的途径。在不久的将来,在此基础上建立一些非传统型磁电器件和应用是可能的。

submitted time 2021-09-27 Hits6492Downloads454 Comment 1

4. chinaXiv:202107.00039 [pdf]

Tracing the origin of SARS-CoV-2: lessons learned from the past

Qihui Wang; Hua Chen; Yi Shi; Alice C. Hughes; William J. Liu; Jingkun Jiang; George F. Gao; Yongbiao Xue; Yigang Tong
Subjects: Biology >> Virology

新冠病毒的起源仍不清楚。了解新冠病毒如何、何时以及在何处从其天然宿主传播给人类对于预防未来由冠状病毒引发的疫情至关重要。 从与病原体无休止的战斗中吸取教训,结合目前已知的关于新冠病毒起源和中间宿主的研究数据,我们提出全球多个地点都有可能是新冠病毒的起源地。

submitted time 2021-07-28 Hits13586Downloads1575 Comment 0

5. chinaXiv:201905.00012 [pdf]

Transfer Learning for Scientific Data Chain Extraction in Small Chemical Corpus with BERT-CRF Model

Na Pang; Li Qian; Weimin Lyu; Jin-Dong Yang
Subjects: Computer Science >> Natural Language Understanding and Machine Translation

Abstract. Computational chemistry develops fast in recent years due to the rapid growth and breakthroughs in AI. Thanks for the progress in natural language processing, researchers can extract more fine-grained knowledge in publications to stimulate the development in computational chemistry. While the works and corpora in chemical entity extraction have been restricted in the biomedicine or life science field instead of the chemistry field, we build a new corpus in chemical bond field anno- tated for 7 types of entities: compound, solvent, method, bond, reaction, pKa and pKa value. This paper presents a novel BERT-CRF model to build scientific chemical data chains by extracting 7 chemical entities and relations from publications. And we propose a joint model to ex- tract the entities and relations simultaneously. Experimental results on our Chemical Special Corpus demonstrate that we achieve state-of-art and competitive NER performance.

submitted time 2019-05-12 Hits23988Downloads1647 Comment 0

6. chinaXiv:201810.00184 [pdf]

Simulating hydrological responses to climate change using dynamic and statistical downscaling methods: a case study in the Kaidu River Basin, Xinjiang, China

BA Wulong; DU Pengfei; LIU Tie; BAO Anming; LUO Min; Mujtaba HASSAN; QIN Chengxin
Subjects: Geosciences >> History of Geosciences

Climate change may affect water resources by altering various processes in natural ecosystems. Dynamic and statistical downscaling methods are commonly used to assess the impacts of climate change on water resources. Objectively, both methods have their own advantages and disadvantages. In the present study, we assessed the impacts of climate change on water resources during the future periods (2020–2029 and 2040–2049) in the upper reaches of the Kaidu River Basin, Xinjiang, China, and discussed the uncertainties in the research processes by integrating dynamic and statistical downscaling methods (regional climate models (RCMs) and general circulation modes (GCMs)) and utilizing these outputs. The reference period for this study is 1990–1999. The climate change trend is represented by three bias-corrected RCMs (i.e., Hadley Centre Global Environmental Model version 3 regional climate model (HadGEM3-RA), Regional Climate Model version 4 (RegCM4), and Seoul National University Meso-scale Model version 5 (SUN-MM5)) and an ensemble of GCMs on the basis of delta change method under two future scenarios (RCP4.5 and RCP8.5). We applied the hydrological SWAT (Soil and Water Assessment Tool) model which uses the RCMs/GCMs outputs as input to analyze the impacts of climate change on the stream flow and peak flow of the upper reaches of the Kaidu River Basin. The simulation of climate factors under future scenarios indicates that both temperature and precipitation in the study area will increase in the future compared with the reference period, with the largest increase of annual mean temperature and largest percentage increase of mean annual precipitation being of 2.4°C and 38.4%, respectively. Based on the results from bias correction of climate model outputs, we conclude that the accuracy of RCM (regional climate model) simulation is much better for temperature than for precipitation. The percentage increase in precipitation simulated by the three RCMs is generally higher than that simulated by the ensemble of GCMs. As for the changes in seasonal precipitation, RCMs exhibit a large percentage increase in seasonal precipitation in the wet season, while the ensemble of GCMs shows a large percentage increase in the dry season. Most of the hydrological simulations indicate that the total stream flow will decrease in the future due to the increase of evaporation, and the maximum percentage decrease can reach up to 22.3%. The possibility of peak flow increasing in the future is expected to higher than 99%. These results indicate that less water is likely to be available in the upper reaches of the Kaidu River Basin in the future, and that the temporal distribution of flow may become more concentrated.

submitted time 2018-10-29 From cooperative journals:《Journal of Arid Land》 Hits4988Downloads1533 Comment 0

7. chinaXiv:201801.00588 [pdf]

Inverse Problem and Variation Method to Optimize Cascade Heat Exchange Network in Central Heating System

ZHANG Yin1,2*, WEI Zhiyuan2, ZHANG Yinping2, WANG Xin2
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics

Urban heating in northern China accounts for 40% of total building energy usage. In central heating systems, heat is often transferred from heat source to users by the heat network where several heat exchangers are installed at heat source, substations and terminals respectively. For given overall heating capacity and heat source temperature, increasing the terminal fluid temperature is an effective way to improve the thermal performance of such cascade heat exchange network for energy saving. In this paper, the mathematical optimization model of the cascade heat exchange network with three-stage heat exchangers in series is established. Aim at maximizing the cold fluid temperature for given hot fluid temperature and overall heating capacity, the optimal heat exchange area distribution and the medium fluids' flow rates are determined through inverse problem and variation method. The preliminary results show that the heat exchange areas should be distributed equally for each heat exchanger. It also indicates that in order to improve the thermal performance of the whole system, more heat exchange areas should be allocated to the heat exchanger where flow rate difference between two fluids is relatively small. This work is important for guiding the optimization design of practical cascade heating systems.

submitted time 2018-01-24 From cooperative journals:《热科学学报》 Hits44554Downloads1309 Comment 0

8. chinaXiv:201711.02257 [pdf]

Insight-HXMT observations of the first binary neutron star merger GW170817

TiPei Li; ShaoLin Xiong; ShuangNan Zhang; FangJun Lu; LiMing Song; XueLei Cao; Zhi Chang; Gang Chen; Li Chen; TianXiang Chen; Yong Chen; YiBao Chen; YuPeng Chen; Wei Cui; WeiWei Cui; JingKang Deng; YongWei Dong; YuanYuan Du; MinXue Fu; GuanHua Gao
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Finding the electromagnetic (EM) counterpart of binary compact star merger, especially the binary neutron star (BNS) merger, is critically important for gravitational wave (GW) astronomy, osmology and fundamental physics. On Aug. 17, 2017, Advanced LIGO and Fermi/GBM independently triggered the first BNS merger, GW170817, and its high energy EM counterpart, GRB 170817A, respectively, resulting in a global observation campaign covering gamma-ray, X-ray, UV, optical, IR, radio as well as neutrinos. The High Energy X-ray telescope (HE) onboard Insight-HXMT (Hard X-ray Modulation Telescope) is the unique high-energy gamma-ray telescope that monitored the entire GW localization area and especially the optical counterpart (SSS17a/AT2017gfo) with very large collection area (~1000 cm2) and microsecond time resolution in 0.2-5 MeV. In addition, Insight-HXMT quickly implemented a Target of Opportunity (ToO) observation to scan the GW localization area for potential X-ray emission from the GW source. Although Insight-HXMT did not detect any significant high energy (0.2-5 MeV) radiation from GW170817, its observation helped to confirm the nexpected weak and soft nature of GRB 170817A. Meanwhile, Insight-HXMT/HE provides one of the most stringent constraints (~10-7 to 10-6 erg/cm2/s) for both GRB170817A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger. Therefore the observation of Insight-HXMT constitutes an important chapter in the full context of multi-wavelength and multi-messenger observation of this historical GW event.

submitted time 2017-11-10 Hits1975Downloads1071 Comment 0

9. chinaXiv:201711.02292 [pdf]

Analytic Forms for Cross Sections of Di-lepton Production from e+e? Collisions around the J/ψ Resonance

Xing-Yu Zhou; Ya-Di Wang; Li-Gang Xia
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

A detailed theoretical derivation of the cross sections of e+e? → e+e? and e+e? → ?+?? around the J/ψ resonance is reported. The resonance and interference parts of the cross sections, related to J/ψ resonance parameters, are calculated. Higher-order corrections for vacuum polarization and initial-state radiation are consid-ered. An arbitrary upper limit of radiative correction integration is involved. Full and simpli?ed versions of analytic formulae are given with precision at the level of 0.1% and 0.2%, respectively. Moreover, the results obtained in the paper can be applied to the case of the ψ(3686) resonance.

submitted time 2017-11-10 Hits1758Downloads994 Comment 0

10. chinaXiv:201705.00046 [pdf]

Evaluation of PHBHHx and PHBV/PLA fibers used as medical sutures

He, Y [He, Yu][ 1 ]; Hu, ZW [Hu, Zhiwei][ 2 ]; Ren, MD [Ren, Mengda][ 1 ]; Ding, CK [Ding, Changkun][ 3 ]; Chen, P [Chen, Peng][ 4 ]; Gu, Q [Gu, Qun][ 4 ]; Wu, Q [Wu, Qiong][ 1,5,6 ]
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Two types of fibers were prepared by using bio- based materials: a mono-filament made from poly(3- hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and a multi-filament made from poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV) and polylactic acid (PLA) blend. The two fibers were evaluated for mechanical properties, biocompatibility and degradability for the potential appli- cation as medical sutures. The PHBHHx fiber showed remarkable biocompatibility by H.E. Stainning, with very little impact to the surrounding tissues. The degradation of the fiber was observed by SEM after implantation for 36 weeks, and the major degradation product was detected after 96 weeks. Consistently, the PHBHHx fiber main- tained more than half of the mechanical properties after 96 weeks. The other fiber was prepared by twisting PHBV/PLA blend strands to a bunch, and showed high biocom- patibility and relatively high degradability. The bunched structure loosed after 36 weeks of implantation. These low- cost and easily prepared fibers have great potential in medical applications, since they could avoid the formation of fibrous capsule, reduce the size of scar, and degrade into non-toxic and even beneficial products.

submitted time 2017-05-02 Hits1547Downloads894 Comment 0

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