Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Information Science and Systems Science >> Basic Disciplines of Information Science and Systems Science submitted time 2024-06-05
Wenlong Sun
Fengfeng Shi
Yuting Lin
Jinfeng Xu
Shaofeng He
Yongxin Lin
Guocheng Wang
Run Zhao
Pei Ma
Abstract： The precise estimation of the satellite clock bias (SCB) holds considerable importance in ensuring accurate timekeeping, navigation, and positioning. This studyintroduces a novel SCB prediction approach that integrates variational mode decomposition (VMD) and long short-term memory (LSTM) network techniques, combining signal decomposition with deep learning methodologies. Initially, the raw SCB data undergoespreprocessing, followed by decomposition using the VMD method to generate multiple intrinsic mode functions (IMFs). These decomposed IMFs serve as inputs for LSTM, where several independent LSTM models are established for training and prediction purposes. Subsequently, the predicted outcomes are aggregated and reconstructed to derive the finalSCB prediction. Experimental findings demonstrate notable advancements in clock bias prediction for the spaceborne hydrogen atomic clock for BDS, with prediction accuracies of 0.048 ns, 0.204 ns and 1.397 ns for 6 hours, 3 days and 15 days, respectively. These results exhibit significant enhancements compared to both the LSTM network and the Back Propagation (BP) neural network, with improvements of 56%, 84% and 83% for the aforementioned time intervals in comparison to LSTM, and enhancements of 59%, 82% and 83% relative to the BP neural network.
Peer Review Status:
Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2024-06-04
Abstract： In this study, we revisit the previous mass relations of mirror nuclei by considering 1/N- and 1/Z-dependent terms and the shell effect across a shell. The root-mean-squared deviation is 66 keV for 116 nuclei with neutron number N ≥ 10, as compared with experimental data compiled in the AME2020 database. The predicted mass excesses of 173 proton-rich nuclei, including 98 unknown nuclei, are tabulated in the Supplemental Material herein with competitive accuracy.
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties submitted time 2024-06-04
Siyan Gao
Junlin Jia
Xu Wang
Yue-Yu Zhang
Yijie Xiang
Pei Li
Ruobing Yi
Xuchang Su
Guosheng Shi
Feifei Qin
Yi-Feng Zheng
Lei Chen
Yu Qiang
Junjie Zhang
Lei Zhang
Haiping Fang
Abstract： The expanding applications call for novel new-generation wide-bandgap semiconductors. Here, we show that a compound only composed of the ordinary elements Na and Cl, namely three-dimensional NaCl2 crystal, is a wide-bandgap semiconductor. This finding benefits from the breaking of conventional stoichiometry frameworks in the theoretical design, leading to the discovery of three-dimensional XY2 (X = Na, Li, K; Y = Cl, F, Br, I) crystals, with covalent bonds of Y pairs inducing the wide bandgap from 2.24 to 4.45 eV. Crucially, such an unexpected NaCl2 crystal was successfully synthesized under ambient conditions. The unconventional stoichiometric strategy with other chemical elements potentially yields more wide-bandgap semiconductors, offering the capability for bandgap tuning. These unconventional stoichiometric materials may also exhibit superconductivity, transparent inorganic electrides, high-energy-density, and beyond.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2024-06-03
Abstract： The medium temperature $T$ dependence of jet transport coefficient $ hat q$ is studied via nuclear modification factor $R_{AA}(p_{ rm T})$ and elliptical flow parameter $v_2(p_{ rm T})$ for large transverse momentum $p_{ rm T}$ hadrons in high-energy nucleus-nucleus collisions. Within a next-to-leading order perturbative QCD parton model for hard scatterings with modified fragmentation functions due to jet quenching controlled by $ hat q$, we check the suppression as well as the azimuthal anisotropy for large $p_{ rm T}$ hadrons, and extract $ hat q$ by global fits to $R_{AA}(p_{ rm T})$ and $v_2(p_{ rm T})$ data in $A+A$ collisions at RHIC and the LHC, respectively. Numerical results from the best fits show that $ hat q/T^3$ goes down with the local medium temperature $T$ in the parton jet trajectory. Compared with the case of a constant $ hat{q}/T^3$, the going-down $T$ dependence of $ hat{q}/T^3$ makes a hard parton jet to lose more energy near $T_c$ and therefore strengthens the azimuthal anisotropy for large $p_{ rm T}$ hadrons. As a result, $v_2(p_{ rm T})$ for large $p_{ rm T}$ hadrons is enhanced by about 10 % to fit data better at RHIC/LHC. Considering the first-order phase transition from QGP to the hadron phase and additional energy loss in the hadron phase, $v_2(p_{ rm T})$ is again enhanced by 5-10 % at RHIC/LHC.
Subjects: Geosciences >> Space Physics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Astronomy >> Galaxy and Cosmology submitted time 2024-06-02
JI Jianghui
LI Haitao
ZHANG Junbo
LI Dong
FANG Liang
WANG Su
DENG Lei
CHEN Guo
LI Fei
DONG Yao
LI Baoquan
GAO Xiaodong
XIAN Hao
Abstract： The Closeby Habitable Exoplanet Survey (CHES) employs state-of-the-art, high-precision astrometry and positioning technology at the microarcsecond level in space. Its primary objective is to conduct a thorough survey of approximately 100 FGK-type stars within the Sun’s proximity (within 10 parsecs), with the goal of detecting potentially habitable Earth-like planets or super-Earths. This pioneering mission involves a detailed census of habitable planets, providing intricate information on their numbers, true masses, and three-dimensional orbits. Notably, CHES marks a historic milestone as the inaugural international space exploration mission exclusively dedicated to the study of terrestrial planets within the nearby habitable zone. CHES’s payload features a cutting-edge optical telescope with a 1.2 m aperture, a field of view measuring 0.44°×0.44°, and a focal length of 36 m. The telescope utilizes a coaxial three-mirror TMA optical imaging system. Impressively, CHES is designed with a positioning measurement accuracy of 1 μas, solidifying its status as the most precise space exploration project globally in terms of positioning accuracy. To achieve the detection objectives of CHES, it is essential to refine and further substantiate the scientific goals through comprehensive argumentation. Overcoming three key technological challenges is crucial: advancing optical systems for large field of view, developing high-quality space telescopes with minimal distortion; breaking through measurement technology for stellar separations at the 10–5 pixel level; and achieving high stability in satellite system attitude control and thermal control precision. CHES stands on the threshold of groundbreaking discoveries, with the exciting prospect of revealing 50 Earth-like planets. This announces a significant leap forward in China’s space science exploration technology.
Subjects: Physics >> Nuclear Physics submitted time 2024-06-02
Abstract： The Circular Electron Positron Collider (CEPC) is designed to precisely measure the properties of the Higgs boson, study electroweak interactions at the Z-boson peak, and search for new physics beyond the Standard Model. As a component of the 4th Conceptual CEPC detector, the drift chamber facilitates the measurement of charged particles. This study implemented a Geant4-based simulation and track reconstruction for the drift chamber. For the simulation, detector construction and response were implemented and added to the CEPC simulation chain. The development of track reconstruction involved track finding using the Combinatorial Kalman Filter method and track fitting using the tool of GenFit. Using the simulated data, the tracking performance was studied. The results showed that both the reconstruction resolution and tracking efficiency satisfied the requirements of the CEPC experiment.
Subjects: Physics >> Nuclear Physics submitted time 2024-05-29
Abstract： The fast X-ray imaging beamline (BL16U2) at Shanghai Synchrotron Radiation Facility (SSRF) is a new beamline that provides X-ray micro-imaging capabilities across a wide range of time scales, spanning from 100 ps to μs and ms. This beamline has been specifically designed to facilitate the investigation of a wide range of rapid phenomena, such as the deformation and failure of materials subjected to intense dynamic loads. In addition, it enables the study of high-pressure and high-speed fuel spray processes in automotive engines. The light source of this beamline is a cryogenic permanent magnet undulator (CPMU) that is cooled by liquid nitrogen. This CPMU can generate X-ray photons within an energy range of 8.7-30 keV. The beamline offers two modes of operation: monochromatic beam mode with a liquid nitrogen-cooled double-crystal monochromator (DCM) and pink beam mode with the first crystal of the DCM out of the beam path. Four X-ray imaging methods were implemented in BL16U2: single-pulse ultrafast X-ray imaging, microsecond-resolved X-ray dynamic imaging, millisecond-resolved X-ray dynamic micro-CT, and high-resolution quantitative micro-CT. Furthermore, BL16U2 is equipped with various in situ impact loading systems, such as a split Hopkinson bar system, light gas gun, and fuel spray chamber. Following the completion of the final commissioning in 2021 and subsequent trial operations in 2022, the beamline has been officially available to users from 2023.
Subjects: Physics >> Nuclear Physics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-05-29
Abstract： It is hypothesized that, though atomic nuclei are made of nucleons, strongly interacting matter with baryon number from $A simeq 10^{3-9}$ to $ sim 10^{57}$ would be composed of strangeons if Nature favors always the flavor symmetry of quarks. According to that logic, strangeon matter with $A sim 10^{57}$ could manifest in the form of pulsar-like compact stars, and multi-messenger observations with advanced facilities (e.g., China’s FAST) could eventually provide a disproof/proof. It is worth emphasizing that this point of view, based on established “old physics”, may have particular consequences for understanding our material world, for both normal luminous matter and the dark sector.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2024-05-24
Abstract： The recently discovered, extremely proton-rich nuclide 18Mg exhibits ground-state decay via two sequential two-proton (2p) emissions through the intermediate nucleus, 16Ne. This study investigates the structure and the initial 2p decay mechanism of 18Mg by examining the density and correlations of the valence protons using a three-body Gamow-coupled-channel method. The results show that the ground state of 18Mg is significantly influenced by the continuum, resulting in a significant s-wave component. However, based on the current frame- work, this does not lead to a significant deviation in mirror symmetry in either the structure or spectroscopy of the 18Mg-18C pair. Additionally, the time evolution analysis of the 18Mg ground state suggests a simultaneous 2p emission during the first step of decay. The observed nucleon–nucleon correlations align with those of the light–mass 2p emitters, indicating a consistent decay behavior within this nuclear region.
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties submitted time 2024-05-24
Abstract： The electron-diffraction patterns with 5-fold rotational symmetry of the experimental Al-Mn alloy phase reported by Shechtman et al. are assumed to be produced by a periodic structure. A three-dimensional periodic structure is presented based on two kind polyhedrons. The structure can be used as an atomic model to describe the alloy phase. The Fourier-transform patterns of the model are simulated along six “symmetry directions”. The chemical composition of the model is similar to that of the Al-Mn alloy phase. Details of the motivations and approaches that lead to these models are discussed. This study suggests that non classical periodic structures are also well candidates to describe quasicrystals
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2024-05-23
wang ruoxu
Yuan He
shi longbo
Li chenxing
xue zongheng
jiang tiancai
xu xianbo
sun liepeng
zhang zhouli
Abstract： To verify the rationality of the design of the power coupler for the RFQ cavity and to reduce contamination of the cavity, the low loss offline conditioning cavity was designed and high power test was conducted. The offline cavity was composed of two coupling ports and two tuners. Furthermore, the loss of the cavity could be minimized by the installation angle of the coupling ring and the insertion depth of the tuner. Electromagnetic structural and multiphysics simulations of the cavity were conducted, and the minimal theoretical power loss of the cavity was 4.3%. When the frequency variation of cavity was 110kHz, the theoretical power losses increased to 10%. Therefore, the tuner was always in motion during conditioning. Multiphysics simulations showed that the increased temperature of the cavity did not affect the frequency variation. When the offline high power conditioning platform was completed, the transmission performance of the conditioning system was measured. The power loss was 6.3%, larger than the theoretical calculation value. The conditioning employed efficient automatic range scanning and standing wave resonant conditioning methods. In order to fully condition the power coupler, 13 standing wave points were selected. The maximum continuous wave power is greater than 20kW, better than the expected target.
Subjects: Information Science and Systems Science >> Basic Disciplines of Information Science and Systems Science Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Astronomy >> Astrophysical processes submitted time 2024-05-22
Abstract： The electromagnetic fields of point sources with time varying charges moving in the vacuum are derived using the Liénard-Wiechert potentials. The properties of the propagation velocities and the Doppler effect are discussed based on their far fields. The results show that the velocity of the electromagnetic waves and the velocity of the sources cannot be added like vectors; the velocity of electromagnetic waves of moving sources are anisotropic in the vacuum; the transverse Doppler shift is intrinsically included in the fields of the moving sources and is not a pure relativity effect caused by time dilation. Since the fields are rigorous solutions of the Maxwell’s equations, the findings can help us to abort the long-standing misinterpretations concerning about the classic mechanics and the classic electromagnetic theory. Although it may violate the theory of the special relativity, we show mathematically that, when the sources move faster than the light in the vacuum, the electromagnetic barriers and the electromagnetic shock waves can be clearly predicted using the exact solutions. Since they cannot be detected by observers in the region outside their shock wave zones, an intuitive and reasonable hypothesis can be made that the superluminal sources may be considered as a kind of electromagnetic blackholes.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2024-05-20
Abstract： 氚是核电站排放的一种放射性核素，对去除氚提出了挑战。水中氚的连续在线监测对于实时辐射数据至关重要，因为它主要存在于环境中，就像水一样。本文介绍了利用塑料闪烁光纤 （PSF） 阵列的氚监测设备的设计、仿真和开发。实验验证证实了该器件的检测效率和最小可检测活性。该器件记录的检测效率为1.6×10−3，比理论模拟值4×10−4高出4倍。在没有屏蔽的情况下，该器件可以在 1600 秒的测量持续时间内实现 3165 Bq L−1 的最小可检测活性。根据仿真和实验结果，通过增加PSF的数量和长度以及实施严格的屏蔽措施，可以提高检测效率。此外，减小PSF的直径也可以提高检测效率。使用上述方法可以进一步降低设备的最小可检测活性。
Subjects: Physics >> Nuclear Physics submitted time 2024-05-20
Abstract： Background : The molten salt pump is one of the main equipment in the thorium based molten salt reactor circuit system, responsible for driving the circulation of molten salt in the circuit. The safety and economy of reactor operation are influenced by the safety and reliability of molten salt pump operation. State monitoring is one of the effective methods to ensure the safe operation of the system. Purpose : In order to detect abnormalities in equipment and system operation timely and provide a basis for condition based maintenance, a study was conducted on the state monitoring and abnormal signal localization of the molten salt pump system. Methods :A desktop application for the real-time monitoring system of molten salt pumps was developed based on the Windows Presentation Foundation (WPF) and Model-View-ViewModel(MVVM). The system is consisted of modules such as monitoring model management, real-time monitoring and alarm, abnormal signal localization, and log query. Results : The relevant operating parameters of the molten salt pump system can be centrally monitored by the system, and the current operating status of the equipment can be displayed in real-time. Signal parameters that may cause abnormalities can be quickly provided after the abnormality occurred. Conclusions : The necessary operational information can be provided by the system for operators. The system is helpful for operators to make operational decisions. Compared to traditional DCS threshold alarms, the timeliness and effectiveness of monitoring have been improved. The foundation for the subsequent application implementation of intelligent operation support is laid.
Subjects: Physics >> Nuclear Physics submitted time 2024-05-17
Abstract： A sustainability-oriented assessment of the nuclear energy system can provide informative and convincing decision-making support for nuclear development strategies in China. In our previous study, four authentic nuclear fuel cycle (NFC) transition scenarios were proposed, featuring different development stages and exhibiting distinct environmental, economic, and technical characteristics. However, because of the multiple and often conflicting criteria embedded therein, determining the top-priority NFC alternative for a sustainability orientation remains challenging. To address this issue, this study proposed a novel hybrid multi-criteria decision-making framework comprising fuzzy Analytic Hierarchy Process (AHP), Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE)-Geometrical Analysis for Interactive Aid (GAIA), and MOORA. Initially, an improved fuzzy AHP weighting model was developed to determine criteria weights under uncertainty and investigate the influence of various weight aggregation and defuzzification approaches. Subsequently, PROMETHEE-GAIA was used to address conflicts among the criteria and prioritize alternatives on a visualized k-dimensional GAIA plane. As a result, the alternative for direct recycling pressurized water reactor spent fuel in fast reactors is considered the most sustainable. Furthermore, a sensitivity analysis was conducted to examine the influence of criteria weight variation and validate the screening results. Finally, using MOORA, some significant optimization ideas and valuable insights were provided to support decision-makers in shaping nuclear development strategies.
Subjects: Physics >> Nuclear Physics submitted time 2024-05-17
Yan Zhang
Hao-Ran Zhang
Ren-Bo Wang
Ming-Yu Li
Rui Chen
Hai-Tao Wang
Xiang-Ting Meng
Shu-Min Zhou
Bin Tang
Abstract： A passive neutron multiplicity measurement device, FH-NCM/S1, based on field-programmable gate arrays (FPGAs), is developed specifically for measuring the mass of plutonium-240 (240Pu) in mixed oxide fuel. FHNCM/S1 adopts an integrated approach, combining the shift-register analysis mode with the pulse-position timestamp mode using an FPGA. The optimal effective length of the 3He neutron detector was determined to be 30 cm, and the thickness of the graphite reflector was ascertained to be 15 cm through MCNP simulations. After fabricating the device, calibration measurements were performed using a 252Cf neutron source; a detection efficiency of 43.07% and detector die-away time of 55.79 μs were observed. Nine samples of plutonium oxide were measured under identical conditions using the FH-NCM/S1 in shift-register analysis mode and a plutonium-waste multiplicity counter. The obtained double rates underwent corrections for detection efficiency(ε) and double gate fraction (f d), resulting in corrected double rates (Dc), which were used to validate the accuracy of the shift-register analysis mode. Furthermore, the device exhibited fluctuations in the measurement results, and within a single 20-s measurement, these fluctuations remained below 10%. After 30 cycles, the relative error in the mass of 240Pu was less than 5%. Finally, correlation calculations confirmed the robust consistency of both measurement modes. This study holds specific significance for the subsequent design and development of neutron multiplicity devices.
Subjects: Astronomy >> Celestial Mechanics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-05-16
Abstract： This paper presents a systematic improvement in celestial dynamics theory by introducing a new symmetric form of particle dynamics equation. For open multi-body systems, the symmetric new equation can be applied to any translational reference frame, thus avoiding the need for inertial reference frame approximations and enhancing the accuracy of theoretical predictions. In the case of bound multi-body systems, applying the symmetric new equation allows for an extremely simplified derivation of the planetary perturbation equation in one step. Furthermore, by considering temporary thrust or impact forces acting on planets, or even considering any external forces acting on the bound system further to enhance the computational precision, a new correction equation is now established for the planetary perturbation that can be further imposed with non-perturbative interactions. This will assist in the prediction of the trajectory of asteroids affected by external forces and in the accurate calculation of the orbit of satellites.
Peer Review Status:Awaiting Review
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. Subjects: Computer Science >> Other Disciplines of Computer Science submitted time 2024-05-14
Abstract： In his 1950 paper cite{Turing1950}, Turing proposed the notion of a thinking machine, namely a machine that can think. But a thinking machine has to follow a certain law of physics, provided it is realized physically. In this paper, we show that Turing’s thinking machine necessrily obeys ’t Hooft’s principle of superposition of states, which was presented by ’t Hooft cite{Hooft2016} in 2016 beyond the usual one as described by Dirac cite{Dirac1958} in the conventional quantum mechanics. Precisely, Turing’s thinking machine must be a quantum machine, while ’t Hooft’s principle characterizes its thinking behavior in a probabilistic way.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2024-05-11
Abstract： Reliable calculations of nuclear binding energies are crucial for advancing the research of nuclear physics. Machine learning provides an innovative approach to exploring complex physical problems. In this study, the nuclear binding energies are modeled directly using a machine-learning method called the Gaussian process. First, the binding energies for 2238 nuclei with Z > 20 and N > 20 are calculated using the Gaussian process in a physically motivated feature space, yielding an average deviation of 0.046 MeV and a standard deviation of 0.066 MeV. The results show the good learning ability of the Gaussian process in the studies of binding energies. Then, the predictive power of the Gaussian process is studied by calculating the binding energies for 108 nuclei newly included in AME2020. The theoretical results are in good agreement with the experimental data, reflecting the good predictive power of the Gaussian process. Moreover, the α-decay energies for 1169 nuclei with 50 ≤ Z ≤ 110 are derived from the theoretical binding energies calculated using the Gaussian process. The average deviation and the standard deviation are, respectively, 0.047 MeV and 0.070 MeV. Noticeably, the calculated α-decay energies for the two new isotopes 204Ac M. H. Huang et al., Phys. Lett. B 834, 137484 (2022) and 207Th H. B. Yang et al., Phys. Rev. C 105, L051302 (2022) agree well with the latest experimental data. These results demonstrate that the Gaussian process is reliable for the calculations of nuclear binding energies. Finally, the α-decay properties of some unknown actinide nuclei are predicted using the Gaussian process. The predicted results can be useful guides for future research on binding energies and α-decay properties.
Subjects: Physics >> Nuclear Physics submitted time 2024-05-10
Abstract： [Background]: The China Spallation Neutron Source (CSNS) provides a white neutron beam with an energy range from 0.5 eV to 300 MeV and a total beam intensity of up to 107n/s/cm2, serving as an excellent experimental platform for the measurement of neutron capture reaction cross sections. During normal operation, the CSNS generates two proton bunches separated by 410 ns, consecutively striking the target, resulting in a mixed neutron beam composed of two bunches with a 410 ns interval. To avoid interference between the effects of the two bunches and maintain the energy precision of neutron capture cross sections, experimental data need to be analyzed and reconstructed to restore the effects of individual bunches. [Purpose]: The existing parsing method can yield very refined unfolding results, but it is relatively complex and has a certain usage threshold. Therefore, a more convenient data processing method needs to be found. [Methods]: This work utilized mathematical operations to analyze and reconstruct the data, with 410 ns as the unit time, and processed the data with a channel width of 4100 ns. Additionally, a comparison was made of the impacts of this method and existing methods on the accuracy of neutron incident energy. [Results]: This work proposes a simplified data processing method that achieves the same energy resolution as existing methods in the low-to-medium energy range, providing a new data processing approach for similar experimental work. [Conclusions]: The simplified data processing method presented in this study effectively addresses the issue of excessive computational costs in analyzing low to medium energy neutron data from the CSNS. It offers a practical solution for experimental work requiring accurate analysis of neutron capture reactions in this energy range.
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