分类： 物理学 >> 核物理学 提交时间： 2024-01-09
摘要： In nuclear reactors, temperature fluctuations of fluids may cause fatigue damage to adjacent structures; this is referred to as thermal striping. Research on thermal striping in the upper plenum has mainly focused on fluid fields. Few experimental studies have been reported on solid structures in a fluid field with a coaxial jet. This study entailed an experimental study of the temperature fluctuations in the fluid and on a plate surface caused by a coaxial jet. The temperature fluctuations of the fluid and plate surfaces located at different heights were analyzed. The cause of the temperature fluctuation was analyzed using a transient temperature distribution. The results show that the mixing of the hot and cold fluids gradually becomes uniform in the positive axial direction. The average surface temperatures tended to be consistent. When the jet reaches the plate surface, the swing of the jet center, contraction and expansion of the cold jet, and changes in the jet shape result in temperature fluctuations. The intensity of the temperature fluctuation was affected by the position. More attention should be paid when the plate is located at a lower height, and between the hot and cold-fluid nozzles.In nuclear reactors, temperature fluctuations of fluids may cause fatigue damage to adjacent structures; this is referred to as thermal striping. Research on thermal striping in the upper plenum has mainly focused on fluid fields. Few experimental studies have been reported on solid structures in a fluid field with a coaxial jet. This study entailed an experimental study of the temperature fluctuations in the fluid and on a plate surface caused by a coaxial jet. The temperature fluctuations of the fluid and plate surfaces located at different heights were analyzed. The cause of the temperature fluctuation was analyzed using a transient temperature distribution. The results show that the mixing of the hot and cold fluids gradually becomes uniform in the positive axial direction. The average surface temperatures tended to be consistent. When the jet reaches the plate surface, the swing of the jet center, contraction and expansion of the cold jet, and changes in the jet shape result in temperature fluctuations. The intensity of the temperature fluctuation was affected by the position. More attention should be paid when the plate is located at a lower height, and between the hot and cold-fluid nozzles.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Cyanamide (NH2CN) and its isomer, carbodiimide (HNCNH), may form adenine in the interstellar medium (ISM) via a series of reactions. Therefore, they are considered key prebiotic molecules in the study of the origin of life. We used the three-phase NAUTILUS chemical code, which includes the gas, the dust surface, and the icy mantle, to investigate the formation and destruction of cyanamide and carbodiimide. We added over 200 new chemical reactions of the two isomers and related species, and established a relatively complete network. We applied cold core, hot corino/core and shock models to simulate the different physical environments, and found that the two isomers are mainly produced by the free radical reactions on grain surfaces. Our simulated results suggest that cyanamide and carbodiimide molecules come from surface chemistry at early evolutionary stages. Then they are released back to the gas phase, either by thermal process (in hot cores, hot corinos) or shock-induced desorption (in shock regions).We speculate that it is an inefficient route to form a tautomer of adenine by starting from molecules cyanoacetylene (C3NH), cyanamide and carbodiimide in ISM.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Cyanamide (NH2CN) and its isomer, carbodiimide (HNCNH), may form adenine in the interstellar medium (ISM) via a series of reactions. Therefore, they are considered key prebiotic molecules in the study of the origin of life. We used the three-phase NAUTILUS chemical code, which includes the gas, the dust surface, and the icy mantle, to investigate the formation and destruction of cyanamide and carbodiimide. We added over 200 new chemical reactions of the two isomers and related species, and established a relatively complete network. We applied cold core, hot corino/core and shock models to simulate the different physical environments, and found that the two isomers are mainly produced by the free radical reactions on grain surfaces. Our simulated results suggest that cyanamide and carbodiimide molecules come from surface chemistry at early evolutionary stages. Then they are released back to the gas phase, either by thermal process (in hot cores, hot corinos) or shock-induced desorption (in shock regions).We speculate that it is an inefficient route to form a tautomer of adenine by starting from molecules cyanoacetylene (C3NH), cyanamide and carbodiimide in ISM.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Yuansheng Tao
Fenghe Yang
Zihan Tao
Lin Chang
Haowen Shu
Ming Jin
Yan Zhou
Zhangfeng Ge
Xingjun Wang
摘要： Microwave photonics (MWP), harnessing the tremendous bandwidth of light to generate, process and measure wideband microwave signals, are poised to spark a new revolution for the information and communication fields. Within the past decade, new opportunity for MWP has emerged driven by the advances of integrated photonics. However, despite significant progress made in terms of integration level, a fully on-chip MWP functional system comprising all the necessary photonic and electronic components, is yet to be demonstrated. Here, we break the status quo and provide a complete on-chip solution for MWP system, by exploiting hybrid integration of indium phosphide, silicon photonics and complementary metal-oxide-semiconductor (CMOS) electronics platforms. Applying this hybrid integration methodology, a fully chip-based MWP microwave instantaneous frequency measurement (IFM) system is experimentally demonstrated. The unprecedented integration level brings great promotion to the compactness, reliability, and performances of the overall MWP IFM system, including a wide frequency measurement range (2-34 GHz), ultralow estimation errors (10.85 MHz) and a fast response speed (0.3 ns). Furthermore, we deploy the chip-scale MWP IFM system into realistic application tasks, where diverse microwave signals with rapid-varying frequencies at X-band (8-12 GHz) are accurately identified in real-time. This demonstration marks a milestone for the development of integrated MWP, by providing the technology basis for the miniaturization and massive implementations of various MWP functional systems.
分类： 物理学 >> 核物理学 提交时间： 2023-12-29
Dawei Si
Yan Zhou
Sheng Xiao
Zhi Qin
Dong Guo
Yuhao Qin
Yijie Wang
Boyuan Zhang
Baiting Tian
Zhigang Xiao
摘要： The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as asensitive probe to the short range correlation in atomic nuclei. The energy of the -rays can be measuredby collecting theˇCerenkov light in medium induced by the fast electrons generated in Compton scattering orelectromagnetic shower of the incident ray. Two types of detectors, based on pure water and lead glass asthe sensitive material respectively, are designed for the above purpose. The response and optical photonpropagation in detectors have been simulated based on the electromagnetic and optical processes in Geant4.The inherent energy resolution of 0.022(4) + 0.51(2)/E 1/2 for water and 0.0026(3) + 0.446(3)/E 1/2 forlead glass are obtained. The geometry size of lead glass and water are optimized at 30 30 30 cm3 and60 60 120 cm3 , respectively, for detecting high energy -rays at 160 MeV. Hough transform method hasbeen applied to reconstruct the direction of the incident -rays, giving the ability to distinguish experimentallythe high-energy rays produced in the reactions on the target from the random background cosmic ray muons.
分类： 核科学技术 >> 粒子加速器 提交时间： 2021-12-31
Bai, Shi-Wei
Yang, Xiao-Fei
Wang, Shu-Jing
Liu, Yong-Chao
Zhang, Peng
Liu, Yin-Shen
Hu, Han-Rui
Guo, Yang-Fan
Wang, Jin
Du, Ze-Yu
Yan, Zhou
Zhang, Yun-Kai
Ye, Yan-Lin
Li, Qi-Te
Ge, Yu-Cheng
He, Chuang-Ye
摘要： Collinear laser spectroscopy is a powerful tool for studying the nuclear spins, electromagnetic moments, and charge radii of exotic nuclei. To study the nuclear properties of unstable nuclei at the Beijing Radioactive Ion#2;beam Facility (BRIF) and the future High Intensity Heavy-ion Accelerator Facility (HIAF), we developed a collinear laser spectroscopy apparatus integrated with an offline laser ablation ion source and a laser system. The overall performance of this state-of-the-art technique was evaluated and the system was commissioned using a bunched stable ion beam. The high-resolution optical spectra for the 4s 2S1/2 → 4p 2P3/2 (D2) ionic transition of 40,42,44,48Ca isotopes were successfully measured. The extracted isotope shifts relative to 40Ca showed excellent agreement with the literature values. This system is now ready for use at radioactive ion beam facilities such as the BRIF and paves the way for the further development of higher-sensitivity collinear resonant ionization spectroscopy techniques.
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