分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Field Programmable Gate Array (FPGA), combined with ARM (Advanced RISC Machines) is increasingly employed in the portable data acquisition (DAQ) system for nuclear experiments to reduce the system volume and achieve powerful and multifunctional capacity. High-speed data transmission between FPGA and ARM is one of the most challenging issues for system implementation. In this paper, we propose a method to realize the high-speed data transmission by using the FPGA to acquire massive data from FEE (Front-end electronics) and send it to the ARM whilst the ARM to transmit the data to the remote computer through the TCP/IP protocol for later process. This paper mainly introduces the interface design of the high-speed transmission method between the FPGA and the ARM, the transmission logic of the FPGA, and the program design of the ARM. The theoretical research shows that the maximal transmission speed between the FPGA and the ARM through this way can reach 50 MB/s. In a realistic nuclear physics experiment, this portable DAQ system achieved 2.2 MB/s data acquisition speed.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Dynamical dipole mode in heavy-ion collisions has been studied by using an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) model. We investigate the dependence of centroid energy and strength of the spectrum on beam energy, N/Z ratio and mass asymmetry. The calculated yield and angular distribution of the -ray produced by dynamical dipole emission are consistent with the experimental data. The results show that the detailed study of dynamical dipole radiation can provide information on the isospin evolution of charge-asymmetric heavy-ion collisions around the normal nuclear density.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: Dislocations would be induced after plastic deformation, which might change the mechanical properties of solids. FeCrNi austenitic model alloy and its Mo-diluted alloy were cold rolled with different degree of thickness reduction. Positrons are sensitive to point defects, which are easily trapped and annihilated around the trapping sites. The mean positron lifetimes have been used to estimate the average dislocation concentration in solids. Meanwhile, the trapping efficiency μ was calculated from the lifetime results. The trapping efficiency value is estimated about 3.31×10-7 cm3s-1 for FeCrNi alloy and 3.31×10-7 cm3s-1 for Mo-diluted alloy, respectively. The increment of the hardness value during plastic deformation is related to the increase of the dislocation density and dislocation pile up in solids.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: Solution annealed type 316L austenitic stainless steels were irradiated using 2 MeV Fe ions at room temperature. The implanted fluences were 2012 ions/cm2 and 1013 ions/cm2, respectively. Variable mono-energetic positron beam was performed to characterize the evolution of microstructure and irradiation induced defects. Results show that large amount of vacancy defects formed after heavy ion irradiation. In which, some of mono-vacancies might migrate to form small-sized clusters at room temperature. After irradiation, implanted Fe atoms mainly be interstitials atoms, but some Fe atoms might recombine with vacancies due to their high mobility, which could decrease the defect concentration, effectively.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: A C-band RF pulse compressor is in development at SINAP. It comprises of two resonant cavities, two mode convertors and a 3 dB power divider. TE0.1.15 mode is selected for obtaining higher quality factor Q0 of the RF pulse compressor cavities, so that the power gain factor can be 3.2, which is supposed to multiply the RF power from 50 MW to 160 MW. In this paper, we report our work on C-band RF pulse compressor, namely the design simulation and cold test results.
分类: 生物学 >> 动物学 提交时间: 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要: The tetrapod assemblage from the Middle Triassic upper part of the Ermaying Formation of northern China has been known for two decades as the Sinokannemeyeria-Shansisuchus Assemblage because of the characteristic presence of the dicynodont therapsid Sinokannemeyeria and the erythrosuchid archosauriform Shansisuchus. Recently a Sinokannemeyeria species has been described from Member I of the Tongchuan Formation, which overlies the Ermaying, near Baidaoyu, Linxian, Shanxi Province. Here we document archosauriform specimens from the Baidaoyu site, including a partial Shansisuchus skeleton and some additional bones from probable suchian archosaurs, which constitute the first archosauriform material known from Member I of the Tongchuan. The most intriguing archosauriform specimens are a large ilium probably attributable to an unusual poposauroid, and a small, strangely shaped element that appears to represent a highly autapomorphic suchian calcaneum. Given the presence of both Sinokannemeyeria and Shansisuchus at Baidaoyu, the stratigraphic range of the Sinokannemeyeria-Shansisuchus Assemblage can be considered to extend upward into the Tongchuan Formation, although with possible changes in faunal composition. The occurrence of a poposauroid ilium at the Baidaoyu locality adds to the evidence that poposauroids diversified extensively during the Middle Triassic.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: Doppler broadening and Coincidence Doppler broadening of annihilation radiation experiments have been performed in three kinds of polyethylene glycol (PEG) membrane formed with different average molecular weight using the tunable monoenergy slow positron probe as a function of implantion energy. The obtained positron annihilation parameters are interpreted from two aspects: surface effect and differences in micro-structure or chemical environment of positron annihilation. The experimental results show that the regulation of densification of PEG molecular packing and distribution uniformity from the near surface layer to bulk region in film forming process can be well realized by changing its molecular weight. Combining a variable monoenergetic slow positron beam and these two positron annihilation spectroscopy methods are powerful tool to study positron annihilation characteristics and for polymeric thin-film fine structure analysis.
分类: 生物学 >> 动物学 提交时间: 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要: New specimens from a new locality at Chutoulang in eastern Nei Mongol were identified as Canis chihliensis, Coelodonta nihowanensis, Hipparion (Proboscidipparion) sinense, Equus sanmeniensis, Sus lydekkeri, Muntiacus cf. M. lacustris, Axis shansius, Eucladoceros boulei, Spirocerus cf. S. wongi and Bison palaeosinensis. They enriched the mammalian fauna of Chutoulang to 30 taxa together with the material from Dongliang, Dongcun Beigou and Dongcun Nangou localities. The mammalian fossils from these four localities are all from the same horizon and can be regarded as the same fauna, i.e. Chutoulang fauna. The composition of Chutoulang fauna is the closest to that of Nihewan (s.s.) by binary faunal similarity coefficients. The age of Chutoulang fauna is between those of Nihewan (s.s.) and Juyuandong at Liucheng according to Brainerd-Robinson’s sequence, extinction rates and antiquity coefficients. The numerical age of Chutoulang fauna is estimated between 1.4–1.6 Ma based on those of compared faunas. Carnivora are the most numerous in Chutoulang fauna with 11 taxa, but mostly the small sized ones. Perissodactyla and Artiodactyla make about half of the fauna. They are mostly large sized forms. The presence of numerous browsers or forest dwellers implies the existence of forest or woodland in Chutoulang area during that period. The presence of grazers and openland dwellers indicates the existence of larger area of grassland or steppes than that of woodland or forests. Most members of Chutoulang fauna are temperate habitat dwellers with a few cold-prone forms such as Ochotona and Coelodonta. The climate in Chutoulang area in the Early Pleistocene was thus similar to that of today. Chutoulang fauna is the most northeastern Early Pleistocene fauna in China and it can be recommended as a type site of the Early Pleistocene mammalian fauna in northeastern China.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: An element analysis method, coincidence Doppler broadening spectroscopy of slow positron annihilation, was employed to detect helium in ion irradiated Fe9Cr alloys. Spectra with higher peak to background ratio were recorded using a two-HPGe-detector coincidence measuring system. It means that information in the high-momentum area of the spectra can be used to identify helium in metals. This identification is not entirely dependent on the helium concentration in the specimens, but is related to the structure and microscopic arrangement of atoms surrounding the positron annihilation site. The results of Doppler broadening spectroscopy and transmission electron microscopy show that vacancies and dislocations were formed in ion irradiated specimens. Thermal helium desorption spectrometry was performed to obtain the types of He traps.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In this paper, we propose a two-mode polarizable deflecting structure, as a new concept for bunch measurement and beam control. With two modes of HEM11 and HEM12 operating in the same structure on horizontal and vertical directions, respectively, the operation status can be switched between the two polarization modes. They can be operated simultaneously with two independent input power sources. With two-mode deflecting structure, the bunch distortion caused by the geometric wake-fields in the accelerating structure can be measured by one structure.
分类: 生物学 >> 动物学 提交时间: 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要: A new skull of Urmiatherium intermedium (Bovidae, Artiodactyla) from the Linxia Basin, Gansu Province is described here. U. intermedium is a large Late Miocene bovid with an odd-looking horn apparatus, consisting of a pair of degenerate, closely situated horn-cores, and a large area of exostoses on the frontal and the parietal bones. Plenty of skulls, teeth, and bone fragments of U. intermedium have been reported from North China, but the skull to be described is the first discovery from the Linxia Basin, expanding the geographic distribution of U. intermedium to the northeast edge of the Tibetan Plateau. Although Urmiatherium is generally thought to be closely related to Plesiaddax, Hezhengia, Tsaidamotherium, and some other Late Miocene “ovibovines”, the phylogenetic position of Urmiatherium is still in debate. The distribution of Urmiatherium is wide, spanning from Iran to North China. Urmiatherium seldom accompanies with other Late Miocene “ovibovines” in North China, but is accompanied by other bovids like Sinotragus.
分类: 地球科学 >> 地理学 提交时间: 2021-06-04 合作期刊: 《干旱区科学》
摘要: Relatively little is known about fire regimes in grassland and cropland in Central Asia. In this study, eleven variables of fire regimes were measured from 2001 to 2019 by utilizing the burned area and active fire product, which was obtained and processed from the GEE (Google Earth Engine) platform, to describe the incidence, inter-annual variability, peak month and size of fire in four land cover types (forest, grassland, cropland and bare land). Then all variables were clustered to define clusters of fire regimes with unique fire attributes using the K-means algorithm. Results showed that Kazakhstan (KAZ) was the most affected by fire in Central Asia. Fire regimes in cropland in KAZ had the frequent, large and intense characters, which covered large burned areas and had a long duration. Fires in grassland mainly occurred in central KAZ and had the small scale and high-intensity characters with different quarterly frequencies. Fires in forest were mainly distributed in northern KAZ and eastern KAZ. Although fires in grassland underwent a shift from more to less frequent from 2001 to 2019 in Central Asia, vigilance is needed because most fires in grassland occur suddenly and cause harm to humans and livestock.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: The evolution of microstruture for Fe16.7Cr14.5Ni model alloy and 316 stainless steel irradiated with 140 keV He ions were studied by Positron annihilation spectroscopy. The fluences were 1016 and 5016 He ions/cm2. The irradiation temperature was room temperature and 573 K, respectively. The variation of S parameter-incident positron energy profile indicated that large amount of vacancy-type defects formed after He ion irradiation. Meanwhile, helium atoms deposited in bulk and certain amount of He-vacancy complexes were formed. The vacancy-type defects could be the major defects in track region and He-vacancy complexes would be the main defects in cascade region. The vacancy-type defects could migrate and aggregate to form vacancy clusters and even microvoids at elevated temperature irradiation. The diffusion mechanism of helium atoms might be changed at different irradiation temperature.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-24
摘要: In order to study the microstructural evolution of the He+ irradiated FeCrNi model alloy, 140 keV He+ ions were implanted into the specimen with the fluence of 1015 ions/cm2 at room temperature. Positron Annihilation Spectroscopy was used to characterize the evolution of micro defects during isochronal annealing between 423 K and 873 K. The decrease of the S parameter between 573 K and 623 K has been associated to the annihilation of vacancy clusters, which were not trapped by helium atom. While the decline of the S parameter between 773 K and 823 K in the damage region might be caused by the dissociation of HenVm clusters. The dissociated vacancy clusters were unstable and annihilated rapidly, which decreases the concentration of vacancy defects.
分类: 物理学 >> 核物理学 提交时间: 2016-09-02
摘要: We explore the discovery potential of Higgs pair production at a 100 TeV collider via full leptonic mode. The same mode can be explored at the LHC when Higgs pair production is enhanced by new physics. We examine two types of fully leptonic final states and propose a partial reconstruction method. The reconstruction method can reconstruct some kinematic observables. It is found that the mT2 variable determined by this reconstruction method and the reconstructed visible Higgs mass are important and crucial to discriminate the signal and background events. It is also noticed that a new variable, denoted as Δm which is defined as the mass difference of two possible combinations, is very useful as a discriminant. We also investigate the interplay between the direct measurements of tt¯h couplings and other related couplings and trilinear Higgs coupling at hadron colliders and electron-positron colliders.
分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: We perform a detailed hadron-level study on the sensitivity of Higgs boson pair production via the WW∗WW∗channel with the final state 3ℓ2j + missing ET at the LHC with the collision energy S√=14 TeV and a future 100 TeV collider. To avoid the huge background from pp→ZW+jets processes, we confine to consider the four lepton patterns: e±e±μ∓ and μ±μ±e∓. We propose a partial reconstruction method to determine the most reliable combination. After that, we examine a few crucial observables which can discriminate efficiently signal and background events, especially we notice that the observable mT2 is very efficient. For the LHC 14 TeV collisions, with an accumulated 3000 fb−1 dataset, we find that the sensitivity of this mode can reach up to 1.5 σ for the Standard Model and the triple coupling of Higgs boson λ3 in the simplest effective theory can be constrained into the range [-1, 8] at 95% confidence level; at a 100 TeV collider with the integrated luminosity 3000 fb−1, the sensitivity can reach up to 13 σ for the Standard Model and we find that all values of λ3 in the effective theory can be covered up to 3σ even without optimising signals. To precisely measure the triple coupling of Higgs boson λ3=1 of the Standard Model at a 100 TeV collider, by using the invariant mass of three leptons which is robust to against the contamination of underlying events and pileup effects and by performing a χ2 analysis, we find that it can be determined into a range [0.8, 1.5] at 95% confidence level.
分类: 生物学 >> 生物学其他学科 提交时间: 2018-12-04 合作期刊: 《古脊椎动物学报》
摘要: Abstract Here the posterior cranial portion of the tetrapodomorph Tungsenia from the Lower Devonian (Pragian, ~409 million years ago) of Yunnan, southwest China, is reported for the first time. The pattern of posterior skull roof and the morphology of the otoccipital region of the neurocranium are described in detail, providing precious insight into the combination of cranial characters of the earliest known tetrapodomorph to date. The posterior cranium of Tungseniadisplays a mosaic of features previously linked either to basal dipnomorphs such as Youngolepis(e.g., the well-developed subjugular ridge, the strong adotic process, and the poorly developed fossa bridgei) or to typical tetrapodomorphs (e.g., the lateral dorsal aortae commenced from the median dorsal aorta postcranially). The independent ventral arcual plate is also found in the advanced tetrapodomorph Eusthenopteron. The new endocranial material of Tungsenia further fills in the morphological gap between Tetrapodomorpha (tetrapod lineage) and Dipnomorpha (lungfish lineage) and unveils the sequence of character acquisition during the initial diversification of the tetrapod lineage. The new phylogenetic analysis strongly supports the basalmost position of Tungsenia amongst the tetrapod lineage.
分类: 环境科学技术及资源科学技术 >> 环境科学技术基础学科 提交时间: 2019-10-26 合作期刊: 《干旱区科学》
摘要: Climate change and human activities can influence vegetation net primary productivity (NPP), a key component of natural ecosystems. The Qinghai-Tibet Plateau of China, in spite of its significant natural and cultural values, is one of the most susceptible regions to climate change and human disturbances in the world. To assess the impact of climate change and human activities on vegetation dynamics in the grassland ecosystems of the northeastern Qinghai-Tibet Plateau, we applied a time-series trend analysis to normalized difference vegetation index (NDVI) datasets from 2000 to 2015 and compared these spatiotemporal variations with trends in climatic variables over the same time period. The constrained ordination approach (redundancy analysis) was used to determine which climatic variables or human-related factors mostly influenced the variation of NDVI. Furthermore, in order to determine whether current conservation measures and programs are effective in ecological protection and reconstruction, we divided the northeastern Qinghai-Tibet Plateau into two parts: the Three-River Headwater conservation area (TRH zone) in the south and the non-conservation area (NTRH zone) in the north. The results indicated an overall (73.32%) increasing trend of vegetation NPP in grasslands throughout the study area. During the period 2000–2015, NDVI in the TRH and NTRH zones increased at the rates of 0.0015/a and 0.0020/a, respectively. Specifically, precipitation accounted for 9.2% of the total variation in NDVI, while temperature accounted for 13.4%. In addition, variation in vegetation NPP of grasslands responded not only to long- and short-term changes in climate, as conceptualized in non-equilibrium theory, but also to the impact of human activities and their associated perturbations. The redundancy analysis successfully separated the relative contributions of climate change and human activities, of which village population and agricultural gross domestic product were the two most important contributors to the NDVI changes, explaining 17.8% and 17.1% of the total variation of NDVI (with the total contribution >30.0%), respectively. The total contribution percentages of climate change and human activities to the NDVI variation were 27.5% and 34.9%, respectively, in the northeastern Qinghai-Tibet Plateau. Finally, our study shows that the grassland restoration in the study area was enhanced by protection measures and programs in the TRH zone, which explained 7.6% of the total variation in NDVI.