分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The existing 210Pbex mass balance models for the assessment of cultivated soil erosion are based on an assumption that 210Pbex is quite evenly mixed within the plough layer. However, the amount of 210Pbex distributed in the soils below the plough depth, like a downward tail in the lower part of the 210Pbex profile, has been largely ignored. In fact, after the initial cultivation of undisturbed soils, 210Pbex will diffuse downward from plough layer to the plough pan layer due to the concentration gradient. Assuming 210Pbex inventory is constant, the depth distribution in the two layers of the cultivated soils will achieve a steady state after continuous cultivation for 10.37 years, when 210Pbex is evenly distributed in the soils of the plough layer with an exponential concentration decline with depth in the soils of the plough pan layer, and the 210Pbex concentration at any depth will be invariable with time. The work reported in this paper attempts to explain the formation of the 210Pbex tail in the soil profile below the plough depth by theoretical derivation of the 210Pbex depth distribution process in the two layers of the cultivated soils, propose a 210Pbex mass balance model considering 210Pbex diffusion based on the existing model, and discuss the influence of the 210Pbex tail to the existing model.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： In this paper we investigate the possible direct, non-gravitational interaction between holographic dark energy (HDE) and dark matter. Firstly, we start with two simple models with the interaction terms Q proportional to rho(dm) and Q proportional to rho(de), and then we move on to the general form Q proportional to rho(alpha)(m)rho(beta)(de). The cosmological constraints of the models are obtained from the joint analysis of the present Union 2.1+BAO+CMB+H-0 data. We find that the data slightly favor an energy flow from dark matter to dark energy, although the original HDE model still lies in the 95.4% confidence level (CL) region. For all models we find c -1. We show that this solution cannot be accomplished in the two simple models, while for the general model such a solution can be achieved with a large beta, and the big rip may be avoided at the 95.4% CL.
分类： 核科学技术 >> 核科学与技术 提交时间： 2023-08-27
摘要： As a unique probe, precision measurement of textit{pp} solar neutrinos is important for studying the Sun's energy mechanism, monitoring thermodynamic equilibrium, and studying neutrino oscillation in the vacuum-dominated region. For a large-scale liquid scintillator detector, one bottleneck for textit{pp} solar neutrino detection comes from pile-up events of intrinsic $^{14}$C decays. This paper presents a few approaches to discriminate textit{pp} solar neutrinos and $^{14}$C pile-up events by considering the difference in their time and spatial distributions. In this work, a Geant4-based Monte Carlo simulation is constructed. Then multivariate analysis and deep learning technology were adopted respectively to investigate the capability of $^{14}$C pile-up reduction. As a result, the BDTG model and VGG network showed good performance in discriminating textit{pp} solar neutrinos and $^{14}$C double pile-up events. hl{At the $^{14}$C concentration assumption $5 times10^{-18} g/g$,} their signal significance can achieve 10.3 and 15.6 using only one day of statistics. In this case, the signal efficiency is 51.1 % for discrimination using the BDTG model when rejecting 99.18 % $^{14}$C double pile-up events, and the signal efficiency is 42.7 % for the case using the VGG network when rejecting 99.81 % $^{14}$C double pile-up events.
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： Here we briefly review the history of research on the Laiyang dinosaur and dinosaur egg faunas, summarize the contributions of C. C. Young and other elder paleontologists to the discoveries of the Late Cretaceous dinosaurs and dinosaur eggs from Laiyang, and introduce the new discoveries and the advances in the research on the Laiyang faunas. The new investigations in Laiyang from 2008 have found a series of valley developed in plain and more than ten new dinosaur or dinosaur egg fossil beds. In 2010, we began the massive excavations at two localities in Jingangkou and collected abundant dinosaurs and other vertebrate fossils, such as a new saurolophine, some theropod material and a new taxon of turtle egg. The bone beds in Locality 2 with the typical sedimentary and burial patterns of mudflow, and these fossil deposits are interpreted as having been carried and deposited by mudflow. The re-observation and the CT scanning data of the crest of Tsintaosaurus spinorhinus (IVPP V 725) show that the crest is fractured and solid. However, based on the re-observations of its cranial and postcranial specimens, we consider that Tsintaosaurus spinorhinus is a valid taxon of lambeosaurines, which have the hollow crest. Therefore, the crest of Tsintaosaurus might not belong to the skull of this individual, and the true form of the crest needs to be confirmed in the future work. We reassess the three species of Tanius, and obtain several results. 1) Tanius sinensis and Tanius chingkankouensis are the valid species of Tanius; 2) Tanius laiyangensis is invalid.; 3) the sacrum and ilium of Tanius chingkankouensis with typical hadrosaurid features should not be referred to Tanius.
分类： 地球科学 >> 地质学 提交时间： 2017-08-10 合作期刊: 《古脊椎动物学报》
摘要： Here we briefly review the history of research on the Laiyang dinosaur and dinosaur egg faunas, summarize the contributions of C. C. Young and other elder paleontologists to the discoveries of the Late Cretaceous dinosaurs and dinosaur eggs from Laiyang, and introduce the new discoveries and the advances in the research on the Laiyang faunas. The new investigations in Laiyang from 2008 have found a series of valley developed in plain and more than ten new dinosaur or dinosaur egg fossil beds. In 2010, we began the massive excavations at two localities in Jingangkou and collected abundant dinosaurs and other vertebrate fossils, such as a new saurolophine, some theropod material and a new taxon of turtle egg. The bone beds in Locality 2 with the typical sedimentary and burial patterns of mudflow, and these fossil deposits are interpreted as having been carried and deposited by mudflow. The re-observation and the CT scanning data of the crest of Tsintaosaurus spinorhinus (IVPP V 725) show that the crest is fractured and solid. However, based on the re-observations of its cranial and postcranial specimens, we consider that Tsintaosaurus spinorhinus is a valid taxon of lambeosaurines, which have the hollow crest. Therefore, the crest of Tsintaosaurus might not belong to the skull of this individual, and the true form of the crest needs to be confirmed in the future work. We reassess the three species of Tanius, and obtain several results. 1) Tanius sinensis and Tanius chingkankouensis are the valid species of Tanius; 2) Tanius laiyangensis is invalid.; 3) the sacrum and ilium of Tanius chingkankouensis with typical hadrosaurid features should not be referred to Tanius. 简要回顾了莱阳恐龙和恐龙蛋化石群的研究历史和以杨钟健为代表的老一代地质古生物学者对莱阳恐龙和恐龙蛋研究和发现的杰出贡献，并介绍了莱阳恐龙和恐龙蛋的最新发现和若干研究进展。在近年来对莱阳周边地层进行的大规模考察中，发现了一系列发育在平原上的恐龙峡谷群；以及其中蕴含的十几个恐龙和恐龙蛋新地点和新层位。2010年开始，在对莱阳金岗口村附近的2个化石地点的发掘中，发现了以鸭嘴龙科为主的大量脊椎动物化石和蛋化石，包括一类新的栉龙亚科成员，一些大型兽脚类恐龙化石，以及一新的龟鳖类蛋化石等。2号地点化石富集层具有典型的泥石流沉积特征和骨骼埋藏特征。对棘鼻青岛龙的特殊头饰进行了CT扫描和三维重建，发现其头饰是实心结构，但其他骨骼特征证明棘鼻青岛龙属于具有头饰的赖氏龙亚科是确定无疑的，所以目前发现的头饰应不是其真实状态或根本不属于其头部骨骼。此外，对谭氏龙1属3种的重新观察研究得出以下结论：中国谭氏龙和金刚口谭氏龙应是有效属种，但部分骨骼还有疑问，还需要进一步研究，而莱阳谭氏龙为无效属种。
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