Subjects: Physics >> Nuclear Physics submitted time 2023-09-04 Cooperative journals: 《核技术》
LI Kangning
KAN Chaoxin
WANG Xiaofei
HU Yueming
YANG Bingfan
QIN Jiuchang
GUAN Xialing
SU Shengyong
BAO Yiwen
YOU Qubo
WANG Hua
ZHOU Jianming
FAN Qiwen
LIU Dezhong
YANG Tao
HU Renwei
YANG Baojun
Abstract： The HI-13 tandem accelerator, located at the Beijing Tandem Accelerator National Laboratory, has been in operation for 35 years. To ensure the continued performance of the accelerator, the operation and maintenance team has prioritized focus on various aspects. The operation team conducted research that involved developing key components, cultivating a high-quality operational team, improving the machine time efficiency, and increasing the participation of users outside the China Institute of Atomic Energy (CIAE). The primary emphasis has been on developing key components and upgrading subsystems. These efforts have successfully maintained and improved the accelerator's performance, ensuring its safe and stable operation. Finally, the paper alse discusses the challenges faced by tandem accelerators and presents future development plans.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The mechanical properties of materials are related to the integrity of interfaces (phase and grain boundaries). For substitutional alloys, the Kirkendall voids tend to form more easily at the phase boundary or grain boundary when the atomic mobilities of different species are unequal, which will degrade the bounding quality of interfaces. So far, there have many experimental studies on the evolution of Kirkendall voids and the formation mechanism. However, allowing for the fast process of the Kirkendall voids from formation to evolution, it is hard to capture such process in real experimental conditionals. So the formation and evolution mechanism of the Kirkendall void need to be studied. A binary phase field crystal model was used to simulate the process of void formation and expansion at phase boundaries induced by the Kirkendall effect. Simulated results show that for the low misorientation phase boundary (PB), the void moves toward the side with large atomic mobility (a phase) and the void shape evolves from the initial parallelogram to hexagon. The atomic annihilation rate around a void is faster than that of growth rate, which results in void expansion. The PB migration, phase growth and shrinkage can also be observed in void expansion. For the large misorientation PB, voids can also expand along the PB direction, resulting in the connection of voids, therefore, the PB is separated and presents zigzag shape. In the interdiffusion system, the free energy decreases. The descending speed of the free energy is almost equal for the low misorientation PB while is increasing for the large misorientation PB when the atomic mobility difference becomes larger. The descending speed of the free energy is proportional to PB misorientations. The PB void predicted from our computer simulation is consistent with the experiment observation.
Subjects: Biology >> Botany submitted time 2022-11-24 Cooperative journals: 《广西植物》
Abstract：
To explore the influence of topographic factors on the diversity and spatial distribution of plant species around FAST (Five-hundred-meter Aperture Spherical radio Telescope), three typical plant communities (tree layer, shrub layer, vine layer) in the Karst peak-cluster depression around FAST were selected as the study objects, and ANOVA and Canonical Correspondence Analysis (CCA) were used to investigate the species diversity and spatial distribution of plant communities under different topographic factors (altitude, slope, aspect, and gradient). The results were as follows: (1) The α-diversity index of plant communities around FAST shows a trend of shrub layer > tree layer > vine layer, and the α-diversity index of plants in the tree layer and vine layer gradually increases with altitude (P<0.05), while the topographic factor has no significant effect on the α-diversity of plants in shrub layer. (2) The spatial distribution of plant community species around FAST was most influenced by the altitude, followed by the slope. (P<0.05) (3) The β-diversity indices of the plant communities around FAST show a trend of vine layer > shrub layer > tree layer along the altitude and slope. The Jaccard similarity index above 70% is extremely dissimilar and moderately dissimilar at altitude and slope gradients. The Jaccard similarity index of the three plant communities tended to increase with altitude and then decrease along the slope. In summary, species differ in their habitat selection, and altitude and slope are key factors affecting the spatial distribution of plant communities in the Karst depressions around FAST. Species diversity can better reflect the differences in plant communities in terms of species composition. Species diversity is not only influenced by topographic factors, but also related to biotic and abiotic factors, such as temperature, precipitation, human activities, and functional plant traits. Therefore, corresponding environmental factors need to be added in future studies to further investigate the intrinsic mechanisms of plant species diversity and species spatial distribution at the regional scale and to strengthen the ecological protection of the surrounding area, improve the forest composition, and provide a good natural environment around FAST and in the Karst peak-cluster depression.
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. submitted time 2022-11-22 Cooperative journals: 《中国全科医学》
Abstract：
Objective The purpose of this study is to discuss the expert consensus process of the determination of PICO questions, which were included in the practice guideline for acupuncture and moxibustion for nonspecific low back pain. Method The modified Delphi method was used to investigate and consult the target population, and calculate the positive coefficient,coordination coefficient and authority coefficient for quality control, and then determine the clinical questions included in the guidelines. Results In the end, 10 clinical questions were finally included. Conclusion The clinical questions that need to be included in this guideline were identified by the modified Delphi method,which has an important guiding role for the follow-up development of the guideline. The reflection and shortcomings of this guide in the construction of clinical questions have certain reference significance for the development of acupuncture guidelines.
Subjects: Geosciences >> Atmospheric Sciences submitted time 2022-06-07 Cooperative journals: 《干旱区地理》
Abstract：新疆北部是我国降雪高频区之一，随着全球变暖降雪量呈显著增加趋势，对新疆气候产生重要影响，由于观测资料限制对该区域小时降雪研究还未开展，影响降雪精细化预报和服务能力提升。因此，利用新疆天山山区及其以北（以下称新疆北部）2012年11月2021年2月50个国家气象站小时降雪观测资料，分析了冷季（11月翌年2月）小时降雪特征，并按日降雪量从高到低挑选30个大暴雪过程分析其小时降雪特征、影响系统及典型环流配置。结果表明：（1）阿勒泰北部、塔城盆地、伊犁河谷为降雪小时数（SHN）高频区，可达200 ha-1以上;天山山区SHN高频区为海拔1800~2000 m的中山带，达127.3 ha-1，2000 m以上降雪很少。（2）北疆和天山山区小时降雪量（R）1.0 mmh-1量级SHN占比分别为91.7%和91.9%，对降雪量贡献分别为70.7%和68.9%，R>1.0mmh-1为小时极端降雪事件，对北疆和天山山区降雪量贡献分别为29.3%和31.1%。（3）极端暴雪过程平均SHN为25.5 h，平均降雪量为30.7 mm，雪强约为1.2 mmh-1，大暴雪过程由长时间降雪导致，降雪持续时间是开展大暴雪研究和进行预报服务的关键点，造成大暴雪过程的影响系统主要 有中亚长波槽、中亚低涡、乌拉尔山长波槽和西西伯利亚低涡（槽），占比分别为30.0%、6.7%、13.3%和50.0%，中纬度长波槽（涡）和北方西西伯利亚低涡（槽）系统各为50.0%。
Subjects: Biology >> Botany >> Applied botany submitted time 2020-08-02 Cooperative journals: 《广西植物》
Abstract：病程相关蛋白（PRs）在植物抗病抗逆过程中发挥重要作用。盐穗木病程相关蛋白基因HcPR10（GenBank：KF673356）来自盐穗木（Halostachys capsica）在600 mmol·L-1 NaCl胁迫下的盐抑制差减文库。为探究盐穗木病程相关蛋白HcPR10发挥生物学功能的机制，通过体外表达和纯化HcPR10重组蛋白，制备特异性的HcPR10多克隆抗体。本研究采用双酶切构建原核重组表达载体pET28a-HcPR10，转化至大肠杆菌（Escherichia coli）BL21诱导表达，通过正交分析优化重组蛋白可溶性诱导表达的条件，利用Ni-NTA亲和层析柱纯化融合蛋白，免疫BALB/c小鼠制备多克隆抗体，基于纯化获得的His-HcPR10重组蛋白和转HcPR10拟南芥总蛋白，分别利用ELISA和Western Blotting检测抗血清效价和特异性。结果表明：成功构建重组表达载体pET28a-HcPR10；正交结果显示诱导温度27 ℃，诱导转速200 r·min-1，IPTG浓度0.7 mmol·L-1，诱导时间6 h条件下可诱导表达大量可溶性目的蛋白；ELISA检测抗HcPR10血清效价达1:243 000，Western Blotting印迹结果显示制备的抗血清可以与重组蛋白和转基因拟南芥（Arabidopsis thaliana）中异源表达的HcPR10蛋白特异性结合。获得了效价高、特异性强的盐穗木病程相关蛋白HcPR10抗血清，为进一步研究HcPR10的亚细胞定位及生物学功能奠定了基础。
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-06-19 Cooperative journals: 《计算机应用研究》
Abstract： Aiming at the problem that it is difficult for the traditional fault diagnosis method to extract effective features from QAR data, this paper proposed a dual-channel fusion model, CNN-LSTM, which combines the Convolutional Neural Network(CNN) and the Long Short-Term Memory(LSTM) . Respectively as two channels, CNN and LSTM fused through the attention mechanism to make the model able to simultaneously express the features of the data in both space dimension and time dimension and verified the validity of the feature extraction of the fusion model through time series prediction. Results of the experiment show that when compared with single CNN or LSTM, the dual-channel fusion model can extract data features more effectively, make the errors of both single-step prediction and multi-step prediction reduce by an average of 35.3%, and provide a new research idea for fault diagnosis based on QAR data.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-05-24 Cooperative journals: 《计算机应用研究》
Abstract： This paper proposed a new threshold secret sharing scheme based on the Shamir(n, t) threshold secret sharing scheme. Used the characteristic that the characteristic equation of the n-th order matrix has multiple roots, realized the secret sharing of participants in different sets. The secondary master key corresponding to the same participation set is the same, that is, the eigenvalue are the same. The algorithm firstly used the feature vector corresponding to the same eigenvalue as a subkey , then it distributed the subkey to the participating members of the same participating set. what's more, the members of the same collection could use the black box to verify the authenticity of the sub-keys in their own hands so as to achieve the purpose of fraud prevention. The analysis result shows that this scheme is safe and ideal .
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-04-12 Cooperative journals: 《计算机应用研究》
Abstract： On the basis of compressed sensing(CS) , this paper proposed an improved FOCUSS algorithm for the reconstruction of electrical capacitance tomography (ECT) , which aiming at the ill-conditionedness and ill-posedness of the inverse problem of ECT. The discrete cosine transform (DCT) basis made the grayscale signals of original images sparse. In the process of solving the inverse problem by employing the regularized FOCUSS algorithm, it introduced the quasi-Newton method to approximate and solve the intermediate sparse variables to improve the accuracy of signal reconstruction. Results of the simulation show that compared with LBP, Tikhonov, Landweber and FOCUSS algorithm, the improved FOCUSS algorithm can effectively distinguish the different media in the substance field, alleviate the over-smoothing effect, reduce the image error between the original image and the reconstructed image to 0.23, increase the correlation coefficient to 0.80, offer better image quality, and provide a new idea for the research on the algorithm for the reconstruction of ECT.
Subjects: Geosciences >> Space Physics submitted time 2017-03-10
Abstract：介质-导体相间结构是航天器部件的常见结构。为研究影响此种结构深层充电特性的内在因素，设计了不同构型的实验样品，利用Sr90放射源模拟空间高能电子环境对样品进行了深层充电辐照实验，测量了充电电位的差异。并借助深层充电三维仿真软件计算了此种结构在不同几何构型情况下的深层充电电位、电场分布。实验和仿真结果表明，介质最高表面电位以及介质内部最大电场均与介质宽度和高度呈正相关。其它条件不变时，介质越宽，或越高于导体表面，发生放电的风险就越高。在介质与导体侧面存在微小缝隙情况下，介质内最大电场显著增强，易发生内部击穿。而在介质与导体之间的真空间隙内，电场很容易超过击穿阈值，在一定的触发条件下放电风险很大。航天工程应用中为降低此种结构深层充放电的风险，在满足绝缘性能及其他要求的前提下应尽量减小介质的宽度，降低介质与导体间高度差，并确保介质与导体侧面接触良好。
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