[en] Many typical non lightning failures of transmission lines are caused by foreign matter, such as bird streamer, floating objects, branches and so on. In this paper, 110kV composite insulators are taken as the research object. First, the mechanism of flashover caused by foreign matter is analysed theoretically, and then a three-dimensional model of composite insulators is built by using the Maxwell simulation software. Electric field and potential changes of the composite insulator in the presence of different foreign matter are studied, and the flashover mechanism and related influencing factors are analysed. Based on this, through a large number of simulation calculations, the area of 110kV composite insulator caused by foreign matter flashover is finally given, which provides guidance for the typical non-lightning fault of 110kV line protection. (paper)

[en] Due to its computational efficiency and geometrical flexibility, the Method of Characteristics (MOC) has been widely used for light water reactor lattice physics analysis. Usually acceleration methods are necessary for MOC to achieve acceptable convergence on practical reactor physics problems. Among them, Coarse Mesh Finite Difference (CMFD) is very popular and can drastically reduce the number of transport iterations. In OpenMOC, CMFD acceleration was implemented but had the limitation of supporting only a uniform CMFD mesh, which would often lead to splitting MOC source regions, thus creating an unnecessary increase in computation and memory use. In this study, CMFD acceleration with a non-uniform Cartesian mesh is implemented into OpenMOC. We also propose a quadratic fit based CMFD prolongation method in the axial direction to further improve the acceleration when multiple MOC source regions are contained in one CMFD coarse mesh. Numerical results are presented to demonstrate the improvement of the CMFD acceleration capability in OpenMOC in terms of both efficiency and stability

[en] The higher eigenpairs of the neutron transport (or diffusion) equation are useful in core flux distribution reconstruction, transient analysis, stability analysis, and loading pattern optimization. There are various methods for the calculation of higher eigenpairs, such as the power iteration method with filtering technique, the Generalized Modified Power Method (GMPM), the power iteration method with innovative boundary conditions for symmetric cores, and Krylov subspace methods. In regard to Krylov subspace methods, the Implicitly Restarted Arnoldi Method (IRAM) and ORTHOMIN were implemented to calculate higher eigenpairs for both transport and diffusion equations. In Warsa's work, however, there was a significant drawback that problems with energy upscatter could not be treated efficiently. In Modak's work, the mode to which his method was likely to converge depended on the shape of initial guess flux, and only one mode could be computed each time, making it impractical for real use. Furthermore, the computational burden for higher eigenpairs is generally much larger than for only the first eigenpair, especially for neutron transport equations. Therefore, the implementation of parallel computation for higher eigenpairs is essential to improve the efficiency, and no such work has been reported in literature so far. In this summary, we propose an innovative method to calculate higher eigenpairs of the neutron transport equation based on high performance computation. In this method, 2D Matrix Method of Characteristic (MMOC) is used to discretize the neutron transport equation; IRAM is used to evaluate higher eigenpairs; spatial domain decomposition is used to realize parallel computation. The highlight of this method is using the MGMD PGMRES (Multi-Group and Multi-Domain coupled Parallel Generalized Minimal Residual Method) algorithm to simultaneously accelerate the upscatter iterations and the inner interface angular fluxes iterations, avoiding the drawback in Warsa's method and the efficiency problem of conventional Jacobi iteration. To the best of our knowledge, our work represents the first application of IRAM based on domain decomposition for higher eigenpairs

[en] Objective: To analyze the risk factors of 30-day mortality in patients with malignant hilar obstruction (MHO) after percutaneous transhepatic biliary metal stent deployment. Methods: One hundred and fifty-nine consecutive patients with MHO caused by cholangiocarcinoma or gallbladder carcinoma were enrolled in this study. Percutaneous transhepatic biliary stent (PTBS) implantation was carried out in all the patients. Independent predictors for 30-day mortality were evaluated by logistic regression analysis. Covariates that were incorporated into the multivariate analysis were the variables that reached statistical significance (P < 0.1) in univariate analysis. Two-tailed, P value of less than 0.05 was considered to be statistically significant. Results: The 30-day mortality of patient with MHO after metal stent deployment was 9.4%. Univariate analysis indicated that the differences in WBC (OR = 1.224.95%CI [1.07 - 1.44], P < 0.01), INR (OR = 78.75, 95%CI [5.02 - 1 235.70], P < 0.01), PT(OR = 1.55, 95%CI [1.18 - 2.04], P <0.01), BUN (OR = 1.19, 95%CI [1.02 - 1.38], P < 0.05), CRE (OR = 1.02, 95%CI [1.000 - 1.041], P < 0.1) and lymph nodes metastasis (OR = 0.334. 95%CI[0.105 - 1.131], P < 0.1) were statistically significantly between 30-day mortality group and non-30-day mortality group. Multivariate analysis showed that statistically significant differences in WBC (OR = 1.19, 95%CI [1.026 - 1.380], P < 0.05), INR (OR = 151.5, 95%CI [3.13 - 5440.7], P < 0.05) and CRE (OR = 1.025, 95%CI [1.002 - 1.048], P < 0.05) also existed between 30-day mortality group and non-30-day mortality group. Conclusion: Percutaneous transhepatic biliary metal stent placement is a safe and effective palliative treatment for patients with malignant hilar obstruction. Active preoperative measures to improve hepatic and renal functions as well as to control infection are necessary in order to reduce 30-day mortality. (authors)

[en] X-ray photoemission spectroscopy and X-ray diffraction reveal that N⁺ ion irradiation causes the occurrence of the metallic bismuth and the surface decomposition in Bi₂Sr₂CaCu₂O_y crystals. We think that such change results in the change of oxygen content. Due to this fact, a possible reason for the decrease of the superconducting transition temperature is suggested as the change of oxygen content. (author)

[en] Nuclear design and fuel management of submarine reactors and NPP reactors are based on solving 3D multi-group neutron diffusion equation accurately and efficiently. One of the methods for this equation is finite difference method (FDM), which is simple, accurate and mature. However, the computation burden of FDM is huge and the memory requirement is high, thus limiting FDM's scale and application scope. In this paper, FDM for 3D multi-group neutron diffusion equation based on large-scale parallel computation is researched. Mesh-centered FDM is used to discrete the neutron diffusion equation. Large-scale parallel computation is realized by domain decomposition based on MPI, and it's accelerated with multi-group multi-domain coupled PGMRES algorithm. ParaFiDi code is developed on high performance cluster and verified by several benchmarks such as IAEA3D and PHWR. Numerical results demonstrate that ParaFiDi code could obtain good efficiency and accuracy. (authors)

[en] The changes of profiles along the a, b and c directions of a Bi₂Sr₂CaCu₂O_δ single crystal were examined by the X-ray diffraction method over the temperature range from 297 K to 77. Splitting of the (0k0) and (h00) diffraction peaks appeared in the temperature regions from 262 to 222 K and from 226 to 156 K, respectively. Changes of the modulation structure appear in the temperature regions from 207 to 202 K and from 112 to 102 K. Moreover, there is no remarkable change of the (00l) diffraction peaks. Below the temperature of 91 K, the (040) diffraction peak obviously begins to broaden. (authors)

[en] Based on the AutoCAD software, this paper proposes the advanced grid automatic recognition algorithm, nested attribute editing mode, modular modeling methods and other advanced technologies, and develops the visual graphic modeling software KYEYE. The software supports multiple geometric description, currently supports KYLIN-Ⅱ software and HELIOS program. Adequate test and verification show that the software can accurately and quickly establish a variety of complex problems. (authors)

[en] The Ailaoshan tectonic belt, where the effects of the Paleo-Tethyan ocean evolution and Indian–Eurasian plate collision are superimposed, is one of the most significant geological discontinuities in western Yunnan province of southeast Tibet. An Ailaoshan micro-block within the belt is bounded by the Ailaoshan suture zone to the west and the Red River Fault to the east, and consists of low- and high-grade metamorphic belts. Late Permian–Middle Triassic granitoids that are widely distributed to the west of the Ailaoshan suture zone and within the Ailaoshan micro-block may yield significant information on the Tethyan tectonic evolution of the Ailaoshan tectonic belt. This study reports new LA–ICP–MS zircon U–Pb geochronology and Hf isotope data of four granitoids from the Ailaoshan high-grade metamorphic belt. Zircon grains from the Yinjie granitoid do not have inherited cores and yield a weighted mean U–Pb age of 247.1 ± 2.0 Ma. The zircon ε_Hf(t) values range from 7.8 to 12.1, and Hf model ages from 775 to 546 Ma, indicating that the granitoid was derived from juvenile crust. The rims of zircons from the Majie and Yuanjiang granitoids yield weighted mean U–Pb ages of 239.5 ± 1.8 and 237.9 ± 2.6 Ma, respectively, whereas the cores yield ages of 1608–352 Ma. The ε_Hf(t) values of zircon rims range from −20.4 to −5.3, yielding Hf model ages from 2557 to 1606 Ma and suggesting that the source magma of the Majie and Yuanjiang granitoids was derived from ancient crust. An additional granitoid located near the Majie Village yields a zircon U–Pb age of 241.2 ± 1.0 Ma. Based on our geochronological and geochemical data, combined with geological observations, we propose that the Ailaoshan micro-block was derived from the western margin of the Yangtze block, and is comparable to the Zhongzan and Nam Co micro-blocks. The presence of late Permian mafic rocks with rift-related geochemical characteristics within the Ailaoshan micro-block, together with granitoids derived from partial melting of ancient/juvenile crust, indicates the presence of an Ailaoshan rift. This possible rift may correspond to the Ganzi–Litang Ocean to the northwest and the Jinping–Song Da rift to the southeast. It is suggested that westward subduction of the Jinshajiang–Ailaoshan–Song Ma oceanic lithosphere triggered the separation of the Zhongzan, Ailaoshan, and Nam Co micro-blocks from the western passive continental margin of the Yangtze block through the opening of the Ganzi–Litang–Ailaoshan–Jinping–Song Da ocean/rift. This ocean/rift may represent a subsidiary branch of the Paleo-Tethyan Ocean along the western margin of the Yangtze block.

[en] The temperature and carrier concentration dependence of the thermopower (TEP) S in Bi₂Sr₂Ca_1-xR_xCu₂O_y (R=Gd, Pr) single crystals were carefully studied. Upon Gd or Pr doping, the superconductivity changes systematically from overdoping to underdoping with the TEP increasing monotonically. S(T)/S(T_scale) against T/T_scale for all the underdoped crystals can be well scaled into a universal curve, where T_scale is the temperature at which S begins to deviate from T-linear behaviour. This scaling behaviour is assumed to correlate with the opening of the pseudogap. Furthermore, the temperature dependence of the TEP is analysed and discussed in terms of two different two-band models and the Nagaosa-Lee model. (author)