Finding any given 2‐factor in sparse pseudorandom graphs efficiently

Given an $n$‐vertex pseudorandom graph $G$ and an $n$‐vertex graph $H$ with maximum degree at most two, we wish to find a copy of $H$ in $G$, that is, an embedding $\phi :V\left(H\right)\to V\left(G\right)$ so that $\phi \left(u\right)\phi \left(v\right)\in E\left(G\right)$ for all $uv\in E\left(H\right)$. Particular instances of this problem include finding a triangle‐factor and finding a Hamilton cycle in $G$. Here, we provide a deterministic polynomial time algorithm that finds a given $H$ in any suitably pseudorandom graph $G$. The pseudorandom graphs we consider are $\left(p,\lambda \right)$‐bijumbled graphs of minimum degree which is a constant proportion of the average degree, that is, $\mathrm{\Omega }\left(pn\right)$. A $\left(p,\lambda \right)$‐bijumbled graph is characterised through the discrepancy property: $|e\left(A,B\right)?p|A||B||<\lambda \sqrt{|A||B|}$ for any two sets of vertices $A$ and $B$. Our condition $\lambda =O(p^{2}n/\log n)$ on bijumbledness is within a log factor from being tight and provides a positive answer to a recent question of Nenadov. We combine novel variants of the absorption‐reservoir method, a powerful tool from extremal graph theory and random graphs. Our approach builds on our previous work, incorporating the work of Nenadov, together with additional ideas and simplifications.     

全球海洋潜水旅游目的地分布特征及其自然影响因素研究

以全球海洋潜水旅游目的地为研究对象, 借助地理信息系统(GIS), 运用基尼系数、层次分析法(AHP)等方法, 研究全球海洋潜水旅游目的地的分布特征及其自然影响因素. 结果显示: (1)全球海洋潜水旅游目的地的分布数量由低纬向高纬递减; 洲际分布呈现高度集中, 主要聚集区是东亚与东南亚、地中海-红海以及加勒比海沿岸, 太平洋、印度洋与大西洋为散点分布. (2)影响海洋潜水旅游目的地的自然因素主要为海洋地形、海水温度、陆地气温、洋流、潮汐、海水能见度、珊瑚礁等, 相关因素影响程度与广度因海域呈现地域综合导控, 使得海洋潜水旅游目的地主要聚集在热带海域等地.     

5年制学前教育专业学生科学核心素养的调查研究

从知识、方法能力、情感态度等3个维度阐释了幼儿教师科学核心素养的含义。为了解5年制学前教育专业学生是否具有幼儿教师的科学核心素养，对唐山市5年制学前教育专业2015级403名在校生的科学核心素养进行了问卷调查。通过对调查结果进行统计分析，揭示了唐山市5年制学前教育专业学生科学核心素养的现状，分析了影响因素。在此基础上，为培养5年制学前教育专业学生具有幼儿教师的科学核心素养提出了一些建议。     

Transition probabilities of the X1Σ+, A1Π, B1Δ, C1Σ+, and D1Π states of the AlO+ cation

ABSTRACT

This study computes the potential energy curves of the X¹Σ⁺, A¹Π, B¹Δ, C¹Σ⁺, and D¹Π states of AlO⁺ cation and the transition dipole moments between them. The orders of the rotationless radiative lifetimes are 10–100?μs for the A¹Π state, 1–1000?ms for the B¹Δ state, 10?ns for the first well and 100?ns for the second well of the C¹Σ⁺ state, and 1?μs for the D¹Π state. Emissions of the B¹Δ–A¹Π and D¹Π–C¹Σ⁺ systems are so weak that they are hardly measured via spectroscopy, the emissions of the C¹Σ⁺–X¹Σ⁺, C¹Σ⁺–A¹Π, and D¹Π–X¹Σ⁺ systems are so strong that they can be detected readily, and emissions of the A¹Π–X¹Σ⁺ and D¹Π–A¹Π systems can be observed through spectroscopy only by a significant effort. There is a strong great similarity between spontaneous emissions of the A¹Π–X¹Σ⁺ system of the AlO⁺ cation and the A²Π–X²Σ⁺ system of the AlO radical. The emissions of the A²Π–X²Σ⁺ system of the AlO radical have been measured in outer space Therefore, it is highly possible that the emissions of the A¹Π–X¹Σ⁺ system of the AlO⁺ cation can be detected in the astrophysical media.     

An Improved Composite Multiscale Fuzzy Entropy for Feature Extraction of MI-EEG

Motor Imagery Electroencephalography (MI-EEG) has shown good prospects in neurorehabilitation, and the entropy-based nonlinear dynamic methods have been successfully applied to feature extraction of MI-EEG. Especially based on Multiscale Fuzzy Entropy (MFE), the fuzzy entropies of the τ coarse-grained sequences in τ scale are calculated and averaged to develop the Composite MFE (CMFE) with more feature information. However, the coarse-grained process fails to match the nonstationary characteristic of MI-EEG by a mean filtering algorithm. In this paper, CMFE is improved by assigning the different weight factors to the different sample points in the coarse-grained process, i.e., using the weighted mean filters instead of the original mean filters, which is conductive to signal filtering and feature extraction, and the resulting personalized Weighted CMFE (WCMFE) is more suitable to represent the nonstationary MI-EEG for different subjects. All the WCMFEs of multi-channel MI-EEG are fused in serial to construct the feature vector, which is evaluated by a back-propagation neural network. Based on a public dataset, extensive experiments are conducted, yielding a relatively higher classification accuracy by WCMFE, and the statistical significance is examined by two-sample t-test. The results suggest that WCMFE is superior to the other entropy-based and traditional feature extraction methods.     

拉伸载荷作用下单边缺陷-边裂纹应力强度因子研究

利用杂交位移不连续法研究拉伸载荷作用下矩形板中单边缺陷-边裂纹(半圆孔裂纹和半方孔裂纹)问题,给出了这三种平面弹性裂纹问题的应力强度因子的详细数值解。通过半圆孔裂纹问题和半方孔裂纹问题与单边裂纹问题的应力强度因子的比较,发现半圆孔和半方孔对单边裂纹有屏蔽影响。此外,本文的研究结果表明,杂交位移不连续法用于分析平面弹性有限体中复杂裂纹问题的应力强度因子简单且又准确。     

Key Factors for Simultaneous Improvements of Performance and Durability of Core‐Shell Pt3Ni/Carbon Electrocatalysts Toward Superior Polymer Electrolyte Fuel Cell

It remains a big challenge to remarkably improve both oxygen reduction reaction (ORR) activity and long‐term durability of Pt?M bimetal electrocatalysts simultaneously in the harsh cathode environment toward widespread commercialization of polymer electrolyte fuel cells (PEFC). In this account we found double‐promotional effects of carbon micro coil (CMC) support on ORR performance and durability of octahedral Pt₃Ni nanoparticles (Oh Pt₃Ni/CMC). The Oh Pt₃Ni/CMC displayed remarkable improvements of mass activity (MA; 13.6 and 34.1 times) and surface specific activity (SA; 31.3 and 37.0 times) compared to those of benchmark Pt/C (TEC10E20E) and Pt/C (TEC10E50E‐HT), respectively. Notably, the Oh Pt₃Ni/CMC revealed a negligible MA loss after 50,000 triangular‐wave 1.0–1.5 V_RHE (startup/shutdown) load cycles, contrasted to MA losses of 40 % (TEC10E20E) and 21.5 % (TEC10E50E‐HT) by only 10,000 load cycles. It was also found that the SA increased exponentially with the decrease in the CO stripping peak potential in a series of Pt?M/carbon (M: Ni and Co), which predicts a maximum SA at the curve asymptote. Key factors for simultaneous improvements of performance and durability of core‐shell Pt₃Ni/carbon electrocatalysts toward superior PEFC is also discussed.     

Stafia-1: a STAT5a-Selective Inhibitor Developed via Docking-Based Screening of in Silico O-Phosphorylated Fragments

We present a new approach for the identification of inhibitors of phosphorylation-dependent protein–protein interaction domains, in which phenolic fragments are adapted by in silico O-phosphorylation before docking-based screening. From a database of 10 369 180 compounds, we identified 85 021 natural product-derived phenolic fragments, which were virtually O-phosphorylated and screened for in silico binding to the STAT3 SH2 domain. Nine screening hits were then synthesized, eight of which showed a degree of in vitro inhibition of STAT3. After analysis of its selectivity profile, the most potent inhibitor was then developed to Stafia-1, the first small molecule shown to preferentially inhibit the STAT family member STAT5a over the close homologue STAT5b. A phosphonate prodrug based on Stafia-1 inhibited STAT5a with selectivity over STAT5b in human leukemia cells, providing the first demonstration of selective in vitro and intracellular inhibition of STAT5a by a small-molecule inhibitor.     

地方高校化学师范生对教师职业认同现状及影响因素调查研究

采用问卷和访谈的方式对化学师范生对教师职业认同情况进行了调查。结果表明：化学师范生对教师职业认同总体水平较高；教师职业认同水平在性别上差异不显著；教师职业认同水平在年级上差异显著，大一师范生的认同水平较高。根据调查结果，分析了化学师范生对教师职业认同的影响因素，并就提升化学师范生对教师职业认同提出了建议。     

高精度四极质谱检测限测试和影响因素分析

高精度四极质谱仪(QMS)的气体分压精确测量功能与其使用方法关系密切.采用包含有四极质谱仪、真空系统和进样系统的质谱参数测试装置,针对工作及系统参数对质谱测试结果的影响开展研究.试验结果表明:无论是扫描速率、质量数分辨率、电压和探测器等质谱工作参数,还是真空本底、工作真空和气体种类等系统参数都会对质谱测试结果尤其检测限产生一定影响.试验获得了特定条件下的最优参数并进行比较.采用获得的最优参数组合,通过测量空气中极低含量稀有氪气和氙气的同位素谱图,可获得一定条件下法拉第杯(FC)、二次电子倍增器(SEM)和离子计数器(CP)等3种探测器的最小可检浓度,分别为17.3×10-9、0.34×10-9和0.15×10-9.其中SEM和CP的检测限最低,适合用于微量气体分析.