我国少数民族学前儿童国家通用语言研究现状与趋势--基于CiteSpace Ⅴ的可视化知识图谱分析

学前教育是终身学习的开端,依据语言发展规律,提高学前儿童尤其是少数民族学前儿童国家通用语言教育质量,对于铸牢中华民族共同体意识具有重要意义,也是实现推普脱贫和乡村振兴“从娃娃抓起”、切实阻断贫困代际传递的起点性民生工程,是多民族国家认同建构的基础性工程,是民族地区发展进步的必由之路。基于此,文章采用CiteSpace Ⅴ数据分析软件,对CNKI数据库中近二十年来与少数民族学前儿童国家通用语言相关的研究文献进行梳理和分析,绘制知识图谱,以直观、清晰的方式呈现我国近二十年来少数民族学前儿童国家通用语言研究现状,以期为我国少数民族学前儿童国家通用语言研究的理论和实践提供参考。

Investigation of non-uniform leading-edge tubercles in compressor cascade:Based on multi-objective optimization and data mining

Corner stall receives noticeable attention in the aeroengine field as an important phenomenon in highly-load compressors.Non-uniform leading-edge tubercles,as an effective method to delay stall,are introduced into the compressor.In this paper,the shape of leading-edge tubercles was controlled by a third-order Fourier function.To judge corner stall,a more precise stall indicator for compressor cascade with flow control methods was defined.Besides,the total kinetic energy of the secondary flow at large incidence was adopted as a parameter for stall evaluation to save computing resources.The results of multiobjective optimization reveal that the loss coefficient exhibited negligible variation at design incidence,while the total kinetic energy of secondary flow showed a significant reduction at large incidence,resulting in a substantial increase in stall incidence.In the optimal profiling cases,the stall incidencewas delayed from 7.9°to 11.6°.The major purpose of the research is to provide proper design guidelines for nonuniformleading-edge tubercles and uncover the flow controlmechanisms of leading-edge profiling.Hence,the geometric features that meet different optimization objectives were extracted through geometric analysis near the Pareto Front and through Self-OrganizingMap(SOM)dataminingmethods in the optimization database.Besides,flow field analysis reveals the flow control mechanism of leading-edge tubercles.The convex-concave-convex structure at the 0%-70%blade height region can form two branches of leading-edge vortex pairs that are opposite in the rotation direction to the passage vortex.The two branches of leading-edge vortex pairs mixed with the leading-edge separation vortex to form two stronger mixed vortices,which can effectively suppress the development of passage vortex and delay stall incidence.

Dietary energy intake affects fetal survival and development during early and middle pregnancy in Large White and Meishan gilts

This experiment was designed to determine the effects of variations in dietary energy intake on reproductive performance and gene expression of luteal and endometrium tissues in Large White(LW)and Meishan(MS) gilts during early and middle pregnancy. After insemination, 32 LW gilts were assigned to high and low(HE_Land LE_L, 14.23 and 12.56 MJ DE/kg, respectively) diet treatment groups,while 32 MS gilts were allocated to HE_M and LE_M(12.56 and 10.88 MJ DE/kg) groups. Gilts were slaughtered on days 35, 55 and 90 of gestation. The fetal survival and luteal progesterone(P_4) concentration in the HE_Lgroup were higher on day 35 but lower on day 90 of gestation compared with the LE_L group(P < 0.05) for LW gilts. However, fetal survival and luteal P_4 concentration on day 35 of gestation were greater(P < 0.05) in the LE_M group than in the HE_M group for MS gilts, but no significant difference in mid-gestation was showed. The fetal weights of both breeds were higher for the high energy diets compared with the respective control group on day 90 of gestation(P < 0.05). In addition,the m RNA levels of P_4 synthesis-related proteins had correlated with luteal P_4 concentration in both breeds. Further, endometrial levels of uteroferrin(ACP5), retinol-binding protein 4(RBP_4) and secreted phosphoprotein 1(SPP1) m RNA were upregulated in the HE_Lgroup on day 35 of gestation but ACP5 and SPP1 were downregulated on day 55 of gestation compared with the LE_Lgroup(P < 0.05) for LW gilts. In MS gilts, diet only affected the expression of SPP1(P < 0.05). Our results revealed the differential sensitivity of LW and MS breeds to variations in dietary energy intake. For LW gilts, the HE_Lgroup improved fetal survival on day 35 but a sustained high energy diet decreased fetal survival on day 90 of gestation. The differences in dietary energy intake did not influence fetal survival on day 90 of gestation but the higher energy diet did increase fetal weight in the MS breed compared with the lower energy intake diet. These results may be due to differential luteal secretion activity and endometrium gene expression in these two breeds.

Electrocatalytic C0_(2) Reduction with Re-Based Spiro Bipyridine Complexes: Effects of the Local Proton in the Second Coordination Sphere

We report herein a Re-based tricarbonyl catalyst[fac-Re(L1)(CO)_(3)Cl](Re1)bearing a spiro center and a phenol group as a local proton source in the second coordination sphere.Due to the large steric spiro group,dimerization of one-electron reduced species was completely eliminated,improving the stability of Re1.Simultaneously,the phenol group in the second coordination sphere improves the formation of an H-bonding chain that promotes the protonation of C0_(2) reduction intermediates,boosting the electrocatalytic C0_(2) reduction activity of Re1.Mechanistic studies reveal that the doubly reduced complex Re1b is active for C0_(2) addition.