Noncentrosymmetric Tetrel Pnictides RuSi4P4 and IrSi3P3: Nonlinear Optical Materials with Outstanding Laser Damage Threshold

Noncentrosymmetric (NCS) tetrel pnictides have recently generated interest as nonlinear optical (NLO) materials due to their second harmonic generation (SHG) activity and large laser damage threshold (LDT). Herein nonmetal-rich silicon phosphides RuSi₄P₄ and IrSi₃P₃ are synthesized and characterized. Their crystal structures are reinvestigated using single crystal X-ray diffraction and ²⁹Si and ³¹P magic angle spinning NMR. In agreement with previous report RuSi₄P₄ crystallizes in NCS space group P1, while IrSi₃P₃ is found to crystallize in NCS space group Cm, in contrast with the previously reported space group C2. A combination of DFT calculations and diffuse reflectance measurements reveals RuSi₄P₄ and IrSi₃P₃ to be wide bandgap (E_g) semiconductors, E_g = 1.9 and 1.8 eV, respectively. RuSi₄P₄ and IrSi₃P₃ outperform the current state-of-the-art infrared SHG material, AgGaS₂, both in SHG activity and laser inducer damage threshold. Due to the combination of high thermal stabilities (up to 1373 K), wide bandgaps (≈2 eV), NCS crystal structures, strong SHG responses, and large LDT values, RuSi₄P₄ and IrSi₃P₃ are promising candidates for longer wavelength NLO materials.     

Assessing students' conceptual understanding using an online three‐tier diagnostic test

When solving a mathematical problem, students who do not have sufficient conceptual understanding may perform poorly and exhibit misconceptions. This study was aimed to examine students' conceptual understanding and significant misconceptions when solving number sense‐related problems. An online three‐tier diagnostic test was administered to 125 fifth‐grade students with varied socio‐economic backgrounds in Hong Kong. Only 14.40% of the students exhibited high performance with high confidence, indicating that these students had a profound conceptual understanding of number sense. In addition, the majority of the students (66.40%) did not demonstrate number sense; these students exhibited several significant misconceptions and could solve the questions only by using a rule‐based method or guessing. Accordingly, most students performed unsatisfactorily on number sense‐related problems. This study is imperative in identifying early predictors and provides information for further compatible interventions in the teaching and learning of number sense in Hong Kong in particular and worldwide in general.     

Unsteady free convection of second‐grade nanofluid with a new time‐space fractional heat conduction

The Caputo and Caputo–Fabrizio derivative are applied to study a second‐grade nanofluid over a vertical plate. A comparative analysis is presented to study the unsteady free convection of a second‐grade nanofluid with a new time–space fractional heat conduction. The governing equations with mixed time–space fractional derivatives are non‐dimensionalized and solved numerically, and a comparison between the Caputo and the Caputo–Fabrizio models is made. It is found that the temperature is higher for the Caputo–Fabrizio fractional model than the Caputo model, but the higher velocity only exists near the vertical plate for the Caputo–Fabrizio model than the Caputo model. Moreover, the velocity for the Caputo model will exceed the Caputo–Fabrizio model as y evolves.     

层序单元体系域划分及勘探意义

体系域是层序地层学理论体系中的重要概念，在隐蔽油气藏的勘探中，勘探家们极为重视低位体系域。但体系域的成因意义、是否有不同级别层序的体系域以及如何划分，在实际工作中认识不一致。结合勃海湾盆地的勘探实例，分析体系域的成因机制、组合特征和勘探规律，认为：体系域是基准面变化等因素作用的产物，不同级别的层序都发育着与其对应的体系域：一般情况下，三级层序对应的体系域单元与含油气层的规模相匹配，但四级层序对应的体系域才是隐蔽油气藏赋存的有利部位。图5参6。     

滑坡相似材料试验结果优化分析研究

在运用模糊综合评判确定的滑坡相似材料试验配合比隶属度基础上，利用方差分析确定各因素的数学优化区间，结合变量有上下界的改进单纯形法，获得技术，经济上的最佳配合比，克服了统计优化理论不能在连续区间寻优的缺点，这对从事滑坡相似材料试验研究具有一定的实际意义。     

Sorting Second-Grade Students: Differentiating Those Retained From Those Promoted.

A cohort of 2nd-grade students provided comparisons of academic and social competence based on school retention/promotion decisions. Sample groups were (a) retained, (b) at risk for retention, (c) special education, and (d) promoted. Findings suggested most children with academic deficiencies are identified by schools early and are sorted into educational treatments differing in intensity that represent a continuum of competence. The authors provide empirical evidence counter to the assumptions that retained students have the requisite ability to catch up and have more problem behaviors than other low-achieving students. The relevance of high-stakes test scores for promotion/retention decisions and the parallels between schools' implementation of retention policy and implementation of regulations for identifying children with disabilities are included in the discussion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

碳纤维连续抽油杆作业车自动调平系统设计

为保证碳纤维连续抽油杆作业车作业时工作平台处于水平状态,防止侧翻,开展了作业车自动调平系统的设计。在给出自动调平系统构成的基础上,着重论述了系统的自动调平控制方案、自动调平控制原理以及自动调平控制软件的设计,给出作业车自动调平控制系统流程图。     

激光冶炼太阳级硅材料的实验研究

通过实验研究表明，大功率ＣＯ２激光器在廉价硅材料制备中应用的可能性。     

低品位硼矿的富集加工技术

报道了青海大柴旦地区低品位硼矿富集加工的新工艺，该工艺使硼矿品位30％－35％，B2O3收率大于80％，该工艺路线已工业化。     

选矿工艺流程的计算

选矿工艺流程计算很繁琐 ,试通过对磁选工艺流程的分析计算举例 ,展示较为简单适用的计算方法。