Controlled Element Specific Nanoscale Domains by Self-Assembly for High Performance Bifunctional Alkaline Water Splitting Catalyst

A stable bifunctional water-splitting catalyst can simplify the development of alkaline medium electrolyzers. In this study, a catalytic material with controlled nanoscale domains of Pt and Ni is formed by a self-assembly process at room temperature. The final structure of the catalyst is achieved through two-stage transformation, first is the formation of Pt-Ni nanoscale domains and then inducing Ni to higher oxidation states. The material has a nanowire-like morphology at the macroscale, which ensures rapid kinetics and mass transfer. The results prove that the nanoscale domains of Pt, Ni, and Ni²⁺ and Ni³⁺ with close interfacing are crucial for the performance of the electrocatalyst and ensure the presence of Ni in a high oxidation state, leading to both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity. The catalyst has a low overpotential and ultralow Tafel slope for both HER and OER, 13.7 and 32 mV dec⁻¹, respectively, crucial for high power applications.     

基于不同蒸散方法的SPEI在天山南北坡气象干旱的差异性分析

为更好的研究与指导天山南北坡干旱灾害的预警与应对,采用Penman-Monteith、器测法和Thornthwaite方法确定潜在蒸散量(PET),并分别计算相应的标准化降水蒸散指数(SPEI),分别记为SPEI-PM、SPEI-SJ和SPEITH,探讨1960-2016年气象干旱时空变化特征与分析不同蒸散方法下干旱指数的差异性,并评估与历史干旱事件的相符性。结果表明:(1)从趋势变化分析可知,天山南北坡在SPEI-SJ和SPEI-PM指数下呈现湿润化和干旱面积率下降的特征,SPEI-TH指数则相反;(2)空间频率分析显示SPEI-SJ和SPEI-PM指数下研究区年和季节尺度上干旱发生频率一致,即春、夏干旱频发、秋季次之、冬季最少,而SPEI-TH指数下干旱发生频率在各时间变化特征相差不大,SPEI-SJ和SPEI-PM指数下干旱发生频率在空间上保持一致,局部区域存一定的偏差,总体与干旱强度变化趋势一致;(3)基于历次干旱事件可知,SPEI-PM指数对于1986年前的旱灾有较为准确的描述,而SPEI-SJ指数仅针对1990年后对干旱有较准确的描述,SPEI-TH指数对干旱的监测能力较差。综合分析表明SPEI-PM指数对历史干旱事件监测适用性较好,20世纪90年代后,SPEI-SJ指数对干旱的监测有重要的参考价值。     

Improving Electrical Stability and Ideality in Organic Field‐Effect Transistors by the Addition of Fullerenes: Understanding the Working Mechanism

Electrical instability and nonideality due to undesirable electron injection are often‐encountered problems for high‐mobility organic field‐effect transistors (OFETs) with low‐bandgap polymer semiconductors. Due to electron trapping and the resulting accumulation of negative charges on the silicon dioxide dielectric, transfer curves deviate from ideality characteristics and double‐slopes are observed as the devices are operated for extended periods of time. One way to circumvent those is to use an electron‐acceptor additive, such as fullerene and its derivatives. This work interprets the mechanisms of how fullerene derivatives suppress electron transport and electrical instability while maintaining high hole mobility in p‐type OFETs. This study shows that hole transport of the active layer is uninterrupted upon the addition of the electron acceptors. Most importantly, the added fullerene derivatives out‐compete SiO₂ to acquire electrons that are injected into the polymers. Electrical instability and double‐slope induced from electron trapping at SiO₂ surface are thereby suppressed.     

Influence of surface roughness features on mixed‐film lubrication

An optical technique (three‐dimensional spacer layer imaging) has been developed to map accurately lubricant film thickness in thin‐film elastohydrodynamic (EHD) contacts. This experimental technique has been used to study the influence of surface roughness features, asperity height, and slope on EHD film thickness and pressure. Single ridges transverse to the entrainment direction were used to represent asperities. It was found that the ridges with lower slopes generate films of greater minimum thickness. Below a certain entrainment speed, the minimum film thickness declined at a rate dependent on the ridge slope. At low speeds, the ridges with higher slopes entrapped a larger volume of lubricant ahead of the ridge and along the entrainment direction. For all speeds, the highest ridges entrapped the most lubricant. Both ridge slope and ridge height had a negligible effect on mean film thickness in the contact. Asperity pressure increased with higher ridge slope, but was not influenced by entrainment speed. An increase in pressure was found where lubricant is entrapped upstream of a ridge.     

Optical Activation of TrkB (E281A) in Excitatory and Inhibitory Neurons of the Mouse Visual Cortex

The activation of tropomyosin receptor kinase B (TrkB), the receptor of brain-derived neurotrophic factor (BDNF), plays a key role in induced juvenile-like plasticity (iPlasticity), which allows restructuring of neural networks in adulthood. Optically activatable TrkB (optoTrkB) can temporarily and spatially evoke iPlasticity, and recently, optoTrkB (E281A) was developed as a variant that is highly sensitive to light stimulation while having lower basal activity compared to the original optoTrkB. In this study, we validate optoTrkB (E281A) activated in alpha calcium/calmodulin-dependent protein kinase type II positive (CKII⁺) pyramidal neurons or parvalbumin-positive (PV⁺) interneurons in the mouse visual cortex by immunohistochemistry. OptoTrkB (E281A) was activated in PV⁺ interneurons and CKII⁺ pyramidal neurons with blue light (488 nm) through the intact skull and fur, and through a transparent skull, respectively. LED light stimulation significantly increased the intensity of phosphorylated ERK and CREB even through intact skull and fur. These findings indicate that the highly sensitive optoTrkB (E281A) can be used in iPlasticity studies of both inhibitory and excitatory neurons, with flexible stimulation protocols in behavioural studies.     

考虑二维降雨入渗的非饱和土边坡瞬态体积含水率分析

降雨是非饱和土边坡失稳的关键因素之一,非饱和土体的强度与体积含水率有密切的关系.考虑二维降雨入渗条件,基于非饱和土达西渗流定理及质量守恒定律建立了非饱和土的二维降雨入渗模型方程.基于交替隐式有限差分法,采用MATLAB编制了计算程序,对方程进行了数值计算,研究了不同降雨条件、边坡内部不同位置的瞬态体积含水率分布.研究表明,由于考虑了水平方向的入渗,边坡内随着深度和水平距离的增加,体积含水率都发生了变化,在距离边坡表面1 m左右时,体积含水率变化率变小,边坡表层的体积含水率变化远远大于边坡深部.初始体积含水率越小,边坡体积含水率变化越大,这对边坡的稳定性不利.     

三峡库区巫峡段反倾岩石边坡的破坏机制及判据

 三峡库区巫峡段龚家坊2#斜坡属反倾岩石边坡,发育薄厚互层和软硬相间的岩体结构,在库水位抬升后发生了大型滑塌。为了研究该类岩石边坡的破坏机制和判据,基于龚家坊2#斜坡岩体结构的调查成果,分析厚薄互层的反倾岩石斜坡弯曲变形过程,及库水作用下斜坡的破坏机制。基于叠合悬臂梁模型、独立悬臂梁模型,提出薄厚互层反倾岩石斜坡各破坏阶段的应力判据。采用有限元分析库水软化作用下,龚家坊2#斜坡岩石的强度折减参数及变形破坏规律。研究结果表明：(1) 上硬(嘉陵江组)下软(大冶组)的沉积结构和快速下切的河谷,是巫峡龚家坊至独龙段反倾斜坡普遍发育弯曲变形的关键因素;(2) 厚薄相间的岩层结构,使反倾岩石边坡表现为多阶段破坏,其中,薄层弯曲岩层和厚层坚硬岩层,分别以叠合悬臂梁模型和独立悬臂梁模型建立破坏判据;(3) 库水对该区薄层泥灰岩软化后的抗剪强度小于天然强度的85%,斜坡发生自下而上的渐进式破坏。     

圆弧滑动边坡反演设计的自适应神经模糊推理方法研究

圆弧滑动边坡反演设计的神经网络方法存在着收敛速度慢、拟合能力差、预测精度低、训练结果不具有唯一性等缺陷。针对这些缺陷,应用自适应神经模糊推理系统的原理,建立了圆弧滑动边坡反演设计的自适应神经模糊推理方法,并应用该方法对部分实例进行了反演设计。反演设计结果表明,该方法具有收敛速度快、拟合能力强、预测精度高、训练结果具有唯一性等优点,是一种优异的反演设计方法。     

露天矿山高陡边坡智能在线监测及预警系统研究

为实时掌握边坡安全状况,尖山铁矿采用了边坡智能在线监测及预警系统,该系统运行稳定,效果明显。     

Numerical modeling of failure mechanisms in phyllite mine slopes in Brazil

This paper presents three case studies comprising failure mechanisms in phyllite mine slopes at Quadrilá-tero Ferrífero, State of Minas Gerais, Brazil. Numerical modeling techniques were used in this s...