Buffer anion effects on water oxidation catalysis: The case of Cu(Ⅲ) complex

Water oxidation is the bottleneck of artificial photosynthesis.Since the first ruthenium-based molecular water oxidation catalyst,the blue dimer,was reported by Meyer’ s group in 1982,catalysts based on transition metals have been widely employed to explore the mechanism of water oxidation.Because the oxidation of water requires harsh oxidative conditions,the stability of transition complexes under the relevant catalytic conditions has always been a challenge.In this work,we report the redox properties of a CuⅢ complex(TAML-CuⅢ] with a redox-active macrocyclic ligand(TAML) and its reactivity toward catalytic water oxidation.TAML-CuⅢ displayed a completely different electrochemical behavior from that of the TAML-CoⅢ complex previously reported by our group.TAML-CuⅢ can only be oxidized by one-electron oxidation of the ligand to form TAML·+-CuⅢand cannot achieve water activation through the ligand-centered proton-coupled electron transfer that takes place in the case of TAML-CoⅢ.The generated TAML·+-CuⅢ intermediate can undergo further oxidation and ligand hydrolysis with the assistance of borate anions,triggering the formation of a heterogeneous B/CuOx nanocatalyst Therefore,the choice of the buffer solution has a significant influence on the electrochemical behavior and stability of molecular water oxidation catalysts.

Enhanced charge carrier injection in heterojunction organic field-effect transistor by inserting an MoO_3 buffer layer

A top-contact organic field-effect transistor （OFET） is fabricated by adopting a pentacene/1,11-bis（di-4- tolylaminophenyl） cyclohexane （TAPC） heterojunction structure and inserting an MoO3 buffer layer between the TAPC organic semiconductor layer and the source/drain electrode. The performances of the heterojunction OFET, including output current, field-effect mobility, and threshed voltage~ are all significantly improved by introducing the MoO3 thin buffer layer. The performance improvement of the modified heterojunction OFET is attributed to a better contact formed at the Au/TAPC interface due to the MoO3 thin buffer layer, thereby leading to a remarkable reduction of the contact resistance at the metal/organic interface.

Improved performance of 4H-SiC metal-semiconductor field-effect transistors with step p-buffer layer

An improved 4H-SiC metal-semiconductor field-effect transistors （MESFETs） with step p-buffer layer is proposed, and the static and dynamic electrical performances are analysed in this paper. A step p-buffer layer has been applied not only to increase the channel current, but also to improve the transconductance. This is due to the fact that the variation in p-buffer layer depth leads to the decrease in parasitic series resistance resulting from the change in the active channel thickness and modulation in the electric field distribution inside the channel. Detailed numerical simulations demonstrate that the saturation drain current and the maximum theoretical output power density of the proposed structure are about 30% and 37% larger than those of the conventional structure. The cut-off frequency and the maximum oscillation frequency of the proposed MESFETs are 14.5 and 62 GHz, respectively, which are higher than that of the conventional structure. Therefore, the 4H-SiC MESFETs with step p-buffer layer have superior direct-current and radio-frequency performances compared to the similar devices based on the conventional structure.

Effects of gate-buffer combined with a p-type spacer structure on silicon carbide metal semiconductor field-effect transistors

An improved structure of silicon carbide metal-semiconductor field-effect transistors （MESFET） is proposed for high power microwave applications. Numerical models for the physical and electrical mechanisms of the device are presented, and the static and dynamic electrical performances are analysed. By comparison with the conventional structure, the proposed structure exhibits a superior frequency response while possessing better DC characteristics. A p-type spacer layer, inserted between the oxide and the channel, is shown to suppress the surface trap effect and improve the distribution of the electric field at the gate edge. Meanwhile, a lightly doped n-type buffer layer under the gate reduces depletion in the channel, resulting in an increase in the output current and a reduction in the gate-capacitance. The structural parameter dependences of the device performance are discussed, and an optimized design is obtained. The results show that the maximum saturation current density of 325 mA/mm is yielded, compared with 182 mA/mm for conventional MESFETs under the condition that the breakdown voltage of the proposed MESFET is larger than that of the conventional MESFET, leading to an increase of 79% in the output power density. In addition, improvements of 27% cut-off frequency and 28% maximum oscillation frequency are achieved compared with a conventional MESFET, respectively.

A DESIGN METHODOLOGY FOR LOW-LEAKAGE AND HIGHPERFORMANCE BUFFER BASED ON DEVIANT BEHAVIOR OF GATE LEAKAGE

Based on the observation that both subthreshold and gate leakage depend on transistors width, this paper introduces a feasible method to fast estimate leakage current in buffers. In simulating of leakage current with swept transistor width, we found that gate leakage is not always a linear function of the device geometry. Subsequently, this paper presented the theoretical analysis and experimental evidence of this exceptional gate leakage behavior and developed a design methodology to devise a low-leakage and high-performance buffer with no penalty in area using this deviation.

Study on the Carbon Nanotube Separative Structure for the Extended Gate H^+-Ion Sensitive Field Effect Transistor

We use the carbon nanotube (CNT) as the material of the pH sensing layer of the separative structure for the extended gate H^+-ion sensitive field effect transistor (EGFET) device.The CNT paste was prepared with CNT powder,Ag powder,silicagel,the di-n-butyl phthalate and the toluene solvents by appropriate ratio,then immobilized on the silicon substrate to form the carbon nanotube sensing layer.We measured theⅠ_(DS)-Ⅴ_G curves of the carbon nanotube separative structure EGFET device in the different pH buffer solutions by the Keithley 236Ⅰ-Ⅴmeasurement system.According to the experimental results,we can obtain the pH sensitivities of the carbon nanotube separative structure EGFET device,which is 62.54mV/pH from pH1 to pH13.

基于TCAD模拟的Buffer单粒子效应解析分析

半导体器件和集成电路的辐射效应,其本质就是电子空穴对的产生和复合、电荷的传输与收集、界面态和氧化层陷阱电荷积累等一系列的物理过程。这些物理过程会受到各种因素的影响,例如上拉补偿管的尺寸、重离子入射角度、器件的外延层浓度等。使用TCAD器件/电路混合模式仿真了以上这些关键变量,同时分析了以上效应对对Buffer电路单粒子效应的影响。最终实验结果证明该模拟方法接近于真实情景。

具有独立缓冲结构的PDC—牙轮复合钻头研制

油气勘探开发过程中,难钻地层钻井效率低、钻头寿命短是影响深井、超深井钻井周期和成本的瓶颈问题。钻头工作过程中切削结构轮流与井壁接触而产生的多边形效应是导致钻头不稳定工作、切削齿冲击失效的主要因素。为提高钻头工作稳定性,提出了具有独立缓冲结构的PDC—牙轮复合钻头新结构,并针对四川盆地茅口组Ø311.2 mm井段常规PDC钻头冲击失效严重的问题,设计了3+3+3型(3个主刀翼、3个牙轮以及3个独立缓冲刀翼)的独立缓冲结构复合钻头,开展了全尺寸钻头室内钻进对比实验,并在川渝页岩气区块茅口组—栖霞组地层进行了实钻应用。研究结果表明:①独立缓冲结构复合钻头在常规复合钻头的牙轮切削结构和固定切削结构之间的空隙部位增设独立缓冲刀翼,有效缓解了多边形效应,对PDC齿形成很好的缓冲保护,同时分担了过大的钻压,限制了切削齿吃入深度,进而防止了钻头产生粘滑振动;②独立缓冲结构复合钻头钻压和扭矩波动小,扭矩为PDC钻头的1/5;③独立缓冲结构复合钻头取得了单只钻头进尺170 m的记录,比邻井同层位单只PDC钻头最高进尺提高了73.5%。结论认为,独立缓冲刀翼对提高钻头的稳定性起到了关键作用,不仅提高了钻头寿命,而且有效提高了复杂难钻地层及复杂结构井的综合钻井时效,有效降低了油气勘探开发成本。

Research on Two Types of Buffer Zone Impact on Surrounding Office Space Environment in Winter in Cold Climate Zone—a Fieldwork in Architectural Design Institute Building of Tsinghua University,Beijing

Building buffer zone space is not only one of essential approaches for better mental quality of interior building space, but also an important factor that may influence interior thermal comfort and energy consumption. This study aims to analyze regulative advantages of buffer zone to the surrounding functional spaces. Based on a fieldwork test in a typical office building in cold climate zone in Beijing,China,the monitor data show interior physical performance in the Winter. The research selects two types of different buffer zones in the same building. One is a south-faced greenhouse which has large dimension with plenty of vegetation,and the other is a simple atrium in the middle of five floor building with mount of skylights. The factors and their influence to surrounding functional spaces and the whole building are found out from the comparisons of collected data by floor to floor monitor test on both buffer zones at the same time. The comparisons of two types of buffer zones conclude that the greenhouse is more effective to air quality regulation but not so clearly wellperformed to thermal buffering as expected due to the dominate active central heating in the Winter. This fieldwork test results for building performance can be helpful for both architects and engineers in the early phase of sustainable design.

“缓冲溶液的配制及性质”的创新设计

缓冲溶液是一种能使体系pH值稳定的溶液,在生活中有广泛的应用。无机化学实验、无机及分析化学实验课程中均设置了该实验内容。但根据实践教学发现,传统的实验内容只是设置了单一浓度条件,用pH试纸测试溶液的pH变化,这样的设计存在不直观、设置条件单一等问题,达不到本实验的教学目的。为此,我们重新设计了这部分实验内容:采用指示剂的显色变化代替pH试纸来检验溶液酸碱度的变化;增设不同浓度、不同缓冲比的缓冲溶液及使用精密pH计,考察缓冲容量的影响因素。以上创新设计,学生可以直观地观察溶液颜色的变化,从而理解缓冲溶液的缓冲作用,又可以通过多因素的实验设计,系统地掌握不同的缓冲条件对缓冲容量的影响。从而达到本实验的教学目的及培养学生的自主思考能力和归纳总结能力。

An all-optical buffer based on polarization rotation in an EAM

A theoretical model of the refractive index changes of the TE and TM modes in an electro-absorption modulator （EAM） is deduced. The photon absorption and refractive index changes are analyzed numerically. The influence of pump intensity on the phase difference between the TE and TM modes is studied. The polarization rotation effect is obtained in the EAM, and a novel all-optical fiber loop buffer is designed.

Study on Extended Gate Field Effect Transistor with Nano-TiO-2 Sensing Membrane by Sol-Gel Method

The nano-titanium dioxide (nano-TiO_2) sensing membrane,fabricated by sol-gel technology,was used as the pH-sensing layer of the extended gate field effect transistor (EGFET) device.The objective of this research is the preparation of titanium dioxide materials by sol-gel method using Ti(OBu)_4 as the precursor.In this study,we fabricated a nano-titanium dioxide sensing layer on the ITO glass by dip coating.In order to examine the sensitivity of the nano-TiO_2 films applied to the EGFET devices,we adopted the ITO glass as substrate,and measured theⅠ_(DS)-Ⅴ_G curves of the nano-titanium dioxide separative structure EGFET device in the pH buffer solutions that have different pH values by the Keithley 236 Instrument.By the experimental results,we can obtain the pH sensitivities of the EGFET with nano-TiO_2 sensing membrane prepared by sol-gel method,which is 59.86mV/pH from pH 1 to pH 9.

基于逆Leidenfrost效应的多孔地聚合物微球孔结构及pH缓冲性能

以水玻璃、矿渣粉为材料,基于逆Leidenfrost效应制备了多孔地聚合物微球,研究了其孔结构及pH缓冲性能.结果表明:改变水玻璃掺量和水固比可以调控多孔地聚合物微球的孔结构和pH缓冲性能;当水固比为1.0、水玻璃掺量由4%增大至8%时,微球的孔隙率、中位孔径和孔比表面积均减小,pH值波动范围为1.50~1.90;当水玻璃掺量为4%、水固比由1.0增大至1.2时,微球的孔隙率、中位孔径和孔比表面积均增大,pH值波动范围超过2.00;与双氧水直接发气法制备的多孔地聚合物相比,基于逆Leidenfrost效应制备的多孔地聚合物具有更好的pH缓冲性能和更高的OH-累积浸出量.

Impact resistance performance and optimization of the sand-EPE composite cushion in rock sheds

Rock sheds are widely used to prevent rockfall disasters along roads in mountainous areas.To improve the capacity of rock sheds for resisting rockfall impact,a sand and expandable polyethylene(EPE)composite cushion was proposed.A series of model experiments of rockfall impact on rock sheds were conducted,and the buried depth of the EPE foam board in the sand layer was considered.The impact load and dynamic response of the rock shed were investigated.The results show that the maximum impact load and dynamic response of the rock shed roof are all significantly less than those of the sand cushion.Moreover,as the distance between the EPE foam board and rock shed roof decreases,the maximum rockfall impact force and impact pressure gradually decrease,and the maximum displacement,acceleration and strain of the rock shed first decrease and then change little.In addition,the vibration acceleration and vertical displacement of the rock shed roof decrease from the centre to the edge and decrease faster along the longitudinal direction than that along the transverse direction.In conclusion,the buffering effect of the sand-EPE composite cushion is better than that of the pure sand cushion,and the EPE foam board at a depth of 1/3 the thickness of the sand layer is appropriate.

基于ALE方法的弹体入水硬质聚氨酯泡沫缓冲器降载性能分析

针对弹体高速入水过程中的降载问题,设计一种硬质聚氨酯泡沫缓冲器。基于霍普金森压杆实验技术,获取冲击载荷下硬质聚氨酯泡沫密度和应变率效应,构建其宏观本构模型。采用拉格朗日-欧拉流固耦合方法(ALE),建立弹体入水冲击数值仿真模型,验证所建本构关系及ALE方法的合理性,对加装缓冲器的弹体高速入水问题进行数值仿真计算,获得入水过程中硬质聚氨酯泡沫的动态破坏过程及弹体运动参数,从而分析硬质聚氨酯泡沫密度、厚度对降载特性影响规律,讨论不同入水速度下硬质聚氨酯泡沫参数的设计方法。研究结果表明:硬质聚氨酯泡沫动态力学性能应变率效应不明显,但密度效应明显,缓冲降载性能随硬质聚氨酯泡沫密度和厚度的增大而升高。

生物炭特性及其促进厌氧消化效率的研究进展

厌氧消化是处理污水污泥和有机废弃物的有效方式之一,能够产生丰富的清洁能源。但在实际运行中也存在一些问题,例如消化器不稳定,易出现氨、酸抑制等现象。生物炭作为一种吸附剂被广泛应用在去除废水中有毒金属、有机污染等方面,并且通过加生物炭,可有效缓解酸积累和氨抑制,提高厌氧消化产甲烷能力。分析生物炭的理化性质及其表面特性,探究生物炭提升厌氧消化体系缓冲能力、缓解氨抑制的原理,论述了生物炭在厌氧消化体系中对微生物群落结构的影响。

家庭状况对青少年发展的影响——同胞的调节作用

生育政策变迁凸显了同胞在青少年发展中的作用。基于家庭系统视角和中国教育追踪调查(CEPS)数据,文章探讨了同胞在家庭中影响青少年发展的内在机制。研究发现,家庭状况对青少年发展的影响在独生子与非独生子之间存在差异,同胞对青少年发展具有“缓冲效应”,即同胞的存在难以让青少年从家庭社会经济地位的提高、非忽视型教养方式、非吵闹型夫妻关系、亲密的亲子关系中获取更多的“发展红利”,但也不会更多地遭遇家庭社会经济地位弱势、忽视型教养方式、吵闹型夫妻关系、疏离的亲子关系导致的“发展赤字”。同胞对青少年发展的影响更趋近于“雪中送炭”,而非“锦上添花”。这一发现有助于回应“越穷越生”“有条件生二孩却不生”等社会现象,同时预示“少子化”可能会加剧青少年发展的两极分化。

多相体系的酸碱解离平衡:气相的影响

酸碱平衡是化学教学中十分重要的内容,而在目前的教学中仅仅描述了均相溶液中的酸碱解离与pH缓冲问题,并未描述多相体系中气相成分对体系酸碱解离与pH缓冲的影响。针对该问题,本文以典型的气溶胶多相体系为例,通过对多相缓冲理论和有效解离常数pK_(a)^(*)的分析,讨论了多相体系中组分挥发性和吸湿性对体系酸碱平衡的影响,进而开拓学生思维,并为多相体系酸碱平衡的教学提供新范例。

合肥市夏季城市公园降温效应与优化策略研究

随着我国城镇的快速化发展,城市热环境问题日益恶化。作为城市绿色空间的重要构成部分,城市公园在优化城市热环境方面具有明显效果。本文以安徽省合肥市主城区的18个城市公园为例,基于Landsat8OLI/TIRS遥感数据通过单窗算法反演出地温数据,采用缓冲区分析法计算城市公园的降温效应特征,从降温幅度和降温距离2个维度量化合肥市城市公园的冷岛效应,并分析公园中影响降温效应的主要因素,以期为城市热环境优化与绿地规划提供参考。

质子注入缓冲层结构的高压FS-IGBT动态坚固性研究

具有多重质子注入(multiple proton injection,MPI)缓冲层结构的FS-IGBT,相比传统磷注入缓冲层结构的同类型器件,其动态坚固性发生了改变。通过对MPI缓冲层结构的FS-IGBT的短路特性研究发现,MPI缓冲层的峰数越多,抗短路热失效能力越强,但是峰数太多,可能会引起IGBT在短路时的栅极电压振荡,造成器件失效。这与IGBT在短路大电流下的Kirk效应有关。Kirk效应造成短路时IGBT栅电极下电场降低,电子运动速率减小,进而栅电极下累积的电子造成栅极输入电容的改变,引起栅电压振荡。此外,实验发现,MPI缓冲层峰的氢相关施主(hydrogen-related donors,HDs)浓度不仅与注入剂量和激活温度有关,还与注入次数有关,具体表现为注入次数多,辐射损伤多,HDs浓度越高。文中研究不同MPI缓冲层结构的IGBT关断坚固性。