基于Hyperion高光谱数据的植被冠层含水量反演

植被冠层含水量广泛应用于农业、生态和水文等研究中。本文基于PROSAIL模型,建立了利用Hyperion高光谱数据定量反演植被冠层含水量的模型。首先,PROSAIL模型模拟植被冠层反射特征表明,970 nm水吸收带右侧曲线(980～1 070 nm)一阶导数D_{980～1 070}与冠层含水量关系密切,决定系数达0.96。基于此,利用Hyperion数据的983, 993, 1 003, 1 013, 1 023, 1 033, 1 043, 1 053, 1 063 nm共9个波段计算D_{980～1 070},并利用所建模型反演植被冠层含水量。最后,利用黑河流域盈科绿洲的实测数据对反演结果进行了验证,其平均相对误差为12.5%,均方根误差在0.1 kg·m-2内,结果表明该模型可靠。该研究可以为大范围获取植被含水量信息提供有效方法。     

Y-Cu共掺杂ZnO电子结构与光学性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理平面波赝势法研究了本征ZnO、Y和Cu单掺杂ZnO、Y-Cu共掺杂ZnO的电子结构和光学性质. 计算结果表明, 在本文的掺杂浓度下, Y和Cu单掺杂可以提高ZnO的载流子浓度, 从而改善ZnO的导电性, Y-Cu共掺时ZnO半导体进入简并状态, 呈现金属性. Y 掺杂ZnO可以提高体系在紫外区域的吸收, 而Cu掺杂ZnO在可见光和近紫外区域发生吸收增强现象, 其中由于Y离子和Cu离子之间的协同效应, Y-Cu共掺杂ZnO时体系对可见光和近紫外区域的光子能量吸收大幅增加, 因此Y-Cu共掺杂ZnO可以用于制作光电感应器件.     

ITER第一壁铍铜连接部件在高热负荷作用下的热性能分析

对ITER屏蔽包层第一壁板铍铜连接件在高热负荷作用下的传热性能进行了分析,模拟了第一壁铍铜连接手指部件的热应力和热应变,得到其对应的热疲劳寿命.计算结果表明,在局部4.7MW?m-2高热负荷作用和ITER水冷条件下,现有设计方案中的铍铜连接件的热性能和热疲劳性能均满足设计要求.     

基于第一性原理的Si/SiC、Al/SiC界面成键特性和结合强度对比研究

采用半固态搅拌铸造法制备Al Si7-Si C复合材料,并利用真空压铸工艺实现了其近净成形,结合第一性原理计算方法研究了共晶Si对Si C颗粒和基体界面结合强度的影响.结果显示,在Al Si7-Si C复合材料中,发现较为严重的共晶Si偏析现象,当Si C颗粒同时处于共晶Si和α-Al边界时,形成了少量的共晶Si夹杂、被大量共晶Si包裹、完全被共晶Si包裹三种典型的界面.第一性原理计算结果显示,在C端和Si端的Si/Si C界面中,弛豫后top Si¹配位方式具有最大的粘附功,与Al/Si C界面相比,Si/Si C界面具有更高的结合强度.Si偏析相提高了界面处的电荷密度,因而具有更好的界面结构稳定性.     

第一性原理计算Mo浓度对Mo掺杂BiVO4光催化性能的影响

本文利用基于密度泛函理论的第一性原理研究了不同浓度的Mo掺杂BiVO₄的V位的电子结构、光学性质和光催化性能.缺陷形成能的计算结果说明BiMo_xV_1-xO₄(x=0.0625, 0.125, 0.25)三种掺杂体系都是可以稳定存在的.电子结构计算结果表明：BiMo_xV_1-xO₄(x=0, 0.0625, 0.125, 0.25)四种体系的带隙分别为2.123 eV,2.142 eV,2.160 eV和2.213 eV.掺杂BiVO₄体系的带隙值均大于本征BiVO₄,且带隙随着Mo浓度的增加而增大. BiMo_xV_1-xO₄(x=0.0625, 0.125, 0.25)三种掺杂体系的能带结构全部向低能量区域移动,导致掺杂体系导带底越过费米能级,Mo掺杂BiVO₄后具...     

汞在Ti2NO2 MXene表面吸附氧化的第一性原理计算

汞是一种有毒的重金属,在生产生活中以各种形式排放的汞对生态及人类健康都存在一定程度的威胁.因此,寻找高效的汞吸附剂具有十分重要的意义.本文基于密度泛函理论的第一性原理计算方法,研究了汞在Ti₂NO₂(MXene)和具有一个氧空位缺陷的Ti₂NO₂(Ov-Ti₂NO₂)上的吸附和氧化机理.计算结果表明Hg⁰在Ti₂NO₂表面的吸附为物理吸附,在Ov-Ti₂NO₂表面为化学吸附. Ti₂NO₂表面氧空位的存在可以改善HgO与Ov-Ti₂NO₂之间的相互作用,从而使吸附能提高116 kJ/mol. Hg⁰在Ov-Ti₂NO₂表面氧化为HgO的反应能垒为92.55 kJ/mol,小于其在Ti_2<...     

Molybdenum carbide nano-sheet as a high capacity anode material for monovalent alkali metal-ion batteries—Theoretical investigation

This contribution presents a theoretical investigation of monovalent metal-ion adsorption and diffusion on two-dimensional (2D) buckled nanostructure of molybdenum carbide (MoC) by using the first principle method. We find that buckled MoC nanostructure exhibits great stability, semiconducting electronic property, and high performance as electrode material. Interestingly, Crystal Orbital Hamilton population (COHP) method results show that buckled MoC is chemically stable in a wide range of temperatures, and various Li, Na, ions adsorbed configurations, which is beneficial for anode materials. Especially, single-layer MoC exhibits a superior theoretical capacity of 993.16 mA h g⁻¹ for Li-ions and 496.58 mA h g⁻¹ for Na/K-ions. The storage capacity of 1200 mA h g⁻¹ is found for the adsorption of ions on multilayer bulk MoC. Moreover, migration energy barriers are predicted as 0.38 eV for Li, 0.32 eV for Na, and 0.24 eV for K; these remarkable results determine the applicability of buckled MoC as ideal anode material for metal-ion battery applications.     

Surface,Size and Thermal Effects in Alkali Metal with Core-Electron Binding-Energy Shifts

Consistency between density functional theory calculations and X-ray photoelectron spectroscopy measurements confirms our predications on the undercoordination-induced local bond relaxation and core level shift of alkali metal, which determine the surface, size and thermal properties of materials. Zone-resolved photoelectron spectroscopy analysis method and bond order-length-strength theory can be utilized to quantify the physical parameters regarding bonding identities and electronic property of metal surfaces, which allows for the study of the core-electron binding-energy shifts in alkali metals. By employing these methods and first principle calculation in this work, we can obtain the information of bond and atomic cohesive energy of under-coordinated atoms at the alkali metal surface. In addition, the effect of size and temperature towards the binding-energy in the surface region can be seen from the view point of Hamiltonian perturbation by atomic relaxation with atomic bonding.     

Theoretically exploring the possible configurations,the electronic and transport properties of MoS2-OH bilayer

Inspired by MoS₂-OH bilayer framework (Zhu et al. 2019 [19]), first principles calculations are applied to explore its possible configurations as well as their electronic and transport properties. The calculated results indicate O-MoS₂ and OH…O-MoS₂ are two primary configuration in MoS₂-OH bilayer. It shows negligible difference in electronic structure between O-MoS₂ and pure MoS₂, but a flat band arise at the Fermi level in OH…O-MoS₂. Their contact characteristics show larger binding energy with selected metals and smaller contact barrier with Pt electrode. Besides, the currents of both O-MoS₂ and OH…O-MoS₂ are enlarged compared with that of pure MoS₂ in finite bias, indicating MoS₂-OH bilayer may be potential candidate for future electron device applications.