城市河道系统的景观敏感性与景观规划

运用景观生态学的原理,通过对城市河道系统的景观敏感性与视觉美学敏感性的分析,指出景观系统的敏感性是指不同时间和空间尺度上系统对干扰的反应.揭示了城市化的快速发展使土地利用方式发生大规模改变的同时,城市河道及其沿岸景观系统在结构、形态上也发生巨大变化,导致河流水文、生态系统的破坏与功能的退化,城市水文洪涝灾害频发、水质污染严重和美学质量下降等问题,提出用景观规划探讨城市河道系统的保护、修复与补偿系统及可持续发展途径.     

单向KFRP的应变率相关的本构方程

在旋转盘式杆杆型冲击拉伸试验装置上 ,对单向Kevlar 49纤维增强酚醛树脂复合材料(KFRP)进行了冲击拉伸试验 ,得到了应变率为 15 0 ,40 0和 15 0 0s-1下的单向KFRP的完整拉伸应力应变曲线 ;结果表明 ,单向KFRP的力学性能是应变率相关的。通过改进复合丝束模型 ,建立了计及应变率效应的单向KFRP的一维损伤宏观本构方程。     

4.3 THz quantum-well photodetectors with high detection sensitivity

We demonstrate a high performance GaAs/AlGaAs-based quantum-well photodetector(QWP) device with a peak response frequency of 4.3 THz. The negative differential resistance(NDR) phenomenon is found in the dark current–voltage(I–V) curve in the current sweeping measurement mode, from which the breakdown voltage is determined. The photocurrent spectra and blackbody current responsivities at different voltages are measured. Based on the experimental data, the peak responsivity of 0.3 A/W(at 0.15 V, 8 K) is derived, and the detection sensitivity is higher than 10~(11) Jones,which is in the similar level as that of the commercialized liquid-helium-cooled silicon bolometers. We attribute the high detection performance of the device to the small ohmic contact resistance of ～ 2 ? and the big breakdown bias.     

超高压液相色谱-静电场轨道阱高分辨质谱筛查渔用饲料中175种药物EI北大核心CSCD

建立了超高压液相色谱-静电场轨道阱高分辨质谱快速筛查渔用饲料中多种类药物残留的方法。饲料样品经1%甲酸乙腈溶液提取,浓缩复溶后加水稀释,离心除沉淀,以0.1%甲酸水溶液和0.1%甲酸乙腈溶液为流动相,经Accucore RP-MS色谱柱(100 mm×2.1 mm i.d.,2.6μm)梯度洗脱分离,H-ESI(Heated Electrospray Ionization)离子化,采用Full M S/dd-M S2(Top N)模式采集数据,利用自建的数据库进行定性分析。当满足母离子质荷比偏差<3×10-6;保留时间偏差<15 s;同位素质荷比偏差<1×10-5、相对丰度偏差<25%、综合比对>75%;碎片离子质荷比偏差<2×10-5且至少有一个碎片与数据库中匹配时认为确证检出。方法在200μg/kg可同时定性确证175种药物,50μg/kg同时定性确证136种药物,10μg/kg同时定性确证116种药物,RSD<30%,母离子相对偏差均小于1.9×10-6。200μg/kg加标时,81%的化合物回收率在30%~110%之间。     

网格重分中关于守恒重映的几个问题

首先针对离散情况,对垸恒重映中的“守恒”给出数学上严格的解释。在此基础上,对守恒重映问题中所固有的守恒量协调问题作了描述,并提出一种基于最小二乘法的处理方案,同时,还分析了容易混淆的“质量密度”和“体积密度”,网格中心量和网格节点量等基本概念,并采用两种不同的辅助网格来对网格节点量进行重映。     

用分子轨道理论研究NO气体在TiO2表面吸附

根据一氧化氮(NO)气体在二氧化钛(TiO)表面吸附和脱附的实验结果,揭示了气体脱附量的变化规律．利用MOPAC和GAUSSIAN分子轨道理论计算了在TiO2(110)表面上吸附NO分子的原子簇模型,电荷分布以及原子簇的能级,推断了NO在TiO(110)表面吸附的稳定性．     

石墨炉原子吸收光谱法测定酒中铅

铅是一种毒性很强的金属元素,可以破坏儿童的神经系统,导致血液循环系统和脑的疾病。铅有积蓄作用,人体长期摄入微量铅可引发铅中毒,并且,铅在人体内积蓄后很难自动排除,只能通过某些药物来清除。酒中铅主要来源于生产设备、原辅材料及贮存容器。根据我国食品卫生标准的要求,铅是酒类卫生指标的必检项目之一。目前测定酒     

Security of a practical semi-device-independent quantum key distribution protocol against collective attacks

Similar to device-independent quantum key distribution(DI-QKD), semi-device-independent quantum key distribution(SDI-QKD) provides secure key distribution without any assumptions about the internal workings of the QKD devices.The only assumption is that the dimension of the Hilbert space is bounded. But SDI-QKD can be implemented in a oneway prepare-and-measure configuration without entanglement compared with DI-QKD. We propose a practical SDI-QKD protocol with four preparation states and three measurement bases by considering the maximal violation of dimension witnesses and specific processes of a QKD protocol. Moreover, we prove the security of the SDI-QKD protocol against collective attacks based on the min-entropy and dimension witnesses. We also show a comparison of the secret key rate between the SDI-QKD protocol and the standard QKD.     

基于非共价键制备高韧性可修复聚合物复合材料

Interfaces between nacreous tablets are crucial to the outstanding mechanical properties of nacre in natural shells and inspired by the “brick-and-mortar” structure and remarkable mechanical performance of nacre. Excellent research has been conducted to probe the effect of interfaces on strength and toughness of nacre, providing critical guidelines for the design of human-made laminated composites. Herein, a class of graphene oxide (GO) based artificial nacre composite material with self-healing capacity due to non-covalent bonding interactions was fabricated by functionalization of GO with ellagic acid through π-π stacking followed by evaporation-induced self assembling process between ellagic acid modified graphene oxide(EGO) and polyurethane(PU). The artificial nacre displays a strict “brick-and-mortar” structure, with EGO nanosheets as the brick and PU as the mortar. The structure of EGO was characterized by infrared spectroscopy, potential analyzer and X-ray diffraction, and the mechanical properties of PU-EGO were tested by universal testing machine. The results show that ellagic acid (ELA) is successfully adsorbed on GO surface, and when the mass ratio of PU to EGO is 3∶1, the tensile strength and toughness of the material reach 111.2 MPa and 81.5 MJ/m3, respectively (9.6 times and 1.8 times higher than that of PU), attributing to the interlayer slip of GO by breaking and recombing the π-π bond dynamically through which the energy can dissipate when PU-EGO is subjected to tensile stress. In addition, owning to the existence of non-covalent bonds, the resulting polymer composites display good recyclability. This work provides a pathway for the development of artificial nacre with self-healing capacity and recyclability. © 2023 The Author(s).