Instantaneous visual imaging of latent fingerprints in water

Science China Chemistry -     

1980—2018年镇赉县湿地景观格局变化与人为干扰的关系

以吉林省最大湿地保留区镇赉县为研究区，基于1980—2018年8期土地利用数据，采用网格分析法研究湿地景观格局变化规律及景观指数与人为干扰度的关系。结果表明：（1）镇赉县湿地面积减少290.7 km2，水体、滩地、沼泽变化率分别为-0.45，-2.97和-4.84 km²·a^-1。（2）镇赉县湿地率（PLAND）下降6.1%，且从西北部向东南部逐渐递增；斑块数量（NP）与斑块平均面积（AREA_MN）均呈先上升后下降的趋势，东南部湿地景观破碎化加剧，中部破碎化减缓；湿地连通度的空间分布格局为西北向东南递增，斑块结合度指数（COHESION）在中部地区显著增加，在东南部地区缓慢降低。（3）镇赉县湿地人为干扰度逐渐增强、耕地面积的增加和交通网的扩张是镇赉县湿地面积萎缩、景观破碎化加剧和连通度降低的主要人为原因。人为干扰度与NP呈显著正相关，与PLAND、AREA_MN、COHESION均呈负相关。稳定西南部和东北部耕地中湿地斑块，进一步加强中部湿地水体连通性，排查东南部湿地核心区违规建筑，实施分区治理，加强对镇赉县现有湿地的保护，以期实现区域可持续发展。     

Stability analysis of switched fractional-order continuous-time systems

Nonlinear Dynamics - In this paper, a class of switched fractional-order continuous-time systems with order $$0<\alpha <1$$ is investigated. First, an interesting property of...     

正电子冲击下氦电离三重微分截面的理论计算

我们发展了一种正电子碰撞原子电离的畸变波Born近似方法， 在这个方法中，正负电子偶素通道通过一个ab initio的光学势附加到入射粒子和靶的相互作用势上，且通道对电离作用被第一次被考虑在正电子碰撞原子电离的过程中. 应用这个方法计算了在50 eV入射能量范围氦的电离的三重微分截面，计算结果和实验数据很好的符合.     

小孔流速实验中的排水时间和流量系数的研究

本文以水作为理想流体,考虑到水头损失和孔口缩流效应,对小孔流速实验涉及的容器排水问题进行了系统的理论和实验研究.从理论上推导得出了圆柱形容器排水时间的解析解,分析了排水时间和自由液面速度、流量系数之间的规律,提出了排水时间的等效性.实验上,加工了底部开有不同小孔的大型圆柱形容器,测量了容器排水时间随液面高度的变化关系,借助实验结果计算了流量系数值,验证了容器排水时间的等效性关系,实验结果与理论计算符合较好.     

Magnetic behaviors and multitransition temperatures in a nanoisland

A nanoisland consists of center spin-5/2 and perimeter spin-3/2 atoms, which is described by transverse Ising model with single-ion anisotropy. Magnetic behaviors of the nanoisland are studied by the effective-field theory with correlations and the differential operator technique. The formulas of the magnetization and the phase transition of the system are given. The numerical results of the phase transition, the magnetization, the initial susceptibility and the internal energy have been discussed. Some interesting phenomena, such as a new reentrant, are found. Namely there are multitransition temperatures dependent on competition among the single-ion anisotropies, the transverse field and the interlayer coupling. These results can provide some guidance to structure design in the nanoislands.     

Proteins as functional interlayer in organic field-effect transistor

The paper summarizes and discusses the recent advances of proteins as functional interlayers in organic field-effect transistors (OFETs). Specific focus is given on the proteins integrated into the device structure, either to act as dielectric materials or to perform as the functional interlayer between the dielectric and the organic semiconductor (OSC). The main emphasis is give to the location and the specific effect of protein layers in the structure of OFETs. Besides, the possibility of amyloid serving as useful building blocks for OFET is discussed.     

皮肤组织容积脉搏波400~1000 nm光谱特性仿真研究

根据皮肤组织解剖结构特性建立了六层层状模型,并给出了皮肤组织各层的特性参数;考虑了氧合血红蛋白和还原血红蛋白的吸收特性,依据皮肤组织各层的水、血、脂肪、血氧饱和度含量以及血管大小给出了皮肤组织各层的光谱吸收系数;对不同波长散射系数做了适当简化,给出了皮肤组织各层的光谱散射系数。利用蒙特卡罗方法仿真血管组织在收缩与舒张两种状态下, 400~1 000 nm波长光在皮肤组织多层模型中的传输过程,并通过统计大量光子的分布特性,获得了皮肤组织光谱反射系数,并利用模拟所得的两种状态下的反射系数计算得到了光谱容积脉搏波幅度。仿真结果表明,当入射光强一定时,绿光的容积脉搏波幅度优于红光和蓝光。通过计算不同波长光沿皮肤组织深度方向光能流率衰减为1/e时对应的皮肤组织深度,获得了皮肤组织光谱穿透深度。结果显示,血管舒张状态下蓝光和绿光的穿透深度较小,蓝光大部分只能达到表皮层,绿光能到达微循环层,红光可直达真皮层。考虑到光在皮肤组织中传播包含了一个从收缩到舒张的动态过程,基于此,根据穿透深度定义了脉搏波信号产生深度,利用血管舒张与收缩两种不同状态下的穿透深度计算得到了光谱产生深度。结果表明,不同波长光产生深度大于其穿透深度,蓝光产生深度较浅,且其受到的血液吸收调制较小,因而其获得的脉搏信号易受噪声干扰;红光的容积脉搏波产生深度较大,但是相比于绿光其受血液吸收调制较小,且绿光产生深度足够达到真皮血管层,因而红光容积脉搏波的幅度小于绿光。上述仿真结果明确了皮肤组织部分光谱特性,为皮肤组织多光谱容积脉搏波的精确获取及其他相关研究提供了一定的理论基础。     

Heterointerface Engineering of ZnO/CdS Heterostructures through ZnS Layers for Photocatalytic Water Splitting

Solar-driven water splitting to produce clean and renewable hydrogen offers a green strategy to address the energy crisis and environmental pollution. Heterostructure catalysts are receiving increasing attention for photocatalytic hydrogen generation. ZnO/ZnS/CdS and ZnO/CdS heterostructures have been successfully designed and prepared according to two different strategies. By introducing a heterointerface layer of ZnS between ZnO and CdS, a Z scheme charge-transfer channel was promoted and achieved superior photocatalytic performance. A highest hydrogen generation rate of 156.7 μmol g⁻¹ h⁻¹ was achieved by precise control of the thickness of the heterointerface layer and of the CdS shell. These findings demonstrated that heterostructures are promising catalysts for solar-driven water splitting, and that heterointerface engineering is an effective way to improve the photocatalytic properties of heterostructures.     

海洋声场中分布式无源定位系统的节点配置方法

为了提高海洋声场中分布式无源定位系统的定位精度,提出一种基于自适应遗传算法的节点配置方法。首先,基于到达时间TOA(Time of Arrival)定位算法推导出均匀物理场与海洋声场中定位误差的CRLB(Cramer Rao Lower Bound)。之后,利用BELLHOP模型对海洋声场进行建模,获得任意位置处目标声源与节点接收信号相关的传递函数并对等效声速进行计算.以目标声源在观测区域内服从均匀分布为例,将定位误差的平均CRLB最小为优化准则,采用自适应遗传算法对节点进行优化配置。结果表明,该方法能够有效降低海洋声场中分布式无源定位系统的定位误差,并给出定位误差随节点个数增加呈非线性递减的变化趋势,可为工程应用提供理论指导。