长江口新成陆区域土壤重金属分布及风险评价——以上海市横沙东滩为例

为了解长江口新成陆区域土壤中重金属污染特征及其生态风险,对上海市横沙东滩71个采样点土壤中8种重金属(铜、铬、镍、锌、铅、镉、砷、汞)的含量进行检测和统计分析,并结合蒙特卡洛模拟对其生态风险进行评价。结果表明：(1)表层土壤中重金属的含量由高到低依次为锌、铬、镍、铅、铜、砷、镉、汞,其平均值均低于上海市土壤背景值。铬、镍、锌、铅、汞服从对数正态分布,铜、镉、砷既不服从正态分布也非对数正态分布。(2) Hakanson潜在生态风险指数法评价结果表明,各重金属潜在生态风险因子高低顺序为汞>镉>砷>镍>铅>铜>铬>锌,8种重金属的潜在生态风险指数(RI)为36.80～150.96,处于轻微至中等生态风险水平,且以轻微生态风险水平为主(概率为93.34%)。ERL/ERM法评价结果表明,8种重金属时常发生生态风险的概率极小(<0.72%),镉、铅、锌、铜、汞、铬、砷很少或者无负面生态风险,而镍则偶尔发生生态风险(概率为95.04%)。8种重金属总体发生生态风险的等级和频率均较低,但部分重金属(如汞、镍)须予以一定关注。     

Hierarchical Magnetic Network Constructed by CoFe Nanoparticles Suspended Within “Tubes on Rods” Matrix Toward Enhanced Microwave Absorption

Hierarchical magnetic-dielectric composites are promising functional materials with prospective applications in microwave absorption(MA)field.Herein,a three-dimension hierarchical“nanotubes on microrods,”core–shell magnetic metal–carbon composite is rationally constructed for the first time via a fast metal–organic frameworksbased ligand exchange strategy followed by a carbonization treatment with melamine.Abundant magnetic CoFe nanoparticles are embedded within one-dimensional graphitized carbon/carbon nanotubes supported on micro-scale Mo2N rod(Mo2N@CoFe@C/CNT),constructing a special multi-dimension hierarchical MA material.Ligand exchange reaction is found to determine the formation of hierarchical magnetic-dielectric composite,which is assembled by dielectric Mo2N as core and spatially dispersed CoFe nanoparticles within C/CNTs as shell.Mo2N@CoFe@C/CNT composites exhibit superior MA performance with maximum reflection loss of−53.5 dB at 2 mm thickness and show a broad effective absorption bandwidth of 5.0 GHz.The Mo2N@CoFe@C/CNT composites hold the following advantages:(1)hierarchical core–shell structure offers plentiful of heterojunction interfaces and triggers interfacial polarization,(2)unique electronic migration/hop paths in the graphitized C/CNTs and Mo2N rod facilitate conductive loss,(3)highly dispersed magnetic CoFe nanoparticles within“tubes on rods”matrix build multi-scale magnetic coupling network and reinforce magnetic response capability,confirmed by the off-axis electron holography.     

基于二阶滤波器的高阶带通滤波器设计和仿真

根据n阶带通滤波器传递函数的特点和低通与高通级联的思想,给出了高阶RC有源带宽可调的带通滤波器的一般设计方法和VCVS结构电路的设计步骤,并成功设计出一款高性能的四阶有源带通滤波器,其电路简单,通频带宽,精度高,成本低廉.经Multisim10仿真测试,其性能完全达到了预期效果和设计要求.     

电缆电视的传输系统

本文证明了放大器的等利用差原理。按此原理设计，传输系统的放大器将有最大实用功率输出。详细分析了环境温度对传输系统的影响，阐述了一些新概念，并提出一种论理严密，实用性强的新设计方法。     

Blue Luminescence of ZnO Nanoparticles Based on Non‐Equilibrium Processes: Defect Origins and Emission Controls

High concentrations of defects are introduced into nanoscale ZnO through non‐equilibrium processes and resultant blue emissions are comprehensively analyzed, focusing on defect origins and broad controls. Some ZnO nanoparticles exhibit very strong blue emissions, the intensity of which first increase and then decrease with annealing. These visible emissions exhibit strong and interesting excitation dependences: 1) the optimal excitation energy for blue emissions is near the bandgap energy, but the effective excitation can obviously be lower, even 420 nm (2.95 eV < E_g = 3.26 eV); in contrast, green emissions can be excited only by energies larger than the bandgap energy; and, 2) there are several fixed emitting wavelengths at 415, 440, 455 and 488 nm in the blue wave band, which exhibit considerable stability in different excitation and annealing conditions. Mechanisms for blue emissions from ZnO are proposed with interstitial‐zinc‐related defect levels as initial states. EPR spectra reveal the predominance of interstitial zinc in as‐prepared samples, and the evolutions of coexisting interstitial zinc and oxygen vacancies with annealing. Furthermore, good controllability of visible emissions is achieved, including the co‐emission of blue and green emissions and peak adjustment from blue to yellow.     

激光处理对油松种子活力指数的影响

用激光分别处理油松干、湿种子,干种子发芽率与活力指数分别为对照组的 １３６％ 和 １６７％ ,浸水 ３６ｈ后的湿种子发芽率与活力指数分别为对照组的 １３７％ 和 １５９％ 。     

一种H．323穿越NAT的通用方案

提出了一种通用的H.323穿越NAT的方案,并且在不改变现有NAT设备的前提下,通过对H.323协议进行适当的扩展,尽量保证音视频数据包直接到达接受方,减少传输延时和丢包,保证音视频的质量.     

房间采暖技术与变频调速综述

本文对房间采暖技术的发展状况、技术原理、构造特点进行了归纳总结,重点分析了地板供暖的优缺点,指出了地板供暖技术在房间采暖设计中的应用前景。针对低温地板热水辐射供暖系统存在的一些工程问题,通过对水泵的控制算法的研究和探讨,提出了地板水供暖系统采用以uPD78F1213为核心的无传感器永磁同步电机矢量控制系统的方案。     

基于改进BP算法的网络态势预测模型

准确的网络态势预测可以有效的减小网络拥塞程度.本文对网络拓扑和流量数据进行分析,提取了节点数、OD流数、大象流数、总流量等反应网络态势的参数,建立了基于BP神经网络算法的预测模型进行模拟,能够有效的预测上述参数的发展趋势,在网络管理中有较好的应用前景.