Unsupervised robust adaptive filtering against impulsive noise

An implementation of adaptive filtering, composed of an unsupervised adaptive filter (UAF), a multi-step forward linear predictor (FLP), and an unsupervised multi-step adaptive predictor (UMAP), is built for suppressing impulsive noise in unknown circumstances. This filtering scheme, called unsupervised robust adaptive filter (URAF), possesses a switching structure, which ensures the robustness against impulsive noise. The FLP is used to detect the possible impulsive noise added to the signal. If the signal is "impulse-free", the filter UAF can estimate the clean signal. If there exists impulsive noise, the impulse corrupted samples are replaced by predicted ones from the FLP, and then the UMAP estimates the clean signal. Both the simulation and experimental results show that the URAF has a better rate of convergence than the most recent universal filter, and is effective to restrict large disturbance like impulsive noise when the universal filter fails.     

不同叶面积指数反演方法比较研究

以PROSAIL模型模拟数据和地面实测数据为基础,分别分析了土壤背景、冠层反射率非各向同性以及随机噪声等因素对几类代表性反演方法的影响（植被指数法、二阶微分法、模型反演法以及方向性二阶微分法）。结果表明在不同条件下,各类反演方法的反演精度差别较大。植被指数NDVI对几种因素的滤除能力都较差,反演精度最低;模型反演精度高于植被指数方法,但会受到土壤背景的影响;二阶微分方法虽然能部分消除土壤背景的影响,但受冠层反射率非各向同性的限制。文中提出的方向性二阶微分法能较好地消除土壤背景和冠层反射率非各向同性的影响,反演精度较前者有所提高,但二阶微分方法易受噪声影响。     

Impact of land surface degradation in northern China and southern Mongolia on regional climate

Clear evidence provided by the singular value decomposition (SVD) analysis to the normalized difference vegetation index (NDVI) and precipitation data identifies that there exists a sensitive region of vegetation-climate interaction located in the transitional zone over northern China and its surrounding areas, where the vegetation cover change has the most significant influence on summer precipitation over China.““ Comparison of reanalysis data with station data provides a good method to assess the impacts of land use change on surface temperature, and the most obvious contribution of land use change may be to lead to notable warming over northern China in the interdecadal time scale. Based on the new statistical results, a high-resolution regional integrated environmental model system (RIEMS) is employed to investigate the effects of land surface degradation over the transitional zone and its surrounding areas (northern China and southern Mongolia) on the regional climate. Land degradation results in the decreases in precipitation over northern and southern China, and the increase in between, and increased and decreased temperature over vegetation change areas and the adjacent area to the south, respectively. Not only would it change the surface climate, but also bring the significant influence on the atmospheric circulation. Both the surface climate and circulation changes generally agree to the observed interdecadal anomalies over the last five decades. These integrated statistical and simulated results imply that land surface degradation over the transitional zone in northern China and its surrounding areas could be one of the main causes responsible for the climate anomalies over China, especially the drought over northern China.     

Kondo resonance in a single-molecule transistor

When an individual molecule, nanocrystal, nanotube or lithographically defined quantum dot is attached to metallic electrodes via tunnel barriers, electron transport is dominated by single-electron charging and energy-level quantization. As the coupling to the electrodes increases, higher-order tunnelling and correlated electron motion give rise to new phenomena, including the Kondo resonance. To date, all of the studies of Kondo phenomena in quantum dots have been performed on systems where precise control over the spin degrees of freedom is difficult. Molecules incorporating transition-metal atoms provide powerful new systems in this regard, because the spin and orbital degrees of freedom can be controlled through well-defined chemistry. Here we report the observation of the Kondo effect in single-molecule transistors, where an individual divanadium molecule serves as a spin impurity. We find that the Kondo resonance can be tuned reversibly using the gate voltage to alter the charge and spin state of the molecule. The resonance persists at temperatures up to 30 K and when the energy separation between the molecular state and the Fermi level of the metal exceeds 100 meV.     

稀土烯丙基化合物的研究(VII)——镧、铈、镨、钕和钐的2-甲基烯丙基化合物的合成

用无水稀土氯化物与2-甲基烯丙基氯化镁及四甲基乙二胺(tmed),在四氢呋喃中反应,合成了五个对空气和湿气相当敏感的轻稀土元素2-甲基烯丙基化合物Ln(C_4H_7)_2Cl_5Mg_2(tmed)_2[Ln=La,Ce,Pr,Nd和Sm].化合物均经元素分析、红外光谱及质谱的鉴定,并进行了摩尔电导的测定.     

一种实用的数字音量控制器

本文介绍利用数模转换器件设计的数字音量控制器。     

青藏高原的抬升和夷平过程对气候与环境的影响

系统地讨论了高原隆起前的早第三纪至现代青藏高原的７次抬升过程对气候和环境的影响，应用气象学理论分析了当时气候形成的原因。主要结论：（１）高原隆起前的干热气候是由于隆起前全球地势平坦，致使大气热机效率很低之故；（２）渐新世初高原的水平尺度达到了斜压大气地转适应的临界尺度，大气环流从南北两极“两涡对峙”突变成地球三极的“三涡鼎立”，气候发生突变；（３）分析了２．５Ｍａ时高原抬升到２０００ｍ这一重要临界高度后大气环流的一系列相应变化；（４）计算、比较了最大冰期地气系统能量平衡与现代的差异，并由此分析了当时的气候状况     

胆绿素衍生物的制备与纯化

从新鲜猪血中提取血红蛋白，以氧合血红蛋白为原料，通过偶联氧化制备胆绿素二盐酸盐（ＢＶ．２ＨＣｌ）和胆绿素二甲酯（ＢＶＥＤ），用溶剂萃取和相液相层析技术对产物进行确证和表征。对分离与纯化过程中由于ＢＶ的不稳定性所造成的困难问题及其解决办法进行了讨论。     

用红外光谱法测定饱和烃中亚甲基与甲基的比值

通过对正构烷烃(C_5～C_(16))红外光谱的考察,发现其 1460cm~(-1)及1380cm~(-1)峰的吸光度之比与分子中亚甲基与甲基的比值之间存在着良好的线性关系。借助于方程式 n_(CH_2)/n_(CH_3)=2.93A_(1460)/A_(1380)-3.70,可方便地由红外光谱计算出此比值。此方程式中的常数项表示在1460cm~(-1)峰中甲基与亚甲基的相对贡献。