基于均值置信区间带的高光谱特征波段选择与树种识别

以柏木、雷竹和无患子野外高光谱数据为基础,在统计学理论和实践分析的基础上,提出了利用均值置信区间带筛选树种间最佳特征区分波段及利用Manhattan距离和Min-Max区间相似度识别树种的问题。研究结果表明:(1)柏木与雷竹之间的最佳区分波段为358～386,452～1 145和1 314～2 500 nm,柏木与无患子之间的最佳区分波段为350～446,497～527,553～1 330,1 355～2 400和2 436～2 500 nm,雷竹与无患子之间的最佳区分波段为434～555,580～1 903,1 914～2 089,2 172～2 457和2 475～2 500 nm;(2)在最佳区分波段内,同种树种间的Manhattan距离远小于异种树种间的Manhattan距离,同种树种间的Min～Max区间相似度远大于异种树种间的Min～Max区间相似度,Manhattan距离和Min～Max区间相似度可以有效区分和识别不同类型的树种。     

激光剥蚀-电感耦合等离子体质谱测定植物样品中的元素

采用193 nm准分子激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)对标准植物粉末样品(GBW07602-GBW07603灌木枝叶、GBW07604杨树叶、GBW07605茶叶、GBW08514烟草)中13种元素(Li,B,Na,Mg,Al,K,Ca,Cr,Mn,Fe,Ni,Cu,Ba)进行定量测试.向植物粉末样...     

Detecting hidden spatial and spatio-temporal structures in glasses and complex physical systems by multiresolution network clustering

We elaborate on a general method that we recently introduced for characterizing the “natural” structures in complex physical systems via multi-scale network analysis. The method is based on “community detection” wherein interacting particles are partitioned into an “ideal gas” of optimally decoupled groups of particles. Specifically, we construct a set of network representations (“replicas”) of the physical system based on interatomic potentials and apply a multiscale clustering (“multiresolution community detection”) analysis using information-based correlations among the replicas. Replicas may i) be different representations of an identical static system, ii) embody dynamics by considering replicas to be time separated snapshots of the system (with a tunable time separation), or iii) encode general correlations when different replicas correspond to different representations of the entire history of the system as it evolves in space-time. Inputs for our method are the inter-particle potentials or experimentally measured two (or higher order) particle correlations. We apply our method to computer simulations of a binary Kob-Andersen Lennard-Jones system in a mixture ratio of A₈₀B₂₀ , a ternary model system with components “A”, “B”, and “C” in ratios of A₈₈B₇C₅ (as in Al₈₈Y₇Fe₅ , and to atomic coordinates in a Zr₈₀Pt₂₀ system as gleaned by reverse Monte Carlo analysis of experimentally determined structure factors. We identify the dominant structures (disjoint or overlapping) and general length scales by analyzing extrema of the information theory measures. We speculate on possible links between i) physical transitions or crossovers and ii) changes in structures found by this method as well as phase transitions associated with the computational complexity of the community detection problem. We also briefly consider continuum approaches and discuss rigidity and the shear penetration depth in amorphous systems; this latter length scale increases as the system becomes progressively rigid.     

Electronic structure and magnetism in full-Heusler compound Mn2ZnGe

The first-principle calculations within density functional theory are used to investigate the electronic structure and magnetism of the Mn₂ZnGe Heusler alloy with CuHg₂Ti-type structure. The half-metallic ferrimagnets (HMFs) in Mn₂ZnGe are predicted. The energy gap lies in the minority-spin band for the Mn₂ZnGe alloy. The calculated total spin magnetic moment is −2μ_B per unit cell for Mn₂ZnGe alloy, the magnetic moments of Zn and Mn(B) are antiparallel to that of Mn(A), and we also found that the half-metallic properties of Mn₂ZnGe are insensitive to the dependence of lattice within the wide range of 5.69 and 5.80 Å where exhibiting perfect 100% spin polarization at the Fermi energy.     

Synchronization of complex community networks with nonidentical nodes and adaptive coupling strength

In this Letter, the complex dynamical networks with community structure and nonidentical nodes are considered. The globally asymptotical synchronization of the time-delayed complex community networks onto any uniformly smooth state is studied. Some simple and useful criteria are derived by constructing an effective control scheme and adjusting automatically the adaptive coupling strength. Finally, the developed techniques are applied to two complex community networks which are respectively synchronized to a chaotic trajectory and a periodic orbit, and numerical simulations are provided to show the feasibility of the developed methods.     

Wave propagation characterization and design of two-dimensional elastic chiral metacomposite

In this work, a chiral metacomposite is proposed by integrating two-dimensional periodic chiral lattice with elastic metamaterial inclusions for low-frequency wave applications. The plane harmonic wave propagation in the proposed metacomposite is investigated through the finite element technique and Bloch's theorem. Band diagrams are obtained to illustrate wave properties of the chiral metacomposite. Effective dynamic properties of the chiral metacomposite are numerically calculated to explain low-frequency bandgap behavior in the chiral metacomposite. Interestingly doubly negative effective density and modulus of the chiral metacomposite are found in a specific frequency range, where a pass band with negative group velocity is observed. Tuning of the resulting low-frequency bandgaps is then discussed by adjusting microstructure parameters of the metamaterial inclusion and lattice geometry. Specifically design of a metacomposite beam structure for the broadband low-frequency vibration suppression is demonstrated.     

A cost-effective WDM-PON architecture simultaneously supporting wired, wireless and optical VPN services

It is believed that next-generation passive optical networks (PONs) are required to provide flexible and various services to users in a cost-effective way. To address this issue, for the first time, this paper proposes and demonstrates a novel wavelength-division-multiplexed PON (WDM-PON) architecture to simultaneously support three types of services: 1) wireless access traffic, 2) optical virtual passive network (VPN) communications, and 3) conventional wired services. In the optical line terminal (OLT), we use two cascaded Mach-Zehnder modulators (MZMs) on each wavelength channel to generate an optical carrier, and produce the wireless and the downstream traffic using the orthogonal modulation technique. In each optical network unit (ONU), the obtained optical carrier is modulated by a single MZM to provide the VPN and upstream communications. Consequently, the light sources in the ONUs are saved and the system cost is reduced. The feasibility of our proposal is experimentally and numerically verified.     

薄膜SOI上SiGe HBT集电结耗尽电荷和电容改进模型

文章研究了SOI衬底上SiGe npn异质结晶体管集电结耗尽电荷和电容.根据器件实际工作情况,基于课题组前面的工作,对耗尽电荷和电容模型进行扩展和优化.研究结果表明,耗尽电荷模型具有更好的光滑性;耗尽电容模型为纵向耗尽与横向耗尽电容的串联,考虑了不同电流流动面积,与常规器件相比,SOI器件全耗尽工作模式下表现出更小的集电结耗尽电容,因此更大的正向Early电压;在纵向工作模式到横向工作模式转变的电压偏置点,耗尽电荷和电容的变化趋势发生改变.SOI薄膜上纵向SiGe HBT集电结耗尽电荷和电容模型的建立和扩展为毫米波SOI BiCMOS工艺中双极器件核心参数如Early电压、特征频率等的设计提供了有价值的参考. 关键词： 耗尽电容 SiGe HBT SOI     

光声内窥镜系统在人体直肠癌离体组织中的实验研究

研制了基于4阵列传感器的光声内窥镜探头,并基于此搭建了光声内窥镜成像系统,开展了仿体实验成像研究,通过内窥镜探头4个阵元位置激光吸收强度的变化情况来分析仿体中吸收体的位置,论证了其定位能力,利用光声内窥镜系统对人体离体的正常组织、直肠癌早期组织进行成像研究;通过对不同阵元位置的光吸收强度分布进行统计分析,证明了光声内窥镜对早期直肠癌组织和正常组织的辨别能力,此项技术有望提高直肠癌早期诊断的准确率,具有潜在的临床应用前景。     

紫外可见光谱的水产养殖水体有机物浓度快速检测研究

应用紫外可见（ultraviolet/visible,UV/Vis）光谱技术对表征水产养殖水体中有机物浓度的指标化学需氧量（chemical oxygen demand,COD）进行快速测量,对采集到的135份甲鱼养殖水样进行UV/Vis波段全光谱扫描,采用无信息变量消除（uninformative variable elimination,UVE）和连续投影算法（successive projections algorithm,SPA）相结合的变量选择算法选取全波段光谱中的特征波长,从201个UV/Vis光谱变量中选取了7个特征波长,只占全波段光谱变量的3.48%,降低了建模的时间和模型的复杂度。结合最小二乘支持向量机（least-square support vector machine,LS-SVM）算法进行COD预测建模,结果表明：使用特征波长建模的预测效果（相关系数r（correlation coefficient）=0.89,预测均方根误差（root mean square error of prediction,RMSEP）=15.46 mg·L-1）好于使用全波段光谱建模的预测效果（r=0.88,RMSEP = 15.71 mg·L-1）。使用UVE-SPA变量选择算法获取UV/Vis光谱特征波长,结合LS-SVM建模,可以快速、准确的测量水产养殖水体中的COD浓度,为进一步实现水产养殖水质的在线检测以及其他水质参数的快速测定奠定了基础。