基于机载高光谱成像的柑橘产量预测模型研究

果树的隔年结果现象严重影响果园的果实产量和经济效益。选择受隔年结果现象影响较为严重的柑橘作为研究对象,运用机载高光谱成像仪在较早生长季节(2003年4、5、6月)获取柑橘果树的高光谱图像,利用偏最小二乘回归(PLS)确定基于高光谱图像数据的模型预测变量,建立柑橘产量的多元线性回归(MLR)和人工神经网络(ANN)预测模型。研究结果表明,利用5月份获得的高光谱图像建立的模型具有最优的产量预测效果, 而且PLS-MLR模型比PLS-ANN模型具有更好的稳定性和一致性。该研究结果为今后研制和开发基于高光谱成像技术的柑橘产量预测方法提供了重要的理论和技术基础。     

Synthesis of fully conjugated aromatic polyazomethine from AB-type monomer using soluble precursor method

A new AB-type monomer, N,N-bistrimethylsilylated p-aminobenz-aldehyde diethyl acetal was prepared via three steps from p-bromoaniline as a starting material. The two-stage polymerization involving a soluble precursor polymer process gave a poly(p-phenylenevinylene)-type polyazomethine, poly(1,4-phenylene-nitrilomethylidyne). The first stage of polymerization was carried out in tetrahydrofuran or hexamethylphosphoramide containing water at room temperature. In the second stage, the polymer was thermally converted into the final polyazomethine by heating over 300°C to form a free-standing film. The film was reddish brown and insoluble in common organic solvents. The investigation of the first-stage products by means of MALDI-TOF mass spectroscopy proved the oligomers with 4-11 repeating units per molecule. From the ¹H-NMR analysis of the model reaction, the polymerization mechanism was found to be a stepwise polycondensation of 4-diethoxymethylaniline which was formed by removal of two silyl groups of the monomer.     

Synthesis,Structure, and Photophysical Properties of Yellow-Green and Blue Photoluminescent Dinuclear and Octanuclear Copper(I) Iodide Complexes with a Disilanylene-Bridged Bispyridine Ligand

The synthesis, structural, and photophysical investigations of CuI complexes with a disilanylene-bridged bispyridine ligand 1 are herein presented. Dinuclear (2) and ladder-like (3) octanuclear copper(I) complexes were straightforwardly prepared by exactly controlling the ratio of CuI/ligand 1. Single-crystal X-ray analysis confirmed that dinuclear complex 2 had no apparent π…π stacking whereas octanuclear complex 3 had π…π stacking in the crystal packing. In the solid state, the complexes display yellow-green (λ_em = 519 nm, Φ = 0.60, τ = 11 µs, 2) and blue (λ_em = 478 nm, Φ = 0.04, τ = 2.6 µs, 3) phosphorescence, respectively. The density functional theory calculations validate the differences in their optical properties. The difference in the luminescence efficiency between 2 and 3 is attributed to the presence of π…π stacking and the different luminescence processes.     

Preparation,Structural Determination,and Characterization of Electronic Properties of Bis‐silylated and Bis‐germylated Lu3N@Ih‐C80

Bis‐silylated and bis‐germylated derivatives of Lu₃N@I_h‐C₈₀ ( 3 , 4 , 5 ) were successfully synthesized by the photochemical addition of disiliranes 1 a , 1 b or digermirane 2 , and fully characterized by spectroscopic, electrochemical, and theoretical studies. Interestingly, digermirane 2 reacts more efficiently than disiliranes 1 a and 1 b because of its good electron‐donor properties and lower steric hindrance around the Ge?Ge bond. The 1,4‐adduct structures of 3 , 4 , 5 were unequivocally established by single‐crystal X‐ray crystallographic analyses. The electrochemical and theoretical studies reveal that the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the 1,4‐adducts are remarkably smaller than those of Lu₃N@I_h‐C₈₀, because the electron‐donating groups effectively raise the HOMO levels. It is also observed that germyl groups are slightly more electron‐donating than the silyl groups on the basis of the redox properties and the HOMO–LUMO energies of 4 and 5 . Bis‐silylation and bis‐germylation are effective and versatile methods for tuning the electronic characteristics of endohedral metallofullerenes.     

Theoretical analysis of a wheel driven root crop harvester

A prototype of a wheel driven trailer was developed to simulate a wheel driven trailed root crop harvester. The mobility of the prototype tractor-trailer system was improved by driving the trailer wheels by a mounted engine. A mathematical model to predict the mobility and the stability of the system was developed. The model was validated by field experiments conducted in plowed, rotary tilled and untilled fields. The model was found to predict performance with a high accuracy. Parameter studies were conducted to investigate the effects of several design parameters, such as the peripheral velocity ratio (R_s), the weight of the trailer (m₁), the trailer's C.G. location (L_L) and the height of a hitch point (h), on the mobility and the stability of the system.     

Triviality of Hierarchical Models with Small Negative φ4 Coupling in Four Dimensions

The Kadanoff-Wilson renormalization group (RG) for a class of hierarchical spin models including small negative φ⁴ terms in four dimensions are studied by using Gawędzki and Kupiainen's analysis. We prove triviality for the class, namely prove existence of critical trajectory that leads to the Gaussian fixed point.     

Relative invariants of some 2-simple prehomogeneous vector spaces

In this paper, we shall construct explicitly irreducible relative invariants of two 2-simple prehomogeneous vector spaces. Together with a preprint by the same authors, this completes the list of all relative invariants of regular 2-simple prehomogeneous vector spaces of type I.