Local detrended fluctuation analysis for spectral red-edge parameters extraction

Nowadays, spectrum technology makes it possible to nondestructively monitor crop and provide real-time diagnostic advice. Spectral red-edge parameters are important detection target for the growth of rapeseed. In this work, we propose a new method to acquire the rapeseed’s spectral red-edge parameters based on local detrended fluctuation analysis (L-DFA). In practice, by using the L-DFA, local Hurst exponent of the spectrum is calculated firstly. And then, six traditional red-edge parameter extraction methods, namely maximum first derivative method, adjusted linear extrapolation method, linear four-point interpolation method, inverted Gaussian method, Lagrangian interpolation method, and polynomial fitting interpolation, are employed to act on the estimated local Hurst exponent, and thus four red-edge parameters, i.e., red-edge position, red-edge amplitude, and left and right red-edge area, are obtained. In our experiments, by using the above four local Hurst exponent-based red-edge parameters as argument, a prediction model is developed to forecast the SPAD values (soil and plant analyzer development, often used as a parameter to indicate the chlorophyll content) for the five rapeseed’s growth periods based on random decision forest method. The results show that the local Hurst exponent-based red-edge feature can produce better model effect than the original spectrum-based one for the all phenological periods. Significance test for the four kinds of plant patterns shows that there is huge difference of the proposed four-dimensional red-edge features between the transplant and direct plant in the whole process of rapeseed’s growth. The differences between the other three groups of plant factors (two planting densities, two fertilizer types, and two weed controls) are not significant in certain specific growth periods of rapeseed. These findings provide a basis for studying difference of rapeseed yield and oil differences between different planting patterns.     

非线性Schrdinger方程初边值问题的守恒数值格式

该文对非线性 Schrodinger方程提出了一种新的守恒差分格式 ,并证明了该格式的收敛性与稳定性 ,通过数值计算获得如下结论 ,提出的差分格式在取适当的参数后 ,精度上好于文 [7]中的格式     

A conservative compact difference scheme for the coupled Klein–Gordon–Schrödinger equation

In this article, a conservative compact difference scheme is presented for the periodic initial‐value problem of Klein–Gordon–Schrödinger equation. On the basis of some inequalities about norms and the priori estimates, convergence of the difference solution is proved with order O(h⁴ +τ ²) in maximum norm. Numerical experiments demonstrate the accuracy and efficiency of the compact scheme. © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2013     

Inorganic nanotubes formation through the synergic evolution of dynamic templates and metallophosphates: from vesicles to nanotubes

A novel synergic evolution of dynamic assembly, from vesicles to nanotubes, between the metallophosphates and organic amines, is disclosed, by which the multicomponent metallophosphate (Cu(2)(OH)PO(4)) nanotubes are synthesized for the first time.     

Measuring Brønsted acid densites in zeolite HY with diphosphine molecules and solid state NMR spectroscopy

The use of 31P MAS NMR spectroscopy, combined with diphenyldiphosphine Ph2P(CH2)nPPh2 probe molecules with two basic groups (n = 1, 3, and 6, corresponding to maximum P-P separations of approximately 3.0, 5.6, and 9.4 A, respectively), to investigate both acidities and distances between Br?nsted acid sites in zeolite HY (Si/Al = 2.6) is demonstrated in this communication. More than 90% of the Ph2P(CH2)6PPh2 molecules are doubly protonated on zeolite HY at a loading level of 12 molecules per unit cell, indicating that there are at least 12 pairs of Br?nsted acid sites about 9 A apart. Similarly, experiments involving Ph2P(CH2)3PPh2 show that there are only six pairs of Br?nsted acid sites separated by a distance of 6 A. Only approximately 60% of the Ph2PCH2PPh2 molecules were doubly protonated for a loading level of 4 molecules/unit cell, as not all of the Br?nsted acid sites were sufficiently acidic to protonate both ends of this molecule. 31P 2D double quantum NMR spectroscopy was used to confirm the spectral assignments.     

HZSM-5沸石中Lewis酸与Brönsted酸协同作用下的甲基环己烷开环反应

由于水蒸气处理HZSM-5生成的骨架外铝在分子筛中体现Lewis酸性, 分子筛中骨架外铝物种的可移动性导致Lewis酸与分子筛本身的Brönsted酸在空间上具有临近性. 当甲基环己烷分子在HZSM-5的笼中转化时, Lewis酸与Brönsted酸的协同作用加快了甲基环己烷分子的转化速率, 且骨架外铝物种浓度越高, 这种协同效应越明显. 而产物的选择性只与催化剂的孔道结构有关, 与水蒸气处理所导致的酸性质的变化无关.     

Morphology-Reserved Synthesis of Discrete Nanosheets of CuO@SAPO-34 and Pore Mouth Catalysis for One-Pot Oxidation of Cyclohexane

Discrete nanosheets of silicon-doped AlPO₄ molecular sieves (SAPO-34) with a thickness of ≈7 nm have been prepared through morphology-reserved synthesis with a lamellar aluminum phosphate as precursor. Cages of the nanosheets are in situ incorporated with copper oxide clusters. The CuO@SAPO-34 nanosheets exhibit a large external surface area with a high number of (010) channel pores on the surface. Due to the thin morphology, copper oxide clusters occupy the outmost cages with a probability >50 %. The distinctive configuration facilitates a new concept of pore mouth catalysis, i.e., reactant molecules larger than the pores cannot enter the interior of the molecular sieves but can interact with the CuO clusters at “the mouth” of the pore. In heterogeneous catalysis, CuO@SAPO-34 nanosheets have shown top performance in one-pot oxidation of cyclohexane to adipic acid by O₂, a key compound for the manufacture of nylon-66, which is so far produced using non-green nitric acid oxidation.     

Isoreticular Linker Substitution in Conductive Metal–Organic Frameworks with Through-Space Transport Pathways

The extension of reticular chemistry concepts to electrically conductive three-dimensional metal–organic frameworks (MOFs) has been challenging, particularly for cases in which strong interactions between electroactive linkers create the charge transport pathways. Here, we report the successful replacement of tetrathiafulvalene (TTF) with a nickel glyoximate core in a family of isostructural conductive MOFs with Mn²⁺, Zn²⁺, and Cd²⁺. Different coordination environments of the framework metals lead to variations in the linker stacking geometries and optical properties. Single-crystal conductivity data are consistent with charge transport along the linker stacking direction, with conductivity values only slightly lower than those reported for the analogous TTF materials. These results serve as a case study demonstrating how reticular chemistry design principles can be extended to conductive frameworks with significant intermolecular contacts.     

Porous Mn2+ Magnet with a Pt−Cl Framework: Correlation between Water Vapor Adsorption/Desorption and Slow Magnetic Relaxation

We report the water adsorption/desorption behavior and dynamic magnetic properties of the Pt−Cl chain complex [{[Pt(en)₂][PtCl₂(en)₂]}₃][{(MnCl₅)Cl₃}₂] ⋅ 12H₂O ( 1 ). Upon heating 1 in a vacuum, we obtained the dehydrated form [{[Pt(en)₂][PtCl₂(en)₂]}₃][{(MnCl₅)Cl₃}₂] ( 1DH ). The framework structures of 1 and 1DH are identical, and both complexes underwent slow magnetic relaxation. However, the magnetic relaxation times for 1DH were shorter than those for 1 , meaning that the dynamic magnetic properties were controlled upon water vapor adsorption/desorption. From detailed analyses of the dynamic magnetic behavior, a phonon-bottleneck effect contributes to the magnetic relaxation processes. We discuss the mechanism for the changes in the magnetic relaxation processes upon dehydration in terms of the heat capacity and thermal conductivity.