近红外光谱小波分析在土壤参数预测中的应用

从田间采集了150个田间土壤样本,在分析了所有样本的土壤参数统计特征之后,对原始近红外光谱数据进行了聚类分析,分别得到了50个土壤全氮和50个土壤有机质的等价样本及其对应光谱。对样本光谱曲线进行8层Biorthogonal小波包分解,分解得到的最低低频[80]结点对应着土壤水分以及土壤质地的光谱变化趋势,最高高频[8 255]结点对应着土壤粒度、光谱仪精度等引起的高频震荡。对以上两个结点进行重构并从样本光谱曲线中剔除以上影响成分,得到了对应的土壤参数特征光谱。基于特征光谱建立了土壤参数偏最小二乘回归模型：全氮偏最小二乘预测模型的预测系数r_c达到了0.960,验证系数r_v达到了0.920;有机质偏最小二乘预测模型的预测系数r_c达到0.922,验证系数r_v达到0.883。模型精度明显提高,满足实际生产的需要。     

网络视频技术与物理远程教学

流媒体的应用近几年来Internet发展的产物，特别是视频流技术，广泛应用于远程教学、网络电台、视频点播、收费播放等。视频流技术是应用前景极好的Web多媒体新技术。物理教学的传统方式已经不能满足人们对物理知识的需求，网上物理教学就显得十分重要。因此，利用现代视频流技术改善物理教学的手段，提高物理教学的质量成为当前物理教学关注的问题。     

Nonlinear elastic waves in a monatomic chain with nonlinear interaction

1　ＩＮＴＲＯＤＵＣＴＩＯＮＢｅｃａｕｓｅｓｏｍｅｉｍｐｏｒｔａｎｔ ｐｒｏｐｅｒｔｉｅｓｏｆｃｒｙｓｔａｌ(ｓｕｃｈａｓｓｐｅｃｉｆｉｃｈｅａｔａｔｈｉｇｈｔｅｍｐｅｒａｔｕｒｅ ,ｍｅｌｔｉｎｇ ,ｔｈｅｒｍａｌｅｘｐａｎｓｉｏｎ ,ｔｅｍｐｅｒａｔｕｒｅｄｅ     

Critical Behaviors in a Stochastic One-Dimensional Sand-Pile Model

A one-dimensional sand-pile model (Manna model), which has a stochastic redistribution process, is studied both in discrete and continuous manners. The system evolves into a critical state after a transient period. A detailed analysis of the probability distribution of the avalanche size and duration is numerically investigated. Interestingly,contrary to the deterministic one-dimensional sand-pile model, where multifractal analysis works well, the analysis based on simple finite-size scaling is suited to fitting the data on the distribution of the avalanche size and duration. The exponents characterizing these probability distributions are measured. Scaling relations of these scaling exponents and their universality class are discussed.     

Electron acceleration in a tightly focused laser beam

Electron acceleration in a tightly focused ultra-intensity linear polarized laser beam is investigated numerically. It has been found that the acceleration is strong phase dependent and is periodic to the variety of the initial laser field phase. When optimal initial parameters are chosen, the electron can be accelerated effectively. The accelerated electrons are emitted in pulses of which the full width is less than the half period of the laser field.     

Stilbene 420激光染料的光谱特性分析

配制了Stilbene 420染料溶液。测量了其吸收光谱。以调Q倍频Nd∶YAG激光为抽运源,实现了对Stilbene 420染料的激光光谱和荧光光谱的分析。激光光谱在425 nm处获得最强峰值,半峰高宽(FWHM)为1 nm,光谱范围为420～440 nm。荧光光谱峰值在428.5 nm,与激光最强峰值相差3.5 nm。最高染料转换效率为9.26%。     

Synthesis of 3-aminoindan-1-one derivatives from 2-acetylbenzaldehydes and secondary amines by Mannich annulation

An acid-promoted 2-component Mannich annulation reaction of readily available acetylbenzaldehydes and secondary amines has been reported. The approach provides a simple and efficient method under mild conditions to synthesize 3-aminoindan-1-one derivatives in moderate to good yields.     

High Uptake of ReO4− and CO2 Conversion by a Radiation‐Resistant Thorium–Nickle [Th48Ni6] Nanocage‐Based Metal–Organic Framework

Assembled from [Th₄₈Ni₆] nanocages, the first transition‐metal (TM)‐thorium metal–organic framework (MOF, 1 ) has been synthesized and structurally characterized. 1 exhibits high solvent and acid/base stability, and resistance to 400 kGy β irradiation. Notably, 1 captures ReO₄^? (an analogue of radioactive ⁹⁹TcO₄^?, a key species in nuclear wastes) with a maximum capacity of 807 mg g^?1, falling among the largest values known to date. Furthermore, 1 can enrich methylene blue (MB) and can also serve as an effective and recyclable catalyst for CO₂ fixation with epoxides; there is no significant loss of catalytic activity after 10 cycles. Theoretical studies with nucleus‐independent chemical shifts and natural bond orbital analysis reveal that the [Th₆O₈] clusters in 1 have a unique stable electronic structure with (d–p)π aromaticity, partially rationalising 1 ′s stability.     

Synthesis of arylsulfonyl-substituted indolo[2,1-a]isoquinolin-6(5H)-one derivatives via a TBAI-catalyzed radical cascade cyclization

We have developed a metal-free radical cascade reaction of N-substituted 2-aryl indoles with readily available sulfonyl hydrazides for the rapid construction of arylsulfonyl-substituted indolo[2,1-a]isoquinolin-6(5H)-one derivatives. With the TBAI–TBHP catalytic system, a broad series of structurally diverse indolo[2,1-a]isoquinolin-6(5H)-one derivatives were obtained in moderate to excellent yields. The reaction features mild reaction conditions, operationally easiness, scaled-up feasibility, and high functional-group-tolerance.     

纳米复合固体超强酸SO42-/CoFe2O4的制备和表征

采用纳米化学制备技术合成了新型的纳米复合团体超强酸催化剂ＳＯ４２－／ＣｏＦｅ２Ｏ４。用ＸＲＤ、ＴＥＭ、ＸＰＳ、红 外光谱和比表面测定等技术研究了该催化剂的结构形态,结果表明：所研制的ＳＯ４２－／ＣｏＦｅ２Ｏ４催化剂为晶态纳 米粒子（＜ ５０ｎｍ）,比表面积很大（１５７ｍ２· ｇ－１）,ＳＯ４２－与氧化物的金属离子呈无机双齿螯合状配位化合物的结 合形式。以乙酸乙酯合成为模型反应考察了该催化剂的催化活性,比较了酸性和酸强度,推断出该催化剂的酸 强度Ｈ０＜－１４．５。