Effects of long-term green manure application on the content and structure of dissolved organic matter in red paddy soil

Dissolved organic matter (DOM) plays important roles in soil biogeochemistry activity and nutrients transportation in soils, but studies regarding the long-term effects of green manures on the content and structure of DOM in red paddy soil have not been reported yet. A long-term green manure experiment established in 1982 was utilized to test the DOM contents in different treatments, and the spectral characteristics of DOM were investigated by using ultraviolet-visible (UV-Vis) spectrometry and Fourier transform infrared (FTIR) spectrometry. The experiment included four cropping systems: rice-rice-milk vetch (RRV), rice-rice-rape (RRP), rice-rice-ryegrass (RRG) and rice-rice-winter fallow (RRF), among them, milk vetch, rape, and ryegrass are popular winter green manure species in southern China. The results showed that the content of dissolved organic carbon (DOC), which is widely used to estimate the concentration of DOM, was significantly promoted after the incorporation of green manures compared with the other sampling stages. The contents of aromatic groups and the degree of humification of DOM increased in RRV and RRP, suggesting more complex compositions of the soil DOM after long-term application of milk vetch and rape. The contents of phenol, alcohol and carboxylic acid group at the mature stage of early rice were significantly higher than those at the stage of after green manures turned over, especially for the RRV treatment. The absorption ratio of FTIR indicated that winter plantation of rape increased the aromatic-C/aliphatic-C ratio, and ryegrass increased the aromatic-C/carboxyl-C ratio. In conclusion, long-term planting of milk vetch and rape as green manures increased the degree of aromaticity, humification and average molecular weight of DOM, and made the DOM more stable in red paddy soil.     

基于热诱导的绿咖啡油氧化过程解析及活性成分变化规律研究

绿咖啡油是一种富含生物活性成分的功能性油脂,贮藏过程中极易氧化酸败影响产品品质。本文以海南地区兴隆咖啡为原料提取绿咖啡油,系统研究在60 ℃加速贮藏36 d内氧化指标、生物活性成分及表征氧化的光谱特征峰变化。结果表明：过氧化值、茴香胺值、硫代巴比妥酸、总氧化值初始值分别为0.97±0.04 meq/kg、4.19±0.14、55.08± 1.98 nmol/mL、8.05±0.06,经过36 d的氧化分别显著升高到28.56±0.15 meq/kg、19.19±0.13、102.38±2.18 nmol/mL、133.43± 0.45。本研究中共鉴定出11种脂肪酸,在绿咖啡油氧化过程中,饱和脂肪酸与不饱和脂肪酸比值由1.14上升至1.49。利用高效液相色谱测定绿咖啡油中的二萜类物质和生育酚,咖啡豆醇、咖啡醇的初始含量分别为21.01±0.31 mg/g、23.44±0.52 mg/g,在氧化24 d后升高至8.21±0.10 mg/g、8.99±0.02 mg/g,随后含量趋于稳定。共定性出α、δ和γ-生育酚,总生育酚含量由初始的49.75±0.88 mg/100 g在氧化18 d达到最大值53.70±1.72 mg/100 g,在氧化结束时降至34.58± 0.05 mg/100 g。利用傅里叶变换红外光谱（FTIR）从特征官能团的角度分析绿咖啡油的氧化过程,油脂在3008、2927、2854、1745、1461、1375、1238、1164、721 cm^-1处有特征吸收峰。采用拉曼光谱技术表征绿咖啡油加速贮藏中的氧化变质,在1000~1800 cm^-1波段的峰强度有明显减弱趋势。本研究表明绿咖啡油在热诱导下的贮藏过程中发生了明显的氧化反应,可为提升绿咖啡油贮藏稳定性提供理论参考。     

基于NDFT Goertzel滤波器的DTMF信号检测的改进方法

提出了一种基于NDFT Goertzel滤波器和逻辑判断的DTMF信号检测的改进方法.传统的基于Goertzel算法的检测方法需要计算8个频率点上的DFT,而改进方法根据按键不同只计算最多6个,最少2个频率点的NDFT.检测数字按键时,对于每个按键计算频率点数的期望值为4.1.改进的检测方法满足ITU的大部分规定.     

不同年代的埃特纳火山土壤上用甘油萃取有机质的特性

We characterized humic acids (HAs) and glycerol-extractable organic fractions (GEOFs) extracted from four Andisols, taken from comparable soil-climate conditions on the east side of Mount Etna. The soils were formed on old lava (about 9 000 years ago), old tephra (about 8 700 years ago), recent lava (about 2 600 years ago) and recent tephra (about 3 600 years ago). A part of the organic matter of the soils, deprived of HAs and fulvic acids (FAs), was isolated by glycerol extraction. The GEOF can not be extracted with alkaline solutions, probably because it is closely bound to the mineral component of the soil. The characterization of the extracted organic fraction was carried out using elementary and functional group analysis and Fourier transform infrared (FT-IR) spectroscopy. About 20 extractions were necessary to extract the HA and FA from the older soils and about 10 extractions to extract them from the younger soils. Data showed that the GEOFs had a greater ash content and a smaller N content, as well as a greater presence of aliphatic compounds and carboxylic groups as compared to the HA extracted from the same soil. The GEOFs extracted from younger soils also had a lower yield, ash and COOH-group content, and were more aliphatic than the GEOF extracted from older soils. Finally, the GEOFs were more closely bound to the amorphous component of the soil (‘short-range’ minerals) and consequently less subject to biodegradation.     

傅里叶红外标准加入法测定银杏叶提取物(EGb)中的总内酯

银杏叶提取物（ＥＧｂ）经ＫＢｒ压片后,在１８４０～１７２６ｃｍ－１区间,用傅里叶变换红外光谱仪测量峰面积,以美国Ｓｉｇｍａ的银杏内酯Ｂ为标准品,用ＦＴＩＲ标准加入法测定ＥＧｂ中的总内酯含量,其结果与ＲＰＨＰＬＣ、ＲＩ法接近,平均回收率９６．８％,ＳＤ０．４,ＲＳＤ５．５％,方法简便,结果可靠,适于ＥＧｂ及其制剂在生产过程中作质量控制的测定方法用。     

甘蔗蔗汁锤度和还原糖分傅立叶变换近红外定量分析数学模型

以傅立叶变换近红外光谱技术为基础，采用透射测定方式和PLS算法，建立蔗汁锤度和还原糖分定量分析数学模型．蔗汁锤度和还原糖分预测数学模型的决定系数(R^2)分别为0．9990和0．9953，均方根差分别为0．1150％和0．0722％，预测误差接近常规分析方法的误差．     

Time-frequency Analysis of Heart Sound

The structural defects of the heart are often reflected in the sounds that heart produces. Because of the non-stationary of the PCG signal, it is important to maintain its time-frequency character. We discuss the Short-Time Fourier Transform (STFT) method and the wavelet method. Some normal and abnormal heart sounds were analyzed by these methods. We can see the advantage and disadvantage of them obviously from the examples.     

基于近红外傅里叶特征提取方法的土壤含水率检测

以湖北地区的3种土壤为研究对象,利用偏最小二乘法建立了处理后样品的土壤含水率分析模型,模型预测值与标准值的决定系数为0.995,交叉验证预测均方差为0.801%,模型预测决定系数为0.992,预测均方差为0.912%,利用该模型预测黄土高原地区黄绵土含水率误差均大于4%.利用近红外光谱傅里叶变换特征提取方法对湖北地区黄棕壤、稻田土和潮土建立土壤含水率PLS预测模型,模型决定系数为0.988,交叉验证预测均方差为1.106%,且该模型预测黄绵土的误差均在2%左右,精度较传统模型有较大提高.     

小波理论与振动分析

小波理论是近年来迅速发展起来的新兴学科。已成为多领域的研究热点。本文介绍了连续小波变换和离散小波变换的构造及部分性能；分析了波变换与Ｆｏｕｒｉｅｒ变换的关系；小波分析的特点与适用领域。给出了振动工程上的三个典型应胜。并就小波理论这一前沿领域的发展现状做了相应的评述。     

基于离散傅立叶变换的水稻作物数字图像压缩技术研究

[目的]研究水稻监控系统中的数字图像压缩技术。[方法]提出了一种基于离散傅立叶变换的数字图像压缩技术方案,并通过仿真试验对图像进行了不同压缩比的压缩。[结果]对于压缩比在30以内的数字图像的压缩,衡量编码压缩质量的5个参数(压缩比、图像的熵、平均码字长度、编码效率、冗余度)和评价压缩图像逼真度的参数(PSNR)均达到较好效果,人眼几乎不能分辨出解压缩图像和原始图像之间的差异;在压缩比超过30的数字图像的压缩上,解压缩图像存在一定的失真。当压缩比为91.516 3时,虽然图像有一定的失真,但PSNR仍能达到21.528 2,从直观上人眼在一定的误差范围内仍能接受解压缩图像。[结论]该研究结果表明提出的图像压缩方案是一种可行的、有效的、较好的图像压缩技术,完全可以满足农作物监控系统中图像存储、交换与传输的要求。