由汉诺塔游戏想到的汉诺塔简单非递归算法

汉诺塔问题是一个古典的数学问题，也是程序设计中的经典递归问题，其递归算法由于简洁清晰，为大家所熟悉，编写出来的程序也比较简单，缺点是占用太多的内存空间。本文对汉诺塔问题进行了数学建模，并用几个简单的判断条件，对问题迅速求解，程序用C语言实现。     

Critical Comparison of Humic Acid Test Methods

The colorimetric method and the California Department of Food and Agriculture (CDFA) method of evaluating the humic acid content of five raw humate ores and three humate products were compared to the classical technique of extraction in a dilute base followed by precipitation of humic acid by extract acidification and ash removal by hydrochloric/hydrofluoric acid (HCl/HF) wash. Compared to the classical procedure, the colorimetric and CDFA methods overestimated the humic acid content of the eight samples by 120% and 52%, respectively. Therefore, these procedures do not produce a reliably accurate value for the humic acid contents of humates and products produced using materials extracted from them.     

QuEChERS提取法在农产品农药残留检测中的应用进展

食品中的农药残留检测长期以来一直是一项艰巨的挑战,其杂质干扰多,残留含量低,传统的提取方法常常因为无法将杂质分离而影响检测结果。由于食品中杂质种类众多,农药的种类繁多且理化性质各异,新型农药日益涌现,所以对样品的前处理提出了更高的要求。近年来,QuEChERS(Quick,Easy,Cheap,Effective,Rugged and Safe)作为一种新型的提取方法,由于具有快速、简单、廉价、有效、可靠、安全的特点,成为国内外广泛采用的样品前处理新技术,在多种农药、医药、兽药的气相或液相色谱分析中已经得到广泛应用。本文就国内外对QuEChERS法在各类食品以及其他动植物性农产品的农药残留检测中的应用和方法的改进进行了综述,并对QuEChERS法在今后农药残留检测的应用前景以及发展方向进行了展望。     

基于遥感图像的城镇用地信息提取方法研究

如何快捷、准确与客观的提取城镇用地信息,以获得城镇用地的分布范围和面积资料,是有关城镇问题研究中的一个基本问题。利用遥感技术可以有效的解决这个问题,从城镇用地的遥感信息机理分析入手,根据各地物不同的光谱信息值,深入研究了基于遥感影像下的城镇用地的信息提取方法,并对提出的提取方法进行了若干讨论。研究结果表明,与传统的计算机分类方法和人工目视解译的屏幕数字化方法相比,本文所探讨的方法是一种行之有效的方法。     

Simultaneous determination of saccharin and aspartame in commercial noncaloric sweeteners using the PLS-2 multivariate calibration method and validation by capillary electrophoresis

A new method to determine a mixture for sweetener sodium saccharin and aspartame in commercial noncaloric sweeteners is proposed. A classical full factorial design for standards was used in the calibration step to build the partial least-squares (PLS-2) model. Instrumental data were obtained by means of UV-visible spectrophotometry. Salicylic acid was used as an internal standard to evaluate the adjustment of the real samples to the PLS model. The concentration of analytes in the commercial samples was evaluated using the obtained model by UV spectral data. The PLS-2 method was validated by capillary zone electrophoresis (CZE), finding in all cases a relative error of less than 11% between the PLS-2 and the CZE methods. The proposed procedure was applied successfully to the determination of saccharin and aspartame in noncaloric commercial sweeteners.     

Analysis of unbalanced mixed model data: A case study comparison of ANOVA versus REML/GLS

Major transition has occurred in recent years in statistical methods for analysis of linear mixed model data from analysis of variance (ANOVA) to likelihood-based methods. Prior to the early 1990s, most applications used some version of analysis of variance because computer software was either not available or not easy to use for likelihood-based methods. ANOVA is based on ordinary least squares computations, with adoptions for mixed models. Computer programs for such methodology were plagued with technical problems of estimability, weighting, and handling missing data. Likelihood-based methods mainly use a combination of residual maximum likelihood (REML) estimation of covariance parameters and generalized least squares (GLS) estimation of mean parameters. Software for REML/GLS methods became readily available early in the 1990s, but the methodology still is not universally embraced. Although many of the computational inadequacies have been overcome, conceptual problems remain. Also, technical problems with REML/GLS have emerged, such as the need for adjustments for effects due to estimating covariance parameters. This article attempts to identify the major problems with ANOVA, describe the problems which remain with REML/GLS, and discuss new problems with REML/GLS.     

Modeling Bromus diandrus Seedling Emergence Using Nonparametric Estimation

Hydrothermal time (HTT) is a valuable environmental index to predict weed emergence. In this paper, we focus on the problem of predicting weed emergence given some HTT observations from a distribution point of view. This is an alternative approach to classical parametric regression, often employed in this framework. The cumulative distribution function (cumulative emergence) of the cumulative hydrothermal time (CHTT) is considered for this task. Due to the monitoring process, it is not possible to observe the exact emergence time of every seedling. On the contrary, these emergence times are observed in an aggregated way. To address these facts, a new nonparametric distribution function estimator has been proposed. A bootstrap bandwidth selection method is also presented. Moreover, bootstrap techniques are also used to develop simultaneous confidence intervals for the HTT cumulative distribution function. The proposed methods have been applied to an emergence data set of Bromus diandrus.     

Comparison of the acetyl bromide spectrophotometric method with other analytical lignin methods for determining lignin concentration in forage samples

Present analytical methods to quantify lignin in herbaceous plants are not totally satisfactory. A spectrophotometric method, acetyl bromide soluble lignin (ABSL), has been employed to determine lignin concentration in a range of plant materials. In this work, lignin extracted with acidic dioxane was used to develop standard curves and to calculate the derived linear regression equation (slope equals absorptivity value or extinction coefficient) for determining the lignin concentration of respective cell wall samples. This procedure yielded lignin values that were different from those obtained with Klason lignin, acid detergent acid insoluble lignin, or permanganate lignin procedures. Correlations with in vitro dry matter or cell wall digestibility of samples were highest with data from the spectrophotometric technique. The ABSL method employing as standard lignin extracted with acidic dioxane has the potential to be employed as an analytical method to determine lignin concentration in a range of forage materials. It may be useful in developing a quick and easy method to predict in vitro digestibility on the basis of the total lignin content of a sample.     

地下滴灌田间管网室内试验测试系统(简报)

针对地下滴灌管网中各灌水器出流量难以测量的问题,提出一种新的试验测试方法--称重测量法,可获得各灌水器的出流量.测试系统由称重传感器、压力变送器、数据采集系统和计算机及相关软件构成,可同时间接获得地下滴灌管网中各灌水器的出流量和直接测量出支管与毛管的沿程压力.而且还可实现自动监控、自动采集和存储测试数据的功能.实测结果表明:系统测试精度可满足试验要求.该测试系统操作简便,是室内试验研究地下滴灌田间管网水力要素变化规律的有效方法.     

Characterization of Royal Gala apple aroma using electronic nose technology-potential maturity indicator

Changes in aroma of apple harvested at four different maturities were measured at harvest and after short-term storage using electronic aroma sensors ("electronic nose") and classical headspace/gas chromatography methods. Stored fruits were also evaluated by a trained sensory panel. Compared with headspace/gas chromatography, the electronic nose was found to be more sensitive ( approximately 40 times) in terms of sample size. The sampling procedure for the electronic nose was much less complex. Using discriminant function analysis, both methods classified the apples tested into groups according to harvest date. After storage, the groupings were more diffuse. Results from sensory testing showed partial separation along the first linear discriminant but did not classify the apple into distinct groups. Important differences between treatments were found for "overall flavor", "acid flavor" intensity, "crispness", "cider/fermented aroma", "vegetative aroma", and "canned pear aroma".     

甲亚胺测定土壤有效硼的前处理方法研究

土壤有效硼测定通常采用甲亚胺-H比色法,该方法前处理(煮沸)过程分析效率低、操作步骤不易掌控,极易给测定结果带来较大误差。为此,以山西省标准土样TCB-2为检测样品,对甲亚胺-H比色法的煮沸提取步骤进行了改进,分别试验了水浴提取、微波提取时间对土壤有效硼测定的影响,确定水浴法最佳提取时间为50 min,微波提取时间为90 s。对国家土壤标准物质GBW07412a检测结果表明,水浴提取和微波提取测定结果与标准参照值符合,相对标准偏差分别为3.43%和8.91%。     

Estimating soil labile organic carbon and potential turnover rates using a sequential fumigation-incubation procedure

Labile carbon is the fraction of soil organic carbon with most rapid turnover times and its oxidation drives the flux of CO₂ between soils and atmosphere. Available chemical and physical fractionation methods for estimating soil labile organic carbon are indirect and lack a clear biological definition. We have modified the well-established Jenkinson and Powlson's fumigation-incubation technique to estimate soil labile organic carbon using a sequential fumigation-incubation procedure. We define soil labile organic carbon as the fraction of soil organic carbon degradable during microbial growth, assuming that labile organic carbon oxidizes according to a simple negative exponential model. We used five mineral soils and a forest Oa horizon to represent a wide range of organic carbon levels. Soil labile organic carbon varied from 0.8 mg/g in an Entisol to 17.3 mg/g in the Oa materials. Potential turnover time ranged from 24 days in an Alfisol to 102 days in an Ultisol. Soil labile organic carbon contributed from 4.8% in the Alfisol to 11.1% in the Ultisol to the total organic carbon. This new procedure is a relatively easy and simple method for obtaining indices for both the pool sizes and potential turnover rates of soil labile organic carbon and provides a new approach to studying soil organic carbon.     

Calculation of gross nitrogen immobilization and mineralization in soil

In a laboratory experiment, soil was treated with ¹⁵NH₄- and ¹⁵NO₃-N compounds at various times during the incubation. Several approaches in the calculation of gross immobilization and gross mineralization between two sampling dates were compared and a new method was developed. It is based on a dynamic simulation model designed to interpret isotopic data and an optimization procedure used to determine the best fit between model output and experimental data. This flexible method was used to examine the validity of the assumptions usually made when calculating the gross transformations.
The results indicate that seriously erroneous estimates of the gross transformations can follow if it is assumed that remineralization of immobilized N does not occur. Less serious errors can result from the assumption that both opposing processes occur at a constant rate during the interval between sampling dates.
The combined use of the model and the optimization procedure has several advantages over traditional methods and some of the gross transformation estimates reported would not have been obtainable using older methods.     

DEM构建过程质量控制

提高DEM精度,控制其质量是DEM构建者和使用者共同关心的问题。从如何减少DEM构建过程中的人为误差入手,对数字化过程中容易出现的人为误差进行了总结,指出相应的改进方法,并提出一种简便易行的快速检查DEM中错误的办法,对于指导生产实践有一定意义。     

应用DPSIR体系解决长江、珠江三角洲地区环境问题的初步思考

长江、珠江三角洲地区是我国经济高速发展而环境问题突出的典型区域。本文将引入DPSIR体系(驱动力-压力-状态-影响-响应模型),并结合对策论的初步分析,寻找解决该区域整体环境问题的研究方法和思路。     

Enzymatic assay for the determination of olive oil polyphenol content: assay conditions and validation of the method

A new spectrophotometric assay for the determination of the polyphenolic content of olive oil is presented. It is a substrate-recycling assay for phenolic compounds that employs tyrosinase in the presence of excess NADH. The reaction of various phenols with the enzyme produces an o-quinone, which is detected by recycling between reactions with the enzyme and NADH. The method offers some advantages over the classical methods employed to determine the polyphenolic content of olive oil, that is, ease and reproducibility of the analysis, highly increased sensitivity, and selectivity toward phenolic compounds. The amount of total polyphenols was determined in virgin olive oils both with the Folin-Ciocalteu reagent and with the proposed enzymatic method. The results suggest a better estimation of the polyphenol content, as compared with the colorimetric method. This has to be attributed to the different reactivities of the two methods toward phenols and catechols. Finally, the enzymatic method demonstrates that there is a linear relationship between the olive oil phenolic content and the antioxidative capacity of oil extracts.     

黄芩甙提取分离方法及工艺研究

黄芩甙是药用黄芩的主要有效成分,如何提高其得率和含量一直是实际生产中存在的问题。该文研究了温浸法、煎煮法、加碱温浸法3种传统的黄芩甙提取方法对黄芩甙得率和含量的影响。根据黄芩甙在碱性条件下易于溶解的特性,首次研究提出了用碱性离子水提取黄芩甙的新方法及该法提取黄芩甙的条件和效果。结果表明,碱性离子水提取法优于传统提取方法。该文还探讨了黄芩甙提取过程中水提液杂质去除、酸沉和沉淀物洗涤等方法对黄芩甙得率和含量的影响。     

QUICK格式在土壤水分运动数值模拟中的应用

运用有限体积法中的QUICK格式,对一维非饱和土壤水分运动方程中的对流项进行了高精度离散,通过经典的数值算例验证了本格式具有精度高、编程简单,计算速度快等特点。并与中心差分格式、迎风格式进行比较,QUICK格式不但能很好地避免数值振荡现象,而且与实测结果吻合较好。     

Determination of antioxidant power of red and white wines by a new electrochemical method and its correlation with polyphenolic content

A new method for measuring the antioxidant power of wine has been developed based on the accelerated electrochemical oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). The calibration (R = 0.9922) and repeatability study (RSD = 7%) have provided good statistical parameters. The method is easy and quick to apply and gives reliable results, requiring only the monitoring of time and absorbance. It has been applied to various red and white wines of different origins. The results have been compared with those obtained by the total antioxidant status (TAS) method. Both methods reveal that the more antioxidant wines are those with higher polyphenolic content. From the HPLC study of the polyphenolic content of the same samples, it is confirmed that there is a positive correlation between the resveratrol content of a wine and its antioxidant power.     

Change-Point Estimation in the Multivariate Model Taking into Account the Dependence: Application to the Vegetative Development of Oilseed Rape

In this paper, we address the change-point estimation issue in multivariate observations which consist in functions having piecewise constant first derivatives corrupted by some additional noise. We propose to solve this problem by rewriting it as a variable selection issue in a sparse multivariate linear model. Moreover, the methodology that we propose takes into account the dependence that may exist within the multivariate observations. Then, the performance of our approach is assessed through some numerical experiments and compared to other alternative and classical methods. Finally, we apply our methodology to experimental data in order to study the vegetative development of oilseed rape. The evolution of the number of leaves of oilseed rape can be modeled as a function having piecewise constant first derivatives corrupted by some additional noise where the change-points correspond to key times in the plant phenology. Our novel estimation method increases the accuracy of the change-point estimation in comparison with classical approaches. Moreover, we show that the parameters of the covariance matrix depend on the level of competition between plants. Supplementary materials accompanying this paper appear online.