自动电位滴定仪测定饲料及饲料添加剂中氟化物的探讨

本文比较了自动电位滴定仪与pH计测定饲料及饲料添加剂中氟化物,自动电位滴定仪用于测定饲料及饲料添加剂中的氟化物具有较高的精密度和较高的准确性。     

A Comparison of Methods Used to Determine Biomass on Naturalized Swards

An experiment was conducted in 2000 to compare simple visual estimate, sward height and rising plate meter (RPM) methods for determining forage biomass in mixed-species, naturalized, rotationally grazed dairy and beef pastures. Measurements were taken pre- and post-grazing on 10 sampling dates at the dairy pasture, and post-grazing at 13 sampling dates at the beef pasture. For each sampling date, the effectiveness of each method for estimating the actual biomass from a quadrat was evaluated using regression analysis. The results for the visual estimate method were not consistent, with non-linear relationships occurring early and late in the season. While the meter stick was most effective in the dairy pasture, the RPM was most effective in the beef pasture. Species composition and structural characteristics of the stand were important factors affecting accuracy of biomass estimation. Equations developed for each method and site using data from all dates had low R²-adjusted values, and were unreliable predictors of biomass. The results from individual sites and dates were extremely variable, with no single method effective in all circumstances. To estimate forage biomass in mixed-species, naturalized pastures, standard quadrat harvesting remains the most reliable method, provided that enough quadrats are clipped to adequately represent a given area.     

欧盟法和国标法对食品中苏丹红检测的比较

采用欧盟法和国标法对食品中苏丹红的含量进行了检测,并比较了两种方法的差异。结果表明,欧盟法灵敏度高,粉状样品回收率高,但成本较高;国标法油状样品回收率高,成本低,大部分机构可用此法,但氧化铝活性需要控制适当才不会影响检测结果。     

常用流量计及其使用选择

流量计量是专门研究物质质量变化的一门科学,在各行各业中应用非常广泛,对其进行深入了解和科学使用具有非常重要的现实意义。为此,介绍了工农业生产和科研中常用的各种流量计及其工作原理;分析了各种流量计的特点及其使用场合;并以中小流量计为例,分析了流量计的选择方法。     

在线含水监测系统在原油交接过程中的应用

介绍了在线含水监测系统的工作原理,在原油交接过程中,该系统可有效地控制和捕捉瞬间含水率的变化,解决了原油含水频繁变化带来的计量误差,减少了输差损失,确保了原油交接计量的准确性。     

Soil surface roughness measurement—methods, applicability, and surface representation

In a laboratory rainfall simulator study soil surface roughness was measured using contact (roller chain, pin meter) and noncontact devices (laser scanner, photogrammetry). Soil surfaces with two initial roughness conditions (aggregates < 20 mm and < 63 mm) were investigated before and after 90 mm of simulated rainfall. Measured plot area was 50 by 55 cm. A comparison of soil roughness measurement techniques was undertaken with regard to data acquisition and computation efforts, resolution, precision and capability to represent soil surface features.As for the contact methods, resolution (cm range) and precision (mm range) is limited which constrains their application to calculation of simple surface parameters. Resolution and precision in the sub millimeter range could be obtained with the laser scanner, while for the photogrammetric method the measurement uncertainty was approximately 1–2 mm. Measurement time was highest (90 min) for the pin meter technique, though data were ready to use for analyses. Laser scanner measurements took 34 min. Several steps of data post-processing required 30 more minutes. Data acquisition was fastest for photogrammetry (5 min), but expert knowledge as well as special hard- and software were necessary for time-consuming photo analyses, taking about 120 min.The chain and pin meter were compared using a profile index. Profile lengths matched well for smooth surfaces; on rough surfaces, the chain meter gave shorter profile lines. Between profile index from chain measurements and the random roughness derived from pin meter data a polynomial regression could be found. Parameters of distributions of elevations as well as inclinations and depressions were used to compare the laser scanner and the photogrammetric technique. Generally the laser scanner was able to reproduce small aggregates as well as voids in between them, while DEM from stereophotos was smoothed between major aggregates. This led to skewed distributions of elevations and inclinations, as well as to a lower surface area (up to 39%), and a lower depression volume (up to 68%). Shapes of depressions were significantly different as well. The used photogrammetric technique is supposed to be successful in producing adequate DEMs for already smoothed surfaces, e.g. after rainfall events.The study revealed different fields of application and limitations of the compared devices. Using a non-adequate technique for certain situations will definitely have implications on further analyses concerning connectivity of runoff pathways, surface protection from raindrop impact or runoff detachment and sediment transport.     

The influence of clipping frequency on reserve carbohydrates and regrowth of Eragrostis curvula

Increasing the frequency of clipping over a 12 week period resulted in decreasing root and stubble weight at the end of the 12 week period. During the regrowth period, following the clipping treatment, the aerial dry matter production was found to increase with the more lenient treatments.

The pattern of depletion and restoration of Total Available Carbohydrates (TAC) following clipping was found to conform to a U‐shaped curve, except where the initial TAC values were low. This pattern was found for the roots and stubble, whether expressed on an intensity of deposition or quantity of TAC basis. The degree of reduction in TAC during the first week of regrowth was found to be dependent on the level of TAC at the time of cutting, the higher the initial value the greater the reduction.

The results indicate that reserve carbohydrates play an important role in regrowth, although the relationship is of relatively short duration.     

Establishment of Chlorophyll Meter Measurements to Manage Crop Nitrogen Status in Potato Crop

Management of nitrogen (N) use is necessary to promote maximum development and production of tubers. For this reason, chlorophyll meters have been used to make N-fertilizer recommendations in potato. An assay was carried out with increasing doses of N. To define the thresholds IV for potato crops, correlations among IV, ISN, RR, and N content had been established. IV is the green index of the leaf measured by the chlorophyll meter. This index estimates the chlorophyll content in the leaf and through this the N concentration in vegetal tissue, based on the assumption that N and chlorophyll content have a strong correlation. ISN is the sufficiency nitrogen index. It was determined as the relation between the green index reading of each experimental unit and the highest average green index reading of the assay. RR is the relative yield. It was calculated as the ratio between the yield of each treatment and the highest average yield of the assay. The results had shown that varieties did not present N deficiencies during the vegetative growth phase, with IV and ISN values respectively equal to 41 SPAD units and 93 percent. During the tuber bulking phase, the necessary IV and ISN thresholds to reach maximum yields, for N content equal to 3 percent, were, respectively, between 38.5 and 40.5 SPAD units and between 84 and 94.8 at 70 and 89 days after planting. We concluded that the chlorophyll meter is an appropriate tool to determine the nutritional status in potato crops.     

基于SOA的计量自动化应用平台设计

针对计量自动化应用系统现状，提出基于SOA的计量自动化应用平台设计方法。该应用平台设计方法利用面向服务体系结构灵活性高、易扩展性强等特点，将计量自动化系统划分为若干服务，并对外提供统一的描述接口，将支持服务的主要实现功能封装到业务逻辑层，较好地解决计量自动化系统与电力系统中各子系统集成的难题。给出数据采集终端管理服务的服务描述案例，证实该方案的可行性。     

Estimating root mass in maize genotypes using the electrical capacitance method

A two-year field hydroponic study was conducted on root mass of maize (Zea mays L.) using the root electrical capacitance (C_root) method. The primary objective of the study was to test the utility of the C_root method in estimating root mass of maize (on a fresh and dry weight basis), and to determine any influence of maize genotype on this relationship. Secondary objectives were: (i) To determine if the volume of the Turface®-filled hydroponic containers had an effect on root mass-C_root relationships, and (ii) to determine if the number of plants/container affected the C_root measurements of individual plant root systems. Firstly, it was concluded that different maize genotypes appeared to have uniquely different root dry mass vs. C_root relationships. Secondly, the massing of the maize plant roots at the bottom of smaller (20-litre) pails seemed to frequently have a negative effect on the strength of the root mass-C_root relationship. Thirdly, multiple plants could be regarded as a single experimental unit in C_root studies when their root electrical capacitance was measured simultaneously. The predictive capability of the equations developed from this hydroponic study was reasonably good, but research is needed on similar genotype-specific relationships under field soil conditions to determine if they might have some utility in broader agronomic field applications.