Evaluation of methods of measurement of nitrogen in poultry and animal manures

Kjeldahl nitrogen (N), total N and forms of inorganic N (ammoniacal (NH₄)-N, nitrate (NO₃)-N and nitrite (NO₂)-N) were measured in a range of animal manures. The manures include fresh samples of poultry manure, sheep manure, horse manure, dairy slurry and pig slurry and composted poultry manure. Kjeldahl N was measured by standard micro-Kjeldahl digestion. For total N measurements, NO₃-N and NO₂-N were recovered during Kjeldahl digestion by pretreatments with various oxidizing and reducing agents. Inorganic forms of N were measured by extraction with 2M KCl solution.Kjeldahl digestion alone allowed measurement only of organic N and NH₄-N. Amongst various modifications to the Kjeldahl, pretreatment with either acidified (H₂SO₄) Zn-CrK(SO₄)₂ or acidified (H₂SO₄) reduced Fe achieved complete recovery of NO₃-N. Nitrite N was only recovered by first oxidising the NO ₂ ^- to NO ₃ ^- with KMnO₄ followed by reduction to NH₄-N with acidified (H₂SO₄) reduced Fe.More than 95% of the total N in fresh animal manure was present as organic N and NH₄-N which were recovered by the standard Kjeldahl digestion. In the case of fresh manures there was no difference between the amount of total N measured by the Kjeldahl digestion and its modified methods. However composting of poultry manure or drying of poultry manure, pig slurry and dairy slurry resulted in an increase in NO₃-N which was not recovered during Kjeldahl digestion alone. Under these conditions the total N could be measured by pretreating the samples with KMnO₄ and reduced Fe prior to Kjeldahl digestion.Drying of animal manures caused a decrease in organic N and NH₄-N, especially in poultry, pig and dairy manures. There was a slight increase in NO₃-N; but most of the decrease in N content with drying was attributed to the volatilization loss of ammonia (NH₃). Amongst various drying methods examined air drying caused maximum loss of N as NH₃ whereas freeze drying caused minimum loss of N. This suggests that fresh animal manures can be freeze dried for analysis of N which causes minimum loss of N.     

Mass transfer between solid particles and liquid in a three phase fluidized bed

Particle-liquid mass transfer in a co-current three-phase fluidized bed of glass beads, water and air was studied with two measurement techniques. Both techniques measured the weight loss of a few particles coated with benzoic acid in a bed of inert glass beads. The effects of liquid and gas velocities, gas distribution and surface active agents on particle-liquid mass transfer in a three-phase fluidized bed were thus determined. In the absence of surface active agents in the liquid, particle-liquid mass transfer rates in a three-phase fluidized bed were up to 30% higher than in the corresponding liquid fluidized bed. When surface active agents were added to the liquid, the particle-liquid mass transfer rate was increased by up to about 100% in the three-phase fluidized bed, relative to the liquid fluidized bed. The particle-liquid mass transfer coefficient was found to be inversely proportional to the liquid hold-up in the three-phase fluidized bed.     

球窝型动态混合器结构和机理的研究

介绍研制的题示混合器结构及其混合机理。在分析球窝流场各节点速度分布的基础上,用加权平均总应变和分流混合度作为评定指标,对球窝型混合器的混合行为进行分析。通过对比实验证明球窝型混合器对于高粘流体具有良好的混合功效。     

185nmUV降解水中4-CP、4-NP和RhB的研究

本文以对氯苯酚（4-cP）、对硝基苯酚（4-NP）和罗丹明B（RhB）为模型有机物（以4-CP和4-NP为小分子模型有机物，以RhB为大分子模型有机物），分别研究了185nmUV对水中这3种模型有机物的降解规律、性能和效果．研究结果表明，185nmUV直接对水中4-CP、4-NP和RhB有很好的降解效果．研究内容包括：185nmUV降解模型有机物的浓度、TOC（Totalorganic carbon）浓度、185nmUV降解模型有机物过程中溶液pH及电导率变化、以及降解模型有机物过程中产生的无机离子等几个方面．     

面向综合集成研讨环境的主动信息获取方法*

针对在综合集成研讨环境中,由于存在时间压力,传统的网络信息获取方法难以直接使用,提出了一种面向综合集成研讨环境的主动信息获取方法。该方法将领域词条与通用词条相结合,从发言文本流中实时提取话题,并在话题发生变化时自动生成检索词送入搜索引擎进行检索,再通过多个用户之间的协作推荐实现对重要检索结果的筛选。实验结果表明,这种方法可为综合集成研讨系统的用户提供及时、准确、上下文相关的信息服务。     

一种适用于地衣总DNA提取的改进方法

目的：针对地衣初生、次生代谢产物丰富的特点,提出了一种适于地衣总DNA的提取方法。方法：应用改良的CTAB法,对3种常见地衣进行了总DNA提取,经过琼脂糖电泳、紫外吸收分析DNA质量。结果：3个样本DNA的A260/A280值均在1.8～2.0之间,琼脂糖电泳图像清晰。结论：改良的CTAB法简便、省时、价廉,适合于地衣总DNA的提取,获得的DNA含量高,纯度好。     

三相光伏发电系统在小型低压配网中的应用研究

研究了光伏电池的数学模型,采用扰动观察法实现在光照变化时的最大功率跟踪.将多组光伏电池串并联,通过boost升压电路连到三相逆变器的直流侧,逆变器的交流侧通过LC滤波器直接连到电网.三相逆变器采用PQ解耦的控制策略,在Matlab/Simulink中建立其详细模型.研究三相光伏发电系统在0.4kV小型低压配网中的应用,分析了低压配网在并网和孤岛运行时的功率电压特性,验证了这种应用的可行性.     

各向异性特异材料界面的反常折射与反射性质

根据电磁场边界条件和色散关系,理论研究了电磁波从各向同性右手材料向各向异性特异材料入射时的反常折射与反射性质,结果表明,从各向同性右手材料向never cutoff型特异材料入射时,透射波的波矢和坡印廷矢量的反射角具有相反的符号,折射角的幅度随着入射角的增大而增大并趋于一定值;研究了磁导率张量参数对折射角的影响,对于anti-cutoff型特异材料界面,当入射角小于临界角θc时可以发生反常的全反射,而对于always cutoff型特异材料界面总会发生全向全反射。这些电磁性质将在部分聚焦与全向反射镜方面具有潜在的应用价值。     

一种基于全变分模型的图像修复改进算法

为了恢复图像中划痕、文字等小目标去除后丢失的相关信息,对全变分(TV)模型及其自适应算法进行了分析和改进。在Chan提出的图像修复原则的基础上给出了两个阈值参数,对原有算法中的权值系数进行了改进。仿真实验结果表明,本文算法在保证原有算法修复效果的同时能够有效地提高运算速度,取得了较好的实际效果。     

三相单级全桥PFC电压尖峰机理分析与抑制

介绍了一种基于全桥结构的三相单级功率因数校正(PFC)变换器,该变换器工作于电感电流断续模式(DCM),电感电流即输入电流的峰值自动跟踪输入电压,可实现功率因数校正.建立了桥臂开关对臂导通时变换器的简化模型,并分析了该阶段变压器原边电压尖峰的产生机理.分析结果表明,由于变压器漏感的存在,变压器原边于桥臂开关对臂导通期间将产生很大的电压尖峰,该电压尖峰大小由变压器原边的漏感、电流与并联电容三个参数决定.最后,结合电路的工作原理,提出了一种变压器原边无源缓冲电路来抑制该电压尖峰.实验结果表明,变压器原边的电压尖峰得到了有效抑制.