不同出口结构旋流板分离器内流场的数值模拟

基于Fluent软件,采用雷诺应力（RSM）湍流模型对不同出口结构分离器内气相旋流流场进行了数值模拟。模拟结果表明：分离器出口角度Ф变化对流场的影响显著,出口直径H变化对流场的影响甚微;有出口装置分离器内的切向速度均有所增加,最大切向速度向轴心方向移动。     

CO2等温室气体对全球气候影响的数值模拟研究

一、引言近30年来,由于世界性天气气候异常现象的频繁发生,和全球性平均气温增高的趋势,引起了气候学家和环境科学家对温室效应的普遍注意。在CO_2等微量气体的温室效应对全球气候影响的作用究竟有多大;以及哪些气候变量有影响等方面,科学工作者进行了大量研究。大气中CO_2含量的变化趋势预测,则是另一个更为复杂的研究问题。近20年来,随着计算技术和气候动力学的迅速发展,人们对CO_2温室效应的研究,已从定性分析发展到应用气候模式对CO_2浓度变化引起的诸如地表温度、地面温度、土壤湿度、降     

吸收分光光度法(分析仪器评论)

<正> 分折化学家完成的大量测定中,依据比尔定律并使用分光光度计完成的测定所占的比例一直在增长。虽然可通过测量吸收值将范围较宽的电磁光谱用来测定气相、液相或固相中原子、自由基和分子的浓度,然而这类测量大多是在可见或紫外区进行的。这部分是因为所发展的这一部分光谱的检测器件具有较高的效率和快速的响应;部分是因为分辨不同分子产生的特征吸收所需要的设备相对简单的缘故。因此,本评论只限于专为测量可见及紫外电磁光谱吸收而设计的仪器设备。要追溯最早出现的这类仪器是困难的,因为     

亚热带常绿阔叶林土壤微生物量动态变化及其对氮磷添加的响应

土壤微生物是土壤生物化学过程的驱动者,对环境变化极其敏感。为了探讨不同年份气候差异及不同坡位土壤微生物对氮沉降的响应机制,在安徽南部查湾自然保护区选择不同坡位亚热带常绿阔叶林,就氮、磷添加对土壤微生物量碳(MBC)、氮(MBN)的影响进行了为期3年的试验研究。选择中坡和坡顶两种立地类型,分别设置3种控制实验,对照(CK,0 kg N?hm~(-2)?a~(-1))、氮添加(N,100 kg N?hm~(-2)?a~(-1))、氮磷添加(N+P,100 kg N?hm~(-2)?a~(-1)+50 kg P?hm~(-2)?a~(-1))。取样后,测试不同处理土壤MBC、MBN及土壤理化性质。结果表明,氮磷添加后,不同坡位MBC和MBN季节变化存在差异。与対照相比,氮磷和氮添加中坡MBC分别降低了14.6%和15.4%,而在坡顶,两种处理MBC分别提高5.8%和2.1%。中坡MBC变化范围为171.94~2 151.35 mg?kg~(-1),MBN变化范围为52.14~203.3 mg?kg~(-1);坡顶MBC变化范围为102.49~2 219.95 mg?kg~(-1),MBN变化范围为38.56~203.3 mg?kg~(-1)。中坡第2年、第3年及坡顶第3年氮磷和氮添加降低了ω(MBC)/ω(MBN)比,不同坡位ω(MBC)/ω(MBN)比均值为7.88~14.21。土壤微生物量的季节变化显著,土壤MBN在生长季节(5月、7月、9月及11月)较高,最低值出现在休眠期(1月);养分添加改变了土壤MBN季节变化规律。季节、坡位改变了土壤微生物量碳氮和土壤养分的相关性。因此,养分添加对不同立地土壤微生物的影响不同,且不同年份存在差异。长期氮、磷添加降低了ω(MBC)/ω(MBN)比值,但不同坡位反应时间存在差异。土壤MBC、MBN不同年份之间差异显著,主要受不同年份降雨和气温变化控制。冗余分析(RDA)表明,月降水频率、不同年份气温及降水差异、林分因子及土壤理化性质均对土壤微生物量存在显著影响,其季节变化由降水频率(月降水天数)、降水量及气温变化和月降水量及气温波动差异(月标准差)所控制。     

Biological activity and environmental impact of anionic surfactants

The newest results concerning the biological activity and environmental fate of anionic surfactants are collected and critically evaluated. The chemical and physicochemical parameters related to the biological activity and the field of application are briefly discussed. Examples on the effect of anionic surfactants on the cell membranes, on the activity of enzymes, on the binding to various proteins and to other cell components and on their human toxicity are presented and the possible mode of action is elucidated. The sources of environmental pollution caused by anionic surfactants are listed and the methods developed for their removal from liquid, semiliquid and solid matrices are collected. Both the beneficial and adversary effects of anionic surfactants on the environment are reported and critically discussed. It was concluded that the role of anionic surfactants in the environment is ambiguous: they can cause serous environmental pollution with toxic effect on living organisms; otherwise, they can promote the decomposition and/or removal of other inorganic and organic pollutants from the environment. The relationship between their chemical structure, physicochemical parameters, biological activity and environmental impact is notwell understood. A considerable number of data are needed for the development of new anionic surfactants and for the successful application of the existing ones to reduce the adversary and to promote beneficial effects.     

Removal of synthetic dyes from wastewaters: a review

The more recent methods for the removal of synthetic dyes from waters and wastewater are complied. The various methods of removal such as adsorption on various sorbents, chemical decomposition by oxidation, photodegradation, and microbiological decoloration, employing activated sludge, pure cultures and microbe consortiums are described. The advantages and disadvantages of the various methods are discussed and their efficacies are compared.     

Separation of the strength and selectivity of the microbiological effect of synthetic dyes by spectral mapping technique

The growth inhibitory effect of 30 synthetic dyes on 22 bacteria (test organisms) belonging to various taxonomic groups was determined. The strength (potency) and selectivity of the biological effect were separated by the spectral mapping technique, reducing the dimensionality of the selectivity maps to two by the nonlinear mapping technique. The relationship between biological effect and physicochemical parameters of dyes was elucidated by stepwise regression analysis. It has been established that the strength of the effect of anthracene and trityl derivatives was higher than that of azobenzene dyes and significantly depended on the hydrophobicity of the compound. The selectivity of the effect also depended on hydrophobicity and on the nonpolar unsaturated surface area of the dyes. Gram negative and Gram positive bacteria differed in the strength and selectivity of their response to dyes indicating the marked impact of the taxonomical position on the response. Contrary to other multivariate mathematical statistical methods biological activity may be divided by SPM into potency and selectivity values, therefore, application of the technique in future QSAR studies is highly recommended.