磷石膏用作硫肥及其理化性质的探讨

<正> 近十多年来,许多地区都相继报道了土壤缺硫的现象。土壤的硫素营养问题逐渐为人们所重视。当今,农业上普遍施用高浓度不含硫的肥料。因此进入土壤的硫逐年减少。另外由于作物的高产,每年从土壤中带走大量的硫,致使硫的正常循环过程遭到破坏,严重地影响了农业生产。所以增施硫肥对许多地区来说是     

中·小型复(混)合肥料厂的发展及前景

农业是国民经济的重要组成部分之一,特别是粮食生产的稳定增长,尤为重要。增施化学肥料,是增加粮食和其他经济作物产量主要措施之一,高浓度、多元素、物理性状好的复(混)合肥料的优点,已越来越受到农业工作者和广大农户的重视与欢迎。随之兴起的中,小型复(混)合肥料厂在支援农业方面将发挥重要作用,对如何引导其在正确的轨道上巩固和发展,以及提高为农业服务的质量,是一个发展战略问题。本文即对此进行探讨。     

开展农化服务 寻求发展机遇

1农化服务的概念农化服务即农业化学服务。它是指以化肥产品为中心，以农民和耕地为服务对象，应用系统工程和农业化学基本原理，对化肥的生产、销售和使用予以科学的组织、调配和使用，以期最大限度地提高化肥的经济、社会和生态效益，提高农业劳动生产率，提供社会服务。2搞好农化服务的必要性2．1养分归还学说德国农业化学家李比希的养分归还学说认为：“由于人类在土地上种植作物并把这些产物拿走，这就必然会使地力逐渐下降，从而使土壤所含的养分愈来愈少。因此，要恢复地力，就么、须归还从土壤中拿走的全部东西，不然就难以再获得过…     

浅谈硫肥在农业生产中的作用

分析了我国土壤缺硫的现状以及土壤缺硫的原因，阐述了硫肥对农业生产的重要作用。     

测土施肥、因土供肥试验应用效果

引言化肥在农业生产上的应用,是人类自古以来在农业生产上的最大变革。目前,世界各国生产的谷物,约有50％左右是增施化肥所获,可见化肥在农业生产上的重要地位。据说我国有15亿亩可耕地。目前,每年供应农业生产的标准商品化肥(下同)5千多万吨(总值140亿元左右,约占农业生产投资的40％)。总产粮食6千亿斤左右。化肥与粮食的比例为1∶6。如果扣出土壤本身的养分和施农家肥等的增产因素,全国平均约每斤化肥增产粮食只有3斤左右。辽宁省1979年比1966年增施化肥200万吨,增产粮食500万吨,平均每斤化肥只增产粮食2.5斤。全国5千多万吨化肥,真正被作物吸收利用的不超过1500万吨,肥料利用率不     

对泡沫排液采气技术的一点认识

泡沫排液采气技术是药剂生产中的重要技术，掌握这一生产技术为工业生产过程服务是培训职工生产技术的必要手段。     

腐植酸对土壤固碳减排效应的应用研究进展

随着农业生产规模的不断扩大和人类需求的日益提高,农业生产活动引起的碳排放已严重影响土壤碳平衡。如何利用减少化肥滥施、改良土壤理化性质等方式促进土壤固碳减排一直是当前的研究热点。本文通过检索大量相关文献,综述了农业生产中固碳减排研究的背景以及腐植酸在农业固碳减排中的应用效果。从腐植酸对土壤酶活性、农药减量、化肥减施、土壤理化性质及固碳、作物生长发育5个方面的影响阐述了腐植酸在固碳减排中的重要作用,将其施用于土壤有望解决当前农业中的碳排放问题,同时提出了腐植酸作用于农业固碳减排的建议,以期为腐植酸在农业固碳减排上的研究和进一步应用提供理论依据和参考。     

酰胺类除草剂对红小豆的安全性

针对当前红小豆农业生产中大量应用的酰胺类除草剂并丙草胺、并丙甲草胺，研究其对红小豆苗期的安全性。研究表明，在低温、土壤墒情好的条件下两种药剂均对红小豆不安全，主要表现在影响出苗率、抑制生长、根体积明显减少、真叶叶片皱缩扭曲、严重的叶缘开始发黄、根瘤减少、逐渐枯死。两种药剂药害程度相近、随剂量增加症状明显加重，高用量时拱土期施药比播后立即施药的药害相对较轻，随有机质含量的降低而药害加重。     

农药发展与综合治理——一个植保工作者的建议与希望

农药是防治农作物免受病虫草鼠等有害生物侵害的重要的农业生产资料，农药在农业生产中具有十分重要的作用。二十一世纪即将来临，福建农药该怎样发展，如何更好地为农业安全生产服务？这是个大课题。笔者仅从做为一个植保工作者角度，提些建议与希望。１科学应用前景广阔...     

不同植被下土壤有机质含量的测定

土壤有机质（soil organic matter,SOM）是一项评判土壤质量状况的重要因子,其含量的高低对农业生产活动具有重要作用。本文采集了江南地区三种不同植被下的土壤样品,在实验室使用重铬酸钾外加热容量法测定土壤有机质含量。结果发现,原始树林土壤有机质含量为11.6 g/kg,茶田为19.2 g/kg,竹林为36.8 g/kg。     

低Reynolds数空气来流正庚烷液滴蒸发过程熵产特性

车用内燃机、航空发动机燃料的主要成分为正庚烷液体。液体燃烧属于扩散型燃烧,燃料先雾化成油雾,然后蒸发,燃油蒸气在气态扩散火焰中燃烧。油雾蒸发是液体燃烧中的重要过程,是决定液体燃烧的燃烧速率的关键步骤。建立了一个二维准稳态的液滴蒸发数值模型,分析了液滴蒸发的熵产,推导出了三维笛卡尔坐标系下的传质熵产公式。基于Fluent软件进行了数值模拟,结果显示低Reynolds数空气来流中的液滴蒸发过程的熵产主要由导热熵产组成,且液滴蒸发越容易,相对总熵产越小,从热力学角度来看其液滴蒸发过程更优。     

熵函数的教学探讨

熵的概念源于热力学，自提出以来，不断地得到发展，应用也日益广泛。并将熵函数热力学推导和熵函数物理实质相结合探讨熵函数的教学。     

Entropy of fluidized bed—a measure of particles mixing

The paper presents an attempt to define the physical entropy of the dense phase of a fluidized bed, based on liquid-like properties of fluidized systems. The quantity U was used as the analogy of temperature in classical thermodynamics. The obtained expression for physical entropy was compared to the correlation suggested for the Kolmogorov entropy in bubbling bed.     

膜全热交换器内热湿交换过程的熵分析

目前,在空调新风热回收领域常用的热回收装置有金属壁换热器、热管换热器、转轮全热回收器和膜全热交换器（MHME）．在这些热回收装置中,金属壁换热器和热管换热器只能回收显热,而转轮全热回收器和膜全热交换器除显热外,还能回收潜热,因此效率较高．尤其膜全热交换器由于没有运动部件,维护容易,更有发展前途．膜全热交换器与传统的只有空气与空气的显热交换的金属板式热交换器相比,     

Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number

This paper analyzes the entropy generation rate of simple pure droplet combustion in a temperature-elevated air convective environment based on the solutions of flow, and heat and mass transfer between the two phases. The flow-field calculations are carried out by solving the respective conservation equations for each phase, accounting for the droplet deformation with the axisymmetric model. The effects of the temperature, velocity and oxygen fraction of the free stream air on the total entropy generation rate in the process of the droplet combustion are investigated. Special attention is given to analyze the quantitative effects of droplet deformation. The results reveal that the entropy generation rate due to chemical reaction occupies a large fraction of the total entropy generated, as a result of the large areas covered by the flame. Although, the magnitude of the entropy generation rate per volume due to heat transfer and combined mass and heat transfer has a magnitude of one order greater than that due to chemical reaction, they cover a very limited area, leading to a small fraction of the total entropy generated. The entropy generation rate due to mass transfer is negligible. High temperature and high velocity of the free stream are advantageous to increase the exergy efficiency in the range of small Reynolds number (<1) from the viewpoint of the second-law analysis over the droplet lifetime. The effect of droplet deformation on the total entropy generation is the modest.     

化肥与农业简析化肥对现代农业的作用

主要讨论3个方面的问题(1)从农业生产的历史发展和现状看使用化肥的必然性;(2)化肥在多方面的巨大作用;(3)使用化肥能显著增加贮藏在农产品中的生物能.强调化肥不仅不会破坏耕地土壤,而且有助于土壤肥力的逐步提高.     

CO2-空气微通道蒸发器两相区熵产分析

微通道已成为换热器研究领域的热点,以CO₂微通道蒸发器为研究对象,建立了CO₂微通道蒸发器两相区内、外侧均有相变的熵产模型,通过建立的CO₂微通道蒸发器二维分布参数模型求解系统熵产数.分析CO₂与空气侧质量流率、空气入口温度及CO₂蒸发温度对系统熵产数的影响.结果表明:CO₂质量流率对系统熵产数影响很小;系统熵产数主要由CO₂与空气两侧温差传热引起;系统熵产数随空气入口温度的增大而增大,随CO₂的蒸发温度的增大而减小;随着空气质量流率的增大,系统熵产数增大,且蒸发温度越高,空气质量流率对系统熵产数的影响越大.     

Entropy Time Evolution In A Twin-flight Single-screw Extruder And Its Relationship To Chaos

The flow fields in polymer processing exhibit complex behavior with chaotic characteristics, due in part to the nonlinearity of the field equations describing them. In chaotic flows fluid elements are highly sensitive to their initial positions and velocities. A fundamental understanding of such characteristics is essential for optimization and design of equipment used for distributive mixing.

In this work we analyze the flow in a twin-flight single-screw extruder, obtained through 3-D FEM numerical simulations. We study particle motion and, implicitly, mixing in the extruder. Here, particles are massless points whose presence does not affect the flow field or other particle motion.

We visualize chaos through Poincaré sections and calculate Lyapunov exponents as a measure of divergence of initial conditions, signaling chaotic features of flow. We use entropic measures to probe disorder or system homogeneity. The time evolution of the Renyi entropy of β?=?1 for the 3-D spatial distribution of particles using different initial conditions is followed. The Kolmogorov-Sinai entropy rate, calculated by the sum of positive Lyapunov exponents, is correlated with the rate of evolution of entropy. In the same context we also examine the eccentric Couette flow.

We find that the Renyi entropy dependence on time is logarithmic. To gain further understanding of this numerical observation, we analyze analytically the diffusion with drift entropy and find that it also depends logarithmically on time. Using the logarithmic coefficient of the Shannon entropy (β?=?1) as a measure of the overall rate of mixing, we find that the eccentric Couette device has the highest rate of mixing, followed by the twin-flight single-screw extruder, and by the 1-D diffusion with drift.     

专虑(火用)和熵而得到的催化剂粒内活性最优分布

It is generally recognized that the optimal distribution of catalyst activity in a spherical catalyst is a Dirac δ-function. However, catalyst with other alternative distribution may accomplish the same reaction task without necessarily concentrating the catalyst activity in an inside thin layer.Moreover, the alternative with activity on catalyst surface may offer higher reaction rate and better utilization of reaction heat (higher exergy output). Simple cases of first-order exothermal reactions, in particular when the catalyst is limited by the maximum working temperature, are presented to demonstrate the above advantages and to show the importance of studying the optimal activity distribution with the consideration on exergy maximization and entroov oroduction minimization.     

Contribution of nitrification and denitrification to N2O production in peat, clay and loamy sand soils under different soil moisture conditions

Agricultural soils are a significant source of nitrous oxide (N₂O). Since mitigation of greenhouse gas emissions is needed in all sectors of society, it is important to identify the processes producing N₂O and the factors affecting the production rates in agricultural soils. This study aimed to elucidate the N₂O production in peat, clay and loamy sand at four different soil moisture conditions (40, 60, 80 and 100% Water Filled Pore Space). The ace­tylene inhibition technique was used to evaluate the contribution of nitrification to N₂O production. Nitrous oxide production responded markedly to soil moisture in all three soils. The highest N₂O production, measured at the wettest soils (100% WFPS), was up to four orders of magnitude higher than that at the dry soils (40% WFPS). In dry conditions N₂O production decreased in the order of peat > clay > loamy sand, while in wet conditions the highest N₂O production was measured in loamy sand, then in peat, and the lowest in clay soils. Nitrification was the dominant N₂O producing process in all the soils at 60% WFPS. In the sandy soil 70% of the total N₂O production originated from nitrification, while in the peat soil most of the total N₂O production originated from denitrification. Data on processes producing N₂O in agricultural soils are needed to develop process-based models that could reduce the uncertainty of the emission estimates in greenhouse gas inventories.