Economic control of fertilizer in highly productive pastoral systems. IV. An appropriate model for a stable upgraded state

Data from a stable upgraded grass-clover system were used to show that an exponential model, based on the ideas of Liebig and Mitscherlich, may be simplified to permit a prediction of yields over years through three constant parameters for the fertilizer effect and one varying parameter for the climatic effect; this result is in accord with the Mitscherlich relative yield theory. When the model was applied to an economic analysis of the data, the result emphasized the importance of the concept of an average year in calculating fertilizer recommendations; also, it became apparent that completely unfertilized plots should be excluded from field trials intended as a base for such economic advice.     

Economic control of fertilizer in highly productive pastoral systems. III. A hypothetical model to quantify upgrading from a primitive into a highly productive state

A model suitable for quantifying the upgrading of primitive pasture by phosphatic fertilizer is described; the model, based on the Mitscherlich-Spillman equation, provides a criterion for judging when upgrading is complete. Such information is essential to permit a successful experimental attack on the problem of providing fertilizer-advice for highly productive systems where the nutritional requirements both of pasture plants and grazing animals have to be satisfied. The advice must therefore have a sound basis in physiology as well as in economics; but, the generally accepted modern approach cannot be integrated into a logically consistent and practically possible solution to this complex problem. Consequently, the present proposals involve a number of innovations to replace inadequate concepts in the current approach; the most important of these are as follows.

1. Replacement of the economic theory of isoquantal substitution by production function analysis of long term average response by pasture to a complete (physiologically balanced) mixture of fertilizers.
2. Use of a hypothetical model justified by biological theory rather than an empirical model justified by a least squares-best fit criterion.
3. Replacement of multilevel factorial field experiments by simple 3-level trials representatively dispersed over the whole of the commercially productive area and carried on for a decade.
4. Exclusion of grazing animals from the main phase of a simple trial, but with their heterotrophic cycling of nutrients effectively simulated by a modified experimental technique.
5. Systematic use of foliar chemical analysis, which in one way or another is essential to supplement each of the first 4 innovations.

     

Economic control of fertilizer in highly productive pastoral systems. II. Designing field trials with physiologically balanced fertilizer through subtractive pot experiments

Deficiencies in essential chemical elements were diagnosed for two soils in a pot trial, using a subtractive technique and two different test plants: perennial ryegrass for ‘major’ elements and white clover for ‘minor’ elements. This information was required in a pastoral area to permit field trials to be designed with a suitably fortified superphosphate as the fertilizer input. The trials themselves are wanted to provide economic advice soundly based in relation to nutritional needs of pasture plants and grazing animals. Accordingly, a complex argument has been developed to justify using simple 3-level trials with physiologically balanced fertilizer instead of conventional multilevel factorial types; also to show how the simple trials should be designed.     

Economic control of fertiliser in highly productive pastoral systems. V. Extending advice through the Mitscherlich-Liebig model

A general solution is proposed to the problem of extending economic fertilizer advice over a highly productive pastoral area. The scheme implies a subdivision of the area through objective information obtained from widely dispersed, long-term, 3 level field trials; within sub-areas advice appropriate to a particular farm, or part thereof, is specified by incorporating more or less subjective estimates concerning level of output from the current input of fertilizer and carry-over of fertility in the field from one year to the next. The mathematical model used to facilitate an economic evaluation has been termed ML because it combines two cardinal principles: Mitscherlich's Law of Diminishing Returns and Liebig's Law of the Minimum, and is thus in accord with both economic and physiological theory. The model has been used to assess the effectiveness of chemical soil testing as a means of estimating carryover of fertility and to study the sensitivity of economic advice to error in the vital ratio: cost of input/selling price of output. The concept of a common response curve for essential elements has been developed as a basis for calculating the composition of a complete physiologically balanced fertilizer.The articles I–IV appeared inFertilizer Research 4:4 (1984)     

A multicontinuum approach for the problem of filtration of oily water systems across thin flat membranes: I. The framework

A multicontinuum model is built to estimate the permeate flux of an oily water system across a thin flat membrane in cross filtration methodology is demonstrated. Several continua are constructed to represent droplet and pore‐size distribution of both the dispersed oil phase and the porous membrane, respectively. The possible permeation of the oil phase has been divided into three criteria. In the first criterion, oil droplets of a given size range may permeate through a given size range of the porous membrane, in the second criterion, oil droplets of another size range may be rejected through another pore size range, and in the third criterion, oil droplets may break apart leaving a tail inside the pore space, which will eventually permeate, and the rest will sweep off due to shear stress. These protocols identify the methodology of the proposed multicontinuum approach, which is introduced in this first part. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4604–4615, 2017     

Fundamentals of plasticating extrusion. I. A theoretical model for melting

A steady state model for melting in a screw extruder has been developed based on the assumption that a stable solid bed of polymer granules is melted by heat that is conducted from a hot barrel and heat that is generated by viscous dissipation in the film that separates the solid bed and the surface of the barrel. The solid bed gradually decreases in width, as it proceeds in the channel, until it disappears at which point the melting is terminated. The model predicts the solid bed width profile and the required length of melting in terms of physical properties, operating conditions, and geometry of the screw. The model has been tested based on experimental data.     

Frequency domain solution of the optimal control problem for linear distributed systems

This paper describes a numerical method for the spectrum factorization procedure. This numerical method enables the solution of the optimal control problem for linear distributed systems with quadratic performance indices. The numerical method is demonstrated on an optimal feed forward—feed back control system for a heat exchanger.     

A learning fedforward control strategy for the concentration control of recycle reactors. Part I: Set-point control

Unknown reaction rates make concentration control in laboratory recycle reactors a difficult task, particularly when gas chromatographs or other analytical equipment with long analysis times from part of the control system. For such time-delay systems, a model-based feedforward control technique is developed which uses some kind of learning linear mapping to provide estimates of the reaction rates. Regarding the number of time steps necessary to satisfy a new set point, in a variety of simulation studies, this technique has proven superior to similar but simpler control strategies.     

1.有机复合肥养分高效优化技术研究

介绍了全国及北京、湖南、陕西、广东、河南、吉林、山东、重庆的有机肥料资源及利用情况;有机肥料企业、有机无机复合(混)肥料行业的概况;有机无机复合(混)优化配方、技术开发;我国发展有机肥、有机无机肥存在的问题及发展前景.     

A discrete element model for simulation of a spinning disc fertilizer spreader I. Single particle simulations

Modeling approaches for centrifugal fertilizer spreaders have so far been based on analytical expressions for single particle trajectories derived in the early 60's. However elegant this approach was, it suffers from several disadvantages, the most important of which is failing to incorporate the interaction between the particles in the flow. This paper is the first in a series aiming at simulating the complete spreading process based on the laws of physics and a physically meaningful model for the interactions between the particles, c.q. the contact forces. The result is a model that allows the development of a deeper understanding of the physics underlying the spreading process and provides better predictions. In this paper the model is presented in detail and a series of simple computer experiments are analysed and compared to theoretical predictions. Also, single particle trajectories from DEM simulations are compared to experimental results. Further, some effects of the model parameters are analysed. This paper demonstrates that the model is not only capable of producing realistic simulations, but also provides detailed insight in the physics of the spreading process.     

A diverse approach for the solution of the isothermal multiphase flash problem. Application to vapor-liquid-liquid systems

The paper presents a novel approach for the solution of the isothermal multiphase flash problem with particular application to systems exhibiting liquid-liquid-vapor equilibria. The approach includes a rigorous method for thermodynamic stability analysis as a first step and an efficient phase identification procedure. The stability analysis, exercised only once, uses a modification of the Gibbs tangent plane criterion. The identification procedure implements the results of the stability test in a sequence of liquid-liquid and liquid-vapor calculations only till the phase configuration with a minimum Gibbs energy is determined. The efficiency and reliability of the proposed new method is illustrated by solving three typical problems encountered in enhanced oil recovery, natural gas processing and petrochemical industry.     

我国氮肥工业原料路线的经济分析

叙述我国农业对氮肥的需求、氮肥生产及其采用原料的现状和存在问题，介绍采用不同原料生产合成氨和氮肥的工艺技术路线及经济分析．根据分析结果对我国氮肥工业的原料路线提出了几点看法，仅供决策部门研究参考．     

Nitrogen fertilizer in leucaena alley cropping. I. Maize response to nitrogen fertilizer and fate of fertilizer-15N

Field microplot experiments were conducted in the semi-arid tropics of northern Australia to evaluate the response of maize (Zea mays L.) growth to addition of N fertilizer and plant residues and to examine the fate of fertilizer¹⁵N in a leucaena (Leucaena leucocephala) alley cropping system, in which supplemental irrigation was used. Leucaena prunings, maize residues and N fertilizer were applied to alley-cropped maize grown in microplots which were installed in the alleys formed by leucaena hedgerows spaced 4.5 metres apart. The¹⁵N-labelled fertilizer was used to examine the fate of fertilizer N applied in the presence of mulched leucaena prunings and maize residues.Application of leucaena prunings increased maize yield while addition of N fertilizer in the presence of the prunings produced a further increase in maize production. There was a significant positive interaction between N fertilizer and leucaena prunings in increasing maize production. The addition of maize residues in the presence of N fertilizer and leucaena prunings decreased maize yield and N uptake and increased fertilizer¹⁵N loss from 38% to 47%. Maize recovered 24–79% of fertilizer¹⁵N in one cropping season, depending on application rate of N fertilizer and field management of plant residues. About 20–34% of fertilizer¹⁵N remained in the soil. More than 37% of fertilizer¹⁵N was apparently lost from the soil and plant system largely through denitrification when N fertilizer was applied at 40 kg N ha^–1 or more in the presence or absence of plant residues. Application of N fertilizer improved maize yield and increased the contribution of mulched leucaena prunings to crop production in the alley cropping system.     

A theoretical unsteady‐state model for kL of bubbles based on the framework of wide energy spectrum

An unsteady‐state model for predicting mass‐transfer coefficient k_L of bubbles with mobile surface was developed for turbulent gas‐liquid dispersions. This model was derived from an unsteady‐state convection and diffusion equation through a characteristics method. Unlike the previous work, this model considered the contributions of the amount of fluid structures of different scales (i.e., eddies) existing in the turbulent flows, the frequency of eddies arriving at the surface, the deformation and oscillation of bubbles to mass transfer. This model was based on the framework of wide energy spectrum and can account for the role of eddies of different sizes in mass transfer. Thus the assumption adopted by the previous models that mass transfer was controlled by eddies of certain sizes is no more needed. The overall k_L predicted by the proposed model showed a better agreement with the reported experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1007–1022, 2016     

A new theoretical equation for thermal conductivity of two‐phase systems

A new theoretical equation that describes the thermal conductivity of two‐phase composite materials has been proposed. The Cheng‐Vachon equation has been modified by introducing a new parameter named P_{d max}, permitting the new equation to describe the thermal conductivity of composite materials for a wide variety of filler shapes and states of dispersion. The new equation can describe the thermal conductivity of two‐phase materials more accurately than any of the previous equations. Furthermore, this new equation will make it possible to evaluate the dispersion state of the discontinuous phase by measuring the thermal conductivity of the filled polymers or the polymer blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1689–1697, 1999     

草甘膦生产过程及控制系统综述

广谱除草剂草甘膦（glyphosate）是世界上应用最广、产量最大的农药品种。阐述了目前草甘膦生产的主要工艺路线以及它们各自的特点,针对我国草甘膦生产的主要工艺路线亚磷酸二甲酯法的合成和酸解工序,综述了其主要控制方案和控制算法,分析了目前控制方案中存在的难点以及进一步研究的方向。对草甘膦生产前景进行了展望。     

TeCSMART: A hierarchical framework for modeling and analyzing systemic risk in sociotechnical systems

Recent systemic failures in different domains continue to remind us of the fragility of complex sociotechnical systems. Although these failures occurred in different domains, there are common failure mechanisms that often underlie such events. Hence, it is important to study these disasters from a unifying systems engineering perspective so that one can understand the commonalities as well as the differences to prevent or mitigate future events. A new conceptual framework that systematically identifies the failure mechanisms in a sociotechnical system, across different domains is proposed. Our analysis includes multiple levels of a system, both social and technical, and identifies the potential failure modes of equipment, humans, policies, and institutions. With the aid of three major recent disasters, how this framework could help us compare systemic failures in different domains and identify the common failure mechanisms at all levels of the system is demonstrated. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3065–3084, 2016     

Melt spinning of polymers I. An elementary framework for analyzing the development of orientation

An elementary framework to describe the evolution of orientational order in melt spinning of polymers is presented. By dividing this process into fundamentally different zones of structure development (melt zone with T > temperature of initiation of crystallization T_c; crystallization zone with T_c > T > T_g; static zone with T < T_g), it is shown that a generalized framework can be developed into which different homopolymers can be fitted on the basis of their physical transition temperatures. Sources of deviation from the simplified framework are also discussed.     

快速发展BB肥是推广科学施肥建设现代农业的必然选择

论述BB肥是适合我国国情的测土配方肥料,快速健康发展BB肥产业是推广科学施肥,建设现代农业的必然选择。我国BB肥产业起步晚,发展慢,未进入大工业生产阶段。发展缓释BB肥、有机-无机BB肥、添加中微量元素BB肥,提高有效养分利用率;改进掺混工艺,解决BB肥原料的相容性及优化施用技术,推广测土配方套餐施肥;强化肥料企业与农业部门有机结合,做好农化服务,才能做大做强我国BB肥产业。