Gaseous emissions (NH₃, N₂O and CH₄) following manure or urea application to soil as influenced by amendments

Increasing concentrations of greenhouse gases in the atmosphere may contribute to global warming. The three most important greenhouse gases are carbon dioxide (mainly from burning fossil fuels and deforestation), methane (mainly from ruminant animals and waste management) and nitrous oxide (mainly from dung, urine, and nitrogenous fertilisers). Dairy farms contribute to greenhouse gas emissions because of nitrous oxide and methane emissions (Whitehead et al., 2009). Herd-homes or stand-off pads are increasingly used on dairy farms to minimise soil pugging and compaction. The manure collected from herd-home bunkers or stand-off pads, may be a source of gaseous emissions (NH₃, N₂O and CH₄). Addition of soil or sawdust to manure prior to land application of manure is a potential best farm management practice to minimise gaseous losses. The specific objectives of the study were to: 1. Determine the optimum flow rate for measurement of ammonia emissions from manure or urea application to soil using a chamber method. 2. Quantify gaseous (NH₃, N₂O and CH₄) emissions from manure or urea after application to soil. 3. Determine the effects of addition of soil or sawdust to manure prior to land application of manure on subsequent gaseous emissions. 4. Determine the effects of surface or incorporated land application of manure or urea on gaseous emissions. A preliminary experiment was undertaken to determine the optimum flow rate to measure ammonia emissions, from manure or urea after application to soil, using a chamber method. The flow rate experiment was set up in the glasshouse with 3 replications of 9 flow rate treatments. A flow rate of 5 L min-¹ (1 exchange volume min-¹) was determined as the optimum air flow rate to use in the chamber method to measure ammonia volatilisation. An experiment was undertaken, with 27 pots and 3 replications of 9 treatments, to investigate the effect of soil or sawdust addition to manure on gaseous emissions (NH₃, N₂O and CH₄), when applied on the land surface or incorporated. The physical and chemical properties of the soil, urine, dung, and sawdust were determined in the laboratory. Addition of sawdust was more effective in reducing ammonia emissions, than addition of soil, to manure prior to land application. The incorporated application of all manure treatments resulted in less NH₃ volatilisation compared to surface application. Total ammonia losses were 51% of the applied N from the surface application and 2% of the applied N from incorporated application of urine and dung with soil, and 15% of the applied N from the surface application and 4% of the applied N from incorporated application of urine and dung with sawdust. Ammonia emissions followed a general pattern of rapid emission on day 2 after the application of the urine and dung to soil followed by a progressive decline over time for both the surface and incorporated application for all the manure treatments applied. Total N₂O loss of 14% of applied N was observed with incorporated application of manure with sawdust. Most treatments had no net methane emission. Addition of soil and sawdust to manure, prior to application to soil, reduced ammonia emissions and increased nitrous oxide emissions

A Verified Type System for CakeML

CakeML is a dialect of the (strongly typed) ML family of programming languages, designed to play a central role in high-assurance software systems. To date, the main artefact supporting this is a verified compiler from CakeML source code to x86-64 machine code. The verification effort addresses each phase of compilation from parsing through to code generation and garbage collection. In this paper, we focus on the type system: its declarative speci- fication, type soundness theorem, and the soundness and completeness of an implementation of type inference – all formally veri- fied in the HOL4 proof assistant. Each of these aspects of a type system is important in any design and implementation of a typed functional programming language. They allow the programmer to soundly employ (informal) type-based reasoning, and the compiler to apply optimisations that assume type-correctness. So naturally, their verification is a critical part of a verified compiler

Dry and wet spells at Itabaina (NE Brazil)

Results of a study of dry and wet spells at Itabaina, a semi-arid station in northeast Brazil, are presented in this paper. Frequency distributions of dry spells of different durations at the station are compared with those derived from three statistical models. It is found that the Eggenberger-Polya and the geometric model provide better results than the logarithmic model. Frequency distribution of wet spells during the three rainiest months of the year shows that rainfall persistency reaches a maximum value on the fifth day of a rainy spell

An Improved Chaotic Grey Wolf Optimization Algorithm (CGWO)

Grey Wolf Optimization (GWO) is a new type of swarm-based technique for dealing with realistic engineering design constraints and unconstrained problems in the field of metaheuristic research. Swarm-based techniques are a type of population-based algorithm inspired by nature that can produce low-cost, quick, and dependable solutions to a wider variety of complications. It is the best choice when it can achieve faster convergence by avoiding local optima trapping. This work incorporates chaos theory with the standard GWO to improve the algorithm's performance due to the ergodicity of chaos. The proposed methodology is referred to as Chaos-GWO (CGWO). The CGWO improves the search space's exploration and exploitation abilities while avoiding local optima trapping. Using different benchmark functions, five distinct chaotic map functions are examined, and the best chaotic map is considered to have great mobility and ergodicity characteristics. The results demonstrated that the best performance comes from using the suitable chaotic map function, and that CGWO can clearly outperform standard GWO

Comparison between experimental and analytical behaviour of the steel – concrete composite pushout specimen with stud and channel shear connector

To investigate the behaviour of composite action with various shear connectors, push-out tests were performed for eight specimens. Test parameters includes are type of shear connector (headed stud connector and channel connector), number of connectors (one and two) and specimen with or without decking sheet. Test results showed that performance of the push-out specimens depends greatly on type of connector and decking sheet. From the experimental study it was observed that the performance and shear capacity of channel connector was 60 % more than the stud connector. The shear resistance between the steel and concrete was enhanced up to 50 % for the push out specimen without decking. The specimen with two numbers of stud and channel connector increases the strength by 58% and 23% respectively as compared to specimen with single connector. The behaviour of the push out specimen was stimulated by three-dimensional finite element model using software ANSYS workbench. The analytical behaviour was well agreement with the real push out specimen studied experimentally

Comparison between experimental and analytical behaviour of the steel – concrete composite pushout specimen with stud and channel shear connector

To investigate the behaviour of composite action with various shear connectors, push-out tests were performed for eight specimens. Test parameters includes are type of shear connector (headed stud connector and channel connector), number of connectors (one and two) and specimen with or without decking sheet. Test results showed that performance of the push-out specimens depends greatly on type of connector and decking sheet. From the experimental study it was observed that the performance and shear capacity of channel connector was 60 % more than the stud connector. The shear resistance between the steel and concrete was enhanced up to 50 % for the push out specimen without decking. The specimen with two numbers of stud and channel connector increases the strength by 58% and 23% respectively as compared to specimen with single connector. The behaviour of the push out specimen was stimulated by three-dimensional finite element model using software ANSYS workbench. The analytical behaviour was well agreement with the real push out specimen studied experimentally