202 resultados para atmospheric deep convection


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In pre-Fitzgerald Queensland, the existence of corruption was widely known but its extent and modes of operation were not fully evident. The Fitzgerald Report identified the need for reform of the structure, procedures and efficiency in public administration in Queensland. What was most striking in the Queensland reform process was that a new model for combatting corruption had been developed. Rather than rely upon a single law and a single institution, existing institutions were strengthened and new institutions were introduced to create a set of mutually supporting and mutually checking institutions, agencies and laws that jointly sought to improve governmental standards and combat corruption. Some of the reforms were either unique to Queensland or very rare. One of the strengths of this approach was that it avoided creating a single over-arching institution to fight corruption. There are many powerful opponents of reform. Influential institutions and individuals resist any interference with their privileges. In order to cause a mass exodus from an entrenched corruption system, a seminal event or defining process is needed to alter expectations and incentives that are sufficient to encourage significant numbers of individuals to desert the corruption system and assist the integrity system in exposing and destroying it. The Fitzgerald Inquiry was such an event. This article also briefly addresses methods for destroying national corruption systems where they emerge and exist.

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The role of ions in the production of atmospheric particles has gained wide interest due to their profound impact on climate. Away from anthropogenic sources, molecules are ionized by alpha radiation from radon exhaled from the ground and cosmic gamma radiation from space. These molecular ions quickly form into ‘cluster ions’, typically smaller than about 1.5 nm. Using our measurements and the published literature, we present evidence to show that cluster ion concentrations in forest areas are consistently higher than outside. Since alpha radiation cannot penetrate more than a few centimetres of soil, radon present deep in the ground cannot directly contribute to the measured cluster ion concentrations. We propose an additional mechanism whereby radon, which is water soluble, is brought up by trees and plants through the uptake of groundwater and released into the atmosphere by transpiration. We estimate that, in a forest comprising eucalyptus trees spaced 4m apart, approximately 28% of the radon in the air may be released by transpiration. Considering that 24% of the earth’s land area is still covered in forests; these findings have potentially important implications for atmospheric aerosol formation and climate.

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Dr Mills is also the invited author of the Deep End Series Teacher Guides by ERA publications. This 3-volume series for teachers is used in more than 200 schools in Australia, the USA, Canada, New Zealand, Sweden, Norway, and South America.

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Dr Mills is the invited author of the Deep End Series Teacher Guides by ERA publications. This 3-volume series for teachers is used in more than 200 schools in Australia, the USA, Canada, New Zealand, Sweden, Norway, and South America.

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Dr Mills is also the invited author of the Deep End Series Teacher Guides by ERA publications. This 3-volume series for teachers is used in more than 200 schools in Australia, the USA, Canada, New Zealand, Sweden, Norway, and South America.

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In pre-Fitzgerald Queensland, the existence of corruption was widely known but its extent and modes of operation were not fully evident. The Fitzgerald Report identified the need for reform of the structure, procedures and efficiency in public administration in Queensland. What was most striking in the Queensland reform process was that a new model for combating corruption had been developed. Rather than rely upon a single law and a single institution, existing institutions were strengthened and new institutions were instituted to create a set of mutually supporting and mutually checking institutions, agencies and laws that jointly sought to improve governmental standards and combat corruption. Some of the reforms were either unique to Queensland or very rare. One of the strengths of this approach was that it avoided creating a single overarching institution to fight corruption. There are many powerful opponents of reform. Influential institutions and individuals resist any interference with their privileges. In order to cause a mass exodus from an entrenched corruption system, a seminal event or defining process is needed to alter expectations and incentives that are sufficient to encourage significant numbers of individuals to desert the corruption system and assist the integrity system in exposing and destroying it. The Fitzgerald Inquiry was such an event. The article also briefly addresses methods for destroying national corruption system where they emerge and exist.

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The fluid flow and heat transfer inside a triangular enclosure due to instantaneous heating on the inclined walls are investigated using an improved scaling analysis and direct numerical simulations. The development of the unsteady natural convection boundary layer under the inclined walls may be classified into three distinct stages including a start-up stage, a transitional stage and a steady state stage, which can be clearly identified in the analytical and numerical results. A new triple-layer integral approach of scaling analysis has been considered to obtain major scaling relations of the velocity, thicknesses, Nusselt number and the flow development time of the natural convection boundary layer and verified by direct numerical simulations over a wide range of flow parameters.

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A scaling analysis is performed for the transient boundary layer established adjacent to an inclined flat plate following a ramp cooling boundary condition. The imposed wall temperature decreases linearly up to a specific value over a specific time. It is revealed that if the ramp time is sufficiently large then the boundary layer reaches quasi-steady mode before the growth of the temperature is finished. However, if the ramp time is shorter then the steady state of the boundary layer may be reached after the growth of the temperature is completed. In this case, the ultimate steady state is the same as if the start up had been instantaneous. Note that the cold boundary layer adjacent to the plate is potentially unstable to Rayleigh-Bénard instability if the Rayleigh number exceeds a certain critical value for this cooling case. The onset of instability may set in at different stages of the boundary layer development. A proper identification of the time when the instability may set in is discussed. A numerical verification of the time for the onset of instability is presented in this study. Different flow regimes based on the stability of the boundary layer have also been discussed with numerical results.

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The natural convection thermal boundary layer adjacent to an inclined flat plate subject to sudden heating and a temperature boundary condition which follows a ramp function up until a specified time and then remains constant is investigated. The development of the flow from start-up to a steady-state has been described based on scaling analyses and verified by numerical simulations. Different flow regimes based on the Rayleigh number are discussed with numerical results for both boundary conditions. For ramp heating, the boundary layer flow depends on the comparison of the time at which the ramp heating is completed and the time at which the boundary layer completes its growth. If the ramp time is long compared with the steady state time, the layer reaches a quasi steady mode in which the growth of the layer is governed solely by the thermal balance between convection and conduction. On the other hand, if the ramp is completed before the layer becomes steady; the subsequent growth is governed by the balance between buoyancy and inertia, as for the case of instantaneous heating.

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The natural convection boundary layer adjacent to an inclined plate subject to sudden cooling boundary condition has been studied. It is found that the cold boundary layer adjacent to the plate is potentially unstable to Rayleigh-Bénard instability if the Rayleigh number exceeds a certain critical value. A scaling relation for the onset of instability of the boundary layer is achieved. The scaling relations have been developed by equating important terms of the governing equations based on the development of the boundary layer with time. The flow adjacent to the plate can be classified broadly into a conductive, a stable convective or an unstable convective regime determined by the Rayleigh number. Proper scales have been established to quantify the flow properties in each of these flow regimes. An appropriate identification of the time when the instability may set in is discussed. A numerical verification of the time for the onset of instability is also presented in this study. Different flow regimes based on the stability of the boundary layer have been discussed with numerical results.

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In this study, a discussion of the fluid dynamics in the attic space is reported, focusing on its transient response to sudden and linear changes of temperature along the two inclined walls. The transient behaviour of an attic space is relevant to our daily life. The instantaneous and non-instantaneous (ramp) heating boundary condition is applied on the sloping walls of the attic space. A theoretical understanding of the transient behaviour of the flow in the enclosure is performed through scaling analysis. A proper identification of the timescales, the velocity and the thickness relevant to the flow that develops inside the cavity makes it possible to predict theoretically the basic flow features that will survive once the thermal flow in the enclosure reaches a steady state. A time scale for the heating-up of the whole cavity together with the heat transfer scales through the inclined walls has also been obtained through scaling analysis. All scales are verified by the numerical simulations.

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A fundamental study of the fluid dynamics inside an attic shaped triangular enclosure with cold upper walls and adiabatic horizontal bottom wall is reported in this study. The transient behaviour of the attic fluid which is relevant to our daily life is examined based on a scaling analysis. The transient phenomenon begins with the instantaneous cooling and the cooling with linear decreases of temperature up to some specific time (ramp time) and then maintain constant of the upper sloped walls. It is shown that both inclined walls develop a thermal boundary layer whose thicknesses increase towards steady-state or quasi-steady values. A proper identification of the timescales, the velocity and the thickness relevant to the flow that develops inside the cavity makes it possible to predict theoretically the basic flow features that will survive once the thermal flow in the enclosure reaches a steady state. A time scale for the cooling-down of the whole cavity together with the heat transfer scales through the inclined walls has also been obtained through scaling analysis. All scales are verified by the numerical simulations.

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The heat transfer through the attics of buildings under realistic thermal forcing has been considered in this study. A periodic temperature boundary condition is applied on the sloping walls of the attic to show the basic flow features in the attic space over diurnal cycles. The numerical results reveal that, during the daytime heating stage, the flow in the attic space is stratified; whereas at the night-time cooling stage, the flow becomes unstable. A symmetrical solution is seen for relatively low Rayleigh numbers. However, as the Ra gradually increases, a transition occurs at a critical value of Ra. Above this critical value, an asymmetrical solution exhibiting a pitchfork bifurcation arises at the night-time. It is also found that the calculated heat transfer rate at the night-time cooling stage is much higher than that during the daytime heating stage.