A new connection between the opening angle and the large-scale morphology of extragalactic radio sources

In the case of an initially conical jet, we study the relation between jet collimation by the external pressure and large-scale morphology. We first consider the important length-scales in the problem, and then carry out axisymmetric hydrodynamic simulations that include, for certain parameters, all these length-scales. We find three important scales related to the collimation region: (i) where the sideways ram-pressure equals the external pressure, (ii) where the jet density equals the ambient density, and (iii) where the forward ram-pressure falls below the ambient pressure. These scales are set by the external Mach-number and opening angle of the jet. We demonstrate that the relative magnitudes of these scales determine the collimation, Mach-number, density and morphology of the large scale jet. Based on analysis of the shock structure, we reproduce successfully the morphology of Fanaroff-Riley (FR) class I and II radio sources. Within the framework of the model, an FR I radio source must have a large intrinsic opening angle. Entrainment of ambient gas might also be important. We also show that all FR I sources with radio lobes or similar features must have had an earlier FR II phase.Comment: 14 pages, 10 figures, accepted by MNRAS, same as previous versio

Public Perception Of Coastal Hazards At Waikīkī Beach, Hawaiʻi, With A Focus On The Box Jellyfish Alatina Alata

M.S. Thesis. University of Hawaiʻi at Mānoa 2018

Designing a low-cost electricity-generating cooking stove for high-volume implementation

The PhD describes the social science and technical design of an innovative clean cooking stove that also generates electricity for use in developing countries. Key areas of learning adding to the research pool are: 1. Method for comparing costs of competing designs early in the research process before detailed design has been undertaken. 2. Use of state-of-the-art industrial design processes combined with social science investigations to direct research to meet end-user needs 3. Design of a low-cost, low thermal mass hot heat exchanger for use in thermo-acoustic engines 4. Design of a low-cost, low-mass Linear Alternator suitable for use in thermo-acoustic engines 5. Half-wave thermo-acoustic engine configuration with low-onset temperature suitable for operation with wood or dung as the fuel. 6. Use of an electrical analogue to predict unusual thermo-acoustic behaviour such as squegging and time-based pressure variations. The document is an extended abstract pulling together Riley’s 6 years of research and publications from the Score project, into one coherent theme as required by the University of Nottingham quality manual for staff engaged in research. The document describes the background of thermo-acoustics and how the project has enabled the science to progress from mainly rig-based engines to a manufacturable product. The research management process and techniques used to reduce project risk are highlighted, beginning with social science research into end-user requirements, system design, component design, testing and production cost predictions

On‐line student feedback: A pilot study

This paper reports on the outcomes of two experimental trials of the use of on‐line questionnaires to assess student satisfaction with courses at the London School of Economics and Political Science. In the first year, eighteen course modules were selected from three departments, surveying a total of 1,100 student places. Students on ten of the courses were invited to complete the ‘experimental’ on‐line survey and the remainder were invited to complete the paper‐based questionnaires which have been in use for several years. In the second year, the scale of the experiment was increased, to include forty‐six courses across seven departments. Response rates were compared and possible barriers to completion of the on‐line questionnaire were considered Whilst electronic monitoring indicated that 95 per cent (first trial) and 80 per cent (second trial) of those contacted for the on‐line survey opened the introductory email, only 23 per cent (first trial) and 27 per cent (second trial) completed the on‐line survey, compared with a 60 per cent response rate on the paper‐based survey. The on‐line response is also slightly lower than that achieved by postal surveys of LSE students (30–50 per cent response rates). Whilst some technical difficulties could have acted as a barrier, motivation appeared to be the main barrier. Initial results from the second trial, which included two reminder emails and some small incentives, show that it is possible to increase the response rate, but this may still be unacceptably low for staff whose promotion prospects may be affected by results. A third trial has been proposed, looking at ways in which the process as a whole could be amended, to overcome the problem of ‘survey fatigue’ that the current system faces

The myth of the high-efficiency external-combustion Stirling engine

The reported discrepancy between theory and experiment for external combustion Stirling engines is explained by the addition of thermal resistance of the combustion gasses to the standard Carnot model. In these cases, the Stirling engine ideal efficiency is not as is normally reported equal to the Carnot cycle efficiency but is significantly lower. A new equation for ideal Stirling engine efficiency when the heat is obtained through external combustion without pre-heating the air, is presented and results for various fuels tabulated. The results show that petrol and diesel, internal combustion engines (Otto cycle) have a higher ideal efficiency than the Stirling engine. When comparing thermoacoustic engines heated by wood, efficiency should not be quoted as a percentage of the Carnot efficiency, but against a figure 48% lower than Carnot. The effect is not seen with electrically heated rigs, solar or nuclear fission heated engines

Drainage of Land Overlying an Artesian Aquifer: Logan-Cache Airport

Drainage problem Logan-Cache Airport is situated approximately 4 miles northwest of Logan, Utah, in sections 8, 9, 16, and 17, Township 12 north, Range 1 east, of Salt Lake Base and Meridian. The area of approximately 200 acres is a part of what is known as cache County Drainage District No.2. This district in itself contains more than 8,400 acres of waterlogged lands. Drainage of the se lands has, for many years, been a baffling and unsolved problem, complicated by 3 factors: (a) The whole of the valley in this area is underlain by an artesian ground-water reservoir. (b) The artesian aquifer is overlain by a layer of heavy clay of very lo~ permeability, ranging in depth from 40 to 70 feet. (c) Human relations with farmers within the area , who consider that drainage will deprive them of their plentiful groundwater Supply

Computer Simulation of Water Resource Systems at Utah State University

Introduction: The problems of managing water-resource systems are basically those of decision making based upon a consideration of the physical, economic, and sociological processes involved. These processes are strongly interrelated and constitute a dynamic and continuous system. Any combination of these interrelated and numerous system variables yields a management solution. At Utah State University the problem of investigating system response to various possible management alternatives is being approached by hybrid computer simulation. The concept of simulation is fundamentally simple. Basically, it is a technique of analysis whereby a model is developed for investigating the behavior or performance of a dynamic prototype system subject to particular constraints and input functions. The model behaves like the prototype system with regard to certain selected variables and can be used to predict probable resopnses when some of the system parameters or input functions are altered. The model represents the interrelated processes of the system by arithmetic and algebraic functions, and by non-mathematical logic processes. Simulation is a useful tool for the creative manipulation of highly complex systems and thus can greatly facilitate appraisals of proposed changes within the corresponding prototypes. In a computer model the various functions and operations of the different parts of the system are interrelated by the concepts of continuity of mass and momentum. These concepts are applied over the particular increments of time and space adopted for the model. It should, therefore, be emphasized that the adquacy of a simulation model is dependent upon the theory and the field data upon which the model is based. Consequently, both the mathematical relationships and the physical input data constitute major contraints in a simulation analysis. In addition, simulation alone does not readily provide optimal solutions. However, each computer run for a set of model parameters and inputs yields and estimate of the probable response of the prototype under the particular conditions established. Thus, through numerous and repetitive computer runs, it is possible to investiage many combinations of system variables and thereby to evolve optimal or near-optimal system design and operation procedures