Helicopter main-rotor speed effects: A comparison of predicted ranges of detection from the aural detection program ICHIN and the electronic detection program ARCAS

NASA LaRC personnel have conducted a strudy of the predicted acoustic detection ranges associated with reduced helicopter main rotor speeds. This was accomplished by providing identical input information to both the aural detection program ICHIN 6, (I Can Hear It Now, version 6) and the electronic acoustic detection program ARCAS (Assessment of Rotorcraft Detection by Acoustics Sensing). In this study, it was concluded that reducing the main rotor speed of the helicopter by 27 percent reduced both the predicted aural and electronic detection ranges by approximately 50 percent. Additionally, ARCAS was observed to function better with narrowband spectral input than with one-third octave band spectral inputs and the predicted electronic range of acoustic detection is greater than the predicted aural detection range

Helicopter far-field acoustic levels as a function of reduced main-rotor advancing blade-tip Mach number

During the design of a helicopter, the weight, engine, rotor speed, and rotor geometry are given significant attention when considering the specific operations for which the helicopter will be used. However, the noise radiated from the helicopter and its relationship to the design variables is currently not well modeled with only a limited set of full-scale field test data to study. In general, limited field data have shown that reduced main-rotor advancing blade-tip Mach numbers result in reduced far-field noise levels. The status of a recent helicopter noise research project is reviewed. It is designed to provide flight experimental data which may be used to further understand helicopter main-rotor advancing blade-tip Mach number effects on far-field acoustic levels. Preliminary results are presented relative to tests conducted with a Sikorsky S-76A helicopter operating with both the rotor speed and the flight speed as the control variable. The rotor speed was operated within the range of 107 to 90 percent NR at nominal forward speeds of 35, 100, and 155 knots

An experience of modularity through design

We aim to utilise the experiences of a marine industry-based design team to determine the need for research into a modular design methodology in an industrial environment. In order to achieve this we couple the outcome of a current design project with the findings of a recent literature survey with the objectives of firstly, clarifying why a methodology is required and, secondly, defining the key elements which the methodology would have to realise or address. The potential benefits of modularity have long been recognised in the shipbuilding industry. Many shipbuilders adopt a 'module' approach to ship construction whereby the ship structure is separated into a number of large structural 'blocks' to ease manufacture and manoeuvrability during construction. However, as understanding of the capabilities of modularity as a design tool develops there is increased interest in capitalising on the differing life phase benefits of modularity such as reduced design costs and time, increased ease of maintenance, upgrade, re-use, redesign and standardisation across individual products and product families. This is especially pertinent in naval shipbuilding where the maintenance of a class of ship requires that all previously designed ships in that class must be of similar outfitting and must be able to interface with the new ship, in terms of propulsion, weapons, communications and electronics, and thus often require some form of retrofit. Therefore, many shipbuilders are moving from viewing modularity as a purely 'manufacturing' principle to a design centred principle. However, as noted by Chang and Ward 'none of the design theories or tools in the mechanical world serves as an articulate procedure for designers to follow in practising modular design'. Thus, despite the identification of a need to introduce modular principles at an earlier stage than detail design and construction, there is little aid in the form of tools, techniques and methodologies for designers in practice

Alfred Russel Wallace Notes 11: Wallace, Darwin, Education, & the Class Question

In a recent paper by John van Wyhe (2020), the issue of class was discussed and whether Wallace came from a “working class” background. As a result of class differences could or should Wallace be considered differently from Darwin, who supposedly came from a higher class? An additional “myth” highlighted was whether Wallace left school, aged 14, due to difficult family financial circumstances. Van Wyhe contends that Darwin and Wallace were both middle class, and Wallace left school at the “normal” school-leaving age. This article shows that both contentions are mistaken. Class in the 19th century was complex and difficult, indeed a developing concept. The idea of a “middle class” was new and within this there was a stratification between the upper and lower middle classes. As for schools and education, there was no set leaving age specified and education was usually determined by class and family finance

How Industrial Relations Informs the Teaching of Ethics in Human Resource Management

Charles G. Smith, Ph.D., is professor of management, in the Department of Business, Accounting, and Economics, Otterbein College, Westerville, OH 43081. Hugh D. Hindman, Ph.D., is professor of labor & human resources, in the Walker College of Business, Appalachian State University, Boone, NC 28608

IMPACTS OF REDUCED PESTICIDE USE ON THE PROFITABILITY OF THE FRUIT AND VEGETABLE SECTOR

Environmental Economics and Policy,

Discount Points, Effective Yields and Mortgage Prepayments

This study addresses the perceived rankings of real estate publications and their impact in meeting the tenure requirements at AACSB member school. Roughly half of the respondents in the sample studied are AACSB accredited. The results indicate that the rank ordering of publications in the sample are consistent between the accredited and non-accredited schools, although accredited schools demonstrate systematically lower point ratings for each publication and require more points for tenure.