Empirical measurements of small unmanned aerial vehicle co-axial rotor systems

Small unmanned aerial vehicles (SUAV) are beginning to dominate the area of intelligence, surveillance, target acquisition and reconnaissance (ISTAR) in forward operating battlefield scenarios. Of particular interest are vertical take-off and landing (VTOL) variants. Within this category co-axial rotor designs have been adopted due to their inherent advantages of size and power to weight ratio. The inter-rotor spacing attribute of a co-axial rotor system appears to offer insight into the optimum design characteristic. The H/D ratio has been cited as a significant factor in many research papers, but to date has lacked an empirical value or an optimal dimensionless condition. In this paper the H/D ratio of a SUAV has been explored thoroughly, reviewing the performance of these systems at incremental stages, the findings from this study have shown that a range of H/D ratios in the region of (0.41-0.65) is advantageous in the performance of SUAV systems. This finding lends itself to the theory of inter-rotor spacing as a non-dimensionally similar figure, which cannot be applied across a spectrum of systems; this could be attributed to the viscous losses of flight at low Reynolds Numbers (< 50,000

Revisiting revisitation in computer interaction: organic bookmark management.

According to Milic-Frayling et al. (2004), there are two general ways of user browsing i.e. search (finding a website where the user has never visited before) and revisitation (returning to a website where the user has visited in the past). The issue of search is relevant to search engine technology, whilst revisitation concerns web usage and browser history mechanisms. The support for revisitation is normally through a set of functional built-in icons e.g. History, Back, Forward and Bookmarks. Nevertheless, for returning web users, they normally find it is easier and faster to re-launch an online search again, rather than spending time to find a particular web site from their personal bookmark and history records. Tauscher and Greenberg (1997) showed that revisiting web pages forms up to 58% of the recurrence rate of web browsing. Cockburn and McKenzie (2001) also stated that 81% of web pages have been previously visited by the user. According to Obendorf et al. (2007), revisitation can be divided into four classifications based on time: short-term (72.6% revisits within an hour), medium-term (12% revisits within a day and 7.8% revisits within a week), and long-term (7.6% revisits longer than a week)

Blending arts and sciences: gimmick or necessity?

The shortage of degree qualified engineers in the UK is well documented. On the other hand the surplus of art and design graduates is growing. Whilst acknowledging the shortage in engineering graduates, there is also the need to recognise the breadth and increased skill level that engineering graduates require. Is it therefore possible to convert some of the excess graduates in art and design to careers in design and development engineering? The success of many engineering businesses depends not only on technical excellence but also on understanding of the market needs and the speed of response to this demand. To make this task even harder, businesses are also expected to compete in markets that are open to global competition and are also faced with much more sophisticated consumers. Businesses that are engaged in the manufacture of goods now require a new breed of engineer. These are not only technically competent individuals, but also possess what is known as “soft” or “creative” skills traditionally found in graduates of art and design disciplines. This paper details an innovative curriculum model offered at postgraduate level to address the 21 st century needs of engineering businesses. The paper also details rigorous recruitment tools developed and used for selecting students exclusively from the art and design discipline

Including design in e-manufacturing

This paper reviews major issues in the implementation of e-manufacturing, particularly the design aspects. It will examine recent progress, drawing out particular issues that are being addressed. Use will be made of the work by the author and colleagues to devise rule-based design and Internet-based control of machines to illustrate how these developments affect the integrated e-manufacturing environment. A dynamic Simulink model of the way e-manufacture is affected by overall design delays is used to evaluate general solutions for partial and complete e-based companies. These models show how changing to improved designs reduces WI

A low-cost vision-based unmanned aerial system for extremely low-light GPS-denied navigation and thermal imaging

A Low-Cost Vision-Based Unmanned Aerial System for Extremely Low-Light GPS-Denied Navigation and Thermal Imaging}, abstract = {This paper presents the design and implementation details of a complete unmanned aerial system (UAS) based on commercial-off-the-shelf (COTS) components, focusing on safety, security, search and rescue scenarios in GPS-denied environments. In particular, the aerial platform is capable of semi-autonomously navigating through extremely low-light, GPS-denied indoor environments based on onboard sensors only, including a downward-facing optical flow camera. Besides, an additional low-cost payload camera system is developed to stream both infrared video and visible light video to a ground station in real-time, for the purpose of detecting sign of life and hidden humans. The total cost of the complete system is estimated to be $1150, and the effectiveness of the system has been tested and validated in practical scenarios

A review of autonomous docking technologies for an unmanned aircraft carrier

Aerial carrier is becoming a hotspot in Remote Piloted Aircraft System (RPAS) research area recently. As a variant of the general RPAS swarm, this technology is believed to be promising in both military and civilian applications. For example, it could enhance the safety of a military surveillance mission, it could enlarge the surveillance region coverage and it could extend the communication range of any single RPAS. One essential problem for the realisation of the aerial carrier is the autonomous docking in the air. This paper presents a review of autonomous docking techniques ranging from active LED recognition to passive laser scanning and three-dimensional (3D) remodelling. It is aimed at providing a broad perspective on the statues of the recognition and position estimation problems

The effect of copper ions on methane oxidation by the obligate methylotroph 'Methylococcus capsulatus' (Bath)

The work presented in this thesis provided the first report of membrane- bound methane monooxygenase (MMO) activity in the obligate methylotroph Methylococcus capsulatus (Bath). Experiments in batch and continuous culture showed that the intracellular location of the MMO enzyme was regulated by the copper:biomass ratio. Membrane-bound (particulate) MMO activity was associated with a high copper:biomass ratio, whereas, at low copper:biomass ratios the soluble form of the enzyme predominates. Growth of the organism on methanol showed that the expression of the particulate form of the enzyme was constitutive and that expression of the enzyme increased with increasing concentrations of copper in the growth medium. Thin-section electron microscopy of M. capsulatus (Bath) grown on methane and methanol showed that the cell exhibited changes in intracellular morphology which could be correlated with the presence or absence of particulate MMO activity, although a direct connection between particulate MMO activity and intracytoplasmic membranes was not demonstrated. The change in intracellular location of the MMO was accompanied by changes in the protein banding pattern on SDS- polyacrylamide gels. Particulate MMO activity was characterized by an increase in at least 3 major proteins in the membrane fractions of cell extracts. Addition of copper ions to chemostat cultures of Methylococcus capsulatus expressing wholly soluble MMO activity led to a rapid "switch-off" of soluble MMO activity and an equally rapid increase in particulate MMO activity. Studies on in vitro MMO activity demonstrated that particulate MMO activity was stimulated by the addition of copper ions to the assay system; however, addition of copper ions to fractions expressing soluble MMO activity led to a rapid inhibition of this form of the enzyme by irreversible inactivation of the NADH acceptor:reductase activity of the protein complex. The stimulation of particulate MMO activity by copper ions was found to be pH dependent due to the binding of the copper ions to the sodium/potassium phosphate buffer used in the assay system. The particulate MMO was compared with the soluble enzyme from M. capsulatus (Bath) and was shown to differ in several respects including: inhibitor sensitivity, substrate specificity and activity in the presence of various metal ions. Studies using radiolabelled acetylene demonstrated that this compound appeared to act as a suicide-substrate for both forms of the enzyme by irreversibly binding to the active site of the proteins, a method for the partial purification of the particulate enzyme was developed which provided some stabilization of the protein. Studies on copper uptake by the organism demonstrated that this process was energy-dependent and occurred very rapidly when copper was added to copper-limited cultures of the organism

Chinese users’ preference for web browser icons

This paper compares the perspicacity, appropriateness and preference of web browser icons from leading software providers with those of a culture-specific design. The history and future direction of web browsers is outlined, together with the implications for the future growth of Chinese internet users. China, with its rapidly expanding young netizens has now overtaken the USA in terms of the number of internet users (253 million) and we predict it will reach saturation (?70% internet penetration rate) by 2012. If correct, this will have a dramatic effect on the use of English as the ‘Lingua Franca’ of the Internet. This online study was conducted in Taiwan and involved 103 participants (mean age 21 years), who were given three sets of web browser icons to review, namely Microsoft Internet Explorer 7.0, Macintosh Safari 3.0, and culturally specific icons created using the Culture-Centred Design methodology. The findings of the study show that all three sets have generally high recognition rates, but that some icon functions (e.g. Go/Visit and Favourite) in all three sets have poor recognition rates and are considered inappropriate. Furthermore, some significant differences were found when we analysed the level of user experience amongst several icon

Density Matrix Renormalization Group in the Heisenberg Picture

In some cases the state of a quantum system with a large number of subsystems can be approximated efficiently by the density matrix renormalization group, which makes use of redundancies in the description of the state. Here we show that the achievable efficiency can be much better when performing density matrix renormalization group calculations in the Heisenberg picture, as only the observable of interest but not the entire state is considered. In some non-trivial cases, this approach can even be exact for finite bond dimensions.Comment: version to appear in PRL, acronyms in title and abstract expanded, new improved numerical example