Morphing Concept for Multirotor UAVs Enabling Stability Augmentation and Multiple-Parcel Delivery

This paper presents a novel morphing concept for multirotor Unmanned Aerial Vehicles (UAVs) to optimize the vehicle ight performance during multi-parcel deliveries. Abrupt changes in the vehicle weight distribution during a parcel delivery can cause the UAVs to be unbalanced. This is usually compensated by the vehicle ight control system but the motors may need to operate outside their design range which can deteriorate the stability and performance of the system. Morphing the geometry of a conventional multirotor airframe enables the vehicle to continuously re-balanced itself which improves the overall vehicle performance and safety. The paper derives expressions for the static stability of multirotor UAVs and discusses the experimental implementation of the morphing technology on a Y6 tricopter configuration. Flight test results of multi-parcel delivery scenarios demonstrate the capability of the proposed technology to balance the throttle outputs of all rotors

Computer literacy and attitudes towards e-learning among first year medical students

BACKGROUND: At the Medical University of Vienna, most information for students is available only online. In 2005, an e-learning project was initiated and there are plans to introduce a learning management system. In this study, we estimate the level of students' computer skills, the number of students having difficulty with e-learning, and the number of students opposed to e-learning. METHODS: The study was conducted in an introductory course on computer-based and web-based training (CBT/WBT). Students were asked to fill out a questionnaire online that covered a wide range of relevant attitudes and experiences. RESULTS: While the great majority of students possess sufficient computer skills and acknowledge the advantages of interactive and multimedia-enhanced learning material, a small percentage lacks basic computer skills and/or is very skeptical about e-learning. There is also a consistently significant albeit weak gender difference in available computer infrastructure and Internet access. As for student attitudes toward e-learning, we found that age, computer use, and previous exposure to computers are more important than gender. A sizable number of students, 12% of the total, make little or no use of existing e-learning offerings. CONCLUSION: Many students would benefit from a basic introduction to computers and to the relevant computer-based resources of the university. Given to the wide range of computer skills among students, a single computer course for all students would not be useful nor would it be accepted. Special measures should be taken to prevent students who lack computer skills from being disadvantaged or from developing computer-hostile attitudes

Informational Efficiency in Futures Markets for Crude Oil

This paper develops a methodology to test whether recent developments on world oil markets are in line with the hypothesis of efficient markets. We treat the joint hypothesis problem as stated by Fama (1970), Fama (1991), that market efficiency can only be assessed in conjunction with a price model of market equilibrium. Data on spot and futures prices for Brent crude oil in the period 2002-2008 are used in combination with a multi factor model to investigate whether futures prices are efficient forecasts of future spot prices. The hypothesis of market efficiency is assessed by comparing the observed developments of crude oil spot prices to the ex-ante expected distributions of spot prices using the Rosenblatt transform. For the Brent crude oil futures market, the results are in line with the hypothesis of market efficiency in the short-term but during our sample period the hypothesis is refuted when forecast horizons of one year are considered. Our findings suggest that it can lead to rather wrong investment decisions when relying on longer-term crude oil futures prices and the information contained therein

High-Spatial Resolution Observations Of A Small

. The Big Bear Solar Observatory (BBSO) has a long tradition of flare observations. In this letter, we would like to direct the reader's attention to observations of a small ffi-spot which produced a moderate flare activity characterized by 18 C-class and 2 M-class flares. Active region NOAA 8076 (BBSO 3877) was one of the first active regions in the new Solar Cycle No. 23. We present high spatial resolution white-light observations obtained on August 31st, 1997 with the speckle masking technique (Weigelt 1977; Weigelt & Wirnitzer1983; Lohmann et al. 1983). Almost diffraction limited speckle reconstructions revealed the complex and highly dynamical behavior of a small emerging ffi-configuration in the central part of NOAA 8076. We found strong shear flows and indications of strong transverse fields in the small ffi-spot. The flare-producing mechanism for this small activity complex was very similar to that of the outstanding flare-producing region NOAA 5395 of March 1989 (Wang et al. 1..

An adaptive mesh method for phase-field simulation of alloy solidification in three dimensions

We present our computational method for binary alloy solidification which takes advantage of high performance computing where up to 1024 cores are employed. Much of the simulation at a sufficiently fine resolution is possible on a modern 12 core PC and the 1024 core simulation is only necessary for very mature dendrite and convergence testing where high resolution puts extreme demands on memory. In outline, the method uses implicit time stepping in conjunction with an iterative solver, adaptive meshing and a scheme for dividing the work load across processors. We include three dimensional results for a Lewis number of 100 and a snapshot for a mature dendrite for a Lewis number of 40

Perennial, biennial and annual plants, iris, cut garden flowers in season : spring 1929 [catalog] /

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