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The purpose of this paper is to propose a method for simulating the profile of part edges as a result of the FDM process. Deviations from nominal edge shape are predicted as a function of the layer thickness and three characteristic angles depending on part geometry and build orientation.

Typical patterns of edge profiles were observed on sample FDM parts and interpreted as the effects of possible toolpath generation strategies. An algorithm was developed to generate edge profiles consistent with the patterns expected for any combination of input variables.

Experimental tests confirmed that the simulation procedure can correctly predict basic geometric properties of edge profiles such as frequency, amplitude and shape of periodic asperities.

The algorithm takes into account only a subset of the error causes recognized in previous studies. Additional causes could be integrated in the simulation to improve the estimation of geometric errors.

Edge simulation may help avoid process choices that result in aesthetic and functional defects on FDM parts.

Compared to the statistical estimation of geometric errors, graphical simulation allows a more detailed characterization of edge quality and a better diagnosis of error causes.

This study seeks to explore the aerodynamic performance of wings with different shapes at low Reynolds numbers.

The airfoils of these wings are made from aluminum plates, and the maximum cord length and wingspan are 15 cm. Wings A to D are plates with 6 percent Gottingen camber but different wing planforms. The forward‐half sections of wings E and F are dragonfly‐like, whereas the rear‐half sections of wings E and F are flat and positively cambered, respectively. The aspect ratios of these wings are close to one, and the ratios of plate thickness to the maximum cord length are 1.3 percent. Experimental results indicate that the wings with Gottingen camber have a superior lift and lift‐to‐drag ratio, whereas the wings with dragonfly‐like airfoils perform well in terms of drag and pitch moment.

The aerodynamic measurements of the wings demonstrate that the wing with the Gottingen camber airfoil, a swept‐back leading edge and a straight trailing edge is suitable for use in micro aerial vehicle (MAV). An MAV is fabricated with this wing and the aerodynamic performance of the MAV is examined and compared with the bare wing data.

This study develops several criteria to the design of MAV‐sized wings. For example, the thickness ratio of airfoil must be small, usually less than 2 percent. Besides, the airfoil must be cambered adequately. Furthermore, a wing planform with a swept‐back leading edge and a straight trailing edge would be contributive to the successful flights of MAVs.

An extension of the Schwarz‐Christoffel transformation is described to formally map polygons which contain curved boundaries. The curved boundaries are divided into small ‘curved elements’ and each element is approximated by a second degree polynomial (higher degree polynomials can also be used). The iterative algorithm of evaluating the unknown constants of the basic S‐C transformation described in a companion paper is applied to the extended S‐C transformation to compute its unknown constants, including the coefficients of the polynomials. Excellent results are achieved as far as accuracy and convergence are concerned. Examples including a practical application, are provided. The mapping of curved polygons is important because they provide a better model of a physical device.

THE change from the parallel wings of the now obsolescent biplane to the tapered wings of the monoplane, usually fitted with flaps, raised a great number of problems, both aerodynamic and structural. Work on these has been pursued vigorously during the past few years, but the designer is still some considerable distance from having all his questions answered. For instance, further information is required as to the relation between wing thickness and profile drag before it can be decided what is the maximum thickness which can be used, taking both aero‐dynamical and structural considerations into account. This question is complicated by the fact that, so far as the tip sections are concerned,. the indications are that the thickness ratio has important effects on the nature of the stall, violent or gentle. So, too, will such factors as centre line camber and position of maximum ordinate affect the nature of the stall in greater or Jess degree. Added to these factors there is, of course, the important one of the taper itself, including—as is now realised—the question as to the way in which the tapering is done, that is, whether by sweeping the trailing edge forward or the leading edge back, or, as is more usual, a combination of the two.

This study aims to design and test some fixed‐wing micro aerial vehicles (MAV).

The MAV wing planform in this study was designed based on previous results and the need to reduce the weight of the MAV. The MAV had a wing planform with a 6 percent Gottingen‐329 camber airfoil, a 20° swept‐back leading edge and a straight trailing edge. The fuselage was designed to contain a motor, an electronic control system and a video camera with a built‐in transmitter. The battery was located outside the fuselage to trim the center of gravity and enable the battery to be changed easily when it has run out. Two exaggerated vertical stabilizers were installed to prevent the MAV from rolling. The materials, the power plant and the electronics used to fabricate the MAV herein were either the lightest or the smallest from that could be obtained off‐the‐shelf. Since, MAVs should be expendable, the cost was kept under US$250 (including the cost of an onboard video camera system, which costs US$170).

Flight tests were performed following fabrication. The MAV was launched by hand, flew within a radius of 30 ∼ 50 m, and eventually glided to a grassy ground. The flight was stable and the quality of the downlink video was acceptable for surveillance purpose. The MAVs presented in this work were proven to have successful designs.

MAVs were successfully designed herein based on previous results. The materials and the fabrication processes were carefully selected and tested, to keep the mass of a flyable MAV under 65 g, while ensuring it has sufficient structural strength. The cost was reduced to US$250, making the MAV truly expendable.

A major challenge for mission planning of aircraft is to generate flight paths in highly dynamic environments. This paper presents a new approach for online flight path planning with flight time constraints for fixed-wing UAVs. The flight paths must take into account the kinematic restrictions of the vehicle and be collision-free with terrain, obstacles and no-fly areas. Moreover, the flight paths are subject to time constraints such as predetermined time of arrival at the target or arrival within a specified time interval.

The proposed flight path planning algorithm is an evolution of the well-known RRT* algorithm. It uses three-dimensional Dubins paths to reflect the flight capabilities of the air vehicle. Requirements for the flight time are realized by skillfully concatenating two rapidly exploring random trees rooted in the start and target point, respectively.

The approach allows to consider static obstacles, obstacles which might pop up unexpectedly, as well as moving obstacles. Targets might be static or moving with constantly changing course. Even a change of the target during flight, a change of the target approach direction or a change of the requested time of arrival is included.

The capability of the flight path algorithm is demonstrated by simulation results. Response times of fractions of a second qualify the algorithm for real-time applications in highly dynamic scenarios.

The special course for technicians needs a more thoughtful approach to the practical work. Ways of furthering an experimental attitude towards materials and simple hand processes are described here. The second half of the article, next month, extends these ideas to lathe‐work, with suggestions for progressive exercises and experimental methods

In order to emphasize in-depth analyses of individual life stories, seven informants were selected. Since breadth of experience will contribute to a more detailed contextualization of the consumer's use of products in identity negotiation, diversity across informants was emphasized. Interviews generally followed the format as suggested by Thompson, Locander, and Pollio (1989). A comfortable setting was chosen and pseudonyms were used to ensure anonymity. Interviews were audio-taped and lasted anywhere from one to just over two hours. Grand tour questions (McCracken, 1988) focused on the meaning of the tattoo design, the experience of being tattooed, perceptions of the body, words the informants used to describe themselves, and other biographical information important for understanding the informant's personal myth. Every effort was made to present a natural front, keep the informant on track without being too directive, demonstrate active listening, and prompt the informant as a way of probing for details (Spradley, 1979). To ensure accuracy, an experienced and trained transcriptionist transcribed each of the seven interviews. The final text totaled 450 typed double-spaced pages.

Purpose − The purpose of this paper is to propose a novel and simple strategy for construction of hybrid‐“stress function” plane element. Design/methodology/approach − First, a complementary energy functional, in which the Airy stress function is taken as the functional variable, is established within an element for analysis of plane problems. Second, 15 basic analytical solutions (in global Cartesian coordinates) of the stress function are taken as the trial functions for an 8‐node element, and meanwhile, 15 unknown constants are then introduced. Third, according to the principle of minimum complementary energy, the unknown constants can be expressed in terms of the displacements along element edges, which are interpolated by element nodal displacements. Finally, the whole system can be rewritten in terms of element nodal displacement vector. Findings − A new hybrid element stiffness matrix is obtained. The resulting 8‐node plane element, denoted as analytical trial function (ATF‐Q8), possesses excellent performance in numerical examples. Furthermore, some numerical defects, such as direction dependence and interpolation failure, are not found in present model. Originality/value − This paper presents a new strategy for developing finite element models exhibits advantages of both analytical and discrete method.

A PRECISION Scribing and Lofting Table, which provides an accurate mechanical means whereby layout and lofting processes can be performed to close tolerances in the minimum of time, has been developed by Short Bros. & Harland Ltd.