Identification of Sharp Edge Non-Slender Delta Wing Aerodynamic Coefficient Using Neural Network

Delta wing formed a vortical flow on its surface which produced higher lift compared to conventional wing. The vortical flow is complex and non-linear which requires more studies to understand its flow physics. However, conventional flow analysis (wind tunnel test and computational flow dynamic) comes with several significant drawbacks. In recent times, application of neural network as alternative to conventional flow analysis has increased. This study is about utilization of Multi-Layer Perceptron (MLP) neural network to predict the coefficient of pressure (Cp ) on a delta wing model. The physical model that was used is a sharp edge non-slender delta wing. The training data was taken from wind tunnel tests. 70% of data is used as training, 15% is used as validation and another 15% is used as test set. The wind tunnel test was done at angle of attack from 0°-18° with increment of 3°. The flow velocity was set at 25m/s which correspond to 800,000 Reynolds number. The inputs are angle of attack and location of pressure tube (y/cr) while the output is Cp . The MLP models were fitted with 3 different transfer functions (linear, sigmoid, and tanh) and trained with Lavenberg-Marquadt backpropagation algorithm. The results of the models were compared to determine the best performing model. Results show that large amount of data is required to produce accurate prediction model because the model suffer from condition called overfitting.

An homage to Peru’s bicentenary: Maxillaria bicentenaria (Orchidaceae), a new species previously misidentified as M. pyhalae

We propose the new species Maxillaria bicentenaria from the montane forest of central Peru and provide an amendment of the description of Maxillaria pyhalae. Maxillaria bicentenaria is similar to M. pyhalae but differs by the elliptic to sub-elliptic labellum, the labellum distal half irregularly plicate, the flattened and transversally sub-trapezoidal labellar callus, the campanulate to sub-campanulate protuberance at the labellum apex centre, and the conspicuous carina with a sharp edge towards the top of the anther. Illustrations, pictures, and a distribution map are provided for both Maxillaria species. The differential features of both species are presented and previous misidentified records are discussed. Finally, a comment on the author name of Maxillaria fletcheriana is also provided.

Beam characterization of a microfading tester: evaluation of several methods

Microfading testing allows to evaluate the sensitivity to light of a specific artwork. Characterization of the illumination spot is important to determine its shape, dimensions, light distribution, and intensity in order to limit and account for possible damage. In this research the advantages and disadvantages of several methods used to determine the beam shape and intensity profiles are described with the aim of providing various options to microfading researchers interested in characterizing their irradiation spots. Conventional and imaging methods were employed and are compared in terms of their accuracy, cost, reliability, and technical features. Conventional methods consisted of an aperture technique using aluminium foil and four different materials namely stainless steel, silicon, muscovite, and Teflon used as sharp edges. The imaging methods consisted of digital photography of illumination spot, direct beam measurement using a CMOS camera, and direct beam measurement using a laser beam profiler. The results show that both conventional and imaging methods provide beam width measurements, which are in satisfactory agreement within experimental error. The two best methods were direct measurement of the beam using a CMOS camera and sharp-edge procedure. MFT illumination beam with a CMOS camera followed by a determination of the beam diameter using a direct method, more specifically one involving a sharp-edge technique.