Plant-pollinator Specialization: Origin and measurement of curvature

A feature of biodiversity is the abundance of curves displayed by organs and organisms. Curvature is a widespread, convergent trait that has important ecological and evolutionary implications. In pollination ecology, the curvature of flowers and pollinator mouthparts (e.g. hummingbird bills) along the dorsiventral plane has been associated with specialization, competition, and species co-existence. Six methods have historically been used to measure curvature in pollination systems; we provide a solution to this inconsistency by defining curvature using well-established concepts from differential geometry. Intuitively, curvature is the degree to which a line is not straight, but more formally, it is the rate at which the tangent of a curve changes direction with respect to arc length. Here, we establish a protocol wherein a line is fitted against landmarks placed on an image of a curved organ or organism, then curvature is computed at many points along the fitted line and the sum taken. The protocol is demonstrated by studying the development of nectar spur curvature in the flowering plant genus Epimedium (Berberidaceae). By clarifying the definition of curvature, our aim is to make the language of comparative morphology more precise and broadly applicable to capture other curved structures in nature.

Experimental sound power from curved plates using the radiation resistance matrix and a scanning vibrometer

Vibration-based sound power (VBSP) methods based on elemental radiators and measurements from a scanning vibrometer have been shown to be accurate for flat plates and cylinders. In this paper, the VBSP method is extended to account for simple curved structures, with a constant radius of curvature. Data are also presented that suggest the VBSP method is more accurate than the ISO 3741 standard for measuring sound power when significant background noise is present. Experimental results from ISO 3741 and the VBSP methods are compared for three simple curved plate structures with different radii of curvature. The results show good agreement for all three structures over a wide frequency range. The experimental results also indicate that the VBSP method is more accurate in the low frequency range where the curved plates radiated relatively little and significant background noise was present.

Selection of mixtures for 3D printing

Currently, the construction industry needs to reduce material and technical, energy, labor, and as a result, financial costs, reduce the risk of injury in the production process and improve the quality of finished products through mechanization and automation, increases interest in the possibilities of additive technologies in the construction of structures of buildings and structures. Every year, the volume of work on the construction of objects using 3D technologies is growing quite intensively and this is becoming more and more relevant. The high rate of construction, the lack of decking, the reduction of the possibility of design deviations, thanks to the accuracy of the 3D printer, the widespread use of curved structures, which allows not only to reduce stress, but also to increase the level of stylistic quality, all this creates a demand for additive technologies. This article presents the results of experiments that allow us to continue the development in the field of optimizing the composition of building mixes in experimental construction with the use of 3D printing, since in the Russian Federation, a direction in the field of research of building materials for additive technologies is emerging. This article presents the results of optimizing the composition of building mixes used for additive technologies for the Lipetsk region, since it includes blast furnace slag, which is a by-product of PJSC Novolipetsk Metallurgical Combine. As a result of tests of the concrete mixture, it was found that the density is 1940.3 kg/m3, the setting time: the beginning — 3 hours 20 minutes, the end — 4 hours, the mobility of the cone immersion, 3.40 mm, the strength (28 days): compressed — 30.4 MPa, bending — 4.7 MРа. The data indicate that the resulting mixture has the necessary rheological properties and optimal setting times and can be used for the construction of buildings and structures using 3D printing. Thus, the results of this work will allow us to continue the development in the field of optimizing the composition of building mixes in experimental construction using 3D printing, since in the Russian Federation, a direction in the field of research of building materials for additive technologies is emerging.

Towards airborne laser Doppler vibrometry for structural health monitoring of large and curved structures

Laser Doppler vibrometry is an important sensing technology for many structural health monitoring (SHM) methods, such as modal analysis. However, when it comes to large civil structures, for example historic structures and bridges, the applicability of laser Doppler vibrometry is significantly constrained by inaccessible remote surfaces. Some of these surfaces are fully inaccessible to a ground-mounted laser Doppler vibrometer (LDV), while others are partially inaccessible, and measurements are only possible for low incident angles. Consequently, LDV measurements are either impossible or have a weak signal strength. In this study, the concept of constructing an airborne LDV for SHM is explored, including the examination of a recently developed mechanism, the partially airborne LDV, comprising a reflective mirror attached to a drone. Preliminary proof of concept laboratory tests have been successfully conducted using two different set-ups and drone models.

Solar Radiation on a Parabolic Concave Surface

Curved structures are used in buildings and may be integrated with photovoltaic modules. Self-shading occurs on non-flat (curved) surface collectors resulting in a non-uniform distribution of the direct beam and the diffuse incident solar radiation along the curvature the surface. The present study uses analytical expressions for calculating and analyzing the incident solar radiation on a general parabolic concave surface. Concave surfaces facing north, south and east/west are considered, and numerical values for the annual incident irradiations (in kWh) are demonstrated for two locations: 32° N (Tel Aviv, Israel) and 52.2° N (Lindenberg, Germany). The numerical results show that the difference in the incident global irradiation for the different surface orientations is not very wide. At 32° N, the irradiation difference between the south and north-oriented surface is about 15 percent, and between the south and east surface orientation it is about 9.6 percent. For latitude 52.2° N, the global irradiation difference between the south and north-oriented surface is about 16 percent, and between the south and east orientation it is about 3 percent.