China
Africa
Explore chapters and articles related to this topic
The Cable and the Membrane
Published in Bjørn N. Sandaker, Arne P. Eggen, Mark R. Cruvellier, The Structural Basis of Architecture, 2019
Bjørn N. Sandaker, Arne P. Eggen, Mark R. Cruvellier
Alas, a spider’s web is not a stiff structure, but instead moves in the smallest of winds. To see how we might accomplish something like a natural web in the context of real building structures where major deflections are not permitted, we begin by briefly going back to a single suspended cable held up at both ends, but one which is now connected to a second cable oriented at 90° to the first. (Fig. 11.9.) Pulling downward at both ends of the transverse cable puts the suspended cable into the shape of a V; moreover, the tensioning of the downward cable will ensure that the system of two cables will be stabilized, one locked into the other. The same can be done with a series of suspended cables spanning in one direction. If we connect these to a second set of perpendicular cables having opposite downward curvature, the first set will form into a concave shape while the second set of cables will form into a convex shape (Fig. 11.10.) As with the single cable pair, these two cable sets will mutually provide each other with stiffness and stability. In order to do so, however, the cables need to be pre-stressed (i.e., slack, loose cables will do nothing for this system) and the system must have double curvature of the anticlastic type just described. In other words, the curvatures in the two main directions must be opposite to each other (the seat of a saddle is perhaps the most familiar analogous form that comes to mind to help visualize this shape).7 For reasons that are self-evident from the pattern of the grid of interconnected tensioned cables thus established, we call such a system a cable net structure.
Bioremediation of artificially contaminated soil with petroleum using animal waste: cow and poultry dung
Published in Cogent Engineering, 2020
O. Olawale, K. S. Obayomi, S. O. Dahunsi, O. Folarin
The dimensional plots for the cow dung and poultry dung interaction are depicted in Figures 2–4. Figure 1 shows the effect of cow dung and poultry dung on the percentage removal of petroleum in the soil. The interaction as seen in the plots is minimal with F-value of 0.23. The poultry dung interaction is more as compared to the cow dung in terms of singular interaction. Figure 2 shows that the bioremediation effect is relatively flat as seen in the 3D contour plots; the 3D plot shows it actually as a saddle or minimal nature. The saddle is a surface that curves up in one direction, and curves down in a different direction, resembling a riding saddle or a mountain pass between two peaks forming a landform saddle. This implies that the biodegradation is stable for most part of the values uses in the plot. As the cow dung composition increases, higher removal percentage was observed. The exit of the saddle is observed at the upper quadrant of the 3D contour plot at values of cow dung higher than 3.75 and cow dung/poultry dung ratio higher than 2.5. Hence, for effective bioremediation of petrol, the cow dung and cow dung/poultry dung ratio should be maintained with the ranges that allow for optimal removal of petrol. Figure 3 shows a similar saddle nature as Figure 2. However, the contour lines are more pronounced indicating the fact that with the poultry dung, the removal of petrol has a higher level of sensitivity to the low and extreme values of poultry dung and at all levels of the cow dung/poultry dung ratio.
Active textile: woven-cloth-like mechanisms consist of thin McKibben actuators
Published in Advanced Robotics, 2023
Tatsuhiro Hiramitsu, Koichi Suzumori, Hiroyuki Nabae, Gen Endo
The characteristic shape types of active textile confirmed here are classified into four types: flat type, warp-curve type, saddle type, and weft-curve type. Only the contraction in the warp and weft directions occurs, and the shape is flat. The gap between the strings become very small, and the state becomes tighter than in the initial state. It occurs in plain weave cloths with no bias on the front and back.By bending on an axis parallel to the weft, the front surface is convex and curved. Bending due to contraction of artificial muscles is dominant, and bending due to expansion is rarely seen. It occurs in woven cloths that use wefts made of hard materials. The greater the bias between the front and back, the greater the bend.By bending with a shaft parallel to the warp, it has a curved shape with a convex back. Bending due to expansion of artificial muscles is dominant. It occurs in woven cloths that use flexible wefts. It occurs in a twill weave with many intersections. It seems that the bending is less to occur in a satin weave with many float points.It has a saddle shape with irregularities and bends with different axes superimposed on each other. This is a basic deformation form of active textile, which includes bending in both the warp and weft directions. The bending hardness of the weft determines which bending is dominant, and if a hard material is used, it approaches a warp-curve shape, and if a flexible material is used, it approaches a weft-curve shape. In addition, since a large deformation was confirmed on the cloth with a small bias on the front and back, it is considered that there is an optimum condition depending on the degree of interlacing of the threads.