Generalized Ridges and Ravines on an Equiform Motion

In this paper we investigate a new type of ridges and ravines of the configuration space corresponding to an equiform motion in the Euclidean space R3. Necessary and sufficient conditions for the existence of generalized ridges and ravines are expressed as a partial differential inequalities involving the principal curvatures. For special case we obtain the solution of the differential equations which characterize some type of singularities. The singularities are displayed through figures [1, 2, 3].Key words Equiform motion; Configuration space; Generalized ridges and ravine

Local Study of Singularities on an Equiform Motion

In this paper we investigate the local singularities of the configuration space corresponding to an equiform motion in the Euclidean space $R^3$. The chaotic behavior of singularities are displayed through figures

Scaling Law for Criticality Conditions in Heterogeneous Energetic Materials under Shock Loading

Initiation in heterogeneous energetic material (HEM) subjected to shock loading occurs due to the formation of hot spots. The criticality of the hot spots governs the initiation and sensitivity of HEMs. In porous energetic materials, collapse of pores under impact leads to the formation of hot spots. Depending on the size and strength of the hot spots chemical reaction can initiate. The criticality of the hot spots is dependent on the imposed shock load, void morphology and the type of energetic material. This work evaluates the relative importance of material constitutive and reactive properties on the criticality condition of spots. Using a scaling-based approach, the criticality criterion for cylindrical voids as a function of shock pressure, Ps and void diameter, Dvoid is obtained for two different energetic material HMX and TATB. It is shown that the criticality of different energetic materials is significantly dependent on their reactive properties

Geometry of Evolving Plane Curves Problem via Lie Group Analysis

The purpose of the present work is to construct new geometrical models for motion of plane curves. We have obtained nonlinear partial differential equations and have discussed the solutions of these equations using symmetry groups methods. Also, geometric interpretation for these solutions are given through the Gaussian and mean curvatures to the soliton surfaces attached to the solution of the evolving problem. Key Words: Motion of curve; Symmetry groups; Monge for

Robotic hands with intrinsic tactile sensing via 3D printed soft pressure sensors

Herein, the development of complex 3D intelligent structures such as robotic hands using innovative designs and multimaterial additive manufacturing technology is presented. The distal phalanges of the 3D printed hand presented herein have inherent soft capacitive touch or pressure sensors and embedded electronics. Materials such as thermoplastic polyurethane (TPU), silver paint, conductive polylactic acid composite, graphite ink, etc. are explored to develop five different variants of the sensors using a modified 3D printer, which is capable of extruding conductive ink, metal paste, and polymers. The best‐performing 3D printed soft capacitive touch sensors, formed with silver paint and soft rubber (Ecoflex 00‐30), are integrated on the distal phalanges of the 3D printed robotic hand. These sensors exhibit a stable response with sensitivity of 0.00348 kPa−1 for pressure [less than] 10 kPa and 0.00134 kPa−1 for higher pressure. To demonstrate the practical applicability, the 3D printed hand with embedded soft capacitive touch sensors is used for interacting with everyday objects. The tightly integrated sensing elements within the 3D printed structures, as presented herein, can pave the way for a new generation of truly smart material systems that can possibly change their appearance and shape autonomously

Frustration propagation in tubular foldable mechanisms

Shell mechanisms are patterned surface-like structures with compliant deformation modes that allow them to change shape drastically. Examples include many origami and kirigami tessellations as well as other periodic truss mechanisms. The deployment paths of a shell mechanism are greatly constrained by the inextensibility of the constitutive material locally and by the compatibility requirements of surface geometry globally. With notable exceptions (e.g., Miura-ori), the deployment of a shell mechanism often couples in-plane stretching and out-of-plane bending. Here, we investigate the repercussions of this kinematic coupling in the presence of geometric confinement, specifically in tubular states. We demonstrate that the confinement in the hoop direction leads to a frustration that propagates axially, as if by buckling. We fully characterize this phenomenon in terms of amplitude, wavelength, and mode shape in the asymptotic regime, where the size of the unit cell of the mechanism r is small compared to the typical radius of curvature ρ. In particular, we conclude that the amplitude and wavelength of the frustration are of order r/ρ and that the mode shape is an elastica solution. Derivations are carried out for a particular pyramidal truss mechanism. The findings are supported by numerical solutions of the exact kinematics

Egyptian Propolis Alleviates Gentamicin-Induced Nephrotoxicity in Rats

The objective of this study was to evaluate the effectiveness of oral administration of ethanol extract of propolis against gentamicin induced nephrotoxicity in rats. Oral administration of ethanol extract of propolis (EEP) at doses 25, 50 and 100 mg/kg.b.wt. orally/daily for 7 days) against gentamicin- (GM) at dose 100 mg/kg b.wt., i.p./daily for 7days) induced nephrotoxicity in six equal groups of adult male Sprague-Dawley rats. Blood was collected 24 h after the last injection for determination of serum creatinine, urea, and aspartate aminotransferase (AST) activity. Rats were euthanized and kidney tissue specimens were collected for determination of oxidative/antioxidative biomarkers, gene expression for antioxidative enzymes and DNA fragmentation. Significant increase in serum creatinine, urea and AST activity at the same time, and a depletion of aspartate aminotransferase activity was recorded in renal homogenate of GM only–treated rats compared to control group. Lipid peroxidation in renal tissue showed significant elevation in GM-only treated group, however, superoxide dismutase, glutathione peroxidase and catalase and its gene expression were markedly decreased. DNA fragmentation was significantly increased in renal tissue of GM- only treated rats. Oral administration of EEP exhibited curative effects by reversing GM-induced alterations in serum biochemical and renal tissue oxidative stress biomarkers. In conclusion, propolis is effective in preventing or ameliorating oxidative stress of gentamicin