Defensive wallA defensive wall is a fortification usually used to protect a city, town or other settlement from potential aggressors. The walls can range from simple palisades or earthworks to extensive military fortifications with towers, bastions and gates for access to the city. From ancient to modern times, they were used to enclose settlements. Generally, these are referred to as city walls or town walls, although there were also walls, such as the Great Wall of China, Walls of Benin, Hadrian's Wall, Anastasian Wall, and the Atlantic Wall, which extended far beyond the borders of a city and were used to enclose regions or mark territorial boundaries.
Electric displacement fieldIn physics, the electric displacement field (denoted by D) or electric induction is a vector field that appears in Maxwell's equations. It accounts for the electromagnetic effects of polarization and that of an electric field, combining the two in an auxiliary field. It plays a major role in topics such as the capacitance of a material, as well the response of dielectrics to electric field, and how shapes can change due to electric fields in piezoelectricity or flexoelectricity as well as the creation of voltages and charge transfer due to elastic strains.
Shear forceIn solid mechanics, shearing forces are unaligned forces acting on one part of a body in a specific direction, and another part of the body in the opposite direction. When the forces are collinear (aligned with each other), they are called tension forces and compression forces. William A. Nash defines shear force in terms of planes: "If a plane is passed through a body, a force acting along this plane is called a shear force or shearing force." This section calculates the force required to cut a piece of material with a shearing action.
