A real pendulum with friction will oscillate for a while after a short push, but will eventually come to rest close to a location where is potential energy has a minimum. If the system is closed, i.e. without a source of energy, it will eventually stop moving at a location near a minimum of the potential, no matter what type of friction force acts on the pendulum. This ‘variation principle’ is ...

The valves of oysters act as a physical barrier between tissues and the external environment, thereby protecting the oyster from environmental stress and predation. To better understand differences in shell properties and predation susceptibilities of two physiologically and morphologically similar oysters, Crassostrea virginica and Crassostrea ariakensis, we quantified and compared two mechani...

In this paper, the dynamic responses of cracked beams under different moving forces, including moving load, moving mass, moving oscillator, and four-degrees-of-freedom moving system, are investigated. Structural elements such as beams are designed to withstand the predicted loads, but unfortunately, they are always exposed to unpredictable damage such as cracks. Several factors may cause these ...

Concrete is a material whose performance is governed by the subtle interaction of its cohesive and frictional constituents. Since the theories of plasticity, damage mechanics, and fracture mechanics cannot, by themselves, capture both of these phenomena, a novel constitutive model is proposed which combines the theories of plasticity and damage mechanics in a multi-surface formulation. Synthesi...

existence of cracks in industrial structures is one of the important causes of their failure, especially when they are subjected to important axial compressive forces that might lead to buckling. therefore, it must be considered in stress analysis and designing and loading of such structures. in this paper, the buckling and post-buckling behaviors of stainless-steel cracked plates under axial c...

We estimated the patellofemoral joint forces generated during pedaling on a bicycle ergometer. Our calculations were based on measurements from a force transducer mounted on the pedal, 16-mm cine-film sequences, and biomechanical models of the cycling motion and of the patellofemoral joint. Six healthy male subjects cycled at different work loads, pedaling rates, saddle heights, and pedal foot ...

The notion of assumption plays an important role in the literature on critical thinking. However, the critical imperative of revealing one’s assumptions forces one either to follow some predefined scheme in which they are defined—in which case it restricts thinking and runs counter to the critical ideal—or to recognise that one cannot know those assumptions— in which case it is impossible. In t...

Sandwich structure composites produced by epoxy core and aluminium skin were developed as potential building materials. Interface bonding between core and skin was controlled by varying kenaf content. Five different weight percentage of kenaf loading ranging from 10 wt% to 50 wt% were employed in the core manufacturing in order to study the mechanical properties of the sandwich composite. Prope...

Strict, often conflicting requirements are imposed on modern engineering structures. On the one hand, they must be light, and other their load-bearing capacity high. The exhaustion of bearing occurs due to loss stability structural elements: shells, plates rods. There no reliable formulas for determining critical loads and, moreover, shells. purpose this paper is find such formulas. A new appro...