China
Africa
Explore chapters and articles related to this topic
Neurons
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
It is seen that there are now three points of intersection. The resting state and the state corresponding to point Q represent stable equilibrium. A small depolarizing perturbation results in an outward current that repolarizes the membrane. Conversely, a small hyperpolarizing perturbation results in an inward current that again repolarizes the membrane. At point P, however, a small depolarizing perturbation results in an inward current that further depolarizes the membrane, taking the operating point to Q. Similarly, a small hyperpolarizing perturbation results in an outward current that further hyperpolarizes the membrane, taking the operating point to that of the resting state. Point P, therefore, represents an unstable operating point. The existence of two distinct states of stable equilibrium is termed bistability.
Liquid crystal displays
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
Bistability results where a device has two stable states with similar free energies that are separated by an energy barrier, wherein transitions from one state to the other are discontinuous, or first order. An early approach was the BTN mode [142], which followed similar principles to that of the STN, but set the d/P ratio of the chiral nematic to lie halfway between states of low and high twist angles Φ. For example, setting d/P = 0.5 with parallel surface alignment should give a π twist state. However, if the pretilt on both surfaces is sufficiently high, the cost of the induced splay energy becomes greater than that for twist. Thus, the chiral nematic may either unwind to a uniform 0π state to match the surface condition or may wind further to form the Φ = 2π twist state (Figure 6.33a). Switching from one state to the other then relies on whether or not flow is induced immediately after a high electrical pulse coupling to a positive Δε. If the pulse returns to 0 V via an intermediate voltage, there is little induced flow and the 0π state is formed, whereas a direct transition to 0 V induces flow that encourages director twist at the cell center and the Φ = 2π state is formed. The two states are metastable, so the texture relaxes back to the intermediate π-state after a second or two on removal of power. This means that the device was not suited to zero power applications. Rather, Seiko Epson used it as the display for Hi-Fi Graphic Equalizer displays due to its very fast optical response [143].
Introduction to Nonvolatile Organic Thin-Film Memory Devices
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
The organic thin-film memory device utilizes electrical bistability of the organic thin film. Electrical bistability means that the device is stable in two electrical states. Figure 22.5 illustrates the current–voltage (I–V) curve of such a device. The original device first exhibits a low conductivity state; therefore, very little current flows through it. It then transits to a state of high conductivity (high current level) when the external electric voltage is higher than the threshold voltage. The devices at the high conductivity state can return to the low conductivity state (low current level) by applying a voltage of negative polarity. The device in these two states could be different in conductivity by several orders in magnitude. When the high and low conductivity states are defined as “1” and “0,” respectively, the device with electrical bistability can be used as a nonvolatile memory device.
Design for energy absorption using snap-through bistable metamaterials
Published in Mechanics Based Design of Structures and Machines, 2023
Andrew Montalbano, Georges M. Fadel, Gang Li
The bistable curved beam is of interest due to two of its properties: bistability and snap-through behavior. Bistability refers to a system that has two separate stable states. Snap-through occurs when a system rapidly translates along its force–displacement curve, in this case, from one stable state to the other. In this paper, we take the bistable curved beam structure discussed in Qiu, Lang, and Slocum (2004) and shown in Figure 1 as the smallest building block (i.e., unit cell) for the metamaterial. The structure features two cosine shaped curved beams connected at their centers. The connection is used to prevent the twisting of the structure during snap-through. This is achieved by forcing the structure to undergo an odd mode of buckling rather than an even mode.