In wireless communications, fading is variation of the attenuation of a signal with various variables. These variables include time, geographical position, and radio frequency. Fading is often modeled as a random process. A fading channel is a communication channel that experiences fading. In wireless systems, fading may either be due to multipath propagation, referred to as multipath-induced fading, weather, or shadowing from obstacles affecting the wave propagation, sometimes referred to as shadow fading.
Perturbation theory comprises mathematical methods for finding an approximate solution to a problem, by starting from the exact solution of a related, simpler problem. A critical feature of the technique is a middle step that breaks the problem into "solvable" and "perturbation" parts. Perturbation theory is applicable if the problem at hand cannot be solved exactly, but can be formulated by adding a "small" term to the mathematical description of the exactly solvable problem.
Diurnal ("daily") may refer to:
A Klemperer rosette is a gravitational system of heavier and lighter bodies orbiting in a regular repeating pattern around a common barycenter. It was first described by W. B. Klemperer in 1962.
Rate of fire is the frequency at which a specific weapon can fire or launch its projectiles. It is usually measured in rounds per minute, or rounds per second.
The cyclic alternating pattern is a pattern of two, long-lasting alternate electroencephalogram (EEG) patterns that occur in sleep, as described by Terzano, et al, in 1985. It is a pattern of spontaneous cortical activity, which is ongoing and in the absence of sensory stimulation. It is the reorganization of the sleeping brain challenged by the modification of environmental conditions and it is characterized by periodic abnormal electrocortical activity that recurs with a frequency of up to one minute. It is considered "the EEG marker of unstable sleep". CAP does not occur during REM. In Lennox-Gastaut syndrome, CAP modulates the occurrence of clinical seizures and generalized epileptic discharges by means of a gate-control mechanism.
In physical cosmology, structure formation is the formation of galaxies, galaxy clusters and larger structures from small early density fluctuations. The universe, as is now known from observations of the cosmic microwave background radiation, began in a hot, dense, nearly uniform state approximately 13.8 billion years ago. However, looking in the sky today, we see structures on all scales, from stars and planets to galaxies and, on still larger scales, galaxy clusters and sheet-like structures of galaxies separated by enormous voids containing few galaxies. Structure formation attempts to model how these structures formed by gravitational instability of small early density ripples.
The cyclical theory refers to a model used by historians Arthur M. Schlesinger Sr. and Arthur M. Schlesinger Jr. to explain the fluctuations in politics throughout American history. In this theory, the national mood alternates between liberalism and conservatism. Each phase has characteristic features, and each phase is self-limiting, generating the other phase. This alternation has repeated itself several times over the history of the United States.
In the aerodynamics of rotorcraft such as helicopters, phase lag refers to the angular difference between the point at which a control input to a rotor blade occurs and the point of maximum displacement of the blade in response to that control input, said displacement occurring in the direction of rotor rotation. Phase lag differs from advance angle in that the latter refers to the mechanically fixed angle between the pitch link attachments at the blade and swashplate. Phase lag can vary as a function on rotor tilt rate and aerodynamic damping and results in cross-coupling between the aircraft control axes; advance angle is fixed and cannot vary.
The pacemaker current is an electric current in the heart that flows through the HCN channel or pacemaker channel. Such channels are important parts of the electrical conduction system of the heart and form a component of the natural pacemaker.
The center of gravity (CG) of an aircraft is the point over which the aircraft would balance. Its position is calculated after supporting the aircraft on at least two sets of weighing scales or load cells and noting the weight shown on each set of scales or load cells. The center of gravity affects the stability of the aircraft. To ensure the aircraft is safe to fly, the center of gravity must fall within specified limits established by the aircraft manufacturer.
Phased array optics also known as the optical phased array (OPA) is the technology of controlling the phase and amplitude of light waves transmitting, reflecting, or captured (received) by a two-dimensional surface using adjustable surface elements. It is the optical analog of phased array radar. By dynamically controlling the optical properties of a surface on a microscopic scale, it is possible to steer the direction of light beams, or the view direction of sensors, without any moving parts. Hardware associated with beam steering applications is commonly called an optical phased array (OPA). Phased array beam steering is used for optical switching and multiplexing in optoelectronic devices, and for aiming laser beams on a macroscopic scale.
Lahore Metro is an automated rapid transit system under construction in Lahore, Punjab, Pakistan. Three metro lines have been proposed, of which the Orange Line is under construction. When operational sometime in 2019, it will become Pakistan's first metro line.
cAMP-specific 3',5'-cyclic phosphodiesterase 4A is an enzyme that in humans is encoded by the PDE4A gene.
In ecology, the theory of alternative stable states predicts that ecosystems can exist under multiple "states". These alternative states are non-transitory and therefore considered stable over ecologically-relevant timescales. Ecosystems may transition from one stable state to another, in what is known as a state shift, when perturbed. Due to ecological feedbacks, ecosystems display resistance to state shifts and therefore tend to remain in one state unless perturbations are large enough. Multiple states may persist under equal environmental conditions, a phenomenon known as hysteresis. Alternative stable state theory suggests that discrete states are separated by ecological thresholds, in contrast to ecosystems which change smoothly and continuously along an environmental gradient.
The digits of some specific integers permute or shift cyclically when they are multiplied by a number n. Examples are:
Cavity perturbation theory describes methods for derivation of perturbation formulae for performance changes of a cavity resonator. These performance changes are assumed to be caused by either introduction of a small foreign object into the cavity or a small deformation of its boundary.
Gurugram Rapid Metro is a metro system serving the city of Gurugram, Haryana, India. The system provides interchange with the Delhi Metro's Yellow Line at Sikandarpur Metro Station. Rapid Metro has a total length of 11.7 kilometres serving 11 stations. The system is fully elevated using standard-gauge tracks. Rapid Metro connects the commercial areas of Gurgaon, and acts as a feeder link to the Delhi Metro.
Phase resetting in neurons is a behavior observed in different biological oscillators and plays a role in creating neural synchronization as well as different processes within the body. Phase resetting in neurons is when the dynamical behavior of an oscillation is shifted. This occurs when a stimulus perturbs the phase within an oscillatory cycle and a change in period occurs. The periods of these oscillations can vary depending on the biological system, with examples such as: (1) neural responses can change within a millisecond to quickly relay information; (2) In cardiac and respiratory changes that occur throughout the day, could be within seconds; (3) circadian rhythms may vary throughout a series of days; (4) rhythms such as hibernation may have periods that are measured in years. This activity pattern of neurons is a phenomenon seen in various neural circuits throughout the body and is seen in single neuron models and within clusters of neurons. Many of these models utilize phase response (resetting) curves where the oscillation of a neuron is perturbed and the effect the perturbation has on the phase cycle of a neuron is measured.
