Children: Physics stubs
An exceptional point (EP) is a concept in mathematics and physics, particularly in the field of linear algebra and non-Hermitian systems. It refers to a particular type of degeneracy that occurs in the parameter space of a system where two or more eigenvalues and their corresponding eigenvectors coalesce, meaning they become identical. This phenomenon can lead to unique and often counterintuitive behavior in physical systems, particularly in the contexts of quantum mechanics, optics, and wave systems.
The extinction paradox generally refers to the observation that despite the ongoing loss of species and biodiversity, there can be scenarios where certain aspects of ecosystems or groups of species do not show expected declines in abundance or ecological function. This can lead to a disconnect between the apparent health of ecosystems and the reality of ongoing species losses. One interpretation of the extinction paradox is that some ecological processes may continue to function adequately even as specific species go extinct. For example, ecosystems often have redundancy, where multiple species perform similar roles.
A first-order fluid, also known as a Newtonian fluid, is a type of fluid that adheres to Newton's law of viscosity. This means that the fluid's shear stress is directly proportional to the shear rate (or velocity gradient) at a given temperature and pressure. Mathematically, this relationship is represented as: \[ \tau = \mu \frac{du}{dy} \] Where: - \(\tau\) is the shear stress.
Foot per second squared (ft/s²) is a unit of acceleration in the imperial system. It describes the rate of change of velocity of an object in terms of feet traveled per second for each second of time. In other words, if an object's velocity increases by a certain amount of feet per second over the course of one second, this increase in velocity is quantified in feet per second squared.
Frank–Van der Merwe growth refers to a model of crystal growth, specifically describing the process of how materials grow in a layered fashion, especially in the context of thin films and semiconductor crystals. This growth mode is named after the researchers who contributed to its development, Frank and Van der Merwe. In this model, the growth of the film occurs through a process called "layer-by-layer" growth, or more specifically, "two-dimensional nucleation.
Fuel mass fraction is a term commonly used in aerospace engineering, propulsion, and combustion systems. It refers to the ratio of the mass of the fuel to the total mass of the propellant or fuel mixture being considered. This fraction is significant in the context of rocket propulsion, jet engines, and other systems where fuel efficiency and performance are critical.
The Goddard problem refers to a classical problem in astrodynamics that involves the optimal control and trajectory optimization of a rocket moving under the influence of gravity. It is named after Robert H. Goddard, an American engineer and physicist who is considered one of the pioneers of rocketry.
Grazing incidence diffraction (GID) is a specialized diffraction technique used primarily in the study of thin films, surfaces, and layered materials. It involves directing a beam of X-rays, neutrons, or other incident particles at a very shallow angle (the grazing angle) with respect to the surface of a sample. This technique is particularly valuable for investigating the structural properties of materials at or near their surfaces.
Helical boundary conditions are a type of boundary condition used in physical and computational simulations, particularly in the fields of fluid dynamics, materials science, and some areas of computational physics. They are particularly useful for problems involving periodic systems that exhibit helical or twisted geometries. In simple terms, helical boundary conditions imply that the behavior of the system at one boundary is related to the behavior at a corresponding point on the opposite boundary in a way that mimics a helical or spiral structure.
An ideally hard superconductor refers to a type of superconductor that exhibits high thermal, chemical, and mechanical stability while maintaining its superconducting properties. The term "hard" in this context often implies that the material is not easily degraded by environmental factors such as temperature fluctuations, magnetic fields, or impurities.
Inherent viscosity is a measure of the viscosity of a polymer solution, providing insight into the molecular weight and the flow characteristics of the polymer. It is defined as the natural logarithm of the ratio of the viscosity of a dilute solution of the polymer to the viscosity of the solvent alone, normalized by the concentration of the polymer.
In the context of matter, an "interface" refers to the boundary or surface that separates two different phases or states of matter. This could include, but is not limited to, the boundaries between: 1. **Solids and liquids**: For example, the surface of a glass of water. 2. **Liquids and gases**: Such as the surface of a lake where water meets air.
An ion drift meter is an analytical instrument used to measure the mobility of ions in a gas phase. It operates on the principle of ion mobility spectrometry (IMS), where ions are generated, separated based on their sizes and shapes, and then detected. The key working principle involves applying an electric field that causes the ions to drift through a medium, typically a buffer gas, allowing for the measurement of their velocities.
Isotropic radiation refers to the emission of energy, such as electromagnetic radiation or particles, uniformly in all directions from a source. In other words, an isotropic source emits radiation with the same intensity regardless of the observer's position or angle relative to the source. This concept is often used in various fields including physics, astronomy, and engineering. For example, in astrophysics, many stars can be approximated as isotropic radiators, emitting light and heat evenly into space.
A Jolly balance, also known as a Jolly balance scale or Jolly balance beam, is a type of balance scale used in educational settings and laboratories to demonstrate the principles of mass and weight measurement. It consists of a horizontal beam that is pivoted at a central fulcrum. Different weights can be placed on either side of the beam, and the balance will tip to one side or the other based on the relative masses of the weights.
The K band is a designation used in the electromagnetic spectrum and is commonly associated with both microwave and infrared portions of the spectrum, depending on the context. In the context of infrared radiation, K band typically refers to a specific range of wavelengths or frequencies. In infrared terms, the K band generally covers wavelengths from about 18 to 27 micrometers (μm).
A karat meter, often referred to in the context of measuring the purity of gold, is a tool used to determine the karat (or carat) value of gold or other precious metals. The karat system is a standard measure of the purity of gold alloys, with 24 karats representing pure gold. A karat meter typically uses electronic sensors to analyze the metal's composition, providing a quick and accurate assessment of its gold content.
The Kleemenko cycle is a term used in the context of thermodynamics and heat engines, particularly in discussions of idealized cycles for heat engines. Although there are several heat cycle models, the Kleemenko cycle is characterized by a specific sequence of thermodynamic processes which typically includes isothermal (constant temperature) and adiabatic (no heat exchange) processes.
The LARMOR neutron microscope is an advanced imaging tool that utilizes neutrons to provide high-resolution images of materials and biological specimens. It operates based on the principle of neutron scattering, where neutrons interact with atomic nuclei in a sample. This interaction allows for detailed imaging and analysis of the internal structure of the material being observed.
Laser dye refers to organic compounds that are used as laser gain media. These dyes can be dissolved in a solvent and are commonly utilized in dye lasers, which are a type of laser that produces laser light over a wide range of wavelengths. The specific wavelengths depend on the chemical structure of the dye. There are several key points about laser dyes: 1. **Organic Composition**: Laser dyes are typically organic molecules. Common examples include rhodamines, fluoresceins, and phthalocyanines.