Atmospheric focusing is a phenomenon that occurs when atmospheric conditions enhance the propagation and intensity of electromagnetic signals, particularly in the context of radio waves and other types of waves. This effect can occur due to variations in the atmospheric density, temperature, and humidity, which can refract (bend) the waves in such a way that they are concentrated or focused along certain paths, often over considerable distances.

Bow shock is a phenomenon that occurs in aerodynamics when an object moves through a fluid (usually air) at a speed that exceeds the speed of sound in that medium, which is referred to as supersonic speed. When an object, such as an aircraft, travels faster than the speed of sound, it generates a shock wave due to the compressibility of the fluid.

The Chelyabinsk meteor refers to a significant meteor explosion that occurred on February 15, 2013, over the city of Chelyabinsk in Russia. The event involved a small asteroid, estimated to be about 20 meters in diameter and weighing approximately 13,000 metric tons, which entered Earth's atmosphere at a high speed of around 19 kilometers per second (over 42,000 miles per hour).

A hail cannon is a device that is claimed to prevent or reduce hail damage to crops by creating shock waves that disrupt the formation of hailstones in the atmosphere. The theory behind the hail cannon is that by generating loud sounds or explosive shock waves, the device can interfere with the conditions necessary for hail formation. Hail cannons typically consist of a large metal tube that is fired using an explosive charge or similar mechanism to create a loud noise.

"Moving shock" is not a widely recognized term in mainstream academic literature, so its interpretation can vary depending on the context. However, it could refer to different phenomena in different fields: 1. **Physics/Engineering**: In fluid dynamics, "moving shock" might refer to shock waves that travel through a medium, such as air or water, caused by an object moving faster than the speed of sound. This is often seen in supersonic flows, such as those involving aircraft or missiles.

The number 139 is a natural number that follows 138 and precedes 140. It is an odd number and is considered a prime number because it has no positive divisors other than 1 and itself. In Roman numerals, it is written as CXXXIX. The number 139 can also hold significance in various contexts, such as mathematics, science, or culture, but without additional context, this is a general overview of the number itself.

Muzzle blast refers to the rapidly expanding gases that are expelled from the muzzle (the open end) of a firearm or artillery piece when it is discharged. This phenomenon occurs due to the rapid combustion of gunpowder or other propellants within the firearm's chamber, generating high-pressure gases that propel the projectile out of the barrel.

Overpressure refers to a pressure that exceeds the normal or atmospheric pressure levels in a given environment. It is commonly discussed in various contexts, including: 1. **Explosions**: In the context of bomb blasts or other explosive events, overpressure is the sudden increase in air pressure caused by the shockwave produced by the explosion, which can cause significant damage to structures and harm to people.

A shock wave is a type of disturbance that moves through a medium at a speed greater than the speed of sound in that medium. This phenomenon is often characterized by a sudden and sharp change in pressure, temperature, and density, forming a steep front.

Thermodynamic relations across normal shocks are essential for understanding the behavior of fluids—specifically, gases—when they experience a sudden change in pressure and density, such as across a shock wave. A normal shock wave is one that is perpendicular to the direction of the flow. When a fluid (often a gas) passes through a normal shock, several key thermodynamic and flow properties change. These changes can be described using the conservation equations and thermodynamic relations.

A board game record typically refers to either a documented achievement or performance in a board game. This can include high scores, fastest game completions, largest wins, or other notable accomplishments that are recorded for competitive or personal purposes. Record-keeping can occur in various contexts, such as: 1. **High Scores:** Many board games, especially those with a scoring system, might record the highest scores achieved by players.

In shogi, which is often referred to as Japanese chess, a "handicap" is a method used to level the playing field between players of different skill levels. The handicap system allows a less experienced player to have a better chance of winning against a more experienced player by providing the weaker player with certain advantages. Typically, handicaps in shogi are implemented by allowing the weaker player to start the game with one or more extra pieces.

Tsume shogi is a type of puzzle in shogi (Japanese chess) that focuses on finding a sequence of moves leading to checkmate. In tsume shogi, the problem typically presents a scenario where one player, the "shiro" (white) or "kuro" (black), must deliver checkmate in a specified number of moves, regardless of the opponent's responses. The puzzles vary in complexity and can involve different pieces and arrangements on the board.

The Black–Karasinski model is a mathematical model used in finance to describe the dynamics of interest rates. It is specifically used for modeling the evolution of the logarithm of interest rates, leading to log-normal distributions. The model is a variation of the popular Vasicek and Cox-Ingersoll-Ross (CIR) models, and it captures the behavior of interest rates with mean reversion, which is a characteristic of many interest rate processes.

The Chen model often refers to a specific framework or model in finance and economics developed by Xiangyu Chen and his colleagues, primarily used to analyze the implications of various factors on asset pricing, performance measurement, and risk assessment. It typically focuses on the interplay between macroeconomic variables, investor behavior, and asset returns.

An **Alpha-Beta filter** is a type of recursive filter commonly used in signal processing and control systems, especially for estimating the state of a dynamic system over time. It is a simplified version of the Kalman filter, which is more complex but provides optimal estimations under certain conditions. ### Key Characteristics of the Alpha-Beta Filter: 1. **Purpose**: - The primary goal of an Alpha-Beta filter is to estimate the position and velocity of an object based on noisy measurements.

Automatic Link Establishment (ALE) is a technology used primarily in radio communications to facilitate the automatic establishment of communication links between radio stations. It is particularly useful in environments where multiple radios are operating and needing to communicate over varying conditions or frequencies. ### Key Features of Automatic Link Establishment (ALE): 1. **Automation**: ALE automates the process of establishing contact between radio stations, reducing the need for manual tuning and frequency selection.

An autoregressive (AR) model is a type of statistical model used for analyzing and forecasting time series data. It is based on the idea that the current value of a time series can be expressed as a linear combination of its previous values. The basic concept is that past values have a direct influence on current values, allowing the model to capture temporal dependencies.

The Rendleman–Bartter model, developed by Dale Rendleman and William Bartter in the early 1980s, is a financial model used to estimate the term structure of interest rates, particularly for zero-coupon bonds. This model is part of the broader class of term structure models, which seek to explain how interest rates vary with different maturities of debt instruments.

Luminous intensity is a measure of the amount of light emitted from a source in a particular direction per unit solid angle. It is a fundamental concept in photometry, which is the science of measuring visible light as perceived by the human eye. The unit of luminous intensity in the International System of Units (SI) is the candela (cd).