Walther recursion is a method used in functional programming and formal language theory to define functions that can be computed via recursive calls. It builds on the concept of general recursion while emphasizing the structure of recursive definitions. The central idea of Walther recursion is to express a function in terms of a "primitive recursion" along with an additional layer that allows for the use of previously computed values in the recursive process.

Many-one reduction, also known as **mapping reduction**, is a concept in computational complexity theory used to compare the difficulty of decision problems. It involves transforming instances of one decision problem into instances of another decision problem in such a way that the answer to the original problem can be easily derived from the answer to the transformed problem.

Cross-sectional regression is a statistical technique used to analyze data collected at a single point in time across various subjects, such as individuals, companies, or countries. This method involves estimating the relationships between one or more independent variables (predictors or explanatory variables) and a dependent variable (the outcome or response variable) by fitting a regression model.

Meta-regression is a statistical technique used in meta-analysis to examine the relationship between study-level characteristics (often referred to as moderators) and the effect sizes reported in different studies. Its primary purpose is to explore how variations in study design, sample characteristics, or measurement methods may influence the outcomes of interest. In essence, meta-regression extends traditional meta-analysis by allowing researchers to assess how certain factors (e.g., age of participants, length of intervention, type of treatment, etc.

The Principle of Marginality, often associated with economics and decision-making theories, suggests that in assessing the impact or utility of a decision, one should focus on the effects of incremental changes rather than the total or average effects. This principle emphasizes that when making decisions, individuals or organizations should consider the marginal benefits and marginal costs—the additional benefits gained from an action compared to the additional costs incurred.

The Heckman correction, also known as the Heckman two-step procedure, is a statistical method used to correct for selection bias in econometric models. Selection bias occurs when the sample collected for analysis is not randomly selected from the population, which can lead to biased parameter estimates if ignored.

Homoscedasticity and heteroscedasticity are terms used in statistics and regression analysis to describe the variability of the error terms (or residuals) in a model. Understanding these concepts is important for validating the assumptions of linear regression and ensuring the reliability of the model's results.

Interaction cost refers to the resources expended—such as time, effort, or financial expenditure—when individuals or organizations engage in communications or interactions with one another. This concept is commonly discussed in various fields, including economics, business, and information technology. Key aspects of interaction cost include: 1. **Time Costs**: The amount of time spent in communication, whether face-to-face, via email, or other forms.

Multinomial probit is a statistical model used to analyze dependent variables that are categorical and have more than two outcomes. It is particularly useful when the choice or outcome is not ordinal (i.e., there's no inherent order among the categories) but is rather nominal. ### Key Features of Multinomial Probit: 1. **Categorical Dependent Variable**: The model is designed for dependent variables that can take on multiple categories.

SIMNET (Simulated Network) is a distributed simulation environment originally developed for training military personnel, particularly for tank warfare. It allows different users to connect over a network and participate in realistic combat scenarios using simulators. The goal of SIMNET is to create a virtual battlefield where participants can operate vehicles, command units, and interact with others in real-time.

A polygenic score (also known as a polygenic risk score or PRS) is a numerical value that reflects an individual's genetic predisposition to a particular trait or disease. It is calculated based on the cumulative effects of multiple genetic variants, each of which may contribute a small amount to the overall risk or expression of that trait.

Strongly regular graphs are a special class of graphs characterized by their regularity and specific connection properties between vertices. A graph \( G \) is called strongly regular with parameters \( (n, k, \lambda, \mu) \) if it satisfies the following conditions: 1. **Regularity**: The graph has \( n \) vertices, and each vertex has degree \( k \) (i.e., it is \( k \)-regular).

The Iofinova–Ivanov graph is a type of vertex-transitive graph that is defined using a specific set of rules based on combinatorial properties. The 110-vertex version of this graph specifically contains 110 vertices and has edges defined through particular mathematical relationships.

The Coxeter graph is an important concept in the fields of algebra, geometry, and graph theory. Specifically, it is a particular type of graph that represents the symmetric group and the properties of certain mathematical structures, particularly in relation to Coxeter groups. Here are some key features of the Coxeter graph: 1. **Definition and Structure**: The Coxeter graph is a finite undirected graph with 12 vertices and 18 edges.

A Platonic graph is a representation of a Platonic solid, which are the five regular, convex polyhedra that can exist in three-dimensional space. These solids are characterized by having faces that are congruent regular polygons and the same number of faces meeting at each vertex. The five Platonic solids are: 1. Tetrahedron (4 triangular faces) 2. Cube (6 square faces) 3. Octahedron (8 triangular faces) 4.

A Sudoku graph is a mathematical representation of a Sudoku puzzle using graph theory concepts. In this representation, the elements of the puzzle—such as the numbers in the grid—are mapped to vertices (or nodes) in a graph, and the constraints of Sudoku are represented by edges connecting those vertices. ### Basic Structure of a Sudoku Graph: 1. **Vertices**: Each cell in the Sudoku grid can be represented as a vertex.

PC strand, or prestressed concrete strand, is a type of high-strength steel wire strand used in the construction of prestressed concrete structures. It is primarily employed in the production of precast concrete elements and in post-tensioned concrete applications. Here are some key points about PC strand: 1. **Composition**: PC strands are typically made from multiple high-strength steel wires twisted together. The strands are often coated with a protective layer to prevent corrosion.

Eurocode 7, formally known as EN 1997, is a part of the Eurocode standards that deals with geotechnical design. It provides a comprehensive framework for geotechnical engineering, focusing on ensuring safety, serviceability, and durability in the design of structures in relation to the ground and soil conditions.

Prestressed concrete construction is a technique used to enhance the strength and performance of concrete structures. This method involves the application of a pre-compression force to the concrete before it is subjected to external loads. The primary goal of prestressing is to counteract tensile stresses that occur when loads are applied, thus improving the structural performance and durability of the concrete.

BS 8110 is a British Standard that provides guidelines for the design and construction of structural concrete. Officially known as "BS 8110: Structural use of concrete," this standard specifies the principles and requirements for designing concrete structures to ensure safety, serviceability, and durability. The standard covers various aspects of concrete design, including: 1. **Material Specifications**: It outlines the requirements for concrete and reinforcing materials. 2. **Structural Analysis**: The methods to analyze structural behavior under loads.