Time-of-Flight Diffraction (TOFD) Technique

The ratio of Biochemical Oxygen Demand (BOD) to Chemical Oxygen Demand (COD) is a key indicator of the biodegradability of organic pollutants in wastewater. COD measures nearly all chemically oxidizable organic material, while BOD measures only the fraction that microorganisms can readily degrade. A higher BOD/COD ratio indicates a more biodegradable effluent, suitable for biological treatment.

The use of computer systems to assist in the creation, modification, analysis, or optimization of a design. CAD software allows product designers and engineers to create precise 2D and 3D models, replacing manual drafting. This technology dramatically increases productivity, improves the quality of design, and facilitates better communication through detailed visualizations and simulations.

Passive solar design is a building design strategy that uses a building's components—walls, floors, windows, and orientation—to collect, store, reflect, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer. Unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.

The C-rate is a standardized measure of the rate at which a battery is charged or discharged relative to its nominal capacity. A rate of 1C means the current will fully charge or discharge the battery in one hour. Higher C-rates (e.g., 5C) indicate faster charging/discharging (12 minutes), while lower rates (e.g., C/2) indicate slower processes (2 hours).

The Buying Center is a model representing all individuals and groups within an organization who participate in a purchase decision. It's not a fixed unit but a set of roles assumed by different people for different purchases. These roles include initiators, users, influencers, deciders, approvers, buyers, and gatekeepers, each impacting the final decision through their specific function and authority.

The fire tetrahedron is an advanced model that adds a fourth element to the classic fire triangle: a sustained chemical chain reaction. This fourth element represents the process where the heat produced by the combustion reaction is sufficient to sustain the fire by creating further flammable vapors and radicals. This model better explains flaming combustion.

FTA is a top-down, deductive failure analysis technique. It starts with a potential undesired event (the "top event") and uses Boolean logic gates (AND, OR, etc.) to determine the combinations of component failures or human errors that could cause it. It provides a graphical model for understanding and quantifying system risk, identifying critical failure paths.

Ultrasonic welding joins plastics using high-frequency acoustic vibrations, typically between 15 kHz and 70 kHz. The vibrations are applied to parts clamped under pressure, generating intense frictional heat at their interface. This localized heat rapidly melts the thermoplastic. Once the vibration ceases, the molten material solidifies under pressure, creating a strong, solid-state weld without the need for adhesives or fasteners.

Solid modeling in CAD represents objects as unambiguous, voluminous 3D shapes. Two primary techniques dominate: Boundary Representation (B-rep), which defines a solid by its bounding surfaces (faces, edges, vertices), and Constructive Solid Geometry (CSG), which builds complex shapes by applying Boolean operations (union, subtract, intersect) to simpler primitive solids like cubes, spheres, and cylinders.

Time-temperature indicators (TTIs) are devices or smart labels that visually show the cumulative time-temperature history of a product. They change appearance, often through a color change, when the product has been exposed to temperature conditions that could compromise its safety or quality. This provides a more accurate, dynamic indication of remaining shelf life than a static printed date label.