Supply Chain and Operations Management Glossary (H)
Hectare: A unit of land area, originally French = 2.47 acres = 11954.8 square yards.
HEPA: High Efficiency Particulate Air filter. By DOE rules, a dry, disposable filter that removes at least
99.97% of particles that are .3 micrometers in diameter. May be required for production processes that
generate hazardous particulate pollution.
Hopper car: A railcar for carrying loose material such as grain. It has either an open top or hatches, so that it can be loaded from the top. It typically has a sloped bottom, so that the car can be emptied over a pit by opening slits in the bottom of the car. In contrast, see box car or flat car. HR (Human Resources): that part of the business concerned with hiring, payroll, health, and pension plan management, etc.
HTML (Hyper Text Markup Language): Standard format for describing Web pages. See
http://www.w3.org/HTML/. See also XML.
Hub: A central facility through which all shipments pass in a transportation system, or all communications are routed in a communications network. Given n sites with each site requiring shipments to up to n-1 other sites, there are three basic methods of handling these requirements: 1) hub system, 2) direct ship or link, 3) traveling salesperson (TSP)/ring network. If capacity is lumpy (e.g., it only comes in 20 ton)) truck increments, and the amount to be shipped from any origin to any destination is typically less than half of one of these lumps, then a hub system may be the cheapest method. Thus, a vehicle will pick up all outgoing material from given site, deliver it to the hub where it is sorted onto outgoing vehicles, and then for a given site, a single vehicle will deliver all incoming demand. If the amount to be shipped from any origin to another destination is large relative to a capacity lump, then direct ship may be the cheapest method. If the amount to be shipped from any origin to any destination is substantially less than the capacity lump size, then the TSP structure may be cheapest. That is, a single vehicle makes a tour of all sites, picking up and dropping off product as appropriate. For a telecommunication network, this corresponds to a so-called ring network. See also DC. HVAC (Heating, Ventilating, Air Conditioning)