ballast


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ballast

(bal'ăst),
1. Material of doubtful value itself used to stabilize something (for example, maritime practice). 2. Something largely without intrinsic value.

ballast 

Additional weight of material incorporated in a part of a contact lens to maintain it in a given orientation (Fig. B1). This is often provided by giving prismatic power to the lens (prism ballast lens).
Fig. B1 Truncated and prism-ballasted toric contact lensenlarge picture
Fig. B1 Truncated and prism-ballasted toric contact lens
References in periodicals archive ?
Under the BWM Convention all ships must carry a ballast water record book and an International Ballast Water Management Certificate.
Constellation Brands plans to purchase Ballast Point for approximately $1 billion.
The crane and ballast plate are attached to the derrick jib using a cross beam with strap loops.
Ballast water, which is used to maintain balance and stability when the ship is empty of cargo, has been identified as a key factor responsible for bringing invasive species of microorganisms such as plankton and bacteria into non-indigenous environments, causing a major threat to marine ecosystems.
Under the Convention, all ships in international traffic are required to manage their ballast water and sediments to a certain standard, according to a ship-specific ballast water management plan.
Total material cost to replace one ballast) (Number of ballasts) = Material c:ost to replace all ballasts at the end of their rated litehrne in hours Divide by 12 for annualized cost.
To reduce the risk for transfer of invasive species and pathogens between harbors by introduction of contaminated ballast water, the International Maritime Organization (IMO) adopted the International Convention for the Control and Management of Ships' Ballast Water and Sediments (BWM Convention) on February 13, 2004 (6).
Since you are all sophisticated lighting experts, I would like to pose the following question: Is there a way to tell if a 30-plus-year-old PCB ballast still lurks beyond a ballast cover without climbing up to remove the cover and making a visual inspection?
It is said that, towards the middle of the 19th century, a number of exotic plants established themselves on Ballast Island, an artificial dump of spent ballast from incoming ships near the mouth of the harbour.
While pulse start ballast systems for QMH lamps have been around for quite some time, there remain significant numbers of sockets designed for the more conventional probe start lamps.
BASED PHILIPS LIGHTING ELECTRONICS NORTH AMERICA introduced a 250W magnetic pulse start (PS) metal halide ballast with 90% ballast efficiency, which company officials say is an industry first.
It already has three systems for track renewal and ballast cleaning in other parts of the country but will use a new technologically advanced version of these systems on the West Coast mainline.