They are not considered in this manual as they cannot be constructed from readily available local materials and require expensive plastic moulding equipment.
Dr. David A. Waldman, vice president for research and development at Aprilis Inc. in Cambridge, Mass., said that recording a hologram with the new material would require expensive lasers consuming a great deal of energy.
These methods offer the advantage of directly measuring ingested material, but require expensive and specialized equipment and, again, can only measure the rate of feeding over short intervals of time (You et al. 2008; Avery and You 2012; Paek et al. 2012).
What's more, free-piston engines don't require expensive materials such as the platinum catalysts needed in fuel cells, so they could be cheaper too.
Baseflow separation methods are often impractical, require expensive materials and time-consuming methods, and/or are not designed for individual events in small watersheds.
The main problem with solid-oxide fuel cells has been that they operate at extremely high temperatures that require expensive materials, make startup times slow, and make the cells difficult to package for portable applications.
The reason is that many new projects—especially in dense cities--are vertical towers that require expensive materials and construction costs.
Chemical engineers have figured out how to synthesize many of these molecules in bulk, but the intricate reactions require expensive materials and often produce poisonous byproducts.
But because it doesn't require expensive materials to deal with bromine, it's likely to be far cheaper to produce and friendlier to use.
The results are typically beautiful, elaborate, and don't require expensive materials to execute what more could you ask for?
