—by Richard Mandel

The French company GTM Construction is developing a complete guidance and control system for construction equipment such as graders and bulldozers by using satellites that can guarantee sub-centimeter altimetric accuracy. Superior to conventional guidance methods that use probes, lasers, or automated units, applications based on GPS measurements remove the need for unwieldy installations of limited efficiency. The guidance of construction machines using GPS is the result of a technological advance achieved in two phases. The first led to the development of a processing technique for GPS measurements. The second resulted in the construction of the first fine grading machine equipped with a complete automation unit. Recently, a third phase was the development of software to handle all operations on the construction site. As GPS measurements cannot be reproduced on the ground without some fluctuations, GTM Construction’s solution consisted of processing the differences using software that directs the server controlling the machine. The processing of this “GPS measurement noise” is the basis of the programmable servo control software that is capable of handling all operations on the construction site. The first module, Project, facilitates the capture of data from the construction project. The second, Walker, handles the tracking of the daily progress of the work through surveyors, and the third, Driver, directs the control of the construction machines. This module adheres to the altimetric and planimetric tolerances of the construction site without intervention from workers. The guidance system is flexible, safe, appeals to the workforce and generates savings by reducing costs and eliminating idle time due to off-site conditions. The flexibility of the system in using a fixed station for the whole of a large construction site makes it possible to employ an unlimited number of machines that have a single and unique reference. The advantages of improved accuracy and quality assurance are in addition to the reductions in construction site costs. An example of this is the “Port 2000” construction site in Le Havre. For several days, assistance with the guidance of a hydraulic excavator bucket has been in operation using this technology. It has allowed the slope of the underwater dike to be controlled without any outside human intervention. GTM Terrassement, or connect directly to their website at www.rsleads.com/212df-151

Pinching pennies will produce less discernible results, if work from Johns Hopkins University should make its way into production. Engineers at the institution applied extreme cold and mechanical manipulation, followed by a carefully measured heat treatment, to achieve a form of pure copper that is six times stronger than normal with no significant loss of ductility. The new material was made by starting with a 1-in. cube of pure commercial copper and immersing it in liquid nitrogen — temperature: -321ºF — for 3 to 5 minutes. After removal, the cube was progressively rolled flat to a thickness of 1 mm, cooling the sample between passes. This step affected the metal’s microscopic crystals, each consisting of atoms arranged in a lattice. The rolling deformation creates a high density of dislocations of atomic plane structures from their proper positions within the lattice, while the cold temperatures kept these defects from returning back to their original alignment. The copper was next placed in an oven for 3 minutes at 392ºF, causing the formation of new, ultra-fine crystal grains that were almost dislocation-free, while the existing dislocations began to disappear. The higher the stored dislocations’ density after rolling, the finer the re-crystallized grains during heating. In the lab’s sample, the new grains were only a couple of nanometers in size, several hundred times smaller than the original crystals. By carefully controlling temperature and timing of the heating phase, the Johns Hopkins engineers allowed about 20-25 percent of the copper’s crystals to grow to a larger size in a process called “abnormal grain growth.” This non-uniform mix of grain sizes gives the new copper its coexisting high strength and ductility. The researchers plan next to test their process with other pure metals, as well as metal alloys. Nanostructured materials like the new copper could have applications in microelectromechanical systems, for which suitable alloys may be more difficult to produce and may be more prone to corrosion, and in biomedical devices, where pure metals are preferable to alloys that could expose the body to toxic metallic or non-metallic elements. Johns Hopkins University, or connect directly to their website at www.rsleads.com/212df-152