elements of a product's life-cycle—from functionality, production, assembly, testing, maintenance, environmental impact, and finally disposal and recycling—should be taken into careful consideration in the early design phases. The second concept is that design activities should all be occurring at the same time, i.e., concurrently. The idea is that the concurrent nature of these activities significantly increases productivity and product quality. This way, errors and redesigns can be discovered early in the design process when the project is still flexible. By locating and fixing these issues early, the design team can avoid what often become costly errors as the project moves to more complicated computational models and eventually into the actual manufacturing of hardware. As mentioned above, part of the design process is to ensure that the product's entire life cycle is taken into consideration. This includes establishing user requirements, propagating early conceptual designs, running computational models, creating physical prototypes, and eventually manufacturing the product. Included in this process is taking into full account funding, workforce capability, and time requirements. A 2006 study claimed that a correct implementation of the concurrent design process can save a significant amount of money, and that organizations have been moving to concurrent design for this reason. It is also highly compatible with systems thinking and green engineering. Concurrent engineering replaces the more traditional sequential design flow, or "Waterfall Model". In Concurrent Engineering an iterative or integrated development method is used instead. The Waterfall method moves in a linear fashion, starting with user requirements and sequentially moving forward to design and implementation, until you have a finished product. In this design system, a design team would not quickly look backward or forward from the step it is on to fix or anticipate problems. In the case that something does go wrong, the design usually must be scrapped or heavily altered. The concurrent or iterative design process encourages prompt changes of tack, so that all aspects of the life cycle of the product are taken into account, allowing for a more evolutionary approach to design. The difference between the two design processes can be seen graphically in Figure 1. A significant part of the concurrent design method is that the individual engineer is given much more say in the overall design process due to the collaborative nature of concurrent engineering. Giving the designer ownership is claimed to improve the productivity of the employee and quality of the