Detroit has lost more than half its population since 1950, from about 1.8 million to fewer than 700,000 people today.
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December 1
,
1943
:
US President Franklin Roosevelt, UK Prime Minister Winston Churchill, and USSR leader Joseph Stalin signed the Tehran Declaration.
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Thermodynamic analysis is used by engineers to evaluate how energy affects the performance of mechanical systems. It uses mathematical models to determine the effects of different energy inputs and some of the energy outputs that result from a machine's operation. Engineers develop models to illustrate the variables that have a direct impact on the system's energy cycle. Common systems that are evaluated with this type of analysis are combustion engines and steam cycles.
Part of a thermodynamic analysis examines how energy moves throughout a mechanical system, such as an engine. It explains how that energy causes the system to perform. For example, a vehicle's combustion engine, the energy produced by burning gasoline interacts with the engine's parts, producing the power needed for the car or truck to keep moving. The analysis attempts to explain how this process works.
Given different energy input values, this analysis can be used to determine the performance ranges of a mechanical system. Mathematical models are constructed to establish certain parameters or laws. In simple terms, these models explain how if "x" amount of energy is put into the system, it will perform at "y" level. Potential responses are also measured in a thermodynamic analysis to determine the performance limits of systems.
The analytic process breaks down and isolates the different sources of energy that a system needs in order to produce power. It examines how those energy sources interact with each other at each step of the process. Again using the example of an automobile engine, each major element of the system — such as gasoline, pressure, and temperature — would be separated and it would be determined at what point certain elements and interactions would cause different reactions within the engine. For instance, engineers know that when the gasoline is heated, which is triggered by the car's ignition process, it expands and combusts to provide the vehicle with the power to move.
In a thermodynamic analysis, the performance of a mechanical system is usually characterized as a process that is separated into specific steps. While the separate steps will typically build upon each other, each one is examined to determine how it contributes to the operation of the system and whether it directly affects the amount of power that the system generates. From these process steps, engineers develop a likely mathematical model that can be used to predict performance.
The mathematical models that engineers develop will vary depending upon the type of mechanical system that is being evaluated. Most involve algebraic equations since a thermodynamic analysis often deals with a set of known and unknown variables. Several equations may be created in order to explain the interdynamics of the mechanical system and its sources of power.