In Portland cement concrete (and other hydraulic cement concretes), when the aggregate is mixed together with the dry cement and water, they form a fluid mass that is easily molded into shape. The cement reacts chemically with the water and other ingredients to form a hard matrix which binds all the materials together into a durable stone-like material that has many uses. Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix or the finished material. Most concrete is poured with reinforcing materials (such as rebar) embedded to provide tensile strength, yielding reinforced concrete.
Abstract and concrete are classifications that denote whether a term describes an object with a physical referent or one with no physical referents. They are most commonly used in philosophy and semantics. Abstract objects are sometimes called abstracta (sing. abstractum) and concrete objects are sometimes called concreta (sing. concretum). An abstract object is an object which does not exist at any particular time or place, but rather exists as a type of thing, i.e., an idea, or abstraction. The term 'abstract object' is said to have been coined by Willard Van Orman Quine. The study of abstract objects is called abstract object theory.
The type-token distinction identifies physical objects that are tokens of a particular type of thing. The "type" that it is a part of, is in itself an abstract object. The abstract-concrete distinction is often introduced and initially understood in terms of paradigmatic examples of objects of each kind:
An audio engineer works on the recording, manipulation, mixing, reproduction, and reinforcement of sound. Audio engineers work on the "...technical aspect of recording—the placing of microphones, the turning of pre-amp knobs, the setting of levels. The physical recording of any project is done by an engineer... the nuts and bolts." Many audio engineers creatively use technologies to produce sound for film, radio, television, music, electronic products and computer games. Audio engineers also set up and operate sound reinforcement systems for concert, corporate, theatre, sporting and other events.
Audio engineering concerns the creative and practical aspects of sounds including speech and music, as well as the development of new audio technologies and advancing scientific understanding of audible sound.
The Cal Poly Pomona College of Engineering is the engineering college at California State Polytechnic University, Pomona (Cal Poly Pomona) located in Pomona, California, United States. With over 5,600 undergraduate students (as of fall 2015), it is the largest engineering college in Southern California, the second largest college of engineering in the California State University system, and the seventeenth largest engineering college in the United States. In 2013 U.S. News & World Report ranks Cal Poly Pomona's undergraduate program 14th in the nation (for Master's-granting universities), and mentions that Cal Poly Pomona "has one of the top ranked engineering programs, and graduates roughly 1 of every 14 engineers in the state of California."
Because of the hands-on approach to academics and undergraduate focus, the college of engineering at Cal Poly Pomona is among the most selective engineering colleges in the nation and most of its departments are currently declared impacted (hold stringent standards for admissions). For fall 2015, the college admitted 45.3 percent of its total freshmen applicants who held an average unweighted GPA of 3.72 (out of 4.00) and SATs of 1178 (out of 1600), making the college admissions process statistically comparable to the University of California campuses at Davis, Irvine, and Santa Barbara.