Traffic Control

Traffic Control Traffic Control: The Need For ChangeAs the population of the United States dramatically increases and the number of vehicles on the nation's roads and highways skyrockets, new methods of traffic control and organization have become necessary, by utilizing new methods of transportation or by revising the current system. In the past 15 years, the number of vehicles on American roads has increased 41.9%, the number of licensed drivers has increased 29.3%, but the size of the general population has only risen 15.9% (Clark 387-404). Between the years 1975 and 1985, the number of miles driven by Americans rose 34.6%, but the number of miles of roads increased by only 4.4% (Doan 64).Cars and other vehicles are an enormous cost to society, costing between $300 billion and $700 billion per year. These expenses are caused mainly by traffic accidents, traffic jams, and the environmental hazards created by the large number of vehicles on the road.Mezzanine of the Berkeley station. Bay Area Rapid ...Traffic accidents account for one of the major reasons that the current techniques of traffic control need revision. Traffic jams, along with broken cars and the lack of alternate routes, account for one half of the traffic congestion in the United States (Clark 387-404). Although the number of traffic accidents in the United States has slowly decreased over the past several years, it is still alarmingly high. In 1990, approximately 7 deaths occurred for every 10,000 people in the United States due to traffic accidents (Wallich 14).In addition, traffic jams also demonstrate the need for better methods of traffic management. Due to both the increase of women in the work force and the expansion of businesses to the suburbs, traffic jams have increased dramatically over the past few years (Koepp 55). As a consequence of traffic jams, the American population was delayed 722...

What You Need to Know About the Weak Force

What You Need to Know About the Weak Force The weak nuclear force is one of the four fundamental forces of physics through which particles interact with each other, together with the strong force, gravity, and electromagnetism. Compared to both electromagnetism and the strong nuclear force, the weak nuclear force has a much weaker intensity, which is why it has the name weak nuclear force. The theory of the weak force was first proposed by Enrico Fermi in 1933 and was known at that time as Fermis interaction. The weak force is mediated by two types of gauge bosons: the Z boson and W boson. Weak Nuclear Force Examples The weak interaction plays a key role in radioactive decay, the violation of both parity symmetry and  CP symmetry, and changing the flavor of quarks (as in beta decay). The theory that describes the weak force is called quantum flavourdynamics (QFD), which is analogous to quantum chromodynamics (QCD) for the strong force and quantum electrodynamics (QFD) for the electromagnetic force. Electro-weak theory (EWT) is the more popular model of the nuclear force. Also Known As:  The weak nuclear force is also referred to as: the weak force, the weak nuclear interaction, and the weak interaction. Properties of the Weak Interaction The weak force is different from the other forces: It is the only force that violates  parity-symmetry (P).It is the only force that violates charge-parity symmetry (CP).It is the only interaction that can change one kind of quark into another or its flavor.The weak force is propagated by carrier particles that have significant masses (about 90  GeV/c). The key quantum number for particles in the weak interaction is a physical property known as the weak isospin, which is equivalent to the role that electric spin plays in the electromagnetic force and color charge in the strong force. This is a conserved quantity, meaning that any weak interaction will have a total isospin sum at the end of the interaction as it had at the beginning of the interaction. The following particles have a weak isospin of 1/2: electron neutrinomuon neutrinotau neutrinoup quarkcharm quarktop quark The following particles have a weak isospin of -1/2: electronmuontaudown quarkstrange quarkbottom quark The Z boson and W boson are both much more massive than the other gauge bosons that mediate the other forces (the photon for electromagnetism and the gluon for the strong nuclear force). The particles are so massive that they decay very quickly in most circumstances. The weak force has been unified together with the electromagnetic force as a single fundamental electroweak force, which manifests at high energy (such as those found within particle accelerators). This unification work received the 1979 Nobel Prize in Physics, and further work on proving that the mathematical foundations of the electroweak force were renormalizable received the 1999 Nobel Prize in Physics. Edited by Anne Marie Helmenstine, Ph.D.