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Physics and engineering.

Article Excerpt
Chair: Erdem Topsakal, Mississippi State University

Vice-chair: Alina Gearbe, University of Southern Mississippi

THURSDAY MORNING

Amphitheater

O10.01

8:30 MICRO-MANUFACTURING

Kant Vajpayee

The University of Southern Mississippi

Evolution in electronics during the last two decades and the needs of the medical equipment market are leading us into the micro-world. Minimally invasive surgical (MIS) procedures involving dime-size incisions, robots that assist surgeons, desktop machine tools, and similar developments rely on micro-manufacturing. Our progress toward the micro-world depends to a large extend on our being able to manufacture parts/products of small dimensions. Many a times, the tools and techniques of conventional manufacturing are insufficient at these dimensions. For example, being able to physically hold micro-parts is a challenging task. Micro-machining involves tools that are under 0.3 mm in diameter. Holes of such diameters may be required to be as deep as 2 cm. Spindles can run at speeds as high as 40,000 rpm. Robots are increasingly being used in micro-manufacturing. Major challenges exist in micro-molding and its systems, such as lack of fundamental physics at the micro scale, thermal effects, problems with static electricity, higher precision, and many others. Smaller parts can become airborne if not properly grounded. Very limited measuring instruments capable of measuring to submicron tolerances are available. Some recent milestones covered have been: achieving tolerances as tight as 0.001 mm, drilling 19 mm deep holes of 0.5 mm diameter, and using 0.13 mm diameter end-mills.

O10.02

8:45 THE BIGGEST MYSTERY OF THE UNIVERSE--DARK ENERGY.

Amin Haque

Alcorn State University

The surprise findings of the researchers in 1998 that the supernovas were dimmer, and that meant they were farther away than they should have been, gave birth to the concept of Dark Energy. This mysterious invisible repulsive force is assumed to cause the accelerated expansion of the Universe. Riess' team analyzed 42 of the most distant supernovae received by Hubble Space Telescope. Allen and his colleagues used Chandra X-Ray Observatory to study 26 clusters of galaxies at distances corresponding to between one and eight billion light years. Better limits on the amount of dark energy and how it varies with time were obtained by combining the X-ray results with data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), which used observations of the cosmic microwave background radiation to discover evidence for dark energy in the very early Universe. Using the combined data, astronomers have found that dark energy makes up about 75% of the Universe, dark matter about 21%, and visible matter about 4%. Thus we do not understand 96% of the universe. Dark energy has profound implications on the fate of the universe. If acceleration were to continue indefinitely, the universe could expand so incredibly that it would end in a Big Rip. All matter--galaxies, stars, planets, and even an atom--would be torn apart. If dark energy becomes attractive with time, the universe would start contracting., ending in the Big Crunch.

O10.03

9:00 Understanding Mysterious Dark Energy.

Amin Haque

Alcorn State University

Einstein introduced Cosmological Constant to balance the attractive gravitational force. Edwin Hubble discovered that the farther away the galaxy, the greater its recessional velocity. Dark Energy entered the astronomical scene after several groups of astronomers discovered independently the expansion of the universe at an accelerating rate, and the repulsive force responsible for the expansion is called Dark Energy. Using the combined data, astronomers have found that dark energy makes up about 75% of the Universe, dark matter about 21%, and visible matter about 4%. Our understanding of Dark Energy currently is vague. The simplest model for dark energy is the Lambda--Cold Dark Matter. CDM could be made up of Axions or WIMPs. Axions are non-thermal particles, and massless at high temperature and they undergo no energy loss. WIMPs are Supersymmetry (SUSY) particles associated to every standard model particle. The spins of these two particles differ by one-half. The R-parity number is 1 for ordinary particles and -1 for SUSY particles. Neutralino were created at the time of the Big-bang when temperatures were extremely high. Although neutralino are stable, they can annihilate each other. Quintessence theory proposes a low-mass (light) dynamical field that varies with time and could effectively act as dark energy. Chaplyin Gas is a negative pressure gas...

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