6,345 research outputs found
Firmware Development Improves System Efficiency
Most manufacturing processes require physical pointwise positioning of the components or tools from one location to another. Typical mechanical systems utilize either stop-and-go or fixed feed-rate procession to accomplish the task. The first approach achieves positional accuracy but prolongs overall time and increases wear on the mechanical system. The second approach sustains the throughput but compromises positional accuracy. A computer firmware approach has been developed to optimize this point wise mechanism by utilizing programmable interrupt controls to synchronize engineering processes 'on the fly'. This principle has been implemented in an eddy current imaging system to demonstrate the improvement. Software programs were developed that enable a mechanical controller card to transmit interrupts to a system controller as a trigger signal to initiate an eddy current data acquisition routine. The advantages are: (1) optimized manufacturing processes, (2) increased throughput of the system, (3) improved positional accuracy, and (4) reduced wear and tear on the mechanical system
Effect of Horizontal Passage Length on Solid Recycle Through a Loop Seal in a Circulating Fluidized Bed
Solid flow through the loop seal of a circulating fluidized bed (CFB) was studied by investigating the effect of the horizontal passage length on solid flow through the loop seal. This was done by investigating the effects of aeration on the inter-particle friction forces, the effect varying horizontal passage lengths had on the overall solid flux around the CFB loop and on the pressure drop across the passage. The division of air flow through the loop seal was also investigated in order to determine how the solids were driven through the loop seal. It was found that for a measurable amount of solid flow to occur, a minimum aeration was required, in excess of the minimum fluidizing velocity of the particles. As horizontal passage length increased the minimum aeration required also increased. As well the maximum obtainable solid flux decreased with increasing passage length due to the increased resistance in the longer passage. The increased resistance to solid flow through the passage was seen in the increasing pressure drop per unit length across the passage, as the passage length increased. This was a result of an area of stationary solids near the end of the horizontal passage that constricted the flow of solids and got larger as the passage length increased. At low solid flow rates the supply chamber aeration was split, such that the velocity of air in the supply chamber or the stand pipe remained below the minimum fluidization velocity with the remaining flow conveying solids through the horizontal passage. At high solid flow rates all of the supply chamber aeration flowed into the horizontal passage along with an amount of air entrained by the solids falling down the standpipe
Determining the Anisotropic Exchange Coupling of CrO_2 via First-Principles Density Functional Theory Calculations
We report a study of the anisotropic exchange interactions in bulk CrO_2
calculated from first principles within density functional theory. We determine
the exchange coupling energies, using both the experimental lattice parameters
and those obtained within DFT, within a modified Heisenberg model Hamiltonian
in two ways. We employ a supercell method in which certain spins within a cell
are rotated and the energy dependence is calculated and a spin-spiral method
that modifies the periodic boundary conditions of the problem to allow for an
overall rotation of the spins between unit cells. Using the results from each
of these methods, we calculate the spin-wave stiffness constant D from the
exchange energies using the magnon dispersion relation. We employ a Monte Carlo
method to determine the DFT-predicted Curie temperature from these calculated
energies and compare with accepted values. Finally, we offer an evaluation of
the accuracy of the DFT-based methods and suggest implications of the competing
ferro- and antiferromagnetic interactions.Comment: 10 pages, 13 figure
A versatile nondestructive evaluation imaging workstation
Ultrasonic C-scan and eddy current imaging systems are of the pointwise type evaluation systems that rely on a mechanical scanner to physically maneuver a probe relative to the specimen point by point in order to acquire data and generate images. Since the ultrasonic C-scan and eddy current imaging systems are based on the same mechanical scanning mechanisms, the two systems can be combined using the same PC platform with a common mechanical manipulation subsystem and integrated data acquisition software. Based on this concept, we have developed an IBM PC-based combined ultrasonic C-scan and eddy current imaging system. The system is modularized and provides capacity for future hardware and software expansions. Advantages associated with the combined system are: (1) eliminated duplication of the computer and mechanical hardware, (2) unified data acquisition, processing and storage software, (3) reduced setup time for repetitious ultrasonic and eddy current scans, and (4) improved system efficiency. The concept can be adapted to many engineering systems by integrating related PC-based instruments into one multipurpose workstation such as dispensing, machining, packaging, sorting, and other industrial applications
Aerobrake assembly with minimum Space Station accommodation
The minimum Space Station Freedom accommodations required for initial assembly, repair, and refurbishment of the Lunar aerobrake were investigated. Baseline Space Station Freedom support services were assumed, as well as reasonable earth-to-orbit possibilities. A set of three aerobrake configurations representative of the major themes in aerobraking were developed. Structural assembly concepts, along with on-orbit assembly and refurbishment scenarios were created. The scenarios were exercised to identify required Space Station Freedom accommodations. Finally, important areas for follow-on study were also identified
Guidelines for reducing porpoise mortality in tuna purse seining
More than a decade has passed since the passage of the Marine Mammal Protection Act of 1972. During that time the U.S. tuna purse seine neet reduced its incidental porpoise mortality rate more than 10-fold. This was made possible through the development of gear and techniques aimed at reducing the frequency of many low probability events that contribute to the kill.
Porpoise are killed by becoming entangled or entrapped in folds and canopies of the net and suffocating. The configuration of the net, both before and during the backdown release procedure, is a major determinant of
the number of porpoise killed. Speedboats can be used to tow on the corkllne to prevent net collapse and also to
adjust the net configuration to reduce net canopies prior to backdown. Deepening a net can reduce the probability of porpoise being killed by prebackdown net collapse. The effects of environmental conditions and mechanical
failures on net configuration can result in high porpoise mortality unless mitigated by skilled vessel maneuvers or
prevented by the timely use of speedboats to adjust the net.
The backdown procedure is the only means to effectively release captured porpoise from a purse seine. It is
also the time during the set when most of the mortality occurs. The use of small mesh safety panels and aprons in
the backdown areas of nets reduces porpoise entanglement, and Increases the probability of an effective release.
The tie-down points on the net for preparing the backdown channel must be properly located in order to optimize porpoise release. A formula uses the stretched depth of the net to calculate one of these points, making it a simple matter to locate the other. Understanding the dynamics of the backdown procedure permits a thorough troubleshooting of performance, thus preventing the repetition of poorly executed backdowns and thereby reducing mortality.
Porpoise that cannot be released must be rescued by hand. A rescuer in a rigidly inflated raft can rescue porpoise
effectively at any time during a net set. Hand rescue can make the difference between above average kill and zero kill sets. In all circumstances, the skill and motivation of the captain and his crew are the final determinants in the prevention of incidental porpoise mortality in tuna seining. (PDF file contains 22 pages.
The Long Road to Developing Native Herbaceous Summer Forage Legume Ecotypes
Only a handful of well-adapted herbaceous summer forage legumes are currently marketed for drier regions of North America and even fewer are true natives. There is a growing demand for native germplasm in the region as a new generation of landowner attempts to return grasslands to a semblance of their original species and diversity. The objective of this paper is to describe preliminary research results of a grasslands team collecting, studying and promulgating native leguminous germplasm in Texas
High level design proof of a reliable computing platform
The main objectives are: to establish hardware/software platform for ultra-reliable computing; to use fault tolerant computer architecture; to use formal methods to prevent design and implementation errors; and to construct reliability model to quantify reliability estimate. The results show that: ultra-reliable control systems are hard to achieve; simple fault tolerant design is postulated; formal specification of design is constructed; and preliminary correctness proofs are obtained
Corporate Inversions: New challenges, New Opportunities
With a wave of recent tax inversion and corporate reorganization discussions, corporate tax strategy has begun to move to the forefront of media, public and Congressional attention. These high-profile inversion strategies have gained momentum and achieved heightened attention, becoming a matter of public policy matter in 2014. While corporate international tax strategies have existed since the dawn of the U.S. federal income tax, inversions in their current form have been active only since the 1980s. Using three predominate inversion cases as a lens, this research intends to fill a gap in the existing literature relating to corporate inversions. By combining existing case law, tax legislation, and Treasury regulations, this paper develops a framework for supporting strategic global tax initiatives. The conclusions and recommendations reached are generalizable and appropriate for use in developing best practice solutions
Antietam Colossal Granite Statue. Sculpted at Batterson\u27s Quarry Westerly, R.I.
The stereograph features a black and white image of the statue The American Volunteer, which depicts a man dressed in a military uniform. The statue is full-length and the subject stands at parade rest and holds a gun. Two beams and a rope frame the statue on either side. Two houses stand in the background. The albumen print is mounted on a yellow card with rounded edges. The card\u27s reverse contains contributor information as well as additional information about the statue.https://scholarsjunction.msstate.edu/fvw-photographs/1210/thumbnail.jp
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