Transformational part-count in layered octahedral-tetrahedral truss configurations

The number of component part (nodes, struts and panels) termed part count, is an important factor in the design, manufacture, and assembly of modular space structures. Part count expressions are presented for a variety of profiles derived from the layered octahedral-tetrahedral truss configuration. Referred to as the tetrahedral truss in the NASA projects, this specific geometry has been used in several missions. The general expressions presented here transforms to others as one profile changes to another. Such transformational part count relations provide a measure of flexibility and generality, and may be useful when dealing with a wider range of geometric configurations

A Procurement Auction Model Under Supplier Uncertainty

As business-to-business commerce shifts to the Internet, newer suppliers with cheaper but unreliable technologies enter the market place to win orders from firms by beating the price of their perfectly reliable (but expensive) competitors. The dilemma facing purchasing firms is the allocation of the tender across suppliers of varying supply reliability. We model the procurement problem as a sealed-bid auction where the buyer has to allocate purchases between an expensive but reliable supplier and a cheaper but unreliable supplier, and the suppliers specify prices for different proportions of the tender awarded to them. A unique feature of our model is that it allows the purchasing firm to reserve the right to change the size of the total tender awarded depending on the nature of the bids received from the suppliers. We prove that the set of Nash equilibrium outcomes coincides with the set of efficient outcomes, and for strictly convex cost functions, the outcome is unique. Further, we show that the possibility of implicit supplier collusion is strengthened in that the suppliers may structure their bids forcing the buyer to allocate the tender resulting in the worst-case (highest price) scenario for him. We also show that the Anton-Yao (A-Y, 1989) model can be interpreted as a limiting case of our model and that the efficient outcome derived in this paper is the only robust outcome in the A-Y model.

Comparative morphology of configurations with reduced part count derived from the octahedral-tetrahedral truss

Morphology (the study of structure and form) of the octahedral-tetrahedral (octet) truss is described. Both the geometry and symmetry of the octet truss are considered. Morphological techniques based on symmetry operations are presented which enable the derivation of reduced-part-count truss configurations from the octet truss by removing struts and nodes. These techniques are unique because their Morphological origination and they allow for the systematic generation and analysis of a large variety of structures. Methods for easily determining the part count and redundancy of infinite truss configurations are presented. Nine examples of truss configurations obtained by applying the derivation techniques are considered. These configurations are structurally stable while at the same time exhibiting significant reductions in part count. Some practical and analytical considerations, such as structural performance, regarding the example reduced-part-count truss geometries are briefly discussed

PUBH 6541 01F - Biostatistics (Online)

This course examines statistics in public health and related sciences, including sampling, probability, basic discrete and continuous distributions, descriptive statistics, hypothesis testing, confidence intervals, categorical data analysis, regression, and correlation. Emphasis will be on the development of critical thinking skills and health data analysis applications with computer software

PUBH 6541 – Biostatistics

This course examines statistics in public health and related sciences, including sampling, probability, basic discrete and continuous distributions, descriptive statistics, hypothesis testing, confidence intervals, categorical data analysis, regression, and correlation. Emphasis will be on the development of critical thinking skills and health data analysis applications with computer software