Expressions are very useful in a number of applications for describing the interest of the user in particular data items. Examples of such application domains include publish/subscribe, ecommerce, web site personalization. In recent work, database techniques have been utilized for efficiently matching large number of expressions with data. These techniques include storing expressions as data in the database and then indexing these expressions to quickly identify expressions that match a given data item. In this thesis a new model for expressions is presented that allows definition of richer expressions than provided in previous work. Implementation of this expression model is then described. The implementation includes sequential search as well as an indexing approach. The thesis then presents an experimental performance study that shows the benefit of the indexing approach.

"During the solidification process in casting, hot tearing may occur. It is a severe defect that normally involves the formation of a macroscopic tear, which generates cracks either on the surface or inside the casting. Over the past decades, many strategies have been developed to evaluate the hot tearing tendency. Unfortunately, most of the tests can only provide qualitative information. Therefore, a reliable and quantitative test to evaluate hot tearing in aluminum alloys is highly desirable. To address this issue, WPI and CANMET MTL (both members of the Light Metal Alliance) jointly developed a quantitative hot tearing test and established a specific methodology. Using a constrained rod mold, the hot tearing formation can be quantitatively studied by measuring the contraction force, time and temperature during solidification for a restrained casting or linear contraction, time and temperature for a relaxed casting. This study investigated cast aluminum alloys A380.1 and A390 and wrought aluminum alloys 6061 and 7075. The results show that wrought aluminum alloys have a much stronger hot tearing tendency than cast aluminum alloys based on a quantitative analysis. Also, the study involves the effects of adding strontium and oxides respectively into the cast aluminum alloy A380.1. Compared with the pure A380.1 alloy, the introduction of strontium decreases the hot tearing tendency, while the inclusion of oxide greatly increases the hot tearing. The information obtained through these tests provides a database of hot tearing phenomenon and establishes a new hot tearing index."

Long period gratings (LPGs) are formed by inducing a permanent periodic modulation of the refractive index (RI) of the core of an optical fibre. The transmission spectrum of the LPG contains a series of attenuation bands centered at discrete wavelengths. The exact form of the transmission spectrum and the central wavelengths of the attenuation bands, are sensitive to the period and the length of the LPG and to the local environment. The sensitivity of a LPG to a particular measurand is dependant upon the composition of the fibre and upon the order of the cladding mode to which the guided mode is coupled to and is thus different for each attenuation band.

In accordance with the federally mandated Highway Safety Improvement Program (HSIP), every state is required to “develop and implement, on a continuous basis, a highway safety improvement program which has the overall objective of reducing the number and severity of crashes and decreasing the potential for crashes on all highways” (FHWA, 1979). The federal government via the HSIP provides a significant amount of funding that allows every state to improve the safety of their highway network. With such large amounts of federal funds involved, it becomes essential that state transportation agencies take appropriate measures to utilize these funds in the most cost effective manner. As part of this program, the Texas Department of Transportation (TxDOT) uses a formula known as the “Safety Improvement Index” (SII) for identification, ranking and selection of eligible projects. The SII is in essence used to rank potential projects by giving priority to projects that have a higher benefit-cost (B/C) ratio. Since the SII has not been updated within the last two decades, there is a need to determine whether the current formulation needs to be revised or updated. This concern has been reported in the literature. The objective of this thesis is to evaluate the SII in its current functional form and its usefulness to rank and prioritize projects for safety improvement. The evaluation procedure proposed in this thesis uses sensitivity analyses to study the effects of different input variables on the SII. The sensitivity analysis is performed with respect to five critical variables chosen on the basis of a literature review. The five variables studied are the Interest Rate, Removal of PDO Crashes, Crash Reduction Factors, Crash Rates, and Crash – Flow Relationship. The focus of the evaluation is to compare the ranking of projects with respect to changes in the value of these input variables. The ranking are evaluated using various statistical methods, such as the Spearman Rank Order Correlation Test and Kendall’s Tau Test. The results of the analysis indicated that, although changes in the value of input variables affect the SII output, the ranking of projects is usually not affected, with the exception of the crash reduction factor variable. Hence, the same projects will be selected for safety improvement, even if different values are used in the SII. Therefore, it is recommended that the current formulation of the SII and the value of input variables used in the formula be retained by TxDOT for prioritizing safety improvement projects. However, it is suggested to examine the accuracy and uncertainty associated with reduction factors, since in some cases they were found to affect the ranking of projects.

It was in 2004 that the first case study was done by on the ongoing Reverse Auction Bidding at Texas A&M University. This long-term study has developed from a single case study, completed by van Vleet, to a series of case studies, now combined with personality testing of all participants. van Vleet developed a Microsoft Access database system and Active Server Pages web based user interface for the study. The first case study involved five participants with no prior experience in Reverse Auction Bidding. A study with five participants is considered competitive in accordance with the standard economic Herfindahl Index. van Vleet, concluded that the results showed a level of co-operation in the bidding game between the nominal competitors. In 2010 John Nichols coined the term "tacit collusion" to identify this apparent behavioural pattern observed in the bidding. A significant element of the studies from 2005 to 2009 has been to investigate the "tacit collusion" behaviour. Tacit collusion is not considered an illegal economic behaviour. In 2006 Seth Gregory encountered significant problems with a study involving ten participants using the Access database, as a result of Access' limitations on the number of connections. Gregory's study was migrated to a Microsoft SQL database that was developed by Wellington (2006) and which overcame the limitations. SQL database systems can generate a significant quantity of data which create a computer science problem, now commonly termed 'Data rich - analysis poor'. This study is the first in a series of studies to undertake a detailed statistical study of the early case studies to provide a set of algorithms for development of SQL queries for automated real-time data analysis of future Reverse Auction Bidding case studies. This study showed that a fifth order polynomial fit the contract time compared to the job number. Analysis of the number of bids per minute for the fifteen minutes of bid time showed a log-polynomial equation which provided a reasonable fit to the data. Two sub-games were postulated to describe the operational aspects of the auction. The first game, termed the - game, is between the players with the objective of maximizing average return and the second game, termed the - game, has the objective of average cost minimization for the purchasers and maximization of revenue for the seller group. In conclusion, Reverse Auction Bidding systems are not bid shopping, but the tenet that the purchaser will reduce costs in this type of system compared to the traditional closed bid system is not confirmed with van Vleet's data and any careful consideration of the results of canny players in the 'game suggests higher than average returns for some bidders. The results show a number of patterns in the data that warrant further study, particularly the characteristics of the canny players in the alpha game suggests higher than average returns for some bidders. The results show a number of patterns in the data that warrant further study, particularly the characteristics of the canny players.

In the beginning of the 2007 crop year, the Federal Crop Insurance Corporation (FCIC) launched the Pasture, Rangeland, Forage Rainfall Index Pilot Program (PRF-RI) for six states. This insurance is an index and not individual insurance. Risk Management Agency officials claim that PRF-RI insurance mitigates the risk because index and forage production move in the same direction. Therefore when the index is low there is the expectation that production will also be low. PRF-RI is a pilot program and ranchers are skeptical as to whether or not it is viable to purchase the insurance. The objective of this research was to determine the economic benefits of rainfall insurance in selected counties in Texas and estimate the probability of indemnities under different types of coverage levels and index intervals. Historical rainfall indices were simulated for all index intervals and a multivariate empirical distribution of rainfall indices were used. The model was run for alternative scenarios on the available coverage levels (90%, 85%, 80%, 75%, 70%) and relevant premium rates. Each scenario resulted in an estimate of the insurance benefits variable probability density function for a particular coverage level. Stochastic Dominance with Respect to a Function (SDRF), Stochastic Efficiency with Respect to a Function (SERF), and StopLight chart were used to rank the benefits of alternative coverage levels. The results indicated that for all regions tested, the best alternative when purchasing PRF-RI was to buy the 90% coverage level. Probabilities of earning net indemnities decreased at lower coverage levels. December-January is a critical time period that should be taken into consideration by the ranchers. The results indicated also that insurance returns depend on the region where the policy is purchased. In southern and eastern parts of Texas net indemnities appeared to be significantly less and have lower probabilities of being positive than in West Texas. Ranchers from West Texas may be able to significantly benefit from the insurance.

Suppose $G$ is a graph and $e=ab$ is an edge of $G$. For a positive integer $k$, the $G$-necklace of length $k$ (with respect to edge $e$), denoted by $N_k(G)$, is the graph constructed as follows: Take the vertex disjoint union of $k$ copies of $G$, say $Q_1 cup Q_2 cup cdots cup Q_k$, where each $Q_i$ is a copy of $G$, with $e_i=a_ib_i$ be the copy of $e=a b$ in $Q_i$. Add a vertex $u$, delete the edges $e_i$ for $i=1, 2, cdots, k$ and add edges: $ua_1, b_1a_2, b_2a_3, cdots, b_{k-1}a_k, b_ku$. This thesis determines the circular chromatic indexes of $G$-necklaces for $G = K_{2n}$ and $G= K_{m, m}$.(¨£¹q¤l½×¤å²Ä¤»­¶)

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Abtract In this thesis, our purpose is to improve the refractive index models for direct-gap semiconductors. For refractive index spectrum of direct-gap compound semiconductors, most experimental data is available only bellow the bandgap absorption edge. For used in the optimum design of eltro-optic devices, such as waveguide, electro-absorption modulator and Mach-Zehnder interferometer. We have to utilize a little experimental data to extend refractive index spectrum to near and just above the band-gap edge. We have known that square of refractive index ( ) is dielectric constant ( ), so we decompose the dielectric constant ( ) into the part of band-to-band absorption and another part of single-oscillator high energy absorption. For the part of band-to-band absorption, we added broadening parameter ( ) and used Kramers-Kronig relation to transform the absorption coefficient into dielectric constant. For another part of single-oscillator high energy background absorption, we first cut the absorption part form experimental data and then use Sellmeier¡¦s equation to fit the residue data. Finally, recombine all equations and extend refractive index spectrum to near and just above the band-gap edge. We successfully built whole model and confirm our model with GaAs. The calculation result on GaAs shows an excellent agreement with the reported experimental data. Furthermore, We apply our model to direct-gap binary¡Bternary and quaternary compounded materials and extend our model to near and just above the band-gap edge very well.

In accordance with the federally mandated Highway Safety Improvement Program (HSIP), every state is required to "develop and implement, on a continuous basis, a highway safety improvement program which has the overall objective of reducing the number and severity of crashes and decreasing the potential for crashes on all highways" (FHWA, 1979). The federal government via the HSIP provides a significant amount of funding that allows every state to improve the safety of their highway network. With such large amounts of federal funds involved, it becomes essential that state transportation agencies take appropriate measures to utilize these funds in the most cost effective manner. As part of this program, the Texas Department of Transportation (TxDOT) uses a formula known as the "Safety Improvement Index" (SII) for identification, ranking and selection of eligible projects. The SII is in essence used to rank potential projects by giving priority to projects that have a higher benefit-cost (B/C) ratio. Since the SII has not been updated within the last two decades, there is a need to determine whether the current formulation needs to be revised or updated. This concern has been reported in the literature. The objective of this thesis is to evaluate the SII in its current functional form and its usefulness to rank and prioritize projects for safety improvement. The evaluation procedure proposed in this thesis uses sensitivity analyses to study the effects of different input variables on the SII. The sensitivity analysis is performed with respect to five critical variables chosen on the basis of a literature review. The five variables studied are the Interest Rate, Removal of PDO Crashes, Crash Reduction Factors, Crash Rates, and Crash -- Flow Relationship. The focus of the evaluation is to compare the ranking of projects with respect to changes in the value of these input variables. The ranking are evaluated using various statistical methods, such as the Spearman Rank Order Correlation Test and Kendall's Tau Test. The results of the analysis indicated that, although changes in the value of input variables affect the SII output, the ranking of projects is usually not affected, with the exception of the crash reduction factor variable. Hence, the same projects will be selected for safety improvement, even if different values are used in the SII. Therefore, it is recommended that the current formulation of the SII and the value of input variables used in the formula be retained by TxDOT for prioritizing safety improvement projects. However, it is suggested to examine the accuracy and uncertainty associated with reduction factors, since in some cases they were found to affect the ranking of projects.