Likelihood and Cost Impact of Engineering Change Requirements for DoD Contracts

Purpose: There appears to be no empirical-based method in the literature for estimating if an engineering change proposal (ECP) will occur or the dollar amount incurred. This paper aims to present an empirically based approach to address this shortfall.Design/Methodology/Approach: Using the cost assessment data enterprise database, 533 contracts were randomly selected via a stratified sampling plan to build two regression models: one to predict the likelihood of a contract experiencing an ECP and the other to determine the expected median per cent increase in baseline contract cost if an ECP was likely. Both models adopted a stepwise approach. A validation set was placed aside prior to any model building.Findings: Not every contract incurs an ECP; approximately 80 per cent of the contracts in the database did not have an ECP. The likelihood of an ECP and the additional amount incurred appears to be statistically independent of acquisition phase, branch of service, commodity, contract type or any other factor except for the basic contract amount and the number of contract line item numbers; both of these later variables equally affected the contract percentage increase because of an ECP. The combined model overall bested current anecdotal approaches to ECP withhold

Effects of Phosphonic Acid Monolayers on the Dehydration Mechanism of Aliphatic Alcohols on TiO2

The kinetics for surface-catalyzed alcohol dehydration reactions often depends on the structure of the alcohol.Studies of structure-activity relations across primary, secondary, and tertiary alcohols can provide fundamental information onthe nature of active sites on the surface. Here, we investigated the dehydration of 1-butanol, 2-butanol and tert-butanol overTiO2 anatase catalysts modified with various phosphonic acid (PA) self-assembled monolayers (SAMs). As a response to thepresence of PAs, the three C4 alcohol isomers showed different dehydration rates, with 1-butanol dehydration being enhancedto the greatest extent by PA modification. Furthermore, the fluorinated, more polar 4-fluorobenzyl phosphonic acid outperformedalkyl PAs across all alcohols. Steady-state kinetic measurements and temperature programmed desorption studiesindicated that PA SAMs significantly lowered the dehydration activation barrier; the extent of reduction in the barrier wassensitive to both the substitution of the alcohol and the charge distribution on the PA in a way that was consistent withstabilization of a carbenium-like transition state. Overall, the effect of PA modifiers on alcohol dehydration rates was found tobe determined from a balance between transition state stabilization and active site blocking effects, with the potential to tuneactivity and selectivity based on the structure and coverage of the SAM.</p

Effects of metal oxide surface doping with phosphonic acid monolayers on alcohol dehydration activity and selectivity

Controlling the near-surface environment of heterogeneous catalysts is of fundamental importance for high selectivity and activity. Self-assembled monolayers (SAMs) are effective tools to control reaction selectivity and activity for both supported noble metal and metal oxide catalysts. We previously demonstrated tunable dehydration activity of alcohols on phosphonic acid-modified, anatase-phase TiO2. In this work, we investigated the generality of this approach by studying the modification of other metal oxides including Al2O3, CeO2, CuO, Fe2O3, MgO, rutile-TiO2, SnO2, V2O5, WO3, ZrO2, and ZnO. Modification of these materials with phosphonic acids results in the formation of SAMs on the surface, as determined by infrared spectroscopy; studies of the thermal stability on selected catalysts indicated that the SAMs remained intact up to approximately 400&thinsp;&deg;C in inert environments. Decomposition of alcohols on these native materials resulted in dehydration, dehydrogenation, and condensation. Upon functionalization with phosphonic acid modifiers, the activity of all pathways decreased significantly, except for dehydration on CeO2, anatase-TiO2, and SnO2. We explored the properties of these oxides that may be responsible for this increase in dehydration activity using correlations to bulk properties. This analysis supported the hypothesis that phosphonic acid monolayers act as surface-level dopants for metal oxides of specific metal-oxygen bond strength and oxidation state.</p

Twenty Years of SUGRA

A brief review is given of the developments of mSUGRA and its extensions since the formulation of these models in 1982. Future directions and prospects are also discussed.Comment: Invited talk at the International Conference BEYOND-2003, Schloss Ringberg, Germany, June 10-14, 2003; 21 pages, Late

Large Angle MSW Solution in Grand Unified Theories with SU(3) X U(1) Horizontal Symmetry

We construct a model with a SU(3) X U(1) horizontal symmetry in the context of Grand Unified Theories. In our models, the bi-maximal lepton mixing and suitable neutrino masses for the large angle MSW solution are obtained without any fine-tuning due to the spontaneously broken SU(3)_H symmetry. The three generations of quarks and leptons are unified as members of the SU(3)_H fundamental representation, and the U(1)_H charge gives the origin of the fermion mass hierarchy and mixing angles. We present two explicit examples of SU(5)_GUT and SO(10)_GUT models, in which the Yukawa structures are given successfully.Comment: 23 pages, 6 figures, references adde

Nucleon Decay in a Realistic SO(10) SUSY GUT

In this paper, we calculate neutron and proton decay rates and branching ratios in a predictive SO(10) SUSY GUT which agrees well with low energy data. We show that the nucleon lifetimes are consistent with the experimental bounds. The nucleon decay rates are calculated using all one-loop chargino and gluino dressed diagrams regardless of their chiral structure. We show that the four-fermion operator $C_{jk} (u_R {d_j}_R)({d_k}_L {\nu_\tau}_L)$, commonly neglected in previous nucleon decay calculations, not only contributes significantly to nucleon decay, but, for many values of the initial GUT parameters and for large $\tan\beta$, actually dominates the decay rate. As a consequence, we find that $\tau_p/\tau_n$ is often substantially larger than the prediction obtained in small $\tan\beta$ models. We also find that gluino-dressed diagrams, often neglected in nucleon decay calculations, contribute significantly to nucleon decay. In addition we find that the branching ratios obtained from this realistic SO(10) SUSY GUT differ significantly from the predictions obtained from ``generic" SU(5) SUSY GUTS. Thus nucleon decay branching ratios, when observed, can be used to test theories of fermion masses.Comment: 42 pages, LaTe

Quantitative or momentum-based multi-style rotation? UK experience

The objective of this article is to examine whether short-term variation in the ranking of size and style index returns in the UK equity market is better predictable and exploitable by means of quantitative or momentum style-rotation strategies. Using UK index data, we assess the profitability of a number of long-only and long/short multi-stylerotation strategies based on these two alternative methods. The findings suggest that trading rules based on simple short-term momentum strategies are able to generate higher Sharpe ratios and greater end-of-period wealth at a reasonable level of transaction costs than our quantitatively based trading rules. This result is particularly pronounced among the long-only strategies

Total Synthesis of Brevetoxin A

A total synthesis of brevetoxin A is reported. Two tetracyclic coupling partners, prepared from previously reported advanced fragments, were effectively united via a Horner—Wittig olefination. The resulting octacycle was progressed to substrates that were explored for reductive etherification, the success of which led to a penultimate tetraol intermediate. The tetraol was converted to the natural product through an expeditious selective oxidative process, followed by methylenation

Enantioselective Total Synthesis of Brevetoxin A: Unified Strategy for the B, E, G, and J Subunits

Brevetoxin A is a decacyclic ladder toxin that possesses five-,six-, seven-, eight-, and nine-membered oxacycles, as well as 22 tetrahedral stereocenters. Herein, we describe a unified approach to the B, E, G, and J rings predicated upon a ring-closing metathesis strategy from the corresponding dienes. The enolate technologies developed in our laboratory allowed access to the precursor acyclic dienes for the B, E, and G medium ring ethers. The strategies developed for the syntheses of these four monocycles ultimately provided multigram quantities of each of the rings, supporting our efforts toward the convergent completion of brevetoxin A