Analysis of the Design-Build Delivery Method in Air Force Construction Projects

The design-build (DB) method for construction project delivery continues to grow in both the private and public sector; additionally, research has shown that the DB method outperforms the design-bid-build (DBB) method. The Air Force has applied the results of these previous research efforts to its military construction (MILCON) program without performing empirical studies to validate the approach. Therefore, the objective of this study was to compare the performance of the DB delivery method with the traditional DBB approach for the Air Force MILCON program. Data related to 835 (278 DB and 557 DBB) MILCON projects for fiscal years 1996–2006 were subsequently analyzed. The DB method had better performance in three of six metrics with the performance being significantly better for cost growth and the number of modifications per million dollars. The traditional DBB method performed significantly better in terms of total project time. Furthermore, the DB method was best suited for various facility types. This study provides empirical evidence of how the DB method provides an advantage over the traditional DBB method for Air Force MILCON projects.     

Iterative algorithm for optimal fiducials under weak perspective projection

In previous work, we designed space fiducials with the aim of making camera pose determination as noise‐insensitive as possible. These fiducials turned out to be sets of points that formed concentric regular polyhedra. Here, we apply an idea of Dementhon and Davis and test and analyze an iterative linear algorithm in conjunction with our optimal fiducials to increase the accuracy of the computed camera pose. We also analyze under what circumstances this iterative algorithm is guaranteed to converge to the correct solution. Comprehensive computer simulations illustrate the behavior of the algorithm and the degree of improvement in pose determination in case of convergence. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 27–36, 2009     

Tunable Spectrum Selectivity for Multiphoton Absorption with Enhanced Visible Light Trapping in ZnO Nanorods

Observation of visible light trapping in zinc oxide (ZnO) nanorods (NRs) correlated to the optical and photoelectrochemical properties is reported. In this study, ZnO NR diameter and c‐axis length respond primarily at two different regions, UV and visible light, respectively. ZnO NR diameter exhibits UV absorption where large ZnO NR diameter area increases light absorption ability leading to high efficient electron–hole pair separation. On the other hand, ZnO NR c‐axis length has a dominant effect in visible light resulting from a multiphoton absorption mechanism due to light reflection and trapping behavior in the free space between adjacent ZnO NRs. Furthermore, oxygen vacancies and defects in ZnO NRs are associated with the broad visible emission band of different energy levels also highlighting the possibility of the multiphoton absorption mechanism. It is demonstrated that the minimum average of ZnO NR c‐axis length must satisfy the linear regression model of Z _p,min = 6.31d to initiate the multiphoton absorption mechanism under visible light. This work indicates the broadening of absorption spectrum from UV to visible light region by incorporating a controllable diameter and c‐axis length on vertically aligned ZnO NRs, which is important in optimizing the design and functionality of electronic devices based on light absorption mechanism.     

Isomerization of 9c11t/10t12c CLA in Triacylglycerols

Isomers of conjugated linoleic acid from 7t9c through 12t14t can be induced by thermal treatment of triacylglycerol samples of 9c11t or 10t12c fatty acids in glass tubes. The formation of conjugated linoleic acids (CLAs) has been observed during thermal induction of the above-mentioned triacylglycerols at 250, 280 and 320°C. The concentrations of isomers formed in the mixture varied depending on the temperature and duration of the heating experiments. The objective of this study was to find a suitable thermal induction temperature and time that can produce most of the isomers of CLAs from the above-mentioned triacylglycerols. Such a mixture would give researchers a reference standard that can be used in the identification of CLAs in GC analyses of relevant samples. Fifteen-microlitre portions of the triacylglycerol samples containing 9c11t/10t12c fatty acid were placed in micro-glass ampoules, sealed under nitrogen and then subjected to thermal treatment. The glass ampoules were removed at regular time intervals, cut open, and part of the samples was analysed by infrared spectroscopy using attenuated internal reflectance technique. The remainder of the samples was subjected to derivatisation into their methyl esters. The methyl esters of the isomerised fatty acids were then analysed by gas chromatography after appropriate dilution in heptane. The results show that the thermally induced glyceride samples of 9c11t/10t12c fatty acids gave CLA profiles containing isomers ranging from 7t9c to 12t14t. However, the concentrations of the isomers are different depending on the duration of the thermal induction. It appears that [1,5] sigmatropic rearrangements and positional isomerisations take place in the heated mixtures. The rearrangements and positional isomerisations are accelerated by increasing temperature. The glyceride samples heated to 325°C form isomers within 30 min and provide a mixture of CLA isomers that can be used as reference sample containing the methyl esters of CLAs.     

Direct numerical inversion method for kinetic ellipsometric data. I. Presentation of the method and numerical evaluation

A direct numerical inversion method for the determination of the refractive index and the thickness of the outermost layer of a thin transparent film on top of a multilayer has been developed. This method is based on a second-order Taylor decomposition of the coefficients of the Abelès matrices of the newly grown layer. The variations of the real-time spectroscopic ellipsometry data are expressed as polynomial fuctions depending on the dielectric constant and the thickness of the newly grown layer. The method is fast, capable of single-wavelength and multiwavelength inversion of continuous as well as discontinuous-index profiles, and can be adapted to many different polarimetric instruments.     

Image segmentation and edge enhancement with stabilized inversediffusion equations

We introduce a family of first-order multidimensional ordinary differential equations (ODEs) with discontinuous right-hand sides and demonstrate their applicability in image processing. An equation belonging to this family is an inverse diffusion everywhere except at local extrema, where some stabilization is introduced. For this reason, we call these equations "stabilized inverse diffusion equations" (SIDEs). Existence and uniqueness of solutions, as well as stability, are proven for SIDEs. A SIDE in one spatial dimension may be interpreted as a limiting case of a semi-discretized Perona-Malik equation (1990, 19994). In an experiment, SIDE's are shown to suppress noise while sharpening edges present in the input signal. Their application to image segmentation is also demonstrated.     

Modulation spectroscopy study of a strained layer GaAs/GaAsP multiple quantum well structure

Using contactless electroreflectance (CER) and piezoreflectance at 300 K we have characterized a GaAs/GaAs_1?xP_x multiple quantum well (MQW) structure, “GaAs” (nominal) and GaAsP epilayers grown by chloride transport chemical vapor deposition on GaAs (001) substrates. From a detailed lineshape fit to the CER data from the epilayers we have determined the energies of the fundamental band gap and hence the phosphorous composition. The nominal “GaAs” epilayers were found to have phosphorous compositions of about 2.5–3.2%, a result of the phosphorous diffusion between growth chambers in the reactor. The GaAs_1?xP_x epilayer had x=0.29. For the GaAs_0.97P_0.03/GaAs_0.71P_0.29MQW comparison between the experimentally observed energies of a number of quantum transitions with a theoretical envelope function calculation, including the effects of strain in the barriers, made it possible to evaluate the unstrained conduction band offset parameter Q_c=0.50±0.05. Our value for this parameter is discussed in relation to other works. Atomic force microscopy was employed to investigate the surface morphology of the 230 Å GaAsP top layer of the MQW in addition to a 2000 Å GaAsP epilayer. From the absence of any cross-hatch pattern associated with misfit dislocations on the former we concluded that the GaAsP in the MQW is pseudomorphic. On the other hand the 2000 Å epilayer exhibited signs of strain relaxation.     

Challenges and solutions for recruiting pregnant smokers into a nicotine replacement therapy trial.

Improvements in smoking cessation interventions for pregnant smokers are needed. One major step is to examine the potential effectiveness of nicotine replacement therapy (NRT). The potential benefits of providing pregnant women with NRT to help them quit smoking are still unknown; early interventions to test the effectiveness and efficacy are vital to advancing the field. This paper describes recruitment efforts for a multiclinic trial to test the effectiveness of NRT use in addition to behavioral therapy in promoting cessation during pregnancy. The biggest challenge is recruiting sufficient numbers of pregnant women. This paper discusses specific obstacles for recruitment and solutions. Knowing the potential pitfalls to recruiting pregnant women into these trials can lead to better studies and thus improved outcomes.