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Structures Used (structure + used)
Selected AbstractsSpatial prediction of river channel topography by krigingEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2008Carl J. Legleiter Abstract Topographic information is fundamental to geomorphic inquiry, and spatial prediction of bed elevation from irregular survey data is an important component of many reach-scale studies. Kriging is a geostatistical technique for obtaining these predictions along with measures of their reliability, and this paper outlines a specialized framework intended for application to river channels. Our modular approach includes an algorithm for transforming the coordinates of data and prediction locations to a channel-centered coordinate system, several different methods of representing the trend component of topographic variation and search strategies that incorporate geomorphic information to determine which survey data are used to make a prediction at a specific location. For example, a relationship between curvature and the lateral position of maximum depth can be used to include cross-sectional asymmetry in a two-dimensional trend surface model, and topographic breaklines can be used to restrict which data are retained in a local neighborhood around each prediction location. Using survey data from a restored gravel-bed river, we demonstrate how transformation to the channel-centered coordinate system facilitates interpretation of the variogram, a statistical model of reach-scale spatial structure used in kriging, and how the choice of a trend model affects the variogram of the residuals from that trend. Similarly, we show how decomposing kriging predictions into their trend and residual components can yield useful information on channel morphology. Cross-validation analyses involving different data configurations and kriging variants indicate that kriging is quite robust and that survey density is the primary control on the accuracy of bed elevation predictions. The root mean-square error of these predictions is directly proportional to the spacing between surveyed cross-sections, even in a reconfigured channel with a relatively simple morphology; sophisticated methods of spatial prediction are no substitute for field data. Copyright © 2007 John Wiley & Sons, Ltd. [source] Fluctuation analysis and accuracy of a large-scale in silico screenJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2004H. Merlitz Abstract Using a cascadic version of the stochastic tunneling method we perform an all-atom database screen over 186,000 flexible ligands of the NCI 3D database against the thymidine kinase receptor. By analyzing the errors in the binding energy we demonstrate how the cascadic technique is superior to conventional sequential docking techniques and how reliable results for the determination of the top-scoring ligands could be achieved. The substrate corresponding to the crystal structure used in the screen ranks in the upper 0.05% of the database, validating both docking methodology and the applicability of the scoring function to this substrate. Several high ranking ligands of the database display significant structural similarity with known substrates. A detailed analysis of the accuracy of the screening method is carried out, and its dependence on the flexibility of the ligand is quantified. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1568,1575, 2004 [source] Vibration and stability control of robotic manipulator systems consisting of a thin-walled beam and a spinning tip rotorJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 10 2002Ohseop Song Vibration and stability feedback control of a robotic manipulator modeled as a cantilevered thin-walled beam carrying a spinning rotor at its tip is investigated. The control is achieved via incorporation of adaptive capabilities that are provided by a system of piezoactuators, bonded or embedded into the host structure. Based on converse piezoelectric effect, the piezoactuators produce a localized strain field in response to an applied voltage, and as a result, an adaptive change of vibrational and stability response characteristics is obtained. A feedback control law relating the piezoelectrically induced bending moments at the beam tip with the appropriately selected kinematical response quantities is used, and the beneficial effects of this control methodology upon the closed-loop eigenvibration characteristics and stability boundaries are highlighted. The cantilevered structure modeled as a thin-walled beam, and built from a composite material, encompasses non-classical features, such as anisotropy, transverse shear, and secondary warping, and in this context, a special ply-angle configuration inducing a structural coupling between flapping-lagging and transverse shear is implemented. It is also shown that the directionality property of the material of the host structure used in conjunction with piezoelectric strain actuation capability, yields a dramatic enhancement of both the vibrational and stability behavior of the considered structural system. © 2002 Wiley Periodicals, Inc. [source] An empirical investigation of interviewer-related factors that discourage the use of high structure interviewsJOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 1 2004Filip Lievens High structure interviews appear to be less frequently used in personnel management practice than might be expected given their good reliability and validity. Although several authors have speculated on the factors of resistance to high structure interviews, empirical research is very scarce. Two studies are conducted among experienced human resources representatives who frequently conduct employment interviews. The first study provides a fine-grained description of the degree of structure used in interviews, showing that in most interviews constraints are placed only on the topical areas to be covered and that scoring is done only on multiple criteria. The second study tests various hypotheses regarding interviewer-related factors, which may lead to lower levels of structure in interviews. Results show that when interviewers are concerned about establishing an informal contact with interviewees, want to have discretion over interview questions, and want to develop interviews efficiently, they are less inclined to use higher levels of structure in interviews. Conversely, people who participated in interviewing workshops and Conventional types report using significantly higher levels of structure. Implications for improving interviewer motivation to use higher levels of structure in interviews are discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Silicon Microstructures: Detachment Lithography of Photosensitive Polymers: A Route to Fabricating Three-Dimensional Structures (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Mater. The scanning electron microscope image featured on the front cover shows a three-dimensional polydimethylsiloxane (PDMS) molded film bonded on a glass rod. Multilevel silicon structures used to mold the PDMS film were fabricated from successive steps of detachment lithography of photoresist films, which are patterned with lithography and reactive ion etching, as reported by J. Yeom and M. A. Shannon on page 289. The smallest feature on the pyramid is 2 µm in diameter. [source] Fabrication of Precise Fluidic Structures in LTCCINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2009Fred Barlow A number of emerging applications of low-temperature co-fired ceramic (LTCC) require embedded fluidic structure within the co-fired ceramic and or precise external dimensional tolerances. These structures enable the control of fluids for cooling, sensing, and biomedical applications, and variations in their geometry from the design can have a significant impact on the overall performance of the devices. One example of this type of application is a multilayer cooler developed recently by the authors for cooling laser diode bars. In many laser systems, laser diodes are the primary emitters, or assemblies of these diode bars are used to pump traditional laser crystals such as Nd:YLF. Assemblies of these diodes require large amounts of electrical current for proper operation, and the device operating temperature must be carefully controlled in order to avoid a shift in the output wavelength. These diodes are packaged into water-cooled assemblies and by their nature dissipate enormous amounts of heat, with waste heat fluxes on the order of 2000 W/cm2. The traditional solution to this problem has been the development of copper multilayer coolers. Assemblies of laser diodes are then formed by stacking these diode bars and coolers. Several problems exist with this approach including the erosion of the copper coolers by the coolant, a requirement for the use of deionized water within the system, and a significant CTE mismatch between the diode bar and the metal cooler. Diodes are bonded to these metal structures and liquid coolant is circulated through the metal layers in order to cool the diode bar. In contrast, the coolers developed by the authors utilize fluid channels and jets formed within LTCC as well as embedded cavity structures to control the flow of a high-velocity liquid and actively cool the laser diode bars mounted on the surface of the LTCC., The dimensional tolerances of these cooler assemblies and complex shapes that are used to control the fluid can have a significant impact on the overall performance of the laser system. This paper describes the fabrication process used to create the precise channel and jet structures used in these LTCC-based coolers, as well as some of the challenges associated with these processes. [source] Is your IT structure obsolete?JOURNAL OF CORPORATE ACCOUNTING & FINANCE, Issue 5 2008Timothy Iijima Today's big companies rely on their IT systems and networks in a huge way,and that concentrates a substantial portion of a company's risk in the IT organization. Virtually no activity within a company can now happen without major help from IT. So IT organization structure can no longer function as an afterthought,because a poorly performing IT organization creates unacceptable risk for the company. The author takes a close look at today's critical functions and roles for IT, the organization structures used, and why older IT organization models are no longer adequate. Is your firm's IT organization obsolete in today's world? © 2008 Wiley Periodicals, Inc. [source] Talairach-Based Parcellation of Neonatal Brain Magnetic Resonance Imaging Data: Validation of a New ApproachJOURNAL OF NEUROIMAGING, Issue 4 2005Haissam Haidar PhD ABSTRACT Background and Purpose. Talairach-based parcellation (TP) of human brain magnetic resonance imaging (MRI) data has been used increasingly in clinical research to make regional measurements of brain structures in vivo. Recently, TP has been applied to pediatric research to elucidate the changes in regional brain volumes related to several neurological disorders. However, all freely available tools have been designed to parcellate adult brain MRI data. Parcellation of neonatal MRI data is very challenging owing to the lack of strong signal contrast, variability in signal intensity within tissues, and the small size and thus difficulty in identifying small structures used as landmarks for TP. Hence the authors designed and validated a new interactive tool to parcellate brain MRI data from newborns and young infants. Methods. The authors' tool was developed as part of a postprocessing pipeline, which includes registration of multichannel MR images, segmentation, and parcellation of the segmented data. The tool employs user-friendly interactive software to visualize and assign the anatomic landmarks required for parcellation, after which the planes and parcels are generated automatically by the algorithm. The authors then performed 3 sets of validation experiments to test the precision and reliability of their tool. Results. Validation experiments of intra-and interrater reliability on data obtained from newborn and 1-year-old children showed a very high sensitivity of >95% and specificity >99.9%. The authors also showed that rotating and reformatting the original MRI data results in a statistically significant difference in parcel volumes, demonstrating the importance of using a tool such as theirs that does not require realignment of the data prior to parcellation. Conclusions. To the authors' knowledge, the presented approach is the first TP method that has been developed and validated specifically for neonatal brain MRI data. Their approach would also be valuable for the analysis of brain MRI data from older children and adults. [source] Prediction of the gap of electromagnetic band gap structures in a parallel-plate waveguide environmentMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010Shahrooz Shahparnia Abstract In this article the design, fabrication, and testing of several electromagnetic band gap (EBG) structures used to mitigate switching noise in high speed printed circuit boards is presented. Some features of these surfaces are considered as variables and results from different band gap prediction techniques are compared to actual fabricated parallel plate waveguides. The strength and weaknesses of these prediction techniques is shown and the power of full wave analysis to predict the band gap of these EBG structures and the limitation of simple L - C models are discussed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1792,1795, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25327 [source] A Two-Part Joint Model for the Analysis of Survival and Longitudinal Binary Data with Excess ZerosBIOMETRICS, Issue 2 2008Dimitris Rizopoulos Summary Many longitudinal studies generate both the time to some event of interest and repeated measures data. This article is motivated by a study on patients with a renal allograft, in which interest lies in the association between longitudinal proteinuria (a dichotomous variable) measurements and the time to renal graft failure. An interesting feature of the sample at hand is that nearly half of the patients were never tested positive for proteinuria (,1g/day) during follow-up, which introduces a degenerate part in the random-effects density for the longitudinal process. In this article we propose a two-part shared parameter model framework that effectively takes this feature into account, and we investigate sensitivity to the various dependence structures used to describe the association between the longitudinal measurements of proteinuria and the time to renal graft failure. [source] Oligomerization of BenM, a LysR-type transcriptional regulator: structural basis for the aggregation of proteins in this familyACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2007Sandra Haddad LysR-type transcriptional regulators comprise the largest family of homologous regulatory DNA-binding proteins in bacteria. A problematic challenge in the crystallization of LysR-type regulators stems from the insolubility and precipitation difficulties encountered with high concentrations of the full-length versions of these proteins. A general oligomerization scheme is proposed for this protein family based on the structures of the effector-binding domain of BenM in two different space groups, P4322 and C2221. These structures used the same oligomerization scheme of dimer,dimer interactions as another LysR-type regulator, CbnR, the full-length structure of which is available [Muraoka et al. (2003), J. Mol. Biol.328, 555,566]. Evaluation of packing relationships and surface features suggests that BenM can form infinite oligomeric arrays in crystals through these dimer,dimer interactions. By extrapolation to the liquid phase, such dimer,dimer interactions may contribute to the significant difficulty in crystallizing full-length members of this family. The oligomerization of dimeric units to form biologically important tetramers appears to leave unsatisfied oligomerization sites. Under conditions that favor association, such as neutral pH and concentrations appropriate for crystallization, higher order oligomerization could cause solubility problems with purified proteins. A detailed model by which BenM and other LysR-type transcriptional regulators may form these arrays is proposed. [source] | |||||||||||||||||||