Platinum Assisted Vapor–Liquid–Solid Growth of Er–Si Nanowires and Their Optical Properties

We report the optical activation of erbium coated silicon nanowires (Er–SiNWs) grown with the assist of platinum (Pt) and gold (Au), respectively. The NWs were grown on Si substrates by using a chemical vapor transport process using SiCl₄ and ErCl₄ as precursors. Pt as well as Au worked successfully as vapor–liquid–solid (VLS) catalysts for growing SiNWs with diameters of ~100 nm and length of several micrometers, respectively. The SiNWs have core–shell structures where the Er-crystalline layer is sandwiched between silica layers. Photoluminescence spectra analyses showed the optical activity of SiNWs from both Pt and Au. A stronger Er³⁺ luminescence of 1,534 nm was observed from the SiNWs with Pt at room- and low-temperature (25 K) using the 488- and/or 477-nm line of an Ar laser that may be due to the uniform incorporation of more Er ions into NWs with the exclusion of the formation of catalyst-induced deep levels in the band-gap. Pt would be used as a VLS catalyst for high performance optically active Er–SiNWs.     

Synthesis and properties of an ionic polyacetylene with norbornene moieties

New conjugated ionic polymer with the pendent norborene moieties was prepared by the activated polymerization of 2-ethynylpyridine by using 5-[(5-bromopenthoxy)methyl]-2-norborene without any additional initiator or catalyst. This polymerization proceeded well in the mild reaction condition to give a high yield of polymer (polymer yield: 90%). The chemical structure of poly{2-ethynyl-N-[(5-norborenylmethoxy)pentyl]pyridinium bromide} (PENPPB) was characterized by such instrumental methods as NMR (¹H and ¹³C), IR, UV–vis spectroscopies, and elemental analysis to have the conjugated polymer backbone bearing norbornyl moieties. The photoluminescence maximum peak of polymer was located at 519 nm, which corresponds to the photon energy of 2.39 eV. The norbornyl substituents within the polyacetylene-based polymers shifted PL maximum values because substituent size affects the molecule arrangement. The cyclovoltammograms of polymer exhibited the electrochemically stable window at ?1.6 to 2.3 V region. It was found that the kinetics of the redox process of polymer might be mainly controlled by the electron transfer process based on the experiment of the oxidation current density of polymer versus the scan rate.     

Empirical evaluation of ductility factors for the special steel moment‐resisting frames in view of soil condition

It is well known that the response modification factor (R) takes into account the ductility, over‐strength, redundancy and damping of structural systems. The ductility factor has played an important role in seismic design, as it is a key component of R. In this study, the ductility factors (R_μ,MDOF) of special steel moment‐resisting frames are calculated by multiplying the ductility factor of single degree of freedom (SDOF) systems (R_μ,SDOF) with the multi‐degree of freedom (MDOF) modification factors (R_M). The ductility factors (R_μ,SDOF) of SDOF systems are computed from non‐linear dynamic analysis undergoing different levels of displacement ductility demands and periods when subjected to a large number of recorded earthquake ground motions. To compute the R_μ,SDOF, a group of 1,860 ground motions recorded from 47 earthquakes were considered. R_M factors are proposed to account for the MDOF systems, based on previous studies. A total of 108 prototype steel frames were designed to investigate the ductility factors, considering design parameters such as the number of stories (4, 8 and 16), framing systems (perimeter frames and distributed frames), failure mechanisms (strong column‐weak beam and weak column‐strong beam), soil profiles (S_A, S_C and S_E in Uniform Building Code 1997) and seismic zone factors (Z = 0·075, 0·2, and 0·4 in UBC 1997). The effects of these design parameters on the R_μ,MDOF of special steel‐moment‐resisting frames were investigated. Copyright © 2009 John Wiley & Sons, Ltd.     

Damage detection method for large structures using static and dynamic strain data from distributed fiber optic sensor

A method for damage detection applicable to large slender steel structures such as towers of large-scale wind turbines, long-span bridges, and high-rise buildings is presented. This method is based on continuous strain data obtained by distributed fiber optic sensor (FOS) and neural network (NN) analysis. An analytical model for cracked beam based on an energy balance approach was used to train a NN. The continuous static strains and the natural frequencies obtained from the distributed FOSs were used as the input to the trained NN to estimate the crack depths and locations. An experimental study was carried out on a cracked cantilever beam to verify the present method for damage identification. The cracks were inflicted on the beam, and static and free vibration tests were performed for the intact case and the damage cases. The distributed FOSs were used to measure the continuous strains. The damage estimation was carried out for the 5 damage cases using the NN technique. It has been found that the identified crack depths and locations agree reasonably well with the inflicted cracks on the structure.     

Simulation of smoke plumes from agricultural burns: application to the San Luis/Rio Colorado airshed along the U.S./Mexico border

Vegetation fires emit a number of air pollutants, thus impacting air quality at local, regional and global scales. One such pollutant is the particulate matter (PM) that is known to trigger adverse health effects. In this study, the CALPUFF/CALMET/MM5 modeling system is employed to simulate PM(10) dispersion (PM with aerodynamic diameter less than 10 microm) from agricultural fires in the Yuma/San Luis area along the U.S./Mexico border, with the aim of investigating local and regional air quality impacts of fires. To the extent possible the data collected from and observations made in the study area were employed to infer inputs to the modeling system, but insufficient information available on burning practices and input parameters, such as the duration of fire, PM(10) emission rate and plume rise, necessitated relying on some previously published research as well as the Fire Emission Production Simulator (FEPS) model to provide necessary inputs. Under the simulated conditions the fire plumes did not disperse much, and thus mostly affected the area near the sources. The PM impact of fires on populated (receptor) areas in Yuma/San Luis was less than 15 microg/m(3), calculated on the basis of EPA-recommended 24-hr averaged PM(10). If the formation of secondary particles is considered, the impacts could have been greater. In order to conduct more realistic fire plume simulations, it is imperative to have accurate fire-activity records such as the firing technique applied, fuel condition, time of burning as well as some model updates. In all, this paper presents a methodology for calculating agricultural-burns introduced PM, while identifying critical improvements that need to be made in future work.     

Effect of steaming,freezing, and re-steaming on the texture properties of non-glutinous rice cakes

The effects of steaming time (6, 8, and 10 min), freezing storage period, and re-steaming for thawing on the textural properties of non-glutinous rice cakes (baekseolgi) were investigated. As the steaming time increased, the rice cakes softened. In particular, the sample that was steamed for 10 min showed lower hardness than those steamed for shorter periods. A short period of steaming was insufficient for water bound to the surface of the starch granules to penetrate the granules in the dough. During the re-steaming process of the frozen non-glutinous rice cake samples, the retrogradation of starch and water syneresis contributed to the increased hardness of non-glutinous rice cakes.     

Nuclear-cytoplasmic incompatibility and inefficient development of pig-mouse cytoplasmic hybrid embryos

Inter-species somatic cell nuclear transfer (iSCNT) embryos usually fail to develop to the blastocyst stage and beyond due to incomplete reprogramming of donor cell. We evaluated whether using a karyoplast that would require less extensive reprogramming such as an embryonic blastomere or the meiotic spindle from metaphase II oocytes would provide additional insight into the development of iSCNT embryos. Our results showed that karyoplasts of embryonic or oocyte origin are no different from somatic cells; all iSCNT embryos, irrespective of karyoplast origin, were arrested during early development. We hypothesized that nuclear-cytoplasmic incompatibility could be another reason for failure of embryonic development from iSCNT. We used pig-mouse cytoplasmic hybrids as a model to address nuclear-cytoplasmic incompatibility in iSCNT embryos. Fertilized murine zygotes were reconstructed by fusing with porcine cytoplasts of varying cytoplasmic volumes (1/10 (small) and 1/5 (large) total volume of mouse zygote). The presence of pig cytoplasm significantly reduced the development of mouse zygotes to the blastocyst stage compared with control embryos at 120?h post-human chorionic gondotropin (41 vs 6 vs 94%, P<0.05; 1/10, 1/5, control respectively). While mitochondrial DNA copy numbers remained relatively unchanged, expression of several important genes namely Tfam, Polg, Polg2, Mfn2, Slc2a3 (Glut3), Slc2a1 (Glut1), Bcl2, Hspb1, Pou5f1 (Oct4), Nanog, Cdx2, Gata3, Tcfap2c, mt-Cox1 and mt-Cox2 was significantly reduced in cytoplasmic hybrids compared with control embryos. These results demonstrate that the presence of even a small amount of porcine cytoplasm is detrimental to murine embryo development and suggest that a range of factors are likely to contribute to the failure of inter-species nuclear transfer embryos.     

Active wafer shape modulation using a multi-actuator chucking system

Jet and Flash Imprint Lithography has proven to be a viable alternative to optical lithography for fabrication of sub 30 nm nanostructures for large volume semiconductor manufacturing. Machine throughput, overlay and process defectivity that meet and exceed the International Technology Roadmap for Semiconductors (ITRS) are essential for commercial viability of any new lithography technology. Jet and Flash Imprint Lithography uses an inkjet head to dispense a grid of liquid drops on the wafer surface to match the volume requirements of the pattern being imprinted. Wafer shape modulation has been shown to increase imprinting speed significantly by reducing air bubble trapping in the drop interstitial sites. A wafer shape modulation chuck that can address arbitrary field locations and sizes on a wafer with a novel actuation scheme that minimizes the number of actuators while increasing imprinting speed and reducing process defects significantly is presented.     

Reliability estimation of washing machine spider assembly via classification

This paper presents a study on the reliability estimation of the spider assembly of the front loading washing machine. To achieve the analytical certification of the current design of the spider assembly of the washing machine, fatigue life test, finite element analysis, physical experimentation, and a classification processes were conducted. First, the conventional finite element analysis and fatigue life analysis were conducted and their simulation results have been validated by physical experiments in this research. The probability of failure is estimated by a classification process. Specifically, the probabilistic neural network classifier is incorporated into the simulation process to reduce the number of finite element analysis calculations while ensuring the prediction accuracy of the failure probability. Based on the estimated failure probability and other structural analysis results, the margin of the performance of the spider assembly is fully identified.     

An efficient one-step lookahead A* algorithm for PM-CT scheduling problems

In this paper, we present an improved one-step lookahead A* algorithm for the scheduling problem for parallel-mode cluster tools, where n wafer types are simultaneously processed on a cluster tool with m chambers. Specifically, we suggest a refined cost function, priority-based node selection, N-chamber cycle detection to identify deadlock situations, and a one-step lookahead method to reduce the number of unsafe states generated. Using numerical experiments, we show that the proposed algorithm leads to a significant reduction in the number of explored states and execution time necessary to find an optimal solution.