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Formation of alkaline-earth template layers on Ge(100) for oxide heteroepitaxy: Self-organization of ordered islands and trenches

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Physical Review B 2011年第7期84卷 075330-075330页

作者： B. R. Lukanov J. W. Reiner F. J. Walker C. H. Ahn E. I. Altman Center for Research on Interface Structures and Phenomena Yale University New Haven Connecticut 06520 USA Department of Mechanical Engineering and Materials Science Yale University New Haven Connecticut 06520 USA Department of Applied Physics Yale University New Haven Connecticut 06520 USA Department of Chemical and Environmental Engineering Yale University New Haven Connecticut 06520 USA

The first step required for oxide heteroepitaxy with atomically abrupt interfaces on Si and Ge(100) is the formation of an alkaline-earth template layer. The atomic structure of this template layer on Ge(100) was characterized using scanning tunneling microscopy and electron diffraction. At elevated temperatures, Sr immediately roughens the surface; a transition that can be associated with Sr displacing Ge from the surface. With increasing Sr coverage a series of ordered (3 × 4), (3 × 2), (9 × 1), and (6 × 1) phases were observed. Transitions between these phases were accompanied by morphological changes: formation of the (3 × 4) phase smoothed surface; transition to a local (3 × 2) ordering was accompanied by trench formation; ordering of the trenches led to the (9 × 1) structure; and finally, the (6 × 1) structure was characterized by atomic rows. For both Sr and Ba, highly ordered arrays of one-dimensional islands could be produced with double-height steps preventing orthogonal domain formation. We associate the morphological transitions with strain relief of the surface phases and interactions of step ledges.

关键词： OXIDES ATOMIC structure ATOMIC theory ELECTRON diffraction QUANTUM theory

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The Influence of Biocomposite Processing and Composition on Natural Fiber Length, Dispersion and Orientation

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材料科学与工程（中英文A版） 2011年第2X期1卷 190-198页

作者： Peltola Heidi Madsen Bo Joffe Roberts Naittinen Kalle Vtt Technical Research Centre of Finland 33101 Tampere Finland Technical University of Denmark Riso National Laboratory for Sustainable Energy Materials Research Division Roskilde DK-4000 Denmark Department of Applied Physics and Mechanical Engineering Luleh University of Technology Luleh SE-97187 Sweden

In the study, the effect of process steps, melt viscosity and fiber type on the fiber length of biocomposites from triethyl citrate plasticized starch acetate and natural fibers was investigated. Composites were prepared by melt processing (compounding and injection molding). The lengths of fully processed fibers were determined by dissolving the starch acetate matrix and measuring the length of the remaining fibers by optical microscopy and image analysis. A clear reductive effect of the pelletising and melt processing on the fiber length was noticed. Also a reduction of fiber length along the increasing fiber content and the decreasing plasticizer content was detected. This reduction was originated from the increasing shear forces during compounding, which again depended on the increased viscosity of the material. When comparing the fully processed hemp and flax fibers, hemp fibers remained longer and fibrillated more than flax fibers, leading to higher aspect ratio. Thus, the reinforcement efficiency of hemp fibers by the processing was improved, on the contrary to the reduced reinforcement efficiency of flax fibers. In addition, the analysis of fiber dispersion and orientation showed a good dispersion of fibers in the matrix, and a predominant orientation of the fibers in the melt flow direction.

关键词：生物复合材料纤维长度纤维分散性熔融加工天然纤维淀粉醋酸酯组成取向

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Development of continuous wrapping tantalum barriers for internal-tin Nb3Sn multi-filamentary wires

Development of continuous wrapping tantalum barriers for int...

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2011 International Conference on applied Superconductivity and Electromagnetic Devices, ASEMD 2011

作者： Chen, Wu Ming Yavuz, Mustafa Fu, Xue Kui Kambe, Shiro McIntyre, Peter Jin, Jian Xun School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia Waterloo Institute for Nanotechnology University of Waterloo Waterloo ON N2L 3G1 Canada Cankaya University Ankara Turkey Human Sensing Program Graduate School of Science and Engineering Yamagata University 4-3-16 Johnan Yonezawa 992-8510 Japan Department of Physics Texas A and M University TX United States Center of Applied Superconductivity and Electrical Engineering University of Electronic Science and Technology of China China

ISBN: (纸本)9781424478521

A process, continuous wrapping tantalum barrier, has been developed and investigated in order to reduce the manufacturing cost. By avoiding inserting expensive tantalum tube, a long sheet barrier was directly used to wrap a prior restack. In this work, a tantalum barrier with 20 % overlap was wrapped onto sub-elements. Then 18-filament Nb3Sn plus 1 copper core restack billet was successfully drawn down and extruded into round wire as thin as a diameter of 0.84 mm. The longitudinal and cross-sectional images revealed most of barriers were continuous and intact. However, further experiments are needed to optimize the process in order to keep the all barriers continuous and intact after manufacturing. © 2011 IEEE.

关键词： Tin alloys

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WIRELESS NDE SENSOR SYSTEM FOR CONTINUOUS MONITORING

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AIP Conference Proceedings 2011年第1期1335卷 1758-1765页

作者： G. Dib L. Mhamdi T. Khan L. Udpa N. Lajnef J.‐W. Hong S. Udpa P. Ramuhalli K. Balasubramaniam aMichigan State University ECE Department East Lansing MI 48824 USA bMichigan State University CEE Department East Lansing MI 48824 USA cPacific Northwest National Laboratory Applied Physics and Materials Characterization Sciences Richland WA 99352 USA dIndian Institute of Technology Madras Department of Mechanical Engineering Chennai Tamil Nadu India 600036

For continuous monitoring of power‐plant components, the use of in‐situ sensors (i.e., sensors that are permanently mounted on the structure) is necessary. In‐situ wired sensors require an unrealistic amount of cabling for power and data transfer, which can drive up costs of installation and maintenance. In addition, the use of cabling in hostile environments (high temperature/pressure environments) is not a viable option. This paper presents a wireless system for continuous monitoring, identification of anomalous events, NDE data acquisition and data transfer. NDE sensors are integrated with a wireless radio unit such as a MICA mote. Measurements from the sensors are typically acquired at prescribed intervals, encoded and compressed, and transmitted to a central processing server, where appropriate signal processing techniques may be used to filter out noise in the measurements, enhance the desired signal and quantify the damage in terms of severity.

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Communication protocols for underwater data collection using a robotic sensor network

Communication protocols for underwater data collection using...

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IEEE Globecom Workshops

作者： Geoffrey A. Hollinger Sunav Choudhary Parastoo Qarabaqi Christopher Murphy Urbashi Mitra Gaurav S. Sukhatme Milica Stojanovic Hanumant Singh Franz Hover Computer Science Department Viterbi School of Engineering University of Southern California Los Angeles CA USA Department of Electrical Engineering Viterbi School of Engineering University of Southern California Los Angeles CA USA Department of Electrical and Computer Engineering Northeastern University Boston MA USA Deep Submergence Laboratory Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA Center for Ocean Engineering Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge MA USA

We examine the problem of collecting data from an underwater sensor network using an autonomous underwater vehicle (AUV). The sensors in the network are equipped with acoustic modems that provide noisy, range-limited communication to the AUV. One challenge in this scenario is to plan paths that maximize the information collected and minimize travel time. While executing a path, the AUV can improve performance by communicating with multiple nodes in the network at once. Such multi-node communication requires a scheduling protocol that is robust to channel variations and interference. To solve this problem, we develop and test a multiple access control protocol for the underwater data collection scenario. We perform simulated experiments that utilize a realistic model of acoustic communication taken from experimental test data. These simulations demonstrate that properly designed scheduling protocols are essential for choosing the appropriate path planning algorithms for data collection.

关键词： Protocols Robot sensing systems Path planning Acoustics Vehicles Algorithm design and analysis Probabilistic logic

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Highly sensitive temperature sensor based on the side-hole optical fiber filled with indium

Highly sensitive temperature sensor based on the side-hole o...

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European Conference on Optical Communication (ECOC)

作者： B. H. Kim S. H. Lee D. H. Son T.-J. Ahn S. Kim W.-T. Han Advanced Photonics Research Institute Gwangju Institute of Science and Technology Gwangju South Korea Graduate Program of Photonics and Applied Physics School of Information and Communications GIST Gwangju South Korea Department Photonic Engineering Chosun University Gwangju South Korea

A highly sensitive temperature sensor based on a side-hole fiber filled with indium was proposed and its optical characteristics were experimentally demonstrated. The temperature sensitivity of the sensor was estimate... 详细信息

ISBN: (纸本)9781557529312

关键词： Optical fiber sensors Optical fiber polarization Temperature sensors Indium Sensitivity

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Phonon transport and thermoelectricity in defect-engineered InAs nanowires

Phonon transport and thermoelectricity in defect-engineered ...

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2011 MRS Fall Meeting

作者： Weathers, Annie Moore, Arden L. Pettes, Michael T. Salta, Daniel Kim, Jaehyun Dick, Kimberly Samuelson, Lars Linke, Heiner Caroff, Philippe Shi, Li Department of Mechanical Engineering University of Texas at Austin Austin TX United States Material Science and Engineering Graduate Program University of Texas at Austin Austin TX United States Center for Nano and Molecular Science University of Texas at Austin Austin TX United States Division of Solid State Physics Lund University S-22100 Lund Sweden Polymer and Materials Chemistry Lund University S-22100 Lund Sweden Institut d'Electronique de Microelectronique et de Nanotechnologie UMR CNRS 8520 F-59652 Villeneuve d'Ascq France

ISBN: (纸本)9781627482219

There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the combined effects of defect planes and surface scattering on phonon transport and thermoelectric properties of defect-engineered InAs nanowires. A microfabricated device is employed to measure the thermal conductivity and thermopower of individual suspended indium arsenide nanowires grown by metal organic vapor phase epitaxy. The four-probe measurement device consists of platinum resistance thermometers and electrodes patterned on two adjacent SiNx membranes. A nanowire was suspended between the two membranes, and electrical contact between the nanowire and the platinum electrodes was made with the evaporation of a Ni/Pd film through a shadow mask. The exposed back side of the device substrate allows for characterization of the crystal structure of the suspended nanowire with transmission electron microscopy (TEM) following measurement. The 100-200 nm diameter zincblende (ZB) InAs nanowire samples were grown with randomly spaced twin defects, stacking faults, or phases boundaries perpendicular to the nanowire growth direction, as revealed by transmission electron microscopy (TEM) analysis. Compared to single-crystal ZB InAs nanowires with a similar lateral dimension, the thermal conductivity of the defect-engineered nanowires is reduced by fifty percent at room temperature. © 2012 Materials Research Society.

关键词： Nanowires

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Optical spectroscopy for quantitative sensing in human pancreatic tissues

Optical spectroscopy for quantitative sensing in human pancr...

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European Conference on Biomedical Optics, ECBO 2011

作者： Wilson, Robert H. Chandra, Malavika Lloyd, William Chen, Leng-Chun Scheiman, James Simeone, Diane McKenna, Barbara Mycek, Mary-Ann Applied Physics Program Univ. of Michigan Ann Arbor MI 48109-1040 United States Department of Biomedical Engineering Univ. of Michigan Ann Arbor MI 48109-2099 United States Department of Internal Medicine Univ. of Michigan Ann Arbor MI 48109-0362 United States Comprehensive Cancer Center Univ. of Michigan Medical School Ann Arbor MI 48109-0944 United States Department of Surgery Univ. of Michigan Ann Arbor MI 48109-5331 United States Department of Pathology Univ. of Michigan Ann Arbor MI 48109-0602 United States

ISBN: (纸本)9780819486837

Pancreatic adenocarcinoma has a five-year survival rate of only 6%, largely because current diagnostic methods cannot reliably detect the disease in its early stages. Reflectance and fluorescence spectroscopies have the potential to provide quantitative, minimally-invasive means of distinguishing pancreatic adenocarcinoma from normal pancreatic tissue and chronic pancreatitis. The first collection of wavelength-resolved reflectance and fluorescence spectra and time-resolved fluorescence decay curves from human pancreatic tissues was acquired with clinically-compatible instrumentation. Mathematical models of reflectance and fluorescence extracted parameters related to tissue morphology and biochemistry that were statistically significant for distinguishing between pancreatic tissue types. These results suggest that optical spectroscopy has the potential to detect pancreatic disease in a clinical setting. © 2011 SPIE-OSA.

关键词： Fluorescence

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Work in progress — Merging science inquiry and engineering design: A summer workshop series for middle and high school science teachers

Work in progress — Merging science inquiry and engineering ...

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Frontiers in Education (FIE) Conference

作者： Patricia Carlson Peter Hylton Michael Robinson Renee Rogge Justin Shearer Maarij Syed Deborah Walter The PRISM Program Rose-Hulamn Institute of Technology USA Mechanical Engineering Technology Indiana University Purdue University Indianapolis USA Civil and Environmental Engineering Rose-Hulamn Institute of Technology USA Applied Biology and Biomedical Engineering Rose-Hulamn Institute of Technology USA Chemistry and Biochemistry Rose-Hulamn Institute of Technology USA Physics and Optical Engineering Rose-Hulamn Institute of Technology USA Electrical and Computer Engineering Rose-Hulamn Institute of Technology USA

We report on a two-week professional development workshop for middle and high school science teachers offered as part of a three-year Indiana department of Education Math-Science Partnership grant awarded to Rose-Hulm... 详细信息

关键词： Conferences Materials Educational institutions engineering education Standards Adaptation models

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Analysis of Nanoscale Deformation in GaAs(100): Towards Patterned Growth of Quantum Dots

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MRS Online Proceedings Library (OPL) 2011年第1期864卷 E5.7-E5.7页

作者： Curtis R. Taylor Eric A. Stach Ajay P. Malshe Gregory Salamo Department of Physics Microelectronics-photonics Program University of Arkansas Fayetteville AR 72703 U.S.A email: curtis.taylor@uark.edu National Center for Electron Microscopy Materials Science Division Lawrence Berkeley National Laboratory Berkeley CA 94720 U.S.A. Department of Mechanical Engineering Microelectronics-photonics Program University of Arkansas Fayetteville AR 72703 U.S.A. email: apm2@engr.uark.edu Department of Physics University of Arkansas Fayetteville AR 72703 U.S.A. Present address: School of Materials Engineering Purdue University West Lafayette IN 47907 U.S.A.

Nanoindentations were created in the GaAs(100) surface to act as strain centers for the controlled nucleation and patterning of InAs quantum dots. A systematic approach is taken to understand the indent deformation processes that may lead to precision patterning capabilities for a broad range of nanostructures. Indents were generated using loads below 450 μN with a sharp cube corner indenter. Site-specific cross-sectional thinning of nanoindents (down to 100 nm in size) has been achieved using the in-situ ‘lift-out’ technique. This allowed for observation of subsurface deformation by transmission electron microscopy (TEM). The crystal was observed to deform solely by dislocation activity with no evidence of amorphization, twinning, fracture, or phase transformation. It is shown that the single phase deformation of GaAs can be well characterized and controlled, which should allow for exploitation of the dislocation strain field to bias nucleation of self-assembled quantum dots.

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