The detection of improvised nonmilitary peroxide based explosives using a titania nanotube array sensor.

PubMed

Banerjee, Subarna; Mohapatra, Susanta K; Misra, Mano; Mishra, Indu B

2009-02-18

There is a critical need to develop an efficient, reliable and highly selective sensor for the detection of improvised nonmilitary explosives. This paper describes the utilization of functionalized titania nanotube arrays for sensing improvised organic peroxide explosives such as triacetone triperoxide (TATP). TATP forms complexes with titania nanotube arrays (prepared by anodization and sensitized with zinc ions) and thus affects the electron state of the nanosensing device, which is signaled as a change in current of the overall nanotube material. The response is rapid and a signal of five to eight orders of magnitude is observed. These nanotube array sensors can be used as hand-held miniaturized devices as well as large scale portable units for military and homeland security applications.

Suppression of Higher Order Modes in an Array of Cavities Using Waveguides

NASA Astrophysics Data System (ADS)

Shashkov, Ya. V.; Sobenin, N. P.; Bazyl, D. S.; Kaminskiy, V. I.; Mitrofanov, A. A.; Zobov, M. M.

An application of additional harmonic cavities operating at multiplies of the main RF system frequency of 400 MHz is currently under discussionin the framework of the High Luminosity LHC upgrade program [1,2]. A structure consisting of two 800 MHz single cell superconducting cavities with grooved beam pipes coupled by drift tubes has been suggested for implementation. However, it is desirable to increase the number of single cells installed in one cryomodule in order to decrease the number of transitions between "warm" and "cold" parts of the collider vacuum chamber. Unfortunately, it can lead to the appearance of higher order modes (HOM) trapped between the cavities. In order to solve this problem the methods of HOM damping with rectangular waveguides connected to the drift tubes were investigated and compared. We describe the results obtained for arrays of 2, 4 and 8 cavitiesin this paper.

Wettability and Contact Time on a Biomimetic Superhydrophobic Surface.

PubMed

Liang, Yunhong; Peng, Jian; Li, Xiujuan; Huang, Jubin; Qiu, Rongxian; Zhang, Zhihui; Ren, Luquan

2017-03-02

Inspired by the array microstructure of natural superhydrophobic surfaces (lotus leaf and cicada wing), an array microstructure was successfully constructed by high speed wire electrical discharge machining (HS-WEDM) on the surfaces of a 7075 aluminum alloy without any chemical treatment. The artificial surfaces had a high apparent contact angle of 153° ± 1° with a contact angle hysteresis less than 5° and showed a good superhydrophobic property. Wettability, contact time, and the corresponding superhydrophobic mechanism of artificial superhydrophobic surface were investigated. The results indicated that the micro-scale array microstructure was an important factor for the superhydrophobic surface, while different array microstructures exhibited different effects on the wettability and contact time of the artificial superhydrophobic surface. The length ( L ), interval ( S ), and height ( H ) of the array microstructure are the main influential factors on the wettability and contact time. The order of importance of these factors is H > S > L for increasing the apparent contact angle and reducing the contact time. The method, using HS-WEDM to fabricate superhydrophobic surface, is simple, low-cost, and environmentally friendly and can easily control the wettability and contact time on the artificial surfaces by changing the array microstructure.

Wettability and Contact Time on a Biomimetic Superhydrophobic Surface

PubMed Central

Liang, Yunhong; Peng, Jian; Li, Xiujuan; Huang, Jubin; Qiu, Rongxian; Zhang, Zhihui; Ren, Luquan

2017-01-01

Inspired by the array microstructure of natural superhydrophobic surfaces (lotus leaf and cicada wing), an array microstructure was successfully constructed by high speed wire electrical discharge machining (HS-WEDM) on the surfaces of a 7075 aluminum alloy without any chemical treatment. The artificial surfaces had a high apparent contact angle of 153° ± 1° with a contact angle hysteresis less than 5° and showed a good superhydrophobic property. Wettability, contact time, and the corresponding superhydrophobic mechanism of artificial superhydrophobic surface were investigated. The results indicated that the micro-scale array microstructure was an important factor for the superhydrophobic surface, while different array microstructures exhibited different effects on the wettability and contact time of the artificial superhydrophobic surface. The length (L), interval (S), and height (H) of the array microstructure are the main influential factors on the wettability and contact time. The order of importance of these factors is H > S > L for increasing the apparent contact angle and reducing the contact time. The method, using HS-WEDM to fabricate superhydrophobic surface, is simple, low-cost, and environmentally friendly and can easily control the wettability and contact time on the artificial surfaces by changing the array microstructure. PMID:28772613

Experimental Study of Arcing on High-voltage Solar Arrays

NASA Technical Reports Server (NTRS)

Vayner, Boris; Galofaro, Joel; Ferguson, Dale

2005-01-01

The main obstacle to the implementation of a high-voltage solar array in space is arcing on the conductor-dielectric junctions exposed to the surrounding plasma. One obvious solution to this problem would be the installation of fully encapsulated solar arrays which were not having exposed conductors at all. However, there are many technological difficulties that must be overcome before the employment of fully encapsulated arrays will turn into reality. An alternative solution to raise arc threshold by modifications of conventionally designed solar arrays looks more appealing, at least in the nearest future. A comprehensive study of arc inception mechanism [1-4] suggests that such modifications can be done in the following directions: i) to insulate conductor-dielectric junction from a plasma environment (wrapthrough interconnects); ii) to change a coverglass geometry (overhang); iii) to increase a coverglass thickness; iiii) to outgas areas of conductor-dielectric junctions. The operation of high-voltage array in LEO produces also the parasitic current power drain on the electrical system. Moreover, the current collected from space plasma by solar arrays determines the spacecraft floating potential that is very important for the design of spacecraft and its scientific apparatus. In order to verify the validity of suggested modifications and to measure current collection five different solar array samples have been tested in large vacuum chamber. Each sample (36 silicon based cells) consists of three strings containing 12 cells connected in series. Thus, arc rate and current collection can be measured on every string independently, or on a whole sample when strings are connected in parallel. The heater installed in the chamber provides the possibility to test samples under temperature as high as 80 C that simulates the LEO operational temperature. The experimental setup is described below.

Experimental Study of Arcing on High-Voltage Solar Arrays

NASA Technical Reports Server (NTRS)

Vayner, Boris; Galofaro, Joel; Ferguson, Dale

2003-01-01

The main obstacle to the implementation of a high-voltage solar array in space is arcing on the conductor-dielectric junctions exposed to the surrounding plasma. One obvious solution to this problem would be the installation of fully encapsulated solar arrays which were not having exposed conductors at all. However, there are many technological difficulties that must be overcome before the employment of fully encapsulated arrays will turn into reality. An alternative solution to raise arc threshold by modifications of conventionally designed solar arrays looks more appealing, at least in the nearest future. A comprehensive study of arc inception mechanism suggests that such modifications can be done in the following directions: 1) To insulate conductor-dielectric junction from a plasma environment (wrapthrough interconnects); 2) To change a coverglass geometry (overhang); 3) To increase a coverglass thickness; 4) To outgas areas of conductor-dielectric junctions. The operation of high-voltage array in LEO produces also the parasitic current power drain on the electrical system. Moreover, the current collected from space plasma by solar arrays determines the spacecraft floating potential that is very important for the design of spacecraft and its scientific apparatus. In order to verify the validity of suggested modifications and to measure current collection five different solar array samples have been tested in a large vacuum chamber. Each sample (36 silicon based cells) consists of three strings containing 12 cells connected in series. Thus, arc rate and current collection can be measured on every string independently, or on a whole sample when strings are connected in parallel. The heater installed in the chamber provides the possibility to test samples under temperature as high as 80 C that stimulates the LEO operational temperature. The experimental setup is described below.

Engineered Metallic Nanostructures: Fabrication, Characterization, and Applications

NASA Astrophysics Data System (ADS)

Bohloul, Arash

Metallic nanostructures have garnered a great deal of attention due to their fascinating optical properties, which differ from the bulk metal. They have been proven to exceed expectations in wide variety of applications including chemical and biological sensing. Nevertheless, high-throughput and low cost nanofabrication techniques are required to implant metallic nanostructures in widespread applications. With that vision, this thesis presents a versatile and reliable method for scalable fabrication of gold nanostructures. In this approach, a plasma-treated ordered array of polystyrene nanospheres acts as an initial mask. The key step in this process is the vapor-deposition of nickel as a sacrificial mask. Thereby, gold nanostructures are directly formed on the substrate through the nickel mask. This is an easy, powerful, and straightforward method that offers several degrees of freedom to precisely control the shape and size of nanostructures. We made a library of nanostructures including gold nanocrescents, double crescents, nanorings, and nanodisks with the ability to tune the size in the range of 150 to 650 nm. The fabricated nanostructures are highly packed and uniformly cover the centimeter scale substrate. The optical properties of metallic nanostructures were extensively studied by a combination of UV-Vis-NIR and Fourier transform infrared (FTIR) spectroscopies, and correlation between optical response and geometrical parameters were investigated. In the next part of this thesis, highly sensitive surface enhanced infrared absorption (SEIRA) analysis was demonstrated on gold nanocrescent arrays. Theoretical modeling was confirmed that these substrates provide highly dense and strong hot-spots over the substrate, which is required for surface enhanced spectroscopic studies. Gold nanocrescent arrays exhibit highly tunable plasmon resonance to cover desired molecular vibrational bands. These substrates experimentally illustrated 3 orders of magnitude enhancement of IR signal over the entire substrate and up to 5 orders of magnitude enhancement on hot-spot area. Finally, we showed that fabricated substrates are completely biocompatible for growth, adhesion, and proliferation of human dermal fibroblast cells. Leveraging the capability of gold nanocrescent arrays to enhance IR signals, we developed a real time SEIRA spectroscopic technique for label-free biological cell analysis. The performance of proposed method was assessed by in situ tracking the SEIRA signal of human dermal fibroblast cells cultured on gold nanocrescent arrays.

High-energy photon spectra from a coaxial gas-puff experiment

NASA Astrophysics Data System (ADS)

Warren, S. W. R.; Degnan, J. H.; Beason, C. W.; Price, D. W.; Snell, M. P.

1987-04-01

An array of plastic scintillator/photomultiplier detectors was used to determine the high-energy (h x nu greater than 35 keV) photon spectra of a 130-kJ, 60-kV gas-injected coaxial-gun experiment. The detector array used six different filter-material/thickness combinations. High-energy photon signals were readily observed. The spectra were determined by deconvolution. The spectra have three characteristic components: radiative emission from high-Z impurities in the plasma, beam-target excited line emission, and thick-target bremsstrahlung from an electron beam generated in the plasma column. The electron beam consistent with the thick-target bremsstrahlung assumption was of the order of 100 A above 10 keV.

Fresnel Lorentz Microscopy Imaging of Domains in Fe3O4 Nanoparticle Arrays

NASA Astrophysics Data System (ADS)

Majetich, S. A.; Evarts, E. R.; Hogg, C.; Yamamoto, K.; Hirayama, T.

2009-03-01

Fresnel Lorentz microscopy was used to study the magnetic domain structures of self-assembled nanoparticle arrays as a function of temperature, from 24 to 605 C. 11 nm diameter Fe3O4 nanoparticles with an edge-to-edge spacing of 2.5 nm form magnetic domains through magnetostatic interactions alone. At room temperature stripe domains were evident in monolayer arrays. The average domain size in monolayer regions is larger than that in bilayers. Mean field theories predict a reduced stabilization energy for bilayers, relative to that for monolayers. The domain wall positions were fairly stable up to 500 C, though the contrast in the walls diminished, indicating reduced magnetic order. Above 500 C there were large temperature-dependent changes. The walls surrounding the smaller domains disappeared at lower temperatures than those of the larger domains. Some magnetic contrast was visible up to 575 C, close to the Curie temperature of Fe3O4 (585 C). Transmission electron microscopy after cooling showed that the particle shape and position in the ordered arrays had been preserved during the high temperature imaging experiments.

Efficient and scalable ionization of neutral atoms by an orderly array of gold-doped silicon nanowires

NASA Astrophysics Data System (ADS)

Bucay, Igal; Helal, Ahmed; Dunsky, David; Leviyev, Alex; Mallavarapu, Akhila; Sreenivasan, S. V.; Raizen, Mark

2017-04-01

Ionization of atoms and molecules is an important process in many applications and processes such as mass spectrometry. Ionization is typically accomplished by electron bombardment, and while it is scalable to large volumes, is also very inefficient due to the small cross section of electron-atom collisions. Photoionization methods can be highly efficient, but are not scalable due to the small ionization volume. Electric field ionization is accomplished using ultra-sharp conducting tips biased to a few kilovolts, but suffers from a low ionization volume and tip fabrication limitations. We report on our progress towards an efficient, robust, and scalable method of atomic and molecular ionization using orderly arrays of sharp, gold-doped silicon nanowires. As demonstrated in earlier work, the presence of the gold greatly enhances the ionization probability, which was attributed to an increase in available acceptor surface states. We present here a novel process used to fabricate the nanowire array, results of simulations aimed at optimizing the configuration of the array, and our progress towards demonstrating efficient and scalable ionization.

High-yield growth of vertically aligned carbon nanotubes on a continuously moving substrate.

PubMed

Guzmán de Villoria, R; Figueredo, S L; Hart, A J; Steiner, S A; Slocum, A H; Wardle, B L

2009-10-07

Vertically aligned carbon nanotube (CNT) arrays are grown on a moving substrate, demonstrating continuous growth of nanoscale materials with long-range order. A cold-wall chamber with an oscillating moving platform is used to locally heat a silicon growth substrate coated with an Fe/Al2O3 catalyst film for CNT growth via chemical vapor deposition. The reactant gases are introduced over the substrate through a directed nozzle to attain high-yield CNT growth. Aligned multi-wall carbon nanotube arrays (or 'forests') with heights of approximately 1 mm are achieved at substrate speeds up to 2.4 mm s(-1). Arrays grown on moving substrates at different velocities are studied in order to identify potential physical limitations of repeatable and fast growth on a continuous basis. No significant differences are noted between static and moving growth as characterized by scanning electron microscopy and Raman spectroscopy, although overall growth height is marginally reduced at the highest substrate velocity. CNT arrays produced on moving substrates are also found to be comparable to those produced through well-characterized batch processes consistent with a base-growth mechanism. Growth parameters required for the moving furnace are found to differ only slightly from those used in a comparable batch process; thermal uniformity appears to be the critical parameter for achieving large-area uniform array growth. If the continuous-growth technology is combined with a reaction zone isolation scheme common in other types of processing (e.g., in the manufacture of carbon fibers), large-scale dense and aligned CNT arrays may be efficiently grown and harvested for numerous applications including providing interlayers for advanced composite reinforcement and improved electrical and thermal transport.

Experimental Demonstration of Adaptive Infrared Multispectral Imaging using Plasmonic Filter Array

PubMed Central

Jang, Woo-Yong; Ku, Zahyun; Jeon, Jiyeon; Kim, Jun Oh; Lee, Sang Jun; Park, James; Noyola, Michael J.; Urbas, Augustine

2016-01-01

In our previous theoretical study, we performed target detection using a plasmonic sensor array incorporating the data-processing technique termed “algorithmic spectrometry”. We achieved the reconstruction of a target spectrum by extracting intensity at multiple wavelengths with high resolution from the image data obtained from the plasmonic array. The ultimate goal is to develop a full-scale focal plane array with a plasmonic opto-coupler in order to move towards the next generation of versatile infrared cameras. To this end, and as an intermediate step, this paper reports the experimental demonstration of adaptive multispectral imagery using fabricated plasmonic spectral filter arrays and proposed target detection scenarios. Each plasmonic filter was designed using periodic circular holes perforated through a gold layer, and an enhanced target detection strategy was proposed to refine the original spectrometry concept for spatial and spectral computation of the data measured from the plasmonic array. Both the spectrum of blackbody radiation and a metal ring object at multiple wavelengths were successfully reconstructed using the weighted superposition of plasmonic output images as specified in the proposed detection strategy. In addition, plasmonic filter arrays were theoretically tested on a target at extremely high temperature as a challenging scenario for the detection scheme. PMID:27721506

Design of hybrid two-dimensional and three-dimensional nanostructured arrays for electronic and sensing applications

NASA Astrophysics Data System (ADS)

Ko, Hyunhyub

This dissertation presents the design of organic/inorganic hybrid 2D and 3D nanostructured arrays via controlled assembly of nanoscale building blocks. Two representative nanoscale building blocks such as carbon nanotubes (one-dimension) and metal nanoparticles (zero-dimension) are the core materials for the study of solution-based assembly of nanostructured arrays. The electrical, mechanical, and optical properties of the assembled nanostructure arrays have been investigated for future device applications. We successfully demonstrated the prospective use of assembled nanostructure arrays for electronic and sensing applications by designing flexible carbon nanotube nanomembranes as mechanical sensors, highly-oriented carbon nanotubes arrays for thin-film transistors, and gold nanoparticle arrays for SERS chemical sensors. In first section, we fabricated highly ordered carbon nanotube (CNT) arrays by tilted drop-casting or dip-coating of CNT solution on silicon substrates functionalized with micropatterned self-assembled monolayers. We further exploited the electronic performance of thin-film transistors based on highly-oriented, densely packed CNT micropatterns and showed that the carrier mobility is largely improved compared to randomly oriented CNTs. The prospective use of Raman-active CNTs for potential mechanical sensors has been investigated by studying the mechano-optical properties of flexible carbon nanotube nanomembranes, which contain freely-suspended carbon nanotube array encapsulated into ultrathin (<50 nm) layer-by-layer (LbL) polymer multilayers. In second section, we fabricated 3D nano-canal arrays of porous alumina membranes decorated with gold nanoparticles for prospective SERS sensors. We showed extraordinary SERS enhancement and suggested that the high performance is associated with the combined effects of Raman-active hot spots of nanoparticle aggregates and the optical waveguide properties of nano-canals. We demonstrated the ability of this SERS substrate for trace level sensing of nitroaromatic explosives by detecting down to 100 zeptogram (˜330 molecules) of DNT.

Development of an Influenza virus protein array using Sortagging technology

PubMed Central

Sinisi, Antonia; Popp, Maximilian Wei-Lin; Antos, John M.; Pansegrau, Werner; Savino, Silvana; Nissum, Mikkel; Rappuoli, Rino; Ploegh, Hidde L.; Buti, Ludovico

2013-01-01

Protein array technology is an emerging tool that enables high throughput screening of protein-protein or protein-lipid interactions and identification of immunodominant antigens during the course of a bacterial or viral infection. In this work we developed an Influenza virus protein array using the sortase-mediated transpeptidation reaction known as “Sortagging”. LPETG-tagged Influenza virus proteins from bacterial and eukaryotic cellular extracts were immobilized at their carboxyl-termini onto a pre-activated amine-glass slide coated with a Gly3 linker. Immobilized proteins were revealed by specific antibodies and the newly generated Sortag-protein chip can be used as a device for antigen and/or antibody screening. The specificity of the Sortase A (SrtA) reaction avoids purification steps in array building and allows immobilization of proteins in an oriented fashion. Previously, this versatile technology has been successfully employed for protein labeling and protein conjugation. Here, the tool is implemented to covalently link proteins of a viral genome onto a solid support. The system could readily be scaled up to proteins of larger genomes in order to develop protein arrays for high throughput screening. PMID:22594688

Spectral and angular characteristics of dielectric resonator metasurface at optical frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Longfang; Department of Electrical and Electronic Engineering, The University of Bristol, Bristol, BS8 1TH; López-García, Martin

2014-11-10

The capability of manipulating light at subwavelength scale has fostered the applications of flat metasurfaces in various fields. Compared to metallic structure, metasurfaces made of high permittivity low-loss dielectric resonators hold the promise of high efficiency by avoiding high conductive losses of metals at optical frequencies. This letter investigates the spectral and angular characteristics of a dielectric resonator metasurface composed of periodic sub-arrays of resonators with a linearly varying phase response. The far-field response of the metasurface can be decomposed into the response of a single grating element (sub-array) and the grating arrangement response. The analysis also reveals that couplingmore » between resonators has a non-negligible impact on the angular response. Over a wide wavelength range, the simulated and measured angular characteristics of the metasurface provide a definite illustration of how different grating diffraction orders can be selectively suppressed or enhanced through antenna sub-array design.« less

Wafer-scale high-throughput ordered arrays of Si and coaxial Si/Si(1-x)Ge(x) wires: fabrication, characterization, and photovoltaic application.

PubMed

Pan, Caofeng; Luo, Zhixiang; Xu, Chen; Luo, Jun; Liang, Renrong; Zhu, Guang; Wu, Wenzhuo; Guo, Wenxi; Yan, Xingxu; Xu, Jun; Wang, Zhong Lin; Zhu, Jing

2011-08-23

We have developed a method combining lithography and catalytic etching to fabricate large-area (uniform coverage over an entire 5-in. wafer) arrays of vertically aligned single-crystal Si nanowires with high throughput. Coaxial n-Si/p-SiGe wire arrays are also fabricated by further coating single-crystal epitaxial SiGe layers on the Si wires using ultrahigh vacuum chemical vapor deposition (UHVCVD). This method allows precise control over the diameter, length, density, spacing, orientation, shape, pattern and location of the Si and Si/SiGe nanowire arrays, making it possible to fabricate an array of devices based on rationally designed nanowire arrays. A proposed fabrication mechanism of the etching process is presented. Inspired by the excellent antireflection properties of the Si/SiGe wire arrays, we built solar cells based on the arrays of these wires containing radial junctions, an example of which exhibits an open circuit voltage (V(oc)) of 650 mV, a short-circuit current density (J(sc)) of 8.38 mA/cm(2), a fill factor of 0.60, and an energy conversion efficiency (η) of 3.26%. Such a p-n radial structure will have a great potential application for cost-efficient photovoltaic (PV) solar energy conversion. © 2011 American Chemical Society

Active terahertz imaging with Ne indicator lamp detector arrays

NASA Astrophysics Data System (ADS)

Kopeika, N. S.; Abramovich, A.; Yadid-Pecht, O.; Yitzhaky, Y.

2009-08-01

The advantages of terahertz (THz) imaging are well known. They penetrate well most non-conducting media and there are no known biological hazards, This makes such imaging systems important for homeland security, as they can be used to image concealed objects and often into rooms or buildings from the outside. There are also biomedical applications that are arising. Unfortunately, THz imaging is quite expensive, especially for real time systems, largely because of the price of the detector. Bolometers and pyroelectric detectors can each easily cost at least hundreds of dollars if not more, thus making focal plane arrays of them quite expensive. We have found that common miniature commercial neon indicator lamps costing typically about 30 cents each exhibit high sensitivity to THz radiation [1-3], with microsecond order rise times, thus making them excellent candidates for such focal plane arrays. NEP is on the order of 10-10 W/Hz1/2. Significant improvement of detection performance is expected when heterodyne detection is used Efforts are being made to develop focal plane array imagers using such devices at 300 GHz. Indeed, preliminary images using 4x4 arrays have already been obtained. An 8x8 VLSI board has been developed and is presently being tested. Since no similar imaging systems have been developed previously, there are many new problems to be solved with such a novel and unconventional imaging system. These devices act as square law detectors, with detected signal proportional to THz power. This allows them to act as mixers in heterodyne detection, thus allowing NEP to be reduced further by almost two orders of magnitude. Plans are to expand the arrays to larger sizes, and to employ super resolution techniques to improve image quality beyond that ordinarily obtainable at THz frequencies.

A Large Signal Model for CMUT Arrays with Arbitrary Membrane Geometries Operating in Non-Collapsed Mode

PubMed Central

Satir, Sarp; Zahorian, Jaime; Degertekin, F. Levent

2014-01-01

A large signal, transient model has been developed to predict the output characteristics of a CMUT array operated in the non-collapse mode. The model is based on separation of the nonlinear electrostatic voltage-to-force relation and the linear acoustic array response. For linear acoustic radiation and crosstalk effects, the boundary element method is used. The stiffness matrix in the vibroacoustics calculations is obtained using static finite element analysis of a single membrane which can have arbitrary geometry and boundary conditions. A lumped modeling approach is used to reduce the order of the system for modeling the transient nonlinear electrostatic actuation. To accurately capture the dynamics of the non-uniform electrostatic force distribution over the CMUT electrode during large deflections, the membrane electrode is divided into patches shaped to match higher order membrane modes, each introducing a variable to the system model. This reduced order nonlinear lumped model is solved in the time domain using Simulink. The model has two linear blocks to calculate the displacement profile of the electrode patches and the output pressure for a given force distribution over the array, respectively. The force to array displacement block uses the linear acoustic model, and the Rayleigh integral is evaluated to calculate the pressure at any field point. Using the model, the transient transmitted pressure can be simulated for different large signal drive signal configurations. The acoustic model is verified by comparison to harmonic FEA in vacuum and fluid for high and low aspect ratio membranes as well as mass-loaded membranes. The overall Simulink model is verified by comparison to transient 3D FEA and experimental results for different large drive signals; and an example for a phased array simulation is given. PMID:24158297

Thermal Conduction in Vertically Aligned Copper Nanowire Arrays and Composites.

PubMed

Barako, Michael T; Roy-Panzer, Shilpi; English, Timothy S; Kodama, Takashi; Asheghi, Mehdi; Kenny, Thomas W; Goodson, Kenneth E

2015-09-02

The ability to efficiently and reliably transfer heat between sources and sinks is often a bottleneck in the thermal management of modern energy conversion technologies ranging from microelectronics to thermoelectric power generation. These interfaces contribute parasitic thermal resistances that reduce device performance and are subjected to thermomechanical stresses that degrade device lifetime. Dense arrays of vertically aligned metal nanowires (NWs) offer the unique combination of thermal conductance from the constituent metal and mechanical compliance from the high aspect ratio geometry to increase interfacial heat transfer and device reliability. In the present work, we synthesize copper NW arrays directly onto substrates via templated electrodeposition and extend this technique through the use of a sacrificial overplating layer to achieve improved uniformity. Furthermore, we infiltrate the array with an organic phase change material and demonstrate the preservation of thermal properties. We use the 3ω method to measure the axial thermal conductivity of freestanding copper NW arrays to be as high as 70 W m(-1) K(-1), which is more than an order of magnitude larger than most commercial interface materials and enhanced-conductivity nanocomposites reported in the literature. These arrays are highly anisotropic, and the lateral thermal conductivity is found to be only 1-2 W m(-1) K(-1). We use these measured properties to elucidate the governing array-scale transport mechanisms, which include the effects of morphology and energy carrier scattering from size effects and grain boundaries.

Voltage noise of current-driven vortices in disordered Josephson junction arrays.

PubMed

He, G L; Zhao, Z G; Liu, S; Yang, Y H; Liu, M; Xing, D Y

2006-08-16

Dynamical phenomena of moving vortices and voltage noise spectra are studied in disordered Josephson junction arrays (JJAs). The plastic motion of vortices, smectic flow, and moving Bragg glass phases are separated by two dynamic melting transitions driven by current. From the voltage noise spectra of moving vortices, it is found that the driving current plays an important role in the melting of pinning vortices glass and ordering of moving vortices. The features of noise spectra obtained in the disordered JJA model have been observed recently in the high-temperature superconductor Bi(2)Sr(2)CaCu(2)O(y) near the first-order melting transition, indicating that both of them are related to each other.

The application of sparse arrays in high frequency transcranial focused ultrasound therapy: A simulation study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pajek, Daniel, E-mail: dpajek@sri.utoronto.ca; Hynynen, Kullervo

2013-12-15

Purpose: Transcranial focused ultrasound is an emerging therapeutic modality that can be used to perform noninvasive neurosurgical procedures. The current clinical transcranial phased array operates at 650 kHz, however the development of a higher frequency array would enable more precision, while reducing the risk of standing waves. However, the smaller wavelength and the skull's increased distortion at this frequency are problematic. It would require an order of magnitude more elements to create such an array. Random sparse arrays enable steering of a therapeutic array with fewer elements. However, the tradeoffs inherent in the use of sparsity in a transcranial phasedmore » array have not been systematically investigated and so the objective of this simulation study is to investigate the effect of sparsity on transcranial arrays at a frequency of 1.5 MHz that provides small focal spots for precise exposure control. Methods: Transcranial sonication simulations were conducted using a multilayer Rayleigh-Sommerfeld propagation model. Element size and element population were varied and the phased array's ability to steer was assessed. Results: The focal pressures decreased proportionally as elements were removed. However, off-focus hotspots were generated if a high degree of steering was attempted with very sparse arrays. A phased array consisting of 1588 elements 3 mm in size, a 10% population, was appropriate for steering up to 4 cm in all directions. However, a higher element population would be required if near-skull sonication is desired. Conclusions: This study demonstrated that the development of a sparse, hemispherical array at 1.5 MHz could enable more precision in therapies that utilize lower intensity sonications.« less

A Compressed Sensing Based Method for Reducing the Sampling Time of A High Resolution Pressure Sensor Array System

PubMed Central

Sun, Chenglu; Li, Wei; Chen, Wei

2017-01-01

For extracting the pressure distribution image and respiratory waveform unobtrusively and comfortably, we proposed a smart mat which utilized a flexible pressure sensor array, printed electrodes and novel soft seven-layer structure to monitor those physiological information. However, in order to obtain high-resolution pressure distribution and more accurate respiratory waveform, it needs more time to acquire the pressure signal of all the pressure sensors embedded in the smart mat. In order to reduce the sampling time while keeping the same resolution and accuracy, a novel method based on compressed sensing (CS) theory was proposed. By utilizing the CS based method, 40% of the sampling time can be decreased by means of acquiring nearly one-third of original sampling points. Then several experiments were carried out to validate the performance of the CS based method. While less than one-third of original sampling points were measured, the correlation degree coefficient between reconstructed respiratory waveform and original waveform can achieve 0.9078, and the accuracy of the respiratory rate (RR) extracted from the reconstructed respiratory waveform can reach 95.54%. The experimental results demonstrated that the novel method can fit the high resolution smart mat system and be a viable option for reducing the sampling time of the pressure sensor array. PMID:28796188

GMR biosensor arrays: a system perspective.

PubMed

Hall, D A; Gaster, R S; Lin, T; Osterfeld, S J; Han, S; Murmann, B; Wang, S X

2010-05-15

Giant magnetoresistive biosensors are becoming more prevalent for sensitive, quantifiable biomolecular detection. However, in order for magnetic biosensing to become competitive with current optical protein microarray technology, there is a need to increase the number of sensors while maintaining the high sensitivity and fast readout time characteristic of smaller arrays (1-8 sensors). In this paper, we present a circuit architecture scalable for larger sensor arrays (64 individually addressable sensors) while maintaining a high readout rate (scanning the entire array in less than 4s). The system utilizes both time domain multiplexing and frequency domain multiplexing in order to achieve this scan rate. For the implementation, we propose a new circuit architecture that does not use a classical Wheatstone bridge to measure the small change in resistance of the sensor. Instead, an architecture designed around a transimpedance amplifier is employed. A detailed analysis of this architecture including the noise, distortion, and potential sources of errors is presented, followed by a global optimization strategy for the entire system comprising the magnetic tags, sensors, and interface electronics. To demonstrate the sensitivity, quantifiable detection of two blindly spiked samples of unknown concentrations has been performed at concentrations below the limit of detection for the enzyme-linked immunosorbent assay. Lastly, the multiplexing capability and reproducibility of the system was demonstrated by simultaneously monitoring sensors functionalized with three unique proteins at different concentrations in real-time. 2010 Elsevier B.V. All rights reserved.

GMR Biosensor Arrays: A System Perspective

PubMed Central

Hall, D. A.; Gaster, R. S.; Lin, T.; Osterfeld, S. J.; Han, S.; Murmann, B.; Wang, S. X.

2010-01-01

Giant magnetoresistive biosensors are becoming more prevalent for sensitive, quantifiable biomolecular detection. However, in order for magnetic biosensing to become competitive with current optical protein microarray technology, there is a need to increase the number of sensors while maintaining the high sensitivity and fast readout time characteristic of smaller arrays (1 – 8 sensors). In this paper, we present a circuit architecture scalable for larger sensor arrays (64 individually addressable sensors) while maintaining a high readout rate (scanning the entire array in less than 4 seconds). The system utilizes both time domain multiplexing and frequency domain multiplexing in order to achieve this scan rate. For the implementation, we propose a new circuit architecture that does not use a classical Wheatstone bridge to measure the small change in resistance of the sensor. Instead, an architecture designed around a transimpedance amplifier is employed. A detailed analysis of this architecture including the noise, distortion, and potential sources of errors is presented, followed by a global optimization strategy for the entire system comprising the magnetic tags, sensors, and interface electronics. To demonstrate the sensitivity, quantifiable detection of two blindly spiked samples of unknown concentrations has been performed at concentrations below the limit of detection for the enzyme-linked immunosorbent assay. Lastly, the multipexability and reproducibility of the system was demonstrated by simultaneously monitoring sensors functionalized with three unique proteins at different concentrations in real-time. PMID:20207130

Unique Three-Dimensional InP Nanopore Arrays for Improved Photoelectrochemical Hydrogen Production.

PubMed

Li, Qiang; Zheng, Maojun; Ma, Liguo; Zhong, Miao; Zhu, Changqing; Zhang, Bin; Wang, Faze; Song, Jingnan; Ma, Li; Shen, Wenzhong

2016-08-31

Ordered three-dimensional (3D) nanostructure arrays hold promise for high-performance energy harvesting and storage devices. Here, we report the fabrication of InP nanopore arrays (NPs) in unique 3D architectures with excellent light trapping characteristic and large surface areas for use as highly active photoelectrodes in photoelectrochemical (PEC) hydrogen evolution devices. The ordered 3D NPs were scalably synthesized by a facile two-step etching process of (1) anodic etching of InP in neutral 3 M NaCl electrolytes to realize nanoporous structures and (2) wet chemical etching in HCl/H3PO4 (volume ratio of 1:3) solutions for removing the remaining top irregular layer. Importantly, we demonstrated that the use of neutral electrolyte of NaCl instead of other solutions, such as HCl, in anodic etching of InP can significantly passivate the surface states of 3D NPs. As a result, the maximum photoconversion efficiency obtained with ∼15.7 μm thick 3D NPs was 0.95%, which was 7.3 and 1.4 times higher than that of planar and 2D NPs. Electrochemical impedance spectroscopy and photoluminescence analyses further clarified that the improved PEC performance was attributed to the enhanced charge transfer across 3D NPs/electrolyte interfaces, the improved charge separation at 3D NPs/electrolyte junction, and the increased PEC active surface areas with our unique 3D NP arrays.

Functionalized vertical GaN micro pillar arrays with high signal-to-background ratio for detection and analysis of proteins secreted from breast tumor cells.

PubMed

Choi, Mun-Ki; Kim, Gil-Sung; Jeong, Jin-Tak; Lim, Jung-Taek; Lee, Won-Yong; Umar, Ahmad; Lee, Sang-Kwon

2017-11-02

The detection of cancer biomarkers has recently attracted significant attention as a means of determining the correct course of treatment with targeted therapeutics. However, because the concentration of these biomarkers in blood is usually relatively low, highly sensitive biosensors for fluorescence imaging and precise detection are needed. In this study, we have successfully developed vertical GaN micropillar (MP) based biosensors for fluorescence sensing and quantitative measurement of CA15-3 antigens. The highly ordered vertical GaN MP arrays result in the successful immobilization of CA15-3 antigens on each feature of the arrays, thereby allowing the detection of an individual fluorescence signal from the top surface of the arrays owing to the high regularity of fluorophore-tagged MP spots and relatively low background signal. Therefore, our fluorescence-labeled and CA15-3 functionalized vertical GaN-MP-based biosensor is suitable for the selective quantitative analysis of secreted CA15-3 antigens from MCF-7 cell lines, and helps in the early diagnosis and prognosis of serious diseases as well as the monitoring of the therapeutic response of breast cancer patients.

Fast and robust control of nanopositioning systems: Performance limits enabled by field programmable analog arrays.

PubMed

Baranwal, Mayank; Gorugantu, Ram S; Salapaka, Srinivasa M

2015-08-01

This paper aims at control design and its implementation for robust high-bandwidth precision (nanoscale) positioning systems. Even though modern model-based control theoretic designs for robust broadband high-resolution positioning have enabled orders of magnitude improvement in performance over existing model independent designs, their scope is severely limited by the inefficacies of digital implementation of the control designs. High-order control laws that result from model-based designs typically have to be approximated with reduced-order systems to facilitate digital implementation. Digital systems, even those that have very high sampling frequencies, provide low effective control bandwidth when implementing high-order systems. In this context, field programmable analog arrays (FPAAs) provide a good alternative to the use of digital-logic based processors since they enable very high implementation speeds, moreover with cheaper resources. The superior flexibility of digital systems in terms of the implementable mathematical and logical functions does not give significant edge over FPAAs when implementing linear dynamic control laws. In this paper, we pose the control design objectives for positioning systems in different configurations as optimal control problems and demonstrate significant improvements in performance when the resulting control laws are applied using FPAAs as opposed to their digital counterparts. An improvement of over 200% in positioning bandwidth is achieved over an earlier digital signal processor (DSP) based implementation for the same system and same control design, even when for the DSP-based system, the sampling frequency is about 100 times the desired positioning bandwidth.

Isotropic-resolution linear-array-based photoacoustic computed tomography through inverse Radon transform

NASA Astrophysics Data System (ADS)

Li, Guo; Xia, Jun; Li, Lei; Wang, Lidai; Wang, Lihong V.

2015-03-01

Linear transducer arrays are readily available for ultrasonic detection in photoacoustic computed tomography. They offer low cost, hand-held convenience, and conventional ultrasonic imaging. However, the elevational resolution of linear transducer arrays, which is usually determined by the weak focus of the cylindrical acoustic lens, is about one order of magnitude worse than the in-plane axial and lateral spatial resolutions. Therefore, conventional linear scanning along the elevational direction cannot provide high-quality three-dimensional photoacoustic images due to the anisotropic spatial resolutions. Here we propose an innovative method to achieve isotropic resolutions for three-dimensional photoacoustic images through combined linear and rotational scanning. In each scan step, we first elevationally scan the linear transducer array, and then rotate the linear transducer array along its center in small steps, and scan again until 180 degrees have been covered. To reconstruct isotropic three-dimensional images from the multiple-directional scanning dataset, we use the standard inverse Radon transform originating from X-ray CT. We acquired a three-dimensional microsphere phantom image through the inverse Radon transform method and compared it with a single-elevational-scan three-dimensional image. The comparison shows that our method improves the elevational resolution by up to one order of magnitude, approaching the in-plane lateral-direction resolution. In vivo rat images were also acquired.

Phased-array sources based on nonlinear metamaterial nanocavities

PubMed Central

Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P.; Liu, Sheng; Luk, Ting S.; Kadlec, Emil A.; Shaner, Eric A.; Klem, John F.; Sinclair, Michael B.; Brener, Igal

2015-01-01

Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum. PMID:26126879

Tracking and Navigation of Future NASA Spacecraft with the Square Kilometer Array

NASA Astrophysics Data System (ADS)

Resch, G. M.; Jones, D. L.; Connally, M. J.; Weinreb, S.; Preston, R. A.

2001-12-01

The international radio astronomy community is currently working on the design of an array of small radio antennas with a total collecting area of one square kilometer - more than a hundred times that of the largest existing (100-m) steerable antennas. An array of this size would provide obvious advantages for high data rate telemetry reception and for spacecraft navigation. Among these advantages are a two-orders-of-magnitude increase in sensitivity for telemetry downlink, flexible sub-arraying to track multiple spacecraft simultaneously, increased reliability through the use of large numbers of identical array elements, very accurate real-time angular spacecraft tracking, and a dramatic reduction in cost per unit area. NASA missions in many disciplines, including planetary science, would benefit from this increased ground-based tracking capability. The science return from planned missions could be increased, and opportunities for less expensive or completely new kinds of missions would be created.

Performance of ethanol electro-oxidation on Ni-Cu alloy nanowires through composition modulation.

PubMed

Tian, Xi-Ke; Zhao, Xiao-Yu; Zhang, Li-de; Yang, Chao; Pi, Zhen-Bang; Zhang, Su-Xin

2008-05-28

To reduce the cost of the catalyst for direct ethanol fuel cells and improve its catalytic activity, highly ordered Ni-Cu alloy nanowire arrays have been fabricated successfully by differential pulse current electro-deposition into the pores of a porous anodic alumina membrane (AAMs). The energy dispersion spectrum, scanning and transmission electron microscopy were utilized to characterize the composition and morphology of the Ni-Cu alloy nanowire arrays. The results reveal that the nanowires in the array are uniform, well isolated and parallel to each other. The catalytic activity of the nanowire electrode arrays for ethanol oxidation was tested and the binary alloy nanowire array possesses good catalytic activity for the electro-oxidation of ethanol. The performance of ethanol electro-oxidation was controlled by varying the Cu content in the Ni-Cu alloy and the Ni-Cu alloy nanowire electrode shows much better stability than the pure Ni one.

A titania nanotube-array room-temperature sensor for selective detection of hydrogen at low concentrations.

PubMed

Varghese, Oomman K; Mor, Gopal K; Grimes, Craig A; Paulose, Maggie; Mukherjee, Niloy

2004-09-01

A tremendous variation in electrical resistance, from the semiconductor to metallic range, has been observed in titania nanotube arrays at room temperature, approximately 25 degrees C, in the presence of < or = 1000 ppm hydrogen gas. The nanotube arrays are fabricated by anodizing titanium foil in an aqueous electrolyte solution containing hydrofluoric acid and acetic acid. Subsequently, the arrays are coated with a 10 nm layer of palladium by evaporation. Electrical contacts are made by sputtering a 2 mm diameter platinum disk atop the Pd-coated nanotube array. These sensors exhibit a resistance variation of the order of 10(4) in the presence of 100 ppm hydrogen at 25 degrees C. The sensors demonstrate complete reversibility, repeatability, high selectivity, negligible drift and wide dynamic range. The nanoscale geometry of the nanotubes, in particular the points of tube-to-tube contact, is believed to be responsible for the outstanding hydrogen gas sensitivities.

Enhanced electrochemical performance of orientated VO2(B) raft-like nanobelt arrays through direct lithiation for lithium ion batteries.

PubMed

Liu, Liang; Liu, Qiang; Zhao, Wen; Li, Guochun; Wang, Limei; Shi, Weidong; Chen, Long

2017-02-10

Lithiation modification of VO 2 (B) has been carried out by a facile hydrothermal process, and the compact and locally ordered VO 2 (B) raft-like nanobelt arrays have been prepared. The synthesis route provides a new approach to elaborate a VO 2 (B) nanostructure under a mild environment condition. It is found that the growth mechanism of VO 2 (B) raft-like nanobelt arrays is different from the traditional nucleation-growth process. A novel chemical lithiating-exfoliating-splitting model is proposed. Compared with the bulk counterpart, the lithiated VO 2 (B) raft-like nanobelt arrays as cathodes exhibit a higher discharge capacity and an enhanced high-rate performance owing to their increased structural anisotropy and decreased polarization. This work indicates that VO 2 (B) raft-like nanobelt arrays have great potential applications as cathode materials for lithium ion batteries.

Enhanced electrochemical performance of orientated VO2(B) raft-like nanobelt arrays through direct lithiation for lithium ion batteries

NASA Astrophysics Data System (ADS)

Liu, Liang; Liu, Qiang; Zhao, Wen; Li, Guochun; Wang, Limei; Shi, Weidong; Chen, Long

2017-02-01

Lithiation modification of VO2(B) has been carried out by a facile hydrothermal process, and the compact and locally ordered VO2(B) raft-like nanobelt arrays have been prepared. The synthesis route provides a new approach to elaborate a VO2(B) nanostructure under a mild environment condition. It is found that the growth mechanism of VO2(B) raft-like nanobelt arrays is different from the traditional nucleation-growth process. A novel chemical lithiating-exfoliating-splitting model is proposed. Compared with the bulk counterpart, the lithiated VO2(B) raft-like nanobelt arrays as cathodes exhibit a higher discharge capacity and an enhanced high-rate performance owing to their increased structural anisotropy and decreased polarization. This work indicates that VO2(B) raft-like nanobelt arrays have great potential applications as cathode materials for lithium ion batteries.

Integrated arrays of air-dielectric graphene transistors as transparent active-matrix pressure sensors for wide pressure ranges.

PubMed

Shin, Sung-Ho; Ji, Sangyoon; Choi, Seiho; Pyo, Kyoung-Hee; Wan An, Byeong; Park, Jihun; Kim, Joohee; Kim, Ju-Young; Lee, Ki-Suk; Kwon, Soon-Yong; Heo, Jaeyeong; Park, Byong-Guk; Park, Jang-Ung

2017-03-31

Integrated electronic circuitries with pressure sensors have been extensively researched as a key component for emerging electronics applications such as electronic skins and health-monitoring devices. Although existing pressure sensors display high sensitivities, they can only be used for specific purposes due to the narrow range of detectable pressure (under tens of kPa) and the difficulty of forming highly integrated arrays. However, it is essential to develop tactile pressure sensors with a wide pressure range in order to use them for diverse application areas including medical diagnosis, robotics or automotive electronics. Here we report an unconventional approach for fabricating fully integrated active-matrix arrays of pressure-sensitive graphene transistors with air-dielectric layers simply formed by folding two opposing panels. Furthermore, this realizes a wide tactile pressure sensing range from 250 Pa to ∼3 MPa. Additionally, fabrication of pressure sensor arrays and transparent pressure sensors are demonstrated, suggesting their substantial promise as next-generation electronics.

Integrated arrays of air-dielectric graphene transistors as transparent active-matrix pressure sensors for wide pressure ranges

NASA Astrophysics Data System (ADS)

Shin, Sung-Ho; Ji, Sangyoon; Choi, Seiho; Pyo, Kyoung-Hee; Wan An, Byeong; Park, Jihun; Kim, Joohee; Kim, Ju-Young; Lee, Ki-Suk; Kwon, Soon-Yong; Heo, Jaeyeong; Park, Byong-Guk; Park, Jang-Ung

2017-03-01

Integrated electronic circuitries with pressure sensors have been extensively researched as a key component for emerging electronics applications such as electronic skins and health-monitoring devices. Although existing pressure sensors display high sensitivities, they can only be used for specific purposes due to the narrow range of detectable pressure (under tens of kPa) and the difficulty of forming highly integrated arrays. However, it is essential to develop tactile pressure sensors with a wide pressure range in order to use them for diverse application areas including medical diagnosis, robotics or automotive electronics. Here we report an unconventional approach for fabricating fully integrated active-matrix arrays of pressure-sensitive graphene transistors with air-dielectric layers simply formed by folding two opposing panels. Furthermore, this realizes a wide tactile pressure sensing range from 250 Pa to ~3 MPa. Additionally, fabrication of pressure sensor arrays and transparent pressure sensors are demonstrated, suggesting their substantial promise as next-generation electronics.

Antennas for mobile satellite communications

NASA Technical Reports Server (NTRS)

Huang, John

1991-01-01

A NASA sponsored program, called the Mobile Satellite (MSAT) system, has prompted the development of several innovative antennas at L-band frequencies. In the space segment of the MSAT system, an efficient, light weight, circularly polarized microstrip array that uses linearly polarized elements was developed as a multiple beam reflector feed system. In the ground segment, a low-cost, low-profile, and very efficient microstrip Yagi array was developed as a medium-gain mechanically steered vehicle antenna. Circularly shaped microstrip patches excited at higher-order modes were also developed as low-gain vehicle antennas. A more recent effort called for the development of a 20/30 GHz mobile terminal antenna for future-generation mobile satellite communications. To combat the high insertion loss encountered at 20/30 GHz, series-fed Monolithic Microwave Integrated Circuit (MMIC) microstrip array antennas are currently being developed. These MMIC arrays may lead to the development of several small but high-gain Ka-band antennas for the Personal Access Satellite Service planned for the 2000s.

Building biochips: a protein production pipeline

NASA Astrophysics Data System (ADS)

de Carvalho-Kavanagh, Marianne G. S.; Albala, Joanna S.

2004-06-01

Protein arrays are emerging as a practical format in which to study proteins in high-throughput using many of the same techniques as that of the DNA microarray. The key advantage to array-based methods for protein study is the potential for parallel analysis of thousands of samples in an automated, high-throughput fashion. Building protein arrays capable of this analysis capacity requires a robust expression and purification system capable of generating hundreds to thousands of purified recombinant proteins. We have developed a method to utilize LLNL-I.M.A.G.E. cDNAs to generate recombinant protein libraries using a baculovirus-insect cell expression system. We have used this strategy to produce proteins for analysis of protein/DNA and protein/protein interactions using protein microarrays in order to understand the complex interactions of proteins involved in homologous recombination and DNA repair. Using protein array techniques, a novel interaction between the DNA repair protein, Rad51B, and histones has been identified.

Integrated arrays of air-dielectric graphene transistors as transparent active-matrix pressure sensors for wide pressure ranges

PubMed Central

Shin, Sung-Ho; Ji, Sangyoon; Choi, Seiho; Pyo, Kyoung-Hee; Wan An, Byeong; Park, Jihun; Kim, Joohee; Kim, Ju-Young; Lee, Ki-Suk; Kwon, Soon-Yong; Heo, Jaeyeong; Park, Byong-Guk; Park, Jang-Ung

2017-01-01

Integrated electronic circuitries with pressure sensors have been extensively researched as a key component for emerging electronics applications such as electronic skins and health-monitoring devices. Although existing pressure sensors display high sensitivities, they can only be used for specific purposes due to the narrow range of detectable pressure (under tens of kPa) and the difficulty of forming highly integrated arrays. However, it is essential to develop tactile pressure sensors with a wide pressure range in order to use them for diverse application areas including medical diagnosis, robotics or automotive electronics. Here we report an unconventional approach for fabricating fully integrated active-matrix arrays of pressure-sensitive graphene transistors with air-dielectric layers simply formed by folding two opposing panels. Furthermore, this realizes a wide tactile pressure sensing range from 250 Pa to ∼3 MPa. Additionally, fabrication of pressure sensor arrays and transparent pressure sensors are demonstrated, suggesting their substantial promise as next-generation electronics. PMID:28361867

Shape-coded silica nanotubes for multiplexed bioassay: rapid and reliable magnetic decoding protocols

PubMed Central

He, Bo; Kim, Sung Kyoung; Son, Sang Jun; Lee, Sang Bok

2010-01-01

Aims The recent development of 1D barcode arrays has proved their capabilities to be applicable to highly multiplexed bioassays. This article introduces two magnetic decoding protocols for suspension arrays of shape-coded silica nanotubes to process multiplexed assays rapidly and easily, which will benefit the minimization and automation of the arrays. Methods In the first protocol, the magnetic nanocrystals are incorporated into the inner voids of barcoded silica nanotubes in order to give the nanotubes magnetic properties. The second protocol is performed by trapping the barcoded silica nanotubes onto streptavidin-modified magnetic beads. Results The rapid and easy decoding process was demonstrated by applying the above two protocols to multiplexed assays, resulting in high selectivity. Furthermore, the magnetic bead-trapped barcode nanotubes provided a great opportunity to exclude the use of dye molecules in multiplexed assays by using barcode nanotubes as signals. Conclusion The rapid and easy manipulation of encoded carriers using magnetic properties could be used to develop promising suspension arrays for portable bioassays. PMID:20025466

Simulation of non-linear acoustic field and thermal pattern of phased-array high-intensity focused ultrasound (HIFU).

PubMed

Wang, Mingjun; Zhou, Yufeng

2016-08-01

HIFU becomes an effective and non-invasive modality of solid tumour/cancer ablation. Simulation of the non-linear acoustic wave propagation using a phased-array transducer in multiple layered media using different focusing strategies and the consequent lesion formation are essential in HIFU planning in order to enhance the efficacy and efficiency of treatment. An angular spectrum approach with marching fractional steps was applied in the wave propagation from phased-array HIFU transducer, and diffraction, attenuation, and non-linearity effects were accounted for by a second-order operator splitting scheme. The simulated distributions of the first three harmonics along and transverse to the transducer axis were compared to the hydrophone measurements. The bioheat equation was used to simulate the subsequent temperature elevation using the deposited acoustic energy, and lesion formation was determined by the thermal dose. Better agreement was found between the measured harmonics distribution and simulation using the proposed algorithm than the Khokhlov-Zabozotskaya-Kuznetsov equation. Variable focusing of the phased-array transducer (geometric focusing, transverse shifting and the generation of multiple foci) can be simulated successfully. The shifting and splitting of focus was found to result in significantly less temperature elevation at the focus and the subsequently, the smaller lesion size, but the larger grating lobe grating lobe in the pre-focal region. The proposed algorithm could simulate the non-linear wave propagation from the source with arbitrary shape and distribution of excitation through multiple tissue layers in high computation accuracy. The performance of phased-array HIFU can be optimised in the treatment planning.

ASIC Readout Circuit Architecture for Large Geiger Photodiode Arrays

NASA Technical Reports Server (NTRS)

Vasile, Stefan; Lipson, Jerold

2012-01-01

The objective of this work was to develop a new class of readout integrated circuit (ROIC) arrays to be operated with Geiger avalanche photodiode (GPD) arrays, by integrating multiple functions at the pixel level (smart-pixel or active pixel technology) in 250-nm CMOS (complementary metal oxide semiconductor) processes. In order to pack a maximum of functions within a minimum pixel size, the ROIC array is a full, custom application-specific integrated circuit (ASIC) design using a mixed-signal CMOS process with compact primitive layout cells. The ROIC array was processed to allow assembly in bump-bonding technology with photon-counting infrared detector arrays into 3-D imaging cameras (LADAR). The ROIC architecture was designed to work with either common- anode Si GPD arrays or common-cathode InGaAs GPD arrays. The current ROIC pixel design is hardwired prior to processing one of the two GPD array configurations, and it has the provision to allow soft reconfiguration to either array (to be implemented into the next ROIC array generation). The ROIC pixel architecture implements the Geiger avalanche quenching, bias, reset, and time to digital conversion (TDC) functions in full-digital design, and uses time domain over-sampling (vernier) to allow high temporal resolution at low clock rates, increased data yield, and improved utilization of the laser beam.

A 400 KHz line rate 2048-pixel stitched SWIR linear array

NASA Astrophysics Data System (ADS)

Anchlia, Ankur; Vinella, Rosa M.; Gielen, Daphne; Wouters, Kristof; Vervenne, Vincent; Hooylaerts, Peter; Deroo, Pieter; Ruythooren, Wouter; De Gaspari, Danny; Das, Jo; Merken, Patrick

2016-05-01

Xenics has developed a family of stitched SWIR long linear arrays that operate up to 400 KHz of line rate. These arrays serve medical and industrial applications that require high line rates as well as space applications that require long linear arrays. The arrays are based on a modular ROIC design concept: modules of 512 pixels are stitched during fabrication to achieve 512, 1024 and 2048 pixel arrays. Each 512-pixel module has its own on-chip digital sequencer, analog readout chain and 4 output buffers. This modular concept enables a long array to run at a high line rates irrespective of the array length, which limits the line rate in a traditional linear array. The ROIC is flip-chipped with InGaAs detector arrays. The FPA has a pixel pitch of 12.5μm and has two pixel flavors: square (12.5μm) and rectangular (250μm). The frontend circuit is based on Capacitive Trans-impedance Amplifier (CTIA) to attain stable detector bias, and good linearity and signal integrity, especially at high speeds. The CTIA has an input auto-zero mechanism that allows to have low detector bias (<20mV). An on-chip Correlated Double Sample (CDS) facilitates removal of CTIA KTC and 1/f noise, and other offsets, achieving low noise performance. There are five gain modes in the FPA giving the full well range from 85Ke- to 40Me-. The measured input referred noise is 35e-rms in the highest gain mode. The FPA operates in Integrate While Read mode and, at a master clock rate of 60MHz and a minimum integration time of 1.4μs, achieves the highest line rate of 400 KHz. In this paper, design details and measurements results are presented in order to demonstrate the array performance.

Zonal wavefront sensor with reduced number of rows in the detector array.

PubMed

Boruah, Bosanta R; Das, Abhijit

2011-07-10

In this paper, we describe a zonal wavefront sensor in which the photodetector array can have a smaller number of rows. The test wavefront is incident on a two-dimensional array of diffraction gratings followed by a single focusing lens. The periodicity and the orientation of the grating rulings of each grating can be chosen such that the +1 order beam from the gratings forms an array of focal spots in the detector plane. We show that by using a square array of zones, it is possible to generate an array of +1 order focal spots having a smaller number of rows, thus reducing the height of the required detector array. The phase profile of the test wavefront can be estimated by measuring the displacements of the +1 order focal spots for the test wavefront relative to the +1 order focal spots for a plane reference wavefront. The narrower width of the photodetector array can offer several advantages, such as a faster frame rate of the wavefront sensor, a reduced amount of cross talk between the nearby detector zones, and a decrease in the maximum thermal noise. We also present experimental results of a proof-of-concept experimental arrangement using the proposed wavefront sensing scheme. © 2011 Optical Society of America

Achieving ultra-high temperatures with a resistive emitter array

NASA Astrophysics Data System (ADS)

Danielson, Tom; Franks, Greg; Holmes, Nicholas; LaVeigne, Joe; Matis, Greg; McHugh, Steve; Norton, Dennis; Vengel, Tony; Lannon, John; Goodwin, Scott

2016-05-01

The rapid development of very-large format infrared detector arrays has challenged the IR scene projector community to also develop larger-format infrared emitter arrays to support the testing of systems incorporating these detectors. In addition to larger formats, many scene projector users require much higher simulated temperatures than can be generated with current technology in order to fully evaluate the performance of their systems and associated processing algorithms. Under the Ultra High Temperature (UHT) development program, Santa Barbara Infrared Inc. (SBIR) is developing a new infrared scene projector architecture capable of producing both very large format (>1024 x 1024) resistive emitter arrays and improved emitter pixel technology capable of simulating very high apparent temperatures. During earlier phases of the program, SBIR demonstrated materials with MWIR apparent temperatures in excess of 1400 K. New emitter materials have subsequently been selected to produce pixels that achieve even higher apparent temperatures. Test results from pixels fabricated using the new material set will be presented and discussed. A 'scalable' Read In Integrated Circuit (RIIC) is also being developed under the same UHT program to drive the high temperature pixels. This RIIC will utilize through-silicon via (TSV) and Quilt Packaging (QP) technologies to allow seamless tiling of multiple chips to fabricate very large arrays, and thus overcome the yield limitations inherent in large-scale integrated circuits. Results of design verification testing of the completed RIIC will be presented and discussed.

Battery Charge Equalizer with Transformer Array

NASA Technical Reports Server (NTRS)

Davies, Francis

2013-01-01

High-power batteries generally consist of a series connection of many cells or cell banks. In order to maintain high performance over battery life, it is desirable to keep the state of charge of all the cell banks equal. A method provides individual charging for battery cells in a large, high-voltage battery array with a minimum number of transformers while maintaining reasonable efficiency. This is designed to augment a simple highcurrent charger that supplies the main charge energy. The innovation will form part of a larger battery charge system. It consists of a transformer array connected to the battery array through rectification and filtering circuits. The transformer array is connected to a drive circuit and a timing and control circuit that allow individual battery cells or cell banks to be charged. The timing circuit and control circuit connect to a charge controller that uses battery instrumentation to determine which battery bank to charge. It is important to note that the innovation can charge an individual cell bank at the same time that the main battery charger is charging the high-voltage battery. The fact that the battery cell banks are at a non-zero voltage, and that they are all at similar voltages, can be used to allow charging of individual cell banks. A set of transformers can be connected with secondary windings in series to make weighted sums of the voltages on the primaries.

A C++11 implementation of arbitrary-rank tensors for high-performance computing

NASA Astrophysics Data System (ADS)

Aragón, Alejandro M.

2014-06-01

This article discusses an efficient implementation of tensors of arbitrary rank by using some of the idioms introduced by the recently published C++ ISO Standard (C++11). With the aims at providing a basic building block for high-performance computing, a single Array class template is carefully crafted, from which vectors, matrices, and even higher-order tensors can be created. An expression template facility is also built around the array class template to provide convenient mathematical syntax. As a result, by using templates, an extra high-level layer is added to the C++ language when dealing with algebraic objects and their operations, without compromising performance. The implementation is tested running on both CPU and GPU.

A C++11 implementation of arbitrary-rank tensors for high-performance computing

NASA Astrophysics Data System (ADS)

Aragón, Alejandro M.

2014-11-01

This article discusses an efficient implementation of tensors of arbitrary rank by using some of the idioms introduced by the recently published C++ ISO Standard (C++11). With the aims at providing a basic building block for high-performance computing, a single Array class template is carefully crafted, from which vectors, matrices, and even higher-order tensors can be created. An expression template facility is also built around the array class template to provide convenient mathematical syntax. As a result, by using templates, an extra high-level layer is added to the C++ language when dealing with algebraic objects and their operations, without compromising performance. The implementation is tested running on both CPU and GPU.

Creation of Frustrated Systems by d-dot Array

NASA Astrophysics Data System (ADS)

Masahiko, Machida

2004-03-01

When a square shape dot of High-Tc superconductor is embedded in s-wave superconducting matrix, half quantized vortices are spontaneously generated at the corners of the dot. This feature gives the magnetic interactions between neighboring dots in array systems composed of sevaral dots of High-Tc superconductor and allows us to make magnetic interaction systems. We propose that we can create interesting frustrated systems like the spin-ice by setting the dots in various manners. In order to demonstrate which types of frustrated systems are possible, we perform numerical simulations for the time-dependent Ginzburg-Landau equation describing dynamics of the superconducting order parameters with d-wave and s-wave symmetries. The simulations reveal that the proposed system has two parameters originated from the magnetic interaction between emerged half vortices. We tune the parameters and show various patterns of half vortices from the Ising to the ice model.

Programmable assembly of nanoarchitectures using genetically engineered viruses.

PubMed

Huang, Yu; Chiang, Chung-Yi; Lee, Soo Kwan; Gao, Yan; Hu, Evelyn L; De Yoreo, James; Belcher, Angela M

2005-07-01

Biological systems possess inherent molecular recognition and self-assembly capabilities and are attractive templates for constructing complex material structures with molecular precision. Here we report the assembly of various nanoachitectures including nanoparticle arrays, hetero-nanoparticle architectures, and nanowires utilizing highly engineered M13 bacteriophage as templates. The genome of M13 phage can be rationally engineered to produce viral particles with distinct substrate-specific peptides expressed on the filamentous capsid and the ends, providing a generic template for programmable assembly of complex nanostructures. Phage clones with gold-binding motifs on the capsid and streptavidin-binding motifs at one end are created and used to assemble Au and CdSe nanocrytals into ordered one-dimensional arrays and more complex geometries. Initial studies show such nanoparticle arrays can further function as templates to nucleate highly conductive nanowires that are important for addressing/interconnecting individual nanostructures.

Templated dewetting: designing entirely self-organized platforms for photocatalysis.

PubMed

Altomare, Marco; Nguyen, Nhat Truong; Schmuki, Patrik

2016-12-01

Formation and dispersion of metal nanoparticles on oxide surfaces in site-specific or even arrayed configuration are key in various technological processes such as catalysis, photonics, electrochemistry and for fabricating electrodes, sensors, memory devices, and magnetic, optical, and plasmonic platforms. A crucial aspect towards an efficient performance of many of these metal/metal oxide arrangements is a reliable fabrication approach. Since the early works on graphoepitaxy in the 70s, solid state dewetting of metal films on patterned surfaces has been much explored and regarded as a most effective tool to form defined arrays of ordered metal particles on a desired substrate. While templated dewetting has been studied in detail, particularly from a mechanistic perspective on lithographically patterned Si surfaces, the resulting outstanding potential of its applications on metal oxide semiconductors, such as titania, has received only limited attention. In this perspective we illustrate how dewetting and particularly templated dewetting can be used to fabricate highly efficient metal/TiO 2 photocatalyst assemblies e.g. for green hydrogen evolution. A remarkable advantage is that the synthesis of such photocatalysts is completely based on self-ordering principles: anodic self-organized TiO 2 nanotube arrays that self-align to a highest degree of hexagonal ordering are an ideal topographical substrate for a second self-ordering process, that is, templated-dewetting of sputter-deposited metal thin films. The controllable metal/semiconductor coupling delivers intriguing features and functionalities. We review concepts inherent to dewetting and particularly templated dewetting, and outline a series of effective tools that can be synergistically interlaced to reach fine control with nanoscopic precision over the resulting metal/TiO 2 structures (in terms of e.g. high ordering, size distribution, site specific placement, alloy formation) to maximize their photocatalytic efficiency. These processes are easy to scale up and have a high throughput and great potential to be applied to fabricate not only (photo)catalytic materials but also a large palette of other functional nanostructured elements and devices.

Templated dewetting: designing entirely self-organized platforms for photocatalysis

PubMed Central

Altomare, Marco; Nguyen, Nhat Truong

2016-01-01

Formation and dispersion of metal nanoparticles on oxide surfaces in site-specific or even arrayed configuration are key in various technological processes such as catalysis, photonics, electrochemistry and for fabricating electrodes, sensors, memory devices, and magnetic, optical, and plasmonic platforms. A crucial aspect towards an efficient performance of many of these metal/metal oxide arrangements is a reliable fabrication approach. Since the early works on graphoepitaxy in the 70s, solid state dewetting of metal films on patterned surfaces has been much explored and regarded as a most effective tool to form defined arrays of ordered metal particles on a desired substrate. While templated dewetting has been studied in detail, particularly from a mechanistic perspective on lithographically patterned Si surfaces, the resulting outstanding potential of its applications on metal oxide semiconductors, such as titania, has received only limited attention. In this perspective we illustrate how dewetting and particularly templated dewetting can be used to fabricate highly efficient metal/TiO2 photocatalyst assemblies e.g. for green hydrogen evolution. A remarkable advantage is that the synthesis of such photocatalysts is completely based on self-ordering principles: anodic self-organized TiO2 nanotube arrays that self-align to a highest degree of hexagonal ordering are an ideal topographical substrate for a second self-ordering process, that is, templated-dewetting of sputter-deposited metal thin films. The controllable metal/semiconductor coupling delivers intriguing features and functionalities. We review concepts inherent to dewetting and particularly templated dewetting, and outline a series of effective tools that can be synergistically interlaced to reach fine control with nanoscopic precision over the resulting metal/TiO2 structures (in terms of e.g. high ordering, size distribution, site specific placement, alloy formation) to maximize their photocatalytic efficiency. These processes are easy to scale up and have a high throughput and great potential to be applied to fabricate not only (photo)catalytic materials but also a large palette of other functional nanostructured elements and devices. PMID:28567258

Nanostructure array plasmas generated by femtosecond pulses at highly relativistic intensities

NASA Astrophysics Data System (ADS)

Hollinger, R. C.; Wong, Y.; Wong, S.; Rockwood, A.; Glasby, J.; Shlyaptsev, V.; Rocca, J. J.; Capeluto, M. G.; Kaymak, V.; Pukhov, A.

2017-10-01

The irradiation of high aspect ratio ordered nanostructure arrays with ultra-high contrast femtosecond laser pulses of relativistic intensity provides a unique combination of nearly complete optical absorption and drastically enhanced light penetration into near-solid density targets. This allows the material to be volumetrically heated deep into the ultra-high energy density regime. In previous experiments we have shown that irradiation of Ni and Au nanostructures with femtosecond pulses focused to an intensity of 5x1018 Wcm-2 generate multi-KeV near solid density plasmas in which atoms are ionized to the Ni+26 and Au+52 charge states. Here we present the first results of the irradiation of nanostructure arrays with highly relativistic pulses of intensities up to 5x1021Wcm-2. Silver and Rhodium nanowire arrays were irradiated with frequency-doubled pulses of 30 fs duration from a petawatt-class Ti:Sa laser. Time integrated x-ray spectra show the presence of He-like and Li-like emission. Results of experiments conducted with a variety of different nanowires diameters with a range of interwire spacings will be presented and compared to the result of 3D particle-in-cell-simulations. This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy.

Fabrication of ordered metallic glass nanotube arrays for label-free biosensing with diffractive reflectance.

PubMed

Chen, Wei-Ting; Li, Shao-Sian; Chu, Jinn P; Feng, Kuei Chih; Chen, Jem-Kun

2018-04-15

In this study, a photoresist template with well-defined contact hole array was fabricated, to which radio frequency magnetron sputtering process was then applied to deposit an alloyed Zr 55 Cu 30 Al 10 Ni 5 target, and finally resulted in ordered metallic glass nanotube (MGNT) arrays after removal of the photoresist template. The thickness of the MGNT walls increased from 98 to 126nm upon increasing the deposition time from 225 to 675s. The wall thickness of the MGNT arrays also increased while the dimensions of MGNT reduced under the same deposition condition. The MGNT could be filled with biomacromolecules to change the effective refractive index. The air fraction of the medium layer were evaluated through static water contact angle measurements and, thereby, the effective refractive indices the transverse magnetic (TM) and transverse electric (TE) polarized modes were calculated. A standard biotin-streptavidin affinity model was tested using the MGNT arrays and the fundamental response of the system was investigated. Results show that filling the MGNT with streptavidin altered the effective refractive index of the layer, the angle of reflectance and color changes identified by an L*a*b* color space and color circle on an a*b* chromaticity diagram. The limit of detection (LOD) of the MGNT arrays for detection of streptavidin was estimated as 25nM, with a detection time of 10min. Thus, the MGNT arrays may be used as a versatile platform for high-sensitive label-free optical biosensing. Copyright © 2017 Elsevier B.V. All rights reserved.

The use of integrated focal plane array technologies in laser microsatellite networks

NASA Astrophysics Data System (ADS)

Arnon, Shlomi

2004-10-01

Clustering micro satellites in cooperative fly formation constellations leads to high-performance space systems. The only way to achieve high-speed communication between the satellites is by a laser beam with a narrow divergence angle. In order to make the communication successful three types of focal plane detector arrays are required in the communication terminal: acquisition, tracking and communication detector arrays. The acquisition detector array is used to acquire the neighbor satellite using a wide field-of-view telescope. The tracking detector provides fast, real time and accurate direction location of the neighbor satellite. Based on the information from the acquisition and tracking detectors the receiver and transmitter maintain line of sight. The development of large, fast and very sensitive focal plane detector arrays makes it possible to implement the acquisition, tracking and communication with only one focal plane detector array. By doing so it is possible to reduce dramatically the size, weight, and cost of the optics and electronics which leads to lightweight communication terminals. As a result, the satellites are smaller and lighter, which reduces the space mission cost and increases the booster efficiency. In this paper we will present an overview of the concept of integrated focal plane arrays for laser satellite communication. We also present simulation results based on real system parameters and compare different implementation options.

FIR Detector Sensitivity, Dynamic Range, and Multiplexing Requirements for the Origins Space Telescope (OST)

NASA Astrophysics Data System (ADS)

Staguhn, Johannes G.

2018-05-01

Spectroscopic, cold, space-based mid-to-far-infrared (FIR) missions, such as the Origins Space Telescope, will require large (tens of kilopixels), ultra-sensitive FIR detector arrays with sufficient dynamic range and high-density multiplexing schemes for the readout, in order to optimize the scientific return while staying within a realistic cost range. Issues like power consumption of multiplexers and their readout are significantly more important for space missions than they are for ground-based or suborbital applications. In terms of the detectors and their configuration into large arrays, significant development efforts are needed even for both of the most mature candidate superconducting detector technologies, namely transition edge sensors and (microwave) kinetic inductance detectors. Here we explore both practical and fundamental limits for those technologies in order to lay out a realistic path forward for both technologies. We conclude that beyond the need to enhance the detector sensitivities and pixel numbers by about an order of magnitude over currently existing devices, improved concepts for larger dynamic range and multiplexing density will be needed in order to optimize the scientific return of future cold FIR space missions. Background-limited, very high spectral resolution instruments will require photon-counting detectors.

Opportunistic Beamforming with Wireless Powered 1-bit Feedback Through Rectenna Array

NASA Astrophysics Data System (ADS)

Krikidis, Ioannis

2015-11-01

This letter deals with the opportunistic beamforming (OBF) scheme for multi-antenna downlink with spatial randomness. In contrast to conventional OBF, the terminals return only 1-bit feedback, which is powered by wireless power transfer through a rectenna array. We study two fundamental topologies for the combination of the rectenna elements; the direct-current combiner and the radio-frequency combiner. The beam outage probability is derived in closed form for both combination schemes, by using high order statistics and stochastic geometry.

Generation of Hermite-Gaussian modes and vortex arrays based on two-dimensional gain distribution controlled microchip laser.

PubMed

Kong, Weipeng; Sugita, Atsushi; Taira, Takunori

2012-07-01

We have demonstrated high-order Hermite-Gaussian (HG) mode generation based on 2D gain distribution control edge-pumped, composite all-ceramic Yb:YAG/YAG microchip lasers using a V-type cavity. Several hundred milliwatts to several watts HG(mn) modes are achieved. We also generated different kinds of vortex arrays directly from the oscillator with the same power level. In addition, a more than 7 W doughnut-shape mode can be generated in the same cavity.

Simulated and Real Sheet-of-Light 3D Object Scanning Using a-Si:H Thin Film PSD Arrays.

PubMed

Contreras, Javier; Tornero, Josep; Ferreira, Isabel; Martins, Rodrigo; Gomes, Luis; Fortunato, Elvira

2015-11-30

A MATLAB/SIMULINK software simulation model (structure and component blocks) has been constructed in order to view and analyze the potential of the PSD (Position Sensitive Detector) array concept technology before it is further expanded or developed. This simulation allows changing most of its parameters, such as the number of elements in the PSD array, the direction of vision, the viewing/scanning angle, the object rotation, translation, sample/scan/simulation time, etc. In addition, results show for the first time the possibility of scanning an object in 3D when using an a-Si:H thin film 128 PSD array sensor and hardware/software system. Moreover, this sensor technology is able to perform these scans and render 3D objects at high speeds and high resolutions when using a sheet-of-light laser within a triangulation platform. As shown by the simulation, a substantial enhancement in 3D object profile image quality and realism can be achieved by increasing the number of elements of the PSD array sensor as well as by achieving an optimal position response from the sensor since clearly the definition of the 3D object profile depends on the correct and accurate position response of each detector as well as on the size of the PSD array.

Hybrid nanostructures of well-organized arrays of colloidal quantum dots and a self-assembled monolayer of gold nanoparticles for enhanced fluorescence

NASA Astrophysics Data System (ADS)

Liu, Xiaoying; McBride, Sean P.; Jaeger, Heinrich M.; Nealey, Paul F.

2016-07-01

Hybrid nanomaterials comprised of well-organized arrays of colloidal semiconductor quantum dots (QDs) in close proximity to metal nanoparticles (NPs) represent an appealing system for high-performance, spectrum-tunable photon sources with controlled photoluminescence. Experimental realization of such materials requires well-defined QD arrays and precisely controlled QD-metal interspacing. This long-standing challenge is tackled through a strategy that synergistically combines lateral confinement and vertical stacking. Lithographically generated nanoscale patterns with tailored surface chemistry confine the QDs into well-organized arrays with high selectivity through chemical pattern directed assembly, while subsequent coating with a monolayer of close-packed Au NPs introduces the plasmonic component for fluorescence enhancement. The results show uniform fluorescence emission in large-area ordered arrays for the fabricated QD structures and demonstrate five-fold fluorescence amplification for red, yellow, and green QDs in the presence of the Au NP monolayer. Encapsulation of QDs with a silica shell is shown to extend the design space for reliable QD/metal coupling with stronger enhancement of 11 times through the tuning of QD-metal spatial separation. This approach provides new opportunities for designing hybrid nanomaterials with tailored array structures and multiple functionalities for applications such as multiplexed optical coding, color display, and quantum transduction.

Cobalt selenide hollow nanorods array with exceptionally high electrocatalytic activity for high-efficiency quasi-solid-state dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Jin, Zhitong; Zhang, Meirong; Wang, Min; Feng, Chuanqi; Wang, Zhong-Sheng

2018-02-01

In quasi-solid-state dye-sensitized solar cells (QSDSSCs), electron transport through a random network of catalyst in the counter electrode (CE) and electrolyte diffusion therein are limited by the grain boundaries of catalyst particles, thus diminishing the electrocatalytic performance of CE and the corresponding photovoltaic performance of QSDSSCs. We demonstrate herein an ordered Co0.85Se hollow nanorods array film as the Pt-free CE of QSDSSCs. The Co0.85Se hollow nanorods array displays excellent electrocatalytic activity for the reduction of I3- in the quasi-solid-state electrolyte with extremely low charge transfer resistance at the CE/electrolyte interface, and the diffusion of redox species within the Co0.85Se hollow nanorods array CE is pretty fast. The QSDSSC device with the Co0.85Se hollow nanorods array CE produces much higher photovoltaic conversion efficiency (8.35%) than that (4.94%) with the Co0.85Se randomly packed nanorods CE, against the control device with the Pt CE (7.75%). Moreover, the QSDSSC device based on the Co0.85Se hollow nanorods array CE presents good long-term stability with only 4% drop of power conversion efficiency after 1086 h one-sun soaking.

3.4-Inch Quarter High Definition Flexible Active Matrix Organic Light Emitting Display with Oxide Thin Film Transistor

NASA Astrophysics Data System (ADS)

Hatano, Kaoru; Chida, Akihiro; Okano, Tatsuya; Sugisawa, Nozomu; Inoue, Tatsunori; Seo, Satoshi; Suzuki, Kunihiko; Oikawa, Yoshiaki; Miyake, Hiroyuki; Koyama, Jun; Yamazaki, Shunpei; Eguchi, Shingo; Katayama, Masahiro; Sakakura, Masayuki

2011-03-01

In this paper, we report a 3.4-in. flexible active matrix organic light emitting display (AMOLED) display with remarkably high definition (quarter high definition: QHD) in which oxide thin film transistors (TFTs) are used. We have developed a transfer technology in which a TFT array formed on a glass substrate is separated from the substrate by physical force and then attached to a flexible plastic substrate. Unlike a normal process in which a TFT array is directly fabricated on a thin plastic substrate, our transfer technology permits a high integration of high performance TFTs, such as low-temperature polycrystalline silicon TFTs (LTPS TFTs) and oxide TFTs, on a plastic substrate, because a flat, rigid, and thermally-stable glass substrate can be used in the TFT fabrication process in our transfer technology. As a result, this technology realized an oxide TFT array for an AMOLED on a plastic substrate. Furthermore, in order to achieve a high-definition AMOLED, color filters were incorporated in the TFT array and a white organic light-emitting diode (OLED) was combined. One of the features of this device is that the whole body of the device can be bent freely because a source driver and a gate driver can be integrated on the substrate due to the high mobility of an oxide TFT. This feature means “true” flexibility.

Efficient Photocatalytic H2 Evolution: Controlled Dewetting-Dealloying to Fabricate Site-Selective High-Activity Nanoporous Au Particles on Highly Ordered TiO2 Nanotube Arrays.

PubMed

Nguyen, Nhat Truong; Altomare, Marco; Yoo, JeongEun; Schmuki, Patrik

2015-05-27

Anodic self-organized TiO2 nanostumps are formed and exploited for self-ordering dewetting of Au-Ag sputtered films. This forms ordered particle configurations at the tube top (crown position) or bottom (ground position). By dealloying from a minimal amount of noble metal, porous Au nanoparticles are then formed, which, when in the crown position, allow for a drastically improved photocatalytic H2 production compared with nanoparticles produced by conventional dewetting processes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High intensity click statistics from a 10 × 10 avalanche photodiode array

NASA Astrophysics Data System (ADS)

Kröger, Johannes; Ahrens, Thomas; Sperling, Jan; Vogel, Werner; Stolz, Heinrich; Hage, Boris

2017-11-01

Photon-number measurements are a fundamental technique for the discrimination and characterization of quantum states of light. Beyond the abilities of state-of-the-art devices, we present measurements with an array of 100 avalanche photodiodes exposed to photon-numbers ranging from well below to significantly above one photon per diode. Despite each single diode only discriminating between zero and non-zero photon-numbers we were able to extract a second order moment, which acts as a nonclassicality indicator. We demonstrate a vast enhancement of the applicable intensity range by two orders of magnitude relative to the standard application of such devices. It turns out that the probabilistic mapping of arbitrary photon-numbers on a finite number of registered clicks is not per se a disadvantage compared with true photon counters. Such detector arrays can bridge the gap between single-photon and linear detection, by investigation of the click statistics, without the necessity of photon statistics reconstruction.

Massively parallel processor computer

NASA Technical Reports Server (NTRS)

Fung, L. W. (Inventor)

1983-01-01

An apparatus for processing multidimensional data with strong spatial characteristics, such as raw image data, characterized by a large number of parallel data streams in an ordered array is described. It comprises a large number (e.g., 16,384 in a 128 x 128 array) of parallel processing elements operating simultaneously and independently on single bit slices of a corresponding array of incoming data streams under control of a single set of instructions. Each of the processing elements comprises a bidirectional data bus in communication with a register for storing single bit slices together with a random access memory unit and associated circuitry, including a binary counter/shift register device, for performing logical and arithmetical computations on the bit slices, and an I/O unit for interfacing the bidirectional data bus with the data stream source. The massively parallel processor architecture enables very high speed processing of large amounts of ordered parallel data, including spatial translation by shifting or sliding of bits vertically or horizontally to neighboring processing elements.

Superconducting Detector Arrays for Astrophysics

NASA Technical Reports Server (NTRS)

Chervenak, James

2008-01-01

The next generation of astrophysics instruments will feature an order of magnitude more photon sensors or sensors that have an order of magnitude greater sensitivity. Since detector noise scales with temperature, a number of candidate technologies have been developed that use the intrinsic advantages of detector systems that operate below 1 Kelvin. Many of these systems employ of the superconducting phenomena that occur in metals at these temperatures to build ultrasensitive detectors and low-noise, low-power readout architectures. I will present one such system in use today to meet the needs of the astrophysics community at millimeter and x-ray wavelengths. Our group at NASA in collaboration with Princeton, NIST, Boulder and a number of other groups is building large format arrays of superconducting transition edge sensors (TES) read out with multiplexed superconducting quantum interference devices (SQUID). I will present the high sensitivity we have achieved in multiplexed x-ray sensors with the TES technology and describe the construction of a 1000-sensor TES/SQUID array for microwave measurements. With our collaboration's deployment of a kilopixel TES array for 2 mm radiation at the Atacarna Cosmology Telescope in November 2007, we have first images of the lensed Cosmic Microwave Background at fine angular scales.

Fabrication of Highly Ordered and Well-Aligned PbTiO 3/TiN Core–Shell Nanotube Arrays

DOE PAGES

Yoon, Jaesung; Kim, Sangjoon; Kim, Dongjin; ...

2015-04-30

Highly ordered and well-aligned PbTiO 3/TiN core–shell nanotubes are fabricated in this paper via an anodic aluminum oxide templating route followed by TiN and TiO 2 atomic layer deposition deposition and a subsequent PbO vapor reaction. Finally, PbTiO 3/TiN nanotubes keep their original shape after the vapor phase reaction, and they display well-defined piezoresponse hysteresis curves with remnant piezoresponse of 38 pm V -1.

Highly ordered gold nanotubes using thiols at a cleavable block copolymer interface.

PubMed

Ryu, Ja-Hyoung; Park, Soojin; Kim, Bokyung; Klaikherd, Akamol; Russell, Thomas P; Thayumanavan, S

2009-07-29

We have prepared functionalized nanoporous thin films from a polystyrene-block-polyethylene oxide block copolymer, which was made cleavable due to the intervening disulfide bond. The cleavage reaction of the disulfide bond leaves behind free thiol groups inside the nanopores of polystyrene thin film. This nanoporous thin film can be used as a template for generating gold nanoring structures. This strategy can provide a facile method to form a highly ordered array of biopolymer or metal-polymer composite structures.

The Space Infrared Interferometric Telescope (SPIRIT)

NASA Technical Reports Server (NTRS)

Rinehart, Stephen

2007-01-01

The Space Infrared Interferometric Telescope (SPIRIT) is a candidate NASA Origins Probe Mission. SPIRIT is a two-telescope Michelson interferometer covering wavelengths from 25-400 microns, providing simultaneously high spectral resolution and high angular resolution. With comparable sensitivity to Spitzer, but two orders of magnitude improvement in angular resolution, SPIRIT will enable us to address a wide array of compelling scientific questions, including how planetary systems form in disks and how new planets interact with the disk. Further, SPIRIT will lay the technological groundwork for an array of future interferometry missions with ambitious scientific goals, including the Terrestrial Planet Finder Interferometer / Darwin, and the Submillimeter Probe of the Evolution of Cosmic Structure.

The Space Infrared Interferometric Telescope (SPIRIT)

NASA Technical Reports Server (NTRS)

Rinehart, Stephen

2007-01-01

The Space Infrared Interferometric Telescope (SPIRIT) is a candidate NASA Origins Probe Mission. SPIRIT is a two-telescope Michelson interferometer covering wavelengths from 25-400 microns, providing simultaneously high spectral resolution and high angular resolution. With comparable sensitivity to Spitzer, but two orders of magnitude improvement in angular resolution, SPIRIT will enable us to address a wide array of compelling scientific questions, including how planetary systems form in disks and how new planets interact with the disk. Further, SPIRIT will lay the technological groundwork for an array of future interferometry missions with ambitious scientific goals, including the Terrestrial Planet Finder Interferometer/Darwin, and the Submillimeter Probe of the Evolution of Cosmic Structure.

Multiband Photonic Phased-Array Antenna

NASA Technical Reports Server (NTRS)

Tang, Suning

2015-01-01

A multiband phased-array antenna (PAA) can reduce the number of antennas on shipboard platforms while offering significantly improved performance. Crystal Research, Inc., has developed a multiband photonic antenna that is based on a high-speed, optical, true-time-delay beamformer. It is capable of simultaneously steering multiple independent radio frequency (RF) beams in less than 1,000 nanoseconds. This high steering speed is 3 orders of magnitude faster than any existing optical beamformer. Unlike other approaches, this technology uses a single controlling device per operation band, eliminating the need for massive optical switches, laser diodes, and fiber Bragg gratings. More importantly, only one beamformer is needed for all antenna elements.

Construction and evaluation of a capillary array DNA sequencer based on a micromachined sheath-flow cuvette.

PubMed

Crabtree, H J; Bay, S J; Lewis, D F; Zhang, J; Coulson, L D; Fitzpatrick, G A; Delinger, S L; Harrison, D J; Dovichi, N J

2000-04-01

A capillary array electrophoresis DNA sequencer is reported based on a micromachined sheath-flow cuvette as the detection chamber. This cuvette is equipped with a set of micromachined features that hold the capillaries in precise registration to ensure uniform spacing between the capillaries, in order to generate uniform hydrodynamic flow in the cuvette. A laser beam excites all of the samples simultaneously, and a microscope objective images fluorescence onto a set of avalanche photodiodes, which operate in the analog mode. A high-gain transimpedance amplifier is used for each photodiode, providing high duty-cycle detection of fluorescence.

High power transcranial beam steering for ultrasonic brain therapy

PubMed Central

Pernot, Mathieu; Aubry, Jean-François; Tanter, Mickaël; Thomas, Jean-Louis; Fink, Mathias

2003-01-01

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single-elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5cm2 and works at 0.9 MHz central frequency with a maximum 20W.cm−2 intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducers distributions on a spherical surface are simulated: hexagonal, annular, and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/− 15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system. PMID:12974575

Construction of NiO/MnO2/CeO2 hybrid nanoflake arrays as platform for electrochemical energy storage

NASA Astrophysics Data System (ADS)

Cui, Lihua; Cui, Jiewu; Zheng, Hongmei; Wang, Yan; Qin, Yongqiang; Shu, Xia; Liu, Jiaqin; Zhang, Yong; Wu, Yucheng

2017-09-01

Rational design and fabrication of novel electrode materials are of great importance for developing supercapacitors with remarkable capacitance and enhanced cycling stability. In this paper, we present a simple one-pot hydrothermal deposition followed by calcinations process for the in situ construction of homogeneous NiO/MnO2/CeO2 (NMC) nanoflake arrays on Ni foam substrate, which could be directly adopted as the binder-free electrode materials for high performance supercapacitors. The field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) are carried out to investigate the morphology, microstructure and composition of NMC nanoflake arrays. As-prepared hierarchical NMC nanoflake arrays exhibit the specific capacitance of 1027.8 F g-1 at a current density of 3.1 A g-1 and excellent cycling stability of 97.8% after 5000 charge/discharge cycles. This facile, cost-effective and controllable fabrication route and the robust supercapacitive activity suggest that the ordered NMC nanoflake arrays could be promising candidate electrode materials for high performance electrochemical energy storage devices.

Three-dimensional crossbar arrays of self-rectifying Si/SiO 2/Si memristors

DOE PAGES

Li, Can; Han, Lili; Jiang, Hao; ...

2017-06-05

Memristors are promising building blocks for the next generation memory, unconventional computing systems and beyond. Currently common materials used to build memristors are not necessarily compatible with the silicon dominant complementary metal-oxide-semiconductor (CMOS) technology. Furthermore, external selector devices or circuits are usually required in order for large memristor arrays to function properly, resulting in increased circuit complexity. Here we demonstrate fully CMOS-compatible, all-silicon based and self-rectifying memristors that negate the need for external selectors in large arrays. It consists of p- and n-type doped single crystalline silicon electrodes and a thin chemically produced silicon oxide switching layer. The device exhibitsmore » repeatable resistance switching behavior with high rectifying ratio (10 5), high ON/OFF conductance ratio (10 4) and attractive retention at 300 °C. We further build a 5-layer 3-dimensional (3D) crossbar array of 100 nm memristors by stacking fluid supported silicon membranes. The CMOS compatibility and self-rectifying behavior open up opportunities for mass production of memristor arrays and 3D hybrid circuits on full-wafer scale silicon and flexible substrates without increasing circuit complexity.« less

High power transcranial beam steering for ultrasonic brain therapy

NASA Astrophysics Data System (ADS)

Pernot, M.; Aubry, J.-F.; Tanter, M.; Thomas, J.-L.; Fink, M.

2003-08-01

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5 cm2 and works at 0.9 MHz central frequency with a maximum 20 W cm-2 intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducer distributions on a spherical surface are simulated: hexagonal, annular and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/-15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system.

Role of photonic angular momentum states in nonreciprocal diffraction from magneto-optical cylinder arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Tian-Jing; Wu, Li-Ting; Yang, Mu

2014-07-15

Optical eigenstates in a concentrically symmetric resonator are photonic angular momentum states (PAMSs) with quantized optical orbital angular momentums (OAMs). Nonreciprocal optical phenomena can be obtained if we lift the degeneracy of PAMSs. In this article, we provide a comprehensive study of nonreciprocal optical diffraction of various orders from a magneto-optical cylinder array. We show that nonreciprocal diffraction can be obtained only for these nonzero orders. Role of PAMSs, the excitation of which is sensitive to the directions of incidence, applied magnetic field, and arrangement of the cylinders, are studied. Some interesting phenomena such as a dispersionless quasi-omnidirectional nonreciprocal diffractionmore » and spikes associated with high-OAM PAMSs are present and discussed.« less

Proposal of a Bulk HTSC Staggered Array Undulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kii, Toshiteru; Kinjo, Ryota; Bakr, Mahmoud A.

We proposed a new type of undulator based on bulk high-T{sub c} superconductors (HTSC) which consists of a single solenoid and a stacked array of bulk HTSC. The main advantage of this configuration is that a mechanical structure is not required to produce and control the undulator field. In order to perform a proof of principle experiment, we have developed a prototype of bulk HTSC staggered array undulator using 11 pairs of DyBaCuO bulk superconductors and a normal conducting solenoid. Experimental results obtained by using the prototype undulator and numerical results obtained by a loop current model based on themore » Bean mode for a type-II superconductor were compared.« less

Comparing highly ordered monolayers of nanoparticles fabricated using electrophoretic deposition: Cobalt ferrite nanoparticles versus iron oxide nanoparticles

DOE PAGES

Dickerson, James H.; Krejci, Alex J.; Garcia, Adriana -Mendoza; ...

2015-08-01

Ordered assemblies of nanoparticles remain challenging to fabricate, yet could open the door to many potential applications of nanomaterials. Here, we demonstrate that locally ordered arrays of nanoparticles, using electrophoretic deposition, can be extended to produce long-range order among the constituents. Voronoi tessellations along with multiple statistical analyses show dramatic increases in order compared with previously reported assemblies formed through electric field-assisted assembly. As a result, based on subsequent physical measurements of the nanoparticles and the deposition system, the underlying mechanisms that generate increased order are inferred.

Shape induced magnetic vortex state in hexagonal ordered cofe nanodot arrays using ultrathin alumina shadow mask

NASA Astrophysics Data System (ADS)

Sellarajan, B.; Saravanan, P.; Ghosh, S. K.; Nagaraja, H. S.; Barshilia, Harish C.; Chowdhury, P.

2018-04-01

The magnetization reversal process of hexagonal ordered CoFe nanodot arrays was investigated as a function of nanodot thickness (td) varying from 10 to 30 nm with fixed diameter. For this purpose, ordered CoFe nanodots with a diameter of 80 ± 4 nm were grown by sputtering using ultra-thin alumina mask. The vortex annihilation and the dynamic spin configuration in the ordered CoFe nanodots were analyzed by means of magnetic hysteresis loops in complement with the micromagnetic simulation studies. A highly pinched hysteresis loop observed at 20 nm thickness suggests the occurrence of vortex state in these nanodots. With increase in dot thickness from 10 to 30 nm, the estimated coercivity values tend to increase from 80 to 175 Oe, indicating irreversible change in the nucleation/annihilation field of vortex state. The measured magnetic properties were then corroborated with the change in the shape of the nanodots from disk to hemisphere through micromagnetic simulation.

Self-assembly of water-soluble nanocrystals

DOEpatents

Fan, Hongyou [Albuquerque, NM; Brinker, C Jeffrey [Albuquerque, NM; Lopez, Gabriel P [Albuquerque, NM

2012-01-10

A method for forming an ordered array of nanocrystals where a hydrophobic precursor solution with a hydrophobic core material in an organic solvent is added to a solution of a surfactant in water, followed by removal of a least a portion of the organic solvent to form a micellar solution of nanocrystals. A precursor co-assembling material, generally water-soluble, that can co-assemble with individual micelles formed in the micellar solution of nanocrystals can be added to this micellar solution under specified reaction conditions (for example, pH conditions) to form an ordered-array mesophase material. For example, basic conditions are used to precipitate an ordered nanocrystal/silica array material in bulk form and acidic conditions are used to form an ordered nanocrystal/silica array material as a thin film.

Process-morphology scaling relations quantify self-organization in capillary densified nanofiber arrays.

PubMed

Kaiser, Ashley L; Stein, Itai Y; Cui, Kehang; Wardle, Brian L

2018-02-07

Capillary-mediated densification is an inexpensive and versatile approach to tune the application-specific properties and packing morphology of bulk nanofiber (NF) arrays, such as aligned carbon nanotubes. While NF length governs elasto-capillary self-assembly, the geometry of cellular patterns formed by capillary densified NFs cannot be precisely predicted by existing theories. This originates from the recently quantified orders of magnitude lower than expected NF array effective axial elastic modulus (E), and here we show via parametric experimentation and modeling that E determines the width, area, and wall thickness of the resulting cellular pattern. Both experiments and models show that further tuning of the cellular pattern is possible by altering the NF-substrate adhesion strength, which could enable the broad use of this facile approach to predictably pattern NF arrays for high value applications.

Ordered nanoparticle arrays formed on engineered chaperonin protein templates

NASA Technical Reports Server (NTRS)

McMillan, R. Andrew; Paavola, Chad D.; Howard, Jeanie; Chan, Suzanne L.; Zaluzec, Nestor J.; Trent, Jonathan D.

2002-01-01

Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Some proteins, for example, have been used to form ordered two-dimensional arrays. Here, we fabricated nanoscale ordered arrays of metal and semiconductor quantum dots by binding preformed nanoparticles onto crystalline protein templates made from genetically engineered hollow double-ring structures called chaperonins. Using structural information as a guide, a thermostable recombinant chaperonin subunit was modified to assemble into chaperonins with either 3 nm or 9 nm apical pores surrounded by chemically reactive thiols. These engineered chaperonins were crystallized into two-dimensional templates up to 20 microm in diameter. The periodic solvent-exposed thiols within these crystalline templates were used to size-selectively bind and organize either gold (1.4, 5 or 10nm) or CdSe-ZnS semiconductor (4.5 nm) quantum dots into arrays. The order within the arrays was defined by the lattice of the underlying protein crystal. By combining the self-assembling properties of chaperonins with mutations guided by structural modelling, we demonstrate that quantum dots can be manipulated using modified chaperonins and organized into arrays for use in next-generation electronic and photonic devices.

Mount control system of the ASTRI SST-2M prototype for the Cherenkov Telescope Array

NASA Astrophysics Data System (ADS)

Antolini, Elisa; Tosti, Gino; Tanci, Claudio; Bagaglia, Marco; Canestrari, Rodolfo; Cascone, Enrico; Gambini, Giorgio; Nucciarelli, Giuliano; Pareschi, Giovanni; Scuderi, Salvo; Stringhetti, Luca; Busatta, Andrea; Giacomel, Stefano; Marchiori, Gianpietro; Manfrin, Cristiana; Marcuzzi, Enrico; Di Michele, Daniele; Grigolon, Carlo; Guarise, Paolo

2016-08-01

The ASTRI SST-2M telescope is an end-to-end prototype proposed for the Small Size class of Telescopes (SST) of the future Cherenkov Telescope Array (CTA). The prototype is installed in Italy at the INAF observing station located at Serra La Nave on Mount Etna (Sicily) and it was inaugurated in September 2014. This paper presents the software and hardware architecture and development of the system dedicated to the control of the mount, health, safety and monitoring systems of the ASTRI SST-2M telescope prototype. The mount control system installed on the ASTRI SST-2M telescope prototype makes use of standard and widely deployed industrial hardware and software. State of the art of the control and automation industries was selected in order to fulfill the mount related functional and safety requirements with assembly compactness, high reliability, and reduced maintenance. The software package was implemented with the Beckhoff TwinCAT version 3 environment for the software Programmable Logical Controller (PLC), while the control electronics have been chosen in order to maximize the homogeneity and the real time performance of the system. The integration with the high level controller (Telescope Control System) has been carried out by choosing the open platform communications Unified Architecture (UA) protocol, supporting rich data model while offering compatibility with the PLC platform. In this contribution we show how the ASTRI approach for the design and implementation of the mount control system has made the ASTRI SST-2M prototype a standalone intelligent machine, able to fulfill requirements and easy to be integrated in an array configuration such as the future ASTRI mini-array proposed to be installed at the southern site of the Cherenkov Telescope Array (CTA).

Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

PubMed Central

Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; Grant, Richard P.; Monson, Todd C.

2017-01-01

Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers. The tethered array of nanoparticles, MnO in this case, bound directly to a gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). This strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles. PMID:28287183

Library API for Z-Order Memory Layout

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bethel, E. Wes

This library provides a simple-to-use API for implementing an altnerative to traditional row-major order in-memory layout, one based on a Morton- order space filling curve (SFC) , specifically, a Z-order variant of the Morton order curve. The library enables programmers to, after a simple initialization step, to convert a multidimensional array from row-major to Z- order layouts, then use a single, generic API call to access data from any arbitrary (i,j,k) location from within the array, whether it it be stored in row- major or z-order format. The motivation for using a SFC in-memory layout is for improved spatial locality,more » which results in increased use of local high speed cache memory. The basic idea is that with row-major order layouts, a data access to some location that is nearby in index space is likely far away in physical memory, resulting in poor spatial locality and slow runtime. On the other hand, with a SFC-based layout, accesses that are nearby in index space are much more likely to also be nearby in physical memory, resulting in much better spatial locality, and better runtime performance. Numerous studies over the years have shown significant runtime performance gains are realized by using a SFC-based memory layout compared to a row-major layout, sometimes by as much as 50%, which result from the better use of the memory and cache hierarchy that are attendant with a SFC-based layout (see, for example, [Beth2012]). This library implementation is intended for use with codes that work with structured, array-based data in 2 or 3 dimensions. It is not appropriate for use with unstructured or point-based data.« less

Magnetic Resonance Imaging of the anal canal using high resolution sequences and phased array coil: visualization of anal sphincter complex.

PubMed

Laghi, A; Iafrate, F; Paolantonio, P; Iannaccone, R; Baeli, I; Ferrari, R; Catalano, C; Passariello, R

2002-04-01

To assess the normal anatomy of the anal sphincter complex using high-resolution MR imaging with phased -array coil. Twenty patients, 13 males and 7 females, ranging in age between 27 and 56 years underwent MRI evaluation of the pelvic region, using a superconductive 1.5 T magnet (maximum gradient strength, 25 mT/m; minimum rise time 600 microseconds, equipped with phased-array coil. High-resolution T2-weighted Turbo Spin Echo sequences (TR, 4055 ms; TE, 132 ms; matrix 390x512; in-plane resolution, 0.67x0.57 mm) were acquired on multiple axial, sagittal and coronal planes. Images were reviewed by two experienced gastrointestinal radiologists in order to evaluate the normal anal sphincter complex. Optimal image quality of the anal sphincter complex was obtained in all cases. Different muscular layers were observed between the upper and lower aspects of the anal canal. In the lower part of the anal canal, internal and external sphincter muscles could be observed; in the upper part, puborectal and internal sphincter muscles were depicted. Good visualization of intersphincteric space, levator ani muscle and ischioanal space was also obtained in all cases. High-resolution MR images with phased-array coil provide optimal depiction of the anal canal and the anal sphincter complex.

X-ray Emission Characteristics of Ultra-High Energy Density Relativistic Plasmas Created by Ultrafast Laser Irradiation of Nanowire Arrays

NASA Astrophysics Data System (ADS)

Hollinger, R. C.; Bargsten, C.; Shlyaptsev, V. N.; Pukhov, A.; Purvis, M. A.; Townsend, A.; Keiss, D.; Wang, Y.; Wang, S.; Prieto, A.; Rocca, J. J.

2014-10-01

Irradiation of ordered nanowire arrays with high contrast femtosecond laser pulses of relativistic intensity creates volumetrically heated near solid density plasmas characterized by multi-KeV temperatures and extreme degrees of ionization. The large hydrodynamic-to-radiative lifetime ratio of these plasmas results in very efficient X-ray generation. Au nanowire array plasmas irradiated at I 5×1018 Wcm-2 are measured to convert ~ 5 percent of the laser energy into h ν > 0.9 KeV X-rays, and >1 × 10-4 into h ν > 9 KeV photons, creating bright picosecond X-ray sources. The angular distribution of the higher energy photons is measured to change from isotropic into annular as the intensity increases, while softer X-ray emission (h ν >1 KeV) remains isotropic and nearly unchanged. Model simulations suggest the unexpected annular distribution of the hard X-rays might result from bremsstrahlung of fast electrons confined in a high aspect ratio near solid density plasma in which the electron-ion collision mean free-path is of the order of the plasma thickness. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency Grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

Ordering nanoparticles with polymer brushes

NASA Astrophysics Data System (ADS)

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

2017-12-01

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a single layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. An interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.

Polyaniline nanowire arrays aligned on nitrogen-doped carbon fabric for high-performance flexible supercapacitors.

PubMed

Yu, Pingping; Li, Yingzhi; Yu, Xinyi; Zhao, Xin; Wu, Lihao; Zhang, Qinghua

2013-09-24

A combination of vertical polyaniline (PANI) nanowire arrays and nitrogen plasma etched carbon fiber cloths (eCFC) was fabricated to create 3D nanostructured PANI/eCFC composites. The small size of the highly ordered PANI nanowires can greatly reduce the scale of the diffusion length, allowing for the improved utilization of electrode materials. A two-electrode flexible supercapacitor based on PANI/eCFC demonstrates a high specific capacitance (1035 F g(-1) at a current density of 1 A g(-1)), good rate capability (88% capacity retention at 8 A g(-1)), and long-term cycle life (10% capacity loss after 5000 cycles). The lightweight, low-cost, flexible composites are promising candidates for use in energy storage device applications.

Design aspects of a solar array drive for spot, with a high platform stability objective

NASA Technical Reports Server (NTRS)

Cabillic, J.; Fournier, J. P.; Anstett, P.; Souliac, M.; Thomin, G.

1981-01-01

A solar array drive mechanism (MEGS) for the SPOT platform, which is a prototype of a multimission platform, is described. High-resolution cameras and other optical instruments are carried by the platform, requiring excellent platform stability in order to obtain high-quality pictures. Therefore, a severe requirement for the MEGS is the low level of disturbing torques it may generate considering the 0.6 times 10 to the minus 3 power deg/sec stability required. The mechanical design aspects aiming at reducing the mean friction torque, and therefore its fluctuations, are described as well as the method of compensation of the motor imperfections. It was concluded, however, that this is not sufficient to reach the stability requirement.

Control over self-assembly of diblock copolymers on hexagonal and square templates for high area density circuit boards.

PubMed

Feng, Jie; Cavicchi, Kevin A; Heinz, Hendrik

2011-12-27

Self-assembled diblock copolymer melts on patterned substrates can induce a smaller characteristic domain spacing compared to predefined lithographic patterns and enable the manufacture of circuit boards with a high area density of computing and storage units. Monte Carlo simulation using coarse-grain models of polystyrene-b-polydimethylsiloxane shows that the generation of high-density hexagonal and square patterns is controlled by the ratio N(D) of the surface area per post and the surface area per spherical domain of neat block copolymer. N(D) represents the preferred number of block copolymer domains per post. Selected integer numbers support the formation of ordered structures on hexagonal (1, 3, 4, 7, 9) and square (1, 2, 5, 7) templates. On square templates, only smaller numbers of block copolymer domains per post support the formation of ordered arrays with significant stabilization energies relative to hexagonal morphology. Deviation from suitable integer numbers N(D) increases the likelihood of transitional morphologies between square and hexagonal. Upon increasing the spacing of posts on the substrate, square arrays, nested square arrays, and disordered hexagonal morphologies with multiple coordination numbers were identified, accompanied by a decrease in stabilization energy. Control over the main design parameter N(D) may allow an up to 7-fold increase in density of spherical block copolymer domains per surface area in comparison to the density of square posts and provide access to a wide range of high-density nanostructures to pattern electronic devices.

Optical Characteristics of Vertical Cavity Surface Emitting Lasers and Two Dimensional Coherently Coupled Arrays.

NASA Astrophysics Data System (ADS)

Catchmark, Jeffrey Michael

1995-01-01

The following describes extensive experimental and theoretical research concerning the optical, electrical and thermal characteristics of GaAs/AlGaAs vertical cavity surface emitting lasers (VCSELs) and coherently coupled two dimensional VCSEL arrays grown by molecular beam epitaxy. The temperature and wavelength performance of VCSELs containing various epitaxial designs is discussed in detail. By employing a high barrier confinement spacer region and by blue shifting the optical gain with respect to the Fabry Perot transmission wavelength, greater than 150^circ rm C continuous wave operation was obtained. This is accomplished while maintaining a variation in the threshold current of only +/-0.93mA over a temperature range of 150^circrm C. This exceptional performance is achieved while attaining a minimum threshold current of approximately 4.3mA at 75^circrm C. In addition, the optical characteristics of multi-transverse mode VCSEL arrays are examined experimentally. A total of nine transverse modes have been identified and are found to couple coherently into distinct array modes. While operating in higher order transverse modes, a record 1.4W (pulsed) of optical power is obtained from a 15 x 15 VCSEL array. Array mode formation in coherently coupled VCSEL arrays is also examined theoretically. A numerical model is developed to describe the formation of supermodes in reflectivity modulated VCSEL arrays. Using this model, the effects of depth of reflectivity modulation, cavity length, window size and grid size on mode formation are explored. The array modes predicted by this model are in agreement with those observed experimentally. Analytic models will also be presented describing the effects of thermally induced waveguiding on the optical characteristics of VCSELs operating in the fundamental transverse mode. A thermal waveguide is found to have a significant effect on the spot size and radius of curvature of the phase of the fundamental optical mode. In addition, an analytic model is developed to predict the higher order transverse modes of a VCSEL exhibiting a cruciform type geometry.

Integrated electronics for time-resolved array of single-photon avalanche diodes

NASA Astrophysics Data System (ADS)

Acconcia, G.; Crotti, M.; Rech, I.; Ghioni, M.

2013-12-01

The Time Correlated Single Photon Counting (TCSPC) technique has reached a prominent position among analytical methods employed in a great variety of fields, from medicine and biology (fluorescence spectroscopy) to telemetry (laser ranging) and communication (quantum cryptography). Nevertheless the development of TCSPC acquisition systems featuring both a high number of parallel channels and very high performance is still an open challenge: to satisfy the tight requirements set by the applications, a fully parallel acquisition system requires not only high efficiency single photon detectors but also a read-out electronics specifically designed to obtain the highest performance in conjunction with these sensors. To this aim three main blocks have been designed: a gigahertz bandwidth front-end stage to directly read the custom technology SPAD array avalanche current, a reconfigurable logic to route the detectors output signals to the acquisition chain and an array of time measurement circuits capable of recording the photon arrival times with picoseconds time resolution and a very high linearity. An innovative architecture based on these three circuits will feature a very high number of detectors to perform a truly parallel spatial or spectral analysis and a smaller number of high performance time-to-amplitude converter offering very high performance and a very high conversion frequency while limiting the area occupation and power dissipation. The routing logic will make the dynamic connection between the two arrays possible in order to guarantee that no information gets lost.

High figure of merit ultra-compact 3-channel parallel-connected photonic crystal mini-hexagonal-H1 defect microcavity sensor array

NASA Astrophysics Data System (ADS)

Wang, Chunhong; Sun, Fujun; Fu, Zhongyuan; Ding, Zhaoxiang; Wang, Chao; Zhou, Jian; Wang, Jiawen; Tian, Huiping

2017-08-01

In this paper, a photonic crystal (PhC) butt-coupled mini-hexagonal-H1 defect (MHHD) microcavity sensor is proposed. The MHHD microcavity is designed by introducing six mini-holes into the initial H1 defect region. Further, based on a well-designed 1 ×3 PhC Beam Splitter and three optimal MHHD microcavity sensors with different lattice constants (a), a 3-channel parallel-connected PhC sensor array on monolithic silicon on insulator (SOI) is proposed. Finite-difference time-domain (FDTD) simulations method is performed to demonstrate the high performance of our structures. As statistics show, the quality factor (Q) of our optimal MHHD microcavity attains higher than 7×104, while the sensitivity (S) reaches up to 233 nm/RIU(RIU = refractive index unit). Thus, the figure of merit (FOM) >104 of the sensor is obtained, which is enhanced by two orders of magnitude compared to the previous butt-coupled sensors [1-4]. As for the 3-channel parallel-connected PhC MHHD microcavity sensor array, the FOMs of three independent MHHD microcavity sensors are 8071, 8250 and 8250, respectively. In addition, the total footprint of the proposed 3-channel parallel-connected PhC sensor array is ultra-compactness of 12.5 μm ×31 μm (width × length). Therefore, the proposed high FOM sensor array is an ideal platform for realizing ultra-compact highly parallel refractive index (RI) sensing.

Effects of process parameters on the molding quality of the micro-needle array

NASA Astrophysics Data System (ADS)

Qiu, Z. J.; Ma, Z.; Gao, S.

2016-07-01

Micro-needle array, which is used in medical applications, is a kind of typical injection molded products with microstructures. Due to its tiny micro-features size and high aspect ratios, it is more likely to produce short shots defects, leading to poor molding quality. The injection molding process of the micro-needle array was studied in this paper to find the effects of the process parameters on the molding quality of the micro-needle array and to provide theoretical guidance for practical production of high-quality products. With the shrinkage ratio and warpage of micro needles as the evaluation indices of the molding quality, the orthogonal experiment was conducted and the analysis of variance was carried out. According to the results, the contribution rates were calculated to determine the influence of various process parameters on molding quality. The single parameter method was used to analyse the main process parameter. It was found that the contribution rate of the holding pressure on shrinkage ratio and warpage reached 83.55% and 94.71% respectively, far higher than that of the other parameters. The study revealed that the holding pressure is the main factor which affects the molding quality of micro-needle array so that it should be focused on in order to obtain plastic parts with high quality in the practical production.

Reliability of spring interconnects for high channel-count polyimide electrode arrays

NASA Astrophysics Data System (ADS)

Khan, Sharif; Ordonez, Juan Sebastian; Stieglitz, Thomas

2018-05-01

Active neural implants with a high channel-count need robust and reliable operational assembly for the targeted environment in order to be classified as viable fully implantable systems. The discrete functionality of the electrode array and the implant electronics is vital for intact assembly. A critical interface exists at the interconnection sites between the electrode array and the implant electronics, especially in hybrid assemblies (e.g. retinal implants) where electrodes and electronics are not on the same substrate. Since the interconnects in such assemblies cannot be hermetically sealed, reliable protection against the physiological environment is essential for delivering high insulation resistance and low defusibility of salt ions, which are limited in complexity by current assembly techniques. This work reports on a combination of spring-type interconnects on a polyimide array with silicone rubber gasket insulation for chronically active implantable systems. The spring design of the interconnects on the backend of the electrode array compensates for the uniform thickness of the sandwiched gasket during bonding in assembly and relieves the propagation of extrinsic stresses to the bulk polyimide substrate. The contact resistance of the microflex-bonded spring interconnects with the underlying metallized ceramic test vehicles and insulation through the gasket between adjacent contacts was investigated against the MIL883 standard. The contact and insulation resistances remained stable in the exhausting environmental conditions.

A source array for generating higher order acoustic modes in circular ducts

NASA Technical Reports Server (NTRS)

Wyerman, B. R.; Reethof, G.

1976-01-01

A unique source array has been developed for the generation of both spinning and non-spinning higher order modes in a circular duct. The array consists of two concentric rings of sources. Through individual control of the response of each element, the array provided phase and amplitude control in the radial as well as circumferential directions. Radial modes shapes were measured in a 12-inch diameter anechoically-terminated hollow duct. These modes could be generated at their cut-off frequency and throughout a frequency range extending to the cut-off frequency for the next higher order radial mode. Comparisons are given between theory and experiment for the generation of specific modes. The radial dependence of the measured mode shapes was enhanced considerably by the design of this array. The results indicate a significant improvement over previous mode generation mechanisms. The contamination of the generated mode by additional spurious modes is also considered for variations between individual elements within the source array.

A Large Array of Small Antennas to Support Future NASA Missions

NASA Astrophysics Data System (ADS)

Jones, D. L.; Weinreb, S.; Preston, R. A.

2001-01-01

A team of engineers and scientists at JPL is currently working on the design of an array of small radio antennas with a total collecting area up to twenty times that of the largest existing (70 m) DSN antennas. An array of this size would provide obvious advantages for high data rate telemetry reception and for spacecraft navigation. Among these advantages are an order-of-magnitude increase in sensitivity for telemetry downlink, flexible sub-arraying to track multiple spacecraft simultaneously, increased reliability through the use of large numbers of identical array elements, very accurate real-time angular spacecraft tracking, and a dramatic reduction in cost per unit area. NASA missions in many disciplines, including planetary science, would benefit from this increased DSN capability. The science return from planned missions could be increased, and opportunities for less expensive or completely new kinds of missions would be created. The DSN array would also bean immensely valuable instrument for radio astronomy. Indeed, it would be by far the most sensitive radio telescope in the world. Additional information is contained in the original extended abstract.

Survey of Experimental Results From One Year of PASP PLUS Orbital Operation

NASA Technical Reports Server (NTRS)

Guidice, D. A.; Curtis, H. B.; Piszczor, M. F.; Palys, J. R.

1996-01-01

With PASP Plus as its primary payload, the APEX satellite was launched by a standard Pegasus rocket released from a NASA B-52 aircraft on 3 August 1994. A 70 deg inclination, 363 km X 2550 km orbit was achieved, allowing both investigation of space plasma effects on high-voltage operation in the perigee region and investigation of space radiation effects on array power output from passage through the inner radiation belt in the apogee region. Data gathering by PASP Plus was begun on 7 Aug 94 and ended on 11 Aug 95. In one year, PASP Plus collected an order of magnitude more data on environmental interactions on solar arrays than all previous space-borne photovoltaic experiments combined. The test arrays flown and the interactions-measuring and space-environment sensors of PASP Plus are described. The results of measurements of leakage current under test-array positive biasing and arc rates under negative biasing as a function of bias voltage, plasma density, array orientation, and other conditions are presented. The results of measurements of test-array power-output degradation caused by space radiation are also examined.

Upgrade of the Mirnov probe arrays on the J-TEXT tokamak.

PubMed

Guo, Daojing; Hu, Qiming; Li, Da; Shen, Chengshuo; Wang, Nengchao; Huang, Zhuo; Huang, Mingxiang; Ding, Yonghua; Xu, Guo; Yu, Qingquan; Tang, Yuejin; Zhuang, Ge

2017-12-01

The magnetic diagnostic of Mirnov probe arrays has been upgraded on the J-TEXT tokamak to measure the magnetohydrodynamic instabilities with higher spatial resolution and better amplitude-frequency characteristics. The upgraded Mirnov probe array contains one poloidal array with 48 probe modules and two toroidal arrays with 25 probe modules. Each probe module contains two probes which measure both the poloidal and the radial magnetic fields (B p and B r ). To ensure that the Mirnov probe possess better amplitude-frequency characteristics, a novel kind of Mirnov probe made of low temperature co-fired ceramics is utilized. The parameters and frequency response of the probe are measured and can meet the experiment requirement. The new Mirnov arrays have been normally applied for a round of experiments, including the observation of tearing modes and their coupling as well as high frequency magnetic perturbation due to the Alfvén eigenmode. In order to extract useful information from raw signals, visualization processing methods based on singular value decomposition and cross-power spectrum are applied to decompose the coupled modes and to determine the mode number.

Upgrade of the Mirnov probe arrays on the J-TEXT tokamak

NASA Astrophysics Data System (ADS)

Guo, Daojing; Hu, Qiming; Li, Da; Shen, Chengshuo; Wang, Nengchao; Huang, Zhuo; Huang, Mingxiang; Ding, Yonghua; Xu, Guo; Yu, Qingquan; Tang, Yuejin; Zhuang, Ge

2017-12-01

The magnetic diagnostic of Mirnov probe arrays has been upgraded on the J-TEXT tokamak to measure the magnetohydrodynamic instabilities with higher spatial resolution and better amplitude-frequency characteristics. The upgraded Mirnov probe array contains one poloidal array with 48 probe modules and two toroidal arrays with 25 probe modules. Each probe module contains two probes which measure both the poloidal and the radial magnetic fields (Bp and Br). To ensure that the Mirnov probe possess better amplitude-frequency characteristics, a novel kind of Mirnov probe made of low temperature co-fired ceramics is utilized. The parameters and frequency response of the probe are measured and can meet the experiment requirement. The new Mirnov arrays have been normally applied for a round of experiments, including the observation of tearing modes and their coupling as well as high frequency magnetic perturbation due to the Alfvén eigenmode. In order to extract useful information from raw signals, visualization processing methods based on singular value decomposition and cross-power spectrum are applied to decompose the coupled modes and to determine the mode number.

Ultrasoft x-ray imaging system for the National Spherical Torus Experiment

NASA Astrophysics Data System (ADS)

Stutman, D.; Finkenthal, M.; Soukhanovskii, V.; May, M. J.; Moos, H. W.; Kaita, R.

1999-01-01

A spectrally resolved ultrasoft x-ray imaging system, consisting of arrays of high resolution (<2 Å) and throughput (⩾tens of kHz) miniature monochromators, and based on multilayer mirrors and absolute photodiodes, is being designed for the National Spherical Torus Experiment. Initially, three poloidal arrays of diodes filtered for C 1s-np emission will be implemented for fast tomographic imaging of the colder start-up plasmas. Later on, mirrors tuned to the C Lyα emission will be added in order to enable the arrays to "see" the periphery through the hot core and to study magnetohydrodynamic activity and impurity transport in this region. We also discuss possible core diagnostics, based on tomographic imaging of the Lyα emission from the plume of recombined, low Z impurity ions left by neutral beams or fueling pellets. The arrays can also be used for radiated power measurements and to map the distribution of high Z impurities injected for transport studies. The performance of the proposed system is illustrated with results from test channels on the CDX-U spherical torus at Princeton Plasma Physics Laboratory.

Synthesis of NiMn-LDH Nanosheet@Ni3S2 Nanorod Hybrid Structures for Supercapacitor Electrode Materials with Ultrahigh Specific Capacitance.

PubMed

Yu, Shuai; Zhang, Yingxi; Lou, Gaobo; Wu, Yatao; Zhu, Xinqiang; Chen, Hao; Shen, Zhehong; Fu, Shenyuan; Bao, Binfu; Wu, Limin

2018-03-27

One of the key challenges for pseudocapacitive electrode materials with highly effective capacitance output and future practical applications is how to rationally construct hierarchical and ordered hybrid nanoarchitecture through the simple process. Herein, we design and synthesize a novel NiMn-layered double hydroxide nanosheet@Ni 3 S 2 nanorod hybrid array supported on porous nickel foam via a one-pot hydrothermal method. Benefited from the ultrathin and rough nature, the well-defined porous structure of the hybrid array, as well as the synergetic effect between NiMn-layered double hydroxide nanosheets and Ni 3 S 2 nanorods, the as-fabricated hybrid array-based electrode exhibits an ultrahigh specific capacitance of 2703 F g -1 at 3 A g -1 . Moreover, the asymmetric supercapacitor with this hybrid array as a positive electrode and wood-derived activated carbon as a negative electrode demonstrates high energy density (57 Wh Kg -1 at 738 W Kg -1 ) and very good electrochemical cycling stability.

Synthesis and characterization of barium silicide (BaSi2) nanowire arrays for potential solar applications.

PubMed

Pokhrel, Ankit; Samad, Leith; Meng, Fei; Jin, Song

2015-11-07

In order to utilize nanostructured materials for potential solar and other energy-harvesting applications, scalable synthetic techniques for these materials must be developed. Herein we use a vapor phase conversion approach to synthesize nanowire (NW) arrays of semiconducting barium silicide (BaSi2) in high yield for the first time for potential solar applications. Dense arrays of silicon NWs obtained by metal-assisted chemical etching were converted to single-crystalline BaSi2 NW arrays by reacting with Ba vapor at about 930 °C. Structural characterization by X-ray diffraction and high-resolution transmission electron microscopy confirm that the converted NWs are single-crystalline BaSi2. The optimal conversion reaction conditions allow the phase-pure synthesis of BaSi2 NWs that maintain the original NW morphology, and tuning the reaction parameters led to a controllable synthesis of BaSi2 films on silicon substrates. The optical bandgap and electrochemical measurements of these BaSi2 NWs reveal a bandgap and carrier concentrations comparable to previously reported values for BaSi2 thin films.

Optical properties of ordered vertical arrays of multi-walled carbon nanotubes from FDTD simulations.

PubMed

Bao, Hua; Ruan, Xiulin; Fisher, Timothy S

2010-03-15

A finite-difference time-domain (FDTD) method is used to model thermal radiative properties of vertical arrays of multi-walled carbon nanotubes (MWCNT). Individual CNTs are treated as solid circular cylinders with an effective dielectric tensor. Consistent with experiments, the results confirm that CNT arrays are highly absorptive. Compared with the commonly used Maxwell-Garnett theory, the FDTD calculations generally predict larger reflectance and absorbance, and smaller transmittance, which are attributed to the diffraction and scattering within the cylinder array structure. The effects of volume fraction, tube length, tube distance, and incident angle on radiative properties are investigated systematically. Low volume fraction and long tubes are more favorable to achieve low reflectance and high absorbance. For a fixed volume fraction and finite tube length, larger periodicity results in larger reflectance and absorbance. The angular dependence studies reveal an optimum incident angle at which the reflectance can be minimized. The results also suggest that an even darker material could be achieved by using CNTs with good alignment on the top surface.

Primary gamma ray selection in a hybrid timing/imaging Cherenkov array

NASA Astrophysics Data System (ADS)

Postnikov, E. B.; Grinyuk, A. A.; Kuzmichev, L. A.; Sveshnikova, L. G.

2017-06-01

This work is a methodical study on hybrid reconstruction techniques for hybrid imaging/timing Cherenkov observations. This type of hybrid array is to be realized at the gamma-observatory TAIGA intended for very high energy gamma-ray astronomy (> 30 TeV). It aims at combining the cost-effective timing-array technique with imaging telescopes. Hybrid operation of both of these techniques can lead to a relatively cheap way of development of a large area array. The joint approach of gamma event selection was investigated on both types of simulated data: the image parameters from the telescopes, and the shower parameters reconstructed from the timing array. The optimal set of imaging parameters and shower parameters to be combined is revealed. The cosmic ray background suppression factor depending on distance and energy is calculated. The optimal selection technique leads to cosmic ray background suppression of about 2 orders of magnitude on distances up to 450 m for energies greater than 50 TeV.

Phased-array sources based on nonlinear metamaterial nanocavities

DOE PAGES

Wolf, Omri; Campione, Salvatore; Benz, Alexander; ...

2015-07-01

Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization.more » As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (~5 μm): a beam splitter and a polarizing beam splitter. As a result, proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.« less

AlGaAs phased array laser for optical communications

NASA Technical Reports Server (NTRS)

Carlson, N. W.

1989-01-01

Phased locked arrays of multiple AlGaAs diode laser emitters were investigated both in edge emitting and surface emitting configurations. CSP edge emitter structures, coupled by either evanescent waves or Y-guides, could not achieve the required powers (greater than or similar to 500 mW) while maintaining a diffraction limited, single lobed output beam. Indeed, although the diffraction limit was achieved in this type of device, it was at low powers and in the double lobed radiation pattern characteristic of out-of-phase coupling. Grating surface emitting (GSE) arrays were, therefore, investigated with more promising results. The incorporation of second order gratings in distribute Bragg reflector (DBR) structures allows surface emission, and can be configured to allow injection locking and lateral coupling to populate 2-D arrays that should be able to reach power levels commensurate with the needs of high performance, free space optical communications levels. Also, a new amplitude modulation scheme was developed for GSE array operation.

Hybrid Ni/SiO2/Au dimer arrays for high-resolution refractive index sensing

NASA Astrophysics Data System (ADS)

Pourjamal, Sara; Kataja, Mikko; Maccaferri, Nicolò; Vavassori, Paolo; van Dijken, Sebastiaan

2018-05-01

We introduce a novel magnetoplasmonic sensor concept for sensitive detection of refractive index changes. The sensor consists of a periodic array of Ni/SiO2/Au dimer nanodisks. Combined effects of near-field interactions between the Ni and Au disks within the individual dimers and far-field diffractive coupling between the dimers of the array produce narrow linewidth features in the magneto-optical Faraday spectrum. We associate these features with the excitation of surface lattice resonances and show that they exhibit a spectral shift when the refractive index of the surrounding environment is varied. Because the resonances are sharp, refractive index changes are accurately detected by tracking the wavelength where the Faraday signal crosses 0. Compared to random distributions of pure Ni nanodisks or Ni/SiO2/Au dimers or periodic arrays of Ni nanodisks, the sensing figure of merit of the hybrid magnetoplasmonic array is more than one order of magnitude larger.

Rapid fabrication of three-dimensional structures for dielectrophoretic sorting of lipid-containing organisms

NASA Astrophysics Data System (ADS)

Schor, Alisha R.; Buie, Cullen R.

2016-10-01

In this work, we demonstrate a microfluidic particle sorter consisting of three-dimensional, conducting microposts. Our sorter uses dielectrophoresis (DEP) to sort high- and low-lipid phenotypes of the yeast Yarrowia lipolytica. Y. lipolytica is one of the many microorganisms being explored as a hydrocarbon source for biodiesel, Omega-3 additives, and other products derived from fatty acids. A rapid, non-destructive, lipid-based sorting tool would accelerate the commercialization of these products. Our device consists of an array of 105, 25 μm wide gold microposts that span the height of a 15 μm channel. This array generates an electric field in a microfluidic device that is uniform through the channel height, but has a custom-shaped non-uniformity in the horizontal directions. This is crucial in order to achieve continuous sorting using DEP, as it ensures all cells are exposed to the same conditions throughout the channel height. By using very low currents (100 μA), we are able to electroplate these post arrays in fewer than 15 min. This is an order of magnitude improvement over previous reports of electroplated microstructures. With an applied signal of 250 MHz, 2.6 V pp in our device, we separate a heterogeneous population with a purity of 97.8% in the low-lipid stream and 71.4% in the high-lipid stream. The high-lipid stream purity can be improved by adjusting the spacing of the array. This unique protocol for the rapid fabrication of 3D microstructures has enabled the creation of a non-invasive sorting tool for genetically engineered, lipid-producing organisms. The ability to screen organisms based on lipid content will alleviate one of the major bottlenecks in commercialization of microbial biofuels.

Force sensitive carbon nanotube arrays for biologically inspired airflow sensing

NASA Astrophysics Data System (ADS)

Maschmann, Matthew R.; Dickinson, Ben; Ehlert, Gregory J.; Baur, Jeffery W.

2012-09-01

The compressive electromechanical response of aligned carbon nanotube (CNT) arrays is evaluated for use as an artificial hair sensor (AHS) transduction element. CNT arrays with heights of 12, 75, and 225 µm are examined. The quasi-static and dynamic sensitivity to force, response time, and signal drift are examined within the range of applied stresses predicted by a mechanical model applicable to the conceptual CNT array-based AHS (0-1 kPa). Each array is highly sensitive to compressive loading, with a maximum observed gauge factor of 114. The arrays demonstrate a repeatable response to dynamic cycling after a break-in period of approximately 50 cycles. Utilizing a four-wire measurement electrode configuration, the change in contact resistance between the array and the electrodes is observed to dominate the electromechanical response of the arrays. The response time of the CNT arrays is of the order of 10 ms. When the arrays are subjected to constant stress, mechanical creep is observed that results in a signal drift that generally diminishes the responsiveness of the arrays, particularly at stress approaching 1 kPa. The results of this study serve as a preliminary proof of concept for utilizing CNT arrays as a transduction mechanism for a proposed artificial hair sensor. Such a low profile and light-weight flow sensor is expected to have application in a number of applications including navigation and state awareness of small air vehicles, similar in function to natural hair cell receptors utilized by insects and bats.

The ALMA Phasing System: A Beamforming Capability for Ultra-high-resolution Science at (Sub)Millimeter Wavelengths

NASA Astrophysics Data System (ADS)

Matthews, L. D.; Crew, G. B.; Doeleman, S. S.; Lacasse, R.; Saez, A. F.; Alef, W.; Akiyama, K.; Amestica, R.; Anderson, J. M.; Barkats, D. A.; Baudry, A.; Broguière, D.; Escoffier, R.; Fish, V. L.; Greenberg, J.; Hecht, M. H.; Hiriart, R.; Hirota, A.; Honma, M.; Ho, P. T. P.; Impellizzeri, C. M. V.; Inoue, M.; Kohno, Y.; Lopez, B.; Martí-Vidal, I.; Messias, H.; Meyer-Zhao, Z.; Mora-Klein, M.; Nagar, N. M.; Nishioka, H.; Oyama, T.; Pankratius, V.; Perez, J.; Phillips, N.; Pradel, N.; Rottmann, H.; Roy, A. L.; Ruszczyk, C. A.; Shillue, B.; Suzuki, S.; Treacy, R.

2018-01-01

The Atacama Millimeter/submillimeter Array (ALMA) Phasing Project (APP) has developed and deployed the hardware and software necessary to coherently sum the signals of individual ALMA antennas and record the aggregate sum in Very Long Baseline Interferometry (VLBI) Data Exchange Format. These beamforming capabilities allow the ALMA array to collectively function as the equivalent of a single large aperture and participate in global VLBI arrays. The inclusion of phased ALMA in current VLBI networks operating at (sub)millimeter wavelengths provides an order of magnitude improvement in sensitivity, as well as enhancements in u–v coverage and north–south angular resolution. The availability of a phased ALMA enables a wide range of new ultra-high angular resolution science applications, including the resolution of supermassive black holes on event horizon scales and studies of the launch and collimation of astrophysical jets. It also provides a high-sensitivity aperture that may be used for investigations such as pulsar searches at high frequencies. This paper provides an overview of the ALMA Phasing System design, implementation, and performance characteristics.

Hierarchical TiN nanoparticles-assembled nanopillars for flexible supercapacitors with high volumetric capacitance.

PubMed

Qin, Ping; Li, Xingxing; Gao, Biao; Fu, Jijiang; Xia, Lu; Zhang, Xuming; Huo, Kaifu; Shen, Wenli; Chu, Paul K

2018-05-10

Titanium nitride (TiN) is an attractive electrode material in fast charging/discharging supercapacitors because of its excellent conductivity. However, the low capacitance and mechanical brittleness of TiN restricts its further application in flexible supercapacitors with high energy density. Thus, it is still a challenge to rationally design TiN electrodes with both high electrochemical and mechanical properties. Herein, the hierarchical TiN nanoparticles-assembled nanopillars (H-TiN NPs) array as binder free electrodes were obtained by nitriding of hierarchical titanium dioxide (TiO2) nanopillars, which was produced by a simple hydrothermal treatment of anodic TiO2 nanotubes (NTs) array in water. The porous TiN nanoparticles connected to each other to form ordered nanopillar arrays, effectively providing larger specific surface area and more active sites for charge storage. The H-TiN NPs delivered a high volumetric capacitance of 120 F cm-3 at 0.83 A cm-3, which is better than that of TiN NTs arrays (69 F cm-3 at 0.83 A cm-3). After assembling into all-solid-state devices, the H-TiN NPs based supercapacitors exhibited outstanding volumetric capacitance of 5.9 F cm-3 at 0.02 A cm-3 and a high energy density of 0.53 mW h cm-3. Our results reveal a new strategy to optimize the supercapacitive performance of metal nitrides.

Coupled-mode analysis of gain and wavelength oscillation characteristics of diode laser phased arrays

NASA Technical Reports Server (NTRS)

Butler, J. K.; Ettenberg, M.; Ackley, D. E.

1985-01-01

The lasing wavelengths and gain characteristics of the modes of phase-locked arrays of channel-substrate-planar (CSP) lasers are presented. The gain values for the array modes are determined from complex coupling coefficients calculated using the fields of neighboring elements of the array. The computations show that, for index guided lasers which have nearly planar phase fronts, the highest order array mode will be preferred. The 'in-phase' or fundamental mode, which produces only one major lobe in the far-field radiation pattern, has the lowest modal gain of all array modes. The modal gain differential between the highest order and fundamental modes is less than 10/cm for weak coupling between the elements.

Three-Dimensional NiCo2O4@Polypyrrole Coaxial Nanowire Arrays on Carbon Textiles for High-Performance Flexible Asymmetric Solid-State Supercapacitor.

PubMed

Kong, Dezhi; Ren, Weina; Cheng, Chuanwei; Wang, Ye; Huang, Zhixiang; Yang, Hui Ying

2015-09-30

In this article, we report a novel electrode of NiCo2O4 nanowire arrays (NWAs) on carbon textiles with a polypyrrole (PPy) nanosphere shell layer to enhance the pseudocapacitive performance. The merits of highly conductive PPy and short ion transport channels in ordered NiCo2O4 mesoporous nanowire arrays together with the synergistic effect between NiCo2O4 and PPy result in a high specific capacitance of 2244 F g(-1), excellent rate capability, and cycling stability in NiCo2O4/PPy electrode. Moreover, a lightweight and flexible asymmetric supercapacitor (ASC) device is successfully assembled using the hybrid NiCo2O4@PPy NWAs and activated carbon (AC) as electrodes, achieving high energy density (58.8 W h kg(-1) at 365 W kg(-1)), outstanding power density (10.2 kW kg(-1) at 28.4 W h kg(-1)) and excellent cycling stability (∼89.2% retention after 5000 cycles), as well as high flexibility. The three-dimensional coaxial architecture design opens up new opportunities to fabricate a high-performance flexible supercapacitor for future portable and wearable electronic devices.

Compact Focal Plane Assembly for Planetary Science

NASA Technical Reports Server (NTRS)

Brown, Ari; Aslam, Shahid; Huang, Wei-Chung; Steptoe-Jackson, Rosalind

2013-01-01

A compact radiometric focal plane assembly (FPA) has been designed in which the filters are individually co-registered over compact thermopile pixels. This allows for construction of an ultralightweight and compact radiometric instrument. The FPA also incorporates micromachined baffles in order to mitigate crosstalk and low-pass filter windows in order to eliminate high-frequency radiation. Compact metal mesh bandpass filters were fabricated for the far infrared (FIR) spectral range (17 to 100 microns), a game-changing technology for future planetary FIR instruments. This fabrication approach allows the dimensions of individual metal mesh filters to be tailored with better than 10- micron precision. In contrast, conventional compact filters employed in recent missions and in near-term instruments consist of large filter sheets manually cut into much smaller pieces, which is a much less precise and much more labor-intensive, expensive, and difficult process. Filter performance was validated by integrating them with thermopile arrays. Demonstration of the FPA will require the integration of two technologies. The first technology is compact, lightweight, robust against cryogenic thermal cycling, and radiation-hard micromachined bandpass filters. They consist of a copper mesh supported on a deep reactive ion-etched silicon frame. This design architecture is advantageous when constructing a lightweight and compact instrument because (1) the frame acts like a jig and facilitates filter integration with the FPA, (2) the frame can be designed so as to maximize the FPA field of view, (3) the frame can be simultaneously used as a baffle for mitigating crosstalk, and (4) micron-scale alignment features can be patterned so as to permit high-precision filter stacking and, consequently, increase the filter bandwidth and sharpen the out-of-band rolloff. The second technology consists of leveraging, from another project, compact and lightweight Bi0.87Sb0.13/Sb arrayed thermopiles. These detectors consist of 30-layer thermopiles deposited in series upon a silicon nitride membrane. At 300 K, the thermopile arrays are highly linear over many orders of magnitude of incident IR power, and have a reported specific detectivity that exceeds the requirements imposed on future mission concepts. The bandpass filter array board is integrated with a thermopile array board by mounting both boards on a machined aluminum jig.

The Self- and Directed Assembly of Nanowires

NASA Astrophysics Data System (ADS)

Smith, Benjamin David

This thesis explores the self- and directed assembly of nanowires. Specifically, we examine the driving forces behind nanowire self-assembly and the macro-structures that are formed. Particle-dense, oriented nanowire structures show promise in the fields of photonics, energy, sensing, catalysis, and electronics. Arrays of spherical particles have already found uses in electronic inks, sensing arrays, and many other commercial applications; but, it is a challenge to create specific arrays of morphologically and/or compositionally anisotropic particles. The following chapters illuminate the interactions that drive the assembly of anisotropic particles in high density solutions in the absence of applied fields or solution drying. Special emphasis is placed on the structures that are formed. The properties of micro- and nanoparticles and their assembly are introduced in Chapter 1. In particular, the properties of shape and material anisotropic particles are highlighted, while challenges in producing desired arrays are discussed. In this thesis, metallic nanowires of increasing complexity were used to examine the self-assembly behavior of both shape and material anisotropic particles. Nanowires were synthesized through templated electrodeposition. In this process, porous alumina membranes served as a template in which metal salts were reduced to form particles. Upon template dissolution, billions of nominally identical particles were released. We specifically focused on segmented, metallic nanowires 2-13 mum in length and 180 to 350 nm in diameter. Since these particles have strong van der Waals (VDWs) attractions, an electrostatically repulsive coating was necessary to prevent aggregation; we used small molecule, DNA, or amorphous silica coatings. Nanowires and their coatings were characterized by electron microscopy. In order to study self-assembly behavior, particle-dense aqueous suspensions were placed within an assembly chamber defined by a silicone spacer. The nanowires rapidly sedimented due to gravity onto a glass cover slip to concentrate and form a dense film. Particles and assemblies were imaged using inverted optical microscopy. We quantitatively analyzed the images and movies captured in order to track and classify particles and classify the overall arrays formed. We then correlated how particle characteristics, e.g., materials, size, segmentation, etc. changed the ordering and alignment observed. With that knowledge, we hope to be able to form new and interesting structures. We began our studies by examining the assembly of single component nanowires. Chapter 2 describes this work, in which solid Au nanowires measuring 2-7 mum in length and 290 nm in diameter self-assembled into smectic rows. By both experiment and theory, we determined that these rows formed due to a balance of electrostatic repulsions and van der Waals attractions. Final assemblies were stable for at least several days. Monte Carlo methods were used to simulate assemblies and showed structures that mirrored those experimentally observed. Simulations indicated that the smectic phase was preferred over others, i.e., nematic, when an additional small charge was added to the ends of the nanowires. Our particles have rough tips, which might create these additional electrostatic repulsions. To increase the particle and array complexity, two-component, metallic nanowire assembly was explored in Chapter 3. We examined numerous types of nanowires by changing the segment length, ratio, and material, the nanowire length, the surface coating, and the presence of small third segments. These segmented nanowires were generally Au-Ag and also ordered into smectic rows. Segmented wires arranged in rows, however, can be aligned in two possible ways with respect to a neighboring particle. The Au segments on neighboring particles can be oriented in the same direction or opposed to each other. Orientation was quantified in terms of an order parameter that took into account alignment with respect to nearest neighbor particles. All experiments showed order parameters indicating a slight preference for orientational ordering that was relatively insensitive to segment size, nanowire size, and nanowire coating. Monte Carlo simulations pointed towards this alignment as a consequence of small differences in the van der Waals attractions between the segments. Experimentally, ordering might to be limited by the large size of the nanowires, which results in kinetically trapped structures. In an attempt to obtain better ordering within rows, silica coated nanowires with partial Au cores were made. The synthesis involved silica-coating the nanowires and selectively etching a Ag segment. These particles have extremely different VDWs attractions between their segments, as the Au cores are much more attractive than the solvent-filled etched ends. The assembly of these partially etched nanowires (PENs) is detailed in Chapters 4, 5, and 6. When allowed to self-assemble, we observed the formation of either vertically or horizontally oriented arrays depending on PEN composition. The formation of vertically oriented arrays of anisotropic particles is important, since not many methods to produce these structures are currently available for particles of this size. We examined the effects of PEN length, PEN diameter, and the size, number, and location of the core segments. Our findings showed a large etched segment at one end (which resulted in a large offset in the center of mass and concentrated the VDWs attractions to one end of the particle) resulted in the best columnar assemblies. These vertically orientated arrays formed in a two part process. First, after PENs sedimented, they fell flat and oriented parallel to the surface. These PENs then sampled many orientations, including rotating out of the surface plane. When higher surface concentrations of particles built as more PENs fell to the surface of the cover slip, neighboring particles stabilized vertical orientations. Second, particles fell oriented vertically and when the surface concentrations were high, they retained this orientation upon reaching the substrate. Since vertically aligned PENs supported each other, assembly into vertical arrays was highly dependent on the surface concentration. But, oriented arrays could be easily formed on larger or smaller substrates, provided a particle concentration scaled to the substrate were used. The mixing of these particles to form heterogeneous arrays was examined. The overall array structure favored that of particles which sedimented more quickly and/or were present in higher amounts. The semi-automated counting of PENs in images by software is used heavily in Chapters 4 and 5. Appendix A describes the use, development, and validation of macros within Image-Pro. The structure, syntax, and use are specifically examined for three nanowire counting macros. The counting results; including: number of particles in an image, number of horizontally vs. vertically oriented PENs, and PENs in microwells; are compared with manual hand counts. Chapter 7 examines the overall conclusions and future directions for this research. By combining our assembly techniques with known directing forces (e.g., electric or magnetic fields) more specific alignment and/or positioning could be achieved. We have also begun to explore directing assembly through lithographic microwells. Further work needs to explore the integration of arrays into devices and the use of functional materials. Then, high density, oriented arrays could be created for photonic, energy, sensing, catalytic, and electronic applications.

High-performance ferroelectric and magnetoresistive materials for next-generation thermal detector arrays

NASA Astrophysics Data System (ADS)

Todd, Michael A.; Donohue, Paul P.; Watton, Rex; Williams, Dennis J.; Anthony, Carl J.; Blamire, Mark G.

2002-12-01

This paper discusses the potential thermal imaging performance achievable from thermal detector arrays and concludes that the current generation of thin-film ferroelectric and resistance bolometer based detector arrays are limited by the detector materials used. It is proposed that the next generation of large uncooled focal plane arrays will need to look towards higher performance detector materials - particularly if they aim to approach the fundamental performance limits and compete with cooled photon detector arrays. Two examples of bolometer thin-film materials are described that achieve high performance from operating around phase transitions. The material Lead Scandium Tantalate (PST) has a paraelectric-to-ferroelectric phase transition around room temperature and is used with an applied field in the dielectric bolometer mode for thermal imaging. PST films grown by sputtering and liquid-source CVD have shown merit figures for thermal imaging a factor of 2 to 3 times higher than PZT-based pyroelectric thin films. The material Lanthanum Calcium Manganite (LCMO) has a paramagnetic to ferromagnetic phase transition around -20oC. This paper describes recent measurements of TCR and 1/f noise in pulsed laser-deposited LCMO films on Neodymium Gallate substrates. These results show that LCMO not only has high TCR's - up to 30%/K - but also low 1/f excess noise, with bolometer merit figures at least an order of magnitude higher than Vanadium Oxide, making it ideal for the next generation of microbolometer arrays. These high performance properties come at the expense of processing complexities and novel device designs will need to be introduced to realize the potential of these materials in the next generation of thermal detectors.

Detection and imaging of moving objects with SAR by a joint space-time-frequency processing

NASA Astrophysics Data System (ADS)

Barbarossa, Sergio; Farina, Alfonso

This paper proposes a joint spacetime-frequency processing scheme for the detection and imaging of moving targets by Synthetic Aperture Radars (SAR). The method is based on the availability of an array antenna. The signals received by the array elements are combined, in a spacetime processor, to cancel the clutter. Then, they are analyzed in the time-frequency domain, by computing their Wigner-Ville Distribution (WVD), in order to estimate the instantaneous frequency, to be used for the successive phase compensation, necessary to produce a high resolution image.

Formation and dissolution of microbubbles on highly-ordered plasmonic nanopillar arrays

PubMed Central

Liu, Xiumei; Bao, Lei; Dipalo, Michele; De Angelis, Francesco; Zhang, Xuehua

2015-01-01

Bubble formation from plasmonic heating of nanostructures is of great interest in many applications. In this work, we study experimentally the intrinsic effects of the number of three-dimensional plasmonic nanostructures on the dynamics of microbubbles, largely decoupled from the effects of dissolved air. The formation and dissolution of microbubbles is observed on exciting groups of 1, 4, and 9 nanopillars. Our results show that the power threshold for the bubble formation depends on the number density of the nanopillars in highly-ordered arrays. In the degassed water, both the growth rate and the maximal radius of the plasmonic microbubbles increase with an increase of the illuminated pillar number, due to the heat balance between the heat loss across the bubble and the collective heating generated from the nanopillars. Interestingly, our results show that the bubble dissolution is affected by the spatial arrangement of the underlying nanopillars, due to the pinning effect on the bubble boundary. The bubbles on nanopillar arrays dissolve in a jumping mode with step-wise features on the dissolution curves, prior to a smooth dissolution phase for the bubble pinned by a single pillar. The insight from this work may facilitate the design of nanostructures for efficient energy conversion. PMID:26687143

High performance superconducting devices enabled by three dimensionally ordered nanodots and/or nanorods

DOEpatents

Goyal, Amit

2013-09-17

Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

High performance electrical, magnetic, electromagnetic and electrooptical devices enabled by three dimensionally ordered nanodots and nanorods

DOEpatents

Goyal, Amit , Kang; Sukill, [Knoxville, TN

2012-02-21

Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

Array microscopy technology and its application to digital detection of Mycobacterium tuberculosis

NASA Astrophysics Data System (ADS)

McCall, Brian P.

Tuberculosis causes more deaths worldwide than any other curable infectious disease. This is the case despite tuberculosis appearing to be on the verge of eradication midway through the last century. Efforts at reversing the spread of tuberculosis have intensified since the early 1990s. Since then, microscopy has been the primary frontline diagnostic. In this dissertation, advances in clinical microscopy towards array microscopy for digital detection of Mycobacterium tuberculosis are presented. Digital array microscopy separates the tasks of microscope operation and pathogen detection and will reduce the specialization needed in order to operate the microscope. Distributing the work and reducing specialization will allow this technology to be deployed at the point of care, taking the front-line diagnostic for tuberculosis from the microscopy center to the community health center. By improving access to microscopy centers, hundreds of thousands of lives can be saved. For this dissertation, a lens was designed that can be manufactured as 4x6 array of microscopes. This lens design is diffraction limited, having less than 0.071 waves of aberration (root mean square) over the entire field of view. A total area imaged onto a full-frame digital image sensor is expected to be 3.94 mm2, which according to tuberculosis microscopy guidelines is more than sufficient for a sensitive diagnosis. The design is tolerant to single point diamond turning manufacturing errors, as found by tolerance analysis and by fabricating a prototype. Diamond micro-milling, a fabrication technique for lens array molds, was applied to plastic plano-concave and plano-convex lens arrays, and found to produce high quality optical surfaces. The micro-milling technique did not prove robust enough to produce bi-convex and meniscus lens arrays in a variety of lens shapes, however, and it required lengthy fabrication times. In order to rapidly prototype new lenses, a new diamond machining technique was developed called 4-axis single point diamond machining. This technique is 2-10x faster than micro-milling, depending on how advanced the micro-milling equipment is. With array microscope fabrication still in development, a single prototype of the lens designed for an array microscope was fabricated using single point diamond turning. The prototype microscope objective was validated in a pre-clinical trial. The prototype was compared with a standard clinical microscope objective in diagnostic tests. High concordance, a Fleiss's kappa of 0.88, was found between diagnoses made using the prototype and standard microscope objectives and a reference test. With the lens designed and validated and an advanced fabrication process developed, array microscopy technology is advanced to the point where it is feasible to rapidly prototype an array microscope for detection of tuberculosis and translate array microscope from an innovative concept to a device that can save lives.

Zenith angle distribution of cosmic ray showers measured with the Yakutsk array and its application to the analysis of arrival directions in equatorial coordinates

NASA Astrophysics Data System (ADS)

Ivanov, A. A.

2018-04-01

The Yakutsk array data set in the energy interval (1017,1019) eV is revisited in order to interpret the zenith angle distribution of an extensive air shower event rate of ultra-high-energy cosmic rays. The close relation of the distribution to the attenuation of the main measurable parameter of showers, ρ600, is examined. Measured and expected distributions are used to analyze the arrival directions of cosmic rays on an equatorial map including the energy range below 1018 eV , which was previously avoided due to the reduced trigger efficiency of the array in the range. While the null hypothesis cannot be rejected with data from the Yakutsk array, an upper limit on the fraction of cosmic rays from a separable source in the uniform background is derived as a function of declination and energy.

Monte Carlo performance studies for the site selection of the Cherenkov Telescope Array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassan, T.; Arrabito, L.; Bernlöhr, K.

The Cherenkov Telescope Array (CTA) represents the next generation of ground-based instruments for very-high-energy (VHE) gamma-ray astronomy, aimed at improving on the sensitivity of current-generation experiments by an order of magnitude and providing coverage over four decades of energy. The current CTA design consists of two arrays of tens of imaging atmospheric Cherenkov Telescopes, comprising Small, Medium and Large-Sized Telescopes, with one array located in each of the Northern and Southern Hemispheres. To study the effect of the site choice on the overall CTA performance and support the site evaluation process, detailed Monte Carlo simulations have been performed. These resultsmore » show the impact of different site-related attributes such as altitude, night-sky background and local geomagnetic field on CTA performance for the observation of VHE gamma rays.« less

Monte Carlo performance studies for the site selection of the Cherenkov Telescope Array

DOE PAGES

Hassan, T.; Arrabito, L.; Bernlöhr, K.; ...

2017-05-03

The Cherenkov Telescope Array (CTA) represents the next generation of ground-based instruments for very-high-energy (VHE) gamma-ray astronomy, aimed at improving on the sensitivity of current-generation experiments by an order of magnitude and providing coverage over four decades of energy. The current CTA design consists of two arrays of tens of imaging atmospheric Cherenkov Telescopes, comprising Small, Medium and Large-Sized Telescopes, with one array located in each of the Northern and Southern Hemispheres. To study the effect of the site choice on the overall CTA performance and support the site evaluation process, detailed Monte Carlo simulations have been performed. These resultsmore » show the impact of different site-related attributes such as altitude, night-sky background and local geomagnetic field on CTA performance for the observation of VHE gamma rays.« less

Directed growth of horizontally aligned gallium nitride nanowires for nanoelectromechanical resonator arrays.

PubMed

Henry, Tania; Kim, Kyungkon; Ren, Zaiyuan; Yerino, Christopher; Han, Jung; Tang, Hong X

2007-11-01

We report the growth of horizontally aligned arrays and networks of GaN nanowires (NWs) as resonant components in nanoelectromechanical systems (NEMS). A combination of top-down selective area growth (SAG) and bottom-up vapor-liquid-solid (VLS) synthesis enables flexible fabrication of highly ordered nanowire arrays in situ with no postgrowth dispersion. Mechanical resonance of free-standing nanowires are measured, with quality factors (Q) ranging from 400 to 1000. We obtained a Young's modulus (E) of approximately 338 GPa from an array of NWs with varying diameters and lengths. The measurement allows detection of nanowire motion with a rotating frame and reveals dual fundamental resonant modes in two orthogonal planes. A universal ratio between the resonant frequencies of these two fundamental modes, irrespective of their dimensions, is observed and attributed to an isosceles cross section of GaN NWs.

Depth extraction method with high accuracy in integral imaging based on moving array lenslet technique

NASA Astrophysics Data System (ADS)

Wang, Yao-yao; Zhang, Juan; Zhao, Xue-wei; Song, Li-pei; Zhang, Bo; Zhao, Xing

2018-03-01

In order to improve depth extraction accuracy, a method using moving array lenslet technique (MALT) in pickup stage is proposed, which can decrease the depth interval caused by pixelation. In this method, the lenslet array is moved along the horizontal and vertical directions simultaneously for N times in a pitch to get N sets of elemental images. Computational integral imaging reconstruction method for MALT is taken to obtain the slice images of the 3D scene, and the sum modulus (SMD) blur metric is taken on these slice images to achieve the depth information of the 3D scene. Simulation and optical experiments are carried out to verify the feasibility of this method.

Study of dispersion of mass distribution of ultra-high energy cosmic rays using a surface array of muon and electromagnetic detectors

NASA Astrophysics Data System (ADS)

Vícha, Jakub; Trávníček, Petr; Nosek, Dalibor; Ebr, Jan

2015-09-01

We consider a hypothetical observatory of ultra-high energy cosmic rays consisting of two surface detector arrays that measure independently electromagnetic and muon signals induced by air showers. Using the constant intensity cut method, sets of events ordered according to each of both signal sizes are compared giving the number of matched events. Based on its dependence on the zenith angle, a parameter sensitive to the dispersion of the distribution of the logarithmic mass of cosmic rays is introduced. The results obtained using two post-LHC models of hadronic interactions are very similar and indicate a weak dependence on details of these interactions.

Detection of chemical residues in food oil via surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Sun, Kexi; Huang, Qing

2016-05-01

Highly ordered hexagonally patterned Ag-nanorod (Ag-NR) arrays for surface-enhanced Raman scattering (SERS) detection of unhealthy chemical residues in food oil was reported, which was obtained by sputtering Ag on the alumina nanotip arrays stuck out of conical-pore anodic aluminum oxide (AAO) templates. SERS measurements demonstrate that the as-fabricated large-scale Ag-nanostructures can serve as highly sensitive and reproducible SERS substrates for detection of trace amount of chemicals in oil with the lower detection limits of 2×10-6 M for thiram and 10-7 M for rhodamine B, showing the potential of application of SERS in rapid trace detection of pesticide residues and illegal additives in food oils.

Size-dependent physicochemical and mechanical interactions in battery paste anodes of Si-microwires revealed by Fast-Fourier-Transform Impedance Spectroscopy

NASA Astrophysics Data System (ADS)

Hansen, Sandra; Quiroga-González, Enrique; Carstensen, Jürgen; Adelung, Rainer; Föll, Helmut

2017-05-01

Perfectly aligned silicon microwire arrays show exceptionally high cycling stability with record setting (high) areal capacities of 4.25 mAh cm-2. Those wires have a special, modified length and thickness in order to perform this good. Geometry and sizes are the most important parameters of an anode to obtain batteries with high cycling stability without irreversible losses. The wires are prepared with a unique etching fabrication method, which allows to fabricate wires of very precise sizes. In order to investigate how good randomly oriented silicon wires perform in contrast to the perfect order of the array, the wires are embedded in a paste. This study reveals the fundamental correlation between geometry, mechanics and charge transfer kinetics of silicon electrodes. Using a suitable RC equivalent circuit allows to evaluate data from cyclic voltammetry and simultaneous FFT-Impedance Spectroscopy (FFT-IS), yielding in time-resolved resistances, time constants, and their direct correlation to the phase transformations. The change of the resistances during lithiation and delithiation correlates to kinetics and charge transfer mechanisms. This study demonstrates how the mechanical and physiochemical interactions at the silicon/paste interface inside the paste electrodes lead to void formation around silicon and with it to material loss and capacity fading.

Hubble Space Telescope solar cell module thermal cycle test

NASA Technical Reports Server (NTRS)

Douglas, Alexander; Edge, Ted; Willowby, Douglas; Gerlach, Lothar

1992-01-01

The Hubble Space Telescope (HST) solar array consists of two identical double roll-out wings designed after the Hughes flexible roll-up solar array (FRUSA) and was developed by the European Space Agency (ESA) to meet specified HST power output requirements at the end of 2 years, with a functional lifetime of 5 years. The requirement that the HST solar array remain functional both mechanically and electrically during its 5-year lifetime meant that the array must withstand 30,000 low Earth orbit (LEO) thermal cycles between approximately +100 and -100 C. In order to evaluate the ability of the array to meet this requirement, an accelerated thermal cycle test in vacuum was conducted at NASA's Marshall Space Flight Center (MSFC), using two 128-cell solar array modules which duplicated the flight HST solar array. Several other tests were performed on the modules. The thermal cycle test was interrupted after 2,577 cycles, and a 'cold-roll' test was performed on one of the modules in order to evaluate the ability of the flight array to survive an emergency deployment during the dark (cold) portion of an orbit. A posttest static shadow test was performed on one of the modules in order to analyze temperature gradients across the module. Finally, current in-flight electrical performance data from the actual HST flight solar array will be tested.

Directivity of a Sparse Array in the Presence of Atmospheric-Induced Phase Fluctuations for Deep Space Communications

NASA Technical Reports Server (NTRS)

Nessel, James A.; Acosta, Robert J.

2010-01-01

Widely distributed (sparse) ground-based arrays have been utilized for decades in the radio science community for imaging celestial objects, but have only recently become an option for deep space communications applications with the advent of the proposed Next Generation Deep Space Network (DSN) array. But whereas in astronomical imaging, observations (receive-mode only) are made on the order of minutes to hours and atmospheric-induced aberrations can be mostly corrected for in post-processing, communications applications require transmit capabilities and real-time corrections over time scales as short as fractions of a second. This presents an unavoidable problem with the use of sparse arrays for deep space communications at Ka-band which has yet to be successfully resolved, particularly for uplink arraying. In this paper, an analysis of the performance of a sparse antenna array, in terms of its directivity, is performed to derive a closed form solution to the expected array loss in the presence of atmospheric-induced phase fluctuations. The theoretical derivation for array directivity degradation is validated with interferometric measurements for a two-element array taken at Goldstone, California. With the validity of the model established, an arbitrary 27-element array geometry is defined at Goldstone, California, to ascertain its performance in the presence of phase fluctuations. It is concluded that a combination of compact array geometry and atmospheric compensation is necessary to ensure high levels of availability.

Scalable Top-Down Approach Tailored by Interferometric Lithography to Achieve Large-Area Single-Mode GaN Nanowire Laser Arrays on Sapphire Substrate.

PubMed

Behzadirad, Mahmoud; Nami, Mohsen; Wostbrock, Neal; Zamani Kouhpanji, Mohammad Reza; Feezell, Daniel F; Brueck, Steven R J; Busani, Tito

2018-03-27

GaN nanowires are promising for optical and optoelectronic applications because of their waveguiding properties and large optical band gap. However, developing a precise, scalable, and cost-effective fabrication method with a high degree of controllability to obtain high-aspect-ratio nanowires with high optical properties and minimum crystal defects remains a challenge. Here, we present a scalable two-step top-down approach using interferometric lithography, for which parameters can be controlled precisely to achieve highly ordered arrays of nanowires with excellent quality and desired aspect ratios. The wet-etch mechanism is investigated, and the etch rates of m-planes {11̅00} (sidewalls) were measured to be 2.5 to 70 nm/h depending on the Si doping concentration. Using this method, uniform nanowire arrays were achieved over a large area (>10 5 μm 2 ) with an spect ratio as large as 50, a radius as small as 17 nm, and atomic-scale sidewall roughness (<1 nm). FDTD modeling demonstrated HE 11 is the dominant transverse mode in the nanowires with a radius of sub-100 nm, and single-mode lasing from vertical cavity nanowire arrays with different doping concentrations on a sapphire substrate was interestingly observed in photoluminescence measurements. High Q-factors of ∼1139-2443 were obtained in nanowire array lasers with a radius and length of 65 nm and 2 μm, respectively, corresponding to a line width of 0.32-0.15 nm (minimum threshold of 3.31 MW/cm 2 ). Our results show that fabrication of high-quality GaN nanowire arrays with adaptable aspect ratio and large-area uniformity is feasible through a top-down approach using interferometric lithography and is promising for fabrication of III-nitride-based nanophotonic devices (radial/axial) on the original substrate.

Formation of TiO2 nanotube arrays in KOH added fluoride-ethylene glycol (EG) electrolyte and its photoelectrochemical response

NASA Astrophysics Data System (ADS)

Nyein, Nyein; Lockman, Zainovia; Matsuda, Astunori; Kawamura, Go; Tan, Wai Kian; Oo, Than Zaw

2016-07-01

In this study, highly ordered TiO2 nanotube arrays were prepared by anodic oxidation of titanium foil in fluoride -EG electrolyte containing a small amount of potassium hydroxide, KOH at 60 V for 30 min. This electrolyte resulted in the formation of long nanotubes with an average length of 10 µm and diameter of 170 nm. For comparison, TiO2 nanotubes anodized in H2O added EG electrolyte which produces short nanotubes with an average tube length of 5 µm and diameter of 170 nm. It appears that the addition of KOH into the fluoride EG electrolyte accelerated the formation of the TiO2 nanotubes as it is believed that the chemical dissolution at the tips of the nanotubes is suppressed. Highly ordered TiO2 nanotubes anodized in KOH added EG electrolyte exhibited the photocurrent density of 2 mA/cm2, which is significantly higher than H2O added sample (1.5 mA/cm2).

Structure Function Scaling Exponent and Intermittency in the Wake of a Wind Turbine Array

NASA Astrophysics Data System (ADS)

Aseyev, Aleksandr; Ali, Naseem; Cal, Raul

2015-11-01

Hot-wire measurements obtained in a 3 × 3 wind turbine array boundary layer are utilized to analyze high order structure functions, intermittency effects as well as the probability density functions of velocity increments at different scales within the energy cascade. The intermittency exponent is found to be greater in the far wake region in comparison to the near wake. At hub height, the intermittency exponent is found to be null. ESS scaling exponents of the second, fourth, and fifth order structure functions remain relatively constant as a function of height in the far-wake whereas in the near-wake these highly affected by the passage of the rotor thus showing a dependence on physical location. When comparing with proposed models, these generally over predict the structure functions in the far wake region. The pdf distributions in the far wake region display wider tails compared to the near wake region, and constant skewness hypothesis based on the local isotropy is verified in the wake. CBET-1034581.

One-step Synthesis of Ordered Pd@TiO2 Nanofibers Array Film as Outstanding NH3 Gas Sensor at Room Temperature.

PubMed

Wu, Hongyuan; Huang, Haitao; Zhou, Jiao; Hong, Dahai; Ikram, Muhammad; Rehman, Afrasiab Ur; Li, Li; Shi, Keying

2017-11-07

The one dimensional (1D) ordered porous Pd@TiO 2 nanofibers (NFs) array film have been fabricated via a facile one-step synthesis of the electrospinning approach. The Pd@TiO 2 NFs (PTND3) contained Pd (2.0 wt %) and C, N element (16.2 wt %) display high dispersion of Pd nanoparticles (NPs) on TiO 2 NFs. Adding Pd meshed with C, N element to TiO 2 based NFs might contribute to generation of Lewis acid sites and Brønsted acid sites, which have been recently shown to enhance NH 3 adsorption-desorption ability; Pd NPs could increase the quantity of adsorbed O 2 on the surface of TiO 2 based NFs, and accelerated the O 2 molecule-ion conversion rate, enhanced the ability of electron transmission. The response time of PTND3 sensor towards 100 ppm NH 3 is only 3 s at room temperature (RT). Meantime, the response and response time of the PTND3 to the NH 3 is 1 and 14s even at the concentration of 100 ppb. Therefore, the ordered Pd@TiO 2 NFs array NH 3 sensor display great potential for practical applications.

Sub-wavelength grating mode transformers in silicon slab waveguides.

PubMed

Bock, Przemek J; Cheben, Pavel; Schmid, Jens H; Delâge, André; Xu, Dan-Xia; Janz, Siegfried; Hall, Trevor J

2009-10-12

We report on several new types of sub-wavelength grating (SWG) gradient index structures for efficient mode coupling in high index contrast slab waveguides. Using a SWG, an adiabatic transition is achieved at the interface between silicon-on-insulator waveguides of different geometries. The SWG transition region minimizes both fundamental mode mismatch loss and coupling to higher order modes. By creating the gradient effective index region in the direction of propagation, we demonstrate that efficient vertical mode transformation can be achieved between slab waveguides of different core thickness. The structures which we propose can be fabricated by a single etch step. Using 3D finite-difference time-domain simulations we study the loss, polarization dependence and the higher order mode excitation for two types (triangular and triangular-transverse) of SWG transition regions between silicon-on-insulator slab waveguides of different core thicknesses. We demonstrate two solutions to reduce the polarization dependent loss of these structures. Finally, we propose an implementation of SWG structures to reduce loss and higher order mode excitation between a slab waveguide and a phase array of an array waveguide grating (AWG). Compared to a conventional AWG, the loss is reduced from -1.4 dB to < -0.2 dB at the slab-array interface.

On-line monitoring system of PV array based on internet of things technology

NASA Astrophysics Data System (ADS)

Li, Y. F.; Lin, P. J.; Zhou, H. F.; Chen, Z. C.; Wu, L. J.; Cheng, S. Y.; Su, F. P.

2017-11-01

The Internet of Things (IoT) Technology is used to inspect photovoltaic (PV) array which can greatly improve the monitoring, performance and maintenance of the PV array. In order to efficiently realize the remote monitoring of PV operating environment, an on-line monitoring system of PV array based on IoT is designed in this paper. The system includes data acquisition, data gateway and PV monitoring centre (PVMC) website. Firstly, the DSP-TMS320F28335 is applied to collect indicators of PV array using sensors, then the data are transmitted to data gateway through ZigBee network. Secondly, the data gateway receives the data from data acquisition part, obtains geographic information via GPS module, and captures the scenes around PV array via USB camera, then uploads them to PVMC website. Finally, the PVMC website based on Laravel framework receives all data from data gateway and displays them with abundant charts. Moreover, a fault diagnosis approach for PV array based on Extreme Learning Machine (ELM) is applied in PVMC. Once fault occurs, a user alert can be sent via E-mail. The designed system enables users to browse the operating conditions of PV array on PVMC website, including electrical, environmental parameters and video. Experimental results show that the presented monitoring system can efficiently real-time monitor the PV array, and the fault diagnosis approach reaches a high accuracy of 97.5%.

Large depth high-precision FMCW tomography using a distributed feedback laser array

NASA Astrophysics Data System (ADS)

DiLazaro, Thomas; Nehmetallah, George

2018-02-01

Swept-source optical coherence tomography (SS-OCT) has been widely employed in the medical industry for the high resolution imaging of subsurface biological structures. SS-OCT typically exhibits axial resolutions on the order of tens of microns at speeds of hundreds of kilohertz. Using the same coherent heterodyne detection technique, frequency modulated continuous wave (FMCW) ladar has been used for highly precise ranging for distances up to kilometers. Distributed feedback lasers (DFBs) have been used as a simple and inexpensive source for FMCW ranging. Here, we use a bandwidth-combined DFB array for sub-surface volume imaging at a 27 μm axial resolution over meters of distance. 2D and 3D tomographic images of several semi-transparent and diffuse objects at distances up to 10 m will be presented.

Space and power efficient hybrid counters array

DOEpatents

Gara, Alan G [Mount Kisco, NY; Salapura, Valentina [Chappaqua, NY

2009-05-12

A hybrid counter array device for counting events. The hybrid counter array includes a first counter portion comprising N counter devices, each counter device for receiving signals representing occurrences of events from an event source and providing a first count value corresponding to a lower order bits of the hybrid counter array. The hybrid counter array includes a second counter portion comprising a memory array device having N addressable memory locations in correspondence with the N counter devices, each addressable memory location for storing a second count value representing higher order bits of the hybrid counter array. A control device monitors each of the N counter devices of the first counter portion and initiates updating a value of a corresponding second count value stored at the corresponding addressable memory location in the second counter portion. Thus, a combination of the first and second count values provide an instantaneous measure of number of events received.

Space and power efficient hybrid counters array

DOEpatents

Gara, Alan G.; Salapura, Valentina

2010-03-30

A hybrid counter array device for counting events. The hybrid counter array includes a first counter portion comprising N counter devices, each counter device for receiving signals representing occurrences of events from an event source and providing a first count value corresponding to a lower order bits of the hybrid counter array. The hybrid counter array includes a second counter portion comprising a memory array device having N addressable memory locations in correspondence with the N counter devices, each addressable memory location for storing a second count value representing higher order bits of the hybrid counter array. A control device monitors each of the N counter devices of the first counter portion and initiates updating a value of a corresponding second count value stored at the corresponding addressable memory location in the second counter portion. Thus, a combination of the first and second count values provide an instantaneous measure of number of events received.

Self-assembled synthesis of 3D Cu(In1 - xGax)Se2 nanoarrays by one-step electroless deposition into ordered AAO template

NASA Astrophysics Data System (ADS)

Zhang, Bin; Zhou, Tao; Zheng, Maojun; Xiong, Zuzhou; Zhu, Changqing; Li, Hong; Wang, Faze; Ma, Li; Shen, Wenzhong

2014-07-01

Quaternary nanostructured Cu(In1 - xGax)Se2 (CIGS) arrays were successfully fabricated via a novel and simple solution-based protocol on the electroless deposition method, using a flexible, highly ordered anodic aluminium oxide (AAO) substrate. This method does not require electric power, complicated sensitization processes, or complexing agents, but provides nearly 100% pore fill factor to AAO templates. The field emission scanning electron microscopy (FE-SEM) images show that we obtained uniformly three-dimensional nanostructured CIGS arrays, and we can tailor the diameter and wall thicknesses of the nanostructure by adjusting the pore diameter of the AAO and metal Mo layer. Their chemical composition was determined by energy-dispersive spectroscopy analysis, which is very close to the stoichiometric value. The Raman spectroscopy, x-ray diffraction (XRD) pattern, and transmission electron microscopy (TEM) further confirm the formation of nanostructured CIGS with prominent chalcopyrite structure. The nanostructured CIGS arrays can support the design of low-cost, highlight-trapping, and enhanced carrier collection nanostructured solar cells.

Validation of the high-throughput marker technology DArT using the model plant Arabidopsis thaliana.

PubMed

Wittenberg, Alexander H J; van der Lee, Theo; Cayla, Cyril; Kilian, Andrzej; Visser, Richard G F; Schouten, Henk J

2005-08-01

Diversity Arrays Technology (DArT) is a microarray-based DNA marker technique for genome-wide discovery and genotyping of genetic variation. DArT allows simultaneous scoring of hundreds of restriction site based polymorphisms between genotypes and does not require DNA sequence information or site-specific oligonucleotides. This paper demonstrates the potential of DArT for genetic mapping by validating the quality and molecular basis of the markers, using the model plant Arabidopsis thaliana. Restriction fragments from a genomic representation of the ecotype Landsberg erecta (Ler) were amplified by PCR, individualized by cloning and spotted onto glass slides. The arrays were then hybridized with labeled genomic representations of the ecotypes Columbia (Col) and Ler and of individuals from an F(2) population obtained from a Col x Ler cross. The scoring of markers with specialized software was highly reproducible and 107 markers could unambiguously be ordered on a genetic linkage map. The marker order on the genetic linkage map coincided with the order on the DNA sequence map. Sequencing of the Ler markers and alignment with the available Col genome sequence confirmed that the polymorphism in DArT markers is largely a result of restriction site polymorphisms.

Field emission from optimized structure of carbon nanotube field emitter array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chouhan, V., E-mail: vchouhan@post.kek.jp, E-mail: vijaychouhan84@gmail.com; Noguchi, T.; Kato, S.

The authors report a detail study on the emission properties of field emitter array (FEA) of micro-circular emitters of multiwall carbon nanotubes (CNTs). The FEAs were fabricated on patterned substrates prepared with an array of circular titanium (Ti) islands on titanium nitride coated tantalum substrates. CNTs were rooted into these Ti islands to prepare an array of circular emitters. The circular emitters were prepared in different diameters and pitches in order to optimize their structure for acquiring a high emission current. The pitch was varied from 0 to 600 μm, while a diameter of circular emitters was kept constant to bemore » 50 μm in order to optimize a pitch. For diameter optimization, a diameter was changed from 50 to 200 μm while keeping a constant edge-to-edge distance of 150 μm between the circular emitters. The FEA with a diameter of 50 μm and a pitch of 120 μm was found to be the best to achieve an emission current of 47 mA corresponding to an effective current density of 30.5 A/cm{sup 2} at 7 V/μm. The excellent emission current was attributed to good quality of CNT rooting into the substrate and optimized FEA structure, which provided a high electric field on a whole circular emitter of 50 μm and the best combination of the strong edge effect and CNT coverage. The experimental results were confirmed with computer simulation.« less

Comparison of modeled and experimental PV array temperature profiles for accurate interpretation of module performance and degradation

NASA Astrophysics Data System (ADS)

Elwood, Teri; Simmons-Potter, Kelly

2017-08-01

Quantification of the effect of temperature on photovoltaic (PV) module efficiency is vital to the correct interpretation of PV module performance under varied environmental conditions. However, previous work has demonstrated that PV module arrays in the field are subject to significant location-based temperature variations associated with, for example, local heating/cooling and array edge effects. Such thermal non-uniformity can potentially lead to under-prediction or over-prediction of PV array performance due to an incorrect interpretation of individual module temperature de-rating. In the current work, a simulated method for modeling the thermal profile of an extended PV array has been investigated through extensive computational modeling utilizing ANSYS, a high-performance computational fluid dynamics (CFD) software tool. Using the local wind speed as an input, simulations were run to determine the velocity at particular points along modular strings corresponding to the locations of temperature sensors along strings in the field. The point velocities were utilized along with laminar flow theories in order to calculate Nusselt's number for each point. These calculations produced a heat flux profile which, when combined with local thermal and solar radiation profiles, were used as inputs in an ANSYS Thermal Transient model that generated a solar string operating temperature profile. A comparison of the data collected during field testing, and the data fabricated by ANSYS simulations, will be discussed in order to authenticate the accuracy of the model.

UV-enhanced CO sensing using Ga 2O 3-based nanorod arrays at elevated temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Hui-Jan; Gao, Haiyong; Gao, Pu-Xian

Monitoring and control of gaseous combustion process are critically important in advanced energy systems such as power plants, gas turbines, and automotive engines. However, very limited gas sensing solutions are available in the market for such application due to the inherent high temperature of combustion gaseous atmosphere. In this study, we fabricated and demonstrated high-performance metal oxide based nanorod array sensors assisted with ultra-violet (UV) illumination for in situ and real-time high-temperature gas detection. Without UV-illumination, it was found surface decoration of either 5 nm LSFO or 1 nm Pt nanoparticles can enhance the sensitivity over CO at 500 °Cmore » by an order of magnitude. Under the 254 nm UV illumination, CO gas-sensing performance of Ga 2O 3-based nanorod array sensors was further enhanced with the sensitivity boosted by 125 %, and the response time reduced by 30 % for La 0.8Sr 0.2FeO 3(LSFO)-decorated sample. The UV-enhanced detecting of CO might be due to the increased population of photo-induced electron-hole pairs. While for LSFO-decorated nanorod array sensor under UV illumination, the enhancement is through a combination of sensitizing effect and photocurrent effect.« less

Implementation of High Time Delay Accuracy of Ultrasonic Phased Array Based on Interpolation CIC Filter

PubMed Central

Liu, Peilu; Li, Xinghua; Li, Haopeng; Su, Zhikun; Zhang, Hongxu

2017-01-01

In order to improve the accuracy of ultrasonic phased array focusing time delay, analyzing the original interpolation Cascade-Integrator-Comb (CIC) filter, an 8× interpolation CIC filter parallel algorithm was proposed, so that interpolation and multichannel decomposition can simultaneously process. Moreover, we summarized the general formula of arbitrary multiple interpolation CIC filter parallel algorithm and established an ultrasonic phased array focusing time delay system based on 8× interpolation CIC filter parallel algorithm. Improving the algorithmic structure, 12.5% of addition and 29.2% of multiplication was reduced, meanwhile the speed of computation is still very fast. Considering the existing problems of the CIC filter, we compensated the CIC filter; the compensated CIC filter’s pass band is flatter, the transition band becomes steep, and the stop band attenuation increases. Finally, we verified the feasibility of this algorithm on Field Programming Gate Array (FPGA). In the case of system clock is 125 MHz, after 8× interpolation filtering and decomposition, time delay accuracy of the defect echo becomes 1 ns. Simulation and experimental results both show that the algorithm we proposed has strong feasibility. Because of the fast calculation, small computational amount and high resolution, this algorithm is especially suitable for applications with high time delay accuracy and fast detection. PMID:29023385

Implementation of High Time Delay Accuracy of Ultrasonic Phased Array Based on Interpolation CIC Filter.

PubMed

Liu, Peilu; Li, Xinghua; Li, Haopeng; Su, Zhikun; Zhang, Hongxu

2017-10-12

In order to improve the accuracy of ultrasonic phased array focusing time delay, analyzing the original interpolation Cascade-Integrator-Comb (CIC) filter, an 8× interpolation CIC filter parallel algorithm was proposed, so that interpolation and multichannel decomposition can simultaneously process. Moreover, we summarized the general formula of arbitrary multiple interpolation CIC filter parallel algorithm and established an ultrasonic phased array focusing time delay system based on 8× interpolation CIC filter parallel algorithm. Improving the algorithmic structure, 12.5% of addition and 29.2% of multiplication was reduced, meanwhile the speed of computation is still very fast. Considering the existing problems of the CIC filter, we compensated the CIC filter; the compensated CIC filter's pass band is flatter, the transition band becomes steep, and the stop band attenuation increases. Finally, we verified the feasibility of this algorithm on Field Programming Gate Array (FPGA). In the case of system clock is 125 MHz, after 8× interpolation filtering and decomposition, time delay accuracy of the defect echo becomes 1 ns. Simulation and experimental results both show that the algorithm we proposed has strong feasibility. Because of the fast calculation, small computational amount and high resolution, this algorithm is especially suitable for applications with high time delay accuracy and fast detection.

Temperature-Modulated Array High-Performance Liquid Chromatography

PubMed Central

Premstaller, Andreas; Xiao, Wenzhong; Oberacher, Herbert; O'Keefe, Matthew; Stern, David; Willis, Thomas; Huber, Christian G.; Oefner, Peter J.

2001-01-01

Using novel monolithic poly(styrene-divinylbenzene) capillary columns with an internal diameter of 0.2 mm, we demonstrate for the first time the feasibility of constructing high-performance liquid chromatography arrays for the detection of mutations by heteroduplex analysis under partially denaturing conditions. In one embodiment, such an array can be used to analyze one sample simultaneously at different temperatures to maximize the detection of mutations in DNA fragments containing multiple discrete melting domains. Alternatively, one may inject different samples onto columns kept at the same effective temperature. Further improvements in throughput can be obtained by means of laser-induced fluorescence detection and the differential labeling of samples with up to four different fluorophores. Major advantages of monolithic capillary high-performance liquid chromatographic arrays over their capillary electrophoretic analogs are the chemical inertness of the poly(styrene-divinylbenzene) stationary phase, the physical robustness of the column bed due to its covalent linkage to the inner surface of the fused silica capillary, and the feasibility to modify the stationary phase thereby allowing the separation of compounds not only on the principle of size exclusion, but also adsorption, distribution, and ion exchange. Analyses times are on the order of a few minutes and turnaround time is extremely short as there is no need for the replenishment of the separation matrix between runs. PMID:11691859

UV-enhanced CO sensing using Ga 2O 3-based nanorod arrays at elevated temperature

DOE PAGES

Lin, Hui-Jan; Gao, Haiyong; Gao, Pu-Xian

2017-01-23

Monitoring and control of gaseous combustion process are critically important in advanced energy systems such as power plants, gas turbines, and automotive engines. However, very limited gas sensing solutions are available in the market for such application due to the inherent high temperature of combustion gaseous atmosphere. In this study, we fabricated and demonstrated high-performance metal oxide based nanorod array sensors assisted with ultra-violet (UV) illumination for in situ and real-time high-temperature gas detection. Without UV-illumination, it was found surface decoration of either 5 nm LSFO or 1 nm Pt nanoparticles can enhance the sensitivity over CO at 500 °Cmore » by an order of magnitude. Under the 254 nm UV illumination, CO gas-sensing performance of Ga 2O 3-based nanorod array sensors was further enhanced with the sensitivity boosted by 125 %, and the response time reduced by 30 % for La 0.8Sr 0.2FeO 3(LSFO)-decorated sample. The UV-enhanced detecting of CO might be due to the increased population of photo-induced electron-hole pairs. While for LSFO-decorated nanorod array sensor under UV illumination, the enhancement is through a combination of sensitizing effect and photocurrent effect.« less

Composite films of highly ordered Si nanowires embedded in SiGe0.3 for thermoelectric applications

NASA Astrophysics Data System (ADS)

Kikuchi, Akiou; Yao, Akifumi; Mori, Isamu; Ono, Takahito; Samukawa, Seiji

2017-10-01

We fabricated a high-density array of silicon nanowires (SiNWs) with a diameter of 10 nm embedded in silicon germanium (SiGe0.3) to give a composite thin film for thermoelectric device applications. The SiNW array was first fabricated by bio-template mask and neutral beam etching techniques. The SiNW array was then embedded in SiGe0.3 by thermal chemical vapor deposition. The cross-plane thermal conductivity of the SiNW-SiGe0.3 composite film with a thickness of 100 nm was 3.5 ± 0.3 W/mK in the temperature range of 300-350 K. Moreover, the temperature dependences of the in-plane electrical conductivity and in-plane Seebeck coefficient of the SiNW-SiGe0.3 composite were evaluated. The fabricated SiNW-SiGe0.3 composite film displayed a maximum power factor of 1 × 103 W/m K2 (a Seebeck coefficient of 4.8 × 103 μV/K and an electrical conductivity of 4.4 × 103 S/m) at 873 K. The present high-density SiNW array structure represents a new route to realize practical thermoelectric devices using mature Si processes without any rare metals.

UV-enhanced CO sensing using Ga2O3-based nanorod arrays at elevated temperature

NASA Astrophysics Data System (ADS)

Lin, Hui-Jan; Gao, Haiyong; Gao, Pu-Xian

2017-01-01

Monitoring and control of the gaseous combustion process are critically important in advanced energy systems such as power plants, gas turbines, and automotive engines. However, very limited gas sensing solutions are available in the market for such applications due to the inherent high temperature of the combustion gaseous atmosphere. In this study, we fabricated and demonstrated high-performance metal oxide based nanorod array sensors assisted with ultra-violet (UV) illumination for in situ and real-time high-temperature gas detection. Without UV-illumination, it was found that surface decoration of either 5 nm LSFO or 1 nm Pt nanoparticles can enhance the sensitivity over CO at 500 °C by an order of magnitude. Under the 254 nm UV illumination, the CO gas-sensing performance of Ga2O3-based nanorod array sensors was further enhanced with the sensitivity boosted by 125% and the response time reduced by 30% for the La0.8Sr0.2FeO3(LSFO)-decorated sample. The UV-enhanced detection of CO might be due to the increased population of photo-induced electron-hole pairs, whereas for LSFO-decorated nanorod array sensor under UV illumination, the enhancement is through a combination of the sensitizing effect and photocurrent effect.

Nanoengineered Thermal Materials Based on Carbon Nanotube Array Composites

NASA Technical Reports Server (NTRS)

Li, Jun; Meyyappan, Meyya; Dangelo, Carols

2012-01-01

State-of-the-art integrated circuits (ICs) for microprocessors routinely dissipate power densities on the order of 50 W/cm2. This large power is due to the localized heating of ICs operating at high frequencies and must be managed for future high-frequency microelectronic applications. As the size of components and devices for ICs and other appliances becomes smaller, it becomes more difficult to provide heat dissipation and transport for such components and devices. A thermal conductor for a macro-sized thermal conductor is generally inadequate for use with a microsized component or device, in part due to scaling problems. A method has been developed for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler-composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place, and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Assembly of ordered contigs of cosmids selected with YACs of human chromosome 13

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, S.G.; Cayanis, E.; Boukhgalter, B.

1994-06-01

The authors have developed an efficient method for assembling ordered cosmid contigs aligned to mega-YACs and midi-YACs (average insert sizes of 1.0 and 0.35 Mb, respectively) and used this general method to initiate high-resolution physical mapping of human chromosome 13 (Chr 13). Chr 13-enriched midi-YAC (mYAC) and mega-YAC (MYAC) sublibraries were obtained from corresponding CEPH total human YAC libraries by selecting colonies with inter-Alu PCR probes derived from Chr 13 monochromosomal cell hybrid DNA. These sublibraries were arrayed on filters at high density. In this approach, the MYAC 13 sublibrary is screened by hybridization with cytogenetically assigned Chr 13 DNAmore » probes to select one or a small subset of MYACs. Inter-Alu PCR products from each mYAC are then hybridized to the MYAC and mYAC sublibraries to identify overlapping YACs and to an arrayed Chr 13-specific cosmid library to select corresponding cosmids. The set of selected cosmids, gridded on filters at high density, is hybridized with inter-Alu PCR products from each of the overlapping YACs to identify subsets of cosmids and also with riboprobes from each cosmid of the arrayed set ({open_quotes}cosmid matrix cross-hybridization{close_quotes}). From these data, cosmid contigs are assembled by a specifically designed computer program. Application of this method generates cosmid contigs spanning the length of a MYAC with few gaps. To provide a high-resolution map, ends of cosmids are sequenced at preselected sites to position densely spaced sequence-tagged sites. 33 refs., 7 figs., 1 tab.« less

The potential of a Čerenkov Array for Supersymmetry and Cosmology

NASA Astrophysics Data System (ADS)

Vasileiadis, G.; Falvard, A.; Giraud, E.; Lavalle, J.; Sajjad, S.

2005-02-01

If R-parity is sufficiently well conserved, most of the supersymmetric models predict the existence of a stable, neutral particle, the neutralino, which would be a natural candidate for dark matter. Such particles can annihilate through various channels producing in particular, a faint flux of high energy photons in galactic and extragalactic high density regions. We have considered the potential of a Čerenkov array for exploring a significant fraction of the supersymmetric parameter space. The main constraints are the flux limit, which requires a very large effective area, and the energy threshold which needs reaching lower limit of the order of 15-20 GeV due to the lowest neutralino mass given by accelerators. Combining such constaints leads to an array of at least 16-19 Čerenkov reflectors with diameters of the order of 18m, located at high altitude (5000 m). This instrument would combine wide angle camera and large detection areas. It would also serve as a major tool in Observational Cosmology and Astrophysics above 15-20 GeV up to 1 TeV. Coming after GLAST, it would allow studying in details, at higher energy, the sources detected by this satellite. This instrument would not be able to explore the 10 GeV to sub-10 GeV domain unless higher QE detectors are discovered or larger diameters are considered. A very interesting site would be the Chajnantor-Toco area for this project which requires clear UBV photometric nights.

Efficient photocatalytic degradation of gaseous N,N-dimethylformamide in tannery waste gas using doubly open-ended Ag/TiO2 nanotube array membranes

NASA Astrophysics Data System (ADS)

Zhao, Yang; Ma, Lin; Chang, Wenkai; Huang, Zhiding; Feng, Xugen; Qi, Xiaoxia; Li, Zenghe

2018-06-01

Gaseous N,N-dimethylformamide (DMF), typical volatile organic compound exhausted from manufacturing factories, may damage the health of workers under long-term exposure even at low levels. The defined geometry, porous surface and highly ordered channels make the free-standing anodic TiO2 nanotube (TiNT) arrays particularly suitable for applications of practical air purification by flow-through photocatalysis. In the present work, crystallized doubly open-ended Ag/TiNT array membranes were designed and prepared by employing a lift-off process based on an anodization-annealing-anodization-etching sequence, followed by uniform Ag nanoparticles decoration. For the photocatalytic degradation of gaseous DMF at low concentration levels close to that found in realistic pollutant air, an analytical methodology for the monitoring and determination of degradation process was developed based on the coupling of headspace sampling with gas chromatography mass spectrometry (HS-GC-MS). The doubly open-ended Ag/TiNT arrays exhibited higher removal efficiency of gaseous DMF from air compared with conventional bottom-closed Ag/TiNT arrays and pure bottomless TiNT arrays. These results indicated that the photocatalytic properties of TiNT arrays were improved with the open-bottom morphology and the Ag nanoparticles decoration. Based on the analysis with GC-MS and high performance ion chromatography (HPIC), it was found that demethylation is the main pathway of DMF degradation in photocatalytic reactions. Furthermore, decontamination of actual polluted tannery waste gas collected in leather factory proved that the photocatalysis on doubly open-ended Ag/TiNT array membrane is an efficient way and a promising application to treat air contaminated by DMF despite the complexity of various volatile organic compounds.

Arrays of Carbon Nanotubes as RF Filters in Waveguides

NASA Technical Reports Server (NTRS)

Hoppe, Daniel; Hunt, Brian; Hoenk, Michael; Noca, Flavio; Xu, Jimmy

2003-01-01

Brushlike arrays of carbon nanotubes embedded in microstrip waveguides provide highly efficient (high-Q) mechanical resonators that will enable ultraminiature radio-frequency (RF) integrated circuits. In its basic form, this invention is an RF filter based on a carbon nanotube array embedded in a microstrip (or coplanar) waveguide, as shown in Figure 1. In addition, arrays of these nanotube-based RF filters can be used as an RF filter bank. Applications of this new nanotube array device include a variety of communications and signal-processing technologies. High-Q resonators are essential for stable, low-noise communications, and radar applications. Mechanical oscillators can exhibit orders of magnitude higher Qs than electronic resonant circuits, which are limited by resistive losses. This has motivated the development of a variety of mechanical resonators, including bulk acoustic wave (BAW) resonators, surface acoustic wave (SAW) resonators, and Si and SiC micromachined resonators (known as microelectromechanical systems or MEMS). There is also a strong push to extend the resonant frequencies of these oscillators into the GHz regime of state-of-the-art electronics. Unfortunately, the BAW and SAW devices tend to be large and are not easily integrated into electronic circuits. MEMS structures have been integrated into circuits, but efforts to extend MEMS resonant frequencies into the GHz regime have been difficult because of scaling problems with the capacitively-coupled drive and readout. In contrast, the proposed devices would be much smaller and hence could be more readily incorporated into advanced RF (more specifically, microwave) integrated circuits.

Image Decoding of Photonic Crystal Beads Array in the Microfluidic Chip for Multiplex Assays

PubMed Central

Yuan, Junjie; Zhao, Xiangwei; Wang, Xiaoxia; Gu, Zhongze

2014-01-01

Along with the miniaturization and intellectualization of biomedical instruments, the increasing demand of health monitoring at anywhere and anytime elevates the need for the development of point of care testing (POCT). Photonic crystal beads (PCBs) as one kind of good encoded microcarriers can be integrated with microfluidic chips in order to realize cost-effective and high sensitive multiplex bioassays. However, there are difficulties in analyzing them towards automated analysis due to the characters of the PCBs and the unique detection manner. In this paper, we propose a strategy to take advantage of automated image processing for the color decoding of the PCBs array in the microfluidic chip for multiplex assays. By processing and alignment of two modal images of epi-fluorescence and epi-white light, every intact bead in the image is accurately extracted and decoded by PC colors, which stand for the target species. This method, which shows high robustness and accuracy under various configurations, eliminates the high hardware requirement of spectroscopy analysis and user-interaction software, and provides adequate supports for the general automated analysis of POCT based on PCBs array. PMID:25341876

Ordered CdTe/CdS Arrays for High-Performance Solar Cells

NASA Astrophysics Data System (ADS)

Zubía, David; López, Cesar; Rodríguez, Mario; Escobedo, Arev; Oyer, Sandra; Romo, Luis; Rogers, Scott; Quiñónez, Stella; McClure, John

2007-12-01

The deposition of uniform arrays of CdTe/CdS heterostructures suitable for solar cells via close-spaced sublimation is presented. The approach used to create the arrays consists of two basic steps: the deposition of a patterned growth mask on CdS, and the selective-area deposition of CdTe. CdTe grains grow selectively on the CdS but not on the SiO2 due to the differential surface mobility between the two surfaces. Furthermore, the CdTe mesas mimic the size and shape of the window opening in the SiO2. Measurements of the current density in the CdTe were high at 28 mA/cm2. To our knowledge, this is the highest reported current density for these devices. This implies that either the quantum efficiency is very high or the electrons generated throughout the CdTe are being concentrated by the patterned structure analogous to solar concentration. The enhancement in crystal uniformity and the relatively unexplored current concentration phenomenon could lead to significant performance improvements.

Ordering nanoparticles with polymer brushes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a singlemore » layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. As a result, an interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.« less

Ordering nanoparticles with polymer brushes

DOE PAGES

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

2017-12-08

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a singlemore » layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. As a result, an interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.« less

Electrodeposition of bismuth:tellurium nanowire arrays into porous alumina templates for thermoelectric applications

NASA Astrophysics Data System (ADS)

Trahey, Lynn

Bismuth telluride is a well-known thermoelectric material for refrigeration applications. Thermoelectrics possess several advantages over conventional refrigeration and power generation devices, yet are not widely-used due to low efficiencies. It has been predicted and shown experimentally that the efficiency of thermoelectric devices increases when the semiconducting materials have reduced dimensions. Therefore, the aim of this research was to show enhanced thermoelectric efficiency in one-dimensional nanowires. The nanowires were synthesized via electrochemical deposition into porous alumina templates. Electrodeposition is a versatile technique that ensures electrical continuity in the deposited material. The nanowire templates, porous alumina, were made by the double anodization of high-purity aluminum foil in oxalic acid solutions. This technique produces parallel, hexagonally packed, and nanometer-range diameter pores that can reach high aspect ratios (greater than 2000:1). The main anodization variables (electrolyte concentration, applied potential, 2nd anodization time, and temperature) were studied systematically in order to deconvolute their effects on the resulting pores and to obtain high aspect ratio pores. The porous alumina is of great importance because the pore dimensions determine the dimensions of the electrodeposited nanowires, which influence the thermoelectric performance of the nanowire arrays. Nanowire arrays were characterized in several ways. Powder X-ray diffraction was used to assess crystallinity and preferred orientation of the nanowires, revealing that the nanowires are highly crystalline and grow with strong preferred orientation such that the material is suited for optimal thermoelectric performance. Scanning electron microscopy was used to evaluate the nanowire nucleation percentage and growth-front uniformity, both of which were enhanced by pulsed-potential electrodeposition. Compositional analysis via electron microprobe indicates that the as-grown nanowires are Te-rich or Bi-deficient, which agrees with Seebeck coefficient data showing the arrays are n-type semiconductors. In collaboration with Marlow Industries, the thermoelectric performance of the arrays was gauged. The nanowire arrays were successfully contacted with robust nickel layers as revealed by the low AC resistances of the arrays. One array was incorporated into a hybrid thermoelectric device and a DeltaT of 14.8°C was measured, indicating that the measurement and electrical contact approaches were successful despite further optimization being needed.

Atomic force microscopy of gastric mucin

NASA Astrophysics Data System (ADS)

Chasan, Bernard; Hong, Zhenning; Bansil, Rama; Turner, Bradley; Ramakrishnan Bhaskar, K.; Afdhal, Nezam

2001-03-01

We report on the first results from an AFM study of porcine gastric mucin employing the tapping mode technique in aqueous solution. This glycoprotein is responsible for protecting the stomach epithelium from acid damage. Mucin was imaged on a mica substrate at pH7, and at pH2. At the higher pH we detected individual molecules in disordered configuration, with characteristic lengths of 20-40 nm. At the lower pH the mucin forms extended rod-like clusters that, at high concentrations, are aligned into planar arrays. Individual clusters are of order 50 nm long and 20 nm wide while the entire array is of order several hundred nm both in length and width. The clustering behavior at low pH is consistent with that previously detected in dynamic light scattering experiments by Cao et. al. (Biophysical J. 76:120-1258 1999).

Large-area zinc oxide nanorod arrays templated by nanoimprint lithography: control of morphologies and optical properties

NASA Astrophysics Data System (ADS)

Zhang, Chen; Huang, Xiaohu; Liu, Hongfei; Chua, Soo Jin; Ross, Caroline A.

2016-12-01

Vertically aligned, highly ordered, large area arrays of nanostructures are important building blocks for multifunctional devices. Here, ZnO nanorod arrays are selectively synthesized on Si substrates by a solution method within patterns created by nanoimprint lithography. The growth modes of two dimensional nucleation-driven wedding cakes and screw dislocation-driven spirals are inferred to determine the top end morphologies of the nanorods. Sub-bandgap photoluminescence of the nanorods is greatly enhanced by the manipulation of the hydrogen donors via a post-growth thermal treatment. Lasing behavior is facilitated in the nanorods with faceted top ends formed from wedding cakes growth mode. This work demonstrates the control of morphologies of oxide nanostructures in a large scale and the optimization of the optical performance.

Self-assembled vertically aligned Au nanorod arrays for surface-enhanced Raman scattering (SERS) detection of Cannabinol

NASA Astrophysics Data System (ADS)

Milliken, Sarah; Fraser, Jeff; Poirier, Shawn; Hulse, John; Tay, Li-Lin

2018-05-01

Self-assembled multi-layered vertically aligned gold nanorod (AuNR) arrays have been fabricated by a simple preparation process that requires a balance between the particle concentration and the ionic strength of the solvent. An experimentally determined critical AuNR concentration of 2.0 nM and 50 mM NaCl produces well-ordered vertically aligned hexagonally close-packed AuNR arrays. We demonstrate surface treatment via UV Ozone cleaning of such samples to allow introduction of analyte molecules (benzenethiol and cannabinol) for effective surface enhanced Raman scattering detection. This is the first demonstration of the SERS analysis of cannabinol. This approach demonstrates a cost-effective, high-yield and simple fabrication route to SERS sensors with application in the screening for the cannabinoids.

Hexagonal Nanopyramidal Prisms of Nearly Intrinsic InN on Patterned GaN Nanowire Arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golam Sarwar, A. T. M.; Leung, Benjamin; Wang, George T.

By using multiple growth steps that separate the nucleation and growth processes, we show that nearly intrinsic InN single nanocrystals of high optical quality can be formed on patterned GaN nanowire arrays by molecular beam epitaxy. The InN nanostructures form into well-defined hexagonal prisms with pyramidal tops. Micro-photoluminescence (μ-PL) is carried out at low temperature (LT: 28.2 K) and room temperature (RT: 285 K) to gauge the relative material quality of the InN nanostructures. Nanopyramidal prisms grown using a three-step growth method are found to show superior quantum efficiency. In conclusion, excitation and temperature dependent μ-PL demonstrates the very highmore » quality and nearly intrinsic nature of the ordered InN nanostructure arrays.« less

Hexagonal Nanopyramidal Prisms of Nearly Intrinsic InN on Patterned GaN Nanowire Arrays

DOE PAGES

Golam Sarwar, A. T. M.; Leung, Benjamin; Wang, George T.; ...

2018-01-04

By using multiple growth steps that separate the nucleation and growth processes, we show that nearly intrinsic InN single nanocrystals of high optical quality can be formed on patterned GaN nanowire arrays by molecular beam epitaxy. The InN nanostructures form into well-defined hexagonal prisms with pyramidal tops. Micro-photoluminescence (μ-PL) is carried out at low temperature (LT: 28.2 K) and room temperature (RT: 285 K) to gauge the relative material quality of the InN nanostructures. Nanopyramidal prisms grown using a three-step growth method are found to show superior quantum efficiency. In conclusion, excitation and temperature dependent μ-PL demonstrates the very highmore » quality and nearly intrinsic nature of the ordered InN nanostructure arrays.« less

Fabrication of micro-lens array on convex surface by meaning of micro-milling

NASA Astrophysics Data System (ADS)

Zhang, Peng; Du, Yunlong; Wang, Bo; Shan, Debin

2014-08-01

In order to develop the application of the micro-milling technology, and to fabricate ultra-precision optical surface with complex microstructure, in this paper, the primary experimental research on micro-milling complex microstructure array is carried out. A complex microstructure array surface with vary parameters is designed, and the mathematic model of the surface is set up and simulated. For the fabrication of the designed microstructure array surface, a micro three-axis ultra-precision milling machine tool is developed, aerostatic guideway drove directly by linear motor is adopted in order to guarantee the enough stiffness of the machine, and novel numerical control strategy with linear encoders of 5nm resolution used as the feedback of the control system is employed to ensure the extremely high motion control accuracy. With the help of CAD/CAM technology, convex micro lens array on convex spherical surface with different scales on material of polyvinyl chloride (PVC) and pure copper is fabricated using micro tungsten carbide ball end milling tool based on the ultra-precision micro-milling machine. Excellent nanometer-level micro-movement performance of the axis is proved by motion control experiment. The fabrication is nearly as the same as the design, the characteristic scale of the microstructure is less than 200μm and the accuracy is better than 1μm. It prove that ultra-precision micro-milling technology based on micro ultra-precision machine tool is a suitable and optional method for micro manufacture of microstructure array surface on different kinds of materials, and with the development of micro milling cutter, ultraprecision micro-milling complex microstructure surface will be achieved in future.

Molecular dynamics study of the growth of a metal nanoparticle array by solid dewetting

NASA Astrophysics Data System (ADS)

Luan, Yanhua; Li, Yanru; Nie, Tiaoping; Yu, Jun; Meng, Lijun

2018-03-01

We investigated the effect of the substrate and the ambient temperature on the growth of a metal nanoparticle array (nanoarray) on a solid-patterned substrate by dewetting a Au liquid film using an atomic simulation technique. The patterned substrate was constructed by introducing different interaction potentials for two atom groups ( C 1 and C 2) in the graphene-like substrate. The C 1 group had a stronger interaction between the Au film and the substrate and was composed of regularly distributed circular disks with radius R and distance D between the centers of neighboring disks. Our simulation results demonstrate that R and D have a strikingly different influence on the growth of the nanoparticle arrays. The degree of order of the nanoarray increases first before it reaches a peak and then decreases for increasing R at fixed D. However, the degree of order increases monotonously when D is increased and reaches a saturated value beyond a critical value of D for a fixed R. Interestingly, a labyrinth-like structure appeared during the dewetting process of the metal film. The simulation results also indicated that the temperature was an important factor in controlling the properties of the nanoarray. An appropriate temperature leads to an optimized nanoarray with a uniform grain size and well-ordered particle distribution. These results are important for understanding the dewetting behaviors of metal films on solid substrates and understanding the growth of highly ordered metal nanoarrays using a solid-patterned substrate method.

Development of transducer arrays for ultrasound-computer tomography

NASA Astrophysics Data System (ADS)

Stotzka, Rainer; Gobel, Georg; Schlote-Holubek, Klaus

2003-05-01

Ultrasound computer-tomography (USCT) is a novel ultrasound imaging method capable of producing volume images with both high spatial and temporal resolution. Several thousand ultrasound transducers are arranged in a cylindrical array around a tank containing the object to be examined coupled by water. Every single transducer is small enough to emit an almost spherical sound-wave. While one transducer is transmitting, all others receive simultaneously. Our experimental setup, using only a few transducers simulating a ring-shaped geometry, showed even nylon threads (0.1 mm) with an image quality superior to clinical in-use ultrasound scanners. In order to build a complete circular array several thousand transducers, with cylindrical sound field characteristics, are needed. Since such transducer arrays are hardly available and expensive, we developed inexpensive transducer arrays consisting of 8 elements. Each array is based on a plate of lead titanate zirconate ceramics (PZT) sawn into 8 elements of 0.3 mm width, 3.8 mm height and 0.5 mm pitch. Each element has a mean frequency of 3.8 MHz and can be triggered separately. The main challenge was the development of production steps with reproducible results. Our transducer arrays show only small variances in the sound field characteristics which are strongly required for ultrasound tomography.

SAR Reduction in 7T C-Spine Imaging Using a “Dark Modes” Transmit Array Strategy

PubMed Central

Eryaman, Yigitcan; Guerin, Bastien; Keil, Boris; Mareyam, Azma; Herraiz, Joaquin L.; Kosior, Robert K.; Martin, Adrian; Torrado-Carvajal, Angel; Malpica, Norberto; Hernandez-Tamames, Juan A.; Schiavi, Emanuele; Adalsteinsson, Elfar; Wald, Lawrence L.

2016-01-01

Purpose Local specific absorption rate (SAR) limits many applications of parallel transmit (pTx) in ultra high-field imaging. In this Note, we introduce the use of an array element, which is intentionally inefficient at generating spin excitation (a “dark mode”) to attempt a partial cancellation of the electric field from those elements that do generate excitation. We show that adding dipole elements oriented orthogonal to their conventional orientation to a linear array of conventional loop elements can lower the local SAR hotspot in a C-spine array at 7 T. Methods We model electromagnetic fields in a head/torso model to calculate SAR and excitation B1+ patterns generated by conventional loop arrays and loop arrays with added electric dipole elements. We utilize the dark modes that are generated by the intentional and inefficient orientation of dipole elements in order to reduce peak 10g local SAR while maintaining excitation fidelity. Results For B1+ shimming in the spine, the addition of dipole elements did not significantly alter the B1+ spatial pattern but reduced local SAR by 36%. Conclusion The dipole elements provide a sufficiently complimentary B1+ and electric field pattern to the loop array that can be exploited by the radiofrequency shimming algorithm to reduce local SAR. PMID:24753012

Optical diffraction in ordered VO2 nanoparticle arrays

NASA Astrophysics Data System (ADS)

Lopez, Rene; Feldman, Leonard; Haglund, Richard

2006-03-01

The potential of oxide electronic materials as multifunctional building blocks is one of the driving concepts of the field. In this presentation, we show how nanostructured particle arrays with long-range order can be used to modulate an optical response through exploiting the metal-insulator transition of vanadium dioxide. Arrays of VO2 nanoparticles with long-range order were fabricated by pulsed laser deposition in an arbitrary pattern defined by focused ion-beam lithography. The interaction of light with the nanoparticles is controlled by the nanoparticle size, spacing and geometrical arrangement and by switching between the metallic and semiconducting phases of VO2. In addition to the near-infrared surface plasmon response observed in previous VO2 studies, the VO2 nanoparticle arrays exhibit size-dependent optical resonances in the visible region that likewise show an enhanced optical contrast between the semiconducting and metallic phases. The collective optical response as a function of temperature gives rise to an enhanced scattering state during the evolving phase transition, while the incoherent coupling between the nanoparticles produces an order-disorder-order transition.

Propagation of a phase-locked circular dark hollow beams array in a turbulent atmosphere

NASA Astrophysics Data System (ADS)

Zhou, Pu; Wang, Xiaolin; Ma, Yanxing; Ma, Haotong; Xu, Xiaojun; Liu, Zejin

2010-10-01

The propagation of phase-locked circular dark hollow beams array in a turbulent atmosphere is studied. An analytical expression for the average intensity distribution at the receiving plane is obtained based on the extended Huygens-Fresnel principle. The effects of turbulence, dark parameter and beam order of the beams array on the intensity pattern are studied and analyzed. It is found that the intensity pattern of the phase-locked circular dark hollow beams array will evolve from a multiple-spot-pattern into a Gaussian beam spot under the isotropic influence of the turbulence. The intensity pattern of beam array with a larger dark parameter and beam order evolves into the Gaussian-shape faster with increasing propagation distance.

Sweetwater, Texas Large N Experiment

NASA Astrophysics Data System (ADS)

Sumy, D. F.; Woodward, R.; Barklage, M.; Hollis, D.; Spriggs, N.; Gridley, J. M.; Parker, T.

2015-12-01

From 7 March to 30 April 2014, NodalSeismic, Nanometrics, and IRIS PASSCAL conducted a collaborative, spatially-dense seismic survey with several thousand nodal short-period geophones complemented by a backbone array of broadband sensors near Sweetwater, Texas. This pilot project demonstrates the efficacy of industry and academic partnerships, and leveraged a larger, commercial 3D survey to collect passive source seismic recordings to image the subsurface. This innovative deployment of a large-N mixed-mode array allows industry to explore array geometries and investigate the value of broadband recordings, while affording academics a dense wavefield imaging capability and an operational model for high volume instrument deployment. The broadband array consists of 25 continuously-recording stations from IRIS PASSCAL and Nanometrics, with an array design that maximized recording of horizontal-traveling seismic energy for surface wave analysis over the primary target area with sufficient offset for imaging objectives at depth. In addition, 2639 FairfieldNodal Zland nodes from NodalSeismic were deployed in three sub-arrays: the outlier, backbone, and active source arrays. The backbone array consisted of 292 nodes that covered the entire survey area, while the outlier array consisted of 25 continuously-recording nodes distributed at a ~3 km distance away from the survey perimeter. Both the backbone and outlier array provide valuable constraints for the passive source portion of the analysis. This project serves as a learning platform to develop best practices in the support of large-N arrays with joint industry and academic expertise. Here we investigate lessons learned from a facility perspective, and present examples of data from the various sensors and array geometries. We will explore first-order results from local and teleseismic earthquakes, and show visualizations of the data across the array. Data are archived at the IRIS DMC under stations codes XB and 1B.

Building one-dimensional oxide nanostructure arrays on conductive metal substrates for lithium-ion battery anodes.

PubMed

Jiang, Jian; Li, Yuanyuan; Liu, Jinping; Huang, Xintang

2011-01-01

Lithium ion battery (LIB) is potentially one of the most attractive energy storage devices. To meet the demands of future high-power and high-energy density requirements in both thin-film microbatteries and conventional batteries, it is challenging to explore novel nanostructured anode materials instead of conventional graphite. Compared to traditional electrodes based on nanostructure powder paste, directly grown ordered nanostructure array electrodes not only simplify the electrode processing, but also offer remarkable advantages such as fast electron transport/collection and ion diffusion, sufficient electrochemical reaction of individual nanostructures, enhanced material-electrolyte contact area and facile accommodation of the strains caused by lithium intercalation and de-intercalation. This article provides a brief overview of the present status in the area of LIB anodes based on one-dimensional nanostructure arrays growing directly on conductive inert metal substrates, with particular attention to metal oxides synthesized by an anodized alumina membrane (AAM)-free solution-based or hydrothermal methods. Both the scientific developments and the techniques and challenges are critically analyzed.

Building one-dimensional oxidenanostructure arrays on conductive metal substrates for lithium-ion battery anodes

NASA Astrophysics Data System (ADS)

Jiang, Jian; Li, Yuanyuan; Liu, Jinping; Huang, Xintang

2011-01-01

Lithium ion battery (LIB) is potentially one of the most attractive energy storage devices. To meet the demands of future high-power and high-energy density requirements in both thin-film microbatteries and conventional batteries, it is challenging to explore novel nanostructured anode materials instead of conventional graphite. Compared to traditional electrodes based on nanostructure powder paste, directly grown ordered nanostructure array electrodes not only simplify the electrode processing, but also offer remarkable advantages such as fast electron transport/collection and ion diffusion, sufficient electrochemical reaction of individual nanostructures, enhanced material-electrolyte contact area and facile accommodation of the strains caused by lithium intercalation and de-intercalation. This article provides a brief overview of the present status in the area of LIB anodes based on one-dimensional nanostructure arrays growing directly on conductive inert metal substrates, with particular attention to metal oxides synthesized by an anodized aluminamembrane (AAM)-free solution-based or hydrothermal methods. Both the scientific developments and the techniques and challenges are critically analyzed.

Emerging Array Antenna Technologies at JPL

NASA Technical Reports Server (NTRS)

Huang, J.

1998-01-01

JPL/NASA's Earth remote sensing and deep-space exploration programs have been placing emphasis on their spacecraft's high-gain and large-aperture antennas. At the same time, however, low mass and small storage volume are demanded in order to reduce payload weight and reduce shroud size and thus reduce launch cost.

Laser-based microstructuring of materials surfaces using low-cost microlens arrays

NASA Astrophysics Data System (ADS)

Nieto, Daniel; Vara, G.; Diez, J. A.; O`Connor, Gerard M.; Arines, Justo; Gómez-Reino, C.; Flores-Arias, M.

2012-03-01

Since frictional interactions in microscopically small components are becoming increasingly important for the development of new products for all modern technology, we present a laser-based technique for micro-patterning surfaces of materials using low-cost microlens arrays. The microlens used were fabricated on soda-lime glass using a laser direct-write technique, followed by a thermal treatment into an oven. By combining laser direct-write and the thermal treatment it was possible to obtain high quality elements using a low cost infrared laser widely implemented in industry which makes this technique attractive in comparison with other more expensive methods. The main advantage of using microlens arrays for micropatterning surfaces is the possibility of fabricating a large number of identical structures simultaneously, leading to a highly efficient process. In order to study the capabilities of the microlens fabricated for microstructuring materials, identical structures and arrays of holes were fabricated over a variety of materials, such us, stainless steel, polymer and ceramic. The minimum diameter of the individual microstructure generated at surface is 5 μm. Different nanosecond lasers operating at Infrared, Green and UV were used. The topography and morphology of the elements obtained were determined using a confocal microscope SENSOFAR 2300 Plμ.

Nonlinear vibration behaviors of high-Tc superconducting bulks in an applied permanent magnetic array field

NASA Astrophysics Data System (ADS)

Li, Jipeng; Li, Haitao; Zheng, Jun; Zheng, Botian; Huang, Huan; Deng, Zigang

2017-06-01

The nonlinear vibration of high temperature superconducting (HTS) bulks in an applied permanent magnetic array (Halbach array) field, as a precondition for commercial application to HTS maglev train and HTS bearing, is systematically investigated. This article reports the actual vibration rules of HTS bulks from three aspects. First, we propose a new numerical model to simplify the calculation of levitation force. This model could provide precise simulations, especially the estimation of eigenfrequency. Second, an approximate analytic solution of the vibration of the HTS bulks is obtained by using the method of harmonic balance. Finally, to verify the results mentioned above, we measure the vertical vibration acceleration signals of an HTS maglev model, consisting of eight YBaCuO bulks, oscillating freely above a Halbach array with large displacement excitation. Higher order harmonic components, which indicate the nonlinear vibration phenomenon, are detected in the responses. All the three results are compared and agreed well with each other. This study combines the experimental and theoretical analyses and provides a deep understanding of the physical phenomenon of the nonlinear vibration and is meaningful for the vibration control of the relevant applications.

Atomic force microscopy of chromatin arrays reveal non-monotonic salt dependence of array compaction in solution

PubMed Central

Krzemien, Katarzyna M.; Beckers, Maximilian; Quack, Salina; Michaelis, Jens

2017-01-01

Compaction of DNA in chromatin is a hallmark of the eukaryotic cell and unravelling its structure is required for an understanding of DNA involving processes. Despite strong experimental efforts, many questions concerning the DNA packing are open. In particular, it is heavily debated whether an ordered structure referred to as the “30 nm fibre” exist in vivo. Scanning probe microscopy has become a cutting edge technology for the high-resolution imaging of DNA- protein complexes. Here, we perform high-resolution atomic force microscopy of non-cross-linked chromatin arrays in liquid, under different salt conditions. A statistical analysis of the data reveals that array compaction is salt dependent in a non-monotonic fashion. A simple physical model can qualitatively explain the observed findings due to the opposing effects of salt dependent stiffening of DNA, nucleosome stability and histone-histone interactions. While for different salt concentrations different compaction states are observed, our data do not provide support for the existence of regular chromatin fibres. Our studies add new insights into chromatin structure, and with that contribute to a further understanding of the DNA condensation. PMID:28296908

A Facile Method for Loading CeO2 Nanoparticles on Anodic TiO2 Nanotube Arrays.

PubMed

Liao, Yulong; Yuan, Botao; Zhang, Dainan; Wang, Xiaoyi; Li, Yuanxun; Wen, Qiye; Zhang, Huaiwu; Zhong, Zhiyong

2018-04-03

In this paper, a facile method was proposed to load CeO 2 nanoparticles (NPs) on anodic TiO 2 nanotube (NT) arrays, which leads to a formation of CeO 2 /TiO 2 heterojunctions. Highly ordered anatase phase TiO 2 NT arrays were fabricated by using anodic oxidation method, then these individual TiO 2 NTs were used as tiny "nano-containers" to load a small amount of Ce(NO 3 ) 3 solutions. The loaded anodic TiO 2 NTs were baked and heated to a high temperature of 450 °C, under which the Ce(NO 3 ) 3 would be thermally decomposed inside those nano-containers. After the thermal decomposition of Ce(NO 3 ) 3 , cubic crystal CeO 2 NPs were obtained and successfully loaded into the anodic TiO 2 NT arrays. The prepared CeO 2 /TiO 2 heterojunction structures were characterized by a variety of analytical technologies, including XRD, SEM, and Raman spectra. This study provides a facile approach to prepare CeO 2 /TiO 2 films, which could be very useful for environmental and energy-related areas.

Continuous Beam Steering From a Segmented Liquid Crystal Optical Phased Array

NASA Technical Reports Server (NTRS)

Titus, Charles M.; Pouch, John; Nguyen, Hung; Miranda, Felix; Bos, Philip J.

2002-01-01

Optical communications to and from deep space probes will require beams possessing divergence on the order of a microradian, and must be steered with sub-microradian precision. Segmented liquid crystal spatial phase modulators, a type of optical phased array, are considered for this ultra-high resolution beam steering. It is shown here that in an ideal device of this type, there are ultimately no restrictions on the angular resolution. Computer simulations are used to obtain that result, and to analyze the influence of beam truncation and substrate flatness on the performance of this type of device.

Breast Cancer Nodes Detection Using Ultrasonic Microscale Subarrayed MIMO RADAR

PubMed Central

Siwamogsatham, Siwaruk; Pomalaza-Ráez, Carlos

2014-01-01

This paper proposes the use of ultrasonic microscale subarrayed MIMO RADARs to estimate the position of breast cancer nodes. The transmit and receive antenna arrays are divided into subarrays. In order to increase the signal diversity each subarray is assigned a different waveform from an orthogonal set. High-frequency ultrasonic transducers are used since a breast is considered to be a superficial structure. Closed form expressions for the optimal Neyman-Pearson detector are derived. The combination of the waveform diversity present in the subarrayed deployment and traditional phased-array RADAR techniques provides promising results. PMID:25309591

A control system based on field programmable gate array for papermaking sewage treatment

NASA Astrophysics Data System (ADS)

Zhang, Zi Sheng; Xie, Chang; Qing Xiong, Yan; Liu, Zhi Qiang; Li, Qing

2013-03-01

A sewage treatment control system is designed to improve the efficiency of papermaking wastewater treatment system. The automation control system is based on Field Programmable Gate Array (FPGA), coded with Very-High-Speed Integrate Circuit Hardware Description Language (VHDL), compiled and simulated with Quartus. In order to ensure the stability of the data used in FPGA, the data is collected through temperature sensors, water level sensor and online PH measurement system. The automatic control system is more sensitive, and both the treatment efficiency and processing power are increased. This work provides a new method for sewage treatment control.

Evaluation of the Telecommunications Protocol Processing Subsystem Using Reconfigurable Interoperable Gate Array

NASA Technical Reports Server (NTRS)

Pang, Jackson; Liddicoat, Albert; Ralston, Jesse; Pingree, Paula

2006-01-01

The current implementation of the Telecommunications Protocol Processing Subsystem Using Reconfigurable Interoperable Gate Arrays (TRIGA) is equipped with CFDP protocol and CCSDS Telemetry and Telecommand framing schemes to replace the CPU intensive software counterpart implementation for reliable deep space communication. We present the hardware/software co-design methodology used to accomplish high data rate throughput. The hardware CFDP protocol stack implementation is then compared against the two recent flight implementations. The results from our experiments show that TRIGA offers more than 3 orders of magnitude throughput improvement with less than one-tenth of the power consumption.

Continuous Beam Steering From A Segmented Liquid Crystal Optical Phased Array

NASA Technical Reports Server (NTRS)

Pouch, John; Nguyen, Hung; Miranda, Felix; Titus, Charles M.; Bos, Philip J.

2002-01-01

Optical communications to and from deep space probes will require beams possessing divergence on the order of a microradian, and must be steered with sub-microradian precision. Segmented liquid crystal spatial phase modulators, a type of optical phased array, are considered for this ultra-high resolution beam steering. It is shown here that in an ideal device of this type, there are ultimately no restrictions on the angular resolution. Computer simulations are used to obtain that result, and to analyze the influence of beam truncation and substrate flatness on the performance of this type of device.

A class of least-squares filtering and identification algorithms with systolic array architectures

NASA Technical Reports Server (NTRS)

Kalson, Seth Z.; Yao, Kung

1991-01-01

A unified approach is presented for deriving a large class of new and previously known time- and order-recursive least-squares algorithms with systolic array architectures, suitable for high-throughput-rate and VLSI implementations of space-time filtering and system identification problems. The geometrical derivation given is unique in that no assumption is made concerning the rank of the sample data correlation matrix. This method utilizes and extends the concept of oblique projections, as used previously in the derivations of the least-squares lattice algorithms. Exponentially weighted least-squares criteria are considered for both sliding and growing memory.

Polymer nanoimprinting using an anodized aluminum mold for structural coloration

NASA Astrophysics Data System (ADS)

Kikuchi, Tatsuya; Nishinaga, Osamu; Natsui, Shungo; Suzuki, Ryosuke O.

2015-06-01

Polymer nanoimprinting of submicrometer-scale dimple arrays with structural coloration was demonstrated. Highly ordered aluminum dimple arrays measuring 530-670 nm in diameter were formed on an aluminum substrate via etidronic acid anodizing at 210-270 V and subsequent anodic oxide dissolution. The nanostructured aluminum surface led to bright structural coloration with a rainbow spectrum, and the reflected wavelength strongly depends on the angle of the specimen and the period of the dimple array. The reflection peak shifts gradually with the dimple diameter toward longer wavelength, reaching 800 nm in wavelength at 670 nm in diameter. The shape of the aluminum dimple arrays were successfully transferred to a mercapto-ester ultra-violet curable polymer via self-assembled monolayer coating and polymer replications using a nanoimprinting technique. The nanostructured polymer surfaces with positively and negatively shaped dimple arrays also exhibited structural coloration based on the periodic nanostructure, and reflected light mostly in the visible region, 400-800 nm. This nanostructuring with structural coloration can be easily realized by simple techniques such as anodizing, SAM coating, and nanoimprinting.

Two-Dimensional Si-Nanodisk Array Fabricated Using Bio-Nano-Process and Neutral Beam Etching for Realistic Quantum Effect Devices

NASA Astrophysics Data System (ADS)

Huang, Chi-Hsien; Igarashi, Makoto; Woné, Michel; Uraoka, Yukiharu; Fuyuki, Takashi; Takeguchi, Masaki; Yamashita, Ichiro; Samukawa, Seiji

2009-04-01

A high-density, large-area, and uniform two-dimensional (2D) Si-nanodisk array was successfully fabricated using the bio-nano-process, advanced etching techniques, including a treatment using nitrogen trifluoride and hydrogen radical (NF3 treatment) and a damage-free chlorine neutral beam (NB). By using the surface oxide formed by neutral beam oxidation (NBO) for the preparation of a 2D nanometer-sized iron core array as an etching mask, a well-ordered 2D Si-nanodisk array was obtained owing to the dangling bonds of the surface oxide. By changing the NF3 treatment time without changing the quantum effect of each nanodisk, we could control the gap between adjacent nanodisks. A device with two electrodes was fabricated to investigate the electron transport in a 2D Si-nanodisk array. Current fluctuation and time-dependent currents were clearly observed owing to the charging-discharging of the nanodisks adjacent to the current percolation path. The new structure may have great potential for future novel quantum effect devices.

Velocity Data in a Fully Developed Wind Turbine Array Boundary Layer

NASA Astrophysics Data System (ADS)

Turner, John; Wosnik, Martin

2016-11-01

Results are reported from an experimental study of an array of porous disks simulating offshore wind turbines. The disks mimic power extraction of similarly scaled wind turbines via drag matching, and the array consists of 19x5 disks of 0.25 m diameter. The study was conducted in the UNH Flow Physics Facility (FPF), which has test section dimensions of 6.0 m wide, 2.7 m high and 72.0 m long. The FPF can achieve a boundary layer height on the order of 1 m at the entrance of the wind turbine array which puts the model turbines in the bottom third of the boundary layer, which is typical of field application. Careful consideration was given to an expanded uncertainty analysis, to determine possible measurements in this type of flow. For a given configuration (spacing, initial conditions, etc.), the velocity levels out and the wind farm approaches fully developed behavior, even within the maintained growth of the simulated atmospheric boundary layer. Benchmark pitot tube data was acquired in vertical profiles progressing streamwise behind the centered column at every row in the array.

Bi-sensory, striped representations: comparative insights from owl and platypus.

PubMed

Pettigrew, John D

2004-01-01

Bi-sensory striped arrays are described in owl and platypus that share some similarities with the other variant of bi-sensory striped array found in primate and carnivore striate cortex: ocular dominance columns. Like ocular dominance columns, the owl and platypus striped systems each involve two different topographic arrays that are cut into parallel stripes, and interdigitated, so that higher-order neurons can integrate across both arrays. Unlike ocular dominance stripes, which have a separate array for each eye, the striped array in the middle third of the owl tectum has a separate array for each cerebral hemisphere. Binocular neurons send outputs from both hemispheres to the striped array where they are segregated into parallel stripes according to hemisphere of origin. In platypus primary somatosensory cortex (S1), the two arrays of interdigitated stripes are derived from separate sensory systems in the bill, 40,000 electroreceptors and 60,000 mechanoreceptors. The stripes in platypus S1 cortex produce bimodal electrosensory-mechanosensory neurons with specificity for the time-of-arrival difference between the two systems. This "thunder-and-lightning" system would allow the platypus to estimate the distance of the prey using time disparities generated at the bill between the earlier electrical wave and the later mechanical wave caused by the motion of benthic prey. The functional significance of parallel, striped arrays is not clear, even for the highly-studied ocular dominance system, but a general strategy is proposed here that is based on the detection of temporal disparities between the two arrays that can be used to estimate distance.

Construction of high-capacitance 3D CoO@polypyrrole nanowire array electrode for aqueous asymmetric supercapacitor.

PubMed

Zhou, Cheng; Zhang, Yangwei; Li, Yuanyuan; Liu, Jinping

2013-05-08

We have developed a supercapacitor electrode composed of well-aligned CoO nanowire array grown on 3D nickel foam with polypyrrole (PPy) uniformly immobilized onto or firmly anchored to each nanowire surface to boost the pseudocapacitive performance. The electrode architecture takes advantage of the high electrochemical activity from both the CoO and PPy, the high electronic conductivity of PPy, and the short ion diffusion pathway in ordered mesoporous nanowires. These merits together with the elegant synergy between CoO and PPy lead to a high specific capacitance of 2223 F g(-1) approaching the theoretical value, good rate capability, and cycling stability (99.8% capacitance retention after 2000 cycles). An aqueous asymmetric supercapacitor device with a maximum voltage of 1.8 V fabricated by using our hybrid array as the positive electrode and activated carbon film as the negative electrode has demonstrated high energy density (~43.5 Wh kg(-1)), high power density (~5500 W kg(-1) at 11.8 Wh kg(-1)) and outstanding cycleability (~20,000 times). After charging for only ~10 s, two such 4 cm(2) asymmetric supercapacitors connected in series can efficiently power 5 mm diameter red, yellow, and green round LED indicators (lasting for 1 h for red LED) and drive a mini 130 rotation-motor robustly.

A large array of high-performance artificial stars using airship-supported small mirrors

NASA Astrophysics Data System (ADS)

Content, Robert; Foxwell, Mark; Murray, Graham J.

2004-10-01

We propose a practical system that can provide a large number of high performance artificial stars, of the order of a few hundred, using an array of small mirrors on an airship supported platform illuminated from the ground by a laser. Our concept offers several advantages over other guide star schemes: Airborne mirror arrays can furnish tip-tilt information; they also permit a considerable reduction in the total ground-laser power required; high intensity guide stars with very small angular image size are possible; and finally they offer very low scattered parasite laser light. More basic & simpler launch-laser & AO technologies can therefore be employed, with potentially huge cost savings, with potentially significant improvement in the quality of the AO correction. The general platform scheme and suitable lift technologies are also discussed. A novel concept for achieving precise positioning is presented whereby the platform & the lifting vehicle are linked by a tether, the platform having a degree of independent control. Our proposal would employ as the lift vehicle an autonomous high altitude airship of the type currently under widespread development in the commercial sector, for use as hubs for telecommunication networks, mobile telephone relay stations, etc.

An Expedient but Fascinating Geophysical Chimera: The Pinyon Flat Seismic Strain Point Array

NASA Astrophysics Data System (ADS)

Langston, C. A.

2016-12-01

The combination of a borehole Gladwin Tensor Strain Meter (GTSM) and a co-located three component broadband seismometer (BB) can theoretically be used to determine the propagation attributes of P-SV waves in vertically inhomogeneous media such as horizontal phase velocity and azimuth of propagation through application of wave gradiometry. A major requirement for this to be successful is to have well-calibrated strain and seismic sensors to be able to rely on using absolute wave amplitude from both systems. A "point" seismic array is constructed using the PBO GTSM station B084 and co-located BB seismic stations from an open array experiment deployed by UCSD as well as PFO station at the Pinyon Flat facility. Site amplitude statics for all three ground motion components are found for the 14-element (13 PY stations + PFO), small aperture seismic array using data from 47 teleseisms recorded from 2014 until present. Precision of amplitude measurement at each site is better than 0.2% for vertical components, 0.5% for EW components, and 1% for NS components. Relative amplitudes among sites of the array are often better than 1% attesting to the high quality of the instrumentation and installation. The wavefield and related horizontal strains are computed for the location of B084 using a second order Taylor's expansion of observed waveforms from moderate ( M4) regional events. The computed seismic array areal, differential, and shear strains show excellent correlation in both phase and amplitude with those recorded by B084 when using the calibration matrix previously determined using teleseismic strains from the entire ANZA seismic network. Use of the GTSM-BB "point" array significantly extends the bandwidth of gradiometry calculations over the small-aperture seismic array by nearly two orders of magnitude from 0.5 Hz to 0.01 Hz. In principle, a seismic strain point array could be constructed from every PBO GTSM with a co-located seismometer to help serve earthquake early warning for large regional events on North America's west coast.

Detector Having A Transmission Grating Beam Splitter For Multi-Wavelength Sample Analysis.

DOEpatents

Liu, Changsheng; Li, Qingbo

2000-09-12

A detector for DNA sample identification is provided with a transmission grating beam splitter (TGBS). The TGBS split fluoresced light from a tagged DNA sample into 0th order and a 1st order components, both of which are detected on a two-dimensional detector array of a CCD camera. The 0th and 1st order components are detected along a column of pixels in the detector array, and are spaced apart from one another. The DNA samples are tagged with four fluorescent dyes, one dye specific for each nucleotide, and all four dyes responding in slightly different manner to the same monochromatic excitation signal. The TGBS splits fluoresced incoming light into 0th and 1st order components, which are then spread out among a number of pixels in the detector array. The 1st component of this light is received by pixels whose position relative to the 0th order component depends on the frequency of fluorescence. Thus, the position at which signal energy is detected on the array is indicative of the particular dye, and therefore, the corresponding nucleotide tagged by that dye. Monitoring signal energy at the 0th order pixel and selected 1st order pixels, provides a set of data from which one may then identify the particular nucleotide.

Detector Having A Transmission Grating Beam Splitter For Multi-Wavelength.

DOEpatents

Liu, Changsheng; Li, Qingbo (State College, PA

1999-12-07

A detector for DNA sample identification is provided with a transmission grating beam splitter (TGBS). The TGBS split fluoresced light from a tagged DNA sample into 0th order and a 1st order components, both of which are detected on a two-dimensional detector array of a CCD camera. The 0th and 1st order components are detected along a column of pixels in the detector array, and are spaced apart from one another. The DNA samples are tagged with four fluorescent dyes, one dye specific for each nucleotide, and all four dyes responding in slightly different manner to the same monochromatic excitation signal. The TGBS splits fluoresced incoming light into 0th and 1st order components, which are then spread out among a number of pixels in the detector array. The 1st component of this light is received by pixels whose position relative to the 0th order component depends on the frequency of fluorescence. Thus, the position at which signal energy is detected on the array is indicative of the particular dye, and therefore, the corresponding nucleotide tagged by that dye. Monitoring signal energy at the 0th order pixel and selected 1st order pixels, provides a set of data from which one may then identify the particular nucleotide.

Solar Power for Near Sun, High-Temperature Missions

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

2008-01-01

Existing solar cells lose performance at the high temperatures encountered in Mercury orbit and inward toward the sun. For future missions designed to probe environments close to the sun, it is desirable to develop array technologies for high temperature and high light intensity. Approaches to solar array design for near-sun missions include modifying the terms governing temperature of the cell and the efficiency at elevated temperature, or use of techniques to reduce the incident solar energy to limit operating temperature. An additional problem is found in missions that involve a range of intensities, such as the Solar Probe + mission, which ranges from a starting distance of 1 AU from the sun to a minimum distance of 9.5 solar radii, or 0.044 AU. During the mission, the solar intensity ranges from one to about 500 times AM0. This requires a power system to operate over nearly three orders of magnitude of incident intensity.

Solid-state Image Sensor with Focal-plane Digital Photon-counting Pixel Array

NASA Technical Reports Server (NTRS)

Fossum, Eric R.; Pain, Bedabrata

1997-01-01

A solid-state focal-plane imaging system comprises an NxN array of high gain. low-noise unit cells. each unit cell being connected to a different one of photovoltaic detector diodes, one for each unit cell, interspersed in the array for ultra low level image detection and a plurality of digital counters coupled to the outputs of the unit cell by a multiplexer(either a separate counter for each unit cell or a row of N of counters time shared with N rows of digital counters). Each unit cell includes two self-biasing cascode amplifiers in cascade for a high charge-to-voltage conversion gain (greater than 1mV/e(-)) and an electronic switch to reset input capacitance to a reference potential in order to be able to discriminate detection of an incident photon by the photoelectron (e(-))generated in the detector diode at the input of the first cascode amplifier in order to count incident photons individually in a digital counter connected to the output of the second cascade amplifier. Reseting the input capacitance and initiating self-biasing of the amplifiers occurs every clock cycle of an integratng period to enable ultralow light level image detection by the may of photovoltaic detector diodes under such ultralow light level conditions that the photon flux will statistically provide only a single photon at a time incident on anyone detector diode during any clock cycle.

New electronics for the Cherenkov Telescope Array (NECTAr)

NASA Astrophysics Data System (ADS)

Naumann, C. L.; Delagnes, E.; Bolmont, J.; Corona, P.; Dzahini, D.; Feinstein, F.; Gascón, D.; Glicenstein, J.-F.; Guilloux, F.; Nayman, P.; Rarbi, F.; Sanuy, A.; Tavernet, J.-P.; Toussenel, F.; Vincent, P.; Vorobiov, S.

2012-12-01

The international CTA consortium has recently entered into its preparatory phase towards the construction of the next-generation Cherenkov Telescope Array CTA. This experiment will be a successor, and based on the return of experience from the three major current-generation arrays H.E.S.S., MAGIC and VERITAS, and aims to significantly improve upon the sensitivity as well as the energy range of its highly successful predecessors. Construction is planned to begin by 2013, and when finished, CTA will be able to explore the highest-energy gamma ray sky in unprecedented detail. To achieve this increase in sensitivity and energy range, CTA will employ the order of 100 telescopes of three different sizes on two sites, with around 1000-4000 channels per camera, depending on the telescope size. To equip and reliably operate the order of 100000 channels of photodetectors (compared to 6000 of the H.E.S.S. array), a new kind of flexible and powerful yet inexpensive front-end hardware will be required. One possible solution is pursued by the NECTAr (New Electronics for the Cherenkov Telescope Array) project. Its main feature is the integration of as much as possible of the front-end electronics (amplifiers, fast analogue samplers, memory and ADCs) into a single ASIC, which will allow very fast readout performances while significantly reducing the cost and the power consumption per channel. Also included is a low-cost FPGA for digital treatment and online data processing, as well as an Ethernet connection. Other priorities of NECTAr are the modularity of the system, a high degree of flexibility in the trigger system as well as the possibility of flexible readout modes to optimise the signal-to-noise ratio while at the same time allowing a significant reduction of data rates, both of which could improve the sensitivity of CTA compared to current detection systems. This paper gives an overview over the development work for the Nectar system, with particular focus on its main component, the NECTAr ASIC.

Ordered arrays of multiferroic epitaxial nanostructures.

PubMed

Vrejoiu, Ionela; Morelli, Alessio; Biggemann, Daniel; Pippel, Eckhard

2011-01-01

Epitaxial heterostructures combining ferroelectric (FE) and ferromagnetic (FiM) oxides are a possible route to explore coupling mechanisms between the two independent order parameters, polarization and magnetization of the component phases. We report on the fabrication and properties of arrays of hybrid epitaxial nanostructures of FiM NiFe(2)O(4) (NFO) and FE PbZr(0.52)Ti(0.48)O(3) or PbZr(0.2)Ti(0.8)O(3), with large range order and lateral dimensions from 200 nm to 1 micron. The structures were fabricated by pulsed-laser deposition. High resolution transmission electron microscopy and high angle annular dark-field scanning transmission electron microscopy were employed to investigate the microstructure and the epitaxial growth of the structures. Room temperature ferroelectric and ferrimagnetic domains of the heterostructures were imaged by piezoresponse force microscopy (PFM) and magnetic force microscopy (MFM), respectively. PFM and MFM investigations proved that the hybrid epitaxial nanostructures show ferroelectric and magnetic order at room temperature. Dielectric effects occurring after repeated switching of the polarization in large planar capacitors, comprising ferrimagnetic NiFe2O4 dots embedded in ferroelectric PbZr0.52Ti0.48O3 matrix, were studied. These hybrid multiferroic structures with clean and well defined epitaxial interfaces hold promise for reliable investigations of magnetoelectric coupling between the ferrimagnetic / magnetostrictive and ferroelectric / piezoelectric phases.

Behavior of Combined Dielectric-Metallic Systems in a Charged Particle Environment

NASA Technical Reports Server (NTRS)

Gordon, W. L.; Hoffman, R. W.

1984-01-01

The charging and discharging characteristics of an electrically isolated solar array segment were studied in order to simulate discharges seen during geomagnetic substorms. A solar array segment was floated while bombarded with monoenergetic electrons at various angles of incidence. The potentials of the array surface and of the interconnects were monitored using Trek voltage probes to maintain electrical isolation. A back plate was capacitively coupled to the array to provide information on the characteristics of the transients accompanying the discharges. Several modes of discharging of the array were observed at relatively low differential and absolute potentials (a few kilovolts). A relatively slow discharge response in the array was observed, discharging over one second with currents of nanoamps. Two types of faster discharges were also seen which lasted a few hundredths of a millisecond and with currents on the order of microamps. Some results indicate an electron emission process associated with the arcs.

Hydrostar Thermal and Structural Deformation Analyses of Antenna Array Concept

NASA Technical Reports Server (NTRS)

Amundsen, Ruth M.; Hope, Drew J.

1998-01-01

The proposed Hydrostar mission used a large orbiting antenna array to demonstrate synthetic aperture technology in space while obtaining global soil moisture data. In order to produce accurate data, the array was required to remain as close as possible to its perfectly aligned placement while undergoing the mechanical and thermal stresses induced by orbital changes. Thermal and structural analyses for a design concept of this antenna array were performed. The thermal analysis included orbital radiation calculations, as well as parametric studies of orbit altitude, material properties and coating types. The thermal results included predicted thermal distributions over the array for several cases. The structural analysis provided thermally-driven deflections based on these cases, as well as based on a 1-g inertial load. In order to minimize the deflections of the array in orbit, the use of XN70, a carbon-reinforced polycyanate composite, was recommended.

Nanocylinder arrays

DOEpatents

Tuominen, Mark; Schotter, Joerg; Thurn-Albrecht, Thomas; Russell, Thomas P.

2007-03-13

Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

Nanocylinder arrays

DOEpatents

Tuominen, Mark [Shutesbury, MA; Schotter, Joerg [Bielefeld, DE; Thurn-Albrecht, Thomas [Freiburg, DE; Russell, Thomas P [Amherst, MA

2009-08-11

Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

Thermal/Dynamic Characterization Test of the Solar Array Panel for Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Jenkins, Kathleen; Hershfeld, Donald J.

1999-01-01

The Hubble Space Telescope has experienced a problem maintaining pointing accuracy during emergence of the spacecraft from the Earth's shadow. The problem has been attributed to the rapid thermal gradient that develops when the heat from the Sun strikes the cold solar arrays. The thermal gradient causes the solar arrays to deflect or bend and this motion is sufficient to disturb the pointing control system. In order to alleviate this problem, a new design for the solar arrays has been fabricated. These new solar arrays will replace the current solar arrays during a future Hubble servicing mission. The new solar arrays have been designed so that the effective net motion of the center of mass of each panel is essentially zero. Although the solar array thermal deflection problem has been studied extensively over a period of years, a full scale test of the actual flight panels was required in order to establish confidence in the analyses. This test was conducted in the JPL Solar Simulation Facility in April, 1999. This presentation will discuss the objectives and methods of the test and present some typical test data.

Practical Considerations for Optimizing Position Sensitivity in Arrays of Position-sensitive TES's

NASA Technical Reports Server (NTRS)

Smith, Stephen J.; Bandler, Simon R.; Figueroa-Feliciano, Encetali; Iyomoto, Naoko; Kelley, Richard L.; Kilbourne, Caroline A.; Porder, Frederick S.; Sadleir, John E.

2007-01-01

We are developing Position-Sensitive Transitions-Edge Sensors (PoST's) for future X-ray astronomy missions such as NASA's Constellation-X. The PoST consists of one or more Transitions Edge Sensors (TES's) thermally connected to a large X-ray absorber, which through heat diffusion, gives rise to position dependence. The development of PoST's is motivated by the desire to achieve the largest the focal-plan coverage with the fewest number of readout channels. In order to develop a practical array, consisting of an inner pixellated core with an outer array of large absorber PoST's, we must be able to simultaneously read out all (-1800) channels in the array. This is achievable using time division multiplexing (TDM), but does set stringent slew rate requirements on the array. Typically, we must damp the pulses to reduce the slew rate of the input signal to the TDM. This is achieved by applying a low-pass analog filter with large inductance to the signal. This attenuates the high frequency components of the signal, essential for position discrimination in PoST's, relative to the white noise of the readout chain and degrades the position sensitivity. Using numerically simulated data, we investigate the position sensing ability of typical PoST designs under such high inductance conditions. We investigate signal-processing techniques for optimal determination of the event position and discuss the practical considerations for real-time implementation.

Design and Performance of a Miniature Radar L-Band Transceiver

NASA Technical Reports Server (NTRS)

McWatters, D.; Price, D.; Edelstein, W.

2004-01-01

Radar electronics developed for past JPL space missions historically had been custom designed and as such, given budgetary, time, and risk constraints, had not been optimized for maximum flexibility or miniaturization. To help reduce cost and risk of future radar missions, a generic radar module was conceived. The module includes a 1.25-GHz (L-band) transceiver and incorporates miniature high-density packaging of integrated circuits in die/chip form. The technology challenges include overcoming the effect of miniaturization and high packaging density to achieve the performance, reliability, and environmental ruggedness required for space missions. The module was chosen to have representative (generic) functionality most likely required from an L-band radar. For very large aperture phased-array spaceborne radar missions, the large dimensions of the array suggest the benefit of distributing the radar electronics into the antenna array. For such applications, this technology is essential in order to bring down the cost, mass, and power of the radar electronics module replicated in each panel of the array. For smaller sized arrays, a single module can be combined with the central radar controller and still provide the bene.ts of configuration .exibility, low power, and low mass. We present the design approach for the radar electronics module and the test results for its radio frequency (RF) portion: a miniature, low-power, radiation-hard L-band transceiver.

A novel piezoelectric quartz micro-array immunosensor for detection of immunoglobulinE.

PubMed

Yao, Chunyan; Chen, Qinghai; Chen, Ming; Zhang, Bo; Luo, Yang; Huang, Qing; Huang, Junfu; Fu, Weiling

2006-12-01

A novel multi-channel 2 x 5 model of piezoelectric (PZ) micro-array immunosensor has been developed for quantitative detection of human immunoglobulinE (IgE) in serum. Every crystal unit of the fabricated piezoelectric IgE micro-array immunosensor can oscillate without interfering each other. A multi-channel 2 x 5 model micro-array immunosensor as compared with the traditional one-channel immunosensor can provide eight times higher detection speeds for IgE assay. The anti-IgE antibody is deposited on the gold electrode's surface of 10 MHz AT-cut quartz crystals by SPA (staphylococcal protein A), and serves as an antibody recognizing layer. The highly ordered antibody monolayers ensure well-controlled surface structure and offer many advantages to the performance of the sensor. The uniform amount of antibody monolayer coated by the SPA is good, and non-specific reaction caused by other immunoglobulin in sample is found. The fabricated PZ immunosensor can be used for human IgE determination in the range of 5-300 IU/ml with high precision (CV is 4%). 50 human serum samples were detected by the micro-array immunosensor, and the results agreed well with those given by the commercially ELISA test kits. The correlation coefficient is 0.94 between ELISA and PZ immunosensor. After regeneration with NaOH the coated immunosensor can be reused 6 times without appreciable loss of activity.

The control system of the 12-m medium-size telescope prototype: a test-ground for the CTA array control

NASA Astrophysics Data System (ADS)

Oya, I.; Anguner, E. A.; Behera, B.; Birsin, E.; Fuessling, M.; Lindemann, R.; Melkumyan, D.; Schlenstedt, S.; Schmidt, T.; Schwanke, U.; Sternberger, R.; Wegner, P.; Wiesand, S.

2014-07-01

The Cherenkov Telescope Array (CTA) will be the next generation ground-based very-high energy -ray observatory. CTA will consist of two arrays: one in the Northern hemisphere composed of about 20 telescopes, and the other one in the Southern hemisphere composed of about 100 telescopes, both arrays containing telescopes of different sizes and types and in addition numerous auxiliary devices. In order to provide a test-ground for the CTA array control, the steering software of the 12-m medium size telescope (MST) prototype deployed in Berlin has been implemented using the tools and design concepts under consideration to be used for the control of the CTA array. The prototype control system is implemented based on the Atacama Large Millimeter/submillimeter Array (ALMA) Common Software (ACS) control middleware, with components implemented in Java, C++ and Python. The interfacing to the hardware is standardized via the Object Linking and Embedding for Process Control Unified Architecture (OPC UA). In order to access the OPC UA servers from the ACS framework in a common way, a library has been developed that allows to tie the OPC UA server nodes, methods and events to the equivalents in ACS components. The front-end of the archive system is able to identify the deployed components and to perform the sampling of the monitoring points of each component following time and value change triggers according to the selected configurations. The back-end of the archive system of the prototype is composed by two different databases: MySQL and MongoDB. MySQL has been selected as storage of the system configurations, while MongoDB is used to have an efficient storage of device monitoring data, CCD images, logging and alarm information. In this contribution, the details and conclusions on the implementation of the control software of the MST prototype are presented.

Performance of photovoltaic arrays in-vivo and characteristics of prosthetic vision in animals with retinal degeneration

PubMed Central

Lorach, Henri; Goetz, Georges; Mandel, Yossi; Lei, Xin; Kamins, Theodore I.; Mathieson, Keith; Huie, Philip; Dalal, Roopa; Harris, James S.; Palanker, Daniel

2014-01-01

Summary Loss of photoreceptors during retinal degeneration leads to blindness, but information can be reintroduced into the visual system using electrical stimulation of the remaining retinal neurons. Subretinal photovoltaic arrays convert pulsed illumination into pulsed electric current to stimulate the inner retinal neurons. Since required irradiance exceeds the natural luminance levels, an invisible near-infrared (915nm) light is used to avoid photophobic effects. We characterized the thresholds and dynamic range of cortical responses to prosthetic stimulation with arrays of various pixel sizes and with different number of photodiodes. Stimulation thresholds for devices with 140µm pixels were approximately half those of 70µm pixels, and with both pixel sizes, thresholds were lower with 2 diodes than with 3 diodes per pixel. In all cases these thresholds were more than two orders of magnitude below the ocular safety limit. At high stimulation frequencies (>20Hz), the cortical response exhibited flicker fusion. Over one order of magnitude of dynamic range could be achieved by varying either pulse duration or irradiance. However, contrast sensitivity was very limited. Cortical responses could be detected even with only a few illuminated pixels. Finally, we demonstrate that recording of the corneal electric potential in response to patterned illumination of the subretinal arrays allows monitoring the current produced by each pixel, and thereby assessing the changes in the implant performance over time. PMID:25255990

NECTAR: New electronics for the Cherenkov Telescope Array

NASA Astrophysics Data System (ADS)

Naumann, Christopher Lindsay; Bolmont, J.; Corona, P.; Delagnes, E.; Dzahini, D.; Feinstein, F.; Gascon, D.; Glicenstein, J.-F.; Nayman, P.; Rarbi, F.; Ribo, M.; Sanuy, A.; Siero, X.; Tavernet, J.-P.; Toussenel, F.; Vincent, P.; Vorobiov, S.

2012-12-01

The international CTA consortium is currently in the preparatory phase for the development of the next-generation Cherenkov Telescope Array (CTA [1]), based on the return of experience from the three major current-generation arrays H.E.S.S., MAGIC and VERITAS. To achieve an unprecedented sensitivity and energy range for TeV gamma rays, a new kind of flexible and powerful yet inexpensive front-end hardware will be required for the order of 105 channels of photodetectors in up to 100 telescopes. One possible solution is the NECTAr (New Electronics for the Cherenkov Telescope Array) system, based on the integration of as much as possible of the front-end electronics (amplifiers, fast analogue samplers, memory and ADCs) into a single ASIC for very fast readout performance and a significant reduction of the cost and the lower consumption per channel, while offering a high degree of flexibility both for the triggering and the readout of the telescope. The current status of its development is presented, along with newest results from measurements and simulation studies.

On the Suitability of Suffix Arrays for Lempel-Ziv Data Compression

NASA Astrophysics Data System (ADS)

Ferreira, Artur J.; Oliveira, Arlindo L.; Figueiredo, Mário A. T.

Lossless compression algorithms of the Lempel-Ziv (LZ) family are widely used nowadays. Regarding time and memory requirements, LZ encoding is much more demanding than decoding. In order to speed up the encoding process, efficient data structures, like suffix trees, have been used. In this paper, we explore the use of suffix arrays to hold the dictionary of the LZ encoder, and propose an algorithm to search over it. We show that the resulting encoder attains roughly the same compression ratios as those based on suffix trees. However, the amount of memory required by the suffix array is fixed, and much lower than the variable amount of memory used by encoders based on suffix trees (which depends on the text to encode). We conclude that suffix arrays, when compared to suffix trees in terms of the trade-off among time, memory, and compression ratio, may be preferable in scenarios (e.g., embedded systems) where memory is at a premium and high speed is not critical.

Towards a flexible array control and operation framework for CTA

NASA Astrophysics Data System (ADS)

Birsin, E.; Colomé, J.; Hoffmann, D.; Koeppel, H.; Lamanna, G.; Le Flour, T.; Lopatin, A.; Lyard, E.; Melkumyan, D.; Oya, I.; Panazol, J.-L.; Schlenstedt, S.; Schmidt, T.; Schwanke, U.; Stegmann, C.; Walter, R.; Wegner, P.; CTA Consortium

2012-12-01

The Cherenkov Telescope Array (CTA) [1] will be the successor to current Imaging Atmospheric Cherenkov Telescopes (IACT) like H.E.S.S., MAGIC and VERITAS. CTA will improve in sensitivity by about an order of magnitude compared to the current generation of IACTs. The energy range will extend from well below 100 GeV to above 100 TeV. To accomplish these goals, CTA will consist of two arrays, one in each hemisphere, consisting of 50-80 telescopes and composed of three different telescope types with different mirror sizes. It will be the first open observatory for very high energy γ-ray astronomy. The Array Control working group of CTA is currently evaluating existing technologies which are best suited for a project like CTA. The considered solutions comprise the ALMA Common Software (ACS), the OPC Unified Architecture (OPC UA) and the Data Distribution Service (DDS) for bulk data transfer. The first applications, like an automatic observation scheduler and the control software for some prototype instrumentation have been developed.

Artificial ice using superconducting vortices (Conference Presentation)

NASA Astrophysics Data System (ADS)

Trastoy Quintela, Juan; Malnou, Maxime; Ulysse, Christian; Bernard, Rozenn; Bergeal, Nicolas; Faini, Giancarlo; Lesueur, Jerome; Briatico, Javier; Villegas, Javier E.

2016-10-01

We use magnetic flux quanta (superconducting vortices) on artificial energy landscapes (pinning arrays) to create a new type of artificial ice. This vortex ice shows unusual temperature effects that offer new possibilities in the study of ice systems. We have investigated the matching of the flux lattice to pinning arrays that present geometrical frustration. The pinning arrays are fabricated on YBCO films using masked O+ ion irradiation. The details of the magneto-resistance imply that the flux lattice organizes into a vortex ice. The absence of history-dependent effects suggests that the vortex ice is highly ordered. Due to the technique used for the artificial energy landscape fabrication, we have the ability to change the pinning array geometry using temperature as a control knob. In particular we can switch the geometrical frustration on and off, which opens the door to performing a new type of annealing absent in other artificial ice systems. * Work supported by the French ANR "MASTHER", and the Fundación Barrié (Galicia, Spain)

Plasmonic gold mushroom arrays with refractive index sensing figures of merit approaching the theoretical limit

NASA Astrophysics Data System (ADS)

Shen, Yang; Zhou, Jianhua; Liu, Tianran; Tao, Yuting; Jiang, Ruibin; Liu, Mingxuan; Xiao, Guohui; Zhu, Jinhao; Zhou, Zhang-Kai; Wang, Xuehua; Jin, Chongjun; Wang, Jianfang

2013-08-01

Localized surface plasmon resonance (LSPR)-based sensing has found wide applications in medical diagnosis, food safety regulation and environmental monitoring. Compared with commercial propagating surface plasmon resonance (PSPR)-based sensors, LSPR ones are simple, cost-effective and suitable for measuring local refractive index changes. However, the figure of merit (FOM) values of LSPR sensors are generally 1-2 orders of magnitude smaller than those of PSPR ones, preventing the widespread use of LSPR sensors. Here we describe an array of submicrometer gold mushrooms with a FOM reaching ~108, which is comparable to the theoretically predicted upper limit for standard PSPR sensors. Such a high FOM arises from the interference between Wood’s anomaly and the LSPRs. We further demonstrate the array as a biosensor for detecting cytochrome c and alpha-fetoprotein, with their detection limits down to 200 pM and 15 ng ml-1, respectively, suggesting that the array is a promising candidate for label-free biomedical sensing.

Time-resolved second-harmonic generation from gold nanoparticle arrays

NASA Astrophysics Data System (ADS)

Ferrara, D. W.; Tetz, K. A.; McMahon, M. D.; Haglund, R. F., Jr.

2007-09-01

We have studied the effects of planar inversion symmetry and particle-coupling of gold nanoparticle (NP) arrays by angle dependent second-harmonic generation (SHG). Time- and angle- resolved measurements were made using a mode-locked Ti:sapphire 800 nm laser onto gold NP arrays with plasmon resonance tuned to match the laser wavelength in order to produce maximum SHG signal. Finite-difference time domain simulations are used to model the near-field distributions for the various geometries and compared to experiment. The arrays were fabricated by focused ion-beam lithography and metal vapor deposition followed by standard lift-off protocols, producing NPs approximately 20nm high with various in-plane dimensions and interparticle gaps. Above a threshold fluence of ~ 7.3 × 10 -5 mJ/cm2 we find that the SHG scales with the third power of intensity, rather than the second, and atomic-force microscopy shows that the NPs have undergone a reshaping process leading to more nearly spherical shapes.

Description of a prototype emission-transmission computed tomography imaging system

NASA Technical Reports Server (NTRS)

Lang, T. F.; Hasegawa, B. H.; Liew, S. C.; Brown, J. K.; Blankespoor, S. C.; Reilly, S. M.; Gingold, E. L.; Cann, C. E.

1992-01-01

We have developed a prototype imaging system that can perform simultaneous x-ray transmission CT and SPECT phantom studies. This system employs a 23-element high-purity-germanium detector array. The detector array is coupled to a collimator with septa angled toward the focal spot of an x-ray tube. During image acquisition, the x-ray fan beam and the detector array move synchronously along an arc pivoted at the x-ray source. Multiple projections are obtained by rotating the object, which is mounted at the center of rotation of the system. The detector array and electronics can count up to 10(6) cps/element with sufficient energy-resolution to discriminate between x-rays at 100-120 kVp and gamma rays from 99mTc. We have used this device to acquire x-ray CT and SPECT images of a three-dimensional Hoffman brain phantom. The emission and transmission images may be superimposed in order to localize the emission image on the transmission map.

Patterning highly ordered arrays of complex nanofeatures through EUV directed polarity switching of non chemically amplified photoresist

PubMed Central

Ghosh, Subrata; Satyanarayana, V. S. V.; Pramanick, Bulti; Sharma, Satinder K.; Pradeep, Chullikkattil P.; Morales-Reyes, Israel; Batina, Nikola; Gonsalves, Kenneth E.

2016-01-01

Given the importance of complex nanofeatures in the filed of micro-/nanoelectronics particularly in the area of high-density magnetic recording, photonic crystals, information storage, micro-lens arrays, tissue engineering and catalysis, the present work demonstrates the development of new methodology for patterning complex nanofeatures using a recently developed non-chemically amplified photoresist (n-CARs) poly(4-(methacryloyloxy)phenyl)dimethylsulfoniumtriflate) (polyMAPDST) with the help of extreme ultraviolet lithography (EUVL) as patterning tool. The photosensitivity of polyMAPDST is mainly due to the presence of radiation sensitive trifluoromethanesulfonate unit (triflate group) which undergoes photodegradation upon exposure with EUV photons, and thus brings in polarity change in the polymer structure. Integration of such radiation sensitive unit into polymer network avoids the need of chemical amplification which is otherwise needed for polarity switching in the case of chemically amplified photoresists (CARs). Indeed, we successfully patterned highly ordered wide-raging dense nanofeatures that include nanodots, nanowaves, nanoboats, star-elbow etc. All these developed nanopatterns have been well characterized by FESEM and AFM techniques. Finally, the potential of polyMAPDST has been established by successful transfer of patterns into silicon substrate through adaptation of compatible etch recipes. PMID:26975782

The Cherenkov Telescope Array For Very High-Energy Astrophysics

NASA Astrophysics Data System (ADS)

Kaaret, Philip

2015-08-01

The field of very high energy (VHE) astrophysics had been revolutionized by the results from ground-based gamma-ray telescopes, including the current imaging atmospheric Cherenkov telescope (IACT) arrays: HESS, MAGIC and VERITAS. A worldwide consortium of scientists from 29 countries has formed to propose the Cherenkov Telescope Array (CTA) that will capitalize on the power of this technique to greatly expand the scientific reach of ground-based gamma-ray telescopes. CTA science will include key topics such as the origin of cosmic rays and cosmic particle acceleration, understanding extreme environments in regions close to neutron stars and black holes, and exploring physics frontiers through, e.g., the search for WIMP dark matter, axion-like particles and Lorentz invariance violation. CTA is envisioned to consist of two large arrays of Cherenkov telescopes, one in the southern hemisphere and one in the north. Each array will contain telescopes of different sizes to provide a balance between cost and array performance over an energy range from below 100 GeV to above 100 TeV. Compared to the existing IACT arrays, CTA will have substantially better angular resolution and energy resolution, will cover a much wider energy range, and will have up to an order of magnitude better sensitivity. CTA will also be operated as an open observatory and high-level CTA data will be placed into the public domain; these aspects will enable broad participation in CTA science from the worldwide scientific community to fully capitalize on CTA's potential. This talk will: 1) review the scientific motivation and capabilities of CTA, 2) provide an overview of the technical design and the status of prototype development, and 3) summarize the current status of the project in terms of its proposed organization and timeline. The plans for access to CTA data and opportunities to propose for CTA observing time will be highlighed.Presented on behalf of the CTA Consortium.

Array servo scanning micro EDM of 3D micro cavities

NASA Astrophysics Data System (ADS)

Tong, Hao; Li, Yong; Yi, Futing

2011-05-01

Micro electro discharge machining (Micro EDM) is a non-traditional processing technology with the special advantages of low set-up cost and few cutting force in machining any conductive materials regardless of their hardness. As well known, die-sinking EDM is unsuitable for machining the complex 3D micro cavity less than 1mm due to the high-priced fabrication of 3D microelectrode itself and its serous wear during EDM process. In our former study, a servo scanning 3D micro-EDM (3D SSMEDM) method was put forward, and our experiments showed it was available to fabricate complex 3D micro-cavities. In this study, in order to improve machining efficiency and consistency accuracy for array 3D micro-cavities, an array-servo-scanning 3D micro EDM (3D ASSMEDM) method is presented considering the complementary advantages of the 3D SSMEDM and the array micro electrodes with simple cross-section. During 3D ASSMEDM process, the array cavities designed by CAD / CAM system can be batch-manufactured by servo scanning layer by layer using array-rod-like micro tool electrodes, and the axial wear of the array electrodes is compensated in real time by keeping discharge gap. To verify the effectiveness of the 3D ASSMEDM, the array-triangle-micro cavities (side length 630 μm) are batch-manufactured on P-doped silicon by applying the array-micro-electrodes with square-cross-section fabricated by LIGA process. Our exploratory experiment shows that the 3D ASSMEDM provides a feasible approach for the batch-manufacture of 3D array-micro-cavities of conductive materials.

Order parameters from image analysis: a honeycomb example

NASA Astrophysics Data System (ADS)

Kaatz, Forrest H.; Bultheel, Adhemar; Egami, Takeshi

2008-11-01

Honeybee combs have aroused interest in the ability of honeybees to form regular hexagonal geometric constructs since ancient times. Here we use a real space technique based on the pair distribution function (PDF) and radial distribution function (RDF), and a reciprocal space method utilizing the Debye-Waller Factor (DWF) to quantify the order for a range of honeycombs made by Apis mellifera ligustica. The PDFs and RDFs are fit with a series of Gaussian curves. We characterize the order in the honeycomb using a real space order parameter, OP 3 , to describe the order in the combs and a two-dimensional Fourier transform from which a Debye-Waller order parameter, u, is derived. Both OP 3 and u take values from [0, 1] where the value one represents perfect order. The analyzed combs have values of OP 3 from 0.33 to 0.60 and values of u from 0.59 to 0.69. RDF fits of honeycomb histograms show that naturally made comb can be crystalline in a 2D ordered structural sense, yet is more ‘liquid-like’ than cells made on ‘foundation’ wax. We show that with the assistance of man-made foundation wax, honeybees can manufacture highly ordered arrays of hexagonal cells. This is the first description of honeycomb utilizing the Debye-Waller Factor, and provides a complete analysis of the order in comb from a real-space order parameter and a reciprocal space order parameter. It is noted that the techniques used are general in nature and could be applied to any digital photograph of an ordered array.

Low-Cost Phased Array Antenna for Sounding Rockets, Missiles, and Expendable Launch Vehicles

NASA Technical Reports Server (NTRS)

Mullinix, Daniel; Hall, Kenneth; Smith, Bruce; Corbin, Brian

2012-01-01

A low-cost beamformer phased array antenna has been developed for expendable launch vehicles, rockets, and missiles. It utilizes a conformal array antenna of ring or individual radiators (design varies depending on application) that is designed to be fed by the recently developed hybrid electrical/mechanical (vendor-supplied) phased array beamformer. The combination of these new array antennas and the hybrid beamformer results in a conformal phased array antenna that has significantly higher gain than traditional omni antennas, and costs an order of magnitude or more less than traditional phased array designs. Existing omnidirectional antennas for sounding rockets, missiles, and expendable launch vehicles (ELVs) do not have sufficient gain to support the required communication data rates via the space network. Missiles and smaller ELVs are often stabilized in flight by a fast (i.e. 4 Hz) roll rate. This fast roll rate, combined with vehicle attitude changes, greatly increases the complexity of the high-gain antenna beam-tracking problem. Phased arrays for larger ELVs with roll control are prohibitively expensive. Prior techniques involved a traditional fully electronic phased array solution, combined with highly complex and very fast inertial measurement unit phased array beamformers. The functional operation of this phased array is substantially different from traditional phased arrays in that it uses a hybrid electrical/mechanical beamformer that creates the relative time delays for steering the antenna beam via a small physical movement of variable delay lines. This movement is controlled via an innovative antenna control unit that accesses an internal measurement unit for vehicle attitude information, computes a beam-pointing angle to the target, then points the beam via a stepper motor controller. The stepper motor on the beamformer controls the beamformer variable delay lines that apply the appropriate time delays to the individual array elements to properly steer the beam. The array of phased ring radiators is unique in that it provides improved gain for a small rocket or missile that uses spin stabilization for stability. The antenna pattern created is symmetric about the roll axis (like an omnidirectional wraparound), and is thus capable of providing continuous coverage that is compatible with very fast spinning rockets. For larger ELVs with roll control, a linear array of elements can be used for the 1D scanned beamformer and phased array, or a 2D scanned beamformer can be used with an NxN element array.

dc properties of series-parallel arrays of Josephson junctions in an external magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewandowski, S.J.

1991-04-01

A detailed dc theory of superconducting multijunction interferometers has previously been developed by several authors for the case of parallel junction arrays. The theory is now extended to cover the case of a loop containing several junctions connected in series. The problem is closely associated with high-{ital T}{sub {ital c}} superconductors and their clusters of intrinsic Josephson junctions. These materials exhibit spontaneous interferometric effects, and there is no reason to assume that the intrinsic junctions form only parallel arrays. A simple formalism of phase states is developed in order to express the superconducting phase differences across the junctions forming amore » series array as functions of the phase difference across the weakest junction of the system, and to relate the differences in critical currents of the junctions to gaps in the allowed ranges of their phase functions. This formalism is used to investigate the energy states of the array, which in the case of different junctions are split and separated by energy barriers of height depending on the phase gaps. Modifications of the washboard model of a single junction are shown. Next a superconducting inductive loop containing a series array of two junctions is considered, and this model is used to demonstrate the transitions between phase states and the associated instabilities. Finally, the critical current of a parallel connection of two series arrays is analyzed and shown to be a multivalued function of the externally applied magnetic flux. The instabilities caused by the presence of intrinsic serial junctions in granular high-{ital T}{sub {ital c}} materials are pointed out as a potential source of additional noise.« less

Solar Array at Very High Temperatures: Ground Tests

NASA Technical Reports Server (NTRS)

Vayner, Boris

2016-01-01

Solar array design for any spacecraft is determined by the orbit parameters. For example, operational voltage for spacecraft in Low Earth Orbit (LEO) is limited by significant differential charging due to interactions with low temperature plasma. In order to avoid arcing in LEO, solar array is designed to generate electrical power at comparatively low voltages (below 100 V) or to operate at higher voltages with encapsulated of all suspected discharge locations. In Geosynchronous Orbit (GEO) differential charging is caused by energetic electrons that produce differential potential between coverglass and conductive spacecraft body in a kilovolt range. In such a case, weakly conductive layer over coverglass (ITO) is one of possible measures to eliminate dangerous discharges on array surface. Temperature variations for solar arrays in both orbits are measured and documented within the range of -150 C +110 C. This wide interval of operational temperatures is regularly reproduced in ground tests with radiative heating and cooling inside shroud with flowing liquid nitrogen. The requirements to solar array design and tests turn out to be more complicated when planned trajectory crosses these two orbits and goes closer to Sun. Conductive layer over coverglass causes sharp increase in parasitic current collected from LEO plasma, high temperature may cause cracks in encapsulating material (RTV), radiative heating of coupon in vacuum chamber becomes practically impossible above 150 C, conductivities of glass and adhesive go up with temperature that decrease array efficiency, and mechanical stresses grow up to critical magnitudes. A few test arrangements and respective results are presented in current paper. Coupons were tested against arcing in simulated LEO and GEO environments under elevated temperatures up to 200 C. The dependence of leakage current on temperature was measured, and electrostatic cleanness was verified for coupons with antireflection (AR) coating over ITO layer.

Rapid Synthesis of Thin and Long Mo17O47 Nanowire-Arrays in an Oxygen Deficient Flame

PubMed Central

Allen, Patrick; Cai, Lili; Zhou, Lite; Zhao, Chenqi; Rao, Pratap M.

2016-01-01

Mo17O47 nanowire-arrays are promising active materials and electrically-conductive supports for batteries and other devices. While high surface area resulting from long, thin, densely packed nanowires generally leads to improved performance in a wide variety of applications, the Mo17O47 nanowire-arrays synthesized previously by electrically-heated chemical vapor deposition under vacuum conditions were relatively thick and short. Here, we demonstrate a method to grow significantly thinner and longer, densely packed, high-purity Mo17O47 nanowire-arrays with diameters of 20–60 nm and lengths of 4–6 μm on metal foil substrates using rapid atmospheric flame vapor deposition without any chamber or walls. The atmospheric pressure and 1000 °C evaporation temperature resulted in smaller diameters, longer lengths and order-of-magnitude faster growth rate than previously demonstrated. As explained by kinetic and thermodynamic calculations, the selective synthesis of high-purity Mo17O47 nanowires is achieved due to low oxygen partial pressure in the flame products as a result of the high ratio of fuel to oxidizer supplied to the flame, which enables the correct ratio of MoO2 and MoO3 vapor concentrations for the growth of Mo17O47. This flame synthesis method is therefore a promising route for the growth of composition-controlled one-dimensional metal oxide nanomaterials for many applications. PMID:27271194

Method to fabricate hollow microneedle arrays

DOEpatents

Kravitz, Stanley H [Placitas, NM; Ingersoll, David [Albuquerque, NM; Schmidt, Carrie [Los Lunas, NM; Flemming, Jeb [Albuquerque, NM

2006-11-07

An inexpensive and rapid method for fabricating arrays of hollow microneedles uses a photoetchable glass. Furthermore, the glass hollow microneedle array can be used to form a negative mold for replicating microneedles in biocompatible polymers or metals. These microneedle arrays can be used to extract fluids from plants or animals. Glucose transport through these hollow microneedles arrays has been found to be orders of magnitude more rapid than natural diffusion.

Comparison of Sewage and Animal Fecal Microbiomes by using Oligotyping Reveals Potential Human Fecal Indicators in Multiple Taxonomic Groups

EPA Science Inventory

Most DNA-based microbial source tracking (MST) approaches target host-associated organisms within the order Bacteroidales, but human and other animal gut microbiota contain an array of other taxonomic groups that might serve as indicators for sources of fecal pollution. High thr...

Self-assembled vertically aligned Au nanorod arrays for surface-enhanced Raman scattering (SERS) detection of Cannabinol.

PubMed

Milliken, Sarah; Fraser, Jeff; Poirier, Shawn; Hulse, John; Tay, Li-Lin

2018-05-05

Self-assembled multi-layered vertically aligned gold nanorod (AuNR) arrays have been fabricated by a simple preparation process that requires a balance between the particle concentration and the ionic strength of the solvent. An experimentally determined critical AuNR concentration of 2.0nM and 50mM NaCl produces well-ordered vertically aligned hexagonally close-packed AuNR arrays. We demonstrate surface treatment via UV Ozone cleaning of such samples to allow introduction of analyte molecules (benzenethiol and cannabinol) for effective surface enhanced Raman scattering detection. This is the first demonstration of the SERS analysis of cannabinol. This approach demonstrates a cost-effective, high-yield and simple fabrication route to SERS sensors with application in the screening for the cannabinoids. Copyright © 2018. Published by Elsevier B.V.

The energy spectrum of cosmic rays above 1017.2 eV measured by the fluorescence detectors of the Telescope Array experiment in seven years

NASA Astrophysics Data System (ADS)

Abbasi, R. U.; Abe, M.; Abu-Zayyad, T.; Allen, M.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, W. R.; Fujii, T.; Fukushima, M.; Goto, T.; Hanlon, W.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Honda, K.; Ikeda, D.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kawata, K.; Kido, E.; Kim, H. B.; Kim, J. H.; Kim, J. H.; Kitamura, S.; Kitamura, Y.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lundquist, J. P.; Machida, K.; Martens, K.; Matsuda, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Mukai, Y.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nonaka, T.; Nozato, A.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Shin, H. S.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzawa, T.; Takamura, M.; Takeda, M.; Takeishi, R.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Uchihori, Y.; Udo, S.; Urban, F.; Vasiloff, G.; Wong, T.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yashiro, K.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.

2016-07-01

The Telescope Array (TA) experiment is the largest detector to observe ultra-high-energy cosmic rays in the northern hemisphere. The fluorescence detectors at two stations of TA are newly constructed and have now completed seven years of steady operation. One advantage of monocular analysis of the fluorescence detectors is a lower energy threshold for cosmic rays than that of other techniques like stereoscopic observations or coincidences with the surface detector array, allowing the measurement of an energy spectrum covering three orders of magnitude in energy. Analyzing data collected during those seven years, we report the energy spectrum of cosmic rays covering a broad range of energies above 1017.2eV measured by the fluorescence detectors and a comparison with previously published results.

Implementation of context independent code on a new array processor: The Super-65

NASA Technical Reports Server (NTRS)

Colbert, R. O.; Bowhill, S. A.

1981-01-01

The feasibility of rewriting standard uniprocessor programs into code which contains no context-dependent branches is explored. Context independent code (CIC) would contain no branches that might require different processing elements to branch different ways. In order to investigate the possibilities and restrictions of CIC, several programs were recoded into CIC and a four-element array processor was built. This processor (the Super-65) consisted of three 6502 microprocessors and the Apple II microcomputer. The results obtained were somewhat dependent upon the specific architecture of the Super-65 but within bounds, the throughput of the array processor was found to increase linearly with the number of processing elements (PEs). The slope of throughput versus PEs is highly dependent on the program and varied from 0.33 to 1.00 for the sample programs.

Large solar arrays

NASA Technical Reports Server (NTRS)

Crabtree, W. L.

1980-01-01

A spectrophotovoltaic converter, a thermophotovoltaic converter, a cassegrainian concentrator, a large silicon cell blanket, and a high flux approach are among the concepts being investigated as part of the multihundred kW solar array program for reducing the cost of photovoltaic energy in space. These concepts involve a range of technology risks, the highest risk being represented by the thermophotovoltaics and spectrophotovoltaics approaches which involve manipulation to of the incoming spectrum to enhance system efficiency. The planar array (solar blanket) has no technology risk and a moderate payback. The primary characteristics, components, and technology concerns of each of these concepts are summarized. An orbital power platform mission in the late 1980's is being used to allow a coherent technology advancement program in order to achieve a ten year life with maintenance at a capital recurring cost of $30/watt based on 1978 dollars.

High Packing Density Unidirectional Arrays of Vertically Aligned Graphene with Enhanced Areal Capacitance for High-Power Micro-Supercapacitors.

PubMed

Zheng, Shuanghao; Li, Zhilin; Wu, Zhong-Shuai; Dong, Yanfeng; Zhou, Feng; Wang, Sen; Fu, Qiang; Sun, Chenglin; Guo, Liwei; Bao, Xinhe

2017-04-25

Interfacial integration of a shape-engineered electrode with a strongly bonded current collector is the key for minimizing both ionic and electronic resistance and then developing high-power supercapacitors. Herein, we demonstrated the construction of high-power micro-supercapacitors (VG-MSCs) based on high-density unidirectional arrays of vertically aligned graphene (VG) nanosheets, derived from a thermally decomposed SiC substrate. The as-grown VG arrays showed a standing basal plane orientation grown on a (0001̅) SiC substrate, tailored thickness (3.5-28 μm), high-density structurally ordering alignment of graphene consisting of 1-5 layers, vertically oriented edges, open intersheet channels, high electrical conductivity (192 S cm -1 ), and strong bonding of the VG edges to the SiC substrate. As a result, the demonstrated VG-MSCs displayed a high areal capacitance of ∼7.3 mF cm -2 and a fast frequency response with a short time constant of 9 ms. Furthermore, VG-MSCs in both an aqueous polymer gel electrolyte and nonaqueous ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate operated well at high scan rates of up to 200 V s -1 . More importantly, VG-MSCs offered a high power density of ∼15 W cm -3 in gel electrolyte and ∼61 W cm -3 in ionic liquid. Therefore, this strategy of producing high-density unidirectional VG nanosheets directly bonded on a SiC current collector demonstrated the feasibility of manufacturing high-power compact supercapacitors.

Ultra-low-noise transition edge sensors for the SAFARI L-band on SPICA

NASA Astrophysics Data System (ADS)

Goldie, D. J.; Gao, J. R.; Glowacka, D. M.; Griffin, D. K.; Hijmering, R.; Khosropanah, P.; Jackson, B. D.; Mauskopf, P. D.; Morozov, D.; Murphy, J. A.; Ridder, M.; Trappe, N.; O'Sullivan, C.; Withington, S.

2012-09-01

The Far-Infrared Fourier transform spectrometer instrument SAFARI-SPICA which will operate with cooled optics in a low-background space environment requires ultra-sensitive detector arrays with high optical coupling efficiencies over extremely wide bandwidths. In earlier papers we described the design, fabrication and performance of ultra-low-noise Transition Edge Sensors (TESs) operated close to 100mk having dark Noise Equivalent Powers (NEPs) of order 4 × 10-19W/√Hz close to the phonon noise limit and an improvement of two orders of magnitude over TESs for ground-based applications. Here we describe the design, fabrication and testing of 388-element arrays of MoAu TESs integrated with far-infrared absorbers and optical coupling structures in a geometry appropriate for the SAFARI L-band (110 - 210 μm). The measured performance shows intrinsic response time τ ~ 11ms and saturation powers of order 10 fW, and a dark noise equivalent powers of order 7 × 10-19W/√Hz. The 100 × 100μm2 MoAu TESs have transition temperatures of order 110mK and are coupled to 320×320μm2 thin-film β-phase Ta absorbers to provide impedance matching to the incoming fields. We describe results of dark tests (i.e without optical power) to determine intrinsic pixel characteristics and their uniformity, and measurements of the optical performance of representative pixels operated with flat back-shorts coupled to pyramidal horn arrays. The measured and modeled optical efficiency is dominated by the 95Ω sheet resistance of the Ta absorbers, indicating a clear route to achieve the required performance in these ultra-sensitive detectors.

Design of Feedforward Controller to Reduce Force Ripple for Linear Motor using Halbach Magnet Array with T Shape Magnet

NASA Astrophysics Data System (ADS)

Kim, Moojong; Kim, Jinyoung; Lee, Moon G.

Recently, in micro/nano fabrication equipments, linear motors are widely used as an actuator to position workpiece, machining tool and measurement head. To control them faster and more precise, the motor should have high actuating force and small force ripple. High actuating force enable us to more workpiece with high acceleration. Eventually, it may provide higher throughput. Force ripple gives detrimental effect on the precision and tracking performance of the equipments. In order to accomplish more precise motion, it is important to make lower the force ripple. Force ripple is categorized into cogging and mutual ripple. First is dependent on the shape of magnets and/or core. The second is not dependent on them but dependent on current commutation. In this work, coreless mover i.e. coil winding is applied to the linear motor to avoid the cogging ripple. Therefore, the mutual ripple is only considered to be minimized. Ideal Halbach magnet array has continuously varying magnetization. The THMA (Halbach magnet array with T shape magnets) is proposed to approximate the ideal one. The THMA can not produce ideal sinusoidal flux, therefore, the linear motor with THMA and sinusoidal commutation of current generates the mutual force ripple. In this paper, in order to compensate mutual force ripple by feedforward(FF) controller, we calculate the optimized commutation of input current. The ripple is lower than 1.17% of actuating force if the commutation current agree with the magnetic flux from THMA. The performance of feedforward(FF) controller is verified by experiment.

Magnetic nanohole superlattices

DOEpatents

Liu, Feng

2013-05-14

A magnetic material is disclosed including a two-dimensional array of carbon atoms and a two-dimensional array of nanoholes patterned in the two-dimensional array of carbon atoms. The magnetic material has long-range magnetic ordering at a temperature below a critical temperature Tc.

Photonic Crystal/Nano-Electronic Device Structures for Large Array Thermal Imaging

DTIC Science & Technology

2007-11-19

order to improve the signal to noise ratio of the detection, a larger photocurrent is desirable. To increase the photocurrent of QWIPs , one needs to...CLASSIFICATION OF: Lattice-matched InGaAs/Inp quantum well infrared detector ( QWIP ) exhibits high photoconductive gain but un-adjustable detection wavelength...Title ABSTRACT Lattice-matched InGaAs/Inp quantum well infrared detector ( QWIP ) exhibits high photoconductive gain but un-adjustable detection

Two-dimensional inverse opal hydrogel for pH sensing.

PubMed

Xue, Fei; Meng, Zihui; Qi, Fenglian; Xue, Min; Wang, Fengyan; Chen, Wei; Yan, Zequn

2014-12-07

A novel hydrogel film with a highly ordered macropore monolayer on its surface was prepared by templated photo-polymerization of hydrogel monomers on a two-dimensional (2D) polystyrene colloidal array. The 2D inverse opal hydrogel has prominent advantages over traditional three-dimensional (3D) inverse opal hydrogels. First, the formation of the 2D array template through a self-assembly method is considerably faster and simpler. Second, the stable ordering structure of the 2D array template makes it easier to introduce the polymerization solution into the template. Third, a simple measurement, a Debye diffraction ring, is utilized to characterize the neighboring pore spacing of the 2D inverse opal hydrogel. Acrylic acid was copolymerized into the hydrogel; thus, the hydrogel responded to pH through volume change, which resulted from the formation of the Donnan potential. The 2D inverse opal hydrogel showed that the neighboring pore spacing increased by about 150 nm and diffracted color red-shifted from blue to red as the pH increased from pH 2 to 7. In addition, the pH response kinetics and ionic strength effect of this 2D mesoporous polymer film were also investigated.

Development of Ordered, Porous (Sub-25 nm Dimensions) Surface Membrane Structures Using a Block Copolymer Approach.

PubMed

Ghoshal, Tandra; Holmes, Justin D; Morris, Michael A

2018-05-08

In an effort to develop block copolymer lithography to create high aspect vertical pore arrangements in a substrate surface we have used a microphase separated poly(ethylene oxide) -b- polystyrene (PEO-b-PS) block copolymer (BCP) thin film where (and most unusually) PS not PEO is the cylinder forming phase and PEO is the majority block. Compared to previous work, we can amplify etch contrast by inclusion of hard mask material into the matrix block allowing the cylinder polymer to be removed and the exposed substrate subject to deep etching thereby generating uniform, arranged, sub-25 nm cylindrical nanopore arrays. Briefly, selective metal ion inclusion into the PEO matrix and subsequent processing (etch/modification) was applied for creating iron oxide nanohole arrays. The oxide nanoholes (22 nm diameter) were cylindrical, uniform diameter and mimics the original BCP nanopatterns. The oxide nanohole network is demonstrated as a resistant mask to fabricate ultra dense, well ordered, good sidewall profile silicon nanopore arrays on substrate surface through the pattern transfer approach. The Si nanopores have uniform diameter and smooth sidewalls throughout their depth. The depth of the porous structure can be controlled via the etch process.

The Atmospheric Monitoring Strategy for the Cherenkov Telescope Array

NASA Astrophysics Data System (ADS)

Daniel, M. K.; CTA Consortium

2015-04-01

The Imaging Atmospheric Cherenkov Technique (IACT) is unusual in astronomy as the atmosphere actually forms an intrinsic part of the detector system, with telescopes indirectly detecting very high energy particles by the generation and transport of Cherenkov photons deep within the atmosphere. This means that accurate measurement, characterisation and monitoring of the atmosphere is at the very heart of successfully operating an IACT system. The Cherenkov Telescope Array (CTA) will be the next generation IACT observatory with an ambitious aim to improve the sensitivity of an order of magnitude over current facilities, along with corresponding improvements in angular and energy resolution and extended energy coverage, through an array of Large (23 m), Medium (12 m) and Small (4 m) sized telescopes spread over an area of order ~km2. Whole sky coverage will be achieved by operating at two sites: one in the northern hemisphere and one in the southern hemisphere. This proceedings will cover the characterisation of the candidate sites and the atmospheric calibration strategy. CTA will utilise a suite of instrumentation and analysis techniques for atmospheric modelling and monitoring regarding pointing forecasts, intelligent pointing selection for the observatory operations and for offline data correction.

Ordered Array of Gold Nanoparticles Promoted by Functional Peptides

NASA Astrophysics Data System (ADS)

Matsukawa, Nozomu; Yamashita, Ichiro

2011-05-01

It was successfully demonstrated that 5-nm-diameter gold nanoparticles (GNPs) with 15% size distribution, the surface of which was modified by the synthesized peptides composed of the carbonaceous material affinity peptide (NHBP-1), linker of 11 amino acids and C-terminal cysteine, self-assembled into a two-dimensional (2D) ordered array on a silicon substrate in a spin drying process. NHBP-1 generated an attractive force large enough for the GNP to make 2D collections of GNPs in the course of the spin drying process, and the long linker of 11 amino acids cancelled out the ill effect of size distribution of GNP on the 2D ordered array formation.

Reproduction of a higher-order circular harmonic field using a linear array of loudspeakers.

PubMed

Lee, Jung-Min; Choi, Jung-Woo; Kim, Yang-Hann

2015-03-01

This paper presents a direct formula for reproducing a sound field consisting of higher-order circular harmonics with polar phase variation. Sound fields with phase variation can be used for synthesizing various spatial attributes, such as the perceived width or the location of a virtual sound source. To reproduce such a sound field using a linear loudspeaker array, the driving function of the array is derived in the format of an integral formula. The proposed function shows fewer reproduction errors than a conventional formula focused on magnitude variations. In addition, analysis of the sweet spot reveals that its shape can be asymmetric, depending on the order of harmonics.

Thermal Conductivity of Carbon Nanotube Composite Films

NASA Technical Reports Server (NTRS)

Ngo, Quoc; Cruden, Brett A.; Cassell, Alan M.; Walker, Megan D.; Koehne, Jessica E.; Meyyappan, M.; Li, Jun; Yang, Cary Y.

2004-01-01

State-of-the-art ICs for microprocessors routinely dissipate power densities on the order of 50 W/sq cm. This large power is due to the localized heating of ICs operating at high frequencies, and must be managed for future high-frequency microelectronic applications. Our approach involves finding new and efficient thermally conductive materials. Exploiting carbon nanotube (CNT) films and composites for their superior axial thermal conductance properties has the potential for such an application requiring efficient heat transfer. In this work, we present thermal contact resistance measurement results for CNT and CNT-Cu composite films. It is shown that Cu-filled CNT arrays enhance thermal conductance when compared to as-grown CNT arrays. Furthermore, the CNT-Cu composite material provides a mechanically robust alternative to current IC packaging technology.

InP nanopore arrays for photoelectrochemical hydrogen generation.

PubMed

Li, Qiang; Zheng, Maojun; Zhang, Bin; Zhu, Changqing; Wang, Faze; Song, Jingnan; Zhong, Miao; Ma, Li; Shen, Wenzhong

2016-02-19

We report a facile and large-scale fabrication of highly ordered one-dimensional (1D) indium phosphide (InP) nanopore arrays (NPs) and their application as photoelectrodes for photoelectrochemical (PEC) hydrogen production. These InP NPs exhibit superior PEC performance due to their excellent light-trapping characteristics, high-quality 1D conducting channels and large surface areas. The photocurrent density of optimized InP NPs is 8.9 times higher than that of planar counterpart at an applied potential of +0.3 V versus RHE under AM 1.5G illumination (100 mW cm(-2)). In addition, the onset potential of InP NPs exhibits 105 mV of cathodic shift relative to planar control. The superior performance of the nanoporous samples is further explained by Mott-Schottky and electrochemical impedance spectroscopy ananlysis.

Copper Antimonide Nanowire Array Lithium Ion Anodes Stabilized by Electrolyte Additives.

PubMed

Jackson, Everett D; Prieto, Amy L

2016-11-09

Nanowires of electrochemically active electrode materials for lithium ion batteries represent a unique system that allows for intensive investigations of surface phenomena. In particular, highly ordered nanowire arrays produced by electrodeposition into anodic aluminum oxide templates can lead to new insights into a material's electrochemical performance by providing a high-surface-area electrode with negligible volume expansion induced pulverization. Here we show that for the Li-Cu x Sb ternary system, stabilizing the surface chemistry is the most critical factor for promoting long electrode life. The resulting solid electrolyte interphase is analyzed using a mix of electron microscopy, X-ray photoelectron spectroscopy, and lithium ion battery half-cell testing to provide a better understanding of the importance of electrolyte composition on this multicomponent alloy anode material.

Characterization of the Auroral Electrojet and the Ambient and Modified D Region for HAARP Using Long-Path VLF Diagnostics

DTIC Science & Technology

2001-03-15

order to characterize the auroral electrojet and the ambient and modified D-region directly above and near the HAARP (High Frequency Active Auroral...near the HAARP facility and along the west coast of Alaska. In addition in order to characterize the auroral electrojet on a continental scale and to...United States and Canada. Data from the complete array of D-region diagnostic systems was acquired during a number of Fall and Spring HAARP campaigns

Controlled growth of ordered nanopore arrays in GaN.

PubMed

Wildeson, Isaac H; Ewoldt, David A; Colby, Robert; Stach, Eric A; Sands, Timothy D

2011-02-09

High-quality, ordered nanopores in semiconductors are attractive for numerous biological, electrical, and optical applications. Here, GaN nanorods with continuous pores running axially through their centers were grown by organometallic vapor phase epitaxy. The porous nanorods nucleate on an underlying (0001)-oriented GaN film through openings in a SiN(x) template that are milled by a focused ion beam, allowing direct placement of porous nanorods. Nanopores with diameters ranging from 20-155 nm were synthesized with crystalline sidewalls.

Assembling Ordered Nanorod Superstructures and Their Application as Microcavity Lasers

NASA Astrophysics Data System (ADS)

Liu, Pai; Singh, Shalini; Guo, Yina; Wang, Jian-Jun; Xu, Hongxing; Silien, Christophe; Liu, Ning; Ryan, Kevin M.

2017-03-01

Herein we report the formation of multi-layered arrays of vertically aligned and close packed semiconductor nanorods in perfect registry at a substrate using electric field assisted assembly. The collective properties of these CdSexS1-x nanorod emitters are harnessed by demonstrating a relatively low amplified spontaneous emission (ASE) threshold and a high net optical gain at medium pump intensity. The importance of order in the system is highlighted where a lower ASE threshold is observed compared to disordered samples.

Peptide π-Electron Conjugates: Organic Electronics for Biology?

PubMed

Ardoña, Herdeline Ann M; Tovar, John D

2015-12-16

Highly ordered arrays of π-conjugated molecules are often viewed as a prerequisite for effective charge-transporting materials. Studies involving these materials have traditionally focused on organic electronic devices, with more recent emphasis on biological systems. In order to facilitate the transition to biological environments, biomolecules that can promote hierarchical ordering and water solubility are often covalently appended to the π-electron unit. This review highlights recent work on π-conjugated systems bound to peptide moieties that exhibit self-assembly and aims to provide an overview on the development and emerging applications of peptide-based supramolecular π-electron systems.

Fabrication and structural characterization of highly ordered titania nanotube arrays

NASA Astrophysics Data System (ADS)

Shi, Hongtao; Ordonez, Rosita

Titanium (Ti) dioxide nanotubes have drawn much attention in the past decade due to the fact that titania is an extremely versatile material with a variety of technological applications. Anodizing Ti in different electrolytes has proved to be quite successful so far in creating the nanotubes, however, their degree of order is still not nearly as good as nanoporous anodic alumina. In this work, we first deposit a thin layer of aluminum (Al) onto electropolished Ti substrates, using thermal evaporation. Such an Al layer is then anodized in 0.3 M oxalic acid, forming an ordered nanoporous alumina mask on top of Ti. Afterwards, the anodization of Ti is accomplished at 20 V in solutions containing 1 M NaH2PO4 and 0.5% HF or H2SO4, which results in the creation of ordered titania nanotube arrays. The inner pore diameter of the nanotubes can be tuned from ~50 nm to ~75 nm, depending on the anodization voltage applied to Al or Ti. X-ray diffractometry shows the as-grown titania nanotubes are amorphous. Samples annealed at different temperatures in ambient atmosphere will be also reported.

Higher order moments, structure functions and spectral ratios in near- and far-wakes of a wind turbine array

NASA Astrophysics Data System (ADS)

Ali, Naseem; Aseyev, A.; McCraney, J.; Vuppuluri, V.; Abbass, O.; Al Jubaree, T.; Melius, M.; Cal, R. B.

2014-11-01

Hot-wire measurements obtained in a 3 × 3 wind turbine array boundary layer are utilized to analyze higher order statistics which include skewness, kurtosis as well as the ratios of structure functions and spectra. The ratios consist of wall-normal to streamwise components for both quantities. The aim is to understand the degree of anisotropy in the flow for the near- and far-wakes of the flow field where profiles at one diameter and five diameters are considered, respectively. The skewness at top tip for both wakes show a negative skewness while below the turbine canopy, this terms are positive. The kurtosis shows a Gaussian behavior in the near-wake immediately at hub-height. In addition, the effect due to the passage of the rotor in tandem with the shear layer at the top tip renders relatively high differences in the fourth order moment. The second order structure function and spectral ratios are found to exhibit anisotropic behavior at the top and bottom-tips for the large scales. Mixed structure functions and co-spectra are also considered in the context of isotropy.

Improved field emission properties of carbon nanotubes grown on stainless steel substrate and its application in ionization gauge

NASA Astrophysics Data System (ADS)

Li, Detian; Cheng, Yongjun; Wang, Yongjun; Zhang, Huzhong; Dong, Changkun; Li, Da

2016-03-01

Vertically aligned carbon nanotube (CNT) arrays were fabricated by chemical vapor deposition (CVD) technique on different substrates. Microstructures and field emission characteristics of the as-grown CNT arrays were investigated systematically, and its application in ionization gauge was also evaluated preliminarily. The results indicate that the as-grown CNT arrays are vertically well-aligned relating to the substrate surfaces, but the CNTs grown on stainless steel substrate are longer and more crystalline than the ones grown on silicon wafer substrate. The field emission behaviors of the as-grown CNT arrays are strongly dependent upon substrate properties. Namely, the CNT array grown on stainless steel substrate has better field emission properties, including lower turn on and threshold fields, better emission stability and repeatability, compared with the one grown on silicon wafer substrate. The superior field emission properties of the CNT array grown on stainless steel substrate are mainly attributed to low contact resistance, high thermal conductivity, good adhesion strength, etc. In addition, the metrological behaviors of ionization gauge with the CNT array grown on stainless steel substrate as an electron source were investigated, and this novel cathode ionization gauge extends the lower limit of linear pressure measurement to 10-8 Pa, which is one order of magnitude lower than the result reported for the same of gauge with CNT cathode.

One- and two-dimensional antenna arrays for microwave wireless power transfer (MWPT) systems and dual-antenna transceivers

NASA Astrophysics Data System (ADS)

Lin, Yo-Sheng; Hu, Chun-Hao; Chang, Chi-Ho; Tsao, Ping-Chang

2018-06-01

In this work, we demonstrate novel one-dimensional (1D) and two-dimensional (2D) antenna arrays for both microwave wireless power transfer (MWPT) systems and dual-antenna transceivers. The antenna array can be used as the MWPT receiving antenna of an integrated MWPT and Bluetooth (BLE) communication module (MWPT-BLE module) for smart CNC (computer numerical control) spindle incorporated with the cloud computing system SkyMars. The 2D antenna array has n rows of 1 × m 1D array, and each array is composed of multiple (m) differential feeding antenna elements. Each differential feeding antenna element is a differential feeding structure with a microstrip antenna stripe. The stripe length is shorter than one wavelength to minimise the antenna area and to prevent being excited to a high-order mode. That is, the differential feeding antenna element can suppress the even mode. The mutual coupling between the antenna elements can be suppressed, and the isolation between the receiver and the transmitter can be enhanced. An inclination angle of the main beam aligns with the broadside, and the main beam is further concentrated and shrunk at the elevation direction. Moreover, if more differential feeding antenna elements are used, antenna gain and isolation can be further enhanced. The excellent performance of the proposed antenna arrays indicates that they are suitable for both MWPT systems and dual-antenna transceivers.

High resolution telescope

DOEpatents

Massie, Norbert A.; Oster, Yale

1992-01-01

A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employs speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by an electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activites. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes.

Design of bent waveguide semiconductor lasers using nonlinear equivalent chirp

NASA Astrophysics Data System (ADS)

Li, Lianyan; Shi, Yuechun; Zhang, Yunshan; Chen, Xiangfei

2018-01-01

Reconstruction equivalent chirp (REC) technique is widely used in the design and fabrication of semiconductor laser arrays and tunable lasers with low cost and high wavelength accuracy. Bent waveguide is a promising method to suppress the zeroth order resonance, which is an intrinsic problem in REC technique. However, it may introduce basic grating chirp and deteriorate the single longitudinal mode (SLM) property of the laser. A nonlinear equivalent chirp pattern is proposed in this paper to compensate the grating chirp and improve the SLM property. It will benefit the realization of low-cost Distributed feedback (DFB) semiconductor laser arrays with accurate lasing wavelength.

Design, optimization, and analysis of a self-deploying PV tent array

NASA Astrophysics Data System (ADS)

Collozza, Anthony J.

1991-06-01

A tent shaped PV array was designed and the design was optimized for maximum specific power. In order to minimize output power variation a tent angle of 60 deg was chosen. Based on the chosen tent angle an array structure was designed. The design considerations were minimal deployment time, high reliability, and small stowage volume. To meet these considerations the array was chosen to be self-deployable, form a compact storage configuration, using a passive pressurized gas deployment mechanism. Each structural component of the design was analyzed to determine the size necessary to withstand the various forces to which it would be subjected. Through this analysis the component weights were determined. An optimization was performed to determine the array dimensions and blanket geometry which produce the maximum specific power for a given PV blanket. This optimization was performed for both lunar and Martian environmental conditions. Other factors such as PV blanket types, structural material, and wind velocity (for Mars array), were varied to determine what influence they had on the design point. The performance specifications for the array at both locations and with each type of PV blanket were determined. These specifications were calculated using the Arimid fiber composite as the structural material. The four PV blanket types considered were silicon, GaAs/Ge, GaAsCLEFT, and amorphous silicon. The specifications used for each blanket represented either present day or near term technology. For both the Moon and Mars the amorphous silicon arrays produced the highest specific power.

Pathway-engineering for highly-aligned block copolymer arrays.

PubMed

Choo, Youngwoo; Majewski, Paweł W; Fukuto, Masafumi; Osuji, Chinedum O; Yager, Kevin G

2017-12-21

While the ultimate driving force in self-assembly is energy minimization and the corresponding evolution towards equilibrium, kinetic effects can also play a very strong role. These kinetic effects, such as trapping in metastable states, slow coarsening kinetics, and pathway-dependent assembly, are often viewed as complications to be overcome. Here, we instead exploit these effects to engineer a desired final nano-structure in a block copolymer thin film, by selecting a particular ordering pathway through the self-assembly energy landscape. In particular, we combine photothermal shearing with high-temperature annealing to yield hexagonal arrays of block copolymer cylinders that are aligned in a single prescribed direction over macroscopic sample dimensions. Photothermal shearing is first used to generate a highly-aligned horizontal cylinder state, with subsequent thermal processing used to reorient the morphology to the vertical cylinder state in a templated manner. Finally, we demonstrate the successful transfer of engineered morphologies into inorganic replicas.

Gold nanoparticle array formation on dimpled Ta templates using pulsed laser-induced thin film dewetting.

PubMed

El-Sayed, Hany A; Horwood, Corie A; Owusu-Ansah, Ebenezer; Shi, Yujun J; Birss, Viola I

2015-04-28

Here we show that pulsed laser-induced dewetting (PLiD) of a thin Au metallic film on a nano-scale ordered dimpled tantalum (DT) surface results in the formation of a high quality Au nanoparticle (NP) array. In contrast to thermal dewetting, PLiD does not result in deformation of the substrate, even when the Au film is heated to above its melting point. PLiD causes local heating of only the metal film and thus thermal oxidation of the Ta substrate can be avoided, also because of the high vacuum (low pO2) environment employed. Therefore, this technique can potentially be used to fabricate NP arrays composed of high melting point metals, such as Pt, not previously possible using conventional thermal annealing methods. We also show that the Au NPs formed by PLiD are more spherical in shape than those formed by thermal dewetting, likely demonstrating a different dewetting mechanism in the two cases. As the metallic NPs formed on DT templates are electrochemically addressable, a longer-term objective of this work is to determine the effect of NP size and shape (formed by laser vs. thermal dewetting) on their electrocatalytic properties.

High carrier concentration ZnO nanowire arrays for binder-free conductive support of supercapacitors electrodes by Al doping.

PubMed

Zheng, Xin; Sun, Yihui; Yan, Xiaoqin; Sun, Xu; Zhang, Guangjie; Zhang, Qian; Jiang, Yaru; Gao, Wenchao; Zhang, Yue

2016-12-15

Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. Here, we prepared in situ Al-doped ZnO nanowire arrays by using continuous flow injection (CFI) hydrothermal method to promote the conductivity. This reasonable method offers highly stable precursor concentration for doping that effectively avoid the appearance of the low conductivity ZnO nanosheets. Benefit from this, three orders of magnitude rise of the carrier concentration from 10 16 cm -3 to 10 19 cm -3 can be achieved compared with the common hydrothermal (CH) mothed in Mott-Schottky measurement. Possible effect of Al-doping was discussed by first-principle theory. On this basis, Al-doped ZnO nanowire arrays was developed as a binder-free conductive support for supercapacitor electrodes and high capacitance was triggered. It is owing to the dramatically decreased transfer resistance induced by the growing free-moving electrons and holes. Our results have a profound significance not merely in the controlled synthesis of other doping nanomaterials by co-precipitation method but also in the application of binder-free energy materials or other materials. Copyright © 2016 Elsevier Inc. All rights reserved.

Array seismological investigation of the South Atlantic 'Superplume'

NASA Astrophysics Data System (ADS)

Hempel, Stefanie; Gassmöller, Rene; Thomas, Christine

2015-04-01

We apply the axisymmetric, spherical Earth spectral elements code AxiSEM to model seismic compressional waves which sample complex `superplume' structures in the lower mantle. High-resolution array seismological stacking techniques are evaluated regarding their capability to resolve large-scale high-density low-velocity bodies including interior structure such as inner upwellings, high density lenses, ultra-low velocity zones (ULVZs), neighboring remnant slabs and adjacent small-scale uprisings. Synthetic seismograms are also computed and processed for models of the Earth resulting from geodynamic modelling of the South Atlantic mantle including plate reconstruction. We discuss the interference and suppression of the resulting seismic signals and implications for a seismic data study in terms of visibility of the South Atlantic `superplume' structure. This knowledge is used to process, invert and interpret our data set of seismic sources from the Andes and the South Sandwich Islands detected at seismic arrays spanning from Ethiopia over Cameroon to South Africa mapping the South Atlantic `superplume' structure including its interior structure. In order too present the model of the South Atlantic `superplume' structure that best fits the seismic data set, we iteratively compute synthetic seismograms while adjusting the model according to the dependencies found in the parameter study.

Acoustic Transmitters for Underwater Neutrino Telescopes

PubMed Central

Ardid, Miguel; Martínez-Mora, Juan A.; Bou-Cabo, Manuel; Larosa, Giuseppina; Adrián-Martínez, Silvia; Llorens, Carlos D.

2012-01-01

In this paper acoustic transmitters that were developed for use in underwater neutrino telescopes are presented. Firstly, an acoustic transceiver has been developed as part of the acoustic positioning system of neutrino telescopes. These infrastructures are not completely rigid and require a positioning system in order to monitor the position of the optical sensors which move due to sea currents. To guarantee a reliable and versatile system, the transceiver has the requirements of reduced cost, low power consumption, high pressure withstanding (up to 500 bars), high intensity for emission, low intrinsic noise, arbitrary signals for emission and the capacity of acquiring and processing received signals. Secondly, a compact acoustic transmitter array has been developed for the calibration of acoustic neutrino detection systems. The array is able to mimic the signature of ultra-high-energy neutrino interaction in emission directivity and signal shape. The technique of parametric acoustic sources has been used to achieve the proposed aim. The developed compact array has practical features such as easy manageability and operation. The prototype designs and the results of different tests are described. The techniques applied for these two acoustic systems are so powerful and versatile that may be of interest in other marine applications using acoustic transmitters. PMID:22666022

Low-Cost Photolithographic Fabrication of Nanowires and Microfilters for Advanced Bioassay Devices

PubMed Central

Doan, Nhi M.; Qiang, Liangliang; Li, Zhe; Vaddiraju, Santhisagar; Bishop, Gregory W.; Rusling, James F.; Papadimitrakopoulos, Fotios

2015-01-01

Integrated microfluidic devices with nanosized array electrodes and microfiltration capabilities can greatly increase sensitivity and enhance automation in immunoassay devices. In this contribution, we utilize the edge-patterning method of thin aluminum (Al) films in order to form nano- to micron-sized gaps. Evaporation of high work-function metals (i.e., Au, Ag, etc.) on these gaps, followed by Al lift-off, enables the formation of electrical uniform nanowires from low-cost, plastic-based, photomasks. By replacing Al with chromium (Cr), the formation of high resolution, custom-made photomasks that are ideal for low-cost fabrication of a plurality of array devices were realized. To demonstrate the feasibility of such Cr photomasks, SU-8 micro-pillar masters were formed and replicated into PDMS to produce micron-sized filters with 3–4 µm gaps and an aspect ratio of 3. These microfilters were capable of retaining 6 µm beads within a localized site, while allowing solvent flow. The combination of nanowire arrays and micro-pillar filtration opens new perspectives for rapid R&D screening of various microfluidic-based immunoassay geometries, where analyte pre-concentration and highly sensitive, electrochemical detection can be readily co-localized. PMID:25774709

Ordered alternating binary polymer nanodroplet array by sequential spin dewetting.

PubMed

Bhandaru, Nandini; Das, Anuja; Salunke, Namrata; Mukherjee, Rabibrata

2014-12-10

We report a facile technique for fabricating an ordered array of nearly equal-sized mesoscale polymer droplets of two constituent polymers (polystyrene, PS and poly(methyl methacrylate), PMMA) arranged in an alternating manner on a topographically patterned substrate. The self-organized array of binary polymers is realized by sequential spin dewetting. First, a dilute solution of PMMA is spin-dewetted on a patterned substrate, resulting in an array of isolated PMMA droplets arranged along the substrate grooves due to self-organization during spin coating itself. The sample is then silanized with octadecyltrichlorosilane (OTS), and subsequently, a dilute solution of PS is spin-coated on to it, which also undergoes spin dewetting. The spin-dewetted PS drops having a size nearly equal to the pre-existing PMMA droplets position themselves between two adjacent PMMA drops under appropriate conditions, forming an alternating binary polymer droplet array. The alternating array formation takes place for a narrow range of solution concentration for both the polymers and depends on the geometry of the substrate. The size of the droplets depends on the extent of confinement, and droplets as small as 100 nm can be obtained by this method, on a suitable template. The findings open up the possibility of creating novel surfaces having ordered multimaterial domains with a potential multifunctional capability.

Array of nanoparticles coupling with quantum-dot: Lattice plasmon quantum features

NASA Astrophysics Data System (ADS)

Salmanogli, Ahmad; Gecim, H. Selcuk

2018-06-01

In this study, we analyze the interaction of lattice plasmon with quantum-dot in order to mainly examine the quantum features of the lattice plasmon containing the photonic/plasmonic properties. Despite optical properties of the localized plasmon, the lattice plasmon severely depends on the array geometry, which may influence its quantum features such as uncertainty and the second-order correlation function. To investigate this interaction, we consider a closed system containing an array of the plasmonic nanoparticles and quantum-dot. We analyze this system with full quantum theory by which the array electric far field is quantized and the strength coupling of the quantum-dot array is analytically calculated. Moreover, the system's dynamics are evaluated and studied via the Heisenberg-Langevin equations to attain the system optical modes. We also analytically examine the Purcell factor, which shows the effect of the lattice plasmon on the quantum-dot spontaneous emission. Finally, the lattice plasmon uncertainty and its time evolution of the second-order correlation function at different spatial points are examined. These parameters are dramatically affected by the retarded field effect of the array nanoparticles. We found a severe quantum fluctuation at points where the lattice plasmon occurs, suggesting that the lattice plasmon photons are correlated.

An innovative approach to synthesize highly-ordered TiO2 nanotubes.

PubMed

Isimjan, Tayirjan T; Yang, D Q; Rohani, Sohrab; Ray, Ajay K

2011-02-01

An innovative route to prepare highly-ordered and dimensionally controlled TiO2 nanotubes has been proposed using a mild sonication method. The nanotube arrays were prepared by the anodization of titanium in an electrolyte containing 3% NH4F and 5% H2O in glycerol. It is demonstrated that the TiO2 nanostructures has two layers: the top layer is TiO2 nanowire and underneath is well-ordered TiO2 nanotubes. The top layer can easily fall off and form nanowires bundles by implementing a mild sonication after a short annealing time. We found that the dimensions of the TiO2 nanotubes were only dependent on the anodizing condition. The proposed technique may be extended to fabricate reproducible well-ordered TiO2 nanotubes with large area on other metals.

Differently ordered TiO2 nanoarrays regulated by solvent polarity, and their photocatalytic performances

NASA Astrophysics Data System (ADS)

Hu, Wenyuan; Dong, Faqin; Zhang, Jing; Liu, Mingxue; He, Huichao; Wu, Yadong; Yang, Dingming; Deng, Hongquan

2018-06-01

Special TiO2 arrays with exposed facets were prepared in different solvents by low- temperature solvothermal synthesis. The morphology, phase and photocatalytic performance influenced by the various solvent polarities were characterized using field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra and electrochemical testing. The results show that differences of solvent polarity are the main force driving differences in array growth; therefore, anatase TiO2 arrays with different crystal facets can be synthesized by tuning solvent polarity. TiO2 arrays prepared in cyclohexane are the best at oxidizing methyl orange through photocatalysis, followed by arrays prepared in toluene and ethanol. Arrays prepared in toluene are the best at reducing Cr(VI) photocatalytically, followed by those prepared in cyclohexane and ethanol. These differences in photocatalytic power are due to the ratio among the different crystal facets that are exposed, which affects the migration behavior of the photogenerated electrons and holes. In addition, the probable growth mechanisms of self-assembled ordered TiO2 arrays in different solvents are described.

Ultrasonic phased array controller for hyperthermia applications.

PubMed

Benkeser, P J; Pao, T L; Yoon, Y J

1991-01-01

Multiple and mechanically scanned ultrasound transducer systems have demonstrated the efficacy of using ultrasound to produce deep localized hyperthermia. The use of ultrasonic phased arrays has been proposed as an alternative to these systems. A phased array offers a more flexible approach to heating tumours in that the size, shape, and position of its focal region can be altered during the course of treatment in order to achieve the desired temperature distribution. This added flexibility comes at the cost of increased complexity of the hardware necessary to drive the transducer because each element requires its own amplifer with both phase and amplitude control. In order for phased arrays with large numbers of elements to be feasible for hyperthermia applications, the complexity of this circuitry must be minimized. This paper describes a circuit design which simplifies the electronics required to control a phased array transducer system for hyperthermia applications. The design is capable of controlling virtually any type of phased array transducer operating at frequencies less than 2 MHz. The system performance was verified through beam profile measurements using a 48-element tapered phased array transducer.

FIB-tomographic studies on chemical vapor deposition grown SnO2 nanowire arrays on TiO2 (001)

NASA Astrophysics Data System (ADS)

Chen, Haoyun; Liu, Yi; Wu, Hong; Xiong, Xiang; Pan, Jun

2016-12-01

Tin oxide nanowire arrays on titania (001) have been successfully fabricated by chemical vapor deposition of Sn(O t Bu)4 precursor. The morphologies and structures of ordered SnO2 nanowires (NWs) were analyzed by cross-sectional SEM, HR-TEM and AFM. An FIB-tomography technique was applied in order to reconstruct a 3D presentation of ordered SnO2 nanowires. The achieved 3D analysis showed the spatial orientation and angles of ordered SnO2 NWs can be obtained in a one-shot experiment, and the distribution of Au catalysts showed the competition between 1D and 2D growth. The SnO2 nanowire arrays can be potentially used as a diameter- and surface-dependent sensing unit for the detection of gas- and bio-molecules.

Modulation transfer function measurement of microbolometer focal plane array by Lloyd's mirror method

NASA Astrophysics Data System (ADS)

Druart, Guillaume; Rommeluere, Sylvain; Viale, Thibault; Guerineau, Nicolas; Ribet-Mohamed, Isabelle; Crastes, Arnaud; Durand, Alain; Taboury, Jean

2014-05-01

Today, both military and civilian applications require miniaturized and cheap optical systems. One way to achieve this trend consists in decreasing the pixel pitch of focal plane arrays (FPA). In order to evaluate the performance of the overall optical systems, it is necessary to measure the modulation transfer function (MTF) of these pixels. However, small pixels lead to higher cut-off frequencies and therefore, original MTF measurements that are able to extract frequencies up to these high cut-off frequencies, are needed. In this paper, we will present a way to extract 1D MTF at high frequencies by projecting fringes on the FPA. The device uses a Lloyd mirror placed near and perpendicular to the focal plane array. Consequently, an interference pattern of fringes can be projected on the detector. By varying the angle of incidence of the light beam, we can tune the period of the interference fringes and, thus, explore a wide range of spatial frequencies, and mainly around the cut-off frequency of the pixel which is one of the most interesting area. Illustration of this method will be applied to a 640×480 microbolometer focal plane array with a pixel pitch of 17µm in the LWIR spectral region.

Mesoscale martensitic transformation in single crystals of topological defects

PubMed Central

Martínez-González, José A.; Ramírez-Hernández, Abelardo; Zhou, Ye; Sadati, Monirosadat; Zhang, Rui; Nealey, Paul F.; de Pablo, Juan J.

2017-01-01

Liquid-crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of double-twisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by the existence of grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with precision by relying on chemically nanopatterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of mesocrystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local reorganization of the crystalline array, without diffusion of the double-twisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the submicron regime, is found to be martensitic in nature when one considers the collective behavior of the double-twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal nucleation and the controlled growth of soft matter. PMID:28874557

Water Masers and Accretion Disks in Galactic Nuclei

NASA Astrophysics Data System (ADS)

Greenhill, L. J.

2005-12-01

There are over 50 sources of H2O maser emission in type-2 active galactic nuclei, a large fraction discovered in the last two years. Interferometer maps of water masers are presently the only means by which structures ⪉ 1 pc from massive black holes can be mapped directly, which is particularly important for type-2 systems because edge-on orientation and obscuration complicate study by other means. Investigations of several sources have demonstrated convincingly that the maser emission traces warped accretion disks 0.1 to 1 pc from central engines of order 106-108 M⊙. The same may be true for almost half the known (but unmapped) sources, based on spectral characteristics consistent with emission from edge-on accretion disks. Mapping these sources is a high priority. Study of most recently discovered masers requires long baseline arrays that include 100-m class apertures and would benefit from aggregate bit rates on the order of 1 gigabit per second. The Square Kilometer Array should provide an order of magnitude boost in mapping sensitivity, but outrigger antennas will be needed to achieve necesssary angular resolutions, as may be space-borne antennas.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xiao; Martínez-González, José A.; Hernández-Ortiz, Juan P.

Liquid crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of doubletwisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with considerable precision by relying on chemically nano-patterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of meso-crystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local re-organization of the crystalline array,more » without diffusion of the double twisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the sub-micron regime, is found to be martensitic in nature, with the diffusion-less feature associated to the collective behavior of the double twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal-nucleation and the controlled growth of soft matter.« less

PhylArray: phylogenetic probe design algorithm for microarray.

PubMed

Militon, Cécile; Rimour, Sébastien; Missaoui, Mohieddine; Biderre, Corinne; Barra, Vincent; Hill, David; Moné, Anne; Gagne, Geneviève; Meier, Harald; Peyretaillade, Eric; Peyret, Pierre

2007-10-01

Microbial diversity is still largely unknown in most environments, such as soils. In order to get access to this microbial 'black-box', the development of powerful tools such as microarrays are necessary. However, the reliability of this approach relies on probe efficiency, in particular sensitivity, specificity and explorative power, in order to obtain an image of the microbial communities that is close to reality. We propose a new probe design algorithm that is able to select microarray probes targeting SSU rRNA at any phylogenetic level. This original approach, implemented in a program called 'PhylArray', designs a combination of degenerate and non-degenerate probes for each target taxon. Comparative experimental evaluations indicate that probes designed with PhylArray yield a higher sensitivity and specificity than those designed by conventional approaches. Applying the combined PhyArray/GoArrays strategy helps to optimize the hybridization performance of short probes. Finally, hybridizations with environmental targets have shown that the use of the PhylArray strategy can draw attention to even previously unknown bacteria.

Three Element Phased Array Coil for Imaging of Rat Spinal Cord at 7T

PubMed Central

Mogatadakala, Kishore V.; Bankson, James A.; Narayana, Ponnada A.

2008-01-01

In order to overcome some of the limitations of an implantable coil, including its invasive nature and limited spatial coverage, a three element phased array coil is described for high resolution magnetic resonance imaging (MRI) of rat spinal cord. This coil allows imaging both thoracic and cervical segments of rat spinal cord. In the current design, coupling between the nearest neighbors was minimized by overlapping the coil elements. A simple capacitive network was used for decoupling the next neighbor elements. The dimensions of individual coils in the array were determined based on the signal-to-noise ratio (SNR) measurements performed on a phantom with three different surface coils. SNR measurements on a phantom demonstrated higher SNR of the phased array coil relative to two different volume coils. In-vivo images acquired on rat spinal cord with our coil demonstrated excellent gray and white matter contrast. To evaluate the performance of the phased array coil under parallel imaging, g-factor maps were obtained for two different acceleration factors of 2 and 3. These simulations indicate that parallel imaging with acceleration factor of 2 would be possible without significant image reconstruction related noise amplifications. PMID:19025892

Conceptual design of the early implementation of the NEutron Detector Array (NEDA) with AGATA

NASA Astrophysics Data System (ADS)

Hüyük, Tayfun; Di Nitto, Antonio; Jaworski, Grzegorz; Gadea, Andrés; Javier Valiente-Dobón, José; Nyberg, Johan; Palacz, Marcin; Söderström, Pär-Anders; Jose Aliaga-Varea, Ramon; de Angelis, Giacomo; Ataç, Ayşe; Collado, Javier; Domingo-Pardo, Cesar; Egea, Francisco Javier; Erduran, Nizamettin; Ertürk, Sefa; de France, Gilles; Gadea, Rafael; González, Vicente; Herrero-Bosch, Vicente; Kaşkaş, Ayşe; Modamio, Victor; Moszynski, Marek; Sanchis, Enrique; Triossi, Andrea; Wadsworth, Robert

2016-03-01

The NEutron Detector Array (NEDA) project aims at the construction of a new high-efficiency compact neutron detector array to be coupled with large γ-ray arrays such as AGATA. The application of NEDA ranges from its use as selective neutron multiplicity filter for fusion-evaporation reaction to a large solid angle neutron tagging device. In the present work, possible configurations for the NEDA coupled with the Neutron Wall for the early implementation with AGATA has been simulated, using Monte Carlo techniques, in order to evaluate their performance figures. The goal of this early NEDA implementation is to improve, with respect to previous instruments, efficiency and capability to select multiplicity for fusion-evaporation reaction channels in which 1, 2 or 3 neutrons are emitted. Each NEDA detector unit has the shape of a regular hexagonal prism with a volume of about 3.23l and it is filled with the EJ301 liquid scintillator, that presents good neutron- γ discrimination properties. The simulations have been performed using a fusion-evaporation event generator that has been validated with a set of experimental data obtained in the 58Ni + 56Fe reaction measured with the Neutron Wall detector array.

High performance devices enabled by epitaxial, preferentially oriented, nanodots and/or nanorods

DOEpatents

Goyal, Amit [Knoxville, TN

2011-10-11

Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic, superconducting and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

Prospects for PWNe and SNRs science with the ASTRI mini-array of pre-production small-sized telescopes of the Cherenkov telescope array

NASA Astrophysics Data System (ADS)

Burtovoi, A.; Zampieri, L.; Giuliani, A.; Bigongiari, C.; Di Pierro, F.; Stamerra, A.

2017-01-01

The development and construction of the Cherenkov Telescope Array (CTA) opens up new opportunities for the study of very high energy (VHE, E > 100 GeV) sources. As a part of CTA, the ASTRI project, led by INAF, has one of the main goals to develop one of the mini-arrays of CTA pre-production telescopes, proposed to be installed at the CTA southern site. Thanks to the innovative dual-mirror optical design of its small-sized telescopes, the ASTRI mini-array will be characterized by a large field of view, an excellent angular resolution and a good sensitivity up to energies of several tens of TeV. Pulsar wind nebulae, along with Supernova Remnants, are among the most abundant sources that will be identified and investigated, with the ultimate goal to move significantly closer to an understanding of the origin of cosmic rays (CR). As part of the ongoing effort to investigate the scientific capabilities for both CTA as a whole and the ASTRI mini-array, we performed simulations of the Vela X region. We simulated its extended VHE γ-ray emission using the results of the detailed H.E.S.S. analysis of this source. We estimated the resolving capabilities of the diffuse emission and the detection significance of the pulsar with both CTA as a whole and the ASTRI mini-array. Moreover with these instruments it will be possible to observe the high-energy end of SNRs spectrum, searching for particles with energies near the cosmic-rays "knee" (E ˜ 1015 eV). We simulated a set of ASTRI mini-array observations for one young and an evolved SNRs in order to test the capabilities of this instrument to discover and study PeVatrons on the Galactic plane.

Facile fabrication of super-hydrophobic nano-needle arrays via breath figures method.

PubMed

Kim, Jiseok; Lew, Brian; Kim, Woo Soo

2011-12-06

Super-hydrophobic surfaces which have been fabricated by various methods such as photolithography, chemical treatment, self-assembly, and imprinting have gained enormous attention in recent years. Especially 2D arrays of nano-needles have been shown to have super-hydrophobicity due to their sharp surface roughness. These arrays can be easily generated by removing the top portion of the honeycomb films prepared by the breath figures method. The hydrophilic block of an amphiphilic polymer helps in the fabrication of the nano-needle arrays through the production of well-ordered honeycomb films and good adhesion of the film to a substrate. Anisotropic patterns with water wettability difference can be useful for patterning cells and other materials using their selective growth on the hydrophilic part of the pattern. However, there has not been a simple way to generate patterns with highly different wettability. Mechanical stamping of the nano-needle array with a polyurethane stamp might be the simplest way to fabricate patterns with wettability difference. In this study, super-hydrophobic nano-needle arrays were simply fabricated by removing the top portion of the honeycomb films. The maximum water contact angle obtained with the nano-needle array was 150°. By controlling the pore size and the density of the honeycomb films, the height, width, and density of nano-needle arrays were determined. Anisotropic patterns with different wettability were fabricated by simply pressing the nano-needle array at ambient temperature with polyurethane stamps which were flexible but tough. Mechanical stamping of nano-needle arrays with micron patterns produced hierarchical super-hydrophobic structures.PACS: 05.70.Np, 68.55.am, 68.55.jm.

Facile fabrication of super-hydrophobic nano-needle arrays via breath figures method

PubMed Central

2011-01-01

Super-hydrophobic surfaces which have been fabricated by various methods such as photolithography, chemical treatment, self-assembly, and imprinting have gained enormous attention in recent years. Especially 2D arrays of nano-needles have been shown to have super-hydrophobicity due to their sharp surface roughness. These arrays can be easily generated by removing the top portion of the honeycomb films prepared by the breath figures method. The hydrophilic block of an amphiphilic polymer helps in the fabrication of the nano-needle arrays through the production of well-ordered honeycomb films and good adhesion of the film to a substrate. Anisotropic patterns with water wettability difference can be useful for patterning cells and other materials using their selective growth on the hydrophilic part of the pattern. However, there has not been a simple way to generate patterns with highly different wettability. Mechanical stamping of the nano-needle array with a polyurethane stamp might be the simplest way to fabricate patterns with wettability difference. In this study, super-hydrophobic nano-needle arrays were simply fabricated by removing the top portion of the honeycomb films. The maximum water contact angle obtained with the nano-needle array was 150°. By controlling the pore size and the density of the honeycomb films, the height, width, and density of nano-needle arrays were determined. Anisotropic patterns with different wettability were fabricated by simply pressing the nano-needle array at ambient temperature with polyurethane stamps which were flexible but tough. Mechanical stamping of nano-needle arrays with micron patterns produced hierarchical super-hydrophobic structures. PACS: 05.70.Np, 68.55.am, 68.55.jm PMID:22145673

Mutual capacitance of liquid conductors in deformable tactile sensing arrays

NASA Astrophysics Data System (ADS)

Li, Bin; Fontecchio, Adam K.; Visell, Yon

2016-01-01

Advances in highly deformable electronics are needed in order to enable emerging categories of soft computing devices ranging from wearable electronics, to medical devices, and soft robotic components. The combination of highly elastic substrates with intrinsically stretchable conductors holds the promise of enabling electronic sensors that can conform to curved objects, reconfigurable displays, or soft biological tissues, including the skin. Here, we contribute sensing principles for tactile (mechanical image) sensors based on very low modulus polymer substrates with embedded liquid metal microfluidic arrays. The sensors are fabricated using a single-step casting method that utilizes fine nylon filaments to produce arrays of cylindrical channels on two layers. The liquid metal (gallium indium alloy) conductors that fill these channels readily adopt the shape of the embedding membrane, yielding levels of deformability greater than 400%, due to the use of soft polymer substrates. We modeled the sensor performance using electrostatic theory and continuum mechanics, yielding excellent agreement with experiments. Using a matrix-addressed capacitance measurement technique, we are able to resolve strain distributions with millimeter resolution over areas of several square centimeters.

High-density arrays of titania nanoparticles using monolayer micellar films of diblock copolymers as templates.

PubMed

Li, Xue; Lau, King Hang Aaron; Kim, Dong Ha; Knoll, Wolfgang

2005-05-24

Highly dense arrays of titania nanoparticles were fabricated using surface micellar films of poly(styrene-block-2-vinylpyridine) diblock copolymers (PS-b-P2VP) as reaction scaffolds. Titania could be introduced selectively within P2VP nanodomains in PS-b-P2VP films through the binary reaction between water molecules trapped in the P2VP domains and the TiCl(4) vapor precursors. Subsequent UV exposure or oxygen plasma treatment removed the organic matrix, leading to titania nanoparticle arrays on the substrate surface. The diameter of the titania domains and the interparticle distance were defined by the lateral scale present in the microphase-separated morphology of the initial PS-b-P2VP films. The typical diameter of titania nanoparticles obtained by oxygen plasma treatment was of the order of approximately 23 nm. Photoluminescence (PL) properties were investigated for films before and after plasma treatment. Both samples showed PL properties with major physical origin due to self-trapped excitons, indicating that the local environment of the titanium atoms is similar.

Generic Synthesis of Carbon Nanotube Branches on Metal Oxide Arrays Exhibiting Stable High-Rate and Long-Cycle Sodium-Ion Storage.

PubMed

Xia, Xinhui; Chao, Dongliang; Zhang, Yongqi; Zhan, Jiye; Zhong, Yu; Wang, Xiuli; Wang, Yadong; Shen, Ze Xiang; Tu, Jiangping; Fan, Hong Jin

2016-06-01

A new and generic strategy to construct interwoven carbon nanotube (CNT) branches on various metal oxide nanostructure arrays (exemplified by V2 O3 nanoflakes, Co3 O4 nanowires, Co3 O4 -CoTiO3 composite nanotubes, and ZnO microrods), in order to enhance their electrochemical performance, is demonstrated for the first time. In the second part, the V2 O3 /CNTs core/branch composite arrays as the host for Na(+) storage are investigated in detail. This V2 O3 /CNTs hybrid electrode achieves a reversible charge storage capacity of 612 mAh g(-1) at 0.1 A g(-1) and outstanding high-rate cycling stability (a capacity retention of 100% after 6000 cycles at 2 A g(-1) , and 70% after 10 000 cycles at 10 A g(-1) ). Kinetics analysis reveals that the Na(+) storage is a pseudocapacitive dominating process and the CNTs improve the levels of pseudocapacitive energy by providing a conductive network. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inclusion in High-Achieving Singapore: Challenges of Building an Inclusive Society in Policy and Practice

ERIC Educational Resources Information Center

Walker, Zachary; Musti-Rao, Shobana

2016-01-01

Building an inclusive society in which all people can participate effectively and live together requires understanding inclusive education and its impact on the social order. As countries of different regions face the vast array of challenges unique to their educational systems, it becomes apparent that inclusive societies are intricately tied to…

High density group IV semiconductor nanowire arrays fabricated in nanoporous alumina templates

NASA Astrophysics Data System (ADS)

Redwing, Joan M.; Dilts, Sarah M.; Lew, Kok-Keong; Cranmer, Alexana E.; Mohney, Suzanne E.

2005-11-01

The fabrication of high density arrays of semiconductor nanowires is of interest for nanoscale electronics, chemical and biological sensing and energy conversion applications. We have investigated the synthesis, intentional doping and electrical characterization of Si and Ge nanowires grown by the vapor-liquid-solid (VLS) method in nanoporous alumina membranes. Nanoporous membranes provide a convenient platform for nanowire growth and processing, enabling control of wire diameter via pore size and the integration of contact metals for electrical testing. For VLS growth in nanoporous materials, reduced pressures and temperatures are required in order to promote the diffusion of reactants into the pore without premature decomposition on the membrane surface or pore walls. The effect of growth conditions on the growth rate of Si and Ge nanowires from SiH 4 and GeH 4 sources, respectively, was investigated and compared. In both cases, the measured activation energies for nanowire growth were substantially lower than activation energies typically reported for Si and Ge thin film deposition under similar growth conditions, suggesting that gold plays a catalytic role in the VLS growth process. Intentionally doped SiNW arrays were also prepared using trimethylboron (TMB) and phosphine (PH 3) as p-type and n-type dopant sources, respectively. Nanowire resistivities were calculated from plots of the array resistance as a function of nanowire length. A decrease in resistivity was observed for both n-type and p-type doped SiNW arrays compared to those grown without the addition of a dopant source.

Smart photodetector arrays for error control in page-oriented optical memory

NASA Astrophysics Data System (ADS)

Schaffer, Maureen Elizabeth

1998-12-01

Page-oriented optical memories (POMs) have been proposed to meet high speed, high capacity storage requirements for input/output intensive computer applications. This technology offers the capability for storage and retrieval of optical data in two-dimensional pages resulting in high throughput data rates. Since currently measured raw bit error rates for these systems fall several orders of magnitude short of industry requirements for binary data storage, powerful error control codes must be adopted. These codes must be designed to take advantage of the two-dimensional memory output. In addition, POMs require an optoelectronic interface to transfer the optical data pages to one or more electronic host systems. Conventional charge coupled device (CCD) arrays can receive optical data in parallel, but the relatively slow serial electronic output of these devices creates a system bottleneck thereby eliminating the POM advantage of high transfer rates. Also, CCD arrays are "unintelligent" interfaces in that they offer little data processing capabilities. The optical data page can be received by two-dimensional arrays of "smart" photo-detector elements that replace conventional CCD arrays. These smart photodetector arrays (SPAs) can perform fast parallel data decoding and error control, thereby providing an efficient optoelectronic interface between the memory and the electronic computer. This approach optimizes the computer memory system by combining the massive parallelism and high speed of optics with the diverse functionality, low cost, and local interconnection efficiency of electronics. In this dissertation we examine the design of smart photodetector arrays for use as the optoelectronic interface for page-oriented optical memory. We review options and technologies for SPA fabrication, develop SPA requirements, and determine SPA scalability constraints with respect to pixel complexity, electrical power dissipation, and optical power limits. Next, we examine data modulation and error correction coding for the purpose of error control in the POM system. These techniques are adapted, where possible, for 2D data and evaluated as to their suitability for a SPA implementation in terms of BER, code rate, decoder time and pixel complexity. Our analysis shows that differential data modulation combined with relatively simple block codes known as array codes provide a powerful means to achieve the desired data transfer rates while reducing error rates to industry requirements. Finally, we demonstrate the first smart photodetector array designed to perform parallel error correction on an entire page of data and satisfy the sustained data rates of page-oriented optical memories. Our implementation integrates a monolithic PN photodiode array and differential input receiver for optoelectronic signal conversion with a cluster error correction code using 0.35-mum CMOS. This approach provides high sensitivity, low electrical power dissipation, and fast parallel correction of 2 x 2-bit cluster errors in an 8 x 8 bit code block to achieve corrected output data rates scalable to 102 Gbps in the current technology increasing to 1.88 Tbps in 0.1-mum CMOS.

Mark 6: A Next-Generation VLBI Data System

NASA Astrophysics Data System (ADS)

Whitney, A. R.; Lapsley, D. E.; Taveniku, M.

2011-07-01

A new real-time high-data-rate disk-array system based on entirely commercial-off-the-shelf hardware components is being evaluated for possible use as a next-generation VLBI data system. The system, developed by XCube Communications of Nashua, NH, USA was originally developed for the automotive industry for testing/evaluation of autonomous driving systems that require continuous capture of an array of video cameras and automotive sensors at ~8Gbps from multiple 10GigE data links and other data sources. In order to sustain the required recording data rate, the system is designed to account for slow and/or failed disks by shifting the load to other disks as necessary in order to maintain the target data rate. The system is based on a Linux OS with some modifications to memory management and drivers in order to guarantee the timely movement of data, and the hardware/software combination is highly tuned to achieve the target data rate; data are stored in standard Linux files. A kit is also being designed that will allow existing Mark 5 disk modules to be modified to be used with the XCube system (though PATA disks will need to be replaced by SATA disks). Demonstrations of the system at Haystack Observatory and NRAO Socorro have proved very encouraging; some modest software upgrades/revisions are being made by XCube in order to meet VLBI-specific requirements. The system is easily expandable, with sustained 16 Gbps likely to be supported before end CY2011.

Fast beampattern evaluation by polynomial rooting

NASA Astrophysics Data System (ADS)

Häcker, P.; Uhlich, S.; Yang, B.

2011-07-01

Current automotive radar systems measure the distance, the relative velocity and the direction of objects in their environment. This information enables the car to support the driver. The direction estimation capabilities of a sensor array depend on its beampattern. To find the array configuration leading to the best angle estimation by a global optimization algorithm, a huge amount of beampatterns have to be calculated to detect their maxima. In this paper, a novel algorithm is proposed to find all maxima of an array's beampattern fast and reliably, leading to accelerated array optimizations. The algorithm works for arrays having the sensors on a uniformly spaced grid. We use a general version of the gcd (greatest common divisor) function in order to write the problem as a polynomial. We differentiate and root the polynomial to get the extrema of the beampattern. In addition, we show a method to reduce the computational burden even more by decreasing the order of the polynomial.

Electromagnetic enhancement of ordered silver nanorod arrays evaluated by discrete dipole approximation.

PubMed

Wei, Guoke; Wang, Jinliang; Chen, Yu

2015-01-01

The enhancement factor (EF) of surface-enhanced Raman scattering (SERS) from two-dimensional (2D) hexagonal silver nanorod (AgNR) arrays were investigated in terms of electromagnetic (EM) mechanism by using the discrete dipole approximation (DDA) method. The dependence of EF on several parameters, i.e., structure, length, excitation wavelength, incident angle and polarization, and gap size has been investigated. "Hotspots" were found distributed in the gaps between adjacent nanorods. Simulations of AgNR arrays of different lengths revealed that increasing the rod length from 374 to 937 nm (aspect ratio from 2.0 to 5.0) generated more "hotspots" but not necessarily increased EF under both 514 and 532 nm excitation. A narrow lateral gap (in the incident plane) was found to result in strong EF, while the dependence of EF on the diagonal gap (out of the incident plane) showed an oscillating behavior. The EF of the array was highly dependent on the angle and polarization of the incident light. The structure of AgNR and the excitation wavelength were also found to affect the EF. The EF of random arrays was stronger than that of an ordered one with the same average gap of 21 nm, which could be explained by the exponential dependence of EF on the lateral gap size. Our results also suggested that absorption rather than extinction or scattering could be a good indicator of EM enhancement. It is expected that the understanding of the dependence of local field enhancement on the structure of the nanoarrays and incident excitations will shine light on the optimal design of efficient SERS substrates and improved performance.

Macroscopic Violation of Three Cauchy-Schwarz Inequalities Using Correlated Light Beams From an Infra-Red Emitting Semiconductor Diode Array

NASA Technical Reports Server (NTRS)

Edwards, P. J.; Huang, X.; Li, Y. Q. (Editor); Wang, Y. Z. (Editor)

1996-01-01

We briefly review quantum mechanical and semi-classical descriptions of experiments which demonstrate the macroscopic violation of the three Cauchy-Schwarz inequalities: g(sup 2)(sub 11)(0) greater than or equal to 1; g(sup 2)(sub 11)(0) greater than or equal to g(sup 2)(sub 11)(t), (t approaches infinity); (the absolute value of g(sup 2)(sub 11)(0))(exp 2) less than or equal to g(sup 2)(sub 11)(0) g(sup 2)(sub 11)(0). Our measurements demonstrate the violation, at macroscopic intensities, of each of these inequalities. We show that their violation, although weak, can be demonstrated through photodetector current covariance measurements on correlated sub-Poissonian Poissonian, and super Poissonian light beams. Such beams are readily generated by a tandem array of infrared-emitting semiconductor junction diodes. Our measurements utilize an electrically coupled array of one or more infrared-emitting diodes, optically coupled to a detector array. The emitting array is operated in such a way as to generate highly correlated beams of variable photon Fano Factor. Because the measurements are made on time scales long compared with the first order coherence time and with detector areas large compared with the corresponding coherence areas, first order interference effects are negligible. The first and second inequalities are violated, as expected, when a sub-Poissonian light beam is split and the intensity fluctuations of the two split beams are measured by two photodetectors and subsequently cross-correlated. The third inequality is violated by bunched (as well as anti-bunched) beams of equal intensity provided the measured cross correlation coefficient exceeds (F - 1)/F, where F is the measured Fano Factor of each beam. We also investigate the violation for the case of unequal beams.

Ka-Band Phased Array System Characterization

NASA Technical Reports Server (NTRS)

Acosta, R.; Johnson, S.; Sands, O.; Lambert, K.

2001-01-01

Phased Array Antennas (PAAs) using patch-radiating elements are projected to transmit data at rates several orders of magnitude higher than currently offered with reflector-based systems. However, there are a number of potential sources of degradation in the Bit Error Rate (BER) performance of the communications link that are unique to PAA-based links. Short spacing of radiating elements can induce mutual coupling between radiating elements, long spacing can induce grating lobes, modulo 2 pi phase errors can add to Inter Symbol Interference (ISI), phase shifters and power divider network introduce losses into the system. This paper describes efforts underway to test and evaluate the effects of the performance degrading features of phased-array antennas when used in a high data rate modulation link. The tests and evaluations described here uncover the interaction between the electrical characteristics of a PAA and the BER performance of a communication link.

Electron lithography STAR design guidelines. Part 3: The mosaic transistor array applied to custom microprocessors. Part 4: Stores logic arrays, SLAs implemented with clocked CMOS

NASA Technical Reports Server (NTRS)

Trotter, J. D.

1982-01-01

The Mosaic Transistor Array is an extension of the STAR system developed by NASA which has dedicated field cells designed to be specifically used in semicustom microprocessor applications. The Sandia radiation hard bulk CMOS process is utilized in order to satisfy the requirements of space flights. A design philosophy is developed which utilizes the strengths and recognizes the weaknesses of the Sandia process. A style of circuitry is developed which incorporates the low power and high drive capability of CMOS. In addition the density achieved is better than that for classic CMOS, although not as good as for NMOS. The basic logic functions for a data path are designed with compatible interface to the STAR grid system. In this manner either random logic or PLA type structures can be utilized for the control logic.

Observations and interpretation of fundamental mode Rayleigh wavefields recorded by the Transportable Array (USArray)

USGS Publications Warehouse

Pollitz, F.F.

2008-01-01

Broadband recordings of the dense Transportable Array (TA) in the western United States provide unparalleled detailed images of long-period seismic surface wavefields. With 400 stations spanning most of the western United States, wavefronts of fundamental mode Rayleigh waves may be visualized coherently across the array at periods ???40 s. In order to constrain the Rayleigh wave phase velocity structure in the western United States, I assemble a data set of vertical component seismograms from 53 teleseismic events recorded by the TA from April 2006 to October 2007. Complex amplitude spectra from these recordings at peni ods 27-100 s are interpreted using the multiplane wave tomographic method of Friederich and Wielandt (1995) and Pollitz (1999). This analysis yields detailed surface wave phase velocity and three-dimensional shear wave velocity patterns across the North American plate boundary zone, elucidating the active processes in the highly heterogeneous western U.S. upper mantle.

High performance flexible pH sensor based on polyaniline nanopillar array electrode.

PubMed

Yoon, Jo Hee; Hong, Seok Bok; Yun, Seok-Oh; Lee, Seok Jae; Lee, Tae Jae; Lee, Kyoung G; Choi, Bong Gill

2017-03-15

Flexible pH sensor technologies have attracted a great deal of attention in many applications, such as, wearable health care devices and monitors for chemical and biological processes. Here, we fabricated flexible and thin pH sensors using a two electrode configuration comprised of a polyaniline nanopillar (PAN) array working electrode and an Ag/AgCl reference electrode. In order to provide nanostructure, soft lithography using a polymeric blend was employed to create a flexible nanopillar backbone film. Polyaniline-sensing materials were deposited on a patterned-nanopillar array by electrochemical deposition. The pH sensors produced exhibited a near-Nernstian response (∼60.3mV/pH), which was maintained in a bent state. In addition, pH sensors showed other excellent sensor performances in terms of response time, reversibility, repeatability, selectivity, and stability. Copyright © 2016 Elsevier Inc. All rights reserved.

Reduced-Scale Transition-Edge Sensor Detectors for Solar and X-Ray Astrophysics

NASA Technical Reports Server (NTRS)

Datesman, Aaron M.; Adams, Joseph S.; Bandler, Simon R.; Betancourt-Martinez, Gabriele L.; Chang, Meng-Ping; Chervenak, James A.; Eckart, Megan E.; Ewin, Audrey E.; Finkbeiner, Fred M.; Ha, Jong Yoon;

The Giant Radio Array for Neutrino Detection

NASA Astrophysics Data System (ADS)

Kotera, K.; GRAND Collaboration

2017-12-01

The Giant Radio Array for Neutrino Detection (GRAND) project aims at detecting ultrahigh-energy neutrinos and cosmic rays with a ˜10^5 radio antenna array over 200'000 km^2 in mountainous regions in China, in order to solve the mystery of the origin of these two linked particles. Its strategy is to detect extensive air showers of the highest energies, above 10^{17} eV, that are triggered by the interaction of high-energy particles in the atmosphere or underground. In its first stages, GRAND will be competitive to detect the first cosmogenic neutrinos for favorable source scenarios. Ultimately, GRAND aims at reaching a sensitivity and angular resolution that should launch neutrino astronomy, and that will ensure the detection of these neutrinos, even in the most pessimistic cases. We present preliminary results of our simulations, plans for the ongoing, staged approach to the construction of GRAND, and the rich research program made possible by the design of GRAND.

Motion stability of the magnetic levitation and suspension with YBa2Cu3O7-x high-Tc superconducting bulks and NdFeB magnets

NASA Astrophysics Data System (ADS)

Li, Jipeng; Zheng, Jun; Huang, Huan; Li, Yanxing; Li, Haitao; Deng, Zigang

2017-10-01

The flux pinning effect of YBa2Cu3O7-x high temperature superconducting (HTS) bulk can achieve self-stable levitation over a permanent magnet or magnet array. Devices based on this phenomenon have been widely developed. However, the self-stable flux pinning effect is not unconditional, under disturbances, for example. To disclose the roots of this amazing self-stable levitation phenomenon in theory, mathematical and mechanical calculations using Lyapunov's stability theorem and the Hurwitz criterion were performed under the conditions of magnetic levitation and suspension of HTS bulk near permanent magnets in Halbach array. It is found that the whole dynamical system, in the case of levitation, has only one equilibrium solution, and the singular point is a stable focus. In the general case of suspension, the system has two singular points: one is a stable focus, and the other is an unstable saddle. With the variation of suspension force, the two first-order singular points mentioned earlier will get closer and closer, and finally degenerate to a high-order singular point, which means the stable region gets smaller and smaller, and finally vanishes. According to the center manifold theorem, the high-order singular point is unstable. With the interaction force varying, the HTS suspension dynamical system undergoes a saddle-node bifurcation. Moreover, a deficient damping can also decrease the stable region. These findings, together with existing experiments, could enlighten the improvement of HTS devices with strong anti-interference ability.

Performance bounds for modal analysis using sparse linear arrays

NASA Astrophysics Data System (ADS)

Li, Yuanxin; Pezeshki, Ali; Scharf, Louis L.; Chi, Yuejie

2017-05-01

We study the performance of modal analysis using sparse linear arrays (SLAs) such as nested and co-prime arrays, in both first-order and second-order measurement models. We treat SLAs as constructed from a subset of sensors in a dense uniform linear array (ULA), and characterize the performance loss of SLAs with respect to the ULA due to using much fewer sensors. In particular, we claim that, provided the same aperture, in order to achieve comparable performance in terms of Cramér-Rao bound (CRB) for modal analysis, SLAs require more snapshots, of which the number is about the number of snapshots used by ULA times the compression ratio in the number of sensors. This is shown analytically for the case with one undamped mode, as well as empirically via extensive numerical experiments for more complex scenarios. Moreover, the misspecified CRB proposed by Richmond and Horowitz is also studied, where SLAs suffer more performance loss than their ULA counterpart.

Wind Farm Flow Modeling using an Input-Output Reduced-Order Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annoni, Jennifer; Gebraad, Pieter; Seiler, Peter

Wind turbines in a wind farm operate individually to maximize their own power regardless of the impact of aerodynamic interactions on neighboring turbines. There is the potential to increase power and reduce overall structural loads by properly coordinating turbines. To perform control design and analysis, a model needs to be of low computational cost, but retains the necessary dynamics seen in high-fidelity models. The objective of this work is to obtain a reduced-order model that represents the full-order flow computed using a high-fidelity model. A variety of methods, including proper orthogonal decomposition and dynamic mode decomposition, can be used tomore » extract the dominant flow structures and obtain a reduced-order model. In this paper, we combine proper orthogonal decomposition with a system identification technique to produce an input-output reduced-order model. This technique is used to construct a reduced-order model of the flow within a two-turbine array computed using a large-eddy simulation.« less

Three-dimensionally ordered array of air bubbles in a polymer film

NASA Technical Reports Server (NTRS)

Srinivasarao, M.; Collings, D.; Philips, A.; Patel, S.; Brown, C. S. (Principal Investigator)

2001-01-01

We report the formation of a three-dimensionally ordered array of air bubbles of monodisperse pore size in a polymer film through a templating mechanism based on thermocapillary convection. Dilute solutions of a simple, coil-like polymer in a volatile solvent are cast on a glass slide in the presence of moist air flowing across the surface. Evaporative cooling and the generation of an ordered array of breath figures leads to the formation of multilayers of hexagonally packed water droplets that are preserved in the final, solid polymer film as spherical air bubbles. The dimensions of these bubbles can be controlled simply by changing the velocity of the airflow across the surface. When these three-dimensionally ordered macroporous materials have pore dimensions comparable to the wavelength of visible light, they are of interest as photonic band gaps and optical stop-bands.

Universal optical transmission features in periodic and quasiperiodic hole arrays.

PubMed

Pacifici, Domenico; Lezec, Henri J; Sweatlock, Luke A; Walters, Robert J; Atwater, Harry A

2008-06-09

We investigate the influence of array order in the optical transmission properties of subwavelength hole arrays, by comparing the experimental spectral transmittance of periodic and quasiperiodic hole arrays as a function of frequency. We find that periodicity and long-range order are not necessary requirements for obtaining enhanced and suppressed optical transmission, provided short-range order is maintained. Transmission maxima and minima are shown to result, respectively, from constructive and destructive interference at each hole, between the light incident upon and exiting from a given hole, and surface plasmon polaritons (SPPs) arriving from individual neighboring holes. These SPPs are launched along both illuminated and exit surfaces, by diffraction of the incident and emerging light at the neighboring individual subwavelength holes. By characterizing the optical transmission of a pair of subwavelength holes as a function of hole-hole distance, we demonstrate that a subwavelength hole can launch SPPs with an efficiency up to 35%, and with an experimentally determined launch phase phi = pi /2, for both input-side and exit-side SPPs. This characteristic phase has a crucial influence on the shape of the transmission spectra, determining transmission minima in periodic arrays at those frequencies where grating coupling arguments would instead predict maxima.

Downsampling Photodetector Array with Windowing

NASA Technical Reports Server (NTRS)

Patawaran, Ferze D.; Farr, William H.; Nguyen, Danh H.; Quirk, Kevin J.; Sahasrabudhe, Adit

2012-01-01

In a photon counting detector array, each pixel in the array produces an electrical pulse when an incident photon on that pixel is detected. Detection and demodulation of an optical communication signal that modulated the intensity of the optical signal requires counting the number of photon arrivals over a given interval. As the size of photon counting photodetector arrays increases, parallel processing of all the pixels exceeds the resources available in current application-specific integrated circuit (ASIC) and gate array (GA) technology; the desire for a high fill factor in avalanche photodiode (APD) detector arrays also precludes this. Through the use of downsampling and windowing portions of the detector array, the processing is distributed between the ASIC and GA. This allows demodulation of the optical communication signal incident on a large photon counting detector array, as well as providing architecture amenable to algorithmic changes. The detector array readout ASIC functions as a parallel-to-serial converter, serializing the photodetector array output for subsequent processing. Additional downsampling functionality for each pixel is added to this ASIC. Due to the large number of pixels in the array, the readout time of the entire photodetector is greater than the time between photon arrivals; therefore, a downsampling pre-processing step is done in order to increase the time allowed for the readout to occur. Each pixel drives a small counter that is incremented at every detected photon arrival or, equivalently, the charge in a storage capacitor is incremented. At the end of a user-configurable counting period (calculated independently from the ASIC), the counters are sampled and cleared. This downsampled photon count information is then sent one counter word at a time to the GA. For a large array, processing even the downsampled pixel counts exceeds the capabilities of the GA. Windowing of the array, whereby several subsets of pixels are designated for processing, is used to further reduce the computational requirements. The grouping of the designated pixel frame as the photon count information is sent one word at a time to the GA, the aggregation of the pixels in a window can be achieved by selecting only the designated pixel counts from the serial stream of photon counts, thereby obviating the need to store the entire frame of pixel count in the gate array. The pixel count se quence from each window can then be processed, forming lower-rate pixel statistics for each window. By having this processing occur in the GA rather than in the ASIC, future changes to the processing algorithm can be readily implemented. The high-bandwidth requirements of a photon counting array combined with the properties of the optical modulation being detected by the array present a unique problem that has not been addressed by current CCD or CMOS sensor array solutions.

Understanding and manipulating the RF fields at high field MRI

PubMed Central

Ibrahim, Tamer S.; Hue, YiK-Kiong; Tang, Lin

2015-01-01

This paper presents a complete overview of the electromagnetics (radiofrequency aspect) of MRI at low and high fields. Using analytical formulations, numerical modeling (computational electromagnetics), and ultrahigh field imaging experiments, the physics that impacts the electromagnetic quantities associated with MRI, namely (1) the transmit field, (2) receive field, and (3) total electromagnetic power absorption, is analyzed. The physical interpretation of the above-mentioned quantities is investigated by electromagnetic theory, to understand ‘What happens, in terms of electromagnetics, when operating at different static field strengths?’ Using experimental studies and numerical simulations, this paper also examines the physical and technological feasibilities by which all or any of these specified electromagnetic quantities can be manipulated through techniques such as B1 shimming (phased array excitation) and signal combination using a receive array in order to advance MRI at high field strengths. Pertinent to this subject and with highly coupled coils operating at 7 T, this paper also presents the first phantom work on B1 shimming without B1 measurements. PMID:19621335

The SCARLET{trademark} array for high power GEO satellites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spence, B.R.; Jones, P.A.; Eskenazi, M.I.

1997-12-31

The GEO satellite market is demanding increasingly capable spacecraft which, in turn, drives commercial spacecraft manufacturers to require significantly higher power solar arrays. As satellite capability increases the demand for high power array systems which are both cost and performance competitive becomes more crucial. Conventional rigid panel planar arrays, although suitable in the past, negatively impact spacecraft competitiveness for these new applications. The Solar Concentrator Array with Refractive Linear Element Technology (SCARLET{trademark}) represents an economically attractive solution for meeting these new high power requirements. When compared to conventional planar arrays, SCARLET provides substantially lower cost and higher deployed stiffness, competitivemore » mass, better producibility, and affordable use of high efficiency multijunction cells. This paper compares cost/performance characteristics of the SCARLET array to conventional planar arrays for high power GEO spacecraft applications. High power SCARLET array configurations are described, and inherent spacecraft and array level cost/performance benefits are presented.« less

Two-dimensional radiant energy array computers and computing devices

NASA Technical Reports Server (NTRS)

Schaefer, D. H.; Strong, J. P., III (Inventor)

1976-01-01

Two dimensional digital computers and computer devices operate in parallel on rectangular arrays of digital radiant energy optical signal elements which are arranged in ordered rows and columns. Logic gate devices receive two input arrays and provide an output array having digital states dependent only on the digital states of the signal elements of the two input arrays at corresponding row and column positions. The logic devices include an array of photoconductors responsive to at least one of the input arrays for either selectively accelerating electrons to a phosphor output surface, applying potentials to an electroluminescent output layer, exciting an array of discrete radiant energy sources, or exciting a liquid crystal to influence crystal transparency or reflectivity.

Double-side illuminated titania nanotubes for high volume hydrogen generation by water splitting

NASA Astrophysics Data System (ADS)

Mohapatra, Susanta K.; Mahajan, Vishal K.; Misra, Mano

2007-11-01

A sonoelectrochemical anodization method is proposed to synthesize TiO2 nanotubular arrays on both sides of a titanium foil (TiO2/Ti/TiO2). Highly ordered TiO2 nanotubular arrays of 16 cm2 area with uniform surface distribution can be obtained using this anodization procedure. These double-sided TiO2/Ti/TiO2 materials are used as both photoanode (carbon-doped titania nanotubes) and cathode (Pt nanoparticles dispersed on TiO2 nanotubes; PtTiO2/Ti/PtTiO2) in a specially designed photoelectrochemical cell to generate hydrogen by water splitting at a rate of 38 ml h-1. The nanomaterials are characterized by FESEM, HRTEM, STEM, EDS, FFT, SAED and XPS techniques. The present approach can be used for large-scale hydrogen generation using renewable energy sources.

5,120 Superconducting Bolometers for the PIPER Balloon-Borne CMB Polarization Experiment

NASA Technical Reports Server (NTRS)

Benford, Dominic J.; Chuss, David T.; Hilton, Gene C.; Irwin, Kent D.; Jethava, Nikhil; Jhabvala, Christine A.; Kogut, Alan J.; Miller, Timothy M.; Moseley, S. Harvey; Rostem, Karwan;

5,120 Superconducting Bolometers for the PIPER Balloon-Borne CMB Polarization Experiment

NASA Technical Reports Server (NTRS)

Benford, Dominic J.; Chuss, David T.; Hilton, Gene C.; Irwin, Kent D.; Jethava, Nikhil S.; Jhabvala, Christine A.; Kogut, Alan J.; Miller, Timothy M.; Mirel, Paul; Moseley, S. Harvey;

Acoustic contrast, planarity and robustness of sound zone methods using a circular loudspeaker array.

PubMed

Coleman, Philip; Jackson, Philip J B; Olik, Marek; Møller, Martin; Olsen, Martin; Abildgaard Pedersen, Jan

2014-04-01

Since the mid 1990s, acoustics research has been undertaken relating to the sound zone problem-using loudspeakers to deliver a region of high sound pressure while simultaneously creating an area where the sound is suppressed-in order to facilitate independent listening within the same acoustic enclosure. The published solutions to the sound zone problem are derived from areas such as wave field synthesis and beamforming. However, the properties of such methods differ and performance tends to be compared against similar approaches. In this study, the suitability of energy focusing, energy cancelation, and synthesis approaches for sound zone reproduction is investigated. Anechoic simulations based on two zones surrounded by a circular array show each of the methods to have a characteristic performance, quantified in terms of acoustic contrast, array control effort and target sound field planarity. Regularization is shown to have a significant effect on the array effort and achieved acoustic contrast, particularly when mismatched conditions are considered between calculation of the source weights and their application to the system.

Tailoring of Perpendicular Magnetic Anisotropy in Dy13Fe87 Thin Films with Hexagonal Antidot Lattice Nanostructure

PubMed Central

Vega, Victor; Ibabe, Angel; Jaafar, Miriam; Asenjo, Agustina

2018-01-01

In this article, the magnetic properties of hexagonally ordered antidot arrays made of Dy13Fe87 alloy are studied and compared with corresponding ones of continuous thin films with the same compositions and thicknesses, varying between 20 nm and 50 nm. Both samples, the continuous thin films and antidot arrays, were prepared by high vacuum e-beam evaporation of the alloy on the top-surface of glass and hexagonally self-ordered nanoporous alumina templates, which serve as substrates, respectively. By using a highly sensitive magneto-optical Kerr effect (MOKE) and vibrating sample magnetometer (VSM) measurements an interesting phenomenon has been observed, consisting in the easy magnetization axis transfer from a purely in-plane (INP) magnetic anisotropy to out-of-plane (OOP) magnetization. For the 30 nm film thickness we have measured the volume hysteresis loops by VSM with the easy magnetization axis lying along the OOP direction. Using magnetic force microscopy measurements (MFM), there is strong evidence to suggest that the formation of magnetic domains with OOP magnetization occurs in this sample. This phenomenon can be of high interest for the development of novel magnetic and magneto-optic perpendicular recording patterned media based on template-assisted deposition techniques. PMID:29642476

Tailoring of Perpendicular Magnetic Anisotropy in Dy13Fe87 Thin Films with Hexagonal Antidot Lattice Nanostructure.

PubMed

Salaheldeen, Mohamed; Vega, Victor; Ibabe, Angel; Jaafar, Miriam; Asenjo, Agustina; Fernandez, Agustin; Prida, Victor M

2018-04-08

In this article, the magnetic properties of hexagonally ordered antidot arrays made of Dy 13 Fe 87 alloy are studied and compared with corresponding ones of continuous thin films with the same compositions and thicknesses, varying between 20 nm and 50 nm. Both samples, the continuous thin films and antidot arrays, were prepared by high vacuum e-beam evaporation of the alloy on the top-surface of glass and hexagonally self-ordered nanoporous alumina templates, which serve as substrates, respectively. By using a highly sensitive magneto-optical Kerr effect (MOKE) and vibrating sample magnetometer (VSM) measurements an interesting phenomenon has been observed, consisting in the easy magnetization axis transfer from a purely in-plane (INP) magnetic anisotropy to out-of-plane (OOP) magnetization. For the 30 nm film thickness we have measured the volume hysteresis loops by VSM with the easy magnetization axis lying along the OOP direction. Using magnetic force microscopy measurements (MFM), there is strong evidence to suggest that the formation of magnetic domains with OOP magnetization occurs in this sample. This phenomenon can be of high interest for the development of novel magnetic and magneto-optic perpendicular recording patterned media based on template-assisted deposition techniques.

Microintaglio Printing for Soft Lithography-Based in Situ Microarrays

PubMed Central

Biyani, Manish; Ichiki, Takanori

2015-01-01

Advances in lithographic approaches to fabricating bio-microarrays have been extensively explored over the last two decades. However, the need for pattern flexibility, a high density, a high resolution, affordability and on-demand fabrication is promoting the development of unconventional routes for microarray fabrication. This review highlights the development and uses of a new molecular lithography approach, called “microintaglio printing technology”, for large-scale bio-microarray fabrication using a microreactor array (µRA)-based chip consisting of uniformly-arranged, femtoliter-size µRA molds. In this method, a single-molecule-amplified DNA microarray pattern is self-assembled onto a µRA mold and subsequently converted into a messenger RNA or protein microarray pattern by simultaneously producing and transferring (immobilizing) a messenger RNA or a protein from a µRA mold to a glass surface. Microintaglio printing allows the self-assembly and patterning of in situ-synthesized biomolecules into high-density (kilo-giga-density), ordered arrays on a chip surface with µm-order precision. This holistic aim, which is difficult to achieve using conventional printing and microarray approaches, is expected to revolutionize and reshape proteomics. This review is not written comprehensively, but rather substantively, highlighting the versatility of microintaglio printing for developing a prerequisite platform for microarray technology for the postgenomic era. PMID:27600226

Magnetocaloric effect: permanent magnet array for generation of high magnetic fields

NASA Astrophysics Data System (ADS)

Lee, Seong-Jae; Kenkel, John; Jiles, David

2002-03-01

The magnetocaloric effect (MCE), the heating or cooling of magnetic materials in a magnetic field, is unusually large in the Gd_5(Si_xGe_1-x)4 alloy system. Normally the maximum in the MCE occurs at the Curie temperature (Tc) because the spin entropy change is a maximum. By suitable selection of the composition of this alloy system the Curie temperature can be changed over the range 25 K for x = 0 to 340 K for x =1, and the composition range around x = 0.5 exhibits the largest magnetocaloric effect. In order to increase the amount of heat exchanged the change in applied magnetic field should be as large as possible, and in this research values above 1.5 Tesla are suggested. We have studied a permanent magnet array based on NdFeB, which with a remanent magnetization of only 1.2 Tesla can still generate a magnetic flux density, or magnetic induction B of 2-3 Tesla. In order to generate the high magnetic induction in the absence of a power supply, a modified hollow cylindrical permanent magnet array (HCPMA) has been designed to produce the required strength of magnetic field. Soft magnetic materials including permalloy (NiFe) were used for focusing the magnetic field in the central region. The magnitude of the magnetic flux density at the center was about 2 Tesla. The magnitude and homogeneity of the magnetic field for this design are comparable with the conventional C-shaped yoke and HCPMA. This can be easily adapted for a low power rotary system in which the magnetocaloric material can be exposed alternately to high and low magnetic fields so that it can accept and reject heat from its surroundings.

Optimized micromirror arrays for adaptive optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michalicek, M. Adrian

This paper describes the design, layout, fabrication, and surface characterization of highly optimized surface micromachined micromirror devices. Design considerations and fabrication capabilities are presented. These devices are fabricated in the state-of-the-art, four-level, planarized, ultra-low-stress polysilicon process available at Sandia National Laboratories known as the Sandia Ultra-planar Multi-level MEMS Technology (SUMMiT). This enabling process permits the development of micromirror devices with near-ideal characteristics that have previously been unrealizable in standard three-layer polysilicon processes. The reduced 1 {mu}m minimum feature sizes and 0.1 {mu}m mask resolution make it possible to produce dense wiring patterns and irregularly shaped flexures. Likewise, mirror surfaces canmore » be uniquely distributed and segmented in advanced patterns and often irregular shapes in order to minimize wavefront error across the pupil. The ultra-low-stress polysilicon and planarized upper layer allow designers to make larger and more complex micromirrors of varying shape and surface area within an array while maintaining uniform performance of optical surfaces. Powerful layout functions of the AutoCAD editor simplify the design of advanced micromirror arrays and make it possible to optimize devices according to the capabilities of the fabrication process. Micromirrors fabricated in this process have demonstrated a surface variance across the array from only 2{endash}3 nm to a worst case of roughly 25 nm while boasting active surface areas of 98{percent} or better. Combining the process planarization with a {open_quotes}planarized-by-design{close_quotes} approach will produce micromirror array surfaces that are limited in flatness only by the surface deposition roughness of the structural material. Ultimately, the combination of advanced process and layout capabilities have permitted the fabrication of highly optimized micromirror arrays for adaptive optics. {copyright} {ital 1999 American Institute of Physics.}« less

High-aggregate-capacity visible light communication links using stacked multimode polymer waveguides and micro-pixelated LED arrays

NASA Astrophysics Data System (ADS)

Bamiedakis, N.; McKendry, J. J. D.; Xie, E.; Gu, E.; Dawson, M. D.; Penty, R. V.; White, I. H.

2018-02-01

In recent years, light emitting diodes (LEDs) have gained renewed interest for use in visible light communication links (VLC) owing to their potential use as both high-quality power-efficient illumination sources as well as low-cost optical transmitters in free-space and guided-wave links. Applications that can benefit from their use include optical wireless systems (LiFi and Internet of Things), in-home and automotive networks, optical USBs and short-reach low-cost optical interconnects. However, VLC links suffer from the limited LED bandwidth (typically 100 MHz). As a result, a combination of novel LED devices, advanced modulation formats and multiplexing methods are employed to overcome this limitation and achieve high-speed (>1 Gb/s) data transmission over such links. In this work, we present recent advances in the formation of high-aggregate-capacity low cost guided wave VLC links using stacked polymer multimode waveguides and matching micro-pixelated LED (μLED) arrays. μLEDs have been shown to exhibit larger bandwidths (>200 MHz) than conventional broad-area LEDs and can be formed in large array configurations, while multimode polymer waveguides enable the formation of low-cost optical links onto standard PCBs. Here, three- and four-layered stacks of multimode waveguides, as well as matching GaN μLED arrays, are fabricated in order to generate high-density yet low-cost optical interconnects. Different waveguide topologies are implemented and are investigated in terms of loss and crosstalk performance. The initial results presented herein demonstrate good intrinsic crosstalk performance and indicate the potential to achieve >= 0.5 Tb/s/mm2 aggregate interconnection capacity using this low-cost technology.

Optical design of microlens array for CMOS image sensors

NASA Astrophysics Data System (ADS)

Zhang, Rongzhu; Lai, Liping

2016-10-01

The optical crosstalk between the pixel units can influence the image quality of CMOS image sensor. In the meantime, the duty ratio of CMOS is low because of its pixel structure. These two factors cause the low detection sensitivity of CMOS. In order to reduce the optical crosstalk and improve the fill factor of CMOS image sensor, a microlens array has been designed and integrated with CMOS. The initial parameters of the microlens array have been calculated according to the structure of a CMOS. Then the parameters have been optimized by using ZEMAX and the microlens arrays with different substrate thicknesses have been compared. The results show that in order to obtain the best imaging quality, when the effect of optical crosstalk for CMOS is the minimum, the best distance between microlens array and CMOS is about 19.3 μm. When incident light successively passes through microlens array and the distance, obtaining the minimum facula is around 0.347 um in the active area. In addition, when the incident angle of the light is 0o 22o, the microlens array has obvious inhibitory effect on the optical crosstalk. And the anti-crosstalk distance between microlens array and CMOS is 0 μm 162 μm.

A Near IR Fabry-Perot Interferometer for Wide Field, Low Resolution Hyperspectral Imaging on the Next Generation Space Telescope

NASA Technical Reports Server (NTRS)

Barry, R. K.; Satyapal, S.; Greenhouse, M. A.; Barclay, R.; Amato, D.; Arritt, B.; Brown, G.; Harvey, V.; Holt, C.; Kuhn, J.

2000-01-01

We discuss work in progress on a near-infrared tunable bandpass filter for the Goddard baseline wide field camera concept of the Next Generation Space Telescope (NGST) Integrated Science Instrument Module (ISIM). This filter, the Demonstration Unit for Low Order Cryogenic Etalon (DULCE), is designed to demonstrate a high efficiency scanning Fabry-Perot etalon operating in interference orders 1 - 4 at 30K with a high stability DSP based servo control system. DULCE is currently the only available tunable filter for lower order cryogenic operation in the near infrared. In this application, scanning etalons will illuminate the focal plane arrays with a single order of interference to enable wide field lower resolution hyperspectral imaging over a wide range of redshifts. We discuss why tunable filters are an important instrument component in future space-based observatories.

High-performance ultra-low power VLSI analog processor for data compression

NASA Technical Reports Server (NTRS)

Tawel, Raoul (Inventor)

1996-01-01

An apparatus for data compression employing a parallel analog processor. The apparatus includes an array of processor cells with N columns and M rows wherein the processor cells have an input device, memory device, and processor device. The input device is used for inputting a series of input vectors. Each input vector is simultaneously input into each column of the array of processor cells in a pre-determined sequential order. An input vector is made up of M components, ones of which are input into ones of M processor cells making up a column of the array. The memory device is used for providing ones of M components of a codebook vector to ones of the processor cells making up a column of the array. A different codebook vector is provided to each of the N columns of the array. The processor device is used for simultaneously comparing the components of each input vector to corresponding components of each codebook vector, and for outputting a signal representative of the closeness between the compared vector components. A combination device is used to combine the signal output from each processor cell in each column of the array and to output a combined signal. A closeness determination device is then used for determining which codebook vector is closest to an input vector from the combined signals, and for outputting a codebook vector index indicating which of the N codebook vectors was the closest to each input vector input into the array.

High resolution telescope including an array of elemental telescopes aligned along a common axis and supported on a space frame with a pivot at its geometric center

DOEpatents

Norbert, M.A.; Yale, O.

1992-04-28

A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employes speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by a electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activities. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes. 15 figs.

High resolution telescope including an array of elemental telescopes aligned along a common axis and supported on a space frame with a pivot at its geometric center

DOEpatents

Norbert, Massie A.; Yale, Oster

1992-01-01

A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employes speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by a electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activities. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes.