Flowfield computer graphics

Science.gov (United States)

Desautel, Richard

1993-01-01

The objectives of this research include supporting the Aerothermodynamics Branch's research by developing graphical visualization tools for both the branch's adaptive grid code and flow field ray tracing code. The completed research for the reporting period includes development of a graphical user interface (GUI) and its implementation into the NAS Flowfield Analysis Software Tool kit (FAST), for both the adaptive grid code (SAGE) and the flow field ray tracing code (CISS).

Near-Field Acoustic Power Level Analysis of F31/A31 Open Rotor Model at Simulated Cruise Conditions, Technical Report II

Science.gov (United States)

Sree, Dave

2015-01-01

Near-field acoustic power level analysis of F31A31 open rotor model has been performed to determine its noise characteristics at simulated cruise flight conditions. The non-proprietary parts of the test data obtained from experiments in the 8x6 supersonic wind tunnel were provided by NASA-Glenn Research Center. The tone and broadband components of total noise have been separated from raw test data by using a new data analysis tool. Results in terms of sound pressure levels, acoustic power levels, and their variations with rotor speed, freestream Mach number, and input shaft power, with different blade-pitch setting angles at simulated cruise flight conditions, are presented and discussed. Empirical equations relating models acoustic power level and input shaft power have been developed. The near-field acoustic efficiency of the model at simulated cruise conditions is also determined. It is hoped that the results presented in this work will serve as a database for comparison and improvement of other open rotor blade designs and also for validating open rotor noise prediction codes.

Direct subwavelength imaging and control of near-field localization in individual silver nanocubes

Energy Technology Data Exchange (ETDEWEB)

Mårsell, Erik; Svärd, Robin; Miranda, Miguel; Guo, Chen; Harth, Anne; Lorek, Eleonora; Mauritsson, Johan; Arnold, Cord L.; L' Huillier, Anne; Mikkelsen, Anders; Losquin, Arthur, E-mail: arthur.losquin@fysik.lth.se [Department of Physics, Lund University, PO Box 118, 221 00 Lund (Sweden); Xu, Hongxing [Department of Physics, Lund University, PO Box 118, 221 00 Lund (Sweden); School of Physics and Technology and Institute for Advanced Studies, Wuhan University, Wuhan 430072 (China)

2015-11-16

We demonstrate the control of near-field localization within individual silver nanocubes through photoemission electron microscopy combined with broadband, few-cycle laser pulses. We find that the near-field is concentrated at the corners of the cubes, and that it can be efficiently localized to different individual corners depending on the polarization of the incoming light. The experimental results are confirmed by finite-difference time-domain simulations, which also provide an intuitive picture of polarization dependent near-field localization in nanocubes.

Flowfield modeling and diagnostics

International Nuclear Information System (INIS)

Gupta, A.K.; Lilley, D.G.

1985-01-01

This textbook is devoted solely to flowfield modeling and diagnostics; their practical use, recent and current research, and projected developments and trends. It provides an account of the use of a broad range of techniques in industrial and research practice, both with and without combustion. Application ideas are complemented by details about experimental and modeling techniques

Transient simulation of chamber flowfield in a rod-and-tube configuration solid rocket motor

International Nuclear Information System (INIS)

Weaver, J.T.; Stowe, R.A.

2004-01-01

Currently, DRDC Valcartier of the Canadian Department of National Defence is designing a prototype rod-and-tube configuration solid propellant rocket motor that will propel a hypersonic velocity missile. This configuration will incorporate a very low port-to-throat area ratio, which in turn results in very high velocity propellant gas traveling across burning propellant surfaces, particularly near the nozzle end of the rocket. This causes an augmentation in the propellant burning rate. While numerical and lumped parameter models are available to design and analyze solid propellant rocket motors and nozzles, many of them provide solutions based on the assumption of quasi-steady flow. Due to the high pressure, high velocity and highly transient nature of the flows expected in the motor under design, it is believed that a CFD simulation will better model the time-dependent phenomena that occur during the functioning of a motor of this type. This simulation couples the fluid dynamics and heat transfer of the gas flowfield within the rocket port to the nozzle and the regression rate of the propellant. By incorporating the regression of the propellant surfaces into the model, the information provided by the resulting time-accurate solution will enable a much improved understanding of the flow phenomena within this rod-and-tube grain motor and a better prediction of the internal ballistics of the motor, which in turn will help in the design of both the motor and the nozzle. (author)

Transient simulation of chamber flowfield in a rod-and-tube configuration solid rocket motor

Energy Technology Data Exchange (ETDEWEB)

Weaver, J.T. [Carleton Univ., Ottawa, Ontario (Canada)]. E-mail: jrweaver@storm.ca; Stowe, R.A. [Defence R and D Canada - Valcartier, Val-Belair, Quebec (Canada)

2004-07-01

Currently, DRDC Valcartier of the Canadian Department of National Defence is designing a prototype rod-and-tube configuration solid propellant rocket motor that will propel a hypersonic velocity missile. This configuration will incorporate a very low port-to-throat area ratio, which in turn results in very high velocity propellant gas traveling across burning propellant surfaces, particularly near the nozzle end of the rocket. This causes an augmentation in the propellant burning rate. While numerical and lumped parameter models are available to design and analyze solid propellant rocket motors and nozzles, many of them provide solutions based on the assumption of quasi-steady flow. Due to the high pressure, high velocity and highly transient nature of the flows expected in the motor under design, it is believed that a CFD simulation will better model the time-dependent phenomena that occur during the functioning of a motor of this type. This simulation couples the fluid dynamics and heat transfer of the gas flowfield within the rocket port to the nozzle and the regression rate of the propellant. By incorporating the regression of the propellant surfaces into the model, the information provided by the resulting time-accurate solution will enable a much improved understanding of the flow phenomena within this rod-and-tube grain motor and a better prediction of the internal ballistics of the motor, which in turn will help in the design of both the motor and the nozzle. (author)

Near-field imaging of femtosecond laser ablated sub-λ/4 holes in lithium niobate

International Nuclear Information System (INIS)

Rodenas, Airan; Lamela, Jorge; Jaque, Daniel; Lifante, Gines; Jaque, Francisco; Garcia-Martin, Antonio; Zhou Guangyong; Gu Min

2009-01-01

We report on the direct femtosecond laser ablation of sub-λ/4 (80-250 nm) holes in LiNbO 3 crystals and on its local near-field imaging. We show that the near-field transmission of holes can feature an attenuation of ∼75% at hole central position, and a ∼20% transmission enhancement at its sides. This high-contrast ring-shaped near-field distribution is found to be in agreement with simulations, suggesting the surface relief as the main contrast mechanism.

The impact of channel path length on PEMFC flow-field design

Energy Technology Data Exchange (ETDEWEB)

Shimpalee, S.; Greenway, S.; Van Zee, J.W. [Chemical Engineering Department, University of South Carolina, Columbia, SC 29208 (United States)

2006-09-29

Distributions in reactant species concentration in a PEMFC due to local consumption of fuel and local transport of water through the membrane cause distributions in current density, temperature, and water concentration in three dimensions in a PEMFC. These distributions can lead to flooding or drying of the membrane that may shorten the life of an MEA. Changing the cell's flow-field pattern to distribute the gas more evenly is one method of minimizing these stresses. This paper investigates how 200cm{sup 2} serpentine flow-fields with different number of gas paths, and thus different gas path lengths, affect performance and species distribution. The results show how the local temperature, water content, and current density distributions become more uniform for serpentine flow-field designs with shorter path lengths or larger number of channels. These results may be used to develop universal heuristics and dimensionless number correlations in the design of flow-fields and stacks. (author)

Near-Field Nanolasers based on Nonradiating Anapole Modes

KAUST Repository

Gongora, J. S. Totero; Miroshnichenko, Andrey E.; Kivshar, Yuri S.; Fratalocchi, Andrea

2016-01-01

By employing ab-initio simulations of Maxwell-Bloch equations with a source of quantum noise, we study a new laser concept based on photonic dark-matter nanostructures that emit only in the near-field, with no far-field radiation pattern.

Near-Field Nanolasers based on Nonradiating Anapole Modes

KAUST Repository

Gongora, J. S. Totero

2016-05-31

By employing ab-initio simulations of Maxwell-Bloch equations with a source of quantum noise, we study a new laser concept based on photonic dark-matter nanostructures that emit only in the near-field, with no far-field radiation pattern.

[Transmission efficiency analysis of near-field fiber probe using FDTD simulation].

Science.gov (United States)

Huang, Wei; Dai, Song-Tao; Wang, Huai-Yu; Zhou, Yun-Song

2011-10-01

A fiber probe is the key component of near-field optical technology which is widely used in high resolution imaging, spectroscopy detection and nano processing. How to improve the transmission efficiency of the fiber probe is a very important problem in the application of near-field optical technology. Based on the results of 3D-FDTD computation, the dependence of the transmission efficiency on the cone angle, the aperture diameter, the wavelength and the thickness of metal cladding is revealed. The authors have also made a comparison between naked probe and the probe with metal cladding in terms of transmission efficiency and spatial resolution. In addition, the authors have discovered the fluctuation phenomena of transmission efficiency as the wavelength of incident laser increases.

Modeling two-phase flow in three-dimensional complex flow-fields of proton exchange membrane fuel cells

Science.gov (United States)

Kim, Jinyong; Luo, Gang; Wang, Chao-Yang

2017-10-01

3D fine-mesh flow-fields recently developed by Toyota Mirai improved water management and mass transport in proton exchange membrane (PEM) fuel cell stacks, suggesting their potential value for robust and high-power PEM fuel cell stack performance. In such complex flow-fields, Forchheimer's inertial effect is dominant at high current density. In this work, a two-phase flow model of 3D complex flow-fields of PEMFCs is developed by accounting for Forchheimer's inertial effect, for the first time, to elucidate the underlying mechanism of liquid water behavior and mass transport inside 3D complex flow-fields and their adjacent gas diffusion layers (GDL). It is found that Forchheimer's inertial effect enhances liquid water removal from flow-fields and adds additional flow resistance around baffles, which improves interfacial liquid water and mass transport. As a result, substantial improvements in high current density cell performance and operational stability are expected in PEMFCs with 3D complex flow-fields, compared to PEMFCs with conventional flow-fields. Higher current density operation required to further reduce PEMFC stack cost per kW in the future will necessitate optimizing complex flow-field designs using the present model, in order to efficiently remove a large amount of product water and hence minimize the mass transport voltage loss.

Near-field and far-field modeling of scattered surface waves. Application to the apertureless scanning near-field optical microscopy

International Nuclear Information System (INIS)

Muller, J.; Parent, G.; Fumeron, S.; Jeandel, G.; Lacroix, D.

2011-01-01

The detection of surface waves through scanning near-field optical microscopy (SNOM) is a promising technique for thermal measurements at very small scales. Recent studies have shown that electromagnetic waves, in the vicinity of a scattering structure such as an atomic force microscopy (AFM) tip, can be scattered from near to far-field and thus detected. In the present work, a model based on the finite difference time domain (FDTD) method and the near-field to far-field (NFTFF) transformation for electromagnetic waves propagation is presented. This model has been validated by studying the electromagnetic field of a dipole in vacuum and close to a dielectric substrate. Then simulations for a tetrahedral tip close to an interface are presented and discussed.

Design of flow-field patterns for proton exchange membrane fuel cell application

International Nuclear Information System (INIS)

Rosli, M.I.; Wan Ramli Wan Daud; Kamaruzzaman Sopian; Jaafar Sahari

2006-01-01

Fuel cells are electrochemical devices that produce electricity at high efficiency without combustion. Fuel cells are emerging as viable candidates as power sources in many applications, including road vehicles, small-scale power stations, and possibly even portable electronics. This paper addresses the design of flow-field patterns for proton exchange membrane fuel cell (PEMFC). The PEMFC is a low-temperature fuel cell, in which a proton conductive polymer membrane is used as the electrolyte. In PEMFC, flow-field pattern is one important thing that effects the performance of PEMFC. This paper present three types of flow-field pattern that will be consider to be testing using CFD analysis and by experimental. The design look detail on to their shape and dimension to get the best pattern in term of more active electrode area compare to electrode area that will be used. Another advantage and disadvantage for these three type of flow-field patterns from literature also compared in this paper

Transfer functions in collection scanning near-field optical microscopy

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Vohnsen, Brian; Bozhevolnaya, Elena A.

1999-01-01

are considered with respect to the relation between near-field optical images and the corresponding intensity distributions. Our conclusions are supported with numerical simulations and experimental results obtained by using a photon scanning tunneling microscope with an uncoated fiber tip....

Transfer function and near-field detection of evanescent waves

DEFF Research Database (Denmark)

Radko, Ylia P.; Bozhevolnyi, Sergey I.; Gregersen, Niels

2006-01-01

of collection and illumination modes. Making use of a collection near-field microscope with a similar fiber tip illuminated by an evanescent field, we measure the collected power as a function of the field spatial frequency in different polarization configurations. Considering a two-dimensional probe...... for the transfer function, which is derived by introducing an effective pointof (dipolelike) detection inside the probe tip. It is found to be possible to fit reasonably well both the experimental and the simulation data for evanescent field components, implying that the developed approximation of the near......-field transfer function can serve as a simple, rational, and sufficiently reliable means of fiber probe characterization....

Near-Field Source Localization Using a Special Cumulant Matrix

Science.gov (United States)

Cui, Han; Wei, Gang

A new near-field source localization algorithm based on a uniform linear array was proposed. The proposed algorithm estimates each parameter separately but does not need pairing parameters. It can be divided into two important steps. The first step is bearing-related electric angle estimation based on the ESPRIT algorithm by constructing a special cumulant matrix. The second step is the other electric angle estimation based on the 1-D MUSIC spectrum. It offers much lower computational complexity than the traditional near-field 2-D MUSIC algorithm and has better performance than the high-order ESPRIT algorithm. Simulation results demonstrate that the performance of the proposed algorithm is close to the Cramer-Rao Bound (CRB).

Analysis of near-field components of a plasmonic optical antenna and their contribution to quantum dot infrared photodetector enhancement.

Science.gov (United States)

Gu, Guiru; Vaillancourt, Jarrod; Lu, Xuejun

2014-10-20

In this paper, we analyze near-field vector components of a metallic circular disk array (MCDA) plasmonic optical antenna and their contribution to quantum dot infrared photodetector (QDIP) enhancement. The near-field vector components of the MCDA optical antenna and their distribution in the QD active region are simulated. The near-field overlap integral with the QD active region is calculated at different wavelengths and compared with the QDIP enhancement spectrum. The x-component (E(x)) of the near-field vector shows a larger intensity overlap integral and stronger correlation with the QDIP enhancement than E(z) and thus is determined to be the major near-field component to the QDIP enhancement.

Chiral near-fields around chiral dolmen nanostructure

International Nuclear Information System (INIS)

Fu, Tong; Wang, Tiankun; Chen, Yuyan; Wang, Yongkai; Qu, Yu; Zhang, Zhongyue

2017-01-01

Discriminating the handedness of the chiral molecule is of great importance in the field of pharmacology and biomedicine. Enhancing the chiral near-field is one way to increase the chiral signal of chiral molecules. In this paper, the chiral dolmen nanostructure (CDN) is proposed to enhance the chiral near-field. Numerical results show that the CDN can increase the optical chirality of the near-field by almost two orders of magnitude compared to that of a circularly polarized incident wave. In addition, the optical chirality of the near-field of the bonding mode is enhanced more than that of the antibonding mode. These results provide an effective method for tailoring the chiral near-field for biophotonics sensors. (paper)

Design and Calibration of a Flowfield Survey Rake for Inlet Flight Research

Science.gov (United States)

Flynn, Darin C.; Ratnayake, Nalin A.; Frederick, Michael

2009-01-01

Flowfield rake was designed to quantify the flowfield for inlet research underneath NASA DFRC s F-15B airplane. Detailed loads and stress analysis performed using CFD and empirical methods to assure structural integrity. Calibration data were generated through wind tunnel testing of the rake. Calibration algorithm was developed to determine the local Mach and flow angularity at each probe. RAGE was flown November, 2008. Data is currently being analyzed.

Simulation of ultra-long term behavior in HLW near-field by centrifugal model test. Part 1. Development of centrifugal equipment and centrifuge model test method

International Nuclear Information System (INIS)

Nishimoto, Soshi; Okada, Tetsuji; Sawada, Masataka

2011-01-01

The objective of this paper is to develop a centrifugal equipment which can continuously be run for a long time and a model test method in order to evaluate a long term behavior which is a coupled thermo-hydro-mechanical processes in the high level wastes geological disposal repository and the neighborhood (called 'near-field'). The centrifugal equipment of CRIEPI, 'CENTURY5000-THM', developed in the present study is able to run continuously up to six months. Therefore, a long term behavior in the near-field can be simulated in a short term, for instance, the behavior for 5000 equivalent years can be simulated in six months by centrifugalizing 100 G using a 1/100 size model. We carried out a test using a nylon specimen in a centrifugal force field of 30 G and confirmed the operations of CENTURY5000-THM, control and measurement for 11 days. As the results, it was able to control the stress in the pressure vessel and measure the values of strain, temperature and pressure. And, as a result of scanning the small model of near-field including the metal overpack, bentonite buffer and rock by a medical X-rays CT scanner, the internal structure of the model was able to be evaluated when the metal artifact was reduced. From these results, the evaluation for a long term behavior of a disposal repository by the method of centrifugal model test became possible. (author)

Novel concepts in near-field optics: from magnetic near-field to optical forces

Science.gov (United States)

Yang, Honghua

near-field response of a linear rod antenna is studied with Babinet's principle. Babinet's principle connects the magnetic field of a structure to the electric field of its complement structure. Using combined far- and near-field spectroscopy, imaging, and theory, I identify magnetic dipole and higher order bright and dark magnetic resonances at mid-infrared frequencies. From resonant length scaling and spatial field distributions, I confirm that the theoretical requirement of Babinet's principle for a structure to be infinitely thin and perfectly conducting is still fulfilled to a good approximation in the mid-infrared. Thus Babinet's principle provides access to spatial and spectral magnetic field properties, leading to targeted design and control of magnetic optical antennas. Lastly, a novel form of nanoscale optical spectroscopy based on mechanical detection of optical gradient force is explored. It is to measure the optical gradient force between induced dipole moments of a sample and an atomic force microscope (AFM) tip. My study provides the theoretical basis in terms of spectral behavior, resonant enhancement, and distance dependence of the optical gradient force from numerical simulations for a coupled nanoparticle model geometry. I show that the optical gradient force is dispersive for local electronic and vibrational resonances, yet can be absorptive for collective polaronic excitations. This spectral behavior together with the distance dependence scaling provides the key characteristics for its measurement and distinction from competing processes such as thermal expansion. Furthermore, I provide a perspective for resonant enhancement and control of optical forces in general.

Vortex rings and jets recent developments in near-field dynamics

CERN Document Server

Yu, Simon

2015-01-01

In this book, recent developments in our understanding of fundamental vortex ring and jet dynamics will be discussed, with a view to shed light upon their near-field behaviour which underpins much of their far-field characteristics. The chapters provide up-to-date research findings by their respective experts and seek to link near-field flow physics of vortex ring and jet flows with end-applications in mind. Over the past decade, our knowledge on vortex ring and jet flows has grown by leaps and bounds, thanks to increasing use of high-fidelity, high-accuracy experimental techniques and numerical simulations. As such, we now have a much better appreciation and understanding on the initiation and near-field developments of vortex ring and jet flows under many varied initial and boundary conditions. Chapter 1 outlines the vortex ring pinch-off phenomenon and how it relates to the initial stages of jet formations and subsequent jet behaviour, while Chapter 2 takes a closer look at the behaviour resulting from vor...

Impact of state-specific flowfield modeling on atomic nitrogen radiation

Science.gov (United States)

Johnston, Christopher O.; Panesi, Marco

2018-01-01

A hypersonic flowfield model that treats electronic levels of the dominant afterbody radiator N as individual species is presented. This model allows electron-ion recombination rate and two-temperature modeling improvements, the latter which are shown to decrease afterbody radiative heating by up to 30%. This decrease is primarily due to the addition of the electron-impact excitation energy-exchange term to the energy equation governing the vibrational-electronic electron temperature. This model also allows the validity of the often applied quasi-steady-state (QSS) approximation to be assessed. The QSS approximation is shown to fail throughout most of the afterbody region for lower electronic states, although this impacts the radiative intensity reaching the surface by less than 15%. By computing the electronic-state populations of N within the flowfield solver, instead of through the QSS approximation in the radiation solver, the coupling of nonlocal radiative transition rates to the species continuity equations becomes feasible. Implementation of this higher-fidelity level of coupling between the flowfield and radiation solvers is shown to increase the afterbody radiation by up to 50% relative to the conventional model.

A simple formula to predict the influence of the near-field in the optical control of confined electron systems

International Nuclear Information System (INIS)

Takeuchi, Takashi; Ohnuki, Shinichiro; Sako, Tokuei

2017-01-01

A simple formula for predicting the ratio between the field strengths of the incident laser pulse and of the near-field created in the vicinity of the target electron system has been proposed, in the context of optically controlling confined electron systems. The formula is easy to use and does not involve elaborate computation, thus enabling one to judge whether to use the time-consuming Maxwell–Schrödinger hybrid simulation or to stay with the conventional time-dependent Schrödinger equation approach that takes no near-field effect into account. As a demonstration we have examined in detail the system of an electron confined in a quasi-one-dimensional nanoscale potential well. The highly accurate Maxwell–Schrödinger hybrid simulation has been employed to demonstrate the usefulness of the proposed formula in predicting the significance of the near-field effect. The near-field effect has shown to depend sensitively on the characteristics of the laser pulse and of the geometry of the confined electron system, which can be predicted well by the proposed formula. (paper)

Near-field radiative heat transfer in mesoporous alumina

International Nuclear Information System (INIS)

Li Jing; Feng Yan-Hui; Zhang Xin-Xin; Huang Cong-Liang; Wang Ge

2015-01-01

The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2∼4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data. The larger the porosity, the more significant the near-field effect is, which cannot be ignored. (paper)

RFID Antenna Near-field Characterization Using a New 3D Magnetic Field Probe

Directory of Open Access Journals (Sweden)

Kassem Jomaa

2017-05-01

Full Text Available In this paper the design of a new 3D magnetic field (H-field probe with a near-field scanning system is presented, then the near electromagnetic fields radiated by a Library RFID system is characterized. The proposed system is developed in order to determine the magnetic near-field emitted by electronic devices. The designed isotropic H-field probe consists of three orthogonal and identical loops each of diameter of 6 mm having 3 turns. The antenna factor of the designed probe is presented for a frequency range from 10 MHz to 1 GHz. The designed probe is tested and validated using a standard passive circuit as a device under test. An RFID reader antenna is also designed and simulated on HFSS (high frequency structural simulator and the radiated magnetic field, obtained by simulations, is then compared to the real measured one above the fabricated circuit. The obtained levels are checked if they satisfy the European and ICNIRP Electromagnetic Fields Guidelines.

Near-Field Source Localization by Using Focusing Technique

Science.gov (United States)

He, Hongyang; Wang, Yide; Saillard, Joseph

2008-12-01

We discuss two fast algorithms to localize multiple sources in near field. The symmetry-based method proposed by Zhi and Chia (2007) is first improved by implementing a search-free procedure for the reduction of computation cost. We present then a focusing-based method which does not require symmetric array configuration. By using focusing technique, the near-field signal model is transformed into a model possessing the same structure as in the far-field situation, which allows the bearing estimation with the well-studied far-field methods. With the estimated bearing, the range estimation of each source is consequently obtained by using 1D MUSIC method without parameter pairing. The performance of the improved symmetry-based method and the proposed focusing-based method is compared by Monte Carlo simulations and with Crammer-Rao bound as well. Unlike other near-field algorithms, these two approaches require neither high-computation cost nor high-order statistics.

Near-Field Source Localization by Using Focusing Technique

Directory of Open Access Journals (Sweden)

Joseph Saillard

2008-12-01

Full Text Available We discuss two fast algorithms to localize multiple sources in near field. The symmetry-based method proposed by Zhi and Chia (2007 is first improved by implementing a search-free procedure for the reduction of computation cost. We present then a focusing-based method which does not require symmetric array configuration. By using focusing technique, the near-field signal model is transformed into a model possessing the same structure as in the far-field situation, which allows the bearing estimation with the well-studied far-field methods. With the estimated bearing, the range estimation of each source is consequently obtained by using 1D MUSIC method without parameter pairing. The performance of the improved symmetry-based method and the proposed focusing-based method is compared by Monte Carlo simulations and with Crammer-Rao bound as well. Unlike other near-field algorithms, these two approaches require neither high-computation cost nor high-order statistics

High performance Solid Rocket Motor (SRM) submerged nozzle/combustion cavity flowfield assessment

Science.gov (United States)

Freeman, J. A.; Chan, J. S.; Murph, J. E.; Xiques, K. E.

1987-01-01

Two and three dimensional internal flowfield solutions for critical points in the Space Shuttle solid rocket booster burn time were developed using the Lockheed Huntsville GIM/PAID Navier-Stokes solvers. These perfect gas, viscous solutions for the high performance motor characterize the flow in the aft segment and nozzle of the booster. Two dimensional axisymmetric solutions were developed at t = 20 and t = 85 sec motor burn times. The t = 85 sec solution indicates that the aft segment forward inhibitor stub produces vortices with are shed and convected downwards. A three dimensional 3.5 deg gimbaled nozzle flowfield solution was developed for the aft segment and nozzle at t = 9 sec motor burn time. This perfect gas, viscous analysis, provided a steady state solution for the core region and the flow through the nozzle, but indicated that unsteady flow exists in the region under the nozzle nose and near the flexible boot and nozzle/case joint. The flow in the nozzle/case joint region is characterized by low magnitude pressure waves which travel in the circumferential direction. From the two and three dimensional flowfield calculations presented it can be concluded that there is no evidence from these results that steady state gas dynamics is the primary mechanism resulting in the nozzle pocketing erosion experienced on SRM nozzles 8A or 17B. The steady state flowfield results indicate pocketing erosion is not directly initiated by a steady state gas dynamics phenomenon.

Near-field flat focusing mirrors

Science.gov (United States)

Cheng, Yu-Chieh; Staliunas, Kestutis

2018-03-01

This article reviews recent progress towards the design of near-field flat focusing mirrors, focusing/imaging light patterns in reflection. An important feature of such flat focusing mirrors is their transverse invariance, as they do not possess any optical axis. We start with a review of the physical background to the different focusing mechanisms of near- and far-field focusing. These near-field focusing devices like flat lenses and the reviewed near-field focusing mirrors can implement planar focusing devices without any optical axis. In contrast, various types of far-field planar focusing devices, such as high-contrast gratings and metasurfaces, unavoidably break the transverse invariance due to their radially symmetrical structures. The particular realizations of near-field flat focusing mirrors including Bragg-like dielectric mirrors and dielectric subwavelength gratings are the main subjects of the review. The first flat focusing mirror was demonstrated with a chirped mirror and was shown to manage an angular dispersion for beam focusing, similar to the management of chromatic dispersion for pulse compression. Furthermore, the reviewed optimized chirped mirror demonstrated a long near-field focal length, hardly achieved by a flat lens or a planar hyperlens. Two more different configurations of dielectric subwavelength gratings that focus a light beam at normal or oblique incidence are also reviewed. We also summarize and compare focusing performance, limitations, and future perspectives between the reviewed flat focusing mirrors and other planar focusing devices including a flat lens with a negative-index material, a planar hyperlens, a high-contrast grating, and a metasurface.

Estimate on the uncertainty of predicting radiated emission from near-field scan caused by insufficient or inaccurate near-field data

DEFF Research Database (Denmark)

Sørensen, Morten; Radchenko, Andriy; Kam, Keong

2012-01-01

Near-field scan on a Huygens’ box can be used in order to predict the maximal radiated emission from a Printed Circuit Board. The significance of step size and phase accuracy, and the importance of a full Huygens’ box are investigated by simulation of two different models with two different...... numerical methods. The prediction of maximal radiated emission is quite robust but the results also show that a full scan on all six surfaces is probably needed....

Navier-Stokes Calculations of Helicopter Fuselage Flowfield and Loads

DEFF Research Database (Denmark)

M, Costes; Filippone, Antonino; N, Kroll

1999-01-01

This paper describes the theoretically basedactivities conducted during the first year of theBrite/Euram Helifuse Porgramme. These activitiesmainly consisted of the numerical prediction ofhelicopter fuselage flowfields with existing Navier-Stokes solvers on a number of pre-selectedcases, taken out...

Modeling of Coastal Effluent Transport: an Approach to Linking of Far-field and Near-field Models

International Nuclear Information System (INIS)

Yang, Zhaoqing; Khangaonkar, Tarang P.

2008-01-01

One of the challenges in effluent transport modeling in coastal tidal environments is the proper calculation of initial dilution in connection with the far-field transport model. In this study, an approach of external linkage of far-field and near-field effluent transport models is presented, and applied to simulate the effluent transport in the Port Angeles Harbor, Washington in the Strait of Juan de Fuca. A near-field plume model was used to calculate the effluent initial dilution and a three-dimensional (3-D) hydrodynamic model was developed to simulate the tidal circulation and far-field effluent transport in the Port Angeles Harbor. In the present study, the hydrodynamic model was driven by tides and surface winds. Observed water surface elevation and velocity data were used to calibrate the model over a period covering the neap-spring tidal cycle. The model was also validated with observed surface drogue trajectory data. The model successfully reproduced the tidal dynamics in the study area and good agreements between model results and observed data were obtained. This study demonstrated that the linkage between the near-field and far-field models in effluent transport modeling can be achieved through iteratively adjusting the model grid sizes such that the far-field modeled dilution ratio and effluent concentration in the effluent discharge model grid cell match the concentration calculated by the near-field plume model

Development and application of theoretical models for Rotating Detonation Engine flowfields

Science.gov (United States)

Fievisohn, Robert

As turbine and rocket engine technology matures, performance increases between successive generations of engine development are becoming smaller. One means of accomplishing significant gains in thermodynamic performance and power density is to use detonation-based heat release instead of deflagration. This work is focused on developing and applying theoretical models to aid in the design and understanding of Rotating Detonation Engines (RDEs). In an RDE, a detonation wave travels circumferentially along the bottom of an annular chamber where continuous injection of fresh reactants sustains the detonation wave. RDEs are currently being designed, tested, and studied as a viable option for developing a new generation of turbine and rocket engines that make use of detonation heat release. One of the main challenges in the development of RDEs is to understand the complex flowfield inside the annular chamber. While simplified models are desirable for obtaining timely performance estimates for design analysis, one-dimensional models may not be adequate as they do not provide flow structure information. In this work, a two-dimensional physics-based model is developed, which is capable of modeling the curved oblique shock wave, exit swirl, counter-flow, detonation inclination, and varying pressure along the inflow boundary. This is accomplished by using a combination of shock-expansion theory, Chapman-Jouguet detonation theory, the Method of Characteristics (MOC), and other compressible flow equations to create a shock-fitted numerical algorithm and generate an RDE flowfield. This novel approach provides a numerically efficient model that can provide performance estimates as well as details of the large-scale flow structures in seconds on a personal computer. Results from this model are validated against high-fidelity numerical simulations that may require a high-performance computing framework to provide similar performance estimates. This work provides a designer a new

Interferograms, schlieren, and shadowgraphs constructed from real- and ideal-gas, two- and three-dimensional computed flowfields

Science.gov (United States)

Yates, Leslie A.

1993-01-01

The construction of interferograms, schlieren, and shadowgraphs from computed flowfield solutions permits one-to-one comparisons of computed and experimental results. A method of constructing these images from both ideal- and real-gas, two and three-dimensional computed flowfields is described. The computational grids can be structured or unstructured, and multiple grids are an option. Constructed images are shown for several types of computed flows including nozzle, wake, and reacting flows; comparisons to experimental images are also shown. In addition, th sensitivity of these images to errors in the flowfield solution is demonstrated, and the constructed images can be used to identify problem areas in the computations.

High Frequency Near-Field Ground Motion Excited by Strike-Slip Step Overs

Science.gov (United States)

Hu, Feng; Wen, Jian; Chen, Xiaofei

2018-03-01

We performed dynamic rupture simulations on step overs with 1-2 km step widths and present their corresponding horizontal peak ground velocity distributions in the near field within different frequency ranges. The rupture speeds on fault segments are determinant in controlling the near-field ground motion. A Mach wave impact area at the free surface, which can be inferred from the distribution of the ratio of the maximum fault-strike particle velocity to the maximum fault-normal particle velocity, is generated in the near field with sustained supershear ruptures on fault segments, and the Mach wave impact area cannot be detected with unsustained supershear ruptures alone. Sub-Rayleigh ruptures produce stronger ground motions beyond the end of fault segments. The existence of a low-velocity layer close to the free surface generates large amounts of high-frequency seismic radiation at step over discontinuities. For near-vertical step overs, normal stress perturbations on the primary fault caused by dipping structures affect the rupture speed transition, which further determines the distribution of the near-field ground motion. The presence of an extensional linking fault enhances the near-field ground motion in the extensional regime. This work helps us understand the characteristics of high-frequency seismic radiation in the vicinities of step overs and provides useful insights for interpreting the rupture speed distributions derived from the characteristics of near-field ground motion.

Parameterized source term in the diffusion approximation for enhanced near-field modeling of collimated light

Science.gov (United States)

Jia, Mengyu; Wang, Shuang; Chen, Xueying; Gao, Feng; Zhao, Huijuan

2016-03-01

Most analytical methods for describing light propagation in turbid medium exhibit low effectiveness in the near-field of a collimated source. Motivated by the Charge Simulation Method in electromagnetic theory as well as the established discrete source based modeling, we have reported on an improved explicit model, referred to as "Virtual Source" (VS) diffuse approximation (DA), to inherit the mathematical simplicity of the DA while considerably extend its validity in modeling the near-field photon migration in low-albedo medium. In this model, the collimated light in the standard DA is analogously approximated as multiple isotropic point sources (VS) distributed along the incident direction. For performance enhancement, a fitting procedure between the calculated and realistic reflectances is adopted in the nearfield to optimize the VS parameters (intensities and locations). To be practically applicable, an explicit 2VS-DA model is established based on close-form derivations of the VS parameters for the typical ranges of the optical parameters. The proposed VS-DA model is validated by comparing with the Monte Carlo simulations, and further introduced in the image reconstruction of the Laminar Optical Tomography system.

Towards phonon photonics: scattering-type near-field optical microscopy reveals phonon-enhanced near-field interaction

International Nuclear Information System (INIS)

Hillenbrand, Rainer

2004-01-01

Diffraction limits the spatial resolution in classical microscopy or the dimensions of optical circuits to about half the illumination wavelength. Scanning near-field microscopy can overcome this limitation by exploiting the evanescent near fields existing close to any illuminated object. We use a scattering-type near-field optical microscope (s-SNOM) that uses the illuminated metal tip of an atomic force microscope (AFM) to act as scattering near-field probe. The presented images are direct evidence that the s-SNOM enables optical imaging at a spatial resolution on a 10 nm scale, independent of the wavelength used (λ=633 nm and 10 μm). Operating the microscope at specific mid-infrared frequencies we found a tip-induced phonon-polariton resonance on flat polar crystals such as SiC and Si 3 N 4 . Being a spectral fingerprint of any polar material such phonon-enhanced near-field interaction has enormous applicability in nondestructive, material-specific infrared microscopy at nanoscale resolution. The potential of s-SNOM to study eigenfields of surface polaritons in nanostructures opens the door to the development of phonon photonics--a proposed infrared nanotechnology that uses localized or propagating surface phonon polaritons for probing, manipulating and guiding infrared light in nanoscale devices, analogous to plasmon photonics

Survey and review of near-field performance assessment

International Nuclear Information System (INIS)

Apted, M.J.

1993-01-01

The aim of this chapter is to describe the performance assessment (PA) context in which near-field models have been developed and applied. An overview is given of a number of PA studies. Although the focus is on near-field models, the overview covers the full context in which the PAs have been performed, including the purpose of the studies and regulatory context. Special emphasis has been given to the scenarios analyzed in the assessments; the scenarios set the framework for model development and application. Another aspect to consider in a study of near-field modeling from the perspective of total PA is the linking between near-field and far-field assessment. (R.P.) 6 tabs

A 60 GHz Dual-Polarized Probe for Spherical Near-Field Measurements

DEFF Research Database (Denmark)

Popa, Paula Irina; Breinbjerg, Olav

2017-01-01

to waveguide adapters up to 67 GHz for OMT-switch connection. A 27 dBi gain conical horn is designed by using WIPL-D software and in-house manufactured. The 60 GHz probe system is being assembled and tested in planar near-field (PNF) setup at DTU. The results are validated by comparison with WIPL-D simulations...

Unidirectional wireless power transfer using near-field plates

International Nuclear Information System (INIS)

Imani, Mohammadreza F.; Grbic, Anthony

2015-01-01

One of the obstacles preventing wireless power transfer from becoming ubiquitous is their leakage of power: high-amplitude electromagnetic fields that can interfere with other electronic devices, increase health concerns, or hinder power metering. In this paper, we present near-field plates (NFPs) as a novel method to tailor the electromagnetic fields generated by a wireless power transfer system while maintaining high efficiency. NFPs are modulated arrays or surfaces designed to form prescribed near-field patterns. The NFP proposed in this paper consists of an array of loaded loops that are designed to confine the electromagnetic fields of a resonant transmitting loop to the desired direction (receiving loop) while suppressing fields in other directions. The step-by-step design procedure for this device is outlined. Two NFPs are designed and examined in full-wave simulation. Their performance is shown to be in close agreement with the design predictions, thereby verifying the proposed design and operation. A NFP is also fabricated and experimentally shown to form a unidirectional wireless power transfer link with high efficiency

Unidirectional wireless power transfer using near-field plates

Energy Technology Data Exchange (ETDEWEB)

Imani, Mohammadreza F., E-mail: mohamad.imani@gmail.com [Center for Metamaterials and Integrated Plasmonics, Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States); Grbic, Anthony [Radiation Laboratory, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2015-05-14

One of the obstacles preventing wireless power transfer from becoming ubiquitous is their leakage of power: high-amplitude electromagnetic fields that can interfere with other electronic devices, increase health concerns, or hinder power metering. In this paper, we present near-field plates (NFPs) as a novel method to tailor the electromagnetic fields generated by a wireless power transfer system while maintaining high efficiency. NFPs are modulated arrays or surfaces designed to form prescribed near-field patterns. The NFP proposed in this paper consists of an array of loaded loops that are designed to confine the electromagnetic fields of a resonant transmitting loop to the desired direction (receiving loop) while suppressing fields in other directions. The step-by-step design procedure for this device is outlined. Two NFPs are designed and examined in full-wave simulation. Their performance is shown to be in close agreement with the design predictions, thereby verifying the proposed design and operation. A NFP is also fabricated and experimentally shown to form a unidirectional wireless power transfer link with high efficiency.

Flowfield characterisation in the wake of a low-velocity heated sphere anemometer

Energy Technology Data Exchange (ETDEWEB)

Olim, A.M. [Associacao para o Desenvolvimento da Aerodinamica Industrial (ADAI), Coimbra (Portugal); Riethmuller, M.L. [Von Karman Institute for Fluid Dynamics (VKI), St. Genese (Belgium); Gameiro da Silva, M.C. [Departamento de Engenharia Mecanica, Faculdade de Ciencias e Tecnologia, Universidade de Coimbra Polo II, Coimbra (Portugal)

2002-06-01

Heated sphere anemometers (HSA) are the most widely used instruments for low-velocity measurements in the heating, ventilation and air-conditioning industry. Experiments were conducted to characterise the flowfield around the spherically shaped sensor and upper probe assembly of a HSA. Particle image velocimetry was the main quantitative experimental technique. Measurements of the flowfield around a HSA probe and a 2:1 scaled-up model were performed in a uniform isothermal axisymmetrical jet air flow at Re around 350, based on sensor diameter, for different pitch angle incident flows. Additionally, extensive flow visualisation studies around scaled-up models of the HSA probe were performed. (orig.)

Detection of concrete dam leakage using an integrated geophysical technique based on flow-field fitting method

Science.gov (United States)

Dai, Qianwei; Lin, Fangpeng; Wang, Xiaoping; Feng, Deshan; Bayless, Richard C.

2017-05-01

An integrated geophysical investigation was performed at S dam located at Dadu basin in China to assess the condition of the dam curtain. The key methodology of the integrated technique used was flow-field fitting method, which allowed identification of the hydraulic connections between the dam foundation and surface water sources (upstream and downstream), and location of the anomalous leakage outlets in the dam foundation. Limitations of the flow-field fitting method were complemented with resistivity logging to identify the internal erosion which had not yet developed into seepage pathways. The results of the flow-field fitting method and resistivity logging were consistent when compared with data provided by seismic tomography, borehole television, water injection test, and rock quality designation.

Near-Field Optical Microscopy of Fractal Structures

DEFF Research Database (Denmark)

Coello, Victor; Bozhevolnyi, Sergey I.

1999-01-01

Using a photon scanning tunnelling microscope combined with a shear-force feedback system, we image both topographical and near-field optical images (at the wavelengths of 633 and 594 nm) of silver colloid fractals. Near-field optical imaging is calibrated with a standing evanescent wave pattern...

Spherical near-field scanning at the Technical University of Denmark

DEFF Research Database (Denmark)

Hansen, J. E.; Jensen, F.

1988-01-01

The early work (1969-79) on spherical near-field antenna measurements at the Technical University of Denmark (TUD) is outlined. A spherical near-field transmission formula is described and the first probe-corrected spherical near-field measurements are discussed. The TUD-ESA (European Space Agency...

Scanning near-field infrared microscopy on semiconductor structures

Energy Technology Data Exchange (ETDEWEB)

Jacob, Rainer

2011-01-15

Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source. In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems. In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from

Scanning near-field infrared microscopy on semiconductor structures

International Nuclear Information System (INIS)

Jacob, Rainer

2011-01-01

Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source. In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems. In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from

Hybrid photonic-plasmonic near-field probe for efficient light conversion into the nanoscale hot spot.

Science.gov (United States)

Koshelev, Alexander; Munechika, Keiko; Cabrini, Stefano

2017-11-01

In this Letter, we present a design and simulations of the novel hybrid photonic-plasmonic near-field probe. Near-field optics is a unique imaging tool that provides optical images with resolution down to tens of nanometers. One of the main limitations of this technology is its low light sensitivity. The presented hybrid probe solves this problem by combining a campanile plasmonic probe with the photonic layer, consisting of the diffractive optic element (DOE). The DOE is designed to match the plasmonic field at the broad side of the campanile probe with the fiber mode. This makes it possible to optimize the size of the campanile tip to convert light efficiently into the hot spot. The simulations show that the hybrid probe is ∼540 times more efficient compared with the conventional campanile on average in the 600-900 nm spectral range.

Polarization resolved imaging with a reflection near-field optical microscope

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Xiao, Mufei; Hvam, Jørn Märcher

1999-01-01

Using a rigorous microscopic point-dipole description of probe-sample interactions, we study imaging with a reflection scanning near-field optical microscope. Optical content, topographical artifacts, sensitivity window-i.e., the scale on which near-field optical images represent mainly optical...... configuration is preferable to the cross-linear one, since it ensures more isotropic (in the surface plane) near-field imaging of surface features. The numerical results are supported with experimental near-field images obtained by using a reflection microscope with an uncoated fiber tip....

Nonlinear emission from dark anapole modes and route to all-dielectric metamaterial near-field lasers

KAUST Repository

Gongora, J. S. Totero; Miroshnichenko, Andrey E.; Kivshar, Yuri S.; Fratalocchi, Andrea

2016-01-01

By employing ab-initio simulations of Maxwell-Bloch equations with a source of quantum noise, we study a new laser concept based on photonic dark-matter nanostructures that emit only in the near-field, with no far-field radiation pattern

Nonlinear emission from dark anapole modes and route to all-dielectric metamaterial near-field lasers

KAUST Repository

Gongora, J. S. Totero

2016-08-29

By employing ab-initio simulations of Maxwell-Bloch equations with a source of quantum noise, we study a new laser concept based on photonic dark-matter nanostructures that emit only in the near-field, with no far-field radiation pattern

Near-field imaging of interacting nano objects with metal and metamaterial superlenses

International Nuclear Information System (INIS)

Hakkarainen, T; Setälä, T; Friberg, A T

2012-01-01

Employing rigorous electromagnetic theory we investigate optical the near-field imaging of two interacting dipole-like objects with metal and slightly lossy metamaterial nanoslab superlenses. Our analysis indicates that the dipole emission is suppressed by near-field interactions when the objects are close to the lens or each other. This strongly influences the image quality, in particular with objects of small size and high polarizability. The interference from two nearby objects also affects the resolution and subwavelength definition can only be obtained for objects with dipole moments predominantly orthogonal to the slab. Such an optimal imaging condition is achieved with excitation by total internal reflection. With simulations we show that in these circumstances, subwavelength resolutions of about λ/5 for silver superlens and λ/10 for metamaterial slab are reached. (paper)

Post-processing computational fluid dynamic simulations of gas turbine combustor

International Nuclear Information System (INIS)

Sturgess, G.J.; Inko-Tariah, W.P.C.; James, R.H.

1986-01-01

The flowfield in combustors for gas turbine engines is extremely complex. Numerical simulation of such flowfields using computational fluid dynamics techniques has much to offer the design and development engineer. It is a difficult task, but it is one which is now being attempted routinely in the industry. The results of such simulations yield enormous amounts of information from which the responsible engineer has to synthesize a comprehensive understanding of the complete flowfield and the processes contained therein. The complex picture so constructed must be distilled down to the essential information upon which rational development decisions can be made. The only way this can be accomplished successfully is by extensive post-processing of the calculation. Post processing of a simulation relies heavily on computer graphics, and requires the enhancement provided by color. The application of one such post-processor is presented, and the strengths and weaknesses of various display techniques are illustrated

Near-field probing of photonic crystal directional couplers

DEFF Research Database (Denmark)

Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

2006-01-01

We report the design, fabrication and characterization of a photonic crystal directional with a size of ~20 x 20 mm2 fabricated in silicon-on-insulator material. Using a scanning near-field optical microscope we demonstrate a high coupling efficiency for TM polarized light at telecom wavelengths....... By comparing the near-field optical images recorded in and after the directional coupler area, the features of light distribution are analyzed. Finally, the scanning near-field optical microscope observations are found to be in agreement with the transmission measurements conducted with the same sample....

Flowfield Analysis of Savonius-type Wind Turbine blade

Energy Technology Data Exchange (ETDEWEB)

Noh, Tae Hyun; Chang, Se Myong [Kunsan National Univ., Kunsan (Korea, Republic of); Seo, Hyun Soo [Korea Institute of Energy Research, Daejeon (Korea, Republic of)

2007-07-01

In this paper, we researched flow of 8000 {approx} 24000 Reynolds number around a blade model of Savonius-type wind turbine with experimental and numerical method. For the blade shape of arc, we analyzed flowfield with streak-image flow visualization, measured wake, computed drag coefficients, and compared them for given angle of attacks. The result of research can be used to design aerodynamic performance of Savonius-type turbine rotor directly.

Virtual-source diffusion approximation for enhanced near-field modeling of photon-migration in low-albedo medium.

Science.gov (United States)

Jia, Mengyu; Chen, Xueying; Zhao, Huijuan; Cui, Shanshan; Liu, Ming; Liu, Lingling; Gao, Feng

2015-01-26

Most analytical methods for describing light propagation in turbid medium exhibit low effectiveness in the near-field of a collimated source. Motivated by the Charge Simulation Method in electromagnetic theory as well as the established discrete source based modeling, we herein report on an improved explicit model for a semi-infinite geometry, referred to as "Virtual Source" (VS) diffuse approximation (DA), to fit for low-albedo medium and short source-detector separation. In this model, the collimated light in the standard DA is analogously approximated as multiple isotropic point sources (VS) distributed along the incident direction. For performance enhancement, a fitting procedure between the calculated and realistic reflectances is adopted in the near-field to optimize the VS parameters (intensities and locations). To be practically applicable, an explicit 2VS-DA model is established based on close-form derivations of the VS parameters for the typical ranges of the optical parameters. This parameterized scheme is proved to inherit the mathematical simplicity of the DA approximation while considerably extending its validity in modeling the near-field photon migration in low-albedo medium. The superiority of the proposed VS-DA method to the established ones is demonstrated in comparison with Monte-Carlo simulations over wide ranges of the source-detector separation and the medium optical properties.

Optimization of s-Polarization Sensitivity in Apertureless Near-Field Optical Microscopy

Directory of Open Access Journals (Sweden)

Yuika Saito

2012-01-01

Full Text Available It is a general belief in apertureless near-field microscopy that the so-called p-polarization configuration, where the incident light is polarized parallel to the axis of the probe, is advantageous to its counterpart, the s-polarization configuration, where the incident light is polarized perpendicular to the probe axis. While this is true for most samples under common near-field experimental conditions, there are samples which respond better to the s-polarization configuration due to their orientations. Indeed, there have been several reports that have discussed such samples. This leads us to an important requirement that the near-field experimental setup should be equipped with proper sensitivity for measurements with s-polarization configuration. This requires not only creation of effective s-polarized illumination at the near-field probe, but also proper enhancement of s-polarized light by the probe. In this paper, we have examined the s-polarization enhancement sensitivity of near-field probes by measuring and evaluating the near-field Rayleigh scattering images constructed by a variety of probes. We found that the s-polarization enhancement sensitivity strongly depends on the sharpness of the apex of near-field probes. We have discussed the efficient value of probe sharpness by considering a balance between the enhancement and the spatial resolution, both of which are essential requirements of apertureless near-field microscopy.

Miniaturized compact water-cooled pitot-pressure probe for flow-field surveys in hypersonic wind tunnels

Science.gov (United States)

Ashby, George C.

1988-01-01

An experimental investigation of the design of pitot probes for flowfield surveys in hypersonic wind tunnels is reported. The results show that a pitot-pressure probe can be miniaturized for minimum interference effects by locating the transducer in the probe support body and water-cooling it so that the pressure-settling time and transducer temperature are compatible with hypersonic tunnel operation and flow conditions. Flowfield surveys around a two-to-one elliptical cone model in a 20-inch Mach 6 wind tunnel using such a probe show that probe interference effects are essentially eliminated.

Computational Fluid Dynamic Modeling of Rocket Based Combined Cycle Engine Flowfields

Science.gov (United States)

Daines, Russell L.; Merkle, Charles L.

1994-01-01

Computational Fluid Dynamic techniques are used to study the flowfield of a fixed geometry Rocket Based Combined Cycle engine operating in rocket ejector mode. Heat addition resulting from the combustion of injected fuel causes the subsonic engine flow to choke and go supersonic in the slightly divergent combustor-mixer section. Reacting flow computations are undertaken to predict the characteristics of solutions where the heat addition is determined by the flowfield. Here, adaptive gridding is used to improve resolution in the shear layers. Results show that the sonic speed is reached in the unheated portions of the flow first, while the heated portions become supersonic later. Comparison with results from another code show reasonable agreement. The coupled solutions show that the character of the combustion-based thermal choking phenomenon can be controlled reasonably well such that there is opportunity to optimize the length and expansion ratio of the combustor-mixer.

High-Density Near-Field Optical Disc Recording

Science.gov (United States)

Shinoda, Masataka; Saito, Kimihiro; Ishimoto, Tsutomu; Kondo, Takao; Nakaoki, Ariyoshi; Ide, Naoki; Furuki, Motohiro; Takeda, Minoru; Akiyama, Yuji; Shimouma, Takashi; Yamamoto, Masanobu

2005-05-01

We developed a high-density near-field optical recording disc system using a solid immersion lens. The near-field optical pick-up consists of a solid immersion lens with a numerical aperture of 1.84. The laser wavelength for recording is 405 nm. In order to realize the near-field optical recording disc, we used a phase-change recording media and a molded polycarbonate substrate. A clear eye pattern of 112 GB capacity with 160 nm track pitch and 50 nm bit length was observed. The equivalent areal density is 80.6 Gbit/in2. The bottom bit error rate of 3 tracks-write was 4.5× 10-5. The readout power margin and the recording power margin were ± 30.4% and ± 11.2%, respectively.

Near-Field Phase-Change Optical Recording of 1.36 Numerical Aperture

Science.gov (United States)

Ichimura, Isao; Kishima, Koichiro; Osato, Kiyoshi; Yamamoto, Kenji; Kuroda, Yuji; Saito, Kimihiro

2000-02-01

A bit density of 125 nm was demonstrated through near-field phase-change (PC) optical recording at the wavelength of 657 nm by using a supersphere solid immersion lens (SIL). The lens unit consists of a standard objective and a φ2.5 mm SIL@. Since this lens size still prevents the unit from being mounted on an air-bearing slider, we developed a one-axis positioning actuator and an active capacitance servo for precise gap control to thoroughly investigate near-field recording. An electrode was fabricated on the bottom of the SIL, and a capacitor was formed facing a disk material. This setup realized a stable air gap below 50 nm, and a new method of simulating modulation transfer function (MTF) optimized the PC disk structure at this gap height. Obtained jitter of 8.8% and a clear eye-pattern prove that our system successfully attained the designed numerical-aperture (\\mathit{NA}) of 1.36.

Some variations of the Kristallin-I near-field model

International Nuclear Information System (INIS)

Smith, P.A.; Curti, E.

1995-11-01

The Kristallin-I project is an integrated analysis of the final disposal of vitrified high-level radioactive waste (HLW) in the crystalline basement of Northern Switzerland. It includes an analysis of the radiological consequences of radionuclide release from a repository. This analysis employs a chain of independent models for the near-field, geosphere and biosphere. In constructing these models, processes are incorporated that are believed to be relevant to repository safety, while other processes are neglected. In the present report, a set of simplified, steady-state models of the near-field is developed to investigate the possible effects of specific processes which are neglected in the time-dependent Kristallin-I near-field model. These processes are neglected, either because they are thought unlikely to occur to a significant degree, or because they are likely to make a positive contribution to the performance of the near-field barrier to radionuclide migration, but are insufficiently understood to justify incorporating them in a safety assessment. The aim of this report is to investigate whether the arguments for neglecting these processes in the Kristallin-I near-field model can be justified. (author) figs., tabs., refs

Near-field optical recording based on solid immersion lens system

Science.gov (United States)

Hong, Tao; Wang, Jia; Wu, Yan; Li, Dacheng

2002-09-01

Near-field optical recording based on solid immersion lens (SIL) system has attracted great attention in the field of high-density data storage in recent years. The diffraction limited spot size in optical recording and lithography can be decreased by utilizing the SIL. The SIL near-field optical storage has advantages of high density, mass storage capacity and compatibility with many technologies well developed. We have set up a SIL near-field static recording system. The recording medium is placed on a 3-D scanning stage with the scanning range of 70×70×70μm and positioning accuracy of sub-nanometer, which will ensure the rigorous separation control in SIL system and the precision motion of the recording medium. The SIL is mounted on an inverted microscope. The focusing between long working distance objective and SIL can be monitored and observed by the CCD camera and eyes. Readout signal can be collected by a detector. Some experiments have been performed based on the SIL near-field recording system. The attempt of the near-field recording on photochromic medium has been made and the resolution improvement of the SIL has been presented. The influence factors in SIL near-field recording system are also discussed in the paper.

SITE-94. Modelling of near-field chemistry for SITE-94

Energy Technology Data Exchange (ETDEWEB)

Arthur, R.; Apted, M. [QuantiSci, Denver, CO (United States)

1996-12-01

This report evaluates methods for the incorporation of site data into models simulating the long-term chemical evolution of the near field. The models are based on limiting conditions at equilibrium, or steady state, in three closed systems representing fully saturated bentonite, Fe{sup o} corrosion products of the canister and spent fuel. A l kg reference mass of site groundwater is assumed to equilibrate first with bentonite and then with the canister`s corrosion products. A third closed system representing spent fuel is modeled in terms of spent-fuel dissolution in 1 kg of water evolved from the canister, coupled with steady-state constraints on the rate of oxidant production by {alpha} radiolysis of H{sub 2}O(l). Precipitation of secondary minerals controlling the solubilities of radioelements dissolved from spent fuel is also simulated in this model. Version 7.2 of the EQ3/6 geochemical software package and its supporting composite thermodynamic database, dataO.com.R22, are used to carry out these calculations. It is concluded that chemical models of near-field evolution combined with thermodynamic models of radionuclide speciation-solubility behavior can assist efforts to assimilate site characterization data into the performance assessment process, and to deal with uncertainties that are inherent in both site properties and in concepts of near field chemistry. It is essential, however, that expert judgement and prudence should be exercised such that model results are conservative with respect to acknowledged and documented uncertainties. Most importantly, it must be recognized that it is probably not possible to model with a high-level of accuracy the complex chemical environments and long timescales involved in disposal technologies for nuclear wastes. For performance assessment, however, only bounding values are needed, and modeling approaches such as described in this report are useful for this purpose. Technical peer review and cross-comparisons of near-field

Near-field ptychography: phase retrieval for inline holography using a structured illumination.

Science.gov (United States)

Stockmar, Marco; Cloetens, Peter; Zanette, Irene; Enders, Bjoern; Dierolf, Martin; Pfeiffer, Franz; Thibault, Pierre

2013-01-01

Inline holography is a common phase-contrast imaging method which uses free-space propagation to encode the phase signal into measured intensities. However, quantitative retrieval of the sample's image remains challenging, imposing constraints on the nature of the sample or on the propagation distance. Here, we present a way of simultaneously retrieving the sample's complex-valued transmission function and the incident illumination function from near-field diffraction patterns. The procedure relies on the measurement diversity created by lateral translations of the sample with respect to a structured illumination. The reconstruction approach, in essence identical to that employed in ptychography, is applied to hard X-ray synchrotron measurements and to simulations. Compared to other inline holography techniques, we expect near-field ptychography to reduce reconstruction artefacts by factoring out wavefront imperfections and relaxing constraints on the sample's scattering properties, thus ultimately improving the robustness of propagation-based X-ray phase tomography.

Near-field characterization of plasmonic waveguides

DEFF Research Database (Denmark)

Zenin, Volodymyr

2014-01-01

simply by changing geometric parameters of the waveguide, keeping in mind the trade-off between confinement and propagation losses. A broad variety of plasmonic waveguides and waveguide components, including antennas for coupling the light in/out of the waveguide, requires correspondent characterization...... capabilities, especially on experimental side. The most straight-forward and powerful technique for such purpose is scanning near-field optical microscopy, which allows to probe and map near-field distribution and therefore becomes the main tool in this project. The detailed description of the used setups...

Near-field second-harmonic generation from gold nanoellipsoids

Energy Technology Data Exchange (ETDEWEB)

Celebrano, M; Zavelani-Rossi, M; Polli, D; Cerullo, G [Istituto di Fotonica e Nanotecnologie, CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Biagioni, P; Finazzi, M; Duo, L [LNESS - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Labardi, M; Allegrini, M [CNR-INFM, polyLab, Dipartimento di Fisica ' Enrico Fermi' , Universita di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); Grand, J; Adam, P M; Royer, P [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP 2060 10010 Troyes cedex (France)

2008-07-01

Second-harmonic generation from single gold nanofabricated particles is experimentally investigated by a nonlinear scanning near-field optical microscope (SNOM). High peak power femtosecond polarized light pulses at the output of a hollow pyramid aperture allow for efficient second-harmonic imaging, with sub-100-nm spatial resolution and high contrast. The near-field nonlinear response is found to be directly related to both local surface plasmon resonances and particle morphology. The combined analysis of linear and second-harmonic SNOM images allows one to discriminate among near-field scattering, absorption and re-emission processes, which would not be possible with linear techniques alone. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Near-field optical microscope using a silicon-nitride probe

NARCIS (Netherlands)

van Hulst, N.F.; Moers, M.H.P.; Moers, M.H.P.; Noordman, O.F.J.; Noordman, O.F.J.; Tack, R.G.; Segerink, Franciscus B.; Bölger, B.; Bölger, B.

1993-01-01

Operation of an alternative near-field optical microscope is presented. The microscope uses a microfabricated silicon- nitride probe with integrated cantilever, as originally developed for force microscopy. The cantilever allows routine close contact near-field imaging o­n arbitrary surfaces without

Review of international near-field modeling for high-level waste disposal

International Nuclear Information System (INIS)

Apted, M.J.; Andersson, K.; Pescatore, C.

1993-01-01

The primary components of nuclear waste repositories that mitigate radionuclide release are the near-field and the far-field subsystems. The near-field encompasses the waste package, which is composed of engineered barriers; the far-field includes the natural barriers. An international survey and review is being conducted on the latest developments in modeling of near-field performance, with particular emphasis on the conceptual and mathematical models for source-term calculations. The objectives of this review will be to establish the status and commonality among models and methods for assessing near-field performance, as well as to identify possible future needs for continued comparison and collaboration. In parallel with the technical evaluation, an international technical Workshop on near-field performance assessment will be held, in association with the Nuclear Energy Agency, on May 11-13, 1993 in Cadarache, France

Engineering the near-field imaging of a rectangular-lattice photonic-crystal slab in the second band

Institute of Scientific and Technical Information of China (English)

无

2009-01-01

Imaging properties of a two-dimensional rectangular-lattice photonic crystal (PC) slab consisting of air holes immersed in a dielectric are studied in this work. The field patterns of electromagnetic waves radiated from a point source through the PC slab are calculated with the finite-difference time-domain method. Comparing the field patterns with the corresponding equifrequency-surface contours simulated by the plane-wave expansion method, we find that an excellent-quality near-field image may be formed through the PC slab by the mechanisms of the simultaneous action of the self-collimation effect and the negative-refraction effect. Near-field imaging may be obtained within two different frequency regions in two vertical directions of the PC slab.

Near-field radiative heat transfer between clusters of dielectric nanoparticles

International Nuclear Information System (INIS)

Dong, J.; Zhao, J.M.; Liu, L.H.

2017-01-01

In this work, we explore the near-field radiative heat transfer between two clusters of silicon carbide (SiC) nanoparticles using the many-body radiative heat transfer theory. The effects of fractal dimension of clusters, many-body interaction between nanoparticles and relative orientation of clusters on the thermal conductance are studied. Meanwhile, the applicability of the equivalent volume spheres (EVS) approximation for near-field radiative heat transfer between clusters is examined. It is observed that the thermal conductance is larger for clusters with larger fractal dimension, which is more significant in the near-field. The thermal conductance of EVS resembles that of the clusters, but EVS overestimates the conductance of clusters, especially in the near-field. Compared to the case of two nanoparticles, the conductance of nanoparticle clusters decays much slower with increasing distance in the near-field, but shares similar dependence on the distance in the far-field. The thermal conductance of SiC nanoparticle clusters is inhibited by the many-body interaction when surface phonon polariton is supported but enhanced at frequencies close to the resonance frequency. The total thermal conductance is decreased due to many-body interaction among particles in the cluster. The relative orientation between the clusters is also an important factor in the near-field, especially for clusters with lower fractal dimension. - Highlights: • Near-field radiative heat transfer between clusters of nanoparticles is studied. • The many-body radiative heat transfer theory is applied for rigorous analysis. • The accuracy of equivalent volume spheres approximation is examined. • Clusters with larger fractal dimension have larger radiative thermal conductance. • Many-body interaction inhibits the total radiative thermal conductance.

Survey and review of near-field performance assessment

International Nuclear Information System (INIS)

Apted, M.J.

1993-01-01

Chemical reactions control the performance, stability, and rate of degradation of natural and engineered barriers to waste repositories of the near field. Chemical processes are overviewed in this context. Temperature, and associated temperature gradients, are also important parameters in near-field performance assessment. The mechanical conditions of the near-field rock will be perturbed by construction of the underground repository. Mechanical analysis in the near field is further complicated by the introduction of HLW canisters and associated engineered barrier materials. Hydrological processes important to near-field performance include those associated with fluid transport. Considerable discussions and studies have been conducted on the issue of coupling among chemical-thermal-mechanical-hydrological processes; they are overviewed. (R.P.) 2 figs., 2 tabs

Performance analysis of near-field thermophotovoltaic devices considering absorption distribution

International Nuclear Information System (INIS)

Park, K.; Basu, S.; King, W.P.; Zhang, Z.M.

2008-01-01

This paper elucidates the energy transfer and conversion processes in near-field thermophotovoltaic (TPV) systems, considering local radiation absorption and photocurrent generation in the TPV cell. Radiation heat transfer in a multilayered structure is modeled using the fluctuation-dissipation theorem, and the electric current generation is evaluated based on the photogeneration and recombination of electron-hole pairs in different regions of the TPV cell. The effects of near-field radiation on the photon penetration depth, photocurrent generation, and quantum efficiency are examined in the spectral region of interest. The detailed analysis performed in the present work demonstrates that, while the near-field operation can enhance the power throughput, the conversion efficiency is not much improved and may even be reduced. Subsequently, a modified design of near-field TPV systems is proposed to improve the efficiency

Near-Field Spectroscopy with Nanoparticles Deposited by AFM

Science.gov (United States)

Anderson, Mark S.

2008-01-01

An alternative approach to apertureless near-field optical spectroscopy involving an atomic-force microscope (AFM) entails less complexity of equipment than does a prior approach. The alternative approach has been demonstrated to be applicable to apertureless near-field optical spectroscopy of the type using an AFM and surface enhanced Raman scattering (SERS), and is expected to be equally applicable in cases in which infrared or fluorescence spectroscopy is used. Apertureless near-field optical spectroscopy is a means of performing spatially resolved analyses of chemical compositions of surface regions of nanostructured materials. In apertureless near-field spectroscopy, it is common practice to utilize nanostructured probe tips or nanoparticles (usually of gold) having shapes and dimensions chosen to exploit plasmon resonances so as to increase spectroscopic-signal strengths. To implement the particular prior approach to which the present approach is an alternative, it is necessary to integrate a Raman spectrometer with an AFM and to utilize a special SERS-active probe tip. The resulting instrumentation system is complex, and the tasks of designing and constructing the system and using the system to acquire spectro-chemical information from nanometer-scale regions on a surface are correspondingly demanding.

Near-field multiple traps of paraxial acoustic vortices with strengthened gradient force generated by sector transducer array

Science.gov (United States)

Wang, Qingdong; Li, Yuzhi; Ma, Qingyu; Guo, Gepu; Tu, Juan; Zhang, Dong

2018-01-01

In order to improve the capability of particle trapping close to the source plane, theoretical and experimental studies on near-field multiple traps of paraxial acoustic vortices (AVs) with a strengthened acoustic gradient force (AGF) generated by a sector transducer array were conducted. By applying the integration of point source radiation, numerical simulations for the acoustic fields generated by the sector transducer array were conducted and compared with those produced by the circular transducer array. It was proved that strengthened AGFs of near-field multiple AVs with higher peak pressures and smaller vortex radii could be produced by the sector transducer array with a small topological charge. The axial distributions of the equivalent potential gradient indicated that the AGFs of paraxial AVs in the near field were much higher than those in the far field, and the distances at the near-field vortex antinodes were also proved to be the ideal trapping positions with relatively higher AGFs. With the established 8-channel AV generation system, theoretical studies were also verified by the experimental measurements of pressure and phase for AVs with various topological charges. The formation of near-field multiple paraxial AVs was verified by the cross-sectional circular pressure distributions with perfect phase spirals around central pressure nulls, and was also proved by the vortex nodes and antinodes along the center axis. The favorable results demonstrated the feasibility of generating near-field multiple traps of paraxial AVs with strengthened AGF using the sector transducer array, and suggested the potential applications of close-range particle trapping in biomedical engineering.

Some variations of the Kristallin-I near-field model

Energy Technology Data Exchange (ETDEWEB)

Smith, P A; Curti, E [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1995-11-01

The Kristallin-I project is an integrated analysis of the final disposal of vitrified high-level radioactive waste (HLW) in the crystalline basement of Northern Switzerland. It includes an analysis of the radiological consequences of radionuclide release from a repository. This analysis employs a chain of independent models for the near-field, geosphere and biosphere. In constructing these models, processes are incorporated that are believed to be relevant to repository safety, while other processes are neglected. In the present report, a set of simplified, steady-state models of the near-field is developed to investigate the possible effects of specific processes which are neglected in the time-dependent Kristallin-I near-field model. These processes are neglected, either because (i) they are thought unlikely to occur to a significant degree, or because (ii) they are likely to make a positive contribution to the performance of the near-field barrier to radionuclide migration, but are insufficiently understood to justify incorporating them in a safety assessment. The aim of this report is to investigate whether the arguments for neglecting these processes in the Kristallin-I near-field model can be justified. This work addresses the following topics: - radionuclide transport at the bentonite-host rock interface, - canister settlement, -chemical conditions and radionuclide transport at the glass-bentonite interface. (author) figs., tabs., refs.

Some variations of the Kristallin-I near-field model

International Nuclear Information System (INIS)

Smith, P.A.; Curti, E.

1995-11-01

The Kristallin-I project is an integrated analysis of the final disposal of vitrified high-level radioactive waste (HLW) in the crystalline basement of Northern Switzerland. It includes an analysis of the radiological consequences of radionuclide release from a repository. This analysis employs a chain of independent models for the near-field, geosphere and biosphere. In constructing these models, processes are incorporated that are believed to be relevant to repository safety, while other processes are neglected. In the present report, a set of simplified, steady-state models of the near-field is developed to investigate the possible effects of specific processes which are neglected in the time-dependent Kristallin-I near-field model. These processes are neglected, either because (i) they are thought unlikely to occur to a significant degree, or because (ii) they are likely to make a positive contribution to the performance of the near-field barrier to radionuclide migration, but are insufficiently understood to justify incorporating them in a safety assessment. The aim of this report is to investigate whether the arguments for neglecting these processes in the Kristallin-I near-field model can be justified. This work addresses the following topics: - radionuclide transport at the bentonite-host rock interface, - canister settlement, -chemical conditions and radionuclide transport at the glass-bentonite interface. (author) figs., tabs., refs

Near-field enhanced thermionic energy conversion for renewable energy recycling

Science.gov (United States)

Ghashami, Mohammad; Cho, Sung Kwon; Park, Keunhan

2017-09-01

This article proposes a new energy harvesting concept that greatly enhances thermionic power generation with high efficiency by exploiting the near-field enhancement of thermal radiation. The proposed near-field enhanced thermionic energy conversion (NETEC) system is uniquely configured with a low-bandgap semiconductor cathode separated from a thermal emitter with a subwavelength gap distance, such that a significant amount of electrons can be photoexcited by near-field thermal radiation to contribute to the enhancement of thermionic current density. We theoretically demonstrate that the NETEC system can generate electric power at a significantly lower temperature than the standard thermionic generator, and the energy conversion efficiency can exceed 40%. The obtained results reveal that near-field photoexcitation can enhance the thermionic power output by more than 10 times, making this hybrid system attractive for renewable energy recycling.

Supersonic acoustic intensity with statistically optimized near-field acoustic holography

DEFF Research Database (Denmark)

Fernandez Grande, Efren; Jacobsen, Finn

2011-01-01

The concept of supersonic acoustic intensity was introduced some years ago for estimating the fraction of the flow of energy radiated by a source that propagates to the far field. It differs from the usual (active) intensity by excluding the near-field energy resulting from evanescent waves...... to the information provided by the near-field acoustic holography technique. This study proposes a version of the supersonic acoustic intensity applied to statistically optimized near-field acoustic holography (SONAH). The theory, numerical results and an experimental study are presented. The possibility of using...

Near-field self-interference cancellation and quality of service multicast beamforming in full-duplex

Science.gov (United States)

Wu, Fei; Shao, Shihai; Tang, Youxi

2016-10-01

To enable simultaneous multicast downlink transmit and receive operations on the same frequency band, also known as full-duplex links between an access point and mobile users. The problem of minimizing the total power of multicast transmit beamforming is considered from the viewpoint of ensuring the suppression amount of near-field line-of-sight self-interference and guaranteeing prescribed minimum signal-to-interference-plus-noise-ratio (SINR) at each receiver of the multicast groups. Based on earlier results for multicast groups beamforming, the joint problem is easily shown to be NP-hard. A semidefinite relaxation (SDR) technique with linear program power adjust method is proposed to solve the NP-hard problem. Simulation shows that the proposed method is feasible even when the local receive antenna in nearfield and the mobile user in far-filed are in the same direction.

Method and system for control of upstream flowfields of vehicle in supersonic or hypersonic atmospheric flight

Science.gov (United States)

Daso, Endwell O. (Inventor); Pritchett, II, Victor E. (Inventor); Wang, Ten-See (Inventor); Farr, Rebecca Ann (Inventor)

2012-01-01

The upstream flowfield of a vehicle traveling in supersonic or hypersonic atmospheric flight is actively controlled using attribute(s) experienced by the vehicle. Sensed attribute(s) include pressure along the vehicle's outer mold line, temperature along the vehicle's outer mold line, heat flux along the vehicle's outer mold line, and/or local acceleration response of the vehicle. A non-heated, non-plasma-producing gas is injected into an upstream flowfield of the vehicle from at least one surface location along the vehicle's outer mold line. The pressure of the gas so-injected is adjusted based on the attribute(s) so-sensed.

Non-contact transportation using near-field acoustic levitation

Science.gov (United States)

Ueha; Hashimoto; Koike

2000-03-01

Near-field acoustic levitation, where planar objects 10 kg in weight can levitate stably near the vibrating plate, is successfully applied both to non-contact transportation of objects and to a non-contact ultrasonic motor. Transporting apparatuses and an ultrasonic motor have been fabricated and their characteristics measured. The theory of near-field acoustic levitation both for a piston-like sound source and a flexural vibration source is also briefly described.

Where is The Dark Matter: The Flow-field From 2MASS

Science.gov (United States)

Crook, Aidan; Huchra, J.; Macri, L.; Masters, K.; Jarrett, T.

2009-01-01

We present a map of the flow-field constructed from groups of galaxies in the 2MASS Redshift Survey. Previous efforts have suffered because the underlying surveys either did not penetrate to low galactic latitudes or were not sensitive to elliptical galaxies, thereby missing a significant fraction of the mass. The 2MASS Redshift Survey provides a uniform all-sky magnitude-limited sample in the J, H and Ks bands, 97% complete to Ks10°, sensitive to both ellipticals and spirals. We demonstrate how utilizing the properties of galaxy groups leads to improved predictions of peculiar velocities in the nearby Universe, and use dynamical mass estimates to construct a reliable flow-field to 12,000 km/s. We demonstrate its effectiveness in providing distance estimates, and discuss the advantages of this model over earlier work. With independent knowledge of the peculiar velocity of the Local Group, we discuss the implications for the matter density parameter and bias. This work is supported by a Whiteman Fellowship and NSF grant AST-0406906.

Janus and Huygens Dipoles: Near-Field Directionality Beyond Spin-Momentum Locking

Science.gov (United States)

Picardi, Michela F.; Zayats, Anatoly V.; Rodríguez-Fortuño, Francisco J.

2018-03-01

Unidirectional scattering from circularly polarized dipoles has been demonstrated in near-field optics, where the quantum spin-Hall effect of light translates into spin-momentum locking. By considering the whole electromagnetic field, instead of its spin component alone, near-field directionality can be achieved beyond spin-momentum locking. This unveils the existence of the Janus dipole, with side-dependent topologically protected coupling to waveguides, and reveals the near-field directionality of Huygens dipoles, generalizing Kerker's condition. Circular dipoles, together with Huygens and Janus sources, form the complete set of all possible directional dipolar sources in the far- and near-field. This allows the designing of directional emission, scattering, and waveguiding, fundamental for quantum optical technology, integrated nanophotonics, and new metasurface designs.

A Comparison of Computed and Experimental Flowfields of the RAH-66 Helicopter

Science.gov (United States)

vanDam, C. P.; Budge, A. M.; Duque, E. P. N.

1996-01-01

This paper compares and evaluates numerical and experimental flowfields of the RAH-66 Comanche helicopter. The numerical predictions were obtained by solving the Thin-Layer Navier-Stokes equations. The computations use actuator disks to investigate the main and tail rotor effects upon the fuselage flowfield. The wind tunnel experiment was performed in the 14 x 22 foot facility located at NASA Langley. A suite of flow conditions, rotor thrusts and fuselage-rotor-tail configurations were tested. In addition, the tunnel model and the computational geometry were based upon the same CAD definition. Computations were performed for an isolated fuselage configuration and for a rotor on configuration. Comparisons between the measured and computed surface pressures show areas of correlation and some discrepancies. Local areas of poor computational grid-quality and local areas of geometry differences account for the differences. These calculations demonstrate the use of advanced computational fluid dynamic methodologies towards a flight vehicle currently under development. It serves as an important verification for future computed results.

THz near-field imaging of biological tissues employing synchrotronradiation

Energy Technology Data Exchange (ETDEWEB)

Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried,Daniel

2004-12-23

Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking onto the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical wave guides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about lambda/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 mu-m at about 12 wave numbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin.

The geochemistry of the near-field

International Nuclear Information System (INIS)

McKinley, I.G.

1985-10-01

This report describes a study of the Swiss disposal concept used in 'Project Gewaehr 1985' safety analysis. The main components of the near-field of a high level waste repository are the waste glass matrix, the thick steel canister and the surrounding backfill of compressed bentonite. In this report it is concluded that mineralogical alteration of the backfill will be negligibly small over the million year period considered. Its physical and chemical properties can thus be relied on for such a period. The canister will retain its integrity for > 10/sup 3/ y and thereafter will act as an Eh/pH buffer. The near-field buffers ensure more alkaline and reducing conditions than in the far-field. Complete degradation of the glass matrix will take > 10/sup 5/ years and nuclide release will be limited by their congruent dissolution although it may be further constrained by low solubility. Diffusion of dissolved nuclides through the backfill is so slow that many species decay to insignificance within it. The large uptake capacity of the bentonite also significantly extends the release duration for longer lived, non-solubility limited nuclides thus decreasing output mixima. Possible perturbing factors such as radiolysis and hydrogen production by anoxic corrosion are of little importance but modelling of speciation/solubility in the near-field and, in particular, colloid formation and mobility are identified as areas in which more work is required. Although the main analysis aims to err on the side of conservatism, the extent of such pessimism is assessed in a 'realistic' appraisal of the near-field. This suggests that the engineered barriers will prevent any radiologically significant releases over periods in excess of a million years which would strengthen their role in the multiple barrier safety concept. (author)

Control and near-field detection of surface plasmon interference patterns.

Science.gov (United States)

Dvořák, Petr; Neuman, Tomáš; Břínek, Lukáš; Šamořil, Tomáš; Kalousek, Radek; Dub, Petr; Varga, Peter; Šikola, Tomáš

2013-06-12

The tailoring of electromagnetic near-field properties is the central task in the field of nanophotonics. In addition to 2D optics for optical nanocircuits, confined and enhanced electric fields are utilized in detection and sensing, photovoltaics, spatially localized spectroscopy (nanoimaging), as well as in nanolithography and nanomanipulation. For practical purposes, it is necessary to develop easy-to-use methods for controlling the electromagnetic near-field distribution. By imaging optical near-fields using a scanning near-field optical microscope, we demonstrate that surface plasmon polaritons propagating from slits along the metal-dielectric interface form tunable interference patterns. We present a simple way how to control the resulting interference patterns both by variation of the angle between two slits and, for a fixed slit geometry, by a proper combination of laser beam polarization and inhomogeneous far-field illumination of the structure. Thus the modulation period of interference patterns has become adjustable and new variable patterns consisting of stripelike and dotlike motifs have been achieved, respectively.

Method to improve near-field nonlinearity of a high-power diode laser array on a microchannel cooler

Science.gov (United States)

Zhang, Hongyou; Jia, Yangtao; Cai, Wanshao; Tao, Chunhua; Zah, Chung-en; Liu, Xingsheng

2018-03-01

Due to thermal stress, each emitter in a semiconductor laser bar or array is vertically displaced along the p-n junction; the result is that each emitter is not in a line, called near-field nonlinearity. Near-field nonlinearity along a laser bar (also known as "SMILE" effect) degrades the laser beam brightness, which causes an adverse effect on optical coupling and beam shaping. A large SMILE value causes a large divergence angle after collimation and a wider line after collimation and focusing. We simulate the factors affecting the SMILE value of a high-power diode laser array on a microchannel cooler (MCC). According to the simulation results, we have fabricated a series of laser bars bonded on MCCs with lower SMILE value. After simulation and experiment analysis, we found the key factor to affect SMILE is the deformation of the thin MCC because of the distribution of strain and stress in it. We also decreased the SMILE value of 1-cm-wide full bar AuSn bonded on MCCs from 12 to 1 μm by balancing force on MCC to minimize the deformation.

Asymmetric active nano-particles for directive near-field radiation

DEFF Research Database (Denmark)

Arslanagic, Samel; Thorsen, Rasmus O.

2016-01-01

In this work, we demonstrate the potential of cylindrical active coated nano-particles with certain geometrical asymmetries for the creation of directive near-field radiation. The particles are excited by a near-by magnetic line source, and their performance characteristics are reported in terms...... of radiated power, near-field and power flow distributions as well as the far-field directivity....

Patch near-field acoustic holography: The influence of acoustic contributions from outside the source

DEFF Research Database (Denmark)

Fernandez Grande, Efren; Jacobsen, Finn; Zhang, Yong-Bin

2009-01-01

It is a requirement of conventional Near-field Acoustic Holography that the measurement area covers the entire surface of the source. In the case of Patch Near-field Acoustic Holography (patch NAH), the measurement area can be reduced to cover only a specific area of the source which...... is of particular interest (known as the “patch” or “source patch”). The area of the source beyond this patch is not of interest in the analysis. However, its acoustic output may nevertheless contribute to the total sound field in the measurement plane, and influence the reconstruction of the field close...... to the patch. The purpose of this paper is to investigate how the acoustic radiation from outside the patch area influences the reconstruction of the sound field close to the source. The reconstruction is based on simulated measurements of sound pressure and particle velocity. The methods used in this paper...

Near-field photon wave mechanics in the Lorenz gauge

International Nuclear Information System (INIS)

Keller, Ole

2007-01-01

Optical near-field interactions are studied theoretically in the perspective of photon wave mechanics paying particular attention to the dynamics in the wave-vector time domain. A unitary transformation is used to replace the scalar and longitudinal photon variables by so-called near-field and gauge photon variables. Dynamical equations are established for these types of photon variables, and it is shown that these equations are invariant against gauge transformations within the Lorenz gauge. The near-field photon is absent in the free-field limit, and the gauge photon can be eliminated by a suitable gauge transformation. Implicit solutions for the near-field, gauge, and transverse photon variables are obtained and discussed. The general theory is applied to an investigation of transverse photon propagation in a uniform solid-state plasma dominated by the diamagnetic field-matter interaction. It is found that the diamagnetic response can be incorporated in a quantum mechanical wave equation for a massive transverse photon. The Compton wave number of the massive photon equals the plasma wave number of the electron system. A dynamical equation describing the emission of a massive transverse photon from a mesoscopic source embedded in the plasma is finally established

Maximal near-field radiative heat transfer between two plates

Science.gov (United States)

Nefzaoui, Elyes; Ezzahri, Younès; Drévillon, Jérémie; Joulain, Karl

2013-09-01

Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the radiative heat flux are reported and compared to real materials usually considered in similar studies, silicon carbide and heavily doped silicon in this case. Results are obtained by exact and approximate (in the extreme near-field regime and the electrostatic limit hypothesis) calculations. The two methods are compared in terms of accuracy and CPU resources consumption. Their differences are explained according to a mesoscopic description of nearfield radiative heat transfer. Finally, the frequently assumed hypothesis which states a maximal radiative heat transfer when the two semi-infinite planes are of identical materials is numerically confirmed. Its subsequent practical constraints are then discussed. Presented results enlighten relevant paths to follow in order to choose or design materials maximizing nano-TPV devices performances.

Graphene as a local probe to investigate near-field properties of plasmonic nanostructures

Science.gov (United States)

Wasserroth, Sören; Bisswanger, Timo; Mueller, Niclas S.; Kusch, Patryk; Heeg, Sebastian; Clark, Nick; Schedin, Fredrik; Gorbachev, Roman; Reich, Stephanie

2018-04-01

Light interacting with metallic nanoparticles creates a strongly localized near-field around the particle that enhances inelastic light scattering by several orders of magnitude. Surface-enhanced Raman scattering describes the enhancement of the Raman intensity by plasmonic nanoparticles. We present an extensive Raman characterization of a plasmonic gold nanodimer covered with graphene. Its two-dimensional nature and energy-independent optical properties make graphene an excellent material for investigating local electromagnetic near-fields. We show the localization of the near-field of the plasmonic dimer by spatial Raman measurements. Energy- and polarization-dependent measurements reveal the local near-field resonance of the plasmonic system. To investigate the far-field resonance we perform dark-field spectroscopy and find that near-field and far-field resonance energies differ by 170 meV, much more than expected from the model of a damped oscillator (40 meV).

Light distribution analysis of optical fibre probe-based near-field optical tweezers using FDTD

Energy Technology Data Exchange (ETDEWEB)

Liu, B H; Yang, L J; Wang, Y [School of Mechanical and Electrical Engineering, Harbin Institute of Technology, Heilongjiang, Harbin, 150001 (China)], E-mail: richelaw@163.com

2009-09-01

Optical fibre probe-based near-field optical tweezers overcomes the diffraction limit of conventional optical tweezers, utilizing strong mechanical forces and torque associated with highly enhanced electric fields to trap and manipulate nano-scale particles. Near-field evanescent wave generated at optical fibre probe decays rapidly with the distance that results a significant reduced trapping volume, thus it is necessary to analyze the near-field distribution of optical fibre probe. The finite difference time domain (FDTD) method is applied to characterize the near-field distribution of optical fibre probe. In terms of the distribution patterns, depolarization and polarization, the near-field distributions in longitudinal sections and cross-sections of tapered metal-coated optical fibre probe are calculated. The calculation results reveal that the incident polarized wave becomes depolarized after exiting from the nano-scale aperture of probe. The near-field distribution of the probe is unsymmetrical, and the near-field distribution in the cross-section vertical to the incident polarized wave is different from that in the cross-section parallel to the incident polarized wave. Moreover, the polarization of incident wave has a great impact on the light intensity distribution.

Near-field millimeter - wave imaging of nonmetallic materials

International Nuclear Information System (INIS)

Gopalsami, N.; Bakhtiari, S.; Raptis, A.C.

1996-01-01

A near-field millimeter-wave (mm-wave) imaging system has been designed and built in the 94-GHz range for on-line inspection of nonmetallic (dielectric) materials. The imaging system consists of a transceiver block coupled to an antenna that scans the material to be imaged; a reflector plate is placed behind the material. A quadrature IF mixer in the transceiver block enables measurement of in-phase and quadrature-phase components of reflected signals with respect to the transmitted signal. All transceiver components, with the exception of the Gunn-diode oscillator and antenna, were fabricated in uniform blocks and integrated and packaged into a compact unit (12.7 x 10.2 x 2.5 cm). The objective of this work is to test the applicability of a near-field compact mm-wave sensor for on-line inspection of sheetlike materials such as paper, fabrics, and plastics. This paper presents initial near-field mm-wave images of paper and fabric samples containing known artifacts

FDTD simulated observation of a gold nanorod by scanning near-field optical microscopy

International Nuclear Information System (INIS)

Sawada, Keiji; Maruoka, Teruto; Nakamura, Hiroaki; Tamura, Yuichi; Imura, Kohei; Saiki, Toshiharu; Okamoto, Hiromi

2010-01-01

The optical properties of a gold nanorod were investigated by Imura et. al. using an apertured-type scanning near-field optical microscope (SNOM). The observed transmission image showed an oscillating pattern along the long axis of the nanorod. We obtain the image using the finite-difference time-domain (FDTD) method. Our model includes a nanorod on a glass substrate, a SNOM, and current as a light source. We develop a simple method for including the Drude-Lorentz dispersion relation of Vial et. al. for gold in the FDTD. The oscillating pattern is explained by the total current in the nanorod, tip of the SNOM, and light source. (author)

Phase retrieval in near-field measurements by array synthesis

DEFF Research Database (Denmark)

Wu, Jian; Larsen, Flemming Holm

1991-01-01

The phase retrieval problem in near-field antenna measurements is formulated as an array synthesis problem. As a test case, a particular synthesis algorithm has been used to retrieve the phase of a linear array......The phase retrieval problem in near-field antenna measurements is formulated as an array synthesis problem. As a test case, a particular synthesis algorithm has been used to retrieve the phase of a linear array...

Maximal near-field radiative heat transfer between two plates

OpenAIRE

Nefzaoui, Elyes; Ezzahri, Younès; Drevillon, Jérémie; Joulain, Karl

2013-01-01

International audience; Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the r...

Near-field mapping by laser ablation of PMMA coatings

DEFF Research Database (Denmark)

Fiutowski, J.; Maibohm, C.; Kostiucenko, O.

2011-01-01

The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field...... that the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures....

Sub-nanosecond time-resolved near-field scanning magneto-optical microscope.

Science.gov (United States)

Rudge, J; Xu, H; Kolthammer, J; Hong, Y K; Choi, B C

2015-02-01

We report on the development of a new magnetic microscope, time-resolved near-field scanning magneto-optical microscope, which combines a near-field scanning optical microscope and magneto-optical contrast. By taking advantage of the high temporal resolution of time-resolved Kerr microscope and the sub-wavelength spatial resolution of a near-field microscope, we achieved a temporal resolution of ∼50 ps and a spatial resolution of microscope, the magnetic field pulse induced gyrotropic vortex dynamics occurring in 1 μm diameter, 20 nm thick CoFeB circular disks has been investigated. The microscope provides sub-wavelength resolution magnetic images of the gyrotropic motion of the vortex core at a resonance frequency of ∼240 MHz.

Frequency-selective near-field radiative heat transfer between photonic crystal slabs: a computational approach for arbitrary geometries and materials.

Science.gov (United States)

Rodriguez, Alejandro W; Ilic, Ognjen; Bermel, Peter; Celanovic, Ivan; Joannopoulos, John D; Soljačić, Marin; Johnson, Steven G

2011-09-09

We demonstrate the possibility of achieving enhanced frequency-selective near-field radiative heat transfer between patterned (photonic-crystal) slabs at designable frequencies and separations, exploiting a general numerical approach for computing heat transfer in arbitrary geometries and materials based on the finite-difference time-domain method. Our simulations reveal a tradeoff between selectivity and near-field enhancement as the slab-slab separation decreases, with the patterned heat transfer eventually reducing to the unpatterned result multiplied by a fill factor (described by a standard proximity approximation). We also find that heat transfer can be further enhanced at selective frequencies when the slabs are brought into a glide-symmetric configuration, a consequence of the degeneracies associated with the nonsymmorphic symmetry group.

THz near-field imaging of biological tissues employing synchrotron radiation

International Nuclear Information System (INIS)

Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried, Daniel

2004-01-01

Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking onto the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical wave guides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about lambda/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 mu-m at about 12 wave numbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin

The near-field acoustic levitation of high-mass rotors

International Nuclear Information System (INIS)

Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B.

2014-01-01

Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope

The near-field acoustic levitation of high-mass rotors

Energy Technology Data Exchange (ETDEWEB)

Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)

2014-10-15

Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

The near-field acoustic levitation of high-mass rotors.

Science.gov (United States)

Hong, Z Y; Lü, P; Geng, D L; Zhai, W; Yan, N; Wei, B

2014-10-01

Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

Laser terahertz emission microscopy with near-field probes

DEFF Research Database (Denmark)

Pedersen, Pernille Klarskov; Mittleman, Daniel M.

2016-01-01

Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm.......Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm....

Nanohybrids Near-Field Optical Microscopy: From Image Shift to Biosensor Application

Directory of Open Access Journals (Sweden)

Nayla El-Kork

2016-01-01

Full Text Available Near-Field Optical Microscopy is a valuable tool for the optical and topographic study of objects at a nanometric scale. Nanoparticles constitute important candidates for such type of investigations, as they bear an important weight for medical, biomedical, and biosensing applications. One, however, has to be careful as artifacts can be easily reproduced. In this study, we examined hybrid nanoparticles (or nanohybrids in the near-field, while in solution and attached to gold nanoplots. We found out that they can be used for wavelength modulable near-field biosensors within conditions of artifact free imaging. In detail, we refer to the use of topographic/optical image shift and the imaging of Local Surface Plasmon hot spots to validate the genuineness of the obtained images. In summary, this study demonstrates a new way of using simple easily achievable comparative methods to prove the authenticity of near-field images and presents nanohybrid biosensors as an application.

Review of near-field optics and superlenses for sub-diffraction-limited nano-imaging

Directory of Open Access Journals (Sweden)

Wyatt Adams

2016-10-01

Full Text Available Near-field optics and superlenses for imaging beyond Abbe’s diffraction limit are reviewed. A comprehensive and contemporary background is given on scanning near-field microscopy and superlensing. Attention is brought to recent research leveraging scanning near-field optical microscopy with superlenses for new nano-imaging capabilities. Future research directions are explored for realizing the goal of low-cost and high-performance sub-diffraction-limited imaging systems.

Characterization of near-field optical probes

DEFF Research Database (Denmark)

Vohnsen, Brian; Bozhevolnyi, Sergey I.

1999-01-01

Radiation and collection characteristics of four different near-field optical-fiber probes, namely, three uncoated probes and an aluminium-coated small-aperture probe, are investigated and compared. Their radiation properties are characterized by observation of light-induced topography changes...... in a photo-sensitive film illuminated with the probes, and it is confirmed that the radiated optical field is unambigiously confined only for the coated probe. Near-field optical imaging of a standing evanescent-wave pattern is used to compare the detection characteristics of the probes, and it is concluded...... that, for the imaging of optical-field intensity distributions containing predominantly evanescent-wave components, a sharp uncoated tip is the probe of choice. Complementary results obtained with optical phase-conjugation experiments with he uncoated probes are discussed in relation to the probe...

Near-field Spectroscopy of Surface Plasmons in Flat Gold Nanoparticles

International Nuclear Information System (INIS)

Achermann, Marc; Shuford, Kevin L.; Schatz, George C.; Dahanayaka, D.H.; Bumm, Lloyd A; Klimov, Victor I.

2007-01-01

We use near-field interference spectroscopy with a broadband femtosecond, white-light probe to study local surface plasmon resonances in flat gold nanoparticles (FGNPs). Depending on nanoparticle dimensions, local near-field extinction spectra exhibit none, one, or two resonances in the range of visible wavelengths (1.6-2.6 eV). The measured spectra can be accurately described in terms of interference between the field emitted by the probe aperture and the field reradiated by driven FGNP surface plasmon oscillations. The measured resonances are in good agreement with those predicted by calculations using discrete dipole approximation. We observe that the amplitudes of these resonances are dependent upon the spatial position of the near-field probe, which indicates the possibility of spatially selective excitation of specific plasmon modes

Comparison of two numerical modelling codes for hydraulic and transport calculations in the near-field

International Nuclear Information System (INIS)

Kalin, J.; Petkovsek, B.; Montarnal, Ph.; Genty, A.; Deville, E.; Krivic, J.; Ratej, J.

2011-01-01

In the past years the Slovenian Performance Analysis/Safety Assessment team has performed many generic studies for the future Slovenian low and intermediate level waste repository, most recently a Special Safety Analysis for the Krsko site. The modelling approach was to split the problem into three parts: near-field (detailed model of the repository), far-field (i.e., geosphere) and biosphere. In the Special Safety Analysis the code used to perform the near-field calculations was Hydrus2D. Recently the team has begun a cooperation with the French Commisariat al'Energie Atomique/Saclay (CEA/Saclay) and, as a part of this cooperation, began investigations into using the Alliances numerical platform for near-field calculations in order to compare the overall approach and calculated results. The article presents the comparison between these two codes for a silo-type repository that was considered in the Special Safety Analysis. The physical layout and characteristics of the repository are presented and a hydraulic and transport model of the repository is developed and implemented in Alliances. Some analysis of sensitivity to mesh fineness and to simulation timestep has been preformed and is also presented. The compared quantity is the output flux of radionuclides on the boundary of the model. Finally the results from Hydrus2D and Alliances are compared and the differences and similarities are commented.

Comparison of two numerical modelling codes for hydraulic and transport calculations in the near-field

Energy Technology Data Exchange (ETDEWEB)

Kalin, J., E-mail: jan.kalin@zag.s [Slovenian National Building and Civil Engineering Institute, Dimiceva 12, SI-1000 Ljubljana (Slovenia); Petkovsek, B., E-mail: borut.petkovsek@zag.s [Slovenian National Building and Civil Engineering Institute, Dimiceva 12, SI-1000 Ljubljana (Slovenia); Montarnal, Ph., E-mail: philippe.montarnal@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Genty, A., E-mail: alain.genty@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Deville, E., E-mail: estelle.deville@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Krivic, J., E-mail: jure.krivic@geo-zs.s [Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana (Slovenia); Ratej, J., E-mail: joze.ratej@geo-zs.s [Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana (Slovenia)

2011-04-15

In the past years the Slovenian Performance Analysis/Safety Assessment team has performed many generic studies for the future Slovenian low and intermediate level waste repository, most recently a Special Safety Analysis for the Krsko site. The modelling approach was to split the problem into three parts: near-field (detailed model of the repository), far-field (i.e., geosphere) and biosphere. In the Special Safety Analysis the code used to perform the near-field calculations was Hydrus2D. Recently the team has begun a cooperation with the French Commisariat al'Energie Atomique/Saclay (CEA/Saclay) and, as a part of this cooperation, began investigations into using the Alliances numerical platform for near-field calculations in order to compare the overall approach and calculated results. The article presents the comparison between these two codes for a silo-type repository that was considered in the Special Safety Analysis. The physical layout and characteristics of the repository are presented and a hydraulic and transport model of the repository is developed and implemented in Alliances. Some analysis of sensitivity to mesh fineness and to simulation timestep has been preformed and is also presented. The compared quantity is the output flux of radionuclides on the boundary of the model. Finally the results from Hydrus2D and Alliances are compared and the differences and similarities are commented.

Quantification of source-term profiles from near-field geochemical models

International Nuclear Information System (INIS)

McKinley, I.G.

1985-01-01

A geochemical model of the near-field is described which quantitatively treats the processes of engineered barrier degradation, buffering of aqueous chemistry by solid phases, nuclide solubilization and transport through the near-field and release to the far-field. The radionuclide source-terms derived from this model are compared with those from a simpler model used for repository safety analysis. 10 refs., 2 figs., 2 tabs

Scanning near-field optical microscopy and near-field optical probes: properties, fabrication, and control of parameters

International Nuclear Information System (INIS)

Dryakhlushin, V F; Veiko, V P; Voznesenskii, N B

2007-01-01

A brief review of modern applications of scanning near-field optical (SNO) devices in microscopy, spectroscopy, and lithography is presented in the introduction. The problem of the development of SNO probes, as the most important elements of SNO devices determining their resolution and efficiency, is discussed. Based on the works of the authors, two different methods for fabricating SNO probes by using the adiabatic tapering of an optical fibre are considered: the laser-heated mechanical drawing and chemical etching. A nondestructive optical method for controlling the nanometre aperture of SNO probes is proposed, substantiated, and tested experimentally. The method is based on the reconstruction of a near-field source with the help of a theoretical algorithm of the inverse problem from the experimental far-filed intensity distribution. Some prospects for a further refinement of the construction and technology of SNO probes are discussed. (optical microscopy)

Experimental investigation of the flowfield of an oscillating airfoil

Science.gov (United States)

Panda, J.; Zaman, K. B. M. Q.

1992-01-01

The flowfield of an airfoil oscillated periodically over a wide range of reduced frequencies, 0 less than or = k less than or = 1.6 is studied experimentally at chord Reynolds numbers of R sub c = 22,000 and 44,000. The NACA0012 airfoil is pitched sinusoidally about one quarter chord between angles of attack (alpha) of 5 and 25 degrees. Detailed flow visualization and phase averaged vorticity measurements are carried out for k = 0.2 to document the evolution and the shedding of the dynamic stall vortex (DSV). In addition to the DSV, an intense vortex of opposite sign originates from the trailing edge just when the DSV is shed. After being shed into the wake, the two together take the shape of a large 'mushroom' while being convected away from the airfoil. The unsteady circulation around the airfoil and, therefore, the time varying component of the lift is estimated in a novel way from the shed vorticity flux and is found to be in good agreement with the lift variation reported by others. The delay in the shedding of the DSV with increasing k, as observed by previous researchers, is documented for the full range of k. The DSV, for example, is shed nearly at the maximum alpha of 25 degrees at k = 0.2, but is shed at the minimum alpha of 5 degrees at k = 0.8. At low k, the flowfield appears quasi-steady and the bluff body shedding corresponding to the maximum alpha (25 degrees) dominates the unsteady fluctuations in the wake.

High-Accuracy Spherical Near-Field Measurements for Satellite Antenna Testing

DEFF Research Database (Denmark)

Breinbjerg, Olav

2017-01-01

The spherical near-field antenna measurement technique is unique in combining several distinct advantages and it generally constitutes the most accurate technique for experimental characterization of radiation from antennas. From the outset in 1970, spherical near-field antenna measurements have...... matured into a well-established technique that is widely used for testing antennas for many wireless applications. In particular, for high-accuracy applications, such as remote sensing satellite missions in ESA's Earth Observation Programme with uncertainty requirements at the level of 0.05dB - 0.10d......B, the spherical near-field antenna measurement technique is generally superior. This paper addresses the means to achieving high measurement accuracy; these include the measurement technique per se, its implementation in terms of proper measurement procedures, the use of uncertainty estimates, as well as facility...

Near-Field Antenna Measurements Using Photonic Sensor of Mach-Zehnder Interferometer

Directory of Open Access Journals (Sweden)

Masanobu Hirose

2012-01-01

Full Text Available We have been developing a photonic sensor system to measure the electric near-field distribution at a distance shorter than one wavelength from the aperture of an antenna. The photonic sensor is a type of Mach-Zehnder interferometer and consists of an array antenna of 2.4 mm height and 2 mm width on a LiNbO3 substrate (0.5 mm thickness, 8 mm length, and 3 mm width supported by a glass pipe. The photonic sensor can be considered to be a receiving infinitesimal dipole antenna that is a tiny metallic part printed on a small dielectric plate at microwave frequency. Those physical and electrical features make the photonic sensor attractive when used as a probe for near-field antenna measurements. We have demonstrated that the system can be applied to planar, spherical, and cylindrical near-field antenna measurements without any probe compensation approximately below 10 GHz. We show the theories and the measurements using the photonic sensor in the three near-field antenna measurement methods.

Cosmological models in globally geodesic coordinates. II. Near-field approximation

International Nuclear Information System (INIS)

Liu Hongya

1987-01-01

A near-field approximation dealing with the cosmological field near a typical freely falling observer is developed within the framework established in the preceding paper [J. Math. Phys. 28, xxxx(1987)]. It is found that for the matter-dominated era the standard cosmological model of general relativity contains the Newtonian cosmological model, proposed by Zel'dovich, as its near-field approximation in the observer's globally geodesic coordinate system

Near-field enhanced femtosecond laser nano-drilling of glass substrate

International Nuclear Information System (INIS)

Zhou, Y.; Hong, M.H.; Fuh, J.Y.H.; Lu, L.; Lukyanchuk, B.S.; Wang, Z.B.

2008-01-01

Particle mask assisted near-field enhanced femtosecond laser nano-drilling of transparent glass substrate was demonstrated in this paper. A particle mask was fabricated by self-assembly of spherical 1 μm silica particles on the substrate surface. Then the samples were exposed to femtosecond laser (800 nm, 100 fs) and characterized by field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). The nano-hole array was found on the glass surface. The hole sizes were measured from 200 to 300 nm with an average depth of 150 nm and increased with laser fluence. Non-linear triple-photon absorption and near-field enhancement were the main mechanisms of the nano-feature formation. Calculations based on Mie theory shows an agreement with experiment results. More debris, however, was found at high laser fluence. This can be attributed to the explosion of silica particles because the focusing point is inside the 1 μm particle. The simulation predicts that the focusing point will move outside the particle if the particle size increases. The experiment performed under 6.84 μm silica particles verified that no debris was formed. And for all the samples, no cracks were found on the substrate surface because of ultra-short pulse width of femtosecond laser. This method has potential applications in nano-patterning of transparent glass substrate for nano-structure device fabrication

Shock Tunnel Studies of the Hypersonic Flowfield around the Hypervelocity Ballistic Models with Aerospikes

Science.gov (United States)

Balakalyani, G.; Saravanan, S.; Jagadeesh, G.

Reduced drag and aerodynamic heating are the two basic design requirements for any hypersonic vehicle [1]. The flowfield around an axisymmetric blunt body is characterized by a bow shockwave standing ahead of its nose. The pressure and temperature behind this shock wave are very high. This increased pressure and temperature are responsible for the high levels of drag and aerodynamic heating over the body. In the past, there have been many investigations on the use of aerospikes as a drag reduction tool. These studies on spiked bodies aim at reducing both the drag and aerodynamic heating by modifying the hypersonic flowfield ahead of the nose of the body [2]. However, most of them used very simple configurations to experimentally study the drag reduction using spikes at hypersonic speeds [3] and therefore very little experimental data is available for a realistic geometric configuration. In the present study, the standard AGARD Hypervelocity Ballistic model 1 is used as the test model. The addition of the spike to the blunt body significantly alters the flowfield ahead of the nose, leading to the formation of a low pressure conical recirculation region, thus causing a reduction in drag and wall heat flux [4]. In the present investigation, aerodynamic drag force is measured over the Hypervelocity Ballistic model-1, with and without spike, at a flow enthalpy of 1.7 MJ/kg. The experiments are carried out at a Mach number of 8 and at zero angle of attack. An internally mountable accelerometer based 3-component force balance system is used to measure the aerodynamic forces on the model. Also computational studies are carried out to complement the experiments.

The near-field acoustic levitation for spheres by transducer with concave spherical radiating surface

International Nuclear Information System (INIS)

Liu, Jian Fang; Sun, Xu Guang; Jiao, Xiao Yang; Chen, Hong Xia; Hua, Shun Ming; Zhang, Hong Chun

2013-01-01

To levitate ICF target spheres in the near-field acoustic levitation, a transducer with concave spherical radiating surface and a nearfield acoustic levitation system is established. The concave spherical radiating surface of the transducer is designed by the finite element parametric method. Then the levitation height and levitation perturbation of spheres with different mass and diameters in the near-field acoustic levitation system are tested and discussed in the driving voltage at 400V, 500V and 600V, respectively, when the levitation system is under the resonant frequency. Finally, based on the experimental results, the height formula of the near-field acoustic levitation for spheres is deduced by introducing a coupling coefficient.

The near-field acoustic levitation for spheres by transducer with concave spherical radiating surface

Energy Technology Data Exchange (ETDEWEB)

Liu, Jian Fang; Sun, Xu Guang; Jiao, Xiao Yang; Chen, Hong Xia [Jilin University, Changchun (China); Hua, Shun Ming [Zhejiang University, Ningbo (China); Zhang, Hong Chun [Aviation University of AirForce, Changchun (China)

2013-02-15

To levitate ICF target spheres in the near-field acoustic levitation, a transducer with concave spherical radiating surface and a nearfield acoustic levitation system is established. The concave spherical radiating surface of the transducer is designed by the finite element parametric method. Then the levitation height and levitation perturbation of spheres with different mass and diameters in the near-field acoustic levitation system are tested and discussed in the driving voltage at 400V, 500V and 600V, respectively, when the levitation system is under the resonant frequency. Finally, based on the experimental results, the height formula of the near-field acoustic levitation for spheres is deduced by introducing a coupling coefficient.

Strain-induced modulation of near-field radiative transfer.

Science.gov (United States)

Ghanekar, Alok; Ricci, Matthew; Tian, Yanpei; Gregory, Otto; Zheng, Yi

2018-06-11

In this theoretical study, we present a near-field thermal modulator that exhibits change in radiative heat transfer when subjected to mechanical stress/strain. The device has two terminals at different temperatures separated by vacuum: one fixed and one stretchable. The stretchable side contains one-dimensional grating. When subjected to mechanical strain, the effective optical properties of the stretchable side are affected upon deformation of the grating. This results in modulation of surface waves across the interfaces influencing near-field radiative heat transfer. We show that for a separation of 100 nm, it is possible to achieve 25% change in radiative heat transfer for a strain of 10%.

Estimation of polarization distribution on gold nanorods system from hierarchical features of optical near-field

Science.gov (United States)

Uchiyama, Kazuharu; Nishikawa, Naoki; Nakagomi, Ryo; Kobayashi, Kiyoshi; Hori, Hirokazu

2018-02-01

To design optoelectronic functionalities in nanometer scale based on interactions of electronic system with optical near-fields, it is essential to evaluate the relationship between optical near-fields and their sources. Several theoretical studies have been performed, so far, to analyze such complex relationship to design the interaction fields of several specific scales. In this study, we have performed detailed and high-precision measurements of optical near-field structures woven by a large number of independent polarizations generated in the gold nanorods array under laser light irradiation at the resonant frequency. We have accumulated the multi-layered data of optical near-field imaging at different heights above the planar surface with the resolution of several nm by a STM-assisted scanning near-field optical microscope. Based on these data, we have performed an inverse calculation to estimate the position, direction, and strength of the local polarization buried under the flat surface of the sample. As a result of the inverse operation, we have confirmed that the complexities in the nanometer scale optical near-fields could be reconstructed by combinations of induced polarization in each gold nanorod. We have demonstrated the hierarchical properties of optical near-fields based on spatial frequency expansion and superposition of dipole fields to provide insightful information for applications such for secure multi-layered information storage.

Investigation of optical nanostructures for photovoltaics with near-field scanning microscopy; Untersuchung optischer Nanostrukturen fuer die Photovoltaik mit Nahfeldmikroskopie

Energy Technology Data Exchange (ETDEWEB)

Beckers, Thomas

2011-09-26

Textured and rough surfaces are known to increase light trapping in solar cells significantly. The development and optimization of these nano-structures is essential to improve the energy conversion efficiency of thin-film solar cells. In the past, first research approaches covered classical and macroscopic investigations, e.g. determining the haze or angularly resolved scattering. These methods do not provide precise explanation for the optical improvement of the devices, because layer thicknesses and structure sizes in thin-film solar cells are smaller than the wavelength of visible light. The impact of local nano-structures and their contribution to the local absorption enhancement is not resolved by macroscopic measurements. In this thesis, near-field scanning optical microscopy is introduced as first near-field investigations of nano-structures for photovoltaics. This provides an insight into local optical effects for relevant surfaces of photovoltaic devices. Investigating the distribution of the electric fields in layer stacks is crucial to understand the absorption in solar cells. Evanescent fields, which occur due to total internal reflection at the interfaces, are measurable by near-field scanning optical microscopy and yield important information about local light trapping. Within the framework of this thesis, correlations between local surface structures and optical near-field effects are shown. In this case structure features of randomly textured surfaces, which optimize local light trapping, are identified. It paves the way to connect microscopic optical effects on the surface with the macroscopic performance of thin-film solar cells. Moreover, the measurement yields a 3D illustration of the electric field distribution over the sample surface. It is an important criterion to prove the results of rigorous diffraction theory. An excellent agreement between experiment and simulation is found. The simulations provide an insight into the material, which is

Quantitative Near-field Microscopy of Heterogeneous and Correlated Electron Oxides

Science.gov (United States)

McLeod, Alexander Swinton

Scanning near-field optical microscopy (SNOM) is a novel scanning probe microscopy technique capable of circumventing the conventional diffraction limit of light, affording unparalleled optical resolution (down to 10 nanometers) even for radiation in the infrared and terahertz energy regimes, with light wavelengths exceeding 10 micrometers. However, although this technique has been developed and employed for more than a decade to a qualitatively impressive effect, researchers have lacked a practically quantitative grasp of its capabilities, and its application scope has so far remained restricted by implementations limited to ambient atmospheric conditions. The two-fold objective of this dissertation work has been to address both these shortcomings. The first half of the dissertation presents a realistic, semi-analytic, and benchmarked theoretical description of probe-sample near-field interactions that form the basis of SNOM. Owing its name to the efficient nano-focusing of light at a sharp metallic apex, the "lightning rod model" of probe-sample near-field interactions is mathematically developed from a flexible and realistic scattering formalism. Powerful and practical applications are demonstrated through the accurate prediction of spectroscopic near-field optical contrasts, as well as the "inversion" of these spectroscopic contrasts into a quantitative description of material optical properties. Thus enabled, this thesis work proceeds to present quantitative applications of infrared near-field spectroscopy to investigate nano-resolved chemical compositions in a diverse host of samples, including technologically relevant lithium ion battery materials, astrophysical planetary materials, and invaluable returned extraterrestrial samples. The second half of the dissertation presents the design, construction, and demonstration of a sophisticated low-temperature scanning near-field infrared microscope. This instrument operates in an ultra-high vacuum environment

Enhanced energy transfer by near-field coupling of a nanostructured metamaterial with a graphene-covered plate

International Nuclear Information System (INIS)

Chang, Jui-Yung; Yang, Yue; Wang, Liping

2016-01-01

Coupled surface plasmon/phonon polaritons and hyperbolic modes are known to enhance radiative transfer across nanometer vacuum gaps but usually require identical materials. It becomes crucial to achieve strong near-field energy transfer between dissimilar materials for applications like near-field thermophotovoltaic and thermal rectification. In this work, we theoretically demonstrate enhanced near-field radiative transfer between a nanostructured metamaterial emitter and a graphene-covered planar receiver. Strong near-field coupling with two orders of magnitude enhancement in the spectral heat flux is achieved at the gap distance of 20 nm. By carefully selecting the graphene chemical potential and doping levels of silicon nanohole emitter and silicon plate receiver, the total near-field radiative heat flux can reach about 500 times higher than the far-field blackbody limit between 400 K and 300 K. The physical mechanism is elucidated by the near-field surface plasmon coupling with fluctuational electrodynamics and dispersion relations. The effects of graphene chemical potential, emitter and receiver doping levels, and vacuum gap distance on the near-field coupling and radiative energy transfer are analyzed in detail. - Highlights: • Near-field radiative transfer between a metamaterial and a graphene-covered plate is studied. • Effective medium theory with uniaxial optics is employed to model nanohole metamaterials. • Enhancement by 2 orders is found between dissimilar materials with graphene coating. • Extraordinary coupling of the nanostructured emitter with graphene is elucidated. • Effects of doping level of silicon and graphene chemical potential are investigated.

Electrical alignment of antenna coordinate system in a planar near-field setup

DEFF Research Database (Denmark)

Mynster, Anders P.; Nielsen, Jeppe Majlund; Pivnenko, Sergey

2011-01-01

In this paper, a simple and efficient electrical alignment procedure known as flip-test is adapted and applied to check and correct two errors in the mechanical setup of a planar near-field system: the mis-pointing of the z-axis of the antenna coordinate system with respect to the scan plane...... and the displacement of the center point of the scan plane with respect to the z-axis of the antenna coordinate system. Simulations of the errors and their correction algorithms were carried out with different models of antennas composed of Hertzian dipoles and an optimum algorithm was then selected. The proposed...

Errors of first-order probe correction for higher-order probes in spherical near-field antenna measurements

DEFF Research Database (Denmark)

Laitinen, Tommi; Nielsen, Jeppe Majlund; Pivnenko, Sergiy

2004-01-01

An investigation is performed to study the error of the far-field pattern determined from a spherical near-field antenna measurement in the case where a first-order (mu=+-1) probe correction scheme is applied to the near-field signal measured by a higher-order probe.......An investigation is performed to study the error of the far-field pattern determined from a spherical near-field antenna measurement in the case where a first-order (mu=+-1) probe correction scheme is applied to the near-field signal measured by a higher-order probe....

Gold nanocone probes for near-field scanning optical microscopy

Energy Technology Data Exchange (ETDEWEB)

Zeeb, Bastian; Schaefer, Christian; Nill, Peter; Fleischer, Monika; Kern, Dieter P. [Institute of Applied Physics, University of Tuebingen, Auf der Morgenstelle 10, 72076 Tuebingen (Germany)

2010-07-01

Apertureless near-field scanning optical microscopy (ANSOM) provides the possibility to collect simultaneously high-resolution topographical and sub-diffraction limited optical information from a surface. When optically excited, the scanning probes act as optical antennae with a strong near-field enhancement near the tip apex. Spatial resolution and optical near-field enhancement depend strongly on the properties and geometry of the scanning probe - in particular on very sharp tip radii. Various possibilities for fabricating good antennae have been pursued. Most commonly, scanning probes consist of electrochemically etched gold wires which are sharp but not well-defined in geometry. We present two different approaches for ultra sharp and well-defined antennae based upon fabricating gold nanocones with a tip radius smaller than 10 nm which can be used in ANSOM. A transfer process is presented that can be used to attach single gold nanocones to non-metallic probes such as sharp glass fiber tips. Alternatively, new processes are presented to fabricate cones directly on pillars of different materials such as silicon or bismuth, which can be applied to cantilever tips for ANSOM scanning applications.

Non-Intrusive Optical Diagnostic Methods for Flowfield Characterization

Science.gov (United States)

Tabibi, Bagher M.; Terrell, Charles A.; Spraggins, Darrell; Lee, Ja. H.; Weinstein, Leonard M.

1997-01-01

Non-intrusive optical diagnostic techniques such as Electron Beam Fluorescence (EBF), Laser-Induced Fluorescence (LIF), and Focusing Schlieren (FS) have been setup for high-speed flow characterization and large flowfield visualization, respectively. Fluorescence emission from the First Negative band of N2(+) with the (0,0) vibration transition (at lambda =391.44 nm) was obtained using the EBF technique and a quenching rate of N2(+)* molecules by argon gas was reported. A very high sensitivity FS system was built and applied in the High-Speed Flow Generator (HFG) at NASA LaRC. A LIF system is available at the Advanced Propulsion Laboratory (APL) on campus and a plume exhaust velocity measurement, measuring the Doppler shift from lambda = 728.7 nm of argon gas, is under way.

Near-field NanoThermoMechanical memory

International Nuclear Information System (INIS)

Elzouka, Mahmoud; Ndao, Sidy

2014-01-01

In this letter, we introduce the concept of NanoThermoMechanical Memory. Unlike electronic memory, a NanoThermoMechanical memory device uses heat instead of electricity to record, store, and recover data. Memory function is achieved through the coupling of near-field thermal radiation and thermal expansion resulting in negative differential thermal resistance and thermal latching. Here, we demonstrate theoretically via numerical modeling the concept of near-field thermal radiation enabled negative differential thermal resistance that achieves bistable states. Design and implementation of a practical silicon based NanoThermoMechanical memory device are proposed along with a study of its dynamic response under write/read cycles. With more than 50% of the world's energy losses being in the form of heat along with the ever increasing need to develop computer technologies which can operate in harsh environments (e.g., very high temperatures), NanoThermoMechanical memory and logic devices may hold the answer

Flowfield analysis of modern helicopter rotors in hover by Navier-Stokes method

Science.gov (United States)

Srinivasan, G. R.; Raghavan, V.; Duque, E. P. N.

1991-01-01

The viscous, three-dimensional, flowfields of UH60 and BERP rotors are calculated for lifting hover configurations using a Navier-Stokes computational fluid dynamics method with a view to understand the importance of planform effects on the airloads. In this method, the induced effects of the wake, including the interaction of tip vortices with successive blades, are captured as a part of the overall flowfield solution without prescribing any wake models. Numerical results in the form of surface pressures, hover performance parameters, surface skin friction and tip vortex patterns, and vortex wake trajectory are presented at two thrust conditions for UH60 and BERP rotors. Comparison of results for the UH60 model rotor show good agreement with experiments at moderate thrust conditions. Comparison of results with equivalent rectangular UH60 blade and BERP blade indicates that the BERP blade, with an unconventional planform, gives more thrust at the cost of more power and a reduced figure of merit. The high thrust conditions considered produce severe shock-induced flow separation for UH60 blade, while the BERP blade develops more thrust and minimal separation. The BERP blade produces a tighter tip vortex structure compared with the UH60 blade. These results and the discussion presented bring out the similarities and differences between the two rotors.

Near-field heat transfer between graphene/hBN multilayers

Science.gov (United States)

Zhao, Bo; Guizal, Brahim; Zhang, Zhuomin M.; Fan, Shanhui; Antezza, Mauro

2017-06-01

We study the radiative heat transfer between multilayer structures made by a periodic repetition of a graphene sheet and a hexagonal boron nitride (hBN) slab. Surface plasmons in a monolayer graphene can couple with hyperbolic phonon polaritons in a single hBN film to form hybrid polaritons that can assist photon tunneling. For periodic multilayer graphene/hBN structures, the stacked metallic/dielectric array can give rise to a further effective hyperbolic behavior, in addition to the intrinsic natural hyperbolic behavior of hBN. The effective hyperbolicity can enable more hyperbolic polaritons that enhance the photon tunneling and hence the near-field heat transfer. However, the hybrid polaritons on the surface, i.e., surface plasmon-phonon polaritons, dominate the near-field heat transfer between multilayer structures when the topmost layer is graphene. The effective hyperbolic regions can be well predicted by the effective medium theory (EMT), thought EMT fails to capture the hybrid surface polaritons and results in a heat transfer rate much lower compared to the exact calculation. The chemical potential of the graphene sheets can be tuned through electrical gating and results in an additional modulation of the heat transfer. We found that the near-field heat transfer between multilayer structures does not increase monotonously with the number of layers in the stack, which provides a way to control the heat transfer rate by the number of graphene layers in the multilayer structure. The results may benefit the applications of near-field energy harvesting and radiative cooling based on hybrid polaritons in two-dimensional materials.

Terahertz Near-Field Imaging Using Enhanced Transmission through a Single Subwavelength Aperture

Science.gov (United States)

Ishihara, Kunihiko; Ikari, Tomofumi; Minamide, Hiroaki; Shikata, Jun-ichi; Ohashi, Keishi; Yokoyama, Hiroyuki; Ito, Hiromasa

2005-07-01

We demonstrate terahertz (THz) near-field imaging using resonantly enhanced transmission of THz-wave radiation (λ˜ 200 μm) through a bull’s eye structure (a single subwavelength aperture surrounded by concentric periodic grooves in a metal plate). The bull’s eye structure shows extremely large enhanced transmission, which has the advantage for a single subwavelength aperture. The spatial resolution for the bull’s eye structure (with an aperture diameter d=100 μm) is evaluated in the near-field region, and a resolution of 50 μm (corresponding to λ/4) is achieved. We obtain the THz near-field images of the subwavelength metal pattern with a spatial resolution below the diffraction limit.

A review of models for near-field exposure pathways of chemicals in consumer products

DEFF Research Database (Denmark)

Huang, Lei; Ernstoff, Alexi; Fantke, Peter

2017-01-01

able to quantify the multiple transfers of chemicals from products used near-field to humans. The present review therefore aims at an in-depth overview of modeling approaches for near-field chemical release and human exposure pathways associated with consumer products. It focuses on lower......-tier, mechanistic models suitable for life cycle assessments (LCA), chemical alternative assessment (CAA) and high-throughput screening risk assessment (HTS). Chemicals in a product enter the near-field via a defined “compartment of entry”, are transformed or transferred to adjacent compartments, and eventually end......Exposure to chemicals in consumer products has been gaining increasing attention, with multiple studies showing that near-field exposures from products is high compared to far-field exposures. Regarding the numerous chemical-product combinations, there is a need for an overarching review of models...

Superresolution Near-field Imaging with Surface Waves

KAUST Repository

Fu, Lei; Liu, Zhaolun; Schuster, Gerard T.

2017-01-01

We present the theory for near-field superresolution imaging with surface waves and time reverse mirrors (TRMs). Theoretical formulas and numerical results show that applying the TRM operation to surface waves in an elastic half-space can achieve

THz near-field imaging of biological tissues employing synchrotron radiation (Invited Paper)

Science.gov (United States)

Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried, Daniel

2005-04-01

Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking on to the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical waveguides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about λ/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 μm at about 12 wavenumbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06 and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin.

Closed-Form Algorithm for 3-D Near-Field OFDM Signal Localization under Uniform Circular Array.

Science.gov (United States)

Su, Xiaolong; Liu, Zhen; Chen, Xin; Wei, Xizhang

2018-01-14

Due to its widespread application in communications, radar, etc., the orthogonal frequency division multiplexing (OFDM) signal has become increasingly urgent in the field of localization. Under uniform circular array (UCA) and near-field conditions, this paper presents a closed-form algorithm based on phase difference for estimating the three-dimensional (3-D) location (azimuth angle, elevation angle, and range) of the OFDM signal. In the algorithm, considering that it is difficult to distinguish the frequency of the OFDM signal's subcarriers and the phase-based method is always affected by errors of the frequency estimation, this paper employs sparse representation (SR) to obtain the super-resolution frequencies and the corresponding phases of subcarriers. Further, as the phase differences of the adjacent sensors including azimuth angle, elevation angle and range parameters can be expressed as indefinite equations, the near-field OFDM signal's 3-D location is obtained by employing the least square method, where the phase differences are based on the average of the estimated subcarriers. Finally, the performance of the proposed algorithm is demonstrated by several simulations.

Robust Nearfield Wideband Beamforming Design Based on Adaptive-Weighted Convex Optimization

Directory of Open Access Journals (Sweden)

Guo Ye-Cai

2017-01-01

Full Text Available Nearfield wideband beamformers for microphone arrays have wide applications in multichannel speech enhancement. The nearfield wideband beamformer design based on convex optimization is one of the typical representatives of robust approaches. However, in this approach, the coefficient of convex optimization is a constant, which has not used all the freedom provided by the weighting coefficient efficiently. Therefore, it is still necessary to further improve the performance. To solve this problem, we developed a robust nearfield wideband beamformer design approach based on adaptive-weighted convex optimization. The proposed approach defines an adaptive-weighted function by the adaptive array signal processing theory and adjusts its value flexibly, which has improved the beamforming performance. During each process of the adaptive updating of the weighting function, the convex optimization problem can be formulated as a SOCP (Second-Order Cone Program problem, which could be solved efficiently using the well-established interior-point methods. This method is suitable for the case where the sound source is in the nearfield range, can work well in the presence of microphone mismatches, and is applicable to arbitrary array geometries. Several design examples are presented to verify the effectiveness of the proposed approach and the correctness of the theoretical analysis.

Principles of planar near-field antenna measurements

CERN Document Server

Gregson, Stuart; Parini, Clive

2007-01-01

This single volume provides a comprehensive introduction and explanation of both the theory and practice of 'Planar Near-Field Antenna Measurement' from its basic postulates and assumptions, to the intricacies of its deployment in complex and demanding measurement scenarios.

Characterization of nearfield rock - A basis for comparison of repository concepts

International Nuclear Information System (INIS)

Pusch, R.; Hoekmark, H.

1991-12-01

The hydraulic conductivity of the nearfield rock controls the rate of wetting of adjacent buffer material as well as the rate of degradation of its smectite content and of the transport of radionuclides from the buffer/rock interface. Comparison of different repository concepts with respect to the function of the nearfield rock requires a common rock structure model, which is suggested in the report. Applying this model and 2D and 3D numerical calculations for evaluation of stress-induced structural changes, major differences between the three concepts VDH, KBS3 and VLH concerning the hydraulic conductivity of the nearfield have been identified. The importance of the orientation of the excavations turns out to be particularly obvious. Further development of the rock structure model is concluded to offer ways of quantifying more accurately the damaging effects of blasting and TBM-drilling. (au)

CFD analyses of coolant channel flowfields

Science.gov (United States)

Yagley, Jennifer A.; Feng, Jinzhang; Merkle, Charles L.

1993-01-01

The flowfield characteristics in rocket engine coolant channels are analyzed by means of a numerical model. The channels are characterized by large length to diameter ratios, high Reynolds numbers, and asymmetrical heating. At representative flow conditions, the channel length is approximately twice the hydraulic entrance length so that fully developed conditions would be reached for a constant property fluid. For the supercritical hydrogen that is used as the coolant, the strong property variations create significant secondary flows in the cross-plane which have a major influence on the flow and the resulting heat transfer. Comparison of constant and variable property solutions show substantial differences. In addition, the property variations prevent fully developed flow. The density variation accelerates the fluid in the channels increasing the pressure drop without an accompanying increase in heat flux. Analyses of the inlet configuration suggest that side entry from a manifold can affect the development of the velocity profile because of vortices generated as the flow enters the channel. Current work is focused on studying the effects of channel bifurcation on the flow field and the heat transfer characteristics.

Panel discussion on near-field coupled processes with emphasis on performance assessment

International Nuclear Information System (INIS)

Codell, R.B.; Baca, R.G.; Ahola, M.P.

1996-01-01

The presentations in this panel discussion involve the general topic of near-field coupled processes and postclosure performance assessment with an emphasis on rock mechanics. The potential impact of near-field rock mass deformation on repository performance was discussed, as well as topics including long term excavation deterioration, the performance of geologic seals, and coupled processes concerning rock mechanics in performance assessments

Fabrication of a novel nano-probe slide for near-field optical microscopy

International Nuclear Information System (INIS)

Yim, Sang-Youp; Jeang, Eun-Hee; Lee, Jae-Hoon; Park, Seung-Han; Cho, Kyu-Man

2004-01-01

A novel probe structure, which can act as a planar nano-probe slide for near-field microscopy, was proposed and fabricated. Sub-wavelength apertures on a Si substrate are successfully produced by means of standard photolithography techniques with properly selected masks. In particular, the anisotropic etching characteristics of Si substrate and the hardness of the Si 3 N 4 film are utilized. Probe-to-probe scanning of the fabricated near-field nano-probe slide shows sub-wavelength confinement of light and comparable throughput to the conventional optical fiber probe. We also show that the nano-probe slide can serve as a supporting base and a sub-wavelength aperture to obtain the near-field photoluminescence spectra of a limited number of CdSe nanocrystals.

Near-field visualization of plasmonic lenses: an overall analysis of characterization errors

Directory of Open Access Journals (Sweden)

Jing Wang

2015-10-01

Full Text Available Many factors influence the near-field visualization of plasmonic structures that are based on perforated elliptical slits. Here, characterization errors are experimentally analyzed in detail from both fabrication and measurement points of view. Some issues such as geometrical parameter, probe–sample surface interaction, misalignment, stigmation, and internal stress, have influence on the final near-field probing results. In comparison to the theoretical ideal case of near-field probing of the structures, numerical calculation is carried out on the basis of a finite-difference and time-domain (FDTD algorithm so as to support the error analyses. The analyses performed on the basis of both theoretical calculation and experimental probing can provide a helpful reference for the researchers probing their plasmonic structures and nanophotonic devices.

Effects of a power and photon energy of incident light on near-field etching properties

Science.gov (United States)

Yatsui, T.; Saito, H.; Nishioka, K.; Leuschel, B.; Soppera, O.; Nobusada, K.

2017-12-01

We developed a near-field etching technique for realizing an ultra-flat surfaces of various materials and structures. To elucidate the near-field etching properties, we have investigated the effects of power and the photon energy of the incident light. First, we established theoretically that an optical near-field with photon energy lower than the absorption edge of the molecules can induce molecular vibrations. We used nanodiamonds to study the power dependence of the near-field etching properties. From the topological changes of the nanodiamonds, we confirmed the linear-dependence of the etching volume with the incident power. Furthermore, we studied the photon energy dependence using TiO2 nanostriped structures, which revealed that a lower photon energy results in a lower etching rate.

Optical measurement of acoustic radiation pressure of the near-field acoustic levitation through transparent object

OpenAIRE

Nakamura, Satoshi; Furusawa, Toshiaki; Sasao, Yasuhiro; Katsura, Kogure; Naoki, Kondo

2013-01-01

It is known that macroscopic objects can be levitated for few to several hundred micrometers by near-field acoustic field and this phenomenon is called near-field acoustic levitation (NFAL). Although there are various experiments conducted to measure integrated acoustic pressure on the object surface, up to now there was no direct method to measure pressure distribution. In this study we measured the acoustic radiation pressure of the near-field acoustic levitation via pressure-sensitive paint.

Near-field radiation between graphene-covered carbon nanotube arrays

Energy Technology Data Exchange (ETDEWEB)

Zhang, Richard Z.; Liu, Xianglei; Zhang, Zhuomin M., E-mail: zhuomin.zhang@me.gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2015-05-15

It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT) arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP). In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level) that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

Near-field scanning optical microscopy based nanostructuring of glass

International Nuclear Information System (INIS)

Chimmalgi, A; Hwang, D J; Grigoropoulos, C P

2007-01-01

Nanofabrication, at lateral resolutions beyond the capability of conventional optical lithography techniques, is demonstrated here. Femtosecond laser was used in conjunction with Near-field Scanning Optical Microscopes (NSOMs) to nanostructure thin metal films. Also, the possibility of using these nanostructured metal films as masks to effectively transfer the pattern to the underlying substrate by wet etching process is shown. Two different optical nearfiled processing schemes were studied for near-field nanostructuring. In the first scheme, local field enhancement in the near-field of a scanning probe microscope (SPM) probe tip irradiated with femtosecond laser pulses was utilized (apertureless NSOM mode) and as a second approach, femtosecond laser beam was spatially confined by cantilevered NSOM fiber tip (apertured NOSM mode). The minimized heat- and shock-affected areas introduced during ultrafast laser based machining process, allows processing of even high conductivity thin metal films with minimized formation of any interfacial compounds between the metal films and the underlying substrate. Potential applications of this method may be in the fields of nanolithography, nanofluidics, nanoscale chemical and gas sensors, high-density data storage, nano-opto-electronics, as well as biotechnology related applications

Preparation of non-spherical particles by shell-shield etching for near-field nanopatterning

International Nuclear Information System (INIS)

Ye, Jian; Liesbet, Lagae

2014-01-01

The shape of polymer particles plays an important role in determining their function. In this paper, we describe a simple and unconventional method called shell-shield etching (SSE) that allows us to prepare freestanding submicrometer- or micrometer-sized polymer particles with various shapes. By precisely varying the time of ultraviolet ozone treatment under the partial shielding effect of the silica shell, we controllably reshape polymer spheres into symmetry-reduced polymer peaches, mushrooms, bowls, and plates. Finite difference time domain simulations indicate that the non-spherical particles obtained from the SSE method might have potential for near-field nanopatterning applications. (papers)

Near-Field Enhanced Photochemistry of Single Molecules in a Scanning Tunneling Microscope Junction.

Science.gov (United States)

Böckmann, Hannes; Gawinkowski, Sylwester; Waluk, Jacek; Raschke, Markus B; Wolf, Martin; Kumagai, Takashi

2018-01-10

Optical near-field excitation of metallic nanostructures can be used to enhance photochemical reactions. The enhancement under visible light illumination is of particular interest because it can facilitate the use of sunlight to promote photocatalytic chemical and energy conversion. However, few studies have yet addressed optical near-field induced chemistry, in particular at the single-molecule level. In this Letter, we report the near-field enhanced tautomerization of porphycene on a Cu(111) surface in a scanning tunneling microscope (STM) junction. The light-induced tautomerization is mediated by photogenerated carriers in the Cu substrate. It is revealed that the reaction cross section is significantly enhanced in the presence of a Au tip compared to the far-field induced process. The strong enhancement occurs in the red and near-infrared spectral range for Au tips, whereas a W tip shows a much weaker enhancement, suggesting that excitation of the localized plasmon resonance contributes to the process. Additionally, using the precise tip-surface distance control of the STM, the near-field enhanced tautomerization is examined in and out of the tunneling regime. Our results suggest that the enhancement is attributed to the increased carrier generation rate via decay of the excited near-field in the STM junction. Additionally, optically excited tunneling electrons also contribute to the process in the tunneling regime.

New developments in near-field acoustic holography

NARCIS (Netherlands)

Roozen, N.B.; Geerlings, A.C.; Verhaar, B.T.; Vliegenthart, T.

2007-01-01

In the field of noise-control engineering, information about the individual strength, andlocation, of the most dominant sources is of vital importance. This information allows theacoustic engineer to take effective measures in his effort to reduce the emitted acoustic noiselevels. Near-field

Method of Characteristic (MOC) Nozzle Flowfield Solver - User’s Guide and Input Manual Version 2.0

Science.gov (United States)

2018-01-01

TECHNICAL REPORT RDMR-SS-17-13 METHOD OF CHARACTERISTIC (MOC) NOZZLE FLOWFIELD SOLVER—USER’S GUIDE AND INPUT MANUAL VERSION 2.0 Kevin D. Kennedy...1 II. PROGRAM READS AND WRITES ...2 B. Program Reads .................................................................................................. 4 C. Program Writes

The biogeochemical behaviour of U(VI) in the simulated near-field of a low-level radioactive waste repository

International Nuclear Information System (INIS)

Fox, James R.; Mortimer, Robert J.G.; Lear, Gavin; Lloyd, Jonathan R.; Beadle, Ian; Morris, Katherine

2006-01-01

Microbial processes have the potential to affect the mobility of radionuclides, including U in radioactive wastes. A range of geochemical, molecular biological and mineralogical techniques were applied to investigate stable element biogeochemistry and U solubility in the simulated 'near-field' (or local environment) of a low-level radioactive waste (LLW) repository. The experiments used a microbial inoculum from the trench disposal area of the UK LLW repository at Drigg, Cumbria, England, in combination with a synthetic trench leachate representing the local environment at the Drigg site. In batch culture experiments in the absence of U, a classic redox progression of terminal electron accepting processes (TEAPs) occurred in the order NO 3 - , Fe(III) and SO 4 2- reduction. When 126μM U was added to the system as U(VI) aq , up to 80% was reduced to U(IV) by the indigenous microbial consortium. The U(IV) was retained in solution in these experiments, most likely by complexation with citrate present in the experimental medium. No U(VI) aq was reduced in sterile cultures, confirming that U(VI) aq reduction was microbially mediated. Interestingly, when U(VI) aq was present, the progression of TEAPs was altered. The rate of Fe(III) reduction slowed compared to experiments without U(VI) aq , and SO 4 reduction occurred at the same time as U(VI) reduction. Finally, an experiment where SO 4 2- -reducing microorgansisms were inhibited by Na molybdate showed no ingrowth of sulfide minerals, but U(VI) reduction continued in this experiment. This suggested that sulfide minerals did not play a significant role in abiotically reducing U(VI) in these systems, and that metal-reducing microorganisms were dominant in mediating U(VI) reduction. Bacteria closely related to microorganisms found in engineered and U-contaminated environments dominated in the experiments. Denaturing gradient gel electrophoresis (DGGE) on 16SrRNA products amplified from broad specificity primers showed

Near-field strong coupling of single quantum dots.

Science.gov (United States)

Groß, Heiko; Hamm, Joachim M; Tufarelli, Tommaso; Hess, Ortwin; Hecht, Bert

2018-03-01

Strong coupling and the resultant mixing of light and matter states is an important asset for future quantum technologies. We demonstrate deterministic room temperature strong coupling of a mesoscopic colloidal quantum dot to a plasmonic nanoresonator at the apex of a scanning probe. Enormous Rabi splittings of up to 110 meV are accomplished by nanometer-precise positioning of the quantum dot with respect to the nanoresonator probe. We find that, in addition to a small mode volume of the nanoresonator, collective coherent coupling of quantum dot band-edge states and near-field proximity interaction are vital ingredients for the realization of near-field strong coupling of mesoscopic quantum dots. The broadband nature of the interaction paves the road toward ultrafast coherent manipulation of the coupled quantum dot-plasmon system under ambient conditions.

Intercostal high intensity focused ultrasound for liver ablation: The influence of beam shaping on sonication efficacy and near-field risks

Energy Technology Data Exchange (ETDEWEB)

Greef, M. de, E-mail: m.degreef@umcutrecht.nl; Wijlemans, J. W.; Bartels, L. W.; Moonen, C. T. W.; Ries, M. [Imaging Division, University Medical Center Utrecht, Utrecht 3508GA (Netherlands); Schubert, G.; Koskela, J. [Philips Healthcare, Vantaa FI-01511 (Finland)

2015-08-15

Purpose: One of the major issues in high intensity focused ultrasound ablation of abdominal lesions is obstruction of the ultrasound beam by the thoracic cage. Beam shaping strategies have been shown by several authors to increase focal point intensity while limiting rib exposure. However, as rib obstruction leaves only part of the aperture available for energy transmission, conserving total emitted acoustic power, the intensity in the near-field tissues inherently increases after beam shaping. Despite of effective rib sparing, those tissues are therefore subjected to increased risk of thermal damage. In this study, for a number of clinically representative intercostal sonication geometries, modeling clinically available hardware, the effect of beam shaping on both the exposure of the ribs and near-field to acoustic energy was evaluated and the implications for the volumetric ablation rate were addressed. Methods: A relationship between rib temperature rise and acoustic energy density was established by means of in vivo MR thermometry and simulations of the incident acoustic energy for the corresponding anatomies. This relationship was used for interpretation of rib exposure in subsequent numerical simulations in which rib spacing, focal point placement, and the focal point trajectory were varied. The time required to heat a targeted region to 65 °C was determined without and with the application of beam shaping. The required sonication time was used to calculate the acoustic energy density at the fat–muscle interface and at the surface of the ribs. At the fat–muscle interface, exposure was compared to available literature data and rib exposure was interpreted based on the earlier obtained relation between measured temperature rise and simulated acoustic energy density. To estimate the volumetric ablation rate, the cool-down time between periods of energy exposure was estimated using a time-averaged power limit of 100 kJ/h. Results: At the level of the ribs

The long term behaviour of the near-field barrier surrounding a deep underground repository

International Nuclear Information System (INIS)

1992-02-01

This report describes research to identify the factors which govern or influence the long-term behaviour of the near-field of a nuclear waste repository. The near-field components include the engineered barriers and the natural rock mass although the behaviour of the rock mass is of greater significance over the long-term. The factors which govern the near-field behaviour consist of the processes which operate, and the properties or parameters of the rock mass which might be modified by them. The methods which are available for the prediction of the near-field behaviour have been identified, and the emphasis on computer based methods is noted. Summary details of generic computer techniques are provided for different process modelling requirements. An attempt is made to indicate how different processes will be important at various stages during the life of the repository and how the evaluation of performance assessment process modelling requires input from empirical models and the results of other process predictions. (Author)

Geochemical evolution of the L/ILW near-field

International Nuclear Information System (INIS)

Kosakowski, G.; Berner, U.; Wieland, E.; Glaus, M.; Degueldre, C.

2014-10-01

The deep geological repository for low- and intermediate-level radioactive waste (L/ILW) contains large amounts of cement based materials used for waste conditioning, tunnel support and the backfill of cavities. The waste inventory is composed of a wide range of organic and inorganic materials. This study describes the spatial and temporal geochemical evolution of the cementitious near-field, and the interactions with the technical barriers and the surrounding host rock. This evolution is governed by several coupled processes, an important one being the development of saturation by groundwater ingress from the host rock. Saturation of the near-field is controlled by the inflow of water from the host rock, by the transport of dissolved gases from the near-field into the host rock and in the engineered gas transport system, and by the transport of humidity in the gas phase. The production of gas by anoxic corrosion of metals and by microbial degradation of organic wastes consumes water. The mineral reactions which give rise to concrete degradation, such as carbonation or alkali-silica-aggregate reactions may also consume or produce water. The first phase of cementitious near-field degradation, which persists only for a short period of time, is related to the hydration of cement minerals. The pore water has a pH of 13 or even higher because of the high content of dissolved alkali hydroxides. A constant pH of 12.5 determines the second phase of the cement degradation. The alkali concentration is reduced by mineral reactions and/or solute transport. This phase persists for a long time. In the third phase the portlandite is completely dissolved due to the reaction with silicates/aluminates present in the near-field and carbonate in the groundwater of the host rock or associated with reactive waste materials. The pore water is in equilibrium with calcium-silicate-hydrates (C-S-H) which gives rise to a pH value near 11 or lower. The Ca/Si ratio of C-S-H changes towards

Geochemical evolution of the L/ILW near-field

Energy Technology Data Exchange (ETDEWEB)

Kosakowski, G.; Berner, U.; Wieland, E.; Glaus, M.; Degueldre, C.

2014-10-15

The deep geological repository for low- and intermediate-level radioactive waste (L/ILW) contains large amounts of cement based materials used for waste conditioning, tunnel support and the backfill of cavities. The waste inventory is composed of a wide range of organic and inorganic materials. This study describes the spatial and temporal geochemical evolution of the cementitious near-field, and the interactions with the technical barriers and the surrounding host rock. This evolution is governed by several coupled processes, an important one being the development of saturation by groundwater ingress from the host rock. Saturation of the near-field is controlled by the inflow of water from the host rock, by the transport of dissolved gases from the near-field into the host rock and in the engineered gas transport system, and by the transport of humidity in the gas phase. The production of gas by anoxic corrosion of metals and by microbial degradation of organic wastes consumes water. The mineral reactions which give rise to concrete degradation, such as carbonation or alkali-silica-aggregate reactions may also consume or produce water. The first phase of cementitious near-field degradation, which persists only for a short period of time, is related to the hydration of cement minerals. The pore water has a pH of 13 or even higher because of the high content of dissolved alkali hydroxides. A constant pH of 12.5 determines the second phase of the cement degradation. The alkali concentration is reduced by mineral reactions and/or solute transport. This phase persists for a long time. In the third phase the portlandite is completely dissolved due to the reaction with silicates/aluminates present in the near-field and carbonate in the groundwater of the host rock or associated with reactive waste materials. The pore water is in equilibrium with calcium-silicate-hydrates (C-S-H) which gives rise to a pH value near 11 or lower. The Ca/Si ratio of C-S-H changes towards

Photocurrent mapping of near-field optical antenna resonances

KAUST Repository

Barnard, Edward S.; Pala, Ragip A.; Brongersma, Mark L.

2011-01-01

An increasing number of photonics applications make use of nanoscale optical antennas that exhibit a strong, resonant interaction with photons of a specific frequency. The resonant properties of such antennas are conventionally characterized by far-field light-scattering techniques. However, many applications require quantitative knowledge of the near-field behaviour, and existing local field measurement techniques provide only relative, rather than absolute, data. Here, we demonstrate a photodetector platform that uses a silicon-on-insulator substrate to spectrally and spatially map the absolute values of enhanced fields near any type of optical antenna by transducing local electric fields into photocurrent. We are able to quantify the resonant optical and materials properties of nanoscale (∼50nm) and wavelength-scale (∼1μm) metallic antennas as well as high-refractive-index semiconductor antennas. The data agree well with light-scattering measurements, full-field simulations and intuitive resonator models. © 2011 Macmillan Publishers Limited. All rights reserved.

Photocurrent mapping of near-field optical antenna resonances

KAUST Repository

Barnard, Edward S.

2011-08-21

An increasing number of photonics applications make use of nanoscale optical antennas that exhibit a strong, resonant interaction with photons of a specific frequency. The resonant properties of such antennas are conventionally characterized by far-field light-scattering techniques. However, many applications require quantitative knowledge of the near-field behaviour, and existing local field measurement techniques provide only relative, rather than absolute, data. Here, we demonstrate a photodetector platform that uses a silicon-on-insulator substrate to spectrally and spatially map the absolute values of enhanced fields near any type of optical antenna by transducing local electric fields into photocurrent. We are able to quantify the resonant optical and materials properties of nanoscale (∼50nm) and wavelength-scale (∼1μm) metallic antennas as well as high-refractive-index semiconductor antennas. The data agree well with light-scattering measurements, full-field simulations and intuitive resonator models. © 2011 Macmillan Publishers Limited. All rights reserved.

Characteristics of near-field earthquake ground motion

International Nuclear Information System (INIS)

Kim, H. K.; Choi, I. G.; Jeon, Y. S.; Seo, J. M.

2002-01-01

The near-field ground motions exhibit special response characteristics that are different from those of ordinary ground motions in the velocity and displacement response. This study first examines the characteristics of near-field ground motion depending on fault directivity and fault normal and parallel component. And the response spectra of the near field ground motion are statistically processed, and are compared with the Regulatory Guide 1.60 spectrum that is present design spectrum of the nuclear power plant. The response spectrum of the near filed ground motions shows large spectral velocity and displacement in the low frequency range. The spectral accelerations of near field ground motion are greatly amplified in the high frequency range for the rock site motions, and in the low frequency range for the soil site motions. As a result, the near field ground motion effects should be considered in the seismic design and seismic safety evaluation of the nuclear power plant structures and equipment

Far- and near-field second-harmonic imaging of ferroelectric domain walls

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Pedersen, K.; Skettrup, Torben

1998-01-01

Domain walls in periodically poled ferroelectric LiNbO3 crystals are observed with both far- and near-field imaging techniques that make use of second harmonic generation in the transition regions between neighbouring domains. Second harmonic images of domain walls represent bright lines of about.......5 micrometers in width (as measured with the near-field microscope) for the polarization of the second harmonic radiation perpendicular to the domain walls. Origin and selection rules for the constrast in second harmonic images of domain walls are discussed....

Graphene-on-Silicon Near-Field Thermophotovoltaic Cell

NARCIS (Netherlands)

Svetovoy, V. B.; Palasantzas, G.

2014-01-01

A graphene layer on top of a dielectric can dramatically influence the ability of the material for radiative heat transfer. This property of graphene is used to improve the performance and reduce costs of near-field thermophotovoltaic cells. Instead of low-band-gap semiconductors it is proposed to

Biological applications of near-field scanning optical microscopy

NARCIS (Netherlands)

Moers, M.H.P.; Moers, Marco H.P.; Ruiter, A.G.T.; Jalocha, A.; Jalocha, Alain; van Hulst, N.F.

1995-01-01

Near-field Scanning Optical Microscopy (NSOM) is a true optical microscopic technique allowing fluorescence, absorption, reflection and polarization contrast with the additional advantage of nanometer lateral resolution, unlimited by diffraction and operation at ambient conditions. NSOM based on

Very high-accuracy calibration of radiation pattern and gain of a near-field probe

DEFF Research Database (Denmark)

Pivnenko, Sergey; Nielsen, Jeppe Majlund; Breinbjerg, Olav

2014-01-01

In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission of the Europ...

Fast Near-Field Calculation for Volume Integral Equations for Layered Media

DEFF Research Database (Denmark)

Kim, Oleksiy S.; Meincke, Peter; Breinbjerg, Olav

2005-01-01

. Afterwards, the scattered electric field can be easily computed at a regular rectangular grid on any horizontal plane us-ing a 2-dimensional FFT. This approach provides significant speedup in the near-field calculation in comparison to a straightforward numerical evaluation of the ra-diation integral since......An efficient technique based on the Fast Fourier Transform (FFT) for calculating near-field scattering by dielectric objects in layered media is presented. A higher or-der method of moments technique is employed to solve the volume integral equation for the unknown induced volume current density...

Plasmonic superfocusing on metallic tips for near-field optical imaging and spectroscopy

Science.gov (United States)

Neacsu, Catalin C.; Olmon, Rob; Berweger, Samuel; Kappus, Alexandria; Kirchner, Friedrich; Ropers, Claus; Saraf, Lax; Raschke, Markus B.

2008-03-01

Realization of localized light sources through nonlocal excitation is important in the context of plasmon photonics, molecular sensing, and in particular near-field optical techniques. Here, the efficient conversion of propagating surface plasmons, launched on the shaft of a scanning probe tip, into localized plasmon at the apex provides a true nanoconfined light source. Focused ion beam milling is used to generate periodic surface nanostructures on the tip shaft that allow for tailoring the plasmon excitation. Using ultrashort visible and mid-IR transients the dynamics of the propagation and subsequent scattered emission is characterized. The strong field enhancement and spatial field confinement at the apex is demonstrated studying the coupling of the tip in near-field interaction with a flat sample surface. It is used in scattering near-field spectroscopic imaging (s-SNOM) to probe surface nanostructures with spatial resolution down to 10 nm.

Near-field light design with colloidal quantum dots for photonics and plasmonics.

Science.gov (United States)

Kress, Stephan J P; Richner, Patrizia; Jayanti, Sriharsha V; Galliker, Patrick; Kim, David K; Poulikakos, Dimos; Norris, David J

2014-10-08

Colloidal quantum-dots are bright, tunable emitters that are ideal for studying near-field quantum-optical interactions. However, their colloidal nature has hindered their facile and precise placement at desired near-field positions, particularly on the structured substrates prevalent in plasmonics. Here, we use high-resolution electro-hydrodynamic printing (quantum dots on both flat and structured substrates with a few nanometer precision. We also demonstrate that the autofocusing capability of the printing method enables placement of quantum dots preferentially at plasmonic hot spots. We exploit this control and design diffraction-limited photonic and plasmonic sources with arbitrary wavelength, shape, and intensity. We show that simple far-field illumination can excite these near-field sources and generate fundamental plasmonic wave-patterns (plane and spherical waves). The ability to tailor subdiffraction sources of plasmons with quantum dots provides a complementary technique to traditional scattering approaches, offering new capabilities for nanophotonics.

Benchmark Modeling of the Near-Field and Far-Field Wave Effects of Wave Energy Arrays

Energy Technology Data Exchange (ETDEWEB)

Rhinefrank, Kenneth E; Haller, Merrick C; Ozkan-Haller, H Tuba

2013-01-26

high-resolution (fine scale, very near-field) fluid/structure interaction simulations of buoy motions, as well as array-scale, phase-resolving wave scattering simulations. These modeling efforts will utilize state-of-the-art research quality models, which have not yet been brought to bear on this complex problem of large array wave/structure interaction problem.

Mathematical Modeling of Air Flowfield at Urban Environment: the Case of Road Network at the Historical Centre of Kifissia's Municipality

Science.gov (United States)

Papakonstantinou, K.; Belias, C.

2008-09-01

The present paper refers to the numerical analysis of air flowfield at urban environments and the conducting thermal comfort after the evaluation of the examined space using CFD methods, taking into account bioclimatic principles at the architectural design. More specially, the paper draws attention to the physical procedures governing air movement at an urban environment (a road network) at Kifissia (a Municipality of north Athens), trying to form them in such way that will lead to the thermal comfort of the area's users. The study presents a mathematical model, implemented in a general computer code that can provide detailed information on velocity, prevailing in three-dimensional spaces of any geometrical complexity. Turbulent flow is simulated and buoyancy effects are taken into account. This simulation procedure is intended to contribute to the effort towards designing urban environments, using thermal comfort criteria at the bioclimatic design. A computer model of this kind will provide the architects or the environmental engineers with powerful and economical means of evaluating alternative spaces' designs.

Simulation of water movement and NaCl transport

International Nuclear Information System (INIS)

Li Xun; Zheng Zhihong; Yang Zeping

2008-01-01

Modeling of water flow and solute transport in the near-field of a high-level radioactive waste repository with TOUGH2 is done. The results show that salt accumulation in buffer material is not so significant, precipitation does not occur throughout the period covered by our simualtions. Further more, the changeable law of volumetric water content, liquid velocity and dissolved concentration of sodium chloride with simulated time or distance are attained, which is the base of understanding evolvement of near-field. (authors)

Study on the near-field non-linearity (SMILE) of high power diode laser arrays

Science.gov (United States)

Zhang, Hongyou; Jia, Yangtao; Li, Changxuan; Zah, Chung-en; Liu, Xingsheng

2018-02-01

High power laser diodes have been found a wide range of industrial, space, medical applications, characterized by high conversion efficiency, small size, light weight and a long lifetime. However, due to thermal induced stress, each emitter in a semiconductor laser bar or array is displaced along p-n junction, resulting of each emitter is not in a line, called Near-field Non-linearity. Near-field Non-linearity along laser bar (also known as "SMILE") determines the outcome of optical coupling and beam shaping [1]. The SMILE of a laser array is the main obstacle to obtain good optical coupling efficiency and beam shaping from a laser array. Larger SMILE value causes a larger divergence angle and a wider line after collimation and focusing, respectively. In this letter, we simulate two different package structures based on MCC (Micro Channel Cooler) with Indium and AuSn solders, including the distribution of normal stress and the SMILE value. According to the theoretical results, we found the distribution of normal stress on laser bar shows the largest in the middle and drops rapidly near both ends. At last, we did another experiment to prove that the SMILE value of a laser bar was mainly affected by the die bonding process, rather than the operating condition.

Design of a Scaled Model for Experimental Flowfield Studies of Louvered Plate Fins.

Science.gov (United States)

Springer, Marlow E.; Thole, Karen A.

1997-11-01

The optimization of compact heat exchangers maximizing heat transfer while minimizing pressure drop is important for many industrial applications. Because the dominant thermal resistance for most air-and-water or air-and-oil heat exchangers occurs on the air side, an understanding of the flowfield on the air side is needed to further optimize the heat exchanger. Louvered plate fin heat exchangers are used not only to increase the convective heat transfer surface area, but also to initiate the growth of multiple boundary layers. There is also evidence that vortex shedding occurs from the trailing edge of the louvers, which would increase heat transfer. Computational fluid dynamics models have been used to design a scaled up model of a louvered plate fin geometry representative of what would occur in a compact heat exchanger. The current model has a louver angle of 27^circ and a louver-to-fin pitch ratio of 1.31. The same technique can be used to design models for other geometries. Critical issues in the design include endwall spacings to maintain a straight inlet flow, and the required number of louver rows to capture the periodic nature of a heat exchanger with perhaps hundreds of rows. Within the louver passages, measurements of mean and time-resolved velocities to characterize the mean flowfield and vortex shedding have been obtained using laser Doppler velocimetry.

Spectral tuning of near-field radiative heat transfer by graphene-covered metasurfaces

Science.gov (United States)

Zheng, Zhiheng; Wang, Ao; Xuan, Yimin

2018-03-01

When two gratings are respectively covered by a layer of graphene sheet, the near-field radiative heat transfer between two parallel gratings made of silica (SiO2) could be greatly improved. As the material properties of doped silicon (n-type doping concentration is 1020 cm-3, marked as Si-20) and SiO2 differ greatly, we theoretically investigate the near-field radiative heat transfer between two parallel graphene-covered gratings made of Si-20 to explore some different phenomena, especially for modulating the spectral properties. The radiative heat flux between two parallel bulks made of Si-20 can be enhanced by using gratings instead of bulks. When the two gratings are respectively covered by a layer of graphene sheet, the radiative heat flux between two gratings made of Si-20 can be further enhanced. By tuning graphene chemical potential μ and grating filling factor f, due to the interaction between surface plasmon polaritons (SPPs) of graphene sheets and grating structures, the spectral properties of the radiative heat flux between two parallel graphene-covered gratings can be effectively regulated. This work will develop and supplement the effects of materials on the near-field radiative heat transfer for this kind of system configuration, paving a way to modulate the spectral properties of near-field radiative heat transfer.

Development of a backscattering type ultraviolet apertureless near-field scanning optical microscope.

Science.gov (United States)

Kwon, Sangjin; Jeong, Hyun; Jeong, Mun Seok; Jeong, Sungho

2011-08-01

A backscattering type ultraviolet apertureless near-field scanning optical microscope (ANSOM) for the correlated measurement of topographical and optical characteristics of photonic materials with high optical resolution was developed. The near-field Rayleigh scattering image of GaN covered with periodic submicron Cr dots showed that optical resolution around 40 nm was achievable. By measuring the tip scattered photoluminescence of InGaN/GaN multi quantum wells, the applicability of the developed microscope for high resolution fluorescence measurement was also demonstrated.

Time-resolved ultraviolet near-field scanning optical microscope for characterizing photoluminescence lifetime of light-emitting devices.

Science.gov (United States)

Park, Kyoung-Duck; Jeong, Hyun; Kim, Yong Hwan; Yim, Sang-Youp; Lee, Hong Seok; Suh, Eun-Kyung; Jeong, Mun Seok

2013-03-01

We developed a instrument consisting of an ultraviolet (UV) near-field scanning optical microscope (NSOM) combined with time-correlated single photon counting, which allows efficient observation of temporal dynamics of near-field photoluminescence (PL) down to the sub-wavelength scale. The developed time-resolved UV NSOM system showed a spatial resolution of 110 nm and a temporal resolution of 130 ps in the optical signal. The proposed microscope system was successfully demonstrated by characterizing the near-field PL lifetime of InGaN/GaN multiple quantum wells.

Building Practical Apertureless Scanning Near-Field Microscopy

Science.gov (United States)

Gungordu, M. Zeki

The fundamental objective of this study is to establish a functional, practical apertureless type scanning near-field optical microscope, and to figure out the working mechanism behind it. Whereas a far-field microscope can measure the propagating field's components, this gives us little information about the features of the sample. The resolution is limited to about half of the wavelength of the illuminating light. On the other hand, the a-SNOM system enables achieving non-propagating components of the field, which provides more details about the sample's features. It is really difficult to measure because the amplitude of this field decays exponentially when the tip is moved away from the sample. The sharpness of the tip is the only limitation for resolution of the a-SNOM system. Consequently, the sharp tips are achieved by using electrochemical etching, and these tips are used to detect near-field signal. Separating the weak a-SNOM system signals from the undesired background signal, the higher demodulation background suppression is utilized by lock-in detection.

Optical near-field studies of waveguiding organic nanofibers by angular dependent excitation

DEFF Research Database (Denmark)

Maibohm, Christian

.                    2) Institute of General Physics, Russian Academy of Science, 119991 Moscow, Russia. Abstract:   Single crystalline organic nanofibers of para-phenylene are grown in UHV by MBE and dipole assisted self-assembly. In the optical far-field the fluorescence from a single nanofiber is spectrally well...... defined and highly polarized. By UV excitation in a fluorescence microscope it has also been shown that nanofibers have waveguiding properties. To further characterize the waveguiding properties the optical near-field has to be investigated. This is done by transferring nanofibers to an quartz half sphere...... where they are excited by the evanescent wave from a total internal reflected UV laser. The optical near-field is probed by the fiber tip of a SNOM (scanning near-field optical microscope). In the setup it is possible to change the angle of incidence of the excitation laser i.e. change the k...

Optical detection of ultrasound using an apertureless near-field scanning optical microscopy system

Science.gov (United States)

Ahn, Phillip; Zhang, Zhen; Sun, Cheng; Balogun, Oluwaseyi

2013-01-01

Laser ultrasonics techniques are power approaches for non-contact generation and detection of high frequency ultrasound on a local scale. In these techniques, optical diffraction limits the spatial information that can be accessed from a measurement. In order to improve the lateral spatial resolution, we incorporate an apertureless near-field scanning optical microscope (aNSOM) into laser ultrasonics setup for local detection of laser generated ultrasound. The aNSOM technique relies on the measurement of a weak backscattered near-field light intensity resulting from the oblique illumination of a nanoscale probe-tip positioned close to a sample surface. We enhance the optical near-field intensity by coupling light to surface plasmon polaritons (SPPs) on the shaft of an atomic force microscopy (AFM) cantilever. The SPPs propagate down the AFM shaft, localize at the tip apex, and are backscattered to the far-field when the separation distance between the probe tip and the sample surface is comparable to the probe-tip radius. The backscattered near-field intensity is dynamically modulated when an ultrasonic wave arrives at the sample surface leading to a transient change in the tip-sample separation distance. We present experimental results detailing measurement of broadband and narrowband laser generated ultrasound in solids with frequencies reaching up to 180 MHz range.

A New Method for Analyzing Near-Field Faraday Probe Data in Hall Thrusters

Science.gov (United States)

Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

2013-01-01

This paper presents a new method for analyzing near-field Faraday probe data obtained from Hall thrusters. Traditional methods spawned from far-field Faraday probe analysis rely on assumptions that are not applicable to near-field Faraday probe data. In particular, arbitrary choices for the point of origin and limits of integration have made interpretation of the results difficult. The new method, called iterative pathfinding, uses the evolution of the near-field plume with distance to provide feedback for determining the location of the point of origin. Although still susceptible to the choice of integration limits, this method presents a systematic approach to determining the origin point for calculating the divergence angle. The iterative pathfinding method is applied to near-field Faraday probe data taken in a previous study from the NASA-300M and NASA-457Mv2 Hall thrusters. Since these two thrusters use centrally mounted cathodes the current density associated with the cathode plume is removed before applying iterative pathfinding. A procedure is presented for removing the cathode plume. The results of the analysis are compared to far-field probe analysis results. This paper ends with checks on the validity of the new method and discussions on the implications of the results.

The status of near-field modelling

International Nuclear Information System (INIS)

Apted, M.J.

1993-01-01

The near-field of a high-level nuclear waste repository consists of the waste itself and of the man-made barriers engineered around it (Engineered Barrier System, EBS). The conceptual and mathematical models of repositories and EBS, and the state of the air of performance assessment of waste repositories with EBS are discussed at the meeting. 18 individual items have been indexed and abstracted for the INIS database. (R.P.)

Near-field thermal radiation between hyperbolic metamaterials: Graphite and carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Liu, X. L.; Zhang, R. Z.; Zhang, Z. M., E-mail: zhuomin.zhang@me.gatech.edu [G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2013-11-18

The near-field radiative heat transfer for two hyperbolic metamaterials, namely, graphite and vertically aligned carbon nanotubes (CNTs), is investigated. Graphite is a naturally existing uniaxial medium, while CNT arrays can be modeled as an effective anisotropic medium. Different hyperbolic modes can be separately supported by these materials in certain infrared regions, resulting in a strong enhancement in near-field heat transfer. It is predicted that the heat flux between two CNT arrays can exceed that between SiC plates at any vacuum gap distance and is about 10 times higher with a 10 nm gap.

Nanospectrofluorometry inside single living cell by scanning near-field optical microscopy

Science.gov (United States)

Lei, F. H.; Shang, G. Y.; Troyon, M.; Spajer, M.; Morjani, H.; Angiboust, J. F.; Manfait, M.

2001-10-01

Near-field fluorescence spectra with subdiffraction limit spatial resolution have been taken in the proximity of mitochondrial membrane inside breast adenocarcinoma cells (MCF7) treated with the fluorescent dye (JC-1) by using a scanning near-field optical microscope coupled with a confocal laser microspectrofluorometer. The probe-sample distance control is based on a piezoelectric bimorph shear force sensor having a static spring constant k=5 μN/nm and a quality factor Q=40 in a physiological medium of viscosity η=1.0 cp. The sensitivity of the force sensor has been tested by imaging a MCF7 cell surface.

Graphene-assisted near-field radiative heat transfer between corrugated polar materials

International Nuclear Information System (INIS)

Liu, X. L.; Zhang, Z. M.

2014-01-01

Graphene has attracted great attention in nanoelectronics, optics, and energy harvesting. Here, the near-field radiative heat transfer between graphene-covered corrugated silica is investigated based on the exact scattering theory. It is found that graphene can improve the radiative heat flux between silica gratings by more than one order of magnitude and alleviate the performance sensitivity to lateral shift. The underlying mechanism is mainly attributed to the improved photon tunneling of modes away from phonon resonances. Besides, coating with graphene leads to nonlocal radiative transfer that breaks Derjaguin's proximity approximation and enables corrugated silica to outperform bulk silica in near-field radiation.

Near-field effects of asteroid impacts in deep water

Energy Technology Data Exchange (ETDEWEB)

Gisler, Galen R [Los Alamos National Laboratory; Weaver, Robert P [Los Alamos National Laboratory; Gittings, Michael L [Los Alamos National Laboratory

2009-06-11

Our previous work has shown that ocean impacts of asteroids below 500 m in diameter do not produce devastating long-distance tsunamis. Nevertheless, a significant portion of the ocean lies close enough to land that near-field effects may prove to be the greatest danger from asteroid impacts in the ocean. Crown splashes and central jets that rise up many kilometres into the atmosphere can produce, upon their collapse, highly non-linear breaking waves that could devastate shorelines within a hundred kilometres of the impact site. We present illustrative calculations, in two and three dimensions, of such impacts for a range of asteroid sizes and impact angles. We find that, as for land impacts, the greatest dangers from oceanic impacts are the short-term near-field, and long-term atmospheric effects.

Application of Chimera Grid Scheme to Combustor Flowfields at all Speeds

Science.gov (United States)

Yungster, Shaye; Chen, Kuo-Huey

1997-01-01

A CFD method for solving combustor flowfields at all speeds on complex configurations is presented. The approach is based on the ALLSPD-3D code which uses the compressible formulation of the flow equations including real gas effects, nonequilibrium chemistry and spray combustion. To facilitate the analysis of complex geometries, the chimera grid method is utilized. To the best of our knowledge, this is the first application of the chimera scheme to reacting flows. In order to evaluate the effectiveness of this numerical approach, several benchmark calculations of subsonic flows are presented. These include steady and unsteady flows, and bluff-body stabilized spray and premixed combustion flames.

Sub-wavelength imaging by depolarization in a reflection near-field optical microscope using an uncoated fiber probe

DEFF Research Database (Denmark)

Madsen, Steen; Bozhevolnyi, Sergey I.; Hvam, Jørn Märcher

1998-01-01

We present a reflection scanning near-field optical microscope utilizing counter-directional light propagation in an uncoated fiber probe, cross-polarized detection and shear-force feedback. Topographical and near-field optical imaging with a scanning speed of up to 10 mu m/s and a lateral...... resolution better than 40 nm are demonstrated with a latex projection test sample. Determination of the optical resolution as well as correlation between topographical and near-field optical images are discussed. (C) 1998 Elsevier Science B.V....

Double phi-Step theta-Scanning Technique for Spherical Near-Field Antenna Measurements

DEFF Research Database (Denmark)

Laitinen, Tommi

2008-01-01

Probe-corrected spherical near-field antenna measurements with an arbitrary probe set certain requirements on an applicable scanning technique. The computational complexity of the general high-order probe correction technique for an arbitrary probe, that is based on the Phi scanning, is O(N4...... a specific double Phi-step thetas scanning technique for spherical near-field antenna measurements. This technique not only constitutes an alternative spherical scanning technique, but it also enables formulating an associated probe correction technique for arbitrary probes with the computational complexity...

Near-Field Imaging of Free Carriers in ZnO Nanowires with a Scanning Probe Tip Made of Heavily Doped Germanium

Science.gov (United States)

Sakat, Emilie; Giliberti, Valeria; Bollani, Monica; Notargiacomo, Andrea; Pea, Marialilia; Finazzi, Marco; Pellegrini, Giovanni; Hugonin, Jean-Paul; Weber-Bargioni, Alexander; Melli, Mauro; Sassolini, Simone; Cabrini, Stefano; Biagioni, Paolo; Ortolani, Michele; Baldassarre, Leonetta

2017-11-01

A novel scanning probe tip made of heavily doped semiconductor is fabricated and used instead of standard gold-coated tips in infrared scattering-type near-field microscopy. Midinfrared near-field microscopy experiments are conducted on ZnO nanowires with a lateral resolution better than 100 nm, using tips made of heavily electron-doped germanium with a plasma frequency in the midinfrared (plasma wavelength of 9.5 μ m ). Nanowires embedded in a dielectric matrix are imaged at two wavelengths, 11.3 and 8.0 μ m , above and below the plasma wavelength of the tips. An opposite sign of the imaging contrasts between the nanowire and the dielectric matrix is observed at the two infrared wavelengths, indicating a clear role of the free-electron plasma in the heavily doped germanium tip in building the imaging contrast. Electromagnetic simulations with a multispherical dipole model accounting for the finite size of the tip are well consistent with the experiments. By comparison of the simulated and measured imaging contrasts, an estimate for the local free-carrier density in the investigated ZnO nanowires in the low 1019 cm-3 range is retrieved. The results are benchmarked against the scattering intensity and phase maps obtained on the same sample with a gold-coated probe tip in pseudoheterodyne detection mode.

Design of an electrically small circularly polarised turnstile antenna and its application to near-field wireless power transfer

DEFF Research Database (Denmark)

Yoon, Ick-Jae; Ling, Hao

2014-01-01

An electrically small circularly polarised antenna is designed and applied to near-field wireless power transfer as a means of alleviating orientation dependence. The antenna is miniaturised from a spl lambda//2-turnstile antenna by utilising the top loading and multiple folding techniques. A loc...... performance is verified in the far field. The power transfer efficiency is then examined in the near field via simulation and measurement. It is shown that the designed circularly polarised antenna is effective in mitigating orientation dependence down to a distance of 0.2λ.......An electrically small circularly polarised antenna is designed and applied to near-field wireless power transfer as a means of alleviating orientation dependence. The antenna is miniaturised from a spl lambda//2-turnstile antenna by utilising the top loading and multiple folding techniques. A local...... numerical search is used to determine the optimal antenna dimensions to achieve good axial ratio and impedance matching. The resulting design has a kr of 0.67 and shows good circular polarisation characteristic with a 3% axial ratio bandwidth. The designed antenna is fabricated and its circular polarisation...

Navier-Stokes Aerodynamic Simulation of the V-22 Osprey on the Intel Paragon MPP

Science.gov (United States)

Vadyak, Joseph; Shrewsbury, George E.; Narramore, Jim C.; Montry, Gary; Holst, Terry; Kwak, Dochan (Technical Monitor)

1995-01-01

The paper will describe the Development of a general three-dimensional multiple grid zone Navier-Stokes flowfield simulation program (ENS3D-MPP) designed for efficient execution on the Intel Paragon Massively Parallel Processor (MPP) supercomputer, and the subsequent application of this method to the prediction of the viscous flowfield about the V-22 Osprey tiltrotor vehicle. The flowfield simulation code solves the thin Layer or full Navier-Stoke's equation - for viscous flow modeling, or the Euler equations for inviscid flow modeling on a structured multi-zone mesh. In the present paper only viscous simulations will be shown. The governing difference equations are solved using a time marching implicit approximate factorization method with either TVD upwind or central differencing used for the convective terms and central differencing used for the viscous diffusion terms. Steady state or Lime accurate solutions can be calculated. The present paper will focus on steady state applications, although time accurate solution analysis is the ultimate goal of this effort. Laminar viscosity is calculated using Sutherland's law and the Baldwin-Lomax two layer algebraic turbulence model is used to compute the eddy viscosity. The Simulation method uses an arbitrary block, curvilinear grid topology. An automatic grid adaption scheme is incorporated which concentrates grid points in high density gradient regions. A variety of user-specified boundary conditions are available. This paper will present the application of the scalable and superscalable versions to the steady state viscous flow analysis of the V-22 Osprey using a multiple zone global mesh. The mesh consists of a series of sheared cartesian grid blocks with polar grids embedded within to better simulate the wing tip mounted nacelle. MPP solutions will be shown in comparison to equivalent Cray C-90 results and also in comparison to experimental data. Discussions on meshing considerations, wall clock execution time

Convergence analysis in near-field imaging

International Nuclear Information System (INIS)

Bao, Gang; Li, Peijun

2014-01-01

This paper is devoted to the mathematical analysis of the direct and inverse modeling of the diffraction by a perfectly conducting grating surface in the near-field regime. It is motivated by our effort to analyze recent significant numerical results, in order to solve a class of inverse rough surface scattering problems in near-field imaging. In a model problem, the diffractive grating surface is assumed to be a small and smooth deformation of a plane surface. On the basis of the variational method, the direct problem is shown to have a unique weak solution. An analytical solution is introduced as a convergent power series in the deformation parameter by using the transformed field and Fourier series expansions. A local uniqueness result is proved for the inverse problem where only a single incident field is needed. On the basis of the analytic solution of the direct problem, an explicit reconstruction formula is presented for recovering the grating surface function with resolution beyond the Rayleigh criterion. Error estimates for the reconstructed grating surface are established with fully revealed dependence on such quantities as the surface deformation parameter, measurement distance, noise level of the scattering data, and regularity of the exact grating surface function. (paper)

Investigating chaotic wake dynamics past a flapping airfoil and the role of vortex interactions behind the chaotic transition

Science.gov (United States)

Bose, Chandan; Sarkar, Sunetra

2018-04-01

The present study investigates the complex vortex interactions in two-dimensional flow-field behind a symmetric NACA0012 airfoil undergoing a prescribed periodic pitching-plunging motion in low Reynolds number regime. The flow-field transitions from periodic to chaotic through a quasi-periodic route as the plunge amplitude is gradually increased. This study unravels the role of the complex interactions that take place among the main vortex structures in making the unsteady flow-field transition from periodicity to chaos. The leading-edge separation plays a key role in providing the very first trigger for aperiodicity. Subsequent mechanisms like shredding, merging, splitting, and collision of vortices in the near-field that propagate and sustain the disturbance have also been followed and presented. These fundamental mechanisms are seen to give rise to spontaneous and irregular formation of new vortex couples at arbitrary locations, which are the primary agencies for sustaining chaos in the flow-field. The interactions have been studied for each dynamical state to understand the course of transition in the flow-field. The qualitative changes observed in the flow-field are manifestation of changes in the underlying dynamical system. The overall dynamics are established in the present study by means of robust quantitative measures derived from classical and non-classical tools from the dynamical system theory. As the present analysis involves a high fidelity multi-unknown system, non-classical dynamical tools such as recurrence-based time series methods are seen to be very efficient. Moreover, their application is novel in the context of pitch-plunge flapping flight.

Calculation of near-field concentrations of hydrogen sulphide

International Nuclear Information System (INIS)

Baynes, C.J.

1985-03-01

This report provides simulations of the near-field dispersion in the atmosphere of postulated releases of hydrogen sulphide gas (H2S) at a heavy water plant. The size and extent of the flammable or detonable gas clouds which might result are estimated. This work was undertaken to support experimental studies of the detonability of H2S releases. Thirty-six different cases were simulated involving the catastrophic failure of a liquid H2S storage tank or tank car of H2S. The major variables were the size of the release, the initial mixing ratio of gas with ambient air, and the wind speed. Since the gas/air mixture is initially heavier than air, an existing heavy gas mathematical model (DENZ) was used for these simulations. The model was modified to provide the outputs needed to support the experimental studies. The outputs were the mass of H2S in the cloud, the mass and volume of the cloud, its radius at ground level and its temperature, all as functions of distance and time from release. The edge of the cloud was defined by a given concentration of H2S in air. The simulations were repeated for ten different values of this parameter, ranging between 3% and 40% H2S by volume. Simulations were also performed using a simple 'top-hat' mixing model to predict the length of the flammable or detonable jet formed at the break in a pipe carrying H2S vapour under pressure. The analysis was conducted for four postulated pipe break diameters and repeated for the same ten concentration levels used in the storage tank studies. The report presents a summary of the results. The complete outputs from the 36 storage tank failure simulations are available on floppy disks in a format suitable for detailed examination using any IBM-PC compatible microcomputer system

Polarization contrast in reflection near-field optical microscopy with uncoated fibre tips

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Langbein, Wolfgang; Hvam, Jørn Märcher

1999-01-01

Using cross-hatched, patterned semiconductor surfaces and round 20-nm-thick gold pads on semiconductor wafers, we investigate the imaging characteristics of a reflection near-field optical microscope with an uncoated fibre tip for different polarization configurations and light wavelengths....... Is is shown that cross-polarized detection allows one to effectively suppress far-field components in the detected signal and to realise imaging of optical contrast on the sub-wavelength scale. The sensitivity window of our microscope, i.e. the scale on which near-field optical images represent mainly optical...

Group velocity measurement using spectral interference in near-field scanning optical microscopy

International Nuclear Information System (INIS)

Mills, John D.; Chaipiboonwong, Tipsuda; Brocklesby, William S.; Charlton, Martin D. B.; Netti, Caterina; Zoorob, Majd E.; Baumberg, Jeremy J.

2006-01-01

Near-field scanning optical microscopy provides a tool for studying the behavior of optical fields inside waveguides. In this experiment the authors measure directly the variation of group velocity between different modes of a planar slab waveguide as the modes propagate along the guide. The measurement is made using the spectral interference between pulses propagating inside the waveguide with different group velocities, collected using a near-field scanning optical microscope at different points down the guide and spectrally resolved. The results are compared to models of group velocities in simple guides

A comparison of inverse boundary element method and near-field acoustical holography

DEFF Research Database (Denmark)

Schuhmacher, Andreas; Hald, Jørgen; Saemann, E.-U.

1999-01-01

An inverse boundary element method (IBEM) is used to estimate the surface velocity of a rolling tyre from measurements of the near-field pressure. Subsequently, the sound pressure is calculated over a finite plane surface next to the tyre from the reconstructed velocity field on the tyre surface........ In order to verify the reconstruction process, part of the measurement data is used together with Near-Field Acoustical Holography (NAH). Estimated distributions of sound pressure and particle velocity over a plane surface obtained from the two methods are compared....

Near-field characterization of photonic crystal Y-splitters

DEFF Research Database (Denmark)

Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

2005-01-01

A scanning near-field optical microscope (SNOM) is used to directly map the propagation of light in a specially designed 50/50 photonic crystal (PC) Y-splitter fabricated on silicon-on-insulator (SOI) wafers. SNOM images are obtained for TE- and TM-polarized light in the wavelength range 1425...

Proceedings from the technical workshop on near-field performance assessment for high-level waste

International Nuclear Information System (INIS)

Sellin, P.; Apted, M.; Gago, J.

1991-12-01

This report contains the proceedings of 'Technical workshop of near-filed performance assessment for high-level waste' held in Madrid October 15-17, 1990. It includes the invited presentations and summaries of the scientific discussions. The workshop covered several topics: * post-emplacement environment, * benchmarking of computer codes, * glass release, * spent-fuel release, * radionuclide solubility, * near-field transport processes, * coupled processes in the near-field, * integrated assessments, * sensitivity analyses and validation. There was an invited presentation on each topic followed by an extensive discussion. One of the points highlighted in the closing discussion of the workshop was the need for international cooperation in the field of near-field performance assessment. The general opinion was that this was best achieved in smaller groups discussing specific questions. (au) Separate abstracts were prepared for 9 papers in this volume

Beam alignment based on two-dimensional power spectral density of a near-field image.

Science.gov (United States)

Wang, Shenzhen; Yuan, Qiang; Zeng, Fa; Zhang, Xin; Zhao, Junpu; Li, Kehong; Zhang, Xiaolu; Xue, Qiao; Yang, Ying; Dai, Wanjun; Zhou, Wei; Wang, Yuanchen; Zheng, Kuixing; Su, Jingqin; Hu, Dongxia; Zhu, Qihua

2017-10-30

Beam alignment is crucial to high-power laser facilities and is used to adjust the laser beams quickly and accurately to meet stringent requirements of pointing and centering. In this paper, a novel alignment method is presented, which employs data processing of the two-dimensional power spectral density (2D-PSD) for a near-field image and resolves the beam pointing error relative to the spatial filter pinhole directly. Combining this with a near-field fiducial mark, the operation of beam alignment is achieved. It is experimentally demonstrated that this scheme realizes a far-field alignment precision of approximately 3% of the pinhole size. This scheme adopts only one near-field camera to construct the alignment system, which provides a simple, efficient, and low-cost way to align lasers.

Advanced Optical Diagnostic Methods for Describing Fuel Injection and Combustion Flowfield Phenomena

Science.gov (United States)

Locke, Randy J.; Hicks, Yolanda R.; Anderson, Robert C.

2004-01-01

Over the past decade advanced optical diagnostic techniques have evolved and matured to a point where they are now widely applied in the interrogation of high pressure combusting flows. At NASA Glenn Research Center (GRC), imaging techniques have been used successfully in on-going work to develop the next generation of commercial aircraft gas turbine combustors. This work has centered on providing a means by which researchers and designers can obtain direct visual observation and measurements of the fuel injection/mixing/combustion processes and combustor flowfield in two- and three-dimensional views at actual operational conditions. Obtaining a thorough understanding of the chemical and physical processes at the extreme operating conditions of the next generation of combustors is critical to reducing emissions and increasing fuel efficiency. To accomplish this and other tasks, the diagnostic team at GRC has designed and constructed optically accessible, high pressurer high temperature flame tubes and sectar rigs capable of optically probing the 20-60 atm flowfields of these aero-combustors. Among the techniques employed at GRC are planar laser-induced fluorescence (PLIF) for imaging molecular species as well as liquid and gaseous fuel; planar light scattering (PLS) for imaging fuel sprays and droplets; and spontaneous Raman scattering for species and temperature measurement. Using these techniques, optical measurements never before possible have been made in the actual environments of liquid fueled gas turbines. 2-D mapping of such parameters as species (e.g. OH-, NO and kerosene-based jet fuel) distribution, injector spray angle, and fuel/air distribution are just some of the measurements that are now routinely made. Optical imaging has also provided prompt feedback to researchers regarding the effects of changes in the fuel injector configuration on both combustor performance and flowfield character. Several injector design modifications and improvements have

Numerical simulations of nanostructured gold films

DEFF Research Database (Denmark)

Repän, Taavi; Frydendahl, Christian; Novikov, Sergey M.

2017-01-01

We present an approach to analyse near-field effects on nanostructured gold films by finite element simulations. The studied samples are formed by fabricating gold films near the percolation threshold and then applying laser damage. Resulting samples have complicated structures, which...

Three-dimensional propagation in near-field tomographic X-ray phase retrieval

International Nuclear Information System (INIS)

Ruhlandt, Aike; Salditt, Tim

2016-01-01

An extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions is presented, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints. This paper presents an extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints. The approach is based on a novel three-dimensional propagator and is derived for the case of optically weak objects. It can be easily implemented in current phase retrieval architectures, is computationally efficient and reduces the need for restrictive prior assumptions, resulting in superior reconstruction quality

Groundwater flow modeling for near-field of a hypothetical near-surface disposal facility

International Nuclear Information System (INIS)

Park, H. Y.; Park, J. W.; Jang, G. M.; Kim, C. R.

2000-01-01

For a hypothetical near-surface radioactive disposal facility, the behavior of groundwater flow around the near-field of disposal vault located at the unsaturated zone were analyzed. Three alternative conceptual models proposed as the hydraulic barrier layer design were simulated to assess the hydrologic performance of engineered barriers for the facility. In order to evaluate the seepage possibility of the infiltrated water passed through the final disposal cover after the facility closure, the flow path around and water flux through each disposal vault were compared. The hydrologic parameters variation that accounts for the long-term aging and degradation of the cover and engineered materials was considered in the simulations. The results showed that it is necessary to construct the hydraulic barrier at the upper and sides of the vault, and that, for this case, achieving design hydraulic properties of bentonite/sand mixture barrier in the as-built condition is crucial to limit the seepage into the waste

Seismic scanning tunneling macroscope - Elastic simulations and Arizona mine test

KAUST Repository

Hanafy, Sherif M.; Schuster, Gerard T.

2012-01-01

Elastic seismic simulations and field data tests are used to validate the theory of a seismic scanning tunneling macroscope (SSTM). For nearfield elastic simulation, the SSTM results show superresolution to be better than λ/8 if the only scattered data are used as input data. If the direct P and S waves are muted then the resolution of the scatterer locations are within about λ/5. Seismic data collected in an Arizona tunnel showed a superresolution limit of at least λ/19. These test results are consistent with the theory of the SSTM and suggest that the SSTM can be a tool used by geophysicists as a probe for near-field scatterers.

Toehold-mediated internal control to probe the near-field interaction between the metallic nanoparticle and the fluorophore

Science.gov (United States)

Ang, Y. S.; Yung, L. Y. L.

2014-10-01

Metallic nanoparticles (MNPs) are known to alter the emission of vicinal fluorophores through the near-field interaction, leading to either fluorescence quenching or enhancement. Much ambiguity remains in the experimental outcome of such a near-field interaction, particularly for bulk colloidal solution. It is hypothesized that the strong far-field interference from the inner filter effect of the MNPs could mask the true near-field MNP-fluorophore interaction significantly. Thus, in this work, a reliable internal control capable of decoupling the near-field interaction from far-field interference is established by the use of the DNA toehold concept to mediate the in situ assembly and disassembly of the MNP-fluorophore conjugate. A model gold nanoparticle (AuNP)-Cy3 system is used to investigate our proposed toehold-mediated internal control system. The maximum fluorescence enhancement is obtained for large-sized AuNP (58 nm) separated from Cy3 at an intermediate distance of 6.8 nm, while fluorescence quenching is observed for smaller-sized AuNP (11 nm and 23 nm), which is in agreement with the theoretical values reported in the literature. This work shows that the toehold-mediated internal control design can serve as a central system for evaluating the near-field interaction of other MNP-fluorophore combinations and facilitate the rational design of specific MNP-fluorophore systems for various applications.Metallic nanoparticles (MNPs) are known to alter the emission of vicinal fluorophores through the near-field interaction, leading to either fluorescence quenching or enhancement. Much ambiguity remains in the experimental outcome of such a near-field interaction, particularly for bulk colloidal solution. It is hypothesized that the strong far-field interference from the inner filter effect of the MNPs could mask the true near-field MNP-fluorophore interaction significantly. Thus, in this work, a reliable internal control capable of decoupling the near-field

Room-temperature near-field reflection spectrocopy of semiconductor nanostructures

DEFF Research Database (Denmark)

Langbein, Wolfgang; Hvam, Jørn Märcher; Madsen, Steen

1999-01-01

We investigate the properties of near-field reflection spectroscopy in different polarization and detection modes using uncoated fiber probes. The results show, that cross-polarized detection suppresses to a large extent far-field contributions. Using the fiber dithering as a modulation source fo...

Project-90 Near-field calculations using CALIBRE

International Nuclear Information System (INIS)

Worgan, K.; Robinson, P.

1992-02-01

A comprehensive set of near-field calculations for the Swedish Nuclear Power Inspectorates Project-90 safety assessment has been performed using the CALIBRE model. In the majority of cases considered the redox front migrates through the bentonite buffer and into the rock, where it becomes effectively immobilised. The fracture remains in a reducing state, which means that for solubility-limited nuclides, the concentration at the bentonite/fracture interface can never be greater than the reducing solubility limit. The calculations also show that significant retardation occurs for nuclides which are even moderately sorbed. The effect is less pronounced in the wider fracture and high flow cases, as the opportunity for diffusion from the fracture to the rock matrix is reduced. In contrast, the release from the near-field of poorly-sorbed nuclides which are not solubility limited is governed by the release rate from the fuel, the diffusive mass transfer resistance of the buffer, rock matrix and fracture, the initial inventories and the nuclide half-lives. In the reference case, the maximum dose potential of nuclides emerging from the near-field occur for I-129 and was 3.2 x 10 -7 Sv per canister-year, assuming the flux to be discharged directly into the wall receptor biosphere. The parameters which have the most impact on the reference base results are high flow, wide aperture and poor chemistry (i.e. high solubility limits and low sorption distribution coefficients). The effects of combining extreme values of parameters does not give results which are in proportion to their effect when applied in isolation. In the worst case variant (early canister failure high flow, wide aperture and poor chemistry) the maximum dose potential is 1.0 x 10 -4 Sv per canister-year, compared with 8.9 x 10 -6 Sv in the high flow case, 4.5 x 10 -7 in the wide aperture case, 2.3 x 10 -6 in the poor chemistry case and 3.9 x 10 -6 in the early failure, wide aperture and high flow case. (au)

Design of a Class of Antennas Utilizing MEMS, EBG and Septum Polarizers including Near-field Coupling Analysis

Science.gov (United States)

Kim, Ilkyu

Recent developments in mobile communications have led to an increased appearance of short-range communications and high data-rate signal transmission. New technologies provides the need for an accurate near-field coupling analysis and novel antenna designs. An ability to effectively estimate the coupling within the near-field region is required to realize short-range communications. Currently, two common techniques that are applicable to the near-field coupling problem are 1) integral form of coupling formula and 2) generalized Friis formula. These formulas are investigated with an emphasis on straightforward calculation and accuracy for various distances between the two antennas. The coupling formulas are computed for a variety of antennas, and several antenna configurations are evaluated through full-wave simulation and indoor measurement in order to validate these techniques. In addition, this research aims to design multi-functional and high performance antennas based on MEMS (Microelectromechanical Systems) switches, EBG (Electromagnetic Bandgap) structures, and septum polarizers. A MEMS switch is incorporated into a slot loaded patch antenna to attain frequency reconfigurability. The resonant frequency of the patch antenna can be shifted using the MEM switch, which is actuated by the integrated bias networks. Furthermore, a high gain base-station antenna utilizing beam-tilting is designed to maximize gain for tilted beam applications. To realize this base-station antenna, an array of four dipole-EBG elements is constructed to implement a fixed down-tilt main beam with application in base station arrays. An improvement of the operating range with the EBG-dipole array is evaluated using a simple linkbudget analysis. The septum polarizer has been widely used in circularly polarized antenna systems due to its simple and compact design and high quality of circularity. In this research, the sigmoid function is used to smoothen the edge in the septum design, which

Computational Simulations of the NASA Langley HyMETS Arc-Jet Facility

Science.gov (United States)

Brune, A. J.; Bruce, W. E., III; Glass, D. E.; Splinter, S. C.

2017-01-01

The Hypersonic Materials Environmental Test System (HyMETS) arc-jet facility located at the NASA Langley Research Center in Hampton, Virginia, is primarily used for the research, development, and evaluation of high-temperature thermal protection systems for hypersonic vehicles and reentry systems. In order to improve testing capabilities and knowledge of the test article environment, an effort is underway to computationally simulate the flow-field using computational fluid dynamics (CFD). A detailed three-dimensional model of the arc-jet nozzle and free-jet portion of the flow-field has been developed and compared to calibration probe Pitot pressure and stagnation-point heat flux for three test conditions at low, medium, and high enthalpy. The CFD model takes into account uniform pressure and non-uniform enthalpy profiles at the nozzle inlet as well as catalytic recombination efficiency effects at the probe surface. Comparing the CFD results and test data indicates an effectively fully-catalytic copper surface on the heat flux probe of about 10% efficiency and a 2-3 kpa pressure drop from the arc heater bore, where the pressure is measured, to the plenum section, prior to the nozzle. With these assumptions, the CFD results are well within the uncertainty of the stagnation pressure and heat flux measurements. The conditions at the nozzle exit were also compared with radial and axial velocimetry. This simulation capability will be used to evaluate various three-dimensional models that are tested in the HyMETS facility. An end-to-end aerothermal and thermal simulation of HyMETS test articles will follow this work to provide a better understanding of the test environment, test results, and to aid in test planning. Additional flow-field diagnostic measurements will also be considered to improve the modeling capability.

Near-field photochemical and radiation-induced chemical fabrication of nanopatterns of a self-assembled silane monolayer

Directory of Open Access Journals (Sweden)

Ulrich C. Fischer

2014-09-01

Full Text Available A general concept for parallel near-field photochemical and radiation-induced chemical processes for the fabrication of nanopatterns of a self-assembled monolayer (SAM of (3-aminopropyltriethoxysilane (APTES is explored with three different processes: 1 a near-field photochemical process by photochemical bleaching of a monomolecular layer of dye molecules chemically bound to an APTES SAM, 2 a chemical process induced by oxygen plasma etching as well as 3 a combined near-field UV-photochemical and ozone-induced chemical process, which is applied directly to an APTES SAM. All approaches employ a sandwich configuration of the surface-supported SAM, and a lithographic mask in form of gold nanostructures fabricated through colloidal sphere lithography (CL, which is either exposed to visible light, oxygen plasma or an UV–ozone atmosphere. The gold mask has the function to inhibit the photochemical reactions by highly localized near-field interactions between metal mask and SAM and to inhibit the radiation-induced chemical reactions by casting a highly localized shadow. The removal of the gold mask reveals the SAM nanopattern.

Complete analysis of steady and transient missile aerodynamic/propulsive/plume flowfield interactions

Science.gov (United States)

York, B. J.; Sinha, N.; Dash, S. M.; Hosangadi, A.; Kenzakowski, D. C.; Lee, R. A.

1992-07-01

The analysis of steady and transient aerodynamic/propulsive/plume flowfield interactions utilizing several state-of-the-art computer codes (PARCH, CRAFT, and SCHAFT) is discussed. These codes have been extended to include advanced turbulence models, generalized thermochemistry, and multiphase nonequilibrium capabilities. Several specialized versions of these codes have been developed for specific applications. This paper presents a brief overview of these codes followed by selected cases demonstrating steady and transient analyses of conventional as well as advanced missile systems. Areas requiring upgrades include turbulence modeling in a highly compressible environment and the treatment of particulates in general. Recent progress in these areas are highlighted.

Computationally efficient near-field source localization using third-order moments

Science.gov (United States)

Chen, Jian; Liu, Guohong; Sun, Xiaoying

2014-12-01

In this paper, a third-order moment-based estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm is proposed for passive localization of near-field sources. By properly choosing sensor outputs of the symmetric uniform linear array, two special third-order moment matrices are constructed, in which the steering matrix is the function of electric angle γ, while the rotational factor is the function of electric angles γ and ϕ. With the singular value decomposition (SVD) operation, all direction-of-arrivals (DOAs) are estimated from a polynomial rooting version. After substituting the DOA information into the steering matrix, the rotational factor is determined via the total least squares (TLS) version, and the related range estimations are performed. Compared with the high-order ESPRIT method, the proposed algorithm requires a lower computational burden, and it avoids the parameter-match procedure. Computer simulations are carried out to demonstrate the performance of the proposed algorithm.

The solubility of uranium in cementitious near-field chemical conditions

Energy Technology Data Exchange (ETDEWEB)

Baston, G.M.N.; Brownsword, M.; Cross, J.E.; Hobley, J.; Moreton, A.D.; Smith-Briggs, J.L.; Thomason, H.P. [AEA Decommissioning and Waste Management, Harwell (United Kingdom)

1993-05-01

Tetravalent and hexavalent uranium solubilities have been measured in cement-equilibriated water for pH values from 4 to 13. Tetravalent uranium solubilities at pH 12 have been measured by three experimental techniques: oversaturation, undersaturation and by the use of an electrochemical cell which controlled the redox conditions. The experimentally obtained data have been simulated using the thermodynamic equilibrium program HARPHRQ in conjunction with three different sets of thermodynamic data for uranium. In each case, differences were found between the predicted and measured uranium behaviour. For hexavalent uranium at high pH values the model suggested the formation of anionic hydrolysis products which led to the prediction of uranium solubilities significantly higher than those observed. Refinement of the thermodynamic data used in the model enabled the derivation of maximum values for the formation constants of these species under cementitious conditions. Similarly, the experimental data have been used to refine a model of tetravalent uranium solubility under cementitious near-field conditions. (author).

The solubility of uranium in cementitious near-field chemical conditions

International Nuclear Information System (INIS)

Baston, G.M.N.; Brownsword, M.; Cross, J.E.; Hobley, J.; Moreton, A.D.; Smith-Briggs, J.L.; Thomason, H.P.

1993-05-01

Tetravalent and hexavalent uranium solubilities have been measured in cement-equilibriated water for pH values from 4 to 13. Tetravalent uranium solubilities at pH 12 have been measured by three experimental techniques: oversaturation, undersaturation and by the use of an electrochemical cell which controlled the redox conditions. The experimentally obtained data have been simulated using the thermodynamic equilibrium program HARPHRQ in conjunction with three different sets of thermodynamic data for uranium. In each case, differences were found between the predicted and measured uranium behaviour. For hexavalent uranium at high pH values the model suggested the formation of anionic hydrolysis products which led to the prediction of uranium solubilities significantly higher than those observed. Refinement of the thermodynamic data used in the model enabled the derivation of maximum values for the formation constants of these species under cementitious conditions. Similarly, the experimental data have been used to refine a model of tetravalent uranium solubility under cementitious near-field conditions. (author)

Terahertz-wave near-field imaging with subwavelength resolution using surface-wave-assisted bow-tie aperture

Science.gov (United States)

Ishihara, Kunihiko; Ohashi, Keishi; Ikari, Tomofumi; Minamide, Hiroaki; Yokoyama, Hiroyuki; Shikata, Jun-ichi; Ito, Hiromasa

2006-11-01

We demonstrate the terahertz-wave near-field imaging with subwavelength resolution using a bow-tie shaped aperture surrounded by concentric periodic structures in a metal film. A subwavelength aperture with concentric periodic grooves, which are known as a bull's eye structure, shows extremely large enhanced transmission beyond the diffraction limit caused by the resonant excitation of surface waves. Additionally, a bow-tie aperture exhibits extraordinary field enhancement at the sharp tips of the metal, which enhances the transmission and the subwavelength spatial resolution. We introduced a bow-tie aperture to the bull's eye structure and achieved high spatial resolution (˜λ/17) in the near-field region. The terahertz-wave near-field image of the subwavelength metal pattern (pattern width=20μm) was obtained for the wavelength of 207μm.

Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers.

Science.gov (United States)

Kyoya, K; Matsunaga, D; Imai, Y; Omori, T; Ishikawa, T

2015-12-01

Microswimmers show a variety of collective motions. Despite extensive study, questions remain regarding the role of near-field fluid mechanics in collective motion. In this paper, we describe precisely the Stokes flow around hydrodynamically interacting ellipsoidal squirmers in a monolayer suspension. The results showed that various collective motions, such as ordering, aggregation, and whirls, are dominated by the swimming mode and the aspect ratio. The collective motions are mainly induced by near-field fluid mechanics, despite Stokes flow propagation over a long range. These results emphasize the importance of particle shape in collective motion.

Near-field characterization of low-loss photonic crystal waveguides

DEFF Research Database (Denmark)

Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

2005-01-01

-nm-period lattices with different filling factors (0.76 and 0.82) and connected to access ridge waveguides. Using the near-field optical images we investigate the light propagation along PCWs for TM and TE polarization (the electric field is perpendicular/parallel to the sample surface). Efficient...

Evaluating Multiple Levels of an Interaction Fidelity Continuum on Performance and Learning in Near-Field Training Simulations.

Science.gov (United States)

Bhargava, Ayush; Bertrand, Jeffrey W; Gramopadhye, Anand K; Madathil, Kapil C; Babu, Sabarish V

2018-04-01

With costs of head-mounted displays (HMDs) and tracking technology decreasing rapidly, various virtual reality applications are being widely adopted for education and training. Hardware advancements have enabled replication of real-world interactions in virtual environments to a large extent, paving the way for commercial grade applications that provide a safe and risk-free training environment at a fraction of the cost. But this also mandates the need to develop more intrinsic interaction techniques and to empirically evaluate them in a more comprehensive manner. Although there exists a body of previous research that examines the benefits of selected levels of interaction fidelity on performance, few studies have investigated the constituent components of fidelity in a Interaction Fidelity Continuum (IFC) with several system instances and their respective effects on performance and learning in the context of a real-world skills training application. Our work describes a large between-subjects investigation conducted over several years that utilizes bimanual interaction metaphors at six discrete levels of interaction fidelity to teach basic precision metrology concepts in a near-field spatial interaction task in VR. A combined analysis performed on the data compares and contrasts the six different conditions and their overall effects on performance and learning outcomes, eliciting patterns in the results between the discrete application points on the IFC. With respect to some performance variables, results indicate that simpler restrictive interaction metaphors and highest fidelity metaphors perform better than medium fidelity interaction metaphors. In light of these results, a set of general guidelines are created for developers of spatial interaction metaphors in immersive virtual environments for precise fine-motor skills training simulations.

A fusion-spliced near-field optical fiber probe using photonic crystal fiber for nanoscale thermometry based on fluorescence-lifetime measurement of quantum dots.

Science.gov (United States)

Fujii, Takuro; Taguchi, Yoshihiro; Saiki, Toshiharu; Nagasaka, Yuji

2011-01-01

We have developed a novel nanoscale temperature-measurement method using fluorescence in the near-field called fluorescence near-field optics thermal nanoscopy (Fluor-NOTN). Fluor-NOTN enables the temperature distributions of nanoscale materials to be measured in vivo/in situ. The proposed method measures temperature by detecting the temperature dependent fluorescence lifetimes of Cd/Se quantum dots (QDs). For a high-sensitivity temperature measurement, the auto-fluorescence generated from a fiber probe should be reduced. In order to decrease the noise, we have fabricated a novel near-field optical-fiber probe by fusion-splicing a photonic crystal fiber (PCF) and a conventional single-mode fiber (SMF). The validity of the novel fiber probe was assessed experimentally by evaluating the auto-fluorescence spectra of the PCF. Due to the decrease of auto-fluorescence, a six- to ten-fold increase of S/N in the near-field fluorescence lifetime detection was achieved with the newly fabricated fusion-spliced near-field optical fiber probe. Additionally, the near-field fluorescence lifetime of the quantum dots was successfully measured by the fabricated fusion-spliced near-field optical fiber probe at room temperature, and was estimated to be 10.0 ns.

Directivity of Spherical Polyhedron Sound Source Used in Near-Field HRTF Measurements

International Nuclear Information System (INIS)

Yu Guang-Zheng; Xie Bo-Sun; Rao Dan

2010-01-01

The omnidirectional character is one of important requirements for the sound source used in near-field head-related transfer function (HRTF) measurements. Based on the analysis on the radiation sound pressure and directivity character of various spherical polyhedron sound sources, a spherical dodecahedral sound source with radius of 0.035m is proposed and manufactured. Theoretical and measured results indicate that the sound source is approximately omnidirectional below the frequency of 8 kHz. In addition, the sound source has reasonable magnitude response from 350Hz to 20kHz and linear phase characteristics. Therefore, it is suitable for the near-field HRTF measurements. (fundamental areas of phenomenology(including applications))

Piezoresistor-equipped fluorescence-based cantilever probe for near-field scanning.

Science.gov (United States)

Kan, Tetsuo; Matsumoto, Kiyoshi; Shimoyama, Isao

2007-08-01

Scanning near-field optical microscopes (SNOMs) with fluorescence-based probes are promising tools for evaluating the optical characteristics of nanoaperture devices used for biological investigations, and this article reports on the development of a microfabricated fluorescence-based SNOM probe with a piezoresistor. The piezoresistor was built into a two-legged root of a 160-microm-long cantilever. To improve the displacement sensitivity of the cantilever, the piezoresistor's doped area was shallowly formed on the cantilever surface. A fluorescent bead, 500 nm in diameter, was attached to the bottom of the cantilever end as a light-intensity-sensitive material in the visible-light range. The surface of the scanned sample was simply detected by the probe's end being displaced by contact with the sample. Measuring displacements piezoresistively is advantageous because it eliminates the noise arising from the use of the optical-lever method and is free of any disturbance in the absorption or the emission spectrum of the fluorescent material at the probe tip. The displacement sensitivity was estimated to be 6.1 x 10(-6) nm(-1), and the minimum measurable displacement was small enough for near-field measurement. This probe enabled clear scanning images of the light field near a 300 x 300 nm(2) aperture to be obtained in the near-field region where the tip-sample distance is much shorter than the light wavelength. This scanning result indicates that the piezoresistive way of tip-sample distance regulation is effective for characterizing nanoaperture optical devices.

Achieving swift equilibration of a Brownian particle using flow-fields

Science.gov (United States)

Patra, Ayoti; Jarzynski, Christopher

Can a system be driven to a targeted equilibrium state on a timescale that is much shorter than its natural equilibration time? In a recent experiment, the swift equilibration of an overdamped Brownian particle was achieved by use of an appropriately designed, time-dependent optical trap potential. Motivated by these results, we develop a general theoretical approach for guiding an ensemble of Brownian particles to track the instantaneous equilibrium distribution of a desired potential U (q , t) . In our approach, we use flow-fields associated with the parametric evolution of the targeted equilibrium state to construct an auxiliary potential U (q , t) , such that dynamics under the composite potential U (t) + U (t) achieves the desired evolution. Our results establish a close connection between the swift equilibration of Brownian particles, quantum shortcuts to adiabaticity, and the dissipationless driving of a classical, Hamiltonian system.

Direct measurement of source RDP's and yields from near-field Soviet seismic data. Final report

International Nuclear Information System (INIS)

Saikia, C.K.; McLaren, J.P.; Helmberger, D.V.

1994-01-01

The objective of this study was to investigate the source characteristics represented in the form of a reduced displacement potential (RDP) of Soviet nuclear explosions and was based on the availability of in-country near-field data. At the start of the project, it was thought that data would be readily accessible to us with the start of the open exchange of seismic data between the US and the Soviet Union. In fact, we did receive near-field waveforms of two Soviet nuclear explosions from Azghir test site near the Caspian Sea following which the transfer of data stopped till the end of the project. Consequently, the research effort was descoped. Only recently, some additional data have become available at CSS (Center for Seismic Studies). We have undertaken a thorough investigation of the limited data available from a large coupled shot (64 kT) in Azghir followed five years later by a decoupled shot (8 kT). We have successfully modeled the near-field data from these events to determine their source RDP's and establish a decoupling factor of 15 using a time-domain waveform modeling technique. The results of this study are presented in the enclosed manuscript: Analysis of near-field data from a Soviet decoupling experiment

A near-field scanning microwave microscope based on a superconducting resonator for low power measurements.

Science.gov (United States)

de Graaf, S E; Danilov, A V; Adamyan, A; Kubatkin, S E

2013-02-01

We report on the design and performance of a cryogenic (300 mK) near-field scanning microwave microscope. It uses a microwave resonator as the near-field sensor, operating at a frequency of 6 GHz and microwave probing amplitudes down to 100 μV, approaching low enough photon population (N ∼ 1000) of the resonator such that coherent quantum manipulation becomes feasible. The resonator is made out of a miniaturized distributed fractal superconducting circuit that is integrated with the probing tip, micromachined to be compact enough such that it can be mounted directly on a quartz tuning-fork, and used for parallel operation as an atomic force microscope (AFM). The resonator is magnetically coupled to a transmission line for readout, and to achieve enhanced sensitivity we employ a Pound-Drever-Hall measurement scheme to lock to the resonance frequency. We achieve a well localized near-field around the tip such that the microwave resolution is comparable to the AFM resolution, and a capacitive sensitivity down to 6.4 × 10(-20) F/Hz, limited by mechanical noise. We believe that the results presented here are a significant step towards probing quantum systems at the nanoscale using near-field scanning microwave microscopy.

Antenna diagnostics for power flow in extreme near-field of a standard gain horn

DEFF Research Database (Denmark)

Popa, Paula Irina; Breinbjerg, Olav

2016-01-01

The plane wave spectrum of an aperture antenna can be calculated from a complex measurement of the radiated near- or far-field and it facilitates antenna diagnostics for the extreme near-field of the antenna. While antenna diagnostics often concerns the magnitude of the co-polar field, the plane...... wave spectrum actually allows for determination of both magnitude and phase of all three components of the electric as well as the magnetic field - and thus also the Poynting vector. In this work we focus on the Poynting vector and thus the power flow in the extreme near-field; as an example we employ...... that these oscillations are not merely a “Gibbs-like” phenomenon due to the availability of only the visible region of the plane wave spectrum and they are not caused by multiple reflections between the horn and the near-field probe - but resulted from the interference between the direct field and the edge...

Near-field enhanced electron acceleration from dielectric nanospheres in intense few-cycle laser fields

International Nuclear Information System (INIS)

Zherebtsov, S.; Znakovskaya, I.; Wirth, A.; Herrwerth, O.; Suessmann, F.; Ahmad, I.; Trushin, S.; Fennel, Th.; Plenge, J.; Antonsson, E.

2010-01-01

Complete text of publication follows. The interaction of nanostructured materials with few-cycle laser light has attracted significant attention lately. This interest is driven by both the quest for fundamental insight into the real-time dynamics of many-electron systems and a wide range of far-reaching applications, such as, e.g. ultrafast computation and information storage on the nanoscale and the generation of XUV frequency combs. We investigated the above-threshold electron emission from isolated SiO 2 nanoparticles in waveform controlled few-cycle laser fields at intensities close to the tunneling regime. The enhancement of the electron acceleration from the silica nanoparticles was explored as a function of the particle size (ranging from 50 to 147 nm) and the laser peak intensity (1 - 4x10 13 W/cm 2 ). Obtained cut-off values in the kinetic energy spectra are displayed in Fig. 1. The cut-off values show a linear dependence with intensity within the studied intensity range, with the average cut-off energy being 53 U P , indicated by the black line. Quasi-classical simulations of the emission process reveal that electron rescattering in the locally enhanced near-field of the particle is responsible for the large energy gain. The observed near-field enhancement offers promising new routes for pushing the limits of strong-field phenomena relying on electron rescattering, such as, high-harmonic generation and molecular imaging.

Large-area parallel near-field optical nanopatterning of functional materials using microsphere mask

Energy Technology Data Exchange (ETDEWEB)

Chen, G.X. [NUS Nanoscience and Nanotechnology Initiative, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Hong, M.H. [NUS Nanoscience and Nanotechnology Initiative, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, ASTAR, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore)], E-mail: Hong_Minghui@dsi.a-star.edu.sg; Lin, Y. [NUS Nanoscience and Nanotechnology Initiative, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Wang, Z.B. [Data Storage Institute, ASTAR, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Ng, D.K.T. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, ASTAR, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Xie, Q. [Data Storage Institute, ASTAR, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Tan, L.S. [NUS Nanoscience and Nanotechnology Initiative, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Chong, T.C. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, ASTAR, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore)

2008-01-31

Large-area parallel near-field optical nanopatterning on functional material surfaces was investigated with KrF excimer laser irradiation. A monolayer of silicon dioxide microspheres was self-assembled on the sample surfaces as the processing mask. Nanoholes and nanospots were obtained on silicon surfaces and thin silver films, respectively. The nanopatterning results were affected by the refractive indices of the surrounding media. Near-field optical enhancement beneath the microspheres is the physical origin of nanostructure formation. Theoretical calculation was performed to study the intensity of optical field distributions under the microspheres according to the light scattering model of a sphere on the substrate.

Oxidation of hydrogen-passivated silicon surfaces by scanning near-field optical lithography using uncoated and aluminum-coated fiber probes

DEFF Research Database (Denmark)

Madsen, Steen; Bozhevolnyi, Sergey I.; Birkelund, Karen

1997-01-01

Optically induced oxidation of hydrogen-passivated silicon surfaces using a scanning near-field optical microscope was achieved with both uncoated and aluminum-coated fiber probes. Line scans on amorphous silicon using uncoated fiber probes display a three-peak profile after etching in potassium...... hydroxide. Numerical simulations of the electromagnetic field around the probe-sample interaction region are used to explain the experimental observations. With an aluminum-coated fiber probe, lines of 35 nm in width were transferred into the amorphous silicon layer. (C) 1997 American Institute of Physics....

Meshed doped silicon photonic crystals for manipulating near-field thermal radiation

Science.gov (United States)

Elzouka, Mahmoud; Ndao, Sidy

2018-01-01

The ability to control and manipulate heat flow is of great interest to thermal management and thermal logic and memory devices. Particularly, near-field thermal radiation presents a unique opportunity to enhance heat transfer while being able to tailor its characteristics (e.g., spectral selectivity). However, achieving nanometric gaps, necessary for near-field, has been and remains a formidable challenge. Here, we demonstrate significant enhancement of the near-field heat transfer through meshed photonic crystals with separation gaps above 0.5 μm. Using a first-principle method, we investigate the meshed photonic structures numerically via finite-difference time-domain technique (FDTD) along with the Langevin approach. Results for doped-silicon meshed structures show significant enhancement in heat transfer; 26 times over the non-meshed corrugated structures. This is especially important for thermal management and thermal rectification applications. The results also support the premise that thermal radiation at micro scale is a bulk (rather than a surface) phenomenon; the increase in heat transfer between two meshed-corrugated surfaces compared to the flat surface (8.2) wasn't proportional to the increase in the surface area due to the corrugations (9). Results were further validated through good agreements between the resonant modes predicted from the dispersion relation (calculated using a finite-element method), and transmission factors (calculated from FDTD).

A total generalized variation approach for near-field acoustic holography

DEFF Research Database (Denmark)

Fernandez Grande, Efren

2017-01-01

Near-field methods based on microphone array measurements are useful to understand how a source radiates sound. Due to discretization errors, these methods are typically restricted to low frequencies. Sparse approaches have gained considerable attention, as they can potentially recover a seemingl...

Macroscopic self-consistent model for external-reflection near-field microscopy

International Nuclear Information System (INIS)

Berntsen, S.; Bozhevolnaya, E.; Bozhevolnyi, S.

1993-01-01

The self-consistent macroscopic approach based on the Maxwell equations in two-dimensional geometry is developed to describe tip-surface interaction in external-reflection near-field microscopy. The problem is reduced to a single one-dimensional integral equation in terms of the Fourier components of the field at the plane of the sample surface. This equation is extended to take into account a pointlike scatterer placed on the sample surface. The power of light propagating toward the detector as the fiber mode is expressed by using the self-consistent field at the tip surface. Numerical results for trapezium-shaped tips are presented. The authors show that the sharper tip and the more confined fiber mode result in better resolution of the near-field microscope. Moreover, it is found that the tip-surface distance should not be too small so that better resolution is ensured. 14 refs., 10 figs

Experimental Validation of UTDefect: Scattering in Anisotropic Media and Near-field Behavior

International Nuclear Information System (INIS)

Pecorari, Claudio

2002-11-01

Theoretical models that simulate measurements of ultrasonic waves undergoing scattering by material defects have been developed by Prof. Bostroem and co-workers at Chalmers Univ. of Tech. for a variety of experimental configurations and defects. A software program named UTDefect has been developed at the same time, which gathers the theoretical results obtained so far in a single package. A discussion of the motivations behind such an effort and details concerning UTDefect can be found in articles by Bostroem. Following an initial effort to validate some of the theoretical predictions available at the time, the present project has been conceived as a support to the on-going theoretical work. In fact, the goal of the project described in this report has been the experimental validation of two aspects of the above theory that have not yet been tested: the scattering of a finite ultrasonic beam by a surface-breaking crack in an anisotropic medium, and an improved model of the behaviour of a finite ultrasonic beam in the near-field region of the source. In the last case, the supporting medium is supposed to be isotropic. To carry out the first task, a single crystal, silicon sample was employed. A surface-breaking notch with a depth of approximately 1.8 mm was introduced by means of a wire-cutting saw to simulate a scattering defect. Two kinds of measurements were performed of this sample. The first one considered the signal amplitude as a function of the transducer position. To this end, three wedges generating beams propagating in different directions were used. The second series of measurements concerned the frequency content of the backscattered signals at the position where the amplitude was maximum. All three wedges mentioned above were used also in this part of the work. The experimental results were compared to the values of the physical quantities of interest as predicted by UTDefect, with the only difference that UTDefect was run for a sub-surface rectangular

Flow-Field Characteristics of High-Temperature Annular Buoyant Jets and Their Development Laws Influenced by Ventilation System

OpenAIRE

Wang, Yi; Huang, Yanqiu; Liu, Jiaping; Wang, Hai; Liu, Qiuhan

2013-01-01

The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and veloc...

Application of the planar-scanning technique to the near-field dosimetry of millimeter-wave radiators.

Science.gov (United States)

Zhao, Jianxun; Lu, Hongmin; Deng, Jun

2015-02-01

The planar-scanning technique was applied to the experimental measurement of the electric field and power flux density (PFD) in the exposure area close to the millimeter-wave (MMW) radiator. In the near-field region, the field and PFD were calculated from the plane-wave spectrum of the field sampled on a scan plane far from the radiator. The measurement resolution was improved by reducing the spatial interval between the field samples to a fraction of half the wavelength and implementing multiple iterations of the fast Fourier transform. With the reference to the results from the numerical calculation, an experimental evaluation of the planar-scanning measurement was made for a 50 GHz radiator. Placing the probe 1 to 3 wavelengths from the aperture of the radiator, the direct measurement gave the near-field data with significant differences from the numerical results. The planar-scanning measurement placed the probe 9 wavelengths away from the aperture and effectively reduced the maximum and averaged differences in the near-field data by 70.6% and 65.5%, respectively. Applied to the dosimetry of an open-ended waveguide and a choke ring antenna for 60 GHz exposure, the technique proved useful to the measurement of the PFD in the near-field exposure area of MMW radiators. © 2015 Wiley Periodicals, Inc.

Conference Paper NFO-7:7^th International Conference on Near-Field Optics and Related Technologies

Energy Technology Data Exchange (ETDEWEB)

Novotny, Lukas [Univ. of Rochester, NY (United States)

2004-10-18

The seventh conference in the NFO conference series, held here in Rochester, provided to be the principal forum for advances in sub-wavelength optics, near-field optical microscopy, local field enhancement, instrumental developments and the ever-increasing range of applications. This conference brought together the diverse scientific communities working on the theory and application of near-field optics (NFO) and related techniques.

Broadband X-ray Imaging in the Near-Field Region of an Airblast Atomizer

Science.gov (United States)

Li, Danyu; Bothell, Julie; Morgan, Timothy; Heindel, Theodore

2017-11-01

The atomization process has a close connection to the efficiency of many spray applications. Examples include improved fuel atomization increasing the combustion efficiency of aircraft engines, or controlled droplet size and spray angle enhancing the quality and speed of the painting process. Therefore, it is vital to understand the physics of the atomization process, but the near-field region is typically optically dense and difficult to probe with laser-based or intrusive measurement techniques. In this project, broadband X-ray radiography and X-ray computed tomography (CT) imaging were performed in the near-field region of a canonical coaxial airblast atomizer. The X-ray absorption rate was enhanced by adding 20% by weight of Potassium Iodide to the liquid phase to increase image contrast. The radiographs provided an estimate of the liquid effective mean path length and spray angle at the nozzle exit for different flow conditions. The reconstructed CT images provided a 3D map of the time-average liquid spray distribution. X-ray imaging was used to quantify the changes in the near-field spray characteristics for various coaxial airblast atomizer flow conditions. Office of Naval Research.

Cancer cell imaging by stable wet near-field scanning optical microscope with resonance tracking method

International Nuclear Information System (INIS)

Park, Kyoung-Duck; Park, Doo-Jae; Jeong, Mun-Seok; Choi, Geun-Chang; Lee, Seung-Gol; Byeon, Clare-Chisu; Choi, Soo-Bong

2014-01-01

We report on a successful topographical and optical imaging of various cancer cells in liquid and in air by using a stable wet near-field scanning optical microscope that utilizes a resonance tracking method. We observed a clear dehydration which gives rise to a decrease in the cell volume down to 51%. In addition, a micro-ball lens effect due to the round-shaped young cancer cells was observed from near-field imaging, where the refractive index of young cancer cells was deduced.

Cancer cell imaging by stable wet near-field scanning optical microscope with resonance tracking method

Energy Technology Data Exchange (ETDEWEB)

Park, Kyoung-Duck [Sungkyunkwan University, Suwon (Korea, Republic of); Inha University, Incheon (Korea, Republic of); Park, Doo-Jae; Jeong, Mun-Seok [Sungkyunkwan University, Suwon (Korea, Republic of); Choi, Geun-Chang [Seoul National University, Seoul (Korea, Republic of); Lee, Seung-Gol [Inha University, Incheon (Korea, Republic of); Byeon, Clare-Chisu [Kyungpook National University, Daegu (Korea, Republic of); Choi, Soo-Bong [Incheon National University, Incheon (Korea, Republic of)

2014-05-15

We report on a successful topographical and optical imaging of various cancer cells in liquid and in air by using a stable wet near-field scanning optical microscope that utilizes a resonance tracking method. We observed a clear dehydration which gives rise to a decrease in the cell volume down to 51%. In addition, a micro-ball lens effect due to the round-shaped young cancer cells was observed from near-field imaging, where the refractive index of young cancer cells was deduced.

Flow-Field Characteristics of High-Temperature Annular Buoyant Jets and Their Development Laws Influenced by Ventilation System

Directory of Open Access Journals (Sweden)

Yi Wang

2013-01-01

Full Text Available The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0 Pa to −5 Pa.

Flow-field characteristics of high-temperature annular buoyant jets and their development laws influenced by ventilation system.

Science.gov (United States)

Wang, Yi; Huang, Yanqiu; Liu, Jiaping; Wang, Hai; Liu, Qiuhan

2013-01-01

The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0 Pa to -5 Pa.

Radiation Entropy and Near-Field Thermophotovoltaics

Science.gov (United States)

Zhang, Zhuomin M.

2008-08-01

Radiation entropy was key to the original derivation of Planck's law of blackbody radiation, in 1900. This discovery opened the door to quantum mechanical theory and Planck was awarded the Nobel Prize in Physics in 1918. Thermal radiation plays an important role in incandescent lamps, solar energy utilization, temperature measurements, materials processing, remote sensing for astronomy and space exploration, combustion and furnace design, food processing, cryogenic engineering, as well as numerous agricultural, health, and military applications. While Planck's law has been fruitfully applied to a large number of engineering problems for over 100 years, questions have been raised about its limitation in micro/nano systems, especially at subwavelength distances or in the near field. When two objects are located closer than the characteristic wavelength, wave interference and photon tunneling occurs that can result in significant enhancement of the radiative transfer. Recent studies have shown that the near-field effects can realize emerging technologies, such as superlens, sub-wavelength light source, polariton-assisted nanolithography, thermophotovoltaic (TPV) systems, scanning tunneling thermal microscopy, etc. The concept of entropy has also been applied to explain laser cooling of solids as well as the second law efficiency of devices that utilize thermal radiation to produce electricity. However, little is known as regards the nature of entropy in near-field radiation. Some history and recent advances are reviewed in this presentation with a call for research of radiation entropy in the near field, due to the important applications in the optimization of thermophotovoltaic converters and in the design of practical systems that can harvest photon energies efficiently.

On the slow dynamics of near-field acoustically levitated objects under High excitation frequencies

Science.gov (United States)

Ilssar, Dotan; Bucher, Izhak

2015-10-01

This paper introduces a simplified analytical model describing the governing dynamics of near-field acoustically levitated objects. The simplification converts the equation of motion coupled with the partial differential equation of a compressible fluid, into a compact, second order ordinary differential equation, where the local stiffness and damping are transparent. The simplified model allows one to more easily analyse and design near-field acoustic levitation based systems, and it also helps to devise closed-loop controller algorithms for such systems. Near-field acoustic levitation employs fast ultrasonic vibrations of a driving surface and exploits the viscosity and the compressibility of a gaseous medium to achieve average, load carrying pressure. It is demonstrated that the slow dynamics dominates the transient behaviour, while the time-scale associated with the fast, ultrasonic excitation has a small presence in the oscillations of the levitated object. Indeed, the present paper formulates the slow dynamics under an ultrasonic excitation without the need to explicitly consider the latter. The simplified model is compared with a numerical scheme based on Reynolds equation and with experiments, both showing reasonably good results.

Topography characterization of a deep grating using near-field imaging

DEFF Research Database (Denmark)

Gregersen, Niels; Tromborg, Bjarne; Volkov, Valentyn S.

2006-01-01

Using near-field optical microscopy at the wavelength of 633 nm, we image light intensity distributions at several distances above an ~2-mm deep and a 1-mm-period glass grating illuminated from below under the condition of total internal reflection. The intensity distributions are numerically mod...

Experimental investigation into wing span and angle-of-attack effects on sub-scale race car wing/wheel interaction aerodynamics

Energy Technology Data Exchange (ETDEWEB)

Diasinos, S. [Toyota F1, Koeln (Germany); Gatto, A. [Brunel University, Department of Mechanical Engineering, School of Engineering and Design, Uxbridge (United Kingdom)

2008-09-15

This paper details a quantitative 3D investigation using LDA into the interaction aerodynamics on a sub-scale open wheel race car inverted front wing and wheel. Of primary importance to this study was the influence of changing wing angle of attack and span on the resulting near-field and far-field flow characteristics. Results obtained showed that both variables do have a significant influence on the resultant flow-field, particularly on wing vortex and wheel wake development and propagation. (orig.)

Experimental investigation into wing span and angle-of-attack effects on sub-scale race car wing/wheel interaction aerodynamics

Science.gov (United States)

Diasinos, S.; Gatto, A.

2008-09-01

This paper details a quantitative 3D investigation using LDA into the interaction aerodynamics on a sub-scale open wheel race car inverted front wing and wheel. Of primary importance to this study was the influence of changing wing angle of attack and span on the resulting near-field and far-field flow characteristics. Results obtained showed that both variables do have a significant influence on the resultant flow-field, particularly on wing vortex and wheel wake development and propagation.

Detached Eddy Simulation of Flap Side-Edge Flow

Science.gov (United States)

Balakrishnan, Shankar K.; Shariff, Karim R.

2016-01-01

Detached Eddy Simulation (DES) of flap side-edge flow was performed with a wing and half-span flap configuration used in previous experimental and numerical studies. The focus of the study is the unsteady flow features responsible for the production of far-field noise. The simulation was performed at a Reynolds number (based on the main wing chord) of 3.7 million. Reynolds Averaged Navier-Stokes (RANS) simulations were performed as a precursor to the DES. The results of these precursor simulations match previous experimental and RANS results closely. Although the present DES simulations have not reached statistical stationary yet, some unsteady features of the developing flap side-edge flowfield are presented. In the final paper it is expected that statistically stationary results will be presented including comparisons of surface pressure spectra with experimental data.

Laminar and turbulent nozzle-jet flows and their acoustic near-field

International Nuclear Information System (INIS)

Bühler, Stefan; Obrist, Dominik; Kleiser, Leonhard

2014-01-01

We investigate numerically the effects of nozzle-exit flow conditions on the jet-flow development and the near-field sound at a diameter-based Reynolds number of Re D = 18 100 and Mach number Ma = 0.9. Our computational setup features the inclusion of a cylindrical nozzle which allows to establish a physical nozzle-exit flow and therefore well-defined initial jet-flow conditions. Within the nozzle, the flow is modeled by a potential flow core and a laminar, transitional, or developing turbulent boundary layer. The goal is to document and to compare the effects of the different jet inflows on the jet flow development and the sound radiation. For laminar and transitional boundary layers, transition to turbulence in the jet shear layer is governed by the development of Kelvin-Helmholtz instabilities. With the turbulent nozzle boundary layer, the jet flow development is characterized by a rapid changeover to a turbulent free shear layer within about one nozzle diameter. Sound pressure levels are strongly enhanced for laminar and transitional exit conditions compared to the turbulent case. However, a frequency and frequency-wavenumber analysis of the near-field pressure indicates that the dominant sound radiation characteristics remain largely unaffected. By applying a recently developed scaling procedure, we obtain a close match of the scaled near-field sound spectra for all nozzle-exit turbulence levels and also a reasonable agreement with experimental far-field data

Induced Light Emission from Quantum Dots: The Directional Near-Field Pattern

DEFF Research Database (Denmark)

Iezhokin, Igor; Keller, Ole; Lozovski, Valeri

2010-01-01

The optical Lippmann-Schwinger equation, supplemented by the microscopic conductivity tensor, is used to establish a near-field radiation theory for a mesoscopic particle. The present theory deviates from previous ones in that it allows one to take into account the finite size of the particle...... in a selfconsistent local-field calculation. The main result of the basic theory is illustrated by a number of numerical calculations on box-shaped quantum dots keeping only two optically mobile electrons. Particular attendance is paid to the distance and angular dependences of the near-field radiation pattern When...... the distance between the particle and observation point exceeds just a few times the linear dimension of the particle the directional radiation diagrams all become qualitatively identical to those of an electric point-dipole radiator The result of the present theory may be of particular interest for studies...

Optical fiber plasmonic lens for near-field focusing fabricated through focused ion beam

Science.gov (United States)

Sloyan, Karen; Melkonyan, Henrik; Moreira, Paulo; Dahlem, Marcus S.

2017-02-01

We report on numerical simulations and fabrication of an optical fiber plasmonic lens for near-field focusing applications. The plasmonic lens consists of an Archimedean spiral structure etched through a 100 nm-thick Au layer on the tip of a single-mode SM600 optical fiber operating at a wavelength of 632:8 nm. Three-dimensional finite-difference time-domain computations show that the relative electric field intensity of the focused spot increases 2:1 times when the number of turns increases from 2 to 12. Furthermore, a reduction of the intensity is observed when the initial inner radius is increased. The optimized plasmonic lens focuses light into a spot with a full-width at half-maximum of 182 nm, beyond the diffraction limit. The lens was fabricated by focused ion beam milling, with a 200nm slit width.

A conceptual design of multidisciplinary-integrated C.F.D. simulation on parallel computers

International Nuclear Information System (INIS)

Onishi, Ryoichi; Ohta, Takashi; Kimura, Toshiya.

1996-11-01

A design of a parallel aeroelastic code for aircraft integrated simulations is conducted. The method for integrating aerodynamics and structural dynamics software on parallel computers is devised by using the Euler/Navier-Stokes equations coupled with wing-box finite element structures. A synthesis of modern aircraft requires the optimizations of aerodynamics, structures, controls, operabilities, or other design disciplines, and the R and D efforts to implement Multidisciplinary Design Optimization environments using high performance computers are made especially among the U.S. aerospace industries. This report describes a Multiple Program Multiple Data (MPMD) parallelization of aerodynamics and structural dynamics codes with a dynamic deformation grid. A three-dimensional computation of a flowfield with dynamic deformation caused by a structural deformation is performed, and a pressure data calculated is used for a computation of the structural deformation which is input again to a fluid dynamics code. This process is repeated exchanging the computed data of pressures and deformations between flowfield grids and structural elements. It enables to simulate the structure movements which take into account of the interaction of fluid and structure. The conceptual design for achieving the aforementioned various functions is reported. Also the future extensions to incorporate control systems, which enable to simulate a realistic aircraft configuration to be a major tool for Aircraft Integrated Simulation, are investigated. (author)

On the Seismic Response of Protected and Unprotected Middle-Rise Steel Frames in Far-Field and Near-Field Areas

Directory of Open Access Journals (Sweden)

Dora Foti

2014-01-01

Full Text Available Several steel moment-resisting framed buildings were seriously damaged during Northridge (1994; Kobe (1995; Kocaeli, Turkey (1999, earthquakes. Indeed, for all these cases, the earthquake source was located under the urban area and most victims were in near-field areas. In fact near-field ground motions show velocity and displacement peaks higher than far-field ones. Therefore, the importance of considering near-field ground motion effects in the seismic design of structures is clear. This study analyzes the seismic response of five-story steel moment-resisting frames subjected to Loma Prieta (1989 earthquake—Gilroy (far-field register and Santa Cruz (near-field register. The design of the frames verifies all the resistance and stability Eurocodes’ requirements and the first mode has been determined from previous shaking-table tests. In the frames two diagonal braces are installed in different positions. Therefore, ten cases with different periods are considered. Also, friction dampers are installed in substitution of the braces. The behaviour of the braced models under the far-field and the near-field records is analysed. The responses of the aforementioned frames equipped with friction dampers and subjected to the same ground motions are discussed. The maximum response of the examined model structures with and without passive dampers is analysed in terms of damage indices, acceleration amplification, base shear, and interstory drifts.

SHEDS-HT: an integrated probabilistic exposure model for prioritizing exposures to chemicals with near-field and dietary sources.

Science.gov (United States)

Isaacs, Kristin K; Glen, W Graham; Egeghy, Peter; Goldsmith, Michael-Rock; Smith, Luther; Vallero, Daniel; Brooks, Raina; Grulke, Christopher M; Özkaynak, Halûk

2014-11-04

United States Environmental Protection Agency (USEPA) researchers are developing a strategy for high-throughput (HT) exposure-based prioritization of chemicals under the ExpoCast program. These novel modeling approaches for evaluating chemicals based on their potential for biologically relevant human exposures will inform toxicity testing and prioritization for chemical risk assessment. Based on probabilistic methods and algorithms developed for The Stochastic Human Exposure and Dose Simulation Model for Multimedia, Multipathway Chemicals (SHEDS-MM), a new mechanistic modeling approach has been developed to accommodate high-throughput (HT) assessment of exposure potential. In this SHEDS-HT model, the residential and dietary modules of SHEDS-MM have been operationally modified to reduce the user burden, input data demands, and run times of the higher-tier model, while maintaining critical features and inputs that influence exposure. The model has been implemented in R; the modeling framework links chemicals to consumer product categories or food groups (and thus exposure scenarios) to predict HT exposures and intake doses. Initially, SHEDS-HT has been applied to 2507 organic chemicals associated with consumer products and agricultural pesticides. These evaluations employ data from recent USEPA efforts to characterize usage (prevalence, frequency, and magnitude), chemical composition, and exposure scenarios for a wide range of consumer products. In modeling indirect exposures from near-field sources, SHEDS-HT employs a fugacity-based module to estimate concentrations in indoor environmental media. The concentration estimates, along with relevant exposure factors and human activity data, are then used by the model to rapidly generate probabilistic population distributions of near-field indirect exposures via dermal, nondietary ingestion, and inhalation pathways. Pathway-specific estimates of near-field direct exposures from consumer products are also modeled

Minimal BRDF Sampling for Two-Shot Near-Field Reflectance Acquisition

DEFF Research Database (Denmark)

Xu, Zexiang; Nielsen, Jannik Boll; Yu, Jiyang

2016-01-01

We develop a method to acquire the BRDF of a homogeneous flat sample from only two images, taken by a near-field perspective camera, and lit by a directional light source. Our method uses the MERL BRDF database to determine the optimal set of lightview pairs for data-driven reflectance acquisition...

Analysis of optical near-field energy transfer by stochastic model unifying architectural dependencies

Energy Technology Data Exchange (ETDEWEB)

Naruse, Makoto, E-mail: naruse@nict.go.jp [Photonic Network Research Institute, National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795 (Japan); Nanophotonics Research Center, Graduate School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Akahane, Kouichi; Yamamoto, Naokatsu [Photonic Network Research Institute, National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795 (Japan); Holmström, Petter [Laboratory of Photonics and Microwave Engineering, Royal Institute of Technology (KTH), SE-164 40 Kista (Sweden); Thylén, Lars [Laboratory of Photonics and Microwave Engineering, Royal Institute of Technology (KTH), SE-164 40 Kista (Sweden); Hewlett-Packard Laboratories, Palo Alto, California 94304 (United States); Huant, Serge [Institut Néel, CNRS and Université Joseph Fourier, 25 rue des Martyrs BP 166, 38042 Grenoble Cedex 9 (France); Ohtsu, Motoichi [Nanophotonics Research Center, Graduate School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Electrical Engineering and Information Systems, Graduate School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan)

2014-04-21

We theoretically and experimentally demonstrate energy transfer mediated by optical near-field interactions in a multi-layer InAs quantum dot (QD) structure composed of a single layer of larger dots and N layers of smaller ones. We construct a stochastic model in which optical near-field interactions that follow a Yukawa potential, QD size fluctuations, and temperature-dependent energy level broadening are unified, enabling us to examine device-architecture-dependent energy transfer efficiencies. The model results are consistent with the experiments. This study provides an insight into optical energy transfer involving inherent disorders in materials and paves the way to systematic design principles of nanophotonic devices that will allow optimized performance and the realization of designated functions.

Analysis of optical near-field energy transfer by stochastic model unifying architectural dependencies

International Nuclear Information System (INIS)

Naruse, Makoto; Akahane, Kouichi; Yamamoto, Naokatsu; Holmström, Petter; Thylén, Lars; Huant, Serge; Ohtsu, Motoichi

2014-01-01

We theoretically and experimentally demonstrate energy transfer mediated by optical near-field interactions in a multi-layer InAs quantum dot (QD) structure composed of a single layer of larger dots and N layers of smaller ones. We construct a stochastic model in which optical near-field interactions that follow a Yukawa potential, QD size fluctuations, and temperature-dependent energy level broadening are unified, enabling us to examine device-architecture-dependent energy transfer efficiencies. The model results are consistent with the experiments. This study provides an insight into optical energy transfer involving inherent disorders in materials and paves the way to systematic design principles of nanophotonic devices that will allow optimized performance and the realization of designated functions

X-ray near-field holography. Beyond idealized assumptions of the probe

Energy Technology Data Exchange (ETDEWEB)

Hagemann, Johannes

2017-07-01

The work at hand considers the imperfect, often neglected, aspects of X-ray nearfield phase-contrast propagation imaging, or in short: X-ray near-field holography (NFH). NFH is a X-ray microscopy technique able to yield high resolution, yet low dose imaging of a wide range of specimen. Derived from wave optical theory, propagation-based imaging methods rely on assumptions for the illuminating wave field. These are for example the assumptions of a perfect plane wave or spherical wave emanating from a point source or monochromaticity. Violation of the point source assumption implies for example at the same time the occurrence of a distorted wave front and a finite degree of coherence, both crucial for NFH. With the advances in X-ray focusing, instrumentation and X-ray wave guiding, NFH has become of high interest, since the barriers for practical implementation have been overcome. The idea of holography originates from electron microscopy to overcome the lack of high-quality electron lenses. With holography the need for optics between the specimen and detector is circumvented. The drawback, however, is that the measurement obtained at the detector is not a direct image of the specimen under survey but a ''propagated version'' of it, the so-called hologram. The problem with the optics is replaced by another problem, also referred to as the phase problem. The phase problem is caused by the fact that only the intensities of a wave field can be measured but not the phase information. The phase information is crucial for obtaining the image of the specimen and thus needs to be reconstructed. In recent years the methodology, sometimes also mythology, has been developed to reconstruct the specimen from the measured hologram. For a long time, the standard approach to deal with deviations from the ideal assumptions in real world holography experiments has been to simply ignore these. The prime example for this is the method of the standard flat

X-ray near-field holography. Beyond idealized assumptions of the probe

International Nuclear Information System (INIS)

Hagemann, Johannes

2017-01-01

The work at hand considers the imperfect, often neglected, aspects of X-ray nearfield phase-contrast propagation imaging, or in short: X-ray near-field holography (NFH). NFH is a X-ray microscopy technique able to yield high resolution, yet low dose imaging of a wide range of specimen. Derived from wave optical theory, propagation-based imaging methods rely on assumptions for the illuminating wave field. These are for example the assumptions of a perfect plane wave or spherical wave emanating from a point source or monochromaticity. Violation of the point source assumption implies for example at the same time the occurrence of a distorted wave front and a finite degree of coherence, both crucial for NFH. With the advances in X-ray focusing, instrumentation and X-ray wave guiding, NFH has become of high interest, since the barriers for practical implementation have been overcome. The idea of holography originates from electron microscopy to overcome the lack of high-quality electron lenses. With holography the need for optics between the specimen and detector is circumvented. The drawback, however, is that the measurement obtained at the detector is not a direct image of the specimen under survey but a ''propagated version'' of it, the so-called hologram. The problem with the optics is replaced by another problem, also referred to as the phase problem. The phase problem is caused by the fact that only the intensities of a wave field can be measured but not the phase information. The phase information is crucial for obtaining the image of the specimen and thus needs to be reconstructed. In recent years the methodology, sometimes also mythology, has been developed to reconstruct the specimen from the measured hologram. For a long time, the standard approach to deal with deviations from the ideal assumptions in real world holography experiments has been to simply ignore these. The prime example for this is the method of the standard flat

A computational study of the near-field generation and decay of wingtip vortices

International Nuclear Information System (INIS)

Craft, T.J.; Gerasimov, A.V.; Launder, B.E.; Robinson, C.M.E.

2006-01-01

The numerical prediction of the downstream trailing vortex shed from an aircraft wingtip is a particularly challenging CFD task because, besides predicting the development of the strong vortex itself, one needs to compute accurately the flow over the wing to resolve the boundary layer roll-up and shedding which provide the initial conditions for the free vortex. Computations are here reported of the flow over a NACA 0012 half-wing with rounded wing tip and the near-field wake as measured by [Chow, J.S., Zilliac, G., Bradshaw, P., 1997. Turbulence measurements in the near-field of a wingtip vortex. NASA Tech Mem 110418, NASA.]. The aim is to assess the performance of two turbulence models which, in principle, might be seen as capable of resolving both the three dimensional boundary layer on the wing and the generation and near-field decay of the strongly accelerated vortex that develops from the wingtip. Results using linear and non-linear eddy-viscosity models are presented, but these both exhibit a far too rapid decay of the vortex core. Only a stress-transport (or second-moment) model that satisfies the 'two-component limit', [Lumley, J.L., 1978. Computational modelling of turbulent flows. Adv. Appl. Mech. 18, 123-176.], reproduces the principal features found in the experimental measurements

Iced airfoil separation bubble measurements by particle image velocimetry

Science.gov (United States)

Jacobs, Jason J.

Not long after the birth of aviation, pilots began to recognize the dangers posed by aircraft icing. Since that time, research has improved the awareness of this problem and the scientific understanding of the associated aerodynamic impacts, however, few studies have involved detailed, quantitative, flowfield measurements. For this reason, the current investigation was conducted in which high spatial-resolution flowfield measurements were acquired of a NACA 0012 airfoil with two- and three-dimensional, simulated, leading-edge, horn-ice accretions utilizing particle image velocimetry (PIV). These measurements complemented existing iced airfoil performance measurements, revealed previously unknown details regarding the structure and behavior of these flowfields, and could potentially facilitate the development and improvement of computational schemes used to predict largely separated flows, including that of an iced airfoil near stall. Previous iced airfoil investigations have demonstrated somewhat reduced aerodynamic penalties resulting from a three-dimensional ice simulation, compared to those of a two-dimensional ice simulation of a representative cross section. Correspondingly, the current measurements revealed accelerated transition of the separated shear layer emanating from a three-dimensional ice simulation and therefore enhanced pressure recovery and reduced mean separation bubble length, each relative to the flowfield of a representative two-dimensional ice simulation. These effects appeared to result from the quasi-steady distribution of discrete, streamwise vortices which aided the turbulent entrainment of fluid from the recirculation region of the three-dimensional ice simulation separation bubble flowfield. These vortices were generated by a streamwise-vortex instability excited by roughness along the three-dimensional ice simulation and produced spanwise-cell structures throughout this flowfield, as well as significant spanwise variation in peak

Active control of near-field radiative heat transfer between graphene-covered metamaterials

Science.gov (United States)

Zhao, Qimei; Zhou, Ting; Wang, Tongbiao; Liu, Wenxing; Liu, Jiangtao; Yu, Tianbao; Liao, Qinghua; Liu, Nianhua

2017-04-01

In this study, the near-field radiative heat transfer between graphene-covered metamaterials is investigated. The electric surface plasmons (SPs) supported by metamaterials can be coupled with the SPs supported by graphene. The near-field heat transfer between the graphene-covered metamaterials is significantly larger than that between metamaterials because of the strong coupling in our studied frequency range. The relationship between heat flux and chemical potential is studied for different vacuum gaps. Given that the chemical potential of graphene can be tuned by the external electric field, heat transfer can be actively controlled by modulating the chemical potential. The heat flux for certain vacuum gaps can reach a maximum value when the chemical potential is at a particular value. The results of this study are beneficial for actively controlling energy transfer.

Active control of near-field radiative heat transfer between graphene-covered metamaterials

International Nuclear Information System (INIS)

Zhao, Qimei; Zhou, Ting; Wang, Tongbiao; Liu, Wenxing; Liu, Jiangtao; Yu, Tianbao; Liao, Qinghua; Liu, Nianhua

2017-01-01

In this study, the near-field radiative heat transfer between graphene-covered metamaterials is investigated. The electric surface plasmons (SPs) supported by metamaterials can be coupled with the SPs supported by graphene. The near-field heat transfer between the graphene-covered metamaterials is significantly larger than that between metamaterials because of the strong coupling in our studied frequency range. The relationship between heat flux and chemical potential is studied for different vacuum gaps. Given that the chemical potential of graphene can be tuned by the external electric field, heat transfer can be actively controlled by modulating the chemical potential. The heat flux for certain vacuum gaps can reach a maximum value when the chemical potential is at a particular value. The results of this study are beneficial for actively controlling energy transfer. (paper)

Numerical simulation of the effects of variation of angle of attack and sweep angle on vortex breakdown over delta wings

Science.gov (United States)

Ekaterinaris, J. A.; Schiff, Lewis B.

1990-01-01

In the present investigation of the vortical flowfield structure over delta wings at high angles of attack, three-dimensional Navier-Stokes numerical simulations were conducted to predict the complex leeward flowfield characteristics; these encompass leading-edge separation, secondary separation, and vortex breakdown. Attention is given to the effect on solution accuracy of circumferential grid-resolution variations in the vicinity of the wing leading edge, and well as to the effect of turbulence modeling on the solutions. When a critical angle-of-attack was reached, bubble-type vortex breakdown was found. With further angle-of-attack increase, a change from bubble-type to spiral-type vortex breakdown was predicted by the numerical solution.

Online Coupling of Flow-Field Flow Fractionation and Single Particle Inductively Coupled Plasma-Mass Spectrometry: Characterization of Nanoparticle Surface Coating Thickness and Aggregation State

Science.gov (United States)

Surface coating thickness and aggregation state have strong influence on the environmental fate, transport, and toxicity of engineered nanomaterials. In this study, flow-field flow fractionation coupled on-line with single particle inductively coupled plasma-mass spectrometry i...

Near-field terahertz imaging of ferroelectric domains in barium titanate

Czech Academy of Sciences Publication Activity Database

Berta, Milan; Kadlec, Filip

2010-01-01

Roč. 83, 10-11 (2010), 985-993 ISSN 0141-1594 R&D Projects: GA MŠk LC512 Institutional research plan: CEZ:AV0Z10100520 Keywords : singular value decomposition * domain structure imaging * near-field terahertz microscopy * subwavelength resolution Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.006, year: 2010

Mixed Far-Field and Near-Field Source Localization Algorithm via Sparse Subarrays

Directory of Open Access Journals (Sweden)

Jiaqi Song

2018-01-01

Full Text Available Based on a dual-size shift invariance sparse linear array, this paper presents a novel algorithm for the localization of mixed far-field and near-field sources. First, by constructing a cumulant matrix with only direction-of-arrival (DOA information, the proposed algorithm decouples the DOA estimation from the range estimation. The cumulant-domain quarter-wavelength invariance yields unambiguous estimates of DOAs, which are then used as coarse references to disambiguate the phase ambiguities in fine estimates induced from the larger spatial invariance. Then, based on the estimated DOAs, another cumulant matrix is derived and decoupled to generate unambiguous and cyclically ambiguous estimates of range parameter. According to the coarse range estimation, the types of sources can be identified and the unambiguous fine range estimates of NF sources are obtained after disambiguation. Compared with some existing algorithms, the proposed algorithm enjoys extended array aperture and higher estimation accuracy. Simulation results are given to validate the performance of the proposed algorithm.

Spherical near-field antenna measurements — The most accurate antenna measurement technique

DEFF Research Database (Denmark)

Breinbjerg, Olav

2016-01-01

The spherical near-field antenna measurement technique combines several advantages and generally constitutes the most accurate technique for experimental characterization of radiation from antennas. This paper/presentation discusses these advantages, briefly reviews the early history and present...

Optical security based on near-field processes at the nanoscale

International Nuclear Information System (INIS)

Naruse, Makoto; Tate, Naoya; Ohtsu, Motoichi

2012-01-01

Optics has been playing crucial roles in security applications ranging from authentication and watermarks to anti-counterfeiting. However, since the fundamental physical principle involves optical far-fields, or propagating light, diffraction of light causes severe difficulties, for example in device scaling and system integration. Moreover, conventional security technologies in use today have been facing increasingly stringent demands to safeguard against threats such as counterfeiting of holograms, requiring innovative physical principles and technologies to overcome their limitations. Nanophotonics, which utilizes interactions between light and matter at the nanometer scale via optical near-field interactions, can break through the diffraction limit of conventional propagating light. Moreover, nanophotonics has some unique physical attributes, such as localized optical energy transfer and the hierarchical nature of optical near-field interactions, which pave the way for novel security functionalities. This paper reviews the physical principles and describes some experimental demonstrations of systems based on nanophotonics with respect to security applications such as tamper resistance against non-invasive and invasive attacks, hierarchical information retrieval, hierarchical holograms, authentication, and traceability. (paper)

Prediction and near-field observation of skull-guided acoustic waves.

Science.gov (United States)

Estrada, Héctor; Rebling, Johannes; Razansky, Daniel

2017-06-21

Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. We observed a skull-guided wave propagation over a lateral distance of at least 3 mm, with a half-decay length in the direction perpendicular to the skull ranging from 35 to 300 μm at 6 and 0.5 MHz, respectively. Propagation losses are mostly attributed to the heterogenous acoustic properties of the skull. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

High-Throughput Near-Field Optical Nanoprocessing of Solution-Deposited Nanoparticles

KAUST Repository

Pan, Heng

2010-07-27

The application of nanoscale electrical and biological devices will benefit from the development of nanomanufacturing technologies that are highthroughput, low-cost, and flexible. Utilizing nanomaterials as building blocks and organizing them in a rational way constitutes an attractive approach towards this goal and has been pursued for the past few years. The optical near-field nanoprocessing of nanoparticles for high-throughput nanomanufacturing is reported. The method utilizes fluidically assembled microspheres as a near-field optical confinement structure array for laserassisted nanosintering and nanoablation of nanoparticles. By taking advantage of the low processing temperature and reduced thermal diffusion in the nanoparticle film, a minimum feature size down to ≈i100nm is realized. In addition, smaller features (50nm) are obtained by furnace annealing of laser-sintered nanodots at 400 °C. The electrical conductivity of sintered nanolines is also studied. Using nanoline electrodes separated by a submicrometer gap, organic field-effect transistors are subsequently fabricated with oxygen-stable semiconducting polymer. © 2010 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.

Near-field scanning optical microscopy using polymethylmethacrylate optical fiber probes

International Nuclear Information System (INIS)

Chibani, H.; Dukenbayev, K.; Mensi, M.; Sekatskii, S.K.; Dietler, G.

2010-01-01

We report the first use of polymethylmethacrylate (PMMA) optical fiber-made probes for scanning near-field optical microscopy (SNOM). The sharp tips were prepared by chemical etching of the fibers in ethyl acetate, and the probes were prepared by proper gluing of sharpened fibers onto the tuning fork in the conditions of the double resonance (working frequency of a tuning fork coincides with the resonance frequency of dithering of the free-standing part of the fiber) reported earlier for the case of glass fibers. Quality factors of the probes in the range 2000-6000 were obtained, which enables the realization of an excellent topographical resolution including state-of-art imaging of single DNA molecules. Near-field optical performance of the microscope is illustrated by the Photon Scanning Tunneling Microscope images of fluorescent beads with a diameter of 100 nm. The preparation of these plastic fiber probes proved to be easy, needs no hazardous material and/or procedures, and typical lifetime of a probe essentially exceeds that characteristic for the glass fiber probe.

Prediction and near-field observation of skull-guided acoustic waves

Science.gov (United States)

Estrada, Héctor; Rebling, Johannes; Razansky, Daniel

2017-06-01

Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. We observed a skull-guided wave propagation over a lateral distance of at least 3 mm, with a half-decay length in the direction perpendicular to the skull ranging from 35 to 300 μm at 6 and 0.5 MHz, respectively. Propagation losses are mostly attributed to the heterogenous acoustic properties of the skull. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

A Compact RFID Reader Antenna for UHF Near-Field and Far-Field Operations

Directory of Open Access Journals (Sweden)

Lai Xiao zheng

2013-01-01

Full Text Available A compact loop antenna is presented for mobile ultrahigh frequency (UHF radio frequency identification (RFID application. This antenna, printed on a 0.8 mm thick FR4 substrate with a small size of 31 mm × 31 mm, achieves good impedance bandwidth from 897 to 928 MHz, which covers USA RFID Band (902–928 MHz. The proposed loop configuration, with a split-ring resonator (SRR coupled inside it, demonstrates strong and uniform magnetic field distribution in the near-field antenna region. Its linearly polarized radiation pattern provides available far-field gain. Finally, the reading capabilities of antenna are up to 56 mm for near-field and 1.05 m for far-field UHF RFID operations, respectively.

Re-centering variable friction device for vibration control of structures subjected to near-field earthquakes

Science.gov (United States)

Ozbulut, Osman E.; Hurlebaus, Stefan

2011-11-01

This paper proposes a re-centering variable friction device (RVFD) for control of civil structures subjected to near-field earthquakes. The proposed hybrid device has two sub-components. The first sub-component of this hybrid device consists of shape memory alloy (SMA) wires that exhibit a unique hysteretic behavior and full recovery following post-transformation deformations. The second sub-component of the hybrid device consists of variable friction damper (VFD) that can be intelligently controlled for adaptive semi-active behavior via modulation of its voltage level. In general, installed SMA devices have the ability to re-center structures at the end of the motion and VFDs can increase the energy dissipation capacity of structures. The full realization of these devices into a singular, hybrid form which complements the performance of each device is investigated in this study. A neuro-fuzzy model is used to capture rate- and temperature-dependent nonlinear behavior of the SMA components of the hybrid device. An optimal fuzzy logic controller (FLC) is developed to modulate voltage level of VFDs for favorable performance in a RVFD hybrid application. To obtain optimal controllers for concurrent mitigation of displacement and acceleration responses, tuning of governing fuzzy rules is conducted by a multi-objective heuristic optimization. Then, numerical simulation of a multi-story building is conducted to evaluate the performance of the hybrid device. Results show that a re-centering variable friction device modulated with a fuzzy logic control strategy can effectively reduce structural deformations without increasing acceleration response during near-field earthquakes.

Hybrid Broadband Ground-Motion Simulation Using Scenario Earthquakes for the Istanbul Area

KAUST Repository

Reshi, Owais A.

2016-01-01

are critical for determining the behavior of ground motions especially in the near-field. Comparison of simulated ground motion intensities with ground-motion prediction quations indicates the need of development of the region-specific ground-motion prediction

Near-field imaging of interference pattern of counterpropagating evanescent waves

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Bozhevolnaya, Elena A.

1999-01-01

It is generally accepted that measurement of of the contrast of the intensity interference pattern formed by two counterpropagating evanescent waves can be used to characterize the resolving power of a collection near-field microscope. We argue that, if the light collected by a fiber probe propag...... be equal to the contrast of the interference pattern....

Scanning Near-Field Optical Microscopy

Directory of Open Access Journals (Sweden)

Dušan Vobornik

2008-02-01

Full Text Available An average human eye can see details down to 0,07 mm in size. The ability to see smaller details of the matter is correlated with the development of the science and the comprehension of the nature. Today’s science needs eyes for the nano-world. Examples are easily found in biology and medical sciences. There is a great need to determine shape, size, chemical composition, molecular structure and dynamic properties of nano-structures. To do this, microscopes with high spatial, spectral and temporal resolution are required. Scanning Near-field Optical Microscopy (SNOM is a new step in the evolution of microscopy. The conventional, lens-based microscopes have their resolution limited by diffraction. SNOM is not subject to this limitation and can offer up to 70 times better resolution.

Scanning near-field optical microscopy.

Science.gov (United States)

Vobornik, Dusan; Vobornik, Slavenka

2008-02-01

An average human eye can see details down to 0,07 mm in size. The ability to see smaller details of the matter is correlated with the development of the science and the comprehension of the nature. Today's science needs eyes for the nano-world. Examples are easily found in biology and medical sciences. There is a great need to determine shape, size, chemical composition, molecular structure and dynamic properties of nano-structures. To do this, microscopes with high spatial, spectral and temporal resolution are required. Scanning Near-field Optical Microscopy (SNOM) is a new step in the evolution of microscopy. The conventional, lens-based microscopes have their resolution limited by diffraction. SNOM is not subject to this limitation and can offer up to 70 times better resolution.

Near-Field Hydrology Data Package for the Immobilized Low-Activity Waste 2001 Performance Assessment

International Nuclear Information System (INIS)

PD Meyer; RJ Serne

1999-01-01

Lockheed Martin Hanford Company (LMHC) is designing and assessing the performance of disposal facilities to receive radioactive wastes that are currently stored in single- and double-shell tanks at the Hanford Site. The preferred method for disposing of the portion that is classified as immobilized low-activity waste (ILAW) is to vitrify the waste and place the product in new-surface, shallow land burial facilities. The LMHC project to assess the performance of these disposal facilities is the Hanford ILAW Performance Assessment (PA) Activity. The goal of this project is to provide a reasonable expectation that the disposal of the waste is protective of the general public, groundwater resources, air resources, surface water resources, and inadvertent intruders. Achieving this goal will require prediction of contaminant migration from the facilities. This migration is expected to occur primarily via the movement of water through the facilities and the consequent transport of dissolved contaminants in the pore water of the vadose zone. Pacific Northwest National Laboratory (PNNL) assists LMHC in its performance assessment activities. One of PNNL's tasks is to provide estimates of the physical, hydraulic, and transport properties of the materials comprising the disposal facilities and the disturbed region around them. These materials are referred to as the near-field materials. Their properties are expressed as parameters of constitutive models used in simulations of subsurface flow and transport. In addition to the best-estimate parameter values, information on uncertainty in the parameter values and estimates of the changes in parameter values over time are required to complete the PA. These parameter estimates and information are contained in this report, the Near-Field Hydrology Data Package

Control strategies for active noise barriers using near-field error sensing

NARCIS (Netherlands)

Berkhoff, Arthur P.

In this paper active noise control strategies for noise barriers are presented which are based on the use of sensors near the noise barrier. Virtual error signals are derived from these near-field sensor signals such that reductions of the far-field sound pressure are obtained with the active

Near-field acoustic imaging based on Laplacian sparsity

DEFF Research Database (Denmark)

Fernandez Grande, Efren; Daudet, Laurent

2016-01-01

We present a sound source identification method for near-field acoustic imaging of extended sources. The methodology is based on a wave superposition method (or equivalent source method) that promotes solutions with sparse higher order spatial derivatives. Instead of promoting direct sparsity......, and the validity of the wave extrapolation used for the reconstruction is examined. It is shown that this methodology can overcome conventional limits of spatial sampling, and is therefore valid for wide-band acoustic imaging of extended sources....

Geochemical evaluation of the near-field for future HLW repository at Olkiluoto

International Nuclear Information System (INIS)

Idiart, A.; Maia, F.; Arcos, D.

2013-10-01

The concept for the final disposal of spent nuclear fuel in Finland considers an engineered and natural (crystalline rock) multi-barrier system surrounding the spent fuel. This work aims at predicting and making a quantitative assessment of the geochemical evolution of the near-field (canister, buffer, backfill and adjacent fractured bedrock) during the unsaturated thermal period and in the long-term, after saturation has been completed. The groundwater/bentonite buffer interaction during the unsaturated thermal period is tackled through a two-dimensional (2D) axisymmetric scheme using the thermo-hydro-geochemical code TOUGHREACT. In turn, the long-term interaction of the fully water-saturated buffer and backfill with groundwater is assessed through 3D numerical models using the reactive transport code PHAST under isothermal conditions. A set of base cases have been set up based on the most plausible set of input data. In addition, a limited number of sensitivity cases have been conducted to analyse the influence of key parameters controlling the system and reduce uncertainty. Predicted mineralogical changes of accessory minerals in the bentonite for the thermal period are controlled by the dependence of mineral solubilities on temperature and on the solute transport by advection during the saturation process, and diffusion during the whole period. The results of the thermal period indicate that a small amount of the primary amorphous silica is redistributed in the buffer: dissolution close to the canister and precipitation close to the buffer - rock interface. Primary calcite dissolution/precipitation is minimal, remaining stable throughout the simulation time in all cases. Anhydrite precipitates near the canister due to the elevated temperature, while it dissolves from the outside of the buffer. The results indicate that there is no significant evaporation of water near the copper canister and thus no chloride salt reaches saturation. The geochemical changes of

The Mathematical Basis of the Inverse Scattering Problem for Cracks from Near-Field Data

Directory of Open Access Journals (Sweden)

Yao Mao

2015-01-01

Full Text Available We consider the acoustic scattering problem from a crack which has Dirichlet boundary condition on one side and impedance boundary condition on the other side. The inverse scattering problem in this paper tries to determine the shape of the crack and the surface impedance coefficient from the near-field measurements of the scattered waves, while the source point is placed on a closed curve. We firstly establish a near-field operator and focus on the operator’s mathematical analysis. Secondly, we obtain a uniqueness theorem for the shape and surface impedance. Finally, by using the operator’s properties and modified linear sampling method, we reconstruct the shape and surface impedance.

High-Density Near-Field Readout over 50 GB Capacity Using Solid Immersion Lens with High Refractive Index

Science.gov (United States)

Shinoda, Masataka; Saito, Kimihiro; Kondo, Takao; Ishimoto, Tsutomu; Nakaoki, Ariyoshi

2003-02-01

We have investigated high-density near-field readout using a solid immersion lens with a high refractive index. By using a glass material with a high refractive index of 2.08, we developed an optical pick-up with the effective numerical aperture of 1.8. We could observe a clear eye pattern for a 50 GB capacity disc in 120 mm diameter. We confirmed that the near-field readout system is promising method of realizing a high-density optical disc system.

Influence of flowfield and vehicle parameters on engineering aerothermal methods

Science.gov (United States)

Wurster, Kathryn E.; Zoby, E. Vincent; Thompson, Richard A.

1989-01-01

The reliability and flexibility of three engineering codes used in the aerosphace industry (AEROHEAT, INCHES, and MINIVER) were investigated by comparing the results of these codes with Reentry F flight data and ground-test heat-transfer data for a range of cone angles, and with the predictions obtained using the detailed VSL3D code; the engineering solutions were also compared. In particular, the impact of several vehicle and flow-field parameters on the heat transfer and the capability of the engineering codes to predict these results were determined. It was found that entropy, pressure gradient, nose bluntness, gas chemistry, and angle of attack all affect heating levels. A comparison of the results of the three engineering codes with Reentry F flight data and with the predictions obtained of the VSL3D code showed a very good agreement in the regions of the applicability of the codes. It is emphasized that the parameters used in this study can significantly influence the actual heating levels and the prediction capability of a code.

Interior near-field acoustical holography in flight.

Science.gov (United States)

Williams, E G; Houston, B H; Herdic, P C; Raveendra, S T; Gardner, B

2000-10-01

In this paper boundary element methods (BEM) are mated with near-field acoustical holography (NAH) in order to determine the normal velocity over a large area of a fuselage of a turboprop airplane from a measurement of the pressure (hologram) on a concentric surface in the interior of the aircraft. This work represents the first time NAH has been applied in situ, in-flight. The normal fuselage velocity was successfully reconstructed at the blade passage frequency (BPF) of the propeller and its first two harmonics. This reconstructed velocity reveals structure-borne and airborne sound-transmission paths from the engine to the interior space.

Enhanced density of optical data storage using near-field concept: fabrication and test of nanometric aperture array

International Nuclear Information System (INIS)

Cha, J.; Park, J. H.; Kim, Myong R.; Jhe, W.

1999-01-01

We have tried to enhance the density of the near-field optical memory and to improve the recording/readout speed. The current optical memory has the limitation in both density and speed. This barrier due to the far-field nature can be overcome by the use of near-field. The optical data storage density can be increased by reducing the size of the nanometric aperture where the near-field is obtained. To fabricate the aperture in precise dimension, we applied the orientation-dependent / anisotropic etching property of crystal Si often employed in the field of MEMS. And so we fabricated the 10 x 10 aperture array. This array will be also the indispensable part for speeding up. One will see the possibility of the multi-tracking pickup in the phase changing type memory through this array. This aperture array will be expected to write the bit-mark whose size is about 100 nm. We will show the recent result obtained. (author)

Reynolds-Averaged Turbulence Model Assessment for a Highly Back-Pressured Isolator Flowfield

Science.gov (United States)

Baurle, Robert A.; Middleton, Troy F.; Wilson, L. G.

2012-01-01

The use of computational fluid dynamics in scramjet engine component development is widespread in the existing literature. Unfortunately, the quantification of model-form uncertainties is rarely addressed with anything other than sensitivity studies, requiring that the computational results be intimately tied to and calibrated against existing test data. This practice must be replaced with a formal uncertainty quantification process for computational fluid dynamics to play an expanded role in the system design, development, and flight certification process. Due to ground test facility limitations, this expanded role is believed to be a requirement by some in the test and evaluation community if scramjet engines are to be given serious consideration as a viable propulsion device. An effort has been initiated at the NASA Langley Research Center to validate several turbulence closure models used for Reynolds-averaged simulations of scramjet isolator flows. The turbulence models considered were the Menter BSL, Menter SST, Wilcox 1998, Wilcox 2006, and the Gatski-Speziale explicit algebraic Reynolds stress models. The simulations were carried out using the VULCAN computational fluid dynamics package developed at the NASA Langley Research Center. A procedure to quantify the numerical errors was developed to account for discretization errors in the validation process. This procedure utilized the grid convergence index defined by Roache as a bounding estimate for the numerical error. The validation data was collected from a mechanically back-pressured constant area (1 2 inch) isolator model with an isolator entrance Mach number of 2.5. As expected, the model-form uncertainty was substantial for the shock-dominated, massively separated flowfield within the isolator as evidenced by a 6 duct height variation in shock train length depending on the turbulence model employed. Generally speaking, the turbulence models that did not include an explicit stress limiter more closely

Experimental measurements of the solubility of technetium under near-field conditions

International Nuclear Information System (INIS)

Pilkington, N.J.; Wilkins, J.D.

1988-05-01

The solubility of technetium in contact with hydrated technetium dioxide under near-field conditions has been measured experimentally. The values obtained were changed little by a change in pH or in the filtration method used. The presence of organic degradation products increased slightly the solution concentration of technetium. (author)

Magnetic anisotropy in a permalloy microgrid fabricated by near-field optical lithography

International Nuclear Information System (INIS)

Li, S. P.; Lebib, A.; Peyrade, D.; Natali, M.; Chen, Y.; Lew, W. S.; Bland, J. A. C.

2001-01-01

We report the fabrication and magnetic properties of permalloy microgrids prepared by near-field optical lithography and characterized using high-sensitivity magneto-optical Kerr effect techniques. A fourfold magnetic anisotropy induced by the grid architecture is identified. [copyright] 2001 American Institute of Physics

Influence of Basalt Mesh Induced Increase of Heterogeneity of Cement Composites with Dispersed Fibers on Its Resistance under Near-Field Blast

Science.gov (United States)

Zíma, J.; Foglar, M.

2017-09-01

This paper describes the influence of multiple basalt meshes in the cement composite specimens on the damage induced by near-field blast. Experimental measurements performed in the Boletice military area in 2014 and 2015 are evaluated by numerical simulations. The evaluation of the results is mainly focused on the stress propagation in the cement composite with dispersed fibers, the propagation of the overpressure caused by the blast and velocity of the ejected parts from the specimen. The influence of the presence and position of the basalt meshes in the specimen on its damage induced by delamination is also examined.

Apertureless near-field terahertz imaging using the self-mixing effect in a quantum cascade laser

Energy Technology Data Exchange (ETDEWEB)

Dean, Paul, E-mail: p.dean@leeds.ac.uk; Keeley, James; Kundu, Iman; Li, Lianhe; Linfield, Edmund H.; Giles Davies, A. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Mitrofanov, Oleg [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)

2016-02-29

We report two-dimensional apertureless near-field terahertz (THz) imaging using a quantum cascade laser (QCL) source and a scattering probe. A near-field enhancement of the scattered field amplitude is observed for small tip-sample separations, allowing image resolutions of ∼1 μm (∼λ/100) and ∼7 μm to be achieved along orthogonal directions on the sample surface. This represents the highest resolution demonstrated to date with a THz QCL. By employing a detection scheme based on self-mixing interferometry, our approach offers experimental simplicity by removing the need for an external detector and also provides sensitivity to the phase of the reinjected field.

Numerical simulation of the RISOe1-airfoil dynamic stall

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F.; Soerensen, N. [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

1997-12-31

In this paper we are concerned with the numerical computation of the dynamic stall that occur in the viscous flowfield over an airfoil. These results are compared to experimental data that were obtained with the new designed RISOe1-airfoil, both for a motionless airfoil and for a pitching motion. Moreover, we present some numerical computations of the plunging and lead-lag motions. We also investigate the possibility of using the pitching motion to simulate the plunging and lead-lag situations. (au)

Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling.

Science.gov (United States)

Kehr, S C; Liu, Y M; Martin, L W; Yu, P; Gajek, M; Yang, S-Y; Yang, C-H; Wenzel, M T; Jacob, R; von Ribbeck, H-G; Helm, M; Zhang, X; Eng, L M; Ramesh, R

2011-01-01

A planar slab of negative-index material works as a superlens with sub-diffraction-limited resolution, as propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of λ/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy and thermal sensors.

Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling

Science.gov (United States)

Kehr, S.C.; Liu, Y.M.; Martin, L.W.; Yu, P.; Gajek, M.; Yang, S.-Y.; Yang, C.-H.; Wenzel, M.T.; Jacob, R.; von Ribbeck, H.-G.; Helm, M.; Zhang, X.; Eng, L.M.; Ramesh, R.

2011-01-01

A planar slab of negative-index material works as a superlens with sub-diffraction-limited resolution, as propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of λ/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy and thermal sensors. PMID:21427720

Poly(diacetylene) Monolayers Studied with a Fluorescence Scanning Near-Field Optical Microscope

NARCIS (Netherlands)

Moers, Marco H.P.; Moers, M.H.P.; Gaub, Hermann E.; van Hulst, N.F.

1994-01-01

A novel and powerful method to study the optical properties of thin lipid films which a resolution superior to confocal microscopy is presented. With a scanning near-field optical microscope, fluorescence images of a Langmuir-Blodgett film of diethylene glycol diamine pentacosadiynoic amide are

Research on Radar Cross Section Measurement Based on Near-field Imaging of Cylindrical Scanning

Directory of Open Access Journals (Sweden)

Xing Shu-guang

2015-04-01

Full Text Available A new method of Radar Cross Section (RCS measurement based on near-field imaging of cylindrical scanning surface is proposed. The method is based on the core assumption that the target consists of ideal isotropic scattered centers. Three-dimensional radar scattered images are obtained by using the proposed method, and then to obtain the RCS of the target, the scattered far field is calculated by summing the fields generated by the equivalent scattered centers. Not only three dimensional radar reflectivity images but also the RCS of targets in certain three dimensional angle areas can be obtained. Compared with circular scanning that can only obtain twodimensional radar reflectivity images and RCS results in two-dimensional angle areas, cylindrical scanning can provide more information about the scattering properties of the targets. The method has strong practicability and its validity is verified by simulations.

Fluorescence detection of single molecules using pulsed near-field optical excitation and time correlated photon counting

International Nuclear Information System (INIS)

Ambrose, W.P.; Goodwin, P.M.; Martin, J.C.; Keller, R.A.

1994-01-01

Pulsed excitation, time correlated single photon counting and time gated detection are used in near-field optical microscopy to enhance fluorescence images and measure the fluorescence lifetimes of single molecules of Rhodamine 6G on silica surfaces. Time gated detection is used to reject prompt scattered background and to improve the image signal to noise ratio. The excited state lifetime of a single Rhodamine 6G molecule is found to depend on the position of the near-field probe. We attribute the lifetime variations to spontaneous emission rate alterations by the fluorescence reflected from and quenching by the aluminum coated probe

Probing the local microwave properties of superconducting thin films by a scanning microwave near-field microscope

CERN Document Server

Wu, L Y; Wang, K L; Jiang, T; Kang, L; Yang, S Z; Wu, P H

2002-01-01

In this paper, we present our approach to probe the local microwave properties of superconducting thin films by using the microwave near-field scanning technique. We have employed a coaxial cavity together with a niobium tip as the probe and established a scanning sample stage cooled by liquid nitrogen to study thin film devices at low temperature in our scanning microwave near-field microscope. Nondestructive images have been obtained on the inhomogeneity of the YBaCuO superconducting thin films at microwave frequency. We believe that these results would be helpful in evaluating the microwave performance of the devices.

Performance assessment of Large Eddy Simulation (LES) for modeling dispersion in an urban street canyon with tree planting

NARCIS (Netherlands)

Moonen, P.; Gromke, C.B.; Dorer, V.

2013-01-01

The potential of a Large Eddy Simulation (LES) model to reliably predict near-field pollutant dispersion is assessed. To that extent, detailed time-resolved numerical simulations of coupled flow and dispersion are conducted for a street canyon with tree planting. Different crown porosities are

Modulation of near-field heat transfer between two gratings

OpenAIRE

Biehs , Svend-Age; Da Rosa , Felipe S. S.; Ben-Abdallah , Philippe

2011-01-01

International audience; We present a theoretical study of near-field heat transfer between two uniaxial anisotropic planar structures. We investigate how the distance and relative orientation (with respect to their optical axes) between the objects affect the heat flux. In particular, we show that by changing the angle between the optical axes it is possible in certain cases to modulate the net heat flux up to 90% at room temperature, and discuss possible applications of such a strong effect.

Thermal management in MoS{sub 2} based integrated device using near-field radiation

Energy Technology Data Exchange (ETDEWEB)

Peng, Jiebin [Department of Physics, National University of Singapore, Singapore 117546 (Singapore); Zhang, Gang, E-mail: zhangg@ihpc.a-star.edu.sg [Institute of High Performance Computing, A*STAR, Singapore 138632 (Singapore); Li, Baowen [Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309 (United States)

2015-09-28

Recently, wafer-scale growth of monolayer MoS{sub 2} films with spatial homogeneity is realized on SiO{sub 2} substrate. Together with the latest reported high mobility, MoS{sub 2} based integrated electronic devices are expected to be fabricated in the near future. Owing to the low lattice thermal conductivity in monolayer MoS{sub 2}, and the increased transistor density accompanied with the increased power density, heat dissipation will become a crucial issue for these integrated devices. In this letter, using the formalism of fluctuation electrodynamics, we explored the near-field radiative heat transfer from a monolayer MoS{sub 2} to graphene. We demonstrate that in resonance, the maximum heat transfer via near-field radiation between MoS{sub 2} and graphene can be ten times higher than the in-plane lattice thermal conduction for MoS{sub 2} sheet. Therefore, an efficient thermal management strategy for MoS{sub 2} integrated device is proposed: Graphene sheet is brought into close proximity, 10–20 nm from MoS{sub 2} device; heat energy transfer from MoS{sub 2} to graphene via near-field radiation; this amount of heat energy then be conducted to contact due to ultra-high lattice thermal conductivity of graphene. Our work sheds light for developing cooling strategy for nano devices constructing with low thermal conductivity materials.

Improved Flow-Field Structures for Direct Methanol Fuel Cells

Energy Technology Data Exchange (ETDEWEB)

Gurau, Bogdan [Nuvant Systems Inc., Crown Point, IN (United States)

2013-05-31

The direct methanol fuel cell (DMFC) is ideal if high energy-density liquid fuels are required. Liquid fuels have advantages over compressed hydrogen including higher energy density and ease of handling. Although state-of-the-art DMFCs exhibit manageable degradation rates, excessive fuel crossover diminishes system energy and power density. Although use of dilute methanol mitigates crossover, the concomitant lowering of the gross fuel energy density (GFED) demands a complex balance-of-plant (BOP) that includes higher flow rates, external exhaust recirculation, etc. An alternative approach is redesign of the fuel delivery system to accommodate concentrated methanol. NuVant Systems Inc. (NuVant) will maximize the GFED by design and assembly of a DMFC that uses near neat methanol. The approach is to tune the diffusion of highly concentrated methanol (to the anode catalytic layer) to the back-diffusion of water formed at the cathode (i.e. in situ generation of dilute methanol at the anode layer). Crossover will be minimized without compromising the GFED by innovative integration of the anode flow-field and the diffusion layer. The integrated flow-field-diffusion-layers (IFDLs) will widen the current and potential DMFC operating ranges and enable the use of cathodes optimized for hydrogen-air fuel cells.

Manipulation of local optical properties and structures in molybdenum-disulfide monolayers using electric field-assisted near-field techniques.

Science.gov (United States)

Nozaki, Junji; Fukumura, Musashi; Aoki, Takaaki; Maniwa, Yutaka; Yomogida, Yohei; Yanagi, Kazuhiro

2017-04-05

Remarkable optical properties, such as quantum light emission and large optical nonlinearity, have been observed in peculiar local sites of transition metal dichalcogenide monolayers, and the ability to tune such properties is of great importance for their optoelectronic applications. For that purpose, it is crucial to elucidate and tune their local optical properties simultaneously. Here, we develop an electric field-assisted near-field technique. Using this technique we can clarify and tune the local optical properties simultaneously with a spatial resolution of approximately 100 nm due to the electric field from the cantilever. The photoluminescence at local sites in molybdenum-disulfide (MoS 2 ) monolayers is reversibly modulated, and the inhomogeneity of the charge neutral points and quantum yields is suggested. We successfully etch MoS 2 crystals and fabricate nanoribbons using near-field techniques in combination with an electric field. This study creates a way to tune the local optical properties and to freely design the structural shapes of atomic monolayers using near-field optics.

Optimization of a near-field thermophotovoltaic system operating at low temperature and large vacuum gap

Science.gov (United States)

Lim, Mikyung; Song, Jaeman; Kim, Jihoon; Lee, Seung S.; Lee, Ikjin; Lee, Bong Jae

2018-05-01

The present work successfully achieves a strong enhancement in performance of a near-field thermophotovoltaic (TPV) system operating at low temperature and large-vacuum-gap width by introducing a hyperbolic-metamaterial (HMM) emitter, multilayered graphene, and an Au-backside reflector. Design variables for the HMM emitter and the multilayered-graphene-covered TPV cell are optimized for maximizing the power output of the near-field TPV system with the genetic algorithm. The near-field TPV system with the optimized configuration results in 24.2 times of enhancement in power output compared with that of the system with a bulk emitter and a bare TPV cell. Through the analysis of the radiative heat transfer together with surface-plasmon-polariton (SPP) dispersion curves, it is found that coupling of SPPs generated from both the HMM emitter and the multilayered-graphene-covered TPV cell plays a key role in a substantial increase in the heat transfer even at a 200-nm vacuum gap. Further, the backside reflector at the bottom of the TPV cell significantly increases not only the conversion efficiency, but also the power output by generating additional polariton modes which can be readily coupled with the existing SPPs of the HMM emitter and the multilayered-graphene-covered TPV cell.

Characterization and fabrication of fully metal-coated scanning near-field optical microscopy SiO2 tips.

Science.gov (United States)

Aeschimann, L; Akiyama, T; Staufer, U; De Rooij, N F; Thiery, L; Eckert, R; Heinzelmann, H

2003-03-01

The fabrication of silicon cantilever-based scanning near-field optical microscope probes with fully aluminium-coated quartz tips was optimized to increase production yield. Different cantilever designs for dynamic- and contact-mode force feedback were implemented. Light transmission through the tips was investigated experimentally in terms of the metal coating and the tip cone-angle. We found that transmittance varies with the skin depth of the metal coating and is inverse to the cone angle, meaning that slender tips showed higher transmission. Near-field optical images of individual fluorescing molecules showed a resolution thermocouple showed no evidence of mechanical defect or orifice formation by thermal effects.

Study on the characteristics of interaction flowfields induced by supersonic jet on a revolution body

Directory of Open Access Journals (Sweden)

S.J. Luo

2017-11-01

Full Text Available The paper focuses on the triple jets interaction with a hypersonic external flow on a revolution body. The experimental model is a ogive-cylinder body with three supersonic nozzles, which are aligned along the flow direction. The freestream Mach numbers are 5 and 6. The spatial and surface flow characteristics are illustrated by the schlieren photographs and the typical pressure distribution. The results show that there are multi-wave system, separation, reattachment, multi-peak pressure, high-pressure and low-pressure zone boundaries obvious distinction in tri-jets interference flowfield. The present paper also analyzes how do the pressure ratio, the angle of attack, and Mach number effect on tri-jets interaction characteristics.

The ACE-DTU Planar Near-Field Ground Penetrating Radar Antenna Test Facility

DEFF Research Database (Denmark)

Lenler-Eriksen, Hans-Rudolph; Meincke, Peter

2004-01-01

The ACE-DTU planar near-field ground penetrating radar (GPR) antenna test facility is used to measure the plane-wave transmitting spectrum of a GPR loop antenna close to the air-soil interface by means of a probe buried in soil. Probe correction is implemented using knowledge about the complex...

Source characterization of underground explosions from hydrodynamic-to-elastic coupling simulations

Science.gov (United States)

Chiang, A.; Pitarka, A.; Ford, S. R.; Ezzedine, S. M.; Vorobiev, O.

2017-12-01

A major improvement in ground motion simulation capabilities for underground explosion monitoring during the first phase of the Source Physics Experiment (SPE) is the development of a wave propagation solver that can propagate explosion generated non-linear near field ground motions to the far-field. The calculation is done using a hybrid modeling approach with a one-way hydrodynamic-to-elastic coupling in three dimensions where near-field motions are computed using GEODYN-L, a Lagrangian hydrodynamics code, and then passed to WPP, an elastic finite-difference code for seismic waveform modeling. The advancement in ground motion simulation capabilities gives us the opportunity to assess moment tensor inversion of a realistic volumetric source with near-field effects in a controlled setting, where we can evaluate the recovered source properties as a function of modeling parameters (i.e. velocity model) and can provide insights into previous source studies on SPE Phase I chemical shots and other historical nuclear explosions. For example the moment tensor inversion of far-field SPE seismic data demonstrated while vertical motions are well-modeled using existing velocity models large misfits still persist in predicting tangential shear wave motions from explosions. One possible explanation we can explore is errors and uncertainties from the underlying Earth model. Here we investigate the recovered moment tensor solution, particularly on the non-volumetric component, by inverting far-field ground motions simulated from physics-based explosion source models in fractured material, where the physics-based source models are based on the modeling of SPE-4P, SPE-5 and SPE-6 near-field data. The hybrid modeling approach provides new prospects in modeling explosion source and understanding the uncertainties associated with it.

Light depolarization induced by metallic tips in apertureless near-field optical microscopy and tip-enhanced Raman spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Gucciardi, P G [CNR-Istituto per i Processi Chimico-Fisici, sezione Messina, Salita Sperone, Contrada Papardo, I-98158 Faro Superiore, Messina (Italy); Lopes, M; Deturche, R; Julien, C; Barchiesi, D; Chapelle, M Lamy de la [Institut Charles Delaunay-CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP2060, 10010 Troyes (France)

2008-05-28

We have investigated the depolarization effects of light scattered by sharp tips used for apertureless near-field optical microscopy. Dielectric and metal coated tips have been investigated and depolarization factors between 5 and 30% have been measured, changing as a function of the incident light polarization and of the tip shape. The experimental results are in good agreement with theoretical calculations performed by the finite element method, giving a near-field depolarization factor close to 10%. The effect of depolarization has been investigated in polarized tip-enhanced Raman spectroscopy (TERS) experiments; the depolarization gives rise to forbidden Raman modes in Si crystals.

Near-field imaging of out-of-plane light scattering in photonic crystal slabs

DEFF Research Database (Denmark)

Volkov, Valentyn; Bozhevolnyi, Sergey; Taillaert, Dirk

2003-01-01

A collection scanning near-field optical microscope (SNOM) is used to image the propagating of light at telecommunication wavelengths (1520-1570 nm) along photonic crystal (PC) slabs, which combine slab waveguides with in-plane PCs consisting of one- and two-dimensional gratings. The efficient out...

Ultrafast modulation of near-field heat transfer with tunable metamaterials

OpenAIRE

Cui, Longji; Huang, Yong; Wang, Ju; Zhu, Ke-Yong

2012-01-01

We propose a mechanism of active near-field heat transfer modulation relying on externally tunable metamaterials. A large modulation effect is observed and can be explained by the coupling of surface modes, which is dramatically varied in the presence of controllable magnetoelectric coupling in metamaterials. We finally discuss how a practical picosecond-scale thermal modulator can be made. This modulator allows manipulating nanoscale heat flux in an ultrafast and noncontact (by optical means...

Local detection efficiency of a NbN superconducting single photon detector explored by a scattering scanning near-field optical microscope.

Science.gov (United States)

Wang, Qiang; Renema, Jelmer J; Engel, Andreas; van Exter, Martin P; de Dood, Michiel J A

2015-09-21

We propose an experiment to directly probe the local response of a superconducting single photon detector using a sharp metal tip in a scattering scanning near-field optical microscope. The optical absorption is obtained by simulating the tip-detector system, where the tip-detector is illuminated from the side, with the tip functioning as an optical antenna. The local detection efficiency is calculated by considering the recently introduced position-dependent threshold current in the detector. The calculated response for a 150 nm wide detector shows a peak close to the edge that can be spatially resolved with an estimated resolution of ∼ 20 nm, using a tip with parameters that are experimentally accessible.

Planar Near-Field Measurements of Ground Penetrating Radar Antennas

DEFF Research Database (Denmark)

Meincke, Peter; Hansen, Thorkild

2004-01-01

Planar near-field measurements are formulated for a general ground penetrating radar (GPR) antenna. A total plane-wave scattering matrix is defined for the system consisting of the GPR antenna and the planar air-soil interface. The transmitting spectrum of the GPR antenna is expressed in terms...... of measurements obtained with a buried probe as the GPR antenna moves over a scan plane on the ground. A numerical example in which the scan plane is finite validates the expressions for the spectrum of the GPR antenna....

Near-field tsunami early warning and emergency planning in the Mediterranean Sea

Directory of Open Access Journals (Sweden)

Gerassimos A. Papadopoulos

2013-04-01

Full Text Available The new European project Near-field Tsunami Early Warning and Emergency Planning in the Mediterranean Sea (NEARTOWARN faces the need to develop operational tsunami early warning systems in near-field (local conditions where the travel time of the first tsunami wave is very short, that is less than 30 min, which is a typical case in the North East Atlantic and the Mediterranean Sea region but also elsewhere around the globe. The operational condition that should be fulfilled is that the time of tsunami detection, plus the time of warning transmitting, plus the time of evacuation should not exceed the travel time of the first tsunami wave from its source to the closest evacuation zone. To this goal the time to detect of the causative earthquake should be compressed at the very minimum. In this context the core of the proposed system is a network of seismic early warning devices, which activate and send alert in a few seconds after the generation of a near-field earthquake, when a seismic ground motion exceeding a prescribed threshold is detected. Then civil protection mobilizes to manage the earthquake crisis but also to detect and manage a possible tsunami through a geographical risk management system. For the tsunami detection the system is supported by tide-gauges of radar type, a database of presimulated tsunami scenarios, and a local tsunami decision matrix. The island of Rhodes in the eastern termination of the Hellenic Arc and Trench has been selected for a pilot and operational development of the local tsunami warning system given that the island is a highly popular tourist destination, historically it was hit by large tsunamigenic earthquakes and was recently the master test-site for the pan-European FP6 tsunami research project Tsunami Risk ANd Strategies For the European Region (TRANSFER.

Development of a shear-force scanning near-field cathodoluminescence microscope for characterization of nanostructures' optical properties.

Science.gov (United States)

Bercu, N B; Troyon, M; Molinari, M

2016-09-01

An original scanning near-field cathodoluminescence microscope for nanostructure characterization has been developed and successfully tested. By using a bimorph piezoelectric stack both as actuator and detector, the developed setup constitutes a real improvement compared to previously reported SEM-based solutions. The technique combines a scanning probe and a scanning electron microscope in order to simultaneously offer near-field cathodoluminescence and topographic images of the sample. Share-force topography and cathodoluminescence measurements on GaN, SiC and ZnO nanostructures using the developed setup are presented showing a nanometric resolution in both topography and cathodoluminescence images with increased sensitivity compared to classical luminescence techniques. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Direct measurement of the near-field super resolved focused spot in InSb

NARCIS (Netherlands)

Assafrao, A.C.; Wachters, A.J.H.; Verheijen, M.; Nugrowati, A.M.; Pereira, S.F.; Urbach, H.P.; Armand, M.F.; Olivier, S.

2012-01-01

Under appropriate laser exposure, a thin film of InSb exhibits a sub-wavelength thermally modified area that can be used to focus light beyond the diffraction limit. This technique, called Super-Resolution Near-Field Structure, is a potential candidate for ultrahigh density optical data storage and

Scanning near-field optical microscopy of quantum dots in photonic crystal cavities

Energy Technology Data Exchange (ETDEWEB)

Skacel, Matthias; Fiore, Andrea [COBRA Research Institute, Technical University Eindhoven, Den Dolech 2, 5600 MB Eindhoven (Netherlands); Prancardi, Marco; Gerardino, Annamaria [Institute of Photonics and Nanotechnology, CNR, via del Cineto Romano 42, 00156 Roma (Italy); Alloing, Blandine; Li Lianhe, E-mail: m.s.skacel@tue.n [Institute of Photonics and Quantum Electronics, EPFL, CH-1015 Lausanne (Switzerland)

2010-09-01

Nanophotonic devices are of major interest for research and future quantum communication applications. Due to their nanometer feature size the resolution limit of far-field microscopy poses a limitation on the characterization of their optical properties. A method to overcome the resolution limit is the Scanning Near-Field Optical Microscope (SNOM). By approaching a fiber tip into the close vicinity of the sample the optical emission in the near-field regime is collected. This way of collecting the light is not affected by the diffraction limit. We employ a low temperature SNOM to investigate the photoluminescence of InAs QDs emitting at 1300nm wavelength embedded in photonic crystal cavities. At each location of an image scan the tip is stopped and a spectrum is acquired. We then plot maps of the photoluminescence for each wavelength. With this instrument it is now possible to directly observe the coupling of QDs to photonic crystal cavities both spectrally and spatially. We show first results of photoluminescence mapping of InAs QDs in photonic crystal cavities.

Near-field Light Scattering Techniques for Measuring Nanoparticle-Surface Interaction Energies and Forces.

Science.gov (United States)

Schein, Perry; Ashcroft, Colby K; O'Dell, Dakota; Adam, Ian S; DiPaolo, Brian; Sabharwal, Manit; Shi, Ce; Hart, Robert; Earhart, Christopher; Erickson, David

2015-08-15

Nanoparticles are quickly becoming commonplace in many commercial and industrial products, ranging from cosmetics to pharmaceuticals to medical diagnostics. Predicting the stability of the engineered nanoparticles within these products a priori remains an important and difficult challenge. Here we describe our techniques for measuring the mechanical interactions between nanoparticles and surfaces using near-field light scattering. Particle-surface interfacial forces are measured by optically "pushing" a particle against a reference surface and observing its motion using scattered near-field light. Unlike atomic force microscopy, this technique is not limited by thermal noise, but instead takes advantage of it. The integrated waveguide and microfluidic architecture allow for high-throughput measurements of about 1000 particles per hour. We characterize the reproducibility of and experimental uncertainty in the measurements made using the NanoTweezer surface instrument. We report surface interaction studies on gold nanoparticles with 50 nm diameters, smaller than previously reported in the literature using similar techniques.

Red-Shift Effects in Surface Enhanced Raman Spectroscopy: Spectral or Intensity Dependence of the Near-Field?

KAUST Repository

Colas, Florent; Cottat, Maximilien; Gillibert, Raymond; Guillot, Nicolas; Djaker, Nadia; Lidgi-Guigui, Nathalie; Toury, Timothé e; Barchiesi, Dominique; Toma, Andrea; Di Fabrizio, Enzo M.; Gucciardi, Pietro Giuseppe; de la Chapelle, Marc Lamy

2016-01-01

Optimum amplification in Surface Enhanced Raman Scattering (SERS) from individual nanoantennas is expected when the excitation is slightly blue-shifted with respect to the Localized Surface Plasmon Resonance (LSPR), so that the LSPR peak falls in the middle between the laser and the Stokes Raman emission. Recent experiments have shown when moving the excitation from the visible to the near-infrared that this rule of thumb is no more valid. The excitation has to be red-shifted with respect to the LSPR peak, up to 80nm, to obtain highest SERS. Such discrepancy is usually attributed to a Near-Field (NF) to Far-Field (FF) spectral shift. Here we critically discuss this hypothesis for the case of gold nanocylinders. By combining multi-wavelength excitation SERS experiments with numerical calculations, we show that the red-shift of the excitation energy does not originate from a spectral shift between the extinction (FF) and the near-field distribution (NF), which is found to be not larger than 10nm. Rather, it can be accounted for by looking at the peculiar spectral dependence of the near-field intensity on the cylinders diameter, characterized by an initial increase, up to 180nm diameter, followed by a decrease and a pronounced skewness.

Near-field study with a photon scanning tunneling microscope: Comparison between dielectric nanostructure and metallic nanostructure

International Nuclear Information System (INIS)

Mahmoud, Mahmoud Youcef; Bassou, Ghaouti; Salomon, Laurant; Chekroun, Z.; Djamai, Nesrine

2007-01-01

Scanning near-field optical microscopy (SNOM) integrates standard optical methods with scanning probe microscopy (SPM) techniques allowing to collect optical information with resolution well beyond the diffraction limit. We study the influence on image formation of several parameters in scanning near-field microscopy. The numerical calculations have been carried out using the differential method. We investigate a 2D-PSTM configuration with a dielectric rectangular object. We will focus on the collection type SNOM in a constant height scanning mode. Various oscillation patterns are observed from both sides of the nanostructure, which we interpret as interference between the diffracted waves scattered by the nanostructure (with the components of the wave vector parallel to the surface) and the evanescent incident wave above the surface. Using an optical near-field analysis and by calculating the electric field intensity distribution, we investigate the probe-sample distance effect. It is found that the distribution of the intensity related to the electric field is depending on sample-probe distance. We noticed the loss of details in the image and the presence of dramatic oscillations. Also, both of the polarization state of the illuminating light effect and the angle of incidence are investigated. We conclude that a differential method provides physical insight into the main features of the different images

Near-field study with a photon scanning tunneling microscope: Comparison between dielectric nanostructure and metallic nanostructure

Energy Technology Data Exchange (ETDEWEB)

Mahmoud, Mahmoud Youcef [Laboratoire d' elaboration et caracterisation des materiaux, Groupe de Microscopie et Microanalyse, Universite Djilali Liabes de Sidi Bel-Abbes, Faculte des sciences (Algeria)], E-mail: mahmoudhamoud@yahoo.com; Bassou, Ghaouti [Laboratoire d' elaboration et caracterisation des materiaux, Groupe de Microscopie et Microanalyse, Universite Djilali Liabes de Sidi Bel-Abbes, Faculte des sciences (Algeria); Laboratoire de Physique (LPUB), CNRS UMR 5027, Groupe d' Optique de Champ Proche, Faculte des Sciences Mirande, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47 870, 21078 Dijon Cedex (France); Salomon, Laurant [Laboratoire de Physique (LPUB), CNRS UMR 5027, Groupe d' Optique de Champ Proche, Faculte des Sciences Mirande, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47 870, 21078 Dijon Cedex (France); Chekroun, Z. [Laboratoire d' elaboration et caracterisation des materiaux, Groupe de Microscopie et Microanalyse, Universite Djilali Liabes de Sidi Bel-Abbes, Faculte des sciences (Algeria); Djamai, Nesrine [Laboratoire de telecommunications et de traitement numerique du signal (LTTNS), Universite Djilali Liabes de Sidi Bel-Abbes, Faculte des sciences de l' ingenieur, Departement d' electronique (Algeria)

2007-08-25

Scanning near-field optical microscopy (SNOM) integrates standard optical methods with scanning probe microscopy (SPM) techniques allowing to collect optical information with resolution well beyond the diffraction limit. We study the influence on image formation of several parameters in scanning near-field microscopy. The numerical calculations have been carried out using the differential method. We investigate a 2D-PSTM configuration with a dielectric rectangular object. We will focus on the collection type SNOM in a constant height scanning mode. Various oscillation patterns are observed from both sides of the nanostructure, which we interpret as interference between the diffracted waves scattered by the nanostructure (with the components of the wave vector parallel to the surface) and the evanescent incident wave above the surface. Using an optical near-field analysis and by calculating the electric field intensity distribution, we investigate the probe-sample distance effect. It is found that the distribution of the intensity related to the electric field is depending on sample-probe distance. We noticed the loss of details in the image and the presence of dramatic oscillations. Also, both of the polarization state of the illuminating light effect and the angle of incidence are investigated. We conclude that a differential method provides physical insight into the main features of the different images.

Red-Shift Effects in Surface Enhanced Raman Spectroscopy: Spectral or Intensity Dependence of the Near-Field?

KAUST Repository

Colas, Florent

2016-06-06

Optimum amplification in Surface Enhanced Raman Scattering (SERS) from individual nanoantennas is expected when the excitation is slightly blue-shifted with respect to the Localized Surface Plasmon Resonance (LSPR), so that the LSPR peak falls in the middle between the laser and the Stokes Raman emission. Recent experiments have shown when moving the excitation from the visible to the near-infrared that this rule of thumb is no more valid. The excitation has to be red-shifted with respect to the LSPR peak, up to 80nm, to obtain highest SERS. Such discrepancy is usually attributed to a Near-Field (NF) to Far-Field (FF) spectral shift. Here we critically discuss this hypothesis for the case of gold nanocylinders. By combining multi-wavelength excitation SERS experiments with numerical calculations, we show that the red-shift of the excitation energy does not originate from a spectral shift between the extinction (FF) and the near-field distribution (NF), which is found to be not larger than 10nm. Rather, it can be accounted for by looking at the peculiar spectral dependence of the near-field intensity on the cylinders diameter, characterized by an initial increase, up to 180nm diameter, followed by a decrease and a pronounced skewness.

Radionuclide transport in the repository near-field and far-field

International Nuclear Information System (INIS)

Poteri, A.; Nordman, H.; Pulkkanen, V.-M.; Smith, P.

2014-01-01

This report is a background report of the TURVA-2012 safety case report 'Assessment of Radionuclide Release Scenarios for the Repository System'. This report gives a comprehensive account of the modelling of radionuclide release from a defective canister and the subsequent migration to the surface groundwater system. The focus of this report is in the radionuclide migration both in the repository near-field and in the repository far-field. Radionuclide releases from the canister and migration through the repository near-field and far-field have also been analysed in the probabilistic sensitivity analysis based on the Monte Carlo simulation method. Those simulations are discussed in a separate report by Cormenzana. Calculation cases are derived from three different types of scenarios: (i) The base scenario that assumes a single initially defective canister located in a cautiously selected canister position, i.e. selecting the failed canister location such that radionuclide release and transport properties are conservative compared to the statistics over all canister locations. Migration processes and parameter values follow the most likely lines of evolution. Repository safety functions are assumed to perform according to the design basis. Calculation cases defined in the Assessment of Radionuclide Release Scenarios report are also supplemented by additional calculation cases that are aimed to study variability between different DFN realisations (additional BS-ALL cases), longitudinal dispersion (BS-RC-ld cases) and alternative realisations of the transport classes along the release paths (BS-RC-tc cases), (ii) Variant scenarios that study declined performance of the repository safety functions. These include enhanced corrosion failure and degradation of the buffer under variant geochemical conditions (iii) Disturbance scenarios that analyse influences of unlikely events on the radionuclide release and migration. Analysis of the variant and disturbance scenarios

Characterization of Alq3 thin films by a near-field microwave microprobe.

Science.gov (United States)

Hovsepyan, Artur; Lee, Huneung; Sargsyan, Tigran; Melikyan, Harutyun; Yoon, Youngwoon; Babajanyan, Arsen; Friedman, Barry; Lee, Kiejin

2008-09-01

We observed tris-8-hydroxyquinoline aluminum (Alq3) thin films dependence on substrate heating temperatures by using a near-field microwave microprobe (NFMM) and by optical absorption at wavelengths between 200 and 900 nm. The changes of absorption intensity at different substrate heating temperatures are correlated to the changes in the sheet resistance of Alq3 thin films.

Observation of magnetic domains using a reflection mode scanning near-field optical microscope

NARCIS (Netherlands)

Durkam, C.; Shvets, I.V.; Lodder, J.C.

1997-01-01

It is demonstrated that it is possible to image magnetic domains with a resolution of better than 60 nm with the Kerr effect in a reflection-mode scanning near-field optical microscope. Images taken of tracks of thermomagnetically prewritten bits in a Co/Pt multilayer structure magnetized out-of

Progress in nano-electro optics characterization of nano-optical materials and optical near-field interactions

CERN Document Server

Ohtsu, Motoichi

2005-01-01

This volume focuses on the characterization of nano-optical materials and optical-near field interactions. It begins with the techniques for characterizing the magneto-optical Kerr effect and continues with methods to determine structural and optical properties in high-quality quantum wires with high spatial uniformity. Further topics include: near-field luminescence mapping in InGaN/GaN single quantum well structures in order to interpret the recombination mechanism in InGaN-based nano-structures; and theoretical treatment of the optical near field and optical near-field interactions, providing the basis for investigating the signal transport and associated dissipation in nano-optical devices. Taken as a whole, this overview will be a valuable resource for engineers and scientists working in the field of nano-electro-optics.

Optical near-field lithography on hydrogen-passivated silicon surfaces

DEFF Research Database (Denmark)

Madsen, Steen; Müllenborn, Matthias; Birkelund, Karen

1996-01-01

by the optical near field, were observed after etching in potassium hydroxide. The uncoated fibers can also induce oxidation without light exposure, in a manner similar to an atomic force microscope, and linewidths of 50 nm have been achieved this way. (C) 1996 American Institute of Physics.......We report on a novel lithography technique for patterning of hydrogen-passivated amorphous silicon surfaces. A reflection mode scanning near-field optical microscope with uncoated fiber probes has been used to locally oxidize a thin amorphous silicon layer. Lines of 110 nm in width, induced...

Near-field optical microscopy with a scanning tunneling microscope

International Nuclear Information System (INIS)

Barbara, A.; Lopez-Rios, T.; Quemerais, P.

2005-01-01

A homemade apertureless near-field optical microscope using a scanning tunneling microscope (STM) is described. The experimental set-up simultaneously provides optical and topographic images of the sample. Technical details and features of the set-up are presented, together with results demonstrating the sub-wavelength resolution achieved as well as its sensitivity to dielectric contrasts. We show that the use of a STM permits to precisely control very small distances between the tip and the sample which is a great advantage to excite localized optical resonances between the tip and the surface

Single molecule mapping of the optical field distribution of probes for near-field microscopy

NARCIS (Netherlands)

Veerman, J.A.; Garcia Parajo, M.F.; Kuipers, L.; van Hulst, N.F.

1999-01-01

The most difficult task in near-field scanning optical microscopy (NSOM) is to make a high quality subwavelength aperture probe, Recently we have developed high definition NSOM probes by focused ion beam (FIB) milling. These probes have a higher brightness, better polarization characteristics,

Decision making based on optical excitation transfer via near-field interactions between quantum dots

International Nuclear Information System (INIS)

Naruse, Makoto; Nomura, Wataru; Ohtsu, Motoichi; Aono, Masashi; Sonnefraud, Yannick; Drezet, Aurélien; Huant, Serge; Kim, Song-Ju

2014-01-01

Optical near-field interactions between nanostructured matters, such as quantum dots, result in unidirectional optical excitation transfer when energy dissipation is induced. This results in versatile spatiotemporal dynamics of the optical excitation, which can be controlled by engineering the dissipation processes and exploited to realize intelligent capabilities such as solution searching and decision making. Here, we experimentally demonstrate the ability to solve a decision making problem on the basis of optical excitation transfer via near-field interactions by using colloidal quantum dots of different sizes, formed on a geometry-controlled substrate. We characterize the energy transfer behavior due to multiple control light patterns and experimentally demonstrate the ability to solve the multi-armed bandit problem. Our work makes a decisive step towards the practical design of nanophotonic systems capable of efficient decision making, one of the most important intellectual attributes of the human brain.

Decision making based on optical excitation transfer via near-field interactions between quantum dots

Energy Technology Data Exchange (ETDEWEB)

Naruse, Makoto, E-mail: naruse@nict.go.jp [Photonic Network Research Institute, National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795 (Japan); Nomura, Wataru; Ohtsu, Motoichi [Department of Electrical Engineering and Information Systems, Graduate School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Aono, Masashi [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguru-ku, Tokyo 152-8550 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi-shi, Saitama 332-0012 (Japan); Sonnefraud, Yannick; Drezet, Aurélien; Huant, Serge [Université Grenoble Alpes, Inst. NEEL, F-38000 Grenoble (France); CNRS, Inst. NEEL, F-38042 Grenoble (France); Kim, Song-Ju [WPI Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2014-10-21

Optical near-field interactions between nanostructured matters, such as quantum dots, result in unidirectional optical excitation transfer when energy dissipation is induced. This results in versatile spatiotemporal dynamics of the optical excitation, which can be controlled by engineering the dissipation processes and exploited to realize intelligent capabilities such as solution searching and decision making. Here, we experimentally demonstrate the ability to solve a decision making problem on the basis of optical excitation transfer via near-field interactions by using colloidal quantum dots of different sizes, formed on a geometry-controlled substrate. We characterize the energy transfer behavior due to multiple control light patterns and experimentally demonstrate the ability to solve the multi-armed bandit problem. Our work makes a decisive step towards the practical design of nanophotonic systems capable of efficient decision making, one of the most important intellectual attributes of the human brain.

Near-Field, On-Chip Optical Brownian Ratchets.

Science.gov (United States)

Wu, Shao-Hua; Huang, Ningfeng; Jaquay, Eric; Povinelli, Michelle L

2016-08-10

Nanoparticles in aqueous solution are subject to collisions with solvent molecules, resulting in random, Brownian motion. By breaking the spatiotemporal symmetry of the system, the motion can be rectified. In nature, Brownian ratchets leverage thermal fluctuations to provide directional motion of proteins and enzymes. In man-made systems, Brownian ratchets have been used for nanoparticle sorting and manipulation. Implementations based on optical traps provide a high degree of tunability along with precise spatiotemporal control. Here, we demonstrate an optical Brownian ratchet based on the near-field traps of an asymmetrically patterned photonic crystal. The system yields over 25 times greater trap stiffness than conventional optical tweezers. Our technique opens up new possibilities for particle manipulation in a microfluidic, lab-on-chip environment.

Near-field optical nanopatterning of crystalline silicon

International Nuclear Information System (INIS)

Wysocki, G.; Heitz, J.; Baeuerle, D.

2004-01-01

Nanoscale photochemical and photophysical etching of Si in Cl 2 atmosphere is demonstrated by means of an optical near-field setup. With 351 nm Ar + -laser radiation and low intensities, the etching mechanism is purely photochemical. In this regime, the width of patterns - which is about 115 nm at full width at half maximum (FWHM) - corresponds, approximately, to the diameter of the fiber tip. The vertical etch rate is of the order of 1 nm/s. With 514.5 nm Ar + -laser light etching is observed only at significantly higher laser-light intensities. Patterns with width down to about 30 nm at FWHM have been achieved. Here, the lateral resolution corresponds to about 1/18 of the laser wavelength employed

Far- and near-field optical properties of gold nanoparticle ensembles

International Nuclear Information System (INIS)

Nedyalkov, N N; Dikovska, A O; Dimitrov, I; Nikov, Ru; Atanasov, P A; Toshkova, R A; Gardeva, E G; Yossifova, L S; Alexandrov, M T

2012-01-01

The optical properties of gold nanoparticle clusters are presented from the point of view of their applications in biophotonics, where the absorption and scattering spectra are crucial. Generalised multiparticle Mie theory and finite difference time domain (FDTD) technique are used for theoretical description of the far- and nearfield optical properties of two dimensional nanoparticle ensembles. The system under consideration consists of spherical gold nanoparticles from 20 to 200 nm in diameter, forming 2D clusters in water. The properties of the far-field absorption and scattering spectra as a function of the cluster size, particle dimensions, and interparticle distance are investigated for ordered hexagonal structure of the particle arrays. It is found that the absorption efficiency can be shifted to the IR spectral range by increasing array size and decreasing interparticle distance. The increase in the array size also results in enhancement of the scattering efficiency while the absorption is reduced. The near-field intensity distribution is inhomogeneous over the array, as formation of zones with intensity enhancement of about two orders of magnitude is observed in specific areas. The optical properties of an ensemble whose configuration is reproduced from real experiments of gold nanoparticle deposition onto cancer cells are also presented. The results obtained can be used in designing of nanoparticle arrays with applications in biophotonics, bioimaging and photothermal therapy. (nanosystems)

Far- and near-field optical properties of gold nanoparticle ensembles

Energy Technology Data Exchange (ETDEWEB)

Nedyalkov, N N; Dikovska, A O; Dimitrov, I; Nikov, Ru; Atanasov, P A; Toshkova, R A; Gardeva, E G; Yossifova, L S; Alexandrov, M T

2012-12-31

The optical properties of gold nanoparticle clusters are presented from the point of view of their applications in biophotonics, where the absorption and scattering spectra are crucial. Generalised multiparticle Mie theory and finite difference time domain (FDTD) technique are used for theoretical description of the far- and nearfield optical properties of two dimensional nanoparticle ensembles. The system under consideration consists of spherical gold nanoparticles from 20 to 200 nm in diameter, forming 2D clusters in water. The properties of the far-field absorption and scattering spectra as a function of the cluster size, particle dimensions, and interparticle distance are investigated for ordered hexagonal structure of the particle arrays. It is found that the absorption efficiency can be shifted to the IR spectral range by increasing array size and decreasing interparticle distance. The increase in the array size also results in enhancement of the scattering efficiency while the absorption is reduced. The near-field intensity distribution is inhomogeneous over the array, as formation of zones with intensity enhancement of about two orders of magnitude is observed in specific areas. The optical properties of an ensemble whose configuration is reproduced from real experiments of gold nanoparticle deposition onto cancer cells are also presented. The results obtained can be used in designing of nanoparticle arrays with applications in biophotonics, bioimaging and photothermal therapy. (nanosystems)

REFREP: a near-field model for a spent fuel repository

International Nuclear Information System (INIS)

Hautojaervi, A.; Vieno, T.

1988-05-01

A code package for near-field performance analysis of spent fuel disposal has been programmed. The conceptual models used are shortly described in connection with th model presentations. For more comprehensive descriptions the previous safety analysis and references therein are referred. The REFREP package consists of nine individual modules performing the following tasks: viewing and updating of the data files (UPDATE), calculating of the breaching times of canisters (CORRFLUX), calculating of stationary nuclide release rates using solubility values (MASSFLUX), calculating of actinide inventories from chain decay (INVENT), calculating of elemental inventories of actinides (ELEMENT), calculating of nuclide release rates according to congruent release (CONGRUNT), performing of sensitivity analysis for one variable (SENSIT), summing of release rates from individual canisters according to given probability distributions of canister breaching times (PROBREL), and forming a compact data file including all the input values (DATAOUT). The results have been shown to agree very well with the results of the previous safety analysis where near-field analysis was performed by means of separate codes and manual calculation. The REFREP model offers already at this stage some additional features to the old procedures and more versatile capabilities can easyly be added into the modular structure of the package. REFREP has been developed in a VAX-environment. Some changes in file handling might be necessary if the code is transferred to another computer

Near-field optical microscopy of localized excitations on rough surfaces: influence of a probe

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.

1999-01-01

Starting from the general principles of near-field optical microscopy. I consider the influence of a probe when being used to image localized dipolar excitations and suggest a way of evaluating the perturbation thus introduced. Using the rigorous microscopic (electric) point-dipole description, I...

Near-field diffraction of laser light by dielectric corner step

Science.gov (United States)

Stafeev, S.; Kotlyar, V.; Kovalev, A.

2014-01-01

The diffraction of a linearly polarized plane wave by a corner dielectric microstep of height equals of two incident wavelengths was studied using finite-difference time domain method and near-field scanning optical microscopy. It was shown that the corner step generates an elongated region of enhanced intensity, termed as a curved laser microjet. The curved laser microjet has a length of about DOF = 9.5λ and the smallest diameter FWHM = (1.94+/-0.15)λ at distance z = 5.5λ.

Hybrid Reynolds-Averaged/Large Eddy Simulation of a Cavity Flameholder; Assessment of Modeling Sensitivities

Science.gov (United States)

Baurle, R. A.

2015-01-01

Steady-state and scale-resolving simulations have been performed for flow in and around a model scramjet combustor flameholder. The cases simulated corresponded to those used to examine this flowfield experimentally using particle image velocimetry. A variety of turbulence models were used for the steady-state Reynolds-averaged simulations which included both linear and non-linear eddy viscosity models. The scale-resolving simulations used a hybrid Reynolds-averaged / large eddy simulation strategy that is designed to be a large eddy simulation everywhere except in the inner portion (log layer and below) of the boundary layer. Hence, this formulation can be regarded as a wall-modeled large eddy simulation. This effort was undertaken to formally assess the performance of the hybrid Reynolds-averaged / large eddy simulation modeling approach in a flowfield of interest to the scramjet research community. The numerical errors were quantified for both the steady-state and scale-resolving simulations prior to making any claims of predictive accuracy relative to the measurements. The steady-state Reynolds-averaged results showed a high degree of variability when comparing the predictions obtained from each turbulence model, with the non-linear eddy viscosity model (an explicit algebraic stress model) providing the most accurate prediction of the measured values. The hybrid Reynolds-averaged/large eddy simulation results were carefully scrutinized to ensure that even the coarsest grid had an acceptable level of resolution for large eddy simulation, and that the time-averaged statistics were acceptably accurate. The autocorrelation and its Fourier transform were the primary tools used for this assessment. The statistics extracted from the hybrid simulation strategy proved to be more accurate than the Reynolds-averaged results obtained using the linear eddy viscosity models. However, there was no predictive improvement noted over the results obtained from the explicit

Properties of Supersonic Impinging Jets

Science.gov (United States)

Alvi, F. S.; Iyer, K. G.; Ladd, J.

1999-11-01

A detailed study examining the behavior of axisymmetric supersonic jets impinging on a ground plane is described. Our objective is to better understand the aeroacoustics governing this complex flowfield which commonly occurs in the vicinity of STOVL aircraft. Flow issuing through a Mach 1.5 C-D and a converging sonic nozzle is examined over a wide parametric range. For some cases a large diameter circular 'lift' plate, with an annular hole through which the jet is issued, is attached at the nozzle exit to simulate a generic airframe. The impinging jet flowfield was examined using Particle Image Velocimetry (PIV), which provides the velocity field for the entire region and shadowgraph visualization techniques. Near-field acoustic, as well as, mean and unsteady pressure measurements on the ground and lift plate surfaces were also obtained. The velocity field data, together with the surface flow measurements have resulted in a much better understanding of this flow from a fundamental standpoint while also identifying critical regions of interest for practical applications. Some of these findings include the presence of a stagnation bubble with recirculating flow; a very high speed (transonic/supersonic) radial wall jet; presence of large, spatially coherent turbulent structures in the primary jet and wall jet and high unsteady loads on the ground plane and lift plates. The results of a companion CFD investigation and its comparison to the experimental data will also be presented. Very good agreement has been found between the computational and experimental results thus providing confidence in the development of computational tools for the study of such flows.

Probing thermal evanescent waves with a scattering-type near-field microscope

International Nuclear Information System (INIS)

Kajihara, Y; Kosaka, K; Komiyama, S

2011-01-01

Long wavelength infrared (LWIR) waves contain many important spectra of matters like molecular motions. Thus, probing spontaneous LWIR radiation without external illumination would reveal detailed mesoscopic phenomena that cannot be probed by any other measurement methods. Here we developed a scattering-type scanning near-field optical microscope (s-SNOM) and demonstrated passive near-field microscopy at 14.5 µm wavelength. Our s-SNOM consists of an atomic force microscope and a confocal microscope equipped with a highly sensitive LWIR detector, called a charge-sensitive infrared phototransistor (CSIP). In our s-SNOM, photons scattered by a tungsten probe are collected by an objective of the confocal LWIR microscope and are finally detected by the CSIP. To suppress the far-field background, we vertically modulated the probe and demodulated the signal with a lock-in amplifier. With the s-SNOM, a clear passive image of 3 µm pitch Au/SiC gratings was successfully obtained and the spatial resolution was estimated to be 60 nm (λ/240). The radiation from Au and GaAs was suggested to be due to thermally excited charge/current fluctuations and surface phonons, respectively. This s-SNOM has the potential to observe mesoscopic phenomena such as molecular motions, biomolecular protein interactions and semiconductor conditions in the future

The origin of fine structure in near-field scanning optical lithography of an electroactive polymer

International Nuclear Information System (INIS)

Cotton, Daniel V; Belcher, Warwick J; Dastoor, Paul C; Fell, Christopher J

2008-01-01

Near-field scanning optical lithography (NSOL) has been used to produce arbitrary structures of the electroactive polymer polyphenylenevinylene at sizes comparable to optical wavelengths, which are of interest for integrated optical devices. The structures are characterized using AFM and SEM and exhibit interesting fine structure. The characteristic size and shape of the lithographic features and their associated fine structure have been examined in the context of the electric field distribution at the near-field scanning optical microscope tip. In particular, the Bethe-Bouwkamp model for electric field distribution at an aperture has been used in combination with a recently developed model for precursor solubility dependence on UV energy dose to predict the characteristics of lithographic features produced by NSOL. The fine structure in the lithographic features is also investigated and explained. Suggestions for the further improvement of the technique are made.

High-fidelity large eddy simulation for supersonic jet noise prediction

Science.gov (United States)

Aikens, Kurt M.

The problem of intense sound radiation from supersonic jets is a concern for both civil and military applications. As a result, many experimental and computational efforts are focused at evaluating possible noise suppression techniques. Large-eddy simulation (LES) is utilized in many computational studies to simulate the turbulent jet flowfield. Integral methods such as the Ffowcs Williams-Hawkings (FWH) method are then used for propagation of the sound waves to the farfield. Improving the accuracy of this two-step methodology and evaluating beveled converging-diverging nozzles for noise suppression are the main tasks of this work. First, a series of numerical experiments are undertaken to ensure adequate numerical accuracy of the FWH methodology. This includes an analysis of different treatments for the downstream integration surface: with or without including an end-cap, averaging over multiple end-caps, and including an approximate surface integral correction term. Secondly, shock-capturing methods based on characteristic filtering and adaptive spatial filtering are used to extend a highly-parallelizable multiblock subsonic LES code to enable simulations of supersonic jets. The code is based on high-order numerical methods for accurate prediction of the acoustic sources and propagation of the sound waves. Furthermore, this new code is more efficient than the legacy version, allows cylindrical multiblock topologies, and is capable of simulating nozzles with resolved turbulent boundary layers when coupled with an approximate turbulent inflow boundary condition. Even though such wall-resolved simulations are more physically accurate, their expense is often prohibitive. To make simulations more economical, a wall model is developed and implemented. The wall modeling methodology is validated for turbulent quasi-incompressible and compressible zero pressure gradient flat plate boundary layers, and for subsonic and supersonic jets. The supersonic code additions and the

Fabrication of sub-diffraction-limit molecular structures by scanning near-field photolithography

Science.gov (United States)

Ducker, Robert E.; Montague, Matthew T.; Sun, Shuqing; Leggett, Graham J.

2007-09-01

Using a scanning near-field optical microscope coupled to a UV laser, an approach we term scanning near-field photolithography (SNP), structures as small as 9 nm (ca. λ/30) may be fabricated in self-assembled monolayers of alkanethiols on gold surfaces. Selective exposure of the adsorbate molecules in the near field leads to photoconversion of the alkylthiolate to a weakly bound alkylsulfonate which may be displaced readily be a contrasting thiol, leading to a chemical pattern, or used as a resist for the selective etching of the underlying metal. A novel ultra-mild etch for gold is reported, and used to etch structures as small as 9 nm. Photopatterning of oligo(ethylene glycol) (OEG) terminated selfassembled monolayers facilitates the fabrication of biomolecular nanostructures. Selective removal of the protein-resistant OEG terminated adsorbates created regions that may be functionalized with a second thiol and derivatized with a biomolecule. Finally, the application of SNP to nanopatterning on oxide surfaces is demonstrated. Selective exposure of monolayers of phosphonic acids adsorbed onto aluminum oxide leads to cleavage of the P-C bond and desorption of the adsorbate molecule. Subsequent etching, using aqueous based, yields structures as small as 100 nm.

Apertureless near-field scanning optical microscope working with or without laser source.

Science.gov (United States)

Formanek, F; De Wilde, Y; Aigouy, L; Chen, Y

2004-01-01

An apertureless near-field scanning optical microscope (ANSOM), used indifferent configurations, is presented. Our versatile home-made setup, based on a sharp tungsten tip glued onto a quartz tuning fork and working in tapping mode, allows to perform imaging over a broad spectral range. We have recorded optical images in the visible (wavelength, lambda = 655 nm) and in the infrared (lambda = 10.6 microm), proving that the setup routinely achieves an optical resolution of images recorded in the visible (lambda = 655 nm) in an inverted configuration where the tip does not perturb the focused spot of the illumination laser. Approach curves as well as image profiles have revealed that on demodulating the optical signal at higher harmonics, we can obtain an effective probe sharpening which results in an improvement of the resolution. Finally, we have presented optical images recorded in the infrared without any illumination, that is, the usual laser source is replaced by a simple heating of the sample. This has shown that the ANSOM can be used as a near-field thermal optical microscope (NTOM) to probe the near field generated by the thermal emission of the sample.

Near-Field Microwave Magnetic Nanoscopy of Superconducting Radio Frequency Cavity Materials

OpenAIRE

Tai, Tamin; Ghamsari, Behnood G.; Bieler, Thomas R.; Tan, Teng; Xi, X. X.; Anlage, Steven M.

2013-01-01

A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two new measurements are performed to demonstrate these capabilities with a novel near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high Residual- Resistance-Ratio bulk Nb sample showing strong localized nonlinear response for the first time, with surfa...

Direct characterization of ultraviolet-light-induced refractive index structures by scanning near-field optical microscopy

DEFF Research Database (Denmark)

Svalgaard, Mikael; Madsen, S.; Hvam, Jørn Märcher

1998-01-01

We have applied a reflection scanning near-field optical microscope to directly probe ultraviolet (UV)-light-induced refractive index structures in planar glass samples. This technique permits direct comparison between topography and refractive index changes (10(-5)-10(-3)) with submicrometer...

Near-Field Three-Dimensional Planar Millimeter-Wave Holographic Imaging by Using Frequency Scaling Algorithm

Directory of Open Access Journals (Sweden)

Ye Zhang

2017-10-01

Full Text Available In this paper, a fast three-dimensional (3-D frequency scaling algorithm (FSA with large depth of focus is presented for near-field planar millimeter-wave (MMW holographic imaging. Considering the cross-range range coupling term which is neglected in the conventional range migration algorithm (RMA, we propose an algorithm performing the range cell migration correction for de-chirped signals without interpolation by using a 3-D frequency scaling operation. First, to deal with the cross-range range coupling term, a 3-D frequency scaling operator is derived to eliminate the space variation of range cell migration. Then, a range migration correction factor is performed to compensate for the residual range cell migration. Finally, the imaging results are obtained by matched filtering in the cross-range direction. Compared with the conventional RMA, the proposed algorithm is comparable in accuracy but more efficient by using only chirp multiplications and fast Fourier transforms (FFTs. The algorithm has been tested with satisfying results by both simulation and experiment.

Atomic force and scanning near-field optical microscopy study of carbocyanine dye J-aggregates

Czech Academy of Sciences Publication Activity Database

Prokhorov, V.V.; Petrova, M.G.; Kovaleva, Natalia; Demikhov, E.I.

2014-01-01

Roč. 10, č. 5 (2014), s. 700-704 ISSN 1573-4137 Institutional support: RVO:68378271 Keywords : carbocyanine dye * elementary fibri * high-resolution atomic force microscopy * J-aggregate * probe microscopy * scanning near-field optical microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.096, year: 2014

Apertureless SNOM study on gold nanoparticles: Experiments and simulations

Energy Technology Data Exchange (ETDEWEB)

Chen, Weizhe; Kimel, Alexey; Kirilyuk, Andrei; Rasing, Theo [Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands)

2010-08-15

Gold nanoparticles (about 10 nm in diameter) are investigated by an apertureless (or scattering-type) scanning near-field optical microscope (aSNOM) at 633 nm and a negative optical amplitude signal contrast is observed. To understand the size effect and the interactions between light, tip, and sample, an analytical solution is obtained by adopting a model considering the tip as a point dipole. This model successfully shows the contrast reversal measured in experiments. Some important aspects, however, are neglected by the quasistatic dipole model. Thus, three-dimensional (3D) numerical calculations by a finite integration technique are applied to study the interactions between tip apex, gold nanoparticle, and the substrate surface. The simulated near-field and far-field results help us not only to understand the experimentally acquired aSNOM images but also to investigate the complicated tip-particle-surface interactions. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Fluorescence in situ hybridization on human metaphase chromosomes detected by near-field scanning optical microscopy

NARCIS (Netherlands)

Moers, M.H.P.; Moers, M.H.P.; Kalle, W.H.J.; Kalle, W.H.J.; Ruiter, A.G.T.; Wiegant, J.C.A.G.; Raap, A.K.; Greve, Jan; de Grooth, B.G.; van Hulst, N.F.

1996-01-01

Fluorescence in situ hybridization o­n human metaphase chromosomes is detected by near-field scanning optical microscopy. This combination of cytochemical and scanning probe techniques enables the localization and identification of several fluorescently labelled genomic DNA fragments o­n a single

Near-field characteristics of highly non-paraxial subwavelength optical fields with hybrid states of polarization

International Nuclear Information System (INIS)

Chen Rui-Pin; Gao Teng-Yue; Chew Khian-Hooi; Dai Chao-Qing; Zhou Guo-Quan; He Sai-Ling

2017-01-01

The vectorial structure of an optical field with hybrid states of polarization (SoP) in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal components of evanescent waves are illustrated and compared with those of the transverse components from the vectorial structure. Our results indicate that the relative weight integrated over the transverse plane of the evanescent wave depends strongly on the number of the polarization topological charges. The shapes of the intensity profiles of the longitudinal components are different from those of the transverse components, and it can be manipulated by changing the initial SoP of the field cross-section. The longitudinal component of evanescent wave dominates the near-field region. In addition, it also leads to three-dimensional shape variations of the optical field and the optical spin angular momentum flux density distributions. (paper)

Numerical simulation of incidence and sweep effects on delta wing vortex breakdown

Science.gov (United States)

Ekaterinaris, J. A.; Schiff, Lewis B.

1994-01-01

The structure of the vortical flowfield over delta wings at high angles of attack was investigated. Three-dimensional Navier-Stokes numerical simulations were carried out to predict the complex leeward-side flowfield characteristics, including leading-edge separation, secondary separation, and vortex breakdown. Flows over a 75- and a 63-deg sweep delta wing with sharp leading edges were investigated and compared with available experimental data. The effect of variation of circumferential grid resolution grid resolution in the vicinity of the wing leading edge on the accuracy of the solutions was addressed. Furthermore, the effect of turbulence modeling on the solutions was investigated. The effects of variation of angle of attack on the computed vortical flow structure for the 75-deg sweep delta wing were examined. At moderate angles of attack no vortex breakdown was observed. When a critical angle of attack was reached, bubble-type vortex breakdown was found. With further increase in angle of attack, a change from bubble-type breakdown to spiral-type vortex breakdown was predicted by the numerical solution. The effects of variation of sweep angle and freestream Mach number were addressed with the solutions on a 63-deg sweep delta wing.

A New Method for Determining Optimal Regularization Parameter in Near-Field Acoustic Holography

Directory of Open Access Journals (Sweden)

Yue Xiao

2018-01-01

Full Text Available Tikhonov regularization method is effective in stabilizing reconstruction process of the near-field acoustic holography (NAH based on the equivalent source method (ESM, and the selection of the optimal regularization parameter is a key problem that determines the regularization effect. In this work, a new method for determining the optimal regularization parameter is proposed. The transfer matrix relating the source strengths of the equivalent sources to the measured pressures on the hologram surface is augmented by adding a fictitious point source with zero strength. The minimization of the norm of this fictitious point source strength is as the criterion for choosing the optimal regularization parameter since the reconstructed value should tend to zero. The original inverse problem in calculating the source strengths is converted into a univariate optimization problem which is solved by a one-dimensional search technique. Two numerical simulations with a point driven simply supported plate and a pulsating sphere are investigated to validate the performance of the proposed method by comparison with the L-curve method. The results demonstrate that the proposed method can determine the regularization parameter correctly and effectively for the reconstruction in NAH.

High definition aperture probes for near-field optical microscopy fabricated by focused ion beam milling

NARCIS (Netherlands)

Veerman, J.A.; Otter, A.M.; Kuipers, L.; van Hulst, N.F.

1998-01-01

We have improved the optical characteristics of aluminum-coated fiber probes used in near-field scanning optical microscopy by milling with a focused ion beam. This treatment produces a flat-end face free of aluminum grains, containing a well- defined circularly-symmetric aperture with controllable

Compensation for the phase-type spatial periodic modulation of the near-field beam at 1053 nm

Science.gov (United States)

Gao, Yaru; Liu, Dean; Yang, Aihua; Tang, Ruyu; Zhu, Jianqiang

2017-10-01

A phase-only spatial light modulator is used to provide and compensate for the spatial periodic modulation (SPM) of the near-field beam at the near infrared at 1053nm wavelength with an improved iterative weight-based method. The transmission characteristics of the incident beam has been changed by a spatial light modulator (SLM) to shape the spatial intensity of the output beam. The propagation and reverse propagation of the light in free space are two important processes in the iterative process. The based theory is the beam angular spectrum transmit formula (ASTF) and the principle of the iterative weight-based method. We have made two improvements to the originally proposed iterative weight-based method. We select the appropriate parameter by choosing the minimum value of the output beam contrast degree and use the MATLAB built-in angle function to acquire the corresponding phase of the light wave function. The required phase that compensates for the intensity distribution of the incident SPM beam is iterated by this algorithm, which can decrease the magnitude of the SPM of the intensity on the observation plane. The experimental results show that the phase-type SPM of the near-field beam is subject to a certain restriction. We have also analyzed some factors that make the results imperfect. The experiment results verifies the possible applicability of this iterative weight-based method to compensate for the SPM of the near-field beam.

Near-Field Sound Localization Based on the Small Profile Monaural Structure

Directory of Open Access Journals (Sweden)

Youngwoong Kim

2015-11-01

Full Text Available The acoustic wave around a sound source in the near-field area presents unconventional properties in the temporal, spectral, and spatial domains due to the propagation mechanism. This paper investigates a near-field sound localizer in a small profile structure with a single microphone. The asymmetric structure around the microphone provides a distinctive spectral variation that can be recognized by the dedicated algorithm for directional localization. The physical structure consists of ten pipes of different lengths in a vertical fashion and rectangular wings positioned between the pipes in radial directions. The sound from an individual direction travels through the nearest open pipe, which generates the particular fundamental frequency according to the acoustic resonance. The Cepstral parameter is modified to evaluate the fundamental frequency. Once the system estimates the fundamental frequency of the received signal, the length of arrival and angle of arrival (AoA are derived by the designed model. From an azimuthal distance of 3–15 cm from the outer body of the pipes, the extensive acoustic experiments with a 3D-printed structure show that the direct and side directions deliver average hit rates of 89% and 73%, respectively. The closer positions to the system demonstrate higher accuracy, and the overall hit rate performance is 78% up to 15 cm away from the structure body.

Advanced spherical near-field antenna measurement techniques

DEFF Research Database (Denmark)

Nielsen, Jeppe Majlund; Pivnenko, Sergey; Breinbjerg, Olav

2011-01-01

The DTU-ESA facility has since the 1980es provided highly accurate antenna radiation pattern measurements and gain calibration by use of the probe corrected spherical nearfield technique, both for ESA (the European Space Agency) and other customers and continues to do so. Recent years activities...... and research carried out at the facility are presented in the article. Since 2004 several antenna test facility comparison campaigns were carried out between a number of European antenna measurement facilities. The first campaigns laid the foundation for the later comparisons in providing experience...... in the period 2005–2006 following a series of investigatory measurements and facility updates during 2003–2005. Antenna diagnostics by a SWE-to-PWE transformation presents a case where highly accurate antenna measurements and a plane wave back-projection enable antenna diagnostics by examination...

Near-field three-dimensional radar imaging techniques and applications.

Science.gov (United States)

Sheen, David; McMakin, Douglas; Hall, Thomas

2010-07-01

Three-dimensional radio frequency imaging techniques have been developed for a variety of near-field applications, including radar cross-section imaging, concealed weapon detection, ground penetrating radar imaging, through-barrier imaging, and nondestructive evaluation. These methods employ active radar transceivers that operate at various frequency ranges covering a wide range, from less than 100 MHz to in excess of 350 GHz, with the frequency range customized for each application. Computational wavefront reconstruction imaging techniques have been developed that optimize the resolution and illumination quality of the images. In this paper, rectilinear and cylindrical three-dimensional imaging techniques are described along with several application results.

Wavelength dependence of the magnetic resolution of the magneto-optical near-field scanning tunneling microscope

NARCIS (Netherlands)

Schad, R.; Jordan, S.M.; Stoelinga, M.J.P.; Prins, M.W.J.; Groeneveld, R.H.M.; Kempen, van H.; Kesteren, van H.W.

1998-01-01

A magneto-optical near-field scanning tunneling microscope is used to image the prewritten magnetic domain structure of a Pt/Co multilayer. A semiconducting tip acts as a local photodetector to measure the magnetic circular dichroism signal coming from the magnetic sample. The resolution of the

Research on evaluation of coupled thermo-hydro-mechanical phenomena in the near-field

International Nuclear Information System (INIS)

Chijimatsu, Masakazu; Imai, Hisashi; Fukutome, Kazuhito; Kayukawa, Koji; Sasaki, Hajime; Moro, Yoshiji

2004-02-01

After emplacement of the engineered barrier system (EBS), it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanisms, infiltration of groundwater from the surrounding rock in the engineered barrier system, stress imposed by the overburden pressure and generation of swelling pressure in the buffer due to water infiltration. In order to recognize and evaluate these coupled thermo-hydro-mechanical (THM) phenomena, it is necessary to make a confidence of the mathematical models and computer codes. Evaluating these coupled THM phenomena is important in order to clarify the initial transient behavior of the EBS within the near field. DECOVALEX project is an international co-operative project for the DEvelopment of COupled models and their VALidation against EXperiments in nuclear waste isolation and it is significance to participate this project and to apply the code for the validation. Therefore, we tried to apply the developed numerical code against the subjects of DECOVALEX. We carried out the simulation against the Task 1 (simulation of FEBEX in-situ full-scale experiment), Task 3 BMT1 (Bench Mark Test against the near field coupling phenomena) and Task 3 BMT2 (Bench Mark Test against the up-scaling of fractured rock mass). This report shows the simulation results against these tasks. Furthermore, technical investigations about the in-situ full-scale experiment (called Prototype Repository Project) in Aespoe HRL facility by SKB of Sweden were performed. In order to evaluate the coupled phenomena in the engineered barrier, we use the new swelling model based on the theoretical approach. In this paper, we introduce the modeling approach and applicability about the new model. (author)

The near-field region behaviour of hydrogen-air turbulent non-premixed flame

Energy Technology Data Exchange (ETDEWEB)

Tabet, F. [EDF R and D, EIFER (European Institute for Energy Research), Karlsruhe (Germany); Sarh, B. [Centre National de la Recherche Scientifique (CNRS), Institut de Combustion, Aerothermique, Reactivite et Environnement (ICARE), Orleans (France); Universite d' Orleans, Institut Universitaire de Technologie d' Orleans (France); Birouk, M. [University of Manitoba, Department of Mechanical and Manufacturing Engineering, Winnipeg, MB (Canada); Goekalp, I. [Centre National de la Recherche Scientifique (CNRS), Institut de Combustion, Aerothermique, Reactivite et Environnement (ICARE), Orleans (France)

2012-02-15

A computational study of mixing process and air entrainment in hydrogen turbulent non-premixed flame characterized by strong gradients of velocity and density at the inlet section is presented. Different approaches for turbulence-combustion interactions are evaluated in the framework of RSM (Reynolds Stress Model) turbulence model and the computational results are compared to experimental data. The combustion models investigated are SLFM (Steady Laminar Flamelet Model) and EDC (Eddy Dissipation Concept). Mixing is described by oxygen atom mixture fraction and air entrainment is characterized by gas mass flow rate. Computational results are compared to measurements in physical space at two locations (the first one represent the near-field region and the second one the far-field region). At the first station, the results showed an overestimation of mixing and air entrainment and an inaccurate consumption of O{sub 2} and H{sub 2}. In addition, the predictions are found to be sensitive to combustion modelling. At the second station, the description of mixing and air entrainment is improved and the predictions are in reasonably agreement with experimental data. Less dependency to combustion modelling is noticed in this location. Further analysis of the near-field region based on the turbulence time scales revealed that turbulence is not well developed in this region of the flame. (orig.)

Near-field electromagnetic holography for high-resolution analysis of network interactions in neuronal tissue.

Science.gov (United States)

Kjeldsen, Henrik D; Kaiser, Marcus; Whittington, Miles A

2015-09-30

Brain function is dependent upon the concerted, dynamical interactions between a great many neurons distributed over many cortical subregions. Current methods of quantifying such interactions are limited by consideration only of single direct or indirect measures of a subsample of all neuronal population activity. Here we present a new derivation of the electromagnetic analogy to near-field acoustic holography allowing high-resolution, vectored estimates of interactions between sources of electromagnetic activity that significantly improves this situation. In vitro voltage potential recordings were used to estimate pseudo-electromagnetic energy flow vector fields, current and energy source densities and energy dissipation in reconstruction planes at depth into the neural tissue parallel to the recording plane of the microelectrode array. The properties of the reconstructed near-field estimate allowed both the utilization of super-resolution techniques to increase the imaging resolution beyond that of the microelectrode array, and facilitated a novel approach to estimating causal relationships between activity in neocortical subregions. The holographic nature of the reconstruction method allowed significantly better estimation of the fine spatiotemporal detail of neuronal population activity, compared with interpolation alone, beyond the spatial resolution of the electrode arrays used. Pseudo-energy flow vector mapping was possible with high temporal precision, allowing a near-realtime estimate of causal interaction dynamics. Basic near-field electromagnetic holography provides a powerful means to increase spatial resolution from electrode array data with careful choice of spatial filters and distance to reconstruction plane. More detailed approaches may provide the ability to volumetrically reconstruct activity patterns on neuronal tissue, but the ability to extract vectored data with the method presented already permits the study of dynamic causal interactions

Flow cytometric assessment of microbial abundance in the near-field area of seawater reverse osmosis concentrate discharge

KAUST Repository

Van Der Merwe, Riaan; Hammes, Frederik A.; Lattemann, Sabine; Amy, Gary L.

2014-01-01

The discharge of concentrate and other process waters from seawater reverse osmosis (SWRO) plant operations into the marine environment may adversely affect water quality in the near-field area surrounding the outfall. The main concerns

SparkJet characterizations in quiescent and supersonic flowfields

Science.gov (United States)

Emerick, T.; Ali, M. Y.; Foster, C.; Alvi, F. S.; Popkin, S.

2014-12-01

The aerodynamic community has studied active flow control actuators for some time, and developments have led to a wide variety of devices with various features and operating mechanisms. The design requirements for a practical actuator used for active flow control include reliable operation, requisite frequency and amplitude modulation capabilities, and a reasonable lifespan while maintaining minimal cost and design complexity. An active flow control device called the SparkJet actuator has been developed for high-speed flight control and incorporates no mechanical/moving parts, zero net mass flux capabilities and the ability to tune the operating frequency and momentum throughput. This actuator utilizes electrical power to deliver high-momentum flow with a very fast response time. The SparkJet actuator was characterized on the benchtop using a laser-based microschlieren visualization technique and maximum blast wave and jet front velocities of ~400 and ~310 m/s were, respectively, measured in the flowfield. An increase in jet front velocity from 240 to 310 m/s during subatmospheric (60 kPa) testing reveals that the actuator may have greater control authority at lower ambient pressures, which correspond to high-altitude flight conditions for air vehicles. A SparkJet array was integrated into a flat plate and tested in a Mach 1.5 crossflow. Phase-conditioned shadowgraph results revealed a maximum flow deflection angle of 5° created by the SparkJet 275 µs after the actuator was triggered in single-shot mode. Burst mode operation of frequencies up to 700 Hz revealed similar results during wind tunnel testing. Following these tests, the actuator trigger mechanism was improved and the ability of the actuator to be discharged in burst mode at a frequency of 1 kHz was achieved.

Near-Field Thermal Radiation for Solar Thermophotovoltaics and High Temperature Thermal Logic and Memory Applications

Science.gov (United States)

Elzouka, Mahmoud

This dissertation investigates Near-Field Thermal Radiation (NFTR) applied to MEMS-based concentrated solar thermophotovoltaics (STPV) energy conversion and thermal memory and logics. NFTR is the exchange of thermal radiation energy at nano/microscale; when separation between the hot and cold objects is less than dominant radiation wavelength (˜1 mum). NFTR is particularly of interest to the above applications due to its high rate of energy transfer, exceeding the blackbody limit by orders of magnitude, and its strong dependence on separation gap size, surface nano/microstructure and material properties. Concentrated STPV system converts solar radiation to electricity using heat as an intermediary through a thermally coupled absorber/emitter, which causes STPV to have one of the highest solar-to-electricity conversion efficiency limits (85.4%). Modeling of a near-field concentrated STPV microsystem is carried out to investigate the use of STPV based solid-state energy conversion as high power density MEMS power generator. Numerical results for In 0.18Ga0.82Sb PV cell illuminated with tungsten emitter showed significant enhancement in energy transfer, resulting in output power densities as high as 60 W/cm2; 30 times higher than the equivalent far-field power density. On thermal computing, this dissertation demonstrates near-field heat transfer enabled high temperature NanoThermoMechanical memory and logics. Unlike electronics, NanoThermoMechanical memory and logic devices use heat instead of electricity to record and process data; hence they can operate in harsh environments where electronics typically fail. NanoThermoMechanical devices achieve memory and thermal rectification functions through the coupling of near-field thermal radiation and thermal expansion in microstructures, resulting in nonlinear heat transfer between two temperature terminals. Numerical modeling of a conceptual NanoThermoMechanical is carried out; results include the dynamic response under

High-Density Near-Field Readout Using Diamond Solid Immersion Lens

Science.gov (United States)

Shinoda, Masataka; Saito, Kimihiro; Kondo, Takao; Nakaoki, Ariyoshi; Furuki, Motohiro; Takeda, Minoru; Yamamoto, Masanobu; Schaich, Thomas J.; van Oerle, Bart M.; Godfried, Herman P.; Kriele, Paul A. C.; Houwman, Evert P.; Nelissen, Wim H. M.; Pels, Gert J.; Spaaij, Paul G. M.

2006-02-01

We investigated high-density near-field readout using a diamond solid immersion lens (SIL). A synthetic single-crystal chemical vapor deposition diamond provides a high refractive index and a high transmission for a wide wavelength range. Since the refractive index at a wavelength of 405 nm is 2.458, we could design a solid immersion lens with an effective numerical aperture of 2.34. Using the diamond SIL, we observed the eye pattern of a 150-GB-capacity (104.3 Gbit/in.2) disk with a track pitch of 130 nm and a bit length of 47.6 nm.

High-Fidelity Trapped-Ion Quantum Logic Using Near-Field Microwaves.

Science.gov (United States)

Harty, T P; Sepiol, M A; Allcock, D T C; Ballance, C J; Tarlton, J E; Lucas, D M

2016-09-30

We demonstrate a two-qubit logic gate driven by near-field microwaves in a room-temperature microfabricated surface ion trap. We introduce a dynamically decoupled gate method, which stabilizes the qubits against fluctuating energy shifts and avoids the need to null the microwave field. We use the gate to produce a Bell state with fidelity 99.7(1)%, after accounting for state preparation and measurement errors. The gate is applied directly to ^{43}Ca^{+} hyperfine "atomic clock" qubits (coherence time T_{2}^{*}≈50  s) using the oscillating magnetic field gradient produced by an integrated microwave electrode.

Ballistic near-field heat transport in dense many-body systems

Science.gov (United States)

Latella, Ivan; Biehs, Svend-Age; Messina, Riccardo; Rodriguez, Alejandro W.; Ben-Abdallah, Philippe

2018-01-01

Radiative heat transport mediated by near-field interactions is known to be superdiffusive in dilute, many-body systems. Here we use a generalized Landauer theory of radiative heat transfer in many-body planar systems to demonstrate a nonmonotonic transition from superdiffusive to ballistic transport in dense systems. We show that such a transition is associated to a change of the polarization of dominant modes. Our findings are complemented by a quantitative study of the relaxation dynamics of the system in the different regimes of heat transport. This result could have important consequences on thermal management at nanoscale of many-body systems.

Spalart–Allmaras model apparent transition and RANS simulations of laminar separation bubbles on airfoils

International Nuclear Information System (INIS)

Crivellini, Andrea; D’Alessandro, Valerio

2014-01-01

Highlights: • RANS simulation of laminar separation bubbles. • Spalart–Allamaras unexpected capability. • Straightforward implementation of our SA modifications. • Applications of a high order DG incompressible solver. - Abstract: The present paper deals with the Reynolds Averaged Navier–Stokes (RANS) simulation of Laminar Separation Bubble (LSB). This phenomenon is of large interest in several engineering fields, such as the study of wind turbines, unmanned aerial vehicles (UAV) and micro-air vehicles (MAV) characterized by a low operating Reynolds number. In such contexts a laminar boundary layer separation followed by a turbulent transition and afterwards by a turbulent reattachment may appear in the flow-field. The main novelty of this work is that an almost standard Spalart–Allmaras (SA) model, without additional equations for transition modeling, was successfully employed. The result achieved is very surprising being the model not developed for this purpose, but for fully-turbulent flows or for cases with imposed transition location. This result is of large interest, since the SA model is widely used in commercial, open-source and research codes. However, our approach cannot be advocated to predict natural transition within an attached boundary layer, indeed it is only able to deal with transitions triggered by a separated flow. The reliability and accuracy of our approach are here proved computing, by means of a high-order Discontinuous Galerkin (DG) incompressible solver, the flow-field over two airfoils at different flow regimes showing the formation of a LSB

Near-field levitated quantum optomechanics with nanodiamonds

Science.gov (United States)

Juan, M. L.; Molina-Terriza, G.; Volz, T.; Romero-Isart, O.

2016-08-01

We theoretically show that the dipole force of an ensemble of quantum emitters embedded in a dielectric nanosphere can be exploited to achieve near-field optical levitation. The key ingredient is that the polarizability from the ensemble of embedded quantum emitters can be larger than the bulk polarizability of the sphere, thereby enabling the use of repulsive optical potentials and consequently the levitation using optical near fields. In levitated cavity quantum optomechanics, this could be used to boost the single-photon coupling by combining larger polarizability to mass ratio, larger field gradients, and smaller cavity volumes while remaining in the resolved sideband regime and at room temperature. A case study is done with a nanodiamond containing a high density of silicon-vacancy color centers that is optically levitated in the evanescent field of a tapered nanofiber and coupled to a high-finesse microsphere cavity.

Near-Field Ground Motion Modal versus Wave Propagation Analysis

Directory of Open Access Journals (Sweden)

Artur Cichowicz

2010-01-01

Full Text Available The response spectrum generally provides a good estimate of the global displacement and acceleration demand of far-field ground motion on a structure. However, it does not provide accurate information on the local shape or internal deformation of the response of the structure. Near-field pulse-like ground motion will propagate through the structure as waves, causing large, localized deformation. Therefore, the response spectrum alone is not a sufficient representation of near-field ground motion features. Results show that the drift-response technique based on a continuous shear-beam model has to be employed here to estimate structure-demand parameters when structure is exposed to the pulse like ground motion. Conduced modeling shows limited applicability of the drift spectrum based on the SDOF approximation. The SDOF drift spectrum approximation can only be applied to structures with smaller natural periods than the dominant period of the ground motion. For periods larger than the dominant period of ground motion the SDOF drift spectra model significantly underestimates maximum deformation. Strong pulse-type motions are observed in the near-source region of large earthquakes; however, there is a lack of waveforms collected from small earthquakes at very close distances that were recorded underground in mines. The results presented in this paper are relevant for structures with a height of a few meters, placed in an underground excavation. The strong ground motion sensors recorded mine-induced earthquakes in a deep gold mine, South Africa. The strongest monitored horizontal ground motion was caused by an event of magnitude 2 at a distance of 90 m with PGA 123 m/s2, causing drifts of 0.25%–0.35%. The weak underground motion has spectral characteristics similar to the strong ground motion observed on the earth's surface; the drift spectrum has a maximum value less than 0.02%.

Scattering of electromagnetic waves from a cone with conformal mapping: Application to scanning near-field optical microscope

Science.gov (United States)

Chui, S. T.; Chen, Xinzhong; Liu, Mengkun; Lin, Zhifang; Zi, Jian

2018-02-01

We study the response of a conical metallic surface to an external electromagnetic (em) field by representing the fields in basis functions containing the integrable singularity at the tip of the cone. A fast analytical solution is obtained by the conformal mapping between the cone and a round disk. We apply our calculation to the scattering-type scanning near-field optical microscope (s-SNOM) and successfully quantify the elastic light scattering from a vibrating metallic tip over a uniform sample. We find that the field-induced charge distribution consists of localized terms at the tip and the base and an extended bulk term along the body of the cone far away from the tip. In recent s-SNOM experiments at the visible and infrared range (600 nm to 1 μ m ) the fundamental of the demodulated near-field signal is found to be much larger than the higher harmonics whereas at THz range (100 μ m to 3 mm) the fundamental becomes comparable to the higher harmonics. We find that the localized tip charge dominates the contribution to the higher harmonics and becomes larger for the THz experiments, thus providing an intuitive understanding of the origin of the near-field signals. We demonstrate the application of our method by extracting a two-dimensional effective dielectric constant map from the s-SNOM image of a finite metallic disk, where the variation comes from the charge density induced by the em field.

Recent Advances in Antenna Measurement Techniques at the DTU-ESA Spherical Near-Field Antenna Test Facility

DEFF Research Database (Denmark)

Breinbjerg, Olav; Pivnenko, Sergey; Kim, Oleksiy S.

2014-01-01

This paper reports recent antenna measurement projects and research at the DTU-ESA Spherical Near-Field Antenna Test Facility at the Technical University of Denmark. High-accuracy measurement projects for the SMOS, SENTINEL-1, and BIOMASS missions of the European Space Agency were driven...

Chemical effects in the near-field

International Nuclear Information System (INIS)

Ewart, F.T.; Tasker, P.W.

1987-01-01

A research program is described which is designed to investigate the chemical conditions in the near-field of a concrete based repository and the behavior of the radiologically important nuclides under these conditions. The chemical conditions are determined by the corrosion of the iron components of the repository and by the soluble components of the concrete. Both of these have been investigated experimentally and models developed which have been validated by further experiment. The effect of these reactions on the repository pH and Eh, and how these develop in time and space have been modelled using a new coupled chemical equilibrium and transport code. The solubility of the important nuclides are being studied experimentally under these conditions, and under sensible variations. Results are reported for plutonium, americium, neptunium and lead; these results have been under to refine the thermodynamic data base used for the geochemical code PHREEQE. The sorption behavior of plutonium and americium, under the same conditions, have been studied, the sorption coefficients were found to be large and independent of the concrete formulation, particle size and solid liquid ratio

Development of Near-Field Microwave Microscope with the Functionality of Scanning Tunneling Spectroscopy

Science.gov (United States)

Machida, Tadashi; Gaifullin, Marat B.; Ooi, Shuuich; Kato, Takuya; Sakata, Hideaki; Hirata, Kazuto

2010-11-01

We describe the details of an original near-field scanning microwave microscope, developed for simultaneous measurements of local density-of-states (LDOS) and local ohmic losses (LOL). Improving microwave detection systems, we have succeeded in distinguishing the LDOS and LOL even between two low resistance materials; gold and highly orientated pyrolitic graphite. The experimental data indicate that our microscope holds a capability to investigate both LDOS and LOL in nanoscale.

Near-field acoustic holography with sound pressure and particle velocity measurements

DEFF Research Database (Denmark)

Fernandez Grande, Efren

of the particle velocity has notable potential in NAH, and furthermore, combined measurement of sound pressure and particle velocity opens a new range of possibilities that are examined in this study. On this basis, sound field separation methods have been studied, and a new measurement principle based on double...... layer measurements of the particle velocity has been proposed. Also, the relation between near-field and far-field radiation from sound sources has been examined using the concept of the supersonic intensity. The calculation of this quantity has been extended to other holographic methods, and studied...

Molecular near-field antenna effect in resonance hyper-Raman scattering: Intermolecular vibronic intensity borrowing of solvent from solute through dipole-dipole and dipole-quadrupole interactions

Energy Technology Data Exchange (ETDEWEB)

Shimada, Rintaro; Hamaguchi, Hiro-o, E-mail: hhama@nctu.edu.tw [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan (China)

2014-05-28

We quantitatively interpret the recently discovered intriguing phenomenon related to resonance Hyper-Raman (HR) scattering. In resonance HR spectra of all-trans-β-carotene (β-carotene) in solution, vibrations of proximate solvent molecules are observed concomitantly with the solute β-carotene HR bands. It has been shown that these solvent bands are subject to marked intensity enhancements by more than 5 orders of magnitude under the presence of β-carotene. We have called this phenomenon the molecular-near field effect. Resonance HR spectra of β-carotene in benzene, deuterated benzene, cyclohexane, and deuterated cyclohexane have been measured precisely for a quantitative analysis of this effect. The assignments of the observed peaks are made by referring to the infrared, Raman, and HR spectra of neat solvents. It has been revealed that infrared active and some Raman active vibrations are active in the HR molecular near-field effect. The observed spectra in the form of difference spectra (between benzene/deuterated benzene and cyclohexane/deuterated cyclohexane) are quantitatively analyzed on the basis of the extended vibronic theory of resonance HR scattering. The theory incorporates the coupling of excited electronic states of β-carotene with the vibrations of a proximate solvent molecule through solute–solvent dipole–dipole and dipole–quadrupole interactions. It is shown that the infrared active modes arise from the dipole–dipole interaction, whereas Raman active modes from the dipole–quadrupole interaction. It is also shown that vibrations that give strongly polarized Raman bands are weak in the HR molecular near-field effect. The observed solvent HR spectra are simulated with the help of quantum chemical calculations for various orientations and distances of a solvent molecule with respect to the solute. The observed spectra are best simulated with random orientations of the solvent molecule at an intermolecular distance of 10 Å.

Reduction of Truncation Errors in Planar Near-Field Aperture Antenna Measurements Using the Gerchberg-Papoulis Algorithm

DEFF Research Database (Denmark)

Martini, Enrica; Breinbjerg, Olav; Maci, Stefano

2008-01-01

A simple and effective procedure for the reduction of truncation errors in planar near-field measurements of aperture antennas is presented. The procedure relies on the consideration that, due to the scan plane truncation, the calculated plane wave spectrum of the field radiated by the antenna is...

Characterization of hypersonic roughness-induced boundary-layer transition

Science.gov (United States)

Tirtey, S. C.; Chazot, O.; Walpot, L.

2011-02-01

The flow-field structure in the vicinity and in the wake of an isolated 3D roughness element has been studied. Different experimental techniques have been coupled and supported by CFD simulation for a good understanding of the flow-field topology. The results have shown strong flow-field similarities for different roughness elements. A model describing the flow structure and interaction mechanisms has been proposed. This model is in good agreement with experimental and CFD results as well as the literature.

Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer

International Nuclear Information System (INIS)

Ito, Kota; Miura, Atsushi; Iizuka, Hideo; Toshiyoshi, Hiroshi

2015-01-01

Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed to the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics

Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer

Energy Technology Data Exchange (ETDEWEB)

Ito, Kota, E-mail: kotaito@mosk.tytlabs.co.jp [Toyota Central Research and Development Laboratories, Nagakute, Aichi 480-1192 (Japan); Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Miura, Atsushi; Iizuka, Hideo [Toyota Central Research and Development Laboratories, Nagakute, Aichi 480-1192 (Japan); Toshiyoshi, Hiroshi [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

2015-02-23

Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed to the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics.

Nanometal Skin of Plasmonic Heterostructures for Highly Efficient Near-Field Scattering Probes

Science.gov (United States)

Zito, Gianluigi; Rusciano, Giulia; Vecchione, Antonio; Pesce, Giuseppe; di Girolamo, Rocco; Malafronte, Anna; Sasso, Antonio

2016-08-01

In this work, atomic force microscopy probes are functionalized by virtue of self-assembling monolayers of block copolymer (BCP) micelles loaded either with clusters of silver nanoparticles or bimetallic heterostructures consisting of mixed species of silver and gold nanoparticles. The resulting self-organized patterns allow coating the tips with a sort of nanometal skin made of geometrically confined nanoislands. This approach favors the reproducible engineering and tuning of the plasmonic properties of the resulting structured tip by varying the nanometal loading of the micelles. The newly conceived tips are applied for experiments of tip-enhanced Raman scattering (TERS) spectroscopy and scattering-type scanning near-field optical microscopy (s-SNOM). TERS and s-SNOM probe characterizations on several standard Raman analytes and patterned nanostructures demonstrate excellent enhancement factor with the possibility of fast scanning and spatial resolution <12 nm. In fact, each metal nanoisland consists of a multiscale heterostructure that favors large scattering and near-field amplification. Then, we verify the tips to allow challenging nongap-TER spectroscopy on thick biosamples. Our approach introduces a synergistic chemical functionalization of the tips for versatile inclusion and delivery of plasmonic nanoparticles at the tip apex, which may promote the tuning of the plasmonic properties, a large enhancement, and the possibility of adding new degrees of freedom for tip functionalization.

Decoding complex flow-field patterns in visual working memory.

Science.gov (United States)

Christophel, Thomas B; Haynes, John-Dylan

2014-05-01

There has been a long history of research on visual working memory. Whereas early studies have focused on the role of lateral prefrontal cortex in the storage of sensory information, this has been challenged by research in humans that has directly assessed the encoding of perceptual contents, pointing towards a role of visual and parietal regions during storage. In a previous study we used pattern classification to investigate the storage of complex visual color patterns across delay periods. This revealed coding of such contents in early visual and parietal brain regions. Here we aim to investigate whether the involvement of visual and parietal cortex is also observable for other types of complex, visuo-spatial pattern stimuli. Specifically, we used a combination of fMRI and multivariate classification to investigate the retention of complex flow-field stimuli defined by the spatial patterning of motion trajectories of random dots. Subjects were trained to memorize the precise spatial layout of these stimuli and to retain this information during an extended delay. We used a multivariate decoding approach to identify brain regions where spatial patterns of activity encoded the memorized stimuli. Content-specific memory signals were observable in motion sensitive visual area MT+ and in posterior parietal cortex that might encode spatial information in a modality independent manner. Interestingly, we also found information about the memorized visual stimulus in somatosensory cortex, suggesting a potential crossmodal contribution to memory. Our findings thus indicate that working memory storage of visual percepts might be distributed across unimodal, multimodal and even crossmodal brain regions. Copyright © 2014 Elsevier Inc. All rights reserved.

Numerical simulation of air hypersonic flows with equilibrium chemical reactions

Science.gov (United States)

Emelyanov, Vladislav; Karpenko, Anton; Volkov, Konstantin

2018-05-01

The finite volume method is applied to solve unsteady three-dimensional compressible Navier-Stokes equations on unstructured meshes. High-temperature gas effects altering the aerodynamics of vehicles are taken into account. Possibilities of the use of graphics processor units (GPUs) for the simulation of hypersonic flows are demonstrated. Solutions of some test cases on GPUs are reported, and a comparison between computational results of equilibrium chemically reacting and perfect air flowfields is performed. Speedup of solution on GPUs with respect to the solution on central processor units (CPUs) is compared. The results obtained provide promising perspective for designing a GPU-based software framework for practical applications.

Near-field heat transfer at the spent fuel test-climax: a comparison of measurements and calculations

International Nuclear Information System (INIS)

Patrick, W.C.; Montan, D.N.; Ballou, L.B.

1981-01-01

The Spent Fuel Test in the Climax granitic stock at the DOE Nevada Test Site is a test of the feasibility of storage and retrieval of spent nuclear reactor fuel in a deep geologic environment. Eleven spent fuel elements, together with six thermally identical electrical resistance heaters and 20 peripheral guard heaters, are emplaced 420 m below surface in a three-drift test array. This array was designed to simulate the near-field effects of thousands of canisters of nuclear waste and to evaluate the effects of heat alone, and heat plus ionizing radiation on the rock. Thermal calculations and measurements are conducted to determine thermal transport from the spent fuel and electrical resistance heaters. Calculations associated with the as-built Spent Fuel Test geometry and thermal source histories are presented and compared with thermocouple measurements made throughout the test array. Comparisons in space begin at the spent fuel canister and include the first few metres outside the test array. Comparisons in time begin at emplacement and progress through the first year of thermal loading in this multi-year test

Linear iterative near-field phase retrieval (LIPR) for dual-energy x-ray imaging and material discrimination.

Science.gov (United States)

Li, Heyang Thomas; Kingston, Andrew M; Myers, Glenn R; Beeching, Levi; Sheppard, Adrian P

2018-01-01

Near-field x-ray refraction (phase) contrast is unavoidable in many lab-based micro-CT imaging systems. Quantitative analysis of x-ray refraction (a.k.a. phase retrieval) is in general an under-constrained problem. Regularizing assumptions may not hold true for interesting samples; popular single-material methods are inappropriate for heterogeneous samples, leading to undesired blurring and/or over-sharpening. In this paper, we constrain and solve the phase-retrieval problem for heterogeneous objects, using the Alvarez-Macovski model for x-ray attenuation. Under this assumption we neglect Rayleigh scattering and pair production, considering only Compton scattering and the photoelectric effect. We formulate and test the resulting method to extract the material properties of density and atomic number from single-distance, dual-energy imaging of both strongly and weakly attenuating multi-material objects with polychromatic x-ray spectra. Simulation and experimental data are used to compare our proposed method with the Paganin single-material phase-retrieval algorithm, and an innovative interpretation of the data-constrained modeling phase-retrieval technique.

Simulating flow around scaled model of a hypersonic vehicle in wind tunnel

Science.gov (United States)

Markova, T. V.; Aksenov, A. A.; Zhluktov, S. V.; Savitsky, D. V.; Gavrilov, A. D.; Son, E. E.; Prokhorov, A. N.

2016-11-01

A prospective hypersonic HEXAFLY aircraft is considered in the given paper. In order to obtain the aerodynamic characteristics of a new construction design of the aircraft, experiments with a scaled model have been carried out in a wind tunnel under different conditions. The runs have been performed at different angles of attack with and without hydrogen combustion in the scaled propulsion engine. However, the measured physical quantities do not provide all the information about the flowfield. Numerical simulation can complete the experimental data as well as to reduce the number of wind tunnel experiments. Besides that, reliable CFD software can be used for calculations of the aerodynamic characteristics for any possible design of the full-scale aircraft under different operation conditions. The reliability of the numerical predictions must be confirmed in verification study of the software. The given work is aimed at numerical investigation of the flowfield around and inside the scaled model of the HEXAFLY-CIAM module under wind tunnel conditions. A cold run (without combustion) was selected for this study. The calculations are performed in the FlowVision CFD software. The flow characteristics are compared against the available experimental data. The carried out verification study confirms the capability of the FlowVision CFD software to calculate the flows discussed.

Sensitivities of Near-field Tsunami Forecasts to Megathrust Deformation Predictions

Science.gov (United States)

Tung, S.; Masterlark, T.

2018-02-01

This study reveals how modeling configurations of forward and inverse analyses of coseismic deformation data influence the estimations of seismic and tsunami sources. We illuminate how the predictions of near-field tsunami change when (1) a heterogeneous (HET) distribution of crustal material is introduced to the elastic dislocation model, and (2) the near-trench rupture is either encouraged or suppressed to invert spontaneous coseismic displacements. Hypothetical scenarios of megathrust earthquakes are studied with synthetic Global Positioning System displacements in Cascadia. Finite-element models are designed to mimic the subsurface heterogeneity across the curved subduction margin. The HET lithospheric domain modifies the seafloor displacement field and alters tsunami predictions from those of a homogeneous (HOM) crust. Uncertainties persist as the inverse analyses of geodetic data produce nonrealistic slip artifacts over the HOM domain, which propagates into the prediction errors of subsequent tsunami arrival and amplitudes. A stochastic analysis further shows that the uncertainties of seismic tomography models do not degrade the solution accuracy of HET over HOM. Whether the source ruptures near the trench also controls the details of the seafloor disturbance. Deeper subsurface slips induce more seafloor uplift near the coast and cause an earlier arrival of tsunami waves than surface-slipping events. We suggest using the solutions of zero-updip-slip and zero-updip-slip-gradient rupture boundary conditions as end-members to constrain the tsunami behavior for forecasting purposes. The findings are important for the near-field tsunami warning that primarily relies on the near-real-time geodetic or seismic data for source calibration before megawaves hit the nearest shore upon tsunamigenic events.

New chemical-DSMC method in numerical simulation of axisymmetric rarefied reactive flow

Science.gov (United States)

Zakeri, Ramin; Kamali Moghadam, Ramin; Mani, Mahmoud

2017-04-01

The modified quantum kinetic (MQK) chemical reaction model introduced by Zakeri et al. is developed for applicable cases in axisymmetric reactive rarefied gas flows using the direct simulation Monte Carlo (DSMC) method. Although, the MQK chemical model uses some modifications in the quantum kinetic (QK) method, it also employs the general soft sphere collision model and Stockmayer potential function to properly select the collision pairs in the DSMC algorithm and capture both the attraction and repulsion intermolecular forces in rarefied gas flows. For assessment of the presented model in the simulation of more complex and applicable reacting flows, first, the air dissociation is studied in a single cell for equilibrium and non-equilibrium conditions. The MQK results agree well with the analytical and experimental data and they accurately predict the characteristics of the rarefied flowfield with chemical reaction. To investigate accuracy of the MQK chemical model in the simulation of the axisymmetric flow, air dissociation is also assessed in an axial hypersonic flow around two geometries, the sphere as a benchmark case and the blunt body (STS-2) as an applicable test case. The computed results including the transient, rotational and vibrational temperatures, species concentration in the stagnation line, and also the heat flux and pressure coefficient on the surface are compared with those of the other chemical methods like the QK and total collision energy (TCE) models and available analytical and experimental data. Generally, the MQK chemical model properly simulates the chemical reactions and predicts flowfield characteristics more accurate rather than the typical QK model. Although in some cases, results of the MQK approaches match with those of the TCE method, the main point is that the MQK does not need any experimental data or unrealistic assumption of specular boundary condition as used in the TCE method. Another advantage of the MQK model is the

Carrier redistribution between different potential sites in semipolar (202¯1) InGaN quantum wells studied by near-field photoluminescence

KAUST Repository

Marcinkevičius, S.

2014-09-15

© 2014 AIP Publishing LLC. Scanning near-field photoluminescence (PL) spectroscopy at different excitation powers was applied to study nanoscale properties of carrier localization and recombination in semipolar (202¯1) InGaN quantum wells (QWs) emitting in violet, blue, and green-yellow spectral regions. With increased excitation power, an untypical PL peak energy shift to lower energies was observed. The shift was attributed to carrier density dependent carrier redistribution between nm-scale sites of different potentials. Near-field PL scans showed that in (202¯1) QWs the in-plane carrier diffusion is modest, and the recombination properties are uniform, which is advantageous for photonic applications.

Effects of Optical Combiner and IPD Change for Convergence on Near-Field Depth Perception in an Optical See-Through HMD.

Science.gov (United States)

Lee, Sangyoon; Hu, Xinda; Hua, Hong

2016-05-01

Many error sources have been explored in regards to the depth perception problem in augmented reality environments using optical see-through head-mounted displays (OST-HMDs). Nonetheless, two error sources are commonly neglected: the ray-shift phenomenon and the change in interpupillary distance (IPD). The first source of error arises from the difference in refraction for virtual and see-through optical paths caused by an optical combiner, which is required of OST-HMDs. The second occurs from the change in the viewer's IPD due to eye convergence. In this paper, we analyze the effects of these two error sources on near-field depth perception and propose methods to compensate for these two types of errors. Furthermore, we investigate their effectiveness through an experiment comparing the conditions with and without our error compensation methods applied. In our experiment, participants estimated the egocentric depth of a virtual and a physical object located at seven different near-field distances (40∼200 cm) using a perceptual matching task. Although the experimental results showed different patterns depending on the target distance, the results demonstrated that the near-field depth perception error can be effectively reduced to a very small level (at most 1 percent error) by compensating for the two mentioned error sources.

Practical aspects of spherical near-field antenna measurements using a high-order probe

DEFF Research Database (Denmark)

Laitinen, Tommi; Pivnenko, Sergey; Nielsen, Jeppe Majlund

2006-01-01

Two practical aspects related to accurate antenna pattern characterization by probe-corrected spherical near-field antenna measurements with a high-order probe are examined. First, the requirements set by an arbitrary high-order probe on the scanning technique are pointed out. Secondly, a channel...... balance calibration procedure for a high-order dual-port probe with non-identical ports is presented, and the requirements set by this procedure for the probe are discussed....

Simulation of saltwater movement in the Floridan aquifer system, Hilton Head Island, South Carolina

Science.gov (United States)

Bush, Peter W.

1988-01-01

Freshwater to supply Hilton Head Island, S.C., is obtained from the upper permeable zone of the Upper Floridan aquifer. Long-term pumping at Savannah, Ga., and the steadily increasing pumping on Hilton Head Island, have lowered Upper Floridan heads near the center of the island from about 10 feet above sea level to about 6 to 7 feet below sea level. The seaward hydraulic gradient that existed before pumping began has been reversed, thus increasing the potential for saltwater intrusion. Simulations of predevelopment, recent, and future ground-water flow in the Floridan aquifer system beneath the north end of Hilton Head Island and Port Royal Sound are presented. A finite-element model for fluid-density-dependent ground-water flow and solute transport was used in cross section. The general configuration of the simulated predevelopment flowfield is typical of a coastal aquifer having a seaward gradient in the freshwater. The freshwater flows toward Port Royal Sound over an intruding wedge of saltwater. The simulated flowfield at the end of 1983 shows that ground water in the Floridan aquifer system beneath most of Hilton Head Island has reversed its predevelopment direction and is moving toward Savannah. The distribution of chloride concentrations, based on simulation at the end of 1983, is about the same as the predevelopment distribution of chloride concentrations obtained from simulation. Results of two 50-year simulations from 1983 to 2034 suggest that there will be no significant threat of saltwater intrusion into the upper permeable zone of the Upper Floridan aquifer if heads on Hilton Head Island remain at current levels for the next 45 to 50 years. However, if head decline continues at the historical rate, any flow that presently occurs from the north end of the island toward Port Royal Sound will cease, allowing lateral intrusion of saltwater to proceed. Even under these conditions, chloride concentrations in the upper permeable zone of the Upper Floridan

Cathodoluminescence-activated nanoimaging: noninvasive near-field optical microscopy in an electron microscope.

Science.gov (United States)

Bischak, Connor G; Hetherington, Craig L; Wang, Zhe; Precht, Jake T; Kaz, David M; Schlom, Darrell G; Ginsberg, Naomi S

2015-05-13

We demonstrate a new nanoimaging platform in which optical excitations generated by a low-energy electron beam in an ultrathin scintillator are used as a noninvasive, near-field optical scanning probe of an underlying sample. We obtain optical images of Al nanostructures with 46 nm resolution and validate the noninvasiveness of this approach by imaging a conjugated polymer film otherwise incompatible with electron microscopy due to electron-induced damage. The high resolution, speed, and noninvasiveness of this "cathodoluminescence-activated" platform also show promise for super-resolution bioimaging.

Near-field microwave magnetic nanoscopy of superconducting radio frequency cavity materials

Science.gov (United States)

Tai, Tamin; Ghamsari, Behnood G.; Bieler, Thomas R.; Tan, Teng; Xi, X. X.; Anlage, Steven M.

2014-06-01

A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two measurements are performed to demonstrate these capabilities with a near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high Residual-Resistance-Ratio bulk Nb sample showing strong localized nonlinear response, with surface RF magnetic field Bsurface˜102 mT. The second is a raster scanned harmonic response image on a MgB2 thin film demonstrating a uniform nonlinear response over large areas.

Human Exposure Model (HEM): A modular, web-based application to characterize near-field chemical exposures and releases

Science.gov (United States)

The U.S. EPA’s Chemical Safety and Sustainability research program is developing the Human Exposure Model (HEM) to assess near-field exposures to chemicals that occur in various populations over the entire life cycle of a consumer product. The model will be implemented as a...

Nearfield acoustic holography. I - Theory of generalized holography and the development of NAH

Science.gov (United States)

Maynard, J. D.; Williams, E. G.; Lee, Y.

1985-01-01

Because its underlying principles are so fundamental, holography has been studied and applied in many areas of science. Recently, a technique has been developed which takes the maximum advantage of the fundamental principles and extracts much more information from a hologram than is customarily associated with such a measurement. In this paper the fundamental principles of holography are reviewed, and a sound radiation measurement system, called nearfield acoustic holography (NAH), which fully exploits the fundamental principles, is described.

Near-field reflection backscattering apertureless optical microscopy: Application to spectroscopy experiments on opaque samples, comparison between lock-in and digital photon counting detection techniques

International Nuclear Information System (INIS)

Diziain, S.; Bijeon, J.-L.; Adam, P.-M.; Lamy de la Chapelle, M.; Thomas, B.; Deturche, R.; Royer, P.

2007-01-01

An apertureless scanning near-field optical microscope (ASNOM) in reflection backscattering configuration is designed to conduct spectroscopic experiments on opaque samples constituted of latex beads. The ASNOM proposed takes advantage of the depth-discrimination properties of confocal microscopes to efficiently extract the near-field optical signal. Given their importance in a spectroscopic experiment, we systematically compare the lock-in and synchronous photon counting detection methods. Some results of Rayleigh's scattering in the near field of the test samples are used to illustrate the possibilities of this technique for reflection backscattering spectroscopy

Near-field reflection backscattering apertureless optical microscopy: Application to spectroscopy experiments on opaque samples, comparison between lock-in and digital photon counting detection techniques

Energy Technology Data Exchange (ETDEWEB)

Diziain, S. [Institut Charles Delaunay, CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France); Bijeon, J.-L. [Institut Charles Delaunay, CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France)]. E-mail: bijeon@utt.fr; Adam, P.-M. [Institut Charles Delaunay, CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France); Lamy de la Chapelle, M. [Institut Charles Delaunay, CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France); Thomas, B. [Institut Charles Delaunay, CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France); Deturche, R. [Institut Charles Delaunay, CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France); Royer, P. [Institut Charles Delaunay, CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France)

2007-01-15

An apertureless scanning near-field optical microscope (ASNOM) in reflection backscattering configuration is designed to conduct spectroscopic experiments on opaque samples constituted of latex beads. The ASNOM proposed takes advantage of the depth-discrimination properties of confocal microscopes to efficiently extract the near-field optical signal. Given their importance in a spectroscopic experiment, we systematically compare the lock-in and synchronous photon counting detection methods. Some results of Rayleigh's scattering in the near field of the test samples are used to illustrate the possibilities of this technique for reflection backscattering spectroscopy.

Nuclide release calculation in the near-field of a reference HLW repository

International Nuclear Information System (INIS)

Lee, Youn Myoung; Hwang, Yong Soo; Kang, Chul Hyung

2004-01-01

The HLW-relevant R and D program for disposal of high-level radioactive waste has been carried out at Korea Atomic Energy Research Institute (KAERI) since early 1997 in order to develop a conceptual Korea Reference Repository System for direct disposal of nuclear spent fuel by the end of 2007. A preliminary reference geologic repository concept considering such established criteria and requirements as waste and generic site characteristics in Korea was roughly envisaged in 2003 focusing on the near-field components of the repository system. According to above basic repository concept, which is similar to that of Swedish KBS-3 repository, the spent fuel is first encapsulated in corrosion resistant canisters, even though the material has not yet been determined, and then emplaced into the deposition holes surrounded by high density bentonite clay in tunnels constructed at a depth of about 500 m in a stable plutonic rock body. Not only to demonstrate how much a reference repository is safe in the generic point of view with several possible scenarios and cases associated with a preliminary repository concept by conducting calculations for nuclide release and transport in the near-field components of the repository, even though enough information has not been available that much yet, but also to show a methodology by which a generic safety assessment could be performed for further development of Korea reference repository concept, nuclide release calculation study strongly seems to be necessary

Sub-microanalysis of solid samples with near-field enhanced atomic emission spectroscopy

Science.gov (United States)

Wang, Xiaohua; Liang, Zhisen; Meng, Yifan; Wang, Tongtong; Hang, Wei; Huang, Benli

2018-03-01

A novel approach, which we have chosen to name it as near-field enhanced atomic emission spectroscopy (NFE-AES), was proposed by introducing a scanning tunnelling microscope (STM) system into a laser-induced breakdown spectrometry (LIBS). The near-field enhancement of a laser-illuminated tip was utilized to improve the lateral resolution tremendously. Using the hybrid arrangement, pure metal tablets were analyzed to verify the performance of NFE-AES both in atmosphere and in vacuum. Due to localized surface plasmon resonance (LSPR), the incident electromagnetic field is enhanced and confined at the apex of tip, resulting in sub-micron scale ablation and elemental emission signal. We discovered that the signal-to-noise ratio (SNR) and the spectral resolution obtained in vacuum condition are better than those acquired in atmospheric condition. The quantitative capability of NFE-AES was demonstrated by analyzing Al and Pb in Cu matrix, respectively. Submicron-sized ablation craters were achieved by performing NFE-AES on a Si wafer with an Al film, and the spectroscopic information from a crater of 650 nm diameter was successfully obtained. Due to its advantage of high lateral resolution, NFE-AES imaging of micro-patterned Al lines on an integrated circuit of a SIM card was demonstrated with a sub-micron lateral resolution. These results reveal the potential of the NFE-AES technique in sub-microanalysis of solids, opening an opportunity to map chemical composition at sub-micron scale.

Analysis of near-field data from a Soviet decoupling experiment

International Nuclear Information System (INIS)

Saikia, C.K.; McLaren, J.P.; Helmberger, D.V.

1993-01-01

Recently Adushkin et al. (1992a) presented some results on a decoupling experiment performed in a salt dome in Azghir near the Caspian Sea. A large coupled shot (64 kT) was followed five years later by a decoupled shot (8 kT) fired in the cavity formed by the earlier event. Both events were recorded locally and this data has been provided by the Soviet scientists in a cooperative effort to better understand the seismic coupling problem. This data, in conjunction with WWSSN observations, is analyzed in an effort to determine the RDP's and an estimate of t. Our preliminary results suggest that RDP appropriate for the large event is quite similar to that of LONGSHOT (80 kT event). Their teleseismic observations are difficult to distinguish in waveshape. The M s for LONGSHOT is 3.9 while that for the coupled Russian event is 3.3. The m b for the LONGSHOT (5.8) is slightly smaller than for the Russian event (m b = 6.0, ISC). This comparison of m b :M s appears to be common to most Azghir events as compared to the US experience. The t* appropriate for Amchitka (t* = 0.9) was established by near-field and teleseismic modeling of waveform data similar to this study where we obtain a t* = 0.5 to 0.6. The RDP for the small event is less well resolved but appears to be only partially decoupled. Prior estimates of decoupling factors range from 30 (based on this data by Adushkin) to 70 (for the Sterling/Salmon experiment). Our analysis produces a decoupling factor of about 15 using near-field data which is similar to the teleseismic modeling result

Simulation of long-term behavior in HLW near-field by centrifugal model test. Part 4. Model test of coupled THM processes in isotropic stress conditions using heatable overpack

International Nuclear Information System (INIS)

Nishimoto, Soshi; Okada, Tetsuji; Sawada, Masataka

2014-01-01

We demonstrated the equivalent long-term behavior in the near-field of a geological repository for high level radioactive waste disposal, using the centrifugal near-field model test under the coupled thermo-hydraulic-mechanical condition. The model consisted of a sedimentary bedrock, buffer, and heating type model overpack, and was enclosed within a pressure vessel. Tests were conducted with a centrifugal force field of 30 G under isotropic stress-constrain conditions with confining pressures and injection of pore water. The temperature condition of the overpack was constantly 95°C. As the result, the values showed similar behaviors to that of the normal temperature tests partially. However, the different behaviors were measured such as the displacement of overpack change from the settlement to the heave, the extreme drop in the soil pressure of the buffer and the strain of side wall of bedrock change from the tension to the compression after injecting pore water of hundreds hours. In addition, the flow rate of the injection pore water suddenly changed after hundreds of hours. Furthermore, the density of the buffer was lower than that of the normal temperature tests by X-ray CT imaging in the post-tests. We infer that the high temperature overpack influenced the stiffness and the pore water distribution of the buffer, and the density and the soil pressure of the buffer decreased. As a result of the change of stiffness in the disposal hole (buffer), the tendency to the strain of the surrounding bedrock and the displacement of the overpack changed. (author)

Inviscid Wall-Modeled Large Eddy Simulations for Improved Efficiency

Science.gov (United States)

Aikens, Kurt; Craft, Kyle; Redman, Andrew

2015-11-01

The accuracy of an inviscid flow assumption for wall-modeled large eddy simulations (LES) is examined because of its ability to reduce simulation costs. This assumption is not generally applicable for wall-bounded flows due to the high velocity gradients found near walls. In wall-modeled LES, however, neither the viscous near-wall region or the viscous length scales in the outer flow are resolved. Therefore, the viscous terms in the Navier-Stokes equations have little impact on the resolved flowfield. Zero pressure gradient flat plate boundary layer results are presented for both viscous and inviscid simulations using a wall model developed previously. The results are very similar and compare favorably to those from another wall model methodology and experimental data. Furthermore, the inviscid assumption reduces simulation costs by about 25% and 39% for supersonic and subsonic flows, respectively. Future research directions are discussed as are preliminary efforts to extend the wall model to include the effects of unresolved wall roughness. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1053575. Computational resources on TACC Stampede were provided under XSEDE allocation ENG150001.

Influence as a challenger to induction for near-field wireless power transfer

International Nuclear Information System (INIS)

Bondar, H; Oree, S; Ichikawa, K

2013-01-01

We introduce what we call 'Influence' WPT technology, which can be perceived as the dual of magnetic induction WPT. In Influence systems, two or more electric circuits are coupled by electric fields whereas Induction systems involve magnetic field coupling. We propose an unconventional approach to describe and study Influence, using coupling matrices, in analogy with the treatment of Inductive coupling, albeit with a larger number of parameters. In spite of their different natures, both technologies enable non-radiative near-field energy transfer at mid-range, and display interesting and sometimes counter-intuitive behaviors.

Near-field radiative heat transfer between graphene-covered hyperbolic metamaterials

Science.gov (United States)

Hong, Xiao-Juan; Li, Jian-Wen; Wang, Tong-Biao; Zhang, De-Jian; Liu, Wen-Xing; Liao, Qing-Hua; Yu, Tian-Bao; Liu, Nian-Hua

2018-04-01

We propose the use of graphene-covered silicon carbide (SiC) nanowire arrays (NWAs) for theoretical studies of near-field radiative heat transfer. The SiC NWAs exhibit a hyperbolic characteristic at an appropriately selected filling-volume fraction. The surface plasmon supported by graphene and the hyperbolic modes supported by SiC NWAs significantly affect radiative heat transfer. The heat-transfer coefficient (HTC) between the proposed structures is larger than that between SiC NWAs. We also find that the chemical potential of graphene plays an important role in modulating the HTC. The tunability of chemical potential through gate voltage enables flexible control of heat transfer using the graphene-covered SiC NWAs.

Fabrication and characterization of optical-fiber nanoprobes for scanning near-field optical microscopy.

Science.gov (United States)

Essaidi, N; Chen, Y; Kottler, V; Cambril, E; Mayeux, C; Ronarch, N; Vieu, C

1998-02-01

The current scanning near-field optical microscopy has been developed with optical-fiber probes obtained by use of either laser-heated pulling or chemical etching. For high-resolution near-field imaging, the detected signal is rapidly attenuated as the aperture size of the probe decreases. It is thus important to fabricate probes optimized for both spot size and optical transmission. We present a two-step fabrication that allowed us to achieve an improved performance of the optical-fiber probes. Initially, a CO(2) laser-heated pulling was used to produce a parabolic transitional taper ending with a top thin filament. Then, a rapid chemical etching with 50% buffered hydrofluoric acid was used to remove the thin filament and to result in a final conical tip on the top of the parabolic transitional taper. Systematically, we obtained optical-fiber nanoprobes with the apex size as small as 10 nm and the final cone angle varying from 15 degrees to 80 degrees . It was found that the optical transmission efficiency increases rapidly as the taper angle increases from 15 degrees to 50 degrees , but a further increase in the taper angle gives rise to important broadening of the spot size. Finally, the fabricated nanoprobes were used in photon-scanning tunneling microscopy, which allowed observation of etched double lines and grating structures with periods as small as 200 nm.

Reciprocity theory of apertureless scanning near-field optical microscopy with point-dipole probes.

Science.gov (United States)

Esslinger, Moritz; Vogelgesang, Ralf

2012-09-25

Near-field microscopy offers the opportunity to reveal optical contrast at deep subwavelength scales. In scanning near-field optical microscopy (SNOM), the diffraction limit is overcome by a nanoscopic probe in close proximity to the sample. The interaction of the probe with the sample fields necessarily perturbs the bare sample response, and a critical issue is the interpretation of recorded signals. For a few specific SNOM configurations, individual descriptions have been modeled, but a general and intuitive framework is still lacking. Here, we give an exact formulation of the measurable signals in SNOM which is easily applicable to experimental configurations. Our results are in close analogy with the description Tersoff and Hamann have derived for the tunneling currents in scanning tunneling microscopy. For point-like scattering probe tips, such as used in apertureless SNOM, the theory simplifies dramatically to a single scalar relation. We find that the measured signal is directly proportional to the field of the coupled tip-sample system at the position of the tip. For weakly interacting probes, the model thus verifies the empirical findings that the recorded signal is proportional to the unperturbed field of the bare sample. In the more general case, it provides guidance to an intuitive and faithful interpretation of recorded images, facilitating the characterization of tip-related distortions and the evaluation of novel SNOM configurations, both for aperture-based and apertureless SNOM.

HCIT Contrast Performance Sensitivity Studies: Simulation Versus Experiment

Science.gov (United States)

Sidick, Erkin; Shaklan, Stuart; Krist, John; Cady, Eric J.; Kern, Brian; Balasubramanian, Kunjithapatham

2013-01-01

Using NASA's High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Laboratory, we have experimentally investigated the sensitivity of dark hole contrast in a Lyot coronagraph for the following factors: 1) Lateral and longitudinal translation of an occulting mask; 2) An opaque spot on the occulting mask; 3) Sizes of the controlled dark hole area. Also, we compared the measured results with simulations obtained using both MACOS (Modeling and Analysis for Controlled Optical Systems) and PROPER optical analysis programs with full three-dimensional near-field diffraction analysis to model HCIT's optical train and coronagraph.

Numerical simulation of shell-side heat transfer and flow of natural circulation heat exchanger

International Nuclear Information System (INIS)

Xue Ruojun; Deng Chengcheng; Li Chaojun; Wang Mingyuan

2012-01-01

In order to analyze the influence on the heat transfer and flow characteristics of the heat exchanger model of different solving models and structures, a variety of transformation to the model equivalent for the heat exchanger was studied. In this paper, Fluent software was used to simulate the temperature-field and flow-field of the equivalent model, and investigate its heat-transferring and flow characteristics. Through comparative analysis of the distribution of temperature-field and flow-field for different models, the heat-transferring process and natural convection situation of heat exchanger were deeply understood. The results show that the temperature difference between the inside and outside of the natural circulation heat exchanger tubes is larger and the flow is more complex, so the turbulence model is the more reasonable choice. Asymmetry of tubes position makes the flow and heat transfer of the fluid on both sides to be dissymmetrical and makes the fluid interaction, and increases the role of natural convection. The complex structure of heat exchanger makes the flow and heat transfer of the fluid on both sides to be irregular to some extent when straight tubes into C-bent are transformed, and all these make the turbulence intensity increase and improve the effect of heat transfer. (authors)

Theoretical and experimental examination of near-field acoustic levitation.

Science.gov (United States)

Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa

2002-04-01

A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense.

The long term geochemical evolution of the nearfield of the HLW repository

Energy Technology Data Exchange (ETDEWEB)

Bradbury, M. H.; Berner, U.; Curti, E.; Hummel, W.; Kosakowski, G.; Thoenen, T.

2014-11-15

The work presented in this report focuses on the spatial and temporal evolution of the near-field of the high level radioactive waste repository situated in the Opalinus Clay formation. The major components of the near-field of such a repository are spent fuel, vitrified high-level waste, canisters (assumed for the purposes of the present report to be made of carbon steel), compacted bentonite and a concrete liner. Over the one million year time period considered in safety analysis, these components will chemically interact with one another and potentially change their retention characteristics. As a starting reference point the 'initial' (unreacted) states of the Opalinus Clay, bentonite, concrete liner (mineralogies and water chemistries) and the canister are briefly described. The main processes considered to influence the evolution of the repository in time and space, and which often operate over different time scales, are: interactions of the concrete tunnel liner with compacted bentonite and Opalinus Clay, temperature gradients caused by the heat generating high level waste, mineralogical changes to the compacted bentonite through interactions with the corrosion products of the iron canisters, and finally, the dissolution of the spent fuel and vitrified high-level waste. The consequences of these processes (as a function of time) on the long term barrier performance of the near-field have been estimated, particularly with respect to radionuclide solubilities and the sorption, diffusion and swelling characteristics of the bentonite. The main conclusions drawn are as follows: The alteration depth into the bentonite due to the interaction with the concrete liner (assumed to be 15 cm thick) is likely to be much less than 13 cm over a one million year time scale, with the main reaction products being clays (illite), hydroxides, carbonates, calcium silicate hydrates, and aluminosilicates. The swelling pressure and the sorption capacity of the bentonite in

The long term geochemical evolution of the nearfield of the HLW repository

International Nuclear Information System (INIS)

Bradbury, M. H.; Berner, U.; Curti, E.; Hummel, W.; Kosakowski, G.; Thoenen, T.

2014-11-01

The work presented in this report focuses on the spatial and temporal evolution of the near-field of the high level radioactive waste repository situated in the Opalinus Clay formation. The major components of the near-field of such a repository are spent fuel, vitrified high-level waste, canisters (assumed for the purposes of the present report to be made of carbon steel), compacted bentonite and a concrete liner. Over the one million year time period considered in safety analysis, these components will chemically interact with one another and potentially change their retention characteristics. As a starting reference point the 'initial' (unreacted) states of the Opalinus Clay, bentonite, concrete liner (mineralogies and water chemistries) and the canister are briefly described. The main processes considered to influence the evolution of the repository in time and space, and which often operate over different time scales, are: interactions of the concrete tunnel liner with compacted bentonite and Opalinus Clay, temperature gradients caused by the heat generating high level waste, mineralogical changes to the compacted bentonite through interactions with the corrosion products of the iron canisters, and finally, the dissolution of the spent fuel and vitrified high-level waste. The consequences of these processes (as a function of time) on the long term barrier performance of the near-field have been estimated, particularly with respect to radionuclide solubilities and the sorption, diffusion and swelling characteristics of the bentonite. The main conclusions drawn are as follows: The alteration depth into the bentonite due to the interaction with the concrete liner (assumed to be 15 cm thick) is likely to be much less than 13 cm over a one million year time scale, with the main reaction products being clays (illite), hydroxides, carbonates, calcium silicate hydrates, and aluminosilicates. The swelling pressure and the sorption capacity of the bentonite in this

Observation of magnetic domains using a reflection-mode scanning near-field optical microscope

OpenAIRE

SHVETS, IGOR

1997-01-01

PUBLISHED It is demonstrated that it is possible to image magnetic domains with a resolution of better than 60 nm with the Kerr effect in a reflection-mode scanning near-field optical microscope. Images taken of tracks of thermomagnetically prewritten bits in a Co/Pt multilayer structure magnetized out-of plane showed optical features in a track pattern whose appearance was determined by the position of an analyzer in front of the photomultiplier tube. These features were not apparent in t...

Observation of magnetic domains using a reflection mode scanning near-field optical microscope

OpenAIRE

Durkam, C.; Shvets, I.V.; Lodder, J.C.

1997-01-01

It is demonstrated that it is possible to image magnetic domains with a resolution of better than 60 nm with the Kerr effect in a reflection-mode scanning near-field optical microscope. Images taken of tracks of thermomagnetically prewritten bits in a Co/Pt multilayer structure magnetized out-of plane showed optical features in a track pattern whose appearance was determined by the position of an analyzer in front of the photomultiplier tube. These features were not apparent in the topography...

Computational Fluid Dynamics of Whole-Body Aircraft

Science.gov (United States)

Agarwal, Ramesh

1999-01-01

The current state of the art in computational aerodynamics for whole-body aircraft flowfield simulations is described. Recent advances in geometry modeling, surface and volume grid generation, and flow simulation algorithms have led to accurate flowfield predictions for increasingly complex and realistic configurations. As a result, computational aerodynamics has emerged as a crucial enabling technology for the design and development of flight vehicles. Examples illustrating the current capability for the prediction of transport and fighter aircraft flowfields are presented. Unfortunately, accurate modeling of turbulence remains a major difficulty in the analysis of viscosity-dominated flows. In the future, inverse design methods, multidisciplinary design optimization methods, artificial intelligence technology, and massively parallel computer technology will be incorporated into computational aerodynamics, opening up greater opportunities for improved product design at substantially reduced costs.

Near-field observation of spatial phase shifts associated with Goos-Hänschen and surface plasmon resonance effects

NARCIS (Netherlands)

Jose, J.; Segerink, Franciscus B.; Korterik, Jeroen P.; Offerhaus, Herman L.

2008-01-01

We report the near-field observation of the phase shifts associated with total internal reflection on a glass-air interface and surface plasmon resonance on a glass-gold-air system. The phase of the evanescent waves on glass and gold surfaces, as a function of incident angle, is measured using a

Mechanical and hydrological characterization of the near-field surrounding excavations in a geologic salt formation

Energy Technology Data Exchange (ETDEWEB)

Howard, Clifford L. [Sandia National Laboratories, Albuquerque, NM (United States)

2014-09-01

The technical basis for salt disposal of nuclear waste resides in salt’s favorable physical, mechanical and hydrological characteristics. Undisturbed salt formations are impermeable. Upon mining, the salt formation experiences damage in the near-field rock proximal to the mined opening and salt permeability increases dramatically. The volume of rock that has been altered by such damage is called the disturbed rock zone (DRZ).

Non-contact distance measurement and profilometry using thermal near-field radiation towards a high resolution inspection and metrology solution

NARCIS (Netherlands)

Bijster, R.J.F.; Sadeghian Marnani, H.; van Keulen, A.; Sanchez, M.I.; Ukraintsev, V.A.

2016-01-01

Optical near-field technologies such as solid immersion lenses and hyperlenses are candidate solutions for high resolution and high throughput wafer inspection and metrology for the next technology nodes. Besides sub-diffraction limited optical performance, these concepts share the necessity of

Apoptosis study of the macrophage via near-field scanning optical microscope

International Nuclear Information System (INIS)

Wang, D-C; Chen, K-Y; Chen, G-Y; Chen, S-H; Wun, S-J

2008-01-01

The cell apoptosis phenomenon was studied by traditional optical microscope with much lower resolution and also observed by Atomic Force Microscope (AFM) with nano-resolution recently. They both detect the cell apoptosis through the change of cell topography. In this study, the cell apoptosis was investigated via Near-Field Scanning Optical Microscope (NSOM). The cell topography, with nano-scaled resolution, and its optical characteristics were observed by NSOM at the same measurement scanning. The macrophage was chosen as the cell investigated. To understand the cell apoptosis process is the goal set for the research. The apoptosis process was related to the variations of the optical characteristics of the cell

Opto-mechatronics issues in solid immersion lens based near-field recording

Science.gov (United States)

Park, No-Cheol; Yoon, Yong-Joong; Lee, Yong-Hyun; Kim, Joong-Gon; Kim, Wan-Chin; Choi, Hyun; Lim, Seungho; Yang, Tae-Man; Choi, Moon-Ho; Yang, Hyunseok; Rhim, Yoon-Chul; Park, Young-Pil

2007-06-01

We analyzed the effects of an external shock on a collision problem in a solid immersion lens (SIL) based near-field recording (NFR) through a shock response analysis and proposed a possible solution to this problem with adopting a protector and safety mode. With this proposed method the collision between SIL and media can be avoided. We showed possible solution for contamination problem in SIL based NFR through a numerical air flow analysis. We also introduced possible solid immersion lens designs to increase the fabrication and assembly tolerances of an optical head with replicated lens. Potentially, these research results could advance NFR technology for commercial product.

Broad-band near-field ground motion simulations in 3-dimensional scattering media

KAUST Repository

Imperatori, W.

2012-12-06

The heterogeneous nature of Earth\\'s crust is manifested in the scattering of propagating seismic waves. In recent years, different techniques have been developed to include such phenomenon in broad-band ground-motion calculations, either considering scattering as a semi-stochastic or purely stochastic process. In this study, we simulate broad-band (0–10 Hz) ground motions with a 3-D finite-difference wave propagation solver using several 3-D media characterized by von Karman correlation functions with different correlation lengths and standard deviation values. Our goal is to investigate scattering characteristics and its influence on the seismic wavefield at short and intermediate distances from the source in terms of ground motion parameters. We also examine scattering phenomena, related to the loss of radiation pattern and the directivity breakdown. We first simulate broad-band ground motions for a point-source characterized by a classic ω2 spectrum model. Fault finiteness is then introduced by means of a Haskell-type source model presenting both subshear and super-shear rupture speed. Results indicate that scattering plays an important role in ground motion even at short distances from the source, where source effects are thought to be dominating. In particular, peak ground motion parameters can be affected even at relatively low frequencies, implying that earthquake ground-motion simulations should include scattering also for peak ground velocity (PGV) calculations. At the same time, we find a gradual loss of the source signature in the 2–5 Hz frequency range, together with a distortion of the Mach cones in case of super-shear rupture. For more complex source models and truly heterogeneous Earth, these effects may occur even at lower frequencies. Our simulations suggests that von Karman correlation functions with correlation length between several hundred metres and few kilometres, Hurst exponent around 0.3 and standard deviation in the 5–10 per cent

Reduction of truncation errors in planar near-field aperture antenna measurements using the method of alternating orthogonal projections

DEFF Research Database (Denmark)

Martini, Enrica; Breinbjerg, Olav; Maci, Stefano

2006-01-01

A simple and effective procedure for the reduction of truncation error in planar near-field to far-field transformations is presented. The starting point is the consideration that the actual scan plane truncation implies a reliability of the reconstructed plane wave spectrum of the field radiated...

Supersonic impinging jet noise reduction using a hybrid control technique

Science.gov (United States)

Wiley, Alex; Kumar, Rajan

2015-07-01

Control of the highly resonant flowfield associated with supersonic impinging jet has been experimentally investigated. Measurements were made in the supersonic impinging jet facility at the Florida State University for a Mach 1.5 ideally expanded jet. Measurements included unsteady pressures on a surface plate near the nozzle exit, acoustics in the nearfield and beneath the impingement plane, and velocity field using particle image velocimetry. Both passive control using porous surface and active control with high momentum microjet injection are effective in reducing nearfield noise and flow unsteadiness over a range of geometrical parameters; however, the type of noise reduction achieved by the two techniques is different. The passive control reduces broadband noise whereas microjet injection attenuates high amplitude impinging tones. The hybrid control, a combination of two control methods, reduces both broadband and high amplitude impinging tones and surprisingly its effectiveness is more that the additive effect of the two control techniques. The flow field measurements show that with hybrid control the impinging jet is stabilized and the turbulence quantities such as streamwise turbulence intensity, transverse turbulence intensity and turbulent shear stress are significantly reduced.

A design tool for direct and non-stochastic calculations of near-field radiative transfer in complex structures: The NF-RT-FDTD algorithm

Science.gov (United States)

Didari, Azadeh; Pinar Mengüç, M.

2017-08-01

Advances in nanotechnology and nanophotonics are inextricably linked with the need for reliable computational algorithms to be adapted as design tools for the development of new concepts in energy harvesting, radiative cooling, nanolithography and nano-scale manufacturing, among others. In this paper, we provide an outline for such a computational tool, named NF-RT-FDTD, to determine the near-field radiative transfer between structured surfaces using Finite Difference Time Domain method. NF-RT-FDTD is a direct and non-stochastic algorithm, which accounts for the statistical nature of the thermal radiation and is easily applicable to any arbitrary geometry at thermal equilibrium. We present a review of the fundamental relations for far- and near-field radiative transfer between different geometries with nano-scale surface and volumetric features and gaps, and then we discuss the details of the NF-RT-FDTD formulation, its application to sample geometries and outline its future expansion to more complex geometries. In addition, we briefly discuss some of the recent numerical works for direct and indirect calculations of near-field thermal radiation transfer, including Scattering Matrix method, Finite Difference Time Domain method (FDTD), Wiener Chaos Expansion, Fluctuating Surface Current (FSC), Fluctuating Volume Current (FVC) and Thermal Discrete Dipole Approximations (TDDA).

Analysis of near-field thermal and psychometric waste package environment using ventilation

International Nuclear Information System (INIS)

Danko, G.

1995-03-01

The ultimate objective of the Civilian Radioactive Waste Management System (CRWMS) Program is to safely emplace and isolate the nations' spent nuclear fuel (SNF) and radioactive wastes in a geologic repository. Radioactive waste emplaced in a geologic repository will generate heat, increasing the temperature in the repository. The magnitude of this temperature increase depends upon (1) the heat source, i.e. the thermal loading of the repository, and (2) the geologic and engineered heat transport characteristics of the repository. Thermal management techniques currently under investigation include ventilation of the emplacement drifts during the preclosure period which could last as long as 100 years. Understanding the amount of heat and moisture removed from the emplacement drifts and near-field rock by ventilation, are important in determining performance of the engineered barrier system (EBS), as well as the corrosive environment of the waste packages, and the interaction of the EBS with the near-field host rock. Since radionuclide releases and repository system performance are significantly affected by the corrosion rate related to the psychometric environment, it is necessary to predict the amount of heat and moisture that are removed from the repository horizon using a realistic model for a wide range of thermal loading. This can be realized by coupling the hydrothermal model of the rock mass to a ventilation/climate model which includes the heat and moisture transport on the rock-air interface and the dilution of water vapor in the drift. This paper deals with the development of the coupled model concept, and determination of the boundary conditions for the calculations

Biological applications of near-field scanning optical microscopy

Science.gov (United States)

Moers, Marco H. P.; Ruiter, A. G. T.; Jalocha, Alain; van Hulst, Niko F.; Kalle, W. H. J.; Wiegant, J. C. A. G.; Raap, A. K.

1995-09-01

Near-field Scanning Optical Microscopy (NSOM) is a true optical microscopic technique allowing fluorescence, absorption, reflection and polarization contrast with the additional advantage of nanometer lateral resolution, unlimited by diffraction and operation at ambient conditions. NSOM based on metal coated adiabatically tapered fibers, combined with shear force feedback and operated in illumination mode, has proven to be the most powerful NSOM arrangement, because of its true localization of the optical interaction, its various optical contrast possibilities and its sensitivity down to the single molecular level. In this paper applications of `aperture' NSOM to Fluorescence In Situ Hybridization of human metaphase chromosomes are presented, where the localized fluorescence allows to identify specific DNA sequences. All images are accompanied by the simultaneously acquired force image, enabling direct comparison of the optical contrast with the sample topography on nanometer scale, far beyond the diffraction limit. Thus the unique combination of high resolution, specific optical contrast and ambient operation offers many new direction possibilities in biological studies.

Flow cytometric assessment of microbial abundance in the near-field area of seawater reverse osmosis concentrate discharge

KAUST Repository

Van Der Merwe, Riaan

2014-06-01

The discharge of concentrate and other process waters from seawater reverse osmosis (SWRO) plant operations into the marine environment may adversely affect water quality in the near-field area surrounding the outfall. The main concerns are the increase in salt concentration in receiving waters, which results in a density increase and potential water stratification near the outfall, and possible increases in turbidity, e.g., due to the discharge of filter backwash waters. Changes in ambient water quality may affect microbial abundance in the area, for example by hindering the photosynthesis process or disrupting biogenesis. It is widely accepted that marine biodiversity is lower in more extreme conditions, such as high salinity environments. As aquatic microbial communities respond very rapidly to changes in their environment, they can be used as indicators for monitoring ambient water quality. The objective of this study was to assess possible changes in microbial abundance as a result of concentrate discharge into the near-field area (<. 25. m) surrounding the outfall of the King Abdullah University of Science and Technology (KAUST) SWRO plant. Flow cytometric (FCM) analysis was conducted in order to rapidly determine microbial abundance on a single-cell level in 107 samples, taken by diving, from the discharge area, the intake area and two control sites. FCM analysis combined the measurement of distinct scatter of cells and particles, autofluorescence of cyanobacteria and algae, and fluorescence after staining of nucleic acids with SYBR® Green for a total bacterial count. The results indicate that changes in microbial abundance in the near-field area of the KAUST SWRO outfall are minor and appear to be the result of a dilution effect rather than a direct impact of the concentrate discharge. © 2014 Elsevier B.V.

Near-field probing of Mie resonances in single TiO.sub.2./sub. microspheres at terahertz frequencies

Czech Academy of Sciences Publication Activity Database

Mitrofanov, O.; Dominec, Filip; Kužel, Petr; Reno, J.L.; Brener, I.; Chung, U.-C.; Elissalde, C.; Maglione, M.; Mounaix, P.

2014-01-01

Roč. 22, č. 19 (2014), s. 23034-23042 ISSN 1094-4087 R&D Projects: GA ČR(CZ) GA14-25639S EU Projects: European Commission(XE) 607521 - NOTEDEV Institutional support: RVO:68378271 Keywords : metamaterials * near-field microscopy * resonators * terahertz imaging Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.488, year: 2014

Application of the iterative probe correction technique for a high-order probe in spherical near-field antenna measurements

DEFF Research Database (Denmark)

Laitinen, Tommi; Pivnenko, Sergey; Breinbjerg, Olav

2006-01-01

An iterative probe-correction technique for spherical near-field antenna measurements is examined. This technique has previously been shown to be well-suited for non-ideal first-order probes. In this paper, its performance in the case of a high-order probe (a dual-ridged horn) is examined....

Broad-band near-field ground motion simulations in 3-dimensional scattering media

KAUST Repository

Imperatori, W.; Mai, Paul Martin

2012-01-01

examine scattering phenomena, related to the loss of radiation pattern and the directivity breakdown. We first simulate broad-band ground motions for a point-source characterized by a classic ω2 spectrum model. Fault finiteness is then introduced by means

Community variations in population exposure to near-field tsunami hazards as a function of pedestrian travel time to safety

Science.gov (United States)

Wood, Nathan J.; Schmidtlein, Mathew C.

2013-01-01

Efforts to characterize population exposure to near-field tsunami threats typically focus on quantifying the number and type of people in tsunami-hazard zones. To develop and prioritize effective risk-reduction strategies, emergency managers also need information on the potential for successful evacuations and how this evacuation potential varies among communities. To improve efforts to properly characterize and differentiate near-field tsunami threats among multiple communities, we assess community variations in population exposure to tsunamis as a function of pedestrian travel time to safety. We focus our efforts on the multiple coastal communities in Grays Harbor and Pacific Counties (State of Washington, USA), where a substantial resident and visitor population is threatened by near-field tsunamis related to a potential Cascadia subduction zone earthquake. Anisotropic, path-distance modeling is conducted to estimate travel times to safety and results are merged with various population data, including residents, employees, public venues, and dependent-care facilities. Results suggest that there is substantial variability among communities in the number of people that may have insufficient time to evacuate. Successful evacuations may be possible in some communities assuming slow-walking speeds, are plausible in others if travel speeds are increased, and are unlikely in another set of communities given the large distances and short time horizon. Emergency managers can use these results to prioritize the location and determine the most appropriate type of tsunami risk-reduction strategies, such as education and training in areas where evacuations are plausible and vertical-evacuation structures in areas where they are not.

Virtual Reality System with Integrated Sound Field Simulation and Reproduction

Directory of Open Access Journals (Sweden)

Ingo Assenmacher

2007-01-01

Full Text Available A real-time audio rendering system is introduced which combines a full room-specific simulation, dynamic crosstalk cancellation, and multitrack binaural synthesis for virtual acoustical imaging. The system is applicable for any room shape (normal, long, flat, coupled, independent of the a priori assumption of a diffuse sound field. This provides the possibility of simulating indoor or outdoor spatially distributed, freely movable sources and a moving listener in virtual environments. In addition to that, near-to-head sources can be simulated by using measured near-field HRTFs. The reproduction component consists of a headphone-free reproduction by dynamic crosstalk cancellation. The focus of the project is mainly on the integration and interaction of all involved subsystems. It is demonstrated that the system is capable of real-time room simulation and reproduction and, thus, can be used as a reliable platform for further research on VR applications.

Longitudinal Seismic Behavior of a Single-Tower Cable-Stayed Bridge Subjected to Near-Field Earthquakes

Directory of Open Access Journals (Sweden)

J. Yi

2017-01-01

Full Text Available Cable-stayed bridges are quite sensitive to large amplitude oscillations from earthquakes and seismic damage was observed for Shipshaw Bridge and Chi-Lu Bridge during past earthquakes. In order to investigate seismic damage of cable-stayed bridges, a 1 : 20 scale model of a single-tower cable-stayed bridge with A-shaped tower was designed, constructed, and tested on shake tables at Tongji University, China. One typical near-field ground motion was used to excite the model from low to high intensity. Test result showed that severe structural damage occurred at the tower of the model including parallel concrete cracks from bottom to nearly half height of the tower, concrete spalling, and exposed bars at top tower 0.2 m above the section where two skewed legs intersect. Posttest analysis was conducted and compared with test results. It is revealed that the numerical model was able to simulate the seismic damage of the test model by modeling nonlinearity of different components for cable-stayed bridges, namely, the tower, bents, superstructure, cables, and bearings. Numerical analysis also revealed that cable relaxation, which was detected during the test, had limited influence on the overall seismic response of the bridge with maximum error of 12%.

Nuclide release from the near-field of a L/ILW repository

International Nuclear Information System (INIS)

Karlsson, L.G.; Hoeglund, L.O.; Pers, K.

1986-12-01

For Project Gewaehr 1985, the release of nuclides from a repository for low- and intermediate-level radioactive waste is calculated. The calculations are made for a reference design repository located in the marl host rock at the Oberbauen Stock reference site. The results are limited to the release of the nuclides from the waste through the engineered barriers into the surrounding host rock and will, therefore, constitute a source term for the far-field and biosphere calculations. The most probable nuclide transport mechanism is diffusion and releases are thus influenced by the nuclide diffusivities in the barriers, nuclide sorption and nuclide solubility limits. Degradation of the engineered concrete barriers is taken into account. The effects of convective flow through the barriers are described elsewhere. A near-field release model is presented. It consists of a set of computer programs suited to handel different repository designs, solubility limitations and the different waste categories. The release calculations were made for a base case in which best estimates of the parameters were used. Sensitivity to the choice of the most important parameters was tested by parameter variations. The numerical models used were checked by comparative calculations with different codes and similar data. The results of the base calculations show that near-field barriers will cause both a delay of the release to the far-field and a reduced rate of release. The sorbed nuclides, comprising the actinides and some activation and fission products, will be delayed by 10'000 years and have a maximum release rate of less than 10 -3 Ci/a each. The non-sorbed nuclides are delayed by only about 100 years and the maximum release rate is less than 10 -2 Ci per year and nuclide. The parameter variations and the design model tests gave only limited deviations from the base case results. (author)

PASSIVE CONTROL OF PARTICLE DISPERSION IN A PARTICLE-LADEN CIRCULAR JET USING ELLIPTIC CO-ANNULAR FLOW: A MEANS FOR IMPROVING UTILIZATION AND EMISSION REDUCTIONS IN PULVERIZED COAL BURNER

Energy Technology Data Exchange (ETDEWEB)

Ahsan R. Choudhuri

2003-06-01

A passive control technology utilizing elliptic co-flow to control the particle flinging and particle dispersion in a particle (coal)-laden flow was investigated using experimental and numerical techniques. Preferential concentration of particles occurs in particle-laden jets used in pulverized coal burner and causes uncontrollable NO{sub x} formation due to inhomogeneous local stoichiometry. This particular project was aimed at characterizing the near-field flow behavior of elliptic coaxial jets. The knowledge gained from the project will serve as the basis of further investigation on fluid-particle interactions in an asymmetric coaxial jet flow-field and thus is important to improve the design of pulverized coal burners where non-homogeneity of particle concentration causes increased NO{sub x} formation.

Measured Sonic Boom Signatures Above and Below the XB-70 Airplane Flying at Mach 1.5 and 37,000 Feet

Science.gov (United States)

Maglieri, Domenic J.; Henderson, Herbert R.; Tinetti, Ana F.

2011-01-01

During the 1966-67 Edwards Air Force Base (EAFB) National Sonic Boom Evaluation Program, a series of in-flight flow-field measurements were made above and below the USAF XB-70 using an instrumented NASA F-104 aircraft with a specially designed nose probe. These were accomplished in the three XB-70 flights at about Mach 1.5 at about 37,000 ft. and gross weights of about 350,000 lbs. Six supersonic passes with the F-104 probe aircraft were made through the XB-70 shock flow-field; one above and five below the XB-70. Separation distances ranged from about 3000 ft. above and 7000 ft. to the side of the XB-70 and about 2000 ft. and 5000 ft. below the XB-70. Complex near-field "sawtooth-type" signatures were observed in all cases. At ground level, the XB-70 shock waves had not coalesced into the two-shock classical sonic boom N-wave signature, but contained three shocks. Included in this report is a description of the generating and probe airplanes, the in-flight and ground pressure measuring instrumentation, the flight test procedure and aircraft positioning, surface and upper air weather observations, and the six in-flight pressure signatures from the three flights.

Atomic force and optical near-field microscopic investigations of polarization holographic gratings in a liquid crystalline azobenzene side-chain polyester

DEFF Research Database (Denmark)

Ramanujam, P.S.; Holme, N.C.R.; Hvilsted, S.

1996-01-01

Atomic force and scanning near-field optical microscopic investigations have been carried out on a polarization holographic grating recorded in an azobenzene side-chain Liquid crystalline polyester. It has been found that immediately following laser irradiation, a topographic surface grating...

Challenge of Near-Field Recording beyond 50.4 Gbit/in2

Science.gov (United States)

Kishima, Koichiro; Ichimura, Isao; Saito, Kimihiro; Yamamoto, Kenji; Kuroda, Yuji; Iida, Atsushi; Masuhara, Shin; Osato, Kiyoshi

2002-03-01

The possibility of an areal density over 50 Gbit/in2 was examined in near-field phase-change recording. The disk structure was optimized to maximize readout signals under the land-and-groove recording condition at a tracking pitch of 160 nm. We also evaluated the signal crosstalk from adjacent tracks. Eye diagrams of 50.4 Gbit/in2 areal density were demonstrated using 1.5 \\mathit{NA} optics and a GaN laser diode. The track pitch and linear bit density are 160 nm and 80 nm/bit, respectively. The transmission electron microscope (TEM) micrograph of recorded amorphous marks at an areal density of 50.4 Gbit/in2 is also presented.

A coupled CFD and wake model simulation of helicopter rotor in hover

Science.gov (United States)

Zhao, Qinghe; Li, Xiaodong

2018-03-01

The helicopter rotor wake plays a dominant role since it affects the flow field structure. It is very difficult to predict accurately of the flow-field. The numerical dissipation is so excessive that it eliminates the vortex structure. A hybrid method of CFD and prescribed wake model was constructed by applying the prescribed wake model as much as possible. The wake vortices were described as a single blade tip vortex in this study. The coupling model is used to simulate the flow field. Both non-lifting and lifting cases have been calculated with subcritical and supercritical tip Mach numbers. Surface pressure distributions are presented and compared with experimental data. The calculated results agree well with the experimental data.

Viscoacoustic model for near-field ultrasonic levitation

Science.gov (United States)

Melikhov, Ivan; Chivilikhin, Sergey; Amosov, Alexey; Jeanson, Romain

2016-11-01

Ultrasonic near-field levitation allows for contactless support and transportation of an object over vibrating surface. We developed an accurate model predicting pressure distribution in the gap between the surface and levitating object. The formulation covers a wide range of the air flow regimes: from viscous squeezed flow dominating in small gap to acoustic wave propagation in larger gap. The paper explains derivation of the governing equations from the basic fluid dynamics. The nonreflective boundary conditions were developed to properly define air flow at the outlet. Comparing to direct computational fluid dynamics modeling our approach allows achieving good accuracy while keeping the computation cost low. Using the model we studied the levitation force as a function of gap distance. It was shown that there are three distinguished flow regimes: purely viscous, viscoacoustic, and acoustic. The regimes are defined by the balance of viscous and inertial forces. In the viscous regime the pressure in the gap is close to uniform while in the intermediate viscoacoustic and the acoustic regimes the pressure profile is wavy. The model was validated by a dedicated levitation experiment and compared to similar published results.

Superresolution Near-field Imaging with Surface Waves

KAUST Repository

Fu, Lei

2017-10-21

We present the theory for near-field superresolution imaging with surface waves and time reverse mirrors (TRMs). Theoretical formulas and numerical results show that applying the TRM operation to surface waves in an elastic half-space can achieve superresolution imaging of subwavelength scatterers if they are located less than about 1/2 of the shear wavelength from the source line. We also show that the TRM operation for a single frequency is equivalent to natural migration, which uses the recorded data to approximate the Green’s functions for migration, and only costs O(N4) algebraic operations for poststack migration compared to O(N6) operations for natural prestack migration. Here, we assume the sources and receivers are on an N × N grid and there are N2 trial image points on the free surface. Our theoretical predictions of superresolution are validated with tests on synthetic data. The field-data tests suggest that hidden faults at the near surface can be detected with subwavelength imaging of surface waves by using the TRM operation if they are no deeper than about 1/2 the dominant shear wavelength.

Numerical simulation of helicopter engine plume in forward flight

Science.gov (United States)

Dimanlig, Arsenio C. B.; Vandam, Cornelis P.; Duque, Earl P. N.

1994-01-01

Flowfields around helicopters contain complex flow features such as large separated flow regions, vortices, shear layers, blown and suction surfaces and an inherently unsteady flow imposed by the rotor system. Another complicated feature of helicopters is their infrared signature. Typically, the aircraft's exhaust plume interacts with the rotor downwash, the fuselage's complicated flowfield, and the fuselage itself giving each aircraft a unique IR signature at given flight conditions. The goal of this project was to compute the flow about a realistic helicopter fuselage including the interaction of the engine air intakes and exhaust plume. The computations solve the Think-Layer Navier Stokes equations using overset type grids and in particular use the OVERFLOW code by Buning of NASA Ames. During this three month effort, an existing grid system of the Comanche Helicopter was to be modified to include the engine inlet and the hot engine exhaust. The engine exhaust was to be modeled as hot air exhaust. However, considerable changes in the fuselage geometry required a complete regriding of the surface and volume grids. The engine plume computations have been delayed to future efforts. The results of the current work consists of a complete regeneration of the surface and volume grids of the most recent Comanche fuselage along with a flowfield computation.

Carrier redistribution between different potential sites in semipolar (202¯1) InGaN quantum wells studied by near-field photoluminescence

KAUST Repository

Marcinkevičius, S.; Gelžinytė, K.; Zhao, Y.; Nakamura, S.; DenBaars, S. P.; Speck, J. S.

2014-01-01

© 2014 AIP Publishing LLC. Scanning near-field photoluminescence (PL) spectroscopy at different excitation powers was applied to study nanoscale properties of carrier localization and recombination in semipolar (202¯1) InGaN quantum wells (QWs

Vectorial near-field imaging of a GaN based photonic crystal cavity

International Nuclear Information System (INIS)

La China, F.; Intonti, F.; Caselli, N.; Lotti, F.; Vinattieri, A.; Gurioli, M.; Vico Triviño, N.; Carlin, J.-F.; Butté, R.; Grandjean, N.

2015-01-01

We report a full optical deep sub-wavelength imaging of the vectorial components of the electric local density of states for the confined modes of a modified GaN L3 photonic crystal nanocavity. The mode mapping is obtained with a scanning near-field optical microscope operating in a resonant forward scattering configuration, allowing the vectorial characterization of optical passive samples. The optical modes of the investigated cavity emerge as Fano resonances and can be probed without the need of embedded light emitters or evanescent light coupling into the nanocavity. The experimental maps, independently measured in the two in-plane polarizations, turn out to be in excellent agreement with numerical predictions

PIV and CFD studies on analyzing intragastric flow phenomena induced by peristalsis using a human gastric flow simulator.

Science.gov (United States)

Kozu, Hiroyuki; Kobayashi, Isao; Neves, Marcos A; Nakajima, Mitsutoshi; Uemura, Kunihiko; Sato, Seigo; Ichikawa, Sosaku

2014-08-01

This study quantitatively analyzed the flow phenomena in model gastric contents induced by peristalsis using a human gastric flow simulator (GFS). Major functions of the GFS include gastric peristalsis simulation by controlled deformation of rubber walls and direct observation of inner flow through parallel transparent windows. For liquid gastric contents (water and starch syrup solutions), retropulsive flow against the direction of peristalsis was observed using both particle image velocimetry (PIV) and computational fluid dynamics (CFD). The maximum flow velocity was obtained in the region occluded by peristalsis. The maximum value was 9 mm s(-1) when the standard value of peristalsis speed in healthy adults (UACW = 2.5 mm s(-1)) was applied. The intragastric flow-field was laminar with the maximum Reynolds number (Re = 125). The viscosity of liquid gastric contents hardly affected the maximum flow velocity in the applied range of this study (1 to 100 mPa s). These PIV results agreed well with the CFD results. The maximum shear rate in the liquid gastric contents was below 20 s(-1) at UACW = 2.5 mm s(-1). We also measured the flow-field in solid-liquid gastric contents containing model solid food particles (plastic beads). The direction of velocity vectors was influenced by the presence of the model solid food particle surface. The maximum flow velocity near the model solid food particles ranged from 8 to 10 mm s(-1) at UACW = 2.5 mm s(-1). The maximum shear rate around the model solid food particles was low, with a value of up to 20 s(-1).

Radiation Pattern Reconstruction from the Near-Field Amplitude Measurement on Two Planes Using PSO

Directory of Open Access Journals (Sweden)

Z. Novacek

2005-12-01

Full Text Available The paper presents a new approach to the radiation patternreconstruction from near-field amplitude only measurement over a twoplanar scanning surfaces. This new method for antenna patternreconstruction is based on the global optimization PSO (Particle SwarmOptimization. The paper presents appropriate phaseless measurementrequirements and phase retrieval algorithm together with a briefdescription of the particle swarm optimization method. In order toexamine the methodologies developed in this paper, phaselessmeasurement results for two different antennas are presented andcompared to results obtained by a complex measurement (amplitude andphase.

Analysis of light scattering from human breast tissue using a custom dual-optical scanning near-field optical microscope.

Science.gov (United States)

Kyle, Jennifer Reiber; Kyle, Michael D; Raghavan, Ravi; Budak, Gurer; Ozkan, Cengiz S; Ozkan, Mihrimah

2011-03-01

In this paper we introduce a custom scanning near-field optical microscope (SNOM) that simultaneously collects reflection and transmission near-field images along with topography. This dual-optical SNOM uses a bent probe, which allows for axial reflection imaging, accurate surface scanning, and easy identification of topographic artifacts. Using this novel dual-optical SNOM, we image desiccated and non-desiccated human breast epithelial tissue. By comparing the simultaneous SNOM images, we isolate the effects of tissue morphology and variations in refractive indices on the forward- and back-scattering of light from the tissue. We find that the reduction in back-scattering from tissue, relative to the glass slide, is caused by dense packing of the scattering sites in the cytoplasm (morphology) in the desiccated tissue and a thin-film of water adhering to the glass slide (refractive index) in the non-desiccated tissue sample. Our work demonstrates the potential of our customized dual-optical SNOM system for label-free tissue diagnostics. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Imaging of phase change materials below a capping layer using correlative infrared near-field microscopy and electron microscopy

Science.gov (United States)

Lewin, M.; Hauer, B.; Bornhöfft, M.; Jung, L.; Benke, J.; Michel, A.-K. U.; Mayer, J.; Wuttig, M.; Taubner, T.

2015-10-01

Phase Change Materials (PCM) show two stable states in the solid phase with significantly different optical and electronic properties. They can be switched reversibly between those two states and are promising candidates for future non-volatile memory applications. The development of phase change devices demands characterization tools, yielding information about the switching process at high spatial resolution. Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) allows for spectroscopic analyses of the different optical properties of the PCMs on the nm-scale. By correlating the optical s-SNOM images with transmission electron microscopy images of the same sample, we unambiguously demonstrate the correlation of the infrared optical contrast with the structural state of the phase change material. The investigated sample consists of sandwiched amorphous and crystalline regions of Ag 4 In 3 Sb 67 Te 26 below a 100 nm thick ( ZnS ) 80 - ( SiO2 ) 20 capping layer. Our results demonstrate the sensitivity of s-SNOM to small dielectric near-field contrasts even below a comparably thick capping layer ( 100 nm ).

The Effect of Focal Distance, Age, and Brightness on Near-Field Augmented Reality Depth Matching

OpenAIRE

Singh, Gujot; Ellis, Stephen R.; Swan II, J. Edward

2017-01-01

Many augmented reality (AR) applications operate within near-field reaching distances, and require matching the depth of a virtual object with a real object. The accuracy of this matching was measured in three experiments, which examined the effect of focal distance, age, and brightness, within distances of 33.3 to 50 cm, using a custom-built AR haploscope. Experiment I examined the effect of focal demand, at the levels of collimated (infinite focal distance), consistent with other depth cues...

Kinematic Earthquake Ground‐Motion Simulations on Listric Normal Faults

KAUST Repository

Passone, Luca

2017-11-28

Complex finite-faulting source processes have important consequences for near-source ground motions, but empirical ground-motion prediction equations still lack near-source data and hence cannot fully capture near-fault shaking effects. Using a simulation-based approach, we study the effects of specific source parameterizations on near-field ground motions where empirical data are limited. Here, we investigate the effects of fault listricity through near-field kinematic ground-motion simulations. Listric faults are defined as curved faults in which dip decreases with depth, resulting in a concave upward profile. The listric profiles used in this article are built by applying a specific shape function and varying the initial dip and the degree of listricity. Furthermore, we consider variable rupture speed and slip distribution to generate ensembles of kinematic source models. These ensembles are then used in a generalized 3D finite-difference method to compute synthetic seismograms; the corresponding shaking levels are then compared in terms of peak ground velocities (PGVs) to quantify the effects of breaking fault planarity. Our results show two general features: (1) as listricity increases, the PGVs decrease on the footwall and increase on the hanging wall, and (2) constructive interference of seismic waves emanated from the listric fault causes PGVs over two times higher than those observed for the planar fault. Our results are relevant for seismic hazard assessment for near-fault areas for which observations are scarce, such as in the listric Campotosto fault (Italy) located in an active seismic area under a dam.

Influence of Spanwise Boundary Conditions on Slat Noise Simulations

Science.gov (United States)

Lockard, David P.; Choudhari, Meelan M.; Buning, Pieter G.

2015-01-01

The slat noise from the 30P/30N high-lift system is being investigated through computational fluid dynamics simulations with the OVERFLOW code in conjunction with a Ffowcs Williams-Hawkings acoustics solver. In the present study, two different spanwise grids are being used to investigate the effect of the spanwise extent and periodicity on the near-field unsteady structures and radiated noise. The baseline grid with periodic boundary conditions has a short span equal to 1/9th of the stowed chord, whereas the other, longer span grid adds stretched grids on both sides of the core, baseline grid to allow inviscid surface boundary conditions at both ends. The results indicate that the near-field mean statistics obtained using the two grids are similar to each other, as are the directivity and spectral shapes of the radiated noise. However, periodicity forces all acoustic waves with less than one wavelength across the span to be two-dimensional, without any variation in the span. The spanwise coherence of the acoustic waves is what is needed to make estimates of the noise that would be radiated from realistic span lengths. Simulations with periodic conditions need spans of at least six slat chords to allow spanwise variation in the low-frequencies associated with the peak of broadband slat noise. Even then, the full influence of the periodicity is unclear, so employing grids with a fine, central region and highly stretched meshes that go to slip walls may be a more efficient means of capturing the spanwise decorrelation of low-frequency acoustic phenomena.

Kinematic Earthquake Ground‐Motion Simulations on Listric Normal Faults

KAUST Repository

Passone, Luca; Mai, Paul Martin

2017-01-01

Complex finite-faulting source processes have important consequences for near-source ground motions, but empirical ground-motion prediction equations still lack near-source data and hence cannot fully capture near-fault shaking effects. Using a simulation-based approach, we study the effects of specific source parameterizations on near-field ground motions where empirical data are limited. Here, we investigate the effects of fault listricity through near-field kinematic ground-motion simulations. Listric faults are defined as curved faults in which dip decreases with depth, resulting in a concave upward profile. The listric profiles used in this article are built by applying a specific shape function and varying the initial dip and the degree of listricity. Furthermore, we consider variable rupture speed and slip distribution to generate ensembles of kinematic source models. These ensembles are then used in a generalized 3D finite-difference method to compute synthetic seismograms; the corresponding shaking levels are then compared in terms of peak ground velocities (PGVs) to quantify the effects of breaking fault planarity. Our results show two general features: (1) as listricity increases, the PGVs decrease on the footwall and increase on the hanging wall, and (2) constructive interference of seismic waves emanated from the listric fault causes PGVs over two times higher than those observed for the planar fault. Our results are relevant for seismic hazard assessment for near-fault areas for which observations are scarce, such as in the listric Campotosto fault (Italy) located in an active seismic area under a dam.

Near-field interference for the unidirectional excitation of electromagnetic guided modes.

Science.gov (United States)

Rodríguez-Fortuño, Francisco J; Marino, Giuseppe; Ginzburg, Pavel; O'Connor, Daniel; Martínez, Alejandro; Wurtz, Gregory A; Zayats, Anatoly V

2013-04-19

Wave interference is a fundamental manifestation of the superposition principle with numerous applications. Although in conventional optics, interference occurs between waves undergoing different phase advances during propagation, we show that the vectorial structure of the near field of an emitter is essential for controlling its radiation as it interferes with itself on interaction with a mediating object. We demonstrate that the near-field interference of a circularly polarized dipole results in the unidirectional excitation of guided electromagnetic modes in the near field, with no preferred far-field radiation direction. By mimicking the dipole with a single illuminated slit in a gold film, we measured unidirectional surface-plasmon excitation in a spatially symmetric structure. The surface wave direction is switchable with the polarization.

Direct-write PVDF nonwoven fiber fabric energy harvesters via the hollow cylindrical near-field electrospinning process

International Nuclear Information System (INIS)

Liu, Z H; Pan, C T; Ou, Z Y; Lin, L W; Huang, J C

2014-01-01

One-dimensional piezoelectric nanomaterials have attracted great attention in recent years for their possible applications in mechanical energy scavenging devices. However, it is difficult to control the structural diameter, length, and density of these fibers fabricated by micro/nano-technologies. This work presents a hollow cylindrical near-field electrospinning (HCNFES) process to address production and performance issues encountered previously in either far-field electrospinning (FFES) or near-field electrospinning (NFES) processes. Oriented polyvinylidene fluoride (PVDF) fibers in the form of nonwoven fabric have been directly written on a glass tube for aligned piezoelectricity. Under a high in situ electrical poling field and strong mechanical stretching (the tangential speed on the glass tube collector is about 1989.3 mm s −1 ), the HCNFES process is able to uniformly deposit large arrays of PVDF fibers with good concentrations of piezoelectric β-phase. The nonwoven fiber fabric (NFF) is transferred onto a polyethylene terephthalate (PET) substrate and fixed at both ends using copper foil electrodes as a flexible textile-fiber-based PVDF energy harvester. Repeated stretching and releasing of PVDF NFF with a strain of 0.05% at 7 Hz produces a maximum peak voltage and current at 76 mV and 39 nA, respectively. (paper)

Thermodynamic coupling of heat and matter flows in near-field regions of nuclear waste repositories

International Nuclear Information System (INIS)

Carnahan, C.L.

1983-11-01

In near-field regions of nuclear waste repositories, thermodynamically coupled flows of heat and matter can occur in addition to the independent flows in the presence of gradients of temperature, hydraulic potential, and composition. The following coupled effects can occur: thermal osmosis, thermal diffusion, chemical osmosis, thermal filtration, diffusion thermal effect, ultrafiltration, and coupled diffusion. Flows of heat and matter associated with these effects can modify the flows predictable from the direct effects, which are expressed by Fourier's law, Darcy's law, and Fick's law. The coupled effects can be treated quantitatively together with the direct effects by the methods of the thermodynamics of irreversible processes. The extent of departure of fully coupled flows from predictions based only on consideration of direct effects depends on the strengths of the gradients driving flows, and may be significant at early times in backfills and in near-field geologic environments of repositories. Approximate calculations using data from the literature and reasonable assumptions of repository conditions indicate that thermal-osmotic and chemical-osmotic flows of water in semipermeable backfills may exceed Darcian flows by two to three orders of magnitude, while flows of solutes may be reduced greatly by ultrafiltration and chemical osmosis, relative to the flows predicted by advection and diffusion alone. In permeable materials, thermal diffusion may contribute to solute flows to a smaller, but still significant, extent

The feasibility of near-field ODR beam-size monitoring at 23 GeV at FACET

International Nuclear Information System (INIS)

Lumpkin, A.H.; Yao, C.-Y.; Hogan, M.; Muggli, P.

2011-01-01

Extension of near-field optical diffraction radiation (ODR) imaging to the 23 GeV beams at the proposed FACET facility at SLAC has been evaluated. The beam-size sensitivity at the 10- to 20-(micro)m sigma level based on a simple model will be reported. Polarization effects are also seen to be important and will be discussed. The comparisons to previous experimental results and the modeling results indicate sufficient feasibility for planning of the experiments in the coming year.

The Feasibility of Near-field ODR Beam-size Monitoring at 23 GeV at FACET

International Nuclear Information System (INIS)

Lumpkin, A.H.; Yao, C.-Y.; Hogan, M.; Muggli, P.

2012-01-01

Extension of near-field optical diffraction radiation (ODR) imaging to the 23 GeV beams at the proposed FACET facility at SLAC has been evaluated. The beam-size sensitivity at the 10- to 20-(micro)m sigma level based on a simple model will be reported. Polarization effects are also seen to be important and will be discussed. The comparisons to previous experimental results and the modeling results indicate sufficient feasibility for planning of the experiments in the coming year.

High speed diagnostics for characterization of oxygen / hydrogen rocket injector flowfields

Science.gov (United States)

Locke, Justin M.

Temporally-resolved diagnostics are needed to characterize the highly-turbulent flowfields of rocket engine combustors. Two different high speed diagnostic techniques have been applied successfully to study the combustion and mixing characteristics of single-element shear-coaxial injector flowfield in a rocket combustor. Tunable diode laser absorption spectroscopy (TDLAS) is applied to make in-situ measurements with combusting gas-gas propellants, and high speed imaging incorporating backlighting is applied to combusting and non-combusting liquid-gas and gas-gas propellants. Tunable diode laser absorption spectroscopy has been used to make path-integrated temperature and H2O mole fraction measurements in a gaseous oxygen / gaseous hydrogen uni-element rocket chamber with hot background flow. Four mixture conditions were studied at a nominal chamber pressure of 115 psia. Near infrared diode lasers were utilized to target rovibrational transitions of water vapor, which is created through the combustion processes. Both direct absorption spectroscopy and wavelength modulation spectroscopy with second harmonic normalized by first harmonic (1f-normalized WMS-2 f) techniques were applied, with the harmonic detection technique found to yield the best results. Centerline measurements were made at two axial locations, in the near-injector region and far-field region further downstream. Time-resolved measurements of temperature and H2O mole fraction in the rocket chamber are presented. The TDLAS measurements shows clear differences between the near-injector and downstream measurement locations. Mean path-integrated temperatures and H2O mole fractions in the near-injector region are lower than the downstream measurement location. Fluctuations in path-integrated temperature and H2O mole fraction in the downstream location are significantly greater than the near-injector region. This suggests increased turbulence and larger-scale mixing processes are occurring in the downstream

On the truncation of the azimuthal mode spectrum of high-order probes in probe-corrected spherical near-field antenna measurements

DEFF Research Database (Denmark)

Pivnenko, Sergey; Laitinen, Tommi

2011-01-01

Azimuthal mode (m mode) truncation of a high-order probe pattern in probe-corrected spherical near-field antenna measurements is studied in this paper. The results of this paper provide rules for appropriate and sufficient m-mode truncation for non-ideal first-order probes and odd-order probes wi...

Nanospot soldering polystyrene nanoparticles with an optical fiber probe laser irradiating a metallic AFM probe based on the near-field enhancement effect.

Science.gov (United States)

Cui, Jianlei; Yang, Lijun; Wang, Yang; Mei, Xuesong; Wang, Wenjun; Hou, Chaojian

2015-02-04

With the development of nanoscience and nanotechnology for the bottom-up nanofabrication of nanostructures formed from polystyrene nanoparticles, joining technology is an essential step in the manufacturing and assembly of nanodevices and nanostructures in order to provide mechanical integration and connection. To study the nanospot welding of polystyrene nanoparticles, we propose a new nanospot-soldering method using the near-field enhancement effect of a metallic atomic force microscope (AFM) probe tip that is irradiated by an optical fiber probe laser. On the basis of our theoretical analysis of the near-field enhancement effect, we set up an experimental system for nanospot soldering; this approach is carried out by using an optical fiber probe laser to irradiate the AFM probe tip to sinter the nanoparticles, providing a promising technical approach for the application of nanosoldering in nanoscience and nanotechnology.

Correlation between the local stress and the grain misorientation in the polycrystalline Al2O3 measured by near-field luminescence spectroscopy

Science.gov (United States)

Tomimatsu, Toru; Takigawa, Ryo

2018-06-01

Owing to its high spatial resolution, near-field spectroscopy is a useful method for sensing the stress in a narrow region of submicron order. Here, on the basis of the highly resolved images obtained by near-field luminescence spectroscopy, we propose a statistical method of analyzing grain anisotropy-induced stress in polycrystalline Al2O3. We focus on two characteristics of a spectra: the intensity ratio and peak shift of luminescence of two lines (R1 and R2) from Al2O3 to discuss crystal orientation and stress, respectively. By incorporating the concept of the crystal misorientation parameter using intensity ratio, an apparent correlation between the magnitude of stress and the misorientation is found. This correlation analysis provides an important insight for the investigation of local thermal stress in Al2O3.

Determination of the spatial resolution of an aperture-type near-field scanning optical microscope using a standard sample of a quantum-dot-embedded polymer film

International Nuclear Information System (INIS)

Kim, J. Y.; Kim, D. C.; Nakajima, K.; Mitsui, T.; Aoki, H.

2010-01-01

The near-field scanning optical microscope (NSOM) is a form of scanning probe microscope that achieves, through the use of the near-field, a spatial resolution significantly superior to that defined by the Abbe diffraction limit. Although the term spatial resolution has a clear meaning, it is often used in different ways in characterizing the NSOM instrument. In this paper, we describe the concept, the cautions, and the general guidelines of a method to measure the spatial resolution of an aperture-type NSOM instrument. As an example, a quantum dot embedded polymer film was prepared and imaged as a test sample, and the determination of the lateral resolution was demonstrated using the described method.

System studies in PA: Development of process influence diagram (PID) for SFR-1 repository near-field + far-field

International Nuclear Information System (INIS)

Stenhouse, M.J.; Miller, W.M.; Chapman, N.A.

2001-05-01

Scenario development is a key component of the performance assessment (PA) process for radioactive waste disposal, the primary objective being to ensure that all relevant factors associated with the future evolution of the repository system are properly considered in PA. As part of scenario development, a list of features, events and processes (FEPs) are identified and assembled, representing the Process System, with interactions/influences between FEPs incorporated in a Process Influence Diagram (PID). This report documents the technical work conducted between 1997 and the end of 1999 under the Systems Studies Project. The overall objective of this project has been the construction of a PID for the SFR-1 repository (final repository for reactor waste), this PID being the first stage in the identification of scenarios to describe future evolution of this repository. The PIDs discussed in this report have been created using two software applications: existing commercial software (Business Modeller, Infotool AB. Stockholm, Sweden) and, more recently, a newly developed software tool SPARTA (Enviros QuantiSci, Henley, U.K.). Although the focus of this report is on the application of SPARTA to PID development, it is important to document the work carried out prior to SPARTA being available, in order to provide a complete record of the entire SFR-1 PID development effort as well as preserving the context of the multi-year project. Following a description of the different disposal sections of the SFR-1 and the various near-field barriers, the sequential development (i.e. near-field of Silo, BMA, BLA, BTF sections; far-field; integrated near-field + far-field) of the PID for SFR-1 repository system using Business Modeller is described. Owing to the complexity of the repository, in terms of number of both different disposal sections (Silo, BLA, BMA, BTF) and barriers associated with each section, the two-dimensional (2D) PID created for SFR-1 using Business Modeller is

Effect of coupling behavior on groundwater flow for geological disposal of radioactive high level waste

International Nuclear Information System (INIS)

Kurikami, Hiroshi; Kobayashi, Akira; Ohnishi, Yuzo; Chijimatsu, Masakazu

2003-01-01

In order to estimate the effects of coupled thermal-hydraulic-mechanical phenomena in near-field for geological disposal of high-level radioactive waste on a vast groundwater flow system, a far-field analysis was simulated based on the results of the simulation of coupled phenomena in near-field using averaged tensor and heat flux. From the results of the coupled analyses of near-field and far-field it was clarified that groundwater flow system was influenced by coupled phenomena in near-field. Moreover, it can be said that groundwater flux into a disposal tunnel is regarded as a complement to safety assessment of a disposal because it strongly correlates with traveling time of groundwater. (author)

Waveguide analysis of heat-drawn and chemically etched probe tips for scanning near-field optical microscopy.

Science.gov (United States)

Moar, Peter N; Love, John D; Ladouceur, François; Cahill, Laurence W

2006-09-01

We analyze two basic aspects of a scanning near-field optical microscope (SNOM) probe's operation: (i) spot-size evolution of the electric field along the probe with and without a metal layer, and (ii) a modal analysis of the SNOM probe, particularly in close proximity to the aperture. A slab waveguide model is utilized to minimize the analytical complexity, yet provides useful quantitative results--including losses associated with the metal coating--which can then be used as design rules.

High-resolution photocurrent microscopy using near-field cathodoluminescence of quantum dots

Directory of Open Access Journals (Sweden)

Heayoung P. Yoon

2013-06-01

Full Text Available We report a fast, versatile photocurrent imaging technique to visualize the local photo response of solar energy devices and optoelectronics using near-field cathodoluminescence (CL from a homogeneous quantum dot layer. This approach is quantitatively compared with direct measurements of high-resolution Electron Beam Induced Current (EBIC using a thin film solar cell (n-CdS / p-CdTe. Qualitatively, the observed image contrast is similar, showing strong enhancement of the carrier collection efficiency at the p-n junction and near the grain boundaries. The spatial resolution of the new technique, termed Q-EBIC (EBIC using quantum dots, is determined by the absorption depth of photons. The results demonstrate a new method for high-resolution, sub-wavelength photocurrent imaging measurement relevant for a wide range of applications.

Long-term behaviour of waste-forms in the near-field environment of a deep underground storage site, overview

International Nuclear Information System (INIS)

Toulhoat, P.; Lassabatere, Th.; Galle, Ch.; Cranga, M.; Trotignon, L.; Maillard, S.; Iracane, D.

1997-01-01

CEA (French Atomic Energy Commission) is responsible for the achievement of high activity and/or long life waste conditioning processes. Various waste-forms are used (glass, bitumen, etc...). ANDRA (French National Agency for Nuclear Waste Management) has to integrate the long-term durability of such waste-forms in the conception of a deep disposal and the assessment of its long-term confinement performances. The influence of near-field and of the boundary conditions imposed by the far-field on the long-term evolution is being more and more documented. Transport properties and reactivity of silica in the near field is one of the best examples of such effects. A coherent framework with relevant successive events (site re-saturation, chemical evolution of the engineered barrier, overpack corrosion) and a thorough analysis of hierarchized couplings are necessary to evaluate the long term durability of waste-form, and finally, to deliver a near-field-integrated source-term of radionuclides versus lime. We present hereafter some preliminary results obtained in the framework of the CEA 'C3P' project - long-term behaviour of waste-forms in their near-field environment. (authors)

Influence of various excavation techniques on the structure and physical properties of 'near-field' rock around large boreholes

International Nuclear Information System (INIS)

Pusch, R.

1989-12-01

The procedure employed in the excavation of canister deposition holes affects the structure and physical properties of the 'near-field' rock. Except for smooth blasting, the generated damage appears to be less important than the increase in 'axial' hydraulic conductivity that is caused by stress release effects, but both combine to yield significant local flow passages. This is particularly obvious where the rock structure yield steep wedges, which is frequently occurring in granite. Percussion drilling is concluded to cause rich fine-fissuring to a distance of up to one centimeter from the borehole wall, and 'discing'. Richer fissuring and some generation of new fractures and growth of preexisting ones are produced within several decimeters from the borehole wall by full-face drilling. Core drilling has the least effect on the rock structure. Smooth blasting produces a particular form of regular fractures which appear to be determinants of the hydraulic conductivity of the near-field rock. Theoretically, its conductivity in the axial direction of blasted big holes or tunnels should be in the range of 10 -8 - 10 -6 m/s, which is in agreement with measurements in the Stripa mine. (orig.)

Buried shallow fault slip from the South Napa earthquake revealed by near-field geodesy.

Science.gov (United States)

Brooks, Benjamin A; Minson, Sarah E; Glennie, Craig L; Nevitt, Johanna M; Dawson, Tim; Rubin, Ron; Ericksen, Todd L; Lockner, David; Hudnut, Kenneth; Langenheim, Victoria; Lutz, Andrew; Mareschal, Maxime; Murray, Jessica; Schwartz, David; Zaccone, Dana

2017-07-01

Earthquake-related fault slip in the upper hundreds of meters of Earth's surface has remained largely unstudied because of challenges measuring deformation in the near field of a fault rupture. We analyze centimeter-scale accuracy mobile laser scanning (MLS) data of deformed vine rows within ±300 m of the principal surface expression of the M (magnitude) 6.0 2014 South Napa earthquake. Rather than assuming surface displacement equivalence to fault slip, we invert the near-field data with a model that allows for, but does not require, the fault to be buried below the surface. The inversion maps the position on a preexisting fault plane of a slip front that terminates ~3 to 25 m below the surface coseismically and within a few hours postseismically. The lack of surface-breaching fault slip is verified by two trenches. We estimate near-surface slip ranging from ~0.5 to 1.25 m. Surface displacement can underestimate fault slip by as much as 30%. This implies that similar biases could be present in short-term geologic slip rates used in seismic hazard analyses. Along strike and downdip, we find deficits in slip: The along-strike deficit is erased after ~1 month by afterslip. We find no evidence of off-fault deformation and conclude that the downdip shallow slip deficit for this event is likely an artifact. As near-field geodetic data rapidly proliferate and will become commonplace, we suggest that analyses of near-surface fault rupture should also use more sophisticated mechanical models and subsurface geomechanical tests.

Buried shallow fault slip from the South Napa earthquake revealed by near-field geodesy

Science.gov (United States)

Brooks, Benjamin A.; Minson, Sarah E.; Glennie, Craig L.; Nevitt, Johanna M.; Dawson, Tim; Rubin, Ron; Ericksen, Todd L.; Lockner, David; Hudnut, Kenneth; Langenheim, Victoria; Lutz, Andrew; Mareschal, Maxime; Murray, Jessica; Schwartz, David; Zaccone, Dana

2017-01-01

Earthquake-related fault slip in the upper hundreds of meters of Earth’s surface has remained largely unstudied because of challenges measuring deformation in the near field of a fault rupture. We analyze centimeter-scale accuracy mobile laser scanning (MLS) data of deformed vine rows within ±300 m of the principal surface expression of the M (magnitude) 6.0 2014 South Napa earthquake. Rather than assuming surface displacement equivalence to fault slip, we invert the near-field data with a model that allows for, but does not require, the fault to be buried below the surface. The inversion maps the position on a preexisting fault plane of a slip front that terminates ~3 to 25 m below the surface coseismically and within a few hours postseismically. The lack of surface-breaching fault slip is verified by two trenches. We estimate near-surface slip ranging from ~0.5 to 1.25 m. Surface displacement can underestimate fault slip by as much as 30%. This implies that similar biases could be present in short-term geologic slip rates used in seismic hazard analyses. Along strike and downdip, we find deficits in slip: The along-strike deficit is erased after ~1 month by afterslip. We find no evidence of off-fault deformation and conclude that the downdip shallow slip deficit for this event is likely an artifact. As near-field geodetic data rapidly proliferate and will become commonplace, we suggest that analyses of near-surface fault rupture should also use more sophisticated mechanical models and subsurface geomechanical tests. PMID:28782026

Radiation effects on materials in the near-field of a nuclear waste repository. 1997 annual progress report

International Nuclear Information System (INIS)

Ewing, R.C.; Wang, L.M.

1997-01-01

'Sheet silicates (e.g. micas and clays) are important constituents of a wide variety of geological formations such as granite, basalt, and sandstone. Sheet silicates, particularly clays such as bentonite are common materials in near-field engineered barriers in high-level nuclear waste (HLW) repositories. This is because migration of radionuclides from an underground HLW repository to the geosphere may be significantly reduced by sorption of radionuclides (e.g., Pu, U and Np) onto sheet silicates (e.g., clays and micas) that line the fractures and pores of the rocks along groundwater flowpaths. In addition to surface sorption, it has been suggested that some sheet silicates may also be able to incorporate many radionuclides, such as Cs and Sr, in the inter-layer sites of the sheet structure. However, the ability of the sheet silicates to incorporate radionuclides and retard release and migration of radionuclides may be significantly affected by the near-field radiation due to the decay of fission products and actinides. for example, the unique properties of the sheet structures will be lost completely if the structure becomes amorphous due to irradiation effects. Thus, the study of irradiation effects on sheet-structures, such as structural damage and modification of chemical properties, are critical to the performance assessment of long-term repository behavior.'

Numerical Simulation of a Laboratory-Scale Turbulent SlotFlame

Energy Technology Data Exchange (ETDEWEB)

Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski,Michael J.; Driscoll, James F.; Filatyev, Sergei A.

2006-04-20

We present three-dimensional, time-dependent simulations ofthe flowfield of a laboratory-scale slot burner. The simulations areperformed using an adaptive time-dependent low Mach number combustionalgorithm based on a second-order projection formulation that conservesboth species mass and total enthalpy. The methodology incorporatesdetailed chemical kinetics and a mixture model for differential speciesdiffusion. Methane chemistry and transport are modeled using the DRM-19mechanism along with its associated thermodynamics and transportdatabases. Adaptive mesh refinementdynamically resolves the flame andturbulent structures. Detailedcomparisons with experimental measurementsshow that the computational results provide a good prediction of theflame height, the shape of the time-averaged parabolic flame surfacearea, and the global consumption speed (the volume per second ofreactants consumed divided by the area of the time-averaged flame). Thethickness of the computed flamebrush increases in the streamwisedirection, and the flamesurface density profiles display the same generalshapes as the experiment. The structure of the simulated flame alsomatches the experiment; reaction layers are thin (typically thinner than1 mm) and the wavelengths of large wrinkles are 5--10 mm. Wrinklesamplify to become long fingers of reactants which burn through at a neckregion, forming isolated pockets of reactants. Thus both the simulatedflame and the experiment are in the "corrugated flameletregime."